JP2011203359A - Reflector using dielectric layer and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflector with a curved surface having a high enhanced reflection effect.SOLUTION: A dielectric layer 23 comprising a plurality of layers disposed on a metal reflection surface 22 in a curved surface shape has a distribution of film thickness in accordance with an incident angle of a beam coming from a light source 10. The layer is formed in such a manner that the film thickness is large in an area 5 where the incident angle is large and the film thickness is small in an area 2 where the incident angle is small. For example, the film thickness L is constant in the direction of the major axis 6 of the beam coming from the light source 10. The dielectric layer has a structure of an enhanced reflection film.

Description

  The present invention relates to a reflector using a dielectric multilayer film.

  By laminating a dielectric multilayer film having a predetermined configuration called a reflection-increasing film on a reflector using a metal thin film layer, the reflectance can be increased as compared with the metal thin film layer alone. In a general high reflection film, the film thicknesses of the high refractive index thin film layer and the low refractive index thin film layer are set to λ / 4n (λ is the wavelength of incident light and n is the refractive index of the thin film), respectively. Patent Document 1 discloses that the reflectance can be further improved by setting the thickness of the low refractive index thin film layer in contact with the metal thin film layer to a specific range thinner than λ / 4n. Further, on page 4 of Patent Document 1, although the reason is not clear, the reflector of Patent Document 1 can realize a higher reflectance than that of a single metal layer film in almost all wide wavelength regions of visible light. It is stated that it is possible.

  Further, Patent Document 2 discloses disposing an increased reflection film on the surface of the micromirror. Patent Document 3 discloses a method of forming an enhanced reflection film by ion-assisted vapor deposition.

  On the other hand, in Patent Document 4, in an optical apparatus using a lens with a small radius of curvature for short wavelength light, such as an exposure apparatus, the optical thin film (reflective film or antireflection film) on the lens surface has a film thickness unevenness. Since the optical performance cannot be sufficiently exhibited, a method for uniformly forming a film is disclosed.

Republished WO2004 / 074887 JP 2010-27776 A JP 2008-260978 A JP 2007-93894 A

  According to the inventors, it has been found that when monochromatic light is reflected by a curved reflector, the effect of increasing the reflection is reduced as compared with a planar reflector. For example, when a planar reflector provided with a predetermined configuration of a reflective reflector is measured for an increased reflection effect at a wavelength of 550 nm by increasing the reflected light flux for a single metal thin film layer, an increase in reflected light flux of about 6% is obtained. In the case of a curved reflector having the same reflective reflection film, only about 3% can be obtained.

  This is because the conventional reflection-enhancing film has a structure that enhances the reflection enhancement effect in a flat reflector as in Patent Documents 1 and 2, and therefore the influence of the shape of the reflection reflector on the reflection enhancement effect is considered in the case of a curved reflector. It is presumed that this is not the case. Conventionally, as described in Patent Document 3, it has been desired to form a uniform dielectric multilayer film on a curved optical element.

  An object of the present invention is to provide a curved reflector exhibiting a high reflection enhancement effect.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a reflector comprising a curved metal reflecting surface and a plurality of dielectric layers laminated on the metal reflecting surface, The dielectric layer is provided with a structure in which the film thickness in the principal axis direction of the light beam incident from the light source is constant.

  According to a second aspect of the present invention, there is provided a reflector comprising a curved metal reflecting surface and a dielectric layer composed of a plurality of layers laminated on the metal reflecting surface, wherein the dielectric layer is a light source The film thickness is distributed according to the incident angle of the light beam incident from the above, and the structure in which the film thickness is formed in the area where the incident angle is large and the film thickness is formed in the area where the incident angle is small is provided. .

  For the dielectric layer, for example, an increased reflection film is used. For example, a metal reflecting surface having a shape that bends light from a light source at a right angle is used.

  According to a third aspect of the present invention, there is provided a method for manufacturing a reflector including a step of forming a dielectric layer on a curved metal reflecting surface by a vapor deposition method, wherein the film is grown by the vapor deposition method. There is provided a method for forming a dielectric layer by aligning the direction in which the light is incident and the principal axis direction of light incident on the metal reflecting surface.

  According to the present invention, since the film thickness of the dielectric layer on the curved metal reflecting surface is set according to the incident direction of the light beam from the light source, the optical characteristics of the dielectric layer are not exhibited depending on the incident angle of light. The phenomenon can be prevented, and a predetermined optical characteristic, that is, an enhanced reflection effect can be obtained on the entire surface of the dielectric layer. Thereby, a curved reflector having a high reflection enhancement effect can be provided.

