Optical filter, manufacturing method of optical filter, optical module and transfer optical filter

Abstract

To provide an optical filter having high degree of whiteness, capable of scattering and reflecting visible light, and excellent in linear transmittance of near-infrared ray.SOLUTION: The optical filter includes a near-infrared ray transmission layer of which a rate of change of water content calculated by the following formula (1) is less than 1.09%. Water content rate of change (%)=(B-A)A×100 ... formula (1), where "A" represents mass of a sample a obtained by leaving to stand the near-infrared ray transmission layer under reduced atmosphere of 0.1 MPa for 24 hours using a vacuum dryer set to 80°C, and "B" represents mass of a sample b obtained by leaving to stand the sample a under an environment of 24.5°C and 68%RH for two hours.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an optical filter, a method for manufacturing an optical filter, an optical module, and an optical filter for transfer. [Background technology]

[0002] Sensor technology and communication technology using near-infrared rays have been developed or put into practical use. Since elements that receive near-infrared rays are also sensitive to visible light, near-infrared transmission filters that selectively transmit only near-infrared rays are used.

[0003] Conventional near-infrared transmission filters have mostly been black in color because they absorb visible light, which has resulted in the problem of poor design.

[0004] For example, Patent Document 1 discloses an optical member having a reflective scattering part that reflects and scatters light in at least a part of the visible wavelength range and transmits light in at least a part of the infrared wavelength range, and has a rectilinear transmittance of 75% or more for light in at least the part of the infrared wavelength range. Patent Document 2 discloses an optical article for infrared communication that uses Rayleigh scattering due to a fine uneven shape formed by roughening the surface of a transparent substrate to scatter visible light, thereby presenting a white color, and has an infrared transmittance of 12% or more. Patent Document 3 discloses an optical article for infrared communication that uses Rayleigh scattering to scatter visible light by uniformly dispersing fine particles having a refractive index different from that of a binder resin transparent in the infrared wavelength range, thereby presenting a white color, and has an infrared transmittance of 12% or more. Patent Documents 4 and 5 disclose systems including a wavelength-selective scattering layer in an optical filter adjacent to one or both of a light emitter and a light receiver, the ratio of average near-infrared scattering to average visible scattering being less than 0.9 and the ratio of average visible diffuse reflectance to average visible total reflectance being greater than 0.5. Patent Document 6 discloses an optical filter having an average visible transmittance of less than 30% for wavelengths between 400 nm and 700 nm and an average near-infrared transmittance of greater than 30% for wavelengths between 830 nm and 900 nm. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 117452 [Patent Document 2] Patent No. 5358793 [Patent Document 3] Patent No. 5756962 [Patent Document 4] Special Publication No. 2019-509510 [Patent Document 5] Special Publication No. 2019-508733 [Patent Document 6] Special Publication No. 2019-507899 Summary of the Invention [Problem to be solved by the invention]

[0006] The optical component described in Patent Document 1 exhibits a white color by scattering visible light using Rayleigh scattering due to its fine uneven shape, but this effect cannot be obtained when used on a curved surface, and there is a problem in that the white color cannot be obtained when the desired shape is formed.

[0007] The optical articles for infrared communication described in Patent Documents 2 to 6 have a problem in that they do not have fully satisfactory near-infrared linear transmittance.

[0008] An object of the embodiments of the present invention is to solve the above-mentioned problems in the prior art and to provide an optical filter that has a high degree of whiteness, is capable of scattering and reflecting visible light, and has excellent linear transmittance of near-infrared light. [Means for solving the problem]

[0009] One embodiment of the present invention is an optical filter having a near-infrared transmitting layer in which the content change rate calculated by the following formula (1) is less than 1.09%. Moisture content change rate (%) = (BA)A × 100 Equation (1) (In the formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer under a reduced pressure of 0.1 MPa for 24 hours using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving the sample a under an environment of 24.5°C and 68% RH for 2 hours.) Effect of the Invention

[0010] The embodiment of the present invention can provide an optical filter that has a high degree of whiteness, is capable of scattering and reflecting visible light, and has excellent linear transmittance of near-infrared light. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a schematic diagram for explaining the optical characteristics of an optical filter according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a method for measuring the linear transmittance of the optical filter according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing an example of a near-infrared transmitting layer in an optical filter according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present invention will be described in detail. Note that the embodiments are not limited by the following description, and can be appropriately modified without departing from the gist of the present invention. In addition, in this specification, "to" indicating a numerical range means that the numerical values ​​before and after it are included as the lower and upper limits, unless otherwise specified.

[0013] In addition, when describing the embodiments of the present invention with reference to the drawings, the same components in each drawing may be given the same reference numerals, and duplicated descriptions may be omitted. Furthermore, the number, position, size, shape, etc. of components are not limited to the embodiments of the present invention, and may be the number, position, size, shape, etc. that are preferable for implementing the present invention.

[0014] (Optical Filter) The optical filter according to the embodiment of the present invention has a near-infrared transmitting layer having a content change rate calculated by formula (1) of less than 1.09%, and further has other layers as necessary.

[0015] The optical characteristics of an optical filter according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram for explaining the optical characteristics of an optical filter according to an embodiment of the present invention. As shown in FIG. 1, when incident light I0 is incident on an optical filter 10, a part of the incident light I0 is transmitted through the optical filter 10 (transmitted light I i ), some of it is reflected at the interface (interface reflected light R i ), and the other part is scattered. The scattered light includes forward scattered light S emitted in front of the optical filter 10.f and the backscattered light S emitted backwards b There is a saying.

[0016] The optical filter 10 converts visible light into backscattered light S b Since the backscattered light S can be scattered and reflected by the b As a result, the optical filter 10 exhibits a white color. Although a portion of the incident light I0 is absorbed by the optical filter 10, the near-infrared transmitting layer of the optical filter according to the embodiment of the present invention has a low absorptance for light with wavelengths of 400 nm to 2,000 nm. In addition, the optical filter 10 has excellent linear transmittance for near-infrared rays. That is, most of the incident light I0 that enters the optical filter 10 is transmitted as light I i The forward scattered light S f Since the optical density is low, when used in image sensors such as InGaAs sensors, InGaAs / GaAsSb sensors, CMOS sensors, NMOS sensors, and CCD sensors, images with strong contrast (light and dark) and sharpness can be obtained.

[0017] The definition of near-infrared light varies depending on the technical field, but in the embodiment of the present invention, "near-infrared light" means light that includes at least light (electromagnetic waves) having a wavelength in the range of 760 nm to 2,000 nm. Such a wavelength range is preferably used for sensing or communication. In addition, in the embodiment of the present invention, "visible light" means light having a wavelength in the range of 400 nm to less than 760 nm.

[0018] [Whiteness] The optical filter according to the embodiment of the present invention may exhibit a white color. In the embodiment of the present invention, the "whiteness" means the degree of whiteness. In the embodiment of the present invention, the whiteness is the L of the backscattered light of the optical filter measured by a spectrophotometer according to the SCE method in the CIE1976 color space when the standard light is a D65 light source. * It can be evaluated by the value of

[0019] L of an optical filter according to an embodiment of the present invention *The value of L is not particularly limited as long as it can exhibit white color and can be appropriately selected depending on the purpose, but it is preferably 40 or more, more preferably 50 or more, and even more preferably 72 or more. * The larger the value of L, the higher the whiteness. * If the value of L is 40 or more, it can be said to be approximately white. * The upper limit for the value is 100.

