JPS62290535A - Polyester film for magnetic record medium and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks;
In particular, the present invention relates to a base film for a magnetic recording medium whose recording layer is a ferromagnetic thin film.

[Conventional technology]

The base film for magnetic recording media, especially for ferromagnetic thin films, is: ■ A composite film in which HA made of thermoplastic resin and thermoplastic resin B to which fine particles are added are laminated;
A discontinuous film having a height of 50 to 1000 people is formed on the outer surface of the film, for example, Japanese Patent Application Laid-open No. 58-153640, 5
Publication No. 8-155940, ■ Grain-like, wrinkle-like, and worm-like protrusions are formed, and there are 100,000 to 10,000 protrusions/mm on the surface that are higher than these protrusions.
2 Plastic films formed, for example, JP-A-58-68225, ■ Polyester films with a height of 100 to 2,000 people and an average of 10,000 to 1,000,000 protrusions per 1 mm2, for example, JP-A-58-100
Publication No. 221.

(2) A polyester film having a height of 50 to 600 people and having mountain-like protrusions with an average size of 1×10 5 to 1×10 8 wU per 11TllT12, for example, Japanese Patent Application Laid-Open No. 60-93636, is known.

[Problem to be Solved by the Invention 3] In the film of item 120, if a ferromagnetic thin film is provided on the discontinuous coating surface, a high-density magnetic recording medium can be produced. The ferromagnetic thin film provided on the surface has good contact and head running properties. However, there was a problem that the head clogging phenomenon was not sufficiently improved.

In the above film of item 0, relatively high ridges are provided on the magnetic recording medium to prevent head clogging by using a kind of abrasive action. There was a problem in that the head clogging prevention effect deteriorated after repeated runs.

In the films described in Items ① and 0 above, high-density magnetic recording media can be produced by providing a ferromagnetic thin film on the surface where the ridges are formed, but because the ridges are steep, it is difficult to use with various rolls in the magnetic recording medium manufacturing process. Although the magnetic recording medium is easily scraped by contact and has scratches, and head clogging does not occur when running under normal temperature and humidity conditions, the protrusions of the ferromagnetic thin film may be damaged by contact with the magnetic head. It has the disadvantage that it is easily scratched, and when it is repeatedly run for a long period of time under harsh conditions, such as high temperature and high humidity conditions, scratches occur on the vapor-deposited surface and the tape performance deteriorates.

[Means for solving problems]

The present invention is a composite stretched film in which a layer made of polyester A and a layer made of polyester B to which fine particles have been added are laminated, and the outer surface of the layer made of polyester B has an average Height is 50 Å or more, 2
00 Å or less, the maximum height is 1.1 times or more the average height, 1.
103 surface protrusions with a size of 5 times or less/more than 2, 107
The present invention is characterized by a polyester film for magnetic recording media formed with a thickness of 1/2 mm or less.

The polyester A forming the film of the present invention may be of any type as long as it is mainly composed of linear polyester. For example, polyethylene terephthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-
Representative examples include 2,6-naphthalene dicarboxylate and polyethylene-oxybenzoate.

Further, the above polyester may be a homopolyester or a copolyester.

In the case of copolyester, the components to be copolymerized include, for example, diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-
Diol components such as xylylene glycol, 1,4-cyclohexane dimetatool, adipic acid, sebacic acid,
Examples include dicarboxylic acid components such as phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, and 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, and oxyethoxybenzoic acid. . In addition, in the case of copolymerization, the component to be copolymerized is 20 mol% or less.

Furthermore, the above polyester is mixed with at least one of an alkali metal salt derivative of sulfonic acid that is non-reactive with the polyester, a polyalkylene glycol that is substantially insoluble in the polyester, etc., to an extent not exceeding 5% by weight. You may.

The polyester A forming the film of the present invention is
It is preferable that the following fine particles are added in an amount of 0.001 wt % without grooves, and more preferably that substantially no particles are added.

Polyester B added with fine particles forming the film of the present invention is obtained by adding the following fine particles to the polyester A described above.

