JP2018197884A - Optical filter - Google Patents

Abstract

To provide an optical filter having a low environmental load.SOLUTION: The optical filter includes: a base material; and a coating layer on at least one surface of the base material, the coating layer containing an optical material. The transmission becomes the smallest in a region with a wavelength of 500nm to 700nm, both inclusive, and the optical material contains complex fine particles including metal and a natural polymer which are physically indivisible. The complex fine particles are each in the shape of a flat surface or a rod.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical material including composite fine particles containing a metal and a natural polymer, and an optical filter using the same.

  Optical filters that transmit light in a specific wavelength range are used in lighting fixture filters and various optical devices. An optical filter is used in a fluorescence microscope used for observing a cell structure of a specimen using fluorescence in the medical / biological field. In a camera module, it is used for the purpose of cutting infrared rays that become noise.

  For example, as an optical filter disposed on the front surface of a plasma display, there is an optical filter blended with a dye having an absorption maximum wavelength in the vicinity of 570 to 600 nm in order to absorb a wavelength that is close to a neon orange color near 590 nm and deteriorates color reproducibility. (Patent Document 1). However, an optical filter using a dye has a problem that it deteriorates when used for a long time.

  Patent Document 2 discloses a light selective transmission filter having a functional film on both surfaces of a base material, wherein the functional film blocks infrared rays made of an inorganic material. However, when manufacturing by vacuum film formation, there exists a problem that cost becomes high.

  In recent years, in order to solve the problem of fossil resource depletion, functional materials using natural polymers, which are environmentally friendly materials that can be used continuously, have been actively developed. Plant materials such as cellulose are known as environmentally friendly natural polymer materials having biodegradability.

  Cellulose, the main component of plants and wood, is a natural polymer material that is accumulated in large quantities on the earth. In wood, dozens or more of cellulose molecules are bundled to form fine fibers (microfibrils) having a high crystallinity and a nanometer order fiber diameter, and many fine fibers are hydrogen-bonded to each other. Cellulosic fibers are formed to become a plant support.

  There is known a method of using this cellulose fiber by making it fine (nanofiber) until the fiber diameter becomes nanometer order. Using an N-oxyl compound as an oxidation catalyst, a part of the hydroxyl group of cellulose is oxidized to at least one functional group selected from the group consisting of a carboxy group and an aldehyde group, and the maximum fiber diameter is 1000 nm or less and the number average fiber diameter is 2 A fine cellulose fiber having a cellulose I-type crystal structure of 150 nm is known (Patent Document 3). As an example using fine cellulose, for example, as a packaging material having gas barrier properties such as oxygen, a packaging material containing at least fine cellulose fibers, an inorganic layered compound and a water-soluble polymer on a substrate is also known (patent) Reference 4).

JP 2001-228323 A JP 2009-154489 A JP 2008-1728 A JP 2012-149114 A

  An object of the present invention is to provide an optical filter with a low environmental load.

  One aspect of the present invention includes a base material and a coating layer containing an optical material, which is formed on at least one surface of the base material, and has a minimum transmittance in a wavelength region of 500 nm to 700 nm. And an optical material including a composite fine particle containing a metal and a natural polymer, wherein the metal and the natural polymer are physically inseparable, and the composite fine particle has a flat plate shape or a rod shape.

The composite fine particles may have a volume of 5 × 10 ⁻¹ nm ³ or more and 5 × 10 ¹⁰ nm ³ or less and a thickness of 1 nm or more and 50 nm or less.

  In addition, the metal may include one or more metals including at least silver or a compound thereof.

  Moreover, the natural polymer may contain fine cellulose fibers.

  Moreover, the number average axis diameter of the short axis of the fine cellulose fiber may be 1 nm or more and 200 nm or less, and the number average axis diameter of the long axis of the fine cellulose fiber may be 0.05 μm or more and 50 μm or less.

  The number average minor axis diameter of the fine cellulose fibers is 1 nm or more and 50 nm or less, the number average major axis diameter of the fine cellulose fibers is 0.1 μm or more and 10 μm or less, and the amount of carboxy groups contained in the fine cellulose fibers is 0.1 mmol. / G or more and 3.0 mmol / g or less may be sufficient.

