JP2016070965A - Near-infrared cut filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near-infrared cut filter that has incident angle dependency attenuated in a region where transmittance is equal to or less than 20%.SOLUTION: A near-infrared cut filter has: a substrate that is made up of phosphate glass containing copper or phosphate glass containing the copper; and an optical multilayer membrane that is laminated on the substrate. The optical multilayer membrane has an infrared anti-reflection membrane in which a high refractive index membrane and a low refractive index membrane are repeatedly laminated. An optical characteristic composed of both the substrate and the optical multilayer membrane is such that an average wavelength shift ((Σ(λ-λ))/16) obtained by dividing a total (Σ(λ-λ)) by a 1% increment from 5% to 20% of transmittance for a wavelength shift (λ-λ) composed of a difference between a wavelength (λ) at a 30° incidence in a region on a long wavelength side with respect to a transmittance band in spectral transmittance and a wavelength (λ) at a vertical incidence therein with the number of times of totals exceeds -19nm.SELECTED DRAWING: Figure 1

Description

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

  In an imaging device such as a digital still camera, a subject is imaged using a solid-state imaging device such as a CCD (Charge Coupled Device) or a CMOS image sensor (Complementary Metal Oxide Semiconductor Image Sensor). These solid-state image sensors have spectral sensitivity in the near-infrared wavelength region near 1100 nm from the visible wavelength region, and since it is not possible to obtain good color reproducibility by itself, light in the near-infrared wavelength region can be obtained. The normal visual sensitivity of the person is corrected using a shielding filter. That is, a filter that blocks light in the near-infrared wavelength region is provided in the optical path from the imaging lens to the solid-state imaging device. A filter used for such applications is required to have a high light transmittance in the visible wavelength range, and a dielectric multilayer film in which a plurality of high refractive index layers and low refractive index layers are alternately stacked is used (for example, , See Patent Document 1).

  However, a filter having a dielectric multilayer film has an incident angle dependency of light, and when applied to an imaging device, the cutoff wavelength moves depending on the incident angle of light incident on the filter through an imaging lens. The color may change between the center and the periphery of the photographed image.

  As a method of reducing the incident angle dependency, for example, a first dielectric multilayer film and a second dielectric multilayer film are used, and the width of the reflection band of the first dielectric multilayer film is set to the second dielectric multilayer film. A method is known in which the width of the reflection band of the film is made narrower and the average refractive index of the entire first dielectric multilayer film is made higher than the average refractive index of the entire second dielectric multilayer film. According to such a method, the incidence angle dependency is reduced by the first dielectric multilayer film having a high average refractive index, and a wide reflection band can be secured together with the second dielectric multilayer film (for example, Patent Documents). 2).

  Also, as a dichroic mirror, a method of combining a first selective transmission multilayer film composed of a high refractive index layer and a medium refractive index layer and a second selective transmission multilayer film composed of a high refractive index layer and a low refractive index layer It has been known. According to such a method, the incident angle dependency can be reduced by the first selective transmission multilayer film including the high refractive index layer and the medium refractive index layer (see, for example, Patent Document 3).

JP 2008-70825 A JP 2007-183525 A Japanese Patent Laid-Open No. 11-202127

  Conventionally, various methods have been studied in order to reduce the incident angle dependency. However, in order to obtain better color reproducibility, it is required to reduce the incident angle dependency in a region where the transmittance is low. For example, in the conventional method, the incident angle dependency when the transmittance is around 50% is reduced, and in the region where the transmittance is lower than this, particularly in the region where the transmittance is 20% or less, the incident angle dependency. Is not reduced sufficiently. In order to obtain better color reproducibility than before, it is required to reduce the incident angle dependency even in such a region where the transmittance is 20% or less.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a near-infrared cut filter with reduced incidence angle dependency in a region where the transmittance is 20% or less.

The first near-infrared cut filter has a substrate made of copper-containing fluorophosphate glass or copper-containing phosphate glass, and an optical multilayer film laminated on the substrate. The optical multilayer film has an infrared reflective film in which a high refractive index film and a low refractive index film are repeatedly laminated. The optical characteristics of both the substrate and the optical multilayer film are as follows: the wavelength at the 30 ° incidence (λ ₁ ) and the wavelength at the normal incidence (λ ₀ ) in the region on the long wavelength side with respect to the transmission band in the spectral transmittance. 0 obtained by dividing the total (Σ (λ ₁ −λ ₀ )) in units of 1% from 5% to 20% of the transmittance for a wavelength shift (λ ₁ −λ ₀ ) consisting of the difference between The average wavelength shift (˜ (Σ (λ ₁ −λ ₀ )) / 16) of ˜30 ° is more than −19 nm.

