JPH0557890A - Ink jet head and method for driving the same - Google Patents

Abstract

PURPOSE:To prevent the lowering of printing quality due to the interference (cross talk) between nozzles. CONSTITUTION:In an ink jet head equipped with a common ink chamber 1 having flight ink stored therein, a plurality of jet nozzles 2 respectively independently connected to the common ink chamber 1 and a flight energy applying means 3 selectively flying the ink in each of the jet nozzles 2 corresponding to an image signal, groups each consisting of two or more adjacent jet nozzles 2 are set to unit blocks B and the fluid resistance FRk of the jet nozzles 2k positioned at the boundary part on the single side or both sides of each unit block B is set larger than the fluid resistance FRj of the jet nozzles 2j of the other part. This head is driven so that the groups of the jet nozzles 2 are successively driven at the same time at every unit blocks B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head and a driving method thereof, and more particularly to a nozzle structure of a so-called multi-nozzle ink jet head having a plurality of nozzles and a head driving method suitable for the ink jet head.

[0002]

2. Description of the Related Art Generally, a so-called multi-nozzle ink jet head is characterized in that high-speed image recording can be performed because nozzles are arranged at intervals corresponding to a printing density.

However, since the distance between adjacent nozzles is close, there is a technical problem that the printing states affect each other due to interference (crosstalk) between adjacent or adjacent nozzles due to pressure propagation during ink ejection. is doing. This technical problem becomes more remarkable when the injection timings from the adjacent or adjacent nozzles are the same time or close to each other.

As means for preventing such interference, the relationship between the number of orifices (nozzles), the minimum cross-sectional area of the channels other than the orifices, and the cross-sectional area of the inlet for introducing the ink into the liquid chamber is defined. However, a proposal has been made in which a multi-nozzle head makes the ejection characteristics uniform even at a high printing frequency (see Japanese Patent Laid-Open No. 1-206059).

Further, as a structure of a thermal ink jet head, in a multi-nozzle head structure composed of a plurality of heat acting surfaces separated by a partition wall, the partition wall is penetrated in order to prevent interference and improve printing frequency. A proposal has been made to specify the distance between the heat-acting surfaces to be measured without any further treatment (Japanese Patent Laid-Open No. 59-138459).

On the other hand, as a driving method for a multi-nozzle head, a divided driving method in which a plurality of nozzles are sequentially ejected in the nozzle arrangement direction is usually adopted in order to increase the printing speed and to simplify the driving circuit. There is.

[0007]

However, in ink jet recording using a multi-nozzle head, particularly in a system in which a plurality of nozzles are sequentially ejected in the order in which the nozzles are arranged, the flow path resistance between the nozzles is limited to a certain value as described above. It was found that interference between nozzles cannot be completely prevented by a method of uniform alignment under certain conditions.

This is effectively prevented from the interference in a plurality of nozzles ejected at the same time, but it is considered that a new interference action occurs between the plurality of nozzles. That is, while simultaneously moving a plurality of nozzles to increase the amount of ink that moves, it is necessary to perform sequential repetition at high speed in order to keep the printing speed low, and to drive the adjacent nozzles before the ink movement has stopped. it is conceivable that.

The present invention has been made in order to solve the above technical problems, and is an ink jet head capable of reliably preventing deterioration of print quality due to interference (crosstalk) between nozzles and the like. A driving method is provided.

[0010]

That is, the present invention is
As shown in FIG. 1, a common ink chamber 1 in which flying ink is stored, a plurality of ejection nozzles 2 that are independently connected to and connected to the common ink chamber 1, and an image of the ink in each ejection nozzle 2 Assuming an inkjet head provided with a flying energy applying means 3 for selectively flying in response to a signal, two or more adjacent ejection nozzles 2 groups are provided as a unit block B.
It is characterized in that the fluid resistance FR _k of the injection nozzle 2 _k located at the boundary portion on one side or both sides of each unit block B is set larger than that FR _j of the injection nozzle 2 _j of the other portion. is there.

When the ink jet head according to the present invention is used, as shown in FIG. 1, the ejection nozzles 2 groups are sequentially and simultaneously arranged in each unit block B in accordance with a drive timing control signal from the block division drive means 4. A driving method characterized by performing ejection driving is adopted.

