JP2012210700A - Method for grinding optical glass and method for manufacturing optical glass lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grind a press-formed lens of optical glass at a lower cost without impairing quality.SOLUTION: A method for grinding an optical glass includes steps for preparing the press-formed glass formed by press-molding the optical glass into a predetermined shape (S5A, S5B), carrying out precise grinding by making a conductive cup grinding wheel having a grinding surface for precise grinding abut on the press-formed glass having a surface to be ground before a rough grinding process and rotating it (S6b), and performing electrolytic in-process dressing that carries out the dressing of a grinding surface by applying a predetermined voltage between an electrode and the cup grinding wheel while supplying a conductive grinding liquid between the electrode arranged at a position opposite to the grinding surface of the cup grinding wheel and the cup grinding wheel during the grinding process.

Description

  The present invention relates to an optical glass grinding method and an optical glass lens manufacturing method.

  An optical glass lens (hereinafter also simply referred to as a lens) used in an optical device such as a camera is obtained by grinding and further polishing an optical glass produced from a glass material having desired optical characteristics. Obtainable.

  Among these, grinding is to perform rough grinding, which is a processing process that prioritizes processing efficiency over the quality of the surface to be ground, such as roughness, and then to fine grinding, which is a process that adjusts shape accuracy and surface condition. A two-step process is required. Specifically, the following grinding methods have been devised.

  For example, in Patent Document 1, a lens grinding process is performed by performing a rough grinding process using a spherical surface generation machine (hereinafter referred to as CG) and then performing a fine grinding process using CG.

  In Patent Document 2, a conductive grindstone is used as a grinding method for roughing a spherical surface by milling and grinding using a cup grindstone, which is widely known as a roughing method for a spherical lens. A technique of applying an electrolytic in-process dressing grinding method (ELID: Electrolytic In-process Dressing) in which a workpiece (workpiece) is ground while dressing is disclosed.

  Patent Document 3 discloses a grinding method by CG processing.

JP-A-8-132340 JP 2000-246613 A Utility Model Registration No. 2600063

  Optical glass lenses are manufactured by various methods, but in order to reduce the amount of reduction due to grinding and polishing processes as much as possible and to reduce costs by shortening the processing time, they are approximated to the optical glass lenses that are finally produced. In many cases, press products having different shapes are used.

  A pressed product is produced by casting a molten glass material (in this case, in the state of molten glass) onto a lower mold, and pressing the cast molten glass lump using the upper mold and the lower mold. ) And optical glass such as RP (Reheat Press) manufactured by heating and softening a glass material preformed into a predetermined shape and pressing it with a mold.

  The RP product is excellent in the accuracy of the refractive index because it is measured by measuring the refractive index of the product (glass material) and then reheating, softening and pressing. On the other hand, the DP product is obtained by melting a glass material as a glass material and pressing the molten glass as it is while it is hot and soft, and is excellent in dimensional accuracy such as an outer shape and a wall thickness.

  Such a pressed product of optical glass is formed after once melting a glass material as a glass material, so that the surface to be ground is very smooth and slippery. Therefore, when grinding such an optical glass press product, it is necessary to first maintain the grindability of the grindstone with respect to the surface to be ground. In other words, the selection of the grindstone is very important.

  When grinding a pressed product of optical glass, for example, even if a grindstone having abrasive grains for fine grinding is used, grinding cannot be performed because the sustainability of the grinding wheel grinding force cannot be obtained on the surface to be ground. Can not. Therefore, a person skilled in the art usually selects a grindstone having abrasive grains for coarse grinding, for example, abrasive grains such as grain size display # 325, and executes the coarse grinding first.

  In other words, even when grinding a pressed product of optical glass, it is necessary to first perform coarse grinding with a grindstone having coarse abrasive grains, and then with a grindstone having fine grinding grains. It is necessary to go through a two-stage grinding process disclosed in Patent Document 1 in which fine grinding is performed.

  Incidentally, in Patent Document 2, for BK7 (borosilicate crown glass, wear degree measured based on Japan Optical Glass Industry Association Standard JOGIS-10 is 118) which is a kind of optical glass, particle size indication # 325, # Using three types of grinding stones of 600 and # 4000, multi-stage grinding is performed, which is divided into rough machining (rough grinding) and finishing (fine grinding). That is, also in Patent Document 2, a two-stage grinding process is performed as in Patent Document 1 described above.

  Thus, in the grinding process performed before the polishing process of the optical glass, in order to ensure the quality of the surface to be ground, the two-stage process of the rough grinding process and the fine grinding process is essential. Accordingly, the time required for the grinding process until polishing is inevitably increased, which causes a problem that the production efficiency is lowered and the production cost is increased.

  In particular, when grinding a pressed product of optical glass, since rough grinding is physically required, it has been difficult to improve the production efficiency further.

  Therefore, the present invention has been devised to solve the above-mentioned problems, and does not reduce the quality (ensure the quality of the surface to be ground) and is low in cost (processing) with respect to optical glass press products. The present invention provides a method for grinding optical glass and a method for producing an optical glass lens, which can perform grinding processing with reduced cost).

According to a first aspect of the present invention, there is provided a preparation step for preparing a press product obtained by press-molding optical glass into a predetermined shape, and a grinding surface for fine grinding for a press product having a surface to be ground before rough grinding. A grinding step of performing precise grinding by contacting and rotating a conductive cup grindstone, and an electrode disposed at a position facing the grinding surface of the cup grindstone during the grinding step, and the cup grindstone An electrolytic in-process dressing step of dressing the ground surface by applying a predetermined voltage between the electrode and the cup grindstone while supplying a conductive grinding liquid between This is a grinding method for optical glass.
According to a second aspect of the present invention, in the invention according to the first aspect, in the preparation step, the glass forming body preliminarily formed into a predetermined shape is softened by heating, and then the glass is formed using a forming die. It is a step of producing a pressed product of the optical glass by press-molding a molded body.
According to a third aspect of the present invention, in the invention described in the first aspect, in the preparation step, a glass raw material adjusted so as to obtain an optical glass having desired optical characteristics is melted to obtain a molten glass. Thereafter, the molten glass is supplied from a pipe outlet to a forming die, and is press-formed using the forming die, thereby producing a pressed product of the optical glass.
According to a fourth aspect of the present invention, in the invention described in the second or third aspect, the optical glass press product has a surface roughness Rz of the ground surface of 2.0 μm or less. To do.
According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the cup grindstone includes an abrasive that grinds the ground surface and a bond material that bonds the abrasive. And the grain size of the abrasive grains is # 2000 to # 8000.
According to a sixth aspect of the present invention, in the invention described in the fifth aspect, the average particle diameter of the abrasive grains is 1.0 to 10.0 μm.
According to a seventh aspect of the present invention, in the invention described in the fifth aspect, the bond material is made of a metal bond or a resin bond.
According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the rotational speed of the cup grindstone in the grinding step is 18000 rpm or more and 30000 rpm or less.
According to a ninth aspect of the present invention, in the invention according to any one of the first to eighth aspects, the relative position movement feed in the contact variable direction of the pressed product of the optical glass and the cup grindstone in the grinding step. The speed is 1.0 μm / sec or more and 15.0 μm / sec or less.
According to a tenth aspect of the present invention, in the invention described in any one of the first to ninth aspects, the optical glass press is made of fluorophosphate glass, phosphate glass, niobium phosphate-containing high refractive index and high refractive index. It consists of any one of dispersion glass or high refractive index low dispersion glass containing lanthanum borate.
According to an eleventh aspect of the present invention, there is provided an optical glass lens for producing an optical glass lens from the optical glass press using the optical glass grinding method according to any one of the first to tenth aspects. Is the method.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to perform a grinding process at low cost, without reducing quality with respect to the press goods of optical glass.

