JPS6093620A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability and wear resistance by making combination use of two kinds of specific resins as a binder for a magnetic layer. CONSTITUTION:The binder consisting essentially of a resin curable by electron rays having the molecular structure in which an acrylic group (CH2=CHCOO-) is added at the terminal of diisocyanate consisting of polyester as skeleton and having <=500mol.wt. in the polyester part and 20,000-30,000mol.wt. over the entire part and a thermoplastic resin is used as the binder curable by electron rays. The acryl modified polyurethane resin to be used as the resin curable by electron rays is expressed representatively by the formula I . The polyester part is, for example, the reaction product of 1,4-butanediol with adipic acid or the reaction product of propylene glycol with adipic acid. The thermoplastic resin is enumerated particularly by a thermoplastic polyester resin, polyurethane resin and PVC resin.

Description

[Detailed description of the invention] Technical field The present invention relates to magnetic recording media.

Prior Art Magnetic recording media, represented by magnetic tapes, floppy disks, etc., include main components such as magnetic particles (for example, r-F@lO1, etc.) and an electron beam curable binder on a non-magnetic support such as a plastic film. It is known that the magnetic layer is provided with a magnetic layer. This type of magnetic recording medium is produced by coating a magnetic coating containing the binder on a support, and then irradiating the surface with electron III to cure the coating.

The manufacturing method of magnetic recording media using such an electron beam curable binder to form a magnetic layer is effective in preventing the solid content in the magnetic paint from coagulating, improving pot life, simplifying the manufacturing process, and saving energy. Generally considered to be advantageous.

However, conventional electron beam hardened magnetic recording media manufactured in this manner lack the performance required for the magnetic layer, particularly the flexibility of the magnetic layer and the adhesion (adhesion) between the support and the magnetic layer. However, the actual situation was that the durability and abrasion resistance could not be sufficiently satisfied.

OBJECT The present invention provides a magnetic recording medium that is improved by using two specific types of resins together as an inder for a magnetic layer.

The present invention provides a magnetic recording medium in which a magnetic layer mainly composed of magnetic particles and an electron beam curable binder is provided on a non-magnetic support, wherein the binder has an acrylic group ( 0H1=C
It has a linear molecular structure with E (Coo −) added,
Moreover, it is characterized in that it is mainly composed of an electron beam curable resin and a thermoplastic resin with a molecular weight of 500 or less in the polyester portion and a total molecular weight of 20,000 to 30,000.

To explain the present invention in more detail below, the acrylic modified polyurethane resin used as the electron beam curable resin of the magnetic layer in the present invention typically has the following general formula %, where the polyester portion is, for example, l, These include a reaction product between 4-butanediol and adipic acid, or a reaction product between propylene glycol and adipic acid.

Therefore, the specific acrylic-modified polyurethane resin in the present invention incorporates a compound having an acrylic double bond into the terminal isocyanate urethane polymer obtained by reacting the reaction product (corresponding to the polyester part) with a diisocyanate. It can be produced by reaction. As a diisocyanate, 2.6-
7 Cyanide), 1. '6-hexamethylene diisocyanate, xylylene diisocyanate, 3-
Icyanatomethyl-3,5.5-)limethylcyclohexyl isocyanate, etc., and compounds with acrylic double bonds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, etc. Examples include hydroxypropyl (meth)acrylate and 2-hydroxyoctyl (meth)acrylate.

The polyester portion of the specific electron beam curable resin (specific acrylic modified polyurethane resin) K used in the present invention has the feature of extremely good adhesion between the nonmagnetic support and the magnetic layer. , as the molecular weight of this portion becomes greater than 500, such effects decrease. Therefore, in the present invention, the molecular weight of the polyester portion is 500.
The following (preferably in the range of 300 to 500) are used. Another reason for setting the molecular weight to 500 or less is that by relatively increasing the number of urethane bonding moieties in the acrylic modified polyurethane resin, the flexibility of the urethane bonds is imparted to the magnetic layer.

This acrylic-modified polyurethane resin has a linear molecular structure, which further improves the flexibility of the magnetic layer, as well as preventing distortion and curling.

However, as mentioned above, the molecular weight of this entire molecular structure is 2.
It must be in the range of 0000 to 30000. This is because if the molecular weight is outside this range, a good quality film cannot be formed.

When a thermoplastic resin is mixed with this acrylic modified polyurethane resin, it is possible to improve the adhesion between the nonmagnetic support and the magnetic layer, and it also contributes to improved flexibility.

Examples of the thermoplastic resin here include thermoplastic polyester resins, polyurethane resins, polyvinyl chloride resins, etc., and they can be used alone or in combination of two or more types.

The thermoplastic resin is preferably used in an amount of 10 to 50 parts by weight per 100 parts by weight of the acrylic modified polyurethane resin (electron beam curable resin).

As the binder for the magnetic layer, the above-mentioned acrylic modified polyurethane resin and thermoplastic resin are essential components, but if necessary, (a) vinylpyrrolidone, 2-ethylhexyl acrylate, lauryl acrylate, hydroΦ7 ethyl acrylate, ethoxymethoxy Monofunctional monomers such as acrylate and tetrahydroxyfuryfuryl acrylate (b) Bifunctional monomers such as diethylene glycol diacrylate, tetraethylene glycol diacrylate, and neopentyl glycol diacrylate, and/or (c) trimethylolpropane triacrylate, tetra Polyfunctional monomers such as methylolmethanetetraacrylate may also be used as crosslinking agents. Further, conventional binders may be used in combination without impairing the purpose of the present invention. However, the amount of the specific electron beam curable resin in the entire binder must be at least 70%.

