JPS62271223A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability and electromagnetic conversion characteristic by subjecting a nonmagnetic base to a non-contact surface treatment, then providing a magnetic layer contg. specific compds. as a binder thereon and irradiating radiations thereto. CONSTITUTION:The nonmagnetic base is subjected to the non-contact surface treatment and thereafter, the magnetic layer contg. respectively >=1 kinds of the groups expressed by A and B as the binder is provided thereon. and the radiations are irradiated thereon. A denotes a polyvinyl chloride compd. contg. respectively >=1 pieces of polar groups and carbon-carbon unsatd. bonds in the molecule and B denotes a polyurethane compd. contg. >=1 pieces of CO2H groups and carbon-carbon unsatd. bonds in the molecule. A magnetic recording medium having the excellent adhesiveness and the improved S/N and running durability is thus obtd. even if an intermediate layer is not provided.

Description

Detailed Description of the Invention 5. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic recording medium, particularly a magnetic recording medium with improved running durability and adhesion between a magnetic layer and a support. The present invention relates to a method for producing a medium.

[Conventional technology and problems]

Conventionally, magnetic recording media used for video, audio, information recording, etc. are made of ferromagnetic powder on a non-magnetic support. Magnetic recording media having an entire magnetic layer dispersed in a binder are widely used.

In recent years, there has been a demand for higher image quality and higher density for magnetic recording media, and it has become necessary to bring the magnetic head into closer contact with the surface of the magnetic layer, improving the smoothness of the surface of the magnetic recording medium. At the same time, it has become important to improve the dispersibility of ferromagnetic powder. On the other hand, as the smoothness of the surface of the magnetic layer improves, the friction in the tape running system increases, leading to higher running tension, and the magnetic recording medium is required to have increasingly severe running durability. In addition, especially as the recording density increases, the recording wavelength becomes smaller, which avoids thickness loss. Attempts have been made to make it thinner.

On the other hand, especially in magnetic recording media for high-density recording, the magnetic head has a precise structure, so even if fine dust or dirt adheres to the magnetic layer, it may affect recording and playback.
As mentioned above, as the recording density increases, there is a tendency to make the magnetic layer thinner, and if the adhesion between the support and the magnetic layer is poor, the magnetic layer tends to peel off easily, and even a small amount of such peeling can occur. This dirt often adheres to the magnetic layer and has an undesirable effect on recording and reproduction. Therefore, for high-density recording, it is desired to further improve the adhesion between the support and the magnetic layer.

[Failure to solve the problem]

In order to improve the adhesion of a magnetic recording medium having an intermediate layer, the present applicant previously proposed that a magnetic layer be provided as an intermediate layer after non-contact surface treatment is applied to the surface of the support (Japanese Patent Application Laid-Open No. 60-1970). -165254 publication).

The inventors proposed such a non-contact surface treatment? A magnetic recording medium that has excellent adhesion and improved S/N and running durability without the use of an intermediate layer by using a specific binder. To manufacture? The present invention has been achieved.

That is, the present invention is a magnetic layer in which ferromagnetic powder is dispersed in a binder on a non-magnetic support. In the method for producing a magnetic recording medium, the non-magnetic support is subjected to non-contact surface treatment, and then one or more of the following groups (A) and (■) are provided. This is a method for manufacturing a magnetic recording medium, which comprises providing a magnetic layer containing a binder and irradiating it with radiation.

(A) Polar groups and carbon-carbon unsaturated bonds? A polyvinyl chloride compound containing one or more of each in the molecule, (B) Co! Polyurethane compounds containing one or more H groups and one or more carbon-carbon unsaturated bonds in the molecule The present invention will be described in detail below.

Supports used in the present invention include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate gropionate. Cellulose derivatives such as;
Vinyl resins such as polyvinyl chloride and polyvinylidene chloride; Plastics such as polycarbonate, polyimide, and polyamideimide; Paper, baryta, or α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, and ethylene-butene copolymers. paper coated or laminated with a similar material.

