JP7491052B2 - Near infrared cut filter - Google Patents

Description

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

Image capture devices such as digital cameras and digital videos are equipped with solid-state image sensors (image sensors) to sense people, scenery, etc. However, solid-state image sensors are more sensitive to infrared light than human vision. For this reason, to bring the image captured by the solid-state image sensor closer to human visual sensitivity, a near-infrared cut filter is also installed in the image capture device.

In general, such a near-infrared cut filter is constructed by providing an optical multilayer film for blocking near-infrared rays on a transparent substrate, which is constructed by alternately laminating thin films made of a dielectric material with a high refractive index (e.g., TiO ₂ ) and thin films made of a dielectric material with a low refractive index (e.g., SiO ₂ ).

International Publication No. WO2014/104370

It is known that the optical characteristics of near-infrared cut filters having optical multilayer coatings often change depending on the angle of incident light. For this reason, for example, while desired optical characteristics can be obtained for light having an incident angle close to the normal direction, problems may arise in that desired optical characteristics cannot be obtained for light having an incident angle that is significantly different from the normal direction.

In addition, the incidence angle dependency of the optical properties of such a near-infrared cut filter can cause problems in terms of image clarity when the near-infrared cut filter is applied to a solid-state imaging device. For example, if a portion of the visible light incident on the near-infrared cut filter is reflected rather than transmitted, such reflected light can cause stray light.

The present invention has been made in consideration of this background, and aims to provide a near-infrared cut filter that can significantly suppress the reflectance in the visible light region over a wide range of incident angles.

In the present invention, there is provided a near-infrared cut filter,
a transparent substrate having a first surface;
an optical multilayer film provided on the first surface side of the transparent substrate;
a first matching film provided on the first surface side of the transparent substrate;
a second matching film disposed on the outermost side of the first surface;
having
The optical multilayer film has an alternate laminate structure of high refractive index layers and low refractive index layers, and has a function of reflecting near infrared rays,
the first and second matching films have a function of suppressing reflection of visible light,
the first matching film is disposed on the optical multi-layer film or between the transparent substrate and the optical multi-layer film;
In the near infrared cut filter,
The specular reflectance of light incident from the second matching film side at an incident angle of 5° is defined as a first reflectance _R1 , and the specular reflectance of light incident from the second matching film side at an incident angle of 40° is defined as a second reflectance _R2 .
When the approximation line of the first reflectance R ₁ in the wavelength range of 480 nm to 680 nm is y ₁ and the approximation line of the second reflectance R ₂ in the wavelength range of 450 nm to 650 nm is y ₂ ,
In the wavelength range of 480 nm to 680 nm, the maximum absolute value ΔR ₁ of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength is less than 5%,
There is provided a near-infrared cut filter, in which the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximate straight line y ₂ at the same wavelength in the wavelength range of 450 nm to 650 nm is less than 6%.

The present invention provides a near-infrared cut filter that can significantly reduce reflectance in the visible light region over a wide range of incident angles.

1 is a diagram showing a schematic cross section of a near-infrared cut filter according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a cross section of a near-infrared cut filter according to another embodiment of the present invention. FIG. 11 is a diagram illustrating a cross section of a near-infrared cut filter according to still another embodiment of the present invention. 1 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 1. 5 is a graph showing an enlarged portion of the optical characteristics at 5° incidence in FIG. 4; 5 is a graph showing an enlarged view of a portion of the optical characteristics at 40° incidence in FIG. 4. 1 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 2. 8 is a graph showing an enlarged portion of the optical characteristics at 5° incidence in FIG. 7; 8 is a graph showing an enlarged portion of the optical characteristics at 40° incidence in FIG. 7 . 1 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 3. 1 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 4. 12 is a graph showing an enlarged portion of the optical characteristics at 5° incidence in FIG. 11 . 12 is a graph showing an enlarged portion of the optical characteristics at 40° incidence in FIG. 11 . 1 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 11. 15 is a graph showing an enlarged portion of the optical characteristics at 5° incidence in FIG. 14. 15 is a graph showing an enlarged portion of the optical characteristics at 40° incidence in FIG. 14. 1 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 11. 18 is a graph showing an enlarged portion of the optical characteristics at 5° incidence in FIG. 17. 18 is a graph showing an enlarged portion of the optical characteristics at 40° incidence in FIG. 17. 13 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 13. 13 is a graph showing the optical characteristics at 5° incidence and 40° incidence obtained in the near-infrared cut filter in Example 14.

One embodiment of the present invention is described below.