  In the fine cellulose fiber, a carboxy group may be introduced on the fiber surface.

  According to the present invention, an optical filter containing a natural polymer having a low environmental load can be provided.

It is sectional drawing of one Embodiment of the optical filter using the optical material of this invention.

Disclosed herein are optical materials and optical filters that use natural polymers with low environmental impact, are excellent in dispersibility, heat resistance, and light resistance, and can be produced at low energy and at low cost.
(Optical material)
The optical material according to the present disclosure includes composite fine particles containing a metal and a natural polymer, both of which are physically indivisible, and has a light selectivity that blocks light in a wavelength region of 500 nm or more. The resin or coating layer containing the optical material having photoselectivity can be used for an optical filter having photoselectivity. In the present disclosure, “shielding” means that light transmittance is reduced by absorption or reflection. It is preferable that the dispersion liquid containing the optical material according to the present disclosure has a minimum wavelength at which the transmittance is minimized by absorption or reflection in a wavelength region of 500 nm to 700 nm. An optical material that shields a wavelength region of 500 nm or more and 700 nm or less can be used for an optical filter disposed in front of the plasma display.
Free electrons on the surface of the metal fine particles may collectively vibrate due to an external electric field such as light (surface plasmon). Since electrons are charged particles, an electric field is generated around them when they vibrate. In the metal fine particle, a phenomenon occurs in which an electric field generated by free electron vibration and an external electric field (light, etc.) resonate (Surface Plasmon Resonance (SPR)). The surface plasmon resonance causes light absorption in a specific wavelength range. This light absorption wavelength region varies depending on the size and shape of the particles.

In general, the higher the aspect ratio of metal fine particles, the easier it is to obtain absorption at longer wavelengths. Therefore, also in the optical material according to the present disclosure, absorption is obtained in the long wavelength region by having anisotropy. Therefore, the shape of the optical material according to the present disclosure is not particularly limited, but preferably has anisotropy in order to shield light in a wavelength region of 500 nm or more. In particular, it is a flat or rod-like composite fine particle having a volume of 5 × 10 ⁻¹ nm ³ or more and 5 × 10 ¹⁰ nm ³ or less and a thickness of 1 nm or more and 50 nm or less. The shape and size of the optical material according to the present disclosure are observed with a scanning electron microscope, a transmission electron microscope, and a scanning transmission electron microscope.
The production method of the optical material according to the present disclosure is not particularly limited, but is reduced by a general liquid phase reduction method in the presence of a natural polymer and in the presence of a precursor metal ion. An optical material with a controlled size can be obtained. In the production of this optical material, it is not necessary to heat to a high temperature, and the optical material can be obtained at low energy and at low cost without undergoing a plurality of reactions. In addition, the optical material according to the present disclosure is excellent in light resistance and heat resistance.

(Natural polymer)
Natural polymers used in the optical material according to the present disclosure are polymers produced by animals, plants, and microorganisms. Natural polymers are not particularly limited, but polysaccharides and polypeptides are generally known. Examples of the polysaccharide include starch, cellulose, chitin / chitosan, cellulose, dextran, pullulan, curdlan, alginic acid, and hyaluronic acid. Examples of the polypeptide include gluten, zein, collagen, gelatin, fibroin, sericin, keratin and the like. Among these, it is preferable to use cellulose. As the cellulose, for example, it is preferable to use fine cellulose fibers refined by the following method.

(Fine cellulose fiber and its manufacturing method)
Although the fine cellulose fiber which concerns on this indication is not specifically limited, It is preferable that the fiber diameter exists in the range shown below. Moreover, the preparation method is not particularly limited. That is, the number average minor axis diameter is preferably 1 nm or more and 200 nm or less, more preferably 1 nm or more and 50 nm or less. When the number average minor axis diameter is 1 nm or more, a highly crystalline rigid fine cellulose fiber structure is adopted, so that an optical material can be stably produced. On the other hand, when it is 200 nm or more, it becomes difficult to stably produce an optical material. In addition, regarding the major axis diameter, the number average major axis diameter is preferably 0.05 μm or more, preferably 50 μm or less, and more preferably 0.1 μm or more and 10 μm or less. When the number average major axis diameter of the major axis diameter is within this range, the optical material can be stably produced.

