rubber composition

Abstract

This rubber composition contains (A) a polymer, (B) a crosslinking agent, and (C) a coloring agent. The coloring agent (C) does not contain an inorganic black pigment. As a rubber sheet, the rubber composition demonstrates: a minimum transmittance at a wavelength of 800-1600 nm of 50% or greater; a minimum transmittance at a wavelength of 900-1100 nm of 80% or greater; a maximum transmittance at a wavelength of 300-700 nm of 40% or less; and a maximum transmittance at a wavelength of 300-650 nm of 1% or less.

Description

Technical Field

[0001] The present invention relates to a rubber composition.

Background Art

[0002] Near-infrared rays are widely used in in-vehicle sensors, biometric sensors, and bio applications, etc., and further expansion of their use is expected in the future. In various sensors using near-infrared rays as described above, resins that selectively absorb light of a specific wavelength are widely used (for example, see Patent Documents 1 to 9).

[0003] For example, Patent Document 1 discloses a selective wavelength absorption resin composition for LiDAR that detects the distance and direction to an object. Here, "LiDAR" is an abbreviation for Light Detection and Ranging, which is a technology for measuring the distance and angle to an object by irradiating the object with laser light while scanning the laser light and observing the reflected light.

[0004] The selective wavelength absorption resin composition for LiDAR disclosed in Patent Document 1 has an epoxy resin as the main component, and a cured body formed to a thickness of 1 mm has an average light transmittance in the range of 380 nm or more and 700 nm or less of 40% or less, and the transmittance of the wavelength of the laser light (850 nm to 950 nm, 1500 nm to 1600 nm) used in LiDAR is defined to be 80% or more.

[0005] Patent Documents 2 and 3 disclose resins containing polycarbonate as a wavelength selective transmissive resin for LiDAR. For example, Patent Document 2 discloses a polycarbonate resin composition having wavelength selective transmittance, and Patent Document 3 discloses a thermoplastic resin containing a polycarbonate resin. And in Patent Documents 2 and 3, a technique for defining the type of pigment for wavelength absorption for the resin containing polycarbonate as described above has been proposed.

[0006] Patent Document 4 discloses a thermoplastic resin composition comprising a thermoplastic resin and a colorant. The thermoplastic resin composition disclosed in Patent Document 4 has a maximum wavelength transmittance of 1% or less at 380-630 nm and an average transmittance of 80% or more at 840-940 nm when the thickness is 1 mm. Patent Document 4 also discloses a technology that specifies pigments to be used as colorants, and states that the thermoplastic resin composition can be used in optical lenses, infrared camera lenses, lenses for biometric authentication cameras, etc.

[0007] Patent Document 5 discloses an optical film capable of absorbing specific wavelengths through multiple filters. The optical film disclosed in Patent Document 5 includes a near-infrared blocking layer having an absorption maximum at wavelengths of 600-800 nm and is said to be used in biometric authentication devices and imaging devices.

[0008] Patent Document 6 discloses an optical filter containing a green dye and a black dye. The optical filter disclosed in Patent Document 6 has a structure having a continuous 50 nm wavelength range in which the average transmittance is 2% or less between 400 and 730 nm and 80% or more between 800 and 1000 nm. In the optical filter disclosed in Patent Document 6, the green dye and the black dye exist in a dispersed or dissolved state in a transparent resin. The optical filter disclosed in Patent Document 6 is said to be used in imaging devices, infrared sensors, biometric authentication devices, and three-dimensional distance imaging cameras.

[0009] Furthermore, Patent Documents 7 to 9 propose visible light-shielding silicone rubber compositions and infrared-transmitting compositions using silicone rubber. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Patent No. 6899061 [Patent Document 2] Japanese Patent Publication No. 2021-147470 [Patent Document 3] International Publication No. 2021 / 025097 [Patent Document 4] International Publication No. 2020 / 138050 [Patent Document 5] Japanese Patent Publication No. 2020-177147 [Patent Document 6] Patent No. 6662299 [Patent Document 7] Patent No. 5170463 [Patent Document 8] Japanese Patent Publication No. 2021-70772 [Patent Document 9] Japanese Patent Publication No. 2019-131806 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] The resin compositions that selectively absorb light of specific wavelengths disclosed in Patent Documents 1 to 6 use resin as the main component, resulting in a hard and inflexible cured body (resin). Consequently, resin compositions like those disclosed in Patent Documents 1 to 6 have problems such as being prone to cracking in their cured bodies and having poor conformability to deformation.

