JP2015225154A - Near-infrared cut filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near-infrared cut filter which offers not only superior near-infrared blocking capability but also good durability with smaller temporal degradation in the near-infrared blocking capability by preventing disintegration of organic pigments caused by properties of an oxide film and a fluoride film that constitutes films laid adjacent to a light absorption film.SOLUTION: A near-infrared cut filter 10 of the present invention includes; a substrate 12 which is transparent in the visible ray range; a first dielectric multilayer film 14 which is provided at least on one surface of the substrate 12 and reflects at least light in the red to near-infrared range; a light absorption film 16 which is provided at least on the other surface of the substrate 12 and absorbs part of light in the red to near-infrared range; and a dielectric film (anti-reflection film) 18 which is provided on the outer side of the light absorption film 16 relative to the substrate 12 and includes a nitride film.

Description

  The present invention relates to a near-infrared cut filter.

  In recent years, mobile phones equipped with cameras and mobile devices called tablets have come into widespread use. In addition, devices equipped with cameras, such as surveillance cameras installed indoors and outdoors, network cameras, sensor cameras, and products called door phones and intercoms, have been rapidly increasing.

  Such a camera uses a solid-state imaging device called a CMOS or CCD that converts an image into electronic information. CMOS and CCD are semiconductor elements, and a semiconductor substrate such as a silicon substrate is used. Since the band gap of silicon is about 1.1 eV, it absorbs light with a wavelength of 1200 nm or less, and as a result, the absorbed near infrared rays affect the image signal as electrical noise, disturbing the image. There was a case. As a method for solving such a problem, a near-infrared cut filter (IR cut filter) is installed in the imaging system to remove unnecessary light (light having a wavelength of about 650 nm to 1200 nm) as an image signal. Is common.

  As a near infrared cut filter, for example, an absorption type near infrared cut filter called “blue glass” in which a metal oxide is mixed with phosphate glass or fluorophosphate glass, and a dielectric in which a plurality of metal oxide films are laminated on a transparent substrate A reflective near-infrared cut filter that reflects near-infrared rays by a multilayer film has been proposed.

  Reflective near-infrared cut filters are less expensive than absorptive near-infrared cut filters, but due to the use of optical interference, when light enters the substrate of the near-infrared cut filter, it depends on the incident angle of the light. Since the spectral transmittance characteristic is changed, there is a problem that the brightness and color are different between the central portion and the peripheral portion of the image due to the change of the spectral transmittance characteristic due to the incident angle. As a technique for improving such a problem, Japanese Patent Application Laid-Open No. 2012-137645 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2014-52482 (Patent Document 2) are known.

  In Patent Document 1, a light absorption structure formed of a resin layer on a transparent substrate and having a predetermined absorption wavelength region, and a plurality of inorganic thin films are laminated on the light absorption structure, and near infrared light is emitted. An infrared cut filter (Example 1) in which a light reflecting structure for reflecting is formed, and a light reflecting structure for reflecting light having a predetermined wavelength is formed on the opposite surface of the transparent substrate and made of a similar inorganic thin film. Has been.

  Patent Document 2 discloses a transparent dielectric substrate, an infrared reflection layer formed on one surface of the transparent dielectric substrate, an infrared absorption layer formed on the other surface of the transparent dielectric substrate, and infrared absorption. An infrared cut filter with a protective layer on the layer is described.

JP 2012-137645 A JP 2014-52482 A

In the infrared cut filter described in Patent Document 1, TiO ₂ is used as a high-refractive material and SiO ₂ is used as a low-refractive material as the material of the dielectric film constituting the light reflecting structure. In addition, Nb ₂ O ₅ , ZrO ₂ , and Ta ₂ O ₅ are described as high refractive materials, and MgF ₂ is described as a low refractive material (see paragraphs 0042 and 0043). In addition, in the infrared cut filter described in Patent Document 2, as a material of the dielectric film constituting the infrared reflection layer, TiO ₂ is described as a high refractive material, SiO ₂ is described as a low refractive material, and others Describes MgF ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , Nb ₂ O ₅ , and Ta ₂ O ₅ (see paragraph 0022). Further, as the material of the protective layer of the infrared-absorbing layer, TEOS SiO ₂ a (tetra d Toshiki silane) is formed by SiO ₂ or vapor deposition of a raw material have been described (see paragraph 0062).

