WO2012147288A1

WO2012147288A1 - Water-repellent substrate, heat exchanger using water-repellent substrate, and method for producing water-repellent substrate

Info

Publication number: WO2012147288A1
Application number: PCT/JP2012/002423
Authority: WO
Inventors: 侑作西岡; 友英西野; 瀧川　賢司
Original assignee: 株式会社デンソー; 外山哲男
Priority date: 2011-04-27
Filing date: 2012-04-06
Publication date: 2012-11-01
Also published as: JP2012228670A

Abstract

A water-repellent substrate (100) is provided with a substrate (110), and a hydrophobic film (120) disposed upon the surface of the substrate (110), wherein a plurality of needle-shaped protrusions (111) is formed on the surface of the substrate (110). The hydrophobic film (120) comprises a plurality of minute protrusions (121) that are finer than the needle-shaped protrusions (111), and the plurality of minute protrusions (121) is disposed upon the needle-shaped protrusions (111) and the surface of the substrate (110) remaining between the surfaces of the needle-shaped protrusions (111). The water-repellent substrate (100) forms at least either a tube (211) that constitutes a heat exchange section (210) of a heat exchanger (200) and is used for circulating a heat transfer medium, or a fin (212) that is connected to the tube (211) and forms a surface that transfers heat to atmospheric air.

Description

Water repellent substrate, heat exchanger using water repellent substrate, and method for producing water repellent substrate

Cross-reference of related applications

This disclosure is based on Japanese Patent Application No. 2011-99198 filed on Apr. 27, 2011, and the contents thereof are disclosed in this specification.

The present disclosure relates to a water-repellent base material that repels condensed water generated from the surface of the base material at low temperatures, a heat exchanger using the water-repellent base material, and a method for producing the water-repellent base material.

As a conventional water-repellent substrate, for example, one described in Patent Document 1 is known. The water-repellent substrate of Patent Document 1 is applied to a window glass for a vehicle and the like, and has a base film having minute irregularities on the surface of the substrate, and a water repellency formed on the minute irregularities of the substrate film. It has a film. The water-repellent film has a surface shape reflecting the minute irregularities of the base film. Furthermore, the surface shape of the water-repellent coating is composed of particulate protrusions and columnar protrusions that are higher in height as measured from the surface of the substrate than the particulate protrusions.

In Patent Document 1 applied to a window glass, CA ≧ 150 degrees, where CA is the contact angle of water droplets on the surface of the water-repellent coating, and TA is the falling angle as the critical angle at which the water droplets fall when dropped. In addition, TA ≦ 15 degrees, or 150 degrees> CA ≧ 145 degrees and TA ≦ 5 degrees, and the water repellency is excellent and water droplets hardly remain on the surface of the window glass.

However, the water-repellent substrate of Patent Document 1 is excellent in dropping water drops dripped on a window glass or the like as described above. On the other hand, for example, when the base material is placed in a low temperature field, water vapor in the air that touches the base material is condensed to generate condensed water from the surface of the base material. The material had a problem that good water repellency of condensed water could not be obtained. That is, in the water-repellent substrate of Patent Document 1, condensed water is generated also from the inside of the recess formed between the particulate protrusions and the columnar protrusions, and the condensed water accumulates in the recess, and further outside the recess. Since the condensed water in each recess is connected to each other to form a large water film, it is difficult to obtain good water repellency of the condensed water and it is difficult for the condensed water to slide down.

Japanese Patent No. 4198598

In view of the above problems, an object of the present disclosure is to provide a water-repellent substrate having good water repellency with respect to condensed water generated on the surface, a heat exchanger using the water-repellent substrate, and a method for producing the water-repellent substrate. Is to provide.

In order to achieve the above object, the present disclosure provides a water-repellent substrate including a substrate and a hydrophobic film provided on the surface of the substrate, and a plurality of needles are provided on the surface of the substrate. A plurality of fine protrusions that are finer than the plurality of needle-like protrusions, and the plurality of fine protrusions are formed of the plurality of needle-like protrusions. Provided is a water-repellent substrate provided on the surface and the remaining substrate surface between the plurality of needle-like protrusions.

