DE3325146A1 - Magnetic recording material with reduced heat shrinkage - Google Patents

Abstract

A magnetic recording material comprising a non-magnetic substrate as a base with a magnetic layer coated thereupon is proposed. The recording material undergoes a heat shrinkage of less than 1.0 % in the direction of greatest heat shrinkage when the material is left for four hours at 100 DEG C. The material exhibits less deformation caused by heat shrinkage at high temperatures and produces a stable output and stable running properties. The material has good dimensional stability and a low frequency shift of the recorded signals.

Description

The invention relates to a magnetic recording material, particularly, a magnetic recording material with low heat shrinkage.

Magnetic recording materials such as audio tapes or video tapes mounted in a cassette half or a cartridge are usually used or stored in a mild atmosphere, for example in a room where the temperature changes are small. Recently, radio cassette tapes, automobile stereo tapes and compact video tape recorders have been widely used and, as a result, the recording materials are often used or stored in severe conditions such as outdoors or in automobiles where the temperature may be very high or very low. For example, it is reported that the highest temperature inside motor vehicles reaches 104 ^° C. on a summer day as measured by the method for testing motor vehicle parts at high and low temperatures

20 (JIS DO204).

If a magnetic recording material at If left to stand at such a high temperature, the material will shrink, causing curling as the edges of the material shrink more than other parts of the material, so that there is a curve in the material in the longitudinal direction trains. Alternatively, the hub is deformed or extruded by the shrinkage force of the material, that is wrapped around the hub. Therefore, if a magnetic recording material, on which music and the like. Recorded is left to stand at a high temperature, the charge level is changed significantly when playing back and the Music does not play correctly and the material

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does not run smoothly. Especially with magnetic recording materials using thin carriers, for example C-80 type audiokoxnpact cassette tapes, C-90 and C-120, the phenomena described above appear very clearly because they are in one half of the cassette An audio cassette or video cassette attached magnetic tapes are long and consequently the number while that the tape is wrapped around the hub is increased.

The main object of the present invention is therefore in a magnetic recording material which shows less deformation due to heat shrinkage at high temperature and which has a stable discharge level.

Another object of the invention is to provide a magnetic recording material which is small in size Shows the amount of heat shrinkage and has stable running properties.

Another object of the invention is to provide a magnetic recording material which is small in size Shows the amount of heat shrinkage, has good dimensional stability and at most a small frequency shift of the recorded signals shows.

A further object of the invention consists in magnetic recording materials which contain thin supports, such as the C-80, C-90, and C-120 compact audio cassette tapes that have only a small amount of heat shrinkage show, have stable running properties and delivery level and show good dimensional stability.

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As a result of extensive investigations, it has now been found that the above objects are achieved by a magnetic recording material which shows a heat shrinkage of less than 1% when it is left to stand in an atmosphere of 100 ^° C. or higher. The heat shrinkage given here is the heat shrinkage in the direction with the greatest shrinkage.

Heretofore, stretched and crystallized polyester films which have been particularly stretched in the longitudinal direction using a high stretching ratio in order to improve mechanical strength in the machine direction have been widely used. As a result of further investigations to solve the disadvantages of magnetic recording materials made from conventional supports when the materials are used at high temperatures, it was found within the scope of the invention that the conventional supports have a heat shrinkage of 1.5 to 2.3% in the Show the direction with the greatest shrinkage when the supports are left to stand at 110 ^° C. for 4 hours.

According to a preferred embodiment of the invention, the magnetic recording medium comprises a flexible support having thereon a coating of a magnetic layer, which exhibits a heat shrinkage of 1% or less, preferably 0.8% or less in the longitudinal direction after the material at 110 ⁰ C was allowed to stand for 4 hours.

According to a preferred embodiment of the present invention, the flexible carrier used according to the invention suffers heat shrinkage of 2% or less, preferably 1.5 or less, in the direction with the greatest shrinkage when it is at 110 ^° C. for 4 hours.

will let. Examples of such supports include polyester films with a small difference in Young's modulus between the longitudinal direction and the widthwise direction due to the setting of the stretching conditions, ie those with a Young's modulus in the longitudinal direction of 450 to 65 0 kg / mm ² and with a Young- module in the widthwise direction of 450 to 550 kg / mm ^2, stretched polyester films which have been subjected to a heat treatment in an atmosphere higher than 110 ⁰ C to reduce the heat shrinkage PoIycarbonatfolien, polyamide films, Polysulfonfolien, polypropylene films or Polyäthersulfonfolien. In particular, polyester films are preferred because they have a high Young's modulus and are economical.