It is a figure for demonstrating schematic structure of the optical glass grinding apparatus shown as embodiment of this invention. It is a flowchart which shows an example of the manufacturing procedure of a general optical glass lens. It is a flowchart which shows an example of the manufacturing procedure of the optical glass lens in embodiment of this invention. It is a figure for demonstrating the mechanism of the electrolytic dressing by ELID grinding method. It is explanatory drawing which shows the processing conditions in Example 1- Example 7 of this invention. It is explanatory drawing which shows the processing conditions in Example 8-Example 10 of this invention. It is explanatory drawing which shows the process conditions in Example 11- Example 12 of this invention. It is explanatory drawing which shows the processing conditions in Example 13-Example 15 of this invention. It is explanatory drawing which shows the processing conditions in the comparative example 1- comparative example 2 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the present embodiment, an optical glass grinding method and an optical glass lens manufacturing method using an optical glass grinding apparatus will be described in the following order.

1. 1. Explanation of workpiece 2. Configuration of optical glass grinding apparatus 3. Operation example of optical glass grinding device Effects of this embodiment

<1. Explanation of work piece>
The object to be ground in the present embodiment is a press product having a shape approximated to the final lens shape. The press product is a reheat press (hereinafter abbreviated as “RP”) product obtained by heating and softening a pre-formed glass material to form a press product and pressing it in a mold, and a molten melt. There is a direct press (hereinafter abbreviated as “DP”) product that is obtained by separating a molten glass lump of a predetermined weight from glass and pressing the molten glass lump with a mold. Reduction by grinding and polishing It is often used to reduce the cost as much as possible and to reduce the cost by shortening the processing time. The RP product is excellent in the accuracy of the refractive index because it is measured after the refractive index of the product is measured and then softened again by heating and then pressed. On the other hand, the DP product is a glass material that is melted, separated from the glass melt that has been clarified and homogenized, and then pressed into a mold while the glass melt is soft at high temperatures. Excellent in dimensional accuracy such as wall thickness. Note that the surface roughness Rz of the pressed product is 2.0 μm or less for both the RP product and the DP product.

Examples of the glass material (glass material) on which the press product is based include, for example, a hardly glass material that is a kind of glass material of optical glass. Unlike a glass material of another type (that is, other than a difficult glass material), the difficult glass material is a glass material that requires some device in the lens processing process in the lens manufacturing process. Therefore, the difficult glass material can be regarded as glass having a property that scratches are easily generated during processing.
The difficult glass material having such properties can be distinguished from glass materials other than the difficult glass material, for example, based on the degree of wear (FA) described later. Here, as an example, when measuring the degree of wear (FA), which will be described later, the degree of wear is measured using a standard sample specified by the Japan Optical Glass Industry Association (a glass material other than a difficult glass material, with a degree of wear of FA = 100). The case will be described. An object to be ground (glass molded body) formed of a difficult glass material is softer and more easily scratched than a standard sample object to be ground (glass molded body). Acid glass, phosphate glass, and high refractive index high dispersion glass containing niobium phosphate) and properties that are too hard to process easily (among the glasses described below, lanthanum borate-containing high refractive index low dispersion glass) ) That is, since it has processing difficulty, some device is required to cope with the processing difficulty. When processing glass that is too hard and difficult to process, it is usually necessary to use a rough grindstone (for example, # 270), which causes large scratches.
In the above description, the standard sample is exemplified as a glass material other than the difficult glass material, and the properties of the glass have been described. However, the present invention is not limited to this, and the “hard glass material” in the present invention has an abrasion degree FA of 45 or more. An optical glass that is 95 or less, or an optical glass that is 160 or more and 500 or less, and a glass material other than a difficult glass material means an optical glass having an abrasion degree FA of more than 95 and less than 160. The present invention can be applied to such a range of glass.

  Specific examples of the glass made of such a difficult glass material include fluorophosphate glass, phosphate glass, niobium phosphate-containing high-refractive index high-dispersion glass, or lanthanum borate-containing high-refractive index low-dispersion glass. That is, the glass forming material mentioned here is defined as “hard glass” in this specification. In the present embodiment, a glass made of any one of these fluorophosphate glass, phosphate glass, high refractive index and high dispersion glass containing niobium phosphate, or high refractive index and low dispersion glass containing lanthanum borate is used. The object to be ground (glass molded body) for spherical surface creation processing.

Fluorophosphate glass is a low refractive index and low dispersion glass, and has the following configuration. Fluorophosphate glass is an optical glass containing P ⁵⁺ , Al ³⁺ and alkaline earth metal ions as essential cation components and F ⁻ and O ²⁻ as essential anion components, and having a refractive index (nd) of 1. It is an optical glass having optical characteristics of 45 or more and an Abbe number (νd) of 65 or more. In particular, P ⁵⁺ preferably contains 3 to 50 cation%, and Al 3+ preferably contains 3 to 40 cation%. F ⁻ contains 20 to 95 anions, O ²⁻ is preferably 5 to 80 anions, and the total content of F ⁻ and O ²⁻ is preferably 100 anions. The alkaline earth metal ions preferably include at least one selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ . Furthermore, the volatility of the fluorophosphate glass, from suppressing the ^erosive, it is desirable that the molar ratio ^(O 2- ^{/ P 5+)} of ^{O 2-} content to the content of ^{P 5+} in 3.5 above.
Specifically, as fluorophosphate glass, P ⁵⁺ ; 3-50%, Al ³⁺ ; 5-40%, Mg ²⁺ ; 0-10%, Ca ²⁺ ; 0-30%, Sr ^{2+ in} terms of cation%. ^{; 0~30%, Ba 2+; 0~40} %, Li +; 0~30%, Y 3+; 0~10%, La 3+; 0~10%, containing at by anionic%, F ^{- ;} 20~95%, O 2-; optical glass and the like containing 5-80%. Moreover, it is preferable that the abrasion degree (FA) in a fluorophosphate glass has 380-500, More preferably, it is good to set it as 400-460.

Phosphate glass is a low-dispersion glass and has the following configuration. Phosphate glass contains P ₂ O ₅ , B ₂ O ₃ , Li ₂ O, MgO, CaO and BaO as essential components, and has a refractive index (nd) of 1.50 to 1.70 and an Abbe number (νd) of It is an optical glass having optical characteristics of 60 to 70.
Specifically, as phosphate glass, P ₂ O ₅ ; 18 to 70%, B ₂ O ₃ ; 1 to 35%, Al ₂ O ₃ ; 0 to 8%, Li ₂ O; 20% (excluding _{0%), Na 2 O;} 0~18%, K 2 O; 0~15%, MgO; 1~25%, CaO; 0~18% ( provided that MgO + CaO> 4% ), SrO; 0~20%, BaO ; 1~40%, ZnO; 0~14%, Gd 2 O 3; 0~18%, Sb 2 O 3; an optical glass and the like containing 0 to 1% . Moreover, it is preferable that the abrasion degree (FA) in phosphate glass has 250-350, More preferably, it is good to set it as 270-310.

