JP2008152839A - Optical recording medium and manufacturing method of optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium wherein loss of recording data due to a scratch and a UV ray can be reduced while recording sensitivity is maintained and to provide a manufacturing method of the optical recording medium. <P>SOLUTION: A hard coat layer containing Si, O and C as constituent elements is provided on a substrate on a light incident side of the optical recording medium. When the refractive index and the extinction coefficient of light having 405 nm wavelength are defined as n<SB>1</SB>and k<SB>1</SB>, respectively and the extinction coefficient of light having 350 nm wavelength is defined as k<SB>2</SB>in the optical constants of the hard coat layer, and when the refractive index of light having 405 nm wavelength in the substrate material is defined as n<SB>0</SB>, relations of ¾n<SB>1</SB>-n<SB>0</SB>¾≤0.15, k<SB>1</SB>≤1×10<SP>-2</SP>and 1×10<SP>-3</SP>≤k<SB>2</SB>are satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical recording medium on which information is recorded and reproduced by laser light irradiation, and a method for manufacturing the optical recording medium.

  In recent years, in the field of optical recording, further higher density has been demanded. To meet this demand, the wavelength of the light source is shortened and the numerical aperture (NA) of the objective lens used in the optical pickup is increased. Development aimed at reducing the diameter of the light spot has been made. Whereas a conventional CD pickup has a light source wavelength of 780 nm and NA of 0.45, a DVD having a recording capacity about 6 to 8 times that of a conventional CD has a light source wavelength of 650 nm and NA of 0.6. The spot diameter is reduced.

  As a next-generation optical disc, development has been made aiming at higher density by further reducing the spot diameter by setting the light source wavelength in the blue-violet region and NA being 0.6 or more. However, reducing the beam spot diameter has the problem that, while it is possible to increase the capacity, it is vulnerable to scratches and recording data is lost due to scratches on the reading surface. In addition, in order to take advantage of the advantage that an optical disc can be carried, excellent durability and reliability in various usage environments are required. For this purpose, it must be able to withstand the use outdoors where there is a lot of ultraviolet rays harmful to the recording layer material.

As a method for preventing the loss of recording data due to scratches and ultraviolet rays as described above, Japanese Patent Application Laid-Open No. 2004-47040 (Patent Document 1) hard coats a transparent inorganic dielectric film on the light incident surface side of the optical recording medium. It is disclosed that SiO ₂ , Si ₃ N ₄ , SiC and the like are preferable as a material for the hard coat layer provided as a layer.
JP 2004-047040 A

  However, this Patent Document 1 does not have a quantitative description regarding the composition and optical constants of the hard coat layer material, and can be easily implemented as to how excellent characteristics as a hard coat layer can be obtained. There is no specific disclosure of the degree.

  Accordingly, an object of the present invention is made to solve the above-described problems, and provides an optical recording medium provided with a hard coat layer that protects against loss of recording data due to scratches and ultraviolet rays. There is.

In order to solve the above-described problems, the present invention provides an optical recording medium including a substrate and a recording layer on which information is recorded by light irradiation. Si, O, A hard coat layer made of a dielectric film containing C as a constituent element is provided, and the refractive index at a wavelength of 405 nm of the hard coat layer is n ₁ , the extinction coefficient is k ₁ , and the extinction coefficient at a wavelength of 350 nm is k. _{2. When} the refractive index at a wavelength of 405 nm of the substrate material is n ₀ , | n ₁ −n ₀ | ≦ 0.15, k ₁ ≦ 1 × 10 ⁻² , 1 × 10 ⁻³ ≦ k ₂ It is characterized by.

  In order to solve the above-described problems, the present invention is to form the hard coat layer of the optical recording medium of the present invention by sputtering in a gas containing oxygen using a sputtering target mainly composed of Si and C. Features.

  According to this invention, since the optical recording medium is provided with a hard coat layer that is resistant to both scratches and ultraviolet rays, the recorded data can be recorded even if it is scratched due to careless handling or dirt wiping. There is an effect that almost no loss is required, and recording data is hardly lost even if it is left outdoors for a long time in a clear day when ultraviolet rays fall.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

As shown in FIG. 1, the optical recording medium according to an embodiment of the present invention is provided with a hard coat layer made of a dielectric film on the light incident side, and preferably contains Si, O, and C as constituent elements. . In addition, N may be included. Polycarbonate is generally used as a substrate for an optical disk, but when a hard coat layer is made of SiO ₂ which is a dielectric film made of Si and O, it is used as recording / reproducing light for the next generation optical disk. Since the optical constants are close to each other in the blue-violet wavelength range, the loss of light due to reflection during recording and reproduction is small, but the film hardness is low, so it is weak to scratches, and because it is transparent in the ultraviolet region, data is obtained by irradiation with ultraviolet light. Be lost.

Since Si ₃ N _4, which is a dielectric film made of Si and N, has a refractive index significantly different from that of polycarbonate in the blue-violet region, the loss of light due to reflection increases during recording and reproduction. SiC, which is a dielectric film made of Si and C, has a very large light loss because of its very large absorption in the blue-violet region. By making the hard coat layer a dielectric film containing Si, O, C, and N as constituent elements, the hardness is high, and in the blue-violet region, the refractive index is close to that of polycarbonate, and at the same time, the absorption is small, and further the ultraviolet region In this case, the absorption can be increased moderately, and the optical recording medium is resistant to ultraviolet rays as well as scratches. Note that the SiOCN film containing Si, O, C, and N as constituent elements, which is the hard coat layer of the present invention, is typically an at. % Means a film that is 99% or more in total.

  The constituent elements of the film forming the hard coat layer are RBS (Rutherford Back Scattering: Rutherford Backscattering Method), EPMA (Electron Probe Micro-Analysis: Electronic Probe X-ray Micro Analyzer), EDX (Energy Dispersive X-ray Fraction X-ray Fraction Qualitative analysis and quantitative analysis using energy dispersive X-ray fluorescence analysis), ICP (Inductively Coupled Plasma) emission spectroscopy, SIMS (Secondary Ion Mass Spectroscopy), etc. it can.

