JPH01220121A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks, and particularly relates to the dispersibility of magnetic powder mixed in the magnetic layer and the durability of the magnetic layer. It concerns sexual improvement.

[Summary of the invention]

The present invention provides a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder, which contains a resin having a carboxyl group as the binder component, and further has an alkoxyl group and an amino group in the magnetic layer. By including a silane coupling agent, it is intended to improve the dispersibility of the magnetic powder and reduce its falling off, thereby improving the deterioration of electromagnetic conversion characteristics and improving the durability of the coating film.

[Conventional technology]

Magnetic recording media are moving toward higher density recording year by year. Under these circumstances, in the magnetic layer, magnetic powder with an extremely fine particle size is highly dispersed in the binder resin, making the surface of the magnetic layer mirror-finished, improving the electromagnetic conversion characteristics, and at the same time improving the magnetic properties. There is a need to improve the durability of paint films.

That is, in the above magnetic recording medium, how well the magnetic powder contained in the magnetic layer is dispersed in the paint;
Furthermore, it is a very important issue how well the magnetic powder contained in the magnetic layer can be bonded to the binder.

Conventionally, as a method to satisfy the above requirements, a so-called dispersant (for example, a surfactant) is added to the magnetic paint to bond the hydrophilic group of the surfactant to the parent group of the magnetic powder. It has been proposed to bond magnetic powder and binder by bonding the lipophilic group of the surfactant and the lipophilic group in the binder, thereby improving durability and dispersibility of the magnetic powder. has been done. However, in this method, since the lipophilic group of the dispersant has no polarity, the bonding force with the binder is very weak, and the interface reinforcing function is not fully exhibited. Additionally, if an excessive amount of dispersant is added in order to exert its interface reinforcing function, the binder may become plasticized or the dispersant may precipitate on the surface of the coating film, resulting in a significant lack of durability of the coating film. There is.

In response to this, in recent years, a method of introducing a polar group into a binder has been proposed, and a technique has been proposed in which the binder has both the functions of a polymer, a dispersant, and an interface reinforcing agent. However, when attempting to introduce a polar group into the binder to strengthen the interface with the magnetic powder as described above, the hydrophilic group of the polar group causes steric hindrance due to the function of the binder as a polymer. In addition, compounds with long-chain alkyl groups and fatty acids added to paints for the purpose of improving durability may not be able to sufficiently adsorb to the hydrophilic groups on the surface of the magnetic powder, resulting in deterioration of dispersibility. If agents, dispersants, etc. are present, they will preferentially be adsorbed to the magnetic powder, which will hinder the adsorption of the binder that has a dispersion function, resulting in problems such as deterioration of the dispersibility of the magnetic powder.

Furthermore, another method has been proposed in which a silane coupling agent is used to chemically bond silanol groups to the surface of magnetic powder. This method attempts to produce a strong coating film by reacting the amine group contained in the silane coupling agent with the NGO group, glycidyl group, etc. introduced into the binder. However, although this method can achieve a strong bond between the magnetic powder and the binder, it is not necessarily sufficient to achieve good dispersion of the magnetic powder.

[Problem to be solved by the invention]

As mentioned above, in the field of magnetic recording media, there are problems such as the lack of ability of the binder used and the polar group added to it, the relationship between the polar group and the surface characteristics of the powder, and the relationship between the binder and the magnetic powder. Due to the unevenness of the abilities of the compounds interposed between the two, various practical properties remain unsatisfactory.

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and aims to prevent the adsorption of lubricant to magnetic powder, improve the dispersibility of magnetic powder, reduce falling off, and improve electromagnetic conversion. The purpose is to provide a magnetic recording medium with excellent characteristics and durability.

[Means to solve the problem]

As a result of intensive research, the inventor of the present invention found that, in order to achieve the above object, instead of making the magnetic powder and the binder interact directly,
By bonding in a binder resin containing carboxyl groups via a silane coupling agent having alkoxyl groups and amino groups, the affinity between the magnetic powder and the binder is significantly improved, and the dispersibility of the magnetic powder is improved. We have come to the knowledge that this can be dramatically improved.

