JPH03176808A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling property, durability and electromagnetic conversion characteristics of a medium by specifying the surface waviness of a magnetic layer, surface waviness of the magnetic layer forming surface of nonmagnetic supporting body, and average height of projections provided on the other side of the supporting body, and specifying that the ratio of the maximum projection height to the average height is <=10. CONSTITUTION:The surface waviness (A) of a magnetic layer, surface waviness (B) of the magnetic layer forming surface of a nonmagnetic supporting body, and average height of projections (H) provided on the other side of the supporting body are specified to satisfy the conditions expressed by formula I. The number of projections having >=0.01 mum height on the opposite side to the magnetic layer forming surface of the nonmagnetic supporting body 1 is specified to >=200 per 1-mm measuring length. The number of projections having >=0.30 mum height on the opposite side to the magnetic layer forming surface of the nonmagnetic supporting body 1 is specified to <=500 per 400-mm measuring length. Further, the ratio of the maximum height to the average height of projections on the opposite side to the magnetic layer forming surface is specified to be <=10. By this method, traveling property, durability and electromagnetic conversion characteristics of the medium are improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium, and more specifically, the present invention relates to a magnetic recording medium, and more specifically, it has low sliding noise, little head cloudiness, and a low degree of head abrasion. The present invention relates to a magnetic recording medium that has good adhesion, excellent runnability, durability, and electromagnetic conversion characteristics.

[Prior art and problems to be solved by the invention] In magnetic recording media such as video tapes and audio tapes,
It is required to have excellent running properties, durability, and electromagnetic conversion characteristics.

Various attempts have been made to meet this requirement.

For example, for the purpose of reducing head cloudiness, PK of the magnetic layer is
and magnetic recording media that specify Rrtss
185224), the magnetic layer contains a vinyl chloride resin containing a phosphoric acid group, a binder having a functional group, and an average particle size of 0.1 to 0.3. Magnetic recording medium containing alumina in the range of
(see Japanese Patent Laid-Open No. 63-27502), or a magnetic recording medium containing carbon black having an average particle size in the range of 20 to 120 mJL instead of alumina (see Japanese Patent Laid-Open No. 63-27502).
(see Publication No. 2) have been proposed.

However, even if gK and Rrms of the magnetic layer are specified, head cloudiness is not necessarily reduced, but rather causes a problem of deterioration of electromagnetic conversion characteristics and an increase in the degree of head wear.

Also, if you try to eliminate head cloudiness by adding alumina, you will not be able to avoid increasing the degree of head wear, and if you try to eliminate head cloudiness by adding carbon black, you will not be able to avoid electromagnetic head cloudiness. The problem is that it is impossible to avoid deterioration of conversion characteristics.

Furthermore, none of these methods is suitable when the surface of magnetic powder is treated with, for example, SiO2 to improve dispersibility.

On the other hand, for the purpose of reducing sliding noise, for example, magnetic recording media containing metal oxide hydrates in the magnetic layer (
JP-A-1-146]29-146131, etc.)
Or, for the purpose of increasing the adhesion between the magnetic layer and the support, for example, magnetic recording media using a plastic film as a support whose contact angle with water is less than a certain value (Japanese Patent Application Laid-Open No.
8 to 77030, etc.) have also been proposed.

However, in a magnetic recording medium in which a hydrate of a metal oxide is contained in the magnetic layer, when a metal oxide is added to the magnetic layer as an abrasive, for example, the metal oxide becomes a hydrate. If the magnetic layer coating liquid contains adsorbed water, the dispersibility of the magnetic layer coating liquid deteriorates and the electromagnetic conversion characteristics deteriorate. In addition, in magnetic recording media that use a plastic film as a support whose contact angle with water is below a certain value, additives are added to the plastic film in order to make the contact angle with water below a certain value. In addition, there is a problem in that the rigidity of the blastic film is reduced, and as a result, the runnability and durability of the magnetic recording medium are reduced.

The present invention has been made based on the above circumstances.

