JPH02270117A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent durability and electromagnetic conversion characteristics by using a polyurethane-urea resin comprising polyester diol containing 3-methyl-1,5-pentane diol as a binder component. CONSTITUTION:Such a polyurethane-urea resin comprising polyester diol containing 3-methyl-1,5-pentane diol is used to prepare the binder component. As 3-methyl-1,5-pentane diol has a methyl group in its side chain, it enhances the solubility of the obtd. polyurethane-urea resin in an org. solvent. This enhances the concentration of urethane couplings in a molecule and the solution has low viscosity even when urea couplings are introduced. Thus, the magnetic coating material can be applied as in a high-solid state. By using the polyurethane-urea resin with improved solubility in an org. solvent as the binder component for the magnetic layer, the obtd. medium is excellent in durability and electromagnetic conversion characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media, and more particularly to improvements in binders thereof.

[Conventional technology]

Conventionally, magnetic recording media have been made using binders with strong magnetic dispersion and wear resistance, such as nitrocellulose, vinyl butyral m5Ft, vinyl-vinyl acetate-vinyl alcohol combination, and vinyl chloride-vinyl acetate-maleic acid combination. Since then, polyurethane resin has been discovered for its properties of strength and strength.

In recent years, there has been an increasing demand for magnetic recording media such as video tapes and floppy disks to have higher recording densities and higher flip-flops during recording and reproduction. For this fL, the polyurethane 4111J resin that has been used conventionally has insufficient running durability and abrasion resistance.
Urethane grade f! 921M1 is being introduced in order to increase the radio security.

However, with this resin, toluene, methyl ethyl ketone,
1 fathom of ethyl vinegar, usually used in the manufacture of magnetic recording media.
The J-solubility of the ia agent or the d agent mixed with these decreases, and as a result, the 5olid/5oluti of the magnetic paint decreases.
As the on ratio (1, id type/'#4 agent) decreases, it is obtained 1j! There are many voids in the 1st layer, which reduces running durability,
Causes a decrease in mg resistance. 7? If the d-solubility decreases and the viscosity of the paint increases, it becomes difficult to produce a uniform, thin magnetic film required for high-density recording.

[Problem that the invention seeks to solve]

This invention improves the solubility of a polyurethane-urea resin for a 6-air recording layer l1tE film in an organic solvent, thereby realizing a high solid paint.

Excellent electromagnetic conversion characteristics and driving durability VC Yu A no Magnetic C
The aim is to provide all m media.・[A friend's means of solving problems] Upper flcj+...Solve the problem (Results of various researches.

1L synthesized using polynisprudiol containing 3-methyl-1,5-pentanediol as a binder component
7'? I discovered that by using polyurethane-urea vB/I metal, a magnetic recording medium with excellent a, tI, magnetic conversion characteristics, and running durability could be obtained.

This means that 3-methyl-1,5-pentanediol is
*The polyurethane with a methyl group on @ increases the solubility of the polyurethane-urea fat in machining, increases the number of urethane bonds in one molecule, and produces a lW liquid with low viscosity even when urea bonds are introduced. Therefore, it is possible to apply magnetic paint while keeping it as a high solid.

Case t1 Molecule #l Historically, the polyurethane-urea resin containing 3-methyl-1,5-pentanediol has a urethane-urea part that is a hard segment and a polyester diol part that is a soft segment. Because of the good layer separation and formation of ξ clodomain #l structure,
It is believed that it will have superior impact resistance compared to IL. This is thought to be helpful in improving the running durability of the magnetic recording medium.

The square plate used in the present invention to produce the polyurethane-Crea-R) product may be produced in accordance with a generally known production method.

The next one is To&ri.

(a) N-organic diincyanate (b) 3-methyl-1,5-pentanediol-functionalized polyester polyol (o) Polymer polyol having a structure other than (b) (d
) Diol performance extender (a) Manufactured by reacting diamine with a stimulant. The ratios of (a), (b), and (c) should be adjusted as necessary, and c) should not be used.

Examples of the organic diisocyanate (a) include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, and hexitemethane diisocyanate.

The 3-methyl-1,5-pentanediol-containing polyester diol (b) is a combination of dicarboxylic acids such as a7abic acid, sebacin fa, terephthalic acid, and isophthalic acid, and 3-methyl-1,5-pentanediol. It is preferable to have a filtration rate of 40 to 5,000 υ per molecule, which is produced by lllia combination. When the molecular weight is less than 400, the obtained Tsuretan-Claire resin lacks flexibility, which is the reason for 5. L.I.
When the OL is 1 or more, the resin lacks hardness and is not suitable for use in magnetic recording media.

Examples of the polymer/N diol (C) include diols such as ethylene diol, 1,4-butanediol, and neopentyl glycol, as well as adipic acid and phthalic acid.

