Magnetic recording medium

A magnetic recording medium having a layer containing as a lubricant one or more organo-polysiloxane compounds having the following formula (I): ##STR1## (wherein each of A.sub.1 and A.sub.2 is independently --CH.sub.3, --CH.sub.2 --CH.sub.2 --(CF.sub.2).sub.q --CF.sub.3 or --R.sub.1 OCOR.sub.2 ; R.sub.1 is a divalent hydrocarbon residue having 1 to 5 carbon atoms; R.sub.2 is a monovalent hydrocarbon residue having from 7 to 21 carbon atoms; each of l, m and n is independently O or an integer ranging from 1 to 200; and each of p and q is independently O or an integer ranging from 1 to 12; provided that when at least one of the groups A.sub.1 and A.sub.2 is the group --R.sub.1 OCOR.sub.2, each l, m and n may be O and that, when each group A.sub.1 and A.sub.2 is one of the groups other than the group --R.sub.1 OCOR.sub.2, each l and m may be O and n is an integer ranging from 1 to 200).

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is in the field of magnetic recording media including a 
non-magnetic base and a magnetic layer containing magnetizable particles 
dispersed in a binder. The invention is concerned with an improved 
lubricating layer consisting of one or more organo-polysiloxane compounds. 
2. Description of the Prior Art 
A magnetic recording medium which is used for audio recording, video 
recording, or other magnetic recording purposes during use is in contact 
with guide members, magnetic heads, and the like. In the case of a video 
tape recorder, where high tape velocities are encountered, the tape must 
have sufficiently high wear resistance and a relatively small friction 
coefficient if it is to run smoothly and steadily for a long time. 
Moreover, the magnetic powder layer including magnetizable particles on 
such a recording medium must be sufficiently bound to the base to resist 
shedding or loosening of the powder during use. The magnetic tape must 
also have good splicing ability. 
Magnetic recording media which have relatively high friction coefficients 
vibrate at the guide members and/or the magnetic heads during recording 
and/or reproducing so that the recorded signals or the reproduced signals 
deviate from the original signals with respect to frequency. In some 
cases, fluttering of the magnetic recording medium can occur to produce 
the so-called "Q" sound due to the vibration of the recording media. 
Various attempts have been made to overcome the above-described defects and 
to impart lubricity or smoothness to a magnetic recording media, but no 
completely satisfactory lubricant for magnetic recording media has yet 
been developed. For example, it has been suggested to use solid lubricants 
such as molybdenum disulfide, graphite or a wax such that the lubricant is 
mixed into the magnetic layer containing a magnetic powder such as 
gamma-Fe.sub.2 O.sub.3, and a binder, such as polyvinyl chloride. Such 
solid lubricants are ineffective to improve the durability of the magnetic 
recording media. When a large quantity of the solid lubricant is mixed 
into the magnetic layer, the magnetic performance of the recording media 
is impaired. It has also been suggested to use lubricants such as higher 
fatty acids or esters, or paraffinic hydrocarbons and silicone oils such 
as dimethylsilicone oil or diphenylsilicone oil as lubricating agents. 
These lubricants do not provide sufficient durability and lubricity so 
that magnetic recording media containing these lubricants cannot be 
effectively used in cassettes for video tape recorders. Magnetic recording 
media containing large quantities of such lubricants may cause "bleeding" 
or "blooming" resulting from the lubricant oozing or diffusing onto the 
surface of the magnetic layer and becoming separated therefrom. Bleeding 
or blooming which occur on the magnetic layer may cause a stick-slip in 
which layers of tape wound upon themselves stick to each other. 
It has further been suggested that certain organopolysilicone compounds 
could be employed as lubricants for providing lubricity to magnetic 
recording media. For example, U.S. Pat. No. 3,993,846 to Higuchi et al 
discloses a polyoxyalkylene substituted silicone compound having the 
formula: 
EQU RO(CHR"CH.sub.2 O).sub.n.sbsb.1 (SiCH.sub.3 CH.sub.3 O).sub.m (CH.sub.2 
CHR"O).sub.n.sbsb.2 R' 
(wherein R and R' stand for an aliphatic hydrocarbon group having from 8 to 
18 carbon atoms, R" is a hydrogen atom or methyl group, m is an integer 
ranging from 1 to 15 and n.sub.1 and n.sub.2 are integers whose sums range 
from 2 to 16). 
This lubricant exhibits considerable promise in providing an improved 
magnetic recording medium wherein at least some if not all of the 
aforementioned prior art problems are alleviated. 
U.S. Pat. No. 4,007,314 to Higuchi et al discloses an organosilicone 
lubricant compound having the formula: 
EQU (RCOO).sub.n Si(CH.sub.3).sub.4-n 
(wherein R is an aliphatic hydrocarbon group containing from 7 to 17 carbon 
atoms and n is an integer ranging from 1 to 3). 
This lubricant also exhibits considerable promise in providing a magnetic 
recording medium with improved lubrication properties. 
