Film formation method

Abstract

To improve uniformity of a film to be formed.SOLUTION: A film formation method for forming a film on a coated material includes a coating step of discharging a liquid from each of a plurality of discharge heads provided in a conveyance direction of the coated material to be conveyed, and coating the liquid onto the coated material, wherein the coating step coats the liquid discharged from each of the plurality of discharge heads to different positions on the coated material in the conveyance direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a film forming method. By law Regarding. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a film forming method for forming a film on a substrate is known.

[0003] Furthermore, in a coating method for coating a substrate with a coating liquid, a method has been disclosed in which a plurality of inkjet heads are provided in the substrate transport direction and droplets of the coating liquid are ejected in multiple stages (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method of Patent Document 1, an inkjet head ejects two types of coating liquid, one layer is formed on a substrate with one type of coating liquid, and then a second layer is formed on the first layer with the other type of liquid different from the first type of coating liquid, so there is room for improvement in the uniformity of the film that is formed.

[0005] An object of the present invention is to improve the uniformity of the film formed. [Means for solving the problem]

[0006] A film forming method according to one aspect of the present invention is a method for forming a film on a coating target, comprising a coating step of coating the coating target with a liquid from each of a plurality of discharge heads provided along a transport direction of the coating target being transported, and applying the liquid to the coating target, wherein in the coating step, teeth , coating at different positions on the workpiece along the conveying direction Be , The substrate includes a layer formed on a non-permeable substrate and containing particles as a main component. . Effect of the Invention

[0007] According to the present invention, the uniformity of the formed film can be improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of the configuration of a film forming apparatus according to an embodiment; [Diagram 2] 4 is a flowchart showing an example of the operation of the film forming apparatus according to the embodiment. [Diagram 3] 5A to 5C are diagrams illustrating an example of a film formed by the film forming apparatus according to the embodiment. [Figure 4] FIG. 11 is a diagram showing a film formed by the film forming apparatus according to Example 2. [Diagram 5] FIG. 11 is a diagram showing a film formed by the film forming apparatus according to Example 3. [Figure 6] FIG. 11 is a diagram showing a film formed by the film forming apparatus according to Example 4. [Figure 7] FIG. 13 is a diagram showing a film formed by the film forming apparatus according to Example 5. [Figure 8] FIG. 13 is a diagram showing a film formed by the film forming apparatus according to Example 6. [Figure 9] FIG. 2 is a diagram showing a film formed by the film forming apparatus according to Comparative Example 1. [Figure 10] FIG. 11 is a diagram showing a film formed by the film forming apparatus according to Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicated explanations will be omitted as appropriate.

[0010] The following embodiments are illustrative of a film forming method and a film forming apparatus for embodying the technical concept of the present invention, and the present invention is not limited to the following embodiments. The dimensions, materials, shapes, and relative positions of the components described below are intended to be illustrative, and are not intended to limit the scope of the present invention, unless otherwise specified. The sizes and positional relationships of the components shown in the drawings may be exaggerated to clarify the explanation.

[0011] The film forming method according to the embodiment forms a film on a substrate. The thickness of the film is not particularly limited, and it may be any film that forms a layer on the substrate. The substrate includes, for example, an electrode substrate (current collector) used in a storage device such as a battery, a power generation device such as a fuel cell, a solar power generation device, etc., and also includes an electrode in which an electrode material layer such as an active material is formed on an electrode substrate. The film forming method applies a liquid in which various materials, including a powdered active material or a catalyst composition, are dispersed in a liquid to the substrate, and then fixes and dries the liquid to form an electrode having a film containing the various materials on the substrate.

[0012] Methods for applying a liquid to a substrate to form a film include spraying, dispenser, die coater or lift-up coating, and printing using an inkjet head.

[0013] However, there is a trade-off between productivity and quality of the above devices, and increasing productivity in response to demands associated with market expansion may result in an increase in defects and a decrease in device quality.

[0014] For example, if defects that occur on the electrode surface, electrode end face, or electrode interface are left as they are and shipped to the market, the accumulation of specific substances at the defective area due to aging or vibration, or a short circuit or leakage due to mechanical contact with the electrode interface may occur, which may lead to fire or shortened lifespan of the device.

[0015] Furthermore, when a liquid is applied to a coating material having a particle-based layer on the outermost surface of a non-permeable substrate, approximately circular defects (point defects) where no ink is present are more likely to occur on the coating material than when a layer mainly made of a resin component is provided. The non-permeable substrate contains, for example, an active material for a battery, and the particle-based layer provided on the non-permeable substrate contains, for example, a graphite layer.

[0016] This phenomenon is thought to occur when, when a liquid is applied onto a substrate, the air inside the layer of the substrate, which is mainly composed of particles, is replaced by the liquid and discharged from the layer, remaining in the liquid on the substrate. When a substrate with a roughly circular defect is used as an electrode, a short circuit may occur.

[0017] In the embodiment, a coating process is performed on the workpiece by discharging liquid from each of a plurality of discharge heads provided along the transport direction of the workpiece being transported. In the coating process, liquid is discharged from each of the plurality of discharge heads and applied to different positions on the workpiece along the transport direction.

[0018] Here, different positions means that the positions that are approximate centers of the liquids ejected from the multiple ejection heads and applied onto the material to be coated are different from one another.

