JPS6066321A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium with which noise is particularly low by providing a magnetic layer dispersed with hexagonal ferromagnetic powder having a specific surface area in a specific range in a resin binder on a base surface and orienting an axis of easy magnetization in a vertical direction. CONSTITUTION:Hexagonal ferromagnetic powder of 400-2,000 Oe coercive force such as Ba ferrite or the like having 23-45m<2>/g specific surface area and average grain size in a range of 0.05-0.2mu in dispersed in a resin binder and is coated on a base surface. The coating is dried while the base is passed through the inside of a vertical magnetic field thereby forming a magnetic layer. The ferrite powder is uniformly dispersed without flocculation by maintaining the specific surface area within the specific range. The magnetic recording medium which has excellent vertical orientability, good dispersibility and low noise is thus obtd.

Description

[Detailed description of the invention] [Technical field of the invention and technical aspects of the invention? 'Y, l [L and -
'L'c;]ii卜1.7'Xj ] The present invention relates to a magnetic recording medium, and relates to /i'f. 4'7, (relating to H<).

Most of the conventional magnetic recording media (bow, magnetic 4';
It is composed of a magnetic paint containing a lipid-bonded rigid binder applied onto a support substrate such as polyester fluorocarbon.Top 6
12 Magnetic powders include γ-Fe, O, type, Fe,...
04 system and these cobalt adsorption systems, or CrO2
Acicular ferromagnetic powders using ferromagnetic powders and the like are mainly used.

However, these acicular ferromagnetic powders
Because the magnetic force is small, the recording density is only 1ift.
3J yen, which meets the recent demands for high-density recording.
There were no drawbacks. For this reason, recently, in order to improve this drawback, the particle length of the acicular ferromagnetic powder has been reduced, or the coercive force (II.), the maximum e1, the flux density, and the
+is) is being considered. However, when the particle length of these acicular ferromagnetic powders is reduced,
Due to the influence of the demagnetizing field, the electromagnetic conversion ratio in the low range deteriorates, and a sufficient improvement in characteristics cannot be expected.

On the other hand, a so-called metal tape is known in which fine powder of magnetic iron powder is dispersed in a resin binder and the resulting magnetic paint is applied to the surface of a supporting substrate. This is different from the conventional γ-
Although Fe201 magnetic iron oxide has the advantage of enabling high-density magnetic recording, it is easily oxidized by oxygen in the air and may cause explosions during the manufacturing process of magnetic iron powder or magnetic paint. The problem arises that not only is there a very high risk of damage and that handling is difficult, but also that the long-term stability of the properties as a magnetic recording medium is poor.

Hexagonal ferromagnetic powder, which is chemically stable and suitable for perpendicular magnetic recording, is attracting attention as a magnetic powder that overcomes these problems and makes high-density recording possible. This is because the perpendicular magnetic recording method is essentially suitable for high-density recording because the higher the recording density, the lower the demagnetizing field in the recording medium.

Hexagonal ferromagnetic powder is usually hexagonal plate-shaped particles,
The axis of easy magnetization is perpendicular to the plate surface.

For this reason, even if this magnetic powder is simply applied, the plate surface easily becomes parallel to the supporting substrate surface, and the magnetic JQ orientation treatment or mechanical distribution treatment can easily cause the +i'j, 1. Ie'
+r easy axis is vertically oriented. Therefore, in this case,
(The hexagonal ferromagnetic powder that completely cures the
'Q If fin powder (average particle size 0.2 μm or less) is applied uniformly to the supporting substrate surface together with a resin binder,
1. It is expected that it will become a magnetic recording medium with high recording density for the first time.

However, when the hexagonal ferromagnetic powder +:I becomes a fine powder with an average particle size of 0.2 μm or less, the cohesive force between the particles increases. “
・Highly dispersed in i]1...1
′(, As a result, the vertical rudder liJ roti 1- of the obtained magnetic recording medium decreases, and 1゛) in the high range.
The raw output power of the iJ1 is not as good as I initially expected, and the noise level is also low. It had the disadvantage of low performance.

When the average particle size of the magnetic powder particles is 0.21 Lm or more, the dispersibility is slightly improved; The above-mentioned circumstances also apply to case b.

For this reason, the dispersibility of hexagonal ferromagnetic powder has been improved! '4
Therefore, it has been desired to improve the orientation and noise characteristics of a magnetic recording medium using this.

[Object 1 of the Invention] The object of the light-emitting single blade is to provide a magnetic recording medium for high-density recording with low noise and excellent orientation.

