JPS61184719A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enable high-speed use and repeated use by forming a magnetic layer on one side of a support and a backing layer on the other side and by using polyurea resin having siloxane bonds in the molecule as resin forming the backing layer so as to increase the softening point and to reduce the coefft. of friction. CONSTITUTION:Polyurea resin is synthesized from polysiloxanepolyamine having two or more amino groups in one molecule and a polyisocyanate compound having two or more isocyanate groups in one molecule. Polydi alkylsiloxanediamine having about 500-10,000 average mol.wt. is preferably used as the polysiloxanepolyamine. The polyisocyanate compound is a general polyisocyanate compound such as toluene-2,4-diisocyanate. The synthesis is carried out so as to regulate the amount of silicon atoms in the resulting polyurea resin to about 5-50wt% per 100pts.wt. polyurea rsin. A dispersion contg. the polyurea resin is prepd., applied to a support, and dried to form a backing layer for a magnetic recording medium.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a magnetic recording medium, and more specifically, the present invention relates to a magnetic recording medium, and more specifically, the present invention relates to a magnetic recording medium, and more specifically, the present invention relates to a magnetic recording medium, and more specifically, the present invention relates to magnetic recording media. Concerning excellent magnetic recording media.

(Prior Art) Conventionally, magnetic recording media such as magnetic tapes used in audio equipment, video equipment, computers, etc. are made of magnetic powder and binder resin on one side of a non-magnetic support such as a polyester film. This is achieved by forming a magnetic layer and also forming a back layer for improving running stability of these tapes, reducing frictional resistance between the tapes, or improving charging characteristics.

As a resin for forming the back layer of such a magnetic recording medium, vinyl chloride resin, polyurethane resin, polyester resin, nitrocellulose resin, epoxy resin, etc. are generally used.

In addition, magnetic recording media such as those described above have smooth surfaces of the magnetic layer and back layer, and can withstand repeated use many times, in order to increase recording speed, increase recording density, and reduce the size and weight of the device. As such, it is required to be wear resistant.

(The problem that the invention is trying to solve) However,
The back layer formed using the resin described above has a friction coefficient of about 0.4 or more, so when the magnetic recording medium is for video tape or audio tape, it can be used for those tapes. The slipperiness of the tape is poor, and it may cause irregular winding during winding and unwinding of the tape, resulting in deformation and damage to the tape, causing dropouts.

In order to solve these drawbacks, attempts have been made to reduce the coefficient of friction of the back layer by adding lubricants such as wax, silicone oil, etc. to the back layer. The greater tendency to bleed onto the surface of the layer creates another problem, clogging the recording head.

As another method, it has been proposed to form the back layer using a polyurethane resin having siloxane bonds in the molecule as the resin (for example, Japanese Patent Laid-Open No. 57-17653
No. 6, No. 58-222436, No. 59-82636, etc.).

However, the back layer formed using such a resin is easily softened by the frictional heat generated between the tapes during high-speed use such as during rewinding or fast forwarding.
Therefore, when used continuously for a long time, the coefficient of friction increases due to softening, causing the problems described above.

In order to solve these drawbacks, when forming the back layer,
It has also been proposed to add a crosslinking agent such as polyisocyanate to the paint for forming the back layer, but products to which such a crosslinking agent is added tend to change over time, and their pot life (
Pot life) is problematic.

As a result of intensive research, the present inventors aimed to solve the above-mentioned drawbacks of the prior art and to obtain a magnetic recording medium that has a high softening point and a small coefficient of friction, and therefore can be used at high speeds and repeatedly used many times. The present invention was completed based on the finding that the above-mentioned drawbacks of the prior art can be solved by using a specific resin as the resin forming the back layer of a magnetic recording medium.

(Means for solving the problems) That is, the present invention consists 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 magnetic recording medium is characterized in that the resin forming the back layer is a polyurea resin having a siloxane bond in the molecule.

Next, to explain the present invention in more detail, the resin used in the present invention and which mainly characterizes the present invention was developed for the first time by the present inventor, and is a polyurea resin having a siloxane bond in its molecule.

The above polyurea resin can be easily produced according to conventional polyurea resin production methods from a polysiloxane polyamine having two or more amine groups in one molecule and a polyisocyanate compound having two or more incyanate groups in one molecule. can be obtained.

