JPS62214513A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To make a magnetic layer thinner and to improve the surface characteristic and running durability thereof by providing a nonmagnetic layer contg. a lubricating agent and having a prescribed Young's modulus and thickness and the magnetic layer contg. a ferromagnetic material on a nonmagnetic base. CONSTITUTION:This recording medium consists of the nonmagnetic layer provided on the nonmagnetic base and the magnetic layer thereon. This nonmagnetic layer consists of a binder, lubricating agent and desired hardener and has 5X10<4>-50X10<4>kg/cm<2> Young's modulus at 5-60 deg.C and >=1.0mum thickness. As a result, the recording medium having the thin magnetic layer and having the good running durability is obtd. and high-density recording is made possible.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magnetic recording medium, and with the increasing density of magnetic recording, it is particularly important to improve running durability in magnetic recording media in which the magnetic layer is thinner than conventional ones. The present invention relates to a magnetic recording medium with improved properties.

The magnetic recording medium of the present invention is suitable as a magnetic tape, a magnetic disk, or a magnetic sheet.

[Prior art and its problems]

In magnetic recording media, especially magnetic recording media such as high-density recording magnetic tapes, magnetic disks, or magnetic sheets that require strong durability, surface smoothness and running durability are simultaneously improved to improve electromagnetic conversion characteristics. Need to improve.

However, conventional magnetic recording media are no longer able to adequately meet the demands for higher density magnetic recording. In other words, in order to increase the recording density of magnetic disks, etc., it is important to smooth the surface of the magnetic layer and to ensure that the fine particles of ferromagnetic powder within the magnetic layer exist in a uniformly dispersed state within the layer. However, it is not possible to provide sufficient durability to the magnetic layer by simply making the magnetic powder into ultra-fine particles, strengthening the requirements for smoothing treatment such as calendering, and improving the dispersion ability of the magnetic liquid in which the magnetic powder is dispersed. I couldn't do that.

Furthermore, as the density of magnetic recording increases, the actual situation is that magnetic layers are becoming thinner and thinner.

Conventionally, one of the methods for improving the running durability of a magnetic layer is to add various lubricants to the magnetic layer. However, if the magnetic layer is further made into an N layer, sufficient running durability cannot be obtained even if a lubricant is added to the magnetic layer to impart durability, and the magnetic recording medium becomes a magnetic recording device. The surface of the magnetic layer is easily damaged by the impact applied by the magnetic recording head while the magnetic recording head is running inside the magnetic recording head, and minute irregularities on the surface of the support such as polyester film affect the surface of the magnetic layer, causing its electromagnetic There was a risk that the conversion characteristics would be impaired.

[Means and effects for solving the problems] As a result of intensive research by the present inventors in order to solve the problems in the prior art associated with the thinning of the magnetic layer of magnetic recording media as described above, we have found that The present invention was achieved by discovering a phenomenon that could not be easily predicted.

That is, the present invention provides a magnetic recording medium in which the surface properties and running durability of the magnetic layer are improved at the same time as the magnetic layer is thinned, and which contains a lubricant on a non-magnetic support, and Young's modulus from °C to 60 °C is 5xto
'~50xlO'kg/c! The thickness of a is 1.0 μm
A magnetic recording medium characterized by comprising the above nonmagnetic layer and a magnetic layer containing a ferromagnetic material provided on the nonmagnetic layer.

The present invention will be explained in detail below.

The magnetic recording medium of the present invention basically consists of a nonmagnetic support, a nonmagnetic layer provided thereon, and a magnetic layer further provided thereon.

Non-magnetic supports include polyethylene terephthalate, cellulose triacetate, polyethylene naphthalate, polyamide,
It is a film-like material made of high tensile strength plastic such as polyimide. The shape can be any desired shape, such as a tape, sheet, or disk shape.

The non-magnetic layer provided on the above-mentioned non-magnetic support basically consists of a binder, a lubricant, and a curing agent used if desired, and is 5×10” to 5×10” at a temperature of 5°C to 60°C.
The layer has a Young's modulus of 50 X 10' kg/cni. When Young's modulus is smaller than 5×10' kg/cA, both disk durability and tap durability deteriorate. Further, when the Young's modulus is larger than 5×10″kg/−, the durability of the disk deteriorates.

A Young's modulus within this range can be achieved by using a combination of binders described below. Here, the Young's modulus of the nonmagnetic layer can be determined by the following equation.

E= (El Tt +EJ Tz) / (T
l + T) (where, Tl: thickness of the support, Tl: thickness of the nonmagnetic layer, El: Young's modulus of the support, El: Young's modulus of the nonmagnetic layer provided on the support.

The above Young's modulus was determined from the stress when 2% strain was applied in a tensile test.

