JPH043311A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a smooth surface of a magnetic layer which causes no deformation of a tape nor clogging of a magnetic head by polishing the magnetic layer with an abrasive tape before curing and before the calendering process removing a low mol.wt. component which is not cured and sufficiently removing a binder layer on the surface of the magnetic layer. CONSTITUTION:The magnetic layer is formed by coating a nonmagnetic supporting body with a magnetic coating material comprising a ferromagnetic powder dispersed in a binder, and drying. A tape containing an abrasive powder of 0.1 - 0.5mum average particle size is made to slide on the magnetic layer to polish its surface in the opposite direction to the traveling direction of the magnetic recording medium having the magnetic layer. Then the magnetic layer is subjected to supercalendering and then cured. This treatment is performed so that the spectrum obtained by X-ray photoelectron spectroscopy of the surface of the magnetic layer shows the integral intensity ratio of Cl-2P line to Fe-2P(3/2) line ranging from 0.35/1 to 0.46/1. Thereby, deformation of a magnetic tape and clogging of a magnetic head can be prevented and the obtd. magnetic layer has a smooth surface.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a magnetic recording medium having a basic structure consisting of a non-magnetic support and a magnetic layer provided on the support. .

(Prior Art) Magnetic recording media in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a non-magnetic support are generally used as magnetic recording media for audio, video, or computers. ing.

Such magnetic recording media are produced by coating a magnetic paint, in which a binder component such as a resin component and a granular component such as ferromagnetic powder are dispersed in a solvent, on a non-magnetic support to form a coating layer. It is manufactured by subjecting the coating layer to treatments such as magnetic field orientation treatment, drying treatment, and surface smoothing treatment, and then cutting it into a desired shape.

Generally, the surface of the magnetic layer manufactured in this way is considered to be very smooth with the granular components firmly fixed to the magnetic layer, but according to the study conducted by the present inventor, the surface of the magnetic layer It was found that there were particulate components such as ferromagnetic powder that were insufficiently fixed.

Such poorly fixed particulate components may detach during running and adhere to the magnetic head, causing clogging of the magnetic head, and may also cause dropouts in, for example, video tapes. There is. and,
Since the amount of ferromagnetic powder near the surface of the magnetic layer decreases due to such detachment of the ferromagnetic powder, there is also the problem that electromagnetic conversion characteristics deteriorate (reduction in output) due to repeated running.

The present inventor has invented a method of grinding the surface of the magnetic layer as a method of reducing the occurrence of such dropouts, clogging, and output reduction, and has already filed an application for this invention (Japanese Patent Laid-Open No. 62172532). .

That is, the present invention removes granular components or the magnetic layer that are easily detached by grinding the smoothed surface of the magnetic layer using a high-hardness grinding tool such as a diamond wheel or a fixed sapphire blade. This removes deposits on the surface and reduces the amount of substances detached from the surface of the magnetic layer.

Against this background, the present inventor further investigated methods for reducing the amount of desorbed substances from the surface of the magnetic layer, and found that
We have discovered that there is an effective method other than grinding the magnetic layer of a magnetic recording medium.

This is a method in which the magnetic layer of a magnetic recording medium is polished using an abrasive tape, and it has been found that this method can produce magnetic recording media with fewer dropouts and clogging, and with better running durability. Ta. (Unexamined Japanese Patent Publication No. 63259830).

However, low molecular weight components are still present during calendering, resulting in the problem of staining of the calender roll. To solve this problem, it is possible to prevent sticking on the lubricating side, especially by using fatty acids, but in order to achieve this, a large amount of fatty acids is required, and when used as a product, fatty acids can cause problems with magnetic heads. etc., and the magnetic layer also became plasticized, weakening the magnetic layer. Also, by adding an abrasive to the magnetic layer, dirt can be removed by its own abrasive ability when it passes through a calendar roll, but if you add a lot of abrasive to get a sufficient effect, the dirt will come off, but the head will wear out. When the amount of raw material was small, there was less head wear, but calender roll staining did not decrease. Furthermore, in the above-mentioned method, when the magnetic layer is ground with a highly hard grinding tool, it cannot be ground unless a strong force is applied since the magnetic layer has already been hardened, which causes tape deformation at the edges and lowers the audio level.

If the horizontal grinding force was weak, the low molecular weight components on the surface layer of the magnetic layer could not be sufficiently removed, causing head clogging.

As another similar technique, a method is known in which burnishing and cleaning are used in combination before calendering for the purpose of smoothing the surface of the magnetic layer. (US4,254°585)
The purpose of this method is to remove the protrusions of the tape after application by burnishing and to improve the surface smoothness by calendering after cleaning the deposits.

However, there were the following problems. When burning the magnetic layer with an abrasive held, a banking roll is installed on the opposite side (back side) of the magnetic layer. Because the surface is treated while maintaining the strain of the magnetic layer, it is difficult to cut the surface layer of the magnetic layer more than necessary. Even if there were large irregularities such as undulations, the tape was cut flat, resulting in deformation of the magnetic tape or the magnetic layer being partially cut more than necessary. In addition, if dust etc. intervenes between the packing roll and the hack layer, local deformation occurs and Do is likely to occur.Furthermore, if the particle size of the abrasive is large, the effect is even stronger and sometimes the abrasive particles themselves may peel off. Burnishing may occur between the polishing layer and the magnetic layer, resulting in thin scratches on the surface of the magnetic layer. It is also known to polish the surface of the magnetic layer using an abrasive tape before calendering (for example, JP-A-64-13228 and JP-A-61-261820).