Further, the optical constant of the hard coat layer is preferably such that the refractive index at the light source wavelength of the optical disk is close to that of the substrate material and the extinction coefficient is small. A larger extinction coefficient in the ultraviolet region is preferable. As specific optical constants, the refractive index at a wavelength of 405 nm of the hard coat layer is n ₁ , the extinction coefficient is k ₁ , the extinction coefficient at a wavelength of 350 nm is k ₂ , and the refractive index of the substrate material at a wavelength of 405 nm is n ₀ . It is preferable that | n ₁ −n ₀ | ≦ 0.15, k ₁ ≦ 1 × 10 ⁻² , 1 × 10 ⁻³ ≦ k ₂ . When | n ₁ −n ₀ | ≧ 0.15 and k ₁ ≧ 1 × 10 ⁻² , absorption by the hard coat layer and reflection at the interface between the hard coat layer and the substrate occur when the recording / reproducing light is irradiated. Since it increases, the loss of light increases, and as a result, the amount of light reaching the recording layer decreases, leading to a reduction in sensitivity of the medium.

In addition, when 1 × 10 ⁻³ ≧ k ₂ , for example, when used outdoors, the ultraviolet rays excessively reach the recording layer of the optical disc, resulting in deterioration of the recording layer and a significant loss of recorded data. Will do.

Moreover, it is more preferable that n ₁ ≦ n ₀ . When n ₁ ≦ n ₀ , due to the presence of the hard coat layer, the reflectance at the interface between the substrate and the atmosphere can be lowered, resulting in higher sensitivity of the medium. The optical constant can be measured by spectroscopic ellipsometry.

  The film thickness of the hard coat layer is preferably 10 nm or more. When the thickness is 10 nm or more, sufficient hardness as a hard coat layer can be obtained. More preferably, it is 50 nm or more and 100 nm or less. By setting the thickness to 50 nm or more and 100 nm or less, the reflectance of the interface between the substrate and the atmosphere can be lowered and the function as an antireflection film can be provided, resulting in higher sensitivity of the medium. The most effective function as such an antireflection film is nxd where λ [nm] is the light source wavelength of the optical disk, n is the refractive index of the hard coat layer and d is the film thickness at λ [nm]. = Λ / 4. Assuming that the light source wavelength is the violet region, λ = 405, and the refractive index is n = 1.55, d = 65 [nm].

  Regarding the composition ratio of the constituent elements of the hard coat layer, the C (carbon) content is 0.01 [at. %] 30 [at. %] Or less is preferable. 0.01 [at. %] Or less, the absorption of the film in the ultraviolet region is reduced, so that the recording layer material is deteriorated by irradiation with ultraviolet rays. 30 [at. %] Or more, absorption increases in the blue-violet region used in the next generation optical disc, so that high power light is required during recording and reproduction, and the sensitivity of the medium is lowered.

  The N (nitrogen) content is 0.01 [at. %] Or more and 60 [at. %] Or less, preferably 1 [at. %] Or more and 50 [at. %] Or less is particularly preferable. 1 [at. %] Or more and 50 [at. %] Or less, sufficient hardness is obtained and scratch resistance is obtained. 50 [at. %] Or more, the refractive index becomes too high, and reflection at the interface between the hard coat layer and the substrate increases, resulting in a large loss of light and low sensitivity.

  Furthermore, the content of O (oxygen) is 10 [at. %] Or more and 70 [at. %] Or less is preferable. 10 [at. %] Or less, the absorption decreases in the blue-violet region, and the sensitivity decreases. 70 [at. %] Or more, the absorption of the film in the ultraviolet region becomes small, so that the recording layer material is deteriorated by irradiation with ultraviolet rays. Moreover, sufficient hardness cannot be obtained. The hard coat layer of the present invention may be a so-called functionally graded material in which a concentration gradient of elements is formed in the film. The concentration gradient of the element can be controlled by the process conditions during film formation.

Further, the hard coat layer need not be limited to Si, O, C, and N as constituent elements, and may be a mixture with a transparent dielectric. The transparent _{dielectric, TiO 2, Al 2 O 3} , Ta 2 O 3, Nb 2 O 5, MgF, CeO 2, ZrO 2, ZnO, ZnS, AlN, and the like.

The specific hardness of the hard coat layer is preferably a Knoop hardness of 1000 [kgf / mm ² ] or more. When the Knoop hardness is 1000 [kgf / mm ² ] or more, the optical recording medium is sufficiently resistant to scratches. Knoop hardness can be obtained by pressing the thin film with a diamond-shaped diamond pyramid indenter and measuring the length of the diagonal line of the conical depression formed on the thin film surface. When the force for pressing the thin film is F [kgf] and the length of the diagonal line of the depression is d [mm], the Knoop hardness HK = (1450.95 × 10 ² × F) ÷ d ² .

The hard coat layer need not be limited to a single SiOCN film having Si, O, C, and N as constituent elements, and may be a laminated film of a plurality of dielectric films having different refractive indexes. Specifically, it is preferable to sequentially stack a high refractive index dielectric film and a low refractive index dielectric film. For example, if the high refractive index dielectric film is abbreviated as H and the low refractive index dielectric film is abbreviated as L, the optical thickness (product of the refractive index and the film thickness) of each film is set as the light source wavelength λ [nm] of the optical disk. And a laminated structure such as HLHLHLHLLLHLHLH, and a SiOCN film is used as the low refractive index film L. By adopting such a laminated structure, it is possible to suppress light loss due to reflection during recording / reproducing light irradiation. The high refractive index film H is made of at least one dielectric selected from ZnS, TiO ₂ , Nb ₂ O ₅ , GeN, GeCrN, CeO, Cr ₂ O ₃ , ZnS · SiO ₂ , and Ta ₂ O _5. It is preferable to use a material having a main component.

