Ink jet printer head

An ink jet printer head for printing dots on demand on a recording medium has ink flow paths formed in a substrate. The ink paths include a pressure chamber, supply path and nozzle for discharging ink droplets, the nozzle terminating in an external front face of the printer head. A piezoelectric element acting on the pressure chamber to reduce chamber volume, causes an ink droplet to be ejected. Ink flow in the paths is perpendicular to the displacement of the piezoelectric element. The front face of the printer head is adapted to contour the ink layer which forms on the front face at rapid printing rates to assure that the droplets are ejected along a line which is a linear, parallel extension of the longitudinal nozzle axis. The design principles are applicable to printer heads having single or double rows of nozzles.

BACKGROUND OF THE INVENTION 
This invention relates generally to an ink-on-demand type ink jet printer 
head in which ink droplets are jetted through a nozzle for printing. A 
variety of ink-on-demand type ink jet printer heads have been proposed in 
the prior art. Typical examples of such ink jet printer heads are the 
Kyser apparatus, described in U.S. Pat. No. 3,946,398, and the Stemme 
apparatus, described in U.S. Pat. No. 3,747,120. 
The Kyser system is briefly described with reference to FIG. 1 wherein the 
apparatus includes an electromechanical transducer 1 having piezoelectric 
elements 2,3. The transducer 1 is disposed in a recess 4 formed in a 
substrate 10 thus forming one side wall of a pressure chamber 7 for 
holding ink. A substrate 5 includes an ink supply path 6, the pressure 
chamber 7 and a nozzle 9. In combination, the substrates 5,10 form a ink 
jet printer head. When an input signal is applied to the input terminals 
8, the transducer 1 is displaced inwardly as indicated by the broken line 
and the arrow to decrease the internal volume of the pressure chamber 7, 
thereby causing an ink droplet to be ejected from the nozzle 9. These are 
the fundamental design and operating principles of an ink-on-demand type 
ink jet printer head. 
The Stemme apparatus is discussed briefly with reference to FIG. 2, wherein 
the ink jet printer head includes a piezoelectric element 14, a first 
pressure chamber 17 which is connected through a path 11 to a second 
pressure chamber 19 and to a nozzle 13, and an ink supply path 12 for 
feeding ink from an ink tank (not shown) to the second pressure chamber 
19. When an input signal is applied to the input terminals 18, the 
piezoelectric element 14 is driven so as to decrease the volume of the 
first pressure chamber 17 causing ink in the chamber 17 to pass through 
the opening 11 and the second chamber 19, and then to be jetted in the 
form of droplets from the nozzle 13. This is the fundamental design and 
operating principles of the so-called double cavity system. 
Ink droplets can be ejected at a high frequency and a plurality of 
chambers, nozzles, and driving transducers can be arranged in a single 
compound head to provide a row or several rows of closely spaced dots in 
the known manner. However, at high printing rates, for example, in excess 
of 500 Hz, an ink layer forms on the front face of the ink jet printer 
head in the vicinity of the nozzle openings. The droplets ejected from the 
nozzles pass through the surface ink layer and are deflected in their 
path. For this reason these ink jet printer heads suffer a disadvantage in 
that print quality is degraded. That is, the printing intervals are not 
regular because the ink droplets are ejected along a slanted or deviant 
axis from the axis of the nozzle. Furthermore, this makes it necessary 
that the ink jet printer head, and more particularly, the nozzles, to be 
set as close to the printing sheet or other recording medium as possible 
so as to minimize the dot shift due to the slanted trajectory of the 
droplets. 
What is needed is an ink jet printer head which ejects ink droplets at a 
high frequency without dot shifting so that print quality is high and the 
nozzle openings need not be very close to the medium being printed upon. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the invention, an ink jet printer 
head especially suitable for high speed on-demand printing is provided. 
