JP2021093229A - Recording layer for optical information recording medium, optical information recording medium, and sputtering target - Google Patents

Abstract

To provide a recording layer for an optical information recording medium with excellent basic characteristics such as degree of modulation and C/N ratio, and excellent power margin, and an optical information recording medium using the recording layer for an optical information recording medium.SOLUTION: A recording layer for an optical information recording medium according to the present invention is a recording layer for an optical information recording medium capable of recording information signals by irradiation with a laser beam, and having metal oxides including Sn oxide or Ta oxide as well as Mn oxide and W oxide, and an atomic number ratio of Mn to the total atomic number of metal elements that make up the metal oxide is 3 atom% or more and 40 atom% or less. The optical information recording medium according to the present invention comprises the recording layer for an optical information recording medium, and a protective layer laminated on the front face and the back face of the recording layer for an optical information recording medium, the protective layer is a dielectric.SELECTED DRAWING: Figure 1

Description

The present invention relates to a recording layer for an optical information recording medium, an optical information recording medium, and a sputtering target.

In recent years, large-capacity optical discs have been commercialized. There are three types of large-capacity optical discs, a playback-only type, a write-once type, and a rewrite type, depending on the recording / playback method. Of these, the recording methods for write-once optical discs are mainly phase change methods that change the phase of the recording layer, interlayer reaction methods that react multiple recording layers, decomposition methods that decompose the compounds that make up the recording layer, and recording layers. It is roughly classified into a drilling method in which recording marks such as holes and pits are locally formed.

As a recording layer of an optical information recording medium constituting this large-capacity optical disc, a recording layer containing Mn oxide has been proposed (see JP-A-2012-139876). In this recording layer is irradiated with laser light, heated Mn oxide by the laser beam, it decomposed to release oxygen (O ₂ gas), so bubbles are generated in the laser irradiated portion. As a result, the film shape changes and a recording mark is formed. That is, this recording layer is classified into a write-once type drilling method.

In the above-mentioned conventional recording layer, by using an irreversible recording method by generating bubbles due to laser irradiation of Mn oxide, the modulation degree is excellent enough to secure the signal amplitude necessary for reproducing the recorded signal, and the reading signal can be read. A recording layer having a high C / N ratio (Carrier to Noise ratio), which is an output ratio with respect to the background noise level, is realized.

By the way, in the optical information recording medium, the power of the laser beam reaching the recording layer fluctuates due to the thickness of the recording layer or the like and the in-plane non-uniformity due to individual differences during mass production. Therefore, in addition to the basic characteristics such as the degree of modulation and the C / N ratio, the recording layer is unlikely to deteriorate the signal characteristics of the recorded signal even when the power of the laser beam to be recorded fluctuates from the optimum value. Desired.

In the conventional recording layer, there is a considerable decrease in signal characteristics when the power of the laser beam fluctuates from the optimum value. Therefore, even if the power of the laser beam fluctuates from the optimum value, the signal characteristics do not deteriorate and the signal can be recorded satisfactorily, that is, a recording layer having a large power margin is required.

Japanese Unexamined Patent Publication No. 2012-139876

The present invention has been made based on the above circumstances, and is excellent in basic characteristics such as modulation degree and C / N ratio, and is also excellent in power margin. For an optical information recording medium recording layer and the optical information recording medium. An object of the present invention is to provide an optical information recording medium using a recording layer and to provide a sputtering target for forming the recording layer for the optical information recording medium.

As a result of diligent studies on a recording layer capable of improving the power margin, the present inventor has determined that the atomic number ratio of Mn is appropriately controlled, including Sn oxide or Ta oxide together with W oxide in addition to Mn oxide. The present invention has been completed by finding that the power margin can be improved. In the recording layer using Mn oxide, recording marks are formed by the generation of bubbles by laser irradiation, but Sn oxide or Ta oxide is further added together with W oxide, and the atomic number ratio of Mn is appropriately adjusted. The present inventor believes that the power margin is improved as a result of changing the mechanical properties of the recording layer and making it easier to stabilize the morphology of the bubbles by controlling the recording layer.

That is, the invention made to solve the above problems is a recording layer for an optical information recording medium capable of recording an information signal by irradiation with laser light, and is a Sn oxide or Ta oxidation together with a Mn oxide and a W oxide. It has a metal oxide containing a substance, and the ratio of the number of atoms of Mn to the total number of atoms of the metal elements constituting the metal oxide is 3 atm% or more and 40 atm% or less.

Since the recording layer for an optical information recording medium uses an irreversible recording method by generating bubbles accompanying laser irradiation of Mn oxide, it is excellent in basic characteristics such as modulation degree and C / N ratio. Further, the recording layer for an optical information recording medium contains Sn oxide or Ta oxide together with W oxide in addition to Mn oxide as a metal oxide, and the atomic number ratio of Mn is controlled within the above range. .. Therefore, the bubbles generated by laser irradiation of the Mn oxide of the recording layer for the optical information recording medium are easily stabilized by the W oxide and the Sn oxide or the Ta oxide, and the power margin is improved. Therefore, the recording layer for the optical information recording medium is excellent in basic characteristics such as the degree of modulation and the C / N ratio, and is also excellent in the power margin.