The purpose of these methods is to remove minute protrusions on the surface of the magnetic layer and polish it to create a smooth magnetic recording medium with fewer dropouts.

However, conventional polishing only removes minute protrusions or grinds to a considerable thickness.
The degree of polishing was not controlled, and problems such as calendar roll stains, dropout electromagnetic conversion characteristics, instantaneous clogging, and hand stains could not be solved at the same time.

(Objective of the Invention) An object of the present invention is to provide a method for manufacturing a magnetic recording medium having good running durability.

More specifically, it is an object of the present invention to provide a method for producing a novel magnetic recording medium with 1tM1 conversion characteristics, less occurrence of calender roll fouling, head fouling, dropouts, and clogging.

(Structure of the Invention) That is, the above object of the present invention is to apply a magnetic paint containing ferromagnetic powder dispersed in a binder onto a non-magnetic support, and after drying, form an abrasive layer with an average particle size of 0.1 to 0. Contains an abrasive of 5 μm, and the surface roughness (Ra) of the polishing layer surface is 0.05 to
The surface of the magnetic layer is polished by sliding a 0.20u (cutoff value 0.8m) polishing tape in the opposite direction to the running direction of the magnetic recording medium, followed by supercalendering and then curing. The integrated intensity ratio α between the Cl-2P spectrum and the Fe-2P ('/t) spectrum using X-ray photoelectron spectroscopy is 0.35/1 to 0.46/
This can be achieved by a method for manufacturing a magnetic recording medium characterized by obtaining a magnetic recording medium having the following characteristics.

More preferably, the above object of the present invention is that the abrasive tape has a Young's modulus of 150 to 800 kg/m" and a total thickness of 1.
Claim (1), characterized in that after polishing with a polishing tape of 0 to 30μ, a cleaning treatment is performed with a nonwoven or woven fabric, and then a supercalender treatment is performed.
This can also be achieved by the method for manufacturing a magnetic recording medium described in .

That is, in the present invention, since polishing is performed using a polishing tape before calendering and before curing, uncured low molecular weight components of the binder present on the surface of the magnetic layer are efficiently removed.
No roll stains occur during the calendering process. Furthermore, since the surface of the magnetic layer is polished with a hardening agent, the surface of the magnetic layer is relatively soft, and stains can be sufficiently removed without applying excessive force. Therefore, there is no tape deformation such as wakame-like appearance in the part of the magnetic tape where audio track signals are recorded.
An excellent magnetic recording medium without audio level fluctuations can be obtained. Furthermore, since the polishing treatment is performed before curing, the binder layer on the surface of the magnetic layer can be sufficiently removed, and the magnetic head will not be clogged. Furthermore, since the surface of the magnetic layer is polished before calendering, smoothing can be carried out extremely efficiently.

The present inventors also discovered a method of quantifying the ratio of the vinyl chloride polymer binder and ferromagnetic powder on the surface of the magnetic layer using X-ray photoelectron spectroscopy. rather than the ratio of binder to ferromagnetic powder.
There is a surprisingly good correlation between the ratio of the vinyl chloride polymer binder and ferromagnetic powder on the surface of the magnetic recording layer and video head clogging, and the amount of video head dirt, which is the cause of video head clogging, is It was found that the ratio is determined by the ratio of the vinyl chloride polymer binder on the surface of the magnetic layer and the ferromagnetic powder. It has also been found that the ratio of the vinyl chloride polymer binder to the ferromagnetic powder on the surface of the magnetic layer can be controlled independently of the ratio of the binder to the ferromagnetic powder in the entire magnetic layer.

That is, Cl-2 measured using X-ray photoelectron spectroscopy
The integrated intensity ratio between the P spectrum and the Fe -2P (3/2) spectrum (corresponding to the ratio of the vinyl chloride polymer binder and ferromagnetic powder on the surface of the magnetic layer) is 0.51/
When it was 1 or less, the binder on the surface of the magnetic recording layer was not scraped by the video head, and therefore the video head was not contaminated, and as a result, a magnetic recording medium was obtained in which the video head was not clogged. Also.

The integrated intensity ratio of the Cl-2P spectrum and the Fe-2P (3/2) spectrum measured using X-ray photoelectron spectroscopy (the ratio of the vinyl chloride polymer binder and ferromagnetic powder on the surface of the magnetic layer) When the ratio (corresponding to the above) was less than 0°35/1, the binder on the surface of the magnetic layer was insufficient to function as a binder, causing video head scratches on the surface of the magnetic layer and deteriorating running durability.

In other words, in conventional products for which durability is particularly important, the integrated intensity ratio α between the Cl-2P spectrum and the Fe-2P (3/2) spectrum is 0.52/1 to 0.60/1.
Therefore, clogging occurred with a relatively small number of baths, and the H friction coefficient was also relatively high. When we analyzed the reason for this, we found that although the exact reason is unknown, vinyl chloride binders are relatively hard binders and are used as the main binder, and from a durability perspective,
This is thought to be because it greatly affects the film properties on the surface of the magnetic layer that comes into direct contact with the magnetic head and the like. In other words, this is considered to be because the usage ratio of the vinyl chloride binder and the ferromagnetic powder to optimally disperse the ferromagnetic powder is different from the usage ratio necessary to ensure durability on the surface of the magnetic layer. When the ratio is set as above, the ferromagnetic powder and the vinyl chloride binder are properly bonded to each other, and durability can be improved. Furthermore, since the amount of binder on the surface of the magnetic layer decreases, the amount of fatty acid that is a lubricant that dissolves in the magnetic layer decreases, and therefore, the amount of fatty acid that oozes out onto the surface of the magnetic layer increases, and the coefficient of friction also decreases.

