JPH04147863A - Ink degassing method, liquid jet recording head equipped with degassing apparatus and liquid jet recording apparatus equipped with the head - Google Patents

Abstract

PURPOSE:To simply perform degassing of ink by bringing ink and an adsorbing body to a contact state to degass the dissolved air in the ink. CONSTITUTION:Ink and an adsorbing body are brought to a contact state to perform the degassing of the ink. As the adsorbing body, an unperforated one composed of a metal or metal oxide can be used. As the porous adsorbing body, a porous high- molecular compound is pref. and, as the porous high-molecular compound, there is a hydrophilic or oleophilic high-molecular gel. The high molecular gel has properties transferring from a swollen state to a contracted state by temp., light, an org. compound, an inorg. compound, a salt, an ion, an electric field, a current or a solvent other than the solvent constituting the high-molecular gel. A container 1 is filled with a liquid 2 and air 2a to be degassed is dissolved in the liquid 2 and the porous substance 3 is put in the liquid 2. In this case, the porous substance 3 is in a swollen state and, when the liquid 2 is heated, the porous substance 3 is contracted to become a contracted porous substance 4. Air bubbles 5 are generated on the surface of the substance 4 to be adsorbed thereon and the degassing of the liquid 2 is performed.

Description

[Detailed Description of the Invention] [Field of Application in Industry A] The present invention relates to a liquid jet recording head that records by ejecting ink, and a liquid jet recording head that uses an adsorbent to remove gas dissolved in the ink. The present invention relates to a degassing method of In7, a recording head equipped with the same degassing device, and a liquid jet recording apparatus equipped with the same head.

[Prior Art] A liquid jet recording device (bubble jet printer) that heats and foams ink in a nozzle to apply voltage to the ink is capable of heating the ink, generating bubble nuclei, growing into bubbles, etc. in a few microseconds. This is a new recording method that controls the continuous phenomenon of ink ejection.

In particular, the generation of foaming nuclei greatly contributes to print quality and power consumption, but if there is dissolved gas in the ink, it becomes difficult to control the generation of foaming nuclei.0 If foaming nuclei occur unevenly within the nozzle, bubbles, Furthermore, since the size and shape of the ink droplets are not uniform, the print quality deteriorates. Further, since gas has poor heat propagation efficiency, there is a problem that power consumption increases due to dissolved gas and non-uniformly generated foaming nuclei.

Conventionally, as a means of degassing gas dissolved in ink,
The main method was to apply a vacuum to the entire ink.

However, there was a drawback in that a device such as a vacuum pump was required to reduce the pressure. In addition, since dissolved gases are taken in again to the solubility level when the pressure is returned to normal pressure from a reduced pressure state, it is preferable to remove the gases immediately before using the ink. The drawback was that it was not convenient.

Another problem with conventionally known porous materials, such as boiling stones, is that if left in ink for a long time, the surface of the porous material will become wet with the ink and will no longer function as a deaerator. Therefore, when using a porous material to degas the ink, it is not only complicated because the porous material must be added immediately before degassing, but also requires recycling treatment in order to repeatedly use the porous material that has been used several times. required. As a method to deal with these problems, measures have been used such as storing the product in a closed container with low gas permeability after degassing it at the time of shipment, but deterioration over time after opening was unavoidable. Further, since such printers are required to be small, lightweight, and low cost, it is difficult to attach pressure reduction means such as a vacuum pump, so ink has not been used while being deaerated.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and its purpose is to incorporate it into a fine structure such as a recording head used in a liquid jet recording device, and to print ink in-line. It is an object of the present invention to provide a degassing method that can easily deaerate.

[Means for Solving the Problems] In order to achieve the above object, the present inventors have conducted various studies on methods of removing dissolved gas in the ink by adsorbing it to the surface of the ink by putting an adsorbent into the ink. I came.

