JPH0513325B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a magnetic recording flexible disk, and more particularly to a magnetic recording flexible disk with improved durability. Prior Art A flexible disk for magnetic recording is generally manufactured by applying a magnetic layer to a biaxially oriented polyethylene terephthalate film and smoothing the surface of the magnetic layer. This magnetic recording flexible disk is used in large quantities in many fields because of its ease of use and high reliability.
In this field, in recent years, there has been a desire for miniaturization and further improvement in reliability of drive devices through high-density recording. In order to achieve high-density recording and improve reliability, improving the durability of flexible disks, which are magnetic recording media, is an extremely important issue. As a method for increasing the recording density of a magnetic recording medium, generally, the thickness of the magnetic layer coated on the film is reduced and the degree of filling of the magnetic material is increased.
Then, in order to increase the degree of filling of the magnetic layer applied on the film, smoothing treatment (calendering) is performed.
The commonly used method is to apply but,
At this time, since the film and the magnetic layer are squeezed under relatively high temperature and pressure, the magnetic layer may peel off from the film and lose its commercial value, resulting in a reduction in product yield. Furthermore, when a magnetic recording flexible disk is used in a drive, repeated impacts from the head or pad can cause problems such as the magnetic layer peeling off from the film surface, so improving durability is not an option in this field. This is a very important issue. The above-mentioned problems in manufacturing and using flexible disks are such that the thinner the magnetic layer is made to increase the density, and the more highly planar the magnetic layer is made, the more difficult it becomes. The more you do it, the more it becomes obvious. One possible technique for improving durability (adhesion between the film and the magnetic layer) is to optimize the manufacturing conditions of polyethylene terephthalate film, that is, to select conditions that reduce the plane orientation of polyethylene terephthalate crystals. This method has only a small improvement effect and cannot significantly improve durability. Furthermore, a technique is known in which the surface of a polyethylene terephthalate film is subjected to physical treatment such as corona discharge treatment to improve the adhesive force with the magnetic layer.
However, even with this method, it is difficult to obtain a significant improvement in durability. Furthermore, the effectiveness of corona discharge-treated films deteriorates over time, and there is a serious drawback in that it is difficult to always maintain stable film surface characteristics. On the other hand, the method of coating the surface of polyethylene terephthalate film to increase adhesive strength requires the creation of new equipment, and the bigger problem is that it tends to cause so-called blocking, where the surfaces of wound products of the film stick together. This has the drawback that the coating agent is limited and its selection is extremely difficult. Purpose of the Invention The present inventors have conducted intensive research to develop a magnetic recording flexible disk with improved durability and are free from such drawbacks. We have discovered that adhesive durability can be improved by making a magnetic recording flexible disk using a biaxially oriented laminated film formed with a layer of 1,4-cyclohexylene dimethylene terephthalate as a base material, and have thus arrived at the present invention. did. The purpose of the present invention is to reduce the minute peeling of the magnetic layer that tends to occur when smoothing the magnetic layer after applying it to a polyester film, thereby suppressing the occurrence of defective products in the manufacture of flexible disks. An object of the present invention is to provide a magnetic recording flexible disk with improved durability in repeated use during recording and reproducing information. Structure of the Invention According to the present invention, a magnetic recording flexible disk is provided in which a magnetic layer is provided on a biaxially oriented polyester film base material and the surface thereof is further smoothed, wherein the film base material is made of polyethylene. A terephthalate film or a polyethylene-2,6-naphthalate film is used as an intermediate layer,
Poly-1,4 with a thickness of 0.1 to 20 μm is coated on both sides of the intermediate layer.