In addition, the Young's modulus of the polishing tape is 150 to 800 kg/kaku2.
By polishing with an abrasive tape with a total thickness of 10 to 30 μm, the abrasive tape has flexibility, and even if there are large irregularities such as undulations on the surface of the magnetic layer, the surface will conform to the shape. This is thought to be due to the fact that low molecular weight components such as curing agents and binders present on the surface of the magnetic layer can be efficiently removed.

Preferred embodiments of the present invention are as follows.

1) A method for manufacturing a magnetic recording medium, characterized in that the amount of residual solvent during polishing with the polishing tape is lθ to 25 μ/rrr.

2) A method for manufacturing a magnetic recording medium, characterized in that no contact portion such as a backing roll is provided on the back side of the original magnetic tape during the polishing process.

3) The binder used in the magnetic layer is composed of a component containing a polar group-containing vinyl chloride copolymer and a polar group-containing polyurethane resin, and a curing agent containing a polyisocyanate compound. A method for manufacturing a magnetic recording medium.

4) A method for producing a magnetic recording medium, characterized in that the abrasive used in the abrasive layer of the abrasive tape is chromium oxide particles.

5) A method for manufacturing a magnetic recording medium, which comprises performing a grinding process using a blade after polishing using an abrasive tape and before cleaning.

The manufacturing method of the present invention will be described in more detail below.

A magnetic recording medium consists of a non-magnetic support and a magnetic layer provided on the support. The magnetic layer consists of a granular component such as a ferromagnetic powder and a binder in which the granular component is dispersed. The binder is composed of a resin component and a curing agent that is further added as desired.

Coating of the magnetic layer can be carried out according to a conventional method. For example, a magnetic paint is prepared by cross-dispersing magnetic layer forming components such as a resin component, a ferromagnetic powder, and an abrasive and a hardening agent blended as desired with a solvent, and this magnetic paint is applied onto a non-magnetic support. method can be used.

Polyethylene terephthalate (
PET), polyesters such as polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyamide, polyamideimide, polyimide, etc. films or sheets made of synthetic resin; non-magnetic metal foils such as aluminum and copper;
Metal foil such as stainless steel foil; selected from paper, ceramic sheet, etc.

The resin component is selected from resins commonly used as resin components of magnetic paints. Examples of resin components include vinyl chloride copolymers (e.g. vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinyl acetate/acrylic acid copolymer, chloride) Vinyl, vinylidene chloride copolymer, vinyl chloride/acrylonitrile copolymer, ethylene/vinyl acetate copolymer,
Carboxylic acid groups or salts thereof, sulfonic acid groups or salts thereof, phosphoric acid groups or salts thereof, amino acid groups, polar groups such as hydroxyl groups, and epoxy groups are IXl0-' per polymer tg.
~50x10-% equivalent introduced vinyl chloride copolymer), cellulose derivatives such as nitrocellulose resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin, polyurethane resin (e.g. polyester polyurethane resin) , carboxylic acid group or its salt, sulfonic acid group or its salt,
Polar groups such as phosphoric acid groups or salts thereof, amino acids, hydroxyl groups, etc. are 0.5 x 10-' to 50 x 10- per 1 g of polymer.
Examples include polyurethane resins and polycarbonate polyurethane resins introduced in equivalent amounts.

Furthermore, when a curing agent is used, a polyisocyanate compound is usually used. The polyisocyanate compound is selected from those commonly used as curing agent components for polyurethane resins and the like. Examples of polyisocyanate compounds include reaction products of tolylene diisocyanate and 1 mol of trimethylolpropane (eg, Desmodur 1, -75) (manufactured by Bayer), diisocyanates such as xylylene diisocyanate or hexamethylene diisocyanate. reaction product of 1 mole of trimethylolpropane, 3 moles of hexamethylene diisocyanate, an isocyanurate compound of 5 moles of tolylene diisocyanate,
Mention may be made of isocyanurate addition compounds of 3 mol of tolylene diisocyanate and 2 mol of hexamethylene diisocyanate, polymers of isophorone diisocyanate and diphenylmethane diisocyanate.

Further, when performing curing treatment by electron beam irradiation, a compound having a reactive double bond (eg, urethane acrylate) can be used.

In the present invention, it is preferable to use a combination of a highly hard resin such as a vinyl chloride copolymer and a flexible resin such as a polyurethane resin as the resin component.

When using a combination of a hard resin such as a vinyl chloride copolymer and a flexible resin such as a polyurethane resin, the weight ratio of the former to the latter is usually 9.
:1 to 5:5 (preferably 9:1 to 6:4). When a curing agent is used, the weight ratio of the resin component to the curing agent is usually 9:1 to 5:5 (
Preferably, it is set within the range of 9:1 to 6:4).