Dissolved gas is the gas that is in contact with the ink, and the amount of dissolved gas is determined by the solubility of the gas in the ink, and is in equilibrium with the gas that is in contact with the ink. Degassing is carried out by shifting the equilibrium using a method such as depressurization to create a state in which the gas is more stable outside the ink than when it is inside the ink. Depressurization moves the gas from inside the ink to outside the ink by reducing the amount of gas in the space in contact with the ink.

Therefore, as described above, if the equilibrium is shifted, the dissolved gas should come out of the ink, but the size of the gas may become a problem. In other words, the dissolved gas has a large surface energy in the size of one or several solvated molecules, so it is difficult to combine with other dissolved gases or to overcome the affinity with the ink and come out of the ink. This is the case.

In order to solve these problems, the present inventors have confirmed that a method of bringing a dissolved gas adsorbent into contact with ink is an excellent method. Furthermore, porous materials such as boiling stones are effective as adsorbents, but conventional porous materials such as boiling stones have limited usage conditions and are generally not recyclable. was there. Therefore,
Further investigation revealed that, for example, in the case of a hydrogel made of N-isopropylacrylamide as a raw monomer and methylenebisacrylamide as a crosslinking agent, if the temperature in a water-soluble ink exceeds approximately 35°C, the gel will shrink and the surface will As a result of research, we discovered that air bubbles are adsorbed.

As a result, the object of the present invention can be prepared using a porous material, but for reasons of cost and adsorption capacity, it is preferable to use a polymer gel, a crosslinked polymer, or a polymer gel in which a liquid coexists with them. Preferably, the amount of dissolved gas adsorbed decreases when the high-density 9 gel swells/shrinks. By utilizing the swelling/contraction of molecular gel,
When degassing is desired, that is, just before ink is ejected, the control state (N-concentration state) is used to form a clear interface with low wettability to liquid, and to demonstrate sufficient performance as a degassing agent, boiling stone is used. I learned that if you put it in a liquid like this, the surface will not get wet and stop functioning. In other words, the present invention utilizes swelling/contraction of a polymer gel and non-aggregation/aggregation of polymers to shift the equilibrium, and also utilizes the interface between the contracted gel and the aggregated polymer as a place for bubble generation. The effect is that when polymers, cross-linked polymers, or polymer gels contract or aggregate, non-uniformity in temperature and concentration occurs near the interface, which shifts the equilibrium and creates conditions for bubbles to form, and also causes bubbles to grow. The ink is degassed and purified by adsorbing the dissolved gas in the form of bubbles at the contraction interface (coagulation interface).

That is, the present invention degass the dissolved gas in the ink by bringing the ink into contact with the adsorbent. This includes being a polymer or a polymer gel. Further, the present invention includes degassing the polymer gel by swelling and contracting it in the ink, and further provides a liquid jet recording head equipped with these degassing methods and a liquid jet recording device equipped with the same head. This includes:

The present invention will be explained in detail below.

In the present invention, the ink is degassed by bringing the ink into contact with the adsorbent.

As the adsorbent, non-porous materials such as metals and metal oxides can be used.

In addition, as the porous adsorbent, for example, 7S tengite, synthetic zeolite, glass, porous glass, ceramics, etc. can be suitably used, but porous polymer compounds are particularly preferred. Both crosslinked and non-crosslinked versions can be used.

Particularly preferred porous polymer compounds include hydrophilic and lipophilic polymer gels. A polymer gel is composed of a crosslinked polymer and a solvent, and is made of acrylamide, its α-substituted product, its N-substituted product, or acrylic acid,
and its salts, its esters, and its a, β
Substituted products, or acrylonitrile, and substituted products thereof, or α, β-unsaturated acids, salts thereof, and acid halides thereof, or α, β-unsaturated aldehydes, or α, β-unsaturated ketones, or vinyl ethers. , vinyl compounds such as aromatic vinyl carboxylates, aliphatic vinyl carboxylates, vinyl acetate, polyvinyl alcohol, or other unsaturated compounds, or polymers containing as main components one or more of them.

