JPH0619826B2 - Magnetic recording material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a novel magnetic recording material having excellent mechanical properties in both the length direction and the direction perpendicular thereto and having good dimensional stability. And particularly to a method of manufacturing a magnetic recording tape.

[Prior art]

Polyethylene terephthalate-based films are mainly used as the films used for industrial purposes in recent years, and they are applied in various fields due to their mechanical properties and electrical properties. Among them, magnetic recording materials, especially audio tapes,
As a base material for video tapes and floppy discs, it shows markedly superior properties, and in terms of cost and performance, it is always an exaggeration to say that it cannot be followed by other films.

However, in recent years, magnetic recording materials have tended to have higher densities and thinner films, and there has been a strong demand for more excellent films in place of polyethylene terephthalate. For example, in the case of video tapes, there is a demand for a longer time in the existing videos, and the base film has been made thinner. However, as a recent trend, the camera-integrated 8m / m video tape has been standardized, and the demand for miniaturization and high density has been increasing more and more toward the market launch.

In particular, in order to increase the density, the conventional method of coating iron oxide with a binder has been changed to a method of directly depositing metal powder on a film, and the film receives heat during this deposition process. Since the higher the film temperature is, the better the adhesion between the evaporated metal and the film is, the heat resistance and dimensional stability of the base film are desired to be improved.

Further, the floppy disk also tends to be a compact disk, and accordingly, high density is demanded. As a method of increasing the density, heat resistance is obtained in a method of improving magnetic characteristics by metal vapor deposition or vertical magnetic vapor deposition,
Further, in the method of increasing the number of tracks, improvement of dimensional stability is desired, such as suppressing expansion coefficient of temperature and humidity and irreversible change due to temperature and humidity.

On the other hand, polyimide films, aromatic polyamide films, etc. have been proposed, but new films especially with many disadvantages such as high price, poor chemical resistance, poor dimensional stability against temperature and humidity, It is desired to develop a film which can be melt extruded and has crystallinity and which is superior in heat resistance, mechanical properties and dimensional stability to a polyethylene terephthalate film. As such a film, for example, as described in JP-B-48-42167, polyethylene-2,6- which is one kind of polyester is used.
Although naphthalene dicarboxylate has been proposed, it is in a situation where it has not been put to practical use because it is not excellent in properties and is expensive.

On the other hand, polyetherketone can be considered as the film base material, but the polyetherketone has a high melting point and a high second-order transition point, and the unstretched film formed from this has a high rigidity. Various difficulties are expected in the production of oriented films by stretching, and in fact, suitable methods for biaxially stretching polyetherketone to produce films having a high Young's modulus and high strength have never been known. Nakatsuta.

[Object of the Invention]

The present invention has been made to solve the above problems, and an object thereof is to provide a magnetic recording material which is more excellent in mechanical properties and heat-resistant dimensional stability than conventionally known ones, and particularly polyether ketone. And a method of manufacturing a magnetic recording tape using the same.

[Structure of Invention]

Briefly describing the present invention, the first invention of the present invention relates to a magnetic recording material, wherein the base material in the magnetic recording material has a second-order transition point of 120 ° C. or more and less than 180 ° C., 280 ° C.
A film or sheet obtained by biaxially orienting an unstretched film or sheet of a polymeric substance having the above melting point and crystallinity and having a polyetherketone and / or a polyetheretherketone skeleton (hereinafter simply referred to as film). 5% in the length direction and the direction perpendicular to it
Both elongation stress is 13kg / mm ² or more, initial elastic modulus in at least one direction is 600kg / mm ² or more, and 180 ℃
Of 4% in the longitudinal direction and in the direction perpendicular to it
It is characterized by the following.

A second invention of the present invention relates to a method for manufacturing a magnetic recording tape, which comprises the following general formula I: It has a repeating unit represented by
An unstretched film (or sheet) obtained by melt-extruding polyetherketone of not less than 1 g / g, at a second-order transition temperature of 210 ° C., in the machine direction and the transverse direction, simultaneously or in any order. A magnetic layer is formed on the surface of a film (or sheet) obtained by biaxially stretching 2.0 times or more in both directions and then heat-setting at a temperature of 200 ° C. to less than the melting point.

