JPH03292612A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce wearing of a magnetic layer, etc., and to improve durability by using such a binder resin selected from specified resins into which a disphenyl structure is introduced as the binder component. CONSTITUTION:Such a binder resin selected from polyester resin, polyurethane resin, vinyl chloride resin, polyamide resin, and epoxy resin, each of which contains a diphenyl structure introduced into the molecule is used for the binder component of a magnetic layer, base coating layer and back coating layer. These magnetic layer, base coating layer and back coating layer containing these resins as the binder component have enough heat resistance against frictional heat with a magnetic head, etc., and show improvement in wearing resistance and durability.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium comprising a magnetic layer provided on a substrate and further provided with an undercoat layer or a backcoat layer as necessary. The present invention relates to the above-mentioned magnetic recording medium having improved durability by improving the binder in the layer, undercoat layer and backcoat layer.

[Conventional technology]

Magnetic recording media, which generally have a magnetic layer on a substrate and an undercoat layer or backcoat layer as necessary, come into intense sliding contact with a magnetic head etc. during recording and reproduction.
It is required that the magnetic layer etc. have less wear and have excellent durability.

For this reason, polyurethane resins and urethane-urea resins with excellent durability have been used as binder components in the magnetic layer, undercoat layer, and backcoat layer of magnetic recording media. This is not sufficient in the current situation where the contact speed with magnetic heads and the like is increasing as technology improves in performance.

Therefore, in recent years, efforts have been made to increase the glass transition temperature and improve durability by increasing the number of urethane bonds in polyurethane resins, or by introducing aromatic rings into the molecules by methods such as using isophthalic acid in the polyester portion of polyester resins. Attempts are being made to improve. (Unexamined Japanese Patent Publication No. 62-28
(No. 920, JP-A No. 64-78421) [Problems to be Solved by the Invention] However, when the number of urethane bonds in a polyurethane resin is increased, the glass transition temperature increases and durability is improved, but the solubility in solvents is significantly reduced. There is a limit to the increase in the number of urethane bonds, and there is also a limit to the improvement in durability.

In addition, polyester resins with aromatic rings, etc. introduced into the molecule, such as by using isophthalic acid in the polyester part, tend to crystallize and have problems with solubility, since there are 2 moles of ester bonds per 1 mole of aromatic rings. However, there is a limit to the amount that can be introduced, and in this case, there is also a limit to the improvement in durability, and durability cannot yet be improved sufficiently.

[Means to solve the problem]

This invention was made as a result of various studies in view of the current situation, and the binder components of the magnetic layer, undercoat layer, and back coat layer are polyester resins and polyurethane resins each having a diphenyl structure introduced into the molecule. resin,
By using a binder resin selected from vinyl chloride resin, polyamide resin, and epoxy resin, the durability of the magnetic recording medium is sufficiently improved.

In this invention, polyester resins, polyurethane resins, vinyl chloride resins, polyamide resins, and epoxy resins in which a diphenyl structure has been introduced into the molecule used as a binder component have an aromatic ring of the introduced diphenyl structure. Because they are easy to rotate, they dissolve well in the organic solvents used to manufacture magnetic recording media. Moreover, the glass transition temperature becomes sufficiently high due to the aromatic ring of diphenyl structure introduced inside the molecule. Therefore, the magnetic layer, undercoat layer, and backcoat layer that use these as binder components have sufficient heat resistance against frictional heat from magnetic heads, etc., and have improved abrasion resistance and sufficient durability. will be improved.

Polyester resins, polyurethane resins, vinyl chloride resins, which have such a diphenyl structure introduced into their molecules,
Polyamide resins and epoxy resins are, for example,
It is synthesized by reacting a diphenyl compound such as diphenic acid or diphenyl alcohol with a diol or dicarboxylic acid in a conventional manner to produce a polyester resin, or by reacting it with an isocyanate compound in a conventional manner to produce a polyurethane resin, etc. , by reacting vinyl chloride resins, polyamide resins, and epoxy resins having functional groups such as hydroxyl groups, carboxyl groups, isocyanate groups, amino groups, and grindyl groups with diphenyl compounds such as diphenic acid or diphenyl alcohol. , vinyl chloride resins, polyamide resins, epoxy resins, etc. in which a diphenyl structure is introduced into the molecule can be obtained.

