JPS60234221A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve surface lubricity of a back coat layer and to obtain a tape, etc. having good running stability without blooming and uneven coating by providing the back coat layer incorporated therein with monoester of dibasic fatty acid. on the rear of a magnetic recording medium. CONSTITUTION:The back coat layer incorporated therein with monoester of dibasic fatty acid aa a lubricating agent is formed on the surface of the base on the opposite side from the magnetic layer by coating the coating liquid prepd. by dissolving the above-described monoester into a soln. of a thermoplastic resin, thermosetting resin, etc. then drying and curing the coating. The lubricating agents such as MoS, graphite and silicone oil may be added together thereto if necessary. The magnetic tape, etc. having a good jitter value and excellent wear resistance and durability are thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a backcoat layer, in which the surface lubricity of the backcoat layer is improved.

BACKGROUND OF THE INVENTION Magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks are widely used in the audio field for recording sound, the video field for recording images, and the computer field. The magnetic recording media used in these various fields include coated type, in which a magnetic layer is formed on the support by applying a magnetic coating mainly consisting of magnetic powder, binder resin, and solvent onto the support and drying it. things are widely used. In addition, as the demand for high-density recording has recently increased, instead of this coated type, which reduces the recording density by the amount of binder, it is possible to use direct vapor deposition, sputtering, ion blating, etc., which has a thicker saturation magnetization and does not require a binder. Thin film magnetic recording media in which a ferromagnetic metal thin film can be formed on a support have come into widespread use.

In such magnetic recording media, electromagnetic conversion is performed when the magnetic layer is rubbed and scanned by a magnetic head during recording and reproduction, so it is important that the magnetic layer has good magnetic properties or electromagnetic conversion properties. is necessary. For that purpose, magnetic head and magnetism ii&(7)rJl(7)tl
[Jei'1A(-"1LTLzL,!fb°':゛4
1+1,,,.

For example, when magnetic tape is used, it is necessary to have stable running properties such that the edges of the tape are aligned in one plane and the frictional condition with the head does not change when it is rewound and used repeatedly. There is. When such a magnetic tape is actually used, it is stored in a cassette, for example, and this cassette is attached to a video recorder, and the tape is guided by guide balls or guide rollers and run while being rubbed and scanned by a magnetic head. Ru. In order to record an image on a magnetic tape or reproduce the image in this way, in order to improve the sensitivity, especially the output in the high frequency range, the magnetic layer is The surface is finished smooth. Since this smooth surface easily sticks to magnetic heads, etc., it improves its running properties. However, if the part of the back side of the magnetic tape that is rubbed by the guide balls and guide rollers does not have good running performance, excessive tension is applied to the running magnetic tape, causing the magnetic layer to move against the magnetic head. Excessive rubbing will not only cause damage to the magnetic layer and peeling off of the magnetic powder in the magnetic layer, but also the tension at which the magnetic tape is wound will fluctuate, causing fluctuations in its spinal pressure, making it difficult to reuse it. Uneven running occurs when

When these things occur, characteristics such as skew, jitter, trunking deviation, and S/N deteriorate. For this reason, a back coat layer is provided on the back surface of the magnetic tape to stabilize running properties.

In particular, trends in magnetic recording technology in recent years include, for example, the use of compact cassettes in the audio tape field is transitioning to the use of microcassettes, and in the field of video, the current VIIS and β systems have been replaced by 8mm video tapes. , and electronic cameras are becoming more compact and denser, making them easier to carry, and cameras that were previously kept in a fixed place are now being taken outdoors. As video recording is increasingly being carried out under a variety of conditions, it is hoped that magnetic tape will also be suitable for all of these situations. In other words, the miniaturization and higher density of video equipment requires higher recording density for magnetic tape, but it is necessary to increase the number of tape turns as much as possible for a given tape winding diameter. Along with the use of thinner supports, efforts have been focused on smoothing the magnetic layer, and for this reason, supports with reasonably smooth surfaces have come to be used. However, the smoother the surface of the magnetic layer and the support on the opposite side, the worse the running properties and durability of the magnetic tape become. As the tape becomes more complicated, the tape comes into contact with guide balls, guide rollers, etc. more often, and is rubbed more frequently, which not only worsens the situation but also causes deformation and damage to the tape.

