JP2000344915A - Roughness-changeable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film having a surface roughness capable of being adjusted according to the purpose by heating the film at the time of processing in the film comprising an organic polymer. SOLUTION: A solution dissolving an organic polymer is formed into a film by a film-producing method by using the solution. The objective roughness- changeable film is obtained by regulating the value of Ra2/Ra1 (Ra1 is the average roughness of the film before the heat treatment; Ra2 is the average roughness after the heat treatment) so as to be <1. The film preferably has >=7 GPa Young's modulus at least in one direction. The organic polymer is preferably an aromatic polyamide containing >=50 mol%; unit of NH-Ar1-NHCO- Ar2-CO and/or NH-Ar3-CO (Ar1 to Ar3 are each phenylene or the like). When the organic polymer is the aromatic polyamide, the heat treatment is preferably carried out at 150-350 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable roughness film whose surface roughness can be adjusted during processing according to the purpose.

[0002]

2. Description of the Related Art Organic polymer films are widely used as industrial materials. There are many uses, such as base films for magnetic recording media, FPCs, TABs, solar batteries, capacitors and other electrical and insulating base films, and packaging and other packaging applications. In all these applications, its surface properties are important.

For example, in a magnetic recording medium, it is preferable that the surface is rough in order to ensure the running property and workability, while it is preferable that the surface is smooth in order to improve the electromagnetic conversion characteristics. In order to meet such demands, various methods and forms have been proposed for film surface formation.

[0004] As a method for this, a method of incorporating inorganic or organic particles into a polymer for forming a film (for example, JP-A-60-127523, JP-A-60-127523).
Japanese Patent Application Laid-Open No. 0-201914), a method of forming a surface projection by coating a slurry containing fine particles during or after film formation (for example, JP-A-3-1-1195).
No. 12) is mentioned as a typical example, and a method for controlling the roughness of both surfaces has been proposed (for example, Japanese Patent Application Laid-Open No. 1-247162). In such a conventional method, the surface of the film once formed is invariant even after the subsequent processing steps, and the smooth one has been processed to the final product while the rough one remains smooth. Therefore, in the case of the film, it is necessary to form individual surfaces in accordance with the requirements of the application.

[0005]

However, since the surface is individually designed according to the application, the number of types increases, which causes a cost increase. Further, when the requirements regarding the surface such as the slipperiness and smoothness required in the processing step and the product are different, the conventional method can no longer cope with it. For example, in the production of a vapor-deposited magnetic recording medium, when forming a magnetic layer and a back coat layer, a smooth surface is required to reduce friction with a roll and increase a process speed, but when a product is used. Requires an extremely smooth surface to ensure output characteristics.

Accordingly, an object of the present invention is to provide a film capable of smoothing the surface of a film by applying a heat treatment, and capable of adjusting the surface roughness required at the time of processing and at the time of using the product. Is what you do.

[0007]

According to the present invention, in a film made of an organic polymer, at least one surface has an average roughness Ra1 before heat treatment and an average roughness Ra2 after heat treatment.
A variable roughness film characterized by satisfying the formula (I).

Ra2 / Ra1 <1 (I)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an organic polymer is
There is no particular limitation, and organic polymers formed by a so-called melt film-forming method such as polyester, aliphatic polyamide, polyethylene, and polypropylene, and organic polymer formed by a so-called solution film-forming method such as aromatic polyamide and aromatic polyimide. A molecular body is an example. Among them, an aromatic polyamide is particularly preferable from the viewpoint of the toughness of the film.

As the aromatic polyamide, those containing 50 mol% or more of the repeating units represented by the following general formulas (1) and / or (2) are preferable, and those containing 70 mol% or more are more preferable. Other repeating units may be copolymerized or blended as other components.

[0011]

Embedded image

[0012]

Embedded image Here, as Ar ₁ , Ar ₂ and Ar ₃ , for example,

[0013]

Embedded image And the like.

[0014] X, Y is _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S -, -
It is selected from C (CH ₃ ) ₂ − and the like, but is not limited thereto.
Further, some of the hydrogen atoms on these aromatic rings may be substituted with halogen groups (especially chlorine) such as fluorine, chlorine, and bromine, alkyl groups (particularly methyl groups) such as nitro, methyl, ethyl, and propyl groups, and methoxy. Group, ethoxy group, propoxy group,
Also included are those substituted with a substituent such as an alkoxy group such as an isopropoxy group, and those in which hydrogen in an amide bond constituting the polymer is substituted with another substituent.

From the viewpoint of properties, a polymer in which the above aromatic rings are bonded in a para-oriented position, which accounts for 50% or more, preferably 75% or more of the total aromatic rings, has high rigidity and good heat resistance of the film. Is preferable. Here, the para-oriented position means that the bonding position is linear. If the aromatic ring in which part of the hydrogen atoms on the aromatic ring is substituted with a halogen group (especially chlorine) is 30% or more of the whole, the moisture resistance is improved, and the characteristics such as dimensional change due to moisture absorption and rigidity decrease are improved. Is preferred.

Further, the variable roughness film of the present invention may contain 0.0001 to 3.0% by weight of particles depending on the use.

