Infrared cut-off filter, camera structure, and method for manufacturing infrared cut-off filter

Abstract

An infrared cut filter (1) for a digital camera according to the present invention is provided with: a near-infrared reflective filter (Fref1) configured so that high-refractive-index layers (Hind) formed from a high-refractive-index resin and low-refractive-index layers (Lind) formed from a low-refractive-index resin are alternately laminated; and an infrared absorbing film filter (Fab1), the near-infrared reflective filter (Fref1) being configured so that the high-refractive-index layers (Hind) and the low-refractive-index layers (Lind) are alternately laminated. The infrared absorbing film filter (Fab1) is configured from a translucent resin containing a dye or a translucent resin coated with a dye. As a result, provided is an infrared cutoff filter in which image quality degradation such as ghosting glare and coloring is suppressed and mass production efficiency is dramatically improved.

Description

Technical Field

[0001] The present invention relates to an infrared cut filter provided in a digital camera or the like. Background Art

[0002] A quarter of a century has passed since the practical application of CMOS image sensors, allowing digital cameras to replace film cameras as the mainstay. Today, digital cameras are an indispensable component of portable information devices, such as smartphones, as well as in-car cameras, web cameras, and security devices. Digital cameras vary greatly in size, from high-end SLR cameras, which are the same size as conventional interchangeable lens cameras, to compact camera modules built into smartphones, which have a volume ratio of approximately 1 / 400 that of high-end SLR cameras. In terms of production volume, the production of compact camera modules built into smartphones and other devices is overwhelmingly high. Over the past decade, production of compact camera modules has increased by approximately 700 times that of dedicated digital cameras, and currently production is estimated to be around 6 billion units per year. Furthermore, smartphones used to be equipped with a single compact camera module, but now, with the increasing trend towards multi-lens cameras, a single smartphone may contain three to five compact camera modules. The trend toward multiple lenses is driven by the increasing thinness of smartphones, which limits the space available for compact camera modules along the optical axis. This makes it difficult for a single compact camera module to handle lens functions from ultra-wide-angle to telephoto, leading to a more dispersed design. High-end SLR digital cameras, on the other hand, maintain ample space along the optical axis, allowing a single lens module to handle functions from ultra-wide-angle to telephoto.

[0003] On the other hand, because the sensitivity curve of CMOS sensors in compact camera modules extends beyond the visible light wavelength range (380nm to 780nm) into the near-infrared region (wavelength approximately 1.1μm), the image captured directly has a different color tone from what the human eye sees. Therefore, infrared cut filters (IRCFs) that block near-infrared (NIR) light are essential for CMOS image sensors. In the early days of digital cameras, IR cut filters with multilayer films that only reflect NIR light were used, but they were prone to image quality degradation caused by ghosting, flare, and shading. Consequently, current IR cut filters (IRCFs) incorporate filters that absorb NIR light.

[0004] An infrared cutoff filter is typically installed between the CMOS image sensor and the lens module. It consists of a combination of a near-infrared absorption filter that absorbs near-infrared light and converts it into heat, a near-infrared reflection filter composed of an inorganic dielectric multilayer film, and an antireflection film formed on the interface between these filters and the air (see, for example, Japanese Patent Application Laid-Open No. 2006-182586).

[0005] The characteristics of an infrared cutoff filter are the combined value of the individual characteristics of the near-infrared absorption filter, the near-infrared reflection filter, and the anti-reflection film. While infrared cutoff filters may have a single, integrated structure where the near-infrared absorption filter, near-infrared reflection filter, and anti-reflection film are combined into one piece, or structures where the near-infrared absorption filter and near-infrared reflection filter are separated within the optical path, the combined characteristic value remains unchanged. Summary of the Invention

[0006] Technical issues Current compact camera modules are approximately 8mm thick along the optical axis and incorporate components such as six to seven lenses, various filters, a CMOS image sensor, and a lens actuator with a 1.5mm range of motion. Consequently, the inter-component distances between components approach their limits, making it prone to image quality degradation due to ghosting and flare caused by repeated reflections between components.

[0007] At the same time, even in compact camera modules, demand for higher resolution is increasing, leading to an increasing number of models equipped with CMOS image sensors whose pixel pitch has been reduced to less than 2μm (particularly sub-μm CMOS image sensors with a pixel pitch of less than 1μm). As a result, the trade-off for higher resolution is the occurrence of petal-shaped ghost images. Consequently, compact camera modules suffer from numerous issues with image quality degradation, contributing to the prolonged development lead times for these modules.

[0008] In view of such actual circumstances, the present invention provides an infrared cut filter that suppresses image quality degradation such as ghosting, flare, and coloration and improves mass productivity.

[0009] Technical Solution The infrared cutoff filter of the present invention, which achieves the above-mentioned object, is an infrared cutoff filter for use in digital cameras and is characterized by comprising: a near-infrared reflection filter composed of a high-refractive index layer formed of a high-refractive index resin and a low-refractive index layer formed of a low-refractive index resin alternately stacked; and an infrared absorption film filter composed of a light-transmitting resin containing a pigment or a light-transmitting resin coated with a pigment.

[0010] The infrared cut filter may further include an antireflection portion formed on a surface of the near-infrared reflection filter and / or the infrared absorption film filter that is in contact with air.

[0011] The infrared cut filter is characterized in that the high refractive index resin, the low refractive index resin, and the light-transmitting resin constituting the infrared absorbing film filter may be composed of organic resins.

[0012] The infrared cut filter is characterized in that the high refractive index resin, the low refractive index resin, the light-transmitting resin constituting the infrared absorbing film filter, and the anti-reflection portion may be formed of an organic resin.

[0013] Regarding the infrared cut filter, the near-infrared reflection filter may be formed by co-extruding the high refractive index layer and the low refractive index layer.

[0014] The infrared cut filter is characterized in that the thickness of each of the high refractive index layer and / or the low refractive index layer may be within a range of 10 nm to 300 nm.

[0015] The infrared cut filter may include the high refractive index layer and the low refractive index layer, each including 30 or more layers in total.

[0016] The infrared cutoff filter is characterized in that the entire thickness of the near-infrared reflection filter may be 100 μm or less.

[0017] The infrared cut filter is characterized in that the near-infrared reflection filter and the infrared absorption film filter can be integrated.

[0018] The infrared cut filter is characterized in that at least one of the high-refractive-index resin and the low-refractive-index resin contains the pigment, thereby allowing the infrared cut filter to also serve as the infrared absorbing film filter.

[0019] The infrared cut filter described above may be characterized in that the antireflection portion may be a structure having projections and depressions formed on a surface of the light-transmitting resin.

[0020] The infrared cut filter is characterized in that the antireflection portion may have a multilayer film structure in which a low-refractive-index resin film and a high-refractive-index resin film are alternately laminated.

[0021] The infrared cut filter is characterized in that a part of the plurality of high refractive index layers and the plurality of low refractive index layers in the near infrared reflection filter can also serve as the low refractive index resin film and the high refractive index resin film of the antireflection portion.

[0022] Regarding the above-mentioned infrared cutoff filter, it is characterized in that the near-infrared reflection filter and the infrared absorption film filter can be bonded to each other to form a whole, and the first anti-reflection film can be formed on the surface of the near-infrared reflection filter on the opposite side of the infrared absorption film filter, and the second anti-reflection film can be formed on the surface of the infrared absorption film filter on the opposite side of the near-infrared reflection filter.

[0023] The infrared cut filter described above is characterized in that the antireflection portion may be a moth-eye structure in which projections and depressions are formed on a surface of a light-transmitting resin.

[0024] The infrared cut filter may be characterized in that the total thickness of the near-infrared reflection filter, the infrared absorption film filter, and the anti-reflection portion may be 300 μm or less.

[0025] The infrared cutoff filter is characterized in that the film thickness occupancy of the near-infrared reflection filter is 20% or more based on the total thickness of the near-infrared reflection filter, the infrared absorption film filter, and the anti-reflection portion.

[0026] The infrared cutoff filter is characterized in that the film thickness occupancy rate of the infrared absorbing film filter is 20% or more based on the total thickness of the near-infrared reflecting filter, the infrared absorbing film filter and the anti-reflection portion.

[0027] Regarding the above-mentioned infrared cutoff filter, it is characterized in that, in the near-infrared reflective filter monomer, when the wavelength at which the light transmittance decreases to 50% as the wavelength of the incident light increases is defined as the reflective film cutoff wavelength, the reflective film cutoff wavelength when the incident angle of the incident light is 0° can be in the range of 750nm to 900nm.

[0028] Regarding the above-mentioned infrared cutoff filter, it is characterized in that, in the near-infrared reflective filter unit, when the wavelength at which the transmittance of light decreases to 50% as the wavelength of the incident light increases is defined as the reflective film cutoff wavelength, the wavelength fluctuation range of the reflective film cutoff wavelength can be made less than 150nm when the incident angle of the incident light varies within the range of 0° to 60°.

