JP2017139042A - Tape recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tape recording medium having a substrate, a recording layer provided on a first principal lane of the substrate and a slide layer provided on a second principal lane, in which running stability and running durability are further improved and the occurrence of powder is further suppressed which is generated by wear of the tape recording medium itself or a member in a recording-playback apparatus.SOLUTION: The slide layer has electric resistance of 1×10Ω/square or less and contains carbon particles and solid particles. The carbon particles have a primary particle diameter of 30 nm or less and a BET specific surface area of 100 m/g or larger. The solid particles have a primary particle diameter of 100 nm or less, a Mohs hardness of 2.5-8 inclusive, a density of 3 g/cmor greater, and a BET specific surface area of 30 m/g or larger.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a tape recording medium used as an audio tape, a video tape, a data tape, and the like.

  As a tape recording medium, a magnetic recording tape for magnetically recording and reproducing, an optical recording tape for optically recording and reproducing data (signal), and the like are known. Regardless of the recording method, the tape recording medium has a recording layer (also referred to as a recording / reproducing layer) from which information is recorded and from which the recorded information is read. In order to increase the recording density of the tape itself, a finer structure is employed in the recording layer. Also, a thinner tape recording medium is desired in order to increase the recording capacity per unit volume. Thereby, for example, the total length of the tape recording medium accommodated in a predetermined cartridge can be made longer.

  The tape recording medium has a surface on which the recording layer is provided on a fixing member such as a head and a stabilizer in the recording / reproducing device depending on the type and / or the type of the recording / reproducing device in which the tape recording medium is used. Slide on. Alternatively, the surface opposite to the side on which the recording layer is provided may slide on the fixing member. In general, in the case of a magnetic recording medium, the surface on which the recording layer is provided slides exclusively on the fixed member, and the surface opposite to the side on which the recording layer is provided slides on a rotating member such as a roller. To do. On the other hand, the medium other than the magnetic recording medium generally slides exclusively on the fixed member on the surface opposite to the side on which the recording layer is provided. For example, with respect to a tape recording medium in which a fine structure is provided in the recording layer and this structure is destroyed by contact with a member in the recording / reproducing apparatus, the surface opposite to the side on which the recording layer is provided is Slides with members in the recording / playback equipment. Such a tape recording medium advances in the recording / reproducing apparatus during recording / reproducing, while only the sliding surface is in contact with various members including a fixing member in the recording / reproducing apparatus.

  Conventionally, in a tape recording medium that has been proposed, a lubricant layer is provided on the surface on which the recording layer is provided, and a back coat containing carbon black as a main component on the surface opposite to the side on which the recording layer is provided. Layers are provided (Patent Documents 1, 2, 4, 5, 6). Patent Document 3 proposes a tape-shaped optical recording medium having a configuration in which a recording layer, a reflective layer, and an antistatic layer are laminated in this order on one main surface of a polymer substrate. This optical recording medium records and reproduces data (signal) by irradiating a recording layer with laser light through a polymer substrate.

JP-A-5-73882 JP-A-11-279443 JP 2004-241007 A JP 2008-165841 A JP 2010-102818 A JP 2005-183898 A

  An object of the present disclosure is to provide a tape recording medium having a support, a recording layer provided on the first main surface of the support, and a sliding layer provided on the second main surface. In this tape recording medium, running stability and running durability are further improved, and generation of powder caused by wear of the tape recording medium itself or members in the recording / reproducing apparatus is further suppressed. Hereinafter, the tape recording medium may be simply referred to as “recording medium” or “medium”.

The tape recording medium according to the present disclosure includes a support, a recording layer provided on the first main surface of the support, and a sliding layer provided on the second main surface. The sliding layer has an electric resistance of 1 × 10 ⁸ Ω / □ or less, and contains carbon particles and solid particles. The carbon particles have a primary particle size of 30 nm or less and a BET specific surface area of 100 m ² / g or more. The solid particles have a primary particle size of 100 nm or less, a Mohs hardness of 2.5 or more and 8 or less, a density of ³ g / cm ³ or more, and a BET specific surface area of 30 m ² / g or more.

  According to the present disclosure, a tape recording medium that can travel more stably can be obtained because the sliding layer is less likely to be charged. Further, according to the present disclosure, since the powder resulting from the sliding of the sliding layer is less likely to be generated from the sliding layer and the fixing member in the recording / reproducing apparatus, the running durability is higher. Further, according to the present disclosure, the quality of the reproduction signal is hardly deteriorated due to the adhesion of the powder and the transfer of the powder shape, and the durability is higher in terms of the signal quality.

FIG. 1 is a schematic cross-sectional view of a tape recording medium according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram showing a method for measuring the Young's modulus in the film thickness direction of the sliding layer. FIG. 3 is a graph showing a load-displacement curve when a force is applied to the sliding layer in the film thickness direction. FIG. 4 is a graph illustrating the measurement results of the Young's modulus of the sliding layers obtained in Example 1-1 and Comparative Example 1-3 in the embodiment of the present disclosure. FIG. 5 is a schematic diagram illustrating a method for evaluating the running durability of the sliding layer in the embodiment of the present disclosure.

  Prior to the description of the embodiments of the present invention, problems in the prior art will be described. As described above, depending on the type of the recording medium, it is necessary to slide the surface opposite to the side on which the recording layer is provided exclusively on the fixing member. For this reason, it is desirable to provide a high durability sliding layer on the second main surface opposite to the first main surface on which the recording layer of the support is provided to ensure running stability and running durability. Structurally, the sliding layer corresponds to a layer referred to as “back coating layer”, “back coating layer”, “back layer” or the like in Patent Documents 1 to 6. However, even if the configuration of the backcoat layer used in these patent documents is applied to the sliding layer that slides on the fixing member of the recording / reproducing apparatus, the sliding layer can withstand sliding with the fixing member. Cannot be obtained. Or generation | occurrence | production of the powder from the medium by wear and the member in a recording / reproducing apparatus cannot fully be suppressed.

  Specifically, Patent Document 1 proposes a configuration having a nonmagnetic support, a magnetic layer, and an intermediate layer provided between the nonmagnetic support and the magnetic layer. The intermediate layer includes a flat inorganic powder having an average diameter of 0.4 to 3.0 μm and an acicular inorganic powder having an average major axis length of 0.05 to 0.5 μm. Patent Document 1 further proposes a configuration in which this intermediate layer is disposed between the nonmagnetic support and the backcoat layer. The plate-like ratio (average diameter / average thickness) of the plate-like inorganic powder is 5 to 150. Patent Document 1 describes a paint containing carbon black, a nitrocellulose resin, a polyurethane resin, and a solvent as a paint for the back coat layer. The back coat layer is formed by applying this paint on a support and drying it.

  By containing carbon black having conductivity, the back coat layer reduces the amount of static electricity generated when sliding on the insulator and when the wound medium is unwound (peeling charging). Can do. Therefore, the medium can be run stably. However, if the back coat layer contains carbon black and a resin, it is easily damaged, and when the back coat layer slides on a relatively hard member such as a stabilizer formed of AlTiC or the like, the back coat layer is scraped by the force received from the stabilizer or the like. It may be lost. When the scraped back coat layer becomes powder and adheres to the recording surface of the recording medium, the quality of the recording / reproducing signal is lowered. Further, when the generated powder is wound up when the recording medium is wound up and accommodated in the cartridge, the shape of the powder is transferred to the recording layer in the cartridge. When the powder is transferred in such a manner, the quality of the recording / reproducing signal is deteriorated. In particular, when the recording layer has a fine surface shape and the surface shape affects recording and reproduction, the quality deterioration is remarkable.

  Moreover, all the powders contained in the intermediate layer have relatively large dimensions. For this reason, when the backcoat layer is formed on the intermediate layer, the surface of the backcoat layer also becomes relatively rough. If the surface of the recording medium on the backcoat layer side is rough, when the recording medium is wound, the shape of the surface of the backcoat layer is transferred to the portion overlapping the backcoat layer, and depending on the configuration of the recording layer As a result, the quality of the recording / reproducing signal is degraded. When the intermediate layer contains coarse particles and the surface roughness is large, the surface can be made flat to some extent by a pressure treatment such as calendering. However, when the surface of the recording layer has a fine shape, the fine shape is destroyed when calendering is performed. Therefore, depending on the configuration of the recording layer, flattening by calendaring cannot be applied. Therefore, the configuration described in Patent Document 1 cannot be used when the recording layer has a fine shape.

  Patent Document 2 is a non-magnetic paint containing carbon black as a main component, a binder, an isocyanate curing agent, and an abrasive component having a Mohs hardness of 6 or more, and obtained by dispersing in an organic solvent, A non-magnetic paint having a moisture content of a predetermined value or less is proposed. This non-magnetic paint is used to form a back coating layer of a magnetic recording medium. Patent Document 2 specifically proposes α-alumina, zirconia, and the like as the abrasive component. In the magnetic recording medium having this back coat layer, when the surface on the back coat layer side slides on a rotating roller such as a stainless steel having a Mohs hardness of about 4 to 5, problems such as wear hardly occur. However, when the surface of the back coat layer side slides on a member such as a stabilizer that is fixed without rotation and made of a hard material having a Mohs hardness of about 8 (for example, AlTiC), the member is Abrasion causes powder to form from the member. The inconvenience caused by such powder is as described in connection with Patent Document 1.

  Patent Document 3 proposes a tape-shaped optical recording medium having a polymer support, a recording layer formed on one surface thereof, and a backcoat layer formed on the other surface. On the surface of the optical recording medium on the recording layer side, a lubricant layer containing a specific compound is provided via a protective layer. Further, as the back coat layer, a layer containing carbon particles, barium ferrite and titanium oxide, and a polyurethane resin as a binder is exemplified. Furthermore, it is described that one or more particles selected from metal particles, metal oxide particles, and metal nitride particles may be used instead of or together with carbon particles.

