JP2005266211A - Multilayer film reflecting mirror - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer film reflecting mirror, capable of providing the high reflectance of visible light and the high illuminance of reflected light by layering a small number of reflecting films. <P>SOLUTION: The multilayer film reflection mirror is constituted by forming, as metallic Si layers having a high refractive index, a plurality of high refractive index thin-film layers out of a multilayer reflection film formed by alternately layering the high refractive index thin-film layers and low-refractive index thin-film layers. For example, by forming the plurality of high-refractive index thin-film layers, existing from the 1st layer to the 8th layer of the multilayer reflection film as the metallic Si layers and the plurality of low-refractive index thin-film layers existing there as SiO<SB>2</SB>layers, high reflectance is obtained by the large difference in the refractive index between them. However, the Si layer has high absorption factor of the visible light. Then, for example, a TiO<SB>2</SB>layer as the high-refractive index thin-film layer and the SiO<SB>2</SB>layer as the low-refractive index thin-film layer are layered alternately and properly as an upper layer than the Si layer, so that the absorption of the visible light by the Si layer is reduced to such an extent that it can be neglected; and the high reflectance of the visible light and the high illuminance of the reflected light are obtained by a small number of layers as a whole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a reflecting mirror that reflects light of a specific wavelength, such as a cold mirror that reflects visible light and transmits infrared rays, and includes a plurality of reflective films formed on a reflective substrate surface. The present invention relates to a multilayer film reflecting mirror in which a refractive index thin film layer is formed of metal Si.

A cold mirror is known in which a multilayer reflective film is provided by alternately laminating a high refractive index thin film layer and a low refractive index thin film layer on the surface of a reflective substrate such as glass (see, for example, Patent Document 1). Further, for example, as a cold mirror used as a reflector of a lighting fixture such as a projector, as shown in FIG. 6, a TiO ₂ layer as a high refractive index thin film layer and a low refractive index thin film layer on a glass substrate B It is known to have a multilayer film 51 in which n layers (36 layers in FIG. 6) are alternately stacked with SiO ₂ layers.
Since such a cold mirror has to form a large number of thin films with different refractive indexes on the surface of the glass substrate, there are disadvantages that require a lot of work and time to manufacture, thereby reducing the cost. There is a request. In addition, there is a demand for reflectors with a high illuminance even in the market.
JP-A-8-292320

  The present invention has been made in view of the problems in the multilayer reflector such as the above-mentioned conventional cold mirror, and can provide a high visible light reflectance and reflected light illuminance by laminating a relatively small number of reflective films. The problem is to provide a reflector.

In the present invention, in order to solve the above problems, a plurality of high refractive index thin film layers of a multilayer reflective film formed by alternately laminating high refractive index thin film layers and low refractive index thin film layers are formed as metal Si layers. As shown in FIG.
For example, a plurality of high refractive index thin film layers of the first to eighth layers of the multilayer reflective film are metal Si layers, and the low refractive index thin film layer is a known low refractive index material layer such as a SiO ₂ layer. be able to.
Further, for example, a plurality of high refractive index thin film layers among the first to eighth layers of the multilayer reflective film are metal Si layers, a low refractive index thin film layer is an SiO ₂ layer, and a low refractive index after the ninth layer. The thin film layer can be an SiO ₂ layer, and the high refractive index thin film layer can be a TiO ₂ layer.

  In the present invention, since the plurality of high-refractive-index thin film layers of the multilayer reflective film are metal Si layers, the same visible light reflectivity due to the large refractive index difference between the combined low-refractive-index thin film layers, With the reflected light illuminance, the number of layers of the multilayer reflective film can be greatly reduced as compared with the conventional multilayer mirror.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a cold mirror showing an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a cold mirror showing another embodiment.

In FIG. 1, a multilayer reflective film 31 is formed on a glass substrate B by vapor deposition or sputtering. The multilayer reflective film 31 is composed of 28 reflective film layers, a metal Si layer is formed as the first, third, fifth and seventh layers, a SiO ₂ layer is formed as the _second , fourth, sixth and eighth layers, From the ninth layer to the 28th layer, TiO ₂ layers and SiO ₂ layers are alternately formed.

The conventional cold mirror in which the reflectance (spectral reflection characteristic) of the cold mirror formed in this way and the 36-layer multilayer reflective film 51 (alternately formed TiO ₂ layer and SiO ₂ layer) are formed as shown in FIG. A comparison with the reflectance is shown in FIG. According to this, it can be seen that the cold mirror of the above embodiment having 28 multilayer reflective films has substantially the same reflectance in the visible light region as the conventional cold mirror having 36 multilayer reflective films.

Further, as shown in FIG. 5, a 150 W halogen spot lamp 2, a sample 3, and an illuminometer sensor 4 are provided at fixed positions in the large sample chamber 1 of the spectrophotometer, and the sample 3 is irradiated from the halogen spot lamp 2. The table below shows the results of comparing the illuminance of the three samples by receiving the reflected light of the incident light on the illuminometer sensor 4. Here, sample No. 1 “Si-based 24 layers” is composed of Si layers as the first, third, fifth and seventh layers, SiO2 layers as the second, fourth, sixth and eighth layers, from the ninth layer to the twenty-fourth layer, A flat glass substrate in which TiO ₂ layers and SiO ₂ layers are alternately laminated, sample No. 2 “Si-based 28 layers” has Si layers, 2, 4, 6, and 8 layers as first, third, fifth, and seventh layers. As a SiO ₂ layer, a flat glass substrate in which a TiO ₂ layer and a SiO ₂ layer are alternately laminated from the ninth layer to the 28th layer, sample No. 3 “TiO ₂ system 40 layer” is a TiO ₂ layer and a SiO ₂ layer. Is a conventional flat glass substrate in which 40 layers are alternately laminated.

