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Description  |
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FIELD OF INVENTION
The present invention relates to a water soluble ink used in on-demand type
ink jet printers for use in, for example, computer systems, electric
calculators, cash registers, automated teller machines (ATM), facsimile
apparatuses and the like. More particularly, the present invention relates
to an ink jet printer having an ink jet head composed of a plastic
material using such water soluble ink.
BACKGROUND OF THE INVENTION
On-demand type ink jet printers are used in, for example, computer systems,
electric calculators, cash registers, automated teller machines (ATM),
facsimile apparatuses and the like. In an ink jet printer, ink droplets
are ejected or jetted to a recording sheet to form letters, figures, or
pictures thereon in accordance with a predetermined dot matrix. That is,
typical ink jet printing systems consists basically of forming a letter or
a figure on a recording medium by ejecting droplets through at least one
small nozzle in a preselected arrangement. These ink droplets can be
formed by, for example, electrostatic charging, application of thermal
energy or application of mechanical energy. One known device for supplying
mechanical energy is the piezoelectric device.
It is advantageous that an ink jet printer have the following
characteristics for use as a high quality printer in the aforementioned
devices:
1. The ink must be consistently discharged by the ink jet printer through
each selected nozzle without any clogging during prolong continuous
operation. A clogged nozzle can result in misformed or unformed
characters.
2. The printer must be free of meandering flying of ink drops. In other
words, the ink drops must be printed in their respective desired
locations. Otherwise, characters may be distorted or misformed.
3. The ink must dry immediately after printing to prevent smudging and
smearing.
4. The printer must consume a minimal amount of electrical energy.
5. The printer must have a small size.
6. The printer must be inexpensive to maintain and manufacture.
It has been proposed to provide an ink jet or recording head, including the
supply passage ways and the ink tank, composed of a plastic material. A
plastic ink head can be fabricated by means of, for example, molding and
welding of performed plastic pieces. These processes are well known for
inexpensively and reliable fabricating such recording heads. Additionally,
plastic possesses superior chemical resistance. In view of the above,
plastic is a very desirable material for use as an ink jet head.
However, conventional techniques do not provide for a plastic ink jet head
which can print images and characters with high quality. This can be
explained as follows. Plastics generally do not have characteristics of
affinity for water or good water characteristics. In other words, plastics
can hardly be wetted by water or ink having water soluble dye. As such,
passage ways fabricated in the ink plastic head are hardly wetted with the
ink so that bubbles may be formed therein. The bubbles absorb the forced
generated by the pressure elements of the ink jet head which reduces
displacement thereof so that the power of the ink ejection is attenuated.
This reduction causes missing dots and or smaller dot size. Additionally
it is difficult to wet the circumference of an orifice of the nozzle so
that the meandering of ink ejection and deformation by the printer printed
characters still exists.
The inventors note that surfactants generally roughen the surface of
plastic materials. However, the selection of suitable plastics in printing
heads using a surfactant-containing ink character has been troublesome.
All the while, each of the above points may have been individually
addressed by conventional inks and ink jet printers, the inventors are not
aware of any means or device which satisfies each and every one of these
characteristics, as explained in detail below
Various attempts have been made to provide an ink jet printer which
satisfied the above-mentioned characteristics. But none of these attempts
overcame the problems for an ink jet printer with a plastic print head.
For example, Japanese Patent Application Laid Open No. 1-123752, which
address points number 1 and 2 above, is directed to a technique of wetting
an ink flow pathway from an ink reservoir to a nozzle surface of a
recording head in order to obtain uniform wetting of this nozzle surface
of the recording head. This technique is accomplished by preventing the
generation of bubbles in the ink. More specifically, grooves are arranged
symmetrically to the series of nozzle orifices for jetting out the ink
there through. The edge of such nozzles are made of Ni, Ti, Si, O.sub.2,
Ti, O.sub.2 or the like. Alternatively, the nozzle maybe surfaced-treated
by plating, vapor deposition, sputtering or some other coating means.
However, the technique discussed in Japanese Patent Application Laid Open
No. 1-123752 requires the additional step of forming the head. This
additional step increases the unit price of such products. In addition, in
accordance with the above-mentioned coating means, it is difficult to
completely and uniformly coat the nozzle surface. As a result, the surface
of the nozzle edge has a portion which can be wetted with ink and a
portion that is not wetted. This configuration causes the jetting
direction of the ink drops to meander and, as such, the printed letters or
characters have a tendency to be deformed.
