JP2008065943A - Manufacturing method of two-layer optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a two-layer optical recording medium having a translucent reflection layer which is hardly corroded on an organic dye recording layer and having high reliability. <P>SOLUTION: (1) In the manufacturing method of the two-layer optical recording medium, the translucent reflection layer is formed on the organic dye recording layer formed on a substrate with a guide groove by sputtering using a target consisting essentially of Ag while applying periodical negative pulse voltage to the target, when a recording constitution body on this side viewed from a recording and reproducing light incident side of the optical recording medium (two-layer optical recording medium) having two layers of recording constitution bodies including the recording layer is layered. (2) In the manufacturing method of the two-layer optical recording medium mentioned in (1), the periodical negative pulse voltage has 1 to 100 kHz frequency. (3) In the manufacturing method of the two-layer optical recording medium mentioned in either of (1) and (2), the periodical negative pulse voltage is -300 V or lower. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a two-layer optical recording medium.

In a sputtering process in the production of optical recording media, a DC or RF potential is applied to a target disposed opposite to the substrate, and a material that has jumped out of the target by the collision of ionized Ar ions is deposited on a glass substrate or a plastic substrate such as polycarbonate. Thus, a thin film is formed.
When manufacturing a normal write-once type optical recording medium, a recording layer made of a cyanine-based, phthalocyanine-based, azo-based or other organic dye is applied and formed on a substrate, and silver, gold, aluminum, or the like is formed thereon. The metal reflection layer is formed by sputtering in vacuum.
In the case of manufacturing a rewritable optical recording medium, for example, a phase change optical recording medium or a magneto-optical recording medium, a lower heat-resistant protective layer, a phase change recording layer or a magneto-optical recording layer, an upper heat-resistant protective layer, a reflective layer are formed on the substrate. The heat dissipation layer and the like are sequentially sputtered in vacuum.
Subsequently, in both the write-once type optical recording medium and the rewritable type optical recording medium, a finished product is obtained by providing a resin protective layer and a printing layer, if necessary, and bonding them to another substrate with an adhesive.

In recent years, social needs for increasing recording capacity have increased, and in DVD + R and DVD-R widely known as write-once DVD standards, two recording layers are formed with an intermediate layer of about 50 μm in thickness. Two-layer optical recording media called DVD + R DL (Double Layer) and DVD-R DL, which double the capacity, are becoming widespread.
FIG. 1 shows a typical configuration thereof.
A first substrate on which a first recording structure (L0) composed of a first recording layer and a first reflective layer (semi-transparent reflective layer) is laminated, and a second recording structure composed of a second reflective layer and a second recording layer ( In this configuration, the second substrate laminated with L1) is joined via an intermediate layer. In general, organic dyes are used for the first and second recording layers. In the usual case, the intermediate layer is also used as an adhesive layer.
In order to perform recording / reproduction on the second recording layer on the back side as viewed from the recording / reproducing light incident side, the first recording structure (L0) on the near side has a reflectance of 15 to 30% at the recording / reproducing wavelength, It is configured to have a transmittance of 40 to 60%.
The translucent reflective layer is usually composed mainly of a metal such as Au, Ag, or Cu, and an additive element of about 0.1 to 5% by weight is added to improve corrosion resistance and weather resistance. In particular, it is common to perform direct current sputtering with the highest sputtering efficiency by using Ag as a main component and using Cu, Pd, Pt, Au, Nd, Bi, Ga, and In as additive elements.
As a known document, for example, in Patent Document 1, it is possible to write on two information recording layers made of organic dyes from one side of an optical information medium during recording, and read from one side of the optical information medium to two information recording layers also during reproduction. An invention having a configuration to perform the above is disclosed. However, there is no description relating to the application of a periodic negative pulse voltage to the target, which is a feature of the present invention.

No. 11-066662

Since the translucent reflective layer made of an Ag alloy formed on the organic dye recording layer in the two-layer optical recording medium is easily corroded, the selection of the Ag alloy as the material and the organic resin formed adjacent thereto The selection of overcoats and adhesives made of is greatly restricted.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly reliable method for producing a two-layer optical recording medium having a semi-transparent reflective layer that hardly corrodes on an organic dye recording layer.