  The number average minor axis diameter of fine cellulose fibers is determined by measuring the minor axis diameter (minimum diameter) of 100 fibers by observation with a transmission electron microscope and atomic force microscope, and obtaining the average value. On the other hand, the number average major axis diameter of fine cellulose fibers is determined by measuring the major axis diameter (maximum diameter) of 100 fibers by observation with a transmission electron microscope and observation with an atomic force microscope, and is obtained as an average value thereof.

  The kind of plant cellulose that can be used as a raw material for fine cellulose fibers is not particularly limited. For example, in addition to wood-based natural cellulose, cotton linter, bamboo, hemp, bagasse, and kenaf can be used. Further, non-wood type natural cellulose such as bacterial cellulose, squirt cellulose, and valonia cellulose, and regenerated cellulose represented by rayon fiber and cupra fiber can also be used.

The method for refining fine cellulose fibers is not particularly limited. For example, in addition to mechanical treatment by a grinder, oxidation treatment using N-oxyl compounds such as TEMPO, dilute acid hydrolysis treatment, enzyme treatment, etc. are used in combination with mechanical treatment. There are known methods for miniaturization. Bacterial cellulose can also be used as fine cellulose fibers. Furthermore, finely regenerated cellulose fibers obtained by dissolving various natural celluloses in various cellulose solvents and then performing electrospinning may be used. In particular, as shown in the method of Patent Document 3, in the oxidation reaction using an N-oxyl compound such as TEMPO, the —CH ₂ OH at the sixth position of the glucopyranose unit of the cellulose molecular chain on the crystal surface is high. It is oxidized selectively and converted to a carboxy group via an aldehyde group. In this way, electrostatic repulsion acts between the fine cellulose fibers having carboxy groups introduced on the crystal surface, so that cellulose single nanofibers (CSNF) dispersed in microfibril units in an aqueous medium can be obtained. Can do. The oxidation reaction using the N-oxyl compound will be described in detail later. If this fine cellulose fiber is used, the optical material of this invention can be manufactured stably.

  The content of carboxy groups in the fine cellulose fibers is preferably in the range of 0.1 mmol to 3.0 mmol, more preferably 0.5 mmol to 3.0 mmol, per 1 g of fine cellulose fibers. When the carboxy group amount is 0.1 mmol / g or more, the dispersion stability is good. When it is 3.0 mmol / g or less, the crystal structure of the fine cellulose fibers is sufficiently retained, and an optical material can be produced stably.

  Hereinafter, an example of a method for preparing a dispersion of fine cellulose fibers having a carboxy group introduced from wood-based natural cellulose by an oxidation reaction using an N-oxyl compound will be described. The preparation method of this example includes a step of oxidizing a wood-based natural cellulose with an N-oxyl compound to obtain oxidized cellulose (oxidation step), and a fine cellulose fiber dispersion by refining the oxidized cellulose in an aqueous medium. And a step of preparing (miniaturization step).

(Oxidation process)
The raw material for the fine cellulose fiber is not particularly limited. When wood cellulose is used, commonly used materials such as softwood pulp, hardwood pulp, and waste paper pulp can be used. Softwood pulp is preferred because it is easily refined and refined. Examples of N-oxyl compounds include TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy radical), 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 4 -Methoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-ethoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetamido-2,2,6,6 -Tetramethylpiperidine-N-oxyl, etc. Among these, TEMPO is preferable. The amount of the N-oxyl compound used is not particularly limited, and may be an amount as a catalyst. Usually, it is about 0.01% by mass to 5.0% by mass with respect to the solid content of wood-based natural cellulose to be oxidized.

  Examples of the oxidation method using an N-oxyl compound include a method in which a cellulose raw material is dispersed in water and oxidized in the presence of the N-oxyl compound. At this time, it is preferable to use a co-oxidant together with the N-oxyl compound. In this case, in the reaction system, the N-oxyl compound is sequentially oxidized by the cooxidant to produce an oxoammonium salt, and the cellulose is oxidized by the oxoammonium salt. According to such oxidation treatment, the oxidation reaction proceeds smoothly even under mild conditions, and the introduction efficiency of the carboxy group is improved. When the oxidation treatment is performed under mild conditions, it is easy to maintain the crystal structure of cellulose. Co-oxidants include halogens, hypohalous acids, halous acids and perhalogen acids, or salts thereof, halogen oxides, nitrogen oxides, peroxides, etc., as long as they can promote the oxidation reaction. Any oxidizing agent can be used. Sodium hypochlorite is preferred because of its availability and reactivity. The amount of the co-oxidant used is not particularly limited, and may be an amount that can promote the oxidation reaction. Usually, it is about 1 mass% to 200 mass% with respect to the solid content of the cellulose to be oxidized.

