WO2016157681A1 - 磁気記録媒体 - Google Patents
磁気記録媒体 Download PDFInfo
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- WO2016157681A1 WO2016157681A1 PCT/JP2016/000631 JP2016000631W WO2016157681A1 WO 2016157681 A1 WO2016157681 A1 WO 2016157681A1 JP 2016000631 W JP2016000631 W JP 2016000631W WO 2016157681 A1 WO2016157681 A1 WO 2016157681A1
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- protective layer
- recording medium
- magnetic recording
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
- G11B5/735—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer characterised by the back layer
- G11B5/7356—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer characterised by the back layer comprising non-magnetic particles in the back layer, e.g. particles of TiO2, ZnO or SiO2
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B5/584—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on tapes
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
- G11B5/70605—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys
- G11B5/70615—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys containing Fe metal or alloys
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
- G11B5/70605—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys
- G11B5/70621—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys containing Co metal or alloys
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/712—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the surface treatment or coating of magnetic particles
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/714—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the dimension of the magnetic particles
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
- G11B5/733—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer characterised by the addition of non-magnetic particles
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
- G11B5/735—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer characterised by the back layer
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/0036—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties showing low dimensional magnetism, i.e. spin rearrangements due to a restriction of dimensions, e.g. showing giant magnetoresistivity
- H01F1/0045—Zero dimensional, e.g. nanoparticles, soft nanoparticles for medical/biological use
- H01F1/0054—Coated nanoparticles, e.g. nanoparticles coated with organic surfactant
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/0551—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 in the form of particles, e.g. rapid quenched powders or ribbon flakes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/059—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and Va elements, e.g. Sm2Fe17N2
Definitions
- This technology relates to a magnetic recording medium.
- the present invention relates to a magnetic recording medium including a support and a recording layer.
- At least one principal surface of the nonmagnetic support is selected from metals, metalloids and alloys thereof, oxides and composites thereof.
- the formation of a reinforcing layer made of a material is described.
- An object of the present technology is to provide a magnetic recording medium that can improve dimensional stability against humidity change and tension.
- the present technology includes a support, a recording layer, and a protective layer including a plate-like particle powder provided on at least one surface of the support.
- the main surfaces of the plate-like particles overlap with each other in the thickness direction of the protective layer so as to face the surface of the support, and the average plate-like ratio of the plate-like particles is 60 or more.
- the dimensional stability of the magnetic recording medium against humidity change and tension can be improved.
- FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a magnetic recording medium according to an embodiment of the present technology.
- FIG. 2A is a schematic diagram for explaining the plate diameter of the plate-like particles.
- FIG. 2B is a schematic view for explaining the plate thickness of the plate-like particle.
- a magnetic recording medium is a so-called coating-type perpendicular magnetic recording medium, and has a nonmagnetic support 11 and one main surface of the nonmagnetic support 11.
- the protective layer 12a provided, the underlayer 13 provided on the protective layer 12a, the recording layer 14 provided on the underlayer 13, and the protection provided on the other main surface of the nonmagnetic support 11 A layer 12b, and a backcoat layer 15 provided on the protective layer 12b.
- the magnetic recording medium may further include a surface protective layer and a lubricant layer provided on the recording layer 14 as necessary.
- the present technology is suitable for application to a magnetic recording medium in which the average thickness of the recording layer 14 is 100 nm or less and the total thickness of the medium is 6 ⁇ m or less. This is because, in such a magnetic recording medium, improvement in dimensional stability against humidity change and tension is particularly desired.
- the magnetic recording medium according to an embodiment of the present technology has a strip shape.
- the longitudinal direction of the magnetic recording medium is sometimes referred to as MD (Machine Direction) direction
- the width direction of the magnetic recording medium is sometimes referred to as TD (Transverse Direction) direction.
- the nonmagnetic support 11 is, for example, a flexible belt-like film.
- the material of the nonmagnetic support 11 include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose butyrate, polyvinyl chloride, and polyvinylidene chloride. Vinyl resins, polycarbonates, polyimides, polyamideimides and other plastics, light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass. Furthermore, in order to increase the mechanical strength, a thin film containing an oxide of Al or Cu may be provided on at least one of the main surfaces of the nonmagnetic support 11 containing a vinyl resin or the like.
- the protective layers 12a and 12b are films that have a low water vapor transmission rate and can reduce the amount of deformation of the magnetic recording medium with respect to tension so that it is difficult for water to pass through the nonmagnetic support 11.
- the protective layers 12a and 12b contain plate-like particle powder and a binder.
- the protective layers 12a and 12b may further contain various additives such as particle powder having a shape other than plate-like particles, pigments, conductive particles, a curing agent, and a rust preventive as necessary.
- the shape of the plate-like particles is not particularly limited, and is generally polygonal plate-like (eg, almost triangular plate-like, almost square-plate-like, almost hexagonal-plate-like), almost elliptical plate-like, almost disc-like, irregular It may be a plate shape.
- the plate shape includes a scale shape.
- the structure of the plate-like particle is not particularly limited, and a coating layer may be provided on at least a part of the surface of the plate-like particle.
- the plate-like particle powder contained in the protective layer 12 a is overlapped in the thickness direction of the protective layer 12 a so that the main surface of the plate-like particle faces one main surface of the nonmagnetic support 11. That is, the plate-like particle powder is oriented so that the short axis of the plate-like particle powder contained in the protective layer 12a is substantially parallel to the thickness direction of the protective layer 12a. Moreover, the plate-like particle powder contained in the protective layer 12b overlaps in the thickness direction of the protective layer 12b so that the main surface of the plate-like particle faces the other main surface of the nonmagnetic support 11.
- the plate-like particle powder is oriented so that the minor axis of the plate-like particle powder contained in the protective layer 12b is substantially parallel to the thickness direction of the protective layer 12b.
- the plate-like particle powder overlaps over almost the entire range from one main surface to the other main surface of the protective layers 12a and 12b. It is preferable. However, even when the plate-like particle powder overlaps in a part of the range from one main surface to the other main surface of the protective layers 12a and 12b, the effect of dimensional stability can be obtained.
- the plate-like particles include, for example, organic particles, inorganic particles, or organic-inorganic hybrid particles.
- the plate-like particles are at least one of clay and ferrite, for example.
- One type of plate-like particle may be included in the protective layers 12a and 12b, or two or more types.
- the kind of the plate-like particle contained in the protective layer 12a and the plate-like particle contained in the protective layer 12b may be different.
- Clay is, for example, kaolinite, dickite, halloysite, chrysotile, lizardite, amesite, pyrophyllite, talc, montmorillonite, beidellite, nontronite, stevensite, saponite, hectorite, soconite, octahedral vermiculite, 3 It includes one or more selected from the group consisting of octahedral vermiculite, muscovite, paragonite, illite, sericite, phlogopite, biotite, lipidoid, magadiite, isralite and kanemite.
- the ferrite includes, for example, one or more selected from the group consisting of barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and ⁇ -iron oxide.
- the average thickness Dm of the protective layers 12a and 12b is preferably 30 nm to 500 nm, more preferably 100 nm to 500 nm, even more preferably 150 nm to 500 nm, and particularly preferably 200 nm to 500 nm.
- the average thickness Dm is 30 nm or more, the dimensional stability of the magnetic recording medium against humidity change and tension can be further improved.
- the average thickness Dm is 500 nm or less, the total thickness of the magnetic recording medium can be reduced.
