JPS62222426A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To permit the use of various resins and to obtain a magnetic recording medium having a low coefft. of friction by providing a rear surface layer modified of a film forming resin by using a specific modifying agent at the time of producing the magnetic recording medium. CONSTITUTION:The modifying agent having <=50,000mol.wt. is prepd. by adding a methyl ethyl ketone as a solvent to an amino acid modified oil having a reactive functional group and phenyl isocyanate, adjusting the ratio of the org. functional group/isocyanate group to 1 or above and bringing the mixture into reaction at 20-80 deg.C. Such agent is coated on the rear surface of a nonmagnetic base having a magnetic layer stop the same. The formation of film can be made by the modifying agent itself. The rear surface layer maintains the various characteristics intrinsically possessed by the film forming resin and has such a low coefft. of friction which cannot be attained by the conventional practice if the rear surface film is formed by adding the modifying agent and binder resin such as vinyl chloride known heretofore at about 1-100:100 by weight. The adequate magnetic recording medium is thus obtd.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a magnetic recording medium, and more particularly, the present invention relates to a high-performance magnetic recording medium whose back layer is formed from a film-forming resin modified with a specific modifier. Regarding the medium.

(Prior Art) Conventionally, magnetic recording media used in audio equipment, computers, etc. are obtained by forming a magnetic layer made of magnetic particles and a film-forming resin on a non-magnetic support such as a polyester film.

Such a magnetic layer is formed by coating a support with a dispersion in which magnetic particles are dispersed in a medium containing a resin.

Further, especially when the magnetic recording medium is in the form of a tape, a back layer is formed in order to improve running stability of the tape, reduce frictional resistance between the tapes, or improve characteristics such as electrical characteristics.

The back layer is required to have various physical properties, but the performance required in particular for the magnetic recording medium is good running properties, and for this purpose it is strongly required that the coefficient of friction between the magnetic recording media be low. Ru. The level of such friction coefficient is mainly determined by the film-forming resin used to form the back layer.

Conventionally, film-forming resins for forming the back layer include:
Mainly vinyl chloride resins, polyurethane resins, polyester resins, nitrocellulose resins, epoxy resins, etc. are used alone or in combination.

(Problems to be Solved by the Invention) The coefficient of friction of the film-forming resins conventionally used as described above is generally 0.
4 or more, and when using a magnetic recording medium with a back layer formed from these film-forming resins as a video tape, audio tape, etc., the tape has insufficient slip properties, so it is difficult to wind the tape. When the tape is used at high speeds, such as during reversing, it causes irregular winding, which causes deformation and damage to the tape, causing dropouts.

As a method to solve these drawbacks and lower the coefficient of friction of magnetic recording media, fatty acids, wax,
A method of adding a lubricant such as silicone oil has been used, but with this method, the lubricant added to the magnetic layer bleeds out to the surface of the back layer and transfers to the magnetic layer, causing damage to the recording head. Another drawback arises in that 11 jams occur.

As a method to solve these drawbacks, it has been proposed to use a resin with a low coefficient of friction as the film-forming resin itself, such as a polyurethane resin having a siloxane bond in one molecule (for example, in 57-176535
No. 59-94237, No. 59-5421, No. 5
No. 8-218034, No. 58-222436, No. 59
-11535, Publication No. 59-82636, etc.)
.

According to this method, it is possible to form a back layer with a relatively low coefficient of friction, but since the polyurethane resin containing the siloxane bonds contains siloxane bonds in the main chain of the polymer, sufficient reaction cannot be achieved. It is difficult to produce a film-forming resin of constant quality, resulting in high cost, and various problems arise due to unreacted silicon compounds.

Furthermore, since the polymer is limited to polyurethane resins, there is a problem in that the range of use thereof is significantly limited.

In order to solve the above-mentioned drawbacks of the conventional technology and to meet the above-mentioned demands, the inventor of the present invention has conducted intensive research to solve the above-mentioned drawbacks of the conventional technology and to meet the above-mentioned demands. When forming the back layer, the above-mentioned drawbacks of the conventional techniques are solved, the film-forming resin is not limited to polyurethane resin, and various film-forming resins can be easily used, and the magnetic recording medium has a low coefficient of friction. The present invention was completed by discovering that it is possible to provide the following.

