JP2002178474A - Polyester film for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film useful as a magnetic recording medium having a magnetic layer of vapor deposition type in particular, in which the surface characteristics of the polyester film consisting of both a polyester having excellent dimensional stability and a polyimide are improved, and dense projections are formed on the surface and thereby electromagnetic conversion characteristics, stability of a vapor deposition process and enhancement of quality are contrived. SOLUTION: The polyester film for the magnetic recording medium has a basic layer part (layer A) comprising a polyester and a polyimide as an essential component. The whole thickness constituted of a film layer of at least two or more layers is 3-8 μm. In the laminated polyester film, projections having 5-25 nm height of a projection exist in a rate of 5-7 million pieces/mm2 on the surface ((f) face) of one hand. Surface roughness Raf on the (f) face side is 0.1-5 nm and the surface roughness Rab of the surface ((b) face) on the opposite side is 5-20 nm. Numbers H1, H2 of rough and large projections on the surface of the film on the (f) face side are in a specified range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film in which the quality of a polyester film, in particular, thermal dimensional stability and surface properties are greatly improved.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are used for various purposes because of their excellent thermal properties, dimensional stability, mechanical properties, and ease of control of surface morphology, and particularly as base films for magnetic tapes and the like. Utility is well known. In recent years, magnetic tapes have been required to have high-density recording in order to reduce the weight, size, and long-time recording of equipment. For high-density recording, it is effective to shorten the recording wavelength and downsize the recording signal.

[0003] With high density recording and downsizing of recording signals,
The form of the magnetic layer has shifted from iron oxide coating type to metal coating type and metal vapor deposition type, especially for applications requiring high-density recording such as digital video tape, and a ferromagnetic metal thin film layer on one surface of the base film. (Hereafter referred to as a vapor deposition layer)
Are widely used. The thickness of the deposited layer is usually 0.04 to
Since the thickness is about 0.5 μm, which is very thin as compared with other types of magnetic layers, the surface of the base film has the surface shape of the magnetic tape as it is. For this reason, the projection height, the number of projections,
It is necessary to control the surface properties of the base film such as surface roughness very precisely.

[0004] Further, when the recording signal is miniaturized, there is a problem that the recording track is likely to be displaced due to heat during running of the magnetic tape and thermal deformation during storage of the tape. In addition, due to the heat generated during the deposition process of forming a magnetic recording medium by providing a ferromagnetic metal thin film layer, the flatness of the film deteriorates and the electromagnetic conversion characteristics decrease due to the generation of oligomers.
Further, since the place where the magnetic recording medium is used is at a high temperature, it is required that the film has a high thermal dimensional stability even under a high temperature environment and that the film does not deteriorate in quality.

[0005] Therefore, at present, the base film for high-density recording, particularly for a vapor deposition type magnetic recording medium, is required to have particularly fine surface morphology control and dimensional stability and quality stability against heat. Needless to say, high productivity is required to supply these products to the market at low cost.

In terms of controlling the surface properties,
Conventionally, a laminated polyester film containing particles for forming surface protrusions (for example, JP-A-7-272249), a method of coating a discontinuous film containing fine particles (for example, JP-A-3-208639), etc. It has been known. However, at present, problems related to the stability of the vapor deposition process, such as generation of “wrinkles” and oligomer precipitation due to heat applied in the vapor deposition process, are left due to the low heat resistance of polyester.

An aramid film (for example, Japanese Patent Application Laid-Open No. H10-114038) is known as a base film which can meet the above-mentioned requirements for heat resistance and dimensional stability. Aramid film is disadvantageous in terms of cost due to its high price, and is disadvantageous in that production efficiency is low because molding by melt extrusion is impossible as in conventional polyethylene terephthalate film. The development of a base film having high productivity is eagerly desired.

On the other hand, as a technique for improving the dimensional stability of a biaxially oriented polyester film having high productivity, as a result of diligent studies, a biaxially oriented polyester film comprising polyethylene terephthalate and polyetherimide (Japanese Patent Laid-Open No. 141475).

However, this highly productive 2
In using an axially oriented polyester film as a base film for a vapor-deposited magnetic recording medium, there is no known method for controlling a preferable surface morphology as a vapor-deposited base film, much less oligomer deposition or a vapor deposition step. At present, no knowledge has been obtained regarding a method for solving the problem of vapor deposition stability such as suppressing the occurrence of "wrinkles". Even when applying the above-mentioned surface control method to the above film, based on the difference in the wetting properties of the polyester and polyimide surfaces and the difference in the affinity of the polymer and the coating solution, the problem of coating unevenness,
Various difficult problems remain, such as deterioration of the lamination state due to the difference in melt viscosity between polyester and polyimide, and no application method is known at present.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to improve the characteristics of a biaxially oriented polyester film composed of polyester and polyimide having high productivity and dimensional stability, and to precisely control the surface morphology such as surface roughness. A biaxially oriented polyester film that is controlled and can produce a high-density magnetic recording tape that exhibits good electromagnetic conversion characteristics when used as a base film for a magnetic recording medium of a vapor deposition type in particular, and is suitable as a base film for a magnetic recording medium. To provide.

[0011]

An object of the present invention is to provide a base layer (A) comprising polyester and polyimide as essential components.
A laminated polyester film having a total thickness of 3 to 8 μm, comprising at least two film layers, and having a protrusion height of 5 nm to one surface (f-plane).
25nm projections 5,000,000 to 70,000,000 pieces / mm ² exist, the surface roughness Ra _F and f surface side of the surface roughness Ra _b, f surface side of the film surface of the surface (b surface) of the opposite large projections Number H
1, H2 can be achieved by forming a polyester film for a magnetic recording medium satisfying the following relationship. 0.1 ≦ Ra _f (nm) ≦ 55 5 ≦ R _ab (nm) ≦ 200 0 ≦ H1 (pieces / 100 cm ² ) ≦ 100 0 ≦ H2 (pieces / 100 cm ² ) ≦ 10 or polyester and polyimide as essential components On one side of the base layer portion (layer A), polyester or polyester and polyimide are essential components, and the average particle size is 0.0
A base film formed by laminating a laminated portion (layer B) containing 0.05 to 1.5% by weight of inert particles of 5 to 1 μm, and provided on at least the surface of the base film opposite to the layer B; In addition, inert particles having an average particle size of 7 to 25 nm
000 becomes because thousands / mm ² and the water-soluble slipperiness smooth layer containing a polymer and (C layer), by the entire film thickness and a polyester film for a magnetic recording medium is 3 to 8 [mu] m, or polyester and polyimide On one side of a base layer portion (layer A) comprising, as an essential component, polyester or a polyester and a polyimide as an essential component, containing 0.05 to 1.5% by weight of inert particles having an average particle size of 0.05 to 1 μm. (Layer B) is laminated, and on the side opposite to the layer B, a laminated part containing polyester or polyester and polyimide as an essential component and containing 0.1 to 3% by weight of inert particles having an average particle size of 10 to 50 nm ( D layer), a polyester film for a magnetic recording medium having a laminated structure of at least three layers of D layer / A layer / B layer and having a total film thickness of 3 to 8 μm. It can also be achieved by the.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The film of the present invention is a laminated polyester film having at least two or more film layers in which a laminated portion (referred to as layer B) is laminated on at least one of a base layer portion (referred to as layer A). . If the film consists of only one layer, the characteristics of the present invention cannot be satisfied. When used for a magnetic recording medium, the A layer is generally the thickest layer in the film, and mainly has strength,
This layer functions to maintain dimensional stability. further,
Generally, it is also the layer that has the greatest effect on film forming properties. The layer B, which is a laminated portion, is a layer having a smaller thickness of the film layer than the layer A, and mainly serves to obtain a tape running property and running durability when used as a magnetic tape, and has a relatively rough surface. By doing so, it is also possible to obtain good running performance.

In the laminated polyester film of the present invention, it is necessary that at least the layer A constituting the laminated polyester film is biaxially oriented. If all the layers are non-oriented or uniaxially oriented, the properties of the present invention cannot be satisfied.

The layer A of the present invention contains a polymer alloy containing polyester and polyimide as essential components. The polymer alloy referred to here is a multi-component polymer, and may be a block copolymer obtained by copolymerization or a polymer blend obtained by mixing. However, this excludes the case where a commercially available particle is externally added. The term "becomes an essential component" as used herein means that the component occupies 80% by weight or more of the whole. For example, in the above case, the total amount of the polyester and the polyimide occupies 80% by weight of the A layer. That means.

The polyester used in the present invention is a polymer containing at least 70% by weight of a polyester unit composed of an acid component such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol component.

As the acid component, terephthalic acid, 2,6-
Naphthalenedicarboxylic acid is particularly preferred. These acid components may be used alone or in combination of two or more.

Particularly preferred examples of the diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and diethylene glycol. These diol components may be used alone or in combination of two or more.

The polyester used in the present invention includes polyethylene terephthalate (PET) and poly (ethylene-2,6-naphthalenedicarboxylate) (PE
N) is particularly preferred, and polyethylene terephthalate (PET) is most preferred from the viewpoint of melt moldability and biaxial stretchability (film forming property).

Polyesters include polyfunctional compounds such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol and 2,4-dioxybenzoic acid; monofunctional compounds such as lauryl alcohol and phenyl isocyanate; An aromatic hydroxycarboxylic acid such as benzoic acid, m-hydroxybenzoic acid, or 2,6-hydroxynaphthoic acid, or p-aminophenol or p-aminobenzoic acid is used in an amount that does not impair the effects of the present invention. Further, they may be copolymerized.

The polyimide of another polymer used in the present invention is not particularly limited as long as it has a good affinity for polyester and is melt-moldable. For example, it contains a structural unit represented by the following general formula. Are preferred.
Here, having good affinity (compatibility) means that, for example, an unstretched or biaxially stretched film is prepared using a polymer alloy composed of polymer 1 and polymer 2, and the cross section of the film is formed by a transmission electron microscope. When observed at a magnification of 30,000 to 500,000 times with a microscope, it means that a structure having a diameter of 200 nm or more (for example, a polymer domain with poor dispersion) not caused by additives such as externally added particles is not observed. However, the method for determining the affinity between the polymer 1 and the polymer 2 is not particularly limited to this, and if necessary, a single glass transition point is observed by a temperature-modulated DSC (MDSC). Thus, it may be determined that there is good affinity.

