Optical filter, method of manufacturing the same, and optical module

Abstract

The optical filter (10) includes a substrate (12), and fine particles (14) dispersed in the substrate (12), the parameter Ds expressed by Ds = λ / (B cos θ Ra) calculated from a pattern of USAXS of the fine particles (14) is 8.0 or more and 30 or less, where λ is the wavelength of X-rays, θ is half of the scattering angle 2θ (rad) at which the scattering intensity peaks, B is the half-value width (FWHM, rad) of the peak, and Ra is the average particle diameter of the fine particles (14).

Description

Technical Field

[0001] This invention relates to filters, methods of manufacturing the same, and optical modules. For example, it relates to infrared filters suitable for use as infrared filters with high linear transmittance for infrared light and high diffuse reflectance for visible light, methods of manufacturing the same, and optical modules in which such filters are provided in front of an infrared light-receiving portion of a device. Such devices are, for example, sensing devices or communication devices. Background Technology

[0002] Infrared sensor and communication technologies are being developed and put into practical use. Elements that receive infrared light are sensitive to visible light; therefore, infrared filters are used to selectively transmit infrared light. The definition of infrared light varies depending on the technical field. In this specification, "infrared light" includes light (electromagnetic waves) in the range of wavelengths from 760 nm to 2000 nm used in sensing or communication. Additionally, "visible light" refers to light in the range of wavelengths from 400 nm to 760 nm.

[0003] Existing infrared filters mostly appear black because they absorb visible light, which results in poor design flexibility.

[0004] Therefore, for example, Patent Document 1 discloses an infrared light-receiving part having a dielectric multilayer film that transmits infrared light and reflects and transmits visible light, and a surface processed into a pear-skin shape. Furthermore, Patent Document 2 discloses an optical article for infrared communication that utilizes Rayleigh scattering caused by the fine unevenness formed by roughening the surface of a transparent substrate to scatter visible light, thereby appearing white, and achieving an infrared transmittance of 12% or more.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-165493 (Japanese Patent No. 4122010)

[0008] Patent Document 2: Japanese Patent Application Publication No. 2013-65052 (Japanese Patent No. 5756962)

[0009] Patent Document 3: Japanese Patent Application Publication No. 2010-058091 (Japanese Patent No. 5274164)

[0010] Non-patent literature

[0011] Non-patent document 1: M.Iwata et al. "Bio-Inspired Bright Structurally ColoredColloidal Amorphous Array Enhanced by Controlling Thickness and BlackBackground", Adv.Mater., 2017, 29, 1605050. Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The infrared light-emitting part described in Patent Document 1 only utilizes visible light reflected through a dielectric multilayer film to achieve a colored appearance, with the color changing depending on the viewing angle. Furthermore, the dielectric multilayer film is also expensive.

[0014] According to the inventors' research, for infrared communication films utilizing dielectric multilayer films as described in Patent Document 1, when a hand's movement is captured through the film by an infrared camera, the hand's outline is blurred, making it difficult to use for motion capture. This is believed to be due to the low linear transmittance of infrared light.

[0015] On the other hand, for example, Patent Document 3 and Non-Patent Document 1 disclose that particulate dispersions or colloidal amorphous aggregates with amorphous structures can exhibit bright structural colors (e.g., blue) with low angle dependence. Patent Document 3 describes that particulate dispersions with amorphous structures are particularly useful for applications that reflect light of specific wavelengths (e.g., color materials, infrared reflective films, etc.).

[0016] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a filter with a novel structure, a method for manufacturing the filter and an optical module thereof, wherein the filter is white and suitable for use as an infrared filter with high linear transmittance of infrared light.

[0017] Problem Solving Methods

[0018] According to embodiments of the present invention, solutions illustrated in the following items are provided.

[0019] [Project 1]

[0020] A filter comprising a matrix and microparticles dispersed in the matrix.

[0021] The parameter Ds of the aforementioned particles, derived from the USAXS pattern and expressed as Ds = λ / (B·cosθ·Ra), is greater than 8.0 and less than 30.

[0022] Where λ is the wavelength of the X-ray, θ is half of the scattering angle 2θ (rad) at which the scattering intensity reaches its peak, B is the half-width of the peak (FWHM, rad), and Ra is the average particle size of the aforementioned particles.

[0023] [Project 2]

[0024] The filter described in Project 1 is white.

[0025] [Project 3]

[0026] According to the filter described in Project 1 or 2, the color it presents when the standard light is set to a D65 light source has x,y coordinates of 0.25≤x≤0.40 and 0.25≤y≤0.40 on the CIE1931 chromaticity diagram.

[0027] [Project 4]

[0028] The filter according to any one of items 1 to 3, wherein...

[0029] The L of the above-mentioned filter was measured using a spectrophotometer and via SCE method. ＊ The value is 20 or higher.

[0030] [Project 5]

[0031] The filter according to any one of items 1 to 4 has a linear transmittance of 60% or more for at least a portion of the wavelengths in the wavelength range of 760 nm and 2000 nm.

[0032] [Project 6]

[0033] According to the filter described in Project 5, its linear transmittance for light with a wavelength of 950nm is over 60%.

[0034] [Project 7]

[0035] According to the filter described in Project 5 or 6, its linear transmittance for light with a wavelength of 1500nm is greater than 60%.

[0036] [Project 8]

[0037] The filter according to any one of items 1 to 7, wherein...

[0038] The aforementioned particles include monodisperse first particles with an average particle size in the range of 80 nm or more and 300 nm or less.

[0039] [Project 9]

[0040] According to the filter described in Project 8, wherein,

[0041] The average particle size of the first particle mentioned above is greater than 150 nm.

[0042] [Project 10]

[0043] The filter according to any one of items 1 to 9, wherein...

