JPS63212549A - Composite film for magnetic recording flexible disk - 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 composite film for magnetic recording 7 flexiple disks, and more particularly to an a-composite film for flexiple disks capable of improving head contact in flexible disks. .

Conventional technology and its problems Magnetic recording and reproducing devices using disks have been developed in recent years due to the increasing density of energy distribution and the increasing use of rice grains.

Smaller disk companies - disks are becoming faster and faster. This-! For example, to narrow the track 9a! The membership fee includes improvements to the touch of the head and disc, etc. If the head touch is affected, Empe a-
The shape will not be clean and the output will fluctuate greatly. Furthermore, when a magnetic head is brought into strong contact with a disk, a so-called uneven contact phenomenon occurs in which the local portion of the contact is scraped. When this uneven contact occurs, the air head wears out in a short period of time, causing the problem that it becomes unusable.

In order to avoid the occurrence of turtles during this period, it is effective to make the disc softer. Therefore, methods have been studied to improve flexibility by reducing the thickness of polyethylene terephthalate biaxially aligned films.
Merely reducing the thickness of the jacket has its limits, as new problems arise, such as the disk not turning smoothly in the jacket, or the disk becoming more likely to bend. Accordingly, the thickness of the ``C%'' film is approximately 33μ compared to the conventional method*7
The appearance of a base film with improved 7 flexibility in machining such as 5 Jlll is eagerly awaited.

In addition, polymer modification and selection of film forming conditions may be considered as means for softening the biaxially oriented polyethylene terephthalate film. For example, it is possible to make a polyethylene terephthalate film soft by lowering its stretch and Young's modulus, but the resulting film has many characteristics such as thermal dimensional stability and coefficient of thermal expansion that are lower than those of conventional films. Another problem arises in that the film becomes visually different and cannot be used as a base film for discs. Therefore, there is a limit to the improvement in flexibility by selecting the w4 film conditions, and the effect is far from being as sufficient as effect 1. Also,
Although it is possible to lower the Young's modulus of the film by using a polyester containing polyethylene terephthalate as its biological material, the obtained film has a low degree of glass transfer S source, and the operating temperature range of the disk forming process is lower than the conventional temperature range. Other problems arise, such as low heat resistance and easy thermal deformation when made into a disk, and high coefficient of thermal expansion, high expansion forces due to moisture absorption, etc. Furthermore, film properties include orientation.

Since crystallinity also plays a role, films made of monopolyester exhibit film properties different from those of conventional films. Therefore, there is a limit to the improvement of flexibility by polymer modification, and its effects are not sufficient.

Purpose of the Invention As a result of intensive research to develop a base film that lowers only the Young's modulus of the base film characteristics of conventionally widely used flexible tapes, the present inventor has developed an outer layer made of polyethylene terephthalate. The laminated film is a film made of polyethylene-L6-naphthalate, and the core layer is a film made of polytetramethylene terephthalate or polytrimethylene terephthalate. It was discovered that the mechanical properties of the film can be substantially the same as those of the original film.

Therefore, an object of the present invention is to provide a composite film for a flexible disk that can improve the contact of the magnetic head on the flexible disk.

Structure/Effect of the Invention The object of the present invention is that the core layer is made of polytetramethylene terephthalate or polytrimethylene terephthalate, the inner and outer layers are made of polyethylene terephthalate, and/or the core layer is made of polyethylene-2,6-naphthalate. A continuous kite is produced by a composite film for a magnetic recording flexible disk, which is a laminated two-S rolled one-dimensional film, and the &t film has a Young's modulus of 250 to 450 &/- in all in-plane directions. be done.