Furthermore, in order to achieve the above-described object, in the present disclosure, a heat-absorbing heat is provided that includes a heat exchange unit and absorbs heat from the air flowing outside the heat exchange unit by a heat medium flowing inside the heat exchange unit. In the exchanger, at least one of the heat medium distribution tube forming the heat exchange part and the fin connected to the tube and forming a heat transfer surface for the air is the water repellent group. A heat exchanger formed of a material is provided.

Furthermore, to achieve the above object, the present disclosure provides a method for producing a water-repellent substrate comprising a substrate and a hydrophobic film provided on the surface of the substrate, the surface of the substrate Forming a plurality of needle-like projections on the surface of the plurality of needle-like projections and the remaining surface of the base material between the plurality of needle-like projections. A method for producing a water-repellent substrate including forming the hydrophobic film by forming a plurality of fine protrusions that are finer than the above is provided.

FIG. 1 is a cross-sectional view showing a water-repellent substrate. FIG. 2 is an enlarged view of a portion indicated by an arrow II in FIG. FIG. 3A and FIG. 3B are enlarged views showing the surface of the base material (magnification 1000 times). 4 (a) and 4 (b) are enlarged views showing the surface (needle-like protrusion) of the substrate (magnification 100000 times). FIG. 5 is a perspective view showing a heat exchanger. FIG. 6 is a model diagram showing a fin cross section and a condensed water droplet diameter. FIG. 7 is a model diagram for obtaining a water drop sliding calculation formula. FIG. 8 is a model diagram for calculating the surface energy of the slidable film. FIG. 9 is a model diagram for calculating the contact angle so that the droplet diameter slides at 0.4 mm. FIG. 10 is a graph for obtaining a contact angle for preventing water droplets from closing in the fin. FIG. 11 (a) is a graph which shows the frost formation time when frost formation and defrost in the heat exchanger based on this indication are repeated, and FIG.11 (b) is frost formation and removal in the heat exchanger of a comparative example. It is a graph which shows frost formation time when frost is repeated.

Hereinafter, a plurality of embodiments of the present disclosure will be described with reference to the drawings. In each embodiment, parts corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals, and redundant description may be omitted. When only a part of the configuration is described in each mode, the other modes described above can be applied to the other parts of the configuration. Not only combinations of parts that clearly indicate that the combination is possible in each embodiment, but also a combination of the embodiments even if they are not clearly specified unless there is a problem with the combination. It is also possible.

(First embodiment)
A water-repellent substrate 100 according to the first embodiment will be described with reference to FIGS. 1 to 4B. 1 is a cross-sectional view showing a water-repellent substrate 100, FIG. 2 is an enlarged view of a portion indicated by an arrow II in FIG. 1, and FIGS. 3 (a) and 3 (b) are enlarged views showing the surface of the substrate 110. (Magnification 1000 times), FIG. 4 (a) and FIG.4 (b) are the enlarged views (magnification 100000 times) which show the surface (needle-shaped projection part 111) of the base material 110. FIG. As shown in FIG. 1, the water-repellent substrate 100 is formed by providing a hydrophobic film 120 on the surface of a substrate 110 formed from an aluminum plate material.

The substrate 110 is a plate member made of metal such as aluminum, aluminum alloy, iron, copper, or resin, and a large number of needle-like protrusions 111 extending in a needle shape are formed on the surface of the substrate 110. Yes. When the dimension between the protrusions of the needle-like protrusions 111 is defined as a period, the period of the needle-like protrusions 111 is about 700 nm to 500 μm. The period of the acicular protrusion 111 is preferably about 1 μm to 10 μm. Thus, the needle-like protrusion 111 is a protrusion on the order of microns.

The hydrophobic film 120 is formed by a plurality of fine protrusions 121. That is, the hydrophobic film 120 is formed as an aggregate of a plurality of fine protrusions 121. The fine protrusions 121 are protrusions that are formed more finely than the needle-like protrusions 111 on the surface of the needle-like protrusions 111 and the remaining surface of the substrate 110 between the needle-like protrusions 111. The period of the fine protrusions 121 is about 1 nm to 500 nm. The period of the fine protrusions 121 is preferably about 1 nm to 10 nm. Thus, the fine protrusion 121 is a nano-order protrusion.

