JPS6093623A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the adhesion between a base and a magnetic layer by providing a specific undercoating layer between the base and the magnetic layer. CONSTITUTION:An undercoating layer contains a resin curable by electron rays which has the linear molecular structure in which an acryl group (CH2= CHCOO-) is added at the terminal of diisocyanate contg. polyester as skeleton, and having <=500mol.wt. in said polyester part and 20,000-30,000mol.wt. over the entire part and a satd. thermoplastic polyester resin. The acryl modified polyurethane resin used as the resin curable by electron rays is representatively expressed by the general formula. The polyester part herein is, for example, the reaction product of 1,4-butanediol with adipic acid. The satd. thermoplastic polyester resin is preferably used at 10-50pts.wt. by 100pts.wt. the electron radiation curing 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 magnetic particles (e.g., r-F, etc.) and electron beam curable, l A type having a magnetic layer mainly composed of an inder is known. This type of magnetic recording medium is produced by coating a support with a magnetic coating containing the binder and then irradiating the surface with an electron beam to cure the coating.

The manufacturing method of magnetic recording media using such an electron beam curable binder for forming the magnetic layer has various advantages such as preventing the solid content in the magnetic cage from coagulating, improving the pot life, simplifying the spreading process, and saving energy. It is generally considered to be advantageous in this respect.

However, conventional electron beam hardened magnetic recording media manufactured in this way have insufficient performance required for the magnetic layer, especially the adhesion between the support and the magnetic layer, and therefore have poor durability. Deficient in sex.

Purpose The present invention provides a magnetic recording medium in which the adhesion between the support and the magnetic layer is improved by providing a specific subbing layer (intermediate layer) between the support and the magnetic layer. It is something.

Structure The present invention provides a magnetic recording medium in which an undercoat layer, a magnetic layer mainly composed of magnetic particles and an electron beam curable binder are sequentially provided on a non-magnetic support, wherein the undercoat layer has a polyester skeleton. An acrylic group (
Electron beam curable resin and saturated thermoplastic polyester resin, which has a linear molecular structure with CU, = cucoo -) added, and whose polyester portion has a molecular weight of 500 or less and a total molecular weight of 2.0000 to 300,000. It is characterized in that it includes.

To explain the present invention in more detail below, the acrylic modified polyurethane resin used as the electron beam curable resin of the undercoat layer in the present invention is typically expressed by the following general formula %, where the polyester portion is, for example, 1 , 4-butanediol and adipic acid, or a reaction product of glopylene glycol and adipic acid.

Therefore, the specific acrylic modified polyurethane resin in the present invention is.

The above reaction product (corresponding to the polyester moiety)
It can be produced by reacting a compound having an acrylic double bond with a terminal isocyanate urethane polymer obtained by reacting the urethane polymer with a diisocyanate. Examples of the diisocyanate include 2,6-dolylene diisocyanate), 1,6-hexamethylene diisocyanate, xylylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, and acrylic diisocyanate. Compounds with heavy bonds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3
-Hydroxypropyl (meth)acrylate, 2-hydroxyoctyl (meth)acrylate, and the like.

The polyester portion of the specific electron beam curable resin (specific acrylic modified polyurethane resin) used in the present invention has the feature of significantly improving the adhesion between the nonmagnetic support and the undercoat 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 to provide the magnetic layer with the flexibility of urethane bonds by relatively increasing the number of urethane bonds in the acrylic modified polyurethane resin.

In addition, this acrylic modified polyurethane resin has a linear molecular structure, thereby providing the undercoat layer with effects such as improved flexibility, distortion prevention, and curl prevention.

However, as mentioned above, the molecular weight of this entire molecular structure is 2.
It needs to 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 saturated thermoplastic polyester resin is mixed with this acrylic modified polyurethane resin, the adhesion between the non-magnetic support and the magnetic layer can be improved, and it also contributes to improved flexibility. Become. It is preferable to use 10 to 50 parts by weight of the saturated thermoplastic polyester resin based on 100 parts by weight of the acrylic modified polyurethane resin (electron beam curable resin).

The binder for the magnetic layer is not particularly limited as long as it is an electron beam curable resin commonly used in this field, but is preferably an acrylic modified polyurethane resin as mentioned in the explanation of the undercoat layer. Of course, polyester skeleton is 5 or more functional groups (particularly preferred number of functional groups is 7 to 13).
Electron beam curable resins having a molecular structure of 2), in which the molecular weight of the polyester portion is in the range of 2000 to 4000 and the total molecular weight in the range of 20000 to 5000, can also be effectively used. In this case, the electron beam curable resin also
It can be manufactured according to the manufacturing method of the specific acrylic modified polyurethane resin used in the above-mentioned undercoat layer.

When an electron beam curable resin is used as a binder for the magnetic layer, the magnetic particles can be well dispersed in the binder, and furthermore, the magnetic layer can have appropriate hardness and flexibility χ.

Furthermore, the electron beam curable resin used in the magnetic layer may optionally contain (a) vinylpyrrolidone, 2-ethylhexyl acrylate, lauryl acrylate, hydroxyethyl acrylate, ethoxymethoxy acrylate, tetrahydroxyfuryfuryl acrylate. Monofunctional monomers such as (b) diethylene glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, and/or (c) difunctional monomers such as trimethylolpropane triacrylate, dimethylolmethanetetriacrylate, etc. Polyfunctional heptamers such as polyfunctional heptamers may be used in combination as crosslinking agents. However, the amount of electron beam curable resin in the entire binder is at least 70% by weight.