First, the first invention of the present invention will be specifically described below.

In the present invention, a polymer substance having a second-order transition point of 120 ° C. or higher and lower than 180 ° C., a melting point of 280 ° C. or higher, and crystallinity and having a polyetherketone and / or a polyetheretherketone skeleton is under this condition. As long as the above conditions are satisfied, any of polyether ketones, polyether ether ketones, and their respective copolymers, and those having a side chain on the benzene ring, etc., can satisfy the above conditions because of ease of extrusion molding. Those are particularly suitable. The upper limit of the melting point of the polymer substance in the present invention is not particularly limited, and when heat fixing is performed, the melting point is only taken into consideration when selecting the temperature.

That is, for example, polyetherketone is represented by the following general formula
II: (Wherein R ₁ and R ₂ represent hydrogen or halogen, an alkyl group or another substituent), or a repeating unit represented by the following general formula III: (Wherein R _{3 to} R ₅ have the same meanings as R ₁ and R ₂ ) and a copolymer capable of forming a repeating unit.

On the other hand, for example, polyetheretherketone is represented by the following general formula IV: (Wherein R _{6 to} R ₈ have the same meanings as R ₁ and R ₂ ), or a copolymer of the repeating unit and a component of the above formula III.

There are various other structures, but in terms of price,
Preference is given to using polyetherketones obtained from phosgene and diphenyl ethers and polyetheretherketones obtained from phosgene and 1,4-diphenoxybenzene.

The polymer substance may contain a matting agent such as titanium dioxide, a stabilizer, a fine particle silica, and a lubricant such as china clay.

The film used as the base material in the magnetic recording material of the present invention is
Further, it must have the following physical properties.

That is, the stress at 5% elongation in the length direction and the direction perpendicular thereto is both 13 kg / mm ² or more, preferably 15 kg / m
m ² or more and an initial elastic modulus in at least one direction of 600
kg / mm ² or more, preferably 800 kg / mm ² or more, 1
Thermal shrinkage at 80 ° C in the length direction and the direction perpendicular thereto is 4% or less, preferably 3% or less, more preferably 1%.
It is the following.

The magnetic recording material satisfying all of the above three conditions is completely novel, and any of the conventionally known magnetic recording materials lacks at least one of the above three conditions. For example, when trying to make a film that has high strength in both the vertical and horizontal directions using polyethylene terephthalate, the heat shrinkage rate becomes high, and conversely, when trying to suppress the heat shrinkage rate, the desired mechanical strength cannot be obtained. It was Further, in the case of polyethylene terephthalate, it has been very difficult to produce a well-balanced film having high strength in both directions.

Therefore, the crystalline film according to the present invention, which has excellent mechanical properties in both length and width and extremely excellent heat resistance and dimensional stability, is an epoch-making film which has never existed before, and a magnetic recording material using this as a base material. Meets the market demand for miniaturization, thinning, and high density.

The magnetic recording material of the present invention is produced by molding the above-described polymer substance by a usual method, biaxially stretching the obtained unstretched film, and then heat-treating it if necessary. As a stretching method, a successive biaxial stretching method, a simultaneous biaxial stretching method, a successive three-stage stretching method, etc. can be adopted. In the case of the sequential biaxial stretching method, the order may be vertical or horizontal, and the stretching temperature is as follows: the first stage is the second-order transition temperature of the polymeric substance to 210 ° C., and the subsequent stage stretching is , 21
A temperature equal to or lower than 0 ° C. and higher than or equal to 3 ° C. is preferable, and the stretching ratio is 2.5 to 5 ° in the machine direction.
0 and 2.5 to 5.0 in the lateral direction are preferable.

The heat treatment temperature is preferably in the range of 210 ° C to less than the melting point.

In order to form a magnetic layer on the surface of the film thus obtained, a conventionally known method that is used in the production of magnetic recording materials can be adopted. For example, a method of applying a mixture of magnetic particles (for example, metal oxide or a simple metal such as cobalt or nickel) and a binder to form a thin layer, or directly fixing the metal by vacuum vapor deposition, ion plating or sputtering. There are ways.