Generally, when using ferromagnetic powder with low hardness such as ferromagnetic metal fine powder, TFe20. Use a larger amount of binder than when using a harder material such as. In this case, the amount of flexible resin such as polyurethane resin is usually increased.

Since the binder tends to soften as the amount of polyurethane resin used increases, a method is usually used to maintain the hardness of the binder by increasing the amount of a hardening agent such as a polyisocyanate compound.

When using a polyurethane resin as a resin component and a polyisocyanate compound as a curing agent, the blending weight ratio of the polyurethane resin and the polyisocyanate compound is usually i:o, s to 1:2 (preferably l: 1-1
:1.5). By doing so, even when using fine ferromagnetic metal powder with low hardness, it becomes possible to effectively prevent softening of the binder caused by using polyurethane resin.

The total weight of the resin component and curing agent is 100% of the ferromagnetic powder.
Usually 10 to 100 parts by weight (15 to 40 parts by weight)
(parts by weight).

Examples of the ferromagnetic powder used in the present invention include r-Fe2
Metal oxide-based ferromagnetic powder such as O2, dissimilar metals such as γ-F+403 containing other components such as cobalt, etc.
Metal oxide-based ferromagnetic powder, barium ferrite), Cr
Examples include fine ferromagnetic metal powders containing O□ and ferromagnetic metals such as iron, cobalt or nickel.

In particular, the present invention is advantageous when used as a method for producing a magnetic recording medium using fine ferromagnetic metal powder. In other words, even if a large amount of hardening agent is used in conjunction with the use of fine ferromagnetic metal powder, the amount of deposits on the magnetic layer or magnetic head can be reduced, reducing dropouts and magnetic problems. , it is possible to manufacture a magnetic recording medium with less clogging.

When using a ferromagnetic metal fine powder, it is a ferromagnetic metal fine powder containing iron, cobalt or nickel, and has a specific surface area of 42rrf/g or more (particularly preferably 45bo/g or more). Preferably, it is a fine powder.

As an example of this ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75% by weight or more, and the metal content is 8% by weight.
0 weight or more of at least one ferromagnetic metal or alloy (eg, Fe, Co, Ni, Fe-Co).

Fe-Ni, Co-Ni, Co-N1-Fe), and other components (e.g., AI, Si, S, Sc, Ti, V, Cr,
Mn, Cu, Zn, Y, Mo, l? h.

Pd, Ag, Sn, Sb, B, Ba, Ta
, W, Re, Au, Hg.

Pb, P, La, Ce, Pr, NdXTe5
Mention may be made of alloys which may contain Bi). Further, the ferromagnetic metal may contain a small amount of water, hydroxide, or oxide.

Methods for producing these ferromagnetic powders are already known, and the ferromagnetic powder used in the present invention can also be produced according to known methods.

There are no particular restrictions on the shape of the ferromagnetic powder, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used. In particular, it is preferable to use acicular ferromagnetic powder.

The above resin component, curing agent, and ferromagnetic powder are mixed and dispersed together with a solvent (e.g., methyl ethyl ketone, dioxane, cyclohexanone, ethyl acetate) that is normally used in the preparation of magnetic paint to obtain a magnetic paint. Crosstalk dispersion can be performed according to conventional methods.

In addition to the above components, the magnetic paint contains abrasives (e.g. a
-Al2O2, Cr203), antistatic agents (e.g. carbon black), lubricants (e.g. fatty acids, fatty acid esters,
Of course, it may also contain commonly used additives or fillers (agents) such as silicone oil) and dispersants. Especially as a lubricant, carbon number is 10 to 2.
When using saturated fatty acids (2), there is a flJi orientation in which the saturated fatty acids are oriented in layers on the surface of the magnetic layer by polishing with an abrasive tape, and the fatty acid film oriented in this way has high strength and also has good lubricity. Therefore, there is an advantage that the running properties of the magnetic recording medium are improved.

The magnetic paint thus prepared is applied onto a non-magnetic support. The coating method can be carried out using a conventional coating method such as a method using a reverse roll.

The magnetic coating layer is applied so that the thickness of the magnetic layer of the obtained magnetic recording medium is usually within the range of 0.5 to 10 m.

The nonmagnetic support used generally has a thickness of 3 to 100 tm (preferably 5 to 30 tm).

A backing layer may be provided on the surface of the nonmagnetic support used in the present invention that is not coated with the magnetic paint. Normally, the back layer is formed by applying a back layer forming paint made of particulate components such as abrasives and antistatic agents and a binder dispersed in an organic solvent to the side of the non-magnetic support that is not coated with the magnetic paint. It is a layer provided.

Note that an adhesive layer may be attached to the surface of the nonmagnetic support on which the magnetic paint and the hard layer forming paint are applied.

Usually, the coated layer of magnetic paint is dried after being subjected to a treatment for orienting the ferromagnetic powder contained in the coated layer of magnetic paint, that is, a magnetic field orientation treatment.

In the manufacturing method of the present invention, the surface of the thus dried magnetic layer, or the surface of the magnetic layer and the surface of the magnetic layer are polished using a polishing tape.

