JPH0347191B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a laminated polyester film for magnetic recording media, and more specifically to a magnetic recording medium that has a low noise level, a good signal-to-noise ratio in data reading, and has excellent running properties by supporting a magnetic thin film. The present invention relates to a laminated polyester film forming a medium. Prior Art A common recording medium in current magnetic recording is a film made of γ-Fe ₂ O ₃ , Co on the surface of a suitable base material, for example, a flexible polymer film (polyester film, etc.) with a thickness of several μm to several tens of μm. -Doped γ-
A laminate in which a magnetic recording layer is formed by coating ferromagnetic powder such as Fe ₂ O ₃ , CrO ₂ or Fe dispersed in an organic binder to a thickness of several μm to approximately 10 μm. is put into practical use. A required improvement in magnetic recording technology is to increase the recording density per given area. In magnetic memory devices used in disk, drum or tape recording devices, the limit of recording density is determined by the ratio of the demagnetizing field to the film coercive field. The strength of the demagnetizing field is also related to the saturation magnetization and thickness of the recording medium. and,
In order to achieve an acceptable level of signal-to-noise ratio, it is necessary to obtain a thin recording medium layer capable of obtaining a sufficient output signal. This becomes easier to achieve as the saturation magnetic flux density and squareness ratio of the B-H curve of the recording medium become higher. In this sense, there is a need for a magnetic recording medium that has a high coercive force, a hysteresis loop with a good squareness ratio, a thin recording medium layer, and a high remanent magnetic moment, and in particular has a low noise level and There is a strong demand for metal thin film magnetic recording media that have a good signal-to-noise ratio when reading data and, in particular, have a low noise level when reproducing high-density recording. In response to this background, in recent years, as high-density magnetic recording media, metal thin films have been deposited on nonmagnetic supports as magnetic recording layers by vacuum deposition methods such as vacuum evaporation and sputtering, or by plating methods without using binders. It has been proposed to form a thin film magnetic recording material using this ferromagnetic metal. For example, Co vapor-deposited tape (Japanese Unexamined Patent Publication No. 147010/1982), a perpendicularly magnetized film made of a Co-Cr alloy (Japanese Unexamined Patent Publication No. 134706/1983), and the like have been proposed. A metal thin film formed by such thin film forming means such as vapor deposition, sputtering, or ion plating has a thickness of 1.5 μm or less and is equivalent to a conventional coated recording medium in which the magnetic layer has a thickness of 3 μm or more. Performance can be obtained. Incidentally, it is considered that magnetic properties such as the coercive force Hc, which is a static property, or the squareness ratio of the hysteresis loop do not depend much on the surface condition of the nonmagnetic support used. An example of a structure based on this idea is a Co--Cr multilayer structure formed by vacuum deposition as disclosed in US Pat. No. 3,787,327. However, the disadvantage of these methods is that the metal thin film formed is thin, and the surface condition (surface irregularities) of the nonmagnetic support directly manifests as irregularities on the magnetic film, which causes noise. Ta. From the viewpoint of noise, it is preferable that the surface condition of the nonmagnetic support is as flat as possible. On the other hand, from the viewpoint of handling such as film winding and unwinding, if the film surface is flat, the film
The surface of the base film is required to be easily slippery because the films have poor sliding properties and a blocking phenomenon occurs, resulting in failure to produce a finished product. Furthermore, as a final product of a metal thin film magnetic recording medium, its runnability and slipperiness are important qualities, and for this purpose as well, the slipperiness of the base film surface is important. Conventionally, as a method for improving the slipperiness of a base film, a method has been known in which microparticles in a polymer are used to form protrusions on the surface of the film to improve slipperiness.One method for incorporating microparticles into the polymer is to use silicon oxide. , a method of adding inert particles such as titanium dioxide, calcium carbonate, talc, and clay into polymers (external particle method), catalyst components used during polyester synthesis,