Polymerization methods include chemical polymerization using a polymerization initiator, or physical polymerization such as radiation polymerization, γ-ray polymerization, and thermal polymerization. 0 Polymerization initiators include one type or the nature of the polymer to be produced. For example, for water-soluble polymers such as acrylamide, derivatives thereof, or acrylic acid, ammonium persulfate and potassium persulfate, which are water-dropping redox polymerization initiators, are preferably used. Other monomers used include hydrogen peroxide and its salts, peroxides such as benzoyl peroxide, azoisobutyronitrile, sodium tert-butoxy, n-butyllithium, metals, and metal salts. In polymerization using a polymerization initiator, the reaction rate is proportional to temperature, so heating may be required. Furthermore, in the case of radical polymerization, since oxygen inhibits polymerization, it is preferable to replace the air with nitrogen, helium, or the like.

The solvent is water, alcohol, ketone, ether, aldehyde, hydrocarbon, etc., or a solution thereof, which swells the crosslinked polymer to form a polymer gel.

The properties of the polymer gel preferably used in the present invention include temperature and
This is the transition of a polymer gel from a swollen state to a contracted state due to light, organic compounds, inorganic compounds, salts, ions, electric fields, currents, or solvents other than the solvents that make up the polymer gel. The swollen state of a polymer gel is a state in which a large amount of solvent is incorporated into the crosslinked polymer network, and the contracted state is a state in which the networks are more entangled than in the swollen state and do not incorporate much solvent. Furthermore, this swelling state and contraction state (
It is preferable to carry out reversible binding (without changing the properties of the polymer gel). In the present invention, the above swelling/
Degassing is carried out more effectively by controlling shrinkage (non-aggregation/aggregation), and among the above-mentioned methods, a method of changing temperature is particularly preferred as a control method.

Next, when ink is degassed using the porous material thus produced, the ink and the porous material are brought into contact, thereby degassing. Figure 1 is a schematic diagram showing this situation.
is satisfied.

A gas 2a to be degassed is dissolved in this liquid 2 (the gas 2a is not actually visible, but it is schematically shown as a dot), and the porous material 3 is placed in this liquid 2. However, in this case, the porous material 3 is in a swollen state. When the liquid 2 is heated in this state, the porous material 3 contracts to become a contracted porous material 4 as shown in FIG. The liquid 2 is degassed.

Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example] 1 0.5 g of bad-containing N-isopropylacrylamide, 13.3 mg of methylenebisacrylamide, N, N, N
Dissolve 6 microliters of ',N'-tetramethylethylenediamine in 9 milliliters of distilled water, and 1
Bubbling was carried out for a period of time to obtain a solution. A polymerization initiator was prepared by dissolving 1 milligram of ammonium persulfate in 1 milliliter of distilled water. Pour the monomer solution into a cube mold,
A polymerization initiator was added while cooling to approximately 5° C., and the mixture was allowed to stand for 1 hour under a nitrogen atmosphere to polymerize, and the mixture was removed from the mold to obtain a polymer gel.

When the ink of the present invention is water-soluble, it is preferable to use a water-soluble polymer for purification of the ink. 1 gram of N-methylolacrylamide, which indicates a polymerizing agent for acrylamide, which is a typical water-soluble polymer. , 20 mg of methylenebisacrylamide was dissolved in methanol, and 1 mg of 2,2°-azobisdimethyleneisobutyramidine (Wako Tsumugi VA-061) was added.
Polymerization was carried out by heating to 0°C.

A mixed aqueous solution of 5 mol % of methacrylamide and methylenebisacrylamide was subjected to gamma ray polymerization using cobalt 6o.

Ink for inkjet printers is generally made by dissolving or dispersing dyes or pigments in water or alcohol (with the addition of a surfactant as necessary). Generally, filtration is used to remove undissolved substances and aggregated dyes, but dissolved gases cannot be removed by this treatment.

