JP4507042B2 - Magnetic recording medium - Google Patents

Description

【００２０】
上記表１において、ＳＡ＝ステアリン酸、ＳＡＡ＝ステアリン酸アミド、ＢＳ＝ステアリン酸ブチルを表し、＊１はＳＡＡ／ＰＡＡ＝７０／３０（重量比、ＰＡＡ＝パルチミン酸）の混合物を表し、ＳＡの欄の括弧は、ＳＡに代えてミリスチン酸を、ＢＳの欄の括弧は、ＢＳに代えてパルチミン酸ブチルを、また、ＳＡＡの欄の括弧は、ＳＡＡに代えてパルチミン酸アミドを用いたことを表している。
【００２１】
【発明の効果】
表１から明らかなように、本発明の範囲の実施例は磁性層表面に吐出がなく、ヘッド付着がなく、耐久性に優れている。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording medium having a nonmagnetic layer and having a magnetic layer thereon, with good head adhesion and excellent durability, especially for recording and reproducing digital signals at a high recording density. It relates to the medium.
[0002]
[Prior art]
Japanese Patent Publication Nos. 57-4967, 56-10688, and 1-225136 disclose the use of fatty acid amides in the magnetic layer, and surface properties, dispersibility, and friction are disclosed. It has been proposed to be used in combination with various lubricants to prove the effect of being reduced. Further, Japanese Patent No. 2822191 proposes using a magnetic layer in combination with a resin having a polar group such as an epoxy group or sulfonic acid and a fatty acid amide.
[0003]
[Problems to be solved by the invention]
However, in recent years, the magnetic layer thickness tends to be as thin as 0.2 μm or less in order to cope with high recording density magnetic recording, and the magnetic recording medium having such a thin magnetic layer is disclosed in each of the above publications. Even if a combination of a lubricant and a resin is applied, the magnetic layer is very thin, so that the absolute amount of the lubricant is insufficient and sufficient durability and reliability cannot be obtained. In addition, when added in a large amount, problems such as discharge of the lubricant during storage at high temperature and high humidity often occur.
[0004]
It is an object of the present invention to obtain a high recording density magnetic recording medium that is excellent in durability and head adhesion even with a thin magnetic layer of 0.2 μm or less, and that does not discharge lubricant even when stored at high temperature and high humidity. And
[0005]
[Means for Solving the Problems]
The above object can be achieved by the following constitution of the present invention.
(1) On a nonmagnetic support, a nonmagnetic layer having a thickness of 0.4 to 2.0 μm mainly containing nonmagnetic powder and a binder is provided, and a magnetic layer having a thickness of 0.2 μm or less is formed thereon. In the magnetic recording medium, the nonmagnetic layer contains fatty acid, fatty acid amide, and fatty acid ester , and the content thereof is the total amount of fatty acid, fatty acid amide, and fatty acid ester in the nonmagnetic layer with respect to 100 parts by weight of the nonmagnetic powder. 1.0 to 2.3 parts by weight, fatty acid 0.2 to 1.0 part by weight, fatty acid amide 0.1 to 0.5 part by weight, fatty acid ester 0.5 to 1.0 part by weight A magnetic recording medium , wherein the fatty acid is stearic acid, the fatty acid amide is stearic acid amide, and the fatty acid ester is butyl stearate.
(2) The magnetic recording medium as described in (1) above, wherein the nonmagnetic powder contains α iron oxide and / or carbon black.
(3) The magnetic recording medium as described in (2) above, wherein the α iron oxide is surface-treated with Al or Si.
(4) The specific surface area (BET value) of carbon black by the BET method is 40 to 70 m ² / g,
The magnetic recording medium as described in (2) or (3) above, having an average particle diameter of 25 to 40 nm and a DBP oil absorption of 40 to 55 cc / 100 g.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, since the nonmagnetic powder and the fatty acid, fatty acid amide, and fatty acid ester as the lubricant are contained in a very limited amount in the nonmagnetic layer, the friction of the magnetic layer is reduced and the durability is improved. Has an effect. When fatty acid amide is added together with fatty acid and fatty acid ester only to the magnetic layer, friction is reduced with a small amount of fatty acid amide, but in a medium with a thin magnetic layer, the amount contained is very small because the magnetic layer is thin. There is no effect to improve durability. On the other hand, when a large amount is added, for example, when about 1 part by weight is added to 100 parts by weight of the magnetic powder, it is discharged onto the surface of the magnetic layer or the coating is aggregated.
