JP2017066018A - Polishing glass lens blank and method for manufacturing optical lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing glass lens blank that can reduce a removal allowance when processing the blank into a lens, and to provide a method for manufacturing an optical lens.SOLUTION: The polishing glass lens blank has 150 μm or less thickness of a surface stria inclusion layer in a main surface and 200 μm or less difference between a maximum value and a minimum value of a thickness at a 80% distance of a radius from an outside diameter center.SELECTED DRAWING: None

Description

  The present invention relates to a polishing glass lens blank and a method for producing an optical lens.

  A reheat press manufacturing method is known as a method for manufacturing a lens. In the reheat press manufacturing method, for example, molten glass is poured into a mold to produce a square or plate-like glass block, and then the glass block is cut out by machining to make a cut piece. Next, rough polishing (barrel polishing) is performed in order to equalize the weight of each cut piece and to easily attach the release agent to the surface. Thereafter, the roughly polished cut piece is reheated and softened, and the softened glass is press-molded to form a lens blank having a shape approximate to the lens shape. Finally, a lens is manufactured by grinding and polishing the lens blank.

  According to this method, a plate-like glass block of a plurality of glass types is manufactured and stored, and if necessary, the plate-like glass block is cut into a desired number and volume of cut pieces, and the cut pieces are pressed to form a lens. Since blanks can be formed, it is suitable for high-mix low-volume production.

  As another lens manufacturing method, a direct press manufacturing method is also known in which molten glass dropped on a mold is directly press-molded. Unlike the reheat press method, the direct press method is suitable for mass production of small varieties. In this manufacturing method, since glass in a molten state is directly press-molded, the shape accuracy of the lens blank is inferior to that of the reheat press manufacturing method, and is not suitable for manufacturing a lens blank that requires high shape accuracy.

  When processing a glass lens blank for polishing after press molding into a lens, surface defects such as surface striation are removed, and furthermore, the lens is adjusted by adjusting the decentering, curvature radius and center thickness of the lens. Polishing and grinding to obtain the desired function and shape. If the machining allowance removed at this time, that is, the grinding allowance and polishing allowance are large, the processing time required for grinding and polishing increases. In addition, material is wasted.

  Patent Document 1 discloses a polishing glass lens blank having a defect-containing layer of 50 μm or less. In Patent Document 1, the defect-containing layer is softened with cracks generated during rough polishing, a portion where the glass component has changed due to contact with the processing liquid, a crystallized portion generated from softening to press molding, and a cut piece. When doing, the part (folded part) into which the corner | angular part was folded in glass is contained. By reducing the thickness of such a defect-containing layer, the machining allowance is reduced, and the processing time required for grinding and polishing can be shortened.

International Publication No. 2014/129657

  However, when actually processing the glass lens blank for polishing into a lens, it is necessary to remove not only the defect-containing layer but also the surface striae. Surface striae are vitreous linear or layered parts that have a refractive index different from that of the base glass, and are not recognized as scratches or bright spots, but ensure the performance and function of the lens. From the point of view, it should be removed. In many cases, the surface striae are generated in a range larger than the thickness of the defect-containing layer, and there are cases where the machining allowance cannot be reduced only by reducing the thickness of the defect-containing layer.

  In addition, when processing a glass lens blank for polishing after press molding into a lens, not only surface defects such as surface striae are removed, but also the inter-surface eccentricity, curvature radius and center thickness of the lens are adjusted. In order to obtain a desired function and shape as a lens, it is necessary to mold by grinding and polishing. At this time, when the most convex (or most concave) point (hereinafter also referred to as the optical center of the surface) and the outer diameter center of the press molding surface of the polishing glass lens blank are greatly deviated This results in a lens with large decentering between surfaces. In such a glass lens blank for polishing, the machining allowance for obtaining a desired function and shape by adjusting the inter-surface eccentricity, the radius of curvature and the center thickness is increased, and as a result, the processing time required for grinding and polishing is increased. Increased.

  Therefore, in press-molded glass lens blanks for polishing, when processing into lenses, the surface striae is removed, and the desired function and shape are adjusted by adjusting the decentering, curvature radius and center thickness of the lens. Therefore, there is a demand for a glass lens blank for polishing that requires a small machining allowance when being molded by grinding and polishing, and that can reduce the processing time required for grinding and polishing.

  As a result of intensive studies, the inventors have found that the thickness of the surface striae-containing layer on the main surface of the polishing glass lens blank is not more than a predetermined value, and the maximum thickness at a distance of 80% of the radius from the center of the outer diameter By using a polishing glass lens blank whose difference from the minimum value is equal to or less than a predetermined value, it has been found that the machining allowance when grinding and polishing into a lens can be reduced, and the present invention is completed based on this knowledge. It came to.

That is, the gist of the present invention is as follows.
(1) The thickness of the surface striae-containing layer on the main surface is 150 μm or less,
A polishing glass lens blank in which a difference between a maximum value and a minimum value at a distance of 80% of the radius from the center of the outer diameter is 200 μm or less.

(2) The polishing glass lens blank according to (1), wherein the polishing glass lens blank is made of fluorophosphate glass.

(3) The glass lens blank for polishing according to (1) or (2), wherein the thickness of the defect-containing layer on the main surface is 150 μm or less.

(4) The glass lens blank for polishing according to any one of (1) to (3), wherein at least the main surface is a press-molded surface.

