JP2002322297A - Aromatic polyamide film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aromatic polyamide film having excellent planarity and excellent magnetic characteristics. SOLUTION: This aromatic polyamide film is regulated so that the arithmetical mean deviation of profile (RaA) of one surface (A-surface) of the film, and the arithmetical mean deviation of profile (RaB) of the opposite surface (B-surface) may satisfy the inequality (1): 0.5<RaA<RaB<10 (nm) (1), and the amount of the generated out gas at 25-175 deg.C may be 100-4,000 ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aromatic polyamide film, particularly to an aromatic polyamide film which can be suitably used for a metal thin film type magnetic recording medium, and a method for producing the same.

[0002]

2. Description of the Related Art Aromatic polyamide films have been developed for various applications by utilizing their excellent heat resistance and mechanical properties. In particular, the aromatic polyamide film of the para-orientation type is superior to other polymers in mechanical properties such as rigidity and strength, so that it is very advantageous for thinning, and is used for printer ribbons, magnetic recording media, capacitors, solar cells, etc. Is considered. Above all, when used as a base film of a magnetic recording medium, it is preferably used because the volume recording density is improved by thinning. In particular, when a metal thin film type magnetic layer is provided, it is more preferably used because the entire magnetic recording medium can be made thinner.

By the way, in order to improve the volume recording density of a magnetic recording medium, it is required to improve the surface recording density at the same time as the thinning of the magnetic recording medium, and therefore it is necessary to improve the magnetic properties of the magnetic layer. . It has been found that the surface properties of the base film greatly contribute to the magnetic properties. In response to such demands, various studies have been made on the surface forming method of the aromatic polyamide film.
For example, to form fine projections on the film surface,
An aromatic polyamide film containing inorganic particles in the film (for example, JP-A-60-127523 and JP-A-60-201914), and a thin film layer containing particles for forming surface projections And an aromatic polyamide film (for example, JP-A-3-119512). Further, attempts have been made to achieve both output characteristics and running durability by incorporating spherical inorganic particles such as silica having different particle diameters.

However, in recent years, it has been required to improve the magnetic characteristics of a magnetic recording medium having a metal thin film type magnetic layer in particular. In some cases, the required magnetic characteristics cannot be achieved only by improving the conventional surface design. Was. Conventionally, this phenomenon has been treated as a mysterious thing, but the present inventors have found that it is a problem caused by a small amount of outgas generated from the film during the vapor deposition processing.

Further, as the base film used becomes thinner, the winding shape of the film roll deteriorates, and wrinkles, breaks, partial sagging, etc. occur during actual use, making processing difficult. There is. For this problem,
Japanese Patent Application Laid-Open No. H11-10812 proposes disposing a hygroscopic material on the roll surface and the end face. However, it is difficult to remove the moisture contained in the film roll, and the fundamental solution is difficult. Also, it has been difficult to solve the deterioration of the magnetic properties due to the outgas during the vapor deposition process.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide an aromatic polyamide film which can exhibit good magnetic properties and has excellent processing properties.

[0007]

According to the present invention for solving the above-mentioned problems, the center line average roughness of one surface (A surface) of the film is defined as RaA (nm), and the other surface (B surface) is defined as RaA (nm). When the center line average roughness is RaB (nm), RaA and Ra
B satisfies the following formula (1), 0.5 <RaA <RaB <10 (1) and an outgas generation amount at 25 to 175 ° C. is 100 to 4,000 ppm with respect to the film weight. It is characterized by a group III polyamide film.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the aromatic polyamide of the present invention, those containing 50 mol% or more of repeating units represented by the following general formulas (I) and / or (II) are preferably used. It is more preferable to use one consisting of mol% or more. General formula (I)

[0009]

Embedded image General formula (II)

[0010]

Embedded image Here, Ar1, Ar2, and Ar3 are, for example,

[0011]

Embedded image And X and Y are -O-,-
CH ₂ —, —CO—, —SO ₂ —, —S—, —C (C
H ₃ ) _2- , and the like, but are not limited thereto. Further, some of the hydrogen atoms on these aromatic rings are halogen groups (especially chlorine) such as fluorine, chlorine, and bromine, nitro groups, and alkyl groups (especially methyl groups) such as methyl, ethyl, and propyl groups; It may be substituted with a substituent such as an alkoxy group such as a methoxy group, an ethoxy group, a propoxy group, or an isopropoxy group, and hydrogen in an amide bond constituting the polymer may be substituted with another substituent. Some are good.

From the viewpoint of characteristics, a polymer in which the above aromatic rings are bonded in a para-oriented position accounts for 50 mol% or more, preferably 75 mol% or more of the total aromatic rings, because the film has high rigidity and high heat resistance. Is also preferable. The term "para orientation" as used herein means that the bonding positions are linear. Some of the hydrogen atoms on the aromatic ring are halogen groups (especially chlorine)
When the aromatic ring substituted with is 30 mol% or more of the whole, moisture resistance is improved, and characteristics such as dimensional change due to moisture absorption and rigidity decrease are preferred.

The aromatic polyamide of the present invention preferably contains at least 50 mol% of the repeating units represented by the general formulas (I) and / or (II). May be copolymerized or blended.

In the aromatic polyamide film of the present invention, the center line average roughness RaA on one side (A side) of the film and the center line average roughness RaB on the opposite side (B side) are represented by the following formula (1).
0.5 <RaA <RaB <10 (nm) (1) and the outgas generation amount at 25 to 175 ° C. is 100 to 4,000 ppm based on the film weight.

