JPS62159333A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the titled medium having an excellent electromagnetic conversion characteristic and excellent running property and running durability by forming binder of a resin component which contains a copolymer contg. a repeating unit derived from a vinyl chloride and repeating unit having a hydroxyl group which is not directly bound with carbon to constitute the main chain of the copolymer. CONSTITUTION:The binder is constituted of the resin component which contains the copolymer contg. the repeating unit derived from the vinyl chloride and the repeating unit having the hydroxyl group which is not directly bound with carbon to constitute the main chain of the copolymer. The hydroxyl group is introduced into the copolymer constituting the binder and since the hydroxyl group is not directly bound with the main chain of the copolymer, the approach of the copolymer and ferromagnetic powder is not hindered by the stereostructure of the copolymer and therefore, affinity between both is good and the dispersion condition of the ferromagnetic powder in a magnetic layer is consequently extremely good. The recording medium exhibits the excellent electromagnetic conversion characteristic as the squareness ratio of the magnetic layer is high and the surface of the magnetic layer is extremely smooth.

Description

[Detailed description of the invention] [Field of invention] The present invention relates to a novel magnetic recording medium.

[Background of the Invention] Generally, γ-Fe2O3゜CO-containing 4j iron oxide, C
A magnetic recording medium is used in which a magnetic layer in which ferromagnetic powder made of acicular crystals such as rO2, ferromagnetic metal fine powder, etc. is dispersed in a binder is provided on a nonmagnetic support.

Recently, demand for high-density recording has increased, and these ferromagnetic powders have become increasingly finer.

- On the other hand, a vinyl chloride copolymer is used as a resin component constituting the binder of the magnetic layer of a magnetic recording medium. In addition to the repeating unit derived from vinyl chloride, the vinyl chloride-based co-consolidation that accompanies the pulverization of ferromagnetic powder includes a repeating unit having a polar group such as a hydroxyl group directly bonded to the Y button. A vinyl chloride copolymer is used.

The polarity directly bonded to the L chain of the vinyl chloride copolymer acts to improve the affinity between the copolymer and the ferromagnetic powder. Then, not only the copolymer having this polar group but also the entire resin component containing this copolymer came to show good affinity with the ferromagnetic powder, resulting in the final state of dispersion of the ferromagnetic powder in the magnetic layer. You will be able to make several pieces.

Note that vinyl alcohol has conventionally been used to introduce a hydroxyl group as a polar group into a vinyl chloride copolymer.

However, from vinyl alcohol and vinyl chloride,
The hydroxyl groups introduced into the vinyl chloride copolymer that is introduced into the ferromagnetic powder are directly bonded to the main chain of the copolymer, so in order to improve the affinity between the ferromagnetic powder and the copolymer, both You will need to get very close.

However, in reality, the L chains of the copolymer are not linear but are complicatedly bent, and moreover, multiple L chains exist in a complicatedly entangled form, so that the surface of the ferromagnetic powder particles and the polar groups of both It is often difficult to approach the affinity sufficiently. In particular, in the case of finely powdered ferromagnetic powder, the ferromagnetic powder itself has a strong tendency to associate, making it extremely difficult to exert the action of polar groups on the surfaces of individual ferromagnetic powder particles.

In this way, if the affinity between the ferromagnetic powder and the resin component is low, the dispersion state yE; of the ferromagnetic powder in the magnetic layer will be low. First, problems arise in that the electromagnetic conversion characteristics are not sufficiently improved and the effect of pulverization is not fully exhibited.

Furthermore, there is a problem in that the strength of the magnetic layer and the supply of lubricant to the surface of the magnetic layer are also reduced due to the poor dispersion state of the ferromagnetic powder.

[Object of the Invention] An object of the present invention is to provide a novel magnetic recording medium exhibiting excellent characteristics.

A further object of the present invention is to provide a magnetic recording medium in which Y has modified electromagnetic conversion characteristics.

Another object of the present invention is to provide a magnetic recording medium that has excellent electromagnetic change characteristics, as well as excellent running properties and running durability.
1 target.

