JPH0719358B2 - Magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium. More specifically, it relates to a coating type magnetic recording medium having an undercoat layer provided between a non-magnetic support and a magnetic layer.

[Conventional technology and its problems]

In recent years, magnetic recording media are required to have a higher recording density. For the purpose of increasing the recording density, improvement of the magnetic layer such as atomization and high packing of the magnetic material and thinning of the magnetic layer is being studied. Has been done. However, when the above-mentioned magnetic layer is improved,
The adhesion of the magnetic layer to the support, the strength of the coating film, etc. tend to decrease, and the durability tends to deteriorate. In order to improve this, conventionally, a method of applying an undercoat liquid obtained by dissolving a polyester resin, a polyurethane resin or the like in an organic solvent onto a substrate has been performed.

However, in the conventionally used undercoat liquid, when the magnetic paint is applied onto the undercoat layer formed after coating and drying, the undercoat layer swells or dissolves due to the organic solvent contained in the magnetic paint, thereby forming a magnetic layer. The smoothness of the interface of the undercoat layer may be impaired, and this may further reduce the smoothness of the magnetic layer surface. As a result, problems such as a decrease in output and an increase in output fluctuation occur. Therefore, a method in which a polyisocyanate compound is added to the undercoat liquid to crosslink the resin contained in the undercoat liquid to suppress swelling or dissolution by a solvent is used, but it cannot be said that a sufficient effect is obtained yet.

[Means for solving problems]

In view of the present situation, the present inventors have made various studies, and as a component forming the undercoat layer, use a specific resin having a hydroxyl group, a polyisocyanate compound, and trisacetylacetonato iron (III). It was found that the magnetic recording medium having sufficient surface property and excellent durability can be sufficiently suppressed from being swollen or dissolved by the solvent in the magnetic coating, and thus the present invention has been completed.

That is, the present invention provides a magnetic recording medium having an undercoat layer provided between a non-magnetic support and a magnetic layer, wherein the undercoat layer comprises the following components: (1) a polyester resin having a hydroxyl group and a hydroxyl group. A magnetic recording medium containing one or more resins selected from the group consisting of polyurethane resins, (2) polyisocyanate compounds, and (3) trisacetylacetonato iron (III). It is related.

The polyester resin and the polyurethane resin used in the present invention are not particularly limited as long as they have a hydroxyl group at the terminal or branched chain of the molecule, for example, commercially available polyester resins include Toyobo Co., Ltd. Byron 103, Byron 200, Byron 280, Byron 290, Byron 300, Byron 500, Unitika Elitel UE-3200, Unitika Elitel UE-3201, Unitika Elitel UE-3300, Unitika Elitel UE-3400 and the like can be used.

Further, as a commercially available polyurethane resin, Nippon Polyurethane Industry Co., Ltd.'s Nippon Run 5032, Nippon Run 5033, Nippon Run 2301 and the like can be used.

The polyisocyanate compound used in the present invention is a compound having two or three or more isocyanate groups in one molecule, which may be aromatic, aliphatic, or cycloaliphatic, and is a commercially available product. For example, Nippon Polyurethane Industry Co., Ltd. Coronate L, Coronate HL, Coronate EH, Sumitomo Bayer Urethane Co., Ltd. Sumidule L, Sumidule IL, Desmodur HL, Sumidule N, Sumidule H
T, Sumidule W and the like.

In the present invention, the total amount of the polyester resin or polyurethane resin having a hydroxyl group or a mixture thereof is 10
It is preferably 0 part by weight, and the polyisocyanate compound is preferably used in an amount of 2 to 40 parts by weight. If the amount of the polyisocyanate compound is less than 2 parts by weight, the crosslinking reaction is not sufficient, and if it exceeds 40 parts by weight, it takes a long time until the reaction of the isocyanate group of the polyisocyanate compound is completed, which is disadvantageous. is there. Further, when the unreacted polyisocyanate compound remains, the blocking property of the undercoat layer becomes high, which causes troubles such as sticking to the roll during the process of applying the magnetic coating material.

Trisacetylacetonato iron (II used in the present invention
I) is a red compound clamped with [Fe (C ₅ H ₇ O ₂ ) ₃ ]. The amount of this compound used is preferably 0.01 to 8 parts by weight based on 100 parts by weight of the total amount of the hydroxyl group-containing polyester resin or polyurethane resin or a mixture thereof. 0.01
If it is less than 8 parts by weight, the completion of the curing reaction of the undercoat layer will be extremely slow, and if it exceeds 8 parts by weight, adverse effects such as blooming on the surface of the undercoat layer will occur.

The undercoat layer contains the components (1) to (3) described above in acetone,
The undercoat liquid dissolved in an organic solvent such as methyl ethyl ketone, cyclohexanone, or ethyl acetate is applied by a gravure coating method,
It is formed by coating on a non-magnetic support by a reverse coating method or another method and drying it. An inorganic pigment such as carbon black or titanium oxide may be added to the undercoating liquid for the purpose of preventing electrification or improving light-shielding properties.