[One blade (required)] As a result of intensive research by the present inventors to achieve all of the above objectives, the hexagonal ferromagnetic powder has an average particle size of 0.05 to 0.
．． 2μm In the Q1 state, there is not necessarily an inverse proportional relationship between the particle size and the size of the specific surface area, and the quality of its dispersibility does not directly depend on after λ has been established, but has a strong correlation with the size of the specific surface area. They discovered the facts and completed the present invention.

That is, the magnetic recording medium of the present invention has a specific surface area of 23 to 457
It is characterized in that yy hexagonal ferromagnetic powder is dispersed in a resin binder.

The hexagonal ferromagnetic powder used is CO+Co-Cr.

Co-Mn, Mn-A6;t':' Metal fine particles that form hexagonal crystals by themselves, with the general formula MO・n(F
e20. ) Hexagonal ferrite (M is Ba
, Sr, PI), Ca, n is 5-5
6, and one γ of Fe;
n r I n + Mn + Cu + G e
+ Nb etc. may be substituted with 71'lj 43 gold 1] 1), etc., and the like +:1. , hexagonal ferrite, and rainbow are preferably Ba-ferrite.

Since hexagonal ferrite generally has a high coercive force, it is preferable as the magnetic powder of the present invention that some of the constituent atoms are replaced with specific atoms to reduce the coercive force to a range suitable for perpendicular magnetic recording. .

The coercive force of the magnetic powder is preferably 400 to 20,000e.
shall be. If the coercive force is less than 4,000e, it is difficult to increase the recording density, and if it exceeds 20,000e, the magnetic recording head tends to be saturated, which is disadvantageous.

The specific surface area of the hexagonal ferromagnetic powder is 23 to 45'/1, preferably 25 to 4 Or'7. shall be. Here, the specific surface area refers to the surface area of the powder per unit weight measured by the nitrogen gas BET adsorption method. The specific surface area is 23
~45'/y is because in this region, the adsorption force of the binder such as resin to the surface of the magnetic powder overcomes the mutual cohesive force of the magnetic powder, and the magnetic powder is applied in the all-magnetic paint or coating. Not only is it uniformly dispersed, but it also improves the fluidity of the material, resulting in a smooth coating surface. the result,
The magnetic recording medium has high orientation, and the reproduction output characteristics and noise characteristics are improved. In other words, the specific surface area is 237
If the specific surface area exceeds 45 nL/, the adsorption of the binder will be insufficient and the cohesive force of the magnetic powder will overcome the adsorption force of the binder.If the specific surface area exceeds 45 nL/, the surface energy of the magnetic powder will decrease. The cohesive force of the magnetic powder increases as the
This results in deterioration of I'J- and noise characteristics.

It's ox, 60,000 items type strong,, t'! -Particle size of powder is 0.0
It is preferable that the average particle size is less than 0.05 μm, the thickness of the non-magnetic layer on the thorny surface of the magnetic powder cannot be ignored, υ, magnetic a: maximum magnetic flux density of the powder (M
s) begins to decrease, and furthermore, the orientation also decreases, making it difficult to perform high-density recording. On the other hand, the average particle size is 0.2
[mu]m), the orientation 1teL improves, but the magnetic cohesive force of the magnetic powder increases, so the noise increases, and high-density recording becomes Tahara 1 as above.

Such hexagonal ferromagnetic powder is disclosed in Japanese Patent Application No. 143859-1985 filed by Motoyama/1it
L produced by the glass crystallization method described in the specification η of If/355-34769 has r3J capability. Adjusting the specific surface area and particle size of these magnetic powders, changing the conditions appropriately during manufacturing, the ratio of 11.1 to 11.1 is wide.
) can be obtained with a specific surface area and particle size between

The resin binder to be used is + ``J'', which is a neulum-forming binder, and has a support material of 11..4'J.
Any material that has an affinity for can be used + iJ. Examples of these include vinyl chloride-7'1i: t
'4 Vinyl copolymer material, NBR-polyvinyl phosphate old material, urethane plasticized vinyl chloride-vinyl acetate copolymer material, Morusu urethane feather 41, No.? Known materials such as Liesdell resins and isocyanate materials can be used.

The magnetic recording medium of the present invention usually uses a supporting substrate having excellent mechanical properties such as flexibility, tensile strength, and dimensional stability, such as +
1? Painted on the lyester film.

By placing RflN on the support substrate in this way, handling of the magnetic recording medium becomes extremely easy.