In such a technical means, each of the jet nozzles 2 may be formed of individual nozzle members, or a groove may be formed on at least one of the opposing surfaces of a pair of substrates. The groove portion may be configured as a nozzle.

Further, as the flying energy applying means 3,
Thermal energy is applied to the ink in each ejection nozzle 2, and the ink is ejected by the pushing force of the bubbles generated by the boiling of the film surface by the thermal energy. The thermal energy and the electrostatic energy are made to cooperate with each other. It is possible to appropriately select such as ejecting the ink by means of ejecting the ink, ejecting the ink only by electrostatic energy, or ejecting the ink by a pressure vibration wave.

Further, as the fluid resistance FR _k of the ejection nozzle 2k at the boundary portion (one side or both sides) of the unit block B, ink from at least the adjacent unit block B side easily flows in when the unit block B is driven. It is necessary to set such that driving in adjacent unit blocks B is not hindered.

Further, in the type in which only the fluid resistance FR _k of the injection nozzle 2k on one side of the boundary of the unit block B is set to be large, the fluid resistance FR _k is large when the unit block B is divided and driven. it is necessary to sequentially driven toward the unit blocks B adjacent to the side where the injection nozzle 2k, largely set the type of fluid resistance FR _k of the injection nozzle 2k on both sides of the boundary of the unit block B In this case, there is no limitation on the driving direction when the unit block B is dividedly driven, and it may be driven sequentially from the end side or may be driven from the center to both sides. Absent.

Further, in the case where the ink flying motion varies due to the setting method of the fluid resistance FR _k , the amount of energy applied by the flying energy applying means 3 is appropriately adjusted to reduce the variation in the ink flying motion. It is preferably designed to compensate.

Furthermore, the fluid resistance FR _j of the injection nozzle 2j other than the boundary portion (one side or both sides) of the unit block B is shown.
With respect to the above, it is necessary to set the fluid resistance FR _{K at the} boundary portion so as not to cause the interference between the ejection nozzles 2 when the bits in the block unit B are simultaneously driven (for example, JP-A-1- 206059, JP-A-59-1
38459) does not necessarily require all fluid resistances FR _j to be equal.

[0018]

According to the technical means as described above, the fluid resistance FR _k of the injection nozzle 2 _k located on one side or both sides of the boundary portion of the unit block B is larger than the fluid resistance FR _{j of} the injection nozzle 2 _j of the other portion. Is set to a large value, a relatively large amount of ink motion generated in each unit block B is located at the boundary of the unit block B even if the unit blocks B are divided and driven adjacent to each other with almost no down time. Each unit block B because it immediately attenuates in the 2 _k portion of the injection nozzle
Interference between them is effectively avoided. Also, each unit block B
For the injection nozzles 2 (2 _k , 2 _j ) in the unit block B, if the flow path resistances FR _k and FR _j are appropriately set so as to prevent mutual interference, the adjacent injection nozzles 2 in the unit block B Mutual interference between them is avoided. Therefore, according to the present invention, interference between adjacent ejection nozzles 2 at the time of simultaneous ejection (prevention of interference between relatively small amounts of ink movement) and interference between adjacent unit blocks B having almost no down time are prevented. Prevention (interference prevention by damping movement of relatively large amount of ink movement)
And can be compatible.

【Example】

The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings. Example 1 FIGS. 2, 3 and 4 show an example of a thermal inkjet head to which the present invention is applied. In the figure,
Reference numeral 10 denotes a groove substrate having a plurality of grooves (channels) 11 having a triangular cross section, which is manufactured by anisotropic etching of a Si wafer. A heating element substrate 20 is arranged to face the groove substrate 10. A heat storage layer 22 of SiO ₂ , a heating resistor 23 made of polycrystalline silicon, and an Al are formed on the Si wafer 21.
A current-carrying electrode 24 made of Cu, a heating resistor 23, and a first protective layer 25 made of SiNx covering the current-carrying electrode 24;
A photosensitive layer having a second protective layer 26 made of Ta laminated on the first protective layer 25, and a pit opening (capturing generation and disappearance of bubbles and stabilizing ink ejection) 27a in a portion corresponding to the heating resistor 23. Each pit layer 27 made of a conductive polyimide is provided. And in this example,
The groove substrate 10 and the heating element substrate 20 are adhered to each other by the adhesive layer 15, and the portion of the groove substrate 10 defined by the channel 11 and the heating element substrate 20 communicates with the common ink chamber 13 that serves as an ink reservoir. The injection nozzle 12 is formed.