[0021]

Embedded image However, R ₁ in the formula is

[0022]

Embedded image

[0023]

Embedded image Represents one or more groups selected from aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups, and R _{2 in} the formula is

[0024]

Embedded image And one or more groups selected from aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups.

Such a polyimide comprises a tetracarboxylic acid and / or an acid anhydride thereof, an aliphatic primary monoamine,
It can be obtained by dehydrating and condensing one or more compounds selected from the group consisting of aromatic primary monoamines, aliphatic primary diamines and aromatic primary diamines.

From the viewpoints of melt moldability with polyester, handleability, and formation of surface projections, a polyetherimide containing an ether bond in a polyimide component as represented by the following general formula is particularly preferred.

[0027]

Embedded image (Where R ₃ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, R ₄ is a divalent aromatic residue having 6 to 30 carbon atoms, From the group consisting of alkylene groups having 2 to 20 carbon atoms, cycloalkylene groups having 2 to 20 carbon atoms, and polydiorganosiloxane groups chain-stopped with alkylene groups having 2 to 8 carbon atoms. It is a selected divalent organic group.)

As the above R ₃ and R ₄ , for example, an aromatic residue represented by the following formula group:

Embedded image Can be mentioned.

In the present invention, from the viewpoint of affinity with polyester, cost, melt moldability and the like, 2,2-bis [4-
A polymer having a repeating unit represented by the following formula, which is a condensate of (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylenediamine or p-phenylenediamine is preferred.

[0030]

Embedded image Or

[0031]

Embedded image (N is an integer of 2 or more, preferably an integer of 20 to 50) The polyether imide is "Ultem" (registered trademark).
Available from GE Plastics.

In the polymer alloy constituting the layer A of the present invention, a compatibilizer may be used in combination, if necessary, in order to control the dispersion diameter. In this case, the type of the compatibilizer differs depending on the type of the polymer, but the amount added is 0.01 to 10%.
% By weight is preferred.

In the present invention, the time when the polyimide is added to the polyester is, for example, before the polymerization of the polyester, for example,
It may be added before the esterification reaction or after the polymerization. Before melt extrusion, polyester and polyimide may be mixed and pelletized.

As another method for adjusting the polymer alloy constituting the layer A of the present invention to a more preferable dispersed state, for example, a method of mixing using a tandem extruder,
A method of finely dispersing the polyimide using at least one kind of polyester, a method of mixing the polyimide after pulverizing it into a powder with a pulverizer, a method of dissolving both in a solvent and mixing by coprecipitation, one of which was dissolved in the solvent A method of forming a solution and then mixing it with the other may be mentioned, but not limited thereto. Particularly preferably, two or more kinds of polyesters are used. First, a high-molecular-weight polyester and a polyimide are pelletized, and then a high-concentration polyimide (for example,
(5 to 65% by weight, more preferably 40 to 60% by weight) is prepared, and then a method of adjusting to a predetermined concentration by diluting with a relatively low molecular weight polyester before melt extrusion is used. In some cases, the dispersibility of the polymers is improved, and the polymer alloy of the present invention may show a more preferable dispersion state. In addition, in this method, the melt viscosity of the entire polymer alloy is suppressed to be low, so that the melt moldability is improved and the productivity is preferably improved, which is preferable.

The polymer species used for the film layers other than the layer A of the present invention is not particularly limited, but the same polyester as that used for the layer A or the same polymer alloy composed of the same polyester and polyimide as the one used for the layer A is used. If so, the difference in melt viscosity between the base layer and the laminate is unlikely to occur,
This is preferable because troubles in the production process such as lamination unevenness and die streaks hardly occur. Most preferably, a polymer alloy containing the same polyester and polyimide as those used for the layer A in the same weight ratio as the layer A is preferably used.

It is preferable that the layer A of the laminated polyester film of the present invention does not substantially contain inert particles, since the formation of coarse projections due to aggregation of the particles in the layer A and the problem of filter clogging are reduced. Here, "substantially does not contain inert particles" means that the inert particles in the layer A are not contained at all, or even if they are contained, the average particle diameter is smaller than 10 nm, or It means that the content of the active particles is less than 0.001% by weight.

However, the layer A of the laminated polyester film of the present invention is not particularly limited, but when used as a magnetic recording medium, the running durability of the magnetic tape and the running performance with the magnetic head are improved, or In order to improve handling properties such as winding property, inert particles may be contained. In the present invention, the term “inert particles” refers to an average particle diameter of 10 nm or more.
Inorganic or organic particles having a particle size of about 1 μm which do not cause a chemical reaction in the polymer of the present invention or have an adverse effect on magnetic recording due to electromagnetic influence. As inert particles, titanium oxide, calcium carbonate, kaolin, talc,
Inorganic particles such as wet or dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina and zirconia, organic particles containing acrylic acid, styrene, silicone, imide, etc., and catalysts added during the polyester polymerization reaction, etc. Particles (so-called internal particles) and surfactants.

When the layer A of the laminated polyester film of the present invention contains inert particles, the average particle size is 0.001.
To 0.5 μm, more preferably 0.01 to
0.3 μm. Average particle size of inert particles is 0.5 μm
If larger, when used as a magnetic recording medium,
The electromagnetic conversion characteristics may be deteriorated or the magnetic head may be easily damaged. Mean particle size of inert particles is 0.001μ
When the particle size is smaller than m, particle aggregation is likely to occur, and it is difficult to disperse the particles satisfactorily in the polymer.

When the inert particles are contained in the layer A of the laminated polyester film of the present invention, the content is 0.01 to 1
% By weight, more preferably 0.02 to 0.05
% By weight. When the content of the inert particles is more than 1% by weight, the projections become coarse due to the aggregation of the particles, and the electromagnetic conversion characteristics may be deteriorated or the projections may be easily chipped. When the content of the inert particles is less than 0.01% by weight, the effect of improving the runnability with the magnetic head is small, which is not preferable.

The layer B of the laminated polyester film of the present invention contains inert particles for the purpose of improving handleability during film formation and processing, and imparting running properties and running durability when used as a magnetic recording medium. In this case, as the inert particles contained in the layer B, the above-mentioned inert particles can be used. The inert particles may be used alone or in combination of two or more. Average particle size d of inert particles in layer B
Is preferably 0.05 to 1 μm, more preferably 0.1 to 1 μm.
1 to 0.5 μm. When the average particle size exceeds 1 μm, when the film is stored in a wound state, the projections are transferred to the smooth magnetic surface side (f-side), and the f-side is roughened to improve the electromagnetic conversion characteristics. May lower. On the other hand, if the average particle size is smaller than 0.05 μm, sufficient effects may not be exerted on handling properties and running properties of the magnetic tape. The content of the inert particles in the layer B is 0.05 to 1.5.
% By weight, preferably 0.1 to 1% by weight. When the content of the inert particles exceeds 1% by weight, the cooling efficiency in the vapor deposition processing step is reduced, which may cause "wrinkles" or oligomer precipitation, or may lower the electromagnetic conversion characteristics due to transfer. .

It is preferable that the thickness of the layer B of the laminated polyester film of the present invention is not more than 20% of the total thickness of the film, since good film forming properties can be obtained. The thickness of the layer B is more preferably 15% or less, and particularly preferably 10% or less, of the thickness of the entire film. The thickness is 0.01 to 1.5 μm
Is preferable because the film-forming property is further improved. Preferably 0.03 to 1 μm, more preferably 0.05 to
0.75 μm. The thickness t of the layer B is preferably 0.1 to 10 times, more preferably 0.2 to 5 times the average particle size d of the inert particles. When t / d is smaller than 0.1, the inert particles may easily fall off.
When the ratio exceeds, the protrusion heights on the layer B side are not uniform, so that sufficient effects may not be exerted on running properties and handling properties.

The laminated polyester film of the present invention comprises A
At least B of the base film having a two-layer laminated structure of layer / layer B
A film structure in which a smooth and smooth layer (C layer) is provided on the surface opposite to the layer, or a laminate comprising polyester or polyester and polyimide and inactive particles as essential components on the side of layer B opposite to layer A D provided with a portion (D layer)
A three-layer structure of layer / layer A / layer B is preferable because the effects of the present invention can be sufficiently exhibited, but is not limited thereto.

When the laminated polyester film of the present invention is provided with a smooth and smooth layer (C layer), the C layer is formed by coating. The C layer is not particularly limited, but is preferably formed from a main component comprising a water-soluble polymer and inert particles. The C layer has a running property with the magnetic head,
From the viewpoint of running durability, it must be provided at least on the surface opposite to the layer B. The provision of the C layer is preferable because a low molecular weight substance precipitated on the surface from within the film can be effectively suppressed in the tape storage step or the vapor deposition processing step. In addition, although not particularly limited, from the viewpoint of the step of processing into a magnetic tape and the prevention of oligomer precipitation during storage, the C layer / A layer having a smooth and smooth layer (C ′ layer) also provided on the surface on the B layer side. A configuration of / B layer / C 'layer may be adopted. However, in this case, the production efficiency is lower than when the C ′ layer is not provided.

When the layer C is provided on the laminated polyester film of the present invention, the water-soluble polymer constituting the layer C includes:
It has a polar group such as a hydroxyl group, an ether group, an ester group, a sulfone group, an amide group, a methoxy group, or a hydroxypropoxy group, and has a molecular weight of 10,000 to 2,000,000, preferably 100,000 to 1
One million can be used, and specific examples include polyhydric carboxylic acids such as polyvinyl alcohol, gum tragacanth, gum arabic, casein, gelatin, methylcellulose, hydroxyethylcellulose, terephthalic acid, isophthalic acid, trimellitic acid and ethylene. A water-soluble polyester made of glycol or the like, a water-soluble polyester ether copolymer, or the like can be used, and a blend of these can also be used. Among them, a blend of methylcellulose and a water-soluble polyester is particularly preferably exemplified from the viewpoint of wettability with the layer A.

When the layer C is provided on the laminated polyester film of the present invention, examples of the kind of the inert particles constituting the layer C include the particles described above. Among them, acrylic acid, styrene, silicone, imide In the case of organic particles having a component such as an acrylic acid or an imide, it is considered that the affinity between the polyester and the layer A containing polyimide as a main component is high. Less coating spots, film formation,
It is preferable because dropping of particles and damage to the surface in the processing step are significantly reduced.

