JPH11198403A - Method and apparatus for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove smoothly air bubbles caught by a filter interposed at a liquid circulation feed path when a liquid discharge head is at a recovery process. SOLUTION: An image-forming apparatus has a circulation inflow path 22 and a circulation outflow path 28 for circulating an ink 11 between a print head 12 discharging the ink 11 and an ink tank 21 storing the ink 11. The ink 11 is discharged to a print sheet from a discharge opening 14 of the print head 12, thereby achieving printing in the apparatus. The apparatus is provided with a filter 35 interposed in the circulation inflow path 22 and circulation outflow path 28 for catching foreign articles in the ink 11 and an ink-heating device 34 for prompting air bubbles to pass the filter 35 at a recovery process to let the ink 11 discharged favorably from the discharge opening 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and apparatus for printing on a print medium by discharging a liquid from a discharge port of a liquid discharge head, and more particularly, to an air bubble for a filter provided in a liquid supply path. Is improved.

[0002]

2. Description of the Related Art An ink or a liquid such as a processing liquid for adjusting the printability of the ink is ejected from an ejection port of an ink jet head, and a desired image is formed on a print medium such as paper, a resin film, or a cloth or metal. Ink-jet printing apparatus that forms a print head is non-contact with such print media, so it is excellent in quietness, printing speed is high, high-density printing is possible, and colorization is easy, Advantages such as miniaturization of the entire apparatus can be obtained.

[0003] In an ink jet printing apparatus using an ink jet head, a filter is interposed in the middle of a liquid supply path so that liquid can be normally ejected from the ink jet head, and foreign matter such as dust contained in the liquid flowing therethrough. Such a matter is captured by a filter, and care is taken to prevent such foreign matter from entering the liquid path connected to the discharge port of the ink jet head and causing clogging.

FIG. 5 shows a schematic structure of such a conventional filter. That is, in the middle of the pipes 1a and 1b constituting the liquid circulation supply path, a filter unit 2 having a cylindrical shape is provided.
The filter unit 2 incorporates a filter 3 capable of capturing a foreign substance having a diameter larger than 10 μm, for example. Therefore, among the foreign substances mixed in the liquid 4 flowing from the right side to the left side in the drawing, those 5 having a diameter larger than 10 μm and bubbles 6 having a diameter larger than 10 μm are captured by the filter 3 and downstream. It does not flow to the side.

[0005] However, if the diameter of the bubble 6 trapped on the upstream side of the filter 3 increases, this becomes a flow path resistance to the pipe 1a, so that a sufficient amount of liquid can be supplied to an unillustrated ink jet head. Therefore, the ejection of the liquid from the inkjet head becomes unstable, and in the worst case, a state occurs in which the ink is not ejected. Therefore, the recovery process of the inkjet head is performed to perform the piping 1a.
Bubbles 6 inside are removed.

At the time of recovery, a pump (not shown) pumps the liquid from the liquid storage tank to the ink jet head via one of the circulation supply paths, that is, the outward path.
That is, the liquid is returned to the liquid storage tank via the return path. Due to this reflux, bubbles existing in the outward path and the return path and in the ink jet head are returned to the liquid storage tank,
The liquid is released from the liquid storage tank into the atmosphere.

At this time, the air bubbles 6 must pass through the filter unit 2 provided on the way to the circulation path and the return path. In order for the bubbles 6 to pass through the filter unit 2, a certain pressure difference is applied between the upstream and downstream sides of the filter 3, that is, upstream, so that the meniscus formed by the liquid and the gas on the surface of the filter 3 is broken. It is necessary to provide between the downstream side.

In the conventional apparatus shown in FIG. 5, when the liquid is pumped by a pump during the recovery process, all the liquid passes through the filter 3 of the filter unit 2 on the outward path, so that the pressure loss in the filter 3 is reduced. As a result, a large pressure difference occurs before and after the filter 3, and the air bubbles 6 pass through the filter unit 2.