That is, the objects of the present invention are to reduce sliding noise, reduce head cloudiness, and reduce the degree of head wear.
Moreover, it is an object of the present invention to provide a magnetic recording medium in which the adhesiveness of the magnetic layer is good, and the running properties, durability, and electromagnetic conversion characteristics are excellent.

[Means for Solving the Problems] The structure of the present invention for solving the problems described above is such that, in a magnetic recording medium having a magnetic layer on a non-magnetic support, surface waviness (A) of the magnetic layer, The surface waviness (B) of the magnetic layer forming surface of the magnetic support and the average protrusion height (H) of the magnetic layer forming surface of the non-magnetic support have the following relationship, (A)≦0.022 g m ( B)≦0.020 μm O0 old pm≦(H)≦0.2 μm, and the height of the nonmagnetic support on the magnetic layer forming surface is 0.
．． The number of protrusions with a height of 0i μm or more is 200 or more per 1 mm of measurement length, and the number of protrusions with a height of 0.30 μm or more on the magnetic layer forming surface of the nonmagnetic support is 500 or less per 400 mm of measurement length. The magnetic recording medium is characterized in that the ratio of (maximum protrusion height)/(average protrusion height) on the magnetic layer forming surface of the nonmagnetic support is 10 or less.

The magnetic recording medium of the present invention has a non-magnetic support 1 and a magnetic layer 2, for example as shown in FIG. 1, and the non-magnetic support 2 has specific protrusions 3 on the surface on which the magnetic layer is formed.

The magnetic recording medium of the present invention will be explained in more detail below.

Non-magnetic support - In the magnetic recording medium of the present invention, materials for forming the non-magnetic support that supports the magnetic layer include, for example, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polypropylene; Mention may be made of cellulose derivatives such as cellulose triacetate and cellulose diacetate; and plastics such as polycarbonates, aromatic polyamides and polyimides. Furthermore, Cu, A text, Zn
Various ceramics such as metals such as glass, so-called new ceramics (for example, boron nitride, silicon carbide, etc.) can also be used.

When the non-magnetic support is formed from the above-mentioned plastic, it is preferable to include filler particles.

In the present invention, the surface undulation (B) of the magnetic layer forming surface of the nonmagnetic support satisfies the relationship (B)≦0.020 g m, and the average protrusion height (H) of the magnetic layer forming surface , 0, old pm≦(H)≦0.2JLm must be satisfied.

The surface waviness (B) of the magnetic layer forming surface of the nonmagnetic support is 0.
020 JLm or less, preferably 0.018 μm or less, more preferably 0.015 p, m or less, the surface waviness (A) of the magnetic layer formed on this nonmagnetic support can be reduced to improve electromagnetic conversion. Characteristics (especially Chroma S
/N) can be improved.

The surface waviness (B) of the magnetic layer forming surface of the nonmagnetic support is 0.
For example, the average particle diameter of the filler particles contained in the non-magnetic support is 2p, m or less.
m or less, preferably 0.01 to 1 μm, and the content thereof may be 2% by weight or less, preferably 0.01 to 1.0% by weight.

Furthermore, by setting the average protrusion height (H) on the magnetic layer forming surface to 0.01 JLm or more, it is possible to reduce sliding noise and head cloudiness.

On the other hand, by setting the average protrusion height (H) on the magnetic layer formation surface to 0.20 JLm or less, the surface waviness (A) of the magnetic layer is prevented from increasing, thereby preventing deterioration of the electromagnetic conversion characteristics. It's coming. That is, when the average protrusion height (H) on the magnetic layer forming surface exceeds 0.20 μm,
As a result, the surface undulation (A) of the magnetic layer increases,
This results in a decrease in electromagnetic conversion characteristics.

Furthermore, in the non-magnetic support of the present invention, the number of protrusions having a height of 0.01 μm or more on the magnetic layer forming surface is 200 or more, preferably 200 or more and 2000 or less per 1 mm of measurement length, The number of protrusions having a height of 0.30 lm or more on the magnetic layer forming surface is 500 or less, preferably 100 or less per 400 mm of measurement length, and (maximum protrusion height)/ (average projection height) is required to be 10 or less, preferably 5 or less.

