JP2012255927A - Optical element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a glass optical element, which makes it possible to let even an optical element using phosphate glass, etc. with poor environmental durability have enough environmental durability to fit for practical use.SOLUTION: In an optical element 1 which is made of phosphate glass or fluorophosphate glass, an optical function film 3 is formed on a surface of an optical function face of core glass 2, and a glass surface on which no optical function film 3 is formed of a side face of the optical element is covered by a waterproof coating film 4 mainly made of polyester. A manufacturing method for the optical element 1 is also provided.

Description

  The present invention relates to an optical element having improved environmental durability and a method for manufacturing the same, and in particular, when phosphoric acid glass or the like is used as a glass material, the optical element is prevented from being spoiled and deteriorated to improve environmental durability. The present invention relates to an optical element and a manufacturing method thereof.

  In recent years, attention has been focused on a direct press molding method in which an optical glass element such as a glass lens is press-molded and can be used as it is without polishing the molding surface.

  The glass material used for this press molding method is adjusted so that the glass transition point is lowered when the press molding temperature is lowered to improve the workability. For example, it is known that a significant reduction in molding temperature can be realized by changing the glass composition system from silica glass to phosphate glass in order to realize a particularly low glass transition point.

  However, when phosphate glass is used, the environmental durability is significantly reduced. In contrast, an optical functional film such as an antireflection film is formed on the glass surface to protect the surface and protect the environment. There are also moves to prevent gender decline. However, even if such an optical functional film is formed, the environmental durability may not be satisfactory.

  Further, not only glass materials for press molding but also optical glasses include phosphoric acid glass containing phosphoric acid as a main component and fluorophosphate glass added with fluorine in order to prioritize optical performance. Since these give priority to optical performance, they are used with low environmental durability, and this low environmental durability is a serious problem in practical use.

In the case where a glass material having poor environmental durability as described above is put into practical use, conventionally, (1) the first layer of the antireflection film is formed as a dense film such as alumina to prevent moisture from entering (for example, (See Patent Document 1), (2) The entire surface of the lens is coated with a film such as an antireflection film to eliminate the influence of moisture (see, for example, Patent Document 2), or (3) Film formation of the antireflection film. The method uses vacuum evaporation using IAD (ion beam assisted film formation) instead of normal vacuum evaporation, or (4) pays attention to the surface-modified layer of the press-molded product, and forms SiO ₂ as the first layer. Improvements have been made by methods such as improving the adhesion between the glass and the antireflection film (see, for example, Patent Document 3).

JP 9-159803 A JP-A-2-178601 JP-A-1-287501

  However, in the method (1), no matter how dense a film is formed on the first layer, the glass is exposed on the side surface of the lens, so that when placed in a humid atmosphere, the phosphoric acid component dissolves from the side surface. It was found that it reacted with the surface of the lens optical surface, resulting in the formation of spiders on the lens.

  In the method (2), since the lens side surface is also covered with a film, phosphoric acid does not dissolve out, so it is effective in preventing spiders. The chemicals used in this method have the effect of melting glass. Soaking a glass material with poor environmental durability makes the glass surface cloudy, the glass itself melts and disappears, and there are restrictions on the applicable glass materials. .

  Further, when the entire surface coating as in (2) is performed by a normal vapor deposition method, it is difficult to coat the side surface, and if only the optical function surface is coated, the film can be formed normally twice on both sides. Because the film formation on the side surface is added, the number of film formation increases significantly from 4 to 6 times, and various problems such as difficulty in securing the performance of the anti-reflection film on the special jig and optical function surface. Will occur.

  In addition, the method (3) is effective in strengthening the adhesion of the film, but the side surface of the lens is exposed, so that the cloud may be generated in the lens as in the method (1). It was. Further, the IAD method is problematic in terms of cost because the price of the apparatus is significantly higher than that in the case of ordinary vacuum deposition.

In the method (4), SiO ₂ is also a dense film like alumina. However, no matter how dense the film is formed on the first layer, the side surface of the lens is exposed and the humidity is high. When placed in an atmosphere, the phosphoric acid component dissolves from the side surface and reacts with the surface of the lens optical surface, resulting in generation of spiders on the lens. Further, in the case of a single layer film of SiO ₂ , the lens seems not to be fogged, but the characteristics (reflectance) as an antireflection film are deteriorated by about 2% compared to the case of normal magnesium fluoride. There is a drawback that the performance of the system is degraded.

