TW202146948A - Near-infrared cutoff filter capable of significantly suppressing reflectance of a visible light region in a wide incident angle range - Google Patents

Abstract

The present invention provides a near-infrared cutoff filter, which can significantly suppress a reflectance of a visible light region in a wide incident angle range. The near-infrared cutoff filter has a transparent substrate, an optical multilayer film, a first matching film, and a second matching film disposed on the outermost side. The first matching film is provided on the optical multilayer film or between the transparent substrate and the optical multilayer film. In the near-infrared cutoff filter, when a regular reflectance of light incident at an incident angle of 5 degrees from the side of the second matching film is defined as a first reflectance R1, a regular reflectance of light incident at an incident angle of 40 degree is defined as a second reflectance R2, an approximate straight line of R1 in a wavelength range from 480nm to 680nm is defined as y1, and an approximate straight line of R2 in a wavelength range from 450nm to 650nm is defined as y2, the maximum value [Delta]R1 of the absolute value of the difference between the values of R1 and y1 is less than 5%, and the maximum value [Delta]R2 of the absolute value of the difference between the values of R2 and y2 is less than 6%.

Description

near infrared cut filter

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

Imaging devices such as digital cameras and digital video cameras include solid-state imaging elements (image sensors) for sensing people, scenery, and the like. However, the solid-state imaging element exhibits a higher sensitivity to infrared light than the human perception. Therefore, in order to make the image obtained by the solid-state imaging element close to the visual sensitivity of human beings, the imaging device is further provided with a near-infrared cut filter.

In general, such a near-infrared cut filter is constituted by disposing a near-infrared-shielding optical multilayer film on a transparent substrate. The optical multilayer film is formed by alternately laminating a thin film containing a dielectric with a high refractive index (eg, TiO ₂ ) and a thin film containing a dielectric with a low refractive index (eg, SiO _{2 ).} [Prior Art Literature] [Patent Literature]

[Patent Document 1] International Publication No. WO2014/104370

[Problems to be Solved by Invention]

It is known that near-infrared cut filters with optical multilayer films often have optical properties that vary depending on the angle of incident light. Therefore, problems such as the following arise: For example, even if the desired optical characteristics can be obtained for light with an incident angle close to the normal direction, the desired optical properties cannot be obtained for light with a large incident angle deviated from the normal direction. characteristics, etc.

Furthermore, when a near-infrared cut filter is applied to a solid-state imaging device, the dependence of the incident angle of the optical characteristics of such a near-infrared cut filter on the sharpness of the image becomes a problem. For example, if part of the visible light incident on the near-infrared cut filter is not transmitted but reflected, the reflected light will cause stray light to be generated.

The present invention has been made in view of the above-mentioned background, and an object of the present invention is to provide a near-infrared cut filter capable of significantly suppressing the reflectance in the visible light region in a wide range of incident angles. [Technical means to solve problems]

The present invention provides a near-infrared cut filter comprising: a transparent substrate having a first surface; an optical multilayer film disposed on the side of the first surface of the transparent substrate; a first matching film disposed on the transparent substrate the side of the above-mentioned first surface; and a second matching film, which is provided on the outermost side of the above-mentioned first surface; and the above-mentioned optical multilayer film has a high-refractive index layer and a low-refractive index layer. The function of reflection, the first and second matching films have the function of suppressing the reflection of visible light, the first matching film is disposed on the optical multilayer film, or between the transparent substrate and the optical multilayer film, and the near infrared rays are cut off. In the filter, when the normal reflectance of light incident from the side of the second matching film at an incident angle of 5° is taken as the first reflectivity R ₁ , the incident angle from the side of the second matching film is 40°. The normal reflectance of incident light is taken as the second reflectance R ₂ , and the approximate straight line _{of the first reflectivity R 1 in} the wavelength range of 480 nm to 680 nm is taken _{as y 1} , and the above-mentioned first reflectivity in the wavelength range of 450 nm to 650 nm When the approximate straight line of the second reflectance R _{2 is set as y 2} , in the wavelength range of 480 nm to 680 nm, the absolute difference between the value _{of the first reflectivity R 1} and the approximate straight line y _{1 at the same wavelength} The maximum value of the value ΔR _{1 is} less than 5%, in the wavelength range of 450 nm to 650 nm, the maximum value of the absolute value of the difference between the _{above-mentioned second reflectance R 2} and the value of the above-mentioned approximate straight line y _{2 at the same wavelength} ΔR _{2 was} less than 6%. [Effect of invention]

The present invention can provide a near-infrared cut filter capable of significantly suppressing the reflectivity of the visible light region in a wide range of incident angles.

Hereinafter, one embodiment of the present invention will be described.

One embodiment of the present invention provides a near-infrared cut filter, comprising: a transparent substrate having a first surface; an optical multilayer film disposed on the side of the first surface of the transparent substrate; a first matching film disposed on the side of the first surface of the transparent substrate; and a second matching film disposed on the outermost side of the first surface; and the optical multilayer film has an alternate lamination structure of high-refractive index layers and low-refractive index layers, and It has the function of reflecting near infrared rays, the first and second matching films have the function of suppressing the reflection of visible light, the first matching film is arranged on the optical multilayer film, or between the transparent substrate and the optical multilayer film, at In the near-infrared cut filter, when the normal reflectance of light incident at an incident angle of 5° from the side of the second matching film is taken as the first reflectance R ₁ , the normal reflectance of light incident from the side of the second matching film is set to be 40 The normal reflectance of incident light at an incident angle of ° is taken as the second reflectance R ₂ , and the approximate straight line _{of the first reflectivity R 1 in} the wavelength range of 480 nm to 680 nm is taken _{as y 1} , and the wavelength of 450 nm to 650 is taken as y 1 . When the approximate straight line of the second reflectance R _{2 in the nm range is set as y 2} , in the wavelength range of 480 nm to 680 nm, the value between _{the first reflectivity R 1} and the approximate straight line y _{1 at the same wavelength} The maximum value of the absolute value of the difference ΔR _{1 is} less than 5%, in the wavelength range of 450 nm to 650 nm, the absolute value of the difference between the _{above-mentioned second reflectance R 2} and the value of the above-mentioned approximate straight line y _{2 at the same wavelength} The maximum value ΔR _{2 is} less than 6%.

