JP2647727B2 - Magnetic recording media - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a coefficient of friction (μ value).
The present invention relates to a magnetic recording medium having low running performance and improved running properties.

(Prior Art) A magnetic recording medium is basically composed of a non-magnetic support and a magnetic layer made of ferromagnetic powder dispersed in a binder (binder) provided on the non-magnetic support. ing.

In recent years, magnetic recording media have been widely used as recording tapes, video tapes or floppy disks,
Various characteristics are required depending on the application.

Recently, video tapes have high video output,
It is required that the electromagnetic conversion characteristics be excellent, such as excellent original image reproduction capability, and that the tapes also have good characteristics in terms of tape running properties.

Particularly, a video tape used for 8 mm video which has recently been put to practical use is used under severer conditions as compared with a conventional video tape. In terms of characteristics, it is required to be at a higher level than conventional video tapes.

In particular, recent magnetic recording media such as 8-mm video tapes have a high magnetic layer surface for the purpose of reducing the spacing loss between the magnetic head and the magnetic layer surface and improving electromagnetic conversion characteristics. It is becoming smoother.

However, when the surface of the magnetic layer is smoothed, the friction coefficient of the magnetic layer increases, and when the magnetic layer comes into contact with the magnetic head or another traveling system, a squeaking sound (so-called tape squeal) is generated. There is.

By the way, conventionally, in order to improve the running property of a magnetic recording medium by lowering the friction coefficient of the magnetic layer, a method of containing a lubricant in the magnetic layer has been adopted.

As a lubricant, use of various substances such as a compound containing a fatty acid, a fatty acid ester, and a silicone oil has been proposed.

These lubricants, although having some effect in the normal use of conventional magnetic recording media, use, for example, very finely divided ferromagnetic metal powders,
In addition, in the case of an 8 mm video tape having a high smoothness on the surface of the magnetic layer, the friction coefficient of the magnetic layer may not be sufficiently reduced.

In other words, the measures for improving the running property of the magnetic recording medium are sufficient for a magnetic recording medium which is required to be at a higher level than the conventional one in various characteristics such as an 8-mm video tape. Not really.

In order to solve these problems, a monoketone compound has been known (Japanese Patent Application Laid-Open No. 57-158026), and a magnetic recording medium containing a diketone represented by the following general formula [II] in a magnetic layer has been proposed (Japanese Patent Application Laid-open No. No. 62-95731).

R ¹ —CO—CO—R ² [II] wherein ^one of R ¹ and R ² is a saturated or unsaturated linear aliphatic hydrocarbon group having 9 to 23 carbon atoms, and the other is It is a saturated or unsaturated chain aliphatic hydrocarbon of several 5 to 23.

However, such diketones have a stronger adsorption of CO groups on the surface of the magnetic layer than monoketones because the polar CO groups are adjacent to each other, but the behavior is similar to that of monoketones. The lubricity at the beginning of running is not sufficiently exhibited, and good lubricity is exhibited in the temperature range of about 23 ° C to 40 ° C.
At high temperatures of ° C., sufficient lubricity may not be exhibited.

(Object of the Invention) A first object of the present invention is to provide a novel magnetic recording medium.

A second object of the present invention is to provide a magnetic recording medium having improved running properties mainly at low to high temperatures, and also having good electromagnetic conversion characteristics.

(Constitution of the Invention) That is, the object of the present invention is to provide a magnetic recording medium having a nonmagnetic support and a magnetic layer provided on the support and having a ferromagnetic powder dispersed in a binder, wherein the magnetic layer comprises: This can be achieved by a magnetic recording medium characterized by containing a diketone represented by the following general formula [I].

R ₁ —CO—R ₃ —CO—R ₂ [I] (where R ¹ and R ² are a saturated or unsaturated linear aliphatic hydrocarbon group having 5 to 23 carbon atoms, and R ³ is Numbers 1-3
Is a divalent saturated hydrocarbon group).

More preferably, the object of the present invention is that the magnetic layer is a saturated or unsaturated and further branched or straight-chain fatty acid having a carbon number of 12 to 22, and a carbon number of 12 to 22. Saturated or saturated and further branched or straight chain fatty acids with 1 carbon atom
It can be attained by a magnetic recording medium characterized by containing an ester with an aliphatic alcohol in the range of from 5 to 5.

More preferably, the object of the present invention is a non-magnetic support,
Magnetic recording having a magnetic layer in which a ferromagnetic powder is dispersed in a binder provided on one surface of the support and a filler dispersed in a binder provided on the other surface, but having a back layer The medium can be achieved by magnetic recording characterized in that the magnetic layer contains the diketone represented by the general formula [1].

 Preferred embodiments of the present invention are as follows.

(1) A magnetic recording medium, wherein the content of the diketone represented by the general formula [I] in the magnetic layer is at least 0.01 part by weight based on 100 parts by weight of the ferromagnetic powder.

(2) The content of the diketone represented by the above general formula [I] in the magnetic layer is 0.02 to 5 with respect to 100 parts by weight of the ferromagnetic powder.
A magnetic recording medium characterized by being in the range of parts by weight.

(3) A magnetic recording medium wherein R ¹ and R ² are the same saturated or unsaturated chain-like aliphatic hydrocarbon group having 5 to 23 carbon atoms.

(4) The total content of fatty acids and fatty acid esters contained in the magnetic layer is 0.02 to 1 with respect to 100 parts by weight of the ferromagnetic powder.
A magnetic recording medium characterized by being within a range of 0 parts by weight.

(5) The ratio of the content of the compound represented by the general formula [I] in the magnetic layer to the total weight content of fatty acids and fatty acid esters is in the range of 1: 2 to 1: 8. Magnetic recording medium.

(6) A magnetic recording medium, wherein the ferromagnetic powder is a ferromagnetic metal fine powder having a specific surface area of 42 m ² / g or more.

The reason why the magnetic recording medium containing the diketone of the present invention exhibits particularly good running properties is not necessarily clear, but the two [-] groups in which the diketone is separated in the molecule are present.
It is presumed to be due to having a [CO-] bond.
That is, a diketone is a compound having no polar group such as a [-CO-] bond in a molecule, and [-CO-] in a molecule.
−] It has a better affinity for components constituting the magnetic layer such as a ferromagnetic powder or a binder and has a higher retention in the magnetic layer than ordinary ketones having one or two adjacent bonds. . Further, since the compound has two [-CO-] bonds as polar groups and thus generally has a higher boiling point than the corresponding ketone, the magnetic recording medium containing a diketone has good properties even under conditions of high temperature and high humidity. It is presumed to have runnability.

That is, in the present invention, an α-type diketone in which a monoketone or a CO group is adjacent easily forms a dense portion or a sparse portion on the surface of the magnetic layer, whereas an alkylene group is present between the CO groups so that they are appropriately separated. It adsorbs to the magnetic layer at the position, and more strongly adsorbs due to the presence of two adsorption points. Further, since the adsorption points are separated, it is difficult to form a dense portion and a sparse portion of the lubricant, and the lubricant exists uniformly. Therefore, it is considered that excellent lubricating properties are exhibited from an early stage and extremely excellent even at a low temperature or a high temperature due to a strong adsorption force. Although the diketone of the present invention has good crystallinity, when used in combination with a fatty acid or a fatty acid ester, a phenomenon of a decrease in melting point occurs, and further excellent lubricating properties are exhibited.

The diketone used in the present invention is the following compound.

R ¹ —CO—R ³ —CO—R ² [I] In the above general formula, R ¹ and R ² are a saturated or unsaturated linear aliphatic hydrocarbon group having 5 to 23 carbon atoms, and R ³ Is a divalent saturated hydrocarbon group having 1 to 3 carbon atoms.