  As described above, the conventional method is insufficient to raise the environmental durability of a glass material with poor durability, particularly phosphate glass, to a level that can completely withstand practical use, and to secure the optical characteristics of the lens.

  The present invention is a glass material having poor environmental durability, for example, a glass optical element made of phosphate glass or fluorophosphate glass. An object of the present invention is to provide an optical element and a method for manufacturing the same.

  The present inventor has made various studies in order to improve the environmental durability of an optical element having an optical functional film such as an antireflection film on the surface using glass material having poor environmental durability, in particular, phosphate glass. It has been found that application of a water-resistant paint to (edge) is very effective.

  That is, the optical element of the present invention is an optical element made of glass in which an optical functional film is formed on the optical functional surface, and the glass surface on the side surface (edge portion) of the optical element in which the optical functional film is not formed Is coated with a water-resistant coating film containing polyester as a main component.

  In the method for producing an optical element of the present invention, an optical functional film is formed on an optical functional surface of an optical element made of glass, and glass on the side surface (edge portion) of the optical element on which the optical functional film is not formed. A water-resistant coating film comprising a polyester as a main component is applied to the surface and dried to form a water-resistant coating film.

  According to the optical element of the present invention and the method for manufacturing the same, the glass material of the glass optical element made of glass having poor environmental durability and the optical functional film formed on the lens surface are not affected even in a high temperature and high humidity atmosphere. The deterioration of the optical element can be effectively suppressed, and the optical function can be stably secured.

  In addition, according to the method for manufacturing an optical element of the present invention, it is only necessary to add a simple operation with a small number of steps using a conventional manufacturing method. An optical element with improved durability can be manufactured at low cost.

It is sectional drawing of the optical element which is one Embodiment of this invention. It is a schematic block diagram of the vacuum evaporation system used when forming the optical function film | membrane by this invention. It is a figure which shows the relationship between the wavelength and spectral reflectance in an optical functional film of Table 4. It is a figure which shows the relationship between the wavelength and spectral reflectance in an optical function film | membrane of Table 5. It is a figure which shows the relationship between the wavelength in the optical function film | membrane of Table 6, and a spectral reflectance.

Hereinafter, the present invention will be described in detail with reference to the drawings.
As described above, the optical element of the present invention is formed by forming an optical functional film on the surface (optical functional surface) of a glass optical element, and further, the side surface (edge portion) of the optical element is water resistant. A coating film is formed, and the entire glass material of the optical element is covered with an optical functional film and a water-resistant paint.

  FIG. 1 is a cross-sectional view showing a schematic configuration of an optical element of the present invention. Here, the optical element 1 includes a core glass 2, a water-resistant paint mainly composed of a polyester formed on a side surface (edge portion) of the core glass 2 and an optical function film 3 formed on the surface (optical function surface) thereof. It consists of the water-resistant coating film 4 which consists of these.

  Here, the core glass 2 is made of a glass material having poor environmental durability, for example, phosphate glass or fluorophosphate glass, and is obtained by processing as an optical element. The core glass 2 is obtained by a known optical element manufacturing method. As a method for manufacturing an optical element (lens), a glass material is cut, rounded, roughened, sanded, polished, centered, or glass. It can be obtained by pressing or centering the material by molding.

  In addition, as a glass material of the core glass 2, the phosphate glass or fluorophosphate glass which has a composition (mass%) shown in Tables 1-3 is mentioned, for example. For these glass materials, their refractive index (nd), Abbe number (vd), glass transition point (Tg), and yield point (At) are also shown.

