JPS5956222A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve both of an electromagnetic conversion characteristic and running and sustained running characteristics, by forming the back layer provided on the rear of a substrate for a magnetic recording medium into an orange peel surface. CONSTITUTION:The back layer provided on the rear of a substrate for a magnetic recording medium is formed into an orange peel surface. The projecting parts (a) in the orange peel surface are coninuously formed in a nearly hexagonal shape. Such orange peel surface is formed with preferably 0.02-0.3mum the depth (d) of a trough part (c) and preferably 2-200mum pitch (p) between the projecting parts facing to each other. If the pitch (p) is <2mum, there is no effect and when it exceeds 100mum, the running and sustained running characteristic are further slightly improved but the deterioration in the electromagnetic conversion characteristic is accelerated. When the thickness T of the back layer (b) is increased, the deterioration in the electromagnetic conversion characteristic occuring in the the depth (d) in the trough part (c) of the orange peel surface and the roughening of the surface is accelerated. The thickness T of the back layer is required to be <=2mum, and the lower limit is required to be >=0.3mum in order to provide the orange peel surface.

Description

[Detailed Description of the Invention] In particular, it relates to a magnetic recording medium with an improved back layer provided on the back surface of a support.1) In general, magnetic recording media include:
That'llJ, magnetic variation 16f! It is necessary to smooth the surface of the magnetic layer to improve the characteristics, such as the sensitivity φ ratio. As the smoothing ratio becomes 1 =>, the running characteristics and running durability of the magnetic recording medium deteriorate. For this reason, conventionally t,
1. The surface of the shibasoku layer has been roughened by sand blasting, etching in an alkaline solution, or filling with solid particles. However, with either method, if the back surface is roughened to a sufficient degree to improve running characteristics and running durability, the rough surface of the back layer will be transferred to the magnetic surface during tape winding or stacking of disks, impairing its smoothness. Therefore, deterioration of electromagnetic conversion characteristics was unavoidable.

On the other hand, when roughening the bank layer with emphasis on electromagnetic conversion characteristics, there is a limit to the running characteristics and running durability that can be obtained. I couldn't get it.

The inventors of the present invention conducted research to provide a magnetic recording medium that does not have the above-mentioned drawbacks, and as a result, they obtained the following knowledge.

In other words, in a magnetic recording medium, if only the electromagnetic conversion characteristics are important, it is desirable that both the magnetic mj and the back layer surface be smooth, but in order to maintain good running characteristics and running durability, the back layer surface should be rough. It is necessary to face the
Along with this, the magnetic surface also undergoes some degree of roughening due to the transfer. However, when the surface of this bank layer exhibits an orange-skinned condition, it is compared with a magnetic recording medium that has a texture layer that has the same surface properties as the bank layer substrate but does not exhibit an orange-skinned condition. It was found that the transfer of the magnetic surface was suppressed, the deterioration of the electromagnetic conversion characteristics was reduced, and the running characteristics and running durability tended to be improved.

The term "Yuzu surface" as used in this specification refers to the protrusion 1 having a substantially hexagonal shape, i.e., a continuation of the shape of a no-nikum or a net 1-1, as shown in FIGS. 1 and 2. 3, which refers to the formed surface condition, (the second yuzu skin surface has a valley (depth 1 of 05 μ771 or more) (preferably 002 to 06 μ7
71), pitch p between mutually opposing protrusions i'%l- is 2 to 1000 μm1L<&:,l,2~
20074771 and -C is formed. When the pitch l] of the protrusions Jl on the Yuzu skin surface is less than 2 μm, the electromagnetic conversion characteristics, running characteristics, and running durability are equivalent to those not exhibiting the Yuzu skin surface condition, and the pinch of the mouth is 100 μm.
If it exceeds 0 μ771, the running characteristics and running durability will further improve slightly, but the electromagnetic conversion characteristics will deteriorate significantly.

