Near-infrared absorbing plate and optical device including same

Abstract

To provide a near-infrared absorbing plate capable of preventing reduction in visible transmittance and near-infrared absorbance due to interactions between a plurality of organic materials forming light-absorbing layers.SOLUTION: A near-infrared absorbing plate is provided, comprising a glass substrate 100, and first and second light-absorbing layers 200, 300 separated from each other. The first light-absorbing layer 200 has an absorption maximum at any one wavelength within a wavelength range of 850 nm to 1,200 nm, inclusive, and the second light-absorbing layer 300 has an absorption maximum at any one wavelength within a wavelength range of 650 nm to 750 nm, inclusive. The first light-absorbing layer 200 contains particles having an average particle diameter of 1 μm or less.EFFECT: The near-infrared absorbing plate can be made thinner and offers superior mechanical properties such as strength and heat resistance.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present application relates to a near-infrared absorbing plate and an optical device including the same. [Background technology]

[0002] Recently, with the widespread use of smartphones and tablet PCs, the demand for digital camera modules using image sensors is increasing dramatically. The direction of development for digital camera modules used in such mobile devices is in the pursuit of thinner designs and higher image quality.

[0003] The image signal of a digital camera module is acquired through an image sensor. Unlike the human eye, an image sensor made of semiconductors also responds to wavelengths in the infrared range. Therefore, in order to obtain image information similar to what the human eye sees, an infrared-ray cut filter (IRCF) that blocks wavelengths in the infrared range is required.

[0004] One example of an IRCF is a reflective filter (1), which is manufactured by depositing a dielectric multilayer film on a glass substrate and reflects infrared light while transmitting only light in the visible light range. However, because reflective filters do not absorb light in the near-infrared range, they experience severe internal reflection within the camera module. Internal reflection is the main cause of image ghosting (the phenomenon in which a developed image appears blurred or an image that does not actually exist appears).

[0005] Another example of an IRCF is the (2) inorganic absorption filter (also called a blue filter), which absorbs and reflects near-infrared light and is manufactured by depositing a dielectric multilayer film on a glass substrate (also known as "blue glass") that has inorganic particles dispersed therein, producing a blue color. Blue filters have the effect of suppressing the aforementioned ghost phenomenon through near-infrared absorption. However, due to their high brittleness, blue filters do not conform to the technological trend of achieving thin IRCFs with a total thickness of 0.2 mm or less.

[0006] Another example of an IRCF is (3) an organic absorption filter, which can absorb and reflect near-infrared light. The organic absorption filter is fabricated by depositing a dielectric multilayer film containing multiple organic materials (light absorbers) with absorption maxima in different wavelength ranges on a transparent substrate. Compared to inorganic absorption filters, organic absorption filters offer greater flexibility in adjusting the wavelengths of light they can absorb, making them advantageous for increasing absorption of light in the infrared wavelength range and decreasing absorption of light in the visible wavelength range. Furthermore, because a separate light absorption layer containing a light absorber is applied, there are no restrictions on the selection of substrates, allowing for the free selection of a strong substrate. However, because interactions between the organic materials occur in the light absorption layer, organic absorption filters suffer from problems such as reduced visible light transmittance and reduced near-infrared absorptance due to the interactions between the organic materials.

[0007] Therefore, there is a need to develop an infrared blocking filter that can prevent the reduction in visible light transmittance and near-infrared light absorptance caused by the interaction between the organic substances that make up the light absorbing layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2009-0051250 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present application is to provide a near-infrared absorbing plate that can prevent a decrease in visible light transmittance and near-infrared absorptance due to interactions between a plurality of organic substances that constitute the light absorbing layer. [Means for solving the problem]

[0010] One embodiment of the present application relates to a near-infrared absorbing plate (particularly, a near-infrared absorbing disk).

[0011] The near-infrared absorbing plate of the present application includes at least a glass substrate and a light absorbing layer present on one or both surfaces of the glass substrate. In addition, in the near-infrared absorbing plate of the present application, the light absorbing layer is present in a plurality of layers.

[0012] Specifically, the near-infrared absorbing plate of the present application includes at least a plurality of light absorbing layers that have different optical properties or different forms of existence of the components that constitute them. The plurality of light absorbing layers exist in a state that is distinct from one another. That is, the near-infrared absorbing plate of the present application includes a glass substrate and a first light absorbing layer and a second light absorbing layer, and the first and second light absorbing layers have different optical properties or different forms of existence of the components that constitute them. The first and second light absorbing layers are physically separated from one another and exist individually (or independently).

[0013] The first and second light absorbing layers have different optical properties, specifically, the wavelength ranges in which the first and second light absorbing layers have their respective absorption maxima are different, because the first and second light absorbing layers contain different dyes, as will be described later.

[0014] The first light-absorbing layer has an absorption maximum at any one wavelength in the range of 850 nm to 1,200 nm. The second light-absorbing layer has an absorption maximum at any one wavelength in the range of 650 nm to 750 nm. That is, the near-infrared absorbing plate of the present application has functional layers that can absorb light in different wavelength bands independently arranged, thereby improving visible light transmittance and near-infrared absorptance. This is completely different from applying components (e.g., dyes) with different absorption maxima to only one layer. Applying components with different absorption maxima to only one layer can result in a problem of reduced visible light transmittance and increased near-infrared transmittance due to interactions between the components.

[0015] In this application, the term "absorption maximum" means the transmittance to absorbance when a spectrum of absorbance to transmittance with respect to wavelength shows the maximum absorbance to the minimum transmittance for light of a specific wavelength.

[0016] Therefore, the first light absorbing layer has a maximum absorptance or a minimum transmittance at any one wavelength in the range of 850 nm to 1,200 nm, and the second light absorbing layer has a maximum absorptance or a minimum transmittance at any one wavelength in the range of 650 nm to 750 nm.

[0017] The method for measuring the absorption maximum of the first light absorbing layer, the second light absorbing layer, etc. is not particularly limited, and for example, the measurement method mentioned in the examples below can be applied.

[0018] The absorption maximum may be measured for the first or second light absorbing layer itself, or may be measured for a laminate in which the light absorbing layer is placed on a known glass substrate.

[0019] The first light absorbing layer contains particles having a size equal to or smaller than a specific value. That is, the first light absorbing layer contains particles having a size (specifically, an average particle size) of 1 μm or less. This is because, as will be described later, the first light absorbing layer contains a dye that is not dissolved within the layer. In other words, the first light absorbing layer contains a specific polymer and a dye dispersed in the polymer, and the dye is dispersed under appropriate conditions.

[0020] As described above, the particle size is the average particle size of the particles. The average particle size may be the known volume mean diameter or the D50 particle size. The volume mean diameter refers to the known De Broucker mean diameter. The D50 particle size refers to the median value in the particle size distribution obtained using the Stokes-Einstein relationship of the dynamic light scattering method.