Here, the glass material shown in Table 1 is a glass containing phosphoric acid as a main component so that it can be molded at a low temperature by lowering the glass transition point for press molding. Its components are _P 2 _O 5 45 to 53 wt%, ZnO 7 to 37 _wt%, K 2 O _{0~9 wt%,} Na 2 O _{0~10 wt%,} Li 2 O _1~4 wt%, _Al 2 O ₃ 1 to 10% by mass, BaO 0 to 10% by mass, CaO 0 to 5% by mass, other trace components (B ₂ O ₃ , SiO ₂ , ZrO ₂ , Sb ₂ O ₃ , SrO, La ₂ O ₃ , MgO, WO _{3, Nb} 2 _{O 5)} is in the 0-2 wt%, respectively. The refractive index nd is in the range of 1.53 to 1.60, and the Abbe number νd is in the range of 59 to 64.

The glass material shown in Table 2 is originally a glass material mainly composed of phosphoric acid in terms of optical characteristics, but is a glass material adjusted so that it can be molded at a lower temperature by further reducing the glass transition point for press molding. Its components are _P 2 _O 5 36-48 _{wt%, B} 2 O 3 _{4~11 wt%,} Li 2 O _3~5 wt%, BaO 15-38 wt%, CaO 2 to 9 wt%, MgO 0 to 7 wt%, SrO 0 to 8 _wt%, Al ₂ O 3 2 to 4 wt%, other minor components _{(ZnO, La 2 O 3,} Gd 2 O 3) is in the 0-4 wt%, respectively. The refractive index nd is 1.58 to 1.62 and the Abbe number νd is 63 to 68.

The glass material shown in Table 3 is ordinary optical glass, not for press molding, but is used for a predetermined application in terms of optical characteristics, and is a fluorophosphate glass containing phosphoric acid as a main component and further containing fluorine. . The environmental durability is remarkably inferior because optical properties are prioritized. Its components are _P 2 _O 5 0 to 7 wt%, NaF 0 to 2 _wt%, AlF 3 12 to 32 _wt%, MgF 2 5 to 11 _wt%, CaF 2 15 to 17 _wt%, SrF 2 19 to 26 weight %, Al (PO ₃ ) _{3 0 to} 27% by mass. The refractive index nd is in the range of 1.43-1.50, and the Abbe number νd is in the range of 81-96.

  As described above, in a severe environment such as high temperature and high humidity, the material of the core glass 2 itself is not so strong, and an antireflection film, which is an optical functional film, has been formed on the surface so far. Although there is an example, there is almost no effect on environmental durability, and an optical element using phosphate glass and fluorophosphate glass as a glass material has not been used for applications in harsh environments.

For example, as a typical example of the antireflection film, there is one having magnesium fluoride (MgF ₂ ) as the outermost surface layer. As a result of conducting an environmental durability test on the phosphate glass on which the antireflection film is formed, the glass surface is It was eroded and spiders were produced.

  As a result of studying the mechanism of the cloud of this optical element, the present inventors have found that the cloud is generated in the following steps 1 to 4.

Step 1: Phosphoric acid in the phosphate glass dissolves from the side surface of the optical element under high temperature and high humidity conditions.
Step 2: The dissolved phosphoric acid adheres to the optical functional film surface of the optical element, that is, the outermost surface layer.
Step 3: Phosphoric acid adhering to the surface reacts with magnesium fluoride employed in the outermost surface layer of the antireflection film.
Step 4: Magnesium fluoride deteriorates and spiders are generated on the optical element surface.

  The above was found as a result of detailed analysis of the optical element deteriorated in the environmental endurance test.Specifically, when the composition of the surface of the lens where the spider is generated is analyzed in detail from the surface side, the deterioration occurs. It was found that only the outermost layer was present and the next layer was not deteriorated at all.

  That is, in phosphate glass or fluorophosphate glass, the phosphoric acid component generated from the side surface of the glass material reacts with the outermost surface layer to produce spiders, and the present inventors have low environmental durability. The cause was clarified for the first time.

  Therefore, the present inventors provide an optical functional film 3 on the surface (optical functional surface) of the core glass 2 made of phosphate glass or fluorophosphate glass, and a water-resistant coating film 4 on the side surface (edge portion). Thus, it has been found that an optical element with improved environmental durability can be obtained.

  Here, examples of the optical functional film 3 include an antireflection film, an IR cut filter, a reflective film, a protective film, a bandpass filter, a low cut filter, and the like. Other film configurations may be configured so as to conform to a predetermined standard by using a known material so as to exhibit a desired function.