The fine particles in the present invention have a particle size of 10 mμ to 300 mμ before being added to polyester, and have a specific
Inorganic particles such as aC[)+, 5in2, A 0.203, etc. are used, but are not limited thereto.

The polyester film of the present invention is a layer made of polyester A (hereinafter referred to as layer A) and a layer made of polyester B containing fine particles (hereinafter referred to as layer B), and , is a composite stretched film stretched into two wheels, and its mechanical properties include a normal balanced type, a type strengthened in the uniaxial direction or perpendicular to the machine axis, and a type strengthened in the biaxial direction. It is desirable that the

On the outer surface of layer B of the composite stretched polyester film of the present invention, surface protrusions are formed by the fine particles, and the average height is 50 Å or more and 200 Å or less (more preferably 100 Å or more and 180 Å or less). , the maximum height is 1.1 times or more and 1.5 times or less (more preferably 1.1 times or more and 1.4 times or less) of the average height, and the number is 103 pieces/closed 2 or more, 107 pieces. /rnm 2 or less (more preferably 103 pieces/n+m'' or more, 106 pieces/mm
2 or less).

The polyester film of the present invention is used as a magnetic recording medium by providing a ferromagnetic thin film on the outer surface of layer B, but the average height of the surface protrusions is less than 50, or the number is 10.
If it is less than 3 pieces/mm2, the running properties of the ferromagnetic thin film with respect to the magnetic head will deteriorate. It is no longer effective against head clogging and current dyeing.

The average height exceeds 200 people, and the number of pieces is 107 pieces/m.
If it exceeds m2, the shape of the ferromagnetic thin film becomes rough and the electromagnetic conversion characteristics deteriorate. If the maximum height exceeds 1.5 times the average height, the electromagnetic conversion characteristics will still deteriorate. In addition, repeated running over long periods of time under high temperature and high humidity conditions causes rough parts to become scratched, resulting in defects and scratches. If the maximum height is less than 1.1 times the average height, the height of the protrusions will be too uniform, reducing the effect of preventing head clogging.

In addition, when the protrusion height is H1 and the diameter is D, the ratio of both is 1/
D is preferably 0.1 to 0.01, and 0°1 to 0.02
is more preferable. When l-1/D is within this range, fine protrusions will not be scraped by various guide rolls during processing of the base film, and protrusions formed on the tape surface after being made into a tape will not be scraped, and the metal thin film will not be scraped. The effect of preventing head clogging after installation is further improved.

The surface roughness of the outer surface of layer B, that is, the surface on which the ferromagnetic metal thin film is provided, is Ra with a cutoff value of 0°25 mm.
If the value (according to DIN476B) is 0°10μ or less, when a ferromagnetic metal thin film is provided on the surface, the surface becomes smooth and the electromagnetic conversion characteristics are further improved.

The surface of the layer B may have a worm-like film structure as seen in Japanese Patent Publication No. 60-5183 and Japanese Patent Publication No. 60-50150. In addition, special public service No. 60-50151
A discontinuous coating as seen in the above publication may also be formed.

Note that a known ferromagnetic metal thin film can be used, and is not particularly limited, but has a thickness of 0.01 to 1μ, more preferably 0.
．． It is about 1 to 0.5 μ and contains iron, cobalt, nickel,
Preferably, the material is made of a ferromagnetic material or an alloy thereof. The protective film is formed on the base film directly or via a base N film of aluminum, titanium, chromium, etc. by vacuum evaporation ion blating, sputtering, or the like.

The above polyester film for magnetic recording media of the present invention is:
It is possible to produce 1q using the following manufacturing method.

That is, polyester A and polyester B to which 0.001 to +wt% of fine particles with a particle size of 10 to 30 Qmμ have been added are melted at a temperature of 260°C or higher and 300°C or lower, respectively, and the two are merged to form a slit. The sheet is coextruded from the nozzle, and the sheet is placed on a moving cooling body for 5~
Production of a polyester film by cooling and solidifying at a temperature of 40°C to obtain an unstretched sheet in which polyesters A and B are laminated, stretching the sheet in biaxial directions, then re-stretching if necessary, and then subjecting it to heat treatment. In the method, (1) the particle size of the fine particles is 10 to 300% before being added to the polyester;
mμ, (2) the thickness of the layer made of polyester B of the unstretched sheet is 5 times or more and 100 times or less the particle diameter of the added fine particles; (2) the biaxial stretching is 70 to 150 times in the uniaxial direction;
2 to 4 times at a temperature of ℃, and 70 to 1 in the direction perpendicular to said direction.
This is a method for producing a polyester film for magnetic recording media, which is characterized by increasing the temperature by 3 to 5 times at a temperature of 50°C.