Hirano et al in U.S. Pat. No. 4,131,717 disclosed a magnetic recording 
medium including a non-magnetic base and a magnetic layer thereon which 
contains and/or is coated with an organopolysiloxane having an average 
unit represented by the formula: 
EQU (CH.sub.3)(RO).sub.n (R'COO).sub.m SiO.sub.3-n-m/2 
(wherein R is a monovalent hydrocarbon group having from 1 to 5 carbon 
atoms, R' is a monovalent aliphatic hydrocarbon group having from 7 to 17 
carbon atoms, n is zero or a positive number, m is a positive number 
provided that n+m is less than 3 and the number of Si atoms in a molecule 
of such organopolysiloxane ranges from 2 to 8). 
Magnetic recording media containing such lubricants exhibit a substantially 
reduced dynamic friction coefficient and a substantially reduced tendency 
for the magnetic layer to lose its magnetic properties, along with an 
improved splicing ability. 
In U.S. Pat. No. 4,007,313 to Higuchi et al there is disclosed a lubricant 
for magnetic recording media comprising an organosilicone-fluoride 
compound having the formula: 
##STR2## 
(wherein R is an aliphatic hydrocarbon group having from 7 to 17 carbon 
atoms and n is an integer ranging from 1 to 3). 
This lubricant also exhibits considerable promise in providing an improved 
magnetic recording medium. 
While the lubricants disclosed in the above prior patents are improvements 
over prior art lubricants, it is nevertheless desirable to provide even 
further improved lubricants for use with magnetic recording media. 
SUMMARY OF THE INVENTION 
The present invention seeks to provide an improved magnetic recording 
medium containing a lubricant that imparts improved lubricity or 
smoothness to the medium. The lubricant provides durability to the 
recording medium permitting it to run smoothly and steadily while being in 
contact with guide members and magnetic heads. The magnetic recording 
medium of the present invention contains a lubricant which can improve and 
stabilize magnetic performance in the still mode, which tends to vary over 
a period of time. 
The lubricant of the present invention provides improved lubricating 
properties to a magnetic recording medium whereby the defects and 
disadvantages prevailing in conventional and prior art lubricants can be 
substantially reduced. 
In accordance with the present invention, a magnetic recording medium is 
provided with a non-magnetic base and a magnetic layer formed thereon 
which includes magnetizable particles dispersed in a binder. The base or 
the overlying layer contains an improved lubricant which provides improved 
properties as hereinabove set forth. 
The lubricants used in the practice of the present invention are 
organo-polysiloxane compounds represented by the following formula (I): 
##STR3## 
(wherein each of A.sub.1 and A.sub.2 is independently --CH.sub.3, 
--CH.sub.2 --CH.sub.2 --(CF.sub.2).sub.q --CF.sub.3 or --R.sub.1 
OCOR.sub.2 ; R.sub.1 is a divalent hydrocarbon residue having 1 to 5 
carbon atoms; R.sub.2 is a monovalent hydrocarbon residue having from 7 to 
21 carbon atoms; each of l, m and n is independently 0 or an integer 
ranging from 1 to 200; and each of p and q is independently 0 or an 
integer ranging from 1 to 12; provided that when at least one of A.sub.1 
and A.sub.2 is the group --R.sub.1 OCOR.sub.2, each of l, m and n may be 0 
and that, when both A.sub.1 and A.sub.2 are groups other than the group 
--R.sub.1 OCOR.sub.2, each of l and m may be 0 and n is an integer ranging 
from 1 to 200).

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention provides an improved magnetic recording medium having 
a non-magnetic base and a magnetic layer thereon comprising magnetic or 
magnetizable particles dispersed in a binder, the base being provided with 
a layer which contains at least one of the lubricants described in this 
application. 
The organo-polysiloxane compounds which can be employed for the purposes of 
the present invention may be represented by the following formula (I): 
##STR4## 
(wherein each of A.sub.1 and A.sub.2 is independently --CH.sub.3, 
--CH.sub.2 --CH.sub.2 --(CF.sub.2).sub.q --CF.sub.3 or --R.sub.1 
OCOR.sub.2 ; R.sub.1 is a divalent hydrocarbon residue having 1 to 5 
carbon atoms; R.sub.2 is a monovalent hydrocarbon residue having from 7 to 
21 carbon atoms; each of l, m and n is independently 0 or an integer 
ranging from 1 to 200; and each of p and q is independently 0 or an 
integer ranging from 1 to 12; provided that when at least one of the 
groups A.sub.1 and A.sub.2 is the group --R.sub.1 OCOR.sub.2, each of l, m 
and n may be 0 and that, when both A.sub.1 and A.sub.2 are one of the 
groups other than the group --R.sub.1 OCOR.sub.2, each of l and m may be 0 
and n is an integer ranging from 1 to 200). 
