JP2003341083A - Deaerator and deaerating method for ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for removing gas dissolved into ink for an ink jet recorder with enhanced efficiency and ejecting ink stably. <P>SOLUTION: In the method for removing gas dissolved into ink by reducing the pressure in a space facing the ink to a level not higher than the atmospheric pressure through a gas permeable film, deaeration efficiency is enhanced by heating the gas permeable film. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degassing apparatus and a degassing method for an ink jet recording apparatus for stably controlling an ink discharge amount with high accuracy.

[0002]

2. Description of the Related Art In an ink jet recording method, a gas dissolved in ink may grow into bubbles during a discharge process, and the bubbles may cause a change in a discharge state. Therefore, in order to stably eject the ink,
It is important to remove the dissolved gas in the ink supplied to the inkjet head. Therefore, in inkjet recording, a structure has been considered in which a dissolved gas in the ink is removed by incorporating a degassing device in the middle of the ink supply path of the inkjet head, especially for the case where it is necessary to suppress the variation of the ejection amount.

For example, as a degassing method for ink jet recording ink, there is a method in which dissolved oxygen in the ink is permeated to the outside through a gas permeable film and is removed.
No. 17712. This is for deaeration of ink in an inkjet recording apparatus that obtains ink ejection energy by using a piezoelectric element, and the effect is that cavitation does not occur even when rapid compression of ink in the compression chamber is repeated, and cavitation This means that printing defects such as ink non-ejection due to the above do not occur. The specific degassing method is as a degassing device for the ink, in which the ink is passed through a tube made of a gas permeable film and the space outside the tube is depressurized to a vacuum to remove the dissolved gas in the ink. The ink is degassed by removing it outside the tube.

[0004]

In the deaerator of the conventional ink jet recording apparatus, the deaerated ink is rarely used for drawing, and the circulated ink is once stored in the reservoir (ink tank). To be done. Many of the reservoirs are open to the atmosphere, where the ink will take up gas again. Therefore, the degassing step is essential again in order to stably operate the discharge. The head temperature rises by ejecting whatever ink is used to eject ink. When the head temperature rises, the ejection characteristics change due to the decrease in the head characteristics and the ink viscosity. Further, since the ink passes through the head, it also has a role of keeping the head temperature at a constant temperature. Therefore, it is possible to keep the temperature of the ink constant and keep the head temperature constant by setting the flow rate to a certain level or more. Therefore, in order to stably operate the ink ejection, it is desired to increase the processing amount of the degassed ink.

Generally, the capacity of the deaerator for performing deaeration treatment above a certain level is limited, and in order to increase the amount of ink to be passed in a unit time, the deaerator is connected in parallel or in series. It is thought to do. Alternatively, a method of attaching two or more deaerating elements in a chamber in one deaerator described in JP-A No. 11-28307 and connecting them in series has been considered. However, these methods have problems that the deaerator becomes large and complicated.

The present invention provides a degassing apparatus and a degassing method for an ink recording apparatus which can easily improve the degassing ability of the existing degassing apparatus.

[0007]

The present invention has been completed as a result of intensive studies to solve the above problems and achieve the object of the present invention.

That is, the present invention is (1) a degassing apparatus capable of removing dissolved gas in ink by depressurizing a space facing the ink through a gas-permeable film to atmospheric pressure or less, A degassing device for an inkjet recording apparatus, comprising a heating mechanism capable of heating a gas-permeable film, (2) In the above (1), a mechanism for controlling the temperature of the gas-permeable film. (3) In the degassing device for an ink jet recording apparatus, comprising: (3) In the above (1), a part of the ink flow tube of the ink jet head is removed from the degassing element including the airtight and permeable membrane. A deaerator for an inkjet recording apparatus, comprising a cooling mechanism for cooling.

(4) A degassing device capable of removing dissolved gas in ink by depressurizing the space facing the ink via the gas permeable film to atmospheric pressure or less, which is gas permeable. A degassing method for an inkjet recording device, characterized in that the film is heated, (5) In the above (4),
A degassing method for an ink jet recording apparatus, characterized in that the temperature of the gas permeable film is controlled. (6) In the above (4), a degassing element including the airtight permeable film is used for an ink jet head. The method for degassing an ink jet recording apparatus, wherein a part of the ink flow path tube is cooled.

