JP2005203071A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which maintains excellent recording characteristics even under a severe environmental condition such as high temperature and high humidity and light (a fluorescent lamp, the sun light) exposure. <P>SOLUTION: The optical recording medium D is formed by bonding a signal substrate A and a dummy substrate B to each other by using an adhesive layer C. The signal substrate A is formed by layering at least a recording layer on which information is recorded by light, a reflective layer composed of Ag or an Ag alloy and a protective layer composed of an organic substance successively on a substrate 1 having a laser beam incident surface A1, the laser beam for recording and reproduction. The dummy substrate B consists of a substrate and a light shielding layer and transmittance T from an incident surface B1 to the reflection layer obtained by irradiating the dummy substrate B with light having 350 nm wavelength from the incident surface B1 side is specified to be in the range of 0%≤T≤25%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical recording medium that records, erases, and reproduces information by irradiation with a laser beam. In particular, the present invention provides an optical recording medium capable of maintaining excellent recording characteristics even under severe storage conditions such as high temperature and high humidity and light irradiation in an optical recording medium such as an optical disk and an optical card.

  Examples of the optical recording medium include a recent CD-R, CD-RW, or higher-density DVD-RW, DVD-RAM, DVD-R, Blu-ray disc, and the like. Here, “CD” means a compact disc, and “DVD” means a digital versatile disc. In these optical recording media, the recording film is heated by light to form a recording mark, and the recording mark is regarded as pits in the reproducing medium and is used as information using a change in reflectance. The optical recording medium is characterized by high compatibility with a read-only medium.

The structure of the optical recording medium has at least a recording layer and a reflective layer on a substrate. Known recording layer materials include organic dyes such as azo, cyanine, and phthalocyanine, phase change inorganic materials mainly composed of SbTe, and two layers of inorganic materials. In addition, the reflective layer, which is mainly composed of Ag, Al, or Au, which has a high reflectance, is often used as a material, but because of its high thermal conductivity and high reflectance in a wide wavelength range, Ag and Ag alloys have been frequently used recently. However, Ag and Ag alloy materials are extremely poor in storage stability under high temperature and high humidity and light irradiation conditions due to high reactivity with S and O ₂ , high photoactivity, and high ability to form granular crystals. There was a drawback.

  In Japanese Patent No. 1709731 (Patent Document 1), an organic protective layer is applied and formed on the reflective layer, and the reflective layer is shielded from the atmosphere such as air, thereby suppressing corrosion of the reflective layer under high temperature and high humidity conditions. Propose to do. As a result of investigation by the present inventor, although the storage stability was high under high temperature and high humidity conditions, when Ag or an Ag alloy was used for the reflective layer, the light irradiated on the reflective layer surface from the opposite side to the recording surface Deterioration of recording characteristics was observed with fluorescent lamps and sunlight, and it was difficult to say that the storage stability was sufficient.

  Further, for the purpose of improving the storage stability under high temperature and high humidity conditions, Japanese Patent Application Laid-Open No. 7-201075 (Patent Document 2) uses an anticorrosion layer between the Ag or Ag alloy reflective layer and the organic protective layer. Propose to do. This publication describes a medium structure in which an anticorrosion layer having high corrosion resistance is laminated on an Ag or Ag alloy reflection layer for the purpose of suppressing corrosion of the reflection layer. However, when the anticorrosion layer described in the example of Patent Document 2 uses Al, Cu, or an alloy thereof, peeling occurs at the interface with the Ag or Ag alloy reflective layer under high temperature and high humidity conditions. Inventor's examination revealed that the recording characteristics deteriorate due to the subsequent light irradiation, and the storage stability under both the high temperature and high humidity condition and the light irradiation condition cannot be maintained.

Japanese Patent No. 1709731 JP-A-7-201075

  As described above, the reflective layer material is preferably Ag or an Ag alloy. However, when the reflective layer of this material is laminated with the organic protective layer, there is a drawback that the storage stability is remarkably deteriorated when the reflective layer is irradiated with light. It was. Further, even if there is an anticorrosion layer, depending on the anticorrosion layer material, it has been difficult to achieve both storage stability under both high temperature and high humidity conditions and light irradiation conditions. Therefore, the present invention was devised to solve the above-described problems, and provides an optical recording medium that can maintain excellent recording characteristics even under severe storage conditions such as high temperature and high humidity and light irradiation. The purpose is to do.

The present invention has been made in view of the above problems, and provides an optical recording medium having the following configurations (a) to (d).
(A) An optical recording medium D for recording information by recording light includes a signal substrate (A) and a support (B, C) laminated on the signal substrate, and the signal substrate is a bottom surface of the signal substrate. A first substrate (1) having a first incident surface (A1) on which the recording light is incident from the side toward the support, and at least a recording layer (3) on the first substrate; A reflective layer (5) made of a substance containing Ag and a protective layer (6) made of an organic substance are sequentially laminated, and the wavelength is 350 nm from the second incident surface (B1) which is the surface of the support. When the specific wavelength light is irradiated, the transmittance T of the specific wavelength light of the layer constituting the range from the second incident surface to the surface of the reflective layer is 0% ≦ T ≦ 25%. A characteristic optical recording medium.
(B) The optical recording medium according to (a), wherein the support includes a dummy substrate (B) having the second incident surface and an adhesive layer (C).
(C) The dummy substrate includes a second substrate (8) and a transmittance control member (9), and the transmittance T is set to 0 to 25%, whereby the transmittance T The optical recording medium according to (b), wherein
(D) The dummy substrate includes a second substrate (8), and the second substrate is a transmittance control member (8, 9) having a transmittance of 0 to 25%, whereby the transmission is performed. The optical recording medium according to (b), wherein the rate T is set.