The present invention has been made based on the above findings, and the present invention is based on the above findings.
As shown in the figure, in a magnetic recording medium having a magnetic layer (2) mainly composed of magnetic powder and a binder on a non-magnetic support (1), the binder component contains a resin having a carboxyl group. In addition, the magnetic layer (2) is characterized in that it contains a silane cuff pulling agent having an alkoxyl group and an amino group.

The present invention also provides a non-magnetic support (1
Applicable to a magnetic recording medium in which a magnetic layer (12) having the above-mentioned structure is formed on one surface of 1), and a back coat layer (13) mainly composed of non-magnetic powder and lubricant, etc. is formed on the other surface. You may.

The magnetic layer of the magnetic recording medium contains a silane coupling agent having an alkoxyl group and an amino group as described above. The purpose of this silane cassopring agent is to bond it to the surface of the magnetic powder mixed in the magnetic layer, thereby changing the apparent surface condition of the magnetic powder.

The above-mentioned silane coupling agent having an alkoxyl group and an amino group contained in the magnetic layer means that the silane coupling agent contains -○R (R represents an alkyl group. Note that this alkyl group has a short carbon chain. is preferable, and if the carbon chain is long, hydrolysis will not be carried out well and chemical bonding with the magnetic powder surface will not be possible.), primary amine (-NR2), and secondary amine. (
-NRH), tertiary amine (-NR,), and the like.

As such a silane coupling agent, ■NHZ (C
To) 3si (OCztls) 3■NH2C*I
IaS+ (OCRs) s■ (HOCJ4) JCJ
aSi (OCzHs) 3■HzNCzHJl'1C
JaSi(OCHt) z■CI(icOOcJaNH
cJJHcJ6si (OCH3) 3■HzNCJ4
NHCJJHCsHiSi(OCHs) s■ CJ5
0CONHCJ6Si(OCzHs)z■ C6H5N
HC3H6SI(OCH3)3■ HJCzHaN)l
ci) T-aminopropyltriethoxysilane (manufactured by Nippon Unicar Co., Ltd.) represented by IaSt(OCHs)s, [Phase] HJ (CHz) JH (CHt) asi (C
N(β-aminoethyl)-γaminopropylmethyldimethoxysilane (manufactured by Toshiba Corporation) represented by H3) (OCH3)z, and the like.

In order to cause the above-mentioned silane cuff pulling agent and magnetic powder to react, for example, (a) a method of adding the silane coupling agent and the magnetic powder at the same time during the preparation of the magnetic coating film, (b) a method of reacting the magnetic powder with the magnetic powder in water, (c) A method in which magnetic powder is treated with a silane coupling agent in an organic solvent and then the organic solvent is dried; (d) [
There is a method in which a silane coupling agent is mixed with a silane coupling agent and then dried.

The amount of the silane coupling agent containing an alkoxyl group and a carboxyl group added to the magnetic layer is 0.3 to 5 parts by weight (0.3 to 5 parts by weight) per 100 parts by weight of magnetic powder.
(expressed as HP) is preferably within the range. If the amount added is less than this range, the effect of adding a silane coupling agent containing an alkoxyl group and an amino group cannot be expected, and if the amount added is increased, the coating film will tend to be acidic. , this leads to deterioration of the corrosion resistance of the magnetic recording medium.

By reacting the magnetic powder with the silane coupling agent by the method described above, the alkoxyl groups present in the silane cuffing agent molecules are hydrolyzed to form -3t-0-, which forms the magnetic powder. chemically bonds well with the surface of As a result, the amino group, which is the other polar group present in the silane cuffing agent molecule, covers the surface of the magnetic powder, and the magnetic powder appears to be superbasic.

As mentioned above, the surface of the magnetic powder to which the silane coupling agent is chemically bonded is in a basic state, and by dispersing it in a binder containing carboxyl groups, the amino acids present on the surface of the magnetic powder are dissolved. An acid-base reaction occurs with the group to achieve a very strong bond, while the carboxyl group in the binder exhibits dispersion power as a hydrophilic polar group. Therefore, the magnetic powder does not come off even when the magnetic recording medium slides, improving durability.
A magnetic layer with excellent dispersibility can be constructed.