[Summary of the Invention] An undeveloped IJ is a magnetic recording medium comprising a non-magnetic support and a magnetic layer provided on the support in which ferromagnetic powder is dispersed in a binder, wherein the binder is chlorinated. From a resin component containing a copolymer containing a repeating unit derived from vinyl and a repeating unit having l:, hydroxyl not directly bonded to the tertiary element constituting the chain), A magnetic recording medium is characterized in that it is composed of:

[Effects of the Invention] The magnetic recording medium of the present invention has a hydroxyl group introduced into the copolymer constituting the binder, and the wood acid group is not directly bonded to the 'E chain of the copolymer. , No I:, T< Since the approach between the coalescence and the ferromagnetic powder is rarely inhibited by the three-dimensional structure of the copolymer, there is good affinity between the two, and therefore, the dispersion of the ferromagnetic powder in the magnetic layer is improved. Condition y8 is very good. That is, the magnetic recording medium of the present invention exhibits excellent electromagnetic conversion characteristics because the squareness ratio of the magnetic layer is high and the surface of the magnetic layer is extremely smooth.

Furthermore, since the magnetic recording medium of the present invention has a good dispersion state of the ferromagnetic powder in the magnetic layer, there are fewer lumps of ferromagnetic powder, and the binder surrounding each particle of the ferromagnetic powder and the adjacent particles Since the bond with the surrounding binder is strong, the magnetic layer has high strength and exhibits good running durability.

Further, in the magnetic recording medium of the present invention, since the ferromagnetic powder is in a well-dispersed state in the magnetic layer, the gap formed by a plurality of adjacent ferromagnetic powder particles does not become excessively large, and a lubricant is applied to this gap. Since it is supplied to the surface of the 111th magnetic layer without being retained, it exhibits good running properties.

[Detailed Description of the Invention] The magnetic recording medium of the present invention has a basic structure in which a non-magnetic support and a magnetic layer made of ferromagnetic powder dispersed in a binder are provided on the non-magnetic support. It has the following.

As the nonmagnetic support for the magnetic recording medium in the present invention, commonly used nonmagnetic supports can be used. Examples of materials forming the nonmagnetic support include various synthetic resin films such as polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamideimide, and polyimide, and metal foils such as aluminum foil and stainless steel foil. can be mentioned.

Further, the nonmagnetic support used generally has a thickness of 3 to 50 pm, preferably 5 to 3071 m.

The nonmagnetic support may be provided with a backing layer on the side where the magnetic layer is not provided.

The magnetic recording medium of Unreleased II is one in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support as described above.

Examples of ferromagnetic powders that can be used in the present invention include those commonly used as ferromagnetic powders:
Ferromagnetic metal fine powder containing iron as a component, γ-Fe2
0. and iron oxide-based ferromagnetic powders such as Fe 304, and modified metal iron oxide-based ferromagnetic powders such as Co-modified iron oxide, barium ferrite, strontium ferrite, and the like.

The ferromagnetic powder contained in the magnetic layer of the magnetic recording medium of the present invention is preferably a finely powdered modified iron oxide-based ferromagnetic powder and a fine ferromagnetic metal powder. This is because even ferromagnetic powder has a good dispersion state. In particular, when the specific surface area of the ferromagnetic metal fine powder is 42rrf/g or more (and even 45rn'/g or more)
It is preferable that the modified iron oxide-based ferromagnetic powder has a specific surface area of 30 m'/g or more (and more preferably 35 rn'/g).
g to 7) is preferable.

Note that as the iron oxide-based ferromagnetic powder, commonly used ones can be used.

As an example of a ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75 ton; Metal or alloy (e.g., Fe, Co, Ni, Fe-Co, F
e-Ni, Co-Ni, Co-Ni-Fe),
Metal content (7) 20%: other components (e.g., An, Si, S, Sc, Ti, ■, Cr) within a range of 1% or less
, Mn, Cu, Zn, Y.

MOlRh, Pd, Ag, Sn, Sb, Te, Ba, T
a, W, Re, Au, Hg, Pb, B, La, Ce, P
Mention may be made of alloys which may contain r, Nd, Bi, P). Further, it may be one containing water, hydroxide, or oxide with a small amount of ferromagnetic metal L. The manufacturing method of these ferromagnetic metal fine powders is already known,
Ferromagnetic metal fine powder, which is an example of ferromagnetic powder used in undeveloped IJJ, can also be produced according to these known methods.