- This is achieved by a magnetic recording flexible disk characterized in that it is a laminated film made of laminated cyclohexylene dimethylene terephthalate films. In the present invention, poly-1,4-cyclohexylene dimethylene terephthalate is a dibasic component in which 80 mol% or more is terephthalic acid and a glycol component in which 90 mol% or more is 1,4-cyclohexanedimethanol. Alternatively, it is a polyester made of glycol selected from trans isomers. Dibasic acid components other than terephthalic acid include isophthalic acid, phthalic acid, adipic acid, sebacic acid, succinic acid, oxalic acid, naphthalene-2,
Dibasic acids such as 6-dicarboxylic acid are exemplified. Preferably it is isophthalic acid. Also 1,
Examples of glycol components other than 4-cyclohexanedimethanol include chain aliphatic glycols such as ethylene glycol, tetramethylene glycol, hexamethylene glycol, and the like. The 1,4-cyclohexanedimethanol in the present invention can be produced, for example, by catalytic reduction of dimethyl terephthalate or terephthalic acid, but there is no problem in producing it by any method. The ratio of cis isomer to trans isomer of 1,4-cyclohexanedimethanol is not particularly limited, but cis isomer/trans isomer = 4/6 to
A range of 0/10 is preferred. In the poly-1,4-cyclohexylene dimethylene terephthalate, for example, stabilizers such as phosphoric acid, phosphorous acid and their esters, titanium dioxide, particulate silica, kaolin, calcium carbonate, calcium phosphate, etc. A matting agent, a lubricant, etc. may be included. Polyethylene terephthalate in the present invention is a polyester in which 80 mol% or more of the dibasic acid component is terephthalic acid and 90 mol% or more of the glycol component is ethylene glycol. Examples of dibasic acid components other than terephthalic acid include dibasic acids such as isophthalic acid and 2,6-naphthalene dicarboxylic acid. Examples of glycol components other than ethylene glycol include alkylene glycols such as propylene glycol, tetramethylene glycol and hexamethylene glycol; and aliphatic glycols such as 1,4-cyclohexanedimethanol. Polyethylene-2,6-naphthalate in the present invention is a polyester in which 80 mol% or more of the dibasic acid component consists of 2,6-naphthalene dicarboxylic acid and 90 mol% or more of the glycol component consists of ethylene glycol. . As dibasic components other than 2,6-naphthalene dicarboxylic acid,
Terephthalic acid, isophthalic acid, naphthalene-2,
Examples include dibasic acids such as 7-dicarboxylic acid. Examples of glycol components other than ethylene glycol include alkylene glycols such as propylene glycol, tetramethylene glycol and hexamethylene glycol; and aliphatic glycols such as 1,4-cyclohexanedimethanol. The polyethylene terephthalate and polyethylene-2,6-naphthalate can each contain compounds that can be contained in the poly-1,4-cyclohexylene dimethylene terephthalate, such as a stabilizer, a matting agent, a lubricant, and the like. The film base material in the present invention is a three-layer laminated film, that is, a polyethylene terephthalate film or a polyethylene-2,6-naphthalate film as an intermediate layer (core layer), and poly-1,4-cyclohexyl film on both sides of the intermediate layer. This is a laminated film made of laminated silane dimethylene terephthalate films, which are biaxially oriented. This laminated film can basically be manufactured by conventional film forming methods. For example, polyethylene terephthalate or polyethylene-2,6-naphthalate (hereinafter sometimes referred to collectively as polyester B) and poly-1,4-cyclohexylene dimethylene terephthalate (hereinafter sometimes referred to as polyester A). Polyester A and Polyester B are dried, melted in separate melting equipment, and merged in a polymer pipe during extrusion, or polyester A and polyester B are merged in an extrusion die consisting of three layers in the thickness direction to form a single sheet. Then, extrude onto a casting drum and cool. Furthermore, the unstretched film can be produced by sequentially or simultaneously biaxially stretching and heat setting. The stretching method may be a known method. For example, longitudinal stretching can be carried out by heating between two rolls with different circumferential speeds, and transverse stretching can be carried out by gripping both ends of the film with clips and heating the film in a row of clips. It is possible to stretch by increasing the row spacing. By heat-setting the obtained biaxially oriented film at 150 to 260°C, preferably 180 to 250°C for 1 to 100 seconds, the highly durable laminated film for magnetic recording flexible disks of the present invention can be obtained. . However, the biaxially oriented laminated film in the present invention is not limited to those obtained by such a method. In the above laminated film, the film thickness of polyester A needs to be 0.1 to 20 μm. If the polyester A film is thinner than 0.1 μm, the adhesive durability will hardly be improved, which is not preferable.