A method has been proposed in which part or all of the components of the coloring inhibitor are precipitated during the polymerization reaction process to form fine particles in the polymer (internal particle method). However, according to the research results of the present inventors, when a metal thin film magnetic recording medium is created using a base film with the same surface properties as that used in conventional coated recording media as a nonmagnetic support, the final product It became clear that it was inferior in terms of running performance and slipperiness, and was not suitable for practical use. The reason for this is that in conventional coated recording media, binder components and lubricant components contained in the coated magnetic layer ooze out and are transferred to the opposite base film surface, resulting in the effect of improving slipperiness. However, in a recording medium in which a metal thin film is formed on a nonmagnetic support without using a binder as a magnetic recording layer, the transfer of the binder component does not have the effect of improving slipperiness. Furthermore, it has been proposed to improve the running properties of this metal thin film magnetic recording medium by applying the above-mentioned method of adding fine particles, and to create a composite film with different surface properties on the magnetic side and the running side (Japanese Patent Application Laid-Open No. 1983-1991). −74910,
JP-A-50-3308, JP-A-50-33805, JP-A-Sho
No. 58-155939, etc.), but in order to obtain the desired running performance and slipperiness using only this method, it is necessary to increase the surface roughness to a very large or large degree, and in this case, the protrusions on the running surface side transferred to the opposite magnetic recording surface,
As a result, the magnetic film becomes uneven, which deteriorates the electromagnetic conversion characteristics.Furthermore, during repeated running, the coefficient of friction increases, worsening running performance, and in extreme cases, it may stick to the metal pins in the running system. It became clear that there was a problem. In order to solve these problems, the inventor of the present invention conducted extensive research and found that by creating a laminated film structure with specific surface characteristics and incorporating a specific compound into the film layer forming the back surface. It has been found that the above-mentioned problems can be significantly improved. OBJECT OF THE INVENTION An object of the present invention is to provide a magnetic recording medium that has a low noise level and a good signal-to-noise ratio when reading data, particularly when playing back high-density recording, and has excellent running properties. The purpose of the present invention is to provide a laminated polyester film. Structure and Effects of the Invention An object of the present invention is to improve the surface roughness [CLA (unit: μm)] of the surface (A) on which the magnetic thin film is supported of the laminated film.
The maximum protrusion height [PV (unit: μm)] and the number of protrusions whose height is in the range of 0.27 μm to 0.54 μm [H ₁
(Unit: Ke/mm ² )] satisfies the following formulas: CLA≦0.008 (μm) PV≦0.06 (μm) H ₁ ≦10 (Ke/mm ² ), and 80% by weight or more of polyester is composed of polyethylene terephthalate. film layer, and the other surface (B) has a surface roughness [CLA (unit: μ
m)], the number of protrusions with a height of 0.54 μm or more [H ₂
(Unit: Ke/mm ² )], dynamic friction coefficient [μ _K ], and surface resistivity [R (Unit: Ωcm)] are each expressed by the following formula: 0.007 (μm) < CLA ≦ 0.030 (μm) 2 (Ke/mm ^{2 )} )<H ₂ ≦150 (Ke/mm ² ) 0.10<μ _K ≦0.25 R≦10 ¹¹ (Ωcm) A polyol having 3 or more hydroxyl groups in a polyester consisting of 80% by weight or more of polyethylene terephthalate and carbon 0.01 to 5 ester products with aliphatic monocarboxylic acids having a number of 8 or more
This is achieved by a laminated polyester film for magnetic recording media formed of a film layer containing a dispersed content in a weight percent. In the present invention, the film layer forming the surface (A) on which the magnetic thin film of the laminated film is supported is composed of polyester in which 80% by weight or more of the polymer weight is polyethylene terephthalate. Here, "80
