DE1298561B - Magnetogram carrier with low electrical surface resistance and process for its production - Google Patents

Description

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The invention relates to magnetogram carriers with then either on this layer or on the second low surface resistance and good magne- surface of the polyester tape,
Table properties, consisting of polyester carrier magnetogram carrier, which are built up in this way foils, which are a layer of ferromagnetic particles, have the disadvantage that they also have an electrically conductive carbon black layer, the layer which makes conductive the thickness and the stiff binder-free firmly adhering on the surface the speed of the tape increases. Said layer interferes with the carrier film is attached, as well as a method for further the usual washing of the carrier film before the production of such magnetogram carriers. Depending on the magnetic coating and is also a hindrance to the film thickness, these magnetograms can take the form of tapes, cards or disks in the hot calendering of the carrier film in front of the carrier.
to have. Will put this type of conductive layer on the side

Known magnetogram carriers applied in tape form opposite the magnetic layer, then made of a flexible carrier film, for example it is mechanical stresses in the tape device biaxially stretched polyester film, the surface of which is strongly exposed and is easily rubbed off. This results in a coating that is made of ferromagnetic 15 to the loss of conductivity among the desired particles, embedded in high polymer binder, minimum value (Table II) and to deposit the. It is a prerequisite for the suitability of abrasion products in the tape device,
The polymeric binder for the said It is in the production of such a known purpose that it firmly adheres to the surface of the carrier film magnetogram carrier also difficult to get the carbon black in if it is in the form of a ferromagnetic ao the binder always in the same, technologically particle-containing layer to incorporate the film upper-optimal degree of distribution. A defective area is applied. Adhesive degree of dispersion leads to lumps of soot in the

Such known magnetic tapes often have a layer. These lumps can get bothersome

high electrical surface resistance. Magnetic affect the magnetic layer. One pushed too far

tapes are played in many cases, 25 on the other hand, the degree of dispersion of soot brings

especially when rewinding, with speed broken soot particles, which affects the conductivity

can reduce speeds of up to 620 cm / sec over a stationary or moving layer.

borrowed parts made of metallic or non-metallic The invention is based on the object Magnetoschem Material exist, guided. To propose to this promotional vehicle who committed the disadvantages will not have the tape due to friction with the mentioned 30 known magnetogram carriers, as well as a Parts are electrostatically charged. Process for producing such magnetogram strengths Electrostatically charged tapes adhere to carriers.

stationary surfaces, and they continue to have this task now in a surprising way

Disadvantage that there are dust particles on the tapes from a magnetogram carrier, consisting of a

fix. 35 biaxially stretched polyester carrier film, with little

There has therefore been no shortage of attempts to find a binder-free, solid surface on it at least

aimed to have these disadvantages of sticky and electrically conductive soot layer of magnetogram carriers,

to avoid. To achieve this, you should use magneto and a second layer made of ferromagnetic

gram carrier consists of at least one square upper particle in high-polymer binders,

sheet resistance of 10 ⁸ ohms, but preferably 40 solved. The magnetogram carriers according to the invention

10 ohms and less. It is known to combine both low surface resistance

To apply layers to polyester film, which in addition to good electromagnetic properties,

ferromagnetic particles and polymeric binding- The layer of conductive carbon black of the improved

contain conductive carbon black. The incorporation of the magnetogram carrier is thinner than 2 μ, preferably

As can be seen from Table I, carbon black produces 45 wise thinner than 1 μ., and has a square shape

a considerable increase in conductivity versus surface resistance on the order of

over such coatings, which consist only of ferromagnetic 10 ⁸ to 10 ³ ohms, preferably of the order of magnitude

table particles and polymeric binders from 10 ⁶ to 10 * ohms.

stand, but at the same time affects the quality of the improved magnetodes according to the invention Magnetogram carrier noticeably disadvantageous. 50 gram carrier with increased electrical conductivity It can be seen from Table I that with increasing and good magnetic properties one obtains Soot content in the layer the saturation remanence of the by one or both surfaces of a stretched Magnetogram carrier decreases significantly. The saturation polyester carrier film with volatile solvent or In the case of the addition of carbon black, the retardation of production essentially takes away swelling agents for the above-mentioned polyester carrier films more than the dilution of the magnetic particles 55 treated, with the solvent or swelling used corresponds to the layer. contain medium conductive carbon black finely divided and one

