JPH0363126B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a magnetic recording medium, and more particularly to a high-performance magnetic recording medium in which the magnetic layer is formed from a binder resin modified with a specific modifier and magnetic particles. (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 binder resin on a nonmagnetic 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 binder resin. Various physical properties are required for the magnetic layer, but
A particularly important required performance is good running properties of the magnetic recording medium, and for this purpose it is strongly required that the coefficient of friction between the recording head and the magnetic recording medium be low. The level of such friction coefficient is mainly determined by the binder resin used to form the magnetic layer. Conventionally, as binder resins, vinyl chloride resins, polyurethane resins, polyester resins, nitrocellulose resins, epoxy resins, etc. are mainly used alone or in combination. (Problem to be solved by the invention) The coefficient of friction of the binder resins conventionally used as described above is generally 0.4 or more, and magnetic recording media formed from these binder resins can be used as video tapes, audio tapes, etc. When using the tape, the slipperiness is insufficient, so
When the tape is used at high speeds such as winding and rewinding, it may cause irregular winding, resulting in deformation or damage to the tape.
This causes dropouts. A method of solving these drawbacks and lowering the coefficient of friction of magnetic recording media is to add lubricants such as fatty acids, wax, and silicone oil to the magnetic layer. However, another drawback arises in that the lubricant added to the magnetic layer bleeds out onto the tape surface, causing clogging of the recording head. As a method to solve the above-mentioned drawbacks, a method has been proposed in which a resin with a low coefficient of friction is used as the binder resin itself, such as a polyurethane resin having a siloxane bond in the molecule (for example, JP-A No. 57-176535 No. 59-94237, No. 59
-5421, 58-218034, 58-222436, 58-218034, 58-222436,
59-11535, 59-82636, etc.). According to such a method, a magnetic layer with a relatively low coefficient of friction can be formed, but since the polyurethane resin having siloxane bonds contains siloxane bonds in the main chain of the polymer, sufficient reaction cannot be achieved. It is difficult to obtain a binder resin of constant quality, the price is high, and various problems arise due to unreacted silicone compounds. Furthermore, since the polymer is limited to polyurethane resins, there is a problem in that the range of use thereof is significantly limited. As a result of intensive research in order to solve the above-mentioned drawbacks of the conventional technology and meet the above-mentioned demands, the present inventor has discovered that when modifying a binder resin using a specific modifier when manufacturing a magnetic recording medium, The present invention was developed based on the discovery that the above-mentioned drawbacks of the prior art are solved, the binder resin is not limited to polyurethane resins, various binder resins can be easily used, and a magnetic recording medium with a low coefficient of friction can be provided. completed. (Means for Solving the Problems) That is, the present invention comprises a non-magnetic support and a magnetic layer provided on one surface of the support, and the magnetic layer includes magnetic particles, a binder resin, and a binder resin. and a medium, the modifier being a reaction product of a silicone compound having a reactive organic functional group and an organic polyisocyanate, wherein at least one free isocyanate A magnetic recording medium characterized by having a base. To explain the present invention in more detail, the binder 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 polyisocyanate. The reaction product has at least one free isocyanate group in one molecule. Preferred examples of the silicone compound having a reactive organic functional group used to obtain such a modifier include the following compounds. (1) Amino-modified silicone oil (m=1~10, n=2~10, R= _CH3 or
_OCH3 ) (m=1~10, n=2~10, R= _CH3 or
_OCH3 ) (m=0~200) (n=2~10) (Branch point = 2-3, R = lower alkyl group, L =
2-200, m=2-200, n=2-200) (n=1-200, R=lower alkyl group) (2) Epoxy-modified silicone oil (n=1~200) (m=1~10, n=2~10) (n=1~200) (Branch point = 2-3, R = lower alkyl group, L =
2-200, m=2-200, n=2-200) (n=1~10) (m=1-10, n=2-10) (3) Alcohol-denatured silicone oil (n=1~200) (m=1~10, n=2~10) (n=0~200) (1=1-10, m=10-200, n=1-5) (n=1-200, R=lower alkyl) (4) Mercapto-modified silicone oil (m=1~10, n=2~10) (n=2~10) (Branch point = 2-3, R = lower alkyl group, L =
