Infrared cut filter, camera structure, method for manufacturing infrared cut filter

Abstract

The infrared cut filter (1) for a digital camera of the present application is provided with a near-infrared reflective filter (Fref1) and an infrared absorbing film filter (Fab1), the near-infrared reflective filter (Fref1) is configured in a manner that a high refractive layer (Hind) formed of a high refractive resin and a low refractive layer (Lind) formed of a low refractive resin are alternately laminated, and the infrared absorbing film filter (Fab1) is configured of a light-transmissive resin containing a pigment or a light-transmissive resin coated with a pigment. Thus, an infrared cut filter is provided, in which ghost flare, coloration, and the like are suppressed, and mass production efficiency is dramatically improved.

Description

TECHNICAL FIELD

[0001] The present application relates to an infrared cut filter provided in a digital photographing apparatus or the like. BACKGROUND

[0002] CMOS image sensors have been put to practical use for a quarter of a century so that digital cameras have replaced film cameras as the mainstream. Now, digital cameras are indispensable parts in portable information terminals typified by smartphones, and in-vehicle cameras, network cameras, security devices, and the like. For digital cameras, the size range is extremely large from an advanced single-lens reflex digital camera which is the same size as a conventional lens replacement camera to a small camera module which is built in a smartphone and has a volume ratio of about 1 / 400 to the advanced single-lens reflex digital camera. In terms of production volume, the production volume of small camera modules built in smartphones and the like is overwhelmingly large, and in the last 10 years, the production volume of small camera modules has expanded to about 700 times the production volume of dedicated digital cameras, and now the production has expanded to about 6 billion units per year. Moreover, in the past, a single small camera module was mounted in a smartphone, but now multi-eye development is progressing, and 3 to 5 small camera modules are mounted in one smartphone. The reason for multi-eye development is because the mounting space in the optical axis direction of the small camera module is limited due to the thinning development of smartphones, and therefore it is difficult for one small camera module to take over the lens function from super wide angle to telephoto, and thus it is dispersed. In addition, in advanced single-lens reflex digital cameras and the like, since a sufficient space volume is maintained in the optical axis direction, it is possible to achieve the function from super wide angle to telephoto with a single lens module.

[0003] On the other hand, since the sensitivity curve of the CMOS sensor in the small camera module extends to the near-infrared region (wavelength of about 1.1 μm) beyond the wavelength region of visible light (380 nm to 780 nm), the directly captured image becomes a different color tone from the visual image of the human eye. Therefore, in the CMOS image sensor, an infrared cut filter (IRCF) that cuts near-infrared light (NIR) is indispensable. In the early days of digital cameras, an infrared cut filter having only a near-infrared light reflecting multilayer film was used, but it was easy to cause quality degradation due to ghost flare, shading, and the like. Therefore, in the current infrared cut filter (IRCF), it has been changed to a combination including a near-infrared light absorbing filter.

[0004] An infrared cut filter is generally installed between a CMOS image sensor and a lens module. The infrared cut filter is configured by combining a near-infrared absorbing filter that absorbs near-infrared light to convert it into heat energy, a near-infrared reflecting filter composed of an inorganic dielectric multilayer film, and an antireflection film formed at the boundary surface between these and air (see, for example, Japanese Patent Application Publication No. 2006-182586).

[0005] The characteristics of the infrared cut filter are the combined values of the individual characteristics of the near-infrared absorbing filter, the near-infrared reflecting filter, and the antireflection film. In the infrared cut filter, there are a one-piece structure in which the near-infrared absorbing filter, the near-infrared reflecting filter, and the antireflection film are integrated into one piece, and a structure in which the near-infrared absorbing filter and the near-infrared reflecting filter are disposed separately in the optical path, but the combined characteristic values of these do not change. SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The thickness of the optical axis direction of a small camera module of the present time is about 8 mm, in which 6 to 7 lenses, various filters, a CMOS image sensor, a lens actuator having a movable range of 1.5 mm, and the like are assembled as constituent elements. Therefore, the element-to-element distance of the constituent elements is close to the limit, and degradation of the image quality caused by ghosting and the like due to repeated reflection between the elements easily occurs.

[0008] Meanwhile, even in a small camera module, because the demand for higher resolution is high, models in which the pixel pitch of the CMOS image sensor is reduced to 2 μm or less (particularly, sub-μ CMOS image sensors of 1 μm or less) are increasing. As a result, a phenomenon in which a ghost image in the shape of a petal is produced as a trade-off for high resolution. As a result, there are many problems of degradation of the image quality in a small camera module, and this becomes a major cause of the extension of the development lead time of a small camera module.

[0009] The present invention provides an infrared cut filter that suppresses degradation of the image quality such as ghosting and coloring and improves the productivity.

[0010] TECHNICAL SOLUTION

[0011] The infrared cut filter of the present invention that achieves the above object is an infrared cut filter for a digital camera, characterized by comprising: a near-infrared reflecting filter configured in a manner in which 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 are alternately laminated; and an infrared absorbing film filter composed of a light-transmissive resin containing a pigment or a light-transmissive resin coated with a pigment.

[0012] The infrared cut filter according to any one of the above aspects can further include an antireflection portion formed on a surface of the near-infrared reflective filter and / or the infrared-absorbing film filter that contacts air.

[0013] The infrared cut filter according to any one of the above aspects can be configured such that the high-refractive-index resin, the low-refractive-index resin, and the light-transmissive resin that constitutes the infrared-absorbing film filter are each composed of an organic resin.

[0014] The infrared cut filter according to any one of the above aspects can be configured such that the high-refractive-index resin, the low-refractive-index resin, the light-transmissive resin that constitutes the infrared-absorbing film filter, and the antireflection portion are each composed of an organic resin.

[0015] The infrared cut filter according to any one of the above aspects can be configured such that the near-infrared reflective filter is formed by co-extrusion of the high-refractive-index layer and the low-refractive-index layer.

[0016] The infrared cut filter according to any one of the above aspects can be configured such that each of the high-refractive-index layer and / or the low-refractive-index layer has a thickness in a range of 10 nm to 300 nm.

[0017] The infrared cut filter according to any one of the above aspects can be configured such that the high-refractive-index layer and the low-refractive-index layer have a total of 30 or more layers.

[0018] The infrared cut filter according to any one of the above aspects can be configured such that the near-infrared reflective filter has a total thickness of 100 μm or less.

[0019] The infrared cut filter according to any one of the above aspects can be configured such that the near-infrared reflective filter and the infrared-absorbing film filter are integrated.

[0020] The infrared cut filter according to any one of the above aspects can be configured such that at least either the high-refractive-index resin or the low-refractive-index resin contains the coloring agent, thereby serving as the infrared-absorbing film filter.

[0021] The infrared cut filter according to any one of the above aspects can be configured such that the antireflection portion is a structure in which concavities and convexities are formed on a surface of the light-transmissive resin.

[0022] The infrared cut filter according to any one of the above aspects can be configured such that the antireflection portion is a multilayer film structure in which a low-refractive-index resin film and a high-refractive-index resin film are alternately stacked.

[0023] In the infrared cut filter described above, a part of the plurality of high refractive index layers and the plurality of low refractive index layers in the near-infrared reflective filter can function as the low refractive index resin film and the high refractive index resin film of the antireflection portion.

[0024] In the infrared cut filter described above, the near-infrared reflective filter and the infrared absorbing film filter can be integrated with each other, a first antireflection film can be formed on a surface of the near-infrared reflective filter opposite to the infrared absorbing film filter, and a second antireflection film can be formed on a surface of the infrared absorbing film filter opposite to the near-infrared reflective filter.

[0025] In the infrared cut filter described above, the antireflection portion can be a moth-eye structure in which a concave-convex structure is formed on a surface of a light-transmissive resin.

[0026] In the infrared cut filter described above, a total thickness of the near-infrared reflective filter, the infrared absorbing film filter, and the antireflection portion can be 300 μm or less.

[0027] In the infrared cut filter described above, a film thickness ratio of the near-infrared reflective filter can be 20% or more, based on a total thickness of the near-infrared reflective filter, the infrared absorbing film filter, and the antireflection portion.

[0028] In the infrared cut filter described above, a film thickness ratio of the infrared absorbing film filter can be 20% or more, based on a total thickness of the near-infrared reflective filter, the infrared absorbing film filter, and the antireflection portion.

[0029] In the infrared cut filter described above, in the near-infrared reflective filter alone, when a wavelength at which a transmittance of light decreases to 50% along with an increase in wavelength of incident light is defined as a reflection film cutoff wavelength, the reflection film cutoff wavelength can be in a range of 750 nm to 900 nm in a case where an incident angle of the incident light is 0°.

[0030] In the infrared cut filter described above, in the near-infrared reflective filter alone, when a wavelength at which a transmittance of light decreases to 50% along with an increase in wavelength of incident light is defined as a reflection film cutoff wavelength, a wavelength fluctuation amplitude of the reflection film cutoff wavelength can be 150 nm or less when the incident angle of the incident light is changed in a range of 0° to 60°.