Here, the surface A and the surface B are either one of the two surfaces of the film, and the surface having a rough center line average roughness is the surface B. When used for a magnetic recording medium, it is preferable to provide a magnetic recording layer on side A.

If the RaA is less than 0.5 nm, the planarity may be deteriorated. If the RaB is 10 nm or more, the magnetic characteristics may be degraded by transfer when the magnetic recording medium is used. The preferred range of RaA is 0.5 <RaA <5 (nm), more preferably,
0.7 <RaA <3 (nm). The preferred range of RaB is 1 <RaB <9 (nm), and more preferably 3 <RaB <6 (nm).

The aromatic polyamide film of the present invention has an outgas generation at 25 to 175 ° C. of 100 to 4,000 ppm based on the weight of the film. Here, the outgas generation amount refers to the total amount of gas generated when the film is heated. Examples of the type of the gas include a solvent remaining in the film, a remaining amount of the coating liquid after the coating step, and moisture, and in any case, it is necessary to control the total amount. When the outgas generation amount is less than 100 ppm, the flatness may be deteriorated, or the winding may easily be displaced when a roll is formed, and the practicality may be lost. In addition, the outgas generation amount is 4,0
When the content exceeds 00 ppm, not only the flatness is deteriorated, but also the magnetic characteristics may be deteriorated when a magnetic recording medium, particularly a metal thin film type magnetic recording medium is used. Although the reason for this is not always clear, it is considered that the crystal growth is inhibited during the formation of the metal film. The outgas generation amount is preferably from 150 to 3,000 ppm, and more preferably from 200 to 2,500 ppm.

Further, the aromatic polyamide film of the present invention has a protrusion A having a height of 5 to 30 nm on the surface A of 10%.
When the density of protrusions having a height of more than 30 to 30 million protrusions / mm ² and more than 30 nm is 0 to 100,000 protrusions / mm ² , the output characteristics are improved and the running durability is improved. Is preferred. If the projection density at a height of 5 to 30 nm is less than 100,000 / mm ² , the running durability may be reduced, and the winding appearance and flatness may be deteriorated due to blocking.
Further, when the projection density exceeds 30 million pieces / mm ² ,
Alternatively, 100,000 protrusions having a height exceeding 30 nm /
Beyond mm ^2, there is a case where the output characteristics are deteriorated. Further, it is preferable that the density of the protrusions having a height exceeding 100 nm on the surface B be 0.10 to 100,000 / mm ² , because the flatness of the film is improved. The projection density is 0.1000 /
If it is less than mm ² , wrinkles are likely to occur, and if it exceeds 100,000 pieces / mm ² , winding misalignment may easily occur.

In order to obtain the film of the present invention, organic or inorganic particles may be contained as a projection-forming product.

As the organic particles, for example, cross-linked polyvinyl benzene, acrylic, cross-linked polystyrene, polyester, polyimide, polyamide, fluororesin particles, etc. can be used. As the inorganic particles, colloidal silica, titanium oxide, aluminum oxide, zirconium oxide can be used. , Calcium carbonate, carbon black, zeolite particles and the like can be used. Further, organic polymer particles obtained by subjecting the organic particles to various treatments such as coating with another organic substance,
Alternatively, inorganic particles or the like whose surface has been subjected to various treatments such as coating with the above-mentioned organic polymer can also be used. As the average particle size,
The thickness is preferably 5 to 100 nm, more preferably 10 to 100 nm.
-50 nm, more preferably 15-30 nm, and it is preferable to use monodisperse particles. In this case, the average particle diameter is determined by using a particle size distribution analyzer (for example, CAPA-700, manufactured by Shimadzu Corporation) using centrifugal separation, and the median of the area average diameter as the average particle diameter. In the state of the film, a transmission electron microscope was used to obtain a magnification of 1
It is also possible to observe 50 or more particles at a magnification of 0000 or more and determine the average particle diameter from the diameter of each particle. Also,
Among these, a plurality of particles may be used in combination, or particles having different sizes may be used in combination. The content of the particles is 0.0001 to 1.0.
%, More preferably 0.001% by weight.
To 0.2% by weight, more preferably 0.005 to 0.1% by weight. Furthermore, in order to improve abrasion resistance and running durability, uniformity of projection height is also important. Therefore, spherical particles are preferable as the particle shape, and those having a uniform particle size should be used. Is desirable.

The film of the present invention contains the above-mentioned composition as a main component, but as long as the object of the present invention is not impaired, an inorganic or inorganic material such as an antioxidant, a heat stabilizer, a lubricant, an ultraviolet absorber, a nucleating agent, etc. Organic additives may be contained.

The surface projections may be formed by incorporating organic and / or inorganic particles as described above. However, a specific projection-forming agent (heteropolymer) is blended with an aromatic polyamide as described later. However, it is also preferable to form projections by utilizing a microphase separation structure that can be generated by adopting specific conditions during molding. The projections obtained by such a method have a high density, a uniform height, and no aggregation.

The film of the present invention has a thickness of 1 to 10 μm.
It is preferable that the film is a thin film because the effects of the present invention can be further exhibited. More preferably 1 to 6μ
m, more preferably 1 to 4 μm.

