Recording device

Abstract

To suppress disposal of unnecessary ink.SOLUTION: A recording device includes a recording head which discharges ink containing a luminescent material for recording, a circulation flow passage formation part forming a circulation flow passage which re-circulates to the recording head, the ink passing through the recording head, to the recording head, and detection means which optically detects a condition of functionality related to light emission of the ink circulating in the circulation flow passage.SELECTED DRAWING: Figure 4

Description

Technical Field

[0006] , ,

[0005] , ,

[0001] The present invention relates to a recording apparatus.

Background Art

[0002] In an inkjet recording apparatus, it is known to recover ejection performance by performing recovery operations such as a flushing operation, a pressurizing operation, and a suction operation on a recording head. Further, Patent Document 1 proposes a recording apparatus that reuses the ink discharged from the recording head during such a recovery operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a recording apparatus, a functional ink containing a light-emitting material may be used. Such ink deteriorates when it comes into contact with moisture or oxygen in the air. Therefore, for example, the ink near the nozzles in the recording head or the ink discharged from the recording head by the recovery operation as performed in the above prior art tends to deteriorate relatively easily.

[0005] [[ID=зо]]If recording is performed using ink that has deteriorated, there is a risk that the recorded matter may not exhibit desired performance. Therefore, it is necessary to discard the ink that has deteriorated. On the other hand, if ink that has not deteriorated as much as necessary is discarded, there is a risk that it will lead to an increase in the consumption of ink.

[0006] The present invention provides a technique capable of suppressing the disposal of unnecessary ink.

Means for Solving the Problems

[0007] According to the present invention, A recording head that ejects ink containing a light-emitting material to perform recording, A circulation channel forming unit that forms a circulation channel for circulating the ink that has passed through the recording head back to the recording head, The system includes a detection means for optically detecting the functional state of the ink circulating in the aforementioned circulation channel, which relates to the emission of light. A recording device characterized by the above is provided. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the waste of unnecessary ink. [Brief explanation of the drawing]

[0009] [Figure 1] (a) and (b) are schematic diagrams showing the configuration of a recording device according to one embodiment. [Figure 2] A control block diagram showing the control configuration of a recording device according to one embodiment. [Figure 3] (a) and (b) are schematic diagrams showing the configuration of a recording head and a retrieval unit according to one embodiment. [Figure 4] A diagram illustrating the configuration of the ink flow path in a recording device according to one embodiment. [Figure 5] A schematic diagram showing the configuration of the detection unit according to one embodiment. [Figure 6] A diagram showing the relative irradiation intensity of the inspection light from the detection unit according to one embodiment. [Figure 7] A flowchart illustrating an example of CPU processing according to one embodiment. [Figure 8] A flowchart illustrating an example of CPU processing according to one embodiment. [Figure 9] A flowchart illustrating an example of CPU processing according to one embodiment. [Figure 10] This figure shows the relationship between the absorption spectrum of the UV curing initiator and the emission spectrum of the test light in the examples and comparative examples. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] [First Embodiment] <Overview of the recording device> Figures 1(a) and 1(b) are schematic diagrams showing the configuration of a recording device 1 according to one embodiment. Figure 1(a) is a top view of the recording device 1, and Figure 1(b) is a side view of the recording device 1. For convenience, only the parts of the recording device 1 necessary for explaining this embodiment are shown. The ink supply system and recovery system mechanism will be described later.

[0012] Recording device 1 is an inkjet type recording device. Recording device 1 in this embodiment performs recording by ejecting functional ink onto the substrate 11.

[0013] Functional ink refers to a liquid containing a functional material. In this embodiment, the functional ink includes a light-emitting material such as a phosphorescent material or a fluorescent material as the functional material. Such a functional ink can be used, for example, to form an organic light-emitting layer or a quantum dot color conversion layer used in an organic EL (Electro-Luminescence) display. For example, in the formation of an organic light-emitting layer, a color display is formed by forming an organic light-emitting layer using organic light-emitting materials that emit light in red, green, and blue. In this embodiment, the functional ink also includes an ultraviolet curing initiator. The substrate 11 is, for example, a glass substrate, but it may be another substrate such as a film substrate, or it may be paper or other sheet-like recording media. In other words, the recording object of the recording device 1 is not particularly limited. In the following, functional ink may be simply referred to as ink.

[0014] The recording apparatus 1 includes a recording head 2, a scanning mechanism 4, a base 9, and a stage 10.

[0015] The recording head 2 performs recording by discharging ink onto a substrate 11. Although details will be described later, a plurality of nozzles 3 (see FIG. 3(a)), not shown, are arranged in a direction facing the substrate 11 on the recording head 2. A pressure generating unit (not shown), which utilizes deformation of a piezo element or film boiling of a heating element, is connected to the nozzle 3, and ink inside the nozzle is discharged thereby. In the present embodiment, as will be described later, the nozzles 3 are arranged on a recording chip 100.

[0016] The scanning mechanism 4 is a mechanism capable of scanning the recording head 2 in the horizontal direction (XY direction). The scanning mechanism 4 includes a main scanner 5 on which the recording head 2 is mounted, a main scanning guide rail 6 that guides the main scanner 5 along the main scanning direction (Y direction), and a sub-scanning guide rail 7 that guides the main scanning guide rail 6 along the sub-scanning direction (X direction). By the scanning mechanism 4, the recording head 2 can freely scan within a plane parallel to the XY plane. For example, the main scanner 5 is movable in the main scanning direction with respect to the main scanning guide rail 6 by a drive source (not shown) such as a motor, and the main scanning guide rail 6 is movable in the sub-scanning direction with respect to the sub-scanning guide rail 7 by a drive source (not shown) such as a motor.