  Along with the N-oxyl compound and the co-oxidant, at least one compound selected from bromide and iodide may be further used in combination. Thereby, an oxidation reaction can be advanced smoothly and the introduction efficiency of a carboxy group can be improved. As the compound, sodium bromide or lithium bromide is preferable, and sodium bromide is more preferable from the viewpoint of cost and stability. The amount of the compound used is not particularly limited, and may be an amount that can promote the oxidation reaction. Usually, it is about 1% by mass to 50% by mass with respect to the solid content of the wood-based natural cellulose to be oxidized.

  Although the reaction temperature of an oxidation reaction is not specifically limited, 4 to 50 degreeC is preferable and 10 to 50 degreeC is more preferable. If it is lower than 4 ° C., the reactivity of the sample is lowered and the reaction time is prolonged. If it is higher than 50 ° C., the side reaction is promoted to lower the molecular weight of the sample, making it difficult to stably produce the optical material. The reaction time for the oxidation treatment can be appropriately set in consideration of the reaction temperature, the desired amount of carboxy group, etc., and is not particularly limited, but is usually about 1 to 5 hours.

  The pH of the reaction system during the oxidation reaction is preferably 9 or more and 11 or less. When the pH is 9 or more, the reaction can be efficiently carried out. If the pH exceeds 11, side reactions may progress and the decomposition of the sample may be accelerated. In the oxidation treatment, as the oxidation proceeds, the pH in the system decreases due to the formation of a carboxy group. Therefore, it is preferable to maintain the pH of the reaction system at 9 or more and 11 or less during the oxidation treatment. Examples of a method for maintaining the pH of the reaction system at 9 or more and 11 or less include a method of adding an alkaline aqueous solution in accordance with a decrease in pH. Examples of alkaline aqueous solutions include sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, potassium hydroxide aqueous solution, ammonia aqueous solution, tetramethylammonium hydroxide aqueous solution, tetraethylammonium hydroxide aqueous solution, tetrabutylammonium hydroxide aqueous solution, and benzyltrimethylammonium hydroxide aqueous solution. And organic alkalis. A sodium hydroxide aqueous solution is preferable from the viewpoint of cost.

  The oxidation reaction with the N-oxyl compound can be stopped by adding alcohol to the reaction system. At this time, the pH of the reaction system is preferably maintained within the above-mentioned range. The alcohol to be added is preferably a low molecular weight alcohol such as methanol, ethanol or propanol in order to quickly terminate the reaction, and ethanol is particularly preferred from the viewpoint of safety of by-products generated by the reaction.

  The reaction solution after the oxidation treatment may be directly subjected to a refinement process, but in order to remove a catalyst such as an N-oxyl compound, impurities, etc., the oxidized cellulose contained in the reaction solution is recovered and washed with a washing solution. It is preferable. Oxidized cellulose can be collected by a known method such as filtration using a glass filter or a nylon mesh having a 20 μm pore size. Distilled water is preferable as the cleaning liquid used for cleaning the oxidized cellulose.

(Miniaturization process)
In order to refine the oxidized cellulose, first, an aqueous medium is added to the oxidized cellulose and suspended. Examples of the aqueous medium include those described above, and water is particularly preferable. If necessary, the pH of the suspension may be adjusted in order to increase the dispersibility of the oxidized cellulose and the fine cellulose fibers to be produced. Examples of the alkaline aqueous solution used for pH adjustment include the same alkaline aqueous solution as mentioned in the description of the oxidation step.