There is no particular restriction on the surface roughness of the support used in the present invention, but it is preferably α001 μm or more, particularly 105 μm or more.

Is there any improvement in running performance etc. on the back of the support? For this purpose, a so-called back layer can be provided.

The non-contact surface treatment used in the present invention means that the surface of the support is treated by ultraviolet irradiation, glow discharge, corona discharge, flame treatment, electron beam irradiation, etc., without using mechanical means.
say.

For ultraviolet irradiation, ultraviolet rays of 220 nm to 370 nm are used, and a high-pressure mercury lamp having a relatively large absorption coefficient at wavelengths of 254, 313, and 365 nm in the bright line spectrum used for irradiating the intermediate layer as described later can be used.

The size and number of mercury lamps may be appropriately selected depending on the size of the base to be processed, processing speed, etc. Ultraviolet irradiation may be applied to both sides of the support, or may be applied only to the side on which the magnetic layer is provided.

In one preferred embodiment, a high pressure mercury lamp whose effective arc length is approximately the same as the width of the support, for example 30 (7) to 1 ff+, is used. Arrange multiple pieces horizontally in a row (for one side only) or two rows (for double-sided treatment) at a distance of 30α to 1m,
- In the case of a row, the surface to be treated faces the mercury lamp, and in the case of two rows, the support is run continuously between them. If necessary, the support may be heated to about 100° C. to 200° C. during irradiation.

The glow discharge treatment used in the present invention is, for example, α01-20
A pair of electrodes is placed in a vacuum of Torr, a high voltage of 500 to 000 s is applied between the electrodes, and the support to be treated is placed between the electrodes, or the support is continuously placed between the electrodes. This is done by running the vehicle. For example, British Patent No. 891.469 and Japanese Unexamined Patent Publication No. 1983
-13672 etc. can be used.

The corona treatment used in the present invention is carried out at 10 to 40 KV in gas.
It is a surface treatment by corona discharge that occurs at a high voltage of about
Flash discharge as described in Publication No. 67? Also includes. A conductive roller such as a metal roll (earth side) is used to run the support continuously, and corona radiation is generated between the roll and one corona electrode placed parallel to the roll. Is it okay to use two parallel electrodes? It is also possible to arrange the electrodes in parallel with the roll, apply a high voltage between both electrodes, and utilize the discharge generated between the electrodes and the rolls. In either case, the surface of the support on the side not supported by the rolls, ie, the side facing the electrode, is treated.

Is the flame treatment used in the present invention a paraffinic or olefinic hydrocarbon gas or a mixture of these gases and oxygen? A combustion gas is used to burn the gas in a burner, and the flame is applied to the surface of a continuously traveling support to treat the surface. In this case, the processing speed is about 100ffi/min, but 50
It can be set to about 0 g/min. These processing speeds may be appropriately selected depending on the distance between the flame and the support, the angle, etc. In this case as well, only one side of the support may be treated, or both sides may be treated simultaneously. If only one side is coated, the other side may be cooled using a cooling roller or the like. These treatment methods are described in British Patent No. 78a
No. 365, U.S. Patent No. 3,072,483, JP-A No. 5
The technology described in 0-11!1578 etc.? Can be used.

Is the electron beam irradiation in the present invention an electron beam accelerator? It is done using As the electron beam accelerator, a scanning method, a double scanning method, or a curtain beam method can be adopted, but the curtain beam method is preferable because it is relatively inexpensive and can provide a large output.

As for the electron beam characteristics, the acceleration voltage is 10 to 300 KV, and the entire surface of the support is irradiated with the electron beam at an absorbed dose of 1 to 10 megarads at 8 degrees.

In the present invention, a magnetic coating as described below is completely coated on a support surface-treated by the above-mentioned non-contact surface treatment, oriented in a magnetic field, dried and irradiated with radiation to form a magnetic layer.