[0021] As described above, by separately providing the first light absorbing layer and the second light absorbing layer having different optical properties and designing the first light absorbing layer, specifically the first light absorbing layer only, to contain particles having an average particle size equal to or less than a specific value, it is possible to provide a near-infrared absorbing plate that is more suitable for the purpose of the present application, for example, for application to an infrared blocking filter having excellent visible light transmittance and near-infrared absorptivity.

[0022] On the other hand, when particles are not present in either the first light absorbing layer or the second light absorbing layer, even if particles are present in the first light absorbing layer, if the size (specifically, average particle size) of the particles exceeds the range specified in the present application, there are problems such as a decrease in heat resistance of the first light absorbing layer or a significant decrease in visible light transmittance and (near) infrared absorptance of the near infrared absorbing plate.

[0023] The average particle size of the particles present in the first light absorbing layer may be, for example, 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, or 0.5 μm or less, or may be 10 nm or more, or 30 nm or more.

[0024] The light absorbing layer of the near-infrared absorbing plate of the present application may contain at least a binder resin and a dye. The binder resin may be applied to ensure the fixing force of the light absorbing layer.

[0025] In contrast, in the present application, at least two types of light-absorbing layers are included, and the optical properties or the presence forms of their components are designed to be different between them, so the types and blending forms of the binder resin and dye can be changed as appropriate. Hereinafter, the binder resin and dye contained in the first light-absorbing layer will be referred to as the first binder resin and the first dye, respectively, and the binder resin and dye contained in the second light-absorbing layer will be referred to as the second binder resin and the second dye, respectively. The method of forming each light-absorbing layer will be described later.

[0026] The type of binder resin is not limited, but from the viewpoint of making the light absorbing layer exhibit the desired optical properties, it is preferable to use an optically transparent resin as the binder resin.

[0027] "Optically clear" can mean that the transmittance for any one wavelength of light in the visible light range (e.g., light with a wavelength of 550 nm) is 90% or more, 95% or more, 99% or more, or approximately 100%.

[0028] Examples of binder resins include cyclic olefin resins, polyarylate resins, polyisocyanate resins, polyimide resins, polyetherimide resins, polyamideimide resins, polyacrylic resins, polycarbonate resins, polyethylene phthalate resins, and mixtures of two or more of these.

[0029] The first binder resin and the second binder resin may be the same or different from each other.

[0030] The first light-absorbing layer includes particles having an average particle size equal to or smaller than a specific value. Such particles may be generated depending on the state of a first dye contained in the first light-absorbing layer. That is, the first light-absorbing layer includes a first binder resin and a first dye. In this case, the first dye may be dispersed in the first binder resin, and the particles mentioned above may be particles of the first dye.

[0031] Here, a specific component being dispersed in a specific binder resin can also mean that the component is not dissolved in the binder resin or the solvent blended therewith, and therefore can be observed with the naked eye, and that multiple substances made up of the component are scattered regularly or irregularly within the binder resin.

[0032] The type of the first dye is not limited as long as it can exhibit the optical properties (such as absorption maximum) of the first light absorbing layer and can be dispersed in the first binder resin. Examples of the first dye include cyanine compounds, phthalocyanine compounds, naphthalocyanine compounds, porphyrin compounds, benzoporphyrin compounds, squarylium compounds, anthraquinone compounds, croconium compounds, dithiol metal complex compounds, and combinations thereof.

[0033] From the viewpoint of most easily ensuring the physical properties such as the absorption maximum, it is appropriate to use a diimonium-based compound as the first dye. The diimonium-based compound may be a compound represented by the following Chemical Formula 1. Therefore, the first dye may include a compound represented by the following Chemical Formula 1.

[0034] [ka]

[0035] In Chemical Formula 1, R1 to R8 are each independently a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkenyl group, or an alkynyl group; R9 to R11 are each independently a hydrogen atom, a halogen group, an amino group, a cyano group, a nitro group, a carboxy group, an alkyl group, or an alkoxy group; and X is an anion.

[0036] The anion can be, for example, Cl - , I - , F - , ClO4 - , BF4 - , SbF6 - , CF3SO3 - or CH3C6H4SO3 - etc.

[0037] The content of the first dye in the first light absorbing layer can be varied depending on the ratio in the composition applied by the method described below, and can be appropriately adjusted within the range that exhibits the above-mentioned absorption maximum.

[0038] The second light-absorbing layer, which has optical properties different from those of the first light-absorbing layer, specifically a different absorption maximum, can also contain a binder resin (second binder resin) and a dye (second dye). Since the second light-absorbing layer exhibits optical properties different from those of the first light-absorbing layer, at least the second dye may be present in a different form and / or of a different type from those of the first dye.

[0039] During the manufacturing process of the first light-absorbing layer, the first dye may be dispersed, for example, in the form of particles, while during the manufacturing process of the second light-absorbing layer, the second dye may be dissolved. As a result, the second dye can color the second binder resin in the second light-absorbing layer. That is, the second light-absorbing layer may include a second binder resin and a second dye that colors the second binder resin. The expression "a certain dye colors a certain resin" may mean that the color of the resin appears as the color of the dye. That is, unlike the first light-absorbing layer, the second light-absorbing layer does not need to contain particles. Specifically, since the dye dissolves during the manufacturing process, the second dye can color the second binder resin in the second light-absorbing layer.

[0040] The type of the second dye is not limited, as is the type of the first dye, and any known dye can be used as the second dye as long as it can exhibit the optical properties (such as absorption maximum) of the second light absorbing layer described above.

[0041] The absorption maximum of the light absorbing layer is usually determined by the optical properties of the dye. Since the first light absorbing layer and the second light absorbing layer have different absorption maxima, the second dye may be a compound different from the first dye, such as a cyanine-based compound, a phthalocyanine-based compound, a naphthalocyanine-based compound, a porphyrin-based compound, a benzoporphyrin-based compound, a squarylium-based compound, an anthraquinone-based compound, a croconium-based compound, a dithiol metal complex compound, or a combination thereof. To ensure that the second light absorbing layer exhibits the above-described absorption maximum, a dye containing a squarylium-based compound may be used as the second dye. The squarylium-based compound may be a compound represented by the following Chemical Formula 2. That is, the second dye may include a compound represented by the following Chemical Formula 2.

[0042] [ka]

[0043] TIFF0007720605000003.tif82168

[0044] In addition, in Formula 2, when one or more hydrogen atoms present in the aminophenyl group, the indolylmethylene group, the indolinyl group, or the pyrimidine group are each independently an aryl group, the aryl group may be further substituted with an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms.

[0045] The compound of Formula 2 may be any one of the compounds of Formulas 2a to 2d below:

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] In Chemical Formulae 2a to 2d, a1, a2, a3, and a4 are each independently hydrogen, a halogen group, a hydroxy group, a cyano group, a nitro group, a carboxy group, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a sulfonamido group, or an amido group substituted or unsubstituted with an alkyl group having 1 to 4 carbon atoms, a haloalkyl group having 1 to 4 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.