The ink jet printer head for printing dots on demand on a recording medium 
has ink flow paths formed in a substrate. The ink flow paths include a 
pressure chamber, an ink supply path and a nozzle for discharging ink 
droplets, the nozzle terminating in an external front face of the printer 
head. A piezoelectric element acting on the pressure chamber to reduce 
chamber volume, causes an ink droplet to be ejected. Ink flow in the paths 
is perpendicular to the displacement of the piezoelectric element. The 
front face of the printer head is adapted to contour the ink layer which 
forms on the front face to assure that the droplets are ejected along the 
line which is a linear, parallel extension of the longitudinal nozzle 
axis. Generally, speaking the ink droplet must pass through the ink layer 
perpendicular to the meniscus between the ink layer and the ambient air if 
a shifting in the trajectory of the ink droplet is to be prevented. This 
is accomplished by providing a physical symmetry around the nozzle 
opening. The design principles are applicable to ink jet printer heads 
having single or double rows of nozzles. In a multi-row nozzle 
arrangement, a layer which is non-affinitive, that is, non-wetting, 
relative to the ink, is provided between two rows of nozzles or a recess 
is provided between the nozzle rows so as to suitably contour the ink 
layer around the nozzle openings and assure a straight trajectory for the 
droplets. 
Accordingly, it is an object of this invention to provide an improved ink 
jet printer head discharging ink droplets from a nozzle along a trajectory 
which is a linear, parallel extension of the longitudinal axis of the 
nozzle. 
Another object of this invention is to provide an improved ink jet printer 
head which provides a regular printing pattern at high printing speeds by 
eliminating dot shift. 
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 features of construction, 
combination of elements, and arrangement of parts which will be 
exemplified in the constructions hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The prior art ink jet printer head of FIGS. 1 and 2 demonstrate the 
fundamental principles of operation. In order to provide a practical 
apparatus, it is necessary to simplify the mechanism, to increase the 
effects of mass production and to thereby decrease the manufacturing cost. 
An ink jet printer head as shown in FIG. 3 is constructed to satisfy these 
requirements. In the ink jet printer head of FIG. 3, a pressure chamber 23 
is formed deeper into a main substrate 21 than are an ink supplying path 
22 and a nozzle 24. These elements are formed by a photo etching 
technique, or the like, preferably by a two-step etching technique. A flat 
substrate 25, that is, a vibration plate, is joined to the main substrate 
21 by welding or bonding to form the ink jet printer head. A piezoelectric 
element 26 is attached to the flat substrate 25 in alignment with the 
pressure chamber 23. Input terminals 27 are provided to the electrodes on 
the piezoelectric element 26 in the known manner. 
When an input voltage signal is applied to the piezoelectric element 26, 
ink droplets are jetted from the nozzle 24 to achieve printing. When the 
printing response frequency exceeds 500 Hz, that is, there is a capability 
to eject more than 500 droplets per second, an ink layer 28 forms on the 
front face 20 of the nozzle 24. As a result of the surface tension of the 
ink layer 28, an ink droplet 29 which is ejected from the nozzle 24 
travels along a path 31 which is inclined downwardly (FIG. 3) from a path 
30 which is a parallel linear extension to the longitudinal axis of the 
ink jet nozzle 24. The inclination of the line 31 from the line 30 is 
determined from the thickness of the ink layer 28, the velocity of the ink 
droplet 29 and the characteristics of the ink. Because of these factors, 
the ink jet printer head suffers from a problem of maintaining print 
quality in that the printing intervals are not regular when the ink 
droplets are jetted along a slanted axis. Furthermore, it is necessary 
with this ink jet printer head for the nozzle 24 to be set as close to the 
printing sheet as possible in order to minimize the dot shift resulting 
from the slanted paths of the droplets. 
An ink-on-demand type ink jet printer head can be readily constructed in 
the form of a multi-nozzle type ink jet printer head. Using a simple 
technique such as photo-etching (FIG. 7-9), three side walls are formed 
for each flow path on both sides of a main substrate 41. The remaining 
side wall, not formed in the substrate 41 is formed by connecting a 
vibrating plate to both sides of the main substrate 41. Addition of the 
vibrating plate 42 completes a flow path including paths 50 and chamber 43 
as well as the nozzle 45. A piezoelectric element 44 is bonded to the 
vibrating plate 42 in correspondence with each pressure chamber 43 along a 
flow path 50. Ink droplets are ejected through the group of nozzles 45 by 
applying a voltage to the selected piezoelectric elements 44 to achieve 
printing in the known manner. 
If the printing response frequency exceeds 500 Hz, an ink layer 46 (FIG. 