Next, an embodiment of a method for producing an optical recording medium provided with the hard coat layer described above will be described. The manufacturing process of the optical recording medium of this embodiment includes a step of sputtering the above-described hard coat layer in a gas containing oxygen using a sputtering target containing Si and C as constituent elements. In order to obtain a suitable hard coat layer, it is preferable to appropriately set the film formation conditions by sputtering. As the sputtering gas, for example, an appropriate amount of oxygen or a mixed gas in which oxygen and nitrogen are added to an inert gas such as argon is used. In addition, CO ₂ or methane gas can be used. By such a sputtering process, a hard coat layer containing Si, O, C, and N as constituent elements is formed. The constituent elements of the target are not limited to Si and C, and may include O and N. Since the optical recording medium manufacturing method according to this embodiment has a high deposition rate of the hard coat layer, the mass productivity of the optical recording medium manufacturing process can be improved. Even if a small amount of impurity elements inevitably contained in the target containing Si and C as constituent elements is incorporated in the hard coat layer, this is not contrary to the gist of the present invention.

(First Embodiment) Single-sided rewritable optical recording medium Next, a first embodiment of the optical recording medium of the present invention will be described. Here, an embodiment in which the above-described optical recording medium provided with the hard coat layer is applied to a phase change optical recording medium will be described. The phase change optical recording medium may be a single-layer medium or a single-sided double-layer medium. In any case, the phase change optical recording medium includes a laminated film in which a first dielectric film, a phase change recording film, a second dielectric film, and a metal reflective film are sequentially laminated from the light incident side as a basic configuration. To do.

  FIG. 2 is a cross-sectional view showing a configuration of an embodiment of the phase change optical recording medium of the present invention. The phase change optical recording medium shown in FIG. 2 has a first substrate 7 disposed on the light incident side, and the hard coat layer 14 of the present invention described above is formed on the light incident surface side of the first substrate 7. Is provided. A first dielectric film 8, a phase change recording film 9 that is reversibly recorded / erased by light irradiation, and a second dielectric are formed on the surface opposite to the light incident surface of the first substrate 7. The body film 10 and the metal reflection film 11 are laminated in order. A second substrate 13 is bonded onto the metal reflective film 11 via an ultraviolet curable resin layer 12, and a phase change optical recording medium is constituted by these.

The hard coat layer 14 containing Si, O, C, and N as constituent elements can be formed by sputtering a target containing Si and C as constituent elements in a gas containing oxygen and nitrogen. In order to obtain an excellent hard coat layer 14, it is preferable to appropriately set the film formation conditions by sputtering. As the discharge gas, a mixed gas of a rare gas such as Ar and O ₂ and N ₂ can be used. As the sputtering method, RF sputtering, RF superimposed DC sputtering, DC sputtering including a pulse mode, DC sputtering, or the like can be applied.

  The first substrate 7 is made of a material that is transparent at the wavelength of the recording / reproducing light and does not prevent light from entering the information layer. The constituent material is not particularly limited. For example, thermoplastic transparent resins such as polycarbonate, amorphous polyolefin, thermoplastic polyimide, PET (polyethylene terephthalate), PEN (polyether nitrile), and PES (polyether sulfone). (Plastic), thermosetting polyimides, thermosetting transparent resins such as ultraviolet curable acrylic resins, and combinations thereof. The thickness of the first substrate 7 is not particularly limited, and a thickness of about 0.1 to 1.2 mm is appropriate.

  As the phase change recording film 9, GeSbTeBi, GeSbTe, GeBiTe, GeSbTeSn, AgInSbTe, InSbTe, AgInGeSbTe, GeInSbTe, or the like is used. An interface layer such as GeN, Cr 2 O 3, ZrO 2, SiC, or Ta 2 O 5 may be provided above or below or one side of the phase change recording film 9.

The first dielectric film 8 disposed on the light incident side of the phase change recording film 9 is a single layer film of a high refractive index dielectric film, or a high refractive index dielectric film, a low refractive index dielectric film, and a high refractive index film. It is composed of a laminated dielectric film in which a dielectric constant film is laminated in order. The constituent material of the high refractive index dielectric film is not particularly limited, but it is preferable to use a material that is transparent to the wavelength of recording / reproducing light and has a high refractive index. As such a dielectric material, a material whose main component is at least one dielectric selected from ZnS, TiO ₂ , Nb ₂ O ₅ , GeN, GeCrN, CeO, Cr ₂ O ₃ and Ta ₂ O ₅ is used. It is preferable to use a material mainly composed of a dielectric made of ZnS · SiO ₂ . As a constituent material of the low refractive index dielectric film, it is preferable to use a material whose main component is at least one dielectric selected from SiO, SiO ₂ , Al ₂ O ₃ , MgF, SiON, and SiOC. Note that the second dielectric film is made of the same material as the above-described high refractive index dielectric film. As a constituent material of the metal reflective film, for example, Ag, Al, Au, Cu, Si and alloys containing these as main components are used.

  The second substrate 13 is made of a material that can give an appropriate strength to the optical recording medium. In addition, the optical characteristic of the material which comprises the 2nd board | substrate 13 is not specifically limited, Transparent or opaque may be sufficient. Examples of the material constituting the substrate include glass, polycarbonate, amorphous polyolefin, thermoplastic polyimide, thermoplastic resins such as PET, PEN, PES, thermosetting polyimide, thermosetting resins such as ultraviolet curable acrylic resin, and the like. The combination of is mentioned. The thickness of the 2nd board | substrate 13 is not specifically limited, For example, the thickness of about 0.3-1.2 mm is suitable.

  Further, on the inner surface of the first substrate 7 or the second substrate 13, uneven pits and guide grooves corresponding to recording information (not shown) are formed. The pitch for pits or guides is suitably about 0.3 to 1.6 μm and about 30 to 200 nm deep.