[0051] In Chemical Formulae 2a to 2d, when a1, a2, a3, and a4 are each independently an aryl group having 6 to 20 carbon atoms, one or more hydrogen atoms of the aryl group may be further substituted with an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms.

[0052] In this application, the term "alkyl group" may mean a substituent derived from a straight-chain or branched-chain saturated hydrocarbon.Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1-ethylpropyl group, a 2-ethylpropyl group, an n-hexyl group, a 1-methyl-2-ethylpropyl group, a 1-ethyl-2-methylpropyl group, a 1,1,2-trimethylpropyl group, and a 1,1,2-trimethylpropyl group. Examples of suitable alkyl groups include 1-propylpropyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group, and 3-methylpentyl group. The alkyl group may have 1 to 20, 1 to 12, 1 to 6, or 1 to 4 carbon atoms.

[0053] In this application, the term "cycloalkyl group" may refer to a substituent derived from a monocyclic saturated hydrocarbon. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. The cycloalkyl group may refer to a cycloalkyl group having 3 to 20, 3 to 12, 3 to 9, or 3 to 6 carbon atoms.

[0054] In this application, the term "aryl group" means a monovalent substituent derived from an aromatic hydrocarbon. Examples of the aryl group include a phenyl group, a naphthyl group, an anthracenyl group, a phenanthryl group, a naphthacenyl group, a pyrenyl group, a tolyl group, a biphenyl group, a terphenyl group, a chrycenyl group, a spirobifluorenyl group, a fluoranthenyl group, a fluorenyl group, a perylenyl group, an indenyl group, an azulenyl group, a heptalenyl group, a phenalenyl group, and a phenanthrenyl group. The aryl group may be an aryl group having 6 to 30, 6 to 24, 6 to 18, or 6 to 12 carbon atoms.

[0055] In this application, the term "aralkyl group" refers to a monovalent substituent derived from a saturated hydrocarbon compound in which a monovalent substituent derived from an aromatic hydrocarbon is bonded to a hydrogen site on the terminal hydrocarbon. That is, the aralkyl group refers to an alkyl group in which the chain end is substituted with an aryl group. Examples of aralkyl groups include a benzyl group, a methylbenzyl group, a phenethyl group, a phenylpropyl group, a naphthalenylmethyl group, and a naphthalenylethyl group.

[0056] As described above, in the near-infrared absorbing plate of the present application, in order to realize appropriate optical properties (for example, improved transmittance for light in the visible light region and maximum absorptance for light in the near-infrared region, etc.), the first light absorbing layer and the second light absorbing layer are configured as independent layers, and are designed so that the first dye of the first light absorbing layer and the second dye of the second light absorbing layer are not mixed, but their arrangement can be adjusted as appropriate.

[0057] In the above description, the first light absorbing layer and the second light absorbing layer being present independently of each other or being individually configured may mean that the components constituting the first light absorbing layer and the second light absorbing layer, specifically the first dye and the second dye, have a structure in which they are arranged so as not to mix with each other.

[0058] There are various known methods for disposing the first and second light absorbing layers separately. For example, in the near-infrared absorbing plate of the present application, the first light absorbing layer may be disposed on one side of the glass substrate, and the second light absorbing layer may be disposed on the other side of the glass substrate, so that the first and second light absorbing layers are disposed separately. That is, the first light absorbing layer (second light absorbing layer) may be disposed on the opposite side of the glass substrate from the second light absorbing layer (first light absorbing layer).

[0059] In the near-infrared absorbing plate of the present application, the first light absorbing layer and the second light absorbing layer may be laminated on one surface of a glass substrate. Specifically, the near-infrared absorbing plate of the present application may include a glass substrate, the first light absorbing layer, and the second light absorbing layer, in that order, or a glass substrate, the second light absorbing layer, and the first light absorbing layer, in that order.

[0060] Such a stacked structure is shown in Figures 1 and 2. The near-infrared absorbing plate of the present application may have a structure in which the first light absorbing layer 200, the glass substrate 100, and the second light absorbing layer 300 are present in this order (see Figure 1), or may have a structure in which the second light absorbing layer 300, the glass substrate 100, and the first light absorbing layer 200 are present in this order (see Figure 2).

[0061] As described above, the first light absorbing layer and the second light absorbing layer may be laminated on one surface of the glass substrate. The near-infrared absorbing plate may have a structure in which, for example, a glass substrate 100, a first light absorbing layer 200, and a second light absorbing layer 300 are present in the order mentioned (see FIG. 3), or a structure in which a glass substrate 100, a second light absorbing layer 300, and a first light absorbing layer 200 are present in the order mentioned (see FIG. 3). Preferably, the near-infrared absorbing plate has a structure including a glass substrate 100, a first light absorbing layer 200, and a second light absorbing layer 300 in the order mentioned (see FIG. 3).

[0062] On the other hand, since mixing of the first dye and the second dye may deteriorate the optical properties of the light absorbing layer, when such a stacked structure (glass substrate / second light absorbing layer / first light absorbing layer or glass substrate / first light absorbing layer / second light absorbing layer) is used, it is necessary to configure the first light absorbing layer and the second light absorbing layer to be clearly separated. For example, the first and second light absorbing layers can be formed separately and then stacked, or a separate separation layer 400 can be introduced between the first and second light absorbing layers to separate the first and second light absorbing layers (see FIG. 4).

[0063] The separation layer refers to a known functional layer that prevents mixing between the components of the first light absorbing layer and the second light absorbing layer. For example, the separation layer may be a known barrier film, or may be formed of a known adhesive. In the present application, an adhesive layer that can adhere the first light absorbing layer and the second light absorbing layer is used as the separation layer. In the above description, the term "adhesion" may refer to the phenomenon in which two substances come into contact and are bonded by physical and / or chemical bonding forces, as is well known, and "adhesive" may refer to a known chemical material that is provided so that the adhesive and the surface of the adherend are bonded by interfacial bonding forces.

[0064] The adhesive layer may generally be formed by curing or crosslinking an adhesive composition containing an adhesive resin or the like. The type of resin forming the adhesive layer is not particularly limited and may be freely selected from known adhesive resins as long as it ensures appropriate adhesion between the first light absorbing layer and the second light absorbing layer. For example, the resin forming the adhesive layer may be one or more of cyclic olefin resins, polyacrylate resins, polyisocyanate resins, polyimide resins, polyetherimide resins, polyamideimide resins, acrylic resins, polycarbonate resins, and polyethylene naphthalate resins.

[0065] In the above description, the thickness of the separation layer (e.g., an adhesive layer or a bonding agent layer) may also be adjusted appropriately in order to prevent mixing of the first dye in the first light absorbing layer and the second dye in the second light absorbing layer.

[0066] The thickness of each of the light absorbing layers is not particularly limited and can be appropriately adjusted within a range that allows the average thickness of the near-infrared absorbing plate described below to be formed. The thickness of each of the first light absorbing layer and the second light absorbing layer can be, for example, in the range of 0.25 μm to 10 μm. As another example, the thickness can be 0.5 μm or more and 5 μm or less. The thickness of the first light absorbing layer and the thickness of the second light absorbing layer can be the same or different.