As described above, the magnetic recording material of the present invention sufficiently meets the demands for extremely thin and high density magnetic materials.

Next, a method for manufacturing the magnetic recording tape according to the second aspect of the present invention will be specifically described.

The polyetherketone used in the method of the present invention can be obtained by various known methods. For example, it is obtained by polymerizing p-phenoxybenzoyl chloride in hydrogen fluoride in the presence of boron trifluoride. However, for cost reduction purposes, phosgene and diphenyl ether are optimally polymerized in carbon disulfide in the presence of aluminum trichloride.

Further, the polyether ketone may contain a matting agent such as titanium dioxide, a stabilizer, and a lubricant such as fine particle silica and china clay.

The method of the present invention is applied to those polyetherketones having an intrinsic viscosity of 0.4 dl / g or more. Intrinsic viscosity here means a concentration of 1.0 g / dl in concentrated sulfuric acid at 30 ° C.
It is the value measured at the temperature of. Thus, the intrinsic viscosity is 0.
If it is less than 4 dl / g, a useful film cannot be obtained, which is not preferable.

The present invention is applied to an unstretched film formed from polyetherketone as described above. The thickness of the unstretched film can be arbitrarily selected. For example, from a thin film having a thickness of several 10 μm, for example, a thickness of 0.5
It is possible to optimize even those with a considerable thickness exceeding mm. However, since the crystallization speed is higher than that of polyester, it is necessary to devise a quenching method. In other words, it is necessary to prevent the formation of spherulites during quenching. In some cases, water cooling or cooling into ice is also a preferable method.

In the method of the present invention, when the unstretched film is successively stretched by adopting the successive stretching method, the first stretching is performed at a temperature of the second-order transition temperature of the used polyether ketone to 210 ° C., The latter stretching (stretching in the direction perpendicular to the first stretching direction) is preferably carried out at a temperature of 210 ° C. or lower and at a temperature equal to or higher than the stretching temperature of the first stage by 5 ° C. or more. Here, it is preferable that the average refractive index (abbreviated as below) after the first-stage stretching is 1.750 or less. In particular, since the present film has a high crystallization rate as described above, if the spherulites are easily formed in the cooling process after stretching and the spherulites are formed, the subsequent stretchability is extremely deteriorated. If the stretching ratio in each stretching is less than 2.0 times, not only the desired strength and Young's modulus cannot be obtained, but also the thickness unevenness of the obtained film is unsuitable for a magnetic recording tape.

Further, in the first stretching, when the stretching temperature is lower than the second-order transition point, cold stretching is performed and the thickness of the film is reduced,
A film with uneven thickness cannot be obtained. On the other hand, when the stretching temperature exceeds 210 ° C., crystallization during stretching proceeds and the temperature after the first stage stretching becomes too high, making the second stage stretching impossible. By the way, when pre-stage stretching is performed between the secondary transition point temperature and 210 ° C., depending on the selected temperature, flow-stretching may occur and insufficient orientation may occur. It is also suitable to divide into a plurality of stages to obtain a desired product after the former stage drawing.

In the latter-stage stretching, the stretching temperature may be selected as appropriate depending on the orientation of the film after the first stretching, but the latter-stage stretching temperature is equal to the former-stage stretching temperature or rather preferably higher than 5 ° C. It is preferable to set. In particular, when the former stage is higher, the latter stretching temperature is preferably set higher.

Generally, the second-order transition temperature of polyetherketone is 154 ° C. as measured by a differential scanning calorimeter (DSC).

The average refractive index in the present invention means a light wavelength of 589 mμ.
(Center of D line), refractive index (nγ) in the principal axis direction in the film plane, measured with an improved version of Atsube's refractometer capable of measuring up to a high refractive index at a temperature of 20 ° C. In-plane refractive index (nβ) and thickness direction refractive index (n
It means the arithmetic mean value of α).

In order to obtain the film according to the present invention by the successive method, the initial stretching temperature is 154 to 210 ° C and the stretching ratio is 2.0 to.
It is preferable to set the stretching ratio to 5.0 and the stretching ratio in the latter stage to 2.0 to 6.0. The stretching speed can be changed in the range of 50 to 100000% / sec in the longitudinal stretching process and in the range of 5 to 500% / sec in the transverse stretching process.

