JPH0651401B2 - Polyester film for magnetic recording media - Google Patents

Description

The present invention relates to a magnetic recording medium such as a magnetic tape and a magnetic disk,
In particular, it relates to a base film for a magnetic recording medium having a ferromagnetic thin film as a recording layer.

[Prior Art] As a base film for a magnetic recording medium, particularly for a ferromagnetic thin film, a smooth polyester film having a granular mixed coating formed on one side thereof, for example, JP-A-54-94574.
Japanese Unexamined Patent Publication No. 56-1045, in which an earthworm-like coating structure is formed on both surfaces of a smooth polyester film.
Japanese Patent Laid-Open No. 58-68225 discloses a plastic film in which granular, wrinkle-shaped, and earthworm-shaped protrusions are formed and ridges higher than their height are formed.

[Problems to be Solved by the Invention] In the film of the above item, if a ferromagnetic thin film is provided on the surface of the granular coating, a high density magnetic recording medium can be produced, but since the granular coating is formed on only one surface. However, there was a problem in that the film did not slide well and handling properties were poor during processing.

In the film of the above item, since the earthworm-like coating film structure is formed on both sides, the slip property is improved, there is no problem of the above item, and the head touch of the ferromagnetic thin film provided on the surface, the head The runnability is good. However, there was a problem that the head clogging phenomenon was not sufficiently improved.

In the film of the above item, a relatively high protrusion is provided on the magnetic recording medium to prevent clogging of the head by utilizing a kind of kicker action. There was a problem that the performance of the head clogging prevention effect deteriorates after repeated running.

[Means for Solving Problems] In the present invention, fine particles having a particle diameter of 10 to 300 mμ are used as 0.00
1 to 1 wt% and the height is 50 to 9 depending on the fine particles.
00Å, fine surface protrusions with a diameter of 0.01-1μ are 10 ³ -1
A polyester film 0 ⁷ month / mm ² are formed, the discontinuous coating on at least one surface polar polymer mainly of the film is formed, the thickness of the discontinuous film (height from the film surface) is 500Å or less And the height of the fine surface protrusions is higher than the height of the discontinuous coating, which is a polyester film for a magnetic recording medium.

The fine particles added to the polyester film of the present invention have a particle size of 10 to 300 mμ (number average),
Inorganic particles such as CaCO ₃ , SiO ₂ , and Al ₂ O ₃ are used, but not limited thereto.

The polyester forming the polyester film of the present invention may be linear or any polyester mainly composed of polyester. For example, polyethylene terephthalate, polytetramethylene terephthalate, poly -1,
Typical examples are 4-cyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, and polyethylene-p-oxybenzoate.

Further, the above polyester may be a homopolyester or a copolyester. In the case of a copolyester, examples of the component to be copolymerized include diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, diol components such as 1,4-cyclohexanedimethanol, adipic acid and sebacic acid. , Phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 5-sodium sulfoisophthalic acid and other dicarboxylic acid components, trimellitic acid, pyromellitic acid and other polyfunctional dicarboxylic acid components, p-
Examples thereof include oxyethoxybenzoic acid. In the case of copolymerization, the component to be copolymerized is 20 mol% or less.

Further, the above-mentioned polyester is mixed with at least one of an alkali metal salt derivative of sulfonic acid which is non-reactive with the polyester, a polyalkylene glycol which is substantially insoluble in the polyester, etc. in an amount not exceeding 5% by weight. May be.

The polyester film of the present invention is a polyester film formed by a known method of the above polyester, that is, a film formed by melting polyester and extruding it into a sheet or a cylindrical shape, and stretching it in at least one direction. It is desirable that the mechanical properties of the film be either a normal balance type, a type strengthened in the uniaxial orientation in the machine axis direction or a direction perpendicular thereto, or a type strengthened in the biaxial direction.