[0012] Furthermore, rubber compositions such as those disclosed in Patent Documents 7-9 have the problem of poor selectivity for the required wavelength of light. In other words, since rubber, which is the cured product of a rubber composition, generally has low transparency, the rubber composition is often supplemented with, for example, carbon black. In rubber made from such a rubber composition, the colorants such as carbon black absorb a wide range of light from visible light to infrared, making it difficult to obtain infrared light transmittance. On the other hand, transparent rubber also exists, but such transparent rubber transmits a wide range of light from ultraviolet to visible light to infrared, making it difficult to selectively transmit light of the required wavelength.

[0013] Currently, sensors utilizing light of specific wavelengths, such as those using silicon semiconductor lasers with a wavelength of 905 nm, have the advantage of being inexpensive and having low power consumption. However, because the laser light is close to visible light, the laser output cannot be increased due to its effect on the retina, and it is also highly susceptible to the effects of sunlight. In recent years, the use of indium gallium arsenide phosphide (InGaAsP) semiconductor lasers with a wavelength of 1550 nm has also been considered as a second-generation mechanical-less technology. InGaAsP semiconductor lasers have the advantage of being costly and having high power consumption, but they have less impact on the retina, allow for increased output, and are less susceptible to the effects of sunlight.

[0014] The rubber compositions disclosed in the aforementioned Patent Documents 7 to 9 have a specified infrared transmission range of 800 nm or 800 to 900 nm. However, in order to provide versatility for various lasers as described above, there is a growing demand for a wider range of infrared transmission.

[0015] In particular, among the above rubber compositions, silicone rubber (vinyl methyl silicone rubber (VMQ)) is known to have low mechanical strength, and furthermore, it is known to have slightly inferior resistance (chemical resistance) to strong acidic solutions, strong alkaline solutions, silicone oil, and chlorinated water. On the other hand, fluororubber (FKM) and ethylene propylene diene rubber (EPDM) are known to exhibit superior properties to silicone rubber in terms of mechanical strength and chemical resistance.

[0016] In these rubber compositions, to improve properties such as mechanical strength and chemical resistance, for example, rubber compositions are prepared by combining multiple organic colorants without incorporating carbon black, which has been conventionally used for reinforcing rubber. As a result, rubber compositions with excellent properties that absorb visible light across a wide wavelength range, which is a hindrance when used in sensors, and selectively transmit infrared light have already been proposed. However, there is a further expectation for the development of even more high-performance rubber compositions that further improve the minimum transmittance, especially in the near-infrared wavelength range.

[0017] The present invention has been made in view of the problems of such conventional technologies, and in particular, it widely absorbs visible light that becomes an obstacle such as a sensor and selectively transmits infrared light, and in particular, it is possible to obtain a rubber material with improved transmittance in the wavelength region of near-infrared light. A rubber composition is provided.

Means for Solving the Problems

[0018] According to the present invention, the following rubber composition is provided.

[0019] [1] (A) Rubber component Polymer as ethylene propylene diene rubber , (B) Ingredients Crosslinking agent Dicumyl peroxide , and (C) Ingredients Colorant The product contains two or more organic colorants for blocking visible light, selected from 1,4-dihydroxyanthraquinone derivatives, sulfonated / aminoalkyl substituted derivatives of 1,4-dihydroxyanthraquinone, 1-(phenylazo)-2-naphthol, N-[9-(2-carboxyphenyl)-6-(diethylamino)-3H-xanthene-3-yl]aniline, or 1-(methylamino)-9,10-anthraquinone, wherein at least one of the organic colorants is an oil-soluble dye, and at least one of the oil-soluble dyes is an anthraquinone-based dye, and the product is formulated with 100 parts by mass of component (A), 2 parts by mass of component (B), and 0.1 to 0.5 parts by mass each of two or more types of component (C). (C) The colorant does not contain an inorganic black pigment, and the minimum transmittance of the rubber sheet at wavelengths of 800 to 1600 nm is 50% or more and the minimum transmittance at wavelengths of 900 to 1100 nm is 80% or more, and the maximum transmittance at wavelengths of 300 to 700 nm is 40% or less and the maximum transmittance at wavelengths of 300 to 650 nm is 1% or less. Rubber composition.

[0024] 2 The rubber composition according to [1 ] described above, which is used for products that use infrared light in the range of 800 to 1600 nm.

[0025] 3 The rubber composition according to [1 ] described above, which is used for selective wavelength absorption for LiDAR or its cover.

[0026] 4 The rubber composition according to [1 ] described above, which is used for an optical lens, an infrared camera lens, a lens for a biometric authentication camera, or a cover thereof.

[0027] 5 The rubber composition according to [1​​​​​​ ] The rubber composition described.

[0028] [ 6 ] Used in imaging devices and their covers, the [1 ] The rubber composition described.