The height on the magnetic layer forming surface is 0. By setting the number of protrusions that are larger than 200 to 200 or more per 1 mm of measurement length, preferably from 200 to 2000,
To provide a magnetic recording medium which can reduce sliding noise and prevent a web from meandering during application of a magnetic layer coating liquid or calendering process, and has improved conveyance and runnability. Something will happen.

Further, by setting the number of protrusions having a height of 0.30 pm or more on the magnetic layer forming surface to 500 or less, preferably 100 or less per 400 mm of measurement length, the surface waviness (A) of the magnetic layer increases. This makes it possible to avoid deterioration of electromagnetic conversion characteristics.

Furthermore, (maximum protrusion height)/
By setting the ratio of (average protrusion height) to 10 or less, preferably 5 or less, the degree of head wear can be reduced.

In the present invention, by using a non-magnetic support having a large number of protrusions on the surface on which the magnetic layer is formed, the effective adhesion area between the non-magnetic support and the magnetic layer is increased, and the adhesion between the non-magnetic support and the magnetic layer is improved. You can improve your sexuality.

The protrusions on the magnetic layer forming surface of the non-magnetic support are, for example, formed on the smooth and unundulated magnetic layer forming surface of the non-magnetic support so that the particle size is as uniform as possible and as close to a spherical shape as possible. 0.1 to 10% by weight of shaped particles,
It is preferably contained in a proportion of 0.1 to 5% by weight, and the average film thickness is 0.01 to Iμm, preferably 0.01 to 0.0μm.
It is sufficient to stack protrusion layers having a thickness of 5 Bm. Here, this protrusion layer can be formed by
It does not necessarily have to form a film; for example, it may have a mesh shape. Further, the protrusions can also be formed by mechanically forming irregularities on the back surface of the nonmagnetic support without stacking such a protrusion layer.

The form of the nonmagnetic support is not particularly limited as long as the surface undulation of the magnetic layer forming surface is within the above range and the magnetic layer forming surface has the above protrusions. It may be in any shape, such as a shape, a disk shape, or a drum shape.

When the nonmagnetic support is in the form of a tape or sheet, the thickness is usually 3 to 150 μm, preferably 4 to 100 μm.
It is Lm. In addition, in the case of disk-shaped or cart-shaped,
Usually, it is 30-]00 pm. Furthermore, in the case of a drum shape, it can be made into a cylindrical shape, etc., depending on the recorder used.

1. A back coat layer may be provided on the back surface of the non-magnetic support (the surface opposite to the surface on which the magnetic layer is formed), if desired, for the purpose of improving running properties of the magnetic recording medium, preventing electrification, and preventing transfer. Good too.

In addition, on the magnetic layer forming surface of the non-magnetic support, for the purpose of improving the adhesion between the magnetic layer and the non-magnetic support, etc.
An intermediate layer (for example, an adhesive layer) can also be provided.

That is, in the present invention, the adhesion between the magnetic layer and the non-magnetic support can be further improved by providing an easy-to-adhesion layer.

(11) Magnetic Layer (11) The magnetic layer formed on the non-magnetic support directly or through a suitable intermediate layer is formed by dispersing ferromagnetic powder in a binder.

In the present invention, the surface undulation (A) of the magnetic layer is
is 0.0224 m or less, preferably (1,0O201
It is necessary that the thickness be less than L, more preferably less than 0.018 μm.

Reduce the surface undulation (A) of the magnetic layer to 0.0221Lm or less
2. By doing so, it is possible to improve electromagnetic conversion characteristics (especially chroma S/N).

In order to reduce the surface undulation (A) of the magnetic layer to 0.022 JLm or less, for example, after applying the magnetic paint forming the magnetic layer onto the non-magnetic support, the surface is coated using, for example, a super calender roll. What is necessary is to perform a smoothing treatment or use ferromagnetic powder with a small particle size. In addition, the surface of the magnetic layer can be improved by improving the dispersibility of the ferromagnetic powder, for example, by using a resin having a functional group as the binder or by using a device with high shearing force such as a pressurized niter. It is possible to reduce the undulation (A) to 0.022 μm or less.

Next, the ferromagnetic powder, binder, etc. that form the magnetic layer will be explained.

