Magnetic recording tape

Abstract

A magnetic recording tape 1a is provided with a base material 10, a base layer 20, and a perpendicular magnetic recording layer 30. The substrate 10, the underlayer 20, and the perpendicular magnetic recording layer 30 are arranged in this order in the thickness direction of the underlayer 20. The base layer 20 contains a metal M. The base layer (20) has a boundary section (21) including a boundary surface closest to the base material (10) in the thickness direction of the base layer (20). The content of the metal (M) and elements other than oxygen in the boundary portion (21) is less than 8% in terms of atomic number. The ratio of the oxygen content in the boundary portion 21 relative to the total amount of the constituent elements and oxygen in the central portion 22 is 5% or more based on the number of atoms.

Description

Technical Field

[0001] This invention relates to magnetic recording tape. Background Technology

[0002] Previously, magnetic recording tapes with vertical magnetic recording layers were proposed.

[0003] For example, Patent Document 1 describes a magnetic recording medium comprising a substrate, a seed layer, a base layer, and a magnetic recording layer. This magnetic recording medium is a single-layer perpendicular magnetic recording medium. The substrate is, for example, a strip-shaped film. The seed layer is disposed on the surface of the substrate. The base layer is disposed on the surface of the seed layer. The magnetic recording layer is disposed on the surface of the base layer. The seed layer is in an amorphous state and contains an alloy containing Ti, Cr, and O. The proportion of Ti in the seed layer relative to the total amount of Ti and Cr is 30 atomic% to 100 atomic% or less. The proportion of O in the seed layer relative to the total amount of Ti, Cr, and O is 15 atomic% or less.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-241182 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] With the development of the IoT society and digital transformation (DX), the amount of data being processed is constantly increasing, and is expected to increase further in the future. In this context, magnetic recording tape, as a data storage medium, is highly anticipated. Magnetic recording tape is a recording medium with a very large data capacity per volume and few write failures and errors. Furthermore, because it is stored offline, it offers advantages such as virtually no risk of unauthorized access from hackers or ransomware. Additionally, compared to hard drives, it produces less CO2 relative to the amount of data, thus attracting significant attention from the perspective of SDGs and the environment.

[0009] For example, compared to coated magnetic recording tapes, magnetic recording tapes with a vertical magnetic recording layer formed by sputtering a material with high magnetic anisotropy can easily improve the planar recording density. As can be understood from the technology described in Patent Document 1, by having an amorphous state and adjusting the proportions of Ti and O in a seed layer containing Ti, Cr, and O to a specified range, the reduction in the orientation of the substrate layer can be suppressed, and magnetic properties can be improved.

[0010] In the magnetic recording medium described in Patent Document 1, the material for forming the seed layer is limited to a specified alloy, which is expected to cause problems due to such alloys. For example, Ti and Cr have a high ionization tendency, so it is foreseeable that the performance of the magnetic recording medium will be reduced due to the modification of these metals by oxygen or moisture, or the diffusion of these metals into the substrate layer. Therefore, from the viewpoint of improving the orientation of the substrate layer without relying on a specific alloy, the technology described in Patent Document 1 has room for further research.

[0011] In view of this situation, the present invention provides a novel magnetic recording tape having a perpendicular magnetic recording layer, which is advantageous from the viewpoint of improving the orientation of the substrate layer.

[0012] Methods for solving problems

[0013] This invention provides a magnetic recording tape comprising:

[0014] Substrate;

[0015] A substrate containing metal; and

[0016] Vertical magnetic recording layer,

[0017] The aforementioned substrate, the aforementioned substrate layer, and the aforementioned perpendicular magnetic recording layer are sequentially disposed in the thickness direction of the aforementioned substrate layer.

[0018] The aforementioned substrate layer has: a boundary portion included in the thickness direction of the aforementioned substrate layer that is closest to the boundary surface of the aforementioned substrate; and a central portion located in the thickness direction of the aforementioned substrate layer between the aforementioned boundary portion and the aforementioned vertical magnetic recording layer.

[0019] The content of the aforementioned metal and elements other than oxygen in the aforementioned boundary region is less than 8% on an atomic basis.

