JPS6139925A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder, etc. and to obtain a magnetic recording medium having excellent durability, etc. by inorporating a specific polyurethane resin, phenoxy resin and low mol.wt. isocyanate compd. as a binder component into a magnetic layer. CONSTITUTION:The magnetic paint contg. the polyurethane resin which is obtd. from a mixture composed of butyrene adipate and tertiary alcohol and 4,4'- diphenyl methane diisocyanate, has tertiary OH in the position except both terminals of the principal chain and has 20,000-30,000 average mol.wt., phenoxy resin and low mol.wt. isocyanate compd., necessary dispersant, lubricating agent, carbon black as an antistatic agent, Al2O3 as a polishing agent, etc. is prepd. Such paint is coated on a non-magnetic substrate consisting of polyester, polyimide, etc. and is cured to manufacture the magnetic recording medium. The magnetic recording medium which has the good dispersibility of the magnetic powder, carbon black, polishing material, etc., has small modulation and excellent electromagnetic conversion characteristic and maintains the excellent durability even in severe environment such as high temp., high humidity, low temp. and low humidity is thus obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium that has excellent dispersibility of magnetic powder carbon black, ht2o5 (aluminum oxide), etc., and has a magnetic layer that has excellent durability. .

[Prior art]

Generally, magnetic recording media such as audio tapes, video tapes, flexible disks, etc. are coated with magnetic powder, binder, solvent, dispersant, lubricant, and antistatic agent on a nonmagnetic support such as polyester film.

The magnetic layer is formed by applying a magnetic paint made of various additives such as abrasives, but with the recent trend toward higher densities, better electromagnetic conversion characteristics are required, and even higher temperature, high humidity, and low temperature There is a demand for highly reliable products that can withstand long-term operation under harsh conditions such as low humidity.

To meet this demand, there is a need for a binder that has excellent dispersibility of magnetic powder, provides excellent electromagnetic conversion characteristics such as reproduction output signal dispersion 2 overwriting characteristics, and has excellent durability such as wear resistance. There is.

Various studies have been conducted on such binders, one of which has been proposed as a combination of polyurethane resin and vinyl chloride-vinyl acetate-vinyl alcohol copolymerization.

The reason for this is that urethane resin alone has difficulty dispersing with magnetic powder, but it is relatively durable and
Although the vinyl chloride-vinyl acetate-vinyl alcohol copolymer alone has excellent dispersibility with the magnetic powder, it lacks the flexibility of the magnetic layer, so both binders are used in combination.

However, in cases where excellent dispersibility and durability are required, they are still insufficient.

[Purpose of the invention]

The present invention provides a particularly excellent flexible disk among magnetic recording media which eliminate the above-mentioned conventional drawbacks, have excellent dispersibility of magnetic powder carbon black, At2'05, etc., and have excellent durability of the magnetic layer. It is something.

[Structure of the invention]

The binder of the present invention is a magnetic layer having a tertiary hydroxyl group at a position other than both ends of the main chain obtained by reacting a mixture of butylene aziide and tertiary alcohol with 4,4'-diphenylmethane diisocyanate. Average molecular weight 2
0. It is characterized by containing a polyurethane resin of O'00 to 30,000, a 7-enoxy resin, and a low molecular weight isocyanate compound.

[Action/Effect]

The present invention has a polyurethane resin having tertiary hydroxyl groups at positions other than both ends of the main chain as a binder for magnetic paint, so it has increased affinity with magnetic powder, and can be used in paints such as Carpin Black + At205. The dispersibility can be improved without causing the color separation phenomenon. Furthermore, by containing phenoxy resin and low molecular weight isocyanate, it is possible to impart appropriate flexibility to the magnetic layer.
A highly reliable magnetic layer is formed that can withstand long-term running under harsh conditions such as high temperature and high humidity, and low temperature and low humidity.

The polyurethane resin used in the present invention is butylene adipate 1,2,3-hydroxy-2-methylolone, which is obtained by polycondensation of adipic dicarboxylic acid and 1,4-butylene glycol.

