 |
Description  |
|
|
In ink jet printing, a stream of ink is supplied under pressure and
periodically perturbed to produce droplets, which impinge upon a suitable
recording medium such as a sheet of moving paper, for example. To obtain
printing on the paper by the ink, it is necessary that the droplets be
spaced substantially uniform distances from each other and be of
substantially uniform size.
To produce the desired print pattern on the paper, the droplets must be
individually directed to the paper or deflected prior to reaching the
paper in accordance with the pattern to be printed. To obtain the
deflection of the droplets, it is necessary that the droplets be capable
of being electrostatically charged or have magnetic properties so as to be
capable of being selectively deflected.
The present invention eliminates the requirement for any charging and
deflection of the droplets to produce a desired print pattern. The present
invention accomplishes this through forming the liquid streams of a
material with photochromic or electrochromic or thermal properties or
combinations thereof so that each of the streams is transparent or
colorless unless subjected to the appropriate energy source to which the
material responds to change from transparent to a color. Thus, only those
portions of each of the streams subjected to the appropriate energy source
will produce a color or ink spot on the paper.
The present invention also enables the ink spots, which are the portions
subjected to an appropriate energy source, to have different contrasts
depending on the amount of energy applied thereto. Thus, the print pattern
produced by the present invention can be of varying contrast.
When deflecting various of the droplets to form a desired print pattern,
the absence of some of the droplets from the stream creates an aerodynamic
problem. This is because the spacing between the droplets is no longer
uniform so that a droplet adjacent to the space from which a droplet was
deflected tends to increase in velocity. As a result, the droplets have
different velocities depending on the spacing therebetween because of the
absence of some of the droplets. Thus, the desired uniform velocity to
obtain the desired print pattern is affected by the deflection of some of
the droplets in the stream.
The present invention overcomes this problem since none of the droplets is
deflected. Thus, the present invention obtains the desired print pattern
without any requirement for deflection so that each of the droplets
strikes the paper even though all are not used to print.
To obtain the desired electrostatic charging of the droplets since the
droplets are selectively charged to be deflected, it is necessary that the
break off point of the droplets from the stream be uniform and
synchronized in accordance with the charging, which occurs adjacent to the
break off point. When the liquid stream is formed of a material with
photochromic or thermal properties or a combination thereof, the need for
critical synchronization of the break off point of the droplets from the
stream is eliminated.
While the need for the critical synchronization of the break off point of
the droplets from the stream is required when the liquid stream is formed
of a material with electrochromic properties, this problem can be avoided
with the present invention through not forming the stream into droplets.
Thus, by merely applying the electric field to the electrochromic
material, light radiation to the photochromic material, or heat radiation
to the thermal material, various portions of the stream can be selected
for printing. Accordingly, by not forming the stream into droplets, the
problem of synchronization of the break off point of the droplets from the
stream is eliminated.
In prior thermal printing, paper has been specially treated to respond to
heat applied to portions of the paper to produce a desired print pattern.
Paper also has been specially treated to respond to light radiation of a
selected wavelength to produce a desired print pattern. However, this
paper has required the expense of special treatment.
The present invention overcomes this problem of the specially treated paper
in that printing can be accomplished on any type of substrate. Thus, the
cost of specially treated paper is eliminated by the present invention.
Furthermore, when subjecting the specially treated paper to heat, the heat
spreads laterally from the area of the paper to which it is applied. Thus,
the resolution of the print pattern produced by the specially treated
paper to which heat is applied is limited because of the lateral spread of
the heat.
Since the application of the heat is to each of the selected droplets in
the present invention, there is no spreading of the heat so that the print
pattern has better resolution. Since the paper is not sensitive to the
heat of the droplets, any spreading of the heat from the droplet after the
droplet strikes the paper does not have any effect on the print
resolution.
Accordingly, the present invention enables the recording of information on
a recording medium without the requirement of any deflection or charging
and without the requirement of any specially treated paper. The present
invention accomplishes this through treating the liquid forming the ink
before it strikes the paper. Thus, by controlling the liquid state rather
than the state of the paper, a much greater flexibility is provided in
preparing the material.
Through applying the energy source to the material having the property
capable of changing from transparent to a color when the material is in a
liquid state, there is a greater selectivity in the utilization of the
materials such as the sensitizers and the print out materials, for
example. Thus, the material forming the ink can be made so as to have one
material responsive for changing to a color and another material
responsive for desensitizing, for example.
Therefore, the present invention enables one to utilize the unique
characteristics of materials formed of photochromic, electrochromic, or
thermally sensitive properties without having to employ a specially
treated paper. Accordingly, the information can be recorded on a variety
of substrates.
