JPS62209727A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve wear resistance by subjecting a back coat layer to a surface smoothing treatment near both ends in the transverse direction thereof. CONSTITUTION:After a magnetic recording medium formed to a large width is cut to a prescribed width, the back coat layer of a magnetic tape is subjected to the surface smoothing treatment near both ends (0.5-2mm from the ends) in the transverse direction thereof, by which the strength of the coated film near said parts is made high and therefore, the wear resistance is improved near both ends which are most liable to be worn in ordinary traveling. As a result, the chipping of the back coat layer and the increase of drop-out by the chipping, etc., are suppressed and since the degree of smoothing is low in the parts except both ends is low, the coefft. of friction is decreased and the deterioration in running property over the entire part of the tape is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes and magnetic sheets used in audio/video equipment, computers, and the like.

BACKGROUND OF THE INVENTION Magnetic recording media are increasingly trending toward higher density recording year by year. As a result, it is necessary to reduce recording and reproducing losses in the short wavelength region, and measures are being taken to further reduce the gap between the magnetic head and the magnetic recording medium. That is, making the surface of the magnetic recording medium highly smooth, making the magnetic powder finer, etc.

However, such a measure causes the following problem. That is, due to the high smoothness of the surface of the magnetic recording medium, the coefficient of friction of the magnetic recording medium increases, so that running performance and durability deteriorate compared to conventional ones.

As a method for solving this problem, it is generally known to provide a back coat layer on the surface of the magnetic recording medium opposite to the magnetic layer on the nonmagnetic support. [For example, Japanese Patent Publication No. 55-80830] This back coat layer is made of nonmagnetic powder and a binder. Nonmagnetic powder is used as a filler to adjust coating strength, surface electrical resistance, etc. The back coat layer is formed by applying a paint for the back coat layer onto a non-magnetic support, and then subjecting it to a smoothing treatment to impart an appropriate surface roughness.

Problems to be Solved by the Invention Barafco - 1 Basic characteristics of the layer length d: Low coefficient of friction and wear resistance 1 no 1 (・<7 (f:, j
It is to be l. However, the conventional back coat layer CI does not satisfy these two requirements at the same time, and the friction coefficient increases or the back coat layer peels off during running. Not obtained. In particular, tape-shaped magnetic recording media (hereinafter referred to as magnetic tape) are susceptible to tension fluctuations during running.
Since the end face of the retape contacts the regulating post etc. with strong pressure, this area is likely to wear out.

On the other hand, if the surface smoothing treatment for the back coat layer is uniform in the width direction, the following problem occurs.

When the treatment is applied to the Barafuko-1 layer, the coating film becomes degenerate and the strength of the coating improves, but on the other hand, the surface roughness decreases. , the coefficient of friction becomes a dog, resulting in poor running performance. On the other hand, if the surface smoothing treatment is weak, the surface roughness increases and the friction coefficient decreases. However, the strength of the coating film is reduced and the abrasion resistance is poor. Furthermore, when the magnetic tape is wound into a roll, the surface roughness is reflected on the magnetic 1/1 layer on the back side, leading to an increase in air gap loss on the surface of the magnetic 1/1 layer and deteriorating the electromagnetic conversion characteristics.

Means for Solving the Problems According to the present invention, there is provided a magnetic layer on one main surface of a non-magnetic support and a non-magnetic powder dispersed in a binder on the other main surface of a non-magnetic support. The layers are fidgety. 11. Tape-shaped magnetic recording IA provided! In the manufacturing method VC of the magnetic recording medium, a coating film is formed over a wide width and cut into a predetermined width. After that, a surface-smooth layer is formed near both ends of the back coat layer in the width direction. By applying 3f (H), a magnetic recording medium with a low friction coefficient of the Barafco-1 layer and excellent wear resistance can be obtained.

According to the present invention, after cutting a magnetic recording medium manufactured to a wide width into a predetermined width, surface smoothing treatment is performed near both ends in the width direction of the Barafco-1 layer of the magnetic tape. As a result, the strength of the coating film in this portion can be strengthened, so that the wear resistance is improved near both ends, which are most likely to be worn during normal driving. Zono Yusong, Tape No J-
? This suppresses the scraping of the Barafco-1 layer due to I and the increase in the number of rough edges caused by scraping 71.Furthermore, since the degree of smoothing is low in areas other than the vicinity of both ends, the coefficient of friction is lowered and the tape Deterioration of overall running performance is suppressed.

In addition, the vicinity of both ends here is 0.5 to 2-
This is the area of

At this time, it is important that the surface quality at the center in the width direction of the magnetic tape is so good that it does not show through to the magnetic layer and adversely affect the electromagnetic conversion characteristics.

Embodiments An embodiment of the magnetic recording medium of the present invention will be described using a magnetic tape as an example. It should be noted that all values of component ratios stated in the Examples indicate parts by weight.

(Example 1) Magnetic paint and paint for Barafco-1 were prepared as follows.
Made around the world.