Niobium phosphate-containing high-refractive index high-dispersion glass is composed of optical glass containing at least one kind of easily-reducing component consisting of W, Ti, Bi and Nb, and the total content of these easily-reducing components is 5 to 60 mol. %, The refractive index (nd) is 1.80 or more, and the Abbe number (νd) is 30 or less.
Specifically, as a high refractive index and high dispersion glass containing niobium phosphate, in terms of mol%, P ₂ O ₅ ; 10 to 45%, Nb ₂ O ₅ ; 3 to 35%, Li ₂ O; 2 to 35 _{%, TiO 2; 0~25%,} WO 3; 0~20%, Bi 2 O 3; 0~40%, B 2 O 3; 0~20%, BaO; 0~25%, ZnO; 0~25 _{%, Na 2 O; 0~50%} , K 2 O; 0~20%, Al 2 O 3; 0~15%, SiO 2; 0~15%, ( provided _{that, WO 3, TiO 2, Bi} 2 O ₃ and Nb ₂ O _{5 in} a total amount of 10% or more and less than 65%). Moreover, it is preferable that the abrasion degree (FA) in the high refractive index high dispersion glass containing niobium phosphate has 150 to 300, and more preferably 160 to 290.

The lanthanum borate-containing high-refractive index low-dispersion glass is an optical glass containing at least one easy-reducing component composed of W, Ti, Bi, and Nb and containing B ₂ O ₃ , La ₂ O ₃ , and ZnO as essential components. In this optical glass, the refractive index (nd) is 1.8 or more and the Abbe number (νd) is 25 to 50. In this optical glass, B ₂ O ₃ is an essential component for the glass network configuration, and La ₂ O ₃ is an essential component for imparting a high refractive index and low dispersion characteristics. By coexisting, the stability of the glass is further improved.
Specifically, as a high refractive index low dispersion glass containing lanthanum borate, expressed in mol%, SiO ₂ = 0 to 50%, B ₂ O ₃ ; 5 to 70%, Li ₂ O; 0 to 20%, Na _{2 O; 0~10%, K 2} O; 0~10%, ZnO; 1~50%, CaO: 0~10%, BaO: 0~10%, SrO: 0~10%, MgO: 0~10 _{%, La 2 O 3; 5~50} %, Gd 2 O 3; 0~22%, Yb 2 O 3; 0~10%, Nb 2 O 5; 0~15%, WO 3; 0~20%, mentioned optical glass containing _{0~10%; TiO 2; 0~40%} , Bi 2 O 3; 0~20%, ZrO 2; 0~15%, Ta 2 O 5; 0~20%, GeO 2 It is done. Moreover, it is preferable that the abrasion degree (FA) in lanthanum borate containing high refractive index low dispersion glass has 45-95, More preferably, it is good to set it as 50-80.

Among the glass made of such a difficult glass material, FCD1 (manufactured by HOYA Corporation, nd = 1.490000, νd = 81.61) is given as a specific example of the fluorophosphate glass. The FCD 1 exemplified here has, for example, mechanical properties such as Knoop hardness Hk ≦ 350 N / mm ² and wear degree FA ≧ 400. Therefore, it is characterized in that it is softer and more easily scratched during processing than optical glass (for example, Hk ≧ 500 N / mm ² , FA ≦ 200) formed of a glass material other than a difficult glass material.
Specific examples of the phosphate glass include PCD4 (manufactured by HOYA Corporation, nd = 1.61800, νd = 63.40) and PCD51 (manufactured by HOYA Corporation, nd = 1.59349, νd = 67.00).
As specific examples of high refractive index and high dispersion glass containing niobium phosphate, E-FDS1 (manufactured by HOYA, nd = 1.92286, νd = 20.88), FDS18 (manufactured by HOYA, nd = 1.94595, νd = 17.98), FDS90 (manufactured by HOYA Corporation, nd = 1.84666, νd = 23.78).
As specific examples of lanthanum borate-containing high refractive index and low dispersion glass, TAFD25 (manufactured by HOYA Corporation, nd = 1.90366, νd = 31.32), TAFD35 (manufactured by HOYA Corporation, nd = 1.91082, νd = 35.25) ), TAFD40 (manufactured by HOYA Corporation, nd = 2.00069, νd = 25.46).

In addition, the above-mentioned abrasion degree (FA) is measured based on Japan Optical Glass Industry Association standard JOGIS-10. The measurement method is to hold a sample with a measurement area of 9 cm ² at a fixed position of 80 mm from the center of a flat plate made of cast iron that rotates horizontally 60 minutes per minute, and add 20 ml of water to 10 g of alumina abrasive grains having an average particle diameter of 20 μm. The supplied lap station is supplied uniformly for 5 minutes and lap is applied with 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 a standard sample designated by the Japan Optical Glass Industry Association was measured, and the degree of wear (FA) was calculated by the following equation.
Degree of wear (FA) = (m / d) / (m ₀ / d ₀ ) × 100 (1) where d is the specific gravity of the sample, and d ₀ is the specific gravity of the standard sample.

<2. Configuration of optical glass grinding machine>
FIG. 1 is a schematic diagram for explaining a schematic configuration example of an optical glass grinding apparatus 1 for grinding a press product of optical glass.

  An optical glass grinding apparatus 1 shown in FIG. 1 is generally a curve generating grinding method (hereinafter referred to as “CG machining process”) using a curve generator (CG) used when grinding into a spherical surface by rough grinding. In contrast, the apparatus has a configuration in which an electrolytic in-process dressing grinding method (hereinafter referred to as an “ELID process”) by electrolytic in-process dressing (ELID) is applied. The “CG processing step” and “ELID step” will be described in detail later.

  As shown in FIG. 1, an optical glass grinding apparatus 1 described in the present embodiment includes a rotary table 2, a cup grindstone 3, an electrode 4, a grinding fluid supply unit 5, a voltage application unit 6, and an operation controller. 7.

  Such an optical glass grinding apparatus 1 automatically performs dressing (sharpening) of the grinding surface of the cup grindstone 3 by the ELID cycle according to the ELID process according to the control of the operation controller 7, while performing the cup grindstone by the GG machining process. The surface to be ground of the optical glass press product 10 according to 3 can be ground into a spherical shape.

  The optical glass grinding apparatus 1 shown in FIG. 1 is a so-called vertical type, and shows an apparatus configuration in which an electrolytic in-process dressing grinding method is applied to a curve generator for grinding a convex surface. The optical glass grinding apparatus 1 shown in FIG. 1 may be a so-called horizontal type, or an electrolytic in-process dressing grinding method may be applied to a curve generator for grinding a concave surface.

  The turntable 2 has a chuck portion 2a that holds an optical glass press product 10 to be ground. The chuck portion 2a is configured to be rotationally driven by a drive source (not shown) while the press product 10 is held. The press product 10 may be held by the chuck portion 2a using a known technique such as vacuum suction or using a fixing jig. Moreover, what is necessary is just to use well-known things, such as an electric motor, also about the drive source which rotationally drives the turntable 2. FIG.

  The cup grindstone 3 is formed in a cup shape (cylindrical shape having an open end), and is arranged so that the open end faces the chuck portion 2a of the rotary table 2, and the end surface on the side facing the chuck portion 2a. An abrasive grain portion 3a that is a grinding surface is provided in the vicinity.

