WO2023248908A1

WO2023248908A1 - Optical filter and imaging device

Info

Publication number: WO2023248908A1
Application number: PCT/JP2023/022132
Authority: WO
Inventors: 和彦塩野; 弥生山森; 貴尋坂上; 崇長田; 克司上條
Original assignee: Ａｇｃ株式会社
Priority date: 2022-06-24
Filing date: 2023-06-14
Publication date: 2023-12-28

Abstract

The present invention provides an optical filter which comprises a glass substrate and a first antireflective layer, wherein: the glass substrate has first and second main surfaces and an end face; the first antireflective layer is arranged on the first main surface side of the glass substrate; the glass substrate is formed of phosphate glass that contains an absorbent; the first main surface of the glass substrate is covered with a first inorganic film; the second main surface of the glass substrate is covered with a second inorganic film; the end face of the glass substrate is covered with a third inorganic film; the first inorganic film is a film that is closest to the glass substrate among the films that constitute the first antireflective layer, or alternatively a film that is different from the films that constitute the first antireflective layer; and the third inorganic film has the maximum thickness on at least one of the first main surface side and the second main surface side.

Description

Optical filters and imaging devices

The present invention relates to an optical filter and an imaging device.

Imaging devices such as in-vehicle cameras and smartphone cameras are equipped with solid-state image sensors (CCD, CMOS, etc.). However, solid-state image sensors exhibit stronger sensitivity to infrared light than human visual sense. Therefore, an optical filter is further installed in the imaging device in order to bring the image taken by the solid-state imaging device closer to the human visibility.

International Publication No. 2014/030628

High-precision optical filters must (1) have high transmittance in the visible light region, (2) have high light-shielding properties in the infrared region, and (3) have optical characteristics that do not change depending on the incident angle of light. is required.

In order to satisfy such characteristics, Patent Document 1 describes an optical filter having a CuO-containing fluorophosphate glass substrate. The CuO-containing fluorophosphate glass substrate has a function of absorbing infrared rays to some extent. Therefore, by combining the CuO-containing fluorophosphate glass substrate, the dye-containing layer, and the dielectric multilayer film, it is possible to provide an optical filter that combines the effects (1) to (3) described above.

However, according to the inventors of the present application, it is understood that even in the optical filter described in Patent Document 1, the effects (2) and (3) described above cannot be said to be sufficient.

In particular, in recent years there has been an increasing demand for optical filters for cameras installed in electronic devices such as smartphones. As such optical filters become less popular, it is expected that the problem of angular dependence of optical characteristics will become more prominent in the future.

The present invention has been made in view of this background, and provides an optical filter that has significantly high light-shielding properties in the infrared region and has significantly suppressed angular dependence of optical characteristics. The purpose is to

In the present invention,
An optical filter having a glass substrate and a first antireflection layer,
The glass substrate has a first main surface and a second main surface facing each other, and an end surface connecting the two main surfaces,
The first antireflection layer is installed on the first main surface side of the glass substrate,
The glass substrate is phosphate glass containing an absorbent,
The first main surface of the glass substrate is coated with a first inorganic film, the second main surface of the glass substrate is coated with a second inorganic film, and the end surface of the glass substrate is coated with a third inorganic film,
The first inorganic film is a film that is closest to the glass substrate among the films that constitute the first antireflection layer, or is a film that is different from the film that constitutes the first antireflection layer. can be,
An optical filter is provided in which the third inorganic film has a maximum thickness on at least one of the first main surface side and the second main surface side.

According to the present invention, it is possible to provide an optical filter that has significantly high light-shielding properties in the infrared region and that has significantly suppressed angular dependence of optical characteristics.

FIG. 2 is a diagram showing a comparison of typical optical properties of fluorophosphate glass (a) and phosphate glass (b) containing CuO. 1 is a cross-sectional view schematically showing a configuration example of an optical filter according to an embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a configuration example of an optical filter according to another embodiment of the present invention. FIG. 7 is a cross-sectional view schematically showing a configuration example of an optical filter according to still another embodiment of the present invention. 1 is a diagram schematically showing an example of optical characteristics of a glass substrate included in an optical filter according to an embodiment of the present invention. FIG. 6 is a diagram schematically showing an example of a cross-sectional form of a third inorganic film formed on an end surface of a glass substrate of an optical filter according to an embodiment of the present invention. FIG. 6 is a diagram schematically showing another example of the cross-sectional form of the third inorganic film formed on the end surface of the glass substrate of the optical filter according to the embodiment of the present invention. FIG. 7 is a diagram schematically showing still another example of the cross-sectional form of the third inorganic film formed on the end surface of the glass substrate of the optical filter according to the embodiment of the present invention. FIG. 3 is a diagram schematically showing an example of optical characteristics of a resin layer that may be included in an optical filter according to an embodiment of the present invention. 1 is a diagram schematically showing an example of optical characteristics of an optical filter according to an embodiment of the present invention. 1 is a flow diagram schematically showing an example of a method for manufacturing an optical filter according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of a transmittance profile obtained in an optical filter according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of a reflectance profile obtained in an optical filter according to an embodiment of the present invention. FIG. 7 is a diagram showing an example of a transmittance profile obtained in an optical filter according to another embodiment of the present invention.

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

As mentioned above, it cannot be said that the effects (2) and (3) described above are still sufficient in conventional optical filters. Therefore, conventional optical filters may not be able to sufficiently suppress light leakage in the infrared region and/or the phenomenon in which optical characteristics change depending on the incident angle of light (hereinafter referred to as "angle-dependent problem").

In particular, as optical filters become more affordable in the future, it is expected that the "angle-dependent problem" will become more prominent.

Against this background, the inventors of the present application have been diligently researching and developing an optical filter configuration that can further enhance the effects (2) and (3).

The inventors of the present application have discovered that when phosphate glass is used instead of fluorophosphate glass as a glass substrate containing an absorbent, absorption in the infrared region can be further enhanced, and that the use of an infrared cut film can be discontinued. We found that the ``angle-dependent problem'' could be solved by this method.

However, phosphate glass has the property of being easily eluted when it comes into contact with water. Therefore, when phosphate glass is used for the glass substrate of an optical filter, a problem may arise in terms of durability.

In particular, adhesives are used when attaching optical filters to electronic devices, and many of these adhesives exhibit water absorption properties. Therefore, in an environment where the phosphate glass substrate in the optical filter comes into contact with the adhesive, the problem of glass elution may become more pronounced.

The inventors of the present application have continued to study such newly emerged durability problems. We have also found that such elution problems can be resolved by configuring the optical filter so that the phosphate glass substrate is not exposed to the outside environment.

Therefore, in one embodiment of the invention:
An optical filter having a glass substrate and a first antireflection layer,
The glass substrate has a first main surface and a second main surface facing each other, and an end surface connecting the two main surfaces,
The first antireflection layer is installed on the first main surface side of the glass substrate,
The glass substrate is phosphate glass containing an absorbent,
The first main surface of the glass substrate is coated with a first inorganic film, the second main surface of the glass substrate is coated with a second inorganic film, and the end surface of the glass substrate is coated with a third inorganic film,
The first inorganic film is a film closest to the glass substrate among the films forming the first antireflection layer, or a film different from the film forming the first antireflection layer. can be,
An optical filter is provided in which the third inorganic film has a maximum thickness on at least one of the first main surface side and the second main surface side.

In the optical filter according to one embodiment of the present invention, no infrared cut film is used.

Therefore, in the optical filter according to an embodiment of the present invention, the "angle-dependent problem" is unlikely to occur, and the optical characteristics do not change much even if the incident angle of light changes from 0° to 50°, for example.

Furthermore, in one embodiment of the present invention, phosphate glass is used as the glass for the absorbent-containing glass substrate.

FIG. 1 shows typical optical properties of fluorophosphate glass and phosphate glass containing an absorbent (CuO). In FIG. 1, the horizontal axis is the wavelength of light, and the vertical axis is the transmittance. Moreover, in FIG. 1, (a) is the transmittance of the absorbent-containing fluorophosphate glass, and (b) is the transmittance of the absorbent-containing phosphate glass.

As shown in FIG. 1, the absorbent-containing phosphate glass has the same transmittance as the absorbent-containing fluorophosphate glass in the wavelength range of 450 nm to 600 nm. Therefore, even if phosphate glass is used instead of fluorophosphate glass as the glass substrate of the optical filter, high transmittance can be maintained in the visible light region.

