JP2013238677A - Reflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflector with better chemical durability than a conventional reflector.SOLUTION: A reflector comprises a first glass plate, a reflection layer and a second glass plate in this order. The first glass plate has a first surface arranged at a side far from the reflection layer and a second surface arranged at the side close to the reflection layer. The second glass plate has a third surface at the side far from the reflection layer and a fourth surface at the side close to the reflection layer. A sodium-aluminum ratio (a Na/Al ratio) of the first surface on the first glass plate is smaller than the sodium-aluminum ratio (the Na/Al ratio) of the third surface on the second glass plate.

Description

  The present invention relates to a reflector. In particular, the present invention relates to a reflector having a high reflectivity.

  A reflector having a glass plate and a reflective layer disposed on the back side of the glass plate is widely applied in various fields such as a cosmetic mirror and an optical system mirror. In recent years, for example, a reflector having a high reflectivity, that is, a so-called highly reflective reflector has been paid attention to for the purpose of, for example, the use of a solar thermal power generation apparatus, and has been developed.

  In a highly reflective reflector, in order to realize the high reflectance, it is necessary to make the glass plate have high transparency. For this reason, for example, in Patent Document 1, in the reflector used in the solar thermal power generation apparatus, the reflector is constituted by two glass plates on the front side and the back side, and the front side glass plate is prepared thinly. Is disclosed.

U.S. Pat. No. 7,871,664

  As described above, Patent Document 1 discloses a reflector having a high reflectance by reducing the thickness of the glass plate on the front side, for example, as thin as 0.5 mm to 2.5 mm. The method of manufacturing is shown.

  In general, a reflector may cause a problem of a so-called “burn” phenomenon. The “discoloration” phenomenon is a phenomenon in which a glass plate chemically changes after a long period of time due to water droplets attached to the glass plate. When the “burning” phenomenon occurs, the transmittance of the glass plate is remarkably lowered, thereby reducing the reflectance of the reflector. In particular, solar thermal power generators are often installed in places where strong sunlight is generally obtained, such as desert areas. In this case, the “burn” phenomenon can occur in a shorter time due to the high temperature of the glass plate. There is sex.

  However, Patent Document 1 does not show any countermeasure for such a problem of chemical deterioration of the glass plate.

  This invention is made | formed in view of such a problem, and an object of this invention is to provide the reflector by which chemical durability was improved compared with the past.

In the present invention,
A first glass plate;
A reflective layer;
A second glass plate;
In this order,
The first glass plate has a first surface far from the reflective layer and a second surface near the reflective layer, and the second glass plate is far from the reflective layer. A third surface and a fourth surface closer to the reflective layer;
The sodium / aluminum ratio (Na / Al ratio) on the first surface of the first glass plate is higher than the sodium / aluminum ratio (Na / Al ratio) on the third surface of the second glass plate. A reflector is provided that is reduced in size.

  Here, in the reflector according to the present invention, a sodium / aluminum ratio (Na / Al ratio) on the first surface of the first glass plate may be 2.0 or less.

  In the reflector according to the present invention, the first surface of the first glass plate may be chemically strengthened.

  In the reflector according to the present invention, the first glass plate may have a thickness of 1 mm or less.

  In the reflector according to the present invention, the second glass plate may have a thickness of 3 mm or more.

  The reflector according to the present invention may have an organic layer between the reflective layer and the second glass plate.

  The reflector according to the present invention may have a curved surface shape.

  The reflector according to the present invention may be a reflector for a solar thermal power generation apparatus.

  In addition, the reflector according to the present invention may have a size of 1 m or more in length × 1 m or more in width.

  The present invention can provide a reflector having improved chemical durability as compared with the prior art.

It is sectional drawing which showed schematically the structure of the reflector by one Example of this invention. It is the flowchart which showed roughly an example of the manufacturing method of the reflector by this invention. It is the graph which showed the relationship between the retention time in a high temperature, high humidity environment, and a haze value obtained in each of the glass sample which concerns on Examples 1-3.

  Hereinafter, the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows a configuration of a reflector according to an embodiment of the present invention.

  As shown in FIG. 1, a reflector 100 according to an embodiment of the present invention includes a first glass plate 110, an adhesion layer 120, a reflective layer 130, an organic layer 140, and a second glass plate 150 in this order.