[0020] In addition, layers other than the near-infrared transmitting layer in the optical filter according to the embodiment of the present invention can be selected so as not to affect the whiteness of the near-infrared transmitting layer. Therefore, the whiteness of the optical filter according to the embodiment of the present invention is synonymous with the whiteness of the near-infrared transmitting layer in the optical filter.

[0021] [Linear transmittance] The linear transmittance of the optical filter according to the embodiment of the present invention to near-infrared light is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 65% ​​or more, more preferably 75% or more, even more preferably 80% or more, and particularly preferably 85% or more.

[0022] The wavelength range of light in which the linear transmittance of the optical filter according to the embodiment of the present invention is 65% or more is not particularly limited as long as it is near-infrared and can be appropriately selected depending on the purpose, but is preferably 810 nm or more and 1,700 nm or less, more preferably 840 nm or more and 1,650 nm or less, even more preferably 840 nm or more and 1,000 nm or less, and particularly preferably 840 nm or more and 950 nm or less.

[0023] If the optical filter according to the embodiment of the present invention has an in-line transmittance of 65% or more for light with a wavelength of 810 nm or more and 1,700 nm or less, it can be suitably used in, for example, InGaAs sensors, InGaAs / GaAsSb sensors, CMOS sensors, NMOS sensors, CCD sensors, etc.

[0024] In addition, layers other than the near-infrared transmitting layer in the optical filter according to the embodiment of the present invention can be selected so as not to affect the linear transmittance of the near-infrared transmitting layer to the near-infrared. Therefore, the linear transmittance of the optical filter according to the embodiment of the present invention to the near-infrared is synonymous with the linear transmittance of the near-infrared transmitting layer in the optical filter to the near-infrared.

[0025] The linear transmittance of the optical filter according to the embodiment of the present invention to near-infrared light can be adjusted by adjusting one or more selected from the group consisting of the average refractive index of the matrix and microparticles in the near-infrared transmitting layer to visible light, the average particle size of the microparticles to visible light, the volume fraction of the matrix and microparticles, the distribution of the microparticles (degree of non-periodicity), and the thickness of the near-infrared transmitting layer.

[0026] The linear transmittance of the optical filter according to the embodiment of the present invention to near infrared rays can be measured as follows. It can be measured using a spectrometer such as an ultraviolet-visible-near infrared spectrophotometer by using the measurement method shown in Fig. 2. A specific method for measuring the linear transmittance of the optical filter to near infrared rays is as described in the examples below.

[0027] In an optical filter according to an embodiment of the present invention, it is preferable that the incidence angle dependency of the linear transmittance spectrum is small, and the linear transmittance when the incidence angle of 940 nm near-infrared radiation is 60° is more preferably 80% or more, further preferably 85% or more, and particularly preferably 90% or more, compared to the linear transmittance when the incidence angle of 940 nm near-infrared radiation is 0°.

[0028] In the optical filter according to the embodiment of the present invention, it is preferable that the curved portion where the linear transmittance increases monotonically from visible light to near infrared light shifts to the longer wavelength side as the incident angle increases. If the curved portion where the linear transmittance increases monotonically from visible light to near infrared light shifts to the shorter wavelength side as the incident angle increases, the short wavelength side light that is intended to be blocked may be transmitted (light leakage) for obliquely incident light. In contrast, when the optical filter according to the embodiment of the present invention shifts to the longer wavelength side as the incident angle increases, this reduces the linear transmittance for short wavelength side light, which is preferable in that light leakage is less likely to occur.

[0029] Such incidence angle dependency of the optical filter according to the embodiment of the present invention is believed to be due to the fact that the particles in the near-infrared transmission layer included in the optical filter described below constitute colloidal amorphous aggregates. In the optical filter according to the embodiment of the present invention, the particles constituting the colloidal amorphous aggregates have a reduced linear transmittance for light on the shorter wavelength side as the incidence angle increases because the intensity of scattered light of visible light, particularly visible light on the longer wavelength side, increases. Therefore, when the optical filter according to the embodiment of the present invention is viewed obliquely, the intensity of diffuse reflected light (backscattered light) increases, and the white luminance (L * ) may rise.

[0030] The structure, shape, and size of the optical filter according to the embodiment of the present invention are not particularly limited and can be appropriately selected according to the purpose. The structure of the optical filter according to the embodiment of the present invention may be a two-dimensional structure (planar structure) or a three-dimensional structure (stereoscopic structure). In addition, the shape of the optical filter according to the embodiment of the present invention can be, for example, a film shape. If the optical filter according to the embodiment of the present invention is a film shape having flexibility, it is preferable in that it is easy to mold into a desired shape. A specific example of the optical filter is a three-dimensional optical filter formed by forming a film-shaped optical filter on the surface of an object having a three-dimensional structure using a known coating method. In such an embodiment, the shape of the surface of the object having a three-dimensional structure is not particularly limited and can be any shape, for example, a shape consisting of a part or all of a sphere, a shape consisting of a curved surface of an arbitrary shape, a shape consisting of a part or all of the surface of a polyhedron, etc. However, it is preferable that the surface of the object does not cause light scattering.

[0031] The thickness of the optical filter according to the embodiment of the present invention is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10 μm to 10 mm, more preferably 10 μm to 1 mm, and even more preferably 10 μm to 500 μm. When the optical filter according to the embodiment of the present invention has a thickness of 10 μm to 10 mm, it can exhibit flexibility.

[0032] <Near infrared transmission layer> The near-infrared transmitting layer refers to a filter layer having spectral characteristics that block at least a part of visible light and transmit at least a part of near-infrared light.

[0033] The near-infrared transmitting layer contains a matrix and fine particles dispersed in the matrix, and further contains other components as necessary.

[0034] [Moisture content change rate] The content change rate of the near-infrared transmitting layer calculated by the following formula (1) is less than 1.09%, preferably 0.95% or less, more preferably 0.90% or less, even more preferably 0.40% or less, and particularly preferably 0.35% or less. The lower limit of the content change rate of the near-infrared transmitting layer is not particularly limited and can be appropriately selected according to the purpose, but is preferably 0.10% or more, more preferably 0.15% or more, even more preferably 0.20% or more, and particularly preferably 0.25% or more. The upper limit and lower limit of the content change rate of the near-infrared transmitting layer can be appropriately combined, and is preferably 0.10% or more and less than 1.09%, more preferably 0.10% or more and 0.95% or less, even more preferably 0.15% or more and 0.90% or less, even more preferably 0.20% or more and 0.40% or less, and particularly preferably 0.25% or more and 0.35% or less. When the content change rate of the near infrared transmitting layer is 1.09% or more, the whiteness is poor. On the other hand, when the content change rate of the near infrared transmitting layer is less than 1.09%, the whiteness is good, and when it is 0.35% or less, the whiteness is even better. The method for measuring the water content change rate is as described in the examples below. The water content change rate of the near infrared transmitting layer can be adjusted by the type of matrix, etc. Moisture content change rate (%) = (BA)A × 100 Equation (1) (In formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer for 24 hours under a reduced pressure of 0.1 MPa using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving sample a for 2 hours in an environment of 24.5°C and 68% RH.)

