March 1999
March 1999
Many years ago, in a pre electronic, pre-PC age, patents were received, read, then issued by hand. They covered many inventions now used by man - a better detergent for mom, longer wearing shoe rubber for the kids, and even longer lasting diamond tipped blades for dad. Some of these inventions have gone on to fame, while others sit idle, collecting dust in the closets of their inventors and in the long halls of storage drawers in the patent offices around the world.
Patents are a man-made agreement -- one that establishes the original author and creator of an invention was this person, and gives to that person the exclusive right to capitalize on their invention in the marketplace. Naturally, patents came about far after the various laws of the land, at a time when people attempted to strive for some 'civility' among each other that was governed by something more than just the 'arbitrary' finger on the trigger of a gun barrel, or the quick stab of the knife into an unlucky competitor. Patents arrived when people truly began to 'believe' in the universal laws espoused by their peers, but only agreed upon after much harsh argument and debate.
Patents are, in fact, an evil, an arbitrary limit on the capitalist marketplace placed by man so that the inventor can have time to bring their inventions to market to make some profit before the other lions arrive. Because of this allowance given to the receiver of the patent, they are hotly contested for and many people will apply for patents the moment they have something new and innovative at hand to gain the advantage.
Due to the differences in patents laws in different countries, some patents that are valid in one country will not be valid in a neighboring country. In short, there are two significant ways of determining the lawful and 'original creator' of an invention. The first way is by the time of application -- thus, the person who gets his patent application into the hands of the patent officer wins, even if he did not 'invent' first. The second way is by the original date an invention was first created -- thus, even if the original creator files last, he still gets the patent.
Well, if you want to know why this point is of vital note: Japan and United States, the two largest manufacturers and creators of ink jet printing devices in the world, use different methods, the two described above. Naturally, this has made some creators in one country extremely wary of filing a patent in the other for fear that another competitor will look over the application, then file the winning patent in the home country.
In any case, let's get on with the show.
After the age of the TRS-80, the age of the Apple II, the age of the Commodore 64, XT, Apple, and PC, we have arrived in the age of the Internet. And unlike days past when the only way to look at a patent was to either visit the Patent Office in person, or to request a copy by mail after submitting some fee, patents can now be viewed online courtesy of IBM, one of the world's most prolific applicants of patents (but surprisingly, not #1 -- a Japanese company has this title).
The IBM Patent Server is located at: www.patents.ibm.com
Scanned pages of almost all issued US Patents from the 1970s are available for browsing online for free.
What this means is you, the average person, now has access to the storehouse of human innovations throughout the past two decades! (unfortunately, there are some bad patents as well; ideas so absurd or obtuse, they will never be used)
And what follows is a walk through some of the various patents that accompany our ink jet printers home with us, to allow us to produce high quality output in a matter of minutes. (You can retrieve the full patent application of the patents described in this article directly from the IBM Patent Server yourself as you read.)
This is my brief journey through 760 pages of more than fifty patents related to modern ink jet printers.
Short Index........................
HP's PhotoRET
Epson's MicroPiezo
HP's Cooling Mechanism
Canon's Plain paper optimisation
Alps Dye-subs
...........................................
Patent Owner, US Patent #
[Search Field] (Patent Issued Date, Patent Application Date)
Canon US 4740796
[346/001.1] (1988, 1986)
Ever a mouthful, this title simply describes what is to follow a complete
description of the Canon Bubblejet concept -- bubbles forcing dots out of the
nozzle -- and their use in a printer.
There are three major methods of forcing inkjet dots onto a paper in use today
in the home inkjet market - bubblejet, thermal, and piezo -- each respectively
used and patented by Canon, HP, and Epson. In the bubblejet method, a resistive
element heats the ink (a liquid) until it changes phase and becomes gas, thus
creating an expanded bubble in the nozzle tubes which forces some ink out the
tip and onto the paper. The patent covers some items of other interest: Dot size
is primarily controlled by ink pressure or pulse width of the electrical signal
driving the heating resistor. They describe how up to 6 resistor can be placed
in line to generate different dot sizes when fired and controlled in parallel.
The ink they use has a basic composition of water (68%), ethylene glycol (30%)
and black pigment/colorant (2%).
