JP3343265B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, such as a magnetic tape or a magnetic disk, provided with a magnetic layer containing a magnetic powder and a binder on a non-magnetic support.

[0002]

2. Description of the Related Art In a magnetic recording medium of this type, examples of a binder used for a magnetic layer include vinyl chloride resins, urethane resins, cellulose resins, polyester resins, and polyvinyl butyral resins. Resin, epoxy resin,
Acrylic resins, phenol resins, amide resins, radiation-curable resins, polyisocyanate compounds as crosslinking agents, and the like are known.

Among these binders, in particular, vinyl chloride resins such as vinyl chloride-vinyl acetate copolymers are used in terms of dispersibility of magnetic powder, and polyester urethane resins are used in terms of mechanical properties of the magnetic layer. Urethane-based resins such as these are considered to be suitable, and conventionally both of these resin components are often used in combination in order to ensure electromagnetic conversion characteristics and durability of a magnetic recording medium.

[0004]

By the way, in recent years, there has been an increasing tendency to perform various types of information management by using magnetic recording media such as magnetic tapes instead of writing. A system is being established in which a medium is stored as a database for a long period of time, and the data can be read out whenever necessary.

However, the conventional general-purpose magnetic recording medium has a disadvantage that the durability such as the still characteristic is significantly deteriorated when stored for a long period of time in a normal indoor environment. Although they are stored in a fixed warehouse or the like, they are not sufficient for preventing the above deterioration, and there is a problem that the reliability as a medium for long-term recording and storage is low.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a magnetic recording medium which has excellent durability such as still characteristics even after long-term storage, and is very suitable for recording and storage. And

[0007]

Means for Solving the Problems The inventors of the present invention conducted a study to achieve the above-mentioned object. First, a conventional method using a vinyl chloride-based resin and a polyester-based urethane resin together as a binder for a magnetic layer. The cause of poor durability after long-term storage of general-purpose magnetic recording media was investigated.Decomposition due to dehydrochlorination of vinyl chloride resin progressed during long-term storage, and polyester urethane resin was also affected by moisture in the air. It has been found that hydrolysis progresses and that deterioration of mechanical properties such as abrasion resistance of the magnetic layer due to deterioration of both resin components leads to deterioration of durability such as still properties.

[0008] As a result of repeated further investigation based on this finding, specific polyvinyl acetals as binders of the magnetic layer - when used in combination with the Le-based resin and a specific urethane resin, and high electromagnetic characteristics As well as ensuring good mechanical strength of the magnetic layer, the resin components hardly deteriorate even after long-term storage, and sufficient durability is exhibited even after long-term storage. The present inventors have found that the magnetic recording medium has excellent reliability, and have accomplished the present invention.

That is, the present invention relates to a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder on a non-magnetic support, wherein the binder has a low glass transition point.
Kutomo 100 ° C. or more polyvinyl acetals - Le resin and polycarbonate - Bonnet - are those according to the magnetic recording medium and preparative urethane resin is characterized by comprising in combination, in this medium, in particular, of the polyvinyl acetals - constitute use those containing sulfonic acid groups or salts thereof as Le resin, also the configuration using the ferromagnetic metal powder or barium ferrite powder as a magnetic powder, respectively a preferred embodiment.

[0010]

[Configuration and operation of the invention Polyvinyl <br/> acetals used in the present invention - Le resin has a function of improving the dispersibility of the magnetic powder, moreover the dehydrochlorination such as vinyl chloride resin It does not have the property of decomposing and has excellent stability. Polycarbonate-based urethane resins have an effect of imparting appropriate viscoelasticity to the magnetic layer to improve mechanical properties such as abrasion resistance, and have the same effect as conventional polyester-based urethane resins. Decomposition does not occur and is also excellent in stability.

Therefore, the magnetic recording medium of the present invention, in which these resin components are used in combination as a binder for the magnetic layer, exhibits high electromagnetic conversion characteristics because the magnetic powder is uniformly dispersed in the magnetic layer, and It has excellent durability such as still characteristics based on the good mechanical properties of the magnetic layer, and has particularly excellent storage stability, and hardly deteriorates the magnetic layer even after long-term storage, and before storage. The same excellent durability is maintained, and good recording / reproducing characteristics can be obtained even if recording / reproducing is repeated after long-term storage.

