JP3320137B2 - Ink jet recording head and ink jet recording apparatus - 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 head, and more particularly to an on-demand type ink jet recording head having a plurality of nozzles.

[0002]

2. Description of the Related Art An ink jet recording method has excellent features such as a simple recording step, high-speed recording, and easy color recording. Among them, an on-demand type ink jet recording method of discharging ink in response to a recording signal has an advantage that a large-scale ink recovery device or the like is not required since ink is discharged only when necessary for recording, and is widely used. ing. In that case, in order to increase the printing speed, it is common to provide a large number of nozzles in one print head.

[0003] As an on-demand type ink jet recording system, a method in which ink is pressurized and ejected according to a recording signal by a piezo element, and a method in which ink is foamed and ejected according to a recording signal by a heater provided in a nozzle, A so-called bubble jet method (hereinafter, referred to as a bubble jet method) is widely used. In particular, in the case of the bubble jet method, a recording head in which a large number of nozzles are integrally formed is widely used because the structure of the recording head is simple and it is easy to arrange the nozzles at high density.

[0004]

However, in a recording head in which a large number of nozzles are integrally formed, there is a problem that so-called crosstalk occurs. The crosstalk includes one caused by an electric signal for driving, and another caused by a change in ink pressure caused by ejection and refilling being propagated to ink of another nozzle.

[0005] Among them, several countermeasures have conventionally been devised for those caused by electric signals, and it has become possible to make them relatively unimpeded in practical use. At present, there are no effective measures for the cause. Therefore, it is difficult to drive at a high frequency especially in a recording head provided with a large number of nozzles at high density due to discharge failure due to crosstalk. Further, even at a low frequency, unevenness may occur in the recorded image.

For example, in a bubble jet type recording head, when foaming and discharging ink, the pressure of the bubble is transmitted to other nozzles through a common liquid chamber that supplies ink to each nozzle, and pushes out a meniscus. At this time, when the nozzle is driven, droplets larger than usual are ejected.

When the bubbles shrink, the pressure in the common liquid chamber decreases. Therefore, the meniscus of the other nozzles is drawn in, and when driving is performed at this time, droplets smaller than usual are ejected. Further, at this time, the time required for refilling the nozzle in the middle of refilling becomes longer, and an abnormality occurs in the next ejection.

As a method of solving this problem, there is a method of making the common liquid chamber sufficiently large so as not to cause a pressure fluctuation. It is necessary to make the chamber extremely large, and there is a problem that the recording head becomes large. Further, when the nozzles are arranged at a high density, the nozzles are close to each other, so that a sufficient effect cannot be obtained even if the common liquid chamber is enlarged.

As another method, an elastic body is provided in a common liquid chamber,
In some cases, a porous body or the like is provided to absorb pressure fluctuations. However, since the ink jet recording head is extremely small, it is difficult to finely process and arrange such a soft material.
In particular, porous materials tend to generate fine dust,
It is easy to cause problems such as clogging nozzles.

As yet another solution, there is a method of providing a hole communicating with the outside air from the common liquid chamber, holding the ink in the portion of the hole by surface tension, and absorbing the pressure fluctuation of the ink by the movement of the meniscus. is there. However, in order to obtain a sufficient effect by this method, the size of the hole must be increased, and since the hole must be provided for each nozzle, the ink in the common liquid chamber is likely to evaporate. This causes problems such as ink leakage due to vibration and the like.

Accordingly, the present invention provides an on-demand type ink-jet system in which a large number of nozzles are integrally formed without crosstalk due to ink pressure fluctuation, stable ejection even when driven at a high frequency, and producing no image unevenness. It is an object to provide a recording head.

[0012]

According to the present invention, there is provided an ink jet recording head having a structure in which a plurality of ink ejection sections are integrally formed and connected to a common liquid chamber. A plurality of holes having a front wall surface connected to the front wall surface and a rear wall surface opposite to the front wall surface, the rear wall surface extending in a direction opposite to the front wall surface, and arranged at predetermined intervals. Ink- jet recording, wherein a cross-section along the direction of arrangement of these holes is formed in a comb-shaped pattern, and the walls in each hole are ink-repellent. Provided are an ink jet recording apparatus equipped with a head and the recording head.

The present invention provides an excellent effect particularly in a recording head and a recording apparatus of an ink jet recording system in which a flying droplet is 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 described briefly. An electrothermal transducer disposed corresponding to a sheet or a liquid path holding a liquid (ink), a liquid (ink) corresponding to recording information. By applying at least one drive signal for exceeding the nucleate boiling phenomenon and giving a rapid temperature rise that causes the film boiling phenomenon, heat energy is generated, and film boiling occurs on the heat-acting 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. The liquid (ink) is ejected through the ejection hole by the growth and shrinkage of the bubble to form at least one droplet. 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 liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. The driving signal in the form of a pulse is disclosed in U.S. Pat.
Those described in US Pat. No. 45262 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.