Examples of polycarbonate films are Makrofol SKG (Bayer AG). Examples of polyamide films are in Japanese Patent Publication 344 94/80 listed. Examples of polyester films are in Japanese Patent Publications 5639/55 and 11774/60 listed. To get a carrier with the desired Young module, the film such as the polyester film becomes in the same stretching ratio in the longitudinal direction and the width direction (3-4 times) stretched and, after the stretched film has been fixed under heating, it will continue stretched in the longitudinal direction at a stretch ratio of about 1.05 to about 1.5 times.

The flexible carrier used in the context of the invention has a surface roughness (Ra) of 0.01 to 0.1 μΐη, preferably 0.02 to 0.08 µm, and most preferred 0.03 to 0.06 μπι, on the surface opposite the Magnetic layer. This surface roughness can be made finer by adding fine particles to the film or by the precipitation Particles within the film or by suitable selection

•• ■ - " ^: ~" ^: '- """" 3325H6

conditions of the film production stages, stretching ratios and / or stretching temperatures are regulated.

The carriers described above are with a Covered with a magnetic layer containing ferromagnetic particles, a binder and, if necessary, various additives. If necessary, a back cover can be applied to the Carriers are formed opposite to the magnetic layer. The magnetic layer of the composition and the back coat are in U.S. Patents 4,135,016, 2,804,401, 2,803,550, 3,293,066, 2,887,462, 3,617,378, 2,923,642, 3,062,676, 2 997 451, 3 734 772, 3 007 892, 3 476 596, 3 041 196, 2,643,048, 3,115,420, 3,166,688 and 3,761,311.

When the above-described support is provided with a magnetic layer, the magnetic recording material obtained suffers from shrinkage of 1 % or less.

The composition of the magnetic layer and methods of making magnetic recording materials are in Japanese Patent Publication No. 26890/81.

The magnetic recording material according to the invention has the following advantages:

(1) The deformation of a tape or a sheet is decreased and the output level is stable even at a temperature of more than about 100 ⁰ C.

(2) The heat shrinkage is small and the frequency shift of the recorded signals can be as small as

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can be made possible so that the frequency shift cannot be detected either visually or by ear.

(3) The dimensional change of an inner diameter the hub (shrinkage) can be made as small as possible

if the tape is wrapped around the hub and stored ^{at a temperature higher than about 100 ° C.} Therefore, the cassette tapes can be easily attached to or detached from the recording reproducing apparatus. 10

(4) If an audio cassette ^{tape is wound around a hub and stored at a temperature higher than about 100 °} C., the hub will not be extruded by the shrinkage force of the tape because of the low heat shrinkage of the wound tape. As a result, the tape always runs smoothly and does not howl.

(5) Even if the tape is ^{stored at a temperature higher than about 100 °} C., the tape is hardly deformed and the tape will practically never whine after repeated use.

The invention is explained in detail below with the aid of the following examples, without the invention thereby being imposed is limited. In the examples, all parts are by weight unless otherwise specified.

The methods of measurements listed in the examples were as follows:
(a) Stability to solvents:

Test samples were immersed in solvent, and the condition of these samples was observed after 24 hours.

^: - · - " ^: ■ - *" - "3325U6

Q: No change.

Δ: The samples were curled in both the lengthwise direction and the widthwise direction, and were by impregnation with the solvent in velvet Directions swollen and were at

grip softly.

(b) heat shrinkage:

The samples were marked at intervals of about 10 cm and the distances (A) were ^{measured by a micrometer at 23 °} C. and 60% relative humidity, whereupon the samples were then loaded with a tension of 0.4 g / 10 mm, and were left to stand at 110 ^° C. for 4 hours and then left to stand in the above-mentioned atmosphere (at 23 ^° C. and 65% relative humidity) for 1 hour. Then the distances (A ¹ ) were measured. The heat shrinkage was calculated according to the following equation:

A — A '20 heat shrinkage = - ^ - χ 100 (%)

(c) Running properties at 23 ^° C. and 60% relative humidity

The runnability tests were carried out using carried out by 40 commercially available audio cassette decks - around the tape windings, the occurrence of tape interruption and to evaluate band deformation.

Interruption of running and irregularly wound tapes did not occur.

