JPH03173924A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the audio output, chroma output and chroma S/N of the medium by incorporating ferromagnetic powders of respectively prescribed major axis lengths into an upper magnetic layer and a lower magnetic layer. CONSTITUTION:The lower magnetic layer (A) and the upper magnetic layer (B) are laminated on this medium in a state having substantially no mixed areas. The ferromagnetic powder (b) of <=0.30mum average major axis length (l2) is incorporated into the layer B and the ferromagnetic powder (a) of the average major axis length (l1) satisfying equation is incorporated into the layer A. Fine powders of Co-deposited gamma-Fe2O3 having the respectively prescribed major axis lengths are usable for these powders (a), (b) and the combination use of polyurethane having a negative function group (e.g. -SO3M, where M denotes H or alkaline metal) for the binders of the layers A, B is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with excellent audio output, chroma output, and chroma-3/H.

[Issue 8 to be solved by the prior art and the invention] In recent years, magnetic recording media with a multilayer (two-layer) structure on a non-magnetic support have become popular as magnetic recording media that can record high-quality images and high-quality audio. Magnetic recording media having layers have been proposed.

In this magnetic recording medium, the lower magnetic layer contains magnetic powder with relatively large particle size, and the upper magnetic layer contains magnetic powder with relatively small particle size, so that the upper layer mainly produces brightness. The signal is recorded, and the lower layer mainly records color signals and audio signals. By specifically recording signals with different characteristics in each layer in this way, it is hoped that signals with different characteristics can be recorded faithfully.

However, the conventional multilayer magnetic recording medium has a problem in that the audio output, chroma output, and chroma-3/N are not improved as much as expected.

The present invention aims to solve the above problems.

That is, an object of the present invention is to provide a magnetic recording medium which is particularly excellent in reproducing color signals, and is also excellent in reproducing video signals and audio signals.

[Means for Solving the Problems] The present invention for solving the problems described above provides a method for solving the problems described above.
In E, an upper layer and a lower layer are laminated with substantially no mixing region, the average major axis length of the ferromagnetic powder in the upper layer is 0.30 gm or less, and the ferromagnetic powder in the lower layer The average major axis length of the ferromagnetic powder (see 2) and the average major axis length of the ferromagnetic powder in the upper layer (see 2), the following relational expression [I] 0.3 < sentence 2 / sentence, ≦1 [11] This is a magnetic recording medium characterized by:

The present invention will be explained in detail below.

One Magnetic Layer (1) Scrap Structure The magnetic layer in the magnetic recording medium of the present invention is formed on a non-magnetic support, and is composed of a two-part magnetic layer and a lower magnetic layer, which are laminated without a mixed region.

Here, "substantially no mixing zone" means that even if a mixing zone is observed, the thickness of the mixing zone is less than 0.1 gm. Conventional multilayer magnetic h! In a magnetic recording medium that has the following characteristics, a mixed region exists between the magnetic layers, but one of the features of the present invention is that two magnetic layers are laminated so that the mixed region does not substantially exist. It is noteworthy that the electromagnetic conversion characteristics can be improved by using these features and the 11F constant ferromagnetic powder described below.

(1;i) l Two-part magnetic R The L-part magnetic layer is formed by dispersing ferromagnetic powder with a fixed particle size of 6 in a binder.

In addition, this upper magnetic layer usually has a coercive force (HO2) of
is 400 to 2.0000 e, preferably 600
~1.9000e. The coercive force of this upper magnetic layer is 4
If the coercive force is less than 2,000e, there may be an inconvenience that Lumi-3/N and chroma S/N are deteriorated, and if the coercive force exceeds 2,0000e, there may be an inconvenience that the chroma output is decreased.

The thickness of the upper magnetic layer is usually 0.1 to 1.7 mm, preferably 0.3 to 0.6 pm. If the thickness of the upper magnetic layer exceeds the above range, color output and audio output may be adversely affected.

(1) Ferromagnetic Powder One of the important things in the present invention is that the average major axis length (cross 2) of the ferromagnetic powder is 0. :lOuLm or less, especially 0
．． It is 12 to 0.20 gm. This average major axis length (text,)
is 0.30 lum or more, Lumi-3/N and Chroma-
3/H becomes so large that the object of the present invention cannot be achieved.

