JPS63104218A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability by incorporating magnetic powder of hexagonal ferrite which is magnetic powder and binder having prescribed characteristics into a magnetic coated film and curing said film by electron ray projection using an oligomer having prescribed characteristics as a crosslinking agent. CONSTITUTION:This medium is formed by coating the magnetic coated film 2 on a nonmagnetic base 1. The fine particles of the magnetic powder of the hexagonal ferrite are used as the magnetic powder which is expressed by the general formula MO.n(Fe2O3). In the formula, M denotes one kind among Ba, Sr and Ca and n=5-6. An electron ray curing type binder having 5,000-100,000 mol.wt. is used as the binder of the magnetic coated film 2. This binder contains the polymer or oligomer of 1,000-3,000mol.wt. having >=1 unsatd. double bonds in one molecule as the crosslinking agent and; for example, esters of acrylic acid are used. Such magnetic coating compd. is cured by the projection of the electron rays adjusted to 2-12Mrad irradiation quantity. The crosslinking density of the coated film is thereby improved and the durability is greatly improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium typified by a flowbee disk, a magnetic tape, etc. The present invention relates to a magnetic recording medium capable of high-density recording.

[Summary of the invention]

The present invention provides a coated magnetic recording medium using hexagonal ferrite as a magnetic powder, in which an electron beam-curable binder is used as a binder, and the electron beam-curable binder has an electron beam-sensitive double bond. The aim is to provide a magnetic recording medium with excellent durability by curing using a low molecular weight oligomer as a crosslinking agent.

(Prior art) Magnetic recording media such as floppy disks and magnetic tapes are
It consists of a flexible non-magnetic support such as polyethylene terephthalate, and a magnetic layer provided on the non-magnetic support and mainly consisting of magnetic fine particles (magnetic powder) and a resin binder.

As the magnetic powder, acicular magnetic powder such as γ-Fezes has been widely used.

In response to this, in order to respond to the rapid increase in recording density,
So-called ferromagnetic metal single-film magnetic recording media in which a ferromagnetic metal material is directly deposited on a non-magnetic support by methods such as vapor deposition or sputtering, and magnetic recording media in which hexagonal ferrite fine particles are used as magnetic powder have been proposed. ing.

Among these, magnetic recording media that use hexagonal ferrite fine particles as magnetic powder have excellent stability because they are oxide materials, and are advantageous in terms of corrosion resistance and durability, and although they are coated media, It has excellent properties such as the ability to perform perpendicular magnetic recording, and development is progressing toward practical use.

[Problem that the invention seeks to solve]

By the way, it is natural that practical characteristics such as durability are important for magnetic recording media that use hexagonal ferrite fine particles as magnetic powder, and particularly with the increase in recording density, strict demands are being placed on durability. is being served. However, when hexagonal ferrite fine particles are used as magnetic powder, the surface properties of the resulting magnetic recording medium are improved1.
However, using conventional thermosetting resin as a binder does not provide sufficient durability.

■For right-handed media, the physical properties of the coating film have a large effect on durability, and therefore improving them is a major issue for improving durability.

From this point of view, electron beams are not only useful in terms of coagulation of paint solids, improvement of pot life, simplification of manufacturing process, energy saving, etc., but also exhibit good properties in terms of physical properties of paint films. It is conceivable to use a curable binder. However, normally used molecules 15000-1000
When considering application to a magnetic recording medium using hexagonal Fe-ray Ha particles as magnetic powder, an electron beam-curable binder of about 0.00 would have insufficient crosslinking density when cured by electron beam irradiation, resulting in the above-mentioned problem. I am left unsatisfied with the durability of the product. That said,
If an electron beam curable binder with a too small molecular weight is used, the coating film will become hard and its durability will actually decrease.