Here, as the binder for dispersing the magnetic powder used in the present invention, a binder having a carboxyl group introduced into the molecule is used. Any resin that has a carboxyl group introduced into its molecules can be used as this binder, but the above binder is not only one that uses a resin that has a carboxyl group introduced alone, but also one that uses a carboxyl group. Combinations of introduced binders and binders with and without carboxyl groups, combinations of different resins with carboxyl groups introduced, and combinations of binders with carboxyl groups and other polar groups (acidic polar groups, etc.) Any combination with a binder into which a neutral polar group (neutral polar group) has been introduced can be used. In addition, in the combination of a resin into which a carboxyl group has been introduced and a resin into which a carboxyl group has not been introduced, the resin into which a carboxyl group has been introduced accounts for at least 10% of the resin.
It is necessary to combine them in the above ratio.

Examples of such resins include urethane resins.

Polyester resin, vinyl chloride resin, vinylidene chloride resin, nitrocellulose resin, acrylic resin, A
Examples include binder resins such as B resin, epoxy resin, phenoxy resin, butadiene resin, phenol resin, urea resin, melamine resin, alkyd resin, or mixtures thereof.

As a method for introducing carboxyl groups into these resins,
Any conventionally known method can be used; for example, in order to introduce carboxyl groups into condensation resins (e.g. polyurethane), (i) a method using a carboxyl group-containing polyol, polyisocyanate, etc. as part of the chain extender; , (11) A method that utilizes active hydrogen, etc. (e.g., hydroxyl group) remaining in the side chain or terminal of a condensation resin, and modifies it with a compound that has both a group that can react with active hydrogen and a carboxyl group in the molecule, etc. According to

In addition, in order to introduce a carboxyl group into a copolymer resin such as a vinyl chloride resin, (iii) both a vinyl monomer such as vinyl chloride and a polar group containing a carboxyl group and having a copolymerizable double bond are required. (iv) a method of introducing active hydrogen in advance and modifying it with a compound having both a group capable of reacting with active hydrogen and a carboxyl group in the molecule; (v) ) A compound containing a hydrophilic polar group and chlorine in the molecule and a carboxyl group-containing resin having a polyfunctional hydroxyl group are dissolved in a solvent such as dimethylformamide in which both components are soluble, and amines, epoxy compounds, etc. A method of introducing the hydroxyl group by a dechlorination reaction between a hydroxyl group and chlorine in the presence of a dehydrochlorination agent may be used.

In addition, the content of carboxyl groups contained in the binder is O, OOI I1 mol/g ~ 0.5 m mo
It is preferably within the range of l/H, and 0.01 ra
More preferably, the range is mol/g to 0, lva mol/g.

Examples of the magnetic powder whose surface is covered with the above-mentioned silane coupling agent include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite grains, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed by the general formula FeOx, that is, magnetite (T - Fe2O2).

X=1.50), magnetite (FeJa,
= 1.33) and their solid solutions (FeOx, 1.3
3<X<1.50). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.

The above-mentioned ferromagnetic chromium dioxide may include CrO□ or Ru for the purpose of improving the coercive force thereof.

A material to which at least one of Sn, Te, Sb, Fe, Ti, V, Mn, etc. is added can be used.

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fe-Ni, Fe-Co-Ni, C.

-Ni, Fe-Co-B, Fe-Co-Cr-B.

Mn-B1. Mn-An, Fe-Co-V, etc. can be used, and in order to improve various properties, Al, Si
, Ti, Cr, Mn, Cu, Zn, and other metal components may be added.

In addition to the above-mentioned magnetic powder, various powders such as abrasives, inorganic pigments, and carbon may be added to the magnetic layer, and in this case, due to the action of the silane coupling agent contained in the binder, As in the case of magnetic powder, the alkoxyl groups present in the silane coupling agent molecules are hydrolyzed to form 1-3i-0-, which forms a good chemical bond with the surface of the powder. As a result, the amino group, which is the other polar group present in the silane coupling agent, covers the surface of the powder and the powder appears to be superbasic. Therefore, a good and strong bond is formed with the carboxyl group-introduced binder constituting the magnetic layer, improving the dispersibility of the powder and reducing powder falling.

