TWI656365B - Wavelength selection filter and light irradiation apparatus - Google Patents

Abstract

The present invention provides a wavelength selective filter and a light irradiation device which can suppress a large increase in the number of films and which can reduce the wavelength shift amount of the spectral light transmission characteristics when the light is obliquely incident on the film surface.

The wavelength selective filter 4 of the present invention has a configuration in which a first laminate including the first dielectric multilayer film G1 and the second dielectric multilayer film G2 and a third dielectric layer are provided on the transparent substrate 21. The second laminate of the electric multilayer film and the fourth dielectric multilayer film, and the first and third dielectric multilayer films G1 and G3 have the first refractive index material 22 having the first refractive index and the first laminate The second refractive index material 23 having the second refractive index having a small refractive index is alternately laminated, and the second and fourth dielectric multilayer films G2 and G4 have the third refractive index material 24 having the third refractive index and having The fourth refractive index material 25 having a fourth refractive index smaller than the third refractive index is alternately laminated, and the first refractive index is different from the third refractive index, and the second refractive index is different from the fourth refractive index.

Description

Wavelength selective filter and light irradiation device

The present invention relates to a wavelength selective filter and a light irradiation device in which a plurality of layers of a film are laminated.

Conventionally, a light irradiation device has been used for photohardening of a resin or an adhesive, and the light irradiation device uses a mercury lamp or a metal halide lamp. The light emitted by the mercury lamp or the metal halide lamp emits light of an unnecessary wavelength which causes some damage to the object to be irradiated, in addition to light of a wavelength required for hardening the resin or the adhesive, and therefore, is used in a light irradiation device. Wavelength selection filter. In the wavelength selective filter, a colored glass colored with a metal is used as a representative, but the transmittance is lowered due to the effect of ultraviolet rays from the lamp. On the other hand, it is conceivable to use a wavelength selective filter in which a dielectric multilayer film is laminated on a transparent substrate, but the wavelength selective filter including the dielectric multilayer film has an incident angle dependency on the transmission characteristics, and the light is incident. The larger the incident angle, the more the penetration wavelength region is shifted toward the short wavelength side. Therefore, there is known a technique of reducing the wavelength shift amount of the spectral light transmission characteristic when the light is obliquely incident on the film surface by using a wavelength selective filter including a dielectric multilayer film. The multilayer film is formed by alternately laminating a layer of a high refractive index material and a layer of a material having a slightly lower refractive index than the layer on a transparent substrate (see, for example, Patent Document 1).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1]

Japanese Patent Laid-Open No. 2008-20563

However, in the above-described conventional configuration, there is a problem that the number of layers of the entire film is greatly increased if the wavelength shift amount is to be reduced. The present invention has been made in view of the above circumstances, and an object thereof is to provide a wavelength selective filter capable of suppressing a large increase in the number of films and capable of reducing a wavelength shift amount of spectral separation characteristics when obliquely incident on a film surface, and Light irradiation device.

In order to achieve the above object, a wavelength selective filter of the present invention is characterized in that a first laminate including a first dielectric multilayer film and a second dielectric multilayer film and a third dielectric layer are provided on a transparent substrate. The second multilayer body of the multilayer multilayer film and the fourth dielectric multilayer film, wherein the first and third dielectric multilayer films have a first refractive index material having a first refractive index and have a smaller refractive index than the first refractive index The second refractive index material having the second refractive index is alternately laminated, and the second and fourth dielectric multilayer films have a third refractive index material having a third refractive index and having a smaller refractive index than the third refractive index. The fourth refractive index material having the fourth refractive index is alternately laminated, and the first refractive index is different from the third refractive index, and the second refractive index is different from the fourth refractive index.

In the above configuration, the first layered body and the second layered body may be formed on different surfaces of the transparent substrate.

In the above configuration, the first refractive index and the second refractive index may be The difference between the first average refractive index and the third refractive index and the average of the fourth refractive index, that is, the second average refractive index, is a value at which the wavelength shift amount is equal to or less than a predetermined value.

In the above configuration, the first laminate may constitute a narrow band pass filter, and the second laminate may constitute a broadband pass filter.

In the above configuration, the first average refractive index which is an average value of the first refractive index and the second refractive index, and the second average refractive index which is an average value of the third refractive index and the fourth refractive index may be The difference is set to 0.1~0.6.

In the above configuration, the refractive index of the transparent substrate may be 1.45 to 1.53, the first refractive index is 2.26 to 2.40, the second refractive index is 1.38 to 1.50, and the third refractive index is 2.42 to 2.70 for light having a wavelength of 500 nm. The fourth refractive index is 1.58 to 2.00.

In the above configuration, the first refractive index material and/or the third refractive index material may be adjacent to the transparent substrate.

In the above configuration, the first layered body and the second layered layer may be on one or both sides of the transparent substrate, and the first portion of the first layered body and the second layered body may be the first The rate material is adjacent to the fourth refractive index material or the second refractive index material is adjacent to the third refractive index material.

In the above configuration, the fourth refractive index may be higher than the second refractive index and the third refractive index may be higher than the first refractive index, and the first laminated body may be sequentially laminated from the transparent substrate. The dielectric multilayer film and the first dielectric multilayer film are formed, and the second multilayer body may be formed by sequentially laminating a third dielectric multilayer film and a fourth dielectric multilayer film from the transparent substrate.

The light irradiation device of the present invention is characterized in that the light source is housed in the casing The wavelength selective filter is disposed in the light exit opening of the housing.

According to the present invention, it is possible to suppress a large increase in the number of films, and it is also possible to reduce the wavelength shift amount of the spectral light transmission characteristics when the light is obliquely incident on the film surface.

1‧‧‧UV irradiation device (light irradiation device)

2‧‧‧Workpiece

2A‧‧‧Irradiated area

3‧‧‧ illuminator

4‧‧‧Wavelength Selection Filter

10‧‧‧ illuminator housing

11‧‧‧ lights

12‧‧‧Mirror

21‧‧‧Transparent substrate

22‧‧‧1st high refractive index material (first refractive index material)

23‧‧‧1st low refractive index material (second refractive index material)

24‧‧‧2nd high refractive index material (third refractive index material)

25‧‧‧2nd low refractive index material (4th refractive index material)

G1‧‧‧1st dielectric multilayer film

G2‧‧‧2nd Dielectric Multilayer Film

G3‧‧‧3rd Dielectric Multilayer Film

G4‧‧‧4th Dielectric Multilayer Film

K‧‧‧Light

L‧‧‧ length

The first layered body of the L1‧‧‧ narrow band pass type

The second layer of the L2‧‧‧ broadband type

M‧‧‧ interval

n _H1 ‧‧‧first refractive index (first high refractive index)

n _L1 ‧‧‧2nd refractive index (first low refractive index)

n _H2 ‧‧‧3rd refractive index (2nd high refractive index)

n _M ‧‧‧4th refractive index (2nd low refractive index)

W‧‧‧Width

Fig. 1 is a perspective view showing a schematic configuration of an ultraviolet irradiation device according to an embodiment of the present invention.

Fig. 2 is a front view showing a schematic configuration of an ultraviolet irradiation device.

Fig. 3 is a view schematically showing a wavelength selective filter.

Fig. 4 is a graph showing the spectral transmittance of the wavelength selective filter, wherein (A) shows the case of the wavelength selective filter of the present embodiment, and (B) shows the case of the conventional wavelength selective filter.

Fig. 5 is a graph showing the spectral transmittance of the wavelength selective filter, wherein (A) shows a case where NBP type and BBP type laminated bodies are formed on both surfaces of the transparent substrate, and (B) shows one side of the transparent substrate. In the case where an NBP type laminated body is formed, (C) shows a case where a BBP type laminated body is formed on one surface of a transparent substrate.

Fig. 6 is a graph showing the spectral transmittance of a wavelength selective filter for forming a multilayer film in the reverse order of the example of Table 1, (A) showing the formation of a double mask, and (B) showing a single mask of only NBP. In the case of formation, (C) shows the case where only a single mask of BBP is formed.

Fig. 7 is a graph showing the spectral transmittance of a wavelength selective filter in which a high refractive index material is used, wherein (A) shows the formation of a double mask, and (B) shows the formation of a single mask of only NBP. (C) shows the case where only a single mask of BBP is formed.

Figure 8 is a view showing the splitting of the wavelength selective filter of the low refractive index material. A graph of the transmittance, (A) shows the formation of a double mask, (B) shows the formation of a single mask of only NBP, and (C) shows the formation of a single mask of only BBP.

Fig. 9 is a graph showing the spectral transmittance of a wavelength selective filter having a refractive index difference of 0.255, wherein (A) shows the formation of a double mask, and (B) shows the formation of a single mask of only NBP, ( C) shows the case where only a single mask of BBP is formed.

Fig. 10 is a graph showing the spectral transmittance of a wavelength selective filter having a refractive index difference of 0.3125, wherein (A) shows the formation of a double mask, and (B) shows the formation of a single mask of only NBP, ( C) shows the case where only a single mask of BBP is formed.

Fig. 11 is a graph showing the spectral transmittance of a wavelength selective filter having a refractive index difference of 0.4125, (A) showing the formation of a double mask, and (B) showing the formation of a single mask of only NBP, ( C) shows the case where only a single mask of BBP is formed.

Figure 12 is a graph showing the spectral transmittance of a wavelength selective filter formed only by a pair of TiO ₂ and an intermediate refractive index material, (A) showing the formation of a double mask, and (B) showing a single mask of only NBP. In the case of formation, (C) shows the case where only a single mask of BBP is formed.

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

1 is a perspective view showing a schematic configuration of an ultraviolet irradiation device 1 of the present embodiment, and FIG. 2 is a front view showing a schematic configuration of the ultraviolet irradiation device 1. As shown in the figures, the ultraviolet irradiation device 1 includes at least one (three in the present embodiment) illuminators 3 that irradiate ultraviolet rays directly under the workpiece 2, and each of the illuminators 3 disposed in each of the illuminators 3. A wavelength selection filter 4 is provided between the workpiece 2. The ultraviolet irradiation device 1 is a light irradiation device that irradiates the ultraviolet light irradiated by the illuminator 3 through the wavelength selection filter 4 to the workpiece 2. The workpiece 2 has a rectangular shape having an irradiation area 2A having a predetermined width W and a length L, and a liquid crystal panel is placed on the irradiation area 2A, for example. The liquid crystal panel is irradiated with ultraviolet rays.

As shown in FIG. 2, the illuminator 3 has a rectangular parallelepiped illuminator casing 10 having a bottom open type, and the illuminator casing 10 is provided with linear ultraviolet rays radiating ultraviolet rays having a wavelength of about 200 nm to 600 nm. The light source lamp 11 and the semi-elliptical cylindrical (cylindrical) mirror 12 surrounding the lamp 11 are reflected by the mirror 12 from the ultraviolet light radiated from the lamp 11 and the light exit opening from the bottom surface of the illuminator housing 10 is lined up. Irradiation of ultraviolet rays. In the lamp 11 of the present embodiment, a metal halide lamp is used.