9a) forms on the front face 47 of the nozzles 45. As a result, ink 
droplets 52a are ejected along inclined paths 52 which are slanted 
inwardly from the jet axes 51 due to the surface tension of the ink layer 
46. Ideally, droplets 51a travelling along the paths 51 parallel to the 
longitudinal axis of the nozzles 45 are desired. The angle of inclination 
between the desired and the actual jet path for the droplets is determined 
by the thickness of the ink layer 46 at the nozzle, the velocity of the 
ink droplets, and the characteristics of the ink. 
Because the ink droplets travel along the inclined paths 52 rather than the 
parallel path 51, a conventional multi-nozzle ink jet printer head suffers 
from the disadvantage that printing at regular printing intervals cannot 
be achieved. Morover, in this construction, as shown in FIG. 9b, when the 
volume of the pressure chamber increases after the signal is removed from 
the piezoelectric element, and the pressure chamber draws in ink from the 
ink tank (not shown) after an ink droplet has been ejected from the 
nozzle, the position of the meniscus 100 between the ink and the air at 
the top end of the nozzle moves inward of the front face 47 of the nozzle 
45 and thereafter the meniscus stops in the position where the forces on 
the meniscus are balanced with atmospheric pressure. However, when there 
is a large amount of ink in the ink layer 46 the opening at the top end of 
the nozzle 45 is subsequently covered with the ink of the ink layer 46 and 
air bubble 101 is formed in the nozzle 45. When this air bubble 101 is 
present in the nozzle 45 and the volume of the pressure chamber is reduced 
at the next printing signal which drives the piezoelectric element, no ink 
droplet is ejected from the nozzle and some dots are missing from the 
printed product. As a result, proper letters cannot be formed. 
An object of this invention is to provide an ink jet printer head wherein 
the above described problems have been resolved, that is, there is no dot 
shift and the distance between the nozzle and a printing sheet can be made 
longer. 
In an ink jet printer head in accordance with this invention, an ink flow 
path including a supply path, a pressure chamber and a nozzle is formed 
between a plurality of substrates. The substrates are arranged such that 
the ink flow path extends substantially perpendicularly to the direction 
of displacement of the pressure chamber wall for the ejection of ink. The 
flow path is also substantially perpendicular to a front face of the ink 
jet printer head from which the nozzles discharge the ink droplets when 
the piezoelectric element is driven. 
Further, in an alternative embodiment of an ink jet printer head in 
accordance with this invention, a plurality of nozzles and flow paths are 
provided and flow paths and pressure chambers and nozzles are formed on 
both sides of the main substrate. A front face of the ink jet printer head 
is substantially perpendicular to the longitudinal axes of the nozzles. 
The nozzles are arranged on both sides of the main substrate in such a 
manner that one group of nozzles is formed in a line on one side of the 
main substrate while another group of nozzles is formed in a second line 
on the other side of the main substrate. A layer is provided on the front 
face between the two groups of nozzles. The layer is of a substance which 
stays free of ink, that is, there is a non-affinity between the ink and 
the layer. The ink does not wet the layer surface. The width of the 
ink-free layer on the front face of the ink jet printer head having the 
nozzle discharge openings thereon, is defined such that the distance 
between the nozzles and one side edge of the front face substantially 
equals the distance between the nozzles and the closest edge of the ink 
free layer. 
In an alternative embodiment of an ink jet printer head having two rows of 
ink jet nozzles, the ink free layer may be omitted and a recess formed in 
the front face of the ink jet printer head between the two lines of 
nozzles is provided. In this embodiment, the configuration of the recess 
is defined such that the distance between the nozzles and the closest side 
edge of the front face of the ink jet printer head is substantially equal 
to the distance between the nozzles and the closest edge of the recess. 
In another embodiment of an ink jet printer head, in accordance with this 
invention, the distance between the closest side edge of the front face of 
the ink jet printer head and the nozzles is at least 0.3 mm. This may be 
done with auxiliary plates joined to the vibrating plates on the main 
substrate. 
In another alternative embodiment of an ink jet printer head, in accordance 
with the invention, the objective to eliminate dot shift is met by setting 
a ratio of the distance between the nozzles and one side of the front face 
of the ink jet printer head to the thickness of the main substrate, at a 
value greater than one. 
The several above-mentioned embodiments of an ink jet printer head, in 
accordance with this invention, are explained more fully hereinafter. 
