Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-12-28
2002-11-05
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S041000, C347S012000
Reexamination Certificate
active
06474779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording method, etc. in which images are formed by ejecting a recording liquid such as ink onto a recording medium while scanning recording means.
In particular, the present invention relates to an ink-jet recording method, etc. in which a deterioration in image quality is prevented by reciprocal scanning.
2. Description of the Related Art
Conventionally, an ink-jet recording method for performing recording on various recording mediums is capable of high-density and high-speed recording operation, so that it is applied to a printer, a portable printer or the like as an output medium of various apparatuses, which have become commercial.
Here, the individual recording apparatuses assume constructions in correspondence with the functions, forms of use, etc. peculiar to them.
Generally speaking, an ink-jet recording apparatus is provided with a carriage on which a recording means (recording head) and an ink tank are mounted, a feeding means for feeding the recording medium, and a control means for controlling these components. And, the recording head, which ejects ink droplets from a plurality of ejection holes, caused to perform serial scanning in a direction which crosses, for example, at right angles, the direction in which the recording medium is fed (sub scanning direction), and, when no recording is being performed, the recording medium is intermittently fed by an amount equal to the recording width.
This recording method, in which ink is ejected onto the recording paper in correspondence with a recording signal, is widely used as a recording system which is of low running cost and quiet. Recently, a number of products which use a plurality of inks and applied to color recording apparatuses have been put into practical use.
When the ink-jet recording method is applied to a color recording apparatus, the construction of the recording head can be roughly classified into two types.
One is a recording head in which, as shown in
FIG. 14
, a number of nozzles ejecting ink are arranged in a line in the sub scanning direction. In the construction shown in
FIG. 1A
, nozzles
100
y
,
100
m
,
100
c
and
100
k
for ejecting yellow, magenta, cyan and black inks are arranged in a line in the sub scanning direction such that the colors do not overlap each other. In the construction shown in
FIG. 1B
, a nozzle
101
k
for ejecting black ink is separate from nozzles
101
y
,
101
m
and
101
c
for ejecting color inks. As is apparent from
FIG. 14
, regarding yellow, magenta and cyan, when so-called secondary colors, blue, red and green are formed to form images of different colors at different positions on the recording medium, the order in which the colors are superimposed on each other is fixed independently of the scanning direction of the recording head. For example, when forming a blue image, recording is first performed in cyan and then recording in magenta is performed thereon. Thus, when the recording head
100
or the recording head
101
is used, no inconsistencies in color are generated if recording is performed through forward scanning and backward scanning.
However, if the number of nozzles for different colors is increased to achieve an increase in speed, the length of the recording head is increased, resulting in an increase in size, or the method of holding the recording medium in the recording portion is complicated, resulting in an increase in the cost of the recording head or the apparatus.
In the second type of construction, recording heads
102
k
,
102
c
,
102
m
and
102
y
for ejecting black ink, cyan ink, magenta ink and yellow ink are arranged in the main scanning direction as shown, for example, in FIG.
2
. When this recording head
102
is used, the inks of all colors are ejected in correspondence with image data by one scanning.
Here, when, to achieve an increase in speed, an image is formed by alternately repeating main scanning (in the direction A) and sub scanning (in the direction B), when so-called secondary colors, for example, blue, red and green, are formed, the order in which colors are superimposed on each other differs between the main scanning (in the direction A) and sub scanning (in the direction B), with the result that the color taste (hue) differs between the main and sub scanning, so that inconsistencies in color are generated, resulting in a substantial deterioration in image quality.
In the following, the problems involved when the recording order differs will be specifically described.
To execute full color recording in an ink-jet recording apparatus forming images using inks of four colors, ink droplets of the inks of the four colors are caused to reach the recording medium in appropriate balance, and other colors are generated through mixing. When recording a green (G) image, recording is performed by mixing C and Y. That is, C and Y dots are placed at the same pixel.
FIG. 3
shows the condition of an ink droplet caused to reach ordinary paper by using the head of FIG.
2
.
FIG. 3A
is a sectional view of an ordinary paper sheet at the time of forward recording (C Y), and
FIG. 3B
is a sectional view thereof at the time of backward recording (Y C). In
FIG. 3A
, recording is first performed in C to cover the surface, and Y, in which recording is performed afterwards, goes deeper than C.
Conversely, in
FIG. 3B
, recording is first performed in Y to cover the surface, and C, in which recording is performed afterwards, goes deeper than Y. When seen on the surface, the recording of
FIG. 3A
appears to be of a green that is rather cyanish, and the recording of
FIG. 3B
appears to be of a green that is rather yellowish. Thus, if the colors mixed are the same C and Y, the hue completely differs between the forward and backward recordings. As a result, color inconsistency is alternately generated at each line feed.
As described above, the construction of the ink-jet recording head applied to the color recording apparatus is of two types, of the type (the latter) in which the nozzles of the different colors are arranged in the scanning direction is suitable for achieving an increase in the speed of the apparatus. However, this type involves a problem that inconsistency in color is generated due to the difference in the order in which the colors are superimposed on each other between the forward scanning and the backward scanning of the recording head.
To prevent the above-described inconsistency in color in reciprocation, Japanese Unexamined Patent Application Publication No. 5-278232 proposes a system in which, to complete the recording of a predetermined region by a plurality of main scanning operations, thinning-out images are sequentially recorded while sequentially selecting a plurality of thinning-out arrangements in a complementary relationship. Disclosed is a method in which the thinning-out arrangement selected in the same scanning differs between the colors. In this method, however, a so-called multi-pulse recording is performed in which recording is completed by a plurality of main scanning operations, so that the requisite time for complete the recording is rather long.
Further, in Japanese Unexamined Patent Application Publication No. 6-106736, when performing recording while reciprocating the recording head of different colors having a recording density higher than the input image data in the arrangement direction, the recording image is composed of a plurality of pixels (2×2) with respect to one pixel of the input image data, so that, when recording a mixed color image, inks of two or more colors are not superimposed on the 2×2 pixels. However, in this method, the recording resolution is lower than the resolution the recording head originally possesses.
To solve the above problem, Japanese Examined Patent Application Publication No. 3-54508 discloses a method in which the color processing method differs between the forward scanning and the backward scanning of the recording head. However, in this method, two k
Inui Toshiharu
Kaneko Takumi
Kanematsu Daigoro
Nakajima Yoshinori
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