  Subsequently, the suspension is subjected to a physical defibrating treatment to refine the oxidized cellulose. For physical fibrillation treatment, high pressure homogenizer, ultra high pressure homogenizer, ball mill, roll mill, cutter mill, planetary mill, jet mill, attritor, grinder, juicer mixer, homomixer, ultrasonic homogenizer, nanogenizer, underwater facing collision, etc. Mechanical treatment is mentioned. By performing such physical fibrillation treatment, the oxidized cellulose in the suspension is refined, and a dispersion of fine cellulose fibers having a carboxy group on the fiber surface can be obtained. The number average minor axis diameter and the number average major axis diameter of the fine cellulose fibers contained in the obtained fine cellulose fiber dispersion can be adjusted by the time and number of times of the physical fibrillation treatment at this time.

  As described above, a dispersion of fine cellulose fibers having a carboxy group introduced therein is obtained. The obtained dispersion can be used as a reaction field for reducing and precipitating metal fine particles as it is or by diluting, concentrating and the like.

  The dispersion of fine cellulose fibers may contain other components than cellulose and components used for pH adjustment, as long as they do not impair the effects of the present invention. Other components are not particularly limited, and can be appropriately selected from known additives depending on the application. Specifically, organometallic compounds such as alkoxysilanes or hydrolysates thereof, inorganic layered compounds, inorganic needle minerals, antifoaming agents, inorganic particles, organic particles, lubricants, antioxidants, antistatic agents, An ultraviolet absorber, a stabilizer, magnetic powder, etc. are mentioned.

(metal)
The metal species contained in the optical material according to the present disclosure is not particularly limited, and gold, silver, copper, aluminum, iron, platinum, zinc, palladium, ruthenium, iridium, rhodium, osmium, chromium, cobalt, Examples thereof include metals such as nickel, manganese, vanadium, molybdenum, gallium, and aluminum, metal salts, metal complexes, alloys thereof, oxides, and double oxides. From the viewpoint of controlling optical characteristics, at least one kind containing at least silver is preferable. The metal fine particles can absorb light of any wavelength ranging from visible light to near infrared light by shape control, and have light selectivity by absorbing in a desired wavelength region according to the use of various compositions. The composite fine particles may be coated with another metal or metal oxide to improve the stability of the composite fine particles. The metal species used for the coating is not particularly limited, for example, gold, silver, copper, aluminum, iron, platinum, zinc, palladium, ruthenium, iridium, rhodium, osmium, chromium, cobalt, nickel, manganese, vanadium, molybdenum, Examples include metals such as gallium and aluminum, metal salts, metal complexes, and alloys thereof, or oxides and double oxides.

(Optical material manufacturing method)
Although the manufacturing method of the optical material which concerns on this indication is not specifically limited, It can prepare with the liquid phase reduction method which is a general wet method. The metal surface and the solvent do not have a strong affinity, and the metal fine particles coagulate and precipitate as they are. Due to the presence of the natural polymer, the characteristics of the metal fine particles are greatly changed. By adding a reducing agent in the presence of a natural polymer and a precursor metal ion, the precursor metal ion is reduced to produce a metal atom, which interacts in the process of producing metal particles through nucleation and growth. As a result, composite fine particles having a controlled shape and size are produced. This composite fine particle has an optical property of shielding a wavelength region of 500 nm or more, and can be used as an optical material. For example, spherical silver fine particles usually have absorption in the vicinity of 400 nm, but composite fine particles containing silver and a natural polymer have an optical property of shielding a wavelength region of 500 nm or more due to the anisotropy.

  The solvent used for dispersing the natural polymer is not particularly limited as long as the natural polymer is sufficiently dispersed or dissolved. It is preferable to use water from the viewpoint of environmental load. In the case of using fine cellulose fibers, it is preferable to use water or a hydrophilic solvent from the viewpoint of dispersibility. Although there is no restriction | limiting in particular about a hydrophilic solvent, Alcohols, such as methanol, ethanol, isopropanol, are preferable.

  The concentration of the natural polymer dispersion used in the production of the optical material is not particularly limited, but is preferably 0.1% or more and less than 50%. If it is less than 0.1%, the shape control effect of the metal fine particles will be insufficient, and if it is 50% or more, the viscosity will increase and a uniform reaction will be difficult. The concentration of the precursor metal ion added to the dispersion of the natural polymer is not limited. Precursor metal ion concentration and natural polymer concentration affect the optical properties of the optical material produced. The optical characteristics of the composite fine particles vary greatly depending on the shape. Details of the specific method for producing the photoselective material are described in Examples.