) As this binder, nitrocellulose, polyvinyl chloride resin, vinyl chloride vinyl acetate copolymer resin, etc. are used. Furthermore, these binders can be used in combination with other binders to improve the smoothness of the nonmagnetic layer. Specific examples include combination resin compositions such as vinyl chloride vinyl acetate copolymer resin-epoxy resin-bolyamide resin, vinyl chloride vinyl acetate copolymer resin-polyurethane-polyisocyanate, and cellulose derivative-polyurethane-polyisocyanate.

The polyurethanes used here include organic dibasic acids such as saturated or unsaturated carboxylic acids such as maleic acid and adipic acid, alicyclic dicarboxylic acids, aromatic dicarboxylic acids such as phthalic acid, and organic dibasic acids such as ethylene glycol and Glycols such as propylene glycol, diethylene glycol, and polyethylene glycol; Polyhydric alcohols such as nitrimethylolpropane hexanetriol, glycerin, and pentaerythritol; Polyhydric phenols such as mihydroquinone and bisphenol A; Polyester polyol synthesized by reaction with two or more arbitrary polyols selected from alcohols or polyhydric phenols; or lactone synthesized from lactones such as ε-caprolactone and T-butyrolactone. Polyester polyurethane resins and polyether polyurethane resins are produced by converting polyols such as polyester polyols (polyether polyols) synthesized from ethylene oxide, propylene oxide, butylene oxide, etc. into urethanes using polyisocyanates as curing agents, which will be described later. These polyurethane resins may have an incyanate group, a hydroxyl group, or a carboxyl group at the end (or may have a mixture thereof, or
These polyurethane resins include “Crisbon 72”
09", "Chrisbon 6119", 'Vandex T
-FM-1” (manufactured by Dainippon Ink Manufacturing), N
There are commercially available products such as -2304 "N-2301" (manufactured by Nippon Polyurethane) and "D-2100" (manufactured by Sumitomo Bayer Urethane).

Cellulose derivatives include nitrocellulose, cellulose acetate butyrate, and cellulose propionate. These cellulose derivatives have an average degree of polymerization of 50 to 800.
, preferably 80 to 500. If a cellulose derivative with a large amount of residual hydroxyl groups is used, the abrasion resistance of the formed nonmagnetic layer will decrease, which is undesirable.On the other hand, if a cellulose derivative with a small amount of hydroxyl groups is used, the dispersibility and abrasion resistance of the formed nonmagnetic layer will gradually decrease. Moreover, manufacturing costs also increase.

Therefore, the residual hydroxyl group of the cellulose derivative is 7.5 to 40.
It is preferable to use %.

The above-mentioned polyisocyanate as a curing agent has −
These include di-, tri-, and tetraisocyanates selected from aliphatic, aromatic, or alicyclic compounds having two or more N=C=O groups. These isocyanates include ethane diisocyanate, butane diisocyanate,
Hexane diisocyanate, 2,2-dimethylpenkune diisocyanate, 2,2,4-)dimethylpenkune diisocyanate, decane diisocyanate, ω, ω゛-diisocyanate)-1,3-dimethylpenzole, ω
, ω1-diisocyanate 1,2-dimethylcyclohexane, ω,ω'-diisocyanate 1.4-diethylpenzole, ω,ω1-diisocyanate 1.5-
Dimethylnaphthalene, ω, ω1-diisocyanate n
-Propylbiphenyl, 1,3-phenylene diisocyanate, 1-methylbenzo-2,4-diisocyanate, 1,3-dimethylbenzo-2,6-diisocyanate, naphthalene-1,4-diisocyanate, 1
2.2 ″
-dimethyldiphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxydiphenylmethane-4,4
'-diisocyanate, 4,4''-jethoxydiphenylmethane-4,4'-diisocyanate, 1-methylbenzo-2.4,6-triisocyanate, 1,3.
5-) Dimethylbenzo-2,4,6-dolyisocyanate, diphenylmethane-2,4,4'-1-diisocyanate, triphenylmethane-4,4',4'
-triisocyanate, tolylene diisocyanate, 1
．． Dimers or trimers of these isocyanates, such as 5-naphthylene diisocyanate, or addition products of these isocyanates and divalent or trivalent polyalcohols. These are, for example, addition products of trimethylpropane and tolylene diisocyanate or hexamethylene diisocyanate.

These curing agents are used in an amount of 10 to 100 parts by weight of the binder.
It is used in an amount within the range of 60 parts by weight.