The configuration of the recording head is a combination of a discharge hole, 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. In addition, as disclosed in U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, those having a configuration in which a heat acting portion is arranged in a bent region are also included in the present invention.

In addition, Japanese Unexamined Patent Publication No. 123670/1984 discloses a configuration in which a common slit is used as a discharge hole of an electrothermal transducer for a plurality of electrothermal transducers, or absorbs a pressure wave of thermal energy. The present invention is also effective in a configuration based on JP-A-59-138461, which discloses a configuration in which the opening to be made corresponds to the discharge section.

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 replaceable with a print head of a replaceable chip type, which can be electrically connected to the main body of the apparatus or supplied with 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. If you list these specifically,
For the recording head, a capping unit, a cleaning unit, a pressure or suction unit, a preheating unit using an electrothermal transducer or another heating element or a combination thereof, and a predischarge mode different from recording. It is also effective to add a means for performing a stable recording.

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

Although the description has been made above using the liquid ink, the present invention can use either an ink that is solid at room temperature or an ink that becomes soft at room temperature.
In general, in the above-described ink jet apparatus, the temperature of the ink itself is controlled 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 the energy of the state change from the solid state to the liquid state of the ink, or the purpose is to prevent the 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 the one in which the ink liquefies and is ejected as an ink liquid by the application according to the recording signal of the thermal energy, or the one that 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 Unexamined Patent Publication No. Sho 60-71260, in a state where it is held as a liquid or solid substance in a concave portion or a through hole of a porous sheet and faces an 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.

FIG. 8 is an external perspective view showing an example of an ink jet recording apparatus (IJRA) in which the recording head obtained according to the present invention is mounted as an ink jet head cartridge (IJC).

In the drawing, reference numeral 20 denotes an ink jet head cartridge (IJC) having a nozzle group for discharging ink while facing a recording surface of a recording sheet sent on a platen 24. Reference numeral 16 denotes a carriage HC that holds the IJC 20, which is connected to a part of a drive belt 18 that transmits the driving force of a drive motor 17, and is slidable with two guide shafts 19A and 19B disposed in parallel with each other. By doing so, the reciprocating movement over the entire width of the recording paper of the IJC 20 becomes possible.

Reference numeral 26 denotes a head recovery device, which is an IJC 20
, For example, at a position facing the home position. The head recovery device 26 is operated by the driving force of the motor 22 via the transmission mechanism 23, and I
JC20 capping is performed. In connection with the capping of the IJC 20 by the cap portion 26A of the head recovery device 26, ink is suctioned by a suitable suction device provided in the head recovery device 26 or by an appropriate pressurizing device provided in an ink supply path to the IJC 20. Discharge recovery processing such as removing the thickened ink in the nozzles by performing ink pressure feeding and forcibly discharging the ink from the discharge ports is performed. Also, by performing capping at the end of recording or the like, the IJC is protected.

Reference numeral 30 denotes a blade as a wiping member which is disposed on a side surface of the head recovery device 26 and is made of silicone rubber. The blade 30 is a blade holding member 30
A is held in a cantilever form, and the head recovery device 26
Similarly to the above, it is operated by the motor 22 and the transmission mechanism 23, and can be engaged with the discharge surface of the IJC 20. Thereby, at an appropriate timing in the recording operation of the IJC 20, or after the ejection recovery processing using the head recovery device 26, the blade 30 is projected into the movement path of the IJC 20, and the ejection surface of the IJC 20 is moved with the movement operation of the IJC 20. It wipes dew, wet or dust.

It is desirable that the characteristic ink-repellent surface of the common liquid chamber surface of the ink jet recording head of the present invention has a contact angle as large as possible with respect to the ink. If it has, the effect is exhibited. When an aqueous ink is used as the ink, a fluorine resin, silicone rubber, polyethylene resin, or the like can be used as the ink repellent material.

In the following, description will be made mainly on the case where the water-based ink is used.

It is desirable that the water-repellent surface is provided in only a part of the common liquid chamber. If the entire wall surface of the common liquid chamber is made water-repellent, bubbles easily accumulate in the common liquid chamber, and it becomes difficult to stably supply ink to the ejection unit. Further, it is desirable that the water-repellent surface is provided at a position not in contact with the ejection portion.

