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`Samsung Electronics Co., Ltd. v. Demaray LLC
`Samsung Electronic's Exhibit 1043
`Exhibit 1043, Page 1
`
`

`

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`Patent Application Publication Oct. 18, 2001
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`US 2001/0031383 Al
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`Fig. 1
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` N F
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`ig. 3
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`Ex. 1043, Page 2
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` VPLLLLLLALLLLLLLLLL
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`CMM
` A
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`PLLLLLZLLLLLLLL
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`SS
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`Ex. 1043, Page 2
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`

`

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`US 2001/0031383 Al
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`Oct. 18, 2001
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`MAGNETIC RECORDING MEDIUM,
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`PRODUCTION PROCESS THEREOF, MAGNETIC
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`RECORDING AND REPRODUCING APPARATUS,
`AND SPUTTERING TARGET
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`CROSS REFERENCE TO RELATED
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`
`APPLICATIONS
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`[0001] This application is an application filed under 35
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`U.S.C. §111(a) claiming benefit pursuant
`to 35 U.S.C.
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`§119(e)(1) of thefiling date of Provisional application No.
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`60/230,810 filed Sep. 7, 2000 pursuant to 35 U.S.C. §111(b).
`FIELD OF THE INVENTION
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`[0002] The present invention relates to a magnetic record-
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`ing medium employed in an apparatus such as a magnetic
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`disk apparatus; a process for producing the magnetic record-
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`ing medium; a sputtering target employed for producing the
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`magnetic recording medium; and a magnetic recording and
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`reproducing apparatus comprising the magnetic recording
`medium.
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`BACKGROUND OF THE INVENTION
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`[0003] Conventionally, a metallic substrate formed of, for
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`example, an aluminum alloy is widely employed as a
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`substrate for producing a magnetic recording medium. Usu-
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`ally, such a metallic substrate undergoes texturing, and is
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`employed for producing a magnetic recording medium.
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`[0004] Texturing is a process for forming an irregular
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`surface on a substrate along a predetermined direction
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`(usually in a circumferential direction) of the substrate.
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`When the surface of a substrate undergoes texturing, the
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`crystalline orientation of an undercoat film and a magnetic
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`film, which are formed on the substrate, is enhanced, and the
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`magnetic film exhibits magnetic anisotropy. Thus magnetic
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`characteristics, such as thermal stability and resolution,of a
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`magnetic recording medium can be enhanced.
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`[0005]
`In recent years,
`instead of a metallic substrate
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`formed of aluminum or similar metal, a non-metallic sub-
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`strate formed of material such as glass or ceramic has been
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`widely employed as a substrate for producing a magnetic
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`recording medium. Such a non-metallic substrate has an
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`advantage that head slap does not easily occur in the
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`substrate, because of the high hardness of the substrate.
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`[0006] However,
`in the case in which a non-metallic
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`substrate such as a glass substrate is employed, the magnetic
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`film may not be imparted with satisfactory magnetic anisot-
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`ropy even when the substrate undergoes texturing. As a
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`result, the resultant magnetic recording medium may exhibit
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`unsatisfactory magnetic characteristics.
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`[0007]
`In order to solve such problems, formation of a
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`hard film which can be easily textured on a non-metallic
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`substrate formed of material such as glass or ceramic has
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`been proposed.
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`[0008] For example, Japanese Patent Application Laid-
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`Open (kokai) No. 5-197941 discloses a magnetic recording
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`medium including a non-metallic substrate formed of mate-
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`rial such as glass or ceramic, and the substrate is coated
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`through sputtering with NiP film serving as a hard film
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`whichis easily textured.
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`Japanese Patent Application Laid-Open (kokai)
`[0009]
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`Nos. 4-29561 and 9-167337 disclose a magnetic recording
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`medium including a non-metallic substrate which is plated
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`with film suchaselectroless platingfilm, and thefilm serves
`as a hard film.
