JP3533679B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly to a method for treating a surface of a magnetic layer. 2. Description of the Related Art Generally, magnetic tapes such as audio tapes and video tapes are prepared by dispersing and kneading a ferromagnetic powder, a binder and various additives in an organic solvent on a non-magnetic support. A magnetic layer is formed by coating. A so-called coating type magnetic tape or a magnetic layer is formed by directly applying a metallic magnetic material on a non-magnetic support by a vacuum thin film forming technique such as a vacuum evaporation method. A so-called metal thin film type magnetic tape is known. [0003] In these magnetic tapes, the magnetic layer is formed by the coating technique and the vacuum thin film forming technique as described above, but in each case, the magnetic layer is not formed completely smooth, and some protrusions are formed on the surface. Usually, it is formed by attaching a foreign substance to a surface or forming a foreign substance. However, if the magnetic layer is in sliding contact with the magnetic head in a state where the surface has defects such as protrusions and deposits, the surface protrusions and deposits are sheared and broken down to generate fine wear powder. It is interposed between the magnetic tape and the magnetic head. If abrasion powder is present between the magnetic tape and the head, the abrasion powder causes dropout. For example, in a VTR, image quality is degraded, sound skips, and the like. And even recording / reproduction becomes impossible. Therefore, when producing a magnetic tape, a magnetic layer is formed on a non-magnetic support, cut into a predetermined tape width, and a lapping tape is slid on the surface of the magnetic layer to form surface protrusions. A surface treatment for grinding and removing the kimono is performed. That is, the magnetic tape and the wrapping tape cut to a predetermined tape width are arranged so that the magnetic layer side and the abrasive layer side face each other, and the contact roll is pressed from the back side of the wrapping tape. The magnetic layer and the abrasive layer are brought into contact. In this state, when the magnetic tape and the wrapping tape run in opposite directions,
The abrasive layer comes into sliding contact with the surface of the magnetic layer, and the polishing effect causes the surface protrusions and deposits to be removed by grinding. Such a surface treatment is generally performed under the following setting conditions. [0006] Three-dimensional center line roughness SR of wrapping tape
a: 300 to 1000 nm Holding angle θ of the raw tape against the contact roll θ: 50
~ 180 ° Surface pressure between magnetic tape and wrapping tape: 0.25-
1.2 g / mm ² Tape tension applied to magnetic tape in surface treatment unit: 2
The running speed of the magnetic tape is 400 to 600 m / min. [0007] The above-mentioned surface treatment reduces defects such as protrusions and deposits on the surface of the magnetic layer. It may be repeatedly performed many times in order to surely remove by grinding. However, when the above surface treatment is repeatedly performed, the polishing effect of the wrapping tape gradually decreases. Then, at a certain point, the polishing effect reaches saturation, and even if the surface treatment is further performed, the defect is not removed any more. This is because the ground material scattered and ground in each processing step adheres to the surface of the magnetic layer again,
This is because the data is accumulated every time the number of processes is followed. Further, the adhered ground material reduces the polishing effect of the wrapping tape and acts to scrape off the binder and the lubricant between the surface of the magnetic layer and the wrapping tape which are in sliding contact with each other. Decreases durability. Therefore, the number of times of the surface treatment is naturally limited, and the surface treatment cannot be performed with the number of times sufficient to sufficiently remove the defect. Further, the reattached defect induces a dropout in the completed magnetic tape and causes a deterioration in recording / reproducing characteristics. Therefore, in order to manufacture a magnetic tape of higher quality, it can be said that it is indispensable to avoid the adverse effect of the adhered abrasive during the surface treatment. Therefore, the present invention has been proposed in view of such a conventional situation, and a surface treatment can be performed without being adversely affected by the adhesion of a ground object. It is an object of the present invention to provide a method of manufacturing a magnetic recording medium that can manufacture a magnetic tape having no surface problems and excellent surface properties and durability. Means for Solving the Problems As a result of diligent studies conducted by the present inventors to achieve the above object, in addition to the conventional surface treatment, a wrapping tape was applied to a magnetic tape at a low surface pressure. In order to obtain the knowledge that the soft lapping process in which sliding contact is performed, the soft lapping process captures and removes the adhered grind, thereby enabling the surface treatment to be performed without being adversely affected by the adherence of the grind. Reached. The present invention has been completed on the basis of these findings, and has a magnetic layer formed on a nonmagnetic support.