The water repellent substrate 110 is manufactured as follows.

1. First step (previous step)
First, a 4 cm ² (2 cm square) aluminum plate material is manufactured as the base material 110. And the uneven | corrugated | grooved part 112 is formed in the surface of the base material 110 by grinding | polishing. This uneven | corrugated | grooved part 112 is made into the uneven | corrugated state equivalent to the surface in the material step of the tube and fin which comprise a heat exchanger, for example.

In actual polishing, for example, # 100 water-resistant sandpaper (Fuji Star manufactured by Sankyo Rikagaku Co., Ltd.) was used. By measuring the surface roughness of the substrate 110 after polishing using a surface roughness measuring instrument (Dektak 6M, manufactured by Digital Instruments), the period of the irregularities 112 (the dimension between the peaks) is measured. can do. It was confirmed that the obtained period (average length RSm of contour curve element: JIS B0601-2001) was 10 μm. At this time, the arithmetic average height Ra of the uneven portion 112 was 0.5 μm. 3A and 3B show surface shape observation images obtained by a scanning electron microscope (SEM) at this time. 3A and 3B are observation results at two representative positions on the surface of the substrate 110. FIG.

2. Second step (projection forming step)
In the first step, the substrate 110 on which the irregularities 112 were formed was immersed in acetone to clean the surface, and the boehmite treatment was performed by immersing in boiling pure water for 5 minutes. Next, the substrate 110 taken out was cooled, washed by blowing ultrapure water, and dried by blowing nitrogen gas. Thereby, a hydroxyl group was generated on the surface of the substrate 110. In addition, a needle-like protrusion 111 was formed on the surface of the substrate 110. An amine such as diethanolamine may be added to boiling water.

There are two purposes for the boehmite treatment of the substrate 110 as described above. One is boehmite treatment to form a hydroxyl group on the surface of the substrate 110, and in the subsequent third step, a molecule having a hydrophobic functional group dissolved in a water-saturated solution is reacted with the hydroxyl group. This is to form a strong bond between the substrate 110 and the substrate 110.

The second purpose of the boehmite treatment is to etch the surface of the base material 110 in the course of the boehmite treatment, thereby forming the needle-like protrusions 111 having a very fine needle-like structure on the surface of the concavo-convex portion 112. Images obtained by observing the substrate 110 after the boehmite treatment with a scanning electron microscope (SEM) are shown in FIGS. 4 (a) and 4 (b). 4A and 4B are observation results at two representative positions on the surface of the substrate 110. FIG. When the roughness was analyzed from the analysis result from the SEM image, the needle-like protrusion 111 was confirmed. At this time, the arithmetic average height Ra of the needle-like protrusion 111 was 20 nm.

3. Third step (film formation step)
In the film forming step, after the first and second steps, the surface of the needle-like protrusion 111 and the needle-like protrusion are formed by immersing the substrate 110 in a water saturated solution of molecules having a hydrophobic functional group. A hydrophobic coating 120 is formed by forming a plurality of fine protrusions 121 each consisting of a molecular chain having a hydrophobic functional group on the surface of the remaining substrate 110 between 111.

Specifically, the base material 110 whose surface was boehmite-treated in the second step was immersed in a 25 mM water saturated xylene solution of ODS (octadecyltrimethylsilane) at room temperature (20 ° C.) for 2 days.

4). Fourth step (post-treatment of film forming process)
The substrate 110 subjected to the film forming process in the third step was washed with acetone and then dried at 80 ° C. for 1 hour.

Through the above steps, a plurality of molecular chains (alkyl) of C ₁₈ H ₃₇ Si (O ⁻ ) ₃ having an alkyl group are formed on the surface of the needle-like protrusion 111 and the remaining surface of the base 110 between the needle-like protrusions 111. Water-repellent substrate in which a plurality of fine protrusions 121 are formed, and a hydrophobic film (water-repellent film) 120 that is a monomolecular film (alkyl monomolecular film) is formed by the plurality of molecular chains. 100 was produced. The fourth step can be omitted.

