JPS6286533A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an electromagnetic conversion characteristic and shelf life by incorporating a polyurethane (meth)acrylate [U(M)A] contg. the metallic base of sulfonic acid and amine compd. into a magnetic layer. CONSTITUTION:The PU(M)A contg. the metallic base of sulfonic acid and the amine compd. are respectively incorporated in >=1 kinds into the magnetic layer of a magnetic recording medium essentially consisting of a nonmagnetic base and magnetic layer and are subjected to radiation irradiation. The metallic base of the sulfonic acid to be incorporated into PU(M)A is made preferably 0.005-0.5mgeq/g per PU(M)A. Aliphat., alicyclic and arom. primary, secondary and ternary amines and diamines are preferably used as the amine compd. The ferromagnetic powder having 30m<2>/g BET specific surface area is preferably used. Such coating liquid has good shelf stability, uniform quality and an excellent shelf life for a long period of time and does not require a heat treatment for curing the coated film. The resulted magnetic film has the excellent magnetic conversion characteristic and the high image quality is obtainable with such magnetic film.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to magnetic recording media such as video tapes, audio tapes, and computer tapes.

[Prior art]

Magnetic recording media that are currently widely used include thermoplastic binders such as vinyl chloride, vinyl acetate, vinyl chloride, vinylidene chloride, cellulose resin, acetal resin, urethane resin, and acrylonitrile butadiene resin. There is a method of using resins alone or in combination, but this method has the disadvantage that the abrasion resistance of the magnetic layer is poor and the running path of the magnetic tape is contaminated.

Also known are methods using thermosetting resins such as melamine resins and urea resins, or adding crosslinkable binders such as isocyanate compounds and compounds having epoxy rings to the thermoplastic resins. It is being However, when the above-mentioned crosslinking binder is used, l) there is a problem in the storage stability of the liquid in which magnetic particles are dispersed, and the uniformity of the physical properties of the magnetic coating liquid and, by extension, the homogeneity of the magnetic recording medium cannot be maintained; λ) A heat treatment step is essential for curing the coating film after application and drying, and it has disadvantages such as requiring a long time.

In order to prevent these drawbacks, a method for producing magnetic recording media using acrylic acid ester oligomers and monomers as binders and curing them by irradiation with radiation after drying has been proposed in Japanese Patent Publication No. 7-12≠-3 and Japanese Patent Application Laid-open No. 7-12≠-3. 4A7-/JtJ number, JP-A Akihiro 7-/J101/L number, JP-A Akihiro J-0-7
No. 74433, Tokukai Sho! 6-2. It is disclosed in various publications such as No. t23/. However, with the manufacturing method disclosed in the above patent publication, a magnetic recording medium having high electromagnetic conversion characteristics and durability could not be obtained.

[Problems to be solved by the present invention]

In recent years, there has been a demand for higher image quality in magnetic recording media.

This requires close contact between the magnetic layer surface and the video head and audio head, which improves the smoothness of the magnetic recording medium surface and further improves the dispersibility of the ferromagnetic fine powder. It is important to improve the

On the other hand, the smoother the surface of the magnetic layer, the greater the friction in the running system of a video tape recorder, the higher the running tension, and the more severe running durability is required of the magnetic recording medium. For this reason, a magnetic recording medium that has smoothness of the magnetic layer surface, good dispersibility of the ferromagnetic fine powder, and running durability has not yet been obtained. On the other hand, magnetic recording media are required to have a high degree of reliability. However, it has not been possible to obtain a magnetic recording medium that does not suffer from a drop in output or loss of recorded signals during playback due to damage to the magnetic recording medium due to oxidation of the ferromagnetic fine powder or deterioration of the binder, even after storage for a long period of time after recording. .

The present inventors have proposed a method using a thermoplastic resin, a thermosetting resin, and a method of adding a crosslinking binder through a chemical reaction.
Furthermore, the present invention was achieved as a result of intensive research to improve the drawbacks of conventional techniques such as methods using radiation-curable binders.

Therefore, an object of the present invention is to provide characteristics that could not be achieved with conventional magnetic recording media, namely: l) electromagnetic variation y1. ! ! ! -2) Excellent dispersibility of ferromagnetic fine powder, 3) Good storage stability of magnetic coating liquid with homogeneous performance, and -2) Excellent long-term storage stability. The object of the present invention is to provide a magnetic recording medium that has excellent running durability, and t) does not require a heat treatment step for curing the coating film.

