WO2023157403A1

WO2023157403A1 - Optical filter and imaging device

Info

Publication number: WO2023157403A1
Application number: PCT/JP2022/042430
Authority: WO
Inventors: 幸治高山
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2022-02-21
Filing date: 2022-11-15
Publication date: 2023-08-24

Abstract

Provided are an optical filter and an imaging device which have further improved incidence angle dependency. An optical filter according to the present disclosure comprises: a transmissive member 11 having one main surface 11a and the other main surface 11b facing the one main surface 11a; an infrared-absorbing resin member 12 provided on the one main surface 11a of the transmissive member 11; and an infrared-blocking film 13 provided on the other main surface 11b of the transmissive member 11 and blocks infrared light passing through the infrared-absorbing resin member 12.　

Description

Optical filters and imagers

The present disclosure relates to optical filters and imaging devices.

Patent Document 1 discloses an optical filter in which an optical multilayer film is provided on near-infrared cut glass. Patent Document 2 describes a compound (A ) and a compound (S) having an absorption maximum at a wavelength of 750 nm or more and 1050 nm or less.

WO2014/192670 WO2016/158461

An object of the present disclosure is to provide an optical filter and an imaging device with improved spectral transmittance characteristics.

The optical filter according to the present disclosure is
a translucent member having one principal surface and the other principal surface facing the one principal surface;
an infrared light absorbing resin member provided on the one main surface of the translucent member;
an infrared light shielding film provided on the other main surface of the translucent member and shielding infrared light transmitted through the infrared light absorbing resin member.

The imaging device according to the present disclosure is
the optical filter;
and an imaging device,
The imaging element is arranged on the one main surface side of the translucent member.

The present disclosure can provide an optical filter and an imaging device with improved spectral transmittance characteristics.

FIG. 1 is a schematic diagram of one embodiment of an imaging device comprising an optical filter of the present disclosure. FIG. 2 is a graph showing the spectral transmittance of the infrared light absorbing resin member of the optical filter of the present disclosure. FIG. 3 is a graph showing the spectral transmittance of the infrared light shielding film of the optical filter of the present disclosure. FIG. 4 is a graph showing the spectral transmittance of an optical filter of the present disclosure; FIG. 5 is a schematic diagram of an embodiment of an imaging device having an optical filter of a comparative example. FIG. 6 is a graph showing the spectral transmittance of the optical filter of Comparative Example.

[Knowledge, etc. on which this disclosure is based]
Imaging devices equipped with imaging elements such as CCD or CMOS image sensors are known, but the imaging elements are sensitive to light with wavelengths in the infrared light region or ultraviolet light region that cannot be detected by the human eye. ing. An optical filter is used to cut these unnecessary wavelength components.

For example, Patent Document 1 discloses an optical filter in which an optical multilayer film is provided on near-infrared cut glass. In other words, an optical multilayer film is used in combination with near-infrared absorption type colored glass to sufficiently cut light in the near-infrared region.

The optical filter using the near-infrared cut glass described in Patent Document 1, as shown in FIGS. Insufficient light shielding. As a result, the near-infrared light is incident on the imaging device, causing ghosts, flares, and the like.

In the above optical filter, it is conceivable to appropriately design the optical characteristics of the optical multilayer film in order to appropriately shield light in the near-infrared region, which is insufficiently shielded. In other words, in the optical filter described in Patent Document 1, it is conceivable to design the optical multilayer film so as to block light in the vicinity of 700 nm.

Here, an optical filter composed of an optical multilayer film is a reflective optical filter that utilizes the refractive index of the multilayer film, unlike an absorption optical filter. It is known that when the incident angle of light increases, the optical characteristics shift to the short wavelength side (for example, about 20 to 30 nm shift). In other words, the optical multilayer film has an optical characteristic of reflecting light shifted to the shorter wavelength side. Therefore, by shifting to the short wavelength side (for example, within the visible region with a wavelength shorter than 700 nm), the reflected light remains in the imaging device, and the reflected light is detected by the imaging device, resulting in the above-described ghost, flare, etc. was a problem.