The ratio of the number of atoms of W to the total number of atoms of the metal elements constituting the metal oxide is preferably 10 atm% or more and 65 atm% or less. By setting the atomic number ratio of W within the above range in this way, it is possible to further improve the power margin while suppressing the deterioration of the jitter characteristics.

The ratio of the number of atoms of Sn or Ta to the total number of atoms of the metal elements constituting the metal oxide is preferably 5 atm% or more. By setting the atomic number ratio of Sn or Ta to the above lower limit or more in this way, the jitter characteristics can be improved.

It is preferable that the metal oxide further contains a Zn oxide. By including Zn oxide in the metal oxide, the power margin can be further improved.

Another invention made to solve the above problems includes a recording layer for an optical information recording medium of the present invention and a protective layer laminated on the front surface and the back surface of the recording layer for an optical information recording medium, and the above protection is provided. An optical information recording medium in which the layer is a dielectric.

Since the optical information recording medium includes the recording layer for the optical information recording medium of the present invention, it is excellent in basic characteristics such as modulation degree and C / N ratio, and is also excellent in power margin. Further, since the protective layer of the optical information recording medium is a dielectric material, the signal strength can be increased and the basic characteristics thereof can be further improved.

Yet another invention made to solve the above problems is a sputtering target for forming a recording layer for an optical information recording medium capable of recording an information signal by irradiation with a laser beam, and is a sputtering target for forming a recording layer for an optical information recording medium, in which at least Mn and metal elements are used. It contains Sn or Ta together with W, and the ratio of the number of atoms of Mn to the total number of atoms of the metal element is 3 atm% or more and 40 atm% or less.

The sputtering target contains Sn or Ta together with at least Mn and W as metal elements, and the ratio of the number of atoms of Mn to the total number of atoms of the metal elements is within the above range. The sputtering target is used as a sputtering target for forming a recording layer for an optical information recording medium while oxidizing a contained metal element, so that in addition to Mn oxide as a metal oxide, Sn oxide together with W oxide. Alternatively, it contains Ta oxide, and the atomic number ratio of Mn can be easily controlled within the above range. Therefore, by using the sputtering target, it is possible to easily manufacture a recording layer for an optical information recording medium which is excellent in basic characteristics such as a degree of modulation and a C / N ratio and also has an excellent power margin.

The ratio of the number of atoms of W to the total number of atoms of the metal elements is preferably 10 atm% or more and 65 atm% or less. By setting the atomic number ratio of W within the above range in this way, it is possible to manufacture a recording layer for an optical information recording medium in which a decrease in jitter characteristics is suppressed and a power margin is further improved.

The ratio of the number of atoms of Sn or Ta to the total number of atoms of the metal elements is preferably 5 atm% or more. By setting the atomic number ratio of Sn or Ta to the above lower limit or more in this way, it is possible to manufacture a recording layer for an optical information recording medium having improved jitter characteristics.

As described above, the recording layer for an optical information recording medium and the optical information recording medium of the present invention are excellent in basic characteristics such as a degree of modulation and a C / N ratio, and are also excellent in a power margin.

FIG. 1 is a schematic side view showing a layer structure of an optical information recording medium according to an embodiment of the present invention. FIG. 2 is a graph showing a measurement example of the degree of modulation in the examples. FIG. 3 is a graph showing a measurement example of jitter in the examples.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Optical information recording medium]
The optical information recording medium shown in FIG. 1 is laminated on the front surface and the back surface of a substrate 1, a recording layer 2 for an optical information recording medium, which is itself an embodiment of the present invention, and a recording layer 2 for an optical information recording medium. A protective layer 3 and a light transmitting layer 4 are provided. Further, the protective layer 3 on the back surface side of the recording layer 2 for the optical information recording medium is laminated on the substrate 1, and the light transmitting layer 4 is laminated on the protective layer 3 on the front surface side of the recording layer 2 for the optical information recording medium. .. That is, in the optical information recording medium, the substrate 1, the protective layer 3, the optical information recording medium recording layer 2, the protective layer 3, and the light transmitting layer 4 are laminated in this order from the bottom.

The optical information recording medium can be used as, for example, a CD, a DVD, a BD, or the like. As an example, when the optical information recording medium is used as a BD-R, for example, a blue laser light having a wavelength of 380 nm or more and 450 nm or less, preferably about 405 nm is irradiated to the recording layer 2 for the optical information recording medium to obtain data. Recording and playback can be performed. The power of the laser beam used at this time is practically 5 mW or more and 15 mW or less.

<Board>
The substrate 1 is a member for ensuring the strength of the optical information recording medium. The shape of the substrate 1 is appropriately determined according to the standard of the optical information recording medium and the like. For example, in the case of complying with the standard of a commercially available large-capacity optical disc, the substrate 1 has a disk shape with an outer diameter of 120 mm, and irregularities (grooves) as wobbling grooves are formed on the surface on the side where the protective layer 3 is laminated. To.

Examples of the material of the substrate 1 include polycarbonate, norbornene-based resin, cyclic olefin-based copolymer, and amorphous polyolefin.

The lower limit of the average thickness of the substrate 1 is preferably 0.5 mm, more preferably 1 mm. On the other hand, the upper limit of the average thickness of the substrate 1 is preferably 1.2 mm, more preferably 1.1 mm. If the average thickness of the substrate 1 is less than the above lower limit, the strength of the optical information recording medium may be insufficient. On the contrary, if the average thickness of the substrate 1 exceeds the above upper limit, it may not conform to the standard of, for example, a large-capacity optical disc.