As you can see, most of the inkjet droplets are wasted carrier -- water and
glycol, and just a small percentage is colorant. This naturally leads to many of
the deficiencies of inkjet printing vs. other methods of printing such as fading
(when light hits the colorant, the UV and IR rays tend to break down the
chemical bonds and cause fading), lack of density (dark colors can not be made
darker than a certain level because the amount of colorant is not very high),
and the small color gamut of the output (the colors that can be created are
limited due to the limited amount of colorant applied).
Yet, this point aside, we see that the 'idea' of a variable dot inkjet printer
has been around for more than a decade (1986, invention made before the
application date). Both methods described push a larger volume of ink out the
nozzles as they increase.
Canon US 5826333
[29/890] (1998, 1995)
In detail, you can read about how inkjet heads are actually made using standard
and microelectronic manufacturing techniques. Needless to say, only the
technically inclined will want to read this in detail; others may pass for the
pretty pictures.
HP US 5359353
[347/086] (1994, 1991)
In the early days (eg. HP 1200 models), inkjet printers simply printed until
they were out of ink, and continued to do so unless the operator realized this
condition and changed the cartridge. Early cartridges had no clear ink level
windows, so it was a guessing game to determine how many pages of life were left
in each cartridge. One of the early innoventions was to create a inkjet
cartridge which had a visible ink level indicator so you can quickly and
reliably check the ink level with a glance at the cartridge. In this HP design,
a bag of ink has two colored strips attached to the sides. As the bag collapses
as the ink runs out, the strips move relative to each other and is visible
through a small window. One strip is colored differently from the other so you
can determine just how much ink is left inside.
HP US 5721573
[347/007] (1997, 1994)
Despite the above invention, people are lazy and often do not want to open the
cover of their printers to check their printers. Also, printers may be networked
and located far away from the operator. Finally, mechanical indicators are
'expensive' to produce and incorportate into an inkjet cartridge, and they do
not tell the computer nor the printer that the ink has run out. Print jobs can
still run without ink in the printer. By HP's second generation of inkjet
printers (eg. HP 6xx series), their engineers had thought of a novel way of
measuring the amount of ink in a cartridge. They measured the time it takes for
the ink head to cool down from the operating temperature to another preset
point. The time difference reflected the amount of ink in the cartridge and how
fast heat was pulled away from the ink head into the ink liquid itself. With
this invention, the printer could simply gauge the temperature difference during
page feeds, or during lengthy head cleaning cycles, to let the computer know how
much ink was left, without slowing down the regular print process. Printers
never do rest...
Various Epson Patents
Epson US 5748214
Same as above, describing the piezo inkjet head used in Epson printers. The
piezo inkjet method is that no bubbles of gas or air are introduced into the
nozzles. In piezo printing, a small piezo element temporarily moves inward when
an electrical signal is applied, thus constricting the nozzle and forcing ink
out the end. Clean, simple, and the epitome of solid-state with no heating
elements to wear or burn out, or gas bubbles to clog the nozzles. The second
patent goes into technical detail as to how the piezo head is driven by
circuitry.
HP US 5650808
[347/043] (1997, 1995)
Besides the basic method used to force ink out of the nozzle, much study and
research has been made to improve their design to improve output quality. Here,
we see that on method of improving the output is to leave enough space between
nozzles on the printhead so that the colors to not mix on the head itself. Since
all liquids tend to adhere to a surface, it is natural to assume that if nozzles
are spaced too closely to one another, the liquid that comes out of each will
flow by way of their surface tension together. This is one limit of inkjet head
sizes and may prevent ultra-thin or -small devices from being capable of rapid
output using inkjet heads.
HP US 5673069
[347/015] (1997, 1994)
One ever popular method of achieving better output from an inkjet printer is
through the use of smaller dots and higher resolution. Reducing the dots is
necessary as resolution increases; otherwise, the dot will be too big and
overflow into the next. We see here that one of the issues that is dealt with is
the uniformity of drop sizes. The temperature of the print head changes the
viscosity of the ink, thus creating variations in drop sizes. In this patent, it
is noted that it is better to keep the temperature at a steady 'reference' value
by firing non-printing pulses of the thermal resistors in the nozzles to keep
the temperature high. By using two different reference temperatures for 300x300
dpi and 300x600 dpi printing, two dot sizes are available for the two print
modes -- a larger dot for the former, a smaller dot for the latter. This idea is
introduced in the early HP printers, such as the 6xx line of inkjets years ago.