  The precursor metal ion is not particularly limited, and a commonly used precursor metal ion such as chloroauric acid, silver nitrate, silver cyanide, and silver acetate can be used. In the case of using the precursor silver ion, silver nitrate is preferably used from the viewpoint of safety.

  A known reducing agent can be used as the reducing agent used for reducing the precursor metal ion. Examples thereof include metal hydride-based, borohydride-based, borane-based, silane-based, hydrazine, and hydrazide-based reducing agents. In general, sodium borohydride, citric acid, hydrazine and the like are used in the liquid phase reduction method. When performing the reaction, stirring may be performed by a known method such as a stirring blade or a magnetic stirrer.

(Optical filter)
The optical material is separated from the dispersion liquid of the optical material thus obtained, and is not particularly limited, but can be used as an optical filter having selectivity in a specific wavelength region by using as a resin dispersion or coating liquid. The optical filter preferably has a wavelength region in which the transmittance is 70% or less at a wavelength of 500 nm or more with an empty state as a reference.

  As a method for fractionating the obtained optical material, a known method such as precipitation, centrifugation, gel filtration column, gel electrophoresis or the like can be used. A plurality of fractionation methods may be combined.

  As a method for redispersing the optical material, a known method can be used. Examples thereof include a dispersion device in liquid such as a stirring type disperser, a high speed rotary shearing device, a mill type dispersing device (ball mill, bead mill, colloid mill, etc.), a high pressure jet device, and an ultrasonic dispersing device. You may disperse | distribute by adding a dispersing agent.

An optical filter having photoselectivity can be manufactured by forming an optical material in combination with a molding material. A known plastic material can be used as the molding material to be combined with the optical material.
The plastic material is not particularly limited, and generally used thermoplastic resins and thermosetting resins can be used. For example, polystyrene, ABS resin (A; acrylonitrile, B; butadiene, S; styrene), AS resin, polyethylene, EVA resin, polypropylene, methacrylic resin, cellulose acetate, polycarbonate, polyamide, polyacetal, polysulfone, polyethylene terephthalate, polybutylene terephthalate And vinyl chloride resin.
In particular, it is preferable to use biomass plastics using renewable resources. Examples of biomass plastics using renewable resources include polylactic acid, polyolefin, and polyamide.
A known method can be used as a compounding method for compounding the optical material and the resin.

  A known method can be used as the molding method. For example, injection molding, compression molding, lamination molding, transfer molding, extrusion molding, inflation molding, T-die molding, extrusion lamination, blow molding, vacuum molding, splash molding, low pressure lamination molding Is mentioned.

An optical filter having photoselectivity can be manufactured by mixing an optical material in a coating solution and coating the substrate. The coating liquid is an aqueous or solvent-based coating liquid that dissolves or disperses a resin, and a coating layer can be formed by coating.
From the viewpoint of environmental burden, it is preferable to use an aqueous coating solution. For example, water-based alkyd resin, water-soluble acrylic resin paint, water-based epoxy resin, water-based urethane resin, and synthetic resin emulsion can be used.

  As a method for forming the coating layer, known methods such as room temperature dry coating, heat-curing coating, and electrodeposition coating can be used. The thickness of the coating layer is not particularly limited.

The base material to which the coating liquid containing the optical material is applied is not particularly limited, and known materials such as plastic and glass can be used. In order to make use of the characteristics of the photoselective material, a transparent substrate is preferable.
Examples of the material of the base material include polyolefin (polyethylene, polypropylene, etc.), polyester (polyethylene naphthalate, polyethylene terephthalate, etc.), polyamide (nylon-6, nylon-66, etc.), polystyrene, ethylene vinyl alcohol, poly And vinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, polyethersulfone, acrylic cellulose (triacetylyl cellulose, diacetyl cellulose, etc.), and the like.

  Although the film thickness of a base material is not specifically limited, From a viewpoint of productivity or moldability, the film thickness of a base material has preferable 5 micrometers or more and 1000 micrometers or less.

