JP2005031538A - Optical element with antireflection surface, optical system having optical element with antireflection surface, and optical equipment equipped with optical system having optical element with antireflection surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element with an antireflection surface having periodical fine ruggedness which is resistant to flawing, is high in productivity, is mild in molding conditions, and can make a layer having the ruggedness thicker, an optical system having the optical element with the antireflection surface and optical equipment equipped with the optical system having the optical element with the antireflection surface. <P>SOLUTION: The optical element with the antireflection surface has a light transparent organic and inorganic composite material 1 on at least the surface and is so constituted that the surface acts as the antireflection surface consisting of the fine ruggedness 10 having a period below the wavelength of the transmitted light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical element with an antireflection surface having a periodic structure smaller than the wavelength of incoming and outgoing light, an optical system having the optical element with antireflection surface, and an optical system including the optical system with the optical element with antireflection surface It relates to equipment.

  When light passes through a boundary having a difference in refractive index, light is reflected according to the difference in refractive index, resulting in a loss of transmitted light amount. Further, the reflected light generated by the reflection may exert an optically undesirable effect. For example, optical devices such as cameras and medical endoscopes that have an imaging optical system and an observation optical system use a large number of optical elements such as lenses and prisms. Since ghost and flare are generated, the reflection of light is reduced as much as possible. Generally, in order to prevent light reflection, a method is used in which a material having a refractive index different from that of an optical element as a base material is formed as a film on the base material by a vacuum deposition method, a sputtering method, or the like. In this method, it is important that the material to be coated has a predetermined thickness. For example, in the case of a single-layer antireflection film, it is known that a reflectance that is minimal with respect to the design light wavelength can be obtained by making the low refractive index material an odd multiple of 1/4 of the wavelength of the light than the base material. It has been. In addition, in the case of a broadband light wavelength, it is known that a high antireflection effect can be obtained by laminating thin films in multiple layers. However, the vacuum deposition method and the sputtering method basically require an expensive vacuum device, and it is necessary to form the film once in the case of a single layer film or multiple times in the case of a multilayer film. Furthermore, it is necessary to control the refractive index and the film thickness of the film with high accuracy, and an expensive control device is required for a control system for this purpose. Further, when the film is formed in the vacuum apparatus, a vacuum process is inevitably performed every time a film is formed, and the productivity is low.

  Further, in the antireflection film using the interference of these thin films, the reflectance changes in principle depending on the incident angle of light. In general, the antireflection film is optimized so that the reflectance is minimized with respect to normal incidence, and the antireflection effect is greatly reduced as the incident angle increases.

On the other hand, an optical element having a structure with periodically fine irregularities on the surface has been studied, and an optical element having periodic fine irregularities on the surface is known to have an antireflection function. [Patent Document 1] and [Patent Document 2] have proposed that the periodic fine irregularities formed by molding on the surface of a transparent resin are used as display window materials. [Patent Document 3] proposes that an inorganic thin film protective layer such as MgF ₂ is provided on periodic fine irregularities formed of polymethyl methacrylate resin. In [Patent Document 4], a metal alkoxide such as titanium alkoxide (organic titanate) is applied to the entire surface of a light-transmitting element substrate by spin coating, and the coated surface has fine irregularities. Proposed to obtain an optical element having a photocatalyst layer by pressing and heating a nickel plate to form periodic fine irregularities by hydrolysis / condensation reaction, then peeling the nickel plate and sintering at high temperature in the atmosphere Yes.
JP 2003-4916 A JP 2003-90902 A JP 2002-182003 A JP 2001-183506 A

  However, even the hardest acrylic of transparent resins has a low surface hardness of about 4H in pencil hardness, and there are problems such as physical damage and low heat resistance. In addition, forming an inorganic thin film protective layer by vapor deposition or sputtering is a batch process, which has a problem of low productivity. In addition, a material using a metal alkoxide such as titanium alkoxide needs to be sintered at a high temperature in order to give sufficient strength in terms of material, and an element substrate used for forming periodic fine irregularities is used. It will be limited to what has heat resistance like glass. In addition, a large curing shrinkage occurs when the metal alkoxide is subjected to a condensation reaction, and the condensate formed after the reaction is highly brittle, so that cracks are likely to occur due to stress accompanying the curing shrinkage, and it is easy to peel off from the element substrate. Become. Further, since the stress due to curing shrinkage is large, there is a problem that the layer having periodic fine irregularities cannot be thickened.

  Accordingly, the object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, prevent scratches, increase productivity, mild the formation conditions, and increase the thickness of the uneven layer. An object of the present invention is to provide an optical device provided with an optical element having an antireflection surface, an optical system having an antireflection surface, and an optical system having an antireflection surface.

  The optical element with an antireflection surface of the present invention that achieves the above-mentioned object is an antireflection surface that has a light-transmitting organic-inorganic composite material at least on the surface, and the surface is composed of fine irregularities having a period of a transmitted light wavelength or less. It is characterized by being.

