Optical elements, light-shielding paints

Abstract

To provide a shading film which does not allow occurrence of crack in lens even if the lens is composed of a base material likely to be subjected to stress and even when subjected to severe thermal shock, nor allow occurrence of bleed-out under a hot and humid environment, and which has high inner surface antireflection performance.SOLUTION: The shading film includes an aggregate of inorganic particles in d-ray refractive index of 2.0 or greater, a coloring agent, a resin and a plasticizer. An average particle diameter of the aggregate is 250 nm or less, and the plasticizer has a pour point of -50°C or below and a boiling point of 200°C to 450°C inclusive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to , blocking an optical element having an optical film and a light-shielding coating. [Background Art]

[0002] A light-shielding film is a film mainly formed on the surface of a base material such as glass or plastic that is a constituent member of an optical element. By providing the light-shielding film, internally reflected light that adversely affects an image is reduced, and flare and ghost can be prevented. Reflected light generated at the interface between a base material and a light-shielding film can be reduced by making the refractive index of the light-shielding film close to that of the base material, or by making the refractive index of the light-shielding film higher than that of the base material. However, along with the increase in the refractive index of base materials such as glass, the light-shielding film is also required to have a higher refractive index. Patent Document 1 discloses a light-shielding film containing a plasticizer, which uses titanium oxide nanoparticles to improve the refractive index of the light-shielding film. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2013-054349 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] However, in recent years, with the increase in base material configurations that are easily subjected to stress, such as bonded portions of cemented lenses, thin-walled portions of lens end surfaces, and soft glass portions, when a light-shielding film is formed on the outer peripheral portion of a base material, stress tends to be easily applied to the base material. In addition, such optical elements are often used in situations where large thermal shock is applied, such as in cold regions or under scorching heat. Therefore, it is required to reduce the stress applied to the base material by the light-shielding film. Furthermore, under high temperature and high humidity conditions, reducing the occurrence of plasticizer bleed-out but is required. This invention has been made in view of the above background technology, and provides a light-shielding film that prevents lens cracking even under severe thermal shock in a substrate configuration that is prone to stress, prevents bleed-out under high temperature and high humidity conditions, and further provides high anti-reflective performance on the inner surface. [Means for solving the problem]

[0005] This invention Optical element teeth, An optical element comprising a substrate and a light-shielding film provided on the side surface of the substrate, The aforementioned light-shielding film is It comprises an aggregate of inorganic particles with a d-line refractive index of 2.0 or higher, a coloring agent, a resin, and a plasticizer. death , The average particle size of the aggregate is 250 nm or less. The aforementioned plasticizer has a pour point of -50°C or lower and a boiling point of 200°C or higher and 450°C or lower. the law of nature, The crosslinking density of the light-shielding film is higher on surfaces other than the interface between the light-shielding film and the substrate. It is characterized by the following:

[0006] Furthermore, the light-shielding coating of the present invention is a light-shielding coating comprising an aggregate of inorganic particles with a d-line refractive index of 2.0 or higher, a colorant, a resin, and a plasticizer. The average particle size of the aggregate is 250 nm or less. The aforementioned plasticizer has a pour point of -50°C or lower and a boiling point of 200°C or higher and 450°C or lower. the law of nature, When cured, the crosslinking density at the interface with air is higher than the crosslinking density at interfaces other than the interface with air. It is characterized by the following: [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a light-shielding film, optical element, and light-shielding coating that do not cause lens cracking even under severe thermal shock, do not cause bleed-out under high temperature and high humidity conditions, and have high anti-reflective performance on the inside. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing an example of the optical element of the present invention. [Figure 2] This is a schematic cross-sectional diagram showing the interface between the light-shielding film and the lens. [Figure 3] It is a schematic diagram showing the method for measuring inner reflectance. [Figure 4] It is a schematic cross-sectional view of a test piece used for evaluating thermal shock resistance. [Figure 5] It is a schematic cross-sectional view showing an example of a cemented lens which is the optical element of the present invention. [Figure 6] It is a schematic cross-sectional view of an imaging device using the cemented lens according to the present invention. MODE FOR CARRYING OUT THE INVENTION

[0009] Preferred embodiments of the present invention will be described below.

[0010] [Role of Light-Shielding Film] A light-shielding film is a film formed mainly on the surface of a base material such as glass or plastic that is a constituent member of an optical element. Here, the base material may be a lens or a prism. It may also be other optical glass or an optical prism.

[0011] First, the role of the light-shielding film for optical elements will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the optical element of the present invention. As shown in FIG. 1, the light-shielding film 1 is formed on an outer peripheral portion outside an arbitrary optically effective surface of a lens serving as the base material 2. Note that, for convenience of description, a part of the outer peripheral portion is not provided with the light-shielding film 1 in FIG. 1, but it is preferable to form the light-shielding film 1 over the entire outer peripheral portion of the base material 2.

