Magnetic tape, magnetic tape cartridge and magnetic tape device

Abstract

To provide a magnetic tape that hardly lowers electromagnetic conversion characteristics even if it repeatedly runs.SOLUTION: A magnetic tape has a non-magnetic support body and a magnetic layer containing ferromagnetic powder. The magnetic tape contains a fluorine-containing compound in a portion on the magnetic layer side of the non-magnetic support body, and a ratio θr of a water contact angle measured on a surface of the magnetic layer after sliding with a magnetic head with respect to the water contact angle estimated on the surface of the magnetic layer before sliding with the magnetic head is 0.70 or more. A magnetic tape cartridge and a magnetic tape device include the magnetic tape.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a magnetic tape, a magnetic tape cartridge, and a magnetic tape device. [Background technology]

[0002] BACKGROUND ART In recent years, magnetic recording media have been widely used as recording media for recording various types of data (see Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-188596 [Patent Document 2] Japanese Patent Application Publication No. 9-16949 [Patent Document 3] Japanese Patent Application Publication No. 7-320254 Summary of the Invention [Problem to be solved by the invention]

[0004] Magnetic recording media include tape-type and disk-type recording media, and tape-type magnetic recording media, i.e., magnetic tape, are primarily used for data storage applications such as data backup and archiving.

[0005] Recording data on magnetic tape and reproducing the recorded data are usually performed by repeatedly running the magnetic tape in a magnetic tape device (commonly called a "drive.") One of the desired performance characteristics of magnetic tape is that there is little deterioration in its electromagnetic conversion characteristics after such repeated running.

[0006] An object of one aspect of the present invention is to provide a magnetic tape whose electromagnetic conversion characteristics are less deteriorated even after repeated running. [Means for solving the problem]

[0007] One aspect of the present invention is A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, a fluorine-containing compound is contained in a portion of the non-magnetic support on the magnetic layer side, a magnetic tape in which the ratio θr of the water contact angle measured on the surface of the magnetic layer after sliding with a magnetic head to the water contact angle measured on the surface of the magnetic layer before sliding with a magnetic head is 0.70 or more; Regarding.

[0008] In one embodiment, the ratio θr can be 0.80 or more.

[0009] In one embodiment, the ratio θr can be 0.85 or more.

[0010] In one embodiment, the magnetic tape can further have one or more non-magnetic layers containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[0011] In one embodiment, the magnetic tape can further have a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite to the surface having the magnetic layer.

[0012] In one embodiment, the ferromagnetic powder can be a hexagonal strontium ferrite powder.

[0013] In one embodiment, the ferromagnetic powder can be a hexagonal barium ferrite powder.

[0014] In one embodiment, the ferromagnetic powder can be an ε-iron oxide powder.

[0015] One aspect of the present invention relates to a magnetic tape cartridge including the above-mentioned magnetic tape.

[0016] One aspect of the present invention relates to a magnetic tape device including the above-mentioned magnetic tape. [Effects of the Invention]

[0017] According to one aspect of the present invention, it is possible to provide a magnetic tape whose electromagnetic conversion characteristics deteriorate little even after repeated running, as well as a magnetic tape cartridge and a magnetic tape device that include this magnetic tape. [Brief explanation of the drawings]

[0018] [Figure 1] An example of a device used to slide a magnetic tape and a magnetic head is shown. [Figure 2] 1 shows an example of the arrangement of data bands and servo bands. [Figure 3] An example of servo pattern layout for an LTO (Linear Tape-Open) Ultrium format tape is shown below. DETAILED DESCRIPTION OF THE INVENTION

[0019] [Magnetic tape] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein the magnetic tape contains a fluorine-containing compound on the portion of the non-magnetic support facing the magnetic layer, and the ratio θr (hereinafter simply referred to as "ratio θr") of the water contact angle measured on the surface of the magnetic layer after sliding with a magnetic head to the water contact angle measured on the surface of the magnetic layer before sliding with a magnetic head is 0.70 or more.

[0020] The magnetic tape contains a fluorine-containing compound in the portion of the non-magnetic support facing the magnetic layer. In the present invention and this specification, "the portion of the non-magnetic support facing the magnetic layer" refers to the magnetic layer in a magnetic tape having a magnetic layer directly on the non-magnetic support, and refers to the magnetic layer and / or non-magnetic layer in a magnetic tape having a non-magnetic layer between the non-magnetic support and the magnetic layer, as will be described in detail later. Hereinafter, "the portion of the non-magnetic support facing the magnetic layer" will also be referred to simply as "the portion facing the magnetic layer." The presence of a fluorine-containing compound on the surface facing the magnetic layer of a magnetic tape is also included in the presence of a fluorine-containing compound in the portion facing the magnetic layer. In the present invention and this specification, the surface of the magnetic layer is synonymous with the surface facing the magnetic layer of a magnetic tape.

[0021] Recording data on magnetic tape and reproducing the recorded data are usually performed by contacting and sliding a magnetic head against the magnetic layer surface of the magnetic tape. Reducing friction during sliding between the magnetic layer surface and the magnetic head is desirable from the perspective of improving electromagnetic conversion characteristics. One way to reduce the friction is to incorporate a component (a so-called lubricant) that can impart lubricity to the magnetic layer surface into the magnetic tape. For example, the previously mentioned Patent Document 1 (JP 2006-188596 A), Patent Document 2 (JP 9-16949 A), and Patent Document 3 (JP 7-320254 A) each describe a fluorine-containing compound as a lubricant. In response to this, the inventors have conducted extensive research and found that magnetic tapes containing a fluorine-containing compound in the magnetic layer and having a ratio θr of 0.70 or greater exhibit minimal degradation in electromagnetic conversion characteristics even after repeated running. The inventors believe that a ratio θr of 0.70 or greater indicates that a small amount of fluorine-containing compound is liberated from the magnetic tape even after repeated running while sliding against the magnetic head, i.e., that most of the fluorine-containing compound remains on the magnetic tape even after repeated running. The inventors speculate that the retention of a large amount of fluorine-containing compound on the magnetic tape even after repeated running suppresses the deterioration of the lubricity of the magnetic layer surface caused by the fluorine-containing compound, thereby making it possible to suppress the deterioration of electromagnetic conversion characteristics after repeated running. However, the present invention is not limited to the speculations described in this specification. The magnetic tape will now be described in more detail.

[0022] <Ratio θr> (Measurement of water contact angle and calculation of θr) The water contact angle before sliding with the magnetic head is defined as "θ before " and the water contact angle after sliding with the magnetic head is called "θ after Two tape samples are cut from any position in the longitudinal direction of the same magnetic tape. One of the two tape samples is 100 m long. The other tape sample can be any length as long as it allows measurement of the water contact angle. For a tape sample of any length, the water contact angle is measured at a randomly selected part of the magnetic layer surface without sliding with the magnetic head. The water contact angle measured for this tape sample is taken as the water contact angle θ before sliding with the magnetic head. before For a 100 m long tape sample, the water contact angle is measured at a randomly selected portion of the magnetic layer surface after sliding with the magnetic head. The water contact angle measured for this tape sample is the water contact angle θ after sliding with the magnetic head. afterThe sliding with the magnetic head will be described later. In the present invention and this specification, the "water contact angle" is a value measured by the sessile drop method. Specifically, the water contact angle is the arithmetic mean of the values ​​obtained by measuring six different parts of the magnetic layer surface of the tape sample to be measured by the θ / 2 method in a measurement environment of an ambient temperature of 25°C and a relative humidity of 50%. The water used is distilled water at a temperature of 25°C. An example of a specific form of the measurement conditions will be described later in the examples. The ratio θr is calculated by the following formula: after / θ before The water contact angle is measured after leaving the tape sample to be measured in an environment of 25°C and 50% relative humidity for at least 2 hours.

[0023] (Sliding with magnetic head) A reel tester with two tape reels is used to slide the magnetic head over the magnetic layer surface of the 100-m-long tape sample. A commercially available reel tester or one assembled by a known method can be used. Figure 1 shows an example of a device used to slide the magnetic tape (specifically, the tape sample) over the magnetic head. The magnetic tape and magnetic head are slid against each other in an environment with an ambient temperature of 23°C ± 1°C and a relative humidity of 50%. The tape sample is attached to a reel tester with one end of the tape sample fixed to one tape reel of the reel tester and the other end fixed to the other tape reel of the reel tester. An LTO (Linear Tape-Open) 8 head is used as the magnetic head attached to the reel tester. In this invention and this specification, an "LTO 8 head" refers to a magnetic head conforming to the LTO 8 standard. The LTO 8 head may be a magnetic head removed from an LTO 8 drive, or a commercially available magnetic head for LTO 8 drives may be used. Here, an "LTO 8 drive" refers to a drive (magnetic tape device) conforming to the LTO 8 standard. This also applies to drives of other generations. For example, an "LTO 9 drive" refers to a drive conforming to the LTO 9 standard. Considering that the LTO 8 standard is compatible with recent trends toward higher density recording, an LTO 8 head is used as the magnetic head for the sliding mechanism, and the magnetic tape is not limited to that used in LTO 8 drives. Data may be recorded and / or reproduced on the magnetic tape in an LTO8 drive, an LTO9 drive or a drive of a later generation, or an earlier generation drive such as an LTO7 drive. The tape sample is run in a reel tester, and the surface of the magnetic layer is brought into contact with the magnetic head and slid. The running conditions for the magnetic tape (the tape sample) are as follows. The tension values ​​applied to the magnetic tape in the longitudinal direction and the running speed of the magnetic tape are the settings for the reel tester. Regarding units, "gf" stands for gram force, and 1 N (Newton) is approximately 102 gf. Magnetic tape running speed: 4 m / s Tension applied to the magnetic tape in the longitudinal direction: 100 gf Magnetic tape travel passes: 20,000 single passes Wrap angle θ: 1°

[0024] In the above magnetic tape, from the viewpoint of suppressing deterioration of the electromagnetic conversion characteristics after repeated running, the ratio θr is 0.70 or more, preferably 0.72 or more, more preferably 0.75 or more, even more preferably 0.77 or more, still more preferably 0.80 or more, even more preferably 0.82 or more, and even more preferably 0.85 or more. before =θ after In this case, the ratio θr is 1.00. The ratio θr can be 1.00, 1.00 or less, or less than 1.00. The ratio θr can be, for example, 0.98 or less, 0.96 or less, or 0.94 or less. However, it can also exceed the values ​​exemplified here. The inventor believes that a larger value of the ratio θr indicates a larger amount of fluorine-containing compound remaining on the magnetic tape after sliding with the magnetic head. The inventor speculates that this is preferable in terms of further suppressing deterioration of electromagnetic conversion characteristics after repeated running.

[0025] <Fluorine-containing compounds> The magnetic tape contains a fluorine-containing compound in the magnetic layer. In the present invention and this specification, the term "fluorine-containing compound" refers to a compound containing one or more fluorine atoms (F) per molecule. To control the ratio θr to 0.70 or greater, the fluorine-containing compound is preferably one that easily remains on the magnetic tape even when the magnetic layer surface slides over the magnetic head. From this perspective, fluorine-containing compounds having functional groups known as "adsorbent functional groups" are preferred, compounds having two or more adsorbent functional groups per molecule are more preferred, and compounds having many more adsorbent functional groups per molecule are even more preferred. In one embodiment, the fluorine-containing compound can be a polymer (also referred to as a "fluorine-containing polymer"). The fluorine-containing polymer can be a homopolymer or a copolymer. The fluorine-containing polymer can have a branched structure including a main chain and one or more side chains branched from the main chain. The adsorbent functional group can be contained at least at one end of the side chain and / or the main chain. The adsorbent functional group may be contained at one or both ends of the main chain. Fluorine-containing polymers containing adsorptive functional groups in their side chains are preferred for increasing the θr value, and it is more preferable for more side chains to have adsorptive functional groups. Furthermore, in fluorine-containing polymers, fluorine atoms can be contained in the side chains and / or the main chain. For example, fluorine-containing polymers can contain functional groups containing fluorine atoms as constituent atoms (also referred to as "fluorine-containing functional groups") in their side chains. From the viewpoint of providing better lubricity to the magnetic layer surface, it is more preferable for fluorine-containing polymers to contain fluorine-containing functional groups in more side chains.

[0026] In one embodiment, the fluorine-containing polymer is A repeating unit represented by the following general formula (1), at least one repeating unit selected from the group consisting of repeating units represented by the following general formula (2) and repeating units represented by the following general formula (3); A polymer having a branched structure (hereinafter also referred to as "polymer A") comprising It can be.

[0027] [ka]

[0028] In general formula (1), R 1 and R 2 each independently represents a hydrogen atom or a methyl group. L 1 and L 2 each independently represents a divalent linking group. Rf 1 , Rf 2 , Rf 3 and Rf 4 are each independently a fluorine atom or a perfluoroalkane Represents a alkyl group. u represents an integer of 1 or greater. p represents an integer of 2 or more. t represents an integer of 0 or greater. Multiple Rf 1 may be the same or different. Multiple Rf 2 may be the same or different. Rf 3 If there are multiple Rf 3 may be the same or different. Rf 4 If there are multiple Rf 4 may be the same or different.

[0029] [ka]

[0030] In general formula (2), R 3 represents a hydrogen atom or a methyl group. L 3 represents a single bond or a divalent linking group. X 1 are -OH, -COOH, -PO3H, {-OP(=O)(OH)2}, -OM 1 , -CO2M 1 , -SO3M1 , -NT 1 T 2 , epoxy group, alicyclic epoxy group, oxazoline group, -NG 1 G 2 G 3 E 1 or a group having a betaine structure. M 1 is an alkali metal, alkaline earth metal, Mg, Al or Q 1 Q 2 Q 3 Q 4 N + Represents. Q 1 , Q 2 , Q 3 and Q 4 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. T 1 and T 2 each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms. T 1 and T 2 and may be combined. E 1 represents an anion. G 1 , G 2 and G 3 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0031] [ka]

[0032] In general formula (3), R 4 represents a hydrogen atom, a fluorine atom, a chlorine atom or an alkyl group having 1 to 20 carbon atoms. U 1 and U 2 each independently represents -O-, -S-, -COO-, -OCO-, -CONH-, -NHCOO- or NH-. R 5 and R 6each independently represents a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heteroaryl group. R 5 and R 6 and may be combined. L 4 represents a single bond or a divalent linking group.

[0033] Polymer A contains at least one type of repeating unit represented by general formula (1), and may contain only one type or two or more types. Polymer A may have only repeating units represented by general formula (2), or may have only repeating units represented by general formula (3), or may have repeating units represented by general formula (2) and repeating units represented by general formula (3). When polymer A has repeating units represented by general formula (2), polymer A may contain only one type of repeating unit represented by general formula (2), or two or more types of repeating units represented by general formula (3). When polymer A has repeating units represented by general formula (3), polymer A may contain only one type of repeating unit represented by general formula (3), or two or more types of repeating units represented by general formula (3). Since the polymer A contains the repeating unit represented by the general formula (1), it can have a fluorine-containing functional group in the side chain. Furthermore, the repeating units represented by general formula (2) and the repeating units represented by general formula (3) can be said to be repeating units having an adsorptive functional group. Because polymer A contains one or more of these repeating units, it can be a compound that is likely to remain on the magnetic tape even when the magnetic layer surface slides over the magnetic head.

[0034] Polymer A will be described in more detail below.

[0035] In the present invention and this specification, when a group (atomic group) is described without specifying whether it is substituted or unsubstituted, it encompasses not only a group having no substituent but also a group having a substituent, unless it is contrary to the spirit of the present invention. For example, the term "alkyl group" encompasses not only an alkyl group having no substituent (an unsubstituted alkyl group) but also an alkyl group having a substituent (a substituted alkyl group). In the present invention and herein, the term "organic group" refers to a group containing at least one carbon atom. Unless otherwise specified, the substituent is preferably a monovalent substituent. In the present invention and herein, "(meth)acrylate" refers to acrylate and methacrylate, (meth)acrylic refers to acrylic and methacrylic, and (meth)acryloyl refers to acryloyl and methacryloyl. In the present invention and this specification, the bonding direction of the divalent linking group is not limited unless otherwise specified. For example, when Y is -COO- in a compound represented by the formula "XYZ", Y may be -CO-O- or -O-CO-. The compound may be "X-CO-OZ" or "XO-CO-Z". In the present invention and this specification, a polymer "having a branched structure" or "being branched" means that the main chain of the polymer is branched. A polymer having a branched structure can typically have a three-dimensional crosslinked structure and / or can have at least one polymerization initiator fragment incorporated at its end.

[0036] As will be described later, polymer A can contain a partial structure obtained by radical polymerization of a fluorine-containing compound having two or more polymerizable groups. During the synthesis of polymer A, by adjusting the amount and type of polymerization initiator, etc., it is possible to incorporate polymerization initiator fragments into polymer A, which is thought to increase the number of polymerization initiation points, compact the crosslink size, and generate many polymer ends, thereby improving solubility. The polymerization initiator fragments differ depending on the structure of the polymerization initiator used when polymerizing polymer A, and incorporation of the polymer fragments into polymer A can be confirmed by methods such as NMR (Nuclear Magnetic Resonance) spectroscopy, IR (Infrared) spectroscopy, mass spectrometry, or elemental analysis.