[0067] In this application, when the thickness of any member is not constant, the thickness may refer to the maximum thickness, the minimum thickness, or the average thickness of the maximum and minimum thicknesses of the member.

[0068] The method for forming the light absorbing layer is not particularly limited. For example, the light absorbing layer may be prepared by curing a composition for forming a light absorbing layer. The curing method is not particularly limited, and known curing methods, such as thermal curing, photocuring, or a dual curing method using heat and light, may be used. That is, the light absorbing layer may include a cured product of the composition for forming a light absorbing layer.

[0069] The first light-absorbing layer-forming composition and the second light-absorbing layer-forming composition may contain a dye and a solvent. Specifically, the first light-absorbing layer-forming composition may contain at least the first dye and a first solvent. The second light-absorbing layer-forming composition may contain at least the second dye and a second solvent.

[0070] As described above, particles are present in the first light absorbing layer, and the particles may be particles of the first dye, so it is preferable that the first dye applied to the composition for forming the first light absorbing layer has low solubility in the first solvent, i.e., solubility below a specific value. In the second light absorbing layer, the second dye dissolves during the manufacturing process and can color the binder resin, so it is preferable that the second dye has high solubility in the second solvent, i.e., solubility above a specific value.

[0071] Solubility refers to the ratio (g / L) of the mass of solute dissolved in a unit volume (L) of solvent. The solubility is measured at room temperature.

[0072] "Room temperature" means a temperature that is not particularly heated or cooled, and may be, for example, a temperature in the range of 15°C or higher and 30°C or lower, or may mean any one temperature in the range of 20°C or higher and 25°C or lower, or a temperature of about 23°C.

[0073] The first dye may have a solubility of 15 g / L or less in the first solvent. For example, the solubility may be 0 g / L or more, 0.001 g / L or more, 0.01 g / L or more, or 0.1 g / L or more, and may be 14 g / L or less, 13 g / L or less, 12 g / L or less, 11 g / L or less, 10 g / L or less, 9 g / L or less, 8 g / L or less, 7 g / L or less, 6 g / L or less, 5 g / L or less, 4 g / L or less, 3 g / L or less, 2 g / L or less, or 1 g / L or less. A solubility of 0 g / L may mean that the solute is completely insoluble in the solvent. In the first light-absorbing layer, the first dye is dispersed without dissolving. To improve dispersibility, it is recommended to incorporate an appropriate amount of a commercially available dispersant. The type of dispersant is not particularly limited, and can be appropriately selected from commercially available dispersants that can improve the visible light transmittance and near-infrared absorptance of the light-absorbing layer and ensure appropriate dispersibility of the first dye.

[0074] The second dye may have a solubility in the second solvent of more than 15 g / L. The upper limit of the solubility of the second dye in the second solvent is not limited, as long as the second dye is soluble in the second solvent.

[0075] The types of the first and second solvents are not particularly limited, and can be freely selected from known solvents, specifically organic solvents, as long as they can satisfy the solubility of the first and second dyes, respectively. Specifically, for the first light-absorbing layer-forming composition and the second light-absorbing layer-forming composition, the first and second solvents can be methyl isobutyl ketone, propylene glycol methyl ether acetate or diethylene glycol monoethyl ether 3-methoxybutanol, ethylene glycol monobutyl ether acetate, 4-hydroxy-4-methyl-2-pentanone, γ-butyrolactone, cyclohexanone, toluene, pyridone, etc.

[0076] The first and second light-absorbing layer-forming compositions are prepared and cured independently to obtain the first and second light-absorbing layers. The near-infrared absorbing plate of the present application can be obtained by arranging the first and second light-absorbing layers in the aforementioned order. The light-absorbing layer-forming composition used in the present application contains a binder resin, a dye, and a solvent. The light-absorbing layer is produced by curing the composition. However, since the solvent typically evaporates during the curing process, the light-absorbing layer typically does not contain a solvent. That is, the light-absorbing layer contains the binder resin and dye as the majority of its components, and contains little or no solvent, or if it does contain any, it contains only a very small amount.

[0077] The ratio of the first dye to the second dye is not particularly limited. For example, when the composition contains a binder resin, the ratio of the first dye to the second dye may be in the range of 0.01 to 10 parts by weight, 0.01 to 8 parts by weight, or 0.01 to 5 parts by weight, based on 100 parts by weight of the binder resin. The ratio of the first dye to the second dye may be the ratio in the first light-absorbing layer and the second light-absorbing layer, respectively, and may also refer to the ratio in the composition for forming the first light-absorbing layer and the composition for forming the second light-absorbing layer.

[0078] To ensure that the first light absorbing layer and / or the second light absorbing layer have an additional absorption maximum other than the absorption maximum of the first dye and / or the second dye, the first light absorbing layer and / or the second light absorbing layer may further include a specific dye (a dye other than the first dye and the second dye). In this case, the ratio of the specific dye may be in the range of 0.01 to 5 parts by weight per 100 parts by weight of the binder used in the composition forming the light absorbing layer. When a single type of dye is further included, the ratio refers to the ratio of that single dye. When a mixture of multiple dyes is further included, the ratio may refer to the ratio of each of the dyes.

[0079] The type of specific dye that can be further included is not particularly limited. The additional dye can be one or more of light absorbers in the ultraviolet region, dyes with an absorption maximum in the infrared region, pigments, or metal complex compounds. Specific examples of the additional dye include indoles, oxazoles, merocyanines, cyanines, naphthalimides, oxadiazoles, oxazines, oxalidines, naphthalic acids, styryls, anthracenes, cyclic carbonyls, triazoles, phthalocyanines, naphthalocyanines, porphyrins, benzoporphyrins, squaryliums, anthraquinones, croconiums, and dithiol metal complex compounds. The specific dye can be used alone in the first or second light-absorbing layer, or, in some cases, in a mixture of two or more types.

[0080] The near-infrared absorbing plate of the present application includes a glass substrate, which is applied to ensure appropriate mechanical properties such as strength of the near-infrared absorbing plate.

[0081] The thickness of the glass substrate may be appropriately adjusted to ensure appropriate mechanical properties of the near-infrared absorbing plate. The thickness of the glass substrate may be in the range of 0.07 mm to 0.3 mm. As described above, the thickness may refer to the maximum thickness, minimum thickness, or average thickness of the maximum and minimum thicknesses of the glass substrate. As another example, the thickness may be in the range of 0.07 mm to 0.2 mm.

[0082] In order to ensure improved mechanical properties of the near-infrared absorbing plate, a tempered glass substrate can be used as the glass substrate.

[0083] The type of glass substrate that can be used as the tempered glass substrate is not particularly limited, and physically tempered glass or chemically tempered glass can be used, and preferably chemically tempered glass can be used.

