DE4141736A1 - Ink-jet printing using line array incremented at end of line - has selection of nozzles active during first pass over paper with others used on return line return - Google Patents

Abstract

The dot matrix printing process uses a number, e.g. 8, of ink jet elements (11-1,11-8) formed in a head (1) that is moved in a line across a sheet of paper. In the first line scan operation up to 4 of the nozzles are activated. The specific nozzles activated are dependent upon the printing required. At the end of the line head is displaced by a half distance and printing continues in the return direction (35), again with upto 4 nozzles selected. ADVANTAGE - Improved reproduction.

Description

The invention relates to a method for recording information with a printhead that is a number in a main direction has column-shaped pressure elements. The printhead is moved back and forth line by line relative to a record carrier moved here, its direction of movement perpendicular to a The direction of advance of the recording medium runs. With this back and forth As it moves, the print head sweeps over a variety of print positions a print line.

From the German patent application P 41 10 776.4 is known for recording information on a Record carrier a printhead with a number of printing elements to move back and forth across print line positions. Partial numbers of the printing elements form according to an individual printing line Educational target subgroups, the print positions of a print line assigned and of at least partially different Pressure elements are formed. At the print positions, the Print elements of the respective subgroup selectively for printing data Generation of a print pattern line controlled. The educational target for a subsequent print line is at least on the connection side to the  Education specification of the previous print line coordinated. As a consequence of Streaks resulting from line connection errors or ribbon structure errors are vertically offset over the printed image by the known method distributed. In contrast to uniform structures, the human takes Disorders such as distributed are barely noticeable.

In particular, a periodic function or suggested a random function.

However, the pressure elements of the selected part number of the respective subgroup in succession selected.

The result is that regardless of the educational target chosen selected part number directly adjacent printing elements. There in the same environment is not preferred Perceptual properties of the human eye, in essentially the creation of horizontal and vertical structures, could be dispensed with, is the same due to the periodic sequence Structural elements do not fully recognize the pattern repeat to exclude. Especially when printing inks from Record carriers with low liquid absorption capacity, such as e.g. B. overhead projection screens is also the most immediate Sequence of ink droplets because of the risk of Blending undesirable.

The invention is therefore based on the object of a method for Record information indicating that the recognizability line termination errors and / or ribbon structure errors  minimized and equally for printing on recording media low liquid absorption capacity by means of inkjet is.

According to the invention this object is achieved in that starting from the known assignment line by line of printing elements of the respective primary subgroup and addition by the following subgroup according to the German patent application (file number P 41 10 476.4) Educational instruction for the assignment of pressure elements in the primary Subgroup both within the subgroup and within the current print line according to independent random functions he follows.

Due to the random assignment of the printing elements at a printing position irregular gaps arise within the range of one Subgroup, so that a direct optical separation of two successive lines of print is avoided.

Due to the random change in the occupancy of the Linear printing elements from print position to print position Row connection errors broken down column by column into micro connection errors and statistically distributed over the printed image.

It also shows a relative cluster of neighboring pressure points avoided at one printing position per printing cycle, so that too Call sign carrier with low liquid absorption capacity can be printed advantageously. Advantageously, the optical effect of so-called misaligned and different Drop masses largely eliminated.

The method according to the invention is described below with reference to drawings explained in more detail. This shows

Fig. 1 is a suitable for carrying out the method of the invention apparatus for recording information,

Fig. 2 is a detail of FIG. 1,

Fig. 3 a signal generated with the inventive method recording pattern,

Fig. 4 is a pattern generated by the known method and

Fig. 5 a signal generated by the novel process pattern.

Fig. 1 shows a schematic perspective view, the basic arrangement of a print head 1 relative to a record carrier 2 to be printed, which can be guided past the print head 1 in a feed direction 4 adjacent to a printing roller 3 . The print head 1 can be moved back and forth perpendicular to the feed direction 4 in the print line direction 5 . The print head 1 covers a large number of print positions 7 with each reciprocating movement. To print on the recording medium 2 , the print head 1 performs an overall relative movement 6 to the recording medium 2 .

Fig. 2 shows the print head 1 is formed as a ink jet print head from the record carrier 2 of its side facing. The print head 1 has a number a = 8 printing elements 11-1 to 11-8 . Each printing element 11 contains an ink outlet nozzle and a drive element, not shown, which, when selectively loaded with print data, causes an ink droplet to emerge from the ink outlet nozzle and generates a corresponding color dot when it hits the recording medium 2 . The pressure elements 11 are arranged along a main direction 12 . A partial number n of printing elements 11 selected from the number a each form a subgroup; only the printing elements 11 of the subgroup are subjected to printing data at the printing positions. After the printhead 1 has been moved and a print pattern line has been generated, the recording medium 2 is moved further in the feed direction 4 by an amount which corresponds to the extension of the subgroup in the main direction 12 plus a division 16 between two printing elements 11 . Subsequently, the print head 1 is subjected to print data either already in the upward movement (bidirectional printing) or after completion of the upward movement in a further outward movement, again only in the context of the respective subgroup. From print position 7 to print position 7 , however, the respective subgroups of at least partially different print elements 11 are formed.