Second Embodiment One-side Write-once Optical Recording Medium Next, a second embodiment of the optical recording medium of the present invention will be described. Here, an embodiment in which the above-described optical recording medium having the hard coat layer is applied to a write-once type optical recording medium will be described. The recordable optical recording medium may be a single-layer medium or a single-sided double-layer medium.

  The basic configuration in the case of a single-layer medium includes a hard coat layer, a first substrate, a recording film, a metal reflection film, and a second substrate in order from the light incident side. FIG. 3 is a cross-sectional view showing a configuration of an embodiment of a write-once type optical recording medium of the present invention. The write-once type optical recording medium shown in FIG. 3 has a first substrate 15 such as a polycarbonate substrate disposed on the light incident side. On top of this, a recording film 16 on which recording is performed irreversibly by light irradiation, and a metal reflection film 17 are sequentially laminated. A laminated substrate is bonded onto the metal reflective film 17 via an ultraviolet curable resin layer 18. The recording film 16 may be an azo metal complex dye or cyanine. The recording film 16 only needs to be irreversibly changed by light, and may be an inorganic recording film such as Te—O—Pd, AlSi, Zn—S—Mg—O—Si, and metal oxide. Good.

  Note that the characteristics, materials, and the like of the substrate and the metal reflection film described here are the same as those described in the first embodiment, and thus description thereof is omitted. Further, a dielectric film is provided between the first substrate 15 and the recording film 16, between the recording film 16 and the metal reflection film 17, and between the metal reflection film 17 and the ultraviolet curable resin layer 18 as necessary. It is provided, but not all must be arranged. The position where the dielectric film is disposed can be changed as appropriate according to conditions such as the characteristics of the film to be combined and the linear velocity of use of the optical recording medium.

(Single-sided single-layer rewritable medium (disks 1 to 18))
Next, 18 types of media (disks 1 to 18) in which the constituent elements and materials of the hard coat layer were changed in a single-sided single-layer rewritable medium were prepared, and the media were evaluated.

  The optical recording medium having the structure shown in FIG. 4 was produced as follows. First, a polycarbonate substrate having a thickness of 0.6 mm was prepared as the first substrate 21. This substrate is provided with a groove having a pitch of 0.68 μm and a depth of 40 nm. When land / groove recording is performed, the track pitch is 0.34 μm. Hereinafter, the groove track refers to a track that is close to the light incident surface, and the land track refers to a track that is far from the light incident surface.

High refractive index dielectric film 22a (ZnS-SiO ₂ ) / low refractive index dielectric film 23 / high refractive index in order from the light incident side on the surface where the groove of first substrate 21 is provided. Dielectric film 22b (ZnS—SiO ₂ ) / phase change recording film 25 / high refractive index dielectric film 22c (ZnS—SiO ₂ ) / Ag alloy reflective film 26 was formed by sputtering. Here, the first dielectric film provided on the light incident side of the phase change recording film 25 is a laminated film of a high refractive index dielectric film 22a / low refractive index dielectric film 23 / high refractive index dielectric film 22b. Configured.

In the disks 1 to 3, SiO ₂ is used as the low refractive index film 23 and GeSbTeBi is used as the phase change recording film 25, and no interface layer is provided. In disks 4 to 6, SiOC is used as the low refractive index film 23 and phase change recording is performed. GeSbTeBi was used as the film 25 and no interface layer was provided. In the disks 7 to 9, SiOC was used as the low refractive index film 23, GeBiTe was used as the phase change recording film 25, and GeN was used as the interface layer.

  Further, an ultraviolet curable resin was applied by spin coating, and then a 0.6 mm thick polycarbonate substrate was bonded and photocured. Thereafter, a SiOC film or a SiOCN film was formed as a hard coat layer 29 on the light incident side surface of the first substrate 21 by sputtering under appropriate process conditions.

On the other hand, in the disks 10 to 12, as in the disks 1 to 3, the layer structure is sequentially changed from the light incident side to the ZnS—SiO ₂ / SiO ₂ / ZnS—SiO ₂ / GeSbTeBi / ZnS—SiO ₂ / Ag alloy reflective film, the disk In the case of the discs 13 to 15, the ZnS—SiO ₂ / SiOC / ZnS—SiO ₂ / GeSbTeBi / ZnS—SiO ₂ / Ag alloy reflective film was used in the same manner as the discs 4 to 6. A SiO ₂ / SiOC / ZnS—SiO ₂ / GeN / GeBiTe / GeN / ZnS—SiO ₂ / Ag alloy reflective film was provided, and a hard coat layer shown in FIG. 10 was provided.

Each of the produced phase change optical recording media was set in an initialization apparatus, and the entire recording film was initialized (crystallized) by irradiating an oval beam having a width of 50 μm and a length of 1 μm.
FIG. 10 shows the constituent elements of the hard coat layer, the film material name, the refractive index n _{1 at} a wavelength of 405 nm, the extinction coefficients k ₁ and n _1, and the refractive index n _{0 of} polycarbonate which is the substrate material on the light incident side. = 1.55 Difference n ₀ −n ₁ , extinction coefficient k ₂ at a wavelength of 350 nm is shown.

The optical constants of the hard coat layers of the disks 1 to 9 are within the scope of the present invention. | N ₁ −n ₀ | ≦ 0.15, k ₁ ≦ 1 × 10 ⁻² , 1 × 10 ⁻³ ≦ k ₂ Met.

  The recording / erasing test of such an optical recording medium was performed as follows. Light was incident from the first substrate 21 side, and a recording / erasing experiment was performed. In the recording / erasing test, an optical disk evaluation apparatus including a pickup having an objective lens with NA = 0.65 and a semiconductor laser with a wavelength of 405 nm was used. The recording linear velocity was set to 5.6 m / s, a random pattern was recorded, and bER (bit error rate) was measured.