  When the lubricant layer is provided as in the optical recording medium of Patent Document 3, the lubricant is transferred to the backcoat layer when the recording medium is wound and accommodated. In general, when the surface of the backcoat layer slides on the fixing member in a state where a lubricant, which is an insulator, is attached, if it is peeled and charged, running stability is reduced due to charging. Such peeling electrification may also occur when the recording medium is unwound from the cartridge. The lubricant transferred to the backcoat layer can also be transferred to the surface of the fixing member. The lubricant transferred to the fixing member becomes powder when accumulated. If this powder adheres to the recording layer, when the medium is an optical recording medium, it becomes an optical contaminant, which degrades the quality of the recording / reproducing signal. As a matter of course, when the powder derived from the lubricant is wound together with the recording medium, the recording surface may be deformed, and the quality of the recording / reproducing signal may be lowered. In addition, since metal nitride particles are generally hard, when metal nitride particles are used instead of carbon particles or together with carbon particles, a fixing member such as a stabilizer is worn to easily generate powder. Further, Patent Document 3 makes no mention of the possibility that the surface roughness of the backcoat layer affects the quality of the recording / reproducing signal.

Patent Document 4 proposes a tape-shaped optical recording medium on which information is recorded and reproduced by irradiating a recording layer with laser light through a polymer substrate. This optical recording medium includes a polymer substrate, a recording layer made of an optical recording material formed on one main surface thereof, a reflective layer, and an antistatic layer in which carbon black is dispersed in a resin in this order. Have. In the antistatic layer, the center line average surface roughness is 3.0 to 15.0 nm, and the surface electrical resistance is 1 × 10 ⁴ to 1 × 10 ⁸ Ω / sq. It is described that other inorganic fine powder may be added to the antistatic layer in addition to carbon black, and various oxides are exemplified as the inorganic fine powder. The problem in the case where the layer sliding on the fixing member contains only carbon black as the conductive particles is as described in connection with Patent Document 1. Moreover, patent document 4 does not explain the specific structure in the case of using inorganic fine powder together. As described in connection with Patent Document 2, depending on the type of inorganic fine powder, the fixing member may be worn to generate powder, and the quality of the recording / reproducing signal may be reduced due to the generation of powder.

  Furthermore, in the optical recording medium of Patent Document 4, no layer is provided on one surface of the polymer substrate, and the surface of the polymer substrate itself constitutes the surface of the recording medium. Since the polymer substrate is an insulator, it is easily charged and the powder in the recording / reproducing apparatus is easily adsorbed on the charged surface. Such powder tends to cause a deterioration in the quality of the recording / reproducing signal as described in connection with Patent Document 1.

  In the backcoat layer of the magnetic recording medium proposed in Patent Document 5, particles having substantially no structure or secondary aggregate and an average primary particle size (D50) of 0.05 to 1.0 μm are formed. Is contained. As particles that do not form a structure or secondary aggregate, for example, polymer particles having a crosslinked structure, or inorganic fine particles such as silicon dioxide, alumina, zirconia, and the like are used. This backcoat layer reduces dents due to show-through of the surface of the magnetic layer, which causes dropout, error rate reduction, and S / N reduction. Patent Document 5 proposes adding carbon black in order to impart conductivity to the backcoat layer.

  Any particle specifically shown as a particle in which Patent Document 5 does not form a structure or a secondary aggregate has a small electrical conductivity. Therefore, in order to avoid charging, it is necessary to use a considerable amount of carbon particles. For example, in the Example of patent document 5, 1.3 weight part of polymer particles are used with respect to 100 weight part of carbon black, and the ratio for which carbon black accounts is quite large. The fact that such a back coat layer is easily damaged when sliding on the fixing member is as described in connection with Patent Document 1. Although it has been proposed to use alumina, zirconia, or the like, since these particles have a relatively high Mohs hardness, as described in connection with Patent Document 2, the fixing member is worn to remove the powder. Easy to generate.

  Patent Document 6 discloses a magnetic recording medium having a support, a magnetic layer provided on the support and containing specific magnetic particles, and a back layer formed on the support on the side where the magnetic layer is not provided. is suggesting. Further, it has been proposed that the back layer is formed using inorganic fine powder together with carbon black. Furthermore, it has been proposed to use a soft inorganic powder having a Mohs hardness of 3 to 4.5 and a hard inorganic powder having a Mohs hardness of 5 to 9 as the inorganic fine powder. However, the electrical resistance of the materials exemplified as the soft inorganic powder and the hard inorganic powder is relatively high, and when added in a large amount, the back layer is easily charged. In addition, when the Mohs hardness of the hard inorganic powder is large, the fixing member is worn and powder is easily generated.

  As described above, the backcoat layer and the antistatic layer described in Patent Documents 1 to 6 are not designed as layers that slide on a fixing member formed of a hard material. Therefore, even if these techniques are applied as they are to a recording medium that does not come into contact with a member in the surface recording / reproducing apparatus on the recording layer side and the surface opposite to the side on which the recording layer is provided is exclusively a sliding surface. Satisfactory characteristics cannot be obtained in terms of durability, antistatic properties and powder generation prevention. In particular, when the thickness of the recording medium is small, running in the recording / reproducing apparatus is likely to become unstable due to charging, and running is likely to become more unstable because the rigidity is small. The surface on the recording layer side is also referred to as “recording surface” for the sake of convenience, and the surface opposite to the side on which the recording layer is provided is also referred to as “back surface” for convenience.

  When the recording layer has a fine structure and this structure is used for recording / reproduction, if the back surface is rough, the shape of the back surface is recorded while the recording medium is wound and stored. The quality of the recording / reproducing signal is lowered by being transferred to the surface. In order to avoid this problem, it is necessary to make the back surface flat by reducing the surface roughness of the back surface. Calendering is known as a flattening method, but calendering has the disadvantage of causing the destruction of the structure of the recording layer as described above and cannot be used.

In order to solve these problems, in a recording medium in which only the back surface slides on a member including a stabilizer in the recording / reproducing apparatus, a configuration of a sliding layer suitable for forming the back surface is required. In the present embodiment, a sliding layer that is excellent in durability and antistatic property and can reduce wear of a fixing member by using specific carbon particles and specific solid particles will be described. Specifically, the material and addition amount of the solid particles used in combination with the carbon particles have a specific Mohs hardness and the electric resistance value of the entire sliding layer is 1 × 10 ⁸ Ω / □ or less. By selecting, a recording medium excellent in running durability and running stability can be obtained. Furthermore, when selecting the solid particles so that the electrical resistance value of the entire sliding layer is equal to or less than the above value, when selecting the material and the addition amount of the solid particles so that the density of the entire sliding layer is a specific value or more, The strength of the sliding layer is greater, and better running durability is obtained.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

  The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure. Therefore, they are not intended to limit the claimed subject matter.

FIG. 1 schematically shows a cross section of a tape recording medium (hereinafter referred to as a recording medium) 40 according to an embodiment of the present disclosure. The recording medium 40 includes a support 10, a recording layer 20 provided on the first main surface 11 of the support 10, and a sliding layer 30 provided on the second main surface 12 on the back side of the first main surface 11. Have The sliding layer 30 has an electric resistance of 1 × 10 ⁸ Ω / □ or less, and contains carbon particles and solid particles. The carbon particles have a primary particle size of 30 nm or less and a BET specific surface area of 100 m ² / g or more. The solid particles have a primary particle size of 100 nm or less, a Mohs hardness of 2.5 or more and 8 or less, a density of ³ g / cm ³ or more, and a BET specific surface area of 30 m ² / g or more. The surface of the recording layer 20 constitutes a recording surface 41, and the surface of the sliding layer 30 constitutes a back surface 42. In FIG. 1, the support 10, the recording layer 20, and the sliding layer 30 are shown to be uniform and flat, but this is not restrictive.

  According to this configuration, even if the total thickness of the recording medium 40 is thin, the running stability and running durability in the recording / reproducing apparatus are excellent, and the generation of powder due to wear and the recording surface 41 or the back surface 42 are excellent. Powder adhesion to the surface is suppressed. Further, the transfer of the powder shape to the recording surface 41 can be suppressed. Moreover, since the sliding layer 30 can be formed by coating, the cost required for forming the sliding layer 30 is lower than that in the case of forming by a vapor phase process.

  Hereinafter, each element constituting the sliding layer 30 will be described.

(Carbon particles)
In the present embodiment, carbon particles having a primary particle size of 30 nm or less and a BET specific surface area of 100 m ² / g or more are used.

  When the primary particle size exceeds 30 nm, the surface property of the sliding layer 30 is lowered, and the arithmetic average roughness Ra is increased. When the surface property of the sliding layer 30 is lowered and the surface becomes rough, the surface shape of the sliding layer 30 is easily transferred to the recording surface 41 while the recording medium 40 is stored in a wound state. When the recording layer 20 has a fine structure, such shape transfer deteriorates the quality of the recording / reproducing signal and causes an error. In the present embodiment, even when calendering cannot be performed due to the recording layer 20 having a fine structure or the like, even when the thickness of the sliding layer 30 is 0.5 μm or less, In order to ensure surface properties, the primary particle size of carbon is set to 30 nm or less. The primary particle diameter of carbon may be, for example, 5 nm or more and 25 nm or less, may be 10 nm or more and 25 nm or less, and may be 10 nm or more and 20 nm or less.

  The primary particle size refers to the particle size of particles measured in a state where no aggregate is formed, and is measured by a dynamic scattering light scattering particle size distribution measuring device in a state dispersed in an appropriate solvent. The When the carbon particles contained in the sliding layer 30 have a particle size distribution, the median diameter D50 is the primary particle size. The median diameter D50 corresponds to a particle size with a cumulative distribution of 50% by volume.