[0031] The infrared cut filter is characterized in that, when a wavelength of 440 nm of incident light is defined as a reference blue wavelength, a transmittance of the reference blue wavelength of the near-infrared reflective filter element can be 70% or more in a case where an incident angle of the incident light is set to 60°.

[0032] The infrared cut filter is characterized in that a wavelength of 450 nm to 500 nm of incident light can be defined as a low wavelength transmittance band, and in the near-infrared reflective filter element, when an average transmittance of the incident light in the low wavelength transmittance band is defined as a reflection film low wavelength transmittance, the reflection film low wavelength transmittance can be 75% or more when the incident angle of the incident light is changed in a range of 0° to 60°.

[0033] The present application for achieving the above object is characterized in that a resin constituting the near-infrared reflective filter and / or the infrared absorbing film filter can contain an ultraviolet absorber.

[0034] The camera structure of the present application for achieving the above object is characterized in that it is a digital camera structure provided with an optical lens group arranged on an incident side of light, and a shooting element that receives light incident via the optical lens group, and the above-described infrared cut filter is arranged between the optical lens group and the shooting element.

[0035] The camera structure of the present application for achieving the above object is characterized in that it is a digital camera structure provided with, in this order from an incident side of light, a cover glass, an optical lens group, and a shooting element, and the above-described infrared cut filter is provided, the near-infrared reflective filter is arranged between the cover glass and the optical lens group, and the infrared absorbing film filter is arranged between the optical lens group and the shooting element.

[0036] The camera structure is characterized in that the near-infrared reflective filter can be attached to the cover glass.

[0037] The manufacturing method of the infrared cut filter of the present application for achieving the above object is characterized in that it is a manufacturing method of an infrared cut filter for a digital camera, and includes: a reflection film manufacturing process of forming a near-infrared reflective filter by 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 through co-extrusion molding; and a chip processing process of making the near-infrared reflective filter into a desired shape at least by cutting processing or blanking processing.

[0038] The manufacturing method of the infrared cut filter is characterized in that an integration process can be provided, in which an infrared-absorbing film filter is laminated or attached to the near-infrared reflecting filter, the infrared-absorbing film filter being composed of a light-transmitting resin containing a pigment or a light-transmitting resin applied to an absorbing film.

[0039] The manufacturing method of the infrared cut filter is characterized in that, in the reflecting film manufacturing process, the high-refractive resin and the low-refractive resin and a light-transmitting resin containing a pigment that absorbs infrared rays are co-extrusion molded, thereby integrally molding a near-infrared reflecting filter and an infrared-absorbing film filter, the near-infrared reflecting filter having high-refractive layers formed of the high-refractive resin and low-refractive layers formed of the low-refractive resin alternately laminated, the infrared-absorbing film filter being formed of the light-transmitting resin.

[0040] The manufacturing method of the infrared cut filter is characterized in that, in the reflecting film manufacturing process, after either of the high-refractive resin and the low-refractive resin is caused to contain a pigment that absorbs infrared rays, the high-refractive resin and the low-refractive resin are co-extrusion molded, thereby integrally molding a near-infrared reflecting filter and an infrared-absorbing film filter, the near-infrared reflecting filter having high-refractive layers formed of the high-refractive resin and low-refractive layers formed of the low-refractive resin alternately laminated, the infrared-absorbing film filter being formed of the side of the high-refractive layers and the low-refractive layers that contains the pigment.

[0041] The manufacturing method of the infrared cut filter is characterized in that an antireflection film attaching process can be provided, which is implemented before the chip processing process, to form an antireflection film on a surface in contact with air.

[0042] The manufacturing method of the infrared cut filter is characterized in that a mask attaching process can be provided, which is implemented before the chip processing process, to print a light-shielding mask.

[0043] The manufacturing method of the infrared cut filter is characterized in that, in the integration process, the near-infrared reflecting filter in a roll shape and the infrared-absorbing film filter in a roll shape are supplied to a laminating device to be integrated and wound in a roll shape.

[0044] Technical Effects

[0045] According to the present application, an infrared cut filter in which ghost flare, coloring, and the like are suppressed and mass production efficiency is dramatically improved can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a cross-sectional view of an infrared cut filter of the first embodiment of the present application.

[0047] Figure 2 is a cross-sectional view of a near-infrared reflective filter of the infrared cut filter shown in an enlarged manner.

[0048] Figure 3 is a spectrogram showing a transmission characteristic of the near-infrared reflective filter.

[0049] Figure 4 is a spectrogram showing a transmission characteristic of an existing near-infrared reflective filter that is a comparative example.

[0050] Figure 5 is a graph showing a wavelength-classified incident angle dependence characteristic of a near-infrared reflective filter according to an additional embodiment of the first embodiment.

[0051] Figure 6 is a graph showing a wavelength-classified incident angle dependence characteristic of a near-infrared reflective filter of Comparative Example 1.

[0052] Figure 7 is a graph showing a wavelength-classified incident angle dependence characteristic of a near-infrared reflective filter of Comparative Example 2.

[0053] Figure 8 is a spectrogram showing an absorption characteristic of an infrared absorbing film filter of the infrared cut filter of the first embodiment.

[0054] Figure 9 is a graph showing a cross-sectional shape and a refractive index of an antireflection film of the infrared cut filter of the first embodiment in an enlarged manner.

[0055] Figure 10 is a spectrogram showing a transmission characteristic and a reflection characteristic of the antireflection film.

[0056] Figure 11 is a side view showing a structure of a laminating apparatus used in a lamination process.

[0057] Figure 12 is a side view showing a structure of a film forming apparatus used in an antireflection film attaching process.

[0058] Figure 13 is a spectrogram showing an optical characteristic of the entire infrared cut filter of the first embodiment.

[0059] Figure 14 is a spectrogram showing an optical characteristic of the entire infrared cut filter of Comparative Example 3.

[0060] Figure 15This is a cross-sectional view of a camera module assembled with the infrared cut-off filter of the first embodiment.

[0061] Figure 16 (A) is a cross-sectional view of the infrared cutoff filter according to the second embodiment of the present invention. Figure 16 (B) is a cross-sectional view of a camera module assembled with the infrared cut-off filter.

[0062] Figure 17 (A) is a cross-sectional view of the infrared cutoff filter according to the third embodiment of the present invention. Figure 17 (B) is a cross-sectional view of the infrared cutoff filter according to the fourth embodiment of the present invention. Figure 17 (C) is a cross-sectional view of the infrared cutoff filter according to the fifth embodiment.

[0063] Figure 18 (A) is a cross-sectional view of the infrared cut-off filter according to the sixth embodiment of the present invention. Figure 18 (B) is a cross-sectional view of the infrared cutoff filter according to the seventh embodiment of the present invention. Figure 18 (C) is a cross-sectional view of the infrared cut-off filter according to the eighth embodiment.

[0064] Figure 19 (A) is using Figure 15 The image shown is captured by the camera module of this embodiment. Figure 19 (B) is an image taken using an existing camera module that serves as a comparative example.

[0065] Figure 20 (A) is using Figure 15 The image shown is captured by the camera module of this embodiment. Figure 20 (B) is an image taken using an existing camera module that serves as a comparative example.

[0066] Figure 21 These are images captured using existing camera modules.

[0067] Figure 22 (A) is a cross-sectional view of the infrared cut-off filter according to the ninth embodiment of the present invention. Figure 22 (B) is a cross-sectional view of the camera structure assembled with the infrared cut-off filter.

[0068] Symbol Explanation

[0069] Infrared cut-off filters: 1, 101, 201, 301, 401, 501, 601, 701, 901

[0070] 20 Camera Modules

[0071] 30 magnetic support

[0072] 40 lens carrier

[0073] 50 lens unit

[0074] 70 imaging element

[0075] 80 substrate

[0076] 120 camera module

[0077] AB absorbing member

[0078] CT adhesive coating device

[0079] CT1 first coating device

[0080] CT2 second coating device

[0081] Fab1 infrared-absorbing film filter

[0082] Far1 antireflection film

[0083] Fref1 near-infrared-reflecting filter

[0084] Hind high-refractive-index layer

[0085] Lind low-refractive-index layer

[0086] M light-blocking mask

[0087] MS film-forming device

[0088] PR1 first transfer roller

[0089] PR2 second transfer roller

[0090] REF reflecting member

[0091] RR laminating roller

[0092] RS laminating device DETAILED DESCRIPTION

[0093] Embodiments of the present application will be described below with reference to the accompanying drawings.

[0094] A cross-sectional structure of an infrared cut filter 1 which will be a first embodiment of the present application is shown in FIG. 1. Figure 1The infrared cut-off filter 1 is an infrared cut-off filter used in digital cameras, comprising a near-infrared reflective filter Fref1, an infrared absorption film filter Fab1, an anti-reflective film (anti-reflective part) Far1, and a light-shielding mask M. The near-infrared reflective filter Fref1 is constructed by alternating layers of a high-refractive-index layer formed of a high-refractive-index resin for reflective film and a low-refractive-index layer formed of a low-refractive-index resin for reflective film. The infrared absorption film filter Fab1 is composed of a light-transmitting resin for absorption film containing pigment or a light-transmitting resin for absorption film coated with pigment. The anti-reflective film Far1 is formed on the air-exposed surfaces of the near-infrared reflective filter Fref1 and / or the infrared absorption film filter Fab1, and is composed of a light-transmitting resin for anti-reflection. Each component will be described in detail below.