This comparison shows that, in the case of the known ones, the polyester carrier film is a thermal magnetogram carrier subject to the required values of the treatment.

square surface resistance only under The heat treatment of the film takes place approximately

Loss of magnetic properties will get 60 1 second or longer, for practical reasons

are, if one is known by adding carbon black in a known manner, preferably 1 to 60 seconds, at temperatures

Way the electrostatic charge of the magneto- above the glass transition point of the high poly-

Tried to reduce gram carriers. meren foil material. There will be in general

It is also known that temperatures of 120 to 160 ° C with good electrical conductivity are used, in particular

Manufacture magnetogram carriers by 65 special, however, it is advantageous at 130 to 135 ° C

towards a surface of a polyester carrier film with a treatment time of about 6 seconds

conductive layer that work from carbon black in a high polymer. Exposure to heat for more than 60 seconds

Binder exists, applies and the magnetic layer is not critical, provided that in the preferred temperature

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area is being worked; one is only for reasons dichloroacetic acid, trifluoropropionic acid, trifluoroacetic acid

a more rational approach interested in acid; however, trichloroacetic acid is particularly suitable

to keep the time as short as possible. The dispersing acid.

of carbon black in the solvents or swelling agents These acids can be carried out as aqueous solutions in by using dispersing devices. 5 concentrations of 5 to 30% are used. Such are, for example, high-speed stirrers, but they are particularly advantageous in ball mills or ultrasonic sonators. In some concentration of 10 to _20/0 ° applied. In some cases it is advisable, in the special cases mentioned, it can be advantageous to use suitable halogenated carboxylic acids or their aqueous solutions mixed with one another in the solvents or swelling agents to achieve the degree of distribution of carbon black , use dispersing agents.

to improve. Suitable dispersants for this Suitable ferromagnetic particles for the Ma-

Purpose are e.g. B. anionic surfactants, such as salts of gnetschicht of the magnetogram according to the invention

Alkylarylsulfonic acids, or nonionic surfactants, such as carriers are, for example, aciculares gamma (III) -Polyoxyäthyllauryläther. 15 oxyd, acicular ferrites and magnetites and aciculares

For the purpose mentioned, these agents are converted into chromium (IV) oxide.

a concentration up to 5 ° / ₀ , but preferably suitable high-polymer binders for the Ma-

up to 3%, based on the amount of soot, applied. gnetschicht can, for example, be of the class of

The means indicated are not capable of applying layers of vinyl chloride-vinyl acetate copolymers, polyvinyl that form on the surface of the polyester ao butyral copolymers, butadiene-acrylonitrile copoly-

anchor the carrier film firmly. You can therefore also mers, copolyesters and copolyether esters, poly-

not the function of binders for fixing amides, polyester urethanes, polyether urethanes, poly-

of the soot on the film surface. carbonates and polyureas and mixtures

These polymers belong to the polyester carrier film pretreated in this way.

