JP2007140201A - Reflector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflector having a long product life by suppressing degeneration of a reflecting film. <P>SOLUTION: The reflector 1 comprises a substrate 10, a reflecting film 12 and an oxide thin film 13. The reflecting film 12 is formed on the substrate 10. The reflecting film 12 is a film, having silver as the major constituent. The oxide thin film 13 is formed on the reflecting film 12 so as to cover the reflecting film 12. The oxide thin film 13 substantially comprises bismuth oxide or neodymium oxide. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reflector. In detail, it is related with the reflector provided with the reflecting film which has silver as a main component.

In recent years, reflectors are widely used in optical devices such as copiers, cameras, projectors, and backlight units. From the viewpoint of improving the light utilization efficiency in these optical devices, a reflector having a high light reflectance is required. As a reflector having a high reflectance, for example, Patent Document 1 discloses a reflector using a silver thin film.
JP 2004-272245 A

  However, silver has the property of being relatively easy to aggregate. In particular, the cohesiveness is further enhanced in a high temperature atmosphere (for example, 80 ° C. or higher). When silver agglomeration occurs in a silver thin film, a phenomenon such as a crack in the silver thin film occurs, and there is a problem that the reflection performance of the silver thin film is lowered.

  Further, the silver thin film has a problem that it is relatively easily oxidized. When a silver thin film is oxidized, there exists a problem that the light reflectivity of a silver thin film falls.

  As described above, the reflector using the conventional silver thin film has problems that the characteristic change with time is large and the product life is short.

  This invention is made | formed in view of the point which concerns, and the place made into the objective is to provide a reflector with a long product life.

  As a result of sincere research, the present inventors have found that the aggregation of silver in a silver thin film can be suppressed by laminating an oxide film substantially consisting of bismuth oxide or neodymium oxide on the silver thin film, and the present invention. It came to make.

  That is, the reflector according to the present invention includes a base material, a reflective film, and an oxide thin film. The reflective film is formed on the substrate. The reflective film is a film mainly composed of silver. The oxide thin film is formed on the reflective film so as to cover the reflective film. The oxide thin film is substantially made of bismuth oxide or neodymium oxide.

  According to the present invention, since the modification of the reflective film is suppressed, a reflector having a long product life can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a reflector 1 according to the first embodiment.

  The reflector 1 according to the first embodiment includes a substrate 10, an adhesion film 11, a reflection film 12, an oxide thin film 13, and a protective film 14.

  The base material 10 may be flat, for example, as shown in FIG. Moreover, the plate shape in which one surface was formed in the concave surface or the convex surface may be sufficient, and spherical shape, ellipsoidal shape, cubic shape, cylindrical shape, prismatic shape, etc. may be sufficient. The substrate 10 is made of, for example, glass (specifically, for example, quartz glass, silicate glass, borosilicate glass, etc.), resin (eg, PET resin, PC resin, etc.), metal (stainless steel, aluminum, etc.). Etc.), ceramics or the like.

  The reflective film 12 is formed on the base material 10. The reflective film 12 is a film mainly composed of silver. That is, the reflective film 12 is formed of silver or an alloy of silver and another metal. Specifically, the silver content of the reflective film 12 is preferably 70% or more. More preferably, it is 90% or more and 99% or more. More preferably, it is 99.9% or more. The higher the silver content, the higher the reflectance of the reflective film 12 tends to be. In addition, it is preferable that the film thickness of the reflective film 12 is 100 nm or more from a viewpoint of obtaining a high reflectance. On the other hand, from the viewpoint of production cost and throughput, it is preferably 200 nm or less.

  The reflective film 12 may be formed directly on the substrate 10. When the adhesion between the reflective film 12 and the substrate 10 is low, an adhesion film 11 may be further formed between the substrate 10 and the reflective film 12, for example, as shown in FIG. By doing so, peeling of the reflective film 12 from the base material 10 can be suppressed.

  The material of the reflective film 12 can be appropriately determined in consideration of the material of the base material 10, but may be formed of chromium, for example. Moreover, the film thickness of the reflective film 12 is not particularly limited, but may be, for example, 1 nm or more and 10 nm or less.