The above problems are solved by the following inventions 1) to 6) (hereinafter referred to as the present inventions 1 to 6).
1) When a recording structure on the near side as viewed from the recording / reproducing light incident side of an optical recording medium (two-layer optical recording medium) having two recording structures including a recording layer is laminated on a substrate with a guide groove A two-layer light characterized in that a semi-transparent reflective layer is formed by sputtering while applying a periodic negative pulse voltage to the target on the organic dye recording layer. Recording medium manufacturing method.
2) The method for producing a two-layer optical recording medium according to 1), wherein the frequency of the periodic negative pulse voltage is 1 to 100 kHz.
3) The method for producing an optical recording medium according to 1) or 2), wherein the periodic negative pulse voltage is −300 V or less.
4) The method for producing a two-layer optical recording medium according to any one of 1) to 3), wherein a positive voltage is applied during at least a part of a time during which no periodic negative pulse voltage is applied.
5) The two layers according to any one of 1) to 4), wherein the time for applying the periodic negative pulse voltage is at least three times the time for applying the positive pulse voltage or the zero voltage. Optical recording medium manufacturing method.
6) The method for producing a two-layer optical recording medium according to any one of 1) to 5), wherein the organic dye contains a cyanine dye.

Hereinafter, the present invention will be described in detail.
In the prior art, when manufacturing a two-layer optical recording medium, the first recording structure is formed by coating an organic dye recording layer on a plastic substrate with a tracking guide groove, on which a translucent film made of an Ag alloy is formed. The reflective layer is formed by sputtering. In the present invention, a negative negative pulse voltage is applied to the target to refine the Ag structure to suppress crystal growth during storage at high temperature and high humidity and over time. To do.
The target mainly composed of Ag used in the present invention may be a commonly used melting target or the like, and may be subjected to forging treatment or the like as necessary to increase the mechanical strength. Here, the main component means that Ag is contained by 95% by weight or more, preferably 98% by weight or more.

As the reflective layer and the translucent reflective layer material, those having a high reflectance with respect to the laser light wavelength are preferable. For example, Au, Ag, Cu, Al, Ti, V, Cr, Ni, Nd, Mg, Pd, Zr, Pt, Mention may be made of metals and metalloids such as Ta, W, Si, Zn. Among them, Au, Ag, Cu, or Al is the main component and is different from these four elements. Au, Ag, Cu, Al, Ti, V, Cr, Ni, Nd, Mg, Pd, Zr, Pt, Ta An alloy to which at least one selected from W, Si, Zn, and In is added in an amount of 0.5 to 10% by weight is preferable. By adding 0.5% by weight or more, the crystal grains become fine and a thin film having excellent corrosion resistance is obtained. However, addition of more than 10% by weight is not preferable because the reflectance decreases.
The translucent reflective layer has a transmittance of about 30 to 60% and a reflectance of about 15 to 30% so that sufficient light reaches the second dye recording layer. The film thickness is preferably in the range of 5 to 30 nm.
On the other hand, the thickness of the reflective layer is preferably 100 to 200 nm, and more preferably 130 nm or more. In order to improve the heat dissipation of the second recording structure on the back side, the thicker one is preferable. However, if the thickness exceeds 200 nm, the film formation takes time and the material cost increases, which is not preferable from the viewpoint of manufacturing cost. The microscopic flatness of the surface is also deteriorated.
As the organic dye, various known dyes such as cyanine-based, phthalocyanine-based, and azo-based dyes can be used, and are not particularly limited.

A negative pulse voltage is periodically applied to the target. The frequency of the negative pulse voltage is preferably in the range of 1 to 100 kHz. The negative pulse voltage is preferably −300 V or less. When these conditions are satisfied, film forming quality such as film thickness uniformity can be improved, and as a result, a highly reliable medium can be obtained.
FIG. 2 and FIG. 3 show an example of the applied pulse voltage. As shown in FIG. 2, when the pulse voltage is set to zero at time T2 when the negative pulse voltage V1 is not applied, sputtering is performed during the time T2. Stop. Further, as shown in FIG. 3, when the positive pulse voltage V2 is applied at the time T2 when the negative pulse voltage V1 is not applied, electrons in the plasma having a small mass are attracted to the Ag alloy target. Argon ions are released earlier than when the voltage is zero. The time during which the positive pulse voltage V2 is applied may be all or part of the time during which the negative pulse voltage V1 is not applied (FIG. 3 corresponds to all cases). The above-described argon ion release promoting effect is reduced.
Moreover, it is preferable that time T1 which applies a periodic negative pulse voltage is 3 times or more of time T2 when a positive pulse voltage or a zero voltage is applied. When the ratio of T1 becomes too small, the effect of applying a negative pulse voltage is reduced.

FIG. 4 is a view showing an example of a sputtering apparatus for carrying out the present invention.
The sputtering apparatus 1 includes a loading / unloading mechanism 2, a main chamber 3, a process chamber 4, and the like, and is connected to a pulsed DC power source. The process chamber 4 is a sputter film formation chamber for forming a translucent reflective layer. In the process chamber 4, after applying a high vacuum of about 10 ⁻⁴ Pa to the inside of the process chamber 4, a pulse voltage is applied in a state where Ar gas is introduced so as to have a pressure of about 10 ⁻³ to 10 ⁻² Pa. Then, plasma is generated, and an Ag alloy target material is formed on the organic dye recording layer coated on the substrate 11 by sputtering.
As an operation, the substrate 11 coated with the organic dye recording layer to be produced is introduced into the main chamber 3 and conveyed to the process chamber 4 by the loading / unloading mechanism 2 to form a translucent reflective layer.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a reliable 2 layer optical recording medium which has a translucent reflective layer which is hard to corrode on an organic dye recording layer can be provided.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples.

