WO2023188838A1 - Printing apparatus and printing method - Google Patents

Abstract

This printing apparatus comprises: an inkjet head having a plurality of nozzles; and a control device that causes ink to be discharged from the respective nozzles to a plurality of target positions that are set for the respective nozzles and are aligned in the scanning direction in which the inkjet head is moved relative to a printing object. The control device causes the discharge amount of the ink to vary for each of the plurality of target positions within a predetermined allowable range from a reference discharge amount which is set for each of the plurality of nozzles.

Description

Printing device and printing method

The present disclosure relates to a printing device and a printing method.

The manufacturing process of devices such as color filters for liquid crystal displays and organic EL displays includes a process of forming a film of a functional material. In this process, droplets of ink containing a functional material (hereinafter sometimes simply referred to as "droplets") are applied to target positions on the printing object through multiple nozzles using, for example, an inkjet method. It is discharged towards the target. The application target position is a position determined as a target landing position when applying ink.

If the amount of ink ejected to a plurality of target application positions on the printing target is uneven, the thickness of the film formed by the ink will be uneven. For example, in color filters and organic EL displays, if the film thickness is non-uniform, uneven color and uneven brightness will appear. For these reasons, techniques have been developed to suppress variations in the amount of ink ejected, that is, variations in the volume of droplets ejected from a nozzle, in forming a film of functional materials.

Patent Document 1 and Patent Document 2 disclose methods for measuring the volume of droplets ejected from the nozzles of an inkjet head. The measurement method disclosed in Patent Document 1 is a method in which a predetermined number of droplets are discharged onto a substrate, the concentration of the discharged droplets is measured, and the volume of the droplets is determined based on the measured concentration.

The measurement method of Patent Document 2 is to eject a droplet onto a substrate, calculate the volume of the droplet based on the shape of the droplet after drying the solvent, and calculate the volume of the droplet before drying. This is a method of converting it into . Moreover, Patent Document 2 discloses adjusting the volume of droplets discharged from a plurality of nozzles based on the measured volume of the droplets.

Japanese Patent Application Publication No. 9-48111 Japanese Patent Application Publication No. 2011-044340

A printing device according to one aspect of the present disclosure includes an inkjet head having a plurality of nozzles, arranged in a scanning direction in which the inkjet head moves relative to an object to be printed, and set to each of the plurality of nozzles. a control device for ejecting ink from each of the plurality of nozzles to a plurality of target positions, the control device ejecting ink from a reference ejection amount set for each of the plurality of nozzles to a predetermined tolerance. The ejection amount of the ink is varied for each of the plurality of target positions within the range.

A printing method according to one aspect of the present disclosure includes printing in which ink is ejected from the plurality of nozzles using an inkjet head that has a plurality of nozzles and moves in a scanning direction relative to a printing target. The method comprises: calculating a predetermined tolerance from a reference discharge amount set for each of the plurality of nozzles with respect to a plurality of target positions arranged in the scanning direction and set for each of the plurality of nozzles. An ink ejection amount is determined so that the ink ejection amount changes within a range, and ink is ejected from each of the plurality of nozzles based on the determined ejection amount.

FIG. 1 is a schematic perspective view showing the overall configuration of a printing apparatus according to an embodiment. FIG. 2 is a functional block diagram of the printing apparatus according to the embodiment. FIG. 3 is a partial cross-sectional view showing the internal configuration of the head section of the inkjet head according to the embodiment. FIG. 4 is a diagram illustrating an example of a voltage signal according to the embodiment. FIG. 5 is a diagram illustrating an example of droplet volume data according to the embodiment. FIG. 6 is a diagram showing the relationship between the volume of a droplet ejected from a specific nozzle and voltage. FIG. 7 is a schematic diagram showing a display panel coated with droplets. FIG. 8 is a schematic diagram showing another display panel with droplets applied. FIG. 9 is a diagram illustrating another voltage signal according to the embodiment. FIG. 10 is a diagram illustrating still another voltage signal according to the embodiment. FIG. 11 is a diagram illustrating a plurality of waveform signals used when a printing apparatus generates a voltage signal. FIG. 12 is a diagram illustrating an example of a control table that the printing apparatus refers to when executing droplet volume control. FIG. 13 is a flowchart illustrating an example of a printing operation performed by the printing device. FIG. 14 is a diagram illustrating an example of the total standard ejection amount and its allowable amount until the completion of printing a predetermined number of times. FIG. 15 is a diagram showing an example of the total standard ejection amount and its allowable amount for each of a plurality of types of ink.

Droplets are applied to a plurality of application target positions arranged in a direction perpendicular to the printing direction on the printing object through different nozzles. On the other hand, droplets ejected from the same nozzle are applied to a plurality of target application positions arranged along the printing direction.

The variation in the volume of droplets discharged from the plurality of nozzles is about 3% or more and 5% or less. On the other hand, the variation in droplet volume between discharges from the same nozzle is about 1% or less, which is smaller than the variation in droplet volume from one nozzle to another. Therefore, periodic differences may occur in the amount of droplets applied in the direction perpendicular to the printing direction. In this case, streaks become noticeable along the printing direction and appear as printing unevenness.

An object of the present disclosure is to provide a printing device and a printing method that can suppress printing unevenness.

Hereinafter, each embodiment and each modification of the present disclosure will be described with reference to the drawings.

[Embodiment]
(Printing device)
FIG. 1 is a schematic perspective view showing the overall configuration of a printing apparatus 1 according to an embodiment. FIG. 2 is a block diagram of the printing device 1 according to the embodiment. This disclosure will be described using a Cartesian coordinate system (X, Y, Z). As shown by arrows in FIG. 1, the Z-axis direction is the height direction of the printing device 1, the Y-axis direction is the width direction of the printing device 1, and the X-axis direction is the depth direction of the printing device 1.

The printing device 1 prints in units of one line or multiple lines while scanning the inkjet head 30. The X-axis direction is the line direction that the inkjet head 30 scans during printing, and is called the "main scanning direction." Furthermore, during printing, ink is ejected in the negative direction of the Z axis.

The printing device 1 is a device that prints on an object to be printed by ejecting ink. The printing apparatus 1 includes a control device 15 (see FIG. 2), an inkjet stage 20, an inkjet head 30, a droplet observation device 40, and a landed droplet observation device 50.

(Control device)
The control device 15 is a computer that performs overall control of the printing device 1, and may be a personal computer, for example. The control device 15 includes a storage section 151, an input section 152, a display section 153, and a CPU (Central Processing Unit) 154.

The storage unit 151 is, for example, a large capacity storage device such as an HDD. The storage unit 151 stores a control program for controlling the inkjet stage 20, the inkjet head 30, the droplet observation device 40, and the landed droplet observation device 50, characteristic data of the inkjet head 30 (described later), and a control table. 700 (described later) etc. are stored.

The input unit 152 is an input device for inputting instructions to the printing apparatus 1, and is, for example, a keyboard or a touch panel. The display section 153 is a display. The display unit 153 displays the observation results obtained by the droplet observation device 40 and the landed droplet observation device 50.

The CPU 154 controls the inkjet stage 20, the inkjet head 30, the droplet observation device 40, and the landed droplet based on the control program stored in the storage unit 151 and instructions input via the input unit 152. The observation device 50 is controlled.

(inkjet stage)
The inkjet stage 20 includes a base 200, a first slide unit 230A, a second slide unit 230B, and a control section 240 (see FIG. 2).

A fixed stage ST and an ink van 60 are arranged on the upper surface of the base 200. A printing target is placed on the fixed stage ST. The ink van 60 is a container used to stabilize the ejection of ink, and has, for example, a dish shape.

The first slide unit 230A has a function of moving the inkjet head 30 relative to the fixed stage ST during printing. The first slide unit 230A includes a pedestal 220A to which the inkjet head 30 is attached. Further, the first slide unit 230A includes, for example, linear motors 204A and 205A as moving means for moving the first slide unit 230A in the X-axis direction (main scanning direction), and moves the base 220A in the Y-axis direction. As a moving means, for example, a servo motor 221A is provided.