The surface of the magnetic layer of the magnetic tape with wrapping tape
The method of manufacturing a magnetic recording medium to be processed, on first the latch <br/> ping tape surface pressure of 0.25~1.2g / mm ²
Serial by sliding contact with the magnetic tape surface of the magnetic layer subjected to hard wrapping, then wrapping tape 0.1-0.2
A soft lapping process is performed by sliding the magnetic tape on the surface of the magnetic layer at a surface pressure of g / mm ² . When a hard lapping treatment is performed by bringing a wrapping tape into sliding contact with the surface of the magnetic layer formed on the nonmagnetic support at a surface pressure of 0.25 to 1.2 g / mm ² , the polishing is performed. By this effect, surface protrusions and deposits on the surface of the magnetic layer are ground. Here, a part of the ground material is separated from the magnetic layer and removed as it is, but the other part is scattered and adheres again to the surface of the magnetic layer. Subsequently, a soft lapping treatment is performed by bringing a lapping tape into sliding contact with the surface of the magnetic layer subjected to the hard lapping treatment at a surface pressure of 0.1 to 0.2 g / mm ² . The grind re-adhered to the layer surface is captured by the soft processing wrapping tape and removed. When such hard wrapping and soft lapping are alternately repeated, the ground material adhering to the surface of the magnetic layer during the hard wrapping is always captured and removed by the next soft lapping.
At the time of the next hard lapping treatment, no ground material is attached to the surface of the magnetic layer. Therefore, the surface treatment can be performed without causing the grinding material to accumulate on the surface of the magnetic layer and reduce the polishing effect of the wrapping tape, or the binder or lubricant on the magnetic layer surface being scraped off by the attached grinding material. Therefore, a magnetic tape having no surface protrusions and deposits on the magnetic layer and having excellent surface properties and durability can be obtained. Preferred embodiments of the present invention will be described with reference to the drawings. To manufacture a magnetic tape, a magnetic layer is formed on a non-magnetic support and cut to a predetermined tape width. When a coating type magnetic tape is produced, for example, a ferromagnetic powder and a binder are dispersed and kneaded in an organic solvent to prepare a magnetic coating, and the magnetic coating is applied to a non-magnetic support. It is formed by coating and drying. Here, any of conventionally known ferromagnetic powders, binders and organic solvents can be used. For example, as magnetic powder, γ-Fe ₂ O
_3, the ferromagnetic iron oxide particles such as cobalt coating gamma-Fe ₂ O _3, ferromagnetic chromium dioxide based particles, Fe, Co, ferromagnetic metallic particles made of a metal or an alloy containing these such as Ni,
Hexagonal plate-like hexagonal ferrite fine particles are exemplified. Examples of the binder include polymers such as vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylate, methacrylate, styrene, butadiene, and acrylonitrile, and copolymers of two or more of these. In addition, polyester resin, epoxy resin and the like are exemplified. From the viewpoint of better dispersing the magnetic powder, a resin containing a metal sulfonic acid salt or a composite resin of a resin containing a metal sulfonic acid salt and another resin may be used. As the organic solvent, ethers, esters, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, chlorinated hydrocarbons and the like which are usually used for dispersing magnetic paints can be used. In addition to the magnetic powder and the binder, a dispersant, an abrasive, an antistatic agent, a rust inhibitor and the like may be added to the magnetic paint. As these additives, any of those usually used can be used. When a metal thin film type magnetic tape is manufactured, a magnetic layer is formed by directly applying a metal magnetic material on a non-magnetic support by a vacuum thin film forming technique. As the metal magnetic material, Co, Co—C
r, Co-Ni, Co-Fe-Ni, Co-Ni-Cr
Any of the ferromagnetic metal materials commonly used in this type of magnetic tape can be used. These metal magnetic materials are formed by a vacuum thin film forming technique such as a vacuum evaporation method, a sputtering method, and an ion plating method. The nonmagnetic support forming the magnetic layer in this manner includes polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose triacetate, cellulose diacetate and the like. Examples include plastics such as cellulose derivatives, polyamides, and polycarbonates. On the surface of these non-magnetic supports,
In order to improve the adhesiveness of the magnetic layer, an intermediate layer or an undercoat layer may be provided. Here, the magnetic layer formed by the coating technique and the vacuum thin film forming technique cannot be said to be completely smooth, and has protrusions and deposits on the surface.