The magnetic recording medium of the present invention can be used, for example, as follows.
I can do it. That is, first, a predetermined amount of the hexagonal ferromagnetic powder, a dendritic binder, and an appropriate solvent were added into a dispersion/mixing machine such as a sand grinder pot, and then the mixture was operated for full mixing. Prepare magnetic paint.

Other than that, the blending ratio of the magnetic powder and the binder is usually 10 to 40 parts by weight of the binder to 100 parts by weight of the magnetic powder. Agents for electrical protection, dispersants such as lecithin,
Known additives such as lubricants, abrasives, stabilizers, etc. can be added.

Next, the obtained 3uF magnetic coating is coated by a known method using a reverse roll coater, doctor grade coke, gravure coater, etc., preferably in a direction perpendicular to the supporting substrate surface (.lambda. field). Orientation treatment], 1) or mechanical orientation treatment, drying and smoothing treatment are performed, and the magnetic 'H'' of the present invention is written, 1.'<t'ifk
get. At that time, the orientation of the magnetic powder (: [2, for example (・,
11. Japanese Patent Application No. 71278, Patent Application No. 132145, filed by the present applicant, was filed by FL, lt.
-Those described in the specification of No. 1321387. It can be carried out by machine and equipment.

〔Effect of the invention〕

As is clear from the above explanation, snoring of the present invention 1. 21i1
Since the recording medium uses hexagonal ferromagnetic powder, it is easy to magnetize vertically. Therefore, the dispersion rate of 1° is good, and as a result, the smoothness, orientation, noise characteristics, etc. of the coating film are excellent. It is effective, and its value is extremely high.

[Embodiments of the invention]

Hereinafter, the magnetic recording medium of the present invention will be explained in detail using Example (1).

Example 1 As a hexagonal ferrite powder, the average particle size is 0. o9/I
nl, specific surface o, “vote 77r’/7, retention cuff 80
0e, maximum magnetic flux +/jW degree 5 g emu4 direct conversion barium ferrite Ba0/6 ((FCo, 1+6C00
, o7Ti0.07) 203) 6 oM parts of powder, 5 M parts of conductive force, 4 parts of lecithin, 1 part of lecithin
11' parts, 60 parts by weight of methyl ethyl ketone, 4 parts of toluene
After adding 0'if 60 parts by weight of urethane resin (trademark N-2301: manufactured by Nihon Tsuki 21J Urethane Co., Ltd.) was added and mixed, and dispersed in a ri-nod grinder pot for about 2 hours.The obtained magnetic paint was completely filtered, Polyincyanate curing agent (trademark Coronate L)
: manufactured by Nippon Polyurethane Co., Ltd.) and then coated with I? using a reverse roll coater. A magnetic layer having a coating thickness of about 2 μm was prepared by drying the film 3a on the Soliester film and passing it through a vertical magnetic field. Finally, this was smoothed by passing it through a super calender roll device to obtain the magnetic recording medium of the present invention.

Regarding this energy recording leech body, li:;% I of the cow layer. PA・211i! 4'lL, vertical orientation ratio and gear 1' rear signal n・1(r1 geometric ratio ((-'/I, )(4
MHz A-Yalya, Chige Speed 3, 5 nV,
ec) was measured. The results are shown in the table below.

In addition, the carrier signal pair 1 in the table is 11C of the sound ratio (C4).
1 is a ferromagnetic metal powder with an average particle diameter of 0.27 tt m, a relative magnetic field angle of 36 m/, a coercive force of 1.2700e, and a maximum (rear angle of 7r1/degree 170° mu/). It is a relative value based on "/Nil' (OdB) of metal density obtained by a method similar to the above using sound.

It is clear from the table that the magnetic recording of the present invention 1I511100 sheets, smooth coating film 1■, high perpendicular alignment rate, vague '/,
I was having a night's sleep.

Example 2 In place of the hexagonal ferrite used in Example 1 - average grain size 0.1.7 p m, ratio r/II 4J'l 3
5″7y, Houni +: 1 cuff '400e, thickest magnetic grave density G
Oe1T]"/y (D (iL conversion 1llQ, barium ferrite Ba06 ((Feo, 5acooBT
A magnetic recording medium of the present invention was obtained by the same method as in Example 1 except that powder was used.
The magnetic layer's dragon i1+j :lj↓sa, down! The I'f 'f crime rate and C/N value were measured.

Part 4] j-kettle is shown in the following table.

As is clear from the table, the magnetic recording medium of the present invention has a so-called normal coating surface, an 11-stone vertical orientation ratio, and an excellent C7. value Tj'
Was.

