JP6432270B2 - Wavelength selection filter and light irradiation device - Google Patents

Description

  The present invention relates to a wavelength selection filter and a light irradiation apparatus in which a plurality of films are stacked.

Conventionally, a light irradiation device using a mercury lamp or a metal halide lamp has been used for photocuring of a resin, an adhesive or the like. The light emitted by mercury lamps and metal halide lamps emits light with an unnecessary wavelength that causes damage to the irradiated object in addition to the light with the wavelength necessary to cure the resin and adhesive. A wavelength selective filter is used. A typical wavelength selective filter uses colored glass colored with metal. However, solarization occurs under the influence of ultraviolet rays from the lamp, resulting in a decrease in transmittance. 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. However, a wavelength selective filter composed of a dielectric multilayer film has an incident angle dependency on transmission characteristics. As the incident angle of light increases, the transmission wavelength region shifts to the short wavelength side.
Therefore, by using a wavelength selective filter composed of a dielectric multilayer film in which a layer of a high refractive index material and a layer of a material having a somewhat lower refractive index are alternately laminated on a transparent substrate, A technique is known in which the wavelength shift amount of spectral transmission characteristics is reduced even when light is obliquely incident on the film surface (see, for example, Patent Document 1).

JP 2008-20563 A

However, the above-described conventional configuration has a problem that the number of layers of the entire film is significantly increased when the wavelength shift amount is reduced.
The present invention has been made in view of the above-described circumstances, and it is possible to reduce the wavelength shift amount of spectral transmission characteristics even when light is obliquely incident on the film surface while suppressing a significant increase in the number of films. An object of the present invention is to provide a wavelength selection filter and a light irradiation device.

  In order to achieve the above-described object, a wavelength selective filter of the present invention includes a first laminated body including a first dielectric multilayer film and a second dielectric multilayer film, a third dielectric multilayer film, and a transparent substrate. A second laminated body composed of a fourth dielectric multilayer film, wherein the first and third dielectric multilayer films comprise a first refractive index material having a first refractive index and the first refractive index. A second refractive index material having a smaller second refractive index, and a third refractive index having a third refractive index. And a fourth refractive index material having a fourth refractive index smaller than the third refractive index, and the first refractive index and the third refractive index are different. The second refractive index and the fourth refractive index are different.

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

In the above configuration, a first average refractive index that is an average value of the first refractive index and the second refractive index, and a second value that is an average value of the third refractive index and the fourth refractive index. When comparing the difference in average refractive index between the transmittance characteristics of normal incidence and oblique incidence of 60 degrees, the transmittance at the short wavelength side of the transmission wavelength region is 50% and the transmittance at the long wavelength side is 50%. It is good also as a value from which the average wavelength shift amount of becomes becomes 35 nm or less.

In the above-described configuration, the first stacked body is configured by stacking the second dielectric multilayer film and the first dielectric multilayer film in order from the transparent substrate, and the second stacked body is in order from the transparent substrate. A third dielectric multilayer film and the fourth dielectric multilayer film may be laminated .

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

  In the above-described configuration, 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 for light having a wavelength of 500 nm. .38 to 1.50, the third refractive index may be 2.42 to 2.70, and the fourth refractive index may be 1.58 to 2.00.

  The light irradiation apparatus of the present invention is characterized in that a light source is housed in a housing, and the above-described wavelength selection filter is provided in a light emission opening of the housing.

  According to the present invention, it is possible to reduce the wavelength shift amount of spectral transmission characteristics even when light is obliquely incident on the film surface while suppressing a significant increase in the number of films.