As the stretching method in the present invention, the sequential biaxial stretching method of stretching in the machine direction and then in the transverse direction is most recommended. However, if the stretching is performed in the transverse direction first and then in the longitudinal direction, the sequential biaxial stretching method, if the stretching temperature conditions are selected so as to match the pre-stage stretching conditions of the sequential biaxial stretching, the simultaneous biaxial stretching method is also possible. It is suitable. As a stretching device, a roll, a tenter, a tumbler, or the like can be selected as needed. Also,
In order to improve the strength in the machine direction, re-stretching, re-stretching and transverse stretching are also desirable. The oriented film thus obtained is
It has high strength and high Young's modulus and is excellent in flatness, but by heat-treating it under the following conditions, heat resistance and dimensional stability can be further improved.

That is, under the above-mentioned conditions, the biaxially stretched polyetherketone film is heat-treated at a temperature of 200 ° C or higher and lower than the melting point to obtain a more excellent film.

When the heat treatment temperature is lower than 200 ° C., the heat treatment time is too long to be effective. On the other hand, above the melting point, the film melts and breaks.

Further, the heat treatment may be carried out under tension or shrinkage, but when it is carried out under shrinkage, it is preferably carried out under restricted shrinkage of 10% or less. If it is more than that, the orientation is relaxed too much and the mechanical strength is remarkably lowered, which is not suitable.

Then, the magnetic layer is formed on the surface of the film which has been stretched and heat-treated as described above, and as the method, the conventionally known method described above can be adopted.

The magnetic recording tape obtained by the method of the present invention described above,
It is superior in strength and dimensional stability to the conventionally known tapes, and can be fully used as a magnetic recording tape even with an extremely thin tape, and is suitable as a vapor deposition tape for 8m / m video. Used for.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Production Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Production Example 1 Using polyetherketone having an intrinsic viscosity of 0.81 dl / g, which was synthesized by a conventional method in the presence of aluminum trichloride in carbon disulfide in a molar ratio of 5: 1 of phosgene and diphenyl ether. The unstretched films of various thicknesses produced were extruded to produce unstretched films.

First, the unstretched film was stretched in the machine direction at a stretching temperature of 175 ° C. at a stretch ratio of 1.9 times (No. 1) and 3.2 times (No. 2).
After stretching 3.5 times (No. 3) and 4.1 times (No. 4), the film was stretched in the transverse direction at the same temperature by 3.2 times, and then 35 times.
Heat-fixed at 0 ° C for 20 seconds and final film thickness is 15μ
A biaxially stretched heat-fixing film of m was obtained. The physical properties thereof are shown in Table 1 below.

It can be seen from Table 1 that the stretching ratio in the machine direction needs to be 2.0 times or more in terms of thickness unevenness.

Example 1 An unstretched film produced from polyetherketone having an intrinsic viscosity of 0.75 was first stretched 3.5 times at 175 ° C. in the machine direction.
Then, after stretching 3.5 times in the transverse direction at 180 ° C., 32
Heat setting was performed at 0 ° C. The performance of the film thus obtained and the commercially available polyethylene terephthalate film for magnetic tape were compared. The results are shown in Table 2 below.

When a magnetic tape prepared by applying a thin layer of a composition composed of needle-shaped magnetic iron oxide and a binder to these films and solidifying them is compared, the strength is the same, but the dimensional stability is particularly high at high temperature and high humidity. In terms of dimensional stability, the magnetic tape based on polyetherketone film is significantly superior to the magnetic tape based on polyethylene terephthalate film, and the length of the magnetic tape in the same case is It turns out that it is much longer.

When cobalt or nickel metal was vacuum-deposited to make a magnetic tape, in the case of polyethylene terephthalate film, the cooling drum on the side opposite to the vapor deposition source,
Room temperature must be kept from the viewpoint of curl and dimensional change, whereas in the case of polyetherketone film,
It was found that raising the drum temperature to 130 ° C did not cause any problems. The vapor-deposited tape thus obtained was remarkably excellent in the adhesiveness between the magnetic layer and the film.