Various HP Patents
HP US 5726690
Yet another mouthful, we see in this patent that the early HP inkjet printers
(6xx line, RET series) could vary the dot sizes between ~66 and ~84 picolitres
by varying the width of the electrical pulse sent to the thermal resistor(s) in
the nozzles. This allows for the use of larger dots at 300x300 dpi, smaller ones
at 300x600 dpi. Pulse width modulation is a very popular idea used to control
dot sizes and you'll see Canon and Epson using this idea, albeit patented for
their respective inkjet technologies.
The second patent introduces timings for the pulses. eg. 1.9 microsecond for a
66 pl. drop size. Also, the RET (resolution enhancement technology) concept is
introduced. To reduce the banding problems often seen in older inkjet printers,
micro stepping and multi-pass printing is introduced along with 4 dot sizes vs.
2. (a precursor to the 16 dot sizes found in today's RET II printers) In short,
a subset of dots for each particular line is printed in one pass of the head.
The paper is fed a small amount, not quite enough to go to a completely new
line, and the head again passes over the area and applies another subset of dots
missing from the first pass. The ability to produce multi-sized dots along with
the ability to place dots in between other dots enhances the output in the HP
printers with RET.
The third patent introduces the idea of rings around the nozzle to control ink
spread across the head. One way of preventing ink dropplets from spreading on
the nozzle and resulting in distorted output is to etch rings around the nozzle.
When a volume of ink forms on the head during droplet formation, it will expand
until it reaches the first ring and stop -- similar to a moat around a castle.
Only when the volume is great enough to overcome the barrier of the first ring
does it expand further, only to stop on the second ring, and so forth. Various
methods are used to coat the surface to head and rings to further control the
spread of ink. As a result, a better formed ink drop is produced by the inkhead.
As you can read, these three patents together let anyone understand how the HP
RET technology, introduced many years ago, led to better inkjet printers on the
marketplace that what had been previously been made available (not anymore
however).
Canon US 5748207
[347/043] (1998, 1993)
One of the problems that was occurring frequently back when inkjet printers
were starting out was bleeding. You see, paper is made of fibers. These fibers
draw water and other liquids into them as well as ink. Although many Chinese
artists have made a name for themselves with their classical images of bamboo
and landscapes with bleeding brushstrokes, almost everyone dislikes inkjet
output that has bled to some degree. This not only makes images blurred, text
characters are also ruined by ink bleed. When inks of the same color bleed into
each other, you notice the effect less. But when colors of differing colors
bleed into each other, you will immediately notice the rainbow of colors that
are created by the mixture. Inkjet printer often use a slightly larger dot than
the resolution they are printing at. Why? Dots are round, not square like the
grid they are to print to, thus there are four areas at each corner where no ink
is. If dots were the same size as the grid, images would appear poor as areas of
white paper show through past each dot. Thus, overlapping dots that are slightly
larger than the resolution of the print is used. Unfortunately, this allows
adjacent dots to touch each other, and bleed if wet. Since all inks take some
time to dry, one method that has been extensively used to prevent this is to
print a subset of dots in one pass, the others in subsequent pass(es) for each
line. And you wonder why some printers take so many passes over each line....
All of this is done to reduce the warping of paper due to being too wet, while
reducing intradot bleeding. As you can see in Canon patent 5831642, a lot of
work and thought goes behind the scenes to figure out how a solid pattern is to
be broken up into multi-pass patterns -- you can view the patterns yourself in
this patent.
HP US 5821957
[347/43] (1998, 1997)
An older idea of the above, HP tries to reduce bleeding by first printing the
color dots, then the black dots later. While this reduces bleeding by letting
inks dry between passes, it is not as advanced as the later Canon patent above.
So, as you can see, a simple idea can be extended in a novel way and patented.
Epson US 5748208
[347/43] (1998, 1993)
You'd be surprised, but even the order dots are placed on the paper, and even
the colors used affect the amount of blurring across colors. When you print
color dots next to black dots on paper, the black ink will tend to bleed into
the color dots while both are still wet. Since it takes far longer for the ink
to dry on the page than a couple seconds, it doesn't make sense to wait several
seconds on each pass. HP has taken the route of adding a heater to some of their
faster printers (eg. HP 1200, HP 2000/2500) to have the ink dry quicker, but it
still doesn't directly address the bleeding of black into adjacent color areas.
