JPH1161490A - Solar heat absorption plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar absorption plate which contributes to the reduction of the cost and weight of a solar collector and is capable of effectively utilizing the sunlight without allowing the internally accumulated heat to escape outside. SOLUTION: An anodically oxidized film 3 having fine ruggedness is formed on the surface of Al or Al alloy 2 and further the surface of this anodically oxidized film 3 is provided with a transparent org. resin 4. The thickness of the anodically oxidized film 3 is 0.5 to 45 μm and more particularly the transparent org. resin 4 is an acrylic resin. The Al alloy 2 contains 0.3 to 4.3 wt.% Mn and the balance Al with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solar heat absorbing plate used for a solar collector such as a solar water heater.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of energy saving, active use of sunlight has become active. The most familiar example of the use of sunlight is a solar water heater equipped with a solar collector. The solar collector has a function of efficiently conducting solar heat to water and increasing the water temperature, and is the most important element of the solar water heater. In general, a solar collector includes an insulating material, a copper pipe for distributing water disposed on the insulating material, a solar heat absorbing plate placed on top of the copper pipe, and a fixed And tempered glass provided with a space therebetween.

[0003] The sunlight incident on the solar collector is
The solar heat absorbing plate is irradiated through the tempered glass. The temperature of the solar heat absorbing plate itself increases due to the intensity of the irradiated sunlight. At this time, the heat absorbed by the solar heat absorbing plate is transmitted to the water flowing through the copper tube, and the water temperature rises. In this way, it is possible to raise the water temperature to about 65 ° C. when the weather is fine in summer and to about 40 ° C. even when it is fine in winter.

A solar heat absorbing plate used in a solar collector is particularly one that easily absorbs short-wavelength sunlight (visible light) (has a large absorption coefficient) and that easily suppresses blackbody radiation (far-infrared radiation). Efficiency is small). Such characteristics are required in order to satisfy the function of a solar heat absorbing plate that quickly conducts heat absorbed by sunlight irradiation to water without escaping to the outside as much as possible. Therefore, as a conventional solar heat absorbing plate, a metal plate having a selective absorption film such as black chromium, black nickel, copper oxide, iron oxide or the like formed on the surface has been used. Such a selective absorption film has a visible light absorption coefficient of 0.8 to 0.96 and a far-infrared radiation efficiency of about 0.1, and sufficiently satisfies the above-described characteristics.

[0005]

However, in the conventional solar heat absorbing plate, the temperature of the solar heat absorbing plate fluctuates depending on weather conditions such as sunshine duration, sunshine state, and ventilation state, and the water temperature cannot be stably maintained. There was a problem that. Since the temperature fluctuation of the solar absorption plate is particularly affected by the ventilation, the actual solar collector is equipped with tempered glass to prevent the intrusion of wind, so it is not possible to reduce the cost and weight of the solar collector There were also issues.

Further, the conventional solar heat absorbing plate has low far-infrared radiation efficiency, which means that the efficiency of conversion between far-infrared rays and heat is low. Therefore, in the conventional solar heat absorbing plate, far-infrared rays in a wavelength range of several to several tens of μm contained in sunlight are not used, and mainly only light in a wavelength range of 0.1 to several μm is used. There was a problem that it was not possible to make effective use of.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has been made to reduce the cost and weight of a solar collector and to effectively release sunlight without dissipating heat accumulated inside to the outside. It is an object to provide a solar heat absorbing plate that can be used.

[0008]

The present invention has the following features to attain the object mentioned above. The solar heat absorbing plate according to claim 1, wherein an anodic oxide film having fine irregularities is formed on a surface of Al or an Al alloy, and further, a transparent organic resin is provided on a surface of the anodic oxide film; The oxide film has a thickness of 0.5 to 45 μm.

A solar heat absorbing plate according to a second aspect is the solar heat absorbing plate according to the first aspect, wherein the transparent organic resin is an acrylic resin. The solar heat absorbing plate according to claim 3 is the solar heat absorbing plate according to claim 1 or 2, wherein the Al alloy has Mn of 0.3 to 0.3.
It is characterized by containing 4.3% by weight, with the balance being Al and unavoidable impurities.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solar heat absorbing plate of the present invention will be described in detail. In FIG. 1, the solar heat absorbing plate 1
Is an Al-Si based or Al-Mn containing Mn
Alloy 2 which is described later and has Si particles or A
The one in which the l-Mn intermetallic compound is dispersed and deposited and the anodic oxide film 3 having fine irregularities on the surface is formed is used. For example, the anodic oxide film 3 having fine irregularities formed on the surface of a plate material made of these materials has a surface roughness of a predetermined range by a mechanical roughening method such as blasting or liquid honing. It is obtained by subjecting this plate material to anodizing treatment after roughening.

