JPH04209313A - Film for high-density recording medium - Google Patents

Abstract

PURPOSE:To obtain a base film suitable for a high-density recording medium by using a para-type aramid film having specified film thickness, double refractive index in the material plane, Young's modulus, thermal shrinkage coefficient and surface average roughness. CONSTITUTION:The thickness of the base film is specified to >=30mum thickness, and such a para-type aramid film is used having <=0.01 double refractive index between two directions perpendicular to each other in the film plane, >=1000kg/mm<2> Young's modulus in all directions, <=0.2 thermal shrinkage coefficient at 250 deg.C in all directions, and <0.01 center line roughness (Ra) of the film surface. This film is obtd. by providing specified treatment on a PPTA polymer. Then a magnetic layer or optical recording layer comprising a metal thin film is formed on this base film by predetermined method. The obtd. recording medium is suitable for a light-weight small-size magnetic recording medium or optical recording medium.

Description

[Detailed description of the invention]

[00011

[Industrial Field of Application] The present invention relates to a film for high-density recording media, and in particular to a para-oriented aramid film suitable for use as a substrate for high-quality, high-performance so-called floppy disks and optical disks. [0002] BACKGROUND OF THE INVENTION Polyethylene terephthalate (PET) films have recently been used in bundles as substrates for magnetic recording media. In particular, thick PET film is used for floppy disks. Furthermore, optical discs use glass plates and acrylic resin plates. [0003] However, floppy disks have the following problems. Firstly, in order to increase the density of information recording, metal thin films such as Co, Ni, Cr, Fe, and alloys of these metals are deposited on film substrates by methods such as vacuum evaporation, sputtering, and ion blasting. However, since the glass transition point of PET film as a base film is low at around 70°C, the film must be sufficiently cooled when forming a magnetic layer by vapor deposition, etc., and as a result, the magnetic properties may deteriorate. , adhesion strength may be low. Therefore, a material with good heat resistance is desired for this type of base film for high-density recording media. [0004] Second, when using a floppy disk indoors, there are few problems with conventional floppy disks, but when using it outdoors, for example when placed in a car in the summer, the temperature can reach nearly 100 degrees Celsius. Because of this, the performance of the PET film substrate deteriorates or it no longer functions as a recording medium. The same thing can happen if you use it indoors, for example, if you accidentally put it next to the stove. Therefore, a material with good heat resistance is desired for this type of base film for high-density recording media. [0005] On the other hand, in the case of optical discs, when writing information, it is generally necessary to heat them to 100°C or higher using a laser or the like, and glass substrates have been used from the viewpoint of heat resistance, but all of them are rigid substrates. However, continuous production was not possible when manufacturing optical discs. For this reason, there is a need for a flexible, heat-resistant substrate that can be manufactured continuously. [0006] Aromatic polyamides (aramids) and aromatic polyimides can withstand high temperatures of 200°C or higher, so they can form metal thin films at higher temperatures than polyethylene terephthalate films, and their static magnetic properties such as coercive force and hysteresis loop It is a very promising material as a base film for this type of magnetic recording medium due to its improved squareness ratio. In addition, it is possible to produce films with a higher zig ratio than polyethylene terephthalate from certain types of aromatic polyamides, and several proposals have been made to use them as substrates for high-density recording media. [0007] For example, JP-A-55-1645 discloses bonding a magnetic layer to an aromatic polyamide film as a base using a binder having a special composition. However, since the film used is originally a meta-aromatic polyamide film that does not easily have a high Young's modulus and has high hygroscopicity, it is difficult to produce a high-quality magnetic recording medium. [0008] Japanese Unexamined Patent Publication No. 129001/1989 discloses a magnetic recording medium having an aromatic polyamide copolymer film as a base. Because this film is a copolymer, it lacks dimensional stability against temperature changes, making it insufficient for high-quality, high-density recording.In particular, magnetic thin films can be formed by vapor deposition or sputtering without using a binder. It is unsuitable for this purpose. [0009] Furthermore, Japanese Patent Publication No. 55-51248 discloses a polyamide or polyamide hydrazide film suitable for use in magnetic tapes. Among them, a poly-p-phenylene terephthalamide (PPTA) film is also described, but it is said that optically anisotropic liquid crystal dope provides a high Young's modulus in the vertical direction, but becomes brittle in the horizontal direction. An example in which a film was formed from an optically isotropic solution is described. However, the PPTA film obtained in this way has a small Young's modulus of 900 K g /mm2, and it is difficult to avoid the occurrence of voids, which are thought to be caused by large shrinkage during solidification, resulting in a film with low light transmittance. The disadvantage is that the film is easily torn, and the film is unsatisfactory in terms of surface smoothness, which is important when used as a magnetic tape.Furthermore, it is prone to curling at high temperatures. It was found that the The publication also discloses a film made of a polyamide hydrazide copolymer and having a high Young's modulus and excellent moisture absorption dimensional stability. However, such a film has a large thermal shrinkage rate and deformation due to heat becomes noticeable at temperatures above 180°C, which is inconvenient for applications such as evaporating ferromagnetic material onto the film and using it as a magnetic recording medium. be. [00101 Next, Japanese Patent Application Laid-Open No. 168655/1989 discloses the use of an aromatic polyamide film as a substrate of a thin film magnetic recording medium by vapor deposition, etc. Because of this, the thermal shrinkage rate is high, causing curling, deformation, and waving when forming a thin metal film by vapor deposition, etc., and the surface smoothness is insufficient and the elongation is still insufficient, which makes it difficult to slit the recording medium. The disadvantage is that there are many problems. Furthermore, although there are a few mentions that it can be used with floppy disks, all of the examples relate to video tapes using a film of 20 μm or less as a base, and there is no mention of the vertical and horizontal balance required for the base film of floppy disks. Not expected. [00111 JP-A-60-15437 discloses a magnetic recording medium using a polyimide film, but the Young's modulus is at most 650 kg/mrn2, which is insufficient in terms of dimensional stability against external forces. , true high-density recording is not possible. Furthermore, since a copolymer is used, the heat shrinkage rate is large, and the same dissatisfaction as in the prior art described above remains. [0012] JP-A-60-127523 discloses the use of an aramid or aromatic polyimide film as a substrate for magnetic or optical recording. However, what is specifically disclosed in the examples of the publication is 25 μm.
Only magnetic tapes using the following films as a base,
The film's Young's modulus, thermal dimensional stability, vertical and
Horizontal balance is ignored. [00131 Furthermore, JP-A No. 61-246918 discloses the use of a chlorine-substituted aramid film as a substrate for magnetic recording or optical recording media. However, since it is a polymer containing chlorine atoms, it has a basic drawback in that chlorine atoms are unavoidably removed under heating. Only magnetic tape using
Also, the heat shrinkage rate is 0. It is quite large at 3%, and has the disadvantage of lacking dimensional stability during heating. [0014] JP-A-1-207331 discloses a film with excellent dimensional stability, but it does not take into consideration the vertical and horizontal balance, and it does not specifically disclose in the examples. is a thin film with a thickness of 20 am or less and cannot be used for floppy disks or optical disks. [0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium which eliminates the many drawbacks of the prior art, has excellent heat resistance and dimensional stability, and can be made lightweight and compact. An object of the present invention is to provide a film for a substrate of an optical recording medium that has flexibility and excellent scratch resistance. [0016]