FIG. 3 is an explanatory diagram showing the configuration of the curved reflector 20 and the light emitting element 10 according to the embodiment and the light incident direction. Explanatory drawing which shows the structure of the curved surface reflector of a comparative example, and a light emitting element, and the incident direction of light. (A) And (b) Explanatory drawing which shows the manufacturing method of the dielectric multilayer film of the curved reflector of a comparative example, (c) Explanatory drawing which shows the manufacturing method of the dielectric multilayer film of the curved reflector of embodiment.

  Hereinafter, an embodiment of the present invention will be described.

  In the present invention, considering the fact that the angle of incidence of light on the reflector surface differs depending on the positional relationship with the light source, the curved reflector increases the reflection enhancement effect of the curved reflector. That is, the effect of increasing reflection using a dielectric thin film depends on the angle of incident light, and as the light incident angle increases, the central wavelength of the increased reflection shifts to a shorter side. The thickness of the dielectric thin film is increased on the reflector surface having a large incident angle. As a result, even when a light source close to monochromatic light such as an LED is used, increased reflection is caused on the entire surface of the curved reflector.

  Hereinafter, the structure of the light emitting device of this embodiment will be described with reference to FIG.

  As shown in FIG. 1, the light emitting device includes a light emitting element 10 and a curved reflector 20. Here, the light emitting element 10 is arranged substantially horizontally with the lower end of the curved reflector 20. The curved reflector 20 has a structure in which a metal film 22 and a dielectric multilayer film 23 are laminated on a curved surface of a casing 21 having a concave curved surface. The curved surface shape of the housing 21 is such that light emitted radially from the light emitting element 10 is directed to a direction of approximately 90 ° with respect to the main axis 6 of the emitted light of the light emitting element 10 by the metal layer 22 and the dielectric multilayer film 23. Designed to be reflected.

  The metal layer 22 is formed of a material having a high reflectance such as Al or Ag. The dielectric multilayer film 23 is a structure in which a low refractive index layer disposed on the metal layer 22 side and a high refractive index layer disposed thereon are combined, and one or more sets thereof are laminated. Exhibits an enhanced reflection effect on light. For example, a silicon dioxide film or an aluminum oxide film is used for the low refractive index layer. For the high refractive index layer, for example, a titanium oxide or zirconium oxide layer having a higher refractive index than that of the low refractive index layer is used.

  The low-refractive index layer and the high-refractive index layer exhibit reflectivity that is amplified more than the reflectivity of the metal layer 22 alone because the light beams reflected at the respective interfaces interfere with each other and strengthen each other.

  The film thickness of the dielectric multilayer film 23 will be described. In the present invention, the film thickness in the direction perpendicular to the substrate surface is increased in a region where the incident angle when light radiated from the light emitting element 10 is incident on the dielectric multilayer film 23 is large. In order to realize this, specifically, the film thickness L of the dielectric multilayer film 23 in the direction parallel to the main axis 6 of the light emitted from the light-emitting element 10 is different in each part (entire surface) of the curved dielectric multilayer film 23. It was made constant.

  In this case, as the incident angle to the dielectric multilayer film 23 increases in the order of the regions 2, 3, 4 and 5 as shown in FIG. 1, the film thickness in the direction perpendicular to the substrate surface also increases in order. The central wavelength of the increased reflection can be kept constant over a wide area of the dielectric multilayer film 23, and the increased reflection effect can be exhibited.

  On the other hand, as a comparative example, as shown in FIG. 2, when a curved reflector 30 having a uniform dielectric multilayer film 33 is used, the incident angle to the dielectric multilayer film 23 is a region. Even if it increases in the order of 12, 13, 14, and 15, the film thickness is constant. Therefore, the dielectric multilayer film 23 shifts the central wavelength of the increased reflection to the short wavelength side. Since the emission wavelength of the light emitting element 10 is constant, it is not possible to obtain the effect of increasing reflection only in a part of the region, and the overall reflectance cannot be increased.

  The curved low-refractive index layer and high-refractive index layer of the dielectric multilayer film 23 of the present embodiment are, as described above, the film thickness L in the direction parallel to the main axis 6 of the emitted light of the light emitting element 10 (uniform film thickness growth direction) The film thickness L) is constant in each part, but this film thickness L is determined as follows. That is, the film thickness L in the direction parallel to the main axis 6 of the emitted light of the light emitting element 10 depends on the condition of the increased reflection film, d = λ / 4n (λ: the emitted light wavelength of the light emitting element 10, n: refractive index). For a fixed d, a value satisfying L = d / (cos θ) (here, θ = 45 °) is set. Alternatively, the thickness d is set so as to satisfy L = d / (cos 45 °) with respect to the film thickness d satisfying the conditions of a known flat reflection increasing film described in Patent Document 1 or the like. Note that θ = 45 ° is a reflector having a reflection angle δ = 90 °, in which the curved reflector 20 of the present embodiment reflects light from the light emitting element 10 in the direction of 90 ° with respect to the main axis 6. This is because the central angle θ = δ / 2 = 45 ° of the incident angle to the dielectric multilayer film 23. Therefore, θ is set to θ = δ / 2 according to the reflection angle δ of the curved reflector 20.