Therefore, the present invention has been proposed in view of the conventional situation, and is a magnetic recording medium that uses an electron beam-curable binder, which has many advantages in manufacturing, as a binder component, has excellent durability, and is capable of high-density recording. The purpose is to provide

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a magnetic recording medium in which a magnetic coating film is formed on a non-magnetic support.
The above magnetic coating film is a hexagonal ferrite (magnetic powder) 6i
It contains an electron beam curable binder with a molecular weight of 5,000 to 100,000 as a binder, and is cured by electron beam irradiation using an oligomer with an electron beam sensitive double bond and a molecular weight of 1,000 to 3,000 as a crosslinking agent. It is characterized by this.

The magnetic recording medium of the present invention has, for example, as shown in FIG.
It is formed by coating a magnetic coating (2) on a non-magnetic support (1). In addition, the magnetic coating film (2) may be formed on one side of the non-magnetic support (1), or may be formed on both sides.

Here, the magnetic recording medium to which the present invention is applied uses hexagonal ferrite magnetic powder as the magnetic powder, and therefore, the magnetic powder has the general formula M○・n (Fego
:+) (However, in the formula, M is at least one of Ba, Sr, and Ca.
represents a species, and n=5-6. ) Hexagonal ferrite particles are used.

In this case, Co, Ti are used to control the coercive force.

At least one of Ni, Mn, Cu, Zn, In, Ge, and Nb is added to improve Fe of the hexagonal ferrite.
A part of may be replaced with these elements. For example, if M is B
In Ba ferrite which is a, when a part of Fe is replaced by the above-mentioned additive element, its composition is expressed by the general formula % (%) (wherein X is Co, Ti, Ni, Mn, Cu, Zn.

Represents at least one of In, Ge, and Nb, and m
is 0 to 0.2, and n is 5 to 6. ).

In addition, the hexagonal ferrite magnetic material used in the present invention)
The particle size is about 0.02 to 0.50 μm.

On the other hand, as the binder for the magnetic image film (2), an electron beam curing binder is used in the present invention. The electron beam curable binder used is a polymer or oligomer having one or more unsaturated double bonds in one molecule, such as esters or amides of acrylic acid or methacrylic acid (
Examples include meth)acrylic oligomers and oligo(meth)acrylates. Alternatively, electron beam-sensitive unsaturated double bonds may be introduced into general-purpose resins such as vinyl chloride resins and polyurethane resins to make them electron beam-curable.

As the electron beam sensitive double bond to be introduced, an acrylic double bond such as (in the formula, R+ represents hydrogen (or methyl ic Hz)) is effective.

In order to introduce these acrylic double bonds into vinyl chloride resin, for example, the following method may be used.

1) A compound (e.g. vinyl alcohol) having a double bond copolymerizable with vinyl chloride and an active hydrogen is copolymerized in advance into a vinyl chloride resin, and this active hydrogen is converted into a compound having an electron beam sensitive double bond. A method of denaturing with a compound. In this case, a compound having an electron beam sensitive double bond and a group capable of reacting with active hydrogen (epoxy group, aziridinyl group, etc.) in the molecule may be used for modification. Or 2
After one functional or higher functional isocyanate compound is reacted with an acrylic or methacrylic compound capable of reacting with isocyanate, the other isocyanate group may be reacted with active hydrogen introduced into the vinyl chloride resin. Furthermore, it is also possible to introduce active hydrogen, particularly hydroxyl groups, which have been introduced in advance, by directly reacting them with acrylic acid chloride or methacrylic acid chloride in the presence of a hydrochloric acid scavenger such as triethylamine or pyridine.

ii) A compound having a double bond that can be copolymerized with vinyl chloride and a group that can react with active hydrogen (such as an epoxy group or an aziridinyl group) is copolymerized in advance into a vinyl chloride resin, and this is then copolymerized with an electron beam. A method of denaturing with a compound having a sensitive double bond. In this case, a compound having an electron vA mechanized double bond and an active hydrogen in the molecule may be used for the modification.

Moreover, the following method may be followed to introduce the electron beam sensitive double bond into the polyurethane resin.

