JP2831748B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a magnetic recording medium having excellent running durability and free from bleeding (powder blowing) during storage.

[Problems to be solved by conventional technology and invention]

Magnetic recording media such as video tapes and floppy disks are generally prepared by applying a magnetic paint consisting of magnetic powder, a binder resin, an organic solvent and other necessary components on a non-magnetic support such as a polyester film. In particular, in the case of a video tape, the head may be stained while the tape is running (particularly in a still mode), and the tape itself may be damaged.

Therefore, as one measure for improving the running durability of the magnetic layer, various lubricants are mixed in the magnetic layer.

Conventionally used lubricants include straight-chain saturated or unsaturated fatty acids and the like, but at present these lubricants are hardly satisfactory.
For example, when a high-molecular-weight linear saturated fatty acid such as myristic acid, palmitic acid, or stearic acid is used, it is easily crystallized and may precipitate (bleed) on the surface of the magnetic layer. When a low molecular weight saturated fatty acid is used to prevent crystallization, the volatility increases and the effect becomes poor. Further, when unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid are used, they are susceptible to change over time due to oxidation, and have a problem in stability.

[Means for solving the problem]

Means for Solving the Problems The present inventors have conducted intensive studies to obtain a magnetic recording medium having good lubricity, improved running durability, and no bleed during storage, and have reached the present invention as a result.

That is, the present invention relates to a magnetic recording medium comprising a non-magnetic support and a magnetic layer coated thereon, wherein the magnetic layer has the general formula (I) Wherein R ₁ is an alkyl group having 4 to 24 carbon atoms, and R ₂ is an alkyl group having 4 carbon atoms.
An alkyl group of 3030, M represents a hydrogen atom or an alkali metal atom, m represents an integer of 1 to 4, and p and q each represent an integer having a total carbon number of 20 to 60 in the carboxylic acid molecule. . And a long-chain hyperbranched carboxylic acid represented by the formula (I) or an alkali metal salt thereof and a general formula (II) R ₃ COOR ₄ (II) wherein R ₃ is an alkyl group or alkenyl group having 5 to 26 carbon atoms, _{And 4} is an alkyl group or an alkenyl group having 3 to 28 carbon atoms.) The present invention provides a magnetic recording medium characterized by comprising:

The carboxylic acid having a branched chain represented by the formula (I) used in the present invention is GINikishin (Izv. Akad. Nauk. SSSR, 1
961 , 1487), and can be easily produced by an addition reaction between a fatty acid and an olefin.

The fatty acid used here is a fatty acid having 6 to 26 carbon atoms, for example, caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid and the like. The olefin is an olefin having 6 to 32 carbon atoms, preferably an α-olefin having 8 to 28 carbon atoms.

In addition, when an olefin is added to a fatty acid, it is necessary to use an organic peroxide as a radical generator. Examples of the organic peroxide include dialkyl peroxide, hydroperoxide, ketone peroxide, and peroxide. Oxyesters, diacyl peroxides, peroxydicarbonates and the like can be mentioned. Specific examples include di-tert-butyl peroxide, dicumyl peroxide, and tert-butyl hydroperoxide. The amount of the organic peroxide to be used is usually 0.01 to 5 times the molar amount of the olefin.

As a reaction condition for adding an olefin to a fatty acid, generally, it is usual to add an olefin and an organic peroxide to a fatty acid heated to 50 to 250 ° C., but it is not limited to this method. .

A reaction route for producing the carboxylic acid having a branched chain represented by the formula (I) used in the present invention by the above reaction is shown in the following formula (III), but actually involves a side reaction, and the formula (I) The compounds shown are formed. The carboxylic acid can be purified and isolated from the above reaction product by a method such as distillation. In the present invention, the carboxylic acid may be used after being purified, but the effect of the present invention is not lost even if the carboxylic acid is used in a mixed state of the reaction products.

Reaction pathway formula (III) The long-chain multi-branched carboxylic acid obtained as described above is subjected to fractionation if necessary, and then an alkali agent such as a metal hydroxide is added thereto and neutralized to obtain a long-chain multi-carboxylic acid. It can be an acid salt.

Examples of the fatty acid ester represented by the formula (II) used in the present invention include butyl stearate, octyl myristate, oleyl oleate, butyl palmitate, octyl stearate, stearyl stearate, oleyl stearate and the like.

In the magnetic recording medium of the present invention, the compounding amounts of the long-chain hyperbranched carboxylic acid represented by the formula (I) or an alkali metal salt thereof and the fatty acid ester represented by the formula (II) are as follows.
The long-chain hyperbranched carboxylic acid represented by the formula (I) or the alkali metal salt thereof is 0.2 to 12 parts by weight, preferably 0.5 to part by weight, relative to 0 parts by weight, and the fatty acid represented by the formula (II) The ester is 0.2 to 15 parts by weight, preferably 0.5 to 12 parts by weight.