<Recording layer for optical information recording medium>
The recording layer 2 for an optical information recording medium is a recording layer for an optical information recording medium capable of recording an information signal by irradiation with a laser beam. The recording layer 2 for an optical information recording medium has a metal oxide containing Sn oxide or Ta oxide together with Mn oxide and W oxide. The recording layer 2 for an optical information recording medium is a write-once type recording layer of a perforation type.

(Mn oxide)
When the recording layer 2 for an optical information recording medium is irradiated with a laser beam, the Mn oxide is heated and decomposed by _{the laser beam to release oxygen (O 2} gas) so that bubbles are generated in the laser-irradiated portion. become. As a result, the shape of the recording layer 2 for the optical information recording medium changes, and a recording mark is formed. In the portion where the bubbles are generated and the recording mark is formed, the transmittance is increased (the reflectance is decreased) as compared with the portion where the bubbles are not generated (that is, the portion where the recording mark is not formed). It is considered that the recording layer 2 for the optical information recording medium can increase the degree of modulation.

Further, since the recording layer 2 for the optical information recording medium contains Mn oxide, the light absorption rate can be increased, so that the energy of the laser light can be efficiently converted into the thermal energy at the time of writing. Therefore, the recording layer 2 for the optical information recording medium can improve the recording sensitivity.

The form of the Mn oxide is not particularly limited as long as it exists as a normal state, and is an oxide composed of only Mn and oxygen (O) such as _{MnO, Mn 3} O ₄ , Mn ₂ O ₃ , _{and Mn O 2.} It may be a composite oxide containing other metals such as W, Zn, and Sn.

The lower limit of the ratio of the number of atoms of Mn to the total number of atoms of the metal elements constituting the metal oxide is 3 atm%, more preferably 10 atm%. On the other hand, the upper limit of the Mn atom number ratio is 40 atm%, more preferably 35 atm%. If the ratio of the number of atoms of Mn is less than the above lower limit, the effect of improving the degree of modulation and the recording sensitivity of the recording layer 2 for the optical information recording medium may be insufficient. On the contrary, when the atomic number ratio of Mn exceeds the upper limit, the atomic number of W, Sn or Ta is relatively reduced, so that the effect of improving the power margin may be insufficient.

The recording layer 2 for the optical information recording medium preferably does not contain the metal Mn. Oxidation and decomposition of the metal Mn are likely to proceed, and when the recording layer 2 for the optical information recording medium contains the metal Mn, the durability of the recording layer 2 for the optical information recording medium and the durability of the optical information recording medium are deteriorated. It may be lowered. In addition, the specific "does not contain a metal element" means that the specific metal element is intentionally not contained, and the metal element inevitably contained may exist. Here, it is considered that the content of the metal element inevitably contained in the recording layer 2 for the optical information recording medium is about 100 mass ppm or less in the recording layer 2 for the optical information recording medium. That is, "does not contain metal Mn" means that metal Mn is not intentionally contained, and therefore the content of metal Mn in the recording layer 2 for the optical information recording medium is 100 mass ppm or less.

(Metal oxides other than Mn oxide)
The recording layer 2 for an optical information recording medium contains a Sn oxide or a Ta oxide together with a W oxide as a metal oxide in addition to the Mn oxide. The W oxide and the Sn oxide or the Ta oxide stabilize the bubbles generated by irradiating the Mn oxide of the recording layer 2 for the optical information recording medium with the laser, and improve the power margin. Further, it is preferable that the metal oxide further contains a Zn oxide. By including Zn oxide in the metal oxide, the power margin can be further improved.

Similar to Mn oxide, the form of the W oxide, Sn oxide, Ta oxide and Zn oxide may be an oxide bonded only to oxygen (O), and is a composite containing other metal elements. It may be an oxide.

The lower limit of the ratio of the number of atoms of W to the total number of atoms of the metal elements constituting the metal oxide is preferably 10 atm%, more preferably 15 atm%. On the other hand, as the upper limit of the atomic number ratio of W, 65 atm% is preferable, and 50 atm% is more preferable. If the atomic number ratio of W is less than the lower limit, the power margin may decrease. On the contrary, when the atomic number ratio of W exceeds the upper limit, the atomic number ratio of Sn or Ta is relatively decreased, so that the jitter characteristic is deteriorated and a reading error may easily occur.

The lower limit of the ratio of the number of atoms of Sn or Ta to the total number of atoms of the metal elements constituting the metal oxide is preferably 5 atm%, more preferably 10 atm%. On the other hand, as the upper limit of the atomic number ratio of Sn or Ta, 60 atm% is preferable, and 50 atm% is more preferable. If the atomic number ratio of Sn or Ta is less than the above lower limit, the jitter characteristic may be deteriorated and a reading error may easily occur. On the contrary, when the atomic number ratio of Sn or Ta exceeds the upper limit, the atomic number ratio of W is relatively decreased, so that the power margin may be decreased.

