Coating method

Abstract

To surely suppress variation in film thickness of a coating film to be coated.SOLUTION: The coating method includes a first coating step S1 of forming the first coating film 33 by coating the first main surface 31, which is one main surface of the conductive substrate 30 and has the first step portion 31A, with the coating solution 40, and a second coating step S1 of forming the second coating film 35 by spraying the coating solution 40 to the first main surface 31 on which the first coating film 33 is formed after the first coating step S2. In the second coating step S2, the coating solution 40 is sprayed in a state where a voltage is applied between the nozzle 22 for spraying the coating solution 40 and the conductive substrate 30.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present technology relates to a coating method. [Background technology]

[0002] Conventionally, methods have been proposed for suppressing variations in film thickness when forming a coating on a substrate having a fine uneven structure on its surface, and one example of such methods is disclosed in Patent Document 1. The film formation method described in Patent Document 1 applies ink by ejecting it from an inkjet head onto the top surface of a step in the thickness direction of the substrate, and then blows air onto the ink that has landed on the flat surface of the step, thereby forming a film that covers the top and side surfaces of the step.

[0003] This allows some of the ink on the top surface to flow around to the side surfaces, which is believed to prevent the film from becoming thinner on the side surfaces of the step and on the corners where the side surfaces of the step join with the top surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2023 / 058613 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the method described in Patent Document 1, if airflow occurs due to the rebound of air blown onto the substrate, the airflow may blow away the film adhering to the side or corner of the step, resulting in a thinner film thickness in those areas. Furthermore, it is difficult to control the airflow while taking into account the effects of such airflow, and adjustments must be made according to the uneven shape.

[0006] The technology described in the present specification has been made in consideration of the above-mentioned circumstances, and aims to reliably suppress variations in the thickness of the coating film to be coated. [Means for solving the problem]

[0007] The coating method according to the technology described in the present specification includes a first coating step of forming a first coating film by coating a first main surface, which is one main surface of a conductive substrate and has a first step portion, with a coating liquid, and a second coating step of forming a second coating film by spraying the coating liquid onto the first main surface on which the first coating film has been formed, after the first coating step. In the second coating step, the coating liquid is sprayed while a voltage is applied between a nozzle that sprays the coating liquid and the conductive substrate.

[0008] The conductive substrate may also have a second step portion on a second main surface, which is the other main surface, and in the first coating step, after forming the first coating film on the first main surface, the first coating film may be formed on the second main surface, and in the second coating step, after forming the second coating film on the first main surface, the first coating film may be formed on the second main surface.

[0009] In addition, the first coating step may form a first coating film by spraying the coating liquid along a swirling flow that swirls around an axis that intersects with the first main surface of the conductive substrate.

[0010] The conductive substrate may also have a base material and a conductive film formed on the surface of the base material, and the first coating film and the second coating film may be photoresist films for patterning the conductive film. [Effects of the Invention]

[0011] According to the present technology, it is possible to reliably suppress variations in the thickness of the coating film to be coated. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view showing the positional relationship between a conductive substrate and a nozzle. [Figure 2] Schematic diagram showing the cross-sectional structure of a conductive substrate [Figure 3] FIG. 1 is a schematic diagram showing a swirling air atomization coating device for performing a first coating step according to the first embodiment. [Figure 4] Schematic diagram showing the first coating step [Figure 5] Schematic diagram showing the first coating step following Figure 4 [Figure 6] Schematic diagram showing the first coating step following Figure 5. [Figure 7] Schematic diagram showing an electrostatic atomization coating device performing a second coating step. [Figure 8] Schematic diagram showing the second coating process [Figure 9] Schematic diagram showing the second coating step following FIG. 8. [Figure 10] Schematic diagram showing the second coating step following FIG. 9. [Figure 11] Schematic diagram showing a cross-sectional structure of a conductive substrate according to another embodiment. [Figure 12] 1 is a schematic diagram showing a cross-sectional structure of a conductive substrate according to another embodiment and a coating film formed thereon; [Figure 13] Block diagram showing the coating system DETAILED DESCRIPTION OF THE INVENTION

[0013] <Embodiment 1> The coating method according to embodiment 1 will be described with reference to Figures 1 to 10. Some of the figures show X-axis, Y-axis, and Z-axis, and the directions of the axes are drawn so as to be common to all the figures.