Δ: Stopped running did not occur, and • loosely wound tapes occurred on 1 to 3 decks on.

- ίο -

X: Irregularly wound tapes stepped on 4 to 6 decks and interruption of the run took place on 1 to 2 decks below these decks.

(d) Change in the tax level:

The change in the release level of the samples was determined by recording signals at 3 KHz - 10 dB, leaving the recorded samples to stand at 110 ^° C. for 4 hours in a state wrapped around a hub, then allowing the samples to stand at room temperature for 1 hour and playing back the recorded ones Signals measured to compare the recording level and the output level.

The above experiments were performed on 20 tapes for one type of tape and the percentage of tapes that were Output levels had changed by more than 6 dB compared to the recording level was calculated.

20 (e) Frequency Shift:

The frequency shift was determined as the percentage shift of the recorded signals from 3 KHz by recording signals at 3 KHz - 10 dB, leaving the recorded samples to stand for 4 hours at 110 ^° C. in a state wrapped around a hub, then allowing the samples to stand for 1 hour Room temperature and playback of the recorded signals to measure the frequency shift between the frequency of the recorded

3Q signals (3 KHz) and the frequency of the reproduced signals certainly.

(f) Percentage shrinkage of the inside diameter of a

Hub:

_v was prepared according to the change in K easurement / Percent shrinkage \ of the inner diameter of a hub with the tape wound before and after the sample had been at 110 ⁰ C for 4 hours and then at room temperature for 1 hour, allowed to stand, calculated

(g) Percentage of Hub Extrusion Occurrence: 10

The hub extrusion was visually observed after the hub was wrapped with the belt and was allowed to stand at 110 ⁰ C for 4 hours. The test was repeated with 20 tapes for each of the samples.
15th

(h) Percentage of running interruption at

110 ⁰ C for 4 hours:

The occurrence of the interruption in running was determined by leaving cassette tapes to stand at 110 ^° C. for 4 hours and running the tapes on 20 commercially available motor vehicle stereo cassette decks for 24 hours.

(i) Sensitivity: 25

The sensitivity is given as a relative value (dB)

to the sensitivity of a standard band at 315 Hz.

The standard tape used was [QP-12] (BASF AG) and the Sensitivity was measured on a compact cassette deck "Nakamichi 582" (Nakamichi KK).

(j) Frequency response:

The frequency response is in units of difference

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the output (dB) between 10 KHz and 315 Hz.

In these examples the supports were made by stretching the film in the manner described above. For example, Samples Nos. 6 to 14 were prepared by using both polyethylene terephthalate in the molten state stretched in the longitudinal direction as well as in the width direction at a stretching ratio of 3.5 times each became - and after the fixation and heating continued in the longitudinal direction in a stretching ratio of 1.5 fold era (Sample No. 6) or 1.15 times (Sample No. 7-14) stretched became. In the same way, Sample Nos. 15 to 18 were prepared by melting polyethylene terephthalate in it Condition both in the longitudinal direction and in the width direction in a stretch ratio of 3.5 times each.

was stretched and then fixed with heating. Sample No. 20 was made of a polycarbonate film which is available under the name Makrofol SKT (Bayer AG). Sample No. 21 was made according to that in Japanese Patent Publication 34494/80 described method produced,

Samples Nos. 22 to 27 were prepared in the same manner as Samples Nos. 6, 7, 15, 19, 20 and 21, however, the thickness of the supports was different.

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example 1

Ferromagnetic Particles (Y-Fe ₉ O) 100 parts

Copolymers of vinyl chloride / vinyl acetate / 5 vinyl alcohol (polymerisation ratio:

90: 3: 7) 20 pieces

Thermoplastic polyurethane 5 parts

Soot 2 parts

Oleic acid 1 part

10 dimethyl polycyloxane (degree of polymerization:

about 60) 0.1 part

α-Olefin Oxide (8 carbon atoms) 1 part

The above composition was made in a ball mill to prepare the magnetic coating composition which is dispersed by a reverse roll to a dry strength of 5 μπι on a polyethylene terephthalate film with a thickness of 12 μΐη, which improves the elasticity and mechanical strength stretched in the longitudinal direction.

The magnetic coating layer was subjected to magnetic orientation in the undried state and, after drying, subjected to a calendering treatment to produce a solid roll of the magnetic tape.

The massive roller of the magnetic tape has undergone a heat treatment in the atmosphere shown in Table I and then to a width of 3/81 mm for manufacture slotted by audio cassette tapes. The properties of the audio cassette tapes are shown in Table I below listed. . ·.