It is a perspective view which shows schematic structure of the ultraviolet irradiation device which concerns on embodiment of this invention. It is a front view which shows schematic structure of an ultraviolet irradiation device. It is a figure which shows a wavelength selection filter typically. It is a table | surface which shows the structure of the NBP-type laminated body of a wavelength selection filter. It is a table | surface which shows the structure of the BBP-type laminated body of a wavelength selection filter. It is a graph which shows the spectral transmittance of a wavelength selection filter, (A) shows the case of the wavelength selection filter of this embodiment, and (B) shows the case of the conventional wavelength selection filter. It is a graph which shows the spectral transmission factor of a wavelength selection filter, (A) is a case where NBP type and BBP type laminates are formed on both sides of a transparent substrate, respectively, and (B) is an NBP type on one side of the transparent substrate. When a laminated body is formed, (C) shows a case where a BBP type laminated body is formed on one surface of the transparent substrate. It is a table | surface which shows the structure which formed the NBP type laminated body of the wavelength selection filter in the reverse order to the example of FIG. It is a table | surface which shows the structure which formed the BBP type | mold laminated body of the wavelength selection filter in the reverse order to the example of FIG. FIG. 5 is a graph showing the spectral transmittance of a wavelength selective filter in which a multilayer film is formed in the reverse order of the example of FIG. 4, (A) in the case of double-sided film formation; Shows the case of forming a single-sided film only for BBP. It is a table | surface which shows the structure of the NBP type | mold laminated body of the wavelength selection filter which made the high refractive index material 1 type. It is a table | surface which shows the structure of the BBP type | mold laminated body of the wavelength selection filter which made the high refractive index material 1 type. FIG. 13 is a continuation of FIG. It is a graph which shows the spectral transmittance of the wavelength selection filter which made the high refractive index material into one kind, (A) is the case of double-sided film formation, (B) is the case of single-sided film formation only of NBP, and (C) is only BBP. The case of single-sided film formation is shown. It is a table | surface which shows the structure of the NBP type | mold laminated body of the wavelength selection filter which made the low refractive index material 1 type. It is a table | surface which shows the structure of the BBP type | mold laminated body of the wavelength selection filter which made the low refractive index material 1 type. It is a graph which shows the spectral transmittance of the wavelength selective filter which made the low refractive index material one type, (A) is the case of double-sided film formation, (B) is the case of single-sided film formation only of NBP, and (C) is only BBP. The case of single-sided film formation is shown. It is a table | surface which shows the structure of the NBP-type laminated body of the wavelength selection filter which made the refractive index difference 0.2555. It is a table | surface which shows the structure of the BBP type | mold laminated body of the wavelength selection filter which made the refractive index difference 0.2555. It is a graph which shows the spectral transmittance of the wavelength selection filter which made the refractive index difference 0.2555, (A) is the case of double-sided film formation, (B) is the case of single-sided film formation only of NBP, (C) is only BBP. The case of single-sided film formation is shown. It is a table | surface which shows the structure of the NBP-type laminated body of the wavelength selection filter which made the refractive index difference 0.3125. It is a table | surface which shows the structure of the BBP-type laminated body of the wavelength selection filter which made the refractive index difference 0.3125. It is a graph which shows the spectral transmittance of the wavelength selection filter which made the refractive index difference 0.3125, (A) is the case of double-sided film formation, (B) is the case of single-sided film formation of only NBP, and (C) is only BBP. The case of single-sided film formation is shown. It is a table | surface which shows the structure of the NBP-type laminated body of the wavelength selection filter which made the refractive index difference 0.4125. It is a table | surface which shows the structure of the BBP-type laminated body of the wavelength selection filter which made the refractive index difference 0.4125. It is a graph which shows the spectral transmittance of the wavelength selection filter which made the refractive index difference 0.4125, (A) is the case of double-sided film formation, (B) is the case of single-sided film formation only of NBP, (C) is only BBP. The case of single-sided film formation is shown. Is a table showing the structure of TiO ₂ and the intermediate refractive index material and the NBP type stack of wavelength selective filter formed only pair. Is a table showing the structure of TiO ₂ and the intermediate refractive index material and BBP-type laminate of a wavelength selective filter formed only pair. Is a graph showing the spectral transmittance of the wavelength selective filter formed only in pairs of TiO ₂ and the intermediate refractive index material, (A) in the case of double-sided film formation, (B) in the case of single-sided film formed only NBP, ( C) shows a case where only BBP is a single-sided film.

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

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

  As shown in FIG. 2, the irradiator 3 includes a rectangular parallelepiped irradiator casing 10 having an open bottom, and the irradiator casing 10 radiates ultraviolet rays having a wavelength of about 200 nm to 600 nm in a linear shape. A lamp 11 serving as a linear ultraviolet light source and a semi-elliptical cylindrical (cylindrical) reflecting mirror 12 surrounding the lamp 11 are provided, and the irradiator is configured to reflect ultraviolet rays emitted from the lamp 11 by the reflecting mirror 12. Ultraviolet rays are irradiated linearly from the light exit opening on the bottom surface of the housing 10. A metal halide lamp is used as the lamp 11 of the present embodiment.

The wavelength selection filter 4 is a transmission filter made of a dielectric multilayer film, and has an area that sufficiently covers the entire light exit opening on the bottom surface of the irradiator 3 as shown in FIGS. 1 and 2. And the work 2 (that is, the irradiation area 2A), and is arranged close to the light exit opening on the bottom surface of the irradiator 3.
The transmission wavelength range transmitted by the wavelength selection filter 4 is appropriately set according to the use application of the ultraviolet irradiation device 1, and in this embodiment, the optimum band for manufacturing a liquid crystal panel (liquid crystal alignment control, bonding, etc.). Is set.

  In this ultraviolet irradiation device 1, as shown in FIG. 2, the three irradiators 3 and the wavelength selection filter 4 are provided in parallel in the width W direction of the workpiece 2 at a predetermined interval M in the width W direction of the workpiece 2. It has been. At this time, the irradiators 3 at both ends of the side-by-side irradiators 3 are arranged such that the built-in lamps 11 are located slightly outside the width W of the workpiece 2 (that is, the irradiation area 2A). That is, substantially the entire irradiation area 2A of the work 2 is irradiated by the central irradiator 3, and the irradiators 3 at both ends sandwiching the central irradiator 3 with respect to places where the illuminance decreases at both ends in the width W direction. Irradiation compensates for the decrease in illuminance. The central irradiator 3 (that is, the irradiator 3 in which the built-in lamp 11 is disposed within the width W of the workpiece 2) is not limited to one, and a plurality of irradiators 3 may be arranged in parallel. This is good, and the width W of the irradiation area 2A can be expanded. Similarly, the irradiators 3 at both ends (that is, the irradiators 3 in which the built-in lamp 11 is arranged outside the width W of the workpiece 2) may be arranged in parallel at each end. good.