[0037] Polymer A is a polymer having a branched structure, which includes at least one repeating unit represented by general formula (1) and at least one repeating unit selected from the group consisting of a repeating unit represented by general formula (2) and a repeating unit represented by the following general formula (3):

[0038] (Repeating unit represented by general formula (1)) The repeating unit represented by general formula (1) is a repeating unit having a perfluoropolyether group.

[0039] R in general formula (1) 1 and R 2 each independently represents a hydrogen atom or a methyl group.

[0040] L in general formula (1) 1 and L 2 each independently represents a divalent linking group. The divalent linking group is not particularly limited, and examples include -COO-, -CO-, -O-, an alkylene group (preferably having 1 to 10 carbon atoms), a cycloalkylene group (preferably having 3 to 20 carbon atoms), an arylene group (preferably having 6 to 20 carbon atoms), -SO-, -SO2-, -NH-, -NR-, and divalent linking groups formed by combining two or more of these. The above R represents an alkyl group (preferably having 1 to 10 carbon atoms), a cycloalkyl group (preferably having 3 to 20 carbon atoms), or an aryl group (preferably having 6 to 20 carbon atoms).

[0041] L in general formula (1) 1 and L 2 is preferably a divalent linking group formed by combining —COO—, an alkylene group, and NH—, and more preferably a divalent linking group represented by the following general formula (L-1).

[0042] [ka]

[0043] In general formula (L-1), A 1 and A 2Each independently represents an alkylene group. *1 and *2 represent the bonding position.

[0044] A in general formula (L-1) 1 and A 2 The alkylene group is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an alkylene group having 1 to 7 carbon atoms, and even more preferably an alkylene group having 1 to 4 carbon atoms. A 1 and A 2 Specific examples of the alkylene group represented by include a methylene group, an ethylene group, a trimethylene group, a methylethylene group, a tetramethylene group, a 1-methyltrimethylene group, a pentamethylene group, a 2,2-dimethyltrimethylene group, a hexamethylene group, a nonamethylene group, a 2-methyloctamethylene group, a decamethylene group, and a dodecamethylene group.

[0045] L in general formula (1) 1 and L 2 is also preferably a divalent linking group formed by combining —O—, an alkylene group, and an arylene group, and is also preferably a divalent linking group represented by the following general formula (L-2).

[0046] [ka]

[0047] In general formula (L-2), Ar 1 represents an arylene group, A 3 and A 4 *3 and *4 represent the bonding positions.

[0048] Ar in general formula (L-2) 1 The arylene group represented by the formula (I) is preferably an arylene group having 6 to 20 carbon atoms, more preferably an arylene group having 6 to 15 carbon atoms, still more preferably an arylene group having 6 to 10 carbon atoms, and particularly preferably a phenylene group. A in general formula (L-2) 3 and A4 The alkylene group represented by the formula (I) is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an alkylene group having 1 to 7 carbon atoms, and even more preferably an alkylene group having 1 to 4 carbon atoms. A 3 and A 4 Specific examples of the alkylene group represented by include a methylene group, an ethylene group, a trimethylene group, a methylethylene group, a tetramethylene group, a 1-methyltrimethylene group, a pentamethylene group, a 2,2-dimethyltrimethylene group, a hexamethylene group, a nonamethylene group, a 2-methyloctamethylene group, a decamethylene group, and a dodecamethylene group.

[0049] Rf in general formula (1) 1 , Rf 2 , Rf 3 and Rf 4 each independently represents a fluorine atom or a perfluoroalkyl group. Rf 1 , Rf 2 , Rf 3 and Rf 4 When one or more of each independently represent a perfluoroalkyl group, the perfluoroalkyl group is preferably a perfluoroalkyl group having 1 to 10 carbon atoms, more preferably a perfluoroalkyl group having 1 to 7 carbon atoms, and even more preferably a perfluoroalkyl group having 1 to 4 carbon atoms. Rf 1 , Rf 2 , Rf 3 and Rf 4 preferably represents a fluorine atom.

[0050] In general formula (1), u represents an integer of 1 or more, preferably an integer in the range of 1 to 10, more preferably an integer in the range of 1 to 6, and even more preferably an integer in the range of 1 to 3.

[0051] In general formula (1), p represents an integer of 2 or more, preferably an integer in the range of 2 to 100, more preferably an integer in the range of 6 to 80, and even more preferably an integer in the range of 10 to 60. p [CRf 1 Rf 2 ]uO may be the same or different.

[0052] In general formula (1), t represents an integer of 0 or more, preferably an integer in the range of 1 to 10, more preferably an integer in the range of 1 to 6, and even more preferably an integer in the range of 1 to 3.

[0053] The repeating unit represented by general formula (1) can be obtained by polymerizing a compound (K1) represented by the following general formula (1m).

[0054] [ka]

[0055] In the general formula (1m), R 1 , R 2 , L 1 , L 2 , Rf 1 , Rf 2 , Rf 3 , Rf 4 , u, p, and t are R in general formula (1), respectively. 1 , R 2 , L 1 , L 2 , Rf 1 , Rf 2 , Rf 3 , Rf 4 , u, p, and t, and the explanations, specific examples, and preferred ranges for each are also the same.

[0056] The content of the repeating unit represented by general formula (1) in polymer A is, in one embodiment, preferably 10 to 99 mass%, more preferably 20 to 95 mass%, even more preferably 30 to 90 mass%, and particularly preferably 40 to 90 mass%, based on the total repeating units in polymer A.

[0057] (Repeating unit represented by general formula (2)) R in general formula (2) 3 represents a hydrogen atom or a methyl group.

[0058] L in general formula (2) 3 represents a single bond or a divalent linking group. The divalent linking group is not particularly limited, and examples include -COO-, -CO-, -O-, an alkylene group (preferably having 1 to 20 carbon atoms), a cycloalkylene group (preferably having 3 to 20 carbon atoms), an arylene group (preferably having 6 to 20 carbon atoms), -SO-, -SO2-, -NH-, -NR-, and divalent linking groups formed by combining two or more of these. The above R represents an alkyl group (preferably having 1 to 10 carbon atoms), a cycloalkyl group (preferably having 3 to 20 carbon atoms), or an aryl group (preferably having 6 to 20 carbon atoms). L 3 represents a divalent linking group, it is preferably at least one divalent linking group selected from the group consisting of -O-, -COO-, -CONH-, -OCO-, and an alkylene group. The alkylene group is preferably an alkylene group having 1 to 20 carbon atoms, more preferably an alkylene group having 1 to 12 carbon atoms, and even more preferably an alkylene group having 1 to 6 carbon atoms.

[0059] L 3 preferably represents a single bond or a divalent linking group represented by the following general formula (L-3).

[0060] [ka]

[0061] In general formula (L-3), Z 1represents -O- or NH-. 5 represents an alkylene group. k represents an integer ranging from 1 to 30. *5 and *6 represent bonding positions.

[0062] A 5 The alkylene group represented by is preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, and even more preferably an alkylene group having 1 to 4 carbon atoms. A 5 The alkylene group represented by may have a substituent. A 5 Specific examples of the alkylene group represented by include a methylene group, an ethylene group, a trimethylene group, a 2-hydroxytrimethylene group, a methylethylene group, a tetramethylene group, a 1-methyltrimethylene group, a pentamethylene group, a 2,2-dimethyltrimethylene group, a hexamethylene group, a nonamethylene group, a 2-methyloctamethylene group, a decamethylene group, and a dodecamethylene group.

[0063] k is an integer ranging from 1 to 30, preferably an integer ranging from 1 to 15, more preferably an integer ranging from 1 to 10, and even more preferably an integer ranging from 1 to 5.

[0064] X in general formula (2) 1 are -OH, -COOH, -PO3H, {-OP(=O)(OH)2}, -OM 1 , -CO2M 1 , -SO3M 1 , -NT 1 T 2 , epoxy group, alicyclic epoxy group, oxazoline group, -NG 1 G 2 G 3 E 1 or a group having a betaine structure. M 1 is an alkali metal, alkaline earth metal, Mg, Al or Q 1 Q 2 Q 3 Q 4 N + Represents. Q 1 , Q 2 , Q 3 and Q 4 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. T 1 and T 2 each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms. T 1 and T 2 and may be combined. E 1 represents an anion. G 1 , G 2 and G 3 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0065] X 1 Ga-OM 1 When the salt is -O, - ·(M 1 ) + It is preferable that 1 ) + are alkali metal ions, alkaline earth metal ions, Mg 2+ , Al 3+ or Q 1 Q 2 Q 3 Q 4 N + It represents (M 1 ) + Mg 2+ If so, one Mg 2+ and two O's - It is preferable that the compound forms a salt with the compound (M 1 ) + Al 3+ If so, one Al 3+ and three O's - It is preferable that the compound forms a salt.

[0066] X 1 -CO2M 1 When expressing the salt form of -CO2 - ·(M1 ) + It is preferable that 1 ) + are alkali metal ions, alkaline earth metal ions, Mg 2+ , Al 3+ or Q 1 Q 2 Q 3 Q 4 N + It represents (M 1 ) + Mg 2+ If so, one Mg 2+ and two CO2 - It is preferable that the compound forms a salt with the compound (M 1 ) + Al 3+ If so, one Al 3+ and three CO2 - It is preferable that the compound forms a salt.

[0067] X 1 Ga-SO3M 1 When expressing the salt -SO3 - ·(M 1 ) + It is preferable that 1 ) + are alkali metal ions, alkaline earth metal ions, Mg 2+ , Al 3+ or Q 1 Q 2 Q 3 Q 4 N + It represents (M 1 ) + Mg 2+ If so, one Mg 2+ and two SO3 - It is preferable that the compound forms a salt with the compound (M 1 ) + Al 3+ If so, one Al 3+ and three SO3 - It is preferable that the compound forms a salt.

[0068] M 1The alkali metals represented by include lithium (Li), sodium (Na), potassium (K) and cesium (Cs). M 1 The alkaline earth metals represented by include calcium (Ca), strontium (Sr), and barium (Ba).

[0069] M 1 Q represents 1 Q 2 Q 3 Q 4 N + Q in (quaternary ammonium salts) 1 , Q 2 , Q 3 and Q 4 Each of Q independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. 1 , Q 2 , Q 3 and Q 4 When one or more of the groups represent an alkyl group, the alkyl group may be linear or branched, and is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms, and even more preferably an alkyl group having 1 to 4 carbon atoms. Q 1 , Q 2 , Q 3 and Q 4 When one or more of the groups represent an alkyl group, the alkyl group may have a substituent. Q 1 , Q 2 , Q 3 and Q 4 Examples of the alkyl group independently represented by one or more of the above include a methyl group, an ethyl group, a 2-hydroxyethyl group, an n (normal)-propyl group, an isopropyl group, a 3-hydroxypropyl group, an n-butyl group, an isobutyl group, a sec (secondary)-butyl group, a tert (tertiary)-butyl group, a 4-hydroxybutyl group, and an n-hexyl group.

[0070] Q 1 Q 2 Q 3 Q 4N + A specific example of this is Q 1 ~Q 4 are all the same, for example, (CH3)4N + , (C2H5)4N + , (C3H7)4N + , (C4H9)4N + , (C5H 11 )4N + , (CH 13 )4N + , (C7H 15 )4N + , (C8H 17 )4N + , (C9H 19 )4N + , (C 10 H 21 )4N + etc. Q 1 ~Q 3 If all are methyl groups, Q 4 For example, (C2H5), (C6H 13 ), (C8H 17 ), (C9H 19 ), (C 10 H 21 ), (C 12 H 25 ), (C 14 H 29 ), (C 16 H 33 ), (C 18 H 37 ) etc. Q 1 and Q 2 When is a methyl group, Q3 and Q4 are, for example, (CH 17 ), (C 10 H 21 ), (C 12 H 25 ), (C 14 H 29 ), (C 16 H 33 ), (C 18 H 37 ) can be. Q 1 is a methyl group, Q2 to Q4 are all, for example, (C4H9), (C8H 17) etc.

[0071] X 1 Ga-NT 1 T 2 When expressing 1 and T 2 each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms. 1 and T2 may be bound. T 1 and T 2 When one or both of the groups represent an alkyl group, the alkyl group may be linear or branched, and is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms, and even more preferably an alkyl group having 1 to 4 carbon atoms. T 1 and T 2 When one or both of the groups represent an alkyl group, the alkyl group may have a substituent. T 1 and T 2 Examples of the alkyl group represented by either or both of the above groups independently include a methyl group, an ethyl group, a 2-hydroxyethyl group, an n-propyl group, an isopropyl group, a 3-hydroxypropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 4-hydroxybutyl group, an n-hexyl group, and the like. T 1 and T 2 When one or both of the groups represent an alkoxy group, the alkoxy group may be linear or branched, and is preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 7 carbon atoms, and even more preferably an alkoxy group having 1 to 4 carbon atoms. T 1 and T 2 When one or both of the groups represents an alkoxy group, the alkoxy group may have a substituent. T 1 and T 2Examples of the alkoxy group independently represented by one or both of the groups include a methoxy group, an ethoxy group, a 2-hydroxyethoxy group, an n-propyloxy group, an isopropyloxy group, a 3-hydroxypropyloxy group, an n-butyloxy group, an isobutyloxy group, a sec-butyloxy group, a tert-butyloxy group, a 4-hydroxybutyloxy group, and an n-hexyloxy group. T 1 and T 2 When and bond, -NT 1 T 2 becomes a cyclic group. Examples of such groups include a morpholino group. T 1 and T 2 Most preferably, represents a hydrogen atom.

[0072] The alicyclic epoxy group refers to a cyclic group having a structure in which an epoxy ring and a saturated hydrocarbon group are condensed, and an example thereof is the following 3,4-epoxycyclohexyl group. In the following, * indicates the bonding position.

[0073] [ka]

[0074] X 1 Ga-NG 1 G 2 G 3 E 1 When the salt is -N + G 1 G 2 G 3 E 1 It is preferable that: E 1 The anion represented by is not particularly limited, and for example, a fluoride ion (F - ), chloride ions (Cl - ), bromide ion (Br - ), iodide ion (I - ) and other halide ions; hydroxide ions (OH - ); Cyanide ion (CN -); Nitrate ion (NO3 - ); Carbonate ion (CO3 2- ); sulfate ion (SO4 2- ); Methanesulfonate anion (CH3SO3 - ), sulfonate anions such as benzenesulfonate anion, p-toluenesulfonate anion, and trifluoromethanesulfonate anion; perchlorate anion; borate anions such as tetrafluoroborate anion and tetraphenylborate anion; hexafluorophosphate anion; acetate anion, etc. 1 If is a divalent anion, one E 1 and two NGs 1 G 2 G 3 It is preferable that the compound forms a salt.

[0075] G 1 , G 2 and G 3 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. G 1 , G 2 and G 3 When one or more of the groups represent an alkyl group, the alkyl group may be linear or branched, and is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms, and even more preferably an alkyl group having 1 to 4 carbon atoms. G 1 , G 2 and G 3 When one or more of the groups represent an alkyl group, the alkyl group may have a substituent. G 1 , G 2 and G 3 Examples of the alkyl group independently represented by one or more of the following include a methyl group, an ethyl group, a 2-hydroxyethyl group, an n-propyl group, an isopropyl group, a 3-hydroxypropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 4-hydroxybutyl group, an n-hexyl group, and the like.

[0076] X in general formula (2) 1 When represents a group having a betaine structure, such a group is not particularly limited as long as it is a group having a betaine structure. As the group having a betaine structure, a group represented by the following general formula (BT1), (BT2), (BT3) or (BT4) is preferred.

[0077] [ka]

[0078] In the general formula (BT1), G 4 and G 5 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. L 5 represents a divalent linking group. * indicates the bond position.

[0079] [ka]

[0080] In the general formula (BT2), G 6 and G 7 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. L 6 represents a divalent linking group. * indicates the bond position.

[0081] [ka]

[0082] In the general formula (BT3), G 8 , G 9 and G 10 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. vinegar. L 7 represents a divalent linking group. * indicates the bond position.

[0083] [ka]

[0084] In the general formula (BT4), G 11 and G 12 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. L8 represents a divalent linking group. * indicates the bond position.

[0085] G in general formula (BT1) 4 and G 5 Each of the groups independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. The details, specific examples, and preferred ranges of the alkyl group having 1 to 20 carbon atoms are described in 1 , G 2 and G 3 The same applies as described for the alkyl group having 1 to 20 carbon atoms represented by the formula (I).

[0086] L 5 represents a divalent linking group, preferably an alkylene group. The alkylene group is preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, and even more preferably an alkylene group having 1 to 4 carbon atoms. L 5 The alkylene group represented by may have a substituent. L 5 Specific examples of the alkylene group represented by include a methylene group, an ethylene group, a trimethylene group, a 2-hydroxytrimethylene group, a methylethylene group, a tetramethylene group, a 1-methyltrimethylene group, a pentamethylene group, a 2,2-dimethyltrimethylene group, a hexamethylene group, a nonamethylene group, a 2-methyloctamethylene group, a decamethylene group, and a dodecamethylene group.