Reference is made to FIG. 4, wherein those components which have been 
previously described with reference to FIG. 3 and perform the same 
function, are identified with similar reference numerals. In the ink jet 
printer head of FIG. 4, an auxiliary ring 33 having a small aperture 32 
therethrough is coupled to the nozzle 24. The diameter of the aperture 32 
is equal to the diameter of the nozzle 24. The auxiliary ring 33 reshapes 
the ink layer 38 and makes it uniform around the nozzle jet axis. 
Accordingly, the ink droplet 29 which is ejected when the piezoelectric 
element 26 is driven, passes only along a path 30, which is a linear 
parallel extension of the longitudinal axis of the nozzle 24. As a result, 
there is very little dot shift. 
When no auxiliary ring 33 is provided, an ink droplet having a speed of 5 
meters per second, after it has moved two millimeters, would have a shift 
of 80 microns, whereas an ink droplet having a speed of 3 meters per 
second, after it has moved 2 mm, would have a shift of 400 microns. On the 
other hand, in an ink jet printer head, in accordance with the invention, 
where the auxiliary ring 33 is provided, the ink droplets have very little 
deflection and accordingly, there is very little dot shift which is 
caused. The inside and outside diameters of the ring differ by at least 
0.3 mm. 
It should be noted that the layer 28 does not deflect the droplet from its 
intended course when the droplet passes through the meniscus between the 
air and the layer 28 at a portion of the meniscus which is perpendicular 
to the longitudinal axis of the nozzle 24. The concentric positioning of 
the auxiliary ring 33 around the nozzle causes the liquid layer 28 to take 
a symmetrical shape due to surface tension concentric with the nozzle 24. 
In FIG. 4, t1=t2 and the opening 32 is concentric within the auxiliary 
ring 33. 
In the above described embodiment (FIG. 4) the auxiliary ring 33 is 
employed. However, the invention is not limited to such a ring. That is, 
the same effect can be obtained by using auxiliary plates with thickness 
t1 approximately equal to t2. Furthermore, a portion of the main substrate 
21 where the nozzle is formed may be cut off as shown in FIG. 5 so that 
the equality of t1 with t2 is maintained without the use of an auxiliary 
ring. All that is necessary is to modify the front face of the ink jet 
printer head where the nozzle discharges so as to maintain t1.apprxeq.t2. 
Another alternative embodiment of an ink jet printer head, in accordance 
with this invention, is shown in FIG. 6 wherein those components which 
have been described with reference to FIGS. 3 and 4 are given similar 
reference numerals. In the ink jet printer head of FIG. 6, the flat 
substrate 25, that is, the vibration plate to which the piezoelectric 
element 26 is attached, is extended by a distance t3 from the front face 
of the main substrate 21. As a result, the ink layer 28 forms with uniform 
thickness in the vicinity of the nozzle discharge opening. In this 
embodiment, the ink droplet 29 follows a trajectory 30 which is the linear 
parallel extension of the longitudinal axis of the nozzle 24. Very little 
dot shift occurs. The dimension t3, which is related to the thickness of 
the ink layer 28, the velocity of the ink droplet 29, the characteristics 
of the ink, and the structure of the head cannot be specifically defined 
lacking this specific data except on a case-by-case basis. However, the 
dimension t3 is greater than zero. 
The above described embodiments of the ink jet printer head, in accordance 
with the invention, are readily produced by extruding plastic material 
although the configuration of the components around the nozzle is somewhat 
intricate. As is apparent from the above description, the ink jet printer 
head is so designed that ejected ink droplets pass along a line which is a 
linear parallel extension of the nozzle longitudinal axis. Thus, an ink 
jet printer head, in accordance with the invention, prints letters and 
characters with a high print quality and is free from dot shift. 
An alternative embodiment of an ink jet printer head, in accordance with 
the invention, is shown in FIGS. 10 and 11 wherein the ink jet printer 
head is of the multi-nozzle type. As seen in FIG. 10, the nozzles 45 are 
arranged in two vertical lines and are formed into opposite sides of the 
main substrate 41. The fourth wall for the nozzles 45 is provided by 
vibration plates 42 which are attached to the sides of the main substrate 
41. The nozzles connect to pressure chambers and feed paths as previously 
described and piezoelectric elements are mounted on the vibration plates 
42 in locations corresponding to the pressure chambers formed in the main 
substrate 41, all as previously described. 
