JPH03214417A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To realize a thin layer of a supporting body with maintaining the electromagnetic conversion characteristics and traveling durability at high level by successively forming a dummy layer and magnetic layer on the one side of the supporting body. CONSTITUTION:A dummy layer 11 is formed on a supporting body having rather bad surface property by coating so that the supporting body 2 can be made thin as 0.014 - 0.009 mm thickness. In this case, the dummy layer 11 is formed by coating with a head 3 immediately after the supporting body 2 is released from a roll 1, and the dummy layer 11 is dried in a zone 5. Then this supporting body is calendered with rolls 6a and 6b, on which a magnetic layer 12 is laminated with a head 7 coating, dried in a zone 9, and wound up on a roll 10. The dummy layer 11 essentially consists of polymer resin or polymer resin and nonmagnetic particles of 0.01 - 2 mum average particle size.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium comprising a magnetic layer formed on a flexible non-magnetic support.

[Conventional technology]

Conventionally, the general manufacturing method for magnetic recording media, such as magnetic tapes such as audio tapes and video tapes, and magnetic disks such as floppy disks, involves applying a magnetic coating liquid onto a non-magnetic support that is wider than normal products. After coating to form a magnetic layer, performing an orientation treatment and drying the magnetic layer, smoothing the surface of the magnetic layer to produce a tape material, and then cutting the tape material in a cutting process. It is manufactured by cutting the tape into a predetermined width or shape.

The surface smoothing treatment is performed to polish or smooth the surface of the magnetic layer, improve the packing density, or make the coating thickness uniform. This is effective for improving playback output and reducing tape noise. Furthermore, in recent years, there has been a strong demand for increasing the storage capacity of magnetic recording media, and it is necessary to increase the information recording density per unit area of magnetic recording media.

Therefore, in order to increase the information recording density, it is necessary to concentrate the write magnetic flux generated from the magnetic head that records and reproduces information in a small area, so the magnetic head is miniaturized and the amount of generated magnetic flux is reduced. reduced. Therefore, in order to reverse the direction of nization of the magnetic layer as desired with the reduced magnetic flux as described above, it is necessary to reduce the volume of the magnetic layer, that is, reduce the thickness of the magnetic layer. Since it is difficult to perform a magnetization reversal and the recording/reproducing characteristics cannot be expected to have a -E direction, it has become necessary to make the magnetic layer of the magnetic recording medium thinner. Also, for example, JP-A-63
No.-102036, No. 63-102037, JP-A-1
As disclosed in No. 106333, etc., the magnetic layer has been made into a two-layer structure with different characteristics to improve its performance, as well as to make the magnetic layer thinner and reduce the cost of raw materials.

Furthermore, coercive force (1) is applied to a coating-type magnetic recording medium in which a magnetic coating solution in which the powdered magnetic material as described above is dispersed in an organic binder is coated on a non-magnetic support and dried. Ferromagnetic metal thin film type, which has a large residual magnetic flux density B1 and can make the thickness of the magnetic layer extremely thin, is made by directly depositing a metal thin film made of a ferromagnetic metal material on a nonmagnetic support by vacuum deposition, etc. Magnetic recording media are beginning to be used.

[Problem to be solved by the invention]

As mentioned above, magnetic layers are becoming thinner as performance improves, but in order to obtain magnetic recording media with good magnetic properties, it is necessary to use nonmagnetic supports with good surface smoothness. However, such nonmagnetic support materials are expensive and have the problem of increasing manufacturing costs. Therefore, from the perspective of reducing material costs, it is conceivable to make the support thickness of the magnetic layer thinner within the limits that satisfy its strength and running durability, but there are restrictions on compatibility with recording and reproducing devices (for example, , total thickness of 17.0μ or more in VHS format T-120)
However, it had not been realized.

