JPH0418370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes and magnetic sheets.

2. Prior Art Generally, in order to create a so-called coating-type magnetic recording medium, magnetic powder is kneaded with additives such as a polymer binder and a dispersant to prepare a magnetic paint, and this is coated on a support. It is coated on the surface, dried, and subjected to processes such as calendaring. In such coated magnetic recording media, improvement in the slipperiness of the magnetic layer surface is achieved solely by adjusting additives. Furthermore, since it is a coating type, the above-mentioned calender treatment must be carried out in order to improve the surface properties of the magnetic layer.

On the other hand, a magnetic recording medium called a metal thin film type is
It is attracting attention because it enables higher-density recording. In this metal thin film magnetic recording medium,
Magnetic particles are deposited directly onto a support without a binder by electroplating, vacuum evaporation, ion plating, sputtering, or the like to form a magnetic layer consisting of a continuous thin film. Various surface layers or overcoat layers (hereinafter sometimes referred to as OC layers) are applied to the surface of this magnetic layer to impart lubricity. 56−
The organic coating film described in the specification of Japanese Patent No. 7235 and the like is considered to be preferable in terms of selectivity in types and combinations of usable materials. In addition, on the support surface opposite to the magnetic layer, a back coat layer (hereinafter referred to as BC
Sometimes called a layer. ) is desirable.

As described above, the present inventor has developed various methods for producing a magnetic recording medium for high-density recording, which has a continuous thin metal film (magnetic layer) and an OC layer on one side of a support and a BC layer on the other side. As a result of further investigation, it was discovered that there are the following special circumstances in obtaining a medium with good characteristics.

That is, in the case of a coating type, the magnetic layer becomes porous and the surface flatness deteriorates due to traces of solvent evaporated by drying after application of the magnetic paint and the presence of additive particles. While it is necessary to apply a calendar to make the magnetic layer uniform and flattened, in the case of a continuous thin film type, the thin film surface is directly formed by vapor deposition on a flat support. exhibits a flat surface that follows the surface of the support and does not require calendering. Moreover, if the magnetic layer is calendered, the magnetic layer will be damaged, which is inappropriate.

However, while calendering is not necessary, when a continuous thin film is formed, for example, by vapor deposition, the support is likely to be thermally deformed by the heat during vapor deposition, resulting in distortion.
In particular, during vapor deposition, the vapor deposition is performed in an area narrower than the width of the support in order to prevent adhesion to the rollers that support the support, so there are always non-evaporated areas on both sides of the vapor deposition area on the support. As a result, there is a significant difference in the heat received by the support at the boundary between these two regions, which causes the thermal deformation described above. Therefore, in order to remove the distortion caused in the support, it is required to heat-treat the support at 60 to 150° C. after vapor deposition.

3. Object of the Invention An object of the present invention is to provide a method that can reduce distortion that may occur in a support and can produce a continuous thin-film magnetic recording medium with stable winding and running properties.

4 Structure of the invention and its effects That is, in the present invention, a magnetic layer consisting of a continuous thin film of magnetic material containing no binder is provided on a support,
When manufacturing a magnetic recording medium in which a back coat layer (BC layer) is provided on the support opposite to the magnetic layer, and an overcoat layer (OC layer) is provided on the magnetic layer, at least forming the magnetic layer by vapor deposition, and then placing the vapor-deposited support in a coating line;
The support is brought into contact with a pair of heat rolls with built-in heaters that are pre-installed in this coating line on its front and back sides, and heat-treated at a heat roll surface temperature of 60 to 150°C. At least one of forming the BC layer by applying a coating liquid containing non-magnetic powder and a binder, and forming the OC layer by applying a lubricant solution containing no binder. The present invention relates to a method of manufacturing a magnetic recording medium characterized by performing the following steps.

According to the present invention, since the heat treatment is performed at least after the magnetic layer is formed, it is possible to eliminate the thermal deformation or distortion of the support that occurs during the formation of the magnetic layer. Moreover, since at least the next BC layer is formed after removing the distortion of the support, the BC layer etc. can be formed uniformly, and the back surface of the support can be moderately roughened by the BC layer. The winding form of the medium (and the transfer of magnetic particles at that time),
It is possible to improve running performance. In this case, since the BC layer is not provided at the time of vapor deposition of the magnetic layer, the cooling rollers and the like used for vapor deposition are not contaminated.