The particles may be either organic particles or inorganic particles, such as cross-linked polyvinyl benzene, acrylic, cross-linked polystyrene, polyester, polyimide,
Particles made of organic polymers such as polyamide and fluororesin, inorganic particles such as colloidal silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black and zeolite, or the above organic polymer particles coated with other organic substances, etc. Particles subjected to various treatments,
Alternatively, particles obtained by subjecting the surface of the above-mentioned inorganic particles to various treatments such as coating with the above-mentioned organic polymer may be used. The particle diameter is preferably from 5 to 100 nm, more preferably from 10 to 50 nm, still more preferably from 15 to 30 nm, and it is preferable to use monodisperse particles. From among these, a plurality of particles may be used in combination, or particles having different sizes may be used in combination. Although the content of the particles is appropriately designed depending on the application, particularly when used for a magnetic recording medium, it is 0.000 in at least one outermost layer of the film.
It is preferably set to 1 to 1.0% by weight, more preferably 0.001 to 0.2% by weight, and further preferably 0.005% by weight.
~ 0.1% by weight.

Since it is preferable that the variable roughness film of the present invention has uniform projections, it is preferable to use spherical particles as the particle shape and to use those having a uniform particle size. Specifically, the relative standard deviation σ (standard deviation / average particle size) of the particle size distribution when the average particle size is D is σ ≦
0.3 is preferable, and σ ≦ is more preferable.
0.15.

The protrusions on the film surface of the above-mentioned particle protrusions
The starting number is appropriately designed according to the application.
The number of projections is 0.1 × 10^FourPieces / mm^TwoMore than 20 × 10^Four
Pieces / mm^TwoBelow, more preferably 0.3 × 10^FourPieces / m
m^TwoMore than 10 × 10^FourPieces / mm ^TwoHereinafter, more preferably,
0.7 × 10^FourPieces / mm^TwoMore than 2 × 10^FourPieces / mm^TwoBelow
In some cases, especially when used as a substrate for magnetic recording media
Is preferable because the slipperiness can be further improved
No.

Further, the average projection height of the particle projections is 10
It is preferable that the thickness be at least 75 nm and at most 75 nm, because the slipperiness of the film can be further improved. More preferably, it is 20 nm or more and 60 nm or less, and still more preferably 3 nm or more.
It is not less than 0 nm and not more than 50 nm.

The variable roughness film of the present invention comprises the above composition as a main component, but within the range not to impair the object of the present invention.
Inorganic or organic additives such as antioxidants, heat stabilizers, lubricants, UV absorbers, nucleating agents and the like may be blended.

The variable roughness film of the present invention has a thickness of 1 to 5.
A thin film having a thickness of 20 μm is preferable because the effects of the present invention can be further exhibited. More preferably, it is 2 to 10 μm, and further preferably, it is 2.5 to 7 μm.

In the variable roughness film of the present invention, it is necessary that at least one surface has an average roughness Ra1 before heat treatment and an average roughness Ra2 after heat treatment satisfy the formula (I).

Ra2 / Ra1 <1 (I) Ra2 / Ra1 is preferably 0.8 or less, more preferably 0.7 or less. The lower limit of Ra2 / Ra1 is not particularly limited, but if it is too small, the cause is not always clear, but macro surface roughness may occur and may become impractical.
More preferably, it is 0.5 or more.

The size of Ra1 is preferably designed appropriately depending on the application, but is preferably from 0.5 nm to 5 nm.
It is in the range of 00 nm, more preferably in the range of 0.8 nm to 50 nm. In particular, when used for a magnetic recording medium, the thickness is preferably in the range of 0.8 nm to 15 nm.

The heat treatment referred to in the present invention is selected according to the type of the selected organic polymer and the surface roughness required at the time of film processing and at the time of product. For example,
In the case of an aromatic polyamide, the adjustment is preferably performed in the range of 120 ° C to 350 ° C.

In particular, when an aromatic polyamide film is used as a base film for a magnetic recording medium, it is necessary to use 300 in order to achieve both smoothness during processing and surface smoothness in a product.
It is more preferable that the average roughness Ra2 after the heat treatment at 1 ° C. for 1 minute and the average roughness Ra1 before the heat treatment satisfy Expression (II).

0.2 ≦ Ra2 / Ra1 ≦ 0.90 (II) More preferably, 0.2 ≦ Ra2 / Ra1 ≦ 0.85, and most preferably, 0.5 ≦ Ra2 / Ra1 ≦ 0.8.
5

By satisfying the above-mentioned properties, the base film for a magnetic recording medium having excellent workability and magnetic properties, in particular, a vapor-deposited magnetic recording medium can be obtained while fully utilizing the heat resistance and rigidity of the aromatic polyamide. Will be obtained.

Further, the variable roughness film of the present invention preferably has a Young's modulus in at least one direction of 7 GPa or more in order to achieve a thinner film as a base material, which has become increasingly remarkable in recent years. For example, the output of a magnetic tape increases with the improvement of the head touch property between the tape and the head. For this purpose, it is required to increase the Young's modulus of the film as the base. When the recording method is a fixed head type, the Young's modulus in the longitudinal direction is particularly required, and when the recording method is a helical scan type, a Young's modulus in the width direction is particularly necessary. . In addition, the Young's modulus of at least one direction of the variable roughness film of the present invention is more preferably 9 GPa or more, and further preferably 11 GPa or more. Needless to say, the Young's modulus in all directions is preferably 7 GPa or more. Although the upper limit of the Young's modulus is not particularly limited, it is usually about 30 GPa.

