JP2010235861A - Surface modifier for powder, magnetic recording medium, production process for the same, magnetic coating material, and non-magnetic coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for enhancing the dispersibility of powders. <P>SOLUTION: The surface modifier for a powder includes compound A and compound B described below. The production process for the magnetic recording medium employing the surface modifier for powders is provided. The magnetic recording medium produced by the production process is presented. The magnetic coating material and the non-magnetic coating material containing the surface modifier for powders are provided. Compound A: a compound involving a lactone ring having at least one substituent selected from the group consisting of a hydroxyl group and groups including a hydroxyl group. Compound B: a compound containing an unsaturated bond including a carboxylic group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a powder surface modifier, and more particularly to a powder surface modifier that can improve the dispersibility of powder in magnetic paints and non-magnetic paints.
Furthermore, this invention relates to the magnetic coating material and nonmagnetic coating material containing the said surface modifier for powders.
The present invention further relates to a magnetic recording medium and a method for producing the same, and more particularly to a magnetic recording medium having excellent surface smoothness and a method for producing the same.

  In recent years, means for transmitting information at a high speed have remarkably developed, and it has become possible to transfer images and data having enormous information. Along with the improvement of this data transfer technique, recording and reproducing devices and recording media for recording, reproducing and storing information are required to have higher density recording.

  In order to obtain good electromagnetic conversion characteristics in a high-density recording region, it is known that it is effective to use fine magnetic particles and to disperse the fine magnetic materials to a high degree to improve the smoothness of the magnetic layer surface. ing. In addition, by increasing the dispersibility of the magnetic material, a magnetic recording medium having a high glossiness can be obtained. Furthermore, as a means for increasing the smoothness of the magnetic layer surface, it is also effective to increase the dispersibility of the nonmagnetic powder contained in the nonmagnetic layer located below the magnetic layer.

Examples of a method for enhancing the dispersibility of powder used in magnetic recording media such as magnetic powder include a method in which a polar group such as SO ₃ Na group is contained in a binder (see Patent Document 1), an additive (dispersion) The method using the agent is widely used. For example, Patent Documents 2 and 3 describe the use of cyclic compounds such as cinnamic acid and benzoic acid as dispersants. In Patent Document 4, cinnamic acid is described as a component that can suppress an increase in error rate by suppressing corrosion of the head surface.

Japanese Patent Laid-Open No. 2003-132931 Japanese Patent Publication No. 7-85305 JP-A-1-232530 JP-A-6-301965

  In order to increase the dispersibility of the powder in a system containing the powder and the binder, it is important to increase the adsorptivity between the powder surface and the binder. However, for example, the binder used in the coating liquid for forming a magnetic recording medium is generally highly hydrophobic, whereas the powder surface used in the coating liquid is highly hydrophilic. It is difficult to adsorb. On the other hand, introducing a polar group into the binder as described above has an effect of efficiently adsorbing the binder on the powder surface due to the affinity of the polar group to the powder surface. This effect tends to increase as the amount of polar groups introduced into the binder increases. However, when the amount of polar groups into the binder increases, the viscosity of the coating solution increases due to the association between the polar groups and the dispersibility decreases. There is a risk. On the other hand, the effect of improving the dispersibility by the cyclic compound such as cinnamic acid is not necessarily sufficient for a magnetic recording medium for high-density recording that requires high surface smoothness.

  Accordingly, an object of the present invention is to provide means for enhancing the dispersibility of powders such as magnetic powder in magnetic paint and nonmagnetic powder in nonmagnetic paint.

  As a result of intensive studies to achieve the above object, the present inventors can modify the powder surface by a combination of the following compound A and compound B, and as a result, include the powder and the binder. The present inventors have newly found that the amount of binder adsorbed on the powder surface can be increased in the system, and the present invention has been completed.

[一般式(I)中、Ｒ^１１〜Ｒ^１６は、それぞれ独立に水素原子または置換基を表し、Ｒ^１１〜Ｒ^１６の少なくとも１つは、水酸基または水酸基を含む基を表す。]

[一般式(II)中、Ｒ^２１〜Ｒ^２８は、それぞれ独立に水素原子または置換基を表し、Ｒ^２１〜Ｒ^２８の少なくとも１つは、水酸基または水酸基を含む基を表す。]
[３]化合物Ａは、１分子中に２つ以上の水酸基を含む[１]または[２]に記載の粉末用表面改質剤。
[４]化合物Ａに含まれる前記水酸基を含む基は、水酸基を含むアルキル基である[１]〜[３]のいずれかに記載の粉末用表面改質剤。
[５]化合物Ａに含まれる前記水酸基を含む基は、一級水酸基を含む基である[１]〜[4]のいずれかに記載の粉末用表面改質剤。
[６]化合物Ｂは、不飽和脂肪酸である[１]〜[５]のいずれかに記載の粉末用表面改質剤。
[７]化合物Ｂは、芳香族化合物である[１]〜[５]のいずれかに記載の粉末用表面改質剤。
[８]前記芳香族化合物は、ベンゼン環またはナフタレン環を含む[７]に記載の粉末用表面改質剤。
[９]前記粉末は磁性粉末および非磁性粉末からなる群から選ばれる[１]〜[８]のいずれかに記載の粉末用表面改質剤。
[１０]磁性塗料用分散剤または非磁性塗料用分散剤として使用される[９]に記載の粉末用表面改質剤。
[１１]イソシアネート化合物と併用される[１]〜[１０]のいずれかに記載の粉末用表面改質剤。
[１２]磁性粉末、結合剤および[１]〜[８]のいずれかに記載の粉末用表面改質剤を混合することにより磁性層形成用塗布液を調製すること、
調製した磁性層形成用塗布液を非磁性支持体上に塗布および乾燥することにより磁性層を形成すること、
を含む磁気記録媒体の製造方法。
[１３]前記磁性層形成用塗布液は、イソシアネート化合物を含む[１２]に記載の磁気記録媒体の製造方法。
[１４]非磁性粉末、結合剤および[１]〜[８]のいずれかに記載の粉末用表面改質剤を混合することにより非磁性層形成用塗布液を調製すること、
調製した非磁性層形成用塗布液を非磁性支持体上に塗布および乾燥することにより非磁性層を形成すること、
を含む磁気記録媒体の製造方法。
[１５]前記非磁性層形成用塗布液は、イソシアネート化合物を含む[１４]に記載の磁気記録媒体の製造方法。
[１６]非磁性支持体上に、強磁性粉末および結合剤を含む磁性層を有する磁気記録媒体であって、
[１２]または[１３]に記載の製造方法により製造されたものである磁気記録媒体。
[１７]非磁性支持体上に、非磁性粉末および結合剤を含む非磁性層と、強磁性粉末および結合剤を含む磁性層とをこの順に有する磁気記録媒体であって、
[１４]または[１５]に記載の製造方法により製造されたものである磁気記録媒体。
[１８][１]〜[８]のいずれかに記載の粉末用表面改質剤と、磁性粉末と、結合剤とを含む磁性塗料。
[１９]磁気記録媒体の磁性層形成用塗布液として使用される[１８]に記載の磁性塗料。
[２０]イソシアネート化合物を更に含む[１８]または[１９]に記載の磁性塗料。
[２１][１]〜[８]のいずれかに記載の粉末用表面改質剤と、非磁性粉末と、結合剤とを含む非磁性塗料。
[２２]磁気記録媒体の非磁性層形成用塗布液として使用される[２１]に記載の非磁性塗料。
[２３]イソシアネート化合物を更に含む[２１]または[２２]に記載の非磁性塗料。 That is, the above object has been achieved by the following means.
[1] A powder surface modifier comprising the following compound A and compound B:
Compound A: Compound containing a lactone ring having at least one substituent selected from the group consisting of a hydroxyl group and a group containing a hydroxyl group Compound B: an unsaturated bond-containing compound containing a carboxyl group
[2] The powder surface modifier according to [1], wherein the compound A is a compound represented by the following general formula (I) or (II).

[In General Formula (I), R ^{11 to} R ¹⁶ each independently represent a hydrogen atom or a substituent, and at least one of R ^{11 to} R ¹⁶ represents a hydroxyl group or a group containing a hydroxyl group. ]

[In General Formula (II), R ^{21 to} R ²⁸ each independently represent a hydrogen atom or a substituent, and at least one of R ^{21 to} R ²⁸ represents a hydroxyl group or a group containing a hydroxyl group. ]
[3] The powder surface modifying agent according to [1] or [2], wherein the compound A contains two or more hydroxyl groups in one molecule.
[4] The powder surface modifier according to any one of [1] to [3], wherein the group containing a hydroxyl group contained in the compound A is an alkyl group containing a hydroxyl group.
[5] The surface modifier for powder according to any one of [1] to [4], wherein the group containing a hydroxyl group contained in the compound A is a group containing a primary hydroxyl group.
[6] The powder surface modifier according to any one of [1] to [5], wherein Compound B is an unsaturated fatty acid.
[7] The powder surface modifier according to any one of [1] to [5], wherein the compound B is an aromatic compound.
[8] The powder surface modifier according to [7], wherein the aromatic compound contains a benzene ring or a naphthalene ring.
[9] The powder surface modifier according to any one of [1] to [8], wherein the powder is selected from the group consisting of a magnetic powder and a nonmagnetic powder.
[10] The surface modifier for powder according to [9], which is used as a dispersant for magnetic paint or a dispersant for nonmagnetic paint.
[11] The surface modifier for powder according to any one of [1] to [10], which is used in combination with an isocyanate compound.
[12] preparing a coating solution for forming a magnetic layer by mixing the magnetic powder, a binder, and the surface modifier for powder according to any one of [1] to [8],
Forming a magnetic layer by coating and drying the prepared coating solution for forming a magnetic layer on a nonmagnetic support;
A method of manufacturing a magnetic recording medium including:
[13] The method for producing a magnetic recording medium according to [12], wherein the coating liquid for forming a magnetic layer contains an isocyanate compound.
[14] preparing a coating solution for forming a nonmagnetic layer by mixing the nonmagnetic powder, a binder, and the surface modifier for powder according to any one of [1] to [8],
Forming a nonmagnetic layer by coating the prepared coating liquid for forming a nonmagnetic layer on a nonmagnetic support and drying;
A method of manufacturing a magnetic recording medium including:
[15] The method for producing a magnetic recording medium according to [14], wherein the coating liquid for forming a nonmagnetic layer contains an isocyanate compound.
[16] A magnetic recording medium having a magnetic layer containing a ferromagnetic powder and a binder on a nonmagnetic support,
A magnetic recording medium manufactured by the manufacturing method according to [12] or [13].
[17] A magnetic recording medium having, on a nonmagnetic support, a nonmagnetic layer containing nonmagnetic powder and a binder, and a magnetic layer containing ferromagnetic powder and a binder in this order,
A magnetic recording medium produced by the production method according to [14] or [15].
[18] A magnetic paint comprising the powdery surface modifying agent according to any one of [1] to [8], a magnetic powder, and a binder.
[19] The magnetic paint according to [18], which is used as a coating liquid for forming a magnetic layer of a magnetic recording medium.
[20] The magnetic paint according to [18] or [19], further comprising an isocyanate compound.
[21] A nonmagnetic paint comprising the powder surface modifier according to any one of [1] to [8], a nonmagnetic powder, and a binder.
[22] The nonmagnetic paint according to [21], which is used as a coating liquid for forming a nonmagnetic layer of a magnetic recording medium.
[23] The nonmagnetic paint according to [21] or [22], further comprising an isocyanate compound.

