Metal-supported polymers

Abstract

This invention provides an optical film with a controllable refractive index that can be effectively used as an optical film, by manufacturing a polymer film with a controllable refractive index using an approach different from the method of dispersing metal particles by post-addition to a polymer solution. [Solution] An optical film obtained from an optical film-forming composition containing a polymer having silver ions.

Description

[Technical Field]

[0001] The present invention relates to an optical film, a composition for forming an optical film, and a method for producing an optical film. [Background technology]

[0002] Traditionally, optical components made from polymer resins have been widely used in displays and lenses. Furthermore, with the recent advancements in AR / VR devices, the performance requirements, particularly regarding refractive index control, have increased, creating a demand for a wide range of refractive index control technologies. As a technique for controlling the refractive index of polymer films, the addition of insulating inorganic nanoparticles is known. For example, techniques for adding titania particles or zirconia particles to achieve a high refractive index, and techniques for adding hollow silica particles to achieve a low refractive index are known. However, in techniques where inorganic nanoparticles are dispersed in a polymer solution afterward, the difference in solvent selectivity between the polymer and the nanoparticles leads to problems with particle precipitation over time. Furthermore, methods for producing conductive pastes (e.g., silver paste) or conductive films by adding conductive metal nanoparticles to a polymer solution are known. In this case as well, the metal nanoparticles are dispersed in the polymer solution afterward, and the stability of the solution is not very high, making it easy for particles to precipitate over time. Incidentally, there is a known technique in which, instead of dispersing metal nanoparticles into a polymer solution afterward, silver nitrate is used as a metal precursor within the polymer solution to grow silver particles from the precursor (see, for example, Non-Patent Document 1). However, Non-Patent Document 1 only describes a method for adjusting the particle size of silver particles by heating, and does not describe using a polymer film containing silver particles as an optical film with a controlled refractive index and applying it to an optical component. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Nanoscale, 2013, 5, pp.12132-12135 [Overview of the project] [Problems that the invention aims to solve]

[0004] As mentioned above, in order to control the refractive index of polymer films, particles such as metals are dispersed in polymer solutions by post-addition. However, this post-addition of metal particles results in particle precipitation, leading to poor stability of the polymer solution over time. Therefore, many techniques are being investigated to improve the long-term stability of polymer solutions. However, if polymer films can be manufactured using an approach other than dispersing metal particles in the polymer solution by post-addition, the problem of metal particle deposition can be resolved. Therefore, in order to obtain an optical film with controllable refractive index, there was a need for a method to produce a polymer film with controllable refractive index using an approach other than the method of dispersing metal particles in a polymer solution by post-addition.

[0005] The present invention has been made in view of the above circumstances, and aims to provide an optical film with a controllable refractive index that can be effectively used as an optical film, by manufacturing a polymer film with a controllable refractive index using an approach different from the method of dispersing metal particles in a polymer solution by post-addition. [Means for solving the problem]

[0006] In order to solve the aforementioned problems, the present inventors conducted diligent research and found that an optical film obtained from an optical film-forming composition containing a polymer having silver ions can be used effectively as an optical film with controllable refractive index, thus completing the present invention.

[0007] In other words, the present invention encompasses the following embodiments. [1] An optical film obtained from an optical film-forming composition containing a polymer having silver ions. [2] The optical film according to [1], wherein the polymer has repeating units having a group represented by the formula "-COOAg". [3] The optical film according to [1] or [2], wherein the polymer is an acrylic polymer. [4] The optical film according to any one of [1] to [3], wherein the polymer is a random copolymer having repeating units having a group represented by the formula "-COOAg", repeating units having hydrophilic side chains, and repeating units having hydrophobic side chains. [5] The optical film according to [4], wherein the repeating unit having a hydrophilic side chain is derived from polyethylene glycol methyl ether acrylate and the repeating unit having a hydrophobic side chain is derived from dodecyl acrylate. [6] A composition for forming optical films, comprising a polymer having silver ions. [7] The optical film-forming composition according to [6], wherein the polymer has repeating units having a group represented by the formula "-COOAg". [8] The optical film-forming composition according to [6] or [7], wherein the polymer is an acrylic polymer. [9] The optical film-forming composition according to any one of [6] to [8], wherein the polymer is a random copolymer having repeating units having a group represented by the formula "-COOAg", repeating units having hydrophilic side chains, and repeating units having hydrophobic side chains.