Here, the diphenyl compound used is of the order of 1,1゛! It is preferable that the diphenyl structure is bonded at the 1,1' position, and has a functional group at a predetermined position. , rotation of the aromatic ring occurs easily, making it easy to dissolve in solvents.Also, it is introduced into the molecules of each binder resin due to the reaction of the functional groups, and the diphenyl structure increases the concentration of aromatic rings within the molecule, raising the glass transition temperature. . Therefore, a binder resin in which a diphenyl structure bonded at the 1.1' position is introduced into the molecule is generally well dissolved in an organic solvent used for manufacturing magnetic recording media, and this binder resin is used as a binder component. The durability of the magnetic layer, undercoat layer and backcoat layer used as the magnetic layer is sufficiently improved.

The functional group of the diphenyl compound having a diphenyl structure bonded at the 1.1' position may be any of a hydroxyl group, a carboxyl group, and an amino group, but from the viewpoint of toxicity, a hydroxyl group and a carboxyl group are preferable. In addition, when the functional group is located at the 2.2', 3,3' or 2.4' position, for example, in the case of polyester or polyurethane, hydrogen bonding is difficult to occur and the concentration of ester bonds in the molecule is low. It is preferable to have the functional group at the 2.2', 3,3' or 2,4' position because it has relatively good solubility; on the other hand, if the functional group is at the 4.4
′ has good molecular symmetry (too much, and it becomes insoluble).

Examples of such diphenyl compounds include (1.1'biphenyl)-2,2'- whose functional group is a hydroxyl group.
diol, (1,1'biphenyl)-373'-diol, (1,1"biphenyl)-2,4'-diol,
The functional group is a carboxyl group (1.1'biphenyl)
-2,2''-carboxylic acid, (1,1'biphenyl)-3
,3'-carboxylic acid, (1,1'biphenyl)-2,4
'-carboxylic acid and the like. When synthesizing polyester resin using these diphenyl compounds, (1,1'biphenyl)-2,2'-diol,
(Ll'biphenyl)-3,3''-diol, (1,1
It is synthesized by reacting aliphatic dicarboxylic acid with 'biphenyl)-2,4'-diol, and succinic acid, oxalic acid, adipic acid, etc. are preferably used as the aliphatic dicarboxylic acid. Also (1,1'biphenyl)-2,2'
-Carboxylic acid, (1,1'biphenyl)-3,3'-carboxylic acid, (1,1'biphenyl)-2,4'-carboxylic acid, etc., as well as ethylene glycol, propylene glycol, butylene glycol, etc. It is synthesized by reacting. Furthermore, when synthesizing polyurethane resin, (CI
'biphenyl)-2,2'-diol, (1,1'biphenyl)-3,3'-diol, (Ll'biphenyl)
It is synthesized by using -2,4'-diol as a chain extender or usual diol component and reacting it directly with an isocyanate compound.

In this way, the aromatic ring concentration of the diphenyl structure in polyester resins, polyurethane resins, vinyl chloride resins, polyamide resins, and epoxy resins obtained by introducing diphenyl structures into molecules is 7 mmol/g.
If the amount is larger, it becomes difficult to dissolve in commonly used tetrahydrofuran, aromatic hydrocarbon solvents, ketone solvents, etc., so it is preferable that the aromatic ring concentration of the diphenyl structure is 7 mmol/g or less.

Polyester resins, polyurethane resins, vinyl chloride resins, which have such a diphenyl structure introduced into their molecules,
Polyamide resins and epoxy resins are also compatible with conventionally known binder resins used in magnetic recording media, and when used in combination with these binder resins,
The excellent dispersibility and toughness of the magnetic powder of the binder resin used in combination are exhibited, and the electromagnetic conversion characteristics and durability are further improved.

Here, the binder resin used in combination is vinyl chloride-
Vinyl acetate-vinyl alcohol copolymer, vinyl chloride-
Vinyl chloride copolymers such as vinyl acetate-acrylic acid copolymer, vinyl chloride-vinyl acetate-acrylic acid glycidyl ester copolymer, vinyl chloride-sulfonic acid-containing acrylic ester-acrylic acid glycidyl ester copolymer, butyral Any of the conventionally known binder resins that are generally used in magnetic recording media, such as resins, cellulose resins, polyurethane resins, polyester resins, and isocyanate compounds, can be suitably used.