In this state, these surface protrusions and deposits cause dropout. Therefore, in the present embodiment, a hard lapping treatment is performed by bringing the wrapping tape into sliding contact with the surface of the magnetic layer at a surface pressure of 0.25 to 1.2 g / mm ² , and then the wrapping tape is added to the surface of the magnetic layer. A soft lapping treatment is performed by bringing the magnetic tape into sliding contact with a surface pressure of 1 to 0.2 g / mm ² , thereby grinding and removing these surface projections and deposits to complete a magnetic tape. FIG. 1 shows an example of a surface treatment apparatus in which the hard wrapping process and the soft lapping process are continuously performed. The surface treatment apparatus includes unwinding rolls 1 and
Take-up roll 2 and a plurality of guide rolls 3, 4, 5,
A magnetic tape running system 13 composed of 6, 7, 8, 9, 10, 11, 12; and a hard processing unit 14 arranged in the middle of the magnetic tape running system 13 in parallel with the magnetic tape running system 13. It is composed of a software processing unit 15. The hardware processing unit 14 includes a magnetic tape 24
And a pair of guide rolls 5 and 6 (which constitute the magnetic tape traveling system 13) for performing a hard lapping process of sliding the lapping tape 25 against the surface of the lapping tape 25 at a surface pressure of 0.25 to 1.2 g / mm ² . Hereinafter, the rolls are referred to as “hard processing guide rolls”. The hard processing unit 14 includes an unwinding roll 16 for hard processing, a winding roll 17 for hard processing, and a contact roll 18, and a long hard wrapping tape 25 for hard processing is used. The wrapping tape 16 for hard processing that has been wrapped around the take-up roll 17 for use in the hard processing is rolled by the contact roll 18 to form the pair of guide rolls 5 for hard processing.
6 overhangs on the magnetic tape 24 side. Here, the pair of hard processing guide rolls 5 and 6 are movable toward the hard processing section 14 and are fixed at arbitrary positions by stoppers (not shown). . In this surface treatment apparatus, the wrapping tape 25 extended by the contact roll 18 and the magnetic tape 24 are brought into contact with each other by adjusting the fixing position of the guide rolls 5 and 6 for hard processing. The hugging angle of the magnetic tape 24 with respect to the contact roll 18 and the surface pressures of the magnetic tape 24 and the wrapping tape 25 for hard processing are respectively controlled. The hard processing unwinding roll 16 and the hard processing unwinding roll 17 constituting the hard processing unit 14 are arranged on the winding roll 2 side where the hard processing unwinding roll 16 winds the magnetic tape. A winding roll 17 for hard processing is disposed on the unwinding roll 1 side for unwinding the magnetic tape. Therefore, the hard processing wrapping tape 25 and the magnetic tape 24 run in opposite directions. On the other hand, the software processing section 15
4 for soft lapping by sliding a lapping tape at a surface pressure of 0.1 to 0.2 g / mm ² on the take-up roll 2 rather than the guide rolls 5 and 6 for hard processing. A pair of guide rolls 8 provided,
9 (hereinafter, referred to as a guide roll for software processing). The soft processing section 15 includes an unwinding roll 19 for soft processing, a winding roll 20 for soft processing, and a contact bar 21, and a long soft wrapping tape 26 for soft processing is used. The soft processing wrapping tape 26 is wrapped around the take-up roll 20, and the wrapping tape 26 for soft processing is brought into contact with the magnetic tape 24 by pushing the contact bar 21 toward the magnetic tape 24. . That is, as shown in FIG. 2, the contact bar 21 is movable toward the magnetic tape 24 in a minute range close to the magnetic tape 24 and is fixed at an arbitrary position. . In this surface treatment apparatus, the fixing position of the contact bar 21 is
4, the soft processing wrapping tape 26 and the magnetic tape 24 are brought into contact with each other, and the contact bar 21 of the magnetic tape 24 at that time is adjusted.