[Means for Solving the Problems] The present inventors have developed various base films for magnetic recording or optical recording media that are capable of truly high-density recording, taking into account the numerous drawbacks of the prior art described above. As a result of our investigation, we discovered that a para-oriented aramid film with a specific thickness, high Young's modulus, particularly small in-plane orientation unevenness, and a low heat shrinkage rate would be suitable for the purpose. After further investigation, we arrived at the present invention. [0017] That is, the present invention provides a para-oriented aramid film having a thickness of 30 μm or more, which has a birefringence index of 0.01 or less between any orthogonal directions in the film plane, and The Young's modulus in the direction of is 1000 kg/m
m2 or more, and 250℃ in all directions within the film plane
A para-oriented aramid film for high-density recording media, which has a heat shrinkage rate of 0.2% or less and a centerline average roughness (Ra) of at least one surface of the film of 0°01 μm or less. . [00181 The para-oriented aramid used in the present invention is substantially composed of units selected from the group consisting of the following structural units. -NHArt -NH-... (I)CO-Ar2
co * 6 @ (II) NHAr3
CO-... (III) Here, Art, Ar
2 and Ar 3 are each a divalent aromatic group, (
I) and (II) when present in the polymer are substantially equimolar. [00191 In order to ensure good mechanical performance in the film of the present invention, Art , Ar:: and A r 3 are each so-called para-oriented groups. Here, para-orientation means that the bonds that grow the molecular chain are located coaxially or parallel to the opposite direction of the aromatic nucleus. Specific examples of such divalent aromatic groups include paraphenylene, 4,4゛-biphenylene, 1
, 4-naphthylene, 1,5-naphthylene, 2,6-naphthylene, 2,5-pyridylene, and the like. They may be substituted one or more with non-reactive groups such as halogen, lower alkyl, nitro, methoxy, sulfonic acid, cyan groups and the like. Each of Art, Arz and Ar3 may be two or more types, and may be the same or different. [0020] The para-oriented aramid used in the present invention may be copolymerized with groups other than those mentioned above in an amount of about 30 mol % or less, or may be blended with a small amount of other polymers. In order to maintain the heat shrinkage rate at a preferable level, the para-oriented aramid of the present invention is preferably a substantially homopolymer, and a typical polymer is poly(p-).
(hereinafter referred to as PPTA), poly(p-benzamide), and fluorine, methyl, and ethyl substituted products thereof. (00211 The degree of polymerization of the para-oriented aramid of the present invention is
If it is too low, it will not be possible to obtain a film with good mechanical properties, so the logarithmic viscosity ηinh is preferably 4.5 or more, more preferably 5 or more (value measured at 30°C by dissolving 0.5 g of polymer in 100 ml of sulfuric acid). ) is selected. The film of the present invention has a Young's modulus of at least 1000 kg/mm2 in any direction (all directions) parallel to the film surface, and has an abnormally large Young's modulus as a film. Preferably 1200 kg/mm
It is 2 or more. This requirement is closely related to the film's resistance to deformation to external forces. [0022] That is, since the film of the present invention has a large Young's modulus, dimensional changes are small when external forces such as bending or tension are applied, and high-density recording can be performed with high accuracy. Such a high Young's modulus is thought to be due to the very high level of plane orientation of molecular chains within the film. The film of the present invention has a thickness of 30 μm or more, preferably 35 μm
The upper limit is preferably 150 μm. If the thickness is less than 3071 m, the resistance to deformation against external forces will be small despite having a high Young's modulus, making it difficult to achieve the goal of high-density recording. However, since the film of the present invention has a high Young's modulus, it is possible to use a relatively thin film compared to conventional floppy disks and optical disks. [0023] It is very important that the film of the present invention has a birefringence index (hereinafter sometimes referred to as Δn) of 0.01 or less between any orthogonal directions within the film plane. Δn is preferably 0.005 or less. Such a small Δn indicates that the plane orientation of the polymer molecular chains is extremely uniform within the plane of the film. Therefore, dimensional changes of the film due to changes in temperature and humidity, application of external force, etc. are uniform in all directions, and high-density recording is possible when used as a substrate of a recording medium. Δn is determined by the compensator attached to the polarizing microscope.