[0017] The base 9 supports each element of the recording apparatus 1. The stage 10 is fixed on the base 9, and the substrate 11 to be recorded is set thereon. Note that it is sufficient that the recording head 2 and the substrate 11 can move relative to each other, and the recording head 2 may be fixed and the substrate 11 may move. The dashed lines in FIGS. 1(a) and 1(b) conceptually represent the ink path and do not represent a physical connection. Also, although details will be described later, a detection unit 108 is provided in this ink path.

[0018] <Control Configuration> FIG. 2 is a control block diagram showing the control configuration of the recording apparatus 1. For convenience of explanation, in FIG. 2, only the elements related to the description of the present embodiment are shown as a control circuit 300.

[0019] The CPU 301 controls the entire recording device 1. For example, the CPU 301 controls the entire system by reading and executing a program stored in the ROM 302. That is, the information processing by the software stored in the ROM 302 is concretely realized by the CPU 301, which is an example of hardware, so that the control circuit 300 can execute each function. At this time, the CPU 301 loads the program into the RAM 312 and uses it as a working area. That is, the RAM 312 temporarily stores data and input data necessary for the processing executed by the CPU 301. The recovery control unit 304 controls the recovery unit 114 (see Figure 3(a)), etc., to perform the recovery operation of the recording head 2. The transport control unit 303 controls the scanning mechanism 4 to transport the recording head 2.

[0020] Furthermore, the CPU 301 also controls the recording operation by the recording head 2 through the drive circuit 307, the binarization circuit 308, and the image processing unit 309. The image processing unit 309 performs predetermined image processing on the input image data to be recorded. Specifically, the image processing unit 309 performs conversion to RGB image data to be recorded by the recording device 1 based on information such as the pixel size, pixel spacing, and required film thickness for each pixel of the input substrate 11. The binarization circuit 308 performs halftone processing on the multi-level density image data converted by the image processing unit 309, and then converts it to binary data (bitmap data). Then, the drive circuit 307 causes the recording head 2 to eject ink droplets according to the binary data obtained by the binarization circuit 308.

[0021] Furthermore, the CPU 301 controls the circulation of ink in the ink circulation channel, which will be described later, via the circulation control unit 313. Also, the CPU 301 controls the detection of the functional state related to ink light emission by the detection unit 108 via the detection control unit 314.

[0022] <Recording head and retrieval unit> Figures 3(a) and 3(b) are schematic diagrams showing the configuration of the recording head 2 and the recovery unit 114. Figure 3(a) is a top view, and Figure 3(b) is a side view. In this embodiment, the recording head 2 includes a recording unit 113 that ejects ink to perform recording. A recovery unit 114 is provided corresponding to the recording unit 113.

[0023] The recording unit 113 includes a plurality of recording chips 100. Each recording chip 100 has a plurality of nozzles 3 arranged on it. For example, each recording chip 100 may have 256 nozzles 3 arranged in 4 rows. Four recording chips 100 are arranged in a staggered pattern on the recording unit 113. The recording unit 113 is also connected to a flow path 110 for supplying ink. The flow path 110 is formed by flow path forming parts 110a, 120a, and 130a, which are flexible members such as tubes.

[0024] In this embodiment, the recording head 2 is configured to include a recording unit 113, thereby enabling recording operations over a wide range of areas at once. Note that the recording chips 100 constituting the recording unit 113 do not need to be physically coupled to the recording head 2; they may be physically separated.

[0025] The recovery unit 114 recovers the ink ejected from the recording unit 113. The recovery unit 114 includes a cap 114a and a suction pump 114b.

[0026] The cap 114a is a unit for receiving ink discharged from the recording unit 113. The cap 114a is configured to cover the recording unit 113. The shape of each cap 114a corresponds to the shape of the corresponding recording unit 113.

[0027] The suction pump 114b draws ink from the recording unit 113 via the cap 114a. The suction pump 114b is located on the ink flow path 117. The flow path 117 is formed between the cap 114a and the waste ink tank 140. The solenoid valve 116 will be described later.

[0028] <Ink flow path> Figure 4 is a diagram illustrating the configuration of the ink flow path of the recording device 1. In this embodiment, the recording device 1 includes flow paths 110, 117, 118, and 119 as ink flow paths. Hereinafter, these may be collectively referred to as flow paths FP. Flow paths FP are formed from flexible members such as tubes.

[0029] The flow path 110 connects the main tank 101, which contains ink, to the recording head 2. In other words, the flow path 110 is a flow path for supplying ink to the recording head 2. An electromagnetic three-way valve 105, a pressure pump 102, a filter 103, a sub-tank 111, and a negative pressure adjustment unit 112 are provided on the flow path 110.

[0030] The electromagnetic three-way valve 105 is connected to both the flow path 110 and the flow path 118. The electromagnetic three-way valve 105 is configured to switch between two states: one in which ink flowing from the main tank 101 is discharged further downstream of the flow path 110, and another in which ink flowing through the flow path 118 is discharged downstream of the electromagnetic three-way valve 105 in the flow path 110. In between these states, the electromagnetic three-way valve 105 can also be configured to discharge both the ink flowing from the main tank 101 and the ink flowing from the flow path 118 downstream of the electromagnetic three-way valve 105.