[0029] [ 7 ] Used in a three-dimensional distance image camera and its cover, the [1 ] The rubber composition described.

[0030] [ 8 ] Used in infrared communication, the aforementioned [1 ] The rubber composition described.

[0031] [ 9 ] Used in near-infrared spectrometers, the aforementioned [1 ] The rubber composition described.

[0032] [ 10 [1 ] The rubber composition described. [Effects of the Invention]

[0033] The rubber composition of the present invention provides a rubber material that broadly absorbs visible light that interferes with sensors and other devices, and selectively transmits infrared light. In particular, because the rubber composition does not contain inorganic black pigments such as carbon black, which are widely used for reinforcing rubber, it exhibits excellent transmittance to infrared light. Furthermore, compared to resin materials, it has superior flexibility, making it applicable to products that undergo deformation, and contributing to improved design flexibility for the entire device using the rubber material. Moreover, compared to resin materials, it has improved shock absorption, and can very effectively suppress the occurrence of damage such as cracking. In particular, in the near-infrared wavelength range, it is possible to obtain a high-performance rubber material that exhibits high transmittance performance, suppressing the transmittance of wavelengths below 650 nm to 1% or less, and the transmittance of wavelengths above 800 nm to 80% or more. [Modes for carrying out the invention]

[0034] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below. Therefore, it should be understood that any modifications, improvements, etc., made to the embodiments described below, based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the present invention, also fall within the scope of the present invention.

[0035] [Rubber composition] One embodiment of the rubber composition comprises (A) a polymer, (B) a crosslinking agent, and (C) a coloring agent, wherein (C) the coloring agent does not contain an inorganic black pigment. In this embodiment, the rubber composition has a minimum transmittance of 50% or more at wavelengths of 800 to 1600 nm and a minimum transmittance of 80% or more at wavelengths of 900 to 1100 nm in a rubber sheet, a maximum transmittance of 40% or less at wavelengths of 300 to 700 nm and a maximum transmittance of 1% or less at wavelengths of 300 to 650 nm. The rubber composition of this embodiment can be used to obtain a rubber material that broadly absorbs visible light that interferes with sensors and the like, and selectively transmits infrared light. In particular, since the rubber composition of this embodiment does not contain an inorganic black pigment, it has excellent transmittance to infrared light. Furthermore, compared to resin materials, it has superior flexibility, making it applicable to products that undergo deformation, and contributing to improved design flexibility for the entire device using the rubber material. Furthermore, compared to resin materials, it has improved shock absorption and can effectively suppress the occurrence of damage such as cracking.

[0036] Here, "inorganic black pigment" refers to a pigment made of an inorganic compound, which, when used as a coloring agent to form a rubber material, produces a color ranging from black to brownish-red. Examples of inorganic black pigments include inorganic oxides such as titanium black and iron(II,III) oxide (iron black), and known inorganic pigments such as carbon black. The rubber composition of this embodiment substantially does not contain such inorganic black pigments. Here, in the rubber composition of this embodiment, "(C) the coloring agent does not contain inorganic black pigment" means that each component constituting the rubber composition substantially does not contain inorganic black pigment. That is, "(C) the coloring agent does not contain inorganic black pigment" means that components other than the coloring agent also substantially do not contain inorganic black pigment. Furthermore, "substantially does not contain" inorganic black pigment means that inorganic black pigment is not actively (in other words, intentionally) blended, except in cases where inorganic black pigment is inevitably mixed in. Therefore, the rubber composition of this embodiment may contain trace amounts of black inorganic compounds as unavoidable impurities. The upper limit of the acceptable concentration of unavoidable impurities varies depending on various conditions, but it is preferable that it is below an amount that does not substantially affect the minimum transmittance at wavelengths of 800-1600 nm and 900-1100 nm, and the maximum transmittance at wavelengths of 300-700 nm and 300-650 nm in the rubber sheet. For example, it is preferable that the amount of inorganic black pigment as an unavoidable impurity is 0.001 parts by mass or less (i.e., 10 ppm or less) per 100 parts by mass of polymer (A).

[0037] The rubber composition of this embodiment can be formed, for example, as a rubber sheet of a predetermined thickness. The thickness of such a rubber sheet is not particularly limited, but for example, a sheet in the range of 0.5 mm to 2 mm can be suitably used. That is, when the thickness of the rubber sheet is in the range of 0.5 mm to 2 mm, the minimum transmittance of the rubber sheet at wavelengths of 800 to 1600 nm is 50% or more, the minimum transmittance at wavelengths of 900 to 1100 nm is 80% or more, the maximum transmittance at wavelengths of 300 to 700 nm is 40% or less, and the maximum transmittance at wavelengths of 300 nm to 650 nm is 1% or less. The transmittance in each wavelength range can be measured, for example, using an ultraviolet-visible-near-infrared spectrophotometer. An example of such a spectrophotometer is the spectrophotometer (product name V-770) manufactured by JASCO Corporation. The transmittance in the wavelength ranges of 800-1600 nm and 900-1100 nm is measured using a spectrophotometer at 1 nm intervals within those ranges, and the minimum value of the measured transmittance is defined as the "minimum transmittance." Similarly, the transmittance in the wavelength ranges of 300-700 nm and 300-650 nm is measured using a spectrophotometer at 1 nm intervals within those ranges, and the maximum value of the measured transmittance is defined as the "maximum transmittance."

[0038] The rubber composition of this embodiment exhibits excellent transmittance to infrared light if the minimum transmittance at wavelengths of 800 to 1600 nm is 50% or more and the minimum transmittance at wavelengths of 900 to 1100 nm is 80% or more. Furthermore, if the maximum transmittance at wavelengths of 300 to 700 nm is 40% or less and the maximum transmittance at wavelengths of 300 nm to 650 nm is 1% or less, the transmission of visible light that interferes with sensors and the like can be effectively suppressed.

[0039] The rubber composition of this embodiment preferably has a minimum transmittance of 60% or more at wavelengths of 800 to 1600 nm. This configuration results in extremely excellent transmittance to infrared light. Another preferred embodiment of the rubber composition of this embodiment is that it has a minimum transmittance of 80% or more at wavelengths of 900 to 1100 nm. This configuration results in even better transmittance to infrared light at specific wavelengths.

[0040] There are no particular restrictions on the upper limit of the minimum transmittance for wavelengths of 800-1600 nm and 900-1100 nm. For example, the upper limit of the minimum transmittance may be 100% or 90%. Similarly, there are no particular restrictions on the lower limit of the maximum transmittance for wavelengths of 300-700 nm and 300-650 nm. For example, the lower limit of the maximum transmittance may be 0%.

[0041] There are no particular restrictions on the method for producing a rubber sheet of a predetermined thickness from the rubber composition of this embodiment, but for example, the rubber sheet can be produced by the following method. First, the rubber composition of this embodiment, which will be used as raw material for producing the rubber sheet, is prepared. For the rubber composition used to produce the rubber sheet, it is preferable to knead it in an open roll until the components are uniform, and then cut the rubber composition into a sheet to make rubber material. Next, the prepared rubber composition is placed in a mold with a depth of 1.9 to 2.0 mm. When placing the rubber composition in the mold, the amount put in is adjusted so that the thickness of the rubber sheet obtained by vulcanization is 2 mm. For example, the method for producing a rubber sheet can be referenced from JIS K6299:2012 "Rubber - Method for preparing test samples". Next, press vulcanization is performed on the rubber composition placed in the mold. Regarding the vulcanization conditions (temperature, time), the vulcanization rate (t90) of the rubber composition to be vulcanized is measured separately, and vulcanization is performed for t90 or a time (minutes) greater than that. The vulcanization rate (t90) is the time (in minutes) from the start of measurement until the torque reaches 90% of (MH-ML), when the maximum torque is MH and the minimum torque is ML, in a vulcanization behavior measurement test of an unvulcanized rubber composition using a rheometer. When performing press vulcanization, vulcanization should be promptly terminated once t90 is exceeded. In this way, a 2 mm thick rubber sheet is produced. When producing the rubber sheet, care should be taken to avoid touching the surface of the rubber sheet sample as much as possible to prevent foreign matter or other components from adhering to its surface. When producing rubber sheets of other thicknesses (for example, a 0.5 mm thick rubber sheet), rubber sheets of any desired thickness can be produced by using a mold with a depth that varies according to the desired thickness (for example, a mold with a depth of 0.4 to 0.5 mm).

[0042] The rubber composition of this embodiment comprises (A) a polymer, (B) a crosslinking agent, and (C) a coloring agent. For example, the components included in the rubber composition are not limited to those described above, and any rubber composition that does not contain an inorganic black pigment and is prepared such that the minimum transmittance at wavelengths of 800 to 1600 nm is 50% or more, the minimum transmittance at wavelengths of 900 to 1100 nm is 80% or more, the maximum transmittance at wavelengths of 300 to 700 nm is 40% or less, and the maximum transmittance at wavelengths of 300 to 650 nm is 1% or less. Hereinafter, (A) the polymer may be referred to as component (A), (B) the crosslinking agent as component (B), and (C) the coloring agent as component (C).