2-200, m=2-200, n=2-200) (n=1-200, R=lower alkyl group) (5) Carboxyl-modified silicone oil (m=1~10, n=2~10) (n=1~200) (Branch point = 2-3, R = lower alkyl group, L =
2-200, m=2-200, n=2-200) (n=1-200, R=lower alkyl group) The silicone compounds having a reactive organic functional group as described above are examples of silicone compounds preferred in the present invention, and the present invention is limited to these examples. Rather, the above-mentioned exemplary compounds and other silicone compounds are currently commercially available and readily available on the market;
Any of these can be used in the present invention. The organic polyisocyanate used in the present invention and which is the second characteristic of the present invention is a compound having at least two isocyanate atoms in an aliphatic or aromatic compound, and has traditionally been used as a synthetic raw material for polyurethane resins. Widely used. Any of these known organic polyisocyanates are useful in the present invention. Particularly preferred organic polyisocyanates are as follows. 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-phenylene diisocyanate, 2,4-diisocyanate-diphenyl ether, mesitylene diisocyanate, 4,4-methylenebis(phenyl isocyanate), diylylene diisocyanate, 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate , 4,4-dibenzyl diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-tetramethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, 4,4-methylene bis (cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, and adducts of these organic polyisocyanates with other compounds, such as those having the following structural formula, but are not limited thereto. (however,

[Formula]) The modifier used in the present invention is a silicone compound having a reactive organic functional group as described above and an organic polyisocyanate as described above. In the presence or absence of an organic solvent and a catalyst, the functional group ratio is such that one or more anate groups are present in excess, preferably 1 to 2, in the presence or absence of an organic solvent and a catalyst, at about 0 to 150 °C, preferably at 20
It can be easily obtained by reacting at a temperature of ~80°C for about 10 minutes to 3 hours. The organic solvent that may be used in the production of such a modifier may be any organic solvent as long as it 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, cellosolve acetate, dimethylformamide, dimethyl sulfokimide, pentane, hexane, cyclohexane, heptane, octane, mineral Spirits, petroleum ether, gasoline, benzene, toluene, xylene, chloroform, carbon tetrachloride, chlorobenzene, perchlorethylene,
Examples include 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 organic solvents used to disperse various magnetic particles. According to various analyzes such as infrared absorption spectrum, elemental analysis, and molecular weight measurement, the modifier used in the present invention as described above shows that the isocyanate group of the organic polyisocyanate and the reactive organic functional group of the silicone compound are added together. For example, when the reactive organic functional group is an amino group, -
It was revealed that the two were bonded together through an NHCONH-bond, and that the compound had at least one free isocyanate group in one molecule. According to detailed research by the present inventor, since the modifier used in the present invention has free isocyanate, for example, hydroxyl group, primary to secondary amino group,
It is reactive with various binder resins that have amide groups, carboxyl groups, etc., and is bonded to the main chain of the binder resin as a side chain rather than the main chain of these binder resins, so that the binder resin originally has without reducing various properties.
It has been found that when binder resin forms magnetic layers, the coefficient of friction of those magnetic layers can be significantly reduced. Furthermore, this unexpected effect is due to the fact that the modifier used in the present invention has a free isocyanate group, so this isocyanate group is converted into an isocyanate group before, during, or after the formation of the coating film. This is thought to be because it also acts as a type of modifier that reacts with each other or with the binder resin. The dispersion used in the present invention contains the above-mentioned modifier, magnetic particles, binder resin, and medium as essential components. Examples of magnetic particles used in the present invention include:
Iron, chromium, nickel, cobalt, alloys or oxides thereof, and modified products thereof, specifically, cobalt-doped γ-Fe ₂ O ₃ , ferrite, magnetite, CrO _{2 ,} etc.
Examples include bertolide compounds of Fe ₂ O ₃ and Fe ₃ O ₄ . The above magnetic particles are merely examples, and
Of course, various magnetic particles other than those exemplified above can also be used in the present invention, and can be used alone or as a mixture. In the present invention, binder resins used include various binder resins conventionally used for forming magnetic layers, and any of these binder resins can be used. resin, vinyl chloride/vinyl acetate/vinyl alcohol copolymer resin, alkyd resin, epoxy resin, acrylonitrile
Examples include butadiene resin, polyurethane resin, polyurea resin, nitrocellulose resin, polybutyral resin, polyester resin, silicone resin, melamine resin, urea resin, acrylic resin, polyamide resin, etc. Particularly preferred are resins having in their structure a reactive group as described above that can react with an isocyanate group. These resins can be used alone or as a mixture, and can be used as a solution or dispersion in an organic solvent. Further, the reaction between the binder resin and the modifier is carried out at a temperature of about 0 to 150°C, preferably 20 to 80°C, for about 10 minutes to 3 hours in the presence or absence of an organic solvent and a catalyst. This can be easily done by The medium used in the present invention is the organic solvent used in the preparation of the modifier described above or a mixture thereof. The dispersion used in the present invention has the above-mentioned components as essential components, and their usage ratios are the same as in conventional dispersions of magnetic particles.For example, if the entire dispersion is 100 parts by weight, The magnetic particles are about 10-50% by weight, the modifier is about 1-50% by weight of the binder resin, and the medium is about 50-90% by weight.
The binder resin is generally in a range of about 5 to 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. inhibitors, stabilizers,
Any additives such as foaming agents and antifoaming agents may be included. The method for producing the dispersion liquid used in the present invention, which consists of the above-mentioned essential components and optional components, may be any conventionally known method, and generally, the necessary components are added simultaneously or sequentially, and ball milling, mixer processing, etc. Mixing and dispersing methods such as , roll milling, bead milling, gravel milling, sand milling, and high-speed impeller processing are suitable. The conditions for such a dispersion method vary depending on the type and size of the magnetic particles to be dispersed, their intended use, etc., but generally they are carried out at a temperature between room temperature and 100°C.
It is sufficient to process for about 5 minutes to 20 hours. In addition, in the above-mentioned present invention, when using a binder resin having a group capable of reacting with an isocyanate group, such as a hydroxyl group, an amino group, a carboxyl group, etc., the modifier used in the present invention and these The binder resin may be reacted before, during or after the preparation of the dispersion. The most preferred embodiment is one in which the modifier and binder resin are reacted in advance in preparing the dispersion. Such reactions are carried out at 0 to 120°C in the presence or absence of organic solvents and catalysts.
Preferably, the reaction can be carried out at a temperature of 40 to 80°C for about 0.5 to 10 hours. Furthermore, in the present invention, a binder resin that does not have a group that reacts with an isocyanate group may be used. In such a case, the modifiers themselves have a high molecular weight by themselves or by a di- or polyfunctional compound such as water or a polyamine, producing the same effect. In addition, any conventionally known support can be used, for example, polyester film, polypropylene film, cellulose triacetate film, cellulose diacetate film, polycarbonate film, etc. with a thickness of 5 to 50 μm can be used arbitrarily. I can do it. The magnetic layer is formed by applying the dispersion as described above to at least one surface of the support as described above by any method so that the thickness when dried is preferably about 5 to 20 μm, and then drying. It can be formed by Both the coating method and the drying method may be conventional methods. (Functions/Effects) The magnetic recording medium of the present invention obtained as described above has various properties inherent to the binder resin, such as strength and electrical properties, depending on the type of binder resin used. Because it has a low coefficient of friction that cannot be achieved with conventional technology while maintaining its physical, chemical, and physical properties, it is used in various magnetic tapes, etc., and can be used at high speeds such as winding and unwinding. Even if the tape is damaged, the tape will not be disturbed, and therefore the tape will not be damaged or broken. Furthermore, the modifier used in the present invention does not become the main chain of the binder resin, but rather binds to the binder resin and becomes the side chain of the binder resin, so it is different from conventional polyurethane resins containing siloxane bonds. This is different and does not reduce the inherently excellent performance of the binder resin. Furthermore, the modifier of the present invention is not limited to modifying polyurethane resins, but can be freely used to modify any binder resin, and therefore can be used with various binders without increasing the manufacturing cost of magnetic recording media. It is made of resin and has the advantage of providing a magnetic recording medium with a low coefficient of friction. Furthermore, since the magnetic layer of the magnetic recording medium of the present invention is formed from a dispersion containing the above-mentioned modifier, after the magnetic layer is formed, the modifier contained in the magnetic layer is mixed with the modifier. However, because the modifier reacts with the binder resin, has a high molecular weight, and is integrated with the binder resin, the modification agent bleeds onto the surface of the magnetic layer over time, causing various problems, as in the conventional technology. has been resolved. 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 (Manufacturing example of modifier) 175 parts of an adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate (TDI) (Coronate L, manufactured by Nippon Polyurethane, NCO% 12.5, solid content 75%) was heated at 50°C. While stirring well,
880 parts of terminal aminopropylpolydimethylsiloxane (molecular weight 2200) having the structure shown below is gradually added dropwise to the mixture and reacted. (n is the value at which the molecular weight is 2200) After the reaction was completed, ethyl acetate was evaporated to obtain 976 parts of the modifier (M1) in the form of a transparent liquid. According to the infrared absorption spectrum of this modifier,
Absorption due to free isocyanate groups at 2270/cm remained, and an absorption band due to Si-O-C groups was shown at 1090/cm. Furthermore, when the amount of free isocyanate groups in this modifier was quantified, the theoretical value was 0.83%, while the actual value was 0.78%. Therefore, the main structure of the above modifier is estimated to be the following formula. Reference Example 2 (Manufacturing example of modifier) Add 24 parts of phenyl isocyanate to 196 parts of terminal hydroxypropyl polydimethylsiloxane (molecular weight 980) having the following structure, stir well at 60°C, and react to produce a transparent liquid reaction product. (A) 213 copies were obtained. (n is the value at which the molecular weight is 980) Next, an adduct of hexamethylene diisocyanate and water (Dyuranate 24A-100, manufactured by Asahi Kasei,
NCO%23.5) 52 parts at 60℃ while stirring well.
220 parts of the above reaction product (A) was gradually added dropwise to this mixture to react, and a colorless and transparent liquid modifier (M2) was obtained.
part was obtained. According to the infrared absorption spectrum of this modifier,
Absorption due to free isocyanate groups at 2270/cm remained, and an absorption band due to Si-O-C groups was shown at 1090/cm. Furthermore, when the amount of free isocyanate groups in this modifier was quantified, the theoretical value was 1.54%, while the actual value was 1.37%. Therefore, the main structure of the above modifier is estimated to be the following formula. Reference Example 3 (Production example of modifier) 230 parts of terminal aminopropyl polydimethylsiloxane (molecular weight 1150) having the following structure, n-
Add 15 parts of butyraldehyde and stir well to react at 80°C. React for 3 hours while removing the generated water from the system under reduced pressure to obtain 238 parts of a transparent liquid reaction product (B). . (n is the value at which the molecular weight is 1150) Next, 186 parts of an adduct of 1 mol of trimethylolpropane and 3 mol of xylylene diisocyanate (Takenate D110N, manufactured by Takeda Pharmaceutical, NCO% 11.5, solid content 75%) was added. While stirring well at room temperature, 490 parts of the above reaction product (B) was gradually added dropwise to the solution.