In addition, lubricants include fatty acids, metal soaps, fatty acid amides, higher aliphatic alcohols, aliphatic alcohols and fatty acids,
Mercapto group-substituted fatty acids, esters with various acids such as phosphoric acid, phosphoric acid, titanic acid, silicic acid, and fluorine-substituted products thereof, paraffins, silicone oils, animal and vegetable oils, mineral oils,
Higher aliphatic amine; Inorganic fine powder such as graphite, silica, molybdenum disulfide, tungsten disulfide; Fine powder of resin such as polyethylene, polypropylene, polyene vinyl chloride, ethylene-vinyl chloride copolymer, polytetrafluoroethylene; α -Olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature, fluorocarbons, etc. Among these, particularly preferred are fatty acids, metal salts (metal soaps) of fatty acids, fatty acid amides, esters of aliphatic alcohols with various acids such as fatty acids, phosphoric acid, titanic acid, silicic acid, and fluorine-substituted products thereof. It is.

The concentration of the lubricant is 1 to 80% by weight, preferably 3% by weight, based on the binder in the nonmagnetic layer and the magnetic layer.
~55% by weight. If it is less than 1% by weight, no effect on durability is observed, and if it is 81% by weight or more, durability is degraded due to plasticization of the binder caused by the lubricant.

In addition to a lubricant, the nonmagnetic layer may contain an abrasive such as carbon black, alumina, chromium oxide, tungsten carbide, garnet, etc., if desired. Furthermore, plasticizers such as tricresyl phosphate and dibutyl phthalate, dispersants such as lecithin, Tenguchi, and Xerex, and stabilizers such as lead stearate and calcium stearate can also be added.

The thickness of the nonmagnetic layer of the present invention is 1.0 μm or more. This thickness is necessary to reduce the impact received by contact with a magnetic head due to the thinness of the magnetic layer.

A magnetic layer is provided on the non-magnetic layer whose components have been explained in detail above. The magnetic layer basically consists of ferromagnetic powder and a binder that binds it together, and if desired, lubricants, carbon black, and abrasives are added, and depending on the purpose, plasticizers, dispersants, stabilizers, etc. is added.

This ferromagnetic material is γ-Fe2O3, Fe20s
, FeOx (1,33<x<1.5), Fe metal fine powder, CrOx, etc., especially Co-containing -Fe
zo3, CO-containing FeOx (1,33<x<1.5
) is preferred. These ferromagnetic materials are approximately 0.1 to 1
It is a powder with a particle size of approximately μm.

The binder that contains and binds this ferromagnetic powder, as well as other lubricants, abrasives, plasticizers, dispersants, stabilizers, etc. that are added depending on the situation, have already been explained as components for the "non-magnetic layer." The same one used is used. When actually constructing the nonmagnetic layer and the magnetic layer, the corresponding components may be the same or different. Further, the composition ratio of each component can be determined by conventional techniques already known in the art, and for special purposes, the composition ratio can be adjusted by selecting the components as appropriate.

To manufacture the magnetic recording medium of the present invention using each of the above-mentioned components, a coating solution having the above-mentioned composition is prepared, and each of these is sequentially coated onto a support and dried to form a non-magnetic layer and a magnetic layer. It causes the formation of In the coating solution for forming the nonmagnetic layer and the magnetic layer, each component is dissolved or uniformly dispersed in an organic solvent so that when coated on a support, all parts have a uniform composition.

Organic solvents include alcoholic solvents such as methanol, ethanol, isopropyl alcohol, butanol,
Examples include ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone, and cyclohexanone, and mixed solvents obtained by mixing these in appropriate ratios. These organic solvents are selected so as to be able to completely dissolve the components to be dissolved, and in the case of a mixed solvent, the selection of the solvent and the respective quantitative ratios are determined as appropriate. Furthermore, these solvents must not deteriorate the properties of the ferromagnetic powder used as a component.

To dissolve components in a solvent, it is usually best to use a ball mill or dissolving equipment equipped with stirring blades.

After coating, conventional drying equipment and drying equipment may be used to dry the coated layer.

〔Example〕

The present invention will be described in more detail below based on examples thereof. Note that the measurement results of the samples in each example are summarized and explained at the end. In addition, all "parts" in the examples are "
"parts by weight".

Example 1 Surface roughness Ra 0.025 μm, thickness 7 as a support
Coating solution ■ prepared as below was applied to both sides of a 5 μm polyethylene terephthalate film to a thickness of 1.8 μm.
A non-magnetic layer with a thickness of 0.6 μm was formed on the non-magnetic layer, and a coating liquid ① prepared in the same manner was further applied thereon to form a magnetic layer with a thickness of 0.6 μm.

■ Preparation composition of coating liquid for forming non-magnetic layer Nitrocellulose −−−−−−−−−−−−−−−−
-----------12 parts polyurethane "Crisbon 611"
9J (manufactured by Dainippon Ink Manufacturing Co., Ltd.> −−−−−−−−・−3
Partly conductive carbon black (average particle size = 30 μm)
−・・−・ 3-part butyl stearate・−−−−−−
−−−−−−−−−−−−−0.5 parts oleic acid・−
−1−−〜−−−−−−−−−−−−−−−1−−〜−
−−−−−・0.1 part myristic acid modified silicon・−
−−−−−−−−1・−0,2 parts Solvent (Mixed solvent mixture ratio of methyl ethyl ketone/toluene/methyl isobutyl ketone = 2:2:1) Put the various components of the above composition into a ball mill, and mix thoroughly to reduce the viscosity. A paint with 10 voids (25°C) was prepared, in which polyisocyanate "coronate" (Japan Polyurethane @ i!)
------ 4 parts were added and thoroughly mixed to obtain a coating liquid for forming a non-magnetic layer.

