JPS5938925A - Magnetic recording material - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape which is thin, has excellent running characteristics, and is free from distortion in recording, by using a film which is a biaxially-oriented polyester film having a specific repetitive unit as specific mol% or above and has specific property values as a substrate. CONSTITUTION:The ethylene bis alpha,beta-(2-chlorophenoxy)ethane 4,4'-dicarboxylate which is polyester contg. >=85mol% the repetitive unit expressed by the formula (X is F, Cl, Br or C1-3 alkyl, l, m are respectively 1-2, p is 2-6, q is 2-4) wherein more particularly l=m=1, p=q=2 is biaxially oriented to form a film of which the Young's modulus in at least one direction is >=550kg/cm<2>, the thermal shrinkage in the Young's modulus direction is <=4%, the intrinsic viscosity is 0.3-1.4, the refractive index ratio in the thickness direction of the film is 0.935-0.975 and the density index is 0.01-0.09 as a substrate. A magnetic layer is formed on such substrate. The magnetic tape which has good running characteristics and is entirely free from distortion in recording is thus obtd. even from a thin tape of about 0.6mu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording materials. Conventionally, as a magnetic recording material, a magnetic tape based on a biaxially oriented polyethylene terephthalate (hereinafter abbreviated as PET) film is often used. However, recording density has increased and recording time has increased.

With the miniaturization of magnetic tapes, magnetic tapes have good running characteristics even though they are thin, but they do not cause distortion in recording.

There is a demand for magnetic tape that does not have the same characteristics. In response to these demands, various improvements have been made to the base material PET film, but as long as the material is PET, if it is thinned to a certain thickness, the running characteristics of the magnetic tape will be impaired. ,
There was a drawback that distortion of the recording occurred.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a magnetic recording material that has good running characteristics as a magnetic tape even when exposed to N, and does not cause recording distortion.

The present invention has the following configuration to achieve the above object.

That is, the repeating unit represented by the following general formula is 85
Biaxially oriented IJ ester film ρ with a Young's modulus in at least one direction of 550 kg/2 plates and a heat shrinkage rate of 4 inches or less in the upper direction. This is a magnetic recording material characterized by the following.

or a halogen group or an alkyl group having 1 to 6 carbon atoms selected from fluorine, chlorine, and bromine.

1 and m are each an integer of 1 to 2, p is an integer of 2 to 6, q
is an integer from 2 to 4.

The polyester constituting the base film of the present invention is a polyester containing 85 moles or more of repeating units represented by the following general formula (A).

If the number of repeating units represented by the general formula (A) is less than 85 moles, the running characteristics as an 8-magnetic tape will deteriorate and recording distortion will occur, which is not preferable.

Here, X in the general formula ('A) is a halogen group selected from fluorine, chlorine, or bromine, or an alkyl group having 1 to 2 carbon atoms, which has particularly good running characteristics as a magnetic tape and has distortion in recording. is especially small for chlorine and bromine, especially chlorine. The position of X in the aromatic ring is not particularly limited, but a position ortho to the oxygen adjacent to the aromatic ring is particularly preferred from the viewpoint of running characteristics as a magnetic tape.

Furthermore, *ta'' is an integer of 1 to 2, respectively.

Particularly preferred from the viewpoint of running characteristics as a magnetic tape and recording distortion is l=1. m=1. p is an integer of 2 to 6, and q is an integer of 2 to 4; however, p = 2+ q is particularly preferable in terms of running characteristics as a magnetic tape and recording distortion.
=2.

In other words, the running characteristics of the magnetic tape are particularly good and the recording distortion is particularly small when polyethylene bis α, β-(2-chlorophenoxy) ethane 4,4'-dicarboxylate is used as the polyester. It is.

The present invention uses a film made of polyester as described above as a base material, but the film must satisfy the following conditions.

(1) It must be a biaxially oriented film. A non-oriented film or a uniaxially oriented film is not preferred because a magnetic tape with good running characteristics cannot be obtained.

(2) If the Young's modulus in at least one direction, preferably in two directions orthogonal to each other, is 550 kg/mm 2 or more, the lighthouse is not preferable because the running characteristics as a magnetic tape will be poor.

(3) The thermal shrinkage rate in the direction having the Young's modulus in (2) above is 4 inches, preferably 2 inches or less. It is not preferable that the thermal shrinkage rate is greater than 4 degrees because the distortion of recording becomes large.

Further, in one aspect of the present invention, it is particularly preferable that the base film satisfies the following conditions.

(1) Intrinsic viscosity is 0.3 to 1.4. Preferably 04
- Must be in the range of 1.6. If the viscosity is lower than the above range, troubles such as the magnetic tape tearing during running will occur, resulting in poor running characteristics.On the other hand, if the viscosity is higher than the above range, recording will likely be distorted.

(2) The refractive index ratio in the thickness direction of the film is 0965~
0.975. Preferably it is in the range of 0.940 to 0.970. If the refractive index ratio is smaller than the above range, the magnetic tape is likely to tear or crease during running, resulting in poor running characteristics.On the other hand, if the refractive index ratio is too low, Also, the running characteristics of the magnetic tape may become poor.