In particular, it is preferable to wipe off the surface polished with a polishing tape using a nonwoven cloth or the like. However, the order in which the polishing treatment and wiping treatment are performed is not limited to the above order. The surface of the magnetic layer, or the surface between the magnetic layer and the surface, is polished by slowly rotating the belt of the polishing tape. At that time, the circumferential speed of the belt is adjusted to 1-10 cm/min, preferably 1-3 cm/min in the opposite direction to the winding direction of the tape of the magnetic recording medium.
The polishing process is performed in minutes. The tension of the original magnetic tape during polishing is preferably in the range of 4 to 10 kg/1 m.

FIG. 1 is a schematic diagram showing an example of polishing, grinding, and wiping steps according to the present invention.

As shown in FIG. 1, the tape is fed out from a feed roll 1, polished with an abrasive tape 2, ground with a fixed blade 3 if necessary, wiped off with a non-woven cloth 4, and then wound with a take-up roll 5. processing is completed.

Reference numeral 10 denotes a feed roll for smoothly feeding the tape.

The polishing tape 3 is moved by a rotary roll 8 at a speed of 1 to 10 cmZ in the direction opposite to the tape feeding, and the polishing tape 3 is moved by a rotating roll 8 at a speed of 1 to 10 cm
The polishing tape 3 is held down and comes into contact with the surface of the magnetic layer to perform polishing treatment. At this time, it is preferable that the side opposite to the magnetic layer (hack layer) is free without any banking roll or the like.

In FIG. 1, there may be two or more polishing points using the polishing tape, and if not only the surface of the magnetic layer but also the back layer surface is to be polished, a similar polishing point using the polishing tape is provided on the opposite side.

The fixed blade 3 for the grinding process may not be used, or a rotating blade may be used instead of the fixed blade. Also, both fixed blades and rotating blades may be used.

Furthermore, when grinding not only the surface of the magnetic layer but also the surface of the back layer, a fixed blade and/or a rotating blade is provided on the opposite side.

The nonwoven fabric 4 is moved by a rotating roll 9 in the opposite direction to the feeding of the tape at a speed of 0.5 to 10CI/min.
The nonwoven fabric 4 is held down by 1. It comes into contact with the surface of the magnetic layer and performs a wiping process.

In addition, there may be two or more locations to be wiped off with a nonwoven fabric, and if the wiping process is to be performed not only on the surface of the magnetic layer but also on the surface of the layer, a similar location on the opposite side is provided with a similar area to be wiped off with a nonwoven fabric.

The polishing tape used in the polishing process of the present invention is preferably a tape for polishing the heads of cassette decks, video decks, etc. The main purpose of this polishing tape is to finish the head surface, create the shape of the tip of the head, and eliminate chipping of the head.

The polishing tape used for these polishing processes has an abrasive hardness in the range of 5 to 9 on the Mohs scale, such as α-^1)02, S+02, CrzOa, α-F.
It contains at least one type of abrasive selected from the group of e203, diamond, ZnO□, and TiO□.

The polishing tape used in the present invention is manufactured, for example, as follows. The abrasive material is dispersed in a binder containing a binder, additives, etc., applied to a support, dried, and then cut into a predetermined size.

As the binder, thermoplastic resins, thermosetting resins, and reactive resins may be used alone or in combination. The mixing ratio of the abrasive material and the binder is 10 to 200 parts by weight based on 100 parts by weight of the abrasive material. The material for the support is polyethylene terephthalate (PET).
), polyolefins such as polypropylene, cellulose derivatives, vinyl resin 1, polycarbonate, polyamide, and other synthetic resin films or sheets; non-magnetic metal foils such as aluminum and copper;
Metal foil such as stainless steel foil; selected from paper, ceramic sheet, etc.

The surface roughness (center line average roughness) Ra of the polishing tape used in the present invention is preferably within the range of 0.05 to 0.254. The measurement conditions for roughness) Ra are as follows.

Center line average roughness measuring machine Safcom 400B, 403B, 4
Using 04B system, cutoff value: 0.8m,
Operating speed: 0.3m, needle pressure: 0.01g, needle thread: 2μR
Range: Measured under the conditions of 20 to 10.5.

The polishing tape is not particularly limited as long as it has the above performance, and any commercially available polishing tape may be used.

The polishing process using the polishing tape described above removes particulate components such as ferromagnetic powder or abrasive material protruding from the surface of the magnetic layer, unreacted hardening agent present on the surface of the magnetic layer, and Deposits (e.g., dust in the air that adheres to the surface during the manufacture of magnetic recording media) are deposited near the surface of the magnetic layer (approximately 0.1 μm, preferably 0.05 μm or less, more preferably 0.025 μm or less). scraped off together with the binder,
The surface of the magnetic layer is smoothed.

If the back layer is also polished, polishing the back layer reduces the detachment of particulate components such as non-magnetic powder, so for example, magnetic recording media cut into tape shapes can be used in a wound state. Even if the granular component is detached from the surface of the back layer, it is less likely that the particulate components will adhere to the surface of the magnetic layer and cause dropouts or clogging.

An example of a material used for the wiping process is a suede-like nonwoven fabric with a single layer structure consisting of densely intertwined bundles of polyester fibers without substantially containing a binding component such as polyurethane (e.g., Ecsaine). Product name)
, manufactured by Toshi ■; Clarino (product name), manufactured by Kuraray ■), non-woven fabrics made by bonding polyester fibers with binding components such as polyurethane (e.g. Vilene (trade name), manufactured by Nippon Vilene ■), and other ultrafine fibers. Examples include woven fabrics using Toraysee (trade name) Toshikan Sei.