  According to the present invention, the surface of the powder can be modified to increase the amount of binder adsorbed on the powder, thereby increasing the dispersibility of the magnetic powder in the magnetic paint and the nonmagnetic powder in the nonmagnetic paint. Can do. Furthermore, the coating film strength can be increased by using Compound A containing two or more hydroxyl groups in one molecule in combination with an isocyanate compound.

[Surface modifier for powder]
The powder surface modifier of the present invention contains the following compound A and compound B.
Compound A: Compound containing a lactone ring having at least one substituent selected from the group consisting of a hydroxyl group and a group containing a hydroxyl group Compound B: an unsaturated bond-containing compound containing a carboxyl group

  The surface modifier for powders of the present invention (hereinafter also simply referred to as “surface modifier” or “modifier”) can contain one or more compounds A and B, and compound A In addition to B and B, other compounds having a surface modification effect and known additives can be optionally contained. The modifying agent of the present invention may be a one-agent type containing all components including Compound A and Compound B as one agent. In use, one agent and two agents are mixed with powder simultaneously or sequentially. It may be a pharmaceutical formulation or a multi-drug formulation of 3 or more. For example, the modifier of the present invention can be a two-part formulation containing Compound A as the first agent and Compound B as the second agent. In particular, when the modifier of the present invention is applied to a coating liquid for forming a magnetic layer of a magnetic recording medium, one or two kinds are used from the viewpoint of improving the magnetic powder density (filling rate) of the magnetic layer. It is preferable to consist of the above compounds A and B.

The present inventors infer the reason why the powder surface can be modified by the combination of compounds A and B and the amount of the binder adsorbed on the powder surface can be increased.
Compound B is considered to have an action of increasing the affinity between the powder surface and the binder by being adsorbable on the powder surface by a carboxyl group and having a high affinity with the binder because it contains an unsaturated bond. . However, the surface modification effect by this action is not always sufficient in a magnetic recording medium for high density recording. This is presumably because the surface of the magnetic powder and the non-magnetic powder is hydrophilic, so that even when Compound B is used, the affinity with the hydrophobic binder is not sufficient.
The hydrophilicity of the surfaces of the magnetic powder and nonmagnetic powder is considered to be due to the presence of adsorbed water on the powder surface. On the other hand, the lactone ring contained in Compound A is opened while decomposing water in the presence of water. When the compound A comes into contact with the powder surface, it causes the ring-opening reaction while decomposing the adsorbed water. As a result, the amount of adsorbed water on the powder surface decreases, so that the hydrophobicity of the powder surface can be increased. In combination with Compound A containing a lactone ring, the inventors of the present invention can improve the adsorptivity with the hydrophobic binder by exhibiting the effect of increasing the hydrophobicity of the powder surface. Therefore, it is presumed that this is the reason why the amount of binder adsorbed on the powder can be increased. Here, one of the hydroxyl groups contained in the compound A is considered to play a role of enhancing the affinity between the compound A and the powder surface and promoting the contact and adsorption of the compound A to the powder surface.

Further, as a result of the study by the present inventors, it has been newly found that Compound A containing two or more hydroxyl groups in one molecule fulfills the effect of improving the coating film strength in combination with an isocyanate compound. This is presumably due to the following reasons.
Polyurethane is widely used as a binder for magnetic recording media. Polyurethane is a polymer with strong mechanical strength due to hydrogen bonding between molecules, but has few functional groups that can react with isocyanate groups such as hydroxyl groups. Therefore, even if an isocyanate compound is used in combination as a curing agent, it is difficult to greatly improve the coating film strength. On the other hand, Compound A generates 1 molar equivalent of a hydroxyl group when the lactone ring is opened, but the monofunctional alcohol may stop curing by capping the end of the isocyanate curing agent. On the other hand, when the compound A has a hydroxyl group in addition to the hydroxyl group for adsorption, the excess hydroxyl group can react with the isocyanate group, so that the curing reaction is considered to proceed well. The reason why a high-strength coating film can be formed by using Compound A containing two or more hydroxyl groups in one molecule is presumed to be due to an increase in the curing rate due to the curing reaction.

For example, as shown in the examples described later, the amount of the binder adsorbed to the powder in the paint changes depending on the presence or absence of the modifier of the present invention, so that the modifier of the present invention modifies the powder surface. Can be confirmed.
Hereinafter, the compounds A and B will be described in more detail.

Compound A
Compound A contains a lactone ring having at least one substituent selected from the group consisting of (i) a hydroxyl group and (ii) a group containing a hydroxyl group. The lactone ring is not particularly limited as long as it contains an ester bond as a part of the ring, but a 5- or 6-membered lactone ring is preferable from the viewpoint of the powder surface modification effect.

  The lactone ring contained in Compound A is substituted with one or more substituents selected from the group consisting of a hydroxyl group and a group containing a hydroxyl group. By including one hydroxyl group in one molecule, a surface modification effect can be exhibited, and by including two or more, a coating film strength improving effect can also be exhibited. The number of hydroxyl groups in one molecule is not particularly limited as long as it is 1 or more. However, it is preferably 2 or more, for example, 2 to 4 for the above reasons.

  When compound A contains one hydroxyl group in one molecule, it can be adsorbed to the powder surface by the action of the hydroxyl group, and as a result, can exhibit the hydrophobicity improving action on the powder surface as described above. Conceivable. On the other hand, the coating liquid for forming a magnetic recording medium usually contains an isocyanate compound as a curing agent (crosslinking agent). Therefore, in the coating liquid for forming a magnetic recording medium containing an isocyanate compound, as described above, if more hydroxyl groups are included than the number that contributes to adsorption of the compound on the powder surface, the excess hydroxyl groups react with the isocyanate compound. It is thought that a urethane bond can be formed. Thus, if the compound which exists on the powder surface forms a crosslinked structure with an isocyanate compound, the intensity | strength of the coating film formed from the said coating liquid can be improved. From the above viewpoint, the compound A preferably contains two or more hydroxyl groups in one molecule. Furthermore, since Compound A generates one hydroxyl group by opening of the lactone ring, this hydroxyl group is also considered to form a crosslinked structure with the isocyanate compound and contribute to improving the coating film strength. Details of the isocyanate compound will be described later.

  The substituent containing a hydroxyl group that can be contained in the compound A is not particularly limited, and examples thereof include an alkyl group and an aryl group substituted by a hydroxyl group. From the viewpoint of reactivity with the aforementioned isocyanate compound, the substituent preferably contains a primary hydroxyl group, more preferably an alkyl group containing a primary hydroxyl group.

  The alkyl group may be linear, branched or cyclic, for example, an alkyl group having 1 to 30 carbon atoms, specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, t- Examples thereof include a butyl group, an n-octyl group, an eicosyl group, a 2-chloroethyl group, a 2-cyanoethyl group, and a 2-ethylhexyl group. Furthermore, a cycloalkyl group (for example, a substituted or unsubstituted cycloalkyl group having 3 to 30 carbon atoms, specifically, a cyclohexyl group, a cyclopentyl group, 4-n-dodecylcyclohexyl group), a bicycloalkyl group (for example, a carbon number A substituted or unsubstituted bicycloalkyl group of 5 to 30, that is, a monovalent group obtained by removing one hydrogen atom from a bicycloalkane having 5 to 30 carbon atoms, specifically, bicyclo [1,2,2] Heptan-2-yl, bicyclo [2,2,2] octane-3-yl), and tricyclo structures with many ring structures are also included. In the present invention, the “carbon number” for a certain group means the carbon number of the portion not containing the substituent when the group has a substituent.

  The aryl group is a substituted or unsubstituted aryl group, for example, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, specifically, a phenyl group, a p-tolyl group, a naphthyl group, an m-chlorophenyl group. , O-hexadecanoylaminophenyl group, and the like.

  The alkyl group is preferably an alkyl group having 1 to 3 carbon atoms, for example, a methyl group, an ethyl group, or a propyl group, from the viewpoint of reactivity with adsorbed water on the powder surface.

  As the compound A, from the viewpoint of the effect of modifying the powder surface, the compound represented by the following general formula (I) containing a 5-membered lactone ring and the following general formula containing a 6-membered lactone ring ( Compounds represented by II) are preferred.

[一般式(I)中、Ｒ^１１〜Ｒ^１６は、それぞれ独立に水素原子または置換基を表し、Ｒ^１１〜Ｒ^１６の少なくとも１つは、水酸基または水酸基を含む基を表す。]

[In General Formula (I), R ^{11 to} R ¹⁶ each independently represent a hydrogen atom or a substituent, and at least one of R ^{11 to} R ¹⁶ represents a hydroxyl group or a group containing a hydroxyl group. ]

[一般式(II)中、Ｒ^２１〜Ｒ^２８は、それぞれ独立に水素原子または置換基を表し、Ｒ^２１〜Ｒ^２８の少なくとも１つは、水酸基または水酸基を含む基を表す。]

[In General Formula (II), R ^{21 to} R ²⁸ each independently represent a hydrogen atom or a substituent, and at least one of R ^{21 to} R ²⁸ represents a hydroxyl group or a group containing a hydroxyl group. ]

  For the reasons described above, the compounds represented by the general formulas (I) and (II) preferably contain two or more hydroxyl groups in one molecule. Hereinafter, the compounds represented by the general formulas (I) and (II) will be described in more detail.

In general formula (I), R ^{11 to} R ¹⁶ each independently represent a hydrogen atom or a substituent, and at least one of R ^{11 to} R ¹⁶ is (i) a hydroxyl group or (ii) a group containing a hydroxyl group. Represents. The details of the above (i) and (ii) are as described above. Substituents represented by R ¹¹ to R ¹⁶ is, when a substituent other than the above (i) and (ii), is not particularly limited as such substituent, an alkyl group (the details described above An aryl group (preferably a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, such as a phenyl group, a tolyl group, a xylyl group, a mesityl group, a biphenylyl group, a naphthyl group, an anthryl group, a phenanthryl group, a fluorenyl group. , Pyrenyl group), alkyl group (preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group) Group, n-pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, cyclopentyl Group, cyclohexyl group, benzyl group, phenethyl group, diphenylmethyl group, and trityl group).

