JP2017064706A - Coating film forming method, and functional material provided with coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which exhibits excellent workability and can easily form a coating film having an even or uniform, and good appearance on a surface of a base material.SOLUTION: A method of forming a coating film on a surface of a base material includes: at least a process of forming a liquid film by applying an aqueous coating composition on the surface of the base material; and a process of forming a coating film by drying the liquid film. The liquid film has a fine uneven shape including a plurality of protruded parts and a plurality of recessed parts. In the coating film forming process, the coating film, on which the fine uneven shape of the liquid film is maintained, is formed by drying the liquid film.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a coating film forming method capable of easily forming a coating film having excellent workability, uniform or homogeneous on the surface of the substrate, and having a good appearance, and the substrate, and the surface of the substrate It is related with the functional material provided with the coating film which has the uniform or homogeneous and the favorable external appearance formed.

  As one means for forming a coating film on the surface of a substrate, an aqueous coating composition containing water as a dispersion medium is used. The aqueous coating composition generally tends to have a lower surface tension and lower viscosity than a non-aqueous coating composition containing a solvent as a dispersion medium. That is, the water-based coating composition has high leveling properties (propensity to easily spread on the surface of the substrate). When applying a water-based coating composition having such a high leveling property to a substrate having a wide surface such as a wall surface or a vertical surface or inclined surface in field construction, appearance defects such as dripping and uneven coating are likely to occur. It may be difficult to form a uniform film. In particular, when applied to a transparent substrate such as glass, poor appearance tends to occur more easily, and it is more difficult to form a uniform film. In order to suppress such problems, there is a situation that requires a high level of skill from the installer, and high technology is required for on-site construction.

  WO98 / 003607 (Patent Document 1) describes that a coating composition can be uniformly applied to the surface of a substrate by adding a surfactant. Japanese Patent Application Laid-Open No. 10-337526 (Patent Document 2) describes a method in which a coating composition is applied after cleaning the surface of an existing base material on which dirt is adhered. It is described that the wettability to the surface of the substrate can be improved by adding a surfactant to the coating composition.

  Japanese Patent Application Laid-Open No. 2000-246115 (Patent Document 3) discloses a photocatalytic member having a photocatalytic coating formed, for example, in a discontinuous manner, preferably in an island shape, in a substantially uniformly dispersed state on the surface of a substrate. Is described. It has been reported that this photocatalytic member can exert its photocatalytic function satisfactorily even in an environment where the substrate is likely to expand and contract due to climate change.

  However, there is still a need for a method that can easily form an excellent coating film having a uniform and good appearance on a surface of a substrate such as a wall surface on which it is difficult to apply an aqueous coating composition without requiring high construction techniques. Yes.

WO98 / 003607 Publication JP-A-10-337526 JP 2000-246115 A

  The present inventors recently formed a liquid film having a fine uneven shape on the surface of the base material, and dried the liquid film so as to maintain this fine uneven shape, thereby forming a film, It was found that a coating film having excellent workability, uniform or homogeneous, and a good appearance can be easily formed on the surface of the substrate. The present invention is based on such knowledge.

  Accordingly, an object of the present invention is to provide a method capable of easily forming a coating film having excellent workability, uniform or homogeneous on the surface of a substrate, and having a good appearance. Another object of the present invention is to provide a functional material comprising a base material and a coating film formed on the surface of the base material that is uniform or homogeneous and has a good appearance.

That is, the present invention is a method of forming a coating film on the surface of a substrate,
The method is
Applying a water-based coating composition to the surface of the substrate to form a liquid film;
Forming a film by drying the liquid film, and
The liquid film has a fine uneven shape including a plurality of convex portions and a plurality of concave portions,
In the coating film forming step, the liquid film is dried to form the coating film in which the fine uneven shape of the liquid film is maintained.

  Further, the present invention is a functional material comprising a base material and a coating film formed on the surface of the base material, wherein the coating film includes a plurality of convex portions and a plurality of concave portions. It is characterized by having.

  The coating film forming method according to the present invention allows the aqueous coating composition and / or the substrate to be used without any special treatment even in an environment where it is difficult to apply the aqueous coating composition to the substrate. A film having a shape in which the shape of the liquid film is maintained can be easily formed while controlling the shape of the liquid film formed from the coating composition to a fine uneven shape. In the present invention, a liquid film having a fine concavo-convex shape is formed, and the liquid film is dried while maintaining this shape, so that a coating film having a uniform and excellent appearance is obtained. When the liquid film has a fine uneven shape, it is considered that this shape is maintained in the liquid film in the middle of drying and further in the film after drying. By maintaining this shape, it is possible to easily form an excellent coating film having a uniform and good appearance without requiring a high construction technique. Specifically, a substrate having a larger area than a window glass or the like such as a wall surface, a substrate having a vertical surface or an inclined surface, or such a substrate and having transparency. It is possible to easily form a uniform coating film without requiring high construction skills without any appearance defects such as coating unevenness and coating stripes being visually recognized. Or, in the summer, when the temperature is high and the drying time of the liquid film is short, when performing on-site construction, poor appearance such as coating unevenness, streaks, etc., and the environment where the temperature is low and the drying time of the liquid film is long, such as in winter A uniform coating film can be easily formed without requiring high construction skills without any visual defects such as liquid sag in the case of site construction. Furthermore, such excellent workability can be stably expressed and maintained.

3 is a flowchart of a coating film forming method according to the present invention. (A) It is a schematic diagram which shows the liquid film and film formed in the coating film formation method by this invention. (B) It is a schematic diagram which shows the liquid film and film which are formed in the conventional coating film formation method. It is a schematic diagram which shows the aspect which applies a water-system coating composition to the surface of a base material, rotating a sponge roller, and forms a liquid film. 3 is a photograph of a liquid film formed by the coating film forming method according to the present invention. 5 is a photograph of a film formed by drying the liquid film shown in FIG. It is a photograph of another liquid film formed by the coating film formation method by this invention. 6 is a photograph of a film formed by drying the liquid film shown in FIG. It is a photograph of the liquid film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by drying the liquid film shown in FIG. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method by this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. It is a photograph of the film formed by the coating film formation method which does not belong to this invention. The surface shape profile of the films | membranes 37-41 obtained by digital holographic microscope observation is shown. The surface shape profile of the films | membranes 42-46 obtained by the digital holographic microscope observation is shown.

Coating Film Forming Method FIG. 1 is a flowchart of a coating film forming method according to the present invention. As shown in FIG. 1, the coating film forming method according to the present invention includes a step of forming a liquid film by applying an aqueous coating composition to the surface of a substrate (step 1), and drying the liquid film to form a film. And forming (step 2) at least.

  The steps shown in the flowchart of FIG. 1 will be described in detail with reference to FIGS. FIG. 2A is a schematic diagram showing a liquid film and a film formed in the coating film forming method according to the present invention. FIG. 2B is a schematic diagram showing a liquid film and a film formed in the conventional coating film forming method. FIG. 3 is a schematic view showing an embodiment in which a liquid film is formed by applying an aqueous coating composition to the surface of a substrate while rotating a sponge roller.

Formation of liquid film (Step 1)
In the coating film forming method according to the present invention, first, a liquid film is formed by applying an aqueous coating composition to the surface of a substrate.

Liquid Film In the present invention, the liquid film refers to a film formed after applying the aqueous coating composition to the surface of the base material and in a wet state before starting to dry. As shown in FIG. 2A, the liquid film 101 has a fine uneven shape including a plurality of convex portions 101a and a plurality of concave portions 101b. Examples of the fine concavo-convex shape include a state in which a plurality of convex portions 101a and a plurality of concave portions 101b are present uniformly over the entire substrate surface. For example, a state in which the plurality of convex portions 101a and the plurality of concave portions 101b are regularly distributed alternately in both the vertical direction and the horizontal direction of the substrate surface can be mentioned.

  Here, the stacking (vertical) direction from the substrate to the liquid film is the Z-axis direction, the direction perpendicular to the Z-axis direction is the X-axis direction, and the direction perpendicular to both the Z-axis direction and the X-axis direction is the Y-axis direction. And The diameter of the convex portion 101a is a distance between two adjacent convex portions 101a on the XY plane, that is, the surface of the liquid film 101. The thickness of the convex portion 101a is the length along the Z-axis direction of the convex portion 101a.

  When the surface (XY plane) of the liquid film 101 is observed, the fine concavo-convex shape of the liquid film 101 is preferably a fine mesh or scale, and more preferably a scale. When the amount of the coating composition per unit volume contained in the liquid film 101 is less than a predetermined value, or when the surface tension and viscosity of the coating composition are larger than a predetermined value, etc. A liquid film 101 having an uneven shape can be formed. On the other hand, when the amount of the coating composition per unit volume contained in the liquid film 101 is larger than a predetermined value or the surface tension and viscosity of the coating composition are smaller than a predetermined value, It is difficult to form the liquid film 101 having a fine concavo-convex shape such as a mesh or scale. Alternatively, even if the liquid film 101 having these fine uneven shapes can be formed, there is a possibility that these fine uneven shapes cannot be maintained during the drying described later. In this case, coating unevenness etc. will be visually recognized in the external appearance in the film after drying.

  According to the present invention, the liquid film 101 has a fine concavo-convex shape, and this shape is maintained in the liquid film in the middle of drying, and further in the coating film 102 after drying. An excellent coating film having an external appearance can be easily formed without requiring a high construction technique.

Formation of film (process 2)
In the coating film forming method according to the present invention, the liquid film formed in step 1 is then dried to form a film. The coating is formed by drying the liquid film so that the fine uneven shape of the liquid film is maintained. That is, the liquid film is dried while maintaining the fine uneven shape of the liquid film to form a coating film. The film thus formed maintains this uneven shape after that. That is, the fine uneven shape of the liquid film is maintained in the liquid film in the middle of drying and further in the dried film. The maintenance of this shape contributes to the formation of a good coating film. It is considered that the following phenomenon occurs as an action mechanism for maintaining a fine uneven shape.