The lower limit of the atomic number ratio of W to the atomic number of Sn or Ta constituting the metal oxide is preferably 0.3, more preferably 0.4. On the other hand, as the upper limit of the atomic number ratio of W to the atomic number of Sn or Ta, 12 is preferable, and 10 is more preferable. If the atomic number ratio of W to the atomic number of Sn or Ta is less than the lower limit, the power margin may decrease. On the contrary, when the atomic number ratio of W to the atomic number of Sn or Ta exceeds the upper limit, the atomic number ratio of Sn or Ta is relatively lowered, so that the jitter characteristic is lowered and a reading error is likely to occur. There is a risk.

When the metal oxide contains Zn oxide, the lower limit of the ratio of the number of Zn atoms to the total number of atoms of the metal elements constituting the metal oxide is preferably 5 atm%, more preferably 10 atm%. On the other hand, as the upper limit of the atomic number ratio of Zn, 70 atm% is preferable, 50 atm% is more preferable, and 40 atm% is further more preferable. If the ratio of the number of atoms of Zn is less than the above lower limit, the effect of improving the power margin may be insufficient due to the Zn oxide. On the contrary, when the atomic number ratio of Zn exceeds the upper limit, the atomic number of W, Sn or Ta is relatively reduced, so that the power margin may be lowered.

The metal oxide may contain oxides other than Mn oxide, W oxide, Sn oxide, Ta oxide and Zn oxide. Examples of such a metal oxide include In oxide and Cu oxide. However, from the viewpoint of the effect of improving the power margin, it is preferable that the metal oxide does not contain oxides other than Mn oxide, W oxide, Sn oxide, Ta oxide and Zn oxide.

Further, with respect to metal oxides other than Mn oxide, it is preferable that the metal constituting these oxides is not contained as a simple substance of the metal element. Above all, it is more preferable that all the metal elements contained in the recording layer 2 for the optical information recording medium are oxidized. For example, metal In, metal Zn, metal Ta, metal Cu, metal Sn, etc. may deprive other oxides of oxygen and oxidize, which may deteriorate the characteristics of the recording layer 2 for the optical information recording medium. ..

When the protective layer 3 is laminated on the front surface and the back surface of the optical information recording medium recording layer 2 like the optical information recording medium, the lower limit of the average thickness of the optical information recording medium recording layer 2 is set as the lower limit. 2 nm is preferable, 5 nm is more preferable, and 10 nm is further preferable. On the other hand, the upper limit of the average thickness of the recording layer 2 for the optical information recording medium is preferably 50 nm, more preferably 40 nm, and even more preferably 15 nm. If the average thickness of the recording layer 2 for the optical information recording medium is less than the above lower limit, the number of Mn atoms in the thickness direction of the recording layer 2 for the optical information recording medium decreases, so that the recording mark is sufficiently formed. This may not be possible and the degree of modulation may be insufficient. On the contrary, when the average thickness of the recording layer 2 for the optical information recording medium exceeds the above upper limit, the recording layer 2 for the optical information recording medium becomes unnecessarily thick, so that the recording layer 2 for the optical information recording medium is formed. It takes a long time to reduce the productivity, and the laser power required for recording may become too large.

(advantage)
Since the recording layer 2 for an optical information recording medium uses an irreversible recording method by generating bubbles accompanying laser irradiation of Mn oxide, it is excellent in basic characteristics such as modulation degree and C / N ratio. Further, the recording layer 2 for an optical information recording medium contains a Sn oxide or a Ta oxide together with a W oxide in addition to the Mn oxide as a metal oxide, and the atomic number ratio of Mn constitutes the metal oxide. It is controlled to be 3 atm% or more and 40 atm% or less with respect to the total number of atoms of the elements. Therefore, the bubbles generated by laser irradiation of the Mn oxide of the recording layer 2 for the optical information recording medium are easily stabilized by the W oxide and the Sn oxide or the Ta oxide, and the power margin is improved. Therefore, the recording layer 2 for the optical information recording medium is excellent in basic characteristics such as the degree of modulation and the C / N ratio, and is also excellent in the power margin.

<Protective layer>
The protective layer 3 is a dielectric. Oxygen bubbles are generated in the recording layer 2 for the optical information recording medium by laser irradiation, but the dielectric prevents the bubbles from escaping, and the reflectance of the recording layer 2 for the optical information recording medium is lowered. Suppress. Therefore, when the optical information recording medium includes a dielectric as the protective layer 3, it becomes easy to secure the degree of modulation of the optical information recording medium recording layer 2.

Examples of the material of the dielectric material constituting the protective layer 3 include oxides such as Si, Al, In, Zn, Zr, Ti, Nb, Ta, Cr and Sn, Si, Al, In, Ge, Cr and Nb. Known dielectrics such as nitrides such as Mo and Ti, Zn sulfides, carbides such as Cr, Si, Al, Ti, Zr and Ta, and fluorides such as Mg, Ca and La can be mentioned. _{Of these, In 2} O _3, which is an oxide of In, is preferable from the viewpoint of productivity of the optical information recording medium and recording sensitivity. In addition, these dielectrics may be mixed and used.

As the lower limit of the average thickness of the protective layer 3, 2 nm is preferable, and 3 nm is more preferable. On the other hand, the upper limit of the average thickness of the protective layer 3 is preferably 30 nm, more preferably 25 nm. If the average thickness of the protective layer 3 is less than the above lower limit, the effect of preventing the escape of bubbles generated when the recording layer 2 for the optical information recording medium is irradiated with the laser may be insufficient. On the contrary, when the average thickness of the protective layer 3 exceeds the above upper limit, light interference is likely to occur, and bubbles are less likely to be generated in the recording layer 2 for the optical information recording medium. Recording sensitivity may decrease.