[0029] Regarding the above-mentioned infrared cutoff filter, it is characterized in that when the wavelength of 440nm of the incident light is defined as the reference blue wavelength, for the near-infrared reflection filter monomer, the transmittance of the near-infrared reflection filter monomer at the reference blue wavelength when the incident angle of the incident light is set to 60° can be greater than 70%.

[0030] Regarding the above-mentioned infrared cutoff filter, it is characterized in that the wavelength of 450nm to 500nm of the incident light can be defined as a low-wavelength transmittance band. In the near-infrared reflective filter monomer, when the average transmittance of the incident light in the low-wavelength transmittance band is defined as the low-wavelength transmittance of the reflective film, the low-wavelength transmittance of the reflective film can be made to be greater than 75% when the incident angle of the incident light varies within the range of 0° to 60°.

[0031] The present invention for achieving the above object is characterized in that the resin constituting the near-infrared reflection filter and / or the infrared absorption film filter may contain an ultraviolet absorber.

[0032] The camera structure of the present invention for achieving the above-mentioned purpose is characterized in that it is a digital camera structure having an optical lens group arranged on the incident side of light, and a shooting element that receives light incident through the optical lens group, and the above-mentioned infrared cutoff filter is arranged between the optical lens group and the shooting element.

[0033] The camera structure of the present invention for achieving the above-mentioned purpose is characterized in that it is a digital camera structure that includes a cover glass, an optical lens group, and a shooting element in sequence from the light incident side, and has the above-mentioned infrared cutoff filter, the near-infrared reflection filter is arranged between the cover glass and the optical lens group, and the infrared absorption film filter is arranged between the optical lens group and the shooting element.

[0034] Regarding the above-mentioned camera structure, it is characterized in that the near-infrared reflection filter can be attached to the cover glass.

[0035] The method for manufacturing an infrared cutoff filter of the present invention, which achieves the above-mentioned object, is characterized in that it is a method for manufacturing an infrared cutoff filter for a digital camera, comprising: a reflective film manufacturing step of alternately laminating a high refractive index layer formed of a high refractive index resin and a low refractive index layer formed of a low refractive index resin by co-extrusion molding to form a near-infrared reflective filter; and a chip processing step of forming the near-infrared reflective filter into a desired shape by at least cutting or punching.

[0036] The method for manufacturing the above-mentioned infrared cutoff filter is characterized in that it can include an integration step, in which an infrared absorption film filter is stacked or bonded to the near-infrared reflection filter, and the infrared absorption film filter is composed of a translucent resin containing a pigment or a translucent resin for an absorption film coated with a pigment.

[0037] Regarding the manufacturing method of the above-mentioned infrared cutoff filter, it is characterized in that the high refractive index resin, the low refractive index resin and the translucent resin containing a pigment that absorbs infrared rays can be co-extruded in the reflective film manufacturing process, so that the near-infrared reflection filter and the infrared absorption film filter are integrally formed, the near-infrared reflection filter is alternately stacked with high refractive index layers formed by the high refractive index resin and low refractive index layers formed by the low refractive index resin, and the infrared absorption film filter is formed by the translucent resin.

[0038] Regarding the manufacturing method of the above-mentioned infrared cut-off filter, it is characterized in that, in the reflective film manufacturing process, after making any one of the high refractive index resin and the low refractive index resin contain a pigment that absorbs infrared rays, the high refractive index resin and the low refractive index resin are co-extruded to form a near-infrared reflection filter and an infrared absorption film filter as one piece, the near-infrared reflection filter is alternately stacked with a high refractive index layer formed by the high refractive index resin and a low refractive index layer formed by the low refractive index resin, and the infrared absorption film filter is formed by the side of the high refractive index layer and the low refractive index layer containing the pigment.

[0039] The above-mentioned method for manufacturing an infrared cut filter may further include an anti-reflection film adding step, which is performed before the chip processing step, and forms an anti-reflection film on the surface in contact with air.

[0040] The above-mentioned method for manufacturing an infrared cut filter may further include a mask adding step, which is performed before the chip processing step, of printing a light-shielding mask.

[0041] The method for manufacturing the infrared cutoff filter is characterized in that, in the integration step, the rolled near-infrared reflective filter and the rolled infrared absorbing film filter are fed to a laminating device for integration and wound into a roll.

[0042] Technical Effects According to the present invention, it is possible to obtain an infrared cut filter in which image quality degradation such as ghosting, flare, and coloration is suppressed and mass production efficiency is dramatically improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1It is a cross-sectional view of the infrared cut filter according to the first embodiment of the present invention.

[0044] Figure 2 It is a cross-sectional view showing an enlarged view of a near-infrared reflection filter of the infrared cut filter.

[0045] Figure 3 : is a spectroscopic graph showing the transmission characteristics of the near-infrared reflection filter.

[0046] Figure 4 Spectral graphs showing transmission characteristics of conventional near-infrared reflection filters for comparative purposes.

[0047] Figure 5 This is a graph showing the incident angle dependency characteristics of the near-infrared reflection filter according to the additional example of the first embodiment, classified by wavelength.

[0048] Figure 6 This is a graph showing the incident angle dependency characteristics of the near-infrared reflection filter of Comparative Example 1 according to wavelength.

[0049] Figure 7 This is a graph showing the incident angle dependency characteristics of the near-infrared reflection filter of Comparative Example 2 according to wavelength.

[0050] Figure 8 This is a spectral chart showing the absorption characteristics of the infrared absorbing film filter of the infrared cut filter according to the first embodiment.

[0051] Figure 9 This is an enlarged view showing the cross-sectional shape and refractive index of the antireflection film of the infrared cut filter according to the first embodiment.

[0052] Figure 10 Spectral graphs showing the transmission characteristics and reflection characteristics of the antireflection film.

[0053] Figure 11 It is a side view showing the structure of a laminating device used in the laminating step.

[0054] Figure 12 It is a side view showing the structure of a film forming apparatus used in the anti-reflection film adding step.

[0055] Figure 13 This is a spectral graph showing the overall optical characteristics of the infrared cut filter according to the first embodiment.

[0056] Figure 14 Spectral graphs showing the overall optical characteristics of the infrared cut filter of Comparative Example 3.

[0057] Figure 15This is a cross-sectional view of a camera module incorporating the infrared cut filter according to the first embodiment.

[0058] Figure 16 (A) is a cross-sectional view of an infrared cut filter according to a second embodiment of the present invention. Figure 16 (B) is a cross-sectional view of a camera module incorporating the infrared cut filter.

[0059] Figure 17 (A) is a cross-sectional view of an infrared cut filter according to a third embodiment of the present invention. Figure 17 (B) is a cross-sectional view of an infrared cut filter according to a fourth embodiment of the present invention. Figure 17 (C) is a cross-sectional view of the infrared cut filter according to the fifth embodiment.

[0060] Figure 18 (A) is a cross-sectional view of an infrared cut filter according to a sixth embodiment of the present invention. Figure 18 (B) is a cross-sectional view of an infrared cut filter according to a seventh embodiment of the present invention. Figure 18 (C) is a cross-sectional view of the infrared cut filter according to the eighth embodiment.

[0061] Figure 19 (A) is the use of Figure 15 The image captured by the camera module of this embodiment shown in FIG. Figure 19 (B) is an image captured by a conventional camera module serving as a comparative example.

[0062] Figure 20 (A) is the use of Figure 15 The image captured by the camera module of this embodiment shown in FIG. Figure 20 (B) is an image captured by a conventional camera module serving as a comparative example.

[0063] Figure 21 It is an image captured using an existing camera module.

[0064] Figure 22 (A) is a cross-sectional view of an infrared cut filter according to a ninth embodiment of the present invention. Figure 22 (B) is a cross-sectional view of a camera structure incorporating the infrared cut filter.

[0065] Explanation of symbols 1, 101, 201, 301, 401, 501, 601, 701, 901 infrared cutoff filters 20 Camera Module 30 Magnetic Brackets 40 lens carrier 50 lens units 70 camera elements 80 substrate 120 Camera Module AB absorption component CT Adhesive Coating Device CT1 first coating device CT2 Second coating device Fab1 infrared absorption film filter Far1 Anti-Reflective Coating Fref1 Near-infrared reflection filter Hind high refractive index layer Lind low refractive index layer M light shielding mask MS film forming equipment PR1 First Transfer Roller PR2 Second Transfer Roller REF reflective component RR Laminating Roller RS Lamination Unit DETAILED DESCRIPTION

[0066] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0067] The cross-sectional structure of the infrared cut filter 1 according to the first embodiment of the present invention is shown in FIG. Figure 1 . The infrared cutoff filter 1 is an infrared cutoff filter for digital cameras, and includes a near-infrared reflection filter Fref1, an infrared absorption film filter Fab1, an anti-reflection film (anti-reflection portion) Far1, and a light-shielding mask M. The near-infrared reflection filter Fref1 is constructed by alternatingly stacking high-refractive index layers formed of a high-refractive index resin for a reflection film and low-refractive index layers formed of a low-refractive index resin for a reflection film. The infrared absorption film filter Fab1 is composed of a light-transmitting resin for an absorption film containing a pigment or a light-transmitting resin for an absorption film coated with a pigment. The anti-reflection film Far1 is formed on the surface of the near-infrared reflection filter Fref1 and / or the infrared absorption film filter Fab1 that is in contact with air, and the anti-reflection film Far1 is composed of a light-transmitting resin for anti-reflection. Below, each component is described in detail separately.