[0020] The oxygen content in the aforementioned boundary portion relative to the total amount of constituent elements and oxygen in the aforementioned central portion is 5% or more, based on atomic number.

[0021] Invention Effects

[0022] The aforementioned magnetic recording tape has a perpendicular magnetic recording layer, which is advantageous from the viewpoint of improving the orientation of the substrate layer. Attached Figure Description

[0023] [ Figure 1 ] Figure 1 This is a cross-sectional view showing an example of an embodiment of a magnetic recording tape. Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the following description is illustrative of the present invention, and the present invention is not limited to the following embodiments.

[0025] like Figure 1 As shown, the magnetic recording tape 1a includes a substrate 10, a base layer 20, and a perpendicular magnetic recording layer 30. The substrate 10, base layer 20, and perpendicular magnetic recording layer 30 are sequentially arranged in the thickness direction of the base layer 20. The base layer 20 contains a metal M. The base layer 20 has a boundary portion 21 and a central portion 22. The central portion 22 is located between the boundary portion 21 and the perpendicular magnetic recording layer 30 in the thickness direction of the base layer 20. The boundary portion 21 is the boundary surface of the base layer 20 closest to the substrate 10 in the thickness direction. The content of metal M and elements other than oxygen in the boundary portion 21 is less than 8% on an atomic basis. The oxygen content in the boundary portion 21 is relatively lower than that in the central portion 22. 22 The total amount of oxygen, measured in atomic numbers, is 5% or more. Constituent element C 22 It contains at least metal M. The substrate 20, by having a boundary portion 21, readily exhibits high orientation in the portion of the substrate 20 between the boundary portion 21 in the thickness direction and the perpendicular magnetic recording layer 30. Consequently, the perpendicular magnetic recording layer 30 readily possesses large perpendicular magnetic anisotropy, and the magnetic recording tape 1a readily possesses the desired magnetic recording characteristics. Furthermore, the orientation of the substrate 20 can be improved without relying on the specific alloy used in the seed layer described in Patent Document 1. From the viewpoint of improving the orientation of the substrate 20 in the aforementioned portion, this ratio can be 5% or more, 10% or more, 12% or more, or 15% or more.

[0026] The oxygen content in boundary region 21 relative to the constituent element C 22 The upper limit of the ratio of oxygen to total oxygen is not limited to a specific value. This ratio, for example, is 50% or less based on the atomic number. In this case, the tightness between the boundary portion 21 and the central portion 22 tends to be higher. From the viewpoint of the tightness between the boundary portion 21 and the central portion 22, this ratio can be 45% or less, 40% or less, 35% or less, or 30% or less. This ratio can be included in any of the ranges determined by any combination of any one of the lower limits of 5%, 10%, 12%, and 15% and any one of the upper limits of 50%, 45%, 40%, 35%, and 30%.

[0027] The oxygen content in the boundary portion 21 is, for example, higher than that in the central portion 22. Based on this configuration, the substrate layer 20 is more likely to have high orientation, and the magnetic recording tape 1a is more likely to have the desired magnetic recording characteristics.

[0028] The oxygen content in the central section 22 is relative to the constituent element C.22 The total amount of oxygen is less than 5% on an atomic basis, for example, less than 3% or less than 1%. As a result, the substrate 20 is more likely to have high orientation, and the magnetic recording tape 1a is more likely to have the desired magnetic recording characteristics.

[0029] For example, in the substrate 20, the oxygen content decreases from the boundary portion 21 toward the central portion 22 in the thickness direction of the substrate 20. On the other hand, in the substrate 20, the metal M content increases from the boundary portion 21 toward the central portion 22 in the thickness direction of the substrate 20.

[0030] The thickness t of the substrate 20 20 Not limited to a specific value. Thickness t 20 For example, the thickness can be 2nm or greater, such as 5nm or greater, 10nm or greater, or 15nm or greater. Therefore, the substrate layer 20 is more likely to have high orientation, and the magnetic recording tape 1a is more likely to have the desired magnetic recording characteristics. Thickness t 20 For example, the wavelength can be below 100nm, such as below 90nm, 80nm, or 70nm. This makes it easier to increase the productivity of magnetic recording tape 1a.