Japanese Patent Application Laid Open No. 62-111749 is directed to a
printer having a heater-combined hot air blowing unit to promote the
drying of the printed ink. This is accomplished by blowing hot air on the
just ejected ink. However, such a device is intended to be used in
large-scale printers, since this device consumes an inordinate amount of
electric power. Additionally, the cost of such devices are high. As such,
the device discussed in Japanese Patent Application Laid Open No.
62-111749 is not particularly well suited for the applications discussed
above.
Japanese Patent Application Laid Open No. 1-252680 and its European
counterpart application 320,223 propose the addition of more than 40 wt. %
of a wetting agent and a nonionic acetylene diol surfactant or dioctyl
sulfocuccinate surfactant intended for the prevention of the clogging of
the print head for the smooth operation of printing on plain paper.
The ink composition comprises a compatible dye, greater than 40 weight %
humectant and a surfactant. The surfactant is utilized to facilitate
printing on plain paper. In these references the weight % is based on the
total ink composition. In this ink composition, the high amounts of
humectant are said to be selected to insure that the viscosity of the ink
is maintained between about 5.5 and 6.5 centipoise. This reference
specifies a dye comprising a liquid mixture of Liquid Blue C.I. 279 and
mixed with Direct Red C.I. 236 and Direct Yellow C.I. 107, in the ratio of
3.53/1.35/1.0, and Mobay Special Black SP liquid ink and discusses the use
of the following surfactants:
Surfynol GA-1 to 10 weight %
Surfynol 82-10 weight %
Surfynol 465-1 to 10 weight %
Surfynol 485-5 to 10 weight %
Surfynol 136-2 weight %
These documents are silent as to the material employed in the print head.
Accordingly, this reference fails to appreciate the problems associated
with plastic print heads. Therefore, this reference could not attempt to
propose solutions for solving the problems discussed above.
Further, Japanese Patent Publication No. 58-6752 proposes the addition of a
tertiary alcohol-ethylene oxide adduct having a chemical structure as
follows:
##STR4##
R.sub.5 -R.sub.8 each present alkyl group, p and q each represents an
integer of at least one and Y represents an acetylene group.
The addition of such adduct is said to improve the smooth operation of
printing with the ink on plain papers including the stability of the ink
to resist smearing and running.
Where the techniques of Japanese Patent Application Laid Open No. 1-252680
and Japanese Patent Publication No. 58-6752 are employed, the time for
drying the printed ink is said to be shortened by some degree. Thus,
printing on plain paper is said to be possible without enlarging the scale
of the printer. Additionally, the clogging of the ink jet is said to be
prevented as the storage stability and the water-proofness of the ink
being used is said to be improved. However, these references do not
address the problems of prevent missing dots of a desired matrix of dots
and the meandering of ink drops.
OBJECTS OF THE INVENTION
It is the object of the present invention to provide a printing apparatus,
method of printing, a water soluble ink that obviates the aforementioned
problems in the ink jet printer.
It is the further object of the present invention to provide an ink jet
printer having a compact plastic print head which can be manufactured
inexpensively.
It is an additional object of the present invention to provide a printer
which can print reliably having high quality without any deformed
characters.
It is still another object of the present invention to provide a water
soluble ink which can be used in printing a high-density print image.
It is still yet a further object of the present invention to provide a
water soluble ink void of bubbles and which may be easily de-foamed in any
de-foaming step.
It is still yet a further object of the present invention to provide an ink
having high storage stability over an extended period of time.
Other objects and features of the present invention will become apparent
from the following detailed description considered in conjunction with the
accompanying drawings. It is to be understood, however, that the drawings
are designed solely for purposes of illustration and not as a definition
of the limits of the invention, for which reference should be made to the
appended claims.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a water-soluble ink and an
ink jet printer capable of printing images having good water-proofness
characteristics and an aqueous ink composition comprised of water-soluble
dye having the chemical structure of:
##STR5##
where R.sub.1 to R.sub.4 each represent either an OH group or an NH.sub.2
group in the range of about 0.1 wt. % to 10.0 wt. % of the aqueous ink.
The ink composition comprises surfactant in the range 0.01 wt. % to 0.1 wt.