[0012] Here, among the light incident on the base material 2, light that does not strike the outer peripheral portion of the base material 2 (incident light 3) is transmitted as transmitted light 4. On the other hand, among the light incident on the base material 2, light that strikes the outer peripheral portion of the base material 2 (incident light 5) strikes the light-shielding film 1 provided on the outer peripheral portion of the base material 2. If the light-shielding film 1 is not formed, the light that has struck the outer peripheral portion of the base material 2 undergoes internal reflection and exits the base material 2 as internally reflected light 6 that is unrelated to an image. This internally reflected light 6 causes flare, ghosting, and the like, which are factors that degrade image quality. For this reason, it is necessary to provide the light-shielding film 1 on the outer periphery of the base material 2 for the purpose of preventing the occurrence of flare, ghosting, and the like. By providing the light-shielding film 1, the amount of internally reflected light 6 that adversely affects an image is reduced, so flare and ghosting can be prevented.

[0013] The principle by which internal reflection is reduced will be described in detail. Figure 2 is a schematic cross-sectional view showing the interface state between the light-shielding film and the base material, in which the light-shielding film is formed on the base material, and is a schematic diagram showing the traveling direction of internally reflected light. Note that Figure 2 shows a state where the light-shielding film 1 is applied to the outer peripheral surface of the base material 2. As shown in Figure 2, internal reflection mainly occurs at two interfaces: the interface between the base material 2 and the light-shielding film 1 (interface 7) and the interface between the light-shielding film 1 and air (interface 8). That is, when the incident light 5 passing through the inside of the base material 2 strikes the interface 7, the incident light 5 is split into light that reflects at this interface 7 (first reflected light 9) and light that transmits through the light-shielding film 1 (transmitted light 10). Further, the transmitted light 10 reflects at the interface 8. The reflected light at this time becomes the second reflected light 11.

[0014] Here, the first reflected light 9 can be reduced by making the refractive index of the light-shielding film 1 close to the refractive index of the base material 2, or by making the refractive index of the light-shielding film 1 higher than the refractive index of the base material 2. As the refractive index of the base material 2 increases, the light-shielding film 1 is also required to have a higher refractive index. Further, the second reflected light 11 can be reduced by absorbing the transmitted light 10. In order to efficiently absorb the transmitted light 10 into the inside of the light-shielding film 1, a coloring agent or the like is used.

[0015] [Characteristic of the present invention] To suppress internal reflections, it is preferable to have a light-shielding film with a refractive index equal to or higher than that of the lens. To significantly improve the refractive index, one method is to add a large amount of high-refractive-index inorganic nanoparticles nano-dispersed in the resin. However, because inorganic nanoparticles have a high elastic modulus, adding a large amount of inorganic nanoparticles makes the film itself hard, and there is a possibility that thermal shock will place a large stress on the lens.

[0016] To reduce stress on the lens even when subjected to thermal shock, plasticizers, which are flexible components, are added in addition to high-refractive-index inorganic fine particles. However, even with the addition of plasticizers, in lens configurations that are prone to stress, microscopic cracks may occur in the lens due to severe thermal shock. Furthermore, increasing the amount of plasticizer added to prevent microscopic cracks may cause plasticizer bleed-out under high temperature and high humidity conditions.

[0017] The inventors of this invention diligently investigated methods to achieve high thermal shock resistance, high temperature and high humidity performance, and anti-reflective properties on the inner surface, and found that it is possible to achieve all of these by adding a plasticizer with a pour point of -50°C or lower and a boiling point of 200°C to 450°C.

[0018] The plasticizer used in this invention has a low pour point of -50°C or lower, so stress does not easily accumulate even in the low-temperature range where the elastic modulus is high. Furthermore, since the boiling point of the plasticizer is between 200°C and 450°C, it is assumed that a small amount of the plasticizer evaporates from the surface during curing. Therefore, it is presumed that a large amount of resin component is present on the surface of the light-shielding film, and the crosslinking density is high, thereby suppressing plasticizer bleed-out. In addition, since a large amount of plasticizer is present at the interface between the light-shielding film and the substrate, it is presumed that the flexibility at low temperatures is high and the thermal shock resistance is high.

[0019] [Blackout paint] The light-shielding coating of the present invention comprises an aggregate of inorganic particles with a d-line refractive index of 2.0 or higher, a colorant, a resin, and a plasticizer. The material composition and manufacturing method of the light-shielding coating of the present invention are described below.

[0020] ≪Material Composition≫ (Inorganic particles) The d-line refractive index of the inorganic particles is 2.0 or higher, preferably 2.0 to 3.1, and more preferably 2.2 to 3.01. Here, the d-line refractive index is the refractive index at room temperature for the d-line (wavelength 587.56 nm). If the d-line refractive index is less than 2.0, a large amount of particles must be added to increase the refractive index of the light-shielding film, which increases the elastic modulus of the light-shielding film and deteriorates its thermal shock resistance.

[0021] In the light-shielding coating, some inorganic particles are present in aggregates (agglomerates) formed by the aggregation of primary inorganic particles. The average particle diameter of these aggregates is 250 nm or less, preferably between 2 nm and 250 nm, and more preferably between 50 nm and 200 nm. If the average particle diameter of the inorganic particle aggregates exceeds 250 nm, scattering of the light-shielding film increases, resulting in a deterioration of its appearance.