As the thickness T of the bank layer increases, the valley C of the yuzu skin surface
Deterioration of the electromagnetic conversion characteristics due to the depth d and surface roughness of the substrate becomes obvious, and the thickness T of the bank layer needs to be 2 it% or less. The lower limit of the thickness of the back layer '1' is determined by the general lower limit of conventional back layers, but in order to obtain an orange skin surface, it is necessary to have a thickness of 03 μm or more. Note that the citron skin surface in the present invention has a regular surface shape different from a normal so-called rough surface.

If the depth 1 of the troughs C is less than 0.02 μn1, the effectiveness of the surface of the citron skin will not be sufficiently utilized.

The present invention has been made based on the knowledge as described in "-", and provides a magnetic recording medium in which a magnetic layer is broken by the force of a non-magnetic support, and a bank layer with a thickness of 2 μm or more is provided on the other surface. The medium is characterized in that the surface of the Tsuku layer is shaped like Yuzu skin.

The back layer of the magnetic recording medium according to the present invention uses a conventionally known binder and solid powder (such as inorganic powder) for roughening the surface.
A powder substance (carbon black, granoite powder, metal powder, etc.) may be added to impart conductivity.

As the binder used in the present invention, binders conventionally known in the art, such as thermoplastic resins, thermosetting resins, reactive resins, or mixtures thereof, are used.

Examples of the thermoplastic resin include vinyl chloride/L.-vinyl acetate copolymer, vinyl chloride-3'; monochlorinated bi-lydene copolymer, vinyl chloride-acrylonitrile, and acrylic ester-acrylic I1. =Tolyl polymer, -acrylic ester-1 crystallized vinylidene coelectrolyte, acrylic ester-
Styrene copolymer, methacrylic acid ester 1'Cry1
1 nitrile! Coalescence, methacrylic acid ester) C□ −
Vinyritine copolymer, methacrylic acid: 1-
Snow loose styrene copolymer, urethane elas 11-,
Polyvinyl fluoride, vinylidene chloride-acrylic to tolyl copolymer, butadiene-acrylic I to monolyl coelectric, polyamide resin, polyvinino 1, Noral, fiber Mf.
Thread resin (cellulose ace-7- -- 1.,,+
f-rate, cellulose diacetate-1, l=.
(tL1+ -

Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins,
Melamine resin, alkyd resin, acrylic reactive resin,
These include polyiso'/anate and polyamine.

Among the above, particularly preferred is a six-component system consisting of a cellulose resin, a thermoplastic polyurethane elastomer, and a poly-inocyanate.

Suitable cellulose resins include cellulose derivatives such as Nido 1Cell J-S, which provide heat resistance, toughness, and blocking resistance.

As the thermoplastic polyurethane elastomer, almost all commercially available products can be used. , i.e., organic dibasic acids such as notaric acid, adipic acid, dimerized ruin acid, maleic acid, and "-f" lengelicol, propylene glycol, diethylene glycol, 1. Nid (1) Polyester polyol obtained by reaction with polyhydric alcohols such as Nifurs or trimethylolpropane, -\xanetriol, glycerin, trimethylconitane, and pentaerythritol. Polyester polyurethane urethanized with a polyisocyanate compound such as diisocyanate, 4,4-diphenylnocundiisonane-1, hexamethylene diisonane-1, metaxylylene diisonane-1 [←(')- 4t., uoe
-+(-co>-oI+, ooCN1+, +1.N+
+Co-)I Formula 19, where m is an integer from 5 to 100, Il, &;l carbon, (
・Hydroxoalkyl group with 1 to 4 streaks or 1 carbon number
introduced by an alicyclic or aromatic compound having at least 2 to 4 hydroxyalkoxyl groups or ←(3
1-12→n, +1 is an integer from 4 to 6.

These molecular weights are preferably 5,000 to soo, preferably 10,000 to 200,000.

Regarding these polyurethanes, patent application No. 54-2688
[Described in No. 1. 1 Furthermore, as polyino7-)'ates, r[,2,4-tolylene diisocyanate, 1,6-hexanotylene diisocyanate!・Triisoocyanates (for example, "J-nate", manufactured by Nippon Polyurethane Industries, Ltd.) can be used. .

