JP3419566B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium,
High C / N ratio in frequency domain, especially digital recording media
The present invention relates to a magnetic recording medium having suitable characteristics for use. [0002] BACKGROUND OF THE INVENTION In recent years, evaporation tapes have been used for digital recording media.
Coating-type thin-layer metal using a non-magnetic layer as the lower layer with
Multilayer media has received attention. In addition, a nonmagnetic needle-like
The performance of recording media by using
The technology is disclosed in JP-A-5-62177 and JP-A-5-34701.
No. 7 is proposed. By the way, digital recording media
In recent years, higher C / N ratios have been required for
In order to achieve this with a coating type metal medium,
It is necessary to master magnetic powder that has become much finer.
It becomes important. By the way, use of ultrafine magnetic powder
Is a necessary condition for improving the C / N ratio.
Running, curling, heat curing, etc.
May cause problems in line durability (especially at low temperatures) or
Touch characteristics (envelope characteristics) and dropout
There was a problem that characteristics and still durability deteriorated.
To solve these problems, Japanese Patent Application Laid-Open No. 5-62177
JP-A-5-347017, JP-A-5-18217
The technique shown in No. 3 was insufficient. above
To solve the problem, the magnetic powder used for the upper and lower layers
Of average major axis length and needle ratio of filler and filler, A in magnetic powder
l, Co, weight of rare earth element, saturation magnetization of magnetic powder, magnetism
There is an appropriate range for the layer surface roughness,
It turns out we need to be satisfied. Also magnetic
In order to improve the running durability of the recording medium, two or more types
Large and small carbon blacks are used together (Japanese Unexamined Patent Publication No.
No. 9-14127). However, the surface of the magnetic layer
As it becomes smoother, the problem of transfer from the back coat layer
Of C / N ratio and repeated running durability under high temperature and high humidity
Is a bigger problem than before, and to solve this problem
Is insufficient with the technology of JP-A-59-14127.
Was. [0003] SUMMARY OF THE INVENTION
The object of the present invention 1) High C / N ratio in high frequency band 2) Running durability at low temperatures (particularly head clogging suppression)
System) 3) Head touch characteristics (envelope characteristics) 4) Excellent dropout characteristics 5) Repeat running durability at high temperature 6) Still durability To provide an excellent magnetic recording medium. [0004] The object of the present invention is as follows.
Achieved by 1. Provide a plurality of layers including a non-magnetic layer and a magnetic layer on a support
And the ferromagnetic powder (A) contained in the magnetic layer contains Fe atoms 1
2 to 20 parts by weight of Al and 10 to 10 parts by weight of Co
60 parts by weight and selected from Sm, Y, Pr, Nd and La
1 to 16 parts by weight of at least one rare earth element
And its saturation magnetization (σs) is 130 to 170 emu
/ G, and the average major axis length of the ferromagnetic powder (A) is La
(Nm), the axial ratio is Xa, and the non-magnetic layer contained in the non-magnetic layer
The average major axis length of the powder (B) is Lb (nm), and the axial ratio is Xb.
and when, 30 ≦ La ≦ 110 3 ≦ Xa ≦ 8 La <L
b 80 ≦ Lb ≦ 280 5 ≦ Xb ≦ 12 And the average surface roughness (Ra) of the uppermost magnetic layer is
A magnetic recording medium having a thickness of 0.0005 to 0.006 μm. [0005] It is to be noted that a preferred embodiment of the present invention
Then, the following 2 to 5 can be mentioned. 2 Provide a plurality of layers including a magnetic layer on one surface of the support.
And a back coat layer is provided on the other side.
Conductive powder with number average particle size of 10 to 30 nm is fully conductive in the layer
70-100% by weight of the conductive powder
Layer has an average surface roughness (Ra) of 0.003 to 0.020.
2. The magnetic recording medium according to the above 1, which has a size of μm. [0007] 3. A plurality of substrates each including a magnetic layer on one surface of a support
A layer is provided, and a back coat layer is provided on the other surface,
The number average particle diameter of the back coat layer is 10 to 30 nm and 35.
At least two kinds of conductive powders of
And the average surface roughness (Ra) of the back coat layer is 0.5.
3. The magnetic recording according to the item 2, which has a thickness of 003 to 0.020 μm.
Medium. [0008] A plurality of substrates each including a magnetic layer on one surface of a support
A layer is provided, and a back coat layer is provided on the other surface,
Conductive with a number average particle size of 50 to 150 nm for the back coat layer
Conductive powder is used in an amount of 70 to 100% by weight of the entire conductive powder,
And the average surface roughness (Ra) of the back coat layer is 0.00
2. The magnetic recording medium according to 1 above, which has a thickness of 3 to 0.020 μm.
body. 5 Number average particle size 0.02 in backcoat layer
~ 0.3μm inorganic or organic powder included
The magnetic recording medium according to any one of the above items 1 to 4. What
In addition, the following are mentioned as reference invention of this invention. support
It has multiple layers including a non-magnetic layer and a magnetic layer on the body,
Ferromagnetic powder (A) contained in the conductive layer is 100 wt.
2-20 parts by weight of Al and 10-60 parts by weight of Co
Part, and a small number selected from Sm, Y, Pr, Nd, La
Contains at least one rare earth element in an amount of 1 to 16 parts by weight, and
The saturation magnetization (σs) is 130 to 170 emu / g.
And the crystallite size of the ferromagnetic powder (A) is Sa (n
m), the non-magnetic powder contained in the non-magnetic layer having an axial ratio of Xa
The crystallite size of (B) is Sb (nm), and the axial ratio is Xb.
When     Xa <Xb 5 ≦ Sa ≦ 178 <Sb ≦ 30 Sa <Sb A magnetic recording medium. [0010] A further preferred embodiment of the present invention provides the following:
It is. In particular, by adopting the configuration of claim 1, the above 1)
3) Head touch characteristics (envelope characteristics)
) Is remarkable. The reason for this is obvious
However, one is that the tape is excessively curled toward the magnetic layer.
It seems to be effective in preventing Here La is good
Preferably 40 ≦ La ≦ 100, more preferably 50 ≦ L
a ≦ 80. Lb is preferably 100 ≦ Lb ≦ 25
0, more preferably 120 ≦ Lb ≦ 200. Also
Xa is preferably 4 ≦ Xa ≦ 8, more preferably
5 ≦ Xa ≦ 7. Xb is preferably 5 ≦ Xb ≦
10, more preferably 6 ≦ Xb ≦ 9. Also
It is preferably 20 ≦ Lb−La ≦ 120, more preferably
Or 40 ≦ Lb−La ≦ 100. Ra is good
Preferably 0.0005 ≦ Ra ≦ 0.005, more preferred
Or 0.001 ≦ Ra ≦ 0.004. [0011] In a preferred embodiment 3, a back coat layer
The number average particle diameter of the conductive powder contained in is preferably 10 to 10
25 nm and 35 to 85 nm, more preferably 10 to 2
0 nm and 40-70 nm. Also back coat layer
Has an average surface roughness (Ra) of preferably 0.005 to 0.5.
015 μm, more preferably 0.007 to 0.012 μm
m. [0013] In a preferred embodiment 4, the back coat layer
The number average particle diameter of the conductive powder contained in is preferably 60 to
It is 130 nm, more preferably 70 to 100 nm.