% of having an acetylene glycol surfactant having a chemical structure of:
##STR6##
and an acetylene glycol-ethylene oxide adduct is provided having a
chemical structure of
##STR7##
wherein m and n are each integers of at least 1.
According to another aspect of the present invention, an aqueous ink
composition is provided having high wettability to plastic surfaces in
contact with the ink comprising a water-soluble dye having the chemical
structure formula as follows:
##STR8##
wherein R.sub.1 to R.sub.4 each represents either an OH group or an
NH.sub.2 group and comprises an amount in the range 0.1 wt. % to 10.0 wt.
% of the ink. The ink composition further comprises at least one of a
first, second or third surfactant. The first surfactant is in the range of
0.01 wt. % to 0.1 wt. % of the ink and comprises acetylene glycol
surfactant having a chemical structure formula of:
##STR9##
The second surfactant is an acetylene glycol-ethylene oxide adduct
surfactant in the range of about 0.01 wt. % to 0.1 wt. % of the aqueous
ink and comprises a chemical structure formula as follows:
##STR10##
wherein the sum of m and n is in the range of 1-5. The third surfactant is
in the range of 0.1 wt. % to 10 wt. % by weight of the ink and comprises
acetylene glycol-ethylene oxide adduct surfactant having a chemical
formula of
##STR11##
wherein the sum of n and m is in the range of 6-40.
In accordance with still another aspect of the present invention an ink jet
printer comprises a plastic molded body and an utilizes an aqueous ink
composition as described above.
Other objects and attainments together with the full understanding of the
invention will become apparent and appreciated by referring to the
following description and claims taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
In the drawings, wherein like referenced characters denote some elements
throughout the several views.
FIG. 1 is a partial perspective view of a recording head in accordance with
the present invention;
FIG. 2 is a cross-sectional view of a first base portion of the recording
head of FIG. 1;
FIG. 3 is a partial cross-sectional view of the recording head of FIG. 1;
FIG. 4 is a cross-sectional view of the recording head of FIG. 1 depicting
the ink being jetted out;
FIG. 5 is a partial perspective, front view of the recording head of FIG.
1;
FIG. 6 is a side view of the recording head of FIG. 1 in which ink drops
are being jetted out;
FIG. 7 is a cross-sectional view of a first base of a recording head in
accordance with a second embodiment of the present invention;
FIG. 8 is a cross-sectional view of the recording head of FIG. 7
illustrating the ink drops being jetted out;
FIG. 9 is a partial perspective, front view of the recording head of FIG. 7
in which ink drops are being jetted out;
FIG. 10 is a side view of the recording head of FIG. 7 in which ink drops
are being jetted out;
FIG. 11 is a cross-sectional view of a conventional recording head in which
ink bubbles are formed;
FIG. 12 a partial perspective view of the recording head in which ink drops
are being jetted out in accordance with a conventional ink formulation;
and
FIG. 13 is a cross-sectional view of the recording head using the
conventional ink formulation.
A DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to FIGS. 1-3, a preferred example of a recording head, generally
referred to by 100, according to the present invention is illustrated. The
recording head comprises a first base 10, which is fabricated by shaping a
plastic resin, by way of example, polysulfone, polycarbonate, polyether
sulfone, polyallyl sulfone, polyacetal or the like by a process, such as
molding or laser machining. As shown in FIG. 2, the recording head also
comprises a common ink chamber 15 in communication with a plurality of ink
flow pathways 14, respective pressure chambers 13, ink flow pathways 12
and nozzle orifices 11. In the preferred embodiment, the number of nozzle
orifices is 9 having a pitch of 350 .mu.m. The profile for each of the
nozzle orifices 11 is, for example trapezoidal, having a dimension of 60
.mu.m (minor edge).times.70 .mu.m (major edge).times.30 .mu.m (height).
The ink flow pathways 12 and 13 are arranged on the nozzle side and the
feed side of pressure chambers 13, respectively, and have been formed by,
for example, engraving the first base 10 in a known manner. The recording
head also comprises an ink feed mouth 16 for supplying ink to recording
head 100. Turing back to FIG. 1, a second base 18 is further provided and
adhered to base 10 by a conventional manner, such as fusion or with an
adhesive, to form the ink flow pathways 12 and 14. Respective
piezoelectric elements 17 are arranged on the second base 18 with, for
example, an adhesive, and face corresponding pressure chambers 13 formed
on first base 10. Referring specifically to FIG. 3, flying ink drops 20
are illustrated advancing toward recording medium 21.