[0035] Average Thickness The average thickness of the near-infrared transmitting layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1,000 μm or less, more preferably 500 μm or less, and even more preferably 350 μm or less. When the average thickness of the near-infrared transmitting layer is 1,000 μm or less, sufficient photocurability can be obtained.

[0036] In the embodiment of the present invention, the "average thickness" of the near-infrared transmitting layer means the average value of thicknesses at five points arbitrarily selected from the near-infrared transmitting layer. The thickness of the near-infrared transmitting layer can be measured by observing a cross section of the near-infrared transmitting layer using a transmission electron microscope (TEM) (e.g., HT7820, manufactured by Hitachi High-Technologies Corporation).

[0037] [Refractive index difference|n M -n P |] The average refractive index of the matrix for visible light is n M The average refractive index of the particles for visible light is n P When the above n M and the n P Absolute difference between |n M -n P | (hereinafter, simply "refractive index difference |n M -n P The refractive index difference |n (sometimes referred to as "refractive index difference" or "refractive index difference") is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.01 or more, more preferably 0.03 or more, even more preferably 0.08 or more, and particularly preferably 0.09 or more. M -n P There is no particular restriction on the upper limit of the refractive index difference |n M -n P The lower limit and upper limit of | can be appropriately combined, and are preferably 0.01 or more and less than 0.10, more preferably 0.03 or more and less than 0.10, further preferably 0.08 or more and less than 0.10, and particularly preferably 0.09 or more and less than 0.10. M -n P When | is 0.01 or more, the scattering intensity is not too weak and desired optical characteristics can be obtained, when | is 0.09 or more, the whiteness of the optical filter is high, and when | is 0.09 or more but less than 0.10, the whiteness of the optical filter is even higher. In the embodiment of the present invention, the average refractive index for visible light refers to the average refractive index for light of 546 nm. The refractive index difference |n M -n Pcan be adjusted by the type of matrix, the type of particles, or a combination of these.

[0038] In an embodiment of the present invention, the refractive index of the matrix for visible light can be measured by an Abbe refractometer (for example, Model: DR-A1, manufactured by Atago Co., Ltd.).

[0039] In the embodiment of the present invention, the refractive index of the fine particles for visible light can be measured by a liquid immersion method. Specifically, the fine particles are dried and turned into a powder state, and mixed with refractive liquids having various refractive indices. The refractive index at which the hollow fine particles become transparent is defined as the refractive index of the fine particles in the embodiment of the present invention.

[0040] In the embodiment of the present invention, the "average refractive index" refers to the average value of the refractive indexes obtained by measuring the matrix or the fine particles three times by the above-mentioned method. Therefore, in the embodiment of the present invention, the refractive index of the matrix for visible light and the refractive index of the fine particles for visible light are the refractive indexes of the matrix (e.g., curable resin) and the fine particles as materials forming the near-infrared transmitting layer before being cured into the near-infrared transmitting layer.

[0041] <<Matrix>> The material constituting the matrix is ​​not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include acrylic resins (e.g., polymethyl methacrylate, polymethyl acrylate, etc.), polycarbonates, polyesters, poly(diethylene glycol bisallyl carbonate), polyurethanes, epoxy resins, polyimides, etc. These may be used alone or in combination of two or more.

[0042] The matrix is ​​preferably formed using a curable resin. The curable resin may be a thermosetting resin or a photocurable resin, but from the viewpoint of mass productivity, it is preferable to use a photocurable resin.

[0043] The photocurable resin is not particularly limited and can be appropriately selected according to the purpose, and may be, for example, a (meth)acrylate resin. The (meth)acrylate is not particularly limited, but preferably contains a bifunctional or trifunctional or higher (meth)acrylate. In the embodiment of the present invention, the term "(meth)acrylate" refers to at least one of "acrylate" and "methacrylate".

[0044] In addition, the matrix preferably has optical isotropy. When a curable resin obtained by curing a polyfunctional monomer is used, a matrix having a crosslinked structure is obtained, and therefore the heat resistance and light resistance of the near-infrared transmitting layer can be improved.

[0045] When using fine particles with a hydrophilic surface as the fine particles, it is preferable to form the matrix by photocuring a hydrophilic monomer. The hydrophilic monomer is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include polyethylene glycol (meth)acrylate, polyethylene glycol di(meth)acrylate, polyethylene glycol tri(meth)acrylate, polypropylene glycol (meth)acrylate, polypropylene glycol di(meth)acrylate, polypropylene glycol tri(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, acrylamide, methylene bisacrylamide, and ethoxylated bisphenol A di(meth)acrylate. These may be used alone or in combination of two or more. When using two or more monomers, they may contain a monofunctional monomer and a polyfunctional monomer, or may contain two or more polyfunctional monomers. These monomers can be cured by a curing reaction using a known photopolymerization initiator.

[0046] The content of the matrix in the near-infrared transmitting layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably from 40 volume % to 96 volume % of the total volume of the near-infrared transmitting layer, more preferably from 50 volume % to 80 volume %, and even more preferably from 60 volume % to 80 volume %.

[0047] The matrix content in the near-infrared transmitting layer can be measured by 3D structure analysis using a real-time 3D analytical FIB-SEM composite device (NX9000, manufactured by Hitachi High-Tech Corporation).

[0048] The average refractive index of the matrix for visible light, n M There is no particular restriction on the average refractive index of the particles, n P The refractive index difference |n M -n P The average refractive index n of the matrix for visible light is preferably in the range of 1.52 or more, more preferably 1.53 or more, and particularly preferably 1.535 or more. M However, if the average refractive index n of the matrix for visible light is 1.52 or more, a high degree of whiteness can be obtained, if the average refractive index n is 1.53 or more, a higher degree of whiteness can be obtained, and if the average refractive index n is 1.535 or more, a particularly high degree of whiteness can be obtained. M When the matrix contains multiple types of curable resins, it means the average refractive index of a mixture of the multiple types of curable resins.

[0049] The average refractive index of the matrix for visible light, n M From the viewpoint of adjusting the refractive index to within the above-mentioned preferred range, it is preferable that the matrix contains a matrix having an average refractive index for visible light of 1.57 or more.

[0050] The content of the matrix having an average refractive index of 1.57 or more for visible light in the matrix is ​​not particularly limited and can be appropriately selected depending on the purpose, but is preferably 40% by mass or less, more preferably 10% by mass to 40% by mass or less, more preferably 20% by mass to 40% by mass or less, and even more preferably 30% by mass to 40% by mass or less. When the content of the matrix having an average refractive index of 1.57 or more for visible light in the matrix is ​​40% by mass or less, high whiteness can be obtained, and when it is 30% by mass to 40% by mass, particularly high whiteness can be obtained.