  The organic-inorganic composite material has a structure composed of an organic skeleton polymer matrix and an inorganic skeleton matrix, or (and) a structure in which nanoscale inorganic fine particles are dispersed in an organic skeleton polymer matrix, or (and) an organic skeleton A structure in which a monomer or oligomer and a monomer or oligomer having an inorganic element are copolymerized is preferable.

  The fine irregularities are tapered, and the cross-sectional area occupancy of the material portion in the cross section when assuming that the fine irregularities are cut in a direction orthogonal to the irregularity direction can be continuously changed in the irregularity direction (thickness direction). preferable.

  An optical system of the present invention that achieves the above object includes an illumination optical system for irradiating an object with illumination light from a light source element, and an imaging optical system that forms an image on the imager with the light reflected by the object. At least a part of the system is composed of an organic-inorganic composite material, and the transmission surface of the illumination optical system that transmits at least illumination light of the organic-inorganic composite material has an antireflection surface composed of fine irregularities having a period equal to or shorter than the transmitted light wavelength. It is characterized by.

  It is preferable that the light incident / exit surface other than the transmission surface of the illumination optical system is a surface having no fine unevenness.

  An optical apparatus according to the present invention that achieves the above object includes an illumination light source element, an illumination optical system that transmits the illumination light to irradiate the object, an imager, and images the light reflected by the object on the imager. An optical device comprising an imaging optical system that performs an input / output operation of the imager, and the optical path of the illumination optical system is made of a light-transmitting organic-inorganic composite material. The transmission surface of the illumination optical system that transmits at least the illumination light has an antireflection surface composed of fine irregularities having a period equal to or less than the transmitted light wavelength.

  An optical apparatus according to the present invention that achieves the above object includes an illumination light source element, an illumination optical system that transmits the illumination light to irradiate the object, an imager, and images the light reflected by the object on the imager. The image forming optical system and the electric circuit section for processing the input / output of the imager are enclosed in a capsule whose light path of the illumination optical system is a light-transmitting organic-inorganic composite material.

  The organic-inorganic composite material can be appropriately implemented if at least the transmission surface of the illumination optical system that transmits the illumination light has an antireflection surface composed of fine irregularities having a period equal to or less than the transmitted light wavelength.

  It is preferable that the antireflection surface is formed at a plurality of locations surrounding a portion having no fine unevenness.

  The portion of the capsule made of a light-transmitting organic-inorganic composite material has a hemispherical dome shape.

  As described above, according to the present invention, since the periodic fine irregularities are formed with the organic-inorganic composite material having high surface hardness and excellent durability, an optical element with an antireflection surface that is physically durable is provided. be able to. Moreover, since an antireflection surface can be formed at an arbitrary site by molding, an optical element with an antireflection surface can be mass-produced efficiently. Furthermore, the optical element with an antireflection surface of the present invention can also have a water repellent effect due to fine irregularities.

  In addition, since the optical system or optical apparatus of the present invention uses the optical element with an antireflection surface of the present invention, the optical system or optical apparatus is hardly damaged when assembled or used, and the productivity is increased. Can do. Furthermore, the optical system has an excellent light transmittance, and the device performance of the optical device is excellent.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  The optical element with an antireflection surface of the present invention, including the antireflection surface, is entirely made of a light-transmitting organic-inorganic composite material, or only the antireflection surface is made of a light-transmitting organic-inorganic composite material. It is. When only the antireflection surface is made of an organic / inorganic composite material, the main body of the optical element is made of a normal glass or plastic material, and an antireflection surface made of an organic / inorganic composite material is bonded thereto. Alternatively, an antireflection surface made of an organic-inorganic composite material is formed on the main body of the optical element.

  As shown in FIG. 1, the antireflection surface is composed of fine irregularities 10 having a period T equal to or shorter than the transmitted light wavelength (for example, visible light wavelength), and the convex portions 3 of each fine irregularity have a tapered structure. In this example, the whole including the antireflection surface (unevenness 10) on the surface is the light-transmitting organic-inorganic composite material 1.

The ratio (T / H) between the period (T) of the fine irregularities 10 and the height (H) of the fine irregularities is preferably 0.2-4.
(Anti-reflection principle)
The reflection of light occurs due to a difference in refractive index when light passes through the interface of media having different refractive indexes. The critical angle θc for total reflection is represented by θc = sin ⁻¹ (n1 / n2). (N1 and n2 are the refractive indexes of the respective media). Since the periodic fine irregularities serving as the antireflection surface can provide the same antireflection effect as a layer having a continuously changing refractive index, the fine irregularity layer is n1≈n2 in the microscopic range, The critical angle is very large. For this reason, the periodic fine unevenness can obtain a good antireflection effect even when the incident angle of light increases.

