JPH0449520A - Magnetic tape - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic tape having a ferromagnetic metal thin film as a magnetic recording layer, and particularly to a magnetic tape most suitable for digital video tape recorders and high-definition video tape recorders.

2. Description of the Related Art Conventionally, attempts have been made to improve the corrosion resistance, still durability, and running durability of magnetic tapes having a magnetic recording layer made of a ferromagnetic metal thin film using various methods. for example,
A method of providing a lubricant layer such as carboxylic acid or phosphoric acid on a ferromagnetic metal thin film, or a method of providing a non-magnetic metal protective film on the metal thin film, or a method of providing a silicon oxide layer on the metal thin film.
For example, a method of providing a protective film of oxide such as n.

Problems to be Solved by the Invention However, the conventional magnetic tape protective film described above still has the problem that running durability and still durability have not been sufficiently improved.Recently, diamond-like carbon films have been used to protect thin-film magnetic tapes. The use of magnetic tape as a film has also been considered, and this technology has significantly improved the still durability, running durability, corrosion resistance, etc. of magnetic tapes.

By using a diamond-like carbon film as a protective film, the reliability of the magnetic recording layer side was significantly improved, but the other side, the back coat side, was not improved, so the balance of the magnetic tape's performance was affected. This made it necessary to improve the back coat layer.

The present invention solves these conventional problems, and provides a metal thin film type magnetic tape in which the friction coefficient of the back coat layer is lowered and the durability and reliability of the back coat layer is improved. The purpose is to

Means for Solving the Problems In order to achieve the above object, the present invention forms a ferromagnetic metal thin film on one side of a non-magnetic substrate, and a plasma polymerized film of hydrocarbon is formed on the ferromagnetic metal thin film on one side of the non-magnetic substrate. A diamond-like carbon film and a lubricant layer are provided in this order, a back coat layer is provided on the other surface of the nonmagnetic substrate, and a plasma polymerized film of hydrocarbon containing fluorine atoms is preferably applied to the surface of the non-magnetic substrate. It is provided with a thickness of 5 Å to 15 Å, more preferably 5 Å to 15 Å, and reduces the friction coefficient of the back coat layer from the conventional 0.20 to 0.15 to 0.16, and improves the scratch resistance. This further improves the running durability of the magnetic tape.

Specifically, hydrocarbons containing fluorine atoms include C
F4. CH2F2. Gases such as C2H6 and CC4Fe can be used, or those that are liquid at room temperature can be used by a reduced pressure introduction method or a heated reduced pressure introduction method. In order to form a plasma polymerized film, plasma is confined within a discharge tube,
This is made possible by exposing the surface of the back coat layer of the magnetic tape into this plasma.

The pressure inside the plasma discharge tube ranges from 0.05 Torr to 0.0 Torr.
It is controlled within a range of 2 Torr.

The plasma polymerized film containing fluorine atoms formed on the surface of this back coat layer will cause the lubricant present on the outer surface of the magnetic recording layer to be absorbed by the bank coat layer if the magnetic tape is left on a reel for a long period of time. It has the role of preventing magnetic tape from moving to the side, and is another means of improving the running durability and still durability of magnetic tape. The ratio of lubricant present on the surface provided with the magnetic recording layer and the surface provided with the backcoat layer is usually about 6:4, but plasma polymerization containing fluorine atoms on the surface of the backcoat layer When a film is formed, the ratio will be about 8:2.

Effect Therefore, according to the present invention, the friction coefficient of the back coat layer is reduced and the scratch resistance is improved, and even after long-term storage, more than a certain percentage of the lubricant present on the magnetic recording layer side migrates to the back coat layer. As a result, the running durability and still durability of the magnetic tape are further improved.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

In the figure, ■ is polyethylene tereph clay I ~ (P
ET) is a non-magnetic substrate made of a film or the like, on the negative side of which a ferromagnetic metal thin film 2, a hydrocarbon plasma polymerized film 3, and a diamond-like carbon film 4 obtained from hydrocarbon and argon are formed. A lubricant layer 5 is provided on the outer surface to improve the slippage of the magnetic tape. Also 6
is a back coat layer formed on the other surface of the nonmagnetic substrate 1, and a plasma polymerized film 7 of fluorine-containing hydrocarbon, which is a feature of the present invention, is formed on the outer surface of the back coat layer.

In the above configuration, the maximum surface roughness is 70 Å to 100 Å, the average roughness at the center line is 30 Å to 50 Å, and the density of the mountain-like protrusions is 10 5 to 10 I0/mr4.
A ferromagnetic metal thin film 2 made of Co (80) - Ni (20) is deposited on the surface of a non-magnetic substrate 1 made of a PET film or the like with a width of 500 mm while introducing oxygen by oblique vacuum evaporation. After forming the ferromagnetic metal thin film 2 to a thickness of 10 mm, a plasma polymerized film 3 is formed to a thickness of 10 mm using propane gas as a raw material under the conditions of a vacuum degree of Q, 1 Torr, a frequency of 15 kHz, and a voltage of 500 μm. do. Furthermore, on the plasma polymerized film 3, a mixed gas pressure of 0 is applied using hydrocarbons such as argon and propane gas as raw materials.
．． 3Torr, frequency 20kHz, voltage 2000
V, plasma C under the condition of DC voltage 1000 volts
A diamond-like carbon film 4 is formed to a thickness of 100 mm using the VD method. Thereafter, a back coat layer 6 with a thickness of 0.5 μm having surface characteristics of a maximum surface roughness of 0.2 μm and an average roughness at the center line of 0.08 μm is coated on the non-magnetic substrate 1 by a coating method using urethane, nitrocellulose, and carbon black. Form on the other side.