  According to the optical recording medium of the present invention, excellent recording / reproducing characteristics can be obtained even under adverse conditions in which the material of the optical recording medium is easily deteriorated under severe environmental conditions such as high temperature and high humidity and light (fluorescent lamp, sunlight). Can be maintained.

  Embodiments of an optical recording medium according to the present invention will be described below with reference to the accompanying drawings. In the following description, a phase-change optical disk is used as an embodiment of the optical recording medium of the present invention. However, the present invention also applies to other optical recording media having the same configuration, such as optical disks and optical cards. It goes without saying that is applicable.

(Configuration of optical recording medium)
FIG. 1 is a diagram showing a schematic configuration of each embodiment of an optical recording medium. The optical recording medium D is a medium capable of repeatedly overwriting information, such as a phase change optical disk such as a DVD-RW or an optical card. The optical recording medium D has a structure in which a signal substrate A and a dummy substrate B are bonded together with an adhesive layer C as shown in FIG. Here, the dummy substrate B and the adhesive layer C further constitute a support. The recording / reproducing laser beam is incident from the incident surface A1 (first incident surface) of the signal substrate A. The storage test light is incident from the incident surface B1 (second incident surface) of the dummy substrate B.

<First Embodiment of Optical Recording Medium D>
FIG. 2 is a diagram showing a signal board Aa which is a first configuration example of the signal board A. The signal substrate Aa has a configuration in which a first protective layer 2, a recording layer 3, a second protective layer 4, a reflective layer 5, and a third protective layer 6 are sequentially stacked on the substrate 1. The configuration of the optical recording medium D using the signal substrate Aa is the first embodiment. The barrier layer 10 is a layer provided as appropriate, which will be described later.

  As the material of the substrate 1, various transparent synthetic resins, transparent glass, and the like can be used. It is preferable that the substrate 1 has a light transmittance with a light transmittance of approximately 100%. In order to avoid the influence of dust adhesion and scratches on the substrate 1, the transparent substrate 1 is used, and information is recorded on the recording layer 3 from the substrate 1 side with the condensed laser light. Examples of the material of the substrate 1 include glass, polycarbonate, polymethyl methacrylate, polyolefin resin, epoxy resin, and polyimide resin. In particular, a polycarbonate resin is preferable because of its small optical birefringence and hygroscopicity and easy molding.

  Although the thickness of the substrate 1 is not particularly limited, it is preferably 0.01 mm to 0.6 mm in consideration of compatibility with the DVD, and most preferably 0.6 mm (the total thickness of the DVD is 1.2 mm). ). This is because if the thickness of the substrate 1 is less than 0.01 mm, even when recording is performed with laser light converged from the incident surface A1 side of the substrate 1, it is easily affected by dust. Moreover, if there is no restriction | limiting in the total thickness of an optical recording medium, it should just be in the range of 0.01 mm-5 mm practically. If the thickness is 5 mm or more, it is difficult to increase the numerical aperture of the objective lens, and the spot size of the irradiation laser light is increased, so that it is difficult to increase the recording density.

  The substrate 1 may be flexible or rigid. The flexible substrate 1 is used as an optical recording medium having a tape shape, a sheet shape, or a card shape. The rigid substrate 1 is used as a card-shaped or disk-shaped optical recording medium.

  The first protective layer 2 and the second protective layer 4 protect the substrate 1 and the recording layer 3 from heat, such as preventing the substrate 1, the recording layer 3 and the like from being deformed by heat and deteriorating the recording characteristics during recording. The effect of improving the signal contrast at the time of reproduction is obtained by the effect and the optical interference effect.

Each of the first protective layer 2 and the second protective layer 4 is preferably transparent to the recording / reproducing laser beam and has a refractive index n in the range of 1.9 ≦ n ≦ 2.3. Further, the materials of the first protective layer 2 and the second protective layer 4 are oxides such as SiO ₂ , SiO, ZnO, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , ZrO ₂ , MgO from the viewpoint of thermal characteristics. ZnS, In ₂ S ₃ , sulfides such as TaS _4, and carbides such as SiC, TaC, WC, and TiC, and mixtures thereof are preferable. Among these, a mixed film of ZnS and SiO ₂ is particularly preferable because deterioration of recording sensitivity, C / N, erasure rate, and the like hardly occurs even when recording and erasing are repeated.
Moreover, the 1st protective layer 2 and the 2nd protective layer 4 do not need to be the same material and composition, and may be comprised from a different material.