(3) The density index of the film is OO1 to 0.09,
Preferably, it is 0.02 to 0.08. If the density index is smaller than the above range, the recording will be easily distorted. Conversely, if the density index is larger than the above range, problems such as the magnetic tape tearing during running may occur. It is easy to use, and it is easy to cause poor running characteristics.

Although the thickness of the film in the present invention is not particularly limited, it is preferably 12μ or less, preferably 8μ or less.

Next, as for the magnetic layer of the magnetic recording material of the present invention.

There is no particular limitation, and any layer using a known magnetic material may be used. Specifically, for example, γ-Fe20.・It is a layer using iron oxide such as CrO, Go''V-p, metals such as Fe, Co, Ni, or alloys thereof, but especially a thin film type magnetic layer that does not substantially contain organic polymers. is preferred.

Next, the manufacturing method of the magnetic recording material of the present invention will be explained. To simplify the explanation, polyesters such as polyethylene bis a, β-(2-chloropheno, xy) ethane 4,4
An explanation will be given by taking as an example a case in which '-dicarboxylate is used.

Mass, pellets of polyethylene bis α, β-(2-chlorophenoxy) ethane 4,4'-dicarboxylate are fed to an extruder, and a slit-shaped die (T-die or circular die) is fed at 270-310'a. Melt extrusion from 20
Cool to ~90°C to solidify to form an unstretched film. In this case, electrostatic casting is effective for uniformly quenching. Next, this unstretched film is biaxially stretched and oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used, but the sequential biaxial stretching method is preferable from the viewpoint of running characteristics as a magnetic tape and recording distortion. In case of sequential biaxial stretching method.

Although it is common to stretch in the longitudinal direction and then in the width direction, this order may be reversed.

The conditions for biaxial stretching are not necessarily constant depending on the stretching method, the viscosity of the polymer, etc. 9 Usually, the conditions are in the longitudinal direction.

105°C to 160°C in both width directions, preferably 11
At a temperature in the range of 5°0 to 125°0, the stretching ratio is 1.5 to 5.0 times, preferably 2.0 to 4.0 times. Stretching speed is 1 x 10~7 x 10%//')
- range is appropriate. Furthermore, a method of further stretching the biaxially stretched film in at least one direction is effective in further improving the running characteristics of the magnetic tape. In this case, the stretching conditions are as follows.

The stretching temperature is in the range of 110°C to 190°C.

The stretching ratio is 1.1 to 6.5 times in both the longitudinal and width directions.

Preferably it is 1.4 to 3.0 times (however, of course, when further stretching is performed only in the longitudinal direction, for example.

The stretching ratio in the width direction is 1).

Next, if necessary, this stretched film can be heat treated. In this case, the heat treatment conditions are as follows:
'c~260°C2 preferably 220°C~245°C
for 1 hour 0.5-120 seconds, preferably 1.0-60
Seconds is appropriate.

A magnetic layer is formed on the thus obtained polyester film for base material. Various known methods can be used for its formation. For example, γ-Fe20.・"r201 +
Co-doped iron oxide, Fe, Ni, Co
A method in which a solution of powders of metals and their alloys, such as, dissolved in a solvent together with a suitable polymeric binder, is applied, or a method in which a specified metal is directly formed by sputtering, vapor deposition, ion blating, etc. But that's fine. Also, before forming the above magnetic layer,
The polyester film serving as the base material may be subjected to a known corona discharge treatment (in air, nitrogen, carbon dioxide, etc.), or may be treated with other types for the purpose of imparting adhesion and surface lubricity. These polymers may be laminated or coated with other types of compositions.

Note that although the present invention is characterized by the above-mentioned magnetic recording material, it may contain other copolymer components as long as it is less than 15 molar proportion of the polyester constituent units of the film serving as the base material of the present invention. good. In this case, the copolymerization components include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid@
Dicarboxylic acids such as 4.4'-biphenyldicarboxylic acid, bis α, β-(phenoxy)ethane 4.4′-dicarboxylic acid.

Alternatively, dioxy compounds such as ° °-' 1,4-cyclohexane dimetatool are common.

Further, the polyester film type polymer serving as the base material of the present invention may be blended or may be added in a normal amount.

The characteristic values of the present invention are based on the following measurement method and evaluation criteria.

(1) Young's modulus of film: Tested at 25°C and 86°C using an Instron type tensile tester according to the method specified in RXS-Z-1702.
The measurement was performed at 5 RH.

(2) Heat shrinkage rate of film Cut a sample film to a width of 10 mm and a length of 250 mm, and insert two marked lines at an interval of about 200 mm.

Accurately measure the distance (this is defined as Amm).

150℃ with a load of 30g applied to the tip of this sample.
After leaving it in a hot air oven for 60 minutes, measure the distance between the marked lines and call it Brnm), 100x
(A-B)/A was defined as the heat shrinkage rate.

(3) Intrinsic viscosity of film This was determined from the relative viscosity measured in 0-chlorophenol at 25°C.