The film of the present invention preferably has a tensile Young's modulus in at least one direction of at least 7 GPa in order to achieve a thinner base film, which has become more and more remarkable in recent years. For example, the output of a magnetic tape increases with the improvement of the head touch between the tape and the head,
For this purpose, it is required to increase the Young's modulus of the base film.
When the recording method is a fixed head type, it is particularly necessary to increase the Young's modulus in the longitudinal direction, and in the case of the helical scan type, it is particularly necessary to increase the Young's modulus in the width direction. , It is difficult to obtain a high output. The Young's modulus of the film of the present invention in at least one direction is more preferably 9 GPa or more, and further preferably 11 GPa or more. If the Young's modulus is too high, the film may be brittle, so the upper limit is usually about 35 GPa. Of course, it is needless to say that the Young's modulus in both the longitudinal direction and the width direction, and further in all directions, is preferably 7 GPa or more. In order to satisfy these characteristics, the organic polymer of the present invention is an aromatic polyamide and the aromatic ring thereof has para-orientation, preferably 50 mol% or more of the total aromatic ring. ,
More preferably, it accounts for 75 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more.

The elongation in at least one direction of the film of the present invention is preferably 10% or more, more preferably 20% or more, and further preferably 30% or more, since it has appropriate flexibility. The upper limit of elongation is determined by the balance with other physical properties, but is usually about 90%.

The moisture absorption of the film of the present invention is 5
% Or less, more preferably 3% or less, and still more preferably 2%.
The following conditions are preferable because expansion and contraction of the tape due to a change in humidity can be suppressed, and good output characteristics can be maintained. In addition, if the moisture absorption rate is to be significantly reduced, other film properties may be impaired. Therefore, the lower limit is preferably about 0.3%. The moisture absorption was determined by the weight (W0) after drying the film in an oven at 200 ° C. for 1 hour and the weight (W1) after the film was allowed to stand at 25 ° C. and 75 RH% for 48 hours. Is defined as the moisture absorption weight (W1-W0), and the value obtained by dividing the difference by W0 is expressed as a percentage.

The film of the present invention can be used for a flexible printed circuit board, a condenser, a printer ribbon, an acoustic diaphragm,
It is preferably used for various applications such as a base film of a solar cell, but when used as a magnetic recording medium provided with a magnetic layer on at least one side, the flatness of the film is good, the workability is high, and the magnetic properties This is particularly preferable because it results in a high magnetic recording medium.

The form of the magnetic recording medium is not particularly limited, such as a disk shape, a card shape, and a tape shape. However, in order to cope with the aromatic polyamide film of the present invention, the aromatic polyamide film can be made thinner by making use of its excellent surface property and high Young's modulus. The support made of an aromatic polyamide film has a thickness of 6.5 μm or less and a width of 2.3 to 2.3 μm.
13 mm, a length of 200 m / roll or more, a shortest recording wavelength of 0.7 μm or less, and a track pitch of 10 μm or less. It is particularly preferable because it can be performed more.

The magnetic recording medium of the present invention can be used for consumer, professional, broadcasting stations such as D-1, D-2, D-3, digital video cassettes, DDS-2, 3, 4, data 8 mm,
Although it can be suitably used for data storage applications such as QIC, AIT, DLT, LTO, and mammoth, it can be optimally used for data storage applications where high recording density is important.

The magnetic layer can be formed by kneading a magnetic powder such as iron oxide or metal powder with a binder such as a thermosetting, thermoplastic or radiation-curing binder, and coating and drying.
Any of dry methods in which a metal such as i, Co, Cr, Fe, γ-Fe ₂ O ₃ or an alloy thereof is formed directly on a substrate film by vapor deposition, sputtering, ion plating, etc. Although a method can be adopted, it is preferable to form by a dry method in order to further exert the effects of the present invention. When the dry method is employed, a protective layer such as a diamond-like coating may be formed on the obtained magnetic recording medium for the purpose of further improving the durability and imparting a slippery property, and a lubricating layer may be further formed thereon. .

Further, when the thickness of the magnetic layer is 0.15 μm or less, the contribution of the surface properties of the film of the present invention becomes large, and the output characteristics and running durability are improved without special measures for the magnetic layer. preferable. More preferably, it is 0.1 μm or less. The lower limit is about 0.02 μm so as not to impair the durability of the magnetic layer.

The most preferred embodiment of the magnetic recording medium of the present invention for maximizing the characteristics of the aromatic polyamide film of the present invention is 0.15 μm thick as described above.
This is a magnetic recording medium having a metal thin film type magnetic layer of m or less, and a protective layer and a lubricating layer provided thereon.

Regarding the magnetizing method, it does not matter whether it is horizontal magnetization or vertical magnetization, and it can be suitably used for an optical recording tape.

The film of the present invention may be a single layer or a multilayer. In the case of using an aromatic polyamide, for example, in the case of two layers, the polymerized aromatic polyamide solution is bisected, and the polymer used in the present invention is laminated on at least one. The same applies to the case of three or more layers. Examples of these lamination methods include lamination in a die, lamination in a composite tube, and a method in which one layer is formed once and another layer is formed thereon. In the case of a multilayer, it is preferable that the film surface of the present invention is laminated on at least one outermost layer, and the laminated thickness is 0.3
It is preferable that the thickness be not less than μm because the effects of the present invention can be sufficiently achieved.

Next, the method for producing the film of the present invention will be described, but is not limited thereto.

First, as for the polymer, it is preferable that the above-mentioned aromatic polyamide contain a heterogeneous polymer which will be described later, so that the surface roughness of the surface A falls within the range of the present invention (first method). .

First, an aromatic polyamide. When it is obtained from an acid chloride and a diamine, it is prepared in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) or dimethylformamide (DMF). It may be synthesized by solution polymerization or interfacial polymerization using an aqueous medium. At this time, in order to suppress the generation of low molecular weight substances, it is necessary to avoid mixing of water and other substances that would hinder the reaction, and it is preferable to use efficient stirring means. Also, the equivalence of raw materials is important,
When there is a risk of impairing the film forming properties, it can be adjusted appropriately. Further, inorganic salts such as calcium chloride, magnesium chloride, lithium chloride, lithium bromide and lithium nitrate may be added as a dissolution aid.

