JPH04247318A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability, corrosion resistance and traveling property of the magnetic recording medium by providing a magnetic layer on a base body and providing a protective layer contg. the reaction product of a fluorine compd. having at least >=1 isocyanate groups at the terminal of a molecule and a high-polymer resin of >=10000 number average mol.wt. having a hydroxyl group or amino group on this magnetic layer. CONSTITUTION:This magnetic recording medium is constituted by providing the magnetic layer on the base body and providing the protective layer contg. the reaction product of the fluorine compd. having at least >=1 isocyanate groups at the terminal of the molecule and the high-polymer resin, such as vinyl chloride resin, polyurethane resin or cellulose resin, of >=100O0 number average mol.wt. having the hydroxyl group or amino group on this magnetic layer.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to magnetic recording media.
More specifically, the present invention relates to a magnetic recording medium that has excellent durability, corrosion resistance, and runnability.

0002

[Prior Art] Generally, magnetic recording media are made by binding magnetic powder together with a binder component onto a base film, or by depositing ferromagnetic metals or their alloys on a base film by vacuum deposition or the like. ferromagnetic metal thin film magnetic recording media, in which a ferromagnetic metal thin film layer is formed by vacuum evaporation, have excellent high-density recording characteristics. On the other hand, it has a large coefficient of friction with the magnetic head and is easily worn out, and is also easily corroded by corrosive gases such as H2S gas, NO2 gas, and Cl2 gas in the air. Therefore, tetrafluoroethylene telomer is coated on the magnetic layer.
, perfluoroalkyl polyether, and fluorine-based lubricants such as perfluoroalkyl polyether containing hydroxyl, carboxyl, and isocyanate groups, or fatty acids, fatty acid esters, aliphatic amines, aliphatic amides, etc. A protective layer made of an aliphatic lubricant is provided to improve durability, corrosion resistance, and running properties. (JP-A-56-30609, JP-A-58-5763, JP-A-62-9525, JP-A-56-124127,
U.S. Patent No. 377830, U.S. Patent No. 4267238
No. 4,268,556, U.S. Pat. No. 3,490
No. 946)

0003

[Problems to be Solved by the Invention] However, the fluorine-based lubricants and aliphatic lubricants that have been used so far have weak interaction with the magnetic layer surface. It easily separates, making it impossible to sufficiently improve durability, corrosion resistance, and runnability.

0004

[Means for Solving the Problems] The present invention has been made as a result of various studies in view of the current situation. A fluorine compound with excellent lubricity and a fluorine compound with a number average molecular weight of 10 and a hydroxyl or amino group.
By forming a protective layer containing a reaction product with a polymeric resin that has excellent bonding strength with the magnetic layer, such as vinyl chloride resin, polyurethane resin, or cellulose resin, which has a strength of 0.000 or more, it can be used for long periods of time. The protective layer is prevented from separating from the surface of the magnetic layer, and its excellent lubricating effect is fully and sustainably exhibited, thereby sufficiently improving durability, corrosion resistance, and runnability.

In this invention, the fluorine compound used as a raw material for the reaction product used in the protective layer preferably has at least one isocyanate group at the end of the molecule. Preferably used are those obtained by reacting a perfluoroalkyl polyether having a hydroxyl group or a carboxyl group at one or both ends with an isocyanate compound such as a diisocyanate compound.

[0006] Here, examples of perfluoroalkyl polyethers having a hydroxyl group or a carboxyl group at one or both ends of the molecule include the following general formula HOCH2 -CF2O-(C2F4O) p
-(CF2 O)q -CF2 CH2 OHHOOC
-CF2O-(C2F4O)p-(CF2O
)q -CF2 -COOHHOCH2 -CF2 O
-(C2F4O)p -(CF2O)q -CF
3 HOOC-CF2O-(C2F4O)p-
(CF2 O)q -CF3 CF3 -(CF2)
p -(OCH2 CH2 )q -COOHCn F
Preferred examples include those represented by 2n+1CH2 COOH Cn F2n+1CH2 CH2 COOH (in the general formula, p and q are integers of 5 to 200, and n is an integer of 4 to 32).