1) A method in which an electron beam and a functionalized double bond gold compound are mixed as starting materials for polyurethane resin. In this case, examples of the electron beam sensitive double bond containing compound include electron beam sensitive double bond containing diols and electron beam sensitive double bond containing diisocyanates. If these compounds are mixed as a starting material for polyurethane resin, they will polymerize with other materials and form part of the polymer molecular chain of polyurethane resin, resulting in electron-absorbing double bonds forming side chains. be introduced. Here, in order to obtain the electron beam sensitive double bond gold-containing diol, a compound having active hydrogen and an electron beam sensitive double bond may be reacted with an organic triisocyanate. Furthermore, in order to obtain a diisocyanate containing an electron beam-sensitive double bond, a compound having an electron beam-sensitive double bond and a functional group that reacts with a hydroxyl group such as an epoxy group or an aziridinyl group may be reacted with an organic triol. .

11) A method of modifying the terminal or side chain hydroxyl group of a polyurethane resin with an electron beam-induced double bond gold compound. In this case, as in the case of the vinyl chloride resin described above, the electron beam sensitive double bond metal compound contains an electron beam sensitive double bond and a group capable of reacting with active hydrogen (epoxy group, aziridinyl group, etc.). A compound contained in the molecule, acrylic acid chloride, methacrylic acid chloride, etc. may be used. Also,
It is also possible to use a difunctional isocyanate.

Of course, in addition to these vinyl chloride resins and polyurethane resins, other general-purpose resins such as polyester resins,
Four electron beam-sensitive double bonds can be formed in phenoxy 4341fl, vinylidene chloride resin, butadiene resin, etc. by the same method.

The resin into which electron beam-sensitive double bonds have been introduced as described above may be used alone as a binder, or two or more thereof may be mixed as a binder.

Furthermore, a hydrophilic polar group may be further introduced into the resin into which these electron beam sensitive double bonds have been introduced. By introducing these hydrophilic polar groups, the dispersibility in hexagonal ferrite (FF) powder is improved.

The four hydrophilic polar groups include -Coon', -303M', -05OJ',
-PO(OM”: h.

-N"(lh)i・X- (However, in the formula, H' is a hydrogen atom or an alkali metal atom, H" is a hydrogen atom, an alkali metal atom, or an alkyl group, and R2 is an alkyl group having 1 to 4 carbon atoms. , X represents a halogen atom, respectively). These hydrophilic polar groups can also be introduced into the resin according to the same method as for the electron beam sensitive double bond described above.

In any case, the electron beam curable binder used has a number average molecular weight of 5,000 to 100,000. If the number average molecular weight of the binder serving as the skeleton is less than 5,000, '4H'A becomes too hard. On the other hand, when the number average molecular weight of the binder exceeds 100,000, the physical properties of the coating film deteriorate.
This causes problems in terms of handling, etc.

Furthermore, in the present invention, in addition to the above-mentioned electron beam curable binder, a crosslinking agent with a molecular weight of 11,000 to 3,000 and a small number (both 2
A functional type electron beam sensitive double bond gold-containing oligomer is used in combination.

As this electron beam sensitive double bond containing oligomer, an electron beam sensitive double bond containing urethane oligomer, an electron beam sensitive double bond containing ester oligomer, etc. are used. These oligomers are synthesized by introducing an electron beam sensitive double bond in the same manner as the above electron beam curable binder.

The oligomer molecule 1 used as the crosslinking agent preferably has a number average molecular weight of 1000 to 3000. If the number of molecules (■) is less than 1000, the crosslinking density of the obtained magnetic coating film will be too high, and the coating film will become hard and have poor resistance.
i'J properties deteriorate. Conversely, if the molecular weight exceeds 3000, the crosslinking density will be insufficient and the desired durability will not be achieved. The electron beam sensitive double bond introduced into the oligomer is preferably bifunctional or more, and the positions of the electron beam sensitive double bond are preferably at both ends of the oligomer.

Further, the amount of the crosslinking agent used is preferably 5 to 30 parts by weight based on 100 parts by weight of the above-mentioned electron beam curable binder. If the amount of crosslinking agent is less than 5 parts by weight, no effect can be expected. If the amount of crosslinking agent exceeds 30 parts by weight, the degree of crosslinking will increase too much, the coating will become too hard, and the durability will deteriorate.

