JP2001312816A - Method and device for manufacturing magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the elongation defect of a magnetic recording medium in manufacture of the magnetic recording medium. SOLUTION: In a method for manufacturing the magnetic recording medium provided with a magnetic layer on a non-magnetic substrate, the non-magnetic substrate or the magnetic recording medium is treated in a temperature range of glass transition temperature ±30 deg.C in a heat treating stage Sa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium and a manufacturing apparatus used for the method. More specifically, a coating type magnetic recording medium having a magnetic layer made of a magnetic dispersion on a nonmagnetic support, or a metal magnetic thin film type magnetic recording medium having a magnetic layer made of a metal magnetic film on a nonmagnetic support For example, the present invention relates to a method of manufacturing a magnetic tape, a magnetic disk, and the like excellent in high-density recording and reproduction for an 8 mm video tape, a digital video tape recorder, and the like, and a manufacturing apparatus therefor.

[0002]

2. Description of the Related Art As a magnetic recording medium, a so-called coating type magnetic recording medium in which a magnetic dispersion composed of a magnetic powder and a binder is coated on a non-magnetic support has been widely used. In recent years, in response to demands for high-density magnetic recording in sound recording, video recording, information processing, and the like, a so-called metal magnetic thin film type in which a metal magnetic material such as a Co-Ni alloy is directly adhered to a nonmagnetic support by vacuum deposition or the like. Have been put to practical use.

[0003]

In the manufacturing process of both the coating type magnetic recording medium and the metal magnetic thin film type magnetic recording medium, specifically, the heat and tension in the manufacturing process are not uniform. In addition, strain accumulates in the magnetic layer, the non-magnetic support, and the like, resulting in poor shape such as elongation.

In particular, tape thinning due to high-density recording and miniaturization creates a disadvantageous condition for deterioration of the shape when subjected to the distortion, which is one of the factors mentioned above. No.

At present, it is judged whether the product is non-defective or defective according to the standard, and the product is shipped without any problem in terms of product quality, but there is a problem that the yield is extremely poor. In the conventional technology, the cause of the shape defect could not be grasped, and various methods, such as reducing the thickness unevenness by introducing a new technology in the coating process, have been tested, but have not been solved yet. Is the current situation. Under such circumstances, a new shape improvement technology has been desired.

The present invention has been made in view of the above circumstances, and provides a method of manufacturing a magnetic recording medium having an excellent shape without defects such as elongation and a manufacturing apparatus used in the method.

[0007]

According to the present invention, a non-magnetic support or a magnetic recording medium is subjected to a heat treatment in a temperature range of its glass transition point ± 30 ° C.

According to the present invention, when a non-magnetic support or a magnetic recording medium is heat-treated in a temperature range of its glass transition temperature ± 30 ° C., the heat shrinkage property of the non-magnetic support or the magnetic recording medium causes uniform heat shrinkage. As a result, the elongation defect of the magnetic recording medium is finally improved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A method for manufacturing a magnetic recording medium according to the present invention is a method for manufacturing a magnetic recording medium having a magnetic layer provided on a non-magnetic support. In a temperature range of ± 30 ° C. of glass transition point.

The tension x of the nonmagnetic support or the magnetic recording medium during the heat treatment is 1 gf <x per 10 mm width.
It is preferable to be within the range of ≦ 200 gf.

The heat treatment can be carried out by using a heat treatment apparatus having a heating roll and running a non-magnetic support or a magnetic recording medium on the heating roll.

The heat treatment is carried out by continuously moving the non-magnetic support or the magnetic recording medium on each of the heating rolls by using a heat treatment apparatus having two or more heating rolls whose temperature is raised stepwise. be able to.

As the magnetic recording medium of the present invention, a so-called coating type magnetic recording medium in which a magnetic layer made of a magnetic dispersion is provided on a non-magnetic support, can be applied. As the magnetic recording medium of the present invention, a so-called metal magnetic thin film type magnetic recording medium in which a magnetic layer made of a metal magnetic film is provided on a non-magnetic support can be applied.

