JPH08147693A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE: To enhance productivity by coating an upper layer by Wet-on-Wet coating method in the wet state of a lower layer which is at least one layer selected from a magnetic layer, coloring layer, a thermally-sensitive recording layer, a protective layer and a high magnetic permeability layer. CONSTITUTION: Each coating material for a magnetic layer and the other layers is applied in multilayer by a Wet-on-Wet method by using coaters 10, 11 to a filtlike supporting body 1 drawn out from a supply roll 32. After that, it is made to pass through an orientation magnet or a vertical orientation magnet 33 and is introduced into a dryer 34 and it is dried by blowing to it a hot wind from a nozzle. Next, the dried supporting body 1 with a coating layer is introduced into a super calender device 37 made in combination with a calender rolls 38 and after calender processing is applied thereto, it is wound by a take-up roll 39. In the multilayer coating by the Wet-on-Wet method, since the upper layer is applied in the wet state of the lower layer, the surface of the lower layer becomes smooth and at the sane time the property of the surface of the upper layer is improved and also the contact quality between the upper and the lower layers is enhanced.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a magnetic recording medium such as a bank card, a commuter pass, a ticket, a telephone card, a credit card, a medical examination card, and a prepaid card, which has productivity, anti-counterfeiting effect, and durability against repeated use. The present invention relates to an excellent magnetic recording medium manufacturing method.

[0002]

BACKGROUND OF THE INVENTION In recent years, bank cards, commuter passes and various prepaid cards have been widely used. Along with this, prevention of counterfeit cards has become an important issue. As means for preventing forgery, 1) a technique in which a magnetic layer is multi-layered and normal data is recorded in a high coercive force layer and dummy data is recorded in a low coercive force layer to make reading difficult is disclosed in JP-A-61-2761.
No. 01-227186, there is disclosed a technique for providing a bar code which can be read optically or magnetically.
Is disclosed in. Also known is a method of providing a high magnetic permeability layer on the magnetic recording layer to prevent leakage of magnetic flux.

However, it takes a lot of time and labor to manufacture them, and it is difficult to reduce the thickness of each layer because the coating property deteriorates, and there is a problem that high density cannot be achieved or the cost increases. Since the adhesion of each layer is not sufficient, there is a problem in durability during repeated use.

Further, in some cases, there is a demand for recording visible information such as the name, expiration date, balance, etc. of the above card, and a thermal recording layer using a leuco dye or a print recording layer such as a metal vapor deposition layer is provided. It is known. Further, a large number of layers such as a coloring layer for concealing coloring of the magnetic layer, a protective layer for improving durability, and a high magnetic permeability layer made of a high magnetic permeability layer material are provided as necessary. Conventionally, these magnetic recording media also have a problem that the manufacturing process is complicated and the cost is increased. Further, when the film is made thin, there are problems that the coating property is deteriorated and the interface is roughened. Further, there is a problem in adhesion of the coating film of each layer and durability in repeated use due to insufficient supply of the lubricant from the lower layer to the upper layer.

[0005]

An object of the present invention is to provide a method for manufacturing a magnetic recording medium, which is 1) having a simple manufacturing process of the magnetic recording medium and excellent in productivity, and 2) having excellent durability in repeated use. It is in.

[0006]

[Means for Solving the Problems]

Invention 1: A magnetic layer is provided on a support, and 1) a colored layer for concealing coloring of the magnetic layer, 2) a thermosensitive recording layer,
3) a protective layer, 4) at least one layer selected from a high-permeability layer containing a high-permeability material, and the magnetic layer and 1).
A method for producing a magnetic recording medium, wherein at least one layer selected from the above 4) is formed by the Wet-on-wet coating method in which the upper layer is applied while the lower layer is in a wet state.

Invention: A method of manufacturing a magnetic recording medium according to claim 1, wherein the two magnetic layers are composed of a plurality of magnetic layers having different coercive forces.

Invention: 3 A magnetic recording medium having a high coercive force magnetic layer, a high magnetic permeability layer containing a high transmissivity material, and a low coercive force magnetic layer coated in this order on a support by a wet-on-wet coating method. Production method.

Invention 4: A magnetic layer, a colored layer for concealing coloring of the magnetic layer, and a protective layer are coated on the support in this order while the lower layer is wet, and the upper layer is applied Wet-on-we.
A method of manufacturing a magnetic recording medium formed by a coating method.

Invention 5: The method for producing a magnetic recording medium according to claim 4, wherein the colored layer and / or the protective layer contain a non-magnetic powder having a Mohs hardness of 6 or more, a fatty acid and a fatty acid ester.

Invention 6: A magnetic layer, a colored layer for concealing the coloring of the magnetic layer, and a heat-sensitive recording layer are coated on a support in this order while the lower layer is wet.
A method of manufacturing a magnetic recording medium formed by a wet coating method.

Invention 7: The method for producing a magnetic recording medium according to claim 6, wherein the heat-sensitive recording layer and / or the protective layer contain a non-magnetic powder having a Mohs hardness of 6 or more, a fatty acid and a fatty acid ester.

[0013]

As a result of continuous research to solve the above technical problems, the present inventor found that the cause of the drawbacks or inconveniences of the prior art is based on the wet-on-dry coating method. I found out. And Wet-on
-It was found that the wet coating method can solve the problems all at once. Hereinafter, the present invention will be described in detail. (Layer Structure) The magnetic recording medium of the present invention basically comprises a non-magnetic support, a magnetic layer, and at least one layer existing on the magnetic layer. A back coat layer is provided on the surface (back surface) of the non-magnetic support on which the magnetic layer is not provided for the purpose of improving the running property and durability of the magnetic recording medium, and preventing electrification and transfer. It is preferable to provide a writing layer, a print recording layer, or an anti-counterfeiting layer, and an undercoat layer may be provided between the magnetic layer and the non-magnetic support.

(Non-magnetic support) As the material for forming the non-magnetic support, for example, polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose triacetate, cellulose diacetate, etc. Examples of the cellulose derivative include plastics such as polyamide and polycarbonate.