[10] The optical film forming composition according to [9], wherein the repeating unit having a hydrophilic side chain is derived from polyethylene glycol methyl ether acrylate and the repeating unit having a hydrophobic side chain is derived from dodecyl acrylate.

[11] The optical film-forming composition according to any one of [6] to

[10] , further comprising a solvent.

[12] The optical film-forming composition according to

[11] , wherein the solvent is water and tetrahydrofuran (THF). A method for manufacturing an optical film, which produces an optical film according to any of

[13] [2] to [5], A polymer b having silver ions is produced by converting the group represented by the formula "-COOH" to the formula "-COOAg" in polymer a, which has a group represented by the formula "-COOH". A step of obtaining an optical film by applying a solution containing the polymer b onto a substrate and then drying the coating film, and a method for manufacturing an optical film including the step.

[14] A method for manufacturing an optical film for manufacturing the optical film according to any one of [2] to [5], A step of producing a polymer b having silver ions by converting a group represented by the formula "-COOH" to a group represented by the formula "-COOAg" with respect to the polymer a having a group represented by the formula "-COOH", A step of producing a powder c composed of the polymer b by drying the solution containing the polymer b under reduced pressure, A step of obtaining an optical film by applying a solution obtained by dissolving the powder c in a solvent onto a substrate and then drying the coating film, and a method for manufacturing an optical film including the step.

Advantages of the Invention

[0008] According to the present invention, by manufacturing a polymer film capable of controlling the refractive index by an approach different from the method of dispersing metal particles by post-addition in a polymer solution, an optical film capable of controlling the refractive index that can be effectively used as an optical film can be provided.

Brief Description of the Drawings

[0009] [Figure 1] An image diagram when an optical film is produced by the production method of the second A embodiment. [Figure 2] An image diagram when an optical film is produced by the production method of the second B embodiment.

Modes for Carrying Out the Invention

[0010] (Optical Film) The optical film of the present invention is obtained from a composition for forming an optical film containing a polymer having silver ions. The optical film of the present invention is used as an optical member. The optical film of the present invention is composed of a polymer film. Hereinafter, the composition for forming an optical film of the present invention used for forming the optical film of the present invention will be described.

[0011] (Composition for forming an optical film) The optical film of the present invention can be formed by the composition for forming an optical film of the present invention. The composition for forming an optical film of the present invention contains a polymer having silver ions. In addition, the composition for forming an optical film of the present invention contains, for example, a solvent. As a more specific embodiment of the polymer having the above silver ions, a polymer having a repeating unit having a group represented by the formula "-COOAg" can be mentioned. As a preferred embodiment of the composition for forming an optical film of the present invention, there is mentioned a composition for forming an optical film which contains a polymer having silver ions and a solvent by partially containing silver carboxylate having a group represented by the formula "-COOAg".

[0012] <Polymer> As described above, the polymer according to the present invention is a polymer having silver ions (supported) having a repeating unit having a group represented by the formula "-COOAg". As long as it is a polymer capable of having silver ions, the type of the polymer is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably an acrylic polymer. In addition, the polymer according to the present invention is preferably a random copolymer having, for example, a repeating unit having a hydrophilic side chain and a repeating unit having a hydrophobic side chain.

[0013] As a preferred embodiment of the polymer according to the present invention, for example, the polymer described in the following First A Embodiment can be mentioned.

[0014] <<Polymer of the First A Embodiment>> As a preferred embodiment of the polymer according to the present invention, there is mentioned a random copolymer having a repeating unit having a group represented by the formula "-COOAg", a repeating unit having a hydrophilic side chain, and a repeating unit having a hydrophobic side chain. More preferably, an acrylic random copolymer is provided, which has repeating units having a group represented by the formula "-COOAg", repeating units having hydrophilic side chains, and repeating units having hydrophobic side chains.

[0015] Examples of hydrophilic groups in the repeating unit having the hydrophilic side chain include polyethylene glycol (PEG) groups, hydroxyl groups, amide groups, sugars, and the like. Examples of hydrophobic groups in the repeating unit having the hydrophobic side chain include various alkyl groups (butyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, docosyl group), oleyl group, and the like.