As the magnetic powder used in the present invention, needle-shaped fine γ
_{-Fe 2 O 3, Fe 3 O} 4, metal oxides such as CrO _2, also Co-coated γ-Fe ₂ O _3, Co-doped γ-Fe ₂ O γ-Fe subjected to processing such as _{3 2} O ₃ , iron metal powder, microplate-shaped barium ferrite and magnetic powder in which a part of Fe atoms are replaced by one or more of Ti, Co, Zn, V, Nd, etc., Co, Fe- Examples include ultrafine powders of metals or alloys such as Co and Fe-Ni. Of these, iron metal powder is particularly poor in chemical stability, so nickel, cobalt, titanium, silicon, aluminum, etc. may be added in small amounts in the form of metal atoms, salts and oxides or surface treated for this improvement. However, these can also be used. Iron metal powder may form a thin oxide film on the surface in a weakly oxidizing atmosphere for stabilization, but metal powder treated in this manner can also be used.

Examples of the binder that can be used in the magnetic layer of the present invention include polyurethane, polyester, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin, polyamide, and polyacrylic acid. Examples include esters, polymethacrylates, polyvinyl acetate, polyvinyl butyral, polyvinylidene chloride, nitrified cotton, maleic acid-modified vinyl chloride / vinyl acetate copolymer, and ethyl cellulose. These may be used alone, but usually used as a mixture of two or more. Further, a plasticizer or a curing agent may be added to adjust the hardness of the resin.

The amount of the binder is generally 15 to 60 parts by weight based on 100 parts by weight of the magnetic powder. Even if the binder has the largest bonding strength, when the amount is less than 15 parts by weight, the strength of the magnetic coating film is weak, and the adhesive strength between the substrate and the magnetic coating film is insufficient. On the other hand, when the amount is more than 60 parts by weight, the concentration of the magnetic powder in the magnetic coating film becomes small, and the reproduction output is disadvantageously reduced. Further, the properties of the coating film may be reduced.

The magnetic layer of the magnetic recording medium of the present invention, in addition to the above components,
Abrasives and antistatic additives commonly used in this field can be added.

In the present invention, a back coat layer may be provided on the back surface (the side opposite to the magnetic layer) of the nonmagnetic support of the magnetic recording medium. As the binder used for the back coat layer, the various binders described above can be used, and among them, a polyurethane resin and a nitrified cotton are used in combination, and a polyisocyanate and a single average particle size as a curing agent are 0.01 to 0.01. It is preferable to use 0.5 μm carbon black. The weight ratio of binder / carbon black in the back coat layer is preferably from 40/60 to 80/20.

Examples of the nonmagnetic support used in producing the magnetic recording medium of the present invention include: polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonate; Polyimide; Plastics such as aromatic polyamides; Metals such as Al and Cu; Paper; The form may be any of film, tape, sheet, disk, card, drum and the like. The surface of the support is corona discharge,
It may be treated with radiation, ultraviolet light, or the like, or may be precoated with a suitable resin.

〔Example〕

Hereinafter, the present invention will be described in more detail by examples,
The present invention is not limited to these examples.

In the examples, parts and percentages are by weight unless otherwise specified.

Example 1 <Formation of Magnetic Layer> A composition having the following paint composition was mixed for 6 hours with a six-cylinder sand grinder manufactured by Igarashi Machine Co., Ltd. Trimethylolpropane triisocyanate (4 parts by weight) was added, and the mixture was further mixed for 15 minutes, and then filtered to separate glass beads, thereby preparing a magnetic paint. Apply this paint 10μm thick
The film is coated on a PET film so that the dry film thickness becomes 3 μm.
A magnetic layer was formed on a T film and wound on a roll.
Next, the magnetic layer was calendered at 80 ° C.

・ Fe-Ni ferromagnetic alloy powder (Fe: Ni = 95: 5, surface area 50m ² / g, H
c = 1480 Oe) 100 parts Gafac RE610 ^* 15 Carbon black (average particle diameter 25 nm) 3 α-Al ₂ O ₃ (average particle diameter 0.3 μm) 10 VAGH ^{* 2} 15 Nipporan 2304 ^{* 3} 10 Lubricant See Table 1 Methyl ethyl ketone 150 parts Toluene 50 Cyclohexanone 75 (Note) * 1: Phosphoric acid dispersant manufactured by Toho Chemical Co., Ltd. * 2: Vinyl chloride / vinyl acetate / polyvinyl alcohol copolymer manufactured by Union Carbide * 3: Nippon Polyurethane Industry Co., Ltd. ) Polyurethane resin <Formation of back coat layer>
After mixing for time, add 20 parts by weight of Coronate L to the mixture,
The mixture was further mixed for 30 minutes to prepare a back coat paint.
This paint was applied to the back surface of the PET film on which the magnetic layer was formed so that the dry film thickness was 0.5 μm, and the paint film was dried to form a back coat layer.