After drying, surface treatment such as calender treatment may be performed if desired.

The shorter the time period from applying the non-contact surface treatment to applying the magnetic paint to the support, the more effective it is.

Although the effect is observed even after 120 hours have passed after the treatment, it is preferably within 50 hours, more preferably within 24 hours.

The magnetic paint used in the present invention is composed of (A) a polyvinyl chloride compound containing one or more magnetic groups and one or more carbon-carbon unsaturated bonds in the molecule; and (1) Co, H groups, and carbon-carbon bonds in the molecule. 1
It is obtained by using one or more polyurethane compounds as a binder and kneading them together with ferromagnetic powder and, if necessary, additives in an organic solvent.

Magnetic group and carbon-carbon unsaturated bond used in the present invention? The polyvinyl chloride compound (A) containing one or more of each in the molecule includes 00tH, OH,
5O3H, 5OINa, 0PO3H.

Vinyl chloride polymer containing at least one group such as 0PO1Na group and a carbon-carbon unsaturated bond, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl propionate copolymer, vinylidene chloride-acetic acid It is a copolymer such as a vinyl copolymer.

The preferred polar group is Co! H and OH groups are preferred, and Co and H groups are particularly preferred. Polar group is Co, H
When it is a group, an acid value containing Co and H groups is preferably about 1 to 30, more preferably 3 to 20, and most preferably 5 to 15.

If it is outside this range, the dispersibility of the ferromagnetic fine powder will be poor and the electromagnetic conversion characteristics will also be significantly reduced. The average content of carbon-carbon unsaturated bonds is 1.5 to 20 per molecule.
It is preferably between 2 and 15. Vi5 as molecular weight
．． noO~s o, o ao preferably 10.00
0 to 30,000. Outside this range, the curing properties may be poor or the durability may be poor.

These compounds are based on polyvinyl chloride polymers such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinyl acetate-vinyl alcohol copolymer. union, vinyl chloride-vinyl acetate-maleic acid-vinyl alcohol copolymer, vinyl chloride-vinyl propionate-vinyl maleate copolymer, vinyl chloride-vinyl propionate-vinyl alcohol copolymer, vinylidene chloride-vinyl acetate- Vinyl chloride systems such as maleic acid copolymer-vinylidene chloride-vinyl propionate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-acrylic acid copolymer, and vinyl chloride-vinyl acetate-acrylic acid-vinyl alcohol copolymer Copolymers and these copolymers may be used after being saponified.

The method for introducing carbon-carbon unsaturated bonds is to use some or all of the hydroxyl groups or shimke carboxyl groups in these copolymers, or some of the hydroxyl groups produced by cyanization. It can be obtained by denaturation. For example, by reacting a compound having an epoxy ring and a carbon-carbon unsaturated bond such as glycidyl acrylate with a part of the hydroxyl group of the base polymer, or by reacting one of the hydroxyl groups or carboxyl groups of the copolymer. Partly polyfunctional incyanates (e.g., 2.5-tolylene diincyanate, 2.6-tolylene diincyanate,
1.3-xylylene diisocyanate, 1.4-xylylene diisocyanate, 1.5-naphthalene diisocyanate, m-7 22 diisocyanate, p-phenylene diisocyanate, 43-dimethylphenylene diisocyanate), 4.4 -diphenylmethane diisocyanate, m3-onemethyl-4,4-diphenylmethane diisocyanate, hexamethylene diinocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate,) tolylene diisocyanate 3-adduct of rimethylolpropane, etc.) By reacting with the NCO group, the remaining NGO group is converted into an active hydrogen compound having a (meth)acryloyl group (hereinafter referred to as an acryloyl group, a methacryloyl group? collectively referred to as a (meth)acryloyl group), such as (meth)acrylic acid, 2- hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, 2-hydroquinpropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth)acrylamide, N-methylol (meth)acrylamide, etc.) It can be obtained by a reaction method.