It can be measured using a conventional method. [0024] Furthermore, the film of the present invention has a heat shrinkage rate of 0.2% or less at 250°C in all directions of the film surface, more preferably 0.2% or less. It is less than 1%. Such preferable characteristics are found in the copolyamide hydrazide films disclosed in Japanese Patent Publications No. 51248/1982 and 44957/1983, the aramid copolymer films disclosed in Japanese Patent Application Laid-open No. 168655/1980, and the aramid copolymer films disclosed in Japanese Patent Publications No. 58-168655 and 60-1543
This is a performance unique to the film of the present invention, which the polyimide copolymer film of Publication No. 7 does not have. A film with a low heat shrinkage rate is useful because it does not cause deformation of the substrate during vapor deposition or sputtering of a recording layer, for example. Also, when it is commercialized as a recording medium, it will be able to be used outdoors, placed indoors near a stove or air conditioner, or even in tropical regions without any worries. [0025] The film of the present invention has excellent surface properties, with a center line average roughness (Ra) of at least one surface of 0.01 μm or less. More preferably, Ra is 0.008 μm or less, even more preferably 0.0
06 μm or less. By using a film with low Ra for the substrate, the surface smoothness of the recording medium is improved, and in the case of magnetic recording media, undesirable situations such as a decrease in output, an increase in dropout, and an increase in noise can be avoided. Furthermore, in an optical recording medium, it becomes possible to accurately reflect or polarize a laser or the like during reading. Centerline average roughness (Ra) can be measured according to JIS B-0601 and JIS B-0651. (Cutoff value: 0.08 mm) For example, a versatile surface profile measuring device Surfcom 3B manufactured by Tokyo Seimitsu Co., Ltd. can be used. [00261 Films of the present invention preferably have an elongation of at least 8% in any direction parallel to the plane of the film. Preferably it is 12% or more. Films with an elongation of less than 8% are brittle and have poor handling. The degree of elongation is also related to the tear strength, and in order to improve the workability of film slitting and other processing, it is preferable that the elongation is 8% or more in any direction. [00271 The film of the present invention preferably weighs 20 kg
It has an end tear resistance of f or more. Therefore, it has excellent durability as a recording medium. The film of the present invention further has a hygroscopic expansion coefficient of 3 in any direction parallel to the film surface.
It is preferably at most X10-5 mm/mm/%RH, more preferably at most 2,5 X10-5 mm/mm/%RH. Hygroscopic expansion coefficient is 3X10-5mm/mm
/%RH means that the film lacks dimensional stability against changes in humidity. [0028] The film of the present invention preferably has very high transparency. High transparency, e.g. 600n
The transmittance of visible light with a wavelength of m is preferably 55% or more,
More preferably, it is 70% or more. The film of the present invention is also preferably substantially void-free. Furthermore, the film of the present invention desirably has a density in the range of 1.39 to 1.43 g/cm<3>. This density value was measured at 30° C. by density gradient tube method using carbon tetrachloride-toluene. The density is 1.39g/
If it is less than cm3, the mechanical properties will deteriorate and the weight will be 1.43g/
If it exceeds cm3, the film becomes brittle and therefore tends to lose its toughness. In any case, because of this low density, a light, high-strength, and high-hardness film can be obtained. This is preferable because it improves scratch resistance during ion blating or painting. [0029] As the film of the present invention, the following X
It is preferable to have a plane orientation defined by a crystal orientation angle determined by line diffraction. That is, it is preferable that the crystal orientation angle with respect to the peak of 2θ #18° caused by X-rays incident on the film surface is 60° or less. The incidence of X-rays can be divided into cases where the X-rays are incident at right angles to the film surface (hereinafter referred to as the TV direction) and cases where they are incident parallel to the surface (hereinafter referred to as the SV force direction). [00301 In the film of the present invention, a large diffraction peak of 2θ≠18° appears on the equator line due to incidence from the SV force direction, but the crystal orientation angle at 2θ≠18° is 60°.
It is preferable that it is less than or equal to °. When this orientation angle condition is satisfied, the plane orientation of the polymer molecular chains is generally high, and as a result, high strength, high Young's modulus, and high moisture absorption dimensional stability are realized. [00311 As a method for measuring the crystal orientation angle, a known method can be adopted, and for example, the following method is used. A diffraction intensity curve is obtained by placing the counter at the predetermined 20 angles and rotating the film 180°. The value of the arc length in degrees in the diffraction photograph corresponding to the point of the highest intensity of this curve that is half the intensity of the baseline drawn between the lowest intensity points (i.e., 50% of the baseline of the highest intensity). (angle