The term "divalent hydrocarbon residue" referred to hereinabove is intended 
to mean a divalent, straight chained or branched chained, saturated or 
unsaturated, aliphatic hydrocarbon residue. The hydrocarbon residue may 
include a divalent, straight or branched chained, lower alkylene group or 
lower alkenylene group. The alkylene group referred to herein may include, 
for example, methylene, ethylene, propylene, methylethylene, 
ethylmethylene, butylene, pentylene, methylpropylene, ethylpropylene, 
methylbutylene and propylmethylene. The alkenylene group referred to 
herein may include, for example, ethenylene, propenylene, 
methylethenylene, butenylene, methylbutenylene, heptenylene and 
methylpropenylene. The term "monovalent hydrocarbon residue" may include a 
monovalent, straight or branched chain, saturated or unsaturated 
hydrocarbon residue. The monovalent hydrocarbon residue may include, a 
monovalent, straight or branched chain, higher alkyl or higher alkenyl 
group. The higher alkyl group may include, for example, heptyl, octyl, 
nonyl, decyl, undecyl, tridecyl, pentadecyl, heptadecyl, nonadecyl, 
heneicosyl, methylheptyl, ethylheptyl, methylnonyl, methylethylhexyl, 
methyltridecyl, propylhexadecyl, ethylnonadecyl and methyleicosyl. The 
higher alkenyl group may include, for example, heptenyl, octenyl, nonenyl, 
decenyl, undecenyl, tridecenyl, pentadecenyl, heptadecenyl, nonadecenyl, 
heneicosenyl, methylhexenyl, ethylpentenyl, methylmethylhexenyl, 
propylheptenyl, methyldodecenyl, ethyltridecenyl, methyltetradecenyl, 
ethylhexadecenyl, methyloctadecenyl and ethylnonadecenyl. 
In the aforesaid formula (I), it is preferred to restrict the quotient 
obtained by dividing n by the sum of l+m+n+2 to a value equal to or 
greater than 0.2. 
The organo-polysiloxane compounds to be employed as lubricants in the 
practice of the present invention may be prepared by several different 
procedures, for example, as follows: 
(1) Addition reaction procedure: 
The organo-polysiloxane compounds of formula (I) may be prepared by 
subjecting a silane compound represented by the following formula (II): 
##STR5## 
(wherein each of A.sub.3 and A.sub.4 is independently a hydrogen atom, 
--CH.sub.3 or --CH.sub.2 CH.sub.2 (CF.sub.2).sub.q CF.sub.3 ; and l, m, n, 
p and q have the same meanings as hereinabove defined) to an addition 
reaction with an ester compound represented by the formula (III): 
EQU R.sub.3 --OCOR.sub.2 
(wherein R.sub.3 is a monovalent unsaturated hydrocarbon residue and 
R.sub.2 has the same meaning as defined above) in the presence of a 
platinum catalyst. 
In formula (III), the term "monovalent unsaturated hydrocarbon residue" 
referred to hereinabove is intended to mean a group which provides the 
group R.sub.1 as defined in formula (I) when the addition reaction of the 
silane compound of the formula (II) with the ester compound of formula 
(III) is carried out. The monovalent unsaturated hydrocarbon residue may 
contain, for example, 3 to 5 carbon atoms. 
(2) Dehydrochlorination or dealkalization procedures: 
The organo-polysiloxane compounds of formula (I) may be prepared by 
reacting a compound represented by the formula (IV): 
##STR6## 
(wherein each of A.sub.5 and A.sub.6 is independently --CH.sub.3, 
--CH.sub.2 CH.sub.2 (CF.sub.2).sub.q CF.sub.3 or a halogenated hydrocarbon 
residue represented by the formula: --R.sub.1 X.sub.2 (in which X.sub.2 is 
a halogen atom); X.sub.1 is a halogen atom; and R.sub.1, l, m, n, p and q 
have the same meanings as defined hereinabove) with a fatty acid 
represented by the formula (V): 
EQU R.sub.2 --COOH 
(wherein R.sub.2 has the same meaning as defined hereinabove) or with a 
fatty acid salt represented by the formula (VI): 
EQU R.sub.2 --COOZ 
(wherein Z is an alkali metal or one valence of an alkaline earth metal and 
R.sub.2 has the same meaning as defined hereinabove). 
In the compound of the formula (IV), the term "halogen atom" referred to 
herein is intended to mean, for example, chlorine or bromine. The term 
"halogenated hydrocarbon residue" in the symbols A.sub.5 and A.sub.6 as 
represented by the group: R.sub.1 X.sub.2 means a group consisting of the 
divalent hydrocarbon residue R.sub.1 substituted by a halogen atom X.sub.2 
which is selected from, for example, chlorine and bromine. In the fatty 
acid salt of the formula (VI), the term "alkali metal" referred to therein 
means, for example, sodium or potassium and the term "alkaline earth 
metal" referred to therein means, for example, calcium. 