Condition of warmth
treatment of mas
siven roller of the magnet
band Run
own
societies
at 23 ° C Table I. from more than
6 dB frequency
various
exercise 0.50% Appear
of run
interrupt
chung Appear
of hub
extrusion shrinkage
of the inner
Durclunessers
the hub 5.5% sample
No. Temp. ( ⁰ C) Time (hours) at 60% rel.
humidity Warmth occurrence
shrink from change
fung d. rungs in
Volume * tax level 0.34 after again
fetched Ge
need 3.4 After the tape at 110 0.22 ⁰ C 4 hours , had confessed 2.8 No heat treatment O 60% 0.14 40% 40% 2.0, 1 90 24 O 2.30% 40 0.09 15th 10 1.7 pounds
I. 2 100 24 O 1.81 5 O O 3 110 8 O 1.00 O 0 O 4th 110 24 O 0.80 O O 0 5 0.62

* Shrinkage in the direction with the greatest shrinkage

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Samples Nos. 2, 3, 4 and 5, which had been produced by treating the solid roller of the magnetic tape by means of heat treatment and then slitting it into the specified width, showed low heat shrinkage after being left to stand at 110 ^° C. for 4 hours was. Specifically, Samples Nos. 3, 4 and 5 showed excellent properties after the slit tapes were exposed ^{to the high temperature of 110 ° C.}

Samples Nos. 4 and 5 showed excellent results in terms of the change in the delivery level, the Frequency shift, the shrinkage of the inside diameter of a hub and the running properties.

15 Example 2

The supports listed in Table II were tested for stability to solvents, namely ethyl acetate, methyl ethyl ketone and toluene, and for percentage heat shrinkage in the direction with the greatest shrinkage after the support had been left to stand at 110 ^° C. for 4 hours. The results obtained are shown in Table III below.

Type of vehicle treatment Table II Widths
direction
(kg / nrn ² ) Surface roughness sample (Thickness 12 μm) Carrier * 400 of the carrier (pm) No. Polyethylene tere-
phthalate 1 the Young module 450 0.048 6th Il 2 machinery
direction
(kg / irm ² ) Il 0.008 7th Il 2 750 Il 0.011 8th Il 2 620 Il 0.024 9 Il 2 Il Il 0.033 10 Il 2 Il Il 0.045 11th Il 2 Il 0.060 12th Il 2 Il Il 0.080 13th Il 2 Il 500 0.112 14th Il 3 Il Il 0.015 15th Il 3 Il Il 0.037 16 Il 3 500 0.058 17th Il Il

sample
No. Type of vehicle
(Thickness 12 pm) Treatment of the
Carrier* 18th Polyalkylene terses
phthalate 3 19th Il 4th 20th Polycarbonate
(Makrofol SKT) 4th 21 polyamide 4th

Table II (continued)

Young module

Surface roughness

Machine width of the carrier (μπ \) direction direction
MD (kg / mm ² ) TD (kg / mnr)

500

500

0.082 0.041

0.022 0.025

* 1) The carrier was biaxially stretched and then stretched in the longitudinal direction.

2) The carrier was biaxially stretched and then gently stretched in the longitudinal direction.

3) The carrier was in the longitudinal direction and then in the width direction with the
stretched to the same stretching ratio.

4) The carrier was biaxially stretched and then stretched in the longitudinal direction,
heat treated at 110 ⁰ C.

IV) Cn

"D

I. Methyl ethyl ketone toluene O Heat shrinkage (%) Sample no. table III O O Stability against solvents O O 4.31 6th Ethyl acetate O O 1.03 7th O O O 1.02 8th O O O 1.02 9 O O O 1.03 10 O O O 1.04 ' 11th O O O 1.03 12th O O O 1.02 13th O O O 1.04 14th O O O 1.44 15th O O O 1.45 16 O O O 1.42 17th O O Δ 1.45 18th O Δ O 0.55 19th O O 0.83 20th O 0.30 21 Δ O

CD

OJ CaJ KJ

cn

CD

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As can be seen from Table III, Sample Nos. 7, 19 and 21 are particularly preferable because they are a low heat shrinkage and high stability compared to Own solvents. Sample No. 19 has fairly low heat shrinkage, but is something worse in terms of stability to solvents. Sample No. 6 has high heat shrinkage.