When the layer C is provided on the laminated polyester film of the present invention, the average particle diameter d of the inert particles constituting the layer C is as follows.
_c is preferably from 5 to 50 nm, more preferably from 6 to 25.
nm, most preferably 7-20 nm. The layer C has a mean particle size of 5 since it is a layer formed by coating.
When the thickness exceeds 0 nm, particles may be remarkably easily dropped in the film forming and processing steps. The average particle size is 5 nm.
If the particle size is smaller, the inert particles tend to agglomerate when preparing the coating liquid, which may cause coarse projections or fall off during the film forming and processing steps.

When the layer C is provided on the laminated polyester film of the present invention, the content of the inert particles constituting the layer C is 3
It is from 100,000 to 70,000,000 pieces / mm ² . Note that the particle content of the C layer is represented by the number per area because the C layer is extremely thin with respect to the average particle diameter of the particles. This is for exposing to the surface layer. When the content is expressed as a ratio with the water-soluble polymer, 100 parts by weight of the water-soluble polymer (when the silane coupling agent or the titanium coupling agent is contained in the C layer, the water-soluble polymer and the coupling agent 5 to 50 parts by weight, more preferably 10 to 50 parts by weight,
４０40 parts by weight. When the content of the particles is within this range, the particles do not fall off the C layer, and the electromagnetic conversion characteristics are improved.

When the layer C is provided on the laminated polyester film of the present invention, the coating thickness of the layer C is not particularly limited, but is preferably 1 nm to 50 nm, more preferably 5 nm.
It is effective for obtaining the film of the present invention to be in the range of nm to 25 nm. When the thickness of the C layer is smaller than 1 nm, the amount of coating per unit area during coating becomes very small, so that stable coating becomes difficult and 50 nm.
If it is larger, drying of the coating liquid in-line becomes insufficient, or the layer C is cracked at the time of stretching and tends to peel off.

The laminated polyester film of the present invention has a D
When a three-layer laminate of layer / layer A / layer B is used, the polymer used for layer D is the same polyester as the polyester forming layer A, or the same polyester as the polymer alloy forming layer A, and the polymer composed of polyimide. Alloys are preferable because problems in the film forming process such as stacking spots and die streaks can be easily suppressed. Above all, when using only polyester for the D layer, use a polyester having a higher molecular weight than the polyester for forming the A layer.When using a polymer alloy composed of polyester and polyimide, polyester for forming the A layer, It is a particularly preferable method to use a material having the same molecular weight as the polyimide and to make the content of the polyimide equal, in order to reduce problems in film formation.

When the polyester used in the D layer of the laminated polyester film of the present invention is a polyester containing ethylene terephthalate as a main component, the polyester may be either a direct-weight method or a DMT method. It is preferable to use calcium acetate as the transesterification catalyst. In the polymerization step, although not particularly limited, it is preferable to use a germanium compound as a polymerization catalyst in order to reduce coarse projections due to foreign matters. As the germanium catalyst, as is known, (1)
Amorphous germanium oxide, (2) crystalline germanium oxide of 5 μm or less, (3) a solution of germanium oxide dissolved in glycol in the presence of an alkali metal or an alkaline earth metal or a compound thereof, and (4) germanium oxide Is dissolved in water, glycol is added thereto, and water is distilled off. A glycol solution of germanium oxide or the like is used.

The laminated polyester film of the present invention has a D
When a three-layer structure of layer / layer A / layer B is used, examples of the type of inert particles contained in layer D include the particles described above. Among them, preferred are organic particles containing colloidal silica, finely dispersed alumina, styrene, silicone, imide and the like as constituent components.

When the laminated polyester film of the present invention is a three-layer laminate of D layer / A layer / B layer, the average particle diameter d _D of the inert particles contained in the D layer is preferably from 10 to 50 nm, more preferably. Is 15 to 50 nm, most preferably 2
0 to 40 nm. If the average particle size exceeds 50 nm, the magnetic tape having a vapor-deposited magnetic layer has coarse protrusions on the magnetic surface side, which deteriorates electromagnetic conversion characteristics and damages the magnetic head, resulting in poor running durability. It may lead to a decrease. If the average particle size is smaller than 20 nm, the protrusion height on the magnetic surface side is low, so that the friction with the magnetic head becomes too high, so that the runnability of the head is deteriorated, and the film is rolled during film formation and processing. It may be easily scratched due to friction with.

When the laminated polyester film of the present invention is formed into a three-layer laminate of layer D / layer A / layer B, the content of inert particles contained in layer D is preferably 0.1 to 3% by weight, more preferably. Is from 0.3 to 1.5% by weight, most preferably from 0.5 to 1% by weight. When the content is more than 3% by weight, particles are aggregated in the melt molding step, and the projections become coarse, so that the electromagnetic conversion characteristics are reduced or the projections are easily shaved. When the content is less than 0.1% by weight, the magnetic surface becomes too flat, the running property of the head is deteriorated, and the film is easily damaged due to friction with a roll during film formation and processing. .

When the laminated polyester film of the present invention has a three-layer structure of D layer / A layer / B layer, the thickness t _{D of the} D layer is preferably 0.01 μm to 0.8 μm, more preferably 0.03 μm to 0.8 μm. 0.5 μm, more preferably 0.05
０．１0.1 μm. When the thickness of the D layer is less than 0.01 μm, the particles of the D layer are liable to fall off, which may cause deterioration of running durability, and when the thickness is more than 0.5 μm, the height of the projections Are not uniform, which may lead to a decrease in the running performance of the head. Further, when the D layer thickness t _D is preferably 0.1 to 10 times the average particle diameter d _D , and more preferably 0.5 to 5 times, both the electromagnetic conversion characteristics and the head running property are improved.

In the case where the laminated polyester film of the present invention is formed into a three-layer laminate of D layer / A layer / B layer, there is no particular limitation, but wax or surfactant such as fatty acid ester is contained in each film layer. In this case, the low molecular weight substance precipitated on the surface from within the film can be effectively suppressed, which is preferable. More preferably, when the B layer and the D layer are contained at a relatively high concentration and the A layer is contained at a low concentration or substantially not contained, there is little concern that the elastic modulus is lowered. Examples of the wax include natural waxes such as carnauba wax, and fatty acid esters such as stearyl stearate and behenyl behenate. Carnauba wax is particularly preferred. Examples of the surfactant include alkali metal salts or alkaline earth metal salts of alkylsulfonic acids such as sodium undecylsulfonate and potassium dodecylsulfonate, and alkylbenzenesulfonic acids such as sodium dodecylbenzenesulfonate and lithium dodecylbenzenesulfonate. Examples thereof include alkali metal salts and alkaline earth metal salts, and particularly preferred is sodium dodecylbenzenesulfonate. The content is 0.1 to
2% by weight is preferred, and more preferably 0.2 to 0.8%.
% By weight.

[0056] The surface roughness Ra _b of the surface (b surface) of the B layer side of the laminated polyester film of the present invention is 5 to 20 nm, preferably 6～17Nm, more preferably 7 to 1
5 nm. If ra _b is 5nm less than sufficient handling property is not productive yield is lowered in the film and processing steps, running properties and wear resistance when processed into a magnetic tape is reduced, sufficient It is not preferable because no excellent magnetic tape characteristics can be obtained. If ra _b is greater than 20nm is when used as a magnetic tape, the form of the running surface side is transferred to the magnetic surface, or exacerbate electromagnetic characteristics, the particles of the running surface side tends to fall off, running It is not preferable because it causes deterioration of characteristics and dropout.
Further, in the case of a magnetic tape having a vapor-deposited magnetic layer, the cooling efficiency in the vapor-deposition step is reduced, which may cause heat loss such as "wrinkles" or easily cause oligomer precipitation.

[0057] The surface roughness Ra _f of the surface (f surface) of the B layer and the opposite side of the laminated polyester film of the present invention is 0.1 to 5
nm, preferably 1-4 nm, more preferably 1.5-3 nm. When R _ab is smaller than 0.1 nm, it may be difficult to manufacture industrially, or the running property with a magnetic head when processed into a magnetic tape may be reduced, and sufficient magnetic tape characteristics may not be obtained. . Ra _f is 5nm
If it is larger than that, it is not preferable because when used as a magnetic tape having a vapor-deposited magnetic layer, the electromagnetic conversion characteristics are lowered and the magnetic head is easily damaged.

[0058] coarse protrusions number H1 of f surface of the laminated polyester film of the present invention, the electromagnetic conversion characteristics, in view of running durability, and 100 or / 100 cm ² or less, preferably 50/100 cm ² or less, more preferably Is 10 pieces / 1
00 cm ² or less. Similarly, the number H2 of the coarse projections is 10/100 cm ² or less, preferably 5 / 100c.
m ² or less, more preferably 2 pieces / 100 cm ² or less. If the number H1 of the coarse projections exceeds 100/100 cm ² , the electromagnetic conversion characteristics deteriorate, which is not preferable. If the number H2 exceeds 10/100 cm ² , the magnetic head is easily damaged and the running durability deteriorates. . In the present invention, H1 and H2 representing the number of coarse protrusions on the f-plane are values defined by a measurement method described later.

The polyimide content in the layer A of the laminated polyester film of the present invention is 5 to 3 in the polymer alloy.
It is preferably in the range of 0% by weight. More preferably, it is 8 to 15% by weight. Generally, since the melt viscosities of polyester and polyimide are largely different, if the content of polyimide is less than 5% by weight, it may be difficult to sufficiently finely disperse in an extruder, and the domain of polyimide may be coarse. In some cases, the surface protrusions become coarse. Further, if the content of the polyimide is more than 30% by weight, it becomes difficult to perform extrusion molding and stretching, which may cause troubles in film formation and processing such as film breakage and die streaks at the time of extrusion. May be.

The laminated polyester film of the present invention may contain a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment, a dye within a range not to impair the effects of the present invention.
Organic lubricants such as fatty acid esters and waxes may be added.

The sum of the Young's modulus in the longitudinal direction and the Young's modulus in the width direction of the laminated polyester film of the present invention is 9 to 20 G
Pa, more preferably 10 Pa
１８18 GPa, more preferably 11-15 GPa. If the sum of the Young's modulus is less than 9 GPa, for example,
When used for magnetic recording media and the like, the tension received from the magnetic recording head and guide pins during running causes the magnetic tape to easily elongate and deform, and further adversely affects the electromagnetic conversion characteristics (output characteristics). It may not be practically usable. Further, a film having a Young's modulus exceeding 20 GPa may be industrially difficult to produce, or the tear resistance and dimensional stability of the film may be significantly reduced.