1.2.3-Hydroxy-ethyl-propane, l,2
．． 5-hydroxy-2-methyl-pronofone 2, etc.
4,4'-diphenylmethane diisocyanate as an organic diisocyanate is reacted with a mixture of alcohols containing tertiary alcohols at positions other than both ends of the main chain.
average molecular weight 20.000 to 30, having 1 hydroxyl group of
000 polyurethane resin.

The amount of hydroxyl groups other than both ends of the polyurethane resin used in the present invention It is not preferable for use as a flexiflexible disk with a large ration.Furthermore, when crosslinking with a low molecular weight isocyanate compound, the magnetic layer is hardened on the contrary, resulting in a decrease in durability. If additives with poor dispersibility are included, it is undesirable because color separation of carbon black, AA205, etc. in the paint will occur.The average molecular weight of the polyurethane resin used in the present invention is 20.00'0 to 30. ,000 is preferable.If the average molecular weight is 20,000 or less, the dispersibility of the magnetic powder is excellent, but the abrasion resistance of the magnetic layer is poor, and stability is lacking in long-term running.If the average molecular weight is 30,000 or more, the magnetic layer Although the abrasion resistance is improved, the dispersibility of magnetic powder is poor and it is not suitable for cines.

The phenoxy resin used in the present invention includes:

It is shown by the following structural formula and has an average degree of polymerization of 80 to 70.
It is sufficient if it is in the range of 0.

14,2.4-1-lylene diisocyanate as a low molecular weight isocyanate compound used in the present invention.

2. Diisocyanates such as 6-tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, sulfur diisocyanate, inholodiisocyanate, xylene diisocyanate, etc., and trifunctional compounds obtained by reacting 3 moles of these diisocyanates with 1 mole of triol. Many commercially available low molecular weight isocyanate compounds can be used.

For example, 1. Coronet (L) manufactured by Nippon Polyurethane Co., Ltd.

Coronate HL, Coronate 2036, Coronate 2
014, Coronate 3015. Coronate 3030゜manufactured by Bayer, Desmodule L, 7'sModule 14. Sumidur, Sumidur T80゜Takenate D102 (manufactured by Takeda Pharmaceutical Company), Takenate D103
, Takenate D103H, Takenate M402, Takenate M403, Takenate M408, Risden NX manufactured by Dainippon Ink and Chemicals, and Crisbon CL-2. Average molecule i having tertiary hydroxyl groups at positions other than both ends of the main chain obtained from the mixture of butylene adipate and tertiary alcohols and 4,4'-diphenylmethane diisocyanate used in the present invention 20,000 to 3
The mixing ratio of the 0,000 polyurethane resin and the phenoxy resin is preferably in the range of 8/2 to 4A by weight; if it deviates from this range, it will not be possible to impart appropriate flexibility to the magnetic layer as a flexible disk. .

In addition, the amount of the low molecular weight isocyanate compound used in the present invention is 10 to 10% based on the total amount of the binder component.
It is preferably 30% by weight; if it is too small, the effects of the present invention cannot be obtained, and if it is too large, the dispersibility of the magnetic powder will be impaired.

As the magnetic powder used in the present invention, commonly known magnetic powders such as γ-Fe205 powder and Co powder method γ-Fe203 powder are used.

Organic solvents include ketones such as acetone, methyl ethyl ketone, methyl imbutyl ketone, and cyclohexanone;
Ester systems such as methyl acetate, ethyl acetate, butyl acetate,
Aromatic hydrocarbons such as benzene, toluene, xylene, etc.
Methyl chloride.

It is desirable to use at least two or more chlorinated hydrocarbons such as ethylene chloride and carbon tetrachloride.

Further, a dispersant, lubricant, abrasive, antistatic agent, etc. may be added as necessary.

The magnetic recording medium of the present invention can be manufactured by a conventional method, and a magnetic paint containing the magnetic powder binder component, a solvent, and various additives as necessary is coated on a non-magnetic support base such as polyester terephthalate by a known method. The magnetic layer may be formed using the following steps.