Preferred as the above polysiloxane polyamine is polysia ILq siloxane diamine, which can be represented by the following general formula.

R in the above formula is an aliphatic, aromatic, or aliphatic divalent group, and preferred in the present invention are C1-
C1 alkyl group or 06-C, (7) aromatic group.

Further, R' is an alkyl group, preferably a methyl group in the present invention.

m is a value such that the average molecular weight of the polysiloxane diamine of the above general formula is about 500 to 10,000, and particularly preferred in the present invention is a value where the average molecular weight is about t, ooo
~5,000.

Incidentally, such polysiloxane diamine can be used alone or as a mixture, and furthermore, in order to adjust various physical properties such as breaking strength, breaking elongation, hardness, etc. of the resulting polyurea resin, other general diamine or more functional compounds may be used. A polyamine can be used in combination as a copolymerization component. Such other common polyamines are preferably used in an amount of 1 mole or less per mole of the polysiloxane polyamine described above.

The polyisocyanate compound to be reacted with the polysiloxane polyamine is a general polyisocyanate compound conventionally used in the production of polyurethane resins, such as 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(phenylisocyanate)
.

Shurylene 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-methylenebis(cyclohexylisocyanate)
g), 1,5-tetrahydronaphthalene diisocyanate, and the like.

The polyurea resin used in the present invention is obtained by reacting the above-mentioned polysiloxane and polyisocyanate by a conventionally known method. It is preferable to adjust the amount to about 5 to 50% by weight in each part.

The amount of silicon atoms can be adjusted by adjusting the average molecular weight of the polysiloxane polyamine to be used. Furthermore, there is a method of using together other polyols such as ethylene glycol, propylene glycol, polyether polyol, and polyester polyol.

If the amount of silicon atoms in the resulting polyurea resin is less than about 5% by weight, it will be difficult to reduce the coefficient of friction of the surface to the desired value, that is, about O1.3 or less when the back layer is formed; If the amount of silicon atoms exceeds 50% by weight, the solubility and flexibility of the resulting polyurea resin in organic solvents will decrease, making it undesirable as a resin for forming a back layer.

The above polyurea resin can be produced according to conventionally known polyurea resin production methods, for example,
The above components are mixed in the presence or absence of an organic solvent and/or catalyst at a temperature of about 0 to 100°C to a temperature of about 0.5°C.
The polyurea resin used in the present invention is obtained by reacting for ~3 hours.

A preferred method is a method in which the polyurea resin to be produced is dissolved in an organic solvent.

The magnetic recording medium of the present invention may be formed by any conventionally known method except for the use of a specific polyurea resin as described above for forming the back layer.1For example, the magnetic layer may be formed using a conventionally known binder for forming a magnetic layer. It can be obtained by adding the resin together with magnetic powder into an organic solvent, preparing a dispersion using a dispersant if necessary, coating this dispersion on a support, and drying it to form a magnetic layer. .

Conventionally known materials and methods may be used for the organic solvent, magnetic powder, support, coating, drying method, etc. used in this case.

For example, binder resins include vinyl chloride-vinyl acetate copolymers, cellulose resins, epoxy resins,
Polyvinyl butyral resin, polyurethane resin, synthetic rubber resin, acrylic resin, polyester resin, etc. are used.

Also, preferred organic solvents include:

For example, 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, dimethyl formamide, dimethyl sulfoxide, pentane,
Hexane, cyclohexane, heptane, octane, mineral spirits, petroleum ether, gasoline, benzene,
Examples include toluene, xylene, chloroform, carbon tetrachloride, chlorobenzene, perchloroethylene, trichlorethylene, and the like.

Examples of the magnetic powder include γ-Fe, O, cobalt-containing γ-Fe, O, Fe, O, cobalt-containing Fe, O, Cr O, Fe, Fe-Ni alloy,
Any conventionally known magnetic powder such as Co-N1-P alloy or Fe-Co-Ni alloy can be used.

For these magnetic powders, the binder resin is used at a ratio of about 10 to 40 parts by weight per 100 parts by weight of the magnetic powder, and the solid content of the resulting coating liquid is about 20 to 40% by weight. is preferred.

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 pm can be used as desired. can.

The magnetic layer is formed by applying the above-mentioned coating solution onto one side of the above-mentioned support by an arbitrary method so that the thickness when dried is about 5 to 20 JLm.