[0022] The average particle size of an aggregate of inorganic particles can be measured using a transmission electron microscope (TEM). Specifically, a cross-section of a light-shielding film is cut out, and an image is taken with the TEM. The captured image is analyzed using ImageJ to calculate the particle size distribution. To measure the particle size, the minimum evaluation screen should contain 10 or more particles (aggregates), and their average diameter is calculated.

[0023] As inorganic particles, any metal, metal oxide, metal nitride, diamond, etc., may be used as long as its d-line refractive index is 2.0 or higher. Examples of inorganic particles include red iron oxide (d-line refractive index = 3.01), magnetite (d-line refractive index = 2.42), rutile-type titanium oxide (d-line refractive index = 2.72), anatase-type titanium oxide (d-line refractive index = 2.52), zirconium oxide (d-line refractive index = 2.05), cerium oxide (d-line refractive index = 2.2), zinc oxide (d-line refractive index = 2.1), tantalum pentoxide (d-line refractive index = 2.16), tungsten oxide (d-line refractive index = 2.2), niobium pentoxide (d-line refractive index = 2.33), indium tin oxide (d-line refractive index = 2.06), chromium oxide (d-line refractive index = 2.24), diamond (d-line refractive index = 2.42), etc.

[0024] Examples of titanium dioxide include TTO-51(A) (Ishihara Sangyo), TTO-51(C) (Ishihara Sangyo), TTO-55(A) (Ishihara Sangyo), TTO-55(B) (Ishihara Sangyo), TTO-55(C) (Ishihara Sangyo), TTO-55(D) (Ishihara Sangyo), STR-100N (Sakai Chemical), STR-100A-LP (Sakai Chemical), STR-100C-LP (Sakai Chemical), STR-100W-LP (Sakai Chemical), STR-100C-LF (Sakai Chemical), and STR-100W-OT. Examples include S (Sakai Chemical), STR-100W(G) (Sakai Chemical), STR-40OTS (Sakai Chemical), MT-01 (Teika), MT-10EX (Teika), MT-05 (Teika), MT-100S (Teika), MT-100TV (Teika), MT-100Z (Teika), MT-150EX (Teika), MT-150W (Teika), MT-100AQ (Teika), MT-100WP (Teika), MT-100SA (Teika), MT-100HD (Teika), etc. These inorganic particles can be of a single type, or they can be a composite material containing multiple types.

[0025] The shape of the inorganic particles can be arbitrary. Examples of inorganic particle shapes include spherical, amorphous, plate-like, needle-like, star-shaped, chain-like, and multilayer structures of stacked plate-like particles. Furthermore, the inorganic particles may be coated with other materials. In addition, the inorganic particle shape may consist of one type or a combination of multiple types.

[0026] The inorganic particle content is preferably 5% to 40% by mass of the nonvolatile content, and more preferably 10% to 30% by mass. In this invention, nonvolatile content refers to the residue after the light-shielding coating is held at 200°C for 2 hours. Therefore, the concentration in the light-shielding film is approximately equal to the concentration in the resin composition consisting of inorganic particles, colorants, resin, plasticizer, etc., excluding the organic solvent of the light-shielding coating. If the inorganic particle content is less than 5% by mass, the refractive index of the light-shielding film may not increase significantly, and the improvement in anti-reflective performance on the inner surface may be insufficient. Also, if the inorganic particle content exceeds 40% by mass, the elastic modulus of the light-shielding film may become too high, and the improvement in thermal shock resistance may be insufficient even with the addition of a plasticizer.

[0027] (Coloring agent) Any material capable of coloring can be used as a coloring agent. Examples of coloring agents include dyes and pigments, which may be used individually or in combination with others.

[0028] Examples of dyes include azo dyes, quinone dyes, cyanine dyes, cationic dyes, dicyanine dyes, indigo dyes, and fulged dyes. Any color can be used, but examples include black, brown, yellow, red, blue, and green, which may be used individually or in mixtures.

[0029] Examples of pigments include carbon black and titanium black. Examples of carbon black include #2650 (Mitsubishi Chemical), #2600 (Mitsubishi Chemical), #2350 (Mitsubishi Chemical), #2300 (Mitsubishi Chemical), #1000 (Mitsubishi Chemical), #980 (Mitsubishi Chemical), #970 (Mitsubishi Chemical), #960 (Mitsubishi Chemical), #950 (Mitsubishi Chemical), #850 (Mitsubishi Chemical), MCF88 (Mitsubishi Chemical), MA600 (Mitsubishi Chemical), #750B (Mitsubishi Chemical), #650B (Mitsubishi Chemical), MA100 (Mitsubishi Chemical), MA220 (Mitsubishi Chemical), etc.

[0030] The pigment can be in any shape. Examples of pigment shapes include spherical, irregular, plate-like, needle-like, star-shaped, chain-like, and multilayer structures of stacked plate-like particles. The pigment may also be coated with other materials. The pigment is contained in the paint as aggregates, and the average particle size of the pigment aggregates is preferably between 1 nm and 250 nm, and more preferably between 5 nm and 50 nm. If the average particle size of the pigment aggregates is less than 1 nm, the paint may become thicker. Also, if the average particle size of the pigment aggregates exceeds 250 nm, film scattering may increase. The average particle size of the pigment aggregates can be measured in the same way as the average particle size of inorganic particle aggregates.