The second near-infrared cut filter has a substrate made of copper-containing fluorophosphate glass or copper-containing phosphate glass, and an optical multilayer film laminated on the substrate. The optical multilayer film has an infrared reflective film in which a high refractive index film and a low refractive index film are repeatedly laminated. The optical characteristics composed of both the substrate and the optical multilayer film are as follows: a wavelength (λ ₂ ) at 40 ° incidence and a wavelength (λ ₀ ) at normal incidence in a region on the long wavelength side with respect to the transmission band in spectral transmittance. Is obtained by dividing the sum (Σ (λ ₂ −λ ₀ )) in increments of 1% from 5% to 20% with respect to the wavelength shift (λ ₂ −λ ₀ ) consisting of the difference between the total number of times. The average wavelength shift ((Σ (λ ₂ −λ ₀ )) / 16) of ˜40 ° is more than −32 nm.

  According to the present invention, there is provided a near-infrared cut filter with reduced incident angle dependency in a region where the transmittance is 20% or less.

It is sectional drawing which shows one Embodiment of a near-infrared cut filter. It is sectional drawing which shows one Embodiment of an imaging device. FIG. 6 is a diagram showing the spectral transmittance of the evaluation filter of Example 1. FIG. 6 is a diagram showing the spectral transmittance of the evaluation filter of Example 2. FIG. 10 is a diagram showing the spectral transmittance of the evaluation filter of Example 3. FIG. 10 is a diagram showing the spectral transmittance of the evaluation filter of Example 4. It is a figure which expands and shows a part of FIG. It is a figure which expands and shows a part of FIG. It is a figure which expands and shows a part of FIG. It is a figure which expands and shows a part of FIG.

Hereinafter, the near infrared cut filter of the present invention will be described.
FIG. 1 is a cross-sectional view showing an embodiment of a near-infrared cut filter.
The near-infrared cut filter 1 includes a substrate 2 and an optical multilayer film 3 laminated on the substrate 2.

  The substrate 2 is made of copper-containing fluorophosphate glass or copper-containing phosphate glass. When the substrate 2 is made of copper-containing fluorophosphate glass or copper-containing phosphate glass, in the spectral transmittance curve of the near-infrared cut filter 1, near-infrared light that blocks near-infrared light from a transmission band that transmits visible light. The inclination toward the side stop band becomes gentle, and a spectral transmittance close to human visibility characteristics can be obtained.

  The optical multilayer film 3 is formed by repeatedly stacking a high refractive index layer 31 and a low refractive index layer 32 and functions as an infrared reflective film. A unit refractive index layer 33 is formed from the high refractive index layer 31 and the low refractive index layer 32 laminated on the opposite side of the high refractive index layer 31 from the substrate 2.

  Although not shown, an antireflection film for preventing reflection may be stacked on the main surface of the substrate 2 on which the optical multilayer film 3 is not stacked. Further, the optical multilayer film 3 may be provided separately on both sides of the substrate 2. Thus, even if the optical multilayer film 3 is divided and provided on both sides of the substrate 2, the same effect as in the case where the optical multilayer film 3 is not divided can be obtained.

  The high-refractive index layer 31 and the low-refractive index layer 32 do not necessarily have a specific refractive index, and it is sufficient that the refractive index of the high-refractive index layer 31 is relatively higher than the refractive index of the low-refractive index layer 32. In general, the high refractive index layer 31 preferably has a refractive index of 2.0 to 2.7, and the low refractive index layer 32 preferably has a refractive index of 1.3 to 1.8. It is more preferable to have a refractive index of 1.4 or more and 1.6 or less. The optical multilayer film 3 includes a low refractive index layer 32 having a refractive index of 1.4 to 1.6 and a low refractive index layer 32 having a refractive index of more than 1.6 and less than 1.8 at the same time. it can. Here, in this specification, a refractive index means the refractive index with respect to the light of wavelength 550nm.

When the optical film thickness of the high refractive index layer 31 is n _H d _H and the optical film thickness of the low refractive index layer 32 is n _L d _L , the optical multilayer film 3 has n _H d _H / n _L d _L ≧ 3. 5 or more, more preferably 8 or more, and even more preferably 10 or more layers.