In one embodiment of the present invention, there is provided a near-infrared cut filter,
a transparent substrate having a first surface;
an optical multilayer film provided on the first surface side of the transparent substrate;
a first matching film provided on the first surface side of the transparent substrate;
a second matching film disposed on the outermost side of the first surface;
having
The optical multilayer film has an alternate laminate structure of high refractive index layers and low refractive index layers, and has a function of reflecting near infrared rays,
the first and second matching films have a function of suppressing reflection of visible light,
the first matching film is disposed on the optical multi-layer film or between the transparent substrate and the optical multi-layer film;
In the near infrared cut filter,
The specular reflectance of light incident from the second matching film side at an incident angle of 5° is defined as a first reflectance _R1 , and the specular reflectance of light incident from the second matching film side at an incident angle of 40° is defined as a second reflectance _R2 .
When the approximation line of the first reflectance R ₁ in the wavelength range of 480 nm to 680 nm is y ₁ and the approximation line of the second reflectance R ₂ in the wavelength range of 450 nm to 650 nm is y ₂ ,
In the wavelength range of 480 nm to 680 nm, the maximum absolute value ΔR ₁ of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength is less than 5%,
There is provided a near-infrared cut filter, in which the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximate straight line y ₂ at the same wavelength in the wavelength range of 450 nm to 650 nm is less than 6%.

The near-infrared cut filter according to one embodiment of the present invention has an optical multilayer film. This optical multilayer film has the function of blocking the transmission of near-infrared light and reflecting the near-infrared light.

The near-infrared cut filter according to one embodiment of the present invention has first and second matching films. The first and second matching films have the function of suppressing reflection of visible light.

The near-infrared cut filter according to one embodiment of the present invention is characterized in that the maximum absolute value ΔR 1 of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength in the wavelength range of 480 nm to 680 nm is less than 5%. Furthermore, the near-infrared cut filter according to one embodiment of the present invention is characterized in that the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength in the wavelength range of 450 nm to 650 nm is less than ₆ %.

As will be described in detail later, a near-infrared cut filter having such a configuration can significantly suppress the reflectance in the visible light region over a wide range of incident angles. Therefore, when a near-infrared cut filter according to one embodiment of the present invention is applied to a solid-state imaging device, it becomes possible to obtain a clear image.

(Near-infrared cut filter according to one embodiment of the present invention)
Next, an embodiment of the present invention will be described in more detail with reference to the drawings.

Figure 1 shows a schematic cross section of a near-infrared cut filter (hereinafter referred to as the "first optical filter") according to one embodiment of the present invention.

As shown in FIG. 1, the first optical filter 100 has a transparent substrate 110 having a first surface 112, an optical multilayer film 120, a first matching film 140, and a second matching film 160.

The optical multilayer film 120 is disposed on the first surface 112 of the transparent substrate 110, and the first matching film 140 is disposed on the optical multilayer film 120. The second matching film 160 is disposed on the outermost side of the first surface 112.

The optical multilayer film 120 has the function of blocking the transmission of near-infrared light and reflecting the near-infrared light. The first matching film 140 and the second matching film 160 have the function of suppressing the reflection of visible light.

Here, the specular reflectance of light incident from the second matching film 160 side at an incident angle of 5° with respect to the normal is referred to as the first reflectance _R1 , and the specular reflectance of light incident at an incident angle of 40° with respect to the normal is referred to as the second reflectance _R2 . Also, the approximate straight line of the first reflectance _R1 in the wavelength range of 480 nm to 680 nm is referred to as _y1 , and the approximate straight line of the second reflectance _R2 in the wavelength range of 450 nm to 650 nm is referred to as _y2 .

In this case, the first optical filter 100 is
In the wavelength range of 480 nm to 680 nm, the maximum absolute value ΔR ₁ of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength is less than 5%,
The optical fiber has a characteristic that the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ at the same wavelength and the value of the approximation line y ₂ is less than 6% in the wavelength range of 450 nm to 650 nm.

For example, ΔR ₁ may be less than 4%, and preferably less than 3%, and for example, ΔR ₂ may be less than 5.5%, and preferably less than 5%.

The first optical filter 100 can significantly suppress the reflectance in the visible light region over a wide range of incident angles. Therefore, when the first optical filter 100 is applied to a solid-state imaging device, it is possible to obtain a clear image.

(Near-infrared cut filter according to another embodiment of the present invention)
Next, another embodiment of the present invention will be described with reference to FIG.

Figure 2 shows a schematic cross section of a near-infrared cut filter according to another embodiment of the present invention (hereinafter referred to as the "second optical filter").

As shown in FIG. 2, the second optical filter 200 has a transparent substrate 210 having a first surface 212, a first matching film 240, an optical multilayer film 220, and a second matching film 260.

The first matching film 240 is disposed on the first surface 212 of the transparent substrate 210, and the optical multilayer film 220 is disposed on the first matching film 240. The second matching film 260 is disposed on the outermost side of the first surface 212.

Here, similarly to the first optical filter 100, the second optical filter 200 also has the following characteristics:
In the wavelength range of 480 nm to 680 nm, the maximum absolute value ΔR ₁ of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength is less than 5%,
The optical fiber has a characteristic that the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ at the same wavelength and the value of the approximation line y ₂ is less than 6% in the wavelength range of 450 nm to 650 nm.