As the ferromagnetic powder, for example, Co-coated-Fe2
0.3 powder, CO coated Fe, 0. Powder, CO coated Fed
.

(4/3 < x <:l/2) powder or Fe
-A1 metal powder, Fe-Ni metal powder, Fe-An-N
i metal powder, FeA5L-P metal powder, FFe-Ni-
3i-A metal powder, FeFe-Ni-3i-Ai-metal powder, Xl-Goo powder, Fe-Mn-Zn metal powder, Fe-Ni-Zn metal powder, Fe-Go-Ni-Cr
Metal powder, Fe-Co-Ni-P metal powder, Co-
Examples include ferromagnetic metal powders such as Ni metal powder and Co-P metal powder.

Among these, preferred is Co-coated-Fe20z
It is a powder.

The shape of the ferromagnetic powder is preferably acicular, but as long as the average major axis length of the ferromagnetic powder has the above value, 1
The shape may be spherical or ellipsoidal.

The specific surface a (according to the BET method) of the ferromagnetic powder is usually 25 m2/g or more, preferably 30 to 80 m2/g.
It is.

The content of the ferromagnetic powder in the h-section magnetic layer is appropriately determined within a range that satisfies the coercive force of the upper magnetic layer specified above, and is usually 65 to 85%, In particular, 70 to 80% of importance is given.

0-2 Binder and Other Components As the binder, a resin having a molecular weight i,) within the range of about 10,000 to 200,000 can be used.

Physically, for example, urethane polymer, vinyl chloride
Vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (e.g. cellulose acetate tstylate, cellulose diacetate,
cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, various synthetic rubber binders, phenolic resins, epoxy resins, urea resins, melamine resins, silicone resins, acrylic reactive resins, high molecular weight Examples include mixtures of polyester resins and incyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols and high molecular weight diol compounds, and mixtures thereof.

In the present invention, polyurethane having a negative functional group can be preferably used together with these resins.

The polyurethane having this negative functional group is -3O
ff M', -0302M'-0504M+ OM'' (where Ml is a hydrogen atom or an alkali metal, and M2 and Ml are a hydrogen atom, an alkali metal, or an alkyl group, respectively. M2 and M3 are long even if they are different from each other, or long even if they are the same.

The amount of negative functional groups in the polyurethane having negative functional groups in the present invention is 0.01 to 1. oOm g/g is desirable.

When the amount of negative functional groups is within the above range, the dispersibility of the ferromagnetic powder is improved, and as a result, the output of the magnetic recording medium is increased and the running stability is also improved.

On the other hand, if the content is outside the above range, these effects may not be sufficiently achieved.

The molecular weight of the polyurethane having the negative functional group is usually 2,000 to 70,000, preferably 4,000 to 5.
It is 0.00 units. If this molecular weight exceeds 70,000, the viscosity of the magnetic paint will exceed the allowable range.
The purpose of this invention is that distant relatives may become unavailable.

On the other hand, if the molecular weight is less than 1 or 2,000, unreacted portions will occur during the step of applying the magnetic paint onto a non-magnetic support and then curing it with a hardening agent, resulting in low molecular weight components remaining. This may deteriorate the physical properties of the paint film.

When using the polyurethane having the negative functional group, the amount thereof is usually 2 to 15 parts by weight, preferably 3 to 10 parts by weight, per 100 parts by weight of the ferromagnetic powder.

If this blending ratio is less than 2 parts by weight, calenderability will decrease and electrical properties will deteriorate. If the number is more than 15, it may cause deterioration of sliding noise and head cloudiness.

In the present invention, the durability of the magnetic layer can be improved by using a polyisocyanate curing agent together with the polyurethane having a negative functional group.

Examples of the polyisocyanate curing agent include bifunctional isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and hexane diisocyanate, Coronate L (trade name: manufactured by Nippon Polyurethane Industries), Desmodur L ( Products that have been conventionally used as curing agents, such as trifunctional incyanates such as those manufactured by Bayer AG, or urethane prepolymers containing incyanate groups at both ends, can also be used as curing agents. Any polyisocyanate can be used.