However, the carbon numbers of R ¹ and R ² do not need to be the same, and different types of saturated or unsaturated chain aliphatic hydrocarbon groups having carbon numbers in the range of 5 to 23 may be used. R ¹
And magnetic recording medium both R ² contains a diketone is a chain aliphatic hydrocarbon group having the range of saturated or unsaturated, can not be ensured improved runnability.

In the present invention, the diketone is preferably contained in an amount of 0.01 part by weight or more based on 100 parts by weight of the ferromagnetic powder contained in the magnetic layer, and particularly preferably contained in the range of 0.02 to 5 parts by weight. . If the content of the diketone is less than 0.01% by weight, the coefficient of friction of the surface of the magnetic layer may not be sufficiently reduced.

Examples of such diketone _{compounds, C 4 H 9 -CO-CH} 2 -CH 2 COC 4 H 9, C 5 H 11 -CO-CH 2 COC 5 H 11, C 9 H 19 -CO- _{CH 2 -CO-C 9 H 19} , C 16 H 33 -CO-CH 2 -CH 2 -CO-C 16 H 33, C 16 H 33 -CO-CH 2 CH 2 CH 2 -CO-C 17 H 35 _{, C 17 H 35 -CO-CH} 2 CH 2 -CO-C 17 H 35, and can include compounds such as _{C 23 H 47 -CO-CH 3} CH 3 CH 3 -CO-C 23 H 47 .

 The method for producing the diketone of the present invention is as follows.

Refer to the following documents Here is an example in which is synthesized.

_BLAISE , Cr ▲, 314; Vgl.B _L. , _MONTAGNE , Cr ▲ ▼, 1345) Glutaric acid-bi together with undecanylmagnesium bromide
(s-diethylamide) by a substitution reaction in a yield of 20 to 30%.

The fatty acids used in combination with the diketone of the present invention include the following.

For example, as an example of a linear saturated fatty acid, Etc., but these branches may be used.

 On the other hand, examples of unsaturated fatty acid monoenoic acid are shown below.

The fatty acid esters used in combination with the diketones of the present invention are as follows.

For example, an ester of a saturated or unsaturated fatty acid and an aliphatic alcohol having 1 to 5 carbon atoms described in the section of examples of the type of fatty acid.

When a fatty acid and a fatty acid ester are included in addition to the diketone, the total content of the fatty acid and the fatty acid ester may be set within a range of 0.02 to 10 parts by weight based on 100 parts by weight of the ferromagnetic powder. preferable.

The ratio between the content of the diketone contained in the magnetic layer and the total weight content of the fatty acid and the fatty acid ester is usually set in the range of 1: 2 to 1: 8.

The magnetic recording medium of the present invention basically has a structure in which a nonmagnetic support and a magnetic layer composed of ferromagnetic powder (ferromagnetic material) dispersed in a binder are provided on one surface of the support. And more preferably a configuration in which a back layer is provided on the other surface.

As a material for forming the non-magnetic support, those usually used as a material for a non-magnetic support of a magnetic recording medium can be used.

Examples of the material include polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamide imide, polyimide, and the like, as well as metal foils such as aluminum foil and stainless steel foil.

The non-magnetic support is generally 3 to 50 μm, preferably 5 to 50 μm.
It has a thickness of 3030 μm.

The nonmagnetic support may have a backcoat layer (backing layer) provided on the side where the magnetic layer is not provided.

The magnetic recording medium of the present invention is provided with a magnetic layer in which ferromagnetic powder is dispersed in a binder on the above-mentioned non-magnetic support.

Examples of the ferromagnetic powder include ferromagnetic powders of metal oxides such as γ-Fe ₂ O ₃ and Fe ₃ O _{4 and} modified metal oxides such as γ-Fe ₂ O ₃ containing Co. Examples thereof include magnetic powder and ferromagnetic metal fine powder containing a ferromagnetic metal such as iron as a main component. In particular, it is preferable to use ferromagnetic metal fine powder.