In general formula (II), R ^{21 to} R ²⁸ each independently represent a hydrogen atom or a substituent, and at least one of R ^{21 to} R ²⁸ is (i) a hydroxyl group or (ii) a group containing a hydroxyl group. Represents. The details of the above (i) and (ii) are as described above. When the substituent represented by R ^{11 to} R ¹⁶ is a substituent other than the above (i) and (ii), details of such a substituent are also as described above.

  Compound A such as the compounds described in the general formulas (I) and (II) can be easily synthesized by known methods, and some of them are available as commercial products.

  Specific examples of Compound A are shown below. However, the present invention is not limited to the following specific examples.

Compound B
Compound B is an unsaturated bond-containing compound containing a carboxyl group. The unsaturated bond in compound B is, for example, a double bond. It is considered that the fact that an unsaturated bond generates an Π-Π interaction with the unsaturated bond in the binder and the binding force is increased also contributes to an improvement in dispersibility.

  From the viewpoint of affinity with the binder, compound B preferably contains a double bond as an unsaturated bond, and more preferably contains an unsaturated bond in a cyclic structure such as an unsaturated fatty acid or an aromatic compound. . The number of unsaturated bonds contained in compound B is not particularly limited as long as it is at least one.

  As the unsaturated fatty acid, an unsaturated fatty acid having about 5 to 30 carbon atoms is preferable from the viewpoint of solvent solubility. Specific examples include oleic acid, palmitoyl acid, linoleic acid, and linolenic acid.

  The cyclic structure that can be included in the compound B may be a single ring or a condensed ring, and may be any of an aromatic ring, an aliphatic ring, and a heterocyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Examples of the aliphatic ring include a cyclohexane ring. Examples of the heterocyclic ring include a pyridine ring and a pyrimidine ring. From the viewpoint of affinity with the binder, an aromatic ring is preferable, and a benzene ring and a naphthalene ring are more preferable.

  The number of carboxyl groups contained in compound B is at least one per molecule, and may be two or more. In addition, from the viewpoint of dispersibility, the number of carboxyl groups contained in compound B is preferably 2 or less in one molecule. When two or more carboxyl groups are contained in one molecule, the carboxyl group is present on the adjacent carbon. It is further preferable to have

  Specific examples of compound B are shown below. However, the present invention is not limited to the following specific examples.

  The ratio (mass ratio) of Compound A and Compound B in the surface modifier of the present invention is preferably Compound A / Compound B = 10/1 to 1/10 from the viewpoint of the surface modification effect. More preferably, it is set to 1 to 1/7. The total amount of Compound A and Compound B can be set as appropriate, for example, 0.1 to 10 parts by mass, and 2 to 8 parts by mass with respect to 100 parts by mass of the powder such as magnetic powder. Is preferred. The method for mixing the surface modifier and powder of the present invention will be described later.

  The surface modifier of the present invention can improve the dispersibility of the powder in the paint containing the powder and the binder by modifying the powder surface such as magnetic powder and non-magnetic powder. Therefore, the surface modifier of the present invention is preferably used as a dispersant in various paints containing powder and binder, and includes magnetic paint containing magnetic powder and binder and non-magnetic powder containing binder and non-magnetic powder. More preferably used as a dispersant in a magnetic coating, and a coating solution for forming a magnetic layer or coating for forming a non-magnetic layer on a magnetic recording medium that is required to enhance the coating film smoothness by highly enhancing the dispersibility of the powder. It is particularly preferable to use it as a dispersant in a liquid. A mode in which the surface modifier of the present invention is applied to magnetic paints and non-magnetic paints will be described later.

[Method of manufacturing magnetic recording medium]
Furthermore, the present invention provides
The magnetic layer forming coating solution is prepared by mixing the magnetic powder, the binder and the powder surface modifying agent of the present invention, and the prepared magnetic layer forming coating solution is coated on a nonmagnetic support and dried. Forming a magnetic layer, thereby producing a magnetic recording medium,
A nonmagnetic powder, a binder, and a surface modifier for powder of the present invention are mixed to prepare a coating solution for forming a nonmagnetic layer, and the prepared coating solution for forming a nonmagnetic layer is coated on a nonmagnetic support. And forming a nonmagnetic layer by drying, a method for producing a magnetic recording medium,
About.
Hereinafter, the method for producing a magnetic recording medium of the present invention will be described in more detail.

Preparation of magnetic layer forming coating solution The magnetic layer forming coating solution can be obtained by mixing the surface modifier of the present invention, magnetic powder, binder, and optional additives. Can be obtained by a general method of preparing a magnetic layer coating solution. A preparation process consists of a kneading | mixing process, a dispersion | distribution process, and the mixing process provided as needed before and after these processes, for example. Each process may be divided into two or more stages. In the kneading step, it is preferable to use a kneading force such as an open kneader, a continuous kneader, a pressure kneader, or an extruder. Details of these kneading treatments are described in JP-A-1-106338 and JP-A-1-79274. Further, glass beads can be used to disperse the magnetic layer forming coating solution. Such glass beads are preferably zirconia beads, titania beads, and steel beads, which are high specific gravity dispersion media. The particle diameter and filling rate of these dispersion media can be optimized and used. A well-known thing can be used for a disperser.

In order to effectively obtain the effect of adding the surface modifier of the present invention, it is preferable that the surface modifier contacts the surface of the magnetic powder before or before the contact between the magnetic powder and the binder. This is because the surface modifier of the present invention can exert its effect by adsorbing to the surface of the magnetic powder. Therefore, before the surface modifier of the present invention comes into contact with the magnetic powder surface, This is for avoiding contact with the touch panel. Therefore, the coating liquid for forming the magnetic layer is prepared by mixing the magnetic powder, the binder, and the surface modifier of the present invention at the same time, or by mixing the magnetic powder and the surface modifier. It is preferred to prepare by mixing the binder. Specifically, it is preferable to mix the components by the following method.
(1) A magnetic powder and a surface modifier are previously dispersed in a dry process for about 15 to 30 minutes, and then added to an organic solvent. The binder may be added simultaneously with the dispersion, or may be added after the dispersion is added.
(2) The magnetic powder and the surface modifier are dispersed in an organic solvent for about 15 to 30 minutes and then dried. The dried mixture is appropriately pulverized and added to an organic solvent. The binder may be added simultaneously with the mixture, or may be added after the mixture is added.
(3) After dispersing the magnetic powder and the surface modifier in an organic solvent for about 15 to 30 minutes, a binder is added.
(4) A magnetic powder, a surface modifier and a binder are simultaneously added and dispersed in an organic solvent.

  Compound A and compound B may be added simultaneously with the magnetic powder or sequentially. For example, (i) First, magnetic powder and compound A are mixed, then compound B is added, (ii) First, magnetic powder and compound B are mixed, then compound A is added, (iii) Compound A and compound B are added simultaneously, In the present invention, any mixing method may be used. From the viewpoint of improving dispersibility, (ii) or (iii) is preferable, and (ii) is more preferable.

As the magnetic powder magnetic powder, a ferromagnetic powder that can be generally contained in a coating solution for forming a magnetic layer of a magnetic recording medium can be used. Since the surface modifying agent of the present invention provides an excellent surface modifying effect, hexagonal ferrite powder and ferromagnetic metal powder are preferred as such ferromagnetic powder.
Hereinafter, the hexagonal ferrite powder and the ferromagnetic metal powder will be described in more detail.

(I) Hexagonal ferrite powder The hexagonal ferrite powder includes, for example, barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and their substitutes such as Co. More specifically, magnetoplumbite type barium ferrite and strontium ferrite, magnetoplumbite type ferrite whose particle surface is coated with spinel, and magnetoplumbite type barium ferrite and strontium ferrite partially containing a spinel phase, etc. Is mentioned. In addition to predetermined atoms, Al, Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Hg , Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, B, Ge, and Nb may be included. In general, elements such as Co—Zn, Co—Ti, Co—Ti—Zr, Co—Ti—Zn, Ni—Ti—Zn, Nb—Zn—Co, Sb—Zn—Co, and Nb—Zn are added. Things can be used. Some raw materials and production methods contain specific impurities.

  It is preferable to use a hexagonal ferrite powder having an average plate diameter of 10 to 50 nm, more preferably 15 to 40 nm, and still more preferably 15 to 30 nm. The hexagonal ferrite powder having the above size is suitable as a magnetic material used in a magnetic recording medium for high density recording. According to the present invention, the dispersibility of the particulate hexagonal ferrite powder having the average plate diameter can be improved.

The average plate ratio [arithmetic average of (plate diameter / plate thickness)] of the hexagonal ferrite powder is preferably 1-15, and more preferably 1-7. When the average plate ratio is 1 to 15, sufficient orientation can be obtained while maintaining high filling properties in the magnetic layer, and noise increase due to stacking between particles can be suppressed. Further, the specific surface area (S _BET ) by the BET method within the above particle size range is preferably 40 m ² / g or more, more preferably 40 to 200 m ² / g, and 60 to 100 m ² / g. Is most preferred.

  The distribution of the particle plate diameter and plate thickness of the hexagonal ferrite powder is generally preferably as narrow as possible. The particle plate diameter and plate thickness can be measured, for example, by randomly measuring 500 particles from a particle TEM photograph. In many cases, the distribution of the particle plate diameter and plate thickness is not a normal distribution, but when calculated and expressed as a standard deviation with respect to the average size, σ / average size = 0.1 to 1.0. In order to sharpen the particle size distribution, in general, the particle generation reaction system is made as uniform as possible, and the generated particles are subjected to a distribution improving process. For example, a method of selectively dissolving ultrafine particles in an acid solution is also known. Further, the pH of the hexagonal ferrite powder is usually about 4 to 12 and has an optimum value depending on the dispersion medium and the polymer, but generally about 6 to 11 is selected from the chemical stability and storage stability at the time of application of the medium. Moisture contained in the hexagonal ferrite powder also affects the dispersion. Although there is an optimum value depending on the dispersion medium and the polymer, 0.01 to 2.0% is usually selected.

The hexagonal ferrite powder is manufactured by mixing (1) barium oxide / iron oxide / metal oxide replacing iron and boron oxide as a glass forming substance so as to have a desired ferrite composition, and then melting and quenching. A glass crystallization method for obtaining a barium ferrite crystal powder by re-heating treatment after being reheated, and (2) neutralizing the barium ferrite composition metal salt solution with an alkali to produce a by-product Hydrothermal reaction method to obtain barium ferrite crystal powder by liquid phase heating at 100 ° C. or higher after removal of water, (3) neutralization of barium ferrite composition metal salt solution with alkali, by-product There is a coprecipitation method or the like in which the product is removed, dried, treated at 1100 ° C. or less, and pulverized to obtain a barium ferrite crystal powder. The hexagonal ferrite powder used in the present invention is Or it may be produced by Les recipe. The hexagonal ferrite powder may be subjected to surface treatment with Al, Si, P, or an oxide thereof as required. The amount thereof is, for example, 0.1 to 10% by mass with respect to the ferromagnetic powder, and surface treatment is preferable because adsorption of a lubricant such as a fatty acid is 100 mg / m ² or less. The hexagonal ferrite powder may contain soluble inorganic ions such as Na, Ca, Fe, Ni, and Sr. Although it is preferable that these are essentially not present, if they are 200 ppm or less, they do not particularly affect the characteristics.

