JPH06295436A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce the magnetic recording medium having high quality without generation of a difference in tape characteristics by decreasing the difference in compressive stresses inside and out of the winding of a raw sheet taken up on a take-up core and to enable a thermal curing treatment in the state of taking up the tape several ten thousand meters. CONSTITUTION:An outer part 4 which is a surface side to be wound with the magnetic recording medium is mainly formed of glass fibers contg. carbons. The take-up core 1 formed of the carbon fibers in an inner part 3 which is an inner side is used. The raw sheet having a thermosetting binder is wound around this take-up core 1 and is subjected to the thermal curing treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a so-called coating type magnetic recording medium, and more particularly to a thermosetting treatment performed after calendering.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder is provided on a non-magnetic support and an organic material such as a vinyl chloride-vinyl acetate polymer, a polyester resin or a polyurethane resin. A so-called coating type magnetic recording medium, which is manufactured by coating and drying a magnetic coating material dispersed in a binder, is widely used.

To manufacture such a coating type magnetic recording medium, the following procedure is carried out. First, a magnetic coating material in which magnetic powder is dispersed in a binder is applied to one surface of the non-magnetic support. Then, this is run in a dryer to dry the magnetic paint to some extent. Next, calendering is performed to smooth the surface of the magnetic layer for the purpose of reducing dropout.

After that, the tape is wound around a winding core having a cylindrical shape.

Next, the raw material wound on the winding core is
The mixture is placed in a heating furnace at 60 ° C. to 70 ° C., and the thermosetting binder and the curing agent are cross-linked. Finally, this raw fabric is slit to have a predetermined width, and this is wound on a tape reel to complete a magnetic tape.

[0006]

By the way, due to the value of the winding tension when winding the tape after calendering on the winding core, a compressive stress in the radial direction is generated in the original fabric, and particularly, inside the winding core near the winding core. Then, problems such as interlayer adhesion, sticking, and transfer occur. Further, in the subsequent heat curing treatment step, thermal stress due to thermal expansion of the winding core is generated like shrinkage shrinkage stress due to thermal contraction of the tape.

For example, FIG. 2 shows a measurement result of the compressive stress in the radial direction of the material roll, in which a load cell is placed in the innermost and outermost part of the material roll in which a tape having a thickness of 19 μm is wound around a winding core for 8000 meters. Show. As can be seen from this figure, the pressure outside the roll of the material is 4.9 kg / cm in the initial state.
² is 11.0 kg / cm ² and 2
It turns out that it is more than twice as expensive. Further, it can be seen that the pressure further increases in the roll of the raw material when the heat curing treatment is performed.

It is considered that the stress in the roll of the original fabric is increased by the heat curing treatment because the winding core is thermally expanded and the stress at that time is applied to the tape. When such a compressive stress occurs, the surface state of the magnetic layer changes, and the surface roughness, friction coefficient, and RF electric characteristics are affected. For example, the inconvenience arises that there is a difference in the coefficient of friction between the inside and outside of the roll.

Conventionally, a plastic core, a paper core, a rubber wound metal core or the like has been used as the winding core. As shown in Table 1, the plastic core has the advantage of being light in weight and having high mechanical strength, but has the drawback of being inferior in thermal stress due to its high coefficient of thermal expansion. On the contrary, the paper core is excellent in thermal stress but has a problem in mechanical strength. Further, the rubber wound metal core is excellent in mechanical strength and thermal stress, but has a problem in weight.

[0010]

[Table 1]

As described above, in the conventional winding core,
As described above, due to problems in handling, mechanical strength, and tape characteristics, it is impossible to make a jumbo roll that weighs more than 500 kg. However, in view of productivity, it is necessary to further lengthen and widen the raw material, and this must be dealt with immediately.

Therefore, the present invention has been proposed in view of such conventional circumstances, and reduces the difference in compressive stress between the inside and outside of the material wound on the winding core, resulting in a difference in tape characteristics. An object of the present invention is to provide a method of manufacturing a magnetic recording medium which enables a high quality magnetic recording medium to be manufactured and which can be heat-cured while a tape is wound up for tens of thousands of meters.

[0013]

In order to achieve the above-mentioned object, the present invention provides a method for producing a coating type magnetic recording medium, which comprises forming a magnetic layer on a non-magnetic support by coating and drying.
It is characterized in that the winding surface side of the magnetic recording medium is made of glass fiber mainly mixed with carbon, and the inside of the winding core is made of carbon fiber, and a raw material having a thermosetting binder is wound around the winding core to perform heat curing treatment.

