WO2015063888A1 - Optical glass material, glass lens blank for polishing and optical lens, and production method for glass lens blank for polishing and optical lens - Google Patents

Abstract

[Problem] To provide an optical glass material, a glass lens blank for polishing and an optical lens, and a production method for a glass lens blank for polishing and an optical lens, that can sufficiently reduce the allowance for the glass lens blank for polishing after press molding, when producing an optical lens, and capable of reducing the machining time required for grinding and polishing. [Solution] A glass lens blank (2b) for polishing, having at least a main surface being a press-molded surface, and the thickness of a defect-containing layer (90a) formed in the center section of the main surface being no more than 50 µm.

Description

Optical glass material, polishing glass lens blank and optical lens, and polishing glass lens blank and optical lens manufacturing method

The present invention relates to an optical glass material, a polishing glass lens blank and an optical lens, and a polishing glass lens blank and an optical lens manufacturing method.

As one method of manufacturing an optical lens (hereinafter, sometimes simply referred to as “lens”), an optical glass material (hereinafter sometimes simply referred to as “glass material”) is reheat pressed and molded. A method of obtaining a lens by grinding and polishing a glass lens blank for polishing (hereinafter sometimes simply referred to as “lens blank”) is known.

More specifically, molten glass is poured into a mold to produce a square or plate-like glass material (so-called glass block), and then the glass block is cut out by machining and is subdivided into a cubic shape. A so-called cut piece is produced. 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 that approximates the shape of the target lens. Finally, a lens is manufactured by grinding and polishing the lens blank.

This method can produce and store multiple plate glass blocks with different glass types in advance, and can cut and press plate glass blocks of the desired glass type into the desired quantity and volume as needed. Suitable for small volume production.

However, in this method, there is a problem that the corner portion is easily crystallized by heating when softening the cut piece, and the corner portion crystallized with the softening of the glass is folded into the glass (hereinafter, Sometimes referred to as “folded part”.) Such a fold portion has been a factor for forming deep surface defects (for example, folds of 300 μm or more) in the obtained lens blank.

In addition, in this method, there is a problem in that the glass component on the surface of the cut piece comes into contact with the polishing processing liquid during the rough surface polishing process, and cracks are generated due to the collision of the cut pieces during the processing. . Such alteration or cracking of the glass component on the surface of the cut piece is caused to crystallize on the glass surface by heating from the time of softening to press molding (as a result, defects are formed on the surface of the lens blank), or press This was a factor such as an increase in waviness on the surface of the lens blank after molding.

Generally, when a lens is manufactured, it is necessary to remove a defect formed on the surface of the lens blank and to form a smooth surface without irregularities by grinding and polishing the surface of the lens blank.

Therefore, when the surface defect extends to the deep part of the lens blank as described above, or when the surface waviness is large, the surface of the lens blank is deeply cut (a lot of machining allowance is taken, for example, the machining allowance is 500 μm). There is a problem that the time required for grinding / polishing becomes longer and the material is wasted, resulting in an increase in production cost.

On the other hand, if the machining allowance at the time of grinding / polishing is reduced, especially when the surface defect of the lens blank extends to the deep part, the defect cannot be sufficiently removed, and the defect remains on the surface of the lens. A lens in which such a defect remains is a defective product, resulting in a problem that the yield rate is reduced.

Therefore, when manufacturing a lens by grinding and polishing the lens blank after press molding, it has been required to reduce the amount of lens blank removal without reducing the yield rate of the lens.

Recently, as shown in Patent Document 1 (Japanese Patent No. 3806288), a method for manufacturing a glass lens blank for polishing in the following steps has been proposed.

That is, in this method, the molten glass supplied from the nozzle is received by a mold and molded to obtain a glass lump, the surface of the glass lump is subjected to a rough polishing process, and the surface of the glass lump is powdered. It has the process of forming a mold release agent, and the process of press-molding by reheating a glass lump.

This method can produce a large number of glass lumps as glass materials and store them in stock, so press molding using multiple molds with different molding surfaces from multiple glass lumps of the same shape according to the order. It is suitable for multi-product production.

Moreover, in this method, since the generation of square portions such as cut pieces on the surface of the glass lump can be suppressed, it is possible to form without forming a fold in the next reheating step. Therefore, it is possible to prevent a surface defect that extends to the deep part of the lens blank that occurs due to the folded portion.

However, also in this method, similar to the above-described manufacturing method, rough surface polishing is performed. Therefore, surface defects are formed entirely on the surface of the lens blank to be obtained, and it is necessary to set a sufficient machining allowance amount, and the machining allowance amount has not been significantly reduced.

As described above, none of the prior arts can sufficiently reduce the machining allowance of the lens blank, and the time required for grinding and polishing cannot be sufficiently shortened.

Therefore, when grinding and polishing a glass lens blank for polishing after press molding to produce a lens, the processing time required for grinding and polishing occupies about half of the entire lens process. There was a need for shortening.

Japanese Patent No. 3806288

The present invention has been made in view of such a situation, and its object is to reduce the amount of machining allowance of a glass lens blank for polishing after press molding when manufacturing a lens, and the processing time required for grinding and polishing. Glass material blank, polishing glass lens blank and optical lens, and a manufacturing method of polishing glass lens blank and optical lens.

As a result of intensive studies on shortening the processing time required for grinding and polishing of a glass lens blank for polishing after press molding, the present inventor has obtained polishing glass obtained by press molding the optical glass material according to the present invention. It has been found for the first time that the amount of machining allowance for grinding and polishing can be significantly reduced by using a lens blank, and the present invention has been completed.

That is, the gist of the present invention is as follows.
[1] A polishing glass lens blank in which at least the main surface is a press-molded surface, and the thickness of the defect-containing layer formed in the central portion of the main surface is 50 μm or less.

[2] The central portion is a region inside the outer periphery of the main surface,
The glass lens blank for polishing according to the above [1], wherein the radius of the central portion is 2/3 or less of the radius of the main surface.

[3] A first main surface and a second main surface which form a trapezoid and are parallel to each other;
A first side surface connecting short sides of the first main surface and the second main surface and a second side surface connecting long sides of the first main surface and the second main surface;
The first side surface and the second side surface are connected to each other, and there are two inclined surfaces each having an obtuse angle with the first side surface,
An optical glass material in which the first side surface and the two inclined surfaces are molding surfaces.

[4] The optical glass material according to [3], wherein the second side surface is a free surface.

[5] The optical glass material according to [3] or [4], wherein the first and second main surfaces are cut surfaces.

[6] The distance according to any one of [3] to [5], wherein a distance between the first and second main surfaces is shorter than a distance between the first side surface and the second side surface. Optical glass material.

[7] The distance described in any one of [3] to [5], wherein a distance between the first and second main surfaces is longer than a distance between the first side surface and the second side surface. Optical glass material.

[8] A polishing glass lens blank formed by press-molding the softened optical glass material by reheating and softening the optical glass material according to [6] above in an air atmosphere.

[9] The polishing glass lens blank according to [8], wherein at least the main surface is a press-molded surface, and the thickness of the defect-containing layer formed in the central portion of the main surface is 50 μm or less.

[10] An optical lens formed by grinding and polishing the glass lens blank for polishing according to [8] or [9] above.

[11] An optical glass material forming step of continuously casting molten glass into a mold and continuously forming a trapezoidal optical glass material while moving the cast glass in one direction from the upstream side to the downstream side. When,
Cutting the optical glass material in a direction perpendicular to the longitudinal direction, and cutting into small pieces,
A reheating step of reheating the optical glass material fragmented in the cutting step to a viscosity of 10 ⁴ to 10 ⁶ dPa · s in an air atmosphere;
The optical glass material reheated in the reheating step is press-molded in a press mold in an air atmosphere to obtain a glass molded product, and
The glass molded article has a press-molded surface at least on the main surface,
The manufacturing method of the glass lens blank for grinding | polishing whose thickness of the defect content layer formed in the center part of the said main surface is 50 micrometers or less.

