JPH0680525B2 - Magnetic recording tape - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording tape, in particular, a magnetic recording tape for a VTR, which is an improved magnetic recording tape capable of recording for a long time. Pertain to.

[Prior art]

As a magnetic recording tape, conventionally, on at least one side of the surface of a biaxially oriented polyethylene terephthalate film,
A magnetic recording tape having a magnetic layer mainly composed of γ-iron oxide and a polymer binder is used. However, these conventional magnetic recording tapes have the following drawbacks. (1) The coercive force of the magnetic recording tape is small.

(2) When used as a magnetic recording tape, if the tape thickness is made thin, the running and durability of the magnetic recording tape may be poor, and the recording may drop out (drop out), so there is a limit to the amount of tape that can be wound in a certain size cassette. Yes Recording cannot be extended.

For this reason, in particular, with the recent miniaturization of household VTRs, the tape width has been reduced from 12.7 mm to 8 mm, and the cassette has also been miniaturized, but in response to this, there is no technology to increase the recording capacity as a thin tape, There was nothing that I could satisfy as a recording tape.

[Object of the Invention]

The object of the present invention is to eliminate the above-mentioned drawbacks, the coercive force of the magnetic recording tape is large, the recording does not drop out, and even if it is thin, the magnetic recording tape is very good in running property and durability. It is intended to provide tape.

[Structure of Invention]

The present invention uses a film of biaxially oriented polyethylene-2,6-naphthalenedicarboxylate having a specific mechanical property and surface structure as a support, and a magnetic layer comprising a metal thin film on one of the surfaces of the support. The magnetic recording tape is formed by applying a coating film of an organic polymer containing a lubricant to the other surface of the support on the opposite side where the magnetic metal thin film is not formed.

The film as the support for the magnetic recording tape of the present invention has a stress at 5% elongation in the length direction (hereinafter referred to as F-5 value) of 18 kg / m.
m ² or more, Young's modulus in the longitudinal direction is 800 kg / mm ² or more, and Young's modulus in the width direction is 500 kg / mm ² or more, and the surface roughness based on the measurement method described later is 0.001 μm.
It is a biaxially oriented polyethylene-2,6-naphthalene dicarboxylate characterized in that it is larger than m and 0.005 μm or less. When this is required, the support of the magnetic recording tape of the present invention has a high Young's modulus, a small dimensional change due to stress, and an extremely smooth surface. Then, by using polyethylene-2,6-naphthalenedicarboxylate, which has excellent heat resistance, as a support film, a magnetic metal thin film is formed on this surface to enable high-density and high-sensitivity recording / reproduction, and By coating a coating film containing a lubricant on another surface, a magnetic recording tape having no problem in distortion and running property during use was obtained. In addition to such a structure, the thickness of the tape as a whole can be made as thin as 3 to 10 μm,
The length of the tape that can be stored in the cassette unit can be increased, the recording time can be significantly extended, and the recording distortion and skew during recording and playback due to the high Young's modulus are dramatically improved. .

To further explain the present invention, the Young's modulus in the lengthwise direction of the support film in the present invention needs to be 800 kg / mm ² or more, and 800 to 1600 kg.
/ mm ² is preferable, and particularly 850 to 1600 kg / mm ² is preferable. If the Young's modulus exceeds 1600 kg / mm ² , the tape is likely to tear, which is not preferable. In addition, the Young's modulus in the width direction must be 500 kg / mm ² or more, and 500-700 kg / mm ²
Is preferred. If the Young's modulus in the width direction is less than 500 kg / mm ² , repeated running of the tape tends to cause wrinkles and scratches in the width direction of the tape. If this value exceeds 700 kg / mm ² , a biaxially oriented polyethylene-2,6-naphthalene dicarboxylate film that simultaneously satisfies Young's modulus in the longitudinal direction of 1000 kg / mm ² or more can be easily or normally stretched. It is no good because it is no longer possible to obtain it.