By applying the energy source to the material when it is in its liquid
state, the time for change from transparent to a color is less than if the
energy source is applied to paper to change a portion of the paper to a
color. Thus, application of the energy source to the liquid results in the
printing speed being increased.
A faster response to the energy source also can be obtained when applying
the energy source to the liquid rather than to a solid through using a
higher degree of solvent, for example, to reduce the time to respond to
the energy source. Since this solvent evaporates when the droplets strike
the paper, the additional solvent does not present a problem as would
exist if it were to be utilized by specially treating the paper.
Therefore, this also enables increased printing speed.
An object of this invention is to provide asynchronous jet printing.
Another object of this invention is to use synchronized generation of
droplets for asynchronous jet printing.
A further object of this invention is to provide a method and apparatus for
producing a desired print pattern with ink jet printing without any
requirement for deflection and charging of the droplets.
Still another object of this invention is to provide a method and apparatus
for producing a desired print pattern on a recording medium from liquid
stream without the formation of droplets therefrom.
A still further object of this invention is to provide a method and
apparatus for producing a desired print pattern on a variety of recording
mediums.
The foregoing and other objects, features, and advantages of the invention
will be apparent from the following more particular description of the
preferred embodiments of the invention as illustrated in the accompanying
drawings.
In the drawings:
FIG. 1 is a schematic view showing one form of the information recording
apparatus of the present invention.
FIG. 2 is a schematic view showing another embodiment of the information
recording apparatus of the present invention.
FIG. 3 is a schematic view showing a further modification of the
information recording apparatus of the present invention.
FIG. 4 is a schematic view showing still another form of the information
recording apparatus of the present invention.
Referring to the drawings and particularly FIG. 1, there is shown an ink
reservoir or manifold 10 to which ink is supplied through a supply tube
11. In this embodiment, the ink is formed of a photosensitive material
capable of changing from colorless to a color when exposed to light
radiation in a selected wavelength range.
The material of the ink can be selected from any of the leuco dye classes,
for example. Ultra-violet light initiates a free radical reaction followed
by a chemical reaction resulting in the formation of dye molecules.
One suitable example of the ink material is sold under the trademark
"Dylux" by duPont. This material is most sensitive to light radiation
having a wavelength range of 320 to 360 nanometers. When subjected to
radiation in this wavelength range, the material changes from transparent
to blue. It is believed that by acting on the liquids, a wider latitude of
combinations of sensitizers and printout materials is possible to enhance
printing speed.
The ink from the reservoir 10, which is under a selected pressure, is
directed through a nozzle plate 15. The nozzle plate 15 has a plurality of
nozzles 16 formed therein with each of the nozzles 16 directing a stream
17 of ink therefrom.
Each of the streams 17 can be subjected to a vibrating frequency source 18
such as a piezoelectric transducer, for example, so that each of the
streams 17 breaks up into a plurality of uniformly spaced droplets 19.
Each of the nozzles 16 directs the droplets 19 in the direction indicated
by an arrow 20. The droplets 19 are directed toward a recording medium
such as a paper 21, which is moving in the direction indicated by an arrow
22.
Between the formation of the droplets 19 from the stream 17 and the
striking of the paper 21 by the droplets 19, each of the droplets 19 in
each of the streams 17 can be subjected to a source of light radiation
having the selected wavelength range which will cause any of the
transparent droplets 19 subjected thereto to become a color. Thus, the
droplets 19, which are exposed, will produce a visible spot on the paper
21 as part of the print pattern.
One suitable source of light radiation is an ultra-violet laser 25
producing light within the selected wavelength range. The light from the
laser 25 is supplied through a modulator 26 to a rotating mirror assembly
27. The mirror assembly 27 is rotated by suitable control means 28 so that
the light from the laser 25 is directed to a droplet 19 in each of the
streams 17 of the droplets 19 separately in a selected sequence. The
modulator 26 is controlled so that it regulates whether the light from the
laser 25 is applied to the droplet 19 to which the rotating mirror
assembly 27 is directing the light from the laser 25 at the particular
time.
Thus, each of the transparent droplets 19 exposed to the laser 25 becomes a
color and prints a spot on the paper 21 when the droplet 19 strikes it.
Any of the droplets 19, which are not subjected to the light from the
laser 25, remain transparent or colorless when it strikes the paper 21.