When the polymer gel of Polymerization Example 1 was added to 1 liter of bubble jet printer ink that had been left indoors and saturated with air at 20°C and the entire ink was heated to 35°C, heating 1
After 0 minutes, the polymer gel contracted and bubbles were generated at its interface. When the bubbles were collected and analyzed, it was confirmed that they were composed of air. When only the ink was separated and collected and compared with ink that was not treated with polymer gel, it was found that
The amount of dissolved air had decreased to below the detection limit.

When we compared the printing quality of this ink with untreated ink, we found that the size and shape of the ink droplets were stable, allowing for constant printing density and fine printing power. In addition, the power consumption was almost as designed, and it was determined that unnecessary foaming was not performed in 6 comparisons! In Example 1, no bubbles were observed in the ink that was heated to 35° C. without adding polymer gel. The results of comparative analysis with ink that was not heated revealed that there was no significant difference. The ink that was heated to nearly 80 degrees Celsius generated bubbles as it boiled, and analysis confirmed that it was degassed.9 In addition, similar analysis results were obtained for the ink that was degassed under reduced pressure with a vacuum pump for one hour. It became. Therefore, according to Example 1, a degassing effect equivalent to heating the ink to near its boiling point or degassing it under reduced pressure for one hour could be achieved at a relatively low temperature of 35° C. and in a short time.

Airi 11 An attempt was made to reuse polymer gel. Ink 1 at 20°C without degassing the polymer gel used as a degassing agent in Example 1
I put it in a little bottle. The polymer gel swelled, and no air bubbles were observed on its surface. This is done in the same manner as in Example 1.
When heated to 5°C, the polymer gel contracted and air bubbles were adsorbed to its surface, indicating that it could be used repeatedly. It was also found that this repeated use is possible any number of times, and that no recycling treatment is required.

Figure 3 is a schematic diagram of a liquid jet recording head, and 6 in the figure is an ink liquid flow path. In the flow path 6, the polymer gel 8 synthesized in Synthesis Example 1 and the electrothermal converter 7, which is an ink ejection energy generating element, were arranged in order from the upstream side of the ink. If printing is performed while heating the ink to 35℃ during ejection,
Since the volume of the ink was small, sufficient deaeration could be achieved in the short time it took to pass over the polymer gel. The printing quality and power consumption were almost the same as in Example 1, and were improved compared to when ink without degassing was used. Note that 5 in the figure is dissolved gas attached due to degassing.

Figure 4 shows a liquid jet recording head with the same configuration as Figure 3, but in this example, the polymer gel is formed into a triangular prism shape to increase the contact area with the ink. It is. In this example, as well as in FIG. 3, good results were obtained.According to this example, the air dissolved in the ink was degassed at a relatively low temperature of 35°C.

In addition, it was possible to easily degas the ink immediately before use without using a second means such as a pressure reducing means such as a vacuum pump.

X Feng I N-isopropylacrylamide 0.5 g, N, N
, N',N'-tetramethylethylenediamine (6 microliters) was dissolved in 9 milliliters of distilled water, and nitrogen gas was bubbled through the solution for 1 hour to obtain a monomer solution. A polymerization initiator was prepared by dissolving 1 milligram of ammonium persulfate in 1 milliliter of distilled water. A polymerization initiator was added to the Setsumar solution while cooling it to approximately 5°C, and the mixture was allowed to stand for 1 hour under a nitrogen atmosphere to polymerize, thereby obtaining a polymer solution containing polyN-isopropylacrylamide as a main component. Unlike the polymer gel polymerized in Example 1, this polymer gel cannot maintain a gel-like structure because no crosslinking agent is added. Add this to ink at 20'C that is saturated with air, and add 35
When heated to ℃, the polymer aggregated and bubbles were generated on its surface. Therefore, deaeration, which is the purpose of the present invention, is achieved in Example 1.
It was confirmed that this can be achieved even if it is not in a gel state like .