[0014]

In the present invention, the winding core for winding the calendered tape is made of glass fiber mainly containing carbon on the winding surface side of the magnetic recording medium, and the inside is made of carbon fiber. While maintaining low weight and high mechanical strength, the coefficient of thermal expansion is significantly smaller than the coefficient of thermal expansion of the plastic core. Therefore, when the raw material wound around the winding core is subjected to the heat curing treatment, the thermal expansion of the winding core is suppressed, so that there is no difference in the compressive stress between the inside and outside of the winding core, and the tape characteristics are improved. It becomes almost uniform inside and outside.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. In order to manufacture a magnetic recording medium, first, a magnetic coating material in which magnetic powder is dispersed in a binder is applied to one main surface of a non-magnetic support which is a wide and long raw material.

As the non-magnetic support, any of those usually used in this type of medium can be used. For example, polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, cellulose triacetate and cellulose die. Cellulose derivatives such as acetate and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride,
Examples include plastics such as polycarbonate, polyimide, polyamide, polyamide imide, and polyphenylene sulphide.

In the magnetic recording medium manufactured in this example, a back coat layer is formed on the surface opposite to the surface on which the magnetic layer is formed in order to ensure stable running of the medium. Good.

On the other hand, as the magnetic powder, any of those used in this kind of field can also be used, for example, ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder,
Examples include iron nitride. The magnetic powder is dispersed in a thermosetting binder such as a thermosetting polyurethane resin and a curing agent such as polyisocyanate.

Next, after the coating process, the non-magnetic support is run in a dryer provided in-line to dry the magnetic paint. Then, the dried tape is wound around the winding core. Next, the surface of the wound tape is smoothed, and a calendering process is performed to wipe and flatten the projections and the like that cause the dropout and the like.

After that, the calendered tape was wound into a winding core 1 shown in FIG. 1, which was composed of carbon fibers on the inside and glass fibers mixed with carbon on the outside.
Roll it up. The winding core 1 used here does not give stress as much as possible to the original fabric wound around the winding core 1 due to thermal expansion of the winding core 1 when the winding core 1 is heat-cured in the next step. In order to prevent a large compressive stress difference between the inside and the outside, it has a structure in which carbon, which serves to reduce the coefficient of thermal expansion, is mixed into the glass fiber. Also,
The winding core 1 can be heat-cured while the tape 2 is wound for tens of thousands of meters, and can bear the weight of the original material, and is easy to handle, so it is light and mechanical. Those with high strength are desired.

Specifically, as shown in FIG. 1, the take-up core 1 is a carbon fiber in which the inner portion 3 of the take-up core 1 is a cylindrical body which is at least longer than the width dimension of the tape 2 and is made of 100% carbon. Since the other outer portion 4 on the winding surface side of the magnetic recording medium is made of glass fiber mixed with carbon, the coefficient of thermal expansion is significantly smaller than that of the plastic core.
It should be noted that core chucks 5 and 6 for rotatably supporting the take-up core 1 face the holes penetrating in the axial direction of the take-up core 1, respectively.

In this embodiment, the buckling resistance is 700 kgw.
In order to maintain the original fabric, the Young's modulus of the core was determined to be 1500 kg / mm ² from the general formula of buckling, and the thermal expansion coefficient of simple plastic core was set to 18 × 10 ^-6 to 5 × 10 ^-6 or less. A winding core 1 is used in which 20% is mixed with glass and the inside is made of carbon fiber made of 100% carbon. As a result, the coefficient of thermal expansion is 4 × 1
It became a 0 ^-6. From the viewpoint of reducing the coefficient of thermal expansion, it is conceivable that all the winding cores 1 are made of 100% carbon, but if this is done, the cost will be very high. Therefore, a carbon fiber of 100% carbon was provided inside.

By the way, in order to manufacture the winding core 1, first, the carbon 100 is applied to a cylindrical or columnar support.
Wrap% cross along the axial direction. Next, a carbon fiber mixed with 20% of carbon is wound around it along the axial direction of the support body. After that, an epoxy resin is applied and these are hardened.