  That is, the cup grindstone 3 is configured such that the abrasive grain portion 3 a can be brought into contact with the optical glass press product 10 held by the chuck portion 2 a of the rotary table 2.

  The abrasive grain portion 3a is obtained by solidifying diamond abrasive grains with a binder (bond material) made of a metal material such as cast iron or bronze. By using a metal material as the binding material, the cup grindstone 3 functions as a conductive metal bond grindstone. However, a resin bond grindstone may be used as long as it has conductivity.

  The cup grindstone 3 is configured to be rotated by a drive source (not shown) such as an electric motor. The rotational axis of the cup grindstone 3 is located on a line that forms an angle α with the rotational axis of the rotary table 2. This angle α is determined on a one-to-one basis by the curvature of the spherical lens to be manufactured. After the angle α is determined in accordance with the curvature of the lens, in principle, continuous processing is performed while maintaining the angle α. The angle α can be varied within a predetermined range (for example, 0 ° to 60 °) by a swing mechanism (not shown) so as to be compatible with a plurality of lens shapes.

  Furthermore, the cup grindstone 3 is configured to be able to vary the relative position with the rotary table 2 along the feeding direction of the cup grindstone 3 by a moving mechanism (not shown). The “feeding direction” refers to a direction in which the contact pressure between the optical glass press 10 and the abrasive grain portion 3a is variable. The moving mechanism for changing the relative position in the feed direction may be configured using a known technique such as an electric motor or a feed screw.

  The moving mechanism may move the rotary table 2 instead of the cup grindstone 3 as long as the relative position of the rotary table 2 and the cup grindstone 3 can be varied.

  The electrode 4 is disposed so as to face the abrasive grain portion 3a of the cup grindstone 3 with a predetermined gap (for example, about 0.1 to 0.3 mm, preferably about 0.2 mm).

  The grinding fluid supply unit 5 is provided between the abrasive grain part 3a of the cup grindstone 3 and the electrode 4, and between the abrasive grain part 3a of the cup grindstone 3 and the press product 10 made of optical glass that is the object to be ground. A conductive grinding fluid is supplied.

  The conductive grinding liquid only needs to have a function of reducing the electrical resistance between the abrasive grain portion 3 a and the electrode 4. Specifically, a water-soluble grinding liquid for ELID grinding having a certain degree of electrical conductivity (for example, about 1300 to 1800 μS / cm, preferably about 1500 to 1600 μS / cm) may be used as the conductive grinding liquid. .

  The voltage application unit 6 applies a DC pulse voltage between these electrodes, with the cup grindstone 3 that is a metal bond grindstone serving as an anode (plus) and the electrode 4 facing the cup grindstone 3 serving as a cathode (minus).

  Therefore, the voltage application unit 6 includes an ELID power source 6a that generates a predetermined direct-current pulse voltage, a power supply brush 6b that is in contact with the rotating shaft of the cup grindstone 3, a contact between the ELID power source 6a and the power supply brush 6b, and A current supply line 6c for connecting the ELID power source 6a and the electrode 4 is provided.

  The operation controller 7 controls the operations of the units 2 to 6 described above. Under the control of the operation controller 7, at least the rotational speed of the cup grindstone 3 and the feed speed of the relative position movement in the feed direction of the rotary table 2 and the cup grindstone 3 are set as will be described in detail later. ing.

<3. Example of operation of optical glass grinding machine>
Next, an operation example of the optical glass grinding apparatus 1 having the above-described configuration will be described.
Here, a case where the optical glass grinding apparatus 1 having the above-described configuration is used in the method for manufacturing an optical glass lens will be described as an example.

(General manufacturing procedure)
In general, an optical glass lens, for example, becomes a lens surface of a glass molded body by sequentially performing a rough grinding process for performing rough grinding and a fine grinding process for performing precise grinding on a glass molded body such as a press product. It is manufactured by grinding a surface to be ground into a spherical shape and further performing a polishing process for polishing the surface to be ground.

  FIG. 2 is a flowchart showing an example of a procedure for manufacturing a general optical glass lens.

(S1: Batch adjustment / mixing)
In the production of the optical glass lens, first, the above-mentioned composition constituting the optical glass is prepared at the above-described predetermined ratio so that an optical glass having desired optical characteristics is obtained. A base glass material (that is, a difficult glass material) is obtained (S1). Glass material here means powder made of metal oxide or inorganic oxide called batch, and / or cullet obtained by roughly melting and cooling the batch once, in many cases Refers to batch.

(S2: Glass melting / clarification)
Thereafter, the glass material obtained in step S1 described above is put into a melting furnace, melted (melted), refined (including defoaming), and homogenized molten glass (that is, the batch melted). Glass) is discharged from the outlet of the glass outlet pipe.

(S3: Glass molding to S5A; RP product)
For example, when using an RP product, the molten glass flowing out from the pipe is taken out in the horizontal direction on the mold. The molten glass taken out from the mold moves horizontally into the continuous annealing furnace and is annealed in the furnace. This is a step of gradual cooling in an inert gas atmosphere such as nitrogen so that no strain or the like remains in the cooled glass. Thereby, the glass molded object which shape | molded the molten glass is obtained (S3). After annealing, what is separated from the glass molded body with a desired length becomes an E-bar (plate-shaped glass body) having a predetermined shape (S4A). After that, the E-bar (plate glass) separated from the continuous glass molded body is divided into a plurality of cubic glass pieces called cut pieces, for example, and subjected to cold processing such as grinding or polishing (cubic processing). There is a process for adjusting chamfering and weight variation), and a glass material for reheat press molding is obtained by making the process into a predetermined shape and a predetermined volume. The reheat press-molded glass material thus obtained is heated and softened and then press-molded using a mold to obtain an RP product as a material for producing an optical glass lens (S5A). . At this time, the reheat press-molding glass material may be supplied with a pre-heated glass material (non-isothermal press molding), or may be supplied to the mold and then heated and pressed together with the mold. Good (isothermal press molding).

(S3: Glass molding to S5B; DP product)
On the other hand, for example, in the case of using a DP product, the molten glass lump is supplied onto a lower mold arranged on a rotary table, and the molten glass lump is press-molded into a desired shape by the upper mold and the lower mold ( S3, S4B, S5B). At this time, the temperature of the lower mold is adjusted so that the molten glass lump supplied (cast) onto the lower mold is rapidly cooled by contact with the lower mold and cannot be press-molded. Since the lower mold temperature is lower than the temperature of the molten glass, the glass and lower mold are in contact until the molded glass molded product (DP product, lens blank) is taken out from the press mold (takeout). The amount of heat of the glass molded product is taken away from the surface. Furthermore, although the temperature of the upper mold is adjusted at the time of press molding, it is generally lower than the temperature of the molten glass. Therefore, while the upper mold is in contact with the molten glass lump or the press molded product, the upper mold is also used. The amount of heat possessed by the molten glass lump and the glass molded product is deprived. When the molten glass lump is separated from the molten glass stream, it may be dropped spontaneously depending on the weight of the glass lump to be obtained, or it is melted using a pair of shear blades cooled so as not to be thermally fused. It can cut | disconnect on both sides of glass and can obtain a molten glass lump. In addition to this, as a method for cutting molten glass, the lower mold is raised below the outlet of the glass outflow pipe to receive the molten glass, and after reaching a predetermined weight, the lower mold is lowered at a speed higher than the flowing speed of the molten glass. You may employ | adopt the fall cutting method which cut | disconnects a molten glass by making it. In the description of the DP product, the molten glass is the name of the glass in a molten state of the batch, the molten glass flow is the molten glass flowing down from the pipe, and the molten glass lump is separated (dropped or cut) from the molten glass flow. It is a lump of glass, and the glass molded body means a glass product after pressing (that is, a DP product). In the above description, the example in which the molten glass lump is supplied onto the lower mold and the molten glass lump contacts the lower mold has been described. However, the gas (N2 gas) for floating the molten glass lump on the lower mold is described. It is possible to press mold in a state where the molten glass lump is floated by using a floating mold in which a gas hole for passing an inert gas) is formed.