[0012] Polyvinyl acetals used in the present invention -
Is a resin having an average molecular weight of about 10,000 to 100,000 having an acetal bond in the molecule.
Those having a low glass transition point (hereinafter referred to as Tg)
Since the durability of the magnetic layer such as the still characteristic becomes insufficient due to the decrease in the mechanical properties of the magnetic layer, it is necessary that the magnetic layer has a Tg of at least 100 ° C. or more, preferably about 100 to 150 ° C.

[0013] Such polyvinyl acetals having a Tg - Among Le resins, especially those having a sulfonic acid group or a salt thereof in the molecule, binding agent to particle surfaces of the magnetic powder by the sulfonic acid group or a salt thereof Since the adsorbability of the magnetic powder is increased, the dispersibility of the magnetic powder, especially when the ferromagnetic metal powder or the barium ferrite powder is used, is improved, and there is an advantage that extremely excellent electromagnetic conversion characteristics can be imparted.

[0014] Polyvinyl acetals having a sulfonic acid group or a salt thereof in the molecule - as Le resins, for example,
It consists of the following repeating units (a) to (d), and the ratio of each unit is (a) 70 to 96 mol%, (b) 0 to 3
Mol%, (c) 0.1-1 mol%, (d) 0-29.9
Those which become mol% are mentioned as suitable.

The polycarbonate-based urethane resin used in the present invention is obtained by a urethanization reaction between a polycarbonate-based polyol and a polyisocyanate, and has an average molecular weight of usually from 10,000 to 100,000. About 000 are preferably used. Commercially available products include, for example, Daifuramin MAU- manufactured by Dainichi Seika Kogyo Co., Ltd.
9031, the same dihuefamine MAU-5022, the same dihuefamine MAU-4025, and the like.

In the present invention, Tg is at least 10
0 ℃ or more polyvinyl acetals - Le resin and polycarbonate - BONNET - mixing ratio of the bets urethane resin, the former / latter weight ratio, good to usually 1 / 5-5 / 1 in the range of about .
If the former ratio is too small, the dispersibility of the magnetic powder becomes insufficient and the electromagnetic conversion characteristics deteriorate.On the other hand, if the latter ratio is too small, the mechanical characteristics of the magnetic layer become insufficient and the still characteristics become poor. It is not preferable because the durability is lowered.

[0017] As the binder, the above-mentioned polyvinyl <br/> acetals - Le resins and polycarbonate - BONNET - with preparative urethane resin, polyisocyanate - can be used a crosslinking agent such as preparative compounds. The amount of such a cross-linking agent to be used may be usually about 10 to 30% by weight based on the total amount of both resin components.

[0018] The above polyvinyl acetals - polycarbonate conventional general purpose vinyl chloride resin in place of the Le resin - Bonnet -
When used in combination with a urethane-based resin, the polycarbonate-based urethane resin is decomposed by hydrogen chloride generated by decomposition of the vinyl chloride-based resin during long-term storage, so that improvement in long-term storage properties cannot be expected. Further, polycarbonate - Bonnet - conventional instead of preparative-based urethane resin purpose polyester urethane resins the above polyvinyl acetals - when used with Le resin, since the polyester urethane resin comes hydrolyzed during long-term storage, Again, good long-term storage properties cannot be obtained.

In the present invention, as the magnetic powder to be contained in the magnetic layer, any of various magnetic powders conventionally known as recording elements for magnetic recording media can be used.
For example, oxides composed of γ-Fe ₂ O ₃ , Fe ₃ O ₄ , iron oxides in their intermediate oxidation state, Co-containing γ-Fe ₂ O ₃ , Co-containing Fe ₃ O ₄ , CrO ₂ , barium ferrite, etc. Magnetic powder, Fe, Co, Fe-Co alloy, F
e-Ni alloy, Fe-Co-Ni alloy, Fe-Ni-C
Examples thereof include a ferromagnetic metal powder composed of an r alloy and the like, and a nitride magnetic powder such as iron nitride.

[0020] Among these magnetic powders, the ferromagnetic metal powder or barium ferrite powder, polyvinylidine described above
Le acetals - Le resin and polycarbonate - BONNET - in combination with comprising a preparative-based urethane resin binder, because of the advantage that dispersibility is particularly greatly improved, most preferably used.