By the way, the wavelength selection filter composed of a dielectric multilayer film has an incident angle dependency in transmission characteristics, and the transmission wavelength region shifts to the short wavelength side as the incident angle of light increases. Therefore, when a wavelength selection filter is used in a light irradiation device configured with an optical system that uses condensed light or diffused light other than parallel light, light with a necessary wavelength is cut and light with an unnecessary wavelength is transmitted. End up. In the present embodiment, the light K that is obliquely incident on the wavelength selection filter 4 from the irradiator 3 and reaches the workpiece 2 contains more components having shorter wavelengths than those at the time of direct incidence due to the angle dependence of the transmission characteristics. It becomes.
In particular, in the configuration in which the irradiator 3 is arranged outside the width W of the workpiece 2 as in the ultraviolet irradiation device 1 of the present embodiment, the light that reaches the workpiece 2 from the irradiator 3 is the wavelength selection filter 4. Since many components that are obliquely incident on and transmitted are included, short wavelength components increase.

  Therefore, in a conventional light irradiation device, a wavelength composed 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 are alternately laminated on a transparent substrate. By using the selection filter, the wavelength shift amount of the spectral transmission characteristic is reduced even when light is obliquely incident on the film surface. However, in the wavelength selective filter having such a configuration, if the amount of wavelength shift is to be reduced, the number of films increases significantly, so that the process of forming the film on the substrate takes time, resulting in production of the wavelength selective filter. Sexuality will deteriorate.

Further, it is known that the short wavelength shift due to the incident angle of the wavelength selective filter composed of a dielectric multilayer film can reduce the wavelength shift amount by utilizing absorption of the film substance. However, in this case, since it is impossible to adjust the absorption wavelength so that the transmission characteristics of the wavelength selection filter necessary for photocuring can be obtained, it is difficult to manufacture with arbitrary transmission characteristics.
Therefore, in the ultraviolet irradiation device 1 of the present embodiment, the wavelength shift amount is reduced while suppressing a significant increase in the number of films by configuring the wavelength selection filter 4 as follows.

FIG. 3 is a diagram schematically illustrating the wavelength selection filter 4.
As shown in FIG. 3, the wavelength selection filter 4 includes a first laminate L1 including a first dielectric multilayer film G1 and a second dielectric multilayer film G2, a third dielectric multilayer film G3, and a first dielectric multilayer film G2. And a second stacked body L2 made of a four-dielectric multilayer film G4.
The transparent substrate 21 is formed of a transparent material (for example, quartz or borosilicate glass). Here, when the wavelength selection filter is made of colored glass as in the prior art, since the heat resistance is low, the wavelength selection filter may be damaged by heat shock because it is heated to a high temperature by high energy from the lamp 11. is there. In this embodiment, the heat resistance of the wavelength selection filter is ensured by forming the transparent substrate 21 from a material having a relatively high heat resistance, such as quartz.

The first and third dielectric multilayer films G1 and G3 include a first high refractive index material (first refractive index material) 22 having a first refractive index (first high refractive index) (n _H1 ), And a first low refractive index material (second refractive index material) 23 having a second refractive index (first low refractive index) (n _L1 ) smaller than a refractive index of 1, and alternately stacked. Yes.
The second and fourth dielectric multilayer films G2 and G4 include a second high refractive index material (third refractive index material) 24 having a third refractive index (second high refractive index) (n _H2 ), And a second low refractive index material (fourth refractive index material) 25 having a fourth refractive index (second low refractive index) (n _M ) smaller than a refractive index of 3, and alternately laminated. Yes.

The second refractive index (n _L1 ) and the fourth refractive index (n _M ) are made different from each other. In the present embodiment, the fourth refractive index (n _M ) is changed from the second refractive index (n _L1 ). Is also high.
In the present embodiment, the first refractive index (n _H1 ) and the third refractive index (n _H2 ) are also different, and the third refractive index (n _H2 ) is changed to the first refractive index (n _H1). ).
In short, in the prior art, the dielectric multilayer film is composed of a combination of two types of material layers having different refractive indexes, whereas in the present embodiment, four types of material layers having different refractive indexes, that is, The first refractive index material, the second refractive index material, the third refractive index material, and the fourth refractive index material are used, and the first and third dielectric multilayer films G1 and G3 are formed by the alternate lamination of the former two. The second and fourth dielectric multilayer films G2 and G4 are formed by the alternate lamination of the latter two.
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 later. To do.