Moreover, since the above heat treatment is carried out by bringing the support into contact with a pair of heat rolls with built-in heaters installed in the coating line on the front and back sides, the treatment temperature for the support is 60 to 150°C. This results in a sufficient effect, and distortion of the support can be removed more effectively. In this case, since there is a pair of heat rolls, temperature control is easy to perform, and for example, even if the temperature of one roll decreases, the temperature can be maintained by the other roll. In addition, since the support can run in contact with a pair of heat rolls on the front and back sides, smooth running is possible, and appropriate tension can be applied to the support depending on the positional relationship of both heat rolls. This is advantageous for removing distortion.

Furthermore, since the BC layer and/or OC layer is formed in the same coating line where the above-mentioned hot rolls are installed, the coating can be performed immediately after removing distortion from the support, and the coating layer can be formed uniformly. At the same time, wrinkles on the support that tend to occur during coating can be eliminated as much as possible, and the number of man-hours can be reduced (no need to wind up the support). Furthermore, transfer from the back surface of the support to the magnetic layer surface can also be reduced.

Regarding the above OC layer, since the coating solution does not contain a binder, the obtained OC layer
The layer is made of a very thin lubricant layer, and has good abrasion against the head during recording and reproduction, and can keep spacing loss to a small level.

5 Examples Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 illustrates the manufacturing process of a magnetic recording medium, such as a magnetic tape, according to the present invention, and shows
Basically, a subbing layer is first coated on the surface of the support, a magnetic layer made of a continuous metal thin film is formed on the subbing layer by vapor deposition, and then heat treatment is applied to remove distortion. Then, a BC layer is formed on the back surface of the support, and an OC layer is further coated and formed on the magnetic layer.
However, as shown by the broken line, the BC layer may be formed after the OC layer is formed after the heat treatment. Next, each of the above-mentioned steps will be explained in detail.

First, as shown in FIGS. 2A and 2B, a subbing layer 2 of a magnetic layer is previously formed on the surface side of a support 1 made of polyethylene terephthalate or the like by a wet coating method. A thin film 15 is deposited. The vacuum evaporation equipment used is such that a support 1 is transferred from a supply roll 7 to a take-up roll 3 in a bell gear 8.
The metal (for example, C ₀ ) 11 in the crucible 10 is heated and evaporated by the electron beam from the electron gun 12 while being brought into close contact with the cooling roller 9 in the middle.
The vapor deposition is performed obliquely and countercurrently to the support 1 .
Note that 13 in the figure is an introduction tube for oxygen gas 14, and by lightly oxidizing the surface of the magnetic layer 15 with this oxygen gas, the magnetic anisotropy is improved and the coercive force ( _HC ) is increased. and wear resistance of the magnetic layer 15,
Improves running performance.

During this vapor deposition, as shown in FIG. 2C, the vapor deposition area of the magnetic layer 15 indicated by diagonal lines is made narrower than the width of the support 1 in order to prevent the roller 9 from becoming dirty due to adhesion of vapor deposition substances as described above. Therefore, there is a significant difference in the heat received by the support 1 at the boundary between the non-evaporated region 16 and the deposition region 15 on both sides, and this tends to cause distortion in the support 1.

In order to remove this distortion, as shown in FIG. 3A, the support 1 (on which the subbing layer 2 and magnetic layer 15 have already been formed), which is fed out from the roll 3, is placed on a pair of heated rolls with a built-in heater. 17 and 18 respectively on the front and back sides, for example, at 60 to 80°C.
(When line speed is high, heat treatment is applied at 150℃ or less).

Further, the hot rolls 17 and 18 are installed in the coating line in advance, and after the support 1 comes out from the hot rolls 17 and 18, a coating liquid 25 for forming a BC layer is applied using a reverse roll system consisting of three rolls 24.
is applied onto the support 1, dried to form the BC layer 6 shown in FIG. 3B, and wound onto a roll 20.