<Light transmission layer>
The light transmitting layer 4 smoothes the surface of the optical information recording medium to facilitate the incident of laser light, and prevents corrosion of the protective layer 3 and the recording layer 2 for the optical information recording medium.

As the material of the light transmitting layer 4, a material having a high transmittance with respect to the laser beam for recording / reproduction and a small light absorption rate is selected. Specifically, as the material of the light transmitting layer 4, for example, polycarbonate, ultraviolet curable resin, or the like can be used.

The lower limit of the average thickness of the light transmitting layer 4 is preferably 0.01 mm, more preferably 0.015 mm. On the other hand, the upper limit of the average thickness of the light transmitting layer 4 is preferably 0.2 mm, more preferably 0.15 mm. If the average thickness of the light transmitting layer 4 is less than the above lower limit, the corrosion prevention effect on the protective layer 3 and the recording layer 2 for the optical information recording medium may be insufficient. On the contrary, if the average thickness of the light transmitting layer 4 exceeds the above upper limit, the NA (numerical aperture) becomes too small, and there is a possibility that fine recording marks cannot be recorded.

<Manufacturing method of optical information recording medium>
The optical information recording medium is manufactured including, for example, a substrate preparation step, a back surface side protective layer laminating step, a recording layer laminating step for an optical information recording medium, a front surface side protective layer laminating step, and a light transmitting layer laminating step. It can be manufactured by the method.

(Board preparation process)
In the substrate preparation step, the substrate 1 having irregularities as wobbling grooves formed on the surface on the side where the protective layer 3 is laminated is prepared.

Such a substrate 1 can be formed by transferring the uneven shape of the wobbling groove for tracking from the mastering master by injection molding or the like.

(Back side protective layer laminating process)
In the back surface side protective layer laminating step, the protective layer 3 is laminated on the surface of the substrate 1 prepared in the substrate preparation step.

As a method for laminating the protective layer 3 on the surface of the substrate 1, a known film forming method such as a sputtering method can be used by using a sputtering target having the same composition as the dielectric constituting the protective layer 3.

(Recording layer stacking process for optical information recording medium)
In the optical information recording medium recording layer laminating step, the optical information recording medium recording layer 2 is laminated on the front surface side of the laminate in which the substrate 1 and the protective layer 3 are laminated after the back surface side protective layer laminating step.

The recording layer 2 for an optical information recording medium contains Sn oxide or Ta oxide together with Mn oxide and W oxide as metal oxides. In order to obtain a recording layer containing a plurality of types of oxides in this way, it is preferable to use a sputtering method. By using the sputtering method, it is easy to ensure the uniformity of the thickness of the recording layer 2 for the optical information recording medium.

As the sputtering target for forming the recording layer 2 for the optical information recording medium, a sputtering target containing Sn or Ta together with at least Mn and W as metal elements is used. The lower limit of the ratio of the number of atoms of Mn to the total number of atoms of the metal elements is 3 atm%, more preferably 10 atm%. On the other hand, the upper limit of the Mn atom number ratio is 40 atm%, more preferably 35 atm%.

The sputtering target is used as a sputtering target for forming the recording layer 2 for an optical information recording medium while oxidizing the contained metal element. As a metal oxide, in addition to Mn oxide, W oxide and Sn oxidation It contains a substance or Ta oxide, and the atomic number ratio of Mn can be easily controlled within the above range. Therefore, by using the sputtering target, it is possible to easily manufacture the recording layer 2 for an optical information recording medium, which is excellent in basic characteristics such as the degree of modulation and the C / N ratio and is also excellent in the power margin.

Further, as the lower limit of the ratio of the number of atoms of W to the total number of atoms of the metal elements, 10 atm% is preferable, and 15 atm% is more preferable. On the other hand, as the upper limit of the atomic number ratio of W, 65 atm% is preferable, and 50 atm% is more preferable. If the atomic number ratio of W is less than the lower limit, the power margin of the recording layer 2 for an optical information recording medium manufactured by using the sputtering target may decrease. On the contrary, when the atomic number ratio of W exceeds the upper limit, the atomic number ratio of Sn or Ta decreases relatively, so that the jitter of the recording layer 2 for the optical information recording medium manufactured by using the sputtering target The characteristics may deteriorate and reading errors may occur easily.

As the lower limit of the ratio of the number of atoms of Sn or Ta to the total number of atoms of the metal elements, 5 atm% is preferable, and 10 atm% is more preferable. On the other hand, as the upper limit of the atomic number ratio of Sn or Ta, 60 atm% is preferable, and 50 atm% is more preferable. If the atomic number ratio of Sn or Ta is less than the above lower limit, the jitter characteristic of the recording layer 2 for an optical information recording medium manufactured by using the sputtering target may be deteriorated, and a reading error may easily occur. On the contrary, when the atomic number ratio of Sn or Ta exceeds the upper limit, the atomic number ratio of W relatively decreases, so that the power of the recording layer 2 for the optical information recording medium manufactured by using the sputtering target Margin may decrease.