The BET specific surface area is a specific surface area determined by the BET method and is measured using nitrogen gas. If the BET specific surface area of the carbon particles is less than 100 m ² / g, the adhesion between the resin functioning as a binder in the sliding layer 30 and the carbon particles may be reduced, and the carbon particles may drop from the sliding layer 30. is there. If the dropped carbon particles adhere to the recording surface 41 of the recording medium 40 or the recording / reproducing head of the recording / reproducing apparatus, the signal quality at the time of recording / reproducing deteriorates, causing an error. On the other hand, if the BET specific surface area is too large, the dispersibility of the carbon particles in the binder is lowered when preparing a paint for forming the sliding layer 30 as described later, making it difficult to prepare the paint. Sometimes. The upper limit of the BET specific surface area is, for example, 1000 m ² / g. The BET specific surface area may be, for example, 100 m ² / g or more and 500 m ² / g or less, 100 m ² / g or more and 400 m ² / g or less, 100 m ² / g or more, 180 m ² / g or less. It may be.

  The type of the carbon particles is not particularly limited as long as the primary particle size and the BET specific surface area satisfy the above ranges. For example, carbon black such as rubber furnace, rubber thermal, color black, and acetylene black may be used as the carbon particles. Two or more types of carbon particles having different materials, dimensions and / or specific surface areas may be used.

(Solid particles)
The solid particles used together with the carbon particles are used to reinforce the sliding layer 30 and suppress damage to the sliding layer 30. The primary particle size of the solid particles is 100 nm or less, the Mohs hardness is 2.5 or more and 8, the density is 3 g / cm ³ or more, and the BET specific surface area is 30 m ² / g or more.

  As described in relation to the carbon particles, if the particle size of the particles constituting the sliding layer 30 is large, the flatness of the sliding layer 30 is lowered, so that the primary particle size of solid particles is also limited. The In the present embodiment, solid particles having a primary particle size of 100 nm or less are used. The primary particle size of the solid particles may be, for example, 1 nm or more and 100 nm or less, and may be 5 nm or more and 50 nm or less. The measuring method of the primary particle size is as described in relation to the carbon particles.

  The primary particle size of the solid particles is preferably as small as possible. However, when the solid particles are formed of a metal other than gold or platinum, if the particle size is small, there is a possibility that the particles react with oxygen in the air and ignite. Or it may be oxidized by oxygen in the air to become an insulator. Therefore, if metal particles are used, they may be operated in an environment purged with an inert gas as necessary, or the metal particles may be coated with a relatively stable material in air such as carbon or gold. May be.

  The solid particles used in the present embodiment have a Mohs hardness of 2.5 or more and 8 or less. The sliding layer 30 of the recording medium 40 slides on a fixed member formed of a relatively hard material (for example, AlTiC having a Mohs hardness of 8). Therefore, when the Mohs hardness of the solid particles is equal to or less than that of carbon, the sliding layer 30 is easily damaged and worn. As a result, powder (wear powder) tends to be generated. On the other hand, when the Mohs hardness of the solid particles is too large, the fixing member is worn and powder (abrasion powder) is easily generated from the fixing member. As described above, the quality of the recording / reproducing signal may be deteriorated when powder is generated from the sliding layer 30 or the fixing member and adheres to the recording surface 41 or the back surface 42. For this reason, in the present embodiment, the Mohs hardness of the solid particles is limited to the above range to increase the wear resistance of the sliding layer 30 and to prevent the fixing member from being worn.

  When each of the solid particles is formed of a plurality of materials, the Mohs hardness as a whole or the Mohs hardness of the material constituting the surface of the solid particles may be in the above range. For example, the Mohs hardness of solid particles in which a soft metal such as platinum (Mohs hardness of 8 or less) is supported (mixed) on alumina having a Mohs hardness of about 9 is 8 or less as a whole. Used as a fixing member. Further, fine particles coated with aluminum hydroxide (for example, NANOFINE manufactured by Sakai Chemical Industry Co., Ltd.) can also be used as solid particles in the present embodiment.

The solid particles used in this embodiment have a density of ³ g / cm ³ or more. The density here is the true density (density when the filling rate is 100%). In the present embodiment, simply “density” refers to true density. If the density is less than 3 g / cm ³ , the effect of improving the rigidity of the recording medium 40 tends to be reduced, and the running stability of the recording medium 40 tends to decrease. Since the rigidity of the recording medium 40 is proportional to its density, it is preferable to secure the rigidity of the recording medium 40 by increasing the density of the sliding layer 30 with solid particles having a density higher than that of the carbon particles. In addition, when the density is less than 3 g / cm ³ , it may be difficult to disperse the solid particles when it is necessary to add the solid particles so as to occupy 50 vol% or more of the nonvolatile content of the sliding layer 30.

The solid particles used in the present embodiment have a BET specific surface area of 30 m ² / g or more. If the BET specific surface area of the solid particles is less than 30 m ² / g, the adhesiveness between the resin functioning as a binder and the solid particles may be reduced, and the solid particles may fall off the sliding layer 30. If the dropped solid particles adhere to the recording surface 41 of the recording medium 40 or the recording / reproducing head of the recording / reproducing apparatus, the signal quality at the time of recording / reproducing deteriorates, causing an error. The upper limit of the BET specific surface area of the solid particles is, for example, 500 m ² / g. The BET specific surface area of the solid particles may be, for example, 30 m ² / g or more and 500 m ² / g or less, or 40 m ² / g or more and 400 m ² / g or less.

The electric resistance of the solid particles is preferably 1 × 10 ⁷ Ω / □ or less. When the electrical resistance exceeds 1 × 10 ⁷ Ω / □, the electrical resistance of the entire sliding layer 30 including an insulating binder such as resin tends to increase. When the electric resistance of the sliding layer 30 exceeds 1 × 10 ⁸ Ω / □, the recording medium 40 is easily charged. For example, peeling electrification occurs when the recording medium 40 wound and accommodated in the cartridge is unwound. When the thin recording medium 40 having a total thickness of less than 8 μm is charged, the running stability of the recording medium 40 is lowered. Furthermore, contaminants (contamination) such as dust in the recording / reproducing apparatus tend to adhere to the charged recording medium 40. If the recording medium 40 is wound and accommodated in the cartridge while the contaminant is attached, the shape of the contaminant may be transferred to the recording surface 41 and the quality of the recording / reproducing signal may deteriorate.

As long as the substance constituting the solid particles has a Mohs hardness and density within the above range, and has a BET specific surface area within the above range in the state of particles, the electric resistance of the entire sliding layer 30 is reduced. It is not particularly limited as long as it is 1 × 10 ⁸ Ω / □ or less. Examples of substances constituting the solid particles will be described below.

(1) The solid particles may be formed of a metal oxide. The metal oxide may be doped with a metal element. For example, solid particles may be formed of zinc oxide or tin oxide doped with one or more metal elements selected from antimony, gallium, aluminum, and indium. These materials preferably have an electrical resistance of 1 × 10 ⁷ Ω / □ or less. For example, conductive fine particles SN-100P manufactured by Ishihara Sangyo Co., Ltd. (antimony-doped tin oxide particles, electrical resistance of 9.8 MPa green compact is 1 to 5Ω / □) may be used as solid particles.

  (2) The solid particles may also be formed of metal (including single metals and alloys) or ceramics. The metal is, for example, gold, platinum, or copper, or an alloy thereof, and the ceramic is, for example, SiC or AlTiC.

(3) The solid particles may be inorganic or organic particles coated with metal (including single metals and alloys). By coating with a metal, particles formed of an inorganic substance such as an oxide, nitride or carbide, and an organic substance such as a polymer having an electric resistance exceeding 1 × 10 ⁷ Ω / □ can be used as a solid particle.

  Examples of the core particles coated with metal include silica fine particles disclosed in Japanese Patent Application Laid-Open No. 2008-285406, carbon alloy fine particles doped with nitrogen atoms disclosed in Japanese Patent Application Laid-Open No. 2007-311026, or platinum on this. Fine particles or the like on which is supported can be suitably used. Alternatively, a styrene-based hyperbranched polymer manufactured by Nissan Chemical Industries, HPS-200 (diameter less than 10 nm), or the like can be used. As a method for coating the core particles, methods disclosed in JP 2007-197755 A, JP 2007-322216 A, and the like can be used. For example, the metal coating may be performed by a method in which a single body or a composite such as silica, titania, zinc oxide, or alumina is used as a core particle, and an organic acid metal salt and an amine compound are reacted with the core particle. Alternatively, metal coating may be performed by a method in which core particles are introduced into a solution containing an organic acid metal salt and an amine compound and a reducing agent is allowed to act.

  In addition, even if it is a metal particle, when electrical resistance is large, you may coat this metal particle with another metal with higher electroconductivity.

  Further, even when a metal film is formed by general electroless nickel plating, solid particles coated with metal or carrying a metal can be obtained. In this case, for example, nickel sulfate 0.1 mol / L, sodium hypophosphite 0.3 mol / L, glycine 0.1 mol / L, trisodium citrate 0.1 mol / L, lead nitrate 2 mg / L, pH 5. Electroless plating is performed at a bath temperature of 80 ° C. using bath No. 5.

  (4) The solid particles may be carbide particles. Specifically, SiC nanoparticles and nano carbide produced by a general plasma arc welding method may be used as solid particles. As the SiC nanoparticles, for example, those provided by Aldrich may be used. Hefei Kaier Nanometer Energy & Technology Co. , Ltd. n-TiC or n-ZrC can be used as solid particles of carbide.

