JP2006302333A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a so-called coating type magnetic recording medium wherein a magnetic layer (3) contains ferromagnetic powder and a binder and the thickness is reduced and dimensional change caused by environmental change of temperature and humidity is small. <P>SOLUTION: The magnetic recording medium (10) includes a non-magnetic support (1), the magnetic layer (3), reinforcement layers (2, 5) and a back coat layer (6). When Young's moduli in the longitudinal direction and the lateral direction of the magnetic recording medium are denoted as Emd1(Gpa) and Etd1 (Gpa), respectively, when the thickness of the magnetic recording medium is denoted as T1 (mm) and when Young's moduli in the longitudinal direction and the lateral direction of the non-magnetic support (1) are denoted as Emd2 and Etd2, respectively, the reinforcement layers (2, 5) are formed so that 1.1≤Etd1/Emd1≤1.5, 35≤Emd1×T1, and 1.5≤Etd2/Emd2≤2.5 are satisfied to obtain the magnetic recording medium (10). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium having a magnetic layer comprising a ferromagnetic powder and a binder as a recording layer, and more particularly to a magnetic recording medium suitable for linear recording and reproduction.

  In recent years, in the magnetic recording field, a smaller magnetic recording medium capable of recording more information has been demanded. As a magnetic recording medium, a coating type magnetic recording medium in which a magnetic layer is formed by applying a paint containing a ferromagnetic powder and a binder has been known. A metal thin film type magnetic recording medium in which a magnetic layer is formed by vapor deposition of a ferromagnetic metal is also known. The metal thin film type magnetic recording medium is a medium that can record information at a higher recording density than a coating type magnetic recording medium, and has attracted attention in recent years and is in practical use. However, particularly when information is recorded by the linear method, the coating type magnetic recording medium is still used, and therefore the coating type magnetic recording medium is also desired to satisfy such a requirement.

  As one method for satisfying this requirement, there is a method in which the magnetic recording medium is made thinner and more magnetic recording media are accommodated in a package having a predetermined size. According to this method, effects such as resource saving and low cost are also brought about. The most effective method of thinning the magnetic recording medium is to reduce the thickness of the nonmagnetic support that occupies most of the thickness of the magnetic recording medium. However, when the thickness of the nonmagnetic support is reduced, the tensile strength in the longitudinal direction of the entire magnetic recording medium is reduced, which may cause practical problems such as poor running.

  As another method that satisfies the above requirement, there is a method of increasing the recording density by narrowing the track width and increasing the number of tracks. However, as the track becomes narrower, especially in linear magnetic recording media, track deviation is more likely to occur when the dimensions of the magnetic recording media change due to environmental changes such as temperature and humidity, resulting in errors during playback. May occur.

For this reason, various configurations have been proposed so far in coating-type magnetic recording media to suppress the decrease in the tensile strength in the longitudinal direction accompanying the thinning of the magnetic recording medium and to reduce the dimensional change in the width direction due to changes in temperature and humidity. . For example, Japanese Patent Laid-Open No. 2002-304721 (Patent Publication 1) discloses that the humidity expansion coefficient of a magnetic recording medium having a magnetic layer containing a ferromagnetic powder and a binder and a reinforcing layer is specified. Japanese Patent Laid-Open No. 2001-6156 (Patent Document 2) defines the ratio of Young's modulus in the longitudinal direction and the width direction of a nonmagnetic support in order to achieve high output and low noise even in high-density recording. It is disclosed.
JP 2002-304721 A JP 2001-6156 A

  As described in Patent Document 1 or 2, various methods for solving the problems associated with thinning and narrowing of the magnetic recording medium have been proposed. However, in the future, it is expected that the magnetic recording medium will become thinner and the track width will become narrower (for example, 14 μm or less). When polyethylene terephthalate (PET), which is inexpensive but has a low Young's modulus, is used. Therefore, the characteristics achieved by the technique described in Patent Document 1 or 2 are not necessarily sufficient.

  Further, when the magnetic recording medium is actually commercialized, it is necessary to select the material and thickness of each layer constituting the nonmagnetic support and the magnetic recording medium in consideration of production costs. That is, without using a special material and without requiring a complicated manufacturing process, achieving a thin magnetic recording medium and ensuring excellent dimensional stability has practicality and economy. There is a need to provide a coated magnetic recording medium.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a large-capacity coating type magnetic recording medium that can be manufactured without requiring high production costs and complicated processes.

  As a result of various studies to solve the above problems, in a coating type magnetic recording medium having at least one reinforcing layer, the Young's modulus and thickness in the longitudinal direction and the width direction of the magnetic recording medium, and the longitudinal direction of the nonmagnetic support. Further, the inventors have found that the magnetic recording medium can be thinned and the recording density can be increased when the Young's modulus in the width direction satisfies a certain condition, and the present invention has been achieved.

  The present invention relates to a magnetic recording medium having a nonmagnetic support, a magnetic layer containing ferromagnetic powder and a binder, and a reinforcing layer, wherein the Young's modulus in the longitudinal direction and the width direction of the magnetic recording medium is Emd1. (GPa) and Etd1 (GPa), the thickness of the magnetic recording medium is T1 (mm), and the Young's modulus in the longitudinal and width directions of the nonmagnetic support is Emd2 (GPa) and Etd2 (GPa). Provided is a magnetic recording medium that satisfies the following conditions: 1 ≦ Etd1 / Emd1 ≦ 1.5, 35 ≦ Emd1 × T1, and 1.5 ≦ Etd2 / Emd2 ≦ 2.5. In this magnetic recording medium, the reinforcing layer is a layer formed of a material that satisfies this condition, ensures the tensile strength in the longitudinal direction of the entire medium, and improves the dimensional stability of the entire medium. Specifically, the reinforcing layer is a thin film comprising one or more materials selected from metals, metalloids, alloys, and compounds thereof (for example, oxides, nitrides, and carbides). Two or more reinforcing layers may be formed, and in that case, it is required to form each reinforcing layer so that the magnetic recording medium after all the reinforcing layers are formed satisfies the above conditions.