The optical multilayer film 3 is not necessarily composed of only the unit refractive index layer 33, and does not constitute the unit refractive index layer 33 at one or both ends in the stacking direction, and exists alone. Alternatively, the low refractive index layer 32 may be provided. In addition, n _H d _H / n _L d _L of each unit refractive index layer 33 may be the same or different.

When the optical multilayer film 3 includes five or more unit refractive index layers 33 satisfying n _H d _H / n _L d _L ≧ 3, the incident angle dependency is easily reduced in a region where the transmittance is 20% or less. The optical multilayer film 3 includes five or more unit refractive index layers 33 satisfying n _H d _H / n _L d _L ≧ 5 from the viewpoint of further reducing the incident angle dependency in a region where the transmittance is 20% or less. Preferably, it contains 8 layers or more, more preferably 10 layers or more.

The optical multilayer film 3 preferably includes 20 or more unit refractive index layers 33 regardless of the size of n _H d _H / n _L d _L. When 20 or more unit refractive index layers 33 are included, the incident angle dependency in a region where the transmittance is 20% or less is likely to be reduced.

  When emphasizing the productivity of the optical multilayer film 3, the smaller the number of unit refractive index layers 33 included in the optical multilayer film 3, the better. The number of unit refractive index layers 33 included in the optical multilayer film 3 is 30. Less than 25 layers are preferred, and less than 25 layers are more preferred.

  On the other hand, when it is important to reduce the incident angle dependency in a region where the transmittance is 20% or less, particularly when importance is placed on reducing the incident angle dependency when the incident angle is large, it is included in the optical multilayer film 3. The greater the number of unit refractive index layers 33, the better. The number of unit refractive index layers 33 included in the optical multilayer film 3 is preferably 30 or more, and more preferably 40 or more. Even in such a case, from the viewpoint of productivity of the optical multilayer film 3, the number of unit refractive index layers 33 included in the optical multilayer film 3 is preferably 50 or less.

When the optical multilayer film 3 includes 30 or more unit refractive index layers 33, the optical multilayer film 3 may include 15 or more unit refractive index layers 33 satisfying n _H d _H / n _L d _L ≧ 3. Preferably, it contains 20 or more layers. When the optical multilayer film 3 includes 30 or more unit refractive index layers 33, the optical multilayer film 3 includes 15 or more unit refractive index layers 33 satisfying n _H d _H / n _L d _L ≧ 5. It is preferable to include 20 layers or more.

In particular, when the optical multilayer film 3 includes 40 or more unit refractive index layers 33, the optical multilayer film 3 includes 20 or more unit refractive index layers 33 satisfying n _H d _H / n _L d _L ≧ 3. It is preferable to include 25 layers or more. When the optical multilayer film 3 includes 40 or more unit refractive index layers 33, the optical multilayer film 3 includes 20 or more unit refractive index layers 33 satisfying n _H d _H / n _L d _L ≧ 5. It is preferable to include 25 layers or more.

The minimum value of n _H d _H / n _L d _L of the unit refractive index layer 33 included in the optical multilayer film 3 is preferably 0.1 or more. The maximum value of n _H d _H / n _L d _L of the unit refractive index layer 33 included in the optical multilayer film 3 is preferably 100 or less, more preferably 50 or less, and the number of unit refractive index layers 33 is less than 30. In this case, 20 or less is more preferable.

_{N H d H / n L d} L a is determined by averaging the average _{n H d H / n L d} L of the optical multilayer film 3 to all the unit refractive index layer 33 included is preferably 3 to 20. In particular, when the number of unit refractive index layers 33 included in the optical multilayer film 3 is less than 30, the average n _H d _H / n _L d _L is preferably 3 to 8, and the unit refractive index included in the optical multilayer film 3 When the number of layers of the rate layer 33 is 30 or more, the average n _H d _H / n _L d _L is preferably 7 to 18.

The average optical thickness _n H _{d H} is the average value of the optical thickness _n H _{d H} of the high refractive index layer 31 included in the optical multilayer film 3, 250 to 400 nm are preferred, more preferably 270～370Nm, 280 to 350 nm is more preferable. The average optical film thickness n _L d _L which is an average value of the optical film thickness n _L d _L of the low refractive index layer 32 included in the optical multilayer film 3 is preferably 50 to 200 nm, more preferably 70 to 160 nm, and 80 to 150 nm is more preferable.