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`[0010] A magnetic recording medium including a hard
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`film formed on a non-metallic substrate is produced through
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`the following process:
`the hard film is formed on the
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`substrate in a film formation apparatus such as a sputtering
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`apparatus; the substrate is temporarily removed from the
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`apparatus and is subjected to texturing by use of a texturing
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`apparatus;
`the resultant substrate is again placed in the
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`apparatus; and then an undercoat film and a magnetic film
`are formed on the substrate.
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`the aforementioned conventional pro-
`[0011] However,
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`duction process for a magnetic recording medium includes
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`complicated production steps, resulting in high production
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`costs. Therefore, there has been keen demand for a produc-
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`tion process for a magnetic recording medium, which
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`encompasses a simplified production procedure.
`SUMMARYOF THE INVENTION
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`[0012]
`In view of the foregoing, an object of the present
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`invention is to provide a process for easily producing a
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`magnetic recording medium exhibiting excellent magnetic
`characteristics.
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`[0013] The present invention provides a process for pro-
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`ducing a magnetic recording medium characterized by form-
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`ing an orientation-determining film, which determines the
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`crystalline orientation of a film provided directly on the
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`orientation-determining film, on a non-metallic substrate
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`which has undergone texturing; subjecting the orientation-
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`determining film to oxidation or nitridation; and forming a
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`non-magnetic undercoat film and a magnetic film on the
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`orientation-determining film.
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`[0014] The oxidation or nitridationis carried out by bring-
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`ing the orientation-determining film into contact with an
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`oxygen-containing gas or a nitrogen-containing gas.
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`[0015] The present invention also provides a process for
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`producing a magnetic recording medium, which comprises
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`forming an orientation-determining film, which determines
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`the crystal orientation of a film provided directly on the
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`orientation-determining film, on a non-metallic substrate
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`which has undergonetexturing; and forming a non-magnetic
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`undercoat film and a magnetic film on the orientation-
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`determining film, wherein the orientation-determining film
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`is formed through sputtering by use of a sputtering gas
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`containing nitrogen or a sputtering gas containing oxygen.
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`[0016] Preferably, the orientation-determining film com-
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`prises NiP (the content of P is 10-40 at %) as a primary
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`component.
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`[0017] Preferably, the orientation-determining film com-
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`prises NiPX (wherein X is one or more species of Cr, Mo,
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`Si, Mn, W, Nb, Ti, and Zr, and the content of X is 0-25 at
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`%) as a primary component.
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`[0018] The present invention also provides a sputtering
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`target for forming the orientation-determining film, which
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`comprises NiPX (wherein X is one or more species of Cr,
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`Mo, Si, Mn, W, Nb, Ti, and Zr, and the content of X is 0-25
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`at %) as a primary component.
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`Ex. 1043, Page 3
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`Ex. 1043, Page 3
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`

`

`
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`US 2001/0031383 Al
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`
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`Oct. 18, 2001
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`[0030] Meanwhile, a ceramic substrate may be a widely-
`[0019] The present invention also provides a magnetic
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`used sintered compact predominantly containing aluminum
`recording medium comprising a non-metallic substrate
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`oxide, aluminum nitride, and silicon nitride; or fiber-rein-
`which has undergone texturing; an orientation-determining
`forced material thereof.
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`film formed on the non-metallic substrate; and a non-
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`magnetic undercoat film and a magnetic film, which are
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`subjected to
`[0031] The non-metallic substrate 1 is
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`formed onthe orientation-determining film, characterized in
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`mechanical
`texturing or similar processing by use of a
`that the ratio of a coercive force in a circumferential direc-
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`lapping tape containing fixed abrasive grains or by use of
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`tion of the medium (Hcc) to a coercive force in a radial
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`free abrasive grains, to have a textured surface.
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`direction of the medium (Her); i.e., Hec/Her, is 1.1 or more.
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`[0032] Texture lines formed on the non-metallic substrate
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`[0020] The orientation-determining film has an average
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`1 through texturing are preferably along the circumferential
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`surface roughness (Ra) of less than 0.5 nm.
`direction of the substrate.
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`[0021] The magnetic recording medium of the present
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`[0033] The average surface roughness (Ra) of the non-
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`invention comprises a structure wherein a non-magnetic
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`metallic substrate 1 is 0.1-1 nm (1-10 A), preferably 0.3-0.8
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`adhesive film, which prevents exfoliation of the orientation-
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`nm (3-8 A).