[0087] G in general formula (BT2) 6 and G 7Each of the groups independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. The details, specific examples, and preferred ranges of the alkyl group having 1 to 20 carbon atoms are described in 1 , G 2 and G 3 The same applies as described for the alkyl group having 1 to 20 carbon atoms represented by the formula (I). L6 represents a divalent linking group. The explanation, specific examples and preferred ranges of L6 are as described above. Similar to that described for L5.

[0088] G in general formula (BT3) 8 , G 9 and G 10 Each of the groups independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. The details, specific examples, and preferred ranges of the alkyl group having 1 to 20 carbon atoms are described in 1 , G 2 and G 3 The same applies as described for the alkyl group having 1 to 20 carbon atoms represented by the formula (I). L 7 represents a divalent linking group. 7 The explanation, specific examples and preferred ranges for L 5 This is similar to what was described for

[0089] G in general formula (BT4) 11 and G 12 Each of the groups independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. The details, specific examples, and preferred ranges of the alkyl group having 1 to 20 carbon atoms are described in 1 , G 2 and G 3 The same applies as described for the alkyl group having 1 to 20 carbon atoms represented by the formula (I). L 8 represents a divalent linking group. 8 The explanation, specific examples and preferred ranges for L 5 This is similar to what was described for

[0090] Polymer A is It contains a repeating unit represented by general formula (2), and X in general formula (2) 1 -COOH, -PO3H, {-OP(=O)(OH)2}, -CO2M 1 , -SO3M 1 , -NT 1 T 2 , oxazoline group, -NG 1 G 2 G 3 E 1 or preferably represents a group having a betaine structure, X 1 Ga-NG 1 G 2 G 3 E 1 or more preferably represents a group having a betaine structure, X 1 more preferably represents a group represented by general formula (BT1), (BT2), (BT3) or (BT4), X 1 It is particularly preferred that represents a group represented by general formula (BT1), (BT2) or (BT3).

[0091] The repeating unit represented by general formula (2) can be obtained by polymerizing a compound (K2) represented by the following general formula (2m).

[0092] [ka]

[0093] In the general formula (2m), R 3 , L 3 and X 1 are R in general formula (2), respectively. 3 , L 3 and X 1 The explanations, specific examples and preferred ranges for each are also the same.

[0094] The compound represented by general formula (2m) is preferably a compound represented by any one of the following general formulae (2m-1) to (2m-4).

[0095] [ka]

[0096] In the general formula (2m-1), R 3 is R in general formula (2) 3 is synonymous with R 3 The explanations, specific examples and preferred ranges for the same are also the same. In the general formula (2m-1), A 5 and k are each A in general formula (L-3). 5 and k, and the explanations, specific examples, and preferred ranges for each are also the same. In the general formula (2m-1), G 1 , G 2 , G 3 and E 1 are X in general formula (2), respectively. 1 Ga-NG 1 G 2 G 3 E 1 G when representing 1 , G 2 , G 3 and E 1 The explanations, specific examples and preferred ranges for each are also the same.

[0097] [ka]

[0098] In the general formula (2m-2), R 3 is R in general formula (2) 3 is synonymous with R 3 The explanations, specific examples and preferred ranges for the same are also the same. In the general formula (2m-2), A 5 and k are each A in general formula (L-3). 5 and k, and the explanations, specific examples, and preferred ranges for each are also the same. In the general formula (2m-2), G 4 , G 5and L 5 respectively represent G4 and G in general formula (BT1). 5 and L 5 The explanations, specific examples and preferred ranges for each are also the same.

[0099] [ka]

[0100] In the general formula (2m-3), R 3 is R in general formula (2) 3 is synonymous with R 3 The explanations, specific examples and preferred ranges for the same are also the same. In the general formula (2m-3), A 5 and k have the same meanings as A5 and k in general formula (L-3), respectively, and the explanations, specific examples, and preferred ranges for each are also the same. In the general formula (2m-3), G 6 , G 7 and L 6 are G in general formula (BT2), respectively. 6 , G 7 and L 6 The explanations, specific examples and preferred ranges for each are also the same.

[0101] [ka]

[0102] In the general formula (2m-4), R 3 is R in general formula (2) 3 is synonymous with R 3 The explanations, specific examples and preferred ranges for the same are also the same. In the general formula (2m-4), A 5 and k are each A in general formula (L-3). 5 and k, and the explanations, specific examples, and preferred ranges for each are also the same. In the general formula (2m-4), G 8 , G9 , G 10 and L 7 are G in general formula (BT3), respectively. 8 , G 9 , G 10 and L 7 The explanations, specific examples and preferred ranges for each are also the same.

[0103] Specific examples of the compound represented by general formula (2m) include acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, s-carboxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 2-hydroxybutyl methacrylate, polypropylene glycol acrylate, polypropylene glycol methacrylate, isopropenyloxazoline, styreneboronic acid, 2-(N,N-dimethylamino)ethyl (meth)acrylate, 2-(N-tert-butyl) aminoalkyl (meth)acrylates such as N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, Nn-propyl (meth)acrylamide, N-isopropyl (meth)acrylamide, Nn-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-(2-hydroxyethyl)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-(2-dimethylaminoethyl) (meth)acrylamide, N-(3-dimethylaminopropyl) (meth)acrylamide, diacetone (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-(meth)acryloylmorpholine, and other acrylamides;N-(2-(meth)acryloyloxyethyl)-N,N,N-trimethylammonium chloride, N-(2-(meth)acryloyloxyethyl)-N,N,N-trimethylammonium bromide, N-(2-(meth)acryloyloxyethyl)-N,N,N-trimethylammonium iodide, N-(2-(meth)acryloyloxyethyl)-N,N,N-trimethylammonium methanesulfonate, N-(2-(meth)acryloyloxyethyl)-N,N-di (Meth)acryloyl group-containing quaternary ammonium salts such as ethyl-N-methylammonium methanesulfonate, N-(2-(meth)acryloyloxyethyl)-N-butyl-N,N-dimethylammonium iodide, and N-(2-(meth)acryloyloxypropyl)-N,N-diethyl-N-methylammonium chloride; 2-((2-(meth)acryloyloxyethyl)dimethylammonio)acetate (N-(2-(meth)acryloyloxyethyl)-N,N-di Carboxybetaines such as methylglycine), 3-((2-(meth)acryloyloxyethyl)dimethylammonio)propanoate, 4-((2-(meth)acryloyloxyethyl)dimethylammonio)butanoate, and 5-((2-(meth)acryloyloxyethyl)dimethylammonio)pentanoate; ((2-(meth)acryloyloxyethyl)dimethylammonio)methanesulfonate, 2-((2-(meth)acryloyloxyethyl)dimethylammonio) Sulfobetaines such as 2-(meth)acryloyloxyethyl)dimethylammonio)ethanesulfonate, 3-((2-(meth)acryloyloxyethyl)dimethylammonio)propane-1-sulfonate, and 4-((2-(meth)acryloyloxyethyl)dimethylammonio)butane-1-sulfonate; (meth)acryloyl group-containing phosphate esters such as 2-(meth)acryloyloxyethyl dihydrogen phosphate and 4-(meth)acryloyloxybutyl dihydrogen phosphate; (2-(meth)acryl; (4-(meth)acryloyloxyethyl)phosphorylcholine, (4-(meth)acryloyloxybutyl)phosphorylcholine Examples include, but are not limited to, phosphorylcholines such as phosphocholine.

[0104] (Repeating unit represented by general formula (3)) R in general formula (3) 4 represents a hydrogen atom, a fluorine atom, a chlorine atom or an alkyl group having 1 to 20 carbon atoms. R 4 The alkyl group represented by may be linear or branched, and is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms, even more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group. R 4 preferably represents a hydrogen atom or a methyl group.

[0105] U in general formula (3) 1 and U 2 each independently represents -O-, -S-, -COO-, -OCO-, -CONH-, -NHCOO- or NH-, preferably represents -O- or NH-, more preferably represents -O-.

[0106] R in general formula (3) 5 and R 6 R each independently represents a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heteroaryl group. 5 and R 6 and may be combined.

[0107] R 5 and R 6 When one or both of the groups represent an aliphatic hydrocarbon group, such an aliphatic hydrocarbon group may have a substituent. R 5 and R 6 When one or both of the groups represent an aliphatic hydrocarbon group, such an aliphatic hydrocarbon group may be an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, or an alkynyl group, each of which may have a substituent. The alkyl group is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, still more preferably an alkyl group having 1 to 7 carbon atoms, and particularly preferably an alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group include linear or branched alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, 1-methylbutyl, isohexyl, and 2-methylhexyl. The cycloalkyl group is preferably a cycloalkyl group having 3 to 20 carbon atoms, more preferably a cycloalkyl group having 5 to 15 carbon atoms. Specific examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, and a 2-norbornyl group. The alkenyl group is preferably an alkenyl group having 2 to 20 carbon atoms, more preferably an alkenyl group having 2 to 10 carbon atoms, still more preferably an alkenyl group having 2 to 7 carbon atoms, and particularly preferably an alkenyl group having 2 to 4 carbon atoms. Specific examples of the alkenyl group include straight-chain or branched alkenyl groups such as vinyl, 1-propenyl, 1-butenyl, and 1-methyl-1-propenyl. The cycloalkenyl group is preferably a cycloalkenyl group having 3 to 20 carbon atoms, and more preferably a cycloalkenyl group having 5 to 15 carbon atoms. Specific examples of the cycloalkenyl group include a 1-cyclopentenyl group and a 1-cyclohexenyl group. The alkynyl group is preferably an alkynyl group having 2 to 20 carbon atoms, more preferably an alkynyl group having 2 to 10 carbon atoms, still more preferably an alkynyl group having 2 to 7 carbon atoms, and particularly preferably an alkynyl group having 2 to 4 carbon atoms. Specific examples of the alkynyl group include an ethynyl group, a 1-propynyl group, a 1-butynyl group, and a 1-octynyl group.

[0108] R 5 and R 6When one or both of the groups represents an aryl group, the aryl group may have a substituent. R 5 and R 6 When one or both of the groups represent an aryl group, the aryl group is preferably an aryl group having 6 to 20 carbon atoms, more preferably an aryl group having 6 to 15 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms. Also, R 5 and R 6 When one or both of the groups represent an aryl group, the aryl group may be, for example, a fused ring formed by one to four benzene rings, a fused ring formed by a benzene ring and an unsaturated five-membered ring, or the like. R 5 and R 6 When one or both of the groups represent an aryl group, specific examples of such an aryl group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, an indenyl group, an acenabutenyl group, a fluorenyl group, and a pyrenyl group.

[0109] R 5 and R 6 When one or both of the groups represents a heteroaryl group, such a heteroaryl group may have a substituent. Examples of the heteroaryl group include a heteroaryl group obtained by removing one hydrogen atom from a heteroaromatic ring containing one or more heteroatoms selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms. Specific examples of heteroaromatic rings containing one or more heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur atoms include pyrrole, furan, thiophene, pyrazole, imidazole, triazole, oxazole, isoxazole, oxadiazole, thiazole, thiadiazole, indole, carbazole, benzofuran, dibenzofuran, thianaphthene, dibenzothiophene, indazole, benzimidazole, anthranil, benzisoxazole, benzoxazole, benzothiazole, purine, pyridine, pyridazine, pyrimidine, pyrazine, triazine, quinoline, acridine, isoquinoline, phthalazine, quinazoline, quinoxaline, naphthyridine, phenanthroline, and pteridine.

[0110] R 5 and R 6 The substituent that may be possessed by may be a monovalent non-metallic atomic group other than a hydrogen atom, and is, for example, selected from the following group of substituents Y.

[0111] Substituent group Y: Halogen atoms (-F, -Br, -Cl, -I), hydroxyl group, alkoxy group, aryloxy group, mercapto group, alkylthio group, arylthio group, alkyldithio group, aryldithio group, amino group, N-alkylamino group, N,N-dialkylamino group, N-arylamino group, N,N-diarylamino group, N-alkyl-N-arylamino group, acyloxy group, carbamoyloxy group, N-alkylcarbamoyloxy group, N-arylcarbamoyloxy group, N,N-dialkylcarbamoyloxy group group, N,N-diarylcarbamoyloxy group, N-alkyl-N-arylcarbamoyloxy group, alkylsulfoxy group, arylsulfoxy group, acylthio group, acylamino group, N-alkylacylamino group, N-arylacylamino group, ureido group, N'-alkylureido group, N',N'-dialkylureido group, N'-arylureido group, N',N'-diarylureido group, N'-alkyl-N'-arylureido group, N-alkylureido group, N-arylureido group, N'-alkyl-N -Alkylureido group, N'-alkyl-N-arylureido group, N',N'-dialkyl-N-alkylureido group, N',N'-dialkyl-N-arylureido group, N'-aryl-N-alkylureido group, N'-aryl-N-arylureido group, N',N'-diaryl-N-alkylureido group, N',N'-diaryl-N-arylureido group, N'-alkyl-N'-aryl-N-alkylureido group, N'-alkyl-N'-aryl-N-arylureido group, alkoxyca N-aryl-N-aryloxycarbonylamino group, aryloxycarbonylamino group, N-alkyl-N-alkoxycarbonylamino group, N-alkyl-N-aryloxycarbonylamino group, N-aryl-N-alkoxycarbonylamino group, N-aryl-N-aryloxycarbonylamino group, formyl group, acyl group, carboxyl group and its conjugate base group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, N-alkylcarbamoyl group, N,N-dialkylcarbamoyl group, N-arylcarbamoyl group, N,N-diarylcarbamoyl group, N-alkyl-N-arylcarbamoyl group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, sulfo group (-SO3H) and its conjugate base group, alkoxysulfonyl group, aryloxysulfonyl group, sulfinamoyl group, N-alkylsulfinamoyl group, N,N-dialkylsulfinamoyl group, N-arylsulfinamoyl group, N,N-diarylsulfinamoyl group, N-alkyl-N-arylsulfinamoyl group, sulfamoyl group, N-alkylsulfamoyl group, N,N-dialkylsulfamoyl group, N-arylsulfamoyl group, N,N-diarylsulfamoyl group, N-alkyl-N-arylsulfamoyl group, N-acylsulfamoyl group and its conjugate base group, N-alkylsulfonylsulfamoyl group (-SONHSO(alkyl)) and its conjugate base group, N-arylsulfonylsulfamoyl group (-SONHSO(aryl)) and its conjugate base group, N-alkylsulfonylcarbamoyl group (-CONHSO(alkyl)) and its conjugate base group, N-arylsulfonylcarbamoyl group (-CONHSO(aryl)) and its conjugate base group, alkoxysilyl group (-Si(Oalkyl)3), aryloxysilyl group (-Si(Oaryl)3), hydroxysilyl group (-Si(OH)3) and its conjugate base group, phosphono group (-PO3H2) and its conjugate base group, dialkylphosphono group (-PO3(alkyl)2), diarylphosphono group (-PO3(aryl)) 2), alkylarylphosphono group (-PO3(alkyl)(aryl)), monoalkylphosphono group (-PO3H(alkyl)) and its conjugate base group, monoarylphosphono group (-PO3H(aryl)) and its conjugate base group, phosphonooxy group (-OPO3H2) and its conjugate base group, dialkylphosphonooxy group (-OPO3(alkyl)2), diarylphosphonooxy group (-OPO3(aryl)2), alkylarylphosphonooxy group (-OPO3(alkyl)(aryl)), monoalkylphosphonooxy group (-OPO3H(alkyl)) and its conjugate base group, monoarylphosphonooxy group (-OPO3H(aryl)) and its conjugate base group, cyano group, nitro group, aryl group, alkenyl group, and alkynyl group. Furthermore, if possible, these substituents may be bonded to each other or to the hydrocarbon group that substitutes them to form a ring.

[0112] R 5 and R 6 preferably each independently represents a hydrogen atom, an alkyl group, or an aryl group, and more preferably represents a hydrogen atom or an alkyl group. R 5 and R 6 represent a hydrogen atom or an alkyl group, and R5 and R 6 and are bonded (i.e., R 5 and R 6 It is more preferred that and represent an alkylene linking group.

[0113] L in general formula (3) 4 represents a single bond or a divalent linking group. L 4 The divalent linking group represented by is -O-, -S-, -COO-, -OCO-, -CONR 13 -, -NR 13 COO-, -CR 13 It is preferable that R represents a divalent linking group selected from the group consisting of N-, a substituted or unsubstituted divalent aliphatic group, a substituted or unsubstituted divalent aromatic group, and a combination thereof. 13 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. L 4 When contains a substituted or unsubstituted divalent aliphatic group, the aliphatic group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and even more preferably 1 to 10 carbon atoms. L 4 When contains a substituted or unsubstituted divalent aromatic group, the number of aromatic rings is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. L 4 -O-, -COO-, -OCO-, -CONR 13 -, -NR 1 It is preferably a divalent linking group selected from the group consisting of 3COO-, a substituted or unsubstituted divalent aliphatic group, a substituted or unsubstituted divalent aromatic group, and a combination thereof; it is more preferably a divalent linking group selected from the group consisting of -O-, -COO-, -OCO-, a substituted or unsubstituted divalent aliphatic group, a substituted or unsubstituted divalent aromatic group, and a combination thereof; and it is even more preferably a divalent linking group selected from the group consisting of -O-, -COO-, -OCO-, a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, and a combination thereof.

