JPH01224920A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain stable traveling durability under wide temp. conditions by incorporating a specific modified silicone compd. into or on a magnetic recording layer. CONSTITUTION:The amine-modified silicone oil expressed by the formula I is used at preferably 0.3-5.0pts.wt. per 100pts.wt. magnetic material in the case of adding said agent into the magnetic layer and at 2-50mg/m<2> in the case of top coating the same on the surface thereof. The amt. of the silicone in the surface increases too much and such leads to a trouble such as sticking when the amt. of the lubricating agent to be used exceeds the above-mentioned range. The amt. in the surface is of course insufficient and the lubricating agent is not effectual if the amt. of said agent to be used is under the above- mentioned range. The excellent traveling property and durability in a high-temp. environment and the traveling property and durability after high-temp. preservation of high-temp. high-humidity preservation are thereby obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium provided with a magnetic layer formed by dispersing ferromagnetic powder in a binder on a non-magnetic support, and particularly relates to a magnetic recording medium provided with a magnetic layer formed by dispersing ferromagnetic powder in a binder on a non-magnetic support. The present invention relates to a magnetic recording medium that has excellent running performance and durability even when used under these conditions.

[Prior art and problems]

In general, magnetic recording media are made by coating a substrate such as a polyester film with a magnetic paint consisting of magnetic powder, a binder, an organic solvent, and other necessary components. , the magnetic layer is required to have a small coefficient of friction and excellent running stability.

Therefore, as a way to improve the lubricity and wear resistance of the magnetic layer, various lubricants have been incorporated into the magnetic layer. For example, silicone oil, which has a large lubricating effect, has been included in the magnetic layer. (See US Pat. No. 2,654,6814).

After that, chemically modified silicone oil was added in order to further improve the properties and to improve the compatibility with binders, which is a disadvantage of silicone oil (Japanese Patent Application Laid-Open No. 47-2852, Kaisho 52-70811,
(Refer to Japanese Patent Application Laid-Open No. 52-108804).

However, in recent years, as recording and reproducing apparatuses have become smaller and thinner, magnetic recording media have been used in a wider range of environments, including high and high temperatures. For this reason, magnetic recording media are now required to have stable running durability over a wide range of temperature conditions.

[Means for solving problems]

The inventors of the present invention have conducted intensive studies on lubricants that solve the above-mentioned problems with magnetic powder-coated magnetic recording media. By using an amine-modified silicone oil represented by the general formula below, we have discovered that conventional lubricants can We have discovered that it is possible to obtain excellent running performance and durability in high-temperature environments, and running properties and durability after high-temperature storage or high-temperature storage, which were previously unachievable, and have led to the creation of the present invention.

I CH, R'NHR"NHl where m = an integer from 10 to 650 n = an integer from 1 to 170 and m/4 or less R: CH3 or 0CRs R": divalent hydrocarbon group with a carbon number of 1 to 1O R″: divalent hydrocarbon group having 1 to 10 carbon atoms Particularly in the present invention, the above-mentioned modified silicone compound is represented by the following general formula: I C1ls C1l□CHgCH2NHCl1□C
H2NI+! However, m, n, and R are the same as in item (1).It is preferable that the amine equivalent of the modified silicone is 5,000 or more, and that the kinematic viscosity of the modified silicone at 25°C is 30 cs or more and 200 cs or less.

The present invention will be explained in detail below.

As mentioned above, the modified silicone compound used in the present invention has R'NHR'Nlh (where Ro, R
” are divalent hydrocarbon groups having 1 to 10 carbon atoms, which may be the same or different from each other) are bonded together. Preferred specific examples include -CH*C
It is a modified silicone compound in which an N-(aminoalkyl)aminoalkyl group is bonded, such as HgCH2N)ICHzCHJHt.

Specific compounds include the following.

I Cl1* CIhCH2NHCHzCIINL
■ CH.

I Cl3 CH2CII□CHzC1hNIIC
HzCHzCHJHt Commercially available products include Shin-Etsu Chemical's KF-393, KF-857, and F-
859, KF860, KF861, etc.

There is no particular restriction on the molecular weight of the amine-modified silicone oil used in the present invention, but a molecular weight of 1,000 or more and 50,000 or less is generally used. Preferably it is 2000 or more and 30000 or less.

The upper silicone oil has a molecular weight per amine of 300 or more and 30,000 or less, preferably 5,000 or more and 30,000 or less, more preferably 10,000 or more and 30,000 or less.

In the above formula, when m is less than 10, the coefficient of friction increases, and when it exceeds 650, stick-slip tends to occur because the viscosity is too high. Moreover, if n is outside the limited range, the solubility in the binder will be too high and the binder will be made homogeneous, which will adversely affect the durability.