(S6: RP / DP product grinding)
After obtaining the RP product or DP product through the above procedure, the RP product or DP product is ground to obtain a lens surface having a desired shape (S6). The grinding process is performed, for example, through a rough grinding step (S6a) for performing rough grinding and a fine grinding step (S6b) for performing fine grinding in this order. The rough grinding step (S6a) is a grinding step that is performed with priority given to the processing efficiency over the quality of the ground surface such as surface roughness. For example, the count of the grindstone particle size is less than # 600, more specifically, # It is a grinding process executed using a cup grindstone of about 325. On the other hand, the fine grinding step (S6b) is a grinding step executed mainly for adjusting the shape accuracy and the surface condition. For example, the grindstone particle size display count is # 600 or more, more specifically, about # 1500 to # 8000. It is a grinding process performed using a cup grindstone.

(S7: Polishing the ground product)
After grinding the portion to be the lens surface of the RP product or DP product through the grinding process (S6, S6a, S6b) into a spherical shape, the scratches on the lens surface after grinding are removed from the ground product. Alternatively, a polishing process for reducing the surface roughness of the lens surface is performed (S7). Through a series of procedures as described above, an optical glass lens (spherical lens) whose lens surface is processed into a spherical shape is manufactured (S8).

(Manufacturing procedure in the present embodiment)
In contrast to the general manufacturing procedure of the optical glass lens described above, in the present embodiment, the grinding process is not performed in two stages as in the rough grinding process and the fine grinding process, but the configuration described above is used. With the optical glass grinding apparatus 1, the result is obtained in a single-stage grinding process using the cup grindstone 3 having the abrasive grain portion 3 a which is a grinding surface formed by a plurality of abrasive grains for fine grinding. In addition, the rough grinding process and the fine grinding process can be performed simultaneously.

  FIG. 3 is a flowchart showing an example of the manufacturing procedure of the optical glass lens in the present embodiment.

  The manufacturing procedure shown in FIG. 3 is different from the general manufacturing procedure described above in the grinding process (S6) for the RP product or the DP product. In the case of the general manufacturing procedure shown in FIG. 2 described above, the rough grinding step (S6a) and the fine grinding step (S6b) are performed in stages. On the other hand, in the manufacturing procedure shown in FIG. 3, the fine grinding step (S6b) is suddenly performed without going through the rough grinding step (S6a). That is, in the grinding process (S6), the rough grinding process (S6a) is omitted. This is because, according to the optical glass grinding apparatus 1 described in the present embodiment, as will be described in detail later, in order to perform electrolytic dressing by the ELID grinding method, the cup grindstone 3 is sharpened while performing CG processing. This is because grinding can be performed efficiently. Furthermore, according to the optical glass grinding apparatus 1 described in the present embodiment, as will be described later, it is possible to achieve both the quality of the processed surface and the reduction of the processing cost. This is because the processing quality after fine grinding can be obtained in a short grinding time.

(Details of operation example of optical glass grinding machine)
Then, the operation example in the optical glass grinding apparatus 1 is demonstrated.
The optical glass grinding apparatus 1 performs a grinding process on a pressed product (RP product or DP product) 10 of optical glass (made of a difficult glass material) that is an object to be ground in the above-described process.

  The ELID process is applied to the above-described CG processing process in the grinding process performed by the optical glass grinding apparatus 1. Hereinafter, these steps will be described in order.

(CG machining process)
The CG processing step is a step of performing CG processing on an optical glass press product 10 formed of a difficult glass material and grinding a surface to be ground (that is, a smooth molten surface) of the press product 10 into a spherical shape. is there.

  First, in the CG processing step, a pressed product 10 of optical glass (made of a difficult glass material) that is an object to be ground is held on the chuck portion 2 a of the rotary table 2. Next, according to a control instruction from the operation controller 7, the swing mechanism is operated so that the rotation axis of the cup grindstone 3 has an angle α corresponding to the curvature of the lens surface to be ground, and the abrasive grain portion 3a and the lens It fixes to the position where the contact point with the surface exists on the lens optical axis.

  In this state, according to a control instruction from the operation controller 7, the rotary table 2 is rotationally driven at a predetermined rotational speed, and the cup grindstone 3 is rotationally driven at a predetermined rotational speed different from that of the rotary table 2.

  Then, the moving mechanism is operated in accordance with a control instruction from the operation controller 7, and the abrasive grains 3 a of the cup grindstone 3 are brought into contact with the optical glass press product 10 held by the chuck 2 a of the rotary table 2. The relative position in the feed direction between the rotary table 2 and the cup grindstone 3 is varied at a predetermined feed speed.

  By performing the above operation, in the CG processing step, the CG processing for the press product 10 of the optical glass is performed by the revolution of the cup grindstone 3 by the rotation of the rotary table 2 and the rotation of the cup grindstone 3 by the rotation of the cup grindstone 3. I do.

  That is, in the optical glass press product 10 formed of a difficult glass material, the abrasive grain portion 3a which is the grinding surface of the rotationally driven cup grindstone 3 is brought into contact with the surface to be ground which is not caught by abrasive grains. By doing so, the surface to be ground is ground into a spherical shape.

(ELID process)
The ELID step is a step of performing electrolytic dressing by the ELID grinding method on the cup grindstone 3 during execution of the CG processing step.

  Therefore, in the ELID process, at least from the start of contact of the cup grindstone 3 to the optical glass press product 10 formed of a difficult glass material to the end of grinding by the cup grindstone 3, the operation controller 7 and the grinding fluid supply unit 5 and The following control instruction is given to the voltage application unit 6.

  That is, the grinding fluid supply unit 5 follows the control instruction from the operation controller 7, between the abrasive grain part 3 a of the cup grindstone 3 and the electrode 4, and between the abrasive grain part 3 a of the cup grindstone 3 and the optical object to be ground. A conductive grinding liquid is supplied between the pressed glass product 10.

  The voltage application unit 6 causes the ELID power source 6a to generate a predetermined DC pulse voltage in accordance with a control instruction from the operation controller 7.

  By performing the above operation, in the ELID process, a direct-current pulse voltage is applied between the cup grindstone 3 and the electrode 4 through the current supply line 6c and the power supply brush 6b of the voltage application unit 6, thereby The sharpening (electrolytic dressing) is automatically performed on the abrasive grain portion 3a which is the grinding surface of the grindstone 3.

  That is, during the execution of the CG processing step, a voltage is applied while supplying a conductive grinding liquid between the cup grindstone 3 and the electrode 4 to perform electrolytic dressing on the cup grindstone 3.

