JP3093322B2 - Ink jet recording head and ink jet recording apparatus using the recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly, to a method in which a plurality of electrothermal transducers are driven in blocks to discharge ink from a discharge port to a recording medium by using thermal energy generated. The present invention relates to an inkjet recording apparatus that performs recording on the recording medium.

(Description of Related Art) Among various recording methods known at present, a non-impact recording method in which almost no noise is generated at the time of recording, high-speed printing is possible, and special printing is performed on plain paper. The so-called ink jet recording method capable of recording without the need for a fixing process has been recognized as an extremely useful recording method. In the ink jet recording method, droplets of a recording liquid called ink are ejected and fly, and the recording liquid is adhered to a recording medium such as paper to perform recording.

[0003] In this ink jet recording method, an electrothermal converter provided in an ink path (hereinafter also referred to as a nozzle) communicating with a fine discharge port for discharging ink is energized to generate heat. In this method, the ink around the heat generating portion (hereinafter, also referred to as a heater) is heated, and the ink is ejected from an ejection port by utilizing a pressure generated by a sudden change in volume generated during foaming. As a driving method of this ink jet recording apparatus, there is a method that employs a so-called divided drive method in which a heater is divided into groups of n digits for each of a plurality of bits of a drive signal, and the heaters of each group are sequentially driven. For this reason, it is usually necessary to pass a current of about 250 mA to drive one heater. Therefore, for example, when driving 64 nozzles at the same time, a current of as much as 16 A is required. Therefore, a large power supply is required, and a thick wiring for flowing a large current is required. On the other hand, if the current is supplied four times, for example, for 16 nozzles, the required current can be greatly reduced to 4 A at the same time. This is because 2A can be achieved by further dividing the nozzles into eight nozzles.

However, there is a problem to be solved in that when recording is performed by such a driving method, the landing positions of the droplets on the recording medium are different in each group, and the image quality may be deteriorated.

[0005]

As a result of observing the phenomenon of the landing position deviation in detail, the present inventors have found that the landing position deviation between each group is caused by the following two. . The first is caused by the necessity of the split drive system. That is, it is due to the difference in the energization timing between the groups and the relative movement between the recording medium and the recording head. Second,
When a plurality of nozzles are divided and driven to discharge substantially simultaneously within each group and with a certain period of time between groups, the discharge speed of the first group driven first is sequentially driven. This is because the ejection speed is higher than the ejection speed of the second and subsequent groups.

A specific example based on the first cause of recording by the recording head and the recording apparatus to which the above-described conventional divided driving is applied will be described below. A head having 64 nozzles
When driven at 60 DPI, 6.3 KHz, pulse width of 3 μs, and four-part drive suspension time of 0.5 μs (see FIG. 7), and the distance between the head and the recording medium is 1.2 mm,
The first cause described above is the landing position shift due to only the difference in the energization timing between the groups,

[0007]

[Outside 1] That is, it is shifted by 0.07 dots on the recording medium.

The landing position deviation due to the difference in the ejection speed between the groups, which is the second cause, is as shown in the following Table 1 according to the experiment of the present inventor.

[0009]

[Table 1]

As described above, the landing position deviation due to the difference in the energization timing between the groups is as small as 0.07 dots, which is almost inconspicuous, but the landing position deviation due to the difference in the ejection speed between the groups is the largest. This corresponds to 0.38 dots, which has an adverse effect on print quality.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head which solves the problems to be solved by the prior art and eliminates the displacement of the landing positions between the groups while utilizing the advantages of the divided drive system. It is an object of the present invention to provide a recording device using the same.

An ink jet recording apparatus according to the present invention includes a plurality of ink jet recording heads each having an ejection port for ejecting ink, an ink path communicating with the ejection port, and an electrothermal converter for applying thermal energy to the ink in the ink path. Means for dividing the electrothermal converter into a plurality of groups for each of a plurality of bits of a drive signal for driving the electrothermal converter, and sequentially supplying the drive signals to each group And a transport unit for transporting a recording medium on which recording is performed by ink discharged from the discharge port, wherein the shape of the ink discharge unit is changed for each group. It is characterized by.

