JPH01109526A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which is less deformed by shrinkage even at a high temp. and has a stable traveling property by coating a magnetic coating compd. on a continuously traveling base film, then subjecting the film to a heating and humidifying treatment at specific tension, temp. and relative humidity. CONSTITUTION:The magnetic coating compd. is coated on the polyethylene terephthalate film by a gravure coating machine and after the coating is subjected by a magnetic field orientation treatment, the film is passed through a drying zone set with successively higher temps. to form a raw sheet roll 7. The film is then subjected to a surface finishing treatment by 5-stages super calender rolls 8-13 and is passed through a heating and humidifying zone 15, by which the row sheet roll 18 having the magnetic layer of 5.0mum thickness is obtd. The tension in the zone 15 is adjusted to 20-50g/cm by nip rolls 14, 17 and dancer rolls 16. The treatment temp. is set at 80-120 deg.C and the relative humidity at >=60%. The magnetic recording medium which has good dimensional stability and travels stably even at a high temp. is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes and magnetic disks for use in audio and video equipment, computers, etc., and particularly for use under high temperatures. The present invention relates to a method of manufacturing a magnetic recording medium having excellent dimensional stability.

2. Description of the Related Art Magnetic tapes are generally manufactured in the following steps: preparation of a magnetic coating solution, application of the coating solution to a support, drying of the coating film, smoothing treatment, cutting, and packaging.

Non-magnetic supports are used as supports for magnetic tapes, including polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose triacetate, cellulose diacetate, and cellulose acetate butylene. - cellulose derivatives of cellulose acetate propionates; polyvinyl chloride;
Examples include vinyl resins such as polyvinylidene chloride; plastic films such as polycarbonate, polyimide, polyetherimide, and polyamideimide.

Currently, polyethylene terephthalate (PET) has excellent dimensional stability, strength and elongation, surface roughness, and cost.
Widely used as a nonmagnetic support for magnetic recording media.

There are two types of PET film: uniaxially stretched and biaxially stretched, the former being called tensarized pace and the latter balanced base.

Conventionally, magnetic recording media (eg, audio tapes and video tapes loaded in cassettes) have been used and stored in environments with moderate indoor temperature changes. In recent years, radio cassette players, video cameras, 8fl videos, etc. have become widely used, and magnetic recording media are increasingly being used and stored outdoors in high or low temperature environments. Especially at high temperatures, the deformation of the magnetic recording medium is markedly skewed (Ske).
y) Not only does it reduce output, but it also tends to cause poor running due to the occurrence of curls, etc. With the recent diversification and higher performance of magnetic recording systems, running reliability is becoming more and more important, and there is a need to maintain the characteristics of magnetic recording media under harsh environments.

Conventionally, in order to solve these problems, the use of a base film with a low heat shrinkage rate (for example, JP-A-59-11531, JP-A-6
9-107424, Japanese Patent Publication No. 8 O-15B30゜ Japanese Patent Publication No. 5
0-98524), and using a pace film that has been heat-treated in advance (for example, JP-A-59-135632, JP-A-6O-103517).

Problems to be Solved by the Invention As mentioned above, in addition to the demand for better dimensional stability of magnetic recording media, base films are also becoming thinner as the density of magnetic recording media increases. The weak mechanical strength makes it even more difficult to maintain the dimensional stability of magnetic recording media. Therefore, conventional methods are insufficient to maintain the characteristics of magnetic recording media at high temperatures.

In view of the above-mentioned problems, the present invention provides a magnetic recording medium that has dimensional stability with little deformation due to thermal contraction even when the magnetic recording medium is placed under high temperatures, and has stable runnability. It is.

Means for Solving the Problems In order to solve the above problems, the method for producing a magnetic recording medium of the present invention involves applying a magnetic paint onto a continuously running base film, drying it, and then, in a surface finishing step, Tension 2
It is characterized by heating and humidifying at a temperature of 80 to 120° C. and a relative humidity of 60% or more.