  The magnetic recording medium of the present invention has a reinforcing layer and satisfies the above conditions. When Etd1 / Emd1 is smaller than 1.1, the ratio of the reinforcing layer to the entire recording medium increases, and when the reinforcing layer is formed of a metal thin film, the internal stress of the film generated when the reinforcing layer is formed is large. Become. Therefore, even when reinforcing layers are formed on the front and back surfaces of the nonmagnetic support, it is difficult to maintain the balance of internal stresses. When the balance of internal stress is lost, so-called “cupping” occurs in the magnetic recording medium. Here, “cupping” means that the magnetic recording medium is curved in the width direction (that is, a cross section cut along the width direction of the magnetic recording medium has a bowl shape). When the degree of cupping increases, the tape locally contacts the head and the running system, resulting in tape damage and decreased output, and the magnetic recording medium cannot be stably put into practical use. When Etd1 / Emd1 is larger than 1.5, the proportion of the reinforcing layer having high stability against humidity contributes to the improvement of the strength of the entire magnetic recording medium, and sufficiently high dimensional stability is obtained against humidity change. I can't.

Emd1 × T1 (N / mm) corresponds to a force per unit width when the magnetic recording medium is deformed within the elastic limit, and is an index indicating the tensile strength of the entire magnetic recording medium. In this specification, the product of Emd1 (GPa = 10 ⁹ N / m ² = 10 ³ N / mm ² ) and T1 (mm) is expressed in N / mm. Even if Emd1 is large, if T1 is small, the entire magnetic recording medium is deformed with a slight force. Therefore, in the present invention, 35 ≦ Emd1 × T1 (N / mm) is required. When Emd1 × T1 is smaller than 35 N / mm, the tape runnability is deteriorated, and edge damage or the like may occur.

  The present invention defines the Young's modulus in the width direction (Etd2) / Young's modulus in the longitudinal direction (Emd2) of the nonmagnetic support as described above. If Etd2 / Emd2 is less than 1.5, the Young's modulus in the width direction of the nonmagnetic support is not sufficiently high, so that it is not possible to obtain sufficiently high dimensional stability against temperature changes. When Etd2 / Emd2 is greater than 2.5, when a PET film is used as a nonmagnetic support, the strength of the nonmagnetic support in the longitudinal direction decreases, and during the vapor deposition process of forming a reinforcing layer made of a metal thin film. Wrinkles are likely to occur, and heat loss (degeneration due to heat) is likely to occur. In particular, when the thickness of the film is 5.0 μm or less, if Etd2 / Emd2 is greater than 2.5, the heat loss becomes severe, and the film is divided during the formation of the reinforcing layer (so-called film breakage). This makes it difficult to form a stable magnetic recording medium.

  In the magnetic recording medium of the present invention, the nonmagnetic support is preferably a film made of polyethylene terephthalate (PET). These materials are preferably used from the viewpoint of cost. Nonmagnetic supports made of polyethylene naphthalate, polyamide, polyimide, etc. generally have high mechanical strength and excellent dimensional stability. Dimensional stability against temperature and humidity changes can be improved. However, non-magnetic supports made of these materials are very expensive and may increase the cost of the product, so their use may not be welcomed. The present invention is characterized in that even when a film made of PET, which is widely used, is used as a nonmagnetic support, the magnetic recording medium is thinned and excellent dimensional stability against changes in the temperature and humidity environment is realized.

  The magnetic recording medium of the present invention preferably has a Young's modulus Emd1 in the longitudinal direction of the magnetic recording medium in the range of 4 to 14 GPa. When Emd1 is less than 4 GPa, when the magnetic recording medium is in a tape shape, the magnetic recording medium is likely to be deformed when subjected to an impact in the deck traveling system at the time of mode transition or the like. If Emd1 is greater than 14 GPa, the strength is too high and the contact with the magnetic head tends to be poor. The magnetic recording medium preferably has a Young's modulus Etd1 in the width direction in the range of 6 to 20 GPa. When Etd1 is less than 6 GPa, the strength in the width direction of the medium is low, and edge damage is likely to occur during driving. On the other hand, if Etd1 is greater than 20 GPa, the strength is too high and the contact with the magnetic head tends to be poor. Such a preferable Young's modulus is achieved by forming a reinforcing layer. By forming the reinforcing layer, even when the nonmagnetic support is thinned, the Young's modulus and strength of the entire magnetic recording medium are increased. Thus, dimensional stability can be improved.

In the magnetic recording medium of the present invention, the total thickness T1 of the magnetic recording medium is preferably in the range of 5.5 to 7.5 × 10 ⁻³ mm (that is, 5.5 to 7.5 μm). T1 is difficult to prepare a 5.5 × ¹⁰ -3 mm smaller than the magnetic recording medium, a larger 7.5 × ¹⁰ -3 mm, of the medium can be accommodated in a package of a predetermined size amount (tape-shaped In the case of a medium, the length) is reduced, which is disadvantageous for a high-density recording medium.

  In the magnetic recording medium of the present invention, the Young's modulus Emd2 in the longitudinal direction of the nonmagnetic support is preferably in the range of 3 to 6 GPa. If Emd2 is less than 3 GPa, it is difficult to increase the tensile strength in the longitudinal direction of the entire magnetic recording medium even if a reinforcing layer is formed. If it is higher than 6 GPa, the Young's modulus in the width direction is reduced by that amount, and even if a reinforcing layer is formed, it becomes difficult to achieve dimensional stability in the width direction against changes in the temperature and humidity environment. The Young's modulus Etd2 in the width direction of the nonmagnetic support is preferably in the range of 6 to 9 GPa. If Etd2 is smaller than 6 GPa, it is difficult to achieve dimensional stability in the width direction against temperature and humidity environment changes even if a reinforcing layer is formed. Further, if Etd2 is larger than 9 GPa, the Young's modulus in the longitudinal direction is lowered correspondingly, and it is difficult to increase the tensile strength in the longitudinal direction of the entire magnetic recording medium even if a reinforcing layer is formed. .

  In the magnetic recording medium of the present invention, the nonmagnetic support preferably has a total thickness of 2 to 5 μm. In general, it is difficult to form a first reinforcing layer and a magnetic layer described later on the surface of a nonmagnetic support having a thickness of less than 2 μm. Further, when the thickness of the nonmagnetic support exceeds 5 μm, the ratio of the nonmagnetic support to the entire magnetic recording medium increases, and the amount of the medium that can be accommodated in a package having a predetermined size decreases. As a disadvantage. According to the present invention, even when such a thin nonmagnetic support is used, the entire medium can be formed by appropriately forming the reinforcing layer in consideration of the balance between the entire medium and the Young's modulus of the nonmagnetic support. It is possible to ensure the rigidity and dimensional stability.

