Ink composition

An ink composition particularly well suited for use in an ink jet printer wherein the ink is jetted at temperatures higher than room temperature. The ink composition includes a metallic complex solvent dye coloring material dispersed in a vehicle of at least one high molecular weight alkyl amine, at least one high molecular weight fatty acid and carnauba wax.

BACKGROUND OF THE INVENTION 
This invention relates to an ink composition which is solid or semi-solid 
at room temperature, and more particularly to an ink composition including 
a metallic complex-type solvent dye which can be used in an ink jet 
recording device wherein the ink is maintained at temperatures above room 
temperature for extended periods of time. 
Ink jet recording is superior to other recording methods because it is 
quiet and can print at high speed. Conventional ink compositions for ink 
jet recording include water based compositions. Recording is accomplished 
by allowing the ink to permeate into the recording paper. Unfortunately, 
with water based compositions, the ink drop tends to blot as it permeates 
fully into the paper. This is particularly true when lesser quality, 
absorbent paper is used. In this case, the edges of a recorded dot of ink 
are unclear and printing quality deteriorates. 
Ink jet recording methods for eliminating defects in water based inks are 
disclosed in U.S. Pat. Nos. 4,390,369, 4,484,948 and 4,659,383 and 
Japanese Patent Application Laid-Open No. 108271/83. In these methods, a 
wax based hot-melt ink composition, which is solid at room temperature, is 
heated so that it melts and the melted ink is propelled onto the recording 
paper. The ink solidifies on the surface of the paper as it cools to form 
a recorded dot. These ink compositions have poor resistance to heat, 
especially when exposed to elevated temperatures over long time periods. 
It is possible to improve the heat resistance of the wax based ink by 
addition of an antioxidant. However, solvent complex dyes, particularly 
metallic complex solvent dyes which have especially good heat resistance, 
dissolve poorly in solid waxes and can not be used. Therefore, a solvent 
dye having good solubility in relatively polar waxes, and having poor heat 
resistance is used, for example, C.I. SOLVENT BLACK 3,7. Thus, the solvent 
dyes used in hot-melt ink compositions tend to decompose and turn brown 
when subjected to high temperatures over long time periods. 
Accordingly, it is desirable to develop an improved ink composition for ink 
jet recording which avoids these shortcomings of the prior art. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the invention, an ink composition 
for use in an ink jet printer including a metallic complex solvent dye in 
a vehicle including at least one high molecular weight alkyl amine, at 
least one high molecular weight fatty acid and carnauba wax is provided. 
The vehicle is a solid or semi-solid material having a melting point or 
pour point above room temperature. The ink composition includes between 
about 0.1 and 10 weight percent of the metallic complex solvent dye, 0.1 
and 10 weight percent of at least one high molecular weight alkyl amine, 
0.1 and 30 weight percent of at least one high molecular weight fatty acid 
and 1 and 30 weight percent carnauba wax, based on the total weight of the 
composition. The ink composition ca be used in an ink jet printer wherein 
the ink composition is maintained at a temperature above room temperature. 
Accordingly, it is an object of the invention to provide an improved ink 
composition. 
A further object of the invention is to provide an improved ink composition 
which does not discolor when maintained at high temperature over a long 
time period. 
It is another object of the invention to provide an improved ink 
composition including at least one metallic complex solvent dye having 
improved heat resistance. 
Still another object of the invention is to provide an ink composition 
which is solid or semi-solid and can be used in an ink jet printer at a 
temperature higher than room temperature. 
Still a further object of the invention is to provide an improved ink jet 
ink composition including at least one high molecular weight alkyl amine, 
at least one high molecular weight alkyl fatty acid and carnauba wax. 
Yet another object of the invention is to provide a method of preparing an 
improved ink jet printing ink composition. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification. 
The invention accordingly comprises the several steps and the relation of 
one or more of such steps with respect to each of the others and the 
composition possessing the characteristics, properties, and the relation 
of components which will be exemplified in the composition hereinafter 
described, and the scope of the invention will be indicated in the claims.

DETAILED DESCRIPTION OF THE INVENTION 
An ink composition for use in an ink jet printer which is solid or 
semi-solid at room temperature includes a vehicle (carrier) for 
transporting a coloring material. The coloring material is a metallic 
complex-type solvent dye. The vehicle includes at least one high molecular 
weight alkyl amine, at least one high molecular weight fatty acid and 
carnauba wax which has a melting point or pour point above room 
temperature. The ink composition includes between about 0.1 and 10 weight 
percent of the metallic complex solvent dye, between about 0.1 and 10 
weight percent of at least one high molecular weight alkyl amine, between 
about 0.1 and 30 weight percent of a high molecular weight fatty acid and 
between about 1 and 30 weight percent carnauba wax based on the total 
weight of the composition. The ink composition may also include additional 
materials such as paraffins, paraffin waxes, micro-crystalline waxes, 
synthetic waxes and antioxidants. 