[0016] As an example of a preferred embodiment of the polymer according to the present invention, for example, a repeating unit having a group represented by the formula "-COOAg" at its end, and a polyethylene oxide group (-(CH2-CH2-O) t Examples include acrylic random copolymers having repeating units with hydrophilic side chains and repeating units with hydrophobic side chains of dodecyl groups. In equation (1), t represents the repeating unit. In the example shown in equation (1) below, t is written as 9, but other lengths such as t=2, 3, average 13, average 23, etc., can also be used.

[0017] [ka] (In equation (1), l, m, and n represent repeating units, respectively, X 1 (This represents a single bond or a divalent organic group.)

[0018] The polymer according to the present invention has silver ions bonded to the carboxylic acid moiety, as represented by formula (1) above. In other words, as represented by formula (1) above, silver ions are supported on the carboxylic acid moiety, and the polymer according to the present invention has silver ions.

[0019] X in equation (1) above1 If X is a divalent organic group, 1 Examples of such groups include the group represented by the following formula (10).

[0020] [ka] R in equation (10) above 11 and R 12 *1 and *2 represent alkylene groups, s represents 0 or an integer greater than or equal to 1, f represents 0 or 1, and *1 and *2 represent bonding sites, with *2 being the side that bonds to the group represented as "-COOAg".

[0021] A preferred embodiment of the repeating unit represented by the following formula (1-1) in formula (1) above is, for example, a repeating unit represented by any of the following formulas (1-1-1) to (1-1-3).

[0022] [ka]

[0023] [ka]

[0024] <<<Method for producing polymer according to Embodiment 1A>>> The polymer represented by formula (1) above can be manufactured, for example, as follows. In the following, in particular, X in equation (1) 1 Let's explain using the case of a single bond as an example. It is synthesized by mixing tert-butyl acrylate (tBA), polyethylene glycol methyl ether acrylate (PEGA) (for example, using Mn=480 and an average number of ethylene glycol units: 9), and dodecyl acrylate (DA), and then performing radical polymerization (solution polymerization) using azobisisobutyronitrile as an initiator. Next, the tBA units in the resulting polymer are converted to acrylic acid units (AA). The reagent used in the reaction for converting the tBA unit to an acrylic acid unit (AA) is a 4M hydrochloric acid - dioxane solution. Thereby, a polymer having each repeating unit represented by the following formula (2) can be obtained. Thereafter, as shown in the following step (I), using water as a solvent, in the reaction for converting the acrylic acid unit (AA) to a unit (ANa) having a group represented by the formula "-COONa", sodium hydroxide is used as a reagent, and further, in the reaction for converting ANa to a unit (AAg) having a group represented by the formula "-COOAg", by using silver nitrate (AgNO3) as a reagent, via the polymer represented by the formula (2) and the polymer represented by the formula (3), the polymer represented by the formula (1) (as described above, in step (I), X in the formula (1) 1 is described in the case of a single bond) can be obtained.

[0025] [Chemical formula]

[0026] As shown in the above step (I), the acrylic random copolymer represented by the formula (1) has a repeating unit having a group represented by the formula "-COOAg" at the terminal, a repeating unit having a hydrophilic side chain of a polyethylene oxide group (-(CH2-CH2-O) t -), and a repeating unit having a hydrophobic side chain of a dodecyl group. As shown in the above step (I), it is preferable that the repeating unit having the hydrophilic side chain is derived from polyethylene glycol methyl ether acrylate, and the repeating unit having the hydrophobic side chain is derived from dodecyl acrylate.

[0027] [Solvent] As the solvent according to the present invention, it is preferable to use water and tetrahydrofuran (THF).

[0028] (Method for manufacturing an optical film) The optical film of the present invention is, for example, It is manufactured by the manufacturing method shown as the embodiment of 2A below, or the manufacturing method shown as the embodiment of 2B below.

[0029] <Method for manufacturing an optical film according to Embodiment 2A> The method for manufacturing the optical film in the second embodiment A is as follows: A polymer a (corresponding to the polymer represented by formula (2) above) having a group represented by formula "-COOH" is converted to formula "-COOAg" to produce a polymer b (corresponding to the polymer represented by formula (1) above) having silver ions, and A method for producing an optical film includes the step of applying a solution containing the polymer b onto a substrate and then drying the coating film to obtain an optical film.