The wavelength selective filter 4 is a penetration filter including a dielectric multilayer film, and has an area covering the entire light exit opening of the bottom surface of the illuminator 3 as shown in FIGS. 1 and 2, and is disposed in the illuminator. 3 is disposed between the workpiece 2 (i.e., the irradiation region 2A) and the light exit opening adjacent to the bottom surface of the illuminator 3. The penetration wavelength region penetrating the wavelength selective filter 4 is appropriately set according to the use of the ultraviolet irradiation device 1. In the present embodiment, it is set to optimally manufacture the liquid crystal panel (alignment control or bonding of the liquid crystal). The band.

In the ultraviolet irradiation device 1, as shown in FIG. 2 described above, the three illuminators 3 and the wavelength selective filter 4 are oriented in the width W direction of the workpiece 2 at a predetermined interval M along the width W of the workpiece 2. Side by side settings. At this time, the illuminators 3 at both ends of the illuminators 3 arranged side by side are disposed such that the built-in lamps 11 are located slightly outside the width W of the workpiece 2 (i.e., the irradiation region 2A). That is, substantially the entire area of the irradiation region 2A of the workpiece 2 is irradiated by the illuminator 3 at the center, and the illuminance at both ends in the width W direction is irradiated by the both ends of the illuminator 3 passing through the center. The illumination of the device 3 compensates for the decrease in illumination. Further, the central illuminator 3 (that is, the illuminator 3 in which the built-in lamp 11 is disposed in the width W of the workpiece 2) is not limited to one, and may be configured by arranging a plurality of illuminators 3 in parallel, thereby expanding The width W of the irradiation area 2A. Further, in the same manner, the illuminators 3 at both ends (that is, the illuminators 3 in which the built-in lamps 11 are disposed outside the width W of the workpiece 2) may be provided with a plurality of illuminators 3 arranged side by side at the respective ends.

However, the wavelength selective filter including the dielectric multilayer film has an incident angle dependency on the transmission characteristics, and the larger the incident angle of light, the more the penetration wavelength region is shifted toward the short wavelength side. Therefore, when a wavelength selective filter is used in a light irradiation device including an optical system that uses concentrated or diffused light other than parallel light, light of a desired wavelength is cut off, and light of a wavelength is not required to be worn. through. In the present embodiment, the light K incident on the workpiece 2 obliquely incident from the illuminator 3 to the wavelength selective filter 4 depends on the angle of the penetration characteristic, and contains more short wavelengths than in the case of direct incidence. ingredient. In particular, when the illuminator 3 is disposed on the outer side of the width W of the workpiece 2 as in the ultraviolet ray irradiation apparatus 1 of the present embodiment, the light reaching the workpiece 2 from the illuminator 3 includes a large amount of oblique incidence to the wavelength. Since the filter 4 is selected to penetrate the component, the composition of the short wavelength is increased.

Therefore, in the conventional light irradiation device, a wavelength of a dielectric multilayer film in which a layer of a high refractive index material and a layer of a material having a slightly lower refractive index than that of the layer are alternately laminated on a transparent substrate is used. The filter is selected so that the wavelength shift amount of the spectral light transmission characteristic is also reduced when the light is obliquely incident on the film surface. However, in the wavelength selective filter having such a configuration, if the wavelength shift amount is to be reduced, the number of films is greatly increased. Therefore, it takes time to form a film on the substrate, and as a result, the wavelength selective filter is obtained. The productivity is deteriorated.

Further, it is known that the short wavelength shift due to the incident angle of the wavelength selective filter including the dielectric multilayer film can reduce the wavelength shift amount by utilizing the absorption of the film substance. However, in this case, the absorption wavelength cannot be adjusted in such a manner that the transmission characteristics of the wavelength selection filter required for photohardening cannot be obtained, and thus Sex production is more difficult. Therefore, in the case of the ultraviolet irradiation device 1 of the present embodiment, the wavelength selective filter 4 is configured as follows, thereby suppressing a large increase in the number of films and reducing the amount of wavelength shift.

FIG. 3 is a view schematically showing the wavelength selective filter 4. As shown in FIG. 3, the wavelength selective filter 4 is provided with a first laminate L1 including the first dielectric multilayer film G1 and the second dielectric multilayer film G2 on the transparent substrate 21, and a third dielectric layer. The multilayer film G3 and the second layered body L2 of the fourth dielectric multilayer film G4 are formed. The transparent substrate 21 is formed of a transparent material such as quartz or borosilicate glass. Here, when a wavelength selective filter is formed by using colored glass as is conventionally known, heat resistance is low, and there is also concern that the light is heated to a high temperature due to high energy from the lamp 11, and wavelength selective filtering is performed. The piece was damaged by thermal shock. In the present embodiment, the transparent substrate 21 is formed of a material having a relatively high heat resistance, for example, quartz, thereby ensuring the heat resistance of the wavelength selective filter.

The first and third dielectric multilayer films G1 and G3 have a first high refractive index material (first refractive index material) 22 having a first refractive index (first high refractive index) (n _H1 ) and have a second The first low refractive index material (second refractive index material) 23 of the second refractive index (first low refractive index) (n _L1 ) having a small refractive index is alternately laminated. The second and fourth dielectric multilayer films G2 and G4 have a second high refractive index material (third refractive index material) 24 having a third refractive index (second high refractive index) (n _H2 ) and have a second The second low refractive index material (fourth refractive index material) 25 of the fourth refractive index (second low refractive index) (n _M ) having a small refractive index is alternately laminated.

