JPS61104327A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which has excellent running stability and S/N ratio, obviates powder dislodgment and has excellent durability by allowing melamine resin powder except benzoguanamine to exist on the surface of the magnetic recording medium to slide with a video deck. CONSTITUTION:The melamine resin powder without contg. the benzoguanamine resin is dispersed into the magnetic layer and back coat (BC) layer of the magnetic recording medium to provide adequate ruggedness by the resin powder to the sliding surface with the magnetic head, guide roll, etc. of the video deck. The resin powder has the high bonding power between the magnetic layer and the binder of the back coat layer, has excellent dispersibility into the binder and eliminates the cause for staining the video deck as result of powder dislodgment or the generation of drop-out during reproduction of an image. The magnetic recording medium which has excellent running property wear resistance and durability and is suitable for high-density recording is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a magnetic recording medium, and particularly to a magnetic layer provided on a support and other structures. The present invention relates to a magnetic recording medium comprising a vJ layer with improved surface properties.

(Prior Art) Magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks are widely used in audio meters, video fields, and convenience stores.
It is widely used in the data field. Of these, for example, in the case of magnetic tape in the video field, when a magnetic tape is stored in a cassette and images are recorded or played back, the cassette is attached to the video deck, and the tape is inserted into the guide ball or It travels guided by guide rollers and is slid and scanned by a magnetic head.

In order to record images on magnetic tape or reproduce them in this way, in order to improve the sensitivity, especially the output in the high frequency range, it is necessary to prevent the sliding condition of the magnetic tape against the magnetic head from changing. The surface of the magnetic layer is finished smooth. This magnetic layer is designed to improve running performance and durability with respect to magnetic headers, guide rollers, etc.

However, when this magnetic tape is run on a video deck, not only the front side of the magnetic tape but also the back side is rubbed by the guide balls and guide rolls, so the magnetic layer on the front side is rubbed against the guide balls and guide rolls. Even if the magnetic tape has good running properties and durability, if the running properties and durability of the scratched part on the back side of the magnetic tape are not good, excessive tension will be applied to the running magnetic tape, and this will cause the magnetic layer to move against the magnetic head. This will not only cause damage to the magnetic layer and peeling off of the magnetic powder in the magnetic layer, but also cause the tension on which the magnetic tape is wound to fluctuate, causing the winding ball to fluctuate. , the winding becomes untidy and the edges of the tape become uneven, resulting in uneven running of the tape when it is reused. When these things happen,
Images such as skinny, jitter, and chroma S/N or electromagnetic characteristics deteriorate. Therefore, improvements have been made to the surface properties of the layer on the magnetic tape support.

As mentioned above, the constituent layers of the magnetic recording medium are designed to improve running performance and durability against guide balls, guide rolls, guide pins, magnetic heads, etc. Among these innovations, inorganic Some resin layers contain powder as a filler. This is a method in which the surface of the back coat layer is made rough to reduce the contact area with guide balls etc. and reduce the coefficient of friction.
No. 1135, No. 57-53825, No. 58-2415
No. 50-3927 all show examples using inorganic powders, and many of these also show those with limited particle sizes. However, even those using these inorganic powders not only do not provide sufficient slipperiness, but also cause the back coat layer to come into contact with guide pins, etc., as with the alumina particles described in Japanese Patent Publication No. 50-3927. Sometimes, I shaved off this pin etc.
Not only may the function of the guide pin that guides the magnetic tape smoothly be impaired, but when the back coat layer containing these is rubbed, the bonding force of the particles to the binder to resist this is insufficient and powder falls off. Also, when the magnetic layer and back coat layer come into contact with each other when the magnetic tape is wound 7, the convex parts of the back coat layer may damage the magnetic layer, and the concave and convex portions may be transferred to the magnetic layer, causing damage to the magnetic layer. When the image is scanned and reproduced, electromagnetic characteristics such as chroma S/N, which indicates the degree of color noise in the image, may be impaired.