Structure of the Invention [Means for Solving the Problems] The above problems can be solved by the magnetic recording medium described below.

That is, the present invention provides a magnetic recording medium mainly consisting of a nonmagnetic support and a magnetic layer, in which the magnetic layer contains one or more of each of polyurethane acrylate or polyurethane methacrylate containing a sulfonic acid metal base and an amine compound, and further provides radiation-resistant magnetic recording media. The present invention relates to a magnetic recording medium characterized in that it is irradiated.

The urethane acrylates and/or polyurethane methacrylates containing sulfonic acid metal bases used in the present invention (hereinafter acrylates and methacrylates are collectively referred to as (meth)acrylates, acryloyl groups and methacryloyl groups are collectively referred to as (meth) It is called an acryloyl group.The backbone of the chain may be either polyester or polyester ether, and specific examples of dibasic acids used in these are oxalic acid, malonic acid, succinic acid,
Glutaric acid, adipic acid, sebacic acid, dodecanochoic acid,
Maleic acid, fumaric acid, itaconic acid, trimethyladipic acid, hexahydrophthalic acid, tetrahydroheptalic acid,
7-thalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, etc. can be used. Examples of dihydric alcohols include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol,
Hexamethylene glycol, octamethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 2,2-dimethylpropane-
/, J-diol, λ, 2-diethylenepropane/,
J-diol, cyclohexane-/,! -diol, cyclohexane-7゜hiro-diol, cyclohexane-l
, ≠-dimethatool, cyclohexane-/, J-dimethatool, 2.2-bis(≠-hydroxyethoxycyclohexyl)furopane, 2.2-bisB-hydroxyethoxyphenyl)propane, λlλlB(Hiro-hydroxyethoxyethoxy -phenyl)propane, etc. can be used. It is also possible to use a lactone-based polyester skeleton made of r-butyrolactone, δ-valerolactone, C-caprolactone, or the like. Examples of incyanates that form urethane bonds include λ, 4cm tolylene diisocyanate, 2,6-tolylene diisocyanate, 1, 3-xylylene diisocyanate, and 1.

≠-xylylene diincyanate, l,! - naphthalene diisocyanate, m-phenylene diisocyanate),
p-phenylene diisocyanate, 3.3-dimethylphenylene diisocyanate, ≠9 μm diphenylmethane diisocyanate, 3゜3-dimethyl-Hiroshi, t-diphenylmethane diisocyanate, hexamethylene diisocyanate, inphorone diisocyanate, dicyclohexylmethane diisocyanate, trimethylolprono-7 Polyhydric incyanates such as the triadduct of tolylene diisocyanate can be used. Further, a part of the dibasic acid and dihydric alcohol may be replaced with trivalent or higher acid and alcohol. The sulfonic acid metal group and the acryloyl group may be located at the terminal or side chain of the polyurethane. As a method for introducing these groups, synthesis can be performed by using a polyester polyol in which part of the polybasic acid is replaced with a polybasic acid containing a sulfonic acid metal base. Polybasic acids containing sulfonic acid metal bases include monosodium sulfoine 7-talate, j-potassium sulfoisophthalic acid, λ-sodium sulfoterephthalate, 2-
Potassium sulfoterephthalate and the like can be used.

The preferred sulfonic acid metal base content of the urethane (meth)acrylate used in the present invention is poly-r −/
51 points p0.005 ~0. It is jll19eq,
It is preferably 00Ol to 0.211I9eq,
More preferably 0.0j to 0. /jQeq. The molecular weight is /, 000, 100,000, preferably λ, 000 to 10,000, particularly preferably j, 0
00~io, ooo.

When the content of the sulfonic acid metal base is out of this range, the dispersibility of the ferromagnetic fine powder is poor, resulting in a decrease in electromagnetic conversion characteristics and deterioration in durability. Moreover, the average content of (meth)acryloyl groups per molecule is j-10, preferably λ to t. If the molecular weight is 100, the magnetic layer of the obtained magnetic recording medium will be too strong,
Problems such as cracking when bent and curling of the magnetic recording medium due to curing shrinkage after irradiation with radiation are likely to occur. On the other hand, if the molecular weight exceeds ioo or ooo, the solubility of urethane (meth)acrylate in solvents tends to be poor, which not only makes handling inconvenient, but also deteriorates the dispersibility of the magnetic material and requires a large amount of energy to harden. This is not desirable.