[0031] The colorant content is preferably 1% to 30% by mass of nonvolatile matter, and more preferably 2% to 20% by mass. If the colorant content is less than 1% by mass, the light entering the film may not be absorbed completely, and the improvement of the internal reflection characteristics may be insufficient. Also, if the colorant content exceeds 30% by mass, the film may become too hard.

[0032] (resin) Any resin capable of forming a light-shielding film can be used. Examples of resins include epoxy resin, acrylic resin, urethane resin, acrylic urethane resin, phenolic resin, melamine resin, polyester resin, alkyd resin, and polyimide.

[0033] The resin content is preferably 5% to 70% by mass of nonvolatile matter, and more preferably 20% to 50% by mass. If the resin content is less than 5% by mass, the light-shielding film may become too hard and crack. If the resin content exceeds 70% by mass, it may become difficult to increase the refractive index of the film.

[0034] (Plasticizer) The pour point of the plasticizer is -50°C or lower, preferably between -70°C and -50°C. If the pour point of the plasticizer exceeds -50°C, the elastic modulus of the light-shielding film increases, and its thermal shock resistance deteriorates.

[0035] The boiling point of the plasticizer is between 200°C and 450°C, preferably between 200°C and 420°C. If the boiling point of the plasticizer is below 200°C, it will evaporate even outside of curing after film formation, increasing the elastic modulus of the light-shielding film and worsening its thermal shock resistance. If the boiling point of the plasticizer exceeds 450°C, the plasticizer will not evaporate easily from the surface during curing, preventing an improvement in the crosslinking density on the surface of the light-shielding film and causing plasticizer bleed-out.

[0036] Any plasticizer can be used as long as its pour point is -50°C or lower and its boiling point is between 200°C and 450°C. Examples of plasticizers include benzyltoluene, soft alkylbenzene, phenylxylethane, phenylethylphenylethane, dialkylbenzene, bis(2-ethylhexyl) phthalate, diisodecyl phthalate, polyalkylbenzene, saturated diisononyl ester, bis(2-ethylhexyl) adipate, diisodecyl adipate, (2-ethylhexyl) azelate, and bis(2-ethylhexyl) sebacate. These plasticizers may be used individually or in combination.

[0037] The d-line refractive index of the plasticizer is preferably 1.40 or more and 1.80 or less, and more preferably 1.51 or more and 1.70 or less. If the d-line refractive index is less than 1.40, the refractive index of the light-shielding film will decrease, and the internal reflectivity may deteriorate. If the d-line refractive index exceeds 1.80, the viscosity of the plasticizer will increase, and the elastic modulus may increase.

[0038] The plasticizer content is preferably 3% to 60% by mass of the non-volatile content, and more preferably 15% to 40% by mass. If the plasticizer content is less than 3% by mass, the light-shielding film may become too hard and crack. If the plasticizer content exceeds 60% by mass, there is a risk of bleed-out if left in high temperature and high humidity conditions.

[0039] (solvent) Light-blocking paints may contain a solvent. Any material may be used as the solvent. Furthermore, if the viscosity of the light-blocking paint is sufficiently low and it can be used as is, there is no need to add a solvent. Examples of solvents include water, thinner, ethanol, isopropyl alcohol, n-butyl alcohol, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, toluene, xylene, acetone, cellosolves, glycol ethers, ether, hexane, cyclohexane, 1-butanol, methylcyclohexane, ethylcyclohexane, isohexane, benzyl alcohol, 2-ethyl-1-hexanol, butyl cellosolve, 1-butoxy-2-propanol, neopentane, Solvesso, trichloroethylene, perchloroethylene, methanol, cellosolve acetate, mineral spirits, tetrahydrofuran, dioxane, N-methyl-2-pyrrolidone, and ethyl lactate. These solvents may be one type or a combination of multiple types.

[0040] The preferred viscosity of the light-shielding paint is 10 mPa·s to 10,000 mPa·s, and more preferably 30 mPa·s to 500 mPa·s. If the viscosity of the light-shielding paint is less than 10 mPa·s, areas with thin film thickness after application may occur. Conversely, if it exceeds 10,000 mPa·s, the applicability of the light-shielding paint may decrease.

[0041] (Other additives) The light-blocking paint may contain other optional additives. Examples include dispersants, hardeners, curing catalysts, defoamers, thixotropic agents, leveling agents, matting agents, preservatives, antibacterial agents, antifungal agents, UV absorbers, antioxidants, coupling agents, and inorganic and organic fine particles for adjusting the color other than those listed above.

[0042] Any material capable of curing resin can be used as the curing agent. To improve thermal shock resistance, a highly flexible curing agent is desirable. Examples of curing agents include amine-based curing agents. Examples of amine-based curing agents include Adeka Hardener EH-6019 (Adeka), Adeka Hardener EH-6024 (Adeka), Adeka Hardener EH-6028 (Adeka), Adeka Hardener EH-479 (Adeka), Adeka Hardener EH-451N (Adeka), Adeka Hardener EH-4602 (Adeka), Adeka Hardener EH2300 (Adeka), Adeka Hardener EH3427A (Adeka), Adeka Hardener EH-4024W (Adeka), ST1 (Mitsubishi Chemical) 1, ST12 (Mitsubishi Chemical), ST14 (Mitsubishi Chemical), ST15 (Mitsubishi Chemical), H3 (Mitsubishi Chemical), H30 (Mitsubishi Chemical), FL11 (Mitsubishi Chemical), FL11W (Mitsubishi Chemical), SA1 (Mitsubishi Chemical), etc.