From the viewpoint that Ra2 / Ra1 and Young's modulus are set in the above ranges, in the present invention, the organic polymer is an aromatic polyamide and the aromatic ring thereof has para-orientation. It is preferable that 50% or more, more preferably 75% or more, even more preferably 80% or more, and even more preferably 90% or more of the total aromatic ring.

In the variable roughness film of the present invention, the number of protrusions having a height of 5 nm or more formed on the film surface after the heat treatment is preferably 2 × 10 ⁵ / mm ² or more. When the number of protrusions is in this range, the transportability and slitting property become favorable during the production of a film or the like, and the running properties and durability when using a magnetic recording medium, particularly a magnetic recording medium having a vapor-deposited magnetic layer formed thereon, are improved. It will be good. The number of protrusions is more preferably 1 × 10 ⁶ / mm ² or more, still more preferably 3 × 10 ⁶ / mm ² or more, and most preferably 5 × 10 ⁶ / mm ^2.
× 10 ⁶ pieces / mm ² or more. The upper limit of the number of protrusions is not particularly limited, but if it exceeds 10 ⁹ / mm ² , when a magnetic recording medium is used, noise may occur depending on the system in which the magnetic recording medium is used. Further, the number of protrusions having a height of 50 nm or more is 2 × 10 ⁵ protrusions / mm ² or less,
It is more preferable that the cross-sectional area of the protrusion cut by a horizontal plane having a height of 5 nm is in the range of 0.5 to 20% of the total area. When the number of protrusions having a height of 50 nm or more exceeds 2 × 10 ⁵ protrusions / mm ² , the initial output when used as a magnetic recording medium is low, and dropout may occur frequently. More preferably 1 × 10
^The number is 5 / mm ² or less, more preferably 5 × 10 ⁴ / mm ² or less. The lower limit of the number is 0 / mm ^2.
In some cases, it is preferable that the number is about pieces / mm ² . Also,
When the cross-sectional area of the protrusion cut in a horizontal plane with a height of 5 nm is less than 0.5% of the total area, when the vehicle is repeatedly driven, the protrusion is easily scraped when sliding with the head or the guide pin, and the durability is reduced. If it exceeds 20%, the contact area with the head or the guide pin may increase, and the durability may decrease. More preferably 1.0 to 15%, further preferably 2.0 to 10%, most preferably 2.0 to 5.0.
%.

Further, the film surface has a height of 10 nm.
The above projections are 1 × 10 ⁵ / mm ² or more, more preferably 5 × 10 ⁵ / mm ² or more, and still more preferably 1 × 10 ⁶ / mm ² or more, and projections cut on a horizontal plane having a height of 10 nm. When the cross-sectional area is 0.01 to 10%, more preferably 0.05 to 8%, and still more preferably 0.1 to 7% of the total area, the electromagnetic conversion characteristics and durability are further improved. Therefore, it is preferable. Although the upper limit of the number of protrusions is not particularly limited, 5 ×
When it exceeds 10 ⁸ pieces / mm ² , when a magnetic recording medium is used,
Noise may occur depending on the system in which such a magnetic recording medium is used.

Further, the film surface has a height of 15 nm.
The above projections are 2 × 10 ⁴ / mm ² or more, more preferably 5 × 10 ⁴ / mm ² or more, and still more preferably 1 × 10 ⁵ / mm ² or more, and projections cut on a horizontal plane with a height of 15 nm. Is preferably 5% or less of the total area, more preferably 3%, and still more preferably 0.001 to 3%, because the electromagnetic conversion characteristics and durability are further improved. The upper limit of the number of protrusions is not particularly limited, but is 3 × 10 ⁸ / m
when the magnetic recording medium exceeds m ^2, the noise may be generated by a system according magnetic recording medium is used. The elongation in at least one direction of the variable roughness film of the present invention is 10% or more, more preferably 20%.
Above, more preferably 30% or more, since it has appropriate flexibility. The upper limit of the elongation is usually about 100%.

When the moisture absorption of the film is 5% or less, more preferably 3% or less, and still more preferably 2% or less, expansion and contraction of the tape due to humidity changes in magnetic recording medium applications can be suppressed, and good results can be obtained. This is preferable because output characteristics can be maintained. The lower limit of the moisture absorption is not particularly limited, but if it is set too low, other physical properties may be adversely affected. Therefore, the lower limit is usually about 0.3%.

The heat shrinkage of the film at 200 ° C. for 10 minutes is preferably 3% or less, more preferably 1.5%.
% Or less is preferable because the elongation of the tape due to a temperature change can be suppressed in a magnetic recording medium application and good output characteristics can be maintained. The lower limit of the heat shrinkage is usually 0%.

It is preferable that at least one side of the variable roughness film of the present invention has a high defect-free surface when used for applications such as a magnetic recording medium. That is, when one surface of the film is the A surface and the other surface is the B surface, at least the A surface has a number of coarse protrusions (h: nm / 100 cm ² ) having a height h (nm) satisfying the following expression. preferable.