  As a test for measuring the strength against scratches, a worn wheel test was performed on the recorded disc based on JIS standard (JIS K7204), and the bER of the disc was measured after the test. In the ultraviolet light resistance test, the recorded disc was irradiated with a xenon lamp at a dose of 12 Mlux × h, and the bER of the disc was measured after irradiation.

  FIG. 11 shows bER-0 of each disk before the test, optimum recording power Pw, bER after the wear wheel test as bER-1, and bER after the ultraviolet light resistance test as bER-2.

When the media of disks 1 to 18 were evaluated before various tests, the bER ranged from the first half of 10 ⁻⁵ to the second half of 10 ⁻⁶ , indicating good recording characteristics.

  The media of disks 1 to 9 were able to be recorded with a low recording power of about 5 to 6 mW. On the other hand, in the disks 12 and 17, since the refractive index of the hard coat layer is too large, the loss of light due to reflection is large, resulting in low sensitivity. Similarly, in the disks 13 and 14, the absorption at the recording / reproducing light wavelength of the hard coat layer is large, so that the sensitivity is low.

Further, the media of the disks 1 to 9 were 10 ⁻⁵ units for both bER-1 and bER-2 with almost no deterioration in recording characteristics after the wear test and the light resistance test. On the other hand, since the hard coat layer was not used in the disks 10, 15 and 18, the recording characteristics of the bER-1 and bER-2 were greatly reduced to 10 ⁻³ units. Further, in the disk 11 and 16, but using the SiO ₂ film, is insufficient hardness of SiO ₂ film, and because transparent in the ultraviolet region, again, bER-1, bER-2 both to ^{10 -3} The recording characteristics deteriorated greatly.

(Single-sided single-layer rewritable medium (disks 19 and 20))
Next, in the single-sided single-layer rewritable medium, two types of media (disks 19 and 20) were prepared, and the media were evaluated.
The optical recording medium having the structure shown in FIG. 5 was produced as follows. First, a polycarbonate substrate having a thickness of 0.6 mm was prepared as the first substrate 30. This substrate is provided with grooves having a pitch of 0.4 μm and a depth of 50 nm. Groove recording is performed.

High refractive index dielectric film 31a (ZnS-SiO ₂ ) / interface layer 32a / phase change recording film 33 / interface on the surface of first substrate 30 on which the groove is provided in order from the light incident side. Layer 32b / high refractive index dielectric film 31b (ZnS-SiO ₂ ) / Ag alloy reflective film 34 was formed by sputtering. The disk 19 used GeBiTe as the phase change recording film and GeN as the interface layer, and the disk 20 used GeSbTeBi as the phase change recording film and (ZrO ₂ ) (Cr ₂ O ₃ ) as the interface layer.

  Further, an ultraviolet curable resin was applied by spin coating, and then a 0.6 mm thick polycarbonate substrate was bonded and photocured. Thereafter, a SiOC film or a SiONC film was formed as a hard coat layer 37 on the light incident side surface of the first substrate 30 by selecting appropriate process conditions.

  Each of the produced phase change optical recording media was set in an initialization apparatus, and the entire recording film was initialized (crystallized) by irradiating an oval beam having a width of 50 μm and a length of 1 μm. The recording / erasing test of such an optical recording medium was performed as follows. Light was incident from the first substrate 30 side, and a recording / erasing experiment was performed. In the recording / erasing test, an optical disk evaluation apparatus including a pickup having an objective lens with NA = 0.65 and a semiconductor laser with a wavelength of 405 nm was used. A recording test was conducted at a recording linear velocity of 6.61 m / s.

(Single-sided, single-layer rewritable medium (disks 21, 22))
Next, in the single-sided single-layer rewritable medium, two types of media (disks 21 and 22) were prepared, and the media were evaluated.
The optical recording medium having the structure shown in FIG. 6 was produced as follows. First, a polycarbonate substrate having a thickness of 1.1 mm was prepared as the first substrate 38. This substrate is provided with grooves having a pitch of 0.32 μm and a depth of 50 nm. Groove recording is performed.

On the surface of the first substrate 38 on which the groove is provided, Ag alloy reflective film 39 / high refractive index dielectric film 40a (ZnS-SiO ₂ ) / interface layer 41a / phase change recording film 42 / interface The layer 41b / the high refractive index dielectric film 40b (ZnS—SiO ₂ ) / were formed in this order by sputtering. The disk 21 uses GeSbTe as the phase change recording film 42 and GeN as the interface layers 41a and 41b. The disk 22 uses GeBiTe as the phase change recording film 42 and (ZrO ₂ ) · (Cr ₂ ) as the interface layers 41a and 41b. O ₃₎ was used.

  Further, an ultraviolet curable resin was applied by a spin coating method, and then a cover substrate 44 made of a polycarbonate resin having a thickness of 0.1 mm was bonded and photocured. Thereafter, a SiOC film or a SiONC film, and a SiONC film as a hard coat layer 45 were formed on the light incident side surface of the cover substrate 44 by sputtering under appropriate process conditions.

  Each of the produced phase change optical recording media was set in an initialization apparatus, and the entire recording film was initialized (crystallized) by irradiating an oval beam having a width of 50 μm and a length of 1 μm. The recording / erasing test of such an optical recording medium was performed as follows. An optical disk evaluation apparatus having a light incident from the cover substrate 44 side and a pickup having an objective lens with NA = 0.85 and a semiconductor laser with a wavelength of 405 was used. A recording test was conducted at a recording linear velocity of 5.6 m / s.