with respect to the point) and use it as the crystal orientation angle of the sample. In the measurement, the diffraction intensity can be measured by stacking several films if necessary. [00321 The film of the present invention may contain dispersed inorganic substances such as silica, talc, and calcium sulfate as a smoothing agent. Further, the film of the present invention may be subjected to various surface treatments and pretreatments for the purpose of facilitating adhesion, improving flatness, coloring, preventing static electricity, imparting abrasion resistance, and the like. Next, a method for obtaining such a para-oriented aramid film will be described. To do this, it is first necessary to prepare an optically anisotropic dope of para-oriented aramid. [0033] A suitable solvent for preparing the dope used to cast the film is sulfuric acid at a concentration of 95% by weight or greater. If the sulfuric acid content is less than 95%, dissolution may be difficult or the dope will have an abnormally high viscosity after dissolution. The dope of the present invention includes:
A small amount of chlorosulfuric acid, fluorosulfuric acid, phosphorus pentoxide, trihalogenated acetic acid, etc. may be mixed. Sulfuric acid is 100
Although it is possible to use a concentration higher than 97% by weight, a concentration of 97 to 100% by weight is preferably used from the viewpoint of stability and solubility of the polymer. [0034] The polymer concentration in the dope is at room temperature (approximately 2
0 to 30° C.) or higher, and specifically, it is used at a concentration of about 10% by weight or more. At polymer concentrations below this range, ie, polymer concentrations that do not exhibit optical anisotropy at room temperature or higher temperatures, the formed film often does not have desirable mechanical properties. The upper limit of the polymer concentration in the dope is not particularly limited, but is usually 20% by weight or less, preferably 18% by weight or less for particularly high ηinh polymers, and more preferably 16% by weight or less. . [0035] The dope may be mixed with conventional additives, such as fillers, deglapers, UV stabilizers, heat stabilizers, antioxidants, pigments, solubilizing agents, and the like. Whether the dope is optically anisotropic or optically isotropic can be determined by a known method, such as the method described in Japanese Patent Publication No. 50-8474, but the critical point depends on the type of solvent, temperature, and polymer concentration. , the degree of polymerization of Bommer, the content of non-solvent, etc., so by investigating these relationships in advance, an optically anisotropic dope can be created, and by changing the conditions for an optically isotropic dope, optically anisotropic It is possible to change from optical isotropy to optical isotropy. [0036] Prior to molding and solidifying the dope, it is preferable to remove as much insoluble dust, foreign matter, etc. as possible by filtration, etc., and to remove gases such as air generated or involved during dissolution. . Deaeration can be performed once the dove is prepared, or can be achieved by performing it under vacuum (reduced pressure) from the stage of charging raw materials for preparation. Preparation of the dope can be carried out continuously or batchwise. [0037] The dope thus prepared is cast onto a supporting surface moving from a die, for example a slit die, while maintaining optical anisotropy. The steps of casting and subsequent conversion to optical isotropy, coagulation, washing, stretching, drying, etc. are preferably carried out continuously, but if necessary, all or some of them may be carried out intermittently, i.e. It may be carried out batchwise. Setting the draft (the ratio of the take-up speed of the support surface to the discharge speed from the die) to be smaller than 5 during casting will bring the centerline average roughness (Ra) of the film to a desirable level of 0.01 μm or less. It is necessary to do so. [0038] The method for obtaining a transparent film with excellent mechanical properties used in the present invention is to cast a dope onto a supporting surface and then convert the dope from optically anisotropic to optically isotropic before solidification. It is something to do. In order to change optical anisotropy to optical isotropy, the optically anisotropic dope cast on the supporting surface is made to absorb moisture to lower the concentration of the solvent forming the dope before solidifying. Transform the dope into an optically isotropic region by changing the solubility and polymer concentration, or increase the temperature of the dope by heating to transform the dope phase into an optically isotropic region, or simultaneously or sequentially absorb moisture and heat. This can be achieved by using them together. [0039] The optically isotropically cast dope on the support surface then undergoes solidification. For example, water, dilute sulfuric acid of up to about 70% by weight, aqueous sodium hydroxide and aqueous ammonia of up to about 20% by weight, sodium sulfate, aqueous sodium chloride and chloride of up to about 10% by weight can be used as the coagulating liquid for the dope. Calcium aqueous solution, etc. The temperature of the coagulating liquid is preferably 15°C or lower, more preferably 5°C or lower. This is because it has been found that, in general, the lower the temperature of the coagulating liquid, the less voids are included in the film. [00401 Since the solidified film as it is contains acid, it is necessary to wash and remove the acid content as much as possible in order to produce a film whose mechanical properties are less likely to deteriorate due to heating. Specifically, the removal of acid content is approximately 500p.