The polyester film of the present invention has a particle size of 10 to 300.
fine particles of mμ (preferably 30 to 200 mμ) to 0.
001 to 1 wt%, and the fine particles have a height of 50 to 900Å (preferably 50 to 500) on the surface of the film.
Å), diameter 0.01-1μ (preferably 0.01-0.8)
(μ) fine protrusions must be formed at 10 ³ to 10 ⁷ pieces / mm ² (preferably 10 ⁴ to 10 ⁶ pieces / mm ² ). By adjusting the particle size of the fine particles and the content in the film to the above values, the height, diameter, and number of the fine projections described above can be achieved on the film surface. When the projection height is H and the diameter is D, the ratio H / D between them is 0.1
0.01 is preferable and 0.1-0.02 is more preferable. When the H / D is in this range, the fine protrusions cannot be scraped off by various guide rolls during the processing of the base film, and the protrusions formed on the tape surface after being formed into a tape cannot be scraped off, and the metal thin film is provided. The effect of preventing the head clogging after the cleaning is further improved.

The height of fine protrusions is less than 50Å, the diameter is 0.01
When the projection density is lower than μ or lower than 10 ³ / mm ^{2, the} effect of preventing head clogging is lost. If the height exceeds 900Å or the number exceeds 10 ⁷ / mm ² , the electromagnetic conversion characteristics of the magnetic recording medium after the metal thin film is formed, especially the dropout, deteriorates.

The metal thin film is well known and is not particularly limited, but has a thickness of about 0.05 to 1 μ, preferably about 0.1 to 0.5 μ, and is made of a ferromagnetic material of iron, cobalt, nickel, or an alloy thereof. The above film is preferable, and the film is formed directly on the base film by vacuum vapor deposition, ion plating, sputtering or the like, or via a base thin film of aluminum, titanium, chromium or the like.

The discontinuous thin film of the present invention is formed from a material mainly composed of a polar polymer, but the shape is a mesh and / or a group of scattered coatings, and the thickness of the discontinuous coating, that is, The height on the film surface should be 500 Å or less, preferably 30 to 300 Å, and lower than the height of the fine protrusions. If the height exceeds 500 Å, the electromagnetic conversion characteristics of the magnetic recording medium after the metal thin film is provided, especially the S / N ratio is deteriorated.

The ratio of the discontinuous coating on the film surface is 10 to 10.
90% is preferable and 30-80% is more preferable.

The polar polymer of the present invention, a hydroxyl group, an ether group,
Those having a polar group such as an ester group, an amide group, a methoxy group and a hydroxypropoxy group and having a molecular weight of 10,000 to 2,000,000, preferably 100,000 to 1,000,000 are used. When the molecular weight is less than 10,000, the coating becomes soft and it becomes difficult to maintain the structure, resulting in poor durability. If the amount exceeds 2,000,000, the coating becomes too hard and brittle, and the durability also deteriorates. As the polar polymer, polyvinyl alcohol, tragacanth gum, gum arabic, casein, gelatin, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, water-soluble polyester ether copolymer and the like can be applied, and blends thereof can also be applied.

Due to the polarity of the polar polymer, the adhesion strength of the ferromagnetic thin film is increased.

The height of the discontinuous coating of the present invention needs to be lower than the height of the fine protrusions. If it is not low, the effect of preventing head clogging by the fine protrusions is not exhibited.

The discontinuous coating of the present invention preferably contains a silane coupling agent or a titanium coupling agent.

Further, in order to impart the durability of the vapor-deposited film under an extremely harsh environment of use (high temperature, high humidity), the particle size is 30 to 50.
0 Å fine particles to the discontinuous film-forming polymer 5 ~
It is desirable to contain 50% by weight, preferably 10 to 40% by weight.

In order to further increase the adhesiveness between the discontinuous coating and the polyester film, it is preferable to add a silane coupling agent or a titanium coupling agent to the discontinuous component.

The silane coupling agent is an organosilicon monomer having two or more different reactive groups in its molecule, one reactive group is a methoxy group, an ethoxy group, a silanol group, etc. The group is a vinyl group, an epoxy group, methacrylic acid, an amino acid, a mercapto group or the like. The reactive group is selected so that it bonds with the side chain, terminal group and polyester of the polymer blend structure, but as the silane coupling agent, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-glycid Xypropyltrimethoxysilane, γ
-Methacryloxypropyl trimexisilane, N-β
(Aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, γ-
Mercaptopropyl trimexisilane, γ-aminopropyltriethoxysilane and the like can be applied.