[12] A mold release agent that applies a release agent to at least one of the surface of the optical glass material fragmented in the cutting step and the holding concave portion in which the optical glass material is disposed in the reheating step. The manufacturing method of the glass lens blank for grinding | polishing as described in said [11] which further has an agent application | coating process.
[13] In the release agent coating step, after the release agent is applied to the holding recess in which the optical glass material is disposed, the optical glass material is disposed in the holding recess. ] The manufacturing method of the glass lens blank for grinding | polishing of description.

[14] The polishing glass lens blank according to any one of [1], [2], [8] and [9] is subjected to spherical grinding and smoothing, and in the smoothing, A process for producing an optical lens, wherein an optical lens is obtained by processing using a resin bond grindstone without using a metal bond grindstone.

According to the present invention, when a lens is manufactured, the machining allowance of the glass lens blank for polishing after press molding can be greatly reduced, and the time required for grinding and polishing can be extremely shortened.

1A is a perspective view of an optical glass material (optical glass material piece) according to an embodiment of the present invention, and FIG. 1B is an optical glass material (optical glass material block) according to another embodiment of the present invention. FIG. FIG. 2 is a schematic cross-sectional view showing a manufacturing process of the optical glass material shown in FIGS. 1 (A) and 1 (B). FIG. 3 is a schematic sectional view taken along line III-III shown in FIG. 4A is a schematic cross-sectional view showing a convection state of the molten glass according to one embodiment of the present invention, and FIG. 4B is a schematic cross-sectional view showing a convection state of the molten glass according to the conventional example. FIG. 5 is a schematic perspective view showing a cutting process of the optical glass material according to one embodiment of the present invention. 6 (A) to 6 (E) are schematic cross-sectional views showing a process of manufacturing a polishing lens blank using the glass material shown in FIG. 1 (A). FIG. 7A is a side view showing an example of the shape of the polishing glass lens blank according to one embodiment of the present invention, and FIG. 7B is the polishing glass lens blank according to one embodiment of the present invention. It is a front view which shows an example of a shape. FIG. 8 is a schematic view schematically showing a portion to be removed by a grinding step and a polishing step in a partial cross section of the surface of the polishing glass lens blank shown in FIG. FIG. 9 is a flowchart showing a process of manufacturing an optical lens from the blank shown in FIG. FIG. 10 is a diagram illustrating the results of bright spot observation according to Examples and Comparative Examples.

<Optical glass material>
The optical glass material of the present invention (hereinafter sometimes simply referred to as “glass material”) includes a first main surface and a second main surface that are trapezoidal and parallel to each other, and the first main surface. And the first side surface connecting the short sides of the second main surface, the second side surface connecting the long sides of the first main surface and the second main surface, the first side surface and the first side surface. Two inclined surfaces that connect the two side surfaces and have an obtuse angle with each of the first side surfaces, and the first side surface and the two inclined surfaces are molding surfaces. And

According to such a glass material, a glass optical element blank for polishing (especially, an amount of machining allowance when producing a glass optical element such as an optical lens can be greatly reduced and a time required for grinding and polishing can be extremely shortened (particularly, , Glass lens blank for polishing, etc.) can be obtained.

Hereinafter, an embodiment of the present invention will be described using the optical glass materials 2 and 20 shown in FIGS. 1A and 1B as examples. In the following, in order to distinguish between the optical glass materials 2 and 20, the segmented optical glass material 2 shown in FIG. 1 (A) is referred to as an “optical glass material piece”, and the length shown in FIG. 1 (B). The optical glass material 20 having a scale is sometimes referred to as an “optical glass material block”.

Optical glass material 2
First, an optical glass material according to an embodiment of the present invention will be described by taking as an example an optical glass material piece 2 (hereinafter, simply referred to as “glass material piece 2”) shown in FIG. As shown to FIG. 1 (A), the glass raw material piece 2 which concerns on one Embodiment of this invention is parallel to this 1st main surface 4 with the trapezoid 1st main surface 4, and the same trapezoid shape. And a second main surface 6.

Furthermore, the glass material piece 2 of the present embodiment includes a first side surface 8 that connects the short sides of the first main surface 4 and the short sides of the second main surface 6, and the long side of the first main surface 4. And a second side surface 10 connecting the long sides of the second main surface 6 to each other.

Further, the glass material piece 2 of the present embodiment connects the first side surface 8 and the second side surface 10, and the two first inclinations in which the angles θ1 and θ2 formed with the first side surface 8 are both obtuse angles. It has a surface 12 and a second inclined surface 14. The angle θ1 and the angle θ2 are preferably the same as each other, but may be slightly different. The angle θ1 and the angle θ2 are each preferably greater than 90 to 135 degrees, more preferably 100 to 130 degrees, and even more preferably 110 to 120 degrees. Note that the corner formed by the first inclined surface 12 and the first side surface 8 and the corner formed by the second inclined surface 14 and the first side surface 8 may be slightly rounded.

In the present embodiment, the first side surface 8, the first inclined surface 12, and the second inclined surface 14 are molding surfaces. Preferably, the first main surface 4 and the second main surface 6 are cut surfaces, and the second side surface 10 is a free surface.

Here, the molding surface is a molding surface formed by contacting the mold. The free surface is a surface formed by softening glass solidified without contacting other objects (solid, liquid) during the cooling process. Further, the cut surface is a surface formed by cutting glass.

In the present embodiment, the first main surface 4 and the second main surface 6 are parallel to the YZ plane. The trapezoidal short and long sides of the first main surface 4 and the second main surface are parallel to the Y axis. The Z axis corresponds to the height of the trapezoid. In the drawings, the X axis, the Y axis, and the Z axis are perpendicular to each other.

In the glass material piece 2 of the present embodiment, the distance L1 (X-axis direction thickness) in the X-axis direction between the first main surface 4 and the second main surface 6 is preferably It is shorter than the distance H1 (Z-axis direction height) between the second side surface 10 and the Z-axis direction. Such a glass material piece 2 is easy to handle because it is fragmented to a desired width, and processing such as pressing is easy. Such a glass material piece 2 of this embodiment is suitable as a glass material for press molding.

In the present embodiment, the distance H1 (the height in the Z direction) between the first side surface 8 and the second side surface 10 is the length W1 of the first side surface 8 in the Y-axis direction or the second side surface 10. It is preferable that the following conditional expression (1) is satisfied, which is determined by the relationship with the length W2 in the Y-axis direction.
W1 × 0.8 ≦ H1 ≦ W2 (1)

Note that the distance H1 is preferably 25 to 60 mm, W1 is preferably 20 to 50 mm, and W2 is preferably 35 to 60 mm.

When the glass material piece 2 satisfies such conditions, the height and width are balanced, and the glass material piece 2 is easy to handle when softened or press-molded.

In this embodiment, it does not specifically limit as a material of the glass which comprises the glass raw material piece 2, (1) The fluorophosphate type glass which contains at least P, O, and F as a glass component, (2) In a glass component Lanthanum borate glass containing a relatively large amount of B ₂ O ₃ and La ₂ O ₃ , (3) SiO ₂ —TiO ₂ containing a relatively large amount of SiO ₂ and TiO _{2 in the} glass component ₂ based glass, ₍₄₎ Nb and P 2 _{O 5} as a main component, Ti, Bi, and the like niobium phosphate optical glass containing readily reducing component from W is exemplified.

Optical glass material 20
Next, another embodiment of the optical glass material according to the present invention will be described using the optical glass material block 20 shown in FIG. 1B (hereinafter sometimes simply referred to as “glass material block 20”) as an example. . In addition, it has the structure and effect similar to one above-mentioned embodiment except the part shown below, and the description which overlaps is partially abbreviate | omitted.

The glass material of the present invention may be a glass material block 20 shown in FIG. The difference between the glass material block 20 according to the present embodiment and the glass material piece 2 exemplified in the above-described embodiment is that the distance between the first main surface 4 and the second main surface 6 in the X-axis direction. It is the length of L0.

Preferably, in the glass material block 20 of the present embodiment, the distance L0 in the X-axis direction between the first main surface 4 and the second main surface 6 is such that the first side surface 8 and the second side surface 10 Longer than the distance H1 in the Z-axis direction. Since such a glass material block 20 can be managed with a certain fixed size, it is suitable for storage and movement.