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`determining film from the substrate, is formed between the
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`[0034] Whenthe average surface roughness (Ra) is below
`non-metallic substrate and the orientation-determining film,
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`the above range, the non-metallic substrate 1 is excessively
`and the non-magnetic adhesive film comprises one or more
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`smooth, and thus the substrate encounters difficulty in
`species of Cr, Mo, Nb, V, Re, Zr, W, and Ti.
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`enhancing the magnetic anisotropy of the magnetic film 4. In
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`[0022] The present invention also provides a magnetic
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`contrast, when the average surface roughness (Ra) is in
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`recording and reproducing apparatus comprising the mag-
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`excess of the above range, the evenness of the medium is
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`netic recording medium and a magnetic head for recording
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`lowered, resulting in poor glide height characteristics. As a
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`data onto the medium and reproducing the data therefrom.
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`result, reducing the flying height of a magnetic head during
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`reproduction of data becomes difficult.
`BRIEF DESCRIPTION OF THE DRAWINGS
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`[0035] As compared with a metallic material, the non-
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`[0023] FIG. 1 is a partially cross-sectional view of one
`metallic substrate 1 has a high hardness andis difficult to
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`embodiment of the magnetic recording medium of the
`texture. Therefore, when the substrate is subjected to tex-
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`present invention.
`turing, abnormal protrusions such as fins are difficult
`to
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`form, with the result that the maximum protrusion height
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`[0024] FIG. 2 is a partially cross-sectional view of one
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`(Rp) is lowered.
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`embodiment of the magnetic recording and reproducing
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`[0036] The orientation-determining film 2 is provided for
`apparatus of the present invention.
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`determining the crystalline orientation of the non-magnetic
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`[0025] FIG.3isa partially cross-sectional view of another
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`undercoat film 3 formed on the film 2 and for determining
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`embodiment of the magnetic recording medium of the
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`the crystalline orientation of the magnetic film 4 formed on
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`present invention.
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`the film 3, to thereby enhance the magnetic anisotropy of the
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`magnetic film 4. The orientation-determining film 2 deter-
`DESCRIPTION OF THE PREFERRED
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`minesthe crystalline orientation of the non-magnetic under-
`EMBODIMENTS
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`coat film 3 and the magnetic film 4, and also functions as a
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`film for formingfine crystal grains;1.e., the film 2 formsfine
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`magnetic grains in the films 3 and 4.
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`[0037] The orientation-determining film 2 is preferably
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`formed from a material containing NiP as a primary com-
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`ponent. The content of P is 10-40 at %, preferably 15-35 at
`%.
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`[0038] The reasonsfor this are that, when the content of P
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`is less than 10 at %, NiP is susceptible to magnetization. In
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`contrast, when the content of P is in excess of 40 at %, the
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`crystal orientation of the non-magnetic undercoatfilm 3 and
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`the magnetic film 4 is easily impaired.
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`[0039] Alternatively, the orientation-determining film 2 is
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`preferably formed from a material containing NiPX
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`(wherein X is one or more species of Cr, Mo, Si, Mn, W, Nb,
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`Ti, and Zr) as a primary component. The content of X is 0-25
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`at %, preferably 5-25 at %, more preferably 10-25 at %.
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`Whenthe content of X is in excess of 25 at %, the crystalline
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`orientation of the non-magnetic undercoat film 3 and the
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`magnetic film 4 is impaired, and the magnetic anisotropy of
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`the magnetic film 4 is lowered.
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`[0040] As used herein,
`the term “primary component”
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`refers to the case in which the content of the componentis
`in excess of 50 at %.
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`[0026] FIG. 1 is a schematic representation showing an
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`example embodiment of the magnetic recording medium of
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`the present
`invention. The magnetic recording medium
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`comprises a non-metallic substrate 1 which has undergone
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`texturing, an orientation-determining film 2 formed on the
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`substrate, a non-magnetic undercoat film 3, a magnetic film
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`4, and a protective film 5, the films 3 to 5 being successively
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`formed on the film 2. Hereinafter,
`the structure of the
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`non-metallic substrate 1 and the orientation-determining
`film 2 will be called a medium substrate 6.