  FIG. 1 shows a cross-sectional view of an embodiment of an optical filter using the optical material according to the present disclosure. It is preferable that the surface of the substrate 11 on the side where the coating layer 14 is provided is subjected to surface treatment and the surface treatment layer 12 is provided. Thereby, the applicability | paintability of the coating liquid which forms the contact bonding layer 13 becomes more favorable. Examples of the surface treatment include corona treatment and plasma treatment.

The optical filter can include an adhesive layer 13. The adhesive layer 13 plays a role of improving the adhesion between the substrate 11 and the coating layer 14.
Examples of the adhesive component used for forming the adhesive layer 13 include phenol resin, urea resin, melamine resin, polyvinyl resin, polyolefin resin, urethane resin, epoxy resin, acrylic resin, polyester resin, polyamide resin, and polystyrene resin. Adhesive resin is mentioned. Among these, as the adhesive resin, it is preferable to use a polyvinyl resin, a polyolefin resin, or an acrylic resin from the viewpoint of good adhesion.

  The composition containing the optical material may have a laminated structure. In addition, the coating layer containing the photoselective material may not be a single layer but may be provided with a plurality of layers.

  The composite layer with the optical material and the coating layer containing the optical material can be mixed with known additives for the purpose of improving moldability, suppressing deterioration, and improving the dispersibility of the optical material. For example, a heat stabilizer, a stabilizing aid, a plasticizer, an antioxidant, a light stabilizer, a flame retardant, a lubricant, and an antistatic agent may be included.

(TEMPO oxidation of wood cellulose)
70 g of softwood kraft pulp was suspended in 3500 g of distilled water, and a solution of 0.7 g of TEMPO and 7 g of sodium bromide dissolved in 350 g of distilled water was added and cooled to 20 ° C. 450 g of sodium hypochlorite aqueous solution having a concentration of 2 mol / L and a density of 1.15 g / mL was added dropwise thereto to initiate an oxidation reaction. The temperature in the system was always kept at 20 ° C., and the decrease in pH during the reaction was kept at pH 10 by adding a 0.5N aqueous sodium hydroxide solution. When sodium hydroxide reached 3.00 mmol / g based on the mass of cellulose, an excessive amount of ethanol was added to stop the reaction. Thereafter, filtration and washing with distilled water were repeated using a glass filter to obtain oxidized pulp.

(Measurement of carboxy group content in oxidized pulp)
Oxidized pulp obtained by the above TEMPO oxidation was weighed by 0.1 g in terms of solid content, dispersed in water at a concentration of 1%, and hydrochloric acid was added to adjust the pH to 2.5. Thereafter, the amount of carboxy groups (mmol / g) was determined by conductivity titration using a 0.5 M aqueous sodium hydroxide solution. The result was 1.6 mmol / g.

(Oxidized pulp defibration)
1 g of oxidized pulp obtained by TEMPO oxidation was dispersed in 99 g of distilled water and refined with a juicer mixer for 30 minutes to obtain a CSNF aqueous dispersion having a CSNF concentration of 1%. The number average minor axis diameter of CSNF contained in the CSNF aqueous dispersion was 4 nm, and the number average major axis diameter was 1110 nm. Further, when steady viscoelasticity measurement was performed using a rheometer, the CSNF dispersion showed thixotropic properties.
(Preparation of silver nitrate aqueous solution)
Silver nitrate was dissolved in 50 mL of distilled water to prepare an aqueous silver nitrate solution.

(Preparation of aqueous sodium borohydride solution)
Sodium borohydride was dissolved in 50 mL of distilled water to prepare a sodium borohydride aqueous solution.

(Production of optical materials)
To 50 g of 1% CSNF aqueous dispersion, 0.5 g of an aqueous silver nitrate solution was added with stirring at room temperature (25 ° C.). After stirring for 30 minutes, an optical material was prepared by adding an aqueous sodium borohydride solution.

<Example 1>
A CSNF aqueous dispersion was prepared by the method described above, an aqueous silver nitrate solution was added to the CSNF aqueous dispersion, and sodium borohydride as a reducing agent was added after a while to produce an optical material.

<Example 2>
Prepare a CSNF aqueous dispersion by the above method, add 0.6 g of 0.01 M NaOH to the CSNF dispersion, add an aqueous silver nitrate solution, and add sodium borohydride as a reducing agent after a while. The material was manufactured.

