JPS60150230A - Magnetic recording body - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium having a back layer having a durable traveling property without any increase in the coefficient of friction which does not damage the S/N characteristic of the magnetic medium by incorporating at least one kind among polyolefin or polytetrafluoroethylene and polyamide powder and carbon black into the back layer. CONSTITUTION:The powder of polyolefin such as polyethylene and polypropylene or polytetrafluoroethylene and polyamide has a lubricating effect, and prevents an increase in the coefficient of friction. When the magnetic recording layer is treated with heat and compression by a calender roll to mirror-grind the surface of the magnetic recording layer for high-density recording, the acute protrusions on the surface of the powder of polyolefin such as polyethylene and polypropylene or polytetrafluoroethylene and polyamide which are contained in the back layer are easily crushed by the temp. and pressure. Since the back layer is elastic and soft, the influence of the back layer on the magnetic recording layer is prevented. The electrically conductive carbon black is simultaneously incorporated to reduce the electric resistance of the surface of the back layer, and an antistatic effect can be provided.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium that reduces the coefficient of friction without reducing 8/N, improves running durability, and prevents edge bending of the tape. The present invention relates to an excellent magnetic recording material that has no dropout, has no scratches on the back surface of the tape, etc.

(Prior art) In general, in magnetic recording tapes for audio, video, or computer use, in order to improve the sensitivity (output in the high frequency range), it is required to make the surface of the magnetic recording layer mirror-finished and smooth. ing. In addition, as magnetic recording layers have become smoother, non-magnetic supports with less surface roughness have come to be used.

Such a smooth magnetic recording tape is not wound neatly during winding and unwinding, and tends to wind irregularly. When such a magnetic recording tape is used, running properties deteriorate due to tension fluctuations, etc., and the output fluctuates. Also, deformation of the tape,
Damage is likely to occur.

In addition, plastic films such as PET are generally widely used as non-magnetic supports, but because of their high surface electrical resistance, they are susceptible to static electricity and are therefore susceptible to dropouts due to dust adhesion, scratches, etc. In order to prevent such drawbacks, a magnetic recording tape has been proposed in which a pack layer is provided on the side of the support opposite to the magnetic recording layer.

However, conventionally used pack layers tend to increase the coefficient of friction, scrape, and bend the tape.
There is still room for further improvement.

In general, when a back layer is provided for the purpose of improving running characteristics and running durability, when a magnetic recording medium (particularly in the form of a tape) is rolled up into a roll or stacked in a sheet form, the back layer It is known that the unevenness is reflected on the surface of the magnetic recording layer, impairing the surface properties of the magnetic recording layer, thereby impairing the electromagnetic conversion characteristics, especially the 8/N characteristics, of the magnetic recording body. S/N characteristics often deteriorate (
Due to the running characteristics of the backing layer, its surface condition is rough, so if magnetic recording media are stored or left in a state where they are rolled up or stacked, the unevenness of the backing layer becomes magnetic. This is because it is reflected on the surface of the recording layer.

Furthermore, in Japanese Patent Publication No. 7-32003, it has been proposed that a powder of polyolefin or a copolymer thereof, such as polyethylene, polypropylene, or polyethylene-vinyl acetate copolymer, be applied together with a binder to form a back layer.
Since the surface electrical resistance is high and it is easily charged, it has the disadvantage that it attracts dust and the like, causing dropouts and damaging the chip due to dust and the like.

In order to solve the above-mentioned drawbacks, the inventors of the present invention have conducted extensive studies on the powder used for the back layer, and have found that a combination of polyolefin, polytetrafluoroethylene, and polyamide powders and carbon black exhibits a remarkable effect. They discovered this and arrived at the present invention.

(Objective of the Invention) That is, the object of the present invention is to provide a magnetic recording medium that does not increase the coefficient of friction and has good running durability, and further,
An object of the present invention is to provide a magnetic recording medium having a back layer that does not impair the S/N ratio of the magnetic medium.

(Structure of the Invention) The above object of the present invention is to provide a magnetic recording layer in which a magnetic recording layer is provided on one side of a non-magnetic support and a back layer made of powder dispersed in a binder is provided on the other side. This is achieved by a magnetic recording medium characterized in that the pack contains carbon black and at least one of powders of polyolefins such as polyethylene and polypropylene, or polytetrafluoroethylene and polyamide.

The polyolefin such as polyethylene, polypropylene, polytetrafluoroethylene, and polyamide powder used in the present invention have a lubricating effect and have the effect of preventing an increase in the coefficient of friction.