The form of the non-magnetic support is not particularly limited, and is mainly tape-like, film-like, sheet-like, card-like,
There are disc shape and drum shape.

The thickness of the non-magnetic support is not particularly limited, but in the case of a film or sheet, it is usually 3 to 1.
00 μm, preferably 5 to 50 μm, about 30 μm to 10 mm in the case of a disk or card, and appropriately selected depending on the recorder etc. in the case of a drum.

The non-magnetic support may have a single structure or a multi-layer structure. Further, the non-magnetic support may be subjected to surface treatment such as corona discharge treatment. A back coat layer may be provided on the surface (front surface) of the non-magnetic support on which the magnetic layer is not provided, for the purpose of improving the running property of the magnetic recording medium, preventing electrification and preventing transfer, and the like. As described above, a writing layer or a print recording layer is preferably provided, and an undercoat layer can be provided between the magnetic layer and the non-magnetic support.

(Magnetic Layer) In the present invention, the magnetic layer is basically formed by dispersing magnetic powder in a binder resin. On this magnetic layer, γ-Fe ₂ O ₃ and Co deposited γ
Known magnetic powders such as —Fe ₂ O ₃ can be used, but it is particularly preferable to contain ferromagnetic metal powder or hexagonal magnetic powder. The thickness of the magnetic layer is usually 5 μm or less, preferably 0.1 to 2.0 μm, and more preferably 0.1 to 1.0 μm. By satisfying these conditions, the magnetic recording medium of the present invention can improve high frequency characteristics.

The ferromagnetic metal powder used for the uppermost layer includes Fe, Co, Fe-Al system, and Fe-Al-.
Ni-based, Fe-Al-Zn-based, Fe-Al-Co-based, F
e-Al-Ca system, Fe-Ni system, Fe-Ni-Al
System, Fe-Ni-Co system, Fe-Ni-Si-Al-M
n-based, Fe-Ni-Si-Al-Zn-based, Fe-Al-
Si-based, Fe-Ni-Zn-based, Fe-Ni-Mn-based, F
e-Ni-Si system, Fe-Mn-Zn system, Fe-Co-
Ferromagnetic powders such as Ni-P-based, Ni-Co-based, metal magnetic powders containing Fe, Ni, Co, etc. as main components are exemplified. Among them, Fe-based metal powder has excellent electrical characteristics.

On the other hand, from the viewpoint of corrosion resistance and dispersibility, Fe-Al type, Fe-Al-Ca type, Fe-Al-type.
Ni-based, Fe-Al-Zn-based, Fe-Al-Co-based, F
e-Ni-Si-Al-Zn system, Fe-Ni-Si-A
Fe-Al-based metal powder such as 1-Mn-based is preferable.

Particularly, the ferromagnetic metal powder preferable for the purpose of the present invention is a metal magnetic powder containing iron as a main component, and Al or Al and Ca, and Al in a weight ratio of Fe:
Al = 100: 0.5 to 100: 20, and Ca is preferably contained in a weight ratio of Fe: Ca = 100: 0.1 to 100: 10.

By setting the ratio of Fe: Al in such a range, the corrosion resistance is remarkably improved, and by setting the ratio of Fe: Ca in such a range, electromagnetic conversion characteristics are improved and dropout is reduced. Can be made. The reason why the electromagnetic conversion characteristics are improved and the dropout is reduced is not clear, but it is considered that the coercive force is increased and the agglomerates are decreased due to the improved dispersibility.

The ferromagnetic metal powder used in the present invention is
The average major axis length is less than 0.25 μm, especially 0.10 to
0.22 μm, more preferably 0.10 to 0.17 μm
And the crystal size is less than 200Å, especially 100 to 180
It is preferably Å. The axial ratio (average major axis length / average minor axis length) is 12 or less, preferably 10 or less, and more preferably 5 to 9. When the average major axis length, crystal size, and axial ratio of the ferromagnetic metal powder are within the above ranges, the electromagnetic conversion characteristics can be further improved.

The average major axis length and the number average particle size (in the case of spherical particles) of the magnetic powder and non-magnetic powder used in the present invention are 500 or less of ferromagnetic powder or non-magnetic powder according to a transmission electron micrograph. It is an average value obtained by measuring the major axis length and the particle size (in the case of spherical particles). The crystallite size was measured by the Scherrer method using Si powder as a reference, using the integral width of the (110) diffraction line of Fe with an X-ray diffractometer. In addition, the axial ratio is measured by electron microscope photographs of the major axis length and minor axis length of 500 particles,
It was calculated as (average major axis length / average minor axis length).

The ferromagnetic metal powder used in the present invention usually has a coercive force (Hc) of 600 to 5,000.
It is preferably in the range of Oe. This coercive force is 600
If it is less than 00e, the electromagnetic conversion characteristics may be deteriorated, and if the coercive force exceeds 5,000 Oe, recording may not be possible with an ordinary head, which is not preferable.

The ferromagnetic powder preferably has a saturation magnetization amount (σs), which is a magnetic characteristic, of usually 70 emu / g or more. If the saturation magnetization amount is less than 70 emu / g, the electromagnetic conversion characteristics may deteriorate. Further, according to the present invention, the BET is increased according to the higher recording density.
A specific surface area of law ^{30 m} 2 / g or more, in particular ^{45 m} 2 /
A ferromagnetic metal powder of g or more is preferably used.

For the specific surface area and the measuring method thereof, see "Measurement of Powder" (JM Dallas).
e, Clyeorr Jr. Co-authored by Muta and other translations: published by Sangyo Tosho Co., Ltd.), and also described in "Chemical Handbook," Applied Edition, P1170-1171 (Chemical Society of Japan, published by Maruzen Co., Ltd., April 30, 1966). Has been done. To measure the specific surface area, for example, the powder is deaerated while being heated at about 105 ° C. for 13 minutes to remove what is adsorbed on the powder, and then the powder is introduced into a measuring device to reduce the initial pressure of nitrogen to 0. The pressure is set to 0.5 kg / m ² and measurement is performed with nitrogen at a liquid nitrogen temperature (−105 ° C.) for 10 minutes. The measuring device is, for example, a counter soap (Yuasa Ionics Co., Ltd.)
Manufactured).