(Single-sided, double-layered rewritable medium (disk 23))
Next, one type of medium (disk 23) was prepared as the single-sided, double-layered rewritable medium, and the medium was evaluated.
The optical recording medium having the structure shown in FIG. 7 was produced as follows. This medium is a so-called single-sided double-layer medium, the front side of the L ₀ substrate 46 viewed from the light incident side, in which bonded to the L ₁ substrate 53 on the back side when viewed from the light incident side. First, it was prepared a polycarbonate substrate having a thickness of 0.59mm as _{L 0} substrate 46. This substrate is provided with a groove having a pitch of 0.68 μm and a depth of 40 nm. When land / groove recording is performed, the track pitch is 0.34 μm. Hereinafter, the groove track refers to a track that is close to the light incident surface, and the land track refers to a track that is far from the light incident surface.

High refractive index dielectric film 49b (ZnS—SiO ₂ ) / interface layer 50b (ZrO ₂ ) (Cr ₂ O ₃ ) / phase change recording film on the surface where the groove of L ₀ substrate 46 is provided. 51 (GeSbTeBi) / interface layer 50a (ZrO ₂ ) (Cr ₂ O ₃ ) / high refractive index dielectric film 49a (ZnS—SiO ₂ ) / Ag alloy reflective film 48 were sequentially formed by sputtering. The transmittance was about 50%.

The L ₁ substrate 53 is made of a polycarbonate substrate having a thickness of 0.59 mm, an Ag alloy reflective film 48 / second high-refractive-index dielectric film 49a (ZnS—SiO ₂ ) / interface layer 50a (ZrO ₂ ) (Cr ₂ O ₃ ) / Phase change recording film 51 / interface layer 50b / first high-refractive-index dielectric film 49b (ZnS—SiO ₂ ) in this order. L ₁ first high refractive index dielectric film 49b of the substrate 53 surface (ZnS-SiO _2), via the ultraviolet curing resin applied on _{L 0} substrate 46 is bonded to _{L 0} substrate 46. Therefore, when the L ₁ substrate 53 is viewed from the light incident side, the order is reverse to that at the time of film formation, and the first high refractive index dielectric film 49b (ZnS—SiO ₂ ) / interface layer 50a (ZrO ₂ ) (Cr ₂ O ₃ ). ) / Phase change recording film 51 (GeSbTeBi) / interface layer 50b (ZrO ₂ ) (Cr ₂ O ₃ ) / second high refractive index dielectric film 49a (ZnS—SiO ₂ ) / Ag alloy reflective film 48.

Thereafter, a SiOC film or a SiONC film was formed as a hard coat layer 54 on the light incident side surface of the L ₀ substrate 53 by sputtering under appropriate process conditions.

(Single-sided, single-layer write-once medium (disk 24))
Next, one type of medium (disk 24) was prepared in the single-sided single layer write-once medium, and the medium was evaluated.
A write-once type optical recording medium having the structure shown in FIG. 3 was produced as follows. First, a polycarbonate substrate having a thickness of 0.6 mm was prepared as a first substrate. The first substrate is provided with grooves having a pitch of 0.4 μm and a depth of 60 nm, and performs groove recording. Hereinafter, the groove track refers to a track having a short distance from the light incident surface.

On the surface provided with the groove of the first substrate, an organic dye film / Ag alloy film was formed in this order from the light incident side.
The organic dye film was formed by spin coating. The Ag alloy film was formed by sputtering an Ag alloy in Ar. Further, an ultraviolet curable resin was applied by spin coating, and then a 0.6 mm thick polycarbonate substrate was bonded and photocured. Thereafter, a SiOC film or a SiONC film was formed as a hard coat layer on the light incident side surface of the first substrate by sputtering under appropriate process conditions.

  The recording test of the write-once type optical recording medium described above was performed as follows. In the test, an optical disk evaluation apparatus including a pickup having an objective lens with NA = 0.65 and a semiconductor laser with a wavelength of 405 nm was used, and the recording linear velocity was set to 6.61 m / s.

(Single-sided, single-layer write-once medium (disk 25))
Next, in the single-sided single layer write-once medium, one type of medium (disk 25) was prepared, and the medium was evaluated.
The optical recording medium having the structure shown in FIG. 8 was produced as follows. First, a polycarbonate substrate having a thickness of 1.1 mm was prepared as the first substrate 55. This substrate is provided with grooves having a pitch of 0.32 μm and a depth of 50 nm. Groove recording is performed.

Such first on the surface on which the grooves of the substrate 55 is provided, in order from the light incident side, a high refractive index dielectric film 57b (ZnS-SiO ₂₎ / the inorganic write-once recording layer 58 (Te-O- Pd) / high refractive index dielectric film 57a (ZnS—SiO ₂ ) / Ag alloy reflective film 56 was formed by sputtering.

  Further, an ultraviolet curable resin was applied by a spin coating method, and then a cover substrate 60 made of a polycarbonate resin having a thickness of 0.1 mm was bonded and photocured. Thereafter, a SiOC film or a SiONC film was formed as a hard coat layer 61 on the light incident side surface of the cover substrate 60 by sputtering under appropriate process conditions.

  An optical disk evaluation apparatus including a pickup having light incident from the cover substrate 60 side and an objective lens having NA = 0.85 and a semiconductor laser having a wavelength of 405 nm was used. A recording test was conducted at a recording linear velocity of 5.6 m / s.

(Single-sided dual-layer write-once medium (disk 26))
Next, one type of medium (disk 26) was prepared in the single-sided dual-layer write-once medium, and the medium was evaluated.
The optical recording medium having the structure shown in FIG. 9 was produced as follows. This medium is a so-called single-sided double-layer medium, and L ₀ substrate 62 on the front side as viewed from the light incident side, in which bonded to the L ₁ substrate 67 on the back side when viewed from the light incident side.

First, it was prepared a polycarbonate substrate having a thickness of 0.59mm as _{L 0} substrate 62. The L ₀ substrate 62 is provided with grooves having a pitch of 0.4 μm and a depth of 60 nm, and performs groove recording. Hereinafter, the groove track refers to a track having a short distance from the light incident surface.

