JPS62202318A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To maintain a good-quality magnetic layer for a long period of time by incorporating a specific multifunctional org. phosphate monomer as a dispersant compsn. into the magnetic layer at the time of forming the magnetic layer dispersed with magnetic powder in a binder onto a nonmagnetic substrate. CONSTITUTION:The multifunctional org. phosphate monomer which is incorporated therein with the terminal double bons. obtd. by bringing an epoxy group- contg. alpha,beta ethylenic unsatd. monomer into the org. phosphate and can be radically polymerized is incorporated as the dispersant compsn. into the magnetic layer at the time of forming the magnetic layer disperse with the magnetic powder into the binder on the nonmagnetic substrate. For example, the compd. expressed by formula I, etc., are used for the org. phosphate and the compd. expressed by formula II, etc., are used for the epoxy group-contg. alpha,beta ethylenic unsatd. monomer. In formula II, R is a hydrogen atom or methyl group, n is 1-8 integer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a dispersant that enables highly uniform dispersion of magnetic powder while maintaining its excellent properties in a binder suitable for curing magnetic recording media such as magnetic tapes with radiation such as electron beams. The present invention relates to a composition. More specifically, an epoxy group-containing α having an epoxy group that can react with the active hydrogen group and an unsaturated bond that is sensitive to radiation such as electron beams is contained in an organic phosphate ester that has good affinity with magnetic particles.

The main component is an acrylated organic phosphate ester, a furylated organic phosphate ester, etc. obtained by reacting β-ethylenically unsaturated monomers, methacrylic acid glycidyl ether, allyl glycidyl ether, etc. as an electron beam curable binder. It is added to a magnetic layer forming liquid to provide a magnetic recording medium that has excellent electromagnetic conversion characteristics and maintains high quality performance over a long period of time.

Generally, magnetic recording media such as magnetic tapes and magnetic cards are manufactured by forming a magnetic layer on a base film typified by polyethylene terephthalate. Recently, in order to improve the curing speed after applying the magnetic layer to the base film and to make the work more efficient, electron beam curable acrylic type 2 bonds have been introduced into the binder. A method of curing a coating film using radiation has been proposed. In order to obtain a high-performance magnetic recording medium, it is extremely important to increase the dispersibility of magnetic particles in the magnetic layer and improve the electromagnetic conversion characteristics. In other words, if the dispersibility of the magnetic powder is north or
It often causes noise generation and a decrease in output, and impairs various performances including the magnetic properties of niobium and the like, so it is an important issue to have properties that allow magnetic powder to be dispersed better. However, when an electron beam curable binder is cured with an electron beam, the affinity between the magnetic powder and the binder is not sufficient, and not only is it impossible to obtain a magnetic recording medium with excellent electromagnetic conversion characteristics, but also the base film and the magnetic The reality is that the adhesion to the layer, abrasion resistance, and durability are not fully satisfactory.

Therefore, in forming the magnetic layer, dispersants such as alkylbenzenesulfonates, alkylphenol phosphates, and lecithin are used to disperse the magnetic powder. Although it is recognized that the dispersibility of magnetic particles in the binder is improved due to the effect of these dispersants, due to poor binding with the binder, the dispersants ooze out onto the surface of the magnetic layer of the magnetic recording medium over time. This has the disadvantage that it causes problems, deteriorates electromagnetic conversion characteristics and runnability, and makes it impossible to maintain a high-quality magnetic layer over a long period of time.

The present invention has been made in view of the above circumstances, and its primary purpose is to provide a magnetic recording medium containing an inder as a component, which is hardened by an electron beam. The dispersibility of the magnetic powder and binder is maintained without sacrificing the advantages of improved pot life, simplified manufacturing process, and energy saving, which are the excellent characteristics of magnetic binders, and the properties of good quality are maintained over a long period of time. It provides a high quality magnetic recording medium.

That is, in forming a magnetic layer in which magnetic powder is dispersed in a binder on a non-magnetic support, the present invention uses an epoxy group-containing α, β as a dispersant composition in an organic phosphate ester.
The present invention relates to a magnetic recording medium characterized by containing a radically polymerizable polyfunctional organic phosphate monomer into which a terminal double bond is introduced by reacting an ethylenically unsaturated monomer (71).

The organic phosphoric acid ester used in the present invention is, for example, the following compounds, and these compounds can be prepared manually under the trade name DQEST manufactured by Mitsubishi Monsanto.

