JP7122663B2 - PRINTING METHOD, PRINTING APPARATUS, EL AND SOLAR CELL MANUFACTURING METHOD - Google Patents

Description

The present disclosure relates to a printing method for printing using an inkjet head, a printing apparatus, an EL, and a method for manufacturing a solar cell.

At present, vapor deposition is the mainstream method of manufacturing organic EL (Electro Luminescence) displays. On the other hand, in order to reduce costs, an inkjet printing apparatus (hereinafter referred to as an inkjet apparatus), which does not require a vacuum and has high material utilization efficiency, is used to form the light-emitting layers and sealing films of organic EL displays. It is being considered to form

In general, when an organic EL display is manufactured using an inkjet device, ink of each color is ejected from nozzles of an inkjet head to pixels separated by partitions called banks to form functional films in the pixels. Since the organic EL emits more light in accordance with the volume of the ink, the smaller the variation in the amount of ink filled in the pixels, the more the color unevenness of the display is reduced. A high-quality organic EL display can be manufactured by reducing this color unevenness.

On the other hand, organic EL displays tend to have finer pixels due to higher resolution and higher definition. As pixels become finer, the pattern pitch applied by the inkjet head becomes narrower. Therefore, it is necessary to perform highly precise control so that the amount of ink ejected from the nozzles (hereafter referred to as ejection volume) is small and uniform. There is Therefore, a method of improving resolution by using an inkjet device in which a plurality of inkjet heads are stacked is used.

However, the discharge amount from each nozzle may differ due to volume variations among the nozzles. In particular, in an inkjet device in which a plurality of inkjet heads are stacked, the amount of ink ejected from one nozzle is very small, so the variation in the amount of ink ejected is relatively large.

In this case, even if ink is ejected from each nozzle the same number of times in order to fill each pixel with the same amount of ink, a difference in final ink fill amount occurs due to variations in volume between nozzles. Specifically, a difference in filling amount occurs between a line of pixels formed by the same nozzle set and a line of pixels formed by a different nozzle set. The difference in the filling amount leads to the occurrence of streak-like color unevenness (hereinafter referred to as streaky unevenness), which causes deterioration in the quality and yield of displays.

A similar problem arises when a sealing film for an organic EL display is manufactured by an inkjet device.

In the production of sealing films, photocurable ink is applied to a workpiece (printing medium) using an inkjet device, and the ink is cured by irradiating the applied ink film with light rays such as ultraviolet light. forming a sealing film; In this case, ink with a constant viscosity is used so as not to excessively wet and spread to areas other than the necessary areas. Therefore, it takes time for the ink ejected from a predetermined nozzle and adhering to the work to combine with the ink ejected from other nozzles having different ink volume and spread to the same height. Therefore, if the hardening process is performed before a sufficient time has passed after the application, streaky unevenness due to the above-described variations in the volume of the nozzles will occur.

A method for reducing such uneven streaks is disclosed in, for example, Patent Document 1. The method of Patent Document 1 is a method of varying the volume of the lines of the ejection pattern formed by the same nozzle set by randomly changing the number of times of ejection for each pixel in the lines of the ejection pattern formed by the same nozzle set.

In this method, when the amount of ink ejected from the nozzles is sufficiently small relative to the amount of ink required for each pixel (for example, when the amount of ink ejected is about 1/100 of the amount of ink charged), streaky unevenness occurs. can be prevented.

Japanese Patent No. 5157348

However, in the method of Patent Document 1, when the amount of ink ejected from a nozzle is larger than the amount of ink required for each pixel to be filled (for example, when the amount of ink ejected is 1/10 or more of the amount of ink to be filled), the pixel If the number of ejections is changed each time, the change in the amount of ink per ejection becomes relatively large. As a result, grainy unevenness occurs, which greatly affects the image quality of the display.

An object of one aspect of the present disclosure is to provide a printing method, a printing apparatus, an EL, and a method for manufacturing a solar cell that can improve the effect of reducing unevenness in printing.

A printing method according to one aspect of the present disclosure is a printing method for ejecting droplets from nozzles of an inkjet head and applying the droplets to a plurality of cells of a print target medium, wherein the cells are A first droplet application step of applying the first droplet to a fixed position within the cell, and a plurality of set areas set in one cell, in areas other than the application position of the first droplet a second droplet applying step of applying a second droplet to a certain set area , wherein in the second droplet applying step, the application position of the second droplet is changed for each cell.