"Polyester whose weight percent or more is polyethylene terephthalate" refers to not only a homopolymer of polyethylene terephthalate, but also a homopolymer of polyethylene terephthalate, where at least 80 weight percent of all repeating units are composed of ethylene terephthalate, and the remaining 20 weight percent or less is other polyester components such as ethylene. Isophthalate, ethylene 2,6
- Copolyesters consisting of naphthalate, tetramethylene terephthalate, etc., mixtures thereof, and also mixtures of these and other polymers (containing 80% by weight of polyethylene terephthalate component), such as polyethylene terephthalate or its copolyester and polyethylene 2,6 - a mixture of naphthalates, a mixture of polyethylene terephthalate or its copolyester and polyethylene isophthalate, a mixture of polyethylene terephthalate or its copolyester and polyarylate, a mixture of polyethylene terephthalate or its copolyester and polyolefin, etc. Among these, homopolymers of polyethylene terephthalate are particularly preferred. Such polyesters contain particulate inert material. Methods for incorporating this inert substance include, for example, adding an inert inorganic compound to the polymer used as a film raw material, or forming an insoluble catalyst residue. This inert inorganic compound is insoluble in the polymer,
and contains substances that do not react. Examples of substances to be blended include MgO, ZnO, MgCO ₃ , CaCO ₃ ,
CaSO ₄ , BaSO ₄ , Al ₂ O ₃ , SiO ₂ , TiO ₂ , typical examples include silica, kaolin, china clay, diatomaceous earth,
Examples include calcium carbonate, aminosilicates and their hydrates, calcium terephthalate, carbon black, calcium phosphate, and the like. In addition, the insoluble catalyst residue is an insoluble catalyst residue formed by a combination of an appropriate amount of a transesterification catalyst and a stabilizer, for example in polyester,
This method forms irregularities on the surface of a polyester film to control surface characteristics. The content of inert substances varies depending on the type of substance, particle size, etc. and cannot be determined in general, but it is usually
0.002 to 2% by weight is better, more preferably 0.005 to 1% by weight
is preferred. In the present invention, the surface (A) of the laminated film is the surface on which the magnetic thin film is formed by means such as plating. This magnetic thin film (metal thin film) is generally used in the range of 0.02~
Since it is as thin as 1.5 μm, the surface condition of the polyester film layer directly manifests itself as unevenness in the magnetic thin film, which causes deterioration of characteristics, such as noise. Therefore, the surface of the polyester film layer (A)
is the average surface roughness [CLA (unit: μm)]
The maximum protrusion height [PV (unit:
μm)] is 0.06 μm or less, and the number of protrusions [H ₁ (unit: ke/mm ² )] with a protrusion height in the range of 0.27 to 0.54 μm is 10 ke/mm ² or less. There is.
Preferably, the average surface roughness [CLA] is 0.006 μm or less, and the height of the protrusions is 5 protrusions/mm ² or less in the range of 0.27 μm to 0.54 μm. The lower limit of CLA is not particularly limited, but is usually about 0.002 μm.
By satisfying these conditions, the noise when used as a magnetic recording medium is dramatically reduced, resulting in a significantly superior noise level. When such surface characteristics are imparted to both sides (A, B) of the film, the sliding properties between the films are poor during operations such as film winding and unwinding, and a blocking phenomenon occurs, and the running after tape processing becomes difficult. It has poor quality and cannot be used as a product. Therefore,
The other surface (B) of the film needs to be given slipperiness. In the present invention, a polyester film layer having different characteristics from that of the polyester forming the film surface (A) is used to form the film surface (B). In the present invention, the film layer forming the other surface (B) of the laminated film has a surface roughness [CLA
(unit: μm)] and the number of protrusions with a height of 0.54 μm or more [H ₂ (unit: ke/mm ² )] are calculated using the following formula: 0.007 (μm) < CLA ≦ 0.030 (μm) 2 (ke/mm 2 ) mm ² )<H ₂ ≦150 (ke/mm ² ), the dynamic friction coefficient [μ _K ] satisfies 0.10< μ _K ≦0.25, and the surface specific resistance [R] satisfies 10 ¹¹ Ωcm.
Satisfies the following. Preferably, a lubricant such as an ester product of a polyol having 3 or more hydroxyl groups and an aliphatic monocarboxylic acid having 8 or more carbon atoms is used.