Ferromagnetic Powder Examples of the ferromagnetic powder include co-containing γFe, O
:l powder, Co-containing Fe50. l powder, Go-containing Fe0
Iron oxide magnetic powder such as x (4/3 < x < 3/2) powder; Fe powder, Ni powder, Go powder, FeN powder, Ha
- Ferrite powder, Fe-A1 alloy powder, Fe-Ni alloy powder, Fe-Al-Ni alloy powder, Fe-A,
u-P alloy powder, Fe-Ni-3i-A cross alloy powder,
Fe-Ni-3i-AIL-Mn alloy powder, N1-
Go alloy powder, Fe-Mn-Zn alloy powder, Fe-Ni
-Zn alloy powder, Fe-Go-Ni-Cr alloy powder, F
Examples include ferromagnetic alloy powders such as e-Go-Ni-P alloy powder, Go-Ni alloy powder, and Go-P alloy powder.

Among these, preferred is CO-containing γFe2O:l
powder, Fe powder, FeN powder, and Ba-ferrite powder.

The shape of the ferromagnetic powder is preferably acicular, but may also be spherical, ellipsoidal, or plate-like.

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

The coercive force of the ferromagnetic powder is between 500 and 2,00 [1 Oe], preferably between 600 and 1,700 Oe.

In addition, the average major axis length of the ferromagnetic powder is usually 0.1 to 0.4
μm, especially 0.1.5 to 0.30 pm. If this average major axis length is less than 0.1 μm, it may be difficult to obtain good dispersibility. On the other hand, 0.4 p, m
Exceeding this may lead to deterioration of electromagnetic conversion characteristics.

Binder, Other Components - The binder includes - inside the shell:
Resins having average molecular weights within the range of about 10,000 to 200,000 can be used.

Specifically, for example, urethane polymer, vinyl chloride resin, 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 copolymer, polyester resin, various synthetic rubber binders phenolic resin, epoxy resin, urea resin , melamine resin, silicone resin, acrylic reactive resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, mixture of low molecular weight glycol and high molecular weight diol compound and mixtures thereof.

In the present invention, a resin having a negative functional group can also be preferably used together with these resins or alone.

As the resin having this negative functional group, -303M',
-0302M' (In the formula, M+ is a hydrogen atom or an alkali metal, and M2 and M3 are each a hydrogen atom, an alkali metal, or an alkyl group. Also, M2 and M3 are different from each other. ) 6 etc.

The resin having the negative functional group can be obtained by, for example, modifying a resin such as a vinyl chloride resin, a polyester resin, or a polyurethane resin and introducing the negative functional group.

The amount of negative functional groups in the resin having negative functional groups is
It is desirable that it is 0.01 to 10.0 mg/g.

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.

When using the resin having the negative functional group, the amount thereof is usually 2 to 2 parts by weight per 100 parts by weight of the ferromagnetic powder.
It is 50 parts by weight, preferably 5 to 40 parts by weight.

If this blending ratio is less than 2 parts by weight, the desired effect that should be achieved when the resin having the negative functional group is blended may not be sufficiently achieved.

On the other hand, if the amount exceeds 50 parts by weight, it may cause deterioration of sliding noise and head cloudiness.

In the present invention, by using a polyisocyanate curing agent together with the resin having the negative functional group,
It is also possible to improve the durability of the magnetic layer.

Examples of the polyisocyanate curing agent include bifunctional isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and hexane diisocyanate; Trifunctional isocyanates such as those manufactured by Bayer AG, or urethane prepolymers containing isocyanate groups at both ends, which are conventionally used as curing agents, and polyisocyanates that can be used as curing agents. You can use any of them.

The amount of the curing agent used is usually 5 to 80 parts by weight based on the total amount of binder.

In the present invention, in addition to the above-mentioned various binders, optional dispersants such as lecithin, phosphoric acid esters, fatty acids, amine compounds, alkyl sulfates, fatty acid amides, higher alcohols, polyethylene oxide, and sulfosuccinic acid are used. , sulfosuccinic acid esters, known surfactants and their salts, negative organic groups (e.g. -GOOR
, -PO3H) salts of polymer dispersants, etc. can be used.