  In the magnetic recording medium of the present invention, the reinforcing layer may be present as the first reinforcing layer formed on the same side as the magnetic layer as viewed from the nonmagnetic support, or viewed from the nonmagnetic support. And may be present as a second reinforcing layer formed on the side opposite to the side where the magnetic layer is located. Each of the first reinforcing layer and the second reinforcing layer has a Young's modulus larger than that of a magnetic layer described later and a backcoat layer described later (usually, this is made of a resin or the like). In this specification, the term “side” is sometimes used to specify the directions of the two main surfaces (surfaces perpendicular to the stacking direction of each layer) of the nonmagnetic support in the magnetic recording medium. .

  In the magnetic recording medium of the present invention, when the first reinforcing layer is provided, the first reinforcing layer is preferably formed between the nonmagnetic support and the magnetic layer. Alternatively, when the magnetic recording medium of the present invention further includes a nonmagnetic layer containing a nonmagnetic powder and a binder, the nonmagnetic layer is preferably located between the first reinforcing layer and the magnetic layer. With such a configuration, the influence (for example, the influence on the recording characteristics of the recording medium) that the first reinforcing layer has on the magnetic layer can be reduced.

  In the magnetic recording medium of the present invention, when the second reinforcing layer is provided, the second reinforcing layer is preferably located between the nonmagnetic support and the backcoat layer. Here, the backcoat layer is a layer provided to stabilize the running property of the surface (that is, the back surface) opposite to the surface on which the magnetic layer of the magnetic recording medium is located. A recording medium is conventionally provided. Therefore, the second reinforcing layer can be disposed between the non-magnetic support and the backcoat layer in order to ensure stable running performance with the uppermost layer (that is, the exposed surface) on the back surface as the surface of the backcoat layer. preferable.

  The first reinforcing layer and / or the second reinforcing layer preferably has a thickness of 20 to 1000 nm. If it is smaller than 20 nm, it will be difficult to play a role as a reinforcing layer, and if it is larger than 1000 nm, it will be difficult to form a film and the cost will be increased, which is not preferable. Here, the term “and / or” in the expression “first reinforcing layer and / or second reinforcing layer” refers to a form having only the first reinforcing layer, a form having only the second reinforcing layer, and the first. It is used to generically refer to a magnetic recording medium having a form having both a reinforcing layer and a second reinforcing layer. The same applies to the following description. The reinforcing layer preferably has a Young's modulus in the range of 10 to 200 GPa. A reinforcing layer having a Young's modulus of less than 10 GPa has a small effect on the tensile strength and dimensional stability of the entire recording medium. When a film made of PET is used as a nonmagnetic support, such a reinforcing layer provides a magnetic recording medium. In general, it is difficult to reduce the thickness and improve the dimensional stability against changes in temperature and humidity. In order to form a reinforcing layer having a Young's modulus greater than 200 GPa, an expensive material is required. Therefore, the use of such a reinforcing layer is not preferable from the viewpoint of commercialization.

  By satisfying the above conditions, it is possible to make the magnetic recording medium thin while using an inexpensive PET support, and to effectively suppress dimensional changes in the width direction of the magnetic recording medium due to temperature and humidity changes. It becomes.

  The first reinforcing layer and / or the second reinforcing layer is preferably made of a nonmagnetic material so as not to adversely affect the magnetic properties of the magnetic layer. In particular, the first reinforcing layer and / or the second reinforcing layer is preferably a layer containing Cu and / or Al as a main component. Here, “a layer containing Cu as a main component” means a layer containing 50 atomic% or more of Cu, and includes a form in which Cu is contained as an alloy. Cu and Al are convenient for constituting the first reinforcing layer and the second reinforcing layer from the viewpoints of cost, film formation rate, mechanical strength, and the like.

  The first reinforcing layer and / or the second reinforcing layer is preferably formed by a vacuum deposition method. The vacuum deposition method is preferably used as a method for forming the first reinforcing layer and / or the second reinforcing layer because it enables a thin film to be formed at a high film formation rate.

  The magnetic recording medium of the present invention is preferably a magnetic recording medium used for recording / reproducing in a linear manner in which signals are recorded in a direction parallel to the longitudinal direction. When narrowing the track in the linear recording method, particularly when recording is performed with a recording track width of 14 μm or less, particularly high dimensional stability is required. According to the present invention, even when such a narrow track width is adopted, it is possible to effectively suppress the dimensional change due to the temperature and humidity change of the recording medium and to prevent the occurrence of errors due to the track deviation at the time of reproduction. Become. Note that the recording track width in the linear recording method that will be employed in the future is generally 3 μm to 15 μm.

  The magnetic recording medium of the present invention is a magnetic recording medium comprising a non-magnetic support, a magnetic layer containing ferromagnetic powder and a binder, and a reinforcing layer, and is provided in the longitudinal direction and the width direction of the magnetic recording medium. When the Young's modulus is Emd1 (GPa) and Etd1 (GPa), the thickness of the magnetic recording medium is T1 (mm), and the Young's modulus in the longitudinal direction and the width direction of the nonmagnetic support is Emd2 and Etd2. ≦ Etd1 / Emd1 ≦ 1.5, 35 ≦ Emd1 × T1, and 1.5 ≦ Etd2 / Emd2 ≦ 2.5 are satisfied. According to this feature, even when an inexpensive film is used, the reinforcing layer is formed in the minimum amount necessary, and the width of the magnetic recording medium can be reduced and the temperature and humidity environment change can be reduced while suppressing the production cost. Improvement in dimensional stability can be realized. Therefore, according to the present invention, it is possible to realize a coated magnetic recording medium (for example, a data storage tape) having a high reliability and a large recording capacity.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below.
In the present specification including the following description, the “surface” of each layer or film constituting the magnetic recording medium is a surface exposed when each layer or film is formed, that is, a nonmagnetic support of each layer or film. It means the surface far from the body. The term “on the surface” of each layer refers to a position in contact with the surface unless otherwise specified. Furthermore, in this specification including the following description, regarding the configuration of the magnetic recording medium, the term “on” each layer or film constituting the magnetic recording medium refers to the nonmagnetic support of each layer or film unless otherwise specified. It means that it touches the surface on the side far from the body. Therefore, for example, “on the magnetic layer” means “at a position adjacent to the surface of the magnetic layer far from the nonmagnetic support”. Further, as described above, the term “side” is used to specify the direction of one of the two main surfaces of the sheet-like material. When a layer is said to be “formed on the side of”, not only is the layer formed directly on the surface of the sheet, but also the surface of another film formed on the surface. It should be noted that the above-described forms are also included.