Liquid and bubbles 6 passing through filter 3
Enters the ink jet head, a part of the liquid flows out from the discharge port thereof, pushes out the bubbles in the liquid path, and exits from the remaining liquid ink jet head and enters the filter unit 2 on the return path. As in the case of the filter unit 2 incorporated in the forward path, a pressure difference occurs before and after the filter 3 due to the pressure loss of the filter 3 of the filter unit 2 provided in the return path, so that the bubbles pass through the filter unit 2. The liquid is returned to the liquid storage tank.

[0010]

In the conventional ink jet printing apparatus, even if the above-described ink jet head recovery processing is performed, bubbles trapped in the filter 3 of the filter unit 2 provided in the middle of the circulation supply path. 6
Could not be completely removed. For this reason, since the bubble 6 becomes large immediately, it is necessary to frequently perform the recovery process.

In the future, as the ink jet head becomes higher in density and the printing speed becomes higher, the filter 3
As a result, the ejection state of the liquid due to the bubbles 6 may become unstable, or a state in which ejection may not be possible may occur significantly. Therefore, the recovery process must be performed more frequently. The operation rate of the device is greatly reduced, which is a serious problem.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-density and high-speed ink jet printing apparatus in which bubbles trapped by a filter provided in a liquid circulation supply path are completely removed during a recovery process of a liquid discharge head. An object of the present invention is to provide an image forming method and an image forming apparatus capable of improving an operation rate.

[0013]

According to a first aspect of the present invention, there is provided:
Using a liquid discharge recording apparatus having a circulation flow path for circulating liquid between a liquid discharge head for discharging liquid and a liquid storage tank for storing liquid, the liquid is discharged from a discharge port of the liquid discharge head to a print medium. An image forming method for performing printing by discharging, wherein a step of capturing a foreign substance in the liquid using a filter in the middle of a liquid supply path to the liquid discharging head and a state of discharging the liquid from the discharge port. A step of promoting the passage of air bubbles to the filter at the time of a recovery process for making the filter better.

According to a second aspect of the present invention, there is provided a liquid discharge head having a circulation flow path for circulating a liquid between a liquid discharge head for discharging a liquid and a liquid storage tank for storing the liquid. An image forming apparatus that performs printing by discharging liquid from a discharge port to a print medium, wherein the filter is interposed in at least one of the circulation flow paths and captures foreign matter in the liquid; It is characterized by comprising a bubble passage promoting means for promoting the passage of bubbles.

According to the present invention, the bubbles trapped by the filter are eliminated by passing through the filter together with the liquid by the bubble passage promoting means during the recovery process for improving the discharge state of the liquid from the discharge port. You.

[0016]

In the image forming method according to the first aspect of the present invention, the step of promoting the passage of bubbles through the filter includes the step of heating the liquid flowing into the filter and the step of heating the liquid flowing into the filter. It may have a step of giving ultrasonic vibration. Further, the liquid may be ink for printing on a print medium or a processing liquid for adjusting printability of the ink on the print medium.

In the image forming apparatus according to a second aspect of the present invention, a first pump for supplying the liquid in the liquid storage tank to the liquid discharge head is provided in one of the circulation flow paths, A second pump for returning the liquid supplied to the head to the liquid storage tank may be provided in the other of the circulation channels. In this case, the bubble passage promoting means includes the first and second pumps. The second pump provided in the other circulation channel may be capable of supplying the liquid in the liquid storage tank to the liquid discharge head. good. Further, the bubble passage promoting means may include a heating means for heating the liquid, or an ultrasonic wave generating means for applying ultrasonic vibration to the liquid, and in this case, the heating means And at least one of the filter and the circulation channel upstream of the filter may be heated. Further, the liquid discharge head may include a discharge energy generation unit for discharging liquid from the discharge port, and in this case, the discharge energy generation unit may include an electrothermal converter that generates heat energy. May be provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a full line type ink jet printing apparatus will be described in detail with reference to FIGS. 1 to 4. However, the present invention is not limited to such an embodiment. Further, the present invention can be combined or applied to technologies in other fields that include similar problems.