[0095] Near-infrared reflective filter

[0096] (The membrane structure of this embodiment)

[0097] like Figure 2 As shown in the enlarged view, the near-infrared reflective filter Fref1 of this embodiment is constructed by alternating layers of a high-refractive-index layer Hind formed from a high-refractive-index resin for the reflective film and a low-refractive-index layer Lind formed from a low-refractive-index resin for the reflective film. The multilayer formation of the high-refractive-index layer Hind and the low-refractive-index layer Lind can be achieved using co-extrusion or spin coating. In this embodiment, a co-extrusion process using a T-die is employed. In the co-extrusion process, by extruding a quantity of high-refractive-index resin and low-refractive-index resin for the reflective film corresponding to the number of layers in the laminate, they flow out of the T-die in a film form while converging, thereby simultaneously performing film formation and lamination (mutual bonding). It should be noted that either the 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 inside the T-die and then merged, or the feedblock method, in which the high-refractive-index resin and the low-refractive-index resin of the reflective film are merged before the individual layers are formed into films and then concentrated into films inside the T-die, can be used. According to the co-extrusion process, high-refractive-index layers Hind and low-refractive-index layers Lind, which are difficult to form individually into films with a thickness of less than 1 μm, can be alternately stacked in hundreds (e.g., several hundred) or thousands of layers, and can be temporarily wound onto a roller as a long strip of near-infrared reflective filter Fref1. It should be noted that the co-extrusion process using a T-die is described here, but a co-extrusion process based on a blow-up method can also be used.

[0098] The high-refractive resin for a reflective film and the low-refractive resin for a reflective film can be any transparent resin as long as the refractive indices of the adjacent films are different from each other. For example, at least two kinds of resin can be selected from among an acrylic resin, a polyester resin (e.g., polyethylene terephthalate), a polycarbonate resin, a polystyrene resin, a polyvinyl resin, a polypropylene resin, a cellulose resin, an olefin resin, a fluorine resin, and an ethylene resin.

[0099] As the high-refractive resin for a reflective film, for example, a resin having a refractive index of 1.53 or more, specifically, a polyester resin, a polystyrene resin, a polyvinyl resin, a polycarbonate resin, an acrylic resin, and an ethylene resin are preferably selected, and a resin having a refractive index of 1.56 or more, specifically, a polystyrene resin, a polyester resin, and a polycarbonate resin are more preferably selected.

[0100] The low-refractive resin for a reflective film is preferably selected from a resin having a refractive index of less than 1.53, specifically, an ethylene resin, a polypropylene resin, an acrylic resin, a cellulose resin, and a fluorine resin, and more preferably a resin having a refractive index of less than 1.50, specifically, an ethylene resin (polyvinyl alcohol), a polypropylene resin, an acrylic resin (e.g., a polymethyl methacrylate resin), a cellulose resin, and a fluorine resin are selected. Note that a plurality of resins selected from among these resins or a copolymer of these resins and other resins can be used to adjust the refractive index. In addition, the high-refractive layers Hind and the low-refractive layers Lind which are alternately stacked do not necessarily need to be made of the same resin material.

[0101] In addition, in order to finely adjust the refractive index, an additive for adjusting the refractive index can be added to the high-refractive resin for a reflective film and / or the low-refractive resin for a reflective film, and the refractive index can be further adjusted by mixing a plurality of resins. In order to further improve the ultraviolet resistance, a quencher (extinction pigment) such as a sulfur compound can be added to the high-refractive resin for a reflective film and / or the low-refractive resin for a reflective film.

[0102] For each film thickness of the high-refractive layers Hind and the low-refractive layers Lind, the wavelength (or wavelength band) to be reflected is set to λ, and the thickness is preferably ¼ of λ or less. For example, in the present embodiment, since the light in the range of 600 nm to 1200 nm of wavelength λ is required to be reflected, each layer thickness of the high-refractive layers Hind and the low-refractive layers Lind is set to a range of 400 nm or less, for example.

[0103] In the case where a high-refractive resin for a reflection film and a low-refractive resin for a reflection film are used, the reflectance of near-infrared light per boundary unit becomes smaller as compared with the existing dielectric film because the refractive index difference has to be set smaller. Therefore, in order to achieve high reflectance of near-infrared light, in the present embodiment, the number of layers is increased while the thickness of each film is reduced. More specifically, in the present embodiment, the thickness of each layer of the high-refractive layer Hind and the low-refractive layer Lind is, for example, preferably 200 nm or less, more preferably 100 nm or less, further preferably 80 nm or less, and still further preferably 50 nm or less. In the present embodiment, it is set to 15 nm or less, for example, 20 nm or less. In addition, the total number of layers of the high-refractive layers Hind and the low-refractive layers Lind alternately stacked is preferably set to 30 layers or more, more preferably 100 layers or more, and further preferably 200 layers or more. Still further preferably, it is set to 300 layers or more, for example, 400 layers.

[0104] By reducing the thickness of each film, the entire film thickness of the near-infrared light reflecting filter Fref1 is preferably 100 μm or less, and more preferably 50 μm or less. Note that, from the viewpoint of handling at the time of mass production, the entire film thickness of the near-infrared light reflecting filter Fref1 is preferably set to 10 μm or more, and preferably 30 μm or more.

[0105] As described above, for the infrared light absorbing film filter Fab1 of the present embodiment, since an organic resin becomes a base material, material selection and adjustment of the refractive index based on additives and / or resin mixing are easily performed. That is, the setting of the refractive index difference between the high-refractive layer Hind and the low-refractive layer Lind can be freely performed. In addition, by using a co-extrusion processing method, each film thickness can be controlled to a film of 1 μm or less. Further, in the demolding processing described later, the advantage that the film characteristics do not deteriorate can also be obtained.

[0106] (Reflection characteristics)

[0107] Figure 3 The reflection characteristics of the individual near-infrared light reflecting filter Fref1 are shown. Here, the wavelength at which the transmittance of light of the near-infrared light reflecting filter Fref1 decreases to 50% as the wavelength of incident light increases is defined as the "reflection film cutoff wavelength". The reflection film cutoff wavelength in the case where the incident angle of incident light is 0° (i.e., the light is perpendicularly incident with respect to the film) is set to a range of 750 nm to 900 nm. More specifically, the reflection film cutoff wavelength is set to a range of 750 nm to 880 nm, further specifically, the reflection film cutoff wavelength is set to a range of 770 nm to 880 nm, and still further specifically, the reflection film cutoff wavelength is set to a range of 780 nm to 880 nm.

[0108] In addition, in the present embodiment, the fluctuation amplitude (wavelength shift amount) Srefl of the reflection film cutoff wavelength when the incident angle of the incident light is varied in the range of 0° to 60° is 170 nm or less, preferably 150 nm or less, more preferably 120 nm or less, and further preferably 100 nm or less. That is, the wavelength difference between the reflection film cutoff wavelength at the incident angle of 0° and the reflection film cutoff wavelength at the incident angle of 60° is 150 nm or less. The greater the incident angle, the more easily the light reaches the near-infrared reflection filter Frefl as the camera module is thinned, but in the near-infrared reflection filter Frefl of the present embodiment, since the wavelength shift amount Srefl of the reflection film cutoff wavelength to the short wavelength side is suppressed, high-quality imaging can be achieved. Note that the reflection film cutoff wavelength at the incident angle of 60° is preferably set to 650 nm or more, since it is not less than the absorption film cutoff wavelength at the incident angle of 60° of the infrared absorption film filter Fabl, and thus the imaging result is not easily disturbed.

[0109] Further, the wavelength range in which the transmittance of the light of the near-infrared reflection filter Frefl is reduced to 10% or less is defined as the "reflection film total reflection wavelength range". The reflection film total reflection wavelength range Wrefl at the incident angle of 0° is approximately 790 nm to 1100 nm. Note that the reflection film total reflection wavelength range Wrefl fluctuates (shifts) to the short wavelength side depending on the incident angle, but the fluctuation amount thereof is approximately the wavelength shift amount Srefl of the reflection film cutoff wavelength.