The magnetic recording medium of the second invention may be manufactured according to conventional methods, such as polyester resins, polyurethane resins, vinyl chloride resins, polyamide resins, etc. in which the above-mentioned diphenyl structure is introduced into the molecule. Epoxy resin is used as a binder component in combination with optional binder resin, etc., and this is mixed and dispersed with magnetic powder, organic solvent, and other additives to prepare a magnetic paint, and this is applied to polyester film. It can be applied to the surface of a substrate by any means such as spraying or roll coating, and dried.
If necessary, polyester resins, polyurethane resins, vinyl chloride resins, polyamide resins, and epoxy resins with the diphenyl structure introduced into the molecule may be used alone or in combination with other binder resins as binders. This is mixed and dispersed with an organic solvent and other additives to prepare an undercoat paint and a back coat layer paint, and these are applied to the surface or back of a substrate such as a polyester film by spraying or roll coating. It can be applied by the following method and dried.

Examples of the magnetic powder used in the magnetic layer include T
FezOa powder, Fe, O, powder, c.

Containing 7-Fe, 03 powder, Co-containing Feign powder, C
ry, powder, Fe powder, Co powder, Ni powder, Fe
-Co alloy powder, Fe-Ni alloy powder, Fe-Ni-C
o Alloy powder, metal powder such as iron nitride powder, and various conventionally known magnetic powders such as barium ferrite are widely included, and small amounts of non-magnetic compounds such as silicon, aluminum, and boron are contained inside or on the surface of these magnetic powders. Magnetic powders are also used.

In addition, the organic solvents used for -i, such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dioxane, and dimethyl formamide, are not particularly limited and may be used alone or in combination of two or more. used.

In addition, conventionally known additives such as the gap forming the magnetic layer, undercoat layer, and backcoat layer, lubricants, and dispersants that are generally added can be used without any restrictions.For example, carbon black and white Inorganic fillers such as carbon, organic fillers such as silicon microparticles and microparticle polystyrene gel, abrasives such as alumina and chromium oxide, fatty acid lubricants such as stearic acid and myristic acid, n-butyl stearate, oleyl oleate, and stearin. A higher fatty acid ester lubricant such as acid-butyl cellosolve, a lubricant such as silicone oil or fluoroyl, etc. may be added as appropriate.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 In a flask equipped with a dropping funnel, a cooling tube, a stirrer for high viscosity substances, and an oil bath, and with a good nitrogen loss, a well-dried (1
．． 6 molar parts of 1'biphenyl)-2,2'-diol were added thereto, and twice the weight of this diol was added with well-dried xylenol as a solvent.Then, the mixture was heated to 150°C under a nitrogen atmosphere. and add adipic acid dichloride to 6
Parts by molar weight were added, and heating under reflux was continued until a predetermined molecular weight was reached. Thereafter, this was poured into a large amount of acetone to precipitate the polymer, washed well, and filtered to obtain a polyester resin with a polystyrene equivalent number average molecular weight of 3.2 x 10' and an aromatic ring concentration of 6.25 mmol/g. I got it.

Using the polyester resin thus obtained, 660 parts by weight of α-Fe (surface alumina treatment) and 70 parts by weight of carbon black (average particle size 30 mu
m) MR-110 (Nippon Zeon Co., Ltd., 80 vinyl chloride resin) Polyester resin 80 Alumina
70 Palmitic acid
2 n-butyl stearate
4 Camethyl ethyl ketone 2000
The composition of Toluene 2000 was mixed and dispersed in a ball mill for 50 hours, then further dispersed in a sand grinder mill for 3 hours, and a trifunctional isocyanate compound (an adduct of tolylene diisocyanate of trimethylolpropane) was added thereto. A magnetic coating material was prepared by adding 40 parts by weight and dispersing and mixing with a sand grinder mill for an additional 30 minutes. This magnetic paint was applied to a polyester film with a thickness of 34 μm, and the thickness after drying was 3 ± 0.5 μm.
After applying it to a mirror finish, it was punched out into a 2-inch disk and attached to a jacket to make a video floppy disk.