Moreover, if the glass raw material block 20 of this embodiment is cut | disconnected in the direction orthogonal to a longitudinal direction and cut into pieces, when necessary, the glass raw material illustrated in the above-mentioned one embodiment with a desired width (L1). Piece 2 can be obtained.

<Method for producing optical glass material>
Next, a method for manufacturing the optical glass materials 2 and 20 will be described.
The method for producing an optical glass material according to the present embodiment is preferably continuously cast in a mold while continuously casting molten glass and moving the cast glass in one direction from the upstream side to the downstream side. A trapezoidal glass material is formed.

2 and 3 show a manufacturing apparatus for the optical glass material 2 (hereinafter simply referred to as “glass material piece 2”) and the optical glass material 20 (hereinafter simply referred to as “glass material block 20”). As shown in FIGS. 2 and 3, the manufacturing apparatus includes a nozzle 30 that causes the glass 20 a that has been heated and melted to flow toward the injection start position of the fixed mold 32.

The fixed mold 32 includes a bottom wall 34, an end wall 36 formed on the upstream side of the injection start position in the bottom wall 34 in the X-axis direction, and predetermined positions above both ends of the bottom wall 34 in the Y-axis direction in the Z-axis direction. And a side wall 38 that is inclined at an angle. The upper part of the fixed mold 32 is opened above the Z axis.

The bottom wall 34, the end wall 36, and the side wall 38 of the fixed mold 32 are integrally formed so as to prevent the molten glass from leaking between them, but they need to be made of the same material. There may be no separate member. As a material of the fixed mold 32, for example, cast iron, stainless steel, carbon material, nickel material or the like is used.

Note that a release agent may be applied to the inner peripheral surface of the fixed mold 32. This is to facilitate the movement of the solidified glass material block 20 from the fixed mold 34 to the conveyor belt 40. As the release agent, for example, a powder release agent such as boron nitride, alumina, silicon oxide, magnesium oxide or the like is used.

As shown in FIG. 3, the inclination angles of the pair of side walls 38 with respect to the bottom wall 34 correspond to the inclination angles θ1 and θ2 shown in FIG. Further, the height H0 of the side wall 38 from the inner bottom surface of the bottom wall 34 in the Z-axis direction is larger than the height H1 of the glass material piece 2 (same for the glass material block 20) shown in FIG. , 38 is larger than the maximum width W2 of the glass material piece 2 (the same is the glass material block 20).

In the present embodiment, by configuring the fixed mold 32 in this way, as shown in FIG. 4A, the molten glass 20a to be cast is molded while being convected smallly in the vicinity of the side wall along the inclined side wall 38. Therefore, a wide range of convection does not occur and no striae are generated inside the glass.

On the other hand, when the glass is formed using the fixed mold 32a having the side wall 38a perpendicular to the bottom surface of the bottom wall 34a as in the conventional case shown in FIG. 4B, a wide range of convection flows along the side wall 38a. This creates striae inside the glass.

In FIG. 2, the end wall 36 is connected to the bottom wall 34 at an angle substantially perpendicular to the bottom wall 34, but the end wall 36 is also obtuse at a predetermined inclination angle, like the side wall 38. It may be inclined to.

As shown in FIG. 2, the downstream side of the fixed mold 32 in the X-axis direction is open, and the molten glass 20a is gradually cooled and solidified as the fixed mold 32 is moved downstream in the X-axis direction. Go. At the downstream position in the X-axis direction where the molten glass 20a is hardened by slow cooling and the glass 20a is hardened to the extent that the molten glass 20a can be held by itself, a transport belt 40 as an X-axis direction transport device is disposed. The glass 20a solidified to such an extent that the shape can be maintained can be conveyed further downstream in the X-axis direction. The glass 20a conveyed on the conveying belt 40 is cooled to a predetermined temperature or lower (for example, Tg or lower) and solidified. The moving speed in the X-axis direction by the transport belt 40 is not particularly limited, but is, for example, about 10 to 50 mm / min.

In this embodiment, a roller (not shown) that presses the upper surface of the molten glass 20a inside the fixed mold 32 may be disposed immediately downstream of the nozzle 30 in the X-axis direction. By providing this roller, the thickness of the glass 20a (in particular, the height H1 shown in FIG. 1) can be easily made constant.

In this embodiment, an annealing device (not shown) may be installed across the fixed mold 32 connected to the transfer device 40. The annealing device has a role of removing distortion by gradually cooling the molded glass 20a.

The glass material block 20 after being conveyed by the conveying belt 40 is shown in FIG. The glass material piece 2 shown in FIG. 1 (A) can be obtained by cutting the glass material block 20 after conveyance at equal intervals in the X-axis direction.

Therefore, it is preferable that the method for manufacturing the glass material piece 2 according to the present embodiment further includes a step of cutting the glass material block 20 in a direction orthogonal to the longitudinal direction.

The cutting tool used for cutting the glass material block 20 shown in FIG. 1 (B) is not particularly limited, and a cutting blade, a wheel cutter, a wire saw, or the like is used. Preferably, a cutting device (multi-wire saw) 70 shown in FIG. 5 is used. In the cutting device 70, the plurality of wire saws 72 simultaneously travel at high speed as the plurality of rollers 74 rotate. If the wire saw 72 that runs at high speed is pressed against the first side surface 8 of the glass material block 20, the glass material block 20 is cut into an equal width at the arrangement interval (predetermined interval in the X-axis direction) of the wire saw 72. The

In addition, the surface cut | disconnected by the wire saw 72 of the cutting device 70 turns into a cut surface. The 1st side surface 8, the 1st inclined surface 12, and the 2nd inclined surface 14 which are not cut | disconnected are molding surfaces, and the 2nd side surface 10 is a free surface. As described above, the free surface is a surface formed by solidifying a softened glass without contacting other objects (solid, liquid) during the cooling process, and the molding surface is obtained by contacting the mold. It is the shape | molded surface and a cut surface is a surface formed by cut | disconnecting glass.

In this embodiment, a rod-shaped glass material block 20 having a trapezoidal cross section is formed, and a glass piece (glass material piece 2) having a trapezoidal cross section is produced by cutting at most twice. As a result, the weight accuracy of the individual glass pieces can be greatly increased, and a glass piece with little surface alteration can be obtained while suppressing material loss. That is, the glass material piece 2 which is a trapezoidal cut piece having a uniform weight accuracy can be obtained by cutting the rod-shaped glass material block 20 at equal intervals substantially without the altered layer except for the cut surface. .

In addition, the conventional glass material with a rectangular cross-section and narrow and narrow shape is prone to striae due to internal convection, and in order to suppress the occurrence of striae, the glass outflow speed is reduced, or the glass material Molding to reduce the plate thickness (for example, to 25 mm or less) is necessary, which is not economical.

On the other hand, in this embodiment, by making the cross section into a trapezoidal shape, the area of the bottom surface where the temperature is low can be reduced, and the influence of the temperature difference between the surface and the bottom surface which is the driving force of convection can be reduced. Shaping is possible at the same outflow speed as the conventional wide glass material. Moreover, the plate | board thickness (height H1 of a Z-axis direction) of a glass raw material can be shape | molded to thickness of 25 mm or more, for example.

Moreover, in this embodiment, by producing the glass material block 20 having a long and narrow shape, the glass material piece 2 can be cut out by a maximum of two cuttings, compared to the conventional case where four or more cuttings are required. Thus, the weight accuracy can be greatly improved.

Since the glass material piece 2 obtained in this way has fewer cut surfaces than a conventional cut piece, there is little weight variation and material loss can be reduced. Further, by performing weight management in the manufacturing process of the glass material block 20, the weight variation can be further reduced, preferably within ± 1%, and more preferably within ± 0.5%. The method of weight management is not particularly limited, and examples thereof include the size of the fixed mold 32, adjustment of the viscosity and outflow speed of the molten glass, selection of a cutting method and apparatus, and the like.

Furthermore, the surface alteration that becomes a problem during reheat pressing promotes the alteration of the cut surface. However, in the glass material piece 2 according to the present embodiment, the alteration is unlikely to occur because there are few cut surfaces. Further, since the glass material piece 2 has high weight accuracy at the time of cutting, it is not necessary to adjust the weight by barrel polishing, and is a surface (molded surface, free surface) that is a surface other than the cut surface and has almost no surface defects. The state can be maintained. In addition, since the trapezoidal glass piece 2 according to the present embodiment does not have a ridge or a corner at the central portion of the main surface, a folded portion is unlikely to occur at the central portion of the reheat-pressed lens blank. Therefore, the amount of removal during grinding and polishing can be reduced, and the processing time can be shortened.

In this embodiment, since the number of times of cutting is small, high-accuracy and high-quality cutting by the wire saw 72 shown in FIG. 5 can be performed at low cost instead of cutting with a wheel cutter or the like, and deterioration of the cut surface can be suppressed. it can.

<Grinding glass lens blank>
The polishing glass lens blank according to the present embodiment is formed by reheating and softening the optical glass material according to the present embodiment in an air atmosphere, and press-molding the softened optical glass material.

In such a reheat press, it is preferable to use an optical glass material (optical glass material piece 2) that has been segmented in advance into a predetermined size by the above-described cutting method.

Hereinafter, with reference to FIG. 6, the optical glass material 2 according to the present embodiment (hereinafter, simply referred to as “glass material”) is reheat-pressed to form a polishing glass lens blank (hereinafter referred to as “glass glass blank”). A method for manufacturing simply “lens blank” may be described.

As shown in FIG. 6A, the glass material 2 is supplied to a tray (softening tray) 50 having a holding recess 52. At this time, the material 2 is supplied in such a posture that the first main surface 4 or the second main surface 6 of the material 2 faces the recess 52 of the tray 50. Further, a release agent such as boron nitride is preferably applied between the glass material 2 and the tray 50. Further, at this time, it is preferable to apply the release agent while maintaining the surface state of the glass material 2 after cutting.

Next, the glass material 2 together with the receiving tray 50 is put into a heating furnace and reheated in an air atmosphere to soften the glass material 2 to a viscosity of 10 ⁴ to 10 ⁶ dPa · s. As shown in FIG. 6C, it is deformed into a predetermined shape.

Next, as shown in FIG. 6 (D), the glass material 2a that has been softened and deformed into a biconvex curved shape is press-molded into a desired shape using a molding die. This press molding is also performed in the atmosphere. The molding die is composed of an upper die 66 and a lower die 60 having a molding surface, and an annular body die 64 that regulates them substantially coaxially, and is heated in advance. Further, a release agent (boron nitride or the like) is applied to the molding surface in order to prevent the glass and the mold from being fused.

First, the softened glass material 2a is supplied onto the molding surface 62 of the lower mold 60 while maintaining the viscosity of 10 ⁴ to 10 ⁶ dPa · s, and immediately thereafter, the upper mold 66 is inserted into the barrel mold 64. . In FIG. 6 (D), since the load by the upper mold | type 66 is not applied to the glass raw material 2a, the glass raw material 2a is maintaining the shape shown in FIG.6 (C). Next, as shown in FIG. 6 (E), the upper die 66 is lowered to press the glass material 2a, the glass material 2a is press-molded into a shape following the molding surface shape of the upper and lower molds, and the lens blank 2b is formed. obtain.

In FIG. 6, (A) to (C) can be referred to as a reheating process or a resoftening process, and (D) to (E) can be referred to as a pressing process.

The shape of the lens blank 2b is not only a shape having a convex surface and a concave surface as shown in FIG. 6E, but also a biconvex shape, a shape having a convex surface and a plane, a shape having a concave surface and a plane, and a biconcave shape. There is no particular limitation as long as the shape approximates the shape of the optical lens (hereinafter, simply referred to as “lens”).

In addition, since the glass raw material 2 which concerns on this embodiment has high weight precision, in the process from obtaining a glass raw material to reheat press molding, the process of roughening the surface for the weight adjustment of a glass raw material ( Barrel polishing step) and polishing / grinding step may be omitted.

Preferably, in the present embodiment, there is no process (barrel polishing process or the like) for roughening the surface of the glass material 2 in the process from obtaining the glass material 2 to press molding. Since the glass material 2 can be press-molded while maintaining the surface state of the first main surface 4 and the second main surface 6 by not performing the surface roughening treatment, generation of surface defects in the lens blank after molding is effective. Can be prevented.

In addition, since the glass material 2 according to the present embodiment has high weight accuracy, even when a large number (for example, 1000 or more) of glass lens blanks are produced at one time, weight variation can be suppressed. For example, the weight variation of the lens blank after molding is ± 1.0% or less, and in some cases, ± 0.5% or less.

Furthermore, since the optical glass material 2 according to the present embodiment is a plate-shaped optical glass material (a main surface is a trapezoidal glass piece) unlike a conventional cubic shaped cut piece, It is possible to manufacture a lens blank that suppresses the occurrence of folding and ridge (side) alteration (thin alteration region is thin and grinding / polishing cost is small).

That is, the polishing glass lens blank according to the present embodiment includes an optical glass material 2 having a molding surface, a cutting surface, and a free plane formed by a molding die, that is, a first main surface 4 and a second main surface 6. A glass material having a distance L1 (X-axis direction thickness) between the first side surface 8 and the second side surface 10 shorter than a distance H1 (Z-axis direction height) between the first side surface 8 and the second side surface 10. Is a molded product obtained by reheat press molding.

Such a polishing glass lens blank according to this embodiment is characterized in that at least the main surface is a press-molded surface, and the thickness of the defect-containing layer formed in the central portion of the main surface is 50 μm or less. To do.

In the present embodiment, the defect-containing layer is a portion where the glass component has changed due to contact with a crack or processing liquid generated when the optical glass material is roughly polished, or a crystallization portion which is generated from softening to press molding. including.

In the present embodiment, the central portion is a region on the inner side of the outer periphery of the main surface, and is a region not more than two thirds of the radius of the main surface from the center point of the main surface.

Hereinafter, a polishing glass lens blank according to an embodiment of the present invention (hereinafter, simply referred to as “lens blank”) will be described in detail with reference to FIGS. 7 and 8.

FIGS. 7A and 7B are a side view and a front view, respectively, showing an example of the shape of the lens blank according to an embodiment of the present invention. FIG. 8 is a schematic view schematically showing a portion to be removed by a grinding step and a polishing step in a partial cross section of the surface central portion of the lens blank shown in FIG.

As shown in FIG. 7A, the lens blank 2b according to one embodiment of the present invention has substantially spherical press-molded surfaces 80 and 82 as main surfaces. The press molding surfaces 80 and 82 are surfaces to which the molding surface shapes of the lower mold 60 and the upper mold 66 are transferred, respectively (see FIG. 6E).

In FIG. 6E, the main surface 80 is a convex curved surface and the main surface 82 is a concave curved surface, but the shape of the lens blank of the present invention is not particularly limited, and either one or both are concave. It may be a curved surface or a flat surface. In addition, the side peripheral surface 84 of the lens blank 2b may be a press-molded surface that is molded on the inner peripheral surface of the barrel die 64, or may be a free surface that does not contact the barrel die 64 (FIG. 6). (See (E)).

As shown in FIG. 7B, in the present embodiment, the central portion 80a is a region on the inner side of the outer periphery of the main surface 80, and the radius R1 of the main surface 80 from the center point 0 of the main surface 80. The area 80a is 2/3 or less. That is, the center point 0 of the center portion 80a is the same position as the center point 0 of the main surface 80, and the radius R2 of the center portion 80a is 2/3 or less, more preferably 1/2 or less of the radius R1 of the main surface. It is. The same applies to the main surface 82.

Lens blank 2b of the present embodiment, as shown in FIG. 8, at its central portion 80a, following the thickness _{t 0} of the defect-containing layer 90a is 50 [mu] m, preferably 30μm or less.

In the present embodiment, since the lens blank 2b is manufactured by the above-described manufacturing method, the defect-containing layer 90a is expected to have a thickness of at least 1 μm or more, but is obtained by a conventional manufacturing method. In comparison, the thickness t ₀ of the defect-containing layer 90a is extremely thin.

In the present embodiment, the defect-containing layer 90a is a layer having a defect that forms a bright spot of reflected light as compared with the bulk portion 90b (a portion that becomes an optical lens) of the lens blank 2b. By removing the defect-containing layer 90a, defects that form bright spots of reflected light are eliminated.

As a specific example of the defect that forms a bright spot of reflected light, for example, a crystallization portion generated by a reheating step and a pressing step in the above-described lens blank manufacturing method can be cited.

In addition, in the main surface central part 80a of the lens blank 2b which concerns on this embodiment, the folding part originating in the corner | angular part of the glass raw material 2 does not exist substantially.

In general, an optical lens (hereinafter sometimes simply referred to as a “lens”) is formed on the surface of a lens blank after press molding by grinding and polishing the lens blank to form a target lens shape. It is manufactured by removing the defect-containing layer. The lens obtained in this way becomes a defective product if defects that become bright spots remain on the surface thereof. Therefore, it is necessary to grind and polish (a large amount of machining allowance) until the defect-containing layer formed on the surface of the lens blank is removed.

In the lens blank of this embodiment, since the thickness of the defect-containing layer in the central portion of the main surface is 50 μm or less, the allowance when performing lens surface spherical grinding (generation grinding) and polishing on this lens blank. The amount can be greatly reduced. As a result, the processing time required for grinding and polishing for obtaining the lens can be extremely shortened, and the tact time for manufacturing the lens can be greatly reduced.

Furthermore, according to the lens blank of the present embodiment, the amount of machining allowance can be greatly reduced when grinding and polishing to obtain a lens, so that it is possible to minimize grinding scraps and polishing scraps. In addition, material waste can be reduced. In addition, since the amount of processing is small, the lens thickness accuracy is also improved.

In such a lens blank according to the present embodiment, even when the amount of machining allowance at the time of manufacturing the lens (the amount of machining at the center of the lens blank surface) is, for example, 200 μm or less, further 150 μm or less. , An excellent non-defective product rate can be achieved (no surface defects or the like remain on the obtained lens). The smaller the machining allowance, the shorter the time required for grinding and polishing, which is preferable. Even in the case of the lens blank according to the present embodiment, if the amount of machining allowance is too small, defects remain on the surface of the obtained lens and the yield rate decreases, so that the amount of machining allowance is more preferably 100 μm or more. .

The size and weight of the lens blank 2b are not particularly limited, but the effect of the present invention is great when the lens blank has a weight of 5 grams or more, more preferably 10 grams or more. The lens blank of the present invention is particularly suitable for molding glass lenses having medium and large diameters. The reason for this is that medium- and large-diameter glass lenses require a longer processing time for grinding and polishing than small-diameter glass lenses. According to the present invention, this processing time can be shortened, resulting in material loss. It is because it can reduce, and the effect by this invention can be exhibited further.

<Optical lens>
The optical lens according to the present embodiment (hereinafter sometimes simply referred to as “lens”) is a polishing glass lens blank (hereinafter also simply referred to as “lens blank”) obtained according to the present embodiment. It is formed by grinding and polishing.

Hereinafter, the grinding and polishing process of the polishing glass lens blank 2b shown in FIG. 7A will be described in detail with reference to FIGS. 8 and 9, but the present invention is not limited to the following embodiment. However, the present invention can be implemented with appropriate modifications within the scope of the object of the present invention.

In step S10 shown in FIG. 9, first, a spherical grinding step (CG processing) of the main surface of the lens blank 2b shown in FIG. 7A is performed. The curve generator used for CG processing is not particularly limited, and a known one is used.

In the CG processing, as shown in FIG. 8, the CG processing region 92 (CG processing allowance) including the defect-containing layer 90a at the center of the main surface of the lens blank 2b is ground. In the CG processing, grinding is performed using a grindstone having an abrasive grain portion of # 400 to # 800 in terms of grain size while supplying a grinding fluid.

Through such CG processing, the main surface of the lens blank 2b becomes a shape close to a spherical surface having a predetermined curvature.

Also, in such CG processing, surface defects formed on the main surface of the lens blank are also removed. Usually, when the surface defect formed on the main surface (especially the central part) of the lens blank extends to the deep part (that is, the defect-containing layer on the main surface (especially the central part) is thick), after grinding and polishing It is necessary to scrape a relatively large amount of the main surface at the stage of CG processing so as not to leave surface defects in the lens.

In the lens blank 2b according to the present embodiment, since the thickness of the defect-containing layer 90a formed in the central portion 80a of the main surface 80 is as small as 50 μm or less (the same is true in the main surface 82), the main surface is removed at the stage of CG processing. It is not necessary to sharpen a large amount (that is, remove most of the defect-containing layer). In other words, even if the processing amount of CG processing is greatly reduced (and excluding CG processing), surface defects formed on the main surface (especially the central portion) are sufficiently removed through all grinding and polishing processes. it can.

In the lens blank 2b according to the present embodiment, a grindstone having a relatively fine particle size can be used as a 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 2b according to the present embodiment can reduce the target processing amount in the CG processing, the CG processing can be completed even with a relatively fine grindstone.

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

Usually, in grinding processing such as CG processing, innumerable micro cracks are newly generated on the surface of the processed lens blank. In particular, when a grindstone with a large particle size is used, the amount that can be processed at a time increases, but on the other hand, micro cracks generated by CG processing tend to reach the deep part of the lens blank, and subsequent processes (such as fine grinding) This makes it difficult to remove microcracks.

On the other hand, when a grindstone having a relatively fine grain size is used, the amount that can be processed at a time is small, but microcracks generated by processing do not become extremely deep (for example, remain at 15 μm or less from the surface), and in a later step Micro cracks can be removed sufficiently.

The thickness of the CG processing region 92 is not particularly limited, but is preferably 50 to 200 μm. The processing time required for CG processing is not particularly limited, but is about 45 to 90 seconds.

Next, as shown in FIG. 9, in step S11, a smoothing process (SM process) by a precision grinding process is performed. The SM processing may be one-step processing, but may be multi-step processing. In the example shown in FIG. 8, SM machining is performed twice under different conditions. That is, in the first SM machining, the first SM machining area 94a (SM machining allowance) shown in FIG. 8 is removed by machining, and in the second SM machining, the second SM machining area 94b is machined. Removed. Therefore, the micro cracks generated by the CG processing are almost removed by these SM processing.

Further, in the present embodiment, in these SM processing, processing using only a resin bond grindstone is preferably 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.

Usually, as in CG processing, in SM processing, the base portion or abrasive grain portion of the grindstone and the lens blank come into contact with each other, and innumerable micro cracks are newly generated on the surface of the processed 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. appear.

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 (eg, 5 μm or less).

In this embodiment using only a resin bond grindstone without using a metal bond grindstone as described above, the depth of micro cracks caused by SM processing can be greatly reduced. As such a resin bond grindstone, it is preferable to use a grindstone of # 1200 to # 2500 in terms of particle size. In the present embodiment, the roughness of the grindstone used in the second SM machining is fine compared to the roughness of the grindstone used in the first SM machining.

Furthermore, in this embodiment, since the resin bond grindstone having a relatively fine particle size is used in the second SM processing, the depth of the generated microcracks can be further reduced as compared with the case of using a grindstone having a large particle size. . 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 machining time required for SM machining is not particularly limited, but is about 80 to 240 seconds in total. In the present embodiment, the machining time for the second SM machining is longer than the machining time for the first SM machining. The thickness of the SM processing regions 94a and 94b is not particularly limited, but is preferably 10 to 70 μm in total, and in this embodiment, the thickness of the first SM processing region 94a is the second SM processing region. Although it is longer than the thickness of 94b, it may be the same or shorter.

Next, as shown in FIG. 9, 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, and the polishing region 96 (polishing allowance) shown in FIG. 8 is polished. The thickness of the polishing region 96 is preferably 3 to 10 μm, and the processing time is about 2 to 10 minutes. By this polishing process, the optical lens surface 90c (main surface) of the optical lens body 90b is formed.

Finally, the centering process is performed in step S13 shown in FIG. 9, but the centering process may be omitted in some cases. In the centering step, for example, the lens body 90b is sandwiched between a pair of lens holders to perform centering, and the lens body 90b is rotated around the center line, and the side peripheral surface of the lens body 90b is rounded with a diamond grindstone or the like. It is a process to grind.

Up to this point, the grinding and polishing process shown in FIG. 9 has been described as an example. However, the manufacturing process of the optical lens using the lens blank 2b according to the present embodiment is not limited to such a process. It can be performed in the process.

For example, in the lens blank 2b according to the present embodiment, it is possible not to perform the CG processing in step S10 shown in FIG.

As described above, in the lens blank 2b according to the present embodiment, the thickness of the defect-containing layer 90a formed in the central portion 80a of the main surface 80 is as small as 50 μm or less (same in the main surface 82), and grinding and polishing are performed. In the first place, the thickness of the main surface to be removed is small. In such a lens blank 2b according to the present embodiment, it is not necessary to perform a large amount of processing in order to remove the defect-containing layer, and the surface defect layer can be sufficiently removed only by processing after SM processing.

In addition, when excluding CG processing, a metal bond grindstone may be used during 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.

Thus, 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.

In the lens blank 2b obtained by the manufacturing method according to the present embodiment, the thickness of the defect-containing layer 90a in the central portion 80a is 50 μm or less. Therefore, the processing time required for grinding and polishing for obtaining a lens for the lens blank 2b can be extremely shortened.

Therefore, according to the manufacturing method of the optical lens according to the present embodiment, the processing time required for grinding and polishing when obtaining the optical lens, as compared with the case where the polishing glass lens blank obtained by the conventional cut piece method is used. Can be reduced to approximately half or less. Further, even when using a polishing glass lens blank obtained by the method described in Patent Document 1 (Japanese Patent No. 3806288), the processing time required for grinding and polishing for obtaining an optical lens is approximately half or less. Can be shortened.

Further, according to the method of manufacturing an optical lens according to the present embodiment, it becomes possible to minimize grinding waste and polishing waste at the time of grinding and polishing, thereby eliminating material waste. In addition, since the processing amount is small, the thickness accuracy of the optical lens is also improved.

Further, 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 embodiment, and can be variously modified within the scope of the present invention.

For example, in the above-described embodiment of the present invention, it has been described that the first main surface 4 and the second main surface 6 of the optical glass material are parallel to each other. It means, and may deviate somewhat from the parallel without departing from the present invention.

Further, in the present 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.

Moreover, in this embodiment, although the glass glass blank for polishing and the aspect which produces an optical lens using the optical glass raw material which concerns on this invention were illustrated, the optical glass raw material which concerns on this invention is limited to these uses. It can be used for the production of various polishing glass optical element blanks, and thus glass optical elements. Examples of such optical elements include prisms and diffraction gratings in addition to the various optical lenses described above. The present invention is suitable for optical lenses, particularly spherical lenses.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

Example 1
The raw materials are prepared and melted so as to have a predetermined composition, and the obtained lanthanum borate-based molten glass is continuously flowed down from a platinum alloy outflow pipe at a constant speed, as shown in FIGS. The glass material 20 (hereinafter referred to as a glass material block) shown in FIG. 1B was molded by pouring toward the fixed mold 34 and cooling. In this molding process, the glass material block 20 was annealed through an annealing furnace slightly higher than the transition temperature (Tg) or Tg of the molten glass, and then the glass material block 20 was cooled to about room temperature.

In addition, when the molten glass 20a was cast, a wide range of convection did not occur along the side wall 38a, and no striae occurred inside the obtained glass material block 20.

Next, the annealed cross section is a trapezoidal glass material block 20 (short side width (W1) 38 mm, long side width (W2) 50 mm, height (H1) 34 mm, angle (θ1) 100 °. , (Θ2) 100 °) was cut with a diamond cutter to produce a plurality of rod-shaped glass material blocks having a length (L0) of about 400 mm. Next, using the wire saw 72 of the cutting device 70 shown in FIG. 5, each rod-shaped glass material block is cut into a certain width, and the glass material 2 (thickness (thickness (thickness)) shown in FIG. L1) 6 mm, and other sizes were the same as those of the glass material block 20, and hereinafter, 100 pieces of glass material pieces) were prepared.

Next, a release agent was applied to the softening tray 50 of the reheating device used in the reheating process.

The glass material piece 2 prepared in advance was supplied on a receiving tray 50 coated with a release agent in such a posture that the main surface 4 faces upward. The glass material piece 2 supplied on the saucer 50 was put together with the saucer 50 into a heating furnace set at 500 to 750 ° C. and reheated in an air atmosphere. The reheated glass material was softened to a viscosity of about 10 ⁵ dPa · s.

Next, 100 glass blanks having a single-sided convex shape (diameter 35 mm, height 14 mm) were produced by press-molding a glass material softened by reheating in a press-molding mold in an air atmosphere. In addition, the mold which applied the mold release agent beforehand to the molding surface of a shaping | molding die, and heated to the temperature of 500 degreeC was used.

(Comparative Example 1)
In Comparative Example 1, the molten glass melted in the same manner as in Example 1 was continuously flowed from a platinum alloy outflow pipe at a constant speed, and the flowed glass was used as a mold for forming a glass lump. A glass lump was continuously formed by using one after another. When the temperature of the glass drops below the glass transition temperature, the glass lump is taken out from the mold, annealed in an annealing furnace slightly higher than the transition temperature (Tg) or Tg of the molten glass, and then cooled to about room temperature. 100 glass lumps (diameter: about 33 mm, thickness: about 10 mm) were produced.

Next, the obtained glass lump was barrel-polished to roughen the surface to make it easier to apply the release agent, and the weight was adjusted to be equal to the weight of the target lens blank. During this step, the glass that had been sufficiently annealed was not damaged. Moreover, the surface of the glass lump which passed through such a preliminary process (barrel grinding | polishing) was a rough shear surface.

Here, barrel polishing is a method in which a particulate abrasive and a compound and water are put in a polishing container together with a glass lump, and polishing is performed by rotating and moving the polishing container up and down. Made by law.

Next, a powdery release agent (boron nitride) was applied to the surface of the glass lump subjected to barrel polishing, placed on the softening tray 50, and reheated in a heating furnace. After this reheating step, 100 lens blanks B were produced in the same manner as in Example 1.

(Comparative Example 2)
In Comparative Example 2, molten glass melted by the same method as in Example 1 is continuously supplied from a platinum alloy outflow pipe to a mold having one side open, and cooled to have a certain width and thickness. The plate glass which has is shape | molded. During the molding process, the sheet glass was annealed through a transition temperature (Tg) of the molten glass or an annealing furnace slightly higher than Tg.

Next, the annealed glass plate was cut into a certain size (length 20 mm × width 20 mm × height 20 mm) to obtain 100 pieces of glass called cut pieces. Further, the cut piece was barrel-polished to round the edge, and the weight was adjusted to be equal to the weight of the target lens blank. During this process, the glass that had been sufficiently annealed did not break. The barrel polishing conditions are the same as the barrel polishing for the glass lump described above.

The surface of the cut piece that had undergone such a preliminary process (barrel polishing) was a rough surface. Next, a powder release agent (boron nitride) was applied to the surface of the cut piece, placed on the softening tray 50, and reheated in a heating furnace. After this reheating step, 100 lens blanks C were produced by the same method as in Example 1.

Next, the obtained lens blanks A to C were evaluated as follows.

(Evaluation 1: Confirmation of existence area of defect-containing layer)
The presence of the defect-containing layer in the central portion of the main surface of the lens blanks A to C was confirmed by the following method.

First, 25 lens blanks A to C obtained were prepared, and the surface of the lens blank was polished from the main surface of each lens blank to a depth of 50 μm, 80 μm and 100 μm.

Polishing performed in Evaluation 1 is polishing for confirming the thickness of the defect-containing layer on the main surface of the lens blank. Therefore, the final lens shape is ignored, and the surface of the lens blank is polished stepwise by only polishing. Note that grinding / polishing in evaluation 2 described later is grinding / polishing that creates the shape of the optical lens, and is different from the polishing treatment in this evaluation. Further, the diameter of the lens after polishing is the same as the diameter of the lens blank before processing.

The surface-finished lens blanks (25 points each) polished from the main surface of the lens blank to a predetermined depth were irradiated with an argon lamp to observe bright spots. The results are shown in FIG.

FIG. 10 is a diagram showing the results of bright spot observation according to the example. Usually, the thickness of the defect-containing layer varies somewhat for each lens blank. Therefore, when a plurality of lens blanks are polished from the main surface to the same depth, the defect-containing layer cannot be sufficiently removed in the lens blank having a relatively thick defect-containing layer, and the lens after polishing has a defect-containing layer. May remain. Such a defect-containing layer remaining on the processed lens scatters light and causes bright spots.

Therefore, the non-defective product was calculated as a non-defective product in which no bright spot was observed in the center of the lens after processing (in the region from the center point of the lens to 2/3 of the lens radius). In this example, a good product rate of 100% after processing was considered good. The results are shown in Table 1.

As shown in Table 1, in the lens blank A according to the present invention, the non-defective rate was already 100% with a surface processing amount of 50 μm depth from the main surface of the lens blank. For this reason, polishing with a surface processing amount of 80 μm and 100 μm in depth from the main surface of the lens blank was not performed.

Thus, the lens blank A according to the present invention has a non-defective product rate of 100% with a surface processing amount (polishing amount) of 50 μm, and as shown in FIG. No bright spot was observed in the part. That is, in the lens blank A according to the present invention, it was confirmed that all the defect-containing layers at the center of the main surface can be removed by polishing at least 50 μm from the main surface.

From this, it was confirmed that in the lens blank A, the thickness of the defect-containing layer formed at the center portion of the main surface of the lens blank is 50 μm or less even when the variation for each lens blank is included.

On the other hand, as shown in FIG. 10B, in the lens blank B corresponding to the comparative example of the present invention, when polishing with a surface processing amount of 50 μm, the non-defective rate is 0%, and all the samples are also in the center of the lens A bright spot was observed. That is, in the case of the lens blank B, even if polishing is performed at a depth of about 50 μm from the main surface of the lens blank, it is not possible to remove all the defect-containing layers present in the central portion of the main surface.

Thus, it was confirmed that the thickness of the defect-containing layer formed in the central portion of the main surface of the lens blank exceeds 50 μm even when the lens blank B includes variations for each lens blank.

For the lens blank B, it was confirmed that the non-defective product rate was improved by polishing the main surface to a depth of 80 μm and further to 100 μm.

Also, the same tendency as the lens blank B was confirmed for the lens blank C corresponding to the comparative example of the present invention.

(Evaluation 2: Confirmation of stock removal amount)
For the lens blanks A to C, the amount of machining allowance was confirmed by the following method.
First, 20 lens blanks A to C obtained were prepared, and ground and polished with the machining allowances at the center of each lens blank being 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 300 μm and 500 μm.

Further, the machining allowance in this evaluation means the machining allowance on the lens blank surface that is lost in all grinding and polishing processes when an optical lens is produced from the lens blank. In addition, the observation point of the machining allowance was the center of the lens blank (polished optical lens).

Further, since the grinding / polishing performed in the evaluation 2 is grinding / polishing that creates the shape of the optical lens, the conditions are different from those of the evaluation 1 in which the polishing is performed so as to follow the surface shape of the lens blank.

An optical lamp (20 pieces each) obtained by processing the lens blank so as to obtain a predetermined machining allowance was irradiated with an argon lamp to observe a bright spot. Light is scattered and becomes a bright spot at the portion where the defect-containing layer remains. Since such a bright spot becomes defective as an optical lens, a product having no bright spot was regarded as a non-defective product, and the yield rate was calculated. In this example, a good product rate of 100% was considered good. The results are shown in Table 2.

As confirmed in Evaluation 1 above, in the lens blank A according to the present invention, the thickness of the defect-containing layer formed in the central portion of the main surface is as thin as 50 μm or less. Therefore, if an optical lens is produced using such a lens blank A, the machining allowance set for removing the defect-containing layer can be greatly reduced while forming the lens shape.

In the lens blank A according to the present invention, there are few surface defects and waviness on the entire surface of the lens blank, and in particular, it is considered that there is no deep defect extending to the deep part of the lens blank at the center of the lens blank surface. Therefore, if an optical lens is produced using such a lens blank A, the machining allowance set for removing surface defects and waviness can be greatly reduced while forming a lens shape.

As shown in Table 2, when an optical lens was produced using the lens blank A according to the present invention, even when the amount of machining allowance at the center of the lens blank was set to 150 μm, It was confirmed that the defect-containing layer could be removed sufficiently and the yield rate was 100%.

On the other hand, in the lens blank B and the lens blank C corresponding to the comparative example of the present invention, the thickness of the defect-containing layer formed in the central portion of the main surface exceeds 50 μm (see Evaluation 1). In particular, in the lens blank C, the corner of the cut piece is crystallized by heating from the time of softening to the time of molding, and is folded into the inside of the glass, and a defect extending deeply is formed in the center of the lens blank surface. Conceivable. Therefore, when an optical lens is manufactured using such lens blanks B and C, it is necessary to set a large machining allowance in order to completely remove the surface defect layer.

That is, as shown in Table 1, when an optical lens was manufactured using the lens blank B and the lens blank C corresponding to the comparative example of the present invention, the variation of each lens blank was taken into consideration, and In order to completely remove the defect-containing layer, it was confirmed that the machining allowance must be set to 500 μm or more.

On the other hand, when producing an optical lens using the lens blank A according to the present invention, the amount of machining allowance can be greatly reduced as compared with the lens blank B and the lens blank C. The time required can be extremely shortened.

The lens blank A according to the present invention has a yield rate of 40% when the machining allowance is 50 μm. This means that even if the lens blank A is processed with a machining allowance of 50 μm, the defect-containing layer has not yet been removed with a 40% sample. However, with this, it cannot be evaluated that the thickness of the defect-containing layer in the central portion of the main surface of the lens blank exceeds 50 μm, and there is no contradiction with Evaluation 1.

That is, the range to be evaluated differs between the machining amount in Evaluation 1 and the machining allowance in Evaluation 2. That is, while the processing amount in Evaluation 1 evaluates the thickness of the defect-containing layer on the main surface of the lens blank itself, Evaluation 2 evaluates the amount of machining allowance when producing the optical lens. .

Therefore, the amount of machining allowance in Evaluation 2 is not only determined solely by the thickness of the defect-containing layer formed on the main surface of the lens blank, but it is also necessary to consider the influence of other factors such as waviness of the lens blank surface. There is.

(Evaluation 3: Grinding / polishing conditions and production of optical lens)
Regarding the lens blanks A to C, the conditions for grinding and polishing of the lens blank until the optical lens was manufactured were confirmed. Specifically, CG processing (lens surface spherical grinding), SM processing (smoothing processing, multi-step processing is performed as necessary), and PO processing (polishing as necessary) are performed as grinding and polishing until an optical lens is manufactured. The optimum processing conditions for each step when performing (polishing) were confirmed. The results are shown in Table 3. The tools, machining amount and machining time are as shown in Table 3.

In the lens blank A according to the present invention, since the thickness of the defect-containing layer formed in the central portion of the main surface is as thin as 50 μm or less, the defect-containing layer is removed when an optical lens is produced using this. The amount of machining allowance required for the process can be greatly reduced (see Evaluation 2).

Therefore, when the lens blank A is used, the grinding amount of the lens blank can be reduced. Therefore, even if CG processing is performed with a relatively fine # 600 grindstone, the grinding time is not significantly extended. In addition, by performing grinding using such a fine grindstone, it is possible to effectively reduce the occurrence and progression of microcracks in the depth direction on the lens surface accompanying grinding, and the glass surface after CG processing (Here, including a region from the outermost surface to about 50 μm) can be maintained relatively well.

