JP2008284509A - Method of cleaning inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of cleaning an inkjet head by which a stable and high quality printed material is obtained easily with a saved space and free from non-discharging in an inkjet printing apparatus. <P>SOLUTION: The method of cleaning the inkjet head is provided with an ink supply tank, the inkjet head provided with a piezoelectric element inside single or a plurality of ink passages each connected to the ink supply tank and a wiping member for wiping the inkjet head and is carried out through a step for imaging an ink droplet on the inkjet head, an image analyzing step for analyzing the diameter and the contact angle of the ink droplet using a two-dimensional image of the imaged inkjet droplet, a calculating step for calculating the volume of the ink droplet based on the contact angle and the diameter of the ink droplet to wipe-cleaning the inkjet head based on the calculated volume of ink droplet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for cleaning an inkjet head in an inkjet printing apparatus. More specifically, the present invention relates to a method for cleaning a nozzle surface portion of an inkjet head of an inkjet printing apparatus used for forming a colored layer of a color filter, an organic electroluminescence element, and the like.

  In recent years, when obtaining patterns such as organic electroluminescence elements and color filters, ink jet printer apparatuses excellent in fine pattern printing have been used. In such an industrial ink jet printer apparatus, an ink jet head having a piezoelectric element is provided inside one or a plurality of ink passages connected to an ink supply tank, and ink is ejected from the nozzles of the ink jet head to perform printing. There is something to do.

In this type of ink jet head, the ink dries in the thin nozzles and causes problems such as nozzle clogging. Therefore, various nozzle cleaning methods and drying prevention methods are employed. As a typical method, as proposed in Patent Document 1, when the ink jet head reaches a non-printing area, the nozzle cap is put on the nozzle to shut off the outside air, and the ink in the nozzle is negatively applied from the outside. Or a method of spraying a cleaning liquid on a wiping material and wiping as proposed in Patent Document 2, but the apparatus becomes complicated and non-ejection occurs. It was insufficient for use as a method for cleaning or preventing drying of the nozzle surface of an inkjet head in the apparatus.
JP-A-6-336018 JP 2005-224700 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the object of the present invention is to provide an inkjet head that is simple and space-saving, and that a stable high-quality printed matter can be obtained without non-ejection in an inkjet printing apparatus. A cleaning method is provided.

As a solution to achieve the above problems,
The invention according to claim 1 includes an ink supply tank, an ink jet head having a piezoelectric element inside one or a plurality of ink passages connected to the ink supply tank, and a wiping member for wiping the ink jet head. Ink jet head cleaning method,
Imaging ink drops on the inkjet head;
An image analysis step of analyzing the diameter and contact angle of the ink droplet using the imaged two-dimensional image of the ink droplet;
Calculating the volume of the ink drop based on the contact angle and diameter of the ink drop;
An inkjet head cleaning method, wherein the wiping cleaning is performed based on the calculated ink droplet volume.

  According to a second aspect of the present invention, in the inkjet head cleaning method according to the first aspect, imaging of ink droplets in the imaging step is performed in units of a plurality of ink droplets of the single or a plurality of heads. is there.

  3. The ink jet head cleaning method according to claim 1, wherein the ink is ejected from the ink jet head by pressurizing an ink supply tank prior to the imaging step. It is.

  The invention according to claim 4 is the inkjet head cleaning method according to any one of claims 1 to 3, wherein the wiping member is either a cloth or a film.

  According to the first aspect of the present invention, the step of imaging the ink droplet on the inkjet head, and the image analysis step of analyzing the diameter and contact angle of the ink droplet using the two-dimensional image of the captured ink droplet; The step of calculating the volume of the ink droplet based on the contact angle and diameter of the ink droplet, and wiping based on the calculated volume of the ink droplet, thereby cleaning the nozzle surface of the inkjet head, and The meniscus can be stabilized and a high-quality printed matter can be obtained.

  According to the invention of claim 2, by performing image processing in units of a plurality of ink droplets, more efficient and stable wiping can be performed.

  According to the invention of claim 3, the dried ink inside can be removed by pressurizing the inside of the nozzle before wiping.

  According to the invention which concerns on Claim 4, since cloth or a film is used as a washing | cleaning member, it is easy to wipe off the ink aggregate which dried and solidified.

Hereinafter, an example of an embodiment of an ink jet head cleaning method in the ink jet printing apparatus of the present invention will be described with reference to the drawings. FIG. 1 is an apparatus diagram of an inkjet head printing apparatus using a water head difference and ink droplet imaging and analysis on the inkjet head surface. FIG. 2 is an apparatus diagram of an inkjet head printing apparatus using a pump and ink droplet imaging and analysis on the inkjet head surface.
(Configuration of inkjet printer)
First, an ink supply apparatus according to the present invention will be described with reference to FIG. The ink 2 used in the ink jet printing apparatus is stored in the supply tank 1 and is sent through the tube 3 to the sub-tank 5 that is open to the atmosphere 4, and then the ink passes through the tube 6 to the ink jet head 8. Sent. By ensuring the liquid level height in the sub tank and the water head difference 7 between the ink jet heads and supplying the ink in a state where the ink surface of each ink discharge port is a meniscus surface, each ink discharge of the ink jet head is performed. The ink surface at the outlet can be in a meniscus state, and the ink can be droplets with an appropriate flow rate.