Next, as shown in FIG. 4A, the support 1 is sequentially fed out from the roll 20, and a coating liquid 35 for forming an OC layer is applied onto the support 1 using a reverse roll method using three rolls 34, and further dried. After forming the OC layer 19 on the magnetic layer 15 as shown in FIG. 4B, it is wound onto a take-up roll 30. Incidentally, this OC layer coating formation step may be performed continuously to the BC layer formation step shown in FIG. 3A. That is, the application roller 34 can be placed in front of the roll 20.

In addition, in the above-described process, the surface roughness (Ra) of the support 1 before forming the subbing layer 2 in FIG. 2B
may be about 20 Å, and Ra of the surface after forming the subbing layer 2 may be 30 to 40 Å. By forming the magnetic layer 15 shown in FIG. 2B after adjusting the Ra to an appropriate value, the magnetic layer 15 suitable for high-density recording can be formed without requiring calendering. Further, the surface roughness (Ra) of the BC layer 6 shown in FIG. 3B can be set to about 100 Å for running properties (and thus to prevent wrinkles on the support 1).

As explained above, in the method according to the present example, heat treatment is performed after forming the magnetic layer (and the subbing layer before it), so that thermal deformation of the support that occurs during vapor deposition of the magnetic layer and Distortion can be removed. Therefore, the next BC layer and OC layer can be formed uniformly.

In addition, due to the formation of the BC layer after heat treatment, the back surface of the support becomes moderately rough, which contributes to the stability of the rolled form of the medium and running stability (reduction of frictional force against rollers, etc.). Transfer of magnetic particles during winding can also be prevented. Furthermore, due to the formation of the OC layer,
It is also possible to improve the slipperiness and surface protection of the magnetic layer surface.

Moreover, since the above heat treatment is carried out by bringing the support into contact with a pair of heat rolls with built-in heaters installed in the coating line on the front and back sides, the treatment temperature for the support is 60 to 150°C. As a result, the strain on the support can be removed more effectively, and the temperature can be easily controlled through the use of double-heated rolls, making it possible to run the support smoothly and apply appropriate tension.

Furthermore, since the BC layer and/or OC layer is formed in the same coating line where the above-mentioned hot rolls are installed, the coating can be performed immediately after removing distortion from the support, and the coating layer can be formed uniformly. At the same time, wrinkles on the support that tend to occur during coating can be eliminated as much as possible, and the number of man-hours can be reduced (no need to wind up the support). Further, transfer from the back surface of the support to the magnetic layer surface is also reduced.

Regarding the above-mentioned OC layer, since the coating liquid does not contain a binder, the obtained OC layer consists of a very thin lubricant layer, and has good abrasion properties against the head during recording and playback, and also has good scratch resistance. Pacing loss can be kept small.

In addition, in the above-mentioned embodiment, as the magnetic powder that can be used for the magnetic layer 15, Fe-Ni-Co alloy, Fe-
Mn-Zn alloy, Fe-Co-Ni-P alloy, Fe-Ni-
Zn alloy, Fe-Ni-Cr-P alloy, Fe-Co-Ni-
Cr alloy, Fe-Co-P alloy, Fe-Ni alloy, Fe-
Ni-Mn alloy, Co-Ni alloy, Co-Ni-P alloy,
Examples include metal-based magnetic powders containing Fe, Ni, and Co as main components, such as Fe-Al alloy, Fe-Mn-Zn alloy, Fe-Al-P alloy, and the like.

Further, as the material of the support body 1 mentioned above, polyethylene terephthalate, polyethylene 2,6-
Polyesters such as naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonate are used. The thickness of these supports is approximately 3 to 100 μm in the case of a film or sheet, preferably 5 μm.
~50μm, in the case of disks and cards
The diameter is about 30 μm to 10 mm, and when it is drum-shaped, it is cylindrical, and its shape is determined depending on the recorder used.