As described above, in the magnetic recording medium of the present invention, the Young's modulus in the longitudinal direction and the width direction of the magnetic recording medium is Emd1 (GPa) and Etd1 (GPa), the thickness of the magnetic recording medium is T1 (mm), and nonmagnetic When the Young's modulus in the longitudinal direction and the width direction of the support is Emd2 (GPa) and Etd2 (GPa),
1.1 ≦ Etd1 / Emd1 ≦ 1.5,
35 ≦ Emd1 × T1 (N / mm), and 1.5 ≦ Etd2 / Emd2 ≦ 2.5
It is characterized by satisfying. When Etd1, Emd1, T1, Etd2 and Emd2 do not satisfy this relationship, a non-magnetic support (for example, an inexpensive PET film) that does not have a high Young's modulus is used to reduce the thickness and change the temperature and humidity environment. It is impossible to solve the problem of the present invention that a magnetic recording medium in which a dimensional change in the width direction due to the occurrence of the magnetic recording medium hardly occurs, preferably at a low production cost.

The Young's modulus in the longitudinal direction and the width direction of the magnetic recording medium and the nonmagnetic support is the load acting on the cross section of the sample when the sample is pulled in the longitudinal direction and the width direction at a predetermined distance between the marked lines (tensile length). It can be calculated from (stress), the elongation of the sample and the cross-sectional area of the sample. Specifically, the formula E = (W · L) / (A · Δl) (where E is the Young's modulus (Pa), W is the load within the elastic limit (N), and L is the standard before the tensile test. The distance between the lines (m), A can be calculated based on the cross-sectional area (m ² ) before the tensile test of the sample, and Δl indicates the elongation between the marked lines at the load W (m)).

  The nonmagnetic support for which Etd2 and Emd2 are to be measured is obtained by etching the magnetic layer and the reinforcing layer of the magnetic recording medium using an organic solvent, acid, or the like. Alternatively, Etd2 and Emd2 can be obtained by measuring the Young's modulus of the nonmagnetic support before forming the magnetic layer or the reinforcing layer in the process of manufacturing the magnetic recording medium.

  For the load acting on the sample and the elongation of the sample, a tensile test apparatus (for example, RTM-25 manufactured by Orientec Co., Ltd.) was used, the tensile length (distance between marked lines) was set to 10 mm, and the tensile speed was set to 1 mm / min. Perform the test and measure. Also, if it is necessary to determine the cross-sectional area of the sample, it can be determined from the width and thickness of the sample. For example, the thickness of a thin sample such as a magnetic tape can be obtained by measuring with a micrometer in a state where 10 samples are stacked.

The Young's modulus of the reinforcing layer (for convenience, E3) indicates that the magnetic recording medium having the reinforcing layer and the magnetic recording medium not having the reinforcing layer (that is, only the reinforcing layer is removed from the magnetic recording medium having the reinforcing layer). The Young's modulus in the width direction (hereinafter simply referred to as “Young's modulus” refers to the Young's modulus in the width direction). If the thickness of the reinforcing layer is T3, the Young's modulus and thickness of the magnetic recording medium having the reinforcing layer are E1 and T1, and the Young's modulus and thickness of the magnetic recording medium having no reinforcing layer are Ex and Tx, then E1, Tx and E3 and T1, Tx and T3 have the following relationship:
E1 = Ex. [Tx / T1] + E3. [T3 / T1]
Meet. From now on,
E1 / T1 = Ex / Tx + ET / T3
The relationship is guided. Therefore, if E1 and Ex and T1 and Tx are obtained by measurement and T3 is calculated by calculation, E3 can be obtained from the above equation.

When it is difficult to remove only the reinforcing layer from the magnetic recording medium having the reinforcing layer (for example, when the reinforcing layer is located between the nonmagnetic support and the magnetic layer), it is possible to remove only the reinforcing layer. Until it becomes possible (that is, until the surface of the reinforcing layer is exposed), a laminate from which the layer located on the reinforcing layer is removed is obtained, and the Young's modulus Ey and thickness Ty thereof, and the The Young's modulus Ez and thickness Tz of the laminate obtained by removing the reinforcing layer from the laminate are determined. In this case, E3, T3, Ey, Ty, Ez, Tz have the following relationship:
Ey = Ez · [Tz / Ty] + E3 · [T3 / Ty]
Meet. From now on,
Ey · Ty = Ez · Tz + E3 · T3
The relationship is guided. Therefore, if Ey and Ez and Ty and Tz are obtained by measurement and T3 is calculated by calculation, E3 can be obtained from the above equation.

  A magnetic recording medium having no reinforcing layer can be obtained by etching the reinforcing layer of the magnetic recording medium using an acid or the like. Similarly, a laminate in which the reinforcing layer and the layer located thereon are removed from the magnetic recording medium is similarly removed by etching or the like to obtain a laminate having the reinforcing layer on the surface. Then, the reinforcing layer is obtained by etching. Then, by measuring the Young's modulus and thickness of the magnetic recording medium or laminate before and after etching, the Young's modulus and thickness in the width direction of the reinforcing layer can be obtained. Alternatively, the Young's modulus of the reinforcing layer can also be obtained by measuring the Young's modulus and thickness of the nonmagnetic support (or laminate) before forming the reinforcing layer in the process of manufacturing the magnetic recording medium. is there.

  In the magnetic recording medium of the present invention, the Young's modulus in the longitudinal direction and the width direction of the magnetic recording medium is Emd1 (GPa) and Etd1 (GPa), the thickness of the magnetic recording medium is T1 (mm), and the longitudinal direction of the nonmagnetic support is As long as the Young's modulus in the width direction is such that Emd2 (GPa) and Etd2 (GPa) satisfy the above relationship, the specific configuration of the reinforcing layer and the configuration of other elements (for example, the magnetic layer) are arbitrary. can do. Hereinafter, an example of a specific configuration of the magnetic recording medium of the present invention will be described with reference to FIG.

  FIG. 1 schematically shows a cross section of a magnetic tape as an example of the magnetic recording medium of the present invention. 1 has a first reinforcing layer 2, a nonmagnetic layer 3, and a magnetic layer 4 formed in this order on one surface side of a nonmagnetic support 1, and the other side of the nonmagnetic support 1 has the other side. A second reinforcing layer 5 and a backcoat layer 6 are formed on the surface side.