The solar heat absorbing plate 1 on which the anodic oxide film 3 having such fine irregularities is formed is considered to be practically effective even when ordinary Al such as pure Al is used as a base material. In this case, the total radiation characteristics of far infrared rays in the wavelength region of 3 to 30 μm can be as high as 70% or more. The fact that the far-infrared radiation characteristics are excellent means that a large amount of far-infrared radiation is emitted from a heated object,
In other words, it means that the conversion efficiency between far infrared rays and heat is high, and it is possible to more efficiently absorb far infrared rays contained in sunlight.

Al or Al having anodized oxide film 3 formed thereon
It is not clear why Alloy 2 has such excellent properties. However, the surface has fine irregularities, so that the apparent surface area increases, and the film growth becomes uneven due to surface roughening. It is conceivable that complicated irregularities and complicatedly branched pores are formed, and the scattering and absorptivity of incident sunlight increases. Anodized film 3
Since Si particles and Al-Mn intermetallic compound particles are present in a dispersed state, the scattered absorption of incident sunlight is further increased by their presence, and far infrared rays can be absorbed more efficiently. .

Further, the solar heat absorbing plate 1 of the present invention is provided with a transparent organic resin 4 on the anodic oxide film 3. As a specific example of the transparent organic resin 4, an acrylic resin is preferable, and a polymethyl methacrylate resin (hereinafter abbreviated as PMMA) is more preferable. Since PMMA has high light transmittance in a wide wavelength range and excellent transparency, it is possible to transmit light in most wavelength regions of sunlight.
Further, the solar heat absorbing plate 1 is irradiated with the far infrared rays of sunlight.
The release of heat accumulated in the battery can be prevented. That is, Al or Al alloy 2 having the anodic oxide film 3 formed on the surface is
Because of the high radiation characteristics of far-infrared rays, it has the property that heat accumulated inside is easily released to the outside by radiation of far-infrared rays. By providing an acrylic resin such as PMMA on such an anodic oxide film 3, the release of heat can be prevented. Therefore, as long as the material has high light transmittance and excellent transparency, it is not limited to PMMA, and polycarbonate, C
Organic resins such as R-39 (diethylene glycol bisallyl carbonate), polystyrene, MS resin, AS resin, and TPX (poly 4-methylpentene-1) can also be used. The thickness of the transparent organic resin 4 is 10 μm or more and 1
0 mm or less, preferably 10 μm or more and 5 mm
The following is more preferred. The thickness of the transparent organic resin 4 is 10 μm
If it is less than the above, it is impossible to prevent the heat accumulated in the solar heat absorbing plate from being released to the outside. On the other hand, if the thickness of the transparent organic resin 4 is 10 mm or more, the optical path length of the transparent organic resin 4 becomes long, and a part of sunlight may be absorbed by the organic resin 4, which is not preferable.

The transparent organic resin 4 may be one obtained by mounting the plate material on the anodic oxide film 3. Further, the film-shaped transparent organic resin 4 may be laminated on the anodic oxide film 3 by a hot press, a heating roller, or the like, or may be adhered to the anodic oxide film 3 by baking or the like. In this case, since the surface after the anodizing treatment is rough, excellent adhesion can be obtained. A selective absorption film is formed by such an anodic oxide film 3 and the transparent organic resin 4.

A when forming the anodic oxide film 3
Examples of a method for roughening the surface of the l or Al alloy 2 include a blast treatment or a liquid honing treatment using a powder having a grinding action such as alumina, silicon carbide, silica sand, or the like, or Such as a method in which a grinding wheel in which corundum-containing nylon fiber or a piano wire having a diameter of about 0.1 to 1.0 mm is implanted is rotated at a high speed, or a method in which the grinding wheel is cut with emery paper (cloth). The surface may be roughened by a chemical method such as electrolytic etching or the like, but in the case of the present invention, the surface is formed to have an average roughness of 0.5 by using a mechanical method. By adjusting the average roughness to a range of from 5.0 μm to a maximum roughness of 5 to 50 μm, more excellent characteristics can be obtained.