In addition, examples of the non-magnetic powder contained in the BC layer 6 include carbon black, silicon oxide, titanium oxide, aluminum oxide, chromium oxide, silicon carbide,
Examples include those made of calcium carbide, zinc oxide, α-Fe ₂ O ₃ , talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide, calcium carbonate, etc., preferably carbon black or titanium oxide. . If these non-magnetic powders are included in the BC layer, the surface of the BC layer can be appropriately roughened (matted) to improve its surface properties, and in the case of carbon black, it can be made to have electrical conductivity. Provides antistatic effect. It is advantageous to use carbon black and other non-magnetic powders in combination, since both the effects of improving surface properties (stabilizing runnability) and improving conductivity can be obtained. However, regarding the surface roughness of the BC layer, the average roughness or height (Ra) of the center line of the surface irregularities is preferably 0.025 μm or less, and the maximum roughness (Rmax) is preferably 0.20 to 0.80 μm. .
Regarding Ra, in order to improve chroma S/N
It is desirable that Ra≦0.025μ. Ra or Rmax
If the value of is too small, the running stability and the winding appearance during tape winding will be insufficient, and if it is too large, transfer from the BC layer to the magnetic layer (during tape winding) will occur, resulting in further roughening of the surface.

In addition, the filler in BC layer 6 (including non-magnetic powder)
The particle size is preferably 0.5 μm or less, preferably 0.2 μm or less in order to obtain the above surface roughness. Also,
The BC layer 6 can be formed by coating in the same manner as described above, but the film thickness after coating and drying is 0.1 to 3.0 μm,
The thickness is preferably 1 μm or less, more preferably 0.6 μm or less.
The amount of non-magnetic powder added to the BC layer is generally 100 to 400.
mg/m ³ , preferably 200 to 300 mg/m ² .

In addition, BC layer 6 (furthermore subbing layer 2, OC layer 19
Thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, or mixtures thereof may be used as the binder for the above-mentioned materials. Also, O.C.
The layer may be formed by coating triolein, butoxyethyl stearate, boric acid, higher alcohols, higher fatty acids such as stearic acid, silicone oil, and the like.

As a thermoplastic resin, the softening temperature is 150℃ or less,
Average molecular weight is 10000~200000, degree of polymerization is about 200~
About 2000, for example, acrylic ester.
Acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, methacrylic ester-acrylonitrile copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer Coalescence, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, styrene-butadiene copolymer, polyester resin, chlorovinyl ether-acrylic acid ester copolymer, amino resin , various synthetic rubber-based thermoplastic resins, and mixtures thereof.

As a thermosetting resin or a reactive resin, it has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Moreover, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, polyurethane, phenolic resin, epoxy resin, urea resin,
Melamine resin, alkyd resin, silicone resin,
These include acrylic reactive resins, mixtures of methacrylate copolymers and diisocyanate prepolymers, urea formaldehyde resins, polyamine resins, and mixtures thereof.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers such as maleic anhydride type, urethane acrylic type, polyester acrylic type,
Polyether acrylic type, polyurethane acrylic type, polyamide acrylic type, etc., and polyfunctional monomers include ether acrylic type, urethane acrylic type, phosphate ester acrylic type, aryl type, hydrocarbon type, etc.

In addition to the above, cellulose resins such as nitrocellulose can be used as binder components for the BC layer and the like.

In addition, solvents used when coating the BC layer 6, etc. include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, and butanol; methyl acetate, ethyl acetate, and acetic acid. Esters such as butyl, ethyl lactate, ethylene glycol monoacetate; ethers such as ethylene glycol dimethyl ether, diethylene glycol monoethyl ether, dioxane, tetrahydrofuran; benzene, toluene,
Aromatic hydrocarbons such as xylene; halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and dichlorobenzene can be used.

This application method includes air doctor coat,
Blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, spray coating, etc. can be used, and other methods are also possible.

Hereinafter, the present invention will be explained with reference to specific examples. The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention. In addition, all "parts" in the following examples represent "parts by weight."

Example A 10 μ thick ultra-smooth polyester base with an undercoat layer applied on the side that will become the magnetic surface is placed in a vacuum evaporator, and Co or FeCo (70:30)
was deposited to a thickness of 0.15 μm in a vacuum of about 10 ^-5 Torr,
A magnetic layer was formed. To form the BC and OC layers, the above vapor-deposited base was placed in the coating line, the surface temperature of the pair of heat rolls pre-installed in the line was set to 120℃, and the line speed was set to 20m. The coating was performed while being heat treated.