Polyethylene terephthalate in the present invention includes polyethylene terephthalate homopolymers, polyethylene terephthalate yarn copolyesters in which ethylene terephthalate repeating units account for 80 moles or more, and polyethylene terephthalate-based mixed polyesters in which these polyesters account for, for example, 901111% or more. This polyethylene terephthalate is a crystalline polymer. The copolyester components include aromatic dicarboxylic acids other than terephthalic acid (e.g., isophthalic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfo/dicarboxylic cR92).
+6-su7 sauce/dicarboxylic tl+5-naphthalene dicarboxylic acid, etc.) I aliphatic dicarboxylic acids (e.g. adipine #!, cepatine IN, fullylene glycols other than ethylene glycol (e.g. trimethylene glycol, detramethylene glycol, hexamethylene glycol,
neopentyl glycol, etc.) diethylene glycol,
Aromatic diol (9IJ is hydroquinone.

resorcin, bisphenol AI bisphenol S, etc.)
, aliphatic diol having an aromatic ring (911, 2.2
-bisC4-hydroxyethoxyphenyl)propane,
Examples include bis(4-hydroxyethoxyphenylsulfone, etc.). Other polymers used in the above mixed polyester include polyolefin, poly7
Examples include Midoya polycarbonate and other polyesters.

Polyethylene terephthalate used in the present invention is known per se, and can be obtained by known methods.

For example, 91J can be produced by a conjugation method using terephthalic acid and ethylene glycol, a transesterification method using terephthalic dimethyl ester and ethylene glycol, and a method in which diethylene glycol terephthalate is polycondensed.

In addition, polyethylene-2,6-naphthalate according to the invention includes polyethylene-2,6-large phthalate homopolymer, polyethylene-2,6-naphthalate repeating units occupying 80 moles or more
, 6-naphthalate copolyesters, and polyethylene-2,6-naphthalate mixed polyesters in which these polyesters account for, for example, 9031 or more. This polyethylene-2,6-naphthalate is a crystalline polymer. Examples of the copolymer component of the above copolyester include the copolymer component of the polyethylene terephthalate copolyester. However, 2,6-s7tanane dicarboxylic acid is substituted with thenphthalic acid. Examples of other polymers used in the mixed polyester include polyolefins, polyamides, polycarbonates, and other polyesters.

Polyethylene-2,6-naphthalate used in the present invention is known per se and can be produced by a known method. It can be produced by a direct method using 2,6-7tale dicarboxylic acid and ethylene glycol, a transesterification method using dimethyl 2,6-naphthalene dicarboxylic acid and ethylene glycol, etc. .

In addition, polytetramethylene terephthalate in the present invention includes polytetramethylene terephthalate homopolymer, polytrimethylene terephthalate copolyester containing 80 mol or more of tetramethylene terephthalate repeating units, and these polyesters. includes a polytetramethylene terephthalate mixed polyester having a weight of 90% or more. This polytetramethylene terephthalate is a crystalline polymer. The copolymer component of the above copolyester is polyethylene tele7.
- The exemplified co-components of the crate-based copolyester can be mentioned. However, tetramethylene glycol should be replaced with ethylene glycol R. Further, other polymers used in the above mixed polyester include polyolefin and polyamide.

Examples include polycarbonate) and other polyesters.

The polytetramethylene terephthalate used in the present invention is known per se, and can be linearized by a known method. For example, it can be produced by a direct polymerization method using terephthalic acid and tetramethylene glycol, or a transesterification method using terephthalic acid methyl ester and tetramethylene glycol.

Moreover, polytrimethylene terephthalate in the present invention includes polytrimethylene terephthalate homopolymer, polytrimethylene terephthalate copolyester in which trimethine/terephthalate repeating units account for 80 moles or more, and these polyesters? Ue includes polytrimethylene terephthalate-based mixed polynisdel which accounts for more than go Shindo. This polytrimethylene terephthalate is a crystalline polymer. Examples of the copolymer component of the above-mentioned copolyester include those exemplified as the copolymer component of the polyethylene terephthalate copolyester. However, trimethylene glycol shall be read as ethylene glycol. Examples of other polymers used in the mixed polyester include polyolefin-bolyad 9 polycarbonate 1 and other polyesters.

Polytrimethylene terephthalate used in the present invention is known per se and can be produced by a known method. It can be produced by transesterification using terephthalic acid.