The reason why this mechanical method is excellent is not clear, but in the mechanical surface roughening method, a large force is locally applied, so that the plastic structure of the aluminum base metal or the metal structure is not formed due to work hardening. It is presumed that homogenization occurred and the irregular shape was complicated due to the scraping of the metal, and further anodization was performed in this state. A complex pore structure that is branched from very uneven unevenness due to differences in the quality and growth rate of the oxide film 3 and the growth of the anodic oxide film 3 in random directions due to complicated uneven shapes. It is considered that the anodic oxide film 3 having the following is formed, whereby the scattered absorption rate of incident sunlight increases, and far infrared rays are more easily absorbed.

The thickness of the anodic oxide film 3 formed by the anodic oxidation treatment is preferably in the range of 0.5 to 45 μm. If the thickness is less than this, sufficient far-infrared emissivity can be obtained. Absent. As the anodizing method,
Many types of commonly used methods can be used. As an electrolytic bath, not only an acidic bath,
Alkaline baths or non-aqueous baths such as formamide and boric acid baths can also be used.

For example, acidic electrifying baths include sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfosalicylic acid, pyrophosphoric acid, sulfamic acid, phosphomolybdic acid, boric acid, malonic acid, succinic acid, maleic acid, citric acid, An aqueous solution in which one or more kinds of tartaric acid, phthalic acid, itaconic acid, malic acid, glycolic acid and the like are dissolved can be used.
In addition, as the alkaline electric field bath, an aqueous solution in which one or more kinds of caustic soda, caustic potash, sodium carbonate, potassium phosphate, aqueous ammonia, and the like are dissolved can be used.

As the current waveform at the time of electrolysis, DC, AC, AC / DC superimposition, AC / DC combined use, incomplete rectified waveform, pulse waveform, rectangular wave, and the like are used. As an electrolysis method, a constant current, a constant voltage, a constant power method, a high-speed alumite method using continuous, intermittent, or current recovery can be used. In the above, a heterogeneous anodic oxide film 3 is generated using a pulse waveform or an incomplete rectified waveform, or a multi-layer anodic oxide film 3 is formed by intermittent electrolysis or a current recovery method.
Higher far-infrared emissivity can also be achieved.

The post-treatment after forming the film by the anodic oxidation treatment includes boiling water immersion,
The sealing treatment may be performed by an ordinary method such as a hot water immersion method containing a metal salt. Also, the anodic oxide film 3 is formed by an electrolytic coloring method.
After depositing metals such as Ni, Cu, Co, Sn, Pb, and Cd in the micropores, the deposited metals are oxidized in an oxidizing atmosphere, or an acid is mixed with an aqueous silicate solution or zirconium salt bath. Alternatively, the silicate or zirconium hydroxide may be deposited in the fine pores by alternately immersing the fine pores and alkalis. By including a metal oxide having excellent far-infrared radiation characteristics in the fine pores of the anodic oxide film 3 by these methods, the solar heat absorbing plate 1 having excellent far-infrared radiation characteristics can be obtained.

Next, the Al—Mn alloy used for the solar heat absorbing plate 1 will be described. Al- containing an appropriate amount of Mn
In a Mn-based alloy, an Al-Mn-based intermetallic compound is generated, and if the precipitation state of the Al-Mn-based intermetallic compound is appropriate, it contributes to far-infrared radiation characteristics. As the Al-Mn intermetallic compound, Al ₆ Mn, Al ₆ (MnF
e), αAlMn (Fe) Si and their Cr,
There is a case where a small amount of Ti or the like is dissolved in a solid solution. However, when the surface of an aluminum alloy on which such an Al-Mn intermetallic compound is dispersed and precipitated is subjected to anodizing treatment,
The particles of the -Mn intermetallic compound are contained in the anodic oxide film 3 in a dispersed state.

The incident light is easily scattered and absorbed by the intermetallic compound particles dispersed in the anodic oxide film 3, and the radiation characteristics of far infrared rays are improved. Further, since the visible light absorption coefficient is high, the visual color tone is also black. Further, in the process of growing the anodic oxide film 3 during the anodic oxidation treatment, the pores have a branched structure, and such a branched pore structure promotes the scattering and absorption of the incident light in the anodic oxide film 3, thereby increasing the distance. The infrared radiation characteristics are further improved.

Here, when the diameter of the Al—Mn intermetallic compound precipitate is less than 0.01 μm, the Al—Mn
The effect due to the dispersion of the intermetallic compound precipitate cannot be obtained. On the other hand, since the coarse Al-Mn intermetallic compound precipitate exceeding 3 μm deteriorates the formability, the particle size is 0.01 to 3 μm.
m are preferably dispersed. The Al-Mn intermetallic compound precipitates having a particle size of 0.01 to ³ µm are preferably dispersed at a density of 1 x 10 ⁵ particles / mm ³ or more.