[0068] <Near-infrared reflection filter> (Membrane Structure of This Embodiment) like Figure 2As shown in the enlarged image, the near-infrared reflective filter Fref1 of this embodiment is constructed by alternating layers of high-refractive-index layers Hind formed from a high-refractive-index resin for a reflective film, and low-refractive-index layers Lind formed from a low-refractive-index resin for a reflective film. The multilayer formation of the high-refractive-index layers Hind and the low-refractive-index layers Lind can be achieved using co-extrusion or spin coating. In this embodiment, co-extrusion using a T-die is employed. In the co-extrusion method, the high-refractive-index resin for a reflective film and the low-refractive-index resin for a reflective film, in an amount consistent with the number of layers required for the stacked structure, are extruded together, and the layers are allowed to merge and flow out of the T-die in a film-like state, thereby simultaneously performing film formation and lamination (bonding). It should be noted that this method can be adopted in a multi-manifold method, in which the individual layers of the high-refractive-index layer Hind and the low-refractive-index layer Lind are formed into films within a T-die and then combined, or in a feedblock method, in which the high-refractive-index resin for the reflective film and the low-refractive-index resin for the reflective film are combined before forming the individual layers into films, and then the films are concentrated within the T-die to form a film. Coextrusion allows for the alternating lamination of hundreds (e.g., several hundred) or thousands of layers of high-refractive-index layers Hind and low-refractive-index layers Lind, which are difficult to form into films on their own, to form a long near-infrared reflective filter Fref1. While the coextrusion method using a T-die is described here, a coextrusion method based on inflation can also be employed.

[0069] The high-refractive-index resin for the reflective film and the low-refractive-index resin for the reflective film can be selected from a variety of resins, as long as they are transparent resins with different refractive indices between adjacent films. For example, at least two resins can be selected from acrylic resins, polyester resins (e.g., polyethylene terephthalate), polycarbonate resins, polystyrene resins, polyethylene resins, polypropylene resins, cellulose resins, olefin resins, fluorine resins, vinyl resins, and the like.

[0070] As the high refractive index resin for the reflective film, for example, it is preferable to select from resins having a refractive index of 1.53 or higher, specifically polyester resins, polystyrene resins, polyethylene resins, polycarbonate resins, acrylic resins, and vinyl resins, and it is more preferable to select from resins having a refractive index of 1.56 or higher, specifically polystyrene resins, polyester resins, and polycarbonate resins.

[0071] The low-refractive-index resin used in the reflective film is preferably selected from resins with a refractive index of less than 1.53, specifically ethylene resins, polypropylene resins, acrylic resins, cellulose resins, and fluorine resins. More preferably, resins with a refractive index of less than 1.50 are selected, specifically ethylene resins (polyvinyl alcohol), polypropylene resins, acrylic resins (e.g., polymethyl methacrylate resins), cellulose resins, and fluorine resins. It should be noted that the refractive index can also be adjusted by using multiple resins selected from these resins, or copolymers formed by (co)polymerizing these resins with other resins. Furthermore, the alternately stacked high-refractive-index layers Hind and low-refractive-index layers Lind do not necessarily all need to be made of the same resin material, and similarly, the multiple low-refractive-index layers Lind do not all need to be made of the same resin material.

[0072] Furthermore, to fine-tune the refractive index, additives for adjusting the refractive index can be added to the high-refractive-index resin and / or the low-refractive-index resin for the reflective film. Furthermore, the refractive index can be adjusted by blending multiple resins. To further improve UV resistance, quenchers (matting pigments) such as sulfur compounds can be added to the high-refractive-index resin and / or the low-refractive-index resin for the reflective film.

[0073] The thickness of each of the high-refractive-index layer Hind and the low-refractive-index layer Lind is preferably set to a thickness of λ / 4 or less, assuming the wavelength (or wavelength band) to be reflected is λ. For example, in this embodiment, since light within the wavelength λ range of 600 nm to 1200 nm is required to be reflected, the thickness of each of the high-refractive-index layer Hind and the low-refractive-index layer Lind is set to be, for example, 400 nm or less.

[0074] When using a high-refractive-index resin for the reflective film and a low-refractive-index resin for the reflective film, the refractive index difference must be set smaller than that of existing dielectric films, resulting in a lower reflectivity of near-infrared light at each boundary unit. Therefore, in order to achieve high reflectivity of near-infrared light, in this embodiment, the thickness of each film is reduced while the number of layers is increased. More specifically, in this embodiment, the thickness of each high-refractive-index layer Hind and low-refractive-index layer Lind is, for example, preferably 200 nm or less, more preferably 100 nm or less, even more preferably 80 nm or less, and even more preferably 50 nm or less. In this embodiment, the thickness is set to 15 nm, which is less than 20 nm. In addition, the total number of layers of the alternating high-refractive-index layers Hind and low-refractive-index layers Lind is preferably 30 or more, more preferably 100 or more, and even more preferably 200 or more. Even more preferably, it is 300 or more, with 400 layers being used, for example.

[0075] By reducing the thickness of each film, the entire film thickness of the near-infrared reflection filter Fref1 is preferably 100 μm or less, more preferably 50 μm or less. Note that, from the perspective of handling during mass production, the entire film thickness of the near-infrared reflection filter Fref1 is preferably 10 μm or more, more preferably 30 μm or more.

[0076] As described above, the infrared-absorbing film filter Fab1 of this embodiment utilizes an organic resin as its base material, making material selection and refractive index adjustment through additives and / or resin mixing easy. This allows for flexible setting of the refractive index difference between the high-refractive-index layer Hind and the low-refractive-index layer Lind. Furthermore, by employing a co-extrusion process, the thickness of each film can be controlled to less than 1 μm. Furthermore, the film's properties are not degraded during the demolding process described later.

[0077] (reflective properties) Figure 3 The reflection characteristics of the near-infrared reflection filter Fref1 alone are shown. Here, the wavelength at which the light transmittance of the near-infrared reflection filter Fref1 decreases to 50% as the wavelength of the incident light increases is defined as the "reflection film cutoff wavelength." When the incident light angle is 0° (i.e., perpendicular to the film), the reflection film cutoff wavelength is set within the range of 750nm to 900nm. More specifically, the reflection film cutoff wavelength is set within the range of 750nm to 880nm, more specifically within the range of 770nm to 880nm, and even more specifically within the range of 780nm to 880nm.

[0078] Furthermore, in this embodiment, the fluctuation range (wavelength shift) Sref1 of the reflective film cutoff wavelength when the incident light angle varies within the range of 0° to 60° is 170 nm or less, preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 100 nm or less. In other words, the wavelength difference between the reflective film cutoff wavelength at an incident angle of 0° and the reflective film cutoff wavelength at an incident angle of 60° is 150 nm or less. As the camera module becomes thinner, light with a larger incident angle is more likely to reach the near-infrared reflective filter Fref1. However, in this embodiment, the near-infrared reflective filter Fref1 suppresses the wavelength shift Sref1 of the reflective film cutoff wavelength toward shorter wavelengths, enabling high-quality imaging. The reflective film cutoff wavelength at an incident angle of 60° is preferably set to 650 nm or greater, but this does not need to be less than the infrared absorption film cutoff wavelength of the infrared absorption filter Fab1 at an incident angle of 60°. This reduces the chance of image distortion.

[0079] Furthermore, the wavelength range in which the transmittance of light through the near-infrared reflection filter Fref1 decreases to 10% or less is defined as the "reflection film total reflection wavelength range." The reflection film total reflection wavelength range Wref1 at an incident angle of 0° is approximately 790 nm to 1100 nm. It should be noted that the reflection film total reflection wavelength range Wref1 fluctuates (shifts) toward shorter wavelengths depending on the incident angle, but the amount of fluctuation is approximately equal to the wavelength shift Sref1 of the reflection film cutoff wavelength.

