JPH04182919A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic transducing characteristics and durability by specifying the mean value of the glass transition temps. of binders weighted by the amts. and the ratio of a binder adsorbed on ferromagnetic metal powder, an abrasive and carbon black to a binder not adsorbed on them. CONSTITUTION:The mean value of the glass transition temps. of binders weighted by the amts. is regulated to 30-45 deg.C, the ratio of a binder adsorbed on ferromagnetic metal powder, an abrasive and carbon black to a binder not adsorbed on them is regulated to 1+ or -0.2 and the binders are incorporated by 16-22 pts.wt. per 100 pts.wt. ferromagnetic metal powder. The surface of the ferromagnetic metal powder can be uniformly coated with the irreducible min. amt. of the binder effective in dispersing the powder, the intertwist of the polar groups of the binder (gelling) is not caused and particles are not cross-linked, accordingly the dispersion stability of the magnetic powder can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetic recording media, and particularly to magnetic recording media such as coated magnetic tapes and magnetic disks that use ferromagnetic metal powder as magnetic powder.

BACKGROUND OF THE INVENTION In recent years, the demand for high-density recording has increased, and magnetic tapes used for video, audio equipment, computers, etc.
In magnetic recording media such as magnetic disks, it has become essential to miniaturize the recording wavelength and track width, and to make the magnetic layer and support thinner.

For this reason, the coercive force (He) and residual magnetic flux density (B
Ferromagnetic metal powder that can increase both r) and is suitable for improving reproduction output in the short wavelength region has come to be used.

However, ferromagnetic metal powders have a larger saturation magnetization (σ5) than conventional oxide-based magnetic powders and tend to be finer particles, so they tend to form agglomerated structures in magnetic paints, and as a result, The orientation of the magnetic powder becomes insufficient,
A problem arose in that the surface properties 1 and mechanical strength of the magnetic layer deteriorated, making it difficult to obtain high levels of electromagnetic conversion characteristics and durability.

Furthermore, with the spread of portable magnetic recording and reproducing devices and camera-integrated devices, the environments in which magnetic recording media are used are expected to become wider and harsher than ever before. Improving this is an extremely important issue.

Therefore, in order to improve the dispersibility of ferromagnetic metal powder, surfactants have been used as dispersants,
As disclosed in the publication, -8
○3M, OS 03M.

A method of introducing a polar group such as -COOM, -PO(OM)2 (in the formula, M is a hydrogen atom or an alkali metal) has been proposed.

In addition, for the purpose of improving the durability of the magnetic layer,
It is possible to specify the mechanical strength (tensile strength, elongation at break) of the binder as disclosed in Japanese Patent Application No. 111325, or to determine the molecular weight (Mn) of the binder as disclosed in Japanese Patent Application Laid-Open No. 60-59522. In addition, methods have been proposed to specify the binder, and furthermore, to introduce a large number of hard segments such as aromatic rings as a skeleton component of the binder.

Problems to be Solved by the Invention However, using conventional methods,
Improving the dispersibility of ferromagnetic metal powder and improving the surface properties of the magnetic layer 1
It is extremely difficult to provide a magnetic recording medium with improved mechanical strength, excellent electromagnetic characteristics and durability, and various problems have arisen.

For example, the concentration of polar groups or the amount of surfactant to be introduced into the binder must be determined by fully considering the specific surface area, shape, and magnitude of shear magnetization (σS) of the ferromagnetic metal powder. Must not be. If the concentration of polar groups is increased unnecessarily, the binder will gel due to the strong interaction between the polar groups, and the amount of binder adsorbed on the surface of the magnetic powder will decrease, resulting in worsening of the dispersibility of the magnetic powder. Furthermore, if the concentration of polar groups is high relative to the amount of binder used, there is a possibility that interparticle crosslinks will be formed. These phenomena are also unfavorable from the viewpoint of workability during paint manufacturing and smoothing performance during coating.

Conversely, if the concentration of polar groups is low, the amount of binder adsorbed to the magnetic powder will be small, and the dispersibility of the magnetic powder will be poor.