In the present invention, the F-5 value in the lengthwise direction of the support film needs to be 18 kg / mm ² or more, and more preferably 20 kg / mm ² or more. When the F-5 value is less than 18 kg / mm ² , repeated running of the tape tends to cause wrinkles and scratches in the width direction of the tape.

The surface roughness (Ra) of the surface on which the magnetic metal thin film of the support film in the present invention is formed is larger than 0.001 μm.
0.005 μm or less is required. If this Ra is 0.001 μm or less, the surface is too smooth and tape squeaking occurs during running,
On the other hand, if it is more than 0.005 μm, the coercive force is lowered and the dropout is increased, which is not preferable.

The surface roughness (Ra) is formed by containing inert fine particles in the support film, for example, 0.1% by weight or less of inorganic fine particles containing elements of Group IIA, IIB, IVA and IVB of the Periodic Table of Elements. Alternatively, it may be formed by another surface treatment. At that time, the average particle diameter and content of the inert fine particles may be selected in the range where Ra is more than 0.001 μm and 0.005 μm or less.

As a method of biaxial orientation, a general roll or a stenter may be stretched simultaneously in the longitudinal and transverse directions, or may be stretched in the longitudinal and transverse directions sequentially. For example, polyethylene-2,6-naphthalenedicarboxylate pellets are dried at a temperature of 150 to 200 ° C, fed into an extruder to melt, and after removing foreign matter with a filter, extruded on a rotating drum cooled with a die. Then, the unstretched film is obtained by adhering it to the rotating drum with an electrostatic wire, cooling and solidifying. At this time, passing through a filter is necessary to obtain a film for making a magnetic recording tape, and it is desirable to use a filter opening having a size of less than 10 μm. The filtration may be carried out during the polymerization step when making pellets, but it is desirable to carry out the filtration immediately before the step of obtaining an unstretched film. If the filter is insufficient, protrusions with three or more interference fringes measured by the multiple interference method will be formed on the surface of the biaxially oriented film, which will cause deterioration of the dropout. The unstretched film thus obtained is uniaxially (longitudinal or transverse) 100
It can be produced by stretching at a temperature of ˜180 ° C. at a magnification of 4.5 to 7.0 times, and then at a temperature of 110 to 210 ° C. at a ratio of 3.0 to 6.0 times at a right angle to the stretching direction. In this case, the area magnification is preferably 13 to 30 times. Further, the biaxially stretched film is preferably heat set at 180 to 255 ° C. The heat setting time is, for example, 1 to 60 seconds.

As the magnetic metal forming the tape of the present invention, cobalt,
It is preferable to use iron, nickel or alloys thereof, or alloys thereof with chromium or tungsten.

As a method for forming the metal thin film, a wet vacuum deposition method using electroless plating or electrolytic plating, and a dry method using sputtering or ion plating can be used. In particular, the vacuum deposition method is the most preferable forming method because it has a very high protrusion rate and can obtain a high coercive force. Thin film is 300
Approximately 1500 nm (0.3 to 1.5 μm) is the standard for the temporary thickness.

Next, a coating film of an organic polymer containing solid lubricant particles is applied to the surface of the support on the side where the magnetic thin film is not formed in order to maintain the running property as a tape. Examples of the solid lubricant particles include aluminum acrylate, molybdenum, fine silica and fluororesin. The solid lubricant particles are an organic polymer having an adhesive force to the support film (for example, a polyether containing glycidyl ether of polyoxyalkylene glycol, naphthalene-2,6-dicarboxylic acid and a part of the aliphatic dicarboxylic acid are fatty acids. Dispersion in a solution or emulsion of a copolyester having an acid component substituted with a group dicarboxylic acid, etc., and applying this on the surface of the support film gives a magnetic recording tape with slipperiness and improved running property. To be The lubricant layer may be as thin as 1 μm or less and about 50 to 500 nm. The surface roughness (Ra) of the lubricant layer is larger than the surface roughness of the surface formed by the magnetic thin film.
It is 0.015 μm.

The tape thickness in the present invention is 3 to 10 μm.
If it is less than 3 μm, the tape has poor running property and durability,
On the other hand, if the thickness is more than 10 μm, the purpose of long-time recording cannot be achieved.