  As a method for forming the dielectric multilayer film 23 having the above-described film thickness, vapor phase growth methods such as vapor deposition, sputtering, and ion plating can be used. Specifically, when a flat film formation target (substrate) is arranged, a direction (uniform film growth direction) 41 in which the film grows with a uniform film thickness is confirmed, and this uniform film growth direction is a curved surface. A method of forming a film by arranging the casing 21 so as to coincide with the direction of the main axis 6 of the emitted light of the light emitting element 10 of the reflector 20 is used. Thereby, the dielectric multilayer film 23 having a changed film thickness can be formed relatively easily.

  Actually, as shown in FIGS. 3A, 3 </ b> B, and 3 </ b> C, the direction of the casing 21 is set so that the direction of the main axis 6 of the emitted light of the light emitting element 10 is in the uniform film thickness growth direction 41. The dielectric multilayer film 23 was formed in each of the vertical, 45 ° and parallel directions, and a sample of the curved reflector 20 was prepared. The sample of FIG. 3C is a dielectric multilayer film in which the uniform film growth direction 41 and the direction of the main axis 6 are parallel, and the film thickness L in the uniform film growth direction 41 of the structure of FIG. 23 was deposited. In the sample of FIG. 3A, the change in the thickness of the dielectric multilayer film 23 was opposite to that of the sample of FIG. 3C of this embodiment. In the sample of FIG. 3B, the change in film thickness of the dielectric multilayer film 23 was small.

  When the light from the light emitting element 10 is incident on these and the amount of the reflected light beam is measured, the increase rate of the reflected light beam is 1% in the sample of FIG. In the sample of (b), it was 3%, whereas in the sample of FIG.

  From these facts, the curved reflector having the dielectric multilayer film 23 whose thickness in the direction perpendicular to the substrate surface and the film forming method of the present embodiment are effective for enhancing the reflection enhancement effect. Was confirmed.

  In the present invention, since the effect of increasing the reflection of the curved reflector can be enhanced, a light emitting device with a large amount of light can be obtained by combining with a light source such as a light emitting element. Such a light emitting device is suitable, for example, as a headlamp for a vehicle, a backlight device of a liquid crystal display device, a light source of a projector device, an illumination device such as indoor / outdoor illumination. In addition, the use of the curved reflector of the present invention is not limited to the light emitting device, and can be applied to all devices using the curved reflector.

  Further, the present invention has been described with respect to the curved reflector provided with the dielectric multilayer film. However, the present invention is not limited to the reflector and can be applied to all products using the dielectric multilayer film formed on the curved surface.

  In the above-described embodiment, the case where a light emitting element is used as a light source has been described. However, the light source of the present invention is not limited to a light emitting element that emits monochromatic light, and is a light source that is not monochromatic light, or a lamp that is not a light emitting element. It is of course possible to use a light source such as

  2 to 5 ... region, 6 ... main axis of emitted light, 10 ... light emitting element, 20 ... curved reflector, 21 ... enclosure, 22 ... metal layer, 23 ... dielectric multilayer film, 33 ... dielectric multilayer film, 41 ... uniform film Thick growth direction

Claims (5)

A curved metal reflective surface, and a dielectric layer composed of a plurality of layers laminated on the metal reflective surface,
The dielectric layer has a constant film thickness in the principal axis direction of light incident from a light source. A curved metal reflective surface, and a dielectric layer composed of a plurality of layers laminated on the metal reflective surface,
The dielectric layer has a thickness distributed according to an incident angle of light incident from a light source, and the region having a large incident angle is thick and the region having a small incident angle is thin. Reflector characterized by being.   3. The reflector according to claim 1, wherein the dielectric layer is a reflection-enhancing film. 4.   4. The reflector according to claim 1, wherein the metal reflecting surface has a shape that bends light from a light source at a right angle. 5. A reflector manufacturing method including a step of forming a dielectric layer on a curved metal reflecting surface by vapor deposition,
A method of manufacturing a reflector, wherein the dielectric layer is formed by aligning a direction in which a film is grown by the vapor phase growth method with a principal axis direction of light incident on the metal reflecting surface.

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