The second slide unit 230B has a function of moving the landed droplet observation device 50 with respect to the fixed stage ST. The second slide unit 230B includes a pedestal 220B to which the landed droplet observing device 50 is attached. Further, the second slide unit 230B includes, for example, linear motors 204B and 205B as a moving means for moving the second slide unit 230B in the X-axis direction, and as a moving means for moving the pedestal 220B in the Y-axis direction. For example, it includes a servo motor 221B.

The control unit 240 is connected to the CPU 154 of the control device 15, and under the control of the CPU 154 controls the drive of the linear motors 204A, 205A, 204B, 205B and the servo motors 221A, 221B. Thereby, the inkjet head 30 and the landed droplet observing device 50 reciprocate along the X-axis direction and the Y-axis direction.

Note that the inkjet stage 20 may be configured to move relative to the inkjet head 30 and the landed droplet observation device 50. Moreover, all of the inkjet stage 20, the inkjet head 30, and the landed droplet observing device 50 may be configured to be movable along the X-axis direction and the Y-axis direction.

(inkjet head)
Next, the inkjet head 30 will be explained with reference to FIGS. 1 to 3. FIG. 3 is a partial sectional view showing the internal configuration of a head section 301 (described later) of the inkjet head 30 according to the embodiment, and is a sectional view taken along the longitudinal direction of the head section 301 (the direction in which the nozzles 331 are arranged).

The inkjet head 30 is a component that applies droplet-shaped ink to an object to be printed.

As shown in FIG. 1, the inkjet head 30 includes a main body section 300, a head section 301, and a control section 310 (see FIG. 2). The inkjet head 30 is fixed to the pedestal 220A via the main body 300.

For example, a servo motor 304 (see FIG. 2) is built into the main body 300 as a means for rotating the head 301 around the Z axis.

The head portion 301 is formed into a rectangular parallelepiped shape, for example, as shown in FIG. Further, the head portion 301 has a central portion of its upper surface connected to a shaft tip of a servo motor 304 . The head section 301 rotates around the Z-axis according to rotational drive of the servo motor 304.

As shown in FIG. 3, the head section 301 includes a head main body section 320, a nozzle plate 330, a diaphragm 340, and a plurality of piezoelectric elements 350. As shown in FIG. 3, a nozzle plate 330, a head main body 320, a diaphragm 340, and a plurality of piezoelectric elements 350 are stacked in this order to form a head section 301.

The head main body portion 320 is formed, for example, in the shape of a rectangular parallelepiped. In the head main body portion 320, a plurality of liquid chambers 321 are formed in a line at regular intervals. The plurality of liquid chambers 321 are arranged in a line along the longitudinal direction of the head section 301. The liquid chamber 321 is a space where ink is stored.

The nozzle plate 330 is arranged on the bottom surface of the head main body part 320. A plurality of nozzles 331 are formed on the nozzle plate 330. The plurality of nozzles 331 are holes formed to correspond to the plurality of liquid chambers 321, respectively. The nozzles 331 communicate with the corresponding liquid chambers 321 , and the ink in the liquid chambers 321 is ejected to the outside of the head section 301 via the nozzles 331 .

The head main body 320 and the nozzle plate 330 are made of, for example, a metal material such as stainless steel (SUS) or a ceramic material. The head main body portion 320 and the nozzle plate 330 are formed by, for example, machining, etching, or electrical discharge machining.

The diaphragm 340 is disposed between the head main body 320 and the plurality of piezoelectric elements 350 so as to cover the plurality of liquid chambers 321, and forms an upper wall of the liquid chamber 321. The diaphragm 340 is a thin plate-like elastic body made of stainless steel or nickel, for example.

The plurality of piezoelectric elements 350 are attached to the surface of the diaphragm 340 on the opposite side from the liquid chamber 321. The piezoelectric elements 350 correspond to the liquid chambers 321 on a one-to-one basis, and are arranged in the same number as the liquid chambers 321.

The piezoelectric element 350 is, for example, a piezo element. The piezoelectric element 350 is configured as a laminate in which a plate-shaped piezoelectric body made of, for example, lead zirconate titanate is sandwiched between a pair or more of electrodes.

In the head section 301, the piezoelectric element 350, the liquid chamber 321, the nozzle 331, and the upper wall of the liquid chamber 321 in the diaphragm 340 constitute an ink ejection mechanism. Therefore, a plurality of ink ejection mechanisms are arranged side by side along the longitudinal direction of the head section 301. FIG. 3 shows three adjacent ink ejection mechanisms. As shown in FIG. 3, the piezoelectric element 350, the liquid chamber 321, and the nozzle 331 are arranged in a one-to-one correspondence. In the example shown in FIG. 3, the ink ejection mechanisms are arranged in one row, but the invention is not limited to this, and they may be arranged in multiple rows. Further, in the example shown in FIG. 3, the distances between adjacent ink ejection mechanisms are equal, but the distance between adjacent ink ejection mechanisms is not limited to this, and the distances between adjacent ink ejection mechanisms may be different.

The plurality of ink ejection mechanisms are each independently driven by being individually supplied with voltage signals to be described later. Specifically, the piezoelectric element 350 expands and contracts in the Z-axis direction when a voltage signal is applied. Accordingly, a portion of the diaphragm 340 corresponding to the upper wall of each liquid chamber 321 is deformed so as to be convex toward the inside and outside of the liquid chamber 321. That is, the diaphragm 340 is deformed so that the volume of the liquid chamber 321 is reduced or restored. When the volume of the liquid chamber 321 decreases, the liquid chamber 321 is pressurized and the ink in the liquid chamber 321 is ejected from the nozzle 331.

FIG. 4 shows an example of the voltage signal S1.

The voltage signal S1 has a first pulse waveform W1 and a second pulse waveform W2. The first pulse waveform W1 and the second pulse waveform W2 are, for example, rectangular pulse waveforms having a frequency of several hundred Hz to several tens of kHz and a time width of approximately several tens of μs.

The first pulse waveform W1 is a waveform for resonating the pressure wave generated in the liquid chamber 321 by the vibration of the diaphragm 340. The first pulse waveform W1 is formed such that the voltage value fluctuates from the reference potential Emid to the first potential Ea, and after being held at the first potential Ea, the voltage value fluctuates to the reference potential Emid. The reference potential Emid is a voltage that is constantly applied to the piezoelectric element 350. By constantly applying the reference potential Emid to the piezoelectric element 350, the liquid level (meniscus) position of the ink inside the nozzle 331 is maintained at a constant position.

The second pulse waveform W2 is a waveform that vibrates the diaphragm 340 so that ink is ejected from the nozzle 331. Specifically, in the second pulse waveform W2, the voltage value fluctuates from the reference potential Emid to the second potential Eb, and after being held at the second potential Eb, the voltage value fluctuates to the third potential Ec. 3. After being held at the potential Ec, the voltage value changes to the reference potential Emid.

As the voltage value changes from the reference potential Emid to the second potential Eb in the second pulse waveform W2, the diaphragm 340 deforms so that the volume of the liquid chamber 321 increases. Thereafter, as the voltage value changes to the third potential Ec, the diaphragm 340 deforms so that the volume of the liquid chamber 321 decreases. As a result, the ink in the liquid chamber 321 is pressurized, and the ink is ejected through the nozzle 331.

The control unit 310 controls the application of a voltage signal to the piezoelectric element 350 under the control of the CPU 154. Although details will be described later, the control unit 310 controls the volume of the ejected droplet by adjusting the potential difference Ed between the second potential Eb and the third potential Ec in FIG. 4. Hereinafter, this potential difference will be referred to as "ejection voltage." The ejection voltage corresponds to the amount of voltage change during ejection of droplets.

Although FIG. 4 shows that the voltage signal is composed of a rectangular pulse waveform, the voltage signal may have a step-shaped pulse waveform and a curved-shaped waveform.

(Droplet observation device)
The droplet observation device 40 is a device that measures the speed of droplets ejected from the inkjet head 30 (hereinafter sometimes referred to as “flying speed”).

If the flight speed is too fast, secondary droplets called satellites are likely to occur. On the other hand, if the flying speed is too slow, the droplet is likely to be affected by air resistance while flying, and the accuracy of the landing position of the droplet will decrease. By using the droplet observation device 40, it is possible to check whether the flying speed of the droplets ejected from the inkjet head 30 is within an appropriate speed range.