Examples of isocyanate compounds include diphenylmethane-p,p-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,2,4-(2,4, 4-) Trimethylhexamethylene diisocyanate, tolylene diisocyanate, 4,4'-methylene-bis-cyclohexyl isocyanate, xylylene diisocyanate, isopylidene-bis-4-cyclohexyl isocyanate bis-2-isocyanatoethyl fumarate, bis-2-isocyanatoethyl carbonate, bis-2-isocyanatoethyl-4-cyclohexane-1,2-dicarboxylate, bis-2-isocyanate -toethyl-1,4
,5,6,7,7-hexachloro-5-nobornene-2
, 3-dicarboxylate, tetramethylene diisocyanate, dimethyl-diphenylmethane-p,p'-diisocyanate, metaphenylene diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate and the like.

Fluorine compounds having at least one isocyanate group at the end of the molecule include perfluoroalkyl polyethers having a hydroxyl group or carboxyl group at one or both ends of the molecule, and isocyanate groups. Specific examples of commercially available products include Fomblin DISOC manufactured by Enimont and the like.

[0009] Furthermore, the polymer resin to be reacted with the fluorine compound having at least one isocyanate group at the end of the molecule is a polymer resin having a number average molecular weight of 10,000 or more and having a hydroxyl group or an amino group. For example, both have a number average molecular weight of 1000.
0 or more vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-dimethylamino methacrylate copolymer, vinyl chloride-2-hydroxypropyl acrylate copolymer, vinyl chloride- vinyl acetate
Vinyl chloride resins such as 2-hydroxypropyl acrylate copolymer, hydroxyl group-containing polyurethane resins, cellulose resins such as nitrocellulose and cellulose acetate are preferably used, and these high Molecular resins containing sulfonic acid, phosphoric acid, or their salts as functional groups are also preferably used.

[0010] The reaction between such a polymer resin and the above-mentioned fluorine compound having an isocyanate group
Since fluorine compounds having 7 groups are difficult to dissolve in ketone solvents and have poor compatibility with polymer resins, it is preferable to react in a dilute emulsion state. For example, a dilute solution of a polymer resin dissolved in methyl ethyl ketone is preferable. The desired product can be obtained by preparing a dilute solution of a fluorine compound having an isocyanate group dissolved in fluorocarbon and creating an emulsion using a strong disperser, and utilizing the interfacial reaction of the emulsion. At this time, if the polymer resin has a number average molecular weight of less than 10,000, it will be inferior in durability, and if it is larger than 120,000, it will be difficult to dissolve in a solvent when reacting with a fluorine compound.
000 to 120,000 is preferably used.

A fluorine compound having at least one isocyanate group at the end of the molecule produced in this manner and a fluorine compound having a hydroxyl group or an amino group and having a number average molecular weight of 1
0000 or more vinyl chloride resin, polyurethane resin,
As for reaction products with polymeric resins such as cellulose resins, fluorine compounds have an excellent lubricating function, and the aforementioned polymeric resins having hydroxyl groups or amino groups have excellent bonding strength with the magnetic layer. .

[0012] Therefore, by immersing the magnetic layer in a solution of a reaction product produced by utilizing the interfacial reaction of this emulsion, or by coating or spraying the solution on the surface of the magnetic layer, When a protective layer containing this reaction product is formed on the surface of the magnetic layer, the protective layer is firmly bonded to the surface of the magnetic layer, and even when running for a long time, the protective layer does not separate from the surface of the magnetic layer, providing excellent lubrication. The effect is fully and sustainably exhibited, and durability, corrosion resistance, and runnability are sufficiently improved.

The magnetic layer formed on the substrate is made of γ-Fe2
O3 powder, Fe3 O4 powder, Co-containing γ-Fe
2 O3 powder, Co-containing Fe3 O4 powder, CrO
2 powder, Fe powder, Co powder, Fe-Ni powder, Fe
- A magnetic paint is prepared by mixing and dispersing magnetic powder such as Co powder or barium ferrite with a binder resin and an organic solvent, and this magnetic paint is applied onto a substrate and dried. , Co-Ni, Co-C
It is formed by depositing a ferromagnetic material such as r, Co--P, or Co--Ni--P on a substrate by means such as vacuum evaporation, ion plating, sputtering, or plating.

[0014] Examples of binder resins used in the magnetic layer include vinyl chloride-vinyl acetate copolymers, cellulose resins, polyurethane resins, polyester resins, polyvinyl butyral resins, and isocyanate resins. Any of those commonly used in magnetic recording media, such as carbonaceous compounds, can be suitably used.