Further, the average surface roughness (Ra) of the back coat layer is preferably
Is 0.005 to 0.015 μm, more preferably 0.0
07 to 0.012 μm. In a preferred embodiment 5, the back coat layer
The number average particle size of the inorganic powder or organic powder contained in
Preferably 0.03-0.25 μm, more preferably
It is 0.05 to 0.20 μm. [0015] The present inventor has conducted various tests to solve the above problems.
As a result of discussion, the following was found. It is an object of the present invention.
In order to obtain a high C / N ratio in a high frequency band,
Ultrafine particles having an average major axis length (La) of 30 to 110 nm in the upper layer
Although it is necessary to use magnetic powder, Japanese Unexamined Patent Publication (Kokai) No. 5-54
No. 381, the non-magnetic powder used for the lower layer
The average particle size is smaller than the average major axis length of the magnetic powder used for the upper layer
When the axial ratio (Xb) of the non-magnetic powder used for
If it is smaller than 5, the curl toward the magnetic layer side becomes large.
And the Young's modulus also decreases, causing head touch characteristics and still
The durability deteriorates. The inventor of the present invention has
Even if the powder (30 ≦ La ≦ 110) is used, it is contained in the lower layer.
The average major axis length (Lb) of the nonmagnetic powder is used for the upper layer.
80 ≦ Lb ≦ so as to be larger than the average major axis length of the magnetic powder
280 and the axis of the non-magnetic powder contained in the lower layer
By setting the ratio (Xb) to 5 ≦ Xb ≦ 12, the medium
Prevents curl to the magnetic layer side and improves Young's modulus
Greatly improves head touch characteristics and still durability
I found that. Further, the present inventors have proposed ultrafine magnetic powder (30 ≦
In the medium using (La ≦ 110), the still durability is improved.
The effect of thermosetting is significant for further improvement
However, even in such a case, Japanese Patent Application Laid-Open
No. 8725, the backcoat layer has an average particle size
Use carbon black larger than 150nm
Transfer occurs, and the C / N ratio deteriorates significantly.
Was. Medium using ultrafine magnetic powder (30 ≦ La ≦ 110)
The backcoat layer used for the body
As shown in Embodiments 2 to 4,
It is preferable to use a specific back coat layer that does not use
Good, and it will not transfer even if cured by heat.
Therefore, deterioration of C / N ratio is small and still durability is low.
It is also possible to obtain a further improved medium. According to the present invention, the configuration of claim 1 is adopted.
Improves head touch characteristics (envelope characteristics)
To obtain a high C / N ratio, especially in the high frequency band
By taking the configurations of the preferred embodiments 3, 4, and 5,
Good repetitive running durability especially at high temperature and high humidity
By adopting the configuration of the preferred embodiment 2, especially the transfer
Improve the title and obtain a high C / N ratio in the high frequency band
Can be used as a back cover as in preferred embodiments 2 to 5.
A heat-curing such as curing is provided to provide C
Less deterioration of the / N ratio and improved still durability
Can be made. [0018] DETAILED DESCRIPTION OF THE INVENTION The magnetic recording medium of the present invention will be described below.
It will be described in detail. -Structure of magnetic recording medium- The magnetic recording medium of the present invention comprises a non-magnetic support (1)
Upper layer containing ferromagnetic powder, preferably ferromagnetic metal powder
The magnetic layer (2) and the non-magnetic support as a lower layer in the constituent layers
At least one nonmagnetic layer between the body and the magnetic layer (3)
Is provided. And, if necessary, a back coat layer (4)
Is provided. (1) Non-magnetic support As a material for forming the nonmagnetic support, for example,
Polyethylene terephthalate, polyethylene-2,6-na
Polyethylenes such as phthalate and polypropylene
Reolefins, cellulose triacetate, cellulose
Cellulose derivatives such as sudiacetate, polyamide,
Plastics such as aramid resin and polycarbonate
Can be mentioned. The form of the non-magnetic support is not particularly limited.
Tape, film, sheet, card, disc
And drum shape. Especially for the thickness of non-magnetic support
There are no restrictions, for example, in the case of a film or sheet
Is usually 2 to 100 mμ, preferably 3 to 50 m
μm, and 30 mμ-10
mm, in the case of a drum,
Selected. The non-magnetic support has a single-layer structure.
Or a multilayer structure. Also this
Non-magnetic support, for example, surface treatment such as corona discharge treatment
May be applied. In addition, non-magnetic support
On the surface (back surface) where the magnetic layer is not provided, a magnetic recording
Aims to improve the runnability of recording media, antistatic and anti-transfer
It is preferable to provide a back coat layer as
An undercoat layer should be provided between the conductive layer and the non-magnetic support.
Can be. If necessary, over the top magnetic layer
A bar coat layer may be provided. (2) Upper magnetic layer The magnetic layer has an average length observed by a transmission electron microscope.
Ferromagnetic powder having an axis length (La) of 30 to 110 nm is preferred.
More preferably, it contains a ferromagnetic metal powder. At this time, the size of the crystallite by X-ray diffraction
(Sa) is preferably 5 ≦ Sa ≦ 17 (nm).
And more preferably 6 ≦ Sa ≦ 15 (nm). Conclusion
If the size of the crystallite is in this range, obtain a sufficient record
If the crystallite size is less than 5 nm, the magnetic powder
It becomes easy to show paramagnetism, and it may not be magnetically recorded.
I will. In addition, if necessary, binder and other components
Can be contained. To control the shape and axial ratio of magnetic powder
Is the selection of the starting substance as a starting material and the selection of redox conditions.
Combination of known methods such as selection and selection of sintering inhibitor
And can be done with. The thickness of the upper magnetic layer is less than 0.5 μm.
Yes, preferably 0.01-0.4 μm, more
Preferably it is 0.02-0.3 μm. Drying of magnetic layer
If the film thickness is less than 0.01 μm, recording is not sufficiently performed.
Output may not be obtained during playback,
On the other hand, when the thickness is 0.5 μm or more, sufficient
Playback output may not be obtained. Furthermore, magnetic recording media
The coercive force Hc is preferably 2000 to 5000 Oe,
More preferably, it is 2000-3000 Oe. this
If it is within the range, a sufficient record can be obtained. (2-1) Magnetic powder In the present invention, the upper layer, which is the magnetic layer,
Of ferromagnetic metal powder. The ferromagnetic metal powder,
Its constituent elements are Fe, Al, Co, and Sm and Nd.
At least one selected from the group consisting of Y, Pr, and La
Contains rare earth elements. The ferromagnetic metal powder according to the present invention is
Fe, Al, Co and Sm and Nd in the overall composition
One or more rare metals selected from the group consisting of Y, Pr and La
The existence ratio of the earth element is based on 100 parts by weight of Fe atoms.
Al atoms are 2 to 20 parts by weight, Co atoms are 10
~ 60 parts by weight, such as Sm, Nd, Y, Pr, La
One or more rare earth elements selected from the group consisting of
6 parts by weight. Also, Fe, Al,
From the group consisting of Co and Sm, Nd, Y, Pr and La
The abundance ratio of the selected one or more rare earth elements depends on the Fe source.
For 100 atoms, the number of Al atoms is 70-300.
Selected from the group consisting of Sm, Nd, Y, Pr, and La.
The number of atoms of the at least one rare earth element is 0.5 to 50.