  The thickness of the first protective layer 2 is in the range of approximately 5 nm to 500 nm. Furthermore, the thickness of the first protective layer 2 is preferably in the range of 40 nm to 300 nm because it is difficult to peel from the substrate 1 and the recording layer 3 and defects such as cracks are difficult to occur. If it is thinner than 40 nm, it is difficult to ensure the optical characteristics of the disk, and if it is thicker than 300 nm, the productivity is poor. In addition, More preferably, it is the range of 50 nm-80 nm.

  The thickness of the second protective layer 4 is preferably in the range of 5 nm to 40 nm from the viewpoint of recording characteristics such as C / N and erasure rate, and stable rewriting many times. If the thickness is less than 5 nm, it becomes difficult to ensure the heat of the recording film, so that the optimum recording power is increased. If the thickness is more than 40 nm, the overwrite characteristic is deteriorated. More preferably, it is the range of 10 nm-20 nm.

  The recording layer 3 is made of Ag—In—Sb—Te alloy, Ge—In—Sb—Te alloy, or Ge—In—Sb—Te alloy with at least one of Ag, Si, Al, Ti, Bi, and Ga. It is a kind of alloy layer. Further, the layer thickness of the recording layer 3 is preferably 10 nm to 25 nm. If the layer thickness is less than 10 nm, the crystallization speed decreases and the high-speed recording characteristics deteriorate, and if it is more than 25 nm, a large laser power is required for recording.

  As the material of the reflective layer 5, Ag or an Ag alloy is particularly used because of its high thermal conductivity and high reflectance in a wide wavelength range. As an example of the Ag alloy, a mixture of Ag and at least one element such as Cr, Au, Cu, Pd, Pt, Ni, Nd, In, Ca, and Bi is generally used.

  The thickness of the reflective layer 5 varies depending on the thermal conductivity of the metal or alloy forming the reflective layer 5, but is preferably 50 nm to 300 nm. If the thickness of the reflective layer 5 is 50 nm or more, the reflective layer 5 does not change optically and does not affect the reflectance value. However, as the thickness of the reflective layer 5 increases, the effect on the cooling rate increases. . In addition, it takes time in manufacturing to form a thickness exceeding 300 nm. Therefore, by using a material having high thermal conductivity, the layer thickness of the reflective layer 5 is controlled in the optimum range as much as possible.

  Here, when a mixture containing an S compound is used for the second protective layer 4, a material that does not contain S is used as the barrier layer 10 for the second protection in order to suppress the formation of an AgS compound with the reflective layer 5. It is preferable to insert between the layer 4 and the reflective layer 5.

  The third protective layer 6 is provided for improving scratch resistance and corrosion resistance. The third protective layer 6 is preferably composed of various organic substances, and in particular, it is preferable to cure the radiation curable compound and the composition thereof by radiation such as electron beams and ultraviolet rays. The thickness of the third protective layer 6 is usually about 0.1 μm to 100 μm, and may be formed by a usual method such as spin coating, gravure coating, spray coating, dipping or the like.

3A to 3D are diagrams showing examples of the configuration of the dummy substrate B. FIG.
The dummy substrate B does not necessarily have to be transparent when the recording / reproducing laser beam is not incident. For example, in order to improve the storage characteristics of the medium by light irradiation, the light shielding layer 9 is formed on the substrate 8 with a colored film or a metal film. The thing of the structure which formed was considered. In particular, the transmittance T at a wavelength λ = 350 nm is preferably 0% to 25%. When the transmittance T is greater than 25%, the light fastness effect is reduced. Here, the transmittance T indicates the light transmittance of a layer constituting the range from the incident surface B1 of the dummy substrate B to the surface of the reflective layer 5 (surface on the dummy substrate B side). That is, the transmittance T is a light transmittance determined by all substances (layers) included in the range from the incident surface B1 to the surface of the reflective layer 5.

FIGS. 3A to 3D are configuration examples of the dummy substrate B using the light shielding layer 9 which is a transmittance control member for controlling the transmittance T. Here, the first configuration example considered as a preferable configuration example is shown. A configuration example Ba to a fourth configuration example Bd are shown. 3A is a first configuration example Ba of the dummy substrate B, FIG. 3B is a second configuration example Bb of the dummy substrate B, FIG. 3C is a third configuration example Bc of the dummy substrate B, FIG. (D) shows a fourth configuration example Bd of the dummy substrate B. FIG.
The first configuration example Ba is a configuration example in which the substrate 8 is provided on the incident surface side B1 of the dummy substrate Ba and the light shielding layer 9 is provided on the bonding surface side B2 of the dummy substrate Ba, and the second configuration example Bb is the light shielding layer 9 on the dummy substrate. A configuration example in which the substrate 8 is provided on the bonding surface side B2 of the dummy substrate Bb on the incident surface side B1 of Bb, a third configuration example Bc is a configuration example in which the light shielding layer 9 is inserted between the two substrates 8, The fourth configuration example Bd is a configuration example in which a color or the like is applied to the substrate 8 and the entire substrate 8 is used as the light shielding layer 9. The transmittance T of the dummy substrate B can be controlled by such configuration examples Ba to Bd.