The magnetic coating composition prepared according to Example 1 was passed through a reverse roll to a dry thickness of 5 µm on each support of Sample No. 6 to 21, as listed in Table II, raised. The magnetic layer thereby drawn up then became one Subjected to magnetic orientation in the undried state and subjected to a calendering treatment after drying. The magnetic recording material was then to a width of 3.81 mm to manufacture \ on audio = cassette tapes were cut and the tape was mounted in a compact audio cassette at a length of 90 m. The characteristics of the audio cassette tapes (samples Nos. 6 'to 21') obtained in this way are shown in FIG listed in Table IV below.

COPY

Run around
societies
at 23 ° C a.
60% more relative
humidity Table IV +2.4 warmth
shrinkage
of the tape *
(%) Occurrence of changes
the tax level by more
than 6 dB * (%) sample
No. O Electromagnetic properties
Sensitivity frequency
approach +3.2 2.30 75 6 ' X +0.8 +3.0 0.67 0 7 ' Δ +0.7 +2.8 0.68 0 8th' O +0.8 +2.7 0.66 0 9 ' O +0.7 +2.5 0.67 0 10 ' O +0.7 +2.1 0.67 0 11 ' O +0.7 * .1.9 0.65 0 12 ' O +0.8 + 1.2 0.66 0 13 ' O +0.6 +2.9 0.65 0 14 ' Δ +0.7 +2.7 0.97 0 15 ' O +0.8 +2.1 0.98 0 16 ' O +0.7 +1.8 0.98 0 17 ' C. +0.7 +2.4 0.98 0 18 ' O +0.7 +2.8 0.35 0 19 ' O +0.8 +2.8 0.78 0 20 ' O +0.7 0.20 0 21 " +0.7

These values were determined after the samples had been left to stand at 110 ^° C. for 4 hours.

Table IV (continued)

sample
No. frequency
shift* Occurrence of
Run interruption
chung for how
repeated Ge
need * 6 ¹ 0.50 40 7 ' 0.10 15th 8th' 0.10 0 9 ' 0.10 0 10 ' 0.10 0 11 ' 0.10 0 12 ' 0.10 0 13 ' 0.10 0 14 ' 0.10 0 15 ' 0.10 5 16 ' 0.10 ι 0 17 ' 0.10 0 18 ' 0.11 0 19 ' 0.07 0 20 ' 0.14 0 21 ' 0.06 0

Occurrence of hub ejection *

Shrinkage of the inner diameter of the hub *

40 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O

5.5 1.7 1.8

1.8 1.8 1.8 1.7 1.8 2.1 2.1 2.1 2.0 1.4 1.9 1.0

Surface roughness of the belt (carrier surface)
(μτα)

0.048 0.008 0.011 0.024 0.045 0.045 0.060 0.080 0.112 0.015 0.037 0.058 0.082 0.041 0.022 0.025

ι ι, ',

* These values were determined -After the samples were allowed to stand at 110 ⁰ C for 4 hours.

CO CO

K) ■

cn

CO

• ^: - ·· - ' ^{: v} - 3325H6

Sample Nos. 8 'to 21' by the use of carriers having a lower heat shrinkage and a high surface roughness Ra showed good running properties at 23 ⁰ C and 60% relative humidity and showed only slight changes in Ausputniveaus, the frequency shift and shrinkage of the inner diameter the hub with good running properties after the samples had been left to stand at 110 ^° C. for 4 hours. However, when the surface roughness (Ra) of the support is excessively high as in Sample No. 14 ', the roughness of the support increases the surface roughness of the magnetic layer, thereby adversely affecting the frequency response of the tape. In this example, particularly preferable results are shown with Sample Nos. 8 ' _f

15 13 ¹ , 15 ¹ and 21 'obtained.

Sample No. 6 ¹ , which is a common magnetic recording medium, exhibits high heat shrinkage when exposed to high temperatures and, as a result, gave large changes in the discharge level, frequency shift and shrinkage of the inner diameter of the hub, and frequent occurrences of extrusion the hub and the stoppage. As a result, Sample No. 6 ¹ could achieve the objects of the present invention

25 cannot be reached.

Example 3

In the same manner as in Example 2, the carriers listed in Table V were tested.