Example 2 The polyester resin was synthesized in the same manner as in Example 1, except that the amount of adipic acid dichloride used was changed from 6 parts by mole to 5 parts by mole, until the polystyrene equivalent number average molecular weight was 1. A polyester resin of 8×10' and an aromatic ring concentration of 6.25 mmol/g was obtained.

The polyester resin thus obtained was prepared in Example 1.
A video floppy disk was produced in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Example 3 Into a flask equipped with a dropping funnel, a cooling tube, a stirrer for high viscosity materials, and an oil bath and well purged with nitrogen, 3 parts by mole of well-dried polybutylene adibate having a molecular weight of about 1000 was placed, and a solvent was added to the flask. Methyl ethyl ketone, which had been thoroughly dried, was added in an amount twice the weight of the polybutylene adipate, and the mixture was heated to 80''C under a nitrogen atmosphere to dissolve the polybutylene adipate.

Next, 6 parts by mole of 4,4' diphenylmethane diisocyanate was added thereto, and the mixture was reacted at 80°C. At this time, a small amount of a catalyst such as hetisoate tin triethylamine was added as necessary. After sufficient reaction, a solution obtained by dissolving 3 molar parts of the polyester resin obtained in Example 2 in a small amount of well-dried methyl ethyl ketone was added dropwise to cause sufficient reaction, and when the required molecular weight was reached. Add a small amount of butanol to terminate the reaction, and the polystyrene equivalent number average molecular weight is 4.2 x 10' and the aromatic ring concentration is 4.
．． A polyurethane resin of 60 mmol/g was obtained, which was further reprecipitated with methanol.

The polyurethane resin thus obtained was used in Example 1.
A video floppy disk was produced in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Example 4 In the synthesis of urethane resin in Example 3, (1,1
A polystyrene equivalent number average molecular weight of 4.2XIO' and an aromatic ring concentration of 3.5 were prepared in the same manner as in Example 3, except that 3 parts by mole of "biphenyl)-2,2'-diol were added.
Millimoles/g of polyurethane resin was obtained.

The polyurethane resin thus obtained was used in Example 1.
A video floppy disk was produced in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Example 5 Using the polyester resin obtained in Example 1, 120 parts by weight of carbon black (average particle size 30
m a m ) MR-110 (Nippon Zeon Co., Ltd., 24 Vinyl chloride resin) Polyester resin 40 Methyl ethyl ketone 400 Toluene
After partially dispersing the composition of No. 400 in a ball mill for about 100 hours, 12 parts by weight of a trifunctional isocyanate compound (adduct of tolylene diisocyanate of trimethylolpropane) was added thereto, and sanding was carried out for an additional 30 minutes. The mixture was dispersed and mixed using a grinder mill to prepare a paint for the undercoat layer. This paint for the undercoat layer was applied onto a polyester film with a thickness of 34 μm so that the thickness of the paint film after drying was 0.1 ± 0.
．． The coating was applied to a thickness of 0.05 μm and dried to form an undercoat layer.

Next, a video floppy disk was produced in the same manner as in Example 1, except that a magnetic paint prepared by omitting carbon black from the magnetic paint composition of Example 1 was applied onto this undercoat layer.

Example 6 A video floppy disk was produced in the same manner as in Example 5, except that a magnetic paint prepared by omitting carbon black from the magnetic paint composition of Example 2 was applied onto the undercoat layer.

Example 7 A video floppy disk was produced in the same manner as in Example 5, except that a magnetic paint prepared by omitting carbon black from the magnetic paint composition of Example 3 was applied onto the undercoat layer.

Example 8 A video floppy disk was produced in the same manner as in Example 5, except that a magnetic paint prepared by omitting carbon black from the magnetic paint composition of Example 4 was applied onto the undercoat layer.

Example 9 The undercoat wear paint prepared in Example 5 was used as it was as a backcoat layer paint, and the back side of a polyester film on which an undercoat layer and magnetic layer were formed in the same manner as in Example 5 was coated with a dry thickness of 0. It was coated to a thickness of 9 μm and dried to form a back coat layer. After that, Example 5
I made a video floppy disk in the same way.

Example 10 A video floppy disk was assembled in the same manner as in Example 9, except that a magnetic paint prepared by omitting carbon black from the magnetic paint composition of Example 2 was applied onto the undercoat layer. Ta.

