Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-05-19
2002-11-19
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06481820
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a line type ink-jet printer which has a line-type head in which a plurality of nozzles are arranged, whose length is corresponding to the width of the recording medium, and in which ink is jetted from the nozzles onto the recording medium, and the recording medium is conveyed in a subsidiary scanning direction to thereby from an image is formed on the recording medium. More particularly, the present invention relates to an ink-jet printer suitable for high speed image formation and image formation with high resolution.
The image formation in the ink-jet printer is carried out as follows: the head is moved in the primary scanning direction while droplets of ink which are jet-controlled by an image signal, are jetted from nozzles of the head onto the recording medium; when the image is recorded on the recording medium by one line, the recording medium is moved in the subsidiary scanning direction by one line; the droplets of ink are jetted again from nozzles of the head onto the recording medium and one line of image is formed; and hereinafter, by repeating these operations, an image is formed on the recording medium.
Alternatively, as another structure, as disclosed in Japanese Tokkaisho No. 62-161547, there is a structure in which ink nozzles of the head are arranged with an equal pitch in the length of almost maximum recording width of the recording medium, and the head is structured as a fixed linetype head.
According to the structure, movement of the head in the primary scanning direction is not necessary, and an image can be formed only by the conveyance of the recording medium in the subsidiary scanning direction which is perpendicular to the primary scanning direction, thereby, high speed image formation can be carried out.
As described above, in the ink-jet printer having a fixed line-type head in which the head is not moved in the primary scanning direction, for example, when there are such nozzle defects as in the cases in which nozzles are blocked by dusts or the like, and ink can not be jetted (hereinafter, called no-jetting of ink), or the peripheral portion of a jetting port of the nozzle is wetted by ink, a liquid drop of the jetted ink is attracted to the wetted portion, and the ink is not recorded on the target position on the recording medium (hereinafter, called curved-shooting of ink), image failure is generated in the image formed on the recording medium.
In more detail, in the case of no-jetting of ink, a longitudinal streak is formed on the recording medium in the subsidiary scanning direction. Further, in the case of the curved-shooting of ink, as shown in
FIG. 12
, when the jetted ink C from the nozzle c causes the curved-shooting of ink due to wetting of ink on the periphery of the nozzle and forms a line C—C, the line C—C formed by dots of the jetted ink approaches a line B—B formed in the same manner, and simultaneously, is apart from a line D—D, and a pitch between lines with respect to other lines A—A and E—E is different, and a longitudinal stripe is formed as the image formed by dots of ink in the subsidiary scanning direction.
When such the image failure due to a defect of the nozzle occurs, the image failure can not be solved if the head is not replaced.
FIG. 20
is a view showing an example of a line type ink-jet printer having the conventional line-type head.
In the line type ink-jet printer
1
, the recording sheet P is nipped by conveyance roller pairs
31
and
32
, and is further conveyed in the direction Y in the drawing, by the roller pair
31
driven by a conveyance motor
33
.
A line-type head
2
is provided in opposite to the surface PS of the recording sheet P as the recording medium between conveyance roller pairs
31
and
32
. The line-type head
2
is connected to a control substrate
51
on which the control section is provided, through a flexible cable
4
(hereinafter called FPC).
Next, referring to
FIG. 2
, the line-type head will be described.
As shown in the drawing, the line-type head
2
can be separated into a base substrate
24
and a cover substrate
25
. Piezoelectric elements
22
are arranged in a line on the base substrate
24
, and each piezoelectric element
22
is connected to the FPC
4
through a circuit lead
23
.
Nozzles
21
, each of which form a pair with each piezoelectric element
22
, are aligned on the cover substrate
25
in a line with the same pitch, each nozzle
21
is connected to a fine tube provided with a portion to receive ink-jet-pressure by the piezoelectric element
22
, and the fine tube is connected to an ink tank provided in the cover substrate
25
.
Next, operations of the above-described structure will be described. A control section on the control substrate
51
makes a conveyance mechanism
3
convey the recording sheet P at a predetermined speed, drives the piezoelectric element
22
according to an image signal, jets liquid drops of ink simultaneously for each line from the nozzles
21
of the line-type head
2
, and forms an image on the recording sheet P.
As compared to a so-called shuttle type ink-jet printer whose head is driven in the primary scanning direction, the line type ink-jet printer with the above-described structure does not need the movement of the head in the primary scanning direction, and can form an image only by the conveyance of the recording sheet P in the subsidiary scanning direction which is perpendicular to the primary scanning direction, thereby, the line type ink-jet printer can conduct high speed image formation.
However, in such the line type ink-jet printer having only one line-type head
2
, for example, when there are such defects of the nozzle
21
as in the cases in which the nozzles
21
of the line-type head
2
are blocked by dusts or the like, and ink can not be jetted (hereinafter, called no-jetting of ink), or the peripheral portion of a jetting port of the nozzle
21
is wetted by ink, a liquid drop of the jetted ink is attracted to the wetted portion, and the ink is not recorded on the target position on the recording medium (hereinafter, called curved-shooting of ink), an image failure (noise) occurs in the image formed on the recording sheet P, which is a problem.
Further, it is necessary to provide piezoelectric elements
22
, ink tanks, fine tubes, etc., in the line-type head
2
corresponding to each nozzle
21
, therefore, there is a limit to make a pitch of the nozzle
21
closer, thereby, an image with high resolution can not be obtained, which is also a problem.
In this case, when the line-type head
2
is slantingly arranged to the primary scanning direction, a pitch of the nozzle in the primary scanning direction is made closer, and the resolution can be increased, however, the distance to move the recording sheet P in the subsidiary scanning direction is increased, and image forming speed is lowered, which is another problem.
Further, the ink-jet head has a proper driving frequency, without depending on its type such as the type using piezoelectric elements, the high voltage system, the bubble-burst type, etc.
Accordingly, there is such a problem that the image forming speed is also determined by the driving frequency of the head.
Further, when a line-type head is produced, in the present, cost is increased for the production of the line-type head longer than 5 inches, accordingly, a plurality of short line-type heads are jointed and one longer line-type head is produced.
On the other hand, in the line-type head, liquid drop jetting characteristics of both end nozzles which are affected by only one side nozzle, and liquid drop jetting characteristics of nozzles except both ends which are affected by both side nozzles, are different from each other.
Accordingly, in the line-type head produced by jointing short line-type heads, nozzles having different liquid drop jetting characteristics exist in one line, there is also a problem that image failure occurs on the recording sheet P.
Further, when the line-type head is produced by jointing short line-type heads, it i
Nishikawa Takuo
Tamura Akihiko
Frishauf Holtz Goodman & Chick P.C.
Gordon Raquel Yvette
Konica Corporation
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