The optical film thickness n _H d _H of each high refractive index layer 31 included in the optical multilayer film 3 is preferably 10 to 1300 nm, more preferably 30 to 1100 nm, and still more preferably 30 to 800 nm. In particular, when the number of unit refractive index layers 33 included in the optical multilayer film 3 is less than 30, the optical film thickness n _H d _H of each high refractive index layer 31 is preferably 30 to 500 nm. The optical film thickness n _L d _L of each low refractive index layer 32 included in the optical multilayer film 3 is preferably 1 to 500 nm, and more preferably 5 to 300 nm.

Examples of the constituent material of the high refractive index layer 31 include TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and composite oxides thereof. Examples of the constituent material of the low refractive index layer 32 include SiO ₂ , MgF ₂ , Al ₂ O ₃ , ZrO ₂ , and complex oxides thereof. The high refractive index layer 31 and the low refractive index layer 32 can contain various components for adjusting the refractive index in addition to these components.

  The high refractive index layer 31 and the low refractive index layer 32 are formed by, for example, a sputtering method, a vacuum evaporation method, an ion beam method, an ion plating method, or a CVD method. According to these forming methods, each refractive index layer can be formed relatively easily while controlling the thickness of each refractive index layer with high accuracy. Further, since the sputtering method or the ion plating method is a so-called plasma atmosphere treatment, the adhesion of the optical multilayer film 3 to the substrate 2 can be improved.

  Next, the spectral transmittance of the near infrared cut filter 1 will be described. Note that the spectral transmittance of the near-infrared cut filter 1 refers to an optical characteristic composed of both the substrate 2 and the optical multilayer film 3.

First, the spectral transmittance at normal incidence (0 ° incidence) will be described.
The spectral transmittance at normal incidence usually has a transmission band, a near infrared light side stop band, and an ultraviolet light side stop band. The transmission band is a band that transmits visible light, is formed within a wavelength range of 400 to 600 nm, and is, for example, a portion having a transmittance of 85% or more. The near-infrared-light-side blocking band is a band that blocks transmission of near-infrared light, and is formed within a wavelength range of 750 to 1000 nm, for example, a portion having a transmittance of 1% or less. The ultraviolet light side blocking band is a band that blocks the transmission of ultraviolet light, and is a part that is formed within a wavelength range of 350 to 400 nm and has a transmittance of 1% or less, for example.

  In the spectral transmittance at normal incidence, the difference between the half-value wavelength on the ultraviolet light side with respect to the transmission band and the half-value wavelength on the near-infrared light side with respect to the transmission band is preferably 150 nm or more, and is 180 nm or more. More preferably, it is 190 nm or more. Usually, the difference is as much as 210 nm. The half-value wavelength means a wavelength when the transmittance is 50%.

  In the spectral transmittance at normal incidence, the half-value wavelength on the ultraviolet light side with respect to the transmission band is preferably 390 to 440 nm, and more preferably 400 to 430 nm. In addition, in the normal incidence spectral transmittance, the half-value wavelength on the near infrared side with respect to the transmission band is preferably 580 to 680 nm, and more preferably 600 to 630 nm.

  The spectral transmittance at 30 ° incidence and 40 ° incidence usually also has a transmission band, a near infrared light side stop band, and an ultraviolet light side stop band. The transmission band is usually formed within a wavelength range of 400 to 600 nm. The near-infrared light side stop band is usually formed within a wavelength range of 750 to 1000 nm. The ultraviolet light side stop band is usually formed within a wavelength range of 350 to 400 nm.

  For the spectral transmittance at 30 ° incidence and 40 ° incidence, the difference between the half-value wavelength on the ultraviolet light side with respect to the transmission band and the half-value wavelength on the near infrared light side with respect to the transmission band is 150 nm or more. Is preferably 180 nm or more, and more preferably 190 nm or more.

  With respect to the spectral transmittance at 30 ° incidence and 40 ° incidence, the half-value wavelength on the ultraviolet light side with respect to the transmission band is preferably 390 to 440 nm, and more preferably 400 to 430 nm. In addition, at 30 ° incidence and 40 ° incidence, the half-value wavelength on the near infrared side with respect to the transmission band is preferably 580 to 680 nm, and more preferably 600 to 630 nm.

  About the near-infrared cut filter 1 of this invention, it is a long wavelength side with respect to a transmission band, and the average wavelength shift of 0-30 degrees defined below in the area | region where the transmittance | permeability is 5% to 20%. Is greater than −19 nm or an average wavelength shift of 0-40 ° defined below is greater than −32 nm.