Polyester diols obtained by OTM combination with dicarboxylic acids such as sebacic acid, polyether diols such as polyethylene glycol and polybutylene glycol, polylactone diols such as polyC-caprolactone, poly1
．． Examples include polycarbonate diols such as 6-hexane carbonate.

Examples of the diol top extender (d) include diols such as ethylene glycol, 1,4-butanediol, and neopentyl glycol. Also, -C(hM.

-805M, -POsM2 (7'j stock 0Mrc water 1g
metal is an alkali metal. ) Diol ratio with polar groups such as (4-hydroxybutyl)-5-sodium sulfoisophthalate, dimethylolgropionic acid, β-
Sodium glycerol phosphate or the like may also be used.

As the diamine l1ai extender (6), in addition to aliphatic ammonium such as ethylene cyanide and tolylene diamine,
．． Aromatic amines such as 3'-dichloro4.41-diaminodiphenylmethane and 4.4'-diazenodiphenylmethane can be found.

In particular, urethane-urea resins using aromatic amines as chain extenders are preferable as binders for magnetic recording media because the layer separation between hard and soft segments is remarkable and the resin is strong. When group Cyanine I is used as a chain spreading agent, the mechanical properties of the resin obtained are the same as above, but the ffI dissolubility for solvent V becomes extremely poor; When combined with a polyester, the SS properties are improved and the resin can be used as a paint resin with 0T performance.

Koreji (a), (b), (c), (d), (・
) has an average molecular type s
, ooo~l 00,0υ0 preferably ri, 10,0O
L) ~60,0011 can also be used for L/1ille. If the molecular weight is smaller than n, the durability of the tape will be poor, and if the zero molecular weight is 100,000 or more, the resin will have poor m-decomposability and poor electromagnetic characteristics.

The length of the urethane-urea bond in the urethane-urea resin used in the present invention is 0.5 +n+no l/k
l~5. Ommol /, ji+, more preferably
u (J, 8 mmol 1 /17 - 4.13 mmol /
The one from I is good. The total amount of urethane-urea bonds is 0.5
If it is smaller than mmol/9, the excellent properties as a didistomer will not be exhibited, and the m-solubility in solvents with a concentration larger than 5.13 mmol/7 will be reduced. Mano, Urea/
The urethane bonding ratio is in the range of 0 to 5, more preferably rio,
The range of 1 to 1 is good. As the proportion of urea bonds increases, the mechanical properties of the resulting resin improve, but f(
3%, or the uncut part becomes cloudy and gets mixed into the temperature profile, causing cracks to occur during recording and reproducing.

Below, polyurethane used in practical examples of the present invention and comparative examples.
A synthetic sequence of urea resins is shown.

, Synthesis Example 1 4.4'-diphenylmethane diisocyanate 37.5
poly(3-methyl-1,5-pentanediol)
(M=l, Ouu) too part 3-
3'-dichloro4,4-diaminodiphenylmethane
13.5 parts tin octylate 0.01 fMS methyl ethyl lactone 104) parts toluene
Using 100 parts of the above ingredients, first mix methyl ethyl ketone and toluene @l/411C4,4
'-Diphenylmethane 2 isocyanate and poly3-methyl-1,5-pentanediol adipate, octyl-
Understand tin.

After reacting at 80°C for 6 hours, add a prolonging agent.
-3'dichloro-4,4'diaminodiphenylmethane is added and further stirred to react until the molecular weight is sufficiently increased. After the reaction, a 15 wt % solution was prepared with a methyl ethyl ketone/toluene mixed bath medium to obtain the desired polyurethane resin. The number average molecular weight was 3.5XlO' in terms of polystyrene by GPC measurement and VC.

Viscosity (measured with a rotating rotor viscometer at 1't2υ℃, 22 poise.This is referred to as polyurethane-urea resin A.Hereinafter, diol tD resin and its use violet, 3゜3'-
Table 1 shows polycrethane-urea resins B to F synthesized in the same manner as in Synthesis Example 1 except that the O-4,4'-cyanodiphenylmethane box was prepared differently.

Margin Table 1 The polyurethane-urea resin of this invention may be used in combination with conventionally known thermal aTffi resins and thermosetting resins.

Examples of hot ffi resins to be used in combination include vinyl chloride-vinyl acetate co-association, vinyl chloride-vinyl acetate-vinyl alcohol co-assembly, vinyl chloride-vinyl acetate-maleic acid butyral combination, polyvinyl butyral, and acrylic acid ester acrylonitrile co-assembly. Polymers, cellulose derivatives (cellulose acetate bunarate, nitrocellulose, etc.), polyurethanes [fats, etc.]

Examples of thermosetting resins include phenol resins, epoxy resins, urea resins, and alkyd resins.

The binder used in the present invention is lO to ferromagnetic powder.
Although it is used at 35%, it is preferable to use it at 1.5 to 30%.

