JP3367487B2 - Manufacturing method of optical disk substrate - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a method for manufacturing an optical disc substrate, when forming the optical disk substrate in particular by using a polycarbonate resin, an optical disc for forming the size required for the groove shape of the optical disc substrate It is a method of manufacturing a substrate.

[0002]

2. Description of the Related Art Optical discs represented by CDs and MOs are
A substrate that is injection-molded (including injection-compression-molded) using an organic resin having high optical properties such as polycarbonate that has high productivity and low cost is used. Then, a recording layer, a reflective layer, a dielectric layer for optical interference, an organic film, and the like are laminated on this substrate by using a technique such as vapor deposition, sputtering, and coating to manufacture.

The optical disk substrate can be obtained by injection-packing a polycarbonate resin onto an optical disk master mounted on a mold. At the time of molding the substrate, the resin is filled toward the optical disc master and is released after cooling for a certain period of time. The portion corresponding to the land of the optical disk master is transferred as the groove of the substrate, and conversely, the groove of the optical disk master is transferred as the land of the substrate. Therefore, ideally, the groove width of the substrate is equal to the land width of the optical disc master, and the land width of the substrate is equal to the groove width of the optical disc master. Therefore, conventionally, in order to obtain a substrate having a land half width L ′ and a groove half width G ′,
The optical disk master was designed so that the groove half-value width G = L 'and the land half-value width L = G'.

[0004]

However, when a substrate is actually formed by the above-mentioned optical disc master and an optical recording medium for land / groove recording is produced using the substrate, the case of recording on the land portion is When recording in the groove portion, the sensitivity and C / N were different, and an optical recording medium having good electric characteristics could not be obtained. As a result of measuring the groove shape of the optical disk substrate used for that with AFM,
It was found that the land width of the substrate was wider than the groove width than expected. On the other hand, when the optical disk master was measured by AFM, the widths of the land and the groove were almost equal. As a result of similarly measuring the groove shape of another optical disk master and a molded substrate using the same, there is a certain correlation between them, and the land width of the molded substrate becomes wider than the groove width of the optical disk master. Moreover, it was found that the groove width of the molded substrate is narrower than the land width of the optical disc master. From this,
Since the expected groove shape of the substrate cannot be obtained, it is considered that when the disk is formed by using the groove shape, C / N, reflectance, signal strength, crosstalk, etc. are affected.

The object of the present invention is to improve the above-mentioned problems,
The groove shape of the substrate, which can be molded into the assumed dimensions
It is to provide a manufacturing method for an optical disk substrate.

[0006]

In order to solve the above problems, the present invention has the following constitution. That is, the manufacturing method of the optical disk substrate of the present invention is the manufacturing method of the optical disc substrate with grooves, the half width of the half-width and the land of the groove of the optical disc master to be used for injection molding and G and L each, the desired optical L '/ G is 1.02 to 1.08 and G' / L is 0.92 to 0.98 when the half width of the land and the half width of the groove of the substrate are L'and G ', respectively. It is characterized in that an optical disc master corrected in a certain manner is used.

[0007]

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. As described above, the land width of the substrate becomes wider than the groove width of the optical disc master used for it, and the groove width of the substrate becomes wider than the land width of the optical disc master used for it. Therefore, when designing an optical disc master, it is necessary to allow for the above-mentioned dimensional deviation.

As a result of repeatedly measuring the groove shapes of a dozen or more kinds of optical disk masters and a substrate using the same with AFM, the groove half width and land half width of the optical disk master shown in FIG. When the molded substrate land half-width and groove half-width shown in FIG. 2 are L ′ and G ′, respectively, as shown in Table 1, L ′ / G falls within 1.02 to 1.08. G '/ L is shown in Table 2
As shown in, the value was within the range of 0.92 to 0.98.
It is considered that the reason why the groove shape changes at different rates is that the releasability of the optical disk master, the groove shape, and the like contribute.

[0010]

[Table 1]

[0011]

[Table 2]

Therefore, L '/ G is 1.02 to 1.0
It is desirable to correct the groove shape of the optical disc master so that the value of 8 and G '/ L are 0.92 to 0.98. More preferably, the groove shape of the optical disc master is corrected so that L '/ G is 1.04 to 1.06 and G' / L is 0.94 to 0.96.