[0014] The coating method according to the first embodiment includes a first coating step S1 performed using a swirling air atomization coating device 10 (an example of a first coating device) and a second coating step S2 performed using an electrostatic atomization coating device 20 (an example of a second coating device). Each step S1 and S2 will be described in detail below.

[0015] The conductive substrate 30, which is the workpiece of this coating method, has a rectangular shape in plan view as shown in Fig. 1, for example, but the planar shape and size are not limited. As shown in Fig. 2, the conductive substrate 30 has a cross-sectional structure including a substrate main body 30A and a conductive film 30B.

[0016] As shown in FIG. 2, the substrate main body 30A has two opposing main surfaces (plate surfaces) 30A1 and 30A2 each having a concave-convex structure, but only one of the main surfaces may have a concave-convex structure. The substrate main body 30A is made of, for example, a base material having a concave-convex structure formed on both main surfaces by etching or the like. Furthermore, for example, the substrate main body 130A may have a concave-convex structure due to the arrangement of electronic elements 30D provided on a base material 30C, as shown in FIG. 11 in another embodiment described later. Furthermore, for example, the substrate main body may have both the concave-convex structure of the base material and the concave-convex structure due to the arrangement of electronic elements. The base material is made of an insulating material such as quartz or glass, but the material is not limited.

[0017] The conductive film 30B is provided so as to cover both main surfaces 30A1, 30A2 of the substrate main body 30A. The conductive film 30B is made of a conductive material, and the type of conductive material is not limited, but is, for example, copper. The conductive film 30B is formed over the entire substrate main body 30A in advance before carrying out the present coating method. As shown in FIG. 2, the conductive film 30B according to this embodiment is formed to have a substantially uniform thickness, but the thickness of the conductive film 30B does not necessarily have to be uniform.

[0018] As shown in FIG. 2, the conductive substrate 30 has a first step portion 31A constituting a concave-convex structure on one of its principal surfaces, the first principal surface 31, and a second step portion 32A constituting a concave-convex structure on the other principal surface, the second principal surface 32. Each step portion 31A, 32A includes a flat surface 31A1, 32A1, a side surface 31A2, 32A2, and a corner 31A3, 32A3 located at the junction between the flat surface and the second principal surface 32. The step portions 31A, 32A may be convex or concave portions as long as they are components that form the concave-convex structure of the principal surface 31, 32. Furthermore, the concave portions may be through-holes that penetrate the conductive substrate 30 in the thickness direction. In other words, the shapes of the step portions 31A, 32A are not limited to those shown in the figure. For example, the side surfaces 31A2, 32A2 may be inclined surfaces, or the side surfaces 31A2, 32A2 may be the inner peripheral surfaces of through-holes that penetrate the conductive substrate 30 in the thickness direction. In another embodiment described later, a case in which one side surface 31A2, 32A2 is the inner peripheral surface of a through hole is shown in FIG.

[0019] Next, the first coating step S1 will be described. The first coating step S1 is a step in which the coating liquid 40 is sprayed onto the conductive substrate 30 along a swirling flow using a swirling flow air atomization coating device 10, thereby forming first coating films 33, 34 on the conductive substrate 30. Note that the first coating device is not limited to the swirling flow air atomization coating device 10, and may be any other type of device that can form a coating film. For example, it may be a general-purpose air atomization coating device or inkjet device that sprays the coating liquid 40 without swirling flow, or it may be a coating device that applies and coats the coating liquid 40 without spraying it.

[0020] The coating liquid 40 may be an insulating material or a conductive material, and various materials can be used depending on the purpose, but is, for example, a photoresist liquid. When the coating liquid 40 is a photoresist liquid, the first coating films 33, 34 and second coating films 35, 36 described below become photoresist films used to pattern the conductive film 30B of the conductive substrate 30.

[0021] 3, the swirl flow air atomization coating apparatus 10 includes a first film formation chamber 11 in which a conductive substrate 30 is placed, a first nozzle 12 that sprays a coating liquid 40, a first liquid container 13 in which the coating liquid 40 is stored, a first liquid supply pipe 14, a first liquid pump 15, an air control panel 17, and a first control unit 19 that controls at least the first liquid pump 15 and the air control panel 17. The first nozzle 12 is disposed in the first film formation chamber 11 with a predetermined distance (for example, less than 50 mm) between it and the conductive substrate 30.