If the amine equivalent is equal to or exceeds the molecular weight (average molecular weight), it cannot be said that all polysiloxane molecules contain amines (i.e., a mixture of modified silicone and unmodified polydimethylsiloxane), but even in this case, There is no problem with the effect.

When added internally to the magnetic layer, the amount used is preferably 0.1 to 10.0 parts by weight, more preferably 0.3 to 5.0 parts by weight, per 100 parts by weight of the magnetic material.

When topcoating the surface of the magnetic recording layer, 2 to 50cm
/M is appropriate.

If the amount used exceeds this range, the amount of surface silicone will be excessive and may cause problems such as sticking.

If the amount used is below this range, the surface amount will be insufficient and no effect will be obtained.

In the present invention, a general lubricant may be mixed with the silicone oil.

Lubricants that can be used in combination include saturated and unsaturated fatty acids (myristic acid, stearic acid, oleic acid, etc.), metal soaps,
Fatty acid amides, fatty acid esters (including various monoesters, fatty acid esters of polyvalent esters such as sorbitan and glycerin, esters of polybasic acids, etc.), higher aliphatic alcohols, monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates, Paraffins, silicone oils, animal and vegetable oils that do not fall under the scope of the present invention,
Mineral oil, higher aliphatic amine; Inorganic fine powder such as graphite, silica, molybdenum disulfide, tungsten disulfide; Fine resin powder such as polyethylene, polypropylene, polyvinyl chloride, ethylene-vinyl chloride copolymer, polytetrafluoroethylene; α-olefin polymer; examples include unsaturated aliphatic hydrocarbons and fluorocarbons that are liquid at room temperature.

The preferred amount of these mixed lubricants varies depending on the usage, but in general, one of the silicone compounds of the present invention is used.
The usage amount is 710 to 2 times.

In the present invention, methods for making the amine-modified silicone oil present in the magnetic layer include a method in which it is included in the magnetic layer I, and a method in which the surface is coated with a top coat (dissolving the material in an organic solvent and coating or spraying it on the substrate, followed by drying). There are methods such as melting the material and applying it to the substrate, and immersing the substrate in a solution of the material dissolved in an organic solvent to adsorb the material to the substrate surface.

In the case of magnetic powder-coated magnetic recording media, there is no particular restriction on the ferromagnetic powder used.0 Ferromagnetic alloy powder, 7 Fe1O
s+ Fe50. , Co-modified iron oxide, loose barium ferrite of CoO*+iron nitride, and modified strontium ferrite.

Although there are no particular restrictions on the shape of the ferromagnetic powder, needle-shaped, granular, dice-shaped, rice-grain-shaped, and plate-shaped powders are usually used. The crystal size of this ferromagnetic powder is preferably 500 Å or less in terms of electromagnetic conversion characteristics.

The binder forming the magnetic layer can be selected from conventional binders. Examples of binders include vinyl chloride/vinyl acetate copolymers, vinyl chloride, copolymers of vinyl acetate and vinyl alcohol, maleic acid and/or acrylic acid,
Vinyl chloride/vinylidene chloride copolymer, vinyl chloride/acrylonitrile copolymer, ethylene/vinyl acetate copolymer, cellulose derivatives such as nitrocellulose resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin, Examples include polyurethane resin, polycarbonate polyurethane resin, and the like. In order to further improve dispersibility and durability, polar groups (epoxy groups, Co
te, OH, NH+502M, O5OffM, P
O3Mz, OPO3Mt (where M is hydrogen, an alkali metal, or ammonium, and when there is a plurality of M's in one group, they may be different from each other) are preferred. The preferred content of polar groups is 10-' to 10-4 equivalents per gram of polymer.

The polymer binders listed above may be used alone or in combination. In addition, curing treatment may be performed by adding a known isocyanate-based crosslinking agent, but the combination of a silicone compound with active hydrogen and an isocyanate-based crosslinking agent, such as the compound of the present invention, may cause a decrease in lubricity, etc. It is easy to cause irritation and is not desirable.

The present invention is also applicable to a binder system that uses an acrylic acid ester oligomer and a monomer as a binder and is cured by radiation irradiation.

As the material of the nonmagnetic support, polyesters such as polyethylene terephthalate and polyethylene 2,6 naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacerate; resins such as polycarbonate, polyimide, and polyamideimide are used. If necessary, it may be metallized with a metal such as aluminum.

The thickness of the support plate is preferably 3 to 100μ, preferably 3 to 20μ for magnetic tape, and 20 to 200μ for magnetic disk.
μ is the commonly used range.