  Since both the reflective structure disclosed in Patent Document 1 and the reflective layer disclosed in Patent Document 2 (hereinafter also referred to as “reflective film”) are an oxide film and a fluoride film, a light absorbing structure. Alternatively, there is a problem that an infrared absorption layer (hereinafter also referred to as “light absorption film”) is likely to deteriorate and is inferior in durability. Specifically, the oxide constituting the reflective film serves as an oxygen supply source for the organic dye contained in the light absorption film, and thus causes deterioration of the organic dye due to oxidation. In addition, the fluoride constituting the reflective film has a low packing density unless heated to several hundred degrees, and thus allows permeation of oxygen and water, which is also an organic dye and a light absorbing film containing the same. Causes deterioration.

  The object of the present invention is not only excellent in near-infrared cutting ability, but also prevents the degradation of the organic dye and the deterioration of the light absorption film due to the characteristics of the oxide film and the fluoride film constituting the film adjacent to the light absorption film. Accordingly, an object of the present invention is to provide a near-infrared cut filter that has little deterioration with time in near-infrared cut ability and good durability.

The near-infrared cut filter according to one aspect of the present invention is
A transparent substrate in the visible range;
A first dielectric multilayer film provided on at least one surface side of the substrate and reflecting light from at least a red region to a near infrared region;
A light absorption film that is provided on at least one surface side of the substrate and absorbs part of light from the red region to the near infrared region;
A dielectric film provided outside the light absorption film with respect to the substrate and including a nitride film;
including.

  According to the present invention, by having a dielectric film including a nitride film outside the light absorption film with respect to the substrate, characteristics of the oxide film and the fluoride film constituting the film adjacent to the light absorption film can be obtained. Providing a near-infrared cut filter that can prevent decomposition of the organic dye caused by it, and further prevent deterioration of the light absorption film itself due to moisture, etc. it can.

  In the near-infrared cut filter according to the present invention, the dielectric film may be a second dielectric multilayer film configured by alternately laminating nitride films and oxide films.

  In the near-infrared cut filter according to the present invention, the second dielectric multilayer film may be an antireflection film having a function of reducing the surface reflectance of the light absorption film at least in a part of the visible range.

  In the near infrared cut filter according to the present invention, the first dielectric multilayer film may be a dielectric multilayer film configured by alternately laminating nitride films and oxide films.

  In the near-infrared cut filter according to the present invention, the first dielectric multilayer film may be a dielectric multilayer film configured by alternately stacking oxide films having different refractive indexes.

  In the near-infrared cut filter according to the present invention, the first dielectric multilayer film can function as a reflection film that reflects light in the ultraviolet region in addition to the red region to the near-infrared region.

  In the near-infrared cut filter according to the present invention, the second dielectric multilayer film, together with the first dielectric multilayer film, functions as a reflective film that reflects light in the ultraviolet region in addition to the red region to the near-infrared region. be able to.

  In the near-infrared cut filter according to the present invention, the nitride film may be silicon nitride or silicon oxynitride.

  In the near-infrared cut filter according to the present invention, the light absorption film may be a resin film containing an organic dye and having a maximum absorption wavelength in the range of 650 nm to 750 nm.

  According to the present invention, it is possible to provide a near-infrared cut filter that has a small incident angle dependency, is suppressed from deterioration of a light absorption film containing an organic dye, and has excellent durability.

It is sectional drawing which shows typically the near-infrared cut off filter concerning 1st Embodiment of this invention. It is sectional drawing which shows typically the near-infrared cut off filter concerning 2nd Embodiment of this invention. It is a figure which shows the spectral transmittance characteristic of an antireflection film. It is a figure which shows the film | membrane structure of the antireflection film shown in FIG. It is a figure which shows the spectral transmittance characteristic of a 1st dielectric multilayer. It is a figure which shows the spectral transmittance characteristic of a 1st dielectric multilayer. It is a figure which shows the test method of an experiment example. (A), (B) is a figure which shows the spectral transmittance characteristic of the infrared rays and ultraviolet-ray cut filter used with the test method shown in FIG. It is a figure which shows the spectral transmittance characteristic of the sample A obtained by the experiment example. It is a figure which shows the spectral transmittance characteristic of the sample B obtained by the experiment example. It is a figure which shows the spectral transmittance characteristic of the sample C obtained by the experiment example. It is a figure which shows the spectral transmittance characteristic of the sample D obtained by the experiment example. It is the figure which plotted the spectral transmittance obtained by the experiment example in a specific wavelength. It is a figure which expands and shows the figure of FIG. It is sectional drawing which shows typically the near-infrared cut off filter concerning 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

1. First Embodiment 1.1 Near-Infrared Cut Filter FIG. 1 is a cross-sectional view schematically showing a near-infrared cut filter 10 according to a first embodiment. The near-infrared cut filter 10 includes a substrate 12, a first dielectric multilayer film 14, a light absorption film 16, and a second dielectric multilayer film (hereinafter also referred to as “antireflection film”) 18.