A near-infrared cut filter according to an embodiment of the present invention has an optical multilayer film. The optical multilayer film has the function of preventing the transmission of near-infrared rays and reflecting the near-infrared rays.

Moreover, the near-infrared cut filter which concerns on one Embodiment of this invention has a 1st and a 2nd matching film. The first and second matching films have a function of suppressing reflection of visible light.

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

The near-infrared cut filter having such a configuration can significantly suppress the reflectance in the visible light region in a wide range of incident angles, as shown in detail below. Therefore, when the near-infrared cut filter according to one embodiment of the present invention is applied to a solid-state imaging element, a clear image can be obtained.

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

In FIG. 1, the cross section of the near-infrared cut filter (henceforth "1st optical filter") which concerns on one Embodiment of this invention is shown typically.

As shown in FIG. 1 , the first optical filter 100 includes 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 . In addition, the second matching film 160 is provided on the outermost side of the first surface 112 .

The optical multilayer film 120 has the function of preventing the transmission of near infrared rays and reflecting the near infrared rays. In addition, the first matching film 140 and the second matching film 160 have a function of suppressing the reflection of visible light.

Here, the normal reflectance of light incident at an incident angle of 5° with respect to the normal from the side of the second matching film 160 is referred to as the first reflectance R ₁ , and the incident light will be incident at an incident angle of 40° with respect to the normal. The normal reflectance of light is called the second reflectance R ₂ . Also, let the approximate straight line _{of the first reflectance R 1 in} the wavelength range of 480 nm to 680 nm _{be y 1 , and the approximate straight line of the second reflectivity R 2 in} the wavelength range of 450 nm to 650 nm will be y ₂ .

In this case, the first optical filter 100 has the following characteristics: In the wavelength range of 480 nm to 680 nm, the absolute value of the difference between the _{first reflectance R 1} and the value of the approximate straight line y _{1 at the same wavelength is the largest} The value ΔR _{1 is} less than 5%, and in the wavelength range of 450 nm to 650 nm, the maximum value of the absolute value of the difference between the _{second reflectivity R 2} and the value of the approximate straight line y _{2 at the same wavelength ΔR 2 is} less than 6 %.

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

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

(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. 2 .

In FIG. 2, the cross section of the near-infrared cut filter (hereinafter, referred to as a "second optical filter") of another embodiment of the present invention is schematically shown.

As shown in FIG. 2 , the second optical filter 200 includes 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 . In addition, the second matching film 260 is provided on the outermost side of the first surface 212 .

Here, like the first optical filter 100, the second optical filter 200 also has the following characteristics, that is, in the wavelength range of 480 nm to 680 nm, the first reflectance R ₁ and the approximate straight line y _{1 at the same wavelength The maximum value ΔR 1} of the absolute value of the difference between the values is less than 5%, in the wavelength range of 450 nm to 650 nm, the difference between the second reflectance R _{2 at the} same wavelength and the value of the approximate straight line y ₂ The absolute value of the maximum value ΔR _{2 is} less than 6%.

The second optical filter 200 can significantly suppress the reflectivity in the visible light region in a wide range of incident angles. Therefore, when the second optical filter 200 is applied to a solid-state imaging element, a clear image can be obtained.

(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. 3 .

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

As shown in FIG. 3 , the third optical filter 300 includes 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 . In addition, 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 . Furthermore, the second matching film 360 is provided on the outermost side of the first surface 312 .

Here, like the first optical filter 100 and the second optical filter 200, the third optical filter 300 also has the following characteristics, that is, in the wavelength range of 480 nm to 680 nm, the first reflectance at the same wavelength _{The maximum value ΔR 1} of the absolute value of the difference between R ₁ and the value of the approximate straight line y ₁ is less than 5%, and in the wavelength range of 450 nm to 650 nm, the second reflectance R _{2 at the} same wavelength and the approximate straight line y maximum absolute value of the difference between the value of [Delta] R ₂ of less than 6% _2.

The third optical filter 300 can significantly suppress the reflectivity 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 element, a clear image can be obtained.

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

Here, as an example, the constituent members of the third optical filter 300 described above will be described as an example. Therefore, when referring to each member, the reference symbols shown in FIG. 3 are used.

(Transparent substrate 310) The transparent substrate 310 may be formed of any material as long as it is transparent to visible light (high transmittance). For example, the transparent substrate 310 may be formed of glass (white 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, "high refractive index layer" refers to a layer with a refractive index of 2.0 or more at a wavelength of 500 nm, and "low refractive index layer" refers to a layer with a refractive index of 1.6 or less at a wavelength of 500 nm.

Examples of the high refractive index layer include titanium oxide, tantalum oxide, and niobium oxide. As a low-refractive-index layer, silicon oxide, magnesium fluoride, etc. are mentioned, for example. For example, although the refractive index of titanium oxide at a wavelength of 500 nm also depends on the crystalline state, it is generally in the range of 2.3 to 2.8, and the refractive index of silicon oxide is generally in the range of 1.4 to 1.5.

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

Furthermore, half of the number of layers of the multilayer film (in the case of a mantissa, the decimal point is rounded off) is also referred to as "repetition number (n)".

The repetition number n of the optical multilayer film 320 is in the range of 2-50, preferably in the range of 3-13.

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

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

(1st matching film 340) As described above, the first matching film 340 has the function of suppressing the reflection of visible light.

The first matching film 340 may have an alternate lamination structure of "high refractive index layers" and "low refractive index layers". As the "high refractive index layer" and the "low refractive index layer", the above description can be referred to.