A printing apparatus according to an aspect of the present disclosure includes an inkjet head that ejects the droplets from a nozzle so that the droplets are applied to a plurality of cells of a print target medium, and the plurality of cells. a first control for controlling the inkjet head to apply a first droplet for restricting the flow of the second droplet; a control unit that performs second control for controlling the inkjet head to apply the second droplet to a set area that is an area other than the droplet application position, the control unit comprising: When performing the second control, the inkjet head is controlled so as to change the application position of the second droplet for each cell.

Using the printing method described above, a method of manufacturing an EL is used.

According to the present disclosure, it is possible to improve the effect of reducing print unevenness.

Schematic diagram showing an example of a print pattern when printing using a conventional inkjet printing method A diagram showing the volume of droplets ejected from each nozzle in a conventional inkjet printing method FIG. 2 is a diagram showing the filling volume of each cell when the print pattern shown in FIG. 1 is formed using a conventional inkjet printing method; A schematic diagram showing an example of a print pattern when printing is performed using the printing method of Patent Document 1. FIG. 4 is a diagram showing the filling volume of each cell when the printing pattern shown in FIG. 4 is formed using the printing method of Patent Document 1; A diagram showing the configuration of the printing apparatus of the present disclosure Diagram showing the flow of the printing method of the present disclosure Schematic diagram showing an example of a print pattern when printing is performed using the printing method of the present disclosure Schematic diagram showing a state in which the first droplet of the present disclosure is applied to the flat portion of the substrate Schematic diagram showing a state in which the first droplet of the present disclosure is applied to the concave portion of the substrate AA sectional view of FIG. 9A Schematic diagram showing a state in which the first droplet of the present disclosure is applied to cover the concave portion of the substrate BB cross-sectional view of FIG. 10A Enlarged view of the set area of the present disclosure A diagram showing the filling volume of each cell when the printing pattern shown in FIG. 7 is formed using the printing method of the present disclosure.

(Problems with conventional printing methods)
First, problems in printing by a conventional inkjet printing method will be described with reference to FIGS. 1 to 3. FIG.

FIG. 1 is a schematic diagram showing an example of a print pattern when printing using a conventional printing method. The substrate 101 is a display substrate and an example of a medium to be printed. The cells 102a, 102b, 102c, 103a, 103b, 103c, 104a, 104b, and 104c are recesses separated by partition walls, and become pixels of a display, for example. A droplet 201 is an ink droplet ejected from a nozzle and landed in a cell.

Further, N1 to N21 shown in FIG. 1 are numbers (also referred to as nozzle numbers) indicating respective nozzles of an inkjet head (not shown). Also, in FIG. 1, the dotted lines shown corresponding to the respective nozzle numbers represent the positions of the nozzles. A droplet 201 on the dotted line is a droplet ejected from one of the nozzles N1 to N21 shown corresponding to the dotted line.

Droplets 201 are ejected from nozzles N1 to N6 to the cells 102a, 102b, and 102c. Droplets 201 are ejected from the nozzles N8 to N13 to the cells 103a, 103b, and 103c. Droplets 201 are ejected from nozzles N15 to N20 to the cells 104a, 104b, and 104c.

FIG. 2 is a graph showing the volume of droplets ejected from the nozzles of the nozzle numbers shown in FIG. 1 (hereinafter referred to as ejection volume). FIG. 2 shows a case where the target volume of droplets ejected from each nozzle is 7 pl, and there is a maximum deviation of about 5%.

FIG. 3 shows the volume of droplets filled in each cell (pixel) when the print pattern shown in FIG. 1 is formed using the nozzles having the discharge volumes shown in FIG. 2 (hereinafter referred to as filling volume). It is a table showing

In the table of FIG. 3, the first row represents the cell number, and the first column represents the alphabet of the cell. For example, the number "42.1" in the second row and second column represents the filling volume of the cell 102a. Looking at the table in FIG. 3 in the column direction, it can be seen that the filling volumes are the same. This is because, as shown in FIG. 1, cells perpendicular to the dotted line indicating the nozzle position use the same nozzles and the same print pattern, so the filling volume of each cell is also the same.

On the other hand, in FIG. 3, focusing on the filling volume of each cell in the nozzle arrangement direction (the row direction in FIG. 3), the filling volume differs for each cell. This is because the filling volume differs due to the variation in discharge volume for each nozzle shown in FIG. Such a volume difference between the ejection volume and the filling volume results in a difference in light emission amount in the light emitting layer of the organic EL display, and is visually recognized as streak unevenness.

(Problem of the printing method of Patent Document 1)
Next, problems in printing by the printing method of Patent Document 1 (Japanese Patent No. 5157348) will be described with reference to FIGS. 4 and 5. FIG.

FIG. 4 is a schematic diagram showing an example of a print pattern when printing using the printing method of Patent Document 1. In FIG. In FIG. 4, the same reference numerals are given to the components common to those in FIG.

In FIG. 4, a non-ejection position 202 is a position where droplets are not ejected. The non-ejection positions 202 are randomly selected.

FIG. 5 is a table showing the filling volume of each cell (pixel) when the print pattern shown in FIG. 4 is formed using the nozzles having the discharge volumes shown in FIG. In FIG. 5, unlike FIG. 3, the volume differs for each row. For example, the fill volumes of cells 102a, 102b, and 102c are different. This is because droplets are not ejected at the non-ejection positions 202 shown in FIG.

Therefore, in the printing method of Patent Document 1, when the discharge volume is sufficiently small with respect to the filling volume required for each cell, it is possible to prevent streak unevenness from occurring. However, in this method, since the number of nozzles for ejecting droplets is made different for each cell, the difference in filling volume between cells becomes larger than the ejection amount for one droplet.

For example, as shown in FIG. 5, the filling volume of the cell 102b is 42.1 pl, while the filling volume of the cell 102a is 35.2 pl, resulting in a volume difference of about 20%. When such a large volume difference occurs, for example, in the light-emitting layer of an organic EL display, the difference in the amount of light emitted from each cell results in an image with a grainy appearance, and the display quality deteriorates.

The present disclosure has been devised in view of the problems of the conventional printing method and the problem of the printing method of Patent Literature 1 described above.

(Embodiment of the present disclosure)
Embodiments of the present disclosure will be described below with reference to the drawings. In addition, the same code|symbol is attached|subjected about the component which is common in each figure, and those description is abbreviate|omitted suitably.

FIG. 6A is a diagram showing the configuration of the printing apparatus 1 of this embodiment. FIG. 6B is a diagram showing the flow of the printing method according to the present embodiment performed by the printing apparatus 1. As shown in FIG. FIG. 7 is a schematic diagram showing an example of a print pattern when printing is performed using the printing method of the present embodiment. In FIG. 7, the same symbols are attached to the same components as in FIG.

The printing apparatus 1 shown in FIG. 6A is an inkjet printing apparatus that executes the printing method shown in FIG. 6B. As shown in FIG. 6A , the printing apparatus 1 includes an inkjet head 10 that ejects ink droplets from a plurality of nozzles, and a controller 20 that controls the inkjet head 10 .

Although not shown, the control unit 20 includes hardware such as a CPU (Central Processing Unit), a ROM (Read Only Memory) storing a computer program, a RAM (Random Access Memory), and a communication circuit. have. Functions of the control unit 20, which will be described later, are realized by the CPU executing a computer program read from the ROM.

The inkjet head 10 has nozzles N1 to N21, for example, as shown in FIG.

The control unit 20 controls the inkjet head 10 so that the first droplet applying step S301 and the second droplet applying step S302 shown in FIG. 6B are executed in this order.

The first droplet applying step S301 is a step of applying a first droplet 203 on the substrate 101 as shown in FIG. 7 to create a base point (anchor) for fixing the droplet. In this step, the controller 20 controls the inkjet head 10 to apply the first droplet 203 onto the substrate 101 .

The second droplet application step S302 is a step of applying a second droplet 205 within the set area 204 of the substrate 101, as shown in FIG. 7, after the first droplet application step S301. In this step, the controller 20 controls the inkjet head 10 to apply the second droplet 205 within the set area 204 .

Details of the first droplet applying step S301 and the second droplet applying step S302 will be described below.

<First droplet application step>
Details of the first droplet applying step S301 will be described.

Substrates commonly used in industrial production, such as glass substrates for displays, do not have ink receptivity. When droplets are applied to such a substrate by an inkjet method, the droplets applied later on the substrate are combined and absorbed by adjacent droplets previously applied to the substrate, and are applied to appropriate positions. A phenomenon that does not occur occurs.

If the distribution of droplets in the cell changes due to the above phenomenon, a difference occurs in the film thickness distribution after the ink is cured, resulting in unevenness. For example, when only the second droplet applying step S302, which will be described later, is performed, depending on the nozzles used in the setting area 204 (see FIG. 7), which will be described later, between the adjacent droplets, the droplets ejected later may come first. The liquid droplets are absorbed by the liquid droplets ejected to the cell, and the distribution of the liquid droplets in the cell becomes uneven, resulting in unevenness.

In this embodiment, the unevenness described above is prevented by performing the first droplet applying step S301 before the second droplet applying step S302. As described above, in the first droplet applying step S301, the first droplet 203 is applied to the substrate 101 as shown in FIG. The first droplet 203 is united with the second droplet applied in the second droplet application step S302. As a result, the distribution of droplets on the substrate 101 can be made uniform as a whole. Below, the droplet applied in the second droplet application step S302 is referred to as a second droplet 205. FIG.

The first droplet 203 is preferably located at at least one edge of the cell, as droplets are less likely to spread to the edges of the cell. Preferably, the first droplets are applied at two diagonal ends of the cell. Furthermore, the end portions at four corners may be used.

As shown in FIG. 7, the first droplet 203 is applied at the same or fixed location in each of the cells 102a-102c, 103a-103c, 104a-104c.

Since the first droplet 203 is combined with the second droplet 205 to form a coating film, a material having a high affinity with the material of the second droplet 205 is preferable.

However, if it is difficult to use a material different from that of the second droplet 205 in terms of product quality, the first droplet 203 is composed of the same material as the second droplet 205 .

As a material of the first droplet 203 and the second droplet 205, for example, ink obtained by dissolving an organic EL material in a solvent and adjusting the viscosity to about 10 CP can be used.

The size relationship between droplets (first droplet 203, second droplet 205) and cells (cells 102a to 102c, 103a to 103c, 104a to 104c) will be described.

For example, when manufacturing a 55-inch 4K display, the cell size is 250 μm wide, 100 μm high, and 2 μm deep, and the cell volume is 50000 μm 3 =50 pl. When droplets of 7 pl per droplet are ejected in a cell of this size with a target filling rate of 80%, about 6 droplets are ejected into the cell.
In the case of an organic EL display, our experiments show that a change in film thickness of 1.6% makes the luminance unevenness visible. Therefore, the method of Patent Document 1 is effective only when the volume of the droplets filled in the cell is at least 50 times the volume of the droplets ejected from the nozzle. On the other hand, in the method of the present invention, the volume of droplets filled in the cell can be used within the range of about 1 to 50 times the volume of droplets ejected from the nozzle.

However, in order to adopt the above coating method, at least three droplets (three times) are required for one cell. Considering the width of the cell, 4 droplets (4 times) are necessary. As a result, at least 3 times or more is necessary, and 4 times or more is preferable. 5 times or more is preferable. And it is up to about 50 times.

Also, when the volume of the first droplet 203 is larger than the volume of the second droplet 205, the first droplet 203 becomes dominant, and the effect of the second droplet applying step S302 is reduced. Therefore, the volume of the first droplet 203 is adjusted to be equal to or less than the volume of the second droplet 205 .

Next, a method of arranging the first droplet 203 will be described.

When the first droplets 203 come into contact with each other and are combined and absorbed, the positions of the second droplets 205 vary and the effect of the first droplets 203 cannot be obtained. Therefore, in order to avoid contact between the first droplets 203, the first droplets 203 are arranged so that the relationship of the following formula (1) holds.

L>Rmax1+Rmax2 (1)
In the above formula (1), L is the distance between the centers of two adjacent first droplets 203, and Rmax1 and Rmax2 are the maximum wetting and spreading distances (see FIGS. 8 to 10).

The maximum wetting and spreading distance is the maximum distance that the first droplet 203 spreads in the direction connecting the center of one first droplet 203 and the center of the other first droplet 203 . The maximum wetting spread distance changes over time. Therefore, the maximum wetting and spreading distance is set to the distance when the first droplet 203 ejected from the inkjet head 10 reaches the maximum wetting and spreading during the time from the moment when the first droplet 203 lands on the substrate 101 until it settles down to the steady state. be.

Next, examples of applying the first droplet 203 to a flat surface or an uneven surface will be described below with reference to FIGS. 8, 9A, 9B, 10A, and 10B.

First, the application example shown in FIG. 8 will be described. FIG. 8 is a schematic diagram showing a state in which two first droplets 203 are applied to the planar portion of the substrate 101. As shown in FIG.

The two first droplets 203 shown in FIG. 8 are adjacent to each other. Further, the wetting and spreading range 203 a is the range where the first droplet 203 wets and spreads when it lands on the substrate 101 .

As can be seen from the circular wetting range 203a shown in FIG. 8, when the first droplet 203 lands on the flat surface of the substrate 101, it spreads evenly in all directions. Therefore, Rmax1 and Rmax2 are equal to the radius when the first droplet 203 spreads out to the maximum extent. Therefore, L shown in FIG. 8 is set to twice or more the radius when the first droplet 203 spreads to the maximum extent. For example, L shown in FIG. 8 is set based on the results of experiments and simulations regarding the presence or absence of bonding between the first droplets 203 .

Next, application examples shown in FIGS. 9A and 9B will be described. FIG. 9A is a schematic diagram showing a state in which two first droplets 203 are applied in the concave portion 105 formed on the substrate 101. FIG. FIG. 9B is a cross-sectional view taken along line AA of FIG. 9A.

As shown in FIGS. 9A and 9B, the recess 105 is formed in a substantially rectangular parallelepiped shape. The volume of the recess 105 is larger than the volume of the two first droplets 203 . Recess 105 is, for example, a cell of a display (eg, cells 102a-102c, 103a-103c, 104a-104c shown in FIG. 7).

When a droplet is applied inside such a recess 105, it is difficult for the droplet to spread to the end of the cell, so the first droplet 203 is applied to the end of the cell as shown in FIG. 9A. At this time, the distance from the edge of the concave portion 105 to the center of the first droplet 203 is arranged so that the relationships of the following formulas (2) and (3) hold.

D1, D2 ≤ Rmax1 (2)
D3, D4 ≤ Rmax2 (3)
In the above formula (2), D1 is the distance between the upper left corner of the recess 105 and the center of the first droplet 203, and D2 is the distance between the lower left corner of the recess 105 and the center of the first droplet 203. . In equation (3), D3 is the distance between the upper right corner of the recess 105 and the center of the first droplet 203, and D4 is the distance between the lower right corner of the recess 105 and the center of the first droplet 203. be.
When the first droplet 203 is ejected so as to satisfy the above formulas (2) and (3), the wetting and spreading range 203a is limited by the edge of the recess 105 as shown in FIG. 9B. Therefore, as shown in FIG. 9A , the first droplet 203 spreads toward the central portion of the recess 105 . As a result, Rmax1 and Rmax2 shown in FIG. 9A are larger than Rmax1 and Rmax2 shown in FIG. Therefore, L shown in FIG. 9A is set to a larger value than L shown in FIG. For example, L shown in FIG. 9A is set based on the results of experiments and simulations regarding the presence or absence of bonding between the first droplets 203 .

As described above, the volume of the recess 105 is larger than the volume of the two first droplets 203, and the shape of the recess 105 is not cylindrical. In such a case, it is difficult for the first liquid droplet 203 to enter the end (corner) of the concave portion 105 . Therefore, it is preferable to apply (arrange) the first droplet 203 to the end of the concave portion 105 . Further, when three or more first droplets 203 can be arranged in the recess 105 so as not to contact each other, the first droplets 203 are arranged at both ends of the recess 105, and the first droplets 203 therebetween are arranged. It is preferable to arrange them at regular intervals.

Next, application examples shown in FIGS. 10A and 10B will be described. FIG. 10A is a schematic diagram showing a state in which the first droplet 203 is applied to cover the concave portion 106 formed in the substrate 101. FIG. FIG. 10B is a cross-sectional view taken along line BB of FIG. 10A.

As shown in FIGS. 10A and 10B, recess 106 is formed in a columnar shape. The volume of the recess 106 is smaller than the volume of the two first droplets 203 . The recess 106 is, for example, a contact hole.

When such recesses 106 are provided in the substrate 101, a plurality of first droplets 206 are discharged to the recesses 106 as shown in FIG. 10A.
At this time, the distances from the center of the recess 106 to the centers of the first droplets 206a and 206b are arranged so that the relationship of the following formula (4) holds.
D1, D2 ≤ Rmax1 (4)
In the above formula (4), D1 is the distance between the center of the recess 106 and the center of the first droplet 206a, and D2 is the distance between the center of the recess 106 and the center of the first droplet 206b.
Thereby, the recess 106 is filled with the first droplet 206 .

At this time, the first droplets 206 a and 206 b overflow from the recess 106 and spread over the surface of the substrate 101 . A wetting and spreading range 206c shown in FIGS. 10A and 10B is a range where the first droplets 206a and 206b wet and spread.

Therefore, the wetting and spreading ranges 203 a and 206 c on the plane portion of the substrate 101 change according to the volume of the recess 106 and the number of ejections of the first droplets 206 . Therefore, L shown in FIG. 10A and the number of ejection times of the first droplet 206 are set so that the wetting and spreading range 203a of the first droplet 203 and the wetting and spreading range 206c of the first droplets 206a and 206b do not come into contact with each other. be. For example, L shown in FIG. 10A is set based on the results of experiments and simulations regarding the presence or absence of bonding between the first droplet 203 and the first droplet 206 .
Here, the contact hole, which is the concave portion 106, is filled with the first droplet 206 first because the inner side thereof is likely to be unwet. If two droplets of the first droplet 206 are injected into the center of the concave portion 106, the concave portion 106, which is a contact hole, can be filled. difficult. For this reason, the center of the contact hole, which is the concave portion 106, is set and applied within a range where the first droplet spreads.

<Second Droplet Application Process>
Details of the second droplet applying step S302 will be described.

As described above, the second droplet applying step S302 is performed after the first droplet applying step S301, and as shown in FIG. be.

As shown in FIG. 7, the setting area 204 is set at the same cell position in each of the cells 102a to 102c, 103a to 103c, and 104a to 104c.

First, the setting area 204 shown in FIG. 7 will be described using FIG. FIG. 11 is an enlarged view of one of the plurality of setting areas 204 shown in FIG.

In the example of FIG. 11, nozzle groups 207 are set for the setting area 204 . The nozzle group 207 is nozzles capable of ejecting the second liquid droplets 205 onto the set area 204 . In the example of FIG. 11, the nozzle group 207 includes four nozzles N1 to N4.

In the second droplet application step S302, one nozzle is randomly selected from the nozzle group 207 and used. For example, when the N1 nozzle is selected and the second droplet 205 is ejected from that nozzle, the second droplet 205 is applied to the set area 204 as shown in FIG.

Further, in the second droplet application step S302, a nozzle to be used is selected for each setting region 204 based on a random number table prepared in advance. Therefore, for example, as shown in FIG. 7, even if the arrangement of the set regions 204 of the cells 102a, 102b, and 102c is the same, the combinations of selected nozzles are different. For example, in FIG. 7, nozzles N1, N2, N5, and N5 are selected in the setting area 204 of the cell 102a, nozzles N1, N3, N4, and N4 are selected in the setting area 204 of the cell 102b, and nozzles N1, N3, N4, and N4 are selected in the setting area 204 of the cell 102c. In the setting area 204, nozzles N2, N2, N4, and N5 are selected. That is, the nozzles are selected so that the application position (landing position) of the second droplet 205 within the setting region 204 changes for each cell.

Note that the number of randomly selected nozzles is not limited to one. Two or more nozzles may be randomly selected, depending on the amount of droplets required.

Next, a method for setting the setting area 204 will be described with reference to FIG.

As an example, a case of setting the setting area 204 in the cell 102a of FIG. 7 will be described.

First, the volume V of ink required to fill the inside of the cell 102a is obtained by the following equation (2). In equation (2), S is the area of the cell 102a and T is the target film thickness.

V=S×T (2)
Next, the number Nrand of the second droplets 205 in the cell 102a is obtained by the following formula (3). In Equation (3), V is the volume of ink required to fill the cell 102a calculated by Equation (2) above. Also, in equation (3), Vanc is the average volume of the first droplets 203 , Nanc is the number of the first droplets 203 in the cell 102 a , and Vrand is the average volume of the second droplets 205 .

Nrand=(V−Vanc×Nanc)/Vrand (3)
Next, the setting area 204 is set so as to satisfy the following formula (4). In equation (4), Nrand is the number of second droplets 205 in cell 102a calculated by equation (3) above. Also, in Expression (4), N is the number of nozzles capable of discharging within the set area 204 .

N>Nrand (4)
Here, the relationship between N in one cell and the setting area 204 will be described with reference to FIG.

FIG. 11 shows a state in which one second droplet 205 exists within the set area 204 . FIG. 11 also shows that the nozzles capable of ejecting within the set region 204 are four nozzles N1, N2, N3, and N4 included in the nozzle group 207. FIG.

The setting area 204 is set in the nozzle arrangement direction (horizontal direction in the figure) as shown in FIG.

In FIG. 7, a plurality of setting regions 204 described with reference to FIG. 11 are set in each cell so that the above formula (4) is satisfied. Note that the number N of nozzles capable of ejecting ink within the set region 204 is preferably twice or more than Nrand.

Further, the position of the setting region 204 may be set so that the landing position of the second droplet 205 and the landing position of the first droplet 203 in the setting region 204 do not overlap from the viewpoint of film thickness uniformity. preferable. However, if the landing position of the second droplet 205 cannot be secured sufficiently, the landing position of the first droplet 203 and the set area 204 may be set so as to overlap.

The details of the first droplet applying step S301 and the second droplet applying step S302 have been described above.
In FIG. 7, one cell has four setting areas 204 . There are two types of setting areas 204, one for two droplets and one for three droplets. This is to increase the number of combination patterns of nozzles used in the cell and to make it a plurality of types.
A setting area 204 for ejecting one droplet with two nozzles and a setting area 204 for ejecting one droplet with three nozzles are provided.
<Evaluation>
Next, the result of performing the printing method shown in FIG. 6B will be described using FIG.

FIG. 12 is a table showing the fill volume of each cell (pixel) when the print pattern shown in FIG. 7 is formed by the printing method shown in FIG. 6B using the nozzles having the discharge volumes shown in FIG. is.

The fill volume of each of the cells 102a, 102b, 102c shown in FIG. 12 is not uniform like the fill volume of each of the cells 102a, 102b, 102c shown in FIG. This is because the set area 204 is randomly set for each cell, and the filling volume varies for each cell. Therefore, the streak unevenness described with reference to FIG. 3 is not observed.

Further, as described above, in the printing method shown in FIG. 6B, unlike the printing method of Patent Document 1, the number of nozzles for ejecting liquid droplets cannot be varied for each cell. Therefore, the difference in filling volume between cells is equal to or less than the discharge amount for one droplet.

For example, as shown in FIG. 12, the fill volume of cell 102b is 42.5 pl, while the fill volume of cell 102a is 42.0 pl, a difference of less than 2%. As described above, the printing method of Patent Document 1 causes a volume difference of about 20%, so the printing method of the present embodiment can considerably reduce the difference in filling volume. Therefore, for example, in the light-emitting layer of an organic EL display, since the difference in the amount of light emitted from cell to cell is small, the image quality is free from graininess and the display quality is not deteriorated.

As described above, in the present embodiment, even when the ink ejection amount (ejection volume) from the nozzles of the inkjet head is relatively large with respect to the ink filling amount (filling volume) required for each pixel, It is possible to reduce printing unevenness (for example, streaky unevenness) due to volume variations, and to improve the product yield.

Further, when an organic EL display is manufactured using the printing method of the present embodiment, it is possible to improve the printing quality of the luminescent layer and the sealing film of the display.

The printing method of this embodiment can be applied not only to the case of applying droplets in the cells of the substrate, but also to the case of forming a film on the flat surface of the substrate or forming a film covering the uneven surface of the substrate. It is possible. In that case, for example, the process shown in FIG. 6 may be repeated by installing the inkjet head 10 or a plurality of nozzles of the inkjet head 10 in the print scanning direction. As a result, it is possible to shorten the leveling time required for making the unevenness of the film surface uniform, thereby shortening the takt time.

It should be noted that the present disclosure is not limited to the description of the above embodiments, and various modifications are possible without departing from the scope of the present disclosure.

For example, in the above embodiments, the explanation was given on the premise that cells exist, but the present disclosure can also be applied when there are no cells. That is, it can also be used to form a solid film (one uniform film) on the substrate 101 .

For example, when forming one film on the entire surface of the substrate 101, the above-described method of the present disclosure can be used. In this case, the method of the present disclosure described above is used assuming that there are no cells, but there are multiple virtual cells.

A virtual cell is a virtual cell that does not actually exist, but is assumed to exist. A more uniform film can be formed by setting a large number of virtual cells and setting a small size for each virtual cell. A droplet is applied in the virtual cell, and finally, the droplet spreads and the whole is connected to form one flat film.

This method can form a uniform film without unevenness on a flat surface, so it can be used to form films such as the hole transport layer, organic semiconductor active layer, and electron transport layer of coating-type solar cells such as perovskite solar cells. available for

This method is particularly effective when the droplet 201 has a high viscosity. This is because even if there is no cell, the range in which the droplet 201 spreads is limited.

In the embodiment, as shown in FIG. 7, the size of the droplet applied to the cell is smaller than the droplets shown in FIGS. In the embodiment, although the droplets are small, a uniform film can be formed by applying the first droplet and the second droplet.

INDUSTRIAL APPLICABILITY The printing method and the printing method of the present disclosure are useful for all techniques for applying liquid droplets to an object using an inkjet method.

1 printing device 10 inkjet head 20 control unit 101 substrate 102a, 102b, 102c, 103a, 103b, 103c, 104a, 104b, 104c cell 105, 106 concave portion 201 droplet 202 non-ejection position 203, 206, 206a, 206b first liquid Droplet 203a, 206c Wetting and spreading range 204 Setting area 205 Second droplet 207 Nozzle group

Claims (11)

A printing method for ejecting droplets from nozzles of an inkjet head and applying the droplets to a plurality of cells of a print target medium,
a first droplet applying step of applying a first droplet to the plurality of cells at fixed positions within the cells;
a second droplet applying step of applying a second droplet to a plurality of set areas set in one cell, which are areas other than the application position of the first droplet. ,
In the second droplet applying step, the application position of the second droplet is changed for each cell,
printing method. In the first droplet applying step,
applying the first droplet to at least one end of the cell;
The printing method according to claim 1. In the first droplet applying step,
applying a plurality of the first droplets to recesses provided in the print target medium;
The printing method according to claim 1 or 2. the application positions of the first droplets in the plurality of cells are the same;
The printing method according to any one of claims 1 to 3 . the positions of the setting regions in the plurality of cells are the same;
The printing method according to any one of claims 1 to 4 . wherein the plurality of cells are a plurality of virtual cells;
The printing method according to any one of claims 1 to 5 . The printing method according to any one of claims 1 to 6 , wherein the volume of the first droplet is equal to or less than the volume of the second droplet. 8. The printing method according to any one of claims 1 to 7 , wherein a plurality of said first droplets are applied to one said cell, but said first droplets do not contact each other. an inkjet head that ejects the droplets from a nozzle so that the droplets are applied to a plurality of cells of a print target medium;
a first control for controlling the inkjet head to apply a first droplet to the plurality of cells to restrict the flow of a second droplet applied later; and a plurality of settings within one of the cells. a second control for controlling the inkjet head to apply the second droplet to a set area other than the application position of the first droplet. and
The control unit
When performing the second control, controlling the inkjet head so as to change the application position of the second droplet for each cell;
printer. A method for manufacturing an EL by the printing method according to any one of claims 1 to 8 . A method for manufacturing a solar cell by the printing method according to any one of claims 1 to 8 .

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