  The substrate 12 is not particularly limited as long as it is transparent in the visible range. Examples of the material of the substrate 12 include inorganic materials such as glass and quartz, and organic materials such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polycarbonate (PC), and polyimide (PI). Can be used. The substrate 12 preferably has a film thickness of 3 mm or less in consideration of the space where the near infrared cut filter 10 is installed, the substrate cost, and the weight.

  The first dielectric multilayer film 14 is provided on one surface of the substrate 12. The first dielectric multilayer film 14 is a reflective film for reflecting light of a specific wavelength, and functions as a reflective film that transmits visible light and reflects light in the near infrared region from at least the red region. In the present embodiment, the first dielectric multilayer film 14 can function as a reflective film that reflects light in the ultraviolet region in addition to the red region to the near infrared region. Since the reflection band of the first dielectric multilayer film 14 extends from the red region to the near infrared region as well as the ultraviolet region, adverse effects due to ultraviolet rays, for example, decomposition of the organic dye of the light absorbing film 16 due to ultraviolet rays are suppressed, thereby reducing the light absorbing film. 16 deterioration can be prevented. The first dielectric multilayer film 14 is configured by alternately laminating a plurality of dielectrics having different refractive indexes, and designing optical characteristics such as spectral transmittance characteristics by controlling the refractive index and film thickness of each layer. Can do.

The first dielectric multilayer film 14 can be configured by alternately laminating nitride films and oxide films. As the nitride film, silicon nitride, silicon oxynitride, aluminum nitride, or the like can be used. When silicon oxynitride is used, the stoichiometric ratio of oxygen to nitrogen (oxygen / nitrogen) is preferably 1 or less. As the oxide film, silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), or the like can be used. By using silicon nitride or silicon oxynitride as the film of the first dielectric multilayer film 14, the first dielectric multilayer film 14 is formed using the same film formation method and film formation apparatus as the antireflection film 18 described later. This is advantageous in terms of process.

The first dielectric multilayer film 14 may be an oxide film instead of a nitride film. As the material of such an oxide film, in addition to silicon oxide, titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ) or the like can be used. When the first dielectric multilayer film 14 is composed of oxide films having different refractive indexes, the oxide is appropriately selected from the oxides.

  The first dielectric multilayer film 14 is formed by a known film formation method such as a vacuum deposition method, a sputtering method, an ion beam assisted deposition method (IAD method), an ion plating method (IP method), or an ion beam sputtering method (IBS method). Etc. can be used. It is desirable to use a sputtering method or an ion beam sputtering method for forming the nitride film.

  The light absorption film 16 is provided on the other surface of the substrate 12, which is opposite to the first dielectric multilayer film 14. The light absorption film 16 has a function of transmitting visible light and absorbing part of light from the red region to the near infrared region. The light absorption film 16 is made of a resin film containing an organic dye and having a maximum absorption wavelength in the range of 650 nm to 750 nm. Since the light absorption film 16 is adjacent to the substrate 12, it is desirable to reduce the refractive index difference between them to reduce the reflectance at the interface. By having such a light absorbing film 16, it is possible to reduce the dependence of the spectral transmittance characteristics depending on the incident angle and to have excellent near-infrared cutting properties.

As the organic dye, an azo compound, a phthalocyanine compound, a cyanine compound, a diimonium compound, or the like can be used. Examples of organic dyes include near infrared absorbing dyes “IR-T” and “IR-13F” manufactured by Showa Denko KK, and near infrared absorbing dyes “IRA 677”, “IRA 735”, and “IRA” manufactured by Indeco Corporation. 742 ”,“ IRA 751 ”,“ IRA 761 ”,“ IRA 788 ”, and the like can be appropriately selected from the viewpoints of spectral characteristics, cost, process, and the like.

  As a resin material as a binder constituting the light absorption film 16, polyacryl, polyester, polycarbonate, polystyrene, polyolefin, or the like can be used. The resin material may be a mixture of a plurality of resins, or may be a copolymer using a monomer of the resin. The resin material may be any material that has high transparency in the visible range, and is selected in consideration of compatibility with organic dyes, film formation process, cost, and the like. Further, in order to improve the ultraviolet resistance of the light absorption film 16, a quencher such as a sulfur compound may be added to the resin material.