Furthermore, production of iron oxide-based ferromagnetic powder and modified iron oxide-based ferromagnetic powder is already known, and the products used in the present invention can also be produced by FA according to these known methods.

There are no particular restrictions on the shape of the ferromagnetic powder, but it is usually acicular,
Granular, dice-shaped, rice grain-shaped, plate-shaped, etc. are used. In particular, it is preferable to use acicular-shaped ferromagnetic powder.The acicular ratio (minor axis length:long axis length) of the ferromagnetic powder is usually 1:
3 or more (preferably 1:8 or more).

The magnetic layer of the magnetic recording medium of the present invention usually contains 10 to 40 modified parts (preferably 15 to 30 parts by weight) of a binder per 100 parts by weight of the ferromagnetic powder listed in L. has been done.

The binder of the magnetic layer of the magnetic recording medium of the present invention contains a repeating position derived from vinyl chloride and a repeating position having a hydroxyl group that is not directly bonded to carbon constituting the main chain of the copolymer. It is composed of a resin component containing a copolymer.

That is, the copolymer of item L is a vinyl chloride copolymer into which hydroxyl S, which has been used conventionally, is introduced.
Basically, it is the distance from the 1st chain of copolymerization (woody acid) & by 1 point.

The hydroxyl group introduced by vinyl alcohol, which is used to introduce the water ll11i group into the vinyl chloride copolymer used in ordinary magnetic recording media, is directly bonded to the r: button of the copolymer. Unless the main chain of the copolymer is close to the ferromagnetic powder, the affinity of the hydroxyl group directly bonded to the main chain cannot effectively act on the surface of the ferromagnetic powder particles Y-.

On the other hand, in the copolymer of the present invention, the hydroxyl groups are not directly bonded, that is, the hydroxyl groups are bonded to the main chain via an alkylene group, etc., and the t-button and the hydroxyl groups are separated. For example, it is less affected by the one-button sea urchin structure of the copolymer. Therefore, the affinity of the hydroxyl groups on the surface of the grains I- of the ferromagnetic powder is more likely to be exerted, so that the state of dispersion of the ferromagnetic powder in the magnetic layer is improved.

The copolymer constituting the binder of the magnetic layer contains repeating units derived from vinyl chloride. This repeating position is usually contained in the copolymer in an amount of 60% by weight or more (preferably more than % g O TORU: %). 601 darkness%
If the amount is less, the strength of the copolymer itself will be low, and the strength of the magnetic layer may not be sufficiently improved.

Examples of repeating units representing hydroxyl groups that are not directly bonded to the carbon atoms forming the main chain of the copolymer constituting the binder include 0=C-0-RI-0H O-Co-R2-OH and , can be mentioned.

However, in formula (I), formula [171 and formula [111], R is a hydrogen atom r- or a methyl group.In addition, in formula 1 ['I], 8 plates are 35 prime numbers 2 to 1O divalent Hydrocarbon nor or carbon a4 to 1O fullkylene oxide B,
~3)), and in formula [II], R2 has 1 carbon number
~10 monovalent hydrocarbon groups or polyalkylene oxide residues having 4 to 10 carbon atoms (e.g., same J:, ), and in formula 1 [[], R3 is a -monovalent carbon group having 1 to 17 carbon atoms. It is a hydrogen group or a polyalkylene oxide residue having 4 to 10 trivalent atoms (eg, 3 L).

The copolymer contains one or more of these repeating units.

Repeating position J of L (content in the polymer is usually 0.5 to 20% by weight (preferably 3 to 20% by weight)
) is within the range. If the amount is less than 0.5% by weight, the effect of introducing hydroxyl groups may not be sufficiently exhibited, and the ferromagnetic powder may not be sufficiently dispersed. On the other hand, if the amount exceeds 20%, the solubility of the copolymer in an organic solvent decreases, and as a result, the dispersion state of the ferromagnetic powder may not be sufficiently improved.

In addition, the copolymer described in item h usually contains vinyl chloride-based ( It may also contain other repeating units contained in the polymer. Examples of other repeating units include:
Examples include repeating units derived from vinyl acetate, repeating units derived from maleic anhydride, repeating units having a polar group such as -3O3N&, and collapsing units having an epoxy group. In particular, the humidity and heat stability of vinyl chloride is improved by introducing Evogojino^.