Furthermore, in order to improve the filling rate of the magnetic powder in the magnetic layer, the magnetic powder tends to be finely divided and have a large specific surface area, so more binder than is necessary for dispersion is adsorbed onto the surface of the magnetic layer. , the amount of non-adsorbed binder that contributes to calenderability decreases, and as a result, it becomes difficult to improve the surface properties of the magnetic layer.Therefore, by simply increasing the amount of binder used, the calenderability can be improved. In this method, an excessive amount of binder exists on the surface of the magnetic layer, which increases the spacing loss between the tape and the head, resulting in a deterioration of the electromagnetic conversion characteristics.

Furthermore, in order to improve the durability of the magnetic layer, it is not possible to simply identify the individual characteristics of the binder, since it is difficult to predict the properties of the binder due to differences in the reaction rate with the crosslinking agent or differences in the adsorption ability to the surface of the magnetic powder. In particular, methods that introduce many hard segments such as aromatic rings as skeletal components of the binder often result in a high glass transition temperature (Tg) of the binder, resulting in poor calenderability. , not only is it impossible to obtain a smooth magnetic layer surface, but
It also has poor reactivity with the crosslinking agent, so calendar adhesion is likely to occur due to the influence of large amounts of unreacted isocyanate groups (-NCO groups) and hydroxyl groups (-○H groups) remaining in the magnetic layer. As a result, problems such as dropouts may occur.

In view of the above problems, the present invention aims to provide a magnetic recording medium with excellent electromagnetic conversion characteristics and durability.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention has an average glass transition temperature (Tg) of the binder used (
The averaged glass transition temperature (weighted by blending amount) is 30 to 45 ('C), and binders that adsorb to ferromagnetic metal powder, abrasives, and carbon black (adsorbent binders) and binders that do not adsorb ( The ratio of the binder to the non-adsorbing binder (non-adsorbing binder) is 1 ± 0.2, and the ratio of the binder to the ferromagnetic powder is 16 parts by weight based on 100 parts by weight of the ferromagnetic powder.
The essential requirement is to contain up to 22 parts by weight.

Function: The magnetic recording medium of the present invention has the above-described structure, so that the surface of the magnetic powder can be uniformly coated with the minimum necessary binder effective for dispersing the ferromagnetic metal powder. As a result, entanglement (gelation) between the binder's polar interludes does not occur,
No interparticle crosslinks are formed (therefore, it is possible to improve the dispersion stability of the magnetic powder. It is also possible to improve workability during paint production and smoothing performance during coating. Furthermore, it is possible to increase the amount of non-adsorbable binder that is not adsorbed and fixed on the surface of magnetic powder, abrasive, and carbon black, and the average value of the glass transition temperature (Tg) of the binder is also set to a moderately low value. The calendering property at low temperatures is improved, the surface properties of the magnetic layer are improved, and excellent electromagnetic conversion properties can be obtained.In addition, the reactivity with the crosslinking agent is also improved, making it possible to improve the surface properties of the magnetic layer. A magnetic recording medium with excellent durability can be obtained without causing calender adhesion that causes out-of-print.

EXAMPLE A magnetic recording medium according to an example of the present invention will be described below with reference to the drawings.

The ferromagnetic metal powder used in the present invention includes Fe,
Examples include acicular metal powders such as Fe-Co and Fe-Co-Ni. Furthermore, in consideration of weather resistance or prevention of sintering during manufacturing, it is also possible to use acicular metal powder containing trace amounts of additive metals such as Ae, Cr, and Si.

As the binder, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylic copolymer, polyurethane resin, Polyester resin, acrylonitrile-butadiene copolymer, epoxy resin, polyvinyl acecool resin,
Polyvinyl butyral resin or the like can be used.

The numbers of parts of the materials described in Examples and Comparative Examples are parts by weight based on 100 parts of the ferromagnetic metal powder.

(Example 1) Ferromagnetic metal powder 100 parts (average major axis diameter 0.17 μm, average axial ratio 1:10° specific surface area 50 d/g, saturation magnetization 125 parts mu/g) Vinyl chloride Resin (PVC) 9 parts [Nippon Zeon Co., Ltd., MR-110, glass transition temperature 59°C] Polyurethane resin (PU) 5 parts [Toyobo Co., Ltd., AM -63 Glass transition temperature 21°C] Polyurethane resin (PU ■) ...4 parts [manufactured by Nippon Polyurethane Industry ■, RM-3 glass transition temperature 5°C] Abrasive agent ...7 parts [Resident Manufactured by Kagaku Kogyo ■, ARP-50) Carbon black ・・・・・・28
[Manufactured by Tokai Carbon ■, G-ST S] Lubricant: 4 parts stearic acid 2 parts myristic acid 1 part n-butyl stearate・1 part crosslinking agent 4 parts C manufactured by Nippon Polyurethane Industries ■, Coronate L] mixed solvent
...300 parts (MEK/toluene/cyclohexanone = 3/2/1) Among the above compositions, ferromagnetic metal powder and carbon black were mixed in a nitrogen atmosphere (02 concentration 2% or less). , placed in a planetary mixer (PLM), first moistened with 10 parts of a mixed solvent, and then mixed with vinyl chloride resin (PLM).
VC), polyurethane resin (PU■), polyurethane resin (PU■), and 45 parts of a mixed solvent were added and kneaded for 10 hours. Next, 180 parts of an abrasive and a mixed solvent were added and dispersed using a sand mill to obtain a magnetic 6 material stock solution. Further, 50 parts of a lubricant, a crosslinking agent, and a mixed solvent were added, and the mixture was mixed and stirred using a day silver to prepare a magnetic material. After that, a filter with an average pore size of 0.4 μm (
10μ of paint filtered through Nippon Wave HT-40)
The film was coated on m-thick polyethylene terephthalate (PET), oriented, dried, and mirror-finished using a supercalender. After further curing treatment, a back coat layer containing carbon black as a main component was provided on the polyethylene terephthalate on the opposite side to the magnetic layer, and the tape was slit to a width of 8M to produce a metal tape for Swan VTR.

The average value of the glass transition temperature (Tg) of the binder used here is 36.4 (° C.).

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

+(59X9)±(21x5)+(5x4N/(18)
-36,4 Also in this case, ferromagnetic metal powder, abrasive,
The ratio of binder adsorbed to carbon black (adsorbed binder) and binder not adsorbed (non-adsorbed binder) was 0.87.

(Example 2) Instead of the binder in Example 1, polyvinyl chloride resin (PVC) ...10
Part [manufactured by Nippon Zeon (4), MR-110 glass transition temperature 59°C] Polyurethane resin (PU ■) 6 parts [manufactured by Nippon Polyurethane Industry ■, RM-3 glass transition temperature 5°C] Polyurethane resin (PU■)...4 parts [manufactured by Nippon Polyurethane Industries ■, R-104 glass transition temperature 11°C]
A metal tape for VTR was created.

The average value of the glass transition temperature (Tg) of the binder used here is 33.2 (° C.).

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

1 (59X 10) + (5X 6) + (11X 4
) l/(20) = 33.2 In this case, the ratio of the binder that adsorbs to the ferromagnetic metal powder, abrasive, and carbon black (adsorbing binder) to the old binder that is not adsorbed (non-adsorbing binder) is 1.07. Met.

(Example 3) Instead of the binder in Example 1, vinyl chloride-acrylic copolymer 10 parts [Sekisui Chemical Co., Ltd., S-LEC E, glass transition temperature 60°C] Polyurethane resin (PU ■) ...5 parts [manufactured by Toyobo ■, AM-97, glass transition temperature 32°C] Polyurethane resin (PU■) ...4
S w
A metal tape for VTR was created.

The average value of the glass transition temperature (Tg) of the binder used here is 35.2 (° C.). This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

1 (60X10) + (32X5) + (-23X4) l/
(19)-35,2 Also in this case, ferromagnetic metal powder,
The ratio of binder adsorbed to the abrasive and carbon black (adsorbed binder) to binder not adsorbed (non-adsorbed binder) was 0.98.

(Comparative Example 1) Instead of the binder in Example 1, vinyl chloride resin (PVC) was used...13
Part [manufactured by Nippon Zeon ■, MR-110 glass transition temperature 59℃] Polyurethane resin (PU■) 5 parts [manufactured by Nippon Polyurethane Industry ■, RM-3 glass transition temperature 5℃] Polyurethane resin (PU ■)...1 part [manufactured by Nippon Polyurethane Industry ■, R-104 glass transition temperature 11°C]
A metal tape for VTR was created.

The average value of the glass transition temperature (Tg) of the binder used here is 42.2 (° C.).

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

1 (59x13) + (5x5) + (11x 1)l/(
19) = 42.2 In this case, the ratio of the binder adsorbed to the ferromagnetic metal powder, abrasive, and carbon black (adsorbed binder) to the binder not adsorbed (non-adsorbed binder) was 1.35.

(Comparative Example 2) Instead of the binder in Example 1, vinyl chloride resin (PVC)...8
Part [manufactured by Nippon Zeon ■, MR-110, glass transition temperature 59°C] Polyurethane resin (PU■) ...8 parts [manufactured by Toyobo Co., Ltd., AM-63, glass transition temperature 21°C] Polyurethane resin ( 8 w in the same manner as in Example 1 except that 5 parts of PU■) (manufactured by Nippon Polyurethane Industries ■, R-104 glass transition temperature 11°C) were used.
A metal tape for VTR was created.

The average value of the glass transition temperature (Tg) of the binder used here is 33.1 ('C).

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

+(59X8)+(21X8)+(11X5))/(2
1)-33,1 In this case, the ratio of the binder adsorbed to the ferromagnetic metal powder, abrasive, and carbon black (adsorbed binder) to the binder not adsorbed (non-adsorbed binder) was 0.74.

(Comparative Example 3) Instead of the binder in Example 1, polyvinyl chloride resin (PVC)...10
Part [manufactured by Nippon Zeon ■, MR-110, glass transition temperature 59°C] Polyurethane resin (PU■) ...... 5 parts [manufactured by Toyobo Co., Ltd., UR-8200, glass transition temperature 79°C] Polyurethane resin (PU■ )......4 parts [manufactured by Nippon Polyurethane Industry ■, RM-3 glass transition temperature 5°C] In the same manner as in Example 1, except that 8 m
A metal tape for VTR was created.

The average value of the glass transition temperature (Tg) of the binder used here is 52.9<°C>.

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

+(59X to)+(79X5)+(5X4)l/(
19) = 52.9 In this case, the ratio of the binder adsorbed to the ferromagnetic metal powder, abrasive, and carbon black (adsorbed binder) to the binder not adsorbed (non-adsorbed binder) was 1.18.

(Comparative Example 4) Instead of the binder in Example 1, vinyl chloride-acrylic copolymer 11 parts [S-LEC E glass transition temperature 60°C, manufactured by Tansui Kagaku Kogyo Co., Ltd.] Polyurethane Resin (PU ■) ... 5 parts [manufactured by Dainippon Ink and Chemicals, T-5206 glass transition temperature -25°C] Polyurethane resin (PU ■) ... 4 parts [Japan Polyurethane Industries, Ltd. S r
A metal tape for RA VTR was created.

The average glass transition temperature (Tg) of the binder used here was 27.8 (°C).

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

+(60X 11)+(-25X5)+(5X4))/
(20)=27.8 Also in this case, ferromagnetic metal powder,
The ratio of the binder adsorbed to the abrasive and carbon black (adsorbed binder) to the binder not adsorbed (non-adsorbed binder) was 0.77.

(Comparative Example 5) Instead of the binder in Example 1, vinyl chloride-acrylic copolymer 1.0
Part [manufactured by Tanezu Chemical Industry ■, S-LEC E, glass transition temperature 60°C] Polyurethane resin (PU■) ...8 parts [manufactured by Toyobo (4), AM-97, glass transition temperature 32°C] Polyurethane resin (PU■) ...... 5 parts [manufactured by Dainippon Ink & Chemicals, Ibara, T-5206 glass transition temperature -258C] 8 m
A metal tape for VTR was created.

The average value of the glass transition temperature (Tg) of the binder used here is 31.8 ('C).

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

1 (60x 10) + (32X8) + (-25X5)l
/(23)-31,8 In this case, the ratio of the binder adsorbed to the ferromagnetic metal powder and the abrasive 9 carbon black (adsorbed binder) to the binder not adsorbed (non-adsorbed binder) was 0.84. Ta.

(Comparative Example 6) Instead of the binder in Example 1, vinyl chloride resin (PVC)...9
Part [manufactured by Nippon Zeon (8), M] '1llO glass transition temperature 59°C] Polyurethane resin (PTIJ ■) ...
3 parts [manufactured by Toyobo ■, AM97, glass transition temperature 32°C] Polyurethane resin (PU■)...3 parts [manufactured by Toyobo ■, AM-63, glass transition temperature 21°C] By the same method as in Example 1, 8 W
A metal tape for llVTR was created.

The average glass transition temperature (Tg) of the binder used here was 46.0 (°C).

This value is the glass transition temperature weighted by the blending amount (parts by weight) and averaged as shown in the calculation formula below.

((59x9)+(32x3)+(21x3))/(1
5) = 46.0 In this case, the ratio of the binder adsorbed to the ferromagnetic metal powder, abrasive, and carbon black (adsorbed binder) to the binder not adsorbed (non-adsorbed binder) was 0.96.

A method for calculating the ratio of the binder that is adsorbed to the above-mentioned ferromagnetic metal powder, abrasive, and carbon black (adsorption binder) and the binder that is not adsorbed (non-adsorption binder) is shown below.

Into a 50me plastic container, put the magnetic paint Log prepared in each example and comparative example and the mixed solvent (MEK/toluene/cyclohexanone-3/2/1).
The solid content concentration of the paint is set to 10%. ), 5hake
Shake for 15 minutes using r. Thereafter, this diluted paint was centrifuged (at 4 x 10'rpm for 30 minutes).Furthermore, the supernatant after centrifugation was collected into a centrifuge tube, and high-speed centrifuged (at 2 x 10'rpm).
It will be held for 2 hours. ). 10ml of supernatant after high-speed centrifugation! Collect it in an aluminum cup and measure its weight. Next, this supernatant liquid is evaporated to dryness on a hot plate, and the weight is measured again. From the above operations, the amount of non-adsorbed binder placed in the supernatant liquid can be calculated,
The amount of binder adsorbed on the ferromagnetic metal powder, abrasive, and carbon black is calculated by subtracting the amount of binder in this supernatant liquid (amount of unadsorbed binder) from the total amount of binder (amount of blended binder). ). Based on the above results, the ratio of adsorbed binder to non-adsorbed binder can be determined.

Each 81IIIV obtained in the above Examples and Comparative Examples
The following measurements were performed on the TR metal tape.

(1) Surface roughness WYKO's non-contact three-dimensional surface roughness meter (TOPO)
-3D) was used for measurement. At this time, as a method of displaying the surface roughness of the magnetic layer, the square of the deviation from the center line to the roughness curve was integrated over the measurement length section, and RMS, which is the square root of the average value over that section, was used.

(2) C/N (5.0MHz/4.5MHz)5.
The ratio of the signal at 0 MHz to the noise at 4.5 MHz was measured. MVS-5000 [manufactured by KODAK Corporation] was used as an 8wn VTR for C/N measurement.

Further, the recording/reproducing head used an amorphous alloy, and the C/N of the 8 vm VTR metal tape of Example 2 was used as a reference (OdB), and the values are shown as relative values.

(3) Using an 8 mm VTR similar to that used for dropout C/N measurement, each videotape sample was exposed to 20°C in an environment of 40°C and 80% RH.
0 pass run (endurance test), 16 dB for 15 μS for each videotape sample before and after the durability test.
The number of pieces per minute at which the above decrease in output occurred was measured.

(4) Head Powder Adhesion After the durability test according to (3) above, the amount of powder adhesion on a part of the magnetic head and cylinder was observed using a microscope, and the degree of the powder adhesion layer was evaluated on a five-point scale. The evaluation was rated 5 if no powdered layer was observed and there was no practical problem at all, and 1 if there was a large amount of powder adhesion and posed a practical problem.

(5) Still life Using a modified 8wn VTR for still measurement,
A pre-recorded still image was played back under the conditions of = 10°C and 30g load, and the time required for the image signal to drop by 6dB is shown. Table 1 shows the evaluation results of the 8 mm V-TR metal tapes prepared in each Example and Comparative Example. In addition, FIG. 1 shows that among the binders in the magnetic paints prepared in each example and comparative example, ferromagnetic metal powder,
The ratio of the binder that adsorbs to the abrasive and carbon black (adsorbed binder) and the binder that does not adsorb (non-adsorbed binder), and the 8 m V created using each of the above paints.
The relationship between the RMS and the magnetic layer surface roughness of the TR metal tape is shown. In the figure, black circles indicate Examples 1 to 3.
White circles represent Comparative Examples 1 to 6.

(Left below) As is clear from Table 1, Examples 1 and 2.3 are based on the average value of the glass transition temperature of the binder, the ratio of the amount of adsorbed binder to the amount of non-adsorbed binder, and the appropriate number of parts by weight of binder added. Therefore, the surface of the magnetic layer becomes smooth and C
/N became a high value. Regarding durability, the amount of powder adhering to a part of the head cylinder after the durability test was small, resulting in a long still life. Furthermore, dropouts were reduced both initially and after the durability test.

Furthermore, from FIG. 1, it can be seen that the surface roughness RMS of the magnetic layer is greatly influenced by the ratio of the amount of adsorbed binder to the amount of non-adsorbed binder.

In Comparative Example 1, the ratio of the amount of adsorbed binder to the amount of non-adsorbed binder is large, that is, the amount of non-adsorbed binder that contributes to calenderability is small, so the surface roughness of the magnetic layer is very poor and the C/N is quite low. It became the value. In Comparative Examples 2 and 4, on the contrary, the ratio between the amount of adsorbed binder and the amount of non-adsorbed binder was small, so the calenderability was improved and the surface roughness of the magnetic layer was also good, but the dispersibility of the magnetic powder was poor. (
Because the amount of binder adsorbed to the magnetic powder surface is small),
C/N became low. In particular, in the case of Comparative Example 4, since the average value of the glass transition temperature (Tg) of the binder was low,
Durability such as powder adhesion amount and still life also deteriorated significantly (dropouts after the durability test also increased abnormally). In Comparative Example 3, the average value of the glass transition temperature (Tg) of the binder was high. As a result, the calenderability deteriorated, the surface roughness of the magnetic layer worsened, and the C/N ratio decreased.In Comparative Example 5, since the amount of binder added was large, excessive binder was present on the surface of the magnetic layer. As a result, the spacing loss between the tape and the head increased and the C/N decreased.In Comparative Example 6, on the other hand, since the amount of binder added was small, the dispersibility of the magnetic powder deteriorated, and at the same time, the calender The amount of binder that contributes to the properties of the magnetic powder also decreases, resulting in a lower C/N ratio.Furthermore, regarding durability, the surface of the magnetic powder cannot be sufficiently coated with the binder, resulting in a decrease in the mechanical strength of the magnetic coating and the possibility of dust adhesion. (The still life has also become shorter.

In the above embodiment, only the metal tape for SWA VTR was explained, but it can be similarly applied to other magnetic recording media such as coated magnetic tapes and magnetic disks using ferromagnetic metal powder. .

Effects of the Invention As is clear from the description of the embodiments above, according to the magnetic recording medium of the present invention, the average value of the glass transition temperature (Tg) of the binder (the average glass transition temperature weighted by the blending amount) ) is 30 to 45 ('C), and the ratio of the binder that is adsorbed to the ferromagnetic metal powder, abrasive, and carbon black (adsorption binder) to the binder that is not adsorbed (non-adsorption binder) is 1 ± 0.2. This configuration makes it possible to provide a magnetic recording medium with excellent electromagnetic conversion characteristics and durability.

[Brief explanation of drawings]

Figure 1 shows the binders that adsorb to ferromagnetic metal powder, abrasive, and carbon black (adsorbing binder) and adsorbing binders of the binders in the magnetic paints used to prepare the magnetic recording media of Examples and Comparative Examples of the present invention. The ratio of binder (non-adsorbing binder) that is not absorbed (non-adsorbing binder) and the ratio of 8
(2) It is a graph showing the relationship between the RMS value and the surface roughness of the magnetic layer of a metal tape for a VTR.

Claims (2)

[Claims] (1) A magnetic recording medium in which a magnetic layer is formed by coating a magnetic paint containing ferromagnetic metal powder, an abrasive, carbon black, and a binder on a nonmagnetic support, the glass transition temperature (Tg ) is 30 to 45°C, and the ratio of the binder adsorbed to the ferromagnetic metal powder, abrasive, and carbon black to the binder not adsorbed is 1±0.2. magnetic recording medium. (2) The magnetic recording medium according to claim 1, wherein the binder is contained in 16 to 22 parts by weight based on 100 parts by weight of the ferromagnetic powder.