(5) The polishing glass lens blank according to any one of the above (1) to (4) is subjected to spherical grinding, smoothing, and polishing without using a metal bond grindstone. A method of manufacturing an optical lens, wherein an optical lens is obtained by performing processing using a resin bond polishing tool.

(6) An optical lens obtained by subjecting the polishing glass lens blank according to any one of (1) to (4) above to smoothing and polishing without performing spherical grinding to obtain an optical lens. Production method.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the glass lens blank for grinding | polishing which can reduce the machining allowance at the time of processing into a lens, and an optical lens can be provided.

FIG. 1A is a side view showing an example of the shape of a polishing glass lens blank according to an embodiment of the present invention. FIG. 1B is a schematic view showing a distance of 80% of the radius from the center of the outer diameter of the glass lens blank for polishing in a top view in a broken line. FIG. 2A is a flowchart showing a process of manufacturing the blank shown in FIG. 1A. FIG. 2B is a flowchart showing a process of manufacturing an optical lens from the blank shown in FIG. 1A. FIG. 3 is a schematic view showing an example of the glass lump forming step shown in FIG. 2A. FIG. 4 is a schematic view showing an example of a release agent coating step shown in FIG. 2A. FIG. 5 is a schematic view showing an example of the pressing step shown in FIG. 2A. FIG. 6 is a schematic diagram illustrating an example of a method for measuring the thickness of the surface striae-containing layer of the lens blank.

<Grinding glass lens blank>
FIG. 1A is a side view showing an example of the shape of a glass lens blank for polishing (hereinafter sometimes simply referred to as “lens blank”) according to one embodiment of the present invention.

  In the present specification, the “polishing glass lens blank” refers to glass in a state before being subjected to grinding or polishing for producing an optical lens. The “press molding surface” refers to a surface to which the molding surface of the mold has been transferred in the pressing process, and refers to a state in which polishing processing has not been performed after the molding surface transfer. It should be noted that the “outer diameter” does not include a defective portion such as a projection that protrudes outside the side peripheral surface of the lens blank in a pressing process or the like.

  As shown in FIG. 1A, a polishing glass lens blank 2 according to an embodiment of the present invention has substantially spherical press-molding surfaces 2A and 2B that are main surfaces. The press molding surfaces 2A and 2B are surfaces to which the molding surface shapes of the upper die 74 and the lower die 72 are transferred (see FIG. 5). Although both surfaces (2A, 2B) are convex curved surfaces, the shape of the lens blank of the present invention is not particularly limited, and either one or both may be concave curved surfaces or flat surfaces. Note that the side peripheral surface 2C of the polishing glass lens blank 2 may be a press-molded surface formed by the inner peripheral surface of the body mold 73, or may be a free surface that does not contact the body mold 73 ( (See FIG. 5).

  The glass lens blank 2 for polishing is subjected to grinding processing or polishing processing, which will be described later, to become an optical lens (hereinafter simply referred to as “lens”).

  In one embodiment of the present invention, the thickness of the surface striae-containing layer on the main surface (2A, 2B) of the lens blank 2 is 150 μm or less from the main surface. The thickness of the surface striae-containing layer is preferably 120 μm or less, and more preferably 100 μm or less and 90 μm or less in order. Although the minimum of the thickness of the said surface striae content layer is not specifically limited, For example, it can be set to more than 50 micrometers or 80 micrometers or more. The thickness of the surface striae-containing layer means the thickness from the main surface of the portion where the surface striae are formed most deeply, that is, the distance to the striae observed at the deepest portion when viewed from the main surface. . These surface striae need to be completely removed in the optical lens.

  Surface striae are portions of slightly different composition from the parent glass that result from the evaporation of some of the glass components in the reheating process, and are glassy linear or layered with a refractive index different from that of the parent glass. It can be observed by using a striae inspection apparatus comprising a point light source and a lens system.

  In the glass lens blank 2 for polishing, since the formation of the surface striae-containing layer can be controlled within the above range by the manufacturing method described later, the machining allowance in the grinding and polishing steps can be reduced. In addition, since the surface striae-containing layer is formed to be the same as or deeper than the thickness of the defect-containing layer described later, in the grinding and polishing process, if the surface striae-containing layer is ground and polished to a thickness that can remove the surface striae-containing layer, it contains defects. The layer can also be removed.

The thickness of the surface striae-containing layer can be measured by the following method.
FIG. 6 is a schematic diagram illustrating an example of a method for measuring the thickness of the surface striae-containing layer of the lens blank. As shown in FIG. 6, the side peripheral surface 2C of the lens blank is polished until it becomes an optical mirror surface in a straight line when viewed from above, thereby forming a first polished surface. The amount of polishing when forming the first polishing surface is set as small as possible within the range where the polishing surface becomes an optical mirror surface. Here, an optical mirror surface means the mirror surface which has the transmittance | permeability of the glass which comprises a lens blank.

  Next, as shown in FIG. 6, by the same formation method as the first polishing surface, on the opposite side peripheral surface across the outer diameter center 2D from the first polishing surface, on the first polishing surface in a top view. A second polished surface having a parallel optical mirror surface is formed. Then, while irradiating light from the second polishing surface toward the first polishing surface with a lamp or the like, the transmitted light is observed from the first polishing surface side using a magnifying mirror with a scale. The part where the surface striae-containing layer exists is compared with the part without the surface striae, and the transmitted light becomes non-uniform and a contrast difference is generated. can do. Using a magnifying glass with a scale, the distance from the main surface to the deepest part of the portion where the transmitted light is non-uniform is measured as the thickness of the surface striae-containing layer.