[0007]
In the present invention, the nonmagnetic layer contains nonmagnetic powder, fatty acid, fatty acid amide, and fatty acid ester, and the total amount of fatty acid, fatty acid amide, and fatty acid ester is 1.0 to 2.3 with respect to 100 parts by weight of the nonmagnetic powder. Discharge because it is part by weight, 0.2 to 1.0 part by weight of fatty acid, 0.1 to 0.5 part by weight of fatty acid amide, and 0.5 to 1.0 part by weight of fatty acid ester The effect that the friction of the magnetic layer is reduced and the durability is improved can be obtained. Preferably, the fatty acid is 0.3 to 0.5 parts by weight, the fatty acid amide is 0.1 to 0.3 parts by weight, and the fatty acid ester is 0.6 to 0.9 parts by weight.
[0008]
The reason why the above effect occurs is not clear, but since the fatty acid contained in the nonmagnetic layer is generally easily adsorbed to the nonmagnetic powder contained in the nonmagnetic layer, the nonmagnetic layer The fatty acid amides and fatty acid esters that are released without adsorbing to the non-magnetic powder can move relatively easily due to the structure, and the fatty acid amide is accompanied by fatty acids. This is probably because the effect is so strong that it gradually emerges from the nonmagnetic layer onto the surface of the magnetic layer. The effect of migration of such fatty acids, fatty acid amides and fatty acid esters appears only when an appropriate amount of fatty acid amide is contained in the nonmagnetic layer. Even if fatty acids and fatty acid amides that are considered to migrate from the nonmagnetic layer are previously added to the magnetic layer, such an effect cannot be obtained.
[0009]
If the total amount of the lubricant is less than 1.0 part by weight with respect to 100 parts by weight of the non-magnetic powder, the intended durability cannot be obtained, and if it exceeds 2.3 parts by weight, the head adheres to the excess lubricant. Becomes worse. Further, when the fatty acid is less than 0.2 parts by weight, the durability deteriorates, and when it exceeds 1.0 parts by weight, the head adhesion deteriorates. When the fatty acid amide is less than 0.1 part by weight, the effect of entraining the fatty acid cannot be obtained, and the durability deteriorates. When the fatty acid amide exceeds 0.5 part by weight, the excess fatty acid amide is converted into the magnetic layer. It discharges to the surface. When the fatty acid ester is less than 0.5 part by weight, the effect of entraining the fatty acid cannot be obtained and the durability is deteriorated. On the other hand, when the amount exceeds 1.0 part by weight, the nonmagnetic layer is plasticized and the durability is deteriorated.
[0010]
Examples of the fatty acid amide that can be used in the present invention include lauric acid amide, myristic acid amide, palmitic acid amide, and stearic acid amide. In particular, when stearic acid amide (hereinafter sometimes abbreviated as “SAA”) and palmitic acid amide (PAA) are used, the effects of the present invention can be exhibited better. Only one type of fatty acid amide may be used, but a mixture of stearic acid amide and palmitic acid amide may be used, and the weight ratio of stearic acid amide / palmitic acid amide is 60/40 to 80/20 Is easily industrially available and can be preferably used. Examples of fatty acids include lauric acid, myristic acid (MA), palmitic acid, stearic acid (SA), oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, elaidic acid, and the like. Myristic acid and palmitic acid are preferred. In particular, stearic acid is effective in improving durability. Examples of fatty acid esters include butyl myristate, butyl palmitate (BP), butyl stearate (BS), neopentyl glycol dioleate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, oleyl oleate, stearin Examples include isocetyl acid, isotridecyl stearate, octyl stearate, isooctyl stearate, amyl stearate, butoxyethyl stearate. For example, when stearic acid is used as the fatty acid, the fatty acid-derived component is stearic acid. However, it is preferable because the entrainment effect of the fatty acid is easily obtained. The same applies to the fatty acid amide. Furthermore, since butyl stearate has a relatively simple structure and can easily move in the non-magnetic layer and the magnetic layer, the stearic acid amide has a high effect of entraining the stearic acid when moving from the non-magnetic layer to the magnetic layer. If used, the effect of the present invention can be easily obtained.