H ≧ 270 a <100 h> 540 a <70 h> 810 a <15 h> 1080 a <5 A high-density recording magnetic recording medium such as a digital video tape has many disadvantages exceeding this range. In terms of data, there are many dropouts, which are indicators of data loss, and cannot be used for the present invention at all. In order to satisfy the above expression, a method of removing coarse foreign substances present in the polymer by passing through a filter having a predetermined filtration accuracy is preferable. Here, the filtration accuracy means that when particles are dispersed in a polymer or a solvent and passed through a filter, just 95%
% Defined as the size of the particles captured on the filter. Naturally, the smaller the value of the filtration accuracy, the smaller the removal of foreign matter. 1000 for filtration accuracy
nm or less, preferably 600 nm or less, more preferably 300 nm or less. The number of the coarse projections is
It is more preferable that the surface B is satisfied.

It is preferable that at least the three-dimensional surface roughness SRa1 at the measurement area of 0.002 mm ² and the three-dimensional surface roughness SRa2 at the measurement area of 1.0 mm ² satisfy the following expression.

0.8 ≦ SRa2 / SRa1 ≦ 2.5 When SRa2 / SRa1 exceeds 2.5, uneven undulations are generated on the film surface, and when a magnetic tape is used, the head touch becomes unstable and the output decreases. Data loss may occur. On the other hand, SRa2 / SRa1 is 0.8
If the amount is less than the above range, the running property of the magnetic tape may be reduced, and blocking may occur when the magnetic tape is wound into a roll. SRa2
/ SRa1 more preferably satisfies the following expression.

1.1 ≦ SRa2 / SRa1 ≦ 1.8 It is more preferable that the above-mentioned range of SRa2 / SRa1 is satisfied also for the B side. Further, it is preferable that the above properties are satisfied in the film after the heat treatment.

For controlling SRa2 / SRa1 within the above range, for example, the following method is effective. In other words, in the film manufacturing process, a method in which the roll surface in contact with the film peeled off from the endless belt or the like is used as a mirror surface, or to prevent the solvent extraction and drying of the film from occurring rapidly, for example, by controlling the temperature in the solvent extraction process. -10 to 50
° C, a method in which the polymer concentration in the film at the time of peeling from an endless belt or the like is 30 to 70% by weight, and a temperature of 50 to 100 ° C before the drying and heat treatment in the tenter. Examples include a method of preheating the film, a combination of the above methods, and the like.

The variable roughness film of the present invention is preferably used for various uses such as a flexible printed circuit board, a capacitor, a printer ribbon, an acoustic diaphragm, and a base film of a solar cell. When used as a medium, it has excellent processing properties such as magnetic paint coating properties and film transportability due to its slipperiness during processing, and has high output and no defects due to good smoothness in products. It is particularly preferable because the magnetic recording medium has the property.

The form of the magnetic recording medium is not particularly limited, such as a disk shape, a card shape, and a tape shape. A specific example of a thin film shape utilizing the excellent surface properties of the variable roughness film of the present invention is a substrate. The film has a thickness of 6.5 μm or less, a width of 2.3 to 13 mm, a length of 100 m / roll or more, and a recording density (uncompressed) of 8 as a magnetic recording medium.
It is particularly preferable since the surface shape is regulated when a long, high-density magnetic tape of kilobytes / mm 2 or more is used, and the excellent effects of having high rigidity can be further exhibited. The recording density defined here is obtained by dividing the total recording capacity per cassette by (length × width) of the used magnetic tape. In recent years, magnetic recording media typified by magnetic tapes have been increasingly demanded for miniaturization and high capacity, but there are the following points in implementing high capacity. One is to increase the overall recording capacity by reducing the thickness of the film as the substrate, and the other is to reduce the track width, shorten the recording wavelength, etc. Is a method for improving the recording capacity per unit area, and generally these are used in combination.

When the thickness of the film is reduced, it is, of course, necessary for the film to have high rigidity. However, the contribution of the head surface and, in turn, the electromagnetic conversion characteristics of the film surface becomes larger than when the film is thick. In other words, when the tape is thick, the running tension and the touch pressure on the head can be set high, so that even if the film surface is unregulated, it can be stably contacted with the head, whereas the tape has been made thinner. In this case, the running tension and the touch pressure of the head must be reduced, and therefore, if the surface of the base is not restricted as in the present invention, the adhesion to the head and the running performance are non-uniform and unstable. As a result, track misalignment and signal loss are likely to occur. Also, due to the demand for higher data transfer speed, the relative speed between the head and the tape tends to be higher than before,
To avoid generating unnecessary frictional heat,
In a product, the roughness variable film of the present invention, which can exhibit an appropriate roughness, is extremely effective.

As described above, the variable roughness film of the present invention can be used as a magnetic tape which can suitably meet such a demand for high capacity.

The thickness of the film as a substrate is preferably 5.5 μm or less, more preferably 4.5 μm or less, and the recording density as a magnetic recording medium is preferably 25 μm or less.
It is not less than kilobytes / mm ^2, more preferably not less than 34 kilobytes / mm ² .

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, 8 mm data,
Although it can be suitably used for data storage applications such as QIC and AIT, it can be optimally used for data storage applications where reliability such as data loss is most important.