The total binder content in the magnetic layer of the magnetic recording medium of the present invention is usually 10 to 100 parts by weight per 100 parts by weight of the ferromagnetic powder.
Parts by weight, preferably 15 to 40 parts.

The magnetic layer of the magnetic recording medium of the present invention preferably further contains inorganic particles having a Mohs hardness of 5 or more.

The inorganic particles used are not particularly limited as long as they have a Mohs hardness of 5 or more. Examples of inorganic particles having a Mohs hardness of 5 or more include AhO3 (Mohs hardness 9) and 5TiO (Mohs hardness 6).
, Ti02 (6.5), 5ift (7).

Examples include 5no2 (6.5), Cr2O (9), and α-FezO3 (5.5), and these can be used alone or in combination.

Particularly preferred are inorganic particles having a Mohs hardness of 8 or more. When using inorganic particles with a Mohs hardness lower than 5, the inorganic particles tend to fall off from the magnetic layer (and since they have almost no abrasive action on the head, they tend to clog the head, and the running durability deteriorates. become scarce.

The content of the inorganic particles is usually in the range of 0.1 to 20 parts by weight, preferably in the range of 1 to 10 parts by weight, based on 100 parts by weight of the ferromagnetic powder.

In addition to the above-mentioned inorganic particles, the magnetic layer preferably contains carbon black (particularly one having an average particle size of 10 to 300 nm (nanometers; 10-'m)).

Next, an example of a method for manufacturing the magnetic recording medium of the present invention will be described.

First, a magnetic coating material is prepared by kneading ferromagnetic powder, a binder, the above-mentioned modified silicone compound, and, if necessary, other fillers, additives, etc. with a solvent.

As the solvent used during kneading, solvents commonly used for preparing magnetic paints can be used.

There is no particular restriction on the kneading method, and the order of addition of each component can be set as appropriate.

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, lubricants, etc. can also be used.

Examples of dispersants include fatty acids having 12 to 22 carbon atoms, salts or esters thereof, compounds in which part or all of the hydrogen atoms of these compounds are replaced with fluorine atoms, amides of the above fatty acids, aliphatic amines, and higher alcohols. , polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl borates, sarcosinates, alkyl ether esters, trialkyl polyolefins, oxyquaternary ammonium salts, and lecithin.

When using a dispersant, the ferromagnetic powder 1 usually used is
It is used in a range of 0.1 to 10 parts by weight per 00 parts by weight.

Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymers; natural surfactants such as saponin; nonionic surfactants such as alwylene oxide, glycerin, and glycidol; Cationic surfactants such as alkylamines, quaternary ammonium salts, pyridine and other multi-ring compound salts, phosphoniums or sulfoniums;
Anionic surfactants containing acidic groups such as carboxylic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; Ampholytic surfactants such as amino acids, aminosulfonsanes, and sulfuric or phosphoric esters of amino alcohols. Can be done. When using the above conductive fine powder as an antistatic agent, for example, 0.1 to 100 parts by weight of ferromagnetic powder is used.
It is used in the range of IO parts by weight, and when a surfactant is used, it is also used in the range of 0.12 to 10 parts by weight.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly limited to having only the above-mentioned effects; for example, if the dispersant is a lubricant, Alternatively, it may act as an antistatic agent. Therefore, it goes without saying that the effects of the compounds exemplified by the above classifications are not limited to those listed in the above classifications, and when using a substance that has multiple effects, the amount added should be It is preferable to decide in consideration of the action and effect.

The magnetic paint thus prepared is coated onto the non-magnetic support described above. Coating can be performed directly onto the non-magnetic support, but it can also be applied onto the non-magnetic support via an intermediate layer such as an adhesive layer.

The intermediate layer herein refers to a layer of adhesive alone or a composite film layer formed by dispersing non-magnetic fine particles such as carbon in a binder.

The carbon-containing intermediate layer can be arbitrarily selected as a binder from among various binders used in magnetic layers. The particle size of carbon is preferably 5 to 50 tIm,
The binder:carbon weight ratio is preferably 100:1 to 100:150. The thickness of the intermediate layer is 0.1 to 24 mm in the case of a simple adhesive layer. In the case of a composite layer containing nonmagnetic powder, the length is preferably 0.5 to 411 m.

In addition, a lubricant that is the same as or different from the lubricant used in the magnetic layer may be added to the intermediate layer.

Details of the method of dispersing the above-mentioned ferromagnetic powder and binder and the method of coating it on a support are described in Japanese Patent Laid-Open Publications No. 54-46011 and No. 54-21805.

The thickness of the magnetic layer thus applied after drying is generally in the range of about 0.5 to 10-1, usually 0.7-10.
It is applied to a range of 6.0-.