The water-repellent surface may be provided on one of the inner surfaces of the common liquid chamber. However, it is more effective to provide the water-repellent surface on a plurality of bottom, side, and top surfaces.

It is also effective to provide a hole having a water-repellent surface in the common liquid chamber.

[0035]

In the ink jet recording head,
In general, dissolved air in ink often evaporates due to pressure fluctuations and the like accompanying ejection, and fine bubbles are generated. These fine bubbles are usually discharged together with the ink or disappear by re-dissolving in the ink. However, as described above, when there is a water-repellent surface in the common liquid chamber, the bubbles in contact with that portion are difficult to move and remain at that position. In general, microbubbles have a high internal pressure due to surface tension, and therefore rapidly dissolve. However, bubbles in contact with the water-repellent surface have a flattened shape, a large radius of curvature, and a small effect of surface tension.
The internal pressure is not very high and does not dissolve in a short time.

FIG. 7 is an explanatory diagram of this. FIG. 7A shows air bubbles in contact with a hydrophilic surface having a small contact angle, and FIG.
Represents a bubble in contact with a water-repellent surface having a large contact angle. As shown in this figure, if the bubbles have the same volume, the bubble in contact with the water-repellent surface has a larger radius of curvature.

The minute bubbles in the ink may accumulate in large amounts depending on the use conditions of the recording head and adversely affect the ejection. Therefore, conventionally, a method of discharging a part of ink from a nozzle by a pressure pump, a suction pump, or the like, and discharging bubbles in the common liquid chamber together with the nozzle has been performed. On the other hand, in the recording head having the common liquid chamber having the water-repellent surface of the present invention, the minimum number of bubbles necessary for preventing the crosstalk adhere to the water-repellent surface in the common liquid chamber and remain.

[0038]

EXAMPLES (Example 1) Next, 1 participation of the ink jet recording head of the present invention in FIG. 1
The main part of the embodiment is shown. This recording head is of a so-called bubble jet type, in which ink is heated by a heater 5 to cause foaming in the ink to be discharged.

To manufacture this recording head, a heater 5, an electrode, a protective film and the like are formed on a silicon wafer by sputtering and photolithography techniques to produce a heater board 4 on which a nozzle wall and a negative dry film 3 are used. This is performed by forming a wall of the liquid chamber, bonding a glass top plate 1 thereon, and finally cutting the periphery and the discharge port portion.

In FIG. 1, for ease of understanding, the top plate 1 is drawn away. A concave portion is provided on the lower surface of the top plate to secure the capacity of the common liquid chamber, and a through hole for supplying ink is provided in that portion, and a filter 2 is attached to this through hole.

The recording head is completed by connecting the main part of the recording head to a support, an electric mounting component, an ink supply system and the like.

In the above manufacturing process, the water-repellent surface 6 is formed on the heater board 4 before joining the negative dry film 3 to the heater board 4. As the water-repellent surface, a surface having an extremely small contact angle can be formed by eutectoid plating of a fluororesin powder together with nickel on the surface. Further, a fluorine resin paint, a silicone resin paint, or the like may be applied.

FIG. 2 is a sectional view of a main part of the recording head of FIG. As shown in this figure, when ink is supplied into the recording head, bubbles 8 remain at the position of the water-repellent surface 6. As a result, fluctuations in ink pressure are absorbed, and crosstalk is prevented.

( Embodiment 1 ) FIG. 3 shows a rear portion of a recording head in which the wall portion of the common liquid chamber opposite to the nozzle has a comb shape different from the head of FIG. The top plate is not shown. In this recording head, a comb-shaped pattern is formed by a negative dry film 3 on a heater board as shown in the figure, and a fluororesin-based paint is applied thereon to make it water-repellent. The interval between the comb-shaped patterns is 5 μm to 100 μm.
μm and the length is preferably 10 μm to 500 μm, but the length may be larger. When applying the water-repellent paint, it is sufficient to apply it only to the part inside the comb-shaped pattern that will be the inner wall of the common liquid chamber, but it is difficult to process, so apply the part in contact with the top plate at the same time No problem. Water-repellent paint is also applied to a position facing the comb pattern of the top plate.

FIG. 4 is a sectional view of a main part of the recording head of FIG. In the head of this figure, since the comb-shaped pattern portion has a hole shape formed of a water-repellent surface,
It is difficult for ink to enter, and air bubbles accumulate in that part. The bubbles absorb fluctuations in the pressure of the ink and prevent crosstalk.

Although this head has a more complicated shape than that of FIG. 1, the portion where the air bubbles accumulate is a hole, so that not only the accumulated air bubbles are hard to move but also the capacity is large. Since bubbles are formed, the method is particularly suitable for driving a recording head provided with a large number of nozzles at a high speed. In this case, bubbles are accumulated in the hole-shaped portion,
Since this hole does not penetrate, there is no problem such as evaporation of the ink.