In the wavelength selective filter 4 of the present embodiment, the first stacked body L1 and the second stacked body L2 are formed on different surfaces of the transparent substrate 21, respectively. Moreover, in the wavelength selection filter 4 of this embodiment, in order to selectively transmit the light of a desired wavelength range, the 1st laminated body L1 formed in one surface of the transparent substrate 21 is a narrow band pass type (NBP type) filter. The second laminate L2 formed on the other surface of the transparent substrate 21 constitutes a broadband path type (BBP type) filter.
The NBP-type first laminated body L1 is configured by laminating a second dielectric multilayer film G2 and a first dielectric multilayer film G1 in order from the transparent substrate 21.
The BBP-type second stacked body L2 is configured by stacking a third dielectric multilayer film G3 and a fourth dielectric multilayer film G4 in order from the transparent substrate 21.

The first dielectric multilayer film G1 and the second dielectric multilayer film G2 have a basic film configuration in which one is a short wave path type (SWP type) filter and the other is a long wave path type (LWP type) filter. It is configured by optimizing the film thickness of each layer.
Similarly, the third dielectric multilayer film G3 and the fourth dielectric multilayer film G4 are basically composed of a short wave path type (SWP type) filter on one side and a long wave path type (LWP type) filter on the other side. And the thickness of each layer is optimized.

In this embodiment, the center wavelength is set to 680 nm, and commercially available film design software (TFCalc of Software Spectra) is used to optimize the film thickness of each layer so as to satisfy the desired spectral transmittance. The result was obtained.
Here, the desired spectral transmittance in the present embodiment refers to a transmission wavelength region where the maximum transmittance is 85% or more in a wavelength range of 400 to 600 nm and a wavelength of 600 to 800 nm in the transmittance characteristics at normal incidence. Visible and near-infrared light cut wavelength range where the minimum transmittance is 1% or less in at least a part of the range, and ultraviolet side where the minimum transmittance is 1% or less in at least a part of the wavelength range of 200 to 400 nm It has a cut wavelength range.
Specifically, with the BBP-type first laminate L1, the transmission wavelength region where the maximum transmittance is 85% or more in the wavelength range of 400 to 600 nm and the transmittance on the short wavelength side of the transmission wavelength region are from 85%. The slope of the transmittance curve is 5% or less, and the slope of the transmittance curve is that the transmittance on the long wavelength side is 85% to 5% or less. Further, the NBP-type second laminate L2 allows the visible and near-infrared light-side cut wavelength regions where the minimum transmittance is 1% or less in at least part of the wavelength range of 600 to 800 nm, and the wavelength of 200 to 400 nm. An ultraviolet side cut wavelength region having a minimum transmittance of 1% or less is formed in at least a part of the range.

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 ), 4 with a refractive index (n _M ) of 2.26 to 2.40, 1.38 to 1.50, 2.42 to 2.70, and 1.58 to 2.00 for light with a wavelength of 500 nm, respectively. By doing so, such a desired spectral transmittance can be satisfied.

4 is a table showing the configuration of the NBP-type first laminate L1 of the wavelength selective filter 4, and FIG. 5 is a table showing the configuration of the BBP-type second laminate L2 of the wavelength selective filter 4.
The wavelength selection filter 4 includes Ta ₂ O ₅ for the first high refractive index material 22, SiO ₂ for the first low refractive index material 23, TiO ₂ for the second high refractive index material 24, and the second low refractive index material. 25 is selected from Al ₂ O ₃ . Here, the refractive index of each layer of Ta ₂ O ₅ , SiO ₂ , TiO ₂ , and Al ₂ O ₃ is 2.27, 1.48, 2.57, and 1.70 for light having a wavelength of 500 nm, respectively. . In the present embodiment, the refractive index of the transparent substrate 21 is 1.462.

More specifically, as shown in FIG. 4, the second high refractive index material 24 made of TiO ₂ and the second low refractive index material 25 made of Al ₂ O ₃ are alternately arranged on one surface of the transparent substrate 21. To form a second dielectric multilayer film G2. Further, the first dielectric is formed by alternately laminating the first high refractive index material 22 made of Ta ₂ O ₅ and the first low refractive index material 23 made of SiO ₂ on the second dielectric multilayer film G2. The multilayer film G1 is configured.
Further, as shown in FIG. 5, the first high refractive index material 22 made of Ta ₂ O ₅ and the first low refractive index material 23 made of SiO ₂ are alternately laminated on the other surface of the transparent substrate 21. Thus, the third dielectric multilayer film G3 is configured. Furthermore, the fourth dielectric multilayer is formed by alternately laminating the second high refractive index material 24 made of TiO ₂ and the second low refractive index material 25 made of Al ₂ O ₃ on the third dielectric multilayer film G3. The film G4 is configured.

Whether 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 this embodiment, since the refractive index of the transparent substrate 21 made of quartz glass is 1.462, a so-called intermediate refractive index material causes a difference in refractive index between the transparent substrate 21 and adjacent to the transparent substrate 21. Is possible. Here, in this specification, the intermediate refractive index material has a fourth refractive index (n _M : 1.58 to 2.00).
In 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, the NBP type 31st layer And the 32nd layer, or the BBP type 20th layer and the 21st layer, the high refractive index material and the low refractive index material are arranged adjacent to each other. The wavelength selection filter 4 of the present embodiment is obtained using ion plating as a vapor deposition technique.