It can then be formed by drying.

The magnetic recording medium of the present invention can be obtained by forming a back layer using a specific polyurea resin as described above on the back surface of a magnetic recording medium obtained by a conventionally known method.

Formation of such a back layer is carried out by dissolving the above-mentioned polyurea resin in the above-mentioned organic solvent to a concentration of about 10 to 50% by weight to prepare a coating solution, and applying this coating solution to the back surface of the support and drying. Apply so that the thickness is about 5 to 50 ILm,
This is done by drying.

Various conventionally known coating methods can be used as they are, and drying is performed at about 50 to 120° C. for about 0.5 to 2 hours.

In addition to the polyurea resin used above,
Conventionally used resins such as polyurethane resins and polyesters may be used in combination to adjust Young's modulus and improve adhesion, and various additives such as antistatic agents may also be used in combination.

In the above description, the magnetic layer is first formed and then the back layer is formed, but the same effect can be obtained by forming the back layer first and then forming the magnetic layer.

(Function/Effect) In the magnetic recording medium of the present invention obtained as described above, the back layer is formed from a polyurea resin containing siloxane bonds in its molecules. As demonstrated in the examples, the coefficient of friction of the material is very low, and the softening point is very high. This remarkable effect is thought to be due to the fact that the polyurea resin used in the present invention has stronger hydrogen bonds between urea bonds than conventional polyurethane resins containing siloxane bonds. There is.

Therefore, the magnetic recording medium of the present invention exhibits extremely superior tape running properties compared to conventional magnetic recording media, and even when used continuously for a long time, the back layer does not soften due to frictional heat. It can be used extremely stably.

The present invention will be explained in more detail with reference to the following Examples and Comparative Examples. Note that parts and percentages in the text are based on weight.

Example 1 (Synthesis of polyurea resin) 150 parts of dimethylpolysiloxane diamine of the above formula (average molecular weight 3,880) and 710 parts of 1,3-propylene diamide were added to 250 parts of dimethylformamide,
Stir this mixture.

Charge the reactor equipped with a reflux condenser, dropping funnel, and gas inlet tube. Cool the contents externally to bring the internal temperature to O~-5℃, and continue to flow carbon dioxide gas through the gas inlet tube while maintaining this temperature. .

Next, a solution of 15 parts of hydrogenated MDI dissolved in 65 parts of dimethylformamide was dropped into the reactor through the dropping funnel to cause a reaction. After the completion of the dropwise addition, the internal temperature was gradually raised to reach 50°C. By the way, stirring was continued at 50°C for 1 hour.

The resulting polyurea resin solution had a solids content of 35% and a viscosity of 15,000 cps (25°C).

The breaking strength of the film formed from this solution (kg/am
) was 450, the elongation at break (%) was 550, and the softening point was 150°C or higher.

Example 2 (Synthesis of polyurea resin) 150 parts of the polysiloxane diamine in Example 1 having an average molecular weight of about 1,000 were added to a mixed organic solvent consisting of 1100 parts of dimethylformamide and 150 parts of methyl ethyl ketone. , also 39 parts of hydrogenated MD
A polyurea resin solution was obtained in the same manner as in Example 1 except that I was added to 100 parts of methyl ethyl ketone.

The solids content of this solution is 35% and 10,000 cps
(25°C).

The breaking strength of the film formed from this solution (kg/C
) was 210, the elongation at break (%) was 650, and the softening point was 150°C or higher.

Comparative Example 1 (Synthesis of conventionally known binder resin) 150 parts of polydimethylsiloxane diol and 10 parts of 1,3-propanediol, which are represented by the above formula and have an average molecular weight of about 3.200, were mixed with 200 parts of methyl ethyl ketone. Siloxane bonding was carried out in the same manner as in Example 1, except that in addition to a mixed organic solvent consisting of A polyurethane resin solution was obtained.

The solids content of this solution is 35% and 13,000 cps
(25°C).

The elongation at break of the film formed from this solution (kg/am
) was 200, the breaking strength (%) was 560, and the softening point was 100°C or less.