FIG. 4 shows the relationship between the transmittance T (transmittancy) of irradiation light (specific wavelength light) with a wavelength of 350 nm on the dummy substrate B and the recording / reproducing error rate on the optical recording medium after irradiation with white light of 30,000 lux (lx) for 600 hours. Indicates. From FIG. 4, when the transmittance T is 30% or more, the error rate exceeds 1 × 10 ⁻³ . When the error rate exceeds 1 × 10 ⁻³ , error correction is said to be considerably difficult. Therefore, the transmittance T of the dummy substrate B is preferably 0% to 25%, more preferably 10% or less. It is good to be.
The reason why the wavelength λ of the specific wavelength light is 350 nm is that the third protective layer 6 is generally an ultraviolet curable organic protective layer, and therefore the photochemical reaction becomes most intense when the wavelength λ in the ultraviolet region is around 350 nm. Because.

  As described above, the transmittance T is the transmittance of light from the incident surface B1 to the surface of the reflective layer 5, and therefore the transmittance T does not have to be controlled by the light transmittance of the dummy substrate B alone. For example, like the dummy substrate B and the adhesive layer C, the light transmittance obtained by adding the light transmittances of the respective members (each layer and each film) existing between the dummy substrate B and the surface of the reflective layer 5 is described above. The transmittance T is preferably in the range of 0% to 25%, more preferably 10% or less.

As the material of the substrate 8, various kinds of transparent synthetic resins and glass can be used. Examples of the material of the substrate 8 include glass, polycarbonate, polymethyl methacrylate, polyolefin resin, epoxy resin, and polyimide resin. In particular, a polycarbonate resin is preferable because of its low hygroscopicity and easy molding.
The material of the light shielding layer 9 may be anything as long as it blocks light incident from the incident surface B1. In view of productivity, it is preferable to make the light shielding layer 9 thin. For this reason, for example, a metal material such as an Al alloy is preferably used as the material of the light shielding layer 9.

  FIG. 5 shows an example of the transmittance T with respect to the thickness of the light shielding layer 9 made of an Al alloy (the substrate 8 uses a polycarbonate with a thickness of 0.6 mm, and the measurement wavelength is λ = 350 nm). Here, as the dummy substrate B, any one of the dummy substrates Ba to Bd shown in FIGS. As shown in FIG. 5, when the thickness of the light shielding layer 9 is smaller than 40 nm, the transmittance T increases rapidly. It can be seen that a layer thickness of 14 nm or more should be ensured to make the transmittance 25% or less, and a layer thickness of 25 nm or more should be secured to make the transmittance 10% or less.

The signal substrate A and the dummy substrate B are bonded to each other by bonding a radiation curable compound composed of an organic substance or a composition thereof by a method of curing and bonding with radiation such as an electron beam or ultraviolet rays, or an adhesive sheet. There is a way. In order to obtain a light resistance effect, it is also preferable that the light transmittance of the adhesive or pressure-sensitive adhesive sheet used as the adhesive layer C in FIG. 1 is 0% to 25% (when the measurement wavelength λ = 350 nm is used).
The signal substrate A and the dummy substrate B are bonded to each other by an air sandwich structure, an air incident structure, a close bonding structure, or the like. Alternatively, the signal substrate A having a configuration excluding the substrate 1 may be laminated on the signal substrate A and bonded to the dummy substrate B via the adhesive layer C to form a single-sided two-layer optical recording medium.

(Method for producing optical recording medium)
Next, a method for manufacturing the optical recording medium D of the first embodiment will be described.
First, as a method of laminating the first protective layer 2, the recording layer 3, the second protective layer 4, the reflective layer 5, etc. on the substrate 1, a known thin film forming method in a vacuum can be mentioned. For example, vacuum deposition method (resistance heating type or electron beam type), ion plating method, sputtering method (direct current or alternating current sputtering, reactive sputtering), especially because the composition and layer thickness can be easily controlled, A sputtering method is preferred.

  In addition, it is preferable to use a batch method in which a plurality of substrates 1 are simultaneously formed in a vacuum chamber or a single wafer type film forming apparatus that processes the substrates 1 one by one. The thickness of the first protective layer 2, recording layer 3, second protective layer 4, reflective layer 5, etc. to be formed is controlled by controlling the power and time for turning on the sputtering power source or by using a quartz vibration type film thickness meter. It can be easily done by monitoring.

  Further, the formation of the first protective layer 2, the recording layer 3, the second protective layer 4, the reflective layer 5 and the like may be performed while the substrate 1 is fixed or moved or rotated. Since the in-plane uniformity of the layer thickness is excellent, it is preferable to rotate the substrate 1, and it is more preferable to combine revolution. When the substrate 1 is cooled as necessary, the amount of warpage of the substrate 1 can be reduced.

In addition, after forming the reflective layer 5 and the like within a range that does not significantly impair the effects of the present invention, a third protective layer such as a dielectric layer such as ZnS or SiO ₂ or an ultraviolet curable resin is used to prevent deformation of these thin films. The layer 6 or the like may be provided as necessary.
After the reflective layer 5 or the third protective layer 6 is formed, the adhesive surface A2 of the third protective layer 6 (the reflective layer 5 when the third protective layer 6 is not provided) shown in FIG. The adhesive surface B2 is bonded with an adhesive layer C such as an adhesive.