Actual power 11 Example 3 In place of the hexagonal ferrite used in Example 1, average grain size 0.25 μm, specific surface area 33◇, coercive force 8300e
s maximum'? J bundle preference degree 61°””/y ノfrt,
J'AR'! Barium ferrite Ba0/6 (Ql
i″co,ascoo,.7Ti0.07),0.)
After using the powder, a magnetic recording medium of the present invention was obtained by the same method as in Example 1, and the height, perpendicular orientation rate, and C4 value of the magnetic layer were measured.The results are shown in the following table. Shown below.

-J! (It is clear from υ that the magnetic recording medium of the present invention is
It had a smooth painted surface, a relatively high vertical orientation rate, and a disappointing 9 mark value.

Ratio revision example 1 actual h1. ! i Having almost the same chemical composition as Example 1, average particle size 0.08 fi m, specific surface area 19 nt"/ta, 1
1℃ power 8 ], (10e, f & fat E, east qf
f 5 Q en, ILl/, ) substitution) ((I ha IJ uj, except that ferrite powder was used;
5. The surface roughness, perpendicular orientation ratio, and value of the magnetic recording medium k +1 , +', '<'r1 layer were determined by the method of '-Jfii White 7 1 and 4) j. i
, l I ~ da 1, the result is also written in the entire next garment.

By comparing these results with the results of Examples, it is clear that all of the characteristics of throughput, coated surface smoothness, vertical orientation ratio, and manufacturing value of 1. The characteristics of the medium were inferior.

Comparative Example 2 Average particle size 0.24 having almost the same chemical composition as Example 1
A magnetic recording medium was prepared by the same method (1) as in Example 1, except that substituted barium ferrite powder with a μm1 specific surface area of 22 cm, a coercivity of 1 cuff of 800 G, and a maximum magnetic flux density of 61 eTnu/ was used. (I, Z2 with one magnetic layer and two layers!
11-1 Roughness, vertical orientation ratio and "/Nfii:i" were measured.The results are also shown in the following table.

By comparing these results with the results of Examples, it is clear that all of the characteristics of consistency, coated surface smoothness, and 9-point value are not found in the above-mentioned 4. : i, r It was inferior to the characteristics and notes of the core.

Ratio J bite example 3 Average particle size 0.06 with almost the same chemical composition as Example 1
A magnetic recording medium was obtained in the same manner as in Example 1, except that substituted barium ferrite powder with a specific surface area of 51 m/μm, a coercive cuff of 600e, and a maximum magnetic flux density of #: 52en1uh was used. The surface of the layer was then measured for vertical orientation and 9 loss value. Part 1: Old rice is also listed in the table below.

As is clear from comparing these results with the results of Examples, all of the characteristics of coated surface smoothness, vertical orientation ratio, and 9 manufacturing value are superior to those of the Im2 comb recording eaves of the present invention! It was inferior to JT quality.

*The metal tape is used as the standard (OdB), and the value test is 1. It has almost the same chemical composition as Example 1, 1 piece has a χ diameter of 0.06 to 0.1 μm, and a specific surface precision. Regarding various substituted barium ferrite powders of 14 to 45 m,
A magnetic recording medium was obtained by the same method as in Example i.

For these, the carrier signal-to-noise ratio "/N (++
1 (41v'LHz carrier, tape speed 3.51
7+, /, e, , ) was measured, and the coefficient of 15"1 was calculated between the value and the specific surface area of the magnetic powder. The results are shown in the figure.

It is clear from the figure that the distance is 23-45 m7. Specific surface of A7
The magnetic powder with 4 degrees showed an excellent 041 value.

In addition, in the figure, the vertical ii' + I + 5 columns are the above-mentioned interval 4.
J% (7) Metal tape 07. It represents a relative value based on the value (Od13).

[Brief explanation of the drawing]

The figure is an explanatory diagram of the present invention showing the relationship between the specific surface area of magnetic powder and the C/N value of a magnetic recording medium.

Claims (1)

[Scope of Claims] 1. A magnetic recording medium characterized in that hexagonal ferromagnetic powder having a specific surface position of 23 to 45 is dispersed in a resin binder. 2 The average particle size of the hexagonal ferromagnetic powder is 0.05 to 0.2
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is μm. 3. The magnetic recording medium according to claim 1, wherein the hexagonal ferromagnetic powder is Ba-ferrite. 4 Coercive force of hexagonal ferromagnetic powder is 400 to 20,000
The magnetic recording medium according to claim 1, which is e. 5. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is coated on a support convex body, and the axis of easy magnetization of the magnetic powder is oriented in a direction perpendicular to the surface of the support base.