[0011]
In the present invention, α iron oxide and / or carbon black is preferred as the nonmagnetic powder contained in the nonmagnetic layer. The α iron oxide is preferably surface-treated with Al or Si, and the specific surface area (BET value) of carbon black is 40 to 70 m ² / g, the average particle size is 25 to 40 nm, the DBP oil absorption is 40 to 55 cc / It is preferable that it is 100 g. By doing in this way, it becomes possible to exhibit the said accompanying effect more. The thickness of the magnetic layer is 0.2 μm or less, preferably 0.20 to 0.05 μm in terms of dry thickness. The dry film thickness of the nonmagnetic layer is preferably 0.4 to 2.0 μm.
It becomes easy to acquire the said accompanying effect by setting it as these thickness structures. As the ferromagnetic powder used in the present invention, conventionally known magnetic powder can be used, and magnetic powder having a coercive force and particle size suitable for a magnetic recording apparatus can be used. In order to obtain the characteristics required for the recording medium, the ferromagnetic alloy powder mainly composed of Fe has a large coercive force and saturation magnetization and is more effective in designing the medium.
[0012]
Conventionally known non-magnetic powders, binders, abrasives, dispersants, carbon, and curing agents used in the present invention can be used, and manufacturing methods (dispersion method, coating method, etc.) have also been conventionally used. Can be used.
【Example】
Hereinafter, specific examples of the present invention will be described together with comparative examples.
A magnetic recording medium having a nonmagnetic layer, a magnetic layer and a backcoat layer having the following composition was produced.
Example 1 A nonmagnetic paint for forming a nonmagnetic layer was prepared.
<Nonmagnetic coating composition for nonmagnetic layer formation>
Nonmagnetic powder (DPN250BW manufactured by Toda Kogyo)
Acicular iron oxide: 75 parts by weight Al / SiO ₂ : 0.16 / 0.23 parts by weight BET value: 53 m ² / g
pH: 5.5
Soluble Na content: 24ppm
Soluble Ca content: 9ppm
Bulk density: 0.7g / ml
Long axis length: 0.15 μm
Short axis length: 0.03 μm
Carbon black (RavenR760B made by Colombian Carbon) ... 25 parts by weight average particle size 30 nm
BET63m ² / g
DBP oil absorption 48cc / 100g
Resin (Toyobo TB0246) ... 9 parts by weight Vinyl chloride-epoxy-containing monomer copolymer (electron beam curable resin)
Average degree of polymerization: 310
Epoxy content: 3 parts by weight potassium persulfate used S content: 0.6 parts by weight 2-isocyanatoethyl methacrylate (MOI) is used to acrylically modify MR110 manufactured by Nippon Zeon Co., Ltd.
Acrylic content: 6 mol / 1 mol resin (Toyobo TB0216) ... 9 parts by weight polyurethane (electron beam curable resin)
Hydroxy-containing acrylic compound-phosphonic acid group-containing phosphorus compound-
Hydroxy-containing polyester polyol Tg 15 ° C
Dispersant (Toho Chemical RE610) ... 3 parts by weight organophosphate compound abrasive (Sumitomo Chemical HIT60A) ... 5 parts by weight α-alumina average particle size 0.22 μm
Methyl ethyl ketone: 100 parts by weight Toluene: 100 parts by weight Cyclohexanone: 40 parts by weight This composition was sufficiently kneaded with a kneader and then dispersed with a horizontal pin mill. Thereafter, the following composition was added and further dispersed for 1 hour.
Fatty acid (Japanese fat and oil NAA180, stearic acid) ... 0.4 part by weight Fatty acid ester (Nippon Seikatsu BS-S, butyl stearate) ... 0.8 part by weight fatty acid amide (Kao Fatty Acid Amide S) ... 0.2 part by weight stearin Acid amide = 70
Palmitic acid amide = 30 mixture methyl ethyl ketone ... 30 parts by weight Toluene ... 30 parts by weight cyclohexanone ... 15 parts by weight The non-magnetic paint thus obtained is further filtered through a filter having an average pore size of 0.3 µm to produce a non-magnetic paint. did.
[0013]
Next, a magnetic paint for forming the magnetic layer was prepared.