  For example, the following method can be used to form the light absorption film 16. First, a resin binder is dissolved with a known solvent such as methyl ethyl ketone and toluene, and an organic dye is added to prepare a coating solution. Next, this coating solution is applied to the substrate 12 with a desired film thickness by, for example, spin coating, and dried and cured in a drying furnace.

  The antireflection film 18 is provided on the surface of the light absorption film 16. The antireflection film 18 is a dielectric film including a nitride film. In this embodiment, the antireflection film 18 constitutes a second dielectric multilayer film formed by alternately laminating nitride films and oxide films. The antireflection film 18 has a function of reducing the surface reflectance of the light absorption film 16 at least in a part of the visible range.

As the nitride film constituting the antireflection film 18, silicon nitride, silicon oxynitride, aluminum nitride or the like can be used, and silicon nitride is particularly desirable. When silicon oxynitride is used, it is desirable that the stoichiometric ratio of oxygen to nitrogen (oxygen / nitrogen) is 1 or less in order to prevent the silicon oxynitride film from being a supply source of oxygen. As the oxide film, silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), or the like can be used. The antireflection film 18 prevents reflection of light in the visible range and improves the transmittance of visible light as the entire near-infrared cut filter 10 to prevent so-called ghost, and functions as a protective film for the light absorption film 16. . Specifically, the light absorption film 16 includes an organic dye that is easily decomposed by ultraviolet rays, oxygen, and the like, and the resin binder of the light absorption film 16 is easily deteriorated by moisture. Therefore, an antireflection film is formed on the surface of the light absorption film 16. By forming 18, the antireflection film 18 can prevent entry of oxygen, water, and the like into the light absorption film 16, and can suppress deterioration of the light absorption film 16. The antireflection film 18 may be a single layer of nitride film, but is preferably a laminate of a plurality of nitride films and oxide films. The number of laminated antireflection films 18 can be set as appropriate, but is preferably 4 to 10 layers. The antireflection film 18 is preferably formed so that the nitride film constituting the antireflection film 18 is in contact with the light absorption film 16. By forming the antireflection film 18 in such a state, the nitride film does not contain oxygen or its content is small, so that the supply of oxygen to the light absorption film 16 can be suppressed, and the antireflection film 18. The barrier property can be further increased.

  Furthermore, in this embodiment, by using a nitride film as one of the films constituting the antireflection film 18, it is possible to reliably prevent the entry of oxygen, water, and the like into the light absorption film 16 and to exhibit excellent barrier properties. be able to. In other words, nitride films are usually denser and denser than oxide films, although they depend on the deposition method, and they do not serve as oxygen supply sources. Can be prevented. This is clear from the experimental examples described later. Therefore, according to the antireflection film 18 using a nitride film, the deterioration of the light absorption film can be remarkably suppressed as compared with the protective film made of an oxide film described in Patent Document 2, for example, and the durability of the near-infrared cut filter is improved. In addition, since the nitride film has a higher hardness than the oxide film, the scratch resistance of the near infrared cut filter 10 can be improved. The effect obtained by using the nitride film as described above is the same in other embodiments.

The antireflection film 18 can be formed by using the above-described known film formation method. However, in consideration of the film formation of the nitride film, for example, the ion beam sputtering method (IBS method), ion beam assist can be used as the sputtering method. It is desirable to use a vapor deposition method (IAD method) or an ion plating method (IP method).

1.2 Optical Characteristics Next, spectral transmittance characteristics of a dielectric multilayer film including a nitride film will be described.

FIG. 3 is a graph showing the spectral reflectance of the sample of the antireflection film 18. As shown in FIG. 4, a sample of the antireflection film is formed by alternately forming a nitride film (silicon nitride Si ₃ N ₄ ) and an oxide film (silicon dioxide SiO ₂ ) at a predetermined thickness on an acrylic resin substrate. Four layers are laminated. For forming the nitride film and the oxide film, a direct current sputtering method was used, a silicon target was used as a target for silicon oxide, and a silicon target was used as a target for silicon nitride. A silicon nitride target can also be used as a target for silicon nitride.

  From FIG. 3, it was confirmed that the sample of the antireflection film reduced the reflection of light in the visible region (approximately 450 nm to 650 nm).