The longitudinal Young's modulus of the laminated polyester film of the present invention is preferably 4.3 GPa or more from the viewpoint of contact with the magnetic head. It is more preferably at least 4.5 GPa, most preferably at least 5 GPa.

The Young's modulus in the width direction of the laminated polyester film of the present invention is preferably 4.7 GPa or more from the viewpoint of suppressing tape edge damage and longitudinal elongation. It is more preferably at least 5 GPa, most preferably at least 5.5 GPa.

The heat shrinkage of the laminated polyester film of the present invention in the longitudinal direction at a temperature of 100 ° C. for 30 minutes is preferably 1.2% or less from the viewpoints of elongation deformability and storage stability of the tape. More preferably, it is 1% or less. If the heat shrinkage exceeds 1.2%, dimensional stability may be easily impaired. For example, in the case of a magnetic recording medium, thermal deformation of the tape due to heat history in a film processing step such as coating a magnetic layer of a base film or frictional heat between a magnetic tape and a magnetic recording head during traveling increases the temperature of the magnetic tape. This may easily occur, the durability of the film surface may be deteriorated, or the storage stability of the tape may be deteriorated.

The heat shrinkage of the laminated polyester film of the present invention in the longitudinal direction at a temperature of 80 ° C. for 30 minutes is preferably 0.3% or less from the viewpoints of elongation deformability and storage stability of the tape. More preferably, it is 0.25% or less.

The heat shrinkage of the laminated polyester film of the present invention at a temperature in the width direction of 100 ° C. for 30 minutes is preferably 0.5% or less from the viewpoint of elongation and deformation of the tape and storage stability. More preferably, it is 0.3% or less. If the heat shrinkage exceeds 0.5%, dimensional stability may be easily impaired. For example, in the case of a magnetic recording medium, thermal deformation of the tape due to heat history in a film processing step such as coating a magnetic layer of a base film or frictional heat between a magnetic tape and a magnetic recording head during traveling increases the temperature of the magnetic tape. This may easily occur, the durability of the film surface may be deteriorated, or the storage stability of the tape may be deteriorated.

The heat shrinkage of the laminated polyester film of the present invention at a temperature of 80 ° C. in the width direction for 30 minutes is preferably 0.1% or less from the viewpoints of elongation deformability and storage stability of the tape. More preferably, it is 0.05% or less.

The extrapolated glass transition _onset temperature (Tg _onset ) of the polymer of the layer A of the present invention is not particularly limited, but may be from 92 to 92.
The temperature is preferably 150 ° C, more preferably 96 to
130 ° C, more preferably in the range of 98 to 120 ° C. Further, the glass transition temperature (Tg) of the polymer in the A layer
Although it does not specifically limit, It is preferable that it is 105-170 degreeC, More preferably, it is 110-140 degreeC. When Tg _onset and Tg are _below this range, dimensional stability during running of the magnetic tape is reduced, wrinkles due to heat shrinkage are liable to be generated during storage of the tape, and when used as a magnetic recording medium for vapor deposition, "Wrinkles" may occur due to heat shrinkage of the film in the process. Further, when Tg _onset and Tg exceed this range, the temperature required for stretching or the like becomes too high, so that productivity may decrease or durability of equipment such as a stretching roll may decrease.

The intrinsic viscosity of the polymer alloy constituting the layer A of the present invention is from 0.55 to 3.0 (dl / g) from the viewpoint of the stability of the film forming process and the compatibility with the thermoplastic resin.
, And more preferably 0.1.
60 to 2.0 (dl / g). In addition, the intrinsic viscosity of the film after film formation is preferably in the range of 0.50 to 2.0 (dl / g), more preferably from the viewpoints of stability of film forming process and dimensional stability. 0.55
~ 1.0 (dl / g).

The total thickness of the laminated polyester film of the present invention is 3 to 8 μm. Preferably it is 4-7 micrometers, More preferably, it is 4.5-6.5 micrometers. If the thickness is less than 3 μm, the tape will not be rigid,
Electromagnetic conversion characteristics decrease. If the thickness is more than 8 μm, the tape length per one roll of the tape becomes short, which makes it difficult to reduce the size and increase the capacity of the magnetic tape.

In the laminated polyester film of the present invention, another polymer layer, for example, a polyolefin, polyamide, polyvinylidene chloride and acrylic polymer may be laminated directly or via a layer such as an adhesive.

The biaxially stretched film of the present invention may be subjected to any processing such as heat treatment, molding, surface treatment, laminating, coating, printing, embossing, etching and the like, if necessary.

By providing a magnetic layer on at least one side of the laminated polyester film of the present invention, it can be used as a magnetic recording medium. The surface on which the magnetic layer is provided may be either surface of the film or both surfaces. When a film having the above-mentioned laminated structure is used, the magnetic layer is preferably provided on the A layer side.

Preferred examples of the magnetic layer include a magnetic layer formed by dispersing a ferromagnetic metal thin film or a ferromagnetic metal fine powder in a binder, and a magnetic layer formed by coating a metal oxide.
As the metal used for the ferromagnetic metal thin film, iron, cobalt, nickel, an alloy thereof, and the like are preferable. Further, as the ferromagnetic metal fine powder used in the magnetic layer formed by dispersing the ferromagnetic metal fine powder in a binder, a ferromagnetic hexagonal ferrite fine powder, or a powder composed of iron, cobalt, nickel or an alloy thereof. preferable. The binder is preferably a thermoplastic resin, a thermosetting resin, a reactive resin, or a mixture thereof.

The magnetic layer may be formed by kneading the magnetic powder with a binder such as thermosetting, thermoplastic or radiation-curing, and applying and drying the metal powder or a metal or alloy.
By sputtering, ion plating, etc.
Any of dry methods in which a magnetic metal thin film layer is directly formed on a substrate film can be adopted.

In the magnetic recording medium of the present invention, a protective film may be provided on the magnetic layer. The running durability and corrosion resistance can be further improved by this protective film.
Examples of the protective film include oxide protective films such as silica, alumina, titania, zirconia, cobalt oxide, and nickel oxide; nitride protective films such as titanium nitride, silicon nitride, and boron nitride; silicon carbide, chromium carbide, and boron carbide. Examples of the protective film include a carbon protective film made of carbon such as a carbide protective film, graphite, and amorphous carbon.

The carbon protective film is a carbon film made of an amorphous, graphite, diamond structure or a mixture thereof formed by a plasma CVD method, a sputtering method or the like, and is particularly preferably a hard carbon film generally called diamond-like carbon. is there.

For the purpose of further improving the adhesion with the lubricant applied on the hard carbon protective film, the surface of the hard carbon protective film may be subjected to surface treatment with oxidizing or inert gas plasma.

In the present invention, in order to improve the running durability and corrosion resistance of the magnetic recording medium, it is preferable to add a lubricant or a rust inhibitor to the magnetic layer or the protective film.

The application of the laminated polyester film of the present invention is a digital recording type magnetic recording medium which requires a uniform and fine surface morphology and high dimensional stability. Among them, it can be particularly preferably used for a magnetic recording medium having a deposition type magnetic layer. Specifically, it is suitable for base films such as high-density magnetic recording tapes for data storage and digital video tapes.

Hereinafter, an example of the method for producing a laminated polyester film of the present invention will be described, but the present invention is not limited thereto. Here, polyethylene terephthalate was used as the polyester of the layer A polymer, and polyetherimide “Ultem” was used as the polyimide.
An example of a / A / B three-layer laminated polyester film is shown. Further, when the smooth / smooth layer (C layer) is provided on the base film having the A / B two-layer structure, the manufacturing method of the base film is the same as that of the present example except that the D layer portion is not used. I just need. Manufacturing conditions vary depending on the polyester and polyimide used or the lamination configuration.

First, bis-β-hydroxyethyl terephthalate (BHT) is obtained by esterifying terephthalic acid and ethylene glycol or by transesterifying dimethyl terephthalate and ethylene glycol according to a conventional method. Next, while transferring the BHT to the polymerization tank, the polymerization reaction is advanced by heating to 280 ° C. under vacuum. Here, a polyester having an intrinsic viscosity of about 0.5 is obtained. The obtained polyester is formed into pellets, placed under reduced pressure, and subjected to solid phase polymerization. In the case of solid phase polymerization, pelletized polyester is preliminarily crystallized at a temperature of 180 ° C. or less, and then at 190 to 250 ° C. and 1 mmHg.
The solid-phase polymerization is performed under a reduced pressure of about 10 to 50 hours. Also,
When the polyester constituting the film contains inert particles, it is preferable to disperse the inert particles in a predetermined ratio in a form of slurry in ethylene glycol, and to add the ethylene glycol during polymerization. When adding inert particles, for example, if the water sol or alcohol sol obtained at the time of synthesis is added without once drying, the particles have good dispersibility. Further, a method is also effective in which a water slurry of inert particles is directly mixed with polyester pellets and kneaded into the polyester using a vented twin-screw extruder. As a method for adjusting the content of inert particles, a master of high concentration of inert particles is prepared by the above method, and the master is diluted with a polyester substantially containing no inert particles at the time of forming a film to be inert. A method of adjusting the content of particles is effective.

Next, polyethylene terephthalate pellets and polyetherimide pellets were mixed and mixed.
The mixture is supplied to a vent-type twin-screw kneading extruder heated to 0 to 300 ° C. and melt-extruded. The shear rate at this time is 50 ~
300 sec ^-1 is preferable, and more preferably 100 to 2
00 sec ⁻¹ , the residence time is preferably 0.5 to 10 minutes,
More preferably, the condition is 1 to 5 minutes. The mixing ratio is 2
It is preferably from 0 to 80%, more preferably from 40 to 60%. If the mixing ratio of the polyetherimide is too high or too low, the two may not be sufficiently compatible by kneading. Further, when the two are not compatible under the above conditions, the obtained chips may be again introduced into the twin-screw extruder and the extrusion may be repeated until they are compatible.

The obtained polyetherimide-containing polyester pellets, the inert pellet master pellets, and the polyester pellets were mixed at a predetermined ratio and dried in vacuum at 180 ° C. for 3 hours or more. It is supplied to an extruder heated to 280 to 320 ° C. under a nitrogen stream or vacuum so as not to lower the intrinsic viscosity, extruded from a slit die, and cooled on a casting roll to obtain an unstretched film.

