JPH0474776B2 - - 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 whose back layer is formed from a film-forming resin modified with a specific modifier. (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 liquid in which magnetic particles are dispersed in a medium containing a binder 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 properties such as electrical properties. Various physical properties are required for the back layer, but
A particularly important required performance is good running properties of the magnetic recording media, and for this purpose it is strongly required that the coefficient of friction between the magnetic recording media be low. The level of the friction coefficient is mainly determined by the film-forming resin used to form the back layer. Conventionally, as film-forming resins for forming the back layer, vinyl chloride resins, polyurethane resins, polyester resins, nitrocellulose resins, epoxy resins, and the like have been used singly 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 magnetic recording media with back layers formed from these film-forming resins can be used for video tapes. When used as an audio tape, etc., the slipperiness of the tape is insufficient, so when the tape is used at high speeds such as winding and rewinding, uneven winding may occur, causing deformation and damage to the tape. , causing dropout. One way to solve these drawbacks and lower the coefficient of friction of magnetic recording media is to add lubricants such as fatty acids, wax, and silicone oil to the back layer. Another drawback arises in that the lubricant added to the magnetic layer bleeds out to the surface of the back layer and transfers to the magnetic layer, 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 film-forming resin itself, for example, a polyurethane resin having a siloxane bond in the molecule (for example, JP-A-57-1999). No. 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, it is possible to form a back layer with a relatively low coefficient of friction, but since the siloxane bond-containing polyurethane resin contains a siloxane bond in the main chain of the polymer, sufficient reaction may not occur. It is difficult to obtain a film-forming resin of constant quality, resulting in high costs, 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 scope of its use is severely 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 technology 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 the Problems) That is, the present invention comprises a non-magnetic support, a magnetic layer provided on one surface of the support, and a back layer provided on the other surface of the support, The back layer is made of a film-forming resin modified with a modifier that is a reaction product of a fluorine compound having a reactive organic functional group and an organic polyisocyanate and has substantially no free isocyanate groups. This is a magnetic recording medium characterized by the following. 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 fluorine compound having a reactive organic functional group and an organic polyisocyanate. The reaction product is substantially free of free isocyanate groups. Fluorine compounds having reactive organic functional groups used to obtain such modifiers include amino groups,
Any compound may be used as long as it has a group capable of reacting with an isocyanate group such as a carboxyl group, hydroxyl group, thioalcohol group, etc., but a particularly preferred example is a fluorine compound represented by the following formula. (1) H (CF ₂ CF ₂ ) _o CH ₂ OH (n=1 to 7) (2) CF ₃ (CF ₂ CF ₂ ) _o CH ₂ CH ₂ OH (n=1 to 10) (3) CF ₃ (CF ₂ CF ₂ ) _o COOH (n=1 to 10) (4) CF ₃ (CF ₂ CF ₂ ) _o CH ₂ CH ₂ SH (n=1 to 10) (5) H (CF ₂ CF ₂ ) ₁ (CH ₂ ) _n (OCH ₂ CH ₂ (OH)
CH ₂ ) _o OH (l=1 to 10, m=1 to 10, n=
1 to 3) (6) F (CF ₂ CF ₂ ) ₁ (CH ₂ ) _n (OCH ₂ CH ₂ (OH)
CH ₂ ) _o OH (l=1 to 10, m=1 to 10, n=
1 to 3) The fluorine compounds having the above-mentioned reactive organic functional groups are preferred examples of fluorine compounds in the present invention, and the present invention is not limited to these examples. The compound and other fluorine compounds are currently commercially available and readily available from the market, and any of them 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, etc.Furthermore, adducts of these organic polyisocyanates and other compounds, such as those having the following structural formula, may be mentioned, but are not limited to these. The modifier used in the present invention is a fluorine compound having a reactive organic functional group as described above and an organic polyisocyanate as described above. Preferably 1:1 so that no residue remains.
from about 0 to 150°C, preferably from 20 to 80°C, in the presence or absence of an organic solvent and a catalyst.