[0051] In addition, the matrix is ​​preferably transparent to visible light (hereinafter simply referred to as "transparent").

[0052] <<Fine particles>> The fine particles are preferably transparent to visible light (hereinafter simply referred to as "transparent"). The transparent fine particles may have optical isotropy.

[0053] The fine particles are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include inorganic fine particles, resin fine particles, etc. These may be used alone or in combination of two or more kinds.

[0054] The inorganic fine particles are not particularly limited and can be appropriately selected according to the purpose, and include silica fine particles, titanium oxide fine particles, zirconia fine particles, etc. Among these, silica fine particles are preferable as the fine particles. The silica fine particles are not particularly limited and can be appropriately selected according to the purpose, and include, for example, silica fine particles synthesized by the Stöber method, hollow silica fine particles containing air, etc.

[0055] The resin microparticles are not particularly limited and can be appropriately selected according to the purpose, but microparticles made of at least one selected from the group consisting of polystyrene and polymethyl methacrylate are preferred, and microparticles made of at least one selected from the group consisting of crosslinked polystyrene, crosslinked polymethyl methacrylate, and crosslinked styrene-methyl methacrylate copolymer are more preferred. As such microparticles, for example, polystyrene microparticles or polymethyl methacrylate microparticles synthesized by emulsion polymerization can be appropriately used. In addition, hollow resin microparticles containing air can also be used.

[0056] Among these, inorganic fine particles are preferred as the fine particles because they have excellent heat resistance and light resistance, and silica fine particles are more preferred because they provide a sharp particle size distribution.

[0057] The fine particles preferably form a colloidal amorphous aggregate in the near-infrared transmitting layer. In the embodiment of the present invention, the "colloidal amorphous aggregate" refers to an aggregate of colloidal particles having a particle size of 1 nm to 1 μm, which does not have a long-range order and does not cause Bragg reflection. When colloidal particles are distributed so as to have a long-range order, they become a so-called colloidal crystal (a type of photonic crystal), which is in contrast to the case where Bragg reflection occurs. In other words, the fine particles (colloidal particles) in the near-infrared transmitting layer preferably do not form a diffraction grating.

[0058] Colloidal crystals having an orderly structure in which colloidal particles are regularly arranged reflect light of a wavelength corresponding to the lattice constant due to Bragg diffraction. For example, colloidal crystals in which submicron-order colloidal particles are regularly arranged reflect light of wavelengths ranging from ultraviolet light or visible light to infrared light. When such colloidal crystals are used to reflect visible light, they can produce so-called structural colors such as iridescence. Therefore, whether or not the fine particles form a colloidal amorphous aggregate can be confirmed by visually checking the presence or absence of an iridescent color.

[0059] In addition, whether or not the microparticles form a colloidal amorphous aggregate, and the distribution state of the microparticles in the colloidal amorphous aggregate can also be confirmed using the average value (La) and standard deviation (Ld) of the distance between the centers of gravity of adjacent microparticles as indicators. The average value (La) of the distance between the centers of gravity of adjacent microparticles is not particularly limited, but is preferably 100 nm or more, more preferably 150 nm or more, even more preferably 175 nm or more, and particularly preferably 200 nm or more. The upper limit of the average value (La) of the distance between the centers of gravity of adjacent microparticles is also not particularly limited, but is preferably 600 nm or less, and more preferably 500 nm or less.

[0060] The average value (La) and standard deviation (Ld) of the distance between the centers of gravity of adjacent particles can be calculated from a cross-sectional transmission electron microscope (TEM) image of the near-infrared transmitting layer. Specifically, when the thickness of the near-infrared transmitting layer is d, a sample piece having the same thickness as the average particle diameter of the particles is cut by cutting with a microtome in a direction perpendicular to the thickness direction of the near-infrared transmitting layer at a position of d / 2 with respect to the cross-sectional direction, and a sample for TEM observation is obtained. The average value (La) and standard deviation (Ld) of the distance between the centers of gravity of adjacent particles can be obtained by performing automatic identification Delaunay diagram analysis on the particles using an image processing software (e.g., Image J, open source) from a cross-sectional TEM image containing images of 200 or more particles using a TEM (e.g., HT7820, manufactured by Hitachi High-Tech Corporation). In addition, the coefficient of variation (CV value of distance) is obtained from the average value of the distance between the centers of gravity (hereinafter sometimes referred to as the "average distance between the centers of gravity") and the standard deviation. In the embodiment of the present invention, when determining the distance between the centers of gravity, only particles having a particle size of 150 nm or more are considered, and particles having a particle size of less than 150 nm are not considered.

[0061] The coefficient of variation of the average distance between the centers of gravity of the fine particles is not particularly limited, but is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and particularly preferably 25% or more. The upper limit of the coefficient of variation of the average distance between the centers of gravity of the fine particles is also not particularly limited, but is preferably 45% or less, more preferably 40% or less, and even more preferably 35% or less. The lower limit and upper limit of the coefficient of variation of the average distance between the centers of gravity of the fine particles can be appropriately combined, and are preferably 10% or more and 45% or less, more preferably 15% or more and 40% or less, even more preferably 20% or more and 40% or less, and particularly preferably 25% or more and 35% or less. When the coefficient of variation of the average distance between the centers of gravity of the fine particles is 10% or more, the long-range order is small, and the reflection color with angle dependency caused by Bragg reflection is difficult to appear. In addition, when the coefficient of variation of the average distance between the centers of gravity of the fine particles is 45% or less, the effect of Mie scattering is small, and the wavelength dependency of light scattering tends to be large.

[0062] The average particle size of the fine particles is not particularly limited and can be appropriately selected according to the purpose, but it is preferable to include monodisperse fine particles having a wavelength of at least 1 / 10 of the wavelength of the near infrared ray, and for near infrared rays having a wavelength of 760 nm to 2,000 nm, the average particle size of the fine particles is more preferably at least 80 nm, more preferably 150 nm or more, and particularly preferably 200 nm or more. There is also no particular limit to the upper limit of the average particle size of the fine particles, but it is preferably 300 nm or less. The lower limit and upper limit of the average particle size of the fine particles can be appropriately combined, and for near infrared rays having a wavelength of 760 nm to 2,000 nm, the average particle size of the fine particles is more preferably 80 nm to 300 nm, more preferably 150 nm to 300 nm, and particularly preferably 200 nm to 300 nm. In addition, the fine particles may include two or more monodisperse fine particles having different average particle sizes. By using monodisperse fine particles having an average particle size of at least 1 / 10 of the wavelength of the near infrared ray, the linear transmittance of the near infrared ray can be increased. This is a different principle from that of the optical articles described in Patent Documents 2 and 3, which utilize Rayleigh scattering.

[0063] The shape of the fine particles is not particularly limited, but is preferably approximately spherical.

[0064] In the embodiment of the present invention, the term "microparticles (multiple microparticles)" is also used to mean an aggregate of microparticles. Furthermore, the coefficient of variation (standard deviation / average particle diameter expressed as a percentage) of "monodispersed microparticles" is preferably 20% or less, more preferably 10% or less, and even more preferably 1% to 5%.