(ii) Ferromagnetic metal powder The ferromagnetic metal powder is not particularly limited, but it is preferable to use a ferromagnetic metal powder containing α-Fe as a main component. These ferromagnetic metal powders include Al, Si, S, Sc, Ca, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, other than predetermined atoms. Atoms such as Ta, W, Re, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, and B may be included. In particular, at least one of Al, Si, Ca, Y, Ba, La, Nd, Co, Ni, and B is preferably included in addition to α-Fe, and further includes at least one of Co, Y, and Al. preferable. The Co content is preferably 0 atom% or more and 40 atom% or less, more preferably 15 atom% or more and 35 atom% or less, more preferably 20 atom% or more and 35 atom% or less with respect to Fe. The Y content is preferably from 1.5 atomic percent to 12 atomic percent, more preferably from 3 atomic percent to 10 atomic percent, and particularly preferably from 4 atomic percent to 9 atomic percent. Al is preferably from 1.5 atomic percent to 12 atomic percent, more preferably from 3 atomic percent to 10 atomic percent, and even more preferably from 4 atomic percent to 9 atomic percent.

  The ferromagnetic metal powder may contain a small amount of hydroxide or oxide. As the ferromagnetic metal powder, those obtained by a known production method can be used, and the following methods can be mentioned. A method of reducing a complex organic acid salt (mainly oxalate) with a reducing gas such as hydrogen, a method of reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe-Co particles, a metal carbonyl compound A method of thermal decomposition, a method of reducing by adding a reducing agent such as sodium borohydride, hypophosphite, or hydrazine to an aqueous solution of a ferromagnetic metal, and evaporating the metal in a low-pressure inert gas to form a fine powder. How to get. The ferromagnetic metal powder obtained in this manner is a known gradual oxidation treatment, that is, a method of drying after immersing in an organic solvent, an oxygen-containing gas is sent after immersing in an organic solvent, and an oxide film is formed on the surface. Thereafter, either a drying method or a method of adjusting the partial pressures of oxygen gas and inert gas without using an organic solvent to form an oxide film on the surface can be applied.

The specific surface area by BET method of the ferromagnetic metal powder is preferably 45~100m ² / g, more preferably 50-80 m ² / g. If it is 45 m ² / g or more, the noise is low, and if it is 100 m ² / g or less, a magnetic layer having good surface properties can be formed. The crystallite size of the ferromagnetic metal powder is preferably 40 to 180 mm, more preferably 40 to 150 mm, and still more preferably 40 to 110 mm. The average major axis length (average particle size) of the ferromagnetic metal powder is preferably 10 to 50 nm, more preferably 10 to 40 nm, and further preferably 15 to 30 nm. According to the present invention, the dispersibility of the particulate ferromagnetic metal powder having the average major axis length can be enhanced. The acicular ratio of the ferromagnetic metal powder is preferably 3 or more and 15 or less, more preferably 3 or more and 12 or less.

The moisture content of the ferromagnetic metal powder is preferably 0.01 to 2%. It is preferable to optimize the moisture content of the ferromagnetic metal powder depending on the type of the binder. The pH of the ferromagnetic metal powder is preferably optimized depending on the combination with the binder used. The range can be 4-12, preferably 6-10. The ferromagnetic metal powder may be surface-treated with Al, Si, P, or an oxide thereof as required. The amount thereof can be 0.1 to 10% with respect to the ferromagnetic metal powder, and the surface treatment is preferable because the adsorption amount of a lubricant such as a fatty acid is 100 mg / m ² or less. The ferromagnetic metal powder may contain inorganic ions such as soluble Na, Ca, Fe, Ni, and Sr. Although it is preferable that these are essentially not present, if they are 200 ppm or less, they hardly affect the characteristics. The ferromagnetic metal powder used in the present invention preferably has fewer vacancies, and its value is 20% by volume or less, more preferably 5% by volume or less. As for the shape, any of needle shape, rice grain shape, or spindle shape may be used as long as the above-mentioned characteristics regarding the particle size are satisfied.

As the binder, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof can be used. As the thermoplastic resin, those having a glass transition temperature of −100 to 150 ° C., a number average molecular weight of 1,000 to 200,000, preferably 10,000 to 100,000, and a polymerization degree of about 50 to 1000 are used. can do.

  Examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, There are polymers or copolymers containing vinyl ether as a structural unit, polyurethane resins, and various rubber resins. Thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, acrylic reactive resins, formaldehyde resins, silicone resins, epoxy-polyamide resins, polyester resins. And a mixture of an isocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, a mixture of a polyurethane and a polyisocyanate, and the like. These resins are described in detail in “Plastic Handbook” published by Asakura Shoten. It is also possible to use a known electron beam curable resin for each layer. These examples and their production methods are described in detail in JP-A No. 62-256219. The above resins can be used alone or in combination, but preferred are polyurethane resins, vinyl chloride resins, vinyl chloride vinyl acetate copolymers, vinyl chloride vinyl acetate vinyl alcohol copolymers, vinyl chloride vinyl acetate maleic anhydride copolymers. A combination of at least one selected from coalesce and a polyurethane resin, or a combination of these with a polyisocyanate may be mentioned. The resin used as the binder can be synthesized by a known method or can be obtained as a commercial product.

As the structure of the polyurethane resin, known structures such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all binding agents indicated herein, if necessary in order to obtain more excellent dispersibility and _{durability, -COOM, -SO 3 M, -OSO} 3 M, -P = O (OM) 2, - O—P═O (OM) ₂ (wherein M is a hydrogen atom or an alkali metal base), —OH, —NR ₂ , —N ⁺ R ₃ (R is a hydrocarbon group), epoxy group, —SH, — It is preferable to use one in which at least one polar group selected from CN and the like is introduced by copolymerization or addition reaction. The amount of such a polar group is, for example, 10 ⁻¹ to 10 ⁻⁸ mol / g, preferably 10 ⁻² to 10 ⁻⁶ mol / g. The surface modifier of the present invention is preferably used in combination with a sulfonic acid (salt) group-containing binder from the viewpoint of affinity with the binder. In the present invention, the sulfonic acid (salt) group includes a sulfonic acid group (—SO ₃ H) and a sulfonic acid group (SO ₃ M ^′ : M ^′ is an alkali metal atom such as lithium, sodium, or potassium). .

  In the coating liquid for forming a magnetic layer, a binder can be used in the range of, for example, 5 to 50% by mass, preferably 10 to 30% by mass, based on the magnetic powder. It is preferable to use a combination of 5 to 30% by mass when using a vinyl chloride resin, 2 to 20% by mass when using a polyurethane resin, and 2 to 20% by mass of polyisocyanate. However, for example, when head corrosion occurs due to a small amount of dechlorination, it is possible to use only polyurethane or only polyurethane and isocyanate.

  Examples of polyisocyanates include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate and the like. Moreover, the product of these isocyanates and polyalcohol, the polyisocyanate produced | generated by condensation of isocyanate, etc. can be used. These isocyanates are commercially available, and can be used for each layer alone or in combination of two or more using the difference in curing reactivity.

  As described above, since compound A has two or more hydroxyl groups in one molecule, a urethane bond can be formed by reaction with an isocyanate compound. As an isocyanate compound that is preferably used in combination with the modifier of the present invention from the viewpoint of forming a urethane bond and increasing the coating film strength, a polyfunctional isocyanate compound having two or more functions can be exemplified. Specific examples thereof are as described above. In addition, by using an isocyanate compound as a binder component of the coating solution for forming a nonmagnetic layer, which will be described later, the lower-layer isocyanate compound migrates to the magnetic layer located in the upper layer and is adsorbed on the surface of the ferromagnetic powder. It is also possible to obtain the above action by reacting with the containing compound.

  In addition to the surface modifier, magnetic powder, and binder, an additive may be added to the magnetic layer forming coating solution as necessary. Examples of the additive include an abrasive, a lubricant, an antifungal agent, an antistatic agent, an antioxidant, a solvent, carbon black and the like that are generally used in a coating solution for forming a magnetic layer of a magnetic recording medium.

  Known organic solvents can be used. As the organic solvent, specifically, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran, etc., methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, in any ratio Alcohols such as methylcyclohexanol, esters such as methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, benzene, toluene, xylene , Aromatic hydrocarbons such as cresol, chlorobenzene, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethyl Nkuroruhidorin, chlorinated hydrocarbons such as dichlorobenzene, N, N- dimethylformamide, may be used hexane.

  The organic solvent is not necessarily 100% pure, and may contain impurities such as isomers, unreacted materials, by-products, decomposition products, oxides, and moisture in addition to the main components. These impurities are preferably 30% by mass or less, more preferably 10% by mass or less. In order to improve the dispersibility, it is preferable that the polarity is somewhat strong, and it is preferable that 50% by mass or more of the solvent having a dielectric constant of 15 or more is included in the solvent composition. Moreover, it is preferable that a solubility parameter is 8-11.

  The magnetic layer can be formed by coating and drying the prepared coating solution for forming a magnetic layer directly on the nonmagnetic support or via another layer. Prior to application of the magnetic layer forming coating solution, a nonmagnetic layer forming coating solution containing a nonmagnetic powder and a binder may be applied onto the nonmagnetic support. Thereby, a magnetic recording medium having a nonmagnetic layer and a magnetic layer in this order on the nonmagnetic support can be obtained.

The method for producing a magnetic recording medium of the present invention uses a magnetic layer forming coating solution and / or a nonmagnetic layer forming coating solution containing the surface modifier of the present invention. By adding the surface modifier of the present invention to the coating solution for forming the nonmagnetic layer, the surface of the nonmagnetic powder is modified to improve the adsorptivity between the nonmagnetic powder and the binder in the nonmagnetic layer. Dispersibility can be improved.
Hereinafter, the coating liquid for forming the nonmagnetic layer will be described in more detail.

Preparation of coating solution for forming nonmagnetic layer A coating solution for forming a nonmagnetic layer can be obtained by mixing a nonmagnetic powder, a binder, and optionally used additives. By adding, the surface of the nonmagnetic powder can be modified, the adsorptivity between the nonmagnetic powder and the binder in the nonmagnetic layer can be increased, and the dispersibility of the nonmagnetic powder can be increased.