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`[0027] The non-metallic substrate 1 is formed from a
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`non-metallic material such as glass, ceramic,silicon, silicon
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`carbide, or carbon. Particularly, from the viewpoint of
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`durability and cost, a glass substrate is preferably employed.
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`[0028] The glass substrate is formed from amorphous
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`glass or crystallized glass. The amorphous glass may be
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`widely-used soda-lime glass, aluminocate glass, or alumi-
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`nosilicate glass. The crystallized glass may be lithium-based
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`crystallized glass.
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`[0029] Particularly, amorphous glass exhibiting uniform
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`physical properties such as hardnessis preferably employed
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`as a material of the substrate, since the substrate can be
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`subjected to uniform texturing.
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`Ex. 1043, Page 4
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`Ex. 1043, Page 4
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`

`

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`US 2001/0031383 Al
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`Oct. 18, 2001
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`[0041] The thickness of the orientation-determining film 2
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`is preferably 2-100 nm (20-1,000 A). When the thickness is
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`below the above range,
`the magnetic anisotropy of the
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`magnetic film 4 is lowered, whereas whenthe thicknessis in
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`excess of the above range, the orientation-determining film
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`2 is easily exfoliated and production costs increase, which is
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`unsatisfactory.
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`[0042] The orientation-determining film 2 may be or may
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`not be subjected to texturing.
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`[0043] When orientation-determining film 2 is subjected
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`to texturing, texture lines are preferably along the circum-
`ferential direction of the substrate.
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`CoCrPt-, CoCrPtB- or CoCrPtTa-based alloy. Of these
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`alloys, in particular, a CoCrPtTa-based alloy is preferably
`
`employed.
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`[0054] The thickness of the magnetic film 4 may be 5-30
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`nom (50-300 A).
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`[0055]
`Thecrystalline orientation of the magnetic film 4 is
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`preferably (110).
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`[0056] The magnetic film 4 may be of a single-layer
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`structure, or of a multi-layer structure formed of a plurality
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`of films which are of the same composition or of different
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`compositions.
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`[0057] Preferably, a non-magnetic intermediate layer is
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`[0044] The orientation-determining film 2 preferably has
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`provided between the non-magnetic undercoat film and the
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`an average surface roughness (Ra) of 1 nm orless, from the
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`magnetic film, in order to further improve the crystal ori-
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`viewpoint of glide height characteristics.
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`entation of the magnetic film and to further enhance the
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`[0045] The average surface roughness (Ra) of the orien-
`effects of the present invention.
`
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`tation-determiningfilm 2 is more preferably less than 0.5 nm
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`[0058] The non-magnetic intermediate layer may be
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`(5 A), much more preferably less than 0.3 nm.
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`formed from a CoCr alloy (content of Cr: 20-40 at %).
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`[0046] The orientation-determining film 2 is formed from
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`[0059] The protective film 5 may be formed from conven-
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`a metallic material which hasa relatively low hardness and
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`tionally known materials. For example,
`the film may be
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`is easily processed, such as NiPX. Therefore, when the film
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`formed from a material containing a single component such
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`2 is subjected to texturing, large protrusions such as fins and
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`as carbon,silicon oxide, silicon nitride, or zirconium oxide;
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`burrs are easily produced on the surface of the film, and thus
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`or a material predominantly containing such components.
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`the maximum protrusion height (Rp) tends to increase.
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`[0060] The thickness of the protective film 5 is preferably
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`[0047] When the average surface roughness (Ra) of the
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`2-10 nm (20-100 A).
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`orientation-determiningfilm2is less than 0.5 nm (5 A),the
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`amount of abraded substance is reduced during texturing,
`[0061]
`If necessary, a lubrication film formed from a
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`and an increase in the maximum protrusion height (Rp) of
`lubricant such as a fluorine-based liquid lubricant (e.g.,
`
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`the film 2 is prevented. Consequently, the maximum pro-
`perfluoropolyether) may be provided on the protective film
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`trusion height (Rp) of the medium can be reduced, and
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`deterioration of the glide height characteristics can be pre-
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`vented.