Also, if the thickness is thicker than 20 μm, polyester A
It is not preferable because the properties of the flexible disk, particularly its mechanical weakness, may become apparent, and practical problems may arise, such as significant wear of the central hole of the flexible disk and vulnerability to tearing. The polyester A film must be closely bonded to the polyester B film at the interface and must be biaxially oriented. However, polyester A
Of course, the technology of the present invention does not include a method in which the surface of biaxially oriented polyester B is simply coated with polyester B, but in such a case, polyester A often dissolves in the solvent and falls off when coating the magnetic layer. . The film thickness of polyester A is particularly preferably 2 to 20 μm. The larger the thickness of this film layer, the smaller the hygroscopic expansion of the base material, which is preferable. In order to closely bond polyester A and polyester B at the interface, it is preferable to use a technique such as extruding an unstretched sheet using the above-mentioned three-layer structure tie or combining them within a flow path of molten polymer. When stretching an unstretched sheet, polyester A becomes polyester B
The fact that the polyester is present on both sides is advantageous in that curling due to the difference in properties between the two polyesters can be prevented. If there is a large difference in properties (for example, melt viscosity) between polyester A and polyester B, and the interface between polyester A and polyester B does not bond sufficiently, add 20% by weight or less of polyester B to polyester A. It is best to blend in the amount of The biaxially oriented laminated film in the present invention is usually
The thickness is selected from the range of 25 to 125 μm, more preferably 50 to 100 μm. However, the thickness is not limited to this range. The magnetic recording flexible disk of the present invention is composed of a magnetic layer and the above-mentioned base film. The magnetic layer is made of magnetic powder or metal. Examples of the ferromagnetic powder or metal that can be used in the present invention include γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , Fe ₃ O ₄ ,
Co-containing Fe ₃ O ₄ , CrO ₂ , Co-Ni-P alloy, Co-
Examples include ferromagnetic materials such as Ni-Fe alloy, Co-Cr alloy, Co-Ni alloy, and barium ferrite. The binder used with the magnetic powder in the present invention includes known thermoplastic resins, thermosetting resins,
Examples include reactive resins or mixtures thereof. Specifically, for example, vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrol copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid Ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer ,
Polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate,
cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and their Mixtures etc. can be used. Examples of methods for coating the magnetic layer on the support film (biaxially oriented laminated film) include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, Gravure coat, kiss coat, cast coat, spray coat, etc. can be used. Preferably, a magnetic layer is applied to the base film to a thickness of 0.1 to 3 μm. The method for measuring characteristic values in the present invention is as follows. (1) Adhesion After applying the magnetic layer and smoothing the web, leave it for at least 24 hours at a temperature of 20°C and a humidity of 60% RH. (manufactured by 3M, USA) and press firmly. Then, pull the tape rapidly by hand and peel it off in a direction of approximately 180°C. Adhesiveness is determined by the amount (area) of the magnetic layer adhering to the adhesive tape. Good adhesion is when the magnetic layer does not stick to the adhesive tape at all, or when it peels off and sticks, very little of it sticks to the adhesive tape. Poor adhesion occurs when the magnetic layer completely peels off from the polyester film surface and almost the entire surface of the adhesive tape is covered with the magnetic layer. In the middle between the two, when 0 to 30% of the surface of the adhesive tape is covered with the magnetic layer, the rating is 1st grade, when 31 to 60% is covered with the magnetic layer, the rating is 2nd grade, and when 61 to 100% is covered with the magnetic layer, the rating is 1 grade. When it is covered, it is evaluated as grade 3. The smaller the score, the better the adhesive durability between the magnetic layer and the film. (2) Drop-out measurement Measured using a drop-in-out counter SK-444B manufactured by Tokyo Engineering Co., Ltd. A commercially available actual drive is used as the drive device. Drop-outs on the surface of a magnetic recording flexible disk detected by a measuring device are observed under a microscope, and the number of drop-outs caused by minute peeling of the magnetic layer is counted. That is, a flexible disk in which dropout occurs at even one location (when the output level drops by 30% or more from the basic level) is extracted as a defective product. The proportion of the extracted dropout locations that are caused by minute peeling of the magnetic layer is displayed as a percentage. EXAMPLES Next, the present invention will be specifically explained using examples. Examples 1 to 4 and Comparative Example 1 85 mol% of terephthalic acid and 15 mol% of isophthalic acid were used as dibasic acid components, 1,4-cyclohexanedimethanol was used as a glycol component, and 0.05 mol% of titanium oxide was used as a catalyst. (with respect to the acid component) is placed in an autoclave, heated under stirring to transesterify, and then polycondensed to obtain 1,
Poly-1,4-cyclohexylene dimethylene terephthalate (polyester A) consisting of 4-cyclohexanedimethanol, terephthanoic acid and isophthalic acid was obtained. At this time, as a lubricant, the average particle size
0.5% by weight of 0.3 μm titanium oxide was added. Polyethylene-
2,6-naphthalate (PEN-2,6) was obtained. Furthermore, polyethylene terephthalate (PET) was obtained by polymerization using a conventional method. These poly-1,4-cyclohexylene dimethylene terephthalate and polyethylene-2,6-
Naphthalate or polyethylene terephthalate is melted in separate melt extrusion equipment, and both molten polyesters are combined in a three-layer extrusion die, extruded, and cooled to produce an unstretched sheet with a thickness of 1050 microns made of three layers of polyester. Obtained. At this time, the extrusion amount of the polyester during unstretched molding was adjusted so that the layer thickness of the polyester after biaxial orientation was the value shown in Table 1. The obtained unstretched sheet
Stretched 3.6 times in the longitudinal direction at 105℃, 3.8 times in the transverse direction at 115℃, and then heat-set at 220℃ for 30 seconds to increase the thickness.