The present invention brings about excellent effects particularly in a bubble jet recording head and recording apparatus among liquid jet recording (ink jet recording) systems.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. By applying at least one drive signal corresponding to the recording information to the electrothermal transducer element, thermal energy is generated that causes the electrothermal transducer to rapidly rise in temperature beyond nucleate boiling, thereby reducing the heat of the recording head. This is effective because it causes film boiling on the action surface, resulting in the formation of bubbles in the liquid (ink) that correspond one-to-one to this drive signal. The growth and contraction of the bubble causes liquid (ink) to be ejected through the ejection hole to form at least one drop. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, so that ejection of liquid (ink) with particularly excellent responsiveness can be achieved. As this pulse-shaped drive signal, those described in US Pat. No. 4,463,359 and US Pat. No. 4,345,262 are suitable. Incidentally, as an invention regarding the temperature increase rate of the heat acting surface, U.S. Patent No. 4
If the conditions described in No. 313124 are adopted, even better recording can be achieved.

The configuration of the recording head includes, in addition to the combination configuration of ejection holes, liquid flow paths, and electrothermal converter elements (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications. U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459 disclose a configuration in which the action portion is arranged in a bending region.
A configuration using the specification of No. 600 is also included in the present invention. In addition, Japanese Patent Application Laid-Open No. 123670 of 1982 discloses a configuration in which a common slit is used as a discharge part for a plurality of electrothermal transducer elements, and a method for absorbing pressure waves of thermal energy is disclosed. The present invention is also effective with a configuration based on Japanese Patent Application Laid-open No. 138461 of 1982, which discloses a configuration in which the openings correspond to the discharge holes.

Furthermore, as a full-line type recording head that can simultaneously record across the entire width of recording paper, it is possible to use a configuration that satisfies the length by a combination of multiple recording heads as disclosed in the above-mentioned specification, or a configuration that can be used as a single unit. Although any structure may be used as a single recording head, the present invention can more effectively exhibit the above-mentioned effects.

In addition, a replaceable chip-type recording head that is attached to the device body enables electrical connection to the device body and ink supply from the device body, or a chip-type recording head that is installed integrally with the recording head itself. The present invention is also effective in cartridge type recording heads.

Further, it is preferable to add a recovery means or a preliminary auxiliary means for the recording head to the recording apparatus, since this can further stabilize the effect of the recording head obtained by the present invention. Specifically, these include capping means, cleaning means, pressurizing or suction means, electrothermal transducer elements, separate heating elements, or a combination of these for the recording head. It is also effective to add a preheating means, a means for performing a preliminary ejection mode in which ejection is performed other than printing, etc. to perform stable printing.

Furthermore, the recording mode of the recording device is not limited to a mode in which only mainstream colors such as black are recorded, but also a mode in which the recording head is configured integrally or by a combination of multiple heads, but it is also possible to configure the recording head in a single unit, or in a combination of multiple heads. Alternatively, the present invention is also extremely effective for a recording head of an apparatus equipped with at least one of full colors by mixed colors.

In addition, the recording head obtained by the present invention may be an ink that solidifies at room temperature or below, but softens or becomes a liquid at room temperature, even if the ink is not a liquid, or an ink that is generally used in inkjet. It can also be applied to materials that become soft or liquid in the temperature adjustment range of 30° C. or higher and 70° C. or lower. That is, it is sufficient if the ink is in a liquid state when the recording signal is applied. In addition, ink that actively prevents temperature rise due to thermal energy by absorbing it as energy to transform the ink from a solid state to a liquid state, or ink that solidifies when left standing for the purpose of preventing ink evaporation. In any case, by applying thermal energy according to the recording signal, the ink is liquefied and ejected as liquid ink, or the ink has already begun to solidify by the time it reaches the recording medium. The use of ink that is liquefied only by energy is also applicable to the recording head according to the present invention. In such a case, the ink is held in a liquid or solid state in the recesses or through holes of the porous sheet, as described in JP-A-54-56847 or JP-A-60-71260. It may also be configured to face the electrothermal transducer element. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

FIG. 5 is an external perspective view showing an example of an inkjet recording apparatus (IJRAI) equipped with a recording head obtained according to the present invention as an inkjet head cartridge (IJC).