Examples of magnetic particles used in the magnetic layer include γ-F.
0. , F・104 and these with metals such as Co added #Crag F・, C (alloys containing at least two of 1 and Nl, such as Fs-Co alloy,
Examples include powders such as Co-Ni alloy.

In addition to the magnetic particles and binder mentioned above, it is desirable to add appropriate additives such as antistatic agents, lubricants, abrasives, and dispersants to the magnetic layer.

As the antistatic agent, conductive fine powder such as carzen black, graphite, carzen black graft polymer, etc. is used. When these antistatic agents are added, the amount thereof is 10 parts by weight or less, preferably 3 to 10 parts by weight, per 100 parts by weight of the magnetic particles.

As the lubricant, silicone oil, graphite, molybdenum disulfide, fatty acid esters consisting of basic fatty acids of C1ff1 to C16 and m alcohols of C1 to ctm, etc. are used. When adding these lubricants,
The amount thereof is 10 parts by weight or less, preferably 3 to 10 parts by weight, per 100 parts by weight of the magnetic particles.

As a dispersant, fatty acids having 12 to 18 carbon atoms (R' GOOFI
, R Kamoko C1, ~C, Ma is an alkyl group or an alkenyl group. ); alkali metal of the fatty acid (L l,
N a # K, etc.) or alkaline earth metals (Mg, C, etc.)
(a, Ba, etc.): The above-mentioned fluorine-containing compounds of fatty acid esters are used. These dispersants are magnetic particles io.

It is preferable to add 2 to 5 parts by weight based on the weight part.

In addition, an abrasive may be added if necessary.

The amount may be determined appropriately.

In order to produce the magnetic recording medium of the present invention, magnetic particles, the above-mentioned specific electron beam curable resin and thermoplastic resin are essential components, and the above-mentioned additives and other usual binders are added as appropriate. A magnetic paint is obtained by dispersing or dissolving it in an organic solvent, and this is applied onto a non-magnetic support such as a plastic film or synthetic paper using a doctor blade or other means, and then heated and dried to remove the diluent. The electron beam curable binder is cured by electron beam irradiation.
A magnetic layer having a thickness of approximately 10 μm may be formed. Note that acetone, toluene, methyl ethyl ketone, cyclohexanone, etc. are used as the solvent for preparing the magnetic paint.

Examples and comparative examples of the present invention are shown below. Note that all parts here are parts by weight.

Example 1 A mixture consisting of 0 g of electron beam curable binder γ-Fed according to the present invention, 100 parts, 2-ethylhexyl acrylate, 3 parts, lecithin, 5 parts, silicone oil, 3 parts, and 5 parts of Kazen black was dispersed for 24 hours using an i-lumil. A viscous magnetic paint was prepared.

Next, this magnetic paint was coated on a polyethylene Q sinterepthalate film of about 50 μm.

After drying at ~120°C to remove the solvent, an accelerating voltage of 30
E8I (curtain method) with 0KV and beam current of 10mA
Electron beam irradiation was performed using an electron beam accelerator at an absorbed dose of 10 Mrad to form a magnetic layer with a thickness of about 2 μm, thereby producing a magnetic recording medium (Product 1 of the present invention).

Example 2 A magnetic recording medium was produced by pressing in exactly the same manner as in Example 1, except that Tuboran N-, 3022 (manufactured by Nippon Polyurethane Co., Ltd.) was used as the polyurethane resin instead of the thermoplastic polyester resin (product of the present invention 2). .

Example 3 A magnetic recording medium was produced in exactly the same manner as in Example 1, except that polyvinyl chloride resin (SA-SOO, manufactured by Mitsubishi Nansanto Kasei Co., Ltd.) was used in place of the thermoplastic polyester resin. Invention 3).

Comparative Example 1 A magnetic recording medium was produced in exactly the same manner as in Example except that the electron beam curable binder 6 according to the present invention was changed from 20 parts to 25 parts without using a thermoplastic polyester resin (Comparative Example 1) Item l).

Comparative Example 2 1 Same as Example 1 except that the electron beam curable binder 1 according to the present invention was not used and the thermoplastic polyester resin was changed from 5 parts to 25 parts - However, the electron beam irradiation was omitted. The performance of these five samples was investigated and the results shown in Table IK were obtained.

Table-1 *1) After attaching cellophane tape to the sample surface (magnetic layer surface), strongly peel it off at a 45° angle. I turned things into books.

*2) Apply MEK to absorbent cotton and rub it over the magnetic layer by hand to see how many times the magnetic layer peels off.

*3) Using a surface nodule measuring device, measure the tip diameter of approximately 0.0 mm on the sample surface. The strain stress was measured when the IJII needle was moved while in contact with a load of 100 JI.

*4) Apply a load of 500 g to a needle with a tip diameter of O or SS, bring it into contact with the surface of the magnetic layer, rotate it, and observe the time Y until the magnetic layer peels off.

Effects The magnetic recording medium of the present invention has particularly excellent durability compared to conventional ones. This seems to be because the magnetic particles are well dispersed in the binder and the adhesion between the nonmagnetic support and the magnetic layer is extremely good.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic layer mainly composed of magnetic particles and an electron beam curable binder is provided on a non-magnetic support, the binder is a diisocyanate having a polyester skeleton with an acrylic group added to the end. Magnetism characterized by having a chain-like molecular structure and mainly consisting of an electron beam curable resin and a thermoplastic resin, in which the polyester portion has a molecular weight of 500 or less and a total molecular weight of 20,000 to 30,000. recoding media.