(3) Dechlorination or dehydration-esterification procedure: 
The organo-polysiloxane compounds of formula (I) may be prepared by 
reacting a hydroxy-containing compound represented by the formula (VII): 
##STR7## 
(wherein each of A.sub.7 and A.sub.8 is independently --CH.sub.3, 
--CH.sub.2 CH.sub.2 (CF.sub.2).sub.q CF.sub.3 or the group: --R.sub.1 OH; 
and R.sub.1, l, m, n, p and q have the same meanings as defined 
hereinabove) with an acid halide represented by the formula (VIII): 
EQU R.sub.2 --COX.sub.3 
(wherein X.sub.3 is a halogen atom and R.sub.2 has the same meaning as 
defined hereinabove) or with a fatty acid of the formula (V): 
EQU R.sub.2 --COOH 
(wherein R.sub.2 has the same meaning as defined hereinabove). 
In the acid halide of the formula (VIII), the term "halogen atom" referred 
to therein means a halogen atom as defined for the halogen atoms for the 
symbols X.sub.1 and X.sub.2 referred to hereinabove. 
In the organo-polysiloxane compounds of formula (I), where an ester moiety 
represented by the group --OCOR.sub.2 is bound through the divalent 
hydrocarbon residue represented by the group --R.sub.1 -- having from 1 to 
5 carbon atoms, the binding of the ester group to the Si atom is rendered 
much stronger than in instances where the ester group is joined directly 
to the Si atom without the interposition of the R.sub.1 group because 
hydrolysis may cause the bond between the ester group and the Si atom to 
decompose and eliminate the ester group which might otherwise provide 
lubricating properties to the magnetic recording medium. Accordingly, the 
presence of the R.sub.1 between the ester group and the Si atom serves to 
a great extent to reduce the deterioration in lubricating properties with 
passage of time. Although the number of carbon atoms in the R.sub.1 group 
is restricted to 5 as a matter of convenience because it is hard to 
provide substituents having more than 5 carbon atoms, there is no reason 
in theory why the substituent cannot have more than 5 carbon atoms and 
provide improved lubricating properties in the organo-polysiloxane 
compounds. 
The number of carbon atoms in the group R.sub.2 of the acyloxy group 
preferably ranges from 7 to 21 because a compound having an acyloxy group 
with less than 7 carbon atoms does not provide a sufficient decrease in 
the dynamic friction coefficient of the magnetic recording medium and 
tends to decrease durability of the same. An organo-polysiloxane compound 
having an acyloxy group of more than 21 carbon atoms, on the other hand, 
tends to cause excessive bleeding or blooming because it may cause a 
decrease in the solubility in the magnetic paint or cause an increase in 
the melting point of such compound. 
It is assumed that the presence of fluorine atoms in the substituent 
--CH.sub.2 CH.sub.2 (CF.sub.2).sub.p CF.sub.3 and/or the substituent 
--CH.sub.2 CH.sub.2 (CF.sub.2).sub.q CF.sub.3 tends to decrease the energy 
which may be produced during use on the surface of a magnetic layer or a 
coating containing an organo-polysiloxane compound of formula (I) leading 
to a decrease in the dynamic friction coefficient of a magnetic recording 
medium provided with such compound. An organo-polysiloxane compound having 
a substituent with more than 12 carbon atoms substituted with fluorine 
atoms tends to cause a decrease in solubility in magnetic paint and tends 
to raise the melting point of such compounds. An organo-polysiloxane 
compound having an SiO moiety or moieties with each or all of the symbols 
l, m and n exceeding the upper range or ranges tends to cause a decrease 
in compatibility with a binder. 
In accordance with the present invention, the organo-polysiloxane 
lubricants of formula (I) may be added or intermixed with magnetic 
particles and binders used in forming the magnetic layer formed on the 
non-magnetic base or the organopolysiloxane lubricants may be coated onto 
a magnetic layer as a top coat. The non-magnetic base may be provided with 
a back coating layer comprising the organo-polysiloxane lubricant on the 
surface opposite to the surface on which the magnetic layer is formed or 
the organo-polysiloxane lubricant may be added or intermixed with a back 
coat containing, for example, carbon or coated onto a back coat as a back 
top coat. 
FIG. 1A illustrates an example where the organo-polysiloxane lubricant of 
formula (I) is coated on a non-magnetic base 1 as a magnetic layer 2 
containing magnetizable particles and a binder. FIG. 1B illustrates a top 
coat 3 containing a lubricant coated on the magnetic layer 2. FIG. 1C 
illustrates an example wherein the non-magnetic base 1 has a magnetic 
layer 2 thereon and is provided with a back coating layer 4 on the surface 
of the non-magnetic base opposite to the surface coated with the magnetic 
layer 2. FIG. 1D shows an example of coating a back coat 5 containing the 
organo-polysiloxane lubricant of formula (I) on the surface of the 
non-magnetic base 1 with the magnetic layer 2 formed thereon opposite to 
the surface on which the back coat 5 is coated. FIG. 1E illustrates an 
example where a back top coat 6 is formed on the back coat 5 of the 
embodiment as shown in FIG. 1D. 
In instances where the organo-polysiloxane lubricant of formula (I) is 
added within a magnetic layer as shown in FIG. 1A, it is preferred that 
the amount of the organo-polysiloxane compound range from about 0.5 to 
about 7 parts by weight per 100 parts by weight of magnetizable particles. 
The back coat 5 as shown in FIG. ID may preferably contain lubricant in an 
amount of about 0.5 to 5 parts by weight. In embodiments where the 
organo-polysiloxane compound of formula (I) is employed for a top coat or 
a back top coat, the amounts of organo-polysiloxane lubricant may 
preferably range from about 1 to 1,000 mg/m.sup.2. It should further be 
noted that the organo-polysiloxane lubricants of formula (I) may be 
employed singly or in a mixture thereof or with a lubricant of the 
conventional type. 
The magnetic powder or magnetizable particles to be used in combination 
with the organo-polysiloxane compound of the formula (I) for forming a 
magnetic layer in magnetic recording media in accordance with the present 
invention may be composed of any available magnetic or magnetizable 
material, such as gamma hematite (.gamma.-Fe.sub.2 O.sub.3); magnetite 
(Fe.sub.3 O.sub.4); iron oxides of non-stoichiometric oxidation compounds 
between gamma hematite and magnetite; gamma hematite or magnetite doped 
with non-ferrous atoms, such as cobalt; chromium dioxide (CrO.sub.2); 
barium ferrite; magnetic or magnetizable alloys, such as an iron-cobalt 
alloy (Fe-Co), iron nickel alloy (Fe-Ni), iron-cobalt-nickel alloy 
(Fe-Co-Ni), iron-cobalt-boron alloy (Fe-Co-B), iron-cobalt-chromium-boron 
alloy (Fe-Co-Cr-B), manganese-bismuth alloy (Mn-Bi), manganese-aluminum 
alloy (Mn-Al) or iron-cobalt-vanadium alloy (Fe-Co-V); iron nitride, 
mixtures of the above or other magnetic or magnetizable materials. 
The binder used in magnetic recording media produced in accordance with the 
present invention may be any resinous binder which can be employed for 
this purpose. The resinous binder may include, for example, vinyl 
chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-vinyl 
alcohol copolymers, vinyl chloride-vinyl acetate-maleic acid copolymers, 
vinyl chloride-vinylidene chloride copolymers, vinyl 
chloride-acrylonitrile copolymers, acrylic acid ester-acrylonitrile 
copolymers, acrylic acid ester-vinylidene chloride copolymers, methacrylic 
acid ester-vinylidene chloride copolymers, methacrylic acid ester-styrene 
copolymers, thermoplastic polyurethane resins, phenoxy resins, vinyl 
polyfluoride, vinylidene chloride-acrylonitrile copolymers, 
butadiene-acrylonitrile copolymers, acrylonitrile-butadiene-acrylic acid 
copolymers, acrylonitrile-butadiene-methacrylic acid copolymers, polyvinyl 
butyral, polyvinyl acetal, cellulose derivatives, styrene-butadiene 
copolymers, polyester resins, phenol resins, epoxy resins, thermosetting 
polyurethane resins, urea resins, melamine resins, alkyd resins, 
urea-formaldehyde resins, mixtures thereof or other like resinous binders. 
A reinforcement material capable of being used in the magnetic layer of 
magnetic recording media in accordance with the present invention may 
include, for example, aluminum oxide, chromium oxide, silicon oxide or 
mixtures thereof. 
Magnetic recording media produced in accordance with the present invention 
may also contain antistatic agents of the type that can be used with 
magnetic recording media. An example of a suitable antistatic agent is 
finely divided carbon black. Further, dispersing agents, such as lecithin 
and the like, may be added to a magnetic layer of a magnetic recording 
medium in accordance with the present invention. 
The organic solvent to be used with the magnetic powder or magnetizable 
particles and the binder for preparing a magnetic paint to be coated on a 
non-magnetic base may include, for example, alcohols, such as methanol, 
ethanol, propanol and butanol; ketones, such as acetone, 
methylethylketone, methylisobutylketone and cyclohexanone; esters, such as 
methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and glycol 
diacetate; ethers, such as monoethylether; glycol ethers, such as ethylene 
glycol monoethyl ether, ethylene glycol dimethyl ether and dioxane; 
aromatic hydrocarbons, such as benzene, toluene and xylene; aliphatic 
hydrocarbons, such as hexane and heptane; nitropropane; mixtures thereof 
or other suitable organic solvents. 
The magnetic recording medium in accordance with the present invention may 
comprise any of the known forms, such as magnetic recording tapes having a 
flexible non-magnetic film base and magnetic discs having a relatively 
rigid non-magnetic base. The flexible non-magnetic film bases may include, 
for example, polyesters, such as polyethylene terephthalate; polyolefins, 
such as polypropylene; cellulose derivatives, such as cellulose diacetate 
and cellulose triacetate; polycarbonates; polyimides; metallic materials, 
such as aluminum and copper; papers; or any other suitable materials. The 
rigid non-magnetic bases may be composed of, for example, a ceramic or a 
metal, such as aluminum plate. 