When the optical disk substrate of the present invention is injection compression molded, it is necessary to transfer the groove shape of the optical disk master as faithfully as possible. Therefore, by setting the mold temperature around 130 ° C and the resin temperature around 360 ° C,
Good transferability.

The full width at half maximum of the track pitch (T in FIG. 1) of the optical disk master described in the present invention is 1.0 μm to
It is preferably about 1.5 μm. This is because it is preferable that the beam spot diameter is approximately the same as the beam spot diameter of the drive unit for the optical recording medium.

The groove depth of the optical disk master is 60 n.
It is preferably about m to 80 nm. The optimum groove depth is generally determined by the laser wavelength λ of the optical recording medium driving device. When the refractive index of the resin material used for the substrate is n, the optimum groove depth is λ / 8n to λ / 3n. There is about λ / 6n in the land groove recording. If polycarbonate resin (n = 1.58) is used as the substrate material and the laser wavelength of the driving device is 650 nm, the optimum groove depth is approximately 69 nm.

As the substrate material, it is preferable to use a material through which laser light can be satisfactorily transmitted in order to perform recording / reproduction from the substrate side. For example, an organic resin such as polymethylmethacrylate resin, polycarbonate resin, polyolefin resin or epoxy resin can be used. A molecular resin, a mixture thereof, a copolymer, or the like can be used. Among them, the polycarbonate resin can be most preferably used from the viewpoint of optical characteristics and heat resistance. Further, by using a grade having high fluidity, good transferability and optical characteristics can be satisfied.

The size of the substrate needs to conform to the standard required by the optical recording medium drive device. For example, the diameter is 80mm, 90mm, 120mm or 130mm.
Substrate, etc. are specified, and the thickness is 0.6 mm,
1.2 mm or the like is specified.

On such a substrate, for example, the first layer / second layer / third layer / fourth layer is laminated by sputtering. An organic resin protective layer may be provided on this layer. As the organic resin protective layer, a photocurable resin composition containing a polymerizable monomer and an oligomer as a main component or a thermosetting resin composition is used and is generally formed by a spin coating method. In addition, a protective layer made of the same organic resin composition is provided on the substrate on the light incident surface side for the purpose of protecting the substrate such as improving abrasion resistance and printing durability, and imparting antistatic property to prevent dust adhesion. It can also be provided for the purpose of.

Regarding the process for producing an optical disk master, a glass plate is used as a substrate, a photoresist is applied on the substrate, a predetermined signal is recorded on this with a laser beam, and then the photoresist is removed to form an uneven pattern. . Then, it is possible to apply a general method in which the concavo-convex pattern is transferred to a metal master by nickel electroforming to prepare an optical disk master. Further, it is preferable that the mold release property between the optical disc master and the optical disc substrate is improved by subsequently performing a surface treatment such as plasma treatment on the optical disc master.

The optical recording medium according to the present invention has at least a recording layer and a protective layer on a substrate. Preferably, it has a plurality of laminated structures, for example, a first layer (first protective layer) / second layer (recording layer) / third layer (second protective layer) / fourth layer (reflection) on a substrate. Layers provided in this order, or first layer (first protective layer) / second layer (boundary layer) / third layer (recording layer) / fourth layer (second protective layer) / fifth layer
A layer (reflection layer) etc. are mentioned.

The effects of the first and second protective layers are: prevention of corrosion of the recording layer, prevention of deterioration of recording characteristics caused by deformation of the substrate, recording layer, etc. during recording, and signal contrast during reproduction due to optical interference effect. Has the effect of improving. In this case, the thickness of the first protective layer is usually 50 nm to 400 nm. The "quench cooling structure" in which the second protective layer has a thin thickness of about 20 nm has less deterioration in recording characteristics due to repeated rewriting, and the erasing power is smaller than the "slow cooling structure" in which the dielectric layer has a thickness of about 200 nm. Is excellent in that it has a wide power margin. Therefore, the thickness of the second protective layer is preferably 10 nm to 100 nm.