FIG. 4 is an explanatory diagram showing the drive circuit configuration of the thermal ink jet head. In this embodiment, four ejection nozzles 12 are simultaneously driven as one unit block B. In order to make the following description easy to understand, the symbols (alphabets: a to c) representing the unit blocks and the symbols (numerals: -1, -2, -3, -4) representing the nozzles that are driven simultaneously are distinguished. did. In the figure, the heating resistor 23 (specifically 23a-3 to 2
3c-2), one of them is connected to the common return electrode 31 and the other independently of the individual control electrode 32 (specifically 32a-3).
~ 32c-2). The individual control electrodes 32 are connected to the drive elements 33 (specifically 33a-3
To 33c-2), the drive element 33 is connected to the AND gate 34 (specifically 34a).
-3 to 34c-2) by the signal input from the heating resistor 2
3 is heated to eject ink.

Here, the AND gate 34 has four data input signals 35 (specifically 35-1, 35-2, 35-.
3, 35-4), and one input of the AND gate 34 is connected to the block input signals (36-a, 36-b, 36-c) for each unit block B.

The block input signal is about 3 μsec on at 36-a, 0.25 μsec off at 36-a, about 3 μsec on signal at 16-b, 0.25 μsec off, 16-c.
Then, signals are sequentially input in a sequence of about 3 μsec on and 0.25 μsec off. Therefore, 32a-1 (not shown) to 3 are included in the data input signals 35-1 to 35-4 in accordance with the on timing of the block input signal 36-a.
Image information to be recorded by the heating resistor 23 of 2a-4 is input, and 32b-1 is input to the data input signals 35-1 to 35-4 in accordance with the on timing of the block input signal 36-b.
Image information to be recorded by the heating resistors 23 of 32b-4 to 32b-4 and 32c of the data input signals 35-1 to 35-4 in accordance with the on timing of the block input signal 36-c.
Image information to be recorded by the heating resistors 23 of -1 to 32c-4 (not shown) is input. That is, the unit blocks B including the four heating resistors 23 (equivalent to the jet nozzles) are sequentially driven in the order in which they are arranged.

In the type in which the heating resistor 23 is formed on the Si wafer 21 as in this embodiment, the drive element 33, the AND gate 34, and the external data signal and block signal are converted into parallel outputs. When the shift register to be used is formed on the same Si substrate 21 by the LSI process, if the adjacent unit blocks B are sequentially driven, the wiring pattern can be simplified, which is advantageous for downsizing the head and improving manufacturability. ..

In the thermal ink jet head and the driving method having such a structure, the adjacent four nozzles 12 in one unit block B are driven at the same time, and the adjacent unit block B has almost no down time. It is driven sequentially without holding.

Further, in this embodiment, each injection nozzle 12
The flow path resistance is set to change regularly for each unit block B. That is, as shown in FIG. 5, the length of the groove (channel) 11 provided in the groove substrate 10 bonded to the heating element substrate 20 and forming the ink passage is in units of 4 which is the number of bits of the unit block B. Has changed to. Specifically, each channel 11b of the injection nozzles 12b-1 and 12b-4 located at both ends (boundary) of the unit block B.
The length L'of one side wall at -1, 11b-4 corresponds to each channel 11b-2 of the injection nozzles 12b-2 and 12b-3.
It is set longer than that L of 11b-3.

Next, the performance of the ink jet head according to this embodiment will be evaluated. Now channels 11b-1, 11
One side wall length L'of b-4 and the other channel 11b-2, 1
An example head (300 dpi, 192 nozzles) having a length L of 1b-3 of 400 μm and 320 μm, respectively, and a head having a total channel length of 340 μm (Comparative Example 1) were manufactured and subjected to the above-mentioned drive timing. When the print quality is compared with each other by performing the printing operation in the case of Comparative Example 1, in the case of Comparative Example 1 in which all channels have a uniform length, droplets called satellites are formed around the dots in the case of linear printing across the array direction of 192 nozzles. Although the image was discolored by the ink of No. 1 and the image was distorted, the image was not distorted at all in the example heads.