Dispersed in the polymer at 0.01 to 5% by weight,
Composed of polyester, at least 80% by weight of which is polyethylene terephthalate. Therefore, the polyester should contain a lubricant, such as an ester product of a polyol having three or more hydroxyl groups and an aliphatic monocarboxylic acid having eight or more carbon atoms, in an amount of 0.01 to 5% by weight, and have a surface resistivity.
The same explanation can be given as for the polyester constituting the film layer forming the surface (A), except that it is 10 ¹¹ Ω·cm or less. The polyol used as a raw material for the ester product to be dispersed in the polyester as a lubricant must have three or more hydroxyl groups.
If an alcohol with two or fewer hydroxyl groups is used,
Although the reason is not clear, even if the produced ester is dispersed in polyester, the slipperiness of the film cannot be improved. In particular, polyols having 3 to 6 hydroxyl groups are preferred from the viewpoint of easy availability. Such polyols having three or more hydroxyl groups include glycerin, erythritol, trait, pentaerythritol, arabite, ximeritol, adonite,
Examples include, but are not limited to, taritz, sorbit, mannit, and ijitz. Further, as the aliphatic monocarboxylic acid to be reacted with the above polyol, it is necessary to use an aliphatic monocarboxylic acid having 8 or more carbon atoms. If an aliphatic monocarboxylic acid with fewer than 8 carbon atoms is used, the resulting ester product will have insufficient heat resistance, and will easily decompose under the heating conditions used for dispersing it in polyester, making it difficult to disperse it in polyester. It is unsuitable as a substance. In particular, aliphatic monocarboxylic acids having 8 to 25 carbon atoms are preferred because they are easily available. Such aliphatic monocarboxylic acids having 8 or more carbon atoms include belargonic acid, cabric acid, undecylic acid, lauric acid, tridecylic acid,
myristic acid, pentadecyl acid, valmitic acid,
heptadecylic acid, stearic acid, nonadecanoic acid,
Examples include arachidic acid, behenic acid, lignoceric acid, and cerotic acid. When the above-mentioned polyol and aliphatic monocarboxylic acid are reacted, mono-, di-, and triesters are usually produced. All of these ester products are effective in improving slipperiness, but triesters are particularly preferred from the viewpoint of heat resistance when dispersed in polyester. The above ester product needs to be dispersed in an amount of 0.01 to 5% by weight based on the weight of the polyester. If it is less than 0.01% by weight, the slipperiness that is the objective of the present invention cannot be obtained, and if it exceeds 5% by weight, the ester component will excessively ooze out on the surface when made into a film, causing blocking and making the film more slippery. It disappears. Any method can be used to disperse the above-mentioned ester product in polyester, such as adding and dispersing it during the polycondensation reaction or kneading it with an extruder. make,
A method of diluting this with unadded polyester can also be used. In addition, the lubricant component can be selected other than the above-mentioned ester products, but depending on the ease of dispersion in the polymer, Polyorganosiloxane, as it is difficult to transfer to A).
Fatty acid ester and silicone lubricants are preferred. Furthermore, in order to effectively develop the slipperiness of the above-mentioned lubricant, the surface B of the polyester film layer must have an average surface roughness CLA of over 0.007 μm and a number of protrusions with a height of 0.54 μm or more. H ₂ is 2
It is preferable that the number of particles/mm ² is greater than 2.0 mm 2 , which greatly improves running properties after tape processing. However, the average surface roughness CLA of surface B of the polyester film layer is larger than 0.030 μm, and the number H ₂ of protrusions with a height of 0.54 μm or more is 150
If the number of particles/ ^mm2 exceeds, the unevenness of surface B will be significantly transferred to the surface of the magnetic film during tape processing and in the rolled state after processing, resulting in significant level fluctuations and noise generation as a high-density recording medium. ,
In severe cases, it may even lead to dropout,
This is not preferable because it causes trouble in electromagnetic conversion characteristics. Therefore, the surface B of the laminated film has an average surface roughness CLA of 0.007 μm<CLA≦0.030 μm, and the number of protrusions H ₂ with a height of 0.54 μm or more is 2<2.