In addition, the ink jet recording head of the present invention comprises a discharge port for discharging ink, an ink path communicating with the discharge port, an electrothermal converter for applying thermal energy to the ink in the ink path, And a plurality of groups of driving signals for driving the electrothermal transducers, each of which is divided into a plurality of groups by the electrothermal transducers. In the ink jet recording head sequentially supplied for each group, the shape of the ink discharge unit is changed for each of the groups.

According to the present invention, it is possible to eliminate the deviation of the landing position between the groups.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. 1A to 6, reference numeral 7 denotes a recording head, 1 denotes a substrate, 2 denotes an ink path (nozzle), 5 denotes a common liquid chamber common to each nozzle, 6 denotes a partition wall, and 8 denotes a top plate. Numeral 3 denotes an electrothermal converter (heating element) that generates thermal energy used for discharging ink from the discharge port 4. The ink ejection section according to the present invention includes an ejection port, an ink path, and an electrothermal converter.

When a voltage is applied, the heating element 3 generates heat rapidly, and the ink near the heating element is instantaneously vaporized and bubbles grow. Due to the growth of the bubbles, the pressure in the nozzle increases, the balance between the ink meniscus and the external pressure on the surface of the discharge port 4 is lost, and the ink is discharged from the discharge port. At this time, no current is already flowing through the heating element, and the heating portion of the heating element is cooled by the propagation of heat from the substrate 1, the ink, and the like, and the temperature of the surface is decreasing. Thereafter, the ink flows backward from the ejection port surface into the nozzles with the contraction of the bubble, and the bubble is contracted while new ink is supplied, so that the ink comes into contact with the surface of the heat generating portion of the heat generating element. Since the external pressure is higher than the internal pressure of the nozzle at the discharge port surface, a large meniscus enters the nozzle. The bubbles are eliminated by the ink supplied again by capillary action.

The ink is ejected by the continuous repetition of the above mechanism, and the heating elements of each group are divided and driven sequentially from the first group.

The ejection speed of the ink is affected by the pressure vibration and temperature propagating from the adjacent nozzles, and is further affected by the fluid interference of the ink from the liquid chamber to the nozzles. I do. Due to such a cause, the ejection speed from the nozzles of the first group is particularly increased.

Next, the embodiment shown in FIGS. 1A and 1B will be described.

Of the total 64 nozzles, 16 nozzles are divided into four groups each, and the first to fourth groups of four nozzles share one common line each, and the driving pulse input of the four nozzles has a pulse width ( 3 μs) The four-division time-division driving (see FIG. 7) shifted by the sufficient split driving suspension time (0.5 μs) (see FIG. 7) is used to discharge recording droplets from all nozzles using a conventional recording head. As described above, it was found that the discharge speed differs between the two.

That is, the average velocities are 12 m / s for the first group, 9 m / s for the second group, and 8 m / s for the third and fourth groups as shown in Table 1. As a result, the fastest first
The difference in speed between the group and the slow third group is 4 m / s,
As shown in FIG. 9, the landing position is shifted by a maximum of 0.38 dots.

Therefore, in this embodiment, as shown in FIGS. 1A and 1B, the discharge port 4 and the heating element 3
Is set to 12 in the first group in consideration of the discharge speed difference.
0 μm (as before), 107 μm for the second group, 103 μm for the third group, and 100 μm for the fourth group. In this case, the average ejection speed of each group when the recording liquid droplets are ejected from all the nozzles is 12 m / s for the first group and 12.4 for the second group, respectively.
m / s, 12.9 m / s for the third group, 13.4 m for the fourth group
/ S, and the maximum speed difference between the groups could be reduced to 1.4 m / s, and the landing position shift on the recording medium was not substantially recognized.

The embodiment shown in FIGS. 2A and 2B has a structure in which the area of the discharge port 4 is gradually reduced from the first group (or is gradually increased from the fourth group).
As in the embodiment shown in FIG. 1A and FIG. 1B, the ejection speed between the groups is compensated to eliminate the displacement of the landing position on the recording medium. In the present embodiment, the discharge speed is increased by reducing the discharge port area, and the discharge port area is determined in consideration of the difference in discharge speed between groups.