Examples 1-6, Comparative Examples 1-2
A squarylium dye compound of [Chemical Formula 1] and a cyanine dye of [Chemical Formula 2] on a polycarbonate substrate having a plate thickness of 0.57 mm on which concave grooves having a groove depth of 160 nm, a groove width of 0.35 μm and a track pitch of 0.74 μm are formed. A compound was mixed at a weight ratio of 50:50, and a coating solution dissolved in 2,2,3,3-tetrafluoropropanol was spin coated to form a first dye recording layer having a thickness of about 40 nm.
Next, an Ag ₉₉ Cu _0.5 In _0.5 (wt%) alloy is sputtered to a thickness of 8 nm on the first dye recording layer under the sputtering conditions shown in Table 1 to form a translucent reflective layer. Thus, a first information substrate having the first recording structure was obtained.
On the other hand, an Ag reflective layer is formed to a thickness of 120 nm by sputtering on a polycarbonate substrate having a plate thickness of 0.6 mm on which convex grooves having a groove depth of 34 nm, a groove width of 0.3 μm, and a track pitch of 0.74 μm are formed. Further, a squarylium dye compound of [Chemical Formula 1] and a cyanine dye compound of [Chemical Formula 2] are mixed at a weight ratio of 4: 6, and a coating solution dissolved in 2,2,3,3-tetrafluoropropanol is spun. By coating, a second dye recording layer having a thickness of about 60 nm was formed.
Next, a 15 nm-thick inorganic protective layer made of ZnS—SiO ₂ (80:20 mol%) is formed on the second dye recording layer by sputtering, and the second information substrate having the second recording structure is formed. Got.
Subsequently, the first and second information substrates were bonded together using an ultraviolet curable adhesive (KARAYAD DVD802 manufactured by Nippon Kayaku Co., Ltd.) so that the thickness of the intermediate layer became 50 μm. Each of the two-layer optical recording media of Comparative Examples 1-2 was obtained.

Conditions for a linear velocity of 30.64 m / s (8 × speed recording) using ODU1000 (wavelength 657 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. for the first recording structure of the two-layer optical recording medium. When a DVD (8-16) signal was recorded by the above and reproduction evaluation was performed at 3.83 m / s, a reflectance of 19% and a modulation degree of I14 / I14H65% were obtained.
The initial PIsum8 after recording of the two-layer optical recording medium was Max 10 to 20. Thereafter, PIsum8 was measured after being stored at 80 ° C. and 85% RH. In Examples 1 to 6, PIsum8 after 400 to 500 hours was a standard value of 280 or less, but in Comparative Examples 1 and 2, it was 50 hours. It was above the standard value and the reliability was low.

The figure which shows the typical structure of a two-layer optical recording medium. The figure which shows the change of the pulse voltage applied to a target. The figure which shows the change of the pulse voltage applied to a target. The figure which shows an example of the sputtering device for implementing this invention.

Explanation of symbols

V1 Negative pulse voltage V2 Positive pulse voltage T1 Time to apply negative pulse voltage T2 Time to apply positive pulse voltage or zero voltage

Claims (6)

  An organic layer formed on a substrate with guide grooves when a recording structure on the near side as viewed from the recording / reproducing light incident side of an optical recording medium (two-layer optical recording medium) having two recording structures including a recording layer is stacked. A two-layer optical recording medium characterized in that a semi-transparent reflective layer is formed by sputtering while applying a periodic negative pulse voltage to the target on a dye recording layer using a target mainly composed of Ag Production method.   The method for producing a two-layer optical recording medium according to claim 1, wherein the frequency of the periodic negative pulse voltage is 1 to 100 kHz.   3. The method for producing a two-layer optical recording medium according to claim 1, wherein the periodic negative pulse voltage is −300 V or less.   4. The method for producing a two-layer optical recording medium according to claim 1, wherein a positive voltage is applied at least during a part of the time during which no periodic negative pulse voltage is applied.   5. The two-layer optical recording according to claim 1, wherein the period for applying the periodic negative pulse voltage is at least three times as long as the period for applying the positive pulse voltage or the zero voltage. Medium manufacturing method. 6. The method for producing a two-layer optical recording medium according to claim 1, wherein the organic dye contains a cyanine dye.

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