[0043] (A) The polymer used as component can be any known rubber polymer. For example, although not particularly limited, general-purpose rubbers include natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), and styrene-butadiene rubber (SBR). Special rubbers include acrylic rubber (ACM), ethylene acrylate rubber (AEM), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), fluororubber (FKM), epichlorohydrin rubber (ECO), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), silicone rubber (vinyl methyl silicone rubber (VMQ)), and urethane rubber (U). By using such polymers, it is possible to solve the problems of conventional resins, such as their hardness and lack of flexibility, and enable suitable application to products that undergo deformation.

[0044] (A) As the polymer component, for example, fluororubber (FKM) and ethylene propylene diene rubber (EPDM) can be more preferably used because the transparency of the rubber can be further enhanced by using a peroxide crosslinking agent. Furthermore, fluororubber (FKM) and ethylene propylene diene rubber (EPDM) have higher mechanical strength compared to silicone rubber (VMQ), for example, and also have high resistance to strong acids, strong alkalis, silicone oil, chlorinated water, etc.

[0045] (B) The crosslinking agent as component (B) can be a crosslinking agent used in known rubber compositions, such as a vulcanizing agent, vulcanizing aid, or vulcanizing accelerator. For example, peroxide-based crosslinking agents, polyol-based crosslinking agents, etc., can be selected depending on the purpose. There are no particular limitations, but in the rubber composition of this embodiment, organic peroxides can be given as preferred examples of crosslinking agents.

[0046] There are no particular restrictions on the amount of crosslinking agent used, and it can be determined as appropriate depending on the type and amount of polymer used as component (A).

[0047] (C) The coloring agent as component (C) can be any known coloring agent other than an inorganic black pigment. In the rubber composition of this embodiment, an organic coloring agent made of organic matter can be suitably used as the coloring agent. There are no particular restrictions on the color of the coloring agent, and it can be appropriately determined according to the intended use of the rubber composition. However, since the coloring agent affects the transmittance, it is preferable to adjust its type and amount appropriately, taking into account the transmittance at wavelengths of 800-1600 nm, 900-1100 nm, 300-700 nm, and 300-650 nm. For example, although not particularly limited, it is preferable that the coloring agent as component (C) is 1 part by mass or less per 100 parts by mass of polymer as component (A).

[0048] The rubber composition of this embodiment preferably contains two or more organic colorants for blocking visible light. By configuring it in this way, a rubber material made from the rubber composition can be effectively obtained that broadly absorbs visible light that interferes with sensors and the like, and selectively transmits infrared light. Even when two or more organic colorants are included, it is preferable that the amount of colorant of component (C) is 1 part by mass or less per 100 parts by mass of polymer of component (A).

[0049] Organic pigments can be cited as colorants. Examples of red pigments include diketopyrrolopyrrole, anthraquinone, and perylene-based red pigments. Examples of yellow pigments include isoindoline and anthraquinone-based yellow pigments. Examples of blue pigments include copper phthalocyanine and anthraquinone-based blue pigments. Examples of green pigments include phthalocyanine and isoindoline-based green pigments.

[0050] More preferably, dyes can be used as organic colorants. Dyes are classified by their chemical structure and include, for example, azo dyes, stilbenzene dyes, triarylmethane dyes, acridine dyes, quinoline dyes, polymethine dyes, anthraquinone dyes, indigo dyes, and phthalocyanine dyes. There are no particular restrictions on the use of these dyes as long as they are miscible with component (A), but from the viewpoint of compatibility, oil-soluble dyes are particularly preferred.

[0051] Here, oil-soluble dyes are those that are insoluble or sparingly soluble in water and readily soluble in organic solvents. An example of an oil-soluble dye is shown below, but many other oil-soluble dyes are available, and the rubber composition of the present invention may also use these oil-soluble dyes.

[0052] Examples of oil-soluble dyes include rhodamine B acetate, tetrachlorotetrabromofluorescein, tetrabromofluorescein, Sudan III, Sudan IV, Sudan II, quinizalin green SS, pyranin concentrate, Sudan Blue, dibromofluorescein, diodofluorescein, orange SS, quinoline yellow SS, yellow AB, yellow OB, quinizalin blue, Sudan Black, phenylazoresorcinol, solvent red 197, oil violet, quinizalin, 4-phenylazo-1-naphthylamine, 4-(diethylamino)azobenzene, methyl yellow, Nile Red, Sudan I, Sudan R, p-phenylazophenol, and solvent black 5 (some of which are trade names).