As the amine compounds that can be used in the present invention, amines and diamines such as aliphatic, alicyclic and aromatic primary amines, secondary amines, and tertiary amines are preferred. Further, polyethoxylated compounds of the above compounds, complexes of the above amines with fatty acids, naphthenic acid, phosphoric acid, etc., amino acids, etc. can also be used. Among these, preferred are octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, icosylamine, diethylamine, dipropylamine, dibutylamine, cyhanthylamine, diethylamine, triethylamine, triisobutylamine, cyclohexylamine, Benzylamine, pyrimidine, naphthylamine, aminoethylbenzene, hexamethylenediamine, octamethylenediamine, xylenediamine, paraphenylenediamine, RNHCH2
CH2CH2N H2 (R is butyl, butyl, hexyl, octyl, etc.) and complexes of these compounds with fatty acids, naphthenic acid, phosphoric acid, etc. More preferred are octylamine, decylamine, dodecylamine, octadecylamine, cyclohexylamine, dibutylamine, etc., and in particular, these amine compounds are used as a complex with fatty acids such as capric acid, lauric acid, myristic acid, normitic acid. is possible.

The content of these amine compounds is 0.0-10 parts by weight, preferably 0.0-10 parts by weight, per 100 parts by weight of the ferromagnetic fine powder. /～! , more preferably 0.5 to 2 parts by weight.

Furthermore, in the present invention, the above-mentioned urethane (
In addition to meth)acrylate, polyvinyl chloride copolymers containing polar groups, cellulose resins, and (meth)acryloyl group-containing compounds of these compounds can be used. That is, C02H, OH, 5oa1.
SO3Na.

Vinyl chloride-vinyl acetate copolymers containing 0PO3H, 0P03Na groups, vinyl chloride-vinyl propionate copolymers, vinylidene chloride-vinyl acetate copolymers, etc., cellulose nitrate, cellulose acetate phthalate, cellulose acetylate, etc. - trobionate and these (meth)acryloyl group-containing compounds.

As the polyvinyl chloride polymer, for example, vinyl chloride-
Vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid-
Vinyl alcohol copolymer, vinyl chloride-vinyl propionate-hinyl maleate copolymer, vinyl chloride-vinyl propionate-vinyl alcohol copolymer, vinylidene chloride-vinyl acetate-maleic acid copolymer, vinylidene chloride-propionic acid Vinyl chloride copolymers such as vinyl-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-acrylic acid copolymer, vinyl chloride-vinyl acetate-acrylic acid-vinyl alcohol copolymer, (meth)acrylate As for the method of introducing groups, a part of the hydroxyl group or carboxyl group of these copolymers, or a part of the hydroxyl group generated by saponification, is converted into a polyfunctional isocyanate (for example, λ, ≠-tri). lylene diisocyanate, x, J-) lylene diisocyanate, 1,3-xylylene diisocyanate, /.

≠-xylylene diisocyanate, l,! -S7thalene diisocyanate, m-fluoride diisocyanate,
p-phenylene diisocyanate, 3.3 dimethylphenylene diisocyanate, ≠.

≠-diphenylmethane diisocyanate, 3,3-dimethyl-≠, Hiro-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, synchlohexylmethane diisocyanate, trimethylolpronomon tolylene diinocyanate 3
adducts, etc.), and the remaining NCO groups are reacted with an active hydrogen compound having a (meth)acryloyl group (e.g. (meth)acrylic acid, co-hydroxyethyl (meth)
acrylate, hydroxyalkyl (meth)acrylates such as hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth)acrylamide, N-methylol (meth)acrylamide, etc.). I can do it. In the case of cellulose resin, the hydroxyl groups of cellulose may be (meth)acryloylated. (meta)
The average content of acryloyl groups is per 7 molecules/
, J- to 20, preferably 2 to IO. Outside this range, curing properties may be poor or durability may be poor.

When the polar group of the vinyl chloride copolymer and its (meth)acrylate compound is a C02H group, the C02H content preferably has an acid value of about 30 to 30, more preferably 3 to 20. If it is outside this range, the dispersibility of the ferromagnetic fine powder will be poor and the electromagnetic conversion characteristics will also be significantly reduced.