[0080] Next, when the wavelength of incident light at 440nm is defined as the base blue wavelength, the transmittance of the near-infrared reflective filter Fref1 alone at the base blue wavelength is 70% or higher when the incident light angle is set to 60°. This reduces the existing drawback of a reduction in blue component due to fluctuations in the incident angle. Furthermore, the wavelength of incident light between 450nm and 500nm is defined as the low-wavelength band, and the average transmittance of incident light in this low-wavelength band is defined as the low-wavelength transmittance of the reflective film. For the near-infrared reflective filter Fref1, the low-wavelength transmittance of the reflective film remains consistently above 75% when the incident light angle varies within the range of 0° to 60°. Specifically, in the near-infrared reflective filter Fref1 alone, the range from the reflective film's onset wavelength at 50% transmittance to the reflective film's cutoff wavelength is defined as the reflective film transmission band Tref1. Even when the incident angle fluctuates between 0° and 60°, the shape of the angular region TR1 on the low-wavelength side of the rectangular waveform of the reflective film transmission band Tref1 remains stable (the angular shape on the long-wavelength side shifts toward the short-wavelength side). As a result, the near-infrared reflective filter Fref1 can reduce the phenomenon of turbulence in the low-wavelength component (the so-called ripple phenomenon) even when the incident angle increases.

[0081] (Comparison with previous years) The existing near-infrared reflection filter uses a PVD process to form an inorganic dielectric multilayer film on the other side of blue glass coated with an infrared absorption film filter material on one side, thereby achieving the infrared reflection function. Figure 4The optical characteristics of a conventional near-infrared reflective filter alone are shown. The fluctuation range (wavelength shift) Sreft of the reflective film cutoff wavelength of conventional near-infrared reflective filters when the incident angle of incident light varies within the range of 0° to 60° is greater than 150nm. In particular, at an incident angle of 60°, the waveform of the spectral characteristics tends to be distorted and rippled. This is because incident light is divided into a P component (where the vibration plane of the incident light aligns with the propagation plane) and an S component (where the vibration plane of the incident light aligns with a plane perpendicular to the propagation plane). As the angle of incidence with respect to the dielectric multilayer film increases, the transmission characteristics of the P and S components deviate. As a result, since the reflective film cutoff wavelength of conventional near-infrared reflective filters is less than 650nm, it becomes smaller than the absorption film cutoff wavelength of infrared absorption filters at an incident angle of 60°, causing distortion in the image quality. Furthermore, when the wavelength of incident light, 440 nm, is defined as the reference blue wavelength, the transmittance of conventional near-infrared reflective filters at this reference blue wavelength fluctuates when the incident light is at an angle of incidence of 60°, sometimes falling below 60%. As a result, the blue component is reduced due to fluctuations in the incident angle. Furthermore, in the low wavelength range of 450 to 500 nm, the average transmittance of conventional near-infrared reflective filters at an angle of incidence of 60° falls below 75%, and ripple increases.

[0082] It should be noted, though for reference purposes, that for the infrared-absorbing filter Fab1 formed of a resin film in this embodiment, forming an inorganic dielectric multilayer film on both its front and back surfaces using a PVD process requires a high level of skill and experience, including the subsequent dicing process, which can easily lead to a reduction in yield. Specifically, the PVD process inevitably creates microscopic defects within the inorganic dielectric multilayer film, requiring thorough inspection and subsequent removal. Furthermore, during the dicing process, the inorganic dielectric multilayer film is prone to peeling, necessitating thorough inspection to visually confirm the peeling status. In other words, from a mass production perspective, resin films and PVD processes are extremely incompatible.

[0083] (Additional Example) The near-infrared reflection filter Fref1 of this embodiment is formed of 200 layers of high-refractive index layers Hind and low-refractive index layers Lind using polyethylene terephthalate resin and polymethyl methacrylate resin. The total thickness of the near-infrared reflection filter Fref1 is set to 50 μm. As a result, the cutoff wavelength of the reflection film is 850 nm when the incident angle of the incident light is 0°. Figure 5As shown, across the entire visible spectrum (R: red 630nm, G: green 546nm, B: blue 436nm), transparency (transmittance) remains high overall even at increasing incident angles, with no interference colors due to reflection visible. Furthermore, even within the incident angle range of 50° to 60°, transmittance remains above 75%, with no extreme decrease in transmittance, and a relatively smooth decrease. While the short-wavelength B band within the RGB spectrum deviates slightly from the remaining R and G bands, the amount of deviation is within a range that does not pose a problem for image quality, and the magnitude of the deviation is stable across the entire incident angle range, minimizing image quality fluctuations due to incident angle fluctuations.

[0084] (Comparative Example 1) Figure 6 The optical properties of a near-infrared reflection filter, referred to as Comparative Example 1, are shown. In this Comparative Example 1, an inorganic dielectric multilayer film is formed on a completely transparent optical glass plate using a PVD process. The cutoff wavelength of the reflective film at an incident angle of 0° is adjusted to 780 nm. In this near-infrared reflection filter, the transmittance in the R band decreases sharply when the incident angle exceeds 50°, and completely disappears at an incident angle of 70°. This is because the cutoff wavelength of the reflective film shifts toward lower wavelengths as the incident angle increases, resulting in reflection of light in the R band. It should be noted that in this near-infrared reflection filter, a red interference color is easily observed visually. An infrared cutoff filter, comprising a conventional near-infrared reflection filter and an absorption film, was assembled into a camera module and image quality was inspected. The green color becomes relatively strong in the periphery of the image (i.e., at higher incident angles), indicating a typical lack of red coloration.

[0085] (Comparative Example 2) Figure 7 The optical properties of the near-infrared reflection filter of Comparative Example 2 are shown. In this Comparative Example 2, an inorganic dielectric multilayer film is formed on an optical glass plate using a PVD process, and the cutoff wavelength of the reflection film at an incident angle of 0° of the inorganic dielectric multilayer film is adjusted to 850nm. In this case, no interference color is found by visual inspection. If the incidence angle dependence of the RGB transmittance is observed, the mutual deviation of RGB is small. However, if the incidence angle is above 40°, the transmittance of the entire RGB is reduced. If the incidence angle is 60°, the transmittance of all RGB is reduced to 65%. In other words, it can be seen that although the transmittance of the R band alone does not decrease, the overall transmittance is insufficient.

[0086] <Infrared absorption filter> (Membrane structure) The infrared-absorbing film filter Fab1 of this embodiment employs a so-called blue film structure (a structure in which a near-infrared-absorbing pigment is added to a translucent resin for the absorption film). The film thickness of the infrared-absorbing film filter Fab1 is preferably 100 μm or less, and more preferably 50 μm or less. For ease of handling during mass production, the film thickness of the infrared-absorbing film filter Fab1 is preferably 10 μm or greater, and more preferably 30 μm or greater.

[0087] Organic dyes with near-infrared light absorption properties include azo compounds, phthalocyanine compounds, cyanine compounds, and diimmonium compounds. The translucent resin for the absorption film (also referred to as a binder or base material for the organic dye) that constitutes the infrared-absorbing filter Fab1 is made of organic polymers such as acrylic resins, polyester resins (e.g., polyethylene terephthalate), polycarbonate resins, polystyrene resins, polyethylene resins, polypropylene resins, cellulose resins (e.g., cellulose triacetate), olefin resins (e.g., cycloolefins, polyolefins), fluorine-based resins, and vinyl resins. The translucent resin for the absorption film can be a blend of multiple resins or a copolymer using monomers of the aforementioned resins. The translucent resin for the absorption film can be any resin with high transmittance for light in the visible light range, and selection is based on factors such as compatibility with the organic dye, film-forming process, and cost. To improve the UV resistance of the infrared-absorbing filter Fab1, a quencher (a matting dye) such as a sulfur compound can be added to the translucent resin for the absorption film.

[0088] (Absorption characteristics) Figure 8 The absorption characteristics of the infrared absorption film filter Fab1 alone are shown. The characteristics of the infrared absorption film filter Fab1 are set in correlation with the near-infrared reflection filter Fref1. The infrared absorption film filter Fab1 has transmission characteristics close to the human visual sensitivity curve in the visible light wavelength range of 400nm to 700nm, and its transmittance is 2% or less, preferably 1% or less, in the wavelength range of 685nm to 800nm. Thus, in the infrared absorption film filter Fab1 alone, if the region with a transmittance of 2% or less is defined as the light absorption region Wab1, the reflective film cutoff wavelength fluctuation region on the near-infrared reflection filter Fref1 side, where the incident angle fluctuates between 0° and 30°, is set to fall entirely within this light absorption region. The infrared absorption filter Fab1 more preferably has a transmittance of 2% or less in the wavelength range of 685nm to 850nm, and the infrared absorption filter Fab1 further preferably has a transmittance of 2% or less in the wavelength range of 685nm to 900nm.

[0089] Furthermore, within the wavelength range of 800 nm to 1150 nm, which overlaps with the total reflection wavelength range Wref1 (e.g., 790 nm to 1100 nm) of the reflective film on the near-infrared reflective filter Fref1 side, the maximum transmittance of the infrared absorbing film filter Fab1 alone is set to 60% or less, preferably 40% or less. Similarly, the average transmittance of the infrared absorbing film filter Fab1 within the wavelength range of 800 nm to 1150 nm is set to 40% or less, preferably 25% or less.