At this time, as a method for removing foreign matters, deteriorated polymer, unmelted material, and the like in the polymer, various filters, for example, a filter made of a material such as a sintered metal, a porous ceramic, a sand, a wire mesh, and the like are used. Is preferred. In particular, in the case of the A layer and the three-layer laminated structure, the polymer of the D layer is preferably exemplified by filtering the polymer with a fiber sintered stainless metal filter having a cut of 1.2 μm or less. More preferably, the filter is 0.8 μm or less. Further, if necessary, it is preferable to pass through two or more filter portions and filter in two or more stages, because unmelted matter can be removed more effectively. Most preferably, a method in which a sand filter, a 1.2 μm cut fiber sintered stainless steel metal filter, and a 0.8 μm cut fiber sintered stainless metal filter are used in this order to perform three-stage filtration is used.

The filter having a cut size of 1.2 μm as used herein means a filtration accuracy of 1.2 μm, and the filtration accuracy means the maximum particle size of glass beads transmitted through a filter medium according to the method of JIS-B8356. .

Further, it is preferable to provide a gear pump as needed in order to improve the quantitative supply.

As a method of laminating films, a method of melt-laminating a plurality of different polymers using two or more extruders and a manifold or a merging block is preferable.

Next, this unstretched film is biaxially stretched,
Biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. here,
A sequential biaxial stretching method in which stretching is performed first in the longitudinal direction and then in the width direction is used. The stretching temperature varies depending on the constituent components of the lamination. For example, a three-layer structure in which the A layer, B layer, and D layer are made of a mixed polymer of polyethylene terephthalate and polyetherimide (mixing weight ratio 9: 1) is exemplified. I will explain. The unstretched film is heated by a group of heating rolls at 70 to 130 ° C. and stretched 3 to 8 times in one or more stages in the longitudinal direction (in the case of re-longitudinal stretching, stretching in the first stage is 2 to 8).
(4 times) and then cooled by a cooling roll group at 20 to 50 ° C. The stretching speed in the longitudinal direction is preferably in the range of 1,000 to 50,000% / min. Subsequently, stretching in the width direction is performed. As a stretching method in the width direction, for example, a method using a tenter is generally used. The stretching ratio in the width direction is 3 to 8 times (when performing re-lateral stretching, the first stage stretching is 2 to 4 times), the stretching speed is 1000 to 20000% / min, and the temperature is 80 to 150 ° C. Is preferred. Further, if necessary, re-longitudinal stretching and / or re-lateral stretching are performed. As the stretching conditions in that case, the stretching in the longitudinal direction is preferably a heating roll group at a temperature of 80 to 170 ° C., and the stretching ratio is 1.1 to 2.5 times, and the stretching method in the width direction is preferably a method using a tenter, It is preferable to carry out at a temperature of 80 to 180 ° C. and a stretching ratio of 1.1 to 2.5 times. Subsequently, the stretched film is heat-treated under tension or while relaxing in the width direction. The heat treatment temperature in this case is 200 ° C to 230 ° C, preferably 210 to 220 ° C.
It is preferable that the heating is performed at a temperature in the range of 0.2 to 10 seconds.

When the two-layer laminated film is coated with the slippery smooth layer (layer C), the coating is theoretically performed before the longitudinal stretching, before the width stretching, after the width stretching, in the above-mentioned film production process. Can be coated off-line after film formation, but since the C layer is an ultra-thin layer, it is coated either before or after the above stretching in the width direction, and rolls or the like until the C layer is fixed after coating. It is preferable not to make contact with. Accordingly, for example, before stretching in the width direction in the sequential biaxial stretching in which the stretching in the longitudinal direction is performed and then stretching in the width direction, or before stretching in the simultaneous biaxial stretching,
It is preferred to coat the layer. The coating is industrially preferable, such as so-called in-line coating, which is performed during the continuous film production process. It may be performed in a separate process dedicated to offline.

(Method of Measuring Physical Properties and Method of Evaluating Effect) The method of measuring characteristic values and the method of evaluating effect in the present invention are as follows.

(1) Height and Number of Protrusions on the Surface Using an atomic force microscope (AFM), measurement is performed 10 times at different locations under the following conditions. Apparatus: NanoScope III AFM (manufactured by 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% 2 to 50 nm from flat surface The number of protrusions in the range is measured, and the average thereof is converted to the number per 1 mm ² .

(2) Surface Roughness Ra The center line average roughness Ra was measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was an average value obtained by scanning 20 times in the film width direction and performing measurement.・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cutoff value: 0.08 mm

(3) Average Particle Size of Inert Particles The cross section of the film was measured using a transmission electron microscope (TEM) for 1
Observe at a magnification of 10,000 times or more. TEM section thickness is about 10
Measure to 100 nm or more at different locations. The weight average of the measured equivalent circle diameters was defined as the average particle diameter d of the inert particles. When two or more types of particles having different particle sizes are present in the film, the number distribution of the equivalent circle equivalent diameter becomes a distribution having two or more types of peaks, and the average particle size is calculated separately for each of them. I do.

(4) Content of Inactive Particles in Polyester, Polyimide, and Film Layer The polyester and polyimide are dissolved in a suitable solvent to dissolve both, and the ¹ H nucleus NMR (nuclear magnetic resonance) spectrum is measured. . Suitable solvents will vary with the type of polymer, but for example, hexafluoroisopropanol (H
FIP) / deuterated chloroform is used. In the obtained spectrum, the peak area intensity of absorption specific to polyester and polyimide (for example, absorption of aromatic protons of terephthalic acid for PET, absorption of aromatic protons of bisphenol A for PEI) is determined. The molar ratio between polyester and polyimide is calculated from the ratio and the number of protons. Further, the weight ratio is calculated from the formula weight corresponding to the unit unit of each polymer. The measurement conditions are, for example,
The conditions are as follows, but are not limited because they vary depending on the type of polymer.

Apparatus: BRUKER DRX-500 (Bruker) Solvent: HFIP / chloroform Observation frequency: 499.8 MHz Reference: TMS (tetramethylsilane) (0 pp
m) Measurement temperature: 30 ° C Observation width: 10 KHz Data point: 64 K acquisiton time: 4.952 seconds pulse delay time: 3.048 seconds Number of integrations: 256 times If necessary, the microscopic FT-IR method (Fourier transform) (Microscopic infrared spectroscopy). In that case, it is determined from the ratio of the peak due to the carbonyl group of the polyester to the peak due to other substances. In addition,
In order to convert the peak height ratio into a weight ratio, a calibration curve is prepared in advance using a sample whose weight ratio is known, and the polyester ratio with respect to the total amount of the polyester and other substances is determined. The PEI ratio is determined from this and the inert particle content. Further, an X-ray microanalyzer may be used together if necessary.

Regarding the content of the inert particles, a solvent which dissolves the polyester and the polyimide but does not dissolve the inert particles is selected, the polyester and the polyimide are dissolved, and the inert particles are centrifuged to obtain a weight percentage. I asked.

(5) Content of Inactive Particles in the Smooth and Smooth Layer (C Layer) The film surface on the C layer side was scanned at a magnification of about 30,000 times using a scanning electron microscope (SEM). Was observed by observing 10 visual fields or more, and the number of protrusions that looked like protrusions was determined by determining the number of protrusions per 1 mm ² .

(6) Lamination Thickness Using a transmission electron microscope (H-600 manufactured by Hitachi) at an accelerating voltage of 100 kV, the cross section of the film was subjected to an ultra-thin section method (R
uO ₄ staining). From the observation result of the interface, the thickness of each layer is determined. As the magnification, an appropriate magnification is selected according to the thickness of the laminated layer to be determined, but 10,000 to 100,000 times is appropriate.

Further, a secondary ion mass spectrometer (SIM)
It can also be measured using S). 30 from the surface
The concentration of the element originating from the particles having the highest concentration among the inert particles in the film in the range of 00 nm (or polyimide when the polyimide content is different between the laminated portion and the base layer portion) and the carbon element concentration of the polyester The ratio (M ⁺ / C ⁺ )
Analysis is performed by SIMS in the thickness direction from the surface to a depth of 3000 nm. In the surface layer, the element concentration due to the inert particles is low, and the element concentration due to the inert particles increases as the distance from the surface increases. In the case of the film of the present invention, the concentration of the element caused by the inert particles which has once reached a maximum value starts to decrease again. In this concentration distribution curve, the depth at which the element concentration caused by the inactive particles is reduced to の of the maximum value is defined as the lamination thickness. The conditions are as follows.

I) Measuring device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany ii) Measurement conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12 KV Primary ion current: 200 nA raster Area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 5.0 × 10 ⁻⁹ Torr E-GUN: 0.5 KV-3.0 A Inactive particles contained most in the range from the surface layer to a depth of 3000 nm Is organic polymer particles, it is difficult to measure by SIMS.
(X-ray photoelectron spectroscopy), IR (infrared spectroscopy) and the like can be used to measure the same depth profile as above to determine the lamination thickness.

(7) Young's modulus Measured using an Instron type tensile tester according to the method specified in ASTM-D882. The measurement was performed under the following conditions. Measuring device: Orientec Co., Ltd. automatic film strength and elongation measuring device "Tensilon" AMF / RTA-100 Sample size: width 10 mm x test length 100 mm, pulling speed: 200 mm / min Measurement environment: temperature 23 ° C, humidity 65 % RH

(8) Number of Coarse Protrusions H1 and H2 ^Two measurement surfaces (100 cm ² ) were superposed on each other and brought into close contact with each other by electrostatic force (applied voltage of 5.4 kv). The height of the coarse projections was determined from the Newton's ring generated by the interference, and the number of coarse projections of a single ring or more was H1, and the number of coarse projections of a double ring or more was H2. The light source used was a halogen lamp with a 564 nm band-pass filter.

(9) Heat Shrinkage (Dimensional Stability During Processing and Storage) Measured according to JIS C2318. Sample size: width 10 mm, mark line interval 200 mm Measurement conditions: temperature 100 ° C., processing time 30 minutes, no load state The heat shrinkage was determined by the following formula. Heat shrinkage (%) = [(L ₀ −L) / L ₀ ] × 100 L ₀ : Marking line interval before heat treatment L: Marking line interval after heat treatment As a result, the heat shrinkage in the longitudinal direction is 1 % Or less, and the heat shrinkage in the width direction is 0.5% or less, the dimensional stability during processing and storage is good (）), and either one of the longitudinal direction and the width direction When it was out of the range, the dimensional stability during processing and storage was determined to be poor (x).