[0110] Next, when the wavelength of 440 nm of the incident light is defined as the reference blue wavelength, the transmittance of the reference blue wavelength of the near-infrared reflection filter Frefl alone at the incident angle of 60° is 70% or more. As a result, the existing defect of reduction of the blue component due to fluctuation of the incident angle can be reduced. Further, the wavelength of 450 nm to 500 nm of the incident light is defined as the low wavelength band, and the average transmittance of the incident light in the low wavelength band is defined as the reflection film low wavelength transmittance. For the near-infrared reflection filter Frefl, the reflection film low wavelength transmittance when the incident angle of the incident light is varied in the range of 0° to 60° is always 75% or more. That is, in the near-infrared reflection filter Frefl alone, when the range from the reflection film start wavelength at which the transmittance is 50% to the reflection film cutoff is defined as the reflection film transmission band Trefl, even if the incident angle fluctuates in the range of 0° to 60°, the shape of the corner region TRl on the low wavelength side in the rectangular waveform shape of the reflection film transmission band Trefl is always stable (the corner shape on the long wavelength side shifts to the short wavelength side). As a result, even if the incident angle increases, the near-infrared reflection filter Frefl can reduce the phenomenon of disturbance of the low wavelength band component (so-called ripple phenomenon).

[0111] (Comparison with the Related Art)

[0112] The existing near-infrared reflective filter forms an inorganic dielectric multilayer film on the other side of the blue glass on which an infrared-absorbing film filter material is coated on one side, thereby realizing an infrared reflective function. Figure 4 The optical characteristics of the existing near-infrared reflective filter element are shown. The fluctuation amplitude (wavelength shift amount) Sreft of the reflective film cutoff wavelength of the existing near-infrared reflective filter when the incident angle of the incident light is changed in the range of 0° to 60° is 150 nm or more. Especially, if the incident angle is 60°, the waveform of the spectral characteristics is easily disturbed and has a ripple. This is because, in the case of the incident light, in which the vibration plane of the incident light coincides with the P component and the vibration plane of the incident light coincides with the S component perpendicular to the propagation plane, if the incident angle with respect to the dielectric multilayer film increases, the transmission characteristics are deviated in the P component and the S component. As a result, since the reflective film cutoff wavelength of the existing near-infrared reflective filter is less than 650 nm, it becomes less than the cutoff wavelength of the absorbing film of the infrared-absorbing film filter at the incident angle of 60°, and the shooting result is also disturbed. In addition, when the wavelength of 440 nm of the incident light is defined as a reference blue wavelength, the transmittance of the reference blue wavelength of the existing near-infrared reflective filter in the case where the incident angle of the incident light is set to 60° is disturbed, and there is a case where the transmittance becomes 60% or less. As a result, the blue component is reduced due to the fluctuation of the incident angle. Furthermore, in the low band of the wavelength of the incident light of 450 nm to 500 nm, in the existing near-infrared reflective filter, in the case where the incident angle of the incident light is 60°, the average transmittance is less than 75% and the ripple is increased.

[0113] It should be noted that, although as a reference, if it is intended to form an inorganic dielectric multilayer film on the surface and the back of the infrared-absorbing film filter Fab1 formed of a resin film of the present embodiment using a PVD process, a high level of technology and experience is required including the cutting process thereafter, and it is easy to cause a reduction in yield. Specifically, in the PVD process, a slight defect is inevitably generated in the inorganic dielectric multilayer film, and it is necessary to remove it after the fact by 100% inspection. In addition, in the cutting process, since the inorganic dielectric multilayer is easily peeled off, it is also necessary to visually confirm the peeling state by 100% inspection. That is, from the viewpoint of mass production, the resin film is extremely poor in compatibility with the PVD process.

[0114] (Additional Embodiment)

[0115] As the near-infrared reflecting filter Frefl of the present embodiment, a 200-layer high refractive index layer Hind and a low refractive index layer Lind were formed using a polyethylene terephthalate resin and a polymethyl methacrylate resin, and the total thickness of the near-infrared reflecting filter Frefl was set to 50 μm. As a result, the reflection film cutoff wavelength at an incident angle of 0° of the incident light was 850 nm. As shown in FIG. 6, in all of the visible light (R: red 630 nm, G: green 546 nm, B: blue 436 nm), even if the incident angle was increased, the transparency (transmittance) was maintained high as a whole, and no interference color caused by reflection was found by visual observation. Also, even if the incident angle was in the range of 50° to 60°, the transmittance was maintained at 75% or more, and no extreme reduction in transmittance occurred, and a relatively smooth reduction tendency was obtained. Note that, in the B band of the short wavelength among RGB, a few percentage points of deviation from the remaining R band and G band was found, but the amount of deviation was within a range in which there was no problem in image quality, and the deviation amplitude was stable throughout the entire incident angle, so that a change in image quality caused by fluctuation in the incident angle was difficult to occur. Figure 5

[0116] (Comparative Example 1)

[0117] Figure 6 The optical characteristics of the near-infrared reflecting filter of Comparative Example 1 were shown. In this Comparative Example 1, an inorganic dielectric multilayer film was formed on an optical glass plate which became completely transparent by a PVD process, and the reflection film cutoff wavelength at an incident angle of 0° of the inorganic dielectric multilayer film was adjusted to 780 nm. In this near-infrared reflecting filter, if the incident angle exceeded 50°, the transmittance of the R band was sharply reduced, and the transmittance of the R band completely disappeared at an incident angle of 70°. This is because the reflection film cutoff wavelength was shifted to the low wavelength side with an increase in the incident angle, and the light of the R band was reflected. Note that, in the case of this near-infrared reflecting filter, the interference color of red could also be easily observed by visual observation. The infrared cutoff filter obtained by combining the existing near-infrared reflecting filter and an absorbing film was assembled to a camera module, and a quality check was performed by a real shot, and in the peripheral portion of the image (i.e., a region in which the incident angle was large), the green color was relatively strong, and thus a typical red coloration deficiency was found.

[0118] (Comparative Example 2)

[0119] Figure 7 ​The optical characteristics of the near-infrared reflective filter of Comparative Example 2 are shown. In this Comparative Example 2, an inorganic dielectric multilayer film was formed on an optical glass plate using a PVD process, and the reflection film cutoff wavelength at an incident angle of 0° of the inorganic dielectric multilayer film was adjusted to 850 nm. In this case, no interference color was found by visual observation. If the incident angle dependence of the RGB transmittances is observed, the RGB mutually deviate little from each other, but if the incident angle is 40° or more, a phenomenon of a decrease in the transmittance of the RGB as a whole occurs, and if the incident angle is 60°, the transmittances of the RGB all decrease to 65%. That is, it is known that although a phenomenon of a decrease in the transmittance of the R band alone does not occur, a decrease in the transmittance of the whole occurs.

[0120] <Infrared-absorbing film filter>

[0121] (Film structure)

[0122] The infrared-absorbing film filter Fabl of the present embodiment adopts a so-called blue film structure (a structure obtained by adding a near-infrared light-absorbing colorant to a light-transmissive resin for an absorbing film). The film thickness of the infrared-absorbing film filter Fabl is preferably 100 μm or less, and desirably 50 μm or less. Note that from the viewpoint of handling in the middle of mass production, the film thickness of the infrared-absorbing film filter Fabl is preferably 10 μm or more, and more preferably 30 μm or more.

[0123] As the organic colorant having a near-infrared light-absorbing function, an azo-based compound, a phthalocyanine-based compound, a cyanine-based compound, a diimmonium-based compound, or the like can be used. The light-transmissive resin for an absorbing film (which can also be referred to as a binder or a substrate with respect to the organic colorant) constituting the infrared-absorbing film filter Fabl uses an organic polymer such as an acrylic resin, a polyester resin (e.g., polyethylene terephthalate), a polycarbonate resin, a polystyrene-based resin, a polyethylene-based resin, a polypropylene resin, a cellulose-based resin (e.g., cellulose triacetate), an olefin-based resin (e.g., a cyclic olefin, a polyolefin), a fluorine-based resin, an ethylene-based resin, or the like. The light-transmissive resin for an absorbing film can be a mixture of a plurality of resins, or can be a copolymer using monomers of the above resins. In addition, the light-transmissive resin for an absorbing film can be a resin having a high transmittance with respect to light in the visible light region, and is selected in consideration of the compatibility with the organic colorant, the film formation process, the cost, and the like. In addition, in order to improve the ultraviolet resistance of the infrared-absorbing film filter Fabl, a quenching agent (extinction colorant) such as a sulfur compound can also be added to the light-transmissive resin for an absorbing film.

[0124] (Absorption characteristics)

[0125] Figure 8The absorption characteristics of the infrared-absorbing film filter Fabl monomer are shown. The characteristics of the infrared-absorbing film filter Fabl are set in correlation with those of the near-infrared-reflecting filter Frefl. The infrared-absorbing film filter Fabl has a transmission characteristic close to the visible sensitivity curve of humans in the visible wavelength region of 400 nm to 700 nm, and a transmittance of 2% or less, preferably 1% or less, in the wavelength range of 685 nm to 800 nm. Thus, in the infrared-absorbing film filter Fabl monomer, if a region having a transmittance of 2% or less is defined as a light-absorbing region Wabl, then the reflection film cutoff wavelength fluctuation region on the near-infrared-reflecting filter Frefl side, in which the incident angle fluctuates in the range of 0° to 30°, is set to fall entirely within this light-absorbing region. Note that, as a more preferable infrared-absorbing film filter Fabl, the transmittance is 2% or less in the wavelength range of 685 nm to 850 nm, and further preferably the transmittance is 2% or less in the wavelength range of 685 nm to 900 nm.