Another polar group? For example, what are the following ways to introduce it? can be mentioned. Some of the hydroxyl groups or carboxyl groups of the above-mentioned base copolymer,
Or is it part of the hydroxyl group formed by saponification? It is reacted with one Neo group of the polyfunctional incyanate, and the remaining NCO group is converted into CotH group, S 03 Na group,
0PO3Na group etc? It can be obtained by reacting the hydroxyl group compounds contained therein. It is also possible to introduce the polar group simultaneously with the (meth)acryloyl group. Alternatively, a compound having both a polar group and a (meth)acyl group may be used.The method for introducing these groups is not limited to the above-mentioned method.

The urethane compound (B) containing at least one Co, H group, and carbon-carbon unsaturated bond in the molecule used in the present invention may have a main chain skeleton of polyester, polyether, or polyester ether. Specific examples of dibasic acids that can be used for these include citric acid, malonic acid, succinic acid, glumeric acid, adipic acid, sebacic acid, dodecanoic acid, maleic acid, fumaric acid, itaconic acid,
Trimethyladipic acid, hexahydrophthalic acid, tetrahydrophthalic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, etc. can be used.

Examples of dihydric alcohols include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 2.
2-dimethylpropane-1,3-diol, 2,2-diethylpropane-1,3-diol, cyclohexa:/
-1,3-diol, cyclohexane-1,4-diol, cyclohexane-1,4-dimetatool, cyclohexane-1,3-dimetatool, 2.2-bis(4-hydroxyethoxy-cyclohexyl)propane, 2.2
-bis(4-hydroxyethoxy-phenyl)furopane, 2,2-bis(4-hydroxyethoxyethoxy-phenyl)propane, etc. can be used. It is also possible to use a lactone-based polyester skeleton made of γ-butyrolactone, δ-valerolactone, 6-caprolactone, or the like. Examples of incyanates that form urethane bonds include 2,4-tolylene diisocyanate, 2,6-
) lylene diisocyanate, 1.3-xylylene diisocyanate, 1.4-xylylene diisocyanate, 1
．． 5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate), 1
5-dimethylphenylene diisocyanate), 4,4-diphenylmethane diisocyanate, 4-dimethyl-4
, 4-diphenylmethane diisocyanate, hexamethylene diisocyanate, inphorone diisocyanate,
Polyvalent isocyanates such as dicyclohexylmethane diisocyanate and tolylene diisocyanate triadduct of trimethylolpropane? Can be used. Further, a part of the dibasic acid and dihydric alcohol may be replaced with trivalent or higher acid and alcohol. CO! The H group and the acryloyl group may be located at the terminal or side chain of the polyurethane. As for the method of introducing these groups, 1) one or more of trivalent or higher acid, alcohol, or isocyanate? Incorporated into the urethane skeleton, Co! H group, OH group or NCO group? Are there carboxylic acid compounds and (meth)acryloyl compounds that can react with these groups in the residual urethane substrate? Co! It can be obtained by reacting an H group with an active hydrogen compound each having one or more (meth)acryloyl groups and one or more OH groups.

The acid value of the urethane compound used in the present invention is preferably 1 to 30, more preferably 3 to 20, and still more preferably 5 to 15. Molecule 9: 1,00
0-1o a, 000"7' dust, preferably 2,00
0 to 50,000, particularly preferably 3, [100 to 3c
It is L000. Is the acid value in this range? If it comes off, the dispersibility of the ferromagnetic fine powder becomes poor and the electromagnetic conversion characteristics deteriorate? This may lead to damage or the durability may deteriorate.

Moreover, the average content of (meth)acryloyl groups is 1.5 to 10 per molecule, preferably 2 to 8.