Therefore, efforts have been made to improve the surface lubricity of the bank coat layer provided on the back surface of the magnetic tape. Among these ideas, there is one in which an inorganic powder is contained in the resin layer. This is made by roughening the surface of the bank coat layer with a coating layer of a liquid in which inorganic powder such as carbon blank, titanium dioxide, calcium carbonate, alumina, graphite, silicon dioxide, etc. is dissolved or dispersed in a polymer or dispersant. - The area of contact with the tape is reduced and the coefficient of friction is reduced to prevent the tape from bending. For example, JP-A-57-130234, JP-A-58-161135, JP-A-57-
No. 53825 and Japanese Unexamined Patent Publication No. 58-2415 both show examples of using inorganic fine powder, and many of these also show that the particle size is limited.

However, even when these inorganic powders are used, not only is it not possible to obtain sufficient slipperiness, but when a single layer of Barakol containing these powders is rubbed, the bonding force of the particles to the binder to resist this is insufficient. Powder fall-off is likely to occur, especially when large particles are mixed in, and when the magnetic layer and bank coat layer come into contact when the magnetic tape is wound, the bank coat layer may become convex. When the magnetic layer is scanned and the image is reproduced, electromagnetic conversion characteristics such as chroma S/N, which indicates the degree of color noise in the image, may be affected. It may cause harm. In addition, the tape may be scraped and the metal portions such as the balls and the metal parts +A that come into contact with the tape layer 1 may be worn out.

In view of this, there are also known examples of using not only the above-mentioned surface roughening agents but also fatty acids or fatty acid esters as lubricants for the hack coat layer. For example, JP-A-57-28637 discloses an example in which lauric acid, butyl stearate, etc. are used together with polyurethane, nitrocel 1 course, vinyl chloride-vinyl acetate copolymer, and isocyanate.

Further, JP-A-58-37840 discloses an example in which fatty acids having 12 or more carbon atoms such as stearic acid or esters thereof are used together with fiber resin, polyurethane, and polyisocyanate. However, such lubricants tend to ooze out onto the surface of Huck Coat I, and if they ooze out excessively onto the Huck Coat 1/J surface, they form particles or oil (-1), which can cause problems between the tape and guide balls, etc. This may increase friction between the tapes, resulting in an increase in running tension, sticking to guide balls, etc., or even the edges of the tape may become uneven when wound, resulting in poor winding appearance, making it difficult to reuse the tape. Also, as a result of poor compatibility with the binder, it also has the disadvantage of causing uneven coating when applying the coating solution.
If this uneven coating occurs, not only will running stability not be obtained, but the wear resistance will also become uneven. In this way, /Ii! of the punk coat layer! If the slipperiness is poor and the running stability of the magnetic tape deteriorates, electromagnetic conversion characteristics such as brightness S/N, jitter, and squareness ratio may be impaired, and output fluctuations and dropouts may occur. Therefore, attempts have been made to use fatty acids or fatty acid esters that have a relatively low melting point, or to use fatty acid esters that have good compatibility with resins, but these are still insufficient and improvements have been desired.

OBJECTS OF THE INVENTION A first object of the present invention is to provide a magnetic recording medium having a bank coat layer that does not cause blooming of additives and has uniform coating.

A second object of the present invention is to provide a magnetic recording medium having a hack coat layer containing additives that can provide high /lQl lubricity with a small amount.

A third object of the present invention is to provide a magnetic recording medium that improves the squareness ratio, S/N, etc., and reduces output drop, output fluctuation, dropout, etc. by achieving the following two objects. Our goal is to provide the following.

Structure of the Invention As a result of intensive research to achieve the above object, the inventor has found that:
It was discovered that when a dibasic carboxylic acid monoester is used as an additive in the hack coat layer, a predetermined /lJl slipping effect can be achieved even with the addition of a small amount, leading to the present invention.

Therefore, the magnetic recording medium of the present invention has a magnetic layer on one side of the support and a hack coat layer on the other side of the support, in which the back coat layer is dibasic carboxylic acid. It is characterized by containing a monoester.

The present invention will be explained in more detail below.

The dibasic carboxylic acid monoester used in the present invention has the general formula % formula % where Y is an organic residue other than the carboxyl group of a compound collectively called dibasic carboxylic acid, for example an alkylene group. Saturated aliphatic hydrocarbon groups such as, for example, unsaturated aliphatic hydrocarbon groups in which an unsaturated bond is introduced into an alkylene group, and some of these saturated or unsaturated aliphatic hydrocarbon groups include aryl groups, ether bonds, and thioethers. A group into which a bond is introduced, a group of a saturated or unsaturated alicyclic compound, a group of a heterocyclic compound, a group of an aromatic compound such as an aryl group, and a saturated or unsaturated linear or Examples include branched alkyl groups, alkenyl groups, aryl groups, and groups substituted with various functional groups.

Further, R is exemplified by an alkyl group, an aryl group, and an alkyl group.

Specifically, the following can be mentioned.

(1) l100c -Cl1=CIl -C00C1
7113,.

(3) l100c (C1l 2 )9 COOC5
1111(4) 1(OOC(CH2)Ill coo
c5 ) 111(5) l100c (C1(2)12
COOC2t15(6) l100c (Cll 2
)5 C00C101121 The dibasic carboxylic acid monoester used in the present invention can be used alone, but other lubricants can also be used in combination.

Lubricants that can be used in combination include fatty basic carboxylic acids, aromatic carboxylic acids, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic 711 fatty acids with 12 to 16 carbon atoms, and 3 carbon atoms. ~12
Examples include fatty acid esters made of a +11i1 monohydric alcohol, and fatty acid esters having 21 to 23 carbon atoms made of a monobasic fatty acid with 17 or more carbon atoms and a monohydric alcohol. For these, please refer to Special Publication No. 43-23889.
It is stated in the No. In particular, when used in combination with a fatty acid ester having 17 or more carbon atoms, the lubricity increases.

The dibasic carboxylic acid monoester used in the present invention is used in combination with a resin. Examples of resins that can be used in combination include thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, and mixtures thereof.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and 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-atarylonitrile copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene Copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate-1)
-butylene 1-, cell 1: I-s diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer,
Polyester resins, chlorovinyl ether-acrylic acid ester copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof are used.

These resins are disclosed in Japanese Patent Publications Nos. 37-6877 and 39-1.
No. 2528, No. 39-19282, No. 40-5349
No. 40-20907, No. 41-9463, No. 4
No. 1-14059, No. 4146985 No. 42-642
No. 8, No. 42-11621, No. 43-4623, No. 43-15206, No. 44-2889, No. 44-1
No. 7947, No. 44-18232, No. 45-1402
No. 0, No. 45-14500, No. 47-18573,
No. 47-22063, No. 47-22064, No. 47
-22068, 47-22069, 47-22
No. 070, U.S. Pat. No. 4B-27886, U.S. Pat. No. 3,144,352, U.S. Pat. Are listed.

The thermosetting resin or reactive resin used is one that has a molecular weight of 200,000 or less in the state of a coating solution and becomes insolubilized by a reaction such as condensation 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 1 to prepolymer, urea formaldehy 1 resin, mixture of polyester polyol and isocyanate 1 to polycarbonate type polyurethane, polyamide resin, low molecular weight glycol/high molecular weight diol/l These include mixtures of liphenylmethane triisocyanate, polyamine resins, and mixtures thereof.

These resins are disclosed in Japanese Patent Publications Nos. 39-8103 and 40-97.
79 No. 41-7192, No. 41-8016, No. 4
No. 1-14275, No. 42-18179, No. 43-1
No. 2081, No. 44-28023, No. 45-1450
No. 1, No. 45-24902, No. 46-13103,
No. 47-22067, No. 47-22072, No. 47
-22073, 47-28045, 47-28
No. 048, No. 47-28922, No. 5B-4051,
Japanese Unexamined Patent Publication No. 57-31919, No. 58-60430, Japanese Patent Application No. 58-151964, No. 58-1206
No. 97, No. 58-120698, U.S. Patent No. 3
, 144,353, 3゜320.090, 3.437,510, 3,597,273, 3,731.210, 3,731,211 is stated in each specification.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
For example, maleic anhydride type, urethane acrylic type, polyester acrylic type, polyether acrylic tarve, 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 durability of the back coat layer of the magnetic recording medium according to the present invention, the bank coat layer can contain various curing agents, such as isocyanate.

Aromatic isocyanates that can be used include, for example, tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (xDI), metaxylylene diisocyanate (MXDI), and combinations of these isocyanates with active hydrogen compounds. There are adducts, etc., and those having an average molecular weight in the range of 100 to 3,000 are suitable.

On the other hand, aliphatic isocyanates include hexamethylene diisocyanate (IIMDI), lysine isocyanate, and trimethylhexylylene diisocyanate (T'
M old) and adducts of these isocyanes 1- and active hydrogen compounds. These aliphatic isocyanes-1
・Among these adducts of isocyane I and active hydrogen compounds, preferable ones have a molecular weight of 100 to 3,00.
It is in the range of 0.

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

In addition, examples of alicyclic isocyanates among aliphatic isocyanates include methylcyclo-K-2.4
-Diisocyanate, (Structural formula) %Formula% (Structural formula) Examples include isoborone diisocyanate and its adduct of an active hydrogen compound.

Examples of the adduct of the above-mentioned isocyanate and an active hydrogen compound include an adduct of a diisocyanate and a trivalent polyol. Polyisocyanates can also be used as curing agents, including, for example, a pentamer of 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 71 moles of trimethyl diisocyanate, an adduct of 3 moles of metaxylylene diisocyanate and 1 mole of 1-dimethylolpropane, and an adduct of 5 moles of tolylene diisocyanate.
There is a pentamer consisting of 3 moles of tolylene diisocyanate and 2 moles of hexamethylene diisocyanate, and these are easily obtained industrially.

In order to form the Basokuko I layer of the magnetic recording medium of the present invention using these isocyanates, a coating material is prepared by mixing and dispersing the above-exemplified resin and, if necessary, various additives described later in an organic solvent. Add to this the above isocyanate (
Preferably, the mixture containing an aromatic isocyanate and an aliphatic isocyanate 1-) is applied onto a support 1- such as a polyester film, and dried if necessary.

In this case, the amount of isocyanate l- added is 5% based on the resin.
~15% by weight is preferred. If it is less than 5% by weight, the coating film tends to be insufficiently cured, and if it is more than 15% by weight, the coating film becomes too hard, which is not preferable.

When the dibasic carboxylic acid monoester used in the present invention is used together with a resin, the amount used is 100% of the resin.
0.5 to 20 parts by weight, preferably 1 to 1 parts by weight
It is desirable to set it to 0 heavy part. When the amount of this dibasic carboxylic acid monoester added is less than 0.5 parts by weight, the lubricity effect on the surface of the Bafukuko-I layer and the effect on the abrasion resistance of the magnetic layer are not significant, and when the amount exceeds 20 parts by weight. This can cause a blooming phenomenon that oozes out onto the surface of the magnetic layer, excessively plasticizes the coating film and reduces its strength, and even causes the tapes to stick together when they are wound.
This may cause so-called glabellar adhesion.

The thickness of the layer containing the dibasic carboxylic acid monoester used in the present invention or a mixture thereof with another moisturizing agent and the above resin is suitably 0.3 to 1.5 μm.

When the dibasic carboxylic acid monoester used in the present invention is used together with a resin, a roughening agent, antistatic I.
Additives such as L agent may also be included.

Examples of the roughening agent include carbon blank, silicon oxide, titanium oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide, zinc oxide, α-Fe20B, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride,
Examples include inorganic powders made of molybdenum dioxide, calcium carbonate, etc., and benzoguanamine resin powders, preferably carbon blanks or titanium oxide.

In addition, antistatic agents include conductive powders such as carbon black, graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds, and carbon black graft polymer; natural surfactants such as saponin; Nonionic surfactants such as alkylene oxide, glycerin, and glycidol; cationic surfactants such as pyridine and other heterocycles, phosphonium or sulfonium; carboxylic acid, sulfonic acid, phosphoric acid,
Examples include, but are not limited to, anionic surfactants containing acidic groups such as sulfuric acid ester groups and phosphoric acid ester groups; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphoric acid esters of amino alcohols.

These surfactants that can be used as antistatic agents include U.S. Patent No. 2,271,623, U.S. Pat. No. 2,676°924, No. 2,676.975
No. 2,691,566, No. 2,727,86
No. 0, No. 2,730,498, No. 2,742゜37
No. 9, No. 2,739,891, No. 3,068.1
No. 01, No. 3,158.484, No. 3,201,
No. 253, No. 3,210, No. 191, No. 3,294
, No. 540, No. 3,415,649, No. 3,44
1,413, OLS No. 3,442,654, West German Patent Publication (OLS) No. 1,942.665, British Patent No. 1.077°317, OLS No. 1, 198.450, etc. First, "Synthesis of Surfactants and Their Applications" by Ryohei Oda et al. (Yokoshoten 1964 edition): ^, "Surface Active Agents" by Peili Aba (Interscience Publications Japan Inc. Vol. 19)
1958 edition): Written by TR Sisley [Encyclopedia
ObSurface Active Agents Volume 2] (
Chemical Pub Brush Company 1964 edition): "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd. 1964)
(February 20th) etc.).

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.

The following method can be used to prepare the coating liquid for forming the bank coat layer of the magnetic recording medium according to the present invention.

/1i of dibasic carboxylic acid monoester etc. in the resin solution
A solution of an Ifk agent dissolved in an organic solvent such as toluene, methylethylkene, ethyl cellosolve, acetone, cyclohexanone, tetrahydrofuran, methanol, etc. is added and mixed with stirring to form a solution. Alternatively, a resin and a lubricant such as a dibasic carboxylic acid monoester are stirred and mixed in these solvents to form a solution. Note that 7II lubricants with poor solubility are milled and dispersed.

The coating method for forming the hack coat layer according to the present invention includes:
A dipping method, a reverse roll method, an eftrusion method, a knife blade method, a doctor blade method, a gravure printing method, a spray method, etc. are used, and the coating film applied by these methods is dried by an appropriate means.

The Basokuko-1 layer thus formed exhibits excellent lubricity by adding a small amount of dibasic carboxylic acid monoester.

A ferromagnetic metal thin film and a coating type are used for the magnetic layer in the present invention, and the ferromagnetic metal thin film includes Fe, Co,
Metals such as Ni or Fe-Co, Fe-Nj
,C.

-Ni Fe-Co-Ni, Fe-Rh + Fe-C
u X Co-Cu X Co-AuCo-Y,, C
o-La, Co-Pr, Co-Gd, Co
-5m, Co-PtNi-Cu XMn-old, Mn
-5b XMn-A7! , Fe-Cr, Go-C
rzNi-Cr, Fe-Go-Cr, Fe-C
A ferromagnetic alloy such as o-Ni-Cr formed into a thin film by vacuum deposition, ion blating, stearic acid, etc. is used. The thickness of this metal thin film is 0.0
A value of 2μ to 5.011 is preferable.

Examples of magnetic materials used in the coated magnetic layer of the present invention include γ-Fe203, Co-containing -Fe20B
, Co-coated y-Fe20B, Fe304, Co-containing Fe
Oxide magnetic materials such as 3O4, Co-coated Fe5o, CrO2, e.g. Fe, Ni-Co, Fe-Ni alloy, Fe
-C.

alloy, Fe-N1-P alloy, Fe-N1-Go gold alloy F
e-Mn-Zn alloy, Fa-Ni-Zn alloy, Fe-G
o-Ni-Cr alloy, Fe-C.

-Ni-P alloy, Co-Ni alloy, Co-P alloy, Co
Examples include various ferromagnetic materials such as -Cr alloy and other metal magnetic powders containing pe, old, and Go as main components. Additives to these metal magnetic materials include 5iXCuXZn, 81. ．． l'
, Mn.

Elements such as Cr or compounds thereof may be included. Also used are hexagonal crystal thread ferrites such as barium ferrite, and iron nitride.

In the coated magnetic layer, the resin used in the Banokko I layer is used as a binder.

A dispersant is also used in this magnetic layer. Examples of the dispersant include lecithin; caprylic acid, capric acid,
Fatty acids having 8 to 18 carbon atoms such as lauric acid, myristic acid, valmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, and linuric acid (R represented by R-COOI+ has 7 to 17 carbon atoms) saturated or unsaturated alkyl groups); alkali metals of the above fatty acids (1,1,
(Na, K, etc.) or alkaline earth metals (Mg, Ca,
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. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the magnetic material.

These dispersants are disclosed in Japanese Patent Publication No. 39-28369, Japanese Patent Publication No. 44-17945, Japanese Patent Publication No. 4B-15001,
U.S. Pat. No. 3,587,993, U.S. Pat. No. 3,47
No. 0,021.

In addition, as a support, polyethylene terephthalate,
Examples include polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyamide and polycarbonate.
Ceramics such as glass, BN, Si carbide, porcelain, and earthenware 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 diameter is about 30 μm to 10 mm, and in the case of a drum shape, a cylindrical shape is used, and the shape is determined depending on the recorder used.

Further, the form of the support may be tape, sheet, card, disk, drum, etc., and various materials are selected depending on the form as necessary.

Note that the back coat layer containing dibasic carboxylic acid monoester includes not only the case where the dibasic carboxylic acid monoester is contained in the polymer film but also the case where it is attached to the surface of the polymer film.

Effects of the Invention According to the present invention, since a dibasic carboxylic acid monoester is contained in the back coat layer, a lubricating effect can be achieved with a small amount added compared to the conventional additive of a mixture of fatty acid and fatty acid ester. improves. If the amount added is small in this way, the blooming phenomenon will not easily occur when it is used together with the resin to form a hack coat layer.
Due to the excessive exudation of the additive on the surface, excessive tension is applied to a magnetic recording medium, such as a magnetic tape, and the magnetic layer is less likely to be damaged or powder to fall off. In addition, there is no uneven coating of the back coat layer.Thus, it is possible to reduce output fluctuations, dropouts, etc. of the magnetic tape, maintain good electromagnetic conversion characteristics such as various S/N, and also improve the winding appearance. Therefore, it is possible to prevent the output characteristics and electromagnetic conversion characteristics from being impaired during reuse.

In this way, it is possible to meet recent demands for high-density recording and further improvement in durability.

EXAMPLES Next, the present invention will be described in detail, but the present invention is not limited to these examples.