FIG. 6 is a graph showing the spectral transmittance of the wavelength selective filter. FIG. 6A shows the case of the wavelength selective filter of this embodiment, and FIG. 6B shows the conventional high refractive index material and low refractive index. The case of the wavelength selective filter comprised by the dielectric multilayer film which consists only of two film | membrane substances of a material is shown. In FIG. 6, the horizontal axis represents wavelength (nm) and the vertical axis represents transmittance (%). The graph in FIG. 6 shows the results obtained by the simulation, the broken line shows the results at the time of normal incidence, and the solid line shows the results at the case of 60 ° oblique incidence.
In the wavelength selective filter 4 of the present embodiment, as shown in FIG. 6A, in the transmittance characteristics at normal incidence, the transmittance from 200 to 400 nm is less than 1%, and the transmittance from 420 to 510 nm is 88. %, The transmittance from 550 to 800 nm was less than 3%. Further, in this wavelength selection filter 4, in the comparison of the transmittance characteristics between normal incidence and 60 ° oblique incidence, the transmittance at the short wavelength side of the transmission wavelength region is 50% and the transmittance at the long wavelength side is 50%. The average wavelength shift amount of the% wavelength was 34 nm.

In an example of a wavelength selective filter made of only two film materials of a conventional high refractive index material (Ta ₂ O ₅ ) and low refractive index material (SiO ₂ ), as shown in FIG. Was 48 nm.
Therefore, by configuring the NBP-type first laminate L1 and the BBP-type second laminate L2 in which the first dielectric multilayer film G1 and the second dielectric multilayer film G2 are laminated so that light is transmitted, Wavelength shift due to incident angle can be reduced.

In the wavelength selective filter 4 of the present embodiment, as shown in FIGS. 4 and 5, the number of film layers of the NBP-type first stacked body L1 is 52, and the film layers of the BBP-type second stacked body L2 The number is 44 layers, and the total number of film layers is 96 layers.
When the conventional wavelength selection filter is formed so as to satisfy the spectral transmittance equivalent to that of the wavelength selection filter 4, the number of film layers is 44 and 38 for NBP type and BBP type, respectively, and the total film layer The number is 82 layers.
Therefore, in the present embodiment, the number of film layers is slightly increased as compared with the prior art. However, the present embodiment has the advantages that the wavelength shift amount is greatly reduced and that the reduction in the width can be reduced even at 60 ° oblique incidence in terms of the wavelength width of the transmission band.
In addition to this, as shown in FIG. 7B, in the conventional wavelength selection filter 4, an unnecessary wavelength region (generally, a region on the long wavelength side of a necessary transmission wavelength region (of FIG. 6B) In the case of 650 to 800 nm region)), light transmission is inevitable. On the other hand, in this embodiment, as shown in FIG. 7A, there is almost no light transmission in such a wavelength region.

Next, the necessity of forming a multilayer film on both surfaces of the transparent substrate 21 will be described.
FIG. 7 is a graph showing the spectral transmittance of the wavelength selection filter 4, and FIG. 7A shows the case where the NBP-type and BBP-type first laminates L1 and L2 are formed on both surfaces of the transparent substrate 21, respectively (hereinafter, FIG. 7B shows a case where the NBP-type first laminate L1 is formed on one surface of the transparent substrate 21 (hereinafter simply referred to as “single-sided film formation only for NBP”). FIG. 7C shows a case where the BBP-type second laminated body L2 is formed on one surface of the transparent substrate 21 (hereinafter simply referred to as “a case where only BBP is a single-sided film”). Indicates.
As shown in FIG. 7, the light on the long wavelength region side slightly away from the transmission band is not sufficiently cut in FIG. 7B, and the light on the long wavelength region side of the transmission band is not cut in FIG. 7C. Not cut enough. The amount of wavelength shift is the same in FIGS. 7 (A) to 7 (C).
That is, it is necessary to form the NBP-type and BBP-type first laminates L1 and L2 on both surfaces of the transparent substrate 21, respectively, because the cut characteristics required as a bandpass filter cannot be obtained individually. There is no relevance to wavelength shift mitigation.
Further, by forming the first stacked bodies L1 and L2 on both surfaces of the transparent substrate 21, the rising of the spectral transmittance curve can be sharpened.

Next, the influence on the wavelength shift amount in the film stacking direction will be described.
FIG. 8 is a table showing a configuration in which an NBP type laminate of wavelength selective filters is formed in the reverse order of the example of FIG. 4, and FIG. 9 is a diagram showing a BBP type laminate of wavelength selective filters formed in the reverse order of the example of FIG. It is a table | surface which showed the structure which carried out. FIG. 10 is a graph showing the spectral transmittance of a wavelength selective filter in which a multilayer film is formed in the reverse order of the example of FIG. 4. FIG. 10A shows a case where a double-sided film is formed, and FIG. In the case of formation, FIG. 10C shows the case of forming a single-sided film only for BBP.
In the wavelength selective filter shown in FIGS. 8 and 9, the NBP type laminate is formed by laminating a first dielectric multilayer film and a second dielectric multilayer film in order from a transparent substrate. Further, the BBP type laminate is formed by laminating a second dielectric multilayer film and a first dielectric multilayer film in order from the transparent substrate.
In all of FIGS. 10A to 10C, although the ripple (rippling) of the transmission band is generated, the wavelength shift amounts are the same in FIGS. 7 and 10 respectively.
That is, the wavelength shift amount is not related to the stacking direction. Moreover, a ripple can be suppressed by laminating | stacking in order of Formula (1) (2) of a film | membrane structure.