When an aromatic diacid chloride and an aromatic diamine are used as monomers, hydrogen chloride is produced as a by-product. When neutralizing this, hydrogen chloride, calcium carbonate, lithium carbonate and other periodic table are used. A Group I or Group II cation;
When an inorganic neutralizer represented by a salt composed of an anion such as hydroxide ion or carbonate ion, or an organic neutralizer such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine, diethanolamine is used. Good. For the purpose of improving the humidity characteristics of the base film, benzoyl chloride, phthalic anhydride, acetic chloride, aniline, or the like may be added to the system after the polymerization to block the terminal of the polymer. The reaction between the isocyanate and the carboxylic acid is preferably performed in an aprotic organic polar solvent in the presence of a catalyst.

These polymer solutions may be used directly as a stock solution for blending with a different polymer, or the polymer may be isolated once and then redissolved in the above organic solvent or an inorganic solvent such as sulfuric acid to form a blend. A stock solution may be prepared.

As the heteropolymer to be added, one or more polymers having a repeating unit other than the above-mentioned aromatic polyamide can be used. The content of the heterogeneous polymer is
The number and height of the protrusions are determined to suit the purpose.However, the total amount of the aromatic polyamide and the heteropolymer is set so as not to impair the excellent mechanical properties and heat resistance of the aromatic polyamide and to form uniform protrusions. 0.1% by weight or more to 30%
Preferably, it is less than about 10% by weight. This weight fraction is 0.
If it is less than 1%, the height of the protrusion tends to be less than 3 nm. On the other hand, when the content is 30% or more, the surface is large and undulates, which is not suitable for practical use, and the mechanical properties of the film may be deteriorated. The content of the heteropolymer should be appropriately designed depending on the kind of aromatic polyamide and heteropolymer used, solubility, molecular weight, size of the molded product, etc., and more preferably from 2 to 18 %, More preferably 5 to 15% by weight.

The object of the present invention is achieved by satisfying the following formula when the solubility parameter of the aromatic polyamide is δa and the solubility parameter of the heteropolymer to be contained is δb. It is preferable in doing.

50 (MJ / m ³ ) ^1/2 ≦ δa ≦ 70 (MJ / m ³ ) ^1/2 2 (MJ / m ³ ) ^1/2 ≦ | δa−δb | ≦ 20 (MJ / m
³ ) ^1/2 The solubility parameter here is a value calculated by the method of Fedors (calculation method is, for example, Pr
operties of Polymers, chapter 7 (DWVan Kreveren
Authors, 1976, Elsevier), etc.). Because the parameters of the chemical species contained are not required depending on the structure of the aromatic polyamide or the heteropolymer, Fedors
Of but some of which can not be calculated in a way, that case is replaced by the use of species approximating (e.g., -SO ₂ - but parameters not for, and -S-, -O -, -
The value of O- will be used instead). The solubility parameter is a parameter serving as a measure of the compatibility between different polymers, and when δa and δb are within the above ranges, the size of the dispersed phase is regulated, and preferably the surface projections satisfy the range of the present invention. be able to. | Δa−δb | is more preferably 2 (MJ / m ³ ) ^1/2 ≦ | δa−δb | ≦ 16 (MJ / m
³ ) ^1/2 , and more preferably 2 (MJ / m ³ ) ^1/2 ≦ | δa−δb | ≦ 12 (MJ / m
³ ) ^1/2 .

In order to sufficiently exhibit the inherent heat resistance and mechanical properties of the aromatic polyamide, it is preferable that the heteropolymer also has excellent heat resistance. If the glass transition temperature or the glass transition temperature is not clear, JIS The heat distortion temperature described in D648 is 150 ° C. or higher, more preferably 2 ° C.
It is preferably at least 00 ° C.

Examples of such heteropolymers include polysulfone, polyether sulfone, polysulfide sulfone, polyphenylene sulfide, polyetherimide, polyphenylene oxide, modified polyphenylene oxide, polyether ketone, polyether ether ketone, polycarbonate, polyethylene terephthalate. ,
Polybutylene terephthalate, polyimide or a polyamic acid that is a precursor thereof, polyvinylidene fluoride, polymethyl methacrylate, polystyrene, it is preferable to use polyvinyl alcohol, etc., from the viewpoint of uniformity of surface projections formed, heat resistance, Aromatic polysulfone polymers such as polysulfone, polyether sulfone, polysulfide sulfone, aromatic polyetherimide polymers, polyphenylene oxide, polyphenylene oxide polymers such as modified polyphenylene oxide, polyether ketone, polyether ether ketone, etc. Aromatic polyester polymers such as aromatic polyketone polymers, polycarbonate polymers, polyethylene terephthalate and polybutylene terephthalate, polyimides or precursors thereof. Preferably contains at least one polymer selected from an aromatic polyimide polymer of using a polyamic acid. Among them, particularly preferred is
It is an aromatic polysulfone polymer. As used herein, the aromatic polysulfone-based polymer includes polycondensation of sodium salt of bisphenol A with 4,4'-dichlorodiphenylsulfone, polycondensation of potassium salt of 4- (4-chlorophenylsulfonyl) phenol, and the like. represented polysulfone manufactured by, at least one sulfone group -SO ₂ in the repeating unit - aromatic polysulfone polymer having a, in particular, having a repeating unit represented by the following formula Aromatic polysulfone-based polymers can be used, and two or more of these can be used.