Generally, the metallic complex solvent dyes used in the ink composition 
are soluble in polar solvents such as low molecular weight aliphatic 
alcohols, but have relatively poor solubility in low polarity waxes. 
However, metallic complex dyes dissolve in a mixture of at least one high 
molecular weight alkyl amine and at least one high molecular weight fatty 
acid. Moreover, the metallic complex solvent dye dissolved in the high 
molecular weight alkyl amine and high molecular weight fatty acid has good 
solubility in non-polar carnauba wax. 
The metallic complex solvent dyes used in the ink composition are generally 
metal complexes of compounds containing azo groups (--N.dbd.N--) which are 
linked to sp.sup.2 hybridized carbon atoms. The metallic complex solvent 
dye should be present between about 3 and 10 weight present, based on the 
total weight of the ink composition. The metallic complex solvent dyes 
include 
##STR1## 
C.I. Acid Red 38 (Perlon Fast Red BS), C.I. Acid Violet 78 (Geigy-Irgalan 
Brown Violet DL), C.I. Acid Black 52 (Nylon Black GL), Palatine Fast 
Violet SRN (BASF), and C.I. Acid Yellow 99 (BASF-Palatine Fast Yellow 
GRN). 
The ink compositions in accordance with the invention are prepared by 
mixing a metallic complex solvent dye with at least one high molecular 
weight alkyl amine and at least one high molecular weight fatty acid and 
the mixture is stirred at a temperature of at least 80.degree. C. to 
dissolve the dye. Carnauba wax is then added to the mixture and stirred. 
Any additional materials are added and the mixture is stirred at a 
temperature of at least 80.degree. C. to form a uniformly dissolved 
mixture. If necessary, the mixture is filtered at high temperature under 
fusing conditions. 
The viscosity of the ink composition at a temperature or between about 
100.degree. C. and 200.degree. C. is less than about 15.0 mPa.s which 
allows for proper droplet formation and jetting stability. Preferably, the 
viscosity is between about 7.0 about 2.0 mPa.s in order to obtain a high 
speed printing response of 2 to 3 kHz or higher. 
The following components are those which are desirable for use in the ink 
compositions prepared in accordance with the invention: 
1. High Molecular Weight Amines 
The high molecular weight amine is preferably a wax having at least 14 
carbon atoms. Acceptable high molecular weight amines include: Stearyl 
amine, distearyl amine, tristearyl amine, cetyl amine, dicetyl amine, 
tricetyl amine, N-ethyl-cetyl amine, myristyl amine, dimyristyl amine, and 
the like; 
2. High Molecular Weight Fatty Acids 
The high molecular weight fatty acid is preferably a fatty acid having at 
least about 15 carbon atoms. Acceptable high molecular weight fatty acids 
include: Lauric acid, palmitic acid, stearic acid, behenic acid, brassidic 
acid, and the like; 
3. Carnauba Wax 
Carnauba wax No. 1 (Noda Wax Co.) 
4. Metallic Complex Solvent Dyes 
Aizen Spilon Black BH, Aizen Spilon Black GSH special, Aizen Spilon 
Black BLH special (Hodogaya Chemical Co. Ltd.) 
Vali Fast Black 3804 (Orient Kagaku Co. Ltd.) 
5. Additional Materials 
a. Paraffins 
n-Paraffins and isoparaffins having between 23-32 carbon atoms. 
b. Paraffin Waxes 
Nos. 115, 120, 125, 130, 135, 140, 150, 155 
NHP-3, 9, 10, 11 
SP-0145, 1035, 3040, 3035, 0110 (Nippon Seiroh Co. Ltd.) 
c. Micro-crystalline Wax 
Hi-Mic-2095,1080,1045 (Nippon Seiroh Co. Ltd.) 
d. Synthetic Waxes 
Stearon, decanediol, monostearine, dodecanediol. 
e. Other Materials 
Antioxidants for limiting the oxidation of the ink composition. 
An acceptable ink composition can be prepared with the following 
composition: between about 5 and 10 weight percent C.I. Acid Black 123 
(Vali Fast Black 3804); between about 3 and 7 weight percent cetyl amine; 
between about 5 and 15 weight percent carnauba wax; and between about 45 
and 72 weight percent paraffin wax. 
The following examples are set forth to describe ink compositions prepared 
in accordance with the invention more clearly. They are set forth for 
purposes of illustration only and are not intended in a limiting sense. 