- the average thickness Dm of the protective layer 12a is obtained as follows. First, a magnetic recording medium is cut out perpendicularly to the main surface, and the cross section is observed with a transmission electron microscope (TEM). Next, 10 points are selected at random from the observed TEM image, and the thickness D of the protective layer 12a is measured at each of these points. Next, these measured values D are simply averaged (arithmetic average) to determine the average thickness Dm of the protective layer 12a. Below, the measurement conditions of TEM are shown. Equipment: TEM (Hitachi, H9000NAR) Acceleration voltage: 300kV Magnification: 100,000 times The average thickness of the protective layer 12b is also determined in the same manner as the above-described method for determining the average thickness Dm of the protective layer 12a.
- TEM Transmission electron microscope
- Plate-like particles are, for example, plate-like nanoparticles.
- the plate-like nanoparticles are those having an average plate thickness Tm of 1 nm or more and 100 nm or less.
- the average plate thickness Tm of the plate-like particles is preferably 1 nm to 50 nm, more preferably 1 nm to 10 nm, even more preferably 1 nm to 8 nm, and particularly preferably 1 nm to 5 nm.
- the average plate-like ratio (Rm / Tm) of the plate-like particles is 60 or more, preferably 60 or more and 1000 or less, more preferably 200 or more and 1000 or less.
- the average plate ratio (Rm / Tm) is 60 or more, the dimensional stability of the magnetic recording medium against humidity change and tension can be improved.
- the average plate ratio (Rm / Tm) is 1000 or less, the plate-like particle powder can be easily handled.
- the plate diameter R of the plate-like particles means the minimum passing length (minimum diameter) of the main surface of the plate-like particles as shown in FIG. 2A.
- the plate thickness T of the plate-like particle means the maximum thickness of the side surface of the plate-like particle as shown in FIG. 2B.
- the plate thickness ratio of the plate-like particles is the ratio (R / T) of the plate diameter R of the plate-like particles to the plate thickness T of the plate-like particles.
- the average plate thickness Tm of the plate-like particles is obtained as follows. First, the magnetic recording medium is cut out perpendicularly to the main surface, and the cross section is observed with a TEM. Next, from the observed TEM image, hundreds of plate-like particles capable of observing the side surface (the thinnest surface of the plate-like particles observed in the TEM image) are randomly selected, and these plate-like particles are selected. Each plate thickness T is obtained. Next, the average plate thickness Tm is obtained by simply averaging (arithmetic average) the plate thickness T of several hundred plate-like particles. Below, the measurement conditions of TEM are shown. Equipment: TEM (Hitachi, H9000NAR) Acceleration voltage: 300kV Magnification: 100,000 times
- the average plate diameter Rm of the plate-like particles is determined as follows. First, the magnetic recording medium is cut out perpendicularly to the main surface, and the cross section is observed with a TEM. Next, from the observed TEM image, hundreds of plate-like particles capable of observing the principal surface (the largest surface among the plate-like particles observed in the TEM image) are randomly selected and their plate-like shape is selected. The plate diameter R of each particle is obtained. Next, the average plate diameter Rm is obtained by simply averaging (arithmetic average) the plate diameters R of the obtained hundreds of plate-like particles. Below, the measurement conditions of TEM are shown. Equipment: TEM (Hitachi, H9000NAR) Acceleration voltage: 300kV Magnification: 100,000 times
- the ratio (Rm / Tm) of the average plate diameter Rm of the plate-like particles to the average plate thickness Tm of the plate-like particles is obtained using the average plate thickness Tm and the average plate diameter Rm of the plate-like particles obtained as described above. .
- the ratio (Dm / Tm) of the average thickness Dm of the protective layer 12a to the average plate thickness Tm of the plate-like particles is preferably 30 or more and 500 or less, more preferably 60 or more and 500 or less, and even more preferably 100 or more and 500 or less, particularly Preferably they are 200 or more and 500 or less.
- the ratio (Dm / Tm) is 30 or more, the dimensional stability of the magnetic recording medium against humidity change and tension can be further improved.
- the ratio (Dm / Tm) is 500 or less, the total thickness of the magnetic recording medium can be reduced.
- the binder a resin having a structure in which a crosslinking reaction is imparted to a polyurethane resin, a vinyl chloride resin, or the like is preferable.
- the binder is not limited to these, and other resins may be appropriately blended depending on the physical properties required for the magnetic recording medium.
- the resin to be blended is not particularly limited as long as it is a resin generally used in a coating type magnetic recording medium.
- thermosetting resins or reactive resins examples include phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, urea formaldehyde resins, and the like.
- Each binder described above is introduced with a polar functional group such as —SO 3 M, —OSO 3 M, —COOM, P ⁇ O (OM) 2 for the purpose of improving the dispersibility of the magnetic powder. It may be.
- M in the formula is a hydrogen atom or an alkali metal such as lithium, potassium, or sodium.
- examples of the polar functional group include a side chain type having terminal groups of —NR1R2 and —NR1R2R3 + X—, and a main chain type of> NR1R2 + X—.
- R1, R2, and R3 in the formula are hydrogen atoms or hydrocarbon groups
- X- is a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion.
- examples of the polar functional group include —OH, —SH, —CN, and an epoxy group.
- a polyisocyanate may be used in combination with the resin, and this may be cross-linked and cured.
- the polyisocyanate include toluene diisocyanate and adducts thereof, alkylene diisocyanate, and adducts thereof.
- the protective layers 12a and 12b further include additives such as particle powders and pigments having shapes other than the plate-like particle powders, from the viewpoint of improving the dimensional stability of the magnetic recording medium against changes in humidity and tension,
- the ratio of the plate-like particle powder to the total amount of the particle powder and the additive is preferably 90 Vol% or more.
- the underlayer 13 is a nonmagnetic layer containing nonmagnetic powder and a binder.
- the underlayer 13 may further contain various additives such as conductive particles, a lubricant, an abrasive, a curing agent, and a rust preventive as necessary.
- the nonmagnetic powder may be an inorganic substance or an organic substance. Carbon black can also be used.
- the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides.
- the shape of the nonmagnetic powder include various shapes such as a needle shape, a spherical shape, and a plate shape, but are not limited thereto.
- the binder is the same as the protective layers 12a and 12b described above.
- the conductive particles fine particles containing carbon as a main component, for example, carbon black can be used.
- carbon black for example, Asahi # 15, # 15HS manufactured by Asahi Carbon Co., Ltd. can be used.
- Examples of the lubricant include esters of monobasic fatty acids having 10 to 24 carbon atoms and any of monohydric to hexahydric alcohols having 2 to 12 carbon atoms, mixed esters thereof, difatty acid esters, and trifatty acid esters. Can be used as appropriate.
- lubricants include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, butyl stearate, pentyl stearate, heptyl stearate, octyl stearate , Isooctyl stearate, octyl myristate, and the like.
- abrasive for example, ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, ⁇ carbide of 90% or more, silicon carbide, chromium oxide, cerium oxide, ⁇ -iron oxide, corundum, silicon nitride, titanium carbide, oxide Needle-like ⁇ obtained by dehydrating and annealing titanium, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and magnetic iron oxide Iron oxide and, if necessary, surface-treated with aluminum and / or silica are used alone or in combination.
- the recording layer 14 is a perpendicular recording layer capable of, for example, short wavelength recording or ultrashort wave super recording.
- the recording layer 14 is a magnetic layer having magnetic anisotropy in the thickness direction of the recording layer 14. That is, the easy axis of magnetization of the recording layer 14 is oriented in the thickness direction of the recording layer 14.
- the average thickness of the recording layer 14 is preferably 30 nm to 100 nm, more preferably 50 nm to 70 nm.
- the average thickness of the recording layer 14 is obtained in the same manner as the average thickness Dm of the protective layers 12a and 12b described above.