It is desirable to carry out the process down to pm or less. Water is usually used as the cleaning solution, but if necessary, hot water may be used.
After neutralization cleaning with an alkaline aqueous solution, cleaning with water or the like may be performed. Cleaning is carried out, for example, by running the film in a cleaning liquid or by spraying the cleaning liquid. [00411 The washed film is then subjected to stretching. Stretching is most preferably carried out using the plasticizing effect of water, and is carried out at room temperature or lower in a water-containing state. Stretching is performed biaxially or sequentially. The stretching ratio is
It is selected from the range of 1.05 to 1.5 times on an area basis, and the ratio of the stretching ratio in the length direction and width direction is usually 1.00 ± 0.
．． 1, and the specific number can be determined from the relationship between the tension in the coagulation to washing steps and the Δn value of the film to be manufactured. Preferably, the stretching ratio in the width direction is 1400 to 1.10 times the stretching ratio in the length direction. If the area stretching ratio is less than 1.05, it is difficult to make the Young's modulus of the film 1000 Kg/mm 2 or more, and the center line average roughness (Ra) also becomes large. Furthermore, if the stretching speed is too high, the Δn and the thermal retraction rate will locally increase and the film will not be homogeneous, so preferably a stretching speed of 100%/min or less is selected. The stretched film is then dried at a temperature below 170°C. At this time, it is important not to substantially shrink the film. To prevent shrinkage during drying, e.g.
In industrial production, tenters can be used. Shrinkage during drying is undesirable because it causes a decrease in Young's modulus, an increase in centerline average roughness, and local variation (disturbance) in Δn. In addition, drying or removing moisture can be done at 17
It is very important to dry the film at a low temperature of 0°C or lower; if a film with a thickness of 30 μm or more is dried at a temperature exceeding 170°C, as in the present invention, voids may occur in the film or the dimensional stability may deteriorate. or The drying temperature is preferably 140°C or lower. [0042] The film thus dried and substantially free of moisture is then subjected to a first heat treatment. This heat treatment is finally carried out at a temperature of 300° C. or higher without causing substantial shrinkage, thereby increasing crystallinity while maintaining or increasing the orientation of the polymer chains. The heat treatment temperature is preferably 350°C or higher. Note that directly introducing the undried film into a heat treatment process at 300°C or higher is
This is undesirable as it causes voids as described above.
- It should be first dried at a temperature below 170°C to substantially remove moisture, and then heat treated at a temperature above 300°C. However, the profile of temperature change from the drying step to the first heat treatment step is not particularly limited. Even in the heat treatment step, it is important that the film does not undergo substantial dimensional shrinkage, and for example, industrially, the treatment can be performed using a tenter. [00431 The film thus subjected to the first heat treatment is then allowed to absorb moisture. The means of moisture absorption is not limited, such as steaming, immersion in a water bath, running in a high temperature atmosphere, etc., and preferably about 0.1% by weight or more,
Approximately 0. Absorb moisture of 2% by weight or more. The dimensional change of the film during moisture absorption and its effects are negligibly small, and the moisture absorption operation can be carried out under tension, without tension, or by tensioning in only one direction. [00443 Next, the moisture-absorbed film is subjected to a second heat treatment. The second stage heat treatment is performed at a temperature of 280° C. or higher and at least 10° C. lower than the first stage heat treatment temperature, without tension or under a low tension of 1 kg/mm 2 or less. If heat treatment is performed without observing these limiting conditions,
