Film thickness prediction method for dip coating and pulling-up speed determination method

Abstract

To provide: a film thickness prediction method for dip coating capable of improving the accuracy of film thickness prediction of when the surface of a base material is coated by dip coating; and a pull-up speed determination method for dip coating for determining a pull-up speed required for obtaining a desired film thickness.SOLUTION: An intermediate layer 22 between an uneven-surfaced substrate 10 and a laminar flow layer 21, whose film thickness is determined in accordance with viscosity and pulling-up speed, is a layer whose film thickness varies in accordance with values of the pulling-up speed, surface tension, and surface roughness. A film thickness prediction method of dip coating: determines a film thickness d of the intermediate layer from pulling-up speed, density, surface tension, and surface roughness; and determines a coating thickness D on the basis of a film thickness h of a laminar flow layer, and the film thickness d of the intermediate layer 22.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for predicting a film thickness and a method for determining a withdrawal rate in dip coating. [Background technology]

[0002] The technique disclosed in Patent Document 1 below is known as a technique for smoothing the surface of a base material having minute irregularities by painting.

[0003] The technology of Patent Document 1 involves applying a photocurable resin to the surface of a substrate to fill in any recesses on the surface, thereby smoothing out any unevenness on the surface through the coating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-337951 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional techniques can apply a smooth film to the surface of a substrate, but they apply a thick film to the surface that is not affected by the base, or apply a high-viscosity resin to the uneven surface. This results in a discrepancy between the surface shape of the substrate itself and the surface shape after coating. For substrates where shape accuracy is not important, it is possible to predict the approximate film thickness and apply the coating.

[0006] However, when shaping a product, such as a 3D printed product, it is not possible to apply a highly smooth film that matches the uneven shape of the substrate surface, which has been created with high shape precision.

[0007] 3D printed molded products require high accuracy of the shape of the molded product itself, so the accuracy of the shape after coating is strict. For this reason, it is necessary to accurately predict the film thickness when painting molded products by dip coating. However, with the current film thickness prediction method, there is a large discrepancy between the actual film thickness and the predicted film thickness due to the influence of surface unevenness.

[0008] Therefore, an object of the present invention is to provide a method for predicting a film thickness of a dip coating, which can improve the accuracy of predicting a film thickness when a substrate surface is painted by dip coating, and a method for determining a pull-up rate of a dip coating, which determines a pull-up rate required to obtain a desired film thickness. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a method for predicting the thickness of a dip coating film, in which an intermediate layer between a laminar layer, the thickness of which is determined by viscosity and pulling speed, and a substrate having a surface irregularity is a layer whose thickness varies depending on the pulling speed, surface tension, and surface roughness, and the thickness (d) of the intermediate layer is calculated from the pulling speed, density, surface tension, and surface roughness, and the coating thickness (D) is calculated based on the thickness (h) of the laminar layer and the calculated thickness (d) of the intermediate layer.

[0010] In addition, in the method for determining the pull-up speed for dip coating of the present invention, an intermediate layer between a laminar layer, the thickness of which is determined by the viscosity and the pull-up speed, and a substrate having a surface irregularity is a layer whose thickness varies depending on the pull-up speed, surface tension, and surface roughness, the thickness (d) of the intermediate layer satisfies the following formula (2), the velocity (V) at the interface between the laminar layer and the intermediate layer satisfies the following formula (4), and the thickness (h) of the laminar layer satisfies the following formula (5). Then, the pull-up speed (U) is determined by the following formula (6) which is a modification of the formulas (4) and (5).

[0011]

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[0012] According to the method for predicting a film thickness of dip coating of the present invention, it is possible to improve the accuracy of predicting a film thickness when painting a substrate by dip coating to fill in surface irregularities.

[0013] According to the method for determining the pull-up speed for dip coating, it is possible to improve the accuracy of determining the pull-up speed required to obtain a desired film thickness when applying a coating to fill in surface irregularities of a substrate by dip coating. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing a schematic diagram of a substrate having an uneven surface coated by dip coating. [Diagram 2] FIG. 2 is an enlarged view of a main part of FIG. [Diagram 3] FIG. 1 is a schematic diagram for explaining the basic concept of predicting a film thickness of a dip coating. [Figure 4] FIG. 1 is a schematic diagram showing the results of a simulation of the flow on a microstructure surface when a substrate having surface irregularities is painted by dip coating. [Diagram 5] FIG. 13 is a schematic diagram for explaining the concept of further improving the accuracy of film thickness prediction by predicting the velocity of the interface between the laminar layer and the intermediate layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the drawings. The embodiments shown here are merely illustrative in order to embody the technical idea of ​​the present invention, and do not limit the present invention. Therefore, all other embodiments, examples, and operational techniques that can be conceived by those skilled in the art without departing from the gist of the present invention are included in the scope and gist of the present invention, and are included in the scope of the inventions described in the claims and their equivalents.

[0016] In addition, for the convenience of illustration and ease of understanding, the drawings attached to this specification may be represented diagrammatically with the scale, aspect ratio, shape, etc. appropriately changed from the actual product; however, these are merely examples and are not intended to limit the interpretation of the present invention.

[0017] In this specification, ordinal numbers such as "first", "second", etc. may be used. However, unless otherwise specified, these ordinal numbers are used to identify components for the convenience of explanation, and do not specify the number or order.

[0018] First Embodiment As shown in Fig. 1, a resin base material 10, for which surface design is important, is painted by dip coating to fill in minute irregularities present on the surface. Examples of vehicle parts that are painted in this way include resin products such as interior parts, bumpers, and lamp finishers, for which surface design is important.

[0019] The inventors have found that in order to improve the accuracy of film thickness predictions for microstructured surfaces, rather than predicting the film thickness using general rheological equations, it is necessary to take into account the effects of the specific surface area (surface roughness) and surface tension near the surface of the substrate 10, and have completed a method for predicting the film thickness of dip coating.

[0020] As shown in Figures 2 and 3, a coating film 20 formed by dip coating includes a laminar layer 21 on the surface side, an intermediate layer 22 between the laminar layer 21 and the substrate 10 having a surface irregularity, and a filling layer 23 that fills in the surface irregularity. The laminar layer 21 is a layer whose thickness is determined by the viscosity of the paint and the lifting speed. The intermediate layer 22 is a layer whose thickness changes depending on the lifting speed, the surface tension of the paint, and the surface roughness. The method for predicting the thickness of a dip coating film is to calculate the film thickness d of the intermediate layer 22 from the lifting speed, the density of the paint, the surface tension of the paint, and the surface roughness of the substrate 10, and to calculate the coating thickness D based on the film thickness h of the laminar layer 21 and the calculated film thickness d of the intermediate layer 22.

[0021] The coating thickness D can be calculated by adding the film thickness h of the laminar layer 21 and the film thickness d of the intermediate layer 22 thus calculated.

[0022] 3, the reference character L1 indicates a first line representing the surface of the coating film 20 (which is also the surface of the laminar layer 21). The reference character L2 indicates a second line representing the boundary between the laminar layer 21 and the intermediate layer 22. The reference character L3 indicates a third line connecting the vertices of the microstructure.

[0023] In this way, by predicting the film thickness taking into account the presence of the intermediate layer 22, it is possible to improve the accuracy of predicting the film thickness when coating the surface of the substrate 10 by dip coating.

[0024] When applying paint to a substrate 10 having an uneven surface by dip coating, the behavior of the fluid near the surface of the substrate 10 is different from that when applying paint to a smooth surface. This is due to the influence of the surface tension between solid and liquid, and the difference in specific surface area relative to a flat surface. We focused on the fact that the film thickness d of the intermediate layer 22 can be expressed as a function of d=C'·f(ρ·U·R) and then corrected. Here, C' is a coefficient, ρ is density, U is pulling speed, and R is specific surface area (surface roughness).

[0025] The reason why the regions where the fluid behavior is different were not taken into consideration is as follows. Since the flow in this microscopic region cannot be seen in an experiment, analysis by simulation is necessary. Also, in the case of precision coating by dip coating, a coating film that is a very thin film on the nanoscale and conforms to the structure is generally used. This is thought to be because the precision of painting to fill the surface irregularities of the substrate 10 by dip coating was not required. For example, dip coating has been used industrially as a very thick film such as an automobile undercoat, or a very thin film such as a monolayer, so precise film thickness control that takes the intermediate layer 22 into consideration has not been performed. Conventionally, it has only been dealt with by adjusting the coefficients of the prediction formula.

[0026] The thickness h of the laminar layer 21 is calculated by the following formula (1). The thickness d of the intermediate layer 22 is calculated by the following formula (2). The total thickness (h+d) of these layers is multiplied by the solid content X of the coating material to calculate the coating thickness D after curing by the following formula (3).

[0027]

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[0028] In this way, by defining the intermediate layer 22 that is affected by surface tension and surface roughness, the accuracy of film thickness prediction when painting the surface of the substrate 10 by dip coating can be further improved.

[0029] As shown in FIGS. 3 and 4, the laminar layer 21 is a region affected by rheology, and is a layer whose thickness h can be calculated using the same formula (the above formula (1)) as for a conventional smooth surface.

[0030] On the other hand, when the surface of the substrate 10 is uneven, a change in the flow of the fluid occurs due to the surface roughness (specific surface area to a flat surface), which is a factor resulting from the uneven surface. Also, because of the unevenness, it is unclear where the starting point of film formation should be to predict the film thickness. In this way, the intermediate layer 22 is a layer that is affected by the surface roughness (specific surface area to a flat surface) and surface tension. The starting point of the film thickness is defined as the line connecting the vertices of the microstructure (the third line L3 in FIG. 3). The film thickness d of the intermediate layer 22 is calculated by adding conditions that are affected by the specific surface area and surface tension to the conventional film thickness prediction formula (above formula (2)). Because R×γ acts as a reaction force against the gravity part ρ×g that reduces the film thickness, the added condition formula is 1 / (R×γ) 0.5 The coating thickness D by dip coating is D = h + d.

[0031] As shown in FIG. 5, when dip coating, the paint moves at a high speed near the substrate 10 and at zero speed at the film surface. To further improve the accuracy of film thickness prediction, it is necessary to correct the initial speed of the laminar layer 21. The film thickness d obtained by the above formula (2) is substituted into the following formula (4), which is a modification of the conventional film thickness calculation formula (1), to obtain the predicted speed V at the interface between the laminar layer 21 and the intermediate layer 22. The coating thickness D after curing is calculated using the following formula (5), which is a correction of the above formula (1). In formula (5), formula (1) is corrected by the speed obtained by subtracting the predicted speed V from the lifting speed U.

[0032]

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[0033] In this way, by determining the predicted velocity V at the interface between the laminar layer 21 and the intermediate layer 22 and correcting the film thickness prediction equation, it is possible to further improve the accuracy of film thickness prediction when painting the surface of the substrate 10 by dip coating.

[0034] The measured values ​​of the film thickness (μm) when the pulling speed (mm / s) was changed to 0.02, 0.09, 0.14, and 0.3 were 16.5, 35.7, 45.0, and 65.2, respectively. The difference between the predicted film thickness and the measured film thickness when the formula of claim 3 was applied, the difference between the predicted film thickness and the measured film thickness when the formula of claim 4 was applied, and the difference between the predicted film thickness and the measured film thickness when the conventional prediction formula was applied are shown in Table 1 below. The formula of claim 3 is a formula that takes into account the intermediate layer 22. The formula of claim 4 is a formula that is corrected by the predicted velocity V at the interface between the laminar layer 21 and the intermediate layer 22. The conventional prediction formula is a formula that does not take into account the intermediate layer 22.

