JPS595430A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape or the like suitable for a VTR, superior in abrasion resistance, good in traveling stability, and low in noise occurring in traveling of the tape, by forming a backing layer contg. a filler and liquid paraffin on the backside of a base provided with a magnetic layer. CONSTITUTION:A magnetic layer is formed on a base film of polyester or the like, and the side of the base film reverse to the magnetic layer is coated with a soln. of a binder resin, such as polyurethane or cellulosic resin, contg. fine particle fillers, such as CaCO3, and liquid paraffin by 0.1-5wt% of the total weight of fillers to form a backing layer. As another method, the backing layer contg. no liquid paraffin may be formed and then impregnated with liquid paraffin by spraying. As a result, the obtained magnetic tape is resistant to peeling of the magnetic layer due to sticking between the layers of the tape in a wound state, and friction of the guide, etc. of a VTR, and superior in abrasion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in the back coat layer described in 1. of a magnetic recording medium such as a video tape, which is formed by providing a back coat layer on the back surface of a base having a magnetic layer on its main surface.

A back coat layer containing carbon black, calcium carbonate, and other fillers is provided on the back of the base, which has a magnetic layer on the main surface, to improve running stability and prevention of winding irregularities. Attempts have been made to improve wear resistance.

However, the conventional back coat layer does not have a sufficient effect of improving abrasion resistance (the back coat layer easily scratches due to sliding contact with a VTR guide, etc., and the coating film is removed when the tape is wound. This transfer to the opposing magnetic layer has an adverse effect on video characteristics.For this reason, a lubricant such as paraffin wax is mixed into the back coat layer containing the filler to further improve wear resistance. Although attempts have been made to improve the performance, the results have not yet been fully satisfactory.Furthermore, products using such lubricants have had the problem of causing tape squeal when sliding in contact with a head or the like.

As a result of intensive studies to avoid the above problems, this invention has developed a bank coat that eliminates the problem of tape squeal by incorporating liquid paraffin as a lubricant into the back coat layer containing filler. This was done after learning that the wear resistance of the layer could be greatly improved.

The content of liquid paraffin is usually about 0.1 to 5 parts by weight based on 100 parts by weight of the total filler. If this amount is too small, the above effects cannot be obtained, and if it is too large, it may cause problems such as interlayer adhesion of the tape. This is not desirable because it causes inconvenience.

Fillers include carphone black, calcium carbonate,
In addition to barium sulfate, titanium oxide, etc., conventionally known materials can be widely used. The amount of the filler used is about 30 to 80% by weight of the total weight of the filler and the binder.

There are no particular restrictions on the binder that binds the filler and impregnates the liquid paraffin, and any binder that has excellent adhesion to the base, abrasion resistance, etc. can be used. Examples include cellulose resin, polyurethane resin, polyester resin, polyisocyanate, and vinyl chloride-vinyl acetate copolymer resin.

The back coat layer in this invention is formed by applying a coating material in which filler and lubricant are mixed and dispersed in the binder described above to a thickness of usually 0.3 to 5 μm on the back surface of a base on which a magnetic layer has been previously formed on the main surface. formed by. Further, liquid paraffin as a lubricant may be impregnated by spraying onto the surface of a back coat layer containing a filler after forming the back coat layer.

As described above, according to the present invention, it is possible to provide a magnetic recording medium in which the back coat layer has excellent abrasion resistance and less tape squeal.

In the following, embodiments of the present invention will be explained. In the following, parts shall mean parts by weight.

Example Co-containing acicular magnetic iron oxide powder 250 parts Carbon black 12 parts Granular σ-iron oxide
10 parts nitrified cotton 22
Part polyurethane resin 19 parts Trifunctional low molecular weight incyanate compound 7 parts Cyclohexanone 340 parts Toluene 34
0 parts n-butyl stearate 3 parts liquid paraffin 2 parts myristic acid 2 parts The magnetic paint consisting of the above composition was applied onto a 14 μ thick polyester base film with good surface smoothness to a dry thickness of 5).
After coating and drying, surface treatment was performed.

A back coat paint having the composition shown below was applied to the back of the obtained magnetic tape so that the dry thickness was 0.8μ, and after drying, surface treatment was carried out, and the tape was cut into the specified 1] size. I made a videotape.

μ Calcium carbonate (average particle size 0.07A)
210 parts carbon black (Black Pearl I7 manufactured by Kisabot, volatile components 5% by weight) 90
Part nitrified cotton 100 parts Polyurethane resin 70 parts The trifunctional low molecule is an isocyanate compound 30 parts Liquid paraffin 3 parts Cyclohexanone
750 parts toluene
750 parts Comparative Example A videotape was produced in the same manner as in Example 1, except that 3 parts of paraffin wax was used instead of liquid paraffin in the back coat paint.

Abrasion resistance of each videotape of the above examples and comparative examples (
The following table shows the results of examining the amount of decrease in video SN ratio) and tape squeal using the methods described below.

<Abrasion resistance> A practical running test of a sample tape with a 50% gray signal recorded in an atmosphere of 40°C and 80% RH using a V HS system VTR was repeated 100 times, and the video S/N ratio was compared with that before running. The amount of decrease in video S/N ratio after running was measured.

<Tape Squeal> Using a VH8 type VTR, a practical running test was conducted on the sample tape in an atmosphere of 40° C. and 80% RH to examine the presence or absence of tape squeal.

As is clear from the table above, the videotape of this invention is
The back of the tape has excellent abrasion resistance, and there is little tape squeal.

Written amendment (method) % formula % 1. Indication of the case Patent Application No. 113369/1982 2. Name of the invention Magnetic recording medium 3. Person making the amendment Relationship to the case Patent applicant (581) +1 Representative of Ritsu Maxell Co., Ltd. Person: Atsushi Nagai 4, Agent postal code: 530 Address: 3-2-9 Nishitenma, Kita-ku, Osaka (Okina Building) ``Detailed description of the invention'' of the specification 7. Contents of amendment A, engraving of the specification ( (No change in content); (1) First, the table on page 6 has been corrected as follows.

Record

Claims (1)

[Claims] (1) A magnetic recording medium characterized in that a back coat layer containing liquid paraffin together with a filler is provided on the back side of a base having a magnetic layer on its main surface.