Further, as shown in FIG. 1, the absorbent-containing phosphate glass exhibits a sufficiently lower transmittance than the absorbent-containing fluorophosphate glass in a wavelength region higher than 750 nm.

Therefore, when using absorbent-containing phosphate glass for the glass substrate of an optical filter, in combination with an anti-reflection layer, the light-shielding property in the infrared region can be significantly improved without using an infrared cut film. .

Furthermore, in one embodiment of the present invention, the glass substrate is placed within the optical filter such that no surface is exposed to the outside world. That is, the glass substrate is arranged such that the first main surface is covered with the first inorganic film, the second main surface is covered with the second inorganic film, and the end surface is covered with the third inorganic film. be done.

Note that the first inorganic film may be the film closest to the glass substrate among the films that constitute the first antireflection layer. Alternatively, the first inorganic film may be a film different from the film constituting the first antireflection layer.

As described above, in one embodiment of the present invention, the glass substrate is surrounded by an inorganic film. Therefore, even if the glass substrate is made of absorbent-containing phosphate glass, the problem of the glass being eluted by moisture in the environment can be significantly suppressed.

Furthermore, in general, among the end faces of the glass substrate, the first main surface side or the second main surface side is likely to come into contact with an adhesive when the optical filter is assembled into an electronic device. Therefore, the portion of the end surface of the glass substrate that is in contact with the adhesive tends to be more easily eluted due to moisture absorption of the adhesive.

In contrast, in one embodiment of the present invention, the third inorganic film installed on the end surface of the glass substrate is configured such that the third inorganic film has a maximum thickness on the side of at least one main surface of the glass substrate. ing. Therefore, in one embodiment of the present invention, the problem of glass elution can be further suppressed by making the side of the glass substrate where the third inorganic film is thicker the side that is more likely to come into contact with the adhesive. .

Thus, in one embodiment of the present invention, the glass substrate is surrounded by an inorganic film, and in particular, the third inorganic film has a thickness on at least one main surface side of the glass substrate. It is configured to be the maximum. Therefore, even if the glass substrate is made of absorbent-containing phosphate glass, the problem of the glass being eluted by moisture in the environment can be significantly suppressed.

As a result of the above effects, one embodiment of the present invention can provide an optical filter that has significantly high light-shielding properties in the infrared region and has significantly suppressed angular dependence of optical characteristics.

(Optical filter according to one embodiment of the present invention)
Hereinafter, an optical filter according to an embodiment of the present invention will be described in more detail with reference to FIG. 2.

FIG. 2 schematically shows a cross section of the configuration of an optical filter according to an embodiment of the present invention.

As shown in FIG. 2, an optical filter (hereinafter referred to as "first optical filter") 100 according to an embodiment of the present invention includes a glass substrate 110 and a first antireflection layer 130.

The glass substrate 110 has a first main surface 112 and a second main surface 114 that face each other, and an end surface 116 between the two main surfaces. First antireflection layer 130 is disposed on the first main surface 112 side of glass substrate 110.

The glass substrate 110 is made of phosphate glass containing an absorbent.

In addition, in this application, phosphate glass means glass containing 50 mass % or more of P ₂ O ₅ in terms of oxide.

The first antireflection layer 130 is composed of a dielectric multilayer film.

Further, the first optical filter 100 further includes a first inorganic film 122, a second inorganic film 124, and a third inorganic film 126.

The first inorganic film 122 is installed to cover the first main surface 112 of the glass substrate 110, and the second inorganic film 124 is installed to cover the second main surface 114 of the glass substrate 310. . Further, the third inorganic film 126 is installed to cover the end surface 116 of the glass substrate 110.

Here, the glass substrate 110 made of phosphate glass tends to be eluted relatively easily when it comes into contact with moisture in the environment.

In particular, the first main surface 112 side or the second main surface 114 side of the end surface 116 of the glass substrate 110 can come into contact with adhesive when the first optical filter 100 is assembled into an electronic device. Highly sexual. Therefore, the portion of the end surface 116 of the glass substrate 110 that comes into contact with the adhesive tends to be more easily eluted due to moisture absorption of the adhesive.

However, in the first optical filter 100, the third inorganic film 126 installed on the end surface 116 of the glass substrate 110 has a maximum thickness on the side of at least one

main surface

112, 114 of the glass substrate 110. It is configured as follows. For example, in the example shown in FIG. 2, the third inorganic film 126 is configured to have the maximum thickness on the first main surface 112 side of the glass substrate 110.

Therefore, in the first optical filter 100, the problem of glass elution can be further suppressed by making the side of the glass substrate 110 on which the third inorganic film 126 is thicker the side that is more likely to come into contact with the adhesive. can.

Furthermore, the first optical filter 100 does not use an infrared cut film, which is a factor in the angle dependence problem. Therefore, in the first optical filter 100, the angle dependence problem can be significantly suppressed.

As a result of the above effects, the first optical filter 100 has significantly high light-shielding properties in the infrared region, and can significantly suppress the angular dependence of optical characteristics.

Note that in the example shown in FIG. 2, the first inorganic film 122 and the first antireflection layer 130 are provided on the first main surface 112 side of the glass substrate 110, respectively.

However, in addition to this, in the first optical filter 100, the first inorganic film 122 may be the film closest to the glass substrate 110 among the films forming the first antireflection layer 130. In this case, the first inorganic film 122 may be apparently omitted.

(Optical filter according to another embodiment of the present invention)
Next, with reference to FIG. 3, an optical filter according to another embodiment of the present invention will be described.

FIG. 3 schematically shows a cross section of the configuration of an optical filter (hereinafter referred to as "second optical filter") according to another embodiment of the present invention.

As shown in FIG. 3, the second optical filter 200 has the same configuration as the first optical filter 100 described above. Therefore, in FIG. 3, reference numerals with 100 added to the reference numerals shown in FIG. 2 are used for members corresponding to those included in the first optical filter 100.

For example, as shown in FIG. 3, the second optical filter 200 includes a glass substrate 210, first to third inorganic films 222 to 226, and a first antireflection layer 230.

However, in the second optical filter 200, unlike the first optical filter 100, a second antireflection layer 250 is provided on the second inorganic film 224.

Also in the second optical filter 200, the first main surface 212 of the glass substrate 210 is covered with the first inorganic film 222, the second main surface 214 is covered with the second inorganic film 224, and the end surface 216 is covered with a third inorganic film 226. In particular, the third inorganic film 226 is configured to have a maximum thickness on the first main surface 112 side of the glass substrate 110.

Therefore, also in the second optical filter 200, the problem that the glass substrate 210 made of phosphate glass reacts with moisture in the outside world and elutes can be significantly suppressed.

Furthermore, the second optical filter 200 does not use an infrared cut film, which is a factor in the angle dependence problem. Therefore, the angle dependence problem can be significantly suppressed in the second optical filter 200 as well.

As a result of the above effects, the second optical filter 200 has significantly high light-shielding properties in the infrared region, and can significantly suppress the angular dependence of optical characteristics.

Note that in the example shown in FIG. 3, a second inorganic film 224 and a second antireflection layer 250 are provided on the second main surface 214 side of the glass substrate 210, respectively.

However, in addition to this, in the second optical filter 200, the second inorganic film 224 may be the film closest to the glass substrate 210 among the films forming the second antireflection layer 250. In this case, the second inorganic film 224 may be apparently omitted.

Furthermore, as described above, the first inorganic film 222 may be the film closest to the glass substrate 210 among the films forming the first antireflection layer 230.

(Optical filter according to yet another embodiment of the present invention)
Next, with reference to FIG. 4, an optical filter according to yet another embodiment of the present invention will be described.

FIG. 4 schematically shows a cross section of the configuration of an optical filter (hereinafter referred to as "third optical filter") according to yet another embodiment of the present invention.

As shown in FIG. 4, the third optical filter 300 has the same configuration as the second optical filter 200 described above. Therefore, in FIG. 4, reference numerals with 100 added to the reference numerals shown in FIG. 4 are used for members corresponding to those included in the second optical filter 200.

For example, as shown in FIG. 4, the third optical filter 300 includes a glass substrate 310, first to third inorganic films 322 to 326, a first antireflection layer 330, and a second antireflection layer. 350.