<Magnetic coating composition for magnetic layer formation>
Ferromagnetic powder (Fe-based acicular magnetic powder) ... 100 parts by weight
Co / Al / Y = 30 parts by weight / 4.7 parts by weight / 4.8 parts by weight (based on 100 parts by weight of Fe)
Hc: 187 kA / m (2370 Oe)
σs: 155 Am ² / kg
BET value: 48 m ² / g
Long axis length: 0.10μm
Crystallite size: 160Å
pH: 9.5
Resin (Nippon ZEON MR110) 8 parts by weight vinyl chloride copolymer PVC / 2HEMA / AGE / molecular end OSO ₃ K: 84.5 / 4.5 / 7.4 / 0.36 (weight ratio)
Resin (Toyobo UR8200): 5 parts by weight polyester polyurethane
SO ₃ Na group-containing molecular weight (Mn): 20,000 dispersant (Toho Chemical RE610, organophosphate compound) 3 parts by weight abrasive (Sumitomo Chemical HIT82, α alumina) 3 parts by weight average particle size 0.09 μm
Methyl ethyl ketone: 100 parts by weight Toluene: 100 parts by weight Cyclohexanone: 40 parts by weight This composition was sufficiently kneaded with a kneader and then dispersed with a horizontal pin mill. Thereafter, the following composition was added and further dispersed for 1 hour.
Fatty acid (Japanese fat and oil NAA180, stearic acid) ... 1.2 parts by weight Fatty acid ester (Nippon Seikatsu BS-S, butyl stearate) ... 1.0 part by weight Methyl ethyl ketone ... 80 parts by weight Toluene ... 80 parts by weight cyclohexanone ... 220 parts by weight 3 parts by weight of a curing agent (Japanese polyurethane C-3041, trimolecular adduct of TDI (tolylene diisocyanate) of trimethylolpropane) was added to and mixed with the magnetic coating material thus obtained. A magnetic paint was prepared by filtration through a 04 μm filter.
[0014]
Subsequently, the following coating material for backcoat layer formation was produced.
<Coating composition for backcoat layer formation>
Carbon black (BP-800 made by Cabot) ... 100 parts by weight average particle diameter 17 nm
BET210m ² / g
Carbon black (Seba curve MT made by Colombian carbon) ... 0.2 parts by weight Thermal carbon particle size: 350 nm
BET value: 7m ² / g
Resin (Asahi Kasei BTH1 / 2, nitrocellulose) ... 80 parts by weight Resin (Toyobo UR-8700) ... 40 parts by weight Polyurethane SO ₃ Na-containing methyl ethyl ketone ... 150 parts by weight Toluene ... 150 parts by weight cyclohexanone ... 80 parts by weight After sufficiently kneading with a kneader, dispersion was performed with a sand grind mill. Thereafter, the following composition was added and further dispersed.
Methyl ethyl ketone: 400 parts by weight Toluene: 400 parts by weight Cyclohexanone: 200 parts by weight Addition of 20 parts by weight of a curing agent (Japanese polyurethane C-3041, trimethylolpropane TDI triadduct) to the backcoat paint thus obtained This was mixed and further filtered through a filter having an average pore size of 0.5 μm to prepare a backcoat paint.
[0015]
Using the coating material for forming the nonmagnetic layer, the coating material for forming the magnetic layer, and the coating material for forming the backcoat layer thus obtained, a sample of the magnetic recording medium was prepared in the following manner.
(Application)
A nonmagnetic layer-forming coating material was applied to a 4.4 μm polyaramid support with a nozzle so that the thickness after drying and calendering was 0.7 μm. Thereafter, calendering was performed under conditions of a temperature of 100 ° C., a linear pressure of 2940 N / cm (300 kg / cm), and 3 nips, and further EB irradiation was performed at 4.5 Mrad by an electron beam irradiation apparatus. At this time, the surface roughness (Ra) of the lower layer was 3.5 nm. On the nonmagnetic layer thus formed, the magnetic layer was coated with a nozzle so that the thickness after processing was 0.15 μm, a 0.7 T (tesla) oriented magnet was applied, and then the coating film was dried, Next, calendering was performed under the conditions of a temperature of 100 ° C., a linear pressure of 2550 N / cm (260 kg / cm), and 3 nips.