It can be easily obtained by reacting for about 10 minutes to 3 hours at a temperature of .degree. 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 each reaction raw material and product. 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 sulfoxide, 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 eluent, or it can be used as a solution in 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 such as infrared absorption spectroscopy, 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 fluorine compound are When an addition reaction occurs, for example, when the reactive organic functional group is an amino group, it becomes clear that the two are bonded through a urethane bond and that the compound is substantially free of free isocyanate groups. Ta. In the present invention, the film-forming resin used is various conventionally known film-forming resins, and any of these conventionally known resins can be used. For example, vinyl chloride resin, vinylidene chloride resin, chloride resin, Vinyl/vinyl acetate/vinyl alcohol copolymer resin, alkyd resin, epoxy resin, acrylonitrile-butadiene resin,
Particularly preferred examples include polyurethane resins, polyurea resins, nitrocellulose resins, polybutyral resins, polyester resins, fluorine resins, melamine resins, urea resins, acrylic resins, and polyamide resins. is a polyurethane resin having urea bonds, urethane bonds, etc. in its structure. 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 preferably about 10 to 55% by weight, and the modifier can be used in a proportion of about 1 to 100 parts by weight per 100 parts by weight of the film-forming resin. As long as the back layer forming solution paint used in the present invention contains the above components as essential components, other subcomponents other than the above, such as pigments, extender pigments, plasticizers, antistatic agents, surfactants, lubricants, crosslinking agents, etc. agent, anti-aging agent,
Optional additives such as stabilizers, blowing agents, and antifoaming agents may be included. The method of forming the back layer itself may be the same as any conventionally known method, and it is preferably formed to a thickness of about 1 to 50 μm. The dispersion liquid used to form the magnetic layer uses the same resin as the film-forming resin as a binder resin, and contains the binder resin, magnetic particles, and a 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, for example, γ-Fe ₂ O ₃ , ferrite, magnetite, CrO _2, etc., cobalt-doped γ-Fe ₂ o ₃
Examples include bertolide compounds of Fe ₃ O ₄ 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. The dispersion liquid used for forming the magnetic layer in the present invention has the above-mentioned components as essential components, and their usage ratios are as follows:
It is similar to that 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 weight %, the medium accounts for about 50 to 90 weight %, and the binder resin accounts for about 5 to 20 weight %. The range is common. 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, while adding the necessary components simultaneously or sequentially, ball milling, mixer treatment, etc. Mixing and dispersing methods such as processing, roll milling, bead milling, gravel milling, sand milling, and high speed impeller processing are suitable. The conditions for such dispersion methods themselves vary depending on the type and size of the magnetic particles to be dispersed, their use, etc., but generally, they are carried out at temperatures between room temperature and 100°C.
The treatment may be carried out for about 5 to 20 hours. Further, as the support used, 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 The coating method and drying method may be any conventionally known method. (Function/Effect) The back layer of the magnetic recording medium of the present invention obtained as described above has various characteristics originally possessed by the film-forming resin, depending on the type of film-forming resin used. For example, while maintaining strength, electrical, chemical, and physical properties, it has a low coefficient of friction that cannot be achieved with conventional technology, so it is used as a variety of magnetic tapes, etc., and can be used for winding, unwinding, etc. Even if the tape is used at high speeds such as the above, 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 modifying polyurethane resins, but can be freely used to modify any film-forming resin, and therefore can be used in various ways without increasing the manufacturing cost of magnetic recording media. This has the advantage that it is possible to provide a magnetic recording medium having a back layer made of a film-forming resin and having a low coefficient of friction. Furthermore, since the surface 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 Because the modifiers react with each other or with the film-forming resin through polar groups such as urethane bonds and urea bonds, the molecular weight is increased and the resin is integrated with the film-forming resin. The drawback that the agent bleeds onto the surface of the back layer, causing various problems, has been solved. Next, the present invention will be explained in more detail by giving reference examples, examples, comparative examples, and usage examples. In addition, in the text,