  The nonmagnetic powder may be an inorganic substance or an organic substance. Carbon black or the like can also be used. Examples of the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. In terms of the surface modification effect, application to nonmagnetic metal powder is effective.

Specifically, titanium oxide such as titanium dioxide, cerium oxide, tin oxide, tungsten oxide, ZnO, ZrO ₂ , SiO ₂ , Cr ₂ O ₃ , α-alumina, β-alumina having an α conversion of 90 to 100%, γ-alumina, α-iron oxide, goethite, corundum, silicon nitride, titanium carbide, magnesium oxide, boron nitride, molybdenum disulfide, copper oxide, MgCO ₃ , CaCO ₃ , BaCO ₃ , SrCO ₃ , BaSO ₄ , silicon carbide Titanium carbide or the like can be used alone or in combination of two or more. Preferred are α-iron oxide and titanium oxide.

  The shape of the nonmagnetic powder may be any of acicular, spherical, polyhedral and plate shapes. The crystallite size of the nonmagnetic powder is preferably 4 nm to 500 nm, more preferably 40 to 100 nm. These nonmagnetic powders preferably have an average particle size of 5 nm to 500 nm, more preferably 10 to 200 nm. The non-magnetic powder having the above size is suitable as a non-magnetic powder for use in a non-magnetic layer coating solution for a high-density recording magnetic recording medium that requires high surface smoothness. According to the surface modifier of the present invention, the nonmagnetic powder of the above size can be well dispersed in the nonmagnetic coating material.

The specific surface area of the nonmagnetic powder is, for example, 1 to 150 m ² / g, preferably 20 to 120 m ² / g, and more preferably 50 to 100 m ² / g. A specific surface area in the range of 1 to 150 m ² / g is preferable because a magnetic recording medium having a suitable surface roughness can be formed and can be dispersed with a desired amount of binder. The oil absorption using dibutyl phthalate (DBP) is, for example, 5 to 100 ml / 100 g, preferably 10 to 80 ml / 100 g, and more preferably 20 to 60 ml / 100 g. The specific gravity is, for example, 1 to 12, preferably 3 to 6. The tap density is, for example, 0.05 to 2 g / ml, preferably 0.2 to 1.5 g / ml. When the tap density is in the range of 0.05 to 2 g / ml, there are few particles to be scattered, the operation is easy, and there is a tendency that it is difficult to adhere to the apparatus. The pH of the non-magnetic powder is preferably 2 to 11, and particularly preferably 6 to 9. When the pH is in the range of 2 to 11, it is possible to prevent the friction coefficient from increasing due to high temperature, high humidity, or liberation of fatty acids. The water content of the nonmagnetic powder is, for example, 0.1 to 5% by mass, preferably 0.2 to 3% by mass, and more preferably 0.3 to 1.5% by mass. A water content in the range of 0.1 to 5% by mass is preferable because the dispersion is good and the viscosity of the paint after dispersion is stable. The ignition loss is preferably 20% by mass or less, and the ignition loss is preferably small.

When the nonmagnetic powder is an inorganic powder, the Mohs hardness is preferably 4-10. If the Mohs hardness is in the range of 4 to 10, the durability of the magnetic recording medium can be ensured. The stearylamine adsorption amount of the nonmagnetic powder is preferably 1 to 20 μmol / m ² , more preferably ² to 15 μmol, from the viewpoint of enhancing the dispersibility of the nonmagnetic powder when used in combination with the surface modifier of the present invention. / M ² . The heat of wetting of the nonmagnetic powder into water at 25 ° C. is preferably in the range of 200 to 600 erg / cm ² (200 to 600 mJ / m ² ). Moreover, the solvent which exists in the range of this heat of wetting can be used. The amount of water molecules on the surface at 100 to 400 ° C. is suitably 1 to 10 / 100Å. The pH of the isoelectric point in water is preferably between 3 and 9. It is preferable that Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , and ZnO are present on the surface of these nonmagnetic powders by surface treatment. Particularly preferred dispersibility _{Al 2 O 3, SiO 2,} TiO 2, is a ZrO _2, further preferred is _{Al 2 O 3, SiO 2,} ZrO 2. These may be used in combination or may be used alone. Further, a surface-treated layer co-precipitated according to the purpose may be used, or a method of treating the surface layer with silica after first treating with alumina, or vice versa may be employed. The surface treatment layer may be a porous layer depending on the purpose, but it is generally preferable that the surface treatment layer is homogeneous and dense.

  Specific examples of the non-magnetic powder include, for example, Showa Denko Nano Tight, Sumitomo Chemical HIT-100, ZA-G1, Toda Kogyo DPN-250, DPN-250BX, DPN-245, DPN-270BX, DPB-550BX, DPN-550RX, Ishihara Sangyo Titanium oxide TTO-51B, TTO-55A, TTO-55B, TTO-55C, TTO-55S, TTO-55D, SN-100, MJ-7, α-iron oxide E270 , E271, E300, STT-4D, STT-30D, STT-30, STT-65C manufactured by Titanium Industry, MT-100S, MT-100T, MT-100T, MT-150W, MT-500B, T-600B, T-100F T-500HD etc. are mentioned. FINEX-25, BF-1, BF-10, BF-20, ST-M, Dowa Mining DEFIC-Y, DEFIC-R, Nippon Aerosil AS2BM, TiO2P25, Ube Industries 100A, 500A, Titanium Industry Y-LOP manufactured and the thing which baked it are mentioned. Particularly preferred nonmagnetic powders are titanium dioxide and α-iron oxide.

  The details of the binder added to the non-magnetic paint are the same as the binder contained in the magnetic paint of the present invention. The nonmagnetic paint may further contain various additives and solvents used for magnetic recording media. Details of each component in the coating solution for forming a nonmagnetic layer, a mixing method thereof, an addition amount, and the like are the same as those described above regarding the coating solution for forming a magnetic layer.

Nonmagnetic support As nonmagnetic support, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, cellulose triacetate, polycarbonate, polyamide, polyimide, polyamideimide, polysulfone, aromatic polyamide, polybenzoxazole and the like are known. Can be used. It is preferable to use a support having a glass transition temperature of 100 ° C. or higher, and it is particularly preferable to use a high-strength support such as polyethylene naphthalate or aramid. Moreover, in order to change the surface roughness of a magnetic surface and a base surface as needed, the laminated type support body as shown in Unexamined-Japanese-Patent No. 3-224127 can also be used. These supports may be subjected in advance to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, and the like.

As the non-magnetic support, the center surface average surface roughness (Ra) measured with a light interference type surface roughness meter HD-2000 manufactured by WYKO is 8.0 nm or less, preferably 4.0 nm or less, more preferably 2. It is preferable to use one having a thickness of 0 nm or less. These supports preferably have not only a small center plane average surface roughness (Ra) but also no coarse protrusions of 0.5 μm or more. The surface roughness shape is freely controlled by the size and amount of filler added to the support as required. Examples of these fillers include organic fine powders such as acrylic, in addition to oxides and carbonates such as Ca, Si, and Ti. The maximum height Rmax of the support is 1 μm or less, the ten-point average roughness Rz is 0.5 μm or less, the center surface mountain height Rp is 0.5 μm or less, the center surface valley depth Rv is 0.5 μm or less, and the center surface area ratio Sr is preferably 10% or more and 90% or less, and the average wavelength λa is preferably 5 μm or more and 300 μm or less. In order to obtain the desired electromagnetic conversion characteristics and durability, the surface protrusion distribution of these supports can be arbitrarily controlled by fillers, each having a size of 0.01 μm to 1 μm, 0 pieces per 0.1 mm ² Can be controlled in the range of 2,000 to 2,000.

The F-5 value of the support used in the present invention is preferably 5 to 50 kg / mm ² (49 to 490 MPa). The heat shrinkage rate of the support at 100 ° C. for 30 minutes is preferably 3% or less, more preferably 1.5% or less, and the heat shrinkage rate at 80 ° C. for 30 minutes is preferably 1% or less, more preferably 0. .5% or less. Breaking strength 5~100kg / mm ² (49~980MPa), it is preferred that each elastic modulus is 100~2000kg / mm ² (0.98~19.6GPa). The temperature expansion coefficient is preferably 10 ⁻⁴ to 10 ⁻⁸ / ° C., more preferably 10 ⁻⁵ to 10 ⁻⁶ / ° C. The humidity expansion coefficient is preferably 10 ⁻⁴ / RH% or less, more preferably 10 ⁻⁵ / RH% or less. These thermal characteristics, dimensional characteristics, and mechanical strength characteristics are preferably substantially equal with a difference within 10% in each in-plane direction of the support.

  In the method for producing a magnetic recording medium of the present invention, an undercoat layer may be provided. By providing the undercoat layer, the adhesive force between the support and the magnetic layer or the nonmagnetic layer can be improved. As an undercoat layer for improving adhesion, a polyester resin soluble in a solvent can be used. As will be described later, a smoothing layer can be provided as an undercoat layer.

Layer structure The thickness structure of the magnetic recording medium produced by the method for producing a magnetic recording medium of the present invention is such that the thickness of the nonmagnetic support is preferably 3 to 80 μm, more preferably 3 to 50 μm, particularly preferably 3 to 10 μm. is there. When an undercoat layer is provided between the nonmagnetic support and the nonmagnetic layer or the magnetic layer, the thickness of the undercoat layer is, for example, 0.01 to 0.8 μm, preferably 0.02 to 0.6 μm.

In addition, an intermediate layer for smoothing can be provided between the support and the nonmagnetic layer or magnetic layer, and between the support and the backcoat layer. For example, the surface of the nonmagnetic support contains a polymer. Apply and dry the applied coating solution, or apply a coating solution containing a compound having a radiation curable functional group in the molecule (radiation curable compound), and then irradiate with radiation to cure the coating solution Can be formed.
The number average molecular weight of the radiation curable compound is preferably in the range of 200 to 2,000. When the molecular weight is within this range, the molecular weight is relatively low, so that the coating film is easy to flow in the calendar process, has high moldability, and a smooth coating film can be formed.
Preferred as the radiation curable compound is a bifunctional acrylate compound having a molecular weight of 200 to 2000, and more preferred are acrylics such as bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, and these alkylene oxide adducts. Acid and methacrylic acid are added.

The radiation curable compound may be used in combination with a polymer-type binder. Examples of the binder used in combination include conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof. When ultraviolet rays are used as radiation, it is preferable to use a polymerization initiator in combination. As the polymerization initiator, known radical photopolymerization initiators, cationic photopolymerization initiators, photoamine generators, and the like can be used.
The radiation curable compound can also be used for the nonmagnetic layer.