However, in the third optical filter 300, unlike the second optical filter 200, a resin layer 340 is provided between the second inorganic film 324 and the second antireflection layer 350.

The resin layer 340 is made of resin containing a pigment. Details of the resin layer 340 will be described later.

Also in the third optical filter 300, the first main surface 312 of the glass substrate 310 is covered with the first inorganic film 322, the second main surface 314 is covered with the second inorganic film 324, and the end surface 316 is covered with a third inorganic film 326. In particular, the third inorganic film 326 is configured to have a maximum thickness on the first main surface 312 side of the glass substrate 310.

Therefore, in the third optical filter 300 as well, the problem that the glass substrate 310 made of phosphate glass reacts with moisture in the outside world and elutes can be significantly suppressed.

Further, the third optical filter 300 does not use an infrared cut film, which is a factor in the angle dependence problem. Therefore, also in the third optical filter 300, the angle dependence problem can be significantly suppressed.

As a result of the above effects, the third optical filter 300 has a significantly high light-shielding property in the infrared region, and can significantly suppress the angular dependence of the optical characteristics.

Note that in the example shown in FIG. 4, a first inorganic film 322 and a first antireflection layer 330 are provided on the first main surface 312 side of the glass substrate 310, respectively.

However, as described above, in the third optical filter 300, the first inorganic film 322 may be the film closest to the glass substrate 310 among the films forming the first antireflection layer 330. In this case, the first inorganic film 322 may be apparently omitted.

(Regarding each member included in the optical filter according to an embodiment of the present invention)
Next, each member constituting the optical filter according to an embodiment of the present invention will be described in more detail. Note that, for clarity, here, constituent members will be described using the third optical filter 300 shown in FIG. 4 as an example. Therefore, when representing each member, the reference numerals shown in FIG. 4 will be used.

(Glass substrate 310)
Hereinafter, a glass substrate 310 used in an optical filter according to an embodiment of the present invention will be described. In the following description, unless otherwise specified, the content of each component and the total content represent mass percentage values based on oxides.

The glass substrate 310 is made of phosphate glass containing an absorbent.

The absorbent contained in the glass substrate 310 is a metal oxide, and may be CuO, for example.

The absorbent may be included in the entire glass substrate 310 in a mass percentage of 4% to 20% on an oxide basis.

For example, the glass substrate 310 has a mass percentage based on oxide,
50% to 80% P ₂ O ₅ ,
5% to 20% Al ₂ O ₃ ,
4% to 20% CuO,
0.5% to 15% R(1) ₂ O, where R(1) is at least one component selected from the group consisting of Li, Na, K, Rb, and Cs, and 0 ~15% R(2)O, where R(2) is at least one component selected from the group consisting of Ca, Mg, Ba, Sr, and Zn;
May include.

P ₂ O ₅ is a main component forming glass, and is a component for improving near-infrared ray cutting properties. If the content of P ₂ O ₅ is 50% or more, the effect can be sufficiently obtained, and if it is 80% or less, problems such as glass becoming unstable and weather resistance decreasing are unlikely to occur. Therefore, P ₂ O ₅ is preferably 50 to 80%, more preferably 52 to 78%, still more preferably 54 to 77%, even more preferably 56 to 76%, and most preferably is 60-75%.

Al ₂ O ₃ is a main component forming glass, and is a component for increasing the strength of glass. If the content of Al ₂ O ₃ is 5% or more, the effect can be sufficiently obtained, and if it is 20% or less, problems such as the glass becoming unstable and the near-infrared cut property decreasing are unlikely to occur. Therefore, Al ₂ O ₃ is preferably 5 to 20%, more preferably 6 to 18%, still more preferably 7 to 17%, even more preferably 8 to 16%, and most preferably is 9-13%. If the content of Al ₂ O ₃ is 9% or more, the weather resistance of the glass can be improved.

R(1) ₂ O is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, and stabilizing the glass. If the total amount of R(1) ₂ O is 0.5% or more, the effect can be sufficiently obtained, and if it is 20% or less, the glass is less likely to become unstable, which is preferable. Therefore, the total amount of R(1) ₂ O is preferably 0.5 to 20%, more preferably 1 to 20%, even more preferably 2 to 20%, even more preferably 3 to 20%. 20%, most preferably 4-20%.

Li ₂ O is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, and stabilizing glass. The content of Li ₂ O is preferably 0 to 15%. It is preferable that the Li ₂ O content is 15% or less because problems such as the glass becoming unstable and the near-infrared cut property being lowered are less likely to occur. The Li ₂ O content is more preferably 0 to 8%, still more preferably 0 to 7%, even more preferably 0 to 6%, and most preferably substantially Li ₂ O. do not.

In this application, "substantially not containing a specific component" means that it is not intentionally added, and excludes content that is unavoidably mixed in from raw materials etc. and does not affect the intended characteristics. It's not something you do.

Na ₂ O is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, and stabilizing glass. The content of Na ₂ O is preferably 0 to 15%. It is preferable that the Na ₂ O content is 15% or less because the glass is less likely to become unstable. The content of Na ₂ O is more preferably 0.5 to 14%, still more preferably 1 to 13%, even more preferably 2 to 13%.

K ₂ O is a component that has effects such as lowering the melting temperature of glass and lowering the liquidus temperature of glass. The content of K ₂ O is preferably 0 to 15%. It is preferable that the content of K ₂ O is 15% or less because the glass is less likely to become unstable. The content of K ₂ O is more preferably 0.5 to 14%, still more preferably 1 to 13%, even more preferably 2 to 13%.

Rb ₂ O is a component that has effects such as lowering the melting temperature of glass and lowering the liquidus temperature of glass. The content of Rb ₂ O is preferably 0 to 15%. It is preferable that the Rb ₂ O content is 15% or less because the glass is less likely to become unstable. The content of Rb ₂ O is more preferably 0.5 to 14%, still more preferably 1 to 13%, even more preferably 2 to 13%.

Cs ₂ O is a component that has effects such as lowering the melting temperature of glass and lowering the liquidus temperature of glass. The content of Cs ₂ O is preferably 0 to 15%. It is preferable that the Cs ₂ O content is 15% or less because the glass is less likely to become unstable. The content of Cs ₂ O is more preferably 0.5 to 14%, still more preferably 1 to 13%, even more preferably 2 to 13%.

R(2)O is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and increasing the strength of the glass. The total amount of R(2)O is preferably 0 to 15%. If the total amount of R(2)O is less than 15%, problems such as glass becoming unstable, near-infrared cut property decreasing, short wavelength infrared transmittance decreasing, and glass strength decreasing. This is preferable because it is less likely to occur. The total amount of R(2)O is more preferably 0 to 13%, even more preferably 0 to 11%. Even more preferably it is 0 to 9%, even more preferably 0 to 8%.

CuO is a component for cutting near-infrared rays. If the content of CuO is 4% or more, the effect can be sufficiently obtained, and if it is 20% or less, the transmittance in the visible light region decreases, the transmittance in the short wavelength infrared region decreases, etc. This is preferable because it is less likely to cause problems. The content of CuO is more preferably 4 to 19.5%, still more preferably 5 to 19%, even more preferably 6 to 18.5%, even more preferably more than 7%. be. In particular, when the glass does not substantially contain divalent cations other than Cu, a CuO content of more than 7% can further improve near-infrared ray cutting properties and short-wavelength infrared ray transmittance. . Most preferably, the CuO content is 7 to 18% (excluding 7%).

It is preferable that the glass substrate 310 does not substantially contain divalent cations other than Cu. The reason for this is explained below.

When the glass of this embodiment contains CuO, light in the near-infrared region is cut due to light absorption by Cu ²⁺ ions. The optical absorption is caused by electronic transition between the d-orbitals of Cu ²⁺ ions split by the electric field of O ^2- ions. Splitting of the d-orbital is promoted when the symmetry of the O ^2- ions around the Cu ²⁺ ions decreases. For example, when a cation exists around an O ^2- ion, the O ^2- ion is attracted by the electric field of the cation, reducing the symmetry of the O ^2- ion. As a result, the splitting of the d-orbitals is promoted, and light absorption occurs due to electronic transition between the split d-orbitals, which weakens the light absorption ability in the near-infrared region and strengthens the light absorption ability in the short-wavelength infrared region. The strength of the electric field of a cation becomes stronger as the valence of the ion increases, so if an oxide containing divalent cations other than Cu is added to the glass, the near-infrared cutting property will decrease, and short-wavelength infrared rays There is a risk that the permeability of

CaO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The content of CaO is preferably 0 to 10%. If the content of CaO is 10% or less, problems such as the glass becoming unstable, the near-infrared cut property decreasing, and the short-wavelength infrared transmittance decreasing are less likely to occur, so it is preferable. More preferably, it is 0 to 8%, still more preferably 0 to 6%, even more preferably 0 to 5%. Most preferably it contains substantially no CaO.