(10) Electromagnetic conversion characteristics of magnetic tape (S /
N) A cobalt-oxygen thin film having a thickness of 150 nm was formed on the surface of the film of the present invention on the surface opposite to the layer B in the presence of a trace amount of oxygen using a continuous vacuum evaporation apparatus. Next, on the cobalt-oxygen thin film, a diamond-like carbon protective film was formed by a conventional method with a thickness of 10 nm by a sputtering method, and a fluorine-containing fatty acid ester-based lubricant was applied with a thickness of 3 nm. Subsequently, a back coat layer made of carbon black, polyurethane, or silicone was provided on the surface on the layer B side with a thickness of 500 nm, and a width of 6.3 was set with a slitter.
The magnetic recording tape (DVC video tape) was slit into 5 mm and wound on a reel.

In the evaluation of the characteristics of the magnetic recording tape, a video S / N ratio was obtained by using a commercially available digital video tape recorder integrated with a camera. For the measurement of the S / N ratio, a signal was supplied from a TV test signal generator, a video noise meter was used to compare and measure a tape made from the film of Comparative Example 1 as 0 decibel (dB), and the following standard was used. evaluated. . The running conditions were 25 ° C and 60% R.
H.

：: +0.5 dB or more Δ: -0.5 dB or more, less than +0.5 dB ×: less than -0.5 dB Here, ○ is an excellent level for use as a vapor deposition type high density recording magnetic tape. Means that it can be used, and x means that it is at an insufficient level.

(11) Vapor deposition stability The continuous vacuum vapor deposition of the above (10) was carried out on 3,000 m of 10 films of the present invention, and the process stability in the vapor deposition process was evaluated according to the following criteria.

○: The number of films which were broken due to adhesion of oligomers, etc., or "wrinkles" due to shrinkage in the width direction, etc., was two or less.

Δ: With 3 or 4 lines, film breakage due to oligomer attachment or the like, or “wrinkles” due to shrinkage in the width direction or the like occurred.

×: With 5 or more lines, film breakage due to oligomer adhesion or the like, or “wrinkles” due to shrinkage in the width direction or the like occurred.

Here, ○ means that the process stability in the vapor deposition process is excellent, Δ means that it can be used, and ×
Means insufficient level.

(12) Oligomer Suppressing Property The film of the present invention was left in an oven at 150 ° C. for 30 minutes to forcibly deposit a low molecular weight substance on the film surface, and the f-side surface was aluminum-deposited. Observe 25 fields with a total magnification of 1000 times using a differential interference microscope. The size of the low molecular weight substance in each field of view is counted on the surface photograph by counting the number of those having a size of 0.5 mm or more, and the total number is converted into about 1 mm ² ,
Was defined as the number of surface oligomers deposited (pieces / mm ² ).

(13) Intrinsic viscosity Calculated from the following formula based on the solution viscosity measured at 25 ° C. in orthochlorophenol.

Η _sp / C = [η] + K [η] ² · C where η _sp = (solution viscosity / solvent viscosity) −1, C is the weight of the dissolved polymer per 100 ml of solvent (g / 100 m
1, usually 1.2), and K is a Haggins constant (assumed to be 0.343). The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

(14) Extrapolated glass transition onset temperature (Tg)
_onset ), glass transition temperature (Tg) Specific heat measurement was carried out using the following apparatus and conditions, and JIS K71
21.

Apparatus: Temperature modulation DSC manufactured by TA Instrument Measurement conditions: Heating temperature: 270 to 570K (RCS cooling method) Temperature calibration: Melting point of high-purity indium and tin Temperature modulation amplitude: ± 1K Temperature modulation cycle: 60 seconds Temperature rise Step: 5K Sample weight: 5 mg Sample container: Aluminum open container (22 mg) Reference container: Aluminum open container (18 mg) The glass transition temperature was calculated by the following equation.

Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2 (15) Overall evaluation Of the above evaluation items (9), (10) and (11),
The judgment was made based on the following criteria.

：: All characteristics are excellent (レ ベ ル), or two items are excellent (○) and one item is usable (△).

X: There is an insufficient level (x) for any one item, or two items are usable (使用).

Here, ○ means that it is suitable for a magnetic recording medium having a vapor-deposited magnetic layer, and × means that it is not suitable for a magnetic recording medium having a vapor-deposited magnetic layer.

[0122]

Embodiments of the present invention will be described based on the following embodiments.

Example 1 A polyethylene terephthalate (PET) pellet (Tg 80 ° C.) 50 having an intrinsic viscosity of 0.85 and obtained by a conventional method.
% By weight and General Electric (GE)
"Ultem" 1010 with an intrinsic viscosity of 0.68 (Tg
216 ° C.) 50% by weight was supplied to a vented twin-screw extruder of the same direction rotating type heated to 290 ° C.
A blend chip (II) containing 50% by weight of I was prepared.

Next, a film was formed using two extruders. Extruder A heated to 290 ° C. was mixed with 20 parts by weight of the blended chips obtained by the above pelletizing operation and 80 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 and containing substantially no inert particles. The raw material (A1) was supplied after being vacuum-dried at 180 ° C. for 3 hours. The extruder B heated to 295 ° C. was charged with 20 parts by weight of the blend chips obtained by the above pelletizing operation and 60 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 and containing substantially no inert particles. A mixed raw material (B) containing 20 parts by weight of pellets of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.62 containing 2% by weight of crosslinked divinylbenzene particles having a particle size of 0.25 μm
1) was supplied after vacuum drying at 180 ° C. for 3 hours. Subsequently, A1 was filtered in three stages in the order of a sand filter, a 1.2 μm-cut fiber sintered stainless metal filter and a 0.8 μm-cut fiber sintered stainless steel filter, and B1 was a sand filter and a 3 μm-cut fiber sintered. After filtering in two stages in the order of the stainless metal filter, a rectangular merging block (feed block) for two layers
A / B was laminated. The thickness of each layer was adjusted by adjusting the rotation speed of a gear pump installed in each line to control the amount of extrusion. This was wound around a casting drum having a surface temperature of 25 ° C. using an electrostatic application casting method, and cooled and solidified to prepare a two-layer laminated unstretched film (laminate thickness ratio A1 / B1 = 10/1).

This unstretched film was stretched 3.1 times in the longitudinal direction at 110 ° C. by a roll stretching machine. This stretching was performed using the difference in peripheral speed between two sets of rolls. The following aqueous solution was applied on layer A of the uniaxially stretched film.

Methyl cellulose 0.10 parts by weight Water-soluble polyester 0.3% by weight Aminoethylsilane coupling agent 0.01% by weight Carnauba wax 0.2% by weight Acrylic particles having an average particle diameter of 20 nm 0.02% by weight Solid content coating concentration 20 mg / m ² further, by using a tenter and stretched 3.4 times at a temperature 100 ° C. in the width direction. Subsequently, the film was re-stretched 1.55 times at a temperature of 150 ° C. in one step in the longitudinal direction by a roll-type stretching machine, and re-stretched 1.6 times at a temperature of 195 ° C. in the width direction using a tenter. After a heat treatment at 205 ° C. for 8 seconds under a constant length, a 5% relaxation treatment was performed in the width direction to obtain a laminated polyester film having a thickness of about 6.0 μm. The film thickness of each layer was 5.5 μm for the A layer and 0.5 μm for the B layer. The Young's modulus in the longitudinal direction is 5.2 GPa, and the Young's modulus in the width direction is 6.1 GPa.
Met.

As shown in Table 3, this laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Example 2 As shown in Table 1, the polymer of the layer A and the layer B was exactly the same as in Example 1, and the two-layer laminated unstretched film (laminated thickness ratio A / B
= 11/1).

The unstretched film was stretched by the same stretching method, stretching temperature and stretching ratio as in Example 1 to a thickness of about 6
A μm laminated polyester film was obtained. However, the aminoethylsilane coupling agent in the applied aqueous solution was added at 0.1%.
The composition was changed from 01% by weight to 0.15% by weight, and the composition of the inert particles was changed to ultrafine silica (0.03% by weight) having an average particle diameter of 12 nm. The film thickness of each layer is A layer 5.
The thickness was 5 μm and the B layer was 0.5 μm. The Young's modulus in the longitudinal direction was 5.1 GPa, and the Young's modulus in the width direction was 6.2 GPa.

As shown in Table 3, this laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for magnetic recording media.

Example 3 As shown in Table 1, the weight ratio between PET and PEI of the polymer in the layer A and the layer B was changed to 85:15, and the inert particles in the layer B were changed to aluminum silicate having an average particle diameter of 0.18 μm. Particles (0.95
Except that the film thickness was changed to a two-layer laminated unstretched film (laminated thickness ratio A / B = 11).
/ 1).

The unstretched film was stretched 3.05 times in the longitudinal direction at a temperature of 120 ° C. with a roll stretching machine, and the inert particles were changed to ultrafine silica (0.16% by weight) having an average particle size of 18 nm. After applying the same aqueous solution as in Example 1 except that the temperature was set to 105 ° C. in the width direction using a tenter.
It was stretched 4 times. Then, in the longitudinal direction with a roll type stretching machine,
The film was re-stretched 1.7 times at a temperature of 150 ° C. and re-stretched 1.7 times at a temperature of 200 ° C. in the width direction using a tenter. After a heat treatment at a constant temperature of 200 ° C. for 8 seconds, a relaxation treatment of 3% was performed in the width direction to obtain a laminated polyester film having a thickness of about 6 μm. The film thickness of each layer was 5.5 μm for the A layer and 0.5 μm for the B layer. Young's modulus in the longitudinal direction is 5.0 GP
a, the Young's modulus in the width direction was 5.7 GPa.

As shown in Table 3, the laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Example 4 A film was formed using three extruders. As shown in Table 1, A
The polymer composition and the particle content of the layer B and the layer B were exactly the same as those in Example 1. As the polymer of the layer D, 20 parts by weight of a blend chip containing 50% by weight of PEI and an intrinsic viscosity of 0 containing substantially no inert particles were used. 5 parts by weight of polyethylene terephthalate (PET) pellets having an average particle diameter of 25 nm
A mixed raw material containing 75 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 and containing 1% by weight of the above crosslinked divinylbenzene particles was used. In addition, layer B,
Sodium dodecylbenzenesulfonate is added to the D layer in an amount of 0.
3% by weight, and 0.1% by weight in the A layer. Also,
The filtration method of the A and B layer polymers is the same as in Example 1,
The D layer polymer was filtered in three steps in the order of a sand filter, a 1.2 μm cut fiber sintered stainless steel metal filter, and a 0.8 μm cut fiber sintered stainless metal filter. Three-layer laminated unstretched film (laminated thickness ratio D /
A / B = 0.15 / 11/1).