The reaction was carried out at 60°C. After the reaction was completed, ethyl acetate was evaporated to obtain 610 parts of a transparent liquid modifier (M3). According to the infrared absorption spectrum of this modifier,
Absorption due to free isocyanate groups at 2270/cm remained, and an absorption band due to Si-O-C groups was shown at 1090/cm. Furthermore, when the amount of free isocyanate groups in this modifier was quantified, the theoretical value was 1.34%, while the actual value was 1.25%. Therefore, the main structure of the above modifier is estimated to be the following formula. Reference Example 4 (Manufacturing example of modifier) 35 parts of 2,6-tolylene diisocyanate and 110 parts of ethyl acetate were stirred well at 60°C, and a terminal mercaptopropyl polydimethylsiloxane (molecular weight 1580) having the following structure was added thereto. Gradually add 316 parts to react. (1, m, and n are values that give a molecular weight of 1580) After the reaction was completed, ethyl acetate was evaporated to obtain 340 parts of a transparent liquid modifier (M4). According to the infrared absorption spectrum of this modifier,
Absorption due to free isocyanate groups at 2270/cm remained, and an absorption band due to Si-O-C groups was shown at 1090/cm. Furthermore, when the amount of free isocyanate groups in this modifier was quantified, the theoretical value was 2.39%, while the actual value was 2.12%. Therefore, the main structure of the above modifier is estimated to be the following formula. (1, m, n are the values that make the molecular weight 1580) Reference Example 5 (Production example of modifier) 52 parts of hexamethylene diisocyanate and 160 parts of ethyl acetate were stirred well at 60°C, and 450 parts of terminal hydroxypropyl polydimethylsiloxane (molecular weight 2250) having the following structure was added thereto. Gradually drop it and let it react. (n is the value at which the molecular weight is 1580) After the reaction was completed, ethyl acetate was evaporated to obtain 488 parts of the modifier (M5) in the form of a transparent liquid. According to the infrared absorption spectrum of this modifier,
Absorption due to free isocyanate groups at 2270/cm remained, and an absorption band due to Si-O-C groups was shown at 1090/cm. Furthermore, when the amount of free isocyanate groups in this modifier was quantified, the theoretical value was 1.67%, while the actual value was 1.52%. Therefore, the main structure of the above modifier is estimated to be the following formula. Reference Example 6 (Preparation of binder resin solution) 150 parts of polybutylene adipate having a molecular weight of 2000 having a hydroxyl group at the end, 20 parts of 1,3-butylene glycol, and 52 parts of tolylene diisocyanate were subjected to an addition reaction in 412 parts of methyl ethyl ketone to obtain a solution with a viscosity of 200. Poise/Polyurethane resin solution at 20℃ (solid content 35
%) was obtained. To 100 parts of this polyurethane resin solution,
5 parts of the modifier (M1) were added and reacted at 80°C for 3 hours to obtain a modified binder resin solution (UB1) in which the modifier and the polyurethane resin were combined. In the binder resin obtained above, no isocyanate group was observed by infrared absorption spectrum. This is presumed to be because the modifier was graft-bonded to the binder resin. Reference Example 7 (Preparation of binder resin solution) A modified binder resin solution (UB2) was obtained in the same manner as in Reference Example 6, except that the modifier (M2) was used instead of the modifier (M1) in Reference Example 6. Ta. Reference Example 8 (Preparation of binder resin solution) A modified binder resin solution (UB3) was obtained in the same manner as in Reference Example 6 except that the modifier (M3) was used instead of the modifier (M1) in Reference Example 8. Ta. Reference Example 9 (Preparation of binder resin solution) A modified binder resin solution (UB4) was obtained in the same manner as in Reference Example 6 except that the modifier (M4) was used instead of the modifier (M1) in Reference Example 6. Ta. Reference Example 10 (Preparation of binder resin solution) A modified binder resin solution (UB5) was obtained in the same manner as in Reference Example 6, except that the modifying agent (M5) was used instead of the modifying agent (M1) in Reference Example 6. Ta. Reference Example 11 (Preparation of dispersion) Co-containing Fe ₂ O ₃ 100 parts Binder solution (UB1) (35% solution) 30 parts Dispersant (lecithin) 1 part Carbon black 5 parts Nitrocellulose 6 parts Methyl ethyl ketone 270 parts Mix the above components The mixture was kneaded in a ball mill for 50 hours, 8 parts of Coronate L was added, and kneaded for another 3 hours, and the kneaded mixture was passed through a filter to obtain a magnetic particle dispersion (UD1). Reference Example 12 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (UD2) was obtained in the same manner as in Reference Example 11 except that a binder resin solution (UB2) was used instead of the binder resin solution in Reference Example 11. . Reference Example 13 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (UD3) was obtained in the same manner as in Reference Example 11 except that a binder resin solution (UB3) was used instead of the binder resin solution in Reference Example 11. . Reference Example 14 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (UD2) was obtained in the same manner as in Reference Example 11 except that a binder resin solution (UB4) was used instead of the binder resin solution in Reference Example 11. . Reference Example 15 (Preparation of dispersion liquid) Instead of the binder resin solution in Reference Example 11, the binder resin solution (UB5) was used,
A dispersion liquid (UD5) of magnetic particles was obtained in the same manner as in Reference Example 11 in other respects. Reference Example 16 (Preparation of binder resin solution) To 100 parts of a methyl ethyl ketone solution (solid content 30%) of vinyl chloride/vinyl acetate/vinyl alcohol copolymer resin (Eslec A, manufactured by Sekisui Chemical),
Add 3 parts of the modifier (M1) obtained in Reference Example 1 and heat at 80°C.