An apparatus for manufacturing a magnetic recording medium according to the present invention comprises:
The non-magnetic support or a magnetic recording medium having a magnetic layer on the non-magnetic support is provided with a heat treatment means for performing a heat treatment in a temperature range of its glass transition point ± 30 ° C. Further, at the time of this heat treatment, the nonmagnetic support or the magnetic recording medium is
It is preferable to add a tension applying means for applying a tension x of 1 gf <x ≦ 200 gf per m width.

The heat treatment means may be composed of a heating roll and a nip roll, and a non-magnetic support or a magnetic recording medium may be passed between the two rolls and run on the heating roll.

[0016] The heat treatment means includes a set of a heating roll and a nip roll in two or more stages, and the temperature of each heating roll is set so as to become higher as it goes to a later stage so that the temperature rises in stages. It is also possible to adopt a configuration in which a non-magnetic support or a magnetic recording medium is sequentially passed between the heating roll and the nip roll of each stage and run on the heating roll.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, a description will be given of factors that cause deterioration of the shape of the magnetic recording medium. The general manufacturing process of a coating type magnetic recording medium is as follows. The non-magnetic support (tape) is sent to the magnetic dispersion application step, and the magnetic dispersion is applied to one surface of the non-magnetic support and dried to form a magnetic layer. The back layer is formed on the surface (so-called back surface), then subjected to a calendering treatment and a curing treatment, and cut into a predetermined width and length in a cutting step to produce a target magnetic recording medium.

The general manufacturing process of a metal magnetic thin film type magnetic recording medium is as follows. The non-magnetic support (tape) is sent to the deposition process, and a metal magnetic film is deposited on one surface,
Next, a protective film is formed on the metal magnetic film in a protective film forming step,
Further, a back layer is formed on the other surface (so-called back surface) of the non-magnetic support in the back layer coating step, and then cut into predetermined widths and lengths in the cutting step to produce a target magnetic recording medium.

In the above-described manufacturing process, a necessary tension acts on the tape because the tape runs in all the steps. In addition, various forces are applied to the tape, such as the heat required for drying in the coating process, the heat in the vapor deposition process, the heat and pressure in the calendering process, and the heat in the curing process. This has a significant effect, resulting in poor elongation of the tape.

In the present invention, a heat treatment is used as a method for uniformizing the distortion, that is, a method for improving poor elongation of the tape (a method for repairing a deteriorated shape due to so-called unevenness of heat and tension). . Furthermore, specifically, when a certain arbitrary temperature is applied, due to the heat shrinkage property of the tape,
This is based on the fact that the tape causes shrinkage, and the purpose of the heat treatment is to uniformly shrink the tape by heat.

FIG. 1 shows an example of an embodiment in which the present invention is applied to the manufacture of a coating type magnetic recording medium. The non-magnetic support (tape) 1 is supplied, and the magnetic dispersion liquid application step S _{11 is performed.}
A magnetic dispersion is applied to one surface of the non-magnetic support 1 and dried to form a magnetic layer. Next, the back layer coating step S ₁₂
Then, a back layer is applied and formed on the other surface (so-called back surface) of the nonmagnetic support 1. Then, calendered to smooth the magnetic layer in the calendering step S ₁₃ is performed, the curing process to ensure the durability of the magnetic layer in the subsequent curing treatment step S ₁₄ is performed. Thereafter, tape cutting step S _15, i.e. a magnetic recording medium a predetermined width, and cut into a length for producing a coating type magnetic recording medium of the dimensions of the object.

[0023] In this embodiment, in particular in FIG. 1, prior to entering the required step of the process S ₁₁ to S _15, or into the entire process S ₁₁ to S ₁₅ steps each for each before,
The heat treatment step Sa of the present invention described above is provided, and the heat treatment is performed on the magnetic recording medium having the nonmagnetic support or the magnetic layer in the heat treatment step Sa.