■ Preparation composition of coating solution for magnetic layer formation Co-added FeOx powder (x=1.4, average particle size -0.3 μm X Q, Q3 μm・-100 parts Vinyl chloride vinyl acetate copolymer Carbide M
) −−−−−−−−−−・−−−−・−−m=−−
~-・-13 parts polyurethane rN-2304J (Japanese polyurethane side layer) ---1-----
4 parts Cr z O3
−−−−−−−−=−−−5 parts carbon black “Asahi #
80'' (Made by Asahi Carbon ■) −1～−−−−−−−−・・−−
-------5 parts Butyl stearate---m=
−−−−・・−1−−−・−2,0 parts oleic acid−=−
・−−−−−−−−−−−−−−−・・−−
--- 1.0 part myristic acid modified silicon ---
-1.5 parts TG agent (methyl ethyl ketone/toluene/methyl isobutyl ketone mixed solvent mixture ratio = 2:2:1) Place the ingredients of the above composition in a ball mill, stir thoroughly, and disperse uniformly. , here polyisocyanate "Urekoat B Mylar #1 Clear" (East Japan paint side layer>
-7 parts of -------.- were added and thoroughly mixed to obtain a coating solution for forming a magnetic layer.

After smoothing the magnetic layer surface of the coated object as described above using a calendar (surface polishing machine),
．． It was processed into a 25-inch disk-shaped "flexible disk" and Sample No. 1 was prepared.

Example 2 The amount ratio of polyisocyanate in the coating liquid composition for forming a non-magnetic layer in Example 1 was set at 6 parts, and the ratio of the polyisocyanate in the coating liquid for forming a magnetic layer in the composition in Example 1 was changed to 6 parts.
Example 1 was repeated except that the amount of polyisocyanate was changed to 2 parts, and Sample 2 of a "flexible disk" was prepared in the same manner.

Comparative Example 1 The ratios of nitrocellulose, polyurethane, and polyisocyanate in the coating liquid composition for forming a nonmagnetic layer in Example 1 were changed to 4 parts, 8 parts, and 2 parts, respectively, and the rest was the same as in Example 1. "Flexible disk" sample 3 was prepared in the same manner.

Comparative Example 2 The f ratio of nitrocellulose and polyurethane in the coating liquid composition for forming a non-magnetic layer in Example 1 was changed to 4 parts and 6 parts respectively, and the rest was the same as in Example 1 except for polyisocyanate. A "flexible disk" sample rlk14 was prepared using the following procedure.

Comparative Example 3 The ratios of nitrocellulose, polyurethane, and polyisocyanate in the coating liquid composition for forming a non-magnetic layer in Example 1 were changed to 10 parts, 2 parts, and 12 parts, respectively, and the rest were as in Example 1.
``Flexible disk''
Sample number 5 was created.

Comparative Example 4 The amount ratio of nitrocellulose and polyisocyanate in the coating liquid composition for forming a non-magnetic layer in Example 1 was 10 parts each,
Example 1 except for the polyurethane.
In the case of "Flexible disk"
Sample N [L6 was created.

When the characteristics of each of sample fish 1 to sample NIIL6 prepared as described above were measured, the results shown in Table 1 were obtained.

As is clear from the measurement results shown in Table 1, sample IVhl and sample lI&12, which are examples according to the present invention.
It can be seen that both the disc durability and the tap durability are sufficient for both samples.

However, the Young's modulus of the nonmagnetic layer of Sample IVkL3 and Sample 4 was less than 5X10 Kg/csA, and both the disk durability and tap durability were significantly reduced. Each sample of 1kL6 had a Young's modulus of the nonmagnetic layer of 50×10 Kg/crA or more, and both disk durability and tap durability were also significantly inferior.

〔Effect of the invention〕

As is clear from the above explanation, the magnetic recording medium according to the present invention has a thinner magnetic layer than the conventional one and has excellent running durability, so it can be used as a magnetic recording medium especially for high-density recording. Kiwa and 2 others・5 go 7

Claims (1)

[Claims] A lubricant is contained on a non-magnetic support, and the Young's modulus at 5°C to 60°C is 5 x 10^4 to 50 x 10^4 kg/c.
A magnetic recording medium comprising a nonmagnetic layer having a thickness of 1.0 μm or more and a magnetic layer containing a ferromagnetic material provided on the nonmagnetic layer.