This wiping process completely removes deposits and organic substances from the magnetic layer and/or backing layer, reducing dropouts or clogging.

A grinding process may be performed before the wiping process of the nonwoven fabric, etc. The grinding process is described in Japanese Patent Laid-Open No. 6
2-172532. Thus, examples of grinding tools that may be used include fixed blades, diamond wheels and rotating blades.

Here, the fixed blade is a blade whose portion that contacts the surface of the magnetic layer or back layer to be ground is made of a highly hard material. Blades are typically made of sapphire, alumina, cermet, or zirconia (zirconium oxide)
, silicon nitride, silicon carbide, diamond, and cemented carbide (mainly composed of WC).

In addition, a diamond wheel refers to a rotating cylindrical grinding tool with sintered diamond around the circumference.

Further, the rotary blade body is a grinding tool that includes a rotary body and at least one blade provided on the outer circumference of the rotary body along the rotation axis of the rotary body.

The above-described treatment can further enhance the effect of polishing using a polishing tape. The amount of change before and after polishing the polar surface of the magnetic layer was determined by Auger electron spectroscopy,
For example, the ratios of CI, N, and AI to Fe on the surface may be compared, which can be confirmed by analytical means such as X-ray photoelectron spectroscopy.

After being polished in this way, the coated layer is subjected to a supercalender treatment, such as a 5-roll or 7-roll supercalender roll. By performing the supercalender treatment, the pores formed by the lithium are eliminated by the removal of the solvent during drying, and the filling rate of the ferromagnetic powder in the magnetic layer is improved, so that the electromagnetic conversion characteristics are improved. The specific method of calender roll treatment is as follows.

Calendering is performed by heating and pressurizing using at least one pair (two stages), preferably three or more stages of metal rolls. Alternatively, a combination of a metal roll (on the magnetic layer side) and an elastic roll (on the back layer side) is used.

Preferably, the metal roll has a center line surface roughness (Ra) of about 2 On- or less, more preferably about 10 nm or less. Examples of metal rolls include hard chrome plating or other metal rolls on the surface of various steel rolls. Examples include those with a ceramic coating, and rolls with a roll surface made of cemented carbide.

The metal roll consists of a cored metal member and a cylindrical member fitted around the outer periphery of the cored metal member, and this cylindrical member has a surface hardness (Vickers hardness) of 450 degrees or more, preferably 1000 degrees or more. Specifically, metals such as carbon steel, hard ceramics, etc. are used as the frame, and Cr, Zn, Sn, Cu,
It is preferable to use one of Ni plating.

The elastic roll can be used in combination with known rolls, examples of which include Japanese Patent Publication No. 60-44725,
There are some disclosed in Japanese Patent Publication No. 61-15807 and the like. In other words, the elastic roll is made of hard resins such as polyamide resins, polyurethane resins, crosslinked polyester resins, phenol resins, and epoxy resins, as well as raw cotton such as cotton rolls, Firman rolls, and woolen rolls. Rolls made of absorbent cotton, valves, cotton, wool, etc. are used (Japanese Patent Laid-Open No. 62-12
Publication No. 921).

Preferably, polyamide resin (Japanese Patent Publication No. 60-44
725 Publication) and epoxy resin (Special Publication No. 1580/1980)
No. 7) is used.

Further, the hardness of the elastic roll forming material used is 70° or more in shore D hardness, preferably 70° to 100°. Further, the surface roughness (center line average roughness; Ra) of the elastic roll is preferably 0.03- or less, 0
．． 031) m or more, it is difficult to obtain desired characteristics. The processing conditions are preferably a linear pressure of 50 to 350 kg/cm, and the processing temperature is preferably in the range of 50 to 1)0°C.

When polyisocyanate is used as a hardening agent in a vinyl chloride-polyurethane binder, dirt often adheres to the metal roll during the calendering process, making continuous processing impossible. This deposit is caused by the accumulation of low molecular weight binder present on the surface of the magnetic layer, and is a problem in the manufacturing process.
By cutting the low molecular weight binder layer present on the extreme surface of the present invention by polishing, roll stains can be eliminated, which is advantageous in terms of the manufacturing process. The calendering process is followed by a curing process.

The curing treatment includes heat curing treatment and electron beam irradiation curing treatment, and either method can be used in the present invention.

Through this curing treatment, the unreacted curing agent contained in the surface-smoothed magnetic layer forms a three-dimensional linear crosslinked structure with resin components such as vinyl chloride copolymer and polyurethane resin. react like that.

The heat treatment process itself is already well known, and the heat treatment can also be performed in the present invention according to these methods.

For example, in heat treatment, the heating time is usually 40"C or higher (
(preferably within the range of 50 to 80°C), and the heating time is usually set to 20 hours or more (preferably 24 hours to 7 days). Further, the process of curing treatment by electron beam irradiation itself is already known, and the heat treatment can be performed according to these methods in the present invention as well.

The magnetic tape material cured in this way is then cut into a desired shape.

The cutting can be carried out under normal conditions using a normal cutting machine such as a slitter.