To manufacture the magnetic recording medium of the present invention,
Prepare a magnetic paint containing various additives such as a lubricant, an abrasive, an antistatic agent, a dispersant, a filler, and a coloring agent to be blended with the binder and the magnetic powder as necessary according to a conventional method. The coating is applied to a non-magnetic support such as a polyester film by a suitable means such as spraying or roll coating and dried to form a magnetic layer having a thickness of about 0.1 to 5 μm. After that, the surface may be subjected to a surface treatment such as calendaring if necessary, and then cut into a required width or shape.

The magnetic recording medium thus obtained is
The Tg of the magnetic layer is at least 40% by using two kinds of the specific resin components as a binder.
It has a high value of ℃ or more, and has excellent reliability such as durability.

When the present invention is applied to a magnetic tape, in order to improve its running stability, a filler is provided on the back side of the non-magnetic support opposite to the side on which the magnetic layer is formed. A backcoat layer may be provided in which a nonmagnetic inorganic powder such as an abrasive or an antistatic agent is bound with a binder.

[0024]

As described above, according to the present invention, by using two kinds of specific resin components in combination as a binder of a magnetic powder, a high electromagnetic conversion characteristic is obtained, and a still characteristic is obtained even after long-term storage. Can provide a magnetic recording medium having good durability and high reliability for recording and storage.

[0025]

Next, examples of the present invention will be specifically described in comparison with comparative examples. In the following, “parts” means “parts by weight”.

Further, polyvinyl acetals - Le resin Tg
Using a viscoelastic spectrum meter manufactured by Rheometrics, using a sample having a length of 25 mm, a width of 5 mm, and a thickness of 20 μm, a measurement temperature range of 0 to 150 ° C., a heating rate of 4 ° C./min.
The measurement frequency was set to 1 Hz, and the value was determined from the peak of the loss tangent angle (Tan δ). Furthermore, the Tg of the magnetic layer was measured by measuring the dynamic viscoelasticity of the magnetic tape and the base film alone of the same sample,
It was determined from the peak of the loss tangent angle (Tan δ) of the difference spectrum.

[0027] EXAMPLE 1 alpha-Fe magnetic metal powder (average major axis diameter 0.15 [mu] m, an average axial ratio of 3) 200 parts Tg110 ° C. polyvinyl acetals - 20 parts Le resin (Sekisui Chemical Co., Ltd. under the trade name Esuretsuku KS-1) Polycarbonate-based urethane resin 20 parts (trade name: Daifueramine MAU-9031 manufactured by Dainichi Seika Industry Co., Ltd.) α-Al ₂ O ₃ powder 8 parts Myristic acid 2 parts n-butyl stearate 2 parts Cyclohexanone 180 parts Toluene 180 parts

The above composition was stirred and mixed by a high-speed day spa for 5 hours, and further dispersed by a sand mill for 20 hours. As a crosslinking agent, a trifunctional polyisocyanate compound (trade name: Coronate, trade name, manufactured by Nippon Polyurethane Co., Ltd.) L) 10
Parts were added and dispersed and mixed for 30 minutes.
Agglomerates were removed by sequentially passing through a filter of 1 μm and 1 μm to prepare a magnetic paint.

This magnetic paint is applied to one side of a non-magnetic support made of polyethylene terephthalate film having a thickness of 10 μm so that the thickness after drying becomes 3 μm.
After drying to form a magnetic layer and calendering it, the other surface is coated with a backcoat paint (including carbon black and calcium carbonate as non-magnetic inorganic powder, nitrocellulose and polyurethane as binder) (Using a resin) so as to have a thickness of 0.6 μm after drying, followed by drying to form a back coat layer, which was cut into a width of 8 mm to produce a video tape.

[0030] Example 2 polyvinyl acetals - as Le resins, Tg110 ℃ of sulfonic acid group-containing polyvinyl acetals - Le resin Polymerization degree 3
00, of the repeating units (a) to (d) shown in the text, (a) (R ₁ : CH ₃ group) = 72.6 mol%
(B) = 1 mol%, (c) (M: Na ion) = 0.4
A prototype having a composition of mol%, (d) = 26 mol%]
Was used in the same manner as in Example 1 except that 20 parts were used.

[0031] Comparative Example 1 Polyvinyl acetals - instead of Le resin, vinyl chloride - except that vinyl acetate copolymer (UCC Co. trade name VAGH) was used 20 parts, in the same manner as in Example 1 A video tape was produced.