FIG. 5 is a graph showing the spectral transmittance and the spectral reflectance of the sample of the first dielectric multilayer film 14. In this graph, “T” indicates spectral transmittance, and “R” indicates spectral reflectance. The sample of the first dielectric multilayer film is obtained by alternately stacking 42 layers of titanium dioxide (TiO ₂ ) and silicon dioxide (SiO ₂ ) with a predetermined film thickness on a glass substrate.

  From FIG. 5, it was confirmed that this dielectric multilayer film sample reflected almost 100% of light from the red region to the near infrared region (approximately 700 nm to 1000 nm).

FIG. 6 is a graph showing the spectral transmittance and spectral reflectance of another sample of the first dielectric multilayer film 14. In this graph, “T” indicates spectral transmittance. This sample of the first dielectric multilayer film is obtained by alternately stacking 72 layers of silicon nitride (Si ₃ N ₄ ) and silicon dioxide (SiO ₂ ) with a predetermined film thickness on an acrylic resin substrate.

  From FIG. 6, it was confirmed that this dielectric multilayer film sample reflected almost 100% of light from the red region to the near infrared region (approximately 700 nm to 1000 nm) and the ultraviolet region (approximately 350 nm to 380 nm).

1.3 Modifications In the first embodiment, in addition to the near infrared cut filter 10 shown in FIG. That is, when the first dielectric multilayer film 14 is formed of a nitride film and an oxide film, since the first dielectric multilayer film 14 has a barrier property, the gap between the substrate 12 and the first dielectric multilayer film 14 is The light absorption film 16 can also be provided.

2. 2nd Embodiment FIG. 2: is sectional drawing which shows typically the near-infrared cut off filter 20 concerning 2nd Embodiment. The near-infrared cut filter 20 includes a substrate 22, a first dielectric multilayer film 24, a light absorption film 26, and a second dielectric multilayer film 28. The near-infrared cut filter 20 according to the second embodiment uses the near-infrared cut filter 10 according to the first embodiment and a second dielectric multilayer film 28 that mainly functions as a reflection film instead of the antireflection film 18. Is different. Accordingly, the substrate 22 and the light absorption film 26 of the near infrared cut filter 20 of the second embodiment have the same configuration as the substrate 10 and the light absorption film 26 of the near infrared cut filter 10 of the first embodiment, and thus detailed Description is omitted.

  The substrate 22 is not particularly limited as long as it is transparent in the visible range. The material of the substrate 22 is the same as that of the substrate 12.

  The first dielectric multilayer film 24 is provided on one surface of the substrate 22. The second dielectric multilayer film 28 is provided on the other side of the substrate 22 and on the surface of the light absorption film 26. The first dielectric multilayer film 24 and the second dielectric multilayer film 28 are both reflection films, and the dielectric multilayer films 24 and 28 reflect both the light from the red region to the near infrared region and the ultraviolet region. Can function as a membrane. The reflection band of the first dielectric multilayer film 24 and the second dielectric multilayer film 28 extends not only from the red region to the near infrared region but also to the ultraviolet region. Degradation of the light absorption film 16 can be prevented. The first dielectric multilayer film 24 and the second dielectric multilayer film 28 are configured by alternately laminating a plurality of dielectrics having different refractive indexes, and by controlling the refractive index and film thickness of each layer, spectral transmittance characteristics Etc. can be designed. The dielectric film constituting the first dielectric multilayer film 24 is the same as the first dielectric multilayer film 14 of the first embodiment.

Since the second dielectric multilayer film 28 needs to function as a protective film for the light absorption film 26, the second dielectric multilayer film 28 is composed of a dielectric multilayer film in which nitride films and oxide films are alternately stacked. As the nitride film constituting the second dielectric multilayer film 28, silicon nitride, silicon oxynitride, aluminum nitride, or the like can be used, and silicon nitride is particularly desirable. When silicon oxynitride is used, it is desirable that the stoichiometric ratio of oxygen to nitrogen (oxygen / nitrogen) is 1 or less in order to prevent the silicon oxynitride film from being a supply source of oxygen. As the oxide film, silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), or the like can be used.

  The light absorption film 26 is provided on the other surface of the substrate 22, which is opposite to the first dielectric multilayer film 24. Therefore, the light absorption film 26 is disposed in a state sandwiched between the substrate 22 and the second dielectric multilayer film 28. The material of the light absorption film 26 is the same as that of the light absorption film 16 of the first embodiment.