`[0062]
`In the magnetic recording medium of the present
`
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`
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`invention, the ratio of a coercive force in a circumferential
`
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`[0048] The non-magnetic undercoat film 3 may be formed
`direction of the medium (Hcc) to a coercive force in a radial
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`from conventionally known materials for undercoat film.
`direction of the medium (Her); i.e., Hec/Hcr, is 1.1 or more,
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`For example, the film may be formed from an alloy of one
`preferably 1.2 or more.
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`or more species of Cr, Ti, Ni, Si, Ta, W, Mo, V, and Nb.
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`[0063] Whenthe ratio Hcc/Heris below the above range,
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`Alternatively, the film 3 may be formed from analloy of one
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`the magnetic anisotropy a of the magnetic recording medium
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`or more of the above elements and other elements, so long
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`is insufficient, and magnetic characteristics of the medium,
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`as such “other elements” do not impede the crystallinity of
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`such as thermal stability, are unsatisfactory.
`the film.
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`[0064]Afirst embodimentof the production process for a
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`[0049] Particularly, the film 3 is preferably formed from
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`magnetic recording medium of the present invention will
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`Cr or a Cr alloy (e.g., CrTi, CrW, CrMo, CrV, or CrSi).
`
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`next be described by taking, as an example, production of
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`[0050] The non-magnetic undercoat film 3 may be of a
`the aforementioned magnetic recording medium.
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`single-layer structure, or of a multi-layer structure formed of
`
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`
`
`[0065]
`Firstly, the non-metallic substrate 1 is subjected to
`
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`
`
`a plurality of films which are of the same composition or of
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`
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`texturing. Preferably,
`the substrate 1
`is
`subjected to
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`
`
`different compositions. The thickness of the non-magnetic
`
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`mechanical texturing by use of lapping tape containing fixed
`undercoatfilm 3 is 1-100 nm (10-1,000 A), preferably 2-50
`
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`
`
`abrasive grains, or by use of free abrasive grains. During
`nm (20-500 A).
`
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`
`
`texturing, texture lines are preferably formed in the circum-
`ferential direction of the substrate.
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`[0051] The crystalline orientation of the non-magnetic
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`
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`undercoatfilm 3 is preferably (002).
`
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`[0052] The magnetic film 4 is preferably formed from a
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`material containing Co as a primary component. The mate-
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`rial may be, for example, an alloy of Co and one or more
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`species of Cr, Pt, Ta, B, Ti, Ag, Cu, Al, Au, W, Nb, Zr, V, Ni,
`
`
`
`Fe, and Mo.
`
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`
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`[0053] Preferable specific examples of the above material
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`
`
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`include materials predominantly containing a CoCrTa-,
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`[0066] The substrate may be subjected to chemical etching
`
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`after mechanical texturing,
`in order to remove fine fins,
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`burrs, and the like which are produced on the surface during
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`mechanical texturing, and to obtain excellent surface even-
`ness.
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`[0067] Subsequently, the orientation-determining film 2 is
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`formed on the non-metallic substrate 1, to thereby form the
`medium substrate 6.
`
`
`
`Ex. 1043, Page 5
`
`Ex. 1043, Page 5
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`

`

`
`
`US 2001/0031383 Al
`
`
`
`Oct. 18, 2001
`
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`[0080] By use of such an oxygen-containing gas, oxida-
`[0068] The orientation-determining film 2 is preferably
`
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`
`
`
`
`
`tion of the film 2 can be easily carried out.
`formed through sputtering by use of a sputtering apparatus
`
`
`
`
`serving as a film formation apparatus.
`
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`
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`
`
`[0081] The process for bringing the orientation-determin-
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`ing film 2 into contact with the oxygen-containing gas is
`[0069] Whenthe orientation-determining film 2 is formed
`
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`preferably carried out at a temperature lower than the
`through sputtering, the aforementioned material constituting
`
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`temperature at which the material constituting the film 2 is
`the film 2 is employed as a sputtering target.