(5) The solid particles may be formed of an inorganic material coated with carbon. Such solid particles may also have an electrical resistance of 1 × 10 ⁷ Ω / □ or less. Specifically, Japanese Unexamined Patent Application Publication No. 2014-116249 discloses an inorganic substance coated with carbon, and such an inorganic substance can be suitably used. This publication describes, for example, that conductive nanoparticles are obtained by subjecting silicon nanoparticles (2 to 20 nm) to chemical vapor deposition in an organic gas such as a hydrocarbon such as methane. Alternatively, JP 2011-240224 A describes other inorganic materials coated with carbon. Such an inorganic substance is formed as follows. First, an organic substance having a high dispersibility and a high carbonization yield such as a lignin compound is used as a dispersant, and an inorganic substance is dispersed in the dispersion medium together with the dispersant. Next, a general carbonization treatment (800 to 1200 ° C. in an inert atmosphere) is performed. The carbide particles obtained after the treatment are pulverized and sized. The particles thus prepared may be used as solid particles.

  (6) The solid particles may be metal particles coated with carbon (including simple metal particles and alloy particles). As described above, metal particles having a particle size of nanometer level are likely to ignite and oxidize, and a carbon coating is provided to prevent these problems. The core metal fine particle may be any metal nanoparticle, or may be a nanometal particle cluster as disclosed in Japanese Patent Application Laid-Open No. 2004-05068. Carbon coating may be applied to these metal particles by the method disclosed in the aforementioned Japanese Patent Application Laid-Open No. 2014-116249. Specifically, conductive nanoparticles can be prepared by chemical vapor deposition in an organic gas such as hydrocarbon such as methane. Alternatively, when the method described in Japanese Patent Application Laid-Open No. 2011-240224 described above is applied to metal nanoparticles instead of inorganic substances, carbon-coated metal particles can be obtained.

  (7) The solid particles may be carbon particles carrying a metal (including a single metal and an alloy) or a metal oxide. As such solid particles, platinum-supported carbon black as disclosed in JP-A-2005-032668 may be used. The metal or metal oxide supported on carbon is selected from platinum, palladium, tin, ruthenium, cobalt, copper, nickel, cerium, and rhodium oxide. The metal or metal oxide to be supported may be one kind or plural kinds. Alternatively, platinum-supported carbon that is a catalyst for a fuel cell as provided by Aldrich as product number 735557 may be used as the solid particles.

(8) The solid particles may be Sb—SnO ₂ particles on which a metal (including a single metal and an alloy) is supported. The metal to be supported may be those exemplified as the metal capable of constituting solid particles in the above (1) to (7). The metal to be supported may be one kind or plural kinds. The loading method is described in Electrochim. Acta, 56, 2881 (2011) and the like. For example, particles in which platinum is supported on Sb—SnO ₂ (support) particles may be used as solid particles. For example, such solid particles may be formed on tin oxide particles (support) in which antimony is substituted and dissolved in platinum. It can be prepared by carrying highly dispersed nanoparticles. As the carrier, in addition to tin oxide, titanium nitride, titanium carbide, or the like can be used. Platinum may be supported using a flame method, an RF plasma method, an energized plasma firing method, or the like.

(9) The solid particles may be ceramic particles on which a metal (including a single metal and an alloy) is supported. Such a method for producing solid particles is disclosed in JP-A-2015-147173 and the like, and particles obtained by the method disclosed in this publication may be used in this embodiment. In the solid particles, the ceramic as a carrier may have a Mohs hardness of more than 8. As long as the solid particles after supporting the metal as a whole have a Mohs hardness of 8 or less, they can be used in this embodiment. Further, the ceramic serving as the carrier may have an electric resistance exceeding 1 × 10 ⁷ Ω / □.

The metal to be supported may be those exemplified as the metal capable of constituting solid particles in the above (1) to (7). The metal to be supported may be one kind or plural kinds. The type and amount of the metal may be selected so that the electric resistance of the sliding layer 30 is 1 × 10 ⁸ Ω / □ or less. Examples of the solid particles in which a metal is supported on ceramics include platinum-alumina 5% code 168-13941 (density 21.45 g / cm ³ ) manufactured by Wako Pure Chemical Industries, Ltd.

  The solid particles described above are examples, and solid particles other than those described here may be used. Moreover, you may use a solid particle combining multiple types, such as the combination of what was described in (1), and what was described in (4), for example.

(Other components contained in the sliding layer)
In addition to the carbon particles and the solid particles, the sliding layer 30 includes a binder that binds these particles and a dispersant that disperses these particles. These components are described below.

[Binder]
The binder constituting the sliding layer 30 is a curable resin (including a thermosetting resin, an ultraviolet curable resin, and an electron beam curable resin) known as a paint resin or an adhesive resin, or a thermoplastic resin. Good. Specifically, examples of the resin constituting the binder include a thermoplastic resin and a curable resin. Examples of the thermoplastic resin include polycarbonate resin, polyamide resin, polyphenylene oxide resin, thermoplastic acrylic resin, vinyl chloride resin, fluororesin, vinyl acetate resin, and silicone rubber. Examples of the curable resin include urethane resin, melamine resin, silicon resin, butyral resin, reactive silicone resin, phenol resin, epoxy resin, unsaturated polyester resin, thermosetting acrylic resin, and ultraviolet curable acrylic resin. Alternatively, the binder may be a copolymer obtained by polymerizing two or more monomers, or may be a modified product of these resins. The binder may be used in combination with one or more additives selected from a dispersant, a leveling agent, and the like as necessary.

As will be described later, the true density of the sliding layer 30 is preferably 1.640 g / cm ³ or more. In order to satisfy this density, the binder may be appropriately changed or a plurality of binders may be used. For example, the binder may be a binder having many pigment-dispersing groups for the purpose of dispersing carbon and solid particles and improving the adhesion to the support. Alternatively, it may be a binder having a high adhesive force to the support and a high true density. These binders may be used alone, or a plurality of combinations selected from these binders may be used.

Further, as a heavy binder, nitrocellulose (density: 1.66 g / cm ³ ) or the like may be used together with the resin binder.

[Dispersant]
The dispersant is added for the purpose of improving the dispersibility of the carbon particles and the solid particles. The dispersant may be any of cationic, nonionic and anionic. The cationic dispersant is, for example, Florene DOPA35 (density 1.185 g / cm ³ ) manufactured by Kyoeisha Chemical Co., Ltd. The nonionic dispersant is, for example, Floren D-90 manufactured by Kyoeisha Chemical Co., Ltd. An anionic dispersant is, for example, SN Sparse 2190 manufactured by Sannobuco.

In order to make the true density of the sliding layer 30 1.640 g / cm ³ or more, a higher density dispersant may be used. Alternatively, when the dispersibility of the carbon particles and the solid particles is sufficient and Ra of the formed sliding layer 30 is 10 nm or less, the sliding layer 30 may be formed without using a dispersant. For example, it is possible to form the sliding layer 30 without using a dispersant by using a binder having high dispersibility.

[Other ingredients]
The sliding layer 30 may contain an isocyanate agent for the purpose of reducing the adhesiveness caused by the hydroxyl group and the like contained in the binder, the dispersant and the like. The isocyanate agent undergoes an addition reaction with a binder or a hydroxyl group of the dispersant (a hydroxyl group other than the group in close contact with the support in the binder and a hydroxyl group other than the dispersing group of the dispersant). The reactivity of the hydroxyl group that undergoes the addition reaction is inversely proportional to the glass transition point of the binder and dispersant. In order to intentionally cause the addition reaction, an isocyanate agent may be added to form a coating film, and then the coating film may be heat-treated.

The isocyanate agents generate carbon dioxide gas (weight ≈ 0 g / cm ³ ) by a condensation reaction, and this carbon dioxide gas may cause bubbles in the coating film. Therefore, in order to increase the true density of the sliding layer 30 as much as possible and ensure running durability, it is preferable to suppress the above condensation reaction. Therefore, it is preferable that the addition amount of the isocyanate agent is not more than a ratio in which the hydroxyl group contained in the binder or the dispersant and the isocyanate group of the isocyanate agent chemically react with each other. For example, in the case of Byron UR4800 used in examples described later, the amount may be 20 parts by weight (non-volatile content) or less with respect to 100 parts by weight of the binder. Moreover, when a dispersing agent is the fluorene DOPA35 used in the below-mentioned Example, it is good also as a quantity below 100 weight part (nonvolatile content) with respect to 100 weight part of dispersing agents. The addition amount of the isocyanate agent may be a value smaller or larger than the above upper limit value depending on the reactivity of the isocyanate agent and the number of hydroxyl groups of the binder and the dispersant.

  In the case where the stickiness caused by hydroxyl groups such as binders and dispersants does not affect the running stability, the isocyanate agent may not be used. Moreover, an isocyanate agent is easy to carry out an addition reaction with a hydroxyl group or moisture. Therefore, when particles having a strong catalytic action (such as a fuel cell catalyst) are used as the solid particles, the reaction between the isocyanate agent and the binder and / or dispersant may be accelerated by the catalytic action of the solid particles in the paint state. is there. As a result, the number (density) of hydroxyl groups contributing to the adhesion of the sliding layer 30 to the support may be significantly reduced by the start of the coating operation, and the adhesion may be lowered. Therefore, when forming the sliding layer 30 by application | coating using an isocyanate agent and the solid particle which has a catalytic action together, it is preferable to suppress reaction with the dispersing agent, a binder, etc. in a coating state. Therefore, it is preferable to add the isocyanate agent to the paint (a composition containing a solvent and the like in addition to the above-mentioned components) and stir immediately before coating (specifically, within about 6 hours at room temperature). In this case, the isocyanate agent is more preferably added in a gas atmosphere that is inert, such as nitrogen, and has little moisture.

(Sliding layer)
In the above, each component contained in the sliding layer 30 was demonstrated. Below, the ratio of each component contained in the sliding layer 30, the preferable true density of the sliding layer 30, etc. are demonstrated.