In embodiments where the organo-polysiloxane compound of the formula (I) is 
employed in the back coat of a magnetic recording medium in accordance 
with the invention, the back coat may comprise, for example, carbon, such 
as furnace carbon, channel carbon, acetylene carbon, thermal carbon and 
lamp carbon; inorganic pigments, such as gamma-FeOOH, alpha-Fe.sub.2 
O.sub.3, Cr.sub.2 O.sub.3, TiO.sub.2, ZnO, SiO, SiO.sub.2.2H.sub.2 O, 
Al.sub.2 O.sub.3.2SiO.sub.2.2H.sub.2 O, 3MgO.4SiO.sub.2.H.sub.2 O, 
MgCO.sub.3.Mg(OH).sub.2.3H.sub.2 O, Al.sub.2 O.sub.3 and Sb.sub.2 O.sub.3. 
In instances where the organo-polysiloxane compound of the formula (I) is 
employed in the top coat formed on the surface of the magnetic layer or 
the back coat or in the coating layer coated on the surface of the 
non-magnetic base, the organo-polysiloxane lubricant or lubricants may be 
added or intermixed with one or more of the aforesaid binders in one or 
more of the aforementioned organic solvents. 
The following organo-polysiloxane compounds which were employed in the 
working examples in the practice of the present invention were prepared as 
follows: 
Preparation of Organo-polysiloxane Compound I 
An organo-polysiloxane compound I having the following formula was 
prepared: 
##STR8## 
A mixture of 212 grams of allyl caproate, 0.26 gram of a 2% 2-ethylhexanol 
solution of chloroplatinic acid and 200 grams of toluene was charged into 
a four-necked flask equipped with a reflux condenser, a thermometer, a 
stirrer and a dropping funnel and heated to 80.degree. C. To this mixture 
was added dropwise 201 grams of a silicone compound having the following 
formula: 
##STR9## 
The dropwise addition of the silicone compound caused an exothermic 
reaction which raised the solution temperature to 106.degree. C. at the 
time when the addition was completed. The solution was further heated to 
110.degree. C. at which it was reacted for 5 hours. The removal of toluene 
by distillation under reduced pressure gave 408 grams of pale yellow 
liquid which in turn was determined to have the structure as hereinabove 
set forth by measurements for its infrared absorption spectrum (IR) and 
nuclear magnetic resonance (NMR). Its specific gravity at 25.degree. C. 
was 1.048, its viscosity was 133 centistokes, and its refractive index was 
1.4252. 
Preparation of Organo-polysiloxane Compound II 
The organo-polysiloxane compound II has the following formula: 
##STR10## 
A three-necked flask equipped with a reflux condenser, a stirrer, and a 
thermometer was supplied with a mixture of 40.5 grams of triethylamine, 
300 grams of toluene and 138.2 grams of a silicone compound having the 
following formula: 
##STR11## 
After the mixture was heated to 80.degree. C., 113.8 grams of stearic acid 
were added thereto with stirring. The mixture was reacted for 7 hours 
under reflux of toluene and then cooled to precipitate triethylamine 
hydrochloride which in turn was removed by filtration. The removal of low 
boiling point materials under reduced pressure gave 219.6 grams of a pale 
yellow waxy solid which was found to have a melting point of 54.degree. C. 
and confirmed to have the structure as hereinabove set forth by 
measurements of its infrared absorption spectrum and nuclear magnetic 
resonance. 
Preparation of Organo-polysiloxane Compounds III-XIV 
The procedures employed for the preparation of the organo-polysiloxane 
compound I or II were followed to provide organo-polysiloxane compounds 
III to XIV, inclusive, as follows: 
##STR12## 
A magnetic paint composition which was employed for all the working 
examples for the magnetic recording media in accordance with the present 
invention had the following components: 
______________________________________ 
Components Parts by weight 
______________________________________ 
gamma-Fe.sub.2 O.sub.3 
100 
Vinyl chloride-vinyl 
acetate copolymer 
(trade name "VAGH", manufac- 
tured by Union Carbide Corp.) 
18 
Polyurethane resin 
(trade name "Estan 5702", 
manufactured by 
B. F. Goodrich Co.) 12 
Carbon (antistatic agent) 
0.5 
Lecithin (dispersing agent) 
1.0 
Solvents 
Methylethylketone 150 
Methylisobutylketone 
150 
______________________________________ 
EXAMPLE 1 
To the aforesaid magnetic paint composition were added 2.0 parts by weight 
of Compound I per 100 parts by weight of gamma-Fe.sub.2 O.sub.3, and the 
mixture was ball milled for 24 hours. After filtration, 3 parts by weight 
of isocyanate were added thereto and the mixture was stirred for 30 
minutes. The resulting mixture was then coated on a 12-micron thick 
polyethylene terephthalate film base so as to give a dry film thickness of 
5 microns. The film base was oriented and rolled upon itself after drying. 