The water-repellent substrate 100 configured as described above has a structure schematically shown in FIGS. In this water-repellent substrate 100, the needle-like protrusion 111 is formed by the second step, and the fine protrusion 121, that is, the hydrophobic film 120 (ODS monomolecular film) is formed by the third step. It has become.

The water repellent substrate 100 thus formed has high water repellency (contact angle = 160 °), and when condensed water is generated on the water repellent substrate 100 arranged at 3 °, the water droplet diameter is 1 mm. When it became, it slipped down.

In this embodiment, under the condition that condensed water is generated on the surface of the substrate 110, the condensed water grows in combination with each other even if condensed water is generated from the bottom surface between the needle-like protrusions 111. Since the fine projections 121 are pushed from the bottom side between the needle-like projections 111 toward the tip side by the fine projections 121, the needle-like projections 111 do not stagnate. Therefore, the condensed water accumulates in the concave portions as in the prior art, and the condensed water in the concave portions is connected to each other outside the concave portions to form a large water film, so that the water is repelled as water droplets of condensed water. You can slide down.

In addition, the water-repellent substrate 100 of the present embodiment exhibits high sliding performance as described above even under conditions where frost can be generated on the surface at low temperatures. It was possible to delay the time of occurrence.

(Second Embodiment)
In the second embodiment, the water-repellent substrate 100 was created by changing the film-forming material in the third step with respect to the first embodiment.

That is, first, the substrate 110 that has undergone the same steps as those of the first embodiment was prepared until the first step and the second step. Then, as a third step (film forming step), a substrate 110 whose surface was boehmite-treated in a FAS17 (perfluorodecyloxysilane) 25 mM water-saturated 1,3-bis (trifluoromethyl) benzene (F6xy) solution in the second step. Was immersed at room temperature (20 ° C.) for 2 days.

After the third step, the same process as in the fourth step of the first embodiment was performed. Through the above steps, a plurality of C ₈ F ₁₇ C ₂ H ₄ Si (O ⁻ ) ₃ having a fluoroalkyl group is formed on the surface of the needle-like protrusion 111 and the remaining surface of the base 110 between the needle-like protrusions 111. The molecular chain (fluoroalkyl chain), that is, a plurality of fine protrusions 121 are formed, and the hydrophobic film 120 that is a monomolecular film (fluoroalkyl monomolecular film) is formed by the plurality of molecular chains. A substrate 100 was produced. Note that the fourth step can be omitted.

The water-repellent substrate 100 prepared in this way showed the same water repellency as the water-repellent substrate 100 prepared in the first embodiment.

(Third embodiment)
In the third embodiment, the water-repellent substrate 100 was created by changing the film-forming material in the third step with respect to the first and second embodiments.

That is, first, the substrate 110 that has undergone the same steps as those of the first and second embodiments was prepared until the first step and the second step. Then, as a third step (film formation step), a surface of the reaction vessel is sealed in the second step in a sealed and pressurizable container having a capacity of 20 ml in which 0.5 g of C ₈ F ₁₇ C ₂ H ₄ NCO (perfluorodeoxycynate) is enclosed. Boehmite-treated substrate 110 was inserted and sealed, and a gas phase reaction was performed at 150 ° C. for 72 hours.

After the third step, the same process as in the fourth step of the first and second embodiments was performed. Through the above-described steps, a plurality of molecular chains of C ₈ F ₁₇ C ₂ H ₄ NHCOO ⁻ having a fluoroalkyl group are formed on the surface of the needle-like protrusion 111 and the remaining surface of the base material 110 between the needle-like protrusions 111 ( A water-repellent substrate 100 in which a plurality of fine protrusions 121 are formed, and a hydrophobic film 120 that is a monomolecular film (fluoroalkyl monomolecular film) is formed by the plurality of molecular chains. Produced. Note that the fourth step can be omitted.

The water-repellent substrate 100 prepared in this way showed the same water repellency as the water-repellent substrate 100 prepared in the first and second embodiments.