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`crystallized; for example, at 280° C. or lower, in order to
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`[0070] The sputtering target is desirably a material con-
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`the possibility that
`the orientation of the non-
`prevent
`
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`
`
`taining, as a primary component, NiPX (wherein X is one or
`
`
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`
`
`magnetic undercoatfilm 3 and the magnetic film 4 might be
`
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`more species of Cr, Mo, Si, Mn, W, Nb, Ti, and Zr; and the
`
`
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`
`
`adversely affected by crystallization of the film 2. The
`
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`content of X is 0-25 at %, preferably 5-25 at %, more
`
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`
`
`temperature at which the process is carried out may be
`
`
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`preferably 10-25 at %).
`
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`determined to be ambient temperature or higher. The period
`
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`of time for the processto be carried out(i.e., the time during
`
`
`
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`
`
`[0071] When the content of X is in excess of the above
`
`
`
`
`
`
`
`which the film 2 is exposed to the oxygen-containing gas)
`
`
`
`
`
`range, the crystalline orientation of the non-magnetic under-
`
`
`
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`
`
`may be appropriately determined in accordance with, for
`
`
`
`
`
`
`
`
`coat film 3 and the magnetic film 4 is impaired, and the
`
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`
`
`
`
`example, the content of oxygen in the oxygen-containing
`
`
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`
`
`magnetic anisotropy of the film 4 is lowered.
`gas.
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`
`
`[0072] The target may beasintered alloy target or an alloy
`
`
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`
`
`
`
`[0082]
`Throughthis process,at least the area in proximity
`
`
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`
`
`target produced through a casting method. Particularly, a
`
`
`
`
`
`
`
`to the surface of the orientation-determining film 2 is
`
`
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`
`
`
`sintered alloy target is preferably employed. Sucha sintered
`oxidized.
`
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`
`
`alloy target may be produced by meansof a conventionally
`
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`
`
`
`knownsintering method such as hotisostatic pressing (HIP)
`
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`
`
`
`
`
`or hot pressing, from alloy powder of the aforementioned
`
`
`
`
`
`
`
`
`composition, a plurality of alloy powders which are mixed
`
`
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`
`
`
`to obtain the aforementioned composition, or a mixture of
`
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`
`
`mono-metallic powders. The aforementioned alloy powder
`
`
`
`
`
`
`
`and metallic powder may be produced by means of a
`
`
`
`
`
`
`conventionally known method such as a gas-atomizing
`method.
`
`
`
`
`
`
`
`
`[0073]
`In order to form the orientation-determining film 2,
`
`
`
`
`
`
`the non-metallic substrate 1 is placed in a chamber of a
`
`
`
`
`
`
`
`sputtering apparatus, a sputtering gas such as argon gasis
`
`
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`
`
`
`
`introduced into the chamber, and electricity is applied to the
`
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`
`
`
`target, thereby depositing the target material onto the non-
`
`
`
`
`metallic substrate 1 through sputtering.
`
`
`
`
`
`
`[0074] The orientation-determining film 2 may be formed
`
`
`
`
`
`
`
`through, instead of sputtering, plating (such as electroless
`
`
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`
`
`
`
`
`plating), vacuum deposition, ion plating, or a similar pro-
`cess.
`
`
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`
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`
`
`
`
`[0075]
`In the production process for the magnetic record-
`
`
`
`
`
`
`
`
`ing medium of the embodiment, after completion of the
`
`
`
`
`
`
`formation of the orientation-determining film 2, the film is
`
`
`subjected to oxidation.
`
`
`
`
`
`
`[0076] Oxidation of the orientation-determining film 2
`
`
`
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`
`
`
`
`
`may becarried out by bringing the film 2 into contact with
`
`
`
`an oxygen-containing gas.
`
`
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`
`
`
`
`[0077] The oxygen-containing gas may beair, pure oxy-
`
`
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`
`
`
`gen, or steam. Alternatively, the oxygen-containing gas may
`
`
`
`
`
`be an oxygen-enriched gas which consists of air containing
`
`
`
`
`a large amount of oxygen.