[0030] Figure 1 shows an illustrative diagram of an optical film fabricated using the manufacturing method of the second embodiment (2A). To describe in more detail the method for manufacturing the optical film according to Embodiment 2A, as shown in Figure 1, a solution containing polymer b (also called a polymer b-containing solution; in Embodiment 2A, this polymer b-containing solution corresponds to the optical film-forming composition referred to in the present invention) is prepared from a solution containing polymer a (also called a polymer a-containing solution). Next, the polymer b-containing solution is applied to a substrate, and the coating is dried to form a film, thereby producing the optical film of the present invention.

[0031] The optical film of the present invention can be obtained by applying a polymer b-containing solution (optical film forming composition) onto a substrate, as described above, and then drying the coating to form a film.

[0032] An optical film is obtained by applying an optical film-forming composition to a substrate, drying the applied film (heating to evaporate the solvent as needed), and then forming an optical film. The method of applying the optical film-forming composition is arbitrary and can include methods such as spin coating, dip coating, flow coating, inkjet coating, jet dispenser coating, spray coating, bar coating, gravure coating, slit coating, roll coating, transfer printing, brush coating, blade coating, and air knife coating.

[0033] Furthermore, suitable substrates include silicon, glass coated with indium tin oxide (ITO), glass coated with indium zinc oxide (IZO), metal nanowires, polyethylene terephthalate (PET), plastics, glass, quartz, ceramics, and other materials. Flexible substrates with flexibility can also be used. The heating (firing) temperature is not particularly limited for the purpose of evaporating the solvent; for example, it can be done at 50-200°C for 0.5-10 minutes. The heating (baking) method is not particularly limited; for example, it can be evaporated using a hot plate or oven under appropriate conditions such as air, an inert gas such as nitrogen, or a vacuum. The heating temperature and heating time should be selected to match the process steps of the target electronic device, and the heating conditions should be chosen so that the physical properties of the resulting film match the required characteristics of the electronic device.

[0034] <Method for manufacturing an optical film according to Embodiment 2B> The method for manufacturing the optical film in the second B embodiment is as follows: A polymer a (corresponding to the polymer represented by formula (2) above) having a group represented by formula "-COOH" is converted to formula "-COOAg" to produce a polymer b (corresponding to the polymer represented by formula (1) above) having silver ions, and A step of drying the solution containing the polymer b under reduced pressure to produce a powder c consisting of polymer b, A method for producing an optical film is provided, which includes the step of applying a solution obtained by dissolving the powder c in a solvent onto a substrate, and then drying the coating film to obtain an optical film.

[0035] Figure 2 shows an illustrative diagram of an optical film fabricated using the manufacturing method of the second embodiment (B). To describe in more detail the method for manufacturing an optical film according to Embodiment 2B, as shown in Figure 2, a solution containing polymer b (also called a polymer b-containing solution) is prepared from a solution containing polymer a (also called a polymer a-containing solution). Next, the polymer b-containing solution is dried under reduced pressure to produce a powder c consisting of polymer b. Next, a solution is prepared by dissolving powder c in a solvent (also called a powder c-dissolved solution; in Embodiment 2B, this powder c-dissolved solution corresponds to the optical film-forming composition referred to in the present invention). Next, the powder c-dissolved solution is applied to a substrate, and the coating is dried to form a film, thereby producing the optical film of the present invention.

[0036] The optical film of the present invention can be obtained by applying a powder c dissolution solution (optical film forming composition) onto a substrate, as described above, and then drying the coating to form a film.

[0037] Furthermore, in the method for manufacturing an optical film according to the second embodiment B, the step of applying the optical film-forming composition onto a substrate and then drying the coating to form an optical film is the same as the step described in the method for manufacturing an optical film according to the second embodiment A described above.

[0038] The difference between the manufacturing method of embodiment 2B and embodiment 2A is that, after producing polymer b, the aqueous solution containing polymer b is dried under reduced pressure to produce a powder. In the present invention, the optical film-forming composition obtained by the manufacturing method of the second embodiment (2B) is more preferable than the optical film-forming composition obtained by the manufacturing method of the second embodiment (2A) because, as shown in the following examples, it can increase the number and size of silver particles in the polymer solution. Furthermore, the optical film produced using the optical film-forming composition obtained by the more preferable manufacturing method of the second embodiment (2B) is preferable because it yields an optical film with a higher refractive index than the optical film produced using the optical film-forming composition obtained by the manufacturing method of the second embodiment (2A).