Examples of the hexagonal magnetic powder include hexagonal ferrite. Such hexagonal ferrite is made of barium ferrite, strontium ferrite, or the like, and a part of iron element is another element (for example, Ti, Co, Zn, In, Mn, Ge, H).
b) or the like). Regarding this ferrite magnetic material, the IEEE Trans, on MAG-1
816 (1982).

In the present invention, a particularly preferable hexagonal magnetic powder is barium ferrite (hereinafter referred to as Ba-ferrite) magnetic powder. A preferable Ba-ferrite magnetic powder that can be used in the present invention is an average particle diameter of Ba-ferrite powder in which a part of Fe is replaced by at least Co and Zn (height of diagonal line of plate surface of hexagonal ferrite). ) 400 to 900Å, plate ratio (value obtained by dividing the length of the diagonal line of the plate surface of the hexagonal ferrite by the plate thickness) 2.0 to 10.0, more preferably 2.0 to
Ba with a coercive force (Hc) of 450 to 1500 Oe of 6.0
-It is ferrite.

In the Ba-ferrite powder, the coercive force is controlled to an appropriate value by partially substituting Fe for Co, and further by partially substituting for Zn, a high value which cannot be obtained only by Co substitution. A magnetic recording medium that realizes saturation magnetization and has a high reproduction output and excellent electromagnetic conversion characteristics can be obtained. Further, by substituting a part of Fe with Nb, it is possible to obtain a magnetic recording medium having a higher reproduction output and excellent in electromagnetic conversion characteristics. Further, in the Ba-ferrite used in the present invention, it does not matter even if a part of Fe is further substituted with a transition metal such as Ti, In, Mn, Cu, Ge or Sn.

The Ba-ferrite used in the present invention is represented by the following general formula. _{BaOn ((Fe 1-m M} m) 2 O 3) [ provided that, m> 0.36 (However, Co + Zn = 0.0
8 to 0.3, Co / Zn = 0.5 to 10), n is 5.4 to 11.0, preferably 5.4 to 6.0, and M represents a substituted metal, Magnetic particles that are a combination of two or more elements having an average valence of 3 are preferable. In the present invention, the reason why the average particle size of Ba-ferrite, the plate ratio, and the coercive force are preferably within the above-mentioned preferred ranges is as follows. That is, if the average particle size is less than 40 nm, the reproduction output when used as a magnetic recording medium becomes insufficient, and conversely, if it exceeds 90 nm, the surface smoothness when used as a magnetic recording medium deteriorates significantly, and the noise level increases. If the plate ratio is less than 2.0, the perpendicular orientation ratio suitable for high density recording cannot be obtained when the magnetic recording medium is used, and conversely the plate ratio becomes 10.0. If it exceeds, the surface smoothness when used as a magnetic recording medium is significantly deteriorated, the noise level becomes too high, and the coercive force becomes 350.
If it is less than Oe, it becomes difficult to hold the recording signal, and 2
This is because if it exceeds 000 Oe, the head limit may decrease in saturation and recording may become difficult.

The hexagonal magnetic powder used in the present invention usually has a saturation magnetization (σs) which is a magnetic characteristic of 50e.
It is preferably mu / g or more. If the saturation magnetization is less than 50 emu / g, electromagnetic conversion characteristics may deteriorate.

A preferred specific example of the Ba-ferrite used in the present invention is Co-substituted Ba ferrite.

As a method for producing the hexagonal magnetic powder used in the present invention, for example, the oxides and carbonates of the respective elements necessary for forming the desired Ba-ferrite are used, such as boric acid. The glass melt is melted together with another glass-forming substance, the resulting melt is rapidly cooled to form glass, and the glass is then heat-treated at a predetermined temperature to precipitate the desired Ba-ferrite crystal powder, and finally the glass component is added. In addition to the glass crystallization method of removing by heat treatment,
A coprecipitation-firing method, a hydrothermal synthesis method, a flux method, an alkoxide method, a plasma jet method and the like can be applied.

In the present invention, the ferromagnetic metal powder and the hexagonal magnetic powder may be mixed and used. The content of the ferromagnetic metal powder and / or the hexagonal magnetic powder in this magnetic layer is usually 50 to 99% by weight, preferably 60 to 99% by weight.

[Layer containing non-magnetic powder, colored layer for hiding coloring of magnetic layer or high-permeability layer containing high-permeability material] In the present invention, a plurality of layers are provided on the non-magnetic support. At least one layer other than the magnetic layer, preferably a layer adjacent to the magnetic layer, contains a non-magnetic powder or a high magnetic permeability material. The thickness of the colored layer and the high magnetic permeability layer is usually 5 μm or less, preferably 0.1 to 2.0 μm.
m, more preferably 0.1 to 1.0 μm.

(Non-Magnetic Powder) As the non-magnetic powder in the present invention, from among various known non-magnetic powders used in this kind of magnetic recording medium, one excellent as a coloring layer is appropriately selected and used. You can Examples of the non-magnetic powder include titanium oxide, barium sulfate, ZnS, M
gCo ₃ , CaCO ₃ , ZnO, CaO, tungsten disulfide, molybdenum disulfide, boric acid nitride, MgO, Sn
O ₂ , SiO ₂ , Cr ₂ O ₃ , α-Al ₂ O ₃ , Si
C, cerium oxide, corundum, artificial diamond, α
-Iron oxide, garnet, garnet, silica stone, silicon nitride, boron nitride, silicon carbide, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, tripoly, diatomaceous earth, dolomite, and polymer powder such as polyethylene. You can

Of these, CaCO is preferable.
₃ , titanium oxide, barium sulfate, α-Al ₂ O ₃ , α-
Inorganic powder such as iron oxide and polymer powder such as polyethylene. This high magnetic permeability material has a coercive force Hc.
Is 0 <Hc ≦ 1.0 × 10 ⁴ [A / m], preferably 0
<Hc ≦ 5.0 × 10 ³ [A / m]. When the coercive force is within the above range, the effect of stabilizing the magnetized region of the uppermost layer is exhibited as the high magnetic permeability material. When the coercive force exceeds the above range, desired properties may not be obtained due to the manifestation of properties as a magnetic material, which is not preferable.