Next, the case where one type of high refractive index material is used will be described.
FIG. 11 is a table showing the configuration of an NBP type laminate of wavelength selective filters with one type of high refractive index material, and FIG. 12 is a BBP type laminate of wavelength selective filters with one type of high refractive index material. FIG. 13 is a continuation of FIG. FIG. 14 is a graph showing the spectral transmittance of a wavelength selective filter using one type of high refractive index material. FIG. 14A shows a case where a double-sided film is formed, and FIG. 14B shows a case where a single-sided film is formed only for NBP. In this case, FIG. 14C shows the case of forming a single-sided film only for BBP.
The wavelength selective filter shown in FIGS. 11 to 13 is formed of a combination of Ta ₂ O ₅ and Al ₂ O ₃ , Ta ₂ O ₅ and SiO ₂ . This wavelength selective filter has 90 and 146 layers for the NBP type and the BBP type, respectively, and the number of layers is excessive, making the film production unrealistic.

FIG. 15 is a table showing the configuration of an NBP type laminate of wavelength selective filters with one type of low refractive index material, and FIG. 16 is a BBP type laminate of wavelength selective filters with one type of low refractive index material. It is a table | surface which shows the structure of these. FIG. 17 is a graph showing the spectral transmittance of a wavelength selective filter using one kind of low refractive index material. FIG. 17A shows a case where a double-sided film is formed, and FIG. 17B shows a case where a single-sided film is formed only for NBP. FIG. 17C shows the case of forming a single-sided film only for BBP.
The wavelength selective filter shown in FIGS. 15 and 16 is formed of a combination of Ta ₂ O ₅ and Al ₂ O ₃ , TiO ₂ and Al ₂ O ₃ . This wavelength selection filter has a large number of layers of 85 and 75 layers for the NBP type and BBP type, respectively.
Therefore, the number of layer films can be reduced by making the second refractive index (n _L1 ) and the fourth refractive index (n _M ) different. Also, the number of layer films can be further reduced by making the first refractive index (n _H1 ) and the third refractive index (n _H2 ) different.
Further, the wavelength shift amount does not change between FIG. 7, FIG. 14 and FIG.

Next, the refractive index difference will be described.
In the wavelength selective filter 4 shown in FIGS. 4 and 5, 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). 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). The difference between the first average refractive index and the second average refractive index (refractive index difference) is 0.26.
Here, when the difference in refractive index is less than 0.1, the first and second dielectric multilayer films are close to the conventional film configuration using the same two kinds of film materials. It goes to the direction which becomes excessive, and there is no effect of this embodiment. On the other hand, when the difference in refractive index exceeds 0.6, the combination of refractive indexes is such that the corresponding film substance does not exist, and the film design itself by simulation is impossible.

FIG. 18 is a table showing the configuration of an NBP type laminate of wavelength selective filters having a refractive index difference of 0.2555, and FIG. 19 is a BBP type laminate of wavelength selective filters having a refractive index difference of 0.2555. It is a table | surface which shows the structure of these. FIG. 20 is a graph showing the spectral transmittance of a wavelength selective filter with a refractive index difference of 0.2555. FIG. 20A shows a case where a double-sided film is formed, and FIG. 20B shows a case where a single-sided film is formed only for NBP. In this case, FIG. 20C shows the case of forming a single-sided film only for BBP.
The wavelength selective filter shown in FIGS. 18 and 19 is formed of a combination of Ta ₂ O ₅ and MgF ₂ (refractive index 1.38), TiO ₂ and LaF ₃ (refractive index 1.586). This wavelength selection filter has NBP type and BBP type film layers of 48 and 47 layers, respectively.
In the wavelength selection filters shown in FIGS. 18 and 19, the average wavelength shift amount is 32 nm as shown in FIG.

FIG. 21 is a table showing the configuration of an NBP type laminate of wavelength selective filters with a refractive index difference of 0.3125, and FIG. 22 is a BBP type laminate of wavelength selective filters with a refractive index difference of 0.3125. It is a table | surface which shows the structure of these. FIG. 23 is a graph showing the spectral transmittance of a wavelength selective filter with a refractive index difference of 0.3125. FIG. 23A shows a case where a double-sided film is formed, and FIG. 23B shows a case where a single-sided film is formed only for NBP. In this case, FIG. 23C shows the case where only one BBP film is formed.
The wavelength selective filter shown in FIGS. 21 and 22 is formed of a combination of Ta ₂ O ₅ and MgF ₂ , TiO ₂ and Al ₂ O ₃ . This wavelength selection filter has NBP type and BBP type film layers of 44 layers and 50 layers, respectively.
In the wavelength selection filter shown in FIGS. 21 and 22, the average wavelength shift amount is 31 nm as shown in FIG.