When the first matching film 340 has an alternate lamination structure of a high refractive index layer and a low refractive index layer, the QWOT (Quarter-wave Optical Thickness, quarter-wavelength optical thickness) at the wavelength of 550 nm of the high refractive index layer is time) is set to Q _H, the wavelength of the low refractive index layer 550 QWOT nm under the set Q _L, first matching film 340 from the side of the transparent substrate 310 may have a sequence _{(H 1 Q H, L 1} Q L _{, H 2 Q H, L 2} Q L, ......, H n Q H, L n Q L) (1) the structure of formula (here, n is a natural number of 1 or more of). In addition, each coefficient may satisfy the formula (2) of 1.7≦W≦2.5. Here, W=(H ₁ +H ₂ +...+H _n )/(L ₁ +L ₂ +... +L _n ) Formula (3).

(1) wherein Q _H before and the Q _L H ₁ ... H _n and L ₁ ... L _n, etc. coefficients represents the physical thickness of each layer is QWOT of times. That is, _{H n} Q H and _{L n} Q L represents the optical thickness of each of the like.

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

(2nd matching film 360) Like the first matching film 340, the second matching film 360 has the function of suppressing the reflection of visible light.

The second matching film 360 preferably has a two-layer structure having a high refractive index layer and a low refractive index layer (that is, the number of repetitions n=1). In addition, as "high-refractive-index layer" and "low-refractive-index layer", the said description can be referred.

Furthermore, in this case, when the QWOT at the wavelength of 550 nm of the high refractive index layer is set as Q _A , and the QWOT at the wavelength of 550 nm of the low refractive index layer is set as Q _B , the second matching film 360 is formed from the transparent substrate. The side has _{the structure of the formula (XQ A} , YQ _B ) (4), where X>Y is preferable.

(3rd matching film 350) Like the first matching film 340 and the second matching film 360, the third matching film 350 has the function of suppressing the reflection of visible light.

The third matching film 350 may have an alternate lamination structure of "high refractive index layers" and "low refractive index layers". As the "high refractive index layer" and the "low refractive index layer", the above description can be referred to.

In particular, the third matching film 350 may be composed of 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 equations (1) to (3).

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

The configuration of the third matching film 350 is not essential, but the reflection of visible light can be further suppressed by providing the third matching film 350 .

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

The components included in the near-infrared cut filter according to one embodiment of the present invention have been described above, taking the third optical filter 300 as an example. However, it is clearly understood by those skilled in the art that the above description is also applicable to the first optical filter 100 and the second optical filter 200 . [Example]

Next, an embodiment of the present invention will be described. In addition, in the following description, Example 1 - Example 4 are an Example, and Example 11 - Example 14 are a comparative example.

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

Furthermore, in the following evaluation, the reflectance of the near-infrared cut filter represents the value obtained when light is incident from the side of the first surface of the transparent substrate (ie, the side on which various films are provided) at a specific angle with respect to the normal line. Normal reflectance.

The incident angles of the light were set at 5° and 40° with respect to the normal. Hereinafter, these incident directions are referred to as "5° incident" and "40° incident", respectively.

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

For the transparent substrate, glass (D263; manufactured by Schott Corporation) was used. In addition, the same glass was used also in another example.

The optical multilayer film is a repeating structure of a low refractive index layer (SiO ₂ layer) and a high refractive index layer (TiO _{2 layer).} The number of layers is set to 17 layers. Moreover, the first matching layer and the TiO ₂ film to the SiO ₂ layer of the repeating structure, the number of layers to 6 layers. Furthermore, the second matching film has a two-layer structure of a _{TiO 2} layer and a SiO _{2 layer.}

In Table 1 below, the layer constitutions of the optical multilayer film, the first matching film, and the second matching film used in Example 1 are collectively shown.

[Table 1] Layer NO. Membrane material Physical film thickness (mm) QWOT Optical multilayer film 1 SiO ₂ 74.34 0.800 2 TiO ₂ 90.84 1.600 3 SiO ₂ 148.69 1.600 4 TiO ₂ 90.84 1.600 5 SiO ₂ 148.69 1.600 6 TiO ₂ 90.84 1.600 7 SiO ₂ 148.69 1.600 8 TiO ₂ 90.84 1.600 9 SiO ₂ 148.69 1.600 10 TiO ₂ 90.84 1.600 11 SiO ₂ 148.69 1.600 12 TiO ₂ 90.84 1.600 13 SiO ₂ 148.69 1.600 14 TiO ₂ 90.84 1.600 15 SiO ₂ 148.69 1.600 16 TiO ₂ 90.84 1.600 17 SiO ₂ 148.69 1.600 1st matching film 1 TiO ₂ 15.00 0.264 2 SiO ₂ 15.00 0.161 3 TiO ₂ 54.17 0.954 4 SiO ₂ 22.62 0.243 5 TiO ₂ 29.04 0.511 6 SiO ₂ 35.51 0.382 2nd matching film 1 TiO ₂ 107.75 1.898 2 SiO ₂ 82.43 0.887 In the first matching film, the value of W represented by the above 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, _{QWOT(Q A} ) at a wavelength of 550 nm of the _{TiO 2} layer was 1.898, _{and QWOT(Q B} ) of the _{SiO 2} layer at a wavelength of 550 nm was 0.887. Furthermore, when the second matching film is represented by the above-mentioned formula (4), X/Y=2.14.

In addition, in Table 1, since each layer is described in the order of approaching a transparent substrate, each layer is arrange|positioned from the upper side to the lower side of Table 1 on the transparent substrate. This description is also the same in the following Tables 2 to 8.

(Example 2) The near-infrared cut filter of Example 2 has the configuration shown in FIG. 1 .

For transparent substrates, glass is used.

The optical multilayer film is a repeating structure of _{TiO 2} layer and SiO _{2 .} The number of layers is set to 18 layers. Moreover, the first matching layer and the TiO ₂ film is set to repeat the SiO ₂ structure, the number of layers to 6 layers. Furthermore, the second matching film has a two-layer structure of a _{TiO 2} layer and a SiO _{2 layer.}

In Table 2 below, the layer constitutions of the optical multilayer film, the first matching film, and the second matching film used in Example 2 are collectively shown.