One of these reasons is that inorganic powders generally not only have a wide variety of particle shapes and are not constant, but also have a wide particle size distribution. Generally, when the particle shape is spherical, the particles tend to be arranged regularly, and if these particles are arranged regularly on the surface of the back coat layer, when the back coat layer comes into contact with, for example, a guide ball, these particles will make point contact, reducing the coefficient of friction. can. Furthermore, if the particle size distribution of the particles is narrow, even if the average particle size is the same, particularly large particles will not be mixed in, but this is difficult to expect in the case of inorganic powder. Therefore, when inorganic particles are used, it is desirable to use particles with a relatively large particle size in order to make the surface of the back coat layer slippery. harm the characteristics. From this, for example, the center line average roughness Ra of the surface roughness of the back coat layer at cut off 0.08 m should be set to 0.010 to 0.050 am, and the dynamic friction coefficient μ should be set to 0.10 or more and 0.36 or less. It is difficult to expect that only the inorganic powders described in the above-mentioned publications can improve the runnability and durability of the back coat layer without causing any unevenness to be transferred to the magnetic layer.

In addition, if the inorganic powders described in the above publications are used, they have a relatively low affinity with water, so magnetic recording media used in various atmospheres can be It easily absorbs moisture in the air, and when a magnetic recording medium absorbs moisture in this way, its surface tends to stick to metal guide balls, etc., and when this stickiness occurs, it stops running in a steady state. The magnetic recording medium is temporarily stopped, and the next instant, it is suddenly pulled, which tends to cause so-called stick-slip, making the running unstable. Not only that, but in magnetic layers that use metal powder or thin metal films formed by vapor deposition, water trapped in the back coat layer can cause
These may corrode and cause performance deterioration.

Furthermore, in general, inorganic powders do not have very good dispersibility in binders, and not only do they require a lot of time to achieve sufficient dispersion, but even once they are dispersed, they tend to aggregate again. For example, when a dispersion of these inorganic powders is stored for a long time, the specific gravity of the particles becomes large, and the
~4, so it is easy to settle. In particular, when the average particle diameter of the inorganic powder is 0.2 μm or less, poor dispersion is likely to occur, and even after dispersion, the dispersion stability is lacking. If inorganic powders with poor dispersibility are used with poor dispersion or agglomerated after dispersion, the surface roughness of the back coat layer will not be well controlled.For example, if too large particles are present, In this case, the unevenness on the surface of the back coat layer becomes too large, resulting in problems such as the unevenness being transferred to the magnetic layer and impairing the electromagnetic properties as described above. On the other hand, when the average particle size of the inorganic powder is 0.2μ or more, the dispersion in the paint is good, but since the raw material particles themselves are large, the particles tend to settle, resulting in poor dispersion stability. The surface roughness of the back coat layer becomes too large, and if it is attempted to reduce it, the filling rate of the inorganic powder in the binder must be lowered. If the filling rate of the explosive substance powder is lowered in this way, it may cause so-called interlayer adhesion in which the tapes stick to each other when the tape is wound, impair wear resistance and slipperiness, and tend to cause stake slip. do.

In addition, in general, inorganic powders do not mix well with binder resins, and may separate from the resin and cause powder drop-offs, which may stain video tapes or reproduce images on the magnetic layer corresponding to the areas where the powder falls off. may cause dropouts.

In place of the above-mentioned inorganic filler, attempts have been made to use an organic substance as a filler, which can control particle size and particle hardness/softness. For example, JP-A-59-11242
No. 8 includes a proposal to use Teflon powder, and there are newspaper reports using benzoguanamine resin.

However, Teflon powder has poor compatibility with the binder used in recording media and is not sufficiently dispersed, and benzoguanamine resin powder tends to agglomerate, making it unsatisfactory as a filler for high-density magnetic recording media. .

Conventional organic fillers, which replace the above-mentioned non-attached fillers, are practical for low-V, high-density storage media such as magnetic cards, but they have poor dispersion, agglomeration, and formation for high-density media such as video tapes. It is prone to powder falling and has not yet reached a state of practical use.

In this way, the roughness of the back coat layer, etc., which is the sliding surface with the video disc, is not appropriate, and powder may fall off, making it impossible to obtain sufficient wear resistance and durability. Problems such as powder falling off of the magnetic layer occur, and not only output fluctuations but also electromagnetic conversion characteristics such as the above-mentioned chroma S/N cannot be improved.

In particular, recently, video equipment such as VH8 video tapes and β movies have become smaller and more dense, making them easier to carry. Video recording is now being done under a variety of conditions, and it is hoped that magnetic tape will also be compatible with these conditions. That is, video flA
The miniaturization and high density of U make the magnetic tape path more complicated.
This tape has many opportunities to come into contact with guide balls, guide rolls, and even magnetic hects, and is often rubbed, so it is required to have even better running performance and improved wear resistance and durability to prevent powder falling off. has been done.