Epson notes that the paper fibers naturally pull ink sideways during the normal
process of inkjet printing. Dots falling on dry paper next to wet areas already
covered with dots lead to the natural migration of inks across the two
boundaries. Surprisingly, the fix is to first print a color dot in the same area
as where the black dot is to go adjacent to a color area! When a black dot is
then printing into this pre-saturated area, the ink does not migrate sideways,
but rather only vertically into the paper. As a result, bleeding between the
black/color boundary is significantly reduced and rapid printing can occur with
the page still wet.
Various Patents/different owners
Canon US 5832185
One of the initial, and most visible, problems that occurred with early inkjet
printers was the banding of colors between different lines/passes of the inkjet
head. The mechanical feed mechanism is simply not accurate enough to provide
exact pixel feed on each pass, nor can there be any guarantees that the print
head itself is perfectly accurate. As a result, the pixels on one row slightly
overlap those of another pass, and banding results. The slight differences that
occur chemically and physically in the paper and inks as they dry also
contribute to this effect. To minimize or eliminate these effects, a variety of
dithering patterns are used. As a quick backgrounder, dithering is used in
printing whenever a limited number of original colors are used to create the
entire gamut of intermediate colors on paper. One would think that if you had
only four colored crayons, you would have a hard time creating other colors.
Luckily, at the resolution used in printing (100 dots per inch or higher), the
human eye makes up for this lack of colors by blending patterns of colors
together. Thus, a pattern of 50% cyan and 50% yellow appears to be green to the
human eye at the usual hand held distances. This mixing of patterns of colors
also applies to monitors, TVs, LCD panels, and other devices which use a limited
set of colors to display images.
The easiest way one can create a pattern is to simply assign them by
percentage. Lets say we have a two by two pixel pattern grid -- with each pixel
assigned to any one of the four CYMK colors (in 4-color printers). If we wanted
green, we could simply color two dots cyan and two yellow. However, if we simply
did this across a large area of green, we would see that these grids aligned
side-by-side suddenly create an even pattern of lines alternating between cyan
and yellow. Since this isn't the desired effect, we can introduce 'random'
dithering patterns which mix up the way we color a grid to reduce the
'patterned' effect we would otherwise expect to see. One common method is the
diffusion array which, by its randomness of dot placement, reduces banding
significantly. However, even with the diffusion array, unexpected groups of
whirls and other defects can appear because the randomizing process introduces
'unwanted' patterns by chance.
Thus, many of these more advanced dithering patterns not only randomly form
grids, by they also modify them based on neighboring grids to further eliminate
dithering patterns and such. Dithering patterns also affect the 'relative'
quality of the final pictures that are printed. As an example, since human skin
is one of the flattest color areas in a photo, your mind expects to see little
variation across the body and face. Using 'normal' dithering patterns, black
dots may unexpectedly get placed in areas of skin. While this would be fine at
matching the 'real' color closely if it were not skin, black dots mar skin areas
and colors to the human eye. A modified dithering pattern that avoids placing
black dots in skin tones 'improves' the picture. You can see this difference in
Epson printer drivers as they have an option to select between photographic and
other types of dithering array biases manually. Also, since the human eye
notices bright colors and adjusts them automatically for slight hue mismatches,
it is 'better' to reduce the presence of dark/black dots in bright/light color
areas to enhance the apparent vividness of pictures. Yes, the colors may not
match as closely, but the human eye loves and accepts slightly off bright 'eye
candy' colors more than bright colors with annoying dark dots here and there --
quite simply because such artifacts of limited color printing does not occur in
'real' life where there are no such dithering effects at all.
Epson US 5844585
[347/43] (1998, 1996)
Combine the two ideas of multi-pass line scanning and dithering with a novel
idea of feeding the paper slightly at each pass and you get this patent. While
one line is being passed over a second time, the inkjet head has already
advanced far enough to begin printing the first pass for the next. With each
pass, the paper is slightly advanced to give the printer a head-start on the
following lines, while the prior lines are completed. No need for the nozzles of
one color to sit idle after it has printed its share of dots for that line as
the heads continues to pass over and over again to finish with the other colors.
Open up any Epson color printer and you'll see this novel idea at work.
Epson US 5684932
[395/109] (1997, 1994)
Novel dither matrixes also help when you have the fundamental problem faced by
all inkjet printers -- round dots vs. square ones. This may take a moment to
sink in, but when you realize that round dots do not cover the area of a square
completely (it leaves the four corners untouched), you see that there's a
problem. How do you create a dither array properly? Most inkjet printers of the
past used slightly larger dots than the width of the square grid to adjust for
this. Unfortunately, this also alters the image (eg. oversaturation of
overlapping areas between dots) and this patent attempts to correct for these
large dots when used in a dither matrix.