The operation of the recording head 10 in an ink jet printer in accordance
with the present invention is as follows. The ink is supplied to recording
head 100 through ink feed mouth 16 and due to capillary action, pathways
12 and 14, and the chambers 13 are filled with the ink. Next an electrical
signal is applied to the piezoelectric elements 17 in a conventional
manner. Upon application of the electrical signal, the piezoelectric
elements 17 are deformed to reduce the capacity of the corresponding
pressure chambers 13, so that the ink drops 20 are jetted out to fly
towards the recording medium 21. In the preferred embodiment the
electrical signal to drive the selected piezoelectric elements is 35 volts
at a frequency of 2.0 kHz, at room temperature. After the ink drops 20
have adhered to recording medium 21 and have been fixed thereon, recording
is attained.
The basic composition of the water-soluble ink to be used in the following
examples comprises a water-soluble dye and a solvent. As a water-soluble
dye, the ink contains at least a compound having the following formula:
##STR12##
wherein R.sub.1 to R.sub.4 each represents an OH group or an NH.sub.2
group. In the preferred embodiment the water-soluble ink comprises 0.1 wt.
% of the water-soluble dye. Even when the water-soluble dye is combined
with any other water-soluble dye in the ink, the content of the water
soluble dye of the ink is at least 0.1 wt. %. The inventors have observed
that a dye containing less than 0.1 wt. % does not print with a sufficient
enough density to provide an acceptable output. On the other hand, if the
water-soluble dye comprised more than 10 wt. %, precipitates are formed
which tend to clog the nozzles of the recording head. As a result of these
clogged nozzles, the printed output contains misformed and/or deformed
characters, such that the output is unacceptable.
Next, examples of demonstrating printing operations with an ink jet printer
equipped the recording head of the present invention as mounted therein,
using the water-soluble ink of the present invention, will be discussed
hereinbelow along with comparative examples. As shown in these examples,
an ink composition in accordance with the present invention achieves
significantly better results by which the effect of the present invention
will be clarified concretely.
EXAMPLE 1
In accordance with the first embodiment of the present invention, the
aqueous ink was constituted by the following components were blended, well
stirred for dissolution, and filtered through a membrane filter having a
pore size of 0.8 .mu.m. The resulting filtrate was subject to a de-foaming
operation. In the de-foaming operation, the filtrate was placed in a
vacuum tank. For example, the vacuum tank was connected with a rotary pump
via a tube, the inside of the tank was made vacuum by discharging the air
therefrom. The contents in the tank was allowed to stand one hour under
the condition to produce a water-soluble ink. During the de-foaming
operation, the ink produced herein did not bubble and almost 100 % of the
de-foamed ink was usable in the following tests.
TABLE 1
______________________________________
Colorant:
Dye having chemical structure of having the following formula:
5.0 wt. %
##STR13##
Penetrating agent:
Surfactant having chemical structure of having the following
formula:
5.0 wt. %
##STR14##
wherein the molar number of ethylene oxide added (m + n) is
from 6 to 40)
Antiseptic:
Compound having a chemcial structure of the following formula:
##STR15##
0.2 wt. %
Solvent:
Polyethylene glycol 10.0 wt. %
Water 79.8 wt. %
______________________________________
The water-soluble ink was fed into an ink jet printer as discussed
hereinabove.
FIG. 4 illustrates the operation of recording head 40 in accordance with
the first example. Recording head 400 has substantially the same structure
as print head 100. As such elements 40-48 correspond to elements 10-18,
respectively. As shown in FIG. 4, during the course of jetting out ink
drops there through, in which ink feed mouth 46, common ink chambers 45,
ink flow pathways 44 on the feed side, pressure chambers 43, ink flow
pathways 42 on the nozzle side and nozzle orifices 41 were all completely
filled with the ink with no invasion of bubbles therein. Accordingly,
printing operations were effected well, without yielding any missing dots.
In other words the printed characters were properly formed without
distortion and deformation.
FIG. 5 is a partial perspective front view of the above-mentioned recording
head 400 illustrating side 52 of first base 40 and side 53 of second base
48; and FIG. 6 is a side view of the recording head through which ink
drops 61 are being jetted out. A shown therein, ink 51 has wetted or has
adhered to the peripheral portion of nozzle orifices 41.
