JPH09235394A - Polyester film for magnetic recording medium and polyester film therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a base film for analog and digital video tapes excellent in productivity as the base film and further quality characteristics of the video tapes having a ferromagnetic metallic thin film formed thereon. SOLUTION: This polyester film for magnetic recording media is used by forming a ferromagnetic metallic thin film on the surface A on one side. The value of SRa on the surface B on the opposite side is 10-50nm and the polyester film has 5-60 protrusions having 0.54-0.81μm height/100cm<2> and <=10 protrusions having >=0.81μm height/100cm<2> on the surface B.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a magnetic recording medium,
Particularly, it relates to a polyester film suitable as a base film for a ferromagnetic metal thin film type magnetic recording medium.

[0002]

2. Description of the Related Art A base film for a magnetic recording medium, particularly for a ferromagnetic metal thin film, comprises a polyester film, a discontinuous film adhered to at least one side of the film, and fine particles present in and on the film. A composite film in which a polyester film (for example, Japanese Patent Publication No. 62-30105), a layer A made of a thermoplastic resin, and a layer B made of a thermoplastic resin containing fine particles are laminated (for example, Japanese Patent Publication No. 1-263337). Publication, Japanese Patent Publication 1-26
No. 338, Japanese Patent Publication No. 1-1218, Japanese Patent Publication No. 1
No. 2224), etc. are known.

[0003]

As a base film for forming a ferromagnetic metal thin film for a high band 8 mm video tape and a consumer digital video tape which has recently been put into practical use by vacuum deposition, the above-mentioned high density is used. Although it gives magnetic recording characteristics, it is not suitable for mass production because it has poor handling properties during base film production and video tape running. In addition, the above-mentioned technique forms a video tape by vacuum-depositing a ferromagnetic metal on the outer surface of the layer A. However, there is an inverse relationship between the productivity of the base film and the dropout quality characteristic of the video tape on which the ferromagnetic metal thin film is formed. There is a correlation,
There was no choice but to make a compromise between base film productivity and vapor deposition tape productivity.

[0004]

In order to solve such a problem, the present invention has the following arrangement.

That is, the present invention is a polyester film which is used by providing a ferromagnetic metal thin film layer on the surface A on one side, and the SRa value on the surface B on the opposite side is 10 to 50 nm.
The number of protrusions having a height of 0.54 to 0.81 μm on the surface B is 5 to 60/100 cm ² , and the height is 0.81 μm.
A polyester film for a magnetic recording medium, characterized in that the number of projections of m or more is 10/100 cm ² or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the present invention may be any polyester which can be a high-strength film by molecular orientation, but polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable. Eighty percent or more of the constituent components are ethylene terephthalate, polyethylene terephthalate which is ethylene naphthalate, and polyethylene naphthalate. Examples of the polyester copolymer components other than ethylene terephthalate and ethylene naphthalate include diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, diol components such as 1,4-cyclohexanedimethanol, adipic acid, Dicarboxylic acid components such as sebacic acid, phthalic acid, isophthalic acid and 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, p
-Oxyethoxybenzoic acid and the like.

Further, the above-mentioned polyester contains at least one of an alkali metal salt derivative of sulfonic acid which is non-reactive with the polyester and polyalkylene glycol which is substantially insoluble in the polyester in an amount not exceeding 5% by weight. You may mix in.

The SRa value of one surface A of the film of the present invention on which the ferromagnetic metal thin film layer is provided is preferably 2 to 6 nm, more preferably 2 to 5 nm. The SRa value of the other surface B is 10 to 50 nm, preferably 1
It is 0 to 30 nm.

If the SRa value of the surface A is less than 2 nm,
The ferromagnetic thin film formed on the outer side of the surface A becomes too smooth, and the ferromagnetic thin film is worn by the video head during recording and reproduction in the digital video tape recorder after forming a video tape, which is not preferable. S outside the layer A
When the Ra value exceeds 6 nm, the ferromagnetic thin film formed on the outer side of the surface A becomes too rough and the electromagnetic conversion characteristics of the video tape deteriorate, which is not preferable.

When the SRa value of the surface B is less than 10 nm, the slip of the surface of the present film B is deteriorated, and it is difficult to wind the film neatly in the production of the present film, which makes stable mass production impossible, which is not preferable. . Surface B
When the SRa value of is more than 50 nm, the shape transfer through the inside of the film is caused, and the surface A is undulated,
This is not desirable because it causes fluctuations in the playback output of the video tape.