(Objective of the Invention) An object of the present invention is to provide a magnetic recording medium which is excellent in running stability, S/N ratio, and excellent in durability and whose performance does not deteriorate even after long-term use.

(Structure of the Invention) An object of the present invention is to provide a magnetic recording medium having at least a magnetic layer as a constituent layer on a support by rubbing melamine-based resin powder other than benzoguanamine-based resin with a magnetic recording medium. This is achieved by a magnetic recording medium characterized in that it exists on a surface.

The melamine resin related to the present invention has a structure shown in the infrared absorption spectrum of Figure 1, in which the vertical axis is the transmittance (%) and the horizontal axis is the wave number (crn-''). It was determined by the permeated potassium bromide tablet method.

The melamine resin can be synthesized from melamine, hydroxymethylmelamine, methylated methylolmelamine, alkoxymethylmelamine, etc. and formaldehyde by a conventional method.

In this case, a known catalyst such as sulfamine can be used as a reaction catalyst, and the reaction is adjusted by adjusting the pH of the reaction system, stirring conditions, addition of a poor solvent, etc. to control the particle size of the resin powder.

Regarding the above synthesis method, please refer to "Polycondensation and Polyaddition" edited by the Editorial Committee of Polymer Experiments, Society of Polymer Science and Technology (published by Kyoritsu Publishing), or "
You can refer to "Plastic Materials Reader" written by Yuji Sakurauchi (published by Kogyo Kenkyukai ■).

Further, it is preferable to use the melamine resin powder with a lubricating component attached or coated thereon. Examples of lubricating components include silicone oil, organic silicon compounds, fatty acid esters, fatty acids, phosphoric esters, boric esters, and organic fluorine compounds. The method of attachment or adhesion may be such that the melamine resin powder is suspended in a solvent containing the lubricant components, stirred, and then dried, or these lubricant components may be added in the final step of synthesizing the resin powder. May be added. Alternatively, esterified hydroxymethylmelamine may be used as a raw material.

Significant ratio of melamine resin to binder in the constituent layers of the magnetic recording medium related to the present invention (melamine resin/
binder) is '/'to in the case of the magnetic layer.

~107, 1/2000~A for back coat layer
With O! 00 A. Ruko1 is preferable. Inorganic powders can also be used in the back coat layer, and these include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, aluminum oxide, and chromium oxide. , silicon carbide, calcium carbide, α
-Fe, 03. Talc, kaolin, calcium sulfate,
Examples include those made of boron nitride, zinc fluoride, molybdenum dioxide, and the like. If an appropriate amount of these inorganic powders is used, the layer strength of the back coat layer will also be increased.

The resins described below are used as the binder for each layer on the support used in the present invention, and among these, mixed resins of urethane resin and vinyl chloride vinyl acetate copolymer resin, mixed resins of urethane resin and phenoxy resin, urethane resin and A mixed resin of resin and nitrocellulose is preferable from the viewpoint of adhesion to the support described later. In particular, vinyl chloride vinyl acetate copolymer resin has better compatibility with urethane resin than other resins, and its mixing ratio can be increased. desirable for this reason. The preferred mixing ratio of the vinyl chloride vinyl acetate copolymer skin oil to the urethane resin is 15% by weight to 75% by weight.

The proportion of each of the above components in the binder is preferably 40% to 50% by weight of the total for the urethane resin, and preferably 50% by weight of the total IO for the curing agent. If the amount of curing agent is too little or too much, the magnetic tape will be prone to stick slip.

Examples of binder resins that can be used in the constituent layers of the medium include thermoplastic resins, thermosetting resins, reactive resins, electron beam curable Vd resins, and mixtures thereof.

The thermoplastic resin used as the binder resin has a softening temperature of 150°C or less and an average molecular weight of 10,000 to 2.
00,000, with a degree of polymerization of about 200 to 2,000, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer,
Methacrylic acid ester-acrylonitrile copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer , polyamide box resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene
Butadiene copolymer, polyester resin, chlorovinyl ether-acrylic acid ester copolymer, Ami7 resin-
1. Various synthetic rubber-based thermoplastic resins and mixtures thereof are used.

The thermosetting resin or reactive resin used has a molecular weight of 200,000 or less in the form of a liquid solution, and is insolubilized by a reaction such as synthesis or addition after coating and drying. 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 resin, alkyd resin, silicone resin, acrylic reaction resin, vinyl chloride-vinyl acetate resin, methacrylate copolymer. and diisocyanate prepolymer mixture, mixture of high molecular weight polyester resin and isocyanate prepolymer, urea formaldehyde resin, mixture of polyester polyol and isocyanate, polycarbonate type polyurethane, polyamide resin, low molecular weight glyfur/polymer ■ diol/triphenylmethane triisocyanate mixtures of polyamine resins, polyamine resins, and mixtures thereof.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
For example, maleic anhydride type, urethane acrylic type, polyester acrylic type, polyether acrylic type, polyurethane acrylic type, polyamide acrylic type, etc., or as a polyfunctional monomer, ether acrylic type, urethane acrylic type, phosphate ester acrylic type, aryl type , hydrocarbon type, etc.

In order to improve the structure of the magnetic recording medium according to the present invention and the durability of the layers, various curing agents can be contained in the constituent layers, such as incyanate.

Aromatic isocyanates that can be used are, for example, tolylene diisocyanate (TDI), 4,41-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), metaxylylene diisocyanate (
MIDI) and adducts of these incyanates and active hydrogen compounds, and have an average molecular weight of 100 to
A range of 3,000 is preferred.

On the other hand, examples of aliphatic incyanates include hexamethylene diisocyanate (IHMDI), lysine isocyanate, and trimethylhexamethylene diisocyanate (T
MDI) and adducts of these incyanates and active hydrogen compounds.

Among these aliphatic isocyanates and adducts of insearford and active hydrogen compounds, those having a molecular weight in the range of 100 to 3,000 are preferred.

Among the aliphatic isocyanates, non-alicyclic incyanates and adducts of these compounds with active hydrogen compounds are preferred.

Examples of the adduct of the above-mentioned isocyanate and a zero-active water compound include an adduct of a diisocyanate and a trivalent polyol. Polyisocyanates can also be used as curing agents, including, for example, a pentagonal diisocyanate, a decarboxylation compound of 3 moles of diisocyanate and water, and the like. Examples of these include an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane, an adduct of 3 moles of metaxylylene diisocyanate and 1 mole of trimethylolpropane, a 5f# derivative of tolylene diisocyanate,
There is a type 5 form consisting of 3 moles of tolylene diisocyanate and 2 moles of hexamethylene diisocyanate.

In addition to the above, it is also preferable to use a lubricant in the constituent layer of the present invention, and for example, an ester of m alcohol with carbon W of 1.13 to 16 and stearic acid is preferable. In addition to these, fatty acid esters used in the magnetic layer, which will be described later, can be used. In addition, the below-mentioned famous dispersants and antistatic agents can be used in the constituent layers of the present invention.

The magnetic layer of the magnetic recording medium of the present invention may be a coated magnetic layer using magnetic powder, a binder, a dispersion, a lubricant, etc., or may be formed by a vapor deposition method, a sputtering method, a paper deposition method, etc. It may also be a thin film type magnetic layer formed by.

Examples of the magnetic material for the magnetic layer include γ-Fe, 03°C
O-containing r -Fe2O3, Co-coated γ-Fe2031F
e, 04. Co-containing Fe50. , Co-coated Fe5
0. , oxide magnetic materials such as CrO2, e.g. Fe,
Ni, Co, Fe-Ni alloy, Fe-Co alloy, Fe-N1-P alloy, Fe-Ni-Co alloy, Fe-
Mn-Zn alloy, Fe-Ni-Zn alloy, Fe-Co-
Ni-Cr alloy, pe-Co-Ni-P alloy.

Co-Ni alloy, Co-P alloy, Co-Cr alloy, etc.Fe
.

Examples include various ferromagnetic materials such as metal magnetic powder containing Ni and Co as main components. Additives to these metal magnetic materials include Si, Cu, Zn, and AI! , P, M
n.

Elements such as Cr or compounds thereof may be included. Also, macrogonal ferrite such as barium ferrite,
Iron nitride is also used.

The paint forming the magnetic layer may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like, if necessary.

For example, dispersants include lecithin; caprylic intoxicant;
Fatty acids with 8 to 18 carbon atoms (R-
R represented by COOH is a saturated or unsaturated alkyl group having 7 to 17 carbon atoms); an alkali metal of the above fatty acid (Li);

(Na, etc.) or alkaline earth metals (Mg, Ca, etc.).