It is necessary to satisfy H ₂ ≦150. average surface roughness
CLA exceeds 0.008μm and is less than 0.020μm, protrusion height
It is more preferable that the number of protrusions H ₂ of 0.54 μm or more exceeds 3 protrusions/mm ² and is less than 100 protrusions/mm ² in terms of balance between improving runnability after tape processing and transferring surface irregularities. . The layers constituting the other surface B of the laminated polyester film may be the same as or different from the layer on the surface A, but in terms of surface roughness, the surface B is rougher than the surface A. preferable. Furthermore, surface B of the laminated polyester film
It is preferable that the dynamic friction coefficient μ _K satisfies 0.10<μ _K ≦0.25 from the viewpoint of improving running performance, and 0.10<μ≦
Particularly preferred is 0.21. If the coefficient of dynamic friction μ _K exceeds 0.25, running properties will deteriorate, the tape will be scratched, and the signal may fall off.
In extreme cases, phenomena such as sticking to the guide pin and not being able to move may occur, which is undesirable. Also, the coefficient of kinetic friction μ _K
If it is less than 0.10, the tape will slip too much and meander, which is not desirable. Furthermore, it is preferable that the layer constituting the surface B of the laminated polyester film has a surface resistivity of 10 ¹¹ Ωcm or less, since this is effective in improving running properties after tape processing, and in particular, reducing deterioration of slipperiness during repeated running. . The reason for this is not obvious, but it can be considered as follows. Surface A after tape processing
A thin metal film is formed on the surface A.
The side surface resistivity is very low, typically 10 ² to 10 ⁸ Ω
cm, so it would be effective for the surface resistivity of the opposite surface B to be as close to that of the surface A as possible for improving running performance. The surface resistivity of the layer constituting surface B is 10 ¹¹ Ω・
Conventionally known methods can be used to reduce the thickness to cm or less. For example, it can be produced by blending specific amounts of polyalkylene glycol, alkyl sulfonic acid metal salts, and the like. For more details,
Alkali metal salts of polyethylene glycol alkyl sulfonic acid with an average molecular weight of 5000 to 50000, etc.
It can be produced by blending 0.5 to 50% by weight, and these methods are preferable in terms of preventing the film forming process from becoming unstable. Any method can be used to disperse the above-mentioned polyalkylene glycol, alkyl sulfonic acid metal salt, etc. into polyester. For example, a method of adding and dispersing during a polycondensation reaction or a method of kneading with an extruder can be used. It is also possible to use a method in which a highly concentrated master polymer is prepared in advance and diluted with unadded polyester. Although the laminated film of the present invention has a multilayer structure of two or more layers, a two-layer structure is particularly preferable. In the case of a laminated film having three or more layers, as long as the outermost layer is the polyester film layer of surfaces A and B described above, the intermediate layer may be any polymer layer. The laminated film of the present invention can be manufactured by a conventional laminated film manufacturing method.
For example, a polyester layer forming surface A and a surface B
The polyester layer forming the polyester layer can be laminated in a molten state or in a cooled and solidified state. More specifically, it can be produced by methods such as coextrusion and extrusion coating. In this case, the thickness of the polyester layer forming the surface A is preferably 40 to 95% of the total thickness of the laminated film. If this ratio is more than 95%, the surface roughening effect of the external particles or internal particles of the polyester layer forming surface B will not be sufficient, and if it is less than 40%, the roughening effect of the external particles or internal particles of the polyester layer forming surface B will not be sufficient. Surface A tends to become uneven due to the influence of particles or internal particles, resulting in poor electromagnetic conversion characteristics. The films laminated by the above method are sequentially biaxially stretched or simultaneously biaxially stretched and further heat treated in a conventional manner. In this heat treatment, the ester product forms on the surface B of the polyester layer forming the surface B.
It is preferable that the tape be leached out to form an appropriate film-like substance, since this further improves the runnability after tape processing. The laminated polyester of the present invention is a base film that provides a magnetic recording medium with low noise level and good signal-to-noise ratio in data reading, especially low noise level in reproduction in high-density recording, and excellent running properties. It is useful as Examples Hereinafter, the present invention will be further explained with reference to Examples.
In addition, the physical properties in the present invention were measured by the following method. 1 CLA [Center Line Average] According to JISB0601, using a stylus type surface roughness meter (SURFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd.
A chart is placed under the conditions of a needle radius of 2 μm and a load of 0.07 g, and a portion of measurement length L is extracted from the film surface roughness curve in the direction of its center line. When the roughness curve is expressed as Y=f(x), with the direction of Y being the Y axis, the value given by the following equation is expressed in μm. CLA=1/L∫ ^L ₀ |f(x)|dx In this measurement, 8 measurements were taken with the reference length as 0.25 mm, and the average value of 5 measurements excluding 3 from the largest value is expressed. 2 Number of surface protrusions A thin layer of aluminum (400 to 500 Å or less thickness) is uniformly vacuum-deposited on the surface of the film to be observed, and a multiple interference microscope [e.g.
Using a NIKON (Surfase Finish Microscope) light source thallium lamp wavelength 5400 Å, the surface of the film was randomly photographed at a magnification of 100 up to an area of 1 ^mm2 , and the height was measured.
Number of protrusions in the range of 0.27μm to 0.54μm H ₁ piece/
mm ² and the number of protrusions with a height of 0.54 μm or more H ₂ pieces/mm ²
Calculate. 3. Motion coefficient As shown in the attached figure, a film cut to 1/2" width is fixed at an angle of 1/2" on a SUS27 fixed rod (surface roughness CLA = 0.030) with an outer diameter of 5 mmφ in an atmosphere of 25°C and 60% relative humidity. Contact with π radians and move at a speed of 3.3 cm/sec. Inlet tension
When the tension controller 2 is adjusted so that T ₁ is 30 gr, the movement coefficient μ _K is calculated using the following formula from the exit tension T ₂ gr (detected by the exit tension detector 10). Let μ _K be the dynamic coefficient of μ _K =1/πlnT ₂ /T ₁ The dynamic coefficient after repeated running 50 times under the same conditions as above was defined as the dynamic coefficient μ _K ′ after repeated running. 4. Surface specific resistance Measured in an atmosphere of 20° C. and 65% RH using a vibrating capacitance micropotential ammeter model TR-84M manufactured by Takeda Riken Co., Ltd. Example 1 A transesterification reaction of dimethyl terephthalate and ethylene glycol using 40 mmol% of manganese acetate as a transesterification catalyst, 20 mmol% of antimony trioxide as a polymerization catalyst, and 40 mmol% of phosphorous acid as a stabilizer. Through a polycondensation reaction under reduced pressure, polyethylene terephthalate with [η] (measured at 25°C using O-chlorophenol as a solvent) = 0.65 was finally obtained [hereinafter referred to as polyester]. On the other hand, polyethylene terephthalate with [η] = 0.65 was obtained in the same manner as polyester, except that 0.40% by weight of kaolin with an average particle size of 0.6 μm was added and polycondensation reaction was performed [hereinafter referred to as polyester]. Furthermore, 8 parts by weight of pentaerythritol tristearate was added to 100 parts by weight of the above polyester, and the mixture was further uniformly blended using an extruder to obtain master chips (hereinafter referred to as polyester). Additionally, 10 parts by weight of sodium polyalkyl sulfonate was added to 100 parts by weight of the above polyester, and the mixture was further uniformly blended using an extruder to obtain master chips (hereinafter referred to as polyester). Polyester, polyester and polyester and polyester, in the resulting polymer, 0.20% by weight of kaolin with an average particle size of 0.6μ, 0.5% by weight of pentaerythritol tristearate,
A polyester blend was obtained by blending the polyalkylsulfonic acid sodium acid to contain 1.0% by weight (hereinafter referred to as polyester). The polyester and the polyester were fed to separate extruders of a coextrusion film forming machine, An unstretched film of 160 μm was obtained by coextrusion through a die so that the polyester layer thickness was 70% of the thickness of the laminated film. This unstretched film was sequentially biaxially stretched at a longitudinal stretching temperature of 90°C, a longitudinal stretching ratio of 3.5 times, a transverse stretching temperature of 110°C, and a transverse stretching ratio of 3.7 times, and was further heat-treated at 205°C. The laminated polyester film thus obtained has a surface A of a layer consisting only of polyester.
The surface roughness of CLA is 0.004μm, and the maximum protrusion height is
PV=0.03 μm, and the number of protrusions with a height of 0.27 μm to 0.54 μm was H ₁ =0.5 pieces/mm ² . In addition, the surface roughness of surface B of the layer made of polyester on the opposite side is CLA = 0.018 μm, and the number of protrusions with a height of 0.54 μm or more
H ₂ was 70 Ω/mm ² and surface resistivity was 5×10 ⁹ Ω·cm. Furthermore, a Mo-low coercivity permalloy layer was formed on the A side of the laminated polyester film thus obtained, and then a Co-Cr perpendicular magnetization film was formed on the permalloy layer by the following method. Mo-permalloy layer: 1mm thick Mo-permalloy target (Ni78%, Fe18%, Mo4%)
using the DC magnetron sputtering method.
A 0.3 μm thick film was prepared at a deposition rate of 500 Å/min in Ar (99.99%) at 10 ^-2 Torr. Co-Cr layer: Using a 4 mm thick Co-Cr alloy target (Cr 17wt%), it was coated in Ar (99.99%) at 1 x 10 ^-2 Torr using the DC magnetron sputtering method.
A 1.0 μm thick Co-Cr alloy film was obtained at a deposition rate of 500 Å/min. The resulting magnetic recording medium was cut into 0.5-inch wide tapes, and the coefficient of dynamic friction was measured using the tape inspection machine shown in the figure. The coefficient of dynamic friction was 0.18, and the coefficient of dynamic friction after repeated running was 0.24, which was good.
Furthermore, when the S/N (dB) ratio during 10 KBPI recording and reproduction was evaluated as an electromagnetic conversion characteristic, this value was 49, which was good. Comparative Example 1 The polyester in Example 1 and the polyester were blended so that the resulting polymer contained 0.20% by weight of kaolin with an average particle size of 0.6 μm to obtain a polyester blend (hereinafter referred to as polyester). A laminated polyester film was obtained by forming and stretching in the same manner as in Example 1, except that this polyester was used in place of the polyester in Example 1. A metal thin film was formed on this laminated polyester film in the same manner as in Example 1, and then it was made into a tape. The obtained tape had a dynamic friction coefficient of 0.46 and had poor running properties. Example 2 and Comparative Examples 2 and 3 Instead of kaolin with an average particle size of 0.6μ, the average particle size was 04μ.
A polyester (hereinafter referred to as polyester') was obtained in the same manner as in Example 1, except that kaolin of 0.8 μm or clay of average particle size of 0.8 μm was used. Using the above polyester' in place of the polyester in the polyester, a polyester blend having the properties (composition) shown in Table 1 was obtained [hereinafter,
It is called polyester. This polyester'
A laminated polyester film was obtained in the same manner as in Example 1 except that the following was used in place of polyester.
Table 1 shows the properties of this laminated polyester film. In Example 2, surface B has surface roughness CLA=
110 protrusions with a height of 0.019μm and a height of 0.54μm or more/
mm ² , and the dynamic friction coefficient S/N ratio is good. In Comparative Example 2, surface B was rough and the coefficient of dynamic friction was good, but since the protrusions on surface B were transferred to the magnetic recording surface laminated on surface A,
The S/N ratio was poor. The film of Comparative Example 3 had a flat surface B, had poor slipperiness during unwinding and unwinding of the film at the production stage, and a blocking phenomenon occurred, so it could not be used as a product. The tape also had poor running properties. Example 3 and Comparative Example 4 Example 1 except that 0.1% or 0.3% by weight of kaolin with an average particle size of 0.1μ was added during the polycondensation reaction of polyester.
Polyethylene terephthalate [hereinafter referred to as polyester I'] was obtained in the same manner as above, and a laminated polyester film having surface A having different surface characteristics was obtained using this polyester I' and polyester. Table 1 shows the properties of this laminated polyester film.

[Table] Example 3 has CLA of 0.0060 μm on surface A.
The number of protrusions in the range of height 0.27μm to 0.54μm _H1 is 5
ke/mm ² , the maximum protrusion height PV is 0.05 μm, and S/
The N ratio was good. On the other hand, in Comparative Example 4, the surface A was rough and the S/N ratio was poor. Example 4 8 parts by weight of sorbitan tristearate was added to 100 parts by weight of the polyester of Example 1, and the mixture was further uniformly blended using an extruder to obtain master chips (hereinafter referred to as polyester'). Using the polyester of Example 1, the polyester, the polyester, and the above polyester', the same procedure as in Example 1 was carried out, and the resulting polymer contained 0.20% by weight of kaolin with an average particle size of 0.6μ and 0.5% by weight of sorbitan tristearate. A polyester blend containing 1.0% by weight of polyalkylsulfonic acid sodium salt was obtained. Using this polyester blend and the polyester of Example 1, film formation and stretching were carried out in the same manner as in Example 1 to obtain a laminated polyester film. This laminated polyester film was formed into a tape shape by forming a metal thin film in the same manner as in Example 1. The coefficient of kinetic friction of this tape is 0.19, and the coefficient of kinetic friction after repetition is
It was 0.24, which was good. Example 5 Using the polyester, polyester, and polyester of Example, the same procedure as Example 1 was carried out, and the resulting polymer contained 0.20% by weight of kaolin with an average particle size of 0.6 μm and pentaerythritol tristearate. A polyester blend containing 0.5% by weight was obtained. Using this polyester blend and the polyester of Example 1, a film was formed and stretched in the same manner as in Example 1 to obtain a laminated polyester. The surface resistivity of surface B of this product was 2×10 ¹⁵ Ω·cm. This laminated polyester film was formed into a tape shape by forming a metal thin film in the same manner as in Example 1. The initial coefficient of animal friction for this tape was 0.20;
The animal friction coefficient μ _K ′ after repeated running is 0.41,
The increase in the coefficient of animal friction during repeated running was large and was poor.

[Brief explanation of drawings]

The figure is a schematic diagram of a tape-based inspection machine that measures the coefficient of dynamic friction on the rough surface of a film. In the drawing, 1 is an unwinding roll, 2 is a tension controller, 4 is a tension detector (inlet), 10
1 is a tension detector (outlet), 12 is a guide roller, and 13 is a take-up reel.

Claims (1)

[Claims] 1. The surface (A) of the laminated film on which the magnetic thin film is supported is defined by the surface roughness [CLA (unit: μm)], the maximum protrusion height [PV (unit: μm)], and the height of the protrusion. is 0.27μm
Number of protrusions in the range of ~0.54 μm [H ₁ (Unit: Ke/
mm ² )] satisfy the following formulas: CLA≦0.008 (μm) PV≦0.06 (μm) H ₁ ≦10 (ke/mm ² ), and is made of a polyester film layer of which 80% by weight or more is made of polyethylene terephthalate. and the other surface (B) has a surface roughness [CLA (unit: μ
m)], the number of protrusions with a height of 0.54 μm or more [H ₂
(unit: ke/mm ² )], dynamic friction coefficient [μ _k ], and surface specific resistance [R (unit: Ωcm)] are each expressed by the following formula: 0.007 (μm) < CLA ≦ 0.030 (μm) 2 (ke/mm ² ) )<H ₂ ≦150 (Ke/mm ² ) 0.10<μ _k ≦0.25 R≦10 ¹¹ (Ωcm) A polyol having 3 or more hydroxyl groups in a polyester consisting of 80% by weight or more of polyethylene terephthalate and carbon 0.01 to 5 ester products with aliphatic monocarboxylic acids having a number of 8 or more
A laminated polyester film for magnetic recording media formed of a film layer containing dispersed content in a weight percent.