MgO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The content of MgO is preferably 0 to 15%. If the content of MgO is 15% or less, problems such as the glass becoming unstable, the near-infrared cut property decreasing, and the transmittance of short wavelength infrared rays decreasing are less likely to occur, so it is preferable. More preferably, it is 0 to 13%, still more preferably 0 to 10%, even more preferably 0 to 9%. Most preferably, it does not substantially contain MgO.

BaO is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, and stabilizing glass. The BaO content is preferably 0.1 to 10%. If the BaO content is 10% or less, it is preferable because problems such as glass becoming unstable, near-infrared cutting properties being reduced, and short-wavelength infrared rays transmittance being reduced are less likely to occur. More preferably, it is 0 to 8%, still more preferably 0 to 6%, even more preferably 0 to 5%. Most preferably it contains substantially no BaO.

SrO is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, and stabilizing glass. The content of SrO is preferably 0 to 10%. If the content of SrO is 10% or less, problems such as glass becoming unstable, near-infrared cut property decreasing, and short-wavelength infrared transmittance decreasing are less likely to occur, which is preferable. More preferably 0 to 8%, still more preferably 0 to 7%. Most preferably, it does not substantially contain SrO.

ZnO has effects such as lowering the melting temperature of glass and lowering the liquidus temperature of glass. The content of ZnO is preferably 0 to 15%. If the content of ZnO is 15% or less, problems such as deterioration of glass solubility, deterioration of near-infrared cut property, and deterioration of short-wavelength infrared transmittance are less likely to occur, which is preferable. More preferably, it is 0 to 13%, still more preferably 0 to 10%, even more preferably 0 to 9%. Most preferably it contains substantially no ZnO.

B ₂ O ₃ may be contained in a range of 10% or less in order to stabilize the glass. If the content of B ₂ O ₃ is 10% or less, problems such as deterioration of weather resistance of the glass, deterioration of near-infrared cut property, and deterioration of short-wavelength infrared transmittance are less likely to occur, which is preferable. Preferably it is 9% or less, more preferably 8% or less, still more preferably 7% or less, even more preferably 6% or less, and most preferably substantially free of B ₂ O ₃ .

In the glass substrate 310, although F is an effective component for increasing weather resistance, it is preferably an environmentally hazardous substance and there is a risk that the near-infrared cut property may be reduced, so it is preferable that F is not substantially contained.

In the glass substrate 310, SiO ₂ , GeO ₂ , ZrO ₂ , SnO ₂ , TiO ₂ , CeO ₂ , WO ₃ , Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , Nb ₂ O ₅ may be contained in an amount of 5% or less in order to improve the weather resistance of the glass. It is preferable that the content of these components is 5% or less, since problems such as a decrease in near-infrared cut property and a decrease in short-wavelength infrared transmittance are unlikely to occur. Preferably it is 4% or less, more preferably 3% or less, still more preferably 2% or less, even more preferably 1% or less.

Fe ₂ O ₃ , Cr ₂ O ₃ , Bi ₂ O ₃ , NiO, V ₂ O ₅ , MoO ₃ , MnO ₂ and CoO are all components that reduce visible transmittance when present in glass. . Therefore, it is preferable that these components are not substantially contained in the glass.

The glass substrate 310 preferably has a thermal expansion coefficient of 60×10 ⁻⁷ /°C to 180×10 ⁻⁷ /°C in the range of 30° C. to 300° C.

The glass substrate 310 may have a thickness in the range of 0.1 mm to 3 mm, for example.

The shape of the glass substrate 310 is not particularly limited. The first main surface 312 and the second main surface 314 of the glass substrate 310 may be rectangular or elliptical (including circular).

When the first main surface 312 and the second main surface 314 are rectangular, the glass substrate 310 has a plurality of end faces 316. On the other hand, when the first main surface 312 and the second main surface 314 are circular, the glass substrate 310 has a single end surface 316.

Furthermore, the shape of the end surface 316 is not particularly limited. For example, end surface 316 may have a shape extending in a direction substantially perpendicular to first major surface 312 and second major surface 314, or may have another shape. For example, the end surface 316 of the glass substrate 310 may have a portion that is inclined with respect to the normal to the first major surface 312 and/or the normal to the second major surface 314.

FIG. 5 schematically shows an example of the optical characteristics of the glass substrate 310. In FIG. 5, the horizontal axis is the wavelength, and the vertical axis is the internal transmittance.

In addition, in this application, "internal transmittance (%)" is

Internal transmittance (%) = T ₍₅₎ / (100-R ₍₅₎ ) × 100 (1) formula
It is expressed as Here, T ₍₅₎ is the transmittance (%) when the incident angle is 5°, and R ₍₅₎ is the reflectance (%) when the incident angle is 5°.

As shown in FIG. 5, the glass substrate 310 is
(i) Internal transmittance T at a wavelength of 450 nm _{(g) 450} is 92% or more,
(ii) Average internal transmittance T in the wavelength range of 450 nm to wavelength 600 nm _{(g) ave1} is 90% or more, (iii) Minimum wavelength λ at which the internal transmittance is 50% _{(g) 50} is in the range of 625 nm to 650 nm (iv) Average internal transmittance T in the wavelength range of 750 nm to 1000 nm _{(g) ave2} is 2.5% or less, (v) Average internal transmittance T in the wavelength range of 1000 nm to 1200 nm _(g) It is preferable to have such spectral characteristics that _ave3 is 7% or less.

(First inorganic film 322, second inorganic film 324, and third inorganic film 326)
The first to third inorganic films 322 to 326 are provided to protect the glass substrate 310 from the outside world. That is, the glass substrate 310 made of phosphate glass tends to dissolve when exposed to moisture in the outside world. However, by covering the periphery of the glass substrate 310 with the first to third inorganic films 322 to 326, such elution can be significantly suppressed.

The first to third inorganic films 322 to 326 do not necessarily need to be made of the same material. For example, the first inorganic film 322, the second inorganic film 324, and the third inorganic film 326 may all be made of different materials.

However, it is preferable that the first to third inorganic films 322 to 326 are all aluminum oxide films. This is because the aluminum oxide film serves as an effective barrier against moisture.

The method of forming the first to third inorganic films 322 to 326 is not particularly limited. The first to third inorganic films 322 to 326 may be formed by, for example, a sputtering method, a vapor deposition method, or the like.

As described above, the third inorganic film 326 is configured to have a maximum thickness on the first main surface 312 side and/or the second main surface 314 side of the glass substrate 310. Hereinafter, such a thickness profile of the third inorganic film 326 will be simply referred to as "thickness distribution."

Hereinafter, one embodiment of the third inorganic film 326 having a "thickness distribution" will be described with reference to FIGS. 6 to 8.

FIGS. 6 to 8 schematically show examples of the cross-sectional form of the third inorganic film 326 formed on the end surface 316 of the glass substrate 310.

Referring first to FIG. 6, in this example, third inorganic film 326 has a maximum thickness t _max on the side of first major surface 312 of glass substrate 310 . Further, the third inorganic film 326 has a minimum thickness t _min on the second main surface 314 side of the glass substrate 310 .

Note that in an embodiment of the present invention, a first inorganic film 322 is provided on the first main surface 312 of the glass substrate 310, and a second inorganic film 324 is provided on the second main surface 314. be done. Therefore, the boundary between the third inorganic film 326 and the first inorganic film 322 and the boundary between the third inorganic film 326 and the second inorganic film 324 tend to become unclear. Moreover, as a result, the definition of the "thickness" of the third inorganic film 326 tends to be unclear.