The droplet observation device 40 includes a droplet observation camera 402 and a control section 410 (see FIGS. 1 and 2).

The tip of the droplet observation camera 402 is directed toward the head section 301 of the inkjet head 30. The droplet observation camera 402 is, for example, a CCD (Charge Coupled Device) camera, and is connected to the control unit 410 via a cable 404.

The control unit 410 is connected to the CPU 154 and controls the drive of the droplet observation camera 402 under the control of the CPU 154.

The control unit 410 causes the droplet observation camera 402 to perform an imaging operation during printing, and acquires still image data and moving image data of the droplet. Note that the still image data and moving image data of the droplet are output to the control device 15 and stored in the storage section 151, and are also displayed on the display section 153.

Note that the droplet observation device 40 can also measure the volume of droplets discharged from each nozzle 331. The droplet observation device 40 can estimate the volume based on the diameter of a two-dimensionally observed droplet, for example, assuming that the flying droplet is spherical.

(Droplet observation device)
The landed droplet observation device 50 is a device that observes droplets that have landed on a printing target. The landed droplet observing device 50 is fixed to the pedestal 220B, as shown in FIG. The landed droplet observation device 50 includes a photographing unit 501 and a control section 510, as shown in FIG.

The photographing unit 501 has a camera that photographs droplets that have landed on the printing target.

The control unit 510 is connected to the CPU 154, and performs imaging control of the imaging unit 501 under the control of the CPU 154.

The landed droplet observation device 50 measures the landing position of the droplet that landed on the printing target, the volume of the droplet, and whether or not secondary droplets such as satellites and mist are generated. can be observed.

(Droplet volume data)
Even if the same voltage signal is applied to each of the plurality of piezoelectric elements 350, the volumes of droplets ejected from the plurality of nozzles 331 will vary. Therefore, the control device 15 determines the ejection voltage for each piezoelectric element 350 based on droplet volume data to be described later, and applies a voltage signal based on the ejection voltage to the piezoelectric element 350. The droplet volume data is data indicating the relationship between the ejection voltage and the droplet volume, and is stored in the storage unit 151 of the control device 15 as characteristic data.

FIG. 5 is a diagram showing an example of actual measurement data of droplet volume. As shown in FIG. 5, the droplet volume when the ejection voltages Ed1 and Ed2 are applied to each nozzle 331 is stored in the storage unit 151. Although FIG. 5 shows the volume of each droplet when two ejection voltages Ed1 and Ed2 are applied, the volume of each droplet when three or more ejection voltages are applied may be measured. The control device 15 derives the relationship between the droplet volume and the ejection voltage of the voltage signal for each nozzle 331 based on the actual measurement data of the droplet volume, for example, by the least squares method.

FIG. 6 illustrates a graph showing the relationship between the volume of a droplet ejected from a specific nozzle 331 and the ejection voltage of the voltage signal. The straight line in FIG. 6 is an approximate straight line derived by the control device 15. The approximate straight line in FIG. 6 indicates that the volume of a droplet ejected from a specific nozzle 331 increases by 0.85 pL when the ejection voltage applied to the piezoelectric element 350 increases by 3V. That is, in order to increase the volume of droplets ejected from a specific nozzle 331 by 0.1 pL, it is necessary to increase the ejection voltage of the voltage signal by 0.35V. Therefore, the control device 15 determines, for example, that when a voltage signal including the ejection voltage Ed1 is applied to a specific nozzle 331, the droplet volume is 3.65 pL, and the droplet volume ejected from each nozzle 331 is 3.55 pL. (3.65 pL-0.1 pL), a voltage signal containing a voltage 0.35 V smaller than Ed1 is applied as the ejection voltage to the piezoelectric element 350 corresponding to the specific nozzle 331.

In this way, the control device 15 derives the relationship between the volume of the droplet and the ejection voltage of the voltage signal based on the droplet volume data, and adjusts the ejection voltage according to the desired droplet volume based on the derivation result. Adjust. Thereby, the volume of droplets discharged from each nozzle 331 can be adjusted for each nozzle 331. For example, if printing unevenness is confirmed on the printing target, the control device 15 can adjust the droplet volume for each nozzle 331 based on the droplet volume data.

By adjusting the ejection voltage for each piezoelectric element 350 based on the droplet volume data, the control device 15 can suppress variations in the volume of the plurality of droplets ejected from the plurality of nozzles 331 to about 5% or less. .

(Variations in droplet volume and uneven printing)
Hereinafter, the relationship between droplet volume variations and printing unevenness will be described using the manufacture of organic EL displays as an example.

FIG. 7 is a schematic diagram showing a display panel 520 coated with droplets. FIG. 8 is a schematic diagram showing another display panel 600 with droplets applied. Note that FIGS. 7 and 8 illustrate that the inkjet head 30 has 15 nozzles 331 formed therein. In addition, in FIGS. 7 and 8, the longitudinal direction of the inkjet head 30 is inclined at a predetermined angle θ with respect to the Y-axis direction. The control device 15 can adjust the interval between the landing positions of the plurality of droplets by controlling the predetermined angle θ via the servo motor 304.

In the display panel 520 in FIG. 7, an ink application area 521 is formed by a line-shaped bank (hereinafter referred to as a "line bank"). The coating target area 521 formed by the line bank is referred to as a "line area 521." The plurality of line regions 521 are arranged along the X-axis direction. Line area 521 extends from one end of display panel 520 to the other end in the Y-axis direction.

By arranging the display panel 520 on the fixed stage ST so that the longitudinal direction of the line area 521 is along the Y-axis direction, droplets discharged from the 15 nozzles 331 are applied to each line area 521. Ru. In other words, 15 nozzles 331 are assigned to each line area 521.

In the display panel 600 in FIG. 8, an ink application area 601 is formed by a bank divided into pixels (hereinafter referred to as a "pixel bank"). The coating target area 601 formed by the pixel bank is referred to as a "cell area 601." The cell area 601 has a shorter longitudinal dimension than the line area 521. In FIG. 8, three cell regions 601 are arranged along the Y-axis direction, and a set of the three cell regions 601 is arranged along the X-axis direction.

By disposing the display panel 600 on the fixed stage ST so that the longitudinal direction of the cell region 601 is along the X-axis direction, droplets discharged from the three nozzles 331 are applied to each cell region 601. . In other words, three nozzles 331 are assigned to each cell region 601.

One or more coating target positions are arranged in the coating target areas 521 and 601. For example, in FIG. 7, 15 coating target positions are arranged in line area 521 in the Y-axis direction. In FIG. 8, three coating target positions are arranged in the cell area 601 in a row in the Y-axis direction.

<Reducing variation>
Variations in the volume of a plurality of droplets applied to the same application target area are alleviated. In the following, mitigation of variations in the volume of droplets will be explained.

When droplets are applied from M nozzles 331 (M is an integer of 2 or more), the standard deviation of the droplet volume in all M nozzles 331 is σ _mean , and the droplet volume by each of the M nozzles 331 is When the standard deviations are σ ₁ , σ ₂ , σ ₃ , ..., σ _M , the following formula (1) holds true.

σ ₁ ² +σ ₂ ² +σ ₃ ² +...+σ _M ² =σ _mean ² ...(1)
When the standard deviations of the droplet volumes of the M nozzles 331 are equal to each other, the following equation (2) is obtained by transforming equation (1).

σ ₁ = σ _mean /M ^1/2 ...(2)
For example, if the standard deviation σ _mean of the droplet volume of all three nozzles 331 is n% (n is 10 or less), the standard deviation σ ₁ of the droplet volume ejected from each nozzle 331 is n/3 ^1/2 (%). Furthermore, if n is 3%, σ ₁ will be approximately 1.7%.

Further, when the standard deviation σ _mean of the droplet volumes of all 15 nozzles 331 is n%, σ ₁ is n/15 ^1/2 (%). Further, if n is 3%, σ ₁ will be approximately 0.8%.

That is, the larger the number of nozzles 331 assigned to the same application target area, the smaller the variation in droplet volume among the nozzles 331.

As shown in FIG. 7, when 15 nozzles 331 are assigned to the line area 521, the variation in volume of the plurality of droplets ejected from the 15 nozzles 331 is about 3%. Furthermore, since a large number of droplets are applied over a relatively wide area, variations in the volume of the 15 droplets are evened out.