Next, the reasons for limiting the component composition in the Al-Mn alloy as described above will be described. Mn: Mn forms an Al-Mn intermetallic compound precipitate and contributes to the improvement of far-infrared radiation characteristics as described above.
Here, if the Mn content is less than 0.3% by weight, good far-infrared radiation characteristics cannot be obtained. On the other hand, when the content exceeds 4.3% by weight, continuous casting from an alloy to a thin plate or the like becomes difficult, which is not practical. That is, in order to obtain the precipitation state of the Al-Mn-based intermetallic compound precipitate as described above, the cooling rate at the time of casting is set to 5 ° C / sec or more, and Mn is sufficiently dissolved to form a solid solution. It is preferable to perform a heat treatment for precipitation of intermetallic compounds, but in order to cast at a cooling rate of 5 ° C./sec or more, it is practically most suitable to apply a continuous thin plate casting method (continuous casting and rolling). However, Mn
If the amount exceeds 4.3% by weight, continuous casting of a thin plate becomes difficult. Therefore, the Mn content is preferably in the range of 0.3 to 4.3% by weight. Mg: Mg is not always an essential element, but Al-M
It promotes the precipitation of the n-type intermetallic compound precipitate and contributes to achieving the above-mentioned precipitation state. Particularly in a range where the amount of Mn is relatively small, it is possible to increase the amount of added Mg.
This is effective for promoting the precipitation of Al-Mn-based intermetallic compound precipitates and improving the far-infrared radiation characteristics. However, if the amount of Mg exceeds 6.0% by weight, continuous casting of a thin plate becomes difficult and is not practical. On the other hand, the Mn content is 0.05% by weight.
If the amount is less than the above range, the above-described effect due to the addition of Mg cannot be obtained. Therefore, the addition amount of Mg is preferably in the range of 0.05 to 6.0% by weight. Fe: Fe has some influence on the precipitation of Al—Mn intermetallic compound precipitates, but has essentially no effect on far-infrared radiation characteristics. From the viewpoint of castability, the Fe content is preferably as small as possible. If it exceeds 0.5% by weight, continuous casting may be difficult. Si: Si has some influence on the precipitation of Al-Mn intermetallic compound precipitates, but has essentially no effect on far-infrared radiation characteristics. From the viewpoint of castability, the amount of Si is preferably small, and if it exceeds 2.0% by weight, continuous casting may be difficult.

Further, in a normal Al alloy, a small amount of Ti may be added alone or in combination with a small amount of B in order to refine the crystal grains of the ingot.
In the case of n-type alloys, Ti is added in the range of 0.003 to 0.15% by weight.
May be added alone or in combination with 1 to 100 ppm of B. That is, Ti has the effect of minimizing the crystal grains of the ingot to prevent streaks and texture of the rolled sheet. However, if Ti is less than 0.003% by weight, the effect cannot be obtained, and Ti is 0.15% by weight. %, TiAl ₃ -based coarse intermetallic compounds are generated. B is an element that coexists with Ti and promotes crystal grain refinement.
If less than 100 ppm, the effect cannot be obtained.
Is exceeded, the effect is saturated, and coarse TiB ₂ particles are generated to cause linear defects. In addition, in an aluminum alloy containing Mg, a small amount of Be has been conventionally added in order to prevent oxidation of the molten metal. However, adding 500 ppm or less of Be particularly hinders. There is no.

In an Al—Mn alloy, Ni, Z
r, V, Cu, Zn, and the like may be included. Of these, Ni, Zr, and V do not essentially affect far-infrared radiation characteristics, but when Ni is 1.0% by weight or more, Zr is 0.3% by weight or more, and V is 0.3% by weight or more, a thin plate is obtained. Since continuous casting becomes difficult, Ni is less than 1.0% by weight and Zr is less than 0.3% by weight.
It is desirable to control the V to less than 0.3% by weight. Further, although Cu and Zn slightly change the color tone of the anodic oxide film 3, they do not essentially affect the far-infrared radiation characteristics. Above, it becomes difficult to cast thin sheet continuously,
It is preferable that Cu be less than 1.0% by weight and Zn be less than 2.0% by weight.