The second refractive index (n _L1 ) is different from the fourth refractive index (n _M ). In the present embodiment, the fourth refractive index (n _M ) is made higher than the second refractive index (n _L1 ). In the present embodiment, the first refractive index (n _H1 ) is different from the third refractive index (n _H2 ), and further, the third refractive index (n _H2 ) is higher than the first refractive index (n _H1 ). In short, in the prior art, a dielectric multilayer film is formed by a combination of layers of two kinds of materials having different refractive indices, whereas in the present embodiment, four kinds of material layers having different refractive indices, that is, the first one are used. The refractive index material, the second refractive index material, the third refractive index material, and the fourth refractive index material are formed by alternately laminating the first two, and the first and third dielectric multilayer films G1 and G3 are formed. The second and fourth dielectric multilayer films G2 and G4 are formed by alternately laminating. The reason why the second refractive index (n _L1 ) and the fourth refractive index (n _M ) and the first refractive index (n _H1 ) and the third refractive index (n _H2 ) are different will be described below. .

Further, in the wavelength selection filter 4 of the present embodiment, the first layered product L1 and the second layered body L2 are formed on different surfaces of the transparent substrate 21, respectively. Further, in the wavelength selective filter 4 of the present embodiment, the first layered body L1 formed on one surface of the transparent substrate 21 is formed to have a narrow band pass type (NBP (in order to selectively penetrate light in a desired wavelength region). A narrow bandpass type filter, the second layered body L2 formed on the other surface of the transparent substrate 21 constitutes a broadband type (BBP) filter. The first layered product L1 of the NBP type is formed by sequentially laminating the second dielectric multilayer film G2 and the first dielectric multilayer film G1 from the transparent substrate 21. The second layered body L2 of the BBP type is formed by sequentially laminating the third dielectric multilayer film G3 and the fourth dielectric multilayer film G4 from the transparent substrate 21.

Further, one of the first dielectric multilayer film G1 and the second dielectric multilayer film G2 is composed of a short wave pass type (SWP) filter as a basic film, and the other is A long wave pass type (LWP) filter is a basic film structure, and is formed by optimizing the film thickness of each layer. Further, in the same manner as the fourth dielectric multilayer film G3, the third dielectric multilayer film G3 is composed of a short-wave type (SWP type) filter as a basic film, and the other is a long-wavelength type ( The LWP type filter is a basic film structure, and is formed by optimizing the film thickness of each layer.

In the present embodiment, a commercially available film design software (TFCalc from Software Spectra) is used to optimize the film thickness of each layer by setting the center wavelength to 680 nm to satisfy the desired spectral transmittance. The results of Tables 1 and 2. Here, the spectral transmittance required in the present embodiment means a penetration wavelength region having a maximum transmittance of 85% or more in a wavelength range of 400 to 600 nm in terms of transmittance characteristics at normal incidence, At least a part of the wavelength range of 600 to 800 nm has a minimum transmittance of 1% or less in the visible light range and a near-infrared light side cutoff wavelength region, and at least a part of the minimum transmittance in the wavelength range of 200 to 400 nm is 1% or less. The outer cutoff wavelength region. Specifically, the first layered body L1 of the BBP type constitutes a penetration wavelength region having a maximum transmittance of 85% or more in a wavelength range of 400 to 600 nm, and a transmittance of a short wavelength side of the penetration wavelength region. The inclination of the transmittance curve of 85% to 5% or less, and the inclination of the transmittance curve of the long wavelength side from 85% to 5% or less. Further, the second layered body L2 of the NBP type has a visible light range and a near-infrared light side cutoff wavelength region in which at least a part of the minimum transmittance of the wavelength range of 600 to 800 nm is 1% or less, and 200 to 400 nm. At least a part of the wavelength range has a minimum transmittance of 1% or less of the ultraviolet side cutoff wavelength region.

When a transparent substrate having a refractive index of 1.45 to 1.53 is used, the first refractive index (n _H1 ), the second refractive index (n _L1 ), the third refractive index (n _H2 ), and the fourth refraction are used for light having a wavelength of 500 nm. The rate (n _M ) is set to 2.26 to 2.40, 1.38 to 1.50, 2.42 to 2.70, and 1.58 to 2.00, respectively, thereby satisfying the required spectral transmittance.

Table 1 is a table showing the configuration of the NBP-type first layered product L1 of the wavelength selective filter 4, and Table 2 is a table showing the configuration of the BBP-type second layered body L2 of the wavelength selective filter 4. In the wavelength selective filter 4, Ta ₂ O _{5 is} selected for the first high refractive index material 22, SiO _{2 is} selected for the first low refractive index material 23, and TiO _{2 is} selected for the second high refractive index material 24, and the second low is selected. The refractive index material 25 is selected from Al ₂ O ₃ . Here, the refractive indices of the respective layers of Ta ₂ O ₅ , SiO ₂ , TiO ₂ , and Al ₂ O ₃ are 2.27, 1.48, 2.57, and 1.70, respectively, for light having a wavelength of 500 nm. Further, in the present embodiment, the refractive index of the transparent substrate 21 is 1.462.

As will be described in detail, as shown in Table 1, one surface of the transparent substrate 21 is formed by alternately laminating a second high refractive index material 24 containing TiO ₂ and a second low refractive index material 25 containing Al ₂ O ₃ . The second dielectric multilayer film G2. Further, on the second dielectric multilayer film G2, the first high refractive index material 22 containing Ta ₂ O _{5 and} the first low refractive index material 23 containing SiO ₂ are alternately laminated to form a first dielectric multilayer. Film G1. Further, as shown in Table 2, on the other surface of the transparent substrate 21, the first high refractive index material 22 containing Ta ₂ O _{5 and} the first low refractive index material 23 containing SiO ₂ are alternately laminated to form a third dielectric layer. Electrical multilayer film G3. Further, on the third dielectric multilayer film G3, the second high refractive index material 24 containing TiO ₂ and the second low refractive index material 25 containing Al ₂ O ₃ are alternately laminated to form a fourth dielectric multilayer. Membrane G4.