In the embodiment shown in FIG. 2, an example is shown in which the area of the discharge port is adjusted in the direction of the discharge port row. However, in the embodiment shown in FIG. This shows an example in which the ejection port area is adjusted by changing the ejection port area for each group. Further, in the present embodiment, the embodiment shown in FIGS. 1A and 1B can also be realized by a configuration in which the center height of the nozzle is sequentially lowered from the first group (or a configuration in which the height is sequentially higher than the fourth group). In the same manner as described above, the ejection speed between the groups is compensated, and the displacement of the landing position on the recording medium is eliminated.

In the embodiment shown in FIG. 4, since the area of the heating element 3 is made larger sequentially from the first group onward, the heat generation power in the group where the ejection speed tends to be slow can be increased. 1) and the embodiment shown in FIG. 1 (B), the ejection speed between the groups is compensated, and the displacement of the landing position on the recording medium is eliminated.

The embodiment shown in FIG. 5 has a structure in which the width of the nozzle 2 is sequentially reduced from that of the first group.
In the same manner as in the embodiment shown in FIG. 1B, the ejection speed between the groups is compensated to eliminate the displacement of the landing position on the recording medium.

The embodiment shown in FIG. 6 has a structure in which the length of the nozzle 2 is sequentially increased from the first group onward, so that FIG.
In the same manner as in the embodiment shown in FIG. 1B, the ejection speed between the groups is compensated to eliminate the displacement of the landing position on the recording medium.

It is needless to say that each of the above examples for compensating the ink ejection speed may be performed independently, or may be used together with other methods.

FIG. 10 shows a case where a recording head to which the present invention is applied is mounted and divided driving is performed. FIG. 2 is a perspective view schematically showing an external configuration of the ink jet recording apparatus. In FIG.
Reference numeral 1 denotes an ink jet recording head (hereinafter, referred to as a recording head) that discharges ink based on a predetermined recording signal to record a desired image, and 2 scans in the recording row direction (main scanning direction) with the recording head 1 mounted thereon. It is a moving carriage. The carriage 2 is slidably supported by guide shafts 3 and 4, and reciprocates in the main scanning direction in conjunction with the timing belt 8. The timing belt 8 engaged with the pulleys 6 and 7 is driven by the carriage motor 5 via the pulley 7.

The recording paper 9 is guided by a paper pan 10 and transported by transport means such as a paper feed roller (not shown) pressed by a pinch roller. This conveyance is performed using the paper feed motor 16 as a drive source.
The transported recording paper 9 is tensioned by a discharge roller 13 and a spur 14 and is pressed against the heater 11 by a paper pressing plate 12 formed of an elastic member. It is conveyed while being performed.
Recording paper 9 to which ink ejected by head 1 adheres
Is heated by the heater 11 and the attached ink is fixed on the recording paper 9 by evaporating the solvent. The heater 11
Is not always necessary, and may be provided in the recording apparatus as appropriate depending on the characteristics of the ink and the like.

Numeral 15 denotes a unit called a recovery system, which removes foreign substances and ink having increased viscosity attached to the discharge ports (not shown) of the recording head 1 to maintain the discharge characteristics in a normal state. belongs to.

Reference numeral 18a denotes a cap which constitutes a part of the recovery system unit 15 for capping the discharge port of the ink jet recording head 1 to prevent clogging. An ink absorber 18 is provided inside the cap 18a.

On the recording area side of the recovery system unit 15, a cleaning blade 17 is in contact with the surface of the recording head 1 where the ejection port is formed, and cleans foreign matter and ink droplets attached to the ejection port surface. Is provided.

The present invention provides an excellent effect particularly in a recording head and a recording apparatus of an ink jet recording system in which flying droplets are formed by utilizing thermal energy and recording is performed among the ink jet recording systems.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
No. 796, and the present invention is preferably performed using these basic principles. This recording method can be applied to any of a so-called on-demand type and a continuity type.