〔The invention's effect〕

In the present invention, a magnetic metal thin film is formed on one side of the surface of a biaxially oriented polyethylene-2,6-naphthalene dicarboxylate film having a surface roughness of more than 0.001 μm and 0.005 μm or less, and a lubricant is dispersed on the opposite side. It has a large coercive force as a magnetic recording tape because it is formed of a coating film made of organic polymer, and the stress at the time of 5% elongation of the support film is 18 kg / mm ² or more, Young's modulus is 800 kg / mm ² The biaxially oriented polyethylene-2,6-naphthandicarboxylate film having a Young's modulus of 500 kg / mm ² or more in the width direction makes the tape runnable and durable even when the magnetic recording tape has a thickness of 3 to 10 μm. The magnetic recording tape can be thinned and the recording can be performed for a long time even in the case of the beta type or the 8 mm type cassette of the VTR for home use.

〔Example〕

 Next, embodiments of the present invention will be described based on examples.

Incidentally, various physical properties and characteristics in the present invention are measured and defined as follows.

(1) Young's modulus film is cut into a sample width of 10 mm and a length of 15 cm, and the space between checks is 100 mm.
mm, and a tensile speed of 10 mm / min and a chart speed of 500 mm / min were pulled by an Instron type universal tensile tester. The Young's modulus was calculated from the tangent line of the rising portion of the obtained load-elongation curve.

(2) F-5 value When measuring the above Young's modulus, pulling speed 200 mm / min, chart speed
It was calculated from the stress at 5% tension when 100 mm / min was set.

(3) Film surface roughness (Ra) It was measured according to JIS B 0601. Using a stylus type surface roughness meter (SURFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd., a chart (film surface roughness curve) was placed under the conditions of a needle radius of 2 μm and a load of 0.07 g. A portion of the measurement length L is extracted from the film surface roughness curve in the direction of the center line, and the center line of the extracted portion is taken as the X axis and the longitudinal magnification direction is taken as the Y axis, and the roughness curve is taken as Y = f (x). When expressed by, the value (Ra: μm) given by the following equation is defined as the film surface roughness.

In the present invention, 8 pieces were measured with a reference length of 0.25 mm, and Ra was expressed as an average value of 5 pieces excluding 3 pieces having the larger values.

(4) Coercive force Magnetic characteristics such as magnetic recording were measured with a sample vibrating magnetometer, and the coercive force was determined from the hysteresis curve.

When the coercive force is 500 Oe (Elsted) or higher, the coercive force:
Good, less than 500 Oe was determined as coercive force: poor.

(5) Drop out The magnetic tape is run for 100 hours continuously with a home video tape recorder (helical scan). 40 ℃ the tape
After keeping it for 48 hours, record the tape returned to room temperature.
It was regenerated and a signal output of 50% or less was counted using a drop-out counter.

In addition, the measurement is performed for 10 rolls with 1/2 inch width and 780 m as one roll. Drop out when the number of rolls per roll is less than 2: good, drop out when 2 rolls or more: It was judged to be defective.

(6) Running performance of magnetic recording tape After being set on a home video tape recorder (Helical scan), the running state was checked by repeating running and stopping for 100 hours, and the output was measured. When all the following items are satisfied in this run, the runnability:
Good, and if not, the running property was determined to be poor.

 The end of the tape does not break or wakame.

 No squeaking of the tape while driving.

 The tape does not tear or break.

(7) Curl A 500 x 500 mm square sample was cut out from the magnetic recording tape stock, and the state of the curl was classified into the following five levels.
And E were determined to be curl: good, and A, B and C were determined to be curl: bad.

A: It has a completely cylindrical shape.

B: A state similar to A, but with a part of the cylinder open.

The opening of C: B is wide, but the longest part of the side can be the diameter of the circle.

D: C has a wider opening, and the longest part of the side cannot be the diameter of the circle.

E: No curl or almost no curl.