  The recording layer 3 is preferably crystallized by irradiating and heating light such as a laser beam or a xenon flash lamp in advance before actual recording. In particular, initialization with a laser beam is preferable because there is little reproduction noise.

Now, Examples 1 to 3 and Comparative Examples 1 and 2 of the optical recording medium D according to the first embodiment will be described in order. Here, a phase change optical disk will be described as an example.
In the following examples and comparative examples, recording / reproduction is performed using an optical disk drive tester (DDU1000) manufactured by Pulstec Corp. equipped with a laser diode having a wavelength of 658 nm and an optical lens having NA = 0.60, and recording characteristics at an error rate. Evaluated.

In the storage characteristic test, the optical recording medium was allowed to stand for 100 hours at a temperature of 80 ° C. and a relative humidity of 85% (80 ° C. and 85% RH) as a high-temperature and high-humidity condition, and then 30,000 lx white light (storage) Test light) was applied to the incident surface B1 for 600 hours. After storage processing under the above high temperature and high humidity conditions and light irradiation conditions (hereinafter referred to as storage processing), it is recorded on an unrecorded portion, and then error rate measurement is performed to make error correction difficult 1 × 10 An error rate of ^-3 or higher was considered bad.
A Hitachi type 330 spectrophotometer was used to measure the transmittance.

(Example 1)
The signal substrate A was prepared by forming each thin film on a substrate 1 made of polycarbonate resin having a diameter of 120 mm and a plate thickness of 0.6 mm. Substrate 1 has a track pitch of 0.74 μm, and vacancies and lands are alternately formed. The groove depth was 25 nm, and the ratio of groove width to land width was approximately 40:60.

First, after evacuating the inside of the vacuum vessel to 3 × 10 ⁻⁴ Pa, ZnS added with 20 mol% of SiO ₂ on one surface of the substrate 1 in an Ar gas atmosphere of 2 × 10 ⁻¹ Pa by a high frequency magnetron sputtering method. Was used to form the first protective layer 2 having a layer thickness of 70 nm.
Subsequently, the recording layer 3 is a Ge-In-Sb-Te four-element single alloy target with a layer thickness of 16 nm, the second protective layer 4 is the same material as the first protective layer 2, and the barrier layer 10 is 2 nm with GeN. Further, the reflective layer 5 was sequentially laminated with an Ag—Pd—Cu target of 120 nm.

After the substrate 1 is taken out from the vacuum vessel, an acrylic ultraviolet curable resin (SK5110 manufactured by Sony Chemical) is spin-coated on the reflective layer 5 and cured by ultraviolet irradiation to form a third protective layer 6 having a layer thickness of 3 μm. As a result, a signal substrate Aa shown in FIG. 2 was obtained.
As described above, the surface (the other surface) opposite to the surface on which each layer of the substrate 1 is formed is the incident surface A1, and the surface of the third protective layer 6 that is not in contact with the reflective layer 5 is the adhesive surface A2.

  In the dummy substrate B, the substrate 8 is made of a polycarbonate resin having a diameter of 120 mm and a plate thickness of 0.6 mm, which is the same as that of the substrate 1, and a light shielding layer 9 is formed on one surface of the substrate 8 by sputtering with an Al target. The film was formed with a thickness of 35 nm. In the present embodiment, since the configuration of the dummy substrate B is the first configuration example Ba shown in FIG. 3A, the surface on which the light shielding layer 9 is formed becomes the adhesive surface B2. The transmittance T at the wavelength λ = 350 nm of the dummy substrate B thus produced was 3%.

  An adhesive seal was used for the adhesive layer C, and the adhesive surface A2 of the signal substrate A (Aa) and the adhesive surface B2 of the dummy substrate B (Ba) were bonded together. Subsequently, in an initialization apparatus (POP120 manufactured by Hitachi Computer Equipment Co., Ltd.), using a laser having a radial laser beam width of 250 μm and a scanning laser beam width of 1.0 μm, a scanning linear velocity of 4.5 m / s, a laser power of 1600 mW, The recording layer 3 was initialized under a feed pitch of 220 μm, and an optical recording medium D was produced.

Using the optical recording medium D thus manufactured, recording was performed from the substrate 1 side (incident surface A1) to the groove portion which is a guide groove of the recording layer 3. The groove has a convex shape when viewed from the incident direction of the recording / reproducing laser beam.
When the above recording was performed under the condition of a linear velocity of 3.5 m / s (DVD standard 1 × speed) and the error rate was measured, it was confirmed that the recording characteristic before storage was 2 × 10 ⁻⁵ . Furthermore, after recording under high temperature and high humidity conditions and after storage treatment under light irradiation conditions, recording and error rate measurement were conducted, and as shown in Table 1, it was as good as 5 × 10 ^−5, and even after storage processing, good characteristics were obtained. Obtained.
In Table 1, OK is indicated when the error rate is good, and NG is indicated when the error rate is poor.

(Example 2)
An optical recording medium similar to that of Example 1 was prepared except that the light shielding layer 9 of the dummy substrate B was changed to a layer thickness of 70 nm. The transmittance T at the wavelength λ = 350 nm of the dummy substrate B thus produced was 0%. When the same measurement as in Example 1 was performed, as shown in Table 1, the error rate of recording and reproduction after the storage process was 2 × 10 ^−5, and good recording characteristics were obtained after the storage process as in Example 1. It was.