Dayquest 2000 (aminotrimethylenephosphonic acid) Dayquest 1-2010 (1-hydroxyethyl.

Chin-1,1-diphosphonic acid) Ramethylenephosphonic acid) An epoxy group that can react with the element and 2 that is sensitive to electron beams.
The epoxy group-containing α,β ethylenically unsaturated monomer which forms a gL bond is an integer of n=1 to 8. ) is a compound that can be expressed as The reaction conditions of the active hydrogen group of the organic phosphoric acid ester compound and the epoxy group-containing α, β ethylenically unsaturated monomer are carried out under the usual conditions. A radically polymerizable dispersant composition having a group can be easily produced. Naturally, the number of double bonds introduced depends on the epoxy group containing α that participates in the reaction,
Needless to say, it depends on the number of moles of the β-ethylenically unsaturated monomer.

It is thought that the composition of the present invention produced in this way effectively coats the surface of the magnetic powder and suppresses +Ij agglomeration of the magnetic powder, thereby improving the dispersibility of the magnetic powder6. When used as a dispersant composition for a magnetic recording medium containing an electron beam curable binder as a main component, any conventional elements constituting the magnetic recording medium can be used. Therefore, usable electron beam curable binders include urethane acrylate oligomers, polyester/acrylate prepolymers, polyether/acrylate prepolymers, epoxy/acrylate prepolymers, polyester/urethane/acrylate prepolymers, and electron beam-sensitive modified vinyl chloride copolymers. Typical examples include vinyl chloride-vinyl acetate-vinyl-alcohol copolymers and vinyl chloride-vinyl alcohol copolymers having 2-type acrylic bonds. In addition, magnetic powders that can be used include y-Fe, 03, Fe
, O, , Co-containing Fe50. , Or○, , Ba ferrite, metal, etc. The binder also contains molybrene disulfide, graphite, silicone oil, olive oil as a lubricant, and aluminum oxide as an abrasive.
Chromium oxide, silicon oxide, etc. and as antistatic agents,
Carbon black etc. can also be added. Solvents that can be used in producing the magnetic layer forming solution include acetone, methyl ether ketone, dioxane, cyclohexanone, methanol, ethanol, methyl acetate, benzene, toluene, and mixtures thereof. Furthermore, materials for the non-magnetic support that can be used include resin films such as polyethylene terephthalate, polypropylene, cellulose triacetate polycarbonate, and polyimide;
Metals such as aluminum and copper, and non-magnetic materials such as paper can be punched.

When producing a magnetic recording medium containing the above-mentioned electron beam curable binder as a main component, at least one of the dispersant compositions of the present invention must be blended.

The proportion of such a dispersant in a magnetic recording medium is important in relation to the dispersibility of the magnetic powder, magnetic properties, bondability with a binder, curability, etc. For any of the binders commonly used in this field, 1 to 10 percent by weight based on the magnetic powder is suitable. If the amount added is less than 1 weight percent, the effect as a dispersant cannot be sufficiently exhibited, while if the amount added is more than 10 weight percent, a highly densely packed magnetic layer cannot be obtained, which is unfavorable in terms of magnetic properties.

Preferably it is 3 to 7 weight percent.

To actually make a magnetic recording medium, an electron beam curable binder, magnetic particles, the dispersant composition of the present invention, and the various additives mentioned above are added as necessary, and then dispersed or dissolved in a solvent to form a magnetic layer. Prepare the forming solution. This is coated onto a non-magnetic support using a doctor blade or the like, dried, and the coated film is calendered and then irradiated with an electron beam. As the electron beam to be irradiated, in addition to electron beams, ionizing radiation such as gamma rays and neutron beams can be used, and from an industrial perspective, electron beams are preferable. The irradiation amount is preferably about 1 to 10 Mrad, more preferably 2 to 7 Mrad. When using an electron beam accelerator for irradiation, the acceleration voltage is preferably 150 to 300 KeV. As described above, according to the present invention, it is possible to provide a magnetic recording medium having good dispersibility while maintaining excellent electron beam curability.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. However, these are not intended to limit the invention. In addition, "parts" in the examples indicate parts by weight.

Example I ■-Hydroxyethylidene-1,1 diphosphonic acid (D-West 2010; Mitsubishi Monsanto Chemical ■Product name) 34
3 parts, 711 parts of glycidyl methacrylate (Acryester G; Mitsubishi Shion ■ product name), and 0.2 parts of hydroquinone monomethyl ether were reacted at 20 to 30°C for 4 hours.