Since ink 51 uniformly wetted the peripheral portion of the nozzle orifice
41, as shown in FIG. 5, ink drops 61 were jetted out to fly vertically to
the sides 52 and 53 of the first and second bases, respectively, as shown
in FIG. 6. Therefore, the recording medium was printed with the ink in the
intended position, and the quality of the printed letters was good.
Using the ink of the present example, printing was effected on neutral
paper PPC (produced by Fuji Xerox Co., Ltd.), acidic paper for
registration (produced by Dai-Showa Paper Mfg. Co., Ltd.), 45 kg-weight
high-quality paper (produced by Jujo Paper Co., Ltd.), and regenerated
paper "Yamayuri (trade name)" (produced by Honshu Paper Co., Ltd.),
whereupon the time needed during the course from penetration of the ink
into the paper to drying of the penetrated ink thereon was observed with
the naked eye to the result of one second or less in every case. Thus, in
accordance with the present invention, the ink drying time is extremely
short irrespective of the characteristics of the type of paper tested.
Next, the print density of the printed papers was measured with a
densitometer (Print Contrast Meter, manufactured by Macbeth Co.). A filter
having a visible ray-sensitive characteristic to show the maximum
transmittance at about 550 nm was inserted into the densitometer and the
reflectivity of the printed dots was measured. Although the reflectivity
somewhat varied depending upon the recording media (printing paper), the
average reflectivity measured was 8%. From that value, the print density
was calculated to be 1.1 as an optical reflective density OD value. In
view of the OD value of being 1.1 to the filter, the printed dots gave
sufficient black appearance when seen with the naked eye.
In addition, the printed papers were dipped into a static water for one
hour, whereupon it was determined if any bleeding of the ink occurred. In
this example, the bleeding was only slight. The print density of each of
the dipped papers was again measured with the above-mentioned
densitometer, having the visible ray filter as inserted therein, to the
result that the mean reflectivity was 10%. From this, the OD value was
calculated to be 1.0.
Next, the printed papers were exposed to the sun light for one month to
check the degree of the decrease of the print density, if any. As a
result, the print density in all cases remained substantially the same.
The OD value of the printed papers after exposure under the condition was
an average of 1.06. Thus, using the water-soluble ink and the ink jet
printer of the present invention, printed papers having excellent
water-proofness and light fastness are obtained.
The flow pathways of the above-mentioned recording head were then filled
with the water-soluble ink and the head was put in a thermal test chamber
or oven at 50.degree. C. for 30 days. After taken out therefrom, the head
was allowed to stand at room temperature for one day. After the operation,
all the ink was sufficiently discharged from the ink flow pathways of the
recording head by means of, for example, a pump. The ink was jetted out
from the head in the manner mentioned above. As a result, the flying ink
drops were stable, similar to that before the treatment. From this
example, it is understood that the ink in the flow pathways in the
recording head hardly vaporized during the treatment and that the ink
formed no solid precipitates during this process.
Further testing of the ink was conducted. More specifically, one sample of
the water-soluble ink was put in a hermetically sealed glass laboratory
bottle and stored at 70.degree. C. for 6 months. Another sample was placed
in a similar bottle and was stored in a freezer for 6 months. After the
storage of each sample, the liquid temperature of the ink was returned to
room temperature. It was observed that the physical properties of the ink,
such as viscosity and surface tension, did not substantially vary and the
ink formed no solid precipitates. Thus, the storage stability of the ink
under high temperature or low temperature conditions is good for a long
period of time.
A further test was conducted in which the water-soluble ink was put in a
glass laboratory bottle along with polysulfone, polycarbonate, polyether
sulfone and polyacetal. The bottle containing the mixture was hermetically
sealed and stored in an oven at 80.degree. C. for 2 months. After the two
months, the surface condition of the respective plastics was observed and
revealed that the surfaces of the plastics were not roughened. From this
observation, the inventors concluded that the water-soluble ink of the
present invention, though containing a surfactant, does not roughen the
surface of plastic materials.
COMPARATIVE EXAMPLE 1
The following components were blended to produce a water-soluble ink, in
the same manner as in Example 1. The ink was de-foamed in the same manner
as in Example 1; however, the ink formed bubbles and a half of the ink was
unusable due to bubbling. Thus, the productability of the ink was low.