A stretching polyester film having a thickness of about 6.1 μm was obtained in the same manner as in Example 1 except for the stretching method, stretching temperature, stretching ratio and the like of the unstretched film. However, application of the aqueous solution as in Example 1 was not performed. The film thickness of each layer is A layer 5.5 μm, B layer 0.5 μm
m and D layer were 0.075 μm. The Young's modulus in the longitudinal direction was 5.2 GPa, and the Young's modulus in the width direction was 6.1 GPa.

As shown in Table 3, the laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Example 5 As shown in Table 1, the polymer of layer A, layer B and layer D was poly (ethylene-2,6-naphthalenedicarboxylate) (PE
N) and a mixed polymer of PEI (weight ratio 90:10), the inert particles in the D layer were changed to ultrafine silica particles (containing 1.2%) having an average particle diameter of 30 nm, and the inactive particles in the B layer were changed. The particles were changed to aluminum silicate particles having an average particle diameter of 0.18 μm (containing 0.5%), and the temperature of the extruders was changed to 320 ° C. for all three extruders. Stretched film (laminated thickness ratio D / A / B = 0.2 / 10 /
1) was created.

This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 135 ° C. by a roll stretching machine, and further stretched 5.5 times in the width direction at a temperature of 130 ° C. using a tenter. Thereafter, after a heat treatment at a temperature of 240 ° C. for 6 seconds under a constant length, a relaxation treatment of 2% is performed in the width direction to obtain a thickness of about 4.5 μm.
Was obtained. Note that re-longitudinal and re-horizontal stretching were not performed. The film thickness of each layer is A layer 4μ
m and B layer were 0.4 μm and 0.08 μm. The Young's modulus in the longitudinal direction is 7.2 GPa, and the Young's modulus in the width direction is 7.5.
GPa.

As shown in Table 3, this laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Example 6 As shown in Table 1, the polymer of the A layer, the B layer, and the D layer was
Changed to a mixed polymer of EI (weight ratio 80:20),
The crosslinked divinylbenzene particles having an average particle diameter of 0.2 μm (containing 0.2% by weight) are used as the inert particles in the layer, and the ultrafine silica particles (containing 1.5% by weight) are used as the inactive particles in the layer D are 20 nm in average particle diameter. The same procedure as in Example 4 was carried out except that the film thickness was changed to (thickness ratio D / A / B = 0.1 / 15).
/ 1).

The unstretched film was stretched three times in the longitudinal direction at a temperature of 125 ° C. by a roll stretching machine, and further stretched 3.3 times in a width direction at a temperature of 115 ° C. using a tenter. Subsequently, at a temperature of 155 in a longitudinal direction by a roll type stretching machine.
The film was re-stretched 1.8 times at a temperature of 200 ° C. and 1.7 times at 200 ° C. in the width direction using a tenter. 200 temperature under fixed length
After heat treatment at 8 ° C for 8 seconds, a 3% relaxation treatment is performed in the width direction.
A laminated polyester film having a thickness of about 8 μm was obtained. The film thickness of each layer is A layer 7.5 μm, B layer 0.5 μm,
It was 0.05 μm. Young's modulus in the longitudinal direction is 4.9G
Pa and the Young's modulus in the width direction were 5.4 GPa.

As shown in Table 3, the laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Example 7 As shown in Table 1, the polymer of the layer A and the layer B was replaced with PET and PEI.
As in Example 1 except that the inert particles in the layer B were changed to aluminum silicate particles having an average particle diameter of 0.18 μm (containing 0.35% by weight). To a two-layer laminated unstretched film (laminated thickness ratio A / B = 1)
1/1).

The unstretched film was stretched 3.05 times in the longitudinal direction at a temperature of 130 ° C. with a roll-type stretching machine to convert the unstretched film into ultrafine silica having an average particle diameter of 12 nm (0. 035% by weight), after applying the same aqueous solution as in Example 1 except that the aqueous solution was changed to
The film was stretched 3.5 times in the width direction at a temperature of 110 ° C. Subsequently, the film was re-stretched 1.75 times in the longitudinal direction at a temperature of 155 ° C. with a roll-type stretching machine, and re-drawn 1.8 times in a width direction at a temperature of 200 ° C. using a tenter. After a heat treatment at a temperature of 205 ° C. for 8 seconds under constant length, a 2% relaxation treatment in the width direction is performed, and a thickness of about 6 μm
Was obtained. The film thickness of each layer was 5.5 μm for the A layer and 0.5 μm for the B layer. The Young's modulus in the longitudinal direction was 4.8 GPa, and the Young's modulus in the width direction was 5.2 GPa.

As shown in Table 3, this laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for magnetic recording media.

Example 8 As shown in Table 1, the polymer of the layer A was changed to a mixed polymer of PEN and PEI (weight ratio 92: 8), and the polymer of the layers B and C was changed to PEN. Crosslinked divinylbenzene particles having an average particle size of 0.2 μm (containing 0.17% by weight) are used as the inert particles in the layer B, and ultrafine silica particles (containing 0.5% by weight are used as the inert particles in the layer D) having an average particle size of 45 nm. Example 5)
In the same manner as in the above, a three-layer laminated unstretched film (laminated thickness ratio D
/A/B=0.2/7.5/1).

The unstretched film was stretched under the same conditions as in Example 5 to obtain a laminated polyester film having a thickness of 3.5 μm. The film thickness of each layer is A layer 3 μm,
The B layer had a thickness of 0.4 μm or 0.08 μm. The Young's modulus in the longitudinal direction is 7.1 GPa, and the Young's modulus in the width direction is 7.4 GP.
a.

As shown in Table 3, the laminated polyester film had little dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as a base film for a magnetic recording medium.

Comparative Example 1 The A / B two-layer laminated structure was the same as in Example 1 except that PET was used instead of the blend polymer of PET and PEI as the A layer and B layer polymers. Was produced. The temperature of the extruder is 2
The temperature was set at 280 ° C. for both tables.

Next, in the same manner as in Example 1, the unstretched film was rolled in a longitudinal direction at a temperature of 105 ° C. with a roll-type stretching machine.
After stretching 3.1 times at ℃ and applying the same aqueous solution as in Example 1, using a tenter at a temperature of 95 ℃ in the width direction and 3.4.
It was stretched twice. Subsequently, the film was re-stretched 1.55 times in the longitudinal direction at a temperature of 150 ° C. by a roll-type stretching machine, and 1.6 times in the width direction at a temperature of 190 ° C. using a tenter. After a heat treatment at 210 ° C. for 8 seconds under a constant length, a 5% relaxation treatment was performed in the width direction to obtain a laminated polyester film having a thickness of about 6 μm. The film thickness of each layer is 5.5 μm for layer A and 0.
It was 5 μm. Young's modulus in the longitudinal direction is 5.3 GPa,
The Young's modulus in the width direction was 6.7 GPa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 2 The polymer of the layer A was PET, and the polymer of the layer B and layer D was PET /
As PEI (weight ratio 90:10), an unstretched film having a three-layer laminated structure was prepared in exactly the same manner as in Example 1 except for the particle content.

Next, the unstretched film was stretched under the same stretching conditions as in Comparative Example 1 to obtain a laminated polyester film having a thickness of about 6.1 μm. However, application of the aqueous solution was not performed. The film thickness of each layer is as follows:
The layer was 0.5 μm. The Young's modulus in the longitudinal direction is 5.2G
Pa and the Young's modulus in the width direction were 6.5 GPa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 3 As shown in Table 2, the inactive particles in the layer B had an average particle diameter of 1.1 μm.
A laminated polyester film having a thickness of about 6 μm was obtained in the same manner as in Example 1 except that the spherical silica particles (containing 0.1% by weight) were changed. The film thickness of each layer is A
The layer was 5.5 μm and the B layer was 0.5 μm. The Young's modulus in the longitudinal direction is 5.2 GPa, and the Young's modulus in the width direction is 6.1 GPa.
a.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 4 As shown in Table 2, except that the content of inert particles in the aqueous solution to be applied was changed to 0.01% by weight, a laminated polyester having a thickness of about 6 μm was obtained in the same manner as in Example 1. A film was obtained. The film thickness of each layer is 5.5 μm for layer A and 0.
It was 5 μm. The Young's modulus in the longitudinal direction is 5.2 GPa,
The Young's modulus in the width direction was 6.1 GPa.

Comparative Example 5 As shown in Table 2, except that the inert particles in the D layer were spherical silica particles having an average particle diameter of 60 nm (containing 2% by weight), the thickness was reduced in the same manner as in Example 4. A 6.1 μm laminated polyester film was obtained. The film thickness of each layer is A layer 5.
The thickness was 5 μm, the B layer was 0.5 μm, and the D layer was 0.075 μm. The Young's modulus in the longitudinal direction was 5.2 GPa, and the Young's modulus in the width direction was 6.1 GPa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 6 The composition of the layer A was the same as that of the layer B of Example 1 (PET / PEI =
90:10, containing 0.3% by weight of divinylbenzene crosslinked particles having an average particle size of 0.27 μm. ), And a single-layer unstretched film was produced without performing lamination.

The composition of the aqueous solution, the stretching method, the stretching conditions, etc. were exactly the same as in Example 1 to obtain a polyester film having a thickness of about 6 μm. The Young's modulus in the longitudinal direction is 5.2 GPa,
The Young's modulus in the width direction was 6.1 GPa.

Comparative Example 7 As shown in Table 2, the PET / P of the A layer, the B layer, and the D layer
The weight ratio of EI was changed to 60:40, the inert particles in the D layer were changed to ultrafine spherical silica particles having an average particle diameter of 30 nm (containing 3.1% by weight), and the filtration method of the polymer in each layer was set to 3 μm. An unstretched film having a three-layer laminated structure was prepared by changing to a method using only a cut fiber sintered stainless steel metal filter. Under the same stretching conditions as in Example 4,
The re-transverse stretchability was poor, and many tears occurred. For this reason,
The unstretched film is rolled at a temperature of 1
Stretched 3.5 times at 10 ° C., and further using a tenter,
The film was stretched 4.5 times at a temperature of 100 ° C. in the width direction. Thereafter, after a heat treatment at a constant length of 205 ° C. for 7 seconds, a relaxation treatment of 5% was performed in the width direction to obtain a laminated polyester film having a thickness of about 6.1 μm. The film thickness of each layer is A layer 5.5μ.
m, B layer 0.5 μm and D layer 0.075 μm. The Young's modulus in the longitudinal direction was 4.1 GPa, and the Young's modulus in the width direction was 4.9 GPa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 8 As shown in Table 2, a three-layer laminated unstretched film was produced in exactly the same manner as in Example 4.