[0044] The aforementioned particles at least constitute colloidal amorphous aggregates.

[0045] [Project 11]

[0046] The filter according to any one of items 1 to 10, wherein,

[0047] The volume fraction of the aforementioned particles is between 6% and 60%.

[0048] [Project 12]

[0049] The filter according to any one of items 1 to 11, wherein,

[0050] Let the refractive index of the above matrix for light with a wavelength of 546 nm be n. M And let the refractive index of the above particles be n P When, |n M -n P | is above 0.03 and below 0.6.

[0051] [Project 13]

[0052] The filter according to any one of items 1 to 12 has a three-dimensional shape.

[0053] [Project 14]

[0054] The filter according to any one of items 1 to 13, wherein...

[0055] The matrix is ​​formed of resin, and the microparticles are formed of inorganic materials.

[0056] [Project 15]

[0057] A manufacturing method for manufacturing the filter described in item 14, the method comprising:

[0058] A process for preparing a curable resin composition in which the above-mentioned particles are dispersed / mixed in a curable resin;

[0059] The process of applying the above-described curable resin composition to the surface of a substrate; and

[0060] A process of curing the curing resin contained in the curing resin composition applied to the surface.

[0061] [Project 16]

[0062] According to the manufacturing method described in item 15, wherein...

[0063] The above-mentioned coating process is carried out by coating method.

[0064] [Project 17]

[0065] According to the manufacturing method described in item 16, wherein,

[0066] The above-mentioned coating process is carried out by dip coating.

[0067] [Project 18]

[0068] An optical module having:

[0069] Equipment with infrared light-receiving parts, and

[0070] The filter described in any one of items 1 to 13 is disposed in front of the infrared light-receiving part of the above-described device.

[0071] [Project 19]

[0072] According to the optical module described in Project 18, wherein,

[0073] The aforementioned equipment includes sensing devices, communication devices, solar cells, heaters, or power supply equipment.

[0074] The effects of the invention

[0075] The filter with a novel structure according to embodiments of the present invention is white and suitable for use as an infrared filter with high linear transmittance of infrared light. According to embodiments of the present invention, a method for manufacturing such a filter and an optical module incorporating such a filter can be applied. Attached Figure Description

[0076] Figure 1 This is a cross-sectional schematic diagram of the filter 10 according to an embodiment of the present invention.

[0077] Figure 2 This is a schematic diagram used to explain the technical meaning of the parameter Ds, which represents the dispersion state of particles in a particle aggregate.

[0078] Figure 3 It is a graph showing the particle size distribution of the particles.

[0079] Figure 4 This is a diagram showing the USAXS pattern of the optical films of Examples 1 to 6.

[0080] Figure 5 This is a diagram showing the USAXS pattern of the optical films of Examples 7 to 12.

[0081] Figure 6 This is a diagram showing the USAXS pattern of the optical films of Examples 13-17.

[0082] Figure 7 This is a diagram showing the patterns of the optical films of Comparative Examples 1 to 4 in USAXS.

[0083] Figure 8 This is a diagram showing the USAXS pattern (standardized) of the optical films of Examples 1 to 6.

[0084] Figure 9 This is a diagram showing the USAXS pattern (standardized) of the optical films of Examples 7-12.

[0085] Figure 10 This is a diagram showing the USAXS pattern (standardized) of the optical films of Examples 13-17.

[0086] Figure 11 This is a diagram showing the pattern (standardized) of USAXS in Comparative Examples 1 to 4.

[0087] Figure 12 This is a schematic diagram used to illustrate the optical characteristics of the filter 10 according to an embodiment of the present invention.

[0088] Figure 13 This is a schematic diagram illustrating the method for measuring the immersion transmittance of a filter.

[0089] Figure 14 This is a schematic diagram of the method for measuring the linear transmittance of a filter.

[0090] Figure 15 These are the linear transmittance spectra of the optical films in Examples 1 to 6.

[0091] Figure 16 These are the linear transmittance spectra of the optical films in Examples 7-12.

[0092] Figure 17 These are the linear transmittance spectra of the optical films in Examples 13-17.

[0093] Figure 18 These are the linear transmittance spectra of the optical films of Comparative Examples 1 to 3.

[0094] Figure 19 This is a bar chart showing the values ​​of parameter Ds for each sample.

[0095] Figure 20A This is a diagram showing the two-dimensional X-ray scattering pattern of the optical film of Comparative Example 3.

[0096] Figure 20BThis is a diagram showing the two-dimensional X-ray scattering pattern of the optical film of Example 12.

[0097] Figure 20C This is a diagram showing the two-dimensional X-ray scattering pattern of the optical film of Comparative Example 4.

[0098] Figure 21 This is a TEM image showing a cross-sectional view of the filter 10A of Embodiment 1.

[0099] Figure 22 This is a TEM image showing a cross-sectional view of filter 20A of Comparative Example 1.

[0100] Figure 23 This is an example of a camera image obtained using motion capture equipment.

[0101] Figure 24 This is an example of a camera image obtained via filter 10A of Embodiment 1 and using a motion capture device.

[0102] Figure 25 Examples of camera images obtained via the filter 20A of Comparative Example 1 and using a motion capture device.

[0103] Figure 26 This is a diagram showing an optical image of the filter 10A of Embodiment 1.

[0104] Figure 27 This is a diagram showing an optical image of filter 20A of Comparative Example 1.

[0105] Figure 28A This is a diagram showing an optical image (visible light) of a filter formed in a hemispherical shape.

[0106] Figure 28B It is shown Figure 28A The image shows an infrared image of the filter of the hemispherical embodiment.