FIG. 4 is an explanatory view showing a mechanism of electrolytic dressing by the ELID grinding method.
In the ELID grinding method, first, by applying a voltage, the binding material 3b of the abrasive grain portion 3a is electrolyzed, and an appropriate projection of the diamond abrasive grain 3c is obtained (see FIG. 4A). During this time, the electrolytically eluted binder 3b is partially made non-conductive and deposited on the end face of the grindstone to form the non-conductive coating 3d, so that the electrolysis current automatically decreases. At this timing, the initial dressing is completed (see FIG. 4B).

  When grinding is actually performed in this state, the non-conductive coating 3d on the end face of the grindstone comes into contact with the surface of the object to be ground (that is, the surface to be ground of the optical glass press product 10 formed of a difficult glass material) and is peeled off by friction. At the same time, the diamond abrasive grains 3c begin to grind the workpiece and abrasive wear occurs (see FIG. 4C).

  Then, the insulating property of the grindstone end face is lowered and the electrolytic current is recovered. As a result, electrolytic elution is resumed from the point where the nonconductive film 3d between the worn diamond abrasive grains 3c becomes thin (see FIG. 4D), and the protrusion of the diamond abrasive grains 3c is obtained again (FIG. 4). 4 (b)).

(Processing conditions in the present embodiment)
Next, processing conditions when the optical glass grinding apparatus 1 executes the above-described CG processing step and ELID step will be described.

  The optical glass grinding apparatus 1 uses a pressed product 10 of optical glass (made of a difficult glass material), which is difficult to execute only a precise grinding process without a rough grinding process, as an object to be ground. Therefore, as already explained, it is very difficult to achieve both the quality of the surface to be ground and the reduction of the machining cost under the conventional machining conditions assuming the press product 10.

  Therefore, the optical glass grinding apparatus 1 performs processing on the pressed product 10 of optical glass formed of a difficult glass material, that is, the above-described CG processing step and ELID step under the processing conditions described below. Such processing conditions are based on the knowledge of the inventors of the present application based on an idea not found in conventional technical common sense.

  The processing conditions for the pressed product 10 of optical glass formed of a difficult glass material are the rotational speed of the cup grindstone 3 and the feed speed of the relative position movement in the feed direction of the rotary table 2 and the cup grindstone 3 in the CG processing step. In other words, it is set higher than the case of executing the two-stage grinding process of rough grinding and fine grinding. These machining conditions are given as control instructions from the operation controller 7 to the rotational drive source, the moving mechanism, and the like of the cup grindstone 3.

  Specifically, the rotational speed of the cup grindstone 3 is 10000 rpm (rotation per minute) or less, which is the rotational speed when performing two-stage grinding processing, that is, rough grinding and fine grinding (see, for example, Patent Document 3). Is set to a condition of 18000 rpm or more, which is a higher rotational speed than the above condition. The upper limit value of the rotational speed may be within the allowable rotational speed of the rotary bearing portion of the cup grindstone 3 (that is, within the mechanical specifications of the apparatus). However, in order to avoid the film breakage of the conductive grinding liquid supplied during the ELID process, it is conceivable that the upper limit is, for example, about 40000 rpm. That is, the rotational speed of the cup grindstone 3 is set to 18000 rpm or more and 40000 rpm or less, preferably about 20000 rpm to 30000 rpm.

  Further, the feed speed of the relative position movement between the rotary table 2 and the cup grindstone 3 may be 1.0 μm / sec or more and 15.0 μm / sec or less, preferably 2.0 μm / sec or more and 15.0 μm / sec. Set the following conditions.

  Other processing conditions may be the same as in the case of grinding an optical glass formed of a glass material other than the difficult glass material. For example, if it is the rotation speed of the turntable 2, the conditions of 1-100 rpm should just be sufficient, Preferably it can consider setting to the conditions of about 50 rpm. Further, for example, the voltage applied by the voltage application unit 6 may be set to a condition of 30 to 150 V, preferably set to a condition of about 150 V.

  In the present embodiment, the ELID process is executed during the execution of the CG processing process while adopting the processing conditions described above, and the abrasive grains 3a of the cup grindstone 3 are automatically set (electrolytic dressing). )I do.

  Therefore, in the present embodiment, the abrasive grain size of the abrasive grain portion 3a of the cup grindstone 3 is not a method of gradually changing from coarse to fine, but from the beginning, the abrasive grain size for fine grinding (for example, In the grinding process in which the grain size of the abrasive grains is # 1500 to # 8000, preferably using the grain size display # 2000, the average grain size is 1 μm to 5 μm, that is, the grinding process (S6). The precision grinding step (S6b) can be performed suddenly without going through (S6a).

  In other words, the surface to be ground before the rough grinding process is not formed in two stages by the rough grinding process and the fine grinding process, but is formed from a plurality of abrasive grains for fine grinding from the beginning. Grinding is performed using a cup grindstone 3 having an abrasive grain portion 3a as a surface.

  As described above, if the cup grindstone 3 having the fine grain part 3a for fine grinding is used and the ELID process is used in combination, it is possible to always make sharpening, so a press product of optical glass formed of a difficult glass material. Even in the case of grinding 10, it is possible to maintain the grinding force of the grinding wheel on the surface to be ground and to perform grinding, and as a result, to ensure the quality of the surface to be ground. It will be very suitable.

<4. Effects of the present embodiment>
According to the optical glass grinding apparatus 1 described in the present embodiment, the optical glass grinding method performed by the optical glass grinding apparatus 1, and the optical glass lens manufacturing method performed using the optical glass grinding method. For example, the following effects can be obtained.

  According to the present embodiment, when grinding is performed on the optical glass press product 10, both the rotational speed and feed speed of the cup grindstone 3 are performed while the ELID process is performed during the execution of the CG machining process. However, the CG processing step is executed under the processing conditions that are set higher than in the case of executing the two-stage grinding processing of rough grinding and fine grinding.

  Therefore, even when the press product 10 is a workpiece, it is difficult to achieve the quality of the surface to be ground, which is difficult to realize under the processing conditions that assume the case where two-stage grinding is performed according to the prior art. It is possible to achieve both processing cost reduction.

  That is, even when the grinding process is performed with the cup grindstone 3 having the abrasive grain portion 3a which is a grinding surface formed by a plurality of abrasive grains for fine grinding, the surface to be ground before the rough grinding process is performed. Thus, sustainability of the grinding wheel grinding force can always be obtained, grinding can be performed, and a surface to be ground having a quality suitable for a lens can be reliably obtained.

  Here, the quality suitable for the lens means that, for example, the surface roughness Rz of the surface to be ground is 1 μm or less in a state after the grinding process and before the polishing process. This is because if the surface roughness Rz is 1 μm or less, the subsequent polishing treatment can be efficiently performed with high accuracy and in a short time. In addition, since scratches on the lens surface can be suppressed, the polishing process does not require much time and skill, etc. more than necessary, and the CG processing process is accelerated by shortening the feed rate (reducing the processing time). As a result, it is possible to suppress an increase in processing cost for the press product 10 as a result.

These are presumed to be due to the following reasons.
In the present embodiment, the ELID process is executed during the execution of the CG machining process. Therefore, by the action of the setting (electrolytic dressing) in the ELID process, the abrasive grains 3a of the cup grindstone 3 can sufficiently maintain the state in which the diamond abrasive grains protrude from the binding material, that is, the so-called blade stands up. Become.

  In addition, the cup grindstone 3 is driven to rotate at a higher speed than in the case of performing two-stage grinding, that is, rough grinding and fine grinding. Therefore, when viewed from the surface to be ground (that is, the smooth melted surface) of the optical glass press 10 formed of a difficult glass material, the diamond abrasive grains with the blade standing by the ELID action are under normal processing conditions. It will be rubbed more per unit time than.