[0114] The repeating unit represented by general formula (3) is a compound represented by the following general formula (3m): ) (hydrophilic monomer) can be polymerized.

[0115] [ka]

[0116] In the general formula (3m), R 4 , U 1 , U 2 , R 5 , R 6 and L 4 are R in general formula (3), respectively. 4 , U 1 , U 2 , R 5 , R 6 and L 4 The explanations, specific examples and preferred ranges for each are also the same.

[0117] Specific examples of the compound represented by general formula (3m) include, but are not limited to, monomers represented by the following formulas 3-1 to 3-26.

[0118] [ka]

[0119] [ka]

[0120] [ka]

[0121] [ka]

[0122] In one embodiment, the sum of the content of the repeating unit represented by general formula (2) and the content of the repeating unit represented by general formula (3) in polymer A is preferably 1 to 90 mass%, more preferably 5 to 80 mass%, even more preferably 10 to 70 mass%, even more preferably 10 to 60 mass%, and even more preferably 10 to 50 mass%, based on the total repeating units in polymer A.

[0123] (Other repeating units) The polymer A may contain only the above repeating units as repeating units, or may have repeating units other than those of the general formulae (1) to (3). The content of repeating units other than those of general formulae (1) to (3) in polymer A is preferably 0 to 20 mass %, more preferably 0 to 10 mass %, and even more preferably 0 to 5 mass %, and is 0 mass % (general formula (1) It is particularly preferred that the copolymer has no repeating units other than those in (1) to (3).

[0124] The weight average molecular weight (Mw) of polymer A is preferably 1,000 to 20,000, more preferably 1,000 to 15,000, and even more preferably 1,000 to 10,000, as determined by converting a value measured by gel permeation chromatography (GPC) into polystyrene equivalent.

[0125] The weight average molecular weight (Mw) of polymer A is determined by measuring the value by gel permeation chromatography (GPC) under the following conditions and converting it into polystyrene equivalent. [Eluent]: tetrahydrofuran (THF) [Device name]: Ecosec HLC-8220GPC (Tosoh Corporation) [Column]: TSKgel Super HZM-H, TSKgel Super HZ4000, TSKgel Super HZM200 (manufactured by Tosoh Corporation) [Column temperature]: 40℃ [Flow rate]: 50ml / min

[0126] (Production method of polymer A) Polymer A can be obtained by polymerizing compound (K1) represented by general formula (1m) above with at least one compound selected from the group consisting of compound (K2) represented by general formula (2m) above and compound (K3) represented by general formula (3m) above in the presence of a polymerization initiator. The amount of the polymerization initiator used can be, for example, 210 to 3000 mol % based on the total amount of compound (K1), compound (K2), and compound (K3).

[0127] The amount of the polymerization initiator used (polymerization initiator amount) is calculated by the following formula (J), and in one embodiment, is preferably 210 to 3000 mol%, more preferably 260 to 1500 mol%, still more preferably 260 to 1000 mol%, and particularly preferably 260 to 700 mol%, relative to the total amount of compound (K1), compound (K2), and compound (K3). Formula (J): Amount of polymerization initiator (mol %)=100×amount of substance of polymerization initiator / (amount of substance of compound (K1)+amount of substance of compound (K2)+amount of substance of compound (K3))

[0128] Polymerization initiator: As the polymerization initiator, an azo-based polymerization initiator can be preferably used. Examples of the azo-based polymerization initiator include the following compounds (1) to (6).

[0129] (1) Azonitrile compounds: 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 1,1'-azobis(1-cyclohexanecarbonitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2-(carbamoylazo)isobutyronitrile, and the like.

[0130] (2) Azoamide compounds: 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis{2-methyl-N-[2-(1-hydroxybutyl)]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), and the like.

[0131] (3) Cyclic azoamidine compounds: 2,2'-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, 2,2'-azobis[2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane)dihydrochloride, and the like.

[0132] (4) Azoamidine compounds: 2,2'-Azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate, and the like.

[0133] (5)Other: Dimethyl 2,2'-azobisisobutyrate, 4,4'-azobis-4-cyanovaleric acid, 2,2'-azobis(2,4,4-trimethylpentane), 1,1'-azobis(1-acetoxy-1-phenylethane), dimethyl 1,1'-azobis(1-cyclohexanecarboxylate), 4,4'-azobis(4-cyanopentanoic acid), and the like.

[0134] (6) Fluoroalkyl-containing azo polymerization initiator: 4,4'-azobis(4-cyanopentanoic acid-2-(perfluoromethyl)ethyl), 4,4'-azobis(4-cyanopentanoic acid-2-(perfluorobutyl)ethyl), 4,4'-azobis(4-cyanopentanoic acid-2-(perfluorohexyl)ethyl) and the like.

[0135] Among the above azo polymerization initiators, those having a relatively low polarity substituent are desirable from the viewpoint of the surface energy of the resulting polymer, and 2,2'-azobisisobutyric acid dimethyl or 2,2'-azobis(2,4,4-trimethylpentane) are particularly preferred. Fluoroalkyl group-containing azo polymerization initiators such as 4,4'-azobis(4-cyanopentanoate-2-(perfluoromethyl)ethyl) and 4,4'-azobis(4-cyanopentanoate-2-(perfluorohexyl)ethyl) are also preferred.

[0136] Polymer A can be polymerized by known methods, such as solution polymerization, dispersion polymerization, precipitation polymerization, bulk polymerization, etc. Among these, solution polymerization or precipitation polymerization is preferred. In particular, from the viewpoint of molecular weight control, it is preferred to carry out the reaction by solution polymerization in an organic solvent. Examples of organic solvents that can be used at this time include aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and tetralin; aliphatic or alicyclic hydrocarbon solvents such as n-hexane, n-heptane, mineral spirits, and cyclohexane; halogenated solvents such as methyl chloride, methyl bromide, methyl iodide, methylene dichloride, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, and o-dichlorobenzene; ester or ester ether solvents such as ethyl acetate, butyl acetate, methoxybutyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, and propylene glycol monomethyl ether acetate; diethyl ether, tetrahydrofuran, 1,4-dioxane, methyl cellosolve, and ethyl cellosolve. ether-based solvents such as butyl cellosolve and propylene glycol monomethyl ether; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, di-n-butyl ketone and cyclohexanone; alcohol-based solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, 2-ethylhexyl alcohol and benzyl alcohol; amide-based solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; sulfoxide-based solvents such as dimethyl sulfoxide, heterocyclic compound-based solvents such as N-methyl-2-pyrrolidone, fluorine-based solvents such as hydrofluoroethers (trade name Novec7200 (manufactured by 3M) and the like), and mixed solvents of two or more of these. Among these, aromatic hydrocarbon solvents, halogenated solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, amide solvents, sulfoxide solvents, fluorinated solvents, etc. are preferred, and particularly preferred are toluene, xylene, orthodichlorobenzene, butyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, 1,4-dioxane, methyl cellosolve, methyl isobutyl ether, methyl ... Examples of suitable solvents include chirketone, N,N-dimethylformamide, N,N-dimethylacetamide, Nocec7200, and Novec7300 (manufactured by 3M), and mixed solvents of two or more of these are also preferred.

[0137] When the polymerization reaction is carried out in the presence of an organic solvent, the content of the organic solvent in the entire polymerization reaction product is preferably 0.1 to 100 parts by mass, more preferably 0.5 to 50 parts by mass, per part by mass of compound (K1).

[0138] The polymerization reaction can be carried out under normal pressure, under a pressurized, sealed atmosphere, or under reduced pressure. For ease of use and operation, normal pressure is preferred. It is also preferred to carry out the polymerization reaction under an inert gas atmosphere such as N2. The polymerization reaction temperature is preferably 50 to 200°C, more preferably 70 to 150°C. More preferably, the polymerization reaction can be carried out at a temperature 10°C or more higher than the 10-hour half-life temperature of the polymerization initiator. More specifically, the polymerization reaction is preferably carried out by dropping a solution containing at least one compound selected from the group consisting of compound (K1), compound (K2), and compound (K3), a polymerization initiator, and an organic solvent into an organic solvent maintained at a temperature 10°C or more higher than the 10-hour half-life temperature of the polymerization initiator. After completion of the polymerization reaction, the resulting polymer A can be recovered by any method and, if necessary, subjected to post-treatment such as washing. Methods for recovering polymer A from the reaction solution include reprecipitation.

[0139] The amount of at least one compound selected from the group consisting of compound (K2) and compound (K3) used is preferably 1 to 1000 mol %, and more preferably 5 to 500 mol %, relative to compound (K1), from the viewpoints of solvent solubility, resin dispersibility, etc.

[0140] In synthesizing the polymer A, the polymerization reaction is preferably a radical polymerization reaction from the viewpoint of controlling the molecular weight.

[0141] The residual double bond ratio in polymer A obtained by radical polymerization reaction is preferably 0.05 mol% or less, more preferably 0.01 mol% or less, and most preferably 0.001 mol% or less, per mole of polymer. The residual double bond ratio can be simply calculated from the peak intensity by performing NMR (nuclear magnetic resonance) measurement.

[0142] Specific examples of polymer A include polymers (1-1) to (1-8) used in the examples described later. Specific examples of polymer A also include the following polymers (1-9) to (1-21). For each polymer, "a" and "b" respectively represent the content (unit: mass %) of each repeating unit relative to all repeating units in the polymer. Details are as described above. In one embodiment, for each polymer, "b" is preferably 10 to 70 mass %, more preferably 10 to 60 mass %, and even more preferably 10 to 50 mass %.

[0143] [ka]

[0144] [ka]

[0145] One or more fluorine-containing compounds can be used for manufacturing magnetic tapes. In one embodiment, a coating solution containing the fluorine-containing compound is prepared, and this coating solution is applied to the surface of the magnetic layer (so-called overcoat), thereby making the fluorine-containing compound present in the magnetic layer side. The coating amount here is 0.1 to 50 mg / m as the coating amount of the fluorine-containing compound per unit area. 2From the viewpoint of increasing the value of the ratio θr, it is preferable to set the above range. A coating liquid containing a fluorine-containing compound can be prepared by mixing the fluorine-containing compound with one or more solvents. The type of solvent used to prepare such a coating liquid and the concentration of the fluorine-containing compound in the coating liquid are not particularly limited. As the solvent, for example, one or more of ketone-based solvents (e.g., methyl ethyl ketone, cyclohexanone, etc.) and fluorine-based solvents (e.g., 1,1,1,2,2,3,4,5,5,5-decafluoropentane, etc.) can be used. In one embodiment, a magnetic tape containing a fluorine-containing compound in the magnetic layer side can also be prepared by adding the fluorine-containing compound as a component of the magnetic layer-forming composition. In this case, from the viewpoint of increasing the value of the ratio θr, the content of the fluorine-containing compound in the magnetic layer-forming composition (or magnetic layer) is preferably in the range of 0.5 to 1.5 parts by mass per 100.0 parts by mass of the ferromagnetic powder.

[0146] The magnetic tape will be further explained below.

[0147] <Magnetic layer> (Ferromagnetic powder) The ferromagnetic powder contained in the magnetic layer can be one or a combination of two or more known ferromagnetic powders used in the magnetic layers of various magnetic recording media. Using a ferromagnetic powder with a small average particle size is preferable from the viewpoint of improving recording density. From this viewpoint, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0148] Regarding the particle size of the ferromagnetic powder, the average particle volume can also be used as an index of particle size. From the viewpoint of improving recording density, the average particle volume is set to 2500 nm 3 Preferably, it is 2300 nm or less. 3 More preferably, it is 2000 nm or less. 3 More preferably, it is 1500 nm or less. 3 From the viewpoint of magnetization stability, the average particle volume of the ferromagnetic powder is more preferably 500 nm or less. 3 It is preferable that the thickness is 600 nm or more. 3 More preferably, it is 650 nm or more. 3 More preferably, it is 700 nm or more. 3 The above average particle volume is a value determined as a sphere-equivalent volume from the average particle size determined by the method described below.

[0149] Hexagonal ferrite powder A preferred example of the ferromagnetic powder is hexagonal ferrite powder. For details of the hexagonal ferrite powder, see, for example, JP 2011-225417 A, paragraphs 0012 to 0030, JP 2011-216149 A, paragraphs 0134 to 0136, JP 2012-204726 A, paragraphs 0013 to 0030, and JP 2015-127985 A, paragraphs 0029 to 0084.

[0150] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, if the highest diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the hexagonal ferrite crystal structure, it is determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure is considered to be the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples of such atoms include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and this specification, "hexagonal strontium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is strontium atom, and "hexagonal barium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is barium atom. "Main divalent metal atom" refers to the divalent metal atom that is the most abundant, on an atomic % basis, among the divalent metal atoms contained in the powder. However, rare earth atoms are not included in the above divalent metal atoms. In the present invention and this specification, "rare earth atom" refers to a powder selected from the group consisting of scandium atom (Sc), yttrium atom (Y), and lanthanoid atom. The lanthanoid atom is selected from the group consisting of lanthanum atom (La), cerium atom (Ce), praseodymium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), europium atom (Eu), gadolinium atom (Gd), terbium atom (Tb), dysprosium atom (Dy), holmium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu).

[0151] Hereinafter, hexagonal strontium ferrite powder, which is one form of hexagonal ferrite powder, will be described in more detail.

[0152] The activation volume of the hexagonal strontium ferrite powder is preferably 800 to 1600 nm 3 The microparticulated hexagonal strontium ferrite powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, for example, 850 nm 3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder can be 1500 nm or more. 3 More preferably, it is 1400 nm or less. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 It is even more preferable that the value is equal to or less than 1100 nm. 3 It is even more preferable that the activation volume of the hexagonal barium ferrite powder is equal to or less than 10 ...

[0153] "Activation volume" is a unit of magnetization reversal and is an index showing the magnetic size of a particle. The activation volume described in this invention and this specification and the anisotropy constant Ku described below are values ​​obtained by measuring the coercive force Hc using a vibrating sample magnetometer at magnetic field sweep rates of 3 minutes and 30 minutes (measurement temperature: 23°C ± 1°C) in the coercive force Hc measurement section, and then calculating from the following relational expression between Hc and activation volume V. The unit of the anisotropy constant Ku is 1 erg / cc = 1.0 x 10 -1 J / m 3 is. Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2} [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm 3 ), A: spin precession frequency (unit: s -1 ), t: magnetic field reversal time (unit: s)]

[0154] The anisotropy constant Ku can be used as an index for reducing thermal fluctuation, in other words, improving thermal stability. The hexagonal strontium ferrite powder preferably has an anisotropy constant of 1.8×10 5 J / m 3 and more preferably 2.0×10 5 J / m 3 The Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0155] The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are contained at a content (bulk content) of 0.5 to 5.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms can have rare earth atoms unevenly distributed in the surface layer portion. In the present invention and this specification, the term "surface layer distribution of rare earth atoms" refers to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by partially dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "surface layer content of rare earth atoms" or simply "surface layer content" with respect to rare earth atoms) to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by completely dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "bulk content of rare earth atoms" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / rare earth atom bulk content > 1.0 This means that the ratio of "surface rare earth atom content / bulk rare earth atom content > 1.0" is satisfied. The rare earth atom content of the hexagonal strontium ferrite powder described below is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the surface rare earth atom content satisfies the ratio "surface rare earth atom content / bulk rare earth atom content > 1.0", this means that the rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder (i.e., present in greater amounts in the surface layer than in the interior). In the present invention and this specification, the surface layer refers to a partial region extending from the surface toward the interior of the particles constituting the hexagonal strontium ferrite powder.

[0156] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. Having rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder is thought to contribute to suppressing a decrease in playback output during repeated playback. This is presumably because the hexagonal strontium ferrite powder contains rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder can increase the anisotropy constant Ku. The higher the anisotropy constant Ku, the more the occurrence of a phenomenon known as thermal fluctuation can be suppressed (in other words, thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, the decrease in playback output during repeated playback can be suppressed. It is speculated that the uneven distribution of rare earth atoms in the surface layer of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of the iron (Fe) sites in the crystal lattice in the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is believed that using a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer as the ferromagnetic powder for the magnetic layer also contributes to preventing the magnetic layer surface from being worn away by friction with the magnetic head. That is, it is believed that a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer can also contribute to improving the running durability of magnetic tapes. This is believed to be because the uneven distribution of rare earth atoms on the surfaces of the particles that make up the hexagonal strontium ferrite powder contributes to improving the interaction between the particle surfaces and organic substances (e.g., binders and / or additives) contained in the magnetic layer, thereby improving the strength of the magnetic layer. From the viewpoint of further suppressing a decrease in reproduction output during repeated reproduction and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic %, even more preferably in the range of 1.0 to 4.5 atomic %, and even more preferably in the range of 1.5 to 4.5 atomic %.