, And the surface pressures of the magnetic tape 24 and the soft processing wrapping tape 26 are precisely controlled. In this software processing unit 15,
As in the case of the above-described hard processing unit 14, the unwinding roll 19 for soft processing and the winding roll 20 for soft processing are used.
The soft processing take-out roll 19 is arranged on the take-up roll 2 side where the magnetic tape is taken up, and the soft processing take-up roll 20 is arranged on the take-up roll 1 side where the magnetic tape is taken out. Therefore, the soft wrapping tape 26 and the magnetic tape 24 run in directions opposite to each other. In this surface treatment apparatus, a capstan roll 22 and a nip roll 23 are further provided on the take-up roll 2 side than the soft processing section 15, so that the tape tension applied to the running magnetic tape 24 is kept constant. It has become. The guide roll 7 between the hard processing guide roll 6 and the soft processing guide roll 8 has a built-in tape tension detecting means, so that the tape tension applied to the magnetic tape 24 can be checked at any time. . In order to perform the surface treatment of the magnetic tape 24 by the surface treatment apparatus having such a configuration, the hardware processing unit 1
4, the wrapping tapes 25 and 26 are respectively set in the software processing unit 15, and the magnetic tape 24 to be subjected to the surface treatment is set.
Over the magnetic tape traveling system 13. In the hard processing section 14, the guide rolls 5 and 6 for hard processing are used.
By adjusting the fixing position of the magnetic tape 24, the holding angle of the magnetic tape 24 with respect to the contact roll 18 and the surface pressure between the hard processing wrapping tape 25 and the magnetic tape 24 are respectively set at the holding angle of 50 to 180 ° and the surface pressure of 0.25 to 1 .2g / m
adjusted within the range of m ^2. The soft processing unit 15 adjusts the fixing position of the contact bar 21 to adjust the angle of the magnetic tape 24 to the contact bar 21, the soft processing wrapping tape 26 and the magnetic tape 2.
4 and the surface pressure of 0.1 to 5 °, respectively.
Adjust within the range of 0.2 g / mm ² . Then, the magnetic tape 24 is caused to travel from the unwinding roll 1 side to the winding roll 2 side, and the wrapping tapes 25 and 26 set in the hard processing section 14 and the soft processing section 15 are respectively transferred to the magnetic tape 24.
The vehicle travels in a direction opposite to the traveling direction. Then, the magnetic tape 24 is first transferred to the hard processing unit 14, where the surface pressure of the hard processing wrapping tape 25 is 0.25 to 0.25.