(Operation) According to the degassing apparatus and degassing method of the present invention, the gas permeation of the gas permeable membrane in the degassing apparatus is achieved by heating the degassing apparatus held in vacuum. It is possible to improve the property. As a result, since the deaeration capacity can be improved, the amount of ink that can be deaerated in a unit time can be increased, and stable ink ejection can be performed.

(Constitution of the Invention) FIG. 1 shows a degassing apparatus for ink jet recording used in this embodiment.

In the figure, 1 is an ink jet head,
Reference numeral 2 is a degassing unit for removing dissolved gas in the ink, and 3 is an exhaust pump for keeping the degassing unit in vacuum. 5 is a tank for storing ink,
Reference numeral 4 denotes a liquid feed pump for feeding the ink in the tank to the ink circulation system.

First, the ink is stored in the tank 5 and sent to the deaeration unit 2 by the pump 4. FIG. 2 is a sectional view showing an embodiment of the degassing unit. The degassing unit 2 used in the present invention is constructed by inserting the degassing element 10 into the adapter 12 of the vacuum chamber 11. The degassing element 10 is composed of a plurality of gas permeable membranes. The vacuum chamber 11 is formed with an exhaust connector 13 to which the vacuum pump 3 for reducing the pressure inside the system is connected.

Here, as the gas permeable tube, for example, a tube made of a material which is non-porous and has gas permeability is often used because it is difficult for a liquid to pass therethrough. By using a non-porous material, it is possible to efficiently remove the gas dissolved in the treatment liquid while minimizing changes in the composition, concentration, etc. of the treatment liquid. In this embodiment,
Although a fluororesin (tetrafluoroethylene) is used as the gas permeable tube, the tube is not limited to this.

Reference numeral 8 is a heater for heating the degassing element. The temperature of the degassing element is monitored by thermocouple 9. The feedthrough 14 connects the thermocouple 9 in the deaerator and a temperature controller (not shown).
The heater 8 is connected to the temperature controller. The temperature controller controls the heater so that the temperature 9 of the thermocouple is controlled to a certain constant temperature.

In FIG. 1, 6 is a dissolved oxygen meter for measuring the amount of dissolved oxygen in the ink.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be further described below with reference to Examples. However, the present invention is not limited to the following embodiments.

Example 1 In this example, the degassing apparatus shown in FIG. 1 was used, and pure water was used as the ink species. Flow rate 50m
l / min. And First, the vacuum chamber 11 is brought to an atmospheric pressure state, and the amount of dissolved oxygen in the initial deionized water in the degassing unit 2 is measured. afterwards,
The deaeration element was heated to 40 ° C. by the heater 8, the thermocouple 9, and the temperature controller connected to the vacuum chamber in FIG. After controlling at 40 ° C., the inside of the vacuum chamber was evacuated by a vacuum pump to perform deaeration.
The pressure in the vacuum chamber is 40 ton with a pressure gauge (not shown).
It was rr. 30 minutes after starting degassing. Then, the amount of dissolved oxygen in pure water was measured. The degassing efficiency was calculated by the following formula.

Degassing efficiency (%) = (initial dissolved oxygen amount−dissolved oxygen amount after degassing for 30 min) / initial dissolved oxygen amount ×
100 (Comparative Example 1) Degassing apparatus Using FIG. 4, the same kind of ink and flow rate were used, and the same measurement was performed with the degassing element at room temperature to calculate the degassing efficiency.

Table 1 shows the degassing efficiency of Example 1 and Comparative Example 1.

[0021]

[Table 1]

The degassing efficiency of this embodiment is improved and the effect is clear.