When the recording layer 2 for an optical information recording medium is formed by a sputtering method, it is preferable to use reactive sputtering. In reactive sputtering, oxygen is supplied to promote oxidation while sputtering is performed on the sputtering target.

Oxygen is supplied by using an atmospheric gas obtained by diluting oxygen gas with an inert gas (for example, Ar gas). The lower limit of the oxygen flow rate ratio to the Ar flow rate in the atmospheric gas is preferably 0.5 times, more preferably 1 time. On the other hand, the upper limit of the oxygen flow rate ratio is preferably 5 times. If the oxygen flow rate ratio is less than the above lower limit, the oxidation of the metal becomes insufficient, and the metal element tends to remain in the recording layer 2 for the optical information recording medium, so that the durability of the optical information recording medium is lowered. There is a risk. On the contrary, when the oxygen flow rate ratio exceeds the upper limit, the oxidation reaction becomes too violent, the denseness of the formed recording layer 2 for the optical information recording medium is lowered, and basic characteristics such as the degree of modulation and the C / N ratio are reduced. May decrease.

Other sputtering conditions can be determined by a conventional method. For example, the gas pressure is 0.1 Pa or more and 1 Pa or less, the sputtering power is 0.2 W / cm ² or more and 20 W / cm ² or less, and the substrate temperature is room temperature. (20 ° C. or higher and 30 ° C. or lower).

(Surface side protective layer laminating process)
In the surface-side protective layer laminating step, the protective layer 3 is further laminated on the surface side of the laminated body in which the optical information recording medium recording layer 2 is laminated in the optical information recording medium recording layer laminating step. This front surface side protective layer laminating step can be performed in the same manner as the back surface side protective layer laminating step.

(Light transmitting layer laminating process)
In the light transmitting layer laminating step, the light transmitting layer 4 is further laminated on the surface side of the laminated body in which the protective layer 3 on the surface side is laminated in the surface side protective layer laminating step.

As the method of laminating the light transmitting layer 4, a known method can be used depending on the characteristics of the material used and the like. For example, when an ultraviolet curable resin is used as the light transmitting layer 4, it can be formed by applying an ultraviolet curable resin composition by spin coating or the like and then irradiating with light.

<Advantage>
Since the optical information recording medium includes the recording layer 2 for the optical information recording medium of the present invention, it is excellent in basic characteristics such as modulation degree and C / N ratio, and is also excellent in power margin. Further, in the optical information recording medium, since the protective layer 3 is a dielectric material, the signal strength can be increased and the basic characteristics thereof can be further improved.

[Other Embodiments]
The present invention is not limited to the above embodiment.

In the above embodiment, the optical information recording medium in which the protective layer is laminated on the front surface and the back surface of the recording layer for the optical information recording medium has been described, but in the recording layer for the optical information recording medium, the protective layer is laminated on only one surface. It may or may not have such a protective layer. When the optical information recording medium does not have a protective layer, it is preferable to provide a metal reflective layer on the back surface of the recording layer for the optical information recording medium. By providing the reflective layer in this way, the signal strength can be increased. Examples of the metal constituting this reflective layer include metals such as Ag, Au, Cu, Al, Ni, Cr, and Ti, and alloys thereof.

When a single layer is used without providing protective layers on the front and back surfaces of the recording layer for an optical information recording medium, the lower limit of the average thickness of the recording layer for an optical information recording medium is preferably 10 nm, more preferably 20 nm, and more preferably 30 nm. Is even more preferable. On the other hand, the upper limit of the average thickness of the recording layer for an optical information recording medium is preferably 60 nm, more preferably 50 nm, and even more preferably 45 nm. If the average thickness of the recording layer for the optical information recording medium is less than the above lower limit, the reflectance required for reading the irradiated laser beam may not be obtained. On the contrary, when the average thickness of the recording layer for the optical information recording medium exceeds the above upper limit, the recording layer for the optical information recording medium becomes unnecessarily thick, so that it takes time to form the recording layer for the optical information recording medium, and the production There is a risk that the property will deteriorate and the laser power required for recording will become too large.

Further, in addition to the protective layer, the optical information recording medium may be provided with an optical adjustment layer such as an oxide, a nitride, or a sulfide on the front surface side or the back surface side of the optical information recording medium recording layer. By providing the optical adjustment layer in this way, the durability of the recording layer for an optical information recording medium can be improved, and the recording characteristics can be further improved.

In the above embodiment, a single-layer optical information recording medium in which one recording layer for an optical information recording medium and one light transmission layer are formed has been described, but two or more recording layers for an optical information recording medium and light transmission have been described. It can also be a multi-layered optical information recording medium having layers.

In a multi-layer optical information recording medium, a recording layer group composed of a recording layer for an optical information recording medium and an optical adjustment layer and a protective layer laminated as needed is formed on the optical information recording medium via a transparent intermediate layer. Stacked in the thickness direction. As the transparent intermediate layer, for example, a transparent resin such as an ultraviolet curable resin or polycarbonate can be used. In such a multi-layered optical information recording medium, the layer on which information is recorded is selected by adjusting the focal position of the laser in the thickness direction during laser irradiation, and multi-layer recording is realized. The thickness of the transparent intermediate layer is appropriately determined so that crosstalk does not occur between the recording layers arranged in the upper and lower layers.