(Fourth embodiment)
In the fourth embodiment, the water-repellent substrate 100 is created by changing the film forming material in the third step as compared with the first to third embodiments.

That is, first, the base material 110 that has undergone the same processes as those of the first to third embodiments until the first process and the second process was prepared. Then, as a third step (film forming step), a surface-boehmite-treated base in the second step is placed in a 100-ml sealed and pressurizable reaction vessel in which 1.4 g of C ₁₈ H ₃₇ NCO (octadecylicocynate) is enclosed. The material 110 was inserted and sealed, and gas phase reaction was performed at 150 ° C. for 72 hours.

After the third step, the same processing as in the fourth step of the first to third embodiments was performed. Through the above steps, a plurality of molecular chains (alkyl chains) of C ₁₈ H ₃₇ NHCOO ^— having an alkyl group are formed on the surface of the needle-like protrusions 111 and the surface of the remaining base 110 between the needle-like protrusions 111, that is, A water-repellent substrate 100 in which a plurality of fine protrusions 121 were formed and a hydrophobic film 120 as a monomolecular film (alkyl monomolecular film) was formed by the plurality of molecular chains was produced.

The water-repellent substrate 100 prepared in this way showed the same water repellency as the water-repellent substrate 100 prepared in the first to third embodiments.

(Fifth embodiment)
In the fifth embodiment, the water-repellent substrate 100 described in the first to fourth embodiments is applied to a heat exchanger 200.

The heat exchanger 200 is an endothermic heat exchanger, and is an evaporator that cools air for air conditioning in a refrigeration cycle of a vehicle air conditioner, for example, as shown in FIG. The heat exchanger 200 includes a heat exchange unit 210 and a pair of header tanks 220 connected to the heat exchange unit 210. The heat exchanging unit 210 includes a plurality of laminated tubes 211 having a flat cross section, and corrugated fins 212 interposed between the tubes 211. The tubes 211 are tube members through which a refrigerant as a heat medium flows, and both ends of each tube 211 are connected to communicate with the inside of the pair of header tanks 220. Further, the fin 212 is a heat transfer member that is formed in a wave shape from a thin strip material and forms a heat transfer surface, and is joined (connected) to the tube 211. As shown in FIG. 6, a plurality of armor-door louvers 212 a are formed on the heat transfer surfaces of the fins 212. In the heat exchanger 200 of the fifth embodiment, the tubes 211 and the fins 212 are formed by the water-repellent substrate 100 described in any one of the first to fourth embodiments.

In the heat exchanger 200, the refrigerant that has been depressurized in the refrigeration cycle to low temperature and low pressure flows through the plurality of tubes 211, and around the outside of the tubes 211 and around the fins 212 (outside of the heat exchanging unit 210). The air for air conditioning passes through the air and the air for air conditioning is cooled by the refrigerant. When the air-conditioning air is cooled, if the temperature of the air-conditioning air falls below the dew point temperature of the water vapor contained in the air, the water vapor becomes condensed water on the surface of the heat exchange unit 210 (tube 211, fin 212). Adhere to. When this condensed water adheres, the ventilation resistance of the conditioned air passing through the heat exchange unit 210 increases and the thermal resistance due to the condensed water increases, so that the heat exchange performance in the heat exchanger 200 decreases. Furthermore, the condensed water freezes when it becomes below the freezing temperature, and adheres to the surface of the heat exchange unit 210 as frost. Therefore, in the heat exchanger 200 for absorbing heat, first, even if condensed water is generated during operation, it is necessary to quickly slide down the generated condensed water by a water repellent action. Hereinafter, the conditions for promptly sliding down the generated condensed water will be examined.

First, as shown in FIG. 6, in the fin 212, the distance between the heat transfer surfaces is usually set to about 1.5 mm, and the pitch of the louvers 212a is set to about 0.8 mm. Therefore, even when condensed water is generated, the condensed water droplet diameter is 0.4 mm or less so that the condensed water does not form curtains (water clogging) due to surface tension between the louvers 212a having a narrow gap. It is necessary to suppress it so that it becomes.