FIG. 2 shows another example of the embodiment in which the present invention is applied to the manufacture of a metal magnetic thin film type magnetic recording medium. A non-magnetic support (tape) 1 is supplied and a vapor deposition step S
_{At 21} , a metal magnetic film is deposited on one surface of the nonmagnetic support 1. Then, the protecting film is formed on the metal magnetic film with a film forming step S _22, further forming a back layer on the back layer coating step S ₂₃ on the other surface of the nonmagnetic support 1 (the so-called back surface).
After that, the tape, that is, the magnetic recording medium is cut into a predetermined width and length to produce a target metal magnetic thin film type magnetic recording medium.

In this embodiment, in particular, in FIG. 2, before entering a required one of the steps S _{21 to} S ₂₄ ,
Alternatively, before entering each of the steps S _{21 to} S ₂₄ , the above-described heat treatment step Sa of the present invention is provided, and in this heat treatment step Sa, a magnetic recording having a non-magnetic support or a magnetic layer is performed. The medium is heat treated.

The heat treatment step Sa is prior to entering the coating step S ₁₁ or the deposition process S ₂₁ as a specific example, or before the back layer coating step S _12, S _23, or prior to the cutting step S _15, S ₂₄ Can be arranged.

The heat treatment mechanism 10 used in the heat treatment step Sa according to the present embodiment is, for example, as shown in FIG. 3, a heating roll 11 composed of a metal roll or the like set to a required temperature, which will be described later, and a nip roll that is in contact with the heating roll 11. 12 A magnetic recording medium having a nonmagnetic support or a magnetic layer to be heat-treated, a so-called tape T, is heated by a heating roll 11.
Nip roll 12, running while contacting on the surface of the heating roll 11, heat-treated and thermally contracted.

In FIG. 3, the number of heat treatment steps is one. However, a heat treatment mechanism having two or more heat treatment steps may be employed. FIG. 4 shows a two-stage heat treatment means 101 and 102 comprising a heating roll 11 and a nip roll 12, respectively.
Is shown. 13 is both heat treatment means 1
Shows a guide roll arranged between 01 and 102. For example, a magnetic recording medium having a nonmagnetic support or a magnetic layer to be heat-treated, that is, a so-called tape T, passes between the first-stage heating roll 11 and the nip roll and travels while contacting the surface of the heating roll 11 for one stage. The second heat treatment is performed, followed by passing through the space between the second-stage heating roll 11 and the nip roll and in contact with the surface of the second heating roll 11, performing the second-stage heat treatment, and thermally shrinking.

The following can be said about the heat shrinkage of the tape. (1) The application of temperature causes thermal shrinkage of the tape.
When the distortion under the condition becomes zero, the tape contraction is completed. (2) The amount of contraction depends on the amount of distortion. (3) The heat shrinkage rate is proportional to the amount of heat shrinkage, and a portion having a large strain (a portion having a large elongation) changes faster and greatly than a portion having a small strain. Regardless of the magnitude of the strain before the heat treatment, after the heat treatment, the shrinkage is completed and becomes uniform when the strain under the condition becomes zero.

Next, the heat treatment conditions will be described. The processing temperature is a temperature at which the tape T shrinks, and more efficiently within a temperature range of ± 30 ° C. based on the glass transition point of the tape (nonmagnetic support, magnetic recording medium). Heat treatment is performed on the tape within the glass transition point ± 30 ° C. If the treatment temperature is lower than the above-mentioned temperature range, the amount of heat shrinkage is too small to improve the shape, or the change takes a very long time. Conversely, if the processing temperature is higher than the above temperature range, the heat shrinkage rate is too fast,
It is easy to cause wrinkles due to heat shrinkage. Preferably, the temperature range is the glass transition point of the tape ± 20 ° C.