[Means for solving problems]

That is, the present invention comprises a non-magnetic support, a magnetic layer provided on one side of the support, and a back layer provided on the other side of the support, and the back layer has a reactive organic functional group. A magnetic recording medium characterized by comprising a film-forming resin modified with a modifier that is a reaction product of a silicone compound having an organic isocyanate and an organic isocyanate and does not have a free isocyanate group.

To explain the present invention in more detail, the film-forming resin modifier used in the present invention and which primarily characterizes the present invention is a reaction product of a silicone compound having a reactive organic functional group and an organic isocyanate. , and the reaction product does not have an isocyanate (*) in the molecule.

Preferred examples of the silicone compound serving as the reactive organic functional group used to obtain such a modifier include the following compounds.

(1) Amino-modified silicone oil (m=1"lo, n-2~10, R=CH3 is OC
H3) (m=I~lo, n=2~10, R=C:H3t
riha OCH3) (ffl bow ~200) CH3 (n=2~10) OrSi(CH3)201 l5i(CH3)3H2N
R51Q[5i(CH3)2(]] m5i(CH3)
30 [S i (CH3)201 nS i (CH
3) 3(branch point=2~3.R=lower alkylno, (,L
±2~200, ts-2~200, n=2~
200) (n-1 to 200, R = lower alkyl group) (2) Epoxy-modified silicone oil (n = 1 to 200) CH3CH3 (m = 1 to 10.n = 2 to 10) 0[5i(CH3)20 ] l5i(CH3)3 (branch point -2~3.R-lower alkyl group, L=2~200
, m=2~200, n-2~200) C3H6
0CH2CH-CH2 (CH3)3SiO(SiO)msi(CH3)3CH
3 (n7l ~10) (CH3)3SiO(SiO)II[5i(CH3)2
0]n5i(CH3)3CH3 (+=1 to 10, n=2 to 10) (3) Alcohol-modified silicone oil (n-1 to 20
0) CH30G)12G:)120H (1-10, n=2-10) CH3CH3 (n=0-200) CH3 (I=1-10.111-10-200,
n-1 to 5) (n = 1 to 200, R = lower alkyl) (4) Mercapto-modified silicone oil (+ = l N
10, n=2~10) 3H6SH ■ (CH3)3SiO(SiO)nSi(CH3)3H3 (n:2~10) 0[5i(CH3)20] 1si(CH3)3■ H9C3H8SiO[5i(CH3)20 ]m5i(f
ll:H3)30[5i(CH3)20]n5i(CH
3) 3 (branch point = 2-3, R==alkyl group, L=
2-200, rn-2-200, n=2-2
00) CH3CH3CH3 (n=1-200, R-lower alkyl group) (5) carboxy) and modified silicone oil (m-1-10, n
= 2-10) (n-1-200) 0[5i(CH3)2011Si(CH3)3 (branch point = 2-3, R = lower lower alkydino (, L = 2-200
, rs=2-200, n=2-200)
C) 13 CH3CH3 CH3SiO(SiO)nsiRcOOHCH3CH3
Silicone compounds having a reactive organic functional group such as C:)13 (n=1-200, R==alkyl group) are examples of preferred silicone compounds in the present invention, and
The present invention is not limited to these examples, and the above-mentioned exemplified compounds and other silicone compounds are currently commercially available and can be easily obtained from the market, and any of them can be used in the present invention. It is possible.

The organic isocyanate used in the present invention and which characterizes the present invention in 52 is a compound having at least one isocyanate group in an aliphatic or aromatic compound, and has been used in various organic synthesis and polyurethane resins. It is widely used as a synthetic raw material.

Any of these known organic isocyanates are useful in the present invention. Particularly preferred organic isocyanates are as follows.

Phenyl isocyanate.

O-chlorophenylisocyanate.

p-Glorphenylincyane-1., methyl isocyanate.

Ethyl isocyanate, n-butyl isocyanate, n-propylisocyanate, toluene-2,4-diisocyanate, 4-methoxy-
1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy-1,3-7 phenylene diisocyanate, 2.4- Diisocyanate-diphenyl ether, mesitylene diisocyanate, 4.4-methylenebis(phenylisocyanate), shrylene diisocyanate, 1.5-naphthalene diisocyanate, benzidine diisocyanate, 0-nitrobenzidine diisocyanate, 4.4-dibenzyl diisocyanate, 1.4-tetra Methylene diisocyanate, 1.6-tetramethylene diisocyanate, 1.10-decamethylene diisocyanate, 1.4
-cyclohexylene diisocyanate, silyl diisocyanate, 4,4-methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate,
Adducts of these organic isocyanates and other compounds,
Examples include, but are not limited to, those of the following structural formulas.