In the magnetic recording medium of the present invention, the magnetic layer may be formed, for example, by dispersing the above-mentioned magnetic powder in a binder and dissolving it in an organic solvent, and applying a magnetic paint to the surface of the non-magnetic support.

Further, various additives that are normally added to the magnetic layer of this type of magnetic recording medium may be added to the magnetic layer. However, it is preferable to add various additives to an extent that does not interfere with the effect of adding the silane coupling agent containing an alkoxyl group and an amino group.

As mentioned above, magnetic powder, a silane cuffing agent containing an alkoxyl group and an amino group added to make the surface of the magnetic powder basic, and various other additives normally used in the magnetic layer of a magnetic recording medium. When a magnetic layer is formed by coating a coating material consisting of an agent and a binder containing a carboxyl group for dispersing these, it may be dissolved in an organic solvent and then coated on a non-magnetic support.

Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, methyl acetate, and ethyl acetate.

Ester systems such as butyl acetate, ethyl lactate, glycol acetate monoethyl ether, glycol dimethyl ether,
Glycol monoethyl ether, glycol ethers such as dioxane, benzene.

Examples include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane and heptane, and chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene. .

On the other hand, a back coat layer is formed on the surface opposite to the magnetic layer formed as described above for the purpose of antistatic function, friction reduction function, and scratch prevention function (improving durability). You can leave it there.

The back coat layer is formed by dispersing non-magnetic powder in a binder, dissolving it in an organic solvent to prepare a bank coat layer paint, and coating it on the surface opposite to the surface on which the magnetic layer is formed. Ru.

As the non-magnetic powder constituting the back coat layer, any powder commonly used as non-magnetic powder for this type of magnetic recording medium can be used, such as contact black, channel black, roll black, disk black, All kinds of carbon black such as furnace black, thermal black, lamp black, CaC01 powder, B a S Oa powder, ZnO powder,
α-pe.

0, powder, TiO2 powder, Al2O3 powder, Cr2O3
Examples include non-magnetic powder such as powder. Further, in the back coat layer, as well as in the magnetic layer, any of the various additives that are commonly added can be used.

Also, in the back coat layer, in order to improve the dispersibility of the non-battery powder used in the back coat layer and the separation and dispersibility of the non-magnetic powder, alkoxyl groups and A silane coupling agent containing an amino group may be added. In that case, the binder used is preferably a binder containing a carboxyl group, similar to the magnetic layer.

In this way, by using a silane coupling agent containing an alkoxyl group and an amino group and a binder into which a carboxyl group is introduced in the back coat layer, the alkoxyl group is firmly bonded to the surface of the non-magnetic powder, and the non-magnetic powder is bonded firmly to the surface of the non-magnetic powder. The surface of the magnetic powder is made basic in appearance. The non-magnetic powder whose surface has become basic has a carboxyl group in the binder and an acid-
Generates a base reaction and achieves a strong bond. Furthermore, the carboxyl group in the binder exhibits good dispersibility as a hydrophilic polar group.

The materials for the non-magnetic support constituting the magnetic recording medium according to the present invention include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, and celluloses such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate. Derivatives, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, and polyimide.

Examples include plastics such as polyamideimide, light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass. The nonmagnetic support may be in any form such as a film, sheet, disk, card, or drum.

[Effect]

In the silane binding agent containing an alkoxyl group and an amino group used in the present invention, the alkoxyl group is strongly bonded to the magnetic powder, and the amine group is well bonded to the carboxyl group in the binder. As a result, a coating film is completed which has remarkable effects on dispersion stability of magnetic powder and interface reinforcement, and a coating film with high magnetic properties and excellent durability is completed.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

1 Cor FezOz (Surface area 30m/g)
12 parts by weight silane coupling agent
0.24 parts by weight (γ-aminopropylethoxysilane.