When the molecular weight is less than 1000, the magnetic layer of the obtained magnetic recording medium becomes too strong, which tends to cause cracks when bent, and the magnetic recording medium tends to curl due to curing shrinkage after irradiation with radiation. . On the other hand, the molecular weight is 10
If it exceeds 0.000i, the solubility of the urethane (meth)acrylate in the solvent will be poor and it will easily drop out, which will not only be inconvenient to handle, but will also deteriorate the dispersibility of the magnetic material and require a large amount of energy for curing. So I don't like it.

Furthermore, does the present invention include vinyl monomers? Can be added. Vinyl yarn threads are compounds that can be polymerized by radiation irradiation and have one or more carbon-carbon unsaturated bonds in the molecule, such as (meth)acrylic esters and (meth)acrylamides. , allyl compound,
Examples include vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, styrenes, acrylic acid, methacrylic acid, crotonic acids, itaconic acids, and olefins. Among these, preferred are the following compounds containing two or more methacryloyl groups. Specifically, diethylene glycol di(meth)
Acrylate, (meth)acrylates of polyethylene glycol such as triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)azirylate, dipentaerythritol Penta(meth)acrylate, Dipentaerythritol hexa(meth)azirylate, Tris(β-(meth)acryloyloxyethyl)
Isocyanurate, bis(β-(meth)acryloyloxyethyl)isocyanurate, polyisocyanate (2,4-)lylene diisocyanate, 2.6-
) lylene diisocyanate, 1.3-xylylene diisocyanate), 1.4-xylylene diisocyanate, 1
．． 5-naphthalene diisocyanate, m-phenylene diisocyanate), p-phenylene diisocyanate*-), 3
．． 5-dimethylphenylene diisocyanate, 4,4-
diphenylmethane incyanate, 3,3-dimethyl-
4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, inphorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate triadduct of trimethylolpropane)
reaction compounds with hydroxy(meth)acrylate compounds (2-hydroxyethyl(meth)azilylate, 2-hydroxypropyl(meth)acrylate, etc.), and other bifunctional or higher functional poly(meth)acrylates. . One type of these monomers may be used, or two or more types may be used.

The preferable composition ratio of the compound represented by (A) above and the compound represented by (5) above is 20 to 90 parts by weight/80
~10 parts by weight, particularly preferably 30-80 parts/70-2
It is 0 copies. If the ratio of the compound represented by (A) is less than this ratio or the ratio of the compound represented by (E) is less than this ratio, durability cannot be obtained. Further, the amount of the above-mentioned monomers added is preferably 50 parts by weight or less based on the total parts by weight of the compounds shown in (A) and (2) above. If the ratio exceeds this ratio, the radiation dose required for polymerization becomes large, which is undesirable, and the magnetic recording medium may curl or may not have sufficient durability.

As the ferromagnetic fine powder used in the present invention, ferromagnetic iron oxide fine powder, Co doped ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, ferromagnetic alloy powder, barium ferrite, etc. can be used. The acicular ratio of ferromagnetic iron oxide and chromium dioxide is about 2/1 to 20/1, preferably 5/1.
Above average length [12 to 2.0 μm and 8 degrees is effective. The ferromagnetic alloy powder has a metal content of 75 wt% or more, and 80 wt% or more of the metal content is a ferromagnetic metal (i.e., Fe).
, Co.

Ni, Fe-Ni, Co-Ni, Fs-C
o -Ni) with a major axis of about 1.0 μm or less. In the present invention, the EET specific surface area is 30, preferably 45 m2, which makes it difficult to disperse the particularly effective ferromagnetic fine powder.
It is a ferromagnetic alloy powder with fine particles of 71 or more.

Organic solvents used for dispersion and application of magnetic coating liquid include acetone, methyl ethyl ketone, methyl isobutyl ketone,
Ketones such as cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ether; ethyl ether, glycol dimethyl ether, glycol monoethyl ether,
Ethers such as dioxane and tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene can be selected and used.