[0031] Thickness t of boundary 21 21 relative to the thickness t of the substrate 20 20 The ratio of t 21 / t 20 Not limited to a specific value. Compared to t... 21 / t 20 For example, it can be 0.07 or higher, or 0.10 or higher, or 0.14 or higher. Therefore, crystal growth is promoted in the substrate layer 20, and high orientation is easily obtained. Furthermore, compared to t... 21 / t 20 For example, it can be below 0.50, or below 0.35 or 0.28. As a result, the adhesion of the base layer 20 can be easily increased.

[0032] The metal M contained in the substrate layer 20 is not limited to a specific metal, provided that a perpendicular magnetic recording layer 30 can be formed. Metal M is, for example, Ru. The substrate layer 20 may contain at least one of the following: elemental Ru and Ru-containing alloys. Examples of Ru-containing alloys are RuTi, RuCr, RuCo, and RuPt. Ru-containing alloys preferably have a close-packed hexagonal crystal structure. With this configuration, the substrate layer 20 is more likely to have high orientation, and the magnetic recording band 1a is more likely to have the desired magnetic recording characteristics.

[0033] like Figure 1As shown, the magnetic recording tape 1a includes, for example, an oxide layer 40. As described above, the orientation of the substrate layer 20 can be easily increased through the boundary portion 21, so the material for forming the oxide layer 40 can be selected without being limited by the orientation of the substrate layer 20. For example, as the material for forming the oxide layer 40, materials that are considered advantageous from the viewpoint of improving durability can also be selected.

[0034] The material forming the oxide layer 40 is not limited to a specific material. Examples of such materials include SiO2, aluminum-doped ZnO (AZO), and titanium oxide (TiO2). x ), aluminum oxide (AlO) x ), zirconium oxide (ZrO x ) and cobalt oxide (CoO) x In this case, the magnetic recording tape 1a tends to have high durability. The oxygen content in the oxide layer 40 is, for example, higher than 30% on an atomic basis. In this case, it is possible to prevent the performance degradation of the magnetic recording tape 1a caused by the components contained in the oxide layer 40.

[0035] like Figure 1 As shown, the substrate layer 20 is, for example, in contact with the oxide layer 40. The boundary portion 21, for example, forms the interface between the substrate layer 20 and the oxide layer 40. In the deposition of a metal onto an oxide, sometimes the wettability of the metal to the oxide becomes low, making it difficult to deposit the film with the desired crystal plane oriented towards the film thickness direction. On the other hand, according to the magnetic recording tape 1a, the boundary portion 21 forms the interface between the substrate layer 20 and the oxide layer 40, thereby, for example, the oxide layer 40 is less likely to affect the orientation of the substrate layer 20 in the central portion 22, and the orientation of the substrate layer 20 is more likely to be higher.

[0036] The thickness t of oxide layer 40 40 Not limited to a specific value. Thickness t 40 For example, it can be 2-20nm, or it can be 4-15nm or 6-10nm.

[0037] The substrate 10 is not limited to a specific substrate. The substrate 10 may include, for example, a surface 11 having an arithmetic mean roughness Ra of 1.0 nm or less. For example, an oxide layer 40, a substrate layer 20, and a perpendicular magnetic recording layer 30 are disposed on the surface 11. The surface 11 has an arithmetic mean roughness Ra of 1.0 nm or less, thereby making it easier for the substrate layer 20 to have high orientation and for the magnetic recording tape 1a to have the desired magnetic recording characteristics. The arithmetic mean roughness Ra in the surface 11 can be determined, for example, by using an atomic force microscope (AFM) to obtain a roughness profile from the surface of the surface 11, according to Japanese Industrial Standard (JIS) B0601 B:2013.

[0038] The arithmetic mean roughness Ra of surface 11 can be less than 0.7 nm or less than 0.5 nm. For example, the arithmetic mean roughness Ra of surface 11 is greater than 0.01 nm.