However, the content of other edging units in the copolymer is usually 10% by weight or less.

Further, the degree of polymerization of the copolymer is usually within the range of 150 to 650 (preferably 200 to 600). Degree of polymerization is 15
If the copolymer is less than 0, the strength of the copolymer itself is not sufficient, so the running durability may not be sufficient. There are times when I do.

Such a Jt-polymer can be produced by adding 41 repeating units to the hydroxyl groups that are not directly bonded to the carbon atoms constituting one main chain of the copolymer, for example, in accordance with the method for producing ordinary vinyl chloride copolymers. It can be produced by copolymerizing the intermediate and vinyl chloride to be derived, and 'El:lS from which other repeating units are derived if necessary.

Of the intermediates that induce repeating units having hydroxyl groups that are not directly bonded to carbon atoms constituting the chain of the copolymer, those with the formula [
Qi-! used to introduce the repeating unit of I]! Examples of @:: bodies include 2-hydroxyethyl acrylate, 10-
Mention may be made of hydroxydecyl acrylate, 2-hydroxyethyl methacrylate and diethylene oxide acrylate. Further, as an example of the intermediate used for introducing the formula [■], vinyl 3-hydroxypropionate can be mentioned. Furthermore, allyl alcohol can be mentioned as an example of the ill cartilage used for introducing Formula 1 [m].

As the binder, the copolymer listed in L can be used alone as a resin component, but in addition to this, it is preferable to use a resin that is commonly used as a resin component of magnetic recording media, especially as a resin component. It is preferable to use polyurethane resins in combination. Examples of polyurethane resins include commonly used polyurethane resins, polyester polyurethane resins, and polyurethane resins having polar groups such as sulfonic acid no^. can.

When using polyurethane resin, the blending ratio of the above copolymer and polyurethane resin, Rjj: ratio is 9:1-1+
It is preferable to set it within the range of 9.

Further, it is preferable to use a curing agent in addition to the resin component L. In particular, when fine ferromagnetic metal powder is used as the ferromagnetic powder, by using a hardening agent, a magnetic layer with high strength can be obtained even though fine ferromagnetic metal powder with low hardness is used. As the curing agent, polyisocyanate compounds that are normally used in the production of polyurethane resins are used.

When using a hardening agent, the combination of the resin component and the hardening agent
The tolerance ratio is preferably within the range of 9:1 to 5:5.

Generally, the magnetic layer of the magnetic recording medium of the present invention contains an abrasive. There is no particular restriction on the abrasive to be used, and commonly used abrasives can be used. The abrasive is usually used in an amount of 0.2 to 1 per 100 parts of ferromagnetic powder.
Q modified: , +L part is blended.

In addition to the abrasive material described above, it is preferable to contain conductive carbon black, a lubricant, and the like.

It is preferable to use the 411 lubricant in combination with a plurality of lubricants, such as a combination of a lubricant that acts on L during low-speed running and a lubricant that acts on 1 during high-speed running.

Next, an example of the method for manufacturing the magnetic recording medium of the present invention will be described.

First, a magnetic paint is prepared by kneading a ferromagnetic powder, a resin component, and, if necessary, an abrasive or an additive described in 1- above with a solvent. As the solvent used during kneading, solvents commonly used in the preparation of magnetic paints can be used.

There is no particular restriction on the kneading method, and the order of addition of each component can be set as appropriate.

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, and lubricants may also be used.

The magnetic paint thus prepared is applied onto the aforementioned non-magnetic support. Coating can also be done directly onto the non-magnetic support.

Moreover, it can also be applied to the support fx via an adhesive layer or the like.

The magnetic layer is generally applied so that the thickness after drying is in the range of 0.5 to 10 m, preferably in the range of 1.5 to 7.0 m.

A magnetic layer coated on a non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. Furthermore, a surface smoothing treatment can be applied if necessary.

Magnetic recording media that have been subjected to surface smoothing treatment, etc.

Next, after performing a curing treatment and a blade treatment as desired, it is cut into a predetermined shape.