[0039] <Characteristics of the optical film-forming composition and optical film obtained by the above optical film manufacturing method> <<Regarding the solution stability of polymer solutions containing silver ions or silver particles>> Regardless of whether the optical film-forming composition is obtained by the manufacturing method of embodiment 2A or embodiment 2B, it consists of a polymer having silver ions (supported by silver ions), or a polymer solution obtained by growing silver ions on a polymer (supported by a polymer) into silver particles, and dissolving the polymer having (supported by the silver particles) in a solvent. The polymer solution according to the present invention can suppress the precipitation of silver particles. The mechanism for suppressing the precipitation of silver particles is thought to be due to the fact that the growth of silver particles near the polymer side chains makes it easy to form micellar states in which the polymer chains surround the silver particles. This is an advantage of the polymer solution according to the present invention over polymer solutions obtained by dispersing metal particles through post-addition.

[0040] <<Regarding silver particles in polymer solutions>> In the present invention, it is preferable to form an optical film using the optical film-forming composition obtained by the manufacturing method of embodiment 2B, rather than using the optical film-forming composition obtained by the manufacturing method of embodiment 2A. This is because, as described above, the optical film-forming composition obtained by the manufacturing method of embodiment 2B has a greater number and size of silver particles in the polymer solution compared to the optical film-forming composition obtained by the manufacturing method of embodiment 2A. This is as shown in the section "Evaluation of Silver Nanoparticles in Solution" in the examples described later. Furthermore, when an optical film is formed using an optical film-forming composition in which the number and size of silver particles in the polymer solution are increased, the refractive index of the optical film can be increased, as shown in the <Evaluation of the refractive index of the thin film> section of the examples described later.

[0041] Comparing the number of Ag particles and the ionic component present in the polymer solution of the optical film-forming composition obtained by the manufacturing method of embodiment 2B and the optical film-forming composition obtained by the manufacturing method of embodiment 2A, the manufacturing method of embodiment 2B increases the proportion of Ag particles by first drying the aqueous solution containing polymer b to produce a powder. As shown in the sections "<Evaluation of Silver Nanoparticles in Solution>" and "<Evaluation of Refractive Index of Thin Film>" of the examples described later, there is a correlation between an increase in the number of Ag particles (and particle size) and an increase in the refractive index of the optical film. Therefore, the drying step in the manufacturing method of Embodiment 2B is an important step for controlling the refractive index and obtaining an optical film exhibiting the desired refractive index.

[0042] As will be shown in the examples described later, the reason why the refractive index increases after going through the drying process (powdering process) in the manufacturing method of embodiment 2B is largely due to an increase in the number of silver particles in the polymer solution (varnish), which is the optical film forming composition, or an increase in the size of the silver particles in the polymer solution (varnish). Furthermore, it is thought that the drying process (powdering process) in the manufacturing method of embodiment 2B oxidizes the silver particles, and this oxidation of the particles, combined with an increase in the number and size of the particles, contributes to the increase in refractive index.

[0043] <Regarding the application of optical films obtained by the above optical film manufacturing method> The optical film of the present invention obtained by the above-described method for manufacturing optical films has a controlled refractive index and exhibits a desired refractive index, making it a good optical film that can be used in various optical components that utilize refractive index. Because the optical film of the present invention exhibits a high refractive index, it can be suitably used in the fields of electronic devices and optical materials, such as liquid crystal displays, organic EL elements (organic EL displays and organic EL lighting), touch panels, optoelectronic semiconductor (LED) elements, solid-state image sensors, organic thin-film solar cells, dye-sensitized solar cells, organic thin-film transistors (TFTs), lenses, prisms, cameras, binoculars, microscopes, semiconductor exposure equipment, and other components used in their manufacture. In particular, the optical film of the present invention is easy to control in terms of refractive index and has a high refractive index, so when used as a planarization layer or light scattering layer in organic EL lighting, it can improve the light extraction efficiency (light diffusion efficiency) and durability.

[0044] The thickness of the optical film is not particularly limited, but it is preferably between 5 nm and 10 μm. [Examples]

[0045] The present invention will be further described in detail below with reference to examples, but the present invention is not limited to these examples. The abbreviations of the compounds used and the methods for measuring each of their physical properties are as follows.