  The reason why the periodic fine irregularities can be regarded as the refractive index continuously changing will be described with reference to FIG. 2A. The example of the optical element formed by the organic inorganic composite material is shown by the antireflection surface in which each convex part 3 of the periodic fine unevenness | corrugation 10 was formed in the cone shape. This optical element is assumed to be placed in the air, and the refractive index of the periodic fine irregularities 10 on the surface S orthogonal to the irregularity direction will be examined. Assuming that the surface S is the base of the convex portion 3 (the back of the concave portion), the organic / inorganic composite material occupies most of the cross-sectional area occupancy and the air is slight. Therefore, the refractive index at the base of the convex portion 3 has the characteristics of an organic-inorganic composite material. As the surface S approaches the surface side of the fine irregularities, that is, from the tip of the conical taper of the convex portion 3, the volume occupancy of the organic-inorganic composite material decreases, the proportion of air increases, and the refractive index is Has characteristics.

  Therefore, it appears to have the same effect as the layer in which the refractive index continuously changes between the bottom and top of the fine irregularities. This is known as the surface microstructure of the eyelet (Moth Eye structure).

FIG. 2B shows an example of an antireflection surface in which each convex portion 3 of the periodic fine irregularities 10 is formed in a substantially quadrangular pyramid. FIG. 2C shows an example of an antireflection surface in which each convex portion 3 of the periodic fine irregularities 10 is formed in a substantially truncated cone shape. FIG. 2D shows an example of an antireflection surface in which each convex portion 3 of the periodic fine irregularities 10 is formed in a shape having a substantially conical tip rounded. In addition, a substantially triangular pyramid shape may be used.
(Description of material)
The organic-inorganic composite material used for the optical element with an antireflection surface of the present invention will be described. The organic-inorganic composite material is obtained by mixing and compounding an organic component and an inorganic component at a molecular level or a nanoscale level.

  As shown in FIG. 3A, there is an IPN structure in which a polymer matrix made of an organic skeleton and a matrix made of an inorganic skeleton are entangled with each other and penetrated into each other as shown in FIG. 3A. As shown in FIG. 3B, a composite structure in which nanoscale inorganic fine particles are dispersed in a polymer matrix having an organic skeleton may be used. Further, as shown in FIG. 3C, a structure in which a monomer or oligomer having an organic skeleton and a monomer or oligomer having an inorganic element are copolymerized may be used. Further, there are composite structures of IPN structure, composite structure, and copolymer structure. Some interaction acts between the organic component and the inorganic component, such as intermolecular forces such as hydrogen bonds, dispersion forces, and Coulomb forces, and attractive forces due to covalent bonds, ionic bonds, and π electron cloud interactions.

  The organic component in the organic-inorganic composite material having an IPN structure is a polymer mainly composed of a so-called organic skeleton having a carbon-carbon bond in the main chain skeleton, and is a chain or a crosslinked one. For example, methyl methacrylate resin, polyolefin resin, polystyrene resin, norbornene resin, polycarbonate resin, ABS resin, polyamide resin, polyester resin, vinyl chloride resin, and their copolymers, thermoplastic resins, and epoxy resins, unsaturated Various types such as ester resins, acrylate resins, urethane resins, polyimide resins, phenol resins, fluororesins, arylate resins, ether resins, silicone resins and thermosetting resins such as resins in which some of these functional groups are modified Can be mentioned. As the inorganic component, an organometallic compound selected from various metal alkoxides such as Si, Ti, Zr, Al, Ba, Ta, Ge, Ga, Cu, Sc, Bi, and lanthanoid, metal acetylacetonate, or metal carboxylate Examples thereof include inorganic polymers having a metalloxane skeleton that has undergone a sol-gel reaction and inorganic metals having a metal element such as Zn, Sn, In, Ge, and Pb in the skeleton. There are others that contain sulfur, boron, selenium, tellurium, etc. in the molecular chain. Since the IPN structure is compounded at the molecular size level, it is compounded in a sufficiently small region with respect to the size of the fine concavo-convex structure, so that a fine concavo-convex structure can be formed.

  As a method for synthesizing an organic / inorganic composite material having an IPN structure, a monomer or oligomer of an organic component thermosetting resin and a metal alkoxide of an inorganic component and, if necessary, a solvent, a catalyst, and a curing agent are mixed to polymerize the resin monomer. There is a method of obtaining a cured product of an organic-inorganic composite material in which an organic component and an inorganic component are entangled with each other by proceeding simultaneously with a sol-gel reaction of a metal alkoxide. In this method, the reaction rate is adjusted depending on the type and addition amount of the solvent and catalyst, the applicability of processing methods such as molding and coating performed after synthesis is adjusted depending on the type and addition amount of the solvent, or the type and addition of the curing agent. The curing method and curing conditions can be adjusted depending on the amount.

Examples of the organic component in the organic-inorganic composite material having the composite structure include the thermoplastic resins and thermosetting resins mentioned in the IPN structure. As an inorganic component, from the viewpoint of filling a transparent and fine concavo-convex structure, a metal oxide, metal sulfide, metal nitride having an average particle diameter of 50 nm or less, more preferably smaller than 10 nm, which is sufficiently smaller than the wavelength of light, Metal carbide, metal halide, or simple metal particles, and the metal elements contained in these are Si, Ti, Zr, Al, Ba, Ta, Ge, lanthanoid, Zn, Sn, In, Y, Various metal elements such as Ni, Co, Cr, Au, Ag, Cu, Ca, Mg, and W are used. _{Specifically,} there are _{SiO 2, TiO 2, ZrO 2} , Al 2 O 3, ZnS, BaTiO 3, MgF 2, In 2 O 3, SnO 2, SiC, c-BN. Moreover, the compound of the magnitude | size close | similar to molecular size, such as silsesquioxane which has a ladder-like structure or a cage-like structure, is also mentioned. In the composite structure, it is necessary to select the size of the inorganic component particles according to the size and shape of the fine concavo-convex structure, and particles of less than 10 nm are preferable.