HP US 5764254
[347/70] (1998, 1995)
In HP printers, especially early ones (eg. HP 1200), the black color cartridge
was capable of printing at 600 dpi and the nozzles were accordingly as small.
Color, unfortunately, printed at 300 dpi and used larger nozzles. Differences in
ink composition also contributed to this. Well, what to do? This patent explains
how they lined everything up to make it all work. Naturally, printers today can
simply avoid this mess by using dots and nozzles of the same size regardless of
color.
Canon US 5717448
[347/43] (1998, 1997)
Highly variable dot technology can improve images by reducing the visible signs
of dithering. If a smaller dot is used to correctly dither an image, the more
natural it will appear. In this patent, we see how generating multiple pulses
creates multiple dots. Placing many smaller dots on top of each other results in
a larger final dot on the paper. This is a precursor to the 16 dot size
technology in the latest HP 7xx/8xx/11xx/2xxx series printers. But, to avoid
bleeding, dots of different colors placed next to each other are limited to a
maximal size, one such that they just barely touch each other, but do not
overlap. Mentioned are there dots sizes, 5, 7 and 10 picolitres for various
implementations but have yet to see an implementation in a commercial, home
Canon inkjet printer. (They do have dual dot size printers.)
Canon US 5805190
[347/100] (1998, 1996) (
Click here for the Patent
)
Introduced in the BJC-7000, the idea behind this invention is to prevent
bleeding by chemical reactions. Ink is 'wet' in that it will bleed into paper.
To prevent this, a liquid chemical is first applied to an area of the paper just
before ink is applied on top. Due to a chemical reaction between the liquid and
ink, the ink 'dries' is made insoluble and permanent -- thus, it stays near the
surface of the paper and does not migrate through the fibers of the paper. Of
course, we've yet to see this idea work perfectly across a broad range of
papers.
Koyu Nikoloff US 5660622
[160/287.34] (1997, 1996)
The easiest way to achieve high quality output from an inkjet printer today is
to simply use specially coated inkjet paper. Vs. the other ideas for improving
quality and reducing bleeding, using paper alone will give you the best
improvements, especially when companies optimize their inks for use on their
inkjet papers. The chemical composition of what goes into an inkjet paper is
disclosed in this patent. In this presentation, hydricated silica, binder,
optical brightner, water, cationic agent, leveling flow modifier, and dispensing
agent are the main ingredients. I'll leave the chemical compound details in the
patent for those who possess a good understanding of chemistry.
Canon US 5825377
[347/15] (1998, 1997)
Epson US 5795082
[400/120.09] (1998, 1997)
The best in inkjet printing today comes from 6-color printers. The wider gamut
due to the expanded color set allows for more natural transitions between color
areas and more subtle gradiants.You can read in both patents in detail how the
various colors are patterned and combined for the best quality output. The Epson
patent covers their Sylus Photo printer, and explains in detail how the color
ranges are matched to the desired colors, how the software determines whether to
use one color or the other, graphs the lightness of each color at various
densities, provides the names of the dyes used for each color and percentages of
total ink volume, etc.
You'll note that their colors do not reach full lightness (ie. the lightest
shades possible) -- about 95% instead -- nor full darkness (ie. the darkest
shades possible) -- even black applied at 100% coverage achieves between 20 and
25%. E.G. The ink composition chart lists four dyes used: Direct Blue 99, Acid
Red 289, Direct Yellow 88, and Food Black 2 in ranges from 0.7 to 4.8%. The rest
of the ink consists of Diethylene Glycol (20-30%), Surfinol 465 (1%), and Water
(63.1-79%). This explains why black text from inkjet printers do not look as
dark as black text from laser printers created from solid carbon. Also, this
means that third-party inks which use the same composition as stated in this
patent, have a very good chance of working just fine in your Epson Photo
printer. (Naturally, it would be ideal to have the actual inks processed though
a gas spectrometer and chemical analyzer...) A fine way of saving money. Mix
your own if you have these components handy.