In the present invention, as the high magnetic permeability material,
It is preferable to appropriately select a material within the range of the coercive force. Examples of such a high magnetic permeability material include a metal soft magnetic material and an oxide soft magnetic material.

Fe-S is used as the metal soft magnetic material.
i alloy, Fe-Al alloy (Alperm, Alfemo
l, Alfer), permalloy (Ni-Fe binary alloy, and multi-component alloy in which Mo, Cu, Cr, etc. are added thereto), sendust (Fe-Si-Al [9.6 wt% Si, 5. 4% Al, the balance being Fe]], Fe—Co alloys, and the like. Among them, sendust is preferable as a preferable metal soft magnetic material. The metal soft magnetic material as the high magnetic permeability material is not limited to those exemplified above, and other metal soft magnetic materials can be used. The high magnetic permeability material can be used alone, or
Also, two or more of them can be used in combination.

As the soft oxide magnetic material, spinel type ferrites such as MnFe ₂ O ₄ , Fe ₃ O ₄ and C are used.
oFe ₂ O _{4 ,} NiFe ₂ O _{4 ,} MgFe ₂ O _{4 ,} Li
_0.5 Fe _2.5 O ₄ , Mn-Zn ferrite, Ni-
Zn-based ferrite, Ni-Cu-based ferrite, Cu-Z
n type ferrite, Mg-Zn type ferrite, Li-Zn
An example is a system ferrite. Among these, Mn-Zn ferrite and Ni-Zn ferrite are preferable. These soft oxide magnetic materials can be used alone or in combination of two or more.

This high-permeability material is made into a fine powder using a ball mill or other crushing device, and its particle size is 1 mμ.
It is preferably 1,000 mμ, and particularly preferably 1 mμ to 500 mμ. In order to obtain such a fine powder, the metal soft magnetic material can be obtained by spraying a molten alloy in a vacuum atmosphere. Further, the soft oxide magnetic material can be made into a fine powder by a glass crystallization method, a coprecipitation firing method, a hydrothermal synthesis method, a flux method, an alkoxide method, a plasma jet method or the like.

(Heat-sensitive recording layer) As the heat-sensitive recording layer, known ones can be used, for example, JP-A-6-23145.
No. 1, JP-A-62-33326, a leuco dye type thermosensitive recording layer (a developer and a color former such as a leuco dye which reacts with the developer under heating are contained in a binder. A thermosensitive coloring layer is formed using a thermosensitive coloring material) and a plastic thermosensitive recording layer as disclosed in JP-A-5-294091 can be used. The thickness of the heat-sensitive recording layer is usually 5 μm or less, preferably 0.1 to 2 μm, and more preferably 0.1 to 1.0 μm.

(Protective Layer) A conventionally known protective layer can be used without particular limitation, such as using a coating material containing a thermoplastic resin, a thermosetting resin or an ultraviolet curable resin. The thickness of the protective layer is usually 2 μm or less, preferably 0.05 to 1
μm, and more preferably 0.05 to 0.5 μm. Further, each of the magnetic layer, the coloring layer, the heat-sensitive recording layer, the protective layer and the high magnetic permeability layer preferably contains a non-magnetic powder having a Mohs hardness of 6 or more, a fatty acid and a fatty acid ester.

In the layer containing the high magnetic permeability material, the content of the high magnetic permeability material is 10 to 99% by weight, preferably 50 to 95% by weight, and more preferably 60 to 90% by weight. When the content of the high permeable material is within the above range, the effect of stabilizing the magnetization of the uppermost layer can be sufficiently obtained.
If the content of the high magnetic permeability material is less than 50% by weight, the effect as the high magnetic permeability layer may not be obtained, which is not preferable. The layer containing the high magnetic permeability material may contain non-magnetic particles.

The magnetic recording medium of the present invention preferably contains a conductive powder. As the conductive powder, carbon black, graphite, tin oxide, silver powder,
Silver oxide, silver nitrate, organic compounds of silver, metal particles such as copper powder, etc., pigments such as zinc oxide, barium nitrate, titanium oxide and other metal oxides, tin oxide film, or conductive material such as antimony solid solution oxide film There are some that have been coated with.

(Binder) Typical binders used for forming the magnetic layer and the layers other than the magnetic layer are, for example, vinyl chloride resins such as polyurethane and polyester vinyl chloride copolymers. It is preferable that these resins include a repeating unit having at least one polar group selected from —SO ₃ M, —OSO ₃ M, —COOM and —PO (OM ¹ ) ₂ . However, in the above polar group, M is a hydrogen atom or Na, K,
Represents an alkali metal such as Li, M ¹ is a hydrogen atom,
It represents an alkali atom such as Na, K, Li or an alkyl group.

The above polar group has the function of improving the dispersibility of the ferromagnetic powder, and the content in each resin is 0.1 to 8.0 mol%, preferably 0.5 to 6.0 mol%. . When the content is less than 0.1 mol%, the dispersibility of the ferromagnetic powder is lowered, and when the content is more than 8.0 mol%, the magnetic coating tends to gel. The weight average molecular weight of each resin is preferably in the range of 15,000 to 50,000.

The content of the binder in the magnetic layer is usually 10 to 100 parts by weight of the ferromagnetic powder.
It is 40 parts by weight, preferably 15 to 30 parts by weight. The binder (binder) is not limited to one kind alone, and two or more kinds can be used in combination. In this case, the ratio of the polyurethane and / or polyester to the vinyl chloride resin is usually 90:10 by weight. 10:90,
It is preferably in the range of 70:30 to 30:70.