Next, the process conditions for producing a rolled plate made of the above Al-Mn alloy will be described. As described above, in order to achieve the far-infrared radiation characteristics obtained by obtaining an appropriate precipitation state of the Al-Mn intermetallic compound, the casting speed and the heat treatment for the precipitation are important. As for casting, by increasing the casting speed and sufficiently dissolving Mn, it is possible to precipitate the Al-Mn intermetallic compound in an appropriate precipitation state in the subsequent precipitation treatment. C./sec or higher casting rates are preferred. In order to obtain a cooling rate of 5 ° C./sec or more, especially in the case of manufacturing a large plate, a thin plate continuous casting method (continuous casting and rolling method) which can easily obtain a thin plate having a thickness of about 5 to 10 mm is applied. Is preferred.

On the other hand, heating for precipitation is preferably performed at a temperature of 300 ° C. or more and 600 ° C. or less for 0.5 hour or more. If the temperature is lower than 300 ° C., the precipitate is too small to obtain excellent far-infrared radiation characteristics, while if it exceeds 600 ° C., the color tone after the anodic oxidation treatment deteriorates and the crystal grains become coarse. Also, the time is kept from the heating process,
The time during which the temperature is 300 ° C. or higher throughout the cooling process is set to 0.
If it is 5 hours or more, and if the time at which the temperature is 300 ° C. or more is less than 0.5 hour, good far-infrared characteristics cannot be obtained after the anodizing treatment.

The heating for the precipitation may be performed on the ingot as it is, during the rolling, or after the rolling. Therefore, this precipitation treatment is a homogenization treatment for the ingot, or a heat treatment for hot rolling, furthermore, an intermediate annealing performed as necessary after hot rolling or in the middle of cold rolling, and further cold rolling. This can be performed together with final annealing performed as needed later. Further, the heating and annealing for hot rolling and pressure welding may be performed together. In addition, hot rolling, cold rolling, and, if necessary, intermediate annealing or final annealing may be performed according to a conventional method.

Next, the reasons for limiting the component composition in the Al-Si alloy will be described. Si: Si is crystallized as primary crystal eutectic and eutectic Si according to the added amount during casting, and the shape of the crystallized Si changes due to heat treatment and composition processing performed as necessary. Further, when heat treatment is performed as necessary, the metal S
i precipitates. These primary crystal Si, eutectic Si, precipitated Si
Is taken into the anodic oxide film 3 as metal Si particles during the anodic oxidation treatment as described above,
Contributes to the improvement of far-infrared radiation characteristics through absorption. Further, the metal Si particles contribute to the formation of a branched structure in the pores in the anodic oxide film 3 as described above, which also contributes to the improvement of far-infrared radiation characteristics. If the amount of Si in the base aluminum alloy is less than 3% by weight, the number of metal Si particles is small, and the far-infrared emissivity is small. On the other hand, when the amount of Si is 15
If the content is more than 10% by weight, the volume ratio of the metal Si particles in the anodic oxide film 3 is too large, and the strength and corrosion resistance of the anodic oxide film 3 are reduced, and the rolling property is also reduced. Therefore, the amount of Si is preferably in the range of 3 to 15% by weight.

The Al-Si alloy may be basically Al and inevitable impurities other than the above-mentioned Si. In addition to Si, in addition to Si, Fe, Mg, C
One, two or more of u, Mn, Ni, Cr, V, Zn, and Zr may be contained. The amounts of these additives are as follows.

Fe: Fe is effective for improving strength and refining crystal grains. If the Fe content is less than 0.05% by weight, the effect cannot be obtained, and if it exceeds 2.0% by weight, the strength and corrosion resistance of the anodic oxide film 3 decrease. Also, the amount of Fe is
If it exceeds 2.0% by weight, Si is combined with Fe and Al-
The amount of the Fe-Si based intermetallic compound increases, and the far-infrared radiation characteristic decreases. Therefore, when Fe is added, the amount of Fe is preferably in the range of 0.05 to 2.0% by weight. Mg: Mg also contributes to strength improvement. If the amount of Mg is less than 0.05% by weight, the effect cannot be obtained.
If the ratio exceeds the range, Mg and Si are combined to increase the amount of Mg ₂ Si generated, and the far-infrared radiation characteristics deteriorate. If the amount of Mg exceeds 2.0% by weight, castability and plastic workability also decrease. Therefore, when adding Mg, the amount of Mg is 0.05 to
It is preferably in the range of 2.0% by weight. Cu: The addition of Cu also contributes to the improvement in strength. Cu content is 0.
If the content is less than 05% by weight, the effect cannot be obtained.
If the ratio exceeds the above range, castability, plastic workability, and corrosion resistance decrease. Therefore, the amount of Cu when Cu is added is preferably in the range of 0.05 to 6.0% by weight.