A first resulting recording pattern is shown in FIG. 3. A continuously printed area is selected as the recording pattern. In FIG. 3, the printing elements 11-1 to 11-8 of the print head 1 are in a position 20 - as they face the record carrier ( FIG. 1). During the subsequent movement of the print head 1 in the direction 21, it sweeps over a first print position 22 . In the exemplary embodiment according to FIG. 3, the number of parts is n = 4 and the subgroup for the printing position 22 comprises the randomly selected printing elements 11-1, 11-2, 11-4 and 11-7 . The remaining printing elements 11-3, 11-5, 11-6 and 11-8 are not activated since, according to the formation specification for this printing line, they do not belong to the subgroup assigned to printing position 22 . The print head 1 is then moved to the next printing position 23 , the rasterization of the printing position 22 , 23 etc. preferably corresponding to the division 16 of the printing elements 11 . In the second printing position 23 , the subgroup is now formed by the printing elements 11-2, 11-3, 11-6 and 11-8 in accordance with the formation specification , so that printing dots are generated at the corresponding positions. In this way, the generation of pressure points is continued in the direction of movement 21 . With the completion of a print position 24 of a first print line 29 and after reaching a rest position 30 , the recording medium 2 is then advanced in the feed direction 4 ( FIG. 1) such that the print head 1 now takes the position 32 relative to the recording medium 2 instead of the rest position 30 . The feed is dimensioned, for example, so that it corresponds to the line formed by the main direction 12 four pressure elements of the sub-group plus a division 16 between the pressure elements 11 .

When skew of the printing head 1, that is, when the feed direction 4 and the main direction 12 is an acute angle, would be for the amount of the advance here, the projection of the line of printing elements 11-1 to 11-4 plus a partition 16 to the feed direction 4 (Fig. 1 ) decisive.

Then, in order to generate a subsequent print pattern line 33, the print head 1 is moved in the direction 35 in a further print line, the same formation specification being used - however in the case of bidirectional printing in the reverse order, ie starting with the print position 24 . As in the outward movement, the subgroup is therefore formed in the printing position 24 from a selection from the printing elements 11-1 to 11-8 , and pressure points are accordingly generated during the moving movement. These pressure points of the further print pattern line 33 are shown as hatched circles in FIG. 3, but in fact all pressure points of a print pattern have the same shape and color and are shown differently in the figures merely for reasons of clarity.

The respective subgroup is correspondingly activated for each print position 24-22 until the print head has reached a starting position 38 . The print head 1 is shown offset to the right in the starting position 38 in comparison to the position 20 only for drawing reasons. The process then begins again in the direction 21 after a corresponding advance of the recording medium 2 has taken place, as described above.

The appearance 39 , known as a line connection error, is broken down in terms of print position into the micro connection error and is statistically distributed over each print line. A regular structure is thus avoided and the perceptibility of the line connection errors is further complicated.

It also shows relative clusters of immediately neighboring ones Pressure points avoided, so that even recording media are low Liquid absorption capacity advantageous by means of ink jet printing can be printed.

In order to obtain a straight end edge of an area filling the recording medium produced by the method according to the invention, a recording movement of the head (without advancing the recording medium 2 ) takes place before the first and after the last possible printing line, in which the upper four printing elements 11-1 to 11 -4 or the lower four pressure elements 11-5 to 11-8 are controlled in such a way that they fill in the gaps marked × or + in FIG. 3. This can also be completed with the first or last print line.

In Figs. 3, or a complete blackening of the area is indicated by dots for purposes of illustration to 5; Letters or the like can of course also be recorded by selectively actuating the respective printing elements of the respective subgroup in alternation.

be given a print date.

Although a bidirectional print is described in connection with FIG. 3, the method according to the invention can of course be correspondingly advantageously used on unidirectional print (recording during the back and forth movement).

Fig. 4 shows a pattern produced by the process known from DE-OS 38 34 709, a printhead with 50 printing elements having been used. For comparison purposes, however, only 25 printing elements were actuated and a 50% gray print was produced by only The pattern clearly shows dark lines 80 , which are caused by a negative line connection of -1.2% (line spacing too narrow) and an associated overlap of the printing lines are caused. In addition, lighter lines 81 can be seen, which represent the optical effect of a lower drop mass per pressure point, and dark lines 82 can be seen , on which the optical effect of so-called oblique splashes is shown.

In contrast, FIG. 5 shows a 50% gray print also produced with 25 controlled printing elements, but as explained in detail above, the respective subgroup of printing elements varies. FIG. 5 shows a random distribution (a random function was selected as the formation default) of the stripes caused by line connection errors, misalignment and different droplet masses, for which the human eye has hardly any sensitivity. As seen in Fig. 4 and 5 is to be noted that the patterns constitute a considerable magnification, so that the gray print of FIG. 5 leaves a nearly uniform impression to original size, while the lines 80, 81 and 82 in Fig. 4 clearly stay. In the method according to the invention, the respective one of the print heads is statistically distributed, so that a vertical, sub-group of printing elements which are offset in the main direction results in the distribution of the linear structures resulting from the line connection errors, misaligned spatter, different drop masses or ribbon structure errors. The mutually overlapping print patterns interlock so that the human eye no longer recognizes any regular disturbing structures.

Claims (2)

Method for recording information according to predetermined print data using a print head with a number of print elements

• in which the print head is moved back and forth over print positions of a print line,
• - At least each sub-group of printing elements is assigned to at least each printing position intended for recording, the sub-groups each being formed by selecting a partial number of printing elements in accordance with a printing line-specific training specification such that the sub-groups assigned to a printing line at least partially consist of different printing elements ,
• - In which a print sample line is formed by selective control of the print elements of the respective subgroup at the print positions of a print line and
• - In which after the creation of a print pattern line, the recording medium is fed relative to the print head, with the feed being measured after the extension of the subgroup in the feed direction for connecting a subsequent print pattern line, and the education specification for a subsequent print line being matched to the education specification of the previous print line in accordance with P 41 10 776.4

characterized in that the formation specification for the assignment of the printing elements in the primary subgroup takes place both within the subgroup and also within the current printing line according to mutually independent random functions.