The magnetic layer may 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. A method can also be adopted. When the dry method is adopted, a protective layer such as a diamond-like coating and a lubricating layer may be further formed on the obtained magnetic recording medium for the purpose of further improving the durability and imparting slipperiness.

Regarding the magnetization method, it can be used for optical recording tapes regardless of horizontal magnetization or vertical magnetization.

Incidentally, the variable roughness film of the present invention may be a single layer or a multilayer. For multi-layer,
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 μm
This is preferable because the effects of the present invention can be sufficiently achieved.

Next, the method for producing the variable roughness film of the present invention will be described for the case where the organic polymer is an aromatic polyamide, but the present invention is not limited thereto.

First, as for the polymer, it is preferable that the above-mentioned aromatic polyamide contains a heteropolymer described later.

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 is 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. In addition, the equivalence of the raw materials is important, but when there is a risk of impairing the film forming property, it can be adjusted appropriately. Further, calcium chloride, magnesium chloride, lithium chloride, lithium bromide, lithium nitrate, or the like may be added as a dissolution aid.

When an aromatic diacid chloride and an aromatic diamine are used as monomers, hydrogen chloride is by-produced. When neutralizing this, hydrogen chloride, calcium carbonate, lithium carbonate and other periodic table are used. Inorganic neutralizers represented by salts of Group I or Group II cations and hydroxide ions, anions such as carbonate ions, ethylene oxide, propylene oxide, ammonia, triethylamine,
Organic neutralizing agents such as triethanolamine and diethanolamine are used. Also, for the purpose of improving the humidity characteristics of the base film, benzoyl chloride, phthalic anhydride, acetic chloride, aniline, etc. are added to the system after polymerization,
The ends of the polymer may be blocked. The reaction between the isocyanate and the carboxylic acid is 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-mentioned organic solvent or an inorganic solvent such as sulfuric acid to form a blend. A stock solution may be prepared.

The heteropolymer to be added is at least one polymer having a repeating unit other than the above-mentioned aromatic polyamide. The content of the heteropolymer is determined so as to be optimal depending on the purpose. However, since the excellent mechanical properties and heat resistance of the aromatic polyamide are not impaired, Ra2 / R
In order to effectively restrict a1 within the range of the present invention, the content is preferably 0.1% by weight or more and 30% by weight or less based on the total amount of the aromatic polyamide and the heteropolymer. When the weight fraction is less than 0.1% by weight, the height and the number of the projections are not sufficient, and the effect of the heat treatment may not be remarkably observed.
On the other hand, if it exceeds 30% by weight, not only is the surface undulating and not suitable for practical use, but also the mechanical properties of the film may deteriorate. The content of the heteropolymer should be appropriately designed according to the type of the aromatic polyamide and the heteropolymer used, the solubility, the molecular weight, the size of the molded article, etc., and more preferably, 0.5 8% by weight or more
Or less, more preferably 1% by weight or more and 6% by weight or less.

The kind of such a heteropolymer is appropriately selected for designing a target surface, and is not particularly limited, but the solubility parameter δa of the aromatic polyamide,
When the solubility parameter δb of the heterogeneous polymer contained is satisfied, it is preferable to satisfy the following expression in order to achieve the object of the present invention.

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 mentioned 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. When δa and δb are within the above ranges, the size of the dispersed phase is regulated, and the surface projections preferable in the present invention are easily formed. 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, polyether imide, polyphenylene oxide, modified polyphenylene oxide, polyether ketone, polyether ether ketone, polycarbonate, and polyethylene terephthalate. ,
Polybutylene terephthalate, polyimide or its precursor polyamic acid, polyvinylidene fluoride, polymethyl methacrylate, polystyrene, polyvinyl alcohol, and the like. Aromatic polysulfone polymers such as ether sulfone and polysulfide sulfone, aromatic polyetherimide polymers, polyphenylene oxide, polyphenylene oxide polymers such as modified polyphenylene oxide, aromatic polyketones such as polyetherketone and polyetheretherketone -Based polymers, polycarbonate-based polymers, aromatic polyester-based polymers such as polyethylene terephthalate and polybutylene terephthalate, polyimides or polyamides that are precursors thereof Preferably contains at least one polymer selected from an aromatic polyimide polymer and the like used. Of these, aromatic polysulfone polymers are particularly preferred. The aromatic polysulfone polymer referred to herein is a sodium salt of bisphenol A,
Polycondensation with 4,4'-dichlorodiphenyl sulfone, 4
- (4-chlorophenyl sulfonyl) phenol - is an aromatic polysulfone polymer having a - -SO ₂ at least one sulfonic group in the repeating unit represented by polysulfone manufactured by such polycondensation of the potassium salt of Le Specifically, a known aromatic polysulfone-based polymer having a repeating unit represented by the following formula may be mentioned, and two or more of these may be used.

[0063]

Embedded image Here, n is a positive integer, and a value of 5 or more and 1000 or less is preferable in terms of heat resistance and solubility in an organic solvent.
In particular,

[0064]

Embedded image Is preferred in that uniform projections can be formed.

