JPH06312513A - Ink jet record head and ink jet recording device - Google Patents

Abstract

PURPOSE:To ensure stable discharging performance of ink liquid so as to form an image without irregularity by making at least a part of a common liquid chamber an ink-repellent face, in a device comprising a plurality of ink discharging sections to be connected to the common liquid chamber formed integrally. CONSTITUTION:In an ink jet record head of bubble jet method, ink is heated by a heater 5 so as to generate bubbles in the ink and is discharged. The ink jet record head comprises a heater board 4 having the heater 5, electrodes, protective films formed on a silicone wafer by sputtering and photographic techniques. On the top of it, a nozzle wall and a wall of a liquid chamber are formed by a negative dry film 3, on which a glass roof plate 1 is connected. In this case, before the negative film 3 is connected to the heater board 4, a water-repellent face 6 formed by eutectoid plating of, for example, fluororesin powder and nickel is formed on the heater board 4. Thus, the pressure fluctuation of the ink is absorbed and crosstalk is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording head, and more particularly to an on-demand type inkjet recording head having a plurality of nozzles.

[0002]

2. Description of the Related Art Ink jet recording methods have excellent features such as a simple recording process, high speed recording, and easy color recording. Among them, the on-demand type ink jet recording method that ejects ink according to a recording signal has an advantage that a large-scale ink recovery device is not required because the ink is ejected only when necessary for recording, and is widely used. ing. In that case, in order to increase the recording speed, it is general to provide a large number of nozzles in one recording head.

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

[0004]

However, there is a problem that so-called crosstalk occurs in a recording head in which a large number of nozzles are integrally formed. There are two types of crosstalk: one caused by an electric signal for driving, and the other caused by a change in ink pressure due to ejection and refill propagating to ink of other nozzles.

Among these, as for those caused by electric signals, several kinds of countermeasures have been devised from the past, and it has become possible to make them relatively unaffected in practice. As for the cause of this, there is currently no effective countermeasure. Therefore, particularly in a recording head provided with a large number of nozzles at high density, it is difficult to drive at a high frequency due to ejection failure due to crosstalk. Even at a low frequency, the recorded image may be uneven.

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

When the bubbles contract, the pressure in the common liquid chamber decreases. Therefore, the meniscus of the other nozzles is pulled in, and if the driving is performed at this time, a droplet smaller than usual is ejected. At this time, the nozzle in the middle of refilling takes a long time to refill, and an abnormality occurs in the next ejection.

As one of the methods for solving this problem, there is a method of making the common liquid chamber sufficiently large so as to prevent pressure fluctuation, but in order to obtain a sufficient effect, the common liquid chamber It is necessary to make the chamber extremely large, which causes 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 even if the common liquid chamber is enlarged, a sufficient effect cannot be obtained.

As another method, an elastic body in the common liquid chamber,
There is one in which a porous body or the like is provided to absorb pressure fluctuations. However, the inkjet recording head is extremely small, and it is difficult to finely process and arrange such a soft material.
In addition, especially porous materials easily generate fine dust,
It is easy to cause problems such as clogged nozzles.

As another solution, there is a method in which a hole communicating from the common liquid chamber to the outside air is provided, the ink in the hole is held by surface tension, and the fluctuation of the ink pressure is absorbed by the movement of the meniscus. is there. However, in order to obtain a sufficient effect with this method, it is necessary to increase the size of the holes, and since it is necessary to provide holes corresponding to each nozzle, the ink in the common liquid chamber easily evaporates. However, problems such as ink leakage due to vibration may occur.

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

[0012]

According to the present invention, in an ink jet recording head having a structure in which a plurality of ink ejection portions are integrally formed and connected to a common liquid chamber, at least a part of the inner surface of the common liquid chamber is Provided is an inkjet recording head having an ink repellency and an inkjet recording device equipped with the recording head.

The present invention provides excellent effects particularly in an ink jet recording type recording head and recording apparatus for recording by forming flying droplets by utilizing thermal energy among the ink jet recording systems.

Regarding the typical structure and principle thereof, see, for example, US Pat. Nos. 4,723,129 and 4740.
No. 796, the present invention is preferably carried out using these basic principles. This recording method is applicable to both the so-called on-demand type and the continuous type.