The components of the magnetic coating material forming the magnetic layer of the magnetic recording medium of the present invention are not particularly limited, and those normally used may be used as they are. For example, as the magnetic powder, γ-iron oxide, γ-iron oxide containing Co, reduced iron powder, and ferromagnetic powder such as alloy powder of iron / cobalt / nickel can be used. As the binder, polyvinyl chloride, vinyl chloride vinyl acetate copolymer and partially saponified product thereof, polyvinyl butyral, phenoxy resin, epoxy resin, polyester resin, polyacrylonitrile, polyurethane, polyacrylic acid ester, polymethacrylic acid ester. Polyvinylidene chloride, cellulose acetate butyrate, nitrified cotton, and other synthetic or semi-synthetic polymer compounds may be used alone or in admixture of two or more. Also, if necessary, plasticizers such as dibutyl phthalate and dioctyl phthalate, curing agents such as polyisocyanate compounds, α-iron oxide, aluminum oxide, abrasives such as chromium oxide, fatty acid esters,
Lubricants such as fatty acids, antistatic agents such as carbon black and quaternary ammonium salts, and dispersants such as lecithin and alkyl phosphates may be added.

As the non-magnetic support used in the present invention, a polyethylene terephthalate film is preferable.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Practical example 1 Byron 200 (Toyobo Co., Ltd. polyester resin) 100
Parts by weight Coronate L (Polyisocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd.) 15 Trisacetylacetonato iron (III) 2 Methyl ethyl ketone 600 Cyclohexanone 300 A solution having the above mixing ratio is dried on a polyethylene terephthalate base film having a thickness of 75 μm Of 0.5 μm was applied on both sides and dried to form an undercoat layer. on the other hand,
After thoroughly kneading and dispersing a mixture having the following composition in a ball mill,
A magnetic paint was prepared by mixing 10 parts by weight of Coronate L as a polyisocyanate compound. The prepared magnetic coating is applied on both surfaces of the above-mentioned undercoat layer so that the dry film thickness will be 1.0 μm, dried, calendered at 70 ° C and linear pressure of 250 kg / cm, and postcured at 50 ° C for 2 days. Then, it was punched out in the shape of a 5.25-inch circle to make a magnetic disk. The produced magnetic disk was surface-treated with a polishing tape and loaded into a jacket for evaluation of the magnetic disk.

(Magnetic coating composition) Co-containing γ-iron oxide powder 100 parts by weight Lecithin 2 S-REC A (Vinyl chloride / vinyl acetate / vinyl alcohol copolymer manufactured by Sekisui Chemical Co., Ltd.) 20 Nipporan 2304 (Polyurethane manufactured by Nippon Polyurethane Industry Co., Ltd.) Resin 20 Condak Tex 975 (carbon black manufactured by Colombian Carbon Co., Ltd.) 4 α-iron oxide 10 Butyl stearate 5 Methyl ethyl ketone 100 Toluene 100 Cyclohexanone 100 Example 2 Condak Tex 975 30 parts by weight Emulgen 910 (Kao (stock) ) Nonionic surfactant) 1
Byron 200 100 parts by weight Nipporan 2301 (Polyurethane resin manufactured by Nippon Polyurethane Industry Co., Ltd.) 100 Coronate EH (Polyisocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd.) 10 Trisacetylacetonato iron (III) 1 Methyl ethyl ketone 900 Cyclohexanone 500 The above mixture Was kneaded and dispersed in a ball mill to prepare an undercoating liquid, and a magnetic disk was produced in exactly the same manner as in Example 1.

Example 3 Nipporan 2301 100 parts by weight Sumidule W (polyisocyanate compound manufactured by Sumitomo Bayer Urethane Co., Ltd.) 20 Trisacetylacetonato iron (III) 0.2 Methyl ethyl ketone 600 Cyclohexanone 300 Example except that the above mixed liquid was used as the undercoat liquid A magnetic disk was made in exactly the same manner as 1.

Comparative Example 1 Trisacetylacetonato iron (II
A magnetic disk was produced in exactly the same manner as in Example 1 except that I) was omitted.

Comparative Example 2 Trisacetylacetonato iron (II
A magnetic disk was prepared in exactly the same manner as in Example 2 except that triethylenediamine was used instead of I).

Comparative Example 3 Trisacetylacetonato iron (II
Except that dibutyltin dilaurate is used instead of I),
A magnetic disk was manufactured in exactly the same manner as in Example 3.

Comparative Example 4 A magnetic disk was prepared in the same manner as in Example 3 except that the undercoat liquid of Example 3 was omitted.

Comparative Example 5 A magnetic disk was produced in exactly the same manner as in Example 1 except that the above mixture was used as the undercoating liquid.

Comparative Example 6 A magnetic disk was produced in exactly the same manner as in Example 1 except that the above mixture was used as the undercoating liquid.

Using commercially available floppy disk drives for the magnetic disks produced in Examples 1 to 3 and Comparative Examples 1 to 6,
The output voltage and output fluctuation at 125 KHz were measured. Here, the output fluctuation is represented by the following equation.

Here, A: About 20 including the maximum output voltage in one track.
00 Average output voltage of magnetic flux reversal B: About 2000 average output voltage of the magnetic flux reversal including the minimum output voltage in one track of the track. Table 1 shows the output voltage of the magnetic disks of Examples 1 to 3 and Comparative Examples 1 to 6 at 125 KHz ( The results are shown in Comparative Example 1) and output fluctuations. The magnetic recording medium of the present invention shows a rapid improvement in solvent resistance of the undercoat layer and a decrease in output voltage due to the provision of the undercoat layer. It can be seen that this is an excellent one with no increase in output fluctuation.

Claims (1)

[Claims] 1. A magnetic recording medium having an undercoat layer provided between a non-magnetic support and a magnetic layer, wherein the undercoat layer has the following components: (1) a polyester resin having a hydroxyl group and a hydroxyl group. A magnetic recording medium containing one or more resins selected from the group consisting of polyurethane resins, (2) a polyisocyanate compound, and (3) trisacetylacetonato iron (III).