C0NH(CH2)6NGO 08111: (CH2)6N C:0NH(C)12)f3Nc.

OCH3 The modifier used in the present invention is a silicone compound having a reactive organic functional group as described above and an organic isocyanate as described above in a functional group ratio such that no free isocyanate group remains, that is, organic functional group/isocyanate group. The ratio of
With the functional group ratio as above, in the presence or absence of an organic solvent and a catalyst, about 0 to 150°C1, preferably 20 to
It can be easily obtained by reacting at a temperature of 80° C. for about 10 minutes to 3 hours.

The above-mentioned modifier has a molecular weight of about 50,000 or less, preferably 20,000 or less. If the molecular weight exceeds about 50,000, the solubility in organic solvents may decrease, or the coating used in combination may This is not preferable because it causes problems such as decreased compatibility with the forming resin. Therefore, if both the silicone compound and the isocyanate compound are polyfunctional, the functional number of either or both may be reduced in advance, or the reaction equivalent ratio of the two may be adjusted so that the silicone compound is in excess. It is preferable to adjust the product molecule -;+- by doing so or by interrupting the reaction midway through.

The organic solvent that may be used in the production of such a modifier may be any organic solvent that is inert to the respective reaction raw materials and products. For example, preferred organic solvents include methyl ethyl ketone, methyl -n-
Propyl ketone, methyl isobutyl ketone, diethyl ketone, methyl formate, ethyl formate, propyl formate, methyl acetate.

Ethyl acetate, butyl acetate, acetone, cyclohexane,
Tetrahydrofuran, dioxane, methanol, ethanol, isopropyl alcohol, butanol, methyl cellosolve, butyl cellosolve, selon rub acetate,
Dimethylformamide, dimethyl sulfoxide, pentane, hexane, cyclohexane, heptane, octane,
Examples include mineral spirit, petroleum ether, gasoline, benzene, toluene, xylene, chloroform, tetrachloride, chlorobenzene, perchlorethylene, and trichlorethylene.

When the modifier obtained as described above and used in the present invention is produced using an organic solvent, it may be separated from the organic solvent, or it can be used as a solution of the organic solvent. The modifier used in the present invention separated from the organic solvent is generally in the form of a white to brown liquid or solid, and is easily soluble in various organic solvents.

According to various analyzes 1, such as infrared absorption spectroscopy, elemental analysis, and molecular needle measurements, the modifier used in the present invention as described above has been found to be a reactive organofunctional compound (1) between the isocyanate group of organic isocyanate and the silicone compound. For example, when the reactive organic functional group is a 7-mino group, -NHC:ON!
It was also revealed that the compound does not have a free isocyanate group in its molecule.

According to the inventor's detailed research, the modifier used in the present invention has film-forming ability by itself, but when it is added to a conventionally known film-forming agent to form a film, the modifying agent Because it has a larger number of molecules, ;,, - than silicone compounds, and has urethane bonds, urea bonds, etc. as polar groups, it integrates with the film-forming resin and forms a film without phase separation. When a film-forming resin forms a back layer, the heat resistance and non-adhesion during heating of the back layer can be improved without reducing the various properties inherent to the resin, such as solubility and zero-grain properties. It has been found that it is possible to significantly improve the

In the present invention, the film-forming resin used is various conventionally known film-forming resins, and any of these resins can be used. For example, vinyl 41 resin, vinylidene chloride resin, vinyl chloride/ Vinyl acetate/vinyl alcohol copolymer resin, alkyd resin, epoxy resin, acrylonitrile-butadiene resin, polyurethane resin, polyurea resin, nitrocellulose resin, polybutyral resin, polyester resin, silicone resin , melamine resins, urea resins, acrylic resins, polyamide resins, etc., and particularly preferred are resins having groups in their structure that form hydrogen bonds with urethane bonds, urea bonds, etc. These resins can be used alone or as a mixture, and can be used as a solution or dispersion in an organic solvent.

For forming the back layer, it is preferable to use a paint formed by dissolving or dispersing a film-forming resin modified with the above-mentioned modifier in the above-mentioned medium.The concentration of the film-forming resin in the paint is about 10 ~55% by weight is suitable, and the modifier is used in an amount of approximately 1~55% by weight per 100 parts by weight of these film-forming resins.
It can be used in a proportion of 100 parts by weight.