(Example 3)
An optical recording medium similar to that of Example 1 was prepared, except that the light shielding layer 9 of the dummy substrate B was changed to 15 nm. The transmittance T at the wavelength λ = 350 nm of the dummy substrate B thus produced was 22%. When the same measurement as in Example 1 was performed, as shown in Table 1, the recording / reproduction error rate after the storage process was 3 × 10 ^−4, and the recording characteristics were good after the storage process as in Example 1. It was.

(Comparative Example 1)
An optical recording medium similar to that of Example 1 was prepared except that the light shielding layer 9 of the dummy substrate B was eliminated (0 nm). The transmittance T of the dummy substrate B thus prepared at a wavelength λ = 350 nm was 82%. When the same measurement as in Example 1 was performed, as shown in Table 1, the error rate of recording and reproduction after the storage process was 2 × 10 ^−3, which was significantly worse than the recording characteristics after the storage process. Was.

(Comparative Example 2)
An optical recording medium similar to that of Example 1 was prepared, except that the thickness of the light shielding layer 9 of the dummy substrate B was 10 nm. The transmittance T at the wavelength λ = 350 nm of the dummy substrate B thus prepared was 37%. When the same measurement as in Example 1 was performed, as shown in Table 1, the recording / reproduction error rate after the storage process was 1 × 10 ^−3, which was significantly deteriorated in the recording characteristics after the storage process as compared with Example 1. Was.

From the above, it was found that if the light shielding layer 9 was not sufficiently provided and the reflective layer 5 was irradiated with light for a long time, the recording characteristics after the light irradiation were remarkably deteriorated. This is presumed that the recording characteristics deteriorate due to activation of the UV curable resin of the third protective layer 6 and Ag or Ag alloy of the reflective layer 5 due to light irradiation, changing the characteristics of the reflective layer 5 and changing the heat dissipation state. Is done. Further, as described above, the error rate at which error correction is possible is said to be 1 × 10 ⁻³ or less. Therefore, the transmittance T of the irradiated light to the reflective layer 5 is in the range of 0% to 25%. It turned out to be preferable.

  Further, as a method for setting the transmittance T of the irradiated laser light of wavelength λ = 350 nm to the reflection layer 5 in the range of 0% to 25%, the light shielding layer 9 attached to the dummy substrate B in Examples 1 to 3. Although the transmittance T is controlled by the thickness of the substrate, the transmittance T may not be controlled by the dummy substrate B. That is, for example, the third protective layer 6 or the signal substrate A and the dummy substrate B formed on the opposite side of the reflection layer 5 with respect to the incident surface A1 of the recording / reproducing laser beam of the optical recording medium D is bonded. Even if the transmittance T is controlled to be in the range of 0% to 25% by mixing a powder such as carbon black into the adhesive (adhesive layer C), the same effect as in Example 1 can be obtained.

<Second Embodiment of Optical Recording Medium D>
If the light transmittance of the dummy substrate B or the adhesive layer C at the wavelength λ = 350 nm cannot be in the range of 0% to 25%, as another method for improving the light resistance, as shown in FIG. A signal substrate Ab having a configuration in which the active layer 7 is inserted between the reflective layer 5 and the third protective layer 6 is used.

  According to the study of the present inventor, the deterioration of the recording characteristics due to light irradiation from the incident surface B1 is that the reflective layer 5 made of Ag or Ag alloy is in direct contact with the third protective layer 6 and the reflective layer 5 made of Ag or Ag alloy. This happens only when the light is irradiated for a long time. Since the metallic luster of the reflective layer 5 is not lost in this deterioration mechanism, the chemical reaction between the components in the third protective layer 6 and Ag or Ag alloy as the material of the reflective layer 5 is activated by light irradiation, and the reflection It is presumed that the metal material of the layer 5 is chemically changed (not corroded). Due to the chemical change of the photoactive property of the reflective layer 5, the thermal conductivity of the metal material of the reflective layer 5 is changed, which deteriorates the heat dissipation state during recording of the recording layer 3, thereby deteriorating the recording characteristics. It is thought that there is. That is, the chemical change of the reflective layer 5 is not a corrosion (a chemical change that is not a metal) but a change from metal to metal, so that the high adhesion inactive layer 7 is interposed between the reflective layer 5 and the third protective layer 6. Insertion improves light resistance.

FIG. 6 is a diagram illustrating a signal board Ab which is a second configuration example of the signal board A. The signal substrate Ab has a configuration in which a first protective layer 2, a recording layer 3, a second protective layer 4, a reflective layer 5, a high adhesion inactive layer 7, and a third protective layer 6 are sequentially laminated on the substrate 1. The configuration of the optical recording medium D using the signal substrate Ab is a second embodiment. As described above, the barrier layer 10 may be provided as appropriate.
The same reference numerals are given to the same substrates and layers that form the signal substrate Ab as the signal substrate Aa used in the first embodiment, and the materials and thicknesses of the substrate and layers in the first embodiment It is the same as already described, and the description is omitted.
The material of the high adhesion inactive layer 7 may be metal, metalloid, nitride, oxide, carbide, or a compound thereof, and adhesion strength with Ag or an Ag alloy used for the reflective layer 5 is 1.6 MPa or more. It is preferable.