[0016]
On the surface of the support opposite to the surface on which the magnetic layer is formed, the backcoat layer-forming coating material is applied with a nozzle so as to have a thickness of 0.5 μm, and then the coating film is dried. Next, calendering was performed under conditions of a temperature of 90 ° C., a linear pressure of 2058 N / cm (210 kg / cm), and 3 nips. The magnetic recording medium film after completion of such a series of treatments was wound on a winding roll. This state was allowed to stand for 24 hours, and then a thermosetting treatment was performed at 60 ° C. for 24 hours.
[0017]
The magnetic recording medium film thus produced was applied to a slitter and cut to a width of 3.81 mm to produce a magnetic tape sample.
(Examples 2-11, Comparative Examples 1-7)
As shown in Table 1, a magnetic tape sample was prepared in the same manner as in Example 1 except that the amounts of fatty acid, fatty acid amide, and fatty acid ester in the nonmagnetic layer were changed. In Examples 6 and 7 and Comparative Examples 5 and 7, the amount of lubricant in the magnetic layer was also changed as shown in Table 1. Except for Example 1, a fatty acid amide having a single component was used.
[0018]
The magnetic tapes of Examples 1 to 6 and Comparative Examples 1 to 7 thus produced were evaluated for (1) durability, (2) head adhesion, and (3) ejection in the following manner.
(1) Durability Durability evaluation was performed with a Sony data drive SDT-10000 having a 3.81 mm format. The durability was determined by writing / reading a part of the magnetic tape up to 2000 times, and when it stopped less than that, the number of times was displayed in Table 1.
(2) Head Adherence A 155 m long magnetic tape was run continuously six times at a time using a Sony data drive SDT-10000 in 3.81 mm format, and the head after running was a microscope made by Keyence Corporation. The head contamination was evaluated.
The evaluation criteria for head adhesion are as follows.
◎ When there is no adhesion to the head.
○ When there is no deposit on the head sliding surface.
× When there is a deposit on the head sliding surface.
(3) The tape was stored for 5 days in a thermostatic chamber set to an environment of 50 ° C. and 80 RH, and the surface of the tape after storage was observed with a microscope to confirm the presence or absence of discharge.
[0019]
The evaluation criteria for ejection are as follows: ○ When there is no ejection on the tape.
△ When there is a slight discharge on a part of the tape.
× When there is discharge on the entire surface of the tape.
The above evaluation results are shown in Table 1.
[Table 1]

[0020]
In Table 1 above, SA = stearic acid, SAA = stearic amide, BS = butyl stearate, * 1 represents a mixture of SAA / PAA = 70/30 (weight ratio, PAA = paltimic acid), The parentheses in the column used are myristic acid instead of SA, the parentheses in the BS column used butyl palmitate instead of BS, and the parentheses in the SAA column used palmitic acid amide instead of SAA. Represents.
[0021]
【The invention's effect】
As is apparent from Table 1, the examples within the scope of the present invention do not discharge on the surface of the magnetic layer, do not adhere to the head, and are excellent in durability.

Claims (4)

A magnetic recording medium having a nonmagnetic layer having a thickness of 0.4 to 2.0 μm mainly containing a nonmagnetic powder and a binder on a nonmagnetic support, and further having a magnetic layer having a thickness of 0.2 μm or less. The nonmagnetic layer contains a fatty acid, a fatty acid amide, and a fatty acid ester . The content of the fatty acid, the fatty acid amide, and the fatty acid ester in the nonmagnetic layer with respect to 100 parts by weight of the nonmagnetic powder is 1. 0 to 2.3 parts by weight, fatty acid 0.2 to 1.0 parts by weight, 0.1 to 0.5 parts by weight fatty acid amides, Ri fatty acid ester is 0.5 to 1.0 parts by weight der, fatty Is a stearic acid, a fatty acid amide is stearic acid amide, and a fatty acid ester is butyl stearate. The magnetic recording medium according to claim 1 , wherein the non-magnetic powder contains α-iron oxide and / or carbon black. The magnetic recording medium according to claim 2 , wherein the iron oxide is surface-treated with Al or Si. Wherein BET specific surface area of carbon black (BET value) of the 40~70m ² / g, average particle size 25 to 40 nm, according to claim 2 or 3 DBP oil absorption amount is equal to or is 40~55cc / 100g Magnetic recording media.