[0126] Furthermore, in the wavelength region of 800 nm to 1150 nm, which overlaps with the reflection film total reflection wavelength range Wrefl (example: 790 nm to 1100 nm) on the near-infrared-reflecting filter Frefl side, the maximum transmittance of the infrared-absorbing film filter Fabl monomer is set to 60% or less, and preferably the maximum transmittance is set to 40% or less. Likewise, the average transmittance of the wavelength region of 800 nm to 1150 nm of the infrared-absorbing film filter Fabl is set to 40% or less, and preferably to 25% or less.

[0127] Note that, in the present embodiment, by combining the near-infrared-reflecting filter Frefl with the infrared-absorbing film filter Fabl, and using the near-infrared-reflecting filter Frefl to cut off (reflect) light of a wavelength of 800 nm or more, which cannot be absorbed to 2% or less by the infrared-absorbing film filter Fabl alone, it is possible to obtain an image with a natural color tone. On the other hand, if it is intended to cut off (reflect) light of the entire near-infrared region using only the near-infrared-reflecting filter Frefl, then, as described above, since the incident angle of the incident light becomes large, the reflection film cutoff wavelength shifts (moves) to the short wavelength side. Therefore, the infrared cutoff on the short wavelength side is achieved by combining the infrared-absorbing film filter Fabl, which has no incident angle dependence, and thus it is possible to construct an infrared cutoff filter 1 in which the infrared cutoff characteristics in a wide region of 700 nm to 1150 nm are independent of the incident angle of light.

[0128] Here, the wavelength at which the transmittance of the infrared absorbing film filter Fabl monomer decreases to 50% with an increase in the wavelength of incident light is defined as the "absorbing film cutoff wavelength". The absorbing film cutoff wavelength is almost independent of the incident angle of incident light. The absorbing film cutoff wavelength is set to a range of 600 nm to 680 nm. In addition, the absorbing film cutoff wavelength is set to be always smaller than the lowest value of the reflecting film cutoff wavelength on the near-infrared reflecting filter Frefl side when the incident angle is changed in a range of 0° to 60°.

[0129] (Comparison with the Related Art)

[0130] The existing infrared absorbing film filter uses a so-called blue glass in which an appropriate amount of Cu is added to phosphoric acid glass as a base material. This blue glass can obtain preferable near-infrared light absorbing properties. However, if the blue glass is thinned, the amount of copper ion dissolution of the blue glass is limited, and as a result, the absorption capacity of near-infrared light is insufficient. Therefore, an auxiliary infrared absorbing film filter is formed by applying an infrared absorbing ink to one surface of the blue glass by spin coating or the like, and the infrared absorption deficiency of the blue glass is compensated as a whole. As a result, the production process is greatly increased.

[0131] <Anti-reflective Film (Anti-reflective Portion)>

[0132] (Film Structure)

[0133] Here, the anti-reflective film Farl is composed of a light-transmitting resin for anti-reflection. This anti-reflective film Farl is indispensable for maintaining the image quality and brightness for a camera module. In particular, in the case of a small camera module, since the distance between optical elements is narrowed to the limit, various image noises such as ghosting and flare are easily generated, but the image noises can be reduced by this anti-reflective film Farl.

[0134] As a basic structure of the anti-reflective film Farl, a "single layer film structure" formed of a low refractive index resin, a "multilayer film structure" in which resin films (low refractive index film and high refractive index film) having different refractive indices are alternately laminated and have a function of converting light into heat and absorbing it, a "porous low refractive index film structure" in which a resin surface is made porous to form a low refractive index, a "porous inclined refractive index structure" in which a resin surface is made porous and the air occupancy rate thereof is inclined to the optical axis direction (film thickness direction) to produce refractive index inclination, a "moth-eye inclined refractive index structure" in which a resin surface is formed with fine protrusions (moth-eyes) having tapered tips to produce refractive index inclination in the optical axis direction (film thickness direction), and the like can be adopted. Note that, in the "moth-eye inclined refractive index structure", there are a regular moth-eye structure in which fine protrusions (moth-eyes) are regularly arranged, and a random moth-eye structure in which irregular fine protrusions having different heights and / or pitches are formed, but any one of them can be adopted.

[0135] From the viewpoint of employing the roll-to-roll manufacturing process described later, the antireflective film Far1 preferably adopts a "multi-layer film structure" and a "moth-eye tilted refractive index structure". Here, the following is adopted: Figure 9 The diagram shows a regular moth-eye structure. The sloping refractive index becomes the refractive index of the anti-reflective transparent resin at the base of the protrusion and the refractive index of air at the protruding end. For example, an ultraviolet-curable resin is used as the anti-reflective transparent resin. The moth-eye shape is formed by applying the liquid ultraviolet-curable resin (here, a near-infrared reflective filter Fref1 or an infrared absorption film filter Fab1) to a substrate, pressing a transfer film or transfer roller with a moth-eye shape while irradiating it with ultraviolet light. The "moth-eye sloping refractive index structure" has the advantage of being less affected by the wavelength range of the incident light and fluctuations in the incident angle. The size of the micro-protrusions is preferably such that the protrusion height is 2 μm or less, and the spacing between the protrusions (grid spacing) is 2 μm or less. Further preferably, the protrusion height is set to less than 1 μm and the spacing between the protrusions (grid spacing) is set to less than 1 μm. Even more preferably, the protrusion height is set to less than 0.5 μm and the spacing between the protrusions (grid spacing) is set to less than 0.5 μm.

[0136] When the antireflective film Far1 is configured as 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 reflective filter Fref1 can simultaneously function as both the low-refractive-index and high-refractive-index layers of the antireflective film Far1. That is, the antireflective film Far1 functions simultaneously near the surface of the near-infrared reflective filter Fref1.

[0137] It should be noted that since the film of the near-infrared reflective filter Fref1 in this embodiment is made of resin, its surface reflection is significantly suppressed compared to existing inorganic dielectric multilayer films. As a result, by combining the surface reflection state of this near-infrared reflective filter Fref1 with the "moth-eye tilted refractive index structure," excellent anti-reflection function can be further obtained, and image quality is significantly improved.

[0138] (Transmission and reflection characteristics)

[0139] Figure 10The spectral characteristics of the antireflection film Farl are shown. In this figure, the spectral characteristics 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) are shown as the transmittance Tm, and the spectral characteristics at an incident angle of 6° (Rm6), an incident angle of 15° (Rml5), an incident angle of 30° (Rm30), an incident angle of 45° (Rm45), and an incident angle of 60° (Rm60) are shown as the reflectance Rm.

[0140] The transmittance Tm in the visible region (400 nm to 700 nm) over a range of incident angles of 0° to 45° is 95% or more, and the reflectance Rm is 3% or less, and the reflectance Rm is preferably 1% or less. Further, even if the incident angle is 60°, the transmittance T in the visible region is 90% or more, and the reflectance R is 5% or less. In addition, the average transmittance in the visible region is 99.2%, and the average reflectance is 0.8%.

[0141] <Method for manufacturing infrared cut filter>

[0142] Next, the manufacturing method of the infrared cut filter 1 will be described.

[0143] (Antireflection film manufacturing step)

[0144] First, the near-infrared reflective filter Frefl is manufactured by a co-extrusion method. The sheet material extruded from the co-extruder is subjected to uniaxial (longitudinal) stretching or biaxial (longitudinal and transverse) stretching by using a stretching device to become the near-infrared reflective filter Frefl. The completed near-infrared reflective filter Frefl is preferably temporarily wound into a roll shape.

[0145] (Infrared absorbing film filter manufacturing step)

[0146] The infrared absorbing film filter Fabl is manufactured by an extrusion method using a light-transmitting resin for an absorbing film containing an organic pigment. The sheet material extruded from the extruder is subjected to uniaxial (longitudinal) stretching or biaxial (longitudinal and transverse) stretching by using a stretching device to become the infrared absorbing film filter Fabl. The completed infrared absorbing film filter Fabl is preferably temporarily wound into a roll shape.

[0147] (Laminating step)

[0148] As Figure 11As shown, a near-infrared reflective filter Fref1 and an infrared absorption film filter Fab1 are bonded together using a roller-to-roll laminating device RS. Specifically, the near-infrared reflective filter Fref1 and the infrared absorption film filter Fab1 are output in roll form. An adhesive is applied to either surface using an adhesive coating device CT. The two films are then bonded together by clamping and pressing them together using a pair of heated laminating rollers RR. The bonded near-infrared reflective filter Fref1 and infrared absorption film filter Fab1 are preferably wound back into a roll. A thermosetting optical adhesive can be used as the adhesive applied by the adhesive coating device CT.

