JPS6093626A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a recording medium reduced in thermal contraction percentage and having stable travelling durability by specifying the surface roughness of both the sides of a nonmagnetic flexible supporting body and also specifying the thermal contraction percentage as a magnetic recording medium. CONSTITUTION:The surface roughness Ra(M) on the side forming a magnetic layer of the nonmagnetic flexible supporting body is 0.03mum or less, the surface roughness Ra(B) on the opposite side is 0.02-0.1mum and the thermal contraction percentage of the magnetic recording medium using said nonmagnetic flexible supporting body after storing the medium at 110 deg.C for 4hr is 1.0% or less. In addition, Ra(M)<Ra(B) is also defined. A polyester film obtained by reducing the difference between Young's moduli of longitudinal and width directions on the basis of expanding conditions, or a polyester film obtained by applying heat treatment to the expanded polyester film in the atmosphere of 110 deg.C or more and reduced in thermal contraction percentage is used as the supporting body having said thermal contraction factor. Said surface roughness can be adjusted by a method adding fine particles, a method analyzing particles in its inside, a method mechanically changing an expansion film process condition, expansion magnification or expanding temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media. More specifically, the present invention relates to a magnetic recording medium that has excellent running performance, durability, and electromagnetic modification characteristics during repeated use, and has a low thermal shrinkage rate.

(Prior Art) Conventionally, magnetic recording media (for example, audio tapes and video tapes loaded in cassettes) are used or stored in environments where temperature changes are gradual, such as indoors. In recent years 1. 2. Description of the Related Art Radio cassette players, car stereos, small video tape recorders, etc. have become widely used, and are often used and stored in high temperature, high temperature, high humidity, and low temperature environments.

For example, high temperature and low temperature test method for automobile parts (JIS
According to Do, Zo-tei), it is reported that the maximum temperature inside a car during the daytime in summer reaches 10 degrees Celsius.

However, magnetic recording media exposed to such high temperatures may shrink and curl, or one ear may shrink more and cause arcuate deformation in the length direction, or the hub may be deformed by the tightening force during shrinkage. or push it out. For this reason, if a magnetic recording medium tube on which music or the like has been recorded is exposed to high temperatures, the output level will fluctuate greatly during playback, not only causing normal playback but also causing poor running. In particular, in the case of magnetic recording media using thin supports (e.g. audio compact cassette c-to%c-tao, c-t2o, etc.), magnetic Since the tape is long, it has to be wound around the hub many times, making the above-mentioned problem due to shrinkage more noticeable.

Furthermore, it has been found that magnetic recording media using flexible supports whose surfaces are too smooth do not provide good running performance when used repeatedly.

Furthermore, since magnetic recording materials, especially audio cassette tapes, have recently been used for music recording, tapes with well-developed frequency characteristics and excellent original sound reproduction capabilities are required.

On the other hand, in the case of video cassettes, by shortening the recording wavelength and narrowing the track width,
Very high-density recording has become possible. Therefore, there is a demand for tapes with high output, high sZN ratio, and excellent ability to reproduce original images. Also, the total thickness is 5oB
71 or less, and with the spread of portable VTRs, there is a demand for hVTR tapes that have better running durability than before.

That is, there is a strong demand for both audio and video tapes that have electromagnetic conversion characteristics, runnability, and durability that are better than those of the past.

2. Description of the Related Art Conventionally, stretched and crystallized polyester films (in particular, stretched at a high stretching ratio in the longitudinal direction and mechanically strengthened in the longitudinal direction) have been used as supports for magnetic recording media.

When we investigated all the reasons why magnetic recording media using these supports are undesirable when used at high temperatures, we found that
Noting that the heat shrinkage rate (/100C, in the longitudinal direction after standing for a certain period of time) of such a magnetic recording medium is in the order of /,j-2,3, further investigation was conducted.