Example 11 A video floppy disk was produced in the same manner as in Example 9, except that a magnetic paint prepared by omitting carbon black from the magnetic paint composition of Example 3 was applied onto the undercoat layer.

Example 12 A video floppy disk was produced in the same manner as in Example 9, except that a magnetic paint prepared by omitting carbon black from the magnetic paint composition of Example 4 was applied onto the undercoat layer.

Comparative Example 1 In the synthesis of polyester resin in Example 1, (
Instead of 1,1'biphenyl)-2,2'-diol,
The polystyrene equivalent number average molecular weight was 5.3X1 in the same manner as in Example 1 except that the same amount of butylene glycol was used.
0' polyester resin was obtained.

The polyester resin thus obtained was prepared in Example 1.
A Videoflow 7P disc was prepared in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Comparative Example 2 In the production of a polyester resin in Comparative Example 1, a polyester resin was produced in the same manner as in Comparative Example 1, except that the same amount of isophthalic acid dichloride was used instead of adipic acid dichloride, and the polystyrene equivalent number average molecular weight was 5.3 x 10', A polyester resin having an aromatic ring concentration of 3.6 mmol/g was obtained.

The polyester resin obtained in Example 1
When the same amount of polyester resin was used in place of the polyester resin used in Example 1 in the magnetic paint composition, the resulting polyester resin did not dissolve in the mixed melting process of methyl ethyl ketone and toluene, and it was not possible to form a magnetic paint. .

Comparative Example 3 In the production of polyester resin in Comparative Example 1, the number average molecular weight in terms of polystyrene was 1.2X10 in the same manner as in Comparative Example 1, except that the amount of butylene glycol used was changed from 6 parts by mole to 7 parts by mole. 'A polyester resin was obtained.

The polyester resin thus obtained was prepared in Example 1.
A video floppy disk was produced in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Comparative Example 4 In the production of polyester resin in Comparative Example 2, the number average molecular weight in terms of polystyrene was 1.5X103 in the same manner as Comparative Example 2, except that the amount of butylene glycol used was changed from 6 parts by mole to 7 parts by mole. Thus, a polyester resin having an aromatic ring concentration of 5 mmol/g was obtained.

The polyester resin thus obtained was prepared in Example 1.
A video floppy disk was produced in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Comparative Example 5 In the synthesis of polyester resin in Example 4, the amount of polybutylene adipate having a molecular weight of about 1000 was changed from 3 parts by mole to 4 parts by mole, and (1,1'biphenyl)-2,2 The procedure was repeated in the same manner as in Example 4, except that 2 parts by mole of butylene glycol was used instead of '-diol, and the polystyrene equivalent number average molecular weight was 4.5×1
0', a polyurethane resin with an aromatic ring concentration of 2.1 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 1.
A video floppy disk was produced in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Comparative Example 6 In the production of polyurethane resin in Comparative Example 5, the same procedure as in Comparative Example 5 was carried out except that the same amount of the polyester resin obtained in Comparative Example 4 was used instead of butylene glycol. .5X10',
A polyurethane resin having an aromatic ring concentration of 3.1 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 1.
A video floppy disk was prepared in the same manner as in Example 1, except that the same amount of polyester resin used in Example 1 was used in the composition of the magnetic paint.

Comparative Example 7 In the synthesis of polyester resin in Example 1, (
Instead of 1,1"biphenyl)-2,2'-diol,
The polystyrene equivalent number average molecular weight was 5.3X1 in the same manner as in Example 1 except that the same amount of butylene glycol was used.
0' polyester resin was obtained.

The polyurethane resin thus obtained was used in Example 5.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 5, and in the composition of the undercoat layer paint in Example 5, the same amount was used in place of the polyester resin used in Example 5. A video floppy disk was produced in the same manner as in Example 5, except that the following was used.

Comparative Example 8 In the production of polyester resin in Comparative Example 1, a polyester resin was produced in the same manner as in Comparative Example 1, except that the same amount of isophthalic acid dichloride was used instead of adipic acid dichloride, and the polystyrene equivalent number average molecular weight was 5.3 x 10', A polyester resin having an aromatic ring concentration of 3.6 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 5.
When the same amount of polyester resin was used in place of the polyester resin used in Example 5 in the composition of the undercoat layer paint, the obtained polyester resin did not dissolve in the mixed solvent of methyl ethyl ketone and toluene, and it could not be used as the undercoat layer paint. could not.