  The first glass plate 110 constitutes the light incident surface 160 of the reflector 100. More specifically, the first glass plate 110 has a first surface 112 and a second surface 114, and the first surface 112 side constitutes the light incident surface 160 of the reflector 100. On the second surface 114 side of the first glass plate 110, an adhesion layer 120, a reflective layer 130, and the like are disposed.

  The reflective layer 130 is typically configured as a layer containing a metal such as silver and provides the reflector 100 with a reflective function.

  In addition, when the reflective layer 130 is directly installed on the second surface 114 of the first glass plate 110, the adhesion between the first glass plate 110 and the reflective layer 130 may be insufficient. The adhesion layer 120 is arranged to cope with such a problem. That is, the adhesion between the first glass plate 110 and the reflective layer 130 is improved by disposing the adhesion layer 120. However, the adhesion layer 120 is not necessarily a necessary member and may be omitted.

  The second glass plate 150 constitutes the back side of the reflector 100. More specifically, the second glass plate 150 has a third surface 152 and a fourth surface 154, and the third surface 152 side constitutes the back surface 170 of the reflector 100. The organic layer 140 and the like are disposed on the fourth surface 154 side of the second glass plate 150.

  The organic layer 140 normally has a role of joining the second surface 114 side of the first glass plate 110 and the fourth surface 154 side of the second glass substrate 150. The organic layer 140 does not have to be a single layer, and may have a layer configuration including a plurality of, for example, three layers.

  Although not shown in FIG. 1, the reflector 100 may further include a protective layer between the reflective layer 130 and the organic layer 140. By providing the protective layer, the surface of the reflective layer 130 can be appropriately protected. However, when the organic layer 150 also serves such a role, the protective layer may be omitted.

  In the example of FIG. 1, the reflector 100 has a curved surface shape, that is, a convex shape toward the back surface 170. However, this shape is not always necessary, and the reflector 100 may be, for example, a flat shape.

  In the reflector 100 having such a configuration, when the incident light 180 is irradiated onto the light incident surface 160, the incident light 180 passes through the first glass plate 110 and reaches the reflective layer 130. The incident light 180 that has reached the reflective layer 130 is reflected by the reflective layer 130. This reflected light then travels in the reverse direction on the first glass plate 110 and is radiated from the reflector 100 via the light incident surface 160 to form a focal point at a desired position.

  For example, when the reflector 100 is used in a solar thermal power generation apparatus, the reflected light from the reflector 100 is condensed on a heat storage member that absorbs solar energy as thermal energy. Thereafter, electric power can be generated by generating high-temperature and high-pressure steam using the thermal energy accumulated in the heat storage member.

  Here, the above-mentioned Patent Document 1 discloses that the thickness of the front glass plate applied to the reflector is reduced to increase the transmittance, thereby increasing the reflectivity of the entire reflector. Yes.

  However, when the reflector described in Patent Document 1 is used for a long period of time, a problem of so-called “burn” phenomenon may occur.

  The “discoloration” phenomenon is a phenomenon in which a glass plate chemically changes after a long period of time due to water droplets attached to the glass plate. When the “burning” phenomenon occurs, the transmittance of the glass plate is remarkably lowered, thereby reducing the reflectance of the reflector. In particular, solar thermal power generation devices are often installed in places where strong sunshine is generally obtained, such as desert areas. In this case, the “burn” phenomenon occurs in a shorter time due to the high temperature of the glass plate on the front side. There is a possibility that.

  On the other hand, in the reflector 100 according to the embodiment of the present invention shown in FIG. 1, the sodium / aluminum ratio (hereinafter referred to as “Na / Al ratio”) on the first surface 112 of the first glass plate 110. ) Is smaller than the Na / Al ratio in the third surface 152 of the second glass plate 150.

  In the reflector 100 having such characteristics, as will be described in detail later, compared to the reflector described in Patent Document 1, the “burn” phenomenon is less likely to occur, and the chemical durability of the first glass plate 110 is less likely to occur. Can be significantly increased. Therefore, in the reflector 100 according to the present invention, the chemical durability of the first glass plate 110 is enhanced, and it is possible to provide the reflector 100 that maintains a high reflectance over a long period of time.

  Here, the relationship between the Na / Al ratio on the surface of the glass plate and the “burn” phenomenon of the glass plate will be described.

  It is considered that the “burn” phenomenon of the glass plate is caused by a chemical reaction of sodium on the surface of the glass plate due to moisture and carbon dioxide in the atmosphere.