  Thereby, the to-be-ground surface of the press product 10 is in a state of being satisfactorily shaved without being left uncut. In combination with these, that is, by rotating the cup grindstone 3 at a high speed while performing the ELID process, the surface to be ground of the press product 10 can be caught by abrasive grains, which is suitable for a lens. It becomes a quality ground surface.

  Furthermore, in the present embodiment, the feed speed of the relative position movement in the feed direction between the rotary table 2 and the cup grindstone 3 is set higher than that in the case of executing the two-stage grinding process of the rough grinding process and the fine grinding process. ing.

  That is, the feed amount of the relative position movement per unit time is larger than that in normal grinding. When the feed amount is large in this way, it becomes easier to get the abrasive grains caught on the surface to be ground. Moreover, in this Embodiment, the cup grindstone 3 is rotationally driven at high speed. Therefore, by increasing the feed amount of the relative position movement, it is possible to perform a good grinding process while maintaining the quality of the surface to be ground.

  Thus, if the feed amount of the relative position movement per unit time is increased, the time required for the grinding process can be shortened, and the efficiency of the grinding process for the press product 10 can be improved accordingly. Therefore, it is possible to suppress an increase in processing cost for the press product 10.

  In the present embodiment, both the rotational speed and feed rate of the cup grindstone 3 are set higher than when two-stage grinding is performed, that is, rough grinding and fine grinding. Therefore, it is possible to ensure both the quality of the surface to be ground and the reduction of processing costs.

  For example, even if only the feed speed is increased, if the rotation speed is not increased, the possibility of scratches on the surface to be ground due to the feed becomes very high. Cannot be said to be compatible. That is, it is possible to realize both the quality of the surface to be ground and the reduction of the machining cost by increasing both the rotational speed and the feed rate.

  On the other hand, if only the rotational speed is increased, the quality of the surface to be ground can be ensured. However, in order to achieve both ensuring the quality of the surface to be ground and reducing the processing cost, it is preferable to increase the feed rate and improve the efficiency of the grinding process.

  Note that this embodiment mode shows a preferable embodiment mode of the present invention. That is, the present invention is not limited to the contents of the present embodiment, and can be appropriately changed without departing from the gist thereof.

Next, an Example is given and this invention is demonstrated concretely. However, it is needless to say that the present invention is not limited to the following examples.
5-8 is explanatory drawing which shows the processing conditions in Example 1- Example 15 of this invention. Moreover, FIG. 9 is explanatory drawing which shows the processing conditions in the comparative example 1- comparative example 2 of this invention.

<Example 1>
In Example 1, a pressed product formed by FCD1 (manufactured by HOYA Corporation, nd = 1.490000, νd = 81.61), which is a difficult glass material, is ground to obtain a lens diameter of 35.8 mm and a surface curvature radius of 44.72 mm. An optical glass lens (spherical lens) was manufactured. The grinding process was performed by executing the ELID process during the execution of the CG machining process in one grinding process in which the rough grinding process and the fine grinding process were combined. The CG processing step was performed using the cup grindstone 3 having a cup diameter of 40 mm and a grindstone count # 2000, with the rotation axis of the cup grindstone 3 being inclined by α = 14 °, under the processing conditions described below. That is, the rotational speed of the cup grindstone 3 was 20000 rpm, and the feed rate was 2 μm / sec. The rotation speed of the rotary table 2 was 50 rpm, and the voltage applied by the voltage application unit 6 was 150V. Moreover, as the conductive grinding fluid supplied by the grinding fluid supply unit 5, Similon CG-7 (manufactured by Daido Chemical Industry Co., Ltd.) was used.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.18 μm. Further, the machining time when the machining allowance was 80 μm was 50 seconds.

<Example 2>
In the second embodiment, the rotational speed and feed speed of the cup grindstone 3 are different from those in the first embodiment. In Example 2, the rotational speed of the cup grindstone 3 was 30000 rpm, and the feed rate was 5 μm / sec. Other conditions are the same as in the first embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.20 μm. Further, the machining time when the machining allowance was 80 μm was 25 seconds.

<Example 3>
In Example 3, the feeding speed of the cup grindstone 3 is different from that in Example 1 described above. In Example 3, the feeding speed of the cup grindstone 3 was 1 μm / sec. Other conditions are the same as in the first embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.60 μm. Further, the machining time when the machining allowance was 80 μm was 90 seconds.

<Example 4>
In the fourth embodiment, the feeding speed and the grindstone count of the cup grindstone 3 are different from those in the first embodiment. In Example 4, the feeding speed of the cup grindstone 3 was 10 μm / sec, and the grindstone count was # 1500. Other conditions are the same as in the first embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.22 μm. Further, the machining time when the machining allowance was 80 μm was 20 seconds.

<Example 5>
In Example 5, the feeding speed of the cup grindstone 3 is different from that in Example 4 described above. In Example 5, the feeding speed of the cup grindstone 3 was 15 μm / sec. Other conditions are the same as in the fourth embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.27 μm. Further, the machining time when the machining allowance was 80 μm was 20 seconds.

<Example 6>
In Example 6, the feeding speed of the cup grindstone 3 and the material of the bond material are different from those in Example 4 described above. In Example 6, the feeding speed of the cup grindstone 3 was 2 μm / sec, and the bond material was not a metal bond but a resin bond. Other conditions are the same as in the fourth embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.16 μm. Further, the machining time when the machining allowance was 80 μm was 50 seconds.

<Example 7>
In Example 7, the rotation speed of the cup grindstone 3 is different from that in Example 3 described above. In Example 2, the rotational speed of the cup grindstone 3 was 18000 rpm. Other conditions are the same as in the third embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.87 μm. Further, the machining time when the machining allowance was 80 μm was 90 seconds.

<Example 8>
In Example 8, the kind of non-glass material and the feed speed of the cup grindstone 3 are different from those in Example 4 described above. In Example 8, the grinding object was E-FDS1 (manufactured by HOYA Corporation, nd = 1.92286, νd = 20.88), and the feed speed of the cup grindstone 3 was 5 μm / sec. Other conditions are the same as in the fourth embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.08 μm. Further, the machining time when the machining allowance was 80 μm was 25 seconds.

<Example 9>
In Example 9, the kind of non-glass material is different from that in Example 8 described above. In Example 9, the object to be ground was FDS18 (manufactured by HOYA Corporation, nd = 1.94595, νd = 17.98). Other conditions are the same as in the eighth embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.05 μm. Further, the machining time when the machining allowance was 80 μm was 25 seconds.

<Example 10>
In Example 10, the kind of non-glass material is different from that in Example 8 described above. In Example 10, the object to be ground was FDS90 (manufactured by HOYA Corporation, nd = 1.84666, νd = 23.78). Other conditions are the same as in the eighth embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.50 μm. Further, the machining time when the machining allowance was 80 μm was 25 seconds.

<Example 11>
In Example 11, the kind of non-glass material and the feed speed of the cup grindstone 3 are different from those in Example 8 described above. In Example 11, the grinding object was PCD4 (manufactured by HOYA Corporation, nd = 1.61800, νd = 63.40), and the feed speed of the cup grindstone 3 was 4 μm / sec. Other conditions are the same as in the eighth embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.56 μm. Further, the machining time when the machining allowance was 80 μm was 30 seconds.