The fine particles added to the discontinuous film forming resin in order to improve the durability of the vapor-deposited film under more severe conditions such as high temperature and high humidity have a size of 30Å to 500Å, preferably 50 to 400Å. It is a thing. Here, the size means the average value of the maximum particle size of each fine particle, and if the size is less than 30Å, the running property of the vapor-deposited thin film surface obtained by vapor-depositing a magnetic substance on the discontinuous coating is not improved. Further, if the size exceeds 500 Å, the electromagnetic conversion characteristics of the magnetic surface deteriorate. The shape of the fine particles may be any of a spherical shape, an elliptic spherical shape, a rectangular shape, a cubic shape and the like. Further, as the particle species, inorganic compound particles such as MgO, ZnO, MgCO ₃ , C
aCO ₃ , CaCO ₄ , BaSO ₄ , Al ₂ O ₃ , Si
O ₂ , TiO ₂ and acid salts such as Ca, Ba, Zn and Mn can be used. A plurality of types of fine particles may be used.

The fine particles are present in the discontinuous coating and on the coating surface, and the number of existing particles is 10 ⁴ to 10 ¹¹ pieces / mm ²
It must be: Number of particles is 10 ¹¹ / mm
^If it exceeds ² , among the electron conversion characteristics of the magnetic surface, especially S
/ N ratio deteriorates. In addition, fine particles easily fall off, which is not preferable. The maximum particle size and the number of particles are determined by observing with an electron microscope.

The ratio of the polar polymer (A), the silane coupling agent or the titanium coupling agent (B) used as a constituent of the discontinuous film is (A) :( B) = 100: 0 to 50 (preferably (A) :( B)). ) :( B) = 100: 1 to 40).

(B) is used for the purpose of improving the running property of the vapor deposition film, but if it is within this range, the adhesion strength of the vapor deposition film is improved and the brittleness of the film is also improved, which is preferable.

The content of the fine particles (C) added to increase the durability of the vapor-deposited film under more severe conditions is (A),
It is 5 to 50% by weight with respect to the sum of (B). When the fine particles (C) are in this range, fine particles do not fall out of the coating film, and electromagnetic conversion characteristics are improved, which is preferable.

Hereinafter, the polyester film of the present invention will be described with reference to the drawings.

The fine surface protrusions of the present invention can be observed by a differential interference optical microscope and an electron micrograph (magnification: 500 to 100,000 times). The height is measured by a highly accurate stylus type surface roughness measuring device.

The discontinuous coating of the present invention is an electron micrograph (magnification: 500).
2 times to 100,000 times), the film surface partially covers the film surface. FIG. 1 is a plan view schematically showing a discontinuous coating 4 which partially covers the surface of a polyester film 3 having fine surface protrusions 2.

FIG. 3 is a schematic plan view showing a state in which fine particles 5 are further contained in the discontinuous coating 4 to form fine protrusions on the surface of the discontinuous coating. This can be seen by observing with an electron microscope at a magnification of 10,000 times or more.

2 and 4 are sectional views taken along the line A-A 'in FIGS.
It is a schematic sectional drawing of a B'section film. The first
In FIG. 2, FIG. 3, FIG. 3, and FIG. 4, 1 is a fine particle,
2 is a fine surface protrusion, 3 is a polyester film, 4 is a discontinuous coating, and 5 is fine particles in the discontinuous coating. In addition,
H is the height of the fine surface protrusions, D is the diameter of the fine surface protrusions, and t is the thickness of the discontinuous coating (height from the film surface). The height H and the thickness t can be obtained by measuring the surface on which the discontinuous coating of the present invention is formed, with a highly accurate needle-implanted surface roughness meter having a small stylus tip diameter.

Next, a method for producing the film of the present invention will be described.

In the polyester raw material of the above description, the raw material containing the fine particles of the above description is melt-extruded by a normal film forming machine, and after cooling, at least one surface of the longitudinally stretched film uniaxially stretched 5 to 3 times, A solution containing a polar polymer, more preferably, a coating solution containing a silane coupling agent is applied and dried, and then stretched in a right-angle direction, or after stretching in a right-angle direction, the film is re-wound in the one direction. Stretch and heat treat. Right-angle stretching may be further performed before heat treatment to increase the transverse strength in the direction perpendicular to the machine axis. Further, in order to impart the durability of the vapor deposition film under an extremely harsh environment of use, it is preferable to include the fine particles described above in the coating liquid.

Although the single layer film has been described above, a composite by co-extrusion of the polyester (containing particles) raw material applied to the present invention and the raw material added with the fine particles having a particle size of 40 mμ or more larger than the fine particles added to the raw material. The present technology may be applied to the production of a film.