Therefore, in the present application, as shown in FIG. 6, the region between the broken line L1 and the broken line L2 is defined as the region R3 of the third inorganic film 326, and the (in a direction parallel to the main surface 312) is defined as the "thickness" of the third inorganic film 326. Note that the broken line L1 is defined as a line extending from the first main surface 312 of the glass substrate 310, and the broken line L2 is defined as a line extended from the second main surface 314 of the glass substrate 310.

Furthermore, the "thickness" of the third inorganic film 326 at each position within the region R3 is determined as the distance from the end surface 316 of the glass substrate 310.

Next, FIG. 7 schematically shows another cross-sectional form of the third inorganic film 326 formed on the end surface 316 of the glass substrate 310. In this example, the third inorganic film 326 has a maximum thickness t _max on the side of the first major surface 312 and the side of the second major surface 314 of the glass substrate 310 .

Further, the third inorganic film 326 has a minimum thickness t _min at the center of the thickness of the glass substrate 310 .

Next, FIG. 8 schematically shows still another cross-sectional form of the third inorganic film 326 formed on the end surface 316 of the glass substrate 310.

As shown in FIG. 8, in this example, third inorganic film 326 has a maximum thickness t _max on the side of first major surface 312 of glass substrate 310 . Additionally, the third inorganic film 326 has a minimum thickness t _min at the center of the thickness of the glass substrate 310 . Additionally, third inorganic film 326 has a thickness between t _min and t _max on the side of second major surface 314 of glass substrate 310 .

In this way, the form of the "thickness distribution" of the third inorganic film 326 has a maximum thickness on the first main surface 312 side and/or the second main surface 314 side of the glass substrate 310. It should be noted that there are no particular limitations as long as the

The maximum thicknesses of the first inorganic film 322 and the second inorganic film 324 are not particularly limited. The maximum thickness of the first inorganic film 322 and the second inorganic film 324 may be in the range of 0.1 μm to 3.0 μm, for example.

(First anti-reflection layer 330 and second anti-reflection layer 350)
In the present application, the term "antireflection layer" refers to a layer configured to have a maximum reflectance of 45% or less for light having a wavelength of 450 nm to 1200 nm.

The first antireflection layer 330 is composed of a multilayer film.

The multilayer film may be composed of alternating films of high refractive index and low refractive index films.

The high refractive index film may be selected from titania and alumina, for example. Furthermore, the low refractive index film may be selected from silica and magnesium fluoride, for example.

The thickness of the first antireflection layer 330 is, for example, in the range of 0.1 μm to 3 μm, although it is not limited thereto.

The same can be said of the second antireflection layer 350.

Note that, as described above, among the films forming the first antireflection layer 330, the film closest to the glass substrate 310 may be the first inorganic film 322.

(Resin layer 340)
The resin layer 340 contains a dye that absorbs infrared rays.

Such dyes may be selected from, for example, squarylium dyes, phthalocyanine dyes, and cyanine dyes.

Furthermore, the resin constituting the resin layer 340 is not particularly limited as long as it is transparent.

Examples of the resin include polyester resin, acrylic resin, epoxy resin, ene-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide. The material may be selected from resins, polyamide resins, polyimide resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, polyurethane resins, polystyrene resins, and the like.

From the viewpoint of the spectral characteristics, glass transition point (Tg), and adhesion of the resin layer 340, the resin is preferably selected from polyimide resin, polycarbonate resin, polyester resin, and acrylic resin.

Further, the glass transition point (Tg) of the resin is preferably 200° C. or higher from the viewpoint of heat resistance.

The resin layer 340 may contain one type of resin, or a mixture of two or more types.

The thickness of the resin layer 340 is not particularly limited. The resin layer 340 may have a thickness in the range of 0.3 μm to 10 μm, for example.

The resin layer 340 (ie, the dye) may have a maximum absorption wavelength in the range of 650 nm to 850 nm. For example, the aforementioned squarylium dye may have a maximum absorption wavelength of 752 nm, and the cyanine dye may have a maximum absorption wavelength of 773 nm.

Furthermore, the resin layer 340 may include a dye that absorbs light in the ultraviolet region. Such a dye may be, for example, a merocyanine dye (maximum absorption wavelength 397 nm).

By providing the resin layer 340, it is possible to further reduce the internal transmittance in the infrared region.

FIG. 9 schematically shows an example of the absorption spectrum of the resin layer 340 (more precisely, the dye contained in the resin layer 340). In FIG. 9, the horizontal axis is the wavelength, and the vertical axis is the internal transmittance.

The resin layer 340 contains a merocyanine dye, a cyanine dye, and a squarylium dye as dyes.

As shown in FIG. 9, in this example, the resin layer 340 exhibits large absorption in a wavelength region of approximately 400 nm and a wavelength region of approximately 750 nm.

Therefore, when such a resin layer 340 and the glass substrate 310 made of dye-containing phosphate glass are combined, the internal transmittance in the infrared region can be further suppressed compared to the case of using only the glass substrate 310. Furthermore, in this case, the internal transmittance in the ultraviolet region can also be sufficiently suppressed.

(First optical filter 100)
FIG. 10 schematically shows an example of the optical characteristics of the first optical filter 100. In FIG. 10, the horizontal axis is wavelength and the vertical axis is transmittance.

FIG. 10 shows the change in transmittance at the incident angle θ=0°. However, in the case of the first optical filter 100, the optical characteristics do not change much even when the incident angle θ=50°.

As shown in FIG. 10, in the first optical filter 100,
(I) At both incident angles θ=0° and 50°, the transmittance T _(t)450 at a wavelength of 450 nm is 80% or more, (II) At both incident angles θ=0° and 50°, The average transmittance T _{(t) ave1} in the wavelength range of 450 nm to 600 nm is 78% or more, and (III) the maximum transmittance in the wavelength range of 450 nm to 600 nm at both incident angles θ = 0° and 50°. T _(t)max1 is 85% or more, and (IV) the minimum wavelength λ _(t)50 at which the transmittance is 50% is in the range of 600 nm to 650 nm at both incident angles θ = 0° and 50°. , (V) At both incident angles θ=0° and 50°, the average transmittance T _{(t) ave2} in the wavelength range of 750 nm to 1200 nm is 2.0% or less, and (VI) When the incident angle θ=0° and 50°, the maximum transmittance T _(t)max2 in the wavelength range of 1000 nm to 1200 nm is 15% or less,
It is possible to obtain such spectral characteristics.

Furthermore, when light is incident from the first main surface 312 side of the glass substrate 310, the first optical filter 100 has a wavelength of 450 nm to (VII) at both incident angles θ=5° and 50°. The maximum reflectance R _(t)max1 in the wavelength range of 700 nm is 7% or less, and (VIII) the maximum reflectance R _(t ) in the wavelength range of 700 nm to 1200 nm at both incident angles 5 = 0° and 50°. _{) max2} is preferably 45% or less.

(Method for manufacturing an optical filter according to an embodiment of the present invention)
Next, with reference to FIG. 11, an example of a method for manufacturing an optical filter according to an embodiment of the present invention will be described.

As shown in FIG. 11, a method for manufacturing an optical filter (hereinafter referred to as "first method") according to an embodiment of the present invention is as follows:
a step of preparing a glass substrate having predetermined dimensions (step S110);
forming an inorganic film on the entire exposed surface of the glass substrate (step S120);
A step of installing a first antireflection layer on the first main surface of the glass substrate, and installing a resin layer and a second antireflection layer on the second main surface of the glass substrate (step S130);
has.

Each step will be explained below.

Here, a method for manufacturing the third optical filter 300 described above will be described as an example. Therefore, when representing each member, the reference numerals shown in FIG. 4 will be used.

(Step S110)
First, a glass substrate is prepared. As previously described, the glass substrate 310 has a first major surface 312, a second major surface 314, and an end surface 316, and is constructed of phosphate glass containing an absorbent.

It is preferable that the glass substrate 310 is cut in advance into the dimensions required for the optical filter. This is because if the glass substrate 310 is cut after forming the inorganic film in the next step S120, the end surface 316 not covered with the inorganic film will be exposed.

(Step S120)
Next, a first inorganic film 322 is installed on the first main surface 312 of the glass substrate 310, a second inorganic film 324 is installed on the second main surface 314, and a third inorganic film 326 is installed on the end surface 316. will be installed.

The first to third inorganic films 322 to 326 (hereinafter collectively referred to as "inorganic films") may be made of the same material or may be made of different materials. For example, all inorganic films may be made of alumina.