TABLE 2
______________________________________
Colorant:
Dye having a chemical structure of the following formula:
5.0 wt. %
##STR16##
Penetrating Agent:
Polyoxyethylene nonylphenyl ether surfactant
5.0 wt. %
Antiseptic:
Compound having a chemical structure of the following formula:
##STR17## 0.2 wt. %
Solvent:
Polyethylene glycol 10.0 wt. %
Water 79.8 wt. %
______________________________________
The water-soluble ink that remained without bubbling was fed to the
recording head of Example 1, through which ink drops were jetted out. The
profile of the recording head and the driving condition of it were the
same as those in Example 1.
FIG. 11 is a perspective view of the recording head 1100, from which ink
drops of Comparative Example 1 are shown being jetted out. Recording head
1100 has a structure which is substantially similar to print head 100. As
such elements 111-116 correspond to elements 11-16, respectively and no
further explanation is required. As shown in FIG. 11, in this example,
bubbles 117 invaded into the ink feed mouth 116, the common ink chambers
115, the ink flow pathways 114 on the feed side, the pressure chambers 113
and the ink flow pathways 112 on the nozzle side. The size of the bubbles
were approximately from 0.05 to 0.1 mm in diameter.
The reason of bubbling of the ink is because the above-mentioned
water-soluble dye, which is a colorant of the ink, and the above-mentioned
surfactant, which is a penetrating agent thereof, have a bubbling
property. Additionally, the other components of the ink do not have a
de-foaming effect so that the ink is bubbled when it was fed into the
recording head via, for example, a pump.
Even if an electric voltage is imparted to the piezoelectric elements under
the condition of having bubbles in the pressure chambers 113 so as to bend
the element to reduce the volume of the pressure chambers 113, the bubbles
117 tend to absorb the capacity to be reduced, so that the ink could not
be effectively jetted out through recording head 1100. This results in
selected orifices 111 not ejecting ink, causing missing dots on the
printed media. As a result, printed characters were misformed and deformed
rendering such difficult to read or even unreadable.
Next, the water-soluble ink was put in a similar glass laboratory bottle as
that employed in Example 1, along with polysulfone, polycarbonate,
polyether sulfone and polyacetal. The bottle was hermetically sealed and
stored in an oven at 80.degree. C. for 2 months. Then, the surface
conditions of the respective plastics were checked and revealed that the
polycarbonate and polyacetal whitened and exhibited a roughened surface.
EXAMPLE 2
The following components were blended and formed into a water-soluble ink
in a similar manner as in Example 1.
TABLE 3
______________________________________
Colorant
Dye having a chemical structure of the following formula:
0.1 wt. %
##STR18##
Dye having a chemical structure of the following formula:
5.0 wt. %
##STR19##
Penetrating Agent:
Surfactant having a chemical structure of the following formula:
##STR20## 0.1 wt. %
Solvent:
Triethylene glycol 15.0 wt. %
Water 79.8 wt. %
______________________________________
FIG. 7 is a cross-sectional view of showing the first base 70 of the
recording head 700 of the present invention as employed for printing with
the water-soluble ink. Recording head 700 is similar to recording head
100. While print head 700 contains three more orifices and corresponding
pathways and chambers, elements 71-78 correspond to elements 11-18,
respectively. As such, no further explanation of elements 71-78 is deemed
necessary. It is noted in print head 700 that each of the pathways 74 have
the same length and each of the pathways 72 also have the same length. In
this example, the water-soluble ink was fed into the ink jet printer of
the present invention having the recording head composed of first base 70
and second base 78 composed of polysulfone of a polysulfone sheet. Ink
drops were jetted out through the head. The profile of the nozzle orifice
71 of the recording head is preferably rectangular, having a dimension of
37 .mu.m (width).times.26 .mu.m (height). The number of the nozzle
orifices is 12 having a nozzle pitch of 282 .mu.m. In this example, the
driving power of the piezoelectric element was 33 V at a frequency of 2.2
kHz at room temperature.
FIG. 8 is a cross-sectional view of recording head 800 of the present
example during the course of jetting out ink drops there through.
Recording head 800 is similar to recording head 700. Accordingly, elements
80-88 correspond to elements 70-78 of recording head | | |