The second optical filter 200 can significantly suppress the reflectance in the visible light region over a wide range of incident angles. Therefore, when the second optical filter 200 is applied to a solid-state imaging device, it is possible to obtain a clear image.

(Near-infrared cut filter according to still another embodiment of the present invention)
Next, with reference to FIG. 3, yet another embodiment of the present invention will be described.

Figure 3 shows a schematic cross section of a near-infrared cut filter according to yet another embodiment of the present invention (hereinafter referred to as the "third optical filter").

As shown in FIG. 3, the third optical filter 300 has a transparent substrate 310 having a first surface 312, a first matching film 340, an optical multilayer film 320, a third matching film 350, and a second matching film 360.

The first matching film 340 is disposed on the first surface 312 of the transparent substrate 310. The optical multilayer film 320 is disposed on the first matching film 340, and the third matching film 350 is disposed on the optical multilayer film 320. The second matching film 360 is disposed on the outermost side of the first surface 312.

Here, similar to the first optical filter 100 and the second optical filter 200, the third optical filter 300 also has the following characteristics:
In the wavelength range of 480 nm to 680 nm, the maximum absolute value ΔR ₁ of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength is less than 5%,
The optical fiber has a characteristic that the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ at the same wavelength and the value of the approximation line y ₂ is less than 6% in the wavelength range of 450 nm to 650 nm.

The third optical filter 300 can significantly suppress the reflectance in the visible light region over a wide range of incident angles. Therefore, when the third optical filter 300 is applied to a solid-state imaging device, it is possible to obtain a clear image.

(Components)
Next, each member constituting the near-infrared cut filter according to one embodiment of the present invention will be described in more detail.

Note that, as an example, the components of the third optical filter 300 described above will be described here. Therefore, when referring to each component, the reference numerals shown in FIG. 3 will be used.

(Transparent substrate 310)
The transparent substrate 310 may be made of any material as long as it is transparent (has high transmittance) to visible light. For example, the transparent substrate 310 may be made of glass (white plate glass, near-infrared absorbing glass, etc.) or resin.

(Optical multilayer film 320)
The optical multilayer film 320 has a repeating structure of a "high refractive index layer" and a "low refractive index layer", and has a function of reflecting near infrared rays (wavelengths of 750 nm to 900 nm).

In this application, a "high refractive index layer" refers to a layer having a refractive index of 2.0 or more at a wavelength of 500 nm, and a "low refractive index layer" refers to a layer having a refractive index of 1.6 or less at a wavelength of 500 nm.

Examples of high refractive index layers include titanium oxide, tantalum oxide, and niobium oxide. Examples of low refractive index layers include silicon oxide and magnesium fluoride. For example, the refractive index of titanium oxide at a wavelength of 500 nm is generally in the range of 2.3 to 2.8, although it depends on the crystal state, and the refractive index of silicon oxide is generally in the range of 1.4 to 1.5.

The number of layers in the optical multilayer film 320 is not particularly limited, but is, for example, in the range of 4 to 100. The number of layers is preferably in the range of 6 to 24.

Half the number of layers in the multilayer film (if it is a fraction, round down to the nearest whole number) is also referred to as the "repetition number (n)."

The number of repetitions n of the optical multilayer film 320 is in the range of 2 to 50, and preferably in the range of 3 to 13.

The total thickness (physical film thickness) of the optical multilayer film 320 is, for example, in the range of 200 nm to 10 μm, and preferably in the range of 1 μm to 6 μm.

The optical multilayer film 320 may further have the function of reflecting near ultraviolet and infrared rays (wavelengths 900 nm to 1200 nm). In this case, the third optical filter 300 can block near ultraviolet and infrared rays.

(First matching film 340)
As described above, the first matching film 340 has the function of suppressing reflection of visible light.

The first matching film 340 may have an alternating laminate structure of a "high refractive index layer" and a "low refractive index layer." For the "high refractive index layer" and the "low refractive index layer," see the above description.

When the first matching film 340 has an alternate laminate structure of high refractive index layers and low refractive index layers, the QWOT (Quarter-wave Optical Thickness) of the high refractive index layer at a wavelength of 550 nm is _QH , and the QWOT of the low refractive index layer at a wavelength of 550 nm is _QL . The first matching film 340 has the following characteristics in order from the transparent substrate 310 side:

( _H1QH , _{L1QL , H2QH , L2QL , ..., HnQH, LnQL ) ( 1} )

(where n is a natural number equal to or greater than 1). In addition, each coefficient may have the following structure:

1.7≦W≦2.5 (2)

where:

W = ( _H1 + _H2 + ... + _Hn ) / ( _L1 + _L2 + ... + _Ln ) (3)

It is.