  On the other hand, an oxide thin film 13 is formed on the reflective film 12 so as to cover the reflective film 12. The oxide thin film 13 is substantially made of bismuth oxide or neodymium oxide. By providing the oxide thin film 13 substantially made of bismuth oxide or neodymium oxide, aggregation of silver in the reflective film 12 can be suppressed. Therefore, it is possible to realize the reflector 1 having a small reflectance change with time and a long product life.

  From the viewpoint of realizing a high reflectance of the reflector 1, the oxide thin film 13 preferably has a high light transmittance. For this reason, it is preferable that the oxide thin film 13 is relatively thin. Specifically, it is preferably 0.1 nm or more and 5 nm or less. More preferably, it is 0.5 nm or more.

  FIG. 2 is a graph showing the reflectance when an oxide thin film (specifically, a bismuth thin film) having a thickness of 10 nm is formed in the form of a pure silver film.

  FIG. 3 is a graph showing the reflectance when an oxide thin film (specifically, a bismuth thin film) having a thickness of 1 nm is formed in the form of a pure silver film.

  As shown in FIG. 2, when the thickness of the oxide thin film is 10 nm or more, the light reflectance on the short wavelength side tends to be lower than that of the pure silver film. On the other hand, as shown in FIG. 3, when the film thickness of the oxide thin film is 1 nm, substantially the same light reflectance as that of the pure silver film is realized on the short wavelength side. For this reason, the thickness of the oxide thin film 13 is particularly preferably 1 nm or less.

  Further, by providing the oxide thin film 13 on the reflective film 12, the reflective film 12 can be shielded from the outside air (specifically, oxygen, moisture, chloride ions, sulfurous acid gas, etc. contained in the outside air). Therefore, the chemical reaction change (oxidation etc.) of the reflective film 12 can be suppressed. Therefore, it is possible to realize the reflector 1 that has a smaller change in reflectance over time and a longer product life.

  As described above, the oxide thin film 13 is a very thin film and is relatively easily scratched. For this reason, the protective film 14 may be further formed on the oxide thin film 13 so as to cover the oxide thin film 13. The protective film 14 preferably has a relatively high hardness. Specifically, the protective film 14 can be formed of an inorganic dielectric material (which may be amorphous or crystalline). Moreover, it is preferable that the protective film 14 is a thing with comparatively high light transmittance from a viewpoint of implement | achieving the high reflectance of the reflector 1. FIG. From the above viewpoints, the protective film 14 is particularly preferably formed of, for example, one or more compounds selected from silicon oxide, magnesium fluoride, zircon oxide, titanium oxide, and aluminum oxide. preferable. Further, the protective film 14 may be formed by stacking a plurality of films. In that case, the plurality of films may be films having the same composition, or may have different compositions from each other.

  Next, a method for manufacturing the reflector 1 according to Embodiment 1 will be described.

  First, the adhesion film 11 is formed on the substrate 10. A reflective film 12 is formed on the adhesion film 11. The adhesion film 11 and the reflection film 12 can be formed using, for example, a sputtering method or a vapor deposition method (for example, an ion assist vapor deposition method) in a reduced-pressure atmosphere. In particular, the reflective film 12 is preferably performed in the absence of oxygen.

  Next, an oxide thin film 13 is formed on the reflective film 12. For example, when the oxide thin film 13 made of bismuth oxide is formed, it is formed by first forming a bismuth thin film in a reduced-pressure atmosphere in the absence of oxygen, and then bringing oxygen gas into contact with the formed bismuth thin film. Can do. Specifically, the oxide thin film 13 can be obtained by placing the formed bismuth thin film in an atmosphere having an oxygen partial pressure of about 8 mPa to 10 mPa for 1 to several minutes. Then, the protective film 14 can be formed on the formed oxide thin film 13 by, for example, sputtering or vapor deposition, and the reflector 1 can be completed. From the viewpoint of forming a dense protective film 14, it is preferable to perform ion assist simultaneously during the formation of the protective film 14. By providing the dense protective film 14 by performing ion assist, it is possible to realize the reflector 1 having higher durability and longer product life.