The recording method will be briefly described. An electrothermal transducer arranged corresponding to a sheet or a liquid path holding a liquid (ink), a liquid (ink) corresponding to recording information, or the like. By applying at least one drive signal to exceed the nucleate boiling phenomenon and to give a rapid temperature rise to cause the film boiling phenomenon, heat energy is generated, and film boiling is caused on the heat working surface of the recording head. . As described above, since bubbles corresponding to the drive signal applied to the electrothermal converter from the liquid (ink) can be formed one-to-one, it is particularly effective for an on-demand type recording method. By discharging the liquid (ink) through the discharge port by the growth and shrinkage of the bubble,
Form at least one drop. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. Examples of the drive signal in the form of a pulse include U.S. Pat. Nos. 4,463,359 and 4,345.
No. 262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, a configuration combining a discharge port, a liquid flow path, and an electrothermal converter (a linear liquid flow path or a right-angle liquid flow path) as disclosed in the above-mentioned respective specifications is used. In addition, as disclosed in U.S. Pat. Nos. 4,558,333 and 4,459,600,
The present invention also includes a configuration in which the heat acting portion is arranged in a bent region.

In addition, JP-A-59-123670 discloses a configuration in which a common slit is used as a discharge port of an electrothermal transducer for a plurality of electrothermal transducers, or a pressure wave of thermal energy is absorbed. The present invention is also effective in a configuration based on Japanese Patent Application Laid-Open No. 138461/1984, which discloses a configuration in which an opening corresponding to a discharge portion is disclosed.

Further, as a recording head in which the present invention is effectively used, there is a full line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. The full line head may be a full line configuration by combining a plurality of recording heads as disclosed in the above specification, or may be a single full line recording head formed integrally.

In addition, the print head is exchangeable with a print head of a chip type, which is electrically connected to the main body of the apparatus and can supply ink from the main body of the apparatus, or is integrated with the print head itself. The present invention is also effective when a cartridge-type recording head provided in a fixed manner is used.

It is preferable to add recovery means for the printhead, preliminary auxiliary means, and the like to the recording apparatus of the present invention, since the recording apparatus of the present invention can be further stabilized. More specifically, preheating of the recording head by capping means, cleaning means, pressurizing or suction means, an electrothermal transducer or another heating element, or a combination thereof. Means and means for performing a preliminary ejection mode for performing ejection that is different from printing are also effective in performing stable printing.

Further, the recording mode of the recording apparatus is not limited to the mode for recording only the mainstream color such as black, and may be either a mode in which the recording head is integrally formed or a mode in which a plurality of recording heads are combined. However, the present invention is also very effective for an apparatus provided with at least one of multiple colors of different colors or full color by mixing colors.

In the embodiments of the present invention described above, the description is made using the liquid ink. However, in the present invention, the ink which is solid in a greenhouse or the ink which becomes soft at room temperature is used. Can be used. In general, in the above-described ink jet device, the temperature of the ink itself is adjusted within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. It is sufficient if the ink is in a liquid state.

In addition, an excessive temperature rise of the head and the ink due to thermal energy is positively prevented by using it as energy for changing the state of the ink from a solid state to a liquid state, or the purpose is to prevent evaporation of the ink. For example, an ink that solidifies in a standing state may be used. In any case, the ink is liquefied for the first time by the application of heat energy, such as one in which the ink is liquefied and ejected as an ink liquid by application of the heat energy according to the recording signal, or one which already starts to solidify when reaching the recording medium. The use of an ink having the following properties is also applicable to the present invention.

Such an ink is disclosed in JP-A-54-568.
No. 47 or Japanese Patent Application Laid-Open No. 60-71260, while being held as a liquid or solid substance in a concave portion or a through hole of a porous sheet, facing the electrothermal converter. It is good also as a form.

In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, the form of the ink jet recording apparatus of the present invention may be used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, or a facsimile apparatus having a transmission / reception function. May be adopted.

[0048]

According to the present invention having the above-described structure, the following effects can be obtained.