More specifically, moisture in the atmosphere adheres to the surface of the glass plate. Thereafter, the adhered water and changes to positive ions such as H ₃ O ⁺ ions, between the sodium ions and H ₃ O ⁺ ions contained in the glass plate, the ion exchange reaction occurs. As a result, sodium ions in the glass are consumed, and it is considered that the “burn” phenomenon occurs.

In general, in a glass structure, one oxygen atom is covalently bonded to each of two silicon atoms, thereby constructing a glass network of -Si-O-Si- units. (Such oxygen atoms are called “bridging oxygen”.) However, when sodium oxide (Na ₂ O) is contained in the glass, positively charged Na ⁺ ions are present in the network. Therefore, a structural unit charged to a negative charge for the charge compensation is required. Further, this oxygen atom needs to be covalently bonded to some silicon atoms. As a result, in the glass structure, while covalently bound to the silicon atom, and containing charged oxygen atoms -Si-O negative charge ^- units would occur. The -Si-O ^- in the unit, an oxygen atom, with only one silicon atom not covalently bound (such oxygen atoms are referred to as "non-bridging oxygen"), a glass network is incomplete It becomes a state.

In a glass plate having such an incomplete glass network, when H ₃ O ⁺ ions adhere to the surface, an ion exchange reaction between sodium ions in the glass and H ₃ O ⁺ ions occurs relatively easily. Then, since the destruction of the network inside the glass proceeds due to the intrusion of water, the glass surface is easily broken by contact with water.

On the other hand, aluminum atoms in the glass structure are replaced with Si atoms, so that they take a structure similar to Si while being charged to a negative charge, so that non-bridging oxygen is generated even in the presence of Na ⁺ ions. It is known that the electric charge balance can be maintained without causing the above-described effects of suppressing non-bridging oxygen as described above.

  In the present invention, by reducing the Na / Al ratio, that is, by relatively reducing the amount of sodium contained in the surface of the glass plate, and conversely increasing the amount of aluminum, the “discoloration” as described above. Suppress the problem of the phenomenon. That is, by relatively reducing the amount of sodium on the surface of the glass plate, the ion exchange reaction with moisture in the environment is suppressed, and the amount of non-crosslinked oxygen in the glass network is suppressed. Moreover, the amount of non-bridging oxygen contained in the network is reduced by relatively increasing the amount of aluminum on the surface of the glass plate.

  Due to such effects, in the present invention, it is possible to significantly suppress the occurrence of the “burn” phenomenon on the glass plate.

  In the reflector 100 according to the embodiment of the present invention shown in FIG. 1, the Na / Al ratio (ratio in terms of content in mol% on the basis of oxide) on the first surface 112 of the first glass plate 110. )) Exceeds 5, the chemical durability is weak and a burn phenomenon may occur. Therefore, the Na / Al ratio is preferably 5.0 or less, and more preferably 2.0 or less. The Na / Al ratio may be 0 (zero).

The content of the first of the first oxide of Al in the surface 112 reference of the glass plate 110 _(Al 2 _{O 3} basis) is preferably in the range of 5 mol% 20 mol%.

  Here, in the present application, the “surface of the glass plate” which is a target for determining the Na / Al ratio refers to a range from the outermost surface of the glass plate to a depth of 10 μm. For the Na / Al ratio of the glass plate in such a region, the sodium content and aluminum content on the surface of the glass plate are measured by, for example, EPMA (electron probe microanalysis) or SIMS (secondary ion mass spectrometry). By doing so, it can be easily analyzed.

  In the reflector 100 according to the embodiment of the present invention shown in FIG. 1, the thickness of the first glass plate 110 may be, for example, in the range of 0.1 mm to 1 mm. By configuring the first glass plate 110 to be “thin” in this way, the transmittance of the first glass plate 110 is reduced, and the reflectance of the reflector 100 can be further increased.

  On the other hand, the thickness of the second glass plate 150 does not affect the reflectance of the reflector 100. For this reason, it is preferable that the 2nd glass plate 150 is the range from which rigidity is acquired by the reflector 100, for example, the range of 2 mm-5 mm.

(About each component of the reflector)
Next, each member which comprises the reflector 100 by one Example of this invention shown in FIG. 1 is demonstrated in detail.

(First glass plate 110)
The first glass plate 110 according to the present invention may be made of any glass. However, as described above, in the first glass plate 110, the Na / Al ratio on the first surface 112 is smaller than the Na / Al ratio on the third surface 152 of the second glass plate 150. It has the characteristics.