As a measuring means for observing the droplet 9 on the surface 12 of the inkjet head, a camera 10 as an imaging means is arranged so as to be perpendicular to the ejection direction of the inkjet head. The camera includes a laser light source 11 as an irradiating means and an optical fiber, and is electrically connected to a control computer 13.
(Inkjet head cleaning method)
Next, an example of a method for cleaning the ink jet head of the present invention in the above ink jet printing apparatus will be described. If the inkjet nozzle is clogged, perform nozzle cleaning. As a nozzle cleaning method, first, dry ink in the nozzle is removed by pressurizing the ink supply tank. Thereafter, by ensuring a water head difference between the inkjet head and the sub-tank opened to the atmosphere, droplets of the inkjet head are drawn inside the nozzle. After that, wiping with cloth, film, etc. is necessary to remove the dry ink and excess ink on the surface of the inkjet nozzle and stabilize the meniscus inside the nozzle, but the droplet on the inkjet head surface when wiping is appropriate If the volume is not large, the meniscus is not stable or air is entrained, resulting in non-ejection.

Therefore, based on the image analysis step of imaging the droplet of the ink jet head after pressurization and analyzing the diameter and contact angle of the ink droplet using the two-dimensional image, and the contact angle and diameter of the ink droplet The ink droplet volume is calculated and the calculated ink droplet volume is used as data to perform wiping when the ink droplet reaches a certain amount. The ink droplet amount is 0 per 1 mm of the nozzle portion. It is desirable to perform wiping in a state of 0005 to 0.001 mm ³ .

In this discharge method using the water head difference, the liquid surface that is in contact with the air dries and adheres as a solid matter to the inner peripheral surface of the tank and accumulates easily. There is a risk of ejection failure such as clogging.
(Inkjet head cleaning method using a pump)
Therefore, another example of the inkjet cleaning method of the present invention in the ink supply apparatus using the diaphragm pump will be described with reference to FIG. The ink 14 used in the ink jet printing apparatus is stored in the supply tank 15 and passes through the tube 16 to the supply source side of the diaphragm pump 17. In the diaphragm pump, the ink supply source side is a suction side for forcibly sucking ink, and the inkjet head 18 side is a sending side 19 for forcibly sending ink. A servo motor 20 for driving the diaphragm pump is connected to the ink delivery means, and a diaphragm pump for accurately ejecting ink by the operation of the servo motor is driven and controlled 21.

  As a measuring means for observing the droplet 23 on the ink jet surface 22, a camera 24 as an imaging means is arranged so as to be perpendicular to the ejection direction of the ink jet head, and the camera has a laser light source 25 as an irradiating means, an optical fiber, And is electrically connected to the control computer 26.

  An image analysis step of analyzing the diameter and contact angle of the ink droplet using the captured two-dimensional image of the ink droplet, and a step of calculating the volume of the ink droplet based on the contact angle and diameter of the ink droplet The calculated ink droplet volume is connected to be sent to a servo motor in the ink delivery means 21, and the two-dimensional image of the ink-jet head after pressurizing the ink is imaged. An image analysis step of analyzing the diameter and contact angle of the ink droplet using an image, a step of calculating the volume of the ink droplet based on the contact angle and diameter of the ink droplet, and the calculated ink droplet Using the volume as data, wiping when ink drops reach a certain amount allows the meniscus inside the nozzle to be removed even if the head surface is cleaned by nozzle cleaning. Constant, and dischargeability is improved.

  Hereinafter, the present invention will be described in detail with specific examples.

An ink jet printing apparatus for a color filter using a diaphragm pump will be exemplified to describe the ink jet head cleaning method of the present invention.
(Create partition walls)
Hereinafter, the partition wall is referred to as a black matrix in the color filter. The black matrix was produced using a photolithography method. Non-alkali glass was used as the substrate. On the substrate, a photosensitive resin composition containing a fluororesin was applied over the entire surface in a thin film having a thickness of 2 μm. Then, it exposed using the photomask which has a grid | lattice-like pattern, developed after that with an alkali, the black matrix was produced by putting this board | substrate into oven and performing a thermosetting process.
(Ink adjustment)
As the ink, the ratio of tightening the pigment to the total solid content of the ink excluding the solvent is adjusted to 50% by mass so that the required spectral characteristics are obtained, and the total solid content concentration of the solvent to the ink is 30% by mass. Adjusted as follows.
(Inkjet printer for color filters)
Ink used in the ink jet printing apparatus is stored in a supply tank and passes through a tube to the supply side of the diaphragm pump. In the diaphragm pump, the ink supply source side is a suction side for forcibly sucking ink, and the ink jet head side is a sending side for forcibly sending ink. In addition, a servo motor for driving the diaphragm pump is connected to the ink delivery means, and the diaphragm pump for accurately ejecting ink is controlled by the operation of the servo motor, and the ink passes through the tube. Sent to the inkjet head.