  As a method for synthesizing an organic-inorganic composite material having a composite structure, these metal compound fine particles may be uniformly dispersed in an organic component while maintaining a size sufficiently smaller than the wavelength of light, and any method may be used. Absent.

  For example, in addition to a general kneading method, a method of generating a fine particle by causing a sol-gel reaction in an organic component, a mixture of an organic resin monomer and a metal complex, and then reducing a metal component to form a fine metal compound particle and organic For example, the components may be polymerized simultaneously, or the surface of the fine particles may be surface-treated in advance to increase the affinity with the organic component to facilitate dispersion.

  In the organic-inorganic composite material having a copolymer structure, examples of the organic component include various organic components such as an acrylate monomer and an epoxy oligomer such as thermoplastic resins and thermosetting resins mentioned in the IPN structure. Examples of the inorganic component include inorganic component-containing organic monomers or oligomers containing elements such as Si, Ti, Al, Ge, Se, and Te. The method for synthesizing the copolymer structure is obtained by mixing the organic component and the inorganic component-containing organic monomer or oligomer, and, if necessary, a solvent, a catalyst, and a curing agent, and copolymerizing them. Similar to the IPN structure, the copolymer structure is also compounded at the molecular size level, so that an antireflection surface of the fine concavo-convex structure can be formed regardless of the size and shape of the fine concavo-convex structure.

  The organic-inorganic composite material thus obtained is reinforced by the action of inorganic components, resulting in improved mechanical properties such as elastic modulus and surface hardness, increased thermal softening point, increased glass transition point, Improvements in thermal characteristics such as a decrease in expansion coefficient can be obtained. In organic-inorganic composite materials, the organic component and inorganic component are configured while interacting at the molecular level or nanoscale, so it is possible to improve the characteristics by suppressing the molecular vibration of the main chain skeleton of the organic component. It has become. In addition, since the structure becomes dense, effects such as a reduction in water absorption and improvement in solvent resistance or weather resistance can be obtained.

  Moreover, in the organic-inorganic composite material, a change also appears in the optical characteristics. As described above, the organic component and the inorganic component are mixed at a molecular level or a scale region smaller than the wavelength of light. For this reason, there is almost no influence on light scattering, and a transparent body can be obtained.

  These organic-inorganic composite materials can be molded into any shape by injection molding, etc., with thermoplastic resin as the organic component, and those with thermosetting resin as the organic component become liquid before curing. Therefore, it can be cast into a mold and molded into a free shape. Thus, since it has a shaping | molding characteristic, the element which has a periodic fine unevenness | corrugation can be shape | molded and produced with a well-known shaping | molding technique.

  The element made of the organic-inorganic composite material thus obtained has a very high surface hardness, and even when it is arranged so as to be exposed on the surface of the optical device, the optical element can be handled by hand. The surface is hardly scratched. Here, the organic-inorganic composite material used preferably has a surface hardness of 6H or more in terms of pencil hardness.

  In addition, compared with conventionally used acrylic, polycarbonate and olefin-based transparent resins, the thermal softening point is increased, the heat resistance is improved, and the thermal expansion coefficient and the refractive index change rate due to temperature change are also reduced. As a result, the optical characteristics are stabilized against environmental temperature changes, and an effect that a highly accurate optical system can be formed is also obtained.

  Although the IPN structure, composite structure, and copolymer structure have been individually described, the organic-inorganic composite material having these structures in combination has excellent characteristics and can form an antireflection surface with periodic fine irregularities. The composite structure is preferably combined with the IPN structure depending on the size and shape of the fine irregularities.

In addition, the antireflection surface having a fine uneven shape is in a state where water repellency is likely to appear as seen in a lotus leaf. Therefore, the optical element with an antireflection surface of the present invention can be suitably used for those requiring anti-reflection and water repellency. In order to further improve water repellency, it is desirable to use a resin containing fluorine as an organic component. Generally, since the surface hardness of fluororesin is low, the surface is easily damaged. However, by using the organic-inorganic composite material, the inorganic component functions to increase the surface hardness, and a durable antireflection surface can be formed.
(Formation of antireflection surface)
An organic-inorganic composite material or an organic-inorganic composite composition that is an intermediate material thereof can be solidified from a fluidized state to form an optical element. A mold having a concavo-convex shape opposite to the periodic fine concavo-convex shape of the antireflection surface is prepared, and a fluid organic / inorganic composite material or composition is brought into close contact with the concavo-convex shape surface of the mold and solidified. Then, by releasing the mold, periodic fine irregularities are formed on the surface of the organic-inorganic composite to obtain an optical element with an antireflection surface.