Further, additives such as a lubricant, an abrasive, a dispersant, an antistatic agent, and a rust preventive may be added to the magnetic coating liquid of the present invention. In particular, lubricants include saturated and unsaturated higher fatty acids with 12 or more carbon atoms, fatty acid esters, higher fatty acid amides, higher alcohols, silicone oils, mineral oils, vegetable oils, fluorine compounds, etc., and these are used when preparing magnetic coating liquids. It may be added, or it may be dissolved in an organic solvent after drying or irradiation with radiation, or applied directly to the surface of the magnetic layer, or
May be sprayed.

In the present invention, it is preferable to irradiate radiation after applying a magnetic paint and performing calender treatment, but it is also possible to perform calender treatment after irradiation. Alternatively, it is possible to administer radiation one more time.

The radiation irradiated to the magnetic layer of the present invention includes electron beam, r
rays, beta rays, ultraviolet rays, etc. can be used, but electron beams are preferred. As the electron beam accelerator, a scanning method, double scanning method, curtain beam method, broad beam curtain method, etc. can be adopted. As for the electron beam, the accelerating voltage is 100 to 1000 KV, preferably 150 to 300 KV, and the absorbed dose is 1 to 20 KV.
Mraa, preferably 3 to 15 Mrad. When the accelerating voltage is less than 100 KV, the amount of energy transmitted is insufficient, and when it exceeds 100 CI KV, the efficiency of energy used in polymerization decreases, making it uneconomical. If the absorbed dose is less than I Mrad, the curing reaction will be insufficient and the strength of the magnetic layer will not be obtained, and if it exceeds 20 Mrad, the energy efficiency used for curing will decrease, the irradiated object will generate heat, and especially This is not preferred because the plastic support will be deformed.

[Implementation row]

The present invention will be explained in detail below using examples and comparative examples. In the following Examples and Comparative Examples, do all "parts" mean "parts by weight"? show.

In addition, in each implementation row, the adhesion between the support and the magnetic layer fr-
The peel strength was measured as follows.

FIG. 1 is an explanatory diagram showing the principle of measuring the peel strength of magnetic tape, in which the surface of the magnetic layer 3 of the magnetic tape 2 is adhered to one surface of the glass plate 1 with a screen adhesive tape 4, and the magnetic tape is
Bend it 80 degrees and have a spring at the end? Attachment, force in the direction of the arrow by the spring balance? In addition, the peel strength was defined as the force required to peel the magnetic layer.

In this run, magnetic tape with a width of 1.26 crn and a length of 5 scratches was tested, and the bonded length was 2G.

Example 1 The surface of a polyethylene terephthalate support having a thickness of 10 μm was subjected to a corona discharge treatment at 35 V and 7 mA.

Next, a magnetic coating liquid having the following composition was kneaded in a ball mill for 50 hours.

Fe-Ni alloy powder 400 parts (
Hl: 10wt%, 13000e BBT specific surface area 48
4) Binder composition Vinyl chloride copolymer acrylate 60 parts Urethane acrylate 40 parts Stearic acid 4 parts Butyl stearate 4 parts At! 0.
4 part carbon blank
10th part MKK
A 800-part dispersed layer was coated on the support using a doctor blade so that the film thickness after drying was 3 μm, oriented using a cobalt magnet, and then the solvent was dried (100° C. for 1 minute) and then calendered f! : Performed. Then acceleration voltage 1
65KV, beam IN, flow 6 mA and 7 Mr
After irradiating the tape with an electron beam to obtain an absorbed dose of AD, the sample was slit into I7 width to obtain a video magnetic tape sample.

Implementation row 2 Instead of the corona discharge in implementation row 1, an electron beam with an acceleration voltage of 150 KV was irradiated to a dose of 1.2 Mrad.