The above-mentioned aromatic polysulfone polymer is contained in a weight fraction of 0.1% or more and less than 10%, more preferably 0.1% by weight.
It is desirable to contain 5% or more and 8% or less, more preferably 1% or more and 6% or less. Although the aromatic polysulfone polymer is not completely compatible with the aromatic polyamide, the present inventors have found that when a polymer solution is used, the compatibility is small if the amount of the aromatic polysulfone polymer is small. If a film is carefully formed from this mixed solution as described later, uniform projections are formed by phase separation between the aromatic polyamide and the aromatic polysulfone polymer, and the surface roughness is further increased by heat treatment after the film formation. Can be controlled. If the weight fraction is less than 0.1%, the height and number of the projections are not sufficient, and the effect of the heat treatment may not be remarkably observed. On the other hand, if it is 10% or more, not only is the surface undulating and not suitable for practical use, but also the mechanical properties of the film may deteriorate.

As a method for blending the aromatic polyamide and the heteropolymer, a pellet or 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, inorganic or organic particles may be added during the above steps.

In order to obtain the aromatic polyamide film of the present invention, the intrinsic viscosity of the polymer (measured at 30 ° C. as a 100 ml solution of 0.5 g of the polymer in sulfuric acid) is 0.1.
It is preferably 5 or more.

Next, the method of forming a variable roughness film of the present invention will be described by taking an aromatic polyamide as an example.

The membrane-forming stock solution prepared as described above is filtered through a filter having a filtration accuracy of 6000 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. In the present invention, the dry-wet method or the dry method is preferred because the formation of surface projections by phase separation is easily controlled. 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 the variable roughness film of the present invention, the drying step condition is one of the important points, and has a great influence on the surface properties of the obtained film. That is,
When the support temperature Tb (° C.) and the hot air temperature Ta (° C.) introduced onto the cast film at the time of casting the undiluted solution are within the range satisfying the following formula, the heterogeneous polymer is placed in the place due to the convection effect generated during solvent drying. Regardless, the aromatic polyamide-based film of the present invention having uniform and fine surface projections can be suitably obtained because it is deposited on the surface.

If 20 ≦ Ta−TbTa−Tb is less than 20 ° C., the convection effect due to temperature is small, so that sufficient projections may not be formed, more preferably 40 ° C. or more, further preferably 50 ° C. or more. is there. 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 a 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. Further, the solvent is scattered from the cast film,
When drying the thin film, it is more preferable to dry at a solvent removal rate of 3 to 20% / min, preferably 5 to 15% / min. When the desolvation rate is less than 3% / min, the projections become flat, and the ratio of the average roughness may not satisfy the range of the present invention. When the solvent removal rate exceeds 20% / min, the number of coarse projections increases, the surface becomes rough, and the ratio of the average roughness may exceed the range of the present invention. Furthermore, by controlling the casting temperature from the die in the range of 40 ° C. to 150 ° C. depending on the type of the aromatic polyamide or the heteropolymer, the aromatic polyamide-based polymer which easily undergoes phase separation in the polymer solution stage is in solution. The film having the surface protrusions according to the present invention can be finished by melting and phase separation at the time of molding. In addition, the surface property of the belt contact surface can be controlled by controlling the frequency of surface defects of the drum and the endless belt used in the drying step. The frequency of surface defects having a diameter of 30 μm or more is preferably 0.001 to 0.02 defects / mm ² , more preferably 0.002 to 0.015 defects / mm ² .

The film having thus obtained 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, the medium used for the wet bath has a filtration accuracy of 6000 nm or less, preferably 5 nm or less.
It needs to be supplied through a filter of 000 nm or less, more preferably 3000 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.

The film is then introduced into a tenter and subjected to drying and / or heat treatment, and such drying and / or heat treatment conditions are one of the important conditions for obtaining the variable roughness film of the present invention. Drying and / or heat treatment is generally performed by blowing hot air from a slit or cylindrical nozzle onto the film surface. The maximum temperature is the glass transition temperature or heat deformation temperature (° C .; hereinafter referred to as Tg) of the heterogeneous polymer. ) Or more, (Tg + 10
0) When carried out at a temperature of not more than 0 ° C., it is preferable to achieve the film of the present invention. The maximum temperature is more preferably Tg or more (T
g + 80) ° C. or lower, more preferably Tg or higher (T
g + 50) ° C. Further, in order to regulate Ra2 / Ra1 within the range of the present invention, it is necessary to regulate the wind speed of the nozzle in the range of 2 m / sec to 13 m / sec, more preferably in the range of 2 m / sec to 8 m / sec. preferable. The drying and / or heat treatment at the maximum temperature may be performed at any time as long as it is in the tenter. For example, heat treatment may be performed once at the maximum temperature after drying, or heat treatment may be performed at a temperature lower than that after the treatment at the maximum temperature.

The film formed as described above is stretched during the film forming process, and the stretching ratio is 0.8 to 4.0 (area ratio). It is defined by the value divided by the area of the previous film. 1 or less means relaxation.) If the areal magnification is less than 0.8, the film surface may have large undulations and may not be suitable for practical use. If the stretching ratio is higher than 4.0, Ra2 / Ra1 may fall outside the range of the present invention. More preferably, it is 1.2 to 1.8. If the areal magnification is less than 0.8, the film surface may have large undulations and may not be suitable for practical use.