To prevent the transparent droplets 19, which have not been exposed to the
light from the laser 25, from changing to a color if the paper 21 should
be exposed to a source of light radiation having a wavelength, which will
expose any of the transparent droplets 19, it is necessary to desensitize
or deactivate the transparent droplets 19 which have not been subjected to
the light from the laser 25. Accordingly, a desensitizer 29 is employed to
deactivate the transparent or colorless droplets 19, which have not been
subjected to the light from the laser 25.
The desensitizer 29 is disposed to deactivate the transparent droplets 19,
which have not been subjected to light from the laser 25, before or after
they strike the paper 21. The desensitizer 29 can be a light source having
a wavelength in the visible range of 400 to 500 nanometers.
Accordingly, the paper 21 has the desired print pattern produced thereon
through the modulator 26 controlling the application of light from the
laser 25 as each of the droplets 19 of each of the streams 17 advances
towards the paper 21 from the nozzles 16 in the nozzle plate 15. The
desensitizer 29 deactivates any of the droplets 19 which have not been
subjected to light from the laser 25 to prevent any inadvertent change of
the transparent droplets 19 to color if the droplets 19 should be
subjected to light radiation in the selected wavelength range.
If desired, the modulator 26 can be employed to control the quantity or
intensity of light applied to each of the droplets 19. Through the
modulator 26 controlling the quantity or intensity of light applied to
each of the droplets 19, varying contrasts of the color of each of the
droplets 19 are obtained and produced on the paper 21. The desensitizer 29
insures that the droplets 19 which have been subjected to less than the
full quantity or intensity of the light from the laser 25 by the modulator
26 also are deactivated insofar as being capable of changing to a darker
shade of the color.
Referring to FIG. 2, there is shown a separate light source 33 producing
light in the selected wave length range as the source of energy for
application to separate streams 34, 35, 36, and 37, respectively, of
droplets. The droplets of the streams 34-37 are preferably produced in the
same manner as described with respect to FIG. 1 with the droplets of the
streams 34-37 moving towards the recording medium such as a paper 38 (This
is into the drawing in FIG. 2). The paper 38 is moved in the direction
indicated by an arrow 39.
One suitable example of the light source 33 is an ultra-violet light. Thus,
the light from the single light source 33 can be employed to cause each of
the transparent droplets of each of the streams 34-37 to change to a color
when subjected thereto.
The light source 33 is connected through light pipes 41, 42, 43, and 44 for
application to each of the droplets of each of the streams 34, 35, 36, and
37, respectively. The light pipes 41, 42, 43, and 44 apply the light from
the light source 33 through light modulating cells 45, 46, 47, and 48,
respectively. One suitable example of the light modulating cells 45-48 is
a liquid crystal. Instead of using the liquid crystal, any other light
scattering or absorbing device can be employed as the light modulating
cell such as a polarizer analyzer, for example.
Each of the light modulating cells 45-48 is separately controlled so as to
determine whether each of the droplets of each of the streams 34-37 is
subjected to the light source 33. The light modulating cells 45-48 are
activated simultaneously for application of the light source 33 to one of
the droplets in each of the streams 34-37 at the same time.
The remainder of the operation of FIG. 2 is the same as that described with
respect to FIG. 1. Thus, the droplets of the streams 34-37 strike the
paper 38, which is moving in the direction of the arrow 39, to record the
desired print pattern, and then the transparent droplets are desensitized
by the desensitizer 29, which is disposed closer to the paper 38 than the
light modulating cells 45-48.
If desired, the light modulating cells 45-48 can be controlled to regulate
the quantity or intensity of light supplied to the droplet. Thus, each of
the droplets of each of the streams 34-37 can have a varying contrast.
Referring to FIG. 3, there are shown separate radiation sources 50, 51, 52,
and 53. Each of the radiation sources 50, 51, 52, and 53 is applied to the
separate streams 34, 35, 36, and 37, respectively, of droplets.
Each of the radiation sources 50-53 is separately controlled from a voltage
control 54. Thus, the control 54 determines which, if any, of the
radiation sources 50-53 are activated when each of the droplets of the
streams 34-37, respectively, passes the radiation sources 50-53,
respectively.
The radiation sources 50-53 must be capable of producing radiation in the
selected wavelength range to change the transparent droplets of the
streams 34-37 to a color when the radiation source is applied thereto. One
suitable example of each of the radiation sources 50-53 is a laser diode.
The laser diode can produce an infrared radiation of a wavelength to act on
a thermally sensitive material of which each of the streams 34-37 is
formed. One example of the thermally sensitive material is a colorless
diazoamino dye base. Another example of the thermally sensitive material
forming the ink is a triazine type of dye base with a napthol coupling
component. By including a light sensitive N-halosulfon-anilide oxidizing
agent, which can be rendered inactive by exposure to an actinic radiation,
the non-exposed areas of the streams can be desensitized against further
action of heat.