[0022] The first liquid supply pipe 14 is a pipe for supplying the coating liquid 40 to the first nozzle 12. The first nozzle 12 is supplied with high-pressure compressed air (an example of gas) from an external air supply source. An air control panel 17 controls the compressed air supplied to the first nozzle 12. The first liquid pump 15 is provided on the path of the first liquid supply pipe 14 and is a power source for feeding the coating liquid from the first liquid container 13. The liquid pump 15 is, for example, a syringe pump, and is preferably capable of stably feeding the coating liquid in small amounts (for example, at 1 mL / min or less). The swirl-flow air atomization coating device 10 is preferably capable of stably feeding and atomizing the coating liquid 40, for example, with a viscosity of less than 100 cP, in small amounts, and spraying it at low pressure and with a low air volume.

[0023] The first nozzle 12 has a substantially cylindrical nozzle body 12A having a liquid outlet through which the coating liquid 40 is ejected and a plurality of air outlets through which compressed air is ejected. The compressed air ejected from the air outlet hits the coating liquid 40 ejected from the liquid outlet, atomizing (atomizing) the coating liquid 40. This causes the coating liquid 40 to spray from the tip 12A1 of the nozzle body 12A of the first nozzle 12. The coating liquid 40 is sprayed as a swirling flow that spirals downward while spreading out and swirling around the axis of the nozzle body 12A (around the Z-axis in the drawing) due to the compressed air being ejected, which includes a velocity component along the horizontal direction.

[0024] In the first film formation chamber 11, the conductive substrate 30 is placed so that its main surface is along a horizontal plane (the XY plane in the drawing), and the first nozzle 12 is placed above it (above in the Z-axis direction). As shown by the dashed-dotted line in FIG. 1, the nozzle main body 12A of the first nozzle 12 moves above the conductive substrate 30 and sprays the coating liquid 40 onto the entire main surface of the conductive substrate 30. Note that the stage supporting the conductive substrate 30 may move without moving the first nozzle 12; the movement method is not limited as long as the first nozzle 12 and the conductive substrate 30 are displaced relative to each other.

[0025] The first nozzle 12 sprays the coating liquid 40 onto each of the main surfaces 31, 32 of the conductive substrate 30. To this end, as shown in FIG. 4, the conductive substrate 30 is first placed so that the first main surface 31 faces the first nozzle 12 (upper side), and the coating liquid 40 is sprayed from the first nozzle 12 in this state. As a result, a first coating film 33 is formed on the first main surface 31. Next, as shown in FIG. 5, the conductive substrate 30 is turned upside down (turned upside down) and placed so that the second main surface 32 faces up. Then, as shown in FIG. 6, when the coating liquid 40 is sprayed from the first nozzle 12 in this placed state, a first coating film 34 is formed on the second main surface 32.

[0026] When the swirl-flow air atomization coating apparatus 10 is used in the first coating step S1, the first coating films 33, 34 are formed with a substantially uniform thickness on the flat surfaces 31A1, 32A1 of the stepped portions 31A, 32A of the conductive substrate 30. The first coating films 33, 34 on the side surfaces 31A2, 32A2 of the stepped portions 31A, 32A are formed with a substantially uniform thickness, although they are slightly thinner than the first coating films 33, 34 on the flat surfaces 31A1, 32A1. On the other hand, the sprayed coating liquid 40 is less likely to remain on the corners 31A3, 32A3 of the stepped portions 31A, 32A due to air flow, etc., making it difficult for the first coating films 33, 34 to form. Therefore, the corners 31A3, 32A3 may be left uncoated and exposed, as shown in FIGS. 4 and 6 .

[0027] Therefore, in this embodiment, in order to suppress coating unevenness (variation in film thickness of the first coating films 33, 34) that occurs in the first coating step S1, a second coating step S2 is performed after the first coating step S1. The second coating step S2 is a step of forming second coating films 35, 36 on the conductive substrate 30 on which the first coating films 33, 34 have been formed by spraying a coating liquid 40 using an electrostatic atomization coating device 20. The coating liquid 40 is made of the same material as the coating liquid used in the first coating step.

[0028] 7, the electrostatic atomization coating device 20 includes a second film formation chamber 21 in which a conductive substrate 30 having first coating films 33 and 34 formed thereon is placed, a second nozzle 22 that sprays a coating liquid 40, a second liquid container 23 that stores the coating liquid 40, a second liquid supply pipe 24, a second liquid pump 25, a high-voltage power supply 28, and a second control unit 29 that controls at least the second liquid pump 25 and the high-voltage power supply 28. The second nozzle 22 is disposed in the second film formation chamber 21 at a predetermined distance from the conductive substrate 30 having the first coating films 33 and 34 formed thereon.