Next, Examples and Comparative Examples of the present invention will be shown. In addition, the expression "part" in the Examples and Comparative Examples is r T< +1
[Example 1] The composition described above was cross-dispersed for 3 hours using a sand grinder, and then passed through a filter having an average pore size of 3 ILm to coat the magnetic paint. Prepared. The obtained magnetic paint was coated with a thickness of 7 gm so that the thickness of the magnetic layer after drying was 5.0 gm.
The surface of the ILm polyethylene terephthalate support was coated using a reverse roll.

Magnetic paint composition CO deposition y - Fe OX (x = 1.45, Co: 5 mol%, Hc: 68
00e, acicular ratio 1:12° Specific surface area: 40rn'/g
20 parts polyester polyurethane resin (minutes IF, ij, 50,000)
5 part α-A intersection, 0° (+- average R/- diameter: 0, 5 JLm)
2KB myristic acid
3-part dimethylpolysiloxane (degree of polymerization 6o) 0.5t
Methyl ethyl ketone 180 parts Cyclohexanone 60 parts However, the vinyl chloride copolymer described in
2-Hydroxyethyl acrylate copolymer (copolymerization)
rji + knee Lt = 92 + 3: 5, degree of polymerization 4
00) was used.

The non-magnetic support coated with magnetic paint 41 was subjected to magnetic field orientation treatment using a 1000 Gauss magnet at y5 with the magnetic paint undried, and after drying, supercalender treatment and blade treatment were performed to give a width of 3.81 mm. slit into
Phillips type compact cassette tape (c-90
) was manufactured.

The squareness ratio of the magnetic layer of the 111 cassette tape, surface gloss, maximum focus ↑ output (MOL), saturation output (SQL),
Bias noise (BN), running performance, and degree of dirt adhesion to the tape pad and magnetic head in the apparatus were measured. The results are shown in Table 1.

The measurements described above were carried out as follows.

An external magnetic field (
Hm) B r at 2 kOe (159 kA/m)
/Bm value was measured.

Surface Glossiness Using a surface gloss meter (Suga Test A1M5J, GK-45D), the glossiness of the surface of the magnetic layer was measured, and the glossiness of the black standard surface was measured by 8.
It was measured as 7%.

The maximum undistorted output of MOL 315Hz (first product frequency 3%) was measured. The values shown are relative values when the MOL of the cassette tape manufactured in Comparative Example 1 is OdB. The measuring device was a TCK-777ESH model (manufactured by Sony ■).

The saturation output of SQL 10kHz was measured. The values shown are relative values when the SQL of the cassette tape manufactured in Comparative Example 1 is OdB. Note that the measuring machines are of the types L and 3.

Bias noise (measured using the BN model)
The measured values of BN) shown in 6 are relative values when the 7 Hayas noise (BN) of the cassette tape manufactured in Comparative Example 1 is taken as OdB.

Running property (1) When 50 rolls of the cassette tape were run back and forth 20 times using 50 commercially available cassette tape decks, the running stop 1 - number of cassette tape turns was measured.

A・Φ Stop F No cassette tape BII - Stop F cassette tape Volumes 1 to 2 71j Adhesion degree ■ - After the recorded running test, observe the degree of dirt adhesion to the tape pad and magnetic head in the cassette deck. Evaluation was made according to the criteria set forth in F.

A-No φ7 cracks attached B--Slight dirt is observed C--Stain is observed although it is not a problem in actual use [Example 2] Example 1 A Phillips-type compact cassette tape was produced in the same manner except that the vinyl chloride copolymer described in F below was used.

Vinyl chloride/vinyl acetate 2-hydroxyethyl acrylate copolymer copolymer [
5 ratio -87:3:10 Degree of polymerization 400 The same types of measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 3] A Phillips-type compact cassette tape was produced in the same manner as in Example 1, except that the vinyl chloride-based composite described below was used.

゛ Vinyl chloride-vinyl acetate/2-hydroquine ethyl acrylate copolymer copolymer
, ;, Ratio = 77: 3: 20 tension degree 400? 1? The same types of measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 4] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride, vinyl acetate, 10-H-F'a-xydenyl acrylate (, jk, 7.
(Combined combination 7. + ratio = 92:3:5 Degree of polymerization 400 The obtained cassette tape was subjected to the same measurements as in Example 1. The results are shown in Table 1.

[Example 5] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described in F below was used.