Therefore, the purpose of the present invention is to solve the above-mentioned problems.It is possible to reduce costs by making the thickness of the support thinner, which could not be achieved in the past, while maintaining electromagnetic conversion characteristics and running durability at a high level. An object of the present invention is to provide a magnetic recording medium.

[Means to solve the problem]

The above object of the present invention is to provide a magnetic recording medium having a magnetic layer on at least one side of a non-magnetic support, in which one side of the non-magnetic support has a polymer resin or a polymer resin and non-magnetic particles as main components. This is achieved by a magnetic recording medium characterized in that the dummy layer and the magnetic layer are sequentially laminated.

(Embodiment) A magnetic tape which is an embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in the cross section of the magnetic tape in FIG. 1, by forming a dummy layer 11 by coating on a support 2 with relatively poor surface properties, for example, VHS system (7) T-12
In the case of the polyethylene terephthalate tape of No. 0, not only can the support 2 be made as thin as 0.014 mm to 0.009 mm, but the surface on which the magnetic layer 12 is formed can have good smoothness, and the back side is rough. Therefore, good tape running properties can be maintained without roughening the back surface of the support as in the case of conventional high-quality supports. Note that the thickness of the dummy layer l1 is the same as that of the support 2.
In this embodiment, when polyethylene terephthalate is used for the
By making the tape thicker than this, it is possible to provide an auxiliary function in terms of strength, maintain quality that exceeds the standard in terms of tape strength, and provide an extremely inexpensive product. Note that the upper limit of the thickness of the dummy layer l1 can be approximately 6 μm based on the strength and thickness standards of the recording medium.

The dummy layer 11 can be formed by various coating methods such as roll coating, gravure coating, roll coating, or one-sided extrusion run plus doctor method. FIG. 2 schematically shows equipment for forming the dummy layer 11 in the process of manufacturing a magnetic tape. That is, immediately after the support 2 is fed out from the outlet 1, the dummy 1ii11 is applied by the first coating head 3 and dried in the drying zone 5. Following this drying, the calender roll 6a. 6b, the magnetic layer is subjected to calendering L, and then a magnetic layer is coated in multiple layers using the second coating head 7, and the magnetic layer is suitably dried using a drying dune 9, and then wound onto a winding roll 10. Incidentally, a magnetic dispersion liquid having the following composition is supplied to both coating heads 3 and 7 by respective liquid supply systems 4, 8a and 8b for the dummy layer and the magnetic layer. When the magnetic tape formed in this way is subsequently subjected to calender treatment, the use of a resin that is relatively easily deformed by heating and pressure for the dummy layer 11 results in surface smoothing treatment such as calender treatment. Since this effect is enhanced, it is possible to obtain a magnetic recording medium having good surface smoothness and good magnetic properties even if the surface properties of the material used for the support are poor.

The polymer resin used in the dummy layer of the present invention may be, for example, a thermoplastic resin, a thermosetting resin, a reactive resin, or a mixture thereof. The thermoplastic resin has a softening temperature of 150'C or less and an average molecular weight of 10
000 to 300,000, and the degree of polymerization is about 50 to 2,000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride polymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer Polymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon Silicone resin, nitrocellulose-polyamide resin, polyfluorinated vinyl, vinylidene chloride-acrylic nitrile copolymer, butadiene-acrylic nitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate, cellulose diacetate, cellulose triacetate,
Cellulose propionate, ditrocellulose, ethylcellulose, methylcellulose, probilcellulose,
methyl ethyl cellulose, carboxymethyl cellulose, acetyl cellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylic acid ester copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof. I can do it.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane curable resin, urea resin,
Melamine resins, alkynd resins, silicone resins, acrylic reactive resins, epoxy polyamide resins, nitrocellulose melamine resins, mixtures of high molecular weight polyester resins and isocyanate prebolimers, mixtures of methacrylate copolymers and diisocyanate prebolimers, polyester polyols and polyisocyanate, urea formaldehyde resin, mixture of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate, polyamine resin, polyimine resin, and mixtures thereof.