[0029] The second liquid supply pipe 24 is a pipe for supplying the coating liquid 40 to the second nozzle 22. The second liquid pump 25 is provided on the path of the second liquid supply pipe 24 and is a power source for pumping the coating liquid 40 from the second liquid container 23. The second liquid pump 25 is, for example, a syringe pump, and is preferably capable of stably supplying the coating liquid in small amounts (for example, 1 mL / min or less). The high-voltage power supply 28 applies a high voltage to the second nozzle 22. The electrostatic atomization coating device 20 is preferably capable of stably pumping and atomizing the coating liquid 40, for example, with a viscosity of less than 100 cP, in small amounts, and spraying the coating liquid 40 with a low exhaust volume and in a state where there are no other conductors around the conductive substrate 30.

[0030] The second nozzle 22 is an electrostatic atomization type spray nozzle. The second nozzle 22 has an electrode therein, and a voltage is applied to this electrode from a high-voltage power supply 28. The coating liquid 40 supplied to the second nozzle 22 is charged by the applied voltage, and the charged coating liquid 40 is sprayed from the tip 22A1 of the nozzle main body 22A.

[0031] In the second film formation chamber 21, the conductive substrate 30 on which the first coating films 33, 34 are formed is placed so that its main surface is along a horizontal plane (the XY plane in the drawing), and the second nozzle 22 is placed above it (above in the Z-axis direction). Furthermore, the conductive substrate 30 on which the first coating films 33, 34 are formed is grounded to serve as an earth electrode, but a predetermined reference potential may be supplied thereto.

[0032] Similar to the nozzle body 12A of the first nozzle 12 described above, the nozzle body 22A of the second nozzle 22 moves above the conductive substrate 30 on which the first coating films 33, 34 have been formed, and sprays the coating liquid 40 onto the entire main surface. However, the second nozzle 22 may not move, and the stage supporting the conductive substrate 30 on which the first coating films 33, 34 have been formed may move, and the method of movement is not limited as long as the two are displaced relative to each other.

[0033] 8, the conductive substrate 30 is first placed so that the first coating film 33 on the first main surface 31 side of the conductive substrate 30 faces the second nozzle 22 (upper side), and in this state, the coating liquid 40 is sprayed from the tip 22A1 of the second nozzle 22. As a result, a second coating film 35 is formed on the first coating film 33.

[0034] At this time, the sprayed coating liquid 40 is electrically charged and is electrostatically attracted by the electric field generated between the nozzle body 22A and the earth electrode (the conductive substrate 30 on which the first coating films 33, 34 are formed). Here, as described above, the corners 31A3, 32A3 of the stepped portions 31A, 32A of the conductive substrate 30 on which the first coating films 33, 34 are formed are not covered by the first coating films 33, 34, and the conductive films 30B on the surfaces of the corners 31A3, 32A3 are exposed. Therefore, when the first coating film 33 is positioned on the second nozzle 22 side (upper side), the sprayed coating liquid 40 (charge) is electrostatically attracted to and concentrated on the conductive film 30B on the corner 31A3, as shown in FIG. 8 . As a result, the second coating film 35 is concentrated and adheres to the vicinity of the corner 31A3.

[0035] By using electrostatic attraction in this way in the second coating step S2, the electric field lines are more concentrated in thinner portions of the first coating film 33, allowing the second coating film 35 to have a thicker film thickness. As a result, the film thickness of the entire coating film 38, which is a laminate of the first coating film 33 and the second coating film 35, can be made uniform. Note that, in order to achieve a uniform film thickness by suitably performing such electrostatic attraction, the conductivity of the coating liquid 40 is preferably lower than that of the conductive film 30B of the conductive substrate 30.

[0036] After the second coating film 35 is formed, the conductive substrate 30 on which the first coating films 33, 34, and second coating film 35 are formed is turned upside down (turned upside down) and placed so that the first coating film 34 on the second main surface 32 faces the first nozzle 12 (upper side), as shown in Fig. 9. When the coating liquid 40 is sprayed from the second nozzle 22 in this placed state, the second coating film 36 is formed on the first coating film 34, as shown in Fig. 10. As with the second coating film 35 described above, the second coating film 36 has a larger electrostatic attraction (more concentrated electric field lines) in the thinner portions of the first coating film 34, allowing the second coating film 36 to be formed with a larger thickness. This allows the thickness of the entire coating film 39 formed by laminating the first coating film 34 and the second coating film 36 to be uniform.