[0045]

Embedded image Here, n is a positive integer, and a value of 5 to 1,000 is preferable in terms of heat resistance and solubility in an organic solvent. In particular,

[0046]

Embedded image Is preferred in that uniform projections can be formed. Further, in the above chemical formula, for the purpose of improving the heat resistance of the resin and the like, part of the hydrogen atoms on the aromatic ring, fluorine or chlorine,
Substitution of halogen groups (especially chlorine) such as bromine, alkyl groups (especially methyl groups) such as nitro group, methyl group, ethyl group and propyl group, and alkoxy groups such as methoxy group, ethoxy group, propoxy group and isopropoxy group. May be substituted with a group.

As a method of blending the aromatic polyamide and the heteropolymer, a pellet or a powdery heteropolymer may be added directly or after being dissolved in a solvent before or after the polymerization of the aromatic polyamide. However, it is preferable to blend the aromatic polyamide and the heterogeneous polymer in a state of being dissolved in a solvent to obtain a stock solution for molding. Solvents for dissolving the aromatic polyamide and the different polymer may be different from each other, but the same type of solvent is preferable in view of industrial advantages such as cost and productivity. Examples of such a solvent include organic solvents such as N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, hexamethylenephosphoramide, dimethylimidazolidinone, and dimethylsulfone, and mineral acids such as concentrated sulfuric acid.

Further, organic or inorganic particles may be added for the purpose of forming the projections independently of the above method.
In order to obtain the film of the present invention, it is necessary to suppress particle aggregation. Addition of particles is generally added to a solvent before polymerization or dissolution, a particle sol sufficiently dispersed by an ultrasonic homogenizer or the like in the same or different solvents,
It is carried out by a method of polymerization or dissolution, or a method of adding a particle sol to a polymer solution after polymerization or dissolution and mixing.

For the surface B, it is preferable to adopt a method of adding organic or inorganic particles, which can be controlled within the range of the present invention by controlling the particle diameter and the amount of addition. Then, by laminating the polymer for side A and the polymer for side B by a method using a composite tube or the like, the aromatic polyamide film of the present invention having different surfaces can be obtained.

The membrane-forming stock solution prepared as described above is filtered through a filter having a filtration accuracy of 6,000 nm or less, and then formed into a film by a so-called solution casting method. The solution casting method includes a dry-wet method, a dry method, and a wet method. To obtain the aromatic polyamide film of the present invention,
The dry-wet method or the dry method is preferred because the formation of surface projections on the surface is easy to control. When a film is formed by a dry-wet method, the undiluted solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and then the solvent is scattered from the thin film layer and dried until the thin film has a self-holding property. In order to obtain protrusions by the first method, the drying process conditions are one of the important points, and greatly affect the surface properties of the obtained film. That is, the support temperature T at the time of casting the undiluted solution
b (° C) and hot air temperature T introduced on the cast film
When the a (° C.) is within a range satisfying the following formula, the aromatic polyamide of the present invention having uniform and non-agglomerated protrusions in order for the heterogeneous polymer to uniformly and desirably undergo phase separation. It is possible to suitably obtain a system film.

If 20 ≦ Ta−Tb is less than 20 ° C., the phase separation structure does not appear remarkably, so that necessary projections may not be formed, more preferably 40 ° C. or more, further preferably 50 ° C. or more. ° C or higher. The upper limit of Ta-Tb is about 100 ° C. as a range in which extreme dry spots do not occur. When an endless belt is used as the support, a temperature difference during polymer casting can be suitably imparted by adjusting the heating temperature of the upper and lower ends of the endless belt, or by cooling the endless belt after peeling the film.

The drum used in this drying step,
The surface property of the belt contact surface can be controlled by controlling the frequency of surface defects of the endless belt. Preferably 30μ in diameter
0.001 to 0.02 defects / mm
² , more preferably 0.002 to 0.015 particles / mm ² .

The film thus obtained with a self-supporting property is then introduced into a wet process. The wet bath is generally composed of an aqueous medium, and may contain an organic or inorganic solvent or an inorganic salt in addition to water. The bath temperature is usually 0 to 100 ° C.
The salt and the solvent contained in the film are extracted by passing through a wet bath. Here, the film when introduced into the wet bath does not yet have a sufficient surface hardness, so if there is contamination or the like in the wet bath medium, the film surface adheres and the surface properties deteriorate. For this reason, it is preferable that the medium used in the wet bath is supplied through a filter having a filtration accuracy of 6,000 nm or less, preferably 5,000 nm or less, and more preferably 3,000 nm or less. The time required to pass through these wet baths is 10 seconds to 30 minutes, depending on the thickness of the film. Further, if necessary, the film is stretched in the longitudinal direction.

After the film subjected to the wet process is dried,
Drying and heat treatment and stretching in the width direction are performed by a tenter. The heat treatment temperature is 200-350 ° C., preferably 250
To 300 ° C. for improving the flatness of the film, and the stretching ratio in the transverse direction is 1.15 to 15.
It is preferably 2.0 times, and more preferably 1.2 to 1.8 times, in order to increase the rigidity of the film.

In order to obtain the aromatic polyamide film of the present invention, it is important to control the atmosphere until the film that has undergone the heat treatment step is wound up as a film roll. In other words, if the film coming out of a heat treatment machine such as a tenter is placed under high humidity, it is likely that the moisture will be absorbed from both sides and the outgas amount will increase, and the moisture absorbed once is stored in a roll state. When done
Even if a dehumidifying operation is performed thereafter, it is difficult to remove the dehumidifying operation. As the atmosphere conditions, at a temperature of 10 to 30 ° C., a relative humidity of 10 to 50%, preferably 10 to 40%
%, More preferably from 10 to 30%, it is possible to reduce moisture absorption into the film and to make the outgassing amount within the range of the present invention.