[0107] Symbol Explanation

[0108] 10, 10A, 20A: Filters

[0109] 12: Matrix

[0110] 14: Particles Detailed Implementation

[0111] Hereinafter, filters according to embodiments of the present invention will be described with reference to the accompanying drawings. The filters according to embodiments of the present invention are not limited to the filters exemplified below.

[0112] The filter of the present invention comprises a matrix and microparticles dispersed in the matrix. The filter is white and can be suitably used as an infrared filter with high linear transmittance of infrared light, and has a novel structure.

[0113] In its earlier applications (Japanese Patent Application No. 2020-045671 and Japanese Patent Application No. 2020-163409), the applicant disclosed that the microparticles preferably dispersed in a matrix constitute at least a colloidal amorphous aggregate. Here, a colloidal amorphous aggregate refers to an aggregate of colloidal particles (particle size 1 nm to 1 μm) that does not have long-range order and does not cause Bragg reflection. If the colloidal particles are distributed in a manner that has long-range order, it becomes a so-called colloidal crystal (a type of photonic crystal), which causes Bragg reflection and serves as a contrast. The microparticles (colloidal particles) constituting the colloidal amorphous aggregate do not form a diffraction grating. The disclosures of Japanese Patent Application Nos. 2020-045671 and 2020-163409 are incorporated herein by reference in their entirety.

[0114] The applicant conducted further research and found that, as detailed in the embodiments and comparative examples shown below, it is possible to obtain a filter that exhibits white color even when exhibiting Bragg reflection in the visible light region and has high linear transmittance for infrared light. The degree of whiteness and the magnitude of linear transmittance for infrared light vary depending on the application and can be adjusted by changing the thickness of the filter, etc. However, for obtaining a filter that exhibits white color and has high linear transmittance for infrared light, it is important to control the dispersion state of the particles.

[0115] The inventors have discovered that, for the purpose of a filter, when the parameter Ds, expressed as Ds = λ / (B·cosθ·Ra), obtained from the pattern of Ultra Small Angle X-ray Scattering (USAXS), is 8.0 or higher and 30 or lower, the particles are in a moderately dispersed state. This results in a white filter, suitable for use as an infrared filter with high linear transmittance for infrared light. Here, λ is the wavelength of the X-rays, θ is half the scattering angle 2θ (rad) at which the scattering intensity peaks, B is the half-width at half-maximum (FWHM, rad), and Ra is the average particle size. It is believed that the dispersed state of the particles characterized by the parameter Ds is white and possesses an order (periodicity) suitable for exhibiting high linear transmittance for infrared light. The dispersed state of the particles characterized by the parameter Ds can include dispersed states that can be classified as colloidal crystals exhibiting Bragg reflection in the visible light region, and colloidal amorphous aggregates without Bragg reflection. If Bragg reflection is present, coloration can be observed when viewed from a specific direction. Therefore, to ensure that white is observed regardless of the viewing angle, it is preferable that the particles form colloidal amorphous aggregates. The technical meaning of parameter Ds will be referred to later. Figure 2 A detailed explanation will be provided.

[0116] The filter of the present invention can be white. A white filter can be designed in various colors. White can be defined in various ways depending on the application. For example, when the standard light is set to a D65 light source, the color produced when the x,y coordinates on the CIE 1931 chromaticity diagram are 0.25≤x≤0.40 and 0.25≤y≤0.40 can be considered white. Of course, the closer to x = 0.333 and y = 0.333, the higher the whiteness. Preferably, it is 0.28≤x≤0.37 and 0.28≤y≤0.37, and more preferably 0.30≤x≤0.35 and 0.30≤y≤0.35. Additionally, the L value measured in the CIE 1976 color space using the SCE method... ＊ Preferably, it is 20 or more; more preferably, 40 or more; further preferably, 50 or more; and especially preferably, 60 or more. ＊ When the value is 20 or higher, it can be considered roughly white. L ＊ The upper limit is, for example, 100.

[0117] The filter according to embodiments of the present invention can have a linear transmittance of 60% or more for at least a portion of the wavelengths in the wavelength range of 760 nm to 2000 nm. For example, a filter with a linear transmittance of 60% or more for light with wavelengths of 950 nm and 1500 nm can be obtained. The wavelength range of light (near-infrared) for which the filter has a linear transmittance of 60% or more is preferably 810 nm to 1700 nm, and more preferably 840 nm to 1650 nm. Such a filter is suitable for application, for example, in InGaAs sensors, InGaAs / GaAsSb sensors, CMOS sensors, NMOS sensors, and CCD sensors. Here, both the substrate and the microparticles are preferably transparent to visible light (hereinafter referred to as "transparent").

[0118] The infrared linear transmittance of the filter can be appropriately set according to the application. The filter of the present invention can be disposed in front of the infrared light-receiving part of various devices to form an optical module. Examples of devices having an infrared light-receiving part include: sensing devices, communication devices, solar cells, heaters, or power supply devices.

[0119] The filter of the present invention contains monodisperse particles with an average particle size of more than one-tenth of the wavelength of infrared light. That is, relative to infrared light with a wavelength range of 760 nm to 2000 nm, the average particle size is preferably at least 80 nm, more preferably 150 nm, and even more preferably 200 nm. The upper limit of the average particle size is, for example, 300 nm. Two or more monodisperse particles with different average particle sizes may be included. Each particle is preferably substantially spherical. It should be noted that in this specification, "particles (multiple)" is used in the sense of an aggregate of particles, and monodisperse particles refer to particles with a variation coefficient (the value of standard deviation / average particle size expressed as a percentage) of 20% or less, preferably 10% or less, and more preferably 1 to 5%. The filter of the present invention improves the linear transmittance of infrared light by utilizing particles with a particle size (particle diameter, equivalent diameter of a sphere) of more than one-tenth of the wavelength. This differs from the optical article described in Patent Document 2 which utilizes the principle of Rayleigh scattering. The average particle size can be determined, for example, by a disc centrifugal particle size analyzer.