This JABA composite film has a core layer made of polytetramethylene terephthalate or polytrimethylene terephthalate, and one outer layer made of polyethylene terephthalate and/or polytrimethylene terephthalate.
Alternatively, it is a laminated two-wheel stretched film made of polyethylene-2,6-naphthalate, and historically, the Young's modulus of the laminated film must be within the range of 250 to 450 h/wP in all in-plane directions. Young's modulus of composite film is 2
If it is less than sokp/d, the disk will wave during high-speed rotation, the contact between the disk and the magnetic head (C touch) will be poor, and input/output fluctuations will occur, which is undesirable. - If the Young's modulus exceeds 4500/d,
As the overall rigidity of the disk increases, the disk and magnetic head become more compatible with each other, resulting in large drops in output in some places on the surface of the disk, and local scratches on the head surface (
This is not desirable as it may cause problems such as uneven hitting.

A known combination method can be used as the combination method.

For example, separate extruders produce m-
It can be produced by compounding and extruding in an extrusion die, rapidly cooling to obtain a composite unstretched film, stretching this unstretched film for 2 seconds using a support, and heat setting. Examples of the above-mentioned composite die include a multi-manifold die, a FeedGlock Dynastack plate die, and the like. Further, as the biaxial stretching method, 41 sequential biaxial stretching method, simultaneous biaxial stretching method, etc. can be used, but the former method is preferable. The stretching conditions may be those known for polyethylene terephthalate or polyethylene-2,6-naphthalate forming the outer layer. For example, in the sequential biaxial stretching method, the composite unstretched film is uniaxially (for example, longitudinally) stretched at a humidity (Tg - 103 to (Tg + 50) 'C (here, Tg is the glass transition temperature of the polyester forming the outer layer)). T, :'C) at least twice, 2.
Stretch at a magnification of 5 times or more, then in the direction perpendicular to this stretching direction (transverse direction K when the first step is longitudinal stretching) T, - (T*
+sO)'C temperature (Tfi:"C) at least twice,
It is preferable that the support is stretched at a # ratio of 2.5 times or more and further heat-set at a higher temperature. Heat fixation is over 380℃,
Furthermore, at a temperature of 190°C or higher for 2 seconds to 30 seconds, and even for 2 seconds.
It is preferable to apply for 15 seconds to 15 seconds.

What is the Young's modulus of the composite film in the present invention?

The combination of polymers in the core layer and inner and outer layers, their thickness ratio, stretching rate, heat rMil! It can be adjusted by degrees, etc. Among these, it is preferable to mainly adjust the combination of polymers and the thickness ratio. For example, the Young's modulus can be lowered by increasing the thickness of the core layer, but if the ratio of the core layer becomes too large, the heat resistance will decrease, which is not preferable.The ratio of the core layer to the total film thickness is 30 ~905゜i+z
rc! 3o-%-90% and 3's "r" lights up.

Further, when the outer layer is made of polyethylene terephthalate, a lower Young's modulus can be obtained.

In the present invention, the polyester constituting the composite film can contain inert fine particles that act as a lubricant, depending on two reasons.

The inert fine particles may be internal particles precipitated during the formation of the polyester surface, especially before or during polymerization, or may be inorganic or organic inert particles added from the outside. This lubricant is preferably contained in the polyester forming the inner and outer layers. The above-mentioned polyester may contain compounding agents other than the above-mentioned lubricant, such as a stabilizer, a beak coloring agent, an antistatic agent, a polarizing agent, etc., depending on the requirements.

When providing a magnetic layer on the composite film of the present invention, known methods can be used. The magnetic layer may be a coated magnetic layer or a metal thin film type abrasive layer. Among these, perpendicular magnetization films are preferred.

Known magnetic materials can be used in the form of the coated magnetic layer. For example, ferromagnetic powders such as y Fez, cellulose acetate butyrate, etc. can be used. Further, in this case, nine known conditions can be applied to the application and drying of the magnetic paint. Furthermore, known means and known processing conditions can be applied to the calender treatment to smooth the magnetic layer.