[Volume fraction combining carbon particles and solid particles]
When the solid particles are metal particles, or inorganic or organic particles coated with a metal, the combined volume of the carbon particles and the solid particles is 20% or more of the non-volatile volume of the sliding layer 30. It is preferable to occupy. When the solid particles are not metal particles but other than inorganic or organic particles coated with metal, the combined volume of the carbon particles and the solid particles is 50% of the non-volatile content of the sliding layer 30. It is preferable to occupy the above.

When the solid particles are metal particles, when the conductivity of the solid particles is high and the density is high, the sliding layer 30 has a low electric resistance and a high density by adding a little solid particles. . As a result, the sliding layer 30 that is favorable in terms of antistatic properties and durability can be obtained. Therefore, if the ratio of the combined volume of carbon particles and solid particles to the nonvolatile content is at least 20%, the desired sliding layer 30 can be obtained. On the other hand, particles such as metal oxides and ceramics have lower conductivity and density than metals. Therefore, when such particles are used as solid particles, in order to make the electric resistance of the sliding layer 30 1 × 10 ⁸ Ω / □ or less and to increase the density of the sliding layer 30, carbon particles and solids are used. A large amount of both particles are used so that their volume fraction in the nonvolatile content is 50% or more.

  In addition, the surface roughness of the sliding layer 30 tends to be smaller as the volume fraction of the carbon particles and the solid particles in the nonvolatile content of the sliding layer 30 is smaller.

[Ratio of solid particles]
When the electrical resistance of the solid particles is 1 × 10 ⁻⁶ Ω / □ or more, the ratio (addition amount) of the solid particles is 1 vol% or more and 60 vol when the carbon particles and the solid particles are combined to 100 vol%. % Or less is preferable. If the ratio of solid particles made of a material having an electrical resistance of 1 × 10 ⁻⁶ Ω / □ or less is less than 1 vol%, the true density of the sliding layer 30 is reduced, and the running stability of the medium and the durability of the sliding surface are reduced. May not be enough. When the addition amount of solid particles made of a material having an electrical resistance of 1 × 10 ⁻⁶ Ω / □ or more is more than 60 vol%, the electrical resistance of the sliding layer 30 increases and the surface is easily charged. As a result, fine particles in the recording / reproducing apparatus or in the air easily adhere to the recording medium 40, and the quality of the recording / reproducing signal may be deteriorated. When the electrical resistance of the solid particles is 1 × 10 ⁻⁶ Ω / □ or less, it is preferable that the ratio of the solid particles is 1 vol% or more when the carbon particles and the solid particles are combined to 100 vol%.

[Electric resistance]
In the present embodiment, the sliding layer 30 has an electric resistance value of 1 × 10 ⁸ Ω / □ or less, preferably 5 × 10 ⁷ Ω / □ or less. If the electric resistance value of the sliding layer 30 is higher than 1 × 10 ⁸ Ω / □, the recording medium 40 is easily charged and the running becomes unstable. In addition, the dust in the recording / reproducing apparatus easily adheres to the recording medium 40 due to charging. As described above, the dust adhering to the recording medium 40 can cause the quality of the recording / reproducing signal to deteriorate. Therefore, the ratio of the solid particles in the total mass or volume of the carbon particles and the solid particles, and the ratio (volume fraction) of the combined volume in the non-volatile content is such that the obtained sliding layer 30 is in the above range. It is selected to satisfy the electrical resistance value. It should be noted that the volume fractions and solid particle ratios described above are preferred examples.

[True density]
It has been found that there is a correlation between the occurrence of scratches or wear due to sliding on the fixed member and the true density of the sliding layer. Specifically, when the true density of the sliding layer is 1.640 g / cm ³ or more, the Young's modulus (Reduce Modulus “Er”) in the thickness direction of the sliding layer is 13 GPa or more, and the sliding layer It was found that the surface was less likely to be scratched or worn. Here, the Young's modulus in the thickness direction is a measured value of hardness up to a depth of 40 to 50 nm with respect to a thickness of 500 nm. The true density refers to a density when it is assumed that the non-volatile content is 100% in the sliding layer, that is, it is filled without any gaps. When the sliding layer is formed by a method such as coating, the sliding layer cannot be formed without any voids. Therefore, the density of the actually formed sliding layer is not a true density but a bulk density. However, if the constituent components of the sliding layer are known, the true density of the sliding layer can be determined from the density and ratio of these components.

When the sliding layer has a true density of 1.640 g / cm ³ or more, for example, the bulk density of the sliding layer is about 1.310 g / cm ³ or more.

  The Young's modulus in the film thickness direction of the sliding layer can be obtained with a Berkovich diamond indenter 50 using a Hystron Triboscope attached to a scanning probe microscope JSPM4200 manufactured by JEOL, as schematically shown in FIG. . At this time, for example, the load P is changed stepwise from 0.7 μN, 10 μN, and 50 μN. First, the contact depth hc is obtained from the unloading curve obtained when the indenter 50 is pushed into the sliding layer sample 30A to the depth (hmax) to remove the load. Next, the contact projected area A of the indenter 50 and the sample 30A and the composite Young's modulus of the indenter 50 and the sample 30A are obtained from the contact depth hc. Further, the Young's modulus of the sample 30A is obtained. The contact depth hc is the intersection of the approximate straight line of the stiffness S, which is the slope of the unloading curve of the load-displacement (Ph) curve shown in FIG. 3, and the horizontal axis. The contact depth hc is preferably about 1/10 of the thickness of the sample 30A, and the Young's modulus calculated based on such a contact depth is not affected by the substrate. The contact projected area is a cross-sectional area A at the contact depth hc. Equation 1 is obtained from the Oliver-Pharr method (OP method), Equation 2 is obtained from the Ph curve, and Young's modulus Er of the indenter and the sample is calculated from Equation 3.

A = 24.5hc ² Formula 1
S = (2 / √π) E ^* √A Formula 2
In Equation 2, S is stiffness, and E ^* is the composite Young's modulus of the indenter 50 and the sample 30A.

1 / E ^* = (1−v ² ) / Er + (1−vi ² ) / Ei Equation 3
In Equation 3, Er is the Young's modulus of the sample 30A, Ei is the Young's modulus of the indenter 50, v is the Poisson ratio of the sample 30A, and vi is the Poisson ratio of the indenter 50.

Therefore, the types and mixing ratios of carbon particles, solid particles, and other nonvolatile components are preferably set so that the true density of the sliding layer 30 is 1.640 g / cm ³ or more. The true density of the carbon particles used in the examples described later can be approximated to about 1.7 g / cm ³ , the true density of the nonvolatile content of the binder is about 1.34 g / cm ³ , and the true density of the nonvolatile content of the dispersant. Is about 1.185 g / cm ³ . In general, the density of the nonvolatile content of the resin and the dispersant is smaller than the true density of the carbon particles and the solid particles, although there are some differences depending on the materials. Therefore, in order to increase the true density of the sliding layer 30, it is preferable to use solid particles having a large true density. Further, in order to increase the true density of the sliding layer 30, the ratio of the combined amount of carbon particles and solid particles to the non-volatile content of the sliding layer 30 may be increased.

(Formation method of sliding layer)
In the present embodiment, the sliding layer 30 is prepared by dispersing or dissolving the carbon particles, solid particles, binder, dispersant, and other components described above in a solvent to prepare a paint (or coating liquid). Is applied to the support and then dried to evaporate the solvent. Below, the solvent which comprises a coating material is demonstrated, Furthermore, the method of preparing a coating material, the method of apply | coating a coating material to a support body, etc. are demonstrated.

[Solvent for paint]
Specifically, the solvent for the paint is selected from water, toluene, cyclohexanone, isophorone, dimethyl sulfoxide, alcohols, esters, ethers, ketones, alkyl cellosolves and the like. Examples of alcohols are methanol, ethanol, propanol, 2-propanol (IPA), butanol, diacetone alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, methylene glycol, ethylene glycol, hexylene glycol, isopropyl glycol, tetrafluoropropanol And octafluoropropanol. Examples of esters include acetic acid methyl ester, acetic acid ethyl ester, butyl acetate. Examples of ethers include diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, acetoacetate. Examples of the alkyl cellosolves include methyl cellosolve, ethyl cellosolve, and butyl cellosolve. Only one type of paint solvent may be used, or a plurality of types may be used in combination.

  As described above, the density of the sliding layer 30 formed on the support 10 is not a true density but a bulk density. The filling rate of the sliding layer 30 can be improved by appropriately selecting a solvent, a non-volatile content, a coating process, or the like. For example, as a solvent, in order to reduce the amount of the solvent that volatilizes from the sliding layer 30 after application, cyclohexanone or cyclohexanone (with a vapor pressure at 20 ° C of 0.45 kPa) equal to or higher than the volatility (vapor at 20 ° C A solvent having a pressure of 0.45 kPa or more, an SP value equivalent to cyclohexanone (7 to 10), and a wettability equivalent to cyclohexanone (surface tension of 35 mN / m or less) may be used. Examples of the solvent having volatility equal to or higher than that of cyclohexanone, SP value, and paintability include ketones, esters, hydrocarbons, alcohols, and ethers. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone. Examples of the esters include ethyl acetate and butyl acetate. Examples of the hydrocarbons include toluene and xylene. Examples of alcohols include methanol, ethanol, 2-propanol. Examples of ethers include tetrahydrofuran. These solvents may be used alone or in combination of two or more.

[Preparation of paint]
The coating material is prepared by dissolving or dispersing carbon particles, solid particles, a binder, a dispersant, and other components in a solvent. In the paint, since it is necessary to disperse carbon particles and solid particles, these particles are dispersed using a dispersing device. Specifically, as a dispersion device, a known dispersion device such as a mixer dispersion device, a kneading dispersion device, a media-type dispersion device, a medialess dispersion device, a bead mill dispersion device, a high-pressure dispersion device, a kneader device, and a stirring device, mixing Equipment and kneading equipment can be used.