[0043] The curing agent content is preferably 0.1% to 30% by mass of nonvolatile matter, and more preferably 3% to 10% by mass. When a curing agent is added, if the curing agent content is less than 0.1% by mass, curing failure may occur. Also, if the curing agent content exceeds 30% by mass, the internal reflectivity may deteriorate.

[0044] ≪Manufacturing method≫ As for the method of manufacturing the light-shielding paint of the present invention, any method can be used as long as inorganic particles are dispersed in the light-shielding paint, and if a pigment is added, preferably the pigment is further dispersed. Examples include stirring using a bead mill, ball mill, jet mill, three-roller, planetary rotating device, mixer, ultrasonic disperser, homogenizer, etc.

[0045] [Light-blocking film] The light-shielding film of the present invention comprises inorganic particles having a d-line refractive index of 2.0 or higher and an average particle diameter of aggregates of 250 nm or less, a colorant, a resin, and a plasticizer. The material composition and formation method of the light-shielding film of the present invention are described below.

[0046] ≪Material Composition≫ (Inorganic particles) Details regarding inorganic particles are as explained in the section on light-blocking paints. The inorganic particle content is preferably 2% to 40% by volume relative to the light-shielding film, and more preferably 10% to 30% by volume. If the inorganic particle content is less than 2% by volume, the refractive index of the light-shielding film may not increase significantly, and the improvement in internal anti-reflective performance may be insufficient. Furthermore, if the inorganic particle content exceeds 40% by volume, the elastic modulus of the light-shielding film may become too high, and even with the addition of plasticizers, the improvement in thermal shock resistance may be insufficient.

[0047] (Coloring agent) Details regarding the absence of colorants are as explained in the section on light-blocking paints. The colorant content is preferably 1% to 30% by volume relative to the light-shielding film, and more preferably 2% to 20% by volume. If the colorant content is less than 1% by volume, the film may not be able to absorb all the light that enters it, and the improvement of the internal reflection characteristics may be insufficient. On the other hand, if the colorant content exceeds 30% by volume, the film may become too hard.

[0048] (resin) Details regarding the resin are as explained in the section on light-blocking paint. The resin content is preferably 5% to 70% by volume relative to the light-shielding film, and more preferably 20% to 50% by volume. If the resin content is less than 5% by volume, the light-shielding film may become too hard and crack. If the resin content exceeds 70% by volume, it may become difficult to increase the refractive index of the film.

[0049] (Plasticizer) Details regarding plasticizers are as explained for light-blocking paints. The plasticizer content is preferably 5% to 40% by volume relative to the light-shielding film, and more preferably 15% to 35% by volume. If the plasticizer content is less than 5% by volume, the light-shielding film may become too hard and crack. If the plasticizer content exceeds 40% by volume, there is a risk of bleed-out if left in high temperature and high humidity conditions.

[0050] (Other additives) The light-shielding film may contain other optional additives. Details of these optional additives are as described in relation to light-shielding paints. The curing agent content is preferably 0.1% to 50% by volume relative to the light-shielding film, and more preferably 5% to 20% by volume. When adding a curing agent, if the curing agent content is less than 0.1% by volume, curing failure may occur. Also, if the curing agent content exceeds 50% by volume, the internal reflectivity may deteriorate.

[0051] ≪Formation method≫ The light-shielding film of the present invention can be formed by applying the light-shielding paint of the present invention described above and curing it.

[0052] The light-shielding film of the present invention is preferably formed with an average film thickness of 1 μm to 40 μm, more preferably 2 μm to 30 μm, and any coating method and curing method can be used as long as the light-shielding coating can be applied uniformly.

[0053] Examples of methods for applying light-blocking coatings include brush application, spray application, dip coating, spin coating, transfer printing, and inkjet printing. The light-blocking film can be a single-layer or multi-layer coating. The glass surface may also be dry-surface-treated with UV ozone, plasma, or excimer, or wet-surface-treated with coupling agents.

[0054] Furthermore, the light-shielding film may be cured by leaving it at room temperature or by accelerating heating with any heat. Methods for curing by applying heat include using a heating furnace, heater, infrared heating, etc. The curing temperature is preferably from room temperature to 200°C, and more preferably from room temperature to 150°C. The light-shielding film may also be cured with UV light.

[0055] [Optical elements] The optical element of the present invention is used, for example, in the lens barrel of optical equipment such as cameras, video cameras, and broadcasting equipment, as well as in other optical equipment that may be used outdoors, such as camera bodies, video cameras, surveillance cameras, in-vehicle cameras, and weather cameras. The optical element of the present invention has a light-shielding film of the present invention on the surface of a substrate such as glass or plastic. Figure 1 is a schematic cross-sectional view showing an example of the optical element of the present invention. The optical element in Figure 1 has a light-shielding film 1 on any outer peripheral portion outside the optically effective surface of the lens, which is the substrate 2. The light-shielding film 1 may be formed on the entire outer peripheral portion of the substrate 2, or on a part of the outer peripheral portion of the substrate 2.