Moreover, a ferromagnetic metal thin film layer can be provided on the composite film to form a magnetic recording medium.

As the ferromagnetic metal, it is most common to use a Co-Cr alloy, such as Co-R., C.

V + Co-Ru, Ba ferrite, Co-0
. In particular, the sputtering method is preferable because it provides a high film strength and is difficult to form pinholes in the film.

When the metal thin film is a perpendicular magnetization film, a permalloy film made of N1-F alloy film may be provided as a soft magnetic film alongside the perpendicular magnetization film. It is economically advantageous to provide one. Further, on the perpendicularly magnetized film, a deposited carbon film, a metal film such as AI, or a coating film made of Fi/and an organic polymer may be formed as a protective film.

The composite film of the present invention has the following excellent advantages.

(1) Since both outer layers of the composite film are made of polyethylene terephthalate or polyethylene-2,6-+7 talate, the surface properties and thermal properties of the composite film are almost the same as those of conventional general-purpose base films. Therefore, it can be used as a base film for general-purpose magnetic recording flexible disks.

(2) Conventional base films have high hardness when used in magnetic recording disks, which tends to cause problems such as deterioration of head contact as the recording density changes; however, the composite film described above Since the Young's modulus is lower than that of film, this problem can be solved, and even higher recording speeds can be achieved, such as NIJ1. You can create flexible disks. For example, when manufacturing a perpendicular magnetic recording medium by forming a thin metal film such as Co-Cr by sputtering, the hardness of a conventional polyethylene terephthalate film increases (because it is a thin metal film, it becomes even harder), and head contact occurs. Although it is easy to do so, the above-mentioned composite film can solve this problem.

Example The present invention will be further explained below with reference to Examples.

In addition, the film properties in the examples were measured by the following method.

(1) The Young's modulus film was prepared with a sample width of 10mm, a length of 15α, a cutting edge chuck of 100K, a tensile speed of 10 cuts/min, and a chard speed of 10.
Tensile test was carried out for 7 tensile cycles using an Instron type universal tensile tester at 0 tensile strength/min, and the Young's modulus was determined from the tangent to the rising part of the obtained load-elongation curve. The Young's modulus in each direction within the plane of the film is measured by cutting out the sample at 30° intervals, and the maximum value, minimum value, and average value in each direction are expressed as the Young's modulus.

Examples 1 and 2 and Comparative Examples 1 to 3 Two melt extruders were used, and one extruder was used to form both outer layers of polyethylene terephthalate or polyethylene-2,6.
- Melt naphthalate, add 0.31 iJ1% of titanium oxide with an average particle size of 0.3 μm to it, mix and disperse it uniformly, melt polytetramethylene terephthalate as a core layer with an extruder of 51 units, and melt these were combined and laminated in a three-layer multi-manifold die, extruded from the die slit onto a rotating cooling drum, and rapidly cooled to obtain a composite unstretched film.
This composite unstretched film had a thickness of 460 μm.

The thickness of each layer of this unstretched film was adjusted by changing the discharge rate of each melt extruder.

This composite unstretched film was stretched longitudinally at the stretching temperature shown in Table 1.
Stretched in the transverse direction using a known sequential biaxial stretching method (stretching ratio: 3.6 times in the longitudinal direction, 3.7 times in the V4 direction), and heat-set under tension at the temperature shown in Table 1 to obtain a thickness. A biaxially oriented composite film with a thickness of 33μ was obtained.

The characteristics of this composite film are shown in the first page.

On the other hand, for comparison, polyethylene terephthalate, polyethylene-2,6-naphthalate, or polytetramethylene 7-talate was used as a lubricant with an average particle size of 0.3 μm.
0.3 weight-dispersed titanium oxide was melted in one melt extruder and extruded through the above Guislit,
Thereafter, the same procedure as in the above Example was carried out to obtain a biaxially oriented single layer film having a thickness of 33 μm. However, the stretching temperature and heat setting temperature were changed to those shown in Table 1.