Furthermore, vinyl monomers can be added to the present invention. Examples of vinyl monomers include compounds that can be polymerized by radiation irradiation and have at least one carbon-carbon saturated bond in the molecule, such as (meth)acrylic esters, (meth)acrylamides, and allyl Compound,
Examples include vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, styrenes, (meth)acrylic acids, crotonic acids, itaconic acids, and olefins. Among these, preferred are the following compounds containing two or more (meth)acryloyl groups f. Specifically, diethylene glycol di(
meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate
(meth) of polyethylene glycols such as acrylates
Acrylates, trimethylolpropane tri(meth)
Acrylate is metaerythritol tetra(meth)acrylate, dipentaerythritol is meta(meth)acrylate, di is metaerythritol hexa(meth)acrylate, tris(β-(meth)acryloyloxyethyl)in cyanurate, bis(β -(meth)acryloyloxyethyl)in cyanurate, or polyisocyanate)(,2,4'-)+J diisocyanate)
,U.

6-tolylene diisocyanate, 1,3-xylylene diisocyanate, l,≠-xylylene diisocyanate, /, j-naphthalene diisocyanate, m-7 22 diisocyanate, p-7 22 diisocyanate, 3,3-dimethyl phenylene diisocyanate, ≠,
μm diphenylmethane diisocyanate, 3,3-dimethyl-≠.

Hiro-Diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, trimethyl-
tolylene diinocyanate 3 adduct of dipropane),
Examples include compounds reacting with hydroxy(meth)acrylate compounds (2-hydroxyethyl(meth)acrylate, co-hydroxypropyl(meth)acrylate, etc.), and other poly(meth)acrylates having more than two functional groups. These monomers may be used alone or in combination of two or more.

The ratio of the binder to the ferromagnetic fine powder in the present invention is 10 to 100 parts by weight of the ferromagnetic fine powder! O parts by weight, preferably 11 to 30 parts by weight. Outside this range, electromagnetic conversion characteristics will deteriorate and durability will deteriorate.

As the ferromagnetic fine powder used in the present invention, ferromagnetic iron oxide fine powder, Co-modified ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, ferromagnetic alloy powder, barium ferrite, etc. can be used. The needle ratio of ferromagnetic iron oxide, chromium dioxide, etc. is about 0/l to 20/l, preferably 371 or more, and the average length is 0.7! A range of approximately i,oμm is effective.

The metal content of ferromagnetic alloy powder is 7! wt% or more, and the towt coefficient or more of the metal component is ferromagnetic metal (i.e., Fe, Co,
N1. Fe-Ni, Co-Ni, Fe-Co-N
i) is a particle with a major axis of about 7.0 μm or less. Particularly effective in the present invention is a fine ferromagnetic alloy powder having an ET specific surface area of 30, preferably 4 tOm2/ or more, since it is difficult to disperse the ferromagnetic fine powder.

It is preferable to use the amine compound of the present invention after surface treatment with the above-mentioned ferromagnetic fine powder in advance by the method disclosed in JP-A-11-10.2!0, etc.; It can also be used as

Organic solvents used for dispersion and application of magnetic coating liquid include acetone, methyl ethyl ketone, methyl imbutyl ketone,
Ketones such as cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ether; ethyl ether, glycol dimethyl ether, glycol monoethyl ether,
Ethers such as dioxane and tetrahydro-7rane; aromatic hydrocarbons such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene can be selected and used.

In addition, gold may be added to the magnetic coating liquid of the present invention as additives such as lubricants, abrasives, dispersants, and antistatic agents.

In particular, lubricants include saturated and unsaturated higher fatty acids having carbon number/-2 or more, fatty acid esters, higher fatty acid amides, higher alcohols, silicone oils, mineral oils, vegetable oils, 7
There are tsuso-based compounds, etc., which may be added when preparing the magnetic coating liquid, or may be dissolved in an organic solvent after drying or irradiation with radiation, or may be directly applied or sprayed onto the surface of the magnetic layer.

Materials for the support on which the magnetic coating liquid is applied include polyesters such as polyethylene terephthalate, polyethylene λ, and 6-naphthalate; polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulo-1-striacetate, polycarbonate, and polyimide. , plastics such as polyamideimide, non-magnetic metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, and plastics on which metals such as aluminum are vapor-deposited can also be used.

In addition, the forms of non-magnetic supports include films, tapes, sheets,
It may be a disk, card, drum, etc., and various materials are selected depending on the form as necessary.

In addition, the support of the present invention has a so-called so-called A back coat may be provided.