  As described above, the second dielectric multilayer film 28 functions as a reflection film having a specific wavelength and also functions as a protective film for the light absorption film 26. Specifically, the light absorption film 26 includes an organic dye that is easily decomposed by ultraviolet rays, oxygen, and the like, and the resin binder of the light absorption film 26 is easily deteriorated by moisture. Therefore, the second dielectric is formed on the surface of the light absorption film 26. By forming the body multilayer film 28, the second dielectric multilayer film 28 can prevent entry of oxygen, water, and the like into the light absorption film 26, and the deterioration of the light absorption film 26 can be suppressed.

  The second dielectric multilayer film 28 is preferably formed so that the nitride film constituting the second dielectric multilayer film 28 is in contact with the light absorption film 26. By forming the second dielectric multilayer film 28 in such a state, the nitride film does not contain oxygen or its content is low, so that the supply of oxygen to the light absorption film 26 can be suppressed, The barrier property of the two-dielectric multilayer film 28 can be further improved.

  Compared to oxide films, nitride films are usually denser and denser, although they depend on the deposition method, and they do not serve as oxygen supply sources. Can be prevented. This is clear from the experimental examples described later. Therefore, according to the second dielectric multilayer film 28 using the nitride film, the deterioration of the light absorption film can be remarkably suppressed as compared with, for example, the protective film made of the oxide film described in Patent Document 2, and the near infrared cut filter The durability of can be improved.

According to the near-infrared cut filter 20 of this embodiment, the second dielectric multilayer film 28 not only functions as a protective film for the light absorption film 26 but also a dielectric multilayer film made of a multilayer dielectric is formed on the substrate 2.
Since the first and second dielectric multilayer films 24 and 28 can be divided and arranged on both sides of the film 2, the film stress can be reduced and the warpage of the substrate 22 can be prevented.

3. Third Embodiment FIG. 15 is a cross-sectional view schematically showing a near-infrared cut filter 30 according to a third embodiment. The near-infrared cut filter 30 includes a substrate 32, a first dielectric multilayer film 34, a light absorption film 36, and a second dielectric multilayer film (hereinafter also referred to as “antireflection film”) 38. The near-infrared cut filter 30 according to the third embodiment is provided with the near-infrared cut filter 10 according to the first embodiment, mainly in a state where the first dielectric multilayer film 34 is divided on both sides of the substrate 32. It is different. Specifically, the first dielectric multilayer film 34 includes an upper first dielectric multilayer film 34 a provided on one side of the substrate 32 and a lower first dielectric multilayer film 34 b provided on the other side of the substrate 32. It consists of and. Therefore, the substrate 32, the light absorption film 36 and the antireflection film 38 of the near infrared cut filter 30 of the third embodiment are the same as the substrate 10, the light absorption film 16 and the antireflection film 18 of the near infrared cut filter 10 of the first embodiment. Since the configuration is the same as that in FIG.

  The substrate 32 is not particularly limited as long as it is transparent in the visible range. The material of the substrate 32 is the same as that of the substrate 12.

  The first dielectric multilayer film 34 is divided into an upper first dielectric multilayer film 34 a provided on the upper surface of the substrate 32 and a lower first dielectric multilayer film 34 b provided on the lower surface of the substrate 32. ing. The antireflection film 38 is provided on the other side of the substrate 32 and on the surface of the light absorption film 36. Each of the upper first dielectric multilayer film 34a and the lower first dielectric multilayer film 34b is a reflection film, and the dielectric multilayer films 34a and 34b of both reflect light from the red region to the near infrared region and the ultraviolet region. It can function as a reflective film. The reflection band of the first dielectric multilayer film 34 extends from the red region to the near infrared region as well as the ultraviolet region, thereby suppressing adverse effects due to the ultraviolet region, for example, decomposition of the organic dye of the light absorbing film 36 by ultraviolet rays, thereby absorbing light. Deterioration of the film 36 can be prevented.

  The first dielectric multilayer film 34 is configured by alternately laminating a plurality of dielectrics having different refractive indexes, and designing optical characteristics such as spectral transmittance characteristics by controlling the refractive index and film thickness of each layer. Can do. The dielectric film constituting the first dielectric multilayer film 34 is the same as the first dielectric multilayer film 14 of the first embodiment. That is, the first dielectric multilayer film 34 is composed of a stack of oxide films having different refractive indexes or a stack of nitride films and oxide films. In addition, since at least the lower first dielectric multilayer film 34b is in contact with the light absorption film 36, when it is desired to function as a barrier layer of the light absorption film 36, a laminate of a nitride film and an oxide film may be used. Good.