[0120] exist Figure 1 The diagram shows a cross-sectional view of a filter 10 according to an embodiment of the present invention. The filter 10 according to an embodiment of the present invention includes a substrate 12 that is transparent to visible light and transparent microparticles 14 dispersed in the transparent substrate 12.

[0121] Filter 10 Figure 1 As schematically shown, it has a substantially flat surface. Here, a substantially flat surface means a surface without any unevenness or concavity that would cause visible light or infrared light to scatter (diffract) or diffusely reflect. Furthermore, the filter 10 does not contain cholesteric liquid crystal (broadly including cholesteric liquid crystals exhibiting a cholesteric phase, which are formed by cross-linking high-molecular-weight liquid crystals, low-molecular-weight liquid crystals, liquid crystal mixtures thereof, and liquid crystal materials thereof with a cross-linking agent, and then curing them). It should be noted that the filter 10 may be, for example, a film, but is not limited to this.

[0122] The transparent microparticles 14 are, for example, silica microparticles. Silica microparticles, for example, can be silica microparticles synthesized by the Stober process. Alternatively, inorganic microparticles other than silica microparticles, or resin microparticles, can be used. As resin microparticles, microparticles preferably include at least one selected from polystyrene and polymethyl methacrylate, and more preferably microparticles including cross-linked polystyrene, cross-linked polymethyl methacrylate, or cross-linked styrene-methyl methacrylate copolymers. It should be noted that, for example, polystyrene microparticles or polymethyl methacrylate microparticles synthesized by emulsion polymerization can be appropriately used. Additionally, hollow silica microparticles containing air and hollow resin microparticles can also be used. It should be noted that microparticles formed from inorganic materials have the advantage of excellent heat resistance and light resistance. The volume fraction relative to the total microparticles (including the matrix and microparticles) is preferably 6% or more and 60% or less, more preferably 20% or more and 50% or less, and more preferably 20% or more and 40% or less. The transparent microparticles 14 can be optically isotropic.

[0123] Examples of the matrix 12 include, but are not limited to, acrylic resins (e.g., polymethyl methacrylate, polymethyl acrylate), polycarbonate, polyester, poly(diethylene glycol dicarbonate), polyurethane, epoxy resin, and polyimide. The matrix 12 is preferably formed using a curable resin (thermosetting or photocurable), and from a mass production perspective, a photocurable resin is preferred. Various (meth)acrylates can be used as photocurable resins. The (meth)acrylates preferably contain two or more functional groups. Furthermore, the matrix 12 is preferably optically isotropic. If a curable resin containing multifunctional monomers is used, a matrix 12 with a cross-linked structure is obtained, thus improving heat resistance and lightfastness.

[0124] The filter 10, formed from a resin material, can be a flexible film. The thickness of the filter 10 is, for example, 10 μm or more and 10 mm or less. When the thickness of the filter 10 is, for example, 10 μm or more and 1 mm or less, and further 10 μm or more and 500 μm or less, it can exhibit significant flexibility.

[0125] When using silica microparticles with a hydrophilic surface as microparticles, it is preferable to form them by photocuring a hydrophilic monomer. Examples of hydrophilic monomers include, but are not limited to: 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 methacrylate, or 2-hydroxypropyl methacrylate, acrylamide, methylenebisacrylamide, ethoxylated bisphenol A di(meth)acrylate. Furthermore, these monomers can be used alone or in combination of two or more. Of course, the two or more monomers can include monofunctional monomers and polyfunctional monomers, or can include two or more polyfunctional monomers.

[0126] These monomers can be cured by using appropriate photopolymerization initiators. Examples of photopolymerization initiators include: benzoin ethers, benzophenone, anthraquinones, and thiazolinone. Carbonyl compounds such as alkanes, ketals, and acetophenones; sulfur compounds such as disulfides and dithiocarbamates; organic peroxides such as benzoyl peroxide; azo compounds; transition metal complexes; polysilane compounds; and pigment sensitizers are included. The amount of photopolymerization initiator added 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 mixture of microparticles and monomers.

[0127] Let the refractive index of the matrix for visible light be n. M And set the refractive index of the particles to n. P When, |n M -n P (Hereinafter referred to simply as refractive index difference.) Preferably, it is 0.01 or more, more preferably 0.6 or less, further preferably 0.03 or more, and even more preferably 0.11 or less. When the refractive index difference is less than 0.03, the scattering intensity weakens, making it difficult to obtain the desired optical properties. Furthermore, when the refractive index difference exceeds 0.11, the linear transmittance of infrared light decreases. Alternatively, for example, by using zirconium oxide particles (refractive index 2.13) and acrylic resin to achieve a refractive index difference of 0.6, the linear transmittance of infrared light can be adjusted by reducing the thickness. In this way, the linear transmittance of infrared light can also be adjusted, for example, by controlling the thickness and refractive index difference of the filter. Additionally, depending on the application, it can be used in conjunction with an infrared-absorbing filter. It should be noted that the refractive index for visible light can be represented, for example, by the refractive index for light at 546 nm. Here, unless otherwise specified, the refractive index refers to the refractive index for light at 546 nm.

[0128] The filter according to embodiments of the present invention can be manufactured, for example, by a manufacturing method including the following steps: a step of preparing a curable resin composition in which particulate matter is dispersed / mixed in a curable resin; a step of applying the curable resin composition to the surface of a substrate; and a step of curing the curable resin contained in the curable resin composition applied to the surface. The substrate can be, for example, a glass substrate, or a resin film such as PET (polyethylene terephthalate), TAC (cellulose triacetate), or PI (polyimide), but is not limited thereto. The step of dispersing / mixing the particulate matter in the curable resin can be performed using known dispersion / mixing apparatus such as a homogenizer or a homogenizer (e.g., an ultrasonic homogenizer or a high-pressure homogenizer). Furthermore, the application step can be performed by various known methods such as coating (e.g., dip coating, spray coating, mold coating), printing, etc.