- the recording layer 14 is a magnetic layer containing, for example, magnetic powder and a binder.
- the recording layer 14 may further contain various additives such as conductive particles, a lubricant, an abrasive, a curing agent, and a rust preventive as necessary.
- Magnetic powder is cubic ferrite magnetic powder.
- magnetic powder composed of cubic ferrite magnetic particles is referred to as cubic ferrite magnetic powder.
- the magnetic recording medium has a high S / N ratio.
- a higher output tends to be obtained when the coercive force Hc is higher due to the influence of the demagnetizing field.
- the higher coercive force is excellent in thermal stability when microparticulated.
- the next generation magnetic recording medium preferably has a high coercive force Hc.
- cubic ferrite magnetic powder having a high possibility of developing a coercive force Hc higher than that of hexagonal barium ferrite magnetic powder is used.
- the cubic ferrite magnetic powder has a cubic shape or a substantially cubic shape.
- “cubic ferrite magnetic powder is almost cubic” means that the average plate ratio (average aspect ratio (average plate diameter L AM / average plate thickness L BM )) of cubic ferrite magnetic powder is 0.75 or more.
- a rectangular parallelepiped that is 1.25 or less. Since the cubic ferrite magnetic powder has a small unit cell size, it is advantageous from the viewpoint of ultrafine particles in the future.
- the cubic ferrite magnetic powder is dispersed in the recording layer 14.
- the easy axis of the cubic ferrite magnetic powder is oriented in the thickness direction of the recording layer 14 or substantially in the thickness direction of the recording layer 14. That is, the cubic ferrite magnetic powder is dispersed in the recording layer 14 such that the square surface thereof is perpendicular or almost perpendicular to the thickness direction of the recording layer 14.
- the contact area between the particles in the thickness direction of the medium can be reduced and aggregation of the particles can be suppressed as compared with the hexagonal barium ferrite magnetic powder. That is, the dispersibility of the magnetic powder can be enhanced.
- the square surface of the cubic ferrite magnetic powder is exposed from the surface of the recording layer 14.
- Performing short wavelength recording on the square surface with a magnetic head is advantageous in terms of high density recording compared to performing short wavelength recording on the hexagonal surface of a hexagonal plate-like barium ferrite magnetic powder having the same volume. It is. From the viewpoint of high density recording, the surface of the recording layer 14 is preferably covered with a square surface of cubic ferrite magnetic powder.
- the cubic ferrite magnetic particles are so-called spinel ferrimagnetic particles.
- the cubic ferrite magnetic particles are iron oxide particles having cubic ferrite as a main phase.
- the cubic ferrite contains one or more selected from the group consisting of Co, Ni, Mn, Al, Cu and Zn.
- the cubic ferrite contains at least Co, and further contains at least one selected from the group consisting of Ni, Mn, Al, Cu and Zn in addition to Co. More specifically, for example, cubic ferrite has an average composition represented by the general formula MFe 2 O 4 .
- M is one or more metals selected from the group consisting of Co, Ni, Mn, Al, Cu and Zn.
- M is a combination of Co and one or more metals selected from the group consisting of Ni, Mn, Al, Cu and Zn.
- the average plate diameter (average particle size) of the cubic ferrite magnetic powder is preferably 14 nm or less, more preferably 10 nm or more and 14 nm or less.
- the average plate diameter exceeds 14 nm, the exposed area of particles on the medium surface increases, and the S / N ratio may decrease.
- the average plate diameter is less than 10 nm, it may be difficult to produce cubic ferrite magnetic powder.
- the average plate ratio (average aspect ratio (average plate diameter L AM / average plate thickness L BM )) of the cubic ferrite magnetic powder is preferably 0.75 or more and 1.25 or less. If the average plate ratio is out of this numerical range, the cubic ferrite magnetic powder does not have a cubic or almost cubic shape, and thus aggregation occurs, which may make short wavelength recording difficult.
- the binder is the same as the protective layers 12a and 12b described above.
- the conductive particles, the lubricant and the abrasive are the same as those of the above-described underlayer 13.
- the recording layer 14 includes non-magnetic reinforcing particles such as aluminum oxide ( ⁇ , ⁇ or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide ( Rutile type or anatase type titanium oxide) and the like.
- non-magnetic reinforcing particles such as aluminum oxide ( ⁇ , ⁇ or ⁇ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide ( Rutile type or anatase type titanium oxide) and the like.
- the back coat layer 15 contains a binder, inorganic particles, and a lubricant.
- the back coat layer 15 may contain various additives such as a curing agent and an antistatic agent as necessary.
- the binder, inorganic particles, and lubricant are the same as those of the above-described underlayer 13.
- a coating material for forming a protective layer is prepared by kneading and dispersing a plate-like particle powder and a binder in a solvent.
- a non-magnetic powder, a binder, and the like are kneaded and dispersed in a solvent to prepare an underlayer-forming coating material.
- a recording powder for forming a recording layer is prepared by kneading and dispersing magnetic powder, a binder and the like in a solvent.
- a backcoat layer-forming coating material is prepared by kneading and dispersing a binder, inorganic particles, a lubricant, and the like in a solvent.
- the underlayer-forming coating material for example, the following solvents, dispersion devices, and kneading devices can be applied.
- Examples of the solvent used in the above-mentioned coating preparation include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohol solvents such as methanol, ethanol, and propanol, methyl acetate, ethyl acetate, butyl acetate, and propyl acetate.
- ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone
- alcohol solvents such as methanol, ethanol, and propanol, methyl acetate, ethyl acetate, butyl acetate, and propyl acetate.
- Ester solvents such as ethyl lactate and ethylene glycol acetate, ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane, aromatic hydrocarbon solvents such as benzene, toluene and xylene, methylene chloride, ethylene chloride, Halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, chlorobenzene and the like. These may be used singly or may be mixed as appropriate.
- Examples of the kneading apparatus used for the coating preparation described above include a continuous biaxial kneader, a continuous biaxial kneader capable of diluting in multiple stages, a kneader, a pressure kneader, and a roll kneader.
- the present invention is not particularly limited to these devices.
- a dispersing device such as a sonic disperser can be used, but is not particularly limited to these devices.
- the coating material for forming the protective layer is applied to one main surface of the belt-like nonmagnetic support 11 to form a coating film.
- the coating material for forming the protective layer is applied to one main surface of the nonmagnetic support 11
- the plate-like particle powder contained in the coating film has the main surface of the plate-like particles opposed to one main surface of the nonmagnetic support 11.
- the protective layer 12a is naturally oriented so as to overlap in the thickness direction. That is, the plate-like particle powder is oriented so that the minor axis of the plate-like particle powder contained in the protective layer 12a is substantially parallel to the thickness direction of the protective layer 12a.
- the plate-like particle powder contained in the coating film may be magnetically oriented.
- the protective layer 12a is formed on one main surface of the nonmagnetic support 11 by drying the coating film.
- the other main surface of the nonmagnetic support 11 is formed in the same manner as the protective layer 12a described above except that the coating for forming the protective layer is applied to the other main surface of the strip-shaped nonmagnetic support 11. Then, the protective layer 12b is formed.
- the base layer 13 is formed on the protective layer 12a by applying a base layer-forming paint on the protective layer 12a formed on one main surface of the nonmagnetic support 11 and drying it.
- the recording layer 14 is formed on the underlayer 13 by applying a recording layer-forming paint on the underlayer 13 and drying it.
- the cubic ferrite magnetic powder contained in the magnetic powder is magnetically oriented so that the easy axis of magnetization of the cubic ferrite magnetic powder is oriented in the thickness direction of the recording layer 14 or substantially the recording layer 14. It is preferable to direct in the thickness direction.