[Table 2] Layer NO. Membrane material Physical film thickness (mm) QWOT Optical multilayer film 1 TiO ₂ 96.52 1.700 2 SiO ₂ 157.98 1.700 3 TiO ₂ 85.17 1.500 4 SiO ₂ 148.69 1.600 5 TiO ₂ 85.17 1.500 6 SiO ₂ 148.69 1.600 7 TiO ₂ 85.17 1.500 8 SiO ₂ 148.69 1.600 9 TiO ₂ 85.17 1.500 10 SiO ₂ 148.69 1.600 11 TiO ₂ 85.17 1.500 12 SiO ₂ 148.69 1.600 13 TiO ₂ 85.17 1.500 14 SiO ₂ 148.69 1.600 15 TiO ₂ 85.17 1.500 16 SiO ₂ 148.69 1.600 17 TiO ₂ 90.84 1.600 18 SiO ₂ 176.57 1.900 1st matching film 1 TiO ₂ 22.71 0.400 2 SiO ₂ 18.59 0.200 3 TiO ₂ 17.03 0.300 4 SiO ₂ 18.59 0.200 5 TiO ₂ 28.39 0.500 6 SiO ₂ 27.88 0.300 2nd matching film 1 TiO ₂ 113.55 2.000 2 SiO ₂ 83.64 0.900 In the first matching film, the value of W represented by the above 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, _{QWOT(Q A} ) at a wavelength of 550 nm of the _{TiO 2} layer was 2.000, _{and QWOT(Q B} ) of the _{SiO 2} layer at a wavelength of 550 nm was 0.900. In addition, when the second matching film is represented by the above-mentioned formula (4), X/Y=2.22.

(Example 3) The near-infrared cut filter of Example 3 has the configuration shown in FIG. 2 .

For transparent substrates, glass is used.

The first matching film was a _{repeating structure of a TiO 2} layer and SiO ₂ , and the number of layers was six. In addition, the optical multilayer film has a repeating structure of the _{SiO 2} layer and the TiO _{2 layer.} The number of layers is set to 17 layers. Furthermore, the second matching film has a two-layer structure of a _{TiO 2} layer and a SiO _{2 layer.}

In Table 3 below, the layer constitutions of the first matching film, the optical multilayer film, and the second matching film used in Example 3 are collectively shown.

[table 3] Layer NO. Membrane material Physical film thickness (mm) QWOT 1st matching film 1 TiO ₂ 15.00 0.264 2 SiO ₂ 24.98 0.269 3 TiO ₂ 41.36 0.728 4 SiO ₂ 15.00 0.161 5 TiO ₂ 23.88 0.421 6 SiO ₂ 22.91 0.247 Optical multilayer film 1 SiO ₂ 148.69 1.600 2 TiO ₂ 90.84 1.600 3 SiO ₂ 148.69 1.600 4 TiO ₂ 90.84 1.600 5 SiO ₂ 148.69 1.600 6 TiO ₂ 90.84 1.600 7 SiO ₂ 148.69 1.600 8 TiO ₂ 90.84 1.600 9 SiO ₂ 148.69 1.600 10 TiO ₂ 90.84 1.600 11 SiO ₂ 148.69 1.600 12 TiO ₂ 90.84 1.600 13 SiO ₂ 148.69 1.600 14 TiO ₂ 90.84 1.600 15 SiO ₂ 148.69 1.600 16 TiO ₂ 90.84 1.600 17 SiO ₂ 148.69 1.600 2nd matching film 1 TiO ₂ 90.11 1.587 2 SiO ₂ 82.17 0.884 In the first matching film, the value of W represented by the above formula (3), that is, the value of (H ₁ +H ₂ +H ₃ )/(L ₁ +L ₂ +L ₃ ) was 2.09.

In addition, in the second matching film, _{QWOT(Q A} ) at a wavelength of 550 nm of the _{TiO 2} layer was 1.587, _{and QWOT(Q B} ) of the _{SiO 2} layer at a wavelength of 550 nm was 0.884. Furthermore, when the second matching film is represented by the above-mentioned formula (4), X/Y=1.80.

(Example 4) The near-infrared cut filter of Example 4 has the configuration shown in FIG. 3 .

For transparent substrates, glass is used.

The first matching film was a _{repeating structure of a SiO 2} layer and a TiO ₂ layer, and the number of layers was six. In addition, the optical multilayer film has a repeating structure of the _{SiO 2} layer and the TiO _{2 layer.} The number of layers is set to 17 layers. In addition, the third matching film was a _{repeating structure of the TiO 2} layer and the SiO ₂ layer, and the number of layers was six. Furthermore, the second matching film has a two-layer structure of a _{TiO 2} layer and a SiO _{2 layer.}

In Table 4 below, the layer structures of the first matching film, the optical multilayer film, the third matching film, and the second matching film used in Example 4 are collectively shown.

[Table 4] Layer NO. Membrane material Physical film thickness (mm) QWOT 1st matching film 1 SiO ₂ 15.00 0.161 2 TiO ₂ 23.14 0.408 3 SiO ₂ 30.41 0.327 4 TiO ₂ 15.00 0.264 5 SiO ₂ 24.15 0.260 6 TiO ₂ 20.69 0.364 Optical multilayer film 1 SiO ₂ 148.69 1.600 2 TiO ₂ 90.84 1.600 3 SiO ₂ 148.69 1.600 4 TiO ₂ 90.84 1.600 5 SiO ₂ 148.69 1.600 6 TiO ₂ 90.84 1.600 7 SiO ₂ 148.69 1.600 8 TiO ₂ 90.84 1.600 9 SiO ₂ 148.69 1.600 10 TiO ₂ 90.84 1.600 11 SiO ₂ 148.69 1.600 12 TiO ₂ 90.84 1.600 13 SiO ₂ 148.69 1.600 14 TiO ₂ 90.84 1.600 15 SiO ₂ 148.69 1.600 16 TiO ₂ 90.84 1.600 17 SiO ₂ 148.69 1.600 3rd matching film 1 TiO ₂ 15.00 0.264 2 SiO ₂ 15.00 0.161 3 TiO ₂ 55.86 0.984 4 SiO ₂ 24.52 0.264 5 TiO ₂ 28.84 0.508 6 SiO ₂ 36.45 0.392 2nd matching film 1 TiO ₂ 112.59 1.983 2 SiO ₂ 85.59 0.921 In the first matching film, the value of W represented 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 addition, in the second matching film, _{QWOT(Q A} ) at a wavelength of 550 nm of the _{TiO 2} layer was 1.983, _{and QWOT(Q B} ) of the _{SiO 2} layer at a wavelength of 550 nm was 0.921. In addition, when the second matching film is represented by the above-mentioned formula (4), X/Y=2.15.