[0039] The material of substrate 10 is not limited to a specific material. Substrate 10 may be, for example, a strip-shaped film. As the material of substrate 10, materials known as substrates for magnetic recording tapes may be used. Examples of materials for substrate 10 include polyesters such as polyethylene terephthalate (PET), polyolefins, cellulose derivatives, vinyl resins, polyimides, polyamides, and polycarbonates.

[0040] The thickness t of substrate 10 10 Not limited to a specific value. Thickness t 10 For example, the range is 2–75 μm.

[0041] The perpendicular magnetic recording layer 30 is not limited to a specific layer as long as it corresponds to perpendicular magnetic recording. The perpendicular magnetic recording layer 30 may, for example, contain an alloy containing Co. In this case, the magnetic recording tape 1a can easily have a high areal recording density.

[0042] The perpendicular magnetic recording layer 30 is preferably a granular magnetic layer comprising an alloy containing Co. For example, the granular magnetic layer comprises strongly magnetic grains containing an alloy containing Co, and non-magnetic grain boundaries (non-magnetic bodies) surrounding the strongly magnetic grains. Alternatively, the granular magnetic layer comprises pillars (columnar crystals) containing an alloy containing Co, and non-magnetic grain boundaries surrounding the pillars and magnetically separated from each pillar. With this configuration, a perpendicular magnetic recording layer 30 having a structure in which each pillar is magnetically separated can be formed.

[0043] Co-containing alloys, for example, have a hexagonal close-packed (hcp) structure, with their c-axis oriented perpendicular to the film surface (thickness direction) of the magnetic recording layer 30. Examples of Co-containing alloys are CoCrPt alloys, which contain Co, Cr, and Pt. Elements other than Co, Cr, and Pt can be added to CoCrPt alloys. Examples of elements that can be added to CoCrPt alloys are Ni and Ta. CoCrPt alloys can also contain only Co, Cr, and Pt.

[0044] The nonmagnetic grain boundaries in the granular magnetic layer may, for example, comprise a nonmagnetic metallic material. Here, the metal may include half-metals. The nonmagnetic grain boundaries may, for example, comprise at least one element selected from the group consisting of metal oxides and metal nitrides as the nonmagnetic metallic material. Examples of metal oxides are metal oxides comprising at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf. Preferably, the metal oxide comprises SiO2. Other examples of metal oxides are Cr2O3, CoO, Al2O3, TiO2, Ta2O5, ZrO2, and HfO2. Examples of metal nitrides are metal nitrides comprising at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf. Specific examples of metal nitrides are SiN, TiN, and AlN.

[0045] The magnetic recording tape 1a can be provided, for example, in a state where it is wound around the sides of a cylindrical core material.

[0046] Example

[0047] The present invention will now be described in more detail through examples. However, the present invention is not limited to the following examples.

[0048] <Example 1>

[0049] A strip of PET film with a thickness of 50 μm is fed at a specified speed, and a SiO2 layer with a thickness of approximately 10 nm is formed on the PET film by RF magnetron sputtering. In this RF magnetron sputtering, a Si target is used as the target material, and a mixture of argon and oxygen is supplied as the process gas. The volume ratio of oxygen in the mixture is 20% based on standard cc / min (sccm). Next, the PET film is fed at a specified speed, and a substrate layer is formed on the SiO2 layer by DC magnetron sputtering. In this DC magnetron sputtering, a Ru target is used as the target material. In the initial stage of this DC magnetron sputtering, a mixture of argon and oxygen is supplied as the process gas to form the boundary of the substrate layer. The thickness of the boundary is approximately 7 nm. The volume ratio of oxygen in the mixture is 16% based on sccm. In stages after the initial stage of this DC magnetron sputtering, only argon is supplied as the process gas. Thus, a Ru-containing region of approximately 40 nm is formed on the boundary.

[0050] Next, the PET film is transported at a specified speed, and a vertical magnetic recording layer with a thickness of approximately 25 nm is formed on the substrate layer by DC magnetron sputtering. In this DC magnetron sputtering, a material with (Co) 74 Pt 16 Cr 10 )92 A target material composed of -(SiO2)8 was used as the target material. Argon gas was supplied as the process gas. In the vertical magnetic recording layer, a granular magnetic layer was formed, containing pillars (columnar crystals) containing a CoPtCr alloy, and non-magnetic grain boundaries containing SiO2 surrounding the pillars and magnetically separating each pillar. The magnetic recording tape according to Example 1 was fabricated in this manner.