[0065] In the embodiment of the present invention, the average particle size of the microparticles means the average particle size determined by a focused ion beam scanning electron microscope (hereinafter, sometimes referred to as "FIB-SEM"). Specifically, the average particle size of the microparticles can be calculated by the method described in the examples.

[0066] Average refractive index of the particle for visible light, n PThere is no particular restriction on the average refractive index of the matrix, n M The refractive index difference |n M -n P The average refractive index n of the fine particles with respect to visible light is preferably in the range of 1.2 to 1.6, more preferably 1.2 to 1.5, and particularly preferably 1.2 to 1.46. P When the average refractive index n of the fine particles with respect to visible light is 1.2 or more and 1.6 or less, a high degree of whiteness can be obtained. P When the fine particles contain a plurality of types of fine particles, the refractive index means the average refractive index of a mixture of the plurality of types of fine particles.

[0067] The content of the fine particles in the near-infrared transmitting layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 6 volume % or more and 60 volume % or less, more preferably 20 volume % or more and 50 volume % or less, and even more preferably 2 volume % or more and 40 volume % or less, relative to the total volume of the near-infrared transmitting layer.

[0068] The content of fine particles in the near-infrared transmitting layer can be measured by 3D structure analysis using a real-time 3D analytical FIB-SEM composite device (NX9000, manufactured by Hitachi High-Tech Corporation).

[0069] <<Other ingredients>> Other components in the near-infrared transmitting layer are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected depending on the purpose, and examples thereof include a polymerization initiator used when curing and forming the matrix. The polymerization initiator can be appropriately selected depending on the curing method, and may be a thermal polymerization initiator or a photopolymerization initiator.

[0070] Examples of photopolymerization initiators include carbonyl compounds (e.g., benzoin ether, benzophenone, anthraquinone, thioxane, ketal, acetophenone, 2-hydroxy-2-methylpropiophenone, etc.), sulfur compounds (e.g., disulfides, dithiocarbamates, etc.), organic peroxides (e.g., benzoyl peroxide, etc.), azo compounds, transition metal complexes, polysilane compounds, dye sensitizers, etc. These may be used alone or in combination of two or more.

[0071] The content of the photopolymerization initiator in the near-infrared transmitting layer is not particularly limited and can be appropriately selected depending on the purpose. However, the content is preferably 0.05 parts by mass or more and 3 parts by mass or less, and more preferably 0.05 parts by mass or more and 1 part by mass or less, relative to 100 parts by mass of the monomer constituting the matrix.

[0072] [[Example of Implementation]] An embodiment of the near-infrared transmission layer will be specifically described with reference to the drawings. FIG. 3 is a schematic cross-sectional view showing an example of the near-infrared transmission layer in the optical filter according to the embodiment of the present invention. The near-infrared transmission layer 11 includes a matrix 12 that is transparent to visible light, and transparent fine particles 14 dispersed in the transparent matrix 12. The fine particles 14 preferably form a colloidal amorphous aggregate. The near-infrared transmission layer 11 may also include other fine particles that do not disturb the colloidal amorphous aggregate formed by the fine particles 14.

[0073] The near-infrared transmitting layer 11 has a substantially flat surface as shown in Fig. 3. Here, a substantially flat surface means a surface that does not have an uneven structure of a size that scatters (diffracts) or diffusely reflects visible light or near-infrared light. The near-infrared transmitting layer 11 does not contain cholesteric liquid crystal (which broadly includes polymer liquid crystal, low molecular liquid crystal, a liquid crystal mixture thereof, and a liquid crystal material thereof mixed with a crosslinking agent and solidified by crosslinking or the like, and which expresses a cholesteric phase).

[0074] <Other layers> The optical filter according to the embodiment of the present invention may have layers other than the near-infrared transmitting layer as long as the effects of the present invention are not impaired.

[0075] Examples of the other layers include a base layer, a filter layer having optical properties different from those of the near-infrared transmitting layer, a near-infrared absorbing layer, a color filter layer, and a print layer.

[0076] The shape, structure and size of the other layers are not particularly limited and may be appropriately selected depending on the purpose. For example, the shape may be a film or a plate.

[0077] The optical filter according to the embodiment of the present invention may have a single layer structure consisting of only a near-infrared transmitting layer, a laminated structure of a near-infrared transmitting layer and other layers, or a laminated structure having a plurality of near-infrared transmitting layers and other layers. When the optical filter according to the embodiment of the present invention has a laminated structure, the order of lamination is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected depending on the purpose.

[0078] <<Base material layer>> The material of the substrate constituting the substrate layer is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include resins such as PET (polyethylene terephthalate), TAC (triacetyl cellulose), PI (polyimide), PMMA (methyl methacrylate), COP (cycloolefin polymer), glass, etc. When a near-infrared transmitting layer is laminated as an optical filter, it may be transferred from the coated substrate to another substrate.

[0079] The linear transmittance of the base layer for near infrared rays is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 85% or more, more preferably 90% or more. The linear transmittance of the base layer can be measured by the same method as that for measuring the linear transmittance of an optical filter.

[0080] The haze of the substrate layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 2% or less, more preferably 1% or less, and even more preferably 0.5% or less. The haze of the substrate layer can be measured by a haze meter (e.g., Model: HM-150N, manufactured by Murakami Color Research Laboratory Co., Ltd.).

[0081] The average refractive index of the substrate layer with respect to visible light is not particularly limited and can be appropriately selected according to the purpose, but the smaller the difference in average refractive index between the substrate layer and the near infrared transmission layer, the smaller the loss due to interface reflection, and is preferably 0.08 or less, more preferably 0.03 or less, and particularly preferably 0.01 or less. The average refractive index of the substrate layer with respect to visible light can be measured by an Abbe refractometer (e.g., model: DR-A1, manufactured by Atago Co., Ltd.).

[0082] From the viewpoint of production efficiency, the near-infrared transmitting layer is preferably disposed on the surface of the base layer.

[0083] <<Near infrared absorbing layer>> The near-infrared absorbing layer is a filter layer that absorbs near-infrared rays. The near-infrared absorbing layer is preferably disposed on the side where the incident light that is incident on the near-infrared absorbing layer is transmitted and the transmitted light is emitted. By adopting such a configuration, for example, in an infrared sensor, the near-infrared absorbing layer can efficiently absorb near-infrared rays.

[0084] <<Color filter layer>> The color filter layer is a filter layer that exhibits black or other colors (e.g., yellow, red, blue, pink, brown, etc.). Since the optical filter according to the embodiment of the present invention exhibits white color, even when color filter layers are used in layers, the colors do not interfere with each other, and the design can be improved.

[0085] <<Printed layer>> The print layer is a layer having a desired printed image such as a color or pattern (e.g., letters, pictures, photographs, etc.). The desired printed image can be printed using infrared-transmitting ink to provide an optical filter having rich colors and excellent design without reducing the linear transmittance of near-infrared rays of the optical filter of the embodiment of the present invention. In addition, since the optical filter of the embodiment of the present invention exhibits white color, the design can be enhanced by further having a print layer.