The average wavelength shift of 0 to 30 ° is a wavelength formed by the difference between the wavelength (λ ₁ ) at 30 ° incidence and the wavelength (λ ₀ ) at normal incidence in the region on the long wavelength side with respect to the transmission band in spectral transmittance. The total transmittance (Σ (λ ₁ -λ ₀ )) in which the transmittance for the shift (λ ₁ -λ ₀ ) is 5% to 20% (Σ (λ ₁ -λ ₀ )) is divided by the total number of times ((Σ (λ ₁ −λ ₀ )) / 16).

The average wavelength shift of 0 to 40 ° is a wavelength formed by the difference between the wavelength at the 40 ° incidence (λ ₂ ) and the wavelength at the normal incidence (λ ₀ ) in the region on the longer wavelength side of the transmission band in the spectral transmittance. The total transmittance (Σ (λ ₂ −λ ₀ )) in which the transmittance for the shift (λ ₂ −λ ₀ ) is 5% to 20% (Σ (λ ₂ −λ ₀ )) is divided by the total number of times ((Σ (λ ₂ −λ ₀ )) / 16).

  The average wavelength shift of 0 to 30 ° and the average wavelength shift of 0 to 40 ° represent the incident angle dependence in the region with a long wavelength side and low transmittance with respect to the transmission band, and these values are 0. This indicates that the closer to the incident angle, the smaller the incident angle dependency. When the average wavelength shift of 0 to 30 ° is more than −19 nm or the average wavelength shift of 0 to 40 ° is more than −32 nm, the incident angle dependency in the region where the transmittance is long and the transmittance is low is effective. And good color reproducibility can be obtained.

  The average wavelength shift of 0 to 30 ° is preferably −18 nm or more, more preferably −16 nm or more, and further preferably −14 nm or more, from the viewpoint of reducing the incident angle dependency.

  The average wavelength shift of 0 to 40 ° is preferably −30 nm or more, more preferably −28 nm or more, and further preferably −26 nm or more, from the viewpoint of reducing the incident angle dependency.

  The near-infrared cut filter 1 has a long wavelength side with respect to the transmission band and a transmittance of 5 from the viewpoint of setting the average wavelength shift of 0 to 30 ° to more than −19 nm or the average wavelength shift of 0 to 40 ° to more than −32 nm. In the region from% to 20%, the slope of the spectral transmittance curve at 30 ° incidence defined below is preferably equal to or smaller than the slope of the spectral transmittance curve at normal incidence defined below.

The slope of the spectral transmittance curve at 30 ° incidence is the difference in transmittance (5-20) between 5% transmittance and 20% transmittance, and the wavelength (λ ₄ ) when the transmittance at 30 ° incidence is 5%. It is obtained by dividing by the wavelength difference (λ ₄ −λ ₅ ) with respect to the wavelength (λ ₅ ) when the transmittance is 20% ((5-20) / (λ ₄ −λ ₅ )).

The slope of the spectral transmittance curve at normal incidence is the difference in transmittance (5-20) between the transmittance 5% and the transmittance 20%, and the wavelength (λ ₆ ) and the transmittance when the transmittance at normal incidence is 5%. Is divided by the wavelength difference (λ ₆ −λ ₇ ) with respect to the wavelength (λ ₇ ) when 20 is 20% ((5-20) / (λ ₆ −λ ₇ )).

  The slope of the portion where the transmittance is 5 to 20% in the spectral transmittance curve at 30 ° incidence is equal to or smaller than the slope of the portion where the transmittance is 5 to 20% in the spectral transmittance curve at normal incidence. When the absolute value becomes large, the position of the spectral transmittance curve at 30 ° incidence tends to approach the position of the spectral transmittance curve at normal incidence, and the average wavelength shift of 0 to 30 ° exceeds -19 nm or 0 to 40 °. The average wavelength shift tends to exceed -32 nm.

The slope ((5-20) / (λ ₆ -λ ₇ )) of the spectral transmittance curve at normal incidence is preferably −0.50 to −0.65, more preferably −0.55 to −0.63. . The slope of the spectral transmittance curve at 30 ° incidence ((5-20) / (λ ₄ −λ ₅ )) is a range that is equal to or less than the slope of the spectral transmittance curve at normal incidence, and is −0.60 to −0. 85 is preferable, and -0.63 to -0.80 is more preferable.