These thermoplastic resins, thermosetting resins, and reactive resins are
In addition to the main functional groups, functional groups include acidic groups such as carboxylic acid, sulfinic acid, sulfenic acid, sulfonic acid, phosphoric acid, sulfuric acid, phosphonic acid, phosphine, boric acid, sulfuric ester groups, phosphoric ester groups, and alkyl ester groups thereof, and amino acids. Aminosulfonic acids, sulfuric or phosphoric acid esters of aminoalcohols, amphoteric groups such as alkyl betaine types, amino groups, imino groups, imido groups, amide groups, eboxylfB, etc. Also, hydroxyl groups, alkosyl groups, thiol groups,
Usually one or more halogen groups, silyl groups, and siloxane groups (6)
Each functional group contains IXIO per gram of resin.
-'eq-I XIO-"eq is preferably included.

By mixing appropriate particles into each resin used for the dummy layer 11, the strength of the dummy layer 11 can be increased. As with the support 2, these particles are preferably non-magnetic, such as carbon black,
α-alumina, T-alumina, α-T-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron monoxide, garnet, emery (main components: corundum and magnetic iron K), Gar 2 y
}, silica, silicon nitride, boron nitride, tungsten carbide, titanium carbide, quartz, tripoli, diatomaceous earth, F lomite, etc. can be used singly or in combination. In addition, if the size of these particles is too large, it will deteriorate the surface properties of the surface to which the magnetic layer is applied.
If it is too small, the reinforcing effect of the dummy layer 11 cannot be expected so much, so the particle size has an appropriate range, and the average particle size is preferably in the range of 0.01 to 2 μm. Further, it is desirable that the mixing ratio of the particles is 70% or less by weight based on the resin constituting the dummy layer l1. In the embodiment described above, as shown in FIG. 2, a case was shown in which a dummy layer was formed immediately before forming the magnetic layer, but the present invention is not limited to the embodiment described above, and of course, the support body 2 may be manufactured. It may be possible to form it sometimes. (Effects of the Invention) As described above, the present invention provides a polymer resin with a thickness corresponding to the thinning of the support between a non-magnetic support and a magnetic layer, or a polymer resin and a non-magnetic resin. Since a thick dummy layer mainly composed of magnetic particles is formed by coating, even if the thickness of the support is made thinner to significantly reduce material costs, it is limited by the recording and reproducing device. The specified thickness of the media can be maintained. Furthermore, by using a resin that is relatively easily deformed by heating and pressurizing for the dummy layer, the effect of surface smoothing treatment such as calender treatment is enhanced, so that the surface properties of the material used for the support are poor. It is possible to obtain a magnetic recording medium having good magnetic properties with good surface smoothness, and furthermore, by using the above-mentioned support with poor surface properties, it is possible to omit roughening treatment by back coating on the back surface of the support. It is also possible to provide a magnetic recording medium that can promote reduction in manufacturing costs and maintain electromagnetic conversion characteristics and running durability at a high level.

Hereinafter, the effects of the present invention can be further clarified through Examples and Comparative Examples.

[1 ship ■] The coating of the dummy layer and the magnetic layer is performed using the coating equipment shown in FIG. This coating equipment is as shown in the figure.
A dummy layer is applied to the support 2 pulled out from the support body 2 by the first application head and dried in the drying zone 5. Following this drying, it is calendered using calender rolls 6a and 6b, and then a magnetic layer is coated in multiple layers using the second coating head 7, dried appropriately in the drying zone 9, and then wound onto the winding roll 1O.