FIG. 24 is a table showing the configuration of a wavelength selective filter NBP laminate having a refractive index difference of 0.4125, and FIG. 25 is a wavelength selective filter BBP laminate having a refractive index difference of 0.4125. It is a table | surface which shows the structure of these. FIG. 26 is a graph showing the spectral transmittance of a wavelength selective filter with a refractive index difference of 0.4125. FIG. 26A shows a case where a double-sided film is formed, and FIG. 26B shows a case where a single-sided film is formed only for NBP. In this case, FIG. 26C shows a case where only one BBP film is formed.
The wavelength selective filter shown in FIGS. 24 and 25 is formed of a combination of Ta ₂ O ₅ and MgF ₂ , TiO ₂ and Y ₂ O ₃ (refractive index 1.90). This wavelength selective filter has NBP type and BBP type film layers of 56 and 51 layers, respectively.
24 and 25, the average wavelength shift amount is 32 nm as shown in FIG.

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

Figure 27 is a table showing the structure of TiO ₂ and the intermediate refractive index material and the NBP type stack of wavelength selective filter formed only pair, Figure 28 is formed only by a pair of TiO ₂ and the intermediate refractive index material It is a table | surface which shows the structure of the BBP type | mold laminated body of the selected wavelength selection filter. FIG. 29 is a graph showing the spectral transmittance of a wavelength selective filter formed with only a pair of TiO ₂ and an intermediate refractive index material. FIG. 29A shows a case where a double-sided film is formed, and FIG. 29B shows an NBP. In the case of only single-sided film formation, FIG. 29C shows the case of single-sided film formation of only BBP.
The wavelength selection filter shown in FIGS. 27 and 28 is formed of a combination of TiO ₂ and Al ₂ O ₃ . The wavelength selection filter layer number becomes NBP type and BBP-type, respectively 79 layers and 74 layers, the number of TiO2 layers with increasing total number of film layers increases, a wavelength of about 400nm by absorption of TiO ₂ The transmittance decreases.
Thus, not enough just simply using TiO _2, and so also used Ta ₂ O ₅ absorption of near-ultraviolet region is low, with use of two types of high-refractive-index material, a first dielectric multilayer film G1 and the second The number of films can be reduced by laminating the dielectric multilayer film G2 and using two kinds of low refractive index materials to make the second refractive index and the fourth refractive index different.
7 and 29, the wavelength shift amount does not change.

  As described above, according to the present embodiment, on the transparent substrate 21, the first stacked body L1 including the first dielectric multilayer film G1 and the second dielectric multilayer film G2, the third dielectric multilayer film, A second laminated body L2 made of a fourth dielectric multilayer film, and the first and third dielectric multilayer films G1 and G3 have a first refractive index material 22 having a first refractive index, and a first And a second refractive index material 23 having a second refractive index smaller than that of the second refractive index material 23, and the second and fourth dielectric multilayer films G2 and G4 have a third refractive index. The third refractive index material 24 and the fourth refractive index material 25 having a fourth refractive index smaller than the third refractive index are alternately stacked, and the first refractive index and the third refractive index material The second refractive index and the fourth refractive index are different from each other. With this configuration, the amount of wavelength shift can be reduced, and as a result, the width of the necessary light transmission wavelength region can be secured and the transmission of light in unnecessary wavelength regions can be suppressed.

  Moreover, according to this embodiment, it was set as the structure by which the 1st laminated body L1 and the 2nd laminated body L2 were each formed in the different surface of the transparent substrate 21. FIG. With this configuration, ripples in the transmittance curve can be suppressed.

  Further, according to the present embodiment, the first laminated body L1 constitutes a narrow bandpass filter, and the second laminated body L2 constitutes a broadband pass filter, so that light in a desired wavelength range can be selectively transmitted. Can do.

  In addition, according to the present embodiment, the first average refractive index that is the average value of the first refractive index and the second refractive index, and the second value that is the average value of the third refractive index and the fourth refractive index. The difference from the average refractive index was set to 0.1 to 0.6. With this configuration, it is possible to reduce the wavelength shift amount to a desired predetermined value or less while satisfying a desired spectral transmittance.

  Further, according to the present embodiment, the refractive index of the transparent substrate is 1.45 to 1.53 for the light with a wavelength of 500 nm, the first refractive index is 2.26 to 2.40, the second The 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. With this configuration, in the comparison of the transmittance characteristics between normal incidence and 60 ° oblique incidence, the wavelength at which the transmittance on the short wavelength side of the transmission wavelength region is 50% and the wavelength at which the transmittance on the long wavelength side is 50%. The average wavelength shift amount can be 35 nm or less.

However, the above-described embodiment is an aspect of the present invention, and it is needless to say that the embodiment can be appropriately changed without departing from the gist of the present invention.
For example, in the above-described embodiment, the wavelength selection filter 4 is configured by forming NBP-type and BBP-type laminates on both sides of the transparent substrate in order to obtain cut characteristics necessary as a bandpass filter. However, the present invention is not limited to this configuration. An NBP type or a BBP type may be formed on one surface of the transparent substrate, and an NBP type and a BBP type may be formed on one surface of the transparent substrate.