[0046] (monomer) tBA:tert-butyl acrylate PEGA: Polyethylene glycol methyl ether acrylate (Mn=480, average number of ethylene glycol units: 9) DA: Dodecyl acrylate SAA: Mono(2-acryloyloxyethyl) succinate EAA: Carboxyethyl Acrylate (Radical polymerization initiator) AIBN: Azobisisobutyronitrile (solvent) toluene 1,4-dioxane

[0047] (Measurement of molecular weight) The weight-average molecular weight (Mw) of the polymers shown in the synthesis examples below was measured using gel permeation chromatography (GPC). A GPC instrument manufactured by Tosoh Corporation was used for the measurement, and the measurement conditions were as follows. • Measuring device: HLC-8020GPC [product name] (manufactured by Tosoh Corporation) Column temperature: 40°C • Solvent: Tetrahydrofuran (THF) ·Flow rate: 1.0mL / min • Standard sample: Polystyrene (manufactured by Tosoh Corporation)

[0048] (Evaluation of silver nanoparticles in solution) The solutions of acrylic polymer silver salts prepared in the following examples were analyzed using single-particle ICP-MS (Sp-ICP-MS) to determine whether or not silver particles were formed in the solution. In the Sp-ICP-MS method, a suspension of the sample diluted with a solvent such as water is directly introduced into an inductively coupled plasma mass spectrometer (ICP-MS), an elemental analysis instrument. The spectrum obtained from the time analysis with a time resolution of approximately 0.1 milliseconds is then analyzed to measure the particle concentration and particle size distribution of the target element contained in the sample suspension. In this measurement, the suspension prepared by appropriately diluting the varnishes W1 to W2 prepared in Examples 1 and 2 with ultrapure water was used as the measurement solution, and the particle size of the detected silver nanoparticles was calculated assuming that they were all perfectly spherical particles of elemental silver. In the analysis of this invention, silver was detected as "particulate" if it existed as particles with a diameter of 20 nm or more, and as "ionic" if it existed as particles or ions with a diameter of 20 nm or less. The analytical apparatus and measurement conditions are as follows. • Measurement device: Triple quadrupole ICP-MS 8900 (manufactured by Agilent Technologies, Inc.) • Time resolution: 0.1 milliseconds • Measurement time: 60 seconds • Ionic standard sample: Silver Standard Solution (Ag 1000) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • Particulate standard sample: Silver, dispersion 730815-25ML (manufactured by Sigma-Aldrich)

[0049] <Synthesis of acrylic polymers> (Synthesis Example 1) It was synthesized by mixing tert-butyl acrylate (tBA), polyethylene glycol methyl ether acrylate (PEGA) (Mn=480, average number of ethylene glycol units: 9), dodecyl acrylate (DA) with toluene as the solvent, and then using azobisisobutyronitrile (AIBN) as an initiator for radical polymerization (solution polymerization). In addition, a small amount of tetralin was added to the polymerization solution to determine the monomer consumption rate by NMR. The polymerization conditions were a polymerization temperature of 60°C and a polymerization time of 24 hours. The monomer consumption rate determined by NMR was: The ratio of tBA / PEGA / DA was 94 mol% / 93 mol% / 93 mol%. Furthermore, the weight-average molecular weight and number-average molecular weight of the tBA / PEGA / DA random copolymer, obtained by GPC before converting the tBA units to acrylic acid units (AA), were as follows: weight-average molecular weight Mw = 53,900, number-average molecular weight Mn = 24,900, and molecular weight distribution Mw / Mn = 2.17.

[0050] As described above, tBA / PEGA / DA was radically polymerized in toluene solvent, and then toluene was removed by evaporation. The obtained tBA / PEGA / DA ternary random copolymer was dissolved in a 4M hydrochloric acid-dioxane solution and reacted at 60°C for 24 hours to convert the tBA units of the tBA / PEGA / DA random copolymer to acrylic acid units (AA). This solution was evaporated to remove hydrochloric acid and dioxane, and the AA / PEGA / DA ternary random copolymer obtained in an acetone / methanol mixed solvent was dialyzed to remove residual monomers and impurities for purification. The acrylic polymer (AA / PEGA / DA ternary random copolymer) obtained after purification was dissolved in water to obtain aqueous solution S1 (acrylic polymer concentration: 30.0 mg / mL).