As long as the coating material for forming the back layer used in the present invention contains the components listed in L as essential components, it also includes 1 subcomponent other than those listed below, such as:
Pigments, extender pigments, plasticizers, antistatic agents, surfactants, lubricants, crosslinking agents, anti-aging agents.

Optional additives such as stabilizers, blowing agents, and antifoaming agents may be included.

The method for forming the back layer itself may be the same as any conventionally known method, and it is preferable to form the back layer to a thickness of about 0.11-1 Op.

The dispersion liquid used for forming the magnetic layer uses the same resin as the film-forming resin as a binder resin, and the binder resin,
The essential components are magnetic particles and a medium.

The magnetic particles used in the present invention include, for example, iron, chromium, nickel, cobalt, alloys or oxides thereof, and modified products thereof, specifically 1, for example, γ
-Fe203. Examples include ferrite, magnetite, CrO2, and cobalt-doped bertolide compounds of γ-Fe2O3 and Fe3O4.

The magnetic particles described above are merely examples, and various types of magnetic particles other than those exemplified in Section J2 can of course be used in the same manner in the present invention, and can be used alone or as a mixture.

The dispersion liquid used for forming the magnetic layer in the present invention is as follows 1-. These components are essential components, and their usage ratios are the same as in conventional magnetic particle dispersions.

For example, if the entire dispersion is 100 parts by weight, the magnetic particles account for about 10 to 50 parts by weight, and the medium accounts for about 50 parts by weight.
~90% modification, with Painter resin typically in the range of about 5-20% by weight.

As long as the dispersion used in the present invention contains these components as essential components, other subcomponents other than those mentioned above, such as pigments, extender pigments, plasticizers, antistatic agents, surfactants, lubricants, crosslinking agents, aging agents, etc. L: can contain any additives such as antifoaming agent, stabilizer, foaming agent, antifoaming agent, etc.

The method for producing the dispersion liquid used in the present invention, which consists of the essential components and optional components described above, may be any conventionally known method, and generally, the necessary components are prepared simultaneously or sequentially using a ball mill. Mixing and dispersing methods such as treatment, mixer treatment, roll mill treatment, bead mill treatment, gravel mill treatment, sand mill treatment, and high speed impeller treatment are suitable.

Such a dispersion method itself consists of: 1) magnetic particles to be dispersed;
Conditions vary depending on the type, size, use, etc., but generally the treatment may be carried out at a temperature of room temperature to 100° C. for about 5 minutes to 20 hours.

In addition, any conventionally known support can be used. For example, a polyester film with a thickness of 5 to 50 pm, a polypropylene film, a cellulose triacetate film, a cellulose diacetate film,
Polycarbonate film or the like can optionally be used.

The magnetic layer is formed by coating the dispersion as described above on at least one side of the support as described in L in such a way that the thickness when rolled is preferably about 5 to 20 gm. and then drying. The coating method and drying method may be any conventionally known method.

(Functions/Effects) The back layer of the magnetic recording medium of the present invention obtained as described above has various characteristics inherent to the film-forming resin, depending on the type of film-forming resin used. For example, it has a low coefficient of friction that cannot be achieved with conventional technology while maintaining strength, mechanical properties, chemical properties, and physical properties, so it can be used as various magnetic tapes, etc., and can be used for winding,
Even if the tape is used at high speeds such as during rewinding, the tape will not be disturbed, and therefore the tape will not be damaged or broken.

Furthermore, the modifier of the present invention is not limited to the modification of polyurethane-based resins, but can be freely used to modify any film-forming resin. (a) There is an advantage that it is possible to provide a magnetic recording medium having a back layer made of various film-forming resins and having a low coefficient of friction without increasing the manufacturing cost of the magnetic recording medium.

Furthermore, since the back layer of the magnetic recording medium of the present invention is formed from a film-forming resin modified with the above-mentioned modifier, after the back layer is formed, the modifier contained in the back layer is removed. Because the modifiers are integrated with each other or with the film-forming resin through polar groups such as urethane bonds and urea bonds, the modifiers bleed onto the surface of the back layer over time, causing various problems, as in the conventional technology. This problem has been solved.

Next, the present invention will be explained in more detail by giving reference examples, examples, comparative examples, and usage examples. Note that parts and percentages in the text are based on weight.