The coefficients _H1 ... _Hn and _L1 ... _Ln before _QH and _QL in formula (1) represent _the physical thickness of each layer as a multiple of _{the QWOT thickness, i.e., HnQH and LnQL represent the} optical thickness of each layer.

The number of layers in the first matching film 340 is not particularly limited, but is preferably in the range of, for example, 2 to 20 layers. If the number of layers exceeds 20, film formation takes time, and the manufacturing cost of the third optical filter 300 increases. The number of layers in the first matching film 340 is more preferably in the range of 6 to 16 layers, and even more preferably 12 layers or less.

(Second matching film 360)
The second matching film 360, like the first matching film 340, has the function of suppressing reflection of visible light.

The second matching film 360 preferably has a two-layer structure of a high refractive index layer and a low refractive index layer (i.e., the number of repetitions n=1). Note that the above description can be referred to for the "high refractive index layer" and "low refractive index layer".

Furthermore, in this case, when the QWOT of the high refractive index layer at a wavelength of 550 nm is _QA and the QWOT of the low refractive index layer at a wavelength of 550 nm is _QB , the second matching film 360 has the following characteristics from the transparent substrate side:

(XQ _A , YQ _B ) (4)

where X>Y is preferably the case.

(Third matching film 350)
The third matching film 350, like the first matching film 340 and the second matching film 360, has the function of suppressing reflection of visible light.

The third matching film 350 may have an alternating laminate structure of a "high refractive index layer" and a "low refractive index layer." For the "high refractive index layer" and the "low refractive index layer," see the above description.

In particular, the third matching film 350 may be configured with the same number of layers as the first matching film 340. In addition, the third matching film 350 may be configured to satisfy the above-mentioned formulas (1) to (3).

For example, the third matching film 350 may be composed of 6 to 16 layers. In this case, the number of repetitions n is 3 to 8.

The third matching film 350 is not a required component, but providing the third matching film 350 can further suppress the reflection of visible light.

In the example shown in FIG. 3, the third matching film 350 is disposed on the optical multilayer film 320 disposed on the first matching film 340. However, the opposite may be true, with the third matching film 350 disposed between the transparent substrate 310 and the optical multilayer film 320, and the first matching film 340 disposed on the optical multilayer film 320.

The above describes the components included in the near-infrared cut filter according to one embodiment of the present invention, using the third optical filter 300 as an example. However, it will be clear to those skilled in the art that the above description can be similarly applied to the first optical filter 100 and the second optical filter 200.

Next, examples of the present invention will be described. In the following description, Examples 1 to 4 are examples, and Examples 11 to 14 are comparative examples.

The optical characteristics of each of the near-infrared cut filters having the configurations shown in the following examples were evaluated. The optical characteristics were evaluated using commercially available optical simulation software (TFCalc from Software Spectra, Inc.).

In the following evaluations, the reflectance of the near-infrared cut filter represents the regular reflectance obtained when light is incident at a specified angle to the normal from the first surface side of the transparent substrate (i.e., the side on which the various films are installed).

The light incidence angles were 5° and 40° with respect to the normal. Hereinafter, these incidence directions will be referred to as "5° incidence" and "40° incidence", respectively.

(Example 1)
The near-infrared cut filter in Example 1 has the configuration shown in FIG.

Glass (D263; manufactured by Schott) was used as the transparent substrate. The same glass was used in other examples as well.

The optical multilayer film had a repeating structure of a low refractive index layer ( _SiO2 layer) and a high refractive index layer ( _TiO2 layer). The number of layers was 17. The first matching film had a repeating structure of a _TiO2 layer and a _SiO2 layer, and the number of layers was 6. The second matching film had a two-layer structure of a _TiO2 layer and a _SiO2 layer.

The layer structures of the optical multilayer film, the first matching film, and the second matching film used in Example 1 are summarized in Table 1 below.

第１の整合膜において、前述の（３）式で表されるＷの値、すなわち（Ｈ_１＋Ｈ_２＋Ｈ_３）／（Ｌ_１＋Ｌ_２＋Ｌ_３）の値は、２．２０であった。

In the first matching film, the value of W expressed by the above-mentioned formula (3), that is, the value of (H ₁ +H ₂ +H ₃ )/(L ₁ +L ₂ +L ₃ ), was 2.20.

In the second matching film, the QWOT (Q _A ) of the TiO ₂ layer at a wavelength of 550 nm was 1.898, and the QWOT (Q _B ) of the SiO ₂ layer at a wavelength of 550 nm was 0.887. When the second matching film is expressed by the above-mentioned formula (4), X/Y was 2.14.

In Table 1, the layers are listed in order of proximity to the transparent substrate, and therefore the layers are arranged on the transparent substrate from top to bottom in Table 1. This description is the same in the following Tables 2 to 8.

(Example 2)
The near-infrared cut filter in Example 2 has the configuration shown in FIG.

Glass was used as the transparent substrate.