Note that the stretching in each direction in the above-mentioned biaxial stretching may be performed in one step or in multiple steps. Further, the re-stretching may be performed as long as it is re-stretched in at least one axial direction, but when re-stretching only in the -axial direction, the re-stretching is performed by 1.1 to 2.0 times in the biaxial direction at 90 to 170°C. When stretching, 1 at 90 to 170°C in each axial direction.
．． It is preferable to set it as 1 to 1.8 times. In addition, heat treatment
It is not particularly limited as long as it is a known condition, but 180~
It is preferable to set it as 5 to 180 seconds at 240 degreeC.

In the above film manufacturing method, when the particle size of the fine particles is less than 10111μ, the average height of the fine protrusions formed on the outer surface of the layer B of the laminated film is less than 50. Furthermore, when the particle size exceeds 300 mμ, the average height of microprotrusions exceeds 200 mμ. When the amount of the fine particles added is less than 0.001 wt%, the effect of surface fine protrusions becomes less than 103 particles/mn2. When the amount added exceeds 1 wt%, the number of microprotrusions exceeds 107 pieces/mm2.

If the thickness of layer B of the coextruded sheet is less than 5 times the diameter of the fine particles, the fine protrusions formed in the subsequent stretching process will easily fall off the surface. Also, this makes the surface very easy to peel off. If the thickness of layer B exceeds 100 times the diameter of the fine particles, the maximum height of the formed fine projections will exceed 1.5 times the average height.

Moreover, if the stretching ratio in the biaxial direction is lower than each of the above-mentioned stretching ratios, the mechanical strength of the film decreases, which is not preferable. When the magnification exceeds the above range, the added fine particles tend to fall off from the film.

Note that the re-stretching ratio is arbitrarily selected depending on the strength required of the film, and is not particularly limited.

In addition, in the above stretching, after -axial stretching,
Layer A may be subjected to the smoothing treatment disclosed in Japanese Patent Publication No. 47050, Japanese Patent Publication No. 59-3°9308, etc. Layer B may be subjected to the worm-like coating or discontinuous coating formation treatment disclosed in Japanese Patent No. 60-50151.

[Function] The laminated and stretched polyester film of the present invention has an average height of 50 to 200 people on one side, and a maximum height of 1.
Since 103 to 107 protrusions/mm2, which is 1 to 1.5 times as large, are formed, providing a ferromagnetic thin film layer on the surface side improves the running properties of the magnetic head and the effect of preventing head clogging. Furthermore, the electromagnetic conversion characteristics are good, and the shear resistance is also ensured.

In addition, in the manufacturing direction of the laminated film of the present invention, in order to make the thickness of the particle-added layer of the laminated unstretched sheet formed by coextrusion to be 5 to 100 times the particle size of the additive particles, the layer is formed by stretching. The fine protrusions are uniform with a maximum height of 1.1 to 1.5 times the average height.

[Evaluation Method/Measurement Method] (1) The height of the surface projections of the film of the present invention is actually measured using a high-precision stylus-type surface roughness measuring device. Measure a distance of at least 500μ and obtain a cross-sectional curve. Each unevenness that appears on the cross-sectional curve is due to individual surface protrusions, and the value calculated and displayed from the top of each unevenness to the bottom of the valley is the height of each surface protrusion, and the average value is the average of the surface protrusions. Let it be the height. The maximum height of each surface protrusion is defined as the maximum height.

(2) The diameter and number of surface protrusions of the film of the present invention are measured using a differential interference optical microscope and an electron microscope, and are measured using an electron microscope at a magnification of 5,000 times or more. The diameter is determined by observing 10 or more protrusions and finding the average value.

