JPH09227883A - Lubricant and magnetic recording medium made by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricant which reduces, when used as the lubricant for the back layer of a magnetic recording medium, the coefficient of friction of the surface of the back layer, maintains the coefficient of friction low for a long time, and gives a magnetic recording medium excellent in electromagnetic transduction characteristics, travelling propertis, and durability by using a specific tryptophan ester compd. SOLUTION: This lubricant is a tryptophan ester compd. represented by the formula (R1 and R2 are each a 6C or lower hydrocarbon group; R3 is a long-chain hydrocarbon group; and R4 is H or a hydrocarbon group) having a dialkylamino group. In a magnetic recording medium comprising a nonmagnetic substrate, a magnetic layer formed on one side of the substrate, and a back layer comprising a binder and a nonmagnetic powder dispersed therein and formed on the other side, the back side holds the tryptophan ester compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a back layer provided on the surface of a non-magnetic support opposite to the side on which the magnetic layer is formed.

[0002]

2. Description of the Related Art Magnetic recording media are widely used for recording electromagnetic signals, and take various forms such as a tape form, a disc form or a card form depending on the application. Of these, tape-shaped magnetic recording media (hereinafter referred to as “magnetic tape”) are used for audio, video, computer, and the like.

By the way, audio and video magnetic tapes are often housed in cassettes and used in the form of cassette tapes. In recent years, there has been a strong demand for long-time recording for cassette tapes, and in order to accommodate the longest possible magnetic tapes inside the standardized cassettes due to such requirements, the thickness of magnetic tapes is gradually reduced. There is a direction to be.

As the thickness of the magnetic tape becomes thinner, the problem is securing the strength. Therefore, it has already been performed to provide strength to the tape by providing a back layer on the surface of the magnetic tape opposite to the side on which the magnetic layer is formed.

Further, the back layer improves the contact between the back surface of the magnetic tape and the running system of the reproducing apparatus, and is effective in improving running performance. In particular, the tape running system of a recent VCR has a structure as shown in FIG. That is, in this tape running system, the supply roll 1
The magnetic tape 12 travels from 0 to the winding roll 11, and the magnetic tape 12 travels in contact with the rotary head 13 in the middle of this travel. A large number of stainless guide pins for guiding the magnetic tape 12 are provided between the supply roll 10 and the rotary head 13 and between the rotary head 13 and the take-up roll 11, of which guide pins 14a, 14b, 14c, 14
The back surface side of the magnetic tape contacts d. In other words, this tape running system is designed so that it is more in contact with the back surface than with the magnetic layer surface. Therefore, it is important to reduce the friction coefficient between the back surface and the running system in order to improve the running property of the magnetic tape.

Such a back layer is generally formed by dispersing nonmagnetic powder in a binder.

Here, if the surface of the back layer is excessively smooth, the contact area with the running system increases, the friction coefficient increases, and the running performance of the magnetic tape deteriorates. For this reason,
It is necessary to impart appropriate irregularities to the back layer surface by controlling the particle size distribution of the non-magnetic powder.

However, if the degree of unevenness on the surface of the back layer becomes too large, the unevenness on the surface of the back layer may come into contact with the surface of the magnetic tape during manufacturing of the magnetic tape, particularly in the heat treatment step in the state where the magnetic tape is wound. Is transferred to the magnetic layer. As a result, remarkable irregularities are formed on the surface of the magnetic layer, and the electromagnetic conversion characteristics of the magnetic tape deteriorate.

For this reason, it is difficult to achieve both electromagnetic conversion characteristics and runnability simply by controlling the particle size distribution of the non-magnetic powder contained in the back layer. By further studying the composition of the back layer itself, It is necessary to reduce the coefficient of friction with the running system while maintaining the smoothness of the layer.

From such a point of view, the following many proposals have been made regarding the binder and the lubricant used in the back layer.