FIG. 1 shows a schematic structure of an ink jet printing apparatus according to the present embodiment, FIG. 2 shows a schematic structure of a print head mounted on the ink jet printing apparatus, and FIG. 3 shows a concept of an ink supply system for the print head. Shown in That is, the four print heads 12 of the bubble jet system corresponding to the black, yellow, magenta, and cyan inks 11, respectively, have the electrothermal converters 13 as the ejection energy generating means, and correspond to the energization. The ink droplets are ejected from the ejection port 14 using bubbles generated in the ink 11 as a pressure source, and are fixed to the head holder 15 at predetermined intervals. Each print head 12 is a full-line type in which 4736 discharge ports 14 are formed at a density of 400 dpi and can simultaneously print over the entire width of a vertically long A3-size print sheet 16. is there.

The print head 12 in this embodiment is
It is composed of an electrothermal transducer 13 formed on a substrate 17 through a semiconductor manufacturing process such as etching, vapor deposition, and sputtering, an electrode 18, a grooved plate 20 for forming an ink path wall 19, and the like. The ink 11 is supplied from the ink tank 21 through the circulation inflow path 22 to the print head 12.
Is supplied to the common ink chamber 23 of the ink jet printer. Common ink chamber 23
The ink 11 supplied into the ink path is supplied to the ink path 24 by capillary action, and is stably held by forming a meniscus at the discharge port 14 at the tip of the ink path 24. Here, when electricity is supplied to the electrothermal converter 13, the ink 11 located on the electrothermal converter 13 is heated to cause a bubbling phenomenon, and ink droplets are ejected from the ejection ports 14 by the foaming energy.

Also, the ejection port 14 of each print head 12
Read head 25 for detecting the location (discharge port number) of the discharge port 14 of the print head 12 from which the ink 11 is not discharged despite the fact that the electrothermal transducer 13 is energized in order to detect the clogged state of Is provided on the head holder 15.

Reference numeral 26 denotes a capping unit. When the ink-jet printing apparatus is not in a standby state, the head holder 15 is pulled up to a position indicated by a two-dot chain line in FIG. It is pressed so as to cover the discharge port surface 27 where the discharge port 14 opens. Further, the capping unit 26 includes the print head 12 and the ink tank 2.
Print head 1 by circulation of ink 11 between
At the time of discharge recovery of 2, the recovery pumps 29 and 30 incorporated in the circulation inflow channel 22 and the circulation outflow channel 28 respectively act as a tray for waste ink pushed out from the discharge port 14, and the waste ink is a waste ink tank (not shown). It is led to. One recovery pump 29 is for supplying the ink 11 in the ink tank 21 to the print head 12, and the other recovery pump 30 is rotated forward when the ink 11 circulates and is supplied to the print head 12. Ink 1
In addition to the function of returning the ink 1 to the ink tank 21, it also has the function of inverting the ink 11 from the ejection port 14 of the print head 12 to the capping unit 26 as a part of the recovery process. The operation and stop operation of the recovery pumps 29 and 30 are performed by a command from the control device 31.

Reference numeral 32 denotes a filter unit provided in the circulation inflow passage 22, and reference numeral 33 denotes a filter unit provided in the circulation outflow passage 28. 34 is a filter unit 3
2, 33, the circulation inflow channel 22 and the circulation outflow channel 2
And an ink heating device provided so as to cover the print head 8, and at the same time as the electrothermal transducer 13 of each print head 12 is driven in accordance with image data by a print start operation, the circulation inflow path 22 and the circulation outflow path 28 The heating of the ink 11 inside starts. At this time, the recovery pumps 29 and 30 are in a state where their operations are stopped, and the ink 11 is supplied to the print head 12.
With the consumption of the ink 11 ejected from the ink tank 21, the ink enters the ink heating device 34 from the ink tank 21 through the circulation inflow channel 22 and the circulation outflow channel 28 by capillary action, where it is heated and incorporated into the filter units 32 and 33, respectively. After passing through the filtered filter 35, it is supplied to the print head 12. During this time, foreign matter contained in the ink 11 is captured by the filter 35 and is not supplied to the print head 12 side.