[0053] The rubber composition of this embodiment may contain other additives, but it is necessary to blend various additives so that the minimum transmittance at wavelengths of 800-1600 nm and 900-1100 nm, and the maximum transmittance at wavelengths of 350-700 nm and 300-650 nm in the rubber sheet fall within the numerical ranges described above. Examples of other additives include processing aids, waxes, and plasticizers. Furthermore, fillers such as nanofillers may be included, to the extent that they do not impair the transmittance performance of the resulting rubber material. The rubber composition of this embodiment may, for example, not contain other additives, taking into consideration the effect on the transmittance of the resulting rubber material.

[0054] The rubber composition of this embodiment can be used as a product obtained by vulcanizing the rubber composition. For example, it can be used as a rubber product that has undergone primary vulcanization, or as a rubber product that has undergone secondary vulcanization depending on the characteristics of the product. For example, the rubber composition of this embodiment can be suitably used in products that use infrared light in the wavelength range of 800 to 1600 nm (such as near-infrared spectrometers and some infrared communication equipment).

[0055] Furthermore, although not particularly limited, the rubber composition of this embodiment can be suitably used in selective wavelength absorbers and their covers for LiDAR, optical lenses, infrared camera lenses, lenses for biometric authentication cameras, and their covers, biometric authentication devices and their covers, imaging devices and their covers, and three-dimensional distance imaging cameras and their covers, etc.

[0056] Furthermore, the rubber composition of this embodiment can be used in a wavelength filter (visible light filter) that can be attached to the lens or the like described above. Such a visible light filter can be configured to have sealing properties. That is, the rubber material formed from the rubber composition of this embodiment has specific transmittance in the infrared or near-infrared wavelength range, and also has rubber elasticity that allows it to be elastically deformed under stress. Therefore, it can be integrally formed as a visible light filter with sealing properties that take advantage of both of these characteristics. As a result, it is possible to form a visible light filter that reduces the number of parts and costs. [Examples]

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0058] (Examples 1-5, Comparative Examples 1-4) [Sample preparation] Each component was weighed and mixed according to the proportions (parts by mass) shown in Table 1 below. The mixture was then kneaded in an open roll until the components were uniformly combined to prepare the rubber compositions of Examples 1-5 and Comparative Examples 1-4. Next, the obtained rubber compositions were cut into sheets to produce rubber dough, which was then placed in a mold with a depth of 2 mm. The rubber compositions (rubber dough) in the mold were then subjected to press vulcanization at 170°C for 12 minutes. In this manner, 2 mm thick rubber sheets were produced from each of the rubber compositions of Examples 1-5 and Comparative Examples 1-4. When producing the rubber sheets, care was taken not to touch the surface of the rubber sheets to prevent foreign matter or other components from adhering to the surface. For Example 5, a mold with a depth of 0.5 mm was used to produce a 0.5 mm thick rubber sheet.

[0059] [(A) Component: Polymer] (A-1): Ethylene propylene diene rubber ("EPT 3045H (product name)"), manufactured by Mitsui Chemicals, Inc.

[0060] [(B) Component: Crosslinking agent (vulcanizing agent / vulcanizing aid)] (B-1): "Parkmill D (product name)", manufactured by NOF Corporation

[0061] [(C) Ingredients: Colorants (organic colorants, non-organic colorants)] (C-1): "Kinizarin Blue", manufactured by Tokyo Chemical Industry Co., Ltd. (C-2): "Kinizarin Green SS", manufactured by Tokyo Chemical Industry Co., Ltd. (C-3): "Sudan II (product name)", manufactured by Tokyo Chemical Industry Co., Ltd. (C-4): "Rhodamine B Base (product name)", manufactured by Kanto Chemical Co., Ltd. (C-5): 1-(methylamino)anthraquinone, manufactured by Tokyo Chemical Industry Co., Ltd. (C-6): Carbon black (black coloring agent) ("THERMAX N990 (product name)"), Cancarb Limited (C-7): Iron oxide (red coloring agent) ("Brown 601" (product name)), manufactured by Regino Color Industries Co., Ltd. (C-8): Organic pigment ("Phthalocyanine Blue"), manufactured by Resino Color Industries Co., Ltd. (C-9): Organic pigment ("Pigment Yellow"), manufactured by Resino Color Industries Co., Ltd.

[0062] In Examples 1-5 and Comparative Examples 1-4, component (A) was (A-1) ethylene propylene diene rubber, and component (B) was "Parkmil D (trade name)". Furthermore, component (B) was added in a ratio of 2 parts by mass to 100 parts by mass of component (A), and the mixture was used. To the mixture of components (A) and (B) thus prepared, component (C) was added as a colorant in the respective types and amounts according to Examples 1-5 and Comparative Examples 1-4. The details are shown in Table 1 below.