If necessary, an O-red bridge accelerator such as a polyiso7anate crosslinking agent, an epoxy7 crosslinking agent, or an amine may be used.

As the nonmagnetic support used in the present invention, commonly used nonmagnetic supports can be used. For example, there may be mentioned various films υ made of polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, polyimide, etc., and metal foils such as aluminum foil and stainless steel W1.

Magnetism m is provided on at least one side of the non-magnetic support, and may be provided on both sides. When a magnetic layer is provided on one side, a back coat layer may be provided on the other side.

As the ferromagnetic powder used for the magnetic layer, r-F・2αhC
o word * r -Fe 20m, Co? a torture γ-F
tHOs, Feas4゜barium ferrite, F
e, Fe-Ni alloy, Go-Ni alloy, etc.

Myristic acid, stearic acid, stearin #n-butyl, octyl stearate, isoamyl stearate, silicone oil, paraffin lubricant, alumina,
It can be machined even if abrasives such as Crabs and red iron oxide, carbon blanks, and dispersants such as lecithin are added.

Furthermore, the polyurethane resin of the present invention can also be applied to a paint used in a bank coat layer that does not contain magnetic powder.

〔Example〕

The present invention will be specifically described below using examples.

Example 1 Co-containing r-Fe snow Os (coercive force 6500e, SBH,
20ze/JJ) too
Nitrocellulose (manufactured by Daicel, Seltsuba BTH)
15g polycretan-7 resin A 2U part carbon black
12 parts alumina (particle size 1μ)
8s n-glythyl stearate
5s Butylseronulp stearate 2
120 parts methyl ethyl lactone 120 parts toluene The above composition was dispersed in a sand grinder for 6 hours,
Add functional isocyanate (Coronate i, manufactured by Nippon Polyurethane Co., Ltd.) ioat violet.

Mix with a high-speed disper, then methyl ethyl ketone/
Prepare a magnetic paint with a viscosity of 4 voids by adding toluene mixed solvent. This LiB-based paint was applied onto a polyethylene terephthalate film with a thickness of 75 μm so that the film thickness after drying was 0.9 μm.
The mixture was coated so as to form a μ-shape, dried, processed on the surface, and then punched out into a 3.5-inch diameter disk and attached to a jacket to produce a magnetic disk.

Example 2 In place of Example 1O polyurethane-urea + M fat A,
Except that polyurethane-urea resin B was used.

A magnetic disk was produced in the same manner as in Example 1.

Example 3 A polyurethane-urea resin C was used instead of a polyurethane-urea resin A in Example 1.

In the same manner as in Example 1, all images were projected on the magnetic disk.

Example 4 Except that polyurethane-urea resin A in Example 1 was replaced with polyurethane-urea resin.

Using the same fliv as Example 1, I made an aS disk.

Comparative Example 1 Except for using polyurethane-urea resin E in place of polyurethane-urea resin A in Example 1.

A magnetic disk was manufactured using the same method as in Example 1.

Comparative Example 2 Polyurethane-urea resin F was used instead of polyurethane-urea resin AVC in Example 1, except for the following.

A hB air disk was prepared using the same ta as in Example 1, and a running durability test was conducted on the 7ts air disk obtained in each of the above examples and comparative examples, and the modulation indicating the uniformity of the coating film thickness was measured. comparison.

Running durability: Y-EDATA! l! A magnetic disk was installed in the YD-8UUC type drive unit and the temperature was 60°C.

The number of runs until the magnetic pattern peels off and the base film is exposed when running in a 1'' cDS atmosphere at 5% RH or higher is shown.

Modulation scene 2, drive unit 25 (l)
Kf (Z) is recorded and reproduced on the outermost circumference (track 00) of the IC, and the reproduction output at the ratio is read and determined according to the formula below and is expressed as a ratio value.

Maximum Output Child Minimum Output [Effects of the Invention] As explained above, in the present invention, a polyurethane-urea resin with excellent mechanical properties is added with a polyester polyol having a methyl group in the a-chain as a constituent part. Convenient use of polyurethane-urea resin with improved solubility in agents as a binder component for magnetic layers, running durability, 1! A magnetic recording medium with excellent fL7'5 magnetic conversion characteristics can be obtained! !几.

Applicant: Hitachi Maxell, Ltd. Representative Atsushi Mizu

Claims (2)

[Claims] (1) In a magnetic recording medium having a magnetic layer formed by dispersing ferromagnetic fine powder in a binder on a nonmagnetic substrate, a polyurethane layer made of polyester diol containing 3-methyl-1,5-pentanediol as a binder component. A magnetic recording medium characterized by using urea resin. (2) A magnetic recording medium, wherein the binder component according to claim (1) is made of a polyurethane-urea resin containing an aromatic amine as a constituent unit.