EXAMPLE 1 
______________________________________ 
Composition Weight % 
______________________________________ 
Coloring Material: 
Vali Fast Black 3804 
7.0 
Vehicle: Cetyl amine 5.0 
Stearic acid 10.0 
Carnauba Wax No. 1 
20.0 
Paraffin Wax HNP 3 
57.0 
Additional Materials: 
Antioxidant; 1.0 
dimyristyl thio 
dipropyonate 
______________________________________ 
Cetyl amine and stearic acid were mixed ad Vali Fast Black 3804 was added 
to the mixture. The mixture was stirred at 100.degree. C. Carnauba Wax No. 
1 was added and the mixture was stirred at 100.degree. C. Paraffin Wax HNP 
3 and antioxidant were added and stirred at 100.degree. C. The mixture was 
filtered under pressure using a teflon membrane filter with 5 .mu.m pores 
to yield an ink composition having a viscosity of 5.5 mPa.s at a 
temperature of 120.degree. C. 
A conventional "ink on demand" type of ink jet head which can use hot melt 
ink was used to print dots with the ink described above. The ink jet was 
filled with this ink and bit image printing and character printing were 
performed on generally high quality paper, bond paper and PPC paper. 
The various ink compositions were evaluated for ability not to fade after 
being maintained at high temperatures using the following tests: 
Heat Fading Test I 
Ink was poured into a Pyrex glass vessel, maintained at 180.degree. C. for 
1000 hours, and printing was performed on PPC paper. The ink compositions 
were evaluated based on the ink concentration as follows: 
______________________________________ 
OD value lowered less than 10% 
ideal (.circleincircle.) 
OD value lowered 10-20% 
suitable (.largecircle.) 
OD value lowered 20% or more 
not suitable 
(X) 
______________________________________ 
The OD value of the ink composition of this Example I before the test was 
1.35 and the OD value after the test was 1.25. Thus, the OD value was 
lowered less than 10% which is considered an ideal result. 
Heat Fading Test II 
Ink was poured into a Pyrex glass vessel, and the temperature was 
maintained at 200.degree. C. for 24 hours and then at room temperature for 
24 hours. This process was repeated twenty times. The ink was then printed 
onto PPC paper. The ink compositions were evaluated based on the ink 
concentration as follows: 
______________________________________ 
OD value lowered less than 10% 
ideal (.circleincircle.) 
OD value lowered 10-20% 
suitable (.largecircle.) 
OD value lowered 20% or more 
not suitable 
(X) 
______________________________________ 
The OD value of the ink composition of this Example I before Heat Fading 
Test II was 1.35 and the OD value after the test was 1.22. Thus, the OD 
value was lowered less than 10% which is considered an ideal result. 
The ink compositions in accordance with the invention shown as Examples 2-9 
were prepared in the same manner as in Example 1. The specific components 
of each ink composition are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Vehicles, Additives, Comparative 
Color materials, Physical-properties, 
Examples Examples 
Others 2 3 4 5 6 7 8 9 1 2 3 
__________________________________________________________________________ 
Kinds of higher alkyl amines 
wt % 
Stearyl amine 0.3 
-- -- -- -- -- -- 10.0 
-- -- -- 
Distearyl amine -- 2.0 
-- -- -- -- -- -- -- -- -- 
Tristearyl amine -- -- 4.0 
-- -- -- -- -- -- -- -- 
Dicetyl amine -- -- -- 6.0 
-- -- -- -- -- -- -- 
N-ethyl-cetyl amine 
-- -- -- -- 7.0 
-- -- -- -- -- -- 
Myristyl amine -- -- -- -- -- 8.0 
-- -- -- -- -- 
Dimyristyl amine -- -- -- -- -- -- 10.0 
-- -- -- -- 
Fatty acid 
Lauric acid 25.0 
-- -- -- -- -- -- 30.0 
-- -- -- 
Palmitic acid -- 30.0 
-- -- -- -- -- -- -- -- -- 
Stearic acid -- -- 20.0 
-- -- -- -- -- -- 20.0 
-- 
Behenic acid -- -- -- 15.0 
-- 5.0 
-- -- 15.0 
-- -- 
Brassidic acid -- -- -- -- 5.0 
-- 0.3 
-- -- -- -- 
Carnauba wax No. 1 
1.0 
3.0 
5.0 
10.0 
15.0 
20.0 
30.0 
30.0 
15.0 
20.0 
30.0 
Metallic solvent complex dyes 
Aizen Spilon Black BH 
3.0 
5.0 
10.0 
-- -- -- -- 10.0 
-- -- -- 
Aizen Spilon Black GSH special 
-- -- -- 5.0 
8.0 
-- -- -- -- -- -- 