[0129] The following describes the structure and optical characteristics of the filters according to embodiments of the present invention through specific experimental examples (exemplary and comparative examples). The structure and optical characteristics of the filters of the examples and comparative examples are shown in Table 1. Various filters as shown in Table 1 were fabricated by combining different types of silica particles and resins, adding coagulants or dispersants, and using different dispersion / mixing methods.

[0130] The filters of Examples 1-17 and Comparative Examples 1-3 were formed into films using acrylic resins and silica microparticles as described in Table 1. Monodisperse silica microparticles synthesized by the Stober method were used as the silica microparticles. Five types of microparticles with different average particle sizes, 1-5, as shown in Table 2, were used. Average particle size, standard deviation, and CV values ​​were measured using a disc centrifugal particle size analyzer (DC24000UHR) manufactured by CPS Instruments. The particle size distributions of microparticles 1-5 are shown in Table 2. Figure 3 It should be noted that Comparative Example 4 uses Photonic Rubber, commercially available from Soft Photonix Corporation. This nanoparticle-based photonic crystal strongly reflects light of a specific color via Bragg reflection. If deformed, the spacing between the nanoparticles constituting the photonic crystal changes, thus altering the color of the reflected light. It should also be noted that the particle size (*) of Comparative Example 4 shown in Table 1 is a value obtained based on the USAXS-based scattering pattern described later.

[0131] A curable resin composition is prepared by mixing / dispersing silica microparticles in acrylic monomers A to E in a given formulation. This composition is then applied to a substrate surface using a coating apparatus to obtain a film of a given thickness, and subsequently cured. Alternatively, 0.2 parts by weight of Darocure 1173 is added as a photopolymerization initiator relative to 100 parts by weight of acrylic monomers, and the mixture is cured by photopolymerization under a UV lamp. Resins (polymers) with different refractive indices are formed depending on the type of monomer.

[0132] The following shows acrylic monomers A through E. Monomers A and E are trifunctional acrylates, monomers B and C are difunctional acrylates, and monomer D is a monofunctional acrylate.

[0133] A: Pentaerythritol triacrylate

[0134] B: Ethoxylated bisphenol A diacrylate (m+n=10)

[0135] C: Ethoxylated bisphenol A diacrylate (m+n=3)

[0136] D: Methoxylated polyethylene glycol #400 methacrylate

[0137] E: Trimethylolpropane (TMP) EO-modified triacrylate

[0138] F: Ethoxylated bisphenol A diacrylate (m+n=4)

[0139] G: Ethoxylated bisphenol A diacrylate (m+n=6)

[0140] It should be noted that acrylic monomers B, C, F and G are represented by the following chemical formula (Chemical Formula 1).

[0141] [Chemical Formula 1]

[0142]

[0143] To investigate changes in the dispersion state of the particles, in Comparative Example 1, 0.1% by mass of polyethylene glycol was added as a coagulant relative to acrylic monomer A. In Example 8, 0.5% by mass of DISPERBYK-111 (manufactured by BYK) was added as a dispersant relative to acrylic monomer B. In Example 11, 0.1% by mass of DISPERBYK-180 (manufactured by BYK) was added as a dispersant relative to acrylic monomer B.

[0144] The filter of the embodiment of the present invention has a particle dispersion state in which the parameter Ds, expressed as Ds = λ / (B·cosθ·Ra), obtained according to the USAXS pattern, is 8.0 or more and 30 or less. Here, λ is the wavelength of the X-ray, θ is half of the scattering angle 2θ (rad) at which the peak scattering intensity is reached, B is the half-width at half-maximum (FWHM, rad), and Ra is the average particle size.

[0145] Reference Figure 2 The technical meaning of parameter Ds will be explained. Figure 2 This is a schematic diagram illustrating the relationship between the dispersion state (degree of periodicity) of particles in a particle aggregate and the half-width of the peak of the scattering intensity from USAXS. Figure 2 The well-known Scherrer formula was used to compare the relationship between the estimated half-width of X-ray diffraction peaks and the size of polycrystalline grains (microcrystals). Figure 2 In the schematic diagram representing a polycrystalline material, ○ represents an atom; conversely, in the schematic diagram representing a microparticle aggregate, ○ represents a microparticle. To obtain information about the dispersion state of microparticles with a diameter of approximately 100 nm, it is necessary to analyze the X-ray scattering pattern in the ultra-small angular region.

[0146] The grain size of polycrystalline materials (aggregates of microcrystals) can be estimated using the well-known Scherrer formula.

[0147] D = K·λ / (B·cosθ)

[0148] Here, B is the width of the diffraction line due to the finite grain size (half-value width), and has the following relationship with the measured diffraction line width Bobs and the line width b depending on the device, as shown in equation (1).

[0149] Bobs = B + b (1)

[0150] Additionally, D represents the grain size, λ is the wavelength of the X-rays, and θ is the Bragg angle (half of the diffraction angle 2θ). The constant K is called the Scherrer constant, and its value varies depending on the approximation used to determine the intensity or the measured quantity used to define the width B. The more repetitions of the structure forming the diffraction period, i.e., the larger the grains, the stronger the diffraction peaks and the narrower the linewidth.

[0151] On the other hand, the wider the particle is distributed at a distance close to the average distance that forms the scattering angle, the greater the intensity of the scattering peak (halo) of the particle aggregate and the narrower the linewidth. When focusing on a certain particle, the closer the distance to the particles located near that particle is to the average distance, and the more such particles there are, the greater the intensity of the scattering peak and the narrower the linewidth. Therefore, the parameter Ds, which represents the "width of the particles distributed at the average distance" in the particle aggregate, relative to the average particle size Ra, is expressed by the following equation (2).