[0019] By applying the liquid ejected from each of the multiple ejection heads to different positions on the substrate along the transport direction, the liquid is applied intermittently onto the substrate, and sufficient time is ensured for the air inside the layer whose main component is particles to be replaced by the liquid and discharged. This suppresses roughly circular defects in the substrate whose main component is particles, improving the uniformity of the formed film.

[0020] The film forming method and the film forming apparatus according to the embodiment will be described in detail below.

[0021] [Embodiment] <Configuration Example of Film Forming Apparatus 100> First, a configuration of a film forming apparatus 100 according to an embodiment will be described. Fig. 1 is a diagram illustrating an example of the configuration of the film forming apparatus 100. Fig. 1 shows the inside of the film forming apparatus 100 seen through from a direction substantially perpendicular to a conveying direction 10 of a material 102 to be coated.

[0022] 1, the film forming apparatus 100 includes an unwinding section 101, an inkjet head 103, a platen 104, a heat drum 105, a hot air drying section 106, a transport roller 107, and a winding section 108. These are provided in this order from upstream to downstream along the transport direction 10 of the material 102 to be coated.

[0023] The film forming device 100 applies ink ejected from an inkjet head 103 to a material 102 to be coated while conveying the material 102 to be coated by an unwinding unit 101 and a winding unit 108, thereby forming a uniform film of ink on the material 102 to be coated. Each component will be described in detail below.

[0024] (Unwinding means, winding means) In this embodiment, an unwinding unit 101 is used as the unwinding means for the material to be coated 102, and a winding unit 108 is used as the winding means for the material to be coated 102. The unwinding unit 101 supplies the material to be coated 102 to the transport path of the film forming device 100 by rotating the material to be coated 102 stored in a roll shape.

[0025] The winding section 108 winds up the material 102 on which the ink has been applied and a film has been formed, and stores the material in a roll.

[0026] (Transportation means) The platen 104 guides the material 102 to be coated so that it is transported along a transport path. In addition to the transport roller 107, transport rollers not indicated with a reference numeral are also used as transport means. The transport means, the unwinding means, and the winding means constitute the transport means for the material 102 to be coated.

[0027] Although this also relates to other processes, the coating speed in the film forming apparatus 100 is preferably 30 [m / min] to 100 [m / min]. This allows it to be suitably used in cases where high-speed film formation is required.

[0028] The material to be coated 102 is a substrate that continues along the conveying direction 10. The film forming apparatus 100 conveys the material to be coated 102 along a conveying path between an unwinding section 101 and a winding section 108. The length of the material to be coated 102 along the conveying direction 10 is at least longer than the conveying path between the unwinding section 101 and the winding section 108. The film forming apparatus 100 is capable of continuously forming a film on the material to be coated 102 that continues along the conveying direction 10.

[0029] (ink) The ink is composed of a liquid that realizes the function of a film, and is an example of a liquid that is ejected from each of the multiple inkjet heads. There are no particular limitations on the ink, as long as it has a viscosity and surface tension that allows it to be ejected from the inkjet head, but it is preferable that the viscosity of the ink is 30 mPa s or less at room temperature and pressure, or when heated or cooled.

[0030] More specifically, they are solutions, suspensions, emulsions, etc. that contain solvents such as water and organic solvents, functionality-imparting materials such as dyes, pigments, polymerizable compounds, resins, surfactants, etc., biocompatible materials such as DNA, amino acids, proteins, calcium, etc., edible materials such as natural dyes, etc. These can be used, for example, as printing inks, surface treatment liquids, components of electronic elements and light-emitting elements, liquids for forming various devices such as electronic circuit resist patterns, etc.

[0031] Furthermore, when the ink contains a large amount of non-volatile components or when ink containing metal oxide particles as a main component is used, it is particularly difficult to form a uniform film, and therefore this embodiment is particularly effective.

[0032] (Liquid application means) The liquid application means is a means for ejecting ink and applying the ink onto a material to be applied 102. As shown in Fig. 1, the film forming apparatus 100 includes an inkjet head 103 as the liquid application means.

[0033] The film forming apparatus 100 is provided with inkjet heads 103A, 103B, 103C, and 103D arranged along the transport direction 10 of the material to be coated 102. However, the present invention is not limited to this, and the film forming apparatus 100 may be provided with two or more inkjet heads arranged along the transport direction 10. Note that the inkjet heads 103A, 103B, 103C, and 103D have the same configuration, and the inkjet head 103 is a general term used when there is no particular distinction between the inkjet heads 103A, 103B, 103C, and 103D.

[0034] The inkjet head 103 has a plurality of nozzle rows in which a plurality of nozzles are arranged along the width direction (direction intersecting with the transport direction 10) of the material 102 to be coated. The film forming device 100 is provided with the inkjet head 103 so that the direction of ink ejection from the nozzles is directed toward the material 102 to be coated. The inkjet heads 103A, 103B, 103C, and 103D are examples of a plurality of ejection heads provided along the transport direction 10 of the material 102 to be coated being transported.

[0035] The inkjet head 103 is a line-type inkjet head. A "line-type inkjet head" is an inkjet head in which nozzles that eject ink are arranged across the entire width of the material to be coated 102. Note that the width of the inkjet head 103 does not necessarily have to be the entire width of the material to be coated 102 in the width direction, and can be determined appropriately.