It is slid on 1.2 g. 0.25 to 1.2 g of the magnetic layer
When the lapping tape 25 is slid in contact with the wrapping tape 25 with a relatively large surface pressure, the polishing effect causes surface protrusions on the magnetic layer surface,
Deposits are ground. Here, a part of the ground material is separated from the magnetic layer and removed as it is, but the other part is scattered and adheres again to the surface of the magnetic layer. The magnetic tape 24 that has passed through the hard processing section 14 is subsequently transferred to the software processing section 15 where the software processing wrapping tape 26
At a contact pressure of 0.1 to 0.2 g. When the magnetic layer is
When the soft processing wrapping tape 26 is slid in contact with the soft processing wrapping tape 26 with a relatively small surface pressure of 1 to 0.2 g, the ground material reattached to the surface of the magnetic layer is captured by the soft processing wrapping tape 26 and removed. Then, when the magnetic layer passes through the soft processing section 15, no ground material is left on the surface of the magnetic layer, and the magnetic layer is wound around the winding roll 2 with good surface properties. Incidentally, such a hard wrapping process,
The soft wrapping treatment may be repeated not only once but also many times in order to surely remove and remove surface protrusions and deposits. However, it is necessary to consider the processing order so that the final treatment is always a soft lapping treatment so that no ground material remains on the surface of the finally obtained magnetic tape. Here, when only the hard lapping process is repeatedly performed without performing the soft lapping process, the ground matter adhering to the surface of the magnetic layer accumulates as the number of times of the process increases, thereby reducing the polishing effect of the wrapping tape. Reduced,
Eventually, even if the treatment is further repeated, a saturated state is reached in which no further wear effect can be obtained. Further, between the magnetic tape and the lapping tape that are in sliding contact, the ground material acts to scrape off the binder and the lubricant on the surface of the magnetic layer, resulting in a disadvantage that the durability of the magnetic tape is deteriorated. On the other hand, when the hard lapping process and the soft lapping process are alternately repeated, the ground material adhering to the magnetic layer surface during the hard lapping process is always captured and removed by the next process of the soft lapping process. At the time of the coming hard lapping treatment, the magnetic layer surface is in a state where no abrasive is attached. Therefore,
The surface treatment is performed without causing the grinding effect of the wrapping tape to be reduced due to accumulation of the grinding material on the surface of the magnetic layer, and without causing the binder and lubricant on the surface of the magnetic layer to be removed by the attached grinding material. As a result, a magnetic tape having no surface protrusions and no deposits and having excellent surface properties and durability can be obtained. The polishing effect by the hard lapping process and the trapping effect by the soft lapping process include the surface pressure of the magnetic tape and the wrapping tape, the surface roughness of the wrapping tape, the feed speed of the wrapping tape, and the tape tension applied to the magnetic tape. , Also depends on the running speed of the magnetic tape. Therefore, in order to perform the surface treatment more efficiently, it is desirable to optimize these conditions.
The approximate ranges of the surface roughness of the wrapping tape, the tape tension, and the running speed of the magnetic tape are shown below. Surface roughness of wrapping tape: 300 to 1000 nm (three-dimensional center line average roughness SRa) Feeding speed of wrapping tape: hard lapping treatment 5
３０30 mm / min soft lapping treatment 5-20 mm / min, preferably 1
0 to 20 mm / min Tape tension applied to the magnetic tape: 200 to 400
g Running speed of the magnetic tape: 400 to 600 m / min. In the above example, the surface treatment is performed on the magnetic tape cut to the tape width. The combined surface treatment may be performed on the magnetic tape before cutting, and may be introduced into the manufacturing process as a substitute for the conventional surface treatment. Next, a magnetic layer is formed by actually applying a magnetic paint on the non-magnetic support, and the surface is treated by using the above-described surface treatment apparatus to thereby obtain a coating type magnetic tape (Example Tape 1). Was prepared. The composition of the magnetic paint is as follows. Magnetic powder Ferromagnetic Fe powder (σ _s = 130 emu / g,
Hc = 110 kA / m) Binder Vinyl chloride resin Polyester polyurethane resin nitrocellulose (vinyl chloride resin: polyester polyurethane resin: nitrocellulose = 50%: 30
%: 20%) Lubricant Myristic acid solvent Methyl ethyl ketone toluene cyclohexanone Wrapping tape having a surface roughness SRa of 700 to 750 nm is used as a wrapping tape for hard treatment and a wrapping tape for soft treatment. Made by Micro Corporation, trade name GC-300
0) was used. The surface roughness SRa was measured by a three-dimensional roughness measuring instrument manufactured by Kosaka Laboratory. Then, regarding the produced magnetic tape,
Using a VTR (manufactured by Sony Corporation) and Shibasoku counter, the incidence of dropout was investigated. Table 1 shows the results. As a comparison, a magnetic tape which was subjected to only a hard wrapping process without performing a soft wrapping process (Comparative Example Tape 1), and instead of the soft wrapping process, the holding angle of the magnetic tape to the contact bar was set to 30 °.