[0152] Ds=λ / (B·cosθ·Ra) (2)

[0153] Here, USAXS uses the BL08B2 small-angle X-ray scattering station of Spring8, so the parallelism of the X-rays is high, and b in the above equation (1) can be ignored, set as Bobs = B. The distance between the sample and the two-dimensional X-ray detector is set to 16 m. CuKα rays (wavelength λ = 0.1542 nm) were used for the X-rays.

[0154] exist Figure 4 , Figure 5 , Figure 6 and Figure 7 The image shown is a baseline-corrected graph of the measurement results for the USAXS pattern. Figure 8 , Figure 9 , Figure 10 and Figure 11 The figure shows the scattering intensity after normalization using the maximum value. The parameter Ds, obtained from the peaks of these scattering patterns and using equation (2) above, is shown in Table 1. It should be noted that... Figures 4 to 11 The horizontal axis is the scattering vector q, and θ = sin -1 The relationship is (qλ / 4π). Furthermore, it has a half-value width B(FWHM, rad) = sin -1 (B q The relationship is λ / 4π. B q It is the half-width (FWHM, nm) represented by the scattering vector q. -1 ).

[0155] The optical properties of a filter can be evaluated as follows.

[0156] like Figure 12 As shown, when incident light I0 is incident on filter 10, a portion of the incident light I0 is transmitted through filter 10 (transmitted light I). i A portion of the light undergoes interface reflection (interface reflected light R). i Another portion is scattered. The scattered light includes forward scattered light S emitted in front of filter 10. f and the backscattered light S emitted backward bThrough backscattered light S b The filter 10 appears white. A portion of the incident light I0 is absorbed by the filter 10, but the resin and silica particles used here have a low absorption rate for light in the 400nm to 2000nm range.

[0157] Figure 13 This is a schematic diagram illustrating the method for measuring the immersion transmittance of a filter. Figure 14 This is a schematic diagram illustrating the method for measuring the linear transmittance of a filter. Immersion transmittance is as follows: Figure 13 As shown, a sample (filter 10) is placed at the opening of the integrating sphere 32, with the intensity of the incident light I0 relative to the transmitted light I. i and forward scattered light S f The total intensity is calculated as a percentage. Furthermore, the linear transmittance is measured by positioning the sample (filter 10) 20 cm from the opening of the integrating sphere 32. The intensity of the incident light I0 at this position is expressed as a percentage of the transmitted light I. i The intensity was calculated as a percentage. The diameter of the opening was 1.8 cm, equivalent to 0.025 sr in solid angle. A UH4150 UV-Vis-NIR spectrophotometer (manufactured by Hitachi High-Tech Science Corporation) was used as the spectrometer. The linear transmittance values ​​for infrared light at 760 nm, 950 nm, and 1500 nm are shown in Table 1. Furthermore, the linear transmittance spectra of each sample are shown in... Figure 15 , Figure 16 , Figure 17 and Figure 18 The presence or absence of Bragg reflection can be determined by the presence or absence of dimples (local decreases in transmittance) in the linear transmittance spectrum.

[0158] Backscattered light S b The whiteness was measured using a CM-2600-D spectrophotometer (manufactured by Konica Minolta, Japan). The L value was determined using the SCE (Specular Removal) method. ＊ The values ​​of L, and the x and y coordinates on the CIE 1931 chromaticity diagram. ＊ The larger the value, the closer the x and y values ​​are to 0.33, and the higher the whiteness. These values ​​are also shown in Table 1.

[0159]

[0160] [Table 2]

[0161] Particle 1 Particle 2 Particle 3 Particle 4 Particle 5 La: Average particle size [nm] 218 280 194 220 229 Ld: Standard deviation [nm] 8.7 9.5 6.3 5.6 6.3 CV value (Ld / La) [%] 4.0 3.4 3.2 2.5 2.8

[0162] As shown in Table 1, all Examples 1-17 exhibit white color. When the standard light is set to a D65 illuminant, the x and y coordinates of the color displayed on the CIE 1931 chromaticity diagram satisfy 0.25 ≤ x ≤ 0.40 and 0.25 ≤ y ≤ 0.40. Furthermore, the L color measured using a spectrophotometer and via SCE method... * The value is 20 or higher.

[0163] Furthermore, in all Examples 1 to 17, the linear transmittance for at least a portion of the wavelengths in the wavelength range of 760 nm to 2000 nm is 60% or more. Specifically, the linear transmittance for light with wavelengths of 950 nm and 1500 nm is 60% or more. The linear transmittance spectra shown above only extend to 1500 nm; however, the linear transmittance in the region exceeding 1500 nm but below 2000 nm may be slightly reduced locally, but the linear transmittance for light at 1500 nm remains approximately the same.

[0164] exist Figure 19 The values ​​of parameter Ds for each sample are shown in a bar chart. The Ds values ​​for all Examples 1 to 17 are greater than the Ds value of Comparative Example 1 (7.7) and less than the Ds value of Comparative Example 2 (31.7). Comparative Example 1 (7.7 Ds) and Comparative Example 2 (7.4 Ds) have sufficient whiteness, but their infrared linear transmittance in the 760nm-1500nm range does not reach 60%, indicating insufficiently high infrared linear transmittance. On the other hand, Comparative Example 2, with a relatively large Ds value of 31.7, has sufficiently high infrared linear transmittance, but low whiteness. Therefore, a Ds value of 8.0 or higher and 30 or lower, and more preferably 8.2 or higher and 22 or lower, is preferred. Examples 2 and 6, with Ds values ​​less than 10, have relatively low infrared transmittance; therefore, from the viewpoint of infrared transmittance, a Ds value of 10 or higher, and more preferably 14 or higher, is preferred.