[0036] In industrial applications, the inkjet method using a line-type inkjet head as shown in Figure 1 is preferred in order to form a film on a large amount of material at high speed. On the other hand, in industrial applications, film formation is performed continuously for a long period of time, so when a line-type head is used, some nozzles may not eject ink for a long period of time depending on the shape of the film. In such nozzles, the ink components in the ink may become non-uniform due to drying of the ink in the nozzle or settling of particle components in the ink, which may result in ejection failure.

[0037] Therefore, in the ink application process, it is preferable to vibrate the interface of the ink in the nozzle or to constantly circulate the ink in the ejection head in the nozzle that does not eject ink. By vibrating the interface of the ink in the nozzle or constantly circulating the ink in the ejection head, the ink in the nozzle and the ink in the ink flow path of the inkjet head, such as a pressure chamber communicating with the nozzle, can be made uniform, and the non-uniformity of the ink in the nozzle can be suppressed. This can further suppress the generation of abnormal films due to ejection defects. The interface of the ink in the nozzle is the interface of the ink that comes into contact with the atmosphere or gas.

[0038] In the inkjet head 103, a means for applying a stimulus to the ink to eject the ink can be appropriately selected depending on the purpose, and for example, a pressure device, a piezoelectric element, a vibration generator, an ultrasonic oscillator, a light, etc. Specific examples include a piezoelectric actuator such as a piezoelectric element, a shape memory alloy actuator that uses a metal phase change due to a temperature change, and an electrostatic actuator that uses an electrostatic force.

[0039] Among these, it is particularly preferable to use a method of applying a voltage to a piezoelectric element attached to a position called a pressure chamber (also called a liquid chamber, etc.) in an ink flow path in the inkjet head 103. In this inkjet head 103, the application of a voltage causes the piezoelectric element to bend, and the volume of the pressure chamber to shrink, thereby pressurizing the ink in the pressure chamber and ejecting the ink as droplets from the nozzle.

[0040] The inkjet head 103 includes an inkjet ejection unit, which is a collection of functional parts and mechanisms related to ink ejection from the inkjet head 103. The inkjet ejection unit includes at least one of a supply mechanism, a maintenance and recovery mechanism, and a liquid ejection head moving mechanism, which are combined with the inkjet head 103.

[0041] (material to be coated) A layer mainly made of particles provided on a non-permeable substrate such as a metal sheet can be used as the substrate 102. The layer mainly made of particles provided on the non-permeable substrate is, for example, a layer mainly made of graphite.

[0042] Non-permeable substrates include metal sheets such as aluminum, aluminum oxide, copper, stainless steel, nickel, and platinum, and resin films such as polypropylene film, polyethylene terephthalate film, and nylon film.

[0043] (Drying means) The drying means is a means for drying the ink on the coating target 102 after the ink has been ejected. In FIG. 1, the drying means 200 includes the heat drum 105 and the hot air drying unit 106.

[0044] The heat drum 105 is a rotatable drum. The heat drum 105 is an example of a temperature adjustment member that brings the outer circumferential surface into contact with the material 102 to be coated with ink and transported, thereby heating or cooling the material 102 to be coated.

[0045] The temperature adjustment method using the heat drum 105 includes a method of heating or cooling the material 102 to be coated using a liquid or gas filled inside the heat drum 105 as a heat exchange medium, a method of providing a heat source device inside the heat drum 105, etc. The drying means 200 uses the liquid or gas filled inside the heat drum 105 as a heat exchange medium, and maintains the heat exchange medium at a predetermined temperature by circulating it between the heat drum 105 and an external device such as a chiller provided outside the heat drum 105. The drying means 200 heats or cools the material 102 to be coated by heat exchange with this heat exchange medium to adjust it to a predetermined temperature.

[0046] The liquid flowing inside the heat drum 105 is not particularly limited as long as it has fluidity, such as water or oil, but water is preferable because it is easy to handle. As the gas flowing inside the heat drum 105, it is preferable to use heated air in terms of cost and safety.

[0047] The drying means 200 draws liquid or gas circulating between an external device such as a chiller into the interior of the heat drum 105 and expels it to the outside via valves provided at both ends of the heat drum 105 (ends in a direction perpendicular to the conveying direction 10).

[0048] The method of providing a heat source device inside the heat drum 105 includes a halogen heater, an infrared heater, a nichrome heater, or the like as the heat source device.

[0049] The hot air drying section 106 is provided facing the outer peripheral surface of the heat drum 105, and includes a nozzle with an opening extending in the width direction. The hot air drying section 106 heats the material 102 to be coated by blowing hot air from a nozzle onto the material 102 to be coated that is wrapped around the heat drum 105, thereby drying the ink on the material 102 to be coated. Alternatively, instead of or in addition to the hot air drying section 106, an infrared heater may be provided, and the ink on the material 102 to be coated may be dried by irradiating the surface of the material 102 with infrared rays.

[0050] When the temperature of the heat drum 105, the temperature of the hot air from the hot air drying section 106, and the wind speed of the hot air blown by the hot air drying section 106 are set within an appropriate range depending on the drying properties of the solvent used in the ink and the effect of damage to the coated material being used, the power consumption required for drying is reduced.

[0051] <Example of a film forming method using the film forming apparatus 100> Next, a film formation method using the film forming apparatus 100 will be described. In forming a film using the film forming apparatus 100, inkjet heads 103A, 103B, 103C, and 103D provided in the transport direction 10 sequentially eject the same type of ink to apply the ink onto the substrate 102. Furthermore, each of the inkjet heads 103A, 103B, 103C, and 103D applies the ejected ink to different positions on the substrate 102 along the transport direction 10.

[0052] Fig. 2 is a flowchart showing an example of the operation of the film forming apparatus 100. Fig. 2 shows the operation starting from the point in time when a user operates the operation unit of the film forming apparatus 100 to start formation and the film forming apparatus 100 accepts the operation.

[0053] First, in step S21, the film forming apparatus 100 causes the unwinding section 101 to start unwinding the material to be coated 102, causes the winding section 108 to start winding the material to be coated 102, and starts transporting the material to be coated 102.

[0054] Next, in step S22, the inkjet head 103A ejects ink from all nozzles in parallel toward the transported material 102, and after the material 102 has been transported a predetermined distance, all nozzles stop ejecting ink. As a result, the inkjet head 103A applies ink to an area on the material 102 that corresponds to a predetermined distance in the transport direction 10 and the entire width in the width direction.

[0055] Next, in step S23, the film forming apparatus 100 determines whether or not to end the film formation. The film forming apparatus 100 determines whether or not to end the film formation by determining whether or not a predetermined end condition is satisfied, or by determining whether or not the film forming apparatus 100 has received an end operation from a user via an operation unit. This point is also the same in the following end determination.

[0056] If it is determined in step S23 that the film formation is to be ended (step S23, Yes), the operation proceeds to step S30. On the other hand, if it is determined that the film formation is not to be ended (step S23, No), the operation proceeds to step S24.

[0057] Next, in step S24, the inkjet head 103B ejects ink from all nozzles in parallel toward the transported material 102, and after the material 102 has been transported a predetermined distance, all nozzles stop ejecting ink. As a result, the inkjet head 103B applies ink to an area on the material 102 that corresponds to a predetermined distance in the transport direction 10 and to the entire width in the width direction, downstream in the transport direction 10 of the area to which the inkjet head 103A has applied ink.

[0058] Inkjet head 103B applies ink to a position different from that of inkjet head 103A in transport direction 10, so that ink is applied intermittently, not continuously, onto substrate 102. Inkjet head 103B applies ink without gaps to the area where ink was applied by inkjet head 103A.

[0059] Furthermore, the inkjet head 103B applies ink onto the coating target 102 so that the area of ​​the region onto which the inkjet head 103B has applied ink is approximately equal to the area of ​​the region onto which the inkjet head 103A has applied ink.

[0060] Next, in step S25, the film forming apparatus 100 determines whether or not to end the film formation.

[0061] If it is determined in step S25 that the film formation is to be ended (step S25, Yes), the operation proceeds to step S30. On the other hand, if it is determined that the film formation is not to be ended (step S25, No), the operation proceeds to step S26.

[0062] Next, in step S26, the inkjet head 103C ejects ink from all nozzles in parallel toward the transported material 102, and stops ejecting ink from all nozzles after the material 102 has been transported a predetermined distance. As a result, the inkjet head 103C applies ink to an area on the material 102 that corresponds to a predetermined distance in the transport direction 10 and to the entire width in the width direction, downstream in the transport direction 10 of the area to which the inkjet head 103B applied ink.

[0063] Inkjet head 103C applies ink at a different position along transport direction 10 from inkjet head 103B, so that ink is applied intermittently, not continuously, onto substrate 102. Inkjet head 103C applies ink without gaps to the area where ink was applied by inkjet head 103B.

[0064] Furthermore, the inkjet head 103C applies ink onto the coating target 102 so that the area of ​​the region onto which the inkjet head 103C has applied ink is equal to the area of ​​the region onto which the inkjet head 103B has applied ink.

[0065] Next, in step S27, the film forming apparatus 100 determines whether or not to end the film formation.

[0066] If it is determined in step S27 that the film formation is to be ended (step S27, Yes), the operation proceeds to step S30. On the other hand, if it is determined that the film formation is not to be ended (step S27, No), the operation proceeds to step S28.

[0067] Next, in step S28, the inkjet head 103D ejects ink from all nozzles in parallel toward the transported material 102, and stops ejecting ink from all nozzles after the material 102 has been transported a predetermined distance. As a result, the inkjet head 103D applies ink to an area on the material 102 that corresponds to a predetermined distance in the transport direction 10 and to the entire width in the width direction, downstream in the transport direction 10 of the area to which the inkjet head 103C applied ink.

[0068] Inkjet head 103D applies ink at a different position along transport direction 10 from inkjet head 103C, so that ink is applied intermittently, not continuously, onto substrate 102. Inkjet head 103D applies ink without gaps to the area where ink was applied by inkjet head 103C.

[0069] Furthermore, the inkjet head 103D applies ink onto the coating target 102 so that the area of ​​the region onto which the inkjet head 103D has applied ink is equal to the area of ​​the region onto which the inkjet head 103C has applied ink.

[0070] Next, in step S29, the film forming apparatus 100 determines whether or not to end the film formation.

[0071] If it is determined in step S29 that the film formation is to be ended (step S29, Yes), the operation proceeds to step S30. On the other hand, if it is determined that the film formation is not to be ended (step S29, No), the operation returns to step S22, and the operations from step S22 onwards are performed again.

[0072] Next, in step S30, the film forming apparatus 100 causes the unwinding section 101 to stop unwinding the material to be coated 102, causes the winding section 108 to stop winding the material to be coated 102, and stops transporting the material to be coated 102.

[0073] In this manner, the film forming apparatus 100 can apply ink onto the substrate 102 .

[0074] <Example of film formation results using the film forming apparatus 100> Next, a description will be given of the result of film formation by the film forming apparatus 100. Fig. 3 is a diagram for explaining an example of the result of film 300 formed by the film forming apparatus 100. Fig. 3 shows a top view of the workpiece 102 on which the film 300 has been formed. The film 300 is formed when ink is discharged from the inkjet head 103 and applied onto the workpiece 102, and then dried by the drying means 200 and fixed (adhered) onto the workpiece 102.

[0075] Region 2A1 indicates the region of the film formed by applying ink by inkjet head 103A. Distance dy corresponds to the above-mentioned predetermined distance in transport direction 10, and distance dx corresponds to the total width in width direction 11. The area of ​​region 2A1 is the product of distance dx and distance dy.

[0076] In region 2A1, the squares arranged along width direction 11 represent the region of the film formed by ink ejected by each nozzle included in inkjet head 103A and arranged in width direction 11. This region of the film can also be called a pixel region. However, since the ink droplets ejected by each nozzle and applied onto substrate 102 are approximately circular and their area is larger than the area of ​​each square, one square is not formed only by ink droplets ejected from one nozzle. The ink is applied so that the center of the circle formed by the ink droplets approximately coincides with the center of the square, forming a film.

[0077] Similarly, region 2B1 indicates the region of the film formed by applying ink with inkjet head 103B, region 2C1 indicates the region of the film formed by applying ink with inkjet head 103C, and region 2D1 indicates the region of the film formed by applying ink with inkjet head 103D.

[0078] The regions 2A1, 2B1, 2C1, and 2D1 are each disposed at a different position along the transport direction 10. The center position of the region 2A1 in the transport direction 10 approximately coincides with the center position of the ink applied by the inkjet head 103A onto the substrate 102, and the center position of the region 2B1 in the transport direction 10 approximately coincides with the center position of the ink applied by the inkjet head 103B onto the substrate 102. The center position of the region 2C1 in the transport direction 10 approximately coincides with the center position of the ink applied by the inkjet head 103C onto the substrate 102, and the center position of the region 2D1 in the transport direction 10 approximately coincides with the center position of the ink applied by the inkjet head 103D onto the substrate 102.

[0079] Therefore, the inkjet heads 103A, 103B, 103C, and 103D apply the ink ejected from each of them to different positions on the material to be coated 102 along the transport direction 10.

[0080] Region 2A2 indicates a film region formed by applying ink next after inkjet head 103A forms region 2A1.

[0081] Similarly, region 2B2 indicates a region of the film formed by applying ink next after inkjet head 103B forms region 2B1. Region 2C2 indicates a region of the film formed by applying ink next after inkjet head 103C forms region 2C1. Region 2D2 indicates a region of the film formed by applying ink next after inkjet head 103D forms region 2D1.

[0082] Similarly, regions 2A3 and 2A4, regions 2B3 and 2B4, regions 2C3 and 2C4, and regions 2D3 and 2D4 also indicate regions formed in sequence by each inkjet head.

[0083] [Example] The embodiment will be described in more detail below with reference to examples, comparative examples and reference examples, but the embodiment is not limited to these examples.

[0084] In addition, in Figures 4 to 10 shown below, the area onto which inkjet head 103A ejects and applies ink is referred to as area 2A, the area onto which inkjet head 103B ejects and applies ink is referred to as area 2B, the area onto which inkjet head 103C ejects and applies ink is referred to as area 2C, and the area onto which inkjet head 103D ejects and applies ink is referred to as area 2D.

[0085] <Ink adjustment example 1> The following composition was dispersed in a ball mill for 24 hours using zirconia media with a diameter of 2 mm to prepare Ink 1 with a non-volatile content of 40%.

[0086] [composition] Aluminum oxide particles AKP-3000 (Sumitomo Chemical) 177 parts Polymer compound (copolymer of ammonium fumarate and a monomer having a side chain containing an oxyalkylene group or a polyoxyalkylene group) Marialim HKM-50A (manufactured by NOF Corp.) 3 parts ·NMP270 copies

[0087] <Ink adjustment example 2> Ink 2 was prepared in the same manner as ink 1, except that the aluminum oxide particles AKP-3000 (manufactured by Sumitomo Chemical) were replaced with titanium oxide particles PT-301M (manufactured by Ishihara Sangyo Kaisha).

[0088] <Ink adjustment example 3> The following composition was dispersed in a ball mill for 24 hours using zirconia media with a diameter of 2 mm to prepare ink 3 having a non-volatile content of 30%.

[0089] [composition] Aluminum oxide particles AKP-3000 (Sumitomo Chemical) 132.7 parts Polymer compound (a copolymer of ammonium fumarate and a monomer having a side chain containing an oxyalkylene group or a polyoxyalkylene group) Marialim HKM-50A (manufactured by NOF Corp.) 2.3 parts ·NMP270 copies

[0090] <Ink adjustment example 4> The following composition was dispersed in a ball mill for 24 hours using zirconia media with a diameter of 2 mm to prepare ink 4 with a non-volatile content of 20%.

[0091] [composition] Aluminum oxide particles AKP-3000 (Sumitomo Chemical) 88.5 parts Polymer compound (a copolymer of ammonium fumarate and a monomer having a side chain containing an oxyalkylene group or a polyoxyalkylene group) Marialim HKM-50A (manufactured by NOF Corp.) 1.5 parts ·NMP270 copies

[0092] <Ink adjustment example 5> The following composition was dispersed in a ball mill for 24 hours using zirconia media with a diameter of 2 mm to prepare ink 5 having a non-volatile content of 10%.

[0093] [composition] Aluminum oxide particles AKP-3000 (Sumitomo Chemical) 44.2 parts Polymer compound (a copolymer of ammonium fumarate and a monomer having a side chain containing an oxyalkylene group or a polyoxyalkylene group) Marialim HKM-50A (manufactured by NOF Corp.) 0.8 parts ·NMP270 copies

[0094] <Ink adjustment example 6> The following composition was stirred and mixed using a stirrer to prepare ink 6 having a non-volatile component content of 40%.

[0095] [composition] Acrylic monomer Viscoat #295 (Osaka Organic Chemical Industry Co., Ltd.) 171 parts Polymerization initiator (1-hydroxycyclohexyl phenyl ketone) (Tokyo Chemical Industry Co., Ltd.) 9 parts ·NMP270 copies

[0096] Example 1 Films were formed by filling ink containers of a modified inkjet recording device (product name: VC-60000, manufactured by Ricoh Co., Ltd.) capable of mounting four types of ink. The configuration of the modified inkjet recording device is shown in Figure 1, and ink is ejected from each of four inkjet heads 103A, 103B, 103C, and 103D. Films were continuously formed under the following formation conditions using this modified inkjet recording device.

[0097] <Coating conditions> Coating speed: 50 [m / min] Inkjet head application time difference: 0.5 seconds Resolution: 1200 x 1200 [dpi] Coating film: Uniform solid coating Number of inkjet heads: Four inkjet heads 103A, 103B, 103C, and 103D are arranged in line along the conveying direction 10. Discharge method: Repeated application of ink to four equally divided areas using four inkjet heads 103A, 103B, 103C and 104D (see FIG. 3). Ink: Ink 1 - Droplet size: 14[pl] · Substrate to be coated: A substrate for battery electrodes, consisting of a 50[μm] layer of graphite particles with an average particle size of 9μm as the main component on a 10[μm] copper foil. Hot air drying method: Hot air temperature 130[℃], wind speed 20[m / s] Heat drum means: IR heater inside drum 120[℃]

[0098] (evaluation) After formation under the conditions of Example 1 above, the quality of the film was evaluated according to the following method and evaluation criteria.

[0099] <Film quality> After cutting out to A4 size, the quality of the film was observed visually and under a microscope and evaluated according to the following criteria: Films with a rating of 3 or higher were judged to be usable.

[0100] (Evaluation Criteria) 5: No point defects observed under microscope 4: Three or fewer point defects not visible to the naked eye but visible under a microscope 3: 10 or less point defects not visible to the naked eye but visible under a microscope 2: Visually visible point defects are partially present 1: Visually visible point defects occur over the entire surface

[0101] Example 2 Continuous film formation was performed under the same conditions as in Example 1, except that only three of the four inkjet heads 103A, 103B, 103C, and 104D arranged in the transport direction were used, and the ejection method was changed so that the three inkjet heads repeatedly applied ink to an area divided equally into three (see Figure 4).

[0102] Example 3 Continuous film formation was performed under the same conditions as in Example 1, except that only two of the four inkjet heads 103A, 103B, 103C, and 104D arranged in the transport direction were used, and the ejection method was changed so that the two inkjet heads repeatedly applied ink to an area divided equally into two (see Figure 5).

[0103] Example 4 In the formation conditions of Example 1, the ejection method was changed so that ink was repeatedly applied to an area divided equally into two by four inkjet heads 103A, 103B, 103C, and 104D (see FIG. 6), and the droplet size ejected by each inkjet head was changed from 14 [pl] to 7 [pl]. However, the film was continuously formed under the same conditions.

[0104] Example 5 Continuous film formation was performed under the same conditions as in Example 1, except that the ejection method was changed so that ink was repeatedly applied to six divided areas using four inkjet heads 103A, 103B, 103C, and 104D (see Figure 7).

[0105] Example 6 Continuous film formation was performed under the same conditions as in Example 1, except that the ejection method was changed so that ink was repeatedly applied to six divided areas using four inkjet heads 103A, 103B, 103C, and 104D (see Figure 8).

[0106] Example 7 Films were continuously formed under the same conditions as in Example 1, except that the distance between the inkjet heads in the transport direction was changed and the coating time difference was changed from 0.5 seconds to 0.4 seconds.

[0107] Example 8 Continuous film formation was performed under the same conditions as in Example 1, except that the distance between the inkjet heads in the transport direction was changed and the coating time difference was changed from 0.5 seconds to 0.3 seconds.

[0108] Example 9 Films were continuously formed under the same conditions as in Example 1, except that the distance between the inkjet heads in the transport direction was changed and the coating time difference was changed from 0.5 seconds to 0.2 seconds.

[0109] Example 10 Continuous film formation was performed under the same conditions as in Example 1, except that the droplet size ejected by the inkjet heads was changed as follows for each of the inkjet heads from inkjet head 103A located most upstream to inkjet head 103D located most downstream. Inkjet head 103A: 8 [pl] Inkjet head 103B:12[pl] Inkjet head 103C: 16[pl] Inkjet head 103D: 20 [pl]

[0110] Example 11 Films were continuously formed under the same conditions as in Example 1, except that the ink used was changed from ink 1 to ink 3.

[0111] Example 12 Films were continuously formed under the same conditions as in Example 1, except that the ink used was changed from ink 1 to ink 2.

[0112] Comparative Example 1 Continuous formation was performed under the same conditions as in Example 1, except that only one of the four inkjet heads 103A, 103B, 103C, and 104D arranged in the transport direction was used, and ink was applied to each area of ​​the substrate by one inkjet head as shown in Figure 9.

[0113] Comparative Example 2 Continuous formation was performed under the same conditions as in Example 1, except that, of the four inkjet heads 103A, 103B, 103C, and 104D arranged in the transport direction, only two inkjet heads were used, and the ink was applied to each area of ​​the substrate by overlapping the ink using the two inkjet heads as shown in Figure 10, and the ejection droplet size of each inkjet head was changed from 14 [pl] to 7 [pl].

[0114] (Reference example 1) Continuous formation was performed under the same conditions as in Comparative Example 1, except that the coating material was changed to a PET resin film having a thickness of 50 μm.

[0115] (Reference example 2) Continuous formation was performed under the same conditions as in Comparative Example 1, except that the ink used was changed from ink 1 to ink 4.

[0116] (Reference example 3) Continuous formation was performed under the same conditions as in Comparative Example 1, except that the ink used was changed from ink 1 to ink 5.

[0117] (Reference example 4) Each ink was filled into the ink storage container of a modified inkjet recording device (product name: VC-60000, manufactured by Ricoh Co., Ltd.) capable of mounting four types of ink, and a film was formed. The configuration of the modified inkjet recording device is configured such that, in addition to the configuration shown in FIG. 1, five LED-UV lamp units are arranged between the inkjet head and the heat drum. With this modified inkjet recording device, continuous formation was performed under the same conditions as in Comparative Example 1, except that the ink used was changed from ink 1 to ink 6. The evaluation results performed in Examples 1 to 12, Comparative Examples 1 to 2, and Reference Examples 1 to 4 are shown in Table 1. [Table 1]

[0118] The evaluation results of Examples 1 to 12, Comparative Examples 1 and 2, and Reference Examples 1 to 4 are shown in Table 1. As shown in Table 1, excellent film quality was obtained by this embodiment. Furthermore, Reference Example 1 uses a resin film instead of the coating material having a layer mainly composed of particles in Comparative Example 1, and the quality of the film is superior to that of the coating material having a layer mainly composed of particles. From this, it was found that this embodiment is particularly effective when a coating material having a layer mainly composed of particles is used.

[0119] In Reference Examples 2 and 3, the ink in Comparative Example 1, which contains 40% non-volatile components per unit area, is replaced by inks containing 20% ​​or 10%, and the inks containing fewer non-volatile components have superior film quality. This shows that the present embodiment is particularly effective when inks containing many non-volatile components are used.

[0120] In other words, it has been found that when applying an ink containing particles as the main component on a layer provided on a non-permeable substrate, it is preferable to apply an ink containing 30% or more of non-volatile components per unit volume. The non-volatile components are applied onto the layer without penetrating into the layer provided on the non-permeable substrate or being replaced by the air in the layer. However, a part of the non-volatile components may penetrate into the layer or be replaced by the air in the layer.

[0121] In Reference Example 4, the main component of the ink in Comparative Example 1 is changed from metal oxide particles to an ink of acrylic monomer, and the ink without metal oxide particles in the ink has excellent film quality. This is expected to be due to the fact that acrylic monomers are better than metal oxides at penetrating into the innermost layer of the coating material, the main component of which is particles, and therefore replacement with air inside the outermost layer is more easily promoted. From this, it was found that the present embodiment is particularly effective when an ink containing metal oxide is used. In other words, it was found that the non-volatile component contained in the ink is preferably one containing metal oxide particles.

[0122] Furthermore, from the evaluation results of Examples 7 to 9, when the time difference between applying ink among the inkjet heads 103A, 103B, 103C, and 103D was 0.2 seconds, the quality of the film was 3, and when it was 0.3 seconds and 0.4 seconds, the quality of the film was 4. Therefore, it was found that a time difference of 0.3 seconds or more is preferable.

[0123] In other words, the inkjet heads 103A, 103B, 103C, and 103D include a first ejection head and a second ejection head provided downstream of the first ejection head along the transport direction 10. It has been found that it is preferable for the second ejection head to apply ink onto the substrate 102 0.3 seconds or more after the first ejection head applies ink onto the substrate 102.

[0124] In this case, the distance between the centers of the ink droplets that land on the material to be coated 102 in the transport direction of the material to be coated 102 is equal to or greater than the transport speed of the material to be coated 102 multiplied by 0.3 [seconds]. In other words, the film forming apparatus 100 applies the inks ejected from the inkjet heads 103A, 103B, 103C, and 103D to different positions on the material to be coated 102 along the transport direction 10 by a distance equal to or greater than the transport speed of the material to be coated 102 multiplied by 0.3 [seconds].

[0125] Moreover, the evaluation results of Example 10 show that the inkjet heads 103A, 103B, 103C, and 103D disposed on the downstream side along the transport direction 10 preferably eject larger droplets.