[0035] As shown in Table 1, it was confirmed that the accuracy of film thickness prediction was higher when the formula of claim 3 was applied than when the conventional prediction formula was applied, and was even higher when the formula of claim 4 was applied.

[0036] [Table 1]

[0037] <Second embodiment> When applying a coating to fill in the surface irregularities of the substrate 10 by dip coating, the withdrawal speed required to obtain the desired film thickness (film thickness d of the intermediate layer 22 and film thickness h of the laminar layer 21) can also be determined.

[0038] 5, similarly to the above, the intermediate layer 22 between the laminar layer 21, whose thickness is determined by the viscosity and the pulling speed, and the substrate 10 having a surface irregularity is a layer whose thickness changes depending on the pulling speed, surface tension, and surface roughness. The thickness d of the intermediate layer 22 satisfies the following formula (2), the predicted velocity V at the interface between the laminar layer 21 and the intermediate layer 22 satisfies the following formula (4), and the thickness h of the laminar layer 21 satisfies the following formula (5). The pulling speed U is determined by the following formula (6) which is a modification of formulas (4) and (5).

[0039]

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[0040] In this way, the method for determining the pull-up speed for dip coating can improve the accuracy of determining the pull-up speed required to obtain a desired film thickness when applying a coating to fill in surface irregularities on the substrate 10 by dip coating. [Explanation of symbols]

[0041] 10 Base material 20 Coating 21 Laminar layer 22 Middle Class 23 Filled bed L1: The first line representing the surface of the coating L2 The second line representing the boundary between the laminar layer and the intermediate layer L3: The third line connecting the vertices of the fine structure U Pulling speed V is the predicted velocity at the interface between the laminar layer and the intermediate layer d Intermediate layer thickness h laminar layer thickness D Coating thickness

Claims

1. an intermediate layer between the laminar layer, the thickness of which is determined by the viscosity and the lifting speed, and the substrate having a surface irregularity is a layer whose thickness changes depending on the lifting speed, surface tension, and surface roughness; The thickness (d) of the intermediate layer is determined from the pulling speed, density, surface tension, and surface roughness, A method for predicting a film thickness of a dip coating, comprising determining a coating thickness (D) based on the film thickness (h) of the laminar layer and the determined film thickness (d) of the intermediate layer.

2. 2. The method for predicting a film thickness of a dip coating according to claim 1, wherein the coating thickness (D) is calculated by adding the film thickness (h) of the laminar layer and the calculated film thickness (d) of the intermediate layer.

3. The thickness (h) of the laminar layer is calculated by the following formula (1): The thickness (d) of the intermediate layer is calculated by the following formula (2): The method for predicting a film thickness of dip coating according to claim 1, wherein the total film thickness (h+d) is multiplied by the solid content (X) of the coating to obtain the coating thickness (D) after curing according to the following formula (3). [0010]

4. A predicted velocity (V) at the interface between the laminar layer and the intermediate layer is calculated by the following formula (4):

4. The method for predicting a film thickness of a dip coating according to claim 3, wherein the coating thickness (D) after curing is calculated using the following formula (5) obtained by correcting the formula (1): [0025]

5. an intermediate layer between the laminar layer, the thickness of which is determined by the viscosity and the lifting speed, and the substrate having a surface irregularity is a layer whose thickness changes depending on the lifting speed, surface tension, and surface roughness; The thickness (d) of the intermediate layer satisfies the following formula (2), A predicted velocity (V) at the interface between the laminar layer and the intermediate layer satisfies the following formula (4): The thickness (h) of the laminar layer satisfies the following formula (5): A method for determining a pulling speed for dip coating, comprising determining a pulling speed (U) according to the following formula (6), which is a modification of the formulas (4) and (5). [0030]

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