[0157] The bulk content is the content determined by completely dissolving the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the content of an atom refers to the bulk content determined by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one rare earth atom or two or more rare earth atoms. When two or more rare earth atoms are contained, the bulk content is determined for the total of the two or more rare earth atoms. This also applies to other components in the present invention and this specification. That is, unless otherwise specified, a certain component may be used alone or in combination with two or more. When two or more components are used, the content or content refers to the total of the two or more components.

[0158] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms may be any one or more of rare earth atoms. From the viewpoint of further suppressing the decrease in playback output during repeated playback, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0159] In a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the rare earth atoms need only be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" ratio greater than 1.0 means that the rare earth atoms are unevenly distributed in the surface layer (i.e., present in greater amounts than in the interior) in the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layers, it is sufficient that the rare earth atoms are unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the exemplified upper or lower limits.

[0160] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder present as a powder, sample powders to be partially and completely dissolved are collected from the same powder lot. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The hexagonal strontium ferrite powder can be removed from the magnetic layer by, for example, the method described in paragraph 0032 of JP 2015-91747 A. The term "partial dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, partial dissolution can dissolve 10 to 20 mass% of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100 mass%. On the other hand, the term "complete dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder cannot be visually confirmed in the liquid at the end of dissolution. The partial dissolution and measurement of the surface layer content are carried out, for example, by the following method. Note that the dissolution conditions such as the amount of sample powder described below are merely examples, and any dissolution conditions that allow partial or complete dissolution can be adopted. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is placed on a hot plate set at 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate is performed using an inductively coupled plasma (ICP) analyzer. This allows the surface content of rare earth atoms relative to 100 atomic percent iron atoms to be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This also applies to measurements of bulk content. On the other hand, the total dissolved and bulk contents are measured, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is placed on a hot plate set at 80°C for 3 hours. After that, the bulk content relative to 100 atomic % of iron atoms can be determined by carrying out the same procedures as for the partial dissolution and surface layer content measurements described above.

[0161] From the viewpoint of increasing the reproduction output when reproducing data recorded on magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, hexagonal strontium ferrite powder that contains rare earth atoms but does not have the rare earth atoms unevenly distributed in the surface layer tends to have a significantly lower σs than hexagonal strontium ferrite powder that does not contain rare earth atoms. On the other hand, hexagonal strontium ferrite powder that has the rare earth atoms unevenly distributed in the surface layer is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of the hexagonal strontium ferrite powder is 45 A·m 2 / kg or more, and 47A m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is 80A·m 2 / kg or less is preferable, and 60A·m 2 / kg or less is more preferable. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0162] Regarding the content (bulk content) of constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content can be, for example, in the range of 2.0 to 15.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms. In another embodiment, the hexagonal strontium ferrite powder can contain one or more other divalent metal atoms in addition to strontium atoms. For example, barium atoms and / or calcium atoms can be contained. When divalent metal atoms other than strontium atoms are contained, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can each be, for example, in the range of 0.05 to 5.0 atomic % relative to 100 atomic % of iron atoms.

[0163] Known crystal structures of hexagonal ferrite include magnetoplumbite type (also called "M type"), W type, Y type, and Z type. The hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder may be one in which a single crystal structure or two or more types of crystal structures are detected by X-ray diffraction analysis. For example, in one embodiment, the hexagonal strontium ferrite powder may be one in which only the M-type crystal structure is detected by X-ray diffraction analysis. For example, the M-type hexagonal ferrite is AFe 12 O 19The composition formula is represented by the formula: where A represents a divalent metal atom. When the hexagonal strontium ferrite powder is of M type, A is only strontium atom (Sr). Alternatively, when A contains multiple divalent metal atoms, strontium atom (Sr) accounts for the largest proportion on an atomic % basis, as described above. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of crystalline structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may further contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain aluminum atoms (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic % relative to 100 atomic % of iron atoms. From the viewpoint of further suppressing a decrease in playback output during repeated playback, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic % or less, more preferably 0 to 5.0 atomic %, relative to 100 atomic % of iron atoms, and may even be 0 atomic %. That is, in one embodiment, the hexagonal strontium ferrite powder may contain no atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in atomic % above is determined by converting the content (unit: mass %) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic % using the atomic weight of each atom. Furthermore, in the present invention and this specification, "not containing" a certain atom means that the content is 0 mass % when completely dissolved and measured by an ICP analyzer. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less by mass. The above term "free from" is used to mean that the substance is contained in an amount below the detection limit of the ICP analyzer.In one form, the hexagonal strontium ferrite powder can be one that does not contain bismuth atoms (Bi).

[0164] metal powder A preferred example of the ferromagnetic powder is ferromagnetic metal powder. For details of the ferromagnetic metal powder, see, for example, paragraphs 0137 to 0141 of JP-A No. 2011-216149 and paragraphs 0009 to 0023 of JP-A No. 2005-251351.

[0165] ε-iron oxide powder A preferred example of the ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, the term "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide crystalline structure is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the ε-iron oxide crystalline structure, it is determined that the ε-iron oxide crystalline structure is detected as the main phase. Known methods for producing ε-iron oxide powder include a method using goethite and a reverse micelle method. All of these production methods are publicly known. For a method for producing ε-iron oxide powder in which part of the Fe atoms are replaced by atoms such as Ga, Co, Ti, Al, or Rh, see, for example, J. Jpn. Soc. Powder Metallurgy, Vol. 61, Supplement, No. S1, pp. S280-S284 and J. Mater. Chem. C, 2013, 1, pp. 5200-5206. However, the method for producing the ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the method given here.

[0166] The activation volume of the ε-iron oxide powder is preferably 300 to 1500 nm 3 The finely divided ε-iron oxide powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the ε-iron oxide powder is preferably 300 nm 3 For example, 500 nm or more3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder can be 1400 nm or more. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 More preferably, it is 1100 nm or less. 3 It is even more preferred that:

[0167] The anisotropy constant Ku can be used as an index of the reduction in thermal fluctuation, in other words, the improvement in thermal stability. The ε-iron oxide powder is preferably 3.0×10 4 J / m 3 and more preferably 8.0×10 4 J / m 3 The Ku of the ε-iron oxide powder can be, for example, 3.0×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0168] From the viewpoint of increasing the reproduction output when reproducing data recorded on a magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, in one embodiment, the σs of the ε-iron oxide powder is 8 A m 2 / kg or more, and 12 A m 2 On the other hand, the σs of ε-iron oxide powder can be 40 A m 2 / kg or less, and 35A·m 2 / kg or less is more preferable.

[0169] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and a photograph of the particles that make up the powder is obtained by printing it on photographic paper or displaying it on a display so that the total magnification is 500,000x. From the obtained particle photograph, the target particle is selected and the particle outline is traced with a digitizer to measure the particle (primary particle) size. Primary particles are independent particles that do not aggregate. The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is the average particle size of the powder. The transmission electron microscope may be, for example, a Hitachi H-9000 transmission electron microscope. Furthermore, particle size measurements can be performed using known image analysis software, such as Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes shown in the examples below are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In this invention and this specification, "powder" refers to a collection of multiple particles. For example, "ferromagnetic powder" refers to a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a configuration in which the particles constituting the collection are in direct contact with each other, but also includes a configuration in which binders, additives, etc., as described below, are interposed between the particles. The term "particle" is sometimes used to refer to powder.

[0170] As a method for collecting sample powder from the magnetic tape for particle size measurement, for example, the method described in paragraph 0015 of JP-A No. 2011-048878 can be used.

[0171] In the present invention and this specification, unless otherwise specified, the size of particles constituting the powder (particle size) is determined by the shape of the particles observed in the particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (where the height is greater than the maximum diameter of the base), etc., the particle size is expressed by the length of the major axis that constitutes the particle, i.e., the major axis length. (2) In the case of a plate or columnar shape (where the thickness or height is smaller than the maximum major axis of the plate surface or base), it is expressed by the maximum major axis of the plate surface or base, (3) When the particle is spherical, polyhedral, irregular, etc., and the long axis of the particle cannot be identified from its shape, it is expressed as the equivalent circle diameter, which is determined by the circle projection method.

[0172] The acicular ratio of a powder is determined by measuring the minor axis length of the particles in the above measurement, i.e., the minor axis length, and calculating the arithmetic mean of the major axis lengths (average major axis length) and the minor axis lengths (average minor axis length) obtained for the 500 particles as "average major axis length / average minor axis length." Here, unless otherwise specified, the minor axis length refers to the length of the minor axis constituting the particle in the above definition of particle size (1), and to the thickness or height in the above definition of particle size (2). In the above definition of particle size (3), since there is no distinction between the major axis and the minor axis, (average major axis length / average minor axis length) is considered to be 1 for convenience. Unless otherwise specified, when the particle shape is specific, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, in the case of definition (2), the average particle size is the average plate diameter, and in the case of definition (3), the average particle size is the average diameter (also called the average particle diameter or average particle size).

[0173] The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90 mass % and more preferably in the range of 60 to 90 mass % relative to the total mass of the magnetic layer. A high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving recording density.

[0174] (binder) The magnetic tape can be a coated magnetic tape, and the magnetic layer can contain a binder. In a magnetic layer containing a binder, since a large portion of the surface of the ferromagnetic powder particles can be coated with the binder, it is believed that the adhesive force of components other than the binder to the particles tends to be lower than that of particles not coated with the binder. In contrast, a fluorine-containing compound containing many adsorptive functional groups is believed to be able to strongly adsorb to particles in such a state. The inventors believe that this is advantageous for increasing the ratio θr in coated magnetic tapes. The binder is one or more resins. Various resins commonly used as binders for coated magnetic recording media can be used as binders. For example, resins selected from polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, acrylic resins copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, polyvinyl butyral, etc. can be used alone or in combination. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the nonmagnetic layer and / or backcoat layer, which will be described later. For details of the binders described above, see paragraphs 0028 to 0031 of JP 2010-24113 A. The average molecular weight of the resin used as the binder can be, for example, 10,000 to 200,000 in weight-average molecular weight. Unless otherwise specified, the weight-average molecular weight in this invention and this specification refers to a value measured by gel permeation chromatography (GPC) under the following measurement conditions and converted into polystyrene equivalents. The weight-average molecular weight of the binder shown in the examples below is a value measured under the following measurement conditions and converted into polystyrene equivalents. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of the ferromagnetic powder. GPC equipment: HLC-8120 (Tosoh Corporation) Column: TSK gel Multipore HXL-M (Tosoh Corporation, 7.8 mm ID (inner diameter) x 30.0 cm) Eluent: tetrahydrofuran (THF)

[0175] (hardening agent) A curing agent can also be used together with a resin usable as a binder. In one embodiment, the curing agent can be a thermosetting compound, which undergoes a curing reaction (crosslinking reaction) upon heating. In another embodiment, the curing agent can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) upon irradiation with light. As the curing reaction progresses during the magnetic layer formation process, at least a portion of the curing agent can be included in the magnetic layer in a state where it has reacted (crosslinked) with other components, such as the binder. This also applies to layers formed using compositions containing a curing agent when the composition used to form other layers contains the curing agent. A preferred curing agent is a thermosetting compound, and polyisocyanate is suitable. For details about polyisocyanates, see paragraphs 0124 to 0125 of JP 2011-216149 A. The curing agent can be used in the magnetic layer-forming composition in an amount of, for example, 0 to 80.0 parts by weight per 100.0 parts by weight of the binder, preferably 50.0 to 80.0 parts by weight from the viewpoint of improving the strength of the magnetic layer.

[0176] (additives) The magnetic layer may contain one or more additives as needed. Examples of additives include the curing agents described above. Examples of additives contained in the magnetic layer include non-magnetic powders, lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, and antioxidants. For details on dispersants, see paragraphs 0061 and 0071 of JP 2012-133837 A. A dispersant may also be added to the non-magnetic layer-forming composition. For details on dispersants that can be added to the non-magnetic layer-forming composition, see paragraph 0061 of JP 2012-133837 A.

[0177] The magnetic tape contains a fluorine-containing compound in the portion adjacent to the magnetic layer. As described above, the fluorine-containing compound can function as a lubricant. Furthermore, the magnetic tape can also be produced using one or more compounds that can function as a lubricant in addition to the fluorine-containing compound. Examples of such compounds include one or more compounds selected from the group consisting of fatty acids and their derivatives (e.g., fatty acid amides, fatty acid esters, etc.). By using a magnetic layer-forming composition and / or a non-magnetic layer-forming composition containing the compound, a magnetic tape containing the compound in the portion adjacent to the magnetic layer can be produced. Examples of fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid, with stearic acid being preferred, myristic acid, and palmitic acid being more preferred. The fatty acid may be contained in the magnetic layer side in the form of a salt such as a metal salt. Examples of the fatty acid amides include amides of the above-mentioned various fatty acids, such as lauric acid amide, myristic acid amide, palmitic acid amide, and stearic acid amide. Examples of fatty acid esters include esters of the above-mentioned various fatty acids, such as butyl myristate, butyl palmitate, butyl stearate (butyl stearate), neopentyl glycol dioleate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, oleyl oleate, isocetyl stearate, isotridecyl stearate, octyl stearate, isooctyl stearate, amyl stearate, and butoxyethyl stearate. The amount of fatty acid, as content in the magnetic layer-forming composition (or magnetic layer; the same applies hereinafter), is, for example, 0.1 to 10.0 parts by mass, preferably 0.5 to 7.0 parts by mass, per 100.0 parts by mass of ferromagnetic powder. When two or more different fatty acids are added to the magnetic layer-forming composition, the content refers to the total content of these. This also applies to the contents of other components in this specification, unless otherwise specified. The fatty acid content in the non-magnetic layer-forming composition (or non-magnetic layer; the same applies hereinafter) is, for example, 1.0 to 10.0 parts by mass, and preferably 0.5 to 7.0 parts by mass per 100.0 parts by mass of non-magnetic powder. The fatty acid amide content in the magnetic layer-forming composition is, for example, 0 to 3.0 parts by mass, preferably 0.1 to 3.0 parts by mass, and more preferably 0.1 to 1.0 part by mass per 100.0 parts by mass of ferromagnetic powder. The content of fatty acid amide in the non-magnetic layer forming composition is, for example, 0.1 to 3.0 parts by mass, and preferably 0.1 to 1.0 part by mass, per 100.0 parts by mass of non-magnetic powder. The amount of fatty acid ester in the magnetic layer-forming composition is, for example, 0 to 10.0 parts by mass, and preferably 1.0 to 7.0 parts by mass per 100.0 parts by mass of ferromagnetic powder. The content of fatty acid ester in the nonmagnetic layer-forming composition is, for example, 0 to 10.0 parts by mass, and preferably 1.0 to 7.0 parts by mass, per 100.0 parts by mass of nonmagnetic powder.

[0178] Examples of non-magnetic powders that can be contained in the magnetic layer include non-magnetic powders that can function as abrasives. Examples of additives that can be used to improve the dispersibility of abrasives in a magnetic layer that contains abrasives include the dispersants described in paragraphs 0012 to 0022 of JP 2013-131285 A.

[0179] Non-magnetic powders that can be contained in the magnetic layer include non-magnetic powders (e.g., non-magnetic colloidal particles, carbon black, etc.) that function as protrusion-forming agents that form moderately protruding protrusions on the surface of the magnetic layer. For example, protrusion-forming agents with an average particle size of 5 to 300 nm can be used. The average particle size of colloidal silica (silica colloidal particles) shown in the examples below is a value determined by the method described as a method for measuring average particle size in paragraph 0015 of JP 2011-048878 A. The content of the protrusion-forming agent in the magnetic layer is preferably 0.1 to 3.5 parts by weight, more preferably 0.1 to 3.0 parts by weight, per 100.0 parts by weight of ferromagnetic powder.

[0180] The magnetic layer described above can be provided directly on the surface of the non-magnetic support, or indirectly via a non-magnetic layer.

[0181] <Nonmagnetic layer> Next, the non-magnetic layer will be described. The magnetic tape may have a magnetic layer directly on the surface of a non-magnetic support, or may have a magnetic layer on the surface of a non-magnetic support via one or more non-magnetic layers containing non-magnetic powder.

[0182] From the viewpoint of improving the smoothness of the magnetic layer surface, it is preferable to improve the surface smoothness of the non-magnetic layer on which the magnetic layer will be formed. From this viewpoint, it is preferable to use a non-magnetic powder with a small average particle size as the non-magnetic powder contained in the non-magnetic layer. The average particle size of the non-magnetic powder is preferably in the range of 500 nm or less, more preferably 200 nm or less, even more preferably 100 nm or less, and even more preferably 50 nm or less. Furthermore, from the viewpoint of facilitating the improvement of the dispersibility of the non-magnetic powder, the average particle size of the non-magnetic powder is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more.

[0183] The non-magnetic powder used in the non-magnetic layer may be either an inorganic powder or an organic powder, and carbon black or the like may also be used.