  Thermoplastic organic-inorganic composite materials can be shaped by injection molding. Thermosetting organic-inorganic composite materials are cast into a mold and then irradiated with energy rays such as heating, ultraviolet rays, and electron beams. The shape can be formed by solidifying and releasing the mold.

  Specifically, after creating a mold having periodic fine irregularities on the surface and transferring the surface of the mold using electroforming technology, this mass production mold By molding using an organic-inorganic composite material, an optical element with an antireflection surface made of an organic-inorganic composite material having initial periodic fine irregularities on the surface is molded.

  In addition, for example, by applying lithography technology in the formation of integrated circuits using semiconductors, forming resist patterns by electron beam drawing or laser interferometry, and etching with atomic beams, ion beams, etc. After forming a first mold by forming predetermined periodic fine irregularities on the surface of a substrate such as glass, a plating layer was formed by performing metal plating such as nickel. Later, an electroforming method or the like can be used in which the plating layer is peeled off to form a mass production mold (second mold) using the plating layer.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples.

-Trial manufacture and properties of organic-inorganic composite materials-
30 parts by weight of isopropanol was added to 37 parts by weight of methanol-dispersed silica sol (average particle size 9 nm, silica fine particle content 25% by weight, organosilica sol MA-ST-S manufactured by Nissan Chemical Co., Ltd.), and further γ-methacryloxypropyltrimethoxy 3.82 parts by weight of silane and 3.05 parts by weight of phenyltrimethoxysilane were added and stirred. While stirring, 0.14 parts by weight of first octyl acid tin (KCS-405T, manufactured by Johoku Chemical Co., Ltd.) was added dropwise and stirred at room temperature for 25 hours, followed by neopentyl glycol diacrylate (NP-A, 7.11 parts by weight of Kyoeisha Chemical Co., Ltd., 2.14 parts by weight of trimethylolpropane triacrylate (TMP-A, Kyoeisha Chemical Co., Ltd.) and 0.20 parts by weight of polymerization initiator Irgacure 500 (manufactured by Ciba Specialty Chemicals) In addition, the mixture was stirred and filtered with a 3 μm mesh filter paper to remove floating dust and the like. From this solution, a volatile solvent such as methanol and isopropanol was distilled off at about 40 ° C. with a vacuum evaporator to obtain a fluid acrylic resin-based organic-inorganic composite composition.

This composition was poured into a cup having a diameter of 20 mm and a depth of 20 mm to a depth of about 10 mm, and irradiated with ultraviolet rays having a light intensity of 1.7 mW / cm ² at a light wavelength of 365 nm for 24 hours under a nitrogen atmosphere. An organic-inorganic composite material having a thickness of about 10 mm was obtained. This organic-inorganic composite material corresponds to a composite type of a composite structure and an IPN structure.

A sample was cut out from the organic-inorganic composite material, and the coefficient of linear expansion β was measured to find 4.9 × 10 ⁻⁵ m / m · ° C. When the refractive index was measured, it was nd = 1.490 (586 nm), and when the refractive index was measured for the temperature change rate, it was 90 × 10 ⁻⁶ / ° C. When the dynamic viscoelasticity was measured, it was confirmed that there was no significant decrease in storage elastic modulus up to 200 ° C. and no softening even at high temperatures. Conventionally, in the acrylic resin and polycarbonate resin in which an optical element is produced by injection molding, the organic-inorganic composite material of Example 1 has sufficient mechanical properties, whereas it softens rapidly after the Tg point. It was. When the pencil hardness was measured, it was 9H or more. Further, this organic-inorganic composite material is visually transparent, and the light transmittance in the thickness direction of a sample having a diameter of 20 mm and a thickness of 3 mm was measured. As a result, as shown in FIG. Had.
-Materials and performance of comparative examples-
The material of the comparative example which hardened only the monomer used for the organic inorganic composite composition of Example 1 on the same conditions was created. The linear expansion coefficient of the material of this comparative example was 7.5 × 10 ⁻⁵ m / m · ° C. The refractive index was nd = 1.490 (586 nm), and the temperature change rate of the refractive index was 135 × 10 ⁻⁶ / ° C.

Therefore, the coefficient of thermal expansion of the organic-inorganic composite material of Example 1 was reduced by 35% from the coefficient of thermal expansion of the material of the comparative example. Further, in the commercially available acrylic resin, the temperature change rate of the refractive index was 130 × 10 ⁻⁶ / ° C., and the temperature change rate of the refractive index of the organic-inorganic composite material of Example 1 was reduced by 30%.
-Antireflective surfaces and properties of organic-inorganic composite materials-
An antireflection surface was formed from the organic-inorganic composite composition obtained as described above. First, periodic fine irregularities were formed on a glass plate in which irregularities with a period T = about 200 nm and a height H = 200 nm having a substantially spindle-shaped cross section (see FIG. 1) were two-dimensionally arranged. This was inverted by an electroforming method to produce a mold having a shape formed. An organic-inorganic composite composition was poured into the mold, and irradiated with ultraviolet rays having a light intensity of 12 mW / cm ² at a light wavelength of 365 nm for 10 minutes in a nitrogen atmosphere to release the mold. As shown in FIG. 5, a sample flat plate 5 having 5 mm square and 1 mm thickness having periodic fine irregularities 10 in the range of 1 mm square at the center was formed.