Alternatively, the magnetic tape was subjected to a surface treatment such that the surface pressure between the wrapping tape and the magnetic tape exceeded 0.1 to 0.2 g / mm ² by setting the angle to 15 ° (Comparative Tape 1,
With respect to Comparative Example Tape 2), the occurrence rate of dropout was investigated. The results are shown in Table 1 together with the results of Example Tape 1. [Table 1] However, the dropout ratio in Table 1 is a relative value when the number of dropouts of Comparative Example Tape 1 is 1. As can be seen from Table 1, the example tape 1 in which the soft wrapping process was performed after the hard wrapping process was the comparative example tape 1 in which only the hard wrapping process was performed, and the wrapping tape and the magnetic tape were used after the hard wrapping process. The dropout occurrence rate is reduced by about 50% as compared with a magnetic tape (Comparative Example Tape 2 and Comparative Example Tape 3) surface-treated so that the surface pressure exceeds 0.1 to 0.2 g / mm ^2. are doing. Therefore, performing the surface treatment by combining the hard wrapping treatment and the soft lapping treatment is effective in improving the surface properties of the magnetic layer and obtaining a magnetic tape with a low frequency of dropout. I found it. As is clear from the above description, the present invention relates to a magnetic tape having a magnetic layer formed on a non-magnetic support.
Of magnetic layer surface treated with wrapping tape
In a method of manufacturing a recording medium, first, a wrapping tape is applied to the magnetic tape at a surface pressure of 0.25 to 1.2 g / mm ² .
Perform a hard lapping treatment by sliding it on the magnetic layer surface ,
Next, a soft lapping treatment is performed by sliding the lapping tape on the surface of the magnetic layer of the magnetic tape at a surface pressure of 0.1 to 0.2 g / mm ² , so that the surface treatment is not affected by the adherence of the abrasive. Thus, a magnetic tape having excellent surface properties and durability free of surface protrusions and attached portions on the magnetic layer can be obtained .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing one configuration example of a surface treatment apparatus to which the present invention is applied. FIG. 2 is a schematic diagram showing a software processing unit of the surface treatment apparatus. [Description of Signs] 14 ... Hard processing unit 15 ... Soft processing unit 16 ... Hard processing unwinding roll 17 ... Hard processing winding roll 18 ... Contact roll 19 ... Soft Processing unwinding roll 20 ... Soft processing take-up roll 21 ... Contact bar 25 ... Hard processing wrapping tape 26 ... Soft processing wrapping tape

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B24B 21/00 G11B 5/84

Claims (1)

(57) [Claims 1] A magnetic layer comprising a magnetic layer formed on a non-magnetic support.
Surface treatment of the magnetic layer surface of the magnetic tape with wrapping tape
In a method for manufacturing a magnetic recording medium, first, a wrapping tape is coated with 0.25 to 1.2 g / mm ²
In surface pressure is in sliding contact with the magnetic layer surface of the magnetic tape performs hard lapping process, then sliding the lapping tape to the magnetic tape of the magnetic layer surface at a surface pressure of 0.1 to 0.2 g / mm ² A method for producing a magnetic recording medium, wherein a soft lapping process is performed by contacting the magnetic recording medium with the recording medium.