Example 1 The following composition is charged into a ball mill and dispersed to prepare a dispersion liquid. This dispersion is filtered through a 1 μm filter, and 5 parts by weight of a polyfunctional isocyanate is added to the filtrate and mixed to prepare a magnetic paint. This magnetic paint was coated on a support to a thickness of 5 μm using a reverse roll coater, dried, and then subjected to supercalender treatment. A solution having the composition shown in column 2 was prepared by stirring and mixing and coated using a reverse roll coater to form a back coat layer. The thickness of this back coat layer was 0.8 μm. After this 1
The magnetic tape of Practical Example 1 was prepared by slitting the magnetic tape to /2 inch.

CO-containing T-Fe203 400 parts by weight Polyurethane (Nistan 5701 manufactured by Gutdrich) 60 parts by weight Nitrocellulose (Daicel R31/2') 20 parts by weight Lecithin 7
Parts by weight Cyclohexanone 500 parts by weight Methyl ethyl ketone 250 parts Toluene 250 parts by weight Examples 2 to 4 In Example 1, instead of using the solution having the composition in the column of Example 1 in Table 1, each of Examples 2 to 4 in Table 1 was used. Magnetic tapes of Examples 2 to 4 were prepared in the same manner except that solutions prepared in the same manner as above and having the compositions shown in the column were used.

Comparative Examples 1 to 4 In Example 1, instead of using the solution having the composition in the Example 1 column of Table 1, solutions prepared in the same manner as above with the compositions shown in the Comparative Examples 1 to 4 columns of Table 1, respectively, were used. Magnetic tapes of Comparative Examples 1 to 4 were prepared in the same manner except that the following magnetic tapes were used.

The magnetic tapes of Examples 1 to 4 and Comparative Examples 1 to 4 were tested for each item shown in Table 2, and the results are shown in the corresponding columns.

The measurement method is as follows.

(δ) Jitter value (μ5ec): A black and white step signal was manually generated and measured using a jitter meter.

(b) Bleed-out: Hold the magnetic tape at -10°C for 12 hours, then hold at 40°C and 80% relative humidity for 12 hours, repeat this 10 times, and observe the surface of the back coat layer with a microscope. Those with granular or oily exudates were rated ×, and those without were rated ○.

(C) Volume: Hitio Tesoki (Equipment name: VICTORH
R-7100) was repeatedly run 400 times, and when the edges of the tape were aligned on one plane, it was rated ○, and when they were not aligned, it was rated x.

(Di abrasion resistance: Using a simulated head) The loop-shaped magnetic tape of each example and comparative example with a length of 5 m was run at 7 m/s.
After sliding at a speed of EC, the surface of the tape was observed with the naked eye and with a microscope, and the judgment was made.

From the results in Table 2, it can be seen that the magnetic tape using the dibasic carboxylic acid monoester of Example 1.2 has a lower dibasic carboxylic acid monoester than the magnetic tape using the capric acid of Comparative Example 1.
It can be seen that even when the amount of I-stell added is less than half of the amount of capric acid added, a better jitter value is exhibited, and because the amount added is small, it is difficult to cause bleed-out. In this way, the magnetic tape of Example has a good winding appearance because the amount of exuded additives is small, whereas the magnetic tape of Comparative Example 1 has an excessive amount of exuded additives, so as a result, the winding appearance is not good. I understand that. Furthermore, although the magnetic tape of Comparative Example 2 does not have bleed-out, it has a poor jitter value and a poor winding appearance. This seems to be due to insufficient lubricity as a result of the small amount of capric acid added. In addition, the magnetic tape of Example 3.4, in which butyl stearate was used in combination with Example 1.2, had good properties, whereas the magnetic tape in Comparative Example 3.4, in which butyl stearate was used in combination with Comparative Example 1.2, had good properties. The properties of magnetic tape are not good.

(Umbrella white below on this page) Table 1 Table 2 May 4, 1982

Claims (1)

[Claims] (1) In a magnetic recording medium having a magnetic layer on one side of the support and a hack coat layer on the other side of the support, the back coat layer contains a dibasic carboxylic acid monoester. Features of magnetic recording media.