[0086] The print layer is preferably disposed on the surface of the near-infrared transmitting layer. The print layer may be formed directly on the surface of the near-infrared transmitting layer, or a transparent film having a print layer formed on its surface may be disposed on the near-infrared transmitting layer.

[0087] As the infrared transmitting ink, a known infrared transmitting ink may be selected depending on the application or the wavelength of the near infrared light to be transmitted.

[0088] In the embodiments of the present invention, the terms "on", "disposed on the surface" and "disposed on the side from which transmitted light is emitted" of one layer mean that one layer can be connected or bonded directly on, above, or on top of the other layer, i.e., there may be another layer interposed between one layer and the other layer.

[0089] <Manufacturing method> The method for producing the optical filter according to the embodiment of the present invention is not particularly limited, and any known method can be used, but the method for producing the optical filter according to the embodiment of the present invention described below is preferably used.

[0090] <Application> The optical filters according to the embodiments of the present invention can be suitably used in image sensors such as InGaAs sensors, InGaAs / GaAsSb sensors, CMOS sensors, NMOS sensors, and CCD sensors, sensing devices using these image sensors (e.g., infrared cameras), communication devices, solar cells, heaters (e.g., heaters using infrared rays), and power supply devices (e.g., optically powered devices using infrared rays).

[0091] As described above, the optical filter according to the embodiment of the present invention can obtain desired optical characteristics (for example, whiteness and near-infrared linear transmittance) by adjusting the content change rate of the near-infrared transmitting layer.

[0092] (Method of manufacturing optical filters) A method for manufacturing an optical filter according to an embodiment of the present invention includes a step of dispersing fine particles in a curable resin to prepare a curable resin composition (hereinafter, may be referred to as a "curable resin composition preparation step"), a step of applying the curable resin composition to the surface of a substrate (hereinafter, may be referred to as an "application step"), and a step of curing the curable resin contained in the curable resin composition applied to the surface of the substrate to form a near-infrared transmitting layer (hereinafter, may be referred to as a "near-infrared transmitting layer formation step"), and further includes other steps as necessary.

[0093] <Curable resin composition preparation process> The curable resin composition preparation step is a step of dispersing fine particles in a curable resin to prepare a curable resin composition.

[0094] The curable resin and the fine particles are as described in the <Near-infrared transmitting layer> section of (Optical filter), and therefore a description thereof will be omitted.

[0095] The method for preparing the curable resin composition is not particularly limited as long as it is a method that can mix the matrix with the fine particles and, if necessary, other components, and can disperse the fine particles in the matrix. Examples of the method include a preparation method using a known device, such as a mixing device or a dispersing device, such as a homomixer or a homogenizer (e.g., an ultrasonic homogenizer, a high-pressure homogenizer, etc.).

[0096] The temperature and time for preparing the curable resin composition are not particularly limited and may be appropriately selected depending on the purpose. However, the temperature must be lower than the curing temperature of the curable resin composition.

[0097] <Application process> The application step is a step of applying the curable resin composition to the surface of a substrate.

[0098] In the application step, in order to impart sufficient photocurability to the optical filter, the curable resin composition is preferably applied to the surface of the substrate so that the average thickness after curing is 1,000 μm or less, more preferably 500 μm or less, and even more preferably 350 μm or less. The near-infrared transmitting layer can be adjusted by the amount of the curable resin composition applied in the application step.

[0099] The substrate is as described in the section <Other layers and other parts> of (Optical filter), and therefore a description thereof will be omitted.

[0100] The method for applying the curable resin composition to the surface of the substrate is not particularly limited and can be appropriately selected from known methods. Examples of the method include coating methods such as dip coating, spray coating, die coating, roll coating, and blade coating, and printing methods.

[0101] <Near-infrared transmitting layer formation process> The near-infrared transmitting layer forming step is a step of forming a near-infrared transmitting layer by curing the curable resin contained in the curable resin composition applied to the surface of the substrate.

[0102] The content change rate of the near-infrared transmitting layer calculated by the following formula (1) is less than 1.09%. Other characteristics of the near-infrared transmitting layer are as described in the <Near-infrared transmitting layer> section of (Optical filter), and therefore will not be described here. Moisture content change rate (%) = (BA)A × 100 Equation (1) (In the formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer under a reduced pressure of 0.1 MPa for 24 hours using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving the sample a under an environment of 24.5°C and 68% RH for 2 hours.)

[0103] The method for curing the curable resin is not particularly limited and can be appropriately selected depending on the properties of the curable resin and the type of polymerization initiator in the curable resin composition. The method may be heat curing or photocuring, but photocuring is preferable from the viewpoint of mass productivity.

[0104] The temperature and time for thermal curing, and the wavelength, illuminance, and time for photocuring are not particularly limited, and can be appropriately selected depending on the characteristics of the curable resin and the type of polymerization initiator in the curable resin composition.

[0105] <Other processes> The other steps in the manufacturing method of the optical filter according to the embodiment of the present invention are not particularly limited, and include the steps of forming other layers described in the item <Other Layers> of (Optical Filter). The method of forming the other layers is not particularly limited, and can be appropriately selected from known methods.

[0106] (Optical module) The optical module of an embodiment of the present invention includes a device having a near-infrared receiving unit, and an optical filter of an embodiment of the present invention arranged in front of the near-infrared receiving unit of the device, and further includes other components as necessary.

[0107] <Device equipped with a near-infrared receiving section> The device having a near-infrared receiving unit is not particularly limited, and examples thereof include a sensing device, a communication device, a solar cell, a heater, and a power supply device. In the optical module according to the embodiment of the present invention, the device having the near-infrared receiving unit may include one type alone or two or more types.

[0108] <Optical filters> The optical filter is an optical filter according to an embodiment of the present invention, and is as described in the (Optical Filter) section, so a description thereof will be omitted.

[0109] <Other materials> Other components in the optical module of the embodiment of the present invention are not particularly limited as long as they do not impair the effects of the present invention, and examples include well-known components commonly used in sensing devices, communication devices, solar cells, heaters, and power supply devices.

[0110] (Optical filter for transfer) The optical filter for transfer according to the embodiment of the present invention has the optical filter according to the embodiment of the present invention in the form of a layer on a temporary support.

[0111] <Optical filters> The optical filter is an optical filter according to an embodiment of the present invention, and is as described in the (Optical Filter) section, so a description thereof will be omitted.

[0112] <Temporary support> The temporary support is not particularly limited as long as it allows the production of an optical filter on its surface and does not affect the optical filter, particularly the near-infrared transmitting layer in the optical filter, and any known release sheet can be used.

[0113] The release sheet is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include paper such as kraft paper, glassine paper, and wood-free paper; resin films such as polyethylene, polypropylene (biaxially oriented polypropylene (OPP), uniaxially oriented polypropylene (CPP)), and polyethylene terephthalate (PET); laminated paper in which paper and a resin film are laminated together; and paper that has been sealed with clay, polyvinyl alcohol, or the like and then subjected to a release treatment with silicone resin or the like on one or both sides. These may be used alone or in combination of two or more types.