[0149] (Additional process for anti-reflective film)

[0150] like Figure 12 As shown, an anti-reflective film Far1 is formed on the outer surfaces of a near-infrared reflective filter Fref1 and an infrared absorption filter Fab1 using a roller-to-roll film-forming apparatus MS. Specifically, an anti-reflective transparent resin (UV-curable resin) is coated onto the outer surface of the near-infrared reflective filter Fref1 using a first coating apparatus CT1, and cured by irradiating it with UV1 while pressing a first transfer roller PR1, thereby forming a first anti-reflective film Far1 with a moth-eye tilted refractive index structure. Next, an anti-reflective transparent resin is coated onto the outer surface of the infrared absorption filter Fab1 using a second coating apparatus CT2, and cured by irradiating it with UV2 while pressing a second transfer roller PR2, thereby forming a second anti-reflective film Far1 with a moth-eye tilted refractive index structure. As a result, a sheet material for an infrared cut-off filter with an all-polymer structure, comprising the near-infrared reflective filter Fref1, the infrared absorption filter Fab1, and a pair of anti-reflective films Far1, is completed. The completed sheet material is preferably temporarily wound into a roll.

[0151] (Light-blocking mask printing process)

[0152] It has passed Figure 12After the infrared cut-off filter sheet material is cut into desired rectangular sheets to become single sheets, a frame-shaped light-shielding mask is printed on each sheet using a printing apparatus. The light-shielding mask serves to block excess peripheral light for the CMOS pixel sensor. For example, for rectangular sheets, a total of 100 or more light-shielding masks are printed in a grid or staggered pattern, preferably 300 or more. It should be noted that the light-shielding mask can be printed on either the near-infrared reflective filter Fref1 side or the infrared absorption film filter Fab1 side, but in this case, it is printed on the infrared absorption film filter Fab1 side. The size of the rectangular sheet is not particularly limited, but from the viewpoint of mass production efficiency, a large size of at least 150 mm in length and 150 mm in width is preferred, more preferably 200 mm or more in length and 200 mm in width, and even more preferably 300 mm or more in length and 300 mm in width. It should be noted that, in the case of existing infrared cut-off filters with blue glass structures, the size of the glass plate is limited to less than 100mm in both length and width due to issues in the processing of the glass substrate.

[0153] (Chip manufacturing process)

[0154] The rectangular sheet printed with the light-blocking mask is entirely made of organic resin. Therefore, by using a punching device on the punching side to punch the rectangular sheet into the desired shape (e.g., a rectangle a few millimeters long and a few millimeters wide), the chip is processed into a single piece of multiple infrared cut-off filters 1. As a result, a complete... Figure 1 The infrared cutoff filter 1 shown is an example. It should be noted that, as a blanking cutter, a double-edged structure with blades on both sides of the die holding the rectangular sheet is preferably used to suppress burrs and the like. Since the rectangular sheet is made of organic resin, compared to glass, inorganic dielectric films, etc., very little foreign matter (fragmentation) is introduced during chip processing. It should be noted that the die is not limited to a double-edged structure; a single-edged structure die can also be used. Furthermore, not limited to stamping, cutting using a cutter or the like can also be employed.

[0155] (Visual inspection procedure)

[0156] In the case of the infrared cut-off filter 1 in this embodiment, since there is almost no deviation between the parts in the mass production process described above, quality can be guaranteed by performing inspections limited to a portion of the components instead of full inspections.

[0157] <Overall Structure and Characteristics of Infrared Cut-off Filters>

[0158] Figure 1The infrared cut filter 1 shown is composed entirely of organic resin, and does not include a glass substrate or a dielectric multilayer film. As a result, the manufacturing process can be greatly simplified, and the optical characteristics at the time of mass production can be stabilized. For example, by setting the film thickness of each of the near-infrared reflective filter Fref1, the infrared-absorbing film filter Fab1, and the antireflection film Far1 to 100 μm or less, the overall thickness of the infrared cut filter 1 can be set to 300 μm or less. As a result, the height of the camera module can be made lower. Note that in the present embodiment, by setting the film thickness of each of the near-infrared reflective filter Fref1, the infrared-absorbing film filter Fab1, and the antireflection film Far1 to 50 μm or less, the overall thickness is set to 150 μm or less, and specifically to 100 μm or less. Note that from the viewpoint of handling at the time of assembly of the camera module, the overall film thickness of the infrared cut filter 1 is preferably set to 30 μm or more. At this time, the overall thickness of the infrared cut filter 1 can be divided into the thickness of the near-infrared reflective filter Fref1 and the thickness of the infrared-absorbing film filter Fab1, and as a result, both the handling characteristics of the near-infrared reflective filter Fref1 and the handling characteristics of the infrared-absorbing film filter Fab1 can be improved at the time of mass production by roll-to-roll. From this viewpoint, in the case where the overall thickness of the infrared cut filter 1 is set to 100%, the film thickness ratio of the near-infrared reflective filter Fref1 is set to 20% or more, and desirably to 30% or more. Similarly, the film thickness ratio of the infrared-absorbing film filter Fab1 is set to 20% or more, and desirably to 30% or more. In addition, the film thickness difference between the near-infrared reflective filter Fref1 and the infrared-absorbing film filter Fab1 is preferably set to 100 μm or less, desirably to 80 μm or less, and further desirably to 50 μm or less.

[0159] Figure 13 The optical characteristics of the infrared cut filter 1 of the present embodiment are shown. The transmittance of the transmission band Q from the start of 50% to the end of 50% in the visible light region (400 nm to 700 nm) 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 this transmission band Q hardly change, and the moiré is small. In particular, with respect to the reference blue wavelength of 440 nm, and the low wavelength band of 450 nm to 500 nm, even if the incident angle is 60°, the amount of decrease in transmittance is small. As a result, in the captured image, the occurrence of coloring and ghosting is greatly suppressed. Furthermore, with respect to the infrared region, it is known that by combining the light-absorbing region Wab1 (refer to Figure 8 ) of the infrared-absorbing film filter Fab1 and the reflection film total reflection wavelength range Wref1 (refer toFigure 3 It maintains low transmittance throughout the entire 700nm–1150nm region. That is, it can suppress the intrusion of infrared images into the captured image.

[0160] (Comparative Example 3)

[0161] Figure 14 This illustration shows Fab1, which incorporates the same infrared absorption film filter as in this embodiment. Figure 8 ) and the existing near-infrared reflective filter shown in Comparative Example 1 ( Figure 4 The optical characteristics of the infrared cutoff filter are described. While the transmittance in the visible light region (400nm–700nm) reflects the spectral dispersive characteristics of the infrared absorption film filter Fab1, ripple caused by existing near-infrared reflective filters occurs at the reference blue wavelength of 440nm and the lower wavelength band of 450nm–500nm. Furthermore, if the incident angle becomes 60°, the overall transmittance in the visible light region (400nm–700nm) decreases, especially at the reference blue wavelength of 440nm and the lower wavelength band of 450nm–500nm, resulting in a significant decrease in transmittance and increased ripple. Consequently, coloration and ghosting are easily observed at the periphery in the captured image.

[0162] <Assembly relative to the camera module>

[0163] Figure 15 A camera module 20 is shown assembled with the infrared cut-off filter 1 of the first embodiment. As a camera structure, the camera module 20 includes: a lens unit 50 that forms an optical lens group; a lens carrier 40 that holds the lens unit 50; a magnetic support 30 that moves the lens unit 50 axially to achieve an autofocus function; an imaging element 70 that receives light incident through the lens unit 50; a substrate 80 for mounting the imaging element 70; and an infrared cut-off filter 1 disposed between the lens unit 50 and the imaging element 70.

[0164] In this camera module 20, the infrared cut-off filter 1 has a thin-walled structure. Furthermore, because it can be close to the lens unit 50 and the imaging element 70, its height can be reduced. Moreover, even if the pixel pitch of the CMOS image sensor that will become the imaging element 70 is set to 2μm or less, and ideally 1μm or less, image quality degradation is less likely to occur. It should be noted that the gap between the infrared cut-off filter 1 and the imaging element 70 can be made close to 0.5mm or less, and ideally close to 0.3mm or less. Similarly, the gap between the infrared cut-off filter 1 and the lens unit 50 can be made close to 0.5mm or less, and ideally close to 0.3mm or less.

[0165] Note that although not particularly shown, a cover glass can also be provided on the light incident side of the camera module 20. A dielectric multilayer film is preferably formed on this cover glass, and this dielectric multilayer film is formed by alternately laminating multiple layers of dielectrics having different refractive indexes. The dielectric multilayer film is laminated on the inner side of the cover glass by vacuum evaporation. The dielectric multilayer film makes up for the reflection function of the near-infrared reflective filter Frefl.

[0166] <Photographing Experiment>

[0167] An image obtained by photographing an object with the camera module 20 is shown in Figure 19 (A) of FIG. 10, and Figure 20 (A) of FIG. 11. Almost no ghost images due to repeated reflection of the constituent elements of the camera module 20 are generated. On the other hand, an image obtained by photographing with a camera module in which a conventional infrared cut filter is assembled is shown in Figure 19 (B) of FIG. 10, Figure 20 (B) of FIG. 11, and Figure 21 In the images of Figure 19 (B) of FIG. 10, and Figure 20 (B) of FIG. 11, a ghost image GST-A that expands in a petal shape (radial shape) and a ghost image GST-B that forms a balloon shape are formed. In addition, in the image of Figure 21 a colored region SHD is formed, and the peripheral portion of the image of this colored region SHD is green compared to the central portion. This colored region SHD coincides with a region in which the incident angle of external light with respect to the infrared cut filter becomes large, which means that the transmittance of R (red) and B (blue) decreases, and the light reduction of red and blue becomes significant, and as a reaction thereto, G (green) is emphasized.