The main substrate 41 is glass having a thickness th=1.27 mm and the flow 
paths 50 are formed in to both sides of the main substrate 41 to a depth 
of approximately 100 microns using a photo-etching technique. In each flow 
path, a nozzle 45 and a filter (not shown) of approximately 20 to 30 
microns in depth are formed using a 2-step etching technique. The 
vibrating plates 42, having a thickness t4 of approximately 0.1 to 0.3 mm, 
are thermally fused to each side of the main substrate 41. The front face 
47 is polished at the nozzles. A layer 71 which is non-affinitive to ink, 
that is, remains free of ink, is provided on the central portion of the 
front face 47 of the main substrate 41 and is substantially flush with the 
front face 47 as best seen in FIG. 11. 
FIG. 10 is a front view of the ink jet printer head looking at the front 
face 47, ink repelling layer 71 and the discharge openings of the nozzles 
45. The width of the non-affinitive layer 71 is established such that the 
distance t4 between the nozzle 45 and the outer side edges 80 of the 
vibrating plates 42 is substantially equal to the distance t5 between the 
nozzle 45 and the nearest edge of the layer 71 which is non-affinitive to 
ink. In other words, the nozzles 45 are centered in a region where a layer 
of ink forms during high frequency printing. Therefore, a plane 82 which 
is tangent to the interface between the ink layer 46 and the air at the 
intersection with the longitudinal axis of the nozzle is substantially 
parallel to the front face 47 as shown in FIG. 11. Accordingly, the ink 
droplets pass through the meniscus of the ink layer 46 in a substantially 
perpendicular intersection, and the ink droplet is not deflected from a 
path which is a linear parallel extension of the longitudinal axis of the 
nozzle 45. Dot shift does not occur. 
As an example, if a water-based ink is used in the ink jet printer head, 
the layer 71 which does not have an affinity toward the ink, is readily 
produced by coating, spraying, or vacuum depositing a plastic, such as, 
Teflon. In FIG. 10, the nozzles are spaced apart laterally by an integer 
number of times of the spacing between dots in a horizontal row of a 
character printed by a combination of dots. In the vertical direction, the 
dots in both rows are equally spaced apart. However, the nozzles 45 are 
staggered such that the nozzles in one row are aligned to the half pitch 
distance, that is, the midpoint location of the nozzles in the other row. 
This staggered arrangement and lateral spacing is not unconventional in an 
ink jet printer head of the multi-row type. 
In the embodiments described above, the vibrating plate 42 forms one 
sidewall of each nozzle 45. However, at least one sidewall of the nozzle 
may be formed with a different material. Further, in the described 
embodiments, the ink flow paths are formed into both sides of the main 
substrate 41. However, in alternative embodiments of an ink jet printer 
head in accordance with the invention, the ink flow paths may be formed in 
the vibrating plates 42 or may be formed in part in both the main 
substrate 41 and in the vibrating plates 42. 
As previously stated, and as is clear from the above descriptions, in an 
ink jet printer head in accordance with the invention, a plane 
perpendicular to the longitudinal axis of the ink nozzle and tangent to 
the meniscus of the ink layer at the point of intersection of said 
longitudinal axis, is made substantially parallel to the front face 47 
where the nozzles discharge. Accordingly, the ink droplets are not 
deflected from a linear parallel extension of the longitudinal axis of the 
nozzle. Thus, an ink jet printer head in which no dot shift is caused and 
in which printing is carried out with a high density and high print 
quality is provided. 
An alternative embodiment of a multi-row ink jet printer head in accordance 
with the invention is shown in FIG. 12. In this ink jet printer head, a 
recess 70 is cut into the central portion of the front face 47 of the main 
substrate 41. The width of the recess 70 is such that the remaining 
thickness t7 at the nozzle 45 substantially equals the thickness t6 of the 
vibrating plate 42 which forms the outer wall surface of the nozzle 45. 
Separate ink layers 46 form at each nozzle 45 with an air/ink meniscus 
which is symmetrical around the discharge opening of the nozzle 45 as seen 
in FIG. 12. 
When printing is performed and the ink layers 46 are formed, a plane 
tangent to the meniscus at the intersection of the linear parallel 
extension of the longitudinal axis of the nozzle 45 with the meniscus, is 
substantially parallel to the front faces 47 adjacent the nozzles. 