On the other hand, as shown in FIG. 8, when the number of nozzles 331 allocated to the cell area 601 is small, the volume of the plurality of droplets applied to the cell area 601 by the plurality of nozzles 331 varies greatly. Become. In this case, even if the variation in the volume of droplets applied from the plurality of nozzles 331 is suppressed to 3% or more and 5% or less, printing unevenness is likely to occur depending on the variation.

The inkjet head 30 is arranged so that a plurality of coating target positions arranged in the main scanning direction are assigned to each of the plurality of nozzles 331, and each time a droplet volume is ejected to one nozzle 331 (in the main scanning direction The variation in the values (for each coating target position) is about 1% or less. This variation is also smaller than the variation in the volume of droplets from one nozzle 331 to another. Therefore, when printing and forming a film on the display panel 600 in FIG. 8, there is a variation in the film thickness of the cell region 601 in the X-axis direction compared to a variation in the film thickness of the cell region 601 in the Y-axis direction. becomes smaller. Therefore, streaks may become noticeable along the X-axis direction, which may appear as printing unevenness.

Therefore, the printing apparatus 1 according to the present embodiment executes droplet volume control, which will be described later, so that the droplet volume for each ejection from the same nozzle 331 is equal to or smaller than the volume of droplets applied from a plurality of nozzles 331. The droplet volume for each ejection is made to vary to the same extent as the variation. Specifically, the printing apparatus 1 varies the droplet volume for each coating target position so that the droplet volume falls within an allowable range at a plurality of coating target positions lined up in the main scanning direction. The allowable range can be expressed as H−dH as the lower limit and H+dH as the upper limit, where H is the reference discharge amount and dH is the allowable amount. The allowable amount is a value that serves as a reference for variation, and is an allowable deviation amount from the reference ejection amount H, and is set based on the variation in droplet volume for each nozzle. The reference discharge amount is set for each nozzle 331. Note that depending on the distribution of coating target areas 521 and 601 formed on the printing object, the reference discharge amount may be set not only for each nozzle 331 but also for each coating target position aligned in the main scanning direction. good.

(droplet volume control)
Droplet volume control according to this embodiment will be described below with reference to FIG. 4 and FIGS. 9 to 13. FIG. 9 is a diagram illustrating the voltage signal S2 according to this embodiment. FIG. 10 is a diagram illustrating the voltage signal S3 according to this embodiment. FIG. 11 is a diagram illustrating a plurality of adjustment signals S11 to S18 used when the printing apparatus 1 generates a voltage signal. FIG. 12 is a diagram illustrating an example of a control table 700 that the printing apparatus 1 refers to when executing droplet volume control.

The printing apparatus 1 according to the present embodiment is configured to eject ink at a reference ejection amount from a plurality of nozzles 331 into a plurality of cells of the same type, that is, to eject ink at a plurality of application target positions on a printing object. When applying ink with a discharge amount, control parameters for the nozzle 331 are changed for each coating target position (that is, the number of discharges) arranged in the X-axis direction (main scanning direction). The control parameter is a parameter that correlates with the amount of ink ejected from the nozzle 331 (that is, the volume of the droplet). In the following explanation, the control parameter is the above-mentioned ejection voltage as an example.

<Explanation of voltage waveform>
For example, by applying the voltage signal S2 in FIG. 9 to the piezoelectric element 350, the control device 15 makes the volume of the droplet ejected from the nozzle 331 larger than when applying the voltage signal S1 in FIG. be able to. The voltage signal S2 in FIG. 9 has a first potential Ea1 smaller than the first potential Ea, a second potential Eb1 smaller than the second potential Eb, and a third potential Ec1 larger than the third potential Ec. Further, the voltage signal S2 has a discharge voltage Ed1 (ie, Ec1-Eb1) that is larger than the discharge voltage Ed (ie, Ec-Eb) of the voltage signal S1.

For example, by applying the voltage signal S3 in FIG. 10 to the piezoelectric element 350, the control device 15 can make the volume of the droplet ejected from the nozzle 331 smaller than when applying the voltage signal S1 in FIG. I can do it. The voltage signal S3 in FIG. 10 has a first potential Ea2 larger than the first potential Ea, a second potential Eb2 larger than the second potential Eb, and a third potential Ec2 smaller than the third potential Ec. Further, the voltage signal S3 has an ejection voltage Ed2 (ie, Ec2-Eb2) smaller than the ejection voltage Ed (ie, Ec-Eb) of the voltage signal S1.

<Droplet volume control>
In this embodiment, the control device 15 applies voltage signals having different ejection voltages to the piezoelectric element 350 for each nozzle 331 and the number of times of ejection. For example, the control device 15 generates a voltage signal for application for each nozzle 331 and for each number of ejections based on the reference voltage signal and the plurality of adjustment signals.

The reference voltage signal is a voltage signal applied when ink is ejected at a reference ejection amount. This reference voltage signal includes a waveform indicating the discharge voltage Ed. The waveform indicating the discharge voltage Ed differs for each nozzle 331. The magnitude of this ejection voltage Ed is adjusted in order to reduce variations in the amount of ink ejected from one nozzle 331 to a certain extent.

More specifically, the control device 15 selects one of the adjustment signals S11 to S18 in FIG. 11, uses the selected voltage signal to perform addition processing or subtraction processing on the reference voltage signal, and applies Generate a voltage signal for In this way, the control device 15 changes the difference value between the reference discharge amount and the discharge amount actually discharged from the nozzle 331 at a plurality of target coating positions.

The addition/subtraction signals S11 to S18 are waveform signals with different amplitudes (maximum voltage and minimum voltage), and in FIG. 11, the amplitudes of the addition/subtraction signals S11 to S18 increase in the order of magnitude. These addition/subtraction signals S11 to S18 are stored in the storage section 151, for example. The ejection voltage included in the voltage signal for application differs depending on the selected adjustment signal. Although eight types of adjustment signals are shown in FIG. 11, the number is not limited to eight types. For example, the storage unit 151 stores an adjustment signal that always shows the same voltage value, that is, a signal in which the reference voltage signal does not change even if addition processing and subtraction processing are performed on the reference voltage signal. May be used for volume control.

The control device 15 randomly selects the adjustment signals S11 to S18 for each nozzle 331 and each number of ejections. For example, the control device 15 selects the adjustment signals S11 to S18 based on the control table 700 in FIG. 12. In the control table 700, adjustment signals S11 to S18 are set for each nozzle 331 and for each number of times of ejection. FIG. 12 illustrates a control table 700 when the number of nozzles 331 of the inkjet head 30 is 15.

The control table 700 is generated, for example, by assigning adjustment signals S11 to S18 to each nozzle 331 and each number of ejections based on a random number sequence generated by a random number sequence generator such as a Mersenne Twister.

In droplet volume control, the reference potential Emid of the voltage signal applied to the piezoelectric element 350 does not change regardless of the nozzle 331 and the number of ejections. Therefore, the position of the ink liquid level inside the nozzle 331 is always maintained at a constant position, so that droplets are stably ejected.

Note that when generating the voltage signal for application, the control device 15 may perform subtraction processing on the reference voltage signal using the selected addition/subtraction signal. Further, the control table 700 may include data indicating whether addition processing or subtraction processing is to be performed, along with the addition/subtraction signals S11 to S18 to be selected.

When the printing apparatus 1 executes the droplet volume control described above, it is possible to increase the variation in droplet volume depending on the number of ejections from the same nozzle 331. Therefore, the droplet volumes at the plurality of coating target positions lined up in the X-axis direction vary to the same extent as the droplet volumes at the plurality of coating target positions lined up in the Y-axis direction. As a result, streaks along the X-axis direction are less likely to appear, and printing unevenness is suppressed.

<Control range of droplet volume>
The flying speed of the droplet discharged from the nozzle 331 changes depending on the volume of the droplet. When the flying speed of the droplet is relatively slow, the airflow generated by the relative movement of the inkjet head 30 with respect to the fixed stage ST prevents the droplet from advancing. As a result, there is a possibility that the droplet landing position may deviate from the coating target position. On the other hand, if the flying speed of the droplet is relatively high, satellites caused by the droplet are likely to occur. Satellites tend to land at positions different from the target application position. For this reason, the landing positions of the droplets vary.