Example 2 FIG. 6 shows another example of an ink jet head to which the present invention is applied. The same components as those in the first embodiment are designated by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted here. Unlike the first embodiment, the ink jet head according to this embodiment changes the flow path resistance of the ink not by the length of the channel 11 but by the cross-sectional area of the channel 11. More specifically, the length of the triangular base of the channel 11 in contact with the heating element substrate 20 is 60 microns for 11b-2 and 11b-3, and 50 microns for 11b-1 and 11b-4. (Length was 340 microns and uniform).

At this time, when the unit blocks B are not simultaneously ejected, the change in the drop amount due to the cross-sectional area of the channel 11 is large, so that as shown in FIG. 7, the ejection nozzles 12b- 1,12b-
The position of the heat generating resistor 23 corresponding to No. 4 is set to another injection nozzle 1
Comparing with those of 2b-2 and 12b-3, δ (for example, about 50 μm) was approached to the end portions of the nozzles 12b-1 and 12b-4 to perform compensation. As a method of compensating for variations in the drop amount, the position of the heating resistor 23 may be fixed and the applied energy may be changed.

Then, when compared with the head of the embodiment (Comparative Example 2) in which the length of the triangular base of the channel 11 in contact with the heating element substrate 20 was 55 μm and 192 nozzles were uniformly manufactured (Comparative Example 2), Comparative Example 2 was obtained. In that case, the image disturbance was seen as in the previous example, but in the example, the image disturbance was not seen at all.

[0031]

As described above, according to the first or second aspect of the present invention, the ejection nozzles of the multi-nozzle inkjet head in which a plurality of ejection nozzles are sequentially driven for each adjacent unit block are By devising the fluid resistance, it is possible to effectively prevent the interference between the adjacent unit blocks that are driven with almost no down time, so it is possible to design it to suppress the interference during simultaneous injection of each injection nozzle. For example, it is possible to prevent the interference due to the ink movement between the adjacent nozzles and the interference prevention due to the ink movement between the unit blocks at the same time, and it is possible to reliably prevent the deterioration of the image quality at the time of recording due to the interference due to the ink movement.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of an inkjet head to which the present invention is applied and a driving method thereof.

FIG. 2 is an explanatory diagram showing a first embodiment of a multi-nozzle thermal inkjet head to which the present invention is applied.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an explanatory diagram showing an example of a drive circuit of the multi-nozzle thermal inkjet head according to the first embodiment.

FIG. 5 is an explanatory diagram showing an example of fluid resistance change of the injection nozzle for each unit block used in the first embodiment.

FIG. 6 is an explanatory view similar to FIG. 5, showing a second embodiment of a multi-nozzle thermal inkjet head to which the present invention is applied.

FIG. 7 is an explanatory diagram showing a positional relationship between heat generating resistors used in a second embodiment.

[Explanation of symbols]

B ... Unit block, FR _k , FR _j ... Fluid resistance, 1 ... Common ink chamber, 2 (2 _k , 2 _j ) ... Jet nozzle, 3 ... Flying energy applying means, 4 ... Block division driving means

Claims (2)

[Claims] 1. A common ink chamber (1) in which flying ink is stored, a plurality of ejection nozzles (2) independently connected to the common ink chamber (1), and respective ejection nozzles (2). In an ink jet head provided with a flying energy applying unit (3) for selectively flying the ink in () in accordance with an image signal, two or more adjacent ejection nozzles (2) are set as a unit block (B), The fluid resistance (FR _k ) of the injection nozzle (2 _k ) located at the boundary on one side or both sides of the unit block (B) is set larger than that (FR _j ) of the injection nozzle (2 _j ) of the other part. An inkjet head characterized in that 2. A method for driving an inkjet head, wherein when the inkjet head according to claim 1 is used, the ejection nozzles (2) group are sequentially and simultaneously ejected for each unit block (B).