JPH0414617A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium which lessens the damaging of tape edges and has excellent durability by providing a magnetic layer on one surface of a nonmagnetic support and a nonmagnetic back coat layer on the other surface and incorporating the compd of prescribed compsn. into the back coat layer. CONSTITUTION:The back coat layer is provided on the surface of the magnetic recording medium, on which surface the magnetic layer is not formed. The perfluoroalkyl compd. is added to this back coat layer, by which the coefft. of friction between the back coat layer and guide pins is lowered. The perfluoroalkyl compd. having a hydroxyl group at the terminal has good compati bility with the binder of the back coat layer and increases the force that the perfluoroalkyl compd. is held in the binder; therefore, the transfer of the perfluoroalkyl compd. to the guide pins, etc., is lessened and the increase in the coefft. of friction of the magnetic recording medium is suppressed. The perfluoroalkyl compd. incorporated into the back coat layer consists of the compsn. of formula I, formula II, where n: 5 to 20 integer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention #4 relates to magnetic recording media, and more specifically relates to reducing the coefficient of friction of a back coat layer.

[Conventional technology]

A magnetic recording medium is provided with a coating called a back coat layer on the surface without a magnetic layer in order to stabilize running and increase light transmission.

In recent video cassette decks, the pin that pulls out the tape from inside the tape cassette when loading the tape, or the kite pin in the tape running system, has been replaced with plastic. In the case of such a deck, there is a problem in that the frictional force between the back layer of the tape and the plastic pin is large. When loading the tape onto a deck or unmeading it, if the coefficient of friction between the back layer and the plastic pin is high, the edges of the tape may break. In particular, in video formats such as VH8 and β, control signals and audio signals are contained in the tape edge portion, and if the tape edge is damaged, problems such as synchronization errors and audio signal output fluctuations occur.

[Problem that the invention seeks to solve]

This invention solves the drawback of conventional video cassette tapes, such as the large coefficient of friction between the back layer and the kite pin, and thereby creates a magnetic recording medium with no tape edge creases. The purpose is to provide

[Rounding method to solve the problem]

In order to solve the above problems, as a result of extensive studies, we decided to provide a back coat layer on the side of the magnetic recording medium that does not have a magnetic layer and add a perfluoroalkyl compound to this back coat layer. Heading 9: The coefficient of friction with the guide bin decreases. In particular, it was found that when a perfluoroalkyl compound having a hydroxyl group at the end was used, the change in friction coefficient over time was small.

A perfluoroalkyl compound having a hydroxyl group at the end has a high compatibility with the binder of the back coat layer, and the perfluoroalkyl compound has a strong ability to be retained in the binder. This is thought to be due to the fact that the transfer to guide pins, etc. is reduced, and an increase in the coefficient of friction of the magnetic recording medium is suppressed.

Perfluoroalkyl compounds having a hydroxyl group at the terminal used in the present invention include those shown by the following structural formula.

CnF2n-tcON(CzH40H)zCnFzn-
1sOzN(CzH40H)z where n is preferably an integer of 5 to 20, particularly preferably an integer of 6 to 9.

Further, the amount of the compound added to the back coat layer is preferably 0.001% or more and 5 ts or less, particularly preferably 0.05% to 1%, based on the binder of the back coat layer. If the amount added is less than 0.001%, no lubricating effect will be observed, while if it is more than 5 inches, blooming will occur and problems will arise in the running properties of the tape.

The binder component used in the back coat layer preferably contains at least a polyurethane resin. This is because it has good compatibility with the perfluoroalkyl compound based on the present invention. Of course, this does not preclude the use of other conventionally used binder components for f.

As additives to the back coat layer, conventionally known carbon black, carbonic acid, barium sulfate, and red iron moiety can be used.

〔Example〕

The final perfect dA will be explained in detail below based on the implementation sequence.

The magnetic materials provided with magnetic layers used in Examples and Comparative Examples were all exploded in the following manner and used again.

Magnetic powder (Con r -FezOa v 5BET
80 parts: 35 doors/I) Vinyl chloride resin (contains -5O3N11, 10〃Average degree of polymerization 550) Polyurethane resin 6〃Carbon black 3.2〃Alumina
3.2 Myristicin a
1.2//Stearic acid n-
Butyl 1.2〃Cyclohexanone
110〃Toluene
110 After dispersing the above composition using a sand grind mill, 4.0 parts of a polyisocyanate compound was added, mixed, and passed through a filter to obtain a care material. This magnetic paint was applied onto a polyester film having a thickness of 14 μm so that the film thickness after drying would be 4.0 μm, subjected to magnetic field orientation treatment, and dried. The surface was smoothed by Rukura and used as a magnetic original fabric.

Example 1 Carbon black 40 parts Charcoal calcium 15 Red iron
5 // 2r cellulose
20〃Polyurethane resin (Tg=0
℃) 15〃C7F15CON(C2H40H)z
o, 04 t/non competing for cyclo
115〃Toluene
115 // The above composition was mixed and dispersed using a sand grind mill, 5 parts of a polyisocyanate compound was added, and after mixing, the mixture was filtered through a filter with a pore size of 5 μm to obtain a back coat paint. Dry this paint on the back side of the magnetic material.
The film was coated to a final film thickness of 1 μm, and after Elk was cut into h-inch widths, a videotape was obtained.

Example 2 In Example 1, 32g of polyurethane resin (Tg = 0C) was used in place of the binder component nido cI tylulose and polyurethane resin (Tg = 0C), and 5 parts of the polyisocyanate compound was replaced with 8 parts of the polyisocyanate compound. Except for changing it to
A videotape was obtained in the same manner as in Example 1.

Example 3 In Example 1, CrFxsCONCCxHaOH)z
Instead, a videotape was obtained in the same manner as in Example 1.

Comparative Example 1 In Example 1, C7F15 C0N (C2H40H
) A videotape was obtained in the same manner as in Example 1 except that Z was not used.

Comparative Example 2 In Example 1, CyFxsCON(CzH40H)z
A videotape was obtained in the same manner as in Example 1, except that the same amount of C7F1sCOOCaFsr'&- was used instead of C7F1sCOOCaFsr'&-.

The output fluctuations of the audio signals of the video tapes obtained in each of the above Examples and Comparative Examples were investigated using the following method, and the results are shown in the table.

Audio signal output variation measurement method: A video tape is inserted into a cassette, and after running for 5 minutes from the beginning of the tape, video signals are recorded for 20 seconds each in the order of black picture, white picture, and black picture, and during this time an 8 kHz sine wave is to the audio track. The recording start position of the first black 1m is set as the playback start position, and it stops once at the switching position from white to black, starts playback again, feeds the tape until the end of black, and then plays. Rewind to the starting position. At the stop position, the tape is unloaded and loaded into the magnetic head cylinder. After repeating this operation 25 times, load
Examine the output fluctuation of the audio signal at the unloading position.

〔Effect of the invention〕

As explained above, by adding a perfluoroalkyl compound having a hydroxyl group at the end to the backcoat layer of a magnetic recording medium having a backcoat layer, the coefficient of friction of the backcoat layer is reduced and the tape edge remains stable even after repeated use. It is clear that a magnetic recording medium with less damage and excellent durability can be obtained.

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer on one side of a non-magnetic support and a non-magnetic back coat layer on the other side, the back coat layer contains ▲mathematical formulas, chemical formulas, tables, etc.▼ ▲ A magnetic recording medium characterized by containing mathematical formulas, chemical formulas, tables, etc. ▼ (n: an integer from 5 to 20).