[0051] <Example 2>

[0052] Except as described below, the magnetic recording tape of Example 2 was fabricated in the same manner as in Example 1. The volume ratio of oxygen in the process gas supplied during the initial stage of DC magnetron sputtering for forming the substrate layer was adjusted to 10% based on sccm.

[0053] <Example 3>

[0054] Except as described below, the magnetic recording tape of Example 3 was fabricated in the same manner as in Example 1. The volume ratio of oxygen in the process gas supplied during the initial stage of DC magnetron sputtering for forming the substrate layer was adjusted to 6% based on sccm.

[0055] <Comparative Example 1>

[0056] Except for the aspects described below, the magnetic recording tape involved in Comparative Example 1 was fabricated in the same manner as in Example 1. In the DC magnetron sputtering assembly used to form the substrate layer, only argon gas was supplied as the process gas.

[0057] [XPS-based composition analysis]

[0058] XPS depth-direction analysis was performed on the magnetic recording tapes involved in each embodiment and Comparative Example 1 using a Quanera SXM X-ray photoelectron spectroscopy (XPS) device manufactured by ULVAC-PHI. In this analysis, sputtering etching using Ar ions was performed from the substrate layer toward the substrate, and the elemental composition contained in the sample was determined at 1 nm intervals. The depth corresponding to the substrate layer was determined when the content of Si, which is an element other than Ru and O, was less than 8% on an atomic number basis, and the boundary between the substrate layer and the SiO2 layer was determined. In the portion corresponding to the substrate layer and the SiO2 layer, the ratio of the content of O on an atomic number basis to the total amount of Ru and O at the maximum depth where the content of Si is less than 8% on an atomic number basis is shown in Table 1. In addition, the content of O in the Ru-containing portion forming the central part of the substrate layer is shown in Table 1.

[0059] [Evaluation of basal layer orientation]

[0060] Samples with substrate forming master surfaces were fabricated using the magnetic recording tapes described in each embodiment and Comparative Example 1. Rocking curves of the (0002) plane of Ru were measured on the master surfaces of these samples using a Smartlab X-ray diffraction apparatus manufactured by Rigaku Corporation. The half-width (FWHM) of the rocking curve (RC) relative to the (0002) plane of Ru was determined from the measurement results. The results are shown in Table 1.

[0061] [Evaluation of Magnetic Properties]

[0062] The magnetic properties of samples made from the magnetic recording tapes described in each embodiment and Comparative Example 1 were evaluated using the vibrating sample magnetometer option of the Versalab miniature refrigerant-free physical property evaluation system manufactured by Quantum Design, Japan. The MH curves of the granular magnetic layer of the magnetic recording tapes described in each embodiment and Comparative Example 1 were obtained. The coercivity [kOe] and rectangularity ratio were determined from the obtained MH curves. The rectangularity ratio is the remanent magnetization M... r Relative saturation magnetization M s The ratio is shown in Table 1.

[0063] [Evaluation of substrate surface roughness]

[0064] The surface condition of the PET films used in the examples and comparative examples, which have SiO2 layers, was measured using a Bruker Multimode atomic force microscope to obtain surface roughness profiles. The arithmetic mean roughness Ra of the PET film surface was calculated from the obtained roughness profiles according to JIS B0601B:2013. The result showed that the arithmetic mean roughness Ra of the surface was 0.27 nm.

[0065] As shown in Table 1, the half-width of the RC (radius square) of the Ru(0002) plane of the substrate layer in each embodiment is smaller than that of the Ru(0002) plane of the substrate layer in Comparative Example 1. Furthermore, compared to the magnetic properties of the perpendicular magnetic recording layer of the magnetic recording tape in Comparative Example 1, the magnetic properties of the perpendicular magnetic recording layer of the magnetic recording tape in each embodiment are superior. Based on the comparison between the embodiments and the comparative examples, it is suggested that in the boundary portion of the substrate layer forming the boundary with the SiO2 layer, when the ratio of O content to the total amount of Ru and O is 5% or more, the orientation of the substrate layer tends to increase, and the magnetic recording tape tends to have the desired magnetic properties.