As a result, the inner portion 3 is made of 100% carbon.
The winding core 1 is made of carbon fiber, and the outer portion 4 on the winding surface side of the magnetic recording medium is made of glass fiber mixed with carbon.

The surface of the outer portion 4 of the winding core 1 is coated with a conductive plastic in order to reduce static electricity of the film of the tape 2 and to prevent dust from adhering to the outer periphery of the core. You may

Next, the winding core 1 formed by winding the tape 2 is put in a heating furnace at 60 ° C. to 70 ° C. for 40 hours to cause a crosslinking reaction between the thermosetting binder and the curing agent. At this time, heat is applied to the winding core 1, but the winding core 1
Since the coefficient of thermal expansion is extremely low, the coefficient of thermal expansion of the winding core 1 is small and a large stress is not applied to the tape 2.

Finally, the raw material taken out from the heating furnace is slit into a predetermined tape width and wound on a tape reel to complete a magnetic tape.

Here, the following experiment was actually conducted. A tape having a thickness of 19 μm was used, and the above steps were sequentially repeated to wind the tape 20000 meters around a winding core 1 mainly made of carbon-containing glass fiber, and then to a heating furnace at 70 ° C. for 20 minutes. A heat-curing treatment was performed for a certain period of time, after which this was slit into a predetermined tape width and then wound on a tape reel. Then, the coefficient of friction of the tape wound on this tape reel (referred to as pancake) outside and inside was measured. The outside of the roll refers to the outer peripheral side of the pancake, and the inside of the roll refers to the inside of the pancake.

On the other hand, as a comparative example, a tape having a thickness of 19 μm was used, and the same steps as those described above were sequentially repeated to wind the tape 3000 meters around the plastic core, and then thermosetting treatment was performed under different temperature conditions and times. And then
Then slit this into a predetermined width to make a pancake,
The coefficient of friction outside and inside the roll was measured. The results are shown in Table 2.

[0030]

[Table 2]

As can be seen from these results, when the tape 2 was wound around the winding core 1 mainly containing carbon (Example), the friction coefficient outside and inside the winding was substantially the same. On the other hand, Comparative Example 1 using a plastic core
In Comparative Example 5, it can be seen that the difference in friction coefficient between the outside and inside is large, and the difference in the friction coefficient is larger as the heating temperature is higher. Therefore, by using the winding core 1 having a low coefficient of thermal expansion, the coefficient of friction inside and outside the winding can be made substantially equal, and as a result, R
It is possible to manufacture a magnetic tape having high F electric characteristics.
Further, by using the winding core 1 made of carbon fiber-mixed glass fiber, while maintaining the advantages of low weight and high mechanical strength of the plastic core,
The thermosetting treatment can be performed in a jumbo roll in which a tape having a thickness of μm is wound up for 20000 meters or more.

[0032]

As is clear from the above description, in the method of the present invention, the winding core for winding the tape after the calendering treatment is made of glass fiber mainly containing carbon on the winding surface side of the magnetic recording medium. Since the inside is made of carbon fiber, the thermal expansion coefficient can be significantly reduced as compared with the thermal expansion coefficient of the plastic core while maintaining the low weight and high mechanical strength of the plastic core. Therefore, when the raw material wound around the winding core is subjected to a heat curing treatment, the thermal expansion of the winding core is suppressed, so that there is no difference in the compressive stress between the inside and outside of the winding core, and the tape characteristics are wound. It can be made substantially uniform inside and outside. As a result, it is possible to manufacture a high-quality magnetic recording medium having no difference in tape characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view of a winding core in which a winding surface side of a magnetic recording medium is made of glass fiber mixed with carbon and an inside is made of carbon fiber of 100% carbon.

FIG. 2 is a characteristic diagram showing the pressure inside and outside the roll in the radial direction of the material wound around the plastic core.

[Explanation of symbols]

 1 ... Winding core 2 ... Tape 3 ... Winding core inner part 4 ... Winding core outer part 5, 6 ... Chucking core

Claims (1)

[Claims] 1. A method of manufacturing a coating type magnetic recording medium, comprising forming a magnetic layer on a non-magnetic support by coating and drying the magnetic layer, wherein the winding surface side of the magnetic recording medium is glass fiber mainly mixed with carbon, and A method for producing a magnetic recording medium, comprising winding a roll having a thermosetting binder around a winding core made of carbon fiber and subjecting the roll to a heat curing treatment.