In addition, for non-magnetic flexible supports, we investigated in detail the surface roughness and electromagnetic conversion characteristics of the side on which the magnetic layer is provided, and the surface roughness of the opposite side to the side where the magnetic layer is provided and the running performance during repeated use. As a result, it was discovered that all of the above-mentioned drawbacks could be overcome, leading to the present invention. (Objective of the Invention) Therefore, the object of the present invention is, firstly, to provide a magnetic recording medium that has good running performance during repeated use, and secondly, to provide a magnetic recording medium that has good running performance when used repeatedly, and secondly, to provide a magnetic recording medium that has good running performance when exposed to high temperatures. Thirdly, the purpose is to provide a magnetic recording medium that is stable in terms of output level and has little deformation of the magnetic recording medium due to heat transfer. The objective is to provide a magnetic recording medium that has a low shrinkage rate and stable running properties. The object of the present invention is to provide a magnetic recording medium having a small frequency shift of a recorded signal.
The object of the present invention is to provide a magnetic recording medium that has a low thermal shrinkage rate (such as tape for 0% c-i2o) and has stable runnability, output level, and dimensional stability.

(Structure of the Invention) The above objects of the present invention are (1) to reduce the surface roughness Ra (M) of the side of the nonmagnetic flexible support on which the magnetic layer is provided. .

03 μm or less, and the surface roughness Ra (B) of the opposite side to the side on which the magnetic layer is provided is 0,02 to 0,/tim, and the magnetic recording medium using the nonmagnetic flexible support has a surface roughness of 1i.
o0c≠Thermal contraction rate after storage time is i.

(2) a magnetic recording medium characterized by a noise level of less than
This can be achieved by the magnetic recording medium f described in (1) above, which is characterized in that Ra (M) and Ra (B) always have a relationship of Ra (M) (Ra (B)).

In a preferred embodiment of the present invention, the non-magnetic flexible support has a tlo 0c, i in the longitudinal direction after being left for a long time,
It has a heat shrinkage rate of less than R, preferably less than J.

For such a support, by changing the stretching conditions, the Young's modulus in the longitudinal direction can be adjusted to 10 to 10 kg/myn2, and the Young's modulus in the width direction can be adjusted to the difference in Young's modulus depending on the direction. Polyester film made smaller or stretched polyester film'frll
There are polyester films, polycarbonate films, polyamide films, polysulfone films, polypropylene films, polyethersulfone films, etc., which are obtained by heat treatment in an atmosphere of o00 or higher and have a reduced heat shrinkage rate. Particularly preferred is a polyester film that has a high Young's modulus in the longitudinal direction and is low in cost.

In addition, the nonmagnetic flexible support has a surface roughness Ra (M) of 0.03 μm or less, preferably 0.0 on the side on which the magnetic layer is provided.
2 μm or less, and the surface roughness Ra (B) on the opposite side to the side where the magnetic layer is provided is 0.02 to 0./μfi, preferably 0.03 to 0.0111 m, particularly preferably O1θ.
It is 3 to o, otμm.

Such surface roughness can be achieved by adding all fine particles, that is, using all external particles, or by using internal particles, in which all particles are precipitated inside, as well as by stretching film forming process conditions, stretching ratio, stretching temperature, and mechanical It can be adjusted by adding unevenness to the surface.

Alternatively, it can also be obtained by a composite film made by combining films with different surface roughnesses.

Also, Tokukai Sho Geta-7≠ri No. 10, same 11-/≠ri oot
It can also be obtained by the coextrusion method described in No.

When a magnetic layer is applied to a non-magnetic flexible support as described above,
The obtained magnetic recording medium has a thermal shrinkage coefficient of less than the l coefficient after being stored for a time of //θ0C, has a smooth magnetic layer surface, and has excellent electromagnetic conversion characteristics.

The magnetic recording medium of the present invention is manufactured by coating a support with a magnetic paint containing a binder composition, ferromagnetic powder, additives, and the like dispersed together with an organic solvent and drying it.

Ferromagnetic powders include r-Fe203, Fea04, Co
In addition to modified iron oxide, alloy fine powder containing iron as a main component is particularly preferred. Particularly, a tape made entirely of fine metal (alloy) powder is suitable for the present invention because it has less deterioration during transfer and erasure over time.

For details on the ferromagnetic powder, additives, organic solvents, dispersion, coating methods, etc., see JP-A-Kokai/θr, t.

J issue, same! Hiro-2/, 104r, same evening≠-≠6゜oi
It is described in Publication No. i, etc.

(Effects of the Invention) The magnetic recording medium of the present invention has the following advantages: (1)
Even if the tape is used repeatedly in an environment where the temperature and humidity change slowly, such as indoors, the tape does not deform much and good running performance can be obtained. In particular, thin magnetic recording media (e.g. audio compact cassette C-tOlC-ta0.C-/
λO, etc.), good running performance can be obtained.