  In order to increase the proportion of carbon particles and solid particles in the sliding layer 30, when the amount of these particles is increased, if the dispersibility of the particles is insufficient, the surface roughness of the resulting sliding layer 30 is increased. Becomes larger. In order to avoid such inconvenience, it is preferable to increase the dispersion force of the apparatus. For example, it is preferable to increase the number of times of dispersion processing in the dispersion apparatus.

  Alternatively, the dispersion force can be increased by appropriately changing the dispersion processing conditions of the dispersion apparatus. For example, in a bead mill disperser, permeability (wetability) and dispersibility are used to reduce the thixotropy of the matrix (consisting of particles and solvent or particles, solvent and dispersant) when the particles are wet disintegrated. A solvent having high (resin compatibility) is used. Or you may adjust the amount of solvent, the dispersing agent, or the addition amount of a dispersing agent. Furthermore, harder, heavier and finer zirconia beads may be used. In the case of using a high-pressure dispersion device, the dispersion force can be changed by adjusting the pressure, so that the dispersion force can be increased by increasing the pressure, for example. Since the dispersion force varies depending on the type of the dispersion device, for example, the dispersibility of the particles in the paint can be improved by using a dispersion device that disperses at high pressure instead of a dispersion device that disperses at normal pressure.

  In preparing the coating material, it is preferable to stir and circulate with an ultrasonic homogenizer or the like without leaving the coating material before coating in order to eliminate or reduce the aggregation of carbon or solid particles in the coating material.

(Formation method of sliding layer)
The sliding layer 30 may be applied to the surface of the support 10 using a known coating method such as a bar coating method, a spray coating method, a gravure coating method, a die coating method, and a reverse roll coating method. The coating thickness is adjusted to obtain the desired thickness after evaporating the volatile solvent and solidifying or curing the matrix precursor. The higher the concentration of the non-volatile content contained in the paint, the more the amount of solvent that volatilizes after application can be reduced, and the bulk density can be made closer to the true density. Further, depending on the type of the recording medium 40, a high-pressure process such as calendar may be performed after the above application. The high pressure process is effective for increasing the density of the sliding layer 30.

(Sliding layer thickness, surface roughness)
The thickness of the sliding layer 30 is not particularly limited. However, the thickness of the sliding layer 30 is adjusted so that the recording medium 40 can be stored in the cartridge. For example, the thickness of the sliding layer 30 may be 0.5 μm or less.

  The sliding layer 30 preferably has a surface flatness such that the arithmetic average roughness Ra is 10 nm or less. When Ra exceeds 10 nm, the shape of the surface roughness (unevenness) of the sliding layer 30 is transferred to the recording surface in the state of being accommodated in the cartridge, and the quality of the recording / reproducing signal is lowered.

(Other elements)
Other elements constituting the recording medium 40 may be elements used in a tape-shaped magnetic recording medium and a tape-shaped optical recording medium.

[Support]
The support 10 is a film or sheet made of a polymer (resin). Examples of the polymer include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers, polycarbonate polymers, and acrylic polymers. These resins may be used alone or in combination of two or more. The support may be a laminate. Moreover, you may provide an adhesive layer in a support body in order to improve the adhesiveness with the sliding layer 30 and another functional layer. The material constituting the adhesive layer is not particularly limited.

[Recording layer]
When the recording medium 40 is an optical recording / reproducing medium, before the sliding layer 30 is formed, a fine surface for recording / reproducing is formed on the surface of the support 10 on the side where the recording layer 20 is formed. Apply grooving. The fine groove may be formed by an existing method. For example, grooving may be performed by a nanoimprint method. In the nanoimprint method, the resin material between the support and the grooved surface of the stamper is cured or plastically deformed while pressing the grooved surface of the stamper on which the finely grooved process has been applied to the surface of the support. The grooved shape is transferred to the support surface. A reflective layer, a dielectric layer, a phase change layer, and a dielectric layer (all not shown) are formed in this order on the grooved surface so as to enable recording and reproduction by light. The reflective layer is formed of a metal having a high reflectance with respect to the recording / reproducing laser wavelength, such as aluminum, silver, or a silver alloy. The dielectric layer controls the heat and light before and after the phase change of the recording layer and during the phase change, and is formed of one or more compounds selected from oxides, nitrides and sulfides. The recording layer is formed of a material that can cause a phase change (reflectance change) by light irradiation, for example, GeSbTe.

When the recording medium 40 is a magnetic recording / reproducing medium, the recording layer 20 may be a known recording layer used for audio tapes, video tapes, data tapes, and the like. The recording layer for magnetic recording may be formed using known methods and materials. For example, in the case of a vapor deposition type magnetic recording medium, the recording layer 20 such as cobalt oxide is formed by vapor deposition. Next, a protective layer (not shown) made of diamond-like carbon (DLC) or the like is formed on the surface of the recording layer 20 by chemical vapor deposition (CVD). Further, a lubricant layer made of a fluorine compound or the like is sequentially formed on the surface of the protective layer by coating or the like. In this way, each layer may be formed. In the case of a coating-type magnetic recording medium, in addition to a magnetic material such as iron oxide or barium ferrite, one or more materials selected from the following materials are added to a binder, and mixed to prepare a coating material. To do.
・ Alumina, etc. as a hard additive to increase the durability of the magnetic layer
・ Fatty acids as lubricating additives,
The recording layer 20 can be formed by applying this paint such as carbon as an antistatic material for preventing electrostatic breakdown of the recording / reproducing head and then applying a calendering process. The recording layer 20 may be a single layer or a laminated structure.

  The recording layer 20 of the magnetic recording medium may be formed to have a thin film and a fine structure by a vapor phase method in order to improve the recording density. Alternatively, except for the outermost surface layer (sliding layer 30) on the side opposite to the surface on which the recording layer 20 of the magnetic recording medium is formed, it may be formed by combining vapor deposition type and coating type methods and materials. .

  The recording medium 40 is slit to a predetermined width according to the recording method and application, and is processed and accommodated in a predetermined cartridge to a length corresponding to a predetermined recording capacity.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In this example, the surface electrical resistance and running durability of sliding layers having various compositions are evaluated. Therefore, a sample in which a sliding layer is formed on one surface of the support is produced, and no recording layer is formed. The recording / reproducing mode of the tape recording medium of the present embodiment is not limited to magnetism, and may be light or magneto-optical.

(About the content of carbon particles and solid particles)
In this example, a blank sliding layer (Comparative Example 1-3) containing 30 parts by weight of carbon particles but no solid particles was first formed. Then, a part of carbon contained in the sliding layer was replaced with solid particles, and changes in antistatic property and running durability of the sliding layer due to inclusion of the solid particles were evaluated.

For example, in Example 1-1, antimony-doped tin oxide (Ishihara Sangyo Co., Ltd. SN-100P (true density 6.6 g / cm ³ )) is used as the solid particles. The solid particles in an amount corresponding to 5.5 vol% of carbon of 30 parts by weight (100 vol%) constituting the moving bed, that is, 5.5 vol% carbon, are added. ) Is 28.35 parts by weight (= 30 parts by weight × 94.5 wt%), and the ratio of the solid particles is 6.4 parts by weight, and the ratio of the solid particles is (30−28.35) × (antimony). The true density of doped tin oxide / the true density of carbon particles is calculated and determined.

  When the addition amount of antimony-doped tin oxide is 60 vol%, the ratio of carbon particles is 12 parts by weight (= 30 parts by weight × 40 wt%), and the ratio of solid particles is 69.88 parts by weight (= ( 30-12) × (true density of antimony-doped tin oxide / true density of carbon particles)).

When determining the content of the solid particles by this method, the solid particles are made of a material other than metal (including an alloy), that is, the electric resistance is made of a material having an electric resistance of 1 × 10 ⁻⁶ Ω / □ or more. In this case, the ratio of the solid particles is preferably 1 vol% or more and 60 vol% or less. The ratio indicated by “vol% carbon” is a ratio when 30 parts by weight of carbon particles are taken as 100 vol% carbon. Within this range, when solid particles formed of a material having an electric resistance of 1 × 10 ⁻⁶ Ω / □ or more are added, a sliding layer having excellent antistatic properties and running durability can be obtained. When the proportion of solid particles formed of a material having an electric resistance of 1 × 10 ⁻⁶ Ω / □ or less is less than 1 vol% carbon, the true density of the sliding layer becomes less than 1.640 g / cm ³ , and the medium travels. Stability and sliding surface durability are not sufficient. On the other hand, if the amount of solid particles formed of a material having an electric resistance of 1 × 10 ⁻⁶ Ω / □ or more is more than 60 vol% carbon, the electric resistance of the sliding layer increases and the surface is easily charged. Become. As a result, fine particles in the recording / reproducing apparatus or in the air easily adhere to the recording medium, and the quality of the recording / reproducing signal may deteriorate.

When the solid particles are made of a metal such as platinum, gold, or an alloy such as nichrome, and the electric resistance is made of a material having an electric resistance of 1 × 10 ⁻⁶ Ω / □ or less, the ratio of the solid particles is It is preferable to set it to 1 vol% or more carbon. In this case, if the content of solid particles is less than 1 vol% carbon, even if the true density of the sliding layer is 1.640 g / cm ³ or more, the surface electrical resistance of the sliding layer is 5 × 10 ⁷ Ω / □. Over. Therefore, sufficient antistatic properties cannot be obtained. However, in the case of solid particles formed of aluminum (true density 2.7 g / cm ³ , Mohs hardness 2.4), even if the true density of the sliding layer is 1.640 g / cm ³ or more, the running of the medium Lower durability. This is due to the low true density and Mohs hardness of aluminum.

  Hereinafter, each sample produced in this example will be described.