The number of pieces is 11III by taking a normal photo and judging from the number in the photo.
It is calculated by converting it into 112 parts.

(2) The characteristics of a magnetic recording medium, that is, a magnetic tape, in which a ferromagnetic thin film is provided on the film of the present invention are measured using a commercially available 8 mm video tape recorder.

Video S/N ratio, dropout,
The number of repetitions until image disturbances started to occur due to head clogging was 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 compared and measured using a commercially available 8 mm video metal tape at zero decibels (dB). Dropout was determined to be attenuation of the reproduced signal of 116 dB or more and length of 15 microseconds or more. The S/N ratio and dropout were measured at room temperature and humidity (25° C., 60% RH), and the initial characteristics after tape production were observed. As for the head clogging prevention properties, after leaving the magnetic tape at 60℃ and 90% RH for one month to allow a slight amount of rust to form on its surface, which causes clogging, it was heated to 25℃ and 90% RH. Video recording and playback were performed repeatedly under RH conditions, and the number of repetitions until image disturbances began to occur due to head clogging was determined. Both tapes were played back 100 times and evaluated. Furthermore, the tape surface was inspected 12 times after being played back 100 times under conditions of 60° C. and 90% RH to check for scratches.

■ In the '84 manufacturing method of the present invention, the particle size of the fine particles is
It is determined by measuring particles using an electron microscope. Observe 10 or more particles and calculate the average diameter.

(2) In the production method of the present invention, the thickness of the layer of the coextruded sheet is determined by cutting the unstretched sheet with a microtome and observing the section under a microscope.

[Example] Next, the present invention will be explained based on examples.

Example 1 A substantially non-oriented, non-crystalline polyethylene terephthalate raw material (A> containing as little as possible fine particles formed based on polymerization catalyst residues, etc.) and 5i02 particles with a particle size of 10 mμ were added to the raw material (A). Using the raw material (B) added at 0.02% by weight, the raw material (B) layer was melted and co-melted so that the thickness of the raw material (B) layer was 1μ (9 times the particle size) and the raw material (A>layer thickness was 137μ). After extrusion, cooling and assimilation, longitudinal stretching was performed at a temperature of 100° C. at a stretching ratio of 3.4 times, and then the following aqueous emulsion was applied to the surface of the raw material (A> layer at a solid content concentration of 20 m (II/m2).

Epoxidized polydimethylsiloxane emulsion: 0
．． 40wt% Silane coupling agent [N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane] 20,050w
t% Alkylphenol nonionic surfactant, agent 20.

2Qwt% Then, pass through a stenter, dry at 115°C, preheat,
Stretched laterally. The lateral stretching ratio was 3.4 times.

Next, heat treatment was performed at 200°C for 1 second, and the average diameter was 0°2μ.
Average height 150 people, maximum height 180 people surface protrusions 3.
A two-wheel stretched polyester laminate film having a thickness of 12 μm was obtained in which Layer B having a surface formed with a coating layer of 0×10 4 layers/mm 2 and Layer A having a surface formed with a coating layer mainly consisting of a lubricant were laminated.

A cobalt-iron alloy thin film was formed on the surface of layer A of this polyester film by vacuum deposition to a thickness of 1500 mm. Next, a protective film layer consisting of epoxy resin, silicone, and a silane coupling agent was placed on the surface of the cobalt-iron alloy thin film to a thickness of 0.1 μm, and on the opposite side of layer 8, an epoxy resin containing carbon black was applied. A back coat layer consisting of , silicone, and a silane coupling agent was applied to a thickness of 1 μm (after printing, the tape was cut into a predetermined width in the longitudinal direction to obtain a magnetic tape.

The properties of the film and magnetic tape are shown in Table 1.