[0168] Next, an infrared cut filter 101 of a second embodiment of the present application is shown in Figure 16 (A) of FIG. 12. For this infrared cut filter 101, the near-infrared reflective filter Frefl and the infrared absorbing film filter Fabl are separated, and an antireflection film Farl is formed on both surfaces of each. That is, the infrared cut filter 101 independently has, as a reflection member REF, the near-infrared reflective filter Frefl having the antireflection film Farl on both surfaces, and, as an absorbing member AB, the infrared absorbing film filter Fabl having the antireflection film Farl on both surfaces. In addition, here, a light-shielding mask M is printed on the side of the absorbing member AB. Note that since the configurations of the near-infrared reflective filter Frefl, the infrared absorbing film filter Fabl, and the antireflection film Farl are the same as those of the infrared cut filter 1 of the first embodiment, the description thereof is omitted here. In addition, the optical characteristics of the infrared cut filter 101 as a whole are almost the same as those of the infrared cut filter 1 of the first embodiment.

[0169] Since the absorbing member AB and the reflecting member REF are independent, the film thickness of the absorbing member AB is preferably in the range of 50 μm to 100 μm from the viewpoint of handling at the time of assembly, and the film thickness of the reflecting member REF is preferably in the range of 50 μm to 100 μm.

[0170] In Figure 16 (B) of FIG. 1 shows a camera module 120 in which the infrared cut filter 101 is assembled. The camera module 120 is provided with: a lens unit 50 that is an optical lens group; a lens carrier 40 that holds the lens unit 50; a magnetic holder 30 that moves the lens unit 50 in the axial direction in order to realize an auto focus function; a shooting element 70 that receives light incident via the lens unit 50; a substrate 80 on which the shooting element 70 is mounted; an absorbing member AB that is disposed between the lens unit 50 and the shooting element 70; and a reflecting member REF that is disposed on the light incident side of the lens unit 50. That is, the camera module 120 separately disposes the absorbing member AB and the reflecting member REF of the infrared cut filter 1. The reflecting member REF can be attached to the inner side of a so-called cover glass. In addition, the reflecting member REF can be inserted into the middle of the optical lens group in the lens unit 50. Note that although not particularly shown here, it is also possible to dispose the reflecting member REF between the lens unit 50 and the shooting element 70 and to dispose the absorbing member AB on the light incident side of the lens unit 50.

[0171] Note that although not particularly shown, it is also possible to dispose a cover glass on the light incident side of the camera module 120. It is preferable to form a dielectric multilayer film on the cover glass, and the dielectric multilayer film is formed by alternately laminating a plurality of layers of dielectrics having different refractive indexes. The dielectric multilayer film is laminated on the inner side of the cover glass by vacuum evaporation. The dielectric multilayer film makes it possible to compensate for the reflecting function of the near-infrared reflecting filter Frefl.

[0172] In Figure 17(A) shows an infrared cut filter 201 of a third embodiment of the present application. The infrared cut filter 201 has an infrared absorbing film filter Fabl inserted in the inside of the multilayer film of the near-infrared reflecting filter Frefl. Therefore, both surfaces become the near-infrared reflecting filter Frefl, and an antireflection film Farl is formed on each surface. In other words, the multilayer film of the near-infrared reflecting filter Frefl is divided into two or more groups, and the infrared absorbing film filter Fabl is interposed between the groups. In this case, the multilayer film of the near-infrared reflecting filter Frefl can be manufactured by the co-extrusion method (Co-Extrusion) in units of groups to be laminated with the infrared absorbing film filter Fabl interposed. Also, the entire near-infrared reflecting filter Frefl and antireflection film Farl can be integrally manufactured by the co-extrusion method (Co-Extrusion). Here, a case where a single-layer infrared absorbing film filter Fabl is inserted is exemplified, but the infrared absorbing film filter Fabl can be provided as a multilayer structure. Also, a plurality of infrared absorbing film filters Fabl can be dispersedly arranged between the near-infrared reflecting filters Frefl that are divided into groups.

[0173] In Figure 17 (B) shows an infrared cut filter 301 of a fourth embodiment of the present application. The infrared cut filter 301 has a multilayer structure near-infrared reflecting filter Frefl inserted in the inside of the dispersedly formed multilayer infrared absorbing film filter Fabl. Therefore, both surfaces become the infrared absorbing film filter Fabl, and an antireflection film Farl is formed on each surface. In this case, the multilayer film of the near-infrared reflecting filter Frefl can be manufactured by the co-extrusion method (Co-Extrusion) in units of groups to be laminated with the near-infrared reflecting filter Frefl interposed by a plurality of infrared absorbing film filters Fabl. Also, the entire near-infrared reflecting filter Frefl and antireflection film Farl can be integrally manufactured by the co-extrusion method (Co-Extrusion). Here, a case where a single group of infrared absorbing film filter Fabl is inserted is exemplified, but the infrared absorbing film filter Fabl can be provided as a multigroup structure.

[0174] In Figure 17(C) shows an infrared cut filter 401 of the fifth embodiment of the present application. The infrared cut filter 401 has the infrared absorbing film filter Fabl and the near-infrared reflecting filter Frefl alternately stacked. In this case, the multilayer film of the near-infrared reflecting filter Frefl can be manufactured by the co-extrusion method (Co-Extrusion) in a group unit, and the multilayer film of the infrared absorbing film filter Fabl can be alternately attached. Alternatively, the entire multilayer film of the near-infrared reflecting filter Frefl and the infrared absorbing film filter Fabl can be integrally manufactured by the co-extrusion method (Co-Extrusion).

[0175] In Figure 18 (A) shows an infrared cut filter 501 of the sixth embodiment of the present application. The infrared cut filter 501 has the infrared absorbing film filter Fabl and the near-infrared reflecting filter Frefl alternately stacked. In this case, the multilayer film of the near-infrared reflecting filter Frefl can be manufactured by the co-extrusion method (Co-Extrusion), and the infrared absorbing film filter Fabl can be simultaneously formed. In the co-extrusion method (Co-Extrusion), only two kinds of resins are used, and thus the production efficiency is improved. Note that the case where the low-refractive layer Lind contains the organic pigment having the near-infrared light absorbing function is exemplified, but the high-refractive layer Hind can contain the organic pigment.

[0176] In Figure 18 (B) shows an infrared cut filter 601 of the seventh embodiment of the present application. The infrared cut filter 601 has the infrared absorbing film filter Fabl and the near-infrared reflecting filter Frefl alternately stacked. In this case, the multilayer film of the near-infrared reflecting filter Frefl can be manufactured by the co-extrusion method (Co-Extrusion) in a group unit, and the multilayer film of the infrared absorbing film filter Fabl can be alternately attached. Alternatively, the entire multilayer film of the near-infrared reflecting filter Frefl and the infrared absorbing film filter Fabl can be integrally manufactured by the co-extrusion method (Co-Extrusion).

[0177] In Figure 18(C) shows an infrared cut filter 701 of an eighth embodiment of the present application. The infrared cut filter 701 makes the low refractive layer Lind and the high refractive layer Hind both function as an infrared absorbing film filter Fabl by making a part of the reflecting film of the near-infrared reflecting filter Frefl contain an organic pigment having a near-infrared light absorbing function, with both a low refractive resin and a high refractive resin for the reflecting film. Here, the low refractive layer Lind and the high refractive layer Hind near the CMOS pixel sensor side (omitted from the drawing) contain the organic pigment. As a result, a part of the multilayer group of the near-infrared reflecting filter Frefl functions as the infrared absorbing film filter Fabl. In this case, if the multilayer film of the near-infrared reflecting filter Frefl is manufactured by a co-extrusion method, the infrared absorbing film filter Fabl is simultaneously formed by being overlapped.

[0178] In Figure 22 (A) shows an infrared cut filter 901 of a ninth embodiment of the present application. For the infrared cut filter 901, the near-infrared reflecting filter Frefl is separated from the infrared absorbing film filter Fabl, and an antireflection film Farl is formed on both surfaces of the infrared absorbing film filter Fabl. On the other hand, the near-infrared reflecting filter Frefl is attached to the inner side of the cover glass 215 that protects the internal mechanism of the imaging device from the outside. The cover glass 215 uses the crystallized glass 130 as a transparent substrate that transmits light. Note that a dielectric multilayer film that is formed by alternately laminating dielectrics having different refractive indexes can be interposed between the cover glass 215 and the infrared absorbing film filter Fabl. The dielectric multilayer film is laminated on the inner side of the cover glass 215 by vacuum evaporation. The dielectric multilayer film compensates for the reflecting function of the near-infrared reflecting filter Frefl.

