JP2011081284A - Light reflector and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light reflector capable of keeping high reflectance and a method for producing the light reflector. <P>SOLUTION: The light reflector for reflecting light includes: a base material 11 comprising aluminum or an aluminum alloy the surface of which is mirror finished so that the reflectance of the light of a range of visible light to infrared light becomes ≥85%; and a titanium dioxide-coated layer 12 formed on the base material 11 by firing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light reflector that reflects light and a method of manufacturing the same.

  Various devices have been proposed for efficiently melting and melting snow in the snowfall area, such as near a traffic signal on a pedestrian crossing, around a bus stop, braille blocks, near an entrance to an underpass, and near a tunnel entrance. In the snow melting device of Patent Document 1, a U-shaped reflecting plate having a lower surface is provided near an infrared heater housed in a case. If comprised in this way, all the infrared rays radiated | emitted from an infrared heater will go to a road surface from an opening part. Therefore, the entire energy of the infrared heater can be used to melt snow, and the irradiation efficiency is high.

JP 2006-138141 A

  However, the reflection plate of the above-described conventional snow melting apparatus has been deformed after the snowfall period (4 to 5 months) of one season, and the reflection efficiency has been greatly reduced.

  The inventors of the present invention diligently studied the cause and obtained the following findings. That is, the conventional aluminum reflector originally had low light reflectance. As shown in FIG. 8, it is about 30% even at the highest light reflectance, and it is only about several% depending on the wavelength. For this reason, the aluminum reflecting plate absorbs infrared light that has not been reflected, thereby causing surface deformation due to heat. After one season, a lot of dirt adheres to the surface of the aluminum reflector. This dirt also easily absorbs heat and easily causes surface deformation.

  The present invention has been made paying attention to such conventional problems, and an object thereof is to provide a light reflector that can maintain a high reflectance and a method for manufacturing the same.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention is a light reflector that reflects light, and has a base (11) made of aluminum or aluminum alloy having a mirror-finished surface, and a titanium dioxide coat layer formed by firing the base (11). (12).

  The present invention also relates to a method of manufacturing a light reflector that reflects light, a polishing step (# 101) for mirror-polishing the surface of a workpiece with aluminum or an aluminum alloy, and the surface-polished workpiece as a titanium dioxide precursor. A dipping step (# 102) dipping in the solution, a lifting coating step (# 103) for pulling up the immersed workpiece to coat the surface, a drying step (# 104) for drying the pulled workpiece, and the drying And a firing step (# 105) for firing the workpiece.

  According to the present invention, since aluminum or an aluminum alloy is used as the base material, it is lightweight and can be manufactured at low cost. Further, light having a wavelength in a range from visible light to infrared light can be almost totally reflected.

  Moreover, by manufacturing like this invention, a titanium dioxide coat layer can be baked with respect to aluminum with melting | fusing point as low as about 650 degreeC.

  A so-called self-cleaning action by the titanium dioxide coat layer can be obtained, dirt can be prevented from adhering to the surface, and the initial reflectance can be maintained for a long period of time.

It is a figure which shows one Embodiment of the light reflector by this invention. It is a figure explaining the reflective characteristic when electropolishing is given to an aluminum plate. It is a figure explaining the relationship between the wavelength of light, and a hue. It is a figure which shows the reflective characteristic of the light of the wavelength of the area | region of visible light to infrared light, and is the figure which put together data in the case where baking temperature was changed by making pulling speed the same. It is a figure which shows the reflective characteristic of the light of the wavelength of the area | region of visible light to infrared light, and is the figure which put together data in the case where pulling-up speed is changed by making baking temperature the same. It is a figure which shows the table | surface which put together the reflectance in short wavelength 380nm of visible light. It is a reflection characteristic figure of the conventional aluminum reflecting plate.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
<Structure of light reflector>
FIG. 1 is a diagram showing an embodiment of a light reflector according to the present invention.

  The light reflector 10 includes a base material 11 and a titanium dioxide coat layer 12.

  The base material 11 is a base material made of aluminum or an aluminum alloy. The base material 11 is mirror-finished so as to reflect light having a wavelength in the range from visible light to infrared light with high reflectance. For example, when a stainless steel plate is used as the base material 11, there is a wavelength at which the reflectance decreases in the region from visible light to infrared light even if mirror finishing is performed. On the other hand, if the mirror surface processing is performed using the mirror-finished base material 11 made of aluminum or an aluminum alloy as in this embodiment, light having a wavelength ranging from visible light to infrared light can be almost totally reflected. is there.

In order to perform mirror processing so that light having a wavelength in the range from visible light to infrared light is substantially totally reflected, it is preferable to perform processing by electrolytic polishing or polishing using a combination of electrolytic polishing and mechanical polishing. Electropolishing is a polishing method that utilizes the dissolution of the metal of the anode by electrolysis. Examples of polishing using both electrolytic polishing and mechanical polishing include electrolytic abrasive polishing and electrolytic composite polishing. Electrolytic abrasive polishing is a processing method in which electrolysis with a current density of 0.1 A / cm ² is combined with abrasive polishing with a pressing pressure of about 5 to 20 kPa. Electrolytic composite polishing is a passive film formed on the surface of the workpiece (anode) by the electrolytic phenomenon, and only the film formed on the convex part is removed by abrasive rubbing, and this part is selectively subjected to electrolytic elution. This is a surface treatment method that efficiently obtains a metal mirror surface by concentrating the particles. In other words, electrolytic abrasive polishing and electrolytic composite polishing are performed by combining electrochemical polishing by electrolytic polishing and physical polishing by an abrasive at the same time, so that metal elution by electrolysis and mechanical abrasion by abrasive Is a method of polishing the surface in combination. According to electrolytic abrasive polishing and electrolytic composite polishing, among the passivation film that occurs on the surface to be polished (anode) due to the electrolytic phenomenon, only the film formed on the convex portion is removed by abrasive rubbing, and this portion is selectively used. It is possible to obtain a metal mirror surface by concentrating the electrolytic elution action on the surface, and to obtain a nano-level ultra-smooth surface.

  FIG. 2 is a diagram for explaining reflection characteristics when electrolytic polishing is applied to an aluminum substrate.

  When the above-described electrolytic polishing is applied to the aluminum base material and mirror-finished, as shown in FIG. 2, light having a wavelength in the visible light to infrared light region has a high reflection of 85% or more over almost the entire region. Reflect at rate. When electrolytic abrasive polishing or electrolytic composite polishing is performed, the reflectance is further improved.

  On the other hand, such a reflectance cannot be obtained with the commercial product A or the commercial product B.

  The relationship between the wavelength of light and the hue is as shown in FIG. The wavelength in the visible light to infrared light region is a wavelength of 380 nm or more.

The titanium dioxide coat layer 12 is formed by firing on the substrate 11. The titanium dioxide coat layer 12 is a layer for coating the substrate 11 with titanium dioxide TiO ₂ . Titanium dioxide TiO ₂ has super-hydrophilic properties, and even if water repels, it does not form water droplets on the surface but flows down as it is. In addition, there is a so-called self-cleaning action in which oily dirt is not fixed, and the surface is washed by water flowing periodically due to rain or the like.

  In order to form a titanium dioxide coat layer by firing on a substrate, it is generally fired by heating at a very high temperature. However, since aluminum, which is the material of the base material 11, has a low melting point of about 650 ° C., it cannot be fired at a high temperature. Therefore, in this embodiment, the light reflector is manufactured by firing by the following method.

<Method for producing light reflector>
(Polishing process # 101)
First, reflectivity of approximately 85% or more of light in the wavelength range from visible light to infrared light for a workpiece made of aluminum (for example, 1050 pure aluminum of JIS H 4000 “aluminum and aluminum alloy plates and strips”) Mirror finish so that the reflection characteristics can be obtained. In order to obtain such reflection characteristics, it is preferable to polish to the nano-order (roughness of 5 nm or less) by electrolytic polishing or polishing (electrolytic abrasive polishing or electrolytic composite polishing) that uses electrolytic polishing and mechanical polishing in combination. The reflectance can be measured with a spectrophotometer.

(Dip process # 102)
The surface-polished workpiece is washed and then immersed in the titanium dioxide precursor solution. In this titanium dioxide precursor solution, 34 mL of titanium (IV) n-butoxide monomer was dissolved in 166 mL of benzene and refluxed for 8 hours, and then hydrolyzed by adding hydrous butanol in which 5% of water was dissolved in n-butanol. The mixture was refluxed again for 8 hours, concentrated, diluted with benzene, and adjusted to a titanium concentration of 1.0 mol / dm ³ .

(Pulling coating process # 103)
The immersed workpiece is pulled up at a predetermined speed in a toluene and butanol atmosphere using a stepping motor pulling device. As a result, the surface of the workpiece is coated with a film.

(Drying process # 104)
The surface-coated workpiece is sufficiently dried at room temperature.

(Baking step # 105)
The dried workpiece is fired in a furnace at a predetermined temperature for about 1 hour.

  Through the above steps, a light reflector coated with titanium dioxide was produced.

  Subsequently, the characteristics of the light reflector manufactured as described above were evaluated by changing the manufacturing conditions (pulling speed and firing temperature).

<Evaluation experiment conditions>
A titanium dioxide coating layer was formed by the above method on an aluminum plate (1050 of JIS H 4000) having a length of 50 mm, a width of 50 mm, and a thickness of 1 mm. The lifting speed in the lifting coating process # 103 was 144, 289, 483 μm / sec. The firing temperature in firing step # 105 was 300, 350, 400 ° C.

<Results of evaluation experiment>
FIG. 4 is a diagram showing the reflection characteristics of light having a wavelength in the range from visible light to infrared light, and the data are summarized when the firing temperature is changed with the same pulling speed. In FIG. 4A, the pulling rate is 144 μm / sec. In FIG. 4B, the pulling rate is 289 μm / sec. In FIG. 4C, the pulling speed is 483 μm / sec.

  As shown in FIG. 4A, when the pulling rate is 144 μm / sec, the reflectance is high with respect to the wavelength in the region of visible light or higher, that is, the wavelength of the region of 380 nm or higher, regardless of the firing temperature.

  4B, when the pulling rate is 289 μm / sec, the reflectance is lower than that of 144 μm / sec, but the reflectance is still high regardless of the firing temperature.

  4C, when the pulling rate is 483 μm / sec, the reflectance is further reduced as compared with 289 μm / sec. Further, when the firing temperature is high, the reflectance is large, and when the firing temperature is low, the reflectance is small. In particular, the variation in reflectance is large on the short wavelength side.

  FIG. 5 is a diagram showing the reflection characteristics of light having a wavelength in the range from visible light to infrared light, and the data is summarized when the firing rate is changed with the firing temperature being the same. In FIG. 5A, the firing temperature is 300.degree. In FIG. 5B, the firing temperature is 350 ° C. FIG. 5C shows a baking temperature of 400 ° C.

  5A, when the firing temperature is 300 ° C., the reflectivity is large when the pulling rate is slow, and the reflectivity is small when the pulling rate is fast. In particular, the variation in reflectance is large on the short wavelength side.

  As shown in FIG. 5B, when the firing temperature is 350 ° C., the reflectance is large when the pulling speed is slow, and the reflectance is small when the pulling speed is fast, but the variation is small. . Further, the reflectance is improved as compared with 300 ° C.

  In FIG. 5C, even when the baking temperature is 400 ° C., the reflectance is large when the pulling speed is slow, and the reflectance is small when the pulling speed is high, but the variation is further small. Further, the reflectance is further improved.

  From the above, the reflection characteristics of light having wavelengths in the visible light to infrared light region vary greatly, particularly on the short wavelength side. Therefore, the reflectances of visible light at a short wavelength of 380 nm are summarized as shown in FIG.

  As can be seen from this table, the reflectance is small when the pulling speed is high. The inventors consider this as follows. That is, the inventors know from the experience so far that the thickness of the titanium dioxide coat layer increases as the pulling speed increases. As the thickness of the titanium dioxide coat layer increases, the reflectivity decreases. Therefore, the inventors know that the reflectance is small when the pulling speed is high. From these results, the inventors consider that the pulling speed is desirably 289 μm / sec or less. Further, the reflectance decreases as the firing temperature decreases. In particular, when the firing temperature is changed from 350 ° C. to 300 ° C. at a pulling rate of 289 μm / sec, the reflectance decreases from 87% to 83%. Therefore, the firing temperature is desirably 350 ° C. or higher. However, if the firing temperature is too high, it will approach the melting point of aluminum. Therefore, the firing temperature must be lower than the melting point of aluminum, 650 ° C. Based on such considerations, the inventors have the light reflector manufacturing conditions that the pulling rate in the pulling coating step # 103 is 289 μm / sec or less and the firing temperature in the firing step # 105 is 350 ° C. or more and 650 ° C. or less. The conclusion was desirable.