  The optical functional film 3 may be a single layer or a laminate of two or more layers.

  The optical functional film 3 is formed on the optical functional surface of the core glass 2 and is not formed on the side surface (edge portion). For this reason, the entire surface of the core glass 2 is not covered with the optical functional film, and the optical functional film 3 is partially formed. In this way, the optical functional film is formed only on the necessary optical functional surface, and not on the optically meaningless side surface, so that the cost and labor can be reduced in manufacturing.

  And the water-resistant coating film 4 formed in a side surface (edge part) is formed in the side surface of the core glass 2 in which the above-mentioned optical function film 3 is not formed. By forming this water-resistant coating film 4, the core glass 2 is covered on the entire surface and does not come into contact with the outside air. For this reason, the glass on the side surface of the optical element is exposed as before, and the phosphoric acid component in the glass starts to melt in an atmosphere with a lot of moisture and reacts with the outermost surface layer of the optical functional surface. Can prevent functional degradation.

  The water-resistant paint used here is preferably a resin mainly composed of polyester. A water-resistant coating film can be easily formed by dissolving such a main component in a solvent and applying it to an optical element, followed by drying and solidifying. I can do it. The polyester as the main component may be any polyester that can be used as a paint having water resistance, and is preferably a polyester obtained by adding a styrene monomer to an unsaturated polyester. As this water-resistant paint, in particular, a paint that can be used by diluting with a solvent such as thinner so as to be easily applied is more preferable. For example, “Fastite No. 140 (N)” (manufactured by Ohashi Chemical Co., Ltd., Product name). As this water-resistant paint, for example, epoxy paint, acrylic paint, silanol paint, fluororesin paint, etc. are not suitable for the present invention because the water cannot actually be completely blocked.

  The water-resistant coating film 4 may be formed of one type of polyester-based paint, or a plurality of polyester-based resins may be overcoated. Depending on the use of the optical element, the edge portion may need to be sanitized. In such a case, after applying the polyester-based paint of the present invention, the conventional black ink may be applied, or the black polyester-based paint of the present invention may be applied.

  By forming the side surface of the core glass 2 as a film made of a water-resistant paint having polyester as a main component, generation of phosphoric acid from the side surface can be prevented, and reaction of the phosphoric acid component can be prevented on the outermost surface layer.

  The film thickness of the water-resistant coating film 4 can be arbitrarily set within a range not impairing its performance, but is preferably in the range of 1 μm or more and 100 μm or less. If the thickness is less than 1 μm, the density of the film may be lowered and the characteristics for preventing the reaction may be insufficient. If the thickness exceeds 100 μm, the variation in the thickness of the film increases, and the tolerance of the diameter required for the optical element (usually ± 5) It is difficult to satisfy (about ˜20 μm) and cracks are likely to occur in the film. If it exceeds 100 μm, it takes time for coating and drying, which is also an economical problem.

Next, the manufacturing method of the optical element of this invention is demonstrated.
The optical element of the present invention is a conventionally known method, for example, a method of cutting, rounding, roughening, sanding, polishing, and centering a glass material, or heat-softening the optical element molding material and pressing it with a molding die. The optical functional thin film 3 is formed by a conventional method on the surface of the core glass 2 obtained by the method of centering as necessary, and then a water-resistant paint is applied to the side surface in the same manner as the ink painting. The water-resistant coating film 4 may be formed by drying.

  In order to form an optical functional film on the optical functional surface of the phosphate glass or fluorophosphate glass, a known thin film forming method can be used. For example, a vacuum vapor deposition method in which a vapor deposition material is vaporized by resistance heating, electron beam, or the like is advantageous in terms of cost. In addition, when vacuum deposition is employed, a plasma assist or ion assisted deposition film forming method is preferable in that film formation can be performed efficiently. In addition to vacuum deposition, known film formation methods such as sputtering and CVD can also be used.

  Hereinafter, a method for forming the optical functional film 3 on the core glass 2 by a vacuum deposition method will be described with reference to FIGS. 1 and 2. Here, FIG. 2 is a diagram showing a schematic configuration of the vacuum deposition apparatus.