NHz(CHt)3Si(OCzHs)i + Nippon Unicar) urethane resin 3
Parts by weight (contains -COOH group 0.05 m mol/g) Methyl ethyl ketone 30 parts by weight The above composition was mixed in a ball mill for 48 hours, taken out through a filter, and the magnetic layer paint was dried on the back side of a 12 μm thick polyethylene terephthalate film. It was coated so that the final thickness was 5 μm, oriented in a magnetic field, and then wound up. After calendering this, it was cut into a 1/2 inch width to produce a sample tape.

Pointed rattan base 1 The silane coupling agent used in Example 1 was
Aminopropylethoxysilane (NHzCJ6Si (
A sample tape was prepared in the same manner as in Example 1, except that OCH3) 31 (manufactured by Nippon Unicar Co., Ltd.) was used.

Next Article I Reference 1 The silane cuff pulling agent used in Example 1 was
Aminopropylethoxysilane (C,H5NHCJaS
i (OCL) s11 manufactured by Nippon Unicar], but otherwise a sample tape was produced in the same manner as in Example 1.

Urethane resin (the binder used in Example 1)
A sample tape was produced in the same manner as in Example 1, except that the urethane resin containing 0.05 mmol/g of tertiary amine was used.

Urethane resin (
-COOH group 0.05mmol/g) is -5OJ
Changed to a urethane resin containing 0905 m mol/g of a group,
A sample tape was produced in the same manner as in Example 1 except for the above.

A sample tape was prepared in the same manner as in Example 1 except that the silane coupling agent was not used in the composition of the magnetic layer used in Example 1.

Comparison ↓ A sample tape was prepared in the same manner as in Comparative Example 1 except that the silane coupling agent was not used in the magnetic layer composition used in Comparative Example 1.

A sample tape was prepared in the same manner as in Comparative Example 2 except that the silane coupling agent was not used in the magnetic layer composition used in Comparative Example 2.

For each sample tape produced as described above, gloss, powder drop, magnetic flux density B11% squareness R3% coercive force Hc were measured.

The above gloss was measured using a gloss meter with an incident angle of 75° and a reflection angle of 75°.
The reflectance at 100°C was measured. In addition, for powder falling off, visually observe the amount of powder falling on the head drum, guide pin, etc. after running the shuttle 100 times for 60 minutes, and score 0 for almost no powder falling off, and 15 points for large amount of powder falling off. evaluated.

Furthermore, the magnetic properties were measured in a magnetic field of 2500 Gauss.

These results are shown in Table 1.

(Margin below) Table 1 As is clear from Table 1, Examples containing a silane coupling agent and a binder into which a carboxyl group is introduced in the magnetic layer do not contain the silane coupling agent. Very good results were obtained in terms of gloss, powder shedding, coefficient of friction, and magnetic properties compared to comparative examples in which no carboxyl group was introduced or no carboxyl group was introduced.

〔Effect of the invention〕

As is clear from the above explanation, in a magnetic layer containing a silane coupling agent containing an alkoxyl group and an amino group, the coupling agent bonds well with the carboxyl group in the magnetic layer and the binder. A coating film with excellent durability can be completed without losing dispersion stability and interfacial reinforcing properties.

Therefore, by using this as the magnetic layer of a magnetic recording medium, it is possible to provide a magnetic recording medium with excellent electromagnetic conversion characteristics, coating durability, etc.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a main part showing an example of the structure of a magnetic recording medium to which the present invention is applied. FIG. 2 is an enlarged sectional view of a main part showing another example of the configuration of a magnetic recording medium to which the present invention is applied. 1.11...Nonmagnetic support 2.12...Magnetic layer 13...Back coat layer Patent applicant Sony Corporation representative Patent attorney Kodo Kobo, Sakae Tamura - Masaru Sao

Claims (1)

[Claims] A magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder on a non-magnetic support, wherein the binder component contains a resin having a carboxyl group, and the magnetic layer contains an alkoxyl group and an amino group. A magnetic recording medium characterized by containing a silane coupling agent having a silane coupling agent.