Parts or percentages are by weight. Reference example 1 (Production example of modifier) Adduct of hexamethylene diisocyanate and water (Dyuranate 24A-100, manufactured by Asahi Kasei, NCO%
23.5) While stirring 52 parts at 60°C, 80 parts of a fluorinated alcohol having the following structure was gradually added dropwise to react, yielding 129 parts of a colorless and transparent liquid modifier (M1). . H(CF ₂ CF ₂ ) ₅ OH According to the infrared absorption spectrum of this modifier,
No absorption due to free isocyanate groups at 2270/cm was observed, and an absorption band due to _-CF2- groups was observed at 1190/cm. Therefore, the main structure of the above modifier is estimated to be the following formula. Reference Example 2 (Manufacturing Example of Modifier) 120 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,
Fluorinated alcohol with the following structure in it
Gradually add 171 parts to react. After completion of the CF ₃ (CF ₂ CF ₂ ) ₃ OH reaction, 251 parts of a transparent liquid modifier (M2) was obtained. According to the infrared absorption spectrum of this modifier,
No absorption due to free isocyanate groups at 2270/cm was observed, and an absorption band due to _-CF2- groups was observed at 1190/cm. Therefore, the main structure of the above modifier is estimated to be the following formula. Reference example 3 (manufacturing example of modifier) Adduct of 1 mol of trimethylolpropane and 3 mol of xylylene diisocyanate (takenate
D110N, Takeda Pharmaceutical, NCO% 11.5, solid content 75%)
While thoroughly stirring 186 parts at room temperature, 258 parts of a fluorinated alcohol having the structure shown below was gradually added dropwise to react. CF ₃ (CF ₂ CF ₂ ) ₃ CH ₂ CH ₂ SH After the reaction was completed, 384 parts of a transparent liquid modifier (M3) was obtained. According to the infrared absorption spectrum of this modifier,
No absorption due to free isocyanate groups at 2270/cm was observed, and an absorption band due to _-CF2- groups was observed at 1190/cm. Therefore, the main structure of the above modifier is estimated to be the following formula. Reference Example 4 (Preparation of film-forming 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, and the viscosity was 200
Poise/Polyurethane resin solution at 20℃ (solid content 35
%) was obtained. To 100 parts of this polyurethane resin solution,
5 parts of a modifier (M1) was added to obtain a modified film-forming resin solution (UF1). Reference Example 5 (Preparation of film-forming resin solution) A modified film-forming resin solution (UF2) was prepared in the same manner as in Reference Example 4, except that the modifying agent (M2) was used instead of the modifying agent (M1) in Reference Example 4. I got it. Reference Example 6 (Preparation of film-forming resin solution) A modified film-forming resin solution (UF3) was prepared in the same manner as in Reference Example 4, except that the modifying agent (M3) was used instead of the modifying agent (M1) in Reference Example 4. I got it. Reference Example 7 (Preparation of film-forming 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),
3 parts of the modifier (M1) obtained in Reference Example 1 was added to obtain a modified film-forming resin solution (VF1). Reference Example 8 (Preparation of film-forming resin solution) Modifying film-forming resin (VF2) was prepared in the same manner as in Reference Example 7 except that the modifying agent (M2) was used instead of the modifying agent (M1) in Reference Example 7. Obtained. Reference Example 9 (Preparation of film-forming resin solution) Modifying film-forming resin (VF3) was prepared in the same manner as in Reference Example 7 except that the modifying agent (M3) was used instead of the modifying agent (M1) in Reference Example 7. Obtained. Reference example 10 (Preparation of film-forming resin solution) Butyral resin (Eslec B, manufactured by Sekisui Chemical)
Add 3 parts of the modifier (M1) obtained in Reference Example 1 to 100 parts of the methyl ethyl ketone solution (solid content 30%),