  Next, a pair of polishing surfaces similar to the first polishing surface and the second polishing surface are sequentially formed so as to surround the side peripheral surface of the lens blank 360 degrees when viewed from above. The thickness of the surface striae-containing layer is measured from each polished surface by the same method as described above. Although the number of polishing surfaces to be formed depends on the size of the lens blank, at least two pairs of polishing surfaces may be formed to measure the thickness of the surface striae-containing layer. In this manner, the maximum thickness of the surface striae-containing layer on the lens blank main surface is measured.

  For example, if the maximum thickness of the surface striae-containing layer on the lens blank main surface thus measured is 100 μm, the thickness of the surface striae-containing layer on the lens blank main surface is estimated to be 100 μm. .

  In the glass lens blank 2 for polishing which concerns on one Embodiment of this invention, the difference of the maximum value of thickness and the minimum value in the distance of 80% of a radius from an outer-diameter center is 200 micrometers or less. The difference between the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter is preferably 150 μm or less, and more preferably 100 μm or less, 80 μm or less, and 50 μm or less in order.

  FIG. 1B is a schematic view showing a distance of 80% of the radius from the outer diameter center 2D of the polishing glass lens blank in a top view by a broken line. The polishing glass lens blank 2 has a substantially perfect circle shape when viewed from above. However, it is not limited to this shape, and is appropriately selected according to the shape of the target optical lens. The outer diameter center 2D is the midpoint of the outer diameter of the glass lens blank 2 for polishing. When the planar shape of the lens blank 2 deviates from a perfect circle, the center of the outer diameter can be defined as the center of gravity in a figure having the same shape as the planar shape of the lens blank 2. The radius is half the outer diameter. When the center of the outer diameter is “center of gravity”, the radius is an average value of the distance from the center of gravity to the outer edge of the lens. The lens blank is usually substantially circular, and the midpoint of the outer diameter and the center of gravity coincide. The distance of 80% of the radius from the outer diameter center 2D indicates a position away from the outer diameter center 2D by a length of 80% of the radius. That is, when a distance of 80% of the radius from the outer diameter center 2D is indicated by a line, it is concentric with the polishing glass lens blank 2 and has a radius of the polishing glass lens blank as a circle drawn by a broken line in FIG. 1B. It can be drawn as a circle that is 80% of the radius of 2.

  When the difference between the maximum value and the minimum value of thickness at a distance of 80% of the radius from the center of the outer diameter exceeds 200 μm, the optical center of the surface of the glass lens blank, that is, the most convex (or the most concave) on the main surface The center of the outer diameter is greatly deviated from the center of the outer diameter, and when processing into an optical lens, the surface is decentered, the radius of curvature and the center thickness are adjusted to obtain the desired function and shape. The machining allowance for polishing and forming increases, and as a result, the processing time required for grinding and polishing increases. In addition, a desired inter-surface eccentricity, a radius of curvature, and a center thickness cannot be ensured, and the lens may not be processed. In the polishing glass lens blank 2 according to one embodiment of the present invention, the difference between the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter is within the above range, so that the optical center of the surface And the center of the outer diameter can be reduced. As a result, when processing into an optical lens, it is possible to adjust the inter-surface eccentricity, the radius of curvature, and the center thickness, and to reduce the machining allowance that must be removed to obtain a desired function / shape.

  Note that the thickness at the distance of 80% of the radius is 100% of the radius, that is, the thickness at the side peripheral surface 2C of the polishing glass lens blank 2 is generated on the side peripheral surface 2C and the vicinity thereof. It is difficult to measure the exact thickness due to the above-mentioned protrusions, etc., and when the thickness is closer to the center of the outer diameter, the difference between the minimum value and the maximum value is small. This is because evaluation may be difficult.

  Further, the size of the lens blank 2 of the present invention is not particularly limited. However, in order to achieve the object of the present invention more effectively, the diameter is preferably 10 mm or more, and further, 15 mm or more, 18 mm or more, 20 mm or more. Is more preferable.

  In the glass lens blank 2 for polishing according to one embodiment of the present invention, the thickness of the defect-containing layer on the main surface (2A, 2B) is preferably 150 μm or less from the main surface, and further 120 μm or less, 100 μm or less, 90 μm. The smaller the order, the better. Although the minimum of the thickness of the said defect content layer is not specifically limited, For example, it can be set to more than 50 micrometers or 80 micrometers or more. The thickness of the defect-containing layer means the thickness from the main surface of the portion where the defect is deepest, that is, the distance to the defect observed at the deepest portion when viewed from the main surface. These defect-containing layers need to be completely removed in the optical lens.

  In the present embodiment, the defect-containing layer includes a portion in which the glass component has been altered by contact with the processing liquid, a crystallized portion that is generated from softening to press molding, and a trace that is generated when the molten glass is cut with a cutting blade. Defects such as (shear mark) are included.

The thickness of the defect-containing layer can be measured by the following method.
A plurality of lens blanks are prepared under the same conditions and the polishing depth is changed stepwise. The polishing depth of each lens blank can be, for example, 100 μm, 120 μm, 140 μm, and 160 μm.
The polished surface of the lens blank polished from the main surface of the lens blank to a predetermined depth is irradiated with an argon lamp to observe bright spots. When the defect-containing layer remains in the lens after processing, the defect-containing layer scatters light and causes a bright spot. Therefore, for example, when the polishing depth is 100 μm and the polishing depth is 120 μm, the bright spot is observed, but when the bright spot is not observed at the polishing depth of 140 μm or more, the thickness of the defect-containing layer is determined to be 120 μm. . On the other hand, when the polishing depth is 100 μm, bright spots are observed, but when the polishing depth is 120 μm or more, no bright spots are observed, the thickness of the defect-containing layer is determined to be 100 μm.