  As a measuring means for observing the droplets, a camera as an imaging means was arranged so as to be perpendicular to the ejection direction of the inkjet head. The camera was equipped with a laser light source and an optical fiber as irradiation means, and was electrically connected to a control computer.

An image analysis step of analyzing the diameter and contact angle of the ink droplet using the captured two-dimensional image of the ink droplet, and a step of calculating the volume of the ink droplet based on the contact angle and diameter of the ink droplet The calculated ink droplet volume is connected as data to be sent to a servo motor in the ink sending means.
(Inkjet head cleaning)
When a signal for cleaning the nozzle of the inkjet head was issued during non-printing, the ink supply tank was pressurized and the ink in the nozzle of the inkjet head was pushed out to remove the dry ink inside the nozzle. Thereafter, the ink droplets on the surface of the inkjet head are imaged from the camera, and the diameter and contact angle of the ink droplets are analyzed using the captured two-dimensional image to calculate the volume of the ink droplets. Based on the volume, the diaphragm pump was sent and sucked to control the droplet volume on the head surface to 0.001 mm ³ per 1 mm of the nozzle portion. With the ink droplets on the head surface controlled, a unit having a cleaning member mounted under the ink jet head moved and pressed against the head surface of the ink jet head.

  As the cleaning member, a roll-shaped microfiber was used. The cleaning unit is provided with a winding mechanism using a clutch brake and a winding mechanism using a servo motor, and can be moved up and down by an air cylinder. After a certain period of time, the cleaning of the inkjet head was completed by moving the cleaning unit downward. By performing this cleaning, the dry ink adhering to the periphery of the nozzle part is wiped off by the cleaning member, and even if printing is performed again, stable discharge is performed without clogging the nozzle, so a high-quality color filter could be obtained. .

  When wiping is performed without controlling the volume of the ink droplets on the ink jet surface for the nozzle cleaning of the ink jet head of the present invention described above, the meniscus inside the nozzle is not stabilized and non-ejection occurs. A quality color filter could not be obtained.

It is an apparatus diagram of ink jet imaging using a water head difference and ink drop imaging and analysis of an ink jet head surface. It is an apparatus diagram of an ink jet head printing apparatus using a pump and ink droplet imaging and analysis of the ink jet head surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ink supply tank 2 ... Ink 3 ... The path | route which leads from an ink supply tank to a sub tank 4 ... Air release part 5 of a sub tank ... Sub tank 6 ... It leads to an inkjet head from a sub tank Path 7: Water head difference between the inkjet head and the sub tank 8 ... Inkjet head 9 ... Ink droplet 10 on the inkjet head surface 10 ... Camera 11 ... Laser light source 12 ... Inkjet head surface 13 ··· PC 14 for analyzing measured image data ··· Ink 15 ··· Ink supply tank 16 ··· Route 17 from ink supply tank to diaphragm pump ··· Diaphragm pump 18 · · · Inkjet head 19 -Path 20 from the diaphragm pump to the inkjet head ... Servo module 21... Data path 22 for sending and suctioning the diaphragm pump based on the calculated volume of ink droplets 22... Inkjet head surface 23... Ink droplet 24 on the inkjet head surface. 25 ... Laser light source 26 ... PC for analyzing measured image data

Claims (4)

An inkjet head cleaning method comprising: an ink supply tank; an inkjet head having a piezoelectric element inside one or a plurality of ink passages connected to the ink supply tank; and a wiping member for wiping the inkjet head. And
Imaging ink drops on the inkjet head;
An image analysis step of analyzing the diameter and contact angle of the ink droplet using the imaged two-dimensional image of the ink droplet;
Calculating the volume of the ink drop based on the contact angle and diameter of the ink drop;
An inkjet head cleaning method, wherein the wiping cleaning is performed based on the calculated ink droplet volume.   The inkjet head cleaning method according to claim 1, wherein imaging of ink droplets in the imaging step is performed in units of a plurality of ink droplets of the single or a plurality of heads.   The method for cleaning an ink jet head according to claim 1, wherein ink is ejected from the ink jet head by pressurizing an ink supply tank prior to the imaging step.   The method of cleaning an ink jet head according to claim 1, wherein the wiping member is either a cloth or a film.