As for the material, polyurethane is used for the BC layer.
A coating liquid was prepared by dispersing 20 parts of titanium white in a solution of 20 parts of polyester, 50 parts of polyester, and 30 parts of cellulose resin in 40 parts of methyl ethyl ketone, 20 parts of cyclohexane, and 40 parts of toluene.

The OC layer was prepared using a toluene solution of stearic acid (0.2
%) was used. During these coatings, the tension balance was maintained at 0.9 kg (per 1 cm width) at the unwinding part, 1.1 kg (per cm width) at the coater part, and 1.9 kg (1 cm) at the winding part.

Both the OC and BC layers were coated using the reverse roll coating method, but regardless of whether the BC layer or the OC layer was formed first, there were fewer defects due to distortion of the base such as wrinkles, and a good tape was created. I was able to do it.

Comparative example A 10 μ thick ultra-smooth polyester base with a subbing layer applied on the side that will become the magnetic surface was placed in a vacuum evaporation device, and Co was applied to a 0.15 μ thick layer at 10 ^-5 Torr.
A magnetic layer was formed by vapor deposition in a vacuum of about 100 mL.

The above vapor-deposited base was placed on the coating line to form the BC layer and the OC layer. The surface temperature of the heat roll installed in the line in advance was set to room temperature (25°C), and the coating was performed at a line speed of 20 m. The material used was the same as in the example. The tension balance is as follows: unwinding part 0.1 to 4 kg (per 1 cm width) coater part 0.1 to 4 kg (per 1 cm width) winding part 0.1 to 4 kg (per 1 cm width) I changed it, but the OC
Regardless of which layer is formed first, many wrinkles occur, and accidents such as wrapping around the drive roll occur frequently, making it difficult to obtain a good tape over a long length. Nakatsuta.

In the above example, when only one heat roll was used, the distortion of the support could not be completely removed.
Partial deformation was observed.

In addition, if the BC layer is applied again after being wound up after heat treatment with a heat roll, the thickness of the BC layer tends to vary due to transfer during winding, and the unevenness of the magnetic layer surface increases. .

[Brief explanation of drawings]

The drawings show examples of the present invention, in which FIG. 1 is a flow diagram of a manufacturing process for a magnetic recording medium, FIG. 2A is a schematic cross-sectional view of a vapor deposition apparatus for forming a magnetic layer,
FIG. 2B is a cross-sectional view of a portion of the magnetic recording medium;
Figure C is a bottom view from below of the cooling roller showing the vapor deposition area, Figure 3A is a schematic diagram during heat treatment and BC layer coating formation, Figure 3B is a cross-sectional view after BC layer formation, and Figure 4A is OC layer coating formation. FIG. 4B is a cross-sectional view of the finally obtained magnetic recording medium. In addition, in the symbols shown in the drawings, 1... Support, 2... Subbing layer, 6... BC layer, 9... Cooling roller, 11... Evaporation source (metal), 15...
Magnetic layer (continuous metal thin film), 17, 18...heat roll, 19...OC layer, 25...coating liquid for forming BC layer, 25... coating liquid for forming OC layer.

Claims (1)

[Claims] 1. A magnetic layer made of a continuous thin film of magnetic material containing no binder is provided on a support, and a back coat layer is provided on the support on the opposite side from the magnetic layer,
In manufacturing a magnetic recording medium in which an overcoat layer is provided on the magnetic layer, at least the magnetic layer is formed by vapor deposition, and then the vapor-deposited support is placed in a coating line. , the support is brought into contact on its front and back sides with a pair of heat rolls with built-in heaters that are pre-installed in the coating line,
performing heat treatment at a hot roll surface temperature of 60 to 150°C, and further forming the back coat layer by applying a coating liquid containing non-magnetic powder and a binder in the coating line; and a lubricant containing no binder. A method for manufacturing a magnetic recording medium, comprising forming at least one of the overcoat layer by applying a solution.