(Example 1 metal oxide particles)
[Example 1-1]
A paint having the following composition was prepared.
Carbon particles: # 1000 manufactured by Mitsubishi Chemical Corporation, primary particle size is 18 nm, true density is 1.6 g / cm ³ or more, 1.8 g / cm ³ or less (average 1.7 g / cm ³ ), BET specific surface area Is 180 m ² / g, and the blending amount is 28.35 parts by weight (94.5 vol% carbon).
Antimony-doped tin oxide particles as solid particles: SN-100P manufactured by Ishihara Sangyo Co., Ltd., the true density is 6.6 g / cm ³ , and the blending amount is 6.4 parts by weight (5.5 vol% carbon).
-Binder: Byron UR4800 manufactured by Toyobo Co., Ltd., the true density of the non-volatile content is 1.34 g / cm ³ , and the blending amount is 13.7 parts by weight.
Dispersant: Florene DOPA35 manufactured by Kyoeisha Chemical Co., Ltd., the true density of the non-volatile content is 1.185 g / cm ³ ), and the blending amount is 7.09 parts by weight (= 25 wt% of carbon particles).
・ Methyl ethyl ketone as solvent: 108.6 parts by weight (including solvent such as binder)
-Toluene as solvent: 26.25 parts by weight (including solvent such as binder)
-Cyclohexanone as a solvent: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone as a solvent: 45 weight part According to this composition, the true density of a sliding layer will be 1.641 g / cm < ³ >.

  The paint having the above composition is wetted, crushed and dispersed using a pressure kneader, a ball mill, a high-pressure mill or the like. The dispersion thus prepared was diluted in a mixed solvent of methyl ethyl ketone: toluene: methyl isobutyl ketone with a weight cost of 20.79: 58.54: 20.68 so that the concentration of the non-volatile content would be 14%. Thus, a sliding layer coating material is prepared. The viscosity of the paint at 25 ° C. is 0.005 ± 0.005 Pa · s. Further, before the coating is subjected to the coating operation, an isocyanate agent (Tosoh Coronate 3041) is added while stirring with a disper so that the nonvolatile content becomes 3 parts by weight. Then, this paint is applied to one surface of a support (polyethylene naphthalate film made by Teijin, film thickness: 4.5 μm), the solvent is dried, and an isocyanate agent or the like is subjected to a curing reaction, so that 0.4 μm ± 0. A sliding layer adjusted to a thickness of 1 μm is produced.

The electric resistance of the obtained sliding layer is evaluated as 9 × 10 ⁶ Ω / □. The Young's modulus (Reduced Modulus “Er”) in the thickness direction of the sliding layer is estimated to be 13 GPa. As described above, this Young's modulus is an average value of Young's modulus having a contact depth of 40 to 50 nm with respect to a thickness of 500 nm. The measurement results are shown in FIG.

[Example 1-2]
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is 12 weight part (40 vol% carbon).
-Solid particle | grains are the same as what was used in Example 1-1, and a compounding quantity is 69.88 weight part (60 vol% carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 3 weight part (25 wt% of carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone: 45 weight part According to this composition, the true density of a sliding layer will be 5.108 g / cm < ³ >.

  Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

Example 2 Ceramic Particle
[Example 2-1]
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is 25.02 weight part (83.4 vol% carbon).
SiC particles as solid particles: Aldrich nanoparticles 549911, true density 3.22 g / cm ³ , blending amount 9.433 parts by weight (15.5 vol% carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 6.255 weight part (25 wt% of carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone: 45 weight part According to this composition, the true density of a sliding layer will be 1.641 g / cm < ³ >.

  Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

[Example 2-2]
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is 12 weight part (40 vol% carbon).
-Solid particle | grains are the same as what was used in Example 2-1, and a compounding quantity is 34.094 weight part (60 vol% carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 3 weight part (25 wt% of carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone: 45 weight part According to this composition, the true density of a sliding layer will be 2.422 g / cm < ³ >.

  Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

Example 3 Metal Particle
[Example 3-1]
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is (98.6 vol% carbon).
Platinum particles as solid particles: Tanaka Kikinzoku, product name PtDA, true density 21.5 g / cm ³ , blending amount 5.33 parts by weight (1.4 vol% carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 7.393 weight part (25 wt% of carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone: 45 weight part According to this composition, the true density of a sliding layer will be 1.641 g / cm < ³ >.

  Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

[Example 3-2]
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is 12 weight part (40 vol% carbon).
-Solid particle | grains are the same as what was used in Example 3-1, and a compounding quantity is 30 weight part (8.1 vol% carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 3 weight part (25 wt% of carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone: 45 weight part According to this composition, the true density of a sliding layer will be 2.763 g / cm < ³ >.

  Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

  In Example 3, since platinum particles having high conductivity are blended in a larger part by weight, the total volume of the particles (48.1 vol% carbon) is smaller than that of the other examples (100 vol% carbon as a whole). Even in this case, a good sliding layer is obtained.

[Reference Example 3-3]
As the solid particles, 54 parts by weight of the same platinum particles as used in Example 3-1 were used, and no paint was used, and the coating material was prepared in the same manner as in Example 1. The blending amount of the solid particles corresponds to 20.1 vol% carbon when 30 parts by weight of carbon particles are 100 vol% carbon. According to this composition, the true density of the sliding layer is 5.291 g / cm ³ . Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

Example 4 Metal Particle
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is 29.46 weight part (98.2 vol% carbon).
Gold particles as solid particles: Aldrich nanoparticles 741973, Mohs hardness 2.5, true density 17.3 g / cm ³ , blending amount 5.498 parts by weight (1.8 vol% carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 7.365 weight part (25 wt% of a carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
Methyl isobutyl ketone: 45 parts by weight According to this composition, the true density of the sliding layer is 1.644 g / cm ³ .

  Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

Example 5 Platinum-alumina particles
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is 29.58 weight part (98.6 vol% carbon).
-Particles in which platinum is supported on alumina as solid particles: platinum alumina 168-1394 manufactured by Wako Pure Chemical Industries, Ltd., the true density is 21.45 g / cm ³ , and the blending amount is 5.299 parts by weight (1.4 vol. % Carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 7.395 weight part (25 wt% of carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone: 45 weight part According to this composition, the true density of a sliding layer will be 1.641 g / cm < ³ >.

  Using this paint, the sliding layer is formed in the same procedure as in Example 1-1.

(Comparative Examples 1-1 to 1-3)
As the solid particles, the same antimony tin oxide particles as in Example 1 are used in Comparative Example 1-1, and the same SiC particles as in Example 2 are used in Comparative Example 1-2. Further, in Comparative Example 1-3, only the carbon particles are used and no solid particles are added, and a blank sliding layer is formed.

  Also in any comparative example, the compounding quantity of carbon particle (Mitsubishi Chemical Corporation # 1000) is 29.73 weight part. The compounding amount of the solid particles is 1.048 parts by weight in Comparative Example 1-1 and 0.511 parts by weight in Comparative Example 1-2. In any of the comparative examples, the dispersant (Kyoeisha Chemical's Floren DOPA 35) is added so that its nonvolatile content is 7.4325 parts by weight. In Comparative Examples 1-1 and 1-2, the blending amount of the dispersant corresponds to 25 wt% of the carbon particles. In Comparative Example 1-3, the blending amount of the dispersant corresponds to 25 wt% of 29.73 parts by weight of the carbon particles. The blending amounts of the other components are the same as in Example 1-1, a paint is prepared in the same procedure as in Example 1-1, and a sliding layer is formed using this paint.

The true density of the sliding layer, in Comparative Example 1-1 1.630g / cm ^3, Comparative Example 1-2 1.545 g / cm ^3, and 1.529g / cm ³ for Comparative Example 1-3 Become. The Young's modulus (Reduce Modulus “Er”) of the sliding layer of each comparative example in the thickness direction of 500 nm is 12 GPa for Comparative Example 1-1, 10 GPa for Comparative Example 1-2, and Comparative Example 1-3. Is evaluated as 10 GPa or less. In any sample, these values are average values of Young's modulus with a contact depth of 40 to 50 nm with respect to a film thickness of 500 nm. The measurement result of Comparative Example 1-3 is shown in FIG.

(Comparative Example 2)
In Comparative Example 2-1, as the solid particles, the same antimony tin oxide particles as those used in Example 1 are used, and in Comparative Example 2-2, the same SiC particles as those used in Example 2 are used.

Also in any comparative example, the compounding quantity of carbon particle (Mitsubishi Chemical Co., Ltd. product # 1000) is 11.7 weight part (39 vol% carbon). The amount of the solid particles is 71.047 parts by weight (61 vol% carbon) in Comparative Example 2-1, and 34.662 (61 vol% carbon) by weight in Comparative Example 2-2. In any of the comparative examples, the dispersant (Kyoeisha Chemical's Floren DOPA 35) is added so that its non-volatile content is 2.925 parts by weight (25 wt% of the carbon particles). The blending amounts of the other components are the same as in Example 1-1, a paint is prepared in the same procedure as in Example 1-1, and a sliding layer is formed using this paint. The true density of the sliding layer, in Comparative Example 2-1 5.139g / cm ^3, a 2.434g / cm ³ for Comparative Example 2-2.

(Comparative Example 3)
As solid particles, aluminum particles having a Mohs hardness of less than 2.5 (# 5 true density 2.7 Mohs hardness 2.4 made of moat metal foil powder) are used. In Comparative Example 3, the amount of carbon particles (# 1000 manufactured by Mitsubishi Chemical Corporation) is 26.4 parts by weight (88 vol% carbon), the amount of solid particles is 5.718 parts by weight (12 vol% carbon), dispersed The blending amount of the non-volatile component of the agent (Kyoeisha Chemical's Floren DOPA 35) is 6.6 parts by weight (25 wt% of the carbon particles). The blending amounts of the other components are the same as in Example 1-1, a paint is prepared in the same procedure as in Example 1-1, and a sliding layer is formed using this paint. The true density of the sliding layer is 1.650 g / cm ³ .

