KR20210041175A - Inspection method of nozzles of inkjet head - Google Patents

Abstract

The present invention relates to a method for inspecting a nozzle of an inkjet head. According to the present invention, the method may perform an accurate and reliable inspection through separating droplets discharged on an inspection substrate into main droplets and satellite droplets by jetting the nozzle of the inkjet head, distinguishing foreign material droplets or mist droplets already existing on the inspection substrate from the discharged droplets based on position data, and inspecting the nozzle of the inkjet head based on the number or size of the satellite droplets.

Description

Inkjet head nozzle inspection method {INSPECTION METHOD OF NOZZLES OF INKJET HEAD}

This document relates to an inkjet printing apparatus having an inkjet head, and relates to a method of inspecting a nozzle of an inkjet head.

Recently, a display device using an organic light emitting diode (OLED) is attracting attention. The organic light-emitting display device has a self-emission characteristic, and unlike a liquid crystal display device, it does not require a separate light source, and thus the thickness and weight can be reduced. The organic light emitting diode display exhibits high quality characteristics such as low power consumption, high luminance, and fast reaction speed. These OLED displays have recently formed thin films of organic and inorganic materials using an inkjet printing method.

In general, an inkjet printing apparatus includes a head for applying a liquid onto a substrate and a maintenance unit for inspecting and managing the head. The head includes a plurality of nozzles for discharging liquid, and applies liquid or droplets to a specific position on the display substrate.

In particular, there are many satellite ink droplets around the ink droplets, but the older or abnormal nozzles, the greater the number and size of satellite ink droplets. In addition, mist is generated in the process of discharging droplets from the nozzle and is often blown by the air stream and falls onto the substrate. These satellite ink droplets and mist reduce the yield in manufacturing OLED panels. The number of satellite ink droplets increases and the size increases when the nozzles of the head become deteriorated, foreign substances get stuck, or when there is a defect such as a malfunction.

Therefore, before the operation of applying ink droplets onto the display substrate in earnest, nozzle inspection is usually performed. In the nozzle inspection, an inspection substrate is prepared, ink droplets are discharged on the inspection substrate, and then an analysis is performed. Since foreign matters already exist on the inspection substrate, they cannot be distinguished from the foreign matters and the discharged ink droplets, thereby reducing the reliability of the inspection results.

1 is a view for explaining an ink droplet discharged through a nozzle on an inspection substrate. As shown, when ink droplets are ejected on the inspection substrate 100 through three nozzles N1, N2, N3, in an ideal nozzle, only the main ink droplets should exist on the inspection substrate, but defects of the nozzles, etc. As a cause, satellite ink droplets were present together. However, mist not only exists on the inspection substrate through the airflow, but also foreign substances are present in the inspection substrate at the initial stage. Due to these external environmental factors, mist or foreign matters cause obstacles in the analysis of satellite ink droplets, thereby deteriorating the reliability of nozzle inspection results.

Therefore, a technical problem to solve the problem of lowering reliability has emerged.

Korean Patent Publication (Publication Publication No.: 10-2008-0088969, "Focus Control Method and Nozzle Inspection Method") performs focus adjustment on the reference nozzle, and then performs physical focus adjustment through stage movement for the remaining nozzles. As a result, a technique for reducing the time required for focusing and reducing the probability of occurrence of an error has been disclosed, but a method of performing an accurate inspection by distinguishing foreign matter and ink droplets has not been disclosed.

The present invention relates to a nozzle inspection method of an inkjet head, and an object of the present invention is to accurately and reliably inspect a nozzle of an inkjet head by distinguishing main ink droplets and satellite ink droplets discharged from the nozzles of the head from foreign matter or mist.

According to an aspect for achieving this object, a method for inspecting a nozzle of an inkjet head,

Preparing an inspection board (S100),

Checking the location of the first droplet present on the inspection substrate and recording the location data (S200),

Arranging the inspection substrate under the nozzle (S300),

Jetting so that a second droplet is discharged to a specific point on the inspection substrate (S400),

Dividing the second droplet discharged on the inspection substrate into a main droplet and a satellite droplet, and distinguishing the first droplet and the satellite droplet based on the position data of the first droplet (S500), and

The reliability of the inspection is improved by checking whether the main droplet is present at a specific point on the inspection substrate and the number or size of satellite droplets present on the inspection substrate (S600).

According to an embodiment of the present invention, it is possible to perform an accurate and reliable inspection by distinguishing the main ink droplets discharged from the nozzle of the head and the satellite ink droplets from foreign matter or mist, and also, the degree of defect and replacement of the nozzle through systematic quality management. You can accurately judge the timing.