  Note that aluminum is contained in the first glass plate 110 at a content exceeding the concentration derived from impurities at least.

  The thickness of the first glass plate 110 may be, for example, in the range of 0.1 mm to 1 mm.

  The first glass plate 110 may be made of, for example, borosilicate or aluminosilicate glass.

  The first glass plate 110 may have a higher energy transmittance than the second glass plate 150. For example, the first glass plate 110 may have an energy transmittance of 90.4% or more.

  Here, the “energy transmittance” is the total solar energy transmittance defined in ISO 9050: 2003 (E).

(Adhesion layer 120)
Usually, an adhesion layer 120 is provided between the first glass plate 110 and the reflective layer 130.

  By installing the adhesion layer 120, the adhesion between the first glass plate 110 and the reflective layer 130 is improved.

  The adhesion layer 120 is composed of, for example, a layer containing tin or a mixed layer of tin and palladium.

  In the reflector 100 according to the embodiment of the present invention, the reflective layer 130 is not exposed to the outside, and is disposed between the first glass plate 110 and the second glass plate 150. For this reason, the reflective layer 130 should just have adhesiveness of the grade which does not peel from the 1st glass plate 110 in the manufacture stage of the reflector 100. FIG. Therefore, the adhesion layer 120 is not necessarily provided.

(Reflective layer 130)
The reflective layer 130 is composed of a layer having high reflectivity.

  The reflective layer 130 may be made of, for example, silver or a silver alloy. Further, the reflective layer 130 may be formed of a stacked body of a plurality of layers.

  The reflective layer 130 may be formed by physical vapor deposition such as sputtering.

  The thickness of the reflective layer 130 is not particularly limited, but may be in the range of 60 nm to 200 nm, for example.

(Organic layer 140)
The organic layer 140 has a role of bonding the first glass plate 110 and the second glass plate 150 to each other.

  The organic layer 140 may be composed of a single layer or a plurality of layers.

  The thickness of the organic layer 140 is not particularly limited, and may be, for example, in the range of 100 μm to 2500 μm.

  Note that the organic layer 140 may be omitted if the first glass plate 110 and the second glass plate 150 can be appropriately bonded without using the organic layer 140.

(Protective layer)
The protective layer is used as necessary to protect the reflective layer 130.

  The protective layer may be composed of, for example, a metal layer such as copper or a layer containing an organic substance. In the latter case, the protective layer may be composed of, for example, a tin compound and a silane coupling agent.

  The thickness of the protective layer is not particularly limited. The thickness may be in the range of 5 nm to 50 nm, for example.

  Note that when the organic layer 140 has a similar function, the protective layer may be omitted.

(Second glass plate 150)
Second glass plate 150 is formed of a glass substrate. The kind of glass is not particularly limited, and the glass may be, for example, soda lime glass.

  As described above, in the second glass plate 150, the Na / Al ratio on the third surface 152 is larger than the Na / Al ratio on the first surface 112 of the first glass plate 110. The Na / Al ratio on the third surface 152 may be, for example, in the range of 5-20.

  The thickness of the second glass plate 150 is not particularly limited, but the thickness is preferably in the range of 2 mm to 5 mm, for example, in order to support each member at the top. Alternatively, the thickness of the second glass plate 150 may be 5 mm or more.

  The transmittance of the second glass plate 150 is not particularly limited, but the second glass plate 150 may have an energy transmittance lower than that of the first glass plate 110. The second glass plate 150 may have a significantly low transmittance (for example, a transmittance of 30% or less) in the ultraviolet wavelength region. In this case, it is possible to significantly suppress chemical degradation of the organic layer 140 due to ultraviolet rays.

  The shape of the second glass plate 150 is not particularly limited, and is selected according to the completed shape of the reflector 100. For example, when the reflector 100 is applied to a solar power generator, the second glass plate 150 may have a curved shape such as a parabolic shape. Alternatively, the second glass plate 150 may have a flat shape.

(Reflector 100)
The reflector 100 may be flat or curved, and the shape of the reflector 100 is appropriately selected depending on the application.

  The application of the reflector 100 is not particularly limited. For example, the reflector 100 can be appropriately applied to applications that require high reflection characteristics. For example, the reflector 100 may be a reflector for a solar thermal power generation apparatus.