These may be used alone or in combination.

Furthermore, 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, tutyl myristate, octyl myristate, octyl palmitate, amyl stearate, and amyl palmitate. Tate stearyl stearate, lauryl oleate, octyl oleate, isobutyl oleate, ethyl oleate, intridecyl oleate, butoxyethyl oleate, 9 lupalmitate, butoxyethyl stearate, 2-ethylhexyl stearate, 2-ethylhexyl myristate, ethyl stearate, 2 - Ethylhexyl palmitate, isopropyl palmitate, inpropyl myristate, inoctyl palmitate, isooctyl myristate, butyl laurate, cetyl-2-ethyl hexalate, dioleyl adipate, diethyl adipate, diisobutyl adipate, diisodecyl adipate Examples include bat. Among these, particularly preferred are butyl stearate, butyl palmitate, butoxyethyl palmitate, butoxyethyl stearate, isooctyl palmitate, and isooctyl myristate.

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

By reducing the amount of a dispersant such as lecithin or a plasticizer such as a fatty acid ester as described above, it is possible to improve the running durability of a magnetic recording medium especially under high temperature and high humidity.

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

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

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

In the present invention, fatty acids can be preferably used among the lubricants.

Examples of the fatty acids include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, balmitic acid, stearic acid, isostearic acid, linoleic acid, oleic acid, elaidic acid, behenic acid, malonic acid, and succinic acid. , maleic acid, glutaric acid, adipic acid,
Examples include pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedicarboxylic acid, and octanedicarboxylic acid.

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

The blending ratio of the lubricant is usually 20 parts by weight or less, preferably 10 parts by weight or less, based on 100 parts by weight of the ferromagnetic powder. If this blending ratio exceeds 20 parts by weight,
Blooming and bleat-out may occur more easily.

In the present invention, the magnetic layer has an average grain size of 10 to 10 (1 m
It is preferable to contain JL carbon black. The magnetic layer has an average grain size of 10 to 100 m7p, preferably 20 to
By containing 30 mg of carbon black, the running durability can be further improved without causing a decrease in the improved electromagnetic conversion characteristics of the magnetic recording medium of the present invention. However, the average particle size of carbon black is 10mp
If it is less than L, running durability may be poor. on the other hand,
If the average particle size of carbon black exceeds 100 mpL, electromagnetic conversion characteristics may deteriorate if the amount added is increased.

Further, the blending ratio of the carbon fluff to sufficiently exhibit the above effects is 5 parts by weight or less, preferably 3 parts by weight or less, based on 100 parts by weight of the ferromagnetic powder. However, when a plurality of magnetic layers are provided, the lower layer is not limited to this.

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

It should be noted that the antistatic agent or the dispersant described above does not have a sole function; for example, a negative compound may act as a lubricant and an antistatic agent.

Therefore, the above-mentioned classifications in this invention indicate the main actions, and the actions of the classified compounds are not limited by the actions shown in the classification.

Further, in the present invention, the magnetic layer can have a multilayer structure, for example, by laminating a plurality of magnetic layers having different characteristics.

3. Method for manufacturing a magnetic recording medium The magnetic recording medium of the present invention is characterized in that: - In other words, the ferromagnetic powder, a binder such as a vinyl chloride resin having a negative functional group, and other magnetic layer forming components are combined. It can be manufactured by preparing a magnetic coating material by cross-dispersing it in a solvent, and then coating the magnetic coating material on the non-magnetic support and drying it.

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; 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, dioxane; Aromatic hydrocarbons such as benzene, toluene and xylene; Methylene chloride, ethyl chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dioxane; Halogenated hydrocarbons such as chlorobenzene can also be used.

For kneading the composition of the magnetic layer forming components, the ferromagnetic powder and other magnetic coating components are charged simultaneously or individually into a kneader. For example, first, the ferromagnetic powder is added to a solution containing a dispersant, and after kneading for a predetermined time, the remaining components are added and continued to be roughly kneaded to obtain a magnetic paint.