After the selected droplets of the streams 34-37 have been subjected to the
radiation sources 50-53 and before or after the droplets of the streams
34-37 have contacted the paper 38, the droplets of the streams 34-37 are
subjected to a desensitizer 55. The desensitizer 55 can be the same as the
desensitizer 29 and is disposed closer to the paper 38 than the radiation
sources 50-53 in the same manner as the desensitizer 29 is disposed.
The desensitizer 55 deactivates any of the droplets of the streams 34-37
which have not been subjected to the radiation sources 50-53. This
prevents any inadvertent changing of the transparent droplets into a color
if later subjected to radiation of the selected wavelength range.
The droplets of the streams 34-37 are sensitized by the radiation sources
50-53 to produce a desired print pattern on the paper 38. The droplets of
each of the streams 34-37 strike a single horizontal row of the paper 38.
The radiation sources 50-53 can be controlled by the voltage control 54 so
that each of the droplets of each of the streams 34-37 can be subjected to
a different quantity or intensity of radiation. Thus, each of the
droplets, which is exposed to the radiation source with which it
cooperates, may be a different intensity of the color to produce a varying
contrast on the paper 38. The desensitizer 55 also prevents any of the
droplets which have not been fully changed in color from changing to a
darker shade of the color if the droplets should be exposed to a source of
radiation in the selected wavelength range.
Instead of the radiation sources 50-53 producing an infrared radiation, it
should be understood that they could produce light radiation within a
selected wavelength range. Thus, the radiation sources 50-53 could be
laser diodes having an appropriate wavelength for the chemical properties
of the ink to cause it to change from transparent to a color when
subjected to the radiation. Thus, the structure of FIG. 3 can be utilized
to apply either light or heat as the radiation source.
Referring to FIG. 4, there are shown the nozzles 16 of the nozzle plate 15
of FIG. 1. An electrode 60 is disposed within each of the nozzles 16 and
connected to a source 61 of voltage by a control 62. It should be
understood that each of the nozzles 16 has one of the electrodes 60 with
all of the electrodes 60 being controlled by the control 62.
In this arrangement, the ink is formed of a suitable electrochromic
material which will change from transparent to a color when subjected to
an electric field. Suitable examples of the electrochromic materials are
tungstates and molybdates.
As a stream 63 passes through the nozzle 16, the application of the
electric field thereto by the control 62 allowing the voltage from the
source 61 to be applied to the electrode 60 causes the portion of the
stream 63 to which the electric field is applied to change from
transparent to a color. This occurs through the stream 63 being in contact
with the electrode 60.
The stream 63 breaks up into droplets 64 after leaving the nozzle 16 in the
same manner as in FIG. 1, and the droplets 64 move in the direction of an
arrow 65. Thus, the timing of the application of the electric field to the
stream 63 must be coordinated with the production of the droplets
therefrom.
It should be understood that the ink can be formed of material having
electrochromic, photochromic, and thermal sensitive properties at the same
time. The selection of one of the properties or a combination thereof
would depend on how the energy source is to be applied.
While the liquid streams have been shown as being formed into droplets, it
should be understood that such is not a requisite for satisfactory
operation. Thus, a continuous liquid stream could be supplied, for
example, and the selected energy source applied to selected portions
thereof with each of the selected portions containing substantially the
same quantity of the stream as the droplet. Only the selected portions of
the stream subjected to the selected energy source would print on the
paper.
An advantage of this invention is that it eliminates the need for charging
and deflection of any ink droplets used in ink jet printing. Another
advantage of this invention is that no critical synchronization of the
break off point of the droplets from the stream is required. A further
advantage of this invention is that it enables the recording medium to be
disposed closer to the nozzles since deflection and charging means are not
required whereby the nozzle tolerances need not be as stringent. Still
another advantage of this invention is that the substantially uniform
spacing between the droplets is maintained until the droplets strike the
recording medium since there is no deflection whereby some of the
aerodynamic problems are significantly reduced. A still further advantage
of this invention is that there is no requirement for any specially
treated paper to function as the recording medium so that recording can be
accomplished on any of a variety of substrates.
While the invention has been particulary shown and described with reference
to preferred embodiments thereof, it will be understood by those skilled
in the art that various changes in form and details may be made therein
without departing from the spirit and scope of the invention.
* * * * *
|
|
 |
|
 |
Description |
|