Mn: Mn contributes to the improvement of strength, the refinement of crystal grains, and the improvement of heat resistance. If the amount of Mn is less than 0.05% by weight, these effects cannot be obtained, while if it exceeds 2.0% by weight, Mn bonds to Si and Al
The amount of -Mn-Si-based intermetallic compounds generated is increased, and the far-infrared radiation characteristics are improved. If the amount of Mn exceeds 2.0% by weight, casting becomes difficult. Therefore, when Mn is added, the Mn content is preferably in the range of 0.05 to 2.0% by weight. Ni: Ni also contributes to improvement in strength and also to improvement in heat resistance. If the Ni content is less than 0.05% by weight, these effects cannot be obtained, while if it exceeds 3.0% by weight, casting becomes difficult. Therefore, the amount of Ni when Ni is added is 0.1.
The range of from 0.05 to 3.0% by weight is preferred. Cr, Zr, V: These elements contribute to the improvement of strength and also to the refinement of crystal grains. 0.05 for all
If the amount is less than 0.5% by weight, the effect cannot be obtained.
If the ratio exceeds the above range, a coarse intermetallic compound is generated, and the strength is rather reduced. Therefore, one or two of Cr, Zr, and V
When adding more than one kind, the addition amount is preferably in the range of 0.05 to 0.5% by weight in a single amount. In addition, when rolling, extrusion, or casting of a slab, a billet, or the like is applied, if the single addition amount of these elements exceeds 0.3% by weight, plastic workability is reduced and casting becomes difficult.
It is preferable that the content of the single addition be 0.3% by weight or less.

Zn: Zn is an element that is inevitably mixed when scrap is used as a raw material for melting, but contributes to an improvement in strength when more than 1% by weight is positively contained. If Zn is less than 1.0% by weight, the effect cannot be obtained.
On the other hand, if the content exceeds 7.0% by weight, castability deteriorates. Therefore, when Zn is positively added, the amount of Zn exceeds 1.0% by weight and is set to 7.0% by weight or less. Further, in the case of an Al-Si alloy, Ti, P, Na, S
One or more of b and Sr are contained. The reasons for limiting these components are as follows. Ti: Ti contributes to the refinement of the structure through the refinement of ingot crystal grains. If the amount of Ti is less than 0.005% by weight, the effect cannot be obtained. If the amount exceeds 0.2% by weight, a coarse intermetallic compound is generated, which is not preferable. Therefore, the amount of Ti added is preferably 0.005 to 0.2% by weight. In order to refine the ingot crystal grains, it is effective to make B coexist with Ti. In this case B
The effect cannot be obtained if the amount of
If the content exceeds 0 ppm, the effect is saturated, so that when B is added together with Ti, the addition amount is preferably in the range of 1 to 100 ppm.

P: P contributes to miniaturization of primary crystal Si. Therefore, the addition amount of P is effective in the case of an alloy containing about 10% by weight or more of Si such that primary crystal Si first appears.
If the amount of P is less than 0.005% by weight, the effect of miniaturizing the primary crystal Si cannot be obtained, and if it exceeds 0.1% by weight, the effect is saturated. Therefore, when P is added,
0.005 to 0.1% by weight is preferred. Na, Sb, S
The elements r, Na, Sb, and Sr contribute to miniaturization of eutectic Si. In any case, if less than 0.005% by weight, the effect cannot be obtained. When the content of Na and Sr exceeds 0.1% by weight, the effect is saturated, and when the content of Sb exceeds 0.3% by weight, the effect is saturated. Therefore, when Na is added, the amount of addition is 0.1.
005 to 0.1% by weight, the addition amount when Sb is added is preferably 0.005 to 0.3% by weight, and the addition amount when Sr is added is preferably 0.005 to 0.1% by weight. Note that N
When b, Sb, and Sr coexist with P, the effect of miniaturization of primary crystal Si by P is lost. Therefore, it is preferable that b does not coexist with P.

In addition to the above elements, there is no particular problem in adding about 1 to 100 ppm of Be to prevent oxidation during dissolution. Also, other elements do not particularly adversely affect far-infrared radiation characteristics as long as the total amount is about 1% by weight or less.