The surface B has a height of 0.54 to 0.81.
There are 5-60 protrusions of 100 μm / 100 cm ² , and
The number of protrusions having a height of 0.81 μm or more must be 10/100 cm ² or less. More preferably, height 0.54
10 to 50 protrusions having a diameter of 0.81 μm / 100 cm ² , and 7 protrusions having a height of 0.81 μm or more
It is 0 cm ² or less.

When the number of protrusions having a surface B height of 0.54 to 0.81 μm is less than 5/100 cm ² , a processing product for producing a video tape from a jumbo-shaped film produced from a video tape. As a result, when slitting a roll-shaped product having a predetermined width, air leakage between the film B surface and the A surface becomes defective, and the film suddenly shifts from the end surface of the product during slitting, and the film can be neatly rolled. It will become difficult and stable mass production will not be possible.

When the number of protrusions having a height of 0.54 to 0.81 μm on the surface B is more than 60/100 cm ² , and the number of protrusions having a height of 0.81 μm or more is more than 10/100 cm ^2. , When providing a ferromagnetic thin film by vacuum deposition,
The coarse protrusions on the surface B come into contact with the cooling can in the vacuum deposition process, deform the film, and deform the outside of the surface A, resulting in coarse defects on the surface of the magnetic layer formed on the surface A, resulting in a drop of the video tape. It is not preferable because it leads to increase in out.

The film of the present invention is preferable because the effect of the present invention is more remarkably exhibited when it is used for an analog or digital recording type magnetic tape for video.

Although a ferromagnetic metal thin film layer is provided on the surface A, a known metal thin film can be used and is not particularly limited, and is made of a ferromagnetic material such as iron, cobalt, nickel or an alloy thereof. Is preferred. The thickness of the metal thin film layer is preferably 100 to 300 nm.

On the surface A, fine particles of preferably 5 to 30 nm, more preferably 8 to 30 nm, preferably 0.1.
5 to 10.0% by weight, more preferably 0.6 to 8.0% by weight of a coating layer made of an organic compound is formed, or a polyester layer forming a surface A when the coating layer is not formed Preferably 10 to 50 nm, more preferably 20 to 40 nm fine particles, preferably 0.01 to 1.0 wt%, more preferably 0.02 to
It is desirable to contain 0.8% by weight.

The fine particles include silica, calcium carbonate, alumina, polyacrylic acid spheres and polystyrene spheres as inorganic compounds, and the organic compounds include polyvinyl alcohol, tragacanth gum, casein, gelatin, cellulose derivatives, water-soluble polyester, polyurethane and the like. Polar polymers can be used, and blends of these are applicable, but are not limited thereto.

A coating layer containing a lubricant may be formed on the surface B. Silicone, wax, silane coupling agent can be used as a lubricant, and polyvinyl alcohol, tragacanth rubber, casein, gelatin, a cellulose derivative, a water-soluble polyester, a polar polymer such as polyurethane can be used as a coating layer binder component, and a blended product thereof can also be used. Applicable, but not limited to. As fine particles, silica, calcium carbonate, alumina, polyacrylic acid spheres, polystyrene spheres, etc. may be contained in the present coating layer.

The surface protrusions on the surface B may be formed by providing fine particles in the coating layer, or by forming various kinds of inert solid fine particles in the polyester layer forming the surface B. Is also good. In that case, the particle size is 50
˜1900 nm, preferably 100 to 1300 nm, and the addition amount is 0.05 to 0.9% by weight, preferably 0.08 to 0.5%. As the fine particles, calcium carbonate, silica, alumina, polystyrene spheres and the like can be used, but the fine particles are not limited to these.

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

The polyester film of the present invention is A / B by using the coextrusion technique in the usual plastic film manufacturing process consisting of melting, molding, biaxial stretching and heat setting.
It can be produced by producing a film in which layers are laminated or by coating a polyester film with fine particles by coating. However, providing fine particles by coating complicates the production process and economically preferably uses a co-extrusion technique. In the present invention, a production method using the co-extrusion technique will be described.

The raw material for layer A in which the contained particles are removed as much as possible and the raw material for layer B in which the fine particles are positively contained are melt-extruded, and cooled and solidified on a casting drum to obtain an unstretched film sheet. It is obtained by uniaxially stretching, adjusting, coating and drying a desired coating liquid for forming the above-mentioned coating layer, and then stretching and orienting in a direction orthogonal to the uniaxially stretching direction and heat-setting. At the time of melt extrusion, the layer B side melt is preferably passed through a high-precision filter having a performance near 3 μm cut (5% cut diameter).