The method of forming the inorganic film is not particularly limited. The inorganic film may be formed by, for example, a vapor deposition method or a sputtering method.

Note that when forming inorganic films of the same material, a first process to form a first inorganic film 322 on the first main surface 312 and a second process to form a second inorganic film 324 on the second main surface 314 are performed. The second process and the third process of forming the third inorganic film 326 on the end surface 316 may be performed in random order.

The method of forming the third inorganic film 326 having a "thickness distribution" on the end surface 316 is not particularly limited.

For example, during the first and second treatments described above, the third inorganic film 326 may be formed on the end surface 316 due to the wraparound of film forming components. The third inorganic film 326 formed in this manner has a minimum thickness at the center of the thickness of the glass substrate 310 and has a minimum thickness on the side of the first main surface 312 and/or on the second main surface 314. A distribution in which the thickness is greatest on the sides (ie, the configuration shown in FIG. 7 or FIG. 8 described above) is likely to be obtained.

Through the above step S120, an inorganic film is formed on the entire exposed surface of the glass substrate 110. In particular, the third inorganic film 126 having a "thickness distribution" can be formed on the end surface 116 of the glass substrate 110.

(Step S130)
After that, members necessary for the first optical filter 100 are sequentially formed on the glass substrate 310.

Specifically, a first antireflection layer 330 is installed on the first inorganic film 322, and a resin layer 340 and a second antireflection layer 350 are installed on the second inorganic film 324.

As described above, the first antireflection layer 330 is composed of multiple films. The first antireflection layer 330 may be formed by alternately depositing a high refractive index film and a low refractive index film.

The method for forming the first antireflection layer 330 is not particularly limited. For example, a general film forming method such as a sputtering method may be used.

Further, the resin layer 340 is formed from a resin solution containing a dye.

The resin solution may be prepared by dissolving the dye in a solution containing a resin, an organic solvent, and the like. Dyes may include infrared absorbing dyes and ultraviolet absorbing dyes as described above.

Next, a resin solution is applied onto the second inorganic film 324 by a coating method such as a spin coating method. Thereafter, the resin layer 340 is formed by drying the coating film.

Note that the second antireflection layer 350 may be formed by the same method as the first antireflection layer 330.

Through the above steps, the third optical filter 300 can be manufactured.

Note that in the above description, the method for manufacturing the third optical filter 300 was explained using the third optical filter 300 as an example. However, it is clear to those skilled in the art that optical filters according to other embodiments of the invention can be manufactured in a similar manner.

For example, when manufacturing the second optical filter 200, the step of installing a resin layer on the first inorganic film in the first method described above is omitted, and the second optical filter is placed on the first inorganic film. The antireflection layer may be applied directly.

Various other changes are also possible.

An optical filter according to an embodiment of the present invention can be applied to, for example, an imaging device such as a digital still camera. Such an imaging device can provide good color reproducibility.

An imaging device including an optical filter according to an embodiment of the present invention further includes a solid-state imaging device and an imaging lens, and the optical filter may be disposed between the imaging lens and the solid-state imaging device, for example. good. Further, the optical filter according to an embodiment of the present invention may be directly attached to a solid-state imaging device and/or an imaging lens of an imaging device, for example, via an adhesive layer.

In order to evaluate the durability of the phosphate glass substrate, the following preliminary experiment was conducted.

(Experiment 1)
A glass substrate whose entire exposed surface was covered with an inorganic film was prepared by the following method.

First, a glass plate measuring 76 mm long x 76 mm wide x 0.28 mm thick was prepared. For the glass plate, phosphate glass having the composition shown in "Glass A" in Table 1 below was used.

The optical characteristics of the glass plate used are shown in FIG. 5 mentioned above. Further, the "Glass A" column in Table 2 below shows various parameters calculated from the measured optical properties.

Next, this glass plate was fully cut by a blade dicing method to produce a glass substrate measuring 20 mm long x 20 mm wide x 0.28 mm thick.

Next, a first alumina film was formed on the first main surface of the glass substrate by a vapor deposition method. The thickness of the first alumina film was targeted to be 143 nm.

Next, a second alumina film was formed on the second main surface of the glass substrate. The thickness of the second alumina film was targeted to be 143 nm.

After film formation, the end surface of the glass substrate was observed using a scanning electron microscope (Fe-SEM). As a result, it was confirmed that the end surface of the glass substrate was coated with an alumina film.

Furthermore, as a result of evaluating the thickness distribution of the alumina film on the end face, it was found that the alumina film had a form as shown in FIG. 7 described above. That is, the alumina film on the end face was thickest on the first main surface side and second main surface side of the glass substrate, and thinnest on the center side in the thickness direction of the glass substrate.

From this result, when the alumina film is deposited from each side of the first main surface and the second main surface of the glass substrate, the vapor deposition material wraps around the end face of the glass substrate, and the alumina film is formed there. I found out that it will be done. However, it is considered that on the central side of the end face in the thickness direction, the vapor deposition material did not wrap around sufficiently even during vapor deposition from either side, and the alumina film became the thinnest.

The "Experiment 1" column in Table 3 below summarizes the thickness of the alumina film at three locations on the end surface of the glass substrate.

In Table 3, "DA" means the vicinity of the first main surface at the line L1 in FIGS. 6 to 8 described above, that is, the end surface. Further, "DB" means the center side of the glass substrate at the end surface, and "DC" means the vicinity of the second main surface at the end surface, which is the line L2 in FIGS. 6 to 8 described above.

Next, a 200-hour high temperature and high humidity test was conducted using a glass substrate coated with an alumina film. The test temperature was 85° C. and the relative humidity was 85%.

After the test, the glass substrate was taken out and its condition was evaluated. As a result, no abnormality was observed on the first main surface and second main surface of the glass substrate. It was also found that glass elution was suppressed to 1 mm or less from the surface also at the end face.

(Experiment 2)
An experiment similar to Experiment 1 was conducted.

However, in Experiment 2, a glass substrate was prepared by cutting a different glass plate than in Experiment 1.

For the glass plate, phosphate glass having the composition shown in "Glass B" in Table 1 above was used. The thickness of the glass plate was 0.35 mm.

The "Glass B" column in Table 2 above shows various parameters calculated from the optical properties of the glass plate.

Thereafter, a glass substrate coated with an alumina film was produced using the same method as in Experiment 1.

The "Experiment 2" column in Table 3 above collectively shows the thickness of the alumina film at three locations on the end surface of the glass substrate.

Next, a high temperature and high humidity test was conducted using a glass substrate coated with an alumina film.

(Experiment 3)
A glass substrate whose entire exposed surface was covered with an inorganic film was prepared by the following method.

A glass plate measuring 76 mm long x 76 mm wide x 0.28 mm thick was prepared.

For the glass plate, phosphate glass having the composition shown in "Glass A" in Table 1 above was used.

Next, a second alumina film was formed on one main surface (second main surface) of the glass plate by a vapor deposition method. The thickness of the second alumina film was targeted to be 143 nm.

Next, this glass plate was fully cut using a blade dicing method to obtain a glass substrate measuring 20 mm long x 20 mm wide x 0.28 mm thick.

Next, a first alumina film was formed on the main surface (first main surface) on which the second alumina film of the glass substrate was not provided by a vapor deposition method. The thickness of the first alumina film was targeted to be 143 nm.

After film formation, the end surface of the glass substrate was observed using a scanning electron microscope (Fe-SEM). As a result, the alumina film on the end surface of the glass substrate is thickest on the first main surface side of the glass substrate and thinnest on the second main surface side of the glass substrate (as shown in FIG. 6 above). form).

In the "Experiment 3" column in Table 3 above, the thicknesses of the alumina film at three locations on the end surface of the glass substrate are collectively shown.

(Experiment 4)
A glass substrate was produced by the following method.

A glass plate measuring 76 mm long x 76 mm wide x 0.28 mm thick was prepared. For the glass plate, phosphate glass having the composition shown in "Glass A" in Table 1 above was used.

Next, an alumina film was formed on both main surfaces of the glass plate by a vapor deposition method. The thickness of the alumina film on each main surface was targeted to be 143 nm.

Next, the glass plate after the film formation was cut by a blade dicing method to produce a glass substrate measuring 20 mm long x 20 mm wide x 0.28 mm thick.