[0114] The method for forming the optical filter in a layer form on the temporary support is not particularly limited, and the optical filter can be formed in the same manner as in the manufacturing method of the optical filter, except that the substrate is replaced by a support.

[0115] Transfer optical filters are advantageous in that they are easy to store and transport, have excellent handleability, and even in cases where it is not possible to form an optical filter directly on a substrate, the transfer optical filter can be attached to the substrate and the support peeled off to easily form an optical filter on the substrate. EXAMPLES

[0116] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0117] Example 1 A monomer mixture was prepared by mixing 90 parts by mass of acrylic monomer A and 10 parts by mass of acrylic monomer B, and 100 parts by mass (solid content) of silica fine particles (monodispersed silica fine particles synthesized by the Stöber method, average particle size 221 nm, Hautform (registered trademark) Sibol 220, manufactured by Fuji Chemical Co., Ltd.) and 0.2 parts by mass of a photopolymerization initiator (Darocur 1173, manufactured by BASF Japan Ltd.) were added to the obtained monomer mixture, mixed, and dispersed to prepare a curable resin composition. Next, the curable resin composition was applied to the surface of a PET film (average refractive index for light with a wavelength of 550 nm: 1.576, linear transmittance for light with a wavelength of 940 nm: 89%, thickness: 100 μm) using an applicator so as to obtain a film-like near-infrared transmitting layer with a thickness of 200 μm. Thereafter, ultraviolet rays were irradiated from a UV lamp to photopolymerize and harden the curable resin composition. The cured product was peeled off from the PET film to prepare an optical filter consisting of a near-infrared transmitting layer having a thickness of 200 μm.

[0118] -Types of acrylic monomers- Acrylic monomer A: ethoxylated bisphenol A diacrylate represented by the following structural formula (1) (average refractive index for light with a wavelength of 546 nm: 1.52) (manufactured by Shin-Nakamura Chemical Co., Ltd.) [ka] (However, in structural formula (1), m+1=10.) Acrylic monomer B: 3-phenoxybenzyl acrylate represented by the following structural formula (2) (average refractive index for light with a wavelength of 546 nm: 1.57) [ka]

[0119] (Examples 2 to 4 and Comparative Example 1) The curable resin compositions of Examples 2 to 4 and Comparative Example 1 were prepared in the same manner as in Example 1, except that the amounts of ethoxylated bisphenol A diacrylate and 3-phenoxybenzyl acrylate in Example 1 were changed to those shown in Table 1, and optical filters were produced in the same manner as in Example 1.

[0120] <Measurement of the average particle size of silica particles> The average particle size of the silica microparticles used in Examples 1 to 4 and Comparative Example 1 was measured by a focused ion beam scanning electron microscope (FIB-SEM). Specifically, a FIB-SEM, model number Helios G4 UX manufactured by FEI, was used to obtain continuous cross-sectional SEM images, and the positions of the continuous images were corrected, and then a three-dimensional image was reconstructed. More specifically, the acquisition of cross-sectional reflected electron images by SEM and FIB (acceleration voltage: 30 kV) processing were repeated 100 times at 50 nm intervals to reconstruct a three-dimensional image. The obtained three-dimensional image was binarized using the Segmentation function of analysis software (AVIZO manufactured by Thermo Fisher Scientific), and the image of the microparticles was extracted. Next, in order to identify each individual microparticle, a Separate object operation was performed, and then the volume of each silica microparticle was calculated. Each silica microparticle was assumed to be a sphere, the volume-equivalent sphere diameter was calculated, and the average value of the particle diameters of the silica microparticles was taken as the average particle size.

[0121] <Measurement of refractive index of acrylic monomer and monomer mixture> The refractive index at a wavelength of 550 nm of the acrylic monomer and monomer mixture used in Examples 1 to 4 and Comparative Example 1 was measured using an Abbe refractometer (Model: DR-A1, manufactured by Atago Co., Ltd.) This measurement was performed three times, and the average value of the three measurements was calculated to obtain the average refractive index of the acrylic monomer and monomer mixture.

[0122] <Measurement of refractive index of silica particles> The refractive index of the silica fine particles used in Examples 1 to 4 and Comparative Example 1 at a wavelength of 550 nm was measured by a liquid immersion method. Specifically, the silica fine particles were dried and turned into a powder state, and mixed with refractive index liquids having various refractive indices, and the refractive index was measured when the hollow silica fine particles became transparent. This measurement was performed three times, and the average value of the three measurements was calculated to obtain the average refractive index of the silica fine particles.

[0123] <Measurement of moisture content change rate> The optical filters of Examples 1 to 4 and Comparative Example 1 were cut into squares measuring 4 cm in length and 4 cm in width with a cutter, placed in a vacuum low-temperature dryer (model: ADP300, manufactured by Yamato Scientific Co., Ltd.), set at a temperature of 80°C, and left to stand for 24 hours under a reduced pressure of 0.1 MPa (checked by the scale of the vacuum gauge), and dried under reduced pressure to obtain "Sample a". The mass A of Sample a was measured using an electronic balance (model: HR-200, manufactured by A&D Co., Ltd.). After that, Sample a was left to stand for 2 hours under an environment of 24.5°C and 68% RH to obtain "Sample b". The mass B of Sample b was measured using an electronic balance (model: HR-200, manufactured by A&D Co., Ltd.). The moisture content change rate of the optical filters of Examples 1 to 4 and Comparative Example 1 was calculated from the masses A and B according to the following formula (1). The results are shown in Table 1 below. Moisture content change rate (%) = (BA)A × 100 Equation (1) (In the formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer under a reduced pressure of 0.1 MPa for 24 hours using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving the sample a under an environment of 24.5°C and 68% RH for 2 hours.)

[0124] <Evaluation of whiteness> The whiteness of the backscattered light of the optical filters of Examples 1 to 4 and Comparative Example 1 was measured using a spectrophotometer (CM-2600-D, manufactured by Konica Minolta Japan, Inc.) with a standard light source of D65, and the L of the SCE (specular reflection excluded) method was * The results are shown in Table 1 below.

[0125] <Evaluation of in-line transmittance> The linear transmittance of the optical filters of Examples 1 to 4 and Comparative Example 1 was measured by the following method. Fig. 2 is a schematic diagram showing the method for measuring linear transmittance. The linear transmittance was measured by placing the sample (optical filter 10) at a distance d of 20 cm from the opening of the integrating sphere 32. The transmitted light I i The intensity of the incident light I0 was calculated as a percentage of the intensity of the incident light I0. The diameter D of the aperture was 1.8 cm, which corresponds to a solid angle of 0.025 sr. The spectrometer used was an ultraviolet-visible-near infrared spectrophotometer (UH4150, manufactured by Hitachi High-Tech Science Corporation). Table 1 shows the linear transmittance values ​​for near infrared rays with wavelengths of 850 nm and 940 nm.