The composition ratio of the binder is 111 parts by weight of binder 1uO, 20-ε (0 city 111 parts) of fiber S・11, and fiber resin.
Especially preferably 3D~60 Jujobu), ri, 4~iTJ'
20 to 50 parts by weight of plastic polyurethane elastomer (
Particularly preferably 30 to 40 parts by weight - 111 parts of polyisocyanate (10 to 50 parts by weight, preferably 20 parts by weight)
3. The inorganic powder as an example of the solid powder used in the present invention preferably includes calcium carbonate/1 cum, silicon dioxide, titanium oxide, tungsten disulfide/,
- Molybdenum sulfide, boron nitride, aluminum oxide, iron oxide, zinc oxide, calcyanotin oxide, tin oxide, carbon blank, graphite, etc., preferably calcium carbonate, nitride oxide, graphite, etc.゛tan et al.
Even more friendly 1. +1, carunium carbonate.

These solid powders are - Father Itt, 1. The roughness of the bank layer surface formed by the powder is transferred to the magnetic surface (to suppress L, the average particle size is O, U2~Q, 51Lnt, preferably tt, <&l
1, 0.02-02 μm is used.

The bank layer having a yuzu skin surface is formed by cross-dispersing a composition in which a solvent (selected according to each binder) is added to the ingredients listed in -, applying it to the surface of the support, and drying it. . This bank layer is selected to make the total thickness of the magnetic recording medium as thin as possible in order to increase the recording density per unit volume. The thickness of such a bank layer is preferably 0.3 to 2 .mu.m, particularly preferably 0.5 to 1 .mu.nt.

Note that a known magnetic layer can be used.

Next, examples of the present invention will be described, and "parts" shown in the examples indicate "parts by weight."

Example 1 A magnetic layer with a thickness of 5μ7n was provided on the surface of a polyethylene terephthalate support with a thickness of 14μ771, the following composition was dispersed and mixed in a ball mill for 10 hours, and a liquid coating composition consisting of -C was applied to the back side of the support layer. After that, by drying appropriately, it becomes 1 which has a citron skin 1n1 with a pitch p of about 50 fins.
A bank layer with a thickness of 11 μm was provided to create a magnetic tape with a total thickness of 20 μm.

Bank layer composition Nitrocellulose 25 parts Polyurekne 10 parts (Nippojin 7 K II 'l manufactured by Nippon Polyurethane) Polyinocyanate-1.
25 parts (Coronate L manufactured by ■ above) Ethyl methyl ketone 300 parts Calcium carbonate Ioo part When the surface of the bank layer of this sample A was observed using a microscope, a citrus skin surface was observed, and the surface roughness was measured using a surface roughness meter. When measured, the R was 0.02411 m at a cutoff of 0 and a Q of 8 mm. Using the following measurement method, we measured the electromagnetic conversion characteristics, ratio, running durability characteristics, output fluctuation, winding shape, and wear, and obtained the results shown in the table below.

The 1S ratio difference measuring device is a noise meter (925C) made by Sibaku KK.
was used, and the reference tape was used as comparative sample C, and the difference in S/c ratio with respect to it was determined.

The noise level was measured using a bypass filter of 10 KHz and a low-pass filter of 4 Ml-1z.

V1'RU, for Matsushita N V-8300.

2. The output of the variable output virgin tape and the 100-pass running tape were compared.

6 Observe the tape after 100 passes using the winding and abrasion sample tape and the above tape deck, and the results are 5 for good and 1 for bad.
It is shown as an average value evaluated in 5 stages.

Example 2 A coating composition prepared by dispersing the same composition as in Example 1 in a ball mill for 50 hours was applied to the same support layer as in Example 1 and dried, thereby producing a magnetic material with a back layer having a citrus skin surface. Recording tape sample 13 was prepared. This tape sample I
Force measurements were performed on Sample No. 3 in the same manner as in Example 1, and the results are shown in the table.

Comparative Examples 1 and 2 Coating 4i compositions were applied using the same composition as in Example 1 and the intervals were 10 hours and 50 hours, respectively. A sample C having a back layer (without plate formation) and a sample I having a bank layer with a smooth surface were prepared, respectively. The same measurements as in Example 1+111 were carried out for each sample, and the results were summarized in the table.