<Example 12>
In the twelfth embodiment, the feeding speed of the cup grindstone 3 and the grindstone count are different from those in the eleventh embodiment. In Example 12, the feeding speed of the cup grindstone 3 was 3 μm / sec, and the stone count was # 2000. Other conditions are the same as in the case of Example 11.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.30 μm. Further, the machining time when the machining allowance was 80 μm was 40 seconds.

<Example 13>
In Example 13, the kind of non-glass material and the feed speed of the cup grindstone 3 are different from those in Example 8 described above. In Example 13, the object to be ground was TAFD 25 (manufactured by HOYA, nd = 1.90366, νd = 31.32), and the feed speed of the cup grindstone 3 was 8 μm / sec. Other conditions are the same as in the eighth embodiment.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.40 μm. Further, the machining time when the machining allowance was 80 μm was 20 seconds.

<Example 14>
In Example 14, the kind of non-glass material is different from that in Example 13 described above. In Example 14, the object to be ground was TAFD35 (manufactured by HOYA Corporation, nd = 1.91082, νd = 35.25). Other conditions are the same as in the case of Example 13.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.19 μm. Further, the machining time when the machining allowance was 80 μm was 20 seconds.

<Example 15>
In the fifteenth embodiment, the kind of the difficult glass material is different from that in the thirteenth embodiment. In Example 15, the object to be ground was TAFD40 (manufactured by HOYA Corporation, nd = 2.00069, νd = 25.46). Other conditions are the same as in the case of Example 13.
As a result of grinding under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after processing was 0.49 μm. Further, the machining time when the machining allowance was 80 μm was 20 seconds.

<Comparative Example 1>
In the first comparative example, unlike the first to fifteenth embodiments described above, two-stage grinding is performed: rough grinding and fine grinding. In the rough grinding process, the feeding speed of the cup grindstone 3 was 20 μm / sec, and the grindstone count was # 325. On the other hand, in precision grinding, the feed speed of the cup grindstone 3 was 10 μm / sec, and the grindstone count was # 1500. The rotational speed of the cup grindstone 3 was set to 6000 rpm for both rough grinding and fine grinding. The rotation speed of the turntable 2 was 50 rpm, and the voltage applied by the voltage application unit 6 was 0 V (that is, the ELID process was not performed). Moreover, as the conductive grinding fluid, Similon CG-7 (manufactured by Daido Chemical Industry Co., Ltd.) was used.
As a result of grinding under the above-described processing conditions, the surface roughness Rz of the lens surface of the non-glass material after rough grinding was 15.0 μm. When the cutting allowance was 80 μm, the processing time for the rough grinding was 15 seconds. Moreover, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after the precision grinding was 1.0 μm. When the cutting allowance was 80 μm, the processing time of the rough grinding was 18 seconds.

<Comparative example 2>
In the comparative example 2, the rotation speed of the cup grindstone 3 is different from the case of the comparative example 1 described above. In Comparative Example 2, the rotational speed of the cup grindstone 3 was set to 15000 rpm. Other conditions are the same as in Comparative Example 1.
As a result of performing the search processing under the above processing conditions, the surface roughness Rz of the lens surface of the lens formed of the difficult glass material after the rough grinding was 13.5 μm. When the cutting allowance was 80 μm, the processing time for the rough grinding was 15 seconds. Moreover, the surface roughness Rz of the lens surface of the difficult glass material after the precision grinding was 1.0 to 2.0 μm. It is considered that the variation of 1.0 to 2.0 μm is caused by the variation of roughness due to the sharpened state of the cup grindstone 3. When the cutting allowance was 80 μm, the processing time of the rough grinding was 18 seconds.

<Summary>
Considering the results of Examples 1 to 15 and Comparative Examples 1 and 2 listed above, the surface to be ground before rough grinding of the optical glass made of a difficult glass material is not subjected to the rough grinding step (S6a). When the precision grinding step (S6b) is performed suddenly, in order to reduce the surface roughness Rz of the processed surface to 1 μm or less after the grinding process, the rotational speed of the cup grindstone 3 with respect to the processing conditions for the optical glass formed of the difficult glass material 18000 rpm to 30000 rpm, the feed rate is 1.0 μm / sec to 15.0 μm / sec, the grain size of the abrasive grains is # 2000 to # 8000, the average grain size of the abrasive grains is 1.0 μm to 10.0 μm, the applied voltage May be 30V to 150V, the bond material may be either metal bond or resin bond, and the rotational speed of the rotary table may be 1 rpm to 100 rpm.

DESCRIPTION OF SYMBOLS 1 Optical glass grinding apparatus 2 Rotary table 3 Cup grindstone 3a Abrasive grain part 4 Electrode 5 Grinding fluid supply part 6 Voltage application part 7 Operation controller 10 Press goods

Claims (11)

A preparation step of preparing a press product obtained by press-molding optical glass into a predetermined shape;
A grinding process for performing fine grinding by bringing a conductive cup grindstone having a grinding surface for fine grinding into contact with a press product having a surface to be ground before rough grinding and rotating it;
During the grinding step, a predetermined voltage is applied between the electrode and the cup grindstone while supplying a conductive grinding liquid between the electrode disposed at a position facing the grinding surface of the cup grindstone and the cup grindstone. And an electrolytic in-process dressing step of performing dressing of the ground surface by applying. An optical glass grinding method comprising: The preparatory step is a step of producing a press product of the optical glass by softening a glass molded body preformed into a predetermined shape by heating and then press molding the glass molded body using a mold. The optical glass grinding method according to claim 1, wherein: The preparatory step is to obtain a molten glass by melting a glass raw material adjusted so as to obtain an optical glass having desired optical characteristics, and then supplying the molten glass from a pipe outlet to a mold, The optical glass grinding method according to claim 1, wherein the optical glass is manufactured by press molding using a molding die. 4. The optical glass grinding method according to claim 2, wherein the pressed product of the optical glass has a surface roughness Rz of the surface to be ground of 2.0 μm or less. 5. The cup grindstone includes abrasive grains for grinding the surface to be ground, and a bond material for bonding the abrasive grains,
The grain size of the abrasive grains is # 2000 to # 8000. The optical glass grinding method according to any one of claims 1 to 4, wherein the abrasive grain size is # 2000 to # 8000. 6. The optical glass grinding method according to claim 5, wherein an average particle diameter of the abrasive grains is 1.0 to 10.0 [mu] m. The optical glass grinding method according to claim 5, wherein the bond material is a metal bond or a resin bond. The optical glass grinding method according to any one of claims 1 to 7, wherein a rotational speed of the cup grindstone in the grinding step is 18000 rpm or more and 30000 rpm or less. The feed rate of the relative position movement in the contact variable direction of the pressed product of the optical glass and the cup grindstone in the grinding step is 1.0 μm / sec or more and 15.0 μm / sec or less. The grinding method of the optical glass of any one of -8. The optical glass press product is made of any one of fluorophosphate glass, phosphate glass, high refractive index and high dispersion glass containing niobium phosphate, or high refractive index and low dispersion glass containing lanthanum borate. The optical glass grinding method according to any one of claims 1 to 9. The manufacturing method of the optical glass lens which manufactures an optical glass lens from the press goods of the said optical glass using the grinding processing method of the optical glass of any one of Claims 1-10.

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