The rolled film was then subjected to surface treatment and cut to a half 
inch. 
The tape thus prepared was then measured for its "still" performance, 
dynamic friction coefficient, and degree of bleeding or blooming by 
visible observation. The results are shown in Table I below. 
EXAMPLES 2-9 
The procedures of Example 1 were followed with the exception that, in place 
of Compound I, each of 2.0 parts by weight, per 100 parts by weight of 
gamma-Fe.sub.2 O.sub.3, of Compound III (Example 2), Compound IV (Example 
3), Compound V (Example 4), Compound VI (Example 5), Compound VII (Example 
6), Compound VIII (Example 7), Compound IX (Example 8) and Compound XIV 
(Example 9) was added. 
The results of their performance with respect to still performance, dynamic 
friction coefficient and a degree of blooming are shown in Table I below. 
The tape prepared in accordance with Example 9 was also measured for 
variations in "still" performance with periods of time in an atmosphere 
having a temperature of 45.degree. C. and a relative humidity of 80%. The 
results are shown in FIG. 2 as line A. 
EXAMPLES 10-13 
The procedures of Example 1 were followed with the exception that, in place 
of 2.0 parts by weight of Compound I, 1.0 part by weight of Compound II 
(Example 10), Compound X (Example 11), Compound XII (Example 12) and 
Compound XIII (Example 13), respectively, was added. 
The results of their performance are shown in Table I below. 
EXAMPLE 14 
The procedures of Example 1 were followed with the exception that, in place 
of 2.0 parts by weight of Compound I, 3.0 parts by weight of Compound XI 
per 100 parts by weight of the magnetic powder were added. 
The results of its performance are shown in Table I below. 
EXAMPLE 15 
The procedures of Example 1 were followed by varying amounts of Compound IX 
to be employed with the aforesaid magnetic paint composition. The 
resulting tapes were determined for their "still" performance and dynamic 
friction coefficients as illustrated in FIG. 3. FIG. 4 illustrates the 
degrees of bleeding or blooming which occurred on the tapes tested. It was 
found in FIGS. 3 and 4 that the preferred amounts of Compound IX and 
consequently the organo-polysiloxane compounds of the formula (I) ranged 
from about 0.5 to about 7 parts by weight. 
Where the lubricant was employed in amounts lower than 0.5 parts by weight, 
the still performance was made shorter while dynamic friction coefficients 
(.mu.d) and degrees of bleeding or blooming were sufficient. Where the 
lubricant was employed in amounts larger than 7 parts by weight, on the 
other hand, increases in the dynamic friction coefficient and the degree 
of blooming occurred. 
COMATIVE EXAMPLES 1-2 
Conventional lubricants were employed with the aforesaid magnetic paint 
composition for comparative purposes in place of the organo-polysiloxane 
lubricants in accordance with the present invention. Comparative Example 1 
employed dimethylsilicone oil (trade name "KF 96", manufactured by 
Shin-Etsu Chemical Co., Ltd.) and Comparative Example 2 employed 
methylphenylsilicone oil (trade name "KF 54", manufactured by Shin-Etsu 
Chemical Co., Ltd.) as lubricants. 
The results for their performance are also shown in Table I below for 
comparative purposes. 
COMATIVE EXAMPLE 3 
The tape was prepared by following the procedures of Example 14 with the 
exception that, in place of Compound I, there was used an 
organo-polysiloxane lubricant having the following formula: 
##STR13## 
The results of its performance are shown in Table 1 below. 
Following Comparative Example 3, the tapes were prepared by using the 
organo-polysiloxane lubricant of the above formula in 0.5 and 7 parts by 
weight, respectively. 
Their still performance when measured as with Example 9 are also shown in 
FIG. 2 as line B. 
TABLE I 
______________________________________ 
Still 
Performance.sup.1 
Dynamic Friction.sup.2 
Degree of 
Tapes (min.) Coefficient (.mu.d) 
Blooming.sup.3 
______________________________________ 
Example 1 
more than 60 
0.190 Little 
Example 2 
" 0.217 " 
Example 3 
" 0.186 " 
Example 4 
" 0.280 " 
Example 5 
" 0.279 " 
Example 6 
" 0.130 " 
Example 7 
" 0.162 " 
Example 8 
" 0.137 " 
Example 9 
" 0.145 " 
Example 10 
more than 30 
0.241 " 
Example 11 
" 0.169 " 
Example 12 
" 0.205 " 
Example 13 
" 0.200 " 
Example 14 
more than 60 
0.335 " 
Comparative 
Example 1 
less than 5 
0.400 Some 
Comparative 
Example 2 
" 0.443 " 
Comparative 
Example 3 
" 0.200 Little 
______________________________________ 
.sup.1 The term "still performance" referred to throughout the 
specification is defined as the period of time required for reduction of 
the reproduction output to onehalf of the original reproduction output in 
still mode where an upper rotary cylinder with a magnetic head is rotated 
while the tape is not transported. 