To briefly explain this recording method, an electrothermal converter is arranged corresponding to a sheet or liquid path holding a liquid (ink), and a liquid (ink) corresponding to recording information. Heat energy is generated by applying at least one driving signal for giving a rapid temperature rise that causes the film boiling phenomenon beyond the nucleate boiling phenomenon, and causes the film boiling on the heat acting surface of the recording head. . In this way, bubbles can be formed in one-to-one correspondence with the drive signal applied from the liquid (ink) to the electrothermal converter, which is particularly effective for the on-demand recording method. The liquid (ink) is ejected through the ejection holes by the growth and contraction of the bubbles to form at least one droplet. It is more preferable to make the driving signal into a pulse shape because bubbles can be grown and contracted immediately and appropriately, and thus a liquid (ink) with excellent responsiveness can be ejected. This pulse-shaped drive signal is described in US Pat. No. 4,463,359 and US Pat.
Those as described in 45262 are suitable. If the conditions described in US Pat. No. 4,313,124, which is an invention relating to the rate of temperature rise on the heat acting surface, are adopted, more excellent recording can be performed.

The structure of the recording head is a combination of a discharge hole, a liquid flow path and an electrothermal converter as disclosed in the above-mentioned specifications (straight liquid flow path or right-angled liquid flow path). In addition, as disclosed in U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, the present invention includes those having a configuration in which a heat acting portion is arranged in a bending region.

In addition, Japanese Laid-Open Patent Publication No. 123670/1984, which discloses a structure in which a common slit is used as a discharge hole for a plurality of electrothermal converters, and a pressure wave of thermal energy is absorbed. The present invention is also effective in a structure based on Japanese Patent Laid-Open No. 138461/1984, which discloses a structure in which the corresponding opening corresponds to the discharge portion.

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 which can be recorded by a recording device. The full line head may be a full line configuration formed by combining a plurality of print heads as disclosed in the above specification, or may be a single full line print head integrally formed.

In addition, by being mounted on the apparatus main body, it can be electrically connected to the apparatus main body and can be supplied with ink from the apparatus main body by a replaceable chip type recording head or the recording head itself. The present invention is also effective when a cartridge-type recording head that is specially provided is used.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc. to the recording apparatus of the present invention because the recording apparatus of the present invention can be made more stable. If you list these specifically,
A capping unit, a cleaning unit, a pressure or suction unit, an electrothermal converter or a heating element other than this, or a preheating unit using a combination of these, and a preliminary ejection mode different from recording are provided for the recording head. Adding a means for performing is also effective for stable recording.

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

Although the liquid ink has been described above, an ink that is solid at room temperature or an ink that is in a softened state at room temperature can be used in the present invention.
In the above-mentioned ink jet device, it is common to control the temperature of the ink itself within a range of 30 ° C. or higher and 70 ° C. or lower to control the temperature of the ink so that the viscosity of the ink is within a stable ejection range. Any liquid may be used as long as the ink is liquid.

In addition, the excessive temperature rise of the head or ink due to thermal energy is positively prevented by using it as the energy for the state change of the ink from the solid state to the liquid state, or the evaporation of the ink is prevented. It is also possible to use an ink that solidifies when left as it is. In any case, liquefaction occurs only when heat energy is applied, such as when ink is liquefied by applying heat energy according to a recording signal and ejected as an ink liquid, or when it reaches the recording medium, it already begins to solidify. The use of an ink having such a property is also applicable to the present invention.

Such an ink is disclosed in JP-A-54-568.
No. 47 or JP-A No. 60-71260, facing the electrothermal converter in the state of being held as a liquid or solid in the recesses or through holes of the porous sheet. It may be in the 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 by the present invention is mounted as an ink jet head cartridge (IJC).

In the figure, reference numeral 20 is an ink jet head cartridge (IJC) provided with a group of nozzles which face the recording surface of the recording paper fed onto the platen 24 and eject ink. Reference numeral 16 is a carriage HC that holds the IJC 20, and is connected to a part of a drive belt 18 that transmits the driving force of the drive motor 17, and is slidable with two guide shafts 19A and 19B arranged in parallel with each other. By doing so, reciprocating movement over the entire width of the recording paper of the IJC 20 is possible.