  The size of the reflector 100 is not particularly limited, but the reflector 100 may be a large reflector. For example, the reflector 100 may have a “large” dimension that is 1 m long × 1 m wide. Moreover, in such a large reflector, it is preferable that the first and second glass plates 110 and 150 are each composed of a single glass plate. Thereby, the number of parts of a reflector is reduced and it becomes possible to suppress cost.

  In general, when the first glass plate has rigidity, it is not easy to form such a first glass plate into a desired curved surface shape with high accuracy.

  However, in one embodiment of the present invention, the first glass plate 110 is configured to be “thin” and the second glass plate 150 is configured to be “thick” so that the second glass plate 150 allows the first glass plate 110 to be The curved surface of the glass plate 110 can be easily formed. That is, in one embodiment of the present invention, even if the reflector 100 has a curved shape such as a parabolic reflector, the “thick” second glass plate 150 manufactured with a desired curved shape is “thin”. The required curved shape can be imparted to the first glass plate 110 simply by attaching the first glass plate 110. In this case, it is not necessary to heat both the glass plates 110 and 150. Therefore, in one embodiment of the present invention, a curved reflector can be manufactured relatively easily and with high accuracy.

(Manufacturing method of reflector 100)
Next, a manufacturing method of the reflector 100 according to the embodiment of the present invention as shown in FIG. 1 will be described with reference to FIG.

  In the following description, a method for manufacturing the curved reflector 100 will be described. However, it will be apparent to those skilled in the art that flat reflectors can be manufactured in a similar manner. Further, the reference numerals shown in FIG. 1 are used to represent each member.

As shown in FIG. 2, the manufacturing method of the reflector 100 is as follows.
Preparing a first glass plate having first and second surfaces and a second glass plate having third and fourth surfaces (step S110);
Installing a reflective layer on the second surface of the first glass plate (step S120);
Placing an organic layer on top of the reflective layer and / or on the fourth surface of the second glass plate (step S130);
Bonding the second side of the first glass plate and the fourth side of the second glass plate via an organic layer (step S140);
Have

  Hereinafter, each step will be described in detail.

(Step S110)
First, the first glass plate 110 and the second glass plate 150 are prepared.

  The first glass plate 110 has a first surface 112 and a second surface 114. The second glass plate 150 has a third surface 152 and a fourth surface 154. The first surface 112 of the first glass plate 110 constitutes the light incident surface 160 of the reflector 100 after the reflector 100 is completed. The third surface 152 of the second glass plate 150 constitutes the back surface 170 of the reflector 100 after the reflector 100 is completed.

  Here, the first glass plate 110 is configured such that the Na / Al ratio on the first surface 112 is smaller than the Na / Al ratio on the third surface 152 of the second glass plate 150. The

  Such a feature is easily achieved by, for example, making the first glass plate 110 a composition having a lower sodium content and a higher aluminum content than the second glass plate 150.

  For example, the first glass plate 110 may be non-alkali glass, and the second glass plate 150 may be glass other than the non-alkali glass, for example, soda lime glass.

  Alternatively, the first glass plate 110 may be chemically strengthened.

  Here, “chemical strengthening treatment (method)” means that a glass material is immersed in a molten salt containing an alkali metal, and an alkali metal (ion) having a small atomic diameter existing on the outermost surface of the glass material is dissolved in the molten salt. Is a generic term for technologies that replace alkali metals (ions) with large atomic diameters. For example, when a glass material containing sodium (Na) is chemically strengthened in a molten salt containing potassium (K), sodium in the glass material is replaced with potassium.

  Therefore, when the first glass plate 110 containing sodium is chemically strengthened and the sodium present on the first surface 112 is replaced with potassium, the same composition is used for the first glass plate 110 and the second glass plate 150. Even when this glass is used, the Na / Al ratio of the first surface 112 of the first glass plate 110 is compared with the Na / Al ratio of the third surface 152 of the second glass plate 150. (However, the case where the second glass plate 150 is sodium-free glass is excluded).

  Moreover, the additional effect that the intensity | strength of the 1st glass plate 110 improves by performing a chemical strengthening process to the 1st glass plate 110 is acquired.

  The first glass plate 110 may have the second surface 114 subjected to chemical strengthening treatment.

  When the second surface 114 is chemically strengthened and sodium in the second surface 114 is replaced with potassium, migration of sodium ions from the first glass plate 110 to the reflective layer 130 side is significantly suppressed. . Therefore, in this case, the reflectance of the reflector 100 can be maintained at a high value over a long period.