If the flying speed of the droplet is less than 3 m/s, the landing position of the droplet will be disturbed. It is known that when the flight speed is higher than 8 m/s, satellites are generated due to droplets.

Therefore, the control device 15 changes the droplet volume within a range where the flying speed of the droplet is 3 m/s or more and 8 m/s or less. More preferably, the control device 15 changes the volume of the droplet within a range where the flight speed of the droplet is 3.5 m/s or more and 6.5 m/s or less.

(Tilt of inkjet head)
When performing a printing operation, the control device 15 drives the servo motor 304 to rotate the inkjet head 30 around the Z-axis, and tilts the arrangement direction of the plurality of nozzles 331 with respect to the Y-axis direction. Specifically, the control device 15 tilts the arrangement direction of the nozzles 331 at a predetermined angle θ with respect to the longitudinal direction of the application target area, as shown in FIGS. 7 and 8. The predetermined angle θ is greater than 0 degrees and less than 90 degrees. In other words, the control device 15 adjusts the arrangement direction of the nozzles 331 in a range greater than 0 degrees and less than 90 degrees so that the intervals between the droplet landing positions in the Y-axis direction are the desired intervals. do.

Then, the control device 15 moves the inkjet head 30 in the X-axis direction while maintaining the state where the inkjet head 30 is tilted at a predetermined angle θ, and directs the inkjet head 30 toward a plurality of coating target positions that are two-dimensionally arranged on the printing target. droplets are ejected through the plurality of nozzles 331.

By printing with the arrangement direction of the nozzles 331 inclined with respect to the longitudinal direction of the application target area, the same application target area can be printed, compared to when the nozzle 331 arrangement direction is parallel to the longitudinal direction of the application target area. More nozzles 331 can be allocated to. Therefore, the occurrence of printing unevenness can be further suppressed.

(Printing operation)
Next, the printing operation of the printing device 1 will be described using an example in which ink is applied to the same application target position multiple times. The printing device 1 performs printing (hereinafter referred to as "outward printing") in which droplets are ejected to a coating target position on a printing object while moving the inkjet head 30 in the positive direction of the X-axis, and printing in the negative direction of the X-axis. Printing in which droplets are ejected while moving the printer (hereinafter referred to as "return printing") is performed alternately.

In the following explanation, it is assumed that printing is performed once when either forward printing or backward printing is performed. Further, it is assumed that the reference ejection amount is set for each nozzle 331 and for each number of times of printing.

Further, when the predetermined unit ejection amount is v, and the adjustment signals S11 to S18 in FIG. Suppose the quantity increases. It is also assumed that when the addition/subtraction signals S11 to S18 are subtracted, the ink ejection amount decreases by an amount of 1v to 8v compared to the ink ejection amount based on the reference voltage signal.

FIG. 13 is a flowchart illustrating an example of a printing operation performed by the printing device 1. In each step, a specific coating target position (hereinafter referred to as a "specific position") may be described in detail.

First, in step S101, the control device 15 determines that the ink ejection amount is within an allowable range based on the reference ejection amount and allowable amount set for each of the plurality of nozzles 331 at a plurality of target application positions lined up in the main scanning direction. The options regarding the ink ejection amount are determined so that the amount of ink is within the range and varies within the allowable range. The options regarding the ink ejection amount are options that are made up of combinations of adjustment signals and processing details.

For example, when the reference discharge amount Hx at a specific position is 10v and the allowable amount dHx is 3v, the allowable range at the specific position is 7v or more and 13v or less. The control device 15 determines options for adjustment signals and processing contents, and selects one option from among them so that the ink ejection amount at a specific position varies within the allowable range while keeping it within the allowable range of 7v or more and 13v or less. do.

Specifically, the control device 15 determines an option that is a minimum of 3v less than the reference discharge amount 10v and a maximum of 3v more. That is, the control device 15 determines the addition processing of the addition/subtraction signals S11 to S13 and the subtraction processing of the addition/subtraction signals S11 to S13 as options, and determines one option from among them. In the following description, it will be assumed that the control device 15 has determined the option of "subtraction processing of the addition/subtraction signal S13" (discharge amount is 7v) for the specific position. Further, the control device 15 performs the same processing as the processing for the specific position on other coating target positions.

Then, in step S102, the control device 15 generates a voltage signal for application to each coating target position based on the determined options, and executes forward printing based on the generated voltage signal. As a result, 7V ink is ejected to the specific position.

In addition to executing step S102, the control device 15 may measure the volume of the ink droplet ejected from the nozzle 331 using, for example, an observation device such as the droplet observation device 40.

Next, in step S103, the control device 15 determines whether it is time to end printing. For example, the control device 15 counts the number of times of printing, and when the count value reaches a preset number of times depending on the object to be printed, it determines that it is time to end printing, and the number of times of printing is reached. If the time has not been reached, it is determined that it is not the timing to end printing.

If it is determined that it is not the timing to end printing (“NO” in step S103), the process moves to step S104. Then, the control device 15 calculates the total amount of ink ejected at the time of determination in step S103 for each coating target position. For example, the control device 15 calculates the total amount of ink ejected by adding up the ink droplet volumes measured each time printing is performed for each application target position. For example, if printing has been performed once at the time of determination in step S103, the amount of ink ejected at the specific position is calculated to be 7V.

Next, in step S105, the control device 15 controls the ink ejection amount to fall within the allowable range based on the calculated total ink ejection amount, total reference ejection amount, and allowable amount for each coating target position. Next, options regarding the amount of ink to be ejected are determined. The total standard ejection amount is the total amount of ink that should be ejected from the first printing to the next printing completion for each application target position, and more specifically, from the first printing to the next printing completion. It is the total of the standard discharge amount.

Hereinafter, step S105 will be described as a process for determining the options to be used for the second printing.

For example, when the second reference ejection amount Hx at a specific position is 15v, the total reference ejection amount for the first and second times at the specific position is 25v (=10v+15v). Further, when the allowable amount dHx for the total reference ejection amount is 5v, the allowable range of the total reference ejection amount is 20v (=25v-5v) or more and 30v (=25v+5v) or less.

Since 7v of ink has already been ejected at the specific position, it is necessary to eject ink of 13v (=20v-7v) or more and 23v (=30v-7v) or less for the second time. Therefore, the control device 15 determines the adjustment signal and the processing content options so that the ink ejection amount at the specific position is 13v or more and 23v or less.

Specifically, the control device 15 determines an option that is a minimum of 2v less and a maximum of 8v more than the reference discharge amount 15v. That is, the control device 15 determines the subtraction processing of the addition/subtraction signals S11 to S12 and the addition processing of the addition/subtraction signals S11 to S18 as options, and determines one option from among them.

The control device 15 executes the process for this specific position for each coating target position.

Note that the amount of ink that has already been ejected varies among the plurality of coating target positions lined up in the main scanning direction. Therefore, selectable options differ depending on the amount of ink for each of the plurality of coating target positions lined up in the main scanning direction. In the above example, the options that can be selected for the specific position are the subtraction process of the addition/subtraction signals S11 to S12 and the addition process of the addition/subtraction signals S11 to S18. On the other hand, for example, if 13V ink has already been applied to another coating target position that is lined up with the specific position in the main scanning direction, the options that can be selected for the other coating target position are the addition/subtraction signals S11 to S18. It is also referred to as subtraction processing of , and addition processing of addition/subtraction signals S11 to S12.

If step S105 is a process of determining options for the adjustment signal and processing content to be used for the i-th printing, the process may be performed in the same manner as for the second printing. Specifically, the control device 15 determines that the total reference ejection amount for the first to i times at the specific position is SH(i), the allowable amount dSH(i) for the total reference ejection amount, and the ink that has already been ejected at the specific position. Based on the total ejection amount SS(i-1), an allowable range of the i-th ink ejection amount is calculated. The minimum value of the allowable range is SH(i)-dSH(i)-SS(i-1), and the maximum value is SH(i)+dSH(i)-SS(i-1). Then, the control device 15 determines options for combinations of adjustment signals and processing contents such that the ink ejection amount falls within an allowable range, and selects one option from among them. The control device 15 performs similar processing for other coating target positions.