After cutting, the end surface of the obtained glass substrate was observed using a scanning electron microscope (Fe-SEM).

In the "Experiment 4" column in Table 3 above, the thickness of the alumina film at three locations on the end surface of the glass substrate is collectively shown.

As shown in Table 3, it was found that no alumina film was formed on the end surface of this glass substrate.

Next, a high temperature and high humidity test was conducted using the glass substrate.

After the test, the glass substrate was taken out and its condition was evaluated. As a result, in this glass substrate, elution of glass occurred in a region exceeding 1 mm from the surface on the end face.

In this way, when phosphate glass is used as a glass substrate, the glass elutes due to moisture from the outside world, and by covering the entire exposed surface of the glass substrate with an alumina film, such elution of glass can be prevented. found to be suppressed.

(Example)
Examples of the present invention will be described below. In addition, in the following description, Example 1 and Example 2 are examples.

(Example 1)
An optical filter was produced by the following method.

A glass substrate whose entire exposed surface was covered with an alumina film was prepared by a method similar to that shown in Experiment 1 above. Hereinafter, this glass substrate will be referred to as "covered glass substrate A." Further, the alumina film installed on the first main surface side of the coated glass substrate A is referred to as a first alumina film, and the alumina film installed on the second main surface side is referred to as a second alumina film. , the alumina film installed on the end face side is referred to as a third alumina film.

Next, a first antireflection layer was formed on the first alumina film of the coated glass substrate A by a vapor deposition method. The first antireflection layer was made of alternating films of silica films and titania films. The total thickness of the first antireflection layer is 200 nm.

Table 4 below shows the structure of the first antireflection layer.

In Table 4, the first film is the film closest to the first main surface of the glass substrate, and the following are the second film, the third film,..., the film closest to the first main surface. 15 membranes are arranged in this order.

Next, a resin layer liquid was prepared. The resin layer liquid was prepared as follows.

First, polyimide varnish C3G30G (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was diluted with cyclohexanone and γ-butyrolactone so that the resin solid content was 8.5 wt%.

A resin layer liquid was prepared by adding Compound A, Compound B, and Compound C as dyes to this diluted liquid. The amounts of Compound A, Compound B, and Compound C added were 2.33% by mass, 6.08% by mass, and 2.56% by mass, respectively, based on the resin content.

Table 5 below summarizes the specifications of Compound A, Compound B, and Compound C.

Compound A, Compound B, and Compound C each have the following general formula.

Next, the resin layer liquid was spin coated onto the second alumina film of the coated glass substrate A. The target thickness was 1 μm.

Thereafter, the resin layer liquid was dried to form a resin layer.

This resin layer has optical properties as shown in FIG. 9 described above.

Next, a second antireflection layer was formed on the resin layer. The second antireflection layer had the same structure as the first antireflection layer, and was formed by vapor deposition.

As a result, an optical filter was obtained. The produced optical filter is referred to as "optical filter 1."

(Example 2)
An optical filter was produced in the same manner as in Example 1.

However, in this Example 2, a glass substrate whose entire exposed surface was covered with an alumina film was prepared by a method similar to that shown in Experiment 2 above. Hereinafter, this glass substrate will be referred to as "covered glass substrate B."

After that, an optical filter was produced using the same steps as in Example 1.

Hereinafter, the obtained optical filter will be referred to as "optical filter 2."

(evaluation)
The following evaluations were performed using each optical filter.

(Durability evaluation)
A high temperature and high humidity test was conducted using Optical Filter 1 and Optical Filter 2 under the conditions described above.

As a result of observation after the test, in optical filter 1 and optical filter 2, almost no elution was observed at the end surface of the glass substrate.

(Evaluation of optical properties)
Optical characteristics were evaluated using each optical filter. For the measurement, an ultraviolet-visible near-infrared spectrophotometer (UH4150: manufactured by Hitachi High-Tech Science) was used.

In the case of transmittance measurement, light was incident on each optical filter from the first antireflection layer side. The angle of incidence was 0 and 50°. On the other hand, in the case of measuring the reflectance, light was incident on each optical filter from the first antireflection layer side at incident angles of 5° and 50°.

FIG. 12 shows an example of a transmittance profile obtained in the optical filter 1. In FIG. 12, the horizontal axis is wavelength and the vertical axis is transmittance. FIG. 12 also shows the results at incident angles θ=0° and θ=50°.

As shown in FIG. 12, it can be seen that in the optical filter 1, the influence of the incident angle θ on the transmittance profile is hardly recognized. That is, in the visible light region, high transmittance was obtained regardless of the incident angle θ. Further, even if the incident angle θ changed, the region where the transmittance sharply decreased hardly changed. Furthermore, it was found that low transmittance was exhibited in a wavelength region exceeding 1000 nm, regardless of the incident angle θ.

FIG. 13 shows an example of the reflectance profile obtained in the optical filter 1. In FIG. 13, the horizontal axis is wavelength and the vertical axis is reflectance. FIG. 13 also shows the results at incident angles θ=5° and θ=50°.

As shown in FIG. 13, it can be seen that in the optical filter 1, the influence of the incident angle θ on the reflectance profile is hardly recognized.

FIG. 14 shows an example of the transmittance profile obtained in the optical filter 2. In FIG. 14, the horizontal axis is wavelength and the vertical axis is transmittance. FIG. 14 also shows the results at incident angles θ=0° and θ=50°.

As shown in FIG. 14, the same results as for optical filter 1 were obtained for optical filter 2 as well. That is, in the visible light region, high transmittance was obtained regardless of the incident angle θ. Further, even if the incident angle θ changed, the region where the transmittance sharply decreased hardly changed. Furthermore, it was found that low transmittance was exhibited in a wavelength region exceeding 1000 nm, regardless of the incident angle θ.

Table 6 below summarizes the parameters related to the transmittance profile measured in Optical Filter 1 and Optical Filter 2.

In addition, Table 7 below summarizes the parameters related to the reflectance profile measured in Optical Filter 1 and Optical Filter 2.

In this way, it was confirmed that in optical filter 1 and optical filter 2, the optical characteristics hardly change even if the incident angle θ changes. Furthermore, it was confirmed that infrared rays were sufficiently blocked by optical filter 1 and optical filter 2.

(Aspects of the present invention)
The present invention includes the following aspects.

(Aspect 1)
An optical filter having a glass substrate and a first antireflection layer,
The glass substrate has a first main surface and a second main surface facing each other, and an end surface connecting the two main surfaces,
The first antireflection layer is installed on the first main surface side of the glass substrate,
The glass substrate is phosphate glass containing an absorbent,
The first main surface of the glass substrate is coated with a first inorganic film, the second main surface of the glass substrate is coated with a second inorganic film, and the end surface of the glass substrate is coated with a third inorganic film,
The first inorganic film is a film that is closest to the glass substrate among the films that constitute the first antireflection layer, or is a film that is different from the film that constitutes the first antireflection layer. can be,
The third inorganic film has a maximum thickness on at least one of the first main surface side and the second main surface side.

(Aspect 2)
The optical filter according to aspect 1, wherein the third inorganic film has a maximum thickness on the first main surface side or the second main surface side.

(Aspect 3)
The optical filter according to

aspect

1 or 2, wherein the third inorganic film has the thinnest shape at the center in the thickness direction of the glass substrate.

(Aspect 4)
A resin layer containing a dye is disposed on the second inorganic film installed on the second main surface side of the glass substrate,
The optical filter according to any one of aspects 1 to 3, wherein the resin layer has a maximum absorption wavelength in a range of 650 nm to 850 nm.

(Aspect 5)
The optical filter according to aspect 4, wherein a second antireflection layer is disposed on the resin layer.

(Aspect 6)
The optical filter according to any one of aspects 1 to 5, wherein the first main surface of the glass substrate is coated with the first antireflection layer.

(Aspect 7)
The optical filter according to any one of aspects 1 to 6, wherein the first inorganic film, the second inorganic film, and the third inorganic film are made of the same material.

(Aspect 8)
The optical filter according to aspect 7, wherein the first inorganic film, the second inorganic film, and the third inorganic film are aluminum oxide films.