Here, a non-magnetic support or a magnetic recording medium,
The so-called glass transition point of a tape is defined as follows. As shown in FIG. 5, the horizontal axis represents the reciprocal of the absolute temperature (1/1).
T), the vertical axis is the natural logarithm (l) of the heat shrinkage rate (k) of the tape.
_In the Arrheniusput _n ), the temperature at the intersection of the two approximate straight lines (a) and (b) is defined as the glass transition point of the tape.

Heat shrink speed k (= ΔL / Δt = − (L ₂ −
(L ₁ ) / (t ₂ −t ₁ ) [μm / min]) is obtained by a heat shrinkage change amount / time when the tape is arbitrarily set using a thermal analyzer or the like (FIG. 6). In other words, FIG. 5 plots the so-called slope of the heat shrinkage change / time of FIG. 6 at each temperature, and sets the intersection of two approximate straight lines (a) and (b) as the glass of the tape. It is a transition point.

To efficiently apply heat to the tape, FIG.
As shown in FIG. 4, it is effective to bring the tape T into direct contact with the heating roll 11 having a high thermal conductivity such as a metal roll. Further, in order to bring the tape T into uniform contact with the heating roll 11, it is preferable to provide a nip roll 12 so as to suppress the floating of the tape T.

Further, more preferably, in order to avoid thermal shrinkage and wrinkles due to a rapid rise in temperature, the heating section is constituted by two or more stages, and the temperature is gradually increased toward the rear stage, for example, the two-stage structure shown in FIG. In this case, the first stage means 101 is used as preheating, and the second stage means 102 is used for the main heat treatment.
As described above, by heating the tape under a stepwise temperature increasing condition, the problem of heat shrinkage wrinkles can be improved.

The tension of the tape during the heat treatment is preferably low from the viewpoint of shrinking. If the tension is high, it will turn into elongation, and quality concerns will increase. However, a certain degree of tension is required for running the tape. For this reason, 10m of tape
The tension x per m width is desirably in the range of more than 1 gf and 200 gf or less (1 gf <x ≦ 200 gf). If it is less than 1 gf, it will hinder tape running,
If it exceeds 200 gf, skew occurs.

EXAMPLES Next, specific examples of the present invention will be described, but the present invention is not limited to the following examples.

A sample magnetic tape is manufactured. Examples 1-34 and Comparative Examples 1-27 A magnetic dispersion is applied to a non-magnetic support with a gravure coater. Next, the back layer dispersion is applied with a gravure coater to a thickness of 0.6 μm. After performing the calendering treatment and the curing treatment, heat treatment was performed under the conditions shown in Tables 1 to 4, and thereafter, the sheet was cut into a width of 8 mm to produce a coating type sample magnetic tape (8 mm video tape). The conditions for producing the coating type sample magnetic tape are as follows.

Non-magnetic support Polyethylene terephthalate (PET) 12 μm thick, 130 mm width Polyethylene naphthalate (PEN) 8 μm thickness, 130 mm width Polyamide 5 μm thickness, 130 mm width Composition of magnetic layer magnetic dispersion 100 parts by weight of metal magnetic powder (Fe) (Specific surface area BET value = 54.0 m ² / g) Binder Polyester polyurethane 40 parts by weight (trade name N-2304, manufactured by Nippon Polyurethane Co.) Additive α-Al ₂ O ₃ 10 parts by weight (trade name AKP-30, Sumitomo) Solvent Methyl ethyl ketone 100 parts by weight Toluene 100 parts by weight Sand mill dispersion Filtration Average particle diameter 3.5 μm Coating thickness 3.5 μm Feeding speed 150 m / min Back coat layer dispersion Non-magnetic powder carbon black 100 parts by weight (trade name RAVEN-) 1255, Colombi Binder Polyester polyurethane 25 parts by weight (trade name: UR-8300, manufactured by Toyobo Co., Ltd.) Binder MG-0202 50 parts by weight Solvent Methyl ethyl ketone 330 parts by weight Toluene 330 parts by weight Ball mill dispersion 48 hours dispersion Filtration Average particle size 1.5 μm Coating thickness 0.6 μm Feed speed 150 m / min Calendering temperature 100 ° C. Feed speed 150 m / min Curing temperature 60 ° C. Time 50 hours Heat treatment Feed speed 150 m / min Temperature Tables 1 to 4 described Cutting process Slit width 8 mm