Reference Example 1 (Production example of modifier) Adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate (TDI) (coronated, made by Nippon Polyurethane, NC0% 12°5, solid content 75%)
While thoroughly stirring 175 parts at 50° C., 1,320 parts of terminal aminopropyl polydimethylsiloxane (molecular weight 2.200) having the structure shown below are gradually added dropwise to the mixture and reacted.

H3 82NC3H8Si[(OSi)nOcH3]3H3 (n is the value that makes the molecular weight 2.200) After the reaction, ethyl acetate is evaporated to form a transparent liquid modifier (Ml
) 1.440 parts were obtained.

According to the infrared absorption spectrum of this modifier, 2270
No absorption by the M# isocyanate group at 1090/cm was observed, and a band of 5i-0-C groups was observed at 1090/cm.

Therefore, the main structure of the above modifier is estimated to be the following formula.

CH3 (X = HNC3H6Si [(O3i)nOcH3
13) CH3 Reference Example 2 (Manufacturing Example of Modifier) Add 24 parts of phenyl isocyanate to 196 parts of terminal hydroxypropyl polydimethylsiloxane (molecule 1980) having the following structure and stir well at 60°C to react to form a transparent liquid reaction. 213 parts of product (A) were obtained.

C1 (3C) 13 G) +3 1.

HOC3H6S+0(S+0)nsNll:3H80)
1C) 13 C83CH3 (n is the molecule r; the value at which i is 980) Next, an adduct of hexamethylene diisocyanate and water (Shurane 1.24A-100, manufactured by Fukaisei, NC0% 23.5) 5
While stirring 2 parts well at 60° C., 330 parts of the above reaction product (A) were gradually added dropwise into the mixture to cause a reaction, thereby obtaining 376 parts of a colorless and transparent liquid modifier (I2).

According to the infrared absorption spectrum of this modifier.

There is no remaining absorption by free isocyanate groups at 2270/am, and 5i-0-CI1 at 1090/cm.
(It showed an absorption band according to

Therefore, the main structure of the modifier described in "2" is estimated to be the following formula.

C0NH(C:I2)8NHCO-X 150) 15 parts of n-butyraldehyde was added to 230 parts, stirred thoroughly at 80°C, and reacted for 3 hours while removing the produced water from the system under reduced pressure to obtain a transparent liquid reaction product ( B) 238 parts were obtained.

CI (3(:)13 CH3 (n is the value where one molecule is 1,150) Next, an adduct of 1 mole of trimethylolpropane and 3 moles of xylylene diisocyanate (Takenate DIION, manufactured by Takeda Pharmaceutical Co., Ltd.) While stirring well at room temperature, 186 parts of the above reaction product (B
735 parts of ) were gradually added dropwise and reacted at 60°C. After the reaction was completed, ethyl acetate was evaporated to obtain 905 parts of modifier (I3) in the form of a transparent liquid.

According to the infrared absorption spectrum of this modifier.

There is no remaining absorption by M# isocyanate group at 2270/cm, and 5i-0 at l090/cm.
-C), showing an absorption band due to q.

Therefore, the main structure of the modifier described in (g) and (g) is presumed to be as shown in the following formula.

Reference Example 4 (Production Example of Modifier) 2.6-1 35 parts of lylene diisocyanate and 110 parts of ethyl acetate are stirred well at 60°C, and a terminal mercaptopropyl polydimethylsiloxane having the following structure is added thereto. (Molecular weight: 1.580) was gradually added dropwise to react.

0[5i(CH3)20] l5i(CH3)3N5C
3H6S iO[S i (CH3)20] as i
(CH3) 3O[5i(C:H3)20]n5i(C
H3) 3 (+, m, n are values at which the molecular weight - is 1,580) After the reaction, ethyl acetate was evaporated to obtain 661 parts of a transparent liquid modifier (M4).

According to the infrared absorption spectrum of this modifier, 2270
There was no remaining absorption by the 'TL# isocyanate group at 1090/cm, and an absorption band due to the 5i-0-C group was shown at 1090/cm.

Therefore, the upper structure of the modifier L is estimated to be the following formula.

0[5i(CH3)20]n5i(CH3)3(1,m
, n is the value that makes the molecular weight 1,580) 0[5i(CH3)20] 1si(CH3)30[5
i(C:H3)20]n5i(CH3)3 Reference Example 5 (Production example of modifier) While stirring 24 parts of phenyl isocyanate and 160 parts of ethyl acetate at 60°C, a terminal having the following structure was added. 450 parts of hydroxypropylpolydimethylsiloxane (molecular weight 2,250) is gradually added dropwise to react.