The mixture was reacted for 3 hours to obtain a modified binder resin solution (VB1) in which the modifier and the vinyl resin were combined. In the binder resin obtained above, no isocyanate group was observed by infrared absorption spectrum. This is presumed to be because the modifier was graft-bonded to the binder resin. Reference Example 17 (Preparation of binder resin solution) A modified binder resin (VB2) was obtained in the same manner as in Reference Example 18, except that the modifier (M2) was used instead of the modifier (M1) in Reference Example 16. . Reference Example 18 (Preparation of binder resin solution) A modified binder resin (VB3) was obtained in the same manner as in Reference Example 16, except that the modifier (M3) was used instead of the modifier (M1) in Reference Example 16. . Reference Example 19 (Preparation of binder resin solution) A modified binder resin (VB4) was obtained in the same manner as in Reference Example 18 except that the modifier (M4) was used instead of the modifier (M1) in Reference Example 16. . Reference Example 20 (Preparation of binder resin solution) A modified binder resin (VB5) was obtained in the same manner as in Reference Example 16, except that a modifier (M5) was used instead of the modifier (M1) in Reference Example 16. . Reference Example 21 (Preparation of dispersion liquid) Co-containing Fe ₂ O ₃ 100 parts Binder solution (VB1) (30% solution) 20 parts Polyester type polyurethane resin solution (Rezamin ME12, manufactured by Dainichiseika Industries) 54 parts Dispersant (lecithin) 1 part carbon black 5 parts nitrocellulose 6 parts methyl ethyl ketone 270 parts The above ingredients were mixed, kneaded in a ball mill for 50 hours, further added 8 parts of Coronate L, kneaded for another 3 hours, and passed the kneaded mixture through a filter to form a dispersion of magnetic particles ( VD1) was obtained. Reference Example 22 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (VD2) was obtained in the same manner as in Reference Example 21 except that a binder resin solution (VB2) was used instead of the binder resin solution in Reference Example 21. . Reference Example 23 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (VD3) was obtained in the same manner as in Reference Example 21 except that a binder resin solution (VB3) was used instead of the binder resin solution in Reference Example 21. . Reference Example 24 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (VD4) was obtained in the same manner as in Reference Example 21 except that a binder resin solution (VB4) was used instead of the binder resin solution in Reference Example 21. . Reference Example 25 (Preparation of dispersion liquid) Instead of the binder resin solution in Reference Example 21, the binder resin solution (VB5) was used,
The other procedures were the same as in Reference Example 21 to obtain a magnetic particle dispersion (VD5). Reference example 26 (Preparation of binder resin solution) Butyral resin (Eslec B, manufactured by Sekisui Chemical)
Add 7 parts of the modifier (M1) obtained in Reference Example 1 to 100 parts of the methyl ethyl ketone solution (solid content 30%),
Modified binder resin solution (BB1) in which the modifier and butyral resin are combined by reacting at 80℃ for 3 hours
I got it. In the binder resin obtained above, no isocyanate group was observed by infrared absorption spectrum. This is presumed to be because the modifier was graft-bonded to the binder resin. Reference Example 27 (Preparation of binder resin solution) A modified binder resin (BB2) was obtained in the same manner as in Reference Example 26 except that the modifier (M2) was used instead of the modifier (M1) in Reference Example 26. . Reference Example 28 (Preparation of binder resin solution) A modified binder resin (BB3) was obtained in the same manner as in Reference Example 26, except that a modifier (M3) was used instead of the modifier (M1) in Reference Example 26. . Reference Example 29 (Preparation of binder resin solution) A modified binder resin (BB4) was obtained in the same manner as in Reference Example 26, except that the modifier (M4) was used instead of the modifier (M1) in Reference Example 26. . Reference Example 30 (Preparation of binder resin solution) Modified binder resin (BB5) was obtained in the same manner as in