(Example 11) The near-infrared cut filter of Example 11 has a configuration in which only the optical multilayer film is provided on the transparent substrate. The optical multilayer film was a _{repeating structure of a TiO 2} layer and a SiO ₂ layer, and the number of layers was 20 layers.

In Table 5 below, the layer constitution of the optical multilayer film used in Example 11 is shown.

[table 5] Layer NO. Membrane material Physical film thickness (mm) Optical multilayer film 1 TiO ₂ 90.84 2 SiO ₂ 148.69 3 TiO ₂ 90.84 4 SiO ₂ 148.69 5 TiO ₂ 90.84 6 SiO ₂ 148.69 7 TiO ₂ 90.84 8 SiO ₂ 148.69 9 TiO ₂ 90.84 10 SiO ₂ 148.69 11 TiO ₂ 90.84 12 SiO ₂ 148.69 13 TiO ₂ 90.84 14 SiO ₂ 148.69 15 TiO ₂ 90.84 16 SiO ₂ 148.69 17 TiO ₂ 90.84 18 SiO ₂ 148.69 19 TiO ₂ 90.84 20 SiO ₂ 148.69 (Example 12) The near-infrared cut filter of Example 12 has a configuration in which only the optical multilayer film is provided on the transparent substrate. The optical multilayer film was a _{repeating structure of a SiO 2} layer and a TiO ₂ layer, and the number of layers was 21 layers.

In Table 6 below, the layer constitution of the optical multilayer film used in Example 12 is shown.

[Table 6] Layer NO. Membrane material Physical film thickness (mm) Optical multilayer film 1 SiO ₂ 74.34 2 TiO ₂ 90.84 3 SiO ₂ 148.69 4 TiO ₂ 90.84 5 SiO ₂ 148.69 6 TiO ₂ 90.84 7 SiO ₂ 148.69 8 TiO ₂ 90.84 9 SiO ₂ 148.69 10 TiO ₂ 90.84 11 SiO ₂ 148.69 12 TiO ₂ 90.84 13 SiO ₂ 148.69 14 TiO ₂ 90.84 15 SiO ₂ 148.69 16 TiO ₂ 90.84 17 SiO ₂ 148.69 18 TiO ₂ 90.84 19 SiO ₂ 148.69 20 TiO ₂ 90.84 twenty one SiO ₂ 74.34 (Example 13) The near-infrared cut filter of Example 13 has a configuration in which the optical multilayer film and the first matching film are sequentially arranged on the transparent substrate.

The optical multilayer film was a _{repeating structure of a SiO 2} layer and a TiO ₂ layer, and the number of layers was 17 layers. Moreover, the first matching layer and the TiO ₂ film to the SiO ₂ layer of the repeating structure, the number of layers to 6 layers.

In Table 7 below, the layer constitutions of the optical multilayer film and the first matching film used in Example 13 are collectively shown.

[Table 7] Layer NO. Membrane material Physical film thickness (mm) QWOT Optical multilayer film 1 SiO ₂ 74.34 0.800 2 TiO ₂ 90.84 1.600 3 SiO ₂ 148.69 1.600 4 TiO ₂ 90.84 1.600 5 SiO ₂ 148.69 1.600 6 TiO ₂ 90.84 1.600 7 SiO ₂ 148.69 1.600 8 TiO ₂ 90.84 1.600 9 SiO ₂ 148.69 1.600 10 TiO ₂ 90.84 1.600 11 SiO ₂ 148.69 1.600 12 TiO ₂ 90.84 1.600 13 SiO ₂ 148.69 1.600 14 TiO ₂ 90.84 1.600 15 SiO ₂ 148.69 1.600 16 TiO ₂ 90.84 1.600 17 SiO ₂ 148.69 1.600 1st matching film 1 TiO ₂ 15.00 0.260 2 SiO ₂ 15.00 0.160 3 TiO ₂ 37.73 0.660 4 SiO ₂ 20.00 0.220 5 TiO ₂ 15.99 0.280 6 SiO ₂ 20.00 0.220 (Example 14) The near-infrared cut filter of Example 14 has the configuration shown in FIG. 1 .

For transparent substrates, glass is used.

The optical multilayer film has a repeating structure of the _{SiO 2} layer and the TiO _{2 layer.} The number of layers is set to 17 layers. Moreover, the first matching layer and the TiO ₂ film to the SiO ₂ layer of the repeating structure, the number of layers to 6 layers. Furthermore, the second matching film has a two-layer structure of a _{TiO 2} layer and a SiO _{2 layer.}

In Table 8 below, the layer constitutions of the optical multilayer film, the first matching film, and the second matching film used in Example 14 are collectively shown.