[0063] [Table 1]

[0064] In Example 1, a rubber composition was prepared by adding 2 parts by mass of component (B) to 100 parts by mass of component (A), and then adding 0.1 parts by mass (= 0.1 phr) each of (C-1) and (C-2) as component (C). Here, "phr" is a unit used in rubber compounding, and indicates how much weight of compounding chemicals or additives is required to be added to 100 units of rubber (corresponding to component (A) in this case). Therefore, Example 1 is composed of 2 phr of component (B) and 0.1 phr each of the two types of component (C) to 100 units of component (A) by weight. Similarly, in Example 2, the same amounts of components (A) and (B) as in Example 1 were blended, and 0.1 parts by mass each of (C-2), (C-3), and (C-4) were added as component (C) to prepare the rubber composition. In Example 3, the same amounts of components (A) and (B) as in Example 1 were blended, and 0.1 parts by mass each of (C-2) and (C-5) were added as component (C) to prepare the rubber composition. In Example 4, the same amounts of components (A) and (B) as in Example 1 were blended, and 0.2 parts by mass each of (C-2) and (C-5) were added as component (C) to prepare the rubber composition. In Example 5, the same amounts of component (A) and component (B) as in Example 1 were blended, and 0.5 parts by mass each of (C-2) and (C-5) were added as component (C) to prepare the rubber composition.

[0065] Comparative Example 1 was prepared by adding 2 parts by mass of component (B) to 100 parts by mass of component (A) as the rubber composition. In other words, it was prepared without adding component (C). Comparative Example 2 was prepared by blending the same amounts of components (A) and (B) as in Comparative Example 1, and adding 0.1 parts by mass of carbon black (C-6), a black coloring agent, as component (C) to create a rubber composition. Comparative Example 3 was prepared by combining the same amounts of components (A) and (B) as in Comparative Example 1, and adding 0.1 parts by mass of iron(C-7) oxide, a red coloring agent, as component (C) to create a rubber composition. Comparative Example 4 was prepared by blending the same amounts of components (A) and (B) as in Comparative Example 1, and adding 0.05 parts by mass each of (C-8) and (C-9) as component (C).

[0066] For rubber sheets with a thickness of 2 mm (0.5 mm for Example 5) prepared from the rubber compositions of Examples 1-5 and Comparative Examples 1-4, the following measurements were taken: "Maximum transmittance (%) at wavelengths of 300-700 nm," "Maximum transmittance (%) at wavelengths of 300-650 nm," "Minimum transmittance (%) at wavelengths of 800-1600 nm," and "Minimum transmittance (%) at wavelengths of 900-1100 nm." The results are shown in Table 1.

[0067] • Maximum transmittance (%) for wavelengths of 300-700nm and 300-650nm Using a spectrophotometer (V-770 (product name)) manufactured by JASCO Corporation, the transmittance (%) of the rubber sheet being measured was measured in the wavelength range of 300 to 1600 nm. The highest transmittance value (%) and the wavelength (nm) at which this value occurred were then determined for the wavelength ranges of 300 to 700 nm and 300 to 650 nm. The highest transmittance value (%) between 300 to 700 nm was defined as the "maximum transmittance (%) for wavelengths of 300 to 700 nm," and the highest transmittance value (%) between 300 to 650 nm was defined as the "maximum transmittance (%) for wavelengths of 300 to 650 nm." The transmittance (%) and wavelength (nm) for each value are recorded in the respective columns of Table 1. Furthermore, the maximum transmittance (%) for wavelengths of 300 to 700 nm and 300 to 650 nm were evaluated based on the evaluation criteria described below. The evaluation results are shown in Table 1. <Evaluation Criteria> (1) Evaluation criteria for wavelengths of 300-700 nm Evaluation "〇": A product is considered acceptable if the maximum transmittance at wavelengths of 300-700nm is 40% or less. Evaluation "×": Failure to meet the criteria if the maximum transmittance at wavelengths of 300-700nm exceeds 40%. (2) Evaluation criteria for wavelengths of 300-650 nm Evaluation "〇": Passed if the maximum transmittance at wavelengths of 300-650nm is 1% or less. Evaluation "×": Failure to meet the criteria if the maximum transmittance at wavelengths of 300-650nm exceeds 1%.