In the magnetic recording medium of the present invention, the magnetic coating film (2) includes a hexagonal ferrite magnetic layer, an electron beam-curable binder, and a crosslinking agent (electron beam-sensitive double bond-containing oligomer, molecular weight 1000
It is formed by coating a magnetic coating material prepared by mixing .about.3000) with a organic solvent on a non-magnetic support (1). In this case, the magnetic paint contains abrasives,
Lubricant 1 Dispersant, antistatic agent, etc. may be added by gravity.

Here, the material of the non-magnetic support (1) may be any material that is normally used in this type of magnetic recording medium (for example, polyesters such as polyethylene terephthalate, polyethylene 1, polypropylene, etc.). Polyolefin length n, cellulose triacetate, etc.
Cellulose Hg 4i 1 such as cellulose diacetate and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate polyimide, polyamide and polyamideimide, paper, metals such as aluminum and copper, and aluminum alloys. , light alloys such as titanium alloys, ceramics, single crystal silicon, and glass.

The non-magnetic support (1) may be in the form of a film 1 tape, sheet, disk, card, drum, or the like.

Further, the applied magnetic compound is cured by irradiation with an electron beam, and the irradiation amount is preferably in the range of 1 to 15 Mrad, more preferably 2 to 12 Mrad. When an electron beam accelerator is used, its irradiation double energy (acceleration voltage) is preferably 100V or more.

[Effect]

In the present invention, an electron beam curing type binder having a number average molecular weight of 5,000 to 100,000 is used as a binder for the magnetic coating film, and at the same time, an electron beam curing type binder having a number average molecular weight of 1,000 to 3,000 is used as a crosslinking agent.
Since the electron beam-sensitive double bond-containing oligomer is used, the crosslinking density of the electron beam curable binder is increased and the durability of the magnetic coating film is improved.

〔Example〕

Hereinafter, the present invention will be explained in detail based on specific examples. It goes without saying that the present invention is not limited to the following examples.

1 standing plate Hexagonal ferrite magnetic powder 100 parts by weight (Surface area 30n?/g) Vinyl chloride copolymer 10 parts by weight (Number average molecular weight 20,000. Equivalent of double bond when heated by electron beam 5oo)
o, polar group equivalent 10000. Type of polar group - 5O3Na
) 10 parts by weight of polyurethane resin (number average molecular weight 20,000. The type of electron beam sensitive double bond 500
0. Polar group number 110000. Type of polar group - COOH) 2 parts by weight of crosslinking agent A (urethane oligomer with number average molecular weight of 2000, amount of wire sensitive double bond 110.00, amount of polar group 5゜oo, species of monovalent group iH-coon > Sharpener (Crz03)
Triple all lubricant (dimethyl silicone oil) 2N RPJ3 dispersant (lecithin)
1 weight 1 part Antistatic agent (carbon) 2
Heavy 1 methyl ethyl ketone 100uff1
Part methyl isobutyl ketone 5 parts Toluene 50 parts The above composition was mixed in a ball mill for 48 hours, filtered with a filter, mixed for an additional 30 minutes, and then mixed with a polyethylene terephthalate filter of 16 μml W as shown in FIG. (
11) was coated on both sides so that the film thickness after drying was 6 μm. Next, after performing magnetic field orientation treatment in ), the magnetic coating film (
12) was cured by irradiation with an electron beam of 5 Mrad and wound up. This was calendered and then cut to a width of 172 inches to produce a sample tape.

Tsubasan■ Magnetism used in Main Example I/i! Gimme) A sample tape was prepared in the same manner as in Example 1 except that the amount of crosslinking agent A added to the composition was changed to 3 parts by weight.

A sample tape was prepared in the same manner as in Example 1, except that the amount of crosslinking agent added to the composition was changed to 4 parts by weight in the same coating 1' used in Example 1.

A sample tape was prepared in the same manner as in Example 1 except that the amount of crosslinking agent A added to the magnetic coating composition used in Example I was changed to 6 parts by weight.