  When the portion having the periodic fine irregularities of the sample flat plate was used as the surface of the antireflection surface and the light reflectance characteristic was examined, a good antireflection effect was obtained as shown in FIG.

  As an inorganic component, 6.6 g of methyltrimethoxysilane as an organic silicon compound, 1.6 g of phenyltrimethoxysilane as a phenyl group-containing organic silicon compound, 6.0 g of 3-methacryloxypropyltrimethoxysilane as a polymerizable group-containing organic silicon compound, and A solution composed of 4.4 g of pure water was stirred at 25 ° C. for 48 hours to cause the inorganic component to undergo a sol-gel reaction. By-products such as water and methanol were removed from this solution to obtain an inorganic component reaction solution. To the inorganic component reaction solution, 10.0 g of methyl (meth) acrylate and 0.1 g of Irgacure R500 (Nagase Sangyo Co., Ltd.), which is an ultraviolet curing agent, were added as organic components to obtain a liquid organic-inorganic composite composition.

  Next, using this organic-inorganic composite composition, using the same mold as in Example 1, molding was performed under the same conditions to obtain a sample flat plate having periodic fine irregularities at the center. This organic-inorganic composite had a pencil hardness of 8H.

（式（１）中、ｎは０または１であり、平均分子量は３８０）
で示されるビスフェノールＡ型エポキシ樹脂９重量部と３−グリシドキシプロピルトリメトキシシラン１３．６７重量部を混合した後、テトラエチレンペンタミン２．８４重量部を加えて、０℃にて攪拌し、純水１．５６重量部を添加して、さらに１時間攪拌し、透明で均質な有機無機複合組成物を得た。これを真空脱泡した後、実施例１と同様の成形型を用いて、成形型に、有機無機複合組成物を注ぎ、常温（２５±５℃）にて２４時間放置した後、成形型から取り出し、得られた平板を８０℃で２時間加熱した。このようにして本発明の有機無機複合材料からなる中央部に周期微細凹凸をもつサンプル平板を得た。この成形されたサンプル平板も他の実施例のサンプル平板と同様、十分な表面硬度を有しており、鉛筆硬度は６Ｈであった。
（反射防止面付光学素子としての利用例）
実施例１で作製した有機無機複合組成物を原料にして、カプセルの一部を構成する有機無機複合材料の光透過性半球状ドームを成型した。図７に示すように、光透過性半球状ドーム６は底辺の直径Ｄ＝１２ｍｍ、肉厚１ｍｍで、半球の内壁、同心状の等間隔の４箇所に、直径ｄ＝２ｍｍの円部の範囲内に周期微細凹凸１０₁・１０₂・１０₃・１０₄を持っている。

(In the formula (1), n is 0 or 1, and the average molecular weight is 380)
9 parts by weight of the bisphenol A type epoxy resin and 13.67 parts by weight of 3-glycidoxypropyltrimethoxysilane were mixed, and 2.84 parts by weight of tetraethylenepentamine was added and stirred at 0 ° C. Then, 1.56 parts by weight of pure water was added and the mixture was further stirred for 1 hour to obtain a transparent and homogeneous organic-inorganic composite composition. After vacuum degassing, using the same mold as in Example 1, the organic-inorganic composite composition was poured into the mold and left at room temperature (25 ± 5 ° C.) for 24 hours. The flat plate thus obtained was heated at 80 ° C. for 2 hours. In this way, a sample flat plate having periodic fine irregularities in the central portion made of the organic-inorganic composite material of the present invention was obtained. The molded sample flat plate had a sufficient surface hardness as in the case of the sample flat plates of the other examples, and the pencil hardness was 6H.
(Example of use as an optical element with an antireflection surface)
Using the organic-inorganic composite composition produced in Example 1 as a raw material, a light-transmitting hemispherical dome of an organic-inorganic composite material constituting a part of the capsule was molded. As shown in FIG. 7, the light-transmitting hemispherical dome 6 has a bottom diameter D = 12 mm, a thickness 1 mm, a hemispheric inner wall, and concentric equidistant areas of a circular portion having a diameter d = 2 mm It has periodic fine irregularities 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ inside.

  This light-transmitting hemispherical dome 6 was molded as follows.

First, a male mold 11 and a female mold 13 shown in FIG. 8 were manufactured. The female mold 13 was made of amorphous polyolefin resin so as to have a cup shape corresponding to the outer surface of the hemispherical dome 6. The male die 11 has a stainless steel hemispherical outer surface corresponding to the inner surface of the hemispherical dome 6 and has a recess of 2 mmφ + (tolerance is on the plus side) drilled corresponding to the positions of four periodic fine irregularities. Nesting molds 14 ₁ , 14 ₂ , 14 _3, and 14 ₄ are fitted and bonded to each other (see enlarged sectional view). Each nesting mold is an electroforming mold in which fine irregularities having a period T = 150 nm and a height H = 155 nm are periodically formed on an aluminum substrate (not shown), and the shape is inverted by electroforming. 15 is a circle having a diameter of 2 mm.