[0090] In this embodiment, the near-infrared reflection filter Fref1 is combined with the infrared absorption filter Fab1. The near-infrared reflection filter Fref1 blocks (reflects) light with wavelengths longer than 800 nm, which is absorbed by the infrared absorption filter Fab1 alone to a level less than 2%. This allows for the capture of images with natural tones. On the other hand, if the near-infrared reflection filter Fref1 alone were to block (reflect) light throughout the near-infrared region, the reflection filter's cutoff wavelength would shift (shift) toward shorter wavelengths as the incident angle of the incident light increases, as described above. Therefore, infrared cutoff at shorter wavelengths is achieved by combining the infrared absorption filter Fab1, which has no dependency on the incident angle. This allows for the creation of an infrared cutoff filter 1 with infrared cutoff characteristics over a wide range of wavelengths, from 700 nm to 1150 nm, that are independent of the incident angle of light.

[0091] Here, the wavelength at which the light transmittance of the infrared absorption filter Fab1 alone decreases to 50% as the wavelength of the incident light increases is defined as the "absorption cutoff wavelength." The absorption cutoff wavelength is largely independent of the incident angle of the incident light. It is set within the range of 600nm to 680nm. Furthermore, the absorption cutoff wavelength is set to be consistently lower than the lowest value of the reflection cutoff wavelength on the near-infrared reflection filter Fref1 side when the incident angle varies within the range of 0° to 60°.

[0092] (Comparison with previous years) Existing infrared-absorbing filters use a so-called blue glass substrate, made by adding an appropriate amount of Cu to phosphate glass. This blue glass offers excellent near-infrared light absorption properties. However, thinning the blue glass limits the amount of copper ions it can dissolve, resulting in insufficient near-infrared light absorption. Therefore, an auxiliary infrared-absorbing filter is created by applying an infrared-absorbing ink to one surface of the blue glass through spin coating or other methods to compensate for the blue glass's overall infrared absorption deficit. This results in a significant increase in the number of production steps.

[0093] <Anti-reflection film (anti-reflection part)> (Membrane structure) Here, the anti-reflection film Far1 is made of a translucent anti-reflection resin. This anti-reflection film Far1 is essential for maintaining image quality and brightness in camera modules. Especially in small camera modules, where the distance between optical elements is extremely narrow, various image noises such as ghosting and flare are easily generated. However, this anti-reflection film Far1 can reduce image noise.

[0094] The basic structure of the antireflection film Far1 can be a "single-layer film structure" formed from a low-refractive-index resin; a "multi-layer film structure" in which resin films with different refractive indices (low-refractive-index films and high-refractive-index films) are alternately stacked to convert light into heat and absorb it; a "porous low-refractive-index film structure" in which a low refractive index is achieved by making the resin surface porous; a "porous gradient refractive-index structure" in which the refractive index is tilted by making the resin surface porous and tilting the air occupancy ratio in the optical axis direction (film thickness direction); and a "moth-eye gradient refractive-index structure" in which the refractive index is tilted in the optical axis direction (film thickness direction) by forming microprotrusions (moth-eyes) with tapered ends on the resin surface. The "moth-eye gradient refractive-index structure" includes a regular moth-eye structure in which microprotrusions (moth-eyes) are regularly arranged, and a random moth-eye structure in which irregular microprotrusions with varying heights and / or pitches are formed, but any of these structures can be adopted.

[0095] From the viewpoint of adopting the roll-to-roll manufacturing process described later, the anti-reflection film Far1 preferably adopts a "multilayer film structure" or a "moth-eye inclined refractive index structure". Figure 9 The regular moth-eye structure shown. The refractive index is tilted to that of the anti-reflective translucent resin at the base end of the protrusion and to that of air at the protruding end of the protrusion. As the anti-reflective translucent resin, for example, a UV-curable resin is used. By applying the liquid UV-curable resin before curing to a substrate (here, the near-infrared reflection filter Fref1 or the infrared absorption film filter Fab1), pressing a transfer film or transfer roller with a moth-eye shape while irradiating it with UV light, the moth-eye shape is transferred to the surface. The "moth-eye tilted refractive index structure" has the advantage of being less susceptible to the wavelength range of the incident light and fluctuations in the incident angle. The size of the fine protrusions is preferably such that the protrusion height is set to be less than 2μm, and the spacing between the protrusions (grid spacing) is set to be less than 2μm. More preferably, the protrusion height is 1 μm or less, and the pitch between protrusions (grid spacing) is 1 μm or less. Even more preferably, the protrusion height is 0.5 μm or less, and the pitch between protrusions (grid spacing) is 0.5 μm or less.

[0096] When the anti-reflection film Far1 has a multilayer film structure, a portion of the surface side of the high-refractive-index layer Hind and a portion of the surface side of the low-refractive-index layer Lind of the near-infrared reflection filter Fref1 can function as both the low-refractive-index film and the high-refractive-index film of the anti-reflection film Far1. In other words, the functions of the anti-reflection film Far1 are simultaneously exerted near the surface of the near-infrared reflection filter Fref1.

[0097] It should be noted that because the near-infrared reflective filter Fref1 of this embodiment is composed of resin, its surface reflection is significantly suppressed compared to conventional inorganic dielectric multilayer films. Consequently, the combination of the near-infrared reflective filter Fref1's surface reflective properties and its "moth-eye tilted refractive index structure" further enhances anti-reflection performance, significantly improving image quality.

[0098] (Transmission characteristics and reflection characteristics) Figure 10 The spectral characteristics of the antireflection coating Far1 are shown. In this figure, the transmittance Tm is shown at an incident angle of 6° (Tm6), an incident angle of 15° (Tm15), an incident angle of 30° (Tm30), an incident angle of 45° (Tm45), and an incident angle of 60° (Tm60). The reflectance Rm is shown at an incident angle of 6° (Rm6), an incident angle of 15° (Rm15), an incident angle of 30° (Rm30), an incident angle of 45° (Rm45), and an incident angle of 60° (Rm60).

[0099] Throughout the incident angle range of 0° to 45°, the transmittance Tm in the visible light region (400nm to 700nm) is 95% or higher, and the reflectance Rm is 3% or lower, preferably 1% or lower. Furthermore, even at an incident angle of 60°, the transmittance T in the visible light region is 90% or higher, and the reflectance R is 5% or lower. Furthermore, the average transmittance in the visible light region is 99.2%, and the average reflectance is 0.8%.

[0100] <Method for Manufacturing Infrared Cutoff Filter> Next, a method for manufacturing the infrared cut filter 1 will be described.

[0101] (Anti-reflection film manufacturing process) First, the near-infrared reflective filter Fref1 is manufactured using co-extrusion. The sheet extruded from the co-extruder is stretched uniaxially (longitudinally) or biaxially (longitudinally and transversely) using a stretching device to form the near-infrared reflective filter Fref1. The completed near-infrared reflective filter Fref1 is preferably temporarily wound into a roll.

[0102] (Infrared absorption filter manufacturing process) The infrared-absorbing film filter Fab1 is manufactured by extrusion using a translucent resin for an absorption film containing an organic pigment. The sheet extruded from the extruder is stretched uniaxially (longitudinally) or biaxially (longitudinally and transversely) using a stretching device to form the infrared-absorbing film filter Fab1. The completed infrared-absorbing film filter Fab1 is preferably temporarily wound into a roll.

[0103] (Lamination process) like Figure 11 As shown, a roll-to-roll laminating device RS is used to laminate the near-infrared reflective filter Fref1 and the infrared absorbing film filter Fab1. Specifically, the near-infrared reflective filter Fref1 and the infrared absorbing film filter Fab1 are fed in roll form, and adhesive is applied to either surface of the roll using an adhesive coating device CT. The two films are then sandwiched and pressed together by a pair of heated laminating rollers RR. The laminated near-infrared reflective filter Fref1 and the infrared absorbing film filter Fab1 are preferably rewound into a roll. A thermosetting optical adhesive can be used as the adhesive applied by the adhesive coating device CT.

[0104] (Anti-reflective film additional process) like Figure 12 As shown, a roll-to-roll film-forming apparatus MS is used to form an antireflection film Far1 on the outer surfaces of the near-infrared reflective filter Fref1 and the outer surfaces of the infrared absorbing filter Fab1. Specifically, a first coating apparatus CT1 applies a light-transmitting antireflection resin (UV-curable resin) to the outer surface of the near-infrared reflective filter Fref1. This resin is then cured by irradiating the resin with UV light UV1 while pressing against a first transfer roller PR1, thereby forming a first antireflection film Far1 having a moth-eye tilted refractive index structure. Subsequently, a second coating apparatus CT2 applies a light-transmitting antireflection resin to the outer surface of the infrared absorbing filter Fab1. This resin is then cured by irradiating the resin with UV light UV2 while pressing against a second transfer roller PR2, thereby forming a second antireflection film Far1 having a moth-eye tilted refractive index structure. As a result, a fully polymer infrared cut filter sheet material is completed, integrating the near-infrared reflective filter Fref1, the infrared absorbing filter Fab1, and the pair of antireflection films Far1. The completed sheet material is preferably temporarily wound into a roll.