  Although it does not specifically limit as a glass material of the glass lens blank 2 of this embodiment, For example, the glass shown below is used.

The glass preferably used as the glass material of the glass lens blank 2 of the present embodiment is a fluorophosphate glass containing at least P (phosphorus), O (oxygen) and F (fluorine) as glass components. In particular, a fluorophosphate glass having a molar ratio O ²⁻ / P ⁵⁺ of less than 3.5 and easily causing surface striae, or a fluorophosphate glass containing highly volatile B (boron) or Si (silicon). It is suitable for this. Also suitable to abrasion degree F _A 400 or more fluorophosphate glass.

  The content of P (phosphorus) in the fluorophosphate glass can be determined by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. The content of O (oxygen) can be determined, for example, by a method such as heat melting-NDIR (Non Dispersive InfraRed) analysis. Each analysis value may include a measurement error of about ± 5% of the analysis value, for example.

ここで、ｄは試料の比重、ｄ_ｏは標準試料（ＢＳＣ７）の比重である。 The degree of wear (F _A ) is determined by the following method.
A sample with a measurement area of 9 cm ² is held at a fixed position of 80 mm from the center of a flat plate made of cast iron that rotates horizontally at 60 revolutions per minute. Feed evenly for minutes and wrap under a load of 9.807N. The sample mass before and after the lapping is weighed to determine the wear mass m. Similarly, the wear mass m ₀ of the standard sample (BSC 7) designated by the Japan Optical Glass Industry Association is measured, and the wear degree (F _A ) is calculated by the following equation.

Here, d is the specific gravity of the sample, _{d o} is the specific gravity of the standard sample (BSC7).

  Next, the specific example of the manufacturing method of the glass lens blank 2 for grinding | polishing shown to FIG. 1A is demonstrated using FIG. 2A-FIG.

  FIG. 2A is a flowchart showing a process of manufacturing the blank shown in FIG. 1A. FIG. 3 is a schematic view showing an example of the glass lump forming step shown in FIG. 2A. As shown in FIG. 2A, a glass lump is formed in step S1. In order to form a glass lump, as shown in FIG. 3, molten glass is dropped from the molten glass nozzle 40 onto the concave receiving part 32 formed on the upper surface of the glass lump tray 30. A glass lump 20 is formed in the interior of the glass.

  The saucer 30 is heated to a predetermined temperature in advance. The temperature of the tray 30 is, for example, 250 to 500 ° C. The nozzle 40 can be controlled to a predetermined temperature. The temperature of the nozzle 40 is, for example, 700 to 1200 ° C. although it depends on the glass material. At this time, the viscosity of the glass dropped from the nozzle is preferably 2 to 30 dPa · s. By setting the viscosity of the molten glass in the glass lump forming step within the above range, a glass lump having a small weight variation can be manufactured with high productivity.

  Examples of the shape of the glass lump 20 include a spherical shape or an approximate shape thereof, a flat spheroid shape, a biconvex curved surface shape, and a single-convex, single-concave curved surface shape, but are not particularly limited.

  The molten glass is cut by a cutting method using a known cutting blade.

  The glass block 20 cooled on the glass block receiver is taken out from the receiver 30 when it reaches a temperature lower than the glass transition temperature Tg and moves to the take-out position. In this way, for example, 5 g of glass lump 20 can be produced with a productivity of 15 or more per minute.

  In the glass lump forming step, it is preferable that the weight is controlled by the viscosity of the molten glass and the cutting conditions. By adjusting the viscosity of the molten glass, the flow rate of the molten glass can be controlled. The cutting amount can be controlled by the cutting conditions (cutting speed, cutting timing or interval) of the molten glass. By controlling the outflow speed and cutting amount of the molten glass, it is possible to suppress the weight variation of the molten glass supplied to the tray 30. In this embodiment, the weight variation can be within ± 1%, preferably within ± 0.5%.

  In the glass lump forming step, the glass lump forming tray 30 is heated to a predetermined temperature and can be continuously supplied. Therefore, the glass lump 20 can be manufactured with high productivity by receiving the molten glass continuously supplied by the receiving tray 30 for forming the glass lump and forming the glass lump by molding. In particular, if the glass lump 20 is produced by continuously supplying a plurality of glass lump forming trays 30 below the nozzle, the effect becomes remarkable.

  Moreover, the dispersion | variation in the weight of a glass lump can also be suppressed by adjusting the viscosity of molten glass, and the feed rate of the saucer 30. FIG. That is, by adjusting the viscosity of the molten glass, the outflow speed of the molten glass flowing out from the nozzle can be controlled, and by adjusting the feeding speed of the tray 30, the amount of cutting of the molten glass can be controlled. .

  In this embodiment, considering that the polishing process of the final lens product is arranged in the next process, the glass lump obtained in the glass lump forming process has wrinkles or the like that can be removed in the polishing process on the surface. It may be.

