JP2732757B2 - Magnetic recording tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording tape,
More specifically, the present invention relates to a magnetic recording tape having a curl opposite to that of a magnetic layer.

[0002]

2. Description of the Related Art Magnetic tapes for video, audio and the like are manufactured by forming a magnetic layer on the surface of a non-magnetic base film such as polyethylene terephthalate and, if necessary, forming a back coat layer on the surface opposite to the magnetic layer. Have been. When the magnetic layer is formed on the base film, curl occurs on the magnetic layer side due to a difference in internal stress between the magnetic layer and the base film. In other words, the magnetic layer contracts, and the tape on the magnetic layer side curls so as to be concave. This curl causes inconveniences such as worsening the contact state between the tape and the recording head or the traveling system, deteriorating electromagnetic characteristics, making traveling unstable, and causing tape deformation (one-sided stretching).
Therefore, in addition to increasing the mechanical strength and durability of the base film so that the base film does not easily curl even if a magnetic layer is formed, especially for video tapes and some audio tapes that require tape flatness, A back coat layer mainly made of carbon black is provided on the surface opposite to the magnetic layer to eliminate curling of the tape (to flatten the tape).

[0003]

As described above, the curl of the magnetic tape causes unstable running, instability of head touch, deformation of the tape, and dropout. Also, if a back coat layer is provided,
Although the tape is flattened to improve the running property and dropout, there are problems that the tape sticks to the case and that the tape cannot be completely prevented from being deformed.

Accordingly, the present invention provides a highly reliable magnetic recording tape which solves the above-mentioned problems, has excellent tape running properties and head touch, and prevents tape deformation and sticking of the tape to a case. The purpose is to do.

[0005]

SUMMARY OF THE INVENTION Under the above-mentioned object, the inventor of the present invention, while carrying out intensive studies in order to solve the problems caused by the curling of the magnetic recording tape, surprisingly added the magnetic recording tape to the magnetic layer. When curled to the side opposite to the magnetic layer instead of to the side, it is found that a magnetic recording tape with excellent tape running property and head touch, and without tape deformation and sticking to the cassette half can be obtained. Thus, the present invention has been completed.

That is, the gist of the present invention is to provide a magnetic recording system characterized in that a magnetic layer is provided on one surface of a tape-shaped non-magnetic base film, and the tape is curled so that the center of the tape on the magnetic layer side protrudes. On the tape. The tape-shaped nonmagnetic base film of the present invention may be any of those commonly used for magnetic recording tapes, and is not particularly limited, and polyesters, polyolefins, cellulose derivatives, and polyimides are used.

The type and manufacturing method of the magnetic layer formed on one surface of the base film can be in accordance with a conventional method. Typically,
It is formed by applying a magnetic paint containing a ferromagnetic fine particle, an organic binder, a pigment, a lubricant, a dispersant, an antistatic agent and the like. The magnetic recording tape of the present invention is characterized in that it is curled not on the magnetic layer side but on the side opposite to the magnetic layer side. That is, the tape is curled so that the center of the tape on the magnetic layer side protrudes. The method of applying the reverse curl is not particularly limited, but it can be performed, for example, by applying a top coat on the magnetic layer. That is, a magnetic layer is provided on a base film, and after curing, the surface of the magnetic layer is coated with a solvent having low dissolving power. According to this top coat, the binder of the magnetic layer is dissolved by the solvent,
The magnetic layer swells to give a curl in the opposite direction. Therefore, it is also possible to adjust the degree of reverse curl depending on the type and amount of the solvent. However, if the dissolving power of the solvent is too large, the magnetic layer will be damaged. Therefore, it is preferable to use a solvent having a low dissolving power and to limit the application amount. As the solvent, an alcohol-based solvent, hexane, or the like is used.

A reverse curl can also be imparted by applying a back coat layer on the side of the base film opposite to the magnetic layer and adjusting the thickness of the back coat layer. By providing a back coat layer, a reverse curl is imparted to the base film by applying a contraction force in a direction opposite to that of the magnetic layer. The back coat layer may be the same as that conventionally used for preventing the tape from curling and flattening, or may have a higher curl imparting ability to the base film. Generally, the curl imparting ability is increased by decreasing the P / B or increasing the thickness of the back coat. Therefore, the degree of reverse curl can be adjusted by the composition and thickness of the back coat. As the back coat layer, a conventional one is used, and a resin alone or a filler such as nonmagnetic powder or carbon may be added.