Further, as the organic solvent, organic solvents commonly used in magnetic recording media such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, ethyl acetate, tetrahydrofuran, dioxane, toluene, and xylene may be used alone or in combination of two or more. used.

[0016]

[Example] Next, an example of the present invention will be described. Example 1 A 12 μm thick polyester film was loaded into a vacuum evaporation apparatus, and the cobalt-nickel alloy was heated and evaporated under a vacuum of 5×10 −5 Torr to form a 0.2 μm thick cobalt film on the polyester film. - A ferromagnetic metal thin film layer made of a nickel alloy was formed. On the other hand, in a 1% by weight solution of vinyl chloride-vinyl acetate-2-hydroxypropyl methacrylate copolymer in methyl ethyl ketone, a compound having the structural formula OCN-C6H3(CH3)NHCO-
CF2 O-(C2 F4)10────┐
OCN-C6 H3 (CH3)-CONH-OC
A 1% by weight Freon solution of a fluorine compound represented by F2-(OCF2)15-┘ was mixed at 30°C, stirred with a high-speed stirrer to create an emulsion, and then reacted at 50°C while evaporating Freon. Ta. Then, this emulsion solution was left to stand for one day, and vinyl chloride-vinyl acetate-vinyl chloride-vinyl acetate-
The hydroxyl groups of the 2-hydroxypropyl methacrylate copolymer and the isocyanate groups of the fluorine compound were completely reacted. Next, the solution of this reaction product was adjusted to have a solid content concentration of 0.5% by weight, and then this suspension solution was applied by gravure coating onto the ferromagnetic metal thin film layer formed on the polyester film. was applied uniformly and dried to form a protective layer. After that, it was cut into a predetermined width to make magnetic tape.

Example 2 Same as Example 1 except that nitrocellulose was used instead of vinyl chloride-vinyl acetate-2-hydroxypropyl methacrylate copolymer in preparing the emulsion in Example 1. An emulsion was prepared, a suspension solution was prepared, and a protective layer was formed to produce a magnetic tape.

Example 3 In the preparation of the emulsion in Example 1, a polyurethane resin containing an average of 5 hydroxyl groups in the molecule was used instead of the vinyl chloride-vinyl acetate-2-hydroxypropyl methacrylate copolymer. Except for the above, an emulsion was prepared in the same manner as in Example 1, a suspension solution was prepared, a protective layer was formed, and a magnetic tape was produced.

Example 4 Fe magnetic powder

80 parts by weight Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 1
0 〃 Polyurethane resin

6 Trifunctional low molecular weight isocyanate compound
4 〃 Methyl ethyl ketone
100 Toluene

100 This composition was mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint.
A magnetic layer was formed by coating on a 2 μm polyester film to a dry thickness of 3 μm and drying. Next, a suspension solution was uniformly applied onto this magnetic layer using the gravure coating method in the same manner as in Example 1, and dried to form a protective layer, thereby producing a magnetic tape.

Example 5 Same as Example 4 except that nitrocellulose was used instead of vinyl chloride-vinyl acetate-2-hydroxypropyl methacrylate copolymer in preparing the emulsion in Example 4. An emulsion was prepared, a suspension solution was prepared, and a protective layer was formed to produce a magnetic tape.

Example 6 In the preparation of the emulsion in Example 4, a polyurethane resin containing an average of 5 hydroxyl groups in the molecule was used instead of the vinyl chloride-vinyl acetate-2-hydroxypropyl methacrylate copolymer. Except for the above, an emulsion was prepared in the same manner as in Example 4, a suspension solution was prepared, a protective layer was formed, and a magnetic tape was produced.

Comparative Example 1 A ferromagnetic metal thin film layer made of a cobalt-nickel alloy was formed on a polyester film in the same manner as in Example 1. Next, on this ferromagnetic metal thin film layer, a 0.25% by weight solution of vinyl chloride-vinyl acetate-2-hydroxypropyl methacrylate copolymer in methyl ethyl ketone was uniformly applied by gravure coating, and further, on top of this, HOCH2
CF2O-(C2F4)10-(CF2O)
Fluorinert FC77 (3M
A magnetic tape was produced by forming two upper and lower protective layers in the same manner as in Example 1, except that the solution (manufactured by Co., Ltd.) was uniformly applied by gravure coating and dried.