As a method of solving the incident angle dependence, the optical filter described in Patent Document 2 is disclosed, but the demand for improving the incident angle characteristics does not stop, leaving room for further improvement.

Therefore, the inventor of the present application attempted to solve the above problem by dealing with it in a new direction, rather than dealing with it on the extension of the conventional technology. As a result, we have disclosed an optical filter and an imaging device that achieve the above main objectives.

Below, the optical filter and imaging device of the present disclosure will be described in more detail. However, more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters or redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity and to facilitate understanding by those skilled in the art.

Applicants provide the accompanying drawings and the following descriptions for the full understanding of the present disclosure by those skilled in the art, and are not intended to limit the claimed subject matter. Various elements in the drawings are only schematically and exemplarily shown for understanding of the optical filter and imaging device of the present disclosure, and the appearance and/or dimensional ratios may differ from the actual ones.

In addition, in the present disclosure, the visible light region means a wavelength region of 400 nm or more and 700 nm or less, the ultraviolet light region means a wavelength region of less than 400 nm, and the infrared light region means a wavelength region longer than 700 nm. Note that there may be an error of about ±10% in any wavelength region.

In addition, the various numerical ranges referred to in this disclosure are intended to include the lower and/or upper numerical values themselves, unless otherwise specified. That is, taking a numerical range of 1 to 10 as an example, it can be interpreted as including the lower limit of "1" and the upper limit of "10". In addition, various numerical values may be "about" or "about", and the terms "about" and "about" mean that they may include variations of several percent, such as ±10%. .

[Optical filter of the present disclosure]
One embodiment of an optical filter 10 of the present disclosure will be described with reference to FIG. The optical filter 10 of the present disclosure includes a translucent member 11 having one principal surface 11a and the other principal surface 11b facing the one principal surface, and one principal surface 11a of the translucent member 11. An infrared light absorbing resin member 12 and an infrared light shielding film 13 provided on the other main surface 11b of the translucent member 11 and blocking infrared light transmitted through the infrared light absorbing resin member 12. ing. It should be noted that the term "light shielding" as used herein means that the spectral transmittance is less than 1%. The term "transmission of light" refers to a state in which light is not blocked, specifically, a spectral transmittance of 1% or more, preferably a spectral transmittance of 90% or more. intended.

With such a configuration, unlike the conventional near-infrared cut glass, the infrared light-absorbing resin member 12 can provide steep filter characteristics. Furthermore, the infrared light absorbing resin member 12 of the present disclosure transmits infrared light, but the optical filter 10 of the present disclosure includes the infrared light shielding film 13 that shields the infrared light. It is possible to reduce ghosts, flares, etc. caused by Each component will be specifically described below.

-translucent member-
The translucent member 11 is a member capable of transmitting at least light in the visible light range. As an example, the translucent member 11 may be clear glass (transparent glass). The spectral transmittance can be improved by using clear glass. In addition, if it is clear glass, it is not necessary to design a material and/or thickness for shielding infrared light, unlike IR cut glass, and it can be prepared simply. Note that the translucent member of the present disclosure is not limited to clear glass, and colored glass such as IR cut glass may be used. As a specific embodiment of the clear glass, known glass such as silicate glass, borosilicate glass, borate glass and/or phosphate glass may be used.

The thickness of the substrate is preferably 0.05 mm or more, more preferably 0.1 mm or more, from the viewpoint of ensuring strength, and preferably 5.0 mm or less from the viewpoint of thinning to be accommodated in an imaging device. 0 mm or less is more preferable. That is, it can be made thinner than the conventional IR cut glass. Specifically, the spectral transmittance characteristics of conventional optical filters are determined by the thickness of the IR-cut glass (colored glass), so there are design restrictions to achieve compatibility between the spectral transmittance characteristics and the size of the optical filter. . However, in the present disclosure, the translucent member 11 (clear glass as an example) is used, and the spectral transmittance characteristics are determined by the infrared light absorbing resin member 12 and the infrared light shielding film 13, which will be described later. It is possible to improve the degree of freedom in design for achieving both the index characteristics and the size of the optical filter.