[0056] The base material for lenses and the like can be any shape. For example, it can be concave, convex, or a combination of both. The outer edge can be flat, have multiple steps, or have grooves. It can also be a shape made by bonding multiple lens or other base materials together. Furthermore, any material can be used as the constituent component of the lens or other base material. Examples include Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, Y2O3, La2O3, Nd2O3, Gd2O3, B2O3, Al2O3, TiO2, ZrO2, HfO2, SiO2, GeO, Nb2O5, Ta2O5, P2O5, Sb2O3, WO3, F2, etc. The constituent component can be one type or a combination of multiple materials.

[0057] Figure 5 shows a bonded lens, which is an example of an optical element according to the present invention. The bonded lens 100 of the present invention has a first lens (first optical element) 101, a second lens (second optical element) 102, and a bonding resin layer (third optical element) 103 that bonds the first lens and the second lens. A light-shielding film 1 is provided on the sides of the first to third optical elements. By using the light-shielding film 1 of the present invention, the stress generated when heat is applied can be reduced, and the occurrence of cracks in the optical elements constituting the bonded lens 100 can be suppressed.

[0058] The first lens 101 and the second lens 102 can be selected and combined from optical glass with shapes that correspond to the optical properties required for the cemented lens 100.

[0059] The bonding resin layer 103 is a hardened layer of adhesive used for bonding glass lenses. The adhesive is required to be optically transparent, have high adhesive strength, and a fast curing speed. Acrylic, epoxy, and polyene / polythiol-based curing adhesives are suitably used. These adhesives can be cured by heat or ultraviolet light by adding a curing initiator; however, curing by heat may cause interfacial delamination or deformation of the surface shape. Therefore, the bonding resin layer 10 For the adhesive in step 3, it is preferable to use an ultraviolet-curing type. Furthermore, from the viewpoint of reducing curing shrinkage of the adhesive and adjusting its optical properties, it is also preferable to mix and disperse inorganic fine particles or the like into the adhesive.

[0060] The principal surfaces 101a and 101b of the first lens 101, and the principal surfaces 102a and 102b of the second lens 102, are interfaces with materials of different refractive indices and are therefore refractive surfaces. When the difference in refractive index between the materials in contact with each other at these interfaces is large, light reflection occurs, so an anti-reflective coating (not shown) is applied as needed to mitigate the refractive index difference. Setting It would be good to do that.

[0061] The cemented lens 100 is used as part of the optical system of optical equipment such as imaging devices (including cameras and video cameras), telescopes, binoculars, photocopiers, and projectors. As an example, Figure 6 shows a schematic cross-section of an imaging device 200 with a lens unit (optical system) 20 mounted on an imaging unit 30. The cemented lens 21 (100) is located inside the housing 22 of the lens unit 20 and is fixed to the imaging unit 30 by a mount 23. The imaging unit 30 includes an image sensor 33 that receives light that has passed through the lens unit 20 and a shutter 32 inside the housing 31. The image sensor 33 is positioned so that the optical axis 40 of the cemented lens 21 passes through its center. Furthermore, it includes a drive unit 34 that opens and closes the shutter 32 and a control unit 35 that controls data reading from the drive unit 34 and the image sensor 33. [Examples]

[0062] The following describes preferred embodiments of the present invention.

[0063] [Evaluation Method] (1) Measurement of the average particle size of aggregates of inorganic particles The average particle size of inorganic particle aggregates was measured using a transmission electron microscope (TEM). A cross-section of the fabricated light-shielding film was cut out, and an image was taken with the TEM. The captured images were analyzed using ImageJ, and the particle size distribution was calculated. For particle size measurement, the minimum evaluation screen was filled with 10 or more particles (aggregates), and the average diameter was calculated. If the average particle size is 250 nm or less, the light-shielding film is considered to have good scattering and is not a good film. If the average particle size exceeds 250 nm, the light-shielding film has high scattering and is not considered a good film.

[0064] (2) Method for measuring internal reflectance The internal reflectance was measured using a spectrophotometer (U-4100: Hitachi High-Tech) as shown in Figure 3. A triangular prism 12 was used as the sample for measurement. The triangular prism 12 has a length of 30 mm on one side enclosing the right angle, a thickness of 10 mm, and is made of S-LAH53 (nd=1.8; manufactured by Ohara).

[0065] Figure 3 shows the measurement method for the incident angle b of 90° with respect to the triangular prism 12. Light emitted from the spectrophotometer is incident on the triangular prism 12 at an incident angle b = 90°. At this time, refraction of light occurs due to the difference between the refractive index of air and the refractive index of the triangular prism 12. The incident angle after refraction is c = 68.13°. The angle e after refraction with respect to the incident angle d was calculated using the following formula (1). Furthermore, the incident angle c was calculated from the angle e after refraction. n = sin d / sin e ... Equation (1)

[0066] Next, the light refracted by the triangular prism 12 strikes the bottom surface of the triangular prism 12, reflects, and exits the triangular prism 12. The intensity of this reflected light was detected by a detector in the visible light region with wavelengths from 400 nm to 700 nm. For the background, a sample with the bottom surface, incident surface, and exit surface being mirrored and nothing coated on the bottom surface of the triangular prism 12 was used. The internal reflectance was measured when a light-shielding film 1 was formed on the bottom surface of the triangular prism 12 with the bottom surface, incident surface, and exit surface being mirrored. The internal reflectance was measured at 1 nm intervals for the internal reflection of visible light from 400 nm to 700 nm, and the average value of the results is recorded.