(Even at temperatures above 2110060 degrees, the tape or sheet is less deformed and a stable output level can be obtained.

(3) Thermal shrinkage rate is small, and the frequency shift of the recording signal is reduced.
This can be suppressed to a small range that cannot be discerned audibly or visually.

(4) Even when the hub is wrapped with tape and stored at a high temperature of ioθ0C or higher, the change in inner diameter dimension (shrinkage) of the bald part can be completely reduced.

Therefore, the cassette can be loaded and unloaded into the recording/reproducing device smoothly.

(5) In audio cassette tapes, even if the tape is wound around a hub and stored at a high temperature of 1oo0c or higher in good condition, the tape has a small thermal shrinkage rate, so the phenomenon of pushing out the hub due to tight winding does not occur, resulting in the inability to run. 0 (6) Even when stored at a high temperature of 1000C or higher, there is little deformation of the tape, and the number of stops due to repeated running can be reduced.

(7) Even if the hub is wrapped with tape and stored at a high temperature of 1OO0C or higher, the surface roughness of the support on the magnetic layer side is small and the thermal shrinkage rate is small, so the shrinkage pressure will cause
The resulting change in the surface roughness of the magnetic layer is also reduced, and in particular, output level fluctuations at recording symbols of 10 KHz or higher can be suppressed to a small level.

(8) It can have excellent electromagnetic conversion characteristics.

(Examples) The present invention will be described in more detail with reference to Examples below, but the present invention should not be limited to these Examples.

In addition, "parts" in the examples indicate "parts by weight."

Example 1 r-Fe 203 (Hc4AOOOe acicular ratio 10//average particle length O6 7 μm) 100 parts Vinyl chloride/vinyl acetate/vinyl alcohol copolymer (manufactured by Tanesui Kagaku KK [Eslec AJ]) 20 parts polyurethane resin (large Nippon Ink Kagaku KK's "Crysbon A// Ri") 3 parts oleic acid 7 parts dimethylpolysiloxane (degree of polymerization approximately 0) 0.1 parts α-olefin oxide (carbon number 1Ir) 1 part carbon black λ part Above composition The mixture was placed in a ball mill, mixed and dispersed for 1 hour, and then filtered through a filter having an average pore size of 3 μm to obtain a magnetic layer coating solution.

The obtained coating solution was coated on a non-magnetic flexible support shown in Table 1 using a reverse roll so that the dry thickness was jμ, and while the coated layer was still wet, it was oriented in a magnetic field using an electromagnet of 1000 Gauss. All treatments were carried out and dried. After drying, suit mo calendering? After smoothing the magnetic layer, it was slit to a width of 3.1/width to obtain an audio cassette tape. Transfer this cassette tape to an audio conno (cut cassette) / Jj
B I put it away. The custom-made tape obtained is shown in Table 3 AT-/~
'l'-/4c.

Comparative Example 1 The entire magnetic layer was coated with the magnetic layer coating solution obtained in Example 1 on the non-magnetic flexible support shown in Table 2, and an audio cassette tape was obtained in the same manner as in Example 1. .

The percentage properties of the obtained tapes are shown in Table 3 AT-It~T Example 2 The magnetic layer coating solution obtained in Example 1 was used to form a magnetic layer on the non-magnetic flexible support shown in Table 3. An audio cassette tape was obtained by the same operation as in Example 1. This tape was stored in an audio compact cassette. The custom made tape obtained is shown in Table j A T -/I -'f
- Shown in Kota.

Example 3 C, Adhering Beltride Iron oxide Vinyl chloride/vinyl acetate/vinyl alcohol copolymer (Tanesui Chemical KK#!r Eslec AJ) 20 parts Polyurethane resin (Dainippon Ink Chemical Exhibition "Crisbon 61/ri") 3 parts oleic acid 1
Part dimethylpolysiloxane (degree of polymerization: approximately 1.0) 0.1 part α-olefin oxide (number of carbon atoms/r) / part Carbon black Part λ The above composition was prepared as a magnetic layer coating solution in the same manner as in Example 1. A magnetic layer was provided on the non-magnetic flexible support shown in Tables 1 and 2, and an audio cassette tape housed in a connoct cassette was obtained in the same manner as in Example 1. Table A T-30-'l' shows the characteristics of this tape.
- Shown in Figure B.