Comparative Example 2 In forming the protective layer in Comparative Example 1, vinyl chloride-
Comparative Example 1 was carried out in the same manner as in Comparative Example 1, except that a 0.25% by weight solution of nitrocellulose in methyl ethyl ketone was used instead of a 0.25% by weight solution of vinyl acetate-2-hydroxypropyl methacrylate copolymer in methyl ethyl ketone. A magnetic tape was produced by forming two upper and lower protective layers.

Comparative Example 3 In forming the protective layer in Comparative Example 1, vinyl chloride-
Except that a 0.25% by weight methyl ethyl ketone solution of a polyurethane resin containing an average of 5 hydroxyl groups in the molecule was used instead of a 0.25% by weight methyl ethyl ketone solution of vinyl acetate-2-hydroxypropyl methacrylate copolymer. In the same manner as in Comparative Example 1, two upper and lower protective layers were formed to produce a magnetic tape.

Comparative Example 4 A magnetic layer was formed on a polyester film in the same manner as in Example 4, and upper and lower layers were formed on this magnetic layer in the same manner as in Comparative Example 1.
A protective layer was formed and a magnetic tape was made.

Comparative Example 5 In forming the protective layer in Comparative Example 4, vinyl chloride-
Comparative Example 4 was carried out in the same manner as in Comparative Example 4, except that a 0.25% by weight solution of nitrocellulose in methyl ethyl ketone was used instead of a 0.25% by weight solution of vinyl acetate-2-hydroxypropyl methacrylate copolymer in methyl ethyl ketone. A magnetic tape was produced by forming two upper and lower protective layers.

Comparative Example 6 In forming the protective layer in Comparative Example 4, vinyl chloride-
Except that a 0.25% by weight methyl ethyl ketone solution of a polyurethane resin containing an average of 5 hydroxyl groups in the molecule was used instead of a 0.25% by weight methyl ethyl ketone solution of vinyl acetate-2-hydroxypropyl methacrylate copolymer. In the same manner as in Comparative Example 4, two upper and lower protective layers were formed to produce a magnetic tape.

Magnetic tape obtained in each example and comparative example
The shuttle durability, jitter characteristics, and corrosion resistance of the sample were tested using the following methods.

<Shuttle durability test> The obtained magnetic tape
When the tape was loaded into an 8mm video deck and each mode such as recording, playback, search, still in recording state, still in playback state was performed for 3 minutes each, each cycle was 500 cycles. This was done by measuring how many dB the initial recording signal would drop.

<Jitter Characteristics Test> Load the obtained magnetic tape into a video deck, record and reproduce a video signal, read the interval of the 15.75 KHz horizontal synchronizing signal of the reproduced signal, and measure the This was done by measuring the gap in the horizontal synchronization signal interval for 1 second.

<Corrosion resistance test> H2S 10ppb, N
A magnetic tape was left in a corrosive gas containing 200 ppb of O2 and 10 ppb of Cl2, and the number of days until the dropout of the magnetic tape at 5 μs became more than 10 times the initial level was measured. Table 1 below shows the results.

[0032]

[0033]

Effects of the Invention As is clear from Table 1 above, the magnetic tapes obtained by the present invention (Examples 1 to 6) are as good as those of Comparative Examples 1 to 6.
Compared to the magnetic tape obtained in 6, the shuttle durability is better, the jitter characteristics are equal or lower, and the corrosion resistance is better. Therefore, the magnetic recording medium obtained by this invention has excellent running properties,
It can be seen that it has excellent durability and corrosion resistance.

Claims (4)

[Claims] 1. A magnetic layer is provided on a substrate, and a fluorine compound having at least one isocyanate group at the end of the molecule and a polymer having a number average molecular weight of 10,000 or more and having a hydroxyl group or an amino group are disposed on the magnetic layer. A magnetic recording medium characterized by having a protective layer containing a reaction product with a resin. 2. The magnetic recording medium according to claim 1, wherein the polymer resin is a vinyl chloride resin having a hydroxyl group or an amino group and having a number average molecular weight of 10,000 or more. 3. The magnetic recording medium according to claim 1, wherein the polymer resin is a polyurethane resin having a hydroxyl group or an amino group and having a number average molecular weight of 10,000 or more. 4. The magnetic recording medium according to claim 1, wherein the polymer resin is a cellulose resin having a hydroxyl group or an amino group and having a number average molecular weight of 10,000 or more.