The polar group-containing vinyl chloride copolymer used as the binder in the present invention is, for example, a vinyl chloride-vinyl alcohol copolymer or other copolymer having a hydroxyl group and a compound having the following polar group and chlorine atom. It can be synthesized by addition reaction with.

Cl-CH ₂ CH ₂ SO ₃ M, Cl-CH
_{2 CH 2 OSO 3 M, Cl} -CH 2 COOM, Cl-C
H ₂ -P (= O) (OM ¹ ) _{2 The} above reaction will be described below by taking Cl-CH ₂ CH ₂ SO ₃ Na from these compounds as an example. _{-CH 2 C (OH) H- +} ClCH 2 CH 2 SO 3 Na
_{→ -CH 2 C (OCH 2 CH} 2 SO 3 Na) H-.

For the polar group-containing vinyl chloride copolymer, a predetermined amount of a reactive monomer having an unsaturated bond into which a repeating unit containing a polar group is introduced is charged into a reaction vessel such as an autoclave to start a general polymerization. Agents, eg BPO
(Benzoyl peroxide), AIBN (azobisisobutyronitrile) and other radical polymerization initiators, redox polymerization initiators, cationic polymerization initiators and the like can be obtained by carrying out a polymerization reaction.

Specific examples of the reactive monomer for introducing a sulfo group or a salt thereof include unsaturated hydrocarbon sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, p-styrene sulfonic acid and the like. Mention may be made of salt.

When the carboxylic acid or its salt is introduced, for example, (meth) acrylic acid or maleic acid is used,
When phosphoric acid or a salt thereof is introduced, for example, (meth) acrylic acid-2-phosphate ester may be used.

It is preferable that an epoxy group is introduced into the vinyl chloride copolymer. This is because the thermal stability of the polymer is improved by doing so.

When an epoxy group is introduced, the content of the repeating unit having an epoxy group in the copolymer is 1
-30 mol% is preferable, and 1-20 mol% is more preferable. As the monomer for introducing an epoxy group, for example, chrysidyl acrylate is preferable.

Regarding the technique for introducing a polar group into a vinyl chloride-based copolymer, JP-A-57-44227 and JP-A-57-42427 are cited.
8-108052, 59-8127, 60-1
No. 01161, No. 60-235814, No. 60-23
No. 8306, No. 60-238371, No. 62-121
No. 923, No. 62-146432, No. 62-1464.
No. 33 and the like are described, and these can be used in the present invention.

Next, the synthesis of polyester and polyurethane used in the present invention will be described. Generally, polyesters are obtained by reacting polyols with polybasic acids. By using this known method, a polyester (polyol) having a polar group can be synthesized from a polyol and a polybasic acid partially having a polar group.

Examples of the polybasic acid having a polar group include 5
-Sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-
Examples thereof include sulfoisophthalic acid, dialkyl 5-sulfoisophthalate, dialkyl 2-sulfoisophthalate, dialkyl 4-sulfoisophthalate, and their sodium salts and potassium salts.

Examples of polyols include trimethylolpropane, hexanetriol, glycerin, trimethylolethane, neopentyl glycol, pentaerythritol, ethylene glycol, propylene glycol, 1.3-butanediol, 1.4-butanediol, 1 6-hexanediol, diethylene glycol, cyclohexanedimethanol and the like can be mentioned. Note that other polar group-introduced polyesters can also be synthesized by a known method.

Next, the polyurethane will be described. It results from the reaction of polyols with polyisocyanates. As the polyol, a polyester polyol obtained by reacting a polyol with a polybasic acid is generally used. Therefore, if a polyester polyol having a polar group is used as a raw material, a polyurethane having a polar group can be synthesized.

Examples of polyisocyanates include diphenylmethane-4-4'-diisocyanate (MDI),
Hexamethylene diisocyanate (HMDI), tolylene diisocyanate (TDI), 1.5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), lysine isocyanate methyl ester (LDI) and the like can be mentioned.

As another method for synthesizing a polyurethane having a polar group, an addition reaction between a polyurethane having a hydroxyl group and the following compound having a polar group and a chlorine atom is also effective. _{Cl-CH 2 CH 2 SO 3} M, Cl-CH 2 CH 2 OS
_{O 2 M, Cl-CH 2} COOM, Cl-CH 2 -P (=
0) (OM ¹ ) _{2 As} a technique for introducing a polar group into polyurethane, JP-B-58-41565 and JP-A-57-9242 are known.
No. 2, No. 57-92423, No. 59-8127, No. 59-5423, No. 59-5424, No. 62-12.
It is described in the publications such as 1923, and these can be used in the present invention.

In the present invention, the following resins can be used together as a binder in an amount of 20% by weight or less based on the total amount of the binder. The resin has a weight average molecular weight of 1
Vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose Derivatives (nitrocellulose etc.), styrene-butadiene copolymers, phenol resins, epoxy resins, urea resins, melamine resins, phenoxy resins, silicone resins, acrylic resins, urea formamide resins, various synthetic rubber resins, etc. .

(Other Components) In the present invention, it is desirable to contain polyisocyanate in order to improve the durability of the magnetic layer and other layers.

Examples of the polyisocyanate include aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and fats such as adducts of hexamethylene diisocyanate (HMDI) and active hydrogen compounds. There are group polyisocyanates. The weight average molecular weight of the polyisocyanate is 100 to
It is preferably in the range of 3,000.

In the present invention, the magnetic layer and other layers may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent and a filler, if necessary. First,
Examples of the dispersant include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid and other aliphatic groups having 12 to 18 carbon atoms; salts of these alkali metals or salts of alkaline earth metals, or These amides: polyalkylene oxide alkyl acid ester; lecithin; trialkyl polyolefinoxy quaternary ammonium salt: azo compounds having a carboxyl group and a sulfonic acid group. These dispersants are usually used in the range of 0.5 to 5% by weight based on the ferromagnetic powder.