[0084] The tempered glass substrate may include a first compressive stress layer present on a first main surface of the glass substrate and a second compressive stress layer present on a second main surface opposite the first main surface. By using a glass substrate tempered through a compressive stress layer in this manner, the near-infrared absorbing plate of the present application may have improved strength. Furthermore, an imaging device incorporating an optical device having the near-infrared absorbing plate may ensure high weather resistance.

[0085] The method for forming the compressive stress layer is not particularly limited, and known physical or chemical strengthening methods for glass substrates may be used. However, in order to minimize damage to the glass substrate, the compressive stress layer may be formed by chemical strengthening. The compressive stress layer may be formed by Na + In conventional glass substrates containing ions, the Na + Ion is K + In this process, the K ions are substituted from one side of the glass substrate. + The layer up to the ion-substituted site is defined as a compressive stress layer. The compressive stress layer is generally known as a DOL (Depth of Compressive Stress Layer). That is, the compressive stress layer is formed by replacing components within the glass substrate with other components through external treatment such as heat, and therefore can exist toward the interior of the glass substrate (this is the same meaning as when the compressive stress layer is referred to as a DOL).

[0086] The thickness of each of the first compressive stress layer and the second compressive stress layer included in the tempered glass substrate may be 30% or less of the total thickness of the near-infrared absorbing plate.

[0087] The thickness of each of the first compressive stress layer and the second compressive stress layer may be in the range of 1 μm to 30 μm. As another example, the thickness may be in the range of 5 μm to 30 μm, 10 μm to 20 μm, or 15 μm to 20 μm. By using a tempered glass substrate including a compressive stress layer formed with a thickness within the above range, the near-infrared absorbing plate of the present application can have excellent strength despite its thinness.

[0088] As described above, when the thickness of the compressive stress layer is not constant, the thickness of the compressive stress layer may refer to the maximum thickness, the minimum thickness, or the average thickness of the maximum and minimum thicknesses of the compressive stress layer.

[0089] The compressive stress of the glass substrate can also be further adjusted. For example, the substrate may have a bending strength of 360 MPa or more when the three-point bending strength is measured according to the ASTM D790 measurement standard. As another example, the three-point bending strength may be 370 MPa or more, 380 MPa or more, 390 MPa or more, 400 MPa or more, 410 MPa or more, 420 MPa or more, 430 MPa or more, 440 MPa or more, 450 MPa or more, 460 MPa or more, 470 MPa or more, 480 MPa or more, 490 MPa or more, or 500 MPa or more.

[0090] The near-infrared absorbing plate of the present application may further include a known functional layer. For example, the substrate and the light absorbing layer may be bonded together via the above-mentioned adhesive layer.

[0091] Furthermore, the near-infrared absorbing plate of the present application may have a thin thickness. Therefore, the thickness of the near-infrared absorbing plate may be, for example, 0.3 mm or less, 0.23 mm or less, or 0.22 mm or less. As another example, the thickness may be in the range of 0.08 mm to 0.15 mm. As described above, when the thickness of the near-infrared absorbing plate is not constant, the thickness may be the maximum thickness, the minimum thickness, or the average thickness of the maximum and minimum thicknesses.

[0092] In another embodiment, the present application relates to an optical device. Specifically, the optical device may be an optical filter, more specifically, a near-infrared blocking filter. The optical device includes the near-infrared absorbing plate and a selective wavelength reflecting layer disposed on one or both sides of the near-infrared absorbing plate.

[0093] In the present application, the term "selective wavelength reflective layer" may refer to a functional optical component formed to reflect light of a specific wavelength and transmit light of a different wavelength without reflecting it. Specifically, the selective wavelength reflective layer used in the optical device of the present application may refer to a functional layer designed to reflect light having a wavelength of 650 nm or more, for example, a wavelength in the range of 700 nm to 1,200 nm, among light incident on the optical device, thereby blocking light within this wavelength range from passing through the optical device and / or preventing light having a wavelength in the range of 400 nm to 650 nm from being reflected, i.e., transmitting light within this wavelength range. In other words, the selective wavelength reflective layer may function as a near-infrared reflective layer that reflects near-infrared light and / or a (visible light) anti-reflection layer that prevents visible light from being reflected.

[0094] The selective wavelength reflective layer may include a dielectric multilayer film, that is, the optical device of the present application may be formed by forming a dielectric multilayer film on one or both surfaces of the near-infrared absorbing plate.

[0095] The dielectric multilayer film may have a structure in which dielectric layers with different refractive indices are alternately formed. For example, the dielectric multilayer film may be formed by repeating a low refractive index-high refractive index-low refractive index dielectric layer sequence, or a high refractive index-low refractive index-high refractive index dielectric layer sequence. The deviation in refractive index between the high refractive index dielectric layer and the low refractive index dielectric layer may be 0.2 or more, 0.3 or more, 0.4 or more, or 0.5 or more, and may be 1.5 or less, or 1.0 or less. The reference wavelength for the refractive index may be 550 nm.

[0096] The refractive index of the low refractive index dielectric film may be in the range of 1.4 to 1.6. Low refractive index dielectric films having such a refractive index may include silicon dioxide, lanthanum fluoride, magnesium fluoride, sodium aluminum hexafluoride, etc. The reference wavelength for the refractive index may be 550 nm.

[0097] The refractive index of the high refractive index dielectric film may be in the range of 2.1 to 2.5. High refractive index dielectric films having such a refractive index may include titanium dioxide, aluminum oxide, zirconium oxide, tantalum pentoxide, niobium pentoxide, lanthanum oxide, yttrium oxide, zinc oxide, zinc sulfide, indium oxide, etc., and the indium oxide may include titanium dioxide, tin oxide, cerium oxide, etc. The reference wavelength for the refractive index may be 550 nm.

[0098] In the optical device, the high-refractive index dielectric film and the low-refractive index dielectric film may be formed separately from each other. For example, a high-refractive index dielectric film or a low-refractive index dielectric film may be present on one surface of the near-infrared absorbing plate, and a low-refractive index dielectric film or a high-refractive index dielectric film may be present on the other surface. For another example, a high-refractive index dielectric film and a low-refractive index dielectric film may be present on one surface of the near-infrared absorbing plate in the above order or the reverse order, and the aforementioned separation layer may be present between the high-refractive index dielectric film and the low-refractive index dielectric film.

[0099] In another embodiment, the present application relates to an imaging device including the optical device (specifically, an optical filter such as a near-infrared blocking filter) or the near-infrared absorbing plate.

[0100] The imaging device may include any known essential components for achieving its function, for example, the imaging device may further include a lens and an image sensor in addition to the optical device or the near-infrared absorbing plate. [Effects of the Invention]

[0101] The near-infrared absorbing plate of the present application can prevent a decrease in visible light transmittance and near-infrared absorptance due to interactions between a plurality of organic substances that constitute the light absorbing layer.

[0102] The near-infrared absorbing plate of the present application also has the advantage that it can be made thinner.