In the above embodiment, Sn or Ta is contained as a metal element together with at least Mn and W as a sputtering target for forming a recording layer for an optical information recording medium, and the ratio of the number of atoms of Mn to the total number of atoms of the metal element is 3 atm%. Although the case where a sputtering target having a content of 40 atm% or less is used has been described above, a recording layer for an optical information recording medium can also be formed by using another sputtering target. As another sputtering target, for example, metal Sn or metal Ta can be used together with a simple substance metal Mn and metal W. Alternatively, as the sputtering target, Sn oxide or Ta oxide may be used together with Mn oxide and W oxide as a simple substance, or a mixture of the above-mentioned metal target and oxide target may be used.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
As a substrate for the optical information recording medium, a polycarbonate substrate (diameter 120 mm, average thickness 1.1 mm, track pitch 0.32 μm, groove depth about 33 nm) was prepared.

A back surface side protective layer, a recording layer for an optical information recording medium (hereinafter, also simply referred to as “recording layer”), and a front surface side protective layer were laminated in this order on this substrate.

The front surface side protective layer and the back surface side protective layer were formed by a conventional DC magnetron sputtering method. The material of the protective layer was a metal oxide containing Sn, Zn and Zr in the atomic number ratios of 40 atm%, 40 atm% and 20 atm%, respectively, on both the front surface side and the back surface side, and the average thickness thereof was 14 nm. As the atmospheric gas during sputtering, the Ar flow rate was 20 sccm and the O ₂ flow rate was 1 sccm.

For the formation of the recording layer, metal Mn, metal Sn, and metal W were prepared as sputtering targets, and the composition was controlled by the multiple sputtering method so as to have the composition shown in Table 1. The sputtering conditions at this time were an Ar flow rate of 10 sccm, an O ₂ flow rate of 10 sccm, a gas pressure of 0.26 Pa, a substrate temperature of 25 ° C. (room temperature), and a sputtering power of 0.2 W / W / according to the target composition. It was adjusted with cm ² or more 3W / cm ² or less. The average thickness of the recording layer was 32 nm.

The light transmitting layer was laminated on the surface of the laminated body (the surface of the surface side protective layer) laminated by the sputtering method in this way. The light transmitting layer was formed by spin-coating an ultraviolet curable resin composition (“BRD-864” of Nippon Kayaku Co., Ltd.) and then irradiating with ultraviolet rays. The average thickness of the light transmitting layer was 0.1 mm.

In this way, the optical information recording medium of Example 1 was obtained.

[Examples 2 to 4]
The optical information recording media of Examples 2 to 4 were obtained in the same manner as in Example 1 except that the composition of the recording layer was controlled so as to have the composition shown in Table 1.

[Examples 5 and 6]
In the formation of the recording layer, the optical information recording media of Examples 5 and 6 were obtained in the same manner as in Example 1 except that the metal Zn was further prepared and controlled so as to have the composition shown in Table 1.

[Examples 7 and 8]
In the formation of the recording layer, the optical information recording media of Examples 7 and 8 were obtained in the same manner as in Example 5 except that the metal Ta was further prepared and controlled so as to have the composition shown in Table 1.

[Comparative Examples 1 to 4]
The optical information recording media of Comparative Examples 1 to 4 were obtained in the same manner as in Example 1 except that the composition of the recording layer was controlled so as to have the composition shown in Table 1.

In Table 1, "-" in the "Number of metal atoms in the metal oxide of the recording layer" column means that the atom is not included. Specifically, sputtering was performed without loading the corresponding sputtering target. Further, in Comparative Example 3, In ₂ O ₃ was newly added as an In sputtering target to perform sputtering.

<Confirmation of composition>
The number of metal atoms in the recording layers of Examples 1 to 8 and Comparative Examples 1 to 4 was confirmed using a fluorescent X-ray analyzer (XRF). Specifically, the atomic number ratio was calculated from the fluorescent X-ray intensity for the target element using a desktop wavelength dispersive fluorescent X-ray analyzer "ZSX-MIN" manufactured by Rigaku. The results are shown in Table 1.

[Evaluation of optical information recording medium]
The modulation degree, jitter, and power margin of the optical information recording media of Examples 1 to 8 and Comparative Examples 1 to 4 were evaluated (however, the modulation degree of Comparative Example 4 was excluded).

<Evaluation device>
"ODU-1000" (recording laser center wavelength: 405 nm, NA (numerical aperture): 0.85) manufactured by Pulsetech Industries, Ltd. was used to evaluate the recording signal characteristics of the optical information recording medium, and the reference clock was reproduced at 66 MHz. -The recording laser was irradiated, and recording and reading were performed on the optical information recording medium. The recording operation is performed by RLL (Run Length Limited) (1,7) PP modulation (Parity presserve / Prohibit rmtr (repeated minimum transmission runlength)), the signal is recorded on the adjacent 5 tracks, and the signal characteristics of the center track are evaluated. did. The linear velocity of the optical information recording medium was 4.92 m / s, and the laser power during reproduction was 0.7 mW.