  As shown in FIG. 2A, after step S1 for forming a glass lump, a release agent coating (attachment) step is performed in step S2. In this release agent coating (adhesion) step, a release agent is interposed between the two in order to prevent the glass from softening plate and glass used for softening the glass lump in the reheating step described later. Let FIG. 4 is a schematic view showing an example of a release agent application (attachment) step shown in FIG. 2A. In the release agent application (adhesion) step, as shown in FIG. 4, the release agent is conveyed along the conveyance direction X of the softening plate 50 in which a plurality of holding recesses 52 are formed. At this position, the release agent is sprayed from the first release agent nozzle 54a toward the empty holding recess 52, and the entire concave surface of the holding recess 52 is spread with the release agent 60a. In addition, the softening dish 50 can be comprised from the ceramic, metal, brick, etc. which have heat resistance. Further, the release agents 60a and 60b prevent the softening plate 50 and the glass from being fused.

  It is preferable that the release agent 60 a is applied so as to protrude from the concave surface of the holding concave portion 52. The application amount (application density) of the release agent 60a is not particularly limited.

  As the release agent 60a, powder release agents such as boron nitride, alumina, silicon oxide, and magnesium oxide are used, and the average particle diameter of the release agent is not particularly limited, but is preferably 1 to 20 μm. The holding recess 52 laid with the release agent 60a is conveyed in the conveyance direction X, and the release agent 60a applied between the first release agent nozzle 54a and the second release agent nozzle 54b. On top of this, a glass mass 20 is supplied.

  Thereafter, at a second position where the second release agent nozzle 54b is present, the release agent 60b is sprayed from the nozzle 54b toward the entire upper surface of the glass lump 20 and applied (attached). The release agent 60b is preferably the same as the release agent 60b described above, but may be a different type of release agent or a release agent having a different average particle diameter. The amount of the release agent applied from the nozzle 54b is preferably the same as the amount of the release agent applied from the nozzle 54a, but may be different. When the release agent 60a is applied (attached) to the holding recess 52 of the softening plate 50, the application (attachment) of the release agent 60b to the glass lump 20 supplied to the holding recess 52 is omitted. Also good.

  As shown in FIG. 2A, after step S2, a reheating step is performed in step S3. In the reheating step, the softening plate 50 on which the glass block 20 to which the release agents 60a and 60b shown in FIG. 4 are applied is fed along the transport direction X into a heating furnace (not shown). Inside the heating furnace, the glass block 20 is reheated.

In the heating furnace, the glass block 20 to which the release agent is applied is heated to a temperature equal to or higher than the softening point of the glass material constituting the glass block 20. For example, it heats with the heating furnace set to the temperature of 500-1000 degreeC. The glass lump 20 is softened by this reheating, and the viscosity is preferably 10 ⁴ to 10 ⁶ dPa · s. The reheating step can be performed in an air atmosphere.

  When the glass lump 20 is softened in a heating furnace, the viscosity of the glass lump 20 is lowered, the height of the glass lump 20 is lowered, and the outer diameter is expanded. At this time, if the release agent 60b on the glass lump 20 wraps around between the glass lump 20 and the holding recess 52, the glass lump 20 can be wrapped with a relatively small amount of the release agent 60a, 60b. Therefore, a sufficient release effect can be achieved without roughening the surface of the glass lump.

  Therefore, in this embodiment, the process (barrel polishing process etc.) which roughens the surface of a glass lump can be abbreviate | omitted in the process from obtaining a glass lump to press-molding. Furthermore, in this embodiment, the process of grinding or polishing the glass lump can be omitted in the steps from obtaining the glass lump 20 to press molding.

As shown in FIG. 2A, after step S3, a pressing process is performed in step S4. FIG. 5 is a schematic view showing an example of the pressing step shown in FIG. 2A. In the pressing step, the glass lump 20 is press-molded by the mold apparatus 70 shown in FIG. The glass lump 20 is transferred onto the lower mold 72 inside the body mold 73 of the press apparatus 70 shown in FIG. 5 in a state of being softened to a predetermined viscosity (10 ⁴ to 10 ⁶ dPa · s) in the reheating process. . A release agent is applied to the upper die 74 and the lower die 72 in advance.

  The upper die 74 and the lower die 72 are preheated to 400 to 800 ° C. After the glass block 20 is supplied to the lower mold 72, the upper mold 74 is relatively close to the lower mold 72, and the glass block 20 is sandwiched between the upper mold 74 and the lower mold 72 and pressed. Note that press molding can be performed in an air atmosphere.

  The press molding is performed by reheating (softening) the glass lump 20 to the viscosity set by the above-described reheating, so that it can be manufactured in a shape close to the final glass product based on the shape of the mold. By this pressing step, the glass lens blank 2 for polishing shown in FIG. 1A is obtained.

  In the glass lens blank for polishing 2 according to one embodiment of the present invention, the difference between the maximum value and the minimum value at a distance of 80% of the radius from the center of the outer diameter is 200 μm or less. Such a glass lens blank for grinding | polishing can be manufactured with the following procedures in a press process, for example using the metal mold | die apparatus shown in FIG.

[1] A glass lump is press-molded as described above to produce a dummy lens blank.
[2] In the dummy lens blank, using a known single-wall measuring jig, a point indicating the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter is specified, and this maximum value Find the difference between and the minimum value.
[3] In order to reduce the difference between the maximum value and the minimum value obtained in [2] above, press axes shown in FIG. 5 (virtual axes connecting the centers of the upper die and the lower die of the mold apparatus) ). For example, the inclination of the upper mold 74 may be adjusted according to the point indicating the specified maximum value and minimum value. At this time, the lens blank is adjusted so that the difference between the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter is 200 μm or less.
[4] Repeat [1] to [3] as necessary.
[5] A glass lump is press-molded using the mold apparatus adjusted in the above [3] and [4]. In the obtained glass lens blank for polishing, the difference between the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter is 200 μm or less.