Further, in storage from winding the film to processing into a magnetic recording medium before use, in addition to packing with a normal gas barrier sheet, a dehumidifier (for example,
It is more preferable to encapsulate the product name “Ozo” (manufactured by Ozo Material Co., Ltd.).

Next, measurement methods and evaluation criteria for various characteristic values related to the present invention will be described. (1) Center Line Average Roughness, Number of Protrusions Using an atomic force microscope (AFM) under the following conditions, measurement was performed 10 times at different locations, and the center line average roughness Ra and the height from a flat surface were measured. 1mm when sliced with
The density of protrusions is calculated by converting the density into ^two .

Apparatus: NanoScope III AFM (Digital Instrument)
(manufactured by ments Inc.) Cantilever: silicon single crystal Scanning mode: tapping mode Scanning range: 5 μm × 5 μm Scanning speed: 0.5 Hz Measurement environment: temperature 25 ° C., relative humidity 55% (2) Amount of outgas generation Sample (film) precisely Weighed and by TG-MS,
Measure the weight of gas generated in the range of 25 ° C to 175 ° C,
The value obtained by dividing the generated gas weight by the sample weight is expressed in parts per million,
The amount of outgas generated.

The conditions for the TG-MS measurement are described below.

Apparatus: Simultaneous TG-MS measuring apparatus manufactured by Shimadzu Corporation Measurement mode: After setting the sample in the apparatus, the carrier gas was set to 1
Start heating after 5 minutes of flow Sample amount: Approximately 40 mg (precisely weighed to the unit of μg) Heating condition: 10 ° C./min Atmosphere: Helium flow (flow rate 30 ml / min) (3) Film flatness 300 mm width The film slit to a length of 3,000 m is stored at a temperature of 40 ° C. and a relative humidity of 65% for 2 weeks, and then the flatness when the film is wound with a tension of 0.1 N / m is evaluated according to the following criteria. did.

：: Wrinkles, breaks, and sagging are not observed. Δ: Wrinkles, breaks, and sagging are partially observed. The measurement was performed at 20 ° C. and a relative humidity of 60% using RTA (manufactured by Orientec). The test piece is 10 mm wide and 50 mm long, and the pulling speed is 300 m
m / min. However, the weight is 0.
The point that passed 98N was defined as the origin of elongation.

Further, ((length when the film is broken: mm-initial sample length: 50 mm) / 50 mm) × 10
0 (%) was defined as the elongation.

The number of measurements n was 5, and the arithmetic average of the measurement results excluding the maximum value and the minimum value was defined as the Young's modulus and elongation. (5) Magnetic Properties A Co-O magnetic layer having a thickness of 90 nm was formed on a non-magnetic support (film) by a continuous oblique vapor deposition method. Next, a diamond-like coating film having a thickness of 5 nm is formed on the magnetic layer by a sputtering method, and a solution of 0.1% by weight of an organic rust inhibitor is applied thereon using a gravure roll. And dried with a drier. Thereafter, a 0.5% by weight solution mainly composed of an organic substance composed of a perfluoropolyether derivative as a lubricant was similarly applied to a gravure roll and dried.

On the other side of the nonmagnetic support, a 0.3 μm-thick back coat layer mainly composed of carbon and using a vinyl acetate resin as a binder was formed.

The magnetic recording medium raw material obtained as described above was cut into a width of 8 mm and a length of 250 m, and assembled into a cassette to form a magnetic tape.

This tape was used as a reproducing head of a commercially available AIT-1 drive by using a FeNi head gap of 0.
The drive was changed to an MR head having a 2 μm element depth of 3 μm, and the S / N ratio was determined. A commercially available AIT-1 tape was compared and measured, and the following judgment was made based on the S / N ratio.

◎: +2 dB or more ：: +1 dB or more and less than +2 dB Δ: −1 dB or more, less than +1 dB ×: less than −1 dB

[0068]

Next, the present invention will be described based on examples, but the present invention is not limited to these examples. (Example 1) N-methyl-2-pyrrolidone (hereinafter referred to as NM
P), 2-chloroparaphenylenediamine corresponding to 85 mol% as an aromatic diamine component and 4,4′-diaminodiphenyl ether corresponding to 15 mol% are dissolved therein, and 99 mol% thereof is dissolved therein. 2-Chloroterephthalic acid chloride was added and stirred for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to obtain an aromatic polyamide solution (hereinafter referred to as solution A) having a polymer concentration of 10% by weight and a viscosity of 300 Pa · s.

On the other hand, polyether sulfone (Sumika Excel PES-7600P manufactured by Sumitomo Chemical Co., Ltd., intrinsic viscosity 0.78 dl / g, hereinafter abbreviated as PES) was added to NMP at 1%.
0% by weight, and blended with Solution A so that the content of PES was 6% by weight based on the total amount of aromatic polyamide and PES, and thoroughly mixed at 50 ° C. for 3 hours. , Solution B).

Further, an aromatic polyamide solution (hereinafter referred to as solution C) was obtained by adding 0.45% by weight of colloidal silica having an average particle diameter of 150 nm to solution A.

Next, the solutions B and C were passed through filters having filtration accuracy of 5,000 nm and 1,000 nm, respectively, and then the solution C was brought into contact with the belt using a composite tube.
The frequency of surface defects with a diameter of 30 μm or more is 0.005 / m
Cast at solution temperature 60 ° C. on endless m ² Belt
Was cast. B and C were laminated so that the lamination ratio of the final film was 2/1.

The temperature of the support at the time of casting (Tb)
Was 120 ° C. and the hot air temperature (Ta) was 155 ° C. The film peeled from the belt was subsequently stretched 1.2 times in the longitudinal direction of the film in a water bath at 40 ° C. to remove the residual solvent, and then introduced into a tenter. The film was stretched 1.5 times in the width direction at 250 ° C. in a tenter. The film that came out of the tenter had a temperature of 20 ° C. and a relative humidity of 30.
% In a room controlled by a winder to obtain an aromatic polyamide film having a thickness of 4.0 μm.

Further, in this film roll, 50 g of “OZO” manufactured by OZO Material Co., Ltd. was sealed and stored in an aluminum-evaporated polypropylene film.

The outgas amount of this film was 1,22.
0 ppm, RaA is 1.3 nm, RaB is 3.6 nm,
The projection density of the A surface with a height of 5 to 30 nm is 8.60 million / mm
^{2. The} density of protrusions with a height exceeding 30 nm is 0.1000 / m
m ² , the protrusion density exceeding 100 nm in height of the B surface is 0.7
10,000 pieces / mm ² , and the Young's modulus was 12.4 GPa and 16.2 GPa in the longitudinal direction and the width direction, respectively.

The flatness was excellent and the magnetic properties were excellent. (Example 2) A film was formed using the same polymer solution as in Example 1, and the atmosphere of the film coming out of the tenter was changed to a temperature of 35 ° C and a relative humidity of 50%, in the same manner as in Example 1. An aromatic polyamide film and a roll having a thickness of 4.0 μm were obtained.

The outgas amount of this film was 3,86
0 ppm, RaA is 1.3 nm, RaB is 3.6 nm,
The projection density at the height of 5 to 30 nm on the A side is 8.70 million / mm.
^{2. The} density of protrusions with a height exceeding 30 nm is 0.1000 / m
m ² , the protrusion density exceeding 100 nm in height of the B surface is 0.7
10,000 pieces / mm ² , and the Young's modulus was 12.4 GPa and 16.3 GPa in the longitudinal direction and the width direction, respectively.

The flatness was Δ and the magnetic characteristics were Δ, which was at a practical level. (Example 3) A film was formed using the same polymer solution as in Example 1, and the atmosphere of the film coming out of the tenter was adjusted to a temperature of 15 ° C and a relative humidity of 13%, in the same manner as in Example 1. An aromatic polyamide film and a roll having a thickness of 4.0 μm were obtained.

The outgas amount of this film is 120 p
pm, RaA is 1.3 nm, RaB is 3.6 nm, the projection density at the height of the A-plane of 5 to 30 nm is 8.6 million / mm ² ,
The protrusion density exceeding 30 nm in height is 0.1000 protrusions / mm ² ,
The protrusion density of the surface B having a height exceeding 100 nm is 0.70
mm ² , Young's modulus is 12.
It was 4 GPa and 16.1 GPa.

Further, the flatness was Δ and the magnetic characteristics were ◎, which were excellent. (Example 4) The amount of colloidal silica added to solution C was 1.0
The same polymer solution as in Example 1 was used except that the amount was changed to% by weight. And the atmosphere of the film that came out of the tenter,
An aromatic polyamide film having a thickness of 4.0 μm in the same manner as in Example 1 except that the temperature is set to 20 ° C. and the relative humidity is set to 20%,
And got the roll.

The outgas amount of this film was 740 p
pm, RaA is 1.4 nm, RaB is 8.6 nm, and the projection density at the height of the A-plane of 5 to 30 nm is 8.30 million / mm ² ,
The protrusion density exceeding 30 nm in height is 11,000 protrusions / mm ² ,
The protrusion density of the surface B having a height exceeding 100 nm is 108,000 / mm ² , and the Young's modulus is 1 in each of the longitudinal direction and the width direction.
The values were 2.3 GPa and 16.2 GPa.

The flatness was ○ and the magnetic characteristics were △, which was at a practical level. (Example 5) 2-chloroparaphenylenediamine corresponding to 85 mol% as an aromatic diamine component in NMP,
15 mol% of 4,4′-diaminodiphenyl ether was dissolved, and an ultrasonically dispersed NMP solution of colloidal silica having an average particle diameter of 45 nm was added thereto. Terephthalic acid chloride was added and stirred for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to obtain an aromatic polyamide solution having a polymer concentration of 10% by weight and a viscosity of 300 Pa · s (hereinafter referred to as solution A ′). The amount of colloidal silica was 0.5% by weight based on the weight of the polymer.

This polymer was laminated with solution C in the same manner as in Example 1, except that the heat treatment temperature was set to 300 ° C.
In the same manner as in the above, an aromatic polyamide film having a thickness of 4.0 μm and a roll were obtained.

The outgas amount of this film is 320 p.
pm, RaA is 0.9 nm, RaB is 3.6 nm, the projection density of the A-plane at a height of 5 to 30 nm is 2.4 million / mm ² ,
The protrusion density exceeding 30 nm in height is 75,000 protrusions / mm ² ,
The protrusion density of the surface B having a height exceeding 100 nm is 88,000 /
mm ² , Young's modulus is 11.
9 GPa and 15.7 GPa.

The flatness was good and the magnetic property was good, which was good. (Example 6) The amount of colloidal silica added was 1.0% by weight.
And a thickness of 4.0 μm in the same manner as in Example 5, except that the temperature at which the tenter emerged was 20 ° C. and the relative humidity was 40%.
m and an aromatic polyamide film were obtained.