Such L ₀ on the surface on which the grooves of the substrate 62 is provided, in order from the light incident side was formed in the order of the organic dye film / Ag alloy film. Transmittance of the L ₀ substrate 62 was approximately 50 [%]. L ₁ substrate 67, a polycarbonate substrate having a thickness of 0.59 mm, Ag alloy film 64 was formed in the order of the organic dye film 65. L ₁ organic dye layer 65 of the substrate 67 surface, are attached to each other in the _{L 0} substrate 62 through the ultraviolet curing resin applied on _{L 0} substrate 62. Thereafter, a SiOC film or a SiONC film was formed as a hard coat layer 68 on the light incident side surface of the L ₀ substrate 62 by sputtering under appropriate process conditions.

  The recording test of the write-once type optical recording medium described above was performed as follows. In the test, an optical disk evaluation apparatus including a pickup having an objective lens with NA = 0.65 and a semiconductor laser with a wavelength of 405 nm was used, and the recording linear velocity was set to 6.61 m / s.

FIG. 12 shows the constituent elements of the hard coat layer, the film material name, the refractive index n _{1 at} a wavelength of 405 nm, the extinction coefficients k ₁ and n _1, and the refractive index n _{0 of} polycarbonate which is the substrate material on the light incident side. = 1.55 Difference n ₀ −n ₁ , extinction coefficient k ₂ at a wavelength of 350 nm is shown.

The optical constants of the hard coat layers of the media of the disks 19 to 26 are within the scope of the present invention, | n ₁ −n ₀ | ≦ 0.15, k ₁ ≦ 1 × 10 ⁻² , 1 × 10 ⁻³ ≦ k ₂ .

FIG. 13 shows bER of the media of the disks 19 to 26 as bER ₀ , optimum recording power Pw, bER after the wear wheel test as bER ₁ , and bER after the ultraviolet light resistance test as bER ₂ .

The media of disks 19 to 26 were ^10-5 units for both bER-1 and bER-2, with almost no deterioration in recording characteristics after the wear test and the light resistance test.

(Various optical recording media (disks 27 to 45))
Next, various media having different hard coat layer thicknesses were prepared. The film thickness was controlled by measuring the film formation speed under the selected film formation conditions and by the film formation time. As the sputtering target, a target mainly composed of Si and C was used. For the disks 27 to 45, media having various film thicknesses of the hard coat layer were prepared using the film configurations of the disks 1 to 9 and 19 to 26 described above.

FIG. 14 shows the optimum recording power Pw ₀ and bit error rate bER ₀ before using the hard coat layer, the film thickness of the hard coat layer, and the optimum recording of the medium provided with the hard coat layer. The power Pw, bER after the wear wheel test is bER ₁ , and bER after the ultraviolet light resistance test is bER ₂ .

Various media of the disks 27 to 43 having a hard coat layer in the range of 10 nm to 100 nm were ^10-5 for both bER ₁ and bER ₂ , and showed good recording characteristics. Furthermore, the recording sensitivity of the medium having the hard coat layer in the range of 50 nm to 100 nm was improved as compared with the case where the hard coat layer was not provided. On the other hand, the recording characteristics of the medium of the disk 44 deteriorated by both the wear test and the light resistance test, and both bER ₁ and bER ₂ became 10 ⁻⁴ units. Further, the medium of the disk 45 has an optimum recording power increased by about 2 mW, and the recording sensitivity has decreased. In addition, when the hard coat layer of the medium described in the disks 27 to 43 was analyzed, the presence of Si.O.C as a constituent element was confirmed from the RBS results. When the optical constant was measured by spectroscopic ellipsometry, the refractive index at a wavelength of 405 nm was n ₁ , the extinction coefficient was k ₁ , the extinction coefficient at a wavelength of 350 nm was k ₂ , and the substrate material was at a wavelength of 405 nm. When the refractive index was n ₀ , | n ₁ −n ₀ | ≦ 0.15, k ₁ ≦ 1 × 10 ⁻² , 1 × 10 ⁻³ ≦ k ₂ were satisfied.