Effect As mentioned above, residual strain is removed by heat treatment under low tension, and by applying not only heat but also humidity, high moisture acts as a plasticizer, forming a non-magnetic support. The residual strain inside the body is gradually removed, the removal effect is improved, and the characteristics at high temperatures can be maintained. Note that if the tension is too low, such as 209,768 or less, the running of the film will become unstable, and if it is higher than 5 oq/cyx, residual strain will not be removed sufficiently. Similarly, if the temperature and humidity are outside the above ranges, the removal effect will not be sufficient.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings regarding the manufacture of magnetic tapes.

FIG. 2 is a diagram showing a part of the magnetic tape manufacturing process.

The PET film is sent out from a raw roll 1, magnetic paint is applied onto the film by a gravure coating machine 2, and after being subjected to a magnetic field orientation treatment 3, it passes through drying zones 4 and 5.6 in which the temperature is successively set high. Dry and create rolls. FIG. 1 is a diagram showing the steps of surface finishing treatment and heating and humidifying treatment of the present invention. The tape subjected to the heating and humidifying treatment is wound up as a raw roll 18 and sent to the next cutting step.

(Example 1) Preparation of magnetic layer paint [A]; (All parts of each component of the magnetic paint indicate parts by weight) 100
Part polyurethane resin 10 parts Vinyl chloride Vinyl acetate copolymer 10 parts Carbon black 3 parts Abrasive agent ('J'2oa)
Part 4
1 part mixed solvent [MEK/) Luene/
300 parts anone==1/1/1) After cross-dispersing the above composition using a ball mill and a sand mill, polyisocyanate (Coronate L
1 (manufactured by Nippon Polyurethane Co., Ltd.) and filtered the resulting kneaded product through a filter with an average pore size of 1 μm to prepare a magnetic layer coating material (A).

The magnetic paint (A) was biaxially stretched and had a heat shrinkage rate MD0.
55% (length direction), TDO, 52% (width direction), thickness 14.5 μm, width 1oOfl, length 2000
After forming a magnetic coating film on the original PET film of 100 m using the gravure coater 2 shown in FIG. 2, magnetic field orientation treatment 3
was applied. Thereafter, the magnetic coating film was sufficiently dried in a drying zone of 4°6.6° to obtain a master roll 7 having a magnetic layer with a thickness of 6.5 μm. Next, the raw fabric roll 7 is transferred to the surface finishing process shown in FIG.
After the surface finishing treatment according to No. 13 was performed, the raw material roll 18 was passed through a heating and humidification treatment zone 15 to obtain a raw roll 18 having a magnetic layer with a thickness of 6.0 μm. Conditioned by tension cover nip rolls 14 , 17 and dancer rolls 16 in heated humidification zone 15 . A videotape sample (250 m length) was then cut into a Z inch width.

The conditions of the heating and humidification treatment zone 16 at this time are that the base material tension is 2
09□ constant, processing temperature 80℃, relative humidity 40. s
The original fabric rolls 18 were produced by changing the o and ao%.

(Example 2) In the same manner as in Example 1, the conditions of the heating and humidification treatment zone 15 were kept constant at a base material tension of 2 oq/cyt+, and were changed to a treatment temperature of 120°C and a relative humidity of 40.60.80%. Each anti-roll 18 was obtained. A videotape sample (250 m long) was then cut into 5-inch widths.

(Example 3) In the same manner as in Example 1, the conditions of the heating and humidification treatment zone 15 were a constant base material tension of soy/++, and a treatment temperature of 80°C.
, and the relative humidity was changed to 40, 60, and 80 degrees, respectively. A videotape sample (250 m long) was then cut into 5-inch widths.

(Example 4) In the same manner as in Example 1, the conditions of the heating and humidification treatment zone 15 were a constant base material tension of 509/Ql, and a treatment temperature of 12
The raw fabric rolls 18 were obtained by changing the temperature to 0° C. and the relative humidity to 40.60.80°C. A videotape sample (250 m long) was then cut into 5-inch widths.

(Comparative Example 1) In the same manner as in Example 1, the conditions of the heating and humidification treatment zone 16 were such that the base material tension was constant at 2 oq/am, and the treatment temperature was
The raw fabric roll 18 was obtained by changing the temperature to 0.degree. C., relative humidity to 40.degree. C., and f to 30.80%. A videotape sample (250 m long) was then cut into 5-inch widths.