The ink 11 passing through the filter 35 is heated by the ink heating device 34 and its viscosity is reduced. Therefore, even if bubbles are mixed in the ink 11, the bubbles are captured by the filter 35. Without passing through the filter 35, the air bubbles are trapped by the filter 35, so that the flow resistance of the ink 11 flowing in the circulation inflow channel 22 and the circulation outflow channel 28 increases. Can be prevented. As a result, even in the full line type print head 12 of this embodiment, which consumes more ink than the serial type, the area of the filter 35 and the circulation inflow path 22 and the circulation outflow path 28
The ink 11 can be smoothly supplied to the print head 12 without setting the passage cross-sectional area of the print head 12 particularly large.

Reference numeral 36 denotes an endless electrostatic attraction belt for transporting the print sheet 16 disposed opposite to each of the print heads 12 at a predetermined interval, and 37 denotes each of the print heads 12 via the electrostatic attraction belt 36. The back platen is disposed opposite to the back platen.

Reference numeral 38 denotes a print sheet 16 such as plain paper.
Is a pickup roller which is detachably mounted on the apparatus main body, and is a pickup roller which sends out and feeds only one uppermost print sheet 16 stored in the feed cassette 38. 40 is the pickup roller 3
Reference numeral 42 denotes a transport roller for transporting the print sheet 16 sent out from the transport path 9 to the transport path 41, and reference numeral 42 denotes a transport roller disposed on the exit side of the transport path 41.

Reference numerals 43 and 44 denote heaters and fans for drying and fixing the ink droplets adhered by the printing operation on the print sheet 16 by hot air. Reference numeral 45 denotes a discharge roller for discharging the fixed print sheet 16 to the outside of the apparatus. Reference numeral 46 denotes a discharge roller. This is a tray for sequentially stacking the printed sheets 16.

In this embodiment, simultaneously with the start of the recovery process,
Heating of the ink 11 in the circulation inflow path 22 and the circulation outflow path 28 starts. At this time, the ink 11 is stored in the ink tank 2
1 enters the ink heating device 34 through the circulation inflow channel 22, passes through the filter 35, which is heated and incorporated in the filter unit 32, passes through the print head 12, and enters the ink heating device 34 again, and the circulation outflow channel Go through 28. During this time, foreign matter contained in the ink 11
5 and is not supplied to the print head 12 side.

The ink 11 passing through the filter 35 is heated by the ink heating device 34 and its viscosity is reduced. Therefore, even if bubbles are mixed in the ink 11, these bubbles are captured by the filter 35. Without passing through the filter 35, the air bubbles are trapped by the filter 35, so that the flow resistance of the ink 11 flowing in the circulation inflow channel 22 and the circulation outflow channel 28 increases. Can be prevented.

As a result, the discharge port 1 of the print head 12
Even when the density of the filter 4 is increased and the mesh of the filter 35 becomes dense, the recovery processing does not leave air bubbles on the filter 35, so that the number of times of the recovery processing can be greatly reduced, and the operation rate of the inkjet printing apparatus is improved. be able to.

On the other hand, when a print start operation is performed,
The print sheet 16 of the designated size is sent out from the feed cassette 38 by the pickup roller 39. The sent print sheet 16 is transported by the transport roller 4.
At 0 and 42, it is rotated in advance in a charged state, and is placed on a charging / adsorbing belt 36 which has a planar shape by a back platen 37. As the leading end of the print sheet 16 arrives at the lower part of each print head 12, the electrothermal converter 13 of each print head 12 is driven according to the image data. The ink droplet flies from the ejection port 14 toward the surface of the print sheet 16 and lands on the print sheet 16.
A color image is formed on the surface of. At this time, as described above, the ink 11 heated by operating the ink heating device 34 is supplied to the print head 12 through the filter units 32 and 33.