  For example, as shown in FIG. 2A, while the liquid film 101 is dried, the height of the convex portion 101a included in the fine concavo-convex shape is reduced as the dispersion medium evaporates. It is considered that a phenomenon in which the fine uneven shape of 101 has hardly changed occurs. That is, when the fine uneven shape before drying (101a, 101b) and the fine uneven shape after drying (102a, 102b) are compared two-dimensionally (planar), the convex portions (101a, 102a) in both This is a phenomenon in which the positions of the recesses (101b, 102b) hardly change. Further, it is thought that the phenomenon that the convex portion 101a does not flow (wet and spread in the vertical direction and / or the horizontal direction), and the shape of the original convex portion 101a and the position on the substrate surface hardly change. It is done. Further, the convex portion 101a does not flow, but comes into contact with the adjacent convex portion 101a, and the shape of the original convex portion 101a, the position on the substrate surface, and the number (density) of the convex portions 101a existing on the substrate surface change. It is thought that a phenomenon with almost no occurrence occurs. As described above, in step 2, the coating film 102 having a fine uneven shape reflecting the fine uneven shape of the liquid film 101 is formed.

Film In the present invention, the film 102 refers to a film in a state after the liquid film 101 is dried. In the coating 102, the fine uneven shape that the liquid film 101 had is maintained. Accordingly, in the coating 102, it is difficult to visually recognize defective appearance such as uneven coating. In addition, occurrence of defects such as sagging is suppressed. The shape of the coating film 102 in a state in which the fine uneven shape of the liquid film 101 is maintained is preferably a fine mesh shape or a scale shape, and more preferably a scale shape.

  As shown in FIG. 3, at the construction site, a liquid film 101 is formed by applying a water-based coating composition to the surface of the substrate using means such as a roller 10. For example, the aqueous coating composition exuded by pressing the roller 10 against the surface of the substrate is spread with a roller to form a liquid film. At this time, depending on various conditions such as the material of the roller and the physical properties of the aqueous coating composition, a concavo-convex shape consisting of a convex portion having a large thickness (for example, convex portion 101a) and a concave portion having a small thickness (for example, concave portion 101b). A liquid film having is formed.

  In general, a water-based coating composition having a high leveling property is suitably used so that a uniform liquid film and a film are formed after being applied to a substrate and spreading on the surface thereof. According to experiments conducted by the present inventors, the following phenomenon was confirmed. That is, when the water-based coating composition having a high leveling property is applied to the base material as described above and the liquid film 201 including the convex portion 201a having a large thickness and diameter as shown in FIG. 2B is formed, After applying to the base material, a force to wet and spread in the direction of the concave portion 201b is generated, and when drying, for example, two adjacent convex portions 201a are bonded to each other to form a large convex portion 202a on the coating 202 unevenly. Is done. Here, the convex portion 202a is formed non-uniformly, both the size of the convex portion 202a itself is non-uniform and the arrangement of the convex portion 202a in the coating 202 is non-uniform. Means. The unevenly formed convex portion 202a is visually recognized as an appearance defect such as uneven coating.

  Further, as shown in FIG. 2B, in the liquid film 201 that is not fine and has an irregular concavo-convex shape, the protrusion 201a wets and spreads when dried, and two adjacent protrusions 201a The films 202 are bonded to each other to form a film 202 having new convex portions 202a. Further, when the liquid contained in the convex portion 201a is wet and spread, a flat concave portion 202b is formed at a position different from the concave portion 201b of the liquid film 201 in the coating film 202, and the height of the convex portion 202a becomes relatively large. Further, the arrangement of the convex portions 202a in the coating 202 is irregular. Furthermore, since the liquid film 201 spreads out in a non-uniform manner, the variation in the height of the convex portion 202a increases. These phenomena are visually recognized as poor appearance such as uneven coating in the coating film 202.

  On the other hand, according to the present invention, the occurrence of the phenomenon described above is suppressed. For example, in the present invention, the liquid film 101 having a fine uneven shape (101a, 101b) is formed by the aqueous coating composition, and the protrusion 101a does not wet and spread in the direction of the recess 101b after application. It is devised to. Therefore, in the liquid film 101, the two adjacent convex portions 101a are suppressed from being bonded to each other during drying. Therefore, the fine uneven shape of the liquid film 101 is maintained in the liquid film in the middle of drying and the film after drying. Since the fine uneven shape of the coating film 102 formed in this way is hardly visible, the coating film 102 has a good appearance.

  In the present invention, the thickness of the coating 102 is, for example, preferably 10 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less. When the thickness of the coating is 10 nm or more, when the coating contains a photocatalyst, the effect of the photocatalyst is sufficiently exhibited. When the thickness of the coating is 200 nm or less, even when the thick protrusions 101a are uniformly formed on the liquid film 101, the coating unevenness of the coating is hardly visible. Moreover, the transparency of the coating is excellent.

  The method for forming a coating film according to the present invention will be further described with reference to FIGS. FIG. 4A is a photograph of a liquid film formed by the coating film forming method according to the present invention. FIG. 4B is a photograph of a film formed by drying the liquid film shown in FIG. FIG. 5 (a) is a photograph of another liquid film formed by the coating film forming method according to the present invention. FIG. 5B is a photograph of a film formed by drying the liquid film shown in FIG. FIG. 6A is a photograph of a liquid film formed by a coating film forming method not belonging to the present invention. FIG. 6B is a photograph of a film formed by drying the liquid film shown in FIG. Note that the black mark located at the center of the photo is a mark for adjusting the focus when taking the photo.

  As shown in FIG. 4A, the liquid film 101 has a scale-like fine uneven shape when the surface is observed. And as shown in FIG.4 (b), the coating film 102 formed by drying this liquid film 101 similarly has a scale-like fine uneven | corrugated shape. That is, as shown in FIGS. 4 (a) and 4 (b), in the method for forming a coating film according to the present invention, it is possible to form the film 102 provided on the liquid film 101 with the fine uneven shape maintained. In the coating film 102 having scale-like fine irregularities, coating unevenness or the like is not visually recognized, and has an excellent appearance.

  As shown in FIG. 5 (a), the liquid film 101 has a fine concavo-convex shape in a mesh shape when the surface is observed. Then, as shown in FIG. 5B, the coating film 102 formed by drying the liquid film 101 similarly has a fine mesh-like uneven shape. That is, as shown in FIGS. 5 (a) and 5 (b), in the method for forming a coating film according to the present invention, it is possible to form the film 102 provided on the liquid film 101 and maintaining the fine uneven shape. Even in the coating film 102 having a fine mesh asperity, uneven coating or the like is hardly visible and has an excellent appearance.

  In the coating film 102 shown in FIG. 5, some of the adjacent convex portions may be bonded, but as a whole, the fine uneven shape of the liquid film 101 is maintained in the coating film 102. The coating 102 has an excellent appearance. Further, in the liquid film 101 shown in FIG. 5, the convex portion 101a is larger than the case of the liquid film 101 shown in FIG. The convex portions shown in FIG. 5 are uniformly arranged in the liquid film 101, and since the relative difference between the thickness of the concave portion and the thickness of the convex portion is small, it is difficult for the coating film 102 to be recognized as uneven coating. .

  On the other hand, as shown in FIG. 6A, the liquid film 201 does not have a fine uneven shape when the surface thereof is observed, and the relative thickness between the thickness of the concave portion and the thickness of the convex portion. There is a big difference. Moreover, the thick part (convex part 201a) of the liquid film is irregularly arranged. Then, as shown in FIG. 6B, the film 202 formed by drying the liquid film 201 has irregularly formed large convex portions 202a at positions different from the convex portion 201a of the liquid film, for example. ing. 6 (a) and 6 (b), when formed in the coating film forming method not belonging to the present invention, the liquid film 201 is moved when the liquid film 201 is dried. It can be seen that the shape of the surface of the coating 202 changes. Further, since this change occurs not uniformly but unevenly, coating unevenness is visually recognized in the coating film 202.

  The method of drying the liquid film may be natural drying, or may be accelerated by heating, airflow, reduced pressure, or the like. In the present invention, it is preferable that the drying time of the liquid film is short. A more preferable drying time is approximately 10 seconds or more and 5 minutes or less. By setting the lower limit of the drying time to 10 seconds or more, that is, a time that is not too short, it becomes possible to prevent the liquid film from drying while the aqueous coating composition is applied to the substrate surface. As a result, it is possible to form a uniform or homogeneous film while maintaining the fine uneven shape of the liquid film. An even more preferable drying time is approximately 10 seconds to 2 minutes.

Surface Shape of Coating According to a preferred embodiment of the present invention, the fine uneven shape of the coating obtained by the method according to the present invention is isotropic. “Isotropic” means that in the coating film, fine irregularities are formed in any direction along the surface of the film, that is, irrespective of the coating direction (for example, the vertical direction and the horizontal direction), This means that the pattern is not visible. In these states, for example, the coating surface can be visually observed. Moreover, it can confirm that the measured value regarding the peak obtained by the digital holographic microscope analysis mentioned later does not have a significant difference in arbitrary directions (for example, a vertical direction and a horizontal direction) along the film surface.

  In the above aspect, in addition to the surface shape of the coating film being isotropic, when the profile obtained by observing the surface shape of the coating film with a digital holographic microscope is measured and measured, The shape further has an average peak width of 300 μm or more and 500 μm or less, and an average peak number of 4 or more and 8 or less in a unit length of 2.5 mm. In the film having such a surface shape, the plurality of convex portions and the plurality of concave portions are fine and exist uniformly or regularly over the entire surface of the substrate.

  The digital holographic microscope is an apparatus that can three-dimensionally analyze the surface shape of a coating film at a very fine level. In the present invention, the measurement data obtained using a digital holographic microscope is profiled, and the three parameters of the width of the peak (convex portion), the number of peaks per unit length, and the ratio of the peak height to the film thickness are set. By deriving them and using them as indices of the surface shape of the coating film, the quantification of fine irregularities is realized. Of the three indicators, the width of the peak (convex part) and the number of peaks per unit length enable two-dimensional visualization of the uniformity or regularity of the surface shape of the coating film. is there. In addition to these two indexes, by considering the ratio of the peak height to the film thickness, it is possible to visualize the uniformity or regularity of the surface shape of the coating film three-dimensionally.