[0066] [Table 1]

[0067]

[0068] A first aspect of the present invention provides a magnetic recording tape comprising:

[0069] Substrate;

[0070] A substrate containing metal; and

[0071] Vertical magnetic recording layer,

[0072] The aforementioned substrate, the aforementioned substrate layer, and the aforementioned perpendicular magnetic recording layer are sequentially disposed in the thickness direction of the aforementioned substrate layer.

[0073] The aforementioned substrate layer has: a boundary portion included in the thickness direction of the aforementioned substrate layer that is closest to the boundary surface of the aforementioned substrate; and a central portion located in the thickness direction of the aforementioned substrate layer between the aforementioned boundary portion and the aforementioned vertical magnetic recording layer.

[0074] The content of the aforementioned metal and elements other than oxygen in the aforementioned boundary region is less than 8% on an atomic basis.

[0075] The oxygen content in the aforementioned boundary portion relative to the total amount of constituent elements and oxygen in the aforementioned central portion is 5% or more, based on atomic number.

[0076] A second aspect of the present invention provides a magnetic recording tape according to the first aspect, wherein the oxygen content in the aforementioned boundary portion is higher than the oxygen content in the aforementioned central portion.

[0077] A third aspect of the present invention provides a magnetic recording tape according to the first or second aspect, the magnetic recording tape further comprising an oxide layer disposed between the aforementioned substrate and the aforementioned substrate layer in the thickness direction of the aforementioned substrate layer.

[0078] A fourth aspect of the present invention provides a magnetic recording tape according to the third aspect, wherein the aforementioned substrate layer is in contact with the aforementioned oxide layer.

[0079] A fifth aspect of the present invention provides a magnetic recording tape according to any one of the first to fourth aspects, wherein the aforementioned substrate comprises a surface having an arithmetic mean roughness Ra of less than 1.0 nm.

[0080] A sixth aspect of the present invention provides a magnetic recording tape according to any one of the first to fifth aspects, wherein the aforementioned substrate layer comprises at least one selected from the group consisting of elemental Ru and Ru-containing alloys.

[0081] A seventh aspect of the present invention provides a magnetic recording tape according to any one of the first to sixth aspects, wherein the aforementioned vertical magnetic recording layer comprises an alloy containing Co.

Claims

1. Magnetic recording tape, which has: Substrate; A substrate containing metal; and Vertical magnetic recording layer, The substrate, the substrate layer, and the perpendicular magnetic recording layer are sequentially arranged in the thickness direction of the substrate layer. The substrate layer has: a boundary portion included in the thickness direction of the substrate layer, which is closest to the boundary surface of the substrate; and a central portion located in the thickness direction of the substrate layer between the boundary portion and the vertical magnetic recording layer. The content of the metal and elements other than oxygen in the boundary region is less than 8% on an atomic basis. The ratio of oxygen content in the boundary portion to the total amount of constituent elements and oxygen in the central portion is 5% or more, based on atomic number.

2. The magnetic recording tape as described in claim 1, wherein, The oxygen content in the boundary portion is higher than the oxygen content in the central portion.

3. The magnetic recording tape as claimed in claim 1, further comprising an oxide layer disposed between the substrate and the substrate layer in the thickness direction of the substrate layer.

4. The magnetic recording tape as described in claim 3, wherein, The base layer is in contact with the oxide layer.

5. The magnetic recording tape as described in claim 1, wherein, The substrate comprises a surface having an arithmetic mean roughness Ra of less than 1.0 nm.

6. The magnetic recording tape as claimed in claim 1, wherein, The base layer comprises at least one selected from the group consisting of elemental Ru and Ru-containing alloys.

7. The magnetic recording tape as claimed in claim 1, wherein, The vertical magnetic recording layer contains a Co-containing alloy.

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