Here, the following mathematical formula 1 is known as a water drop sliding formula. That is,
2πrE = mg · sin α (Formula 1)
In Equation 1, as shown in FIG. 7, 2πrE represents adhesion force, mg · sin α represents gravity along the sliding direction, r represents condensed water droplet radius (m), and E represents surface energy of the sliding film ( J / m ² ), m is the mass of the water drop (kg), g is the acceleration of gravity (m / s ² ), α is the tilt angle (degree), and θ in FIG. 7 is the contact angle (degree). The condensed water droplet radius r can be expressed as a function of the contact angle θ, and the condensed water droplet radius r = (water droplet diameter d / 2) · cos (θ−90).

Next, the surface energy E is obtained based on the formula 1 and the experimental result. For example, as described in the first embodiment, when the water droplet diameter d is 1 mm, the inclination angle α is 3 degrees, the contact angle θ is 160 degrees, and no wind conditions are used as the experimental conditions, the water droplets slide down. This is confirmed (FIG. 8). Therefore, the surface energy E when the water droplet actually slides is obtained by substituting the above conditions into Equation 1. From Equation 1,
2 ・ π ・ 0.5 ・ cos (160-90) ・ E
^{= 4/3 · π · 0.5} 3 · 9.8 · sin (3)
Thus, E = 2.5 × 10 ⁻⁴ (J / m ² ) was obtained.

Next, when the water droplet diameter d is 0.4 mm that can surely pass through the gap (0.8 mm) of the louver 212a, the slidable contact angle θ is calculated from Equation 2. That is,
2πrE = 1/2 · ρ · V ² · A · C _D (Formula 2)
In Equation 2, as shown in FIG. 9, 2πrE represents adhesion, 1/2 · ρ · V ² · A · C _D represents drag, r represents condensed water droplet radius (m), and E represents sliding force. The surface energy (J / m ² ) of the water film, ρ is the air density (kg / m 3), V is the relative velocity (m / s), A is the projected cross section (m ² ), and _CD is the drag coefficient.

The air density is expressed by the following equation, where the condensed water droplet radius r = (water droplet diameter d / 2) · cos (θ−90) and the surface energy E when sliding down is 2.5 × 10 ⁻⁴ (J / m ² ). By substituting ρ = 1000 (kg / m3), relative velocity V = 1 m / s, projected cross-sectional area A = π · 0.2 ² , drag coefficient CD = approximate value, FIG. 10 was obtained by obtaining.

In order for the condensed water not to be blocked between the louvers 212a, it is necessary that the drag of FIG. 10 is in the range of the contact angle θ that exceeds the adhesive force, and the contact angle θ is found to be 148 degrees or more. .

The water repellent substrate 100 of the first to fourth embodiments is obtained at a contact angle of 160 degrees. In the heat exchanger 200 using the water repellent substrate 100, the tube 211 and the fin 212 are used. Condensed water could be satisfactorily slid down and removed without any special operation from the surface. Moreover, since the good sliding down of the condensed water was obtained, it was possible to delay the time for generating frost to a predetermined amount on the surface of the heat exchange unit 210.

Fig.11 (a) is a graph which shows frost formation time when frost formation and defrosting are repeated in the heat exchanger 200 based on this indication. FIG.11 (b) is a graph which shows the frost formation time when frost formation and defrosting are repeated in the heat exchanger of a comparative example. The heat exchanger of the comparative example includes a conventional hydrophilic film and does not include the hydrophobic film in the present embodiment. Experimental conditions are
・ During frosting operation,
As air-side conditions, dry bulb temperature = 2 ± 0.3 ° C., wet bulb temperature = 1 ± 0.3 ° C.,
Front wind speed = 0.8 ± 0.01m / s,
As refrigerant side conditions, refrigerant inlet temperature = −7.4 ± 0.6 ° C., refrigerant flow rate = 10 ± 0.5 L / MIN,
・ During defrosting operation,
As the air side condition, front wind speed = 0m / s,
As refrigerant side conditions, refrigerant inlet temperature = 13 ± 2 ° C., refrigerant flow rate = 2 ± 0.5 L / MIN,
・ Test cycle It ends when the ventilation resistance of the heat exchanger rises to 100 Pa under frosting conditions, and the defrosting operation is 6 minutes.
The following was repeated.