[0105] (Light-shielding mask printing process) will pass Figure 12After the infrared cutoff filter sheet material is cut into the desired rectangular sheets and formed into individual sheets, a frame-shaped light-shielding mask is printed onto the individual sheets using a printing device. The light-shielding mask serves to block excess ambient light from the CMOS pixel sensor. For example, a total of 100 or more light-shielding masks, preferably 300 or more, are printed on the rectangular sheet in a grid or staggered pattern. The light-shielding mask can be printed on either the near-infrared reflective filter Fref1 or the infrared absorbing film filter Fab1 side; however, it is printed on the infrared absorbing film filter Fab1 side in this embodiment. The size of the rectangular sheet is not particularly limited; however, from the perspective of mass production efficiency, it is preferably a large size of at least 150 mm in length and 150 mm in width, more preferably at least 200 mm in length and 200 mm in width, and even more preferably at least 300 mm in length and 300 mm in width. In the case of conventional infrared cut filters having a blue glass structure, the size of the glass plate is limited to 100 mm or less in length and 100 mm or less in width due to problems in handling the glass substrate.

[0106] (Chip processing steps) The rectangular sheet on which the light-shielding mask is printed is entirely made of organic resin. Therefore, by using the punching device on the punching side to punch the rectangular sheet into the desired shape (for example, a rectangular shape of several millimeters in length and width), the chip is processed into a single piece of a plurality of infrared cut filters 1. As a result, the Figure 1 The infrared cut filter 1 shown is shown. It should be noted that a double-edged structure, with blades provided on both sides of the die that sandwich the rectangular sheet, is preferred to suppress the occurrence of burrs on the peripheral edges. Because the rectangular sheet is made of organic resin, compared to glass, inorganic dielectric films, etc., the ingress of foreign matter (debris) during chip processing is minimal. The die is not limited to a double-edged structure; a single-edged die is also acceptable. Furthermore, cutting using a cutter, etc., is also possible, not limited to punching.

[0107] (Appearance inspection process) In the case of the infrared cut filter 1 of this embodiment, since there is little variation among components in the mass production process described above, quality can be guaranteed by inspecting only some elements instead of inspecting all of them.

[0108] <Overall Structure and Characteristics of Infrared Cut Filters> Figure 1The infrared cut filter 1 shown is entirely made of organic resin and does not contain a glass substrate or a dielectric multilayer film. This significantly simplifies the manufacturing process and stabilizes the optical properties during mass production. For example, by setting the thickness of the near-infrared reflective filter Fref1, the infrared absorbing film filter Fab1, and the anti-reflection film Far1 to 100 μm or less, the overall thickness of the infrared cut filter 1 can be reduced to 300 μm or less. This allows for a lower camera module height. In this embodiment, by setting the thickness of the near-infrared reflective filter Fref1, the infrared absorbing film filter Fab1, and the anti-reflection film Far1 to 50 μm or less, the overall thickness is reduced to 150 μm or less, specifically, to 100 μm or less. From a handling perspective during camera module assembly, the overall thickness of the infrared cut filter 1 is preferably 30 μm or greater. In this case, the overall thickness of the infrared cutoff filter 1 can be distributed between the thickness of the near-infrared reflective filter Fref1 and the thickness of the infrared absorbing film filter Fab1. As a result, the handling characteristics of both the near-infrared reflective filter Fref1 and the infrared absorbing film filter Fab1 can be improved during roll-to-roll mass production. From this perspective, when the overall thickness of the infrared cutoff filter 1 is assumed to be 100%, the film thickness occupancy rate of the near-infrared reflective filter Fref1 is set to be at least 20%, preferably at least 30%. Similarly, the film thickness occupancy rate of the infrared absorbing film filter Fab1 is set to be at least 20%, preferably at least 30%. Furthermore, the film thickness difference between the near-infrared reflective filter Fref1 and the infrared absorbing film filter Fab1 is preferably 100 μm or less, preferably 80 μm or less, and more preferably 50 μm or less.

[0109] Figure 13 The optical characteristics of the infrared cut filter 1 of the present embodiment are shown. The transmittance of the transmission band Q starting from 50% and ending at 50% in the visible light region (400nm to 700nm) almost directly reflects the spectral characteristics of the infrared absorbing film filter Fab1. In particular, even if the incident angle changes from 0° to 60°, the spectral characteristics of the transmittance of the transmission band Q hardly change, and there are few ripples. In particular, for the reference blue wavelength of 440nm and the low wavelength band of 450nm to 500nm, the decrease in transmittance is small even if the incident angle is 60°. As a result, the occurrence of coloring and ghosting in the captured image is greatly suppressed. In addition, for the infrared region, it can be seen that by combining the light absorption region Wab1 of the infrared absorbing film filter Fab1 (refer to Figure 8 ) and the total reflection wavelength range Wref1 of the reflective film of the near-infrared reflection filter Fref1 (refer to Figure 3 ), maintaining low transmittance across the entire 700nm to 1150nm range. This means that infrared images can be prevented from being captured in the captured image.

[0110] (Comparative Example 3) Figure 14 The infrared absorption film filter Fab1 ( Figure 8 ) and the conventional near-infrared reflection filter shown in Comparative Example 1 ( Figure 4 ) to examine the optical characteristics of an infrared cutoff filter formed by a 1.5-μm CMOS process. While the transmittance in the visible light region (400 nm to 700 nm) of this infrared cutoff filter reflects the spectral characteristics of the infrared absorbing film filter Fab1, ripples similar to those of conventional near-infrared reflection filters occur in the reference blue wavelength of 440 nm and the low wavelength range of 450 nm to 500 nm. Furthermore, at an incident angle of 60°, the transmittance in the visible light region (400 nm to 700 nm) decreases overall. In particular, the transmittance in the reference blue wavelength of 440 nm and the low wavelength range of 450 nm to 500 nm decreases significantly, and the ripples increase. As a result, peripheral coloration and ghosting are likely to occur in captured images.

[0111] Camera module assembly Figure 15 A camera module 20 incorporating the infrared cut filter 1 of the first embodiment is shown. As a camera structure, the camera module 20 includes: a lens unit 50 constituting an optical lens group; a lens carrier 40 that holds the lens unit 50; a magnetic mount 30 that axially moves the lens unit 50 to implement an autofocus function; an imaging element 70 that receives light incident through the lens unit 50; a substrate 80 on which the imaging element 70 is mounted; and the infrared cut filter 1 disposed between the lens unit 50 and the imaging element 70.

[0112] In this camera module 20, the infrared cut filter 1 has a thin-walled structure. Furthermore, since it can be placed close to the lens unit 50 and the imaging element 70, it can be reduced in height. Furthermore, even if the pixel pitch of the CMOS image sensor serving as the imaging element 70 is set to 2 μm or less, preferably 1 μm or less, image quality degradation is unlikely to occur. The gap between the infrared cut filter 1 and the imaging element 70 can be reduced to 0.5 mm or less, preferably 0.3 mm or less. Similarly, the gap between the infrared cut filter 1 and the lens unit 50 can be reduced to 0.5 mm or less, preferably 0.3 mm or less.

[0113] Although not specifically shown, a cover glass may be provided on the light-incident side of the camera module 20. Preferably, a dielectric multilayer film is formed on the cover glass. This dielectric multilayer film is formed by alternating layers of dielectrics with different refractive indices. The dielectric multilayer film is laminated on the inner side of the cover glass by vacuum deposition. This dielectric multilayer film can complement the reflective function of the near-infrared reflection filter Fref1.

[0114] <Photography Experiment> The image of the subject captured by the camera module 20 is shown in FIG. Figure 19 (A) and Figure 20 (A). Virtual images due to repeated reflections of the components of the module 20 are almost not generated. On the other hand, an image captured by a camera module equipped with a conventional infrared cut filter is shown in FIG. Figure 19 (B) Figure 20 (B) and Figure 21 .exist Figure 19 (B) and Figure 20 In the image (B), a ghost image GST-A that spreads in a petal shape (radially) and a ghost image GST-B that is formed in a balloon shape are formed. Figure 21 The image is colored with a colored area SHD, where the periphery of the image appears green compared to the center. This colored area SHD coincides with the region where the angle of incidence of external light on the infrared cut filter increases. This means that the transmittance of R (red) and B (blue) decreases, resulting in a significant reduction in red and blue light. This, in turn, emphasizes G (green).