Example 4 Fe-Zn alloy fine powder (Fe:Zn = Ri! :riCHci3oo□B Acicular ratio lθ/i = average particle length θ.

3 μ) Ioo part vinyl chloride-vinyl acetate vinyl alcohol copolymer (manufactured by Tanesui Kagaku KK [Esuretsu AJ]) 20 parts polyurethane resin (Dainippon Ink System "Krisgan A//ri J") part oleic acid
7 parts dimethylpolysiloxane (degree of polymerization about 6o) o, i parts α-olefin oxide (carbon number l♂) 1 part carbon black λ part The above composition? A magnetic layer coating solution was prepared in the same manner as in Example 1, and is shown in Tables 1 and 2.

An audio cassette tape housed in a compact cassette was obtained by performing the same operation as in Example 1 on an inn layer tube on a non-magnetic Fi2 flexible support. All characteristics of this tape No. 7
It is shown in Tables AT-≠7 to T-63.

According to Table 3, Ra (M) according to the present invention is 0°03μ
m or less, using a support whose Ra (B) is 0, 0J to 0, /B@, and the thermal shrinkage rate of the magnetic recording medium after storage at 1 to 0c4AHr is 1-o4 or less
~T-J' and AT//-T-/4' have ambiguous electromagnetic conversion characteristics, running properties, and characteristics after storage at 1700C≠Hr.

In particular, black 'l'-3 to T-7 and T-7/ to T-/Hiro are excellent. Furthermore, AT-j~'1'-s, 'I'-ii~T-/
≠ indicates electromagnetic conversion% and /100C after storage.
Hz output level variation is better than other samples.

As for AT-2, since Ra(B) is slightly small, the running performance is slightly inferior on a thin base, but there is no problem in practical use.

AT-A is slightly rough on the M side, and the 8th side is also rough on the tn7'cm lO
KHz output level fluctuation is slightly worse.

This is because the magnetic layer plastically flows during high-temperature storage, and this causes the surface roughness of the support to appear on the surface of the ha layer, which affects the output level of 10KI-Jz in the treble band (short wavelength band). .

In addition, as a comparative example, the surface roughness of the support was within the range of the present invention (
Table 2 A/A%/7) and outside the range (lambda table rot/l), and the heat shrinkage rate after storage at 1/1O0C≠Hr is 3 or more, which is the characteristic of the tape that uses the entire support. Table 3 AT-/
j~'l'-17, but the properties after storage at 110°C≠Hr were poor and could not be used practically.

In Example 2, the thickness of the support was increased to f/2 μ.
When the same characteristics were measured, Ra(B) was 0.0.
The tape (Table 5 AT/R) using a support having a thickness of 20 μm (Table 5) also had improved audio running characteristics. This is because the base thickness is thicker and is used advantageously for running performance.

Regarding the other properties of the sample, the results were similar to those of Example 1 and Comparative Example 1.

In addition, in Examples 3 and 4, the type of ferromagnetic powder was changed, and all the supports of Example 1 and Comparative Example 1 were used as tapes, and custom-made tapes were used for chrome bias and metal bias. The results were similar to those of Example 1 and Comparative Example 1.

From the above results, Ra (M) according to the present invention is 003 μm
Below, if a support with 11 a (B) of 0.02 to θ, 16 m is used, and the heat shrinkage rate of the magnetic recording material after storage for 1100 CII hours is less than the l, θ ratio, electromagnetic conversion custom-made, It was found to be excellent in running characteristics and various percentage properties after storage at IIO 0cIIHr.

The custom measurement method shown in the example is as follows.

(a) Surface roughness This is the center line average roughness defined by the j term of JIS-BOAoi, and the cutoff value is 0.21@q.

(b) Solvent resistance The test sample was immersed in the solvent and the state of the sample could be determined after 1.2 hours.

○: No change Δ: Some swelling or curling of the sample.

(c) Heat shrinkage rate measurement method Approximately 10e
Marks are made at intervals of Wn, and the intervals (A)' are measured with a micrometer. Then, '-”i to the foot sample.
/10W width tension was applied and left in a 1100C atmosphere for a period of time, and then taken out to the above atmosphere and measured at the interval (A')' after 7 hours. A-A' Heat shrinkage rate: = xioo (regret) (d3MOLj Maximum output level of J/jHz when / is the reference tape kOdB (distortion rate 3, ratio) (Reference tape/Bias: NORMAL/EQ: / 20 μs
Fuji Photo Film KK ERC-taO-Bias Nichrome/EQ Near 0μS Fuji Photo Film KK FR-It c-y.