1. Preparation of magnetic paint 61.

CO-containing -F e 203 magnetic iron oxide powder Io
o sound B average particle size length == o, 3 pm acicular ratio -10/1 coercive force e6o0e polyurethane resin 15 parts vinyl chloride-vinyl acetate copolymer 5 parts nitrocellulose resin 6 parts aluminum oxide powder
3 parts Average particle size 063 μm Lecithin 2 parts Methyl ethyl ketone 100 parts Methyl isobutyl ketone 100 parts Toluene
After mixing and dispersing 100 parts of the above composition in a Beau Novel for 48 hours, 6 parts of a hardening agent (Coronate L) was added. 4J
The resulting kneaded material was filtered through a filter having an average particle size of 3 μm to prepare a magnetic coating solution.

2. Preparation of coating for back coat layer 100 parts Ca CO3 powder average particle size 0.1 μm Polyurethane resin 60 parts Nitrocellulose resin 50 parts Notyl ethyl ketone
250 parts toluene
180 parts Cyclohegizanone 70 parts The above H1 composition was mixed and dispersed in a ball mill for 36 hours, and the kneaded product was taken out.After this, 16 parts of a hardening agent (Coronet) L) was added and dispersed in a high-speed dissolver to approximately 30 axiomatics. and
Furthermore, a paint for the back coat layer was prepared by filtering with 3174 L through a filter having an average particle size of 3 μm.

Next, the above magnetic paint was applied onto a 15 μm thick polyester film, oriented and dried, and then the magnetic layer was surface treated using a super calendar roll to obtain a wide jumbo roll with a magnetic layer thickness of 5 μm.

Using this jumbo roll, the above paint for the back coat layer was applied to the surface opposite to the magnetic layer, and after drying, the surface was smoothed using a super calender roll to form a back coat layer with a thickness of 0.7 μm. The conditions at this time are temperature 80
``C1 pressure is 50 kg/ctn, speed is 40 m/min.

This was cut into 1/2 inch width. Next, the surface is smoothed only in the area 1# inside from the edge of the tape using a super calender roll, and the calender pressure at this time is 6
oKg/z. A videotape was produced as described above.

(Example 2) In the production of the videotape of Example 1, the calender pressure after cutting was set to 60 Kg/Cm, and the other conditions were the same as in Example 1 to produce a videotape.

(Comparative Example 1) In the production of the videotape of Example 1, a videotape was produced in the same manner as in Example 1, except that the surface smoothing treatment of J-Nil back coat was not performed on the super calender roll before cutting. .

(Comparative Example 2) In the production of the videotape of Example 1, a videotape was produced in the same manner as in Example 1 except that no surface smoothing treatment was performed on the first layer. .

(Comparative Example 3) In the production of the videotape of Example 1, the super calender roll after cutting was subjected to 1: treatment.
Example 1゜j--A videotape was prepared in the same manner as in Example 1゜j.

The results of tests conducted on each of the above samples are shown in the attached table. In this table, 0) The coefficient of friction (μk) is calculated when the back coat layer side of the sample is
The entry tension (Ti) was read out when the wire was wound around a 180 degree stainless steel pin at a 180 degree angle and rolled in two rows in 7 seconds.The value of the Yoshikawa tension (TO) was read out and calculated using the following formula. .

ttk = In (To/Ti)/yr(2)
The surface roughness of the back coat layer is measured using a stylus type surface 10, phase hl, 1~, Japanese Industrial Standard (JIS) B
Calculate the ten-point average lees Rz from the 60010U surface thickness J.
J) Shita.

(3) Scraping d: Each sample was tested using a VH3 type VTR (NV62 manufactured by Matsushita Electric Industrial ■) under an environment of 40°C and 180% RH.
00) was conducted, and the degree of abrasion of the back coat layer after the test was visually judged by r1. Judgment criteria &) 1 are as follows.

Less wear = 1←→5: More wear (4) Video S/N is VHS < VTR
(NV8200 manufactured by Matsushita Electric Industrial Co., Ltd.), record the specified luminance signal (50% self-leveling signal) from the TV signal generator at the optimal recording current of the reference tape, and use a video color noise meter to record the demodulated signal +3 during playback. The signal contained in the signal and the order are determined and compared with that of the reference tape as odB.

-I-, IC table ``Niri'' As is clear, ``I-I-'' is the second one! The improved magnetic tape has a wear resistance of 1/1 and a balance of running stability of 77% compared to conventional products.

Effects of the Invention As detailed above, according to the present invention, it is possible to obtain a tape-shaped magnetic recording medium having a back coat layer that is excellent in abrasion resistance, has a low coefficient of friction, and has stable running. has great value.

[Brief explanation of drawings]

Figure 17 is a plan view of the tape-shaped magnetic recording medium produced according to the present invention, looking at the Paraco-1 layer side. 1...Near both ends (0.5 to 2 U from the ends)
, 2... Tape width.

Claims (1)

[Claims] Manufacture of a tape-shaped magnetic recording medium in which a magnetic layer is provided on one main surface of a non-magnetic support, and a back coat layer made of non-magnetic powder dispersed in a binder is provided on the other main surface. A method of manufacturing the magnetic recording medium, comprising:
A magnetic recording medium characterized in that a coating film is formed over a wide width on a non-magnetic support, then cut into a predetermined width, and a surface smoothing treatment is performed near both widthwise ends of the back coat layer. manufacturing method.