[0115] Then, in Figure 16 (A) shows an infrared cutoff filter 101 according to a second embodiment of the present invention. This infrared cutoff filter 101 has a separate near-infrared reflective filter Fref1 and an infrared absorbing filter Fab1, each with an antireflection film Far1 formed on both surfaces. Specifically, the infrared cutoff filter 101 independently comprises a reflective member REF, which forms the near-infrared reflective filter Fref1 and has the antireflection film Far1 on both surfaces, and an absorbing member AB, which forms the infrared absorbing filter Fab1 and has the antireflection film Far1 on both surfaces. A light-shielding mask M is printed on the side of the absorbing member AB. The configurations of the near-infrared reflective filter Fref1, the infrared absorbing filter Fab1, and the antireflection film Far1 are identical to those of the infrared cutoff filter 1 according to the first embodiment, and therefore their description is omitted here. The overall optical properties of the infrared cutoff filter 101 are substantially identical to those of the infrared cutoff filter 1 according to the first embodiment.

[0116] Since the absorbing component AB and the reflecting component REF are independent, the film thickness of the absorbing component AB is preferably in the range of 50μm to 100μm, and the film thickness of the reflecting component REF is preferably in the range of 50μm to 100μm from the perspective of their respective handleability during assembly.

[0117] exist Figure 16 (B) shows a camera module 120 incorporating the infrared cut filter 101. The camera module 120 includes a lens unit 50, which forms an optical lens group; a lens carrier 40 that holds the lens unit 50; a magnetic mount 30 that allows the lens unit 50 to move axially to implement an autofocus function; an imaging element 70 that receives light incident through the lens unit 50; a substrate 80 on which the imaging element 70 is mounted; an absorbing member AB disposed between the lens unit 50 and the imaging element 70; and a reflecting member REF disposed on the light-incident side of the lens unit 50. Specifically, the camera module 120 includes the absorbing member AB and the reflecting member REF, which form the infrared cut filter 1, separately. The reflecting member REF can be attached to the inside of a so-called cover glass. Alternatively, the reflecting member REF can be inserted between the optical lens group in the lens unit 50. Although not specifically illustrated here, the reflecting member REF can also be disposed between the lens unit 50 and the imaging element 70, with the absorbing member AB disposed on the light-incident side of the lens unit 50.

[0118] Although not specifically shown, a cover glass may be provided on the light-incident side of the camera module 120. Preferably, a dielectric multilayer film is formed on the cover glass by alternating layers of dielectric materials with different refractive indices. The dielectric multilayer film is laminated on the inner side of the cover glass by vacuum deposition. This dielectric multilayer film can complement the reflective function of the near-infrared reflective filter Fref1.

[0119] exist Figure 17(A) shows an infrared cutoff filter 201 according to a third embodiment of the present invention. This infrared cutoff filter 201 has an infrared absorbing film filter Fab1 inserted within the multilayer film of the near-infrared reflecting filter Fref1. Consequently, both surfaces form the near-infrared reflecting filter Fref1, with the anti-reflection film Far1 formed on each surface. In other words, the multilayer film of the near-infrared reflecting filter Fref1 is divided into two or more groups, with the infrared absorbing film filter Fab1 interposed between these groups. In this case, the multilayer film of the near-infrared reflecting filter Fref1 can be manufactured in groups using co-extrusion, and then laminated to sandwich the infrared absorbing film filter Fab1. Alternatively, the near-infrared reflecting filter Fref1 and the anti-reflection film Far1 can be integrally manufactured using co-extrusion. While this example illustrates the insertion of a single-layer infrared absorbing film filter Fab1, the infrared absorbing film filter Fab1 can also be a multilayer structure. Alternatively, a plurality of infrared absorbing film filters Fab1 may be dispersedly arranged between a plurality of sets of near-infrared reflecting filters Fref1.

[0120] exist Figure 17 (B) shows an infrared cutoff filter 301 according to a fourth embodiment of the present invention. This infrared cutoff filter 301 has a multilayered near-infrared reflective filter Fref1 inserted within a dispersed, multilayered infrared absorbing film filter Fab1. Consequently, both surfaces of the infrared absorbing film filter Fab1 are formed, with an antireflection film Far1 formed on each surface. In this case, the multilayered near-infrared reflective filter Fref1 can be manufactured in groups using co-extrusion, with the multiple infrared absorbing film filters Fab1 sandwiching the near-infrared reflective filter Fref1 and then laminating the layers together. Alternatively, the near-infrared reflective filter Fref1 and the antireflection film Far1 can be integrally manufactured using co-extrusion. While this example illustrates a single set of infrared absorbing film filters Fab1, multiple sets of infrared absorbing film filters Fab1 can also be used.

[0121] exist Figure 17(C) shows an infrared cutoff filter 401 according to the fifth embodiment of the present invention. This infrared cutoff filter 401 alternately stacks infrared absorbing film filters Fab1, which are dispersed into multiple layers, and near-infrared reflecting filters Fref1, which are dispersed into multiple layers. In this case, the multilayered films of the near-infrared reflecting filters Fref1 can be manufactured in groups using co-extrusion, and then alternately laminated to the multiple infrared absorbing film filters Fab1. Alternatively, multiple groups of near-infrared reflecting filters Fref1 and the multilayered anti-reflection film Far1 can be integrally manufactured using co-extrusion.

[0122] exist Figure 18 (A) shows an infrared cutoff filter 501 according to the sixth embodiment of the present invention. In this infrared cutoff filter 501, an organic dye with near-infrared light absorption is incorporated into the low-refractive-index resin used for the reflective film of the near-infrared reflective filter Fref1. This allows the low-refractive-index layer Lind to also function as the infrared-absorbing film filter Fab1. As a result, the infrared-absorbing film filter Fab1 is dispersed throughout the multiple layers of the near-infrared reflective filter Fref1. In this case, if the multilayer film of the near-infrared reflective filter Fref1 is manufactured using co-extrusion, the infrared-absorbing film filter Fab1 is simultaneously formed and superimposed. Co-extrusion improves production efficiency because only two resins are used. While this example illustrates the inclusion of the near-infrared light absorption organic dye on the low-refractive-index layer Lind, the organic dye can also be incorporated on the high-refractive-index layer Hind.

[0123] exist Figure 18 (B) shows an infrared cutoff filter 601 according to the seventh embodiment of the present invention. This infrared cutoff filter 601 incorporates an organic pigment with near-infrared light absorption function into both the low-refractive-index resin and the high-refractive-index resin for the reflective film of the near-infrared reflective filter Fref1. This allows both the low-refractive-index layer Lind and the high-refractive-index layer Hind to function as the infrared-absorbing film filter Fab1. As a result, the entire near-infrared reflective filter Fref1 also functions as the infrared-absorbing film filter Fab1. In this case, when the multilayer film of the near-infrared reflective filter Fref1 is manufactured using co-extrusion, the infrared-absorbing film filter Fab1 is simultaneously formed and superimposed.

[0124] exist Figure 18(C) shows an infrared cutoff filter 701 according to the eighth embodiment of the present invention. This infrared cutoff filter 701 incorporates an organic dye with near-infrared light absorption function into a portion of both the low-refractive-index resin and the high-refractive-index resin for the reflective film of the near-infrared reflective filter Fref1. This allows both the low-refractive-index layer Lind and the high-refractive-index layer Hind to function as the infrared-absorbing film filter Fab1. Here, the low-refractive-index layer Lind and the high-refractive-index layer Hind on the side closest to the CMOS pixel sensor (not shown) contain the organic dye. As a result, a portion of the multilayered layer of the near-infrared reflective filter Fref1 also functions as the infrared-absorbing film filter Fab1. In this case, when the multilayered film of the near-infrared reflective filter Fref1 is manufactured using co-extrusion, the infrared-absorbing film filter Fab1 is formed simultaneously and superimposed.

[0125] exist Figure 22 (A) shows an infrared cutoff filter 901 according to the ninth embodiment of the present invention. In this infrared cutoff filter 901, the near-infrared reflective filter Fref1 is separated from the infrared absorbing filter Fab1, and anti-reflection films Far1 are formed on both surfaces of the infrared absorbing filter Fab1. Meanwhile, the near-infrared reflective filter Fref1 is attached to the inside of the cover glass 215, which protects the internal mechanisms of the imaging device from external influences. The cover glass 215 uses crystallized glass 130 as a transparent substrate that allows light to pass through. It should be noted that a dielectric multilayer film formed by alternating layers of dielectric materials with different refractive indices can be interposed between the cover glass 215 and the infrared absorbing filter Fab1. The dielectric multilayer film can be laminated on the inside of the cover glass 215 by vacuum deposition. This dielectric multilayer film can complement the reflective function of the near-infrared reflective filter Fref1.

[0126] exist Figure 22 (B) shows a camera structure incorporating an infrared cut filter 901. This camera structure includes a cover glass 215 and a camera module 920. The camera module 920 comprises a lens unit 50 constituting an optical lens group; a lens carrier 40 that holds the lens unit 50; a magnetic mount 30 that axially moves the lens unit 50 to achieve an autofocus function; an image sensor 70 that receives light incident through the lens unit 50; a substrate 80 on which the image sensor 70 is mounted; an absorbing member AB disposed between the lens unit 50 and the image sensor 70; and a reflective member REF attached to the inner side of the cover glass 215. The cover glass 215 is fixed to the housing 20 of a camera device such as a smartphone.