Next, on this back coat layer 6, a gas containing fluorine atoms such as C2F4 is used as a raw material, and the pressure inside the discharge tube is 0.
1Torr, gas current 20SCCM (Standard)
dC (:/min, ) Frequency 15kHz, Voltage 50
A plasma-polymerized film 7 of fluorine-containing hydrocarbon is formed by running this discharge tube with the surface of the back coat layer 6 exposed while generating plasma discharge under the condition of 0.0 mm.

FIG. 2 shows the main parts of an apparatus for forming a plasma polymerized film 7 of fluorine-containing hydrocarbon. In the figure, 6a is a back coat surface, and 8 is a discharge tube.

Next, magnetic tapes in which the thickness of the plasma polymerized film 7 of fluorine-containing hydrocarbon was 5, 20, 50, and 200, respectively, were produced as samples 1, 2, and 3.4. Also, C-C is used instead of Cz F b as the raw material gas.

Sample 5 is a magnetic tape on which a fluorine-containing plasma polymerized film 7 with a thickness of 10 people was provided using Fe, and a fluorine-containing plasma polymerized film 7 with a thickness of 15 people was prepared using CF as a source gas instead of CzFb. Sample 6 was a magnetic tape provided with plasma-polymerized film 7 containing plasma. Furthermore, for comparison, a sample of a magnetic tape without a fluorine-containing plasma polymerized film provided on the back coat layer 6 was prepared as sample 7.8.

A lubricant layer 5 is formed by applying fluorine-containing carboxylic acid to a thickness of 20 mm on the diamond-like carbon film 4 of the sample prepared as described above using a known coating method.

Thereafter, the tape is cut into Bnwn widths using a slitter to create a magnetic tape. Using the magnetic tape prototyped in this way, the friction coefficient of the back coat layer 6 was measured with a friction coefficient measuring device, and the amount of lubricant transferred to the back coat layer 6 side after long-term storage was measured. Furthermore, using a video tape recorder for 8-hour recording, a running durability test was conducted on the above-mentioned sample made for 120 minutes, and the number of passes that could be run before the output decreased by 3 dB compared to before the test was measured. The results of these measurements are shown in the table below.

(Margins below) In the table, the amount of lubricant transferred to the surface of the back coat layer 6 is a percentage of the total amount of lubricant used when manufacturing the magnetic tape. All of them exist on the surface on the magnetic recording layer 2 side.

As is clear from the above examples and the measurement results shown in the table, by providing the fluorine-containing plasma polymerized film 7 having a film thickness of 5 Å to 50 on the surface of the back coat layer 6, the friction coefficient of the back coat layer 6 side can be reduced. is reduced, and the ratio of the lubricant layer 5 existing on the diamond-like carbon film 4 can be kept stable at about 80%, and therefore reliability of 500 passes or more can be obtained in terms of running durability. .

In the above embodiment, a magnetic tape on which a ferromagnetic metal made of Co-Ni was deposited was described, but other magnetic tapes using a ferromagnetic metal thin film material such as CaO-based or co-Cr-based as the ferromagnetic metal thin film 2 were described. Similar effects can be obtained with magnetic tapes using PEN (polyethylene naphthalene 1.) or polyindo-based materials in addition to PET film as the tape and nonmagnetic substrate 1.

Effects of the Invention As described above, according to the magnetic tape of the present invention, by providing a plasma polymerized film of fluorine-containing hydrocarbon on the surface of the back coat layer, the scratch resistance of the back coat layer is improved.
Moreover, there is an effect that the durability of the running surface can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a magnetic tape according to an embodiment of the present invention, and FIG. 2 is a schematic front view of main parts of a magnetic tape manufacturing apparatus according to the same embodiment. 1...Nonmagnetic substrate, 2...Ferromagnetic metal thin film, 3...Plasma polymerized film, 4...
Diamond-like carbon film, 5...Lubricant layer, 6.
... Back coat layer, 7 ... Plasma polymerized film of fluorine-containing hydrocarbon. Name of agent: Patent attorney Shigetaka Kurino

Claims (2)

[Claims] (1) A ferromagnetic metal thin film, a plasma-polymerized hydrocarbon film, a diamond-like carbon film obtained from hydrocarbon and argon, and a lubricant layer are provided in this order on one surface of the non-magnetic substrate, and A magnetic tape that has a back coat layer and a fluorine-containing hydrocarbon plasma polymerized film on its surface in this order. (2) The thickness of the plasma polymerized film of fluorine-containing hydrocarbon is
The magnetic tape according to claim 1, which has a thickness of 5 Å to 50 Å.