When the print sheet 16 has poor hygroscopicity,
The droplets adhering to the surface do not dry, and slide on the discharge roller 45 or the print sheet 16 overlaid thereon, so that the surface of the print sheet 16 becomes dirty.
Then, forced drying is performed by the fan 44 to fix the image. The print sheet 16 on which fixing has been completed is discharged onto a tray 46 by a discharge roller 45.

In the above embodiment, the filter unit 3
Although the portions of the circulation inflow channel 22 and the circulation outflow channel 28 connected to the second and the third 33 are heated by the ink heating device 34, the entire filter units 32 and 33 may be further heated by the ink heating device 34. It is possible to provide an ultrasonic generator in place of the ink heating device 34.

FIG. 4 shows the concept of an ink supply system according to another embodiment of the present invention. Members having the same functions as those of the previous embodiment are denoted by the same reference numerals, and the description thereof will not be repeated. It shall be omitted. That is, the ultrasonic generator 4
7 covers not only the circulating inflow channel 22 and the circulating outflow channel 28 connected to the filter units 32 and 33, but also these filter units 32 and 33, and if only the circulating inflow channel 22 and the circulating outflow channel 28, Instead, the filter units 32 and 33 are also ultrasonically vibrated.

The ink 11 enters the ultrasonic generator 34 from the ink tank 21 through the circulation inflow path 22, passes through the filter 35 incorporated in the filter unit 32,
After passing through the print head 12, the ink heating device 34
And passes through the circulation outflow passage 28, during which the ink 11
Foreign matter contained therein is captured by the filter 35 and is not supplied to the print head 12 side.

By the start of the recovery process, ultrasonic vibration is applied to the ink 11 in the circulation inflow channel 22 and the circulation outflow channel 28, and the ink 11 passing through the filter 35 becomes fine bubbles by the ultrasonic generator 34, Since the air passes through the filter 35 without being caught by the filter 35, the air bubbles are caught by the filter 35 and the flow resistance of the ink 11 flowing in the circulation inflow channel 22 and the circulation outflow channel 28 increases. Specifics can be prevented beforehand.

As a result, the discharge port 1 of the print head 12
Even when the density of the filter 4 is increased and the mesh of the filter 35 becomes dense, the recovery processing does not leave air bubbles on the filter 35, so that the number of times of the recovery processing can be greatly reduced, and the operation rate of the inkjet printing apparatus is improved. be able to.

It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging a liquid, particularly in an ink jet system. This provides an excellent effect in an ink jet printing apparatus of a type in which a change in the state of a liquid is caused by thermal energy. According to such a method, it is possible to achieve higher density and higher definition of the print.

The typical configuration and principle are described in, for example, US Pat. No. 4,723,129 and US Pat.
It is preferable to use the basic principle disclosed in Japanese Patent Application No. 0796. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or the flow path holding the liquid. Applying at least one drive signal to the electrothermal transducer that provides a rapid temperature rise exceeding nucleate boiling corresponding to the print information, thereby generating thermal energy in the electrothermal transducer and providing a thermal effect to the inkjet head. This is effective because film boiling occurs on the surface, and consequently, bubbles in the liquid corresponding to this drive signal can be formed one-to-one. By the growth and shrinkage of the bubble, the liquid is discharged through the discharge port 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 the liquid having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. In addition,
US Patent No. 4 of the invention relating to the rate of temperature rise of the heat acting surface
By employing the conditions described in the specification of Japanese Patent No. 313124, more excellent printing can be performed.