When a ferromagnetic metal fine powder is used, the ferromagnetic metal fine powder is a ferromagnetic metal fine powder containing iron, cobalt or nickel, and has a specific surface area (S BET) of at least 42 m ² / g (particularly preferably (45 m ² / g or more). The specific surface area of the ferromagnetic metal powder is 42 m ²
If it is smaller than / g, the electromagnetic conversion characteristics may not be sufficiently improved.

As an example of the ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75% by weight or more, and
At least one ferromagnetic metal or alloy of at least one weight% (eg, Fe, Co, Ni, Fe-Co, Fe-Ni, Co-Ni, Co-Ni
-Fe), and other components (eg, Al, Si, S, Sc, Ti, V, Cr, Mn, Cu, Zn,
Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, A
u, Hg, Pb, Bi, La, Ce, Pr, Nd, B, P). Further, the ferromagnetic metal component may contain a small amount of water, hydroxide or oxide. Methods for producing these ferromagnetic metal fine powders are already known, and the ferromagnetic metal fine powder used in the present invention can also be produced according to these known methods.

The shape of the ferromagnetic metal fine powder is not particularly limited, but usually a needle shape, a die shape, a rice grain shape, a plate shape or the like is used. In particular, it is preferable to use a needle-like material.

As the binder, those commonly used can be used. Examples of resins to be used include cellulose derivatives, vinyl chloride / vinyl acetate copolymer resins containing a third component such as vinyl chloride / vinyl acetate / maleic anhydride copolymer, and vinyl chloride / vinyl acetate copolymer resins. , Vinylidene chloride resin, polyester resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, phenoxy resin, epoxy resin, butadiene / acrylonitrile copolymer resin, polyurethane resin, and urethane epoxy resin. Or in combination.

Furthermore, when using the binder of the present invention, it is preferable to use a polyisocyanate compound in combination. This is because the polyisocyanate compound reacts to form a three-dimensional network cross-linked structure, so that the strength of the magnetic layer increases.

The polyisocyanate compound can be selected from commonly used ones.

The binder used in the present invention is generally a ferromagnetic powder 100.
10 to 100 parts by weight relative to parts by weight, preferably 15 to 5 parts by weight
Used in the range of 0 parts by weight.

In the magnetic layer of the magnetic recording medium of the present invention, the binder described above,
In addition to ferromagnetic powder, diketone and optionally added fatty acids and fatty acid esters, it contains additives such as commonly used dispersants, other lubricants, stabilizers, abrasives and antistatic agents. There may be.

Next, a method for manufacturing the magnetic recording medium of the present invention will be described.

The magnetic recording medium of the present invention is prepared by dispersing a ferromagnetic powder, a binder, a diketone, and the above-described additives used as needed in an organic solvent such as methyl ethyl ketone and cyclohexanone, which are commonly used, to prepare a magnetic paint. ,
After applying this magnetic paint on a non-magnetic support, it is dried,
It can be manufactured by cutting. Usually, the magnetic layer is applied directly on the non-magnetic support, but may be provided via an adhesive layer or an undercoat layer. Alternatively, it can be manufactured by applying a magnetic paint, subjecting the applied layer to a magnetic field orientation treatment before drying, and then passing through a drying step, a surface smoothing step, and a curing step. Methods for preparing a magnetic paint, a coating method, a magnetic field orientation treatment method, a drying method, a surface smoothing treatment method, a curing method, and the like are already known, and the magnetic recording medium of the present invention can also be produced according to these methods.

The magnetic recording medium of the present invention has a low coefficient of friction on the surface of the magnetic layer and exhibits good running properties.

Therefore, a magnetic recording medium having an extremely smooth magnetic layer surface, such as an 8 mm video tape, exhibits good running properties, and at the same time, ensures good contact between the smooth magnetic layer and the magnetic head. Therefore, there is an advantage that a high reproduction output is exhibited.