(n is the value at which the molecular weight is 1.580) After the reaction is complete, ethyl acetate is released from 2 to form a transparent liquid modifier (M
5) 467 parts were obtained.

According to the infrared absorption spectrum of this modifier, 2270
There was no remaining absorption by the M isocyanate group at /cm, and an absorption band due to 5i-0-c4 was shown at 1090/am.

Therefore, the main structure of the above modifier is estimated to be the following formula.

Reference Example 6 (Preparation of film-forming resin solution) 150 parts of polybutylene adipate with molecules iz and ooo having hydroxyl groups at the ends, 20 parts of 1.3-butylene glycol
52 parts of tolylene diisocyanate were subjected to an addition reaction in 412 parts of methyl ethyl ketone, and the viscosity was 200 voids/2.
A polyurethane resin solution (solid content 35%) at 0°C was obtained.

Modifier (Ml) was added to 100 parts of this polyurethane resin solution.
5 parts was added to obtain a modified film-forming resin solution (UPI) in which the modifier and polyurethane resin were integrated.

Reference Example 7 (Preparation of a modified film-forming resin solution) A modified film-forming resin solution ( U
F2) was obtained.

Reference Example 8 (Preparation of film-forming resin solution) In place of the modifier (Ml) in Reference Example 6, the modifier (M
A modified film-forming resin solution (UF3) was obtained using Example 3) in the same manner as in Reference Example 6.

Reference Example 9 (Preparation of film-forming resin solution) In place of the modifier (Ml) in Reference Example 6, the modifier (M
4) and in the same manner as in Reference Example 6 except that a modified film-forming resin solution (U F 4) was obtained.

Reference Example 10 (Preparation of film-forming resin solution) In place of the modifier (Ml) in Reference Example 6, a modifier (M5) was used,
The other conditions were the same as in Reference Example 6, and the modified film-forming resin solution (UF
5) was obtained.

Reference Example 11 (Preparation of paint tA) A paint for the back layer (UCl) was prepared by mixing and dissolving the following components.

Covered 1112 forming resin solution (UPI) (30% solution) 10
0 parts Polyester resin (Vylon-200, manufactured by Toyobo) 5 parts Methyl ethyl ketone 1200 parts Reference example 12
(Preparation of Coating 1) Mix and dissolve the following components to prepare the back layer coating (UC2): A
Manufactured.

Film-forming resin solution (UF2) (30% solution) 10 parts polyester resin (Byron-200, Toyo Hair) 5 parts Methyl ethyl ketone 1200 parts Reference Example 13
(Preparation of paint) The following components were mixed and dissolved to prepare a paint for the back layer (UC3).

Film-forming resin solution (UF3) (30% solution) 100 parts Polyester resin (Byron-200, Toyo-Yukami) 5 parts Methyl ethyl ketone 1200 parts Reference example 14
(Preparation of paint tA) A paint for the back layer (UC4) was prepared by mixing and dissolving the following components.

Film-forming resin solution (UF4) (30% solution) 100 parts Polyester resin (Heiron-200, Toyo Hair) 5 parts Methyl ethyl ketone 1200 parts Reference Example 15
(Preparation of paint) A paint for the back layer (UC5) was prepared by mixing and dissolving the components listed below.

Film-forming resin solution (UF5) (30% solution) 100 parts Polyester resin (Byron-200, Toyo Hair) 5 parts Methyl ethyl ketone 1200 parts Reference Example 1B
(Preparation of film-forming resin solution) Methyl ethyl ketone solution (solid content 30%) of vinyl chloride/vinyl acetate/vinyl alcohol copolymer resin (S-LEC A, manufactured by Block Chemical)
To 100 parts, 3 parts of the modifier (Ml) obtained in Reference Example 1 was added.

A modified film-forming resin solution (VFI) in which a modifier and a vinyl resin were integrated was obtained.

Reference Example 17 (Preparation of film-forming resin solution) A modified film-forming resin (V
F2) was obtained.

Reference Example 18 (Preparation of film-forming resin solution) A modified film-forming resin (VF
3) was obtained.

Reference Example 19 (Preparation of film-forming resin solution) A modified film-forming resin (V
F4) was obtained.

Reference Example 20 (Preparation of film-forming resin solution) A modified film-forming resin (VF
5) was obtained.