.sup.2 The dynamic friction coefficient (.mu.d) is measured as follows: A 
tape of 1/4 inch width is contacted with the periphery of a brass cylinde 
over about a quadrant of the peripheral surface of such cylinder. One end 
of the tape is horizontally fixed to a support and a weight of 100 grams 
is fixed to the other free end of the tape to provide a given tension on 
the latent portion of the tape. The cylinder is then controllably rotated 
at such a rate that the peripheral speed thereof is 0.75 mm per second 
relative to the tape. Tension gauges are arranged on the tape between the 
weight and the cylinder and between the cylinder and the support 
respectively, whereby tensions t.sub.1 and t.sub.2 are then measured. The 
dynamic friction coefficient (.mu.d) is then calculated by the following 
equation: 
##STR14## 
.sup.3 The degree of blooming or bleeding is visibly observed and rated i 
accordance with an extent to which the blooming or bleeding occurs on the 
surface of a tape. 
EXAMPLES 16-18 
A magnetic layer was formed on the surface of a polyethylene terephthalate 
by following the procedures of Example 1 with the exception that 1.5 parts 
by weight of squalane (C.sub.30 H.sub.62) was used in place of the 
lubricant. 
On the surface of the magnetic layer on the non-magnetic layer was coated a 
1% isopropylalcohol solution of each of Compound I, II and XI, 
respectively, as a top coat as shown in FIG. 1B, so as to amount to 43 
mg/m.sup.2. 
COMATIVE EXAMPLES 4-6 
The procedures of Example 16 were followed with the exception that, in 
place of the organo-polysiloxane lubricants of the formula (I), the 
conventional lubricants of Comparative Example 1 and Comparative Example 2 
and the organo-polysiloxane compound of Comparative Example 3 were 
employed, respectively. 
The tapes obtained in Examples 16 to 18 and Comparative Examples 4 to 6, 
respectively, were determined for still performance, dynamic friction 
coefficient and "Q" sound. The test results are shown in Table II below. 
TABLE II 
______________________________________ 
Still 
Performance 
Dynamic Friction 
Tapes (min.) Coefficient (.mu.d) 
"Q" sound.sup.4 
______________________________________ 
Example 16 
more than 60 
0.182 None 
Example 17 
" 0.195 " 
Example 18 
" 0.165 " 
Comparative Pretty 
Example 4 
less than 10 
0.386 much 
Comparative Pretty 
Example 5 
" 0.410 much 
Comparative 
Example 6 
" 0.187- None 
______________________________________ 
.sup.4 The "Q" sound (fluttering of magnetic recording tape is determined 
by loading the 1/4 inch tapes into a professional tape recorder and 
running it under a back tension. 
EXAMPLE 19-20 
A polyethylene terephthalate base is coated with a 0.1% "Freon" solution of 
each of Compound XIV (Example 19) and Compound X (Example 20), 
respectively, so as to amount to 2.1 mg/m.sup.2 as a coating on the 
surface opposite to the surface on which the magnetic layer is formed. 
The tapes were determined for their dynamic friction coefficient, .mu.d, 
respectively, at the first running and the 10th running. The results are 
shown in Table III. 
COMATIVE EXAMPLE 7 
A tape of Example 19 without any coating containing an organo-polysiloxane 
lubricant in accordance with the present invention was prepared and tested 
for its dynamic friction coefficient, .mu.d. The result is shown in Table 
III below. 
TABLE III 
______________________________________ 
Dynamic Friction Coefficient, .mu.d 
Tapes First Running 10th Running 
______________________________________ 
Example 19 0.188 0.241 
Example 20 0.157 0.196 
Comparative 
Example 7 0.254 0.319 
______________________________________ 
EXAMPLE 21 
A paint composition having the following components was employed for a back 
coat to be coated on the surface opposite to the surface on which the 
magnetic layer was coated: 
______________________________________ 
Components Parts by weight 
______________________________________ 
Carbon 100 
Polyurethane resin (trade 
name "Estan 5702") 50 
Epoxy resin (trade name 
"Epiclon 351", manufactured 
by Dainippon Ink & Chemical 
Co., Ltd.) 50 
Methylethylketone 400 
Toluene 400 
"Desmodur L" (trade name of 
Bayer A.G.) 20 
______________________________________ 
The mixture was mixed with 4 parts by weight of Compound XIV and coated on 
the opposite side of a base having a magnetic layer thereon so as to give 
a dry film thickness of 3 microns as a back coat as shown in FIG. 1D. 
The dynamic friction coefficients were found to be 0.150 .mu.d at the first 
running and 0.160 at the 10th running when measured in the same manner as 
hereinabove set forth. 
EXAMPLE 22 
A coating of Compound XIV was formed on the back coat as in Example 21 as a 
top back coat so as to be coated in an amount of 43 mg/m.sup.2 as shown in 
Table 1E. The dynamic friction coefficients of this tape were found to be 
0.167 .mu.d at the first running and 0.167 .mu.d at the 10th running.