For example, the binder used in the back layer has been studied from the viewpoint of the effect of the binder on the surface of the back layer, and Japanese Patent Laid-Open No. 56-98719 discloses a fibrin resin and a thermoplastic resin. A combination of polyurethane elastomer and polyisocyanate is proposed as a binder for the back layer. However, although such a binder is preferable from the viewpoint of improving the smoothness of the back layer surface, it has a problem of increasing the friction coefficient on the back layer surface and lowering the durability of the tape.

Therefore, as a method for avoiding such an increase in the friction coefficient, it has been attempted to internally add or apply a lubricant to the back layer.

As the lubricant, for example, a lubricant containing a higher fatty acid or a higher fatty acid ester as a main component is disclosed in Japanese Patent Laid-Open No. H6-6 / 1994.
-64727 publication. In addition to higher fatty acids and higher fatty acid esters, metal soaps, higher fatty acid amides, mineral oils, organic compounds of fats and oils, silicone oils,
Inorganic fine powders, plastic fine powders, α-olefin polymers and fluorocarbons and mixtures thereof are mentioned. Among these lubricants, a lubricant containing a higher fatty acid or a higher fatty acid ester as a main component is generally used, and one having a total carbon number of 12 or more is particularly preferable, and a fatty acid having 12 to 18 carbon atoms, and Esters of various fatty acids and alcohols having 1 to 12 carbon atoms are said to be preferable.

[0014]

However, although such a lubricant is preferable only from the viewpoint of reducing the coefficient of friction of the back layer, the problem of adhesion between the back layer and the magnetic layer, durability, and storage stability. There is a problem in terms of sex.

Particularly, since carboxylic acid is easily adsorbed to the inorganic pigment which is a component of the back layer, it is difficult to allow the carboxylic acid to exist on the surface of the back layer and the lubricating performance cannot be maintained on the surface of the back layer for a long time. Further, when the surface of the back layer is further smoothed, it may cause the surface of the magnetic layer and the back layer to adhere to each other.

Further, a guide pin made of polyoxymethylene (POM) may be used in a video deck, but when a lubricant containing a higher fatty acid or a higher fatty acid ester as a main component is used in the back layer, this POM is used. The friction coefficient increases with respect to the guide pin made of steel.

The present invention has been proposed in view of such a conventional situation, and when it is held in the back layer of a magnetic recording medium, for example, it is possible to impart excellent lubricating performance to the back layer surface, The lubrication performance is maintained for a long time,
It is an object to provide a lubricant that does not stick to the magnetic layer. Another object of the present invention is to provide a magnetic recording medium having excellent running properties, durability and electromagnetic conversion characteristics by using such a lubricant.

[0018]

[Means for Solving the Problems] In order to achieve the above-mentioned object, as a result of intensive studies by the present inventors, tryptophan ester compounds, especially tryptophan ester compounds having a dialkylamino group, are used in the back layer. We have come to the knowledge that it is suitable as a lubricant.

The lubricant of the present invention was completed on the basis of such findings, and is characterized by being a tryptophan ester compound having a dialkylamino group represented by Chemical formula 3.

[0020]

Embedded image

Further, the magnetic recording medium of the present invention is provided with a magnetic layer on one surface of the non-magnetic support and a back layer on the other surface of which a non-magnetic powder is dispersed in a binder. The magnetic recording medium is characterized in that the back layer is internally added or coated with a tryptophan ester lubricant having a dialkylamino group represented by Chemical formula 4.

The tryptophan ester-based lubricant represented by the chemical formula 3 exhibits excellent lubricating performance not only in a normal temperature and normal humidity environment but also in a high temperature and high humidity environment and a low temperature environment. Also,
In particular, in this tryptophan ester-based lubricant, the active hydrogen of the amino group replaces the alkyl group, so when it is held in the back layer, it is difficult to adsorb with the non-magnetic powder that is the back layer component and on the back layer surface. Lubrication performance can be maintained for a long time. Moreover, the back layer comes into contact with the magnetic layer in the rolled state, but even if this tryptophan ester-based lubricant is held in the back layer, it does not adhere to the magnetic layer.

Therefore, in the magnetic recording medium in which such a tryptophan ester-based lubricant is held in the back layer, the friction coefficient with respect to the running system is sufficiently reduced even when the back layer surface is smoothed, and the electromagnetic conversion characteristics are improved. Excellent and good running performance and durability are obtained.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

In the present invention, a tryptophan ester compound having a dialkylamino group represented by Chemical formula 4 is used as a lubricant.

[0026]

Embedded image

In the chemical formula 4, R ₃ is not limited in molecular weight and carbon number, and may have a linear structure or a branched structure. Further, it may have an unsaturated bond, an aromatic ring or an alicyclic structure, and the type of isomer is not particularly limited. However, a linear or branched hydrocarbon group having 10 or more carbon atoms is preferable from the viewpoint of reducing the friction coefficient and solubility in a diluent solvent.

Among such tryptophan ester compounds, for example, C ₁₈ H ₃₇ is introduced into R ₃ , and R ₁ and R ₂ are introduced.
The compound in which CH ₃ is introduced is synthesized as follows.

That is, tryptophan and stearyl alcohol (C ₁₈ H in which the amino group is not dialkylated)
₃₇ OH) is dissolved in anhydrous toluene, and p is used as a catalyst.
-Add TsOH, and remove water generated while refluxing. By performing this operation for 5 hours, tryptophan stearyl ester is produced. After this, the alkylating agent, for example methyl iodide, is mixed with the produced tryptophan stearyl ester and heated in a seal to alkylate the amino groups. As a result, the tryptophan ester compound is synthesized.

It is also possible to reverse this operation so that the amino group of tryptophan is alkylated and then esterified.

For other tryptophan ester compounds, alkylating agents corresponding to R ₁ , R ₂ and R ₃ ,
It can be similarly synthesized by selecting an esterifying agent.

Further, this synthesizing method is an example, and it goes without saying that the synthesizing may be performed by other synthesizing methods.

Such a tryptophan ester lubricant is applied to, for example, a magnetic recording medium.

That is, in the magnetic recording medium in which the tryptophan ester lubricant is used, the magnetic layer is formed on the non-magnetic support, and the surface of the non-magnetic support opposite to the side on which the magnetic layer is formed. The back layer is formed by dispersing the non-magnetic powder in the binder.

The above tryptophan ester lubricant is
It is held in the back layer of such a magnetic recording medium. When the tryptophan ester-based lubricant is used as the back layer, the running property and the durability are improved by maintaining the electromagnetic conversion characteristics of the medium by the following actions.

That is, the tryptophan ester-based lubricant having a dialkylamino group exhibits excellent lubricating performance not only in a normal temperature and normal humidity environment but also in a high temperature and high humidity environment and a low temperature environment. Further, in particular, since the active hydrogen of the amino group replaces the alkyl group, it is difficult to adsorb the non-magnetic powder as the back layer component, and the lubricating performance can be maintained on the back layer surface for a long period of time. Moreover, the back layer comes into contact with the magnetic layer in the rolled state, but even if this tryptophan ester-based lubricant is held in the back layer, it does not adhere to the magnetic layer.

Therefore, in the magnetic recording medium in which such a tryptophan ester-based lubricant is held in the back layer, the friction coefficient with respect to the running system is sufficiently reduced even when the back layer surface is smoothed, and the electromagnetic conversion characteristics are improved. In addition to being excellent, it exhibits good running performance and durability, and further has excellent durability against edge damage and the like.

When the back layer is top-coated with this tryptophan ester-based lubricant, the coating amount is 0.5 to 10
It is preferable to be 0 mg / m ^2, and more preferably, 1 to 20 mg / m ^2. When internally added, tryptophan ester-based lubricant is added to the non-magnetic powder at 0.5.
It is desirable to add it so as to be ˜5 wt%.

The tryptophan ester-based lubricant may be used alone, or may be used in combination with a conventionally known lubricant such as fatty acid or fatty acid ester.

Further, in order to maintain the lubrication effect even under more severe conditions, the extreme pressure agent is added to the lubricant at 30: 7.
You may use together by the weight ratio of 0-70: 30.

The extreme pressure agent reacts with the metal surface by the frictional heat generated when a metal contact is partially generated in the boundary lubrication region, and forms a reaction product film to prevent friction and wear. It is something to do. As such an extreme pressure agent, a phosphorus-based extreme pressure agent, a sulfur-based extreme pressure agent, a halogen-based extreme pressure agent, an organic metal-based extreme pressure agent, a composite-based extreme pressure agent, or the like can be used.

Such a lubricant or extreme pressure agent is added to the back layer, and the nonmagnetic powder and the binder which are the main components of the back layer are usually used in this type of magnetic recording medium. Any one can be used.

Examples of the binder include a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl acetate-maleic acid copolymer, a vinyl chloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrile copolymer, an acrylic ester. -Acrylonitrile copolymer, acrylic acid ester-
Vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer Coal, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, polyurethane resin, urea resin, melamine resin, alkyd resin, urea-formaldehyde resin Alternatively, a mixture thereof or the like can be given. Especially, when polyester and polyurethane resin are used together, the durability and running property of the medium are improved.

Further, a trifunctional isocyanate compound such as a reaction product of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate may be used in combination as a cross-linking agent to improve durability and the like.

As the non-magnetic powder, carbon black,
Examples include graphite and inorganic fillers. These may be used alone or in combination of two or more.
Specific examples of the inorganic filler include TiO ₂ , TiO, and Z.
nO, CaCO ₃ , CaO, SnO ₂ , SiO ₂ , α-F
e ₂ O ₃ , Cr ₂ O ₃ , α-Al ₂ O ₃ , ZnS, MoS ₂ ,
BaSO ₄ , CaSO ₄ , MgCO ₃ , BN and SiC
Etc. Among these non-magnetic powders, it is preferable to use carbon black, graphite, ZnO, TiO ₂ , BaSO ₄ and CaSO ₄ alone or in combination.

The particle size and shape of the non-magnetic powder are not particularly limited, and those having a commonly used particle size and shape can be used.

For example, in the case of carbon black, it is desirable to use those having an average particle diameter of 10 to 300 nm. In the case of an inorganic filler, the average particle size is 0.1
It is desirable to use the one having a thickness of 10 μm.

The shape of the non-magnetic powder is spherical, needle-like,
It may have any shape such as a plate shape or a dice shape.

To form a back layer made of such a material, various additives such as non-magnetic powder, binder and lubricant are dispersed in an organic solvent to prepare a back layer coating solution. Then, the back layer coating solution is applied onto a non-magnetic support and dried to evaporate the solvent and further cure the resin component.

As the organic solvent for forming the paint, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, methyl acetate,
Ester-based solvents such as ethyl acetate, butyl acetate, ethyl lactate and glycol monoethyl ether, ether-based solvents such as ethyl ether, glycol dimethyl ether, glycol monoethyl ether, dioxane and tetrahydrofuran, aromatic carbonization such as benzene, toluene and xylene. Hydrogen-based solvents, chlorinated hydrocarbon-based solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene can be used.

The thickness of the back layer is preferably 3 μm or less.

On the other hand, a magnetic layer is formed on the surface of the non-magnetic support opposite to the side on which the back layer is formed. This magnetic layer is formed, for example, by dispersing ferromagnetic fine powder in a binder.

As the ferromagnetic fine powder, ferromagnetic iron oxide fine powder, Co-doped ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, ferromagnetic alloy powder, barium ferrite and the like can be used.

Of these, the ferromagnetic iron oxide fine powder and the chromium dioxide fine powder have an acicular ratio of about 3/1 to 30/1, preferably 4/1 or more, and an average length of 0.05 to. 2.
It is preferably about 0 μm.

The ferromagnetic alloy powder contains 75% by weight or more of metal powder, and 80% by weight or more of this metal powder is a ferromagnetic metal, that is, Fe, Co, Ni, Fe-Ni, C.
The particles are o-Ni and Fe-Co-Ni and have a major axis of about 0.5 μm or less.

As the binder, a binder which is conventionally used in this kind of magnetic recording medium, that is, a thermoplastic resin, a thermosetting resin, or a radiation-crosslinking resin which is cured by irradiation with an electron beam or the like is used alone or Used as a mixture.

Here, the thermoplastic resin has a softening point temperature of 150 ° C. or lower and an average molecular weight of 10,000 to 20,000.
It is desirable to use one having a degree of polymerization of 0 and a degree of polymerization of about 150 to 2000. As such a thermoplastic resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer,
Acrylic ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, acrylic acid ester-styrene copolymer, methacrylic acid ester-
Acrylonitrile copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, urethane elastomer, polyvinyl fluoride,
Vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer Examples thereof include polymer, polyester resin, and various synthetic rubber-based thermoplastic resins (polybutadiene, polychloroprene, polyisoprene, styrene-butadiene copolymer, etc.), which may be used alone or in combination.

The magnetic layer may contain additives usually used in this type of magnetic layer, such as an antistatic agent and a lubricant.

In order to form a magnetic layer made of such a material, a ferromagnetic fine powder, a binder and various additives are dispersed in an organic solvent to prepare a magnetic layer coating solution. Then, this magnetic layer coating solution is applied onto a non-magnetic support and dried to evaporate the solvent and further cure the resin component.

As the organic solvent for forming the paint, any of those exemplified for the back layer coating liquid can be used.

Either the magnetic layer or the back layer may be formed first, or both may be formed at the same time.

As the non-magnetic support on which the back layer and the magnetic layer are formed, polyesters such as polyethylene terephthalate and polyethylene 2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, polycarbonate, It is also possible to use plastics such as polyimide and polyamide-imide, and plastics deposited with a metal such as aluminum.

The non-magnetic support has a film-like shape.
It may be tape-shaped or sheet-shaped, and the material of the non-magnetic support is selected according to this form.

[0064]

EXAMPLES Hereinafter, specific examples of the present invention will be described based on experimental results. It goes without saying that the present invention is not limited to this embodiment.

First, the tryptophan ester lubricants (Compound 1 to Compound 6) retained in the back layer in this example.
Of the general formula of, and R ₁ , R ₂ , R ₃ , and
R ₄ is shown in Table 1.

[0066]

Embedded image

[0067]

[Table 1]

(However, Ph is a phenyl group.) Example 1 First, various magnetic layer compositions were weighed out according to the following composition and mixed in a ball mill for 50 hours.

Composition of coating liquid for magnetic layer Ferromagnetic Fe alloy powder 100 parts by weight (coercive force Hc: 1500 Oe, BET specific surface area 50 m ² / g) Vinyl chloride copolymer 10 parts by weight Polyurethane resin 10 parts by weight (Japan Polyurethane Brand name N-2304) Carbon black (antistatic agent) 5 parts by weight Methyl ethyl ketone 150 parts by weight Cyclohexanone 150 parts by weight Butyl stearate 1 part by weight And, in this kneaded product, Coronate L (polyurethane manufactured by Nippon Polyurethane Co., Ltd.) is used as a curing agent. Isocyanate) was added in an amount of 4 parts by weight and further mixed by a ball mill for 10 minutes to obtain a coating liquid for magnetic layer. This coating solution was further diluted with toluene, and then dried on a polyethylene terephthalate support having a thickness of 12 μm using a doctor blade to give a dry film thickness of 2
It was applied to a thickness of μm. Then, the undried coating film was subjected to a magnetic field orientation treatment and then dried to form a magnetic layer.

Next, various back layer compositions were weighed according to the following composition and mixed in a ball mill for 50 hours to prepare a back layer coating solution.

Composition of coating liquid for back layer Carbon black 100 parts by weight (secondary average particle size: 17 nm, trade name Conductex SC) Vinyl chloride polymer 50 parts by weight (UC company trade name VAGH) Polyurethane resin (Japan Polyurethane Brand name N-2304) 50 parts by weight Toluene 50 parts by weight Methyl ethyl ketone 700 parts by weight Tryptophan stearyl ester 4 parts by weight (Compound 1: in Formula 5, R ₃ = C ₁₈ H ₃₇ ) And, as a curing agent for the kneaded product, Coronate L 1
5 parts by weight were added and further mixed by a ball mill for 10 minutes to obtain a coating solution for back layer. This coating solution was applied to the surface of the support opposite to the side on which the magnetic layer was formed so that the dry film thickness was 1 μm, and dried to form a back layer.

Subsequently, the surface of the magnetic layer was smoothed by calendering, heat-cured at a temperature of 60 ° C. for 72 hours, and further cut into a width of 8 mm to prepare a magnetic tape.

Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that perfluoropolyether having a hydroxyl group at the terminal (Fomblin Z-DOL manufactured by Ausimont Co.) was added to the back layer instead of the compound 1. Created.

Comparative Example 2 A magnetic tape was prepared in the same manner as in Example 1 except that perfluoropolyether having a carboxyl group at the terminal (Fomblin Z-DIAC manufactured by Ausimont Co.) was added to the back layer instead of the compound 1. It was created.

Example 2 In the back layer, 2 parts by weight of butyl stearate and 2 parts by weight of myristic acid were added instead of the compound 1, and after calendering the magnetic layer, the compound 1 was coated on the back layer. A magnetic tape was prepared in the same manner as in Example 1. In addition, Compound 1 is made into a paint by dissolving it in toluene, and 2
The coating amount was mg / m ² .

Comparative Example 3 A magnetic tape was prepared in the same manner as in Example 2 except that Compound 1 was not coated on the back layer.

Comparative Example 4 A magnetic tape was prepared in the same manner as in Example 1 except that tryptophan stearyl ester in which the positions of R ₁ and R ₂ were not alkylated was added to the back layer in place of the compound 1.

Example 3 A magnetic tape was prepared in the same manner as in Example 1 except that tryptophan decyl ester (Compound 2: R ₃ = C ₁₀ H ₂₁ in Chemical Formula 5) was added to the back layer in place of Compound 1. did.

Example 4 A magnetic tape was prepared in the same manner as in Example 2 except that Compound 2 was coated on the back layer instead of Compound 1.

Example 5 In the back layer, tryptophan stearyl phenyl ester (compound 3: in the formula 5, R ₃ =
Ph-C ₁₈ H ₃₆₎ except that the addition of created a magnetic tape in the same manner as in Example 1.

Example 6 A magnetic tape was prepared in the same manner as in Example 2 except that the compound 3 was coated on the back layer instead of the compound 1.

Example 7 In the back layer, instead of Compound 1, tryptophan linole ester (Compound 4: R ₃ = C ₁₈ H ₃₃ in Chemical Formula 5) was used.
A magnetic tape was prepared in the same manner as in Example 1 except that was added.

Example 8 A magnetic tape was prepared in the same manner as in Example 2 except that Compound 4 was coated on the back layer instead of Compound 1.

Example 9 In the back layer, instead of Compound 1, tryptophan cyclohexyl ester (Compound 5: in Formula 5, R ₃ ═C ₆ H
_A magnetic tape was prepared in the same manner as in Example 1 except that ₁₁ ) was added.

Example 10 A magnetic tape was prepared in the same manner as in Example 2 except that Compound 5 was coated on the back layer instead of Compound 1.

Example 11 In the back layer, instead of Compound 1, tryptophan isostearyl ester (Compound 6: in Formula 5, R ₃ = is
o-C ₁₈ H ₃₇₎ except that the addition of created a magnetic tape in the same manner as in Example 1.

Example 12 A magnetic tape was prepared in the same manner as in Example 2 except that Compound 6 was coated on the back layer instead of Compound 1.

With respect to the magnetic tape prepared as described above, the friction coefficient, the still durability, and the shuttle durability under the conditions of temperature 25 ° C., relative humidity 60%, temperature 40 ° C., relative humidity 80%, and temperature −5 ° C., respectively. Was evaluated. The results are shown in Tables 2 to 4.

The still durability was evaluated by examining the decay time until the output attenuated by -3 dB in the pause state.

The shuttle durability was determined by repeating the shuttle running with the shuttle running for 2 minutes as one time, and the output was 3d.
It was evaluated by examining the time until the B decreased.

The magnetic tape was stored (aged) at a temperature of 40 ° C. and a relative humidity of 80% for 7 days, and the friction coefficient before and after aging, stick slip and dropout were measured at a temperature of 25 ° C. and a relative humidity of 60%. . The results are shown in Tables 5 and 6.

The stick-slip was judged by whether or not the coefficient of static friction during friction exceeded 0.6. In the table, ○ indicates that the static friction coefficient does not exceed 0.6, Δ indicates that the static friction coefficient is 0.6 to 1.0, and × indicates that the static friction coefficient exceeds 1.0. This is the case where sticking occurs.

Dropout occurs in 3 minutes
It was evaluated by measuring the number of times the output decreased for μsec or more and 10 dB or more.

[0094]

[Table 2]

[0095]

[Table 3]

[0096]

[Table 4]

[0097]

[Table 5]

[0098]

[Table 6]

As can be seen from Tables 2 to 6, the magnetic tapes of Examples 1 to 12 in which a tryptophan ester-based lubricant having a dialkylamino group was internally added or top-coated in the back layer were the normal temperature and normal humidity. Not only in the environment, but also in a high temperature and high humidity environment and a low temperature environment, a low friction coefficient is exhibited and excellent durability is obtained. Also, aging does not increase stick slip or dropout, and these are kept low. In particular, the still durability and shuttle durability are significantly improved as compared with the magnetic tapes using only other types of lubricants (Comparative Examples 1 to 3).

Further, the case where a tryptophan ester type lubricant whose amino groups were not dialkylated was used as Comparative Example 4, and the friction coefficient of the back layer surface increased with time with this lubricant. However, the lubrication performance cannot be maintained for a long time. This is because the active hydrogen of the amino group of this tryptophan ester lubricant is easily adsorbed to the inorganic pigment contained in the back layer.

From the above, it was found that a tryptophan ester compound, in which the amino group was dialkylated, was particularly suitable as the lubricant retained in the back layer.

[0102]

As is apparent from the above description, in the present invention, a tryptophan ester compound having a dialkylamino group is used as a lubricant, which is retained in the back layer of the magnetic recording medium. This tryptophan ester compound having a dialkylamino group exhibits excellent lubricating performance under any conditions of use, can maintain the lubricating performance on the back layer surface for a long period of time, and has low adhesiveness to the magnetic layer. . Therefore, it is possible to improve wear resistance and durability, particularly runnability, while improving the electromagnetic conversion characteristics of the magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a tape running system of a video deck.

Claims (4)

[Claims] 1. A lubricant, which is a tryptophan ester compound having a dialkylamino group represented by Chemical formula 1. Embedded image 2. A magnetic recording medium in which a magnetic layer is provided on one surface of a non-magnetic support and a back layer in which non-magnetic powder is dispersed in a binder is provided on the other surface of the non-magnetic support. Wherein the tryptophan ester compound having a dialkylamino group represented by Chemical formula 2 is retained. Embedded image 3. The magnetic recording medium according to claim 2, wherein the tryptophan ester compound having a dialkylamino group is internally added to the back layer. 4. The magnetic recording medium according to claim 2, wherein the tryptophan ester compound having a dialkylamino group is coated on the surface of the back layer.