  The second glass plate 150 is processed into a desired curved shape such as a parabolic shape by heat treatment or the like.

(Step S120)
Next, the reflective layer 130 is installed on the second surface 114 of the first glass plate 110.

  The reflective layer 130 may be formed directly on the second surface 114 of the first glass plate 110, but usually, the adhesion layer 120 is installed in advance on the second surface 114 of the first glass plate 110. The Thereby, the adhesiveness between the 1st glass plate 110 and the reflection layer 130 improves.

  The adhesion layer 120 is configured as tin alone or a mixed layer of tin and palladium.

  After the adhesion layer 120 is formed, a reflective layer 130 made of, for example, silver or a silver alloy is disposed thereon.

  As described above, when palladium is contained in the adhesion layer 120, the reflectance of the reflective layer 130 may be reduced. Therefore, it is preferable that the adhesion layer 120 does not contain palladium.

  After forming the reflective layer 130, a protective layer may be provided on the upper portion. The protective layer may be composed of, for example, metallic copper or a mixture of tin chloride and a silane coupling agent.

(Step S130)
Next, the organic layer 140 is disposed on the reflective layer 130 and / or on the fourth surface 154 of the second glass plate 150.

  The configuration and material of the organic layer 140 are not particularly limited, but the organic layer 140 preferably contains an adhesive.

  Moreover, the organic layer does not need to be a single layer, and may be composed of a plurality of layers.

(Step S140)
Next, the second surface 114 side of the first glass plate 110 and the fourth surface 154 side of the second glass plate 150 are joined via the organic layer 140.

  Since the organic layer 140 is installed in step S130, the first glass plate 110 can be easily joined even if the second glass plate 150 is curved. In addition, when the first glass plate 110 has a thickness of 1 mm or less, the first glass plate 110 exhibits flexibility. For this reason, the curved surface shape of the first glass plate 110 can be easily matched with the curved surface shape of the second glass plate 150.

  Through the above steps, the reflector 100 having the structure shown in FIG. 1 can be manufactured.

  Note that the manufacturing method of the reflector 100 described above is merely an example, and it will be apparent to those skilled in the art that the reflector 100 may be manufactured by other methods.

  Next, examples according to the present invention will be described.

  Glass samples shown in Examples 1 to 3 below were prepared as samples for the first glass plate, and the characteristics were evaluated.

(Example 1)
A glass sample (glass sample according to Example 1) made of alkali-free borosilicate glass was prepared. The column of “Example 1” in Table 1 shows the composition (oxide equivalent value) of the glass sample according to Example 1.

例１に係るガラス試料は、アルミニウムを含むものの、ナトリウムのようなアルカリ金属を含んでいないため、表面のＮａ／Ａｌ比は、０（ゼロ）である。

Although the glass sample according to Example 1 contains aluminum but does not contain an alkali metal such as sodium, the surface Na / Al ratio is 0 (zero).

  The thickness of the glass sample according to Example 1 was 0.7 mm.

  The glass transition temperature (Tg) of the glass sample according to Example 1 was 710 ° C., and the softening point was 950 ° C.

  Further, the energy transmittance of the glass sample according to Example 1 was measured. The energy transmittance was measured by a Perkin Elmer apparatus: LAMBDA950. As a result of the measurement, the energy transmittance of the glass sample according to Example 1 was 90.4%, and the glass sample according to Example 1 showed good transmittance.

(Example 2)
A glass sample made of aluminosilicate glass having the composition (oxide equivalent value) shown in the column of “Example 2” in Table 1 was prepared.

  The thickness of the glass sample was 2.0 mm.

  This glass sample had a glass transition temperature (Tg) of 604 ° C. and a softening point of 831 ° C.

  Moreover, the energy transmittance of this glass sample was measured. As a result of the measurement, the energy transmittance of the glass sample was 91.2%, indicating good permeability.

  Next, both surfaces of this glass sample were chemically strengthened.

  The chemical strengthening treatment was performed by immersing the entire glass sample in a molten salt of potassium nitrate without masking the glass sample.

  The treatment temperature (molten salt temperature) was 435 ° C., and the treatment time (immersion time) was 90 minutes.

  Thereby, the sodium ion was substituted by the potassium ion in both surfaces of the glass sample, and the glass sample which concerns on Example 2 was obtained.