The unstretched film was stretched 3.5 times in the longitudinal direction at a temperature of 110 ° C. by a roll stretching machine, and further stretched 4.5 times in the width direction at a temperature of 100 ° C. using a tenter. Then, after a heat treatment at a temperature of 205 ° C. for 7 seconds under a constant length, a relaxation treatment of 5% in the width direction is performed to a thickness of about 2.4 μm.
Was obtained. Note that re-longitudinal and re-horizontal stretching were not performed. The Young's modulus in the longitudinal direction is 5.1 GP
a, Young's modulus in the width direction was 5.5 GPa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 9 As shown in Table 2, as the polymer of the layer A, the average particle size was 60 nm.
Using a PET / PEI blend polymer (weight ratio 90:10) containing 0.03% by weight of silica, and containing 0.4% by weight of aluminum silicate particles having an average particle size of 0.25 μm as a layer B polymer. A two-layer laminated unstretched film (laminated thickness ratio A / B = 4/1) was prepared using PET and a well-known technique (3 μm cut fiber sintered stainless steel metal filter, one stage) as the filtration method for layer A. did.

This unstretched film was stretched 3.2 times in the longitudinal direction at 95 ° C. This stretching was performed using the difference in peripheral speed between two sets of rolls. The following aqueous solution was applied on layer A of the uniaxially stretched film.

Methyl cellulose 0.10 parts by weight Water-soluble polyester 0.3% by weight Aminoethylsilane coupling agent 0.01% by weight Ultrafine silica having an average particle diameter of 12 nm 0.03% by weight Solid content concentration 20 mg / m ² The film was stretched 3.4 times in the width direction at 115 ° C. using a tenter. The film was further stretched 1.5 times at 140 ° C. in the longitudinal direction, and then heat-treated at 220 ° C. for 5 seconds under a constant length.
m was obtained. The film thickness of each layer was A layer 4 μm and B layer 1 μm. Young's modulus in the longitudinal direction is 5.3 GPa, Young's modulus in the width direction is 5.4 G
Pa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 10 As shown in Table 2, PET containing substantially no particles was used as the polymer in the A layer, and the polymer having an average particle diameter of 0.1 was used as the polymer in the B layer.
Using PET containing 0.3% by weight of crosslinked divinylbenzene particles of 2 μm, as D-layer polymer, average particle size 30 n
PET / P containing 0.3% by weight of spherical silica particles of m
Using EI blend polymer (weight ratio 90:10), 3
A layer laminated unstretched film was obtained. The filtration method of the D layer is a known method (1.2 μm cut fiber sintered stainless metal filter, one stage), and a two-layer laminated unstretched film (laminated thickness ratio D / A / B = 0.05 / 3. 95/1).

This unstretched film was stretched 3.2 times in the longitudinal direction at 95 ° C. This stretching was performed using the difference in peripheral speed between two sets of rolls. After that, 10
The film was stretched 4.5 times in the width direction at 0 ° C. 1 in the longitudinal direction
The film was stretched 1.5 times at 40 ° C., and then heat-treated at 220 ° C. for 5 seconds under a constant length, and then subjected to a 7% relaxation treatment in the width direction to obtain a laminated polyester film having a thickness of 5 μm. The film thickness of each layer was A layer 3.95 μm, B layer 1 μm, and D layer 0.05 μm. The Young's modulus in the longitudinal direction was 5.5 GPa, and the Young's modulus in the width direction was 5.6 GPa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 11 As shown in Table 2, the inactive particles in the D layer were changed to spherical silica having an average particle diameter of 30 nm (containing 3.1% by weight), and the inactive particles in the B layer were changed to an average particle diameter of 0.1%. A laminated polyester film having a thickness of about 9.9 μm was obtained in exactly the same manner as in Example 4, except that aluminum silicate particles of 18 μm (containing 0.5% by weight) were used. The film thickness of each layer is A layer 9 μm,
The B layer was 0.8 μm and the D layer was 0.1 μm. The Young's modulus in the longitudinal direction is 5.1 GPa, and the Young's modulus in the width direction is 6.2 G
Pa.

As shown in Table 3, this laminated polyester film was inferior as a film for magnetic recording media.

Comparative Example 12 As shown in Table 2, the inert particles in the layer B were changed to ultrafine spherical silica particles (containing 2.5% by weight) having an average particle diameter of 20 nm, and the lamination structure was changed to B / A / B. Three-layer mold (lamination thickness ratio B /
A / B = 1/11/1), except that a laminated polyester film having a thickness of about 6.5 µm was obtained in exactly the same manner as in Example 4. The film thickness of each layer is A layer 5.5μ.
m and B layer were 0.5 μm. The Young's modulus in the longitudinal direction was 5.1 GPa, and the Young's modulus in the width direction was 6.2 GPa.

As shown in Table 3, when this laminated polyester film was used as a magnetic tape, a tape running defect occurred, and it was inferior as a film for a magnetic recording medium.

[0178]

[Table 1]

[0179]

[Table 2]

[0180]

[Table 3]

[0181]

According to the present invention, the height and the number of protrusions and the surface roughness of the surface of a film having good dimensional stability are defined by incorporating a polyimide into a polyester, By defining the average particle size and the particle content of the inert particles to be contained in the polyester film, a polyester film for a magnetic recording medium having both high storage stability and high electromagnetic conversion characteristics can be obtained.

 ──────────────────────────────────────────────────の Continuing on the front page F term (reference) 4F100 AK01C AK41A AK41B AK41C AK42A AK49A AK49B AK49C AL05A AL05B BA03 BA10A BA10C BA16 DD07A DE01B DE01C DE01H GB41 JA20 JA20C JA20H JB09C JK07Y00Y00 JK07Y00Y00 CB08

Claims (12)

[Claims] 1. A laminated polyester film having a base layer (layer A) containing polyester and polyimide as essential components and having at least two or more film layers and a total thickness of 3 to 8 μm. Surface (f-plane)
5 to 25 nm projections with a height of 5 to 25 nm
00,000 pieces / mm ² exist, the surface roughness Ra _f the f surface side of the opposite surface roughness Ra _b of (b plane), the number of coarse protrusions f surface side of the film surface H1, H2 is less than A polyester film for a magnetic recording medium, which satisfies the relationship. 0.1 ≦ Ra _f (nm) ≦ 55 5 ≦ R _ab (nm) ≦ 200 0 ≦ H1 (pieces / 100 cm ² ) ≦ 100 0 ≦ H2 (pieces / 100 cm ² ) ≦ 10 2. On one side of a base layer (A layer) comprising polyester and polyimide as essential components, inactive particles having an average particle size of 0.05 to 1 μm containing polyester or polyester and polyimide as an essential component are added. A base film on which a laminated portion (layer B) containing up to 1.5% by weight is laminated, and an inert particle having an average particle diameter of 7 to 25 nm provided on at least the surface of the base film opposite to the layer B 30 particles
00000-7000 becomes because thousands / mm ² and the water-soluble slipperiness smooth layer containing a polymer and (C layer), the entire film thickness 3~8μ
m, a polyester film for a magnetic recording medium. 3. On one side of a base layer (layer A) containing polyester and polyimide as essential components, inactive particles having an average particle diameter of 0.05 to 1 μm containing polyester or polyester and polyimide as essential components are added. A layered portion (layer B) containing -1.5% by weight is laminated, and on the side opposite to the layer B, polyester or a mixture of polyester and polyimide as an essential component and inert particles having an average particle diameter of 10 to 50 nm is 0.1%. A magnetic layer having a laminated structure of at least three layers of D layer / A layer / B layer in which a laminated portion (D layer) containing 〜3% by weight is laminated, and the total thickness of the film is 3-8 μm. Polyester film for media. 4. On one side of the base layer (layer A), polyester or a mixture of polyester and polyimide as an essential component and inert particles having an average particle size of 0.05 to 1 μm are used.
A base film having a laminated portion (layer B) containing 5% by weight laminated thereon and inactive particles having an average particle diameter of 7 to 25 nm provided on at least the surface of the base film opposite to the layer B are provided. 10,000 to 70,000,000 pieces / mm ² and the water-soluble slipperiness smooth layer containing a polymer magnetic recording medium for a polyester film of claim 1 wherein (C layer) from become a laminated polyester film. 5. On one side of the base layer (layer A), inert particles having an average particle diameter of 0.05 to 1 μm containing polyester or polyester and polyimide as essential components are provided.
A laminated portion (layer B) containing 5% by weight is laminated, and on the side opposite to the layer B, polyester or polyester and polyimide are essential components, and 0.1 to 3% by weight of inert particles having an average particle size of 10 to 50 nm. 2. The polyester film for a magnetic recording medium according to claim 1, wherein the polyester film is a laminated polyester film having a laminated structure of at least three layers of D layer / A layer / B layer in which a laminated portion (D layer) containing 3% is laminated. 6. The polyester film for a magnetic recording medium according to claim 1, wherein the polyimide in the layer A is polyetherimide. 7. The polyester according to claim 1, wherein the polyester in the layer A has an ethylene terephthalate unit as a main component.
The polyester film for a magnetic recording medium according to any one of the above. 8. The polyester film for a magnetic recording medium according to claim 1, wherein the polyimide layer contains 5 to 30% by weight of the polyimide. 9. The sum of the elastic modulus in the film longitudinal direction and the width direction is 9 to 20 GPa, the elastic modulus in the film longitudinal direction is 4.3 GPa or more, and the elastic modulus in the film width direction is 4.7 GPa or more. The polyester film for a magnetic recording medium according to any one of claims 1 to 8, wherein 10. A magnetic recording medium comprising the polyester film for a magnetic recording medium according to claim 1, wherein a magnetic layer is provided on at least one surface of the polyester film. 11. A magnetic recording medium obtained by forming a ferromagnetic metal thin film on at least one surface of the polyester film for a magnetic recording medium according to claim 9. A digital recording cassette tape comprising the magnetic recording medium according to claim 9.