The press load per unit area in the pressing step (hereinafter simply referred to as “press load”) varies depending on the composition and outer diameter of the glass block, the shape of the target glass lens blank 2, and the like, but is 5 to 17 MPa ( 51 to 173 kgf / cm ² ) is desirable. If the press load is out of the above range, the shape accuracy of the molded glass lens blank 2 may deteriorate. In the present embodiment, the shape accuracy of the glass lens blank 2 means the accuracy of the inter-surface eccentricity, the radius of curvature, and the center thickness.

  Although FIG. 5 shows a single mold device 70, there are actually a plurality of mold devices 70, and the shape of the molding surface is not limited to the example shown in the figure, and a biconvex lens, biconcave surface A lens, a plano-convex lens, a plano-concave lens, a convex meniscus lens, or a concave meniscus lens is used.

  Further, since the press molding is performed at a relatively high temperature, the mold release agent described above is provided on the molding surface of the lower mold 72 and / or the upper mold 74 in order to prevent the glass lump 20 and the molds 72 and 74 from being fused. It is desirable to apply (attach).

<Optical lens>
The optical lens according to the present embodiment is formed by grinding and polishing the polishing glass lens blank obtained by the present embodiment.

  Hereinafter, the grinding and polishing process of the lens blank 2 shown in FIG. 1A will be described with reference to FIG. 2B. However, the present invention is not limited to the following embodiments, and is within the scope of the object of the present invention. Can be implemented with appropriate modifications.

  In step S10 shown in FIG. 2B, a spherical grinding process (CG processing) of the main surface of the lens blank 2 shown in FIG. 1A is performed using a curve generator. Although the thickness of a CG processing area | region is not specifically limited, Preferably it is 50-200 micrometers. The processing time required for CG processing is not particularly limited, but is about 40 to 90 seconds.

  In the CG processing, a CG processing region (CG processing allowance) including surface defects such as surface striae on the main surface of the lens blank 2 is ground. In the CG processing, for example, grinding is performed while supplying a grinding liquid using a grindstone having an abrasive grain portion having a grain diameter of 20 to 60 μm (# 800 to # 400 in grain size display) made of diamond particles.

  By such CG processing, the inter-surface eccentricity of the lens blank 2 is adjusted, and its main surface is molded into a shape close to a spherical surface having a predetermined curvature.

  In the lens blank 2 according to this embodiment, the thickness of the surface striae-containing layer on the main surfaces 2A and 2B is as small as 150 μm or less, and the difference between the maximum value and the minimum value at a distance of 80% of the radius from the center of the outer diameter. Is 200 μm or less. Therefore, even if the surface striae-containing layer is sufficiently removed at the stage of CG processing, and even if the shape is close to the desired shape by adjusting the inter-surface eccentricity, the radius of curvature and the center thickness, the main surface There is no need to scrape a lot.

  In the lens blank 2 according to the present embodiment, a grindstone having a relatively fine particle size can be used as the grindstone for CG processing. Usually, with a grindstone with a fine grain size, it is difficult to perform a large amount of processing at a time, so that it cannot be processed when the target processing amount is large. However, since the lens blank 2 according to the present embodiment can reduce the target processing amount in the CG processing, the CG processing can be completed even with a grindstone having a relatively fine particle size.

  Further, in the lens blank 2 according to the present embodiment, since CG processing can be performed with a grindstone having a relatively fine particle size, it is possible to prevent micro cracks generated by the CG processing from reaching the deep part of the glass.

  When using a grindstone with a relatively fine grain size, the amount that can be processed at a time is small, but the microcracks generated by processing do not become extremely deep (for example, remain 15 μm or less from the surface), and the microcracks are sufficiently small in the subsequent process. Can be removed.

  Next, as shown in FIG. 2B, in step S11, a smoothing process (SM process) by a fine grinding process is performed. The SM processing may be one-step processing or multi-step processing. For example, the SM machining may be performed twice under different conditions, that is, the SM machining area may be removed by dividing it into a first SM machining area and a second SM machining area.

Moreover, in this embodiment, in SM processing, the process using only a resin bond grindstone can be performed without using a metal bond grindstone. Thereby, in this embodiment, the depth of the micro crack which arises on the surface of a lens blank at the time of SM process can be suppressed very shallowly. Processing using only a resin bond is particularly suitable for a fluorophosphate glass having an abrasion degree F _{A of} 400 or more.

  Normally, in the SM processing as well as the CG processing, innumerable micro cracks are newly generated on the surface of the processed lens blank by contacting the base portion or the abrasive grain portion of the grindstone with the lens blank. In particular, when a metal bond grindstone is used, a small crack of several tens of microns (for example, 30 to 40 μm) is formed on the surface of the lens blank by contacting the metal base of the grindstone with the lens blank during SM processing. Occur.

  On the other hand, when using a resin bond grindstone, the impact caused by the contact between the base portion of the grindstone and the lens blank is significantly reduced as compared with a metal bond grindstone. The depth can be kept to a few microns or less (for example, 5 μm or less).

  In the present embodiment, when only the resin bond grindstone is used, the depth of micro cracks generated by SM processing can be greatly reduced. As such a resin bond grindstone, a grindstone having a grain size of 8 to 20 μm (# 2500 to # 1200 in terms of grain size) made of diamond particles can be used. In the present embodiment, the roughness of the grindstone used in the second SM machining can be made finer than the roughness of the grindstone used in the first SM machining.