[0103] The near-infrared absorbing plate of the present application also has the advantage of being excellent in mechanical properties such as strength and heat resistance. [Brief explanation of the drawings]

[0104] [Figure 1] 1 shows a laminated structure of a near-infrared absorbing plate according to an embodiment of the present application. [Figure 2] 1 shows a laminated structure of a near-infrared absorbing plate according to an embodiment of the present application. [Figure 3] 1 shows a laminated structure of a near-infrared absorbing plate according to an embodiment of the present application. [Figure 4] 1 shows a laminated structure of a near-infrared absorbing plate according to an embodiment of the present application. [Figure 5] 1 shows transmittance spectra of Production Examples 1 to 3 of the present application. [Figure 6] 1 shows transmittance spectra of Production Examples 4 and 5. [Figure 7] 1 shows transmittance spectra of Production Examples 6 to 13. [Figure 8] 1 shows transmittance spectra of Production Examples 6 to 13. [Figure 9] 1 shows transmittance spectra of Example 1, Example 3, and Comparative Example 1. [Figure 10] 1 shows transmittance spectra of Examples 1 to 2 and Comparative Examples 2 to 4. DETAILED DESCRIPTION OF THE INVENTION

[0105] The present application will be described in detail below through examples and comparative examples, but the scope of the present application is not limited to the following examples and comparative examples.

[0106] <Measurement of light transmittance> The transmittance of each wavelength of the resultant products in Preparation Examples, Examples, and Comparative Examples was measured using a spectrophotometer (Perkin Elmer Lambda 750 spectrophotometer) according to the equipment manual.

[0107] <Haze measurement> The haze of the results of Production Examples 6 to 13 was measured for light with a wavelength of 550 nm using a haze meter (NDH-200N manufactured by NIPPON DENSHOKU Co., Ltd.) according to the equipment manual and the JIS K 7136 test method.

[0108] <Particle size analysis> The average particle size of particles in the Production Examples, Examples, and Comparative Examples was calculated as the median value (D50) of the particle size distribution measured using a nano SAQLA (Otsuka Electronics Co., Ltd.) device.

[0109] <Applicable products> Information on the products mainly used in the following Production Examples, Comparative Examples and Examples is as follows: -Aluminosilicate glass: AS-87, Schott -Polyacrylate binder resin: Sumipex, Sumitomo - First dye: IRA 1032, Exciton, diimonium compound - Second dye: IRA 705, Exciton, squarylium-based compound -Third dye: ADA3232, HW. SANDS, a compound having an absorption maximum in the wavelength range of 300 nm to 400 nm -Fourth dye: S0094, Few Chemicals, a cyanine compound with an absorption maximum in the range of 800 nm to 850 nm - Dispersant: Disperbyk 110, BYK

[0110] Manufacturing Example 1: Formation of light absorbing layer A test piece of the light absorbing layer was prepared in the following manner.

[0111] (1) Aluminosilicate glass is washed with an alkaline aqueous solution to prepare a glass substrate having a thickness of approximately 0.1 mm. (2) The glass substrate is immersed in a potassium nitrate solution and heat-treated with the solution at a temperature of 390°C for approximately 40 minutes to produce a tempered glass substrate having first and second compressive stress layers, each having a thickness of approximately 17.5 μm, formed on both sides of the glass substrate. (3) A composition for forming a light absorbing layer is prepared by mixing 3 parts by weight of the first dye and approximately 500 parts by weight of methyl isobutyl ketone with 100 parts by weight of a polyacrylate binder. (4) The composition for forming a light absorbing layer is spin-coated onto one surface of the tempered glass substrate, and then thermally cured at 140° C. for about 2 hours to form a light absorbing layer having a thickness of approximately 3 μm.

[0112] Manufacturing Example 2: Formation of light absorbing layer A light absorbing layer was formed in the same manner as in Preparation Example 1, except that in step (3), 5 parts by weight of the second dye was used instead of the first dye to prepare a composition for forming a light absorbing layer.

[0113] Manufacturing Example 3: Formation of light absorbing layer In step (3), a light absorbing layer was formed in the same manner as in Preparation Example 1, except that 5 parts by weight of the second dye, 3 parts by weight of the third dye, and 0.1 parts by weight of the fourth dye were mixed instead of the first dye.

[0114] The transmittance spectra measured for the test pieces of the light-absorbing layers produced in Production Examples 1 to 3 are shown in Figure 5. As can be seen from Figure 5, the first dye has an absorption maximum in the wavelength range of 850 nm to 1,200 nm (Production Example 1), the second dye has an absorption maximum in the wavelength range of 650 nm to 750 nm (Production Example 2), and it can be seen that when the second dye and a specific dye are further blended, the visible light transmittance and near-infrared absorptance do not decrease even in the wavelength ranges of 300 nm to 400 nm and 800 nm to 850 nm, and the blended dyes can further enhance the absorption maximum (Production Example 3).

[0115] Manufacturing Example 4: Formation of light absorbing layer In step (3), 100 parts by weight of polyacrylate binder was mixed with 5 parts by weight of the first dye and approximately 500 parts by weight of methyl isobutyl ketone, and 0.2 parts by weight of a dispersant was added. The mixture was dispersed in a disperser using 0.5 mm zirconia beads for approximately 6 hours, and the presence of particles with an appropriate size was confirmed using a particle size analyzer. The mixture was then filtered to prepare a composition for forming a light-absorbing layer. A light-absorbing layer was formed in the same manner as in Preparation Example 1. In the light-absorbing layer of Preparation Example 4, the diimonium-based dye (first dye) was present in the form of particles.

[0116] Manufacturing Example 5: Formation of light absorbing layer A light absorbing layer was formed in the same manner as in Preparation Example 4, except that in step (3), cyclohexanone was mixed instead of methyl isobutyl ketone to prepare a composition for forming a light absorbing layer in which the first dye was dissolved. In the light absorbing layer of Preparation Example 5, the first dye was dissolved to color the binder resin.

[0117] The transmittance spectra measured for the light absorbing layers of Production Examples 4 and 5 are shown in Figure 6, and the transmittance in the main wavelength ranges is shown in Table 1 below. It can be seen that the transmittance in the visible light range (450 nm to 700 nm) and the absorbance in the near-infrared range (approximately 1,050 nm) are higher for the light absorbing layer of Production Example 4 than for the light absorbing layer of Production Example 5. This is confirmed to be due to the first dye dissolving and causing deterioration in the light absorbing layer containing it.

[0118] This shows that when the first dye used in the present application is not dissolved but dispersed in the light absorbing layer and exists in the form of particles, a light absorbing layer having high visible light transmittance and infrared absorbance at the same time can be formed.

[0119] [Table 1]

[0120] Manufacturing Example 6: Formation of light absorbing layer In step (3), the type of solvent and dispersion conditions were adjusted as shown in Table 2 below, and the presence of particles with an average particle size of approximately 0.1 μm was confirmed using a particle size analyzer, followed by filtration. The light absorbing layer was formed in the same manner as in Preparation Example 4.