In addition to the magnetic particles and binder mentioned above, the magnetic layer contains suitable additives such as antistatic agents, groove lubricants, abrasives, etc.
It is desirable to add a dispersant.

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 lubricants, silicone oil, graphite, molybdenum disulfide, C□~C1,0 basic fatty acids and C1~
Jli fatty acid esters consisting of C11 monohydric alcohol and the like are used. When these lubricants are added, the amount thereof is 10 parts by weight or less, preferably 3 to 50 parts by weight, per 100 parts by weight of the magnetic particles.

Caprylic acid and capric acid are used as dispersants.

Fatty acids with 12 to 18 carbon atoms such as lauric acid (R'
C0OH,R” is a C□ to C4 alkyl group or alkenyl group.); alkali metal of the fatty acid (Li, N
etc.) or alkaline earth metals (MgeCm, Ba, etc.); fluorine-containing compounds of the aforementioned fatty acid esters, etc. are used. These dispersants are preferably added in an amount of 2 to 5 parts by weight per 100 parts by weight of the magnetic particles.

Further, an abrasive is added as necessary, but the amount thereof is an appropriate amount.

In order to actually produce the magnetic recording medium of the present invention, an undercoat paint and a magnetic paint are prepared separately, and the undercoat paint is first applied onto a non-magnetic support (plastic film, synthetic paper, etc.) using a doctor blade or other means. After coating, the diluent was removed by heat drying, followed by electron beam irradiation.
．． An undercoat layer with a thickness of 5 to 1 μm is formed, and a layer of 1 to 3 μm is coated with the magnetic paint using the same method on this undercoat layer.
What is necessary is to form a magnetic layer of the layer.

Acetone, toluene, methyl ethyl ketone, cyclohexanone, etc. are used as a low boiling point solvent as a diluent used in the magnetic layer forming liquid (magnetic paint) and the undercoat layer forming liquid (undercoat paint).

As magnetic particles, r -Fe! 01 is cited as the most representative example, but it is not limited thereto, and all magnetic particles known in this technical field can be used.

Examples Electron beam curable binder according to the present invention Saturated thermoplastic polyester resin (Vylon 5 parts by weight)
200, manufactured by Toyobo Co., Ltd.) Methyl ethyl ketone (MIK)-) toluene mixed solvent (
A mixture consisting of 100 parts by weight (volume ratio 1:l) was thoroughly stirred, coated on a polyester film (non-magnetic support) with a thickness of about 5oIi1rL, dried, and then applied at an accelerating voltage of 3
Using an ESI (curtain method) electron beam coupler with a beam current of 00 KV and 10 mA to 15 mA, the absorbed dose is 3 to 1.
Electron beam irradiation was performed in the range of .degree.Mrad to cure the binder and form an undercoat layer with a thickness of about 0.5 .mu.m. On the other hand, r-F @ Hot Os 100 parts lauric acid 41 parts silicone oil 6 parts by weight MEK) Luene mixed solvent (volume ratio 1:1) 200
A mixture consisting of 1 part of Jl was dispersed for 15 hours in a lumen, and a mixed solvent of KMEK-)luene (volume ratio 1:1) was used.
Added @ and dispersed for 15 hours in a Zeel mill, and then added a mixed solvent of Cargin black (5 parts MEK-) and luene (volume ratio 1:1) so
A magnetic coating material was prepared by dispersing the mixture for 15 hours in a lumen mill.

After this magnetic paint was applied onto the undercoat layer and dried, it was irradiated with an electron beam in the same manner as described above to form a magnetic layer with a thickness of about 2 μm, thereby producing a magnetic recording medium (product of the present invention).

Comparative Example 1 A magnetic recording medium was produced in exactly the same manner as in Example except that the provision of an undercoat layer was omitted (Comparative Product 1) 6 Comparative Example 2 Electron beam curable resin was used without using saturated thermoplastic polyester resin A magnetic recording medium t was prepared in exactly the same manner as in the example except that the undercoat layer was formed using only the following materials (comparative product 2).

Comparative Example 3 A magnetic recording medium was produced in exactly the same manner as in Example except that the undercoat layer was formed only from a saturated thermoplastic polyurethane resin without using an electron beam curable resin (Comparative Product 3).

When the quality of these four samples was examined, the results shown in Table 1 were obtained.

ml) After adhering K cellophane tape to the sample surface (magnetic layer surface), peel it off strongly at an angle of 45 degrees. did.

*2) Place the back side of the sample on the floor and evaluate the rising condition of the ear on a JIsx class scale. , 2 or more seagulls were marked as X.

*3) Make the sample into a disk shape and run it through a commercially available taper set scratch tester (manufactured by Toyo Seiki Co., Ltd.) to determine the relative degree of wear of each sample. The higher one was marked as ×.

*4) Using a surface roughness measuring device, measure the tip diameter of approximately 0.0mm on the sample surface. The strain stress (to) was measured when the needle of III was moved while in contact with a load of 100 J.

Effects As described above, the magnetic recording medium according to the present invention is free from curling, distortion, etc., and also has good adhesion between the support and the magnetic layer.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic layer mainly composed of Kia particles and an electron beam curable binder is provided on a non-magnetic support, a diisocyanate having a polyester skeleton is provided between the support and the magnetic layer. It has a linear molecular structure with an acrylic group added to the end, and the molecular weight of the polyester part is 500 or less and the overall molecular weight is 20,000.
A magnetic recording medium comprising an undercoat layer comprising an electron beam curable resin of ~3000G and saturated thermoplastic polyester 111N.