Example 2 In this example, the deaerator shown in FIG. 3 was used. Reference numeral 15 in the drawing is a cooling mechanism for cooling the ink. The ink temperature was set to 23 ° C. and controlled. In this embodiment, clear ink is used as the ink type. The component of the clear ink is pure water 70 wt% / diethylene glycol 30 wt% (however, without dye). Flow rate of 30 ml / min. Set to. First, the vacuum chamber 11 is set to the atmospheric pressure state, and the amount of dissolved oxygen in the initial deionized water that is not subjected to the degassing step in the degassing element is measured. Then, the heater 8 and the thermocouple 9 connected to the vacuum chamber in FIG. 1 and the temperature controller controlled the deaeration element to 40 ° C. by heating. After controlling at 40 ° C., the inside of the vacuum chamber was evacuated by a vacuum pump to perform deaeration. The pressure in the vacuum chamber was 40 torr using a pressure gauge (not shown). 30 mi after starting degassing
n. The amount of dissolved oxygen in the subsequent clear ink was measured.

In this example, a thermocouple (not shown) was connected to the head 1 to monitor the head temperature. The head starts degassing for 30 min. The discharge was started later. Temperature before starting discharge and starting discharge for 30 min. The subsequent head temperature was measured. In addition, discharge start 1 min. After and start discharging 30
min. The average 50-dot average drop velocity was measured. In addition, discharge start 20 min. The variation in the ejection speed of 200 dots after that was also measured. Generally, there is a correlation between the ejection speed and the ejection amount, and the ejection amount increases as the velocity increases. Therefore, the variation of the ejection amount can be indirectly measured by the ejection speed.

Comparative Example 2 Deaeration Device Using FIG. 4, the same kind of ink and same flow rate were used, and the measurement items were also measured in the same manner.

(Comparative Example 3) Degassing apparatus Using FIG. 4, the same kind of ink was used, and the flow rate was reduced so as to be the same as the dissolved oxygen amount after degassing in Example 1. Actually, the flow rate is 21 ml / min. Became. The measurement items were the same as in Example 2.

Table 2 shows the degassing efficiency, head temperature and ejection speed of Example 2 and Comparative Examples 2 and 3.

[0028]

[Table 2]

It can be seen that, at the same ink flow rate, the degassing efficiency of this embodiment is improved, and short-term fluctuations in the ejection state can be suppressed. It is also understood that the same degassing efficiency can suppress the long-term fluctuation because the flow rate can be increased. This is considered to be an effect of suppressing the head temperature rise.

[0030]

As is apparent from the above description, according to the present invention, the gas of the gas permeable film is heated by heating the gas permeable film in the deaeration unit held in vacuum. The permeability can be improved. As a result, since the deaeration capacity can be improved, the amount of ink that can be deaerated in a unit time can be increased, and stable ink ejection can be performed.

[Brief description of drawings]

FIG. 1 is a deaerator of this embodiment.

FIG. 2 is a cross-sectional view of a degassing unit used in this example.

FIG. 3 is a deaerator of this embodiment.

FIG. 4 is a conventional degassing device.

[Explanation of symbols]

1 inkjet head 2 degassing unit 3 vacuum pump 4 Liquid feed pump 5 ink tank 6 Dissolved oxygen meter 7 heating mechanism 8 heater 9 thermocouple 10 Degassing element 11 vacuum chamber 12 Adapter 13 Exhaust connector 14 Thermocouple feedthrough

Claims (6)

[Claims] 1. A degassing device capable of removing dissolved gas in ink by depressurizing a space facing ink through the gas permeable film to atmospheric pressure or less, the gas permeable film. A degassing device for an ink jet recording apparatus, comprising a heating mechanism capable of heating. 2. The deaerator for an inkjet recording apparatus according to claim 1, further comprising a mechanism for controlling a temperature of the gas permeable film. 3. The inkjet recording apparatus according to claim 1, further comprising a cooling mechanism for cooling a part of the ink flow path tube of the inkjet head from the degassing element including the airtight and permeable film. Deaerator. 4. A degassing device capable of removing dissolved gas in ink by depressurizing the space facing the ink through the gas permeable film to atmospheric pressure or less, the film having gas permeable property. A degassing method for an ink jet recording apparatus, which comprises heating. 5. The degassing method for an inkjet recording device according to claim 4, wherein the temperature of the gas-permeable film is controlled. 6. The degassing method for an inkjet recording apparatus according to claim 4, wherein a part of the ink flow path tube of the inkjet head is cooled from the degassing element including the airtight and permeable film.