The structure of the ink jet head is a combination of a discharge port, a flow path, and an electrothermal converter (a linear liquid flow path or a right-angled liquid flow path) as disclosed in the above-mentioned specifications. In addition, the present invention includes a configuration using U.S. Pat. No. 4,558,333 or U.S. Pat. No. 4,459,600, which discloses a configuration in which a heat acting portion is arranged in a bent region. In addition, JP-A-59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and an aperture for absorbing a pressure wave of thermal energy is provided. JP-A-59-138461 which discloses a configuration corresponding to a discharge section
The effects of the present invention are effective even if the configuration is based on the above publication. That is, the present invention can improve the operation rate of the inkjet printing apparatus regardless of the form of the inkjet head.

Further, even in the case of a serial type in which the scanning movement is performed along the width direction of the print area of the print medium, an ink jet head fixed to the apparatus main body or an electric connection with the apparatus main body by being mounted on the apparatus main body. The present invention is also applicable to a case where a replaceable chip type ink jet head which enables connection and supply of liquid from the apparatus main body, or an ink jet cartridge having a tank for storing liquid integrally with the ink jet head itself is used. It is valid.

Further, it is preferable to add an ejection recovery means for the ink jet head, a preliminary auxiliary means, and the like as the constitution of the ink jet printing apparatus of the present invention since the effect of the present invention can be further stabilized. Specific examples include capping means for the ink jet head, cleaning means, pressurizing or sucking means, an auxiliary heating element using an electrothermal transducer, another heating element, or a combination thereof. Examples of the heating unit include a preliminary ejection unit that performs ejection different from printing.

The type and number of ink jet heads to be mounted are, for example, not only one provided for a single color ink but also a plurality of inks having different print colors and densities. A plurality may be provided. That is, for example, the print mode of the ink jet printing apparatus is not limited to a print mode of only a mainstream color such as black, and may be an ink jet head integrally formed or a combination of a plurality of ink jet heads. The present invention is also very effective for an apparatus provided with at least one of the print modes of full-color printing or color mixing. In this case, it is also effective to discharge a processing liquid (printability improving liquid) for adjusting the printability of the ink according to the print medium from the inkjet head to the print medium.

In addition, in the embodiment of the present invention described above, a material which solidifies at room temperature or lower and softens or liquefies at room temperature may be used, or the liquid itself may be heated to 30 ° C. or higher in an ink jet system. In general, the temperature is controlled within the range of not more than ° C. and the temperature is controlled so that the viscosity of the liquid is in a stable ejection range. In addition, in order to positively prevent the temperature rise due to thermal energy by using it as the energy of the state change from the solid state to the liquid state, or to prevent the evaporation of the liquid,
What solidifies in a standing state and liquefies by heating may be used. In any case, the liquid is liquefied by the application of the thermal energy according to the print signal, and is liquefied only by the application of the thermal energy, such as the one from which the liquid is ejected and the one which already starts to solidify when reaching the print medium. The present invention can be applied to the case of using a material having a property. The liquid in such a case is disclosed in JP-A-54-56847.
JP-A No. 60-71260 or Japanese Patent Application Laid-Open No. Sho 60-71260, in a state in which the porous sheet is held as a liquid or solid substance in a concave portion or a through hole and faces the electrothermal converter. Is also good. In the present invention,
The most effective one for each of the above-mentioned liquids is to execute the above-mentioned film boiling method.

In addition to the above, the image forming apparatus according to the present invention may be used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader, or a facsimile having a transmission / reception function. An apparatus or a textile printing apparatus may be used.

[0046]

According to the present invention, the filter provided in the middle of the liquid supply path to the liquid discharge head is provided with means for promoting the passage of bubbles during the recovery processing of the liquid discharge head. In addition, it is possible to prevent a problem that the circulation of the liquid is hindered by trapping the gas in the filter. For this reason, the number of times of recovery processing of the liquid discharge head can be drastically reduced, and the operation rate of the image forming apparatus can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a mechanism of an embodiment in which an image forming apparatus according to the present invention is applied to an ink jet printing apparatus.