Next, in step S106, the control device 15 uses the determined options to generate a voltage signal for application to each coating target position, and executes backward printing or forward printing based on the generated voltage signal. Note that the control device 15 executes backward printing when the number of times of processing in step S106 is an odd number, and executes forward printing when the number of times of processing is an even number.

After that, the process moves to step S103.

The processes of steps S104 to S106 are repeated until it is determined that it is time to end printing.

If it is determined that it is the timing to end printing (“YES” in step S103), the control device 15 ends printing on the print target.

As a result, in a plurality of coating target positions lined up in the main scanning direction, it is possible to keep the total amount of ink ejected for each coating target position within a permissible range each time printing is performed, while making it vary within the permissible range.

<Printing with multiple types of ink>
Next, an example of a printing operation when a plurality of different types of ink are ejected to the same application target position will be described. Hereinafter, an example will be described in which a first ink, a second ink, and a third ink are applied to a specific position of a printing object according to FIGS. 14 and 15.

FIG. 14 is a diagram showing an example of the total standard ejection amount SH(i) and its allowable amount until a predetermined number of printings are completed. FIG. 14 shows that the first ink, second ink, and third ink are printed twice, three times, and three times, respectively, in this order. As mentioned above, "SH(i)" is the total standard ejection amount of ink from the first to i times of printing at a specific position, and "tolerable amount of SH(i)" is the allowable amount from SH(i). This is the amount of deviation.

FIG. 15 is a diagram showing an example of the total standard ejection amount and its allowable amount for each of a plurality of types of ink. In FIG. 15, the total standard ejection amounts SH ₁ (i), SH ₂ (i), and SH ₃ (i) of the first ink, second ink, and third ink are each 25v. , 35v, and 40v, and their respective allowable amounts are shown to be 5v, 5v, and 6v.

The control device 15 executes the printing operation so that at least one of the following conditions (A0), (A1), and (A2) is satisfied depending on the number of times of printing. Note that the condition (A0) is satisfied when the processes in steps S101 to S102 in FIG. 13 described above are executed, and the condition (A1) is satisfied when the processes in steps S104 to S106 in FIG. 13 described above are executed. filled with.
(A0) At the plurality of coating target positions lined up in the main scanning direction, the ink ejection amount is kept within the allowable range based on the reference ejection amount and the allowable amount set for each of the plurality of nozzles 331. Make it vary.
(A1) Based on the amount of ink already ejected to each of the plurality of application target positions, the total amount of ink ejection for each of the plurality of application target positions is allowed from the total standard ejection amount to be ejected for each application target position. Stay within range.
(A2) For each type of ink, set a total reference ejection amount and a tolerance range for the total reference ejection amount, and keep the total ink ejection amount within the allowable range.

First, the control device 15 executes the first printing in forward printing so as to satisfy the condition (A0).

Next, the control device 15 executes the second printing as a return printing so as to satisfy the condition (A1).

Next, the control device 15 performs the third to fifth printings as forward printing, return printing, and Execute on outward printing. For example, the control device 15 executes the third and fourth printings so that the condition (A1) is satisfied, and executes the fifth printing so that both the conditions (A1) and the conditions (A2) are satisfied. The fifth printing will be explained below.

(I) Options for satisfying condition (A1) At a specific position, it is necessary to eject ink of 54v (=60v-6v) or more and 66v (=60v+6v) or less by the fifth time (see FIG. 14). Further, for example, if the total ejection amount for the first to fourth printings is 50v at a specific position, it is necessary to eject ink of 4v or more and 16v or less during the fifth printing.

For example, if the standard ejection amount for the fifth printing is 10v, in order to make the ink ejection amount at a specific position 54v or more and 66v or less, the minimum is 6v less than the standard ejection amount of 10v, and the maximum is 6v more. What is necessary is to determine the options for ejecting ink. That is, the subtraction processing of the addition/subtraction signals S11 to S16 and the addition processing of the addition/subtraction signals S11 to S16 may be determined as options.

(II) Options for satisfying condition (A2) In order to keep the total ejection amount of the second ink within the allowable range of SH ₂ (i), it is necessary to ) or more and 40v (=35v+5v) or less must be ejected (see FIG. 15). Further, for example, if the total ejection amount of the second ink in the third to fourth printings at a specific position is 27v, it is necessary to eject ink of 3v or more and 13v or less during the fifth printing.

Therefore, it is only necessary to determine an option for ejecting ink at a minimum of 7v less than the reference ejection amount of 10v and at a maximum of 3v more. That is, the subtraction processing of the addition/subtraction signals S11 to S17 and the addition processing of the addition/subtraction signals S11 to S13 may be determined as options.

In order to satisfy both conditions (A1) and (A2), the control device 15 narrows down the options to subtraction processing of addition/subtraction signals S11 to S16 and addition processing of addition/subtraction signals S11 to S13, and selects one of the narrowed down options. Decide on one option. Similarly, the control device 15 determines options for adjustment signals and processing contents for other coating target positions, and determines one option from among them. Then, the control device 15 executes the printing process based on the determined options.

Next, the control device 15 performs the 6th to 8th printing, respectively, by performing backward printing, outward printing, and Execute during return printing. For example, the control device 15 executes the 6th to 7th printing so that condition (A1) is satisfied, and executes the 8th printing so that both condition (A1) and condition (A2) are satisfied. The eighth printing will be explained below.

(III) Options for satisfying condition (A1) At a specific position, it is necessary to eject ink of 90v (=100v-10v) or more and 110v (=100v+10v) or less by the eighth time (see FIG. 14). Further, for example, if the total ejection amount for the first to seventh printings is 94v at a specific position, it is necessary to eject ink of 0v or more and 16v or less during the eighth printing.

For example, if the standard ejection amount for the 8th printing is 10v, in order to make the ink ejection amount at a specific position between 90v and 110v, the minimum is 8v less than the standard ejection amount of 10v, and the maximum is 6v more. What is necessary is to determine the options for ejecting ink. That is, it is sufficient to determine options for subtracting the addition/subtraction signals S11 to S18 and addition processing for the addition/subtraction signals S11 to S16, and then determining one option from among them.

(IV) Options to satisfy condition (A2) In order to keep the total ejection amount of the third ink within the allowable range of SH ₃ (i), it is necessary to use 34v (=40v-6v ) or more and 46v (=40v+6v) or less must be ejected (see FIG. 15). For example, if the ejection amount of the third ink during the 6th to 7th printing is 28v at a specific position, it is necessary to eject ink of 6v or more and 18v or less during the 8th printing.

Therefore, it is only necessary to determine an option for ejecting ink at a minimum of 4v less than the eighth reference ejection amount of 10v and at a maximum of 8v more. That is, it is sufficient to determine options for subtracting the addition/subtraction signals S11 to S14 and addition processing for the addition/subtraction signals S11 to S18, and then determining one option from among them.

In order to satisfy conditions (A1) and (A2), the control device 15 narrows down the options to subtraction processing of the addition/subtraction signals S11 to S14 and addition processing of the addition/subtraction signals S11 to S16, and selects one of the narrowed down options. , decide on one option. Similarly, the control device 15 determines options for adjustment signals and processing contents for other coating target positions, and determines one option from among the options. Then, print processing is executed based on the determined options.

Thereby, the total ejection amount of the plurality of types of ink can be varied at the plurality of coating target positions arranged in the main scanning direction while keeping the total ejection amount within the allowable range. Furthermore, it is possible to vary the total amount of ink ejected for each type of ink while keeping it within the allowable range of the total amount of ink ejected.

Note that in the above process, the final printing of the second ink and the third ink is performed so as to satisfy the conditions (A1) and (A2), but the present invention is not limited to this. For example, printing may be performed so that conditions (A1) and (A2) are satisfied in printing the second ink and the third ink, that is, in all printings after the third time.

<Other print controls>
Hereinafter, a printing operation for a printing target having a plurality of panel areas will be described.

A printing target may include a first panel area in which first application target areas are arranged, and a second panel area in which second application target areas narrower than the first application target area are arranged. In that case, a plurality of coating target positions are assigned to each of the first coating target area and the second coating target area, but the arrangement of coating target positions in the first coating target area is different from that in the second coating target area. This is different from the arrangement of the coating target positions.

The amount of ink to be applied to the first application area is greater than the amount of ink to be applied to the second application area. Therefore, the reference discharge amount for the first application target area is greater than the reference discharge amount for the second application target area.

Therefore, the control device 15 makes the allowable range of the ink ejection amount for the second application target area narrower than the allowable range of the ink ejection amount for the first application target area.

For example, when performing a printing operation on the first panel area, the control device 15 selects the addition processing of the addition/subtraction signals S11 to S18 and the addition/subtraction signal S11 as options for the processing contents and the addition/subtraction signals to be applied to the reference voltage signal. - Determine the subtraction process in S18. Then, the control device 15 determines one option from among them for each coating target position. As a result, while keeping the discharge amount within the tolerance range of ±8v with respect to the reference discharge amount, the discharge amount is varied for each coating target position within the tolerance range.

Further, when performing a printing operation on the second panel area, the control device 15 selects the addition processing of the addition and subtraction signals S11 to S14 and the addition processing of the addition and subtraction signals S11 to S14 as options for the processing contents and the addition and subtraction signals to be applied to the reference voltage signal. - Determine the subtraction process in S14. Then, the control device 15 determines one option from among them for each coating target position. Thereby, while keeping the discharge amount within the tolerance range of ±4v with respect to the reference discharge amount, the discharge amount is varied for each coating target position within the tolerance range.

Note that the control device 15 may generate new addition/subtraction signals S21 to S28 by multiplying the amplitude of each of the addition/subtraction signals S11 to S18 by k (k is a number greater than or equal to 0 and less than 1). When the control device 15 executes the printing operation on the second panel area, the control device 15 selects the addition processing of the addition and subtraction signals S21 to S28 and the addition processing of the addition and subtraction signals S21 to S28 as options for the processing contents and the addition and subtraction signals to be applied to the reference voltage signal. The subtraction processing in steps S28 to S28 may be determined.

<Device manufacturing example>
Next, an example of manufacturing a device using the printing apparatus 1 will be described, taking as an example the manufacturing of an organic EL display panel. In addition, in the organic EL display panel, functional layers such as a hole injection layer, a hole transport layer, and a light emitting layer are formed in areas defined by banks on the electrodes.

The control device 15 sequentially discharges a plurality of types of ink toward a coating target position on an electrode, which is an object to be printed. The multiple types of ink include an ink containing the material for the hole injection layer (hereinafter referred to as the "fourth ink"), and an ink containing the material for the hole transport layer (hereinafter referred to as the "fifth ink"). , an ink containing a material for a light-emitting layer (hereinafter referred to as "sixth ink"), and the like. Specifically, the control device 15 discharges the fourth ink, the fifth ink, and the sixth ink according to the above-mentioned <Printing of multiple types of inks>.

Thereby, the control device 15 forms each functional layer so that the total film thickness of the hole injection layer, hole transport layer, and light emitting layer falls within a predetermined tolerance range regardless of the target coating position on the electrode. Can be done. Further, by setting the total standard ejection amount and its allowable range for each ink, the thickness of each layer can be kept within the allowable range for each layer.

For example, the control device 15 may be configured such that the total film thickness of the hole injection layer and the hole transport layer (corresponding to the total ejection amount of the fourth ink and the fifth ink) is the thickness d1 at a certain coating target position, and at another coating target position. When the thickness is d2 (>d1) at the coating target position, the control device 15 controls the thickness of the sixth ink for each coating target position so that the ejection amount of the sixth ink for one coating target position is smaller than that for another coating target position. , options for adjustment signals and processing contents are determined, and one option is determined from among them.

Specifically, the control device 15 measures the thickness of the formed film using an observation device such as the landed droplet observation device 50, and generates adjustment signals for each coating target position based on the measurement results. and determine options for processing contents, and decide one option from among them. More specifically, the control device 15 determines options for adjustment signals and processing contents such that the discharge amount is smaller for coating target positions where the total film thickness is larger than the reference thickness, and selects options from among them. Decide on one option. Further, the control device 15 determines options for adjustment signals and processing contents so that the discharge amount becomes larger for a coating target position where the total film thickness is smaller than the reference thickness, and determines one option from among them. do.

With this type of control, the amount of ink ejected onto the film can be changed for each coating target position depending on the unevenness of the thickness of the film that has already been created, so the film thickness as a whole can be maintained at a predetermined level. It is possible to form a film with a desired thickness within the allowable range.

Note that if the film that has already been formed is thick as a whole, the film that is formed on the film can be made thin as a whole. Similarly, if the film that has already been formed is thin as a whole, the film that is formed on the film can be made thick as a whole.

As explained above, the printing apparatus 1 according to one aspect of the embodiment includes the inkjet head 30 having a plurality of nozzles 331. The printing apparatus 1 also has a plurality of coating target positions lined up in the main scanning direction where the inkjet head 30 moves relative to the printing target, and a plurality of coating targets set for each of the plurality of nozzles 331. A control device 15 for ejecting ink from a plurality of nozzles 331 is provided at a position. Further, the control device 15 changes the ink ejection amount for each of the plurality of application target positions within a predetermined tolerance range from the reference ejection amount set for each of the plurality of nozzles 331.

Thereby, it is possible to increase the variation in the volume of droplets depending on the number of times of ejection from the same nozzle 331. Therefore, the degree of variation in the volume of droplets according to the number of times of ejection from the same nozzle 331 can be brought close to the degree of variation in the volume of droplets ejected from a plurality of nozzles 331. Therefore, printing unevenness can be suppressed on the printing target.

In one aspect of the embodiment, the control device 15 may irregularly change the ink ejection amount for each of a plurality of target application positions.

Further, the control device 15 ejects the ink such that the difference value between the reference ejection amount and the actual ejection amount is different at the first application target position and the second application target position among the plurality of application target positions. You may let them.

More specifically, the control device 15 controls the ink ejection amount based on the control parameter, and adjusts the control parameter corresponding to the reference ejection amount in a plurality of different ways for each of the plurality of application target positions. The ink ejection amount may be determined by selecting one of the signals and performing addition/subtraction processing.

Further, the inkjet head 30 has a liquid chamber 321 in which ink is stored and a piezoelectric element 350 for each nozzle 331, and ink is ejected from the liquid chamber 321 by applying a voltage to the piezoelectric element 350. It may be. The control parameter may be the amount of change in the voltage applied to the piezoelectric element 350.

Therefore, the volume of droplets discharged from the nozzle 331 can be changed in a simple manner.

The control device 15 may apply to the piezoelectric element 350 a voltage signal having a reference potential Emid that is constant regardless of the piezoelectric element 350 and the target position, and a voltage change amount (ejection voltage).

As a result, the position of the ink liquid level inside the nozzle 331 is maintained at a constant position, so that droplets are stably ejected.

The control device 15 may set control parameters such that the flying speed of the ink is 3 m/s or more and 8 m/s or less, and may cause ink to be ejected from the plurality of nozzles 331. This allows ink to be applied accurately to the target position. Further, by setting the control parameters such that the control device 15 sets the flying speed of the ink to be 3.5 m/s or more and 6.5 m/s or less, it is possible to further improve the landing accuracy of the ink. .

The inkjet head 30 may move in the main scanning direction with the arrangement direction of the plurality of nozzles 331 being inclined with respect to the direction perpendicular to the main scanning direction (Y-axis direction). Therefore, the interval between the landing positions of the plurality of droplets discharged from the plurality of nozzles 331 can be narrowed. Therefore, it is possible to increase the number of nozzles 331 assigned to the same application target area, so that it is possible to further prevent uneven printing from occurring.

When ejecting ink multiple times toward the same application target position, the control device 15 determines the total amount of ink ejected to each of the plurality of application target positions based on the amount of ink that has already been ejected to each of the plurality of application target positions. The ink ejection amount may be changed for each of the plurality of coating target positions so that the ink ejection amount falls within a predetermined tolerance range from the total reference ejection amount to be ejected to each coating target position.

Therefore, when printing multiple times, the total amount of ink ejected can be kept within a certain range while being varied appropriately for each target application position. Therefore, when printing multiple times, printing unevenness can be further suppressed.