[0067] The internal reflectivity was evaluated according to the following criteria: A indicates an internal reflectivity of less than 40%, representing an excellent film; B indicates an internal reflectivity of 40% to less than 60%, representing a film with slightly inferior but acceptable internal reflectivity; and C indicates an internal reflectivity of 60% or more, representing a film with poor optical properties. A: Internal reflectivity is less than 40%. B: Internal reflectivity is between 40% and 60%. C: Internal reflectivity is 60% or higher.

[0068] (3) Method for evaluating thermal shock resistance Figure 4 shows a schematic cross-sectional view of the test specimen used to evaluate thermal shock resistance. For the evaluation of thermal shock resistance, as shown in Figure 4, a test specimen was used in which two circular monitor glass 13 were bonded together with adhesive 14, and a light-shielding film 1 with a thickness of approximately 4 μm was formed on the outer surface. The circular monitor glass 13 has a diameter of 100 mm and a thickness of 10 mm, and its outer surface is ground with #1200 grit. The materials of the two circular monitor glass 13 are S-LAH53 (nd=1.8; manufactured by Ohara) and S-FPL55 (nd=1.4; manufactured by Ohara), respectively.

[0069] The prepared test specimens were left in a -50°C environment for 30 minutes, then in a 60°C environment for 30 minutes. This was repeated 10 times as one set, applying thermal shock.

[0070] Furthermore, thermal shock resistance was evaluated according to the following criteria. A represents a light-shielding film with no problems in thermal shock resistance, while B represents a light-shielding film that exhibits cracking and appearance defects and has problems in thermal shock resistance. A: No change in the glass. B: The glass has cracks or cosmetic defects.

[0071] (4) Evaluation method for high temperature and high humidity resistance For the high-temperature and high-humidity test, a test specimen was prepared by forming a light-shielding film with a thickness of 5 μm on the frosted side of a 30 mm diameter, 1 mm thick monitor glass, with one side polished to a frosted surface and the other to a mirror finish. S-LAH53 (nd=1.8; manufactured by Ohara) was used as the monitor glass.

[0072] The prepared test specimens were left in a 60°C, 90% humidity atmosphere for 200 hours to check for any bleed-out from the surface.

[0073] Furthermore, resistance to high temperature and humidity was evaluated according to the following criteria. A represents a good light-shielding film with no bleed-out, while B represents a problematic light-shielding film with bleed-out occurring. A: No bleed-out. B: Bleedout occurred.

[0074] [raw materials] (1) Inorganic particles [Table 1]

[0075] (2) Colorants A: Carbon Black B: Dye (VALIFAST BLACK 1821; Orient Chemical) C: Dye (VALIFAST BLACK 3810; Orient Chemical) (3) Resin Bisphenol A type epoxy resin (jER828; Mitsubishi Chemical) (4) Coupling agent Epoxy silane coupling agent (KBM403; Shin-Etsu Silicone) (5) Dispersant DISPERBYK2155 (Big Chemie Japan)

[0076] (6) Plasticizers [Table 2]

[0077] <Example 1> 1. Preparation of resin composition for light-shielding paint As shown in Table 3, 700g of solvent (toluene), 200g of inorganic particles A, 50g of colorant A, 200g of resin, 10g of coupling agent, 50g of dispersant, and 120g of plasticizer A were weighed. All the weighed raw materials were placed in a container and stirred with a stirring blade for 20 minutes to obtain a pre-dispersion. The pre-dispersion was stirred in a bead mill for 180 minutes to obtain a resin composition for light-shielding paint.

[0078] 2. Fabrication of light-shielding film As shown in Table 3, 150 g of amine-based curing agent was added to the total amount of the obtained light-shielding resin composition and stirred in a roll coater for 30 minutes. The resulting mixture of light-shielding resin composition and curing agent (light-shielding paint) was applied to a glass or prism for evaluation to a predetermined thickness and dried at room temperature for 60 minutes. After drying the film, it was cured in a constant temperature oven at 40°C for 8 hours to obtain a light-shielding film.

[0079] In Tables 3 and 4, "Content (wt%)" indicates the mass-based content relative to the non-volatile content of the paint, while "Content (vol%)" indicates the volume-based content in the film.

[0080] 3. Evaluation The obtained light-shielding film was evaluated for its average particle size of inorganic particle aggregates, internal reflectance, thermal shock resistance, and resistance to high temperature and humidity. The results are shown in Table 3.

[0081] <Examples 2 to 18, Comparative Examples 1 to 4> A light-shielding film was fabricated and evaluated in the same manner as in Example 1, except for the materials and conditions shown in Tables 3 and 4. The results are shown in Tables 3 and 4.