Next, if the surface of the Al-Mn-based or Al-Si-based Al alloy 2 substrate is anodized, the anodized film 3 exhibits excellent far-infrared characteristics. That is, at the time of the anodizing treatment, in the case of the base material of the Al-Mn-based Al alloy, precipitated particles of the Al-Mn-based intermetallic compound, and in the case of the Al-Si-based Al alloy, the metal Si particles are all contained in the film. The anodic oxide film 3 grows as it is. Therefore, the growth of pores in the film
A porous film having fine branched pores is generated, being hindered by -Mn-based intermetallic compound particles or metal Si particles. Further, fine pores which remain and disperse as they are in the anodic oxide film 3 scatter and absorb the incident light, and the radiation characteristics of far-infrared rays are improved.

When the anodic oxidation treatment is performed after the mechanical roughening treatment of the substrate made of Al or Al alloy 2 described above, the surface roughness value of the substrate surface is maintained as it is. It will appear in the surface roughness. Therefore, the average roughness of the substrate surface is 0.5 to 5 μm and the maximum roughness is 5 to 5 μm.
By roughening the surface to 50 μm, the surface roughness of the obtained anodic oxide film 3 is also 0.5 to 5 μm in average roughness and 5 μm in maximum roughness.
It will be roughened to ５０50 μm.

According to the above-mentioned solar heat absorbing plate 1, an anodic oxide film 3 having fine irregularities is formed on the surface of Al or Al alloy 2, and this anodic oxide film 3
The total radiation characteristic of far infrared rays in the wavelength region of 0 μm is 70.
% And high conversion efficiency between far infrared rays and heat, so that far infrared rays contained in sunlight can be more efficiently absorbed. In addition, the anodic oxide film 3 has a high absorption coefficient of visible light and, in addition to the above-described far-infrared absorption ability, can absorb light of most wavelengths of sunlight. The amount of generated heat can be greatly increased, and sunlight can be used effectively.
In addition, since fine irregularities are formed on the surface of the anodic oxide film 3, the apparent surface area is increased.
Complicated irregularities and complicatedly branched pores are formed, and the scattering and absorptivity for incident sunlight can be increased. Further, since the thickness of the anodic oxide film 3 is 0.5 μm or more, a sufficient far-infrared emissivity can be obtained.

The above-mentioned solar heat absorbing plate 1 has an anodized film 3
The transparent organic resin 4 is provided on the substrate, and the transparent organic resin 4 has high light transmittance in a wide wavelength range and is excellent in transparency. It is possible to transmit the heat, and furthermore, it is possible to prevent the release of the heat accumulated in the solar heat absorbing plate 1 due to the irradiation of the far infrared rays of the sunlight. In particular, an acrylic resin such as a polymethyl methacrylate resin as the transparent organic resin 4 has excellent light transmittance, and can prevent the release of heat. The transparent organic resin 4 is made of an anodized film 3
The solar heat absorbing plate 1 provided with the selective absorption film is placed on the anodic oxide film 3 by being mounted on the anodic oxide film 3 by laminating or baking the film-shaped transparent organic resin 4 or the like.
Can be easily manufactured.

The Al alloy of the solar heat absorbing plate 1 is Mn
Containing 0.3 to 4.3% by weight of Al-M
Since the n-based intermetallic compound is generated and the particles of the Al-Mn-based intermetallic compound are contained in the anodic oxide film 3 in a dispersed state, the incident light is easily scattered and absorbed,
The radiation characteristics of far infrared rays can be improved.

[0042]

[Example] Size: 10cm x 15cm, thickness: 0.4mm
A 2 μm anodic oxide film was formed on one surface of an Al plate (JIS 1100 product), and black nickel was uniformly filled in the anodic oxide film to obtain a base material. In addition, size 10cm * 1
Al alloy plate having a small intermetallic compound of Al ₆ Mn with a thickness of 5 cm and a thickness of 0.5 mm (A containing 2% by weight of Mn)
alloy) on one side, a porous oxide film thickness of 10 μm
To form another base material. Furthermore,
Size at which minute intermetallic compound of Al ₆ Mn is precipitated 10
A 25 μm-thick anodic oxide film as a porous oxide film was formed on one surface of an Al plate having a size of cm × 15 cm and a thickness of 0.5 mm to obtain another base material. The anodic oxide film was formed by spraying alumina particles on the surface of the aluminum plate to perform blast treatment, and then performing anodic oxidation treatment in a 20% by weight sulfuric acid bath. For each of the above base materials,
2mm sheet glass as transparent material, 2mm transparent PMM
A plate, 2mm transparent polyvinyl chloride resin (PVC)
Plate, 12 μm transparent PMMA film, 20 μm
The transparent heat-absorbing plates of Examples 1 to 6 and Comparative Examples 1 to 12 were produced by superposing the transparent PMMA films. 12 μm and 20 μm films of PMMA were applied to the substrate by baking. The other top materials were simply superimposed on the base material. In addition, only the base material was used as the solar heat absorbing plate.