The coating head used for coating the dummy layer is JP-A-60238.
It is the same as the extrusion type coating head disclosed in Publication No. 179, and the general configuration of the coating head part is that the slit width is 0.6 mm, the diameter of the pocket part is 20 mm, and the curvature of the doctor edge surface is 15 mm. The effective length of the doctor edge surface is 6 mm, and the pack edge surface has a rounded shape and has an effective length of 7.5 mm. The coating head used for coating the magnetic layer was the same as the two-layer simultaneous coating type coating head shown in JP-A-63-88080, and its schematic configuration is as follows.
The slit width is 0.5 mm on the upper layer side and 0.6 m on the lower layer side.
m, the diameter of the pocket part is 15 mm on the upper layer side and 20 mm on the lower layer side, the curvature of the Doctor Edge surface is 20 mm on the upper layer side and 15 mm on the lower layer side, the effective length of the Doctor Edge surface is 6 mm on the upper layer side, 5 mm on the lower layer side, and 5 mm on the lower layer side. The edge surface has a rounded shape and its effective length is 7.
It is 5mm. The support used was a polyethylene terephthalate film with a thickness of 11.5 μm and a surface roughness of 0.02 μm. No undercoat layer was formed. The composition of the dummy layer was as shown in Table 1, and the coating thickness was 3.3 μm (average). The upper layer of the magnetic layer has the composition shown in Table 2 and has a coating thickness of 0.8 μm, and the lower layer has the composition shown in Table 3 and has a thickness of 3.2 μm.
In this way, sample No. 1 magnetic recording medium was prepared. The results are shown in Table 4.

[Comparative example]

The magnetic layer was coated using the coating equipment shown in FIG. 1, which does not coat the gummy layer.

The support used was a polyethylene terephthalate film with a thickness of 14.8 μm+w (this thickness is the same as the total thickness of the support and dummy layer in the above example) and a surface roughness of 0.02 μm. No undercoat layer was formed.

The composition of the dummy layer was as shown in Table 1, and the coating thickness was 3.3 μm (average).

The composition of the upper layer of the magnetic layer was as shown in Table 2, and the coating thickness was 0.8 μm, and the composition of the lower layer was as shown in Table 3, and the thickness was 3.2 μm, the same as in the example. In this way, a magnetic recording medium of sample Nl12 was created. The results are shown in Table 4. Table 1 (blank below) Table 2 (upper layer magnetic dispersion) Table 3 (lower layer magnetic dispersion) Table 4 Note that the parts marked with a mock mark are based on JIS C231B. Looking at Table 4, it can be seen that the surface characteristics, adhesion strength of the magnetic layer, and mechanical strength of the entire medium are approximately the same between the Example (Sample Level 1) and the Comparative Example (Sample No. 2). Furthermore, the supports of Examples had poor surface properties and a low finish, so they were extremely inexpensive, and the manufacturing costs were significantly lower than those of Comparative Examples.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the magnetic recording medium of the present invention, and FIG. 2 is a schematic diagram of equipment for manufacturing the magnetic recording medium of the present invention. (Symbols in the figure) l...Feeding outlet, 2...Support, 3...First coating head, 4, 8a, 8b...Liquid supply system, 5.9...Drying zone, 6a, 6b.・Calendar roll, lO・
・Take-up roll.

Claims (1)

[Scope of Claims] 1) A magnetic recording medium in which a magnetic layer is provided on at least one side of a non-magnetic support, wherein one side of the non-magnetic support has a polymer resin or a polymer resin and non-magnetic particles as main components. 1. A magnetic recording medium comprising a dummy layer and the magnetic layer sequentially laminated. 2) The magnetic recording medium according to claim 1, wherein the dummy layer is made of at least one type of resin selected from thermoplastic resin, thermosetting resin, and reactive resin. 3) The non-magnetic particles in the dummy layer have an average particle size of 0.01
2. The magnetic recording medium of claim 1, comprising particles of ~2 [mu]m. 4) The dummy layer is made of at least one type of resin selected from thermoplastic resin, thermosetting resin, and reactive resin, and the nonmagnetic particles in the dummy layer have an average particle size of 0.01 to 2 μm.
The magnetic recording medium according to claim 1, comprising particles of.