[0126] [Table 1]

[0127] [Table 2]

[0128] Comparing Examples 1 to 4 with Comparative Example 1, the optical filters of Examples 1 to 4, in which the moisture content change rate of the near-infrared transmission layer was less than 1.09%, had high whiteness. M -n p It was found that the whiteness was higher when the water content change rate of the near-infrared transmitting layer, preferably the refractive index difference |n M -n p It was suggested that the whiteness of the optical filter can be controlled by controlling |. In addition, the optical filters of Examples 1 to 4 also had high linear transmittance of near-infrared light, suggesting that both linear transmittance and whiteness can be achieved.

[0129] Examples of aspects of the present invention include the following. <1> The optical filter is characterized by having a near-infrared transmitting layer having a content change rate calculated by the following formula (1) of less than 1.09%. Moisture content change rate (%) = (BA)A × 100 Equation (1) (In the formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer under a reduced pressure of 0.1 MPa for 24 hours using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving the sample a under an environment of 24.5°C and 68% RH for 2 hours.) <2> The linear transmittance for near infrared rays is 65% or more. <1> 2 is an optical filter according to the first embodiment. <3> L measured using a spectrophotometer with the SCE method * The value of is 72 or more. <1> or <2> 2 is an optical filter according to the first embodiment. <4> The near-infrared transmitting layer contains a matrix and fine particles dispersed in the matrix. <1> from <3> 13. The optical filter according to claim 12, wherein <5> the near-infrared transmitting layer contains a matrix and fine particles dispersed in the matrix, The fine particles are at least composed of colloidal amorphous aggregates. <1> from <3> 13. The optical filter according to claim 12, wherein <6> The average refractive index of the matrix for visible light is n M The average refractive index of the particles for the visible light is n P When the above n M and the n P Absolute difference between |n M -n P | is 0.09 or more, <4> or <5> 2 is an optical filter according to the first embodiment. <7> The matrix includes a matrix having a refractive index of 1.57 or more for visible light. <4> or <5> 2 is an optical filter according to the first embodiment. <8> The content of the matrix having an average refractive index of 1.57 or more for visible light is 40 mass % or less with respect to the total mass of the matrix. <7> 2 is an optical filter according to the first embodiment. <9> The average thickness of the near-infrared transmitting layer is 1,000 μm or less. <1> from <8> 13. The optical filter according to claim 12, wherein <10> A step of dispersing fine particles in a curable resin to prepare a curable resin composition; applying the curable resin composition to a surface of a substrate; A step of curing the curable resin contained in the curable resin composition applied to the surface of the substrate to form a near-infrared transmitting layer; Including, The method for producing an optical filter is characterized in that the near-infrared transmitting layer has a content change rate calculated by the following formula (1) of less than 1.09%. Moisture content change rate (%) = (BA)A × 100 Equation (1) (In the formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer under a reduced pressure of 0.1 MPa for 24 hours using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving the sample a under an environment of 24.5°C and 68% RH for 2 hours.) <11> In the step of applying the curable resin composition to the surface of the substrate, the curable resin composition is applied to the surface of the substrate so that the average thickness after curing is 1,000 μm or less. <10> 2 is a method for producing the optical filter according to the first embodiment of the present invention. <12> A device having a near-infrared receiving unit; The device is provided with a near-infrared receiving unit. <1> from <9> an optical filter according to any one of the preceding claims; The optical module is characterized by having the following features. <13> The device is a sensing device, a communication device, a solar cell, a heater, or a power supply device. <12> 2 is an optical module according to the first embodiment. <14> The above <1> from <9> 1. An optical filter for transfer, comprising the optical filter according to any one of claims 1 to 9 in the form of a layer on a temporary support.

[0130] As described above, the present invention has been described based on specific embodiments and examples, but these embodiments and examples are merely presented as examples, and the present invention is not limited to the above embodiments and examples. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, additions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Industrial Applicability]

[0131] Optical filters according to the embodiments of the present invention can be used, for example, as infrared transmission filters used in sensor technology or communication technology, solar cells, heaters using infrared rays, optically powered devices using infrared rays, and the like. [Explanation of symbols]

[0132] 10 … Optical filters I0… Incident light I i … Transmitted light S b …backscattered light S f …Forward scattered light R i … Interface reflected light 32 … Integrating sphere D … Diameter of the opening d … distance 11 … Near-infrared transmitting layer 12 ... Matrix 14 … Fine particles

Claims

1. An optical filter comprising a near-infrared transmitting layer having a content change rate calculated by the following formula (1) of less than 1.09%: Moisture content change rate (%) = (B - A) A x 100 Formula (1) (In formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer under a reduced pressure of 0.1 MPa for 24 hours using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving the sample a under an environment of 24.5°C and 68% RH for 2 hours.)

2. 2. The optical filter according to claim 1, which has an in-line transmittance for near-infrared light of 65% or more.

3. L measured using a spectrophotometer with the SCE method ＊ The optical filter according to claim 1 , wherein the value of is 72 or greater.

4. The optical filter according to claim 1 , wherein the near-infrared transmitting layer contains a matrix and fine particles dispersed in the matrix.

5. the near-infrared transmitting layer contains a matrix and fine particles dispersed in the matrix, The optical filter according to claim 1 , wherein the fine particles constitute at least a colloidal amorphous aggregate.

6. The average refractive index of the matrix for visible light is n Ｍ The average refractive index of the fine particles with respect to the visible light is n Ｐ When the n Ｍ and the n Ｐ Absolute value of the difference with |n Ｍ -n Ｐ 6. The optical filter according to claim 4, wherein | is 0.09 or more.

7. 6. The optical filter according to claim 4, wherein the matrix has a refractive index of 1.57 or more for visible light.

8. 8. The optical filter according to claim 7, wherein a content of the matrix having an average refractive index of 1.57 or more for visible light is 40 mass % or less with respect to a total mass of the matrix.

9. 2. The optical filter according to claim 1, wherein the near-infrared transmitting layer has an average thickness of 1,000 μm or less.

10. A step of dispersing fine particles in a curable resin to prepare a curable resin composition; applying the curable resin composition to a surface of a substrate; a step of curing the curable resin contained in the curable resin composition applied to the surface of the substrate to form a near-infrared transmitting layer; Including, The method for producing an optical filter, wherein the near-infrared transmitting layer has a content change rate calculated by the following formula (1) of less than 1.09%: Moisture content change rate (%) = (B - A) A x 100 Formula (1) (In formula (1), "A" represents the mass of sample a obtained by leaving the near-infrared transmitting layer under a reduced pressure of 0.1 MPa for 24 hours using a vacuum dryer set at 80°C, and "B" represents the mass of sample b obtained by leaving the sample a under an environment of 24.5°C and 68% RH for 2 hours.)

11. The method for producing an optical filter according to claim 10 , wherein in the step of applying the curable resin composition to the surface of the substrate, the curable resin composition is applied to the surface of the substrate so that an average thickness after curing is 1,000 μm or less.

12. A device having a near-infrared receiving unit; The optical filter according to claim 1 , disposed in front of the near-infrared receiving portion of the device; An optical module comprising:

13. The optical module according to claim 12 , wherein the device is a sensing device, a communication device, a solar cell, a heater, or a power supply device.

14. 10. An optical filter for transfer comprising the optical filter according to claim 1 in the form of a layer on a temporary support.

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