As such a protective layer, ZnS, Si
An inorganic film such as O ₂ , Ta ₂ O ₅ , ITO, ZrC, TiC, MgF ₂ or a mixed film thereof can be used. In particular, ZnS
A mixed film of SiO ₂ and ZnS and MgF ₂ is excellent in moist heat resistance, preferable to suppress the further recording and erasing deterioration during. A mixture of these with carbon is also preferable because the residual stress of the film is small. In particular, ZnS and SiO
The mixed film of ₂ or the mixed film of ZnS, SiO ₂ and carbon can improve the recording sensitivity, C /
It is preferable because deterioration of N, erasing rate, etc. does not easily occur,
A mixed film of ZnS, SiO ₂ and carbon is particularly preferable.

For the recording layer, it is preferable to use an alloy containing at least three elements of Ge, Sb, and Te as constituent elements from the viewpoint of overwriting at high speed. Further, the composition is preferably in the range represented by the following formula from the viewpoint of excellent thermal stability and repeated stability.

M _z (Sb _x Te _1-x ) _1-yz (Ge _0.5 Te _0.5 ) _y 0.35 ≦ x ≦ 0.5 0.2 ≦ y ≦ 0.5 0.0005 ≦ z ≦ 0.01 Here, M is at least one metal selected from palladium, niobium, platinum, silver, gold, and cobalt, Sb is antimony, Te is tellurium, and Ge is germanium. Further, x, y, z, and numbers represent the number of atoms of each element (the number of moles of each element). Particularly, it is preferable that at least one of palladium and niobium is contained.

The light-reflecting layer formed on the second protective layer or the light-absorbing layer improves the signal contrast at the time of reproduction due to the optical interference effect, and at the same time, due to the cooling effect, the amorphous recording mark Techniques for facilitating formation and improving erasing characteristics and repeating characteristics are known. The thickness of this recording layer is preferably 10 to 100 nm.

As the material of the reflective layer, metals such as Al and Au having light reflectivity, and those containing these as the main components, T
Alloys containing additional elements such as i, Cr and Hf, and Al and A
Examples thereof include a metal such as u mixed with a metal nitride such as Al and Si, a metal oxide, a metal compound such as a metal chalcogenide. Metals such as Al and Au, and alloys containing these as the main components are preferable because they have high light reflectivity and high thermal conductivity. As an example of the above alloy, Al, Si, Mg, Cu, Pd, Ti, Cr, H
At least one element such as f, Ta, Nb, and Mn added in a total amount of 5 atomic% or less and 1 atomic% or more, or at least one of Au, Cr, Ag, Cu, Pd, Pt, and Ni. 20 atomic% or less and 1 atomic% in total
There are things added above. In particular, an alloy containing Al as a main component is preferable because the price of the material can be reduced. Above all, Al and Ti and C are preferable because of good corrosion resistance.
5 atom% or less and 0.5 atom% or less in total of at least one metal selected from r, Ta, Hf, Zr, Mn, and Pd.
The alloys added above are preferable. Above all, because it has good corrosion resistance and hillocks are less likely to occur,
Including at least 0.5 atomic% and less than 3 atomic% in total of additional elements,
Al-Hf-Pd alloy, Al-Hf alloy, Al-Ti alloy, Al-Ti-Hf alloy, Al-Cr alloy, Al-T
An alloy containing Al alloy as a main component, such as a-alloy, Al-Ti-Cr alloy, or Al-Si-Mn alloy, is preferable as the reflective layer material.

When the groove shapes of the optical disk master and the optical disk substrate are measured by AFM, it is preferable to use a probe having a small tip radius of curvature and a small half cone angle. If the probe is bent,
The measured width of the protrusion may be larger than it actually is.

[0028]

EXAMPLES Example 1 G = 0.55 μm, L = 0.61 μm, groove depth 67 nm
A molding machine (Sumitomo Heavy Industries, Ltd. DISK5A M) using an optical disk master having the above and a polycarbonate resin (Panlite AD-5503H, Teijin Chemicals Ltd.)
According to III), injection compression molding was performed to obtain an optical disk substrate.

This groove shape is referred to as AFM (digital instrument
nt Nanoscope III tapping mode AFM) probe with a sharp tip (digital instrument S
The measurement was performed using SS-NCH tip curvature radius: 2-5 nm and half cone angle: 10 degrees or less. As a result, G ′ = 0.58 μm, L ′ = 0.58 μm, and G = 0.95 G ′ and L = 1.05 L ′. Using this substrate, a thin film having the structure shown below was formed by using a sputtering apparatus to produce an optical disc.