Further, which of the low refractive index material or the high refractive index material is adjacent to the transparent substrate 21 depends on the simulation result, but the high refractive index material is often adjacent to the transparent substrate 21. In the present embodiment, since the refractive index of the transparent substrate 21 made of quartz glass is 1.462, if it is a so-called intermediate refractive index material, a refractive index difference occurs between the transparent substrate 21 and the like, so that it can be adjacent to the transparent substrate. twenty one. Here, in the present specification, the intermediate refractive index material is set to have a fourth refractive index (n _M : 1.58 to 2.00). Further, the adjacent portion of the first dielectric multilayer film G1 and the second dielectric multilayer film G2, and the adjacent portion of the third dielectric multilayer film G3 and the fourth dielectric multilayer film G4 are, for example, NBP type. The 31st layer and the 32nd layer or the 20th layer and the 21st layer of the BBP type are arranged such that the high refractive index material is adjacent to the low refractive index material. Further, the wavelength selective filter 4 of the present embodiment is obtained by using ion plating as a vapor deposition method.

4 is a graph showing the spectral transmittance of the wavelength selective filter, FIG. 4(A) shows the wavelength selective filter of the present embodiment, and FIG. 4(B) shows that the conventional example includes only A case of a wavelength selective filter of a dielectric multilayer film composed of two kinds of film materials of a high refractive index material and a low refractive index material. In addition, in FIG. 4, the horizontal axis represents wavelength (nm), and the vertical axis represents transmittance (%). Further, the graph in Fig. 4 shows the result obtained by the simulation, the broken line indicates the result at the time of normal incidence, and the solid line indicates the result at the time of the oblique incidence of 60°. As shown in FIG. 4(A), the wavelength selective filter 4 of the present embodiment has a transmittance of 200 to 400 nm of less than 1% and a penetration of 420 to 510 nm in terms of transmittance characteristics at normal incidence. The rate is above 88%, and the penetration rate of 550~800nm is less than 3%. Further, when the filter 4 is selected at the wavelength and the transmittance characteristics of the normal incidence and the oblique incidence of 60 degrees are compared, the transmittance on the short-wavelength side of the penetration wavelength region is 50% of the wavelength and the long wavelength side. The average wavelength shift amount at which the transmittance became 50% was 34 nm.

In an example of a wavelength selective filter composed of only two kinds of film materials of a high refractive index material (Ta ₂ O ₅ ) and a low refractive index material (SiO ₂ ), as shown in FIG. 4(B), the average The wavelength shift amount was 48 nm. Therefore, the first layered product L1 of the NBP type and the second layered body L2 of the BBP type are formed by penetrating the first dielectric multilayer film G1 and the second dielectric multilayer film G2. It is possible to reduce the wavelength shift caused by the incident angle.

Further, as shown in Tables 1 and 2, the wavelength selective filter 4 of the present embodiment has a film layer of the first layered product L1 of the NBP type of 52 layers and a film layer of the second layered body L2 of the BBP type. The number is 44 layers, and the total number of layers is 96 layers. Furthermore, When a conventional wavelength selective filter is formed in such a manner as to satisfy the same spectral transmittance as that of the wavelength selective filter 4, the number of layers is 44 and 38, respectively, in the NBP type and the BBP type, and the total film layer is formed. The number becomes 82 layers. Therefore, in the present embodiment, the number of film layers is slightly increased as compared with the conventional one. However, in the present embodiment, there is an advantage that the amount of wavelength shift is greatly reduced, and the width of the penetration band is small, and the width reduction is small even when obliquely incident at 60°. In addition, as shown in FIG. 5(B), the filter 4 is selected in the wavelength range which is not required in the wavelength range (generally, the long wavelength side of the desired penetration wavelength region). In the case of 4 (B), it is an area of 650 to 800 nm)), and penetration of light cannot be avoided. On the other hand, in the present embodiment, as shown in Fig. 5(A), light penetration in such a wavelength region hardly exists.

Next, the necessity of forming a multilayer film on both surfaces of the transparent substrate 21 will be described. 5 is a graph showing the spectral transmittance of the wavelength selective filter 4, and FIG. 5(A) shows the case where the first laminates L1 and L2 of the NBP type and the BBP type are formed on both sides of the transparent base 21, respectively. (hereinafter, simply referred to as "the case where the two-faced film is formed"), and FIG. 5(B) shows a case where the NBP-type first laminated body L1 is formed on one surface of the transparent substrate 21 (hereinafter, simply referred to as "only NBP single-sided film formation". In the case of the second layered body L2 of the BBP type formed on one surface of the transparent substrate 21 (hereinafter, simply referred to as "the case where only a single mask of BBP is formed"). As shown in FIG. 5, in FIG. 5(B), the light on the side of the long wavelength region which is slightly spaced apart from the penetration band is not sufficiently cut off, and in FIG. 5(C), the side of the long wavelength region of the penetration band is The light is not sufficiently cut off. The wavelength shift amount is equivalent to that in FIGS. 5(A) to 5(C). That is, it is necessary to form the first layered bodies L1 and L2 of the NBP type and the BBP type on both surfaces of the transparent base 21, respectively, because if the laminated body is separately formed, the cutoff required as a band pass filter cannot be obtained. There is no correlation between the characteristics and the mitigation of wavelength shift. Also, by dividing the two sides of the transparent substrate 21 When the first layered bodies L1 and L2 are formed, the rise in the spectral transmittance curve can be made remarkable.