Using a digital holographic microscope, the width of the peak (convex part) of the surface shape of the coating film, the number of peaks per unit length, and the ratio of the peak height to the film thickness can be obtained by the following method, for example. it can.
In the coating film, a surface shape profile for a predetermined length, for example, 10 mm, is measured in a predetermined direction. Since shooting with a field of view of 1 x 1 mm is the maximum for each shot, 13 shots are taken while shifting the field of view by 0.8 mm for each shot. A one-dimensional profile (x, height data) is extracted based on the obtained 13 two-dimensional surface shape profiles (x, y, height data). In order to integrate 13 profiles, the baseline, drift and position of each profile are corrected and integrated into one profile. At that time, the overlapping portion is an average value of the two profile data. A 100-point moving average is taken to remove noise in the obtained profile. The peak width, the number of peaks per unit length, and the peak height are measured from the position-to-height data obtained by such a procedure by the following method.

・ Peak width: Measure the distance between two minimum parts (valleys) on both sides of the peak.
Number of peaks: The profile is divided into, for example, four regions of 0 to 2500 μm, 2500 to 5000 μm, 5000 to 7500 μm, and 7500 to 10,000 μm, and the number of peaks in each region is measured.
・ Peak height: Draw a straight line connecting the two minimum parts when the peak width is obtained, and draw a perpendicular from the peak vertex to find the distance from the peak to the straight line (peak height). The ratio of this distance to the film thickness is measured. The thickness of the coating is obtained by the following method, for example. The sample film is cut with a cutter knife to form a scratch reaching the substrate surface. The scratched portion is measured with a digital holographic microscope, and the thickness of the coating is obtained from the difference in height between the coating surface and the substrate surface.

  According to a preferred aspect of the present invention, the peak with respect to the thickness of the coating film, which is measured by processing a profile obtained by observing the surface shape of the coating film with a digital holographic microscope, of the fine uneven shape of the coating film. The ratio of the height is 10% or less. When the coating film having such a surface shape contains a photocatalyst, the effect of the photocatalyst is sufficiently exhibited. Further, even when the thick convex portions are uniformly formed on the coating, it is difficult to visually recognize defective appearance such as uneven coating. Moreover, the transparency of the coating is excellent.

  Next, the aqueous coating composition used in the method for forming a coating film according to the present invention will be described.

Water-based coating composition <viscosity>
The viscosity of the aqueous coating composition can be appropriately selected depending on, for example, the properties of the sponge roller used in combination with the composition. Details of the combination will be described later. According to a preferred embodiment of the present invention, the water-based coating composition has a viscosity of 4.5 mPa · s or more. By controlling the lower limit of the viscosity of the aqueous coating composition to 4.5 mPa · s or more, that is, the viscosity does not become too small, the convex portion 101a made of the aqueous coating composition is prevented from spreading on the surface of the substrate. As a result, the liquid film 101 having a fine uneven shape can be formed. In addition, in the film formation (liquid film drying) step, it is possible to suppress the movement of the aqueous coating composition that forms the convex portions 101a, that is, the flow of the convex portions 101a, and the liquid can be maintained while maintaining a fine uneven shape. The membrane 101 can be dried. As a result, it is possible to suppress the appearance defect such as uneven coating on the coating 102 from being visually recognized.

  According to a preferred embodiment of the present invention, the viscosity of the aqueous coating composition is less than 3000 mPa · s. By adjusting the upper limit of the viscosity of the aqueous coating composition within this range, it is possible to suppress a decrease in paintability of the aqueous coating composition. Further, as will be described later, for example, when a sponge roller having a small pore diameter is used, the viscosity of the aqueous coating composition is reduced to 1000 mPa · s or less, more preferably 200 mPa · s or less, thereby more reliably coating the film. It is preferable that the coating unevenness and the like are visually recognized. The viscosity of the aqueous coating composition can be adjusted using, for example, a thickener described later.

  The viscosity of the aqueous coating composition is measured using, for example, a B-type viscometer (for example, TV-10 manufactured by Toki Sangyo Co., Ltd.) or a rheometer (for example, HAAKE MARSII manufactured by Thermo Scientific). be able to. The measurement conditions of the B-type viscometer are such that the rotational speed of the rotor is 6 rpm and the measurement temperature is 25 ° C. The rotor uses an L adapter when the viscosity of the sample is less than 100 mPa · s, an M1 rotor when it is 100 mPa · s or more and less than 1000 mPa · s, and an M2 rotor when it is 1000 mPa · s or more and less than 5000 mPa · s. The measurement condition of the rheometer is a temperature of 25 ° C. The sensor uses a cone plate (φ60 mm, 1 °).

<Surface tension>
The surface tension of the water-based coating composition can be appropriately selected depending on, for example, the properties of the sponge roller used in combination therewith. Details of the combination will be described later. According to a preferred embodiment of the present invention, the surface tension of the aqueous coating composition is greater than 25 mN / m and not greater than 72 mN / m. By adjusting the lower limit of the surface tension of the aqueous coating composition to more than 25 mN / m, that is, the surface tension does not become too small, the convex portion 101a made of the aqueous coating composition spreads on the surface of the substrate. As a result, the liquid film 101 having a fine uneven shape can be formed. Further, in the film formation (liquid film drying) step to be described later, it is possible to suppress the adjacent protrusions 101a included in the fine uneven shape of the liquid film 101 from contacting or bonding with each other. The liquid film 101 can be dried while maintaining the uneven shape. As a result, it is possible to suppress the appearance defect such as uneven coating on the coating 102 from being visually recognized. By adjusting the upper limit of the surface tension of the aqueous coating composition to 72 mN / m or less, it is possible to suppress a decrease in wettability of the aqueous coating composition with respect to the substrate, and thus a decrease in paintability. The surface tension of the aqueous coating composition can be adjusted using, for example, a surfactant described later.

  The surface tension of the aqueous coating composition can be measured by a known method. Examples of the measuring method include plate method (Wilhelmy method), ring method (du Nouy method), hanging drop method, maximum bubble pressure method and the like. In the present invention, the surface tension of the aqueous coating composition is measured using the maximum bubble pressure method. As a specific method, the dynamic surface tension is measured with a bubble life of 30 to 20,000 ms using a SITA t60 manufactured by Eihiro Seiki, which is a surface tension measuring device by the maximum bubble pressure method, and the value at 20,000 ms. Is recorded as the surface tension (value according to the static surface tension).

<Ingredients>
The aqueous coating composition used in the present invention contains at least functional particles and a dispersion medium mainly containing water. As the functional particles, photocatalyst particles can be preferably used.
(Photocatalyst particles)
The photocatalyst particles contained in the aqueous coating composition are preferably at least one photocatalyst particle selected from anatase type titanium oxide, rutile type titanium oxide, brookite type titanium oxide, zinc oxide, tin oxide, niobium oxide, and strontium titanate. It is. Among these, anatase-type titanium oxide has high photocatalytic activity and a hydrophilizing effect, and can be suitably used. As these photocatalyst particles, photocatalyst particles that are doped with an element such as nitrogen or have a copper or iron compound supported on the surface to enhance the visible light response can also be used.

  The particle diameter of the photocatalyst particles is preferably in the range of 1 nm to 50 nm, and more preferably in the range of 5 nm to 20 nm. When the particle diameter is 1 nm or more, more preferably 5 nm or more, the photocatalytic activity and the hydrophilization performance can be sufficiently exhibited. When the particle diameter is 50 nm or less, and more preferably 20 nm or less, since visible light hardly scatters, a film having excellent transparency can be obtained. Here, the particle diameter is calculated as a number average value obtained by measuring the length of 100 particles obtained by observing the fracture surface of the coating film with a scanning electron microscope at a magnification of 200,000 times. When the observed particle shape is substantially circular, the particle length means the particle diameter. When the observed particle shape is non-circular, the particle length is approximately calculated as ((major axis + minor axis) / 2).

  The concentration of the photocatalyst particles is preferably in the range of 0.05% by mass to 5% by mass, and more preferably in the range of 0.1% by mass to 1% by mass. By including the photocatalyst particles in this range, the photocatalytic activity and the hydrophilization performance can be sufficiently exhibited, the film can be prevented from becoming too thick, and good transparency can be obtained.

(Dispersion medium)
The dispersion medium contained in the aqueous coating composition mainly contains water. Here, the “dispersion medium mainly containing water” includes water in an amount of 60% by mass to 100% by mass, preferably 80% by mass to 100% by mass. When using a mixed solvent obtained by mixing water and an organic solvent other than water, an organic solvent that is soluble in water can be suitably used.

  Water-soluble organic solvents include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, ethylene glycol , Propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve and the like are preferable. In the present invention, at least one organic solvent selected from these groups can be used.

  The aqueous coating composition preferably contains the dispersion medium so that the solid content concentration is 0.1% by mass or more and 10% by mass or less. By including the dispersion medium in such a range, a transparent and excellent coating film can be obtained.

  The pH of the dispersion medium is preferably 6 or less or 8 or more. Since the pH in this range is sufficiently far from the isoelectric point of the photocatalyst particles or the inorganic oxide fine particles described later, the photocatalyst particles or the inorganic oxide particles can be stably dispersed. As a result, the formation of aggregated particles can be suppressed, and a transparent film having an excellent appearance can be obtained.

(Thickener)
In the present invention, the aqueous coating composition may contain a thickener. By including a thickener, the viscosity of the aqueous coating composition can be adjusted to a desired range. In the present invention, the viscosity of the coating composition is preferably greater than 5 mPa · s.

  In the present invention, as the thickener contained in the aqueous coating composition, various substances that are usually used as a thickener can be used, except for substances having extremely low solubility or dispersibility in water. Examples of thickeners include water soluble or water dispersible thickeners. By including such a thickener, it becomes possible to adjust the water-based coating composition to a target viscosity, and it is possible to prevent the appearance of the coating film from deteriorating due to the formation of aggregates. Examples of water-soluble thickeners include thickening polysaccharides such as xanthan gum, welan gum, gum arabic, locust bean gum, diyutan gum, guar gum, preferably glucuronic acid and / or main chain of welan gum, diyutan gum and the like. Or thickening polysaccharides containing rhamnose; synthetic water-soluble polymers such as polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone; natural water-soluble polymers such as dextrin, pectin, gelatin; sodium alginate, ammonium alginate, etc. And alginic acid derivatives, cellulose derivatives such as methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose. These water-soluble thickeners include satiaxan (cargill) (xanthan gum), welan gum (Sanki Co., Ltd.) (welan gum), arabic coal (Sanei Pharmaceutical Trading Co., Ltd.) (arabic gum), and Genu gum (CP Kerco). (Locust bean gum), Kelco cleat (CP Kelco) (Diyutan gum), Meiprodol (DuPont) (Guar gum), Aron (Toagosei Co., Ltd.) (Polysodium acrylate), Polyvinylpyrrolidone (Nippon Shokubai Co., Ltd.) )) (Polyvinylpyrrolidone) and other commercially available products can be used. Examples of water dispersible thickeners include smectite clay minerals such as synthetic hectorite and synthetic saponite. These water-dispersible thickeners are commercially available under trade names such as Laponite RD, Laponite B (Rockwood), Lucentite (Coop Chemical Co., Ltd.), Smecton SA (Kunimine Industry Co., Ltd.), etc. Can be used. These thickeners may be used alone or in combination of two or more.

  In the present invention, the addition amount of the thickener is preferably an amount that can adjust the viscosity of the aqueous coating composition to a value as large as 4.5 mPa · s or more, and considers the type of the thickener. It is determined as appropriate. For example, when diutan gum (Kelcocrete DG (CP Kelco)) is used as the thickener, the addition amount of the thickener is 0.01% in order to adjust the viscosity of the aqueous coating composition to a desired range. % Or more and 0.25% by mass or less is preferable.

(Surfactant)
In the present invention, the aqueous coating composition may contain a surfactant. By including the surfactant, the surface tension of the aqueous coating composition can be adjusted to a desired range. According to a preferred embodiment of the present invention, the surface tension of the aqueous coating composition is in the range of more than 25 mN / m and not more than 72 mN / m.

  By adjusting the surface tension to a desired range, the wettability of the aqueous coating composition to the substrate surface can be improved, and the liquid film 101 can be uniformly formed on the substrate surface. Further, the evaporation of the dispersion medium from the liquid film 101 becomes uniform, and the coating film 102 can be formed while maintaining the fine uneven shape of the liquid film 101. The surfactant used in the present invention is preferably a substance having a high solubility in water, which is the main component of the dispersion medium, and a high effect of reducing the surface tension. By using a surfactant having a high surface tension reducing effect, the surface tension of the aqueous coating composition can be adjusted to a desired range with a very small amount of addition, and as a result, the durability of the coating film 102 can be improved. Can do. The surfactant is preferably a substance that does not easily foam. When a water-based coating composition containing bubbles is used, bubbles are generated in the liquid film 101 and the traces remain in the film 102. By using a low-foaming surfactant, however, deterioration of the appearance of the coating film due to residual bubbles is prevented. can do. Preferable examples of such surfactants include acetylenediol-based surfactants and polyether-modified silicone-based surfactants.

  In the present invention, the addition amount of the surfactant may be an amount that can adjust the surface tension of the aqueous coating composition to a range of more than 25 mN / m and not more than 72 mN / m. It is determined as appropriate. For example, when an acetylenic diol surfactant or a polyether-modified silicone surfactant is used as the surfactant, in order to adjust the surface tension of the aqueous coating composition to a desired range, The addition amount is preferably 0.01% by mass or more and 0.5% by mass or less. Thereby, it is possible to prevent the surface tension of the aqueous coating composition from being excessively lowered, and as a result, it is possible to form the liquid film 101 and the coating film 102 having fine irregularities.

(Inorganic oxide particles)
In the present invention, the aqueous coating composition may contain inorganic oxide fine particles. As the inorganic oxide fine particles, those functioning as a binder and capable of forming a transparent film can be suitably used. Preferred examples of the material include fine particles of oxide different from the above photocatalyst particles, for example, selected from silicon oxide, aluminum oxide, zirconium oxide, hafnium oxide, cerium oxide and the like. Among these, since the fine particles of silicon oxide are excellent as a binder, the adhesion of the coating film to the substrate is strong and particularly preferable.

  The particle diameter of the inorganic oxide fine particles is preferably 50 nm or less. When the particle diameter is in this range, visible light scattering hardly occurs and a film having excellent transparency can be obtained. Furthermore, when the particle diameter is 20 nm or less, the effect as a binder is enhanced, and the adhesion of the film is excellent. Here, the particle diameter is calculated as a number average value obtained by measuring the length of 100 particles obtained by observing the fracture surface of the coating film with a scanning electron microscope at a magnification of 200,000 times. When the observed particle shape is substantially circular, the particle length means the particle diameter. When the observed particle shape is non-circular, the particle length is approximately calculated as ((major axis + minor axis) / 2).

  The concentration of the inorganic oxide fine particles is preferably in the range of 0.05% by mass to 5% by mass, and more preferably in the range of 0.1% by mass to 1% by mass. By including the inorganic oxide particles within this range, the effect as a binder can be sufficiently exhibited, and the coating can be prevented from becoming too thick, and good transparency can be obtained.

Application of water-based coating composition to substrate <Applied means>
According to a preferred embodiment of the present invention, the aqueous coating composition is applied to the substrate using, for example, a roller. The material of the roller is preferably a sponge.

(Sponge roller)
In the present invention, the sponge of the sponge roller is preferably a wet sponge. In the case of a wet sponge, for example, a raw material resin kneaded with water-soluble salt fine particles (pore generation agent) is cured, and then the salt is washed away to form a porous structure. Accordingly, in the wet foaming, a sponge having a small pore diameter can be easily formed by using small fine particles. On the other hand, in a dry sponge, a porous structure is formed by foaming a raw material resin (for example, urethane) using a foaming agent or a gas generated in a polymerization process. Therefore, it is difficult to form a sponge having a small pore diameter by dry foaming.

Continuous pores According to a preferred embodiment of the present invention, the sponge roller has continuous pores. Continuous pores refer to a state in which at least some of adjacent pores are connected. Here, the term “adjacent” refers to a mode in which they are provided adjacent to each other not only in two dimensions but also in three dimensions.

Average pore diameter According to a preferred embodiment of the present invention, the average pore diameter of the continuous pores of the sponge roller is, for example, 30 μm or more and 150 μm, depending on the viscosity and surface properties of the aqueous coating composition to be applied. It is as follows. More preferably, it is less than 100 micrometers, More preferably, it is 50 micrometers or less. When the average pore diameter of the sponge roller is small and within this range, the liquid film 101 having a fine uneven shape can be formed. The average pore diameter means an average diameter of individual pores constituting the continuous pores. The average pore diameter is measured, for example, by the following method. That is, a scanning electron micrograph of a sponge roller is taken at a magnification of 100 times, two lines of length (l) are drawn on the diagonal of the scanning electron microscope image, and the number of pores (n) crossing each line is counted. . The average pore diameter (μm) is calculated as 2 l / n.

  In the present invention, when the viscosity of the aqueous coating composition is low, it is preferable to use a sponge roller having a small pore diameter. Thus, by devising a combination of the composition and the sponge roller, it is possible to form a uniform or homogeneous liquid film and film having a fine uneven shape.

  In the present invention, when a sponge roller having a small pore diameter is used, it is preferable to use an aqueous coating composition having a small surface tension.

  In addition, it is preferable to consider not only the properties (viscosity, surface tension, etc.) of the aqueous coating composition combined with the sponge roller, the pore diameter of the sponge roller, but also the bubble point diameter of the sponge roller, which will be described later, and the ethanol permeation time. .

Ethanol transmission time According to a preferred embodiment of the present invention, the ethanol transmission time of the sponge roller is 20 seconds or longer and 270 seconds or shorter. The ethanol permeation time is an index of the performance of the sponge roller, and represents, for example, the water absorption performance of the sponge roller. The ethanol permeation time is measured, for example, by the following method. That is, a glass tube having an inner diameter of 17.4 mm is installed vertically, and a plate having a hole with a diameter of 6.8 mm is attached to the lower end thereof so that the cross section of the glass tube and the hole are concentric. Furthermore, a sponge cut to a thickness of 2 mm is closely attached so as to close the hole in the plate. Pour 100 mm (23.7 ml) of ethanol into the glass tube and measure the time until it is completely discharged through the sponge. In the present invention, the ethanol permeation time of the sponge roller is more preferably 27 seconds to 261 seconds, even more preferably 70 seconds to 261 seconds, and particularly preferably 150 seconds to 261 seconds.

Bubble Point Diameter According to a preferred aspect of the present invention, the bubble point diameter of the sponge roller is, for example, 42 μm or less. The bubble point diameter is an index of the performance of the sponge roller, and represents, for example, the water absorption performance of the sponge roller. The bubble point diameter is a maximum pore diameter measured by a method (bubble point method) defined in ASTM F316-03 and JIS K3832. That is, the sponge is immersed in the test solution and the air pressure is increased from the lower side. When a certain pressure is reached, bubbles are first generated from the hole having the maximum pore diameter. Using the pressure (P: bubble point pressure) at this time, the maximum pore diameter (D) is obtained from the following formula. For example, ethanol can be used as the test solution. In the present invention, the bubble point diameter of the sponge roller is more preferably 26 μm or less, and even more preferably 16.5 μm or less.
D = 4γ cos θ / P
(Where D: maximum pore diameter (m), γ: surface tension of test solution (N / m), θ: contact angle between sponge and test solution (rad), P: bubble point pressure (Pa))

Water absorption rate According to a preferred embodiment of the present invention, the water absorption rate of the sponge roller is 1 minute or less. The water absorption speed is an index of the performance of the sponge roller. The water absorption rate is measured with reference to, for example, JIS L1907 “Water absorption test method for textile products” 7.1.1 dropping method. That is, a drop of water (0.04 mL) is dropped from the height of 10 mm onto the surface of the test piece, and when the water drop reaches the surface of the test piece, the specular reflection disappears as the test piece absorbs the water drop, and only wet Measure the time until the remains. In JIS L1907, measurement using a test piece of 200 mm × 200 mm is specified, but in this specification, a cylindrical outer peripheral surface of a roller is used as the test piece. In the present invention, the water absorption speed of the sponge roller is preferably 30 seconds or less, more preferably 5 seconds or less, and even more preferably 1 second or less.

  According to a preferred aspect of the present invention, the sponge roller has at least one performance selected from the group consisting of continuous pores, average pore diameter, bubble point diameter, ethanol permeation time, and water absorption speed. According to a more preferred aspect of the present invention, the sponge roller has continuous pores and further has at least one performance selected from the group consisting of average pore diameter, bubble point diameter, ethanol permeation time, and water absorption speed. It has excellent liquid absorbency. By using a sponge roller having such performance, the liquid film 101 having a fine uneven shape can be more reliably formed. For example, the sponge roller preferably has continuous pores, an average pore diameter of 30 μm or more and 150 μm or less, and an ethanol permeation time of 20 seconds or more and 270 seconds or less.

  The sponge roller preferably has continuous pores, and the average pore diameter is preferably 30 μm or more and 100 μm or less. The sponge roller preferably has continuous pores, and the pore diameter is 30 μm or more and 50 μm or less, and the bubble point diameter is 16.5 μm or less.

  A preferable combination of the aqueous coating composition and the sponge roller used in the present invention is, for example, an aqueous coating composition having a viscosity of 4.5 mPa · s or more and less than 3000 mPa · s, continuous pores, and an average pore diameter of 30 μm. This is a combination with a sponge roller having a thickness of 150 μm or less and an ethanol permeation time of 20 seconds to 270 seconds.

  A preferred combination of the aqueous coating composition and the sponge roller used in the present invention is, for example, an aqueous coating composition having a surface tension of more than 25 mN / m and not more than 72 mN / m, continuous pores, and an average pore diameter of 30 μm. This is a combination with a sponge roller having a thickness of 150 μm or less and an ethanol permeation time of 20 seconds to 270 seconds.

<Applicable amount>
According to a preferred embodiment of the present invention, in the liquid film forming step, the amount of application of the aqueous coating composition applied to the surface of the substrate per time is determined by the surface tension and viscosity of the sponge roller and aqueous coating composition used. Depending on the above, it is 2 g / m ² or more and 15 g / m ² or less. By setting the application amount per time within this range, it is possible to form the liquid film 101 having a fine uneven shape. By setting the lower limit of the application amount per one time to 2 g / m ² or more, the aqueous coating composition can be spread over the entire surface of the substrate, and it can be applied uniformly without causing blur. By setting the upper limit of the application amount per one time to 15 g / m ² or less, it is possible to suppress liquid accumulation, that is, formation of the liquid film 201 having a large convex portion 201a. That is, at the time of forming the liquid film, the movement of the liquid from the convex portion to the concave portion can be suppressed, and as a result, the adjacent convex portions can be prevented from contacting or combining. As a result, it is possible to form a good coating film 102 in which a large convex portion 202a that is visually recognized as coating unevenness is not formed on the coating film, and an appearance defect is not visually recognized. A more preferable application amount per time is 3 g / m ² or more and 10 g / m ² or less, and an even more preferable application amount per time is 5 g / m ² or more and 7 g / m ² or less. For example, when a sponge roller having a large pore diameter is used and a water-based coating composition having a high viscosity is applied, it is preferable to make the coating amount smaller than 10 g / m ² .

<Application method>
According to a preferred embodiment of the present invention, as shown in FIG. 3, a liquid film 101 is formed by applying the aqueous coating composition to the surface of the substrate while rotating the sponge roller 10. Thereby, a water-based coating composition can be applied so that a roller surface may not slip with respect to the base-material surface. Fine irregularities (101a and 101b) are formed due to the pores of the sponge, but formed on the substrate surface when the water-based coating composition was applied with the rotation of the roller stopped like a stop roller. The unevenness is stretched by the movement of the roller, and this is visually recognized as streaky coating unevenness. By rotating the roller, due to the above-mentioned various performances of the sponge roller, the aqueous coating composition oozes out (arrow A _{out in} FIG. 3) and the excess aqueous coating composition already applied to the substrate surface. 3 (arrow A _{in in} FIG. 3) can be performed in an appropriate balance, and the liquid film 101 having a fine uneven shape can be formed.

Substrate In the present invention, preferable base materials to which the water-based coating composition can be applied include ceramic inorganic materials such as glass and tiles, resin materials such as PMMA and polycarbonate, metal materials, and organic materials formed on the surfaces of these substrates. Painted surface.

<Pretreatment of substrate>
In the present invention, for the purpose of preventing film formation failure due to repellency of the aqueous coating composition, the substrate may be washed in advance by a method such as washing with seric powder. In addition, sufficient washing | cleaning for ensuring the wettability of the base-material surface is not necessarily required.

Functional material The functional material according to the present invention includes a base material and a coating film formed on the surface of the base material, and the coating film has a fine uneven shape including a plurality of convex portions and a plurality of concave portions. Is. When the surface (XY plane) of the coating is observed two-dimensionally, the fine uneven shape of the coating is preferably a fine mesh or scale, and more preferably a scale. The “fine concavo-convex shape”, “network fine concavo-convex shape”, and “scale-like fine concavo-convex shape” are as described above.

  According to the preferable aspect of this invention, the fine uneven | corrugated shape which a coating film has isotropic. “Isotropic” is as described above.

  In the above aspect, in addition to the surface shape of the coating film being isotropic, when the profile obtained by observing the surface shape of the coating film with a digital holographic microscope is processed and measured, However, it further has an average peak width of 300 μm or more and 500 μm or less, and an average peak number of 4 or more and 8 or less in a unit length of 2.5 mm. In the film having such a surface shape, the plurality of convex portions and the plurality of concave portions are fine and exist uniformly or regularly over the entire substrate surface.

  The digital holographic microscope, the peak width of the surface profile obtained by using this, the number of peaks per unit length, and the ratio of the peak height to the film thickness are as described above.

  According to a preferred aspect of the present invention, the peak with respect to the thickness of the coating film, which is measured by processing a profile obtained by observing the surface shape of the coating film with a digital holographic microscope, of the fine uneven shape of the coating film. The ratio of the height is 10% or less. The film having such a surface shape is a uniform film in which poor appearance such as uneven coating and streaks are not visually recognized.

Preparation of water-based coating composition <Raw material>
Photocatalyst particles 1: Weakly basic aqueous dispersion containing anatase-type titanium oxide fine particles, particle diameter 20 nm
Photocatalyst particles 2: weakly basic aqueous dispersion containing anatase-type titanium oxide fine particles, particle diameter of 30 to 60 nm
Inorganic oxide particles 1: basic aqueous dispersion containing silica fine particles, particle size 8-11 nm
Inorganic oxide particles 2: Basic aqueous dispersion containing silica fine particles, particle diameter of 4 to 6 nm
・ Surfactant 1
・ Surfactant 2
・ Surfactant 3
・ Thickener 1: Dieutan gum

  Water-based coating compositions 1 to 11 containing the photocatalyst particles, inorganic oxide particles, surfactant, thickener and water shown in Table 1 at concentrations (mass%) shown in Table 1 were prepared.

  The surface tension and viscosity of the aqueous coating compositions 1 to 11 were as shown in Table 2. The surface tension was measured as follows. Using SITA t60 (manufactured by Eihiro Seiki Co., Ltd.), a surface tension measuring device based on the maximum bubble pressure method, the dynamic surface tension is measured at a bubble life of 30 to 20,000 ms. Value according to tension). The viscosity was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., TV-10) or a rheometer (manufactured by Thermo Scientific, HAAKE MARSII). In the B-type viscometer, the rotation speed was 6 rpm and the temperature was 25 ° C. The rotor used for the measurement is an L adapter when the viscosity of the sample is less than 100 mPa · s, an M1 rotor when the sample is less than or equal to 100 mPa · s and less than 1000 mPa · s, and a rotor that is 1000 mPa · s and less than 5000 mPa · s. An M2 rotor was used. In the rheometer, the temperature was 25 ° C., and the sensor used was a cone plate (φ60 mm, 1 °).

Formation of coating film <Preparation of base material>
In the following tests 1 to 7, soda lime glass (200 × 200 × 2 t (mm)) was prepared as a base material. Next, the glass surface was washed with an abrasive containing cerium oxide powder to make the glass surface hydrophilic. Thereafter, the glass surface was rinsed well with ion exchange water and allowed to dry naturally. In Test 8, an organic coating body of an outer wall material was used as a base material. In Test 9, a float glass substrate (normal glass) (100 × 200 × 2 t (mm)) was prepared as a base material, and the same processing as that performed on the base materials in Tests 1 to 7 was performed.

(Test 1) Test using various sponge rollers <Various rollers>
Table 3 shows the materials, production methods, and physical properties (average pore diameter, bubble point diameter, ethanol permeation time, and water absorption speed) of the rollers 1 to 9 used.

  The average pore diameter was determined as follows. A scanning electron micrograph of the sponge roller was taken at a magnification of 100 times, two lines of length (l) were drawn at the diagonal of the scanning electron microscope image, and the number of pores (n) crossing each line was counted. The average pore diameter (μm) was calculated as 2 l / n.

The bubble point diameter was determined as follows according to the bubble point method defined in ASTM F316-03 and JIS K3832. The sponge was immersed in the test solution, and the air pressure was increased from the lower side. The diameter of the hole in which bubbles were first generated was defined as the maximum pore diameter. Using the pressure (P: bubble point pressure) at this time, the maximum pore diameter (D) was determined from the following formula. Ethanol was used as a test solution.
D = 4γ cos θ / P
(Where D: maximum pore diameter (m), γ: surface tension of test solution (N / m), θ: contact angle between sponge and test solution (rad), P: bubble point pressure (Pa))

  The ethanol permeation time was determined as follows. A glass tube having an inner diameter of 17.4 mm was installed vertically, and a plate having a hole with a diameter of 6.8 mm was attached to the lower end thereof so that the cross section of the glass tube and the hole were concentric. Furthermore, a sponge cut to a thickness of 2 mm was brought into close contact with the hole in the plate, and 100 mm (23.7 ml) of ethanol was poured into the glass tube, and the time until it was completely discharged through the sponge was measured.

  The water absorption rate was obtained as follows with reference to JIS L1907 “Water absorption test method for textile products” 7.1.1 dropping method. A drop of water (0.04 mL) is dropped from the height of 10 mm onto the surface of the test piece. When the water drop reaches the surface of the test piece, the specular reflection disappears as the test piece absorbs the water drop, leaving only the wetness. The time to the state was measured. The cylindrical outer peripheral surface of the roller was used as a test piece. For the roller where water absorption was confirmed instantaneously, the slow motion video of the above test was taken and the water absorption speed was measured.

<Formation of liquid film>
Using various sponge rollers with different average pore diameters described in Table 3, the coating amount per time (g / m ² ) was set to the amount shown in Table 4, and the same aqueous coating composition 1 was used as the base material. The liquid film (Liquid films 1-10) of Samples 1-10 was formed by applying to the surface. Only the liquid film 9 was formed without rotating the roller.

<Formation of coating>
The base material on which the liquid films 1 to 10 were formed was left to stand horizontally, and was naturally dried until it was sufficiently dried to form the coating films (the coating films 1 to 10) of the samples 1 to 10.

Evaluation Appearance evaluation The appearance of the coating formed using various rollers was observed by photography. A sample having a very good appearance was determined as A, a sample having a good appearance as B, a sample slightly inferior in appearance but acceptable in practice, and a defective appearance as D.

  The liquid film 1 of the sample 1 formed using the roller 1 having an average pore diameter of 30 μm had a fine uneven shape (scale shape). When the shape of the coating film 1 was photographed and observed, the coating film 1 had a fine concavo-convex shape (scale-like shape) while maintaining the fine concavo-convex shape of the liquid film 1, and the appearance was very good. Appearance judgment was A. An image of the coating 1 is shown in FIG. 4A corresponds to the liquid film 1 of the sample 1, and FIG. 4B corresponds to the coating film 1 of the sample 1. In sample 1, the liquid film was quickly dried in about 10 seconds.

  The liquid film 2 of the sample 2 formed using the roller 2 having an average pore diameter of 50 μm had a fine uneven shape (scale shape). When the shape of the coating film 2 was photographed and observed, the coating film 2 had a fine concavo-convex shape (scale-like shape) while maintaining the fine concavo-convex shape of the liquid film 2, and the appearance was very good. Appearance judgment was A. An image of the coating 2 is shown in FIG. Also in sample 2, the liquid film was quickly dried in about 10 seconds.

  The liquid film 3 of the sample 3 formed using the roller 3 having an average pore diameter of 80 μm had a fine uneven shape (fine mesh shape). When the shape of the coating film 3 was photographed and observed, the coating film 3 had a fine concavo-convex shape (fine mesh shape) while maintaining the fine concavo-convex shape of the liquid film 3, and the appearance was good. Appearance judgment was B. An image of the coating 3 is shown in FIG. In sample 3, the liquid film was quickly dried.

  The liquid film 4 of the sample 4 formed using the roller 4 having an average pore diameter of 150 μm had a fine uneven shape (fine mesh shape). When the shape of the coating film 4 is photographed and observed, the coating film 4 partially flows in the convex portions constituting the fine uneven shape (fine mesh shape) of the liquid film 4, and as a result, the liquid film 4 has a fine structure. Although the uneven shape (fine mesh shape) was not partially maintained, the convex portions were uniformly arranged throughout. In the coating 4, coating unevenness was difficult to be visually recognized, the appearance was practically acceptable, and the appearance determination was C. An image of the coating 4 is shown in FIG. In sample 4, it took a little time to dry the portion where the liquid film flowed. The drying time was about 1 or 2 minutes.

  The liquid film 5 of the sample 5 formed using the roller 5 having an average pore diameter of 200 μm had a mesh shape including large convex portions. When the shape of the coating film 5 was photographed and observed, the coating film 5 was not maintained in a mesh shape including large convex portions of the liquid film 5. In the coating 5, coating unevenness was visually recognized, the appearance was poor, and the appearance determination was D. An image of the film 5 is shown in FIG. 6A corresponds to the liquid film 5 of the sample 5, and FIG. 6B corresponds to the coating film 5 of the sample 5. Moreover, in the sample 5, the large convex part of the liquid film 5 was difficult to dry. The drying of the liquid film 5 took about 5 minutes.

  The liquid film 6 of the sample 6 formed using the low-density olefin type roller 6 having an average pore diameter of 50 μm had a scale shape and a mesh shape. When the shape of the film 6 was photographed and observed, the film 6 maintained the scale-like shape and the net-like shape of the liquid film 6, the appearance was good, and the appearance judgment was B. . An image of the film 6 is shown in FIG. In sample 6, the liquid film was quickly dried.

  The liquid film 7 of the sample 7 formed using the low density olefin type roller 7 having an average pore diameter of 200 μm had a mesh shape including large convex portions. When the shape of the film 7 was photographed and observed, the network shape including the large convex portions of the liquid film 7 was not maintained. In the coating 7, coating unevenness was visually recognized, the appearance was poor, and the appearance determination was D. An image of the film 7 is shown in FIG. In sample 7, it took about 5 minutes to dry the liquid film.

  The liquid film 8 of the sample 8 formed using the roller 8 made of wool included a large convex portion (for example, 201a in FIG. 2B). When the shape of the coating film 8 is photographed and observed, the coating film 8 is included in the large convex portion (for example, 202a in FIG. 2B) reflecting the large convex portion included in the liquid film 8, or in the liquid film 8. The large protrusions that were formed were joined to each other during drying to include new large protrusions. In addition, the thickness and diameter of these large protrusions varied, and the arrangement in the film was not uniform. In the coating 8, the coating unevenness was clearly recognized, the appearance was poor, and the appearance determination was D. An image of the film 8 is shown in FIG. In sample 8, it took about 5 minutes to dry the liquid film.

  The liquid film 9 of the sample 9 formed by using the roller 8 made of wool without rotating includes a large convex portion (for example, 201a in FIG. 2B), which is formed in a streak shape. When the shape of the coating film 9 is photographed and observed, the coating film 9 has a large convex portion (for example, 202a in FIG. 2B) reflecting the large convex portion formed in the streaks included in the liquid film 9. This was formed in a streak shape. In the film 9, this streak was clearly recognized, the appearance was poor, and the appearance determination was D. An image of the film 9 is shown in FIG. In sample 9, it took about 5 minutes to dry the liquid film.

  The liquid film 10 of the sample 10 formed using a roller 9 having a dry sponge material and an average pore diameter of 500 μm included a large convex portion (for example, 201a in FIG. 2B). When the shape of the coating film 10 was photographed and observed, large convex portions (for example, 202a in FIG. 2B) or large convex portions included in the liquid film 10 were also bonded to the coating film 10 during drying. The newly formed large convex part was included. In the coating 10, these large convex portions were clearly recognized as uneven coating, the appearance was poor, and the appearance determination was D. An image of the coating 10 is shown in FIG. In sample 10, it took about 5 minutes to dry the liquid film.

(Test 2) Combination of a coating composition having a low surface tension and a sponge roller having a small pore diameter <Liquid film formation>
As shown in Table 4, the liquid film 11 of the sample 11 was formed using the roller 2 having an average pore diameter of 50 μm. The coating amount per one time was set to 7.75 g / m ² . This is almost the same amount as the amount of application of the sample 2 using the roller 2. On the other hand, in the sample 11, the aqueous coating composition 4 having a smaller surface tension than the aqueous coating composition 1 used in the sample 2 is used. The surface tension of the aqueous coating composition 4 was 30 mN / m.

<Formation of coating>
The base material on which the liquid film 11 was formed was allowed to stand horizontally, and then naturally dried until it was sufficiently dried to form the film 11.

Evaluation Appearance evaluation The liquid film 2 using the aqueous coating composition 1 having a surface tension of 58 mN / m had a scale-like uneven shape. On the other hand, the liquid film 11 using the aqueous coating composition 4 having a surface tension of 30 mN / m had a fine mesh-like uneven shape rather than a scale shape. This is presumably because the surface tension of the aqueous coating composition 4 used was low, so that the uneven shape did not become scale-like and spread wet. That is, it was confirmed that the fine irregularities that the liquid film 11 had immediately after application moved a little during drying. The shape of the film 11 was photographed and observed. An image of the coating 11 is shown in FIG. In the coating 11, fine mesh-like irregularities were uniformly provided, and coating unevenness was not visually recognized. The appearance of the film 11 was practically acceptable, and the appearance determination was C. In this sample 11, it took a longer time to dry the liquid film 11 than the drying time of the liquid film 2.

(Test 4) Overcoat test <Liquid film formation>
As shown in Table 4, using the roller 1 having an average pore diameter of 30 μm, the liquid film 13 of the sample 13 was formed by applying (overcoating) the surface of the base material three times. Specifically, a first liquid film was formed by the first application, and this was dried to form a first film. Thereafter, a second liquid film was formed on the first film by the second application, and this was dried to form a second film. Thereafter, a third liquid film was formed on the second film by the third application (liquid film 13). The coating amount per time was 4 to 5 g / m ² . This is almost the same amount as the amount of application per sample of the sample 1 using the roller 1. The surface tension and viscosity of the aqueous coating composition 2 used in Sample 13 are substantially the same as the surface tension and viscosity of the aqueous coating composition 1 used in Sample 1.

<Formation of coating>
As described above, the coating film 13 was formed by repeating the process of allowing the substrate on which the liquid film was formed for each application to stand horizontally and then naturally drying until sufficiently dried to form the coating 13. In sample 13, the liquid film was quickly dried in about 10 seconds for each application.

Evaluation Appearance evaluation In the liquid film 13, the liquid films in the first to third times all had a scale-like fine uneven shape. The shape of the film 13 was photographed and observed. An image of the coating 13 is shown in FIG. It was confirmed that the shape of the coating 13 formed by applying three times was scale-like. That is, the scale shape of the first film is maintained without disappearing even after the second film is formed, and similarly, the scale shape of the second film is maintained without disappearing after the third film is formed. As a result, it was confirmed that the scale-like film 13 in which the fine irregularities of the first and second times were overlaid was formed even after three times of overcoating. In the coating 13, coating unevenness was not visually recognized, the appearance was very good, and the appearance determination was A.

(Test 5) Test in which the surface tension of the aqueous coating composition was changed For the coating compositions 5 to 8 in which the surface tension was changed, a roller 1 having an average pore diameter of 30 μm and a roller 5 having a pore diameter of 200 μm. And tested.
<Formation of liquid film>
As shown in Table 5, liquid films of Samples 14 to 17 were formed using a roller 1 having an average pore diameter of 30 μm. Moreover, the liquid film of samples 19-21 was formed using the roller 5 whose average pore diameter is 200 micrometers. For Samples 14 to 17, the coating amount was 8 to 11 g / m ² . For samples 19 to 21, the coating amount was 4 to 9 g / m ² .

<Formation of coating>
The base material on which the liquid films 14 to 17 and 19 to 21 were formed was allowed to stand horizontally and dried naturally in the same manner as in Test 1 to form the coating films 14 to 17 and 19 to 21.

Evaluation Appearance evaluation The states of the coating films 14 to 17 and 19 to 21 were visually observed. When the roller 1 having an average pore diameter of 30 μm is used, even if the surface tension of the aqueous coating composition to be applied is in a wide range of 29 to 72 mN / m, the appearance of the coatings 14 to 17 is very It was confirmed that it was good or good. Specifically, when the surface tension of the aqueous coating composition was as large as 48 mN / m or more, coatings 14 to 16 having no coating unevenness and very good appearance were formed. In these coatings, the appearance judgment was A. Even when the surface tension of the aqueous coating composition was as small as 29 mN / m, the film 17 having a fine mesh pattern and a good appearance was formed. In the coating film 17, the appearance determination was B.

  On the other hand, when the roller 5 having an average pore diameter of 200 μm was used, in the case where the surface tension was 54 mN / m or less as in Samples 19 to 21, problems such as coating lima and sagging occurred.

(Test 6) Test in which the viscosity of the aqueous coating composition was changed For the coating compositions 6 and 9 to 11 in which the viscosity was changed, the roller 1 having an average pore diameter of 30 μm, the roller 5 having an average pore diameter of 200 μm, The test was conducted using.

<Formation of liquid film>
As shown in Table 6, liquid films of Samples 15, 22, 24, and 26 were formed using the roller 1 having an average pore diameter of 30 μm. Moreover, the liquid film of the sample 19 was formed using the roller 5 whose average pore diameter is 200 micrometers. For Samples 15, 22, 24, and 26, the coating amount was 6 to 14 g / m ² . For sample 19, the coating amount was ² to 5 g / m ² .

<Formation of coating>
The substrate on which the liquid films 15, 19, 22, 24, and 26 were formed was left to stand horizontally and dried naturally in the same manner as in Test 1 to form the coating films 15, 19, 22, 24, and 26.

Evaluation Appearance evaluation The states of the coating films 15, 19, 22, 24, and 26 were visually observed. When the roller 1 having an average pore diameter of 30 μm is used, even if the viscosity of the aqueous coating composition to be applied ranges from 5.4 to 2079 mPa · s, the coatings 15, 22, 24 and 26 No appearance was evaluated as poor. Specifically, when the viscosity of the water-based coating composition was 185 mPa · s or less, the coating films 15 and 22 having no coating unevenness and very good appearance were formed. The appearance of these coatings was A. Further, even when the viscosity of the aqueous coating composition was as large as 684 mPa · s, the film 24 having scale-like coating marks and good appearance was formed. In the film 24, the appearance determination was B. On the other hand, in the coating film 26 having a high viscosity of 2079 mPa · s of the aqueous coating composition, spotted coating unevenness was slightly visually recognized. However, the coating unevenness visually recognized by the coating 26 was slight, and the appearance was acceptable in practice. In the film 26, the appearance determination was C.

  On the other hand, when the roller 5 having an average pore diameter of 200 μm was used, the coating film 19 having a small viscosity of the aqueous coating composition having a viscosity of 5.4 mPa · s caused problems such as uneven coating and sagging. The appearance of the film 19 was poor, and the appearance determination was D.

(Test 7) Test in which the coating amount was changed Using the roller 1 having an average pore diameter of 30 μm, a test was performed in which the coating amount of the aqueous coating composition 9 was changed.

<Formation of liquid film>
As shown in Table 7, the roller 1 having an average pore diameter of 30 μm was used to change the coating amount (g / m ² ) per one time, and the aqueous coating composition 9 was applied to the surface of the substrate. Thus, liquid films of Samples 22 and 28 were formed.

<Formation of coating>
The base material on which the liquid films 22 and 28 were formed was left to stand horizontally and dried naturally in the same manner as in Test 1 to form the coating films 22 and 28.

Evaluation Appearance evaluation The states of the coating films 22 and 28 were visually observed. In Samples 22 and 28 using the roller 1 having an average pore diameter of 30 μm, the coatings 22 and 28 with no coating unevenness and very good appearance were formed. The appearance of these coatings was A.

(Test 8) Test applied to the outer wall Next, an example in which the aqueous coating composition is applied to the surface of the organic coating body of the outer wall material using various rollers will be described.

  After coating the undercoat and the intermediate coat on the slate substrate, the aqueous coating compositions 12 and 13 were applied to the coated body with various rollers shown in Table 8 to form the liquid films 32-36 of the samples 32-36. The size of the slate substrate was 300 mm × 200 mm × 3 mmt. As an undercoat, a two-pack type epoxy resin paint (SR-50W, manufactured by TOTO) was used. As the intermediate coating, a modified silicone resin coating (ECO-EX intermediate coating, color number # 4000N, manufactured by TOTO) was used. The aqueous coating composition 12 contains 10 mass% of photocatalyst particles 2 and 90 mass% of inorganic oxide particles 1 as particle components. The solid concentration was 5.5 mass%. The aqueous coating composition 13 was obtained by concentrating the aqueous coating composition 12 three times, and the solid content concentration was 16.5 mass%. As shown in Table 8, coatings 32-36 of Samples 32-36 were obtained.

  In the samples 32 and 33 to which the aqueous coating composition 13 having a solid content concentration of 3 times higher was applied using the rollers 1 and 6 having a small pore diameter, the liquid films 32 and 33 had fine uneven shapes. In the drying process of the liquid films 32 and 33, it was quickly dried in about 10 seconds while maintaining this fine uneven shape. In the obtained coating films 32 and 33, the scale-like fine uneven | corrugated shape was formed, and it was the very favorable external appearance by which coating nonuniformity is not visually recognized. Appearance judgments were all A.

  Further, in the sample 35 in which the aqueous coating composition 12 is applied three times by using the roller 6, the same as the film 33 of the sample 33 in which the aqueous coating composition 13 having a solid content concentration of 3 times is applied by the same roller 6. Thus, a coating film 35 having a scale-like fine irregular shape was obtained. The appearance was very good and the appearance judgment was A. In addition, the drying time of the liquid film for each coating was about 10 seconds.

  In the sample 34 to which the aqueous coating composition 13 was applied using the roller 5 having a large pore diameter, an uneven structure was formed in the liquid film 34. Since this concavo-convex structure was somewhat large, a part of the convex portion flowed in the drying process of the liquid film 34, and coating unevenness was partially recognized on the coating 34, but it was within a practically acceptable range. Appearance judgment was C. The drying time of the liquid film 34 was slightly longer than those of the samples 32, 33, and 35, but was within 1 minute.

  In the sample 36 to which the water-based coating composition 12 was applied using the wool roller 8, the liquid film 36 spreads throughout the entire surface, and the uneven shape was not formed. The liquid film 36 flowed as it dried, and coating unevenness was visually recognized on the film 36. It took about 3 to 5 minutes to dry the liquid film 36. Appearance judgment was D.

  From the above test, it was found that a film with a good appearance can be obtained by devising the combination of the type of roller and the coating composition in the same manner regardless of whether the substrate is glass, outer wall, or the like. .

(Test 9) Measurement test of surface shape of coating film <Formation of liquid film>
Using the various coating tools shown in Table 9, the coating amount was set to about 10 g / m ² , and the same aqueous coating composition 2 was applied to the surface of the base material. 37-46) were formed.

  Formation of the liquid films 37 to 44 using the rollers 1 to 5, 8 and 9 was performed as follows. A roller was immersed in the coating composition, and after the roller was sufficiently contained in the coating composition, the impregnation amount of the coating composition was adjusted to about half by squeezing the roller with an iron plate. A roller was brought into close contact with the substrate, and the coating composition was spread two times in the vertical and horizontal directions while rotating, and finish coating was performed in the longitudinal direction of the substrate before the liquid film was dried. Only the liquid film 44 was formed without rotating the roller. Specifically, the coating was performed by fixing to a roller handle so that the roller head did not rotate. The liquid film 45 using a velvet coater (a surface of a sponge with a brushed fabric bonded) is applied several times by dropping an appropriate amount of the coating composition onto the brushed portion of the painted surface with a dropper and pressing it onto the substrate. After spreading, finish coating was applied in one direction. For the liquid film 46 using a spray, a low-pressure atomizing gun (Anest Iwata LPH-101, orifice 1.2 mm) was used. The atomization pressure was 0.15 MPa, and the above coating amount was obtained by applying three times.

<Formation of coating>
The base material on which the liquid films 37 to 46 were formed was allowed to stand horizontally, and then naturally dried until it was sufficiently dried to form the films of the samples 37 to 46 (coating films 37 to 46).

Evaluation (appearance)
The surface shape of the coatings 37 to 46 is photographed and visually checked for isotropic presence or absence, that is, whether a fine uneven shape is formed regardless of the coating direction and the streak pattern is not visually recognized, and coating The presence or absence of unevenness was observed. Photographic images of the coatings 37 to 46 are shown in FIGS. The film was photographed by placing a black matte plate in the background and illuminating a white LED from a direction almost horizontal to the film surface so that the pattern of the film was easy to see. The black line in the photograph is a mark drawn with an oil-based felt pen, and the distance between two points in the middle of the straight line is 1 cm.

(Surface shape profile)
Further, the surface shapes of the coatings 37 to 46 were measured with a digital holographic microscope (manufactured by Lynce Tec). The characteristics of the surface shape of each coating were evaluated by quantifying with three indicators of peak (convex) width, number of peaks per unit length, and peak height (ratio to film thickness). Table 9 shows the number of peaks per unit length, Table 10 shows the evaluation results of the film thickness, and Table 11 shows the overall results. 30 and 31 show surface shape profiles of the films 37 to 46 obtained by digital holographic microscope observation.

  For each coating, a surface shape profile for a length of 10 mm (10,000 μm) was measured in a direction perpendicular to the direction in which the finish coating was performed when the liquid film was formed. Measurement was performed on a line 2 mm away from the mark line drawn with the felt pen. Since shooting with a 1 × 1mm field of view is the largest in one shot, 13 shots were taken while shifting the field of view by 0.8mm for each shot. A one-dimensional profile (x, height data) was extracted based on the 13 obtained two-dimensional surface shape profiles (x, y, height data). In order to integrate 13 profiles, the baseline, drift and position of each profile were corrected and then merged into one profile. At that time, the overlapping portion was an average value of the two profile data. Since the obtained profile was noisy, a 100-point moving average was taken to remove noise. The peak width, the number of peaks per unit length, and the peak height were measured from the position-to-height data obtained by such a procedure by the following method.

-Peak width: The distance between two minimum parts (valleys) on both sides of the peak was measured and used as the peak width.
・ Number of peaks: The profile is divided into four areas (0, 2500, 5000, 5000, 7500, 7500, and 70000 μm (in order, areas 1, 2, 3, and 4), and the number of peaks in each area is measured. did.
・ Peak height: Draw a straight line connecting the two minimum parts when the peak width is obtained, and draw a perpendicular from the peak apex to obtain the distance from the peak to the straight line, and peak the ratio of this distance to the film thickness. Measured as height. The thickness of the coating was determined by the following method. The film of each sample was cut with a cutter knife to form a scratch reaching the substrate surface. The scratched portion was measured with a digital holographic microscope, and the thickness of the coating was determined from the difference in height between the coating surface and the substrate surface.

Results For the coatings 37 to 40 formed using rollers 1 to 4 having an average pore diameter of 30 to 150 μm, both the peak width and the number of peaks are in a desired numerical range (each 300 μm to 500 μm, 4 to 8 The surface of the coating had a two-dimensionally uniform or regular uneven shape. In addition, the coatings 37 to 40 had a uniform periodic structure with little variation in the number of peaks. Furthermore, the coatings 37 to 40 are formed with an uneven shape regardless of the coating direction, the streak pattern or the like is not visually recognized, and isotropic, and the coating unevenness is also not visually recognized. Had. Therefore, it was confirmed that each of the coatings 37 to 40 has a fine uneven shape. In particular, the films 37 and 38 formed using the rollers 1 and 2 not only have a two-dimensionally uniform or regular uneven shape, and the ratio of the peak height to the film thickness is also in a desired numerical range ( 10% or less), and has a three-dimensional uniform or regular uneven shape. Therefore, it was confirmed that the coatings 37 and 38 have a good fine uneven shape. The coatings 39 and 40 formed using the rollers 3 and 4 having an average pore diameter of 80 to 150 μm have a higher peak height ratio than the coatings formed using other coating tools, and a desired numerical range. However, both the peak width and the number of peaks were in a desired numerical range, and had a sufficiently fine uneven shape. If the film has a two-dimensional good uneven shape, the film is judged to have a sufficiently fine uneven shape, and if it has a three-dimensional good uneven shape, The film was judged to have a good fine irregular shape.

  On the other hand, the coating film 41 formed using the roller 5 having an average pore diameter of 200 μm has an isotropic shape regardless of the coating direction, and has no isotropic pattern and is not confirmed. The coating unevenness was conspicuous and the visual appearance was poor. The peak width was in the desired numerical range. However, the number of peaks is not in the desired numerical range, the variation is large, and the structure is aperiodic. Therefore, it was confirmed that the film 41 does not have a fine uneven shape. The peak height was not in the desired numerical range.

  The material 42 is a dry sponge, the average pore diameter is 500 μm, and the coating 42 formed using the roller 9 having no water absorption has an irregular shape regardless of the coating direction, and no streak pattern is confirmed. Although it was isotropic, uneven coating was conspicuous and the visual appearance was poor. However, none of the peak width, the number of peaks, and the peak height are in the desired numerical range, the variation in the number of peaks is large, and the structure is aperiodic. Therefore, it was confirmed that the coating 42 does not have a fine uneven shape.

  The coating film 43 formed using the roller 8 made of wool has an irregular shape regardless of the coating direction, has no isotropic streaks, and isotropic. The conspicuous visual appearance was poor. The peak width was in the desired numerical range. However, the number of peaks is not in the desired numerical range, has variations, and has an aperiodic structure. Therefore, it was confirmed that the film 43 does not have a fine uneven shape. The peak height was not in the desired numerical range.

  The film 44 formed using the roller 8 made of wool without rotating it had all of the peak width, the number of peaks, and the peak height in a desired numerical range, but included a large convex portion. This was a streaky pattern along the painting direction and uneven coating. Therefore, it was confirmed that the coating 44 does not have a fine uneven shape.

  The film 45 formed using a velvet coater (a sponge surface with a brushed fabric bonded) has a peak width that is not in the desired numerical range and includes large protrusions, which are along the coating direction. The pattern was uneven and the coating was uneven. Therefore, it was confirmed that the film 45 does not have a fine uneven shape.

  The coating 46 formed using the spray was not visually recognized with a streak pattern or the like, and was isotropic, but the coating unevenness was conspicuous and the visual appearance was poor. However, none of the peak width, the number of peaks, and the peak height were in the desired numerical range. Therefore, it was confirmed that the film 46 does not have a fine uneven shape.

  As mentioned above, the average pore diameter is 30 μm or more and 150 μm or less, and the surface shape of the film formed using a roller having good water absorption is the same material, but the average pore diameter is larger than the above range. Or isotropic as compared to the surface shape of the film formed using other coating tools such as a roller having a large average pore diameter and not absorbing, or a velvet coater or spray, and It was confirmed that the peak width, the number of peaks, and the peak height are in a desired numerical range and have a fine uneven shape.

101: Liquid film with fine irregularities (immediately after application, before drying)
101a: Convex part that forms the fine irregular shape of the liquid film
101b: Concavities that make up the fine irregular shape of the liquid film
102: Coating with fine irregularities maintained (after drying)
102a: Convex part that forms the fine irregular shape of the coating
102b: Concavities that make up the fine irregular shape of the coating
201: Liquid film with irregularities that are not fine (prior art)
201a: Convex part that forms uneven shape of liquid film
201b: Concave part constituting a non-fine uneven shape of the liquid film
202: Non-fine uneven film (with uneven coating)
202a: Convex part that forms a non-fine uneven shape of the film (convex part visually recognized as uneven coating)
202b: Concave portion that forms a non-fine uneven shape of the coating (a concave portion visually recognized as uneven coating)

Claims (19)

A method of forming a coating film on a surface of a substrate,
The method is
Applying a water-based coating composition to the surface of the substrate to form a liquid film;
Forming a film by drying the liquid film, and
The liquid film has a fine uneven shape including a plurality of convex portions and a plurality of concave portions,
In the film forming step, the liquid film is dried to form the film in which the fine uneven shape of the liquid film is maintained.   The method according to claim 1, wherein the coating film formed by maintaining the fine uneven shape of the liquid film has a scale-like fine uneven shape. The scale-like fine concavo-convex shape is isotropic, and the scale-like fine concavo-convex shape is an average measured from a profile obtained by observing the surface shape of the coating film with a digital holographic microscope. The method according to claim 2, wherein the peak width is 300 μm or more and 500 μm or less, and the average number of peaks in a unit length of 2.5 mm is 4 or more and 8 or less.   The ratio of the peak height to the thickness of the coating film, which is measured from a profile obtained by observing the surface shape of the coating film with a fine concavo-convex shape of the scale with a digital holographic microscope, is 10% or less. The method of claim 3. The step of forming the liquid film is to form the liquid film by applying the aqueous coating composition to the surface of the substrate using a sponge roller,
The said sponge roller has a continuous pore, The average pore diameter of the said continuous pore is 30 micrometers or more and 150 micrometers or less, The ethanol permeation | transmission time is 20 seconds or more and 270 seconds or less, It is any one of Claims 1-4. the method of.   The method according to claim 5, wherein the viscosity of the aqueous coating composition is 4.5 mPa · s or more and less than 3000 mPa · s.   The method according to claim 5 or 6, wherein the surface tension of the aqueous coating composition is greater than 25 mN / m and not greater than 72 mN / m. In the liquid film forming step, applying amount per one of the aqueous coating composition applied to a surface of said substrate is 2 g / m ² or more 15 g / m ² or less, more of claims 1 to 7 The method according to claim 1.   In the said liquid film formation process, applying the aqueous coating composition to the surface of a base material, rotating the said sponge roller, forms the said liquid film, It is any one of Claims 5-8 characterized by the above-mentioned. The method described.   The method according to claim 1, wherein the water-based coating composition comprises functional particles and a dispersion medium mainly containing water.   The method according to claim 10, wherein the functional particles are photocatalytic particles.   The method according to claim 11, wherein the aqueous coating composition further comprises inorganic oxide particles other than the photocatalyst particles. A functional material comprising a base material and a coating film formed on the surface of the base material,
The functional material in which the coating film has a fine uneven shape including a plurality of convex portions and a plurality of concave portions.   The functional material according to claim 13, wherein the fine uneven shape is a scale-like fine uneven shape. The scale-like fine concavo-convex shape is isotropic, and the scale-like fine concavo-convex shape is an average measured from a profile obtained by observing the surface shape of the coating film with a digital holographic microscope. The functional material according to claim 14, wherein the peak width is 300 μm or more and 500 μm or less, and the average number of peaks in a unit length of 2.5 mm is 4 or more and 8 or less.   The ratio of the peak height to the thickness of the coating film, which is measured from the profile obtained by observing the surface shape of the coating film of the scale-like fine irregularities with a digital holographic microscope, is 10% or less. The functional material according to claim 15.   The functional material according to any one of claims 13 to 16, wherein the coating film comprises functional particles.   The functional material according to claim 17, wherein the functional particles are photocatalyst particles.   The functional material according to claim 18, wherein the coating film further comprises inorganic oxide particles other than the photocatalyst particles.