The properties of this single layer film are shown in Table 1.

Furthermore, the following magnetic paint was applied to these biaxially oriented films (
Solid content equivalent: 3.9/m') L, 120℃
It was dried, calendered at 80° C. and 300 kg ZcW, and wound into a roll.

Composition of magnetic paint CO-containing 1- Fe2O3 100 parts by weight Vinyl chloride-vinyl acetate copolymer resin (manufactured by Union Carbide) V
AGH10# Urethane resin 17 Curing agent 10 Butyl acetate 140 Methyl ethyl ketone 200 Next, the obtained rolled coachite web was aged at 60° C. for 72 hours.

Thereafter, a 5.25' disk was punched out using a conventional method, and the envelope was measured and evaluated. those results first
Shown in the table.

It is clear from Jonin that the floppy disk using the composite film of the present invention has little output fluctuation and has excellent thermal dimensional stability.

Example 3.4 and Comparative Examples 4 to 6 Two melt extruders are used, and one extruder is used to form both outer layers of polyethylene terephthalate or polyethylene-2,6.
- Melt naphthalate, add 0.15% by weight of titanium oxide with an average particle size of 0.3 μm and 0.009% by weight of calcium carbonate with an average particle size of 0.5 μm, mix and disperse uniformly, and add another Polytrimethylene terephthalate as a core layer was melted in an extruder, laminated together in a three-layer multi-manifold die, extruded onto a Glyslit rotary cooling drum, and rapidly cooled to obtain a composite unstretched film. This composite unstretched film had a thickness of 390 μm. The thickness of each layer of this unstretched film was adjusted by changing the discharge rate of each melt extruder.

This composite unstretched film is stretched 3.4 times in the machine direction at a temperature of 85°C when both outer layers are made of polyethylene terephthalate, then stretched 3.5 times in the transverse direction at 110°C, and when both outer layers are made of polyethylene In the case of -2,6-naphthalate, it was stretched 3.4 times in the machine direction at a temperature of 120°C, then 3.5 times in the transverse direction at 125°C, and then subjected to a tension heat treatment at 200°C to a thickness of 33 μm. A biaxially oriented composite film was obtained.

The properties of this composite film are shown in Table 2.

On the other hand, for comparison, polyethylene terephthalate, polyethylene-2,6-naphthalate, or polytrimethylene terephthalate was added with 0.15% by weight of titanium oxide with an average particle size of 0.3 μm and 0.15% by weight of calcium carbonate with an average particle size of 0.5 μm as a lubricant. 009% by weight dispersed in 1
The mixture was melted using a stand-mounted melt extruder and extruded through the die slit, followed by the same procedure as in the above example to obtain a biaxially oriented single layer film with a thickness of 33 μm. However, the stretching temperature and heat setting temperature are the same as in Example 3 when polyethylene terephthalate is used! , when polyethylene-2,6-naphthalate is used, the temperature is the same as in Example 4, and when polytrimethylene terephthalate is used, K is the longitudinal stretching temperature of 60°C and the transverse stretching source 1.
1: SO°C, heat fixing temperature 1f: 190°C.

The properties of this single layer film are shown in Table 2.

Furthermore, a 5.25' magnetic disk was prepared in the same manner as in Example 1 except that these biaxially oriented films were used as the base film. These results are shown in the second thorn.

From the above table, it can be seen that the floppy disk using the composite film of the present invention has little output fluctuation and excellent thermal dimensional stability.

Claims (1)

[Claims] A laminated biaxially stretched film in which the core layer is made of polytetramethylene terephthalate or polytrimethylene terephthalate, and both outer layers are made of polyethylene terephthalate and/or polyethylene-2,6-naphthalate, and the Young's modulus of the film is 250-4 in all directions
A composite film for magnetic recording flexible disks, characterized in that it has a weight of 50 kg/mm^2.