-Infrared light absorbing resin material-
The infrared light absorbing resin member 12 is arranged on one main surface 11a of the translucent member 11 and is a member containing a resin that absorbs infrared light without reflecting it. As an example, it may be a resin material containing at least a thermoplastic resin and an oxocarbon compound.

Thermoplastic resins serve as base resins, for example, (meth) acrylic resins, (meth) acrylic urethane resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyolefin resins (e.g., polyethylene resins, polypropylene resin), cycloolefin resin, urethane resin, styrene resin, polyvinyl acetate, polyamide resin (e.g., nylon), aramid resin, polyimide resin, polyamideimide resin, polyester resin (e.g., polybutylene terephthalate (PBT), polyethylene Terephthalate (PET), etc.), butyral resin, polycarbonate resin, polyether resin, polysulfone resin, ABS resin (acrylonitrile butadiene styrene resin), AS resin (acrylonitrile-styrene copolymer), fluorine resin (e.g., fluorinated aromatic polytetrafluoroethylene (PTFE), perfluoroalkoxy fluoroplastic (PFA), fluorinated polyaryletherketone (FPEK), fluorinated polyimide (FPI), fluorinated polyamic acid (FPAA) and/or fluorinated poly ether nitrile (FPEN), etc.). Among these, (meth)acrylic resins, cycloolefin resins, polyimide resins, polyamideimide resins, polyester resins, polyarylate resins, polyamide resins, polycarbonate resins, and polysulfone resins are preferred because of their excellent transparency and/or heat resistance. and/or fluorinated aromatic polymers are preferred.

Oxocarbon-based compounds have spectral characteristics that allow them to transmit light in the visible light range with high spectral transmittance while absorbing light in the infrared light range. As an example of the oxocarbon-based compound, it is preferable to use a squarylium compound and/or a croconium compound that has an absorption wavelength of at least 700 nm or more and 750 nm or less and has a relatively high spectral transmittance in the visible light region.

The infrared light absorbing resin member 12 may be a coated material provided by coating. Specifically, the infrared light absorbing resin member 12 may be a coating layer. Therefore, the coating layer thickness is, for example, thicker than a single film of a typical chemical vapor deposition film and/or physical vapor deposition film. It is preferable that the coating material is obtained by dissolving the resin material described above in a solvent. Solvents include, for example, ketones such as methyl ethyl ketone; glycol derivatives such as PGMEA (2-acetoxy-1-methoxypropane) (ether compounds, ester compounds, ether ester compounds, etc.); amides such as N,N-dimethylacetamide. pyrrolidones such as ethyl acetate; aromatic hydrocarbons such as toluene; aliphatic hydrocarbons such as cyclohexane; ethers such as tetrahydrofuran; These solvents may be used alone or in combination of two or more.

The resin material dissolved in the solvent may contain an infrared light absorbing dye other than the oxocarbon compound. Also, the infrared light absorbing pigment may be an infrared light absorbing pigment. Examples of infrared light absorbing dyes include cyclic tetrapyrrole dyes, cyanine dyes, and azo dyes. When such an infrared light absorbing dye is contained, the infrared light absorbing effect can be enhanced.

A preferred embodiment of the infrared light absorbing resin member 12 may be a single layer. The term "single layer" as used herein refers to a layer composed of the same type of component, and is meant to exclude a laminated structure in which two or more layers composed of different types of components are laminated. In other words, the purpose is to eliminate the reflection of light at the interface of each layer by stacking layers having different refractive indices. Therefore, according to the single-layer infrared light absorbing resin member 12, it is possible to suppress the wavelength shift of the optical characteristics due to the oblique incidence.

From the viewpoint of optical properties, the upper limit of the thickness of the infrared light absorbing resin member 12 may be, for example, 1 mm or less, 500 μm or less, 200 μm or less, or 50 μm or less. When a resin material dissolved in a solvent and made into a paint is applied onto the translucent member 11 by spin coating, the thickness of the infrared light absorbing resin member 12 can be made even thinner.

Here, FIG. 2 shows an example of spectral transmittance characteristics of the infrared light absorbing resin member 12 . According to the spectral transmittance characteristics, the infrared light absorbing resin member 12 has a spectral transmittance of 90% or more for light with a wavelength of 459 to 580 nm. rate is 97.8%. The spectral transmittance is higher than that of IR cut glass.

Furthermore, the infrared light absorbing resin member 12 has a characteristic of less than 1% spectral transmittance for light with a wavelength of 698 to 755 nm. That is, at least light with a wavelength of 700 nm or more and 750 nm or less is absorbed without being reflected.

Furthermore, the absorption wavelength region absorbed by the infrared light absorbing resin member 12 corresponds to the wavelength width in which the transmission characteristics of the infrared light shielding film 13 described later shift due to the light obliquely incident on the optical filter 10 .

Furthermore, the infrared light absorbing resin member 12 preferably has a characteristic of having a spectral transmittance of 90% or more for light with a wavelength of 795 nm or more. That is, it has a characteristic of transmitting light with a wavelength of at least 800 nm or more. Therefore, it is necessary to shield the light of the wavelength by the infrared light shielding film 13, which will be described later.

Furthermore, according to FIG. 2, the infrared light-absorbing resin member 12 preferably has the property of not transmitting light in the ultraviolet region. Therefore, the infrared light shielding film 13, which will be described later, may transmit light in the ultraviolet region.

- Infrared light shielding film -
The infrared light shielding film 13 is disposed on the other main surface 11b of the translucent member 11 and shields at least infrared light transmitted through the infrared light absorbing resin member 12 . As an example, the infrared light shielding film 13 is a film that transmits light in the visible light region. The infrared light shielding film 13 may transmit light in the ultraviolet region.

The infrared light shielding film 13 is a multilayer film including a low refractive index layer and a high refractive index layer. By low refractive index is meant here materials with a refractive index of less than 1.6, more preferably between 1.35 and 1.55. Also, high refractive index means a material with a refractive index of 1.6 or more, more preferably a material with a refractive index of 2.2 to 2.5. As an example, the low refractive index layer includes at least one selected from the group consisting of _SiOx , _SiNx and _MgFx , and the high refractive index layer is selected from the group consisting of _TiOx , _ZrOx and _TaOx . contains at least one In addition, in this specification, the refractive index intends the refractive index for light with a wavelength of 589 nm at 20°C.

The infrared light shielding film 13 is designed to transmit at least light with a wavelength of 400 nm or more and 765 nm or less. That is, the low refractive index layers and the high refractive index layers are alternately laminated so as to transmit light of the above wavelengths. As an example, it is preferable to set the total number of layers to 40 to 50 layers, with the thickness of the SiO ₂ layer and the Ti ₂ O ₃ layer having a thickness of about 5 to 60 nm. In other words, the total film thickness of the infrared light shielding film 13 is preferably 5 μm or less. In other words, the thickness of the infrared light shielding film 13 is preferably set thinner than the thickness of the infrared light absorbing resin member 12 .

The low refractive index layer and the high refractive index layer in the infrared light shielding film 13 may be deposited films. The method of forming the vapor deposition film may be performed by a vapor deposition device. Alternatively, the film may be formed using a sputtering device.

FIG. 3 shows an example of spectral transmittance characteristics of the infrared light shielding film 13. FIG. According to the spectral transmittance characteristics, the infrared light shielding film 13 has a spectral transmittance of more than 1% for light with a wavelength of 390 nm, and a spectral transmittance of more than 90% for light with a wavelength of 402 nm. Further, the spectral transmittance of light with a wavelength of 737 nm is less than 90%, and the spectral transmittance of light with a wavelength of 765 nm or longer is less than 1%, thereby shielding light. That is, since the infrared light-absorbing resin member 12 blocks the infrared light that is transmitted therethrough, it is possible to reduce ghosts, flares, etc. caused by the infrared light.

Furthermore, the infrared light shielding film 13 transmits at least light of 400 to 765 nm. More specifically, the absorption wavelength range (700 to 755 nm) in which the infrared light absorbing resin member 12 absorbs infrared light is included in the wavelength range (390 to 765 nm) of light transmitted by the infrared light shielding film 13. It is According to such a configuration, even if the optical filter 10 is obliquely incident at an angle of about ±30° and the spectral transmittance shifts to the short wavelength side by about 20 to 30 nm, the influence of infrared light due to the shift can be reduced. That is, the shift in spectral transmittance due to oblique incidence described above corresponds to the absorption wavelength region of the infrared light absorbing resin member 12 .

Note that the infrared light shielding film 13 of the present disclosure exemplifies a mode of shielding light with a wavelength of less than 390 nm. The external light shielding film 13 may transmit light of the wavelength. In other words, light in the ultraviolet region may be transmitted.

- Antireflection film (additional structure) -
In the optical filter 10 of this embodiment, an antireflection film 14 may be provided on one main surface 11a of the translucent member 11 . Specifically, the antireflection film 14 is provided on one main surface 11a of the translucent member 11 with the infrared light absorbing resin member 12 interposed therebetween.

The antireflection film 14 is a film having a function of improving spectral transmittance by preventing reflection of light incident on the optical filter 10 and efficiently utilizing the incident light. Materials that can be used as the antireflection coating 14 include, for example, SiO _x or MgF _x used as a single-layer antireflection coating, or TiO _x , ZrO _x or TaO _x used in combination.

The antireflection film 14 may be a vapor deposition film. The method of forming the vapor deposition film may be performed by a vapor deposition device. Alternatively, the film may be formed using a sputtering device.

[Imaging device of the present disclosure]
Next, the imaging device 1 of the present disclosure will be described. The imaging device of the present disclosure includes the optical filter 10 and the imaging element S described above. It should be noted that an optical component such as a lens L for allowing light to enter the optical filter 10 may be provided.

The image sensor S is intended to be a component that converts light into electrical signals. For example, a CCD or CMOS sensor or the like may be used.

The imaging element S is preferably arranged on one main surface 11a side of the translucent member 11 . Specifically, the imaging device S is provided on one main surface 11a side of the translucent member 11 with an infrared light absorbing resin member 12 interposed therebetween. That is, the distance from the imaging device S to the infrared light absorbing resin member 12 is shorter than the distance from the imaging device S to the infrared light shielding film 13 .

With such an arrangement, it is possible to reduce the influence of wavelength shift due to oblique incidence. More specifically, from the viewpoint of preventing the imaging device S from detecting reflected light from each layer of the infrared light shielding film 13, which is a multilayer film, the distance between the image sensor S and the infrared light shielding film 13 is set as much as possible. They are arranged apart from each other to reduce ghosts, flares, and the like that occur in the imaging device 1 .

A verification test was conducted on the "optical filter" according to the present disclosure. Specifically, optical filters of Comparative Examples and Examples shown below were manufactured. Since the antireflection film is an optional additional structure, the description thereof is omitted.

<Optical Filters of Examples>
An optical filter comprising a translucent member 11 shown in FIG. 1, an infrared light absorbing resin member 12, and an infrared light shielding film 13.
・ Translucent member: Clear glass (D263Teco manufactured by SHOTT, thickness 0.7 mm)
・Infrared light absorbing resin material: Nippon Shokubai Co., Ltd. (Part number: KT-B)
・Infrared light shielding film: multilayer film containing SiO ₂ and Ti ₂ O ₃

<Optical filter of comparative example>
An optical filter comprising an IR cut glass 11' and an optical multilayer film 13' shown in FIG. 5 without using an infrared light absorbing resin member.
・ IR cut glass: (QB52 manufactured by Chengdu Guangming Photoelectric Co., Ltd., thickness 0.7 mm)
- Optical multilayer film: _multilayer film containing _SiO2 and _Ti2O3

The spectral transmittance was measured using Hitachi U-4100, the measurement wavelength range was 350 to 1200 nm, the light source was a 50 W halogen lamp, and the measurement mode was transmittance (%T).

The spectral transmittance of the optical filter of Example is shown in FIG. 4, and the spectral transmittance of the optical filter of Comparative Example is shown in FIG. The spectral transmittance of the infrared light-absorbing resin member and the spectral transmittance of the infrared light shielding film of the example are the same as those shown in FIGS.

The optical filters of Examples have a spectral transmittance of less than 90% at a wavelength of 579 nm and a spectral transmittance of less than 1% at a wavelength of 697 nm.
(90%−1%)/(579 nm−697 nm)=−0.75
can be calculated.
On the other hand, the optical filter of the comparative example has a spectral transmittance of less than 90% at a wavelength of 549 nm and a spectral transmittance of less than 1% at a wavelength of 691 nm.
(90%−1%)/(549 nm−691 nm)=−0.62
can be calculated.
In other words, the optical filters of the examples have steeper filter characteristics than the optical filters of the comparative examples, and the result that infrared light can be blocked appropriately was obtained.

Further, in the optical filters of the examples, even if wavelength shift occurs due to oblique incidence at an angle of about ±30°, the absorption wavelength region (390 to 765 nm) of the infrared light absorbing resin member is the same as that of the infrared light shielding film. Since it is included in the wavelength region (700 to 755 nm) of transmitted light, the influence of infrared light caused by the shift can be reduced, and ghosts, flares, etc. can be reduced.
On the other hand, in the optical filter of the comparative example, when a wavelength shift occurs due to oblique incidence, light caused by the wavelength shift is detected by the imaging device, and ghosts, flares, and the like occur.

Further, the optical filters of Examples exhibited a relatively high spectral transmittance of 97.5% between 510 and 520 nm.
On the other hand, the optical filter of the comparative example had a spectral transmittance of 96.1% between 495 and 500 nm, which was lower than the spectral transmittance of the optical filter of the example.

It should be noted that the embodiments disclosed this time are examples in all respects and are not grounds for restrictive interpretation. Therefore, the technical scope of the present disclosure is not to be construed solely by the above-described embodiments, but is defined based on the claims. In addition, the technical scope of the present disclosure includes all modifications within the meaning and range of equivalence to the claims.

The technical idea of the present disclosure can be applied to optical filters and imaging devices.

Reference Signs List 1, 1' imaging device 10, 10' optical filter 11 translucent member 11a one main surface 11b the other main surface 11' IR cut glass 12 infrared light absorbing resin member 13 infrared light shielding film 13' optical multilayer film 14 antireflection film L lens S imaging device

Claims

a translucent member having one principal surface and the other principal surface facing the one principal surface;
an infrared light absorbing resin member provided on the one main surface of the translucent member;
and an infrared light shielding film provided on the other main surface of the translucent member and shielding infrared light transmitted by the infrared light absorbing resin member.
The optical filter according to claim 1, wherein the absorption wavelength range in which the infrared light absorbing resin member absorbs infrared light is included in the wavelength range of light transmitted by the infrared light shielding film.
The optical filter according to claim 2, wherein the absorption wavelength region is at least 700 nm or more and 750 nm or less.
The optical filter according to claim 2 or 3, wherein the absorption wavelength region is a wavelength width in which the transmission characteristics of the infrared light shielding film are shifted by light obliquely incident on the optical filter.
The optical filter according to any one of claims 1 to 4, wherein the infrared light absorbing resin member has a property of transmitting light with a wavelength of 800 nm or more.
The optical filter according to any one of claims 1 to 5, wherein the infrared light absorbing resin member has a property of not transmitting light in the ultraviolet region.
The optical filter according to any one of claims 1 to 6, wherein the infrared light absorbing resin member contains an oxocarbon compound.
The optical filter according to any one of claims 1 to 7, wherein the infrared light absorbing resin member is a coated material containing an infrared light absorbing dye.
The optical filter according to any one of claims 1 to 8, wherein the infrared light shielding film is a vapor deposition film.
The optical filter according to any one of claims 1 to 9, wherein the infrared light shielding film transmits light with a wavelength of at least 400 nm or more and 765 nm or less.
The optical filter according to any one of claims 1 to 10, wherein the infrared light absorbing resin member has a thickness greater than that of the infrared light shielding film.
an optical filter according to any one of claims 1 to 11;
and an imaging device,
An image pickup device, wherein the image pickup element is arranged on the one main surface side of the translucent member.