Reference Example 26, except that the modifier (M5) was used instead of the modifier (M1) in Reference Example 26. . Reference Example 31 (Preparation of dispersion liquid) Co-containing Fe ₂ O ₃ 100 parts Binder solution (BB1) (30% solution) 20 parts Polyester-type polyurethane resin solution (Rezamin ME12, manufactured by Dainichiseika Industries) 54 parts Dispersant (lecithin) 1 part carbon black 5 parts nitrocellulose 6 parts methyl ethyl ketone 270 parts The above ingredients were mixed, kneaded in a ball mill for 50 hours, further added 8 parts of Coronate L, kneaded for another 3 hours, and passed the kneaded mixture through a filter to form a dispersion of magnetic particles ( BD1) was obtained. Reference Example 32 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (BD2) was obtained in the same manner as in Reference Example 31 except that a binder resin solution (BB2) was used instead of the binder resin solution in Reference Example 31. . Reference Example 33 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (BD3) was obtained in the same manner as in Reference Example 31 except that a binder resin solution (BB3) was used instead of the binder resin solution in Reference Example 31. . Reference Example 34 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (BD4) was obtained in the same manner as in Reference Example 31 except that a binder resin solution (BB4) was used instead of the binder resin solution in Reference Example 31. . Reference Example 35 (Preparation of dispersion liquid) A magnetic particle dispersion liquid (BD5) was obtained in the same manner as in Reference Example 31 except that a binder resin solution (BB5) was used instead of the binder resin solution in Reference Example 31. . Examples 1 to 5 Dispersions UD1 to UD5 obtained in Reference Examples were each applied to a 15 μm thick polyester film using a reverse roll coater to a thickness of 5 μm, and the solvent was dried. The magnetic recording medium of the present invention was obtained by surface processing with a super calendar roll and cutting into a predetermined width. Examples 6 to 10 Dispersions VD1 to VD5 obtained in Reference Examples were each applied to a 15 μm thick polyester film using a reverse roll coater to a thickness of 5 μm, and after drying the solvent. The magnetic recording medium of the present invention was obtained by surface processing with a super calendar roll and cutting into a predetermined width. Examples 10 to 15 Dispersions BD1 to BD5 obtained in Reference Examples were each applied to a 15 μm thick polyester film using a reverse roll coater to a thickness of 5 μm, and after drying the solvent. The magnetic recording medium of the present invention was obtained by surface processing with a super calendar roll and cutting into a predetermined width. Comparative Examples 1 to 3 Comparative magnetic recording media were obtained in the same manner as Examples 1 to 15, except that polyurethane resins, ESLEC A and ESLEC B, which were not modified with the modifier of the present invention were used. 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 (μk) measured between the magnetic layer and the support (base film), and other performances are measured by mounting tests as video tapes.
Observations are made of tape squeal (B), jitter lateral wobbling (C), irregular winding during fast forwarding of the tape (D), and wear of the magnetic layer (E) during 200 runs. The overall evaluation was given as F.

[Table] From the above results, it is clear that the magnetic recording medium of the present invention has a low coefficient of friction of the magnetic layer and exhibits excellent running characteristics.

Claims (1)

[Claims] 1. Consisting of a non-magnetic support and a magnetic layer provided on one surface of the support, the magnetic layer contains magnetic particles,
It is formed from a dispersion consisting of a binder resin, a modifier for the binder resin, and a medium, and the modifier is a reaction product of a silicone compound having a reactive organic functional group and an organic polyisocyanate, and at least one 1. A magnetic recording medium characterized by having a number of free isocyanate groups. 2. The magnetic recording medium according to claim 1, wherein the binder resin has a group capable of reacting with an isocyanate group.