  The near-infrared cut filter 1 is used, for example, as a near-infrared cut filter such as a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, a web camera, or an automatic exposure meter, that is, a visibility correction filter. In an imaging apparatus such as a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, or a web camera, the near-infrared cut filter 1 is disposed, for example, between an imaging lens and a solid-state imaging device. In the automatic exposure meter, for example, it is arranged on the front surface of the light receiving element.

  Normally, the near-infrared cut filter 1 is arranged such that the main surface side on which the optical multilayer film 3 is laminated is the light incident side, for example, the imaging lens side when it is arranged between the imaging lens and the solid-state imaging device. The By adopting such an arrangement, it is possible to effectively reduce the incident angle dependency and suppress a change in color at the center portion and the peripheral portion of the captured image.

  In the imaging apparatus, the near-infrared cut filter 1 may be disposed at a position away from the front surface of the solid-state imaging device, or may be directly attached to the solid-state imaging device or the package of the solid-state imaging device. As described above, the near-infrared cut filter 1 may be used as a cover that protects the solid-state imaging device. Further, it may be directly attached to a low-pass filter using a crystal such as quartz or lithium niobate for reducing moire and false color.

FIG. 2 is a cross-sectional view schematically showing an embodiment of an imaging apparatus having a solid-state imaging element.
The imaging device 50 includes, for example, a solid-state imaging device 51, a cover glass 52, a lens group 53, a diaphragm 54, and a housing 55 for fixing them.

  The lens group 53 is disposed on the imaging surface side of the solid-state imaging device 51, and includes, for example, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. The stop 54 is disposed between the third lens L3 and the fourth lens L4. The cover glass 52 is disposed on the lens group 53 side of the solid-state image sensor 51 and protects the solid-state image sensor 51 from the external environment. The solid-state imaging device 51 is an electronic component that converts light that has passed through the lens group 53 into an electrical signal, and is a CCD, CMOS, or the like. The solid-state image sensor 51, the cover glass 52, the lens group 53, and the stop 54 are disposed along the optical axis x.

  In the imaging device 50, light incident from the subject side passes through the first lens L 1, the second lens L 2, the third lens L 3, the diaphragm 54, the fourth lens L 4, and the cover glass 52, and the solid-state imaging device. 51 is incident. The solid-state image sensor 51 converts the incident light into an electric signal and outputs it as an image signal.

  The near-infrared cut filter 1 is used as, for example, a cover glass 52 and a lens group 53, that is, a first lens L1, a second lens L2, a third lens L3, or a fourth lens L4. By applying the near-infrared cut filter 1 to the cover glass 52 and the lens group 53 of the imaging device 50, the incident angle dependency can be effectively reduced even in a region where the transmittance is low, and the center and periphery of the image to be captured It is possible to suppress the change in color between the two parts.

Hereinafter, more specific description will be given with reference to examples.
Examples 1 to 3 correspond to examples of the present invention, and example 4 corresponds to a comparative example of the present invention.

(Example 1)
An optical multilayer film as an infrared reflecting film is laminated on one main surface of a 0.3 mm thick copper-containing fluorophosphate glass plate (manufactured by AGC Techno Glass Co., Ltd., refractive index: 1.55) as the substrate, An evaluation filter was formed by laminating an antireflection film on the main surface.

As shown in Table 1, the optical multilayer film includes a TiO ₂ film (refractive index: 2.52) as a high refractive index layer and a SiO ₂ film (refractive index: 1) as a low refractive index layer in order from the substrate side. .46) or a composite oxide film of ZrO ₂ and Al ₂ O ₃ (refractive index: 1.75). The antireflection film includes, in order from the substrate side, a TiO ₂ film (refractive index: 2.52) as a high refractive index layer and an SiO ₂ film (refractive index: 1.46) as a low refractive index layer. A total of six layers were alternately stacked.

Here, the total number of high refractive index layers and low refractive index layers is 96, and the number of unit refractive index layers is 48. The number of unit refractive index layers satisfying n _H d _H / n _L d _L ≧ 3 is 32, and the number of unit refractive index layers satisfying n _H d _H / n _L d _L ≧ 5 is 27. average _{n H d H / n L d} L is _{9.4, n H d H / n} L d range of _L is 0.7 to 48.8, the average optical thickness _n H _{d H} is 322.2nm, _{n H} The range of d _H is 44.0 to 645.3 nm, the average optical film thickness n _L d _L is 90.7 nm, and the range of n _L d _L is 13.2 to 283.7 nm.