[0179] In Figure 22 (B) shows a camera structure in which the infrared cut filter 901 is assembled. The camera structure has the cover glass 215 and a camera module 920. The camera module 920 has: a lens unit 50 that is an optical lens group; a lens carrier 40 that holds the lens unit 50; a magnetic holder 30 that moves the lens unit 50 in the axial direction in order to realize an auto focus function; a shooting element 70 that receives light that has been incident via the lens unit 50; a substrate 80 on which the shooting element 70 is mounted; an absorbing member AB that is arranged between the lens unit 50 and the shooting element 70; and a reflecting member REF that is attached to the inner side of the cover glass 215. Note that the cover glass 215 is fixed to the housing of an imaging device such as a smartphone.

[0180] In the infrared cut filter 1 of the present embodiment, the antireflection film (antireflection portion) Farl is exemplified as a resin material, but the present application is not limited thereto. The antireflection film (antireflection portion) Farl can be configured using an existing inorganic dielectric multilayer film. In this case, after the near-infrared reflecting filter Frefl and the infrared-absorbing film filter Fabl are laminated using a roll-to-roll lamination device RS as shown in Figure 11 the film is cut into a sheet of a desired size after the near-infrared reflecting filter Frefl and the infrared-absorbing film filter Fabl are laminated, and an inorganic dielectric multilayer film is formed on the surface of the sheet by a vacuum evaporation process.

[0181] It should be noted that the present application is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present application.

Claims

1. An infrared cutoff filter, characterized in that, For use in digital cameras, the infrared cut-off filter comprises: The near-infrared reflective filter is composed of alternating layers of high-refractive-index layer formed of high-refractive-index resin and low-refractive-index layer formed of low-refractive-index resin. Infrared absorption film filters, comprising a light-transmitting resin containing pigment or a light-transmitting resin coated with pigment; and An anti-reflective element is formed on the air-contact surface of the near-infrared reflective filter and / or the infrared absorber filter. The near-infrared reflective filter has a total of 200 or more layers, including the high-refractive-index layer and the low-refractive-index layer. In the aforementioned near-infrared reflective filter unit, when the wavelength at which the light transmittance decreases to 50% with increasing incident light wavelength is defined as the cutoff wavelength of the reflective film, the cutoff wavelength of the reflective film when the incident angle of the incident light is 0° is in the range of 750nm to 880nm. The infrared absorption film filter has a transmittance of less than 2% in the wavelength range of 685nm to 800nm. The anti-reflective part has an uneven structure formed on the surface of the light-transmitting resin.

2. The infrared cutoff filter according to claim 1, characterized in that, For the near-infrared reflective filter unit, when the incident angle of the incident light varies within the range of 0° to 60°, the wavelength fluctuation of the cutoff wavelength of the reflective film is less than 170 nm. For the near-infrared reflective filter unit, when the wavelength of the incident light is defined as 440nm as the reference blue wavelength, the transmittance of the reference blue wavelength is 70% or more when the incident angle of the incident light is set to 60°.

3. The infrared cutoff filter according to claim 1, characterized in that, The high-refractive-index resin, the low-refractive-index resin, and the light-transmitting resin constituting the infrared absorption film filter are all composed of organic resins.

4. The infrared cutoff filter according to claim 3, characterized in that, The anti-reflective part is made of organic resin.

5. The infrared cutoff filter according to claim 1, characterized in that, The thickness of each of the high refractive index layer and / or the low refractive index layer is in the range of 10 nm to 300 nm.

6. The infrared cutoff filter according to claim 1, characterized in that, The overall thickness of the near-infrared reflective filter is less than 100 μm.

7. The infrared cutoff filter according to claim 1, characterized in that, The near-infrared reflective filter and the infrared absorption film filter are integrated into one unit.

8. The infrared cutoff filter according to claim 1, characterized in that, By including the pigment in at least one of the high-refractive-index resin and the low-refractive-index resin, it can also serve as the infrared absorption film filter.

9. The infrared cutoff filter according to claim 1, characterized in that, The near-infrared reflective filter and the infrared absorption film filter are joined together to form a single unit. The first anti-reflective portion is formed on the surface of the near-infrared reflective filter opposite to that of the infrared absorption film filter. A second anti-reflective portion is formed on the surface of the infrared absorption film filter opposite to that of the near-infrared reflection filter.

10. The infrared cutoff filter according to claim 1, characterized in that, The total thickness of the near-infrared reflective filter, the infrared absorption film filter, and the anti-reflective part is less than 300 μm.

11. The infrared cutoff filter according to claim 1, characterized in that, Based on the total thickness of the near-infrared reflective filter, the infrared absorption film filter, and the anti-reflective portion, the film thickness of the near-infrared reflective filter accounts for more than 20% of the total thickness.

12. The infrared cutoff filter according to claim 11, characterized in that, Based on the total thickness of the near-infrared reflective filter, the infrared absorber filter, and the anti-reflective portion, the thickness of the infrared absorber filter accounts for more than 20%.

13. The infrared cutoff filter according to claim 1, characterized in that, The wavelength of the incident light, 450 nm to 500 nm, is defined as the low-wavelength transmission frequency band. In the near-infrared reflective filter unit, when the average transmittance of incident light in the low-wavelength transmission band is defined as the low-wavelength transmittance of the reflective film... The reflective film has a low-wavelength transmittance of 75% or more when the incident angle of the incident light varies in the range of 0° to 60°.

14. The infrared cutoff filter according to claim 1, characterized in that, The resin constituting the near-infrared reflective filter and / or the infrared absorber filter contains an ultraviolet absorber.

15. A camera structure, characterized in that, It is a digital camera structure comprising an optical lens group disposed on the light incident side and an imaging element that receives light incident through the optical lens group. An infrared cutoff filter as described in claim 1 is disposed between the optical lens group and the imaging element.

16. A camera structure, characterized in that, It is a digital camera structure consisting of a cover glass, an optical lens group, and an imaging element, arranged sequentially from the light incident side. Equipped with the infrared cutoff filter as described in claim 1, The near-infrared reflective filter is disposed between the cover glass and the optical lens group. The infrared absorption film filter is disposed between the optical lens group and the imaging element.

17. The camera structure according to claim 16, characterized in that, The near-infrared reflective filter is attached to the cover glass.

18. A method for manufacturing an infrared cutoff filter, characterized in that, This is a manufacturing method for infrared cut-off filters used in digital cameras, which includes: The reflective film manufacturing process involves co-extruding a near-infrared reflective filter by alternately stacking high-refractive-index layers made of high-refractive-index resin and low-refractive-index layers made of low-refractive-index resin, with a total of more than 200 layers. An integrated process in which an infrared absorption film filter is laminated or bonded to the near-infrared reflective filter, wherein the infrared absorption film filter is composed of a light-transmitting resin containing pigment or a light-transmitting resin coated with a pigmented absorption film. An additional process for the anti-reflective film involves forming a textured anti-reflective film of translucent resin relative to the surface in contact with air. as well as In the chip manufacturing process, after the completion of the reflective film manufacturing process, the integration process, and the anti-reflective film attachment process, the near-infrared reflective filter, the infrared absorption film filter, and the anti-reflective film are shaped into the desired form through at least cutting or punching processes. In the aforementioned near-infrared reflective filter unit, when the wavelength at which the light transmittance decreases to 50% with increasing incident light wavelength is defined as the cutoff wavelength of the reflective film, the cutoff wavelength of the reflective film when the incident angle of the incident light is 0° is in the range of 750nm to 880nm. The infrared absorption film filter has a transmittance of less than 2% in the wavelength range of 685nm to 800nm.

19. The method for manufacturing an infrared cutoff filter according to claim 18, characterized in that, As part of the manufacturing process of the reflective film and the integration process, the high-refractive-index resin, the low-refractive-index resin, and the light-transmitting resin containing pigments that absorb infrared rays are co-extruded to form a near-infrared reflective filter and an infrared absorption film filter integrally formed. The near-infrared reflective 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 light-transmitting resin.

20. The method for manufacturing an infrared cutoff filter according to claim 18, characterized in that, As part of the reflective film manufacturing process and the integration process, after containing an infrared-absorbing pigment in either the high-refractive-index resin or the low-refractive-index resin, the high-refractive-index resin and the low-refractive-index resin are co-extruded to form an integral near-infrared reflective filter and an infrared absorption film filter. The near-infrared reflective 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. The infrared absorption film filter is formed from the side of the high-refractive-index layer and the low-refractive-index layer containing the pigment.

21. The method for manufacturing an infrared cutoff filter according to claim 18, characterized in that, The method for manufacturing the infrared cut-off filter includes a mask addition process, which is performed before the chip processing process, wherein a light-shielding mask is printed.

22. The method for manufacturing an infrared cutoff filter according to claim 18, characterized in that, In the integrated process, the roll-shaped near-infrared reflective filter and the roll-shaped infrared absorber filter are fed into a laminating device for integration and then wound into a roll.

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