[0184] For information on carbon black that can be used in the nonmagnetic layer, see, for example, paragraphs 0040 to 0041 of Japanese Patent Laid-Open Publication No. 2010-24113. Carbon black generally tends to have a large particle size distribution and poor dispersibility. As a result, nonmagnetic layers containing carbon black tend to have low surface smoothness. In one embodiment, the nonmagnetic layer adjacent to the magnetic layer preferably contains a nonmagnetic powder other than carbon black as the nonmagnetic powder, or a nonmagnetic layer containing carbon black as one of multiple types of nonmagnetic powder, with a low proportion of carbon black in the total amount of nonmagnetic powder. It is also preferable to provide multiple nonmagnetic layers, with the nonmagnetic layer closest to the magnetic layer containing a nonmagnetic powder other than carbon black as the nonmagnetic powder. For example, it is preferable to provide two non-magnetic layers between the non-magnetic support and the magnetic layer, with the non-magnetic layer on the non-magnetic support side (also referred to as the "lower non-magnetic layer") containing carbon black as the non-magnetic powder, and the non-magnetic layer on the magnetic layer side (also referred to as the "upper non-magnetic layer") containing a non-magnetic powder other than carbon black as the non-magnetic powder. Furthermore, non-magnetic layer-forming compositions containing multiple types of non-magnetic powder tend to have lower dispersibility of the non-magnetic powder than non-magnetic layer-forming compositions containing only one type of non-magnetic powder. From this perspective, it is preferable to provide multiple non-magnetic layers and reduce the number of types of non-magnetic powder contained in each non-magnetic layer. In one embodiment, it is preferable to use a dispersant to improve the dispersibility of the non-magnetic powder in non-magnetic layer-forming compositions containing multiple types of non-magnetic powder. Such dispersants will be described later.

[0185] Examples of inorganic powders include powders of metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders are commercially available or can be produced by known methods. For details, see paragraphs 0146 to 0150 of JP 2011-216149 A.

[0186] One form of non-magnetic powder is non-magnetic iron oxide powder. From the viewpoint of improving the surface smoothness of the non-magnetic layer on which the magnetic layer is formed, it is preferable to use non-magnetic iron oxide powder with a small particle size. From this viewpoint, it is preferable to use non-magnetic iron oxide powder with an average particle size within the range described above. Note that when the non-magnetic iron oxide powder has the particle shape described above in (1), the average particle size refers to the average major axis length. The acicular ratio (average major axis length / average minor axis length) of the non-magnetic iron oxide powder can be greater than 1.0. From the viewpoint of improving the surface smoothness of the non-magnetic layer, it is preferable to use non-magnetic iron oxide powder with a small acicular ratio. The acicular ratio (average major axis length / average minor axis length) of the non-magnetic iron oxide powder can be, for example, 7.0 or less, preferably 3.0 or less, and more preferably 1.5 or less. In one form, α-iron oxide powder is preferable as the non-magnetic iron oxide powder. α-iron oxide is iron oxide whose main phase is the α phase.

[0187] The non-magnetic powder content (filling rate) in the non-magnetic layer is preferably in the range of 50 to 90 mass %, more preferably 60 to 90 mass %, relative to the total mass of the non-magnetic layer. When multiple non-magnetic layers are provided, it is preferable that the non-magnetic powder content in at least one non-magnetic layer be in the above range, and it is even more preferable that the non-magnetic powder content in more non-magnetic layers be in the above range.

[0188] The non-magnetic layer contains a non-magnetic powder and may also contain a binder together with the non-magnetic powder. For details of the binder, additives, etc. of the non-magnetic layer, known techniques related to non-magnetic layers can be applied. Furthermore, for example, known techniques related to magnetic layers can also be applied to the type and content of the binder and the type and content of the additives.

[0189] Additives that can be included in the nonmagnetic layer include dispersants that contribute to improving the dispersibility of nonmagnetic powders. Examples of such dispersants include fatty acids represented by the formula RCOOH (R is an alkyl or alkenyl group) (e.g., caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, etc.); alkali metal salts or alkaline earth metal salts of the above fatty acids; esters of the above fatty acids; fluorine-containing compounds of the above fatty acid esters; amides of the above fatty acids; polyalkylene oxide alkyl phosphate esters; lecithin; trialkyl polyolefinoxy quaternary ammonium salts (containing alkyl groups with 1 to 5 carbon atoms and olefins such as ethylene and propylene); phenylphosphonic acid; and copper phthalocyanine. These may be used alone or in combination. The content of the dispersant is preferably 0.2 to 5.0 parts by mass per 100.0 parts by mass of the nonmagnetic powder.

[0190] Further, an example of an additive is an organic tertiary amine. For details of organic tertiary amines, see paragraphs 0011 to 0018 and 0021 of JP 2013-049832 A. The organic tertiary amine can contribute to improving the dispersibility of carbon black. For details of the formulation of a composition for enhancing the dispersibility of carbon black using an organic tertiary amine, see paragraphs 0022 to 0024 and 0027 of the same publication.

[0191] The amine is more preferably a trialkylamine. The alkyl group in the trialkylamine is preferably an alkyl group having 1 to 18 carbon atoms. The three alkyl groups in the trialkylamine may be the same or different. For details about the alkyl groups, see paragraphs 0015 to 0016 of JP 2013-049832 A. As the trialkylamine, trioctylamine is particularly preferred.

[0192] In the present invention and this specification, the term "nonmagnetic layer" also includes a substantially nonmagnetic layer that contains a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with a nonmagnetic powder. Here, a substantially nonmagnetic layer refers to a layer having a remanence of 10 mT or less, a coercivity of 7.96 kA / m (100 Oe) or less, or a remanence of 10 mT or less and a coercivity of 7.96 kA / m (100 Oe) or less. It is preferable that the nonmagnetic layer have no remanence or coercivity.

[0193] <Nonmagnetic support> Next, the non-magnetic support will be described. Examples of the non-magnetic support (hereinafter also simply referred to as "support") include known biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, aromatic polyamide, etc. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be previously subjected to corona discharge, plasma treatment, easy-adhesion treatment, heat treatment, etc.

[0194] <Backcoat layer> The magnetic tape may or may not have a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite the surface having the magnetic layer. The backcoat layer preferably contains either carbon black or inorganic powder, or both. The backcoat layer may contain a binder and / or additives. Known techniques related to backcoat layers can be applied to the binder and additives of the backcoat layer, and known techniques related to the formulation of magnetic and / or nonmagnetic layers can also be applied. For example, see paragraphs

[0018] to

[0020] of Japanese Patent Laid-Open No. 2006-331625 and U.S. Patent No. 7,029,774, column 4, line 65 to column 5, line 38, for information regarding the backcoat layer.

[0195] <Various thicknesses> With regard to the thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for magnetic tape with an increased recording capacity (higher capacity). One way to increase capacity is to reduce the thickness of the magnetic tape (hereinafter also referred to as "thinning") and increase the length of magnetic tape that can be accommodated in one magnetic tape cartridge. From this perspective, the thickness (total thickness) of the magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, even more preferably 5.4 μm or less, even more preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Furthermore, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0196] For example, the thickness (total thickness) of the magnetic tape can be measured by the following method. Ten tape samples (e.g., 5 to 10 cm long) are cut from any portion of the magnetic tape, and these tape samples are stacked and measured for thickness. The measured thickness is divided by 10 to obtain the value (thickness per tape sample), which is taken as the tape thickness. The thickness measurement can be performed using a known measuring device capable of measuring thickness to the order of 0.1 μm.

[0197] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm.

[0198] The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm. From the viewpoint of high-density recording, it is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers with different magnetic properties, and known configurations related to multilayer magnetic layers can be applied. When the magnetic layer is separated into two or more layers, the thickness of the magnetic layer refers to the total thickness of these layers. This also applies to the thickness of the nonmagnetic layer in a magnetic tape having multiple nonmagnetic layers.

[0199] Regarding the thickness of the nonmagnetic layer, the thicker the nonmagnetic layer, the more likely it is that the nonmagnetic powder particles will be unevenly distributed during the coating and drying processes of the nonmagnetic layer-forming composition, resulting in greater differences in thickness at different locations and a rougher surface for the nonmagnetic layer. From the perspective of improving the smoothness of the magnetic layer surface, a high level of surface smoothness for the nonmagnetic layer is desirable. From this perspective, the thickness of the nonmagnetic layer is preferably 1.5 μm or less, and more preferably 1.0 μm or less. Furthermore, from the perspective of improving the uniformity of the coating of the nonmagnetic layer-forming composition, the thickness of the nonmagnetic layer is preferably 0.05 μm or more, and more preferably 0.1 μm or more.

[0200] The thickness of the backcoat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. The thickness of the magnetic layer and other thicknesses can be determined by the following method. After exposing a cross section of the magnetic tape in the thickness direction with an ion beam, the exposed cross section is observed using a scanning electron microscope. The thicknesses can be calculated as the arithmetic mean of the thicknesses measured at any two points during the cross section observation. Alternatively, the thicknesses can be calculated as the design thickness calculated from the manufacturing conditions, etc.

[0201] <Manufacturing process> (Preparation of compositions for forming each layer) The process for preparing the composition for forming the magnetic layer, nonmagnetic layer, or backcoat layer typically includes at least a kneading step, a dispersion step, and optionally, a mixing step before or after these steps. Each step may be divided into two or more stages. The components used to prepare the composition for each layer may be added at the beginning or during any step. As the solvent, one or more of the various solvents typically used in the manufacture of particulate magnetic recording media may be used. For details about solvents, see, for example, paragraph 0153 of JP 2011-216149 A. Individual components may also be added in separate steps in two or more steps. For example, the binder may be added in separate steps during the kneading step, the dispersion step, and the mixing step for adjusting the viscosity after dispersion. To manufacture the magnetic tape, known manufacturing techniques can be used in the various steps. For the kneading step, it is preferable to use a device with strong kneading power, such as an open kneader, continuous kneader, pressure kneader, or extruder. For details of the kneading treatment, reference can be made to JP-A-1-106338 and JP-A-1-79274. Known dispersers can be used. At any stage in preparing the compositions for forming each layer, filtration may be carried out by a known method. Filtration can be carried out, for example, by filter filtration. Filters used for filtration include those with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.).

[0202] (Coating process) The magnetic layer can be formed by applying the magnetic layer-forming composition directly to the surface of the non-magnetic support, or by sequentially or simultaneously applying the magnetic layer-forming composition and the non-magnetic layer-forming composition in a multilayer. The backcoat layer can be formed by applying the backcoat layer-forming composition to the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or magnetic layer (or on which the non-magnetic layer and / or magnetic layer will be subsequently formed). For details on the coating for forming each layer, see paragraph 0066 of JP 2010-231843 A.

[0203] (Other processes) After the coating step, various treatments can be performed, such as drying, magnetic layer orientation, and surface smoothing (calendering). For details of these processes, see known techniques, such as paragraphs 0052 to 0057 of JP 2010-24113 A. For example, the coated layer of the magnetic layer-forming composition can be subjected to an orientation treatment while still wet. For the orientation treatment, various known techniques, including those described in paragraph 0067 of JP 2010-231843 A, can be applied. For example, vertical orientation can be performed by known methods, such as using magnets with opposite poles facing each other. In the orientation zone, the drying rate of the coated layer can be controlled by the temperature and volume of the drying air and / or the transport speed of the non-magnetic support bearing the coated layer. The coated layer may also be pre-dried before being transported to the orientation zone. Regarding calendering, strengthening the calendering conditions tends to improve the smoothness of the magnetic layer surface. Calendering conditions include the number of calendering passes (hereinafter also referred to as "calendering passes"), calendering pressure, calendering temperature (calender roll surface temperature), calendering speed, and calender roll hardness. The more the calendering passes, the stronger the calendering. The higher the calendering pressure, calendering temperature, and calender roll hardness, the stronger the calendering, and the slower the calendering speed. For example, the calendering pressure (linear pressure) can be 200 to 500 kg / cm, and preferably 250 to 350 kg / cm. The calendering temperature (calender roll surface temperature) can be, for example, 85 to 120°C, and preferably 90 to 110°C, and the calendering speed can be, for example, 50 to 300 m / min, and preferably 50 to 200 m / min. A long magnetic tape roll can be obtained through various processes. The obtained magnetic tape roll is cut (slit) using a known cutting machine to the width of the magnetic tape to be wound into a magnetic tape cartridge, for example. The width is determined according to a standard and is usually 1 / 2 inch. 1 / 2 inch = 12.65 mm. A servo pattern is usually formed on the magnetic tape obtained by slitting, as will be described in detail later.

[0204] (Heat treatment) In one embodiment, the magnetic tape may be a magnetic tape manufactured through the following heat treatment: In another embodiment, the magnetic tape may be a magnetic tape manufactured without the following heat treatment.

[0205] The heat treatment can be carried out by winding the magnetic tape, which has been slit and cut to a width determined in accordance with a standard, around a core member and carrying out the heat treatment in the wound state.

[0206] In one embodiment, the above-mentioned heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as the "heat treatment core"), and the magnetic tape after the heat treatment is wound onto a reel of a magnetic tape cartridge, thereby producing a magnetic tape cartridge with the magnetic tape wound onto a reel. The heat treatment core can be made of metal, resin, paper, or the like. The material of the heat treatment core is preferably a highly rigid material from the viewpoint of suppressing winding defects such as spalling. From this viewpoint, the heat treatment core is preferably made of metal or resin. Furthermore, as an index of rigidity, the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa (gigapascal) or more, more preferably 0.3 GPa or more. On the other hand, since highly rigid materials are generally expensive, using a heat treatment core made of a material with a rigidity exceeding the rigidity required to suppress winding defects leads to increased costs. In consideration of the above, the flexural modulus of the material of the heat treatment core is preferably 250 GPa or less. The flexural modulus is a value measured in accordance with ISO (International Organization for Standardization) 178, and the flexural moduli of various materials are known. Furthermore, the heat treatment core can be a solid or hollow core-shaped member. If the core is hollow, the wall thickness is preferably 2 mm or more from the viewpoint of maintaining rigidity. The core for heat treatment may or may not have a flange.It is preferable to prepare a magnetic tape having a length equal to or greater than the length to be ultimately accommodated in a magnetic tape cartridge (hereinafter referred to as the "final product length") as the magnetic tape to be wound around the heat treatment core, and to perform heat treatment by placing this magnetic tape wound around the heat treatment core in a heat treatment environment. The length of the magnetic tape to be wound around the heat treatment core is equal to or greater than the final product length, and from the viewpoint of ease of winding onto the heat treatment core, it is preferable that it be "final product length + α". From the viewpoint of ease of winding, this α is preferably 5 m or more. The tension during winding onto the heat treatment core is preferably 0.1 N (Newton) or more. Furthermore, from the viewpoint of preventing excessive deformation, the tension during winding onto the heat treatment core is preferably 1.5 N or less, more preferably 1.0 N or less. The outer diameter of the heat treatment core is preferably 20 mm or more, more preferably 40 mm or more, from the viewpoints of ease of winding and prevention of coiling (longitudinal curl). The outer diameter of the heat treatment core is preferably 100 mm or less, more preferably 90 mm or less. The width of the heat treatment core need only be equal to or greater than the width of the magnetic tape wound around the core. After the heat treatment, when removing the magnetic tape from the heat treatment core, it is preferable to remove the magnetic tape from the heat treatment core after the magnetic tape and the heat treatment core have cooled sufficiently to prevent unintended deformation of the tape during the removal operation. The removed magnetic tape is preferably first wound onto another core (referred to as a "temporary take-up core"), and then wound from the temporary take-up core onto a reel of a magnetic tape cartridge (typically with an outer diameter of approximately 40 to 50 mm). This allows the magnetic tape to be wound onto the reel of a magnetic tape cartridge while maintaining the inner and outer positions of the magnetic tape relative to the heat treatment core during the heat treatment. For details about the temporary take-up core and the tension when winding the magnetic tape onto this core, please refer to the previous description of the heat treatment core. In a form in which the above-mentioned heat treatment is performed on a magnetic tape having a length of "final product length + α", the length of "+ α" can be cut off at any stage. For example, in one form, the magnetic tape of the final product length can be wound from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining length of "+ α" can be cut off.From the viewpoint of reducing the portion that is cut off and discarded, it is preferable that the above-mentioned α be 20 m or less.

[0207] A specific example of the heat treatment carried out in the state where the core member is wound as described above will be described below. The atmospheric temperature at which the heat treatment is performed (hereinafter referred to as "heat treatment temperature") is preferably 40° C. or higher, and more preferably 50° C. or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75° C. or lower, more preferably 70° C. or lower, and even more preferably 65° C. or lower. The absolute humidity by weight of the atmosphere in which the heat treatment is carried out is preferably 0.1 g / kg dry air or more, more preferably 1 g / kg dry air or more. An atmosphere with an absolute humidity by weight in the above range is preferred because it can be prepared without using special equipment for reducing moisture. On the other hand, from the viewpoint of preventing condensation from forming and reducing workability, the absolute humidity by weight is preferably 70 g / kg dry air or less, more preferably 66 g / kg dry air or less. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0208] (Servo pattern formation) The magnetic tape can have a servo pattern in the magnetic layer. "Formation of a servo pattern" can also be called "recording of a servo signal." Formation of a servo pattern will be explained below.