Vinyl chloride/vinyl acetate/2-hydroxyethyl methacrylate copolymer copolymer ratio: 92:3:5 Degree of polymerization: 400 The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 6] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl n1-S=donyl acid-2-hydroxyethyl acrylate-glycidyl acrylate copolymer Yatun: Ratio=91+3:5:1 Degree of polymerization 400 The obtained cassette tape was made of the same type as in Example 1. Measurements were made. The results are shown in Table 1.

[Example 7] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride/vinyl acetate/2-hydroxyethyl acrylate copolymer copolymer ratio = 92:3:5 - degree of polymerization 200 The same measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 8] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride/vinyl acetate/2- and droxyethyl acrylate copolymer copolymer ball 1
．． Y ratio = 92:3:5 Degree of combination: 600 The same types of measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 9] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride-2-hydroxyethyl acrylate
Ratio=92:8 Degree of polymerization 400 The same types of measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 10] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

Vinyl chloride φ Vinyl acetate/diethylene oxide acrylate copolymer copolymer I
4 ratio=92:3:5 Degree of polymerization 400 The same types of measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Example 11] A Phillips-type compact cassette tape was produced in the same manner as in Example 1, except that the vinyl chloride-based composite described below was used.

Vinyl chloride/vinyl acetate/vinyl 3-hydroxypropionate H polymer copolymer ball 15
The same type of measurements as in Example 1 were carried out on a cassette tape having a ratio of 92:3:5 and a ratio of 400 to 11I. The results are shown in Table 1.

[Example 12] In Example 1, vinyl chloride-based JC described below
A Phillips-type compact cassette tape was produced in the same manner except that a stretch composite was used.

Vinyl chloride/vinyl acetate JL/'' Allyl alcohol copolymer copolymerization east;,', ratio = 92: 3: 51, degree of 4
00 The same types of measurements as in Example 1 were performed on the obtained cassette tape. The results are shown in Table 1.

[Comparative Example 1] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that the vinyl chloride copolymer described below was used.

■ IA vinyl/vinyl acetate/vinyl alcohol copolymer combination: j-Lt = 92: 3: 5 ratio 40
The same types of measurements as in Example 1 were performed on the cassette tape prepared in Example 1. The results are shown in Table 1.

;°Ding,'1. ．． ．． White Table 1 Squareness Ratio Glossiness) IOL 煕L BN Runnability Depth μ
(X) (dB) (dB) (dB) Example 1 0.91 165 1.31.8-0.5
A A2 0.92 172 1.52.1-
0.5 A A3 0.89 160 0.
91.1-0.2 A 84 0.91 +
65 1.21.9-0.4 A A5 0.
91 1611i 1.31.7-0.4 A
A6 0.9+ 164 1.41.8-
0.5 A A7 0.90 +63 1
．． 51.3-0.3 A B8 0.89 1
59 1.11.0-0.2 B A9 0.
9+ 165 1.41.6-0.4 A
B10 0.90 164 1.21.7-0.
2 A 811 0.92 171 1.4
2.0-0.3 A A12 0.91 16
5 1.21.6-0.3 A A Comparative Example 1 0.87 151 Q, Oo, OO, OB
C [Example 13] The composition of F was cross-dispersed for 5 hours using a sand grinder, filtered using a filter having a uniform pore size of 1 m, and then mixed with a polyisocyanate compound (Desmodur L-75). (manufactured by Bayer AG)) and mixed to prepare a magnetic paint. The obtained magnetic paint was coated on the surface of a polyethylene terephthalate support with a thickness of 10 parts m using a glue/glass roll so that the thickness of the magnetic layer after drying was 3.0 gm.

Magnetic paint composition Ferromagnetic metal fine powder (components: Fe, Zn, AfL, He, 15000
e, acicular ratio, 1:15, specific surface area, 60g/g) 100
Part Vinyl chloride Kyodogougi 10 parts Polyester polyurethane resin (contains sulfonic acid groups in O, 5B%, average molecular weight 50,000) 10 parts α-A 20 parts
3 (uniform particle diameter: 0.2ILm) 3 parts stearin 2 parts butyl stearate 1 part conductive carbon (uniform particle diameter: 10 muL) 1 part methyl ethyl ketone 180 parts cyclohexanone 60 parts However, L
As the vinyl chloride copolymer described above, the vinyl chloride/vinyl acetate/2-hydroxyethyl acrylate copolymer used in Example 1 was used.