Comparative Example 9 In the production of polyester resin in Comparative Example 1, the number average molecular weight in terms of polystyrene was 1.2 A 10' polyester resin was obtained.

The polyurethane resin thus obtained was used in Example 5.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 5, and in the composition of the undercoat layer paint in Example 5, the same amount was used in place of the polyester resin used in Example 5. A video floppy disk was produced in the same manner as in Example 5, except that the following was used.

Comparative Example IO In the production of polyester resin in Comparative Example 2, polystyrene equivalent number average molecular weight was 1.5 x 1 oz in the same manner as Comparative Example 2, except that the amount of butylene glycol used was changed from 6 molar parts to 7 molar parts. Thus, a polyester resin having an aromatic ring concentration of 5 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 5.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 5, and in the composition of the undercoat layer paint in Example 5, the same amount was used in place of the polyester resin used in Example 5. A video floppy disk was produced in the same manner as in Example 5, except that the following was used.

Comparative Example 11 In the synthesis of polyester resin in Example 4, the amount of polybutylene adibate having a molecular weight of about 1000 was changed from 3 parts by mole to 4 parts by mole, and (1,1'biphenyl)-2,2 The same procedure as in Example 4 was carried out except that 2 parts by mole of butylene glycol was used in place of the diol.The polystyrene equivalent number average molecular weight was 4.5
', a polyurethane resin having an aromatic ring concentration of 2.1 mmol/g was obtained.

The polyurethane resin obtained in Example 5
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 5, and in the composition of the undercoat layer paint in Example 5, the same amount was used in place of the polyester resin used in Example 5. A video floppy disk was produced in the same manner as in Example 5, except that the following was used.

Comparative Example 12 In the production of polyurethane resin in Comparative Example 5, the same procedure as in Comparative Example 5 was carried out except that the same amount of the polyester resin obtained in Comparative Example 4 was used instead of butylene glycol. .5X10',
A polyurethane resin having an aromatic ring concentration of 3.1 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 5.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 5, and in the composition of the undercoat layer paint in Example 5, the same amount was used in place of the polyester resin used in Example 5. A video floppy disk was produced in the same manner as in Example 5, except that the following was used.

Comparative Example 13 In the synthesis of polyester resin in Example 1, (
A polystyrene equivalent number average molecular weight of 5.3X10 was prepared in the same manner as in Example 1, except that the same amount of butylene glycol was used instead of C1'biphenyl)-2,2'-diol.
'A polyester resin was obtained.

The polyurethane resin thus obtained was used in Example 9.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 9, and in the composition of the undercoat layer paint in Example 9, the same amount was used in place of the polyester resin used in Example 9. Furthermore, in the composition of the back coat layer paint of Example 9, a videofromby disk was made in the same manner as in Example 9, except that the same amount was used in place of the polyester resin used in Example 9. Ta.

Comparative Example 14 In the production of a polyester resin in Comparative Example 1, a polyester resin was produced in the same manner as in Comparative Example 1, except that the same amount of isophthalic acid dichloride was used instead of adipic acid dichloride, with a polystyrene equivalent number average molecular weight of 5.3 x 10', A polyester resin having an aromatic ring concentration of 3.6 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 9.
When the same amount of polyester resin used in Example 9 was used in the composition of the back coat layer paint,
The obtained polyester resin did not dissolve in a mixed solvent of methyl ethyl ketone and toluene, and could not be used as a paint for a back coat layer.

Comparative Example 15 In the production of polyester resin in Comparative Example 1, the number average molecular weight in terms of polystyrene was 1.2X10 in the same manner as in Comparative Example 1, except that the amount of butylene glycol used was changed from 6 parts by mole weight to 7 parts by mole weight. 'A polyester resin was obtained.

The polyurethane resin thus obtained was used in Example 9.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 9, and in the composition of the undercoat layer paint in Example 9, the same amount was used in place of the polyester resin used in Example 9. Furthermore, a video floppy disk was made in the same manner as in Example 9, except that the polyester resin used in Example 9 was used in the same amount in the composition of the Example 90 back coat paint.