Next, the water contained in the DeWest 2010 width was evaporated under reduced pressure at 40 to 50°C to obtain a methacrylated organic phosphoric acid ester. A magnetic layer forming liquid was prepared from the obtained dispersant composition according to the following formulation and a performance test was conducted. However, vinyl chloride
The vinyl acetate copolymer is V A G l-1 manufactured by LICC.
, urethane acrylate oligomer is manufactured by Toagosei Chemical Industry Co., Ltd. i! iuM-1200X was used.

Co-containing y Fe2O, 100 parts The above methacrylated organic phosphate ester 4 parts Vinyl chloride-vinyl Nate copolymer 20 parts Urethane acrylate oligomer 20 parts Dioxane
180 parts methanol
A mixture consisting of 80 parts was dispersed in a ball mill for 48 hours, filtered with a pressure filter of about 1 μm, and passed through a polyester film of about 12 μm and 10 μm thick.
It was applied using a doctor blade.

Next, after drying at 100°C to remove the solvent,
A magnetic recording medium was produced by irradiating the binder with a KeV-10 Mrad electron beam to harden the binder and form a magnetic layer with a thickness of about 3 μm. The performance of the obtained coating film is shown in the Higa test table.

Example 2 Aminotrimethylenephosphonic acid (DQuest 2000
) 598 parts, glycysyl methacrylate (acryester G) 426 parts, and 3.1 parts of hydroquinone in 20 to 30 parts
The reaction was carried out at ℃ for 4 hours to obtain a methacrylated organic phosphoric acid ester.

A magnetic recording medium was made from the obtained composite in the same manner as in Example 1.

Example 3 1343 parts of DQ-S 1-2010, 600 parts of allyl glycidyl ether (Bunacol EX-111; Choshun Sangyo @product name), and 0 parts of hydroquinone monomethyl ether
．． After reacting 2 parts at 20-30℃ for 3 hours, 40-50℃
The water contained in Dequest 2010 was dehydrated under reduced pressure to obtain an allylated organic phosphate ester. A magnetic recording medium was prepared from the obtained composite in the same manner as in Example-1.

Example 4 598 parts of Dequest 2000, 720 parts of allyl glycidyl ether (Bunacol EX-111), and 0.3 parts of hydroxy monomethyl ether were mixed at 20 to 30°C.
After a time reaction, the reaction mixture was neutralized to PI-13-4 with monoethanolamine. A magnetic recording medium was prepared from the obtained furylated organic phosphate amine salt in the same manner as in Example-1.

Comparative Example 1 The procedure was exactly the same as in Example 1, except that 4 parts of lecithin, which is currently one of the typical dispersants in this field, was used instead of 4 parts of the acrylated phosphoric acid ester synthesized in Example 1. created a magnetic recording medium.

Comparative Example 2 In place of 4 parts of the acrylated organophosphate synthesized in Example 1, polyoxyethylene alkyl phenyl ether phosphate (GAIPACRE-410, Toho Chemical Co., Ltd. A magnetic recording medium was produced in exactly the same manner as in Example 1, except that 4 parts of the magnetic recording medium were used.

Dispersibility test: The cured film was observed with a scanning electron microscope. Cases where the magnetic powders can be clearly distinguished are marked O, and the following marks are △ and ×.

Presence of migration; sump under an environment of 50°C and 180% RH. After standing for 48 hours, electron microscopy Confirm with a photo (photo magnification: 2000x) Approved.

Adhesion test: A magnetic recording medium was applied to a thickness of 10 μm on a polyester film and dried. After attaching adhesive tape to the surface of the magnetic layer and adhering it uniformly to the entire surface, the condition is observed when it is instantly peeled off.If the magnetic layer is completely peeled off from the substrate, The evaluation was rated as △ for the case where the film was peeled off, and ◯ for the case that the film was hardly peeled off.

Square shape ratio: 12.5X for the film used in the adhesion test
A 50 mm piece was cut out and measured using a magnetic property measuring machine.

Claims (1)

[Claims] When forming a magnetic layer on a non-magnetic support with magnetic powder dispersed in a binder, a dispersant composition obtained by reacting an epoxy group-containing α, β ethylenically unsaturated monomer with an organic phosphate ester. , a magnetic recording medium comprising a radically polymerizable polyfunctional organic phosphate monomer having a terminal double bond introduced therein.