Others are the same as implementation row 1. Sample Nh2 Example 5 Instead of the corona discharge in Example 1, an I KW high-pressure mercury lamp made of a quartz tube with a length of 306 nm was used to discharge 300 m from a distance of 30 m.
Ultraviolet irradiation for 8eC, otherwise the same as in Example 1. Sample hermitage 3 Implementation test 4 Instead of the corona discharge in test row 1, a flame consisting of combustion gas of propane 1 9/hr and 0.2 97 hr was heated 80 m/hr.
The flame treatment was carried out by spraying vertically at a distance of 5 m onto the support traveling at a speed of 1.5 m. Sample voltage 4 Implementation pH 5 Instead of the corona discharge treatment in Example 1, 5 x 10-! T
orr, glow discharge treatment at 3 KV. Sample NQ5 comparison column 1 No contactless processing. Sample An 6 Comparative IH+2 Binder composition in Example 1? Changed to below.

1 Binder composition Chlorinated copolymer acrylate) 60 parts (acid value α7, molecule fi 1,7000, average acryloyl group content 2.5 pieces/molecule) Urethane acrylate 40 parts (acid value 8, molecule ff 1a000, average acryloyl group content Content 55
(pieces/molecules) Sample! +7 Example row 6 In Example 1, the magnetic layer was applied after being left for 24 hours after the corona treatment, but the rest was the same as Example 1. Sample 8 For these samples, the adhesion between the magnetic layer and the support as described above (peel test) and the following Video 8/N, Chroma 8/FJ
, still durability and output reduction were measured, and the results are shown in the following table.

Methyl durability: Using a VHS video tape recorder (manufactured by Matsushita Electric Industrial, NV8200),
Constant video signal for each sample)? Shows the time it takes for recorded and reproduced stop images to lose sharpness (experiments were carried out at 5°C and 8°C).
(performed at 0% RH).

Video S/N: Using the above video tape recorder,
50% set up gray light? Record and use Shibatsu G9
Measure the noise with a 2sc type 8/N meter and calculate the sample %
It is shown as a relative value when it is 1i0 (iB).

Chroma-8/N: The above video tape recorder? The green signal with a 1aa% set-up was recorded, and the noise was measured with a Kubasoku 925C S/N meter, and the noise was expressed as a relative value when sample interval 1 was taken as OdB.

Output drop; the above videotape recorder? 50% used
Record the gray signal of the setup, set the output when played back (first pass) to OdB, and play it repeatedly to 100 dB.
The entire reproduction output of the first pass was measured and expressed as a relative value with respect to the first pass.

Samples 6 and 7 are shown in the comparison column [Effects of the Invention] As is clear from the above results, when the method of the present invention is used, a magnetic recording medium with significantly improved durability and electromagnetic conversion characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the principle of measuring the strength of foil used in the implementation of the present invention. Agent Patent Attorney (8107) Kiyoshi Sasaki (and 2 others)

Claims (1)

[Claims] 1) A method for manufacturing a magnetic recording medium comprising providing a magnetic layer of ferromagnetic powder and a binder dispersed on a non-magnetic support, wherein the non-magnetic support is subjected to a non-contact surface treatment. (A) Polarity (B) A polyvinyl chloride compound containing one or more CO_2H group and one or more carbon-carbon unsaturated bond in the molecule; (B) A polyurethane compound containing one or more CO_2H group and one or more carbon-carbon unsaturated bond in the molecule. 2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the non-contact surface treatment is surface treatment by ultraviolet irradiation. 3) The method for manufacturing a magnetic recording medium according to claim 1, wherein the non-contact surface treatment is surface treatment using glow discharge. 4) The method for manufacturing a magnetic recording medium according to claim 1, wherein the non-contact surface treatment is surface treatment by corona discharge. 5) The method for manufacturing a magnetic recording medium according to claim 1, wherein the non-contact surface treatment is surface treatment by flame treatment. 6) The method for manufacturing a magnetic recording medium according to claim 1, wherein the non-contact surface treatment is surface treatment by electron beam irradiation.