[Table 8] Layer NO. Membrane material Physical film thickness (mm) QWOT Optical multilayer film 1 SiO ₂ 74.34 0.800 2 TiO ₂ 90.84 1.600 3 SiO ₂ 148.69 1.600 4 TiO ₂ 90.84 1.600 5 SiO ₂ 148.69 1.600 6 TiO ₂ 90.84 1.600 7 SiO ₂ 148.69 1.600 8 TiO ₂ 90.84 1.600 9 SiO ₂ 148.69 1.600 10 TiO ₂ 90.84 1.600 11 SiO ₂ 148.69 1.600 12 TiO ₂ 90.84 1.600 13 SiO ₂ 148.69 1.600 14 TiO ₂ 90.84 1.600 15 SiO ₂ 148.69 1.600 16 TiO ₂ 90.84 1.600 17 SiO ₂ 148.69 1.600 1st matching film 1 TiO ₂ 15 0.260 2 SiO ₂ 15 0.160 3 TiO ₂ 39.74 0.700 4 SiO ₂ 22.68 0.240 5 TiO ₂ 28.98 0.510 6 SiO ₂ 35.59 0.380 2nd matching film 1 TiO ₂ 107.72 1.900 2 SiO ₂ 82.41 0.890 (Evaluation Results of Optical Characteristics) (Near-Infrared Cut Filter of Example 1) The evaluation results of optical characteristics obtained by the near-infrared cut filter of Example 1 are shown in FIGS. 4 to 6 .

In FIG. 4 , the horizontal axis is the wavelength, and the vertical axis is the reflectance. In FIG. 4 , the results of the normal reflectance obtained at 5° incidence, that is, the first reflectivity R ₁ , and the normal reflectivity obtained at 40° incidence, ie, the second reflectivity R ₂ , are shown together.

According to the results in FIG. 4 , the near-infrared cut-off filter of Example 1 has a transmission section in the visible light region (wavelength of about 450 nm to about 650 nm), and a reflection section in the near-infrared region.

Furthermore, the wavelength range of the reflection section under 5° incidence is in the range of about 750 nm to about 1000 nm, whereas the wavelength range of the reflection section under 40° incidence is in the range of about 700 nm to about 900 nm. That is, the wavelength range of the reflection section under 40° incidence is shifted toward the lower wavelength side than the wavelength range of the reflection section under 5° incidence.

However, it was found on the first reflectance and the second reflectance R ₁ R ₂ according to any of a case, and can sufficiently suppress the reflection in the transmission segment.

_{In FIG. 5 , the change of the first reflectance R 1} in the wavelength range of 480 nm to 680 nm in the behavior shown in FIG. 4 is enlarged and shown.

Furthermore, the straight line y _{1 in FIG. 5 is an approximate straight line of the first reflectance R 1 in} the wavelength range of 480 nm to 680 nm, and is represented by the _{formula y 1} =0.0353λ−16.087 (5). Here, λ is a wavelength (the same applies hereinafter).

Further, in FIG. 6, the second reflectance at a wavelength of behavior shown in FIG. 4 in the range of 450 nm ~ 650 nm of the enlarged R ₂ represents a variation.

The straight line y _{2 in FIG. 6 is an approximate straight line of the second reflectance R 2 in} the wavelength range of 450 nm to 650 nm, and is represented by the following formula: y ₂ =0.0532λ−24.315 (6).

_{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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =2.35%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =5.38%.

(Example 2 near infrared cut filter) In FIGS. 7 to 9 , the evaluation results of the optical properties obtained by the near-infrared cut filter of Example 2 are shown.

In FIG. 7 , the horizontal axis represents the wavelength, and the vertical axis represents the reflectance. In FIG. 7 , the results of the normal reflectance obtained at 5° incidence, that is, the first reflectivity R ₁ , and the normal reflectivity obtained at 40° incidence, ie, the second reflectivity R ₂ , are shown together.

According to the results in FIG. 7 , the near-infrared cut filter of Example 2 has a transmission section in the visible light region (wavelength of about 450 nm to about 650 nm), and a reflection section in the near-infrared region.

And, seen in section through, for the first reflectance and the second reflectance R ₁ of any of R ₂ a case, the reflection can be sufficiently suppressed.

_{In FIG. 8 , the change in the first reflectance R 1} in the wavelength range of 480 nm to 680 nm in the behavior shown in FIG. 7 is enlarged and shown.

The straight line y _{1 in FIG. 8 is an approximate straight line of the first reflectance R 1 in} the wavelength range of 480 nm to 680 nm, and is represented by the following formula: y ₁ =−0.0046λ+4.6073 (7).

And, FIG. 9, the second reflectance at a wavelength of behavior illustrated in Figure 7 the range of 450 nm ~ 650 nm of the enlarged R ₂ represents a variation.

The straight line y _{2 in FIG. 9 is an approximate straight line of the second reflectance R 2 in} the wavelength range of 450 nm to 650 nm, and is represented by the following formula: y ₂ =0.008λ−2.0209 (8).

_{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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =3.25%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =3.98%.

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

In FIG. 10 , the horizontal axis represents the wavelength, and the vertical axis represents the reflectance. In FIG. 10 , the normal reflectance obtained at 5° incidence, that is, the first reflectance R ₁ , and the normal reflectivity obtained at 40° incidence, ie, the second reflectivity R ₂ , are shown together.

According to the results in FIG. 10 , the near-infrared cut-off filter of Example 3 has a transmission section in the visible light region (wavelength of about 450 nm to about 650 nm), and a reflection section in the near-infrared region.

And, seen in section through, for the first reflectance and the second reflectance R ₁ of any of R ₂ a case, the reflection can be sufficiently suppressed.

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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =1.27%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =4.41%.

(Example 4 near-infrared cut-off filter) The evaluation results of the optical characteristics obtained by the near-infrared cut filter of Example 4 are shown in FIGS. 11 to 13 .

In FIG. 11 , the horizontal axis represents the wavelength, and the vertical axis represents the reflectance. FIG. 11 shows the results of the normal reflectance obtained at 5° incidence, namely the first reflectivity R ₁ , and the normal reflectivity obtained at 40° incidence, namely the second reflectivity R ₂ .

According to the results in FIG. 11 , the near-infrared cut-off filter of Example 4 has a transmission section in the visible light region (wavelength of about 450 nm to about 650 nm), and a reflection section in the near-infrared region.