The optical multilayer film had a repeating structure of _TiO2 layers and _{SiO2 layers} . The number of layers was 18. The first matching film had a repeating structure of _TiO2 layers and _SiO2 layers, and the number of layers was 6. The second matching film had a two-layer structure of _TiO2 layers and _SiO2 layers.

Table 2 below summarizes the layer structures of the optical multilayer film, the first matching film, and the second matching film used in Example 2.

第１の整合膜において、前述の（３）式で表されるＷの値、すなわち（Ｈ_１＋Ｈ_２＋Ｈ_３）／（Ｌ_１＋Ｌ_２＋Ｌ_３）の値は、１．７１であった。

In the first matching film, the value of W expressed by the above-mentioned formula (3), that is, the value of (H ₁ +H ₂ +H ₃ )/(L ₁ +L ₂ +L ₃ ), was 1.71.

In the second matching film, the QWOT (Q _A ) of the TiO ₂ layer at a wavelength of 550 nm was 2.000, and the QWOT (Q _B ) of the SiO ₂ layer at a wavelength of 550 nm was 0.900. When the second matching film is expressed by the above formula (4), X/Y was 2.22.

(Example 3)
The near-infrared cut filter in Example 3 has the configuration shown in FIG.

Glass was used as the transparent substrate.

The first matching film had a repeating structure of _TiO2 layers and _SiO2 layers, and the number of layers was 6. The optical multilayer film had a repeating structure of _SiO2 layers and _TiO2 layers, and the number of layers was 17. Furthermore, the second matching film had a two-layer structure of _TiO2 layers and _SiO2 layers.

Table 3 below summarizes the layer structures of the first matching film, optical multilayer film, and second matching film used in Example 3.

第１の整合膜において、前述の（３）式で表されるＷの値、すなわち（Ｈ_１＋Ｈ_２＋Ｈ_３）／（Ｌ_１＋Ｌ_２＋Ｌ_３）の値は、２．０９であった。

In the first matching film, the value of W expressed by the above-mentioned formula (3), that is, the value of (H ₁ +H ₂ +H ₃ )/(L ₁ +L ₂ +L ₃ ), was 2.09.

In the second matching film, the QWOT (Q _A ) of the TiO ₂ layer at a wavelength of 550 nm was 1.587, and the QWOT (Q _B ) of the SiO ₂ layer at a wavelength of 550 nm was 0.884. When the second matching film is expressed by the above-mentioned formula (4), X/Y was 1.80.

(Example 4)
The near-infrared cut filter in Example 4 has the configuration shown in FIG.

Glass was used as the transparent substrate.

The first matching film has a repeating structure of _SiO2 layers and _TiO2 layers, and the number of layers is 6. The optical multilayer film has a repeating structure of _SiO2 layers and _TiO2 layers. The number of layers is 17. The third matching film has a repeating structure of _TiO2 layers and _SiO2 layers, and the number of layers is 6. The second matching film has a two-layer structure of _TiO2 layers and _SiO2 layers.

Table 4 below shows the layer configurations of the first matching film, optical multilayer film, third matching film, and second matching film used in Example 4.

第１の整合膜において、前述の（３）式で表されるＷの値、すなわち（Ｈ_１＋Ｈ_２＋Ｈ_３）／（Ｌ_１＋Ｌ_２＋Ｌ_３）の値は、２．１５であった。

In the first matching film, the value of W expressed by the above formula (3), that is, the value of (H ₁ +H ₂ +H ₃ )/(L ₁ +L ₂ +L ₃ ), was 2.15.

In the second matching film, the QWOT (Q _A ) of the TiO ₂ layer at a wavelength of 550 nm was 1.983, and the QWOT (Q _B ) of the SiO ₂ layer at a wavelength of 550 nm was 0.921. When the second matching film is expressed by the above-mentioned formula (4), X/Y was 2.15.

(Example 11)
The near-infrared cut filter in Example 11 has a configuration having only an optical multilayer film on a transparent substrate. The optical multilayer film has a repeating structure of 2 TiO ₂ layers and 2 SiO ₂ layers, and the number of layers is 20.

Table 5 below shows the layer structure of the optical multilayer film used in Example 11.

（例１２）
例１２における近赤外線カットフィルタは、透明基板の上に光学多層膜のみを有する構成を有する。光学多層膜は、ＳｉＯ_２層とＴｉＯ_２層の繰り返し構造とし、層数は、２１層とした。

(Example 12)
The near infrared cut filter in Example 12 has a configuration having only an optical multilayer film on a transparent substrate. The optical multilayer film has a repeating structure of ₂ SiO layers and ₂ TiO layers, and the number of layers is 21.

Table 6 below shows the layer structure of the optical multilayer film used in Example 12.

（例１３）
例１３における近赤外線カットフィルタは、透明基板の上に、光学多層膜と、第１の整合膜とを、この順に配置した構成を有する。

(Example 13)
The near-infrared cut filter in Example 13 has a configuration in which an optical multilayer film and a first matching film are disposed in this order on a transparent substrate.

The optical multilayer film had a repeating structure of SiO ₂ layers and TiO ₂ layers, and the number of layers was 17. The first matching film had a repeating structure of TiO ₂ layers and SiO ₂ layers, and the number of layers was 6.

Table 7 below summarizes the layer structure of the optical multilayer film and the first matching film used in Example 13.

（例１４）
例１４における近赤外線カットフィルタは、図１に示した構成を有する。

(Example 14)
The near-infrared cut filter in Example 14 has the configuration shown in FIG.

Glass was used as the transparent substrate.

The optical multilayer film had a repeating structure of _SiO2 layers and _TiO2 layers. The number of layers was 17. The first matching film had a repeating structure of _TiO2 layers and _SiO2 layers, and the number of layers was 6. The second matching film had a two-layer structure of _TiO2 layers and _SiO2 layers.

Table 8 below summarizes the layer structures of the optical multilayer film, the first matching film, and the second matching film used in Example 14.

（光学特性の評価結果）
（例１における近赤外線カットフィルタ）
図４～図６には、例１における近赤外線カットフィルタにおいて得られた光学特性の評価結果を示す。

(Evaluation results of optical properties)
(Near-infrared cut filter in Example 1)
4 to 6 show the evaluation results of the optical characteristics obtained in the near infrared cut filter in Example 1. FIG.

In Fig. 4, the horizontal axis is wavelength and the vertical axis is reflectance, and Fig. 4 also shows the results of the specular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the specular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

The results in Figure 4 show that the near-infrared cut filter in Example 1 has a transmission band in the visible light region (wavelengths of approximately 450 nm to approximately 650 nm) and a reflection band in the near-infrared region.

The wavelength range of the reflection band at 5° incidence is from about 750 nm to about 1000 nm, whereas the wavelength range of the reflection band at 40° incidence is from about 700 nm to about 900 nm. In other words, the wavelength range of the reflection band at 40° incidence is shifted to the lower wavelength side compared to the wavelength range of the reflection band at 5° incidence.

However, it can be seen that in both cases of the first reflectance _R1 and the second reflectance _R2 , reflection is sufficiently suppressed in the transmission band.

FIG. 5 shows an enlarged view of the change in the first reflectance _R1 in the wavelength range of 480 nm to 680 nm, out of the behavior shown in FIG.

In addition, the straight line _y1 in FIG. 5 is an approximation straight line of the first reflectance _R1 in the wavelength range of 480 nm to 680 nm,

y ₁ = 0.0353λ - 16.087 (5)

Here, λ is the wavelength (the same applies below).

FIG. 6 shows an enlarged view of the change in the second reflectance _R2 in the wavelength range of 450 nm to 650 nm, among the behaviors shown in FIG.

The straight line _y2 in FIG. 6 is an approximation straight line of the second reflectance _R2 in the wavelength range of 450 nm to 650 nm.

y ₂ = 0.0532λ - 24.315 (6)

It is expressed as:

From these results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =2.35%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =5.38%.

(Near-infrared cut filter in Example 2)
7 to 9 show the evaluation results of the optical characteristics obtained in the near-infrared cut filter in Example 2. FIG.

In Fig. 7, the horizontal axis is wavelength and the vertical axis is reflectance, and Fig. 7 also shows the results of the specular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the specular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

The results in Figure 7 show that the near-infrared cut filter in Example 2 has a transmission band in the visible light region (wavelengths of approximately 450 nm to approximately 650 nm) and a reflection band in the near-infrared region.

It can also be seen that in the transmission band, reflection is sufficiently suppressed in both the cases of the first reflectance _R1 and the second reflectance _R2 .

FIG. 8 shows an enlarged view of the change in the first reflectance _R1 in the wavelength range of 480 nm to 680 nm, out of the behavior shown in FIG.

The straight line _y1 in FIG. 8 is an approximation straight line of the first reflectance _R1 in the wavelength range of 480 nm to 680 nm.

y ₁ = -0.0046λ + 4.6073 (7)

It is expressed as:

FIG. 9 shows an enlarged view of the change in the second reflectance _R2 in the wavelength range of 450 nm to 650 nm, out of the behavior shown in FIG.

The straight line _y2 in FIG. 9 is an approximation straight line of the second reflectance _R2 in the wavelength range of 450 nm to 650 nm.

y ₂ = 0.008λ - 2.0209 (8)

It is expressed as:

From these results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =3.25%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =3.98%.

(Near-infrared cut filter in Example 3)
FIG. 10 shows the evaluation results of the optical characteristics obtained in the near-infrared cut filter in Example 3.

In Fig. 10, the horizontal axis is wavelength and the vertical axis is reflectance. Fig. 10 also shows the results of the specular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the specular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

The results in Figure 10 show that the near-infrared cut filter in Example 3 has a transmission band in the visible light region (wavelengths of approximately 450 nm to approximately 650 nm) and a reflection band in the near-infrared region.

It can also be seen that in the transmission band, reflection is sufficiently suppressed in both the cases of the first reflectance _R1 and the second reflectance _R2 .

From the obtained results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =1.27%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =4.41%.

(Near-infrared cut filter in Example 4)
11 to 13 show the evaluation results of the optical characteristics obtained in the near infrared cut filter of Example 4. FIG.

In Fig. 11, the horizontal axis is wavelength and the vertical axis is reflectance. Fig. 11 also shows the results of the specular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the specular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

The results in Figure 11 show that the near-infrared cut filter in Example 4 has a transmission band in the visible light region (wavelengths of approximately 450 nm to approximately 650 nm) and a reflection band in the near-infrared region.

It can also be seen that in the transmission band, reflection is sufficiently suppressed in both the cases of the first reflectance _R1 and the second reflectance _R2 .
FIG. 12 shows an enlarged view of the change in the first reflectance _R1 in the wavelength range of 480 nm to 680 nm, out of the behavior shown in FIG.

The straight line _y1 in FIG. 12 is an approximation straight line of the first reflectance _R1 in the wavelength range of 480 nm to 680 nm.

y ₁ = 0.0026λ - 0.8325 (9)

It is expressed as:

FIG. 13 shows an enlarged view of the change in the second reflectance _R2 in the wavelength range of 450 nm to 650 nm, out of the behavior shown in FIG.

The straight line _y2 in FIG. 13 is an approximation straight line of the second reflectance _R2 in the wavelength range of 450 nm to 650 nm,

y ₂ = 0.015λ - 6.6515 (10)

It is expressed as:

From these results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =1.03%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =4.98%.

(Near infrared cut filter in Example 11)
14 to 16 show the evaluation results of the optical characteristics obtained in the near infrared cut filter of Example 11.

In Fig. 14, the horizontal axis is wavelength and the vertical axis is reflectance, and Fig. 14 also shows the results of the regular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the regular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

14, in the case of the near-infrared cut filter in Example 11, a decrease in reflectance is observed in the visible light region at both 5° incidence and 40° incidence. However, it can be seen that the values of the first reflectance _R1 and the second reflectance _R2 are not significantly suppressed in this region.

FIG. 15 shows an enlarged view of the change in the first reflectance _R1 in the wavelength range of 480 nm to 680 nm, out of the behavior shown in FIG.

The straight line _y1 in FIG. 15 is an approximation straight line of the first reflectance _R1 in the wavelength range of 480 nm to 680 nm.

y ₁ = 0.0735λ - 27.775 (11)

It is expressed as:

FIG. 16 shows an enlarged view of the change in the second reflectance _R2 in the wavelength range of 450 nm to 650 nm, out of the behavior shown in FIG.

The straight line _y2 in FIG. 16 is an approximation straight line of the second reflectance _R2 in the wavelength range of 450 nm to 650 nm,

y ₂ = 0.0747λ - 27.467 (12)

It is expressed as:

From these results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =17.56%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =12.93%.

(Near infrared cut filter in Example 12)
17 to 19 show the evaluation results of the optical characteristics obtained in the near-infrared cut filter in Example 12. FIG.

In Fig. 17, the horizontal axis is wavelength and the vertical axis is reflectance, and Fig. 17 also shows the results of the specular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the specular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

17, in the case of the near-infrared cut filter in Example 12, a decrease in reflectance is observed in the visible light region for both the first reflectance R ₁ and the second reflectance R _2. However, it can be seen that the values of the first reflectance R ₁ and the second reflectance R ₂ are not significantly suppressed in this region.

FIG. 18 shows an enlarged view of the change in the first reflectance _R1 in the wavelength range of 480 nm to 680 nm, out of the behavior shown in FIG.

The straight line _y1 in FIG. 18 is an approximation straight line of the first reflectance _R1 in the wavelength range of 480 nm to 680 nm,

y ₁ = 0.0435λ - 20.496 (13)

It is expressed as:

FIG. 19 shows an enlarged view of the change in the second reflectance _R2 in the wavelength range of 450 nm to 650 nm, out of the behavior shown in FIG.

The straight line _y2 in FIG. 19 is an approximation straight line of the second reflectance _R2 in the wavelength range of 450 nm to 650 nm,

y ₂ = 0.044λ - 19.138 (14)

It is expressed as:

From these results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =6.75%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =5.35%.

(Near infrared cut filter in Example 13)
FIG. 20 shows the evaluation results of the optical characteristics obtained in the near-infrared cut filter in Example 13.

In Fig. 20, the horizontal axis is wavelength and the vertical axis is reflectance. Fig. 20 also shows the results of the specular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the specular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

20, in the case of the near-infrared cut filter in Example 13, a decrease in reflectance is observed in the visible light region for both the first reflectance _R1 and the second reflectance _R2 . However, it can be seen that the values of the first reflectance _R1 and the second reflectance _R2 are not significantly suppressed in this region.

From the obtained results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =10.10%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =10.30%.

(Near infrared cut filter in Example 14)
FIG. 21 shows the evaluation results of the optical characteristics obtained in the near-infrared cut filter in Example 14.

In Fig. 21, the horizontal axis is wavelength and the vertical axis is reflectance. Fig. 21 also shows the results of the regular reflectance obtained at an incidence angle of 5°, i.e., the first reflectance _R1 , and the regular reflectance obtained at an incidence angle of 40°, i.e., the second reflectance _R2 .

21, in the case of the near-infrared cut filter in Example 14, a decrease in reflectance is observed in the visible light region for both the first reflectance R ₁ and the second reflectance R _2. However, it can be seen that the values of the first reflectance R ₁ and the second reflectance R ₂ are not significantly suppressed in this region.

From the obtained results, the maximum value ΔR ₁ of the absolute value of the difference between the first reflectance R ₁ and the value of the approximation line y ₁ at the same wavelength was found to be ΔR ₁ =10.30%.

Furthermore, when the maximum absolute value ΔR ₂ of the difference between the second reflectance R ₂ and the value of the approximation line y ₂ at the same wavelength was calculated, it was found to be ΔR ₂ =14.77%.

Table 9 below shows the values of _ΔR1 and _ΔR2 obtained for the near-infrared cut filter in each example.

このように、ΔＲ_１＜５％およびΔＲ_２＜６％を満たす、例１～例４における近赤外線カットフィルタでは、光の入射角度によらず、透過帯における光の反射を有意に抑制できることが確認された。

In this way, it was confirmed that the near-infrared cut filters of Examples 1 to 4, which satisfy ΔR ₁ < 5% and ΔR ₂ < 6%, can significantly suppress light reflection in the transmission band, regardless of the angle of incidence of light.

REFERENCE SIGNS LIST 100 First optical filter 110 Transparent substrate 112 First surface 120 Optical multilayer coating 140 First matching film 160 Second matching film 200 Second optical filter 210 Transparent substrate 212 First surface 220 Optical multilayer coating 240 First matching film 260 Second matching film 300 Third optical filter 310 Transparent substrate 312 First surface 320 Optical multilayer coating 340 First matching film 350 Third matching film 360 Second matching film

Claims (7)

A near-infrared cut filter,
a transparent substrate having a first surface;
an optical multilayer film provided on the first surface side of the transparent substrate;
a first matching film provided on the first surface side of the transparent substrate;
a second matching film disposed on the outermost side of the first surface;
having
The optical multilayer film has an alternate laminate structure of high refractive index layers and low refractive index layers, and has a function of reflecting near infrared rays,
the first and second matching films have a function of suppressing reflection of visible light,
the first matching film is disposed on the optical multi-layer film or between the transparent substrate and the optical multi-layer film;
the first matching film has an alternate laminate structure of a high refractive index layer and a low refractive index layer,
When the optical thickness of ¼ of the wavelength of light is defined as QWOT, the QWOT of the high refractive index layer at a wavelength of 550 nm is defined as _QH , and the QWOT of the low refractive index layer at a wavelength of 550 nm is defined as _QL ,
The first matching film is, from the transparent substrate side,

( _H1QH , _{L1QL , H2QH , L2QL , ... HnQH , LnQL )}

(wherein n is a natural number of 1 or more),
Each coefficient is

1.7≦( _H1 + _H2 +...+ _Hn )/( _L1 + _L2 +...+ _Ln )≦ 2.20

Fulfilling the
Here, the coefficients _H1 ... _Hn and _L1 ... _Ln before _QH and _QL represent how many times the physical thickness of each layer is larger than that of the QWOT.
the second matching film has a two-layer structure of a high refractive index layer and a low refractive index layer,
When the QWOT of the high refractive index layer at a wavelength of 550 nm is _QA and the QWOT of the low refractive index layer at a wavelength of 550 nm is _QB ,
The second matching film is, from the transparent substrate side,

( _XQA , _YQB )

A near-infrared cut filter having a structure represented by the formula: The near-infrared cut filter according to claim 1, wherein the first matching film is composed of six or more layers. a third matching film having an alternating laminate structure of a high refractive index layer and a low refractive index layer on the first surface side;
3. The near-infrared cut filter according to claim 1, wherein the optical multilayer film is disposed between the first matching film and the third matching film. 4. The near infrared cut filter according to claim 3 , wherein the third matching film is configured with the same number of layers as the first matching film. The near-infrared cut filter according to claim 1 , wherein the optical multilayer film has a transmission band in a visible light region. 6. The near infrared cut filter according to claim 5 , wherein the optical multilayer film has a reflection band in the near ultraviolet region. An imaging device comprising the near-infrared cut filter according to claim 1 .

Images