Various types of crosstalk devices can be used to disperse crosstalk. Examples of this kneading machine include a two-roll mill, a three-roll mill, a pressure kneader, a continuous kneader, an open kneader, a ball mill, a pebble mill, a side grinder Sqegvari attritor, a high-speed impeller disperser, a high-speed stone mill, and a high-speed impact mill. , dispersion machine, high-speed mixer, homogenizer, ultrasonic dispersion machine, etc.

Application methods that can be used to apply magnetic paint include gravure roll coating, Meyer bar coating, doctor blade coating, and reverse roll coating.

Examples include dip coating, air knife coating, calendar coating, squeegee coating, kiss coating, extrusion coating and fantine coating.

The dry thickness of the magnetic layer coated in this manner is usually 0.1 to 1011. m, preferably 0.5~
5 rivers m.

After the magnetic layer-forming components have been applied in this manner, a magnetic field orientation treatment is performed as necessary in an undried state, and a surface smoothing treatment is further performed using, for example, a super calender roll.

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, as a magnetic tape such as a video tape or audio tape by cutting it into a long shape, or as a floppy disk or the like by cutting it into a disk shape. 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. In addition, in the examples and comparative examples described below, "parts" shall represent "parts by weight."

S 10 x O, 64
Part A: 2030.057 parts PVC resin containing potassium sulfonate 15 parts Thermoplastic polyurethane resin 7 parts Stearic acid
1 part butyl stearate
1 part methyl ethyl ketone 125
1 part toluene 125 parts carbon black 5 parts (average particle size 20 m)
Jj-) (Example 1) A magnetic layer composition having the composition shown below was prepared using Santomil.
After making a dispersion by mixing and dispersing for a time, 5 parts of a polyisocyanate compound is added to this dispersion and mixed,
A magnetic paint was prepared.

Magnetic L11LIIL material Go containing y -Fe2O, ferromagnetic fine powder 100 parts [
Coercive force (Hc) 9000e] 7 The obtained magnetic paint was coated with a thickness of 15#Lm and surface undulations (B) shown in Table 1, as well as protrusions with the height and number shown in Table 1, on the magnetic layer forming surface. The film was coated on a polyethylene terephthalate nonmagnetic support.

Next, after removing the solvent under heating, it is supercalendered at a temperature of 60-80℃ and a pressure of 100-300k.
The surface smoothing treatment was performed under the conditions of g/c+s2, and the surface waviness (A) of the magnetic layer was set to 0.012 #Lm.
A videotape was made by cutting it into 8-inch widths.

Regarding this videotape, the properties of the nonmagnetic support and magnetic layer as well as magnetic properties were measured.

The results are shown in Table 1.

Note that various properties and characteristics were measured as follows.

(a) Surface undulations of the magnetic layer (A) and undulations of the magnetic layer forming surface of the nonmagnetic support (B); Using a Tally Step surface roughness meter (manufactured by Tiller Hobson), the following measurement conditions were used: The line average Tsuneri was calculated.

Measurement length: 1 mm Stylus speed: 0.1 m+a/sec Cutoff: 2 Hz (b) Number of protrusions and protrusion height on the magnetic layer forming surface of the nonmagnetic support; A roughness curve is obtained, and the height from the average line is measured for those that are recognized as peaks on this curve (protrusions that exceed the peak count value), and those that are 0.010 p, m or more and 0.30 pm or more are measured. The number of protrusions was measured under the following conditions.

Measurement length: 1mm Cutoff: 0.3311z (bypass filter) Peak count value: 0.005 lumen, 0.30
Since the frequency of protrusions with a height of .mu.m or more is small, the above measurement was repeated 40!1 times to determine the number of protrusions.

(C) Chroma S/N.

Using a color video noise meter (manufactured by Sivak Co., Ltd., '9250/14), the value (dB) relative to the reference tape was determined using an r HR-57000J type deck manufactured by Victor Company of Japan.

The frequencies of each signal are as follows.

Chroma-3/N: 629KHz (d) Head wear amount: Using a 'HR-35000J type deck manufactured by Victor Japan Co., Ltd., the entire length of the tape was repeatedly run for 100 hours at a temperature of 40°C and a humidity of 80%, and the results were measured before and after running. The wear amount of each head was measured.