The heat shrinkage rate at 250°C exceeds 0.2%. Heating methods for drying and heat treatment are not particularly limited, and include methods using heated gas (air, nitrogen, argon, etc.) or room temperature gas, methods using radiant heat such as electric heaters and infrared lamps, dielectric heating methods, etc. One of the preferred embodiments is to manufacture the film while running it continuously throughout the entire process, but if desired, it may be carried out partially in a batch manner. Further, an oil agent, an identification dye, etc. may be added to the film in any step. [0045] In the present invention, the content of dirt and dust in the dope, moisture absorption gas, heating gas, supporting surface, coagulation liquid, cleaning liquid, drying gas, etc. is made as low as possible. In this respect, producing a film using so-called clean room or clean water is also one of the preferred embodiments. The film of the present invention may contain dispersed inorganic substances such as silica, talc, and calcium sulfate as a smoothing agent. [0046] In addition, the film of the present invention is subjected to various surface treatments for the purpose of facilitating adhesion, improving flatness, coloring, preventing static electricity, imparting abrasion resistance, etc., prior to forming the high-density recording layer described below. Pretreatment may be performed. The high-density recording layer laminated on the film of the present invention includes one for magnetic recording media and one for optical recording media. [0047] A magnetic layer used in a magnetic recording medium is a coated magnetic layer formed by coating, orienting, and drying a magnetic paint in which fine ferromagnetic powder is cross-dispersed in a binder, an additive, a solvent, etc. A metal thin film type magnetic layer is provided by depositing a ferromagnetic metal, alloy, etc. by paper deposition or plating, such as vacuum evaporation, electroless plating, sputtering, or ion blating. [0048] In the case of a metal thin film type magnetic layer, iron, cobalt,
Nickel and other ferromagnetic metals, or Fe-Co, F
e-Ni, Co-Ni, Fe-3i, Fe-R
h, FeV, Co-P, Co-B, Co-5i
, Co-V, Co-Y, Co-La, Co-C
e, Co-Pr, Co-3m, Co-Mn,
Fe-Co-Ni, Co-Ni-P, Co
-N1-B, Co-Ni -Ag, Co-Ni -
Nd, Co-Ni-Ce, Co-Ni-Zn, Co-N
i-Cu, Co-Ni-Hg, Co-Ni-
W, Co-Ni-Re, Co-Mn-P, Co-Z
n-P, Co-Pb-P, Co-3m-Cu, Co-N
1-Zn-P. A magnetic layer is formed by forming a ferromagnetic alloy such as Co--Ni--Mn--P into a thin film by a deposition method such as a paper deposition method or a plating method. Paper deposition method is a method in which the substance or compound to be deposited is deposited on a substrate as vapor or ionized magnetism in a gas or vacuum space, and includes vacuum vapor method, sputtering method, ion blating method, chemical vapor phase plating method, etc. (Chemical Vapor De
-position) method etc. correspond to this. The plating method refers to a method of depositing a substance on a substrate from a liquid phase, such as electroplating or electroless plating. [0049] In the case of a paint-on type magnetic layer, the magnetic coating mainly contains a ferromagnetic fine powder, a binder, and a coating solvent, and also contains a dispersant, a lubricant, an abrasive, an antistatic agent, an antirust agent, and an antifungal agent. It may also contain additives such as agents. As the above-mentioned ferromagnetic fine powder, ferromagnetic iron oxide, ferromagnetic chromium dioxide, ferromagnetic alloy powder, etc. can be used. [00501 The above ferromagnetic iron oxide is a ferromagnetic iron oxide having an X value in the range of 1.33≦X≦1,50 when expressed by the general formula FeOx, that is, magnetite (γ-F203
, X=1.50), magnetite (Fe3O4.
Ox, 1.33<x<1.50). A divalent metal may be added to these ferromagnetic iron oxides. Divalent metals include Cr, Mn, Co, Ni, Cu, Zn, etc., and are present in an amount of 0 to 10 atomic% relative to the above iron oxide.
It is added within the range of [00511 The above ferromagnetic chromium dioxide is composed of CrCh and Na, K, Ti, v, Mn, Fe.
, Co, Ni, Tc, Ru, Sn, Ce, Pb, or other metals, P, Sb, Te, or other semiconductors, or CrOz to which 0 to 20 wt% of oxides of these metals are added is used. The acicular ratio of the above ferromagnetic iron oxide and ferromagnetic chromium dioxide is about 2/1 to 20/1, preferably 5/
1 or more, and an average length in the range of about 0.42 to 2.0 μm is effective. [0052] The above ferromagnetic alloy powder has a metal content of 75 w
t% or more, and 80wt% or more of the metal content is at least one ferromagnetic metal (i.e., Fe, Co
, Ni, Fe-Co, Fe-Ni, Co-Ni,
Or C. 20 wt% or less of the metal content, preferably 0.5 to 5 wt% is Al or Si. S, Sc, Ti, V, Cr, Mn, Cu,
Zn, Y, Mo, Rh, Pd, Ag, S
n, Sb, Te, Ba, Ta, W, Re,
Au, Hg, Pb, Bi, La, Ce. It has a composition of Pr, Nd, B, P, etc., and may also contain a small amount of water, hydroxide, or oxide. [0053] The above ferromagnetic alloy powder has a major axis of about 0.5μ
It is a particle of m or less. As the binder for the magnetic layer, conventionally known thermoplastic resins, thermosetting resins, reactive resins, or mixtures thereof are used. The magnetic recording method may be horizontal magnetization or perpendicular magnetization. On the other hand, in the case of optical recording, the recording layer includes Te, Bi, Sb, Se, Gd, and Tb.
These substances may be used alone, or may consist of compounds such as these, or oxides of these substances. Furthermore, in order to improve the recording characteristics, trace amounts of other elements may be contained in addition to the above-mentioned substances. [0054]