FIG. 7 shows high adhesion inactivity after standing for 100 hours under conditions of a temperature of 80 ° C. and a relative humidity of 85% (high temperature and high humidity: 80 ° C. and 85% RH), and further irradiating 30,000 lx white light for 600 hours. The relationship between the adhesion strength between the layer 7 and the reflective layer 5 made of Ag or Ag alloy and the recording / reproducing error rate is shown. From FIG. 7, when the adhesion strength is less than 1.6 MPa, the error rate exceeds 1 × 10 ⁻³ , which is said to make error correction considerably difficult. Therefore, the adhesion strength is preferably 1.6 MPa or more. . If the adhesion strength is less than 1.6 MPa, it is considered that peeling occurs from the interface between the reflective layer 5 and the high adhesion inactive layer 7 under high temperature and high humidity conditions (80 ° C. and 85% RH). If peeling occurs, the medium becomes whitish and the appearance is deteriorated, and the light resistance effect of the high adhesion inactive layer 7 is lost, and the recording characteristics are deteriorated by light irradiation. The upper limit of the adhesion strength is not particularly limited and may be 1.6 MPa or more.

  For the measurement of the adhesion strength, the tensile test shown in FIG. 8 was performed. As a condition of the tensile test, first, a thin film 5s of Ag or Ag alloy used for the reflective layer 5 is laminated on the glass plate 71 for about 200 nm, and a thin film 7s made of the material of the high adhesion inactive layer 7 is laminated thereon by 200 nm. Is used. The SUS plate 72 and the square bar 73 are joined to the sample with an epoxy adhesive to form a co-test material, and the co-test material is hung on the C-shaped hook 74 so that the pulling direction h is perpendicular to the SUS plate 72. A tensile test is performed after confirming the rest of the co-test material, and the force at which the fracture occurs at the interface between the thin film 5s (reflective layer 5) and the thin film 7s (high adhesion inactive layer 7) is measured, and divided by the area, adhesion strength It was.

Subsequently, Examples 4 to 7 and Comparative Examples 3 and 4 according to the optical recording medium of the second embodiment provided with the high adhesion inactive layer 7 will be described.
The optical recording medium of the second embodiment was manufactured by the same manufacturing method as the optical recording medium of the first embodiment described above. The high adhesion inactive layer 7 was formed in the same manner as the other layers formed on the substrate 1, that is, the first protective layer 2, the recording layer 3, the second protective layer 4, and the reflective layer 5.
In the second embodiment, the dummy substrate B includes only the substrate 8 without providing the light shielding layer 9. The dummy substrate B was bonded to the signal substrate Ab using an adhesive seal on the adhesive layer C.
Further, evaluation of recording characteristics, storage characteristic test, and error rate measurement were performed in the same manner as the optical recording medium of the first embodiment.

Example 4
An optical recording medium similar to that of Example 1 except that the light shielding layer 9 of the dummy substrate B is eliminated and a highly adhesive inactive layer 7 is inserted between Ge and the third protective layer 6 with a thickness of 5 nm of GeN. It was created. In the tensile test, the adhesion strength between AgPdCu and GeN as the material of the reflective layer 5 was 5.1 MPa. When the same measurement as in Example 1 was performed, as shown in Table 2, the recording / reproduction error rate after the storage process was 5 × 10 ^−5, and the recording characteristics were good after the storage process as in Example 1. .

(Example 5)
An optical recording medium similar to that of Example 4 was prepared except that the high adhesion inactive layer 7 was changed to Al ₂ O ₃ . In the tensile test, the adhesion strength between AgPdCu, which is the material of the reflective layer 5, and Al ₂ O ₃ was 3.6 MPa. When the same measurement as in Example 1 was performed, as shown in Table 2, the recording / reproduction error rate after the storage process was 6 × 10 ^−5, and the recording characteristics were good after the storage process as in Example 1. It was.

(Example 6)
An optical recording medium similar to that of Example 4 was prepared except that the high adhesion inactive layer 7 was replaced with Ge. In the tensile test, the adhesion strength between AgPdCu, which is the material of the reflective layer 5, and Ge was 1.6 MPa. When the same measurement as in Example 1 was performed, as shown in Table 2, the recording / playback error rate after the storage process was 9 × 10 ^−5, and the recording characteristics were good after the storage process as in Example 1. It was.

(Example 7)
An optical recording medium similar to that of Example 4 was prepared except that the high adhesion inactive layer 7 was changed to NiCr. In the tensile test, the adhesion strength between AgPdCu, which is the material of the reflective layer 5, and NiCr was 2.5 MPa. When the same measurement as in Example 1 was performed, as shown in Table 2, the recording / reproduction error rate after the storage process was 6 × 10 ^−5, and the recording characteristics were good after the storage process as in Example 1. It was.

(Comparative Example 3)
An optical recording medium similar to that of Example 4 was prepared except that the high adhesion inactive layer 7 was made of Al. In the tensile test, the adhesion strength between AgPdCu, which is the material of the reflective layer 5, and Al was 1.2 MPa. When the same measurement as in Example 1 was performed, as shown in Table 2, the recording / playback error rate after the storage process was 3 × 10 ^−3, which was significantly worse than that in Example 1, compared with Example 1. Was.