After attaching a tape-type thermocouple to the back side of the sunshine surface of these solar heat absorbing plates, the sunshine surface (the surface on which the anodized film was formed) was oriented at an angle of 45 ° toward the sun's solar radiation direction. The temperature of the solar heat absorbing plate was measured while irradiating the solar light at an angle. Measurements were taken from 8:00 to 16 outdoors on a sunny day.
Until the hour (8 hours), the temperature of the solar thermal absorber was recorded at 15 minute intervals. Table 1 shows the average of all the temperature values recorded. In addition, Example 3 (anodized film (25 μm) + polymethyl methacrylate resin plate (2 mm)) and Comparative Example 11 (anodized film with black nickel (2 μm) between 10:30 and 12:15) FIG. 2 shows the change in temperature of the solar heat absorbing plate of FIG.

[0044]

[Table 1]

In Table 1, it can be seen that the solar heat absorbing plates of Examples 1 to 6 have higher temperatures than the solar heat absorbing plates of Comparative Examples 1 to 11. In addition, in Table 1, the solar light absorbing plates of Comparative Example 12 show almost the same temperature as the solar light absorbing plates of Examples 1 to 4. However, in FIG. 2, the solar heat absorbing plate of Example 4 has a small temperature fluctuation,
While relatively stable, the solar heat absorbing plate of Comparative Example 12 has a large fluctuation in temperature and is greatly affected by weather conditions such as sunshine duration, sunshine state, and ventilation state.

[0046]

The solar heat absorbing plate of the present invention is made of Al or A
0.5μm thickness with fine irregularities on the surface of the alloy
With the above anodic oxide film formed, it can absorb far-infrared rays contained in sunlight more efficiently, has high absorption efficiency of visible light, and can absorb light of most wavelengths of sunlight. Therefore, the amount of heat generated by sunlight irradiation can be greatly increased, and sunlight can be used effectively. In addition, the fine irregularities increase the apparent surface area, and the complex irregularities and the complicatedly branched pores are formed, thereby increasing the scattering and absorption of incident sunlight and absorbing far infrared rays. Can be further increased.

The above-mentioned solar heat absorbing plate is provided with a transparent organic resin having high light transmittance and excellent transparency on the anodic oxide film, and transmits light in most of the wavelength region of sunlight. Further, by preventing the release of heat accumulated in the solar heat absorbing plate due to the irradiation of the far infrared rays of sunlight, it is possible to prevent the temperature of the solar heat absorbing plate from fluctuating due to a change in weather conditions. Therefore, when the solar absorbing plate according to the present invention is used for a solar collector or the like, the temperature of the water can be stably maintained regardless of weather conditions without installing tempered glass. Therefore, the cost and weight of the solar collector can be reduced.

Further, the above-mentioned solar heat absorbing plate of the present invention
The alloy contains 0.3 to 4.3% by weight of Mn, and Al-M
Since an n-based intermetallic compound is generated and the particles of the Al-Mn-based intermetallic compound are contained in a dispersed state in the anodic oxide film, incident light is easily scattered and absorbed, and absorption of far infrared rays is reduced. Can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a solar heat absorbing plate according to an embodiment of the present invention.

FIG. 2 is a graph showing the change over time in the temperature of a solar heat absorbing plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solar heat absorption plate 2 Al or Al alloy 3 Anodized film 4 Transparent organic resin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Ito 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd. (72) Katsuji Takahara 1-1-1, Kiba, Koto-ku, Tokyo Stock Inside Fujikura Corporation (72) Inventor Noriyoshi Baba 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Corporation (72) Inventor Hiroshi Okada 1-15-1 Kiba, Koto-ku, Tokyo Fujikura Corporation (72) Inventor Yasushi Iwaizumi Fujikura Co., Ltd., 1-1-1, Kiba, Koto-ku, Tokyo

Claims (3)

[Claims] An anodic oxide film having fine irregularities is formed on the surface of Al or an Al alloy, and a transparent organic resin is provided on the surface of the anodic oxide film. A solar heat absorbing plate having a thickness of 0.5 to 45 μm. 2. The solar heat absorbing plate according to claim 1, wherein said transparent organic resin is an acrylic resin. 3. The solar heat absorbing plate according to claim 1, wherein the Al alloy has a Mn of 0.3 to 4.0.
A solar heat absorbing plate containing 3% by weight, the balance being Al and unavoidable impurities.