Thus, unlike a traditional print, the color gamut and dynamic range of a
picture printed on these very best Epson Photo printers will not have the widest
gamuts of colors possible through other means. This is due to the fact that 3-7%
of inks used in inkjet printers are the actual color dyes/pigments. Still, for
those Epson Stylus Photo owners, this patent provides a very interesting look
behind the workings of your printer and reveals a lot of fascinating facts.
Alps US 5806995
[400/120.02] (1998, 1997)
For those who have or are interested in how the Alps 1300 (and similar Alps
5000) sub-dye printers operate, read this patent. The technology behind thermal
printers is very simple. Simply heat a carrier of color, which melts and is
transferred onto paper. These colors can mix during the melted stage and combine
to form a seemless output characteristic of photo quality sub-dye prints. Today,
the Alps 1300/5000 provide the very best photo output prints for under $500 US
to consumers for use with their computers for general use, bettering even the
best home photo inkjet printers available -- the Epson Photo Stylus series.
Unfortunately, patents do take a couple years to process, so the very latest
technologies are not publicly available. But based on the prior works we have
available to us, we can guess at the innovations being used and how their
applied today. With the IBM Patent Server in hand, you'll soon be looking up
patent numbers from a variety of products and surprise yourself when you learn
what is and can be patented, as well the innovations involved.
I leave you with the patent for the Colgate Tartar Control Toothpaste with
Micro Crystals (copper colored box).
Colgate US 4889712
[424/52] (1989, 1988)
Toothpaste can not be patented by itself. The product is of such universal
importance that the FDA and government would prevent such from occurring if
tried. But, better compositions than just fluoride and paste can be patented and
here, we see that plaque form when it crystallizes on the surface of the teeth.
The patent covers a polymeric polycarboxylate which doesn't dissolve in saliva
that, when applied, prevents the crystallization of plaque. Thus, not all
toothpastes are made equal and spending just a few pennies extra for better
toothpastes can improve your oral health.
Method of Manufacturing an Ink Jet Head
Spring-Bag Printer Cartridge With Volume Indicator
Cooldown Timing System Montiors Inkjet Cartridge Ink Levels
[347/70] (1998, 1995)
Inkjet Recording Head (
click here for the patent
)
Epson US 5818472
[347/10] (1998, 1995)
Inkjet Recording Apparatus
Color Ink Jet Pen Having Nozzle Group Spacing to Prevent Color Bleed
Method and Apparatus for Reducing the Size of Drops Ejected From A Thermal Ink
Jet Printhead
[347/015] (1998, 1994) (
Click here for the Patent
)
Control of Ink Drop Volume In Thermal Inkjet Printheads By Varying The Pulse
Width of the Firing Pulses HP US 5642142
[347/015] (1997, 1995)
Variable Halftone Operation Inkjet Printheads
HP US 5381166
[346/140.1] (1995, 1992)
Ink Dot Size Control For Ink Transfer Printing
Ink Jet Recording System for Preventing Blurring at Color Boundary Portion
Canon US 5831642
[347/9] (1998, 1997)
Ink Jet Recording Method and Apparatus
Method of Ink Jet Printing Using Color Fortification of Black Regions
Color Inkjet Recording Method
[395/109] (1998, 1997)
Alteration of Dither Matrix Size For Full Color Dithering
Epson US 5557709
[395/109] (1996, 1994)
Method And Apparatus For Dither Array Generation To Reduce Artifacts in
Halftones Images
Epson US 5796929
[395/109] (1998, 1996)
Banding And Ink-Bleeding Reduction In Cluster Dither By Screen Displacement
Epson US 5675716
[395/109] (1997, 1994)
Method And Apparatus For Vivid Color Correction In Binary Printing Devices
Epson US 5838885
[395/109] (1998, 1996)
Salt-And-Pepper Noise Reduction
Apparatus And Method For Printing High-Quality Color At High Speed
Method And Apparatus For Dither Array Generation To Reduce Artifacts In
Halftoned Image Data Utilizing Ink Reduction Processing
Alignment of Differently Sized Printheads in a Printer
Ink Jet Printing Apparatus And Ink Jet Printing Method
Method and Apparatus For Ink Jet Printing with Ink and a Print Property
Improving Liquid
Coating for Ink Jet Recording Sheets
Method and Apparatus for Ink-Jet Recording With Inks Having Different Densities
Printing System Utilizing Inks of Different Densities, Cartridges Used
Therefor, and Method of Recording Images
Thermal Transfer Printer
'Anticalculus Composition for a Toothpaste'