(Aspect 9)
When the transmittance (%) when the angle of incidence is 5° is T ₍₅₎ , and the reflectance (%) when the angle of incidence is 5° is R ₍₅₎ ,
The internal transmittance of the glass substrate is calculated by the following formula:
Internal transmittance (%) = T ₍₅₎ / (100 - R ₍₅₎ ) x 100

It is expressed as
The glass substrate is
(i) Internal transmittance T at a wavelength of 450 nm _{(g) 450} is 92% or more,
(ii) Average internal transmittance T in the wavelength range of 450 nm to wavelength 600 nm _{(g) ave1} is 90% or more, (iii) Minimum wavelength λ at which the internal transmittance is 50% _{(g) 50} is in the range of 625 nm to 650 nm (iv) Average internal transmittance T in the wavelength range of 750 nm to 1000 nm _{(g) ave2} is 2.5% or less, (v) Average internal transmittance T in the wavelength range of 1000 nm to 1200 nm _{(g) ave3} is 7% or less,
The optical filter according to any one of aspects 1 to 8, having spectral characteristics.

(Aspect 10)
The glass substrate has a mass percentage based on oxide,
50% to 80% P ₂ O ₅ ,
5% to 20% Al ₂ O ₃ ,
4% to 20% CuO,
0.5% to 15% R(1) ₂ O, where R(1) is at least one component selected from the group consisting of Li, Na, K, Rb, and Cs, and 0 ~15% R(2)O, where R(2) is at least one component selected from the group consisting of Ca, Mg, Ba, Sr, and Zn;
The optical filter according to any one of aspects 1 to 9, comprising:

(Aspect 11)
The optical filter is
(I) At both incident angles θ=0° and 50°, the transmittance T _(t)450 at a wavelength of 450 nm is 80% or more, (II) At both incident angles θ=0° and 50°, The average transmittance T _{(t) ave1} in the wavelength range of 450 nm to 600 nm is 78% or more, and (III) the maximum transmittance in the wavelength range of 450 nm to 600 nm at both incident angles θ = 0° and 50°. T _(t)max1 is 85% or more, and (IV) the minimum wavelength λ _(t)50 at which the transmittance is 50% is in the range of 600 nm to 650 nm at both incident angles θ = 0° and 50°. , (V) At both incident angles θ=0° and 50°, the average transmittance T _{(t) ave2} in the wavelength range of 750 nm to 1200 nm is 2.0% or less, and (VI) When the incident angle θ=0° and 50°, the maximum transmittance T _(t)max2 in the wavelength range of 1000 nm to 1200 nm is 15% or less,
The optical filter according to any one of aspects 1 to 10, having spectral characteristics.

(Aspect 12)
When light is incident from the first main surface side of the glass substrate, the optical filter (VII) has a wavelength range of 450 nm to 700 nm at both incident angles θ=5° and 50°. The maximum reflectance R _(t)max1 is 7% or less, and the maximum reflectance R _(t)max2 is 45% in the wavelength range of 700 nm to wavelength 1200 nm at both incident angles 5=0° and 50°. The following is
The optical filter according to any one of aspects 1 to 11, having spectral characteristics.

(Aspect 13)
An imaging device comprising the optical filter according to any one of aspects 1 to 12.

This application claims priority based on Japanese Patent Application No. 2022-102153 filed on June 24, 2022, and the entire contents of the same Japanese application are incorporated by reference into this application.

100 first optical filter 110 glass substrate 112 first main surface 114 second main surface 116 end face 122 first inorganic film 124 second inorganic film 126 third inorganic film 130 first antireflection layer 200 2 optical filter 210 Glass substrate 212 First main surface 214 Second main surface 216 End surface 222 First inorganic film 224 Second inorganic film 226 Third inorganic film 230 First antireflection layer 250 Second Antireflection layer 300 Third optical filter 310 Glass substrate 312 First main surface 314 Second main surface 316 End surface 322 First inorganic film 324 Second inorganic film 326 Third inorganic film 330 First antireflection Layer 340 Resin layer 350 Second antireflection layer

Claims

An optical filter having a glass substrate and a first antireflection layer,
The glass substrate has a first main surface and a second main surface facing each other, and an end surface connecting the two main surfaces,
The first antireflection layer is installed on the first main surface side of the glass substrate,
The glass substrate is phosphate glass containing an absorbent,
The first main surface of the glass substrate is coated with a first inorganic film, the second main surface of the glass substrate is coated with a second inorganic film, and the end surface of the glass substrate is coated with a third inorganic film,
The first inorganic film is a film that is closest to the glass substrate among the films that constitute the first antireflection layer, or is a film that is different from the film that constitutes the first antireflection layer. can be,
The third inorganic film has a maximum thickness on at least one of the first main surface side and the second main surface side.
The optical filter according to claim 1, wherein the third inorganic film has a maximum thickness on the first main surface side or the second main surface side.
The optical filter according to claim 1 or 2, wherein the third inorganic film has the thinnest shape at the center in the thickness direction of the glass substrate.
A resin layer containing a dye is disposed on the second inorganic film installed on the second main surface side of the glass substrate,
The optical filter according to claim 1 or 2, wherein the resin layer has a maximum absorption wavelength in a range of 650 nm to 850 nm.
The optical filter according to claim 4, wherein a second antireflection layer is disposed on the resin layer.
The optical filter according to claim 1 or 2, wherein the first main surface of the glass substrate is coated with the first antireflection layer.
The optical filter according to claim 1 or 2, wherein the first inorganic film, the second inorganic film, and the third inorganic film are made of the same material.
The optical filter according to claim 7, wherein the first inorganic film, the second inorganic film, and the third inorganic film are aluminum oxide films.
When the transmittance (%) when the angle of incidence is 5° is T (5) , and the reflectance (%) when the angle of incidence is 5° is R (5) ,
The internal transmittance of the glass substrate is calculated by the following formula:
Internal transmittance (%) = T (5) / (100 - R (5) ) x 100

It is expressed as
The glass substrate is
(i) Internal transmittance T at a wavelength of 450 nm (g) 450 is 92% or more,
(ii) Average internal transmittance T in the wavelength range of 450 nm to wavelength 600 nm (g) ave1 is 90% or more, (iii) Minimum wavelength λ at which the internal transmittance is 50% (g) 50 is in the range of 625 nm to 650 nm (iv) Average internal transmittance T in the wavelength range of 750 nm to 1000 nm (g) ave2 is 2.5% or less, (v) Average internal transmittance T in the wavelength range of 1000 nm to 1200 nm (g) ave3 is 7% or less,
The optical filter according to claim 1 or 2, having spectral characteristics.
The glass substrate has a mass percentage based on oxide,
50% to 80% P 2 O 5 ,
5% to 20% Al 2 O 3 ,
4% to 20% CuO,
0.5% to 15% R(1) 2 O, where R(1) is at least one component selected from the group consisting of Li, Na, K, Rb, and Cs, and 0 ~15% R(2)O, where R(2) is at least one component selected from the group consisting of Ca, Mg, Ba, Sr, and Zn;
The optical filter according to claim 1 or 2, comprising:
The optical filter is
(I) At both incident angles θ=0° and 50°, the transmittance T (t)450 at a wavelength of 450 nm is 80% or more, (II) At both incident angles θ=0° and 50°, The average transmittance T (t) ave1 in the wavelength range of 450 nm to 600 nm is 78% or more, and (III) the maximum transmittance in the wavelength range of 450 nm to 600 nm at both incident angles θ = 0° and 50°. T (t)max1 is 85% or more, and (IV) the minimum wavelength λ (t)50 at which the transmittance is 50% is in the range of 600 nm to 650 nm at both incident angles θ = 0° and 50°. , (V) At both incident angles θ=0° and 50°, the average transmittance T (t) ave2 in the wavelength range of 750 nm to 1200 nm is 2.0% or less, and (VI) When the incident angle θ=0° and 50°, the maximum transmittance T (t)max2 in the wavelength range of 1000 nm to 1200 nm is 15% or less,
The optical filter according to claim 1 or 2, having spectral characteristics.
When light is incident from the first main surface side of the glass substrate, the optical filter (VII) has a wavelength range of 450 nm to 700 nm at both incident angles θ=5° and 50°. The maximum reflectance R (t)max1 is 7% or less, and the maximum reflectance R (t)max2 is 45% in the wavelength range of 700 nm to wavelength 1200 nm at both incident angles 5=0° and 50°. The following is
The optical filter according to claim 1 or 2, having spectral characteristics.
An imaging device comprising the optical filter according to claim 1 or 2.