  Furthermore, in the present embodiment, the depth of microcracks generated is further reduced by using a relatively fine particle size resin bond grindstone during the second SM processing compared to the case of using a grindstone with a large particle size. it can. According to the present embodiment as described above, the processing amount of the post-process (polishing process) can be set to 10 μm or less.

  The processing time required for SM processing performed on a lens blank that has undergone CG processing is not particularly limited, but is about 30 to 120 seconds in total. The thickness of the SM processing region (SM processing amount) is not particularly limited, but is preferably 10 to 50 μm in total.

  In SM processing, the processing amount per step is preferably 30 μm or less. In this way, by suppressing the SM processing amount per step, not only SM processing but also polishing time can be shortened. In addition, the shape accuracy of the lens after processing can be improved. In the present embodiment, the shape accuracy of the optical lens means the accuracy of the inter-surface eccentricity, the radius of curvature, and the center thickness.

  Next, as shown in FIG. 2B, in step S12, polishing is performed. In the polishing step, the surface is polished with a polishing liquid containing abrasive grains having a particle size of 5 μm or less to polish the polishing region (polishing allowance). The thickness of the polishing region is preferably 3 to 10 μm, and the processing time is about 2 to 10 minutes. By this polishing process, the optical lens surface 2c (main surface) of the optical lens body 2b is formed.

  Finally, a centering process is performed in step S13 shown in FIG. 2B, but the centering process may be omitted depending on circumstances. In the centering step, for example, the optical lens body 2b is sandwiched between a pair of lens holders for centering, and the lens body 2b is rotated around the center line, and the side peripheral surface of the lens body 2b is secured with a diamond grindstone or the like. Grinding into a circle is performed.

  Up to this point, the grinding and polishing steps shown in FIG. 2B have been described as examples. However, the manufacturing process of the optical lens using the lens blank 2 according to the present embodiment is not limited to such steps, and various This process can be performed.

  For example, in the lens blank 2 according to the present embodiment, the CG processing in step S10 shown in FIG. 2B can be omitted. As described above, in the lens blank 2 according to the present embodiment, the thickness of the surface striae-containing layer on the main surface 2A is as small as 150 μm or less (the same is true on the main surface 2B), and at a distance of 80% of the radius from the center of the outer diameter. The difference between the maximum value and the minimum value of the thickness is also as small as 200 μm or less. Therefore, there is little allowance for sufficiently removing the surface striae-containing layer and adjusting the inter-plane eccentricity, the radius of curvature and the center thickness to obtain a desired function / shape. In such a lens blank 2 according to this embodiment, it is not necessary to perform a large amount of processing in order to remove surface defects such as surface striae and to form a lens having a desired shape, and in step S10 shown in FIG. 2B. It is also possible to omit CG processing. That is, the processing of the lens blank 2 can be started from the SM processing in step S11 shown in FIG. 2B.

  When the CG processing in step S10 is omitted, a metal bond grindstone may be used during the SM processing. In addition, when a metal bond grindstone is used, there exists a problem which the above micro cracks become deep, but it is effective at the point which can set many process amounts compared with a resin bond grindstone.

  In this way, various optical lenses such as a biconvex lens, a biconcave lens, a planoconvex lens, a planoconcave lens, a convex meniscus lens, and a concave meniscus lens can be obtained. Note that the step shown in FIG. 2B may be performed at a different place from the step shown in FIG. 2A.

  The optical functional surface of the obtained lens may be coated with an antireflection film, a total reflection film or the like according to the purpose of use.

  The present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the present invention.

  For example, in the above-described embodiment, when an optical lens is manufactured using the polishing glass lens blank according to the present invention, an example in which a metal bond grindstone is preferably not used in SM processing after CG processing is illustrated. This does not preclude the use of a metal bond grindstone in SM processing. That is, the glass lens blank for polishing according to the present embodiment can be suitably used for various production processes and conditions of optical lenses that have been conventionally performed.

  Hereinafter, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited to these Examples. “Difference between maximum and minimum thickness at a distance of 80% of the radius from the center of outer diameter”, “Thickness of surface striae-containing layer”, “Thickness of defect-containing layer” and “Removal allowance” are as follows: It was evaluated as follows.

(Difference between the maximum and minimum thickness at a distance of 80% of the radius from the center of the outer diameter)
Using a known single-wall measuring jig, the minimum and maximum values of the thickness of the lens blank at a distance of 80% of the radius from the center of the outer diameter were measured. Next, the difference between the minimum value and the maximum value was determined to identify the difference between the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter.

(Thickness of surface striae-containing layer)
A linear polished surface was formed on a part of the side peripheral surface of the lens blank in top view. Another polishing surface parallel to the polishing surface was formed on the opposite side peripheral surface across the center of the outer diameter from the polishing surface. The polished surface was polished until it became an optical mirror surface. Next, while irradiating light with one lamp toward one polished surface, the transmitted light was observed from the other polished surface side using a magnifying mirror with a scale. Using a magnifying glass with a scale, the distance from the main surface to the deepest part of the portion where the transmitted light is non-uniform was measured. Eight polishing surfaces (4 pairs) were formed and measured from each polishing surface, and the maximum value was defined as the thickness of the surface striae-containing layer.