(Comparative Example 2) In the same manner as in Example 1, the conditions of the heating and humidification treatment zone 15 were a constant base material tension of 50 g/3, and a treatment temperature of 60°C.
The raw fabric roll 18 was obtained by changing the relative humidity to 40.60, 80, and 80, respectively. A videotape sample (250 m long) was then cut into 5-inch widths.

(Comparative Example 3) In the same manner as in Example 1, the conditions of the heating and humidification treatment zone 16 were such that the base material tension was constant at 100q/aI&, and the treatment temperature was 8.
The raw fabric rolls 18 were obtained by changing the relative humidity to 0° C. and 40.60.80°, respectively. A videotape sample (260 m long) was then cut into 5-inch widths.

(Comparative Example 4) In the same manner as in Example 1, the conditions of the heating and humidification treatment zone 15 were such that the base material tension was constant at 1009101 and the treatment temperature was 1.
20℃ relative humidity 40. The raw fabric rolls 18 were obtained by changing the angles of θ0 and 80, respectively. A videotape sample (250 m length) was then cut into a Z inch width.

(Comparative Example 5) In the same manner as in Example 1, the heating and humidification processing zone 160 conditions were kept constant at a base material tension of 1 tsoq/ag, and the processing temperature was changed to 80°C and relative humidity of 40.60.80%. 18 were obtained respectively. A videotape sample (250 m long) was then cut into 5-inch widths.

(Comparative Example 6) In the same manner as in Example 1, the heating and humidification treatment zone 160 conditions were such that the base material tension was constant at 1509/3 and the treatment temperature was 12.
Raw fabric rolls 18 were obtained by changing the relative humidity to 40 and 60.80 degrees at 0°C, respectively. Videotape samples (250 m long) were then cut into 250 m wide pieces.

(Comparative Example 7) In the same manner as in Example 1, the raw fabric roll 7 was surface-finished in the surface-finishing step shown in FIG. 1, and then heated and humidified to a thickness of 5. A raw roll 18 having a magnetic layer of OAm was obtained. This was cut to a width of 250 m to create a videotape sample (250 m long).

The amount of skew distortion was measured using the magnetic tape samples obtained in each of the above Examples and Comparative Examples, and the results shown in the following table were obtained.

Nao, skew distortion a, V) 15 system VTR, NV681
An image signal was recorded on each videotape sample using 0 (manufactured by Matsushita Electric Industrial Co., Ltd.), and the tape was heated at a temperature of 3°C and a humidity of 3°C.
After being left in a 0% atmosphere for 10 days, it was returned to an atmosphere of 25°C and AO%, and 6 hours later, the image was reproduced and the amount of skew distortion was measured on the monitor screen.

Effects of the Invention As described above, according to the present invention, after coating a magnetic paint on a non-magnetic support to form a coating film and drying it, the surface is treated in the next step of surface finishing, and then the base material is coated. Tension 20-50
By heating and humidifying the magnetic recording medium at a temperature of 80 to 120 degrees Celsius and a relative humidity of 60 degrees or higher, the deformation of the magnetic recording medium due to heat shrinkage is small and the dimensional stability is maintained even when the magnetic recording medium is placed under high temperatures. It is possible to provide a magnetic recording medium having stable running properties.

Although the above embodiments have been described with reference to magnetic tapes, it goes without saying that the present invention is applicable not only to magnetic tapes but also to other magnetic recording media such as magnetic disks and magnetic cards.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the manufacturing process of the present invention.
The figure shows a part of the manufacturing process of a magnetic tape. 1... PET raw roll, 2... Gravure coating machine, 3... Magnetic field orientation device, 4,5.6
...Drying zone, 7...Material roll,
8... Preheat roll, 9,11.131.
...Mirror roll, 10.12...Elastic roll, 14...Nip roll, 16...
Heating and humidification processing zone, 16... dancer roll,
17...Nip roll, 18...Material roll.

Claims (1)

[Claims] After coating the magnetic paint on the continuously running base film and drying it, a tension of 20 to 50 g is applied in the surface finishing process.
/cm, a temperature of 80 to 120°C, and a relative humidity of 60% or more.