(Comparative Example 4)
An optical recording medium similar to that of Example 4 was prepared except that the high adhesion inactive layer 7 was made of Cu. In the tensile test, the adhesion strength between AgPdCu, which is the material of the reflective layer 5, and Cu was 1.4 MPa. When the same measurement as in Example 1 was performed, as shown in Table 2, the recording / reproduction error rate after the storage process was 1 × 10 ^−3, which was significantly deteriorated after the light irradiation as compared with Example 1. Was.

  As described above, the material of the high adhesion inactive layer 7 is changed to Al or Cu, so that the adhesion strength with the reflective layer 5 is reduced, and as a result, peeling occurs after high temperature and high humidity conditions, and the effect of the intermediate layer is diminished. Thereby, it is presumed that the ultraviolet curable resin of the third protective layer 6 and the Ag or Ag alloy of the reflective layer 5 are activated by the light irradiation condition after the high temperature and high humidity condition, and the recording characteristics deteriorate.

  When the light shielding layer 9 is not formed on the dummy substrate B as in the second embodiment, the activity of the chemical reaction between the UV curable resin of the third protective layer 6 and Ag or Ag alloy of the reflective layer 5 by light irradiation. In order to suppress the formation, it is necessary to use a highly adhesive inactive layer 7 between the reflective layer 5 and the third protective layer 6. The material preferably has an adhesion strength at the interface with the reflective layer 5 of 1.6 MPa or more. When the adhesion strength is less than 1.6 MPa, peeling occurs under high temperature and high humidity conditions, and the recording characteristics deteriorate before the influence of light irradiation.

  As described above, the optical recording medium of the first embodiment in which the dummy substrate B, the third protective layer 6 and the adhesive layer C to be bonded have light shielding properties so that light does not enter the Ag or Ag alloy reflective layer 5, or The optical recording medium of the second embodiment in which the highly adhesive inactive layer 7 is inserted between the Ag or Ag alloy reflective layer 5 and the third protective layer 6, and the medium structure of both are effective for maintaining good recording characteristics. In consideration of productivity, a manufacturing method of any one of the structures described above may be used.

<Third Embodiment of Optical Recording Medium>
An optical recording medium having a configuration in which the signal substrate Ab provided with the high adhesion inactive layer 7 shown in FIG. 6 and the dummy substrate B provided with the light shielding layer 9 shown in FIG. Form. Since the optical recording medium has the configuration of the third embodiment, the transmittance T to the reflective layer 5 can be controlled and the chemical reaction of the reflective layer 5 can be suppressed. Better recording / reproducing characteristics can be maintained under irradiation conditions.

It is a figure which shows schematic structure of each embodiment of the optical recording medium based on this invention. It is a figure which shows the 1st structural example of the signal board | substrate A which concerns on this invention. It is a figure which shows each structural example of the dummy board | substrate B which concerns on this invention. It is a figure which shows the relationship of the recording / reproducing error rate with respect to the transmittance | permeability T in the irradiation light of wavelength 350nm of the dummy substrate B. FIG. It is a figure which shows the relationship of the transmittance | permeability T with respect to the layer thickness of the light shielding layer 9 (Al). It is a figure which shows the 2nd structural example of the signal board | substrate A which concerns on this invention. It is a figure which shows the relationship of the recording / reproducing error rate with respect to the adhesive strength of the high adhesion active layer 7 and the reflection layer 5. FIG. It is explanatory drawing of a tension test.

Explanation of symbols

A Signal board A1 Incident surface (first incident surface)
B Dummy substrate B1 Incident surface (second incident surface)
C Adhesive layer D Optical recording medium 1 Substrate (first substrate)
2 First protective layer 3 Recording layer 4 Second protective layer 5 Reflective layer 6 Third protective layer 7 High adhesion inactive layer 8 Substrate (second substrate)
9 Shading layer (transmittance control member)
10 Barrier layer

Claims (4)

In an optical recording medium for recording information by recording light,
A signal board;
A support laminated on the signal board,
The signal substrate includes a first substrate having a first incident surface on which the recording light is incident from a bottom surface side of the signal substrate toward the support, and at least a recording layer on the first substrate, A reflective layer made of a substance containing Ag and a protective layer made of an organic substance are sequentially laminated,
The specific wavelength of the layer constituting the range from the second incident surface to the surface of the reflective layer when irradiated with light having a specific wavelength of 350 nm from the second incident surface which is the surface of the support Light transmittance T is 0% ≦ T ≦ 25%
An optical recording medium characterized by the above.   2. The optical recording medium according to claim 1, wherein the support includes a dummy substrate having the second incident surface and an adhesive layer. The dummy substrate has a second substrate and a transmittance control member,
3. The optical recording medium according to claim 2, wherein the transmittance T is set by setting the transmittance of the transmittance control member to 0 to 25%.   The dummy substrate includes a second substrate, and the transmittance T is set by using the second substrate as a transmittance control member having a transmittance of 0 to 25%. The optical recording medium according to claim 2.

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