  The light absorption film 36 is provided on the surface of the lower first dielectric multilayer film 34b. Therefore, the light absorption film 36 is arranged in a state sandwiched between the lower first dielectric multilayer film 34 b and the antireflection film 38. The material of the light absorption film 36 is the same as that of the light absorption film 16 of the first embodiment.

  The antireflection film 38 is composed of a laminated body of a nitride film and an oxide film, and functions as a protective film for the light absorption film 36 together with an antireflection function. Specifically, the light absorption film 36 contains an organic dye that is easily decomposed by ultraviolet rays, oxygen, and the like, and the resin binder of the light absorption film 36 is easily deteriorated by moisture and oxygen, so that it is reflected on the surface of the light absorption film 36. By forming the prevention film 38, the deterioration of the light absorption film 36 can be suppressed.

That is, by using a nitride film as one of the films constituting the antireflection film 38, it is possible to exhibit excellent barrier properties that can reliably prevent the entry of oxygen, water, and the like into the light absorption film 36. Compared to oxide films, nitride films are usually denser and denser, although they depend on the deposition method, and they do not serve as oxygen supply sources. Can be prevented. This is clear from the experimental examples described later. Therefore, according to the antireflection film 38 using the nitride film, the deterioration of the light absorption film can be remarkably suppressed as compared with the protective film made of the oxide film described in Patent Document 2, for example, and the durability of the near infrared cut filter is improved. Can be improved.

  Further, according to the near-infrared cut filter 30 of the present embodiment, the antireflection film 38 functions not only as a protective film for the light absorption film 36 but also the first dielectric multilayer film 34 made of a multilayer dielectric is provided on the substrate 32. Therefore, it is possible to reduce the film stress and prevent the substrate 32 from warping. Furthermore, according to the present embodiment, for example, after the first dielectric multilayer film 34 is formed by a vacuum deposition method, the antireflection film 38 can be formed by a sputtering method that is thermally milder than the vacuum deposition method. Therefore, it is advantageous in the process.

4). Experimental Example Hereinafter, an experimental example according to the near-infrared cut filter of the present invention will be described.

(1) Preparation of test sample Test samples used in the experimental examples of the present invention were prepared by the following method.

First, a light absorption film was formed on one side of a glass substrate (“D-263” manufactured by SCHOTT). Specifically, an ultraviolet curable paint containing an organic dye (“ADEKA ARKLES series GPZ-103” manufactured by ADEKA) was applied onto a glass substrate by a spin coater to obtain a coating film having a thickness of 8 μm. Next, ultraviolet rays of 5 KJ / m ² were irradiated with a UV lamp (black light) to cure the coating film and form a light absorption film.

  Next, the glass substrate on which the light absorption film was formed was divided into four parts, which were designated as Sample A, Sample B, Sample C, and Sample D, respectively.

Next, in sample C, a SiO ₂ film having a thickness of 50 nm was formed on the surface of the light absorption film using a sputtering apparatus (manufactured by Optoline, DC metamode sputtering apparatus, silicon target). In Sample D, a Si ₃ N ₄ film having a thickness of 50 nm was formed on the surface of the light absorption film in the same manner as Sample C.

(2) Ultraviolet irradiation test As shown in FIG. 7, each sample A to D was irradiated with ultraviolet rays using a black light (ultraviolet irradiation intensity of 40 W / m ² ) as a light source. At this time, samples B, C, and D were irradiated with ultraviolet rays through an infrared / ultraviolet cut filter (“UVIRCF” manufactured by Tanaka Giken Co., Ltd.). The spectral transmittance characteristics of this infrared / ultraviolet cut filter are shown in FIG. FIG. 8A shows the spectral transmittance in the wavelength region from 350 nm to 1150 nm. FIG. 8B is an enlarged view of the ultraviolet region of FIG. And the spectral transmittance before and behind ultraviolet irradiation was measured about each sample.

The irradiation dose of ultraviolet rays, for sample ^{A, 10.4MJ / m 2, 20.7MJ /} m 2, using a 34.6MJ / ^{m 2,} for Sample B to sample D, 10.4MJ ^{/ m} 2, 20.7 MJ / m ² , 34.6 MJ / m ² , 41.5 MJ / m ² , 58.8 MJ / m ² were used. In the experiment, the irradiation time of ultraviolet rays was 17 days. The experiment was conducted at room temperature in the atmosphere.