It is effective to gradually cool the film after stretching or heat treatment, and it is effective to cool the film at a rate of 50 ° C./sec or less.

The thus-obtained variable roughness film of the present invention can have Ra2 / Ra1 within the range of the present invention by applying a heat treatment in a substantially unconstrained state. In the case of aromatic polyamide, the heat treatment temperature is 250
It is preferable to add a heat treatment of not less than 400 ° C.
The desired Ra2 / R is obtained by changing the heat treatment conditions depending on the kind of the aromatic polyamide and the heteropolymer contained.
a1 can be obtained.

When the film has a multilayer structure, for example, in the case of two layers, the polymerized aromatic polyamide solution is bisected, and at least one is prepared into a polymer preferably used in the present invention and laminated. Can be manufactured by
The same applies to the case of three or more layers. Examples of the lamination method include a well-known method, for example, lamination in a die, lamination in a composite pipe, and a method in which one layer is formed once and another layer is laminated thereon.

Next, measurement methods and evaluation criteria for the characteristic values in the present invention will be described.

(1) About average roughness (Ra), number of protrusions, protrusion height, and protrusion cross-sectional area ratio: Atomic force microscope (AF)
Using M), measurement is performed 10 times at different locations under the following conditions. Apparatus: NanoScopeIII AFM (Digital Instruments) 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% Ra, number of protrusions The average value of the values obtained in the above measurement is used.

The ratio of the cross-sectional area of the projection cut by a horizontal plane at a constant height to the total area is obtained by dividing the cross-sectional area when cutting from a flat surface (0 nm) by a cross section parallel to the flat surface at a constant height. And the value obtained by dividing the cross-sectional area by the measured area is multiplied by 100.

The image subjected to shadowing (5 °) was observed with a scanning electron microscope at a magnification of 30,000 or more.
The number of protrusions may be obtained by counting protrusions having a height of 5 nm or more than the length of the shadow. Also, (major axis + minor axis) / 2 of each projection is defined as the average diameter of the projection, and the projection height / average diameter is obtained for 100 or more projections.
The average may be set to HD.

(2) Tensile Young's Modulus and Elongation The film was cut into a width of 10 mm and a length of 150 mm, and the distance between the chucks was set to 100 mm, and the tensile speed was 300 mm / min.
Chart speed 500 mm / min, temperature 23 ° C, relative humidity 6
Under the condition of 5%, it is pulled with an Instron type tensile tester. The tensile Young's modulus is determined from the tangent at the rising portion of the obtained load-elongation curve. In addition, the elongation was obtained by multiplying the value obtained by subtracting the distance between the chucks from the length at the time of breaking the film by the distance between the chucks and multiplying by 100.

(3) Three-dimensional surface roughness The surface roughness was measured using a fine shape measuring device ET-30HK manufactured by Kosaka Seisakusho Co., Ltd. For the detection, an optical stylus (HIPOSS, trade name) was used, and the film surface was subjected to aluminum evaporation under vacuum, and then measured. The measurement conditions are described below. I. SRa1 (measurement area 0.002 mm ² ) ・ Measurement length in the longitudinal direction 0.02 mm ・ Measurement length in the width direction 0.10 mm ・ Cutoff value 0.08 mm b. SRa2 (measurement area: 1.0 mm ² ) ・ Measurement length in the longitudinal direction 0.50 mm ・ Measurement length in the width direction 2.00 mm ・ Cutoff value 0.08 mm (4) Number of coarse projections Observe under polarized light and mark coarse projections such as foreign matter.
The height of the protrusion is determined by the multiple interference method, and the number is 100 c.
It was converted to the number per m ² .

(5) Average Particle Diameter of Containing Particles The particles are observed with an electron microscope, and the image of the particles (shading of light generated by the particles) is linked to an image analyzer (for example, QTM900 manufactured by Cambridge Instrumental Corporation) and observed. The following numerical processing is performed for 5000 or more particles at different locations, and the number average diameter D obtained thereby is defined as the average particle diameter. D = ΣDi / N Here, Di is the equivalent circle diameter of the particles, and N is the number.

(6) Relative standard deviation of contained particles The standard deviation σ (=) calculated from the individual particle diameter Di, the average particle diameter D, and the total number N of particles measured by the method (5).
{(Di-D) 2 / N}) was divided by the average particle diameter D (σ / D).

(7) Content of Content Particles A solvent that does not dissolve the particles is selected and the film is dissolved.
The particles are centrifuged, and the ratio (% by weight) to the total weight of the particles is defined as the particle content. In some cases, the combined use of infrared spectroscopy is also effective.

(8) Desolvation Rate After drying for t minutes in the dry process, a part of the gel film peeled off from the belt is cut off and the weight (W ₁ ) is measured. This film was washed in a water bath for 10 minutes and then heat-treated at 280 ° C.
From the weight (W ₂ ), the polymer concentration (P ₁ ) in the gel film is calculated by the following equation. Desolvation rate, P ₁ and film initial concentration P ₀ the following equation from _{P 1 = (W 2 / W} 1) × 100 desolvation rate = (P ₁ -P ₀₎ of the stock solution is calculated by / t.