Example 1, Comparative Examples 1 to 4 A polyethylene-2,6-naphthalenedicarboxylate pellet having an intrinsic viscosity of 0.60 and containing 0.05% by weight of silica having an average particle diameter of 0.15 μm was dried at 170 ° C. for 4 hours. This polymer was melt extruded according to a conventional method to give a thickness of 108 μm.
Of unstretched film of 4.5 times in the longitudinal direction at 120 ℃,
Biaxial stretching is carried out 4.0 times in the transverse direction at 130 ° C, and further 24 times.
Heat setting was performed at 5 ° C. for 30 seconds to prepare a biaxially stretched film having a thickness of 6 μm.

The biaxially stretched film was applied with a coating solution having the following composition on one side of the film surface before heat setting.

Composition of coating liquid applied to the film surface: Aluminum acrylate (Asada Chemical K.K.P-3 ) 2 wt% solution
...... 12 kg Polyethylene glycol (Molecular weight 19,000 manufactured by NOF CORPORATION)
2wt% solution …… 5kg Polyethylene glycol diglycidyl ether (Nagase
Industrial NEROIO ) 2wt% solution …… 2kg Polyoxyethylene nonylphenyl ether 2wt% solution
Liquid: 1 kg coating amount is about 2.2 g / m in weight.²And as solid content is about
0.0126g / m²Is.

Remaining surface of this polyethylene-2,6-naphthalenedicarboxylate film (surface not coated with the above coating liquid)
By electron beam evaporation method (oblique evaporation with a minimum incident angle of 50 °),
Depositing a Co-N ₁ layer thickness 1000Å (Co / N ₁ -75/25 weight ratio) to obtain a raw magnetic recording tape.

As shown in Table 1, the characteristics of the magnetic recording tape manufactured by slitting this raw fabric are as follows: coercive force, drop out,
The runnability was good. However, if the type of polymer, surface roughness, mechanical properties, etc. of the support film are outside the scope of the present invention (Comparative Examples 1 to 4), coercive force, drop-out, running and A base film for a magnetic recording medium having good properties has not been obtained.

Examples 2 to 4, Comparative Examples 5 to 10 Biaxially oriented film having various physical properties of the film by changing the silica content and film forming conditions using the same silica and polyethylene 2,6 naphthalene dicarboxylate as in Example 1 Made. Table 2 shows the characteristics of these films as magnetic recording media. As can be seen from Table 2, when the physical properties of the film are within the range of the present invention (Examples 2 to 4), the magnetic tape has good coercive force, drop-out, running property, and good curl. was gotten. However, when the physical properties of the film are outside the scope of the present invention (Comparative Examples 5 to 5)
In 9), a magnetic tape with good coercive force, drop-out, and runnability could not be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeyoshi Shimoda 3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture Teijin Ltd. Plastics Research Institute (72) Junji Kobayashi 3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture No. Teijin Ltd. Plastics Laboratory (56) References JP-A-59-203230 (JP, A) JP-A-58-155939 (JP, A)

Claims (3)

[Claims] 1. A 5% elongation stress in the length direction is 18 kg / mm ² or more, a Young's modulus in the length direction is 800 kg / mm ² or more, and a Young's modulus in the width direction is 500 kg / mm ² or more, and Surface roughness
A support comprising a biaxially oriented polyethylene-2,6-naphthalenedicarboxylate film having a thickness of more than 0.001 μm and not more than 0.005 μm, a magnetic metal thin film formed on one surface of the support, and the support A magnetic recording tape comprising a coating film made of an organic polymer containing solid lubricant particles, which is applied to the other surface, and having a tape thickness of 3 to 10 μm. 2. The magnetic metal thin film is made of cobalt, iron, nickel, an alloy thereof, or an alloy of these with chromium or tungsten.
The magnetic recording tape according to the item. 3. A polyethylene-2,6-naphthalenedicarboxylate film having a 5% elongation stress in the longitudinal direction of 20 kg / m.
The magnetic recording tape according to claim 1, wherein the magnetic recording tape has a m ² or more and a Young's modulus in the longitudinal direction of 850 kg / mm ² or more.