  The nonmagnetic support 1 is preferably a polymer film. The polymer film is formed by appropriately selecting one or more materials from polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyvinyl chloride, polycarbonate, and the like. If the thickness of the nonmagnetic support is too thin, the strength becomes too weak, and if it is too thick, the thickness of the entire medium becomes too large, which is disadvantageous for increasing the recording capacity. Specifically, the thickness of the nonmagnetic support is preferably 2 to 5 μm. It goes without saying that a thinner non-magnetic support may be used as long as the strength according to the application can be ensured, and if a large capacity is not particularly required, a thick non-magnetic support is used. May be used.

  The magnetic recording medium of the illustrated form has two reinforcing layers 2 and 5. The first reinforcing layer 2 is located on the side where the magnetic layer 4 is formed as viewed from the nonmagnetic support 1, and the second reinforcing layer 5 is formed with a backcoat layer 6 when viewed from the nonmagnetic support. Located on the side. The first reinforcing layer 2 and the second reinforcing layer 5 have the Young's modulus in the longitudinal direction and the width direction of the magnetic recording medium as Emd1 and Etd1, the thickness of the magnetic recording medium as T1, and the nonmagnetic support in the longitudinal direction and the width direction. When the Young's modulus is Emd2 and Etd2, it is formed so as to satisfy the above specific relationship. Thereby, it is possible to reduce the overall thickness of the magnetic recording medium and to reduce the dimensional change in the width direction with respect to the temperature and humidity environment change. Furthermore, by satisfying these relationships, it is possible to balance the stress of each layer and prevent the occurrence of cupping (curvature in the width direction).

  Each of the first reinforcing layer 2 and the second reinforcing layer 5 preferably has a Young's modulus of 10 GPa or more, and more preferably has a Young's modulus of 30 to 200 GPa. In order to achieve such Young's modulus, the first reinforcing layer 2 and the second reinforcing layer 5 preferably comprise a metal, a metalloid or an alloy. Alternatively, the first reinforcing layer 2 and the second reinforcing layer 5 may include oxides, nitrides or carbides thereof instead of or together with the metal, metalloid or alloy. Moreover, the 1st reinforcement layer 2 and the 2nd reinforcement layer 5 may contain an organic compound (for example, resin), as long as a high Young's modulus can be ensured. The material constituting the first reinforcing layer 2 and the second reinforcing layer 5 is also preferably a non-magnetic material so that the magnetic properties of the magnetic layer 4 are not affected. Specifically, the first reinforcing layer 2 and the second reinforcing layer 5 are made of Ti, Cr, Mn, Fe, Al, Cu, Zn, Sn, Ni, Ag, Pb, W, Mg, Mo, Si, Au, It is preferable to contain 50 atomic% or more of one or more elements selected from Zr, Pt, Ta, V, Nb and Co as a main component. The first reinforcing layer 2 and the second reinforcing layer 5 may be formed of an alloy containing one or more of these metals. Since Fe, Ni, and Co are magnetic materials, when they are used, it is preferable that they are oxidized and made nonmagnetic.

  In consideration of cost, adhesion speed, and mechanical strength (particularly Young's modulus), the first reinforcing layer 2 and the second reinforcing layer 5 are Cu, Al, or Cu containing Cu or Al as a main component, and preferably containing 50 atomic% or more. It is preferable to use an Al alloy or an Al alloy. When using a Cu-based alloy or an Al-based alloy, the alloy includes, as additives added to improve corrosion resistance and mechanical strength, Al, Ni, Cr, Be, Co, Zr, Sn, Mn, Fe, Commonly used materials such as Si, Mg, Cu or Zn can be arbitrarily added.

  The first reinforcing layer 2 and the second reinforcing layer 5 may be in the form of a single layer film or may be in the form of a multilayer film. As described above, the thicknesses of the first reinforcing layer 2 and the second reinforcing layer 5 are each preferably 20 to 1000 nm, and more preferably 50 to 500 nm.

  When the first reinforcing layer 2 and the second reinforcing layer 5 are formed of the metal exemplified above, the reinforcing layer is formed by a sputtering method, a vacuum deposition method, an ion plating method, or the like. A particularly preferable film forming method is a vacuum evaporation method. When metal vacuum deposition is performed in an atmosphere containing oxygen, the reinforcing layer may contain oxygen in the form of an oxide such as a metal. The presence of such oxygen is allowed as long as Etd1, Emd1, T1, Etd2 and Emd2 satisfy the above predetermined relationship.

  Next, the magnetic layer 4 will be described. In the magnetic recording medium of the present invention, the magnetic layer 4 is conventionally made of magnetic powder, binder, antistatic agent, curing agent, dispersant, abrasive, rust inhibitor, lubricant, additive, organic solvent, and the like. It is formed by preparing a magnetic paint by a known method and applying it. The ferromagnetic powder constituting the magnetic layer of the present invention is preferably a ferromagnetic metal powder or a hexagonal ferrite powder, but is not limited thereto.

The ferromagnetic metal powder constituting the magnetic layer of the present invention is not particularly limited as long as it contains Fe as a main component (including an alloy), but a ferromagnetic alloy powder containing α-Fe as a main component is preferable. In addition to Fe, these ferromagnetic metal powders include Al, Si, S, Sc, Ca, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, It may contain one or more atoms selected from W, Re, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, and B. These ferromagnetic metal powders may be treated in advance with a dispersant, a lubricant, a surfactant, an antistatic agent or the like, which will be described later. The average major axis length of the ferromagnetic metal powder is preferably 0.01 to 0.10 μm, more preferably 0.05 to 0.08 μm. If the average major axis length is 0.01 μm or more, stable magnetization can be obtained without being affected by thermal fluctuations, and if the average major axis length is 0.10 μm or less, noise can be kept low. BET method by the specific surface area of the ferromagnetic metal powder employed in the magnetic layer of the present invention (SBET) is preferably 30 to 50 m ² / g, more preferably from 38~48m ² / g. Thereby, both good surface properties and low noise can be achieved.