(3) Test results The test results of the samples A to D are shown in FIGS. 9 to 12, respectively. Then, based on FIGS. 9 to 12, when the spectral transmittance at each ultraviolet ray irradiation amount at a wavelength of 692 nm was plotted, the result shown in FIG. 13 was obtained. Further, FIG. 14 shows an enlarged vertical axis in order to make the change in FIG. 13 easier to understand. From FIG. 13 and FIG. 14, the change of the spectral transmittance by ultraviolet irradiation in each sample can be seen. In FIGS. 9 to 12, the data indicated by the symbol “a” indicates the spectral transmittance before ultraviolet irradiation.

From FIG. 14, it was found that when the sample A having no SiO ₂ film and Si ₃ N ₄ film was directly irradiated with ultraviolet rays without using an infrared / ultraviolet cut filter, the characteristics of the light absorption film were significantly deteriorated. The deterioration of the light absorption film became more prominent as the amount of ultraviolet irradiation increased.

From FIG. 14, the following was confirmed. It was found that also in Samples B, C, and D, the deterioration of the light absorption film tends to become more prominent as the amount of ultraviolet irradiation increases. However, when sample B without an SiO ₂ film and Si ₃ N ₄ film is irradiated with ultraviolet rays through an infrared / ultraviolet cut filter (FIG. 10), an infrared / ultraviolet cut filter is applied to sample C having an SiO ₂ film. When the sample was irradiated with ultraviolet rays (FIG. 11) and when the sample D having the Si ₃ N ₄ film was irradiated with ultraviolet rays via an infrared / ultraviolet cut filter (FIG. 12), the degree of deterioration was different. That is, in the case of sample B, although the degree of deterioration is less than that of sample A, the change in spectral transmittance is considerably larger than that of sample C and sample D. Further, comparing Sample C and Sample D, it was found that Sample D had a smaller change in transmittance than Sample C. Furthermore, FIG. 14 shows that the difference in spectral characteristics between sample C and sample D increases as the integrated ultraviolet irradiation amount increases.

  From the above, in this experimental example, it was confirmed that the sample D having the nitride film has less deterioration of the light absorption film and superior durability than the sample C having the oxide film. .

  Each of the embodiments described above is an example, and the present invention is not limited to these. For example, in the present invention, the embodiments can be appropriately combined.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

10, 20, 30 Near-infrared cut filter 12, 22, 32 Substrate 14, 24, 34 First dielectric multilayer film 16, 26, 36 Light absorption film 18, 38 Antireflection film

Claims (9)

A transparent substrate in the visible range;
A first dielectric multilayer film provided on at least one surface side of the substrate and reflecting light from at least a red region to a near infrared region;
A light absorption film that is provided on at least one surface side of the substrate and absorbs part of light from the red region to the near infrared region;
A dielectric film provided outside the light absorption film with respect to the substrate and including a nitride film;
Including near-infrared cut filter. In the near-infrared cut filter according to claim 1,
The near-infrared cut filter, wherein the dielectric film is a second dielectric multilayer film configured by alternately laminating nitride films and oxide films. In the near infrared cut filter according to claim 2,
The near-infrared cut filter, wherein the second dielectric multilayer film is an antireflection film having a function of reducing the surface reflectance of the light absorption film at least in a part of the visible range. In the near-infrared cut filter according to any one of claims 1 to 3,
The first dielectric multilayer film is a near-infrared cut filter, which is a dielectric multilayer film configured by alternately laminating nitride films and oxide films. In the near-infrared cut filter according to any one of claims 1 to 3,
The first dielectric multilayer film is a near-infrared cut filter, which is a dielectric multilayer film configured by alternately laminating oxide films having different refractive indexes. In the near-infrared cut filter according to claim 4 or 5,
The first dielectric multilayer film is a near-infrared cut filter that functions as a reflective film that reflects light in the ultraviolet region in addition to the red region to the near-infrared region. In the near-infrared cut filter according to claim 4 or 5,
The second dielectric multilayer film, together with the first dielectric multilayer film, functions as a reflective film that reflects light in the ultraviolet region in addition to the red region to the near infrared region. In the near-infrared cut filter according to any one of claims 1 to 7,
The near-infrared cut filter, wherein the nitride film is silicon nitride or silicon oxynitride. In the near-infrared cut filter according to any one of claims 1 to 8,
The near-infrared cut filter, wherein the light absorption film is a resin film containing an organic dye and having a maximum absorption wavelength in a range of 650 nm to 750 nm.