Comparative Example 16 In the production of polyester resin in Comparative Example 2, the number average molecular weight in terms of polystyrene was 1.5X10 in the same manner as in Comparative Example 2, except that the amount of butylene glycol used was changed from 6 parts by mole to 7 parts by mole. ' A polyester resin having an aromatic ring concentration of 5 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 9.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 9, and in the composition of the undercoat layer paint in Example 9, the same amount was used in place of the polyester resin used in Example 9. Furthermore, a video floppy disk was made in the same manner as in Example 9, except that the polyester resin used in Example 9 was used in the same amount in the composition of the coating for the back coat layer.

Comparative Example 17 In the synthesis of polyester resin in Example 4, the amount of polybutylene adibate having a molecular weight of about 1000 was changed from 3 parts by mole to 4 parts by mole, and (1,1'biphenyl)-2,2 The process was repeated in the same manner as in Example 4, except that 2 parts by mole of butylene glycol was used in place of diol, and the polystyrene equivalent number average molecular weight was 4.5×10
', a polyurethane resin having an aromatic ring concentration of 2.1 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 9.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 9, and in the composition of the undercoat layer paint in Example 9, the same amount was used in place of the polyester resin used in Example 9. Furthermore, a video floppy disk was made in the same manner as in Example 9, except that in the composition of the back coat layer paint of Example 9, the same amount was used in place of the polyester resin used in Example 9. .

Comparative Example 18 In the production of polyurethane resin in Comparative Example 5, the polyester resin was produced in the same manner as in Comparative Example 5, except that the same amount of the polyester resin obtained in Comparative Example 4 was used instead of butylene glycol, and the polystyrene equivalent number average molecular weight was 4. .5X10',
A polyurethane resin having an aromatic ring concentration of 3.1 mmol/g was obtained.

The polyurethane resin thus obtained was used in Example 9.
In the composition of the magnetic paint, the same amount was used in place of the polyester resin used in Example 9, and in the composition of the undercoat layer paint in Example 9, the same amount was used in place of the polyester resin used in Example 9. Furthermore, a video floppy disk was made in the same manner as in Example 9, except that in the composition of the back coat layer paint of Example 9, the same amount was used in place of the polyester resin used in Example 9. .

A 7 MHz signal was recorded on the video floppy disk obtained in each Example and Comparative Example, and the durability was determined by the time it took for the playback signal output to decrease by 6 dB. The gender was evaluated. Note that the regeneration was carried out at 6°C in an air atmosphere.

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from Table 1 above, the video floppy disks (Examples 1 to 12) obtained by the present invention are as follows: Comparative Examples 1.3 to 6, 7.9 to 12, 13. Compared with the video floppy disks obtained in Examples 15 to 18, all of them had better durability, and this shows that the magnetic recording medium obtained by the present invention has sufficiently improved durability.

Claims (1)

[Claims] 1. A polyester resin, a polyurethane resin, a vinyl chloride resin, a polyamide resin, all of which have a diphenyl structure introduced into the molecule as a binder component, on the surface of the substrate;
A magnetic recording medium 2 characterized in that a magnetic layer containing a binder resin selected from epoxy resins is provided, and a diphenyl structure is further introduced into the molecule between the substrate and the magnetic layer as a binder component. The magnetic recording medium 3 according to claim 1, further comprising an undercoat layer containing a binder resin selected from polyester resin, polyurethane resin, vinyl chloride resin, polyamide resin, and epoxy resin, on the back surface of the substrate. Both polyester resins have a diphenyl structure introduced into their molecules as agent components,
3. The magnetic recording medium 4 according to claim 1, further comprising a back coat layer containing a binder resin selected from polyurethane resin, vinyl chloride resin, polyamide resin, and epoxy resin, between the substrate and the magnetic layer. , an undercoat layer containing a binder resin selected from polyester resins, polyurethane resins, vinyl chloride resins, polyamide resins, and epoxy resins, all of which have a diphenyl structure introduced into the molecule, is provided as a binder component. Characteristic magnetic recording medium 5: A polyester resin, a polyurethane resin, a vinyl chloride resin, a polyamide resin, all of which have a diphenyl structure introduced into the molecule as a binder component, on the back side of a substrate with a magnetic layer on the surface. , a magnetic recording medium characterized by being provided with a back coat layer containing a binder resin selected from epoxy resins.