In addition, the magnetic recording layer is subjected to heat and compression treatment using a calendar roll in order to make the surface of the magnetic recording layer mirror-like for high-density recording.
Powders such as polyolefins such as polypropylene, polytetrafluoroethylene, and polyamides have sharp protrusions on the surface that are easily crushed by temperature and pressure, and because they are elastic and flexible, they are less likely to affect the magnetic recording layer. Provides a protective effect.

On the other hand, by simultaneously containing conductive carbon black, the surface electrical resistance of the back layer can be reduced and an antistatic effect can be provided. Also, due to the coexistence of both, the coating film is less likely to be chipped and scratches! − can be reduced.

The average particle size of the polyolefin such as polyethylene or polypropylene or polytetrafluoroethylene and polyamide powder used in the present invention is preferably o, or-pμ, particularly preferably 0°3 to 3μ.

Also, the average single particle size of carbon black is lθ~10
0 mμ, preferably KO-♂jmμ.

Further, the mixing ratio of carbon black and at least one of polyolefins such as polyethylene, polypropylene, or polytetrafluoroethylene and polyamide powder is preferably 277-i'7, particularly preferably j//, ／／It is O.

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

Examples of thermoplastic resins include vinyl chloride-vinylacetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, and acrylic ester-vinylidene chloride copolymer. , acrylic ester-styrene copolymer, methacrylic ester-acrylonitrile copolymer, methacrylic ester-vinylidene chloride copolymer,
Methacrylic acid ester-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose resin (cellulose acetate butyrate, cellulose dye) acetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether-acrylic ester copolymers, amino resins, and various rubber resins.

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 polyisocyanates and polyamines.

Among the above, particularly preferred are cellulose resin, thermoplastic polyurethane elastomer, and polyisocyanate.
It is an ingredient system.

As the cellulose resin, cellulose derivatives such as nitrocellulose are suitable, and these are useful for imparting heat resistance, toughness, and blocking resistance.

As the thermoplastic polyurethane elastomer, almost all commercially available products can be used. That is, organic dibasic acids such as phthalic acid, adipic acid, dimerized sulfuric acid, and maleic acid, and glycols such as ethylene glycol, propylene glycol, phthylene gelicol, and diethylene glycol, or trimethylolpronotone, hexanetriol, Polyester polyols obtained by reaction with polyhydric alcohols such as glycerin, trimethylolethane, and pentaerythritol are converted into tolylene dicyanate, ≠, l/-diphenylmethane diisocyanate, hexamethylene diisocyanate, and metaxylylene diisocyanate. Polyester polyurethane resins and polyether polyurethane resins urethanized with polyisocyanate compounds, such as polyisocyanate compounds, and the present molecule represented by the general formula (I).

[MoO-几-00C-R/-Co)m-OR,0OCN
H-㇠〃-NHC〇-]CI) formula, where m is an integer of s or ioo, and R is a hydroxyalkyl group having l-3 carbon atoms or a hydroxyalkoxyl group having /-1 carbon atoms at least λ. The covalent value H3 or f CH2+ 11%'' introduced by the alicyclic or aromatic compound is an integer from ≠ to B.

The molecular weight of these is 3. ooo~zoo, ooθ preferably 10,000-. 200,000 is valid. Regarding these polyurethanes, patent application No. 74 cmλt
It is described in the rio issue.

Furthermore, as the polyisocyanate, co-,≠-tolylene diisocyanate, /,A-hexamethylene diisocyanate, triisocyanate (for example, "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.), etc. can be used.

The composition ratio of the binder is 20-10 parts by weight of cellulose resin (particularly preferably 10-30 parts by weight) and 20-40 parts by weight of thermoplastic polyurethane elastomer per 100 parts by weight of binding agent. part (particularly preferably 30 to
4AO parts by weight) and 10.30 parts by weight of polyisocyanate (particularly preferably 20 to 4LO parts by weight).

The ratio of the mixed powder to the binder in the back layer used in the present invention is j/I-//, particularly preferably co//-1/II.

The back layer of the present invention is selected so as to make the total thickness of the magnetic recording medium (magnetic recording layer support plus back layer) as thin as possible in order to increase the recording density per unit volume. The thickness of such a back layer is preferably 0.3 to 1,000 μm, and particularly preferably 0.3 μm to 1,000 μm. j~/, jμ.

By using the back layer of the present invention, the coefficient of friction does not increase even when the magnetic recording medium is repeatedly run, and it has stable running performance. It also has an excellent effect on preventing static electricity, and prevents the adsorption of dust, etc. It is possible to prevent the occurrence of dropout due to lack of layers, etc.

Furthermore, deterioration of video S/N can be prevented even in high-density recording with a recording wavelength of /3μ. Furthermore, the magnetic recording body of the present invention can be prepared according to the materials, manufacturing method, etc. described in JP-A-52-10RR.

(Example) Next, an example of the present invention will be described. In Examples, "1 part" indicates "1 part".

EXAMPLE A magnetic recording layer containing cobalt-containing r-iron oxide was provided on the surface of a polyethylene terephthalate base having a thickness of l≠μ, and a back layer was provided on the opposite side. The back layer is coated with a binder composition or a cross-dispersion of the binder composition with a powder of amber powder so that the thickness of the magnetic recording layer after drying is jμ. The thickness is 1. It was applied so that it became jμ.

Thereafter, the magnetic recording layer was subjected to heat and compression treatment using a calendar roll to make it mirror-finished, and then slit into 1/2 inch width to obtain a magnetic recording tape.

The composition of the magnetic recording layer is as follows.

Co-adhered r-Fe203 100 parts PVC/vinyl acetate/maleic anhydride copolymer 10 parts polyurethane resin 1 part carbon black 1 part silicone oil os part oleic acid 7 parts ethyl stearate 1 part α7An□03 powder 3 Part Methyl Ethyl Ketone 210 Parts The above mixture was cross-dispersed in a ball mill for an AT waiting time, and then 5 parts of a polyinocyanate curing agent was added and dispersed for 1 hour to obtain a coating material for a magnetic recording layer.

binder composition person Vinyl chloride-vinyl acetate copolymer (product name: poox-tioh.

Nippon Zeon ■ Manufactured by) 30 copies 73- Polyurethane (Product name: Niraporan 230/, Nippon Polyurethane Manufacturing) 11 parts Polyisocyanate (Product name: Coronate L1 Nippon Polyurethane ■Manufacturing) Part 2 Methyl ethyl ketone 3θO, parts Binder composition Nitrocellulose 30 parts Polyurethane (Product name: Niraporan 2 J O/.

11 parts Polyisocyanate (trade name: Coronate L1 manufactured by Nippon Polyurethane ■) 25 parts Methyl ethyl ketone 300 parts The mixed metal powder was mixed by adding 30 seconds to the above binder composition. The types of mixed powder shown in Table 1 were used.

Each sample of the magnetic recording tape was tested for each ridge, and the results shown in Table 1 were obtained.

−／j− The test method is described below.

Test Method 1 The virgin tape was tested for running durability after running 100 passes. Running durability is determined by the VHS video deck's rotating cylinder rotation (To) and output rotation (y).
This was done by measuring (T 2 ).

Furthermore, the output fluctuations of the virgin tape and the tape after running f100 passes were investigated.

Test method Using Covirgin tape and the tape run for 100 seconds, we tested the coefficient of dynamic friction (3,3
cyxlsec time) μ total magnetic recording layer side, ・(Tsuku layer side).

Test Method 3 After the VHS video deck was exposed to lOθ, the state of wear on the surface of the /ζ layer and the state of damage to the tape were examined.

Test method≠ Dropouts per 7 minutes of a virgin tape and a tape made by running 100 passes were investigated.

Test method The surface electrical resistance of the pack layer surface of the tape was investigated.

Test method t A virgin tape and a tape that has been run for 100 passes are fast-forwarded on a VHS video deck, and the winding disturbance width when the tape is wound around a roll body (maximum width of tape wound around a roll body - specified tape) width) was measured.

As is clear from Table 7, by including one of polyethylene, polypropylene, polyamide and Carlo black in the pack layer filler, the friction coefficient increases due to repeated running without impairing the 8/N characteristics. Therefore, it is possible to obtain a tape that has good running durability, a small number of dropouts, and has an antistatic effect.

Further, it is possible to reduce the amount of trailing tail due to fast forwarding.

Claims (1)

[Scope of Claims] A magnetic recording body in which a magnetic recording layer is provided on one side of a non-magnetic support and a pack layer made of powder dispersed in a binder is provided on the other side, wherein ° A magnetic recording material comprising carbon black and at least one of polyolefin, polytetrafluoroethylene, and polyamide powder.