<Modulation degree>
The degree of modulation was calculated by the following formula (1) by measuring the maximum reflectance and the minimum reflectance of the portion where the signal was recorded using a digital oscilloscope "DL1640" manufactured by Yokogawa Electric Corporation.
Modulation degree = (maximum reflectance-minimum reflectance) / maximum reflectance ... (1)

This degree of modulation changes by changing the laser power at the time of recording as shown in FIG. Therefore, the degree of modulation when recording is performed with the laser power that minimizes the jitter described later is defined as the degree of modulation of each optical information recording medium. In the graph of FIG. 2, since the laser power is standardized by the laser power that minimizes the jitter, the modulation degree of each optical information recording medium corresponds to the modulation degree at the laser power = 1. The results are shown in Table 1.

The larger the value of this modulation degree, the larger the fluctuation of the reflected light and the easier it is to read. Here, it was judged that those having a degree of modulation of 0.5 or more were excellent in the degree of modulation.

<Jitter>
The jitter was measured using a time interval analyzer "TA520" manufactured by Yokogawa Electric Corporation. As shown in FIG. 3, the jitter changes depending on the laser power at the time of recording, and becomes the minimum value at a certain power. This minimum value was taken as the jitter of each optical information recording medium. The results are shown in Table 1.

For jitter, the smaller the value, the higher the reading accuracy. Here, it was judged that the one having a jitter of 6.5% or less was excellent in the jitter.

<Power margin>
The power margin was calculated by the following procedure. First, the laser power was standardized by the laser power that minimizes jitter (see FIG. 3). From the result of standardizing this laser power, a standardized laser power having a jitter of 8.5% was obtained. Since the minimum value of jitter of each optical information recording medium is less than 8.5%, there are two laser powers. Table 1 shows each as a low power side and a high power side.

The power margin is a value after standardization, and the lower the power side (always less than 1) is, the better it is, and the higher the power side (always more than 1) is, the better it is. Here, it was judged that the one having 0.85 or less on the low power side and 1.15 or more on the high power side was excellent in power margin.

In Table 1, the “−” of the modulation degree of Comparative Example 4 means that the modulation degree has not been measured.

From Table 1, the optical information recording media of Examples 1 to 8 having a metal oxide containing Sn oxide or Ta oxide together with Mn oxide and W oxide as a recording layer are used for optical information recording of Comparative Examples 1 to 4. Compared with the medium, it is excellent in jitter and power margin, especially the power margin on the low power side, and the degree of modulation is the same.

On the other hand, the optical information recording media of Comparative Example 2 and Comparative Example 4 in which the recording layer does not have Ta oxide in addition to Mn oxide and has only one of W oxide and Sn oxide. Then, the power margin on the low power side is inferior, and the jitter is further inferior in the optical information recording medium of Comparative Example 4. Further, the optical information recording media of Comparative Example 1 and Comparative Example 3 in which the recording layer does not have all Ta oxide, W oxide, and Sn oxide are inferior in power margin on both the low power side and the high power side. From this, it can be seen that the power margin of the optical information recording medium can be improved by including Sn oxide or Ta oxide together with Mn oxide and W oxide as the recording layer.

More specifically, the optical information recording media of Examples 5 and 6 have smaller jitter than the optical information recording media of Examples 1 to 4, and are excellent in power margin on the low power side. From this, it can be seen that the power margin can be further improved by including the Zn oxide in the metal oxide of the recording layer.

As described above, the recording layer for an optical information recording medium and the optical information recording medium of the present invention are excellent in basic characteristics such as a degree of modulation and a C / N ratio, and are also excellent in a power margin.

1 Substrate 2 Recording layer for optical information recording medium 3 Protective layer 4 Light transmitting layer

Claims (8)

A recording layer for an optical information recording medium capable of recording an information signal by irradiation with a laser beam.
It has a metal oxide containing Sn oxide or Ta oxide together with Mn oxide and W oxide.
A recording layer for an optical information recording medium in which the ratio of the number of atoms of Mn to the total number of atoms of the metal elements constituting the metal oxide is 3 atm% or more and 40 atm% or less. The recording layer for an optical information recording medium according to claim 1, wherein the ratio of the number of atoms of W to the total number of atoms of the metal elements constituting the metal oxide is 10 atm% or more and 65 atm% or less. The recording layer for an optical information recording medium according to claim 1 or 2, wherein the ratio of the number of atoms of Sn or Ta to the total number of atoms of the metal elements constituting the metal oxide is 5 atm% or more. The recording layer for an optical information recording medium according to claim 1, claim 2 or claim 3, wherein the metal oxide further contains a Zn oxide. The recording layer for an optical information recording medium according to any one of claims 1 to 4,
A protective layer laminated on the front surface and the back surface of the recording layer for an optical information recording medium is provided.
An optical information recording medium in which the protective layer is a dielectric material. A sputtering target for forming a recording layer for an optical information recording medium capable of recording an information signal by irradiation with a laser beam.
It contains Sn or Ta as a metal element together with at least Mn and W.
A sputtering target in which the ratio of the number of atoms of Mn to the total number of atoms of the metal elements is 3 atm% or more and 40 atm% or less. The sputtering target according to claim 6, wherein the ratio of the number of atoms of W to the total number of atoms of the metal elements is 10 atm% or more and 65 atm% or less. The sputtering target according to claim 6 or 7, wherein the ratio of the number of atoms of Sn or Ta to the total number of atoms of the metal element is 5 atm% or more.

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