Aizen Spilon Black RLH special 
-- -- -- -- -- 6.0 
-- -- 5.0 
-- -- 
Vali Fast Black 3804 
-- -- -- -- -- -- 10.0 
-- -- -- -- 
Paraffin waxes 
HNP-9 30.0 
-- -- -- -- -- -- -- -- -- 40.0 
HNP-10 -- 30.0 
-- -- -- -- -- -- -- -- -- 
HNP-11 -- -- 40.0 
-- -- -- -- -- -- -- -- 
HNP-0145 -- -- -- -- 40.0 
-- -- -- -- -- -- 
SP-1035 -- -- -- 50.0 
-- -- -- -- 50.0 
-- -- 
SP-3040 -- -- -- -- -- 50.0 
-- -- -- -- -- 
SP-3035 -- -- -- -- -- -- 40.0 
-- -- -- -- 
SP-0110 -- -- -- -- -- -- -- -- -- 40.0 
-- 
Micro crystalline waxes 
Hi-Mic-2095 29.7 
-- -- 13.0 
-- -- -- -- 14.0 
-- -- 
Hi-Mic-1080 -- 10.0 
-- -- 4.0 
-- -- -- -- 19.0 
-- 
Hi-Mic-1045 -- -- 10.0 
-- -- -- 4.0 
-- -- -- 10.0 
Antioxidant 1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
Dimyrestyl thio dipropyonate 
Others 
Stearon 10.0 
-- -- -- -- 7.0 
-- 19.0 
-- -- 14.0 
Decanediol -- -- -- -- 20.0 
-- 4.7 
-- -- -- -- 
Monostearin -- -- 10.0 
-- -- -- -- -- -- -- -- 
Dodecane diol -- 19.0 
-- -- -- -- -- -- -- -- -- 
Usual solvent dyes 
C.I. Solvent Black 7 
-- -- -- -- -- -- -- -- -- 5.0 
-- 
C.I. Solvent Black 3 
-- -- -- -- -- -- -- -- -- -- 5.0 
Viscosity (mPa.s/120.degree. C.) 
6.0 
6.5 
5.7 
4.0 
5.0 
6.2 
7.0 
9.3 
4.8 
6.8 
7.0 
__________________________________________________________________________ 
Heat Fading Tests I and II were performed on the ink compositions of 
Examples 2-9 in the same manner as in Example 1. The results are shown in 
Table 2. 
TABLE 2 
______________________________________ 
Heat-fading 
Heat-fading 
test I test II 
______________________________________ 
(Examples) 
1 .circleincircle. 
.circleincircle. 
2 .circleincircle. 
.circleincircle. 
3 .circleincircle. 
.largecircle. 
4 .largecircle. 
.circleincircle. 
5 .circleincircle. 
.circleincircle. 
6 .largecircle. 
.largecircle. 
7 .circleincircle. 
.circleincircle. 
8 .largecircle. 
.circleincircle. 
9 .circleincircle. 
.circleincircle. 
(Comparative Examples) 
1 -- -- 
2 X X 
3 X X 
______________________________________ 
COMATIVE EXAMPLES 1-3 
The ink compositions shown as Comparative Examples 1-3 in Table 1 were 
prepared in the same manner as in Example 1. 
Comparative Examples 1-3 were evaluated with Heat Fading Tests I and II as 
in Example 1. The results are shown in Table 2 and described below in 
further detail. 
COMATIVE EXAMPLE 1 
The metallic complex solvent dye exhibited poor solubility. The OD value of 
the ink composition was 0.3 after preparation and filtration (prior to 
Heat Tests I and II). 
COMATIVE EXAMPLE 2 
The OD value was lowered 40% in each test. Thus, the ink was characterized 
as not suitable. 
COMATIVE EXAMPLE 3 
The solvent dye exhibited poor heat resistance, and the ink turned brown in 
both tests. 
In summary, the ink compositions prepared in accordance with the invention 
utilize heat resistant metallic complex solvent dyes in a vehicle 
including a high molecular weight alkyl amine, a high molecular weight 
fatty acid and carnauba wax and provide high quality print even when used 
in ink jet recording devices which maintain the ink at temperatures above 
room temperature for extended periods of time. Even in these high 
temperature environments, the ink compositions resist fading and 
discoloration over long time periods. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained and, 
since certain changes may be made in carrying out the above method and in 
the composition set forth without departing from the spirit and scope of 
the invention, it is intended that all matter contained in the above 
description shall be interpreted as illustrative and not in a limiting 
sense. 
It is also to be understood that the following claims are intended to cover 
all of the generic and specific features of the invention herein described 
and all statements of the scope of the invention which, as a matter of 
language, might be said to fall therebetween. 
Particularly it is to be understood that in said claims, ingredients or 
compounds recited in the singular are intended to include compatible 
mixtures of such ingredients wherever the sense permits.