Sample Dispersion time Yuzu skin F-shihe ratio difference Output fluctuation Winding form Abrasion A, 10 hours Yes 4-1odB0.2dl
l 5 513 50 Yes +1.
1 0.6 4 No 4C10
OfJ, 3 5 5D so
None + 1.2 '1.3 1
1 Comparison of bovine sex of each sample listed in the table above: 1
−, the following points become clear. In other words, if the dispersion time of the bank layer composition is shortened by tυ in accordance with the conventional method and the bank layer surface is simply roughened without forming an orange skin surface, it is clear from the measurement and evaluation results of sample C that the running Although the characteristics and running durability are improved, the electromagnetic conversion characteristics are significantly reduced. On the other hand, sample J) has a long dispersion time, so the surface of the bank layer is smooth (no citron surface formation), but in this case, the electromagnetic conversion characteristics are improved, but the running characteristics and running durability are reduced. .

On the other hand, in the case of sample I3, in which the surface of the back layer corresponding to sample 1) was used as the base material and a citrus skin surface was formed, the running characteristics and running durability characteristics were improved without substantially impairing the electromagnetic conversion characteristics. Compared to this sample B, sample A, which has a citrus skin surface and roughened base surface, has slightly improved running characteristics and running durability while suppressing deterioration of electromagnetic conversion characteristics to an appropriate level.

That is, in the present invention, the back layer has a citron-like surface, and whether the substrate is smooth or rough, an improvement over the conventional method is recognized due to the citron-like surface of the back layer. Whether the bank layer has a rough surface or a smooth surface can be selected depending on the purpose.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the pattern of the citron skin surface, and FIG. 2 is a sectional view of a magnetic recording medium (cross section taken along arrow II-II in FIG. 1) showing the unevenness of the yuzu skin surface. a Projection b Back layer C Valley d Valley depth p Pitch e Support f Magnetic layer Applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Asahi Fuji Do Figure 1 Figure 2 Procedural Amendment No. 73B22, 1982 Mr. Kazuo Wakasugi, Commissioner of the Patent Office 1 Case Description Special Fraud Application No. 166661 of 1982 (Showa JI 757)
271 (Application filed) 2 Name of the invention Magnetic recording medium 3 Relationship to the case of the person making the amendment Patent applicant's residence 5.9j (Residence) Name Fuji Photo Film Co., Ltd. 6 Supplementary iE
The number of inventions increases due to organic dibasic acids such as oleic acid: T', ethylene glycol, propylene glycol, butylene glycol, '/:' dif-lene glycol: 'i: t( ,t) Ri!J call 2bQ
Also i+, j t・su7 nochiro・rupropa：／、−＼
Polyesterboliol obtained by reaction with polyhedral alcohols such as xanetriol, glycerin, trimethylolethane, and pentaerythritol is converted into tolylene diisocyanate, 4,4-diphenylmethane di-
Polyester polyurethane which has been urethanized with a polyisocyanate compound such as isocyanate, hexamethylene diisocyanate, metaxylylene diisocyanate, and the like is used. (←o-1←oO0-r(, Co > , 1l-or+
,oo(IN+1-+'C-N11r3o-)(1
) formula, where Ill is an integer from 5 to 100, It & y carbon is an alicyclic or aromatic group having 1 to 4 hydroxyalkyl groups or at least 2 hydroxyalkyl groups having 1 to 4 carbon atoms. introduced by a group compound or ←(J-1,-)-
n, n is an integer from 4 to 6. The molecule of coiL et al. is 5.00 [1 to 500,000
Values of 10 and OO[1 to 200,000 are valid. What about these polyurethanes? is described in Japanese Patent Application No. 54-26880.

Claims (1)

[Claims] The non-magnetic material has a magnetic layer on one side and a thickness of 2 on the other side.
In a magnetic recording medium having a back layer of μnt or less,
A magnetic recording medium characterized by a bank layer surface having a "skin-like" texture.