`
`
`
`
`
`
`
`[0078]
`In order to bring the orientation-determining film 2
`
`
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`
`
`
`
`
`
`into contact with the oxygen-containing gas,after the film 2
`
`
`
`
`
`
`
`
`is formed on the substrate 1 in the film formation apparatus
`
`
`
`
`
`
`(sputtering apparatus) to form the medium substrate 6 as
`
`
`
`
`
`
`described above, the oxygen-containing gas is introduced
`
`
`
`
`
`
`
`
`into the chamber of the film formation apparatus in which
`
`
`
`
`the medium substrate 6 is placed.
`
`
`
`
`
`
`
`
`
`[0079]
`In this case, the content of oxygen in the gas to
`
`
`
`
`
`
`whichthe orientation-determining film 2 is exposed; 1.e., the
`
`
`
`
`
`
`gas in the chamber, may be 1-100 vol %.
`
`
`
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`
`
`
`
`[0083] Subsequently, the non-magnetic undercoatfilm 3 is
`
`
`
`
`
`
`
`
`formed on the orientation-determining film 2. The non-
`
`
`
`
`
`
`
`magnetic undercoatfilm 3 may be formed through sputtering
`
`
`
`
`by use of a sputtering apparatus.
`
`
`
`
`
`
`
`[0084] Subsequently, the magnetic film 4 is formed on the
`
`
`
`
`
`
`
`non-magnetic undercoatfilm 3. The magnetic film 4 may be
`
`
`
`
`
`
`formed through sputtering by use of a sputtering apparatus.
`
`
`
`
`
`
`
`[0085] Subsequently, the protective film 5 is formed on the
`
`
`
`
`
`
`
`
`magnetic film 4. The protective film 5 may be formed
`
`
`
`
`
`
`through, for example, plasma CVDor sputtering.
`
`
`
`
`
`
`
`
`
`[0086]
`In the production process for the magnetic record-
`
`
`
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`ing medium of the embodiment, the orientation-determining
`film 2 is formed on the non-metallic substrate 1 which has
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`undergone texturing, and then the film 2 is subjected to
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`oxidation. Therefore, even though the substrate 1 is formed
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`from a non-metallic substrate, which makes imparting high
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`magnetic anisotropy to the magnetic film difficult, the crys-
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`talline orientation of the non-magnetic undercoatfilm 3 and
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`the magnetic film 4, which are being formed over the
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`substrate 1, can be improved, and the magnetic anisotropy of
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`the magnetic film 4 can be enhanced.
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`[0087] Therefore, magnetic characteristics of the magnetic
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`recording medium, such as thermalstability, error rate, and
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`S/N ratio, can be improved.
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`in a
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`In general,
`thermal stability is excellent
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`medium which has a high crystal magnetic anisotropy
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`constant (Ku). In the magnetic recording medium of the
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`embodiment of the present invention, thermal stability is
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`thought to be enhanced, since the crystal magnetic anisot-
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`ropy constant (Ku) is enhanced by enhancementof magnetic
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`anisotropy in a circumferential direction.
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`[0089] As used herein, the term “thermal stability” refers
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`to the degree of difficulty in occurrence of thermal decay.
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`[0090] As used herein, the term “thermal decay”refers to
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`a phenomenonin whichrecording bits become unstable and
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`recorded data are thermally lost. In a magnetic recording
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`apparatus,
`thermal decay is manifested in the form of
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`reduction in reproduction output of recorded data with the
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`passage of time.
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`Ex. 1043, Page 6
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`Ex. 1043, Page 6
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`US 2001/0031383 Al
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`Oct. 18, 2001
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`the half
`[0091] According to the production process,
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`powerwidth of a reproduction output peak is narrowed, and
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`thus the resolution of the reproduction output can be
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`enhanced. Therefore, a magnetic recording medium in
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`which the error rate is improved can be produced.
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`[0092] When magnetic anisotropy is enhanced, coercive
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`force and reproduction output (S) are improved, yielding an
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`improvementin the S/N ratio.
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`[0093]
`In addition, crystal grains in the non-magnetic
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`undercoat
`film 3 become fine. Consequently, magnetic
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`grains in the magnetic film 4, which is grown under the
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