The liquid organic-inorganic composite composition 17 is poured into the cup of the female mold 13 and the male mold 11 is pressed until the gap between the male mold 11 and the female mold 13 is a predetermined distance. Next, ultraviolet rays having a light intensity of 12 mW / cm ^{2 at} a light wavelength of 365 nm are irradiated for 10 minutes from below the female mold 13 to cure the composition 17 having a dome shape. The male mold 11 was removed, and the light-transmitting hemispherical dome 6 (see FIG. 7) was removed from the female mold 13.

The periodic fine irregularities 10 ₁ , 10 ₂ , 10 _3, and 10 ₄ formed on the inner surface of the light transmissive hemispherical dome 6 have a function as an antireflection surface. This light-transmitting hemispherical dome 6 is used as an optical element with an antireflection surface.

  Next, an embodiment of an optical apparatus to which the present invention is applied will be described in detail.

  FIG. 9 is an example of an optical apparatus, and is a cross-sectional view of an electron observation apparatus 20 in which a light-transmitting hemispherical dome 6 is incorporated as an optical element with an antireflection surface. This electronic observation device 20 is an observation device that observes and diagnoses a lumen such as a body cavity of a subject. The body cavity is swallowed and illuminated in a dark body cavity, an image in the body cavity is formed on an imager by an objective lens, and image data by the imager is transmitted to the outside wirelessly. Then, the image data received externally is accumulated and taken into the display system, so that a doctor or the like observes the body cavity.

As shown in FIG. 9, the electron observation device 20 includes capsule frame bodies 22 and 23 that are detachably fitted in a cylindrical shape. The frame body 22 has the light-transmitting hemispherical dome 6 and the frame body 23 that are molded as described above. Has a structure in which a hemispherical mesh dome 23 in which a large number of holes are formed by an opaque member is fixed. An objective lens 25 constituting an imaging optical system (also referred to as an imaging optical system) that images the inside of the body cavity is attached to the center of the base 24 of the frame body 22. Light emitting diodes (LEDs) 26 serving as illumination light source elements constituting the illumination optical system are provided at a plurality of surrounding locations (four locations in this example), and the antireflection surface (periodic fine irregularities 10 ₁ and 10 ₂ ) of the hemispherical dome 6.・ It is attached so as to face 10 ₃ and 10 ₄ ). Therefore, the visual field range by the objective lens 25 from the periphery of the optical axis of the objective lens 25 can be illuminated through the antireflection surface. An imager 28 such as a CMOS or a CCD is attached to the center of the base 24 at an image forming position by the objective lens 25. The position of the hemispherical dome 6 facing the objective lens 25 is a surface without fine irregularities (both the entrance surface and the exit surface are smooth through surfaces).

  In the interior formed by the two capsule frames 22 and 23, an electric circuit unit 30 that performs signal processing and the like on the imager 28, and performs signal processing on image data obtained by the imager 28, and the circuit unit 30 and the like And an antenna 32 that transmits image data captured by the imager to the outside (outside the body) by radio waves (for example, transmits to the image data storage unit outside the body by radio waves).

  A pH sensor 34 for detecting acidity (pH) is attached so as to be exposed on the outer peripheral surface of the capsule frame 23, and a detection signal from the pH sensor 34 is input to the circuit unit 30. A mesh dome 33 is fitted on the bottom 35 of the frame body 23, and a large number of microcapsules 37 filled with a foaming agent are loaded therein so that the coating is broken and scattered by ultrasonic vibration.

  When the electronic observation device 20 is swallowed by the human body, it passes through the esophagus, stomach, duodenum, small intestine, large intestine, and the like sequentially. At this time, the pH in the stomach is 1.0 to 3.5 because there is a strong acid digestive fluid. In the duodenum, it is neutralized by digestive juice and bile, and is almost neutral (pH 7 or less). After that, the acidity gradually increases with small intestinal bacteria to pH 7 to 6.5, and around pH 6 in the large intestine. Accordingly, the position of the observation device 20 is confirmed while detecting the acidity in the lumen by the pH sensor 34. When the position reaches a predetermined position, the ultrasonic wave is irradiated from outside the body and the microcapsule 37 in the mesh dome 33 is irradiated. The coating is broken and the foaming agent inside is released from the pores and reacts with moisture in the lumen to generate a large amount of gas, leaving the lumen in an expanded state.

  Next, white light for illumination is emitted by the plurality of LEDs 26 via the circuit unit 30 to illuminate the inside of the lumen. The illumination light passes through the spherical surface inclined with respect to the central axis, not on the central axis passing through the top of the hemispherical dome 6, but there is almost no reflection loss due to the antireflection surface of the periodic fine irregularities 10. It can pass through and brightly illuminate the outer wall of the body cavity. Therefore, the observation image obtained by the imager 28 through the objective lens 25 through the reflection of the illumination light is bright and has a high S / N. As a result, the image data stored in the memory via the antenna 32 is also externally stored. The noise is reduced. As a result, diagnostic observation performance and diagnostic performance are improved.