(Various optical recording media (disk 46))
In order from the light incident side, a single-sided single layer provided with a hard coat layer constituted by a laminated film of three layers such as a high refractive index dielectric film ZnS-SiO ₂ / SiOCN film / high refractive dielectric film ZnS-SiO ₂ . A layer write-once medium 46 was produced and evaluated. The disk 46 used the same film configuration as the disk 24 described above. The film thickness of ZnS—SiO ₂ was 45 nm, and the film thickness of the SiOCN film was 63 nm. In the recording test, an optical disk evaluation apparatus including a pickup having an objective lens with NA = 0.65 and a semiconductor laser with a wavelength of 405 nm was used, and the recording linear velocity was set to 6.61 m / s. The optimum recording power Pw ₀ of the same disk not using the hard coat layer was 5.9 mW, whereas the optimum recording power Pw of the disk provided with the hard coat layer was 4.7 mW, and the sensitivity was increased. The bER (bER ₁ ) after the wear wheel test was 1.3 × 10 −5, and the bER (bER ₂ ) after the ultraviolet light resistance test was 1.7 × 10 −5, indicating good recording characteristics.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a cross-sectional view of an optical recording medium of the present invention. 1 is a cross-sectional view of a rewritable optical recording medium according to an embodiment of the present invention. 1 is a cross-sectional view of a write-once type optical recording medium according to an embodiment of the present invention. Sectional drawing of the rewritable optical recording medium of the disks 1-9 of this invention, and the disks 10-18. Sectional drawing of the rewritable optical recording medium of the discs 19 and 20 of this invention. Sectional drawing of the rewritable optical recording medium of the disks 21 and 22 of this invention. Sectional drawing of the single-sided double layer rewritable optical recording medium of the disk 23 of the present invention. Sectional drawing of the write-once type | mold optical recording medium of the disk 25 of this invention. 1 is a cross-sectional view of a single-sided dual-layer write-once optical recording medium of a disk 26 of the present invention. The figure which shows the structure in each hard-coat layer of the disks 1-18 of this invention. The figure which shows the recording characteristic of the disks 1-18 of this invention. The figure which shows the structure in each hard-coat layer of the disks 19-26 of this invention. The figure which shows the recording characteristics of the disks 19-26 of this invention. The figure which shows the structure and recording characteristic in each hard-coat layer of the disks 27-45 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 21 ... 1st board | substrate, 2 ... Recording layer, 3 ... Reflective layer, 4 ... Ultraviolet curable resin layer, 5 ... 2nd board | substrate, 6 ... Hard-coat layer , 7 ... 1st substrate, 8 ... 1st dielectric film, 9 ... Phase change recording film, 10 ... 2nd dielectric film, 11 ... Metal reflecting film, 12 ... UV curable resin layer, 13 ... second substrate, 14 ... hard coat layer, 15 ... first substrate, 16 ... write-once recording film, 17 ... metal reflective film 18 ... UV curable resin layer, 19 ... second substrate, 20 ... hard coat layer, 21 ... first substrate, 22a, b, c ... high refractive index dielectric film , 23... Low refractive index dielectric film, 24 a, b... Interfacial layer, 25... Phase change recording film, 26... Ag alloy reflection film, 27. ..Second Substrate, 29 ... hard coat layer, 30 ... first substrate, 31a, b ... high refractive index dielectric film, 32a, b ... interface layer, 33 ... phase change recording film, 34 ... Ag alloy reflective film, 35 ... UV curable resin layer, 36 ... second substrate, 37 ... hard coat layer, 38 ... first substrate, 39 ... Ag alloy Reflective film, 40a, b ... high refractive index dielectric film, 41a, b ... interface layer, 42 ... phase change recording film, 43 ... UV curable resin layer, 44 ... cover substrate, 45 ... a hard coat layer, 46 ... _{L 0} substrate, 47 ... substrate, 48 ... Ag alloy reflective film, 49a, b ... high refractive index dielectric film, 50a, b ... interface layer 51 ... phase change recording film, 52 ... UV curable resin layer, 53 ... L ₁ substrate, 54 ... hard coat layer, 5 ... 1st substrate, 56 ... Metal reflective film, 57a, b ... High refractive index dielectric film, 58 ... Inorganic write-once recording film, 59 ... UV curable resin layer, 60 ..Cover substrate, 61 ... Hard coat layer, 62 ... L ₀ substrate, 63 ... Substrate, 64 ... Ag alloy reflective film, 65 ... Organic dye film, 66 ... UV curing Resin layer, 67 ... L ₁ substrate, 68 ... hard coat layer

Claims (15)

In an optical recording medium composed of a substrate and a recording layer on which information is recorded by light irradiation,
A hard coat layer made of a dielectric film containing Si, O, and C as constituent elements is provided on the light incident side surface of the substrate, and the refractive index at a wavelength of 405 nm of the hard coat layer is n ₁ . When the extinction coefficient is k ₁ , the extinction coefficient at a wavelength of 350 nm is k ₂ , and the refractive index of the substrate material at a wavelength of 405 nm is n ₀ , | n ₁ −n ₀ | ≦ 0.15, k ₁ ≦ 1 × 10 ^-2 , 1 × 10 ⁻³ ≦ k ₂ .   2. The optical recording medium according to claim 1, wherein N is contained in addition to Si, O, and C as a constituent element of the hard coat layer. The optical recording medium according to claim _1, wherein the n ₀ and n ₁ satisfy n ₁ ≦ n ₀ .   4. The optical recording medium according to claim 1, wherein the hard coat layer is a single layer film, and the film thickness is 10 nm or more, preferably 50 nm or more and 100 nm or less.   The C (carbon) content of the hard coat layer is 0.01 [at. %] 30 [at. %] Or less. 5. The optical recording medium according to claim 1, wherein   The O (oxygen) content of the hard coat layer is 10 [at. %] Or more and 70 [at. %] Or less, the optical recording medium according to any one of claims 1 to 5.   The N (nitrogen) content of the hard coat layer is 0.01 [at. %] Or more and 60 [at. %] Or less, more preferably 1 [at. %] Or more and 50 [at. %] Or less, the optical recording medium according to any one of claims 2 to 6.   The constituent element of the hard coat layer is at least one element selected from the group consisting of Ti, Al, Ta, Ce, Nb, Mg, F, Zn, Zr, and S in addition to Si, O, N, and C The optical recording medium according to claim 1, further comprising: 9. The optical recording medium according to claim 1, wherein the Knoop hardness of the hard coat layer is 1000 [kgf / mm ² ] or more.   9. The hard coat layer is a laminated film of a plurality of dielectric films having different refractive indexes at a wavelength of 405 nm, including a SiONC film having Si, O, N, and C as constituent elements. The optical recording medium described.   11. The optical recording medium according to claim 1, wherein the thicknesses of the substrate on the near side and the substrate on the back side as viewed from the light incident side are both 0.5 mm or more and 0.7 mm or less.   The thickness of the substrate on the near side when viewed from the light incident side is 0.01 mm or more and 0.2 mm or less, and the thickness of the substrate on the back side when viewed from the light incident side is 1 mm or more and 1.2 mm or less. The optical recording medium according to claim 1.   13. The optical recording medium according to claim 1, wherein the hard coat layer of the optical recording medium is formed by sputtering in a gas containing oxygen and nitrogen using a sputtering target mainly composed of Si and C. Manufacturing method.   14. The method of manufacturing an optical recording medium according to claim 13, wherein one or both elements of O and N are contained together with Si and C as constituent elements of the sputtering target.   The sputtering target contains at least one element selected from the group consisting of Al, Ti, Ta, Fe, Ce, Nb, Mg, F, Zr, Sb, and S as a constituent element of the sputtering target. The method for producing an optical recording medium according to claim 13.

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