(Comparative Example 4)
As the solid particles, alumina particles (Aldrich Nanoparticles 544833 density 4.0 g / cm ³ Mohs hardness 9), which is a metal oxide having a Mohs hardness greater than 8, are used. In Comparative Example 4, the compounding amount of carbon particles (# 1000 manufactured by Mitsubishi Chemical Corporation) is 28.95 parts by weight (96.5 vol% carbon), and the compounding amount of solid particles is 2.464 parts by weight (3.5 vol%). Carbon) and the dispersing agent (Kyoeisha Chemical's Floren DOPA 35) have a non-volatile content of 7.365 parts by weight (25 wt% of the carbon particles. The other components are the same as in Example 1-1. A coating material was prepared in the same procedure as in Example 1-1, and a sliding layer was formed using this coating material, and the true density of the sliding layer was 1.642 g / cm ³ .

  The following evaluation is performed on the sliding layer of each tape sample produced.

(Arithmetic mean roughness Ra [nm] of the sliding layer surface)
The arithmetic average roughness Ra of 30 μm □ on the surface of the sliding layer is measured using an AFM surface roughness meter of Shimadzu Corporation.

(Surface electrical resistance)
The electrical resistance of the sliding layer surface is measured with a tester.

(Driving durability)
As shown schematically in FIG. 5, the tape sample 70 and the fixing pin 80 are arranged so that the sliding surface 30 </ b> B of the tape sample 70 with the weight 60 forms an angle of 90 degrees with the fixing pin 80. The fixing pin 80 is formed of an AlTiC material (R3.5 processing, Rmax 70 nm) manufactured by Kyocera Corporation to a diameter of 7 mm, and its Mohs hardness is 8. While maintaining this positional relationship, 100 reciprocating sliding runs are performed at 10 mm / sec. The running durability of the sliding surface 30B is evaluated by visually and observing the surface of the sliding surface 30B and the surface of the fixing pin 80 before and after the running with a 100 × optical microscope. Specifically, it is confirmed whether the sliding surface 30B is scratched or worn, the generation of wear powder from the sliding surface 30B, the surface of the fixing pin 80 is scratched or worn, and the generation of wear powder from the surface of the fixing pin 80 is confirmed. doing.

The running durability is evaluated according to the following evaluation criteria.
GD: No scratches are generated on the surfaces of the sliding surface 30B and the fixing pin 80, and no abrasion powder is generated.
OK: Slight scratches were confirmed on the sliding surface 30B, and slight abrasion powder was confirmed from the sliding surface 30B.
NG: Scratches were generated on the sliding surface 30B, and abrasion powder was frequently generated from the sliding surface 30B.
BD: Although there is little or no scratch on the sliding surface 30B, scratches are generated on the surface of the fixed pin 80, and generation of wear powder is confirmed from the surface of the fixed pin 80.

  Table 1 shows the primary particle size, electrical resistance, Mohs hardness, BET specific surface area, and evaluation results of the sliding layers of the examples and comparative examples used in the examples and comparative examples.

As is clear from Table 1, each example has an electric resistance of 5 × 10 ⁷ Ω / □ or less and good running durability. On the other hand, the comparative example has a problem in either point. In Comparative Examples 1-1 and 1-2, the blended amount of solid particles is smaller than those in Examples 1-1 and 2-1, respectively. Therefore, the true density is reduced, the sliding surface 30B is easily damaged, and the running durability is lowered. On the other hand, Comparative Examples 2-1 and 2-2 each have a larger amount of solid particles than Examples 1-2 and 2-2. Therefore, the electrical resistance exceeds 1 × 10 ⁸ Ω / □. When the electrical resistance is large as described above, the sliding layer is easily charged. In Comparative Example 3, aluminum having a low Mohs hardness is used as the solid particles. Therefore, the sliding surface 30B is easily damaged, and the running durability is lowered. On the other hand, in Comparative Example 4, alumina particles having high Mohs hardness are used as solid particles. For this reason, the hardness of the sliding surface 30B is increased, the fixing pin 80 is easily damaged, and the running durability is lowered.

  The tape recording medium of the present invention can be applied as a recording medium that slides on a relatively hard fixing member during recording and reproduction. Specifically, it can be used as an audio tape, a video tape, a data tape, and the like.

DESCRIPTION OF SYMBOLS 10 Support body 11 1st main surface 12 2nd main surface 20 Recording layer 30 Sliding layer 30A Sample 30B Sliding surface 40 Tape recording medium (recording medium)
41 Recording surface 42 Back surface 50 Berkovich diamond indenter (indenter)
60 spindle 70 tape sample 80 fixing pin

As described above, the backcoat layer and the antistatic layer described in Patent Documents 1 to 6 are not designed as layers that slide on a fixing member formed of a hard material. Therefore, these techniques are applied as they are to a recording medium in which the surface on the recording layer side does not come into contact with members in the recording / reproducing apparatus and the surface opposite to the side on which the recording layer is provided is exclusively a sliding surface. However, satisfactory characteristics cannot be obtained in terms of durability, antistatic properties, and prevention of powder generation. In particular, when the thickness of the recording medium is small, running in the recording / reproducing apparatus is likely to become unstable due to charging, and running is likely to become more unstable because the rigidity is small. The surface on the recording layer side is also referred to as “recording surface” for the sake of convenience, and the surface opposite to the side on which the recording layer is provided is also referred to as “back surface” for convenience.

The solid particles used together with the carbon particles are used to reinforce the sliding layer 30 and suppress damage to the sliding layer 30. The primary particle size of the solid particles is 100 nm or less, the Mohs hardness is 2.5 or more and 8 or less, the density is 3 g / cm ³ or more, and the BET specific surface area is 30 m ² / g or more.

When each of the solid particles is formed of a plurality of materials, the Mohs hardness as a whole or the Mohs hardness of the material constituting the surface of the solid particles may be in the above range. For example, the Mohs hardness of solid particles in which a soft metal such as platinum (Mohs hardness of 8 or less) is supported (mixed) on alumina having a Mohs hardness of about 9 is 8 or less as a whole. Used as solid particles . Further, fine particles coated with aluminum hydroxide (for example, NANOFINE manufactured by Sakai Chemical Industry Co., Ltd.) can also be used as solid particles in the present embodiment.

(7) The solid particles may be carbon particles carrying a metal (including a single metal and an alloy) or a metal oxide. As such solid particles, platinum-supported carbon black as disclosed in JP-A-2005-032668 may be used. The metal or metal oxide supported on the carbon particles is selected from platinum, palladium, tin, ruthenium, cobalt, copper, nickel, cerium, and rhodium oxide. The metal or metal oxide to be supported may be one kind or plural kinds. Alternatively, platinum-supported carbon that is a catalyst for a fuel cell as provided by Aldrich as product number 735557 may be used as the solid particles.

Example 3 Metal Particle
[Example 3-1]
A paint having the following composition was prepared.
-Carbon particle is the same as what was used in Example 1-1, and a compounding quantity is 29.6 weight part (98.6 vol% carbon) .
Platinum particles as solid particles: Tanaka Kikinzoku, product name PtDA, true density 21.5 g / cm ³ , blending amount 5.33 parts by weight (1.4 vol% carbon).
-A binder is the same as what was used in Example 1-1, and a compounding quantity is 13.7 weight part.
-A dispersing agent is the same as what was used in Example 1-1, and a compounding quantity is 7.393 weight part (25 wt% of carbon particle).
・ Methyl ethyl ketone: 108.6 parts by weight (including solvent such as binder)
-Toluene: 26.25 parts by weight (including binder and other solvents)
・ Cyclohexanone: 2.127 parts by weight (including a solvent such as a binder)
-Methyl isobutyl ketone: 45 weight part According to this composition, the true density of a sliding layer will be 1.641 g / cm < ³ >.

Claims (10)

A support;
A recording layer provided on the first main surface of the support;
A sliding layer provided on the second main surface of the support,
The sliding layer has an electric resistance of 1 × 10 ⁸ Ω / □ or less,
Carbon particles having a primary particle size of 30 nm or less and a BET specific surface area of 100 m ² / g or more;
Solid particles having a primary particle size of 100 nm or less, a Mohs hardness of 2.5 or more, 8 or less, a density of ³ g / cm ³ or more, and a BET specific surface area of 30 m ² / g or more,
Tape recording medium. The Young's modulus in the thickness direction of the sliding layer is 13 GPa or more.
The tape recording medium according to claim 1. The true density of the sliding layer is 1.640 g / cm ³ or more.
The tape recording medium according to claim 1 or 2. The sliding layer has an electric resistance of 5 × 10 ⁷ Ω / □ or less,
The tape recording medium of any one of Claims 1-3. The solid particles are
Metal oxide particles,
A single metal or alloy particle;
Ceramic particles,
Inorganic or organic particles coated with a single metal or alloy; and
Carbide particles,
Inorganic particles coated with carbon;
Carbon or single metal or alloy particles,
A single metal, an alloy, or a carbon particle carrying a metal oxide, and at least one selected from
The tape recording medium of any one of Claims 1-4. The solid particles include inorganic particles on which the simple metal or alloy is supported;
The inorganic particles carrying the simple metal or alloy are:
One or more selected from Sb—SnO ₂ particles carrying a single metal or alloy and ceramic particles carrying a single metal or alloy;
The tape recording medium according to claim 5. The solid particles include the metal oxide particles, and the metal oxide particles are doped with a metal element.
The tape recording medium according to claim 5. The metal element is one or more selected from antimony, gallium, aluminum, and indium, and the metal oxide is zinc oxide or tin oxide;
The tape recording medium according to claim 7. The metal element is antimony and the metal oxide is tin oxide;
The tape recording medium according to claim 7. The arithmetic average roughness Ra of the surface of the sliding layer is 10 nm or less,
The tape recording medium of any one of Claims 1-9.

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