Example 2 In the production of the laminated film of Example 1, an aqueous emulsion was applied to the surface of the raw material (A> layer) on the longitudinally stretched pattern, and at the same time, the following aqueous solution was applied to the surface of the raw material (B) layer at a solid concentration. An aqueous solution containing 0.15 wt% methylcellulose and 0.05 wt% silane coupling agent N-β (amine ethyl) T-aminopropylmethyldimethoxysilane was prepared.Others were prepared in the same manner as in Example 1. , Ra value at cutoff value 0.25 mm is 0.0
05μ, a discontinuous film is formed on the surface, and the average diameter is 0.
．． 2μ, average height 140 people, maximum height 170 people The thickness is 12μ, consisting of layer B, in which 2.9 x 104 surface protrusions are formed per square 2, and layer A, in which a coating layer mainly composed of lubricant is formed.
A two-wheel stretched polyester laminate film was obtained. The height of the surface protrusions was determined by focusing only on those that were higher than the discontinuous coating. More specifically, in the unevenness of the roughness meter cross-sectional curve,
The search focused on those with more than 100 people. A magnetic tape was obtained in the same manner as in Example 1 using this base film.

The properties of the film and magnetic tape are shown in Table 1.

Comparative Example 1 A base film was produced in the same manner as in Example 1, except that the raw material (B) layer and the raw material (A>layer thickness were co-extruded at a ratio of 17μ/121μ). and created a magnetic tape.

The properties of the film and magnetic tape are shown in Table 1.

Comparative Example 2 In manufacturing the base film of Example 1, the base film was prepared in the same manner as in Example 1, except that the raw material (B) layer and the raw material (A> layer thickness were co-extruded at a ratio of 0.4μ/138μ). A film was obtained and a magnetic tape was made.

The properties of the film and magnetic tape are shown in Table 1.

Comparative Example 3 In manufacturing the base film of Example 1, the particle size of SiO2 added to raw material (B) was changed to 500 mμ, and raw material 8
The same procedure was carried out except that the thickness of the layer and the raw material A layer was 4μ/134μ. Using this base film, Example 1
A magnetic tape was obtained in the same manner.

The properties of the film and magnetic tape are shown in Table 1.

Comparative Example 4 A base film with a thickness of 12 μm was obtained in the same manner as in Example 1 except that the particle size of the S+O2 particles added to the raw material (B) was changed to 5 μm. Using this base film, 1 q of magnetic tape was prepared in the same manner as in Example 1.

The properties of the film and magnetic tape are shown in Table 1.

Comparative Example 5 1 q of base film having a thickness of 12 μm was prepared in the same manner as in Example 1 except that the 5102 addition port in the raw material <8) was changed to 2 wt %. Using this base film, a magnetic tape was produced in the same manner as in Example 1 except for the above.

The properties of the film and magnetic tape are shown in Table 1.

[Effects of the invention] The ferromagnetic metal thin film provided on the surface of layer B of the composite film of the present invention has excellent head clogging prevention effect, excellent abrasion resistance against magnetic heads, and improves the S/N ratio and dropout of the magnetic tape. Characterized by the effect that is good

Claims (2)

[Claims] (1) A composite stretched film in which a layer made of polyester A and a layer made of polyester B added with fine particles are laminated, and the outer surface of the layer made of polyester B has an average height The length is 50 Å or more, 200
Å or less, the surface protrusions with a maximum height of 1.1 times or more and 1.5 times or less of the average height are 10^3 pieces/mm^2 or more, 10
A polyester film for magnetic recording media formed at a rate of less than ^7 films/mm^2. (2) 0.001-1wt of polyester A and fine particles
% of polyester B added, the two are combined and coextruded into a sheet from a slit-shaped nozzle, and the sheet is cooled and solidified on a moving cooling body at a temperature of 5 to 40°C to form polyester A and polyester B. B is laminated with an unstretched sheet, the sheet is stretched biaxially, then re-stretched as necessary, and then heat-treated. The particle size before addition is 10 to 300 mμ, the thickness of the layer made of polyester B of the unstretched sheet is 5 times or more and 100 times or less the particle size of the added fine particles, and the stretching in the biaxial direction is uniaxial. A method for producing a polyester film for a magnetic recording medium, characterized in that the film is increased 2 to 4 times in a direction at a temperature of 70 to 150°C, and 3 to 5 times in a direction perpendicular to the direction at a temperature of 70 to 150°C.