[0051] <Preparation of aqueous solution of acrylic polymer silver salt> (Synthesis Example 2) In Synthesis Example 1, an aqueous solution S1 of the acrylic polymer was prepared, and an aqueous NaOH solution was added to convert it to sodium acrylate. Specifically, water was used as the solvent, and sodium hydroxide was used as the reagent in a reaction that converted the acrylic acid units (AA) in the acrylic polymer to units (ANa) having a group represented by the formula "-COONa". This yielded an aqueous solution of the sodium acrylic polymer salt. Next, an aqueous solution of AgNO3 was added to the aqueous polymer solution consisting of the sodium salt of this acrylic polymer to perform a reaction to convert it to an AAg salt. In other words, in the reaction to convert the unit having the group represented by the formula "-COONa" (ANa) in the acrylic polymer to the unit having the group represented by the formula "-COOAg" (AAg), silver nitrate (AgNO3) was used as the reagent. This yielded an aqueous solution S2 of the silver salt of the acrylic polymer.

[0052] (Synthesis Example 3) Mono(2-acryloyloxyethyl) succinate (SAA), PEGA, DA, and 1,4-dioxane as a solvent were mixed, and a ternary random copolymer with a molar ratio of SAA / PEGA / DA = 1 / 1 / 2 was synthesized by radical polymerization (solution polymerization) using AIBN as an initiator. The obtained copolymer had a weight-average molecular weight Mw = 58,900, a number-average molecular weight Mn = 27,800, and a molecular weight distribution Mw / Mn = 2.12. This solution was evaporated to remove dioxane, and the resulting SAA / PEGA / DA ternary random copolymer was dialyzed to remove residual monomers and impurities for purification. The acrylic polymer (SAA / PEGA / DA ternary random copolymer) obtained after purification was dissolved in water to obtain aqueous solution S3 (acrylic polymer concentration: 30.0 mg / mL).

[0053] (Synthesis Example 4) A ternary random copolymer with a molar ratio of EAA / PEGA / DA = 1 / 1 / 2 was synthesized by mixing carboxyethyl acrylate (EAA), PEGA, DA, and 1,4-dioxane as a solvent, and then performing radical polymerization (solution polymerization) using AIBN as an initiator. The obtained copolymer had a weight-average molecular weight Mw = 64,400, a number-average molecular weight Mn = 26,200, and a molecular weight distribution Mw / Mn = 2.46. This solution was evaporated to remove dioxane, and the resulting EAA / PEGA / DA ternary random copolymer was dialyzed to remove residual monomers and impurities for purification. The acrylic polymer (EAA / PEGA / DA ternary random copolymer) obtained after purification was dissolved in water to obtain aqueous solution S4 (acrylic polymer concentration: 30.0 mg / mL).

[0054] (Synthesis examples 5 and 6) Using aqueous solutions S3 and S4 of the acrylic polymer, aqueous solutions S5 and S6 of the acrylic polymer silver salt were obtained using the same procedure as in Synthesis Example 2.

[0055] (Comparative Example 1) The aqueous solution S1 of the acrylic polymer prepared in Synthesis Example 1 was diluted with THF, and the resulting solution was filtered through a nylon filter with a pore size of 5.0 μm to obtain varnish CW1 (solvent ratio: water[1]THF[1], solids concentration: 15 mg / mL).

[0056] (Example 1) The aqueous solution S2 of the acrylic polymer silver salt prepared in Synthesis Example 2 was diluted with THF, and the resulting solution was filtered through a nylon filter with a pore size of 5.0 μm to obtain varnish W1 (solvent ratio: water[1]THF[1], solid content concentration: 15 mg / mL).

[0057] (Example 2) <Powdering and redissolution of acrylic polymer silver salt aqueous solution> The solvent of the aqueous solution S2 of the acrylic polymer silver salt prepared in Synthesis Example 2 was removed by distillation using an evaporator, and the resulting residue was dried under reduced pressure at 60°C for 24 hours to obtain the acrylic polymer silver salt powder. Next, the obtained powder was dissolved in a mixed solvent of water and THF, and the resulting solution was filtered through a nylon filter with a pore size of 5.0 μm to obtain varnish W2 (solvent ratio: water[1]THF[1], solid content concentration: 15 mg / mL).