a magnetic layer in the form of a dispersion 95 Compared to previously known ferromagnetic particles distributed for sale in a magnetogram carrier offered, the inventive solution of high-polymer binding agent in suitable conventional magnetogram carriers has many advantages. Solvents for the binder to the first higher electrical conductivity than with previously applied layer and subjecting the so-known means can be achieved. Table III gives a double-coated polyester carrier film of a 30 in comparison with some commercially available heat treatments for the purpose of drying this layer, magnetogram carriers. The conductive layer, preferably in the presence of a gas stream, is in particular abrasion-resistant. The adhesion of the conductive particles to a special air stream, whereby this measure on the film surface is not impaired by washing solutions, the polymeric binders are hardened at the same time, and the polyester film cannot be partially dissolved. The gas stream has a temperature of 60 to 35. The conductive ^{carbon black layer has the same high temperature resistance of 150 °} C., but preferably between 70 and 130 ^° C., of the polyester carrier film. it acts for between 5 and 120 seconds, preferably the conductive magnetogram carrier, but for between 10 and 90 seconds. A conductive layer of the invention in its magnetic exposure time longer than that mentioned is not changed properties; The dispersion is also critical, provided that the temperature range of the magnetic particles in the binding material is specified. The order of the magnet does not affect. The conductivity of the improved layer can also take place on the side of the polyester carrier-magnetogram carrier over a wide area of film that does not have a carbon black layer. Can be adjusted on a case-by-case basis and with a high degree of reproducibility by washing the polyester carrier film from the magnet - the optimal carbon black coating for the respective purpose and applying it to the surface of the film for smoothing at a higher concentration. Calender temperature. It is little dependent on the environmental conditions at 10 to 90 ° / _0. The dispersions used, consisting of relative humidity and temperatures between solvents or swelling agents and electrically conductive -40 and 100 ° C. Carbon black have a solids content of 0.1% by weight. The layer of conductive carbon black has not only percent to 8.0 percent by weight, preferably between 5 ° excellent adhesion to the polyester carrier film, see 0.5 and 5.0 percent by weight. There are also the adhesion of the magnetic layer on it with this between 10 and 50 g of this dispersion per turn of a number of typical binding materials, square meters of coated film surface applied such as vinyl chloride-vinyl acetate copolymers, acrylics, so that the coated film surface from 0.05 to tril-butadiene copolymers, copolyesters and poly-2.5 g of carbon black. Preference is given to 55 ester and polyether urethanes per square meter of surface to be coated 13 g of dispersion. m ² results. the conductive layer can be changed. The slip-suitable stretched polyester carrier films for the properties of the layer are e.g. B. by additions magnetogram carrier according to the invention contain 60 of graphite or finely divided polytetrafluoroethylene at least 80 mol percent polyethylene terephthalate and improved. Further modifications are not limited to biaxial stretching with an areal- these examples are made with a stretch ratio of at least 1: 6.

Suitable solvents are those for polyester example 1 known that are sufficiently effective and sufficient

swell the surface of the film sufficiently quickly or In 100 g of a solution of 10 g of trichloroacetic acid in

Dissolve, such as m-cresol and halogen- 90 g water are 3.0 g by means of a ball mill

nated aliphatic carboxylic acids, such as finely dispersed from electrically conductive carbon black.

13 g of this dispersion are per square meter on a 36 μ thick, applied with an area stretching ratio of 1:14 produced Polyäthylenterephthalatträgerfolie and heated by the action of an air stream of 13O ⁰ C for a period of 10 seconds, the film is mechanically held under tension. The amount of soot per square meter of film surface is 0.4 g. The layer thickness of the soot layer is less than 1 μ.

A magnetic coating composition with a viscosity between 1000 and 2000 cP at 20 ° C is used produced by grinding for 50 hours in a ball mill from the following components:

Gamma-iron (III) "Qxyd, .... ,, ..., ..., 750 vinyl chloride-vinyl acetate copolymer g. 87:13 20 ⁰ /" solution in metal ■

ethyl ethyl ketone .50Og

Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 91: 3: 6 20% solution

solution in methyl ethyl ketone 375 g

Tricresyl phosphate 30 g

Dibutyl phthalate ". 30 g

Lecithin> ... ................ 10g

Lead (II) stearate 5g

Methyl ethyl ketone ................. 300 g

The coating composition obtained in this way is applied to the carbon black layer of the polyester carrier film and dried ^{by exposure for a period of 30 seconds by means of an air stream of 115 ° C.} The layer thickness of the dry magnetic layer is 10 μ. The magnetic layer adheres well to the carbon black layer on the polyester film. The magnetogram carrier obtained in this way has a square surface resistance of 3.9 * 10 * ohms. (Measured according to GSA specification WT-0051 a, section 3.6.2.3.)

_. '; _ Example 2 * °

2.8 g of electrically conductive carbon black and 1.3 g of fine graphite flakes are dispersed in a ball mill in a solution of 88 g of water, 10 g of trichloroacetic acid and 2 g of diehloroacetic acid. 11 g of this dispersion per square meter are applied to a 23 μ thick polyester carrier film stretched with an area stretching ratio of 1:12 and ^{heated by the action of an air stream of 140 °} C. for a period of 8 seconds, the film being held under tension by mechanical means . The amount of carbon black per square meter of film surface is 0.3 g. The layer thickness of the carbon black graphite layer is less than 1μ. The carbon black layer adheres well to the polyester carrier film.