The magnetic recording medium of the present invention is not limited to an 8 mm video tape, but may be a normal video tape, an audio tape,
Of course, it can be used as a magnetic recording medium such as a magnetic tape for computers and a floppy disk.

(Effect of the Invention) The magnetic recording medium of the present invention contains a diketone compound represented by the general formula [I] in the magnetic layer, thereby lowering the friction coefficient of the surface of the magnetic layer and achieving excellent running properties and durability. Show. In particular, since the magnetic layer contains a diketone, not only does the magnetic layer have good running properties under normal use conditions of the magnetic recording medium, but also has a small variation in the friction coefficient of the magnetic layer surface even under conditions of high temperature and high humidity, resulting in stable running. Show the system. Furthermore, the electromagnetic conversion characteristics are not reduced even by the improvement of the running performance, and the electromagnetic conversion characteristics are improved because the contact between the magnetic layer and the magnetic head is improved.

(Examples) Next, examples and comparative examples of the present invention will be described. In Examples and Comparative Examples described below, the expression “parts” represents “parts by weight”.

[Example 1] The following composition was kneaded and dispersed using a ball mill for 48 hours, and then 5 parts of a polyisocyanate (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) was added thereto. The mixture was further kneaded and dispersed for 1 hour, and then had an average pore diameter of 1 µm. The mixture was filtered using a filter having the following formula to prepare a magnetic paint. The obtained magnetic paint was applied to the surface of a 10 μm-thick polyethylene terephthalate support using a reverse roll such that the thickness of the dried magnetic layer was 4.0 μm.

Magnetic paint composition Ferromagnetic metal fine powder (composition: Fe94%, Zn4%, Ni2%, Hc: 15
00Oe, specific surface area: 54m ² / g) 100 parts Vinyl chloride / vinyl acetate / copolymer (VMCH manufactured by Union Carbide) 12 parts Diketone of formula [I] (R ¹ and R ² are C ₁₇ H ₃₅ ) 1 part R ³ is -CH ₂ CH ₂ -α-Al ₂ O ₃ (average particle diameter 0.3 μm) 5 parts Carbon black (average particle diameter 40 μm) 2 parts Myristic acid 2 parts Butyl stearate 2 parts Methyl ethyl ketone 300 parts Magnetic paint The non-magnetic support coated with is subjected to a magnetic field orientation treatment with a 3000 gauss magnet in a state where the magnetic paint is not dried, and further dried, then subjected to a super calender treatment,
An 8 mm video tape was manufactured by slitting to 8 mm width.

The video tape obtained as described above was recorded with a 7 MHz signal using a video recorder (FUJIX-8) and reproduced. The relative reproduction output of the video tape when the reproduction output at 7 MHz recorded on the reference tape (the tape for 8 mm video obtained in Comparative Example 2) was set to 0 dB was measured.

50 g of the obtained video tape and stainless steel pole (T
Contact the tape 180 ° under the tension of ₁ ).
The tension (T ₂ ) required for running at a speed of 3 cm / min was measured. The measurement was performed at 23 ° C. and 65% RH (condition I) and at 50 ° C. and 80% RH (condition II). From the measured values, the friction coefficient μ _{1 of the} video tape (condition I), μ
₂ (Condition II) was determined by the following equation.

_{μ (1, 2) = 1} / π · 1n (T 2 / T 1) Also, the tape 30 volumes for 8-mm video produced by traveling in the above video recorder, tape squeaking during running test occurs tape Was examined for the number of turns.

Table 1 shows the reproduction output, the coefficient of friction (conditions I and II), and the number of turns where tape squealing occurred.

In Examples and Comparative Examples described below,
Reproduction output, friction coefficient (condition I, condition II) and tape squeal were measured under the above conditions.