Preferably. Also, the ferromagnetic metal powder is composed of
And further contains Na and Ca, and
Fe, Al, Co, Sm, Nd, Y, Pr, La
One or more rare earth elements selected from the group consisting of
Of the sum of one or more elements selected from Ba, Sr, and Mg
The abundance ratio is 100 parts by weight of Fe atoms and Al atoms
Is 2 to 20 parts by weight, and Co atom is 10 to 60 parts by weight.
And selected from the group consisting of Sm, Nd, Y, Pr, and La.
One or more rare earth elements selected is from 1 to 16 parts by weight.
And at least one element selected from Ca, Ba, Sr, and Mg
The total number of atoms is 0.001 to 20 parts by weight.
The magnetic metal powder further contains Ni and S as its constituent elements.
i, containing Fe, Co, Ni,
Consisting of Al, Si, and Sm, Nd, Y, Pr, and La
One or more rare earth elements selected from the group, Ca, Ba,
Total abundance of one or more elements selected from Sr and Mg
Rate is 100 parts by weight of Fe atoms and 10 atoms of Co atoms.
６０60 parts by weight, and Ni atom is 2-20 parts by weight.
Al atoms are 2 to 20 parts by weight, and Si atoms are 0.1 to 0.2 parts by weight.
0.01 to 5 parts by weight, whether Sm, Nd, Y, Pr, La
One or more rare earth elements selected from the group consisting of
1 to 16 parts by weight, selected from Ca, Ba, Sr, Mg
The total atom of one or more elements to be exposed is 0.001 to 20
And the weight ratio of Co to Fe is 10 to 10 parts by weight.
It is preferably 60% by weight, and more preferably 15 to 50% by weight.
Is more preferable in increasing the saturation magnetization (σs) of the magnetic powder.
No. [0029] Fe, Co, Ni,
Consisting of Al, Si, and Sm, Nd, Y, Pr, and La
One or more rare earth elements selected from the group, Ca, Ba,
Abundance of one or more elements selected from the group consisting of Sr and Mg
Rate is also the Fe, Co, Ni, A
l, Si, and a group consisting of Sm, Nd, Y, Pr, and La
One or more rare earth elements selected from Ca, Ba, S
r, the abundance of one or more elements selected from the group of Mg
However, the ferromagnetic metal powder within the above range is 1700 O
e or higher coercive force (Hc), 120 emu / g or more
High saturation magnetization (σs) and high dispersibility
preferable. Here, σs is 130 to 170 emu / g.
And preferably 135 to 160 emu / g. The content of the ferromagnetic metal powder is
60 to 95% by weight based on the total solid content in the layer
, Preferably 70 to 90% by weight, particularly preferably
Or 75 to 85% by weight. The ferromagnetic metal powder of the present invention comprises a ferrous salt and an iron salt.
Oxidizing gas is blown into the aqueous suspension mixed with Lucari.
And the iron oxyhydroxide obtained as a starting stock solution.
As a type of the iron oxyhydroxide, α-FeOOH is
Preferably, its production method is to use ferrous salt with an alkali hydroxide
Neutralize with Fe (OH)₂Water suspension and this suspension
An oxidizing gas is blown into the liquid to form acicular α-FeOOH.
There is a first manufacturing method. On the other hand, ferrous salt with alkali carbonate
Neutralize to FeCO₃Water suspension and oxidize this suspension
A second gas is blown to form a spindle-shaped α-FeOOH
There is a manufacturing method. Such ferrous oxyhydroxide is ferrous salt water
The solution reacts with an aqueous alkali solution to contain ferrous hydroxide.
To obtain an aqueous solution that has been oxidized by air oxidation or the like.
It is preferred that it is obtained. At this time, ferrous salt water
Alkaline such as Ni salt, Ca salt, Ba salt, Sr salt etc.
Salts of earth elements, Cr salts, Zn salts, etc. may coexist.
In addition, by selecting and using such salts as appropriate,
The shape of the child (axial ratio) can be controlled. As the ferrous salt, ferrous chloride and sulfuric acid
Iron and the like are preferred. As the alkali, NaOH, NH
₄OH, (NH₄)₂CO₃, Na₂CO₃Etc. are preferred
No. Examples of the Ni salt include nickel chloride, Ca salt, and B salt.
a salt and Sr salt include calcium chloride and salt, respectively.
Barium chloride, strontium chloride, chromium chloride, zinc chloride
Chloride such as lead is preferred. Using the above iron oxide hydroxide as a starting material,
The following operation is performed using this slurry. In addition, the present invention
In the case where Co is introduced, Al and / or S
i, before introducing rare earth elements, but specifically sulfuric acid
Using a Co compound such as cobalt or cobalt chloride,
Stir and mix the solution with the iron oxyhydroxide slurry
It depends. Next, Al and / or Si are introduced.
Is performed as follows. That is, it preferably contains Co.
After preparing a slurry of iron oxyhydroxide having
Rally contains Al compound and / or Si compound
And an aqueous solution containing a compound of a rare earth element.
What is necessary is just to add each and mix by stirring. Aqueous solution containing Al compound and Si compound
May be set to 0.5 to 1.5 M.
It may contain only one of the compounds,
When the compound is contained, the total amount should be within the above range.
No. As the Al compound to be used, sodium aluminate,
Sodium metaaluminate, etc., as Si compound
Include sodium silicate. Rare earth preferably introduced in the present invention
Examples of the class elements include Nd, Sm, Pr, La, and Y.
Can be The dilution used to prepare the above aqueous solution
Neodymium chloride, samarium chloride
Lithium, praseodymium chloride, lanthanum chloride,
Chlorides such as thorium, neodymium nitrate, gadolinium nitrate
And nitrates such as methamine. Two or more rare earth elements
Elements may be used in combination. In the present invention, as described above, Al and
And / or an aqueous solution containing Si and a rare earth element
It is preferable to separately prepare and add an aqueous solution
But, in some cases, Al and / or Si and a rare earth element
And an aqueous solution containing sulfur. In addition, in the mode of separately preparing and adding
Alternatively, both solutions may be added at the same time.
Thereafter, the other liquid may be added. The latter
When the method is adopted, an aqueous solution containing Al and / or Si
First, add an aqueous solution containing a rare earth element
Is more preferred. In the present invention, the alkaline earth
, Al and / or Si and rare earth elements, and
Preferably, iron oxyhydroxide containing Co is obtained. This is thoroughly washed with water, dried, and then put in a non-reducing atmosphere.
Heat treatment is performed at a temperature of 300 to 800 ° C. in an atmosphere. heat
When the processing temperature is lower than 300 ° C., α-FeOOH is dehydrated.
Α-Fe generated₂O₃The number of vacancies in the particles increases,
As a result, the properties of the reduced ferromagnetic metal powder are inferior.
You. When the heat treatment temperature exceeds 800 ° C., α
-Fe₂O₃Melting of the particles began and the shape of the particles changed
Or sintering proceeds and the resulting ferromagnetic gold
The properties of the metal powder deteriorate. Next, the ferromagnetic metal after heat treatment
Reduce powder at 300-600 ° C under hydrogen gas flow
Then, an oxide film is formed on the surface by a known method,
Genus powder is obtained. Further, the magnetic layer contains other magnetic powder.
can do. Other magnetic powders include, for example,
FeOx (1.33 <x <1.5) or Co-FeOx
A ferromagnetic oxide powder represented by (1.33 <x <1.5);
Iron-based metal powder containing Fe as a main component, especially Fe-Al
Ferromagnetic metal powder such as ferromagnetic metal powder, hexagonal plate-like powder
And the like. (2-2) Binder Examples of the binder contained in the magnetic layer include polyurethane.
Chlorination of urethane, polyester, vinyl chloride copolymer, etc.
A typical example is a vinyl resin.
-SO_Three M, -OSO_Three M, -COOM, PO (OM
¹ )_Two And at least one selected from sulfobetaine groups
It is preferable to include a repeating unit having a kind of polar group.
No. However, in the above polar group, M is a hydrogen atom or N
represents an alkali metal such as a, K, and Li;¹ Is water
Elemental atom, alkali atom such as Na, K, Li or alkyl
Represents a group. The above polar group improves the dispersibility of the magnetic powder.
The content in each resin is 0.1 to 8.0 mol.
%, Preferably 0.2 to 6.0 mol%. This
Is less than 0.1 mol%, the dispersion of the magnetic powder
When the content decreases and the content exceeds 8.0 mol%,
The conductive paint tends to gel. The weight average of each resin
The average molecular weight is preferably in the range of 15,000 to 50,000.
New The content of the binder is as follows.
Usually 8 to 25 parts by weight, preferably 100 parts by weight, preferably
It is 10 to 20 parts by weight. Only one kind of binder
Can be used in combination of two or more.
Polyurethane and / or polyester and vinyl chloride
The ratio with the base resin is usually 90:10 to 10: 9 by weight.
0, preferably in the range of 70:30 to 30:70
is there. The electrode used as a binder in the present invention
The vinyl chloride copolymer having a functional group is, for example, vinyl chloride
-Copolymers having hydroxyl groups, such as vinyl alcohol copolymers
Of a compound with a compound having the following polar group and chlorine atom
It can be synthesized by a reaction. In addition, vinyl chloride
Regarding the technique for introducing a polar group into a copolymer, Japanese Patent Laid-Open No.
No. 44227, No. 58-108052, No. 59-8
No. 127, No. 60-101161, No. 60-2358
No. 14, No. 60-238306, No. 60-23837
No. 1, 62-121923, 62-146432
And JP-A-62-146433.
These can also be used in the invention of (1). Next, the polyester used in the present invention is
Obtained by reacting riol with a polybasic acid. In addition, other
A polyester having a polar group introduced therein is also synthesized by a known method.
Can be In addition, polyurethane is
Obtained from reaction with polyisocyanate. Polyol
Generally involves the reaction of a polyol with a polybasic acid.
The polyester polyol obtained by the above is used. Accordingly, a polyester poly having a polar group
If all is used as a raw material, polyurethane having polar groups
Can be synthesized. In addition, to polyurethane
As a technique relating to the introduction of a polar group, Japanese Patent Publication No. 58-415
No. 65, JP-A-57-92422 and JP-A-57-9242.
No. 3, No. 59-8127, No. 59-5423, No. 5
Nos. 9-5424 and 62-121923.
And these can be used in the present invention.
it can. (2-3) Other components In the present invention, in order to improve the quality of the magnetic layer,
Abrasives, lubricants, hardeners, durability improvers, dispersants, charging
Additives such as inhibitors and conductive (fine) powders to other components
Can be contained. As the abrasive, JP-A-4-2142 is used.
Use the known substances described in No. 18 [0105].
Can be. The number average particle size of the abrasive contained in the magnetic layer
The number average particle diameter of the abrasive having a Mohs' hardness of 6 or more is Za
(Μm), preferably 0.03 ≦ Za ≦ 0.
3 μm, more preferably 0.05 ≦ Za ≦ 0.2
5 μm, particularly preferably 0.05 ≦ Za ≦ 0.2
μm. The number average particle diameter of the abrasive in the non-magnetic layer is Z
b (μm), preferably 0.10 ≦ Zb ≦
0.50, more preferably 0.15 ≦ Zb ≦ 0.40,
Particularly preferably, 0.15 ≦ Zb ≦ 0.30, and Za
<Those having a relationship of Zb are particularly suitable for dropout characteristics.
It is preferable in order to increase the value. Including the abrasive in the magnetic layer
The amount is usually 3 to 20 parts by weight, preferably
5 to 15 parts by weight, particularly preferably 5 to 10 parts by weight
It is. As the lubricant, fatty acids and / or fats are used.
Fatty acid esters can be used. In this case, fat
The addition amount of the acid is 0.2 to 10% by weight based on the magnetic powder.
Preferably, it is particularly preferably 0.5 to 5% by weight. Attachment
If the added amount is less than 0.2% by weight, the running property tends to decrease.
If the content exceeds 10% by weight, the fatty acid will
Bleeding and output drop are likely to occur. The amount of the fatty acid ester to be added was also
0.2 to 10% by weight based on the powder is preferred, and particularly preferred.
Or 0.5 to 5% by weight. 0.2 weight
%, The still durability tends to deteriorate, and
When the content exceeds 10% by weight, the fatty acid ester is
Bleeding and output drop are likely to occur. Fatty acids and fats
The fatty acid ester is preferably in a weight ratio of 10:90 to 90:10.
New Fatty acids may be monobasic acids or dibasic acids.
The carbon number is preferably 6 to 30, and 12 to 22
Is more preferable. As a specific example of the fatty acid,
Fatty acids described in [0102] of JP-A-4-214218
No. Specific examples of fatty acid esters are described in
Fatty acid S described in Hei 4-214218 [0103]
Tell. In addition, the above fatty acids, fatty acid esters
Various substances can be used as lubricants other than
For example, silicone oil, carbon fluoride, fatty acid
And α-olefin oxides can be used.
You. As the curing agent, polyisocyanate
Examples of the polyisocyanate include:
For example, tolylene diisocyanate (TDI) and activated water
Aromatic polyisocyanates such as adducts with nitrogen compounds,
Active with hexamethylene diisocyanate (HMDI)
Aliphatic polyisocyanates such as adducts with hydrogen compounds
is there. The weight average molecular weight of the polyisocyanate
Is desirably in the range of 100 to 3,000. As the dispersant, JP-A-4-2142
No. 18 [0093]
You. These dispersants are usually used in an amount of 0.5 to magnetic powder.
It is used in the range of ５5% by weight. As the antistatic agent, JP-A-4-21
No. 4218 [0107].
Can be. The above-mentioned antistatic agent is usually a binder
In the range of 0.01 to 40% by weight. Further, in the present invention, an antistatic agent
Thus, conductive fine powder can be preferably used. The belt
As antistatic agents, carbon black, graphite,
Tin oxide, silver powder, silver oxide, silver nitrate, silver organic compounds, copper powder
Metal particles such as zinc oxide, barium sulfate, titanium oxide
Pigment such as metal oxide such as tin oxide film or solid antimony
Coated with conductive material such as tin oxide coating
And the like. Number average of the conductive powder contained in the magnetic layer
The particle size (Ya) is usually from 5 to 500 nm,
It is preferably 45 to 300 nm, more preferably 60 to 300 nm.
２００200 nm. As the content of the conductive fine powder
Is 0.1 to 3 parts by weight with respect to 100 parts by weight of the magnetic powder.
And preferably 0.1 to 1 part by weight. And non
The number average particle size (Yb) of the conductive powder contained in the magnetic layer
Is usually 5 to 40 nm, preferably 5 to 35 n
m, more preferably 10 to 30 nm,
Points that can improve running durability (especially head clogging suppression)
Is preferred. (3) Non-magnetic layer The non-magnetic layer comprises at least one layer and has a non-magnetic support.
With a single layer or multiple layers between the body and the magnetic layer
You. The non-magnetic layer may be a single layer or two or more layers.
It may be formed of a combination of layers, and there is no particular limitation.
No. In the present invention, the nonmagnetic layer described below is preferable, and
Preferably, a nonmagnetic layer containing a needle-shaped nonmagnetic powder
is there. The non-magnetic layer referred to here is completely non-magnetic.
In addition to the magnetic layer (saturation magnetic flux density Bm is 0),
A non-magnetic layer (a slightly magnetic layer,
Bm is 0.01 to 29 Gauss).
Needle-like α-Fe especially as a filler in the lower layer₂O₃Using
The Bm of the layer is usually about 0.01 to 29 Gauss
However, also in this case, the nonmagnetic layer referred to in the present invention
I will call it. The thickness of the nonmagnetic layer is usually 0.2 to
2.5 μm, preferably 0.5 to 2.0 μm
You. If the thickness is greater than 2.5 μm,
The surface roughness of the layer surface increases, so-called multilayer surface roughness occurs
May not be able to obtain favorable electromagnetic conversion characteristics,
On the other hand, if it is smaller than 0.2 μm, a high flatness during
It becomes difficult to obtain lubricity, electromagnetic conversion characteristics deteriorate,
The meaning of providing the non-magnetic layer below may be reduced. Non-magnetic
To control the shape and axial ratio of the powder,
Of raw material to be used, selection of redox conditions, sintering inhibitor
Can be performed by combining known methods such as selection of
it can. (3-1) Non-magnetic layer The non-magnetic layer contains a non-magnetic powder. Also as needed
Contains binder and other components. Below, this point
Will be described. (3-1-1) Non-magnetic powder In the present invention, the following non-magnetic powder is used.
be able to. As the non-magnetic powder, for example, carbon
Black, graphite, TiO_Two , Barium sulfate, Z
nS, MgCO_Three , CaCO_Three , ZnO, CaO, disulfur
Tungsten nitride, molybdenum disulfide, boron nitride, Mg
O, SnO_Two , SiO_Two , Cr_TwoO_Three , Α-Al_Two O
_Three , Α-Fe₂O₃, Α-FeOOH, SiC, oxide
Lium, corundum, artificial diamond, α-iron oxide,
Garnet, garnet, quartzite, silicon nitride, boron nitride, charcoal
Silicon carbide, molybdenum carbide, boron carbide, tungsten carbide
, Titanium carbide, triboli, diatomaceous earth, dolomite
And the like. Among them, carbon brass is preferable.
Check, CaCO_Three , TiO_Two , Barium sulfate, α-Al
_Two O_Three , Α-Fe_Two O_Three , Α-FeOOH, Cr_Two O_Three
Etc., especially α-Fe_Two O_Three Is preferred. In the present invention, the shape of the powder is acicular.
Α-Fe_Two O_Three It is preferred to use a powder. Said
Needle-like α-Fe_Two O_Three When powder is used, the surface of the lower layer
Upper layer that can improve lubricity and is laminated on it
Surface smoothness can be improved at the same time.
Good. Further, the α-Fe_Two O_Three 0.01-5 for powder
Wt% of γ-Fe_Two O_Three Or Fe_Three O_Four Less of
It is preferable to add at least one of them. Also, α-F
e_Two O_Three As a skeleton (matrix) and γ-Fe as its component
_Two O_Three Or Fe_Three O_Four Including at least one or more of
Those are also preferred. And the coercive force of this powder is 200 ~
600 Oe is preferred. Acicular α-Fe of the present invention₂O₃Powder
Is an oxidizing water suspension mixed with ferrous salt and alkali.
Iron oxyhydroxide obtained by blowing gas
Use as the starting stock solution. As a kind of this iron oxyhydroxide,
α-FeOOH is preferred.
The salt is neutralized with alkali hydroxide and Fe (OH)₂Water suspension
Liquid, and oxidizing gas is blown into this suspension to form a needle-like α
There is a manufacturing method of -FeOOH. On the other hand, carbonic acid ferrous salt
Neutralized with alkali and FeCO₃Water suspension.
Oxidizing gas is blown into the turbid liquid to form a spindle-shaped α-FeOOH
There is a manufacturing method. In the present invention, the latter method is suitable.
You. Such iron oxyhydroxide can be mixed with an aqueous ferrous salt solution.
Water solution containing ferrous hydroxide by reacting with potassium aqueous solution
Liquid obtained by oxidizing it by air oxidation, etc.
It is preferable that At this time, Ni ferrous salt aqueous solution
Salt and alkaline earth elements such as Ca salt, Ba salt and Sr salt
Salt, Cr salt, Zn salt, phosphorus compound, etc.
In addition, by appropriately selecting and using such salts, particles
Shape (needle ratio) can be controlled. As the ferrous salt, ferrous chloride, ferrous sulfate
Iron and ferrous nitrate are preferred. Also, as alkali
NaOH, NH₄OH, (NH₄)₂CO₃, Na₂C
O₃Are preferred. Nickel chloride is used as the Ni salt.
Etc., Ca salt, Ba salt, Sr salt and Mg salt are each salts
Calcium chloride, barium chloride, strontium chloride, salt
Each of magnesium chloride, Cr salt and Zn salt
And chlorides such as zinc chloride. Next, the introduction of Al and Si will be described.
You. The first method is to add an Al compound and / or
Or an aqueous solution containing a Si compound is added and mixed with stirring.
It is a manufacturing method. This slurry is sufficiently filtered, washed and dried
And heated at a temperature of 300 to 800 ° C in a non-reducing atmosphere.
Heat treated, α-Fe₂O₃Obtain a powder. Processing temperature is 30
At 0 ° C. or lower, α-F generated by dehydration of α-FeOOH
e₂O₃The number of vacancies in the powder increases, resulting in α-Fe
₂O₃Dispersibility deteriorates. The processing temperature is 800 ° C.
Above, α-Fe₂O₃Melting begins and the particle shape changes
Or sintering proceeds, and the resulting α
-Fe ₂O₃Characteristics deteriorate. The second method is the slurry
-Wash thoroughly with water and dry, and in a non-reducing atmosphere,
Heat treatment at a temperature of 0 to 800 ° C .;₂O₃particle
Is dispersed in an aqueous solution to form a suspension, and the Al compound is obtained.
And / or Si compound is added and stirred
is there. This is followed by filtration, washing, drying, crushing, degassing, etc.
Α-Fe₂O₃Is obtained. Al compound
Sodium aluminate, sodium metaaluminate
And sodium compounds such as sodium silicate.
You. Using such a manufacturing method, α-Fe₂O₃Powder
To the range shown in the claims, Al, Si, P, Al
Adjust the addition amount of potassium earth element and Na. The existence of Al atoms and Si atoms in the overall composition
Α-F when the abundance and the abundance ratio on the surface are out of the claims.
e₂O₃Because adhesion between powder and binder cannot be ensured
Dispersibility deteriorates, and consequently lower layer smoothness deteriorates
It also reduces the smoothness of the magnetic layer (upper layer). Also, Arca
In the total composition of the elements of lithium earth, P and Na
Α when the abundance and the abundance ratio on the surface are out of the claims.
-Fe₂O₃Poor powder and needleiness. For example, heat treatment
Occasionally sinters, branches, and reduces needleiness
Owing to poor dispersibility and uneven shape
The smoothness is reduced. In the present invention, the shape of the powder is acicular.
Certain non-magnetic powders can be suitably used. The needle
When the non-magnetic powder is used, the smoothness of the surface of the non-magnetic layer is improved.
From the magnetic layer laminated on it
Can also improve the surface smoothness of the upper layer
You. The major axis length (Lb) of the non-magnetic powder is
Is 80 ≦ Lb ≦ 280, preferably 100 ≦ L
b ≦ 250, particularly preferably 120 ≦ Lb ≦ 20
0. As the axial ratio (Xb) of the nonmagnetic powder,
It is always 2 to 20, preferably 5 to 12, and particularly preferably
Preferably it is 6-9. The axial ratio here means the minor axis length
The ratio of the major axis length to the major axis length (major axis length / minor axis length). The above average major axis length is determined by a transmission electron microscope.
500 microscopic or ferromagnetic or non-magnetic powder
This is the average value of the major axis length measured. The crystallite size is
Using an X-ray diffractometer, the integral width of the (110) diffraction line of Fe
And measured by the Scherrer method based on Si powder.
The axial ratio is the average major axis of 500 particles in the electron micrograph.
Measure the length and average minor axis length (average major axis length / average minor axis length) and
I asked. The specific surface area of the nonmagnetic powder is usually
10-250m^Two/ G, preferably from 20 to 150
m^Two/ G, particularly preferably 30 to 100 m^Two/ G
is there. A non-magnetic material having a long axis length, an axial ratio and a specific surface area in the above range
Use of magnetic powder improves the surface properties of the non-magnetic layer
And good surface properties of the upper magnetic layer
It is preferable in that it can be brought into a state of good. In the present invention, the non-magnetic powder
Powder treated with Si compound and / or Al compound
It is preferred that Such surface treatment was performed
Use of non-magnetic powder improves the surface condition of the upper magnetic layer.
Can be good. Si and / or Al content
As the amount, the amount of Si is 0.1 to
10% by weight and 0.1 to 10% by weight of Al are preferred.
New Also, the weight ratio of Si and Al is Si <Al.
Good. The surface treatment is described in JP-A-2-83219.
This can be done by the method described. Content of the Nonmagnetic Powder in Nonmagnetic Layer
The amount is based on the sum of all components constituting the non-magnetic layer.
And usually 50 to 99% by weight, preferably 60 to 9% by weight.
5% by weight, particularly preferably 70 to 95% by weight.
You. When the content of the nonmagnetic powder is within the above range, the magnetic layer
To improve the surface condition of the uppermost layer and the non-magnetic layer
Can be. (3-1-2) Binder As the binder contained in the non-magnetic layer, (2-2)
By the way, the exemplified resins can be used, and the amount
Usually 5 to 150 parts by weight per 100 parts by weight of the nonmagnetic powder.
Parts by weight, preferably 10 to 120 parts by weight. (3-1-3) Other components As other components contained in the nonmagnetic layer in the lower layer
Uses the compound exemplified in (2-3)
Can be. Number average particles of conductive (fine) powder or abrasive used
As described in [Means for solving the problem]
Select and use. (4) Back coat layer Use of various known back coat layers without any special restrictions
Can be. In particular, the backcoat layer has a number average particle size of 10 to 10.
30 nm and at least two types of conductivity of 35-100 nm
Powder is used and the average surface roughness of the back coat layer
(Ra) is 0.003 to 0.020 μm,
Conductive with a number average particle size of 50 to 150 nm for the back coat layer
Conductive powder is used in an amount of 70 to 100% by weight of the entire conductive powder,
And the average surface roughness (Ra) of the back coat layer is 0.00
3 to 0.020 μm, or a back coat layer
An inorganic powder having a number average particle size of 0.02 to 0.3 μm or
Preferably, organic powder is contained. As above
FIG. 1 is a cross-sectional view of the recording medium of the present invention configured as described above.
In FIG. 1, 1 is a support, 2 is a non-magnetic layer, and 3 is an upper magnetic layer.
Layers 4 are back coat layers. -Manufacture of magnetic recording medium- In the magnetic recording medium of the present invention, the magnetic layer is coated and the lower layer is wet.
So-called wet-on-wet when in the wet state
It is preferred to apply by a system. This wet-on-wo
The jet method is used to manufacture a known multilayer-structured magnetic recording medium.
Can be appropriately adopted. example
Generally, magnetic powders, binders, dispersants, lubrication
, Abrasives, antistatic agents, etc., and a solvent
Prepare a paint, then dilute this high-concentration magnetic paint
After preparing the magnetic paint, the magnetic paint is applied to the non-magnetic support.
Apply to the surface. Examples of the solvent include, for example,
Use of a solvent described in JP-A-214218 [0119]
Can be. In kneading and dispersing the components for forming the magnetic layer,
Various kneading and dispersing machines can be used. This kneading dispersion
For example, JP-A-4-214218 [00]
12]. Kneading dispersion
Of the machine, 0.05-0.5 KW (1 kg of magnetic powder
Kneading and dispersing machine that can provide a power consumption load of
Are pressurized kneader, open kneader, continuous kneader,
Mill and three-roll mill. On a non-magnetic support, an upper magnetic layer and a lower layer
Specifically, as shown in FIG.
The non-magnetic support 1 unwound from the supply roll 32
According to the extrusion coating machines 10 and 11 of the extrusion method.
Wet-on-wet top paint and bottom paint
After multi-layer coating, magnet for orientation or magnet for vertical orientation
After passing through 33, it is introduced into a dryer 34, where it is arranged vertically.
Hot air is blown from the nozzle. Then dry
The non-magnetic support 1 provided with each coating layer is
To a super calendar device 37 consisting of a combination of
And then wound up on the take-up roll 39
You. The magnetic film thus obtained is sized to a desired width.
And cut it into a magnetic tape for 8 mm video, for example.
Can be manufactured. In the above method, each paint was not shown.
Extrusion coaters 10, 11 through inline mixers
May be supplied. In the figure, the arrow indicates a non-magnetic support.
3 shows the transport direction. Extrusion coaters 10, 11
Liquid pools 13 and 14 are provided, respectively, from each coater.
Are applied in a wet-on-wet manner. Immediately
Immediately after the application of the lower layer paint (when it is not dried), the upper layer paint is applied.
The coating is applied in multiple layers. As the extrusion coater, FIG.
In addition to the two extrusion coaters shown in Fig.
Extrusion coaters of the type shown in (c) can be used.
it can. Among these, the extrusion core shown in FIG.
Data is preferred in the present invention. For extrusion coater
Lower layer paint and upper layer paint are co-extruded to apply multiple layers
I do. Solvent blended in the above paint or when applying this paint
Examples of the diluting solvent include JP-A-4-214218 [01.
[19] can be used. These various solvents
Can be used alone, or two or more of them
Can also be used in combination. Orientation magnet or vertical
The magnetic field in the magnet for orientation is 20 to 10,000 gauss
The drying temperature by the dryer is about 30-120 ° C
And the drying time is about 0.1 to 10 minutes. In the wet-on-wet method,
Is a combination of reverse roll and extrusion coater,
Combinations of via rolls and extrusion coaters should also be used.
Can be. Furthermore, air doctor coater, blade coater
, Air knife coater, squeeze coater, impregnation coater,
Transfer roll coater, kiss coater, cast coater
, A spray coater or the like can be combined. This c
In multi-layer coating in the wet-on-wet method
The upper layer while the lower layer located below the upper layer remains wet.
Because the coating is applied, the surface of the lower layer (that is, the interface with the upper layer)
It becomes smooth and the surface of the upper layer becomes good, and
The adhesion between the upper and lower layers is also improved. As a result, especially high-density
Recording requires high output and low noise, such as digital
Satisfies the required performance of magnetic tape for magnetic recording
And high durability performance is required
Even if film peeling is eliminated, film strength is improved and durability is sufficient
Become. Wet-on-wet multilayer coating method
Can reduce dropouts and increase reliability
improves. -Smoothing of surface- In the present invention, the surface is flattened by calendaring.
A smoothing process may be performed. After that, if necessary
Slitting by performing nish processing or blade processing
Is done. In the surface smoothing process, the calendar conditions
Temperature, linear pressure, C / S (coating speed), etc.
Can be mentioned. Ra is adjusted to 0.0005 to 0.006 μm.
Control, for example, in the aforementioned manufacturing process.
Set the rendering conditions and control the surface smoothness of the magnetic layer.
All you have to do is That is, in this surface smoothing process,
Are the factors that control the calendar conditions: temperature, line
Include pressure, C / S (coating speed), etc.
Can be. Another factor is kneading of magnetic powder.
Conditions, surface treatment, size and amount of added particles in the magnetic layer, etc.
There is. In the present invention, the above temperature is usually set at 50
~ 140 ° C, the above linear pressure is 50 ~ 1000kg / cm,
The C / S can be maintained at 20 to 1,000 m / min.
preferable. -Curl- Curling should be controlled not only by composition but also by processes, etc.
Can be. For example, when controlling by composition, the magnetic layer, support
Change the balance of the body and backcoat layer thickness,
Increasing the weight ratio of powder to binder or back coating
Use a highly rigid binder such as nitrocellulose for the layer
And so on. When controlling in the process, the temperature during drying
Conditions, tension control during web transport, etc.
I can do it. In the present invention, the reverse curl (the magnetic layer is
(When curled) is preferable, and is preferable.
The curl amount is 0.05 to 0.5 mm. Claim of the invention
As shown in the section, the average major axis of the upper and lower magnetic powders and non-magnetic powders
By controlling the length and axis ratio,
In the composition and process conditions, curl in the preferred reverse direction.
Can be << Measurement of Various Elements in Magnetic Metal Powder >> <Overall composition>: F in the overall composition of the ferromagnetic metal powder
e, Al, Co, and Sm, Nd, Y, Pr, and La groups;
Regarding the abundance ratio of each element of Na and Ca, the wavelength dispersion type
Fluorescence of each element in the sample using an optical X-ray analyzer (WDX)
After measuring the optical X-ray intensity, the fundamental parameters
FP method (hereinafter referred to as FP method). <Size of Crystallite> F is determined by X-ray diffraction.
Using the integration width of the (110) diffraction line of e, based on Si powder
It was determined by the Scherrer method. About how to ask,
X-ray diffraction guide (Rigaku Denki Co., Ltd.)
The correction of the spread due to the double line is described on page 77.
A: It is obtained by correction by Joyes (integral width)
Was. [0092] EXAMPLES Next, the structure and effect of the present invention will be described with reference to examples.
Explain physically. The components, ratios, and operation order shown below are:
Various changes may be made without departing from the scope of the present invention.
Can be In the following examples, "parts"
Unless otherwise specified, "parts by weight" are used. The magnet according to the present invention
Tables 1 and 2 show the properties of the conductive layer (upper layer) and the non-magnetic layer (lower layer).
Show. Of magnetic layer paint and non-magnetic layer paint having the following composition
Knead each component using kneader and sand mill respectively
By dispersing, a magnetic layer paint and a non-magnetic layer paint were prepared. {Magnetic layer paint} Fe-Al ferromagnetic metal powder (average major axis length, crystallite size
And the axial ratio are described in Tables 1 and 2.)
                              100 copies (Magnetic powder A) Fe: Al: Co: Y: Si = 100:
5: 20: 5: 1 (weight ratio) Hc: 2000 Oe, BET: 63m^Two/ G σs: 140 emu / g is fixed, and as shown in the table, L
a, Xa and Sa were changed. (Magnetic Powder B) Fe: Al: Co: Nd:
Si = 100: 5: 20: 5: 1 (weight ratio) Hc: 2000 Oe, BET: 63m^Two/ G σs: 140 emu / g (Magnetic powder C) Fe: Al: Co: Y = 100: 10:
40: 8 (weight ratio) Hc: 2200 Oe, BET: 60m^Two/ G s: 145 emu / g (Magnetic powder D) Fe: Al: Co: Nd: Ca: Ba:
Si = 100: 10: 40: 8: 1: 1: 2 (weight ratio) Hc: 2200 Oe, BET: 60m^Two/ G s: 145 emu / g (Magnetic powder E) Fe: Al: Co: Y: Si = 100:
1: 20: 5: 1 (weight ratio) Hc: 2000 Oe, BET: 60m^Two/ G σs: 140 emu / g (Magnetic Powder F) Fe: Al: Co: Y: S
i = 100: 22: 20: 5: 1 (weight ratio) Hc: 2000 Oe, BET: 60m^Two/ G σs: 140 emu / g (Magnetic powder G) Fe: Al: Co: Y: Si = 100:
5: 5: 5: 1 (weight ratio) Hc: 1800 Oe, BET: 60m^Two/ G σs: 125 emu / g (Magnetic powder H) Fe: Al: Co: Y: Si = 100:
5: 65: 5: 1 (weight ratio) Hc: 2200 Oe, BET: 60m^Two/ G σs: 130 emu / g (Magnetic powder I) Fe: Al: Co: Y: Si = 100:
5: 20: 0.5: 1 (weight ratio) Hc: 1800 Oe, BET: 63m^Two/ G σs: 140 emu / g (Magnetic powder J) Fe: Al: Co: Y: Si = 100:
5: 20: 18: 1 (weight ratio) Hc: 2200 Oe, BET: 63m^Two/ G s: 145 emu / g [0096]   Potassium sulfonate group-containing vinyl chloride resin 10 parts   (MR-110 manufactured by Zeon Corporation)   Sodium sulfonate group-containing polyurethane resin 10 parts   (UR-8700 manufactured by Toyobo Co., Ltd.)   0.5 parts of carbon black (number average particle size 90 nm)   α-alumina (number average particle size 0.15 μm) 8 parts   1 part of stearic acid   1 part butyl stearate   Cyclohexanone 100 parts   100 parts of methyl ethyl ketone   100 parts of toluene [0097] ｛Non-magnetic layer paint｝   Non-magnetic powder a [α-Fe_Two O_Three About average long axis length Lb, crystal size Sb, and axial ratio Xb As described in Tables 1 and 2, they were used after being changed. (Si is α-Fe₂O₃   0.2% by weight of Al₂O₃0.5% by weight with respect to 100 copies   Potassium sulfonate group-containing vinyl chloride resin 12 parts   (MR-110 manufactured by Zeon Corporation)   Sodium sulfonate group-containing polyurethane resin 8 parts   (UR-8700 manufactured by Toyobo Co., Ltd.)   α-alumina (number average particle size 0.2 μm) 5 parts   10 parts of carbon black (number average particle size 15 nm)   1 part of stearic acid   1 part butyl stearate   Cyclohexanone 100 parts   100 parts of methyl ethyl ketone   100 parts of toluene The magnetic layer paint and the non-magnetic layer paint thus obtained were
Each of the polyisocyanate compounds (Coronate L,
5 parts, manufactured by Nippon Polyurethane Industry Co., Ltd.). Examples 1 to 13 and Comparative Examples (1) to (1)
4) Magnetic layer paint containing ferromagnetic metal powder and non-magnetic powder
Using a non-magnetic layer paint containing powder, wet-on-
Polyethylene-2,6-na with a thickness of 5 μm by wet method
After coating on the phthalate film,
Magnetic field orientation treatment, and then 70 ° C, 80 ° C,
After hot air drying at a temperature of 90 ° C., use a calendar
Performs surface smoothing treatment and has the properties shown in Tables 1 and 2.
Constituent layers were formed. Note that the calendar condition is a temperature of 8
5 ° C., linear pressure 300 kg / cm.
Change the temperature to 60 ° C and the line pressure to 150Kg / cm
Was. The tension of the web on the application line is 0.01
Kg / mm. Further, the above-mentioned poly-electrode on the side opposite to the magnetic layer was formed.
On the side (back side) of a styrene-2,6-naphthalate film
Paint I or II having the following composition is applied with III,
This coating film is dried and according to the above-mentioned calendar conditions.
By performing calendar processing, a 0.8 μm thick
A black coat layer was formed to obtain a wide raw magnetic tape.
Thereafter, at a temperature of 60 ° C, Examples 1 to 7, 10 to 13 and
48 hours heat curing for the samples of Comparative Examples 1-13
Of heat for 72 hours for the samples of Examples 9 and 10.
Curing was performed. [0101] ｛Backcoat paint I｝   45 parts of carbon black 1 (number average particle size 23 nm)   5 parts of carbon black 2 (number average particle size 50 nm)   Barium sulfate (average particle size 200nm) 1 part   Nitrocellulose 25 parts   25 parts of polyurethane resin   (N-2301, manufactured by Nippon Polyurethane Co., Ltd.)   10 parts of polyisocyanate compound   (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.)   Cyclohexanone 400 parts   250 parts of methyl ethyl ketone   250 parts of toluene {Backcoat paint II} Backcoat paint
Carbon black 1 and carbon black 2
Carbon black 3 (number average particle size 80 nm) 5
Except for using 0 parts, it was prepared in the same manner as the backcoat paint I.
Was. {Backcoat paint III} Backcoat
Carbon black 1, carbon black in paint I
Carbon black 4 instead of 2 (number average particle size 23 nm)
Produced in the same manner as Backcoat Paint I, except that 50 parts were used.
did. The original magnetic tape thus obtained is slipped.
To produce a magnetic recording medium for video. This magnetic record
The recording media were evaluated as follows. The results are shown in the table above.
Also described in 1. Electric characteristics (dB) CN ratio: Sony Corporation
7 MHZ with 8 mm video camera CCDV-900
The CN ratio of z is the output difference between 7MHz and 6MHz (dB)
And the 9MHz CN ratio is the output difference between 9MHz and 8MHz.
(DB) was measured. (5) Running durability at low temperatures (head blindness)
R) Using S-550 (manufactured by Sony Corporation) in an environment of $ 0 ° C
Run the tape over the entire length and reduce the RF output by 2 dB or less.
Above, the head clogging when it occurs for more than 1 second
And counted. {Head touch characteristics} On an oscilloscope
Observe the envelope characteristics and set the minimum output to the maximum output.
It was measured in a ratio (%) to the ratio. {Dropout characteristics} 8mm manufactured by Sony Corporation
-20 dB, 1 using video camera CCVD-900
The number of dropouts at 5 μs is calculated as the average value per minute.
I did. {Repeated running durability at high temperature} Temperature
S-550 (Sony under the environment of 40 ° C and 80% RH)
After recording the beginning of the tape for 5 minutes using
Decrease in RF output after 200 passes after repeated playback
(DB) was evaluated. {Average surface roughness (Ra)} JIS-B06
3D made by Kosaka Laboratories by the method shown in 5 of 01
Measured with a surface roughness meter (SE-3FK)
0.25 mm). {Still durability} S-550 (Sony
Measurement of the reduction in playback output in still mode using
Measure the time until the playback output drops by 2 dB or more from the initial value.
Specified. ｝ Tape curling｝ Curling state in the width direction of the tape
Is visually observed, and if the magnetic layer is curled inward,
Normal curl (see FIG. 4), the magnetic layer curls outward
The case was reverse curl (see FIG. 5). [0112] [Table 1][0113] [Table 2] [0114] [Table 3][0115] [Table 4] [0116] According to the present invention, especially for digital recording
With a high C / N ratio in a high frequency band
Excellent mechanical properties, running durability at low temperatures, head touch
Characteristics, dropout characteristics and repetition at high temperatures
Providing magnetic recording media with excellent running durability and still durability
Can be offered.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a recording medium of the present invention. FIG. 2 is a view for explaining multilayer coating of a magnetic layer by a wet-on-wet coating method. FIGS. 3A, 3B, and 3C are diagrams showing examples of an extrusion coater of a magnetic paint. FIG. 4 is a perspective view showing a normal curl of a magnetic recording medium. FIG. 5 is a perspective view showing a reverse curl of the magnetic recording medium. DESCRIPTION OF SYMBOLS 1-Non-magnetic support 2-Non-magnetic layer 3-Upper magnetic layer 4-Back coat layer 10-Extrusion coater 11-Extrusion coater 13-Liquid reservoir 14-Liquid reservoir 32-Supply roll 33- Magnet for orientation or magnet for vertical orientation 34-Dryer 37-Super calendar device 38-Calendar roll 39-Winding roll

Continued on the front page (72) Inventor Akira Saito 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Akihiko Seki 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (56) References JP-A-6-215360 (JP, A) JP-A-6-162485 (JP, A) JP-A-5-325170 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) G11B 5/70-5/706

Claims (1)

(57) [Claims 1] A multi-layer comprising a non-magnetic layer and a magnetic layer provided on a support, wherein the ferromagnetic powder (A) contained in the magnetic layer is F
2-20 parts by weight of Al and 100 parts by weight of e atom
10 to 60 parts by weight, and Sm, Y, Pr, Nd, La
At least one rare earth element selected from the group consisting of 1 to 16 parts by weight and having a saturation magnetization (σs) of 130 to 17
0 emu / g, the average major axis length of the ferromagnetic powder (A) is La (nm), the axial ratio is Xa, and the average major axis length of the nonmagnetic powder (B) contained in the nonmagnetic layer is Lb ( nm) and the axial ratio is Xb, 30 ≦ La ≦ 110 3 ≦ Xa ≦ 8 La <Lb 80 ≦ Lb ≦ 280 5 ≦ Xb ≦ 12, and the average surface roughness (Ra) of the uppermost magnetic layer ) Is 0.0005 to 0.006 μm.