A biaxially oriented film of 75 μm was obtained. A magnetic coating liquid having the following composition was applied to the biaxially oriented film thus obtained to a thickness of 2 μm. (Magnetic coating liquid) γ-Fe ₂ O ₃ 200 parts by weight Vinyl chloride-vinyl acetate copolymer resin (manufactured by UCC)
VAGH) 30 parts by weight polyurethane (PP-88 manufactured by Nippon Polyurethane Industries)
20 parts by weight Isocyanate compound (Coronate HL manufactured by Nippon Polyurethane Industries) 40 parts by weight Carbon (average size 0.5 μmφ) 20 parts by weight Dimethylsiloxane 2 parts by weight Toluene 70 parts by weight Methyl ethyl ketone 70 parts by weight Cyclohexanone 70 parts by weight The above paints were thoroughly mixed and stirred. It was then subjected to coating treatment. The coated surface was then subjected to calender roll treatment. It was then cut into a magnetic recording flexible disk with an outer diameter of 20 cm and an inner diameter of 3.8 cm. The obtained disc was put into a recording and reproducing device to perform recording and reproducing operations. At that time, the sheet recorder
It rotated at 360 rpm. Table 1 shows the results. As is clear from the examples, the magnetic recording flexible disk of the present invention has extremely excellent characteristics.

[Table] Effects of the Invention According to the present invention, the following effects can be obtained. 1. Since the adhesiveness of the base film can be improved, dropouts caused by peeling of the magnetic layer that occur during the calendering process for smoothing the magnetic layer can be significantly reduced. Therefore, the yield of products can be significantly improved. 2. Since the adhesiveness between the base film and the magnetic layer is improved, the adhesive durability of the flexible disk can be improved. For this reason, even if the magnetic layer is made thinner than before, durability is unlikely to deteriorate. Therefore, high-density recording on flexible disks can be easily achieved. 3. An oriented film made of poly-1,4-cyclohexylene dimethylene terephthalate has a low hygroscopic expansion coefficient, so when it is used in a magnetic recording flexible disk, this effect is exhibited and a flexible disk with a low hygroscopic expansion coefficient can be provided. By increasing the thickness of the polyester layer, a flexible disk with a lower hygroscopic expansion coefficient can be obtained. Therefore, high track density can be obtained. 4 Polyethylene-2 in the core layer of the base film,
When using a 6-naphthalate film, the thermal expansion coefficient of polyethylene-2,6-naphthalate is relatively small at 10×10 ^-6 /°C;
The thermal expansion coefficient of 1,4-cyclohexylene dimethylene terephthalate is relatively large at 25 to 30 × 10 ^-6 /℃, so by making the thickness ratio of the two almost the same, the thermal expansion coefficient of the flexible disk drive (( 17 to 20) × 10 ^-6 /°C). In the case of this combination, the Young's modulus of poly-1,4-cyclohexylene dimethylene terephthalate is about 60% smaller than that of the currently used polyester film, and the Young's modulus of polyethylene-2,6-naphthalate is smaller than that of the currently used polyester film. The apparent Young's modulus of the composite is approximately 120% larger than that of the currently used polyester film, and conventional design techniques such as disk-head interface technology can be used as is.

Claims (1)

[Claims] 1. In a magnetic recording flexible disk formed by providing a magnetic layer on a biaxially oriented polyester film base material and further smoothing the surface, the film base material has a polyethylene terephthalate film or a polyethylene-2,6-naphthalate film as an intermediate layer. layer, with a thickness of 0.1 to 20 μm on both sides of the intermediate layer.
1. A magnetic recording flexible disk characterized in that it is a laminated film in which poly-1,4-cyclohexylene dimethylene terephthalate films are laminated.