The amount of curing agent used is usually 5 to 80 parts per total binder amount.

In the present invention, in addition to the above-mentioned various binders, optional dispersants such as lecithin, phosphate ester fatty acids, amine compounds, alkyl sulfates, fatty acid amides, higher alcohols, polyethylene oxide, sulfosuccinic acid, and sulfosuccinate esters are used. , known surfactants and their salts, negative organic groups (e.g. -COOII
, -PO:111) A salt of a polymer dispersant or the like may be used.

These may be used singly or in combination of two or more.

Among the dispersants mentioned above, lecithin can be preferably used in the present invention.

Further, in the present invention, a fatty acid ester can be used as an optional plasticizer. Examples of the fatty acid ester include oleyl oleate, oleyl stearate, incetyl stearate, dioleyl maleate, butyl stearate, butyl palmitate, butyl myristate, octyl myristate, octyl palmitate, amyl stearate, and amyl palmitate. , stearyl stearate, lauryl oleate, octyl oleate, isobutyl oleate, ethyl oleate, isotridecyl oleate, 2-ethylhexyl stearate, 2-ethylhexyl myristate.

Examples include ethyl stearate, 2-ethylhexyl palmitate, isopropyl palmitate, isopropyl myristate, butyl laurate, cetyl-2-ethyl hexalate, dioleyl adipate, diethyl adipate, diisobutyl adipate, diisodecyl adipate, and the like. Among these, butyl stearate and butyl palmitate are particularly preferred.

The aforementioned various fatty acid esters may be used alone or in combination of two or more.

By reducing the amount of lubricants such as fatty acids and plasticizers such as fatty acid esters added in this manner, it is possible to improve the running durability of the magnetic recording medium, especially under high temperature and high humidity conditions.

The magnetic layer in the magnetic recording medium of the present MIJI may contain a lubricant.

Examples of lubricants include fatty acid silicone lubricants,
Examples include fatty acid-modified silicone lubricants, fluorine-based lubricants, liquid paraffin, squalane, carbon black, graphite, carbon black graft polymers, molybdenum disulfide, and tungsten disulfide.

Examples of the fatty acids include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, balmitic acid, stearic acid, isostearic acid, linoleic acid, linoleic acid, oleic acid, elaidic acid, behenic acid, malonic acid, and succinic acid. Acid, maleic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1.12-
Examples include dodecanedicarboxylic acid and octanedicarboxylic acid.

Among these, particularly preferred are myristic acid, oleic acid, and stearic acid.

These may be used alone or in combination of two or more.

The blending ratio of the lubricant is usually 20 parts by weight or less, preferably 101 parts by weight or less, based on 100 parts by weight of the ferromagnetic powder. If this blending ratio exceeds 20 parts by weight,
The amount of lubricant may be excessive and dirt may easily adhere to the surface of the magnetic layer.

The magnetic layer may further contain an abrasive and an antistatic agent in addition to the various components described above.

Note that the antistatic agent or the dispersant described below does not have a sole function; for example, a - compound may act as a lubricant and an antistatic agent.

Therefore, the above-mentioned classification in this invention indicates the main effects, and the effects of the classified compounds are not limited by the effects shown in the classification. Like the layer, it is formed by dispersing ferromagnetic powder of a specific particle size in a binder.

It is desirable that the coercive force (HCt) of this F section magnetic layer has the following relationship with the coercive force (Hc2) of the upper magnetic layer.

1.0≦<H(!2)/(MCI)≦5When the ratio of coercive force (HC2)/(Hc+) is less than 1.0,
This may cause a problem of a decrease in chroma output, and if it exceeds 5, a problem of deterioration of erasing characteristics may occur.

In this way, the coercive force of the lower magnetic layer can be made to satisfy the above relational expression by adjusting the coercive force of the ferromagnetic powder as described later.

Note that the thickness of the lower magnetic layer is usually 1.0 to 4.07 Lm.
and preferably 2.0 to 3.5 lm.

If the thickness of the lower magnetic layer exceeds the above range, contact between the tape and the magnetic head may deteriorate.

■-1 Ferromagnetic Powder One of the important things in the present invention is that the average major axis length C1,) of the ferromagnetic powder contained in the lower magnetic layer is the average length of the ferromagnetic powder contained in the upper magnetic layer. The axial length Cl2) satisfies the following relational expression %, preferably 0.5≦2/tachi, ≦1.

In the above formula, if the sentence, /, deviates from the above range, the object of the present invention cannot be achieved, especially the ratio 1- /.
The closer I is to 1, the better the chroma-3/N is. Considering the conventional technology of reducing the size, this is noteworthy.

The ferromagnetic powder that satisfies the above relationship can be appropriately selected from among the various ferromagnetic powders exemplified for the ferromagnetic powder in the upper magnetic layer.

The specific surface 1a (according to the BET method) of the ferromagnetic powder is usually 25 m"/g or more, preferably 30 to 80 m
It is 27g.

The content of the ferromagnetic powder in the lower magnetic layer is appropriately determined within a range that satisfies the coercive force of the lower magnetic layer specified above, and is usually 65 to 90% by weight, particularly 70% by weight. ~85% by weight.

■-2 Binder and other components The binder and other optional components used to form the lower magnetic layer are almost the same as those explained for the upper magnetic layer, so a detailed explanation thereof will be omitted. do.

Non-magnetic support Materials for forming the non-magnetic support on which the plurality of magnetic layers are laminated include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polypropylene; cellulose triacetate and Mention may be made of cellulose derivatives such as cellulose diacetate; as well as plastics such as polycarbonate. Furthermore, Cu, An.

Metals such as Zn, glass, so-called new ceramics (
For example, various ceramics such as boron nitride, silicon carbide, etc. can also be used.

There is no particular restriction on the form of the non-magnetic support, and it may be tape-like, sheet-like, cart-like, disc-like, drum-like, etc., and various materials may be used depending on the form and as necessary. It can be selected and used.

When the support is in the form of a tape or sheet, the thickness of the support is as follows:
Usually, it is 3 to 1100 p, preferably 5 to 50 g, m. In addition, in the case of disk-shaped or card-shaped, usually 3
It is 0 to 1100IL. Furthermore, in the case of a drum shape, it can be made into a cylindrical shape, etc., depending on the recorder used.

On the non-magnetic support where the magnetic layer is not provided (the back side), the running direction of the magnetic recording medium and the charging vJ
A back coat layer may be provided for the purpose of protection against insects and transfer insects.

Further, when the magnetic layer is provided on the non-magnetic support, an intermediate layer (for example, adhesive shavings) may be added for the purpose of improving the adhesiveness between the magnetic layer and the non-magnetic support. I'll come.

-Method for manufacturing a magnetic recording medium The magnetic recording medium of the present invention is characterized in that -the ferromagnetic powder, a binder such as polyurethane that holds the negative functional group, and other magnetic layer forming components are cross-dispersed in a solvent. After preparing a magnetic coating material, the magnetic coating material can be coated on the non-magnetic support and dried.

The solvent used for kneading and dispersing the magnetic layer forming components is as follows:
For example, acetone, methyl ethyl ketone (MEK),
Ketones such as methyl isobutyl ketone (MIBK) and cyclohexanone 1; alcohols such as methanol, ethanol, propatool and butanol; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, propyl acetate and ethylene glycol monoacetate; Ethers such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbons such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetracarbon, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. halogenated hydrocarbons and the like can be used.

When kneading the composition of the magnetic paint components, the ferromagnetic powder and other magnetic paint components (hereinafter sometimes referred to as raw materials) are sequentially introduced into a mixing machine either individually or individually. For example, first, the ferromagnetic powder is added to a solution containing a dispersant, and after kneading for a predetermined distance, the remaining components are added and kneading is continued to obtain a magnetic paint.

For kneading properties, various kneaders can be used. Examples of this mixer include a two-roll mill, a three-roll mill, a pressurized kneader, a single continuous kneader, an open kneader, a ball mill, a pebble mill, a side grinder Sqcgvari attritor, and a high-speed impeller disperser.

Examples include a high-speed stone mill, a high-speed impact mill, a disper kneader-1 high-speed mixer, a homogenizer, and a sonic disperser.

In the present invention, the magnetic layer is formed by applying the lower magnetic layer type J & acid component coating solution prepared as described above and the upper magnetic layer forming component coating solution by a wet-on-weL method. A magnetic recording medium may be manufactured by forming a PIi cloth solution of the lower magnetic layer forming component on the surface of a non-magnetic support, drying, and then applying the PIi cloth solution of the upper magnetic layer forming component. A magnetic recording medium may be manufactured by applying a liquid onto the lower magnetic layer 11 using a 437 wet-on-dry method to form a magnetic layer.

The four coating methods that can be used to apply the coating liquid for the lower magnetic layer forming components and the coating liquid for the upper magnetic layer forming components include, for example, gravure roll coating, Meyer bar coating, doctor blade coating, reverse roll coating, and date coating. coatings, air knife coatings, calendar coach inks, squeeze coatings, kiss coatings, extrusion coach inks, and fantine coatings.

The thickness of the magnetic layer coated in this way is 0.1 to 5 gm, particularly 0.1 to 2 gm, depending on the dry J1 of the upper magnetic layer.
gm, and the dry thickness of the lower magnetic layer is usually 1 to 6 m.
It is.

After applying the magnetic layer type I and the acid component in this way, a magnetic field orientation treatment is performed as necessary in an undried state, and a surface smoothing treatment is usually performed using a super calender roll or the like.

Next, a magnetic recording medium can be obtained by cutting into a desired shape.

The magnetic recording medium of the present invention can be used, for example, by cutting it into a long shape as a magnetic tape such as a video tape or audio tape, or by cutting it into a disk shape to be used as a floppy disk or the like. Furthermore, it can also be used in a cart-like, cylindrical, or other form like a normal magnetic recording medium.

[Example] Next, Examples and Comparative Examples of the present invention will be shown to further specifically explain the present invention.

(Example 1) A magnetic coating material was prepared by thoroughly cross-dispersing a composition for a lower magnetic layer and a composition for an upper magnetic layer having the compositions shown below using a kneader/sand mill.

-, 1' Co coating - Fe, O, ferromagnetic fine powder... 100 parts (
Average major axis length 0.4 l) Polyurethane containing sodium sulfonate 5 parts [Toyobo ■
UR-8700] Potassium sulfonate-containing vinyl chloride resin... 10 parts [Made by Nippon Zeon ■, 'MRIIO,] Stearic acid...... 1 part Myristic acid...・・・・1 part butyl stearate・
・・・・・・・・・ Part 1 Coronate L・・・・・・・・・
・・・ 5 parts cyclohexanone・・・・・・・・・ 15
0 parts Methyl ethyl ketone...508'I
I toluene 50 parts - Co deposited - Fe, 0. Ferromagnetic fine powder... 100 parts (
Uniform long sleeve length 0.16 mm) Sodium sulfonate-containing polyurethane 5 parts [Toyo Yosei ■ 118-87001 Potassium sulfonate-containing PVC resin 10 parts Carbon black・・・・・・・・・ 1 part〈Average particle size 30m
) α-A text, 0:l ・・・・・・・・・・・・ 6 parts (Mohs hardness: 9, average particle size: 0.3) Myristic acid・・・・・・・・・・・・ 1 1 part butyl stearate
・・・・・・・・・ Part 1 Coronate L・・・・・・・・・
...5 parts [manufactured by 11 Polyurethane Industries] Cyclohexanone...150 parts Methyl ethyl ketone...50 parts Toluene...
・・・・・・・・・・・・ 50 parts of the obtained magnetic paint for the lower magnetic layer and the magnetic paint for the upper magnetic layer were placed on a polyethylene terephthalate nonmagnetic support having a thickness of 14 g and m according to the process shown in FIG. After being applied wet-on-wet to the surface, magnetic field orientation treatment is performed, and then drying treatment is performed.

Super calendering was performed to form a magnetic layer consisting of a lower magnetic layer with a thickness of 2.54 m and an upper magnetic layer with a thickness of 0.5 parts m.

To explain the process shown in FIG. 1, first, the film-like nonmagnetic support 2 fed out from the supply roll l is
Extrusion type extrusion coater 3.4 (each with a liquid reservoir 3a).

After the paint for the lower layer and the paint for hair waste are subjected to IWlj in a wet-on-wet manner by the 4a), they are passed through a magnet 5 for non-orientation in the first stage and then transferred to a dryer 7 equipped with a magnet 6 for non-orientation in the latter stage. It is then dried by blowing hot air from a nozzle located below.

The non-magnetic support 2 having the magnetic layer dried in this way is
The sheet is led to a super calender device 9 consisting of a combination of calender rolls 8, where it is calendered and then wound onto a winding roll 10.

The wide magnetic tape film thus obtained was made into a video tape.

The characteristics of this video tape were measured.

The results are shown in Table 1.

Note 1. The various characteristics were measured as follows.

(a) RF-output, Lumi-3/N, Chroma-3/N and Chroma-output.

Using a color video noise meter ('9250/IJ, manufactured by Sivac Co., Ltd.), the value (dB) relative to the reference tape was determined using an r1 (R-3700" type deck manufactured by Victor Company of Japan).

The frequencies of each signal are as follows.

RF-output: 6MHz Lumi-3/N: 6 Mllz Chroma-3/N: 629Kllz Chroma-output crab 629Hz using rBR-3711, type deck made by Victor Japan Co., Ltd.
The value (dB) was determined with respect to a reference tape (manufactured by Konica). The frequency of this output signal was 1.7 Mllz.

Linear audio output; Roki Victor 'BR-371. Using an IJ type deck, the value (dB) was determined with respect to a reference tape (manufactured by Konica).

The frequency of this output signal is l　K11z 1-Fi there were.

sliding noise; (b) Playback without running the tape No system noise spectrum Measured using a mu analyzer.

(b) The sample tape was played back 10 times for 1 minute each, and the sliding noise was measured using a spectrum analyzer.

(c) Regarding the noise level around 8 MHz, the value of the IO bus noise was read as an average value using the system noise as a reference (OdB).

The measurement conditions were as follows. Ta. Temperature 20°C 1 humidity 1%.

Deck used: rllR-37000° manufactured by Victor Japan (Example 2~
4. Comparative Examples 1 to 4) The ferromagnetic powders in the composition for the lower magnetic layer and the composition for the upper magnetic layer in Example 1 were subjected to the average major axis length (21 mm) and coercive force shown in Table 1. Instead of ferromagnetic powder with
A video tape was prepared in the same manner as in Example 1, except that the coercive force of each layer was adjusted as shown in Table 1.

The tape properties were measured.

The results are shown in Table 1.

(Hereinafter, blank space) For video (evaluation) As is clear from Table 1, the magnetic recording medium of the present invention is:
Chroma output, Chroma-3/N, 1IiFi audio output, and linear audio output have been improved.

[Effects of the Invention] According to the present invention, it is possible to provide a magnetic recording medium that exhibits chroma output, chroma-8/N, audio output, and high electromagnetic conversion characteristics.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the manufacturing process of the magnetic recording medium of the present invention. l... Supply roll, 2... Nonmagnetic support, 3.4.
. . . Coater, 5. First-stage non-orientation magnet, 6. Second-stage non-orientation magnet, 7. Dryer, 9. Super calender device, 10. Winding roll.

Claims (1)

[Claims] (1) An upper magnetic layer and a lower magnetic layer are laminated on a non-magnetic support with substantially no mixed region, and the average major axis length (l_2) of the ferromagnetic powder in the upper magnetic layer is 0.30μ
m or less, and the average major axis length (l_1) of the ferromagnetic powder in the lower magnetic layer and the average major axis length (l_2) of the ferromagnetic powder in the upper magnetic layer satisfy the following relational expression [I] 0 A magnetic recording medium that satisfies the following: .3<l_2/l_1≦1[I].