  The thickness of the magnetic layer is optimized according to the saturation magnetization amount, head gap length, and recording signal band of the magnetic head to be used, but is generally 10 to 150 nm, preferably 20 to 120 nm, and more preferably. Is 30 to 100 nm, particularly preferably 30 to 80 nm. Further, the thickness variation rate (σ / δ) of the magnetic layer is preferably within ± 50%, and more preferably within ± 30%. There may be at least one magnetic layer, and the magnetic layer may be separated into two or more layers having different magnetic characteristics, and a configuration related to a known multilayer magnetic layer can be applied.

  The thickness of the nonmagnetic layer is, for example, 0.1 to 3.0 μm, preferably 0.2 to 2.0 μm, and more preferably 0.3 to 1.5 μm. In the present invention, the non-magnetic layer exhibits its effect if it is substantially non-magnetic. For example, the effect of the present invention can be achieved even if impurities are included or a small amount of magnetic material is intentionally included. It can be considered that the configuration is substantially the same as that of the magnetic recording medium of the present invention. Note that “substantially the same” means that the residual magnetic flux density of the nonmagnetic layer is 10 mT or less or the coercive force is 7.96 kA / m (100 Oe) or less, and preferably has no residual magnetic flux density and coercive force. Means.

Back Coat Layer According to the method for producing a magnetic recording medium of the present invention, a magnetic recording medium having a back coat layer on the surface opposite to the surface having the magnetic layer of the nonmagnetic support can be formed. The back coat layer preferably contains carbon black and inorganic powder. It is also possible to add the surface modifier of the present invention to the backcoat layer, and by adding it, the adsorptivity of the powder and binder in the backcoat layer can be increased and the dispersibility of the powder can be increased. Details of the addition amount, addition method, and the like of the surface modifier of the present invention in this case are the same as described above for the coating solution for forming the magnetic layer.

  As the binder and various additives for the backcoat layer, the formulation of the magnetic layer and the nonmagnetic layer can be applied. It is particularly preferable to apply the prescription for the nonmagnetic layer. The thickness of the back coat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm.

  Details of preferable physical properties and the like of the magnetic recording medium manufactured by the manufacturing method of the present invention are as described later for the magnetic recording medium of the present invention.

  The method for preparing the coating solution for forming the magnetic layer is as described above. A coating solution for forming other layers such as a nonmagnetic layer and a backcoat layer can be prepared in the same manner.

  In the manufacturing process of the magnetic recording medium, for example, a nonmagnetic layer coating liquid is applied to the surface of a nonmagnetic support under running so as to have a predetermined film thickness, and then a nonmagnetic layer is formed thereon. Then, the magnetic layer is formed by applying the magnetic layer so that the magnetic layer coating solution has a predetermined thickness. A plurality of magnetic layer coating solutions may be applied sequentially or simultaneously, and a nonmagnetic layer coating solution and a magnetic layer coating solution may be applied sequentially or simultaneously. The coating machine for applying the magnetic layer coating liquid or the nonmagnetic layer coating liquid includes air doctor coat, blade coat, rod coat, extrusion coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure A coat, a kiss coat, a cast coat, a spray coat, a spin coat, etc. can be used. As for these, for example, “Latest Coating Technology” (May 31, 1983) issued by General Technology Center Co., Ltd. can be referred to.

  In the case of a magnetic tape, the magnetic layer coating liquid coating layer may be subjected to magnetic field orientation treatment using a cobalt magnet or solenoid on the ferromagnetic powder contained in the magnetic layer coating liquid coating layer. In the case of a disk, a sufficiently isotropic orientation may be obtained even without non-orientation without using an orientation device, but known random methods such as alternately arranging cobalt magnets obliquely and applying an alternating magnetic field with a solenoid. It is preferable to use an alignment device. In the case of a ferromagnetic metal powder, the isotropic orientation is generally preferably in-plane two-dimensional random, but can also be three-dimensional random with a vertical component. Further, isotropic magnetic characteristics can be imparted in the circumferential direction by using a well-known method such as a counter-polarized magnet and making it vertically oriented. In particular, when performing high density recording, vertical alignment is preferable. Moreover, circumferential orientation can also be achieved using spin coating.

  It is preferable that the drying position of the coating film can be controlled by controlling the temperature, air volume, and coating speed of the drying air, the coating speed is preferably 20 m / min to 1000 m / min, and the temperature of the drying air is preferably 60 ° C. or higher. . Moreover, moderate preliminary drying can also be performed before entering a magnet zone. As described above, the reaction product produced after the surface modifier of the present invention contacts and reacts with the powder surface can be removed by a drying process.

The coating raw material thus obtained is usually wound once by a winding roll, and then unwound from the winding roll and then subjected to a calendering process.
For the calendar process, for example, a super calendar roll or the like can be used. The calendering improves the surface smoothness and eliminates the voids generated by the removal of the solvent during drying and improves the filling rate of the ferromagnetic powder in the magnetic layer. Obtainable. The step of calendering is preferably performed while changing the calendering conditions according to the smoothness of the surface of the coating raw material.

  The surface smoothness of the coating raw material can be achieved by controlling the calender roll temperature, the calender roll speed, and the calender roll tension. In consideration of the characteristics of the coating type medium, it is preferable to control the calender roll pressure and the calender roll temperature. By decreasing the calender roll pressure or lowering the calender roll temperature, the surface smoothness of the final product is lowered. Conversely, increasing the calender roll pressure or the calender roll temperature increases the surface smoothness of the final product.

  Apart from this, the magnetic recording medium obtained after the calendering process can be thermo-processed to allow thermosetting to proceed. Such thermo treatment may be appropriately determined depending on the formulation of the magnetic layer coating solution, and is, for example, 35 to 100 ° C, and preferably 50 to 80 ° C. The thermo treatment time is 12 to 72 hours, preferably 24 to 48 hours.

  As the calender roll, a heat-resistant plastic roll such as epoxy, polyimide, polyamide, polyamideimide or the like can be used. Moreover, it can also process with a metal roll.

  As the calendering conditions, the temperature of the calender roll can be set in the range of, for example, 60 to 100 ° C., preferably in the range of 70 to 100 ° C., and particularly preferably in the range of 80 to 100 ° C. It is in the range of 500 kg / cm (98 to 490 kN / m), preferably in the range of 200 to 450 kg / cm (196 to 441 kN / m), particularly preferably in the range of 300 to 400 kg / cm (294 to 392 kN / m). It can be. Moreover, in order to improve the smoothness of the magnetic layer surface, the nonmagnetic layer surface can be calendered. The calendar treatment for the nonmagnetic layer is also preferably performed under the above conditions.

  The obtained magnetic recording medium can be cut into a desired size using a cutting machine or the like. The cutting machine is not particularly limited, but is preferably provided with a plurality of pairs of rotating upper blades (male blades) and lower blades (female blades). The slitting speed, the engagement depth, and the upper blade (male blade) are appropriately selected. The peripheral speed ratio (upper blade peripheral speed / lower blade peripheral speed) of the blade and the lower blade (female blade), the continuous use time of the slit blade, and the like can be selected.

[Magnetic recording medium]
Furthermore, the present invention provides a magnetic recording medium having a magnetic layer containing a ferromagnetic powder and a binder on a nonmagnetic support, or a nonmagnetic layer containing a nonmagnetic powder and a binder, and a ferromagnetic powder and a binder. The present invention relates to a magnetic recording medium having a magnetic layer including the magnetic layers in this order and manufactured by the above-described method for manufacturing a magnetic recording medium of the present invention. Details of each component and preferred physical properties of each layer included in the magnetic recording medium of the present invention are as described above.
Hereinafter, physical characteristics of the magnetic recording medium of the present invention will be described.

The surface roughness of the physical property magnetic layer is preferably in the range of 1.0 to 3.0 nm as the center line average roughness. When the center line average roughness of the magnetic layer is 3.0 nm or less, better electromagnetic conversion characteristics can be obtained, and when it is 1.0 nm or more, stable running is increased. Further, the center line average roughness of the magnetic layer is preferably 1.5 to 3.0 nm, and more preferably 1.5 to 2.5 nm. By using the surface modifier of the present invention, a magnetic layer excellent in surface smoothness can be formed. Further, the particle size of the ferromagnetic powder, the dispersion condition of the magnetic layer coating solution, the calendar condition, the nonmagnetic support The surface smoothness of the magnetic layer can also be controlled by adjusting the amount of filler in the body and using an undercoat layer for smoothing.

  The coercive force (Hc) of the magnetic layer is preferably 143.2 to 318.3 kA / m (1800 to 4000 Oe), more preferably 159.2 to 278.5 kA / m (2000 to 3500 Oe). The coercive force distribution is preferably narrow, and SFD and SFDr are 0.8 or less, more preferably 0.5 or less.

The friction coefficient with respect to the head of the magnetic recording medium of the present invention is, for example, 0.50 or less, preferably 0.3 or less, in the temperature range of −10 to 40 ° C. and humidity of 0 to 95%. The surface resistivity is preferably 10 ⁴ to 10 ⁸ Ω / sq of the magnetic surface, and the charging position is preferably within −500 V to +500 V. The elastic modulus at 0.5% elongation of the magnetic layer is preferably 0.98 to 19.6 GPa (100 to 2000 kg / mm ² ) in each in-plane direction, and the breaking strength is preferably 98 to 686 MPa (10 to 70 kg). / Mm ² ), the elastic modulus of the magnetic recording medium is preferably 0.98 to 14.7 GPa (100 to 1500 kg / mm ² ) in each in-plane direction, and the residual spread is preferably 0.5% or less, 100 ° C. The thermal shrinkage at any of the following temperatures is preferably 1% or less, more preferably 0.5% or less, and most preferably 0.1% or less.

The glass transition temperature of the magnetic layer (the maximum point of the loss elastic modulus of the dynamic viscoelasticity measurement measured at 110 Hz by a dynamic viscoelasticity measuring device (for example, Leo Vibron)) is preferably 50 to 180 ° C., and that of the nonmagnetic layer is 0-180 degreeC is preferable. The loss elastic modulus is preferably in the range of 1 × 10 ⁷ to 8 × 10 ⁸ Pa (1 × 10 ⁸ to 8 × 10 ⁹ dyne / cm ² ), and the loss tangent is preferably 0.2 or less. If the loss tangent is too large, adhesion failure is likely to occur. These thermal characteristics and mechanical characteristics are preferably almost equal within 10% in each in-plane direction of the medium.

The residual solvent contained in the magnetic layer is preferably 100 mg / m ² or less, more preferably 10 mg / m ² or less. The porosity of the coating layer is preferably 40% by volume or less, more preferably 30% by volume or less for both the nonmagnetic layer and the magnetic layer. The porosity is preferably small in order to achieve high output, but it may be better to ensure a certain value depending on the purpose. For example, in the case of a disk medium in which repeated use is important, a larger void ratio is often preferable for running durability.