  When reproducing using a magnetoresistive head (MR head) for the purpose of increasing the track density, it is necessary to keep the noise of the magnetic recording medium itself low. Therefore, when hexagonal ferrite powder is used as the ferromagnetic metal powder, the average plate diameter needs to be 40 nm or less. However, if the average plate diameter is less than 5 nm, stable magnetization cannot be expected due to thermal fluctuation. Therefore, when using hexagonal ferrite powder, it is preferable to use one having an average plate diameter of 10 to 35 nm, and even more preferable to use one having an average plate diameter of 15 to 30 nm.

  Conventionally known binders, antistatic agents, curing agents, dispersants, lubricants, abrasives, rust inhibitors, additives, and organic solvents that constitute the magnetic layer together with the ferromagnetic powder may be arbitrarily used. . For example, binders include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, And a polymer in which one constitutional unit selected from vinyl ether is polymerized, or a copolymer of a plurality of constitutional units can be used. Alternatively, the binder may be a polyamide resin, a polyester resin, a phenol resin, an epoxy resin, or the like.

  As the antistatic agent, carbon black is mainly used. Preferably, carbon black having an average particle diameter of 10 to 1000 nm is used.

  As the curing agent, for example, an adduct of an aromatic polyisocyanate and an aliphatic polyisocyanate and an active hydrogen compound (for example, ethylene glycol, 1,4-butanediol, glycerin) can be used.

  Examples of the dispersant and the lubricant include, for example, fatty acids having 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, metallic soap of the fatty acid, Amides, silicone oils, fluorine-based lubricants, alkyl phosphates and metal salts, and polyphenyl ethers can be used. Two or more dispersants and lubricants may be used in combination.

  As the abrasive, for example, an amorphous oxide powder is used. Specifically, silicon oxide, titanium oxide, chromium oxide, cerium oxide, iron oxide, or the like can be used. The rust preventive agent and other additives may be arbitrarily selected from those conventionally used in the field of magnetic recording media, if necessary.

  The magnetic layer 4 is formed by preparing a magnetic coating material in which the above-described ferromagnetic powder, binder, and the like are dispersed in a solvent by a known method and applying it. Solvents for preparing magnetic paints include, for example, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as methyl acetate and butyl acetate, glycol ether solvents, and aromatic hydrocarbons such as benzene. Solvents and organic chlorine compound solvents such as methylene chloride and dichlorobenzene can be used.

  The thickness of the magnetic layer 4 (thickness after drying) is preferably 0.01 to 1.0 μm. In particular, in a magnetic recording medium for use in a recording / reproducing apparatus that uses a magnetoresistive head (MR head) as a reproducing head, the thickness of the magnetic layer 4 is preferably 0.01 to 0.3 μm.

  Next, the nonmagnetic layer 3 will be described. The nonmagnetic layer 3 is a layer provided to uniformly apply the magnetic layer 4 and functions as a kind of underlayer. In particular, when the thickness of the magnetic layer 4 is reduced, it is preferable to provide the nonmagnetic layer 3. The nonmagnetic layer 3 includes a nonmagnetic powder and a binder. The nonmagnetic powder may be either an inorganic substance or an organic substance. Alternatively, carbon black or the like can be used as the nonmagnetic powder. Examples of inorganic substances include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. The shape of the nonmagnetic powder may be any of acicular, spherical, polyhedral and plate shapes. When the nonmagnetic layer 3 is formed of a material in which carbon black is mixed with nonmagnetic powder, the surface electrical resistance can be lowered and the light transmittance can be reduced. The light transmittance can also be adjusted using rubber furnace, rubber thermal, color black, acetylene black, and the like. An organic powder can be added to the nonmagnetic layer 3 according to the purpose. As the lubricant, dispersant, additive and solvent used for forming the nonmagnetic layer 3, and the dispersion method of the nonmagnetic powder and the like in the solvent, those used in the magnetic layer can be used. In particular, when selecting the type and mixing ratio of the dispersant and additive, known techniques employed in the magnetic layer can be applied.

  The thickness of the nonmagnetic layer 3 (thickness after drying) is preferably 0.2 to 3.0 μm, and more preferably 1.0 to 2.5 μm.

  The formation (film formation) of the magnetic layer 4 and the nonmagnetic layer 3 is preferably performed by a method of forming the magnetic layer 4 while the nonmagnetic layer 3 is in a wet state. Specifically, the magnetic layer 4 is a so-called magnetic coating, in which a coating liquid for forming the nonmagnetic layer 3 is applied and then a magnetic coating is applied while the formed coating layer (nonmagnetic layer) is in a wet state. It is preferable to form by applying by a wet-on-wet method. Since the wet-on-wet method itself is known, its detailed description is omitted here.

  Next, the back coat layer 6 will be described. The back coat layer 6 is formed on the surface of the second reinforcing layer 5 to ensure the running property of the surface of the magnetic recording medium that does not contact the magnetic head. The back coat layer 6 is made of one or more materials selected from polyurethane-based resins, nitrocellulose-based resins, polyester-based resins (for example, Byron), carbon, calcium carbonate, and the like using a suitable solvent (for example, toluene and A coating solution dissolved and / or dispersed in a mixed solvent of methyl ethyl ketone) is prepared, and this coating solution is applied to the surface of the second reinforcing layer 5 and then dried to evaporate the solvent. Thus, when forming a backcoat layer, it is preferable that the thickness shall be 100-1000 nm.

  The illustrated form is merely an example of the present invention, and the magnetic recording medium of the present invention includes other forms. For example, the first reinforcing layer may be located between the nonmagnetic layer and the magnetic layer, or two first reinforcing layers may sandwich the nonmagnetic layer. Alternatively, a lubricant layer may be formed on the surface of the second reinforcing layer without forming a backcoat layer to ensure running performance. Further, only one of the first reinforcing layer and the second reinforcing layer may be formed as the reinforcing layer. When only one reinforcing layer is formed, the reinforcing layer is preferably formed as a second reinforcing layer. This is because the cupping is effectively prevented by forming the second reinforcing layer. In any form, preferred materials, thicknesses, and the like constituting the reinforcing layer are as described above in relation to the first reinforcing layer and the second reinforcing layer.

  Hereinafter, the present invention will be specifically described by way of examples. In the examples, the Young's modulus in the longitudinal direction and the width direction of the nonmagnetic support of each sample was determined by etching all layers other than the nonmagnetic support after producing the magnetic tape. The tensile test apparatus used for the measurement of Young's modulus was RTM-25 (trade name) manufactured by Orientec Co., Ltd., the tensile length was 10 mm, and the tensile speed was 1 mm / min. Moreover, the thickness (T1: unit mm) of each sample was calculated from the thickness measured with a micrometer (manufactured by Mitutoyo Corporation) in a state where 10 samples were stacked.