In the present disclosure, since the sliding down of the condensed water can be promoted with respect to the comparative example, the condensed water is less likely to stagnate in the heat exchanging unit 210, so that the frosting occurs and the ventilation resistance of the heat exchanging unit 210 is a predetermined value (here, The time to 100 Pa) can be greatly reduced.

(Other embodiments)
The embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the above-described embodiments, and it is needless to say that various forms can be employed as long as they belong to the technical scope of the present disclosure.

For example, in the above embodiments, the hydrophobic coating _{_{_{120, ODS, FAS17, C 8}}} F 17 C 2 H 4 NCO, has formed the monomolecular film by using a _{C 18} H 37 NCO, etc., other than these materials A monomolecular film may be formed. For example, any structure having a hydrophobic group such as fluorine on one side and a functional group that easily binds to a hydroxyl group such as O—Si—O on the other side is applicable. In addition, when the molecule | numerator which has hydrophobic functional groups like an alkyl group and a fluoroalkyl group is contained as a molecule | numerator which comprises the hydrophobic membrane | film | coat 120, high hydrophobicity can be expressed.

Further, the method for creating the needle-like protrusion 111 is not limited to the method of each of the above-described embodiments, and besides this, a nanoimprint method or the like can be used.

Moreover, although the structure which uses an aluminum plate material was illustrated as the base material 110 in each said embodiment, various metals, such as a copper plate and an iron plate, can be used besides an aluminum plate material. Moreover, the base material 110 is not limited to a metal, For example, you may form with resin.

Claims

A substrate (110);
A water-repellent substrate comprising a hydrophobic coating (120) provided on the surface of the substrate (110),
A plurality of needle-like protrusions (111) are formed on the surface of the base material (110),
The hydrophobic coating (120) is composed of a plurality of fine projections (121) finer than the plurality of needle-like projections (111), and the plurality of fine projections (121) are the plurality of needle-like projections. A water-repellent substrate provided on the surface of the projection (111) and the remaining surface of the substrate (110) between the plurality of needle-like projections (111).
The plurality of fine protrusions (121) are a plurality of molecular chains forming a monomolecular film as the hydrophobic coating (120), and each molecular chain has at least one hydrophobic functional group. Item 2. A water-repellent substrate according to Item 1.
The water-repellent substrate according to claim 2, comprising at least one of an alkyl group and a fluoroalkyl group as the at least one hydrophobic functional group.
The water repellent substrate according to claim 2 or 3, wherein the substrate (110) is made of one of a metal and a metal oxide.
A heat exchanger for heat absorption that includes a heat exchange section (210) and absorbs heat from air flowing outside the heat exchange section (210) by a heat medium flowing inside the heat exchange section (210). ,
At least one of the heat medium distribution tube (211) forming the heat exchange part (210) and the fin (212) connected to the tube (211) and forming a heat transfer surface for the air. A heat exchanger formed by the water-repellent substrate (100) according to any one of claims 1 to 4.
A method for producing a water-repellent substrate (100) comprising a substrate (110) and a hydrophobic coating (120) provided on the surface of the substrate (110),
Forming a plurality of needle-like protrusions (111) on the surface of the substrate (110);
The surface of the plurality of needle-like projections (111) and the remaining surface of the base material (110) between the plurality of needle-like projections (111) than the plurality of needle-like projections (111) A method for producing a water-repellent substrate, comprising forming the hydrophobic coating (120) by forming a plurality of fine projections (121).
Before forming the plurality of needle-like projections (111), the substrate (110) further includes forming one of aluminum and an aluminum alloy, and the plurality of needle-like projections (111) Forming the plurality of needle-like protrusions (111) by performing a boehmite treatment on the base material (110).
The formation of the plurality of fine protrusions (121) means that the base material (110) on which the plurality of needle-like protrusions (111) are formed is a molecular water having at least one hydrophobic functional group. The manufacturing method according to claim 7, comprising forming the plurality of fine protrusions (121) on the substrate (110) by immersing in a saturated solution.