Furthermore, the control device 15 may cause different types of ink to be ejected toward the same application target position.

Thereby, the total ejection amount of the plurality of types of ink can be appropriately varied while being kept within a certain range.

Therefore, when applied to device manufacturing, it is possible to suppress variations in film thickness while suppressing printing unevenness in the total film thickness of a plurality of functional layers generated by each of a plurality of types of ink.

For example, when manufacturing a display panel having a hole injection layer, a hole transport layer, and a light emitting layer, the total thickness of the hole injection layer, hole transport layer, and light emitting layer must be adjusted to an appropriate thickness. Can be done. The light emitted from the light emitting layer has a first light component that is directly extracted to the outside of the display panel, and a second light component that is reflected by the electrode that is the lower layer of the hole injection layer.

According to one aspect of the present embodiment, the second light component can be easily outputted to the outside of the display panel by manufacturing the plurality of functional layers described above to have an appropriate total thickness. That is, a display panel with high luminous efficiency can be produced.

The control device 15 may change the combination of a plurality of different adjustment signals, which are options for determining the amount of ink to be ejected, based on the amount of ink that has already been ejected to each of the plurality of application target positions.

As a result, when ink is ejected to the same target coating position multiple times, the amount of ink ejected each time is kept within the allowable range of the standard ejection amount set for each target coating position, while varying the amount of ink ejected each time. You can use it.

Further, according to one aspect of the present embodiment, the control device 15 controls a plurality of third coating target positions (coating target positions in the first panel area) and a plurality of third coating target positions different in arrangement from each other. For the fourth coating target position (coating target position in the second panel area), the tolerance range from the standard discharge amount for the plurality of third coating target positions and the tolerance range from the standard discharge amount for the plurality of fourth coating target positions. The allowable range may be set to a different range.

Therefore, since it is possible to set an appropriate tolerance range for each area for a plurality of areas to be coated with different amounts of ink to be applied, it is possible to suppress printing unevenness for each area.

[Modified example]
In the embodiment, different adjustment signals S11 to S18 are selected for all the nozzles 331 and the number of ejections. The control device 15 may select the adjustment signals S11 to S18 according to (1) to (3) below, for example. Note that the nozzle numbers and coating target position numbers used in the following description correspond to the nozzle numbers and coating target position numbers in FIG. 12, respectively.

(1) The control device 15 may select the same adjustment signals S11 to S18 for a plurality of coating target positions lined up along the X-axis direction. For example, when a droplet is ejected multiple times onto the same application target area using a specific nozzle, the same adjustment signal may be applied to the specific nozzle.

(2) When a plurality of coating target areas such as the cell area 601 are lined up along the X-axis direction, the control device 15 applies the same adjustment to all coating target positions included in two or more adjacent coating target areas. Signals S11 to S18 may be selected.

(3) The control device 15 may select the same adjustment signal for multiple nozzles 331 assigned to the same coating target area. For example, the nozzles 331 with numbers "1", "2", and "3" are applied to the same application target area, and the nozzles 331 with numbers "7", "8", and "9" are applied to another same application target area. If the area, nozzles 331 with numbers "13", "14", and "15" are assigned to another same application target area, nozzles with numbers "1", "2", and "3" 331, the same addition/subtraction signal for nozzles 331 with numbers "7", "8", and "9", and the same addition/subtraction signal for nozzles 331 with numbers "13", "14", and "15". The same addition/subtraction signal may be selected for both.

In the embodiment, the control parameter is described as ejection voltage, but it does not necessarily have to be ejection voltage or may be a parameter other than voltage as long as it is a parameter that correlates with the volume of the droplet.

In the embodiment, the control device 15 has been described as changing the control parameters irregularly, but the control parameters may be changed so that each nozzle 331 has a different periodicity.

In the embodiment, a single nozzle row consisting of a plurality of nozzles 331 was formed in the head portion 301 of the inkjet head 30, but a plurality of nozzle rows may be formed. Further, a plurality of nozzles 331 may be arranged in a staggered manner on the head portion 301. When the plurality of nozzles 331 are formed in a staggered manner, it is easier to narrow the interval between droplet landing positions in the Y-axis direction.

Further, when a plurality of nozzle rows are formed in the head section 301 of the inkjet head 30, the control device 15 may perform the above-described droplet volume control for each nozzle row, for example.

The printing device 1 may include a plurality of inkjet heads 30.

This can be realized by making various modifications to the above embodiments and modifications that those skilled in the art can think of, or by arbitrarily combining the components and functions of the above embodiments without departing from the spirit of the present disclosure. The present disclosure also includes forms in which:

According to one aspect of the present disclosure, it is possible to provide a printing device that can suppress printing unevenness.

The present disclosure can be suitably applied to a semiconductor laser element in which a protective layer is disposed on the laser light emitting end face side.

1 Printing device 15 Control device 20 Inkjet stage 30 Inkjet head 40 Droplet observation device 50 Landed droplet observation device 60 Ink van 151 Storage section 152 Input section 153 Display section 154 CPU
200 Base 204A Linear motor 204B Linear motor 205A Linear motor 205B Linear motor 220A Pedestal 220B Pedestal 221A Servo motor 221B Servo motor 230A First slide unit 230B Second slide unit 240 Control section 300 Main body section 301 Head section 304 Servo motor 310 control part 320 Head main body 321 Liquid chamber 330 Nozzle plate 331 Nozzle 340 Vibration plate 350 Piezoelectric element 402 Droplet observation camera 404 Cable 410 Control section 501 Photographing unit 510 Control section 520 Display panel 521 Line area (coating target area)
600 Display panel 601 Cell area (coating target area)
700 Control table ST Fixed stage

Claims (10)

1. an inkjet head having multiple nozzles;
   Control for ejecting ink from each of the plurality of nozzles to a plurality of target positions arranged in a scanning direction in which the inkjet head moves relative to the printing object and set for each of the plurality of nozzles. comprising a device;
   The control device changes the ink ejection amount for each of the plurality of target positions within a predetermined tolerance range from a reference ejection amount set for each of the plurality of nozzles.
   Printing device.
2. The control device irregularly changes the ejection amount of the ink for each of the plurality of target positions.
   The printing device according to claim 1.
3. The plurality of target positions include a first target position and a second target position,
   In the first target position and the second target position, the difference value between the reference discharge amount and the actual discharge amount is different;
   The printing device according to claim 1 or 2.
4. The control device selects one of a plurality of different addition/subtraction signals and performs addition/subtraction processing on the control parameter corresponding to the reference ejection amount for each of the plurality of target positions to determine the ink ejection amount. decide,
   The printing device according to claim 1 or 2.
5. The control device causes the ink to be ejected from the plurality of nozzles so that the flying speed of the ink is 3 m/s or more and 8 m/s or less.
   The printing device according to claim 1 or 2.
6. When ejecting the ink multiple times toward the same target position, the control device determines the total amount of ink ejected to each of the plurality of target positions based on the amount of ink already ejected to each of the plurality of target positions. changing the ejection amount of the ink for each of the plurality of target positions so that it falls within a predetermined tolerance range from the total reference ejection amount to be ejected to each of the target positions;
   The printing device according to claim 1.
7. The control device causes different types of ink to be ejected toward the same target position.
   The printing device according to claim 6.
8. The control device changes a combination of a plurality of different adjustment signals, which are options for determining the ejection amount, based on the amount of ink already ejected to each of the plurality of target positions.
   The printing device according to claim 6 or 7.
9. The plurality of target positions include a plurality of third target positions and a plurality of fourth target positions having a different arrangement from the plurality of third target positions,
   The allowable range from the reference ejection amount for the plurality of third target positions is different from the allowable range from the reference ejection amount for the plurality of fourth target positions.
   The printing device according to claim 1 or 2.
10. A printing method in which ink is ejected from the plurality of nozzles using an inkjet head that has a plurality of nozzles and moves in a scanning direction relative to a printing target, the method comprising:
    At a plurality of target positions arranged in the scanning direction and set for each of the plurality of nozzles, ink is ejected within a predetermined tolerance range from the reference ejection amount set for each of the plurality of nozzles. Determine the ink ejection amount so that the ejection amount changes,
    ejecting ink from each of the plurality of nozzles based on the determined ejection amount;
    Printing method.

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