In the figure, reference numeral 20 denotes an inkjet head cartridge (IJC) equipped with a group of nozzles that ejects ink toward the recording surface of recording paper fed onto a platen 24. 16 is a carriage HC that holds the IJC 20, and a drive belt 18 that transmits the driving force of the drive motor 17.
By connecting a part of the IJC 20 and making it slidable on two guide shafts 19A and 19B arranged parallel to each other, it is possible to reciprocate over the entire width of the recording paper of the IJC 20.

Reference numeral 26 denotes a head recovery device, which is disposed at one end of the movement path of the IJC 20, for example, at a position opposite to the home position. The head recovery device 26 is operated by the driving force of the motor 22 via the transmission mechanism 23, and the IJC 20 is capped. In connection with the capping of the IJC 20 by the cap portion 26A of the head recovery device 26, ink suction by an appropriate suction means provided in the head recovery device 26 or appropriate pressure means provided in the ink supply path to the IJC 20 is performed. The ink is pumped by
The IJC is protected by performing an ejection recovery process such as removing thickened ink in the nozzle by forcibly discharging the ink from the ejection port, and by capping the nozzle at the end of printing.

A blade 30 is disposed on the side surface of the head recovery device 26 and is made of silicone rubber and serves as a wiping member. The blade 31 is held in the form of a cantilever by a blade holding member 31A, and is operated by a motor 22 and a transmission mechanism 23 similarly to the head recovery device 26, and is operated by the IJC 20.
can be engaged with the discharge surface. As a result, IJC2
At an appropriate timing during the recording operation of 0 or after ejection recovery processing using the head recovery device 26, the blade 31 is projected into the movement path of the IJC 20, and the IJC 20
This is to wipe off condensation, moisture, dust, etc. on the discharge surface of the IJC 20 as the IJC 20 moves.

[Effect of the invention] The present invention has the following effects.

1. Easy degassing is possible without the need for any complicated equipment such as a vacuum pump.

2. Energy saving as it can be degassed at relatively low temperatures;
Less likely to cause ink decomposition or denaturation.

3. Since the nozzle can be degassed immediately before ink is ejected, there is almost no effect of dissolved gas.

4 High quality printing images can be obtained, and power consumption is also reduced, resulting in energy savings.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams explaining the degassing method of the present invention, and FIGS. 3 and 4 are conceptual diagrams showing an example in which the degassing method of the present invention is applied in a liquid jet recording head. , FIG. 5 is a perspective view illustrating the liquid jet recording apparatus. 1... Container 2... Liquid 2a... Dissolved gas 3... Porous substance (swollen state) 4... Porous substance (contracted state) 5... Air bubbles 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 removed twice, almost 30 times Figure 4

Claims (1)

[Scope of Claims] 1. A method for degassing ink for a liquid jet recording head, characterized in that dissolved gas in the ink is degassed by bringing the ink into contact with an adsorbent. 2. The deaeration method according to claim 1, wherein the adsorbent is a porous material. 3. The degassing method according to claim 2, wherein the porous material is made of a polymer material. 4. The degassing method according to claim 3, wherein the polymeric substance comprises a crosslinked polymer or a polymer gel. 5. The degassing method according to claim 4, wherein the degassing is carried out by swelling and contracting the polymer gel within the ink. 6. A liquid having an ink discharge hole, an ink supply hole, an ink liquid flow path that communicates the ink discharge hole and the ink supply hole, and an ink discharge energy generating element disposed in the ink liquid flow path. A liquid jet recording head, characterized in that a porous material is disposed within the ink liquid flow path and between the ejection energy generating element and the ink supply hole. 7. The head according to claim 6, wherein the ejection energy generating element is an electrothermal converter that generates thermal energy. 8. The head is a full line type head in which a predetermined number of ejection holes are arranged over the entire width of the recording area of the recording medium.
Head as described. 9. At least a recording medium, a head according to claim 6, which is provided with an ejection hole for ejecting ink opposite to a recording surface of the recording medium, and a mounting member for mounting the head. A liquid jet recording device comprising: