JP2000283695A - Aluminum fin material for heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aluminum fin material for a heat exchanger which can develop hydrophilic property from the condition before irradiation with an ultraviolet ray, and can raise the hydrophilic property by irradiation with an ultraviolet ray for a short time, and can recover the hydrophilic property decreased once by condensed water by irradiation with an ultraviolet ray for a short time. SOLUTION: A base film 2 consisting of an inorganic oxide having protrusions and recesses at specified intervals is provided in specified thickness on the substrate 1 consisting of aluminum, and further a titanium dioxide film 3 obtained by applying, drying and baking titanium dioxide sol solution and having protrusions and recesses on the surface and a coating amount of 50-500 mg/m2 is made thereon, or the surface of the substrate 1 is roughened in place of the base film 2 so as to form a roughened part, and then the titanium dioxide film 3 is made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fin material for a heat exchanger made of aluminum having a coating film or the like formed on the surface thereof, and particularly to a fin material for a heat exchanger such as a home air conditioner, which has excellent hydrophilicity. The present invention relates to an aluminum fin material suitable for a heat exchanger.

[0002]

2. Description of the Related Art Heat exchangers are used in various fields such as room air conditioners, package air conditioners, freezer showcases, refrigerators, oil coolers and radiators. The heat exchanger is provided with fins for heat exchange. The material (fin material) used for the fins is aluminum because of its excellent thermal conductivity and workability. Hereinafter, in this specification, the term “aluminum” includes an aluminum alloy. Usually, the fin material made of aluminum is subjected to anticorrosion treatment for the purpose of preventing corrosion. When the fins corrode, the heat exchanger characteristics deteriorate. At the same time, in order to prevent the condensed water condensed on the fins during cooling operation from remaining in the gaps between the fins that are densely provided, it is necessary to improve the dropping property of the water droplets or to prevent the water droplets from falling into a water film. The fin material has been subjected to a surface treatment to improve its properties. This is because if condensed water stays in the gap between the fins, the resistance at the time of blowing increases, and the heat exchanger characteristics deteriorate as in the case where the fins are corroded.

As shown in FIG. 2, in general, when the material has good hydrophilicity, the contact angle θ between the water droplet W placed on (adhered to) the material surface S and the material surface S becomes small. The contact angle θ refers to an angle between a tangent L and a material surface S at a point of the water droplet W rising from the material surface S when the water droplet W placed on the material surface S is viewed from the side. Similarly, in the fin material, the smaller the contact angle, the thinner the water film on the fin, and the better the hydrophilicity. In the heat exchanger HE composed of a large number of fins 51, 51, and a pipe 52 serving as a passage for a refrigerant or the like shown in FIG. 3, if the fin material constituting the fin 51 has good hydrophilicity, the fin 51
Water droplets (not shown) easily fall from the fins 51.
The resistance at the time of air blowing due to water droplets or a water film (not shown) attached to the surface is reduced, and excellent heat exchanger characteristics can be obtained.

[0004] The state of the attachment of water droplets to the fins 51 in the heat exchanger HE will be described with reference to FIG. As shown in FIG. 4A, when the fin material has good hydrophilicity, the contact angle between the surface of the fin 51a having good hydrophilicity and the water droplet W is small, so that the water droplet W easily follows the fin 51a. And fall. For this reason, since the water droplets W do not block the blowing, the blowing resistance is reduced. On the other hand, in the heat exchanger HE made of a fin material having slightly inferior hydrophilicity, FIG.
As shown in FIG. 4B, since the contact angle of the water droplet W is large, the water droplet W may remain on the surface of the fin 51b, which is slightly inferior in hydrophilicity, or as shown in FIG.
May stay between two fins 51c having inferior hydrophilicity, so that the water droplets W block the airflow, and the airflow resistance increases significantly.

As a surface treatment method for improving the hydrophilicity of the fin material, a treatment method using a silicate (Japanese Patent No.
No. 769978) and a method of forming a film in which fine silica particles are dispersed in a thermosetting resin (JP-A-3-26972).
No.). However, in the surface treatment method for improving the hydrophilicity of the fin material, although good hydrophilicity can be obtained at the beginning of the surface treatment, the hydrophilicity gradually decreases. When the hydrophilicity is reduced, it is possible to recover the hydrophilicity by using a fin cleaning solution or the like, but labor is required.

In recent years, titanium dioxide (Ti) has been used as a surface treatment method for a fin material made of aluminum.
The use of O ₂ ) has attracted attention and is being studied. Titanium dioxide, which is an n-type semiconductor, shows a strong oxidizing power under ultraviolet irradiation, and its use in various applications is being studied for reasons such as high chemical stability and safety. Applications for which the effects have been reported so far include prevention of dirt adhesion (decomposition of oily dirt), antibacterial and antifungal, decomposition of NOx and odorous components in the air, decomposition of organic wastewater and hardly decomposable harmful substances. There are high expectations for environmentally friendly technologies in the future (Akira Fujishima, Kazuhito Hashimoto, Toshiya Watanabe; Hikari Clean Revolution, P.12
(CMC, 1997)).

Therefore, the present inventors conducted various tests and studies on the hydrophilicity of the titanium dioxide. A titanium dioxide sol solution is applied to a substrate made of aluminum,
When drying and baking to form a titanium dioxide coating film to improve the hydrophilicity of the material surface, when the titanium dioxide sol solution is applied to the substrate and dried at about 100 ° C., adsorbed water is present on the surface of the titanium dioxide particles. There are many. This adsorbed water is
It is thought that it is lost by firing after application of the titanium dioxide sol solution. The loss of adsorbed water by calcination itself has a disadvantageous effect on hydrophilicity, but the hydroxyl group of titanium dioxide itself is not lost. Conversely, calcination increases the photocatalytic activity of titanium dioxide. The good hydrophilicity obtained when the surface of the titanium dioxide coating film is irradiated with ultraviolet rays is considered to be expressed by a combined effect such as the decomposition of the adsorbed organic matter by the hydroxyl group or photocatalytic activity of the titanium dioxide ( T.Morimoto, H.Nagano, F.To
kuda; J. Phys. Chem. 73,243 (1969) / Kazuhiko Mori, Mitsuru Nakamura, Masanobu Tanaka; Japanese Parkerizing Technical Report No. 10 (1998)
p16).

[0008]

However, there are various problems when the titanium dioxide coating film is formed on the surface of the substrate to impart hydrophilicity and is used as a fin material for a heat exchanger. Hereinafter, problems when titanium dioxide is used will be described. First, it is necessary to apply a titanium dioxide sol solution to a substrate made of aluminum and then perform calcination.
It is preferable to perform firing at about 0 ° C. or higher (International Publication No. WO96 / 29375). However, if the firing temperature is increased, the substrate is made of aluminum, so that the substrate is softened and easily deformed, which is not preferable. Therefore, baking is performed at about 250 ° C., which has little effect on the softening of the substrate. However, in the titanium dioxide coating film formed by this, hydrophilicity can be obtained unless ultraviolet irradiation time is sufficiently long. There is a problem that it becomes difficult.

In addition, simply providing a titanium dioxide coating film on an ordinary substrate does not provide hydrophilicity, but rather provides a water-repellent state (Nikkei Mechanical, April 1998, no. 523 P16). In this state, hydrophilicity is developed by irradiating ultraviolet rays from this state. However, when irradiation is performed using a practical ultraviolet lamp of about 10 W, irradiation time of 100 hours or more is required until hydrophilicity is developed. You will need it. Further, even after the hydrophilicity is once exhibited, when the fin material is processed into a fin material for a heat exchanger and used as a heat exchanger, the hydrophilicity gradually deteriorates due to dew condensation water. When the hydrophilicity is deteriorated, ultraviolet irradiation is required again, but the same irradiation time is required to restore the hydrophilicity. As described above, when titanium dioxide is used, it is possible to recover the hydrophilicity once deteriorated by the irradiation of ultraviolet rays, but it is not practical because the irradiation time of the ultraviolet rays needs to be sufficiently long.

The present invention has been made in view of such a mistake when titanium dioxide is used as a fin material for a heat exchanger. Fins for heat exchangers that can improve the hydrophilicity by irradiating for a short time, and can easily recover the hydrophilicity once reduced by condensed water by irradiating ultraviolet rays for a short time. It is intended to provide.

[0011]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, the aluminum fin material for a heat exchanger of the present invention, which has solved the above-mentioned problems, comprises: (a) forming a base film made of an inorganic oxide having irregularities at predetermined intervals with a predetermined thickness on a substrate made of aluminum. Further, (b) a titanium dioxide sol solution is applied thereon, followed by drying and baking to obtain a coating film amount of 50 to 500 mg.
/ M ^{2 on} the surface of which a titanium dioxide coating film having irregularities is formed. According to this, an undercoat having predetermined irregularities and a predetermined film thickness formed on the substrate increases the specific surface area of the titanium dioxide coating film formed on the film. That is, the titanium dioxide coating is formed along the irregularities by providing the titanium dioxide coating after forming the three-dimensional irregularities by the undercoat, and as a result, the specific surface area of the titanium dioxide coating is extremely high. It is large and very wet. In other words, these irregularities increase the contact area between the titanium dioxide coating film and the condensed water droplets, thereby maximizing the photocatalytic activity of titanium dioxide.

Further, the aluminum fin material for a heat exchanger is characterized in that the surface of the substrate is roughened to form a roughened portion having predetermined irregularities instead of forming the base coat. According to this, since the titanium dioxide coating is formed along the irregularities of the rough surface portion, the specific surface area of the titanium dioxide coating can be increased.

[0013]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the structure of the aluminum fin material for a heat exchanger of the present invention. The aluminum fin material F for a heat exchanger of the present invention forms an undercoat 2 on a substrate 1 and
(Claim 1). Base coat 2 and titanium dioxide coat 3
May be formed on one side or both sides of the substrate 1, or may be formed over the entire surface. What is necessary is just to form on the surface which wants to express excellent hydrophilicity. Further, the aluminum fin material F for a heat exchanger of the present invention may have a configuration in which the surface of the substrate 1 is roughened to form the roughened surface portion 1a instead of forming the base coat 2 (claim 2).

[Substrate] First, the substrate 1 is made of aluminum (aluminum plate). Aluminum may be of any alloy as long as it can be used as a fin material for a heat exchanger.

[Undercoating] Next, the undercoating 2 is formed on the substrate 1 as a coating having a predetermined thickness with irregularities at predetermined intervals. The unevenness of the undercoat 2 has a role of increasing the specific surface area of the titanium dioxide coating 3 formed on the undercoat 2. By increasing the specific surface area of the titanium dioxide coating 3, the area of the coating 3 that contacts the condensed water droplets can be increased, so that excellent hydrophilicity can be obtained. The unevenness of the undercoat 2 may be recognized as a protrusion formed on the undercoat 2, for example.
It may be recognized as a dent or a hole formed on the undercoat 2, or may be recognized as a mixture of the two.

The distance between the irregularities of the undercoat 2 is 0.05
A range of １1 μm is preferred. 0.05μ spacing
When the diameter is smaller than m, the titanium dioxide coating film 3 is difficult to be formed along the irregularities, that is, the surface of the titanium dioxide coating film 3 becomes flat. I can't get it. On the other hand, when the interval between the irregularities is larger than 1 μm, the surface of the titanium dioxide coating film 3 becomes almost flat, so that the titanium dioxide coating film 3 cannot have a large specific surface area.
If the titanium dioxide coating film 3 cannot have a large specific surface area, good hydrophilicity cannot be obtained. This is because the photocatalytic activity of titanium dioxide cannot be maximized. In addition, the interval of the unevenness is defined as follows. That is, the scanning electron microscope (S
In the surface morphology photograph (see FIG. 6 and the like) of the undercoating film 2 enlarged to about 10,000 times by EM), an arbitrary point (a vertex of a projection, a center of a depression, etc.) on the surface is selected, and the point is used as a base point. The average value of the longest distance and the shortest distance until reaching the apex of another adjacent unevenness (for example, if the reference point is the apex of the projection, the apex of another adjacent projection) is obtained. This is performed for each of five arbitrary points, and the average is determined to determine the interval between the irregularities.

The thickness of the undercoat 2 affects the height (or depth) of the unevenness formed on the film 2, but in the present invention, the thickness of the undercoat 2 is 0.05 to 0.05. 10μ
It is preferable to form them so as to fall within the range of m. If the thickness of the undercoat film 2 is less than 0.05 μm, three-dimensionally effective unevenness will not be obtained, and the specific surface area of the titanium dioxide coating film formed thereon will be small, making it difficult to obtain hydrophilicity.
On the other hand, if the thickness of the undercoat film 2 exceeds 10 μm, cracks and the like are likely to occur in the undercoat film 2, and even if the titanium dioxide coating film 3 is provided thereon, it is not preferable because it easily peels off.

As a material constituting the base coat 2, an inorganic substance or an organic substance can be selected and used. In the case of an organic substance, the titanium dioxide coating film 3 is formed by firing except for those having heat resistance. This heat is not preferable because the organic matter decomposes and does not serve as a base. In addition, even if it is an inorganic substance, a substance that is oxidized during firing is not preferable. Therefore, as the material constituting the base coat 2, an inorganic oxide that has already been oxidized is suitable. Among these inorganic oxides, alumina (Al ₂ O ₃ ) and silica (SiO ₂ ), which are easy to handle and have good adhesion to titanium dioxide, are suitable for this application.

The means for forming the undercoat 2 is not limited to a specific one, and any known technique can be applied. For example, a film formed by a method using a silicate, which is a surface treatment method conventionally used to improve the hydrophilicity of the fin material (Japanese Patent No. 1769978), is sufficiently washed with water or the like. If the resin is removed from the film, it can be used as the base film 2 of the present invention (the reason for removing the resin will be described later). Furthermore, an alumina film having fine irregularities is also formed by a general boehmite treatment, and this film can be used as the base film 2 of the present invention.

It is to be noted that the three-dimensional irregularities described for the undercoat 2 can also be created by forming the roughened surface portion 1a by roughening the surface of the substrate 1 instead of forming the undercoat 2. . That is, the specific surface area of the titanium dioxide coating film 3 formed thereon can be increased even by the configuration in which the rough surface portion 1a is formed on the surface of the substrate 1, so that the object of the present invention can be achieved. The rough surface portion 1a can be efficiently formed by, for example, pressing a mold having predetermined irregularities onto the substrate 1.

[Titanium Dioxide Coating Film] The titanium dioxide coating film 3 is formed on the undercoat film 2 (rough surface portion 1a).
As a forming method thereof, a method of applying a titanium dioxide sol solution on the undercoat film 2, followed by drying and baking to form the titanium dioxide coating film 3 can be mentioned. The means for drying at this time is not particularly limited. The baking temperature is selected to be a temperature (for example, 250 ° C.) sufficient to form the titanium dioxide coating film of the present invention and not to soften the substrate 1 made of aluminum.

The titanium dioxide coating 3 is preferably formed by previously forming the undercoat 2 having the above-mentioned irregularities at predetermined intervals, so that the coating amount of the titanium dioxide coating 3 is 50 mg / m ² or more. Hydrophilicity is obtained. Here, if the amount of the titanium dioxide coating film 3 is increased, the amount of titanium dioxide per unit area is also increased, so that the hydrophilicity tends to be improved. 05
It must be in the range of 10 to 10 μm. If the amount of the coating film exceeds 500 mg / m ² , the titanium dioxide coating film 3 becomes brittle and easily peels off, which is not preferable.

Here, comparing the configuration in which the undercoating 2 is formed and the configuration in which the roughened surface portion 1a is formed, the formation of the undercoating 2 has better adhesion of the titanium dioxide coating 3, and the coating 3
Tend to be difficult to peel off. However, even when the rough surface portion 1a is formed, a well-known heat-resistant primer layer having good adhesion to both the substrate 1 and the titanium dioxide coating 3 is provided on the rough surface portion 1a. 1 and the titanium dioxide coating 3 can be improved in adhesion.

Then, the aluminum fin material F for a heat exchanger of the present invention configured as described above is assembled into the heat exchanger HE shown in FIG. The aluminum fin material F for a heat exchanger of the present invention has high hydrophilicity from the beginning due to the large specific surface area of the titanium dioxide coating film 3. When ultraviolet rays are irradiated in the initial stage before use, the hydrophilicity is further improved due to the photocatalytic activity of titanium dioxide. Further, the hydrophilicity once reduced by use can be favorably recovered by re-irradiation with ultraviolet rays thereafter. Further, odor components and organic substances can be oxidatively decomposed by the photocatalytic activity effect. Incidentally, the hydrophilicity of the titanium dioxide coating film 3 is mainly expressed by the photocatalytic activity effect of the OH groups of the titanium dioxide particles and the titanium dioxide that decomposes organic substances attached to the surface of the titanium dioxide coating film 3.

[0025]

Next, the present invention will be described in more detail with reference to examples (see FIGS. 1, 2, 5 to 7 and Table 1). Note that the present invention is not limited to the present embodiment.

In this example, test pieces were prepared under the various conditions shown in Table 1 (in addition, test pieces of comparative examples were also prepared). Each test piece (eight kinds of examples, three kinds of comparative examples) has the structure shown in FIG. 1 (substrate 1, base film 2, titanium dioxide coating film 3), and various tests are performed on this test piece. The hydrophilicity and the like were evaluated. The substrate 1 of each test piece is JISA
An aluminum plate having a thickness of 1100H22 and a thickness of 0.110 mm was used. The substrate 1 was previously subjected to alkaline degreasing, washed with water, and dried. An undercoat 2 was formed on the substrate 1 by the processing shown in Table 1 (details will be described later). ST-K03 manufactured by Ishihara Sangyo was used as a titanium dioxide sol solution for forming the titanium dioxide coating film 3. The titanium dioxide sol solution is applied using a bar coater, and the coating is dried for 20 minutes.
The firing was performed at 0 ° C. for 10 seconds, and the firing was performed at 250 ° C. for 10 minutes. The lamp used for ultraviolet irradiation is a black light fluorescent lamp (BLB), and the specification is a lamp power of 10
W, ultraviolet region 315 nm to 400 nm (peak 352
nm), a pipe length of 330 mm, and a pipe diameter of 25.5 mm. FIG. 5 is a schematic diagram illustrating a method of irradiating the test piece with ultraviolet light.

[0027]

[Table 1]

The test pieces of the examples and the test pieces of the comparative examples were tested for the adhesion and hydrophilicity of the titanium dioxide coating film 3, and the results of the investigation of the hydrophilicity are shown in Table 1. In addition, the surface morphology of the unevenness formed on the base film 2 with the pretreatment step finger was measured using a scanning electron microscope (SEM).
And observed at 10,000 times magnification. As a representative example, FIG. 6 shows a surface morphology photograph of the unevenness of each undercoat film 2 of Examples 1, 4 and 7 by a scanning electron microscope, and the undercoat films of Comparative Examples 1 and 2 are shown. FIG. 7 shows a photograph of the surface morphology of the unevenness of No. 2 by a scanning electron microscope. The hydrophilicity was determined by the above-mentioned contact angle measurement (see FIG. 2). The timing for measuring the contact angle is as follows: immediately after the firing of the titanium dioxide coating film 3 (initial stage),
Immediately after irradiating with ultraviolet light for 4 hours (after 24 hours of ultraviolet irradiation), immediately after irradiating the above-mentioned ultraviolet rays with pure water for 100 hours (after 100 hours of immersion in pure water), the one immersed in the pure water was treated with 24 hours.
Immediately after re-irradiation of ultraviolet rays for 24 hours (after 24 hours of re-irradiation of ultraviolet rays), a total of four times. Regarding the evaluation of hydrophilicity, it was determined that the contact angle θ shown in FIG. 2 was 30 degrees or less, which was sufficient as a practical level, and that the contact angle θ was 10 degrees or less, it was judged to be superhydrophilic.

Hereinafter, 0.05 to 1 which is a main part of the present invention will be described.
A method for forming the undercoating 2 having irregularities at intervals of μm will be described (see the pretreatment column in Table 1). Among the examples, Examples 1 to 5 are based on the method using sodium silicate (silicate treatment 1, silicate treatment 2, Patent No. 1769978).
No. 2) to form a base coat 2. In this forming method (pretreatment), surface roughening (formation of irregularities at predetermined intervals) is performed by:
It is realized by using a water-soluble resin such as polyacrylic acid. However, if the resin remains, the resin is decomposed by heat when forming the titanium dioxide coating film 3 by firing, and This is not preferable because the adhesion between the titanium dioxide film 2 and the titanium dioxide coating film 3 is impaired. Therefore, the base film 2 is sufficiently washed with water to remove the remaining resin. On the other hand, among Examples, in Examples 6 to 8, the base film 2 was formed by a general boehmite treatment (boehmite treatment 1, boehmite treatment 2). This boehmite treatment is, for example, 75 to
The treatment is performed in hot water or saturated steam at 120 ° C., and the interval between the irregularities of the base coat 2 can be controlled by the treatment temperature and time. In this example, boehmite treatment 1 and boehmite treatment 2 were performed by immersing the substrate 1 in 80 ° C. pure water.

The results are shown in Table 1. The test piece of this example has good hydrophilicity immediately after the formation of the titanium dioxide coating film 3, and the hydrophilicity improves when irradiated with ultraviolet rays. Then, even if the hydrophilicity is lowered by immersion in pure water, the hydrophilicity is remarkably recovered by re-irradiating with ultraviolet rays. By the way, in this embodiment, the undercoat 2 has unevenness at intervals of 0.05 to 1 μm (the thickness of the undercoat 2 is 0.05 μm or more). 50-50
Although it is within the range of 0 mg / m ² , within this range, as the amount of the titanium dioxide coating film 3 increases, the amount of titanium dioxide per unit area increases, so that the hydrophilicity is good. In addition, from the surface morphology photograph of FIG. 6, 0.05 to 1 for each of the undercoating films 2 of Example 1, Example 4, and Example 7.
It can be seen that irregularities are formed at intervals of about μm.

On the other hand, in the comparative example, the comparative example 1 is a normal phosphoric acid chromate treatment (phosphoric acid chromate treatment 1).
Thus, the undercoat film 2 was formed. In Comparative Example 2, the base coat 2 was formed by the boehmite treatment 3 in which the substrate 1 was immersed in pure water at 80 ° C. for 1 minute. Undercoat film 2 formed by this
Has a thickness of 0.05 μm or less. In Comparative Example 3, the undercoat film 2 was formed by the silicic acid treatment 1, and the amount of the titanium dioxide coating film 3 on the undercoat film 2 was 50%.
mg / m ² or less. From the photograph of the surface morphology in FIG. 7, the distance between the irregularities is small for the undercoat 2 of Comparative Example 1, and the undercoat 2 of Comparative Example 2 has three-dimensionally effective irregularities because the film thickness is insufficient. Absent.