Reference Example 21 (Preparation of paint) A paint for the back layer (vCl) was prepared by mixing and dissolving the following components.

Film-forming resin solution (VFl) (30% solution) 100 parts Polyester resin (Vylon-200, Toyo Hair) 5 parts Methyl ethyl ketone 1200 parts Reference Example 22
(Paint manufactured by iA) A paint for the back layer (vC2) was prepared by mixing and dissolving the following components.

Film-forming resin solution (VF2) (30% solution) 100 parts Polyester resin (Vylon-200, Toyo Hair) 5 parts Methyl ethyl ketone 1200 parts Reference Example 23
(Preparation of paint) A paint for the back layer (■C3) was prepared by mixing and dissolving the following components.

Film-forming resin solution (VF3) (30% solution) 100 parts Polyester resin (Vylon-200, Toyo Hair) 5 parts Methyl ethyl ketone - 1200 parts Reference example 24 (Preparation of paint) The following components were mixed and dissolved to prepare a back layer paint ( (2) C4) was prepared.

Film-forming resin solution (VF5) (30% solution) 100 parts Polyester resin (Vylon-200, Toyo Hair) 5 parts Methyl ethyl ketone 1200 parts Reference Example 25
(Preparation of paint) A paint for the back layer (vC5) was prepared by mixing and dissolving the following components.

Film-forming resin solution (VF6) (30% solution) 100 parts Polyester resin (Vylon-200, Toyo Hair) 5 parts Methyl ethyl ketone 1200 parts Examples 1~
5 The paint UCI-UC5 obtained in the reference example was applied to a polyester film with a thickness of 15 hm using a reverse roll coater so that the dry thickness was 1 m, and the solvent was dried to form a back layer. Next, a magnetic layer is formed on the opposite surface according to a conventional method from a dispersion containing a binder resin consisting of Co-containing -Fe203, an ordinary polyurethane resin, and a vinyl chloride composite resin. Each piece was cut to obtain a magnetic recording medium of the present invention.

Examples 6 to 10 The paint MCI-VC5 obtained in Reference Example was applied onto a polyester film with a thickness of 1.5 pm using a reverse roll coater so that the thickness when dry was 1 #Lm. Then, after drying the solvent and forming the back layer, C
A magnetic layer is formed on the opposite surface according to a conventional method from a dispersion containing O-containing -Fe203 and a binder resin consisting of an ordinary polyurethane resin and a vinyl chloride copolymer resin, and the magnetic layer is cut into a predetermined size of 111 mm. A magnetic recording medium was obtained.

Comparative Examples 1-2 Example 1 except that the polyurethane resin and S-LEC A which were not modified with the modifier in the present invention were used.
Comparative magnetic recording media were obtained in the same manner as in Examples 1 to 10.

Usage Example The performance of the magnetic recording media of the above Examples and Comparative Examples was investigated and the following results were obtained.

The coefficient of friction (A) is the value (pk) measured between the magnetic layer and the back layer. B)
, the lateral wobbling of jitter (C), the state of irregular winding of the tape during fast forwarding (D), and the state of wear of the magnetic layer (E). The overall evaluation was given as F.

-ABCDEF Comparative example 10.52 Yes Yes Yes Yes Defective example 1 0.13 No No No No
Good example 2o, 2o @ None None None
Good examples 3o, 23f! A None None None
Good example 40.12 None None None None Good example 50.10 None None None None Good comparative example 20.31 Slightly present None Stacked stone Stacked stone Slightly poor example 60.12 None None None None Good example 70.15 None None None None Good example 8
0.17 None None None None Good example 90
．． 14 None None None Good example to
From the results of 0.22 None None None Good or better, it is clear that the magnetic recording medium of the present invention has a low coefficient of friction in the back layer and exhibits excellent running characteristics.

Applicant: Dainichiseika Kagyo Co., Ltd. (and 1 other person)/” ′-'
:

Claims (3)

[Claims] (1) Consisting of a non-magnetic support, a magnetic layer provided on one side of the support, and a back layer provided on the other side of the support, the back layer being made of silicone having a reactive organic functional group. 1. A magnetic recording medium comprising a film-forming resin modified with a modifier that is a reaction product of a compound and an organic isocyanate and has no free isocyanate groups. (2) Weight ratio of modifier and binder resin is 1 to 100
:100. The magnetic recording medium according to claim (1). (3) The magnetic recording medium according to claim (1), wherein the modifier has a molecular weight of 50,000 or less.