A magnetic coating compound is applied to the as yet uncoated side of the polyester carrier film. This layer is dried by the action of a stream of air at 115 ° C. for a period of 25 seconds. The resulting layer of 9 μm thickness consists of 65 percent by weight acicular gamma iron (III) oxide, 30 ° / “of a soluble magnetogram tape is passed between two felt disks and loaded ^{in the guide with 150 p / m 2.} The loop goes through 50 cycles per minute. The measure of the abrasion resistance of the soot layer is the square surface resistance of the magnetic tape, measured on the soot layer. The values obtained are shown in Table II.

The examples are intended to illustrate the invention, but not to restrict it to these cases.

Table I.

Saturation remanence and squared surface resistance of magnetic tapes as a function of the soot concentration in the magnetic layer.

Weight percent
soot Saturation remanence
(Gauss) Square upper
sheet resistance
(Ohm) ao
0
. 2
4th
6 .--. 1,100
1 015
900
760 8.4-10 ¹⁴
, 4.7 x 10 ¹⁰
1.2-10 ⁷
, 2.0 x 10 ^{8 β}

Tables

Square surface resistance of carbon black coated Magnetogram carriers

Known magnetic tape carrier film containing binding material
Soot layer, ...

Magnetogram carrier
according to the invention

Wear time in hours 0 I 5 I 100

Square surface resistance

1.2-10 '

8.6 · 10 ⁵

8.3-10 ⁸ 8.9 x 10 ^B

5 _t 9 IQ ⁹ 9.8 10 ⁶

Table III

) y / "one

Polyester urethane, 3% lecithin and 2% dibutyl phthalate.

The square surface resistance of the magnetic recording medium obtained is 8.6 x 10 ^B ohms, measured on the soot layer (measurement method as specified in Example 1). An endless loop of this

65 Square surface resistance of magnetogram carriers

Commercially available computer tape (type 4610)

4.7 · 10 ⁸ ohms Commercially available computer tape (type 498)

2.4 x 10 ^e Ohm tape according to the invention (example no. 1)

3.9 x 10 * ohms tape according to the invention (example no.2)

8.6 x 10 ^s ohms

Claims (9)

Patent claims: 1. Magnetogram carrier, consisting of a biaxially stretched polyester carrier film and a Layer of ferromagnetic particles in high-polymer binders, characterized in that that the polyester carrier film has a binder-free, Has firmly adhering layer of conductive carbon black. 2. Magnetogram carrier according to claim 1, characterized in that it consists of a polyester carrier film exists, the surface of which has a binding has medium-free, firmly adhering layer of conductive carbon black, on which a further layer ferromagnetic particles is applied in high polymer binders. 3. Magnetogram carrier according to claim 1, characterized in that the polyester carrier film on one surface a binder-free layer of electrically conductive carbon black and on the the other surface is a layer of ferromagnetic particles in high-polymer binders having. 4. Magnetogram carrier according to Claims 1 to 3, characterized in that the polyester carrier film consists of at least 80 mole percent polyethylene terephthalate. 5. magnetogram carrier according to claims 1 to 4, characterized in that it has a square surface ^{resistance in the order of 10 8} to 10 ³ ohms. 6. magnetogram carrier according to claims ao 1 to 5, characterized in that it has a square surface ^{resistance in the order of 10 6} to 10 ⁴ ohms. 7. magnetogram carrier according to claims 1 to 4, characterized in that it is a binder-free, has firmly adhering soot layer that is no thicker than 2 μ. 8. magnetogram carrier according to claims 1 to 4, characterized in that it has a fixed adhesive, binder-free carbon black layer that is no thicker than 1 μ. 9. A method for producing a magnetogram carrier according to claims 1 to 8, characterized characterized in that a polyester carrier film with a dispersion of conductive carbon black in a liquid solvent or swelling agent for said polyester carrier films is treated, the Foil is subjected to heat that is sufficient to remove the solvent or swelling agent to evaporate, and that a coating material consisting of ferromagnetic particles dispersed in high polymer binders and a solvent, applied for said binder is and that this coating composition is dried by the action of heat and thereby is optionally hardened. 909 527/400