The layer A contains fine particles inside,
A coating layer may be formed on the outer surface, or fine particles may be contained in the coating layer and the coating may be formed on the outer surface.

The biaxial stretching can be performed by, for example, a sequential biaxial stretching method or a simultaneous biaxial stretching method. If desired, the film is stretched again in the vertical or horizontal direction or in the vertical and horizontal directions before heat setting, and then mechanically. It is also possible to use a so-called reinforced type with increased strength.

The method for forming the coating layer is as described above.
At the stage where the stretching in the axial direction has been completed, a desired coating liquid is applied onto the base film. As a coating method, any of a doctor blade method, a gravure method, a reverse roll method, and a metering bar method may be used.

The polyester film of the present invention is suitable as a base film for a magnetic recording medium, since it gives excellent results when used particularly in analog and digital video tape applications.

[0027]

[Measurement method]

(1) SRa optical stylus type made by Kosaka Laboratory (critical angle focus error detection method)
Was measured using a three-dimensional roughness meter (ET-30HK).

The SRa value means a center line surface average roughness corresponding to JIS Ra.

The test piece was subjected to Al vapor deposition on the measurement surface.

The measurement direction was the width direction, the cutoff value was 0.08 mm, the measurement length was 0.1 to 0.25 mm, the feed pitch was 0.2 μm, the measurement speed was 20 μm / s, and the number of measurement was 100. . The unit was nm.

(2) Surface height 0.54 to 0.81 μm
No. of protrusions, and number of protrusions having a height of 0.81 μm or more Observe and mark foreign matters in the film under polarized light with an optical microscope (observation magnification: 100 times). Marked B
The height of foreign matter on the outer surface of the layer is checked by the number of rings of interference fringes using a multiple interference microscope, and the number of projections of double rings per 100 cm ² is determined, and the number of projections of triple rings or more is calculated, and the height is 0. ．
Number of protrusions (H2) of 54 to 0.81 μm, height 0.81
The number of protrusions is not less than μm (H3 ≦).

Wavelength used: 546 nm.

(3) Film winding shape The wide film obtained by the film-forming machine was used with a slitter for 50 minutes.
It was slit into a length of about 0 mm and a length of about 9000 m, and wound into a roll on a plastic core. The appearance of the roll after winding was observed and evaluated.

⊚: The winding was very clean. ◯: It was wound beautifully. X: Many wrinkles were contained. XX: The end face jumped out and could be wound.

(4) The characteristics of the magnetic tape in which the ferromagnetic thin film is provided on the film of the present invention are measured by using a commercially available Hi8 type 8 mm video tape recorder. The video S / N ratio and dropout (DO) were obtained as electromagnetic conversion characteristics.
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. Video S / N ratio is standard decibel (dB) of commercially available standard Hi8 ME tape.
And comparatively measured. For dropout, a reproduction signal attenuation of −16 dB or more and a length of 15 μsec or more was obtained. The S / N ratio and the dropout were examined for the initial characteristics after tape production and the characteristics after 100 times of running.

[0036]

Next, the present invention will be described based on examples.

Example 1 Polyethylene terephthalate containing substantially no inactive particles, raw material A containing 0.1% by weight of silica having an average particle size of 90 nm, and polyethylene terephthalate containing substantially no inactive particles and average particles A raw material B containing 0.20% by weight of calcium carbonate having a diameter of 300 nm was coextruded at a thickness ratio of 1: 1 and longitudinally stretched at 110 ° C. to 3.0 times by a roll stretching method.

In the step after the longitudinal stretching, the following aqueous solution was applied to the outside of layer A.

Outside of layer A: methyl cellulose 0.10% by weight water-soluble polyester 0.30% by weight aminoethylsilane coupling agent 0.01% by weight average particle size 10 nm ultrafine silica 0.03% by weight solid content concentration 20 mg / m ² After that, it was stretched 3.3 times in the transverse direction at 110 ° C. with a stenter and heat-treated at 200 ° C. to obtain a composite polyester film having a thickness of 9.8 μm.

The raw material B was passed through a high-precision filter capable of cutting foreign matter of 3 μm.