Next, the influence of the lamination direction of the film on the wavelength shift amount will be described. Table 3 is a table showing the constitution of the NBP type laminated body in which the wavelength selective filter is formed in the reverse order of the example of Table 1, and Table 4 shows the BBP forming the wavelength selective filter in the reverse order of the example of Table 1. A table of the composition of a laminated body. Fig. 6 is a graph showing the spectral transmittance of a wavelength selective filter for forming a multilayer film in the reverse order of the example of Table 1, wherein Fig. 6(A) shows the formation of a double mask, and Fig. 6(B) shows only In the case of the formation of a single mask of NBP, Fig. 6(C) shows the case where only a single mask of BBP is formed. In the wavelength selective filter shown in Tables 3 and 4, the NBP type laminated system is formed by sequentially laminating a first dielectric multilayer film and a second dielectric multilayer film from a transparent substrate. Further, the BBP type laminated system is formed by sequentially laminating a fourth dielectric multilayer film and a third dielectric multilayer film from a transparent substrate. In all the graphs of FIGS. 6(A) to 6(C), although the chopping waves (surface corrugations) of the penetrating bands are generated, the wavelength shift amounts are equivalent to those in FIGS. 5 and 6 respectively. That is, the amount of wavelength shift is independent of the direction of the buildup. In addition, in the NBP type, the second dielectric multilayer film G2 and the first dielectric multilayer film G1 are sequentially laminated from the transparent substrate 21 to suppress chopping, and the BBP type is used from the transparent substrate 21 The third dielectric multilayer film G3 and the fourth dielectric multilayer film G4 are sequentially laminated to suppress chopping.

Next, a case where the high refractive index material is one type will be described. Table 5 shows a table in which the high-refractive-index material is a NBP-type layered body of one type of wavelength-selective filter, and Table 6 shows a BBP in which a high-refractive-index material is used as one type of wavelength-selective filter. Table of the composition of the laminated body, Table 7 is a continuation of Table 6. Fig. 7 is a graph showing the spectral transmittance of a wavelength selective filter in which a high refractive index material is used. Fig. 7(A) shows the formation of a double mask, and Fig. 7(B) shows a single NBP only. In the case of mask formation, Fig. 7(C) shows the case where only a single mask of BBP is formed. The wavelength selective filters shown in Tables 5 to 7 were formed by a combination of Ta ₂ O ₅ and Al ₂ O ₃ , Ta ₂ O ₅ and SiO ₂ . In the wavelength selective filter, the number of layers in the NBP type and the BBP type was 90 layers and 147 layers, respectively, and the number of layers was too large, and film production was unrealistic.

Table 8 shows a configuration in which a low-refractive-index material is a NBP-type laminated body of one type of wavelength selective filter, and Table 9 shows a BBP in which a low-refractive-index material is used as one type of wavelength selective filter. A table of the composition of a laminated body. Fig. 8 is a graph showing the spectral transmittance of a wavelength selective filter in which a low refractive index material is used. Fig. 8(A) shows a case where a double mask is formed, and Fig. 8(B) shows a single NBP only. In the case of mask formation, Fig. 8(C) shows the case where only a single mask of BBP is formed. The wavelength selective filters shown in Tables 8 and 9 were formed by a combination of Ta ₂ O ₅ and Al ₂ O ₃ , and TiO ₂ and Al ₂ O ₃ . In the wavelength selective filter, the number of layers in the NBP type and the BBP type is 85 layers and 75 layers, respectively, and the number of layers is large. Therefore, by making the second refractive index (n _L1 ) different from the fourth refractive index (n _M ), the number of layers can be reduced. Further, by also changing the first refractive index (n _H1 ) and the third refractive index (n _H2 ), the number of layers can be further reduced. Further, in Fig. 5, Fig. 7 and Fig. 8, the wavelength shift amount is not changed.

Next, the refractive index difference will be described. In the wavelength selective filter 4 shown in Tables 1 and 2, the first average refractive index which is the average value of the first refractive index (n _H1 ) and the second refractive index (n _L1 ) is 1.875 (= (2.27+) 1.48)/2). Further, the second average refractive index which is the average value of the third refractive index (n _H2 ) and the fourth refractive index (n _M ) is 2.135 (= (2.57 + 1.70)/2). Further, the difference (refractive index difference) between the first average refractive index and the second average refractive index was 0.26. Here, when the refractive index difference is less than 0.1, the conventional film structure using the same two types of film materials in the first and second dielectric multilayer films is close to each other, and therefore, toward the total film layer The number becomes too much in the direction of development, and does not exert the effect of this embodiment. On the other hand, in the case where the refractive index difference exceeds 0.6, the combination of the refractive indices in the absence of the corresponding film substance is impossible, and the film design by simulation itself cannot be realized.

Table 10 is a table showing the configuration of an NBP-type laminate having a wavelength selective filter having a refractive index difference of 0.2555, and Table 11 is a BBP-type laminate having a wavelength selective filter having a refractive index difference of 0.2555. The composition of the table. Fig. 9 is a graph showing the spectral transmittance of a wavelength selective filter having a refractive index difference of 0.2555. Fig. 9(A) shows the formation of a double mask, and Fig. 9(B) shows the formation of a single mask of only NBP. In the case, Fig. 9(C) shows the case where only a single mask of BBP is formed. The wavelength selective filters shown in Tables 10 and 11 were formed by a combination of Ta ₂ O ₅ and MgF ₂ (refractive index of 1.38) and TiO ₂ and LaF ₃ (refractive index of 1.586). In the wavelength selective filter, the number of layers in the NBP type and the BBP type was 48 layers and 47 layers, respectively. Further, in the wavelength selection filters shown in Tables 10 and 11, as shown in Fig. 9, the average wavelength shift amount was 32 nm.