That is, in a printing apparatus that drives a plurality of nozzles for each group, or in a printing head mounted on such a printing apparatus, the shape, size, and the like of the ink ejection section are changed for each group, so that the ink By adjusting the droplet ejection speed, the difference in the ink ejection speed of each group in the conventional head configuration is compensated, the accuracy of the impact point of the droplet on the recording medium is improved, and high quality printing is possible Become.

[Brief description of the drawings]

FIG. 1A is a schematic external perspective view showing one embodiment of an ink jet recording head of the present invention. (B) The schematic diagram which shows the line cross section of AA of (A).

FIG. 2A is a schematic external perspective view showing another embodiment of the ink jet recording head of the present invention. (B) The schematic diagram which shows the line cross section of AA of (A).

FIG. 3 is a schematic external perspective view showing another embodiment of the inkjet recording head of the present invention.

FIG. 4 is a schematic view showing another embodiment of the ink jet recording head of the present invention.

FIG. 5 is a schematic view showing another embodiment of the ink jet recording head of the present invention.

FIG. 6 is a schematic view showing another embodiment of the ink jet recording head of the present invention.

FIG. 7 is a diagram for explaining a time-division driving method.

FIG. 8 is a diagram for explaining a landing point shift due to a difference in energization timing between groups.

FIG. 9 is a view for explaining a landing point shift due to a difference in ejection speed between each group.

FIG. 10 is an inkjet recording apparatus to which the inkjet recording head of the present invention can be applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Nozzle (ink path) 3 Heating element 4 Orifice 5 Liquid chamber 6 Partition wall 7 Recording head 8 Top plate

Claims (12)

(57) [Claims] A plurality of ink ejection sections each having an ejection port for ejecting ink, an ink path communicating with the ejection port, and an electrothermal converter for applying thermal energy to ink in the ink path; Means for dividing the electrothermal converter into a plurality of groups for each of a plurality of bits of a drive signal for driving the electrothermal converter, and sequentially supplying the drive signals to each group; and And a transport means for transporting a recording medium on which recording is performed by the ejected ink, wherein the shape of the ink ejection unit is changed for each of the groups. apparatus. 2. A plurality of ink ejection sections each having an ejection port for ejecting ink, an ink path communicating with the ejection port, and an electrothermal converter for applying thermal energy to ink in the ink path. Ink jet recording wherein the drive signal is sequentially supplied to each group of the electrothermal transducers divided into a plurality of groups for each of a plurality of bits of a drive signal for driving the electrothermal transducers. An ink jet recording head, wherein the shape of the ink discharge unit is changed for each group. 3. The ink jet recording apparatus according to claim 1, wherein a distance between the ejection port and the electrothermal transducer in the shape of the ink ejection section is shorter in a group to which the signal is supplied later. 4. The ink jet recording apparatus according to claim 1, wherein the area of the ejection port in the shape of the ink ejection section is smaller in a group to which the signal is supplied later. 5. The ink jet recording apparatus according to claim 1, wherein the area of the electrothermal transducer in the shape of the ink ejection section is larger in a group to which the signal is supplied later. 6. The ink jet recording apparatus according to claim 1, wherein the width of the ink path in the shape of the ink discharge section is smaller in a group to which the signal is supplied later. 7. The ink jet recording apparatus according to claim 1, wherein the length of the ink path in the shape of the ink discharge unit is longer in a group to which the signal is supplied later. 8. The ink jet recording head according to claim 2, wherein a distance between the discharge port and the electrothermal transducer in the shape of the ink discharge section is shorter in a group to which the signal is supplied later. 9. The ink jet recording head according to claim 2, wherein the area of the ejection port in the shape of the ink ejection section is smaller in a group to which the signal is supplied later. 10. The ink jet recording head according to claim 2, wherein the area of the electrothermal transducer in the shape of the ink ejection section is larger in a group to which the signal is supplied later. 11. The ink jet recording head according to claim 2, wherein the width of the ink path in the shape of the ink discharge section is smaller in a group to which the signal is supplied later. 12. The ink jet recording head according to claim 2, wherein the length of the ink path in the shape of the ink discharge section is longer in a group to which the signal is supplied later.