[0068] • Minimum transmittance (%) for wavelengths of 800-1600nm and 900-1100nm Using a spectrophotometer (V-770 (product name)) manufactured by JASCO Corporation, the transmittance (%) of the rubber sheet being measured was measured in the wavelength range of 300 to 1600 nm. The lowest transmittance value (%) and the wavelength (nm) at which this value occurred were then determined for the wavelength ranges of 800 to 1600 nm and 900 to 1100 nm. The lowest transmittance value (%) between 800 to 1600 nm was defined as the "lowest transmittance (%) at 800 to 1600 nm," and the lowest transmittance value (%) between 900 to 1100 nm was defined as the "lowest transmittance (%) at 900 to 1100 nm." The transmittance (%) and wavelength (nm) for each value are recorded in the respective columns of Table 1. Furthermore, the lowest transmittance (%) at 800 to 1600 nm and 900 to 1100 nm were evaluated based on the evaluation criteria below. The evaluation results are shown in Table 1. <Evaluation Criteria> (3) Evaluation criteria for wavelengths of 800-1600 nm Evaluation "〇": A product is considered acceptable if the minimum transmittance at wavelengths of 800-1600nm is 50% or higher. Evaluation "×": Failure to achieve a minimum transmittance of less than 50% in the wavelength range of 800-1600nm will result in disqualification. (4) Evaluation criteria for wavelengths of 900-1100 nm Evaluation "〇": A product is considered acceptable if the minimum transmittance at wavelengths of 900-1100nm is 80% or higher. Evaluation "×": Failure to achieve a minimum transmittance of less than 80% in the wavelength range of 900-1100nm will result in disqualification.

[0069] 〔result〕 As shown in Table 1, the rubber sheets made from the rubber compositions of Examples 1 to 5 had a maximum transmittance of 40% or less at wavelengths of 300 to 700 nm and a maximum transmittance of 1% or less at wavelengths of 300 to 650 nm, while having a minimum transmittance of 50% or more at wavelengths of 800 to 1600 nm and a minimum transmittance of 800 to 1100 nm. Therefore, the rubber compositions of Examples 1 to 5 were able to produce rubber materials that broadly absorb visible light that interferes with sensors and other devices, and selectively transmit infrared light. On the other hand, the rubber sheet made from the rubber composition of Comparative Example 1 had a maximum transmittance of over 40% at wavelengths of 300 to 700 nm, and the rubber sheets made from the rubber compositions of Comparative Examples 1 and 4 had a maximum transmittance of over 1% at wavelengths of 300 to 650 nm, indicating extremely low visible light shielding ability. Furthermore, the rubber sheets made from the rubber compositions of Comparative Examples 2, 3, and 4 had a minimum transmittance of less than 50% at wavelengths of 800 to 1600 nm, and a minimum transmittance of less than 80% at wavelengths of 900 to 1100 nm, indicating low transmittance to infrared light. [Industrial applicability]

[0070] The rubber composition of the present invention can be used as a rubber material that broadly absorbs visible light that interferes with sensors and the like, and selectively transmits infrared light, and can be used in various products such as lenses and their covers.

Claims

1. The material comprises (A) ethylene propylene diene rubber as the rubber polymer, (B) dicumyl peroxide as the crosslinking agent, and (C) two or more organic colorants selected from 1,4-dihydroxyanthraquinone derivatives, sulfonated / aminoalkyl substituted derivatives of 1,4-dihydroxyanthraquinone, 1-(phenylazo)-2-naphthol, N-[9-(2-carboxyphenyl)-6-(diethylamino)-3H-xanthene-3-yl]aniline, or 1-(methylamino)-9,10-anthraquinone, for blocking visible light, wherein at least one of the organic colorants is an oil-soluble dye, and at least one of the oil-soluble dyes is an anthraquinone-based dye. (A) is mixed with 100 parts by mass of component (B), and 0.1 to 0.5 parts by mass of two or more types of component (C). A rubber composition in which the coloring agent of component (C) does not contain an inorganic black pigment, and when the thickness of the rubber sheet is in the range of 0.5 mm to 2 mm, the minimum transmittance at wavelengths of 800 to 1600 nm is 50% or more, the minimum transmittance at wavelengths of 900 to 1100 nm is 80% or more, the maximum transmittance at wavelengths of 300 to 700 nm is 40% or less, and the maximum transmittance at wavelengths of 300 to 650 nm is 1% or less.

2. The rubber composition according to claim 1, for use in products that use infrared light in the wavelength range of 800 to 1600 nm.

3. The rubber composition according to claim 1, used for selective wavelength absorption for LiDAR or for its cover.

4. The rubber composition according to claim 1, for use in optical lenses, infrared camera lenses, lenses for biometric authentication cameras, or covers thereof.

5. The rubber composition according to claim 1, used for a biometric authentication device or its cover.

6. The rubber composition according to claim 1, used for use in an imaging device or its cover.

7. The rubber composition according to claim 1, used for a three-dimensional distance image camera or its cover.

8. The rubber composition according to claim 1, used for infrared communication.

9. The rubber composition according to claim 1, for use in a near-infrared spectrometer.

10. The rubber composition according to claim 1, integrally formed as a visible light filter having sealing properties.

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