(e) Cloudy head; b) Temperature 20°C, humidity 65%, 6 MHz signal 10
It was recorded for minutes and played back three times.

0) An 8 MHz signal was recorded for 2 minutes at a temperature of 20° C. and a humidity of 65%, and the playback output was measured using a spectrum analyzer (measured value A).

c) The tape was run over its entire length at a temperature of 20°C and a humidity of 20χ.

2) An 8 MHz signal was recorded for 2 minutes at a temperature of 20° C. and a humidity of 20%, and the playback output was measured using a spectrum analyzer (measured value B).

1 h) Difference between the measured value A and the measured value B Evaluate output decrease by finding (A-B) did.

Also, observe the head and It was evaluated in three stages.

O: Look for cloudiness on the glass part of the head. I can't do it.

△: Approximately half of the glass part of the head Cloudiness is visible.

×: White on the entire surface of the glass part of the head Cloudiness can be seen.

(f) Sliding noise; (b) Playback without running the tape No system noise spectrum Measured with 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 system noise was used as a reference (OdB) 2 (g), and the noise values of 10 buses were read as an average value.

Note that the measurement conditions were as follows. Temperature: 20°C, Humidity: 10%, Deck used: rHR-37000, manufactured by Victor Japan Co., Ltd. Magnetic layer adhesion level: The following 3 items are scored on a 5-point scale according to a unique limit sample, and the magnetic layer remains completely. (5 points for those with no magnetic layer, 1 point for those with no magnetic layer, the same applies hereafter), and the total evaluation score of each test result (out of 15 points) was evaluated.

■Tape peel test Adhesive tape attached to a magnetic surface on the non-magnetic support surface when peeled off. Evaluate the amount of magnetic layer remaining in Ta.

■Kneading test Rub part of the tape with your hands and After that, it remains on the non-magnetic support surface. The amount of magnetic layer was evaluated.

■Folding test Make a crease in the width direction of the tape and fold it. The amount of magnetic layer in the eye area was evaluated.

(Examples 2 to 5, Comparative Examples 1 to 10) In the same manner as in Example 1, except that the properties of the nonmagnetic support and/or magnetic layer were changed as shown in Table 1. A videotape was prepared using the same method, and the characteristics of the obtained videotape were measured.

The results are shown in Table 1.

(Wood, hereafter blank) (Evaluation) As is clear from Table 1, the magnetic recording medium of the present invention:
Head wear and sliding noise are reduced, the head does not become cloudy, and the adhesion between the nonmagnetic support and the magnetic layer is high.

[Effects of the Invention] According to the present invention, since the support body has a specific surface undulation and protrusions, and the magnetic layer has a specific surface undulation, there is no clouding of the head and low sliding noise.
Moreover, it is possible to provide a magnetic recording medium which has a low degree of head wear, has high adhesiveness between the nonmagnetic support and the magnetic layer, and has excellent running properties, durability, and electromagnetic conversion characteristics.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing a magnetic recording medium of the present invention. DESCRIPTION OF SYMBOLS 1...Nonmagnetic support, 2...Magnetic layer, 3...Protrusion 7 1st

Claims (1)

[Claims] (1) In a magnetic recording medium having a magnetic layer on a non-magnetic support, surface waviness (A) of the magnetic layer, surface waviness (B) of the magnetic layer forming surface of the non-magnetic support, and the non-magnetic support The average protrusion height (H) of the magnetic layer forming surface satisfies the following relationships: (A)≦0.022 μm (B)≦0.020 μm 0.01 μm≦(H)≦0.2 μm, and the above The number of protrusions having a height of 0.01 μm or more on the magnetic layer forming surface of the nonmagnetic support is 200 or more per 1 mm of measurement length, and the height of the nonmagnetic support on the magnetic layer forming surface is 0.30 μm. The number of protrusions that are above is 500 or less per 400 mm of measurement length,
A magnetic recording medium characterized in that the ratio of (maximum protrusion height)/(average protrusion height) on the magnetic layer forming surface of the nonmagnetic support is 10 or less.