  First, after the core glass 2 is cleaned by an ordinary glass cleaning process using an ultrasonic cleaner, the core glass 2 is set on the film forming dome 13 and placed in the vacuum chamber 11. The core glass 2 is heated to 150 ° C. to 350 ° C. by the heater 12 while evacuating the chamber from the vacuum exhaust port 14. What is necessary is just to select the temperature to heat according to the glass transition point of the core glass 2, and just to make it 100 degreeC or more lower than a glass transition point.

The reason for heating at the time of film formation is to increase the denseness of the film. If the film is not heated, the film will be in a rough state, which is not preferable. After evacuating until the degree of vacuum inside the vacuum chamber 11 becomes 1 × 10 ⁻³ Pa or less, various substances as the evaporation source 16 are evaporated by the electron gun 17, and a thin film that becomes the optical functional film 3 is formed on the core glass 2. Form. Note that oxygen is introduced from the gas inlet 15 during film formation as necessary so that the oxide is in a desired oxidation state when the material to be deposited is an oxide.

  The film structure is designed and determined in advance so as to satisfy the characteristics required for a normal lens and to sufficiently exhibit the function as an optical functional film.

  Next, a water-resistant paint mainly composed of polyester dissolved in a solvent is applied to the side surface of the core glass 2 on which the optical functional film 3 is not formed so that the core glass 2 does not come into contact with the outside air, and is dried. Thus, the optical element 1 of the present invention is obtained.

  The mixing ratio of the thinner and the paint is not particularly limited as long as a viscosity that is easy to apply can be obtained, but is preferably in the range of 1: 4 to 2: 1. The mixing ratio depends on the temperature of the environment in which the coating is to be performed. In an environment where the temperature is high, thinner is better. When drying is performed at 140 ° C. for about 1 hour, a sufficiently strong film can be obtained.

Embodiments of the present invention will be specifically described below with reference to examples.
<Preparation of optical element (core glass)>
Glass material No. in Table 2 A material is cut out from an optical glass block (plate material) mainly composed of phosphoric acid having the composition shown in FIG. 7, and is ground, polished, and centered by an ordinary method, and has an outer diameter of 7 mm, a center thickness of 4.3 mm, and a curvature. The glass was processed into a biconvex lens-shaped core glass 2 having a radius of 7 mm on both sides (edge thickness: 2.424 mm) and (volume 0.13 cc).

<Formation of antireflection film (optical functional thin film)>
After the obtained core glass 2 was cleaned by an ordinary glass cleaning process using an ultrasonic cleaner, an optical functional film 3 functioning as an antireflection film of the present invention was formed by a vacuum vapor deposition apparatus shown in FIG. FIG. 1 is a cross-sectional view showing an embodiment of the optical element of the present invention. The core glass 2 of the optical element is a glass material No. It consists of optical glass which has phosphoric acid shown in 7 as a main component. The optical functional thin film 3 is a normal single layer film (magnesium fluoride film; Table 4) and a normal multi-coat (Tables 5 to 6).

  First, the core glass 2 was set on the dome 13 for film formation and placed in the vacuum chamber 11. The core glass was heated to 150 ° C. to 350 ° C. from the heater 12 while evacuating from the vacuum exhaust port 14. The heating temperature was selected according to the glass transition point. That is, the temperature was 100 ° C. or more lower than the transition point.

After evacuating until the degree of vacuum inside the vacuum chamber 11 became 1 × 10 ⁻³ Pa or less, various substances as evaporation sources were evaporated by the electron gun 17 to form a film on the core glass 2.

  In Tables 4 to 6 described below, the film directly formed on the core glass is defined as the first layer, and numbers are given in the order of stacking sequentially with the second layer, the third layer,. The Nth layer having the maximum number is the outermost surface layer, and AIR represents air (the outermost surface layer is in contact with air).

Table 4 shows the configuration of an antireflection film in which a magnesium fluoride (MgF ₂ ) single layer film is formed on the surface of the core glass, and FIG. 3 shows the reflection characteristics thereof.