Examples 2 to 6 An unstretched film was prepared from polyetherketone obtained by a conventional method. Its second-order transition point is 154 ° C and melting point is 367.
It was ℃. This unstretched film is first stretched 17
Stretched 3.4 times at 5 ° C, then transversely at 180 ° C for 3.
After stretching 4 times, heat setting is performed at 320 ° C to obtain a thickness of 15
A film of μm was obtained (Example 2).

Moreover, the thing which is not heat-fixed was also evaluated (Example 3). Furthermore, using the same unstretched film as described above, the film was simultaneously biaxially stretched at 185 ° C. in the longitudinal and transverse directions by a factor of 3.4, and 3
Heat fixing was carried out at 00 ° C. to obtain a film having a thickness of 15 μm (Example 4).

The properties of the stretched films thus obtained are shown in Table 3 below.
Shown in.

A conventionally known composition of magnetic particles and a binder was applied to the surface of the film to form a thin layer, thereby producing a magnetic recording tape.

This has a stress of about 1 at the time of stretching 5% in the longitudinal and transverse directions, which is commercially available.
It was compared with a magnetic recording tape based on 5 kg / mm ² of polyethylene terephthalate. 180 ° C of this commercial product, 1
The heat shrinkage in minutes was as high as 15% in the longitudinal direction.

Example 5 An unstretched film was prepared from polyetheretherketone obtained by a conventional method. Its second-order transition point was 138 ° C. and its melting point was 320 ° C. This unstretched film is first stretched in the machine direction at a temperature of 160 ° C. by 4.0 times and then stretched in the transverse direction at 170 ° C.
The film was stretched at 2.8 times at 2.8 ° C. and then heat-treated at 300 ° C. to obtain a film having a thickness of 15 μm. The properties of the stretched film thus obtained are shown in Table 4 below.

A magnetic recording tape was produced from this film in the same manner as in Example 2 and a commercially available polyethylene terephthalate-based tensilized film (5% longitudinal stress 1) was used.
It was contrasted with a magnetic recording tape from 9.3 kg / mm ² ).

The commercially available tape and the tape of this example had the same longitudinal strength, but the lateral strength of the tape of this example was 13 kg / mm ² , whereas the commercially available tape was 9 kg. .8 kg
/ Mm ^2, also durability after multiple cars, it was divide the direction of the tape of this embodiment is much better than the commercial tape. Further, regarding the dimensional stability, in the case of the commercially available tape, the heat shrinkage ratio in the longitudinal direction at 180 ° C. for 1 minute was 20%, which was very poor.

〔The invention's effect〕

As described above, the magnetic recording material according to the present invention, particularly the magnetic recording tape, has the remarkable effect of having mechanical properties and heat-resistant dimensional stability superior to those of the conventionally known materials.

Claims (3)

[Claims] 1. A base material in a magnetic recording material is 120 ° C.
A second-order transition point of 180 ° C or higher and a melting point of 280 ° C or higher,
And a film or sheet obtained by biaxially orienting an unstretched film or sheet of a polymeric substance having crystallinity and having a polyetherketone and / or a polyetheretherketone skeleton, in the length direction and at a right angle thereto. The stress at 5% elongation in both directions is 13 kg / mm ² or more, the initial elastic modulus in at least one direction is 600 kg / mm ² or more, and 180
The thermal shrinkage in the longitudinal direction and in the direction perpendicular to it at 4 ° C is 4
% Or less, a magnetic recording material. 2. The polymer substance is polyetherketone or polyetheretherketone.
The magnetic recording material according to the item. 3. The following general formula I: It has a repeating unit represented by
The unstretched film or sheet obtained by melt-extruding polyetherketone of 2 / g or more has a second-order transition temperature of 2 to 2.
At 10 ° C., in the machine direction and the transverse direction, simultaneously or sequentially in any order, biaxially stretched 2.0 times or more in both directions, and then 2
A method for producing a magnetic recording tape, which comprises forming a magnetic layer on the surface of a film or sheet obtained by heat fixing at a temperature of 00 ° C to less than the melting point.