[0209] The servo pattern is usually formed along the length of the magnetic tape. Control methods that use servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0210] As specified in ECMA (European Computer Manufacturers Association)-319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly referred to as "LTO tapes") employ a timing-based servo system. In this timing-based servo system, a servo pattern is formed by a pair of non-parallel magnetic stripes (also called "servo stripes") arranged continuously along the longitudinal direction of the magnetic tape. In this invention and this specification, the term "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. The reason why the servo pattern is formed by a pair of non-parallel magnetic stripes as described above is to inform a servo signal reading element passing over the servo pattern of its passing position. Specifically, the spacing between the pair of magnetic stripes is formed so that it continuously changes along the width direction of the magnetic tape. By reading this spacing, the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element. This relative position information enables tracking of data tracks. For this reason, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.

[0211] A servo band is made up of a continuous servo pattern along the length of the magnetic tape. Typically, multiple servo bands are provided on a magnetic tape. For example, there are five servo bands on an LTO tape. The area between two adjacent servo bands is the data band. A data band is made up of multiple data tracks, and each data track corresponds to one of the servo tracks.

[0212] Also, in one embodiment, as disclosed in Japanese Patent Application Laid-Open No. 2004-318983, information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information") is embedded in each servo band. This servo band ID is recorded by shifting a specific one of a plurality of pairs of servo stripes in the servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the way in which a specific one of a plurality of pairs of servo stripes is shifted varies for each servo band. As a result, the recorded servo band ID is unique for each servo band, and therefore, simply by reading one servo band with a servo signal reading element, that servo band can be uniquely identified.

[0213] One method for uniquely identifying servo bands is the staggered method described in ECMA-319 (June 2001). In this staggered method, pairs of non-parallel magnetic stripes (servo stripes) are continuously arranged along the length of the magnetic tape, and are recorded so that each servo band is offset along the length of the magnetic tape. The combination of this offset between adjacent servo bands is unique across the entire magnetic tape, making it possible to uniquely identify servo bands when reading the servo pattern with two servo signal reading elements.

[0214] As specified in ECMA-319 (June 2001), each servo band also typically contains information indicating the longitudinal position of the magnetic tape (also known as "LPOS (Longitudinal Position) information"). Like UDIM information, this LPOS information is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike UDIM information, the same signal is recorded in each servo band with this LPOS information.

[0215] It is also possible to embed information other than the UDIM information and LPOS information described above in the servo bands. In this case, the embedded information may be different for each servo band, such as UDIM information, or it may be common to all servo bands, such as LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of pairs of servo stripes.

[0216] The head for forming a servo pattern is called a servo write head. A servo write head typically has a pair of gaps corresponding to the pair of magnetic stripes, the number of which is equal to the number of servo bands. Typically, a core and a coil are connected to each pair of gaps. By supplying a current pulse to the coil, the magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. To form a servo pattern, a current pulse is input while running a magnetic tape over the servo write head, thereby transferring the magnetic pattern corresponding to the pair of gaps onto the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set depending on the density of the servo pattern to be formed. The width of each gap can be set, for example, to 1 μm or less, 1 to 10 μm, or 10 μm or more.

[0217] Before forming a servo pattern on a magnetic tape, the magnetic tape is usually subjected to a demagnetization (erase) process. This erase process can be performed by applying a uniform magnetic field to the magnetic tape using a direct current magnet or an alternating current magnet. There are two types of erase processes: direct current (DC) erase and alternating current (AC) erase. AC erase is performed by gradually reducing the strength of the magnetic field applied to the magnetic tape while reversing the direction of the magnetic field. DC erase, on the other hand, is performed by applying a unidirectional magnetic field to the magnetic tape. There are two other DC erase methods. The first method is horizontal DC erase, in which a unidirectional magnetic field is applied along the length of the magnetic tape. The second method is vertical DC erase, in which a unidirectional magnetic field is applied along the thickness of the magnetic tape. The erase process can be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0218] The direction of the magnetic field of the formed servo pattern is determined by the erase direction. For example, when a magnetic tape is subjected to horizontal DC erasure, the servo pattern is formed so that the direction of the magnetic field is opposite to the erase direction. This increases the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred to a magnetic tape that has been vertically DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred to a magnetic tape that has been horizontally DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0219] In one embodiment, the width of the magnetic tape can be controlled by acquiring width dimensional information of the magnetic tape while it is running using a servo signal and adjusting and changing the tension applied to the magnetic tape in the longitudinal direction in accordance with the acquired dimensional information. Adjusting the tension in this manner can contribute to preventing the magnetic head for recording or reproducing data from being displaced from the target track position due to width deformation of the magnetic tape during recording or reproduction.

[0220] [Magnetic tape cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the above-mentioned magnetic tape.

[0221] The details of the magnetic tape contained in the tape cartridge are as described above.

[0222] A magnetic tape cartridge generally contains a magnetic tape wound on a reel within the cartridge body. The reel is rotatably mounted within the cartridge body. Widely used magnetic tape cartridges include single-reel magnetic tape cartridges with one reel within the cartridge body and dual-reel magnetic tape cartridges with two reels within the cartridge body. When a single-reel magnetic tape cartridge is loaded into a magnetic tape device for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and rewound onto a reel on the magnetic tape device. A magnetic head is located in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is fed and rewound between the reel (supply reel) on the magnetic tape cartridge and the reel (take-up reel) on the magnetic tape device. During this process, the magnetic head comes into contact with and slides against the magnetic layer surface of the magnetic tape, thereby recording and / or reproducing data. In contrast, a dual-reel magnetic tape cartridge is provided with both a supply reel and a take-up reel inside the magnetic tape cartridge.

[0223] [Magnetic tape device] One aspect of the present invention relates to a magnetic tape device including the above-mentioned magnetic tape, in which data can be recorded on the magnetic tape and / or data recorded on the magnetic tape can be reproduced, for example, by bringing a magnetic head into contact with the surface of the magnetic layer of the magnetic tape and sliding it over it.

[0224] In this invention and this specification, the term "magnetic tape device" refers to a device capable of at least one of recording data to a magnetic tape and reproducing data recorded on the magnetic tape. Such devices are generally called drives. The magnetic tape device may include a magnetic head. The magnetic head may be a recording head capable of recording data to the magnetic tape, or a reproducing head capable of reproducing data recorded on the magnetic tape. In one embodiment, the magnetic tape device may include both a recording head and a reproducing head as separate magnetic heads. In another embodiment, the magnetic head included in the magnetic tape device may have both a recording element and a reproducing element in a single magnetic head. The reproducing head is preferably a magnetic head (MR head) that includes a magnetoresistive (MR) element as a reproducing element, capable of sensitively reading information recorded on the magnetic tape. Various known MR heads (e.g., giant magnetoresistive (GMR) heads, tunnel magnetoresistive (TMR) heads, etc.) can be used as the MR head. Furthermore, the magnetic head that records and / or reproduces data may include a servo signal read element. Alternatively, the magnetic tape device may include a magnetic head (servo head) equipped with a servo signal read element as a separate head from the magnetic head that records and / or reproduces data. For example, a magnetic head that records and / or reproduces recorded data (hereinafter also referred to as a "recording / reproducing head") may include two servo signal read elements, each of which can simultaneously read two adjacent servo bands sandwiching a data band. One or more data elements may be disposed between the two servo signal read elements. The element for recording data (recording element) and the element for reproducing data (reproducing element) are collectively referred to as the "data element."

[0225] When recording and / or reproducing data, tracking using servo signals can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the data element can be controlled to pass over the target data track. The data track is moved by changing the servo track read by the servo signal reading element in the tape width direction. The read / write head can also record and / or read data from other data bands by using the UDIM information described above to move the servo signal read element to a specific servo band and start tracking that servo band.

[0226] FIG. 2 shows an example of the arrangement of data bands and servo bands. In FIG. 2, multiple servo bands 1 are sandwiched between guide bands 3 on the magnetic layer of the magnetic tape MT. Multiple regions 2 sandwiched between two servo bands form data bands. Servo patterns are magnetized regions formed by magnetizing specific regions of the magnetic layer with a servo write head. The regions magnetized by the servo write head (the positions where servo patterns are formed) are determined by standards. For example, in the industry-standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in FIG. 3. Specifically, in FIG. 3, a servo frame SF on servo band 1 is composed of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). Servo subframe 1 is composed of an A burst (labeled A in FIG. 3) and a B burst (labeled B in FIG. 3). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. On the other hand, servo subframe 2 is composed of a C burst (C in FIG. 3) and a D burst (D in FIG. 3). The C burst is composed of servo patterns C1 through C4, and the D burst is composed of servo patterns D1 through D4. These 18 servo patterns are arranged in sets of 5 and 4 in a 5, 5, 4, 4 arrangement in a subframe, and are used to identify servo frames. For the sake of explanation, FIG. 3 shows one servo frame. However, in reality, on the magnetic layer of a magnetic tape where head tracking is performed using a timing-based servo system, multiple servo frames are arranged in each servo band in the running direction. In FIG. 3, the arrow indicates the running direction. For example, an LTO Ultrium format tape typically has more than 5,000 servo frames per meter of tape length in each servo band of the magnetic layer.

[0227] In one embodiment of the magnetic tape device, the magnetic tape is treated as a removable medium (so-called replaceable medium), and a magnetic tape cartridge containing the magnetic tape is inserted into and removed from the magnetic tape device. In another embodiment, the magnetic tape is not treated as a replaceable medium, and the magnetic tape is wound onto a reel of a magnetic tape device equipped with a magnetic head, and the magnetic tape is contained within the magnetic tape device. In one embodiment, in such a magnetic tape device, the magnetic tape and the magnetic head can be contained within an enclosed space within the magnetic tape device. In the present invention and this specification, the term "enclosed space" refers to a space in which the degree of airtightness evaluated by the immersion method (bombing method) using helium (He) specified in JIS Z 2331:2006 Helium Leak Test Method is 10 x 10 -8 Pa·m 3 / sec or less. The airtightness of an enclosed space is, for example, 5 x 10 ―9 Pa·m 3 / sec or more 10 x 10 -8 Pa·m 3 / sec or less, or may be below the above range. In one embodiment, the entire space in the housing can be the sealed space, and in another embodiment, a portion of the space in the housing can be the sealed space. The sealed space can be the internal space of a housing that covers all or part of the magnetic tape device. The material and shape of the housing are not particularly limited, and can be, for example, the same as the material and shape of the housing of a typical magnetic tape device. Examples of materials for the housing include metal, resin, etc. [Example]

[0228] An embodiment of the present invention will be described below based on an example. However, the present invention is not limited to the embodiment shown in the example. The indications of "parts" and "%" below mean "parts by mass" and "% by mass" unless otherwise specified. "eq" is an equivalent, and is a unit that cannot be converted to SI units. Unless otherwise specified, the following steps and operations were carried out in an environment with a temperature of 20 to 25°C and a relative humidity of 40 to 60%.

[0229] In Table 2 below, "BaFe" represents hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm.

[0230] In Table 2 below, "SrFe" represents hexagonal strontium ferrite powder prepared by the method described below, and "ε-iron oxide" represents ε-iron oxide powder prepared by the method described below. The average particle volumes of the various ferromagnetic powders described below are values ​​determined by the method described above. The various values ​​relating to the particle sizes of the various powders described below are also values ​​determined by the method described above. The anisotropy constant Ku is a value determined for each ferromagnetic powder by the method described above using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.). The mass magnetization σs is a value measured at a magnetic field strength of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.).

[0231] [Method for producing ferromagnetic powder] <Method for producing hexagonal strontium ferrite powder> 1707 g of SrCO3, 687 g of H3BO3, 1120 g of Fe2O3, 45 g of Al(OH)3, 24 g of BaCO3, 13 g of CaCO3, and 235 g of Nd2O3 were weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C, and the melt was stirred while heating the tapping hole at the bottom of the platinum crucible, causing the melt to be poured into a rod shape at a rate of approximately 6 g / sec. The tapped liquid was rolled and quenched using a water-cooled twin roller to produce an amorphous body. 280 g of the produced amorphous body was placed in an electric furnace, heated to 635°C (crystallization temperature) at a rate of 3.5°C / min, and held at that temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. The crystallized material obtained above, containing hexagonal strontium ferrite particles, was then coarsely crushed in a mortar. 1,000 g of 1 mm zirconia beads and 800 ml of 1% acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at 100°C for 3 hours to dissolve the glass components, after which it was precipitated in a centrifuge and washed by repeated decantation. It was then dried for 6 hours in a heating furnace at 110°C to obtain hexagonal strontium ferrite powder. The average particle volume of the hexagonal strontium ferrite powder obtained above ("SrFe" in Table 2 below) was 900 nm 3 , the anisotropy constant Ku is 2.2×10 5 J / m 3 , mass magnetization σs is 49A m 2 / kg. A 12 mg sample powder was taken from the hexagonal strontium ferrite powder obtained above, and this sample powder was partially dissolved under the dissolution conditions exemplified above. The filtrate was subjected to elemental analysis using an ICP analyzer to determine the neodymium atom content in the surface layer. Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and this sample powder was completely dissolved under the dissolution conditions exemplified above. The filtrate thus obtained was subjected to elemental analysis using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) of the hexagonal strontium ferrite powder obtained above relative to 100 atomic percent of iron atoms was 2.9 atomic percent. The neodymium atom content in the surface layer was 8.0 atomic percent. The ratio of the surface layer content to the bulk content, "surface layer content / bulk content," was 2.8, confirming that neodymium atoms were unevenly distributed in the surface layers of the particles.

[0232] The powder obtained above was confirmed to have a hexagonal ferrite crystal structure by scanning with CuKα radiation at a voltage of 45 kV and an intensity of 40 mA and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibited a magnetoplumbite (M-type) hexagonal ferrite crystal structure. Furthermore, the crystalline phase detected by X-ray diffraction analysis was a single magnetoplumbite phase. PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slits for incident and diffracted beams: 0.017 radians Dispersion slit fixed angle: 1 / 4 degree Mask: 10mm Anti-scatter slit: 1 / 4 degree Measurement mode: Continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degrees per second Measurement step: 0.05 degrees

[0233] <Method for producing ε-iron oxide powder> 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved in 90 g of pure water. While stirring using a magnetic stirrer, 4.0 g of 25% aqueous ammonia was added in air at an ambient temperature of 25°C. The mixture was stirred for 2 hours at 25°C. A citric acid solution prepared by dissolving 1 g of citric acid in 9 g of pure water was added to the resulting solution and stirred for 1 hour. The precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating oven at 80°C. 800g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion. The resulting dispersion was heated to 50°C, and 40g of a 25% aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added dropwise and stirred for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried for 24 hours in a heating furnace at 80°C to obtain a precursor of the ferromagnetic powder. The obtained precursor of the ferromagnetic powder was placed in a heating furnace at an internal temperature of 1000° C. in an air atmosphere and subjected to heat treatment for 4 hours. The heat-treated ferromagnetic powder precursor was placed in a 4 mol / L aqueous solution of sodium hydroxide (NaOH), and the liquid temperature was maintained at 70°C while stirring for 24 hours, thereby removing the impurity silicate compound from the heat-treated ferromagnetic powder precursor. Thereafter, the silicate compound was removed by centrifugation, and the ferromagnetic powder was collected and washed with pure water to obtain a ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma optical emission spectrometry (ICP-OES). It was found that the powder consisted of Ga, Co, and Ti substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 O3). Furthermore, X-ray diffraction analysis was performed under the same conditions as those described above for the preparation of hexagonal strontium ferrite powder, and it was confirmed from the peaks in the X-ray diffraction pattern that the obtained ferromagnetic powder had a single-phase ε-phase crystal structure (ε-iron oxide crystal structure) that did not contain α-phase or γ-phase crystal structures. The average particle volume of the obtained ε-iron oxide powder (referred to as "ε-iron oxide" in Table 2 below) was 750 nm 3 , the anisotropy constant Ku is 1.2×10 5 J / m 3 , mass magnetization σs is 16A m 2 / kg.

[0234] [Fluorine-containing compounds] <Polymer (1-1)> A 300 mL three-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with 16.25 g of n-propyl alcohol, 16.25 g of cyclohexanone, and 20.00 g of Novec 7200 (3M), and the liquid temperature was raised to 97 °C. Next, a mixed solution consisting of 9.00 g (5.0 mmol) of Fluorolink MD700 (Solvay), 1.00 g (3.8 mmol) of 3-[[2-(acryloyloxy)ethyl]dimethylammonio]propane-1-sulfonic acid, 7.00 g of n-propyl alcohol, 5.50 g of cyclohexanone, 15.00 g of Novec 7200, and 10.00 g (43.4 mmol) of polymerization initiator V-601 (Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise at a constant rate so that the addition was completed within 60 minutes. After the dropwise addition was completed, stirring was continued for an additional 6 hours to obtain 82.9 g of a polymer solution of the polymer (1-1) shown below. The solids concentration of the polymer solution was 13.2%. In the following, a and b are the values ​​shown in Table 1.