As a result, in Comparative Examples 1 and 2, although the hydrophilicity is improved by sufficiently irradiating ultraviolet rays, the initial hydrophilicity and the hydrophilicity after immersion in pure water are poor, and are not practical. . In Comparative Example 3, since the amount of the titanium dioxide coating film 3 itself was small, the hydrophilicity was poor from the beginning, and the effect of recovering the hydrophilicity was small even when irradiated with ultraviolet light, so that it is practically impossible (Table 1). reference).

It should be noted that the present invention is not necessarily limited to the means and methods described above, but can be appropriately modified and implemented within the scope of achieving the object of the present invention and having the effects of the present invention. Things.

[0034]

As described above in detail, according to the present invention, the titanium dioxide coating film 3 is made to exhibit good hydrophilicity from the state before the irradiation with ultraviolet rays, and is irradiated with ultraviolet rays for a certain time. It is possible to configure the aluminum fin material F for a heat exchanger having excellent hydrophilicity, which improves the hydrophilicity and facilitates the recovery of the hydrophilicity once reduced by the condensed water. Then, the predetermined coating film 3 of titanium dioxide can be formed on the substrate 1 with certainty and good durability by the base coat 2.
Further, according to the configuration in which the surface of the substrate 1 is roughened to form the rough surface portion 1a, the productivity of the aluminum fin material F for a heat exchanger can be improved. Since the titanium dioxide coating film 3 of the present invention has an excellent photocatalytic activity effect, it can oxidatively decompose odor components and organic substances to suppress the growth of mold and prevent the generation of off-flavors.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an aluminum fin material for a heat exchanger of the present invention. (A) shows a configuration in which an undercoat is formed, and (b) shows a configuration in which a rough surface portion is formed.

FIG. 2 is a diagram illustrating a contact angle that is an index of hydrophilicity.

FIG. 3 is a diagram showing a heat exchanger.

FIG. 4 is a view showing a state of attachment of water droplets to fins of a heat exchanger. (A) shows the case of a fin having good hydrophilicity, (b) shows the case of a fin having slightly poor hydrophilicity, and (c) shows the case of a fin having poor hydrophilicity.

FIG. 5 is a schematic diagram illustrating a method of irradiating a test piece with ultraviolet light in an example.

FIG. 6 is a surface morphology photograph by a scanning electron microscope showing a fine pattern of an undercoat film formed on a substrate in an example. (A) shows Example 1, (b) shows Example 4, and (c) shows Example 7.

FIG. 7 is a photograph of a surface morphology by a scanning electron microscope showing a fine pattern of an undercoat film formed on a substrate in a comparative example. (A) shows Comparative Example 1 and (b) shows Comparative Example 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Substrate (1a; rough surface part) 2: Base coat (coating) 3: Titanium dioxide coating (coating) F; Aluminum fin material for heat exchangers 51; Fins (51a, 51b, 51c) 52; Piping HE: Heat Exchanger, L; tangent, S
Material surface W; water droplet; θ; contact angle

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenichi Kamiya 15 Kinuigaoka, Moka-shi, Tochigi F-term in Kobe Steel Moka Works (reference) 4K022 AA02 AA49 BA15 BA22 BA33 BA36 CA14 DA06 EA01 EA02 4K044 AA06 BA12 BA13 BA14 BA21 BB03 BB14 CA24 CA62

Claims (2)

[Claims] 1. On a substrate made of aluminum,
(A) An undercoat film made of an inorganic oxide having irregularities at predetermined intervals is formed with a predetermined thickness, and further thereon,
(B) heat exchange, wherein a titanium dioxide sol solution is applied, dried and calcined to form a titanium dioxide coating having a surface roughness of 50 to 500 mg / m ^2. Aluminum fin material for vessels. 2. The aluminum fin material for a heat exchanger according to claim 1, wherein the surface of said substrate is roughened to form a rough surface having predetermined irregularities, instead of said undercoat. Aluminum fin material for exchangers.