In the present invention, it is preferable to irradiate the material after applying the magnetic paint and calendering, but it is also possible to perform the calendering after the irradiation. Alternatively, it is also possible to irradiate one more time.

The radiation irradiated to the magnetic layer of the present invention includes electron beam, r
Although rays, β rays, ultraviolet rays, etc. can be used, electron beams are preferable. As the electron beam accelerator, a scanning method, double scanning method, curtain beam method, broad beam curtain method, etc. can be adopted. As for the electron beam, the accelerating voltage is 100-1000 KV, preferably /10-300 Kv, and the absorbed dose is /, J O
Mrad, preferably 3 to /j Mrad. When the accelerating voltage is less than 100 Kv, the amount of energy transmitted is insufficient, and when it exceeds 1 OOOKv, the energy efficiency used for polymerization decreases, which is not economical. As absorbed dose, /Mr
If it is less than ad, the curing reaction is insufficient and the strength of the magnetic layer cannot be obtained, and if it is more than 20 MrtLd, the energy efficiency used for curing decreases, the irradiated object generates heat, and the plastic support in particular deforms. Undesirable.

The present invention will be explained in more detail below using Examples and Comparative Examples. In the following Examples and Comparative Examples, all "parts" indicate "parts by weight."

Example/ A magnetic coating liquid having the following composition was kneaded in a ball mill for 50 hours.

Fe alloy powder (ljoooe, 100 parts BET specific surface area lA2m27t) Binder composition Urethane acrylate 70 parts (S
O3N a group-containing to, ozmgecl/g molecule-5j
10,000 Average acryloyl group content 3/molecule) Trimethylolpropane tri 30 parts Acrylate octylamine 7 parts Stearic acid 2 parts Butyl stearate 2 parts α-At203
Co part carbon black
2 parts methyl ethyl ketone 1
After dispersing 00 parts, a 3 μm dry film was applied to a 70 μm thick polyethylene terephthalate support using a doctor blade.
The film was coated so as to have a diameter of m, oriented using a cobalt magnet, and then the solvent was dried (1000 C/min) and then calendered. Next, the acceleration voltage is 76! After irradiating the tape with a '1' beam at a beam current of jmA and an absorbed dose of 7 Mrad, it was slit to a width of 1/-2 inches to obtain a sample of a video magnetic tape.

Hereinafter, the binder composition of Example 1 was changed as shown in Table 1, and the octylamine of Example 1 was changed as shown in Table 2,
A magnetic tape sample was obtained in the same manner as in Example 1. Evaluation results (d are summarized in Table 3.

Evaluation method Demagnetization rate: sample t-70'c90ch RH i.

After storage for several days, the B-H characteristics were measured using a Toei Kogyo magnetometer, and the long-term storage stability was evaluated based on the ratio of each sample to the Bm before storage.

Video S/N: Using the above video tape recorder,
! Record the gray signal of the θ% set-up, measure the noise with a Shibaku Tacho tC type S/N meter, and
It is expressed as a relative value when / is OdB.

Storage stability: After storing the magnetic coating liquid at room temperature for 2 hours, stirring for 10 minutes, a magnetic tape was prepared by the method described in Example 1, and the video S/N was measured. The video S/N of each sample when applied immediately after dispersion preparation was 71.
) Storage stability was evaluated as dB.

〔Effect of the invention〕

The magnetic recording medium of the present invention has good electromagnetic conversion characteristics and storage stability. Furthermore, the magnetic layer coating liquid of the present invention has excellent storage stability.

Claims (4)

[Claims] (1) A magnetic recording medium mainly consisting of a nonmagnetic support and a magnetic layer, in which the magnetic layer contains one or more of each of polyurethane (meth)acrylate containing a sulfonic acid metal base and an amine compound, and is not irradiated with radiation. A magnetic recording medium characterized by: (2) Claim No. (1) characterized in that the polyurethane acrylate or polyurethane methacrylate containing a sulfonic acid metal base is a polyurethane acrylate or polyurethane methacrylate containing 0.005 to 0.5 mgeq/g of a sulfonic acid metal base. The magnetic recording medium described in section. (3) Claims characterized in that the amine compounds are amines and diamines such as aliphatic, alicyclic, and aromatic primary amines, secondary amines, and tertiary amines. The magnetic recording medium according to item (1). (4) The magnetic recording medium according to claim (1), wherein the ferromagnetic fine powder used in the magnetic layer is a ferromagnetic alloy powder having a BET specific surface area of 30 m^2/g or more.