Examples 35 to 52 and Comparative Examples 28 to 30 First, a metal magnetic film was formed on a nonmagnetic support by a vacuum evaporation method using a vacuum evaporation apparatus, and then a carbon protective film was formed by a sputtering method. did. Next, the back coat layer was applied with a gravure coater, heat-treated under the conditions shown in Table 5, and then cut to a width of 8 mm to produce a metal thin film type sample magnetic tape (8 mm video tape). The conditions for producing the metal thin film type sample magnetic tape are as follows.

Non-magnetic support Polyethylene terephthalate (PET) 12 μm thick, 130 mm width Polyethylene naphthalate (PEN) 8 μm thickness, 130 mm width Polyamide 5 μm thickness, 130 mm width Metal magnetic film Alloy 80% by weight Ni 20% by weight Incident angle 45 to 45% 90 degrees feed rate 25 m / min magnetic layer thickness 200nm oxygen introduction amount 250 cc / min during deposition vacuum 7 × 10 ^-2 Pa carbon protective film sputtering conditions scheme DC magnetron sputter target material carbon used gas argon background vacuum degree 4 × 10 ^{- 3} Pa degree of vacuum during deposition 2Pa feed rate 0.15 m / sec protection MakumakuAtsu 10nm backcoat layer dispersion nonmagnetic powder 100 parts by weight of carbon black (trade name RAVEN-1255, manufactured by Columbia Yang carbon Co.) binder Po Ester polyurethane 25 parts by weight (product name: UR-8300, manufactured by Toyobo Co., Ltd.) Binder MG-0202 50 parts by weight Solvent Methyl ethyl ketone 330 parts by weight Toluene 330 parts by weight Ball mill dispersion 48 hours dispersion Filtration Average particle size 1.5 μm Coating thickness 0.6 μm Feed speed 150m / min Heat treatment Feed speed 150m / min Temperature Table 5 Cutting process Slit width 8mm

The sample magnetic tapes which had not been subjected to the heat treatment under the conventional conditions were the same as in Comparative Examples 9, 18, 27, 28, and 2.
9 and 30. The glass transition point of each condition sample was measured and calculated using a thermal analyzer. It is also described in Tables 1 to 5.

The following items were measured for each of the sample magnetic tapes described above, and good and distortion were determined. The results are also shown in Tables 1 to 5.・ Elongation inspection Visual appearance inspection was conducted. Mark the elongation level as ○ (good),
Evaluated in three stages: △ (somewhat good), × (not good). In this case, if the mark is ○ or the mark is 合格, it is judged as pass.・ Wrinkle inspection Visual inspection is performed. Mark the wrinkle level as ○ (good),
Evaluated in three stages: △ (somewhat good), × (not good). Here, if the mark is ○, it passes.・ Skew Record the color bar signal, leave it at 60 ° C for 24 hours, and measure the bending of the color bar during reproduction. If it was 10 μs or less, it was judged as a good o mark, and if it was 10 μs or more, it was a rejection x mark. -Comprehensive Judgment When all the above items passed, the mark was "O", and when any of them was not satisfied, the mark was "X". -When a two-stage heating roll was used, the temperature of the second-stage heating roll was higher than that of the first stage. The glass transition point (° C.) in Tables 1 to 5 is the glass transition point of the total magnetic tape.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[0047]

[Table 5]

According to the examples shown in Tables 1 to 4, the heat treatment was performed within the range of ± 30 ° C. of the glass transition point, and the tension during the heat treatment was more than 1 gf per 10 mm width to 200 g.
By setting the ratio to f or less, it is possible to improve the elongation shape of the magnetic tape without impairing the skew characteristics and wrinkle shape.

In the above example, the present invention was applied to the manufacture of a magnetic tape, but can also be applied to the manufacture of other magnetic disks.

[0050]

According to the method of manufacturing a magnetic recording medium according to the present invention, it is possible to improve the elongation defect of the magnetic recording medium without impairing the skew characteristics and the wrinkled shape. It is possible to manufacture a magnetic recording medium having an excellent appearance and a particularly excellent production yield.

That is, by heat-treating the non-magnetic support or the magnetic recording medium in a temperature range of ± 30 ° C. of its glass transition point, the non-magnetic support or the magnetic recording medium is uniformly thermally shrunk by the heat shrinkage characteristic of the non-magnetic support or the magnetic recording medium. It is possible to eliminate heat shrinkage wrinkles and improve poor elongation.

Further, by setting the tension x of the non-magnetic support or the magnetic recording medium at the time of the heat treatment to 1 gf <x <200 gf, it is possible to perform good tape running without turning into elongation and to reduce poor elongation. Be improved.

When the heat treatment is carried out with two or more heating rolls in a stepwise heating condition, a sharp rise in temperature is suppressed.
The occurrence of heat shrinkage wrinkles can be suppressed more reliably.
According to the apparatus for manufacturing a magnetic recording medium according to the present invention, it is possible to manufacture a high-quality magnetic recording medium free from stretch shape defects.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a coating type magnetic recording medium according to the present invention.

FIG. 2 is a manufacturing process diagram of a metal magnetic thin film type magnetic recording medium according to the present invention.

FIG. 3 is a configuration diagram showing one embodiment of a heat treatment apparatus according to the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the heat treatment apparatus according to the present invention.

FIG. 5 is a graph for explaining the definition of a glass transition point.

FIG. 6 is a graph for explaining a heat shrink speed.

[Explanation of symbols]

1 ‥‥ non-magnetic _{support, S 11 ~S 15, S 21} ~S 24 ‥‥ step, 10 ‥‥ heat treatment mechanism, 101 and 102 ‥‥ thermal treatment means, 11 ‥‥ heated roll, 12 ‥‥ nip rolls 13
‥‥ Guide roll

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukihiko Ichikawa 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Takashi Ishioka 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo No. Sony Corporation F-term (reference) 5D112 AA02 AA21 GB01 KK03

Claims (8)

[Claims] 1. A method for manufacturing a magnetic recording medium comprising a magnetic layer provided on a non-magnetic support, wherein the non-magnetic support or the magnetic recording medium has a glass transition point of ± 30 ° C.
A method for producing a magnetic recording medium, comprising a step of performing a heat treatment in a temperature range of: 2. The magnetic recording medium according to claim 1, wherein the tension x of the nonmagnetic support or the magnetic recording medium during the heat treatment is in the range of 1 gf <x ≦ 200 gf per 10 mm width. Method. 3. The method according to claim 1, wherein the heat treatment is performed using a heat treatment apparatus having a heating roll. 4. The method for manufacturing a magnetic recording medium according to claim 1, wherein the heat treatment is performed using a heat treatment apparatus having two or more heating rolls whose temperature is increased stepwise. 5. The method according to claim 1, wherein the magnetic recording medium is a magnetic recording medium provided with a magnetic layer made of a magnetic dispersion. 6. The method according to claim 1, wherein the magnetic recording medium is a magnetic recording medium provided with a magnetic layer made of a metal magnetic film. 7. A heat treatment means for heat-treating a non-magnetic support or a magnetic recording medium having a magnetic layer on the non-magnetic support in a temperature range of a glass transition point ± 30 ° C. Equipment for manufacturing magnetic recording media. 8. The non-magnetic support or the magnetic recording medium at the time of the heat treatment, wherein 1 gf <x ≦ 2 per 10 mm width.
8. The apparatus for manufacturing a magnetic recording medium according to claim 7, further comprising tension applying means for applying a tension x of 00 gf.