(Defect-containing layer thickness)
A plurality of lens blanks were prepared under the same conditions and the polishing depth was changed stepwise. The polishing depth of each lens blank was 100 μm, 120 μm, 140 μm, and 160 μm.
The polished surface of the lens blank polished from the main surface of each lens blank to a predetermined depth was irradiated with an argon lamp to observe a bright spot. When the polishing depth was 100 μm and the polishing depth was 120 μm, a bright spot was observed, but when no bright spot was observed at a polishing depth of 140 μm or more, the thickness of the defect-containing layer was determined to be 120 μm.

(Reserve)
A plurality of lens blanks prepared under the same conditions were prepared, and the center thickness D1 of the lens blank was measured.
Next, it grind | polished until the surface striae content layer was not recognized with respect to the main surface. Here, the main surface is one surface of the lens blank. Specifically, a plurality of prepared lens blanks were subjected to a polishing process in which the polishing time was changed stepwise, and the presence or absence of a surface striae-containing layer was confirmed for each lens blank. Then, the center thickness D2 of the lens in which the surface striae-containing layer was not recognized was measured. The presence or absence of the surface striae-containing layer was confirmed by the method described in (Thickness of surface striae-containing layer). The difference between the center thickness D1 of the lens blank and the center thickness D2 of the polished lens was used as the allowance for the lens blank.

(Manufacture of glass lens blank for polishing)
The raw materials were mixed and melted to a predetermined composition, and the molten glass made of fluorophosphate glass was continuously flowed down at a constant speed from a platinum alloy outflow pipe. Using a molding die for molding one after another, it was continuously molded into a glass lump. When the temperature of the glass dropped below the glass transition temperature, the glass lump was taken out of the mold to obtain a glass lump. Next, a release agent (boron nitride) was applied to the softening tray of the reheating device used in the reheating step.

The obtained glass lump (diameter of about 30 mm, thickness of about 5 mm, and weight of about 18 g) is subjected to a release agent without performing a preliminary process such as barrel polishing (that is, while maintaining the surface state of the glass lump). Supplied on coated pan. The glass lump supplied on the saucer was put into a heating furnace set at 500 to 750 ° C. together with the saucer, and reheated in an air atmosphere. The reheated glass mass softened to a viscosity of about 10 ⁵ dPa · s.

Next, a release agent was applied to the molding surface of the press molding die apparatus. The glass lump softened by reheating was press-molded in an air atmosphere using a press molding die apparatus. The press molding was performed with a press load of 8 to 8.5 MPa (81 to 87 kgf / cm ² ) using a mold heated to a temperature of 500 ° C. A double-sided convex lens blank (diameter 50 mm, center thickness 3 mm, weight 18 g) was obtained. The molar ratio of the lens blank made of fluorophosphate glass ^O 2- ^{/ P 5+} is less than 3.5, and a wear level _{F A} was 400 or more.

  In addition, the upper and lower mold inclinations of the mold apparatus are finely adjusted, and as shown in Table 1, the difference D between the maximum value and the minimum value at a distance of 80% of the radius from the center of the outer diameter is within a predetermined range. It set so that it might become.

  Table 1 shows the difference D between the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter of the lens blank thus obtained, the surface formed on the main surface (press-molded surface). The thickness (μm) of the striae-containing layer and the necessary machining allowance (μm) are shown. The thickness of the surface striae-containing layer was 150 μm or less (80 to 120 μm) in all lens blanks. Moreover, the thickness of the defect-containing layer was 120 μm in all including the examples and comparative examples.

In Examples 1 to 7, in which the difference D between the maximum value and the minimum value of the thickness at a distance of 80% of the radius from the center of the outer diameter was 200 μm or less, the required machining allowance was 200 μm or less. On the other hand, in Comparative Examples 1 and 2 in which the difference D between the maximum value and the minimum value of the thickness exceeds 200 μm, the machining allowance is remarkably high even though the thickness of the surface striae is about the same as in Examples 1 to 7. Increased.

2 ... Glass lens blank for polishing 2A ... Main surface (press molding surface)
2B ... Main surface (press molding surface)
2C ... Side peripheral surface 2D ... Outer diameter center 20 ... Glass lump 30 ... Glass lump tray 32 ... Receiving portion 40 ... Melting glass nozzle 50 ... Softening plate 52 ... Retaining recesses 54a, 54b ... Release agent nozzles 60a, 60b ... Mold release agent 70 ... Mold device 72 ... Lower mold 73 ... Body mold 74 ... Upper mold X ... Conveying direction

Claims (6)

The thickness of the surface striae-containing layer on the main surface is 150 μm or less,
A polishing glass lens blank in which a difference between a maximum value and a minimum value at a distance of 80% of the radius from the center of the outer diameter is 200 μm or less.   The polishing glass lens blank according to claim 1, wherein the polishing glass lens blank is made of fluorophosphate glass.   The glass lens blank for grinding | polishing of Claim 1 or 2 whose thickness of the defect content layer in the said main surface is 150 micrometers or less.   The glass lens blank for grinding | polishing in any one of Claims 1-3 whose at least said main surface is a press molding surface.   A spherical grinding process, a smoothing process, and a polishing process are performed on the glass lens blank for polishing according to any one of claims 1 to 4, and in the smoothing process, a resin bond polishing tool is used without using a metal bond grindstone. An optical lens manufacturing method that performs processing to obtain an optical lens.   The manufacturing method of the optical lens which performs a smoothing process and a grinding | polishing process with respect to the glass lens blank for grinding | polishing in any one of Claims 1-4, without performing a spherical grinding process, and obtaining an optical lens.

Images