(4) Thickness direction refractive index and refractive index ratio Using an Atsube refractometer with sodium D line (wavelength 589 nm) as a light source, the thickness direction refractive index (referred to as A) of the knee'' triaxially oriented film and the melting After pressing, the refractive index (referred to as B) in the thickness direction of a non-oriented (amorphous) film made by rapidly cooling it in water at 10 ° C. was measured,
A/B was defined as the refractive index ratio in the thickness direction. Methylene iodide was used as the mounting solution, and the measurement was performed at 25"C165%RH.

(5) Film density and density index carbon tetrachloride and n
- Using a density gradient tube made of hebutane, the density (rho) of a biaxially oriented film and the density (rho) of an unoriented (amorphous) film made by melt-pressing and then quenching into 10°C water are determined. ) and ρ−ρ. This was taken as the density index. Note that the measurements were performed at 25°C.

(6) Running characteristics of magnetic tape A sample magnetic tape was repeatedly started and stopped using a commercially available home video tape recorder to check its running condition, and it was found to run smoothly without edge bending (wakame-like) or tape tearing. If this occurred, it was determined that the running characteristics were good, and if edge bending or tape tearing occurred, it was determined that the running characteristics were poor.

(Distortion of power records) 20°C using the video tape recorder described above.

A vertical line image is recorded on the sample magnetic tape at 60% RH. After digitizing this continuously for 10 hours at 60'' at 0.60% RH, we played it back at 20°C and 60% RH to check for the deviation (referred to as skew) between the vertical reference line and the image at the bottom of the TV. It was measured.

If the skew is 10μsec or less, there is no recording distortion, 1
If it was longer than 0 μsec, it was determined that there was distortion in the recording.

(As mentioned above, the present invention is a magnetic recording material in which a magnetic layer is provided on at least one side of a biaxially oriented film made of a specific polyester and having specific physical properties, so it is possible to obtain excellent effects such as first order. It is a finished product, i.e.

(1) Even if it is thin, the magnetic recording material has good running characteristics and does not cause any distortion in recording. As a result, the magnetic recording material can be made thinner, smaller, and more dense.

(2) A magnetic recording material with excellent adhesion between the base film and the magnetic layer is obtained, and as a result, a magnetic recording material is obtained in which no distortion occurs in recording.

The magnetic recording material of the present invention can be used for all types of magnetic recording such as audio and video.

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

Example 1 Polyethylene bisα,β-(2-chlorophenoxy)ethane 4.4′-dicarboxy(jOm
mφ) and melt extruded at 300'a.

This was wound around a casting drum with a surface temperature of 60°C and cooled and solidified to produce an unstretched film with a thickness of about 60 μm. This unstretched film f T, M, Long
using a film stretcher made by the company.

Simultaneous biaxial stretching was carried out at 120° C. by 62 times in both the longitudinal and width directions at a stretching speed of 3,000%/min, and immediately 22 times
Heat treatment was performed at 0°C for 60 seconds under constant length. The biaxially oriented film thus obtained exhibited the following physical properties.

A Co--Ni alloy was formed as a magnetic layer on this film by electron beam evaporation to a thickness of 11 00A to obtain a magnetic tape. Although this tape was as thin as 6 .mu.m, it had good running characteristics and no recording distortion, and had excellent characteristics as a magnetic tape.

Example 2. Comparative Examples 1 to 5 From the polymer composition of Example 1, unstretched films having a thickness of about 65 μm were made in the same manner as in Example 1.

This unstretched film was stretched at a stretching speed of 50.
The film was stretched 6.2 times in the longitudinal direction at 120 degrees OK at 000%/min, and then stretched 64 times in the width direction at 120°C at a stretching speed of 5,000%/min using a stenter.

Immediately, heat treatment was performed at 230°C for 60 seconds at a constant temperature.

This film exhibited the physical properties shown in Table 1.

As shown in the table, the magnetic tape in which a magnetic layer was provided on this film in the same manner as in Example 1 had good running characteristics despite being as thin as 6 μm, and there was no distortion at all in recording. It was excellent. However, as shown in Table 1, other than the present invention, the running characteristics are good, and
It was not possible to obtain anything that would not cause distortion of the record.

Procedures Amendment 1, Indication of the case Patent Application No. 148103 of 1982, Name of the invention Magnetic Recording Materials 3, Person making the amendment Relationship to the case Patent applicant 4, Date of amendment order Voluntary 6, Amendment In Column 7 of "Detailed Description of the Invention" of the subject specification, the content of the amendment (1> Specification, page 10, line 19, r1702) M 702 and [YO ASTM-D-8
82.”

Claims (1)

[Claims] Consisting of polyester containing 85 or more moles of repeating units represented by the following general formula, having a Young's modulus in at least one direction of 550 z/mm' or more and a heat shrinkage rate of 4 in that direction.
1. A magnetic recording material characterized in that a magnetic layer is provided on at least one side of a biaxially oriented polyester film having a biaxially oriented polyester film having a biaxially oriented polyester film. Here, X is a halogen group selected from fluorine, chlorine, and bromine, or an alkyl group having 1 to 2 carbon atoms. 1 and m are each an integer of 1 to 2, p is an integer of 2 to 6, q
is an integer from 2 to 4.