Samples Nos. 1 to 3 have almost the same average reflectance in a wavelength of 450 nm to 720 nm (visible light region). Sample No. 1 “Si type 24 layer” has lower illuminance than Sample No. 3 “TiO ₂ type 40 layer” (experimental results show that this corresponds to the illuminance of “TiO ₂ type 34 to 36 layer”) .) However, it can be seen that Sample No. 2 “Si 28-layer” has higher illuminance than Sample No. 3 “TiO ₂ 40-layer”. That is, in the “Si-based” multilayer reflective film having the first, third, fifth, and seventh Si layers, the illuminance of reflected light (approximately 1.02) is higher than that of the conventional “TiO ₂ -based” multilayer reflective film with a smaller number of film layers. Times) was confirmed. Even if the spectral reflection characteristics of the weak light that is grating of the spectrophotometer are equal, the illuminance of the reflected light is different in the strong light of the halogen lamp.

In the embodiment shown in FIG. 2, the multilayer reflective film 41 is formed on the glass substrate B by vapor deposition or sputtering. The multilayer reflective film 41 is composed of 28 reflective film layers, the first layer of which is a TiO ₂ layer, the _second , fourth, sixth, eighth and tenth layers are SiO ₂ layers, and the third, fifth, seventh and ninth layers are Si layers. Further, a TiO ₂ layer and a SiO ₂ layer are alternately formed from the 11th layer to the 28th layer.

  The reflectance of the cold mirror formed in this way was also almost equivalent to the cold mirror of the embodiment shown in FIG.

In general, a multilayer reflective film of a cold mirror is formed by depositing a high refractive index material layer (for example, TiO ₂ layer) and a low refractive index material layer (for example, SiO ₂ layer) alternately on the surface of a substrate such as a glass substrate. And has the property of reflecting visible light and transmitting infrared light. The combination of layers having a large difference in refractive index improves the reflectivity and can reduce the number of layers of the reflective film.

Since the refractive index of the Si layer is 3 to 3.5, which is larger than the refractive index of the TiO ₂ layer 2.3 to 2.4, it is possible to obtain a larger reflectance in combination with the SiO ₂ layer having a small refractive index. However, the Si layer has a difficulty in absorbing visible light.

When a metal Si layer is formed on the substrate to form an absorption film by vapor deposition or sputtering, visible light is absorbed, but infrared is hardly absorbed. Therefore, as shown in FIG. 3, the Si film has a property of transmitting almost infrared light. This characteristic is almost equivalent to TiO ₂ as a high refractive index material. Visible light cannot be ignored when used for transmission purposes like a filter, but when used as a reflecting mirror, TiO ₂ and SiO ₂ that absorb less in the upper layer as in the above embodiment. If the alternating layers such as these are formed and most of the visible light is reflected thereby, the influence of absorption by the Si film can be reduced to a negligible level, and a high reflectance as a whole can be obtained.

  That is, in FIG. 3, the Si single layer mirror has an absorption of about 9% at a wavelength of 600 nm, for example, but in FIG. 4, the cold mirror having four Si layers formed has an effect of 600 nm on the upper layer. And having a reflectance of 95% or more at the above wavelength. Although the refractive index of the Si film is about 3.5 with respect to the wavelength of 600 nm, the reflection film configuration of the above embodiment uses the high refractive index that is an advantage of the Si film and reduces the absorption that is a disadvantage. .

It should be noted that the combination of alternately laminated TiO ₂ layers and SiO ₂ layers formed in the upper layer is not limited to this, and is replaced with other known combinations of various high refractive index materials and low refractive index materials. be able to.

  The present invention provides a cold mirror suitable for use as, for example, a reflector of a projector lighting fixture.

It is a schematic sectional drawing of the cold mirror which shows the Example of this invention. It is a schematic sectional drawing of the cold mirror which shows another Example. It is a graph which shows the optical absorptivity spectral characteristic of Si single layer film. It is a graph which shows the comparison of the reflectance of an Example and a prior art example. It is explanatory drawing which shows the method of the comparative test of the reflected light illumination intensity of an Example and a prior art example. It is a schematic sectional drawing of the conventional cold mirror.

Explanation of symbols

31, 41 Multilayer reflective film B Reflective substrate

Claims (4)

  A reflecting mirror in which a high-refractive-index thin film layer and a low-refractive-index thin-film layer are alternately laminated on a reflective substrate surface to provide a multilayer reflective film, and the plurality of high-refractive-index thin film layers are metal Si layers A multilayer film reflector characterized by.   The plurality of high-refractive-index thin film layers among the first to eighth layers of the multilayer reflective film are metal Si layers, and the ninth and subsequent layers are alternating with other high-refractive-index thin film layers and low-refractive-index thin film layers. The multilayer reflector according to claim 1, wherein the multilayer reflector is a laminate. The plurality of high refractive index thin film layers of the first to eighth layers of the multilayer reflective film are metal Si layers, and the low refractive index thin film layers are SiO ₂ layers. 2. A multilayer film reflector according to 1. The plurality of high refractive index thin film layers among the first to eighth layers of the multilayer reflective film are metal Si layers, the low refractive index thin film layers are SiO ₂ layers, and the low refractive index thin films after the ninth layer. 3. The multilayer film reflector according to claim 1, wherein the layer is a SiO ₂ layer, and the high refractive index thin film layer is a TiO ₂ layer.

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