[0031] The pressurizing pump 102 supplies ink in the flow path downstream. The filter 103 removes minute foreign matter and other particles contained in the ink. The sub-tank 111 temporarily stores the ink ejected by the recording unit 113. The negative pressure adjustment unit 112 maintains the negative pressure applied to the nozzle 3 of the recording unit 113 appropriately. However, if the negative pressure of the nozzle 3 can be properly managed by a head differential supply system or the like, the negative pressure adjustment unit 112 may be omitted.

[0032] The flow path 117 connects the aforementioned cap 114a to the waste ink tank 140 that contains the waste ink. In other words, the flow path 117 is a flow path for disposing of ink. The aforementioned suction pump 114b and solenoid valve 116 are provided on the flow path 117. The solenoid valve 116 is configured to be switchable between an open state that allows ink flowing from the cap 114a side to flow out to the waste ink tank 140 side and a closed state that restricts the outflow of ink to the waste ink tank 140 side.

[0033] The flow path 118 connects the recording head 2 and the electromagnetic three-way valve 105. Electromagnetic three-way valves 106 and 107 are also provided on the flow path 118. The electromagnetic three-way valve 106 is configured to switch between a state where ink flowing from its upstream side flows downstream (direction A) of the flow path 118 and a state where it flows towards the flow path 119 (direction B). A degassing unit (not shown) may be provided on the flow path 118 to degas the ink flowing into the flow path 110.

[0034] The flow path 119 connects the solenoid three-way valve 106 and the solenoid three-way valve 107 to the flow path 118 via a separate route. That is, the flow path 119 branches off from the flow path 118 and rejoins the flow path 118. A detection unit 108, which will be described later, is provided on the flow path 119.

[0035] In this embodiment, a circulation channel FP1 is formed by a portion of the flow channel 110 (the portion from the electromagnetic three-way valve 105 to the recording head 2), a flow channel 118, and a flow channel 119, which circulate the ink that has passed through the recording head 2 back to the recording head 2. Therefore, the members forming the flow channels 110, 118, and 119 constitute a circulation channel forming section that forms the circulation channel FP1.

[0036] In this embodiment, the circulation channel FP1 includes a channel 119 where the detection unit 108 is provided, and a bypass channel (the portion of the channel 118 between the electromagnetic three-way valve 106 and the electromagnetic three-way valve 107) that bypasses the detection unit 108. The electromagnetic three-way valves 106 and 107 are configured to allow switching between a circulation state in which the ink circulating in the circulation channel FP1 passes only through channel 119 and a circulation state in which the ink circulating in the circulation channel FP1 passes only through the bypass channel. This makes it possible to prevent the ink from passing through the detection unit 108 when detection by the detection unit 108 is not performed. It is also possible to adopt a configuration in which all the ink circulating in the circulation channel FP1 passes through the detection unit 108 without providing such a bypass channel in the circulation channel FP1.

[0037] Furthermore, in this embodiment, the ink discharged to the cap 114a can be discharged downstream by operating the solenoid valve 116 and the suction pump 114b in an appropriate combination. Note that the recording unit 113 included in the recording head 2 uses the same type (same color) of ink, and if multiple types (multiple colors) of ink are to be used, multiple recording heads with similar configurations can be prepared. In the following description, we will assume that a single type (same color) of ink is used.

[0038] <Detection Unit> Figure 5 is a schematic diagram showing the configuration of the detection unit 108. The detection unit 108 optically detects the functional state related to the light emission of ink ejected from the recording head 2 (recording unit 113). The detection unit 108 includes a light irradiation unit 120, a measurement cell 121, and a light receiving unit 122.

[0039] The irradiation unit 120 irradiates the ink with inspection light. In this embodiment, the inspection light irradiated by the irradiation unit 120 is selected to have a wavelength that allows the light-emitting material of the irradiated ink to change color or emit light. The wavelength of the inspection light will be described later.

[0040] The measurement cell 121 is a cell filled with a certain amount of ink to be inspected. The ink filled in the measurement cell 121 changes color or emits light when it receives inspection light emitted from the irradiation unit 120.

[0041] The light-receiving unit 122 receives light from the ink in the measurement cell 121 and detects its intensity. In this embodiment, the light-receiving unit 122 spectrally separates the light from the ink in the measurement cell 121 by wavelength and detects the intensity of the spectrally separated light. Any known light-receiving unit can be used as appropriate. For example, a general spectrophotometer may be used as the light-receiving unit 122, or a combination of a bandpass filter and a general measuring instrument capable of measuring light intensity may be used. In the detection unit 108 illustrated in Figure 5, the irradiation unit 120 and the light-receiving unit 122 are arranged for transmission measurement, but the light-receiving unit 122 may be arranged in a direction perpendicular to the direction of the optical axis of the irradiation unit 120. In other words, the detection unit 108 only needs to be capable of detecting the state of the functional ink.

[0042] In this embodiment, the state of the ink circulating in the circulation channel FP1 can be detected by the detection unit 108. This makes it possible to obtain information necessary to decide whether or not to discard the ink, and based on this information, it becomes possible to suppress the disposal of unnecessary ink.

[0043] <Wavelength of inspection light> As described above, in this embodiment, the state of the ink discharged from the recording unit 113 is detected by the detection unit 108. Now, in the recording device 1, ultraviolet-curable ink containing an ultraviolet curing initiator may be used. Compared to thermosetting ink, ultraviolet-curable ink can form a thicker film layer with a single inkjet application. On the other hand, the ultraviolet curing initiator starts curing when it absorbs ultraviolet light of a predetermined wavelength. Therefore, depending on the wavelength of the inspection light irradiated by the irradiation unit 120 of the detection unit 108, there is a risk that the reaction of the ultraviolet curing initiator will proceed and the ink will become thicker when the state of the ink is detected by the detection unit 108.