(Effects of the Invention) In the present invention, uncured low molecular weight components present on the surface of the magnetic layer are removed because the polishing is performed using an abrasive tape before calendering and before curing, and roll stains do not occur during the calendering process. , and because head contamination is improved, instantaneous clogging is also improved. In addition, dirt can be removed sufficiently without applying strong force, so there is no tape deformation, little audio level fluctuation, and no magnetic head clogging.
By setting the integrated intensity ratio α with the e-2P (3/2) spectrum to 0.3571 to 0.46/1, the vinyl chloride copolymer and the ferromagnetic powder will stick together appropriately, preventing head stains and Head clogging can also be improved at the same time. Furthermore, the abrasive tape of the present invention does not create any unevenness on the surface of the magnetic layer.
Electromagnetic conversion characteristics such as Y S/N are also significantly improved.

(Execution@) Next, Examples and Comparative Examples of the present invention will be shown. In the Examples and Comparative Examples, the expression "parts" indicates "parts by weight."

[Example 1] A magnetic paint was prepared by cross-dispersing the following magnetic paint composition in a ball mill until it became uniform.

After adjusting the viscosity of the obtained magnetic coating, it was coated on the surface of a low-thickness polyethylene terephthalate support using a reverse roll so that the magnetic layer had a thickness of 3.6-.

Nagigoffi ferromagnetic metal fine powder 100 parts (composition: Pe96wtX, Ni4wLχ.

Specific surface area: 48rrf/g) Vinyl chloride copolymer 10 parts (M
R-1) 0 manufactured by Nippon Zeon ■) Polyurethane resin 6 parts Tuboran N-2304, manufactured by Nippon Polyurethane ■) Polyisocyanate compound 9 parts (Des-Module L-75, manufactured by Bayer AG) α-Alumina 10 parts Stearic acid 0.5 parts Olein #0.5 parts Butyl stearate 1.6 parts Carbon black 1 part Methyl ethyl ketone 200 parts Cyclohexanone Each 100 parts of the following bank layer forming coating composition was mixed and dispersed in a ball mill until uniform. A layered paint was prepared.

After adjusting the viscosity of the obtained bank layer forming coating material, it was coated on the back surface of the support coated with the above magnetic coating material using a reverse roll so that the thickness of the bank layer was 0.5-.

Carbon black 35 parts (average particle size: 0.Oha+) α-alumina (average particle size: 0.154 1.8 parts maximum particle size = 0.3 parts) Nitrocellulose 20 parts Polyurethane resin 10 parts of Noborane N-2304, manufactured by Nippon Polyurethane) 10 parts of a polyisocyanate compound (Coronate, manufactured by Nippon Polyurethane) 600 parts of methyl ethyl ketone A non-magnetic support coated with magnetic paint and bank layer paint,
While the magnetic paint is still wet, it is subjected to magnetic field orientation treatment using a 3000 Gauss magnet, and after further drying, the average particle size is 0.
Polishing tape (K-1000) using 3 μ of Cr, O, with surface roughness Ra of 0.07 and Young's modulus of 400 kg/m"
0: Fuji Photo Film (manufactured by Fuji Photo Film) as shown below, followed by cleaning treatment using a woven tray sheet (manufactured by Toshimasu) and supercalendering to remove the non-magnetic support, magnetic layer and A laminate consisting of a back layer and a back layer was prepared.

The Young's modulus of the magnetic layer during polishing is 880 kg/m"
Met.

This laminate was heat-treated at 60° C. for 24 hours to harden the polyisocyanate compound contained in the magnetic layer, and then slit to 172 inches. The Young's modulus of the magnetic layer after curing was 1250 kg/m''.

Polishing Process Yahagi As shown in FIG. 1, the polishing tape 2 is moved by a rotating roll 8 in the opposite direction to the tape feeding at a speed of 1.5 C1/min, and is pressed down by a pad 6 from above. It comes into contact with the surface of the magnetic layer of the tape and performs a polishing process.

C Example 2] Example 1 was carried out in the same manner as in Example 1, except that after the polishing treatment in Example 1, the surface of the magnetic layer was ground with a sapphire blade by the following method.
A 2-inch video tape was manufactured.

Sapphire blade with a 60 degree angle at the tip (width: 5cm,
(Length: 35 m, manufactured by Kyocera ■) and the magnetic layer were brought into contact at a contact angle of 80 degrees and a tension of 6 kg/1 m for grinding. Note that the magnetic layer and the sapphire blade were brought into contact with each other as a set of two sapphire blades.

[Example 3] A 172-inch videotape was manufactured in the same manner as in Example 1 except for the cleaning treatment.

[Example 4] In Example 1, the Young's modulus of the magnetic layer was 800 kg/kaku2.
A 172-inch videotape was manufactured in the same manner as in Example-1, except that the same polishing treatment as in Example-1 was performed at the time of the test.

(Example 5) A 1/2 inch videotape was manufactured in the same manner as in Example 1 except that the abrasive tape was changed as follows.

The polishing tape was made of SiC particles with an average particle size of 0.5 μm, and the polishing tape had a Young's modulus of 500 kg/m'' and a surface roughness Ra of 0.2 trm (C-8000).
: Made by Fuji Photo Film ■).

[Example-6] In Example-1, the Young's modulus of the polishing tape was 690 kg.
A 172-inch videotape was produced in the same manner as in Example 1, except that an abrasive tape having the same surface roughness and the same abrasive agent was used.

[Comparative Example 1] A 172-inch videotape was manufactured in the same manner as in Example 1 except that the polishing treatment and cleaning treatment were performed after curing.