Comparative Example 2 (Synthesis of conventionally known binder resin) Comparative Example 1
However, 150 parts of polydimethylsiloxane diol with an average molecular weight of about 1.000 was dissolved in 250 parts of methyl ethyl ketone, 39 parts of hydrogenated MDI was dissolved in 100 parts of methyl ethyl ketone, and the other Comparative example 1
A polyurethane resin solution having siloxane bonds was obtained in the same manner as above.

The solids content of this solution was 35%, tt,s.

It had a viscosity of 0 cps' (25°C).

The breaking strength of the film formed from this solution (kg/cs
) was 90, the elongation at break (%) was 700, and the softening point was 100°C or less.

Comparative Example 3 (Synthesis of conventionally known polyurethane resin) A mixed organic compound consisting of 150 parts of polybutylene adipate having an average molecular weight of about 2.000 and 10 parts of 1,3-propanediol with 120 parts of methyl ethyl ketone and 130 parts of dimethylformamide Dissolved in the solvent and also 55 parts hydrogenated M
A polyurethane resin solution was obtained in the same manner as in Example 1 except that DI was dissolved in 150 parts of methyl ethyl ketone.

The solids content of this solution is 35% and 14,500 cps
(25°C).

The breaking strength of the film formed from this solution (kg/c+
a) was 250, the elongation at break (%) was 500, and the softening point was 100°C or less.

In addition, the softening point in the above is calculated by cutting the film into a strip, attaching a drill to the bottom end of the film to give a value of 450 g/cm", hanging it in a gear oven, and then
It was determined as the temperature at which the elongation of the film suddenly increased or when the film was cut by increasing the temperature at a rate of °C/in.

Examples 3 to 4 and Comparative Examples 4 to 6 Paints consisting of the following ingredients were prepared, and the thickness was 15 pm.
One side of the polyester film has a dry thickness of l.
JLm, dried the solvent, and formed the back layer.Then, the 0th layer was coated with a binder resin consisting of Co-containing γ-Fe, O, and ordinary polyurethane resin and vinyl chloride copolymer resin. Accordingly, a magnetic layer was formed on the opposite surface and cut to a predetermined width to prepare a video magnetic recording medium of the present invention and a comparative video magnetic recording medium.

Branch 1" Resin solution of Example 1 100 parts Byron-200 (Toyo Dobu Polyester Resin) 5 parts Methyl ethyl ketone 1.200 parts Branch 1" Resin solution of Example 2 100 parts Byron-200 (Toyo Dobu Polyester) Resin) 5 parts Methyl ethyl ketone 1.200 parts Saikogami Resin solution of Comparative Example 1 30 parts Vylon-200 (Toyo Doube Polyester Resin) 5 parts Methyl Ethyl Ketone 1.200 parts Kuishibori 11j Resin solution of Comparative Example 2 30 parts Vylon -200 (Toyo Dobu Polyester Resin) 5 parts Methyl ethyl ketone 1.200 parts Salt 1'' Resin solution of Comparative Example 3 30 parts Byron-200 (Toyo Dobu Polyester Resin) 5 parts Methyl ethyl ketone 1, 200 parts Ll [Il Example The friction coefficients and running characteristics of the tapes obtained in Comparative Examples 3 to 4 and Comparative Examples 4 to 6 were as follows.

LLf21! tlLU21 I O,1B 0.20 0.20 0
．． 21 0.50II None None Slightly present Slightly present Yes ■ None None None Slightly present Yes ■ None Rich None Slightly present YesV
None Slightly Yes Yes Yes Yes ■ Good Good Slightly Good Slightly Poor Defectiveness, work Coefficient of friction (ILk) II Tape squeal ■ Jitter sideways vibration ■ Uneven winding condition ■ Wear ■ Overall evaluation In the above, the friction coefficient is determined by each magnetic property. Measurements between the layer surface and the support (base film).

Other performance tests were conducted as a videotape, including tape squeal, jitter, and lateral vibration when running 200 times.
This is an observation of the state of irregular winding of the tape during fast forwarding and the state of wear of the magnetic layer.

From the above results, it is clear that the magnetic recording medium of the present invention has a lower friction coefficient of the back layer and a significantly higher softening point than conventional magnetic recording media, and thus has excellent running characteristics. It is.

Claims (1)

[Claims] It consists 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, and the resin forming the back layer has a siloxane bond in the molecule. A magnetic recording medium characterized by being made of polyurea resin.