[0127] In the infrared cut filter 1 of this embodiment, the anti-reflection film (anti-reflection portion) Far1 is made of a resin material, but the present invention is not limited to this. The anti-reflection film (anti-reflection portion) Far1 can also be formed using an existing inorganic dielectric multilayer film. In this case, Figure 11 As shown, after the near-infrared reflection filter Fref1 and the infrared absorption film filter Fab1 are laminated using a roll-to-roll laminating device RS, the film is cut into sheets of desired size and an inorganic dielectric multilayer film is formed on the surface of the sheet by a vacuum evaporation process.

[0128] It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

Claims

1. An infrared cutoff filter, characterized in that: For digital cameras, the infrared cut-off filter has: A near-infrared reflection filter comprising a high-refractive-index layer formed of a high-refractive-index resin and a low-refractive-index layer formed of a low-refractive-index resin alternately stacked; and The infrared absorption film filter is composed of a light-transmitting resin containing a pigment or a light-transmitting resin coated with a pigment.

2. The infrared cut filter according to claim 1, wherein The infrared cut filter further includes an antireflection portion formed on a surface of the near-infrared reflection filter and / or the infrared absorption film filter that is in contact with air.

3. The infrared cut filter according to claim 1, wherein The high-refractive-index resin, the low-refractive-index resin, and the light-transmitting resin constituting the infrared-absorbing film filter are made of organic resin.

4. The infrared cutoff filter according to claim 2, wherein: The high-refractive-index resin, the low-refractive-index resin, the light-transmitting resin constituting the infrared-absorbing film filter, and the anti-reflection portion are made of organic resin.

5. The infrared cut filter according to claim 1, wherein The near-infrared reflection filter is formed by co-extruding the high refractive index layer and the low refractive index layer.

6. The infrared cut filter according to claim 1, wherein The thickness of each of the high refractive index layer and / or the low refractive index layer is within a range of 10 nm to 300 nm.

7. The infrared cut filter according to claim 1, wherein The total number of the high refractive index layer and the low refractive index layer is 30 or more.

8. The infrared cut filter according to claim 1, wherein The entire thickness of the near-infrared reflection filter is 100 μm or less.

9. The infrared cut filter according to claim 1, wherein The near-infrared reflection filter and the infrared absorption film filter are integrated.

10. The infrared cut filter according to claim 1, wherein By making at least one of the high-refractive-index resin and the low-refractive-index resin contain the pigment, the resin also serves as the infrared absorption film filter.

11. The infrared cut filter according to claim 2, wherein The anti-reflection portion has a structure in which projections and depressions are formed on the surface of the light-transmitting resin.

12. The infrared cut filter according to claim 2, wherein The antireflection portion has a multilayer film structure in which low-refractive-index resin films and high-refractive-index resin films are alternately stacked.

13. The infrared cut filter according to claim 2, wherein Part of the plurality of high refractive index layers and the plurality of low refractive index layers in the near-infrared reflection filter also serves as the low refractive index resin film and the high refractive index resin film of the antireflection portion.

14. The infrared cut filter according to claim 2, wherein The near infrared reflection filter and the infrared absorption film filter are bonded to each other to form a whole. The first antireflection portion is formed on a surface of the near-infrared reflection filter opposite to the infrared absorption filter. The second antireflection portion is formed on a surface of the infrared absorbing filter on the opposite side to the near-infrared reflecting filter.

15. The infrared cut filter according to claim 11, wherein The antireflection portion has a moth-eye structure in which projections and depressions are formed on the surface of a light-transmitting resin.

16. The infrared cut filter according to claim 2, wherein The total thickness of the near-infrared reflection filter, the infrared absorption film filter, and the anti-reflection portion is 300 μm or less.

17. The infrared cut filter according to claim 2, wherein The film thickness occupancy rate of the near-infrared reflection filter is 20% or more based on the total thickness of the near-infrared reflection filter, the infrared absorption film filter, and the anti-reflection portion.

18. The infrared cut filter according to claim 17, wherein The infrared absorbing film filter has a film thickness occupancy rate of 20% or more based on the total thickness of the near-infrared reflecting filter, the infrared absorbing film filter, and the anti-reflection portion.

19. The infrared cut filter according to claim 1, wherein In the near-infrared reflection filter unit, when the wavelength at which the light transmittance decreases to 50% as the wavelength of the incident light increases is defined as the reflection film cutoff wavelength, The cutoff wavelength of the reflective film when the incident angle of the incident light is 0° is within a range of 750 nm to 900 nm.

20. The infrared cut filter according to claim 1, wherein In the near-infrared reflection filter unit, when the wavelength at which the light transmittance decreases to 50% as the wavelength of the incident light increases is defined as the reflection film cutoff wavelength, The wavelength fluctuation width of the cutoff wavelength of the reflective film when the incident angle of the incident light is changed within the range of 0° to 60° is 170 nm or less.

21. The infrared cut filter according to claim 1, wherein When the wavelength of incident light, 440 nm, is defined as the reference blue wavelength, In the near-infrared reflective filter alone, a transmittance of the near-infrared reflective filter alone at the reference blue wavelength is 70% or higher when the incident angle of the incident light is 60°.

22. The infrared cut filter according to claim 1, wherein The wavelength of incident light from 450nm to 500nm is defined as the low wavelength transmission band. In the near-infrared reflective filter unit, when the average transmittance of incident light in the low-wavelength transmittance band is defined as the reflective film low-wavelength transmittance, The low-wavelength transmittance of the reflective film is 75% or more when the incident angle of the incident light is changed within a range of 0° to 60°.

23. The infrared cut filter according to claim 1, wherein The resin constituting the near-infrared reflection filter and / or the infrared absorption film filter contains an ultraviolet absorber.

24. A camera structure, characterized in that: The digital camera structure includes an optical lens group arranged on the light incident side and an imaging element that receives the light incident through the optical lens group. The infrared cut filter according to claim 1 is arranged between the optical lens group and the imaging element.

25. A camera structure, characterized in that: The digital camera structure is composed of a cover glass, an optical lens group, and an image sensor in order from the light incident side. The camera structure includes the infrared cut filter according to claim 1, The near-infrared reflection filter is arranged between the cover glass and the optical lens group. The infrared absorption filter is arranged between the optical lens group and the imaging element.

26. The camera structure according to claim 25, characterized in that: The near-infrared reflection filter is attached to the cover glass.

27. A method for manufacturing an infrared cutoff filter, characterized in that: A method for manufacturing an infrared cutoff filter for a digital camera, comprising: A reflective film manufacturing process of alternately laminating high refractive index layers formed of a high refractive index resin and low refractive index layers formed of a low refractive index resin by co-extrusion molding to form a near-infrared reflective filter; and The chip processing step is to form the near-infrared reflection filter into a desired shape by at least cutting or punching.

28. The method for manufacturing an infrared cut filter according to claim 27, wherein: The method for manufacturing the infrared cutoff filter includes an integration step in which an infrared absorption film filter is stacked or bonded to the near-infrared reflection filter. The infrared absorption film filter is composed of a light-transmitting resin containing a pigment or a light-transmitting resin for an absorption film coated with a pigment.

29. The method for manufacturing an infrared cut filter according to claim 27, wherein: In the reflective film manufacturing process, the high-refractive index resin, the low-refractive index resin, and a translucent resin containing an infrared-absorbing pigment are co-extruded to form a near-infrared reflective filter and an infrared-absorbing film filter as one piece. The near-infrared reflective filter is alternately stacked with high-refractive index layers formed from the high-refractive index resin and low-refractive index layers formed from the low-refractive index resin, and the infrared-absorbing film filter is formed from the translucent resin.

30. The method for manufacturing an infrared cut filter according to claim 27, wherein: In the reflective film manufacturing process, after making any one of the high refractive index resin and the low refractive index resin contain a pigment that absorbs infrared rays, the high refractive index resin and the low refractive index resin are co-extruded to form a near-infrared reflection filter and an infrared absorption film filter as a whole. The near-infrared reflection filter is alternately stacked with high refractive index layers formed by the high refractive index resin and low refractive index layers formed by the low refractive index resin, and the infrared absorption film filter is formed by the side of the high refractive index layer and the low refractive index layer containing the pigment.

31. The method for manufacturing an infrared cut filter according to any one of claims 27 to 30, wherein: The infrared cut filter manufacturing method includes an anti-reflection film adding step, which is performed before the chip processing step and forms an anti-reflection film on a surface in contact with air.

32. The method for manufacturing an infrared cut filter according to any one of claims 27 to 30, wherein: The infrared cut filter manufacturing method includes a mask adding step, which is performed before the chip processing step and involves printing a light-shielding mask.

33. The method for manufacturing an infrared cut filter according to claim 28, wherein: In the integration step, the roll-shaped near-infrared reflection filter and the roll-shaped infrared absorption film filter are supplied to a laminating device, integrated, and then wound into a roll.

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