[Comparative Example 2] A 172-inch videotape was manufactured in the same manner as in Example 1 except that only the polishing treatment was performed after curing.

[Comparative Example-3] A 1/2-inch videotape was manufactured in the same manner as in Example-5 except that the abrasive tape in Example-5 was changed as follows.

The polishing tape is made of SiC particles with an average particle size of 1 μm, the Young's modulus of the polishing tape is 450 kg/z, the surface roughness Ra is 0.4 n, and the total thickness is 16 μm (C600).
0: Manufactured by Fuji Photo Film ■) [Comparative Example 4] Same as Example 1 except that a rotating banking roller synchronized with the laminate was provided on the back layer side of the contact area between the abrasive tape and the magnetic layer in Example 1. A 172-inch videotape was produced in the same manner.

[Comparative Example-5] In Example-1, the Young's modulus of the polishing tape was 870 k
17 g/sa" and the surface roughness, abrasive agent used, etc. were the same as in Example-1 except that the same abrasive tape was used.
A 2-inch videotape was produced.

[Comparative Example-6] A 172-inch video tape was manufactured in the same manner as in Example-1 except that the abrasive tape was changed as follows.

The polishing tape is α-FezO with an average particle size of 0.054.
Using Z particles, the Young's modulus of the polishing tape is 400 kg/w.
” using an abrasive tape with a surface roughness Ra of 0.044.

The obtained tape was evaluated by the following measuring method, and the results are shown in Table 1.

Measuring method 1: Calendar roll stains The surface of the metal roll in contact with the magnetic surface is visually observed and judged based on the processing length (-) until stains (discoloration) occur on the roll surface.

2. DO (dropout) VTR: The Y signal was recorded using a CVR-75, and the number of dropouts at -16 dβ at 5II sec during playback was run for 90 minutes and is shown as the average value for 1 minute.

3. Magnetic conversion characteristics (Y S/N) VTR: YS/N using CVR-75 (NTSC)
Relative comparison 4, instantaneous clogging VTR: Using BVW-75, run repeatedly up to 300 buses in an environment of 23° CIO% RH for 28 minutes, and instantaneous clogging occurred first. It is expressed as the number of bus occurrences.

5. Head dirt After running up to 300 passes in step 4 above, the degree of dirt on the head nozzle was observed using a microscope and evaluated on a five-point scale. Good is given as 5 points and bad as 1 point.

6. Head wear: Measure the height of the head before and after running when an untraveled tape is run for 25 hours in an environment of 40''C and 80% RH, and the decrease is indicated by -.

7. Audio level down VTR: 23°CIO%R1 (using BVW-75)
Measure the audio level down of ch2 by driving in the following environment, judge whether it occurs after driving 3 times (2d
A decrease of more than β is marked as X.) Note) Items 2 to 7 above were evaluated by incorporating them into a β cam SP half of a commercial 1/2 inch VTR.

[Method of measuring α]

To measure α, an X-ray photoelectron spectrometer (PERKIN-F
(manufactured by LPIER) was used. An Mg anode was used as the X-ray source, and measurements were taken at 300-. First, the lubricated side of the videotape was washed away with n-hexane, and then set in an X-ray photoelectron spectrometer. The distance between the X-ray source and the sample was set to IC1). After 5 minutes of evacuation of the sample, the Cl-2P spectrum and Fe-2P (3/2) spectrum were integrated and measured for 10 minutes. Note that the pass energy was kept constant at 100 eV.

Measured Cl-2P spectrum and Fe-2P (3/2)
The integrated intensity ratio with the spectrum was calculated and set as α.

As is clear from the results in Table 1, it is clear that Example 6 has a remarkable effect on roll staining during the calendaring process compared to Comparative Examples 1 to 5, and is superior in terms of manufacturing suitability. It is also clear that the electrical characteristics and running durability for VTRs are well-balanced and excellent.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of polishing, grinding, and wiping steps according to the present invention. 1: Delivery roll, 2: Polishing tape, 3: Fixed blade, 4: Non-woven fabric, 5: Take-up roll, 6: Pad (for polishing tape), 7: Pad (for non-woven fabric), 8: Rotating roll (for polishing tape) ), 9: Rotating roll (for nonwoven fabric), 1
0: Feed roll.

Claims (2)

[Claims] (1) A magnetic paint containing ferromagnetic powder dispersed in a binder is applied onto a non-magnetic support, dried to form a magnetic layer, and an abrasive with an average particle size of 0.1 to 0.5 μm is placed in the abrasive layer. The surface of the magnetic layer is polished by sliding an abrasive tape containing the same in the direction opposite to the running direction of the magnetic recording medium, followed by supercalendering, and then hardening, so that the X on the surface of the obtained magnetic layer is A magnetic recording medium characterized in that the integrated intensity ratio α between the Cl-2P spectrum and the Fe-2P (3/2) spectrum using line photoelectron spectroscopy is 0.35/1 to 0.46/1. Production method. (2) Young's modulus of the polishing tape is 150 to 800 kg
/mm^2, and the surface roughness (Ra) of the polishing layer surface is
is 0.05 to 0.25 μm (cutoff value 0.8 mm)
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is polished with an abrasive tape having a total thickness of 10 to 30 μm, then cleaned with a woven or nonwoven fabric, and then subjected to a supercalender treatment. Method.