Table 5 shows the configuration of an antireflection film in which a conventional multilayer film (seven layers) is formed on the surface of the core glass, and FIG. 4 shows the reflection characteristics thereof. In the table, OH5 is a trade name of a vapor deposition material manufactured by Canon Optron, and is a mixture of ZrO ₂ and TiO ₂ .

  Next, as a representative example, the glass material No. 12, An antireflection film was formed on glass having an nd of 1.43425.

  Table 6 shows the structure of an antireflection film in which a conventional multilayer film (5 layers) is formed on the surface of the core glass, and FIG. 5 shows the reflection characteristics thereof.

<Formation of edge coating film>
A water-resistant coating film 4 was formed by applying a water-resistant paint to the side surface (edge portion) of the optical element on which the antireflection film was formed, using a blacking machine.
The paint used was Fastite 140 (N) manufactured by Ohashi Chemical Industry. Two colors, matte black and clear, were used. The ratio of Fastite 140 (N) and exclusive thinner 2350 (manufactured by Ohashi Chemical Co., Ltd.) was 1: 1. 525 (manufactured by Ohashi Chemical Industry Co., Ltd.) was added at 3% with respect to the total amount.
The film thickness of the paint was 1, 10, 20, and 50 μm. After applying the paint, baking (drying) was performed at 140 ° C. for 30 minutes using an oven.

<Environmental durability test>
An environmental durability test was performed on the optical element obtained as described above. The environmental durability test was performed by putting the obtained optical element into a constant temperature and humidity apparatus maintained at 60 ° C. and 90% RH. The state of occurrence of cracks and cracks in the optical element at each of 125 hours, 250 hours, 500 hours, 750 hours, and 1000 hours after introduction was visually observed using a high-intensity light source. Furthermore, microscopic observation was also performed. Glass material No. 7. As a result of glass having nd of 1.59216, glass material No. Table 7 shows the results of the glass with 12 and nd of 1.43425.

  From the examples in Table 7, it was found that environmental durability would be better if fastening of polyester paint was applied to the edge. On the other hand, if the coating film was made too thick, the coating film cracked, and water penetrated from there, resulting in poor durability.

  No. 7, no. When glass materials other than 12 (Nos. 1 to 6, 8 to 11) were tested in the same manner, the same tendency was shown although there were some differences. A similar test was performed by changing the sample to a lens produced by press molding, but similar results were obtained.

  In the above embodiment, Fastite 140 (N) manufactured by Ohashi Kogyo Co. was used. However, the present invention is not limited to this. For example, TH-1000 (trade name) manufactured by Kansai Paint Co., Ltd., manufactured by Hamani Paint Co., Ltd. Good results were also obtained with Solless Surfacer NAC-350-50 Black (trade name).

DESCRIPTION OF SYMBOLS 1 ... Optical element, 2 ... Core glass, 3 ... Optical functional film, 4 ... Water-resistant coating film, 11 ... Vacuum chamber, 12 ... Heater, 13 ... Dome, 14 ... Vacuum exhaust port, 15 ... Gas introduction port, 16 ... Evaporation source, 17 ... Electron gun

Claims (7)

An optical element made of glass having an optical functional film formed on the optical functional surface,
An optical element characterized in that the glass surface on the side surface of the optical element on which the optical functional film is not formed is coated with a water-resistant coating film containing polyester as a main component.   The optical element according to claim 1, wherein the glass is made of phosphate glass or fluorophosphate glass.   The optical element according to claim 1, wherein the water-resistant coating film has a thickness of 1 μm to 100 μm.   The optical element according to any one of claims 1 to 3, wherein the water-resistant coating film is a black water-resistant coating film.   An optical functional film is formed on the optical functional surface of an optical element made of glass, and further, a water-resistant paint mainly composed of polyester is applied to the glass surface on the side surface of the optical element on which the optical functional film is not formed and dried. A method for producing an optical element, characterized in that a water-resistant coating film is formed.   The method for producing an optical element according to claim 5, wherein the glass is made of phosphate glass or fluorophosphate glass.   The method for producing an optical element according to claim 5 or 6, wherein thinner is used as a solvent for the water-resistant paint, and the film thickness of the water-resistant coating film after drying is 1 μm or more and 100 μm or less.

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