FIG. 2 is a perspective view showing the internal structure of the inkjet head in the embodiment shown in FIG. 1 in a broken state.

FIG. 3 is a conceptual diagram of a mechanism representing an ink supply system in the embodiment shown in FIG.

FIG. 4 is a conceptual view of a mechanism representing an ink supply system according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a schematic structure of a filter interposed in a circulation path of a liquid according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 ink 12 print head 13 electrothermal transducer 14 discharge port 15 head holder 16 print sheet 17 substrate 18 electrode 19 ink path wall 20 grooved plate 21 ink tank 22 circulation inflow path 23 common ink chamber 24 ink path 25 read head 26 capping Unit 27 Discharge port surface 28 Circulating outflow passage 29, 30 Recovery pump 31 Control device 32, 33 Filter unit 34 Ink heating device 35 Filter 36 Charge adsorption belt 37 Back platen 38 Feeding cassette 39 Pickup roller 40 Transport roller 41 Transport path 42 Transport Roller 43 Heater 44 Fan 45 Discharge roller 46 Tray 47 Ultrasonic generator

Claims (13)

[Claims] 1. A liquid discharge recording apparatus having a circulation flow path for circulating a liquid between a liquid discharge head that discharges a liquid and a liquid storage tank that stores the liquid, wherein the liquid is discharged from a discharge port of the liquid discharge head. An image forming method for performing printing by discharging a liquid to a print medium, wherein a step of capturing a foreign substance in the liquid using a filter in the middle of a liquid supply path to the liquid discharge head; and A step of promoting the passage of bubbles through the filter at the time of recovery processing for improving the ejection state of the liquid. 2. The image forming method according to claim 1, wherein the step of facilitating the passage of bubbles through the filter includes a step of heating a liquid flowing into the filter. 3. The image forming method according to claim 1, wherein the step of facilitating the passage of bubbles through the filter includes the step of applying ultrasonic vibration to a liquid flowing into the filter. 4. The liquid according to claim 1, wherein the liquid is ink for printing on a print medium or a processing liquid for adjusting printability of the ink on the print medium. 2. The image forming method according to 1., 5. A circulation path for circulating a liquid between a liquid discharge head for discharging a liquid and a liquid storage tank for storing the liquid, wherein the liquid is discharged from a discharge port of the liquid discharge head to a print medium. An image forming apparatus for performing printing by discharging, a filter interposed in at least one of the circulation channels to capture foreign matter in the liquid, and a bubble for promoting the passage of bubbles to the filter. An image forming apparatus comprising: a passage promoting unit. 6. A first pump for supplying the liquid in the liquid storage tank to the liquid discharge head is provided in one of the circulation flow paths, and the liquid discharge head is provided in the other circulation flow path. The image forming apparatus according to claim 5, further comprising a second pump that returns the liquid supplied to the head to the liquid storage tank. 7. The image forming apparatus according to claim 6, wherein the bubble passage promoting unit operates in conjunction with the operation of the first and second pumps. 8. The liquid discharge head according to claim 6, wherein the second pump provided in the other circulation flow path can supply the liquid in the liquid storage tank to the liquid discharge head.
Alternatively, the image forming apparatus according to claim 7. 9. An image forming apparatus according to claim 5, wherein said bubble passage promoting means has a heating means for heating said liquid. 10. The image forming apparatus according to claim 9, wherein the heating unit heats at least one of the filter and the circulation channel upstream of the filter. 11. The image forming apparatus according to claim 5, wherein said bubble passage promoting means has an ultrasonic wave generating means for applying ultrasonic vibration to said liquid. 12. The image forming apparatus according to claim 5, wherein the liquid discharge head has a discharge energy generation unit for discharging liquid from the discharge port. 13. The image forming apparatus according to claim 12, wherein the discharge energy generating section has an electrothermal converter that generates thermal energy.