- the backcoat layer 15 is formed by applying a coating material for forming a backcoat layer on the protective layer 12b formed on the other main surface of the nonmagnetic support 11 and drying it. Thereby, a wide magnetic recording medium is obtained.
- the obtained wide magnetic recording medium is rewound around a large-diameter core, and a curing process is performed.
- a calendar process is performed on the wide magnetic recording medium, and then cut into a predetermined width. Thereby, the intended magnetic recording medium is obtained.
- the step of forming the back coat layer 15 may be after the calendar process.
- protective layers 12 a and 12 b containing plate-like particle powder are provided on both surfaces of the nonmagnetic support 11.
- the plate-like particle powder is overlapped in the thickness direction of the protective layers 12a and 12b so that the main surface of the plate-like particle faces the main surface of the nonmagnetic support 11, and the average plate-like ratio of the plate-like particles Is 60 or more.
- a general polymer resin such as polyethylene (PE) is used as a material for the nonmagnetic support 11 even in a magnetic recording medium that requires high performance.
- PE polyethylene
- the configuration in which the protective layers 12a and 12b are provided on both surfaces of the nonmagnetic support 11 has been described as an example. However, at least one main surface of the nonmagnetic support 11 or the nonmagnetic support is described. You may employ
- FIG. When a protective layer is provided on any one of the main surfaces of the nonmagnetic support 11, from the viewpoint of improving dimensional stability against humidity change and tension, the recording layer 14 of the two main surfaces of the nonmagnetic support 11 is It is preferable to provide a protective layer on the opposite main surface.
- the protective layer in one embodiment described above may be provided on any one main surface of the nonmagnetic support 11, and a general protective layer may be provided on the other main surface. Moreover, you may laminate
- the general protective layer means a protective layer used for the purpose of dimensional stability in the technical field of magnetic recording media.
- a general protective film for example, a thin film formed by a vacuum thin film manufacturing technique such as vapor deposition or a sputtered film can be cited.
- the reinforcement layer of patent documents 1 and 2 is mentioned, for example.
- the magnetic recording medium is a perpendicular magnetic recording medium
- the magnetic recording medium may be a horizontal magnetic recording medium.
- the magnetic powder is not limited to this example, and a perpendicular magnetic recording medium or horizontal magnetic recording medium is used. Those generally used in can be used.
- Specific examples of the magnetic powder include Fe-based and Fe-Co-based metal powders, barium ferrite, iron carbide, and iron oxide.
- the underlayer 13 and the recording layer 14 are thin films produced by a coating process (wet process) has been described.
- the underlayer 13 and the recording layer 14 are produced by vacuum thin films such as sputtering. It may be a thin film produced by a technique (dry process).
- the formation process of the protective layer 12a and the foundation layer 13 is not limited to the above example.
- a coating for forming a protective layer is applied to one main surface of the non-magnetic support 11 to form a coating film, and a coating for forming a base layer is applied over the coating film in a wet state.
- the protective layer 12a and the underlayer 13 may be formed on one main surface of the nonmagnetic support 11 by drying both coating films.
- the formation process of the underlayer 13 and the recording layer 14 is not limited to the above example.
- a coating for forming a base layer is applied to one main surface of the protective layer 12a to form a coating film, and a coating for forming a recording layer is applied over the coating film in a wet state to form a coating film.
- the undercoat layer 13 and the recording layer 14 may be formed on one main surface of the protective layer 12a by drying both coating films. Note that the formation process of the underlayer 13 and the recording layer 14 may be combined with the above-described modification of the formation process of the protective layer 12a and the underlayer 13.
- the configuration in which the base layer 13 is provided between the protective layer 12a and the recording layer 14 has been described as an example.
- the base layer 13 is provided as necessary.
- a configuration without 13 may be adopted.
- the configuration in which the back coat layer 15 is provided on the protective layer 12b has been described as an example, but the back coat layer 15 is provided as necessary, and a configuration in which the back coat layer 15 is not provided is adopted. May be.
- the average thickness Dm of the protective layer was determined as described in the above-described embodiment.
- Average thickness of underlayer and recording layer In this example, the average thickness of the underlayer and the recording layer was obtained in the same manner as the above-mentioned “average thickness Dm of the protective layer”.
- the average plate thickness Tm of the plate-like particle powder was determined as described in the above-described embodiment.
- the average plate diameter Rm of the plate-like particle powder was determined as described in the above-described embodiment.
- the average minor axis diameter Tm of the acicular particles is the same as that described above except that the minor axis diameter T of several hundred acicular particles is obtained from the cross-sectional TEM image and is simply averaged (arithmetic average).
- the “average plate thickness Tm of the plate-like particle powder” was obtained in the same manner.
- the average major axis diameter Rm of the acicular particles is the same as that described above except that the major axis diameter R of several hundred acicular particles is obtained from the cross-sectional TEM image and is simply averaged (arithmetic average). It was calculated
- the average needle ratio Rm / Tm of the acicular particle powder was determined using the average minor axis diameter Tm and the average major axis diameter Rm of the acicular particles obtained as described above.
- the ratio of the average thickness Dm of the protective layer to the average minor axis diameter Tm of the acicular particle powder is the average minor axis diameter Tm of the acicular particles determined as described above and the protective layer. The average thickness Dm was obtained.
- the ratio (Dm / Tm) of the average thickness Dm of the protective layer to the average diameter Tm of the spherical particle powder is the average particle diameter Tm of the spherical particles and the average thickness Dm of the protective layer obtained as described above. It was calculated using.
- Example 1 (Preparation process of recording layer forming paint) A recording layer-forming coating material was prepared as follows. First, the following raw materials were kneaded with an extruder to obtain a kneaded product.
- CoNi ferrite crystal magnetic powder 100 parts by mass (shape: almost cubic shape, average plate diameter: 11 nm, average plate ratio: 0.95)
- Aluminum oxide powder 5 parts by mass ( ⁇ -Al 2 O 3 , average particle size 0.2 ⁇ m)
- Carbon black 2 parts by mass (trade name: Seast TA, manufactured by Tokai Carbon Co., Ltd.)
- Vinyl chloride resin 27.8 parts by mass (resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
- Polyisocyanate 4 parts by mass (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.)
- Myristic acid 2 parts by mass n-butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass
- a paint for forming the underlayer was prepared as follows. First, the following raw materials were kneaded with an extruder to obtain a kneaded product.
- Acicular iron oxide powder 100 parts by mass ( ⁇ -Fe 2 O 3 , average major axis length 0.15 ⁇ m)
- Vinyl chloride resin 55.6 parts by mass (resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
- Carbon black 10 parts by mass (average particle size 20 nm)
- a coating for forming a protective layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and filtered to prepare a protective layer-forming coating material.
- Barium ferrite 100 parts by mass (shape: plate, average plate ratio Rm / Tm: 60, average plate thickness Tm: 4 nm, average plate diameter Rm: 240)
- Methyl ethyl ketone 250 parts by mass Toluene: 2000 parts by mass
- a paint for forming a backcoat layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and filtered to prepare a backcoat layer-forming coating material.
- Carbon black (Asahi Co., Ltd., trade name: # 80): 100 parts by mass Polyester polyurethane: 100 parts by mass (Nippon Polyurethanes, trade name: N-2304) Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass
- a protective layer, an underlayer and a recording layer were formed as follows. First, a protective layer-forming coating material is applied onto one main surface of a nonmagnetic support, a thickness of 6.2 ⁇ m, and a strip-shaped PEN film, and dried, whereby an average is formed on one main surface of the PEN film. A protective layer having a thickness of 150 nm was formed. Next, an undercoat layer having an average thickness of 1 ⁇ m was formed on the protective layer by applying and drying a base layer-forming coating material on the protective layer. Next, a recording layer-forming coating material was applied on the underlayer and dried to form a recording layer having an average thickness of 70 nm on the underlayer. Note that the magnetic powder was magnetically oriented during drying.
- the obtained wide magnetic tape was calendered with a metal roll to smooth the recording layer surface.
- the wide magnetic tape was cut into a width of 1/2 inch (12.65 mm) to obtain a target magnetic tape.
- Example 2 In the preparation process of the protective layer-forming paint, ⁇ -iron oxide (shape: plate, average plate ratio Rm / Tm: 60, average plate thickness Tm: 10 nm, average plate diameter Rm: 600 nm) is used instead of barium ferrite. Using. In the protective layer forming step, the average thickness of the protective layer was changed to 300 nm. Except for this, a magnetic tape was obtained in the same manner as in Example 1.
- Example 3 In the process of preparing the protective layer-forming coating material, mica (shape: plate, average plate ratio Rm / Tm: 200, average plate thickness Tm: 5 nm, average plate diameter Rm: 1000 nm) was used instead of barium ferrite. Except for this, a magnetic tape was obtained in the same manner as in Example 1.
- Example 4 Montmorillonite (shape: plate, average plate ratio Rm / Tm: 300, average plate thickness Tm: 1 nm, average plate diameter Rm: 300 nm) was used in place of the barium ferrite in the preparation process of the protective layer forming coating. Except for this, a magnetic tape was obtained in the same manner as in Example 1.
- Example 5 Montmorillonite (shape: plate, average plate ratio Rm / Tm: 300, average plate thickness Tm: 2 nm, average plate diameter Rm: 600 nm) was used in the process of preparing the protective layer-forming paint. In the protective layer forming step, the average thickness of the protective layer was changed to 40 nm. Except for this, a magnetic tape was obtained in the same manner as in Example 4.
- Example 6 In the protective layer forming step, protective layers having an average thickness of 250 nm were formed on both sides of the PEN film. In the underlayer forming step, the average underlayer thickness was changed to 0.6 ⁇ m. Except for this, a magnetic tape was obtained in the same manner as in Example 4.
- Example 7 In the protective layer forming step, protective layers having an average thickness of 100 nm were formed on both sides of the PEN film. Except for this, a magnetic tape was obtained in the same manner as in Example 4.
- Example 1 A base layer was directly formed without forming a protective layer on one main surface of the PEN film. Except for this, a magnetic tape was obtained in the same manner as in Example 1.
- E Young's modulus
- JIS-K7133 and ASTM D882 E (Young's modulus) is the value obtained by dividing the tensile strength giving 1% elongation by the initial film cross-sectional area measured with a sample width of 6.25 mm x sample execution length of 100 mm and a pulling speed of 200 mm / min. It was. The results are shown in Table 1.
- Table 1 shows the configurations and evaluation results of the magnetic tapes of Examples 1 to 7 and Comparative Examples 1 to 5.
- Tm Average thickness of the protective layer
- Tm When the particle shape is plate-like, Tm means the average plate thickness.
- Tm When the particle shape is acicular, Tm means the average minor axis diameter.
- Tm When the particle shape is spherical, Tm means an average diameter.
- Rm When the particle shape is plate-like, Rm means an average plate diameter.
- Rm When the particle shape is acicular, Rm means the average major axis diameter.
- the plate-like particle powder is overlapped in the thickness direction of the protective layer so that the main surface of the plate-like particle faces the main surface of the support, and It can be seen that when the average plate ratio of the plate-like particle powder is 60 or more, an effect of suppressing dimensional deformation against humidity change and tension (hereinafter referred to as “dimensional deformation suppressing effect”) is obtained. From the evaluation results of Examples 1, 3, 4, and Comparative Example 5, it can be seen that as the average plate-like ratio of the plate-like particles is larger, the effect of suppressing dimensional deformation is improved.
- the present technology can also employ the following configurations.
- the magnetic recording medium according to (1) or (2), wherein the ratio (Dm / Tm) of the average thickness Dm of the protective layer to the average plate thickness Tm of the plate-like particles is 30 or more.
- the above clays are kaolinite, dickite, halloysite, chrysotile, lizardite, amesite, pyrophyllite, talc, montmorillonite, beidellite, nontronite, stevensite, saponite, hectorite, soconite, octahedral vermiculite, 38
Abstract
Description
1 磁気記録媒体の構成
2 磁気記録媒体の製造方法
3 効果
4 変形例
図1に示すように、本技術の一実施形態に係る磁気記録媒体は、いわゆる塗布型の垂直磁気記録媒体であり、非磁性支持体11と、非磁性支持体11の一方の主面上に設けられた保護層12aと、保護層12a上に設けられた下地層13と、下地層13上に設けられた記録層14と、非磁性支持体11の他方の主面上に設けられた保護層12bと、保護層12b上に設けられたバックコート層15とを備える。磁気記録媒体が、必要に応じて、記録層14上に設けられた表面保護層および潤滑剤層などをさらに備えるようにしてもよい。
非磁性支持体11は、例えば、可撓性を有する帯状のフィルムである。非磁性支持体11の材料としては、例えば、ポリエチレンテレフタレートなどのポリエステル類、ポリエチレン、ポリプロピレンなどのポリオレフィン類、セルローストリアセテート、セルロースダイアセテート、セルロースブチレートなどのセルロース誘導体、ポリ塩化ビニル、ポリ塩化ビニリデンなどのビニル系樹脂、ポリカーボネート、ポリイミド、ポリアミドイミドなどのプラスチック、アルミニウム合金、チタン合金などの軽金属、アルミナガラスなどのセラミックなどを用いることができる。さらには、機械的強度を高めるために、AlまたはCuの酸化物を含む薄膜を、ビニル系樹脂などを含む非磁性支持体11の主面のうち少なくとも一方に設けてもよい。
保護層12a、12bは、非磁性支持体11に水分を透過しにくいように水蒸気透過率の低く、かつ、張力に対する磁気記録媒体の変形量を少なくすることか可能な膜である。保護層12a、12bは、板状粒子粉および結着剤を含んでいる。保護層12a、12bは、必要に応じて板状粒子以外の形状の粒子粉、顔料、導電性粒子、硬化剤、防錆剤などの各種添加剤をさらに含んでいてもよい。
以下に、TEMの測定条件を示す。
装置:TEM(日立製作所製、H9000NAR)
加速電圧:300kV
倍率:100000倍
なお、保護層12bの平均厚さも、上述の保護層12aの平均厚さDmの求め方と同様にして求められる。
以下に、TEMの測定条件を示す。
装置:TEM(日立製作所製、H9000NAR)
加速電圧:300kV
倍率:100000倍
以下に、TEMの測定条件を示す。
装置:TEM(日立製作所製、H9000NAR)
加速電圧:300kV
倍率:100000倍
下地層13は、非磁性粉および結着剤を含む非磁性層である。下地層13が、必要に応じて、導電性粒子、潤滑剤、研磨剤、硬化剤および防錆剤などの各種添加剤をさらに含んでいてもよい。
記録層14は、例えば、短波長記録または超短波超記録が可能な垂直記録層である。記録層14は、記録層14の厚さ方向に磁気異方性を有する磁性層である。すなわち、記録層14の磁化容易軸は、記録層14の厚さ方向に向いている。記録層14の平均厚さは、好ましくは30nm以上100nm以下、より好ましくは50nm以上70nm以下である。なお、記録層14の平均厚さは、上述の保護層12a、12bの平均厚さDmと同様にして求められる。
バックコート層15は、結着剤、無機粒子および潤滑剤を含んでいる。バックコート層15が、必要に応じて硬化剤および帯電防止剤などの各種添加剤を含んでいてもよい。結着剤、無機粒子および潤滑剤は、上述の下地層13と同様である。
次に、上述の構成を有する磁気記録媒体の製造方法の一例について説明する。
まず、板状粒子粉および結着剤などを溶剤に混練、分散させることにより、保護層形成用塗料を調製する。次に、非磁性粉および結着剤などを溶剤に混練、分散させることにより、下地層形成用塗料を調製する。次に、磁性粉および結着剤などを溶剤に混練、分散させることにより、記録層形成用塗料を調製する。次に、結着剤、無機粒子および潤滑剤などを溶剤に混練、分散させることにより、バックコート層形成用塗料を調製する。保護層形成用塗料、下地層形成用塗料、記録層形成用塗料およびバックコート層形成用塗料の調製には、例えば、以下の溶剤、分散装置および混練装置を適用することができる。
次に、保護層形成用塗料を帯状の非磁性支持体11の一方の主面に塗布して、塗膜を形成する。保護層形成用塗料を非磁性支持体11の一方の主面に塗布すると、塗膜に含まれる板状粒子粉は、板状粒子の主面が非磁性支持体11の一方の主面に対向するとともに、保護層12aの厚さ方向に重なり合うように自然に配向する。すなわち、保護層12aに含まれる板状粒子粉の短軸が保護層12aの厚さ方向にほぼ平行になるように、板状粒子粉は配向する。但し、必要に応じて、塗膜に含まれる板状粒子粉を磁場配向させるようにしてもよい。次に、塗膜を乾燥させることにより、非磁性支持体11の一方の主面に保護層12aを形成する。
次に、非磁性支持体11の一方の主面に形成された保護層12a上に下地層形成用塗料を塗布して乾燥させることにより、下地層13を保護層12a上に形成する。
次に、下地層13上に記録層形成用塗料を塗布して乾燥させることにより、記録層14を下地層13上に形成する。なお、乾燥の際に、磁性粉に含まれる立方晶フェライト磁性粉を磁場配向させることにより、立方晶フェライト磁性粉の磁化容易軸を記録層14の厚さ方向に向けるか、もしくはほぼ記録層14の厚さ方向に向けることが好ましい。
次に、非磁性支持体11の他方の主面に形成された保護層12b上にバックコート層形成用塗料を塗布して乾燥させることにより、バックコート層15を形成する。これにより、幅広の磁気記録媒体が得られる。
次に、得られた幅広の磁気記録媒体を大径コアに巻き直し、硬化処理を行う。次に、幅広の磁気記録媒体に対してカレンダー処理を行った後、所定の幅に裁断する。これにより、目的とする磁気記録媒体が得られる。なお、バックコート層15を形成する工程は、カレンダー処理後であってもよい。
本技術の一実施形態に係る磁気記録媒体では、非磁性支持体11の両面に板状粒子粉を含む保護層12a、12bが設けられている。この板状粒子粉は、板状粒子の主面が非磁性支持体11の主面に対向するように保護層12a、12bの厚さ方向に重なり合っており、また板状粒子の平均板状比は60以上である。これにより、非磁性支持体11に水分が到達しにくくなるので、湿度変化に対する寸法安定性を向上できる。また、長手方向および幅方向の両方向において、引っ張りおよび圧縮に対して変形しにくく、ポアソン比も小さくできるため、張力変形を小さくできる。
上述の一実施形態では、非磁性支持体11の両面に保護層12a、12bが設けられている構成を例として説明したが、非磁性支持体11の少なくも一方の主面、または非磁性支持体11のいずれか一方の主面に保護層が設けられている構成を採用してもよい。非磁性支持体11のいずれか一方の主面に保護層を設ける場合、湿度変化や張力に対する寸法安定性向上の観点からすると、非磁性支持体11の両主面のうち、記録層14とは反対側の主面に保護層を設けることが好ましい。
本実施例において、保護層の平均厚さDmは、上述の一実施形態にて説明したようにして求められた。
本実施例において、下地層および記録層の平均厚さは、上述の「保護層の平均厚さDm」と同様にして求められた。
本実施例において、板状粒子粉の平均板厚Tmは、上述の一実施形態にて説明したようにして求められた。
本実施例において、板状粒子粉の平均板径Rmは、上述の一実施形態にて説明したようにして求められた。
本実施例において、板状粒子粉の平均板状比Rm/Tmは、上述の一実施形態にて説明したようにして求められた。
本実施例において、板状粒子粉の平均板厚Tmに対する保護層の平均厚さDmの割合(Dm/Tm)は、上述の一実施形態にて説明したようにして求められた。
本実施例において、針状粒子の平均短軸径Tmは、断面TEM像から数百個の針状粒子の短軸径Tを求めて、それらを単純に平均(算術平均)する以外は、上述の「板状粒子粉の平均板厚Tm」と同様にして求められた。
本実施例において、針状粒子の平均長軸径Rmは、断面TEM像から数百個の針状粒子の長軸径Rを求めて、それらを単純に平均(算術平均)する以外は、上述の「板状粒子粉の平均板径Rm」と同様にして求められた。
本実施例において、針状粒子粉の平均針状比Rm/Tmは、上述のように求めた針状粒子の平均短軸径Tmおよび平均長軸径Rmを用いて求められた。
本実施例において、針状粒子粉の平均短軸径Tmに対する保護層の平均厚さDmの割合(Dm/Tm)は、上述のように求めた針状粒子の平均短軸径Tmおよび保護層の平均厚さDmを用いて求められた。
本実施例において、球状粒子の平均直径Tm(=Rm)は、断面TEM像から数百個の球状粒子の直径Tを求めて、それらを単純に平均(算術平均)する以外は、上述の「板状粒子粉の平均板厚Tm」と同様にして求められた。
本実施例において、球状粒子粉の平均直径Tmに対する保護層の平均厚さDmの割合(Dm/Tm)は、上述のように求めた球状粒子の平均粒径Tmおよび保護層の平均厚さDmを用いて求められた。
(記録層形成用塗料の調製工程)
記録層形成用塗料を次のようにして調製した。まず、下記原料をエクストルーダで混練して混練物を得た。
CoNiフェライト結晶磁性粉:100質量部
(形状:ほぼ立方体形状、平均板径:11nm、平均板状比:0.95)
塩化ビニル系樹脂(シクロヘキサノン溶液30質量%):55.6質量部
(重合度300、Mn=10000、極性基としてOSO3K=0.07mmol/g、2級OH=0.3mmol/gを含有する。)
酸化アルミニウム粉末:5質量部
(α-Al2O3、平均粒径0.2μm)
カーボンブラック:2質量部
(東海カーボン社製、商品名:シーストTA)
塩化ビニル系樹脂:27.8質量部
(樹脂溶液:樹脂分30質量%、シクロヘキサノン70質量%)
ポリイソシアネート:4質量部
(商品名:コロネートL、日本ポリウレタン社製)
ミリスチン酸:2質量部
n-ブチルステアレート:2質量部
メチルエチルケトン:121.3質量部
トルエン:121.3質量部
シクロヘキサノン:60.7質量部
下地層形成用塗料を次のようにして調製した。まず、下記原料をエクストルーダで混練して混練物を得た。
針状酸化鉄粉末:100質量部
(α-Fe2O3、平均長軸長0.15μm)
塩化ビニル系樹脂:55.6質量部
(樹脂溶液:樹脂分30質量%、シクロヘキサノン70質量%)
カーボンブラック:10質量部
(平均粒径20nm)
ポリウレタン系樹脂UR8200(東洋紡績製):18.5質量部
ポリイソシアネート:4質量部
(商品名:コロネートL、日本ポリウレタン社製)
ミリスチン酸:2質量部
n-ブチルステアレート:2質量部
メチルエチルケトン:108.2質量部
トルエン:108.2質量部
シクロヘキサノン:18.5質量部
保護層形成用塗料を次のようにして調製した。下記原料を、ディスパーを備えた攪拌タンクで混合を行い、フィルター処理を行うことで、保護層形成用塗料を調製した。
バリウムフェライト:100質量部
(形状:板状、平均板状比Rm/Tm:60、平均板厚Tm:4nm、平均板径Rm:240)
ポリウレタン系樹脂UR8200(東洋紡績製): 25質量部
(重合度300、Mn=10000、極性基としてOSO3K=0.07mmol/g、2級OH=0.3mmol/gを含有する。)
メチルエチルケトン:250質量部
トルエン:2000質量部
バックコート層形成用塗料を次のようにして調製した。下記原料を、ディスパーを備えた攪拌タンクで混合を行い、フィルター処理を行うことで、バックコート層形成用塗料を調製した。
カーボンブラック(旭社製、商品名:#80):100質量部
ポリエステルポリウレタン:100質量部
(日本ポリウレタン社製、商品名:N-2304)
メチルエチルケトン:500質量部
トルエン:400質量部
シクロヘキサノン:100質量部
次に、保護層、下地層および記録層を次のようにして形成した。まず、非磁性支持体である、厚さ6.2μm、帯状のPENフィルムの一方の主面上に、保護層形成用塗料を塗布、乾燥させることにより、PENフィルムの一方の主面上に平均厚さ150nmの保護層を形成した。次に、保護層上に、下地層形成用塗料を塗布、乾燥させることにより、保護層上に平均厚さ1μmの下地層を形成した。次に、下地層上に、記録層形成用塗料を塗布、乾燥させることにより、下地層上に平均厚さ70nmの記録層を形成した。なお、乾燥の際に、磁性粉を磁場配向させた。
次に、PENフィルムの他方の主面上に、バックコート層形成用塗料を塗布、乾燥させることにより、PENフィルムの他方の主面上に平均厚さ0.6μmのバックコート層を形成した。これにより、幅広の磁気テープを得た。
次に、得られた幅広の磁気テープに対して、金属ロールによるカレンダー処理を行い、記録層表面を平滑化した。次に、幅広の磁気テープを1/2インチ(12.65mm)幅に裁断して、目的とする磁気テープを得た。
保護層形成用塗料の調製工程において、バリウムフェライトに代えてα-酸化鉄(形状:板状、平均板状比Rm/Tm:60、平均板厚Tm:10nm、平均板径Rm:600nm)を用いた。また、保護層の形成工程において、保護層の平均厚さを300nmに変更した。これ以外のことは実施例1と同様にして磁気テープを得た。
保護層形成用塗料の調製工程において、バリウムフェライトに代えてマイカ(形状:板状、平均板状比Rm/Tm:200、平均板厚Tm:5nm、平均板径Rm:1000nm)を用いた。これ以外のことは実施例1と同様にして磁気テープを得た。
保護層形成用塗料の調製工程において、バリウムフェライトに代えてモンモリロナイト(形状:板状、平均板状比Rm/Tm:300、平均板厚Tm:1nm、平均板径Rm:300nm)を用いた。これ以外のことは実施例1と同様にして磁気テープを得た。
保護層形成用塗料の調製工程において、モンモリロナイト(形状:板状、平均板状比Rm/Tm:300、平均板厚Tm:2nm、平均板径Rm:600nm)を用いた。また、保護層の形成工程において、保護層の平均厚さを40nmに変更した。これ以外のことは実施例4と同様にして磁気テープを得た。
保護層の形成工程において、PENフィルムの両面に平均厚さ250nmの保護層を形成した。また、下地層の形成工程において、下地層の平均厚さを0.6μmに変更した。これ以外のことは実施例4と同様にして磁気テープを得た。
保護層の形成工程において、PENフィルムの両面に平均厚さ100nmの保護層を形成した。これ以外のことは実施例4と同様にして磁気テープを得た。
PENフィルムの一方の主面上に保護層を形成せずに、下地層を直接形成した。これ以外のことは実施例1と同様にして磁気テープを得た。
保護層形成用塗料の調製工程において、バリウムフェライト(形状:板状、平均板状比Rm/Tm:7、平均板厚Tm:4nm、平均板径Rm:28nm)を用いた。また、保護層の形成工程において、保護層の平均厚さを120nmに変更した。これ以外のことは実施例1と同様にして磁気テープを得た。
保護層形成用塗料の調製工程において、バリウムフェライトに代えてα-酸化鉄(形状:針状、平均針状比Rm/Tm:10、平均短軸径Tm:8nm、平均長軸径Rm:80)を用いた。また、保護層の形成工程において、保護層の平均厚さを250nmに変更した。これ以外のことは実施例1と同様にして磁気テープを得た。
保護層形成用塗料の調製工程において、バリウムフェライトに代えてシリカ(形状:球状、平均粒径Tm:18nm)を用いた。また、保護層の形成工程において、PENフィルムの両面に平均厚さ250nmの保護層を形成した。これ以外のことは実施例1と同様にして磁気テープを得た。
保護層形成用塗料の調製工程において、バリウムフェライトに代えてα-酸化鉄(形状:板状、平均板状比Rm/Tm:50、平均板厚Tm:10nm、平均板径Rm:500nm)を用いた。また、保護層の形成工程において、保護層の平均厚さを300nmに変更した。これ以外のことは実施例1と同様にして磁気テープを得た。
上述のようにして得られた磁気テープに以下の評価を行った。
まず、磁気テープをその主面に対して垂直に切り出し、その断面をTEMにより観察した。次に、観察したTEM像から、保護層に含まれる板状粒子粉が、板状粒子の主面がPENフィルム(非磁性支持体)の主面に対向するように保護層の厚さ方向に重なり合っているか否かを判断した。その結果を表1に示す。なお、本評価は、保護層の粒子粉として板状粒子粉を用いたサンプルにのみ行われた。
以下に、TEMの測定条件を示す。
装置:TEM(日立製作所製、H9000NAR)
加速電圧:300kV
倍率:100000倍
JIS-K7133、ASTM D882に基づき、サンプル幅6.25mm×サンプル実行長100mm、引っ張り速度200mm/minで測定し、1%伸びを与える抗張力を初期フィルム断面積で割った値をE(ヤング率)とした。その結果を表1に示す。
サンプルの長手方向に一定の荷重をかけ、25℃で湿度を変化させたときの幅方向の変形から、以下の式(1)に従って湿度膨張率を算出した。その結果を表1に示す。サンプルは幅1/2インチ、標線間隔200mmのものを用いた。荷重はサンプルの長手方向に20gとした。
湿度膨張率(%)=[(L-L0)/12.65]×100 ・・・(1)
但し、L0は25℃、RH20%で24時間保存したときの標線間隔(mm)を示す。
また、Lは25℃、RH80%で24時間保存したときの標線間隔(mm)を示す。
B面:PENフィルムの両面(非磁性支持体)のうち記録層形成側とは反対側の裏面
MD:Machine Direction
TD:Transverse Direction
Dm:保護層の平均厚み
Tm:粒子形状が板状である場合、Tmは平均板厚を意味する。粒子形状が針状である場合、Tmは平均短軸径を意味する。粒子形状が球状である場合、Tmは平均直径を意味する。
Rm:粒子形状が板状である場合、Rmは平均板径を意味する。粒子形状が針状である場合、Rmは平均長軸径を意味する。
実施例1、3、4、比較例5の評価結果等から、板状粒子の平均板状比が大きいほど、寸法変形の抑制効果が向上することがわかる。
比較例1、3、4の評価結果等から、保護層に含まれる粒子分が針状粒子粉または球状粒子粉である場合には、寸法変形の抑制効果を得ることは困難であることがわかる。
実施例1~4の評価結果等から、板状粒子の主面が支持体の主面に対向するように板状粒子粉が保護層の厚さ方向に重なり合っており、かつ、板状粒子粉の平均板状比が60以上であれば、板状粒子粉の種類によらず、寸法変形の抑制効果が発現することがわかる。
実施例4、5の評価結果等から、板状粒子の平均板厚Tmに対する保護層の平均厚みDmの割合(Dm/Tm)が大きいほど、寸法変形の抑制効果が向上することがわかる。
実施例4~7の評価結果等から、非磁性支持体の両面に保護層を設けることで、寸法変形の抑制効果が向上することがわかる。
(1)
支持体と、
記録層と、
上記支持体の少なくとも一方の面に設けられた、板状粒子粉を含む保護層と
を備え、
上記板状粒子粉は、該板状粒子の主面が上記支持体の面に対向するように上記保護層の厚さ方向に重なり合っており、
上記板状粒子の平均板状比は、60以上である磁気記録媒体。
(2)
上記板状粒子の平均板状比は、200以上である(1)に記載の磁気記録媒体。
(3)
上記板状粒子の平均板厚Tmに対する上記保護層の平均厚みDmの割合(Dm/Tm)は、30以上である(1)または(2)に記載の磁気記録媒体。
(4)
上記保護層は、上記支持体の両面のうち、上記記録層とは反対側の面に設けられている(1)から(3)のいずれかに記載の磁気記録媒体。
(5)
上記保護層は、上記支持体の両面に設けられている(1)から(3)のいずれかに記載の磁気記録媒体。
(6)
上記板状粒子は、粘土である(1)から(5)のいずれかに記載の磁気記録媒体。
(7)
上記粘土は、カオリナイト、ディッカイト、ハロイサイト、クリソタイル、リザーダイド、アメサイト、パイロフィライト、タルク、モンモリロナイト、バイデライト、ノントロナイト、スチーブンサイト、サポナイト、ヘクトライト、ソーコナイト、2八面体型バーミキュライト、3八面体型バーミキュライト、白雲母、パラゴナイト、イライト、セリサイト、金雲母、黒雲母、レピドライト、マガディアイト、アイラライトおよびカネマイトからなる群より選ばれる1種以上である(6)に記載の磁気記録媒体。
(8)
上記板状粒子は、フェライトである(1)から(5)のいずれかに記載の磁気記録媒体。
(9)
上記記録層の下に設けられた下地層をさらに備える(1)から(8)のいずれかに記載の磁気記録媒体。
12a、12b 保護層
13 下地層
14 記録層
15 バックコート層
Claims (9)
- 支持体と、
記録層と、
上記支持体の少なくとも一方の面に設けられた、板状粒子粉を含む保護層と
を備え、
上記板状粒子粉は、該板状粒子の主面が上記支持体の面に対向するように上記保護層の厚さ方向に重なり合っており、
上記板状粒子の平均板状比は、60以上である磁気記録媒体。 - 上記板状粒子の平均板状比は、200以上である請求項1に記載の磁気記録媒体。
- 上記板状粒子の平均板厚Tmに対する上記保護層の平均厚みDmの割合(Dm/Tm)は、30以上である請求項1に記載の磁気記録媒体。
- 上記保護層は、上記支持体の両面のうち、上記記録層とは反対側の面に設けられている請求項1に記載の磁気記録媒体。
- 上記保護層は、上記支持体の両面に設けられている請求項1に記載の磁気記録媒体。
- 上記板状粒子は、粘土である請求項1に記載の磁気記録媒体。
- 上記粘土は、カオリナイト、ディッカイト、ハロイサイト、クリソタイル、リザーダイド、アメサイト、パイロフィライト、タルク、モンモリロナイト、バイデライト、ノントロナイト、スチーブンサイト、サポナイト、ヘクトライト、ソーコナイト、2八面体型バーミキュライト、3八面体型バーミキュライト、白雲母、パラゴナイト、イライト、セリサイト、金雲母、黒雲母、レピドライト、マガディアイト、アイラライトおよびカネマイトからなる群より選ばれる1種以上である請求項6に記載の磁気記録媒体。
- 上記板状粒子は、フェライトである請求項1に記載の磁気記録媒体。
- 上記記録層の下に設けられた下地層をさらに備える請求項1に記載の磁気記録媒体。
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JP2020191151A (ja) * | 2018-03-30 | 2020-11-26 | ソニー株式会社 | 磁気記録媒体 |
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US11205455B2 (en) | 2018-03-30 | 2021-12-21 | Sony Corporation | Magnetic recording medium |
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WO2003079333A1 (en) * | 2002-03-18 | 2003-09-25 | Hitachi Maxell, Ltd. | Magnetic recording medium and magnetic recording cartridge |
JP2004005890A (ja) * | 2002-04-16 | 2004-01-08 | Fuji Photo Film Co Ltd | 磁気記録媒体 |
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US6511733B2 (en) * | 2000-03-16 | 2003-01-28 | Toda Kogyo Corporation | Magnetic recording medium containing specific non-magnetic composite particles of coated hematite particles |
JP2002304720A (ja) | 2001-04-09 | 2002-10-18 | Sony Corp | 磁気記録媒体 |
JP2002304721A (ja) | 2001-04-09 | 2002-10-18 | Sony Corp | 磁気記録媒体 |
US6964811B2 (en) * | 2002-09-20 | 2005-11-15 | Hitachi Maxell, Ltd. | Magnetic powder, method for producing the same and magnetic recording medium comprising the same |
JP2004206799A (ja) * | 2002-12-25 | 2004-07-22 | Hitachi Maxell Ltd | 磁気テープ |
JP2006276304A (ja) * | 2005-03-28 | 2006-10-12 | Fuji Xerox Co Ltd | 電子写真用画像転写シート、及び画像記録体、並びに画像記録体の作製方法 |
JP4539723B2 (ja) * | 2008-01-21 | 2010-09-08 | Dic株式会社 | 熱転写用積層体およびこれを用いた磁気記録媒体の製造方法 |
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- 2016-02-08 JP JP2017509193A patent/JP6638725B2/ja not_active Expired - Fee Related
- 2016-02-08 WO PCT/JP2016/000631 patent/WO2016157681A1/ja active Application Filing
- 2016-02-08 US US15/561,397 patent/US10210892B2/en active Active
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WO2003079333A1 (en) * | 2002-03-18 | 2003-09-25 | Hitachi Maxell, Ltd. | Magnetic recording medium and magnetic recording cartridge |
JP2004005890A (ja) * | 2002-04-16 | 2004-01-08 | Fuji Photo Film Co Ltd | 磁気記録媒体 |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2020191151A (ja) * | 2018-03-30 | 2020-11-26 | ソニー株式会社 | 磁気記録媒体 |
US11508407B2 (en) | 2018-03-30 | 2022-11-22 | Sony Corporation | Magnetic recording medium having controlled dimensional characteristics |
Also Published As
Publication number | Publication date |
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JPWO2016157681A1 (ja) | 2018-01-25 |
US20180108375A1 (en) | 2018-04-19 |
JP6638725B2 (ja) | 2020-01-29 |
US10210892B2 (en) | 2019-02-19 |
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