[0165] The reason why Comparative Example 2 has a lower whiteness due to its larger Ds value of 31.7 is because of Bragg reflection. Figure 18 In the linear transmittance spectrum of Comparative Example 2 shown, a steep valley (reduction in transmittance) was observed near 650 nm. This indicates that light at this wavelength was reflected (Bragg reflection). It should be noted that in Example 7 ( Figure 16 Examples 16 and 17 Figure 17 In the linear transmittance spectrum of Example 7, there are also valleys in the visible light region, but they differ from the spectrum of Comparative Example 2. Figure 16The linear transmittance of the visible light region in Examples 16 and 17 is relatively low, causing backscattering of visible light with wavelengths shorter than those present in the valleys. This is considered to relatively suppress the effect of Bragg reflection on the whiteness of the backscattered light. However, if Bragg reflection is present, coloration can be observed when viewed from a specific direction; therefore, to ensure whiteness is observed regardless of the viewing angle, it is preferable that the particles form colloidal amorphous aggregates.

[0166] Here, refer to Figure 20A , Figure 20B and Figure 20C The relationship between the two-dimensional pattern of small-angle X-ray scattering and the value of Ds is explained. Figure 20A The scattering pattern of Comparative Example 3 (Ds value 7.4) is shown. Figure 20B The scattering pattern of Example 12 (Ds value 11.0) is shown. Figure 20C The scattering pattern of Comparative Example 4 (Ds value 37.7) is shown. It can be seen that... Figure 20A The scattering pattern of Comparative Example 3 is a very broad isotropic halo (see reference). Figure 7 and Figure 11 On the other hand, in Figure 20C In the scattering pattern of Comparative Example 4 (Photonic Rubber), diffraction points were observed at point-symmetrical positions, indicating high periodicity. Figure 20B No diffraction points were observed in the scattering pattern of Example 12, and the linewidth ratio of the halo was known. Figure 20A The scattering pattern of Comparative Example 3 is narrow (refer to...) Figure 5 and Figure 9 Therefore, it can be concluded that a large Ds value indicates high periodicity, and a small Ds value indicates low periodicity.

[0167] exist Figure 21 The image shown is a cross-sectional TEM image of filter 10A of Example 1. Figure 22 The figure shows a cross-sectional TEM image of filter 20A of Comparative Example 1. The sample used for TEM observation was obtained as follows: with the thickness of each film set to d, a sample sheet of the same thickness as the average particle size of the silica particles was cut at position d / 2 using a slicer in the cross-sectional direction. In the TEM image, the white circles are silica particles, and the black circles are traces of silica particles detached.

[0168] It can be known that in Figure 21 In the cross-section of the filter 10A shown, the silica particles are dispersed approximately uniformly; in contrast, in... Figure 22In the cross-section of the filter 20A shown, some of the silica particles agglomerate. This is because, when manufacturing the filter 20A of Comparative Example 1, in addition to acrylic monomer A, 0.1% by mass of polyethylene glycol was added as a coagulant relative to acrylic monomer A. As a result, the Ds value of Example 1 is considered to be 10.3, while the Ds value of Comparative Example 1 is smaller, at 7.7.

[0169] It should be noted that no significant difference was observed between Example 8, which included a dispersant, and Example 7, which did not include a dispersant. It is believed that a sufficiently uniform dispersion can be obtained without adding a dispersant, at least until the particle fraction reaches 50% by mass (38% by volume). On the other hand, comparing Example 11, which included a dispersant, with Example 10, which did not include a dispersant, the Ds value of Example 11 was smaller. Therefore, it is indicated that a uniform dispersion is not necessarily easily obtained. Furthermore, it is therefore considered that the Ds value can be an excellent indicator that sensitively reflects differences in the dispersion state of the particles.

[0170] Next, refer to Figure 23 , Figure 24 and Figure 25 This describes the results of comparing the performance of the infrared filter 10A of Example 1 and the filter 20A of Comparative Example 1. Figure 23 These are examples of camera images obtained using motion capture equipment, and they are camera images obtained without using filters. Figure 24 This is an example of a camera image obtained via filter 10A of Embodiment 1 and using a motion capture device. Figure 25 Examples of camera images obtained via the filter 20A of Comparative Example 1 and using a motion capture device.

[0171] Here, as a motion capture device, the Leap Motion Controller (registered trademark) was used to obtain a camera image of a hand located approximately 20cm away. It should be noted that this device uses infrared light with a wavelength of 850nm. Based on... Figure 23 , Figure 24 and Figure 25 A comparison clearly shows that in the case of using filter 10A of the embodiment ( Figure 24 Under these conditions, the results can be obtained compared to the case where no filter is used. Figure 23 Images with the same level of clarity, in contrast, when using the comparative example filter 20A ( Figure 25 Under these conditions, a clear image cannot be obtained, and the hand cannot be recognized.

[0172] exist Figure 26 An optical image of filter 10A of Embodiment 1 is shown in the figure. Figure 27An optical image of filter 20A of Comparative Example 1 is shown. Filter 10A of Example 1 and filter 20A of Comparative Example 1 are made into a film of approximately 5 cm × approximately 10 cm, arranged to cover the front of the device. According to... Figure 26 and Figure 27 As can be seen, all films are white. Therefore, the filter 10A of Example 1 is suitable for use as an infrared filter and is white, thus offering high design flexibility. Of course, the surface of the filter 10A of Example 1 can also be colored or patterned by printing or other means.