Accordingly, the surface tension of the ink layer acts uniformly on the 
ink droplet passing through the ink layer 46. Therefore, the ink droplets 
are jetted perpendicularly to the meniscus and dot shift is not caused. 
The depth of the recess 70 is selected such that even when the ink layers 
46 flow into the recess 70 as their volumes increase, the ink layers 46 
for two rows of nozzles do not connect to each other through the recess. 
In an alternative embodiment of an ink jet printer head in accordance with 
the invention, as shown in FIG. 13, auxiliary plates 72 are thermally 
fused to the vibrating plates 42 in the region of the discharge openings 
of the nozzles 45. The auxiliary plates 72 and the front face 47 of the 
main substrate 41 are polished simultanteously so that a thin ink layer 46 
can spread to the outer edges of the auxiliary plates 72. The auxiliary 
plates 72 extend the width of the front face 47 to such a degree that the 
ink layer 46 is substantially of one thickness where the discharge 
openings of the nozzles 45 are located. Tapering in thickness of the ink 
layer 46 occurs near the outer edges of the auxiliary plates 72. 
Accordingly, the ink droplets pass in a straight line which is a linear 
parallel extension of the longitudinal axis of the nozzles 45 and no dot 
shift is caused. 
In the embodiment of FIG. 13, the auxiliary plates 72 are thermally fused 
with the vibrating plates 42. However, the same result can be achieved by 
increasing the thickness of an end portion of the vibrating plate 42 which 
forms the nozzles 45. Then, the thickness of only a portion of the 
vibrating plate 42 where the piezoelectric element 44 is bonded is 
decreased. As the width of the nozzle front face 47 is increased, the 
nozzle openings can readily be made flat by polishing and the nozzles 45 
can be easily covered with a lid (not shown). 
Another alternative embodiment of an ink jet printer head in accordance 
with the invention is shown in FIG. 14. Ink flow paths 50, having a 
pattern similar to that shown in FIG. 1, are formed in both sides of the 
main substrate 41, which, for example, is glass having a thickness of 0.3 
mm, by photo-etching. The flow paths 50 are etched to a depth of 
approximately 100 microns. In each flow path 50, a nozzle 45 and a filter 
(not shown) having a depth of about 20 to 30 microns are formed by a 
two-step etching process. A vibrating plate 42 having a thickness t9, of 
0.3 to 1.0 mm is thermally fused to each side of the main substrate 41. 
The nozzle front face 47 is polished. A piezoelectric element (not shown) 
is bonded to the vibrating plates 42 in association with each pressure 
chamber and nozzle, and electrodes are connected to the piezoelectric 
element in the known manner. 
An ink jet printer head was constructed with these dimensions and the 
thickness t8 of the main substrate 41 and the thickness t9 of the 
vibrating plate were varied. The ink which was used had a surface tension 
of 45 dyn/cm and a viscosity of 1.8 c.p. The velocity of the ejected 
droplets was approximately 3 to 5 meters per second. Results of the tests 
are indicated graphically in FIG. 15. When the ratio of the vibrating 
plate thickness t9 to the main substrate thickness t8 exceeds 1, there is 
very little dot shift as measured at a distance of 2 mm from the discharge 
opening of the nozzle. When the ratio exceeds 1, the interface between the 
ink layer 4 and the air (FIG. 14) is substantially perpendicular to the 
longitudinal axis of the nozzles. Therefore, surface tension in the ink 
acts substantially uniformly on the ink droplets in both lateral 
directions. As a result, the ink droplets are ejected along a straight 
trajectory which is an elongation of the longitudinal axis of the nozzle. 
In the ink jet printer head of FIG. 14, the ink flow path have been 
described as being formed in the main substrate 41 by etching. However, 
the ink paths may be formed in the vibrating plates 42 be may be formed in 
both the main substrate 41 and the vibrating plates 42. The thickness of 
the ink jet printer head may be controlled by using a different material 
as the vibrating plate 42 which forms one sidewall of the nozzle 45, or 
one sidewall of the nozzle may be formed using a different material. Thus, 
an ink jet printer head in which no dot shift is caused and in which 
printing can be carried out with a high density and a high print quality 
is provided. Additionally, in an ink jet printer head in accordance with 
the invention, ink droplets are ejected without producing air bubbles in 
the nozzles. 
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 the above constructions without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings 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.