(Sample 1)
A tape-like magnetic recording medium having the same mode as that shown in FIG. 1 except that the first reinforcing layer was not provided was produced according to the following procedure. First, as the nonmagnetic support 1, a PET film having a thickness of 3.3 μm, a width of 150 mm, a length of 1000 m, a longitudinal Young's modulus Emd2 of 4.3 GPa, and a widthwise Young's modulus Etd2 of 6.5 GPa was used. A first reinforcing layer 2 made of Cu was formed on the surface by a vacuum deposition method. Deposition was performed while the nonmagnetic support 1 was run along the cooling rotation support in an air atmosphere having a pressure of about 2 × 10 ⁻² Pa. The film thickness of the first reinforcing layer was controlled by the traveling speed. Here, the second reinforcing layer having a thickness of 50 nm was formed at a traveling speed of 60 m / min.

  Next, a non-magnetic paint and a magnetic paint were simultaneously applied in a wet-on-wet manner using a die coater so that the non-magnetic paint was formed on the first reinforcing layer 2. The coating amounts of the nonmagnetic paint and the magnetic paint were adjusted so that the thickness after drying of the nonmagnetic layer 3 was 1.95 μm and the thickness after drying of the magnetic layer 4 was 0.15 μm.

For the magnetic coating material, a ferromagnetic powder, an abrasive, a binder, a lubricant, and a solvent were put into a planetary mixer, and premixed to prepare a mixture. Next, this mixture was subjected to a high shear dispersion treatment with a biaxial continuous kneader. The solvent was added to this, and the dilution process was performed with the stirrer. Further, after fine dispersion treatment with a sand mill, a solvent was added to adjust the viscosity appropriately, and filtration was performed using a filtration filter having an absolute filtration accuracy of 1 μm. Then, the hardening | curing agent was added and the magnetic coating material for magnetic layers was obtained. The composition of the magnetic paint is as shown below.
Ferromagnetic powder: Fe-Co 100 parts by weight,
Abrasive: α-alumina 2 parts by weight,
Binder: 10 parts by weight of vinyl chloride,
Lubricant: 2 parts by weight of stearic acid,
Organic solvent: 100 parts by weight of methyl ethyl ketone.

Non-magnetic paints are prepared by pre-mixing non-magnetic powders with abrasives, carbon black, binder and solvent to prepare a mixture for non-magnetic paints, followed by high shear according to the same method used for the preparation of magnetic paints. Dispersion treatment, dilution treatment, fine dispersion treatment, filtration, and the like were performed to obtain a nonmagnetic paint for the nonmagnetic layer. The composition of the nonmagnetic paint is as shown below.
Nonmagnetic powder: α-Fe ₂ O ₃ 100 parts by weight,
: Carbon black 20 parts by weight,
Abrasive: α-alumina 2 parts by weight,
Binder: 10 parts by weight of vinyl chloride,
Solvent: 150 parts by weight of methyl ethyl ketone.

  Next, a backcoat layer 6 having a thickness of 550 nm made of polyurethane resin added with carbon black was formed on the surface of the nonmagnetic support 1 opposite to the surface on which the first reinforcing layer 2 was formed. The back coat layer was formed by applying a coating solution prepared by dissolving carbon black (50 parts by weight) and polyurethane resin (100 parts by weight) in methyl ethyl ketone, and then drying to evaporate the methyl ethyl ketone. The magnetic recording medium thus produced was slit to a predetermined width (1/2 inch) to obtain a magnetic tape.

(Samples 2 to 25)
A PET film having a Young's modulus and thickness shown in Table 1 was used, and the first reinforcing layer and the second reinforcing layer were formed using the materials shown in Table 1 so as to have the thicknesses shown in Table 1. The magnetic tape was obtained in accordance with the same procedure as that of Sample 1 except that. Sample 19 was prepared without forming a reinforcing layer.

  In the case of a PET film having an Emd2 / Etd2 of greater than 2.5, a sample could not be prepared because the film was frequently cut due to heat loss during the vapor deposition process for forming the reinforcing layer.

  Each of the obtained samples was subjected to the following measurements (a) to (c). The obtained measurement results are shown in Table 2.

(A) Cupping Each film has a film forming condition for each film so that the cupping is within a range of −10% to + 10% (ie, substantially flat) in a low humidity environment (15% RH). Were prepared. About each produced sample, the cupping amount of the sample after storing for 100 hours in 60 degreeC30% RH atmosphere was measured. The cupping amount is obtained by placing a curved magnetic recording medium on a flat plate, measuring the height of the curved vertex from the flat plate surface, dividing this value by the width of the magnetic tape, and multiplying this by 100. It was. The amount of cupping was negative (minus) when the magnetic layer side surface was in a convex state, and positive (plus) when the magnetic layer side surface was in a concave state. The cupping amount in the range of −10% to + 10% is described as “Flat” in the column of the cupping amount.

(B) Recording / reproducing characteristics The recording / reproducing characteristics were measured using a magnetic recording / reproducing apparatus capable of recording / reproducing signals by traveling in two longitudinal directions. Signal recording / reproduction was performed using a fixed head. Recording was performed using a metal-in-gap type inductive head having a gap length of 0.18 μm in a temperature and humidity environment of 10 ° C. and 10% RH. Here, an inductive head having a recording track width of 10 μm was prepared, and recording was performed at a recording wavelength of 0.4 μm using each head. The recorded signal was reproduced using a magnetoresistive head with a reproduction track width of 5 μm. Based on the reproduction output, the track deviation caused by the temperature and humidity change was evaluated. More specifically, the track deviation is 90% or more in the ratio of the reproduction output at 40 ° C. and 60% RH to the reproduction output at 10 ° C. and 10% RH temperature and humidity environment (output ratio (%)). Was marked as ○. For samples with a large cupping, recording failure was not performed because a head contact defect occurred during recording / reproduction, and head contamination and clogging occurred.

(C) Edge damage The tape edge damage level after measuring the recording / reproducing characteristics was observed with a visual observation and a differential interference microscope, and evaluated in five stages. The evaluation criteria are as follows.
○: No problem in practical use.
Δ: Practical but possible to improve.
X: Edge damage is severe and practicality is scarce.