The outgas amount of this film was 2,40
0 ppm, RaA is 3.1 nm, RaB is 3.6 nm,
The projection density of the A surface with a height of 5 to 30 nm is 4.1 million / mm
^{2. The} density of protrusions exceeding 30 nm in height is 132,000 / m
m ² , the density of protrusions exceeding 100 nm in height of the B surface is 0.8
10,000 pieces / mm ² , and the Young's modulus was 11.8 GPa and 15.6 GPa in the longitudinal direction and the width direction, respectively.

The flatness was ○ and the magnetic characteristics were △, which was at a practical level. (Comparative Example 1) The thickness was 4.0 in the same manner as in Example 1 except that the atmosphere from the tenter was at a temperature of 40 ° C and a relative humidity of 60%.
A μm aromatic polyamide film and a roll were obtained.

The outgas amount of this film was 4,08
0 ppm, RaA is 1.3 nm, RaB is 3.6 nm,
The projection density of the A surface with a height of 5 to 30 nm is 8.60 million / mm
^{2. The} density of protrusions with a height exceeding 30 nm is 0.1000 / m
m ² , the protrusion density exceeding 100 nm in height of the B surface is 0.7
10,000 pieces / mm ² , and the Young's modulus was 12.3 GPa and 16.2 GPa in the longitudinal direction and the width direction, respectively.

The flatness was × and the magnetic characteristics were ×, which was not practical. Comparative Example 2 A thickness of 4.0 μm was obtained in the same manner as in Example 5 except that the amount of colloidal silica added was 0.003% by weight.
m and an aromatic polyamide film were obtained.

The outgas amount of this film was 340 p
pm, RaA is 0.4 nm, RaB is 3.6 nm, the projection density of the surface A having a height of 5 to 30 nm is 250,000 protrusions / mm ² , the projection density exceeding the height of 30 nm is 22,000 protrusions / mm ² , B
Projection density exceeding 100 nm in surface height is 70000 / m
m ² and Young's modulus are 11.8 in each of the longitudinal direction and the width direction.
GPa and 15.8 GPa.

The magnetic properties were good at ○, but the flatness was poor at x, making them impractical. (Comparative Example 3) The particle size of the colloidal silica of the solution C was 200
An aromatic polyamide film and a roll having a thickness of 4.0 μm were obtained in the same manner as in Example 4 except that the addition amount was changed to 1.2 nm by weight.

The outgas amount of this film was 1,18
0 ppm, RaA is 1.6 nm, RaB is 10.4 n
m, the projection density at the height of the A-plane of 5 to 30 nm is 9.2 million /
mm ² , the protrusion density exceeding 30 nm in height is 20 thousand protrusions /
mm ² , the protrusion density exceeding 100 nm in height of the B surface is 45
10,000 pieces / mm ² , and the Young's modulus was 12.1 GPa and 16.0 GPa in the longitudinal direction and the width direction, respectively.

Further, the flatness was good, but the magnetic properties were poor as x, so that it could not be put to practical use. (Comparative Example 4) A thickness of 4.0 µm was prepared in the same manner as in Example 1 except that a dehumidified air was directly blown onto the film coming out of the tenter to make it an atmosphere at a temperature of 15 ° C and a relative humidity of 7%.
m and an aromatic polyamide film were obtained.

The outgas amount of this film was 80 pp
m, RaA is 1.3 nm, RaB is 3.6 nm, the projection density of the A surface at a height of 5 to 30 nm is 8.6 million / mm ² , the projection density exceeding 30 nm in height is 0.1 thousand / mm ² , B
Projection density exceeding 100 nm in surface height is 70000 / m
m ² and Young's modulus are 12.1 in each of the longitudinal direction and the width direction.
GPa and 16.0 GPa.

Further, the magnetic properties were ○, which is a practical level, but the flatness was poor, and the magnetic properties were not practical.

[0095]

[Table 1]

[0096]

The film of the present invention has both surface properties,
By setting the outgas amount in a specific range, excellent flatness and excellent magnetic properties when used as a magnetic recording medium can be obtained. The film of the present invention can be suitably used for any applications such as a magnetic recording medium field, an electric / electronic field, a packaging field, etc., and in particular, is preferably used as a base film for a metal thin film type magnetic recording medium. it can.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA56 AF27 AF28 AF41 AG27 AH14 BA02 BB02 BC01 BC10 BC14 BC16 5D006 CB03 CB07 5D112 BA01

Claims (3)

[Claims] When the center line average roughness of one surface (A surface) of a film is RaA (nm) and the center line average roughness of the other surface (B surface) is RaB (nm), RaA And Ra
B satisfies the following formula (1), 0.5 <RaA <RaB <10 (1) and an outgas generation amount at 25 to 175 ° C. is 100 to 4,000 ppm with respect to the film weight. Group polyamide film. 2. A projection is present on the A surface and the B surface. On the A surface, the density of the projections having a height of 5 to 30 nm is 100,000 to 30 million / mm ² , and the height is Is 30n
the density of protrusions greater than m is 0-10 million units / mm ^2, in side B, which is the density of the projections height is greater than 100nm is 01,000 to 100,000 pieces / mm ^2, claim 1
3. The aromatic polyamide film according to item 1. When a film containing an aromatic polyamide is heat-treated and wound up to obtain a film roll,
The relative humidity is 10 to 5 in the process from heat treatment to winding.
A method for producing an aromatic polyamide film performed in an atmosphere of 0%.