Reference numeral 26 is a head recovery device, which is an IJC 20.
Is arranged at one end of the movement path of, for example, at a position facing the home position. The drive force of the motor 22 via the transmission mechanism 23 causes the head recovery device 26 to operate, and
Cap the JC20. In association with the capping of the IJC 20 by the cap portion 26A of the head recovery device 26, ink is sucked by an appropriate suction means provided in the head recovery device 26 or by an appropriate pressure means provided in an ink supply path to the IJC 20. The ejection recovery process is performed such that the ink is pressure-fed and the ink is forcibly discharged from the ejection port to remove the thickened ink in the nozzle. Further, the IJC is protected by capping at the end of recording.

Reference numeral 30 denotes a blade as a wiping member which is disposed on the side surface of the head recovery device 26 and is made of silicon rubber. The blade 30 is a blade holding member 30.
The head recovery device 26 is held by A in a cantilever form.
Similarly to the above, the motor 22 and the transmission mechanism 23 operate to enable engagement with the ejection surface of the IJC 20. As a result, the blade 30 is projected into the movement path of the IJC 20 at an appropriate timing in the recording operation of the IJC 20 or after the ejection recovery process using the head recovery device 26, and the ejection surface of the IJC 20 is moved along with the movement operation of the IJC 20. Wipe off condensation, wetness or dust.

The ink-repellent surface of the common liquid chamber inner surface, which is characteristic of the ink jet recording head of the present invention, preferably has a contact angle with ink as large as possible, but a contact angle with ink of 90 ° or more. If it has, it will be effective. When a water-based ink is used as the ink, fluororesin, silicone rubber, polyethylene resin or the like can be used as the ink repellent material.

Hereinafter, the case where an aqueous ink is used will be mainly described.

It is desirable that the water-repellent surface is provided in a very small part of the common liquid chamber. When the entire wall surface of the common liquid chamber is made water-repellent, bubbles are likely to accumulate in the common liquid chamber, and it becomes difficult to stably supply the ink to the ejection portion. Further, it is desirable that the water-repellent surface is provided at a position where it does not contact the ejection portion.

The water-repellent surface may be provided on one of the inner surfaces of the common liquid chamber, but it is more effective if it is provided on a plurality of surfaces including the bottom surface, the side surface, and the upper surface.

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

[0035]

Operation: Inside the ink jet recording head,
In general, dissolved air in ink is often vaporized due to pressure fluctuations caused by ejection, and minute bubbles are generated. The minute air bubbles are usually discharged together with the ink or redissolved in the ink to disappear. However, as described above, when the common liquid chamber has a water-repellent surface, the bubbles contacting that portion are difficult to move and remain at that position. Generally, minute bubbles have a high internal pressure due to surface tension, and therefore dissolve quickly. However, since the bubble in contact with the water-repellent surface has a flat shape, the radius of curvature is large and the influence of surface tension is small,
The internal pressure is not so high and it does not dissolve in a short time.

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

The minute bubbles in the ink may accumulate in large quantities depending on the use conditions of the recording head, and may adversely affect the ejection. Therefore, conventionally, a method has been used in which a part of ink is discharged from a nozzle by a pressure pump, a suction pump, or the like, and at the same time, bubbles in the common liquid chamber are discharged. On the other hand, in the recording head having the common liquid chamber having the water repellent surface of the present invention, the minimum bubbles necessary for preventing crosstalk adhere to the water repellent surface in the common liquid chamber and remain there.

[0038]

【Example】

(Embodiment 1) Next, FIG. 1 shows a main part of one embodiment of an ink jet recording head of the present invention. This recording head is of a so-called bubble jet type in which the ink is heated by the heater 5 to cause foaming in the ink and the ink is ejected.

This recording head is manufactured by forming a heater 5, electrodes, a protective film, etc. on a silicon wafer by sputtering and a photolithography technique to prepare a heater board 4, on which a negative dry film 3 is used to form a nozzle wall and This is performed by forming a wall of the liquid chamber, joining a glass top plate 1 thereon, and finally cutting the periphery and the discharge port portion.

In FIG. 1, the top plate 1 is shown in a separated state for easy understanding. The lower surface of the top plate is provided with a recess for ensuring the capacity of the common liquid chamber, and there is a through hole for supplying ink to that portion, and the filter 2 is attached to this through hole.

The recording head is completed by connecting the main part of the recording head to the support, the electrical mounting parts, the ink supply system and the like.