(Example 2)
The evaluation filter was the same as in Example 1 except that the optical multilayer film was changed to the configuration shown in Table 2.
Here, the total number of high refractive index layers and low refractive index layers is 94, and the number of unit refractive index layers is 47. The number of unit refractive index layers satisfying n _H d _H / n _L d _L ≧ 3 is 32; the number of unit refractive index layers satisfying n _H d _H / n _L d _L ≧ 5 is 30; The average n _H d _H / n _L d _L is 15.1, the range of n _H d _H / n _L d _L is 0.7-78.4, the average optical film thickness n _H d _H is 338.3 nm, n _H The range of d _H is 46.1 to 1068.6 nm, the average optical film thickness n _L d _L is 83.4 nm, and the range of n _L d _L is 8.8 to 282.5 nm.

(Example 3)
The evaluation filter was the same as that of Example 1 except that the optical multilayer film was changed to the configuration shown in Table 3.
Here, the total number of high refractive index layers and low refractive index layers is 46, and the number of unit refractive index layers is 23. The number of unit refractive index layers satisfying n _H d _H / n _L d _L ≧ 3 is 10, the number of unit refractive index layers satisfying n _H d _H / n _L d _L ≧ 5 is 10, average _{n H d H / n L d} L is _{4.7, n H d H / n} L d range of _L is 1.0 to 13.0, the average optical thickness _n H _{d H} is 295.8nm, _{n H} The range of d _H is 50.9 to 378.6 nm, the average optical film thickness n _L d _L is 138.0 nm, and the range of n _L d _L is 29.2 to 272.3 nm.

(Example 4)
The evaluation filter was the same as that of Example 1 except that the optical multilayer film was changed to the configuration shown in Table 4.
Here, the total number of high refractive index layers and low refractive index layers is 40, and the number of unit refractive index layers is 20. The number of unit refractive index layers satisfying n _H d _H / n _L d _L ≧ 3 is 0, the average n _H d _H / n _L d _L is 1.1, and n _H d _H / n _L d _L The range is 0.5 to 2.1, the average optical film thickness n _H d _H is 262.6 nm, the n _H d _H range is 29.8 to 312.7 nm, and the average optical film thickness n _L d _L is 242.2 nm. , N _L d _L ranges from 58.2 to 289.6 nm.

  Next, for the evaluation filters of Examples 1 to 4, spectral transmittances at normal incidence (0 ° incidence), 30 ° incidence, and 40 ° incidence when incident from the optical multilayer film side by optical simulation are shown. Asked. 3 to 6 show the spectral transmittances for Examples 1 to 4, and FIGS. 7 to 10 show a part of FIGS. 3 to 6 in an enlarged manner.

Further, in Tables 5 to 8, in the region where the wavelength is longer than the transmission band and the transmittance is 5% to 20%, the transmittance is 1% from 5% to 20%. Wavelength shift (λ ₁ −λ ₀ ) and average wavelength shift ((Σ (λ ₁ −λ ₀ )) / 16) between a wavelength of 30 ° incidence (λ ₁ ) and a wavelength of normal incidence (λ ₀ ), Wavelength shift (λ ₂ −λ ₀ ) and average wavelength shift between 40 ° incident wavelength (λ ₂ ) and normal incident wavelength (λ ₀ ) in 1% increments from 5% to 20% transmittance ((Σ (λ ₂ −λ ₀ )) / 16).

Further, Tables 9 to 10 show the slopes at the time of normal incidence ((5−5) for the part on the long wavelength side with respect to the transmission band and the transmittance of 5 to 20% in the spectral transmittance curve. 20) / (λ ₆ −λ ₇ )), and the inclination ((5-20) / (λ ₄ −λ ₅ )) at 30 ° incidence.

  As is apparent from the above results, the evaluation filters of Examples 1 to 3 have an average wavelength shift of 0 to 30 ° exceeding −19 nm and an average wavelength shift of 0 to 40 ° exceeding −32 nm. It can be seen that the incident angle dependency in the region of the long wavelength side and the transmittance of 20% or less is reduced as compared with the evaluation filter of Example 4.

  In addition, the evaluation filters of Examples 1 to 3 are long wavelength side with respect to the transmission band and the transmittance is 20% or less, the inclination of 30 ° incidence is equal to the inclination of normal incidence, It turns out that it is smaller than this.