After that, PET with magnetic layer and back coat layer formed
The film was slit into an 8 mm width and loaded into an 8 mm video cassette to form an evaluation cassette.

・ Backcoat paint composition Carbon black ^{* 1} 100 parts Nitrocellulose 50 Nipporan 2304 50 Lecithin 2 parts Methyl ethyl ketone 400 Toluene 200 (Note) * 1: Average particle diameter 25 nm Examples 2 to 8 and Comparative Examples 1 to 3 An 8 mm video tape was prepared in the same manner as in Example 1 except that the compounds and the compounding amounts shown in Table 1 were used as the lubricant.

Example 9 A mixture having the following paint composition was mixed in a batch sand mill manufactured by Igarashi Kikai Co., Ltd. for 4 hours, 3 parts by weight of coronate L was added to the mixture, and the mixture was further mixed for 15 minutes. Was separated to prepare a magnetic paint. This paint is applied to a 14.5 μm thick PET film so that the dry film thickness is 4.5 μm.The coating film is subjected to magnetic field orientation treatment at 1500 Gauss and then dried to form a magnetic layer on the PET film. Wound up. Next, the magnetic layer was calendered at 80 ° C.

Thereafter, the PET film on which the magnetic layer was formed was slit to a width of 1/2 inch and loaded into a VHS cassette to obtain an evaluation cassette.

・ Magnetic layer coating composition Co-coated γ-Fe ₂ O ₃ (surface area 40 m ² / g, Hc = 650 Oe) 100 parts Gafac RE610 ^{* 13} Carbon black (average particle diameter 25 nm) 6 α-Al ₂ O ₃ (average (Particle size 0.3 μm) 10 VAGH ^{* 2} 12 Nipporan 2301 ^{* 3} 10 Lubricant See Table 1 Methyl ethyl ketone 120 parts Toluene 50 Cyclohexanone 50 (Note) * 1: Phosphoric dispersant manufactured by Toho Chemical Co., Ltd. * 2: Union Carbide * 3: Polyurethane resin manufactured by Nippon Polyurethane Industry Co., Ltd. Examples 10 and 11 Other than using the compounds and amounts in Table 1 as lubricants in the magnetic layer coating composition Produced a VHS videotape in the same manner as in Example 9.

8 mm obtained in the above Examples 1 to 11 and Comparative Examples 1 to 3
The characteristics of the video tape or VHS video tape were evaluated by the following methods.

 Table 1 shows the results.

The video decks used in the evaluation of Table 1 were Examples 1 to
8 and Comparative Examples 1 to 3 were based on an 8 mm video deck, and Examples 9 to 11 were based on a VHS video deck.

<Evaluation method> (a) Still test (a ₁ ) Head dirt After running for 1 hour in Examples 1 to 8 and Comparative Examples 1 to 3 and in Examples 9 to 11 for 3 hours in still mode of each deck, The head of the deck was wiped with a cotton swab impregnated with ethanol, and the degree of contamination of the cotton swab was visually determined.

A: It is difficult to confirm whether there is any dirt or not.

B: There is some dirt but no problem.

C: The stain is quite severe.

(A ₂₎ determining visually the running track of the tape of the scratch resistance head.

A: There is no scar or it is difficult to confirm.

B: Scars are clearly present but no problem.

C: The scar is quite intense.

(B) Bleed test The obtained magnetic tape was stored for 7 days in a cycle of 60 ° C for 12 hours and -5 ° C for 12 hours, and finally left at 20 ° C for 2 hours.
The surface of the magnetic layer was visually observed or observed with a reflection type optical microscope, and the presence or absence of white powder was judged.

Claims (1)

(57) [Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer provided on a non-magnetic support, wherein the magnetic layer has the general formula (I) Wherein R ₁ is an alkyl group having 4 to 24 carbon atoms, and R ₂ is an alkyl group having 4 carbon atoms.
An alkyl group of 3030, M represents a hydrogen atom or an alkali metal atom, m represents an integer of 1 to 4, and p and q each represent an integer having a total carbon number of 20 to 60 in the carboxylic acid molecule. . And a long-chain hyperbranched carboxylic acid represented by the formula (I) or an alkali metal salt thereof and a general formula (II) R ₃ COOR ₄ (II) wherein R ₃ is an alkyl group or alkenyl group having 5 to 26 carbon atoms, _{And 4} is an alkyl or alkenyl group having 3 to 28 carbon atoms.) A fatty acid ester represented by the following formula: