JP2019188387A - Printing method, printing device, el and solar battery manufacturing method - Google Patents

Abstract

To improve effect of reducing printing unevenness caused by variation in discharge volume for every nozzle.SOLUTION: The printing method in which liquid droplets are discharged from a nozzle of an inkjet head and the liquid droplets are applied to a plurality of cells of a medium to be printed, includes a first liquid droplet application step in which first liquid droplets are applied for restricting flow of second liquid droplets which are applied subsequently, to the plurality of cells and a second liquid droplet application step in which the second liquid droplets are applied to a plurality of set regions in one cell. In the second liquid droplet application step, positions of application of the second liquid droplets are changed for every cell.SELECTED DRAWING: Figure 6B

Description

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

  Currently, in the manufacturing method of an organic EL (Electro Luminescence) display, it is mainstream to use vapor deposition. On the other hand, in order to reduce costs, an organic EL display light-emitting layer or sealing film is used by using an ink jet printing apparatus (hereinafter referred to as an ink jet apparatus) that does not require a vacuum and has high material utilization efficiency. It is being considered to form.

  In general, when an organic EL display is manufactured using an ink jet device, ink of each color is ejected from a nozzle of an ink jet head to a pixel partitioned by a partition called a bank, and a functional film is formed in the pixel. Since the amount of light emitted from the organic EL increases according to the volume of the ink, the color unevenness of the display is reduced as the variation in the amount of ink filled in the pixel is smaller. By reducing this color unevenness, a high-quality organic EL display can be manufactured.

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

  However, the discharge amount from each nozzle may vary depending on the volume variation of each nozzle. In particular, in an ink jet apparatus in which a plurality of ink jet heads are stacked, since the discharge amount from one nozzle is very small, the variation in the discharge amount is relatively large.

  In this case, in order to fill each pixel with the same amount of ink, even if the same number of inks are ejected from each nozzle, a difference occurs in the final ink filling amount due to volume variation for each nozzle. Specifically, a difference in filling amount occurs between a pixel line formed with the same nozzle set and a pixel line formed with a different nozzle set. The difference in the filling amount leads to the occurrence of streak-like color unevenness (hereinafter referred to as streak unevenness), which causes a decrease in display quality and yield.

  Similar problems also occur when an organic EL display sealing film is manufactured by an ink jet apparatus.

  In the production of the sealing film, a photocurable ink is applied to a work (medium to be printed) by an inkjet apparatus, and the ink is cured by irradiating the applied ink film with light rays such as ultraviolet light, A sealing film is formed. In this case, an ink having a certain viscosity is used so that it does not get wet excessively except for the necessary part. For this reason, it takes time for the ink ejected from the predetermined nozzles and attached to the work to combine with the ink ejected from other nozzles having different ejected ink volumes and spread out at the same height. Therefore, when the curing process is performed without sufficient time after application, streak unevenness due to the above-described nozzle volume variation occurs.

  For example, Patent Document 1 discloses a method for reducing such unevenness of muscle. The method of Patent Document 1 is a method of changing the volume of a discharge pattern line formed with the same nozzle set by randomly changing the number of discharges for each pixel in the discharge pattern line formed with the same nozzle set.

  In this method, when the ejection amount from the nozzle is sufficiently small with respect to the ink filling amount required for each pixel (for example, when the ejection amount is about 1/100 with respect to the filling amount), streak unevenness occurs. Can be prevented.

Japanese Patent No. 5157348

  However, in the method of Patent Document 1, when the discharge amount from the nozzle is large with respect to the ink filling amount required for each pixel (for example, when the discharge amount is 1/10 or more with respect to the filling amount), the pixel When the number of ejections is changed every time, the change in the ink amount per ejection becomes relatively large. For this reason, granular unevenness occurs, which greatly affects the image quality of the display.

  An object of one embodiment 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 printing unevenness.

  A printing method according to an aspect of the present disclosure is a printing method in which droplets are ejected from nozzles of an inkjet head and the droplets are applied to a plurality of cells of a print target medium. A first droplet applying step for applying a first droplet for restricting the flow of the second droplet to be applied, and applying the second droplet to a plurality of setting areas set in one cell. A second droplet applying step, 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 is applied later to an inkjet head that discharges the droplets from a nozzle so that the droplets are applied to a plurality of cells of a print target medium, and to the plurality of cells. A first control for controlling the inkjet head to apply a first droplet for restricting a flow of the second droplet, and a plurality of the second droplets in a set region set in one cell. And a second control unit that controls the inkjet head so as to apply the liquid droplets, and the control unit applies the second liquid droplets for each cell when performing the second control. The inkjet head is controlled to change the position.

  A method for manufacturing EL is used by using the above printing method.

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

Schematic diagram showing an example of a printing pattern when printing is performed using a conventional inkjet printing method The figure which shows the volume of the droplet discharged from each nozzle in the conventional inkjet printing method The figure which shows the filling volume of each cell at the time of forming the printing pattern shown in FIG. 1 using the conventional inkjet printing method. Schematic diagram showing an example of a printing pattern when printing is performed using the printing method of Patent Document 1 The figure which shows the filling volume of each cell at the time of forming the printing pattern shown in FIG. 4 using the printing method of patent document 1 1 is a diagram illustrating a configuration of a printing apparatus according to the present disclosure. The figure which shows the flow of the printing method of this indication Schematic diagram showing an example of a printing pattern when printing is performed using the printing method of the present disclosure The schematic diagram which shows the state by which the 1st droplet of this indication was apply | coated to the plane part of a board | substrate. The schematic diagram which shows the state by which the 1st droplet of this indication was apply | coated in the recessed part of a board | substrate. AA sectional view of FIG. 9A The schematic diagram which shows the state by which the 1st droplet of this indication was applied covering the recessed part of a board | substrate. BB sectional view of FIG. 10A Enlarged view of the setting area of this disclosure The figure which shows the filling volume of each cell at the time of forming the printing pattern shown in FIG. 7 using the printing method of this indication.

(Problems with conventional printing methods)
First, a problem when printing is performed by a conventional in-jet printing method will be described with reference to FIGS.

  FIG. 1 is a schematic diagram illustrating an example of a print pattern when printing is performed using a conventional printing method. The substrate 101 is a display substrate and is an example of a medium to be printed. Each of the cells 102a, 102b, 102c, 103a, 103b, 103c, 104a, 104b, and 104c is a concave portion partitioned by a partition wall, and serves as a display pixel, for example. A droplet 201 is a droplet of ink 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 nozzles of an inkjet head (not shown). Further, in FIG. 1, the dotted line shown corresponding to each nozzle number represents the position of the nozzle. A droplet 201 on the dotted line is a droplet ejected from any one of the nozzles N1 to N21 shown corresponding to the dotted line.

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

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

  3 shows the volume of liquid droplets (hereinafter referred to as filling volume) filled in each cell (pixel) when the print pattern shown in FIG. 1 is formed using the nozzle having the discharge volume shown in FIG. It is a table | surface which shows.

  In the table of FIG. 3, the first row represents the cell number, and the first column represents the cell alphabet. For example, the numerical value “42.1” in the second row and the second column represents the filling volume of the cell 102a. When the table of FIG. 3 is viewed in the column direction, it can be seen that the filling volume is the same. This is because, as shown in FIG. 1, in the cells orthogonal to the dotted line indicating the position of the nozzles, the nozzles used are the same and the printing patterns are the same, so the filling volume for each cell is also the same.

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

(Problems of the printing method of Patent Document 1)
Next, problems when printing is performed by the printing method disclosed in Patent Document 1 (Japanese Patent No. 5157348) will be described with reference to FIGS.

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

  In FIG. 4, a non-ejection position 202 is a position where no droplet is ejected. The non-ejection position 202 is selected at random.

  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 nozzle having the discharge volume shown in FIG. In FIG. 5, unlike FIG. 3, the volume is different for each row. For example, the filling volumes of the cells 102a, 102b, and 102c are different. This is because droplets are not ejected to the non-ejection position 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 the occurrence of streak unevenness. However, in this method, since the number of nozzles for discharging droplets is made different for each cell, the difference in filling volume between cells becomes larger than the discharge amount for one droplet.

  For example, as shown in FIG. 5, the filling volume of the cell 102b is 42.1 pl, whereas 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 the organic EL display, the image quality becomes grainy due to the difference in the light emission amount for each cell, and the display quality deteriorates.

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

(Embodiment of the present disclosure)
Hereinafter, embodiments of the present disclosure will be described 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 illustrating a configuration of the printing apparatus 1 according to the present embodiment. FIG. 6B is a diagram illustrating a flow of the printing method of the present embodiment performed by the printing apparatus 1. FIG. 7 is a schematic diagram illustrating an example of a print pattern when printing is performed using the printing method of the present embodiment. In FIG. 7, the same components as those in FIG.

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

  Although illustration is omitted, the control unit 20 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) storing a computer program, a RAM (Random Access Memory), and a communication circuit as hardware. Have. The function of the control unit 20 described later is realized by the CPU executing a computer program read from the ROM.

  The inkjet head 10 includes, for example, nozzles N1 to N21 as illustrated in FIG.

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

  The first droplet applying step S301 is a step of applying the first droplet 203 to the substrate 101 as shown in FIG. 7 in order to create a point that becomes a foundation for fixing the droplet. In this step, the control unit 20 controls the inkjet head 10 so as to apply the first droplet 203 to the substrate 101.

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

  Hereinafter, the details of the first droplet application step S301 and the second droplet application step S302 will be described.

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

  A substrate generally used in industrial production (for example, a glass substrate for display) does not have ink acceptability. When droplets are applied to such a substrate by an inkjet method, the droplets subsequently applied to the substrate are combined and absorbed by the adjacent droplets previously applied to the substrate, and applied to an appropriate position. The phenomenon that is not done occurs.

  When the distribution of the droplets in the cell changes due to the above phenomenon, a difference occurs in the film thickness distribution after the ink is cured, which appears as unevenness. For example, when only the second droplet application step S302 described later is performed, depending on the nozzles used in the setting region 204 (see FIG. 7) described later, a droplet discharged later may be first between adjacent droplets. Is absorbed by the droplets discharged in the cell, and the distribution of the droplets in the cell is biased, resulting in unevenness.

  In the present embodiment, the above-described unevenness is prevented by performing the first droplet application step S301 before the second droplet application 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 combined 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. Hereinafter, the droplet applied in the second droplet application step S302 is referred to as a second droplet 205.

  Since the droplets are unlikely to spread at the end of the cell, the first droplet 203 is preferably located at at least one end of the cell. Preferably, the first droplet is applied to two ends on the diagonal of the cell. Furthermore, the edge part of four corners may be sufficient.

  As shown in FIG. 7, the first droplet 203 is applied to the same position, that is, a fixed position in each of the cells 102a to 102c, 103a to 103c, and 104a to 104c.

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

  However, when it is difficult to use a material different from the second droplet 205 because of product quality, the first droplet 203 is made of the same material as the second droplet 205.

  Examples of the material of the first droplet 203 and the second droplet 205 include ink in which an organic EL material is dissolved in a solvent and the viscosity is adjusted to about 10 CP.

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

For example, in the case of 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 μm3 = 50 pl. When droplets of 7 pl per droplet are ejected into a cell of this size with a target of 80% filling rate, approximately 6 droplets are ejected toward the cell.
In the case of an organic EL display, in our experiment, it is known that luminance unevenness becomes visible when the film thickness changes by 1.6%. For this reason, the method of Patent Document 1 is not effective unless the volume of the liquid droplet filled in the cell is 50 times or more the volume of the liquid droplet discharged from the nozzle. On the other hand, according to the method of the present invention, the volume of the liquid droplet filled in the cell can be used in the range of about 1 to 50 times the volume of the liquid droplet discharged from the nozzle.

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

  Further, if 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 application 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 for arranging the first droplet 203 will be described.

  When the first droplets 203 come into contact with each other and are bonded and absorbed, the positions of the second droplets 205 vary, and the effects 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) is satisfied.

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

  The maximum wetting spread distance is the maximum distance at which 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 varies with time. Therefore, the distance when the first droplet 203 ejected from the inkjet head 10 reaches the substrate 101 to the steady state from the moment when it reaches the substrate 101 is set to the maximum wetting spread distance. The

  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.

  Two first droplets 203 shown in FIG. 8 are adjacent to each other. Further, the wet spread range 203a is a range where the first liquid droplet 203 spreads wet when it has landed on the substrate 101.

  As can be seen from the wet spread area 203a shown in FIG. 8, when the first droplet 203 lands on the flat surface of the substrate 101, it spreads equally in all directions. Therefore, Rmax1 and Rmax2 are equal to the radius when the first droplet 203 spreads to the maximum extent. Therefore, L shown in FIG. 8 is set to be twice or more the radius when the first droplet 203 spreads out to the maximum. For example, L shown in FIG. 8 is set based on the results of experiments and simulations regarding the presence or absence of coupling 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 recess 105 formed in the substrate 101. 9B is a cross-sectional view taken along line AA in 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. The recess 105 is, for example, a display cell (for example, the cells 102a to 102c, 103a to 103c, and 104a to 104c shown in FIG. 7).

  When a droplet is applied to the inside of the concave portion 105, the droplet does not easily spread to the end portion of the cell. Therefore, as shown in FIG. 9A, the first droplet 203 is applied to the end portion of the cell. At this time, the distance from the end of the concave portion 105 to the center of the first droplet 203 is arranged so that the following expressions (2) and (3) are satisfied.

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 Expression (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. is there.
When the first droplet 203 is ejected so as to satisfy the above expressions (2) and (3), the wetting spread range 203a is limited by the end of the recess 105 as shown in FIG. 9B. Therefore, as shown in FIG. 9A, the first droplet 203 spreads wet 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 the coupling 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, the first droplet 203 hardly enters the end (corner) of the recess 105. Therefore, it is preferable to apply (arrange) the first droplet 203 to the end of the recess 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 droplet 203 between them is placed. It is preferable to arrange them at equal intervals.

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

  As shown in FIGS. 10A and 10B, the recess 106 is formed in a cylindrical 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 a recess 106 is provided in the substrate 101, a plurality of first droplets 206 are ejected to the recess 106 as shown in FIG. 10A.
At this time, the distance from the center of the recess 106 to the center of the first droplets 206a and 206b is arranged so that the relationship of the following formula (4) is satisfied.
D1, D2 ≦ Rmax1 (4)
In the above equation (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.
As a result, 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 on the surface of the substrate 101. A wet spread area 206c shown in FIGS. 10A and 10B is an area where the first liquid droplets 206a and 206b are wet spread.

Therefore, the wetting and spreading ranges 203a and 206c in the planar portion of the substrate 101 vary depending on the volume of the recess 106 and the number of ejections of the first droplet 206. Therefore, L and the number of ejections of the first droplet 206 shown in FIG. 10A are set so that the wet spread area 203a of the first droplet 203 does not contact the wet spread area 206c of the first droplets 206a and 206b. The For example, L shown in FIG. 10A is set based on the results of experiments and simulations on whether or not the first droplet 203 and the first droplet 206 are coupled to each other.
Here, the inside of the contact hole, which is the concave portion 106, is likely to be unwetted, so it was filled with the first droplet 206 first. If two drops of the first droplet 206 are injected into the center of the concave portion 106, the concave portion 106 that is a contact hole can be filled, but the center of the concave portion 106 may be aimed at due to restrictions on the resolution in the print scan direction and the nozzle pitch. difficult. For this reason, the center of the contact hole, which is the recess 106, is set and applied within a range where the first droplet spreads.

<Second droplet application process>
Details of the second droplet application step S302 will be described.

  As described above, the second droplet application step S302 is performed after the first droplet application step S301, and is a step of applying the second droplet 205 in the setting region 204 of the substrate 101 as shown in FIG. is there.

  As shown in FIG. 7, the setting area 204 is set at a position on the same cell 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 with reference to FIG. FIG. 11 is an enlarged view showing one of the plurality of setting areas 204 shown in FIG.

  In the example of FIG. 11, the nozzle group 207 is set for the setting area 204. The nozzle group 207 is a nozzle that can eject the second droplet 205 to the setting region 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 the nozzle, the second droplet 205 is applied to the setting region 204 as shown in FIG.

  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 created in advance. Therefore, for example, as shown in FIG. 7, even if the arrangement of the setting areas 204 in the cells 102a, 102b, and 102c is the same, the combination of the selected nozzles is different. For example, in FIG. 7, the nozzles N1, N2, N5, and N5 are selected in the setting area 204 of the cell 102a, and the nozzles N1, N3, N4, and N4 are selected in the setting area 204 of the cell 102b. In the setting area 204, nozzles N2, N2, N4, and N5 are selected. That is, the nozzle is selected so that the application position (landing position) of the second droplet 205 in the setting area 204 changes for each cell.

  Note that the number of nozzles selected at random is not limited to one. Two or more nozzles may be selected randomly 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 where the setting area 204 is set in the cell 102a of FIG. 7 will be described.

  First, the volume V of ink necessary for filling 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 equation (3). In Expression (3), V is the volume of ink necessary for filling the cell 102a calculated in Expression (2). In Expression (3), Vanc is the average volume of the first droplets 203, Nanc is the number of the first droplets 203 in the cell 102a, 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 expression (4). In the equation (4), Nrand is the number of the second droplets 205 in the cell 102a calculated by the above equation (3). In Expression (4), N is the number of nozzles that can be discharged into the setting 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 where there is one second droplet 205 in the setting area 204. FIG. 11 illustrates that the nozzles that can be discharged into the setting area 204 are four nozzles N1, N2, N3, and N4 included in the nozzle group 207.

  The setting area 204 is set in the nozzle arrangement direction (left-right direction in the figure) as shown in FIG. 11 in order to exert an effect by randomly changing the nozzles to be used.

  In FIG. 7, a plurality of setting areas 204 described with reference to FIG. 11 are set in each cell so that the above-described formula (4) is satisfied. Note that the number N of nozzles that can be ejected into the setting area 204 is preferably a number that is twice or more the Nrand.

  Also, the position of the setting area 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 area 204 do not overlap from the viewpoint of film thickness uniformity. preferable. However, when the landing position of the second droplet 205 cannot be sufficiently secured, the landing position of the first droplet 203 and the setting area 204 may be set to overlap.

The details of the first droplet application step S301 and the second droplet application step S302 have been described above.
In FIG. 7, there are four setting areas 204 in one cell. There are two types of setting areas 204 for two droplets and three droplets. This is to increase the combination pattern of nozzles used in the cell to a plurality of types.
A setting area 204 for discharging one droplet with two nozzles and a setting area 204 for discharging one droplet with three nozzles are provided.
<Evaluation>
Next, the results of performing the printing method shown in FIG. 6B will be described with reference to FIG.

  FIG. 12 is a table showing the filling 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 nozzle having the discharge volume shown in FIG. It is.

  The filling volumes of the cells 102a, 102b, and 102c shown in FIG. 12 are not as uniform as the filling volumes of the cells 102a, 102b, and 102c shown in FIG. This is because the setting area 204 is randomly set for each cell, so that the filling volume changes for each cell. Therefore, the occurrence of the stripe unevenness described with reference to FIG. 3 is not recognized.

  Further, as described above, in the printing method shown in FIG. 6B, unlike the printing method of Patent Document 1, the number of nozzles that eject droplets is not different 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 filling volume of the cell 102b is 42.5 pl, whereas the filling volume of the cell 102a is 42.0 pl, and the difference between them is 2% or less. As described above, since the volume difference of about 20% occurs in the printing method of Patent Document 1, the difference in filling volume can be considerably reduced in the printing method of the present embodiment. Therefore, for example, in the light emitting layer of the organic EL display, the difference in the amount of light emitted from each cell is small, so that there is no graininess and the display quality is not deteriorated.

  From the above, in this embodiment, even when the ink discharge amount (discharge volume) from the nozzles of the inkjet head is relatively large with respect to the ink fill amount (fill volume) required for each pixel, Printing unevenness (for example, streak unevenness) due to volume variation can be reduced, and the product yield can be improved.

  Moreover, when an organic EL display is manufactured using the printing method of this Embodiment, the printing quality of the light emitting layer and sealing film of a display can be improved.

  Note that the printing method of the present embodiment is applied not only when droplets are applied to cells in a substrate, but also when a film is formed on the plane of the substrate or when a film covering the uneven surface of the substrate is formed. Is possible. In that case, for example, the process shown in FIG. 6 may be repeated by installing a plurality of nozzles of the inkjet head 10 or the inkjet head 10 in the printing scanning direction. Thereby, the leveling time for making the unevenness of the film surface uniform can be shortened, and the tact can be shortened.

  In addition, this indication is not limited to description of the said embodiment, A various deformation | transformation is possible in the range which does not deviate from the meaning.

  For example, although the above embodiment has been described on the assumption that a cell exists, the present disclosure can also be applied when there is no cell. That is, it can also be used when a solid film (a uniform film) is formed on the substrate 101.

  For example, when a single film is formed on the entire surface of the substrate 101, the above-described method of the present disclosure can be used. In this case, although the cell does not exist, the above-described method of the present disclosure is used on the assumption that there are a plurality of virtual cells.

  Note that a virtual cell is a virtual cell that does not actually exist but is assumed to have a cell. If the number of virtual cells is set large and the size of each virtual cell is set small, a more uniform film can be formed. Although droplets are applied into the virtual cell, the droplets eventually spread and connect as a whole to form one flat film.

  This method can form a uniform film without unevenness on a flat surface. For example, a film such as a hole transport layer, an organic semiconductor active layer, or an electron transport layer of a coating type solar cell such as a perovskite solar cell can be formed. Available to:

  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, the droplets are small, but a uniform film can be formed by applying the first liquid drop and the second droplet.

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

DESCRIPTION OF SYMBOLS 1 Printing apparatus 10 Inkjet head 20 Control part 101 Board | substrate 102a, 102b, 102c, 103a, 103b, 103c, 104a, 104b, 104c Cell 105, 106 Concave part 201 Droplet 202 Non-ejection position 203, 206, 206a, 206b 1st liquid Drops 203a and 206c Wetting and spreading range 204 Setting region 205 Second droplet 207 Nozzle group

Claims (12)

A printing method in which droplets are ejected from nozzles of an inkjet head, and the droplets are applied to a plurality of cells of a print target medium,
Applying a first droplet to the plurality of cells at a fixed position in the cell;
A second liquid droplet applying step of applying a second liquid to a plurality of setting areas set in one of the cells,
In the second droplet application step, the application position of the second droplet is changed for each cell.
Printing method. In the first droplet application step,
Applying the first droplet to at least one end of the cell;
The printing method according to claim 1. In the first droplet application step,
Applying a plurality of the first droplets to a recess provided in the print target medium,
The printing method according to claim 1 or 2. The setting area is
An area other than the application position of the first droplet,
The printing method according to claim 1. The application position of the first droplet in the plurality of cells is the same.
The printing method according to any one of claims 1 to 4. The position of the setting area in the plurality of cells is the same;
The printing method according to any one of claims 1 to 5. The plurality of cells are a plurality of virtual cells.
The printing method according to claim 1. The printing method according to claim 1, wherein a volume of the first droplet is equal to or less than a volume of the second droplet. The printing method according to claim 1, wherein a plurality of the first droplets are applied to one cell, but the 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 ink jet head so as to apply a first droplet for restricting a flow of a second droplet applied later to the plurality of cells, and a plurality of settings in one cell. A control unit that performs a second control for controlling the inkjet head so as to apply the second droplet to the set region.
The controller is
When performing the second control, the inkjet head is controlled to change the application position of the second droplet for each cell;
Printing device. The manufacturing method of EL which manufactures EL with the printing method of any one of Claims 1-9. The manufacturing method of the solar cell which manufactures a solar cell with the printing method of any one of Claims 1-9.

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