Comparative Example 2 The procedure of Example 1 was repeated except that 20 parts of a polyester urethane resin (trade name: Pandex T-5250, manufactured by Dainippon Ink) was used in place of the polycarbonate urethane resin. Then, a video tape was produced.

[0033] Comparative Example 3 Poria vinyl Seta - Le resins and polycarbonate - BONNET - instead of preparative-based urethane resin, vinyl chloride - vinyl acetate copolymer (the same as described in Comparative Example 1) 20 parts of polyester Urethane resin (same as described in Comparative Example 2) 2
A video tape was produced in the same manner as in Example 1 except that 0 part was used.

[0034] Reference Example 1 Polyvinyl acetals - as Le resins, poly Tg54 ° C.
Vinyl acetals - except using Le resin (Sekisui Chemical Co., Ltd. under the trade name Esuretsuku BL-S) and 20 parts, in the same manner as in Example 1, video tape - was produced up.

The above Examples 1 and 2 and Comparative Examples 1 to 3
For each magnetic tape of Reference Example 1 , the T
g, surface roughness and squareness ratio were measured, and as a storage stability acceleration test, still characteristics before and after storage for one month under an environmental condition of 60 ° C. and 80% RH were measured. The results are shown in Table 1 below. The surface roughness was determined by measuring the center line average surface roughness (Ra value) using a stylus type surface roughness meter. The still characteristics are as follows: using a commercially available VTR, the output is 6d from the initial output.
The time until B decreased was measured.

[0036]

[Table 1] Table 1

[0037] From the results of Table 1 above, as the binder of the magnetic layer, the specific polyvinyl acetals - Le resin and polycarbonate - Bonnet - in combination with preparative urethane resin video tape of the present invention -
Examples (Examples 1 and 2) were excellent in that the surface roughness of the magnetic layer was small, the squareness ratio was large, the electromagnetic conversion characteristics were excellent, and the durability after long-term storage was extremely good. It is clear that it shows storage stability.

On the other hand, in the case of the video tape in which one of the binder components is different (Comparative Examples 1 and 2) and the conventional general-purpose video tape in which both are different (Comparative Example 3), the durability after long-term storage is large. It can be seen that the storage stability decreased and the storage stability was remarkably poor. Further, polyvinyl acetals - video tape was used having a low glass transition temperature as Le resin - In flop (Reference Example 1), excellent electromagnetic conversion characteristics and durability after long-term storage is also the same as before storage, saving Although it can be said that stability is good, are not inherently sufficiently durable before storage, in this respect, polyvinyl acetals as in example 1 and 2 - having a high glass transition point as Le resin It turns out that it is desirable to use selectively.

Example 3 A video tape was produced in the same manner as in Example 1, except that 200 parts of hexagonal barium ferrite powder (average plate diameter: 0.05 μm) was used instead of the α-Fe metal magnetic powder. .
When the performance of this tape was evaluated in the same manner as described above, the surface roughness [Ra value] was 0.002 μm, the squareness ratio [Br / Bm] was 0.72, and the environment was 60 ° C. and 80% RH. Under the conditions, the still characteristics before and after storage for one month are 120 before and after storage.
Min or more, and both the electromagnetic conversion characteristics and the storage stability were good.

Continuation of front page (56) References JP-A-3-150720 (JP, A) JP-A-5-128485 (JP, A) JP-A-6-96437 (JP, A) JP-A-1-251416 (JP) JP-A-64-72318 (JP, A) JP-A-57-138040 (JP, A) JP-A-50-93104 (JP, A) JP-A-57-210441 (JP, A) JP-A-1-320628 (JP, A) JP-A-3-132921 (JP, A) JP-A-3-132920 (JP, A) JP-A-3-3117 (JP, A) A) JP-A-2-233293 (JP, A)

Claims (3)

(57) [Claims] In the magnetic recording medium having a magnetic layer containing a 1. A non-magnetic support on the magnetic powder and a binder, as the binder, <br/> glass transition point of more than at least 100 ° C. polyvinyl acetals A magnetic recording medium comprising a combination of a polyester resin and a polycarbonate urethane resin. 2. A glass transition point of at least 100 ° C.
Polyvinyl acetals - Le based resin, a magnetic recording medium according to claim 1 consisting of those containing a sulfonic acid group or a salt thereof. 3. The magnetic recording medium according to claim 1, wherein the magnetic powder is a ferromagnetic metal powder or a barium ferrite powder.