A modified film-forming resin solution (BF1) was obtained. Reference Example 11 (Preparation of film-forming resin solution) Modifying film-forming resin (BF2) was prepared in the same manner as in Reference Example 10 except that the modifying agent (M2) was used instead of the modifying agent (M1) in Reference Example 10. Obtained. Reference Example 12 (Preparation of film-forming resin solution) Modifier (M3) was used instead of the modifier (M1) in Reference Example 10, and the modified film-forming resin (BF3) was prepared in the same manner as in Reference Example 10. Obtained. Reference example 13 (Preparation of paint) Mix and dissolve the following ingredients to make paint for the back layer (UC1)
was prepared. Film-forming resin solution (UF1) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 14 (Preparation of paint) Mix and dissolve the following components to create paint for the back layer (UC2)
was prepared. Film-forming resin solution (UF2) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 15 (Preparation of paint) Mix and dissolve the following components to make paint for the back layer (UC3)
was prepared. Film-forming resin solution (UF3) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 16 (Preparation of paint) Mix and dissolve the following components to create paint for the back layer (VC1)
was prepared. Film-forming resin solution (VF1) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 17 (Preparation of paint) Mix and dissolve the following components to create paint for the back layer (VC2)
was prepared. Film-forming resin solution (VF2) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 18 (Preparation of paint) Mix and dissolve the following components to create paint for the back layer (VC3)
was prepared. Film-forming resin solution (VF3) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 19 (Preparation of paint) Mix and dissolve the following components to make paint for the back layer (BC1)
was prepared. Film-forming resin solution (BF1) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 20 (Preparation of paint) Mix and dissolve the following ingredients to make paint for the back layer (BC2)
was prepared. Film-forming resin solution (BF2) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Reference example 21 (Preparation of paint) Mix and dissolve the following ingredients to make paint for the back layer (BC3)
was prepared. Film-forming resin solution (BF3) (30% solution) 100 parts Polyester resin (Vylon-200, manufactured by Toyobo)
5 parts Methyl ethyl ketone 1200 parts Examples 1 to 3 Paints UC1 to UC3 obtained in Reference Examples were coated on polyester films each having a thickness of 15 μm using a reverse roll coater, respectively, to a dry thickness of 1 μm.
m, and the solvent was dried to form a back layer. Next, a magnetic layer is formed on the opposite surface using a conventional method from a dispersion containing Co-containing γ-Fe ₂ O ₃ and a film-forming resin made of ordinary polyurethane resin and vinyl chloride copolymer resin. Each of the magnetic recording media of the present invention was obtained by cutting into widths. Examples 4 to 6 Paints VC1 to VC3 obtained in Reference Examples were coated on polyester films each having a dry thickness of 1 μm using a reverse roll coater.
m, and the solvent was dried to form a back layer. Next, a magnetic layer is formed on the opposite surface using a conventional method from a dispersion containing Co-containing γ-Fe ₂ O ₃ and a film-forming resin made of ordinary polyurethane resin and vinyl chloride copolymer resin. Each of the magnetic recording media of the present invention was obtained by cutting into widths. Examples 7 to 9 Paints BC1 to BC3 obtained in Reference Examples were coated on polyester films each having a dry thickness of 1 μm using a reverse roll coater.
m, and the solvent was dried to form a back layer. Next, a magnetic layer is formed on the opposite surface using a conventional method from a dispersion containing Co-containing γ-Fe ₂ O ₃ and a film-forming resin made of ordinary polyurethane resin and vinyl chloride copolymer resin. Each of the magnetic recording media of the present invention was obtained by cutting into widths. Comparative Examples 1 to 3 Comparative magnetic recording media were obtained in the same manner as in Example 1, except that polyurethane resins that were not modified with the modifier of the present invention and Eslec A and B 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 back layer, and other performances are measured by the tape squeal (B ), lateral wobbling of jitter (C), irregular winding of the tape during fast forwarding (D), and friction of the magnetic layer (E). The overall evaluation was given as F.

【table】

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

Claims (1)

[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 a fluorine compound having a reactive organic functional group. 1. A magnetic recording medium comprising a film-forming resin modified with a modifier which is a reaction product of and an organic polyisocyanate and which has substantially no free isocyanate groups.