Next, it is preferable to use fatty acids and / or fatty acid esters as the lubricant. In this case, the amount of the fatty acid added is preferably 0.2 to 10% by weight, based on the ferromagnetic powder or nonmagnetic powder that is mainly used, and 0.5 to
5% by weight is more preferred. If the addition amount is less than 0.2% by weight, the running property tends to decrease, and if it exceeds 10% by weight, the fatty acid tends to exude to the surface of the layer and the output tends to decrease.

The amount of the fatty acid ester added is preferably 0.2 to 10% by weight, more preferably 0.5 to 5% by weight, based on the ferromagnetic powder or nonmagnetic powder that is mainly used. If the addition amount is less than 0.2% by weight, the still durability is likely to deteriorate, and if it exceeds 10% by weight, the fatty acid ester is likely to seep out to the surface of the layer or the output is likely to be reduced.

When it is desired to use a fatty acid and a fatty acid ester together to further enhance the lubricating effect, the weight ratio of the fatty acid and the fatty acid ester is preferably 10:90 to 90:10. The fatty acid may be a monobasic acid or a dibasic acid,
6-30 are preferable and, as for carbon number, the range of 12-22 is more preferable.

Specific examples of the fatty acid include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, linolenic acid, oleic acid, elaidic acid, behenic acid, malonic acid, succinic acid. Acid, maleic acid, glutaric acid, adipic acid,
Examples thereof include pimelic acid, azelaic acid, sebacic acid, 1.12-dodecanedicarboxylic acid and octanedicarboxylic acid.

Specific examples of the fatty acid ester include oleyl oleate, isocetyl stearate, dioleyl malate, butyl stearate, butyl palmitate, butyl myristate, octyl myristate, octyl palmitate, pentyl stearate, pentyl palmitate. Tate, isobutyl oleate, stearyl stearate,
Lauryl oleate, octyl oleate, isobutyl oleate, ethyl oleate, isotridecyl oleate, 2-ethylhexyl stearate, 2-ethylhexyl palmitate, isopropyl palmitate, isopropyl myristate, butyl laurate, cetyl-2.
-Ethyl hexalate, dioleyl adipate, diethyl adipate, diisobutyl adipate, diisodecyl adipate, oleyl stearate, 2-ethylhexyl myristate, isopentyl palmitate, isopentyl stearate, diethylene glycol mono-butyl ether palmitate, diethylene glycol mono- Butyl ether palmitate and the like.

As the lubricant other than the above fatty acids and fatty acid esters, for example, silicone oil, graphite, carbon fluoride, molybdenum disulfide, tungsten disulfide, fatty acid amide, α-olefin oxide, etc. can be used. Next, specific examples of the abrasive include α-alumina, fused alumina, chromium oxide, titanium oxide, α-iron oxide, silicon oxide, silicon nitride, tungsten carbide, molybdenum carbide, boron carbide, corundum,
Examples thereof include zinc oxide, cerium oxide, magnesium oxide and boron nitride. The average particle size of the polishing agent is 0.05 to
0.6 μm is preferable, and 0.1 to 0.3 μm is more preferable.

Next, as the antistatic agent, conductive powder such as carbon black and graphite; cationic surfactant such as quaternary amine; acid such as sulfonic acid, sulfuric acid, phosphoric acid, phosphoric acid ester and carboxylic acid. Examples thereof include anionic surfactants containing a group; amphoteric surfactants such as aminosulfonic acid; and natural surfactants such as saponin. The above-mentioned antistatic agent is usually added in the range of 0.01 to 40% by weight with respect to the binder.

(Manufacture of Magnetic Recording Medium) The magnetic recording medium of the present invention uses the Wet-on-wet coating method except that
The manufacturing method is not particularly limited, and it can be manufactured according to a known method used for manufacturing a single-layer or multi-layer structure type magnetic recording medium. For example, generally, magnetic powder, binder, dispersant, lubricant, abrasive, antistatic agent, etc. are kneaded and dispersed in a solvent to prepare a magnetic paint, and then this magnetic paint is applied to a non-magnetic support. Apply to the surface of.

Examples of the solvent include ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone; alcohols such as methanol, ethanol and propanol; esters such as methyl acetate, ethyl acetate and butyl acetate. Cyclic ethers such as tetrahydrofuran; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, halogenated carbon hydrogen such as dichlorobenzene, and the like can be used.

Various kneading and dispersing machines can be used for kneading and dispersing the components for forming the magnetic layer and other layers. Examples of this kneading disperser include a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a cobol mill, a tron mill, a sand mill, a sand grinder,
Sqegvari Attritor, High Speed Impeller Disperser, High Speed Stone Mill, High Speed Impact Mill, Disperser,
A high speed mixer, a homogenizer, an ultrasonic disperser, an open kneader, a continuous kneader, a pressure kneader and the like can be mentioned. Of the above kneading dispersers, 0.05-0.5 kW
The kneading dispersers capable of providing a power consumption load (per 1 kg of magnetic powder) are a pressure kneader, an open kneader, a continuous kneader, a two-roll mill, and a three-roll mill.

In order to coat the magnetic layer and other layers on the non-magnetic support, in the production of the magnetic recording medium of the present invention, simultaneous multi-layer coating by the wet-on-wet multi-layer coating method is particularly effective. To do. Specifically, as shown in FIG. 1, first, the film-shaped support 1 fed from the supply roll 32 is wet-coated with each coating material for the magnetic layer and other layers by the extrusion type extrusion coaters 10 and 11. After the multi-layer coating is performed by the on-wet method, it is passed through the magnet for orientation or the magnet for vertical orientation 33, introduced into the dryer 34, and hot air is blown from the nozzles arranged above and below to dry it. Next, the dried support 1 with each coating layer is guided to a super calender device 37 composed of a combination of calender rolls 38, where it is calendered and then wound on a winding roll 39. For example, the magnetic film thus obtained can be stamped on a JIS standard card to manufacture, for example, a magnetic card.