[0121] Production Examples 7 to 13: Formation of light absorbing layer A light-absorbing layer was formed in the same manner as in Preparation Example 6, except that the average particle size of the first dye present in particulate form in the light-absorbing layer was adjusted as shown in Table 2 below. In this case, the average diameter of the diimonium-based dye particles was achieved by adjusting the type of solvent used in forming the light-absorbing layer and adjusting the rotation speed (RPM) and time during the dispersion process using a mechanical dispersion device (Netzsch Wet, Grinding, Dispersing, Bead Mill) as shown in Table 2 below.

[0122] The transmittance spectra of the light absorbing layers of Production Examples 6 to 13 are shown in FIGS. 7 and 8, and the dispersion conditions, transmittance at main wavelengths, and haze for each Production Example are shown in Table 2 below.

[0123] [Table 2]

[0124] 7 and 8, it can be seen that the light absorbing layers formed in Production Examples 6 and 7 have higher transmittance in the visible light region and higher absorbance in the infrared region than the light absorbing layers formed in Production Examples 9 to 13.

[0125] In an imaging device to which a near-infrared absorbing plate is applied, the near-infrared absorbing plate must have high transmittance in the visible light region and high absorptance in the near-infrared region, and at the same time, must have optical characteristics such as a haze of less than 0.3% in the normal visible light region (e.g., light with a wavelength of about 550 nm) in order to ensure image quality.

[0126] Therefore, in light of these conditions, it can be seen that the light absorbing layers prepared under the conditions of Preparation Examples 6 and 7 have optical properties suitable for imaging devices, but the light absorbing layers prepared under the conditions of Preparation Examples 8 to 13 are not suitable for imaging devices. Therefore, it can be seen that in the light absorbing layer applied to the near-infrared absorbing plate of the present application, a specific dye, for example, a dye having an absorption maximum such as the first dye, must be dispersed in the form of particles, and the size of the particles must be within the range specified in the present application.

[0127] Example 1. Near-infrared absorbing plate The near-infrared absorbing plate was manufactured in the following order.

[0128] (1) Composition for forming the first light-absorbing layer To 100 parts by weight of a polyacrylate binder, 1 part by weight of a first dye, 500 parts by weight of methyl isobutyl ketone, and 0.2 parts by weight of a dispersant are added, and then the mixture is dispersed in a dispersing device using 0.5 mm zirconia beads for approximately 6 hours. After confirming with a particle size analyzer that the particles have an average particle size of approximately 0.1 μm, the mixture is filtered to produce a composition for forming a first light-absorbing layer.

[0129] (2) Composition for forming second light-absorbing layer 100 parts by weight of a polyacrylate binder is mixed with 5 parts by weight of a second dye and 500 parts by weight of methyl isobutyl ketone to prepare a composition for forming a second light-absorbing layer in which the second dye is dissolved.

[0130] (3) Adhesive composition An adhesive composition is prepared by mixing a commercially available polyacrylate resin and a polyisocyanate resin in a weight ratio of 99:1.

[0131] (4) Strengthening of the glass substrate 1) Aluminosilicate glass is washed with an alkaline aqueous solution to prepare a glass substrate having a thickness of approximately 0.1 mm. 2) The glass substrate is immersed in a potassium nitrate solution and heat-treated in the solution at a temperature of 390°C for about 40 minutes to produce a glass substrate having first and second compressive stress layers, each having a thickness of about 17.5 μm, formed on both sides of the glass substrate.

[0132] (5) Near-infrared absorbing plate (structure: glass substrate / first light absorbing layer / adhesive layer / second light absorbing layer) The composition for forming the first light absorbing layer is spin-coated onto one surface of the glass substrate and heat-treated at a temperature of about 140° C. for about 2 hours to form a second light absorbing layer having a thickness of about 3 μm.

[0133] Next, the adhesive composition is spin-coated onto the first light-absorbing layer at a speed of 1,000 rpm for 15 seconds, and heat-treated at a temperature of about 130° C. for about 15 minutes to form an adhesive layer with a thickness of about 0.4 μm.

[0134] Next, the composition for forming a second light absorbing layer is spin-coated onto the adhesive layer and heat-treated at a temperature of 140° C. for about 3 hours to form a first light absorbing layer having a thickness of about 3 μm.

[0135] Example 2. Near-infrared absorbing plate A near-infrared absorbing plate was prepared in the same manner as in Example 1, except that the solvent and dispersion conditions were adjusted as in Preparation Example 7 in Table 2 above to prepare a first light absorbing layer in which the first dye was dispersed in the form of particles having an average particle size of approximately 0.5 μm.

[0136] Example 3. Near-infrared absorbing plate A near-infrared absorbing plate was manufactured in the same manner as in Example 1, except that a composition for forming a second light absorbing layer was manufactured by blending 1 part by weight of a second dye, 3 parts by weight of a third dye, 0.1 parts by weight of a fourth dye, and 500 parts by weight of methyl isobutyl ketone with 100 parts by weight of a polyacrylate binder.

[0137] Comparative Example 1: Near-infrared absorbing plate (1) Light-absorbing layer-forming composition A composition for forming a light-absorbing layer is prepared by blending 100 parts by weight of a polyacrylate binder with 1 part by weight of a first dye, 5 parts by weight of a second dye, and 500 parts by weight of methyl isobutyl ketone, adding 0.2 parts by weight of a dispersant, and dispersing the mixture for approximately 6 hours using 0.5 mm zirconia beads in a dispersing device. After confirming with a particle size analyzer that the particles of the first dye have an average particle size of about 0.1 μm and the second dye is dissolved in the mixture, a composition for forming a light-absorbing layer is prepared.

[0138] (2) Strengthening the glass substrate The glass substrate is strengthened in the same manner as described in Example 1.

[0139] (3) Near-infrared absorbing plate The composition for forming a light absorbing layer is spin-coated onto one surface of the tempered glass substrate and heat-treated at a temperature of about 140° C. for about 2 hours to form a light absorbing layer with a thickness of about 3 μm.

[0140] Comparative Example 2: Near-infrared absorbing plate A near-infrared absorbing plate was prepared in the same manner as in Example 1, except that the solvent and dispersion conditions were adjusted as in Preparation Example 8 in Table 2 above to prepare a first light absorbing layer in which the first dye was dispersed in the form of particles having an average particle size of approximately 1.1 μm.

[0141] Comparative Example 3: Near-infrared absorbing plate A near-infrared absorbing plate was prepared in the same manner as in Example 1, except that the solvent and dispersion conditions were adjusted as in Preparation Example 12 in Table 2 to prepare a first light absorbing layer in which the first dye was dispersed in the form of particles having an average particle size of about 3.0 μm.

[0142] Comparative Example 4: Near-infrared absorbing plate A near-infrared absorbing plate was prepared in the same manner as in Example 1, except that the solvent and dispersion conditions were adjusted as in Preparation Example 13 in Table 2 to prepare a first light absorbing layer in which the first dye was dispersed in the form of particles having an average particle size of approximately 5.0 μm.