1 is a view for explaining an ink droplet discharged through a nozzle on an inspection substrate.
2 is a diagram illustrating a method of inspecting a nozzle of an inkjet head.
FIG. 3 is a diagram illustrating a method of inspecting a nozzle of an inkjet head performed after FIG. 2.
4 is a diagram illustrating a method of inspecting a nozzle of an inkjet head according to another exemplary embodiment.
5 is a diagram showing a state of a droplet discharged from a nozzle of an inkjet head.

Hereinafter, the present invention will be described in detail so that those skilled in the art can easily understand and reproduce the present invention through preferred embodiments described with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the embodiments of the present invention, the detailed description thereof will be omitted. Terms used throughout the specification of the present invention are terms defined in consideration of functions in the embodiments of the present invention, and can be sufficiently modified according to the intention and custom of a user or operator, so the definitions of these terms are defined throughout the present specification. It will have to be made based on the contents of

In addition, the above-described and additional aspects of the invention will become apparent through the following embodiments. Aspects or configurations of the embodiments that are selectively described in the present specification may be freely combined with each other, unless otherwise stated, unless otherwise indicated, unless otherwise indicated, the configurations of the embodiments or the configurations selectively described may be freely combined with each other. I understand.

Accordingly, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all the technical spirit of the present invention. It should be understood that there may be equivalents and variations. For example, the meaning of a droplet in this specification includes not only ink droplets but also optically clear resin (OCR) droplets.

2 is a diagram illustrating a method of inspecting a nozzle of an inkjet head. As shown, in the method of inspecting the nozzles of the inkjet head, the inspection substrate 10 is provided (Fig. 2(a)). The inspection substrate 10 may be a DPC (Drop Placement Check) film or an ETFE film. It is preferable to clean the inspection board.

Then, the position of the first droplet 1 existing on the inspection substrate is checked and the position data is recorded (Fig. 2(b)). The first droplet may be a droplet that includes foreign matter and mist present on the inspection substrate and interferes with the inspection. The location of the first droplet on the inspection board may be identified or confirmed using the camera 30. Position data information can be derived and recorded from the x-y coordinate on the substrate for the identified first droplet. Records can be made in the database 40. The camera 30 may be connected to a PC (not shown).

Then, the inspection substrate 10 is disposed under the nozzle 20 (Fig. 2(c)). The nozzle is provided under the head 100 and is made up of a plurality of nozzles. Each of the plurality of nozzles is numbered, so that a specific nozzle can be identified.

Then, jetting is performed so that the second droplet is discharged to a specific point on the inspection substrate (Fig. 2(d)). The second droplet 2 is a droplet discharged from the nozzles N1, N2...N10 according to the current jetting. In the inspection substrate, not only the second droplet 2 but also the first droplet 1 exist together on the inspection substrate 10. The second droplet 2 may further include a main droplet 2-1 and additionally a satellite droplet 2-2. Jetting is an operation in which droplets are discharged by applying pressure to a nozzle.

FIG. 3 is a diagram illustrating a method of inspecting a nozzle of an inkjet head performed after FIG. 2. As shown, the second droplet discharged on the inspection substrate is divided into a main droplet and a satellite droplet, and based on the position data of the first droplet, the first droplet 1 and the satellite droplet 2- 2) is distinguished (Fig. 2(e)). According to an embodiment, on the monitor of the PC, the first droplet 1 may perform an image processing different from that of the second droplet 2. For example, the first droplet 1 may be subjected to a different color, shading treatment, or mask treatment so as not to appear on the display of the PC.

Then, whether or not the main droplet is present at a specific point on the inspection substrate and the number or size of satellite droplets present on the inspection substrate are checked for abnormality in a specific nozzle (FIG. 2(f)). As shown, satellite droplets were generated in the nozzles N1, N8, and N10, and in particular, two were generated in N10. In addition, it can be seen that the satellite droplet of N8 has a relatively large area (60 µm 2 ). Therefore, it can be seen that the nozzles N8 and N10 have a high possibility of replacement.

In a method for inspecting a nozzle of an inkjet head according to another embodiment,

Data for checking whether the specific nozzle is abnormal may be repeatedly generated over time and stored in a time series in a database (Fig. 2(g)).

In a method for inspecting a nozzle of an inkjet head according to another embodiment,

Based on the data stored in a time series in the database, it is possible to track whether or not a specific nozzle is abnormal.