When a magnetic recording medium is used in the form of a tape, the magnetic layer coated on the non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. On the other hand, in the case of a disk-shaped medium, non-orientation treatment is performed using a magnetic field in order to eliminate anisotropy in magnetic properties. Thereafter, surface smoothing treatment is performed if necessary.

〔Example〕

Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to these examples. In addition, in the examples, the expression "1 part" indicates "parts by weight."

Examples and Comparative Examples x = 1.43 Carbon black (average particle size 30 m) 1.0 Lauric acid (industrial) 1.5 α-Alias (average particle size 0.3 μ')
1.0 Magnetic material (Co-FeOx) in the above composition
, a binder (salt vinyl acetate polyurethane), carbon black, and a solvent (butyl acetate, a part of MEK) are kneaded in a kneader, and then a diluted product is prepared. .0. , silicone oil, and a solvent were added, stirred at high speed, and finely dispersed using a sand grinder to obtain a dispersion.

Table 1: After filtering the resulting fine dispersion through a filter with an average pore size of 3μ, the film thickness after drying was deposited on a polyester base with a thickness of 7μ (longitudinal heat shrinkage rate: 1.2χ after storage at 110°C for 14 hours). It is coated to a thickness of 5 μm, and while the coating film is not dry, an orientation treatment is performed, and then the main drying is carried out. After the main drying, the tape was mirror-finished, slit to a width of 3.8 mm, and the length of 135 m was stored in an audio compact cassette to obtain audio cassette tapes (Nos. 1 to 18). The properties of the obtained cassette tape are shown in Table 2.

In addition, the evaluation in the table was performed as follows.

<Evaluation method> (1) This is the maximum output level when the tertiary high frequency of the signal of MOL++5 315112 is 3%, and is the relative value when the ps-n manufactured by Fuji Photo Film ■ is set as Oa'i (2) 5OLIIIK Saturation output level of 10KHz signal, relative value when using Fuji Photo Film ■ ps-n as OdI+ (3) After storage at 110°C for 4 hours at 50°C 80% 1i
After recording the signal of 3KHz-104m running inside the entire length, leaving it in a dry thermometer at 110℃ for 4 hours, and then recording it at 50℃8.
15 with 20 commercially available car stereo decks within 0%RH
Reciprocate and evaluate the following characteristics ■ Number of rolls at which running stop occurs when 20 rolls of tape are reciprocated for 15 times ■ Number of rolls at which tape runs out occur when 20 rolls of tape are reciprocated for 15 times ■ Level reduction tape is reciprocated 15 times At the time, the output level of 3KHz is constantly recorded, and the output level of the 1st round trip is the average value of n = 20 rolls of the value of the lowest output during the 15 round trips Table 2 Tape sample No. 1 to 7 are electromagnetic conversion It has good characteristics, and even when running at 50°C and 80% 11lf after storage at 110″C, there is no stoppage or taping, and there is little level drop (preferable).

Tape samples Nos. 8.9 and 12.13 do not have running stops, but tape blanking is observed, and the levels are much lower than in Examples, which is preferable.

Tape samples 10, 11, 14, 15, 16, 17.
No. 18 is unfavorable, as running stops and tape emptying are observed, and the level also decreases a lot.

The above is a case where silicone oil is contained in the magnetic layer, but in the present invention, an amine-modified silicone oil represented by the above general formula may be contained on the surface of the magnetic layer, and examples in this case and comparative examples are shown below.

After producing a magnetic tape base in the same process as described above using the same method as in the above example except that lauric acid and silicone oil were removed, the surface of the magnetic layer was top coated with the lubricant solution shown in Table 3 using a bar coater. Samples 19 to 22 were prepared.

The obtained samples were evaluated in the same manner as described above, and the results shown in Table 4 were obtained.

From these results, it is clear that the magnetic recording medium using the compound of the present invention on the surface of the magnetic layer maintains appropriate electromagnetic conversion characteristics and has excellent runnability and durability under extreme conditions of high temperature and high humidity. It became.

Of course, it has also been confirmed that the properties at room temperature are equivalent to or better than conventional lubricants.

〔Effect of the invention〕

Claims (1)

[Scope of Claims] A magnetic recording medium in which a magnetic recording layer consisting mainly of magnetic powder and a binder is provided on a non-magnetic support, wherein a modification represented by the following general formula is provided in the magnetic recording layer or on the surface of the recording layer. A magnetic recording medium characterized by containing a silicone compound. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, m = an integer from 10 to 650 n = an integer from 1 to 170 and m/4 or less R: CH_2 or OCH_3 R': Divalent carbonization having 1 to 10 carbon atoms Hydrogen group R”: divalent hydrocarbon group having 1 to 10 carbon atoms