On the film-forming surface of the obtained disk, 8 μm of an acrylic acid ester-based ultraviolet curable resin was applied by spin coating.
m to form an optical recording medium. Further, this optical recording medium was irradiated with a semiconductor laser beam having a wavelength of 820 nm to crystallize the recording layer on the entire surface of the disk and initialize it.

First layer First protective layer 80 ZnS-20SiO ₂ (mol%) 98 nm Second layer Boundary layer C 2 nm Third layer Recording layer 55 Te 19 Ge 26 Sb (at%) 19 nm Fourth layer Second protective layer 80 ZnS-20SiO ₂ (mol %) 27 nm Fifth layer Reflective layer 95Al-5Cr (at%) 220 nm The C / N ratio of this optical recording medium was measured by DD manufactured by Pulstec Co., Ltd.
It measured in U-1000 (wavelength 638nm, NA0.60). The measurement results are shown in Table 3. Comparative Example 1 An optical disk substrate was molded by the same method as in Example 1 except that G = 0.58 μm and L = 0.58 μm, and the groove shape was measured by the AFM as in Example 1. As a result, G ′ = 0.61 μm and L ′ = 0.55 μm,
It was G = 0.95L 'and L = 1.05G'. Using this substrate, an optical recording medium was prepared in the same manner as in Example 1, and C / N was measured with the same measuring equipment. The measurement results are shown in Table 4.

The sensitivity shown here is the ratio of the second harmonic (about 3.75 MHz) to the 8T signal when a (1,7) -modulated 8T signal (about 1.87 MHz) is written. Refers to the minimum power.

The C / N of the optical recording medium of Example 1 is about 56 dB for both the land and the groove, while the C / N of the optical recording medium of Comparative Example 1 is lower for the groove. There is. In addition, regarding the sensitivity,
The sensitivity of the optical recording medium of No. 1 does not differ much between the land and the groove, whereas the sensitivity of the optical recording medium of Comparative Example 1 has a large difference between the land and the groove.

From the above results, it was found that an optical disk substrate having a good groove shape can be formed by using the optical disk master according to the present invention.

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

According to the present invention, in molding an optical disk substrate, a substrate having a desired groove shape can be obtained by a simple process.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a groove shape of an optical disc master.

FIG. 2 is a sectional view showing an example of a groove shape of an optical disc substrate.

[Explanation of symbols]

1 ・ ・ ・ Optical disc master land 2 ... Optical disc master groove 1 '... optical disk substrate land 2 '... Optical disk substrate groove L ・ ・ ・ Half width of optical disc master land G: Optical disc master groove half width L '... Half width of optical disk substrate land G '... Half width of optical disk substrate groove

Continuation of the front page (56) Reference JP-A-9-180271 (JP, A) JP-A-11-283284 (JP, A) JP-A-6-4787 (JP, A) JP-A-8-194970 (JP , A) West German Patent Application Publication 2410740 (DE, A1) (58) Fields searched (Int.Cl. ⁷ , DB name) G11B 7/26 G11B 7/24

Claims (4)

(57) [Claims] 1. A method of manufacturing an optical disc substrate having a groove, G the half width of the half-width and the land of the groove of the optical disc master to be used for injection molding, respectively, and L
And when the half width of the land and the half width of the groove of the desired optical disk substrate are L ′ and G ′, respectively,
L '/ G is 1.02 to 1.08, and G' / L is 0.
A method for manufacturing an optical disk substrate, characterized by using an optical disk master corrected to be 92 to 0.98. 2. An optical disk master corrected so that L '/ G is 1.04 to 1.06 and G' / L is 0.94 to 0.96. 1. The method for manufacturing an optical disc substrate described in 1. 3. The method for manufacturing an optical disc substrate according to claim 1, wherein the full width at half maximum T of the track pitch of the optical disc master is 1.0 μm to 1.5 μm. 4. The groove depth of the optical disk master is 60 nm to 8 nm.
It is 0 nm, The manufacturing method of the optical disk substrate in any one of Claims 1-3.