[Examples] Examples are shown below, but these reference examples and examples are for illustrating the present invention, and are not intended to limit the present invention. In the examples, parts by weight or weight % are shown unless otherwise specified. The evaluation of each characteristic in the examples was carried out by the following method. [0055] Logarithmic viscosity of 1 inh is 100 m of 98% sulfuric acid
0.5 g of polymer was dissolved in 1 and measured at 30° C. in a conventional manner. The strength and elongation and Young's modulus were determined by cutting a film sample into a rectangle of 100 mm x 10 mm using a constant speed extension type strength and elongation measuring machine, and measuring the load-elongation curve at an initial grip length of 30 mm and a tensile speed of 30 mm/min. I drew it twice and calculated it from this. [005612 The heat shrinkage rate at 50°C is 0.05k
3 in an oven at 250°C with a tension of g/mm2.
Leave it for 0 minutes, and then leave it at room temperature (25℃) before and after this oven treatment.
It is calculated from the dimensional change in . [0057]

[Example 1] Y7inh5.5 PPTA polymer was dissolved in 98.5% sulfuric acid at a polymer concentration of 12%.
A dope with optical anisotropy at ℃ was obtained. After degassing under vacuum, the bent tube that passes through the film from the tank, passes through the gear pump, and reaches the die is kept at about 70°C and heated to 0. lmm×700m
cast from a die with a slit of m to a mirror-polished tantalum belt at a temperature of about 105 m at a relative humidity of about 12%.
The cast dope was made optically isotropic by blowing air at a temperature of .degree. C., and the dope was introduced together with the belt into a dilute sulfuric acid bath at 5.degree. C. to solidify. The coagulated film was then peeled off from the belt and washed by running it in water at about 10°C, then in a 0.1% NaOH aqueous solution, and then in warm water at 50°C. The washed film was stretched by 15% each in the length and width directions using a tenter without drying, then dried at 130°C for a fixed length, and then stretched at 370°C for a fixed length using another tenter. The first heat treatment was performed. Furthermore, after placing the film in a water bath at room temperature to absorb about 0.3% moisture, the film is introduced into a third tenter, and the clip-shaped gripping section Adjust to 330℃
heat treated. The tension in the third tenter is approximately 0.3Kg/
It was mm2. [0058] The obtained film has a thickness of 50 μm, y7
inh5.0, and density 1.40g/cm2. Other properties of the film are shown in Table 1. Next, γ-Fe2 was placed on a 50 μm film to a dry thickness of about 5 μm.
A magnetic coating liquid containing O3 as a magnetic material was applied, followed by magnetic field orientation treatment, drying, and calendering, followed by cutting into a 5-inch diameter piece to obtain a floppy disk. I have used this disk in my computer and word processor without any problems. [0059] Further, there was no problem even after this disk was stored at 90° C. for 24 hours. On the other hand, commercially available floppy disks became unusable after being stored at 90°C for 24 hours. [00601 [Example 2] Draft of film manufacturing conditions of Example 1 (
The ratio of the tantalum belt take-up speed to the discharge speed from the die) was changed from 1.6 to draft 1.1, and the stretching rate was 18%.
A film was produced in the same manner as in Example 1, except that the third tester was held at a fixed length to give a tension of about 0.9 kg/mm2. [00611 The obtained film had a thickness of 75 μm, η1
nh4. 8. Density 1.40 g/cm'', and other properties are shown in Table 1. A floppy disk was made in the same manner as in Example 1, and it was confirmed that it had high performance and excellent heat resistance. [0062 [Example 3] A film was produced under the same conditions as in Example 1, except that the draft was changed to 2 or 3 and the stretching ratio was changed to 14% in the length direction and 18% in the width direction. The obtained film had a thickness of 38 μm, η1nh5.1, and a density of 1.40 g/cm3, and other properties are shown in Table 1. [0063] Next, the film was loaded into a vacuum chamber and
The film was treated with glow treatment under an Ar atmosphere of -2 Torr, then the vacuum chamber was evacuated to 10-6 Torr, and the film was heated to 100
A Co--Ni alloy was deposited to a film thickness of 1200A** by electron beam evaporation while running along a drum heated to .degree. The floppy disk thus obtained is thinner and more rigid than conventional products, and also passed the heat resistance test shown in Example 1, so it can be used as a floppy disk for carrying outdoors, such as in electronic still cameras. considered suitable. [0064]