[0047] The (Reference Example 2) FIG. 5, showing an alternative reference embodiment of the recording head of the present invention. In this recording head, compared with the head of FIG. 1,
Two through holes are provided in the top plate. One of the through holes is an ink supply port, which is connected to an ink supply tube 12 via a tube connection portion 11. The other through-hole is closed by the water-repellent porous body 10, and this porous body absorbs the pressure fluctuation of the ink.

Examples of the material of the water-repellent porous body include a fluorine resin, a polyethylene resin, and a silicone rubber. The porous body has a low affinity for the ink and a large contact angle, and therefore absorbs the ink. But does not pass through, but air does. Therefore, this water-repellent porous body 1
Micro air bubbles are always formed on the surface in contact with the 0 ink.

FIG. 6 is a sectional view of the recording head of FIG. As can be seen from this figure, the bubble 8 formed is far from the rear end of the nozzle and does not adversely affect the ejection. In addition, since these bubbles 8 are in contact with the water-repellent porous body 10, even if the bubbles become excessively large, the porous body 10 can be easily formed by pressurizing the ink.
It is released into the outside air through. In this case, in order to prevent the ink component from evaporating through the water-repellent porous body 10, it is also effective to provide a cover on the porous body 10 to such an extent that gas permeation is not completely prevented.

The case where the water-based ink is used has been described above. However, even in the case where the oil-based ink or the ink which is solid at ordinary temperature and is melted and discharged by heating as described above is used, the use of the water-based ink is not limited. By providing a surface having a large contact angle having ink repellency to ink in the common liquid chamber, a recording head having similar performance can be obtained.

Further, in the above description, the recording head of the bubble jet system has been described. However, the ink jet recording head of another system, such as a type in which ejection is performed using a piezo element, does not need to have a nozzle structure. The above-described method can be applied to an inkjet recording head having a structure in which a plurality of ejection sections are integrally formed.

[0052]

According to the present invention, it is possible to obtain an ink jet recording head which does not cause crosstalk due to ink pressure fluctuation, has stable ejection even when driven at a high frequency, and does not cause unevenness in a formed image. .

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of an ink jet recording head of the present invention.

FIG. 2 is a sectional view of the recording head of FIG.

FIG. 3 is a schematic view showing another embodiment of the ink jet recording head of the present invention.

FIG. 4 is a cross-sectional view of the recording head of FIG.

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

FIG. 6 is a cross-sectional view of the recording head of FIG.

FIG. 7 is a diagram illustrating a state in which bubbles in ink are in contact with a plane, where A is a diagram in the case where the plane is a hydrophilic surface, and B is
It is a figure in case a plane is a water-repellent surface.

FIG. 8 is a perspective view illustrating an example of a recording apparatus including an inkjet recording head according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Top plate 2 Filter 3 Negative dry film 4 Heater board 5 Heater 6 Water-repellent surface 7 Nozzle 8 Bubbles 9 Supporter 10 Water-repellent porous body 11 Tube connection part 12 Ink supply tube 13 Ink 16 Carriage 17 Drive motor 18 Drive belt 19A , 19B Guide shaft 20 Inkjet head cartridge 22 Cleaning motor 23 Transmission mechanism 24 Platen 26 Cap member 30 Blade 30A Blade holding member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/05 B41J 2/055 B41J 2/175

Claims (4)

(57) [Claims] 1. A plurality of ink ejection portions are integrally formed,
Moreover, in an ink jet recording head having a structure connected to a common liquid chamber, the common liquid chamber has a front wall surface connected to the ink ejection section, and a rear wall surface opposite to the front wall surface, The rear wall surface is formed by a plurality of holes extending in a direction opposite to the front wall surface and arranged at predetermined intervals.
A structure is provided in which the cross section along the arrangement direction of these holes forms a comb pattern, and the wall surface in each hole is ink-repellent.
An ink jet recording head characterized in that it is a liquid . 2. The ink jet recording head according to claim 1, wherein the ink ejection energy generating element is an electrothermal transducer for generating heat by applying electric energy to cause a change in state of the ink to perform ejection. 3. The ink jet recording head according to claim 1, wherein the ink jet recording head is a full line type having a plurality of discharge ports provided over the entire width of a recording area of a recording medium. 4. A wherein the ink discharge ports for facing the recording surface of the recording medium for ejecting ink is provided in claim 1
An ink jet recording apparatus at least comprising: a recording head; and a member for mounting said recording head.