[0173] As described above, the filter according to embodiments of the present invention can be white. Therefore, by using infrared-transmitting ink to print text, drawings, or photographs onto the surface of the filter, a filter with rich colors and a wide range of designs can be obtained. Specifically, the filter according to embodiments of the present invention can have a filter layer comprising a substrate and microparticles, and a printing layer formed of infrared-transmitting ink disposed on the filter layer. The printing layer can be formed directly on the surface of the filter layer, or a material on which the printing layer is formed on the surface of a transparent film can be disposed on the filter layer. As the infrared-transmitting ink, a known infrared-transmitting ink can be selected according to the application or the wavelength of the infrared light to be transmitted.

[0174] Furthermore, the filter of the present invention increases the intensity of diffuse reflected light when viewed from an oblique angle, thus increasing white brightness and improving the aesthetics (visual recognizability) of the appearance design.

[0175] The filter in this embodiment can be a planar film as shown in the example, but is not limited thereto and can take various forms. The filter in this embodiment can have a three-dimensional shape. For example, it can be a film with a three-dimensional shape. Specifically, for example, the filter can be formed on the surface of an object with a three-dimensional shape using a coating method. The surface of the object can have any shape, such as part or all of a sphere, an arbitrary curved surface, part or all of a polyhedron surface, etc. However, it is preferable that the surface of the object does not scatter light.

[0176] For example, such as Figure 28A and Figure 28B As shown, a filter formed into a hemispherical shape can be obtained. Figure 28A This is a diagram showing an optical image (visible light) of a filter formed in a hemispherical shape, illustrating an embodiment. Figure 28B It is shown Figure 28A The image shows an infrared image of the filter of the hemispherical embodiment. Figure 28A and Figure 28B The images shown were captured using a full HD digital cinema camera, the DVSA10FHDIR, manufactured by KenkoTokina Corporation. Figure 28AThe image was taken in visible light mode under white LED illumination. Figure 28B These are images taken in a dark room using only the light from the infrared LEDs of the aforementioned camera.

[0177] Figure 28A and Figure 28B The filter shown is a 300 μm thick filter formed as described below: it is formed by dip-coating the surface of a hemisphere made of acrylic resin (PMMA) with a radius of 2 cm and a thickness of 1 mm with the same material as in Example 5. Figure 28A As shown, a white filter with a hemispherical shape was obtained. Additionally, as... Figure 28B As shown, this filter allows infrared light to pass through.

[0178] The filters of the embodiments of the present invention are not limited to the illustrated sensing devices (e.g., infrared cameras) and communication devices, but can be used for a variety of purposes. For example, they can be suitably used in solar cells, heaters that use infrared light, and light-powered devices that use infrared light.

[0179] Industrial applicability

[0180] The filters of the embodiments of the present invention can be used, for example, as infrared filters used in sensor technology or communication technology.

Claims

1. An optical filter which exhibits white color, the optical filter comprising a base material, and fine particles dispersed in the base material, a parameter Ds expressed as Ds = λ / (B-cosθ-Ra) obtained from a pattern according to USAXS of the fine particles is 8.0 or greater and 30 or less, wherein, λ is the wavelength of X-rays, θ is half of the scattering angle 2θ (rad) at which the peak of the scattering intensity is reached, B is the half-value width (FWHM, rad) of the peak, and Ra is the average particle diameter of the fine particles.

2. The optical filter according to claim 1, which exhibits a color having x, y coordinates on a CIE 1931 chromaticity diagram of 0.25≤x≤0.40, 0.25≤y≤0.40 when a standard light is set to D65 light source.

3. The optical filter according to claim 1 or 2, wherein The value of L of the filter measured using a spectrophotometer and by the SCE method is 20 or more. ＊ the value of L is 20 or more.

4. The optical filter according to claim 1 or 2, which has a straight-line transmittance of 60% or greater for light of at least a portion of the wavelength range of 760 nm or greater and 2000 nm or less.

5. The optical filter according to claim 4, which has a straight-line transmittance of 60% or greater for light of a wavelength of 950 nm.

6. The optical filter according to claim 4, which has a straight-line transmittance of 60% or greater for light of a wavelength of 1500 nm.

7. The optical filter according to claim 1 or 2, wherein the fine particles comprise monodispersed first fine particles having an average particle diameter in the range of 80 nm or greater and 300 nm or less.

8. The optical filter according to claim 7, wherein the average particle diameter of the first fine particles is 150 nm or greater.

9. The optical filter according to claim 1 or 2, wherein the fine particles constitute at least colloidal amorphous aggregates.

10. The optical filter according to claim 1 or 2, wherein the volume fraction of the fine particles is 6% or greater and 60% or less.

11. The optical filter according to claim 1 or 2, wherein The refractive index of the base for light having a wavelength of 546 nm is set to n M , and the refractive index of the fine particles is set to n P When |n M -n P | is 0.03 or more and 0.6 or less.

12. The optical filter according to claim 1 or 2, which has a three-dimensional shape.

13. The optical filter according to claim 1 or 2, wherein the base material is formed of a resin, and the fine particles are formed of an inorganic material.

14. A production method of producing the optical filter according to any one of claims 1 to 13, the method comprising: a step of preparing a curable resin composition in which the fine particles are dispersed / mixed in a curable resin; a step of imparting the curable resin composition to the surface of a substrate; and a step of curing the curable resin contained in the curable resin composition imparted to the surface.

15. The production method according to claim 14, wherein the imparting step is performed by a coating method.

16. The production method according to claim 15, wherein the imparting step is performed by a dip coating method.

17. An optical module having: an apparatus equipped with an infrared light receiving portion, and the optical filter according to any one of claims 1 to 12 disposed in front of the infrared light receiving portion of the apparatus.

18. The optical module according to claim 17, wherein ​ The device is a sensor device, a communication device, a solar cell, a heater, or a power supply device.

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