  In the wavelength selective filter 4 of the above-described embodiment, the NBP type laminate is configured by laminating the second dielectric multilayer film and the first dielectric multilayer film in order from the transparent substrate, and the BBP type laminate is The first dielectric multilayer film and the second dielectric multilayer film are laminated in order from the transparent substrate. However, the NBP type laminated body is configured by laminating the first dielectric multilayer film and the second dielectric multilayer film in order from the transparent substrate, and the BBP type laminated body is configured by the second dielectric multilayer film in order from the transparent substrate. The first dielectric multilayer film may be laminated.

In the wavelength selection filter 4 of the above-described embodiment, the first high refractive index material 22 is Ta ₂ O ₅ , the first low refractive index material 23 is SiO ₂ , and the second high refractive index material 24 is TiO ₂ . Although Al ₂ O ₃ is used for the second low refractive index material 25, it is not limited to these materials. The film material used for each refractive index material is not limited to a single material, and a plurality of materials may be combined with each refractive index material. In addition to quartz glass, optical glass (BK7 or the like) having a refractive index in the range of 1.45 to 1.53, heat ray absorbing glass, or the like can be used for the transparent substrate.

In the wavelength selection 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 desired spectral transmittance is different from that of the wavelength selection filter 4. In contrast, if the number of film layers can be reduced, the first refractive index and the third refractive index may be the same.
In the above-described embodiment, the wavelength selection filter 4 uses ion plating as a vapor deposition method, but the film forming method is not limited to this.

  In the above-described embodiment, a metal halide lamp is used as the lamp 11, but the type of the lamp is not limited to this, and for example, a mercury lamp may be used.

  In the above-described embodiment, the wavelength selection filter 4 is provided alone, but the wavelength selection filter 4 can be used in combination with another optical member such as a polarizing element, for example.

1 UV irradiation device (light irradiation device)
4 wavelength selection filter 21 transparent substrate 22 first high refractive index material (first refractive index material)
23 First low refractive index material (second refractive index material)
24 Second high refractive index material (third refractive index material)
25 Second low refractive index material (fourth refractive index material)
G1 1st dielectric multilayer film G2 2nd dielectric multilayer film G3 1st dielectric multilayer film G4 2nd dielectric multilayer film L1 Narrow band pass type 1st laminated body L2 Broadband path type 2nd laminated body _nH1 1st Refractive index (first high refractive index)
n _L1 second refractive index (first low refractive index)
n _H2 Third refractive index (second high refractive index)
n _M Fourth refractive index (second low refractive index)

Claims (7)

On the transparent substrate, a first laminated body composed of a first dielectric multilayer film and a second dielectric multilayer film, and a second laminated body composed of a third dielectric multilayer film and a fourth dielectric multilayer film,
The first and third dielectric multilayer films are:
A first refractive index material having a first refractive index;
A second refractive index material having a second refractive index smaller than the first refractive index;
Is composed of alternating layers,
The second and fourth dielectric multilayer films are:
A third refractive index material having a third refractive index;
A fourth refractive index material having a fourth refractive index smaller than the third refractive index;
Is composed of alternating layers,
The first refractive index and the third refractive index are different,
The wavelength selective filter, wherein the second refractive index and the fourth refractive index are different.   2. The wavelength selective filter according to claim 1, wherein the first stacked body and the second stacked body are respectively formed on different surfaces of the transparent substrate. A first average refractive index that is an average value of the first refractive index and the second refractive index, and a second average refractive index that is an average value of the third refractive index and the fourth refractive index. The difference is the average of the wavelength at which the transmittance on the short wavelength side of the transmission wavelength region is 50% and the wavelength at which the transmittance on the long wavelength side is 50% in the comparison of the transmittance characteristics between normal incidence and 60 ° oblique incidence. The wavelength selection filter according to claim 1 or 2, wherein the wavelength shift amount is set to a value of 35 nm or less. The first stacked body is configured by stacking the second dielectric multilayer film and the first dielectric multilayer film in order from the transparent substrate, and the second stacked body is configured by sequentially stacking the third dielectric multilayer from the transparent substrate. film, the wavelength selective filter according to any one of claims 1 to 3 formed by laminating the fourth dielectric multilayer film and said Rukoto. A first average refractive index that is an average value of the first refractive index and the second refractive index, and a second average refractive index that is an average value of the third refractive index and the fourth refractive index. The wavelength selective filter according to claim 1 , wherein the difference is 0.1 to 0.6. For light with a wavelength of 500 nm, the refractive index of the transparent substrate is 1.45 to 1.53,
A first refractive index of 2.26 to 2.40;
A second refractive index of 1.38 to 1.50,
A third refractive index of 2.42 to 2.70,
The fourth refractive index is 1.58 to 2.00
The wavelength selective filter according to any one of claims 1 to 5, wherein   A light irradiation apparatus, wherein a light source is housed in a housing, and the wavelength selection filter according to claim 1 is provided in a light emission opening of the housing.

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