  In the magnetic recording medium of the present invention, these physical characteristics can be changed between the nonmagnetic layer and the magnetic layer according to the purpose. For example, the elastic modulus of the magnetic layer can be increased to improve running durability, and at the same time, the elastic modulus of the nonmagnetic layer can be made lower than that of the magnetic layer to improve the contact of the magnetic recording medium with the head.

[Magnetic paint, non-magnetic paint]
Furthermore, this invention relates to the magnetic coating material containing the modifier for powders of this invention, magnetic powder, and a binder. In the magnetic coating material of the present invention, the adsorptivity between the magnetic powder and the binder is improved by the action of the surface modifying agent, whereby the magnetic powder can be highly dispersed. The details of the magnetic coating material of the present invention are as described above for the coating solution for forming a magnetic layer, and the magnetic coating material of the present invention is preferably used as a coating solution for forming a magnetic layer of a magnetic recording medium.

  Furthermore, this invention relates to the nonmagnetic coating material containing the modifier for powders of this invention, nonmagnetic powder, and a binder. The nonmagnetic coating material of the present invention has a good adsorptivity between the nonmagnetic powder and the binder due to the action of the surface modifier, whereby the nonmagnetic powder can be highly dispersed. The details of the nonmagnetic paint of the present invention are as described above for the coating liquid for forming a nonmagnetic layer, and the nonmagnetic paint of the present invention is preferably used as a coating liquid for forming a nonmagnetic layer of a magnetic recording medium.

  Hereinafter, the present invention will be described more specifically with reference to examples. It should be noted that the components, ratios, operations, order, and the like shown here can be changed without departing from the spirit of the present invention, and should not be limited to the following examples. “Part” described below indicates “part by mass”.

Details of polymers A to D used in the following examples are shown below.
Polymer A
Polyester polyurethane containing 3.3 × 10 ⁻⁴ mol / g SO ₃ Na groups. The polyester part contains adipic acid and neopentyl glycol, and 4,4′-diphenylmethane diisocyanate is used as the urethane component. The mass average molecular weight (Mw) calculated | required in standard polystyrene conversion using the DMF solvent containing 0.3 mass% lithium bromide is about 70000.
Polymer B
A mixed polymer obtained by mixing a polyester polyurethane containing SO ₃ Na groups of 0.6 × 10 ⁻⁴ mol / g and a vinyl chloride resin (MR-104 manufactured by Nippon Zeon Co., Ltd.) in a ratio of 1.2: 1. Polyurethane contains adipic acid and neopentyl glycol at the polyester site and uses 4,4′-diphenylmethane diisocyanate as a urethane component. The mass average molecular weight (Mw) calculated | required in standard polystyrene conversion using the DMF solvent containing 0.3 mass% lithium bromide is about 70000.
Polymer C
A mixed polymer in which a polyether polyurethane containing SO ₃ Na groups of 0.6 × 10 ⁻⁴ mol / g and a vinyl chloride resin (MR-104 manufactured by Nippon Zeon Co., Ltd.) are mixed at a ratio of 1.2: 1. Polyurethane contains a propylene glycol adduct of bisphenol A at the polyether moiety and uses 4,4′-diphenylmethane diisocyanate as a urethane component. The mass average molecular weight (Mw) calculated | required in standard polystyrene conversion using the DMF solvent containing 0.3 mass% lithium bromide is about 70000.
Polymer D
A mixed polymer in which a polyester polyurethane containing SO ₃ Na groups of 0.7 × 10 ⁻⁴ mol / g and a vinyl chloride resin (MR-104 manufactured by Nippon Zeon Co., Ltd.) are mixed at a ratio of 1.2: 1. Polyurethane contains phthalic acid and propylene glycol at the polyester site and uses 4,4′-diphenylmethane diisocyanate as a urethane component. The mass average molecular weight (Mw) calculated | required in standard polystyrene conversion using the DMF solvent containing 0.3 mass% lithium bromide is about 70000.

1. Examples and comparative examples using ferromagnetic hexagonal ferrite powder

[Example 1]
(1) Production of magnetic coating material 2.2 parts by mass of the following ferromagnetic hexagonal ferrite powder, 1 part by mass of SO ₃ Na group-containing polymer B, 0.18 parts by mass of D-glucono-1,5-lactone, 1-naphthoic acid 0.12 parts by mass was suspended in a solution consisting of 3.3 parts by mass of cyclohexanone and 4.9 parts by mass of 2-butanone. 27 parts by mass of zirconia beads (manufactured by Nikkato) was added to the suspension and dispersed for 6 hours to obtain a magnetic paint 1. 0.06 parts by mass of trifunctional isocyanate (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) was added to the magnetic coating material 1, and further dispersed for 10 minutes to obtain the magnetic coating material 2.
Ferromagnetic hexagonal barium ferrite powder Composition excluding oxygen (molar ratio): Ba / Fe / Co / Zn = 1/9 / 0.2 / 1
Hc: 176 kA / m (2200 Oe), average plate diameter: 25 nm, average plate ratio: 3
BET specific surface area: 65m ² / g
σs: 49 A · m ² / kg (49 emu / g)
pH: 7

(2) Confirmation of adsorptivity to magnetic powder The abundance ratio of the binder (polymer B) in the magnetic coating 1 obtained in (1) above in the powder surface / paint was measured by the following method.
[Measuring method]
The powder and the solution were centrifuged under conditions of 100,000 rpm and 80 minutes in a Hitachi separation microcentrifuge CS150GXL. 3 ml of the supernatant was weighed and the mass was measured. After drying at 40 ° C. for 18 hours, it was dried at 140 ° C. for 3 hours under vacuum. The mass of the dried product was defined as the binder non-adsorbed solid content, and the abundance ratio of the binder in the powder surface / paint was calculated.

(3) Production and Evaluation of Magnetic Sheet Magnetic sheet 2 was produced by applying magnetic coating 2 obtained in (1) above and drying it at 70 ° C. for 2 days. The gloss of the produced magnetic sheet was measured using GK-45D manufactured by Suga Test Instruments Co., Ltd. The higher the gloss value, the better the dispersibility of the ferromagnetic powder in the magnetic paint. 1 part by mass of the obtained magnetic sheet was immersed in 100 parts by mass of tetrahydrofuran (THF) and extracted under the conditions of 70 ° C./3 hours, and then the mass of the concentrated solid product obtained by concentrating and drying THF with an evaporator was measured. The mass of the concentrated dried product thus measured was defined as the mass of the sol, and the mass of the gel was determined as (mass of magnetic sheet−mass of sol). The ratio of gel content / sol content is shown in Table 1. It shows that there are many hardened | cured parts and coating-film intensity | strength is so high that there are many gel contents.

[Example 2]
Production and evaluation of magnetic paint and magnetic sheet were carried out in the same manner as in Example 1 except that the polymer used was changed from 1 part by mass of SO ₃ Na group-containing polymer B to 1 part by mass of SO ₃ Na group-containing polymer C. went.

[Example 3]
Production and evaluation of magnetic paint and magnetic sheet were carried out in the same manner as in Example 1 except that the polymer used was changed from 1 part by mass of SO ₃ Na group-containing polymer B to 1 part by mass of SO ₃ Na group-containing polymer D. went.

[Example 4]
A magnetic paint and a magnetic sheet were prepared and evaluated in the same manner as in Example 1 except that 1 part by weight of 1-naphthoic acid was changed to 1 part by weight of oleic acid.

[Example 5]
The magnetic coating material and the magnetic sheet were prepared and evaluated in the same manner as in Example 2 except that 1-naphthoic acid was changed to 1 part by mass and the oleic acid was changed to 1 part by mass.

[Example 6]
A magnetic paint and a magnetic sheet were prepared and evaluated in the same manner as in Example 3 except that 1 part by weight of 1-naphthoic acid was changed to 1 part by weight of oleic acid.

[Comparative Example 1]
A magnetic paint and a magnetic sheet were prepared and evaluated in the same manner as in Example 1 except that D-glucono-1,5-lactone and 1-naphthoic acid were not used.

[Comparative Example 2]
A magnetic paint and a magnetic sheet were prepared and evaluated in the same manner as in Example 2 except that D-glucono-1,5-lactone and 1-naphthoic acid were not used.

[Comparative Example 3]
A magnetic paint and a magnetic sheet were prepared and evaluated in the same manner as in Example 3 except that D-glucono-1,5-lactone and 1-naphthoic acid were not used.

  The above evaluation results are shown in Table 1 below.

2. Examples and comparative examples using non-magnetic powder

[Example 7]
4.9 parts by mass of the following nonmagnetic powder, 1 part by mass of sulfonic acid group-containing polymer A, 0.18 parts by mass of D-erythronolactone, 0.15 parts by mass of cinnamic acid, 5.4 parts by mass of cyclohexanone, 2-butanone It was made to suspend in the solution which consists of 9.6 mass parts. 27 parts by mass of zirconia beads (Nikkato) was added to the suspension and dispersed for 6 hours to obtain a non-magnetic coating material 1. 0.06 parts by mass of trifunctional polyisocyanate (Nihon Polyurethane Co., Ltd. Coronate L) was added to Nonmagnetic Paint 1 and dispersed for 10 minutes to obtain Nonmagnetic Paint 2. Evaluation of the nonmagnetic paint 1 and production / evaluation of the nonmagnetic sheet were performed by the above-described method.
Nonmagnetic powder α-iron oxide Surface treatment layer: Al ₂ O ₃ , SiO ₂
Average long axis length: 0.15 μm
Average needle ratio: 7
Specific surface area by BET method: 52 m ² / g
pH: 8

[Example 8]
Production of nonmagnetic paint and nonmagnetic sheet in the same manner as in Example 7 except that the polymer used was changed from 1 part by mass of SO ₃ Na group-containing polymer A to 1 part by mass of SO ₃ Na group-containing polymer B. Evaluation was performed.

[Example 9]
Production of nonmagnetic paint and nonmagnetic sheet in the same manner as in Example 7 except that the polymer used was changed from 1 part by mass of SO ₃ Na group-containing polymer A to 1 part by mass of SO ₃ Na group-containing polymer C. Evaluation was performed.

[Example 10]
Production of nonmagnetic paint and nonmagnetic sheet in the same manner as in Example 7 except that the polymer used was changed from 1 part by mass of SO ₃ Na group-containing polymer A to 1 part by mass of SO ₃ Na group-containing polymer D. Evaluation was performed.

[Comparative Example 4]
A nonmagnetic paint and a nonmagnetic sheet were prepared and evaluated in the same manner as in Example 7 except that D-erythronolactone and cinnamic acid were not used.

[Comparative Example 5]
A nonmagnetic paint and a nonmagnetic sheet were prepared and evaluated in the same manner as in Example 8 except that D-erythronolactone and cinnamic acid were not used.

[Comparative Example 6]
A nonmagnetic paint and a nonmagnetic sheet were prepared and evaluated in the same manner as in Example 9 except that D-erythronolactone and cinnamic acid were not used.