[0037] When the second coating films 35, 36 are sprayed in the second coating step S2, it is preferable that the first coating films 33, 34 to which they are attached are in a semi-dried state, not completely dried and cured. This prevents interfaces from forming between the first coating film 33 and the second coating film 35, and between the first coating film 34 and the second coating film 36. If such interfaces were to occur, there is a concern that the quality of the laminated coating films 38, 39 would be reduced by the interfaces. For example, if the coating films 38, 39 are photoresist films, there is a concern that if interfaces occur within the coating films 38, 39, irradiated light would be refracted at the interfaces during exposure processing.

[0038] Therefore, in this embodiment, when spraying the coating liquid 40 in the second coating step S2, the second coating film 35 is formed on the first coating film 33, which was formed first in chronological order in the first coating step S1, and then the second coating film 36 is formed on the first coating film 34. More specifically, after the first coating step S1, the conductive substrate 30 on which the first coating films 33 and 34 are formed is turned upside down (inverted), and in the second coating step S2, the conductive substrate 30 is positioned so that the first coating film 33 faces the second nozzle 22 (compare FIGS. 6 and 8). This prevents the first coating film 33, which was formed first in the first coating step S1, from completely drying and becoming hardened. When the second coating film 35 is sprayed in the second coating step S2, the first coating film 33 to which it adheres is in a semi-dried state, preventing it from becoming completely dry and hardened.

[0039] <Other embodiments> The present technology is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included in the technical scope of the present technology.

[0040] (1) In this embodiment, air having the same components as the atmosphere is used as an example of compressed gas, but other gases (nitrogen gas (N 2 ), argon gas (Ar), etc.) may also be used.

[0041] 11, the substrate main body 130A of the conductive substrate 130 has a flat base material 130A1 and electronic elements 130A2 provided on the main surface of the base material 130A1, and may have an uneven structure according to the arrangement of the electronic elements 130A2. Furthermore, the electronic elements 130A2 are not limited to those integrally formed on the base material 130A1, but may be separate bodies (electronic components, etc.) mounted on the base material 130A1.

[0042] (3) When one side surface 31A2, 32A2 of the step portion 31A, 32A of the conductive substrate 30 is the inner surface of the through hole, the formed coating films 38 (first coating film 33, second coating film 35), 39 (first coating film 34, second coating film 36) are shown in Figure 12.

[0043] (4) Some components may be common to the swirl air atomization coating device 10 and the electrostatic atomization coating device 20. For example, the film formation chambers 11, 21, liquid containers 13, 23, liquid pumps 15, 25, and control units 19, 29 do not need to be different for the devices 10, 20 and may be the same.

[0044] (5) The swirling air atomization coating device 10 and the electrostatic atomization coating device 20 may be provided with a central control unit 80 that controls them all together, as shown in Fig. 13. In this case, the coating method described above may be continuously performed by a coating system 100 that includes the swirling air atomization coating device 10, the electrostatic atomization coating device 20, and the central control unit 80. [Explanation of symbols]

[0045] 22... nozzle, 30, 130... conductive substrate, 30A, 130A... substrate main body portion, 30B... conductive film, 31... first main surface, 31A... first step portion, 32... second main surface, 32A... second step portion, 40... coating liquid, S1... first coating step, S2... second coating step

Claims

1. a first coating step of coating a first main surface, which is one main surface of the conductive substrate and has a first step portion, with a coating liquid to form a first coating film; a second coating step of forming a second coating film by spraying the coating liquid onto the first main surface on which the first coating film has been formed, after the first coating step; The second coating step is a coating method in which the coating liquid is sprayed while a voltage is applied between a nozzle that sprays the coating liquid and the conductive substrate.

2. the conductive substrate has a second step portion on a second main surface that is the other main surface, In the first coating step, the first coating film is formed on the first main surface, and then the first coating film is formed on the second main surface; The coating method according to claim 1 , wherein in the second coating step, the second coating film is formed on the first main surface, and then the first coating film is formed on the second main surface.

3. 3. The coating method according to claim 1, wherein the first coating step forms a first coating film by spraying the coating liquid along a swirling flow that swirls around an axis that intersects with the first main surface of the conductive substrate.

4. the conductive substrate has a substrate main body and a conductive film provided on a surface of the substrate main body, 3. The coating method according to claim 1, wherein the first coating film and the second coating film are photoresist films for patterning the conductive film.

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