[Function] Due to the above described fine particles contained in the polyester of the present invention, the above described fine projections are formed on the film surface, and the fine projections provide an effect of preventing head clogging after providing a metal thin film. With the discontinuous coating of the present invention, it is possible to improve the head touch and the head running property of the tape after providing the metal thin film.

[Evaluation Method, Measurement Method] The diameter and number of the fine surface protrusions of the film of the present invention can be observed by a differential interference optical microscope and an electron microscope, but are measured by observation with an electron microscope at a magnification of 500 times or more.

Surface projection height of the above surface roughness maximum value defined in JIS B0601, a value displayed at a distance from the summit of irregularities in accordance with R _max up valley, stylus type surface roughness of the precision It is actually measured by a measuring device. At least a distance of 500 μ or more is measured, and the average value of the heights of protrusions is calculated.

The height of the discontinuous coating is a cross-sectional curve obtained by a stylus type surface roughness meter similar to the above, and is a value obtained by obtaining the average height interval between peaks and valleys.

The characteristics of a magnetic recording medium in which a ferromagnetic thin film is provided on the film of the present invention, that is, the characteristics of a tape are measured using a commercially available 8 mm video tape recorder. As the electromagnetic conversion characteristics, the video S / N ratio, dropout, and the number of repetitions until the occurrence of image disturbance due to head clogging were determined.
To measure the S / N ratio and dropout, a signal was supplied from a TV test signal generator, and a video noise meter and dropout counter were used. The video S / N ratio was measured by comparing a commercially available 8 mm video metal tape with zero decibel (dB). Dropout is the attenuation of the playback signal
Those having a length of 16 dB or more and a length of 15 microseconds or more were obtained. The S / N ratio and the dropout were at room temperature and normal humidity, and the initial characteristics after tape production were observed. To prevent head clogging, the magnetic tape is left for 1 month under the conditions of 60 ° C and 90% RH, and a small amount of rust causing clogging is generated on the surface of the magnetic tape. Repeated video recording and playback with RHF to determine the number of repetitions until the start of image distortion due to head clogging, for unused tape after tape production and for both tapes after 100 playback runs. I performed and evaluated.

[Example] Next, an example will be described.

Example 1 Fine particles formed on the basis of a polymerization catalyst residue or the like, that is, substantially non-oriented, non-crystalline polyethylene terephthalate containing no internal particles as much as possible, containing 0.04% by weight of SiO ₂ particles having a particle diameter of 110 mμ. About 20 ingredients
Melt extruded onto a rotating drum maintained at ℃, then 3.4
Double stretching in the machine direction was performed, and then the following aqueous solution was used at a solid content concentration of 20 mg /
m ² Both sides were applied.

As the aqueous solution, a mixture of 0.15% methylcellulose and 0.05% silane coupling agent N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane was prepared.

Drying, preheating, stretching temperature is 115 ° C and moisture drying rate is 15
% / Sec.

A transverse stretching ratio of 3.4 times, a heat treatment temperature of 200 ° C, a discontinuous coating with a height of 100Å is formed on both sides, and the diameter is 0.2.
A polyethylene terephthalate film having a thickness of 12μ and having a height of 150Å fine protrusions at a rate of 3 × 10 ⁴ pieces / mm ² was obtained.

A cobalt-nickel alloy thin film having a thickness of 1500 Å was formed on the surface of the polyester film by vacuum evaporation.

Subsequently, the film was cut into a predetermined width in the machine direction (longitudinal direction) to obtain a magnetic tape. This characteristic is shown in Table 1.

Example 2 In the production of the base film of Example 1, an aqueous solution prepared by adding 0.35 wt% of a water-soluble polyester ether copolymer and 0.15 wt% of ultrafine silica having an average particle diameter of 200Å to the aqueous solution emulsion to be used is used. In the same manner as in Example 1, a discontinuous coating having a height of 120Å, which contains fine particles on both sides and has protrusions by it, is formed and has a diameter of 0.2.
A polyethylene terephthalate film having a thickness of 12 μ and having micro projections having a height of 150 Å and present at a rate of 3 × 10 ⁴ pieces / mm ² was obtained.

Using this base film, a magnetic tape was obtained in the same manner as in Example 1. The tape properties are shown in Table 1.