4 is a diagram illustrating a method of inspecting a nozzle of an inkjet head according to another exemplary embodiment. As shown, the method of inspecting the nozzles of the inkjet head,

Preparing an inspection board (S100),

Checking the location of the first droplet present on the inspection substrate and recording the location data (S200),

Arranging the inspection substrate under the nozzle (S300),

Jetting so that a second droplet is discharged to a specific point on the inspection substrate (S400),

Dividing the second droplet discharged on the inspection substrate into a main droplet and a satellite droplet, and distinguishing the first droplet and the satellite droplet based on the position data of the first droplet (S500), and

It may include checking whether the main droplet exists at a specific point on the inspection substrate and the number or size of satellite droplets present on the inspection substrate to check whether a specific nozzle is abnormal (S600).

In the method of inspecting the nozzles of the inkjet head according to another embodiment, the step of repeatedly generating data for checking whether the specific nozzle is abnormal according to time and storing the data in a time series in a database (S700) is further performed. Can include.

In the method of inspecting the nozzles of an inkjet head according to another embodiment, the inkjet further comprising the step (S800) of tracking whether a specific nozzle is abnormal based on data stored in a time series in a database How to check the nozzle of the head.

5 is a diagram showing a state of a droplet discharged from a nozzle of an inkjet head. As shown, five droplets are discharged from each of the ten nozzles N1, N2, and N10 at regular intervals (eg, 634 μm) according to the rows of the inspection substrate 10. The distance between the nozzle and the inspection board should be kept constant. The droplets are divided into main droplets (2-1) and satellite droplets (2-2). Foreign matter droplets or mist droplets that originally existed on the substrate do not appear after being masked on the monitor of the PC. The operator can determine the size range of the droplet to be detected (eg, 6.6 ~ 70µm2) and use the droplet within that range as an inspection object.

As for the droplet discharged from the nozzle N1, one satellite droplet was generated. The operator can define the performance of the nozzle N1 (eg,'good'). The droplets discharged from the nozzles N2, N3, and N5 did not generate satellite droplets. The operator can define the performance of the N2, N3, and N5 nozzles as'normal'. On the other hand, in the N7 nozzle, the size of the main droplet is smaller than that of the normal main droplet. Therefore, the operator can separately define the performance of the N7 nozzle.

Although only one satellite droplet ejected from the N8 nozzle was generated, the size of the satellite droplet was larger than that of the N1 and N10 nozzles (eg, 50µm2 in area). This allows the operator to define an N8 nozzle (eg'bad'). Likewise, there are two satellite droplets discharged from the N10 nozzle, and the operator can designate the N10 nozzle as'defective' and use it for replacement.

In addition, the N4 nozzle does not discharge satellite droplets, but discharge of the main droplet is not smooth. In addition, the N6 and N9 nozzles do not discharge droplets. Therefore, the operator can define the N4, N6, and N9 nozzles as'defective' and use them as replacement targets.

The operator can periodically inspect the state of these droplets, record the result in the database 40, and track changes to predict the replacement timing of a specific nozzle. The number of satellite droplets according to the time series of a specific nozzle can be tracked.

In the method for inspecting a nozzle of an inkjet head according to another embodiment, the step of distinguishing the first droplet and the satellite ink droplet based on the position data of the first droplet (S500), on a monitor of a PC It may further include a step (S500-1) of performing an image processing different from that of the first droplet 1 and the second droplet 2 (S500-1).

1: first droplet
2: second droplet
2-1: main droplet
2-2: satellite droplet
10: inspection board
20: nozzle
30: camera
40: database

Claims (4)

In the method of inspecting the nozzle of the inkjet head,
Preparing an inspection substrate (S100);
Checking the location of the first droplet present on the inspection substrate and recording the location data (S200);
Arranging the inspection substrate under the nozzle (S300);
Jetting a second droplet to be discharged to a specific point on the inspection substrate (S400);
Dividing the second droplet discharged on the inspection substrate into a main droplet and a satellite droplet, and distinguishing the first droplet and the satellite droplet based on position data of the first droplet (S500); And
Checking whether the main droplet exists at a specific point on the inspection substrate and the number or size of satellite droplets present on the inspection substrate to check whether a specific nozzle is abnormal (S600);
Method for inspecting the nozzle of the inkjet head comprising a. The method of claim 1,
The method of inspecting the nozzle of the inkjet head further comprising a step of repeatedly generating data for checking whether the specific nozzle is abnormal according to time and storing it in a database in time series (S700). The method of claim 2,
The method of inspecting the nozzles of the inkjet head further comprising: tracking (S800) whether or not a specific nozzle is abnormal based on data stored in a time series in the database. The method of claim 1,
Distinguishing the first droplet from the satellite ink droplet based on the position data of the first droplet (S500);
The method of inspecting the nozzle of the inkjet head further comprising: performing an image processing different from that of the second droplet on the first droplet on the monitor of the PC (S500-1).

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