Example 2 In Example ₁ , R ¹ is C ₁₆ H ₃₃ , R ² is C ₁₇ H ₃₅ , and R ³ is —CH instead of the diketone in which R ¹ and R ² are both C ₁₇ H _{35. 2} −CH ₂ −
An 8-mm video tape was manufactured in the same manner except that diketone as CH ₂ was used.

Reproduction output and friction coefficient of the obtained tape (condition I, condition
II) and the number of turns of the tape on which the tape squeal occurred are shown in Table 1.

Example 3 An 8-mm video tape was manufactured in the same manner as in Example 1, except that the amount of the diketone was changed to 5 parts.

Reproduction output and friction coefficient of the obtained tape (condition I, condition
II) and the number of turns of the tape on which the tape squeal occurred are shown in Table 1.

Example 4 In Example 1, R ¹ and R ² are both C ₂₃ H ₄₇ and R ³ is —CH ₂ CH ₂ CH instead of the diketone in which R ¹ and R ² are both C ₁₇ H _{35. Two}
An 8-mm video tape was produced in the same manner except that diketone was used.

Reproduction output and friction coefficient of the obtained tape (condition I, condition
II) and the number of turns of the tape on which the tape squeal occurred are shown in Table 1.

Comparative Example 1 An 8-mm video tape was manufactured in the same manner as in Example 1, except that no diketone was used.

Reproduction output and friction coefficient of the obtained tape (condition I, condition
II) and the number of turns of the tape on which the tape squeal occurred are shown in Table 1.

Comparative Example 2 In Example 1, R ¹ and R ² were both C ₄ H ₉ and R ³ were —CH ₂ CH ₂ — instead of the diketone in which R ¹ and R ² were both C ₁₇ H _35. An 8 mm video tape was manufactured in the same manner except that diketone was used.

The positive output of the obtained tape and the coefficient of friction (condition I, condition
II) and the number of turns of the tape on which the tape squeal occurred are shown in Table 1.

Comparative Example 3 In Example 1, R ¹ and R ² were C ₅ H ₁₁ , and R ³ was —CH ₂ — in place of the diketone in which R ¹ and R ² were both C ₁₇ H _35.
An 8 mm video tape was manufactured in the same manner except that diketone was used.

Reproduction output and friction coefficient of the obtained tape (condition I, condition
II) and the number of turns of the tape on which the tape squeal occurred are shown in Table 1.

As is clear from the results in Table 1, the general formula [I] of the present invention
Using the diketone represented by the formula, ie, Examples 1 to 5
All have low coefficient of friction, good tape squeal, and high reproduction output. On the other hand, the compounds other than the compound of the present invention (Comparative Examples 1 and 2) have a high coefficient of friction, many tape squeals,
Further, it can be seen that the reproduction output is low and there is a problem.

As described above, according to the present invention, even under the conditions of 23 ° C. and 65% RH (condition I) and the high temperature and high humidity conditions of 50 ° C. and 80% RH, the friction coefficient did not increase, and good results were obtained.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-95731 (JP, A) JP-A-52-4505 (JP, A) JP-A-2-203421 (JP, A)

Claims (2)

(57) [Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer in which ferromagnetic powder is dispersed in a binder provided on the non-magnetic support, wherein the magnetic layer has the following general formula [I] ]
A magnetic recording medium comprising a diketone represented by the formula: R ¹ —CO—R ³ —CO—R ² [I] (where R ¹ and R ² are a saturated or unsaturated chain aliphatic hydrocarbon group having 11 to 23 carbon atoms, and R ³ is 2 carbon atoms
3 is a divalent saturated hydrocarbon group. ) 2. The magnetic layer according to claim 1, wherein said magnetic layer comprises an aliphatic group having 12 to 22 carbon atoms and a saturated or unsaturated, further branched or straight chain fatty acid having 12 to 22 carbon atoms. Number 1-5
2. The magnetic recording medium according to claim 1, further comprising an ester with an aliphatic alcohol falling within the range.