  As is apparent from Table 2, the samples 1 to 24 satisfying 1.1 ≦ Etd1 / Emd1 ≦ 1.5, 35 ≦ Emd1 × T1, and 1.5 ≦ Etd2 / Emd2 ≦ 2.5 have different temperatures and humidity. Even when recording / reproduction with a narrow track was performed in the environment, the track deviation was small. Specifically, even when the recording track width was 10 μm, the output ratio was 90% or more, and a good reproduction signal was obtained. Further, the cupping amount was small, and no tape edge damage was observed after the recording / reproduction characteristics were measured. The excellent results of these samples 1 to 24 show that even when an inexpensive PET film having a relatively low strength is used as a nonmagnetic support, the Young's modulus in the width direction of the PET film is 1.5 times the Young's modulus in the longitudinal direction. By strengthening so as to be -2.5 times, the dimensional stability in the tape width direction against the change in temperature and humidity environment after making the magnetic tape is improved, and the Young's modulus in the width direction of the PET film is enhanced. It shows that the dimensional change with respect to humidity in the tape width direction is further suppressed by reinforcing the decreasing strength in the longitudinal direction with the reinforcing layer so that 1.1 ≦ Etd1 / Emd1 ≦ 1.5.

  Since Samples 25 to 37 do not satisfy any one of the above three conditions, at least one of dimensional stability, tensile strength in the longitudinal direction, and cupping amount with respect to changes in the temperature and humidity environment compared to Samples 1 to 24 is required. Was clearly inferior. That is, when Etd1 / Emd1 is small, cupping is not stable. On the other hand, when Etd1 / Emd1 is large, sufficiently high dimensional stability is not obtained with respect to a change in humidity, resulting in track deviation. Further, edge damage occurred when Emd1 × T1 was small. Furthermore, when Etd2 / Emd2 is not in the range of 1.5 or more and 2.5 or less, the production of the magnetic recording medium itself is impossible, or sufficiently high dimensional stability is obtained against temperature changes. It was not possible to produce a track shift. Thus, from the results of this example, when a plastic film (especially PET film) is used as a non-magnetic support, the recording layer can be thinned and the recording track width can be reduced by simply forming the reinforcing layer. It is not possible to obtain a magnetic recording medium that can be used as a practical one. It can be said that it can be effectively realized.

  Since the magnetic recording medium of the present invention is characterized in that the dimensional change in the width direction is small when the temperature and humidity environment changes even when the thickness is reduced, the magnetic recording medium is manufactured using a thin non-magnetic support and recorded. Even when the track width is narrowed, tape edge damage or track deviation is extremely small or not generated. Therefore, the magnetic recording medium of the present invention is particularly preferably used as a magnetic tape used for data storage such as DLT and LTO.

1 is a cross-sectional view schematically showing an example of a magnetic recording medium of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic support body, 2 ... 1st reinforcement layer, 3 ... Nonmagnetic layer, 4 ... Magnetic layer, 5 ... 2nd reinforcement layer, 6 ... Backcoat layer, 10. Magnetic recording medium

Claims (20)

A magnetic recording medium comprising a nonmagnetic support, a magnetic layer containing ferromagnetic powder and a binder, and a reinforcing layer, wherein the Young's modulus in the longitudinal direction and the width direction of the magnetic recording medium is Emd1 (GPa) and When Etd1 (GPa), the thickness of the magnetic recording medium is T1 (mm), and the Young's modulus in the longitudinal direction and the width direction of the nonmagnetic support is Emd2 (GPa) and Etd2 (GPa),
1.1 ≦ Etd1 / Emd1 ≦ 1.5,
35 ≦ Emd1 × T1 (N / mm), and 1.5 ≦ Etd2 / Emd2 ≦ 2.5
A magnetic recording medium that satisfies the requirements.   2. The magnetic recording medium according to claim 1, wherein the nonmagnetic support is a film made of polyethylene terephthalate.   The magnetic recording medium according to claim 1 or 2, wherein Emd1 is 4 to 14 GPa.   The magnetic recording medium according to any one of claims 1 to 3, wherein Etd1 is 6 to 20 GPa. T1 magnetic recording medium according to any one of claims 1 to 4 is ^{5.5 × 10 -3 ~7.5 × 10 -3} mm.   The magnetic recording medium according to claim 1, wherein Emd2 is 3 to 6 GPa.   Etd2 is 6-9GPa, The magnetic recording medium of any one of Claims 1-6.   The magnetic recording medium according to claim 1, wherein the nonmagnetic support has a thickness of 2 to 5 μm.   The magnetic recording medium according to claim 1, comprising at least a first reinforcing layer formed on the same side as the side on which the magnetic layer is located as viewed from the nonmagnetic support as the reinforcing layer.   The magnetic recording medium according to claim 9, wherein the first reinforcing layer is formed between the nonmagnetic support and the magnetic layer.   The magnetic recording medium according to claim 9, further comprising a nonmagnetic layer containing nonmagnetic powder and a binder, wherein the nonmagnetic layer is formed between the first reinforcing layer and the magnetic layer.   The magnetic recording medium according to claim 1, comprising at least a second reinforcing layer formed as a reinforcing layer on a side opposite to the side on which the magnetic layer is located when viewed from the nonmagnetic support. .   The magnetic recording medium according to claim 1, further comprising a backcoat layer formed on a side opposite to the side on which the magnetic layer is located when viewed from the nonmagnetic support.   The magnetic recording medium according to claim 13, wherein the second reinforcing layer is formed between the nonmagnetic support and the backcoat layer.   The magnetic recording medium according to claim 9, wherein the thickness of the first reinforcing layer and / or the second reinforcing layer is 20 to 1000 nm.   The magnetic recording medium according to claim 9, wherein the Young's modulus of the first reinforcing layer and / or the second reinforcing layer is 10 to 200 GPa.   The magnetic recording medium according to claim 9, wherein the first reinforcing layer and / or the second reinforcing layer is made of a nonmagnetic material.   The magnetic recording medium according to any one of claims 9 to 16, wherein the first reinforcing layer and / or the second reinforcing layer contains Cu and / or Al as a main component.   The magnetic recording medium according to claim 9, wherein the first reinforcing layer and / or the second reinforcing layer is formed by a vacuum deposition method. The magnetic recording medium according to claim 1, wherein a signal having a recording track width of 14 μm or less is recorded by a linear recording method.

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