  Although the hemispherical dome 7 shown in FIG. 7 has a uniform thickness in the above example, the thickness may be changed to partially have a lens action, and may be made a part of the optical system. Further, the periodic fine irregularities 10 formed on the hemispherical dome 7 may be formed not only on the inner surface of the dome 7 but also on the outer surface. Further, it may be formed on the inner surface and / or the outer surface corresponding to the objective lens 25.

It is sectional drawing which shows the Example of the optical element with an antireflection surface of this invention. It is a perspective view which shows the Example of the optical element with an antireflection surface of this invention. It is a perspective view which shows another Example of the optical element with an antireflection surface of this invention. It is a perspective view which shows another Example of the optical element with an antireflection surface of this invention. It is a perspective view which shows another Example of the optical element with an antireflection surface of this invention. It is a figure which shows typically an example of the molecular structure of the organic inorganic composite material used for the optical element with an antireflection surface of this invention. It is a figure which shows another example of the molecular structure of the organic inorganic composite material used for the optical element with an antireflection surface of the present invention in a simulated manner. It is a figure which shows another example of the molecular structure of the organic inorganic composite material used for the optical element with an antireflection surface of the present invention in a simulated manner. It is a figure which shows the light transmittance of the organic inorganic composite material used for the optical element with an antireflection surface of this invention. It is a perspective view which shows schematically the sample flat plate of the optical element with an antireflection surface of the present invention. It is a figure which shows the light reflectivity characteristic of the said sample flat plate. It is an external appearance perspective view which shows the Example of the optical system of this invention. It is sectional drawing which shows the shaping | molding die for shape | molding the optical system of this invention. It is sectional drawing which shows the Example of the optical instrument of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic inorganic composite material 3 Convex part 5 Sample flat plate 6 Hemispherical dome 10 Fine unevenness 11 Male type 13 Female type 14 Nest type 15 Aluminum base material 17 Organic inorganic composite composition 20 Electronic observation apparatus 22, 23 Capsule frames 24, 35 Base 25 Objective lens 26 Light emitting diode 28 Imager 30 Electric circuit section 31 Power supply battery 32 Antenna 33 Mesh dome 34 pH sensor 37 Microcapsule

Claims (10)

An optical element with an antireflection surface, characterized in that it has a light-transmitting organic-inorganic composite material on at least a surface, and the surface is an antireflection surface composed of fine irregularities having a period equal to or less than a transmitted light wavelength. A structure in which the organic-inorganic composite material is composed of an organic skeleton polymer matrix and an inorganic skeleton matrix, and / or a structure in which nanoscale inorganic fine particles are dispersed in an organic skeleton polymer matrix, or / and an organic skeleton monomer or oligomer 2. The optical element with an antireflection surface according to claim 1, which has a structure in which a monomer or oligomer having an inorganic element is copolymerized. The optical element with an antireflection surface according to claim 1, wherein the fine irregularities are tapered. At least a part of an optical system having an illumination optical system for transmitting illumination light from a light source element to irradiate an object and an imaging optical system for imaging the light reflected by the object on an imager is an organic-inorganic composite An optical system made of a material, wherein the transmission surface of an illumination optical system that transmits at least illumination light of the organic-inorganic composite material has an antireflection surface composed of fine irregularities having a period equal to or shorter than the transmitted light wavelength. The optical system according to claim 4, wherein the light incident / exit surface other than the transmission surface of the illumination optical system is a surface having no fine unevenness. Illumination light source element, illumination optical system for transmitting the illumination light to irradiate an object, an imager, an imaging optical system for imaging light reflected by the object on the imager, and input / output of the imager An optical circuit unit for processing the light, and the optical path of the illumination optical system is made of a light-transmitting organic-inorganic composite material and transmits at least illumination light of the organic-inorganic composite material. An optical apparatus characterized in that the surface has an antireflection surface composed of fine irregularities having a period equal to or shorter than the transmitted light wavelength. Illumination light source element, illumination optical system for transmitting the illumination light to irradiate an object, an imager, an imaging optical system for imaging light reflected by the object on the imager, and input / output of the imager And an electric circuit unit for processing the optical circuit unit in a capsule which is an organic-inorganic composite material in which the optical path of the illumination optical system is light transmissive. 8. The optical apparatus according to claim 7, wherein at least a transmission surface of an illumination optical system that transmits illumination light of the organic-inorganic composite material has an antireflection surface composed of fine irregularities having a period equal to or less than a transmitted light wavelength. The optical apparatus according to claim 8, wherein the antireflection surface is formed at a plurality of locations surrounding a portion having no fine unevenness. The optical apparatus according to claim 7, wherein a portion of the capsule made of a light-transmitting organic-inorganic composite material has a hemispherical dome shape.

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