[0044] In more detail, if the ink becomes thicker due to the inspection light from the detection unit 108, the inspected ink must be discarded, incurring disposal costs. Furthermore, it is conceivable that the thickened ink may diffuse, increasing the viscosity of the ink throughout the entire flow path, potentially leading to the need to discard all the ink in the circulation flow path FP1. In other words, while the detection unit 108 detects the functional state of the ink to determine whether or not to discard it, there is a risk that the ink may become thicker due to the inspection light, necessitating ink disposal.

[0045] Therefore, in this embodiment, the wavelength of the inspection light of the detection unit 108 is set so that the relationship is satisfied at the wavelength fx-hwhm, which is obtained by subtracting the half-width at half maximum hwhm from the peak wavelength fx of the inspection light, where the ultraviolet curing initiator is substantially not absorbed. As shown in Figure 6, the peak wavelength fx is the wavelength at which the relative irradiation intensity of the inspection light is maximum. The half-width at half maximum hwhm is the difference between the wavelength at which the relative irradiation intensity is half of the maximum intensity and the peak wavelength fx. In this embodiment, "substantially not absorbed by the ultraviolet curing initiator" means that the ink containing the ultraviolet curing initiator does not thicken even after irradiating the ink with the inspection light for one hour. Furthermore, the specific wavelength of the inspection light may be set in the range of peak wavelength fx 450nm to 490nm. This makes it possible to avoid overlap between the photosensitive wavelength of ultraviolet curing initiators commonly used in inks and the inspection light.

[0046] According to this embodiment, since the overlap between the wavelength range of the inspection light and the photosensitive wavelength of the ultraviolet curing agent contained in the ink can be avoided, the viscosity increase of the ink can be suppressed when the detection unit 108 detects the functional state of the ink.

[0047] <Example of recording device operation> Next, we will explain an example of the operation of the recording device 1, mainly referring to Figure 4. The ink filling and recovery operations will be explained sequentially below.

[0048] (Ink filling operation) First, the CPU 301 commands the recovery control unit 304 to perform the ink filling process. Upon receiving the command, the recovery control unit 304 drives the pressure pump 102 to supply ink from the main tank 101 to the flow path 110. At this time, the solenoid three-way valve 105 is kept in a state where the ink flowing from the main tank 101 flows further downstream in the flow path 110, so that the flow path 110 is filled with ink. During this process, minute foreign matter is filtered out through the filter 103. At this time, the ink supplied from the main tank 101 may be degassed as appropriate using a degassing unit (not shown).

[0049] Furthermore, by providing a sub-tank 111 in the flow path 110, it becomes possible to replace the main tank 101 while the recording unit 113 continues recording even when the main tank 101 is empty. In addition, although the pressurized method of ink filling has been explained here, ink filling by a depressurized method, such as suction with a cap, is also possible.

[0050] (Recovery action) Next, we will explain examples of operations that may be necessary when a recovery operation is required for the nozzle 3 of the recording head 2. Situations that may require a recovery operation include, for example, when the recording head 2 has not been used for a long period of time, when the components of the ink volatilize and viscosity increases near the nozzle. Alternatively, when the recording head 2 is used continuously for recording operations, ink residue or foreign matter may adhere to the nozzle 3 of the recording head 2. In such cases, it is necessary to perform a so-called light recovery operation, such as flushing or wiping, on the nozzle 3 of the recording head 2. On the other hand, if the viscosity of the ink near the nozzle 3 increases or mist adheres to the nozzle 3, the light recovery operation described above may not be sufficient, and a so-called heavy recovery operation may be necessary. An example of a heavy recovery operation is a pressurized recovery operation. That is, by appropriately operating the pressurizing pump 102 and the electromagnetic three-way valve 105 of the flow path 110, the area near the nozzle 3 of the recording unit 113 is pressurized, and ink is discharged onto the cap 114a via the nozzle 3. Another example of a heavy recovery operation is a suction recovery operation. In other words, the recording head 2 and the cap 114a are brought into contact, and the suction pump 114b and the solenoid valve 116 are operated as appropriate to discharge ink from the nozzle 3 by suction.

[0051] In this embodiment, as another method to suppress viscosity increase near nozzle 3, the ink is circulated without remaining near nozzle 3. That is, in this embodiment, the ink near nozzle 3 of the recording head 2 is circulated by the circulation channel FP1. However, even when the ink is circulated, it comes into contact with air in the atmosphere as it passes near nozzle 3 of the recording head 2, so the functional ink containing the aforementioned light-emitting material may deteriorate. If recording is performed using deteriorated ink, the recorded material may not be able to perform as desired, so deteriorated ink must be discarded. On the other hand, if ink that has not deteriorated to the point of needing to be discarded is also discarded, it may lead to an increase in ink consumption. Therefore, in this embodiment, the discarding of unnecessary ink is suppressed by detecting the state of the circulating ink.

[0052] <Example of processing> (Ink disposal) A method for suppressing unnecessary ink waste by detecting the ink status will be explained using Figures 4 and 7. Figure 7 is a flowchart of an example of processing by the CPU 301. This flowchart is implemented, for example, by the CPU 301 reading a program stored in ROM 302 into RAM 312 and executing it. For example, this flowchart is executed at predetermined intervals while the recording device 1 is in operation. Also, for example, this flowchart is executed based on the fact that the power to the recording device 1 has been turned on.

[0053] In S1, the CPU 301 performs ink state detection processing. The CPU 301 commands the detection control unit 314 to perform ink state detection processing. Upon receiving the command, the detection control unit 314 performs detection using the detection unit 108 provided in the flow path 119. The CPU 301 also controls the flow of ink by switching the electromagnetic three-way valves 106 and 107 as needed to ensure that the ink passes through the detection unit 108.

[0054] In S2, the CPU 301 executes a standard determination process. Based on the results of the state detection process in S1, the CPU 301 determines whether the ink meets the standard (hereinafter referred to as standard A) for use in the recording process. For example, the CPU 301 determines whether the functional state of the ink meets standard A based on the degree of ink degradation. The CPU 301 can confirm the degree of degradation based on the change in the detection result by the detection unit 108. Furthermore, the CPU 301 stores the luminescence intensity of the ink at the initial stage of ink filling and can confirm the degree of ink degradation by the difference or ratio between that and the luminescence intensity at the time of the standard determination process. Note that the degree of ink degradation can also be described as the degree of decrease in the functionality of the ink.

[0055] For example, the functionality of the ink color conversion function is tested by setting the initial luminescence intensity (the light intensity detected by the light receiving unit 122) at a wavelength corresponding to the converted color as 100%, and then inspecting the degree of change from there. The CPU 301 may determine that the ink state does not meet standard A if the ratio of the luminescence intensity at the time of the standard judgment process to the initial luminescence intensity falls below 99%. In the following explanation, this ratio of the luminescence intensity at the time of the standard judgment process to the initial luminescence intensity may be referred to as the ink function value. That is, standard A may be an ink function value of 99% or more. However, this standard for the ink function value is an example and may be changed depending on whether to prioritize reducing the amount of ink wasted or maintaining the ink function, etc.

[0056] With a spectrophotometer, you can measure the value around 546 nm when converting to green, and around 640 nm when converting to red. A combination of a bandpass filter and a general measuring instrument capable of measuring light intensity allows you to measure the emission intensity within the wavelength range that includes the wavelengths of each color mentioned above. Furthermore, any general method capable of measuring the intensity and quantum efficiency of the color-converted light can be used.

[0057] In S3, CPU301 terminates the flowchart if it determines that criterion A is met in the criterion determination process in S2; otherwise, it proceeds to S4.

[0058] In S4, the CPU 301 performs ink disposal and refilling. The CPU 301 commands the circulation control unit 313 to dispose of and refill ink from the circulation channel FP1. Upon receiving the command, the circulation control unit 313 operates the cap 114a, suction pump 114b, and solenoid valve 116 as appropriate to discharge the ink circulating in the circulation channel FP1 via the nozzle 3 to the waste ink tank 140. Subsequently, the circulation control unit 313 operates the solenoid three-way valve 105 and pressure pump 102 as appropriate to refill the circulation channel FP1 with ink. Note that ink disposal may involve disposing of almost all of the ink flowing through the circulation channel FP1, or it may involve disposing of a predetermined amount (or a predetermined percentage) of the ink flowing through the circulation channel FP1.

[0059] According to the processing example described above, the decision of whether or not to discard the ink is made according to the detection result of the detection unit 108, thus suppressing the disposal of unnecessary ink.

[0060] Regarding ink disposal, if the detection unit 108 detects a specific area in the circulation channel where deterioration is particularly advanced, control may be implemented to dispose of a larger amount of ink only in the deteriorated area. The CPU 301 may identify areas where ink deterioration is locally advanced by monitoring the detection results of the detection unit 108 for a predetermined period. The predetermined period may be, for example, a period long enough for the ink in the circulation channel FP1 to complete one full circuit. By disposing of a larger amount of ink only in the deteriorated area, the amount of ink to be discarded can be reduced. In addition, to effectively dispose of the deteriorated area, a channel for disposing of the ink may be connected near the downstream side of the detection unit 108.

[0061] (Ink functionality restoration treatment) Figure 8 is a flowchart showing an example of processing by CPU 301. In the example in Figure 7, an example of discarding ink when it no longer meets the standards for use in recording processing was explained. Here, we will explain a process to restore the functionality of the ink when it has deteriorated to a certain extent, before it no longer meets the standards for use in recording processing.

[0062] S11 and S12 are the same processes as S1 and S2 in Figure 7. However, in S12, the CPU 301 also determines whether the ink condition meets criterion B in addition to criterion A mentioned above. Criterion B is, for example, a criterion to confirm that the ink condition has deteriorated to a certain extent, even if it meets the criterion for use in recording processing (criterion A). As an example, criterion A may be set as an ink function value of 99% or higher, and criterion B may be set as an ink function value of 99.5% or higher.

[0063] In S13, CPU 301 proceeds to S14 if it determines that criterion A is met in the criterion determination process in S12, and to S16 otherwise. S16 is the same process as S4.

[0064] In S14, if the CPU 301 determines that criterion B is met in the criterion determination process in S12, it terminates the flowchart; otherwise, it proceeds to S15.

[0065] In S15, the CPU 301 performs an ink functionality restoration process. This process aims to restore the functionality of the ink before it deteriorates to the point where it needs to be discarded, thereby extending the usable period of the ink circulating in the circulation channel FP1. For example, the CPU 301 may appropriately operate the pressure pump 102 and the solenoid three-way valve 105 to supply new ink from the main tank 101 to the circulation channel FP1. Alternatively, some of the ink circulating in the circulation channel FP1 may be discarded by reducing the amount of ink held in the sub-tank 111. By reducing the total amount of ink circulating in the circulation channel FP1, the circulating ink can be consumed as quickly as possible, which can contribute to extending the usable period of the ink. It is also possible to perform both the supply of new ink and the discarding of some of the ink.

[0066] Furthermore, if the ink is heated only near the recording head 2 by a heater (not shown) to adjust the ink viscosity, the ink heating temperature may be lowered as a functional restoration treatment. This suppresses heat-induced degradation of the ink, thereby extending the usable period of the ink circulating in the circulation channel FP1. Also, when lowering the heating temperature, the nozzle 3 needs to eject ink in a high-viscosity state, so the ejection conditions of the nozzle 3 of the recording head 2 may be changed as appropriate.

[0067] (Ink application amount correction process) Figure 9 is a flowchart showing an example of processing by CPU 301. If recording processing is performed when the light-emitting function of the light-emitting material contained in the ink has deteriorated, the light-emitting performance of the output of that recording process (e.g., organic light-emitting layer or quantum dot color conversion layer) will decrease. On the other hand, even if the light-emitting function of the light-emitting material has deteriorated, the light-emitting performance of the output can be maintained by increasing the amount of ink applied. Here, we will explain a process for correcting the amount of ink applied during recording processing when the ink has deteriorated to a certain extent.

[0068] S21 and S22 are the same processes as S11 and S12 in Figure 8. However, in S22, the CPU 301 also determines whether the ink state satisfies criteria A1 and C. Criterion A1, like criterion A, is a criterion for using the ink in the recording process, but it may be set to a lower criterion value than criterion A, for example. Criterion C is a criterion for increasing the amount of ink applied in order to maintain the luminescence performance of the output of the recording process. For example, criterion A1 may be set to an ink function value of 98% or higher, and criterion B may be set to an ink function value of 99% or higher.

[0069] In S23, CPU301 proceeds to S24 if it determines that criterion A1 is met in the criterion determination process in S22, and to S26 otherwise. S26 is the same process as S4.

[0070] In S24, if the CPU 301 determines that criterion C is met in the criterion determination process in S22, it terminates the flowchart; otherwise, it proceeds to S25.

[0071] In S25, the CPU 301 performs ink application amount correction. For example, the CPU 301 may correct the ink application amount so that the greater the decrease in the ink's luminescence intensity at the time of state detection, the greater the increase in the ink application amount. Furthermore, the CPU 301 may correct the ink application amount to compensate for the decrease in the luminescence functionality of the recording object, such as the substrate 11 to which the ink is applied. In other words, if the luminescence function of the luminescent material is degraded, increasing the amount of luminescent material applied can suppress the degradation of the functionality of the output of the recording process (e.g., organic luminescent layer or quantum dot color conversion layer).

[0072] According to this processing example, even if the ink has deteriorated to a certain extent, it can still be used for recording, thus reducing the amount of ink that needs to be discarded.

[0073] <Examples> The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0074] (Example 1) Recording was performed using the recording device 1 according to the above embodiment. The ink was heated to 40°C using a heater (not shown) only near the recording head 2 to adjust its viscosity. The standard for the ink function value (corresponding to standard A in the above embodiment) was set to 99%, and if it fell below 99%, all the ink in the circulation channel FP1 was discarded. The process for discarding the ink followed the flowchart in Figure 7 of the above embodiment. In this case, the amount of ink discarded in one go was 100g.

[0075] In this example, InP / ZnS core-shell type quantum dot 776750 (manufacturing number of Sigma-Aldrich Japan LLC) was used as the quantum dot material. A blue LED NCSB119T (model number of Nichia Corporation) was used as the irradiation light (inspection light). Omnirad 907 (product name of IGM Lesins BV) was used as the ultraviolet curing initiator.

[0076] In Figure 10, the dashed line shows the relative irradiation intensity of the blue LED, and the solid line shows the molar extinction coefficient of the ultraviolet curing initiator (Omnirad 907). The dashed line shows the wavelength obtained by subtracting the half-width at half maximum from the wavelength peak value of the blue LED. As can be seen from the fact that the molar extinction coefficient of Omnirad 907 at this wavelength is less than 0.2% of the peak, it can be said that it is an ultraviolet curing initiator that does not have absorbance characteristics in the wavelength range of the inspection light. By using such an ultraviolet curing initiator, it was possible to understand the degradation state of the quantum dot ink by the detection unit 108 while maintaining a state in which no curing reaction occurs. In other words, in this embodiment, by using such an ultraviolet curing initiator, it was possible to continuously perform the detection unit 108 to check the functional state of the ink without causing ink waste due to inspection by the detection unit 108. Conversely, in this embodiment, it was possible to maintain a state in which no curing reaction occurs by setting the wavelength range of the inspection light to avoid overlap with the absorbance wavelength of the ultraviolet curing agent that is expected to be used.

[0077] (Example 2) The differences from Example 1 are explained below. This example is the same as Example 1 except that the ultraviolet curing initiator contained in the ink is Omnirad 184 (a product name of IGM Lesins BV) instead of Omnirad 907.

[0078] Even with this combination, as shown in Figure 10, the irradiation wavelength of the inspection light and the absorption wavelength of the UV curing initiator do not overlap. Therefore, similar to Example 1, by using such a UV curing initiator, it was possible to understand the degradation state of the quantum dot ink while maintaining a state where no curing reaction occurs.

[0079] (Example 3) The differences from Example 1 are explained below. In this example, after the ink function value fell below 99.3%, the amount of ink held in the sub-tank 111 was reduced to control the amount of ink to be discarded when the entire ink is disposed of. Specifically, in the flowchart of Figure 8 of the above embodiment, reference A was set to an ink function value of 99%, and reference B was set to an ink function value of 99.3%, and as a function recovery treatment, the amount of ink held in the sub-tank 111 was reduced. As a result, the amount of ink to be discarded when the ink function value fell below 99% was 90g. In other words, the amount of ink to be discarded when the functionality of the ink deteriorated and the entire amount of ink circulating in the entire circulation channel FP1 was discarded was reduced. That is, by controlling the amount of ink held in the sub-tank 111, which is an example of a parameter related to ink circulation, the amount of ink to be discarded when the entire ink is discarded was reduced.

[0080] (Example 4) The differences from Example 1 are described below. In this example, when the ink function value fell below 99.5%, the three-way solenoid valve 105 was controlled to supply 10g of new ink and discard 10g of ink into the waste ink tank 140. That is, in the flowchart of Figure 8 of the above embodiment, reference A was set to an ink function value of 99%, and reference B was set to an ink function value of 99.5%, and as a function recovery process, some of the ink in the circulation channel FP1 was discarded. In this case, the ink function value recovered to 99.8%. In other words, this method made it possible to restore the functionality of all the ink circulating in the circulation channel FP1. As a result, it was possible to suppress the complete disposal of the ink circulating in the circulation channel FP1 and reduce the total amount of ink discarded. Note that the amount of ink discarded from the circulation channel FP1 and the amount of ink supplied to the circulation channel FP1 are also examples of parameters related to ink circulation, and by controlling these parameters, it was possible to restore the functionality of the ink circulating in the circulation channel FP1.

[0081] (Example 5) The differences from Example 1 are described below. In this example, if the detected ink function value falls between 98% and 99%, control is performed to increase the amount of ink applied to the substrate according to a pre-set correction table. That is, in the flowchart of Figure 9 of the above embodiment, the reference A1 is set to an ink function value of 98%, and the reference C is set to an ink function value of 99%. This made it possible to lower the reference A1 of the ink function value to 98%. An example of a correction table for the amount of ink applied per nozzle 3 is given below.

[0082] [Table 1]

[0083] While this example illustrates how to correct the ink application amount using a correction table, it is also possible to correct the application amount during ink ejection according to a formula such as the following. Corrected ink application amount (pl) = Uncorrected ink application amount (pl) × (1 / Ink function value (%)) (1)

[0084] (Example 6) The differences from Example 1 are described below. In this example, the ink flow path FP1 was divided into three sections along its length, and the ink function at each section was inspected. If the value of the ink function at one section was 0.3% or more more deteriorated than at another section, the deteriorated ink was circulated back to the print head and discharged under pressure as an example of a function recovery treatment. As a result, it was confirmed that the overall average value of the ink function recovered by 0.1%.

[0085] (Comparative Example 1) The differences from Example 1 are described below. This comparative example is the same as Example 1 except that it does not have a detection unit 108. The ink function value was determined by measuring the luminous efficiency after manufacturing a display device in which the ink was applied to a glass substrate, cured, and various components were assembled.

[0086] After being used for a certain period, some displays fell below the standard for ink performance. The cost incurred during the production of these displays was equivalent to the cost of 500g of ink.

[0087] (Comparative Example 2) The differences from Example 1 are explained below. This comparative example is identical to Example 1 in every respect except that the ultraviolet curing initiator contained in the ink is Omnirad 369 (a product name of IGM Lesins BV) instead of Omnirad 907.

[0088] In this combination, as shown in Figure 10, the irradiation wavelength of the test light and the absorption wavelength of the UV curing initiator overlap. As a result, when the test light was irradiated, the ink underwent a UV curing reaction and became thicker. The tested ink could not be used again, resulting in ink disposal costs.

[0089] (Comparative Example 3) The following will only explain the differences from Example 1. This comparative example is identical to Example 1 in every respect except that the ultraviolet curing initiator contained in the ink is Omnirad TPO H (a product name of IGM Lesins BV) instead of Omnirad 907.

[0090] In this combination, as shown in Figure 10, the irradiation wavelength of the test light and the absorption wavelength of the UV curing initiator overlap. As a result, when the test light was irradiated, the ink underwent a UV curing reaction and became thicker. The tested ink could not be used again, resulting in ink disposal costs.

[0091] As described above, by maintaining a state where the UV curing reaction does not occur while monitoring the degradation state of the quantum dot ink, it becomes possible to use ink that is guaranteed to have a certain level of degradation or less, without unnecessarily discarding ink.

[0092] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0093] [Note] The above embodiments disclose at least the following recording devices. (Item 1) A recording head that ejects ink containing a light-emitting material to perform recording, A circulation channel forming unit that forms a circulation channel for circulating the ink that has passed through the recording head back to the recording head, The system includes a detection means for optically detecting the functional state of the ink circulating in the aforementioned circulation channel, which relates to the emission of light. A recording device characterized by the following features. (Item 2) A recording device as described in item 1, The detection means includes an irradiation unit that irradiates the ink with inspection light and a light receiving unit that receives light from the ink irradiated with the inspection light. A recording device characterized by the following features. (Item 3) A recording device as described in item 2, The ink contains a UV curing initiator. At a wavelength obtained by subtracting the half-width at half maximum from the peak wavelength of the inspection light, the ultraviolet curing initiator is substantially not absorbed. A recording device characterized by the following features. (Item 4) A recording device as described in item 2, The inspection light has a peak wavelength of 450 nm to 490 nm. A recording device characterized by the following features. (Item 5) A recording device described in any one of items 1 to 4, The system further comprises a waste disposal means for discarding ink from the circulation channel based on the aforementioned conditions. A recording device characterized by the following features. (Item 6) A recording device described in any one of items 1 to 5, The system further includes processing means for performing a process to restore the functionality related to the light emission of ink circulating in the circulation channel based on the aforementioned state. A recording device characterized by the following features. (Item 7) A recording device described in any one of items 1 through 6, The system further includes parameter control means for controlling parameters related to ink circulation based on the aforementioned state. A recording device characterized by the following features. (Item 8) A recording device described in any one of items 1 through 7, A first ink tank located outside the aforementioned circulation path, A second ink tank provided on the aforementioned circulation channel, The system further comprises an adjusting means for adjusting the amount of ink stored in the second ink tank based on the aforementioned state. A recording device characterized by the following features. (Item 9) A recording device described in any one of items 1 through 8, The recording device further comprises correction means for correcting the amount of ink applied by the recording head based on the state. A recording device characterized by the following features. (Item 10) A recording device as described in item 9, The correction means corrects the amount of ink applied to compensate for the decrease in the light emission functionality of the recording object to which the ink is applied. A recording device characterized by the following features. (Item 11) A recording device described in any one of items 1 through 10, The system further comprises a supply means for supplying ink to the circulation channel based on the aforementioned state. A recording device characterized by the following features. (Item 12) A recording device described in any one of items 1 through 11, The detection means is provided on the circulation path, A recording device characterized by the following features. (Item 13) A recording device as described in item 12, The circulation path includes a first path on which the detection means is provided, and a second path that bypasses the detection means. The recording device further includes a switching means capable of switching between a first circulation state in which the ink circulating in the circulation channel passes through the first channel and a second circulation state in which the ink circulating in the circulation channel passes only through the second channel. A recording device characterized by the following features. (Item 14) A recording device described in any one of items 1 through 13, The recording head ejects ink used in the quantum dot color conversion layer onto the substrate. A recording device characterized by the following features.

[0094] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0095] 1: Recording device, 2: Recording head, 108: Detection unit, FP1: Circulation channel

Claims

1. A recording head that ejects ink containing a light-emitting material to perform recording, A circulation channel forming unit that forms a circulation channel for circulating the ink that has passed through the recording head back to the recording head, The system includes a detection means for optically detecting the functional state of the ink circulating in the aforementioned circulation channel, which relates to the emission of light. A recording device characterized by the following features.

2. A recording device according to claim 1, The detection means includes an irradiation unit that irradiates the ink with inspection light and a light receiving unit that receives light from the ink irradiated with the inspection light. A recording device characterized by the following features.

3. A recording device according to claim 2, The ink contains a UV curing initiator. At a wavelength obtained by subtracting the half-width at half maximum from the peak wavelength of the inspection light, the ultraviolet curing initiator is substantially not absorbed. A recording device characterized by the following features.

4. A recording device according to claim 2, The inspection light has a peak wavelength of 450 nm to 490 nm. A recording device characterized by the following features.

5. A recording device according to claim 1, The system further comprises a waste disposal means for discarding ink from the circulation channel based on the aforementioned conditions. A recording device characterized by the following features.

6. A recording device according to any one of claims 1 to 5, The system further includes processing means for performing a process to restore the functionality related to the light emission of ink circulating in the circulation channel based on the aforementioned state. A recording device characterized by the following features.

7. A recording device according to any one of claims 1 to 5, The system further includes parameter control means for controlling parameters related to ink circulation based on the aforementioned state. A recording device characterized by the following features.

8. A recording device according to any one of claims 1 to 5, A first ink tank provided outside the aforementioned circulation channel, A second ink tank is provided in the aforementioned circulation channel, The system further includes an adjustment means for adjusting the amount of ink stored in the second ink tank based on the aforementioned state. A recording device characterized by the following features.

9. A recording device according to any one of claims 1 to 5, The recording device further comprises correction means for correcting the amount of ink applied by the recording head based on the state. A recording device characterized by the following features.

10. A recording device according to claim 9, The correction means corrects the amount of ink applied to compensate for the decrease in the light emission functionality of the recording object to which the ink is applied. A recording device characterized by the following features.

11. A recording device according to any one of claims 1 to 5, The system further comprises a supply means for supplying ink to the circulation channel based on the aforementioned state. A recording device characterized by the following features.

12. A recording device according to any one of claims 1 to 5, The detection means is provided on the circulation path, A recording device characterized by the following features.

13. A recording device according to claim 12, The circulation path includes a first path on which the detection means is provided, and a second path that bypasses the detection means. The recording device further includes a switching means capable of switching between a first circulation state in which the ink circulating in the circulation channel passes through the first channel and a second circulation state in which the ink circulating in the circulation channel passes only through the second channel. A recording device characterized by the following features.

14. A recording device according to any one of claims 1 to 5, The recording head ejects ink used in the quantum dot color conversion layer onto the substrate. A recording device characterized by the following features.

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