(9) Thermal Shrinkage At normal temperature, the film is sampled into a strip having a width of 1 cm and a length of 20 cm, and marked lines are drawn at 15 cm intervals in the length direction. Next, the film is heated in a hot air oven set at a predetermined temperature for 5 minutes and then taken out of the oven.
After cooling the film to room temperature, measure the distance between the marked lines,

[0091]

(Equation 1) To determine the heat shrinkage.

(10) Moisture Absorption After the film was completely dried (150 ° C., 2 hours), the relative humidity was 5%.
Cool to room temperature in a desiccator less than and weigh quickly (the weight is W1). Next, after putting in a desiccator at a relative humidity of 75% for 48 hours, the film was taken out and quickly weighed (the weight was W2), and the following formula was used.

[0093]

(Equation 2) Ask by

(11) Frequency of Surface Defects The surface of the support is visually observed with an area of 100 cm 2 or more while being illuminated with a light, and a portion which is considered to be defective is searched for.
The location was observed with a metallographic microscope, and the diameter was 30μ.
The number of objects with m or more is counted and converted into a value per square millimeter.

[0095]

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 abbreviated as NMP) was used as an aromatic diamine component in an amount of 90 mol% of 2-chloroparaphenylenediamine and 10 mol% of 4,4′-diaminodiphenyl. Dissolve ether and
To this, 2-chloroterephthalic acid chloride corresponding to 100 mol% 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 3000 poise.

On the other hand, polyether sulfone (Sumika Excel PES-7300P manufactured by Sumitomo Chemical Co., Ltd .;
Is dissolved in NMP at 10% by weight, and blended with the solution A so that the PES content is 7% by weight based on the total amount of the aromatic polyamide and PES, and mixed well at 50 ° C. for 3 hours. did.

The mixed solution thus obtained was filtered with a filtration accuracy of 50.
After passing through a 00 nm or 1000 nm filter, the frequency of surface defects having a diameter of 30 μm or more is 0.005 / mm ^2.
Was cast at a solution temperature of 60 ° C. during casting. At this time, the support temperature (Tb) at the time of casting was 1
The temperature was 40 ° C., the hot air temperature (Ta) was 170 ° C., and the solvent removal rate was 12.5% / min. The film peeled from the belt was subsequently immersed in a 40 ° C. water bath for 5 minutes,
Drying was performed at 0 ° C. for 30 seconds, and heat treatment was performed using hot air of 250 ° C. at a wind speed of 4 m / sec to obtain an aromatic polyamide-based film having a thickness of 4.3 μm. During film formation, 1.
The film was stretched by a factor of 1 and a ratio of 1.4 in the width direction.

The film had a Ra1 of 1.5 nm and a tensile Young's modulus of 11.6 in each of the longitudinal and width directions.
GPa and 16.7 GPa. This final film is stuck on a frame and heated in a hot air oven at 270 ° C, 300 ° C,
When a heat treatment was performed at 350 ° C. for 1 minute, Ra2 was 1.3 nm, 1.2 nm, and 0.9 nm, respectively.
It was demonstrated that the surface was smoothened by heat treatment after film formation. Ra2 / Ra1 at this time is 0.8, respectively.
7, 0.80 and 0.60.

Comparative Example 1 The solution A used in Example 1 was directly formed into a film in the same manner as in Example 1. Ra1 of this film is 0.8 nm,
The tensile Young's modulus is 11.5 GPa in both the longitudinal and width directions.
Met. On this final film, 27
When heat treatment was performed at 0 ° C., 300 ° C., and 350 ° C. for 1 minute, Ra2 was 0.8 nm, 0.8 nm,
0.7 nm, and the surface could not be roughened by the heat treatment. At this time, Ra2 / Ra1 is 1.
0, 1.0 and 1.0.

[0101]

The roughness variable film of the present invention is a film made of an organic polymer, wherein at least one surface has an average roughness Ra1 before heat treatment and an average roughness Ra2 after heat treatment.
However, since the relationship of Ra2 / Ra1 <1 holds, the surface roughness can be reduced according to the purpose by the heat treatment during the processing. As a result, it is possible to provide a film which is smooth at the time of processing and which is smooth as a product, and the degree of freedom of processing and product design becomes extremely large. The film of the present invention is a magnetic recording medium field, an electric and electronic field,
Although it can be suitably used in any applications such as the packaging field, it can be particularly preferably used in the field of a vapor deposition type magnetic recording medium which requires smoothness in processing and smoothness in products.

Claims (4)

[Claims] 1. A film comprising an organic polymer,
An average roughness Ra1 on at least one side before heat treatment and an average roughness Ra2 after heat treatment satisfy Formula (I). Ra2 / Ra1 <1 (I) 2. The variable roughness film according to claim 1, wherein the Young's modulus in at least one direction is 7 GPa or more. 3. The method according to claim 1, wherein the organic polymer is an aromatic polyamide.
The variable roughness film according to claim 1, wherein the content of the film is not less than mol%. 4. A magnetic recording medium wherein the average roughness Ra2 after heat treatment at 300 ° C. for 1 minute and the average roughness Ra1 before heat treatment satisfy the formula (II), and Ra1 is 0.8 to 15 nm. The variable roughness film according to any one of claims 1 to 3, which is used for applications. 0.2 ≦ Ra2 / Ra1 ≦ 0.90 (II)