Table 12 is a table showing the configuration of an NBP-type laminate having a wavelength selective filter having a refractive index difference of 0.3125, and Table 13 is a BBP-type laminate having a wavelength selective filter having a refractive index difference of 0.3125. The composition of the table. Fig. 10 is a graph showing the spectral transmittance of a wavelength selective filter having a refractive index difference of 0.3125, Fig. 10(A) shows the formation of a double mask, and Fig. 10(B) shows the formation of a single mask of only NBP. In the case, Fig. 10(C) shows the case where only a single mask of BBP is formed. The wavelength selective filters shown in Tables 12 and 13 were formed by a combination of Ta ₂ O ₅ and MgF ₂ , and TiO ₂ and Al ₂ O ₃ . In the wavelength selective filter, the number of layers is 44 layers and 50 layers in the NBP type and the BBP type, respectively. Further, in the wavelength selection filters shown in Tables 12 and 13, as shown in Fig. 10, the average wavelength shift amount was 31 nm.

Table 14 is a table showing the configuration of an NBP-type laminate having a wavelength selective filter having a refractive index difference of 0.4125, and Table 15 is a BBP-type laminate having a wavelength selective filter having a refractive index difference of 0.4125. The composition of the table. Fig. 11 is a graph showing the spectral transmittance of a wavelength selective filter having a refractive index difference of 0.4125, Fig. 11(A) shows the formation of a double mask, and Fig. 11(B) shows the formation of a single mask of only NBP. In the case, Fig. 11(C) shows the case where only a single mask of BBP is formed. The wavelength selective filters shown in Tables 14 and 15 were formed by a combination of Ta ₂ O ₅ and MgF ₂ , and TiO ₂ and Y ₂ O ₃ (refractive index: 1.90). In the wavelength selective filter, the number of layers in the NBP type and the BBP type was 56 layers and 51 layers, respectively. Further, in the wavelength selection filters shown in Tables 14 and 15, as shown in Fig. 11, the average wavelength shift amount was 32 nm.

As described above, the short wavelength shift can be mitigated by utilizing the absorption of the film material. TiO ₂ is a material that absorbs relatively more light. Next, a case where only the pair of TiO ₂ and the intermediate refractive index material is used will be described. In the present specification, as described above, the intermediate refractive index material is set to have a fourth refractive index (n _M : 1.58 to 2.00).

Table 16 is a table showing the constitution of the NBP-type laminate of the wavelength selective filter formed only by the pair of TiO ₂ and the intermediate refractive index material, and Table 17 shows the wavelength formed only by the pair of TiO ₂ and the intermediate refractive index material. A table of the constitution of the BBP type laminate of the filter was selected. Fig. 12 is a graph showing the spectral transmittance of a wavelength selective filter formed only of a pair of TiO ₂ and an intermediate refractive index material, Fig. 12 (A) showing the formation of a double mask, and Fig. 12 (B) showing only In the case of the formation of a single mask of NBP, Fig. 12(C) shows the case where only a single mask of BBP is formed. The wavelength selective filters shown in Tables 16 and 17 were formed by a combination of TiO ₂ and Al ₂ O ₃ . In the wavelength selective filter, the number of layers in the NBP type and the BBP type is 79 layers and 74 layers, respectively, and the number of TiO ₂ layers increases as the total number of layers increases, so that the wavelength is near 400 nm. The rate decreases due to the absorption of TiO ₂ . Therefore, if only TiO ₂ is used, it is insufficient, and two types of high refractive index materials are used in such a manner that Ta ₂ O _{5 having a} low absorption in the near ultraviolet region is used, and the first dielectric multilayer film G1 and the second dielectric layer are used. The electric multilayer film G2 is laminated, and two types of low refractive index materials are used, and the second refractive index is different from the fourth refractive index, whereby the number of films can be reduced. Furthermore, in FIGS. 5 and 12, the wavelength shift amount is not changed.

As described above, according to the present embodiment, the first laminate body L1 including the first dielectric multilayer film G1 and the second dielectric multilayer film G2 and the first layer are provided on the transparent substrate 21. The dielectric laminate film and the second laminate L2 of the fourth dielectric multilayer film, and the first and third dielectric multilayer films G1 and G3 have the first refractive index material 22 having the first refractive index and The second refractive index material 23 having the second refractive index smaller than the first refractive index is alternately laminated, and the second and fourth dielectric multilayer films G2 and G4 are the third refractive index material having the third refractive index. 24 is formed by alternately laminating a fourth refractive index material 25 having a fourth refractive index smaller than the third refractive index, and the first refractive index is different from the third refractive index, and the second refractive index is different from the fourth refractive index. According to this configuration, the amount of wavelength shift can be reduced, and as a result, the required light can be ensured to penetrate the wavelength region, and the penetration of light in the unnecessary wavelength region can be suppressed.

Further, according to the present embodiment, the first layered product L1 and the second layered body L2 are formed on different surfaces of the transparent substrate 21, respectively. With this configuration, the ripple of the transmittance curve can be suppressed.

Moreover, according to the present embodiment, the first layered product L1 constitutes a narrow band-pass type filter, and the second layered body L2 constitutes a broadband-pass type filter, so that light of a desired wavelength region can be selectively penetrated.

Further, according to the present embodiment, the first average refractive index, which is the average of the first refractive index and the second refractive index, and the second average refractive index, which is the average of the third refractive index and the fourth refractive index, are used. The difference is set to 0.1 to 0.6. With this configuration, the required spectral transmittance can be satisfied, and the wavelength shift amount can be made lower than a predetermined value required.