The non-magnetic support coated with the magnetic paint was subjected to magnetic field orientation treatment using a 3000 Gauss magnet while the magnetic paint was not dry, and after drying, supercalender treatment, hardening treatment and blade treatment were performed to obtain a width of 8 mm. It was slit to produce 8mm video tape.

Squareness ratio 1 surface glossiness of the magnetic layer of the obtained videotape,
The C-5/N ratio, Y-S/N ratio, methyl life, runnability and durability were measured and the results are listed in Table 2.

Incidentally, the measurement in item 1- was carried out as follows.

An external magnetic field (H
m) B r at 5 koe (398 kA/m)
/ B m was measured.

Surface gloss It was measured by the same method as in Section 11ii.

Recording wavelength of videotape manufactured in C-fist S/N ratio comparison example 2: 0.7MH
The S/N ratio was measured when the S/N ratio at z was expressed as OdB.

The measuring device is FUJ lX-8 (Futo Photographic Film ■
Made in Japan).

Y・S/N lt Recording wavelength of videotape manufactured in Comparative Example 2 5 MH
The S/N ratio was measured when the S/N ratio at z was expressed as OdB.

Note that the measuring device was FUJ 1X-8.

Still Life In still mode, the time required for the Y-S/N ratio of the image to become 6 dB lower than the starting image was measured.

Note that the measuring device was FUJIX-8.

Running properties were evaluated based on the degree of jitter and skew during running according to the criteria described below.

A. Both jitter and skew are good. B. - Although it is not a problem in actual use, both jitter and skew have increased. Durability After running 100 times, jitter, skew and dropout are observed. The degree of increase was evaluated according to the criteria described in Doki.

A-9 No particular problem B--An increase is seen that does not pose any particular problem in actual use C--Excessive increase is seen Examples 14-23. Comparative Example 2] An 8 mm video tape was produced in the same manner as in Example 13, except that the vinyl chloride copolymer described below was used.

Squareness ratio 1 surface glossiness of the magnetic layer of the obtained videotape,
The C@S/N ratio, Y2, S/N ratio, still life, running performance and durability were measured and the results are listed in Table 2.

Vinyl chloride copolymer used

Claims (1)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer provided on the support in which ferromagnetic powder is dispersed in a binder, wherein the binder is made of vinyl chloride. It is characterized by being composed of a resin component containing a copolymer containing a derived repeating unit and a repeating unit having a hydroxyl group that is not directly bonded to carbon constituting the main chain of the copolymer. magnetic recording media. 2. A repeating unit with a hydroxyl group that is not directly bonded to carbon that constitutes the main chain of a copolymer is a repeating unit represented by the formula, ▲mathematical formula, chemical formula, table, etc. (where R^1 is a carbon Number 2~
10 divalent hydrocarbon groups or polyalkylene oxide residues having 4 to 10 carbon atoms, and R is a hydrogen atom or a methyl group), formula, ▲ Numerical formula, chemical formula, table, etc. ▼ Repetition represented by Unit (However, R^2 has 1 or more carbon atoms
10 divalent hydrocarbon groups or polyalkylene oxide residues having 4 to 10 carbon atoms, R is a hydrogen atom or a methyl group), and is represented by the formula, ▲numeric formula, chemical formula, table, etc.▼ repeating unit (however, R^3 is a carbon number of 1 to
17. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is at least one type of repeating unit selected from the group consisting of 17 divalent hydrocarbon groups, R is a hydrogen atom or a methyl group. 3. A patent characterized in that the content of repeating units having hydroxyl groups that are not directly bonded to carbons constituting the main chain of the copolymer is within the range of 0.5 to 20% by weight. A magnetic recording medium according to claim 1. 4. The magnetic recording medium according to claim 1, wherein the degree of polymerization of the copolymer is within the range of 150 to 650. 5. The magnetic recording medium according to claim 1, wherein the content of repeating units derived from vinyl chloride in the copolymer is 60% by weight or more. 6. The magnetic recording medium according to claim 1, wherein the binder further comprises a resin component containing a polyurethane copolymer.