<Example 3>
Prepare a CSNF aqueous dispersion by the above method, add 1.2 g of 0.01M NaOH to the CSNF dispersion, add an aqueous silver nitrate solution, and add sodium borohydride as a reducing agent after a while to add the optical solution. The material was manufactured.

<Example 4>
Prepare a CSNF aqueous dispersion by the above method, add 1.8 g of 0.01 M NaOH to the CSNF dispersion, add an aqueous silver nitrate solution, and add sodium borohydride as a reducing agent after a while to add the optical solution. The material was manufactured.

<Comparative Example 1>
A silver nitrate aqueous solution was added to water, and sodium borohydride as a reducing agent was added after a while.

<Comparative Example 2>
Silver nitrate was added to polyvinyl alcohol PVA124 (manufactured by Kuraray Co., Ltd.), and sodium borohydride as a reducing agent was added after a while.

<Comparative Example 3>
Sodium borohydride as a reducing agent was added to the CSNF aqueous dispersion.

<Comparative example 4>
Silver nitrate was added to the CSNF aqueous dispersion.

A precipitate was obtained from the dispersions prepared in Examples 1 to 4 and Comparative Examples 1 to 4 by centrifugation at 25000 rpm, and dispersed in an aqueous polyvinyl alcohol solution to prepare a coating solution. The PET film was subjected to corona treatment, and the coating solution was applied using a bar coater and dried at 120 ° C.

(Evaluation method of composite fine particle production)
The formation of composite fine particles is observed using a scanning transmission electron microscope, a scanning electron microscope, and a transmission electron microscope. “○”, and “×” when composite fine particles were not generated.
(Evaluation method of optical characteristics)
With respect to the obtained film, the transmittance in the wavelength region from 220 nm to 1400 nm was measured using a spectrophotometer UV-3600 (manufactured by Shimadzu Corporation) with the empty state as a reference. “Δ” when the transmittance of light having a wavelength of 700 nm is 70% or less, and “◯” when 60% or less. In the case of having light selectivity, the wavelength at which the transmittance was minimized was defined as λmax.

  As shown in Table 1, in Examples 1 to 4, composite fine particles were produced, and the transmittance was 70% or less at 700 nm, and an optical filter having photoselectivity was obtained. In Comparative Examples 1 to 4, composite fine particles were not observed and did not have photoselectivity (the photoselectivity in Table 1 is “x”). According to this example, it was possible to provide an optical material that uses a natural polymer having a low environmental load, is excellent in dispersibility, heat resistance, and light resistance, can be produced at low energy and at low cost, and an optical filter including the same.

  The present invention is useful for optical materials and optical filters using the same.

11 Substrate 12 Surface treatment layer 13 Adhesive layer 14 Coating layer

Claims (7)

A substrate and a coating layer containing an optical material formed on at least one surface of the substrate;
The transmittance becomes minimum in the wavelength region of 500 nm to 700 nm,
The optical material includes composite fine particles containing a metal and a natural polymer, wherein the metal and the natural polymer are physically inseparable, and the composite fine particles have a flat plate shape or a rod shape. 2. The optical filter according to claim 1, wherein the composite fine particles have a volume of 5 × 10 ⁻¹ nm ³ or more and 5 × 10 ¹⁰ nm ³ or less and a thickness of 1 nm or more and 50 nm or less.   The optical filter according to claim 1, wherein the metal includes one or more metals including at least silver or a compound thereof.   The optical filter according to claim 1, wherein the natural polymer includes fine cellulose fibers.   The optical axis according to claim 4, wherein the number average axis diameter of the minor axis of the fine cellulose fiber is from 1 nm to 200 nm, and the number average axis diameter of the major axis of the fine cellulose fiber is from 0.05 μm to 50 μm. filter.   The number average minor axis diameter of the fine cellulose fibers is from 1 nm to 50 nm, the number average major axis diameter of the fine cellulose fibers is from 0.1 μm to 10 μm, and the amount of carboxy groups contained in the fine cellulose fibers is 0.00. The optical filter according to claim 4, wherein the optical filter is 1 mmol / g or more and 3.0 mmol / g or less.   The optical filter according to any one of claims 4 to 6, wherein the fine cellulose fiber has a carboxy group introduced on the fiber surface.

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