A cobalt / nickel (9/1) thin film of 110 n was formed on the surface A of this polyester film by vacuum deposition.
m. Subsequently, a back coat layer composed of carbon black, polyurethane, and silicone was added to 400n.
m, slit by slitter to a width of 8 mm and wound on a reel to prepare a magnetic tape.

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

Example 2 In the production of the base film of Example 1, the average particle size of silica contained in the raw material A was set to 60 nm. The extrusion amount was reduced, and otherwise the thickness was 6.3 in the same manner as in Example 1.
A μm composite polyester film was obtained.

A magnetic tape was prepared in the same manner. However, a cobalt thin film was provided by vacuum evaporation. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.

Example 3 In the production of the base film of Example 2, the polyethylene terephthalate was changed to polyethylene-2,6-naphthalate, the longitudinal stretching temperature and the ratio were set to 5.0 times at 135 ° C., and the transverse stretching temperature and the ratio were adjusted. The temperature was adjusted to 135 ° C. and 6.0 times, and further, the film was laterally stretched 1.2 times at 160 ° C. and heat-treated at 200 ° C. to obtain a composite polyester film having a thickness of 4.5 μm.

A magnetic tape was prepared in the same manner as in Example 2 except for the above. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.

Example 4 In the production of the base film of Example 2, the content of silica contained in the raw material A was 0.04%.

Others are the same as in Example 2 and the thickness is 6.3.
A μm composite polyester film was obtained. A magnetic tape was prepared in the same manner. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.

Example 5 In the production of the base film of Example 2, the average particle size of silica contained in the raw material A was 200 nm, and the content was 0.1.
It was set to 5% by weight.

Others are the same as in the second embodiment, and the thickness is 6.3.
A μm composite polyester film was obtained. A magnetic tape was prepared in the same manner. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.

[0051]

[Comparative example]

Comparative Example 1 In the production of the base film of Example 2, the content of calcium carbonate contained in the raw material B was 0.04%.

Others are the same as in Example 2 and the thickness is 6.3.
A μm composite polyester film was obtained. The winding shape of the obtained film was very bad because of tight wrinkles and the film product could not be put into the vapor deposition process. The properties of the obtained composite polyester film are shown in Table 1.

Comparative Example 2 In the production of the base film of Example 2, the content of calcium carbonate contained in the raw material B was set to 0.5%.

Others are the same as in the second embodiment, and the thickness is 6.3.
A μm composite polyester film was obtained. A magnetic tape was prepared in the same manner. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 3 In the production of the base film of Example 2, the melt of the raw material B was passed through a high precision filter capable of cutting foreign matter of 1 μm.

Others are the same as the second embodiment, and the thickness is 6.3.
A μm composite polyester film was obtained. When the obtained film was slit, the film was abruptly displaced from the end face of the product during slitting and could not be wound neatly, so that the film product could not be put into the vapor deposition step. The properties of the obtained composite polyester film are shown in Table 1.

Comparative Example 4 In the production of the base film of Example 1, the average particle diameter of calcium carbonate contained in the raw material B was changed to 2.0 μm. Otherwise in the same manner as in Example 1, a 9.8 μm thick composite polyester film was obtained. A magnetic tape was prepared in the same manner. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 5 In the production of the base film of Example 1, the melt of the raw material B was passed through a high precision filter capable of cutting foreign matter of 5 μm. Others are the same as in Example 1 and the thickness is 9.8 μm.
A composite polyester film of m was obtained. A magnetic tape was prepared in the same manner. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.

[0059]

[Table 1]

[0060]

As is clear from the characteristics shown in Table 1, the polyester film of the present invention has excellent productivity as a base film and also has excellent quality characteristics of a video tape on which a ferromagnetic metal thin film is formed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location // C08L 67:02

Claims (4)

[Claims] 1. A polyester film used with a ferromagnetic metal thin film layer provided on one surface A, the opposite surface B having an SRa value of 10 to 50 nm, and a surface B height of 0.54 to. The number of protrusions of 0.81 μm is 5 to 60/100 cm ² , and the number of protrusions of height 0.81 μm or more is 1
A polyester film for a magnetic recording medium, characterized in that the number is 0/100 cm ² or less. 2. The polyester film for a magnetic recording medium according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. 3. The polyester film for a magnetic recording medium according to claim 1, which is used for an analog or digital recording type video cassette recorder tape. 4. A magnetic recording medium comprising a ferromagnetic metal thin film layer on one surface A of the polyester film according to claim 1.