Examples include metal soaps made of Ba, etc.). In addition, higher alcohols having 12 or more carbon atoms, sulfuric esters, and the like can also be used. Moreover, commercially available general surfactants can also be used.

These dispersants may be used alone or in combination of two or more. When these dispersants are used in the magnetic layer, 1. ~
When used in the above-mentioned back coat layer, it is added in an amount of 2 to 20 parts by weight per 100 parts by weight of the binder.
It may be added in parts by weight.

In addition, as lubricants, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, fatty acid esters consisting of monobasic fatty acids with 12 to 16 carbon atoms and monohydric alcohols with 3 to 12 carbon atoms, carbon atoms A fatty acid ester or the like consisting of a monobasic fatty acid having 17 or more monobasic fatty acids and a monohydric alcohol having 21 to 23 carbon atoms in total is used. These lubricants are added in an amount of λ to 20 parts by weight per 100 parts by weight of the binder.

An abrasive can also be used in the magnetic layer, and commonly used materials include fused alumina, silicon carbide,
Chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, emery C (main ingredients are corundum and magnetite), titanium dioxide, etc. are used.

These abrasives have an average particle diameter of 0.05 to 5 .mu.m, particularly preferably 0.1 to 2 .mu.m. These abrasives are used in an amount of 1 part by weight per 100 parts by weight of magnetic powder.
It is added in a range of 20 to 20 parts.

In addition to carbon black, antistatic agents include
Conductive powders such as graphite, tin oxide-antimony oxide compounds, titanium diluted, tin diluted antimony oxide compounds, carbon black graft polymer; natural surfactants such as saponin; alkylene oxide type, glycerin type, glycidol type, etc. 7-ion surfactant;
Cationic surfactants such as pyridine and other heterocycles, sulfonium or sulfonium; anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate ester groups, phosphoric ester groups; amino acids, aminosulfones Examples include acids, amphoteric activators such as sulfuric acid or phosphoric acid esters of aminoalfur, and the like.

These surfactants may be added alone or in combination. These are used as antistatic agents, but may also be used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

Solvents to be added to the above paint or diluting solvents when applying this paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propyl, and butanol; methyl acetate. , esters such as ethyl acetate, butyl acetate, ethyl lactate, and ethylene glycol monoacetate; ethers such as glyfur dimethyl needle, glycol monoethyl ether, dioxane, and tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene, and xylene; Halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and dichlorobenzene can be used.

In addition, examples of the support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarbonate. , Cu, Al, Zn, and other metals, glass, BN, Si carbide, porcelain, ceramics, and other ceramics can also be used.

The thickness of these supports is about 3 to 100 μm in the case of a film or sheet, preferably 5 to 50 μm,
In the case of a disk or card shape, the thickness is about (9) to 10 μm, and in the case of a drum shape, it is used in a cylindrical shape, and the shape is determined depending on the recorder used.

An intermediate layer for improving adhesion may be provided between the support and the constituent layers in contact with the support.

Coating methods for forming the above-mentioned constituent layers on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll foot, gravure coating, kiss coating, cast coating, Spray coat etc. can be used.

(Example) Next, the present invention will be specifically explained with reference to Examples.

Example 1 Magnetic layer paint and back coat layer (BC
After dispersing the composition components of the paint (represented as layers), 1μ of each
5 parts by weight of polyfunctional isocyanate was added to the magnetic layer paint, 20 parts by weight was added to the BC layer paint, the magnetic layer was 51 tm, and the BC layer was 0.5 am.
The test samples were coated to a thickness of 100%, applied with a spark calender, and scraped to a width of % inch, and the sample numbers of Examples and Comparative Examples shown in Table 1 were assigned to prepare test samples.

In addition, Examples 1, 2.3 and Comparative Examples 1, 2, and 3゜6 were B
Without C layer, Examples 4, 5, 6.7 and Comparative Example 4,
No. 5.7 has the magnetic layer of Comparative Example 1 as a magnetic layer, and has the composition components listed in Table-1.

Table 2 shows the results of determining the characteristics of the sample using conventional measuring methods.

As is clear from Table 2, the samples of the present invention show good results.

4. Brief explanation of the drawings Figure 1 shows the infrared absorption spectrum of the melamine resin according to the present invention.

Claims (1)

[Claims] A magnetic recording medium having at least a magnetic layer as a constituent layer on a support, characterized in that melamine-based resin powder other than benzoguanamine-based resin powder is present on the surface of the magnetic recording medium that rubs against a video deck. recoding media.