[Example 4] In Example 1, the drying temperature was set to 150°C, and the second stage heat treatment was performed at 300°C without using a tenter.
Example 1 was repeated except that it was carried out under no tension in an oven. The obtained film had a thickness of 50LLm and η1n
h5.0, density 1.40 g/cm3, and other properties are shown in Table 1. [0065] A Co--Ni alloy was laminated to a thickness of 2500A by sputtering on the film thus obtained, thereby obtaining a floppy disk with excellent heat resistance. [0066]

[Example 5] In Example 2, the stretching ratio was set to 14 in the longitudinal direction.
% in the width direction and 18% in the width direction, and Example 2 was repeated except that the tension in the third tenter was approximately 0.5 Kg/mm2. The obtained film had a thickness of 75 μm and η1n
h4.9, density 1.41 g/cm3, and other properties are shown in Table 1. [0067] Next, this film was cut to a diameter of about 130 mm, and 5i02, 5b20
Optical recording layers were laminated in the order of Te 40-Ge 40 recording layer and 5in2. The thickness of each layer is 500 people, 8
It was 00A, 10008. In this way, it was found that the film of the present invention is also useful as an optical recording disc. [0068]

[Table 1] [0069]

[Effects of the Invention] Using the film of the present invention, high-density recording media such as floppy discs and optical discs can be produced. The first characteristic of the floppy disk as a magnetic recording medium is that it has excellent heat resistance.
For floppy disks made of PET) film,
The film of the present invention, which was previously limited to indoor use, can be used outdoors by using it as a base film, and there is no possibility of deterioration or deterioration caused by leaving it in a car in the summer or by direct sunlight. Moreover, even when used indoors, it will not change in quality or deteriorate even if it is brought close to a heat source such as a stove, and the recorded contents will not be lost. Furthermore, since the film of the present invention has a higher bias ratio than PET film, it has greater rigidity, and therefore, a thinner film can be used, and the recording section can be made lighter and smaller. A floppy disk using the film of the present invention is
In addition to the above, high-density recording is possible due to excellent dimensional stability. [00701 Furthermore, the optical disc using the film of the present invention is characterized by having both heat resistance and flexibility, and for this purpose, heating with a laser or the like when writing information can be performed without any problem, and Utilizing its flexibility, it becomes possible to manufacture recording media by continuous vapor deposition, sputtering, etc., which was impossible with rigid substrates. Further, since the film of the present invention has high hardness, it has excellent scratch resistance and is advantageous for continuous production of recording media.

Claims (1)

[Claims] 1. A para-oriented aramid film with a thickness of 30 μm or more, which has a birefringence of 0.01 or less in any orthogonal directions within the film plane, and has a Young's birefringence in all directions within the film plane. The film has a heat shrinkage rate of 1000 kg/mm^2 or more, a heat shrinkage rate of 0.2% or less at 250°C in all directions within the film plane, and a center line average roughness (Ra) of at least one surface of the film. ) is 0.01 μm or less, a para-oriented aramid film for high-density recording media.