The present invention will be explained in detail below.

[Example 1] Magnetic powder...372 parts of γ-Fe2O (slanting ratio 8, average particle size 0.45) Hc=3000e Isocyanate (manufactured by Nippon Polyurethane Co., Ltd.) (average particle size 30 mμ) Abrasive agent... ... At203
2 parts (average particle size 0.5μ) Solvent: MEK/Toluene/Cyclohexanone 60/60/60 parts This composition was mixed and dispersed in a sand mill for 2 hours to prepare a magnetic paint. It was coated on a NoyR liester terephthalate support with a thickness of 75 μm and dried to form a magnetic layer with a thickness of 2 μm.

Next, this magnetic layer was punched out into a disk having an outer diameter of 130 m/m to prepare a sample.

[Example 2] 1-Fe2O3 of Example 1 was replaced with Co-1-Fe205 (
Slanting ratio 10° Average grain size 0.35 Hc=6500e)
Instead, a sample was prepared in the same manner.

[Comparative Example 1] A sample was prepared in the same manner as in Example 1, except that instead of the polyurethane resin in Example 1, a polyurethane resin containing no tertiary hydroxyl group was used at positions other than both ends of the main chain. .

[Comparative Example 2] Same as Example 1 except that instead of the polyurethane resin of Example 1, a polyurethane resin containing 0.04 mmol/gr of tertiary hydroxyl group was used at a position other than both ends of the main chain. A sample was prepared.

[Comparative Example 3] The average molecular weight of the polyurethane resin of Example 1 was 40.00.
A sample was prepared in the same manner as in Example 1 except that the value was set to 0.

The following tests were conducted on the samples prepared in the above Examples and Comparative Examples.

Phenomenon of color separation of paint> Sample the paint mixed in a sand mill into a graduated cylinder, and visually observe the condition after leaving it for 5 hours.Also, check for carbon black on the top and bottom of the paint.

The composition of At203 was analyzed.

Reproduction output signal dispersion〉 Insert the prepared sample into the jacket, and use a magnetic recording/reproduction tester to generate 125 kHz on a specific track (O○ track).
The signal was recorded, and the dispersion of the total reproduced output signal at that time was measured.

Modulation> The prepared sample was inserted into a jacket, and a 125 kHz signal was recorded on a specific track (○○ track) using a magnetic recording and reproducing tester, and measurements were made using a quadratic equation.

A: Average reproduction output signal of approximately 2,000 magnetic flux reversals including the maximum reproduction output signal in one rotation of a specific track B: Average reproduction output of approximately 2,000 magnetic flux reversals including the minimum reproduction output signal in one rotation of a specific track Signal (Durability Test) The prepared sample was inserted into a jacket, a 125 kHz signal was recorded using a magnetic recording and reproducing tester, and the temperature was 50°C.

The temporal change in the reproduced output signal was read while it was brought into contact with a magnetic head under test environmental conditions of 80% RH, 5° C., and 30% RH, and the time required for the reproduced output signal to reach 80% of the initial reproduced output signal was measured.

The results obtained are shown in Table 1.

As can be seen from the table, the samples prepared according to the present invention can obtain excellent electromagnetic conversion characteristics with small reproduction output signal dispersion and modulation without causing color separation in paints such as carbon black r At203. It can be seen that it is an excellent binder that can withstand long-term running under harsh conditions such as high humidity, low temperature, and low humidity.

Umbrella day below

Claims (1)

[Claims] 1. In a magnetic recording medium formed by coating a magnetic paint on a non-magnetic support, both main chains obtained from a mixture of butylene adipate and tertiary alcohols and 4,4'-diphenylmethane diisocyanate are used as binder components of the magnetic layer. Average molecular weight 2 with a tertiary hydroxyl group at a position other than the terminal
A magnetic recording medium containing a polyurethane resin and a phenoxy resin having a molecular weight of 0,000 to 30,000 and a low molecular weight isocyanate compound.