・Biaa: Metal/EQ near θμs Fuji Photo Film KK FRMETALLC-TAO Measuring machine Nakamichi KK 112 type) (e) S Q L / OK 10KHz saturation output level when the reference tape is OdB ( f) Frequency characteristics 10KI-TZ and 37z I) Indicates the difference in the output of z.

(g) Audio Running Ratio A running test was conducted using a commercially available audio cassette deck ≠ θ, and the quality of the winding, the presence or absence of running stops, and the presence or absence of tape deformation were evaluated.

0...Travel stoppage and winding disorder occur together. 0Δ...Travel stoppage does not occur, but winding disorder occurs in 7 to 3 machines.

×... Winding disturbance occurs in t~2 vehicles, and self-propelled stop occurs in 7-2 vehicles.

(h) JKz output level fluctuation After recording the j K HZ s / Od B signal in advance, leave the tape wrapped around the hub in a /100C atmosphere for μ hours, then take it out to a room temperature atmosphere,
After 7 hours, the signal was reproduced and fluctuations in the output level were read.

20 turns were made for each type of test sample, and the incidence of output level fluctuations of JdB or more was determined.

(i) / OKHz output level fluctuation After recording all the signals of / OKW Z% / Od B in advance, leave it wrapped in a cheap wire in a /100C atmosphere for μ hours, then take it out to a room temperature atmosphere,
After one hour, the signal was reproduced and the fluctuations in the output level were read.

Is there an incidence of output level fluctuations of AdB or more when each type of test sample is rolled 20 times? I asked for it.

01 Frequency shift After recording the entire JKI-iz-10dB signal in advance, the tape was wound around the hub and heated to ψ in a 1100C atmosphere.
After leaving it for a while, it was taken out of the room temperature atmosphere. After 1 hour, the signal was reproduced, the frequency f of the reproduced signal was checked, and the shift rate with respect to the recorded signal j K Hz K was determined.

(k3 With the hub inner diameter shrinkage tape wrapped around the hub) Measure the inner diameter of the hub, then leave it in an f/100C atmosphere for a while, take it out to room temperature, and after 1 hour measure the entire inner diameter of the hub. The shrinkage rate was determined.

(1) Incidence of extrusion of bald spots A tape was completely wrapped around the hub, and after leaving it in an atmosphere of 110°C for a period of time, it was visually determined whether the hub was being extruded.

The number of test samples was 7 for each type.

(c) Running stop rate after being left in a 1lO0C1 hour The cassette tape was left in a /100C atmosphere for v hours and then run for one hour on 20 commercially available car stereo cassette decks, and the stop rate at that time was determined.

Patent applicant: Fuji Photo Film Co., Ltd. Procedural amendment 1, case description: Showa J.
Name of the invention Magnetic recording medium 3, Relationship with the case of the person making the amendment Patent applicant name (520) Fuji Photo Film Co., Ltd. 4, Subject of the amendment ``Detailed description of the invention'' column 5 of the specification, Contents of the amendment Akira IRBi! The description in the "Detailed Description of the Invention" section is amended as follows.

/) 211th θ line "Do, 20 Hiro" [oo2ozB and correct it.

, 2) 1st jth nail "During electromagnetic conversion" "Electrical 1df conversion characteristics" and correct it.

3) 37th negative l-1st line “BO60/” "LIot, ol" and correct it.

41:) Sae page 133/line 1 ``3　K　z　j [3K f-1z J and correct it.

Claims (2)

[Claims] (1) The surface roughness Ra (M) of the side on which the magnetic layer is provided of the non-magnetic flexible support is 0.03 μm or less, and the surface roughness Ra (B) of the side opposite to the side where the magnetic layer is provided is θ, Oko ~ 0. /1lyl, and the heat shrinkage rate of the magnetic recording medium using the non-magnetic flexible support after storage for /10'Cl time is /,04 or less. (2) The magnetic recording medium according to claim (1), characterized in that Ra(M) and Ra(B) always have the relationship of Ra(M)<Ra(B).