[0235] [ka]

[0236] <Polymers (1-2) to (1-9), (1-12), (1-15), (1-20)> Polymers (1-2) to (1-9), (1-12), (1-15), and (1-20) having the following structures were each synthesized by a method similar to that described for polymer (1-1), except for the items shown in Table 1. In Table 1, polymers (1-8)(a), (b), and (c) are polymers (1-8) with different composition ratios.

[0237] [ka]

[0238] [Table 1]

[0239] [Example 1] (1) Preparation of alumina dispersion Alpha conversion rate approximately 65%, BET (Brunauer-Emmett-Teller) specific surface area 20m 2 100.0 parts of alumina powder (HIT-80 manufactured by Sumitomo Chemical Co., Ltd.) with a molecular weight of 1 / g was mixed with 3.0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.), 31.3 parts of a 32% solution of polyester polyurethane resin (UR-4800 manufactured by Toyobo Co., Ltd. (polar group amount: 80 meq / kg)) having SO3Na groups as polar groups (solvent: a mixed solvent of methyl ethyl ketone and toluene), and 570.0 parts of a 1:1 (mass ratio) mixed solution of methyl ethyl ketone and cyclohexanone as solvent, and dispersed for 5 hours using a paint shaker in the presence of zirconia beads. After dispersion, the dispersion and the beads were separated using a mesh to obtain an alumina dispersion.

[0240] (2) Formulation of the composition for forming the magnetic layer (Magnetic liquid) Ferromagnetic powder (type: see Table 2) 100.0 parts SO3Na group-containing polyurethane resin 14.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Cyclohexanone 150.0 parts Methyl ethyl ketone 150.0 parts (abrasive liquid) 6.0 parts of the alumina dispersion prepared in (1) above (Protrusion forming agent liquid) Protrusion forming agent 2.0 parts Type: Colloidal silica (average particle size 120 nm) Methyl ethyl ketone 1.4 parts (Other ingredients) Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Polyisocyanate (Tosoh Corporation, Coronate (registered trademark) L) 2.5 parts (Finishing additive solvent) Cyclohexanone 200.0 parts Methyl ethyl ketone 200.0 parts

[0241] (3) Formulation of composition for forming lower non-magnetic layer Carbon black (average particle size: 20 nm) 100.0 parts Trioctylamine 4.0 parts Vinyl chloride resin 12.0 parts 1.5 parts stearic acid Stearic acid amide 0.3 parts Butyl stearate 1.5 parts Cyclohexanone 200.0 parts Methyl ethyl ketone 510.0 parts

[0242] (4) Formulation of composition for forming upper nonmagnetic layer Non-magnetic inorganic powder α-iron oxide 100.0 parts Average particle size (average major axis length): 30nm Average short axis length: 15nm Acicular ratio: 2.0 SO3Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Stearic acid 1.0 parts Cyclohexanone 300.0 parts Methyl ethyl ketone 300.0 parts

[0243] (5) Formulation of the composition for forming the backcoat layer Carbon black 100.0 parts DBP (Dibutyl phthalate) oil absorption: 74cm 3 / 100g Nitrocellulose 27.0 parts Polyester polyurethane resin containing sulfonic acid groups and / or their salts 62.0 copies Polyester resin 4.0 parts Alumina powder (BET specific surface area: 17 m 2 / g) 0.6 parts Methyl ethyl ketone 600.0 parts Toluene 600.0 parts Polyisocyanate (Tosoh Corporation, Coronate (registered trademark) L) 15.0 parts

[0244] (6) Preparation of compositions for forming each layer A magnetic layer-forming composition was prepared by the following method. The magnetic liquid was prepared by dispersing the above components for 24 hours (bead dispersion) using a batch-type vertical sand mill. Zirconia beads with a bead diameter of 0.5 mm were used as the dispersion beads. The prepared magnetic liquid, the abrasive liquid, and other components (protrusion-forming agent liquid, other components, and finishing additive solvent) were mixed using the sand mill and bead-dispersed for 5 minutes, and then treated with a batch-type ultrasonic device (20 kHz, 300 W) for 0.5 minutes (ultrasonic dispersion). The mixture was then filtered using a filter with a pore size of 0.5 μm to prepare the magnetic layer-forming composition. For each of the above lower non-magnetic layer forming compositions and upper non-magnetic layer forming compositions, the above components were kneaded in an open kneader for 240 minutes and then dispersed in a sand mill. The dispersion conditions for each non-magnetic layer forming composition were a dispersion time of 24 hours, and zirconia beads with a bead diameter of 0.1 mm were used as dispersion beads. 4.0 parts of polyisocyanate (Tosoh Corporation's Coronate 3041) were added to the resulting dispersion, and the mixture was stirred and mixed for an additional 20 minutes, after which it was filtered using a filter with a pore size of 0.5 μm. In this way, a lower non-magnetic layer forming composition and an upper non-magnetic layer forming composition were prepared. The backcoat layer-forming composition was prepared by the following method. The above components, excluding the polyisocyanate, were introduced into a dissolver mixer and stirred at a peripheral speed of 10 m / s for 30 minutes, and then dispersed using a horizontal bead mill disperser. The polyisocyanate was then added, and the mixture was stirred and mixed using the dissolver mixer to prepare the backcoat layer-forming composition.

[0245] (7) Manufacturing of magnetic tapes and magnetic tape cartridges A lower nonmagnetic layer-forming composition was applied to the surface of a 4.1 μm thick biaxially stretched polyethylene terephthalate support to a thickness after drying shown in Table 2, and then dried in an environment with an ambient temperature of 100° C. to form a lower nonmagnetic layer. An upper nonmagnetic layer-forming composition was applied to the lower nonmagnetic layer to a thickness after drying shown in Table 2, and then dried in an environment with an ambient temperature of 100° C. to form an upper nonmagnetic layer. Next, the magnetic layer-forming composition prepared in (6) above was applied onto the upper non-magnetic layer so as to have a thickness of 0.1 μm after drying to form a coating layer. Thereafter, while the coating layer of the magnetic layer-forming composition was still wet, a magnetic field with a strength of 0.3 T was applied perpendicular to the surface of the coating layer to perform a vertical alignment treatment, and then the coating layer was dried to form a magnetic layer. Thereafter, the backcoat layer-forming composition prepared in (6) above was applied to the surface of the support opposite to the surface on which the nonmagnetic layer and magnetic layer were formed, and dried to a thickness of 0.3 μm after drying, thereby forming a backcoat layer. Thereafter, a surface smoothing treatment (calendering) was carried out once using a calender roll consisting only of a metal roll at a speed of 100 m / min, a linear pressure of 300 kg / cm, and a calender temperature (surface temperature of the calender roll) of 90°C. After calendering, the fluorine-containing compound shown in Table 2 was mixed with a solvent (a mixed solvent of cyclohexanone and methyl ethyl ketone at a 1:1 (mass ratio)) to prepare a coating solution with a fluorine-containing compound concentration of 0.1%. This coating solution was applied to the magnetic layer surface with a wire bar in an amount such that the coating amount of the fluorine-containing compound was the value shown in Table 2, and then dried. After the overcoating, the long magnetic tape was heat-treated by storing it in a heat treatment furnace at an ambient temperature of 70°C (heat treatment time: 36 hours). After heat treatment, the magnetic tape was slit into 1 / 2-inch widths to obtain magnetic tape. Servo signals were recorded on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, resulting in a magnetic tape with data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and with servo patterns (timing-based servo patterns) on the servo bands arranged and shaped in accordance with the LTO Ultrium format. The servo patterns thus formed conform to the specifications of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands was five, and the total number of data bands was four. The magnetic tape (length 970 m) after the servo pattern formation was taken up onto a core for heat treatment, and was heat treated while still wound on this core. A solid core-shaped member (outer diameter: 50 mm) made of resin with a flexural modulus of elasticity of 0.8 GPa was used as the core for heat treatment, and the tension during winding was 0.6 N. The heat treatment was carried out at a heat treatment temperature of 50°C for 5 hours. The weight absolute humidity of the atmosphere in which the heat treatment was carried out was 10 g / kg dry air. After the above heat treatment, once the magnetic tape and heat treatment core had sufficiently cooled, the magnetic tape was removed from the heat treatment core and wound onto a temporary take-up core. Thereafter, the final product length (960 m) of magnetic tape was wound from the temporary take-up core onto the reel (reel outer diameter: 44 mm) of a magnetic tape cartridge (LTO Ultrium 7 data cartridge). The remaining 10 m was cut off, and a leader tape in accordance with item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) was spliced ​​to the end of the cut-off side using commercially available splicing tape. The temporary take-up core was a solid core-shaped member made of the same material and with the same outer diameter as the heat treatment core, and the tension during winding was 0.6 N. As a result of the above, a single-reel magnetic tape cartridge was produced in which a 960 m long magnetic tape was wound on a reel.

[0246] [Examples 2 and 3] A magnetic tape and a magnetic tape cartridge were prepared by the same method as in Example 1, except that the overcoating was performed using a liquid amount in which the coating amount of the fluorine-containing compound was the value shown in Table 2.

[0247] [Examples 4 to 10, 15 to 20, Comparative Example 2] A magnetic tape and a magnetic tape cartridge were prepared by the method described in Example 1, except that the fluorine-containing compound was changed to one shown in Table 2.

[0248] [Example 11] A magnetic tape and a magnetic tape cartridge were produced by the method described in Example 1, except that the ferromagnetic powder was changed to that shown in Table 2.

[0249] [Example 12] A magnetic tape and a magnetic tape cartridge were produced by the method described in Example 1, except that only one non-magnetic layer was formed as follows.

[0250] <Formulation of composition for forming nonmagnetic layer> Non-magnetic inorganic powder: α-iron oxide 100.0 parts Average particle size (average major axis length): 150nm Acicular ratio: 7.0 BET specific surface area: 52m 2 / g Carbon black 20.0 parts Average particle size: 20nm SO3Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Cyclohexanone 300.0 parts Methyl ethyl ketone 300.0 parts

[0251] The nonmagnetic layer-forming composition was prepared by the following method. The above components, excluding the lubricants (stearic acid, stearic acid amide, and butyl stearate), were kneaded and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. The lubricants (stearic acid, stearic acid amide, and butyl stearate) were then added, and the mixture was stirred and mixed using a dissolver stirrer to prepare the nonmagnetic layer-forming composition.

[0252] The non-magnetic layer-forming composition prepared above was applied to the surface of a 4.1 μm thick biaxially stretched polyethylene terephthalate support and dried to a thickness shown in Table 2, thereby forming one non-magnetic layer.

[0253] [Example 13] A magnetic tape and a magnetic tape cartridge were prepared by the method described in Example 12, except that the ferromagnetic powder was changed to that shown in Table 2.

[0254] [Example 14] A magnetic tape and a magnetic tape cartridge were prepared by the method described for Example 1, except that the fluorine-containing compound shown in Table 2 was added to the magnetic layer-forming composition in an amount of 0.5 parts by mass per 100.0 parts by mass of ferromagnetic powder, and no overcoating with a coating liquid containing the fluorine-containing compound was performed.

[0255] [Comparative Example 1] A magnetic tape and a magnetic tape cartridge were prepared by the method described in Example 1, except that the overcoating with a coating liquid containing a fluorine-containing compound was not carried out.

[0256] For each of the examples and comparative examples, two magnetic tape cartridges were produced, one of which was used to measure the water contact angle to determine the ratio θr below, and the other was used to evaluate the electromagnetic conversion characteristics described below.

[0257] [Ratio θr] A 5 cm long tape sample and a 100 m long tape sample were cut out from a randomly selected position in the longitudinal direction of each magnetic tape of the Examples and Comparative Examples. The 5 cm long tape sample was measured for the water contact angle θ without sliding it over the magnetic head. before The 100 m long tape sample was attached to a 1 / 2 inch reel tester equipped with a fixed recording / playback head mounted on an IBM LTO8 tape drive, as described above, and slid against the magnetic head (LTO8 head) under the running conditions described above in an environment with an ambient temperature of 23°C ± 1°C and a relative humidity of 50%. After this sliding, a 5 cm long tape sample was cut from a randomly selected position on the tape sample, and the water contact angle θ after asked for. The water contact angle was measured on the magnetic layer surface of the tape sample using a contact angle measuring device (DropMaster 700 contact angle measuring device manufactured by Kyowa Interface Science Co., Ltd.) according to the following method. The tape sample was placed on a glass slide so that the backcoat layer surface was in contact with the glass slide surface. 2.0 μl of the measurement liquid (water) was dropped onto the surface of the tape sample (magnetic layer surface). After visually confirming that the dropped liquid had formed a stable droplet, the droplet image was analyzed using the contact angle analysis software FAMAS attached to the contact angle measuring instrument, and the contact angle between the sample piece and the droplet was measured. The contact angle was calculated using the θ / 2 method, and the arithmetic average of the values ​​measured at six different locations on the magnetic layer surface for one tape sample was determined as the water contact angle θ. before or θ after The measurement was carried out in an environment with an ambient temperature of 25°C and a relative humidity of 50%, and the contact angle was calculated under the following analysis conditions. before and θ after From this, the ratio θr was calculated. Method: Droplet method (θ / 2 method) Droplet recognition: automatic Droplet detection line (distance from needle tip): 50 dots Algorithm: Automatic Image Mode: Frame Threshold level: Automatic

[0258] For Comparative Example 1, the friction between the magnetic layer surface and the magnetic head was too high to allow the tape sample to slide repeatedly against the magnetic head, and therefore the ratio θr could not be determined for Comparative Example 1 (indicated as "-" in Table 2).

[0259] [Evaluation of electromagnetic conversion characteristics during repeated driving] The following evaluations were carried out in an environment with an ambient temperature of 23°C ± 1°C and a relative humidity of 50%. For each of the Examples and Comparative Examples, a 100 m long tape sample was cut from a randomly selected position in the longitudinal direction of the magnetic tape removed from the magnetic tape cartridge, and attached to a 1 / 2 inch reel tester equipped with a recording / reproducing head mounted on an IBM LTO8 tape drive as described above, and data was recorded and reproduced. The running conditions during recording and reproduction were the same as those described above for the sliding with the magnetic head performed to determine the ratio θr. Recording was performed at a linear recording density of 300 kfci, and the playback output was measured during playback to determine the signal-to-noise ratio (SNR) (ratio of playback output to noise). The unit kfci is the unit of linear recording density (not convertible to SI units). The difference between the SNR when recording and reproducing on the first single pass and the SNR when recording and reproducing on the 20,000th single pass (SNR on the 20,000th single pass - SNR on the 1st single pass) was calculated. The calculated values ​​are shown in the "SNR Decrease" column in Table 2. In Comparative Example 1, the friction between the magnetic layer surface and the magnetic head was too high to allow the magnetic tape to be run repeatedly, and therefore the SNR at the 20,000th single pass could not be determined (in Table 2, this is indicated as "impossible to measure").

[0260] The above results are shown in Table 2.

[0261] [Table 2]

[0262] As shown in Table 2, in Comparative Example 2, the SNR at the 20,000th single pass was lower than the SNR at the first single pass by more than 5.0 dB, and the deterioration of the electromagnetic conversion characteristics after repeated running was significant. In contrast, in Examples 1 to 20, the decrease in SNR after repeated running was suppressed compared to Comparative Example 2. From this result, it can be confirmed that the magnetic tapes of Examples 1 to 20 are magnetic tapes whose electromagnetic conversion characteristics decrease little even after repeated running. [Industrial Applicability]

[0263] One aspect of the present invention is useful in the field of magnetic tape for data storage.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, a fluorine-containing compound is contained in a portion of the non-magnetic support on the magnetic layer side, A magnetic tape in which the ratio θr of the water contact angle measured on the surface of the magnetic layer after sliding with a magnetic head to the water contact angle measured on the surface of the magnetic layer before sliding with a magnetic head is 0.70 or more.

2. 2. The magnetic tape according to claim 1, wherein the ratio θr is 0.80 or greater.

3. 3. The magnetic tape according to claim 1, wherein the ratio θr is 0.85 or greater.

4. 4. The magnetic tape according to claim 1, further comprising one or more non-magnetic layers containing non-magnetic powder between the non-magnetic support and the magnetic layer.

5. 5. The magnetic tape according to claim 1, further comprising a backcoat layer containing nonmagnetic powder on the surface of said nonmagnetic support opposite to the surface on which said magnetic layer is formed.

6. 6. The magnetic tape according to claim 1, wherein the ferromagnetic powder is a hexagonal strontium ferrite powder.

7. 6. The magnetic tape according to claim 1, wherein the ferromagnetic powder is a hexagonal barium ferrite powder.

8. 6. The magnetic tape according to claim 1, wherein the ferromagnetic powder is ε-iron oxide powder.

9. A magnetic tape cartridge comprising the magnetic tape according to any one of claims 1 to 8.

10. A magnetic tape device comprising the magnetic tape according to any one of claims 1 to 8.

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