Further, according to the present embodiment, the refractive index of the transparent substrate is 1.45 to 1.53, the first refractive index is 2.26 to 2.40, and the second refractive index is 1.38 to 1.50, and the third refractive index is light for a wavelength of 500 nm. It is 2.42~2.70, and the fourth refractive index is 1.58~2.00. According to this configuration, when the transmittance characteristics of the normal incidence and the oblique incidence of 60 degrees are compared, the transmittance at the short wavelength side of the penetration wavelength region becomes 50% and the transmittance at the long wavelength side becomes The average wavelength shift of 50% of the wavelength is 35 nm or less.

However, the above-described embodiments are in the same manner as the present invention, and are not to be considered as appropriate, and may be appropriately changed without departing from the spirit and scope of the invention. For example, in the above embodiment, the wavelength selective filter 4 is formed by forming a laminate of NBP type and BBP type on both surfaces of the transparent substrate to obtain a cutoff characteristic required as a band pass filter, but it is not Limited to this configuration. NBP type or BBP type may be formed on one surface of the transparent substrate, or NBP type and BBP type may be formed on one surface of the transparent substrate.

Further, in the wavelength selective filter 4 of the above-described embodiment, the NBP type laminated system is formed by sequentially laminating the second dielectric multilayer film and the first dielectric multilayer film from the transparent substrate, and the BBP type laminated system is transparent. The substrate is formed by sequentially laminating a first dielectric multilayer film and a second dielectric multilayer film. However, the NBP type laminated system may be formed by sequentially laminating a first dielectric multilayer film and a second dielectric multilayer film from a transparent substrate, and the BBP type laminated system sequentially stacks the second dielectric from the transparent substrate. The multilayer film and the first dielectric multilayer film are formed.

Further, in the wavelength selective filter 4 of the above-described embodiment, Ta ₂ O _{5 is} used for the first high refractive index material 22, SiO _{2 is} used for the first low refractive index material 23, and TiO is used for the second high refractive index material 24 ₂ , Al ₂ O _{3 is} used for the second low refractive index material 25, but is not limited to these. Moreover, the film material used for each refractive index material is not limited to a single substance, and several substances may be combined with each refractive index material. For the transparent substrate, in addition to quartz glass, an optical glass (such as BK7) having a refractive index of 1.45 to 1.53, a heat absorbing glass, or the like can be used.

Further, in the wavelength selective filter 4 of the above-described embodiment, the first refractive index (n _H1 ) and the third refractive index (n _H2 ) are also different, but the required spectral transmittance and the wavelength selective filter are required. When the number of layers is different and the number of layers can be reduced, the first refractive index and the third refractive index can be made the same. Further, in the above embodiment, the wavelength selective filter 4 is formed by ion plating as the vapor deposition method, but the film formation method is not limited thereto.

Further, in the above embodiment, the metal halide lamp is used for the lamp 11, but the type of the lamp is not limited thereto, and may be, for example, a mercury lamp.

Further, in the above embodiment, the wavelength selective filter 4 is provided separately, but the wavelength selective filter 4 can be used in combination with other optical members such as a polarizing element.

Claims (9)

A wavelength selective filter comprising: a first laminate including a first dielectric multilayer film and a second dielectric multilayer film; and a third dielectric multilayer film and a fourth substrate; In the second layered body of the dielectric multilayer film, the first and third dielectric multilayer films have a first refractive index material having a first refractive index and a second refractive index having a smaller refractive index than the first refractive index. The second refractive index material is formed by alternately laminating, and the second and fourth dielectric multilayer films have a third refractive index material having a third refractive index and a fourth refractive index having a third refractive index lower than the third refractive index. The fourth refractive index material is alternately laminated, and the first refractive index is different from the third refractive index, and the second refractive index is different from the fourth refractive index. The wavelength selection filter of claim 1, wherein the first laminate and the second laminate system are formed on different surfaces of the transparent substrate. The wavelength selection filter according to claim 1 or 2, wherein an average of the first average refractive index and the second refractive index, that is, an average of the first average refractive index and the third refractive index and the fourth refractive index The value, that is, the difference between the second average refractive indices is set to 0.1 to 0.6. The wavelength selection filter according to claim 1 or 2, wherein the first laminate body constitutes a narrow band pass filter, and the second laminate body constitutes a broadband pass filter. The wavelength selection filter of claim 1 or 2, wherein, for light having a wavelength of 500 nm, the refractive index of the transparent substrate is 1.45 to 1.53, and the first refractive index is 2.26 to 2.40. The second refractive index is 1.38 to 1.50, the third refractive index is 2.42 to 2.70, and the fourth refractive index is 1.58 to 2.00. The wavelength selection filter according to claim 1 or 2, wherein the first refractive index material and/or the third refractive index material are adjacent to the transparent substrate. The wavelength selection filter according to claim 1 or 2, wherein the first laminate body and the second buildup volume layer are on one surface or both surfaces of the transparent substrate, and the first laminate body and the second laminate body are adjacent to each other The first refractive index material is adjacent to the fourth refractive index material or the second refractive index material is adjacent to the third refractive index material. The wavelength selection filter according to claim 1 or 2, wherein the fourth refractive index is higher than the second refractive index, and the third refractive index is higher than the first refractive index, and the first laminated system is transparent. The substrate is formed by sequentially laminating a second dielectric multilayer film and a first dielectric multilayer film, and the second buildup system sequentially stacks the third dielectric multilayer film and the fourth dielectric multilayer film from the transparent substrate. And constitute. A light irradiation device is characterized in that a light source is housed in a casing, and a wavelength selection filter of any one of claims 1 to 8 is provided in a light exit opening of the casing.