Further, reverse curl can also be imparted by calendering the back coat side after applying the back coat. By performing this calendering strongly, the amount of reverse curl can be increased. These reverse curling methods can be used alone or in combination. By curling the magnetic recording tape of the present invention on the side opposite to the magnetic layer side, it is possible to prevent the tape from sticking to the case and to improve the durability against tape deformation. The tape with the conventional back coat layer adheres to the cassette half because the center of the tape's back coat layer protrudes, so the tape center of the carbon-based back coat layer adheres to the cassette half when the tape is running. It is thought that it becomes to do. On the other hand, since the tape of the present invention is reversely curled, the adhesive force of the center portion of the back coat layer with the cassette half member is relatively weak even when the tape is running, and it is considered that sticking is prevented. Also, when running the tape, if the tape is curled to the magnetic layer side or flat, the stretching force is applied to both ends of the tape, but if it is curled reversely, the stretching force is applied to the center of the tape. As a result, it is considered that one-sided stretching of the tape is prevented. Furthermore, if the tape is curled toward the magnetic layer, the base film or the back coat layer contacts the case during fast-forward or rewind, increasing dropouts. It is considered that the contact force with the central case is weakened and the dropout is reduced. On the other hand, regarding head touch, on the contrary, since the curl is reversed, the contact with the magnetic head is secured at the center of the tape, that is, the main part, so some curl is caused by the tension applied to the tape during running. It will not be a problem.

[0010] The degree of curl of such a tape is determined by measuring the height of the tape on the flat surface and measuring the height of the top as a percentage as described in Examples described later. The expressed curl ratio is 0.4 to 3.
Preferably, it is within the range of 2%. In general, the degree of such curl is determined by setting the drying conditions of the magnetic layer, the tension of the support film at the time of tape production, the thickness of the magnetic layer and the non-magnetic layer, and the filling ratio of the magnetic powder (content in the paint). Amount) and the like.

[0011]

EXAMPLE On a polyester film having a width of 1/2 inch and a thickness of 14 .mu.m, a magnetic paint having the following composition was applied to a thickness of 3.5.
It was applied to a thickness of μm and cured by heating after the orientation treatment. Vinyl chloride / vinyl acetate copolymer 18 g Polyurethane resin 12 g Dispersant 1 g Abrasive 4 g Lubricant 3 g Carbon 7 g Magnetic powder (BET value 40 m ² / g) 130 g Polyisocyanate 10 g Based on this magnetic tape (Comparative Example 1), The reverse curl was applied by the following three methods to produce the tapes of the examples shown in Table 1.

1) Top coat: After heat-hardening the magnetic layer, 100% conc application of isopropyl alcohol is carried out.
Dry at ℃. 2) Back coat: A back coat paint having the following composition is applied to the opposite side of the magnetic layer of the polyester film,
After drying, a backcoat layer having a thickness of 0.8 μm is formed.

Carbon 70 parts by weight α-Fe ₂ O ₃ 30 parts by weight PVC / vinyl acetate / vinyl alcohol 120 parts by weight (manufactured by Sekisui Chemical Co., Ltd., containing Eslek A-5H, H group) Polyurethane 80 parts by weight (manufactured by Nippon Polyurethane Co., Ltd.) N-3136, containing SO ₃ Na, OH group) Myristic acid 5.0 parts by weight Stearic acid 5.0 parts by weight Diisopropyltin dilaurate 0.3 parts by weight 3) Back coat side calendering: After the back coat is applied, high temperature ( (70-80 ° C.) and then wound and cut.

The above-mentioned treatments 1) to 3) were applied alone or in combination to produce tapes of several examples having different curls. As shown in FIG.
The tape having a width of イ ン チ inch and a width of cm inch was placed on a flat table, and the height of the highest portion of the curled portion from the table was measured with a stereoscopic microscope and expressed as a percentage of the width of the tape. The curl rate in the case of reverse curl (Example) is indicated by plus, and the curl rate in the case of curl toward the magnetic layer side (Comparative Example 1) is indicated by minus.

For comparison, a tape in which a back coat layer was formed to a thickness of 0.4 μm and flattened in the same manner as in 2) above was used as Comparative Example 2. The following evaluations were performed on these tapes. 1) Dropout: After 500 passes with a commercially available VTR, the number of signal loss of 18 dB or more and 15 μsec or more is counted per minute, ◎ indicates no change, and を indicates an increase rate of 10% or less.
100% or less was rated as Δ, and more than 100% was rated as x.

2) Tape deformation (single elongation): Commercial VTR
The tape after 500 passes was visually observed, and the tape having no change was evaluated as ◎, the favorable one was evaluated as ○, and the one with severe elongation was evaluated as ×. 3) Half sticking: Whether or not the tape stuck to the case while the tape was running was visually observed and evaluated. When there was no sticking, it was evaluated as ○, and when sticking was observed, as ×.

The results are shown in Table 1.

[0018]

[Table 1]

[0019]

As is apparent from the above description, according to the present invention, the tape running property and the instability of the head touch due to the curl toward the magnetic layer side of the magnetic recording tape and the flattening by the back coat layer, A highly reliable magnetic recording tape is provided by solving the problem of tape deformation (one-sided stretching) and dropout.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a state in which the height of a curl of a tape is measured.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Table 2 ... Tape 3 ... Magnetic layer side 4 ... Back coat side 5 ... Curl height

Continuing on the front page (72) Inventor Ikuko Yanagiuchi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Hiroyuki Yamada 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (56) References JP-A-57-86128 (JP, A) JP-A-1-192012 (JP, A)

Claims (1)

(57) [Claims] 1. A magnetic recording tape having a magnetic layer on one surface of a tape-shaped non-magnetic base film, wherein the tape is curled so that the center of the tape on the magnetic layer side projects.