In addition, it can be seen that in the transmission section, reflection can be sufficiently suppressed in either case of the _{first reflectance R 1} and the second reflectivity R _{2 . In FIG. 12 , the change of the first reflectance R 1} in the wavelength range of 480 nm to 680 nm in the behavior shown in FIG. 11 is enlarged and shown.

The straight line y _{1 in FIG. 12 is an approximate straight line of the first reflectance R 1 in} the wavelength range of 480 nm to 680 nm, and is represented by the following formula: y ₁ =0.0026λ−0.8325 (9).

Further, in FIG. 13, the second reflectance at a wavelength of behavior shown in FIG. 11 of 450 nm ~ 650 nm range of the enlarged R ₂ represents a variation.

The straight line y _{2 in FIG. 13 is an approximate straight line of the second reflectance R 2 in} the wavelength range of 450 nm to 650 nm, and is represented by the following formula: y ₂ =0.015λ−6.6515 (10).

_{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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =1.03%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =4.98%.

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

In FIG. 14 , the horizontal axis represents the wavelength, and the vertical axis represents the reflectance. In FIG. 14 , the results of the normal reflectance obtained at 5° incidence, namely, the first reflectance R ₁ , and the normal reflectivity obtained at 40° incidence, namely, the second reflectivity R ₂ are shown together.

According to the results in FIG. 14 , in the case of the near-infrared cut filter of Example 11, the reflectance in the visible light region is reduced for any one of 5° incidence and 40° incidence. However, it was found in the region, the first reflectance and the second reflectance R & lt _an R ₂ value of not too suppressed.

_{In FIG. 15 , the change in the first reflectance R 1} in the wavelength range of 480 nm to 680 nm in the behavior shown in FIG. 14 is enlarged and shown.

The straight line y _{1 in FIG. 15 is an approximate straight line of the first reflectance R 1 in} the wavelength range of 480 nm to 680 nm, and is represented by the following formula: y ₁ =0.0735λ−27.775 (11).

And, FIG. 16, the second reflectance at a wavelength of behavior shown in FIG. 14 in the range of 450 nm ~ 650 nm of the enlarged R ₂ represents a variation.

The straight line y _{2 in FIG. 16 is an approximate straight line of the second reflectance R 2 in} the wavelength range of 450 nm to 650 nm, and is represented by the following formula: y ₂ =0.0747λ−27.467 (12).

_{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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =17.56%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =12.93%.

(Example 12 of near-infrared cut-off filter) The evaluation results of the optical characteristics obtained by the near-infrared cut filter of Example 12 are shown in FIGS. 17 to 19 .

In FIG. 17 , the horizontal axis represents the wavelength, and the vertical axis represents the reflectance. In FIG. 17 , the results of the normal reflectance obtained at 5° incidence, namely, the first reflectivity R ₁ , and the normal reflectivity obtained at 40° incidence, namely, the second reflectivity R ₂ are shown together.

The obtained results of FIG. 17, when in the near-infrared cutoff case of Example 12 the filter for the first reflectance and the second reflectance R ₁ R ₂ according to any one of, both in the area of reduced reflectivity of visible light. However, it was found in the region, the first reflectance and the second reflectance R & lt _an R ₂ value of not too suppressed.

_{In FIG. 18 , the change in the first reflectance R 1} in the wavelength range of 480 nm to 680 nm in the behavior shown in FIG. 17 is enlarged and shown.

The straight line y _{1 in FIG. 18 is an approximate straight line of the first reflectance R 1 in} the wavelength range of 480 nm to 680 nm, and is represented by the _{formula y 1} =0.0435λ−20.496 (13).

And, FIG. 19, the second reflectance at a wavelength of behavior shown in FIG. 17 of 450 nm ~ 650 nm range of the enlarged R ₂ represents a variation.

The straight line y _{2 in FIG. 19 is an approximate straight line of the second reflectance R 2 in} the wavelength range of 450 nm to 650 nm, and is represented by the following formula: y ₂ =0.044λ−19.138 (14).

_{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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =6.75%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =5.35%.

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

In FIG. 20 , the horizontal axis represents the wavelength, and the vertical axis represents the reflectance. In FIG. 20, the normal reflectance obtained at 5° incidence, that is, the first reflectance R ₁ , and the normal reflectivity obtained at 40° incidence, that is, the second reflectivity R ₂ are shown together.

The obtained results of FIG. 20, when in the near-infrared cutoff case of Example 13 the filter for the first reflectance and the second reflectance R ₁ R ₂ according to any one of, both in the area of reduced reflectivity of visible light. However, it was found in the region, the first reflectance and the second reflectance R & lt _an R ₂ value of not too suppressed.

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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =10.10%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =10.30%.

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

In FIG. 21, the horizontal axis is the wavelength, and the vertical axis is the reflectance. In FIG. 21 , the results of the first reflectance R _{1 , which is the normal reflectance obtained at 5° incidence, and the second reflectivity R 2} , which is the normal reflectivity obtained at 40° incidence, are shown together.

The obtained results of FIG. 21, when in the near-infrared cutoff case of Example 14 the filter for the first reflectance and the second reflectance R ₁ R ₂ according to any one of, both in the area of reduced reflectivity of visible light. However, it was found in the region, the first reflectance and the second reflectance R & lt _an R ₂ value of not too suppressed.

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 approximate straight line y _{1 at} the same wavelength was obtained, and ΔR ₁ =10.30%.

_{Furthermore, the maximum value ΔR 2} of the absolute value of the difference between the _{second reflectance R 2} and the value of the approximate straight line y _{2 at} the same wavelength was obtained, and ΔR ₂ =14.77%.

_{In Table 9 below, the values of ΔR 1} and ΔR ₂ obtained by the near-infrared cut filter of each example are collectively shown.

[Table 9] example ΔR ₁ (%) ∆R ₂ (%) 1 2.35 5.38 2 3.25 3.98 3 1.27 4.41 4 1.03 4.98 11 17.56 12.93 12 6.75 5.35 13 10.10 10.30 14 10.30 14.77 In this way, it was confirmed that _{the near-infrared cut filters of Examples 1 to 4 satisfying ΔR 1} <5% and ΔR ₂ <6% can significantly suppress reflection of light in the transmitted section regardless of the incident angle of the light.