Comparative Example 1 The particle size of SiO ₂ particles used in the production of the base film of Example 1 was changed from 110 mμ to 5 mμ. In addition, the concentration of methylcellulose in the coating liquid is 0.05%
And In the same manner as in Example 1 except that fine particles are contained in the base film, and there are 7 × 10 ⁸ protrusions / mm ² having a diameter of 0.004 μm and a height of 40 Å, and a height of 3
A 12 μm-thick polyethylene terephthalate film on which a 0Å discontinuous film was formed was obtained.

Using this base film, a vapor-deposited magnetic tape was obtained in the same manner as in Example 1. The tape properties are shown in Table 1.

Comparative Example 2 SiO ₂ used in the production of the base film of Example 1
Particles having a particle size of 110 mμ to 500 mμ were used, and other fine particles were contained in the base film in the same manner as in Example 1, and the resulting diameter was 0.6.
A polyethylene terephthalate film having a thickness of 12 μ, in which projections of μ and a height of 1200 Å were present at 3 × 10 ³ pieces / mm ² and a discontinuous coating having a height of 100 Å was formed on both surfaces, was obtained.

Using this base film, a magnetic tape was obtained in the same manner as in Example 1. The tape properties are shown in Table 1.

Comparative Example 3 SiO ₂ used in the production of the base film of Example 1
Content is 2% by weight and the same applies to the other sides with a height of 1
A polyethylene terephthalate film having a thickness of 12 μ, in which a discontinuous film of 00 Å was formed and fine projections having a diameter of 0.2 μ and a height of 150 Å were present at a rate of 5 × 10 ⁸ pieces / mm ² , was obtained.

Using this base film, a magnetic tape was obtained in the same manner as in Example 1. The tape properties are shown in Table 1.

Comparative Example 4 SiO ₂ used in the production of the base film of Example 1
The particle size of the particles is 300 mμ, the concentration of the methylcellulose aqueous solution is 0.40%, the same as the others, and a discontinuous coating with a height of 600 Å is formed on both sides, and the diameter is 0.4 μ,
A polyethylene terephthalate film having a thickness of 12 μm and having a surface on which fine protrusions having a height of 800 Å were present at 6 × 10 ³ pieces / mm ² was obtained.

Using this base film, a magnetic tape was obtained in the same manner as in Example 1. The tape properties are shown in Table 1.

[Effect of the invention] Fine particles are contained, and the height is 50 to 900Å and the diameter is 0.0.
Fine surface protrusions of 1 to 1 μm are formed at 10 ³ to 10 ⁷ pieces / mm ² , and at least one side has a thickness of mainly polar polymer 5
Since a polyester film having a discontinuous coating of 00 Å or less is formed, a magnetic layer is formed on the surface where the discontinuous coating is formed,
In particular, when a magnetic recording medium provided with a ferromagnetic thin film is used, the magnetic recording medium has good head touch and head running property, and the head clogging prevention effect is obtained after long-term repeated running such as after 100 reciprocations. Also has the effect of being excellent.

[Brief description of drawings]

FIG. 1 is a plan view schematically showing a discontinuous coating partially covering the surface of a polyester film having fine surface protrusions, and FIG. 2 is a sectional view taken along the line AA ′ in FIG. FIG. 3 is a plan view schematically showing a state in which fine particles are further contained in the discontinuous coating, whereby fine projections are provided on the surface of the discontinuous coating, and FIG. 4 is B of FIG. -B '
It is a figure which shows a cross section. 1: Fine particles added to polyester film 2: Fine surface protrusions 3: Polyester film 4: Discontinuous coating 5: Fine particles in discontinuous coating H: Height of fine surface protrusions D: Diameter of fine surface protrusions t: Thickness of discontinuous coating (height)

Claims (1)

[Claims] 1. A fine particle having a particle size of 10 to 300 mμ is 0.0
0 to 1 wt% and the height of 50 to 50 depending on the fine particles.
900 Å, fine surface protrusions with a diameter of 0.01 to 1μ are 10 ³ to
10 ⁷ pieces / mm ² formed polyester film, and a discontinuous film mainly composed of polar polymer is formed on at least one surface of the film, and the thickness of the discontinuous film (height from the film surface) is 500 Å or less And the height of the fine surface protrusions is higher than the height of the discontinuous coating, a polyester film for a magnetic recording medium.