Table V

Sample- Type of carrier Treatment of the carrier Young Wbdul (kg / rrrn ² ) Heat shrinkage 3.53 No. (7 μm thick) MD (kg / mm ² ) TD 400 (%) * 0.94 22nd Polyethylene
terephthalate Stretched in the
Longitudinal direction 750 450 1.17 23 M. Slightly stretched
in the longitudinal
direction 620 500 0.50 24 Il Stretched in both
the longitudinal direction as
also of latitudes
direction in the same
stretching ratio
conditions 500 0.61 25th Il Stretched lengthways
direction. Heat re
trades at 11 0 ⁰ C - 0.20 26th Polycarbonate ' - - - 27 polyamide - -

* After standing at 110 ^° C. for 4 hours

CaJ CaJ

■ -'-- · ■ · ' ^: - 3325H6

The same magnetic
as in sample 1, each carrier of samples nos. 22 to 27 was drawn through a reverse roller to a dryness of 5 μm. Then the same procedure as in Example 2 was repeated to produce audio cassette tapes with a total thickness of 12 μm and a width of 3.81 mm.

The tape was mounted in a compact audio cassette at a length of 135 m. The properties of the Compact audio cassette tapes (Samples Nos. 22 'to 27') are listed in Table VI.

Run around warmth Table VI Appear After this 75% frequency Appear Appear Shrinkage of the 5.9% sample societies shrinkage of change 0 various from run un of hub Inside diameter 1.7 No. at 23 ⁰ C of the tape * gen in delivery 0 exercise break extrusion sers the hub 2.0 and 60% rel. level of more 0 after again 1.4 Damp than 6 dB 0 fetched Ge 1.8 speed 0 need 1.0 the band 4 Hours at 110 ⁰ C was left to stand O 1.98% 0.40% 65% 70% 22 ' O 0.56 0.08 0 0 23 ' O 0.78 0.09 0 0 24 ' O 0.26 0.06 O 0 25 ' O 0.42 0.12 O 0 26 ' O 0.10 0.04 0 0 27 '

* Shrinkage in the direction with the greatest shrinkage

■ F-co

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Although Samples Nos. 23 'to 27' were used a film with low heat shrinkage many times over When a hub had been wound, these samples showed at most minor changes in the release level, which Frequency shift and shrinkage of the inner diameter of the hub and good running properties. the Sample No. 22 'which is a common magnetic recording material showed high heat shrinkage when allowed to stand at a high temperature and as a result, had sharp changes in the level of discharge, frequency shift and internal shrinkage Diameter of the hub as well as frequent occurrences of extrusion of the hub and the stoppage of running. With the Sample No. 22 'thus achieved the objects of the invention

15 cannot be reached.

It is found from a comparison between Sample No. 6 ¹ of Example 2 and Sample No. 22 "of Example 3 that Sample No. 22 ', which had a thinner tape thickness, larger changes in the discharge level, more frequent occurrences of stoppage and extrusion of the hub and increased shrinkage of the inner diameter of the hub, which may be due to the different number of wraps of tape around the hub.

The invention has been preferred by way of above

Embodiments described without the invention being limited thereto.

Claims (1)

ίΛΔΚΙΜ + W. 44 360/83 - Ko / Ne July 12, 198; Fuji Photo Film Co., Ltd. Minami Ashigara-Shi, Kanagawa (Japan) Magnetic recording material with reduced Heat shrinkage Claims (j \ ·) Magnetic recording material, consisting of a non-magnetic carrier as a base with a coating of a magnetic layer thereon, characterized in that the material undergoes heat shrinkage. of less than 1.0 $> in the direction with the greatest heat shrinkage when the material is left to stand at 110 ^° C. for 4 hours. 10 2. Magnetic recording material according to claim 1, characterized in that the material shows a heat shrinkage of less than 0.8% in the direction with the greatest heat shrinkage when the material is left to stand at 110 ^° C. for 4 hours. ^: - '- " ^: '■" - ■ '3325U6 ί. Magnetic recording material according to Claim 1 or 2, characterized in that the non-magnetic support shows a shrinkage of less than 2% in the direction with the greatest shrinkage when the material is left to stand at 110 ^° C. for 4 hours. 4. A magnetic recording medium according to claim 3, characterized in that the non-magnetic support exhibits a shrinkage of less than 1.5% in the direction having the largest shrinkage when the material is allowed to stand at 110 ⁰ C for 4 hours. 5. Magnetic recording material according to claim 1 to 4, characterized in that the non-magnetic carrier has a Young's modulus of 450 to 650 kg / mm ² in the longitudinal direction and from 450 to 550 kg / mm ² in the width direction.