100: 1st optical filter 110: Transparent substrate 112: Surface 1 120: Optical multilayer film 140: 1st matching film 160: 2nd matching film 200: 2nd Optical Filter 210: Transparent substrate 212: Surface 1 220: Optical Multilayer Film 240: 1st matching film 260: 2nd matching film 300: 3rd Optical Filter 310: Transparent substrate 312: Surface 1 320: Optical Multilayer Film 340: 1st matching film 350: 3rd Matching Film 360: 2nd Matching Film

FIG. 1 is a diagram schematically showing a cross section of a near-infrared cut filter according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a cross section of a near-infrared cut filter according to another embodiment of the present invention. 3 is a diagram schematically showing a cross section of a near-infrared cut filter according to another embodiment of the present invention. 4 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 1. FIG. FIG. 5 is a graph showing a part of the optical characteristics under 5° incidence of FIG. 4 in an enlarged manner. FIG. 6 is a graph showing a part of the optical characteristics under 40° incidence of FIG. 4 in an enlarged manner. 7 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 2. FIG. FIG. 8 is a graph showing a part of the optical characteristics under 5° incidence of FIG. 7 in an enlarged manner. FIG. 9 is a graph showing a part of the optical characteristics under 40° incidence of FIG. 7 in an enlarged manner. 10 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 3. FIG. 11 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 4. FIG. FIG. 12 is a graph showing a part of the optical characteristics under 5° incidence of FIG. 11 in an enlarged manner. FIG. 13 is a graph showing a part of the optical characteristics under 40° incidence of FIG. 11 in an enlarged manner. 14 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 11. FIG. 15 is a graph showing a part of the optical characteristics under 5° incidence of FIG. 14 in an enlarged manner. FIG. 16 is a graph showing a part of the optical characteristics under 40° incidence of FIG. 14 in an enlarged manner. 17 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 11. FIG. FIG. 18 is a graph showing a part of the optical characteristics under 5° incidence of FIG. 17 in an enlarged manner. Fig. 19 is a graph showing a part of the optical characteristics under 40° incidence of Fig. 17 in an enlarged manner. 20 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 13. FIG. 21 is a graph showing optical characteristics at each of 5° incidence and 40° incidence obtained by the near-infrared cut filter of Example 14. FIG.

100: 1st optical filter

110: Transparent substrate

112: Surface 1

120: Optical multilayer film

140: 1st matching film

160: 2nd matching film

Claims (8)

A near-infrared cut filter comprising: a transparent substrate having a first surface; an optical multilayer film disposed on the side of the first surface of the transparent substrate; a first matching film disposed on the first surface of the transparent substrate 1 side of the surface; and a second matching film disposed on the outermost side of the first surface; and the above-mentioned optical multilayer film has an alternate lamination 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 the function of suppressing the reflection of visible light, the first matching film is arranged on the optical multilayer film, or between the transparent substrate and the optical multilayer film, in the near-infrared cut filter , when the normal reflectivity of the light incident from the side of the second matching film at an incident angle of 5° is taken as the first reflectivity R ₁ , and the light incident from the side of the second matching film at an incident angle of 40° The normal reflectance is taken as the second reflectance R ₂ , and the approximate straight line _{of the first reflectivity R 1 in} the wavelength range of 480 nm to 680 nm is _{denoted as y 1} , and the second reflectance in the wavelength range of 450 nm to 650 nm is set as y 1 . When the approximate straight line of the rate R _{2 is set as y 2} , in the wavelength range of 480 nm to 680 nm, the maximum absolute value of the difference between the value _{of the above-mentioned first reflectance R 1} and the value of the above-mentioned approximate straight line y _{1 at the same wavelength} The value ΔR _{1 is} less than 5%, and in the wavelength range of 450 nm to 650 nm, _{the maximum value ΔR 2} of the absolute value of the difference between the _{above-mentioned second reflectance R 2} and the value of the above-mentioned approximate straight line y _{2 at} the same wavelength is not up to 6%. The requested item of a near-infrared cut filter, wherein the first matching film having a laminated structure of alternating high refractive index layer and the low refractive index layer, the wavelength of the high refractive index layers 550 QWOT nm under the set Q _H, when the wavelength of the low refractive index layers 550 QWOT nm under the set Q _L, the first matching film from the side of the transparent substrate having _{(H 1 Q H, L 1} Q L, H 2 Q H, L 2 Q _{L, ...... H n Q H,} L n Q L) of the structure (here, n is a natural number of 1 or more of), each coefficient satisfies _{1.7 ≦ (H 1 + H 2} + ... + H n) /(L ₁ +L ₂ +...+L _n )≦2.5. The near-infrared cut filter according to claim 1 or 2, wherein the first matching film is composed of six or more layers. The near-infrared cut filter according to any one of claims 1 to 3, wherein the second matching film has a two-layer structure of a high refractive index layer and a low refractive index layer, and the high refractive index layer has a wavelength of 550 nm. when QWOT set Q _A, the wavelength of the low refractive index layer is 550 nm QWOT under the set Q _B, the first matching film 2 from the side of the transparent substrate having a (XQ _A, YQ _B) of the structure, where, X>Y. The near-infrared cut filter according to any one of claims 1 to 4, wherein a third matching film is provided on the side of the first surface, and the third matching film has an alternate lamination structure of high-refractive-index layers and low-refractive-index layers , The said optical multilayer film is arrange|positioned between the said 1st matching film and the said 3rd matching film. The near-infrared cut filter according to claim 5, wherein the third matching film has the same number of layers as the first matching film. The near-infrared cut filter according to any one of claims 1 to 6, wherein the optical multilayer film has a transmission section in the visible light region. The near-infrared cut-off filter of claim 7, wherein the optical multilayer film has a reflection section in the near-ultraviolet region.

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