[0058] (Comparative Examples 2-3) Varnish CW2 was obtained from aqueous solution S3 of the acrylic polymer prepared in Synthesis Example 3, and varnish CW3 was obtained from aqueous solution S4 of the acrylic polymer prepared in Synthesis Example 4, using the same procedure as in Comparative Example 1.

[0059] (Examples 3-4) Varnish W3 was obtained from aqueous solution S5 of the acrylic polymer silver salt prepared in Synthesis Example 5, and varnish W4 was obtained from aqueous solution S6 of the acrylic polymer silver salt prepared in Synthesis Example 6, using the same procedure as in Example 1.

[0060] <Evaluation of silver nanoparticles in solution> The Sp-ICP-MS measurement results for varnishes W1 and W2 obtained in Examples 1 and 2 are shown in Table 1, and the formation of particulate components was confirmed in all cases. In particular, in Example 2, where the varnishes were powdered and then redissolved, an increase in particulate components and an increase in average particle size were confirmed.

[0061] [Table 1]

[0062] <Evaluation of the refractive index of thin films> The varnishes of Examples 1-4 and Comparative Examples 1-3 were each applied to a 4cm x 4cm silicon substrate using a spin coater, and then dried at 120°C for 1 minute in an air atmosphere to produce thin films of 30-50 nm on the substrate. The refractive index n of each thin film (average refractive index in the visible wavelength range of 400 nm to 800 nm) was measured using a multi-incidence angle spectroscopic ellipsometer (VASE, manufactured by J.A. Woolam Japan). The results are shown in section 2.

[0063] [Table 2]

[0064] As shown in Table 2, the silver-supported (silver-containing) acrylic polymer thin films obtained in this invention (Examples 1, 3, and 4) showed a higher average refractive index in the visible range compared to acrylic polymer thin films without silver support (silver-free) (Comparative Examples 1, 2, and 3). Furthermore, the refractive index was further increased by using a varnish that had undergone a powdering process (Example 2).

Claims

1. An optical film obtained from an optical film-forming composition containing a polymer having silver ions.

2. The optical film according to claim 1, wherein the polymer has repeating units having a group represented by the formula "-COOAg".

3. The optical film according to claim 2, wherein the polymer is an acrylic polymer.

4. The optical film according to claim 2, wherein the polymer is a random copolymer having repeating units having a group represented by the formula "-COOAg", repeating units having hydrophilic side chains, and repeating units having hydrophobic side chains.

5. The optical film according to claim 4, wherein the repeating unit having a hydrophilic side chain is derived from polyethylene glycol methyl ether acrylate, and the repeating unit having a hydrophobic side chain is derived from dodecyl acrylate.

6. A composition for forming optical films, containing a polymer having silver ions.

7. The optical film-forming composition according to claim 6, wherein the polymer has repeating units having a group represented by the formula "-COOAg".

8. The optical film forming composition according to claim 7, wherein the polymer is an acrylic polymer.

9. The optical film-forming composition according to claim 7, wherein the polymer is a random copolymer having repeating units having a group represented by the formula "-COOAg", repeating units having hydrophilic side chains, and repeating units having hydrophobic side chains.

10. The optical film-forming composition according to claim 9, wherein the repeating unit having a hydrophilic side chain is derived from polyethylene glycol methyl ether acrylate, and the repeating unit having a hydrophobic side chain is derived from dodecyl acrylate.

11. The optical film-forming composition according to claim 6, further containing a solvent.

12. The optical film-forming composition according to claim 11, wherein the solvent is water and tetrahydrofuran (THF).

13. A method for manufacturing an optical film according to claim 2, A polymer b having silver ions is produced by converting the group represented by the formula "-COOH" to the formula "-COOAg" in polymer a, which has a group represented by the formula "-COOH". A method for producing an optical film, comprising the steps of: applying a solution containing the polymer b onto a substrate, and then drying the coating film to obtain an optical film.

14. A method for manufacturing an optical film according to claim 2, A polymer b having silver ions is produced by converting the group represented by the formula "-COOH" to the formula "-COOAg" in polymer a, which has a group represented by the formula "-COOH". A step of drying the solution containing the polymer b under reduced pressure to produce a powder c consisting of polymer b, A method for producing an optical film, comprising the steps of: applying a solution obtained by dissolving the powder c in a solvent onto a substrate, and then drying the coating film to obtain an optical film.

Images