1 Crazy (H5 Of the magnetic coating composition used in Example 1, crosslinking agent A was replaced with crosslinking agent B (ester oligomer with a number average molecular weight of 2000, wire sensitive double bond ff1loooo, $:i
A sample tape was prepared in the same manner as in Example 1 except that the polar group equivalent was changed to 5 ooo and the type of polar group (COOH) was changed to 3 parts by weight.

Among the magnetic coating compositions used in Example I, 1
Agent A and crosslinking agent C (urethane oligomer with number average molecular weight, 13,000, wire-sensitive double bond, imageability group equivalent: 5,000, insertion of polar group -COOI+) 31
A sample tape was prepared in the same manner as in Example I except for the outermost part.

Oogakimawari 1 Of the magnetic coating composition used in Example 1, crosslinking agent A was replaced with crosslinking agent D (urethane oligomer with a number average molecular weight of 1,000, a wire-sensitive double bond of 11,000, and a polar group equivalent of 50
00. A sample tape was prepared in the same manner as in Example 1 except that the amount of polar group (type of polar group - GOOR) was changed to 3 parts by weight.

A sample tape was prepared in the same manner as in Example 1, except that the magnetic coating composition used in Example I was prepared without adding crosslinking agent A.

Sample tape was prepared in the same manner as in Example 1 except that the amount of crosslinking agent A added to the magnetic coating composition used in Example 1 was changed to 10 parts by weight.

For each sample tape produced as described above,
Gloss, powder drop, and still were measured. The results are shown in the table below.

table From the table above, the sample tape of the example is glossy.

It can be seen that it has excellent properties such as powder shedding, and has very good still durability. On the other hand, it can be seen that the sample tape of the comparative example is not much different from the example in terms of properties such as gloss and powder removal, but the still durability is extremely deteriorated.

〔Effect of the invention〕

As is clear from the above description, in the magnetic recording medium of the present invention, an electron beam curable binder is used as a binder for the magnetic coating film, and a crosslinking agent having a molecular weight of 1000 to 3 is used as a crosslinking agent.
000 electron beam-sensitive double bond-containing oligomer, the crosslinking density of the coating film is improved and the durability is greatly improved.

In addition, electron beam-curable binders allow easy curing of paints and have many manufacturing advantages.

Therefore, it is possible to provide a magnetic recording medium that is easy to manufacture, has excellent durability, and is capable of high-density recording.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a main part showing an example of the structure of a magnetic recording medium with a magnetic coating film formed on one side, and FIG. 2 is a main part showing an example of the structure of a magnetic recording medium with a magnetic coating film formed on both sides. It is an enlarged sectional view. 1...Non-magnetic support 2...Magnetic coating patent applicant Sony Corporation agent Patent attorney Kodo Kobu Ensou Sakae - Figure 2 Procedures Masaaki Toho (voluntary) January 12, 1985 Japan, 1986 Patent Application No. 251368 2, Name of the invention Magnetic recording medium 3, Relationship with the person making the amendment Case Patent applicant address 6-7-35, Tokyo Parts Illustrated Product Name (2
1B) Sony Corporation Representative Ohga
In the statement of contents of the amendment, page 17, line 1 to line 2, the statement ``Polyethylene terephthalate filter (11) J'' was changed to ``Polyethylene terephthalate filter (11) J''
Correct with polyethylene terephthalate film (11) J. From line 6 to line 7 of page 22 of the specification, “l
...Nonmagnetic support 2...Magnetic coating film" is corrected to rl, 11...Nonmagnetic support 2.12...Magnetic coating film". that's all

Claims (1)

Scope of Claims: A magnetic recording medium in which a magnetic coating film is formed on a non-magnetic support, wherein the magnetic coating film comprises a hexagonal ferrite magnetic powder as a magnetic powder and a binder having a molecular weight of 5,000 to 100,000. 1. A magnetic recording medium, which contains an electron beam-curable binder and is cured by electron beam irradiation using an oligomer having an electron beam-sensitive double bond and a molecular weight of 1,000 to 3,000 as a crosslinking agent.