  In the glass sample according to Example 2, since the chemical strengthening treatment was performed, the Na / Al ratio on the surface was at least smaller than 1.6 which is the Na / Al ratio before the chemical strengthening treatment.

(Example 3)
A glass sample made of soda lime glass having the composition shown in the column of “Example 3” in Table 1 (a glass sample according to Example 3) was prepared.

  As is apparent from the composition, the Na / Al ratio of the surface of this glass sample is 12.6.

  The thickness of the glass sample was 3.9 mm.

  The glass transition temperature (Tg) of this glass sample was 550 ° C., and the softening point was 733 ° C.

  Further, the energy transmittance of the glass sample according to Example 3 was measured. As a result of the measurement, the energy transmittance of the glass sample according to Example 3 was 90.3%.

  In each column of Table 1, the glass transition temperature, softening point, thickness, surface Na / Al ratio, and energy transmittance values of the glass samples according to Examples 1 to 3 are collectively shown. In addition, each value (a composition is included) of the glass sample which concerns on Example 2 is a value before implementing a chemical strengthening process.

(Evaluation)
Next, using the glass samples according to Examples 1 to 3, chemical durability was evaluated by the following method.

  Chemical durability was implemented by measuring each haze value after holding each glass sample in a high temperature and high humidity environment for a long time.

  In order to keep the glass samples according to Examples 1 to 3 in a high-temperature and high-humidity environment, each glass sample was placed in a thermostatic bath at a temperature of 65 ° C. and a relative humidity of 95%. After a predetermined period of time, each glass sample was taken out from the thermostat and the haze value was measured. The haze value was measured with a haze meter.

  In FIG. 3, the measurement result obtained in each glass sample is shown. In FIG. 3, the horizontal axis indicates the holding time, and the vertical axis indicates the haze value.

  FIG. 3 shows that in the glass samples according to Example 1 and Example 2, the haze value hardly changes even after 150 hours, and the haze value is maintained at a low value. On the other hand, in the glass sample according to Example 3, when the time exceeded about 70 hours, an increase in the haze value was observed, and thereafter, the haze value tended to increase remarkably with the holding time.

  From this result, the glass samples according to Example 1 and Example 2 have relatively good chemical durability, whereas the glass sample according to Example 3 does not show very good chemical durability. all right. Therefore, by using the glass samples according to Example 1 and Example 2 as the first glass plate for the reflector, the “burn” phenomenon of the first glass plate is significantly suppressed, and a chemically stable reflector is obtained. It is expected that it can be provided.

  The present invention can be used for cosmetic mirrors, optical system mirrors, solar thermal power generation devices, and the like.

DESCRIPTION OF SYMBOLS 100 Reflector 110 1st glass plate 112 1st surface 114 2nd surface 120 Adhesion layer 130 Reflective layer 140 Organic layer 150 2nd glass plate 152 3rd surface 154 4th surface 160 Light incident surface 170 Back surface 180 Incident light

Claims (9)

A first glass plate;
A reflective layer;
A second glass plate;
In this order,
The first glass plate has a first surface far from the reflective layer and a second surface near the reflective layer, and the second glass plate is far from the reflective layer. A third surface and a fourth surface closer to the reflective layer;
The sodium / aluminum ratio (Na / Al ratio) on the first surface of the first glass plate is higher than the sodium / aluminum ratio (Na / Al ratio) on the third surface of the second glass plate. A reflector characterized by being smaller.   2. The reflector according to claim 1, wherein a sodium / aluminum ratio (Na / Al ratio) on the first surface of the first glass plate is 2.0 or less.   3. The reflector according to 1 or 2, wherein the first surface of the first glass plate is subjected to a chemical strengthening treatment.   The reflector according to any one of claims 1 to 3, wherein the first glass plate has a thickness of 1 mm or less.   The reflector according to any one of claims 1 to 4, wherein the second glass plate has a thickness of 3 mm or more.   The said reflector has an organic layer between the said reflection layer and the said 2nd glass plate, The reflector as described in any one of Claim 1 thru | or 5 characterized by the above-mentioned.   The reflector according to any one of claims 1 to 6, wherein the reflector has a curved shape.   The reflector according to claim 7, wherein the reflector is a reflector for a solar thermal power generation apparatus.   The reflector according to any one of claims 1 to 8, wherein the reflector has a size of 1 m or more in length × 1 m or more in width.

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