  The evaluation filters of Examples 1 to 3 have a transmittance of 85% or more as a transmission band in the wavelength range of 400 to 600 nm under any incidence condition of normal incidence, 30 ° incidence, and 40 ° incidence. The part where the transmittance which becomes the near-infrared light side blocking band within the wavelength range of 750 to 1000 nm is 1% or less, the transmittance which becomes the ultraviolet light side blocking band within the wavelength range of 350 to 400 nm is 1% or less The part which becomes.

  In addition, the evaluation filters of Examples 1 to 3 have the half-value wavelength on the ultraviolet light side with respect to the transmission band and the transmission band under any incidence condition of normal incidence, 30 ° incidence, and 40 ° incidence. The difference from the half-value wavelength on the near infrared light side is 190 to 210 nm, the half-value wavelength on the ultraviolet light side is 400 to 430 nm with respect to the transmission band, and the half-value wavelength on the near infrared light side is 600 to 630 nm with respect to the transmission band. is there.

  DESCRIPTION OF SYMBOLS 1 ... Near-infrared cut filter, 2 ... Board | substrate, 3 ... Optical multilayer film, 31 ... High refractive index layer, 32 ... Low refractive index layer, 33 ... Unit refractive index layer, 50 ... Imaging apparatus, 51 ... Solid-state image sensor, 52 ... cover glass, 53 ... lens group, 54 ... aperture, 55 ... housing.

Claims (4)

A near-infrared cut filter having a substrate made of copper-containing fluorophosphate glass or copper-containing phosphate glass, and an optical multilayer film laminated on the substrate,
The optical multilayer film has an infrared reflective film in which a high refractive index film and a low refractive index film are repeatedly laminated,
The optical characteristics composed of both the substrate and the optical multilayer film are as follows: a wavelength (λ ₁ ) at 30 ° incidence and a wavelength (λ ₀ ) at normal incidence in a region on the long wavelength side with respect to the transmission band in spectral transmittance. 0 obtained by dividing the total (Σ (λ ₁ −λ ₀ )) in units of 1% from 5% to 20% of the transmittance for a wavelength shift (λ ₁ −λ ₀ ) consisting of the difference between A near-infrared cut filter having an average wavelength shift ((Σ (λ ₁ −λ ₀ )) / 16) of −30 ° exceeds −19 nm. A near-infrared cut filter having a substrate made of copper-containing fluorophosphate glass or copper-containing phosphate glass, and an optical multilayer film laminated on the substrate,
The optical multilayer film has an infrared reflective film in which a high refractive index film and a low refractive index film are repeatedly laminated,
The optical characteristics composed of both the substrate and the optical multilayer film are as follows: the wavelength at the 40 ° incidence (λ ₂ ) and the wavelength at the normal incidence (λ ₀ ) in the region on the long wavelength side with respect to the transmission band in the spectral transmittance. Is obtained by dividing the sum (Σ (λ ₂ −λ ₀ )) in increments of 1% from 5% to 20% with respect to the wavelength shift (λ ₂ −λ ₀ ) consisting of the difference between the total number of times. A near-infrared cut filter having an average wavelength shift ((Σ (λ ₂ −λ ₀ )) / 16) of −40 ° exceeds −32 nm. The near-infrared cut filter according to claim 1 or 2,
The optical characteristic consisting of both the substrate and the optical multilayer film has a transmittance difference between a transmittance of 5% and a transmittance of 20% in a region on the long wavelength side with respect to the transmission band in the spectral transmittance (5-20). Is obtained by dividing by a wavelength difference (λ ₄ -λ ₅ ) between a wavelength (λ ₄ ) when the transmittance at 30 ° incidence is 5% and a wavelength (λ ₅ ) when the transmittance is 20%. The slope of the transmittance curve ((5-20) / (λ ₄ −λ ₅ )) is the transmittance difference (5-20) between the transmittance 5% and the transmittance 20%, and the transmittance at normal incidence is 5%. The slope of the spectral transmittance curve obtained by dividing by the wavelength difference (λ ₆ −λ ₇ ) between the wavelength (λ ₆ ) and the wavelength (λ ₇ ) when the transmittance is 20% ((5-20 ) / (Λ ₆ −λ ₇ )) In the near-infrared cut filter according to any one of claims 1 to 3,
The high refractive index film is made of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , or a composite oxide thereof, and the low refractive index film is made of SiO ₂ , MgF ₂ , Al ₂ O ₃ , ZrO ₂ , Or a near-infrared cut filter made of these complex oxides.

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