[Comparative Example 7]
A nonmagnetic paint and a nonmagnetic sheet were prepared and evaluated in the same manner as in Example 10 except that D-erythronolactone and cinnamic acid were not used.

  The above evaluation results are shown in Table 2 below.

From Table 1 and Table 2, the following points could be confirmed from comparison between Examples and Comparative Examples using the same binder.
(1) By using Compound A and Compound B, the surface of the powder was modified and the binder adsorption amount could be increased. Increasing the amount of binder adsorbed to the powder in the paint leads to an improvement in the dispersibility of the powder. Therefore, the combination of compound A and compound B used in the examples functions as a dispersant in magnetic paints and non-magnetic paints. We were able to confirm that
(2) Since the sheet produced in the example showed higher glossiness than the sheet produced in the comparative example, the combination of compound A and compound B used in the example showed an effect of increasing the dispersibility of the powder. I understand that.
(3) Since the gel content of the sheet produced in the example was greater than the gel content of the magnetic sheet produced in the comparative example, the sheet produced in the example had a coating film strength higher than that of the sheet produced in the comparative example. It was confirmed that it was expensive. It is thought that the hydroxyl group contained in the compound A used in the Examples formed a crosslinked structure with the isocyanate group of the isocyanate, which contributed to the improvement of the coating film strength.

3. Example / Comparative Example of Magnetic Tape Production [Example 11]
(1) Production of magnetic paint 4.5 parts of the following ferromagnetic metal powder, 0.68 part of sulfonic acid group-containing polyurethane (-SO ₃ Na group content: 0.6 × 10 ⁻⁴ mol / g), vinyl chloride 0.32 part of polymer (-SO ₃ K group sulfonic acid group content: 1.2 × 10 ⁻⁴ mol / g), 0.11 part of transcinnamic acid, D-glucono-1,5-lactone 063 parts were suspended in a solution consisting of 6.8 parts cyclohexanone and 6.3 parts 2-butanone. 27 parts of zirconia beads (manufactured by Nikato) were added to the suspension and dispersed for 6 hours. 0.20 part of trifunctional isocyanate (Nihon Polyurethane Co., Ltd. Coronate L) was added and dispersed for 15 minutes to obtain a magnetic coating.
Ferromagnetic metal powder Composition Co / Fe: 23.7 atomic%, Y / Fe: 15.3 atomic%, Al / Fe: 9.3 atomic%
Hc: 194 kA / m (2400 Oe), long axis length: 45 nm, needle ratio: 4.2
BET specific surface area: 67 m ² / g
σs: 110 A · m ² / kg (110 emu / g)
pH: 9

(2) Production of magnetic tape sample A The magnetic coating material was coated on a support made of polyethylene terephthalate having a thickness of 5.0 μm so that the thickness after drying was 0.4 μm, dried, calendered, and thermally stabilized. Sample A was prepared by slitting to a width of ½ mm.

(3) Production of non-magnetic paint
Ingredient 1
Iron oxide powder (particle size: 0.15 μm × 0.02 μm): 70 parts Alumina (α conversion: 50%, particle size: 0.05 μm): 8 parts
Carbon black (particle size: 15 nm): 25 parts
Stearic acid / butyl stearate (50/50 (mass ratio)): 3.0 parts
Vinyl chloride copolymer (containing —SO ₃ Na group: 1.2 × 10 −4 equivalent / g) 10 parts polyester polyurethane resin (Tg: 40 ° C., containing —SO ₃ Na group: 1 × 10 ⁻⁴ equivalent / g) ): 4.4 parts cyclohexanone: 30 parts methyl ethyl ketone: 60 parts
Ingredient 2
Butyl stearate: 3 parts
Oleyl oleate: 5 parts
Cyclohexanone: 40 parts
Methyl ethyl ketone: 60 parts
Toluene: 15 parts
Ingredient 3
Trifunctional isocyanate (Nihon Polyurethane Co., Ltd. Coronate L): 1.5 parts
Cyclohexanone: 8 parts
Methyl ethyl ketone: 18 parts
Toluene: 8 parts

  Among the above components, component 1 is kneaded with a kneader, then component 2 is added and stirred, and then dispersion treatment is performed with a sand mill with a residence time of 90 minutes. A material was prepared.

(4) Production of magnetic tape sample B The nonmagnetic coating material was coated on a support made of 5.0 μm polyethylene terephthalate so that the thickness after drying was 1.0 μm, and the above (1) The magnetic coating material prepared in (1) was applied, dried, calendered, and heat-stabilized, and slit into a 1/2 inch width to prepare Sample B.

[Comparative Example 8]
Directly on the support in the same manner as in Example 1 except that 0.063 part of D-glucono-1,5-lactone used as a magnetic coating component in Example 11 was changed to 0.068 part of citric acid. Sample C to which a magnetic paint was applied and sample D to which a nonmagnetic paint and a magnetic paint were applied were prepared.

[Comparative Example 9]
Sample E in which a magnetic coating was directly applied on a support in the same manner as in Example 11 except that D-glucono-1,5-lactone was not used as a magnetic coating component, and a nonmagnetic coating and a magnetic coating A sample F coated with was prepared.

Evaluation method <Square ratio>
Each sample was cut into a 12 mm x 32 mm test piece and measured using a high-sensitivity magnetization vector measuring machine manufactured by Toei Kogyo Co., Ltd. and a DATA processing device manufactured by the company under the applied magnetic field of 796 kA / m (10 kOe). did.
<Surface roughness of magnetic layer>
Scan Length was measured at 5 μm by scanning white light interferometry using a general-purpose three-dimensional surface structure analyzer NewView 5000 manufactured by ZYGO. The measurement visual field was 350 μm × 260 μm, and the center line average surface roughness Ra was determined.
<Adhesion amount of sapphire blade>
A magnetic surface of a ½ mm wide slit product was brought into contact with the edge of a regular triangular prism made of sapphire at a touch angle of 12 degrees, and the ½ mm wide slit product was run at a tension of 100 g and a speed of 3 m / sec. The amount of deposits adhering to the ridgeline of the sapphire blade was evaluated by microscopic observation.

  Table 3 below shows each evaluation item and the sample to be evaluated.

  The evaluation results are shown in Table 4 below.

  As shown in Table 4, since a smooth magnetic layer could be formed in Example 11, it was confirmed that the dispersibility of the magnetic powder could be improved by the combined use of Compound A and Compound B. The squareness ratio in Example 11 was higher than the squareness ratios in Comparative Examples 8 and 9. Since the squareness ratio tends to increase as the dispersibility of the magnetic powder increases, it was confirmed that the dispersibility of the magnetic powder could be improved by the combined use of Compound A and Compound B from the fact that a high squareness ratio was obtained. it can. Moreover, since the deposit | attachment of the sapphire blade was not confirmed in Example 11, it can confirm that the magnetic layer formed in Example 11 is excellent in coating film strength.

  The surface modifier of the present invention is suitable as a dispersant for magnetic powder and a dispersant for nonmagnetic powder.

Claims (23)

A powdery surface modifying agent comprising the following compound A and compound B:
Compound A: Compound containing a lactone ring having at least one substituent selected from the group consisting of a hydroxyl group and a group containing a hydroxyl group Compound B: an unsaturated bond-containing compound containing a carboxyl group The surface modifier for powder according to claim 1, wherein compound A is a compound represented by the following general formula (I) or (II).

[In General Formula (I), R ^{11 to} R ¹⁶ each independently represent a hydrogen atom or a substituent, and at least one of R ^{11 to} R ¹⁶ represents a hydroxyl group or a group containing a hydroxyl group. ]

[In General Formula (II), R ^{21 to} R ²⁸ each independently represent a hydrogen atom or a substituent, and at least one of R ^{21 to} R ²⁸ represents a hydroxyl group or a group containing a hydroxyl group. ] The surface modifier for powder according to claim 1 or 2, wherein compound A contains two or more hydroxyl groups in one molecule. The surface modifier for powder according to any one of claims 1 to 3, wherein the group containing a hydroxyl group contained in the compound A is an alkyl group containing a hydroxyl group. The surface modifier for powder according to any one of claims 1 to 4, wherein the group containing a hydroxyl group contained in the compound A is a group containing a primary hydroxyl group. Compound B is an unsaturated fatty acid, The surface modifier for powders of any one of Claims 1-5. Compound B is an aromatic compound, The surface modifier for powders of any one of Claims 1-5. The surface modifier for powder according to claim 7, wherein the aromatic compound contains a benzene ring or a naphthalene ring. The surface modifier for powder according to any one of claims 1 to 8, wherein the powder is selected from the group consisting of magnetic powder and nonmagnetic powder. The surface modifier for powder according to claim 9, which is used as a dispersant for magnetic paint or a dispersant for nonmagnetic paint. The surface modifier for powder according to any one of claims 1 to 10, which is used in combination with an isocyanate compound. Preparing a coating solution for forming a magnetic layer by mixing magnetic powder, a binder and the surface modifier for powder according to any one of claims 1 to 8,
Forming a magnetic layer by coating and drying the prepared coating solution for forming a magnetic layer on a nonmagnetic support;
A method of manufacturing a magnetic recording medium including: The method for producing a magnetic recording medium according to claim 12, wherein the magnetic layer forming coating solution contains an isocyanate compound. Preparing a coating solution for forming a nonmagnetic layer by mixing a nonmagnetic powder, a binder, and the surface modifier for powder according to any one of claims 1 to 8,
Forming a nonmagnetic layer by coating the prepared coating liquid for forming a nonmagnetic layer on a nonmagnetic support and drying;
A method of manufacturing a magnetic recording medium including: The method for manufacturing a magnetic recording medium according to claim 14, wherein the coating liquid for forming the nonmagnetic layer contains an isocyanate compound. A magnetic recording medium having a magnetic layer containing a ferromagnetic powder and a binder on a nonmagnetic support,
A magnetic recording medium manufactured by the manufacturing method according to claim 12 or 13. A magnetic recording medium having, on a nonmagnetic support, a nonmagnetic layer containing nonmagnetic powder and a binder, and a magnetic layer containing ferromagnetic powder and a binder in this order,
A magnetic recording medium manufactured by the manufacturing method according to claim 14. The magnetic coating material containing the surface modifier for powders of any one of Claims 1-8, magnetic powder, and a binder. The magnetic coating material according to claim 18, which is used as a coating liquid for forming a magnetic layer of a magnetic recording medium. The magnetic paint according to claim 18 or 19, further comprising an isocyanate compound. A nonmagnetic paint comprising the surface modifier for powder according to any one of claims 1 to 8, a nonmagnetic powder, and a binder. The nonmagnetic paint according to claim 21, which is used as a coating liquid for forming a nonmagnetic layer of a magnetic recording medium. The nonmagnetic paint according to claim 21 or 22, further comprising an isocyanate compound.