[0082] <Comparative Example 5> A light-shielding film was prepared and evaluated in the same manner as in Example 1, except that the pre-dispersion was not stirred with a bead mill and the pre-dispersion was used as the resin composition for the light-shielding coating. The results are shown in Table 4.

[0083] [Table 3]

[0084] [Table 4]

[0085] As shown in Tables 3 and 4, Examples 1 to 18 showed good performance, with an average particle size of 250 nm or less for the inorganic particle aggregates. The internal reflectivity was also good, at less than 60%. Furthermore, the thermal shock resistance was good, with no changes such as cracking in the appearance. The high temperature and high humidity resistance was also good, with no bleed-out occurring. However, in Example 15, regarding high temperature and high humidity resistance, very slight peeling occurred at the interface between the glass and the film, which did not pose a problem. Similarly, in Example 17, regarding high temperature and high humidity resistance, slight peeling occurred at the interface between the glass and the film, which did not pose a problem.

[0086] In Comparative Example 1, when the plasticizer was changed from Example 1 to plasticizer K, which has a high pour point of -30°C, glass cracking occurred due to thermal shock resistance.

[0087] In Comparative Example 2, when the plasticizer was changed from Example 1 to plasticizer L, which has a lower boiling point of 176°C, cracking of the glass occurred due to thermal shock resistance.

[0088] In Comparative Example 3, the content of plasticizer K was increased compared to Comparative Example 1 to improve thermal shock resistance, but bleed-out was observed in terms of resistance to high temperature and high humidity.

[0089] In Comparative Example 4, the inorganic particles were changed from those in Example 1 to inorganic particles D, which have a d-line refractive index of less than 2.0. As a result, the internal reflectivity was 60% or higher, which was poor.

[0090] In Comparative Example 5, compared to Example 1, only the pre-dispersion step was performed, omitting the bead mill dispersion step. As a result, the average particle size of the inorganic particle aggregates exceeded 250 nm, which was poor. Furthermore, the internal reflectivity was over 60%, which was also poor. [Explanation of Symbols]

[0091] 1. Light-shielding film, 2. Substrate, 3. Incident light, 4. Transmitted light, 5. Incident light, 6. Internally reflected light, 7. Interface, 8. Interface, 9. First reflected light, 10. Transmitted light, 11. Second reflected light, 12. Triangular prism, 13. Monitor glass, 14. Adhesive

Claims

1. An optical element comprising a substrate and a light-shielding film provided on the side surface of the substrate, The light-shielding film comprises an aggregate of inorganic particles with a d-line refractive index of 2.0 or higher, a colorant, a resin, and a plasticizer. The average particle size of the aggregate is 250 nm or less. The plasticizer has a pour point of -50°C or lower and a boiling point of 200°C or higher and 450°C or lower. An optical element characterized in that the crosslinking density of the light-shielding film is higher on surfaces other than the interface of the light-shielding film compared to the crosslinking density of the light-shielding film at the interface with the substrate.

2. The optical element according to claim 1, characterized in that the d-line refractive index of the plasticizer is 1.51 or more and 1.70 or less.

3. The optical element according to claim 1 or 2, characterized in that the plasticizer is at least one selected from benzyltoluene, soft alkylbenzene, phenylxylethane / phenylethylphenylethane mixture, dialkylbenzene, bis(2-ethylhexyl) phthalate, diisodecyl phthalate, polyalkylbenzene, saturated diisononyl ester, bis(2-ethylhexyl) adipate, diisodecyl adipate, (2-ethylhexyl) azelate, and bis(2-ethylhexyl) sebacate.

4. A cemented lens comprising a first optical element, a second optical element, and a third optical element containing resin sandwiched between the first optical element and the second optical element, A cemented lens characterized in that the first to third optical elements are the optical elements described in any one of claims 1 to 3.

5. The casing and The bonded lens according to claim 4, disposed inside the aforementioned housing cylinder, An optical system characterized by having the following features.

6. An imaging device comprising the optical system described in claim 5 and an image sensor that receives light incident through the optical system.

7. A light-shielding paint comprising an aggregate of inorganic particles with a d-line refractive index of 2.0 or higher, a colorant, a resin, and a plasticizer, The average particle size of the aggregate is 250 nm or less. The plasticizer has a pour point of -50°C or lower and a boiling point of 200°C or higher and 450°C or lower. A light-shielding paint characterized in that, upon curing, the crosslinking density at the interface with air is higher than the crosslinking density at interfaces other than the interface with air.

8. The light-shielding paint according to claim 7, characterized in that the d-line refractive index of the plasticizer is 1.51 or more and 1.70 or less.

9. The light-shielding coating according to claim 7 or 8, characterized in that the plasticizer is at least one selected from benzyltoluene, soft alkylbenzene, phenylxylethane / phenylethylphenylethane mixture, dialkylbenzene, bis(2-ethylhexyl) phthalate, diisodecyl phthalate, polyalkylbenzene, saturated diisononyl ester, bis(2-ethylhexyl) adipate, diisodecyl adipate, (2-ethylhexyl) azelate, and bis(2-ethylhexyl) sebacate.

10. The light-shielding paint according to any one of claims 7 to 9, characterized in that the content of the plasticizer is 3% by mass or more and 60% by mass or less of the non-volatile content.

Images