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

FIG. 2 shows a sectional view of the 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 2) 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 unlike the head of FIG. The top plate is not shown. In this recording head, as shown in the drawing, a comb-shaped pattern is formed on the heater board by the negative dry film 3, and the fluororesin-based paint is applied to the comb-shaped pattern to make it water repellent. The comb-shaped pattern has a gap of 5 μm to 100 μm and a length of 10 μm to
The length is preferably 500 μm, but the length may be larger. When applying the water-repellent paint, it is only necessary to apply it to the inner wall of the common liquid chamber inside the comb-shaped pattern. There is no problem. Water-repellent paint is also applied to the position facing the comb pattern on the top plate.

FIG. 4 shows a sectional view of the main part of the recording head of FIG. In the head of this figure, since the comb-shaped pattern portion has a hole-like shape made of a water-repellent surface,
Ink does not easily get in, and bubbles accumulate in that area. The bubbles absorb the pressure fluctuation of the ink and prevent crosstalk.

This head has a more complicated shape than that of FIG. 1, but since the portion where the bubbles are accumulated has a hole shape, not only the accumulated bubbles are difficult to move but also the capacity is large. Since bubbles are formed, it is particularly suitable for driving a recording head provided with a large number of nozzles at high speed. In this case, air bubbles are accumulated in the hole-shaped part,
Since this hole does not penetrate, problems such as ink evaporation do not occur.

(Embodiment 3) FIG. 5 shows another embodiment of the recording head of the present invention. With this recording head, as shown in FIG.
The through-hole is provided in the top plate as compared with the above-mentioned head. One of the through holes is an ink supply port, and is connected to the ink supply tube 12 via the 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 fluororesin, polyethylene resin, silicone rubber and the like. Since this porous body has a small affinity with ink and a large contact angle, it absorbs ink. It does not permeate, but air permeates. Therefore, this water-repellent porous body 1
Minute air bubbles are always formed on the surface in contact with 0 ink.

FIG. 6 shows 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 it does not adversely affect the ejection. Further, since these bubbles 8 are in contact with the water-repellent porous body 10, even if the bubbles become excessively large, they can be easily pressed by pressurizing the ink.
Is released into the atmosphere through. In this case, in order to prevent the ink components from evaporating through the water-repellent porous body 10, it is also effective to provide a cover on the porous body 10 to the extent that gas permeation is not completely blocked.

The case of using the water-based ink has been described above. However, other than that, for example, an oil-based ink, the above-mentioned ink that is solid at room temperature and is melted by heating to be ejected, and the like are also used. By providing a surface having a large contact angle with respect to ink and having a large contact angle in the common liquid chamber, it is possible to obtain a recording head having similar performance.

Further, although the bubble jet type recording head has been described above, an ink jet recording head of another type such as a type which discharges by using a piezo element does not have to have a nozzle structure. The above method can be applied to an inkjet recording head having a structure in which a plurality of ejection portions are integrally formed.

[0052]

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

[Brief description of drawings]

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

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

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

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

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

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

7A and 7B are diagrams showing a state in which bubbles in ink are in contact with a flat surface, where A is a drawing when the flat surface is a hydrophilic surface, and B is a drawing.
It is a figure when a plane is a water-repellent surface.

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

[Explanation of symbols]

 1 Top Plate 2 Filter 3 Negative Type Dry Film 4 Heater Board 5 Heater 6 Water Repellent Surface 7 Nozzle 8 Air Bubble 9 Support 10 Water Repellent Porous Body 11 Tube Connection 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

Claims (5)

[Claims] 1. In an inkjet recording head having a structure in which a plurality of ink ejection portions are integrally formed and connected to a common liquid chamber, at least a part of an inner surface of the common liquid chamber is an ink repellent surface. An inkjet recording head characterized by: 2. The ink jet recording head according to claim 1, wherein the ink repellent surface is formed on the inner surface of the common liquid chamber other than the area in contact with the ejection portion. 3. The ink jet recording according to claim 1, wherein the ink discharge energy generating element is an electrothermal converter for generating heat by applying electric energy and causing a change in the state of the ink for discharging. head. 4. The ink jet recording head according to claim 1, wherein the ink jet recording head is a full line type in which a plurality of ejection openings are provided over the entire width of the recording area of the recording medium. 5. An ink ejection port for ejecting ink is provided facing a recording surface of a recording medium.
Alternatively, an inkjet recording apparatus including at least the recording head according to the item 2 and a member for mounting the recording head.