  If a light reflector is manufactured as in this embodiment, the thickness of the titanium dioxide coat layer is thin and the reflectance can be increased. In particular, when the pulling rate from the titanium dioxide precursor solution is 289 μm / sec or less, the reflectance is almost the same as that of the aluminum substrate. If the firing temperature is 350 ° C. or higher, the reflectance is almost the same as that of the aluminum substrate. Furthermore, if the firing temperature is 650 ° C. or lower, the melting point of aluminum is lower, so that the reflective properties of the aluminum substrate are not impaired even if the titanium dioxide coat layer is fired.

  Titanium dioxide has a so-called self-cleaning property. Therefore, it is possible to prevent dirt from adhering to the surface and maintain the initial reflectance.

  If the reflectance is high, unnecessary energy is not absorbed and surface deformation does not occur.

  Therefore, a high reflectance can be maintained.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  The light reflector is not limited to the snow melting device, and may be used for other purposes. For example, it is suitable for a reflector whose surface may become dirty, such as a reflector installed on a road, a light reflector in a plant factory, or a reflector used in an endoscope.

  In addition, the light reflector is not limited to a plate shape, and the shape may be changed as appropriate according to the intended use.

10 Light Reflector 11 Base Material 12 Titanium Dioxide Coated Layer

Claims (10)

A light reflector that reflects light,
A substrate made of aluminum or aluminum alloy having a mirror-finished surface;
A titanium dioxide coating layer formed by firing on the substrate;
A light reflector comprising: The light reflector according to claim 1,
The substrate has a light reflectance of 85% or more in a region ranging from visible light to infrared light.
A light reflector characterized by that. The light reflector according to claim 1 or 2,
The titanium dioxide coat layer has a thickness equal to or less than a film thickness formed by pulling up the base material immersed in a titanium dioxide precursor solution at a pulling rate of 289 μm / sec.
A light reflector characterized by that. A method of manufacturing a light reflector that reflects light, comprising:
A polishing step of mirror polishing the surface of the workpiece with aluminum or an aluminum alloy;
A dipping step of immersing the surface-polished workpiece in a titanium dioxide precursor solution;
A lifting coating step of lifting the immersed workpiece to coat the surface;
A drying step of drying the raised workpiece;
A firing step of firing the dried workpiece;
A method of manufacturing a light reflector, comprising: In the light reflector manufacturing method according to claim 4,
The polishing step is a step of mirror-finishing so that the reflectance of light in a region from visible light to infrared light on the workpiece surface is 85% or more.
A method of manufacturing a light reflector. In the light reflector manufacturing method according to claim 4 or 5,
The polishing step is a step of mirror polishing by electrolytic polishing.
A method of manufacturing a light reflector. In the light reflector manufacturing method according to claim 4 or 5,
The polishing step is a step of mirror polishing using a combination of electrolytic polishing and mechanical polishing.
A method of manufacturing a light reflector. In the light reflector manufacturing method according to any one of claims 4 to 7,
The titanium dioxide precursor solution in the dip step was prepared by dissolving 34 mL of titanium (IV) n-butoxide monomer in 166 mL of benzene and refluxing for 8 hours, and then adding hydrous butanol in which 5% water was dissolved in n-butanol. Hydrolysis, and after refluxing again for 8 hours, the solution was concentrated and diluted with benzene to adjust the titanium concentration to 1.0 mol / dm ³ .
A method of manufacturing a light reflector. In the light reflector manufacturing method according to any one of claims 4 to 8,
The lifting coating process is a process of lifting and coating at a lifting speed of 289 μm / sec or less,
A method of manufacturing a light reflector. In the light reflector manufacturing method according to any one of claims 4 to 9,
The firing step is a step of heat treatment at 350 ° C. or more and 650 ° C. or less.
A method of manufacturing a light reflector.

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