In the above method, each coating material was extruded through an in-line mixer (not shown), the coater 10,
11 may be supplied. In the figure, arrow D indicates the transport direction of the non-magnetic base film. Extrusion coater 1
0 and 11 are provided with liquid reservoirs 13 and 14, respectively,
Overlay the paint from each coater in a wet-on-wet fashion. That is, the upper layer coating material is applied in multiple layers immediately after the lower magnetic layer coating material is applied (when it is in an undried state). The coater head shown in FIG. 2 (c) is preferable in the present invention.

As the wet-on-wet multilayer coating method, a combination of a reverse roll and an extrusion coater, a combination of a gravure roll and an extrusion coater, and the like can be used. Further, an air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, cast coater, spray coater and the like can be combined.

In the multi-layer coating by the wet-on-wet method, the upper layer is coated while the lower layer is in a wet state, so that the surface of the lower layer (that is, the boundary surface with the upper layer).
And the surface property of the upper layer is improved, and the contact property between the upper and lower layers is also improved. As a result, especially for high-density recording, the performance required for high output and low noise is satisfied, for example, as a magnetic card, and high durability performance is required. It is eliminated, the film strength is improved, and the durability is sufficient. Further, the wet-on-wet multi-layer coating method can also reduce dropout and improve reliability.

As the solvent to be added to the above paint or a diluent solvent for applying this paint, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone: alcohols such as methanol, ethanol, propanol and butanol: methyl acetate , Esters such as ethyl acetate, butyl acetate, ethyl lactate, ethylene glycol cenoacetate: ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, tetrahydrofuran: aromatic hydrocarbons such as benzene, toluene, xylene: methylene chloride, Ethylene chloride, carbon tetrachloride, chloroform,
Halogenated hydrocarbons such as dichlorobenzene can be used. These various solvents may be used alone or in combination of two or more. The magnetic field in the orienting magnet or the vertically orienting magnet is about 20 to 5,000 gauss, the drying temperature by the dryer is about 30 to 120 ° C., and the drying time is about 0.
It is about 1 to 10 minutes.

Next, a surface smoothing process is performed by calendering. After that, if necessary, burnishing or blade processing is performed and slitting is performed. At this time, the surface smoothing treatment is effective for achieving the object of the present invention.

That is, one of the preferred requirements of the present invention is the condition of the surface roughness of the magnetic layer. To meet this condition, this surface smoothing treatment is preferred. In the surface smoothing treatment, temperature, linear pressure,
C / S (coating speed) etc. can be mentioned. To achieve the object of the present invention, the above temperature is usually 50 to 120 ° C., and the linear pressure is 50 to 400 kg / c.
m, and the above C / S is preferably maintained at 20 to 600 m / min.

[0085]

According to the present invention, it is possible to provide a magnetic recording medium which is excellent in productivity and has a high level of electromagnetic conversion characteristics and running durability, and at the same time, a coating layer having excellent coatability is used. A magnetic recording medium can be obtained.

[0086]

Embodiments of the present invention will be described below. The components, ratios, and operation order shown below can be variously changed without departing from the scope of the present invention. In the following examples, all "parts" are parts by weight.

Example 1 The respective components of the magnetic composition for the upper layer below were kneaded and dispersed using a kneader sand mill to prepare a magnetic coating material for the upper layer.

[Coating A1 for Magnetic Layer] Co-substituted barium ferrite (Hc: 3000 Oe, BET: 50 m ² / g, σ
s: 64 emu / g, average particle size: 70 nm, plate ratio:
4) Sulfonic acid metal salt-containing vinyl chloride resin 10 parts [Nippon Zeon Co., Ltd., MR-110] Sulfonic acid metal salt-containing polyester polyurethane resin [Toyobo Co., Ltd., UR-8700] 5 parts Alumina (α- Al ₂ O ₃ , number average particle size: 0.2 μm) 6 parts Carbon black [number average particle size 40 nm] 1 part Stearic acid 1 part Myristic acid 1 part Butyl stearate 1 part Cyclohexanone 100 parts Methyl ethyl ketone 100 parts Toluene 100 parts

[0089] [colored layer paints B] TiO ₂ (average particle size 30 nm, the Si to TiO ₂ 0.8% by weight, the Al TiO ₂ against 0.2 wt% content) 90
Parts carbon black (number average particle size 20 nm) 10 parts sulfonic acid metal salt-containing vinyl chloride resin 6 parts [Nippon Zeon Co., Ltd., MR-110] sulfonic acid metal salt-containing polyester polyurethane resin [Toyobo Co., Ltd., UR -8700] 3 parts Alumina 6 parts (α-Al ₂ O ₃ , number average particle size: 0.2 μm) Myristic acid 1 part Butyl stearate 1 part Cyclohexanone 100 parts Methyl ethyl ketone 100 parts Toluene 100 parts

[Magnetic Layer Coating Material A2] γ-Fe ₂ was used in place of the Co-substituted barium ferrite in the magnetic layer coating material A1.
Same as A1 except that O ₃ (Hc: 350 Oe, BET: 35 m ² / g, average major axis length: 240 nm) was used.

[Coating Material C for High Magnetic Permeability Layer] In the coating material B for coloring layer, TiO ₂ was replaced by Fe—Si—Al sendust alloy powder (coercive force Hc = 40 A / m, μi = 200 H /
m, particle size 50 nm), but the same as B.

[Thermal recording layer D1] α-alumina (number average particle size: 0.3 μm) 0.1 part Stearic acid 1.0 part Butyl stearate 0.5 part Thiodipropionic acid 0.5 part Sulfonic acid metal salt Containing vinyl chloride resin 1.5 parts (Nippon Zeon Co., Ltd. MR-110) 1,3-pentadiene polymer 0.2 parts Tetrahydrofuran 12.0 parts Sulfonic acid metal salt-containing polyester polyurethane resin 1.5 parts (TOYOBO) UR-8700 manufactured by Co., Ltd.)