[0143] Comparative Example 5: Near-infrared absorbing plate A near-infrared absorbing plate was manufactured in the same manner as in Example 1, except that the composition for forming the first light absorbing layer was prepared by mixing 5 parts by weight of the first dye and 500 parts by weight of cyclohexanone with 100 parts by weight of a polyacrylate binder, thereby dissolving the first dye.

[0144] The transmittance spectra of the near-infrared absorbing plates of Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Figs. 9 and 10, and the structural features of the near-infrared absorbing plates of the Examples and Comparative Examples and the transmittance in the main wavelength bands are summarized in Table 3 below.

[0145] [Table 3]

[0146] 9 and Table 4, it can be seen that the visible light transmittance and near-infrared absorptance of the near-infrared absorbing plates of Examples 1 to 3 were improved compared to the near-infrared absorbing plate of Comparative Example 1. This indicates that near-infrared absorbing plates having multiple distinct light absorbing layers as defined in the present application have improved optical properties compared to near-infrared absorbing plates having a single light absorbing layer. This also confirms that near-infrared absorbing plates having the structure defined in the present application have improved heat resistance. This is presumably due to the absence of interactions between organic substances, such as multiple dyes, applied to the light absorbing layer.

[0147] 10 and Table 4, it can be seen that the transmittance spectrum of FIG. 10 and the transmittance spectra shown in FIGS. 7 and 8 show similar trends based on the average particle size of the first dye present in particulate form in the first light absorbing layer.

[0148] It was confirmed that in the near-infrared absorbing plate in which light absorbing layers having different optical properties are present separately from each other as in Comparative Example 5, but none of the light absorbing layers has a particulate dye (e.g., first dye) dispersed therein, the infrared absorptivity decreases, which is understood to be due to the deterioration caused by the first dye in particular.

[0149] That is, in the near-infrared absorbing plate of the present application, even if light absorbing layers to which dyes having different optical properties, for example, different absorption maxima are applied, are separately present, it can be confirmed that the plate can have excellent visible light transmittance and excellent near-infrared absorptance only when a specific dye is dispersed in the light absorbing layer in the form of particles and the particle size is within the range specified in the present application.

[0150] Therefore, it can be confirmed that when any one specific dye contained in the light absorbing layer of the near infrared absorbing plate is contained in a dissolved form, the optical properties are deteriorated due to the interaction between the dyes.

[0151] Furthermore, even if the specific dye applied to the light absorbing layer is dispersed in a particulate form, whether the light absorbing layer is formed as a single layer or is divided into two layers separated from each other, if the size of the specific dye in particulate form is outside the range specified in the present application, it can be seen that the infrared absorption ability and visible light transmittance of the near-infrared absorbing plate will be reduced.

[0152] Meanwhile, the near-infrared absorbing plate of the present application has a light absorbing layer composed of multiple layers, but each light absorbing layer is separated according to the characteristics of the dye applied thereto, thereby ensuring mutual stability between the dyes and / or between the light absorbing layers. Furthermore, it has been confirmed that the near-infrared absorbing plate of the present application has significantly improved visible light transmittance and infrared absorptance by applying a dye having specific optical properties dispersed in the form of particles in any one of the multiple light absorbing layers.

[0153] Furthermore, it can be confirmed that the tendency of the results of evaluating the optical properties of the light absorbing layer containing the first dye is substantially the same as the tendency of the results of evaluating the optical properties of the near-infrared absorbing plate manufactured from the light absorbing layer. From this, it can be seen that the optical properties of the near-infrared absorbing plate are mainly determined by the optical properties of the first light absorbing layer containing the first dye.

[0154] As described above, the near-infrared absorbing plate of the present application has high visible light transmittance and near-infrared absorptance, and has low haze in the visible light region, for example, a haze of less than 3%, so that when the absorbing plate is applied to an imaging element, it can be expected that an image of excellent quality will be obtained.

[0155] [Cross-reference to related applications] This application claims the benefit of the filing date of Korean Patent Application No. 10-2019-0173214, filed with the Korean Intellectual Property Office on December 23, 2019, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0156] 100 Glass substrate 200 First light absorbing layer 300 Second light absorbing layer 400 separation layer

Claims

1. a glass substrate; and a first light absorbing layer and a second light absorbing layer that are separated from each other; the first light absorbing layer has an absorption maximum at any one wavelength within a range of 850 nm or more and 1,200 nm or less, the second light absorbing layer has an absorption maximum at any one wavelength within a range of 650 nm or more and 750 nm or less, the first light absorbing layer contains particles having an average particle size of 1 μm or less, the first light absorbing layer includes a first binder resin and a first dye dispersed in the first binder resin, and particles included in the first light absorbing layer are particles of the first dye; the first dye is a diimonium-based compound, the second light absorbing layer includes a second binder resin and a second dye that colors the second binder resin; The second dye includes a compound represented by the following Chemical Formula 2: 【Chemistry 2】

2. The near-infrared absorbing plate according to claim 1 , wherein the first dye comprises a compound represented by the following Chemical Formula 1: 【Chemical 1】 In Chemical Formula 1, R1 to R8 are each independently a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, an alkenyl group, or an alkynyl group; R9 to R11 are each independently a hydrogen atom, a halogen group, an amino group, a cyano group, a nitro group, a carboxy group, an alkyl group, or an alkoxy group; and X is an anion.

3. The near-infrared absorbing plate according to claim 1 , wherein the first light absorbing layer is present on an opposite side of the second light absorbing layer with respect to the glass substrate.

4. 2. The near-infrared absorbing plate according to claim 1, comprising the glass substrate, the first light absorbing layer, and the second light absorbing layer in this order, or the glass substrate, the second light absorbing layer, and the first light absorbing layer in this order.

5. The near-infrared absorbing plate according to claim 4 , further comprising a separation layer present between the first light absorbing layer and the second light absorbing layer.

6. 2. The near-infrared absorbing plate according to claim 1, wherein the glass substrate includes a first compressive stress layer present on a first main surface of the glass substrate, and a second compressive stress layer present on a second main surface that is a main surface opposite to the first main surface.

7. 7. The near-infrared absorbing plate according to claim 6, wherein the glass substrate has a bending strength of 360 MPa or more when a three-point bending strength is measured according to ASTM D790.

8. 2. The near-infrared absorbing plate according to claim 1, wherein the thickness of the glass substrate is in the range of 0.07 mm to 0.3 mm.

9. An optical device comprising the near-infrared absorbing plate according to claim 1 and a selective wavelength reflecting layer present on one or both surfaces of the near-infrared absorbing plate.

10. The optical device according to claim 9 , wherein the selective wavelength reflective layer includes a dielectric multilayer film.

11. 11. The optical device according to claim 10, wherein the dielectric multilayer film is formed by alternately stacking dielectric films having a refractive index in the range of 1.4 to 1.6 and dielectric films having a refractive index in the range of 2.1 to 2.5.

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