(Embodiment 2)
FIG. 4 is a cross-sectional view of the reflector 2 according to the second embodiment.

  The reflector 2 according to the second embodiment has the same configuration as that of the reflector 1 according to the first embodiment except that the reflector 2 further includes a high refractive index film 15. Here, the high refractive index film 15 will be described in detail. In the description of the second embodiment, components having substantially the same function are described with reference numerals common to the first embodiment, and the description thereof is omitted.

  In the second embodiment, the protective film 14 is formed of a film having a relatively low refractive index, and the high refractive index film 15 having a higher refractive index at the d-line than the protective film 14 is provided on the protective film 14. ing. In this way, by stacking the protective film 14 having a relatively low refractive index and the high refractive index film 15 having a relatively high refractive index on the reflective film 12, the reflector 2 having a higher light reflectance can be realized. Can do. Further, from the viewpoint of increasing the light reflectance, a plurality of protective films 14 and a plurality of high refractive index films 15 may be alternately stacked.

  Further, from the viewpoint of further increasing the light reflectivity, the film thickness of the protective film 14 is preferably equal to a value obtained by dividing the wavelength of light reflected by the reflector 2 by four times the refractive index of the protective film 14. The film thickness of the high refractive index film 15 is preferably equal to a value obtained by dividing the wavelength of light reflected by the reflector 2 by four times the refractive index of the high refractive index film 15.

  Further, it is preferable that the refractive index difference between the protective film 14 and the high refractive index film 15 is large. Specifically, the refractive index difference between the protective film 14 and the high refractive index film 15 is preferably 0.3 or more. More specifically, the refractive index of the protective film 14 is particularly preferably 1.4 or more and 1.6 or less. For example, the protective film 14 is preferably formed of silicon oxide, magnesium fluoride, or the like. On the other hand, the refractive index of the high refractive index film 15 is preferably 1.9 or more. For example, the high refractive index film 15 can be formed of titanium oxide, tantalum oxide, or the like.

  The high refractive index film 15 also has a function as a further protective film for the reflective film 12. Therefore, by providing the high refractive index film 15, the reflector 1 having a longer product life can be realized.

  As described above, since the reflector according to the present invention has high durability, the copying machine, camera, projector (liquid crystal projector, DLP projector, etc.), liquid crystal display (specifically, the back of the liquid crystal display). Light).

1 is a cross-sectional view of a reflector 1 according to Embodiment 1. FIG. It is a graph showing the reflectance at the time of forming an oxide thin film (specifically, bismuth thin film) with a film thickness of 1 nm in a pure silver film shape. It is a graph showing the reflectance at the time of forming an oxide thin film (specifically, bismuth thin film) with a film thickness of 1 nm in a pure silver film shape. 6 is a cross-sectional view of a reflector 2 according to Embodiment 2. FIG.

Explanation of symbols

1, 2 Reflector
2 This embodiment
10 Base material
11 Adhesive film
12 Reflective film
13 Oxide thin film
14 Protective film
15 High refractive index film

Claims (8)

A substrate;
A reflective film formed on the base material, the main component of which is silver;
On the reflective film, an oxide thin film formed so as to cover the reflective film and substantially consisting of bismuth oxide or neodymium oxide,
With reflector. The reflector according to claim 1,
The oxide thin film is a reflector having a thickness of 0.1 nm to 5 nm. The reflector according to claim 1,
A reflector further comprising an adhesion film formed between the base material and the reflective film. The reflector according to claim 1,
A reflector further comprising a protective film formed on the oxide thin film so as to cover the oxide thin film. The reflector according to claim 4,
The protective film is a reflector that is substantially formed of a dielectric material. The reflector according to claim 5, wherein
The dielectric material is a reflector made of one or more compounds selected from silicon oxide, magnesium fluoride, zircon oxide, aluminum oxide, and titanium oxide. The reflector according to claim 4,
A reflector further comprising a high refractive index film formed on the protective film and having a higher refractive index at the d-line than the protective film. The reflector according to claim 7,
The high refractive index film is a reflector substantially made of titanium oxide or tantalum oxide.

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