[0126] From the above results, it was found that the present embodiment can provide a film of excellent quality. It was also found that the present embodiment can provide a film of excellent quality at least when a substrate for a battery electrode is used as a substrate to be coated.

[0127] The battery electrode has a positive electrode including a positive electrode current collector and a positive electrode active material layer, and a negative electrode including a negative electrode current collector and a negative electrode active material layer. The film forming apparatus 100 is suitable for applications such as forming an insulating film that physically insulates the positive electrode and the negative electrode in the battery electrode.

[0128] <Effects of the film forming method using the film forming apparatus 100> Next, the effects of the film forming method using the film forming apparatus 100 will be described.

[0129] When ink (liquid) is applied to a coating material 102 having a particle-based layer on the outermost surface of a non-permeable base material, roughly circular defects where no ink is present on the coating material 102 are more likely to occur than in a coating material having a layer mainly made of a resin component.

[0130] This phenomenon is believed to occur because, when ink is applied onto the substrate 102, the air inside the layer mainly composed of particles in the substrate 102 is replaced by liquid and expelled from the layer, preventing the ink from spreading on the substrate 102. If the substrate 102 with a roughly circular defect is used as an electrode, a short circuit may occur.

[0131] In this embodiment, a coating process is performed in which ink ejected from each of inkjet heads 103A, 103B, 103C, and 103D (multiple ejection heads) provided along a transport direction 10 of a transported material 102 is applied to the material 102. In the coating process, ink ejected from each of inkjet heads 103A, 103B, 103C, and 103D is applied to different positions on the material 102 along the transport direction 10.

[0132] This allows the ink to be applied to the substrate 102 intermittently at regular intervals, rather than continuously, and ensures sufficient time for the air inside the layer mainly composed of particles to be replaced by ink and discharged. As a result, the ink spreads over the substrate 102 and sufficiently covers the substrate, suppressing defects such as substantially circular defects in the substrate 102 and improving the uniformity of the film that is formed.

[0133] In this embodiment, the areas of the regions on the substrate 102 onto which the ink ejected from each of the inkjet heads 103A, 103B, 103C, and 103D is applied are uniform. By making the areas uniform, the thicknesses of the films formed by the ink application from each inkjet head become uniform, and the uniformity of the film thickness can be improved.

[0134] In this case, uniformity does not require that the areas of the films formed by applying ink from each inkjet head be strictly the same. For example, the above effect can be obtained even if there is a difference of 5% or less from the desired area.

[0135] In this embodiment, the configuration in which ink is applied onto a layer mainly composed of particles provided on the outermost surface of the material to be coated 102 has been exemplified, but the present invention is not limited to this. Even if the material to be coated 102 does not have a layer mainly composed of particles, as long as it contains air inside, the above-mentioned action and effect can be obtained by applying this embodiment.

[0136] Although the embodiments have been described above, the present invention is not limited to the above specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0137] In the above-described embodiment, a configuration in which a film is formed uniformly on a substrate is exemplified, but a predetermined pattern can also be formed on the substrate by ejecting ink from an inkjet head. This pattern includes an identification code such as a barcode or a two-dimensional code indicating information on the substrate or electrodes to be manufactured by applying ink to the substrate. This allows the information on the substrate to be formed or the electrodes to be manufactured to be efficiently added without performing a separate process.

[0138] Furthermore, all numbers such as ordinal numbers and quantities used in the description of the embodiments are merely examples for specifically explaining the technology of the present invention, and the present invention is not limited to the exemplified numbers. [Explanation of symbols]

[0139] 10 Conveying direction 11 Width direction 100 Film forming equipment 101 Unwinding section 102 Material to be coated 103, 103A, 103B, 103C, 103D Inkjet heads 104 Platen 105 Heat Drum 106 Hot air drying section 107 Transport roller 108 Winding section 300 membrane dx, dy distance Regions 2A, 2B, 2C, 2D

Prior Art Documents

Patent Documents

[0140]

Patent Document 1

Claims

1. A film forming method for forming a film on a substrate, comprising the steps of: A coating process includes discharging liquid from each of a plurality of discharge heads provided along a transport direction of the transported material to be coated, and coating the liquid on the material to be coated; In the coating step, the liquid discharged from each of the plurality of discharge heads is applied to different positions on the coating target along the transport direction, The film forming method, wherein the material to be coated includes a layer mainly composed of particles provided on a non-permeable substrate.

2. 2. The film forming method according to claim 1, wherein the areas on the substrate coated with the liquid discharged from each of the plurality of discharge heads are substantially uniform.

3. the plurality of ejection heads include a first ejection head and a second ejection head provided downstream of the first ejection head along the transport direction, The film forming method according to claim 1 or 2, wherein the second ejection head applies the liquid onto the substrate 0.3 seconds or more after the first ejection head applies the liquid onto the substrate.

4. 4. The film forming method according to claim 1, wherein in the coating step, the liquid containing 30% or more of non-volatile components per unit volume is coated onto a layer formed on a non-permeable substrate and containing particles as a main component.

5. The film forming method according to claim 4 , wherein the non-volatile component includes metal oxide particles.

6. 6. The film forming method according to claim 1, wherein each of the plurality of ejection heads is arranged in a direction intersecting the transport direction, and has a plurality of nozzles for ejecting the liquid.

7. The substrate includes an electrode, 7. The film forming method according to claim 1, wherein in the coating step, each of the plurality of discharge heads discharges and coats the liquid at a different position on the electrode along the transport direction.

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