[Thermal recording layer D2] 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide 1.0 part α-naphthol 0.2 part Stearic acid 0.2 part Butyl stearate 0. 2 parts α-alumina (number average particle size 0.3 μm) 0.1 part Vinyl chloride resin containing sulfonic acid metal salt 1.5 parts (MR-110 manufactured by Nippon Zeon Co., Ltd.) Polyester polyurethane resin containing sulfonic acid metal salt 1 .5 parts (Toyobo Co., Ltd. UR-8700) Cyclohexanone 30 parts Methyl ethyl ketone 15 parts Toluene 15 parts

[Protective Layer E] Vinyl chloride resin containing sulfonic acid metal salt 2 parts (MR-110 manufactured by Zeon Corporation) Polyester polyurethane resin containing metal sulfonate 2 parts (UR-8700 manufactured by Toyobo Co., Ltd.) α-alumina (number average particle size 0.3 μm) 2 parts Stearic acid 0.2 parts Butyl stearate 0.2 parts Cyclohexanone 50 parts Methyl ethyl ketone 25 parts Toluene 25 parts

Next, polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) 5 was added to each of the obtained magnetic paints A1 and A2, the coloring layer paint B, the high permeability layer paint C, and the protective layer paint E. Parts, 5 parts, 5 parts, 5 parts, and 0.8 parts were added, and then magnetic paint A1, high permeability layer paint C, and magnetic paint were sequentially formed on a white polyester film having a thickness of 188 μm by a wet-on-wet method. A2, coloring paint B, heat-sensitive recording layer paint D1, and protective layer paint E are applied in this order, and then a magnetic field orientation treatment is performed while the coating film is undried, and then dried, and then a calendar. Surface smoothing treatment was carried out to prepare a magnetic recording medium having the thickness shown in Table 1.

Example 2 D2 was used instead of D1 for the thermal recording layer in Example 1.
The same as Example 1 except that was used.

Example 3 5 parts, 5 parts and 5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) were added to each of the magnetic paints A1 and A2 and the paint C for the high magnetic permeability layer prepared in the same manner as in Example 1.
After adding the parts, the magnetic paint A1, the high-permeability layer paint C,
The magnetic paint A2 was applied in this order on a white polyester film having a thickness of 188 μm by the wet-on-wet method, and then the magnetic field orientation treatment was carried out while the coating film was undried, followed by drying and then the surface with a calendar. Smoothing treatment was performed to prepare magnetic recording media having the thickness shown in Table 1.

Example 4 Polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) 5 was added to each of the magnetic paints A1 and A2, the colored layer paint B, and the protective layer paint E prepared in the same manner as in Example 1.
Parts, 5 parts, 5 parts, and 0.8 parts were added, and then magnetic paint A1, magnetic paint A2, colored layer paint B, and protective layer were applied onto a white polyester film having a thickness of 188 μm by a wet-on-wet method. A magnetic recording medium having a thickness shown in Table 1 is prepared by applying the coating material E in this order, and then performing a magnetic field orientation treatment while the coating film is undried, followed by drying and then a surface smoothing treatment with a calendar. It was created.

Comparative Examples 1 to 4 The same procedure as in Examples 1 to 4 was carried out except that a wet-on-dry method (a lower layer was dried and then an upper layer was applied) was used instead of the wet-on-wet method.

<Evaluation> Durability during repeated use A magnetic card with a head pressure of 350 g and a running speed of 190 mm
After repeatedly running 2000 times with a magnetic card reader of 1 / second, the scraped state of the surface of the card was observed and visually judged.

A: There is no abrasion by the magnetic head on the card surface B: There is some abrasion by the magnetic head on the card surface C: Great abrasion by the magnetic head on the card surface

<Coatability> A: The coatability is good and uniform coating is possible. B: Streaks and coating omissions occur on a part of the original fabric (10% or less) C: Most of the original fabric (50% or more) Streaks or missing coating

[0103]

[Table 1]

[Brief description of drawings]

FIG. 1 is a diagram for explaining simultaneous multi-layer coating of magnetic layers by a wet-on-wet coating method.

FIG. 2 is a diagram of a coater head for applying a magnetic layer paint.

Claims (7)

[Claims] 1. A magnetic layer is provided on a support, and 1) on the magnetic layer.
At least one layer selected from a colored layer for hiding the coloring of the magnetic layer, 2) a heat-sensitive recording layer, 3) a protective layer, and 4) a high magnetic permeability layer containing a high magnetic permeability material is provided. Wet-on-wet in which the upper layer is applied while at least one layer selected from (4) to (4) is in a wet state.
A method for manufacturing a magnetic recording medium formed by a coating method. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the magnetic layer is composed of a plurality of magnetic layers having different coercive forces. 3. A high coercive force magnetic layer, a high magnetic permeability layer containing a high transmissivity material, and a low coercive force magnetic layer on a support in this order Wet-
A method for manufacturing a magnetic recording medium, which is applied by an on-wet application method. 4. A Wet-on-wet coating method in which a magnetic layer, a colored layer for hiding the coloring of the magnetic layer, and a protective layer are applied on a support in this order while the lower layer is wet while the upper layer is applied. Method of manufacturing formed magnetic recording medium. 5. The method for producing a magnetic recording medium according to claim 4, wherein the colored layer and / or the protective layer contain a non-magnetic powder having a Mohs hardness of 6 or more, a fatty acid and a fatty acid ester. 6. A wet-on-wet coating method in which a magnetic layer, a colored layer for hiding the coloring of the magnetic layer, and a thermosensitive recording layer are coated on a support while the lower layer is wet in this order. A method of manufacturing a magnetic recording medium formed by the method. 7. The method for producing a magnetic recording medium according to claim 6, wherein the heat-sensitive recording layer and / or the protective layer contain a non-magnetic powder having a Mohs hardness of 6 or more, a fatty acid and a fatty acid ester.