As a result, when the lens blank A according to the present invention is used, since there is little processing damage layer due to grinding on the lens surface after CG processing, the # 2500 resin bond grindstone (for example, alpha Even when using Diamond Industrial Co., Ltd., the processing damage layer due to grinding can be sufficiently removed. In particular, the resin bond grindstone can extremely reduce the depth of microcracks generated by the SM processing itself as compared with the metal bond grindstone. As a result, it is possible to shift to the polishing process (PO process) as the final process without further SM processing. Furthermore, since a fine # 2500 resin bond grindstone is used, the surface condition after SM processing is maintained well, and the processing time of PO processing can be greatly reduced. In particular, the processing amount of PO processing can be reduced to 10 μm or less.

On the other hand, in the lens blanks B and C according to the comparative example of the present invention, the thickness of the defect-containing layer formed in the central portion of the main surface exceeds 50 μm. Therefore, when producing an optical lens using these lens blanks, the defect-containing layer must be completely removed in order to increase the yield rate, and for that purpose, a large machining allowance needs to be set. (See Evaluation 2).

As described above, in the lens blanks B and C, since the machining allowance must be set large, the grinding time is extended. Further, in the case of the lens blanks B and C having a large machining allowance, clogging is likely to occur, and grinding is delayed. Therefore, it is difficult to use a fine grindstone (for example, # 600 or less) during CG processing. Therefore, in order to increase the grinding amount per processing time, it is necessary to start CG processing from a coarse grinding stone such as # 230. However, since a coarse grindstone is used, the generation of deep microcracks (working damage layer) that occur on the lens surface during grinding is unavoidable, and the defect layer caused by grinding tends to increase.

In order to remove the processing damage layer due to grinding in the subsequent process, it is necessary to increase the amount of grinding in the subsequent SM processing, and a plurality of SM processings are required. In particular, in order to remove a large amount of grinding, a metal bond grindstone is used, and new microcracks (for example, a depth of 30 μm) are generated with the grinding by the metal bond grindstone. Further, since clogging due to processing and a significant increase in processing time are caused, it is difficult to start from SM processing using a fine resin bond grindstone (# 2500) as used in the lens blank A.

Therefore, even with SM processing, a grindstone with a fine particle size cannot be used rapidly, and the state of the lens surface after SM processing is inferior compared with the case where the lens blank A according to the present invention is used. That is, the microcracks generated by the CG process or the SM process using the metal bond grindstone cannot be completely removed, and for example, the polishing process must be shifted to the final process while the polishing allowance of 10 μm or more remains. Therefore, also in the polishing process, it is necessary to set the processing amount and the processing time longer than when the lens blank A according to the present invention is used.

As described above, in the lens blank A according to the present invention and the lens blanks B and C corresponding to the comparative examples of the present invention, a difference occurs in a suitable tool, processing amount, and processing time in the lens forming process. It was confirmed. In particular, as shown in Table 3, when the lens blank A according to the present invention is used, the processing amount and processing time through the entire grinding / polishing process are larger than those when the lens blanks B and C are used. It was confirmed that it was greatly reduced.

(Comprehensive evaluation)
As described above, in the lens blank A according to the present invention, the thickness of the defect-containing layer formed in the central portion of the main surface is 50 μm or less. In the case of producing optical glass using such a lens blank A, it is possible to achieve a high yield rate even when the machining allowance is greatly reduced. Furthermore, since the machining allowance can be significantly reduced, a relatively fine grinding stone (# 600) can be used in CG processing. As a result, the subsequent SM processing can be performed sufficiently with a fine resin bond grindstone (# 2500), and the processing amount and processing time in the final process can be reduced. In particular, when the lens blank A according to the present invention is used, the processing amount and the processing time can be greatly reduced throughout the grinding and polishing processes, so that the production cost can be improved.

(Examples 2 to 7)
In Examples 2 to 7, the evaluation of Example 1 was performed except that the glass blank constituting the lens blank and the conditions for grinding and polishing the lens blank until the optical lens were manufactured were changed as shown in Tables 4 and 5. The same confirmation as 3 was performed. The results are shown in Tables 4 and 5.

A lens blank using a lanthanum borate glass material was prepared in the same manner as the lens blank A of Example 1.

In addition, a lens blank using a fluorophosphate-based glass material was prepared in the same manner as the lens blank A of Example 1 except that the raw material was changed and the glass material block 20 was formed from a fluorophosphate-based molten glass. . In addition, a fluorophosphate glass is a soft material as glassy compared with a lanthanum borate glass.

According to the lens blank according to the present invention, the entire processing amount and processing time are greatly increased regardless of the glass material, and even when the grinding and polishing conditions of the lens blank until the optical lens is manufactured are variously changed. It was confirmed that it can be reduced. In particular, it has been confirmed that the processing amount in PO processing can be reduced to 10 μm or less.

Furthermore, according to the lens blank according to the present invention, since the thickness of the defect-containing layer on the main surface (particularly the central portion) is thin, even if CG processing is omitted (only processing after SM processing), surface defects are sufficient. It was confirmed that a good optical lens could be produced.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Finally, embodiments of the present invention will be summarized.
[1] In the polishing glass lens blank of the present embodiment, at least the main surface is a press-molded surface, and the thickness of the defect-containing layer formed in the central portion of the main surface is 50 μm or less.

[2] Preferably, in the glass lens blank for polishing according to [2] above, the central portion is a region inside the outer periphery of the main surface,
The radius of the central portion is 2/3 or less of the radius of the main surface.

[3] In another aspect, the optical glass material according to the present embodiment includes a first main surface and a second main surface that are trapezoidal and parallel to each other.
A first side surface connecting short sides of the first main surface and the second main surface and a second side surface connecting long sides of the first main surface and the second main surface;
The first side surface and the second side surface are connected to each other, and there are two inclined surfaces each having an obtuse angle with the first side surface,
The first side surface and the two inclined surfaces are molding surfaces.

[4] Preferably, in the optical glass material according to [3] above, the second side surface is a free surface.

[5] Preferably, in the optical glass material described in [3] or [4] above, the first and second main surfaces are cut surfaces.

[6] Preferably, in the optical glass material according to any one of [3] to [5], the distance between the first and second main surfaces is such that the first side surface and the second side surface are the same. Shorter than the distance between.

[7] Preferably, in the optical glass material according to any one of [3] to [5], the distance between the first and second main surfaces is such that the first side surface and the second side surface are Longer than the distance between.

[8] In another aspect, the glass lens blank for polishing according to the present embodiment softens the optical glass material according to the above [6] by reheating in the air and softens the optical glass material. Is formed by press molding.

[9] Preferably, in the glass lens blank for polishing according to [8] above, at least the main surface is a press-molded surface, and the thickness of the defect-containing layer formed in the central portion of the main surface is 50 μm or less. is there.

[10] In another aspect, the optical lens of the present embodiment is formed by grinding and polishing the polishing glass lens blank described in [8] or [9].

[11] Furthermore, in another aspect, the manufacturing method of the glass lens blank for polishing according to the present embodiment continuously casts molten glass into a mold and moves the cast glass from the upstream side to the downstream side. An optical glass material molding process for continuously molding a trapezoidal optical glass material while moving in the direction,
Cutting the optical glass material in a direction perpendicular to the longitudinal direction, and cutting into small pieces,
A reheating step of reheating the optical glass material fragmented in the cutting step to a viscosity of 10 ⁴ to 10 ⁶ dPa · s in an air atmosphere;
The optical glass material reheated in the reheating step is press-molded in a press mold in an air atmosphere to obtain a glass molded product, and
The glass molded article has a press-molded surface at least on the main surface,
The thickness of the defect-containing layer formed in the central portion of the main surface is 50 μm or less.

[12] Preferably, in the method for producing a glass lens blank for polishing according to [11] above, the surface of the optical glass material fragmented in the cutting step and the optical glass material in the reheating step are used. There is further provided a release agent application step of applying a release agent to at least one of the holding recesses to be arranged.

[13] Preferably, in the method for producing a polishing glass lens blank described in [11] or [12] above, in the release agent coating step, a release agent is placed in the holding recess in which the optical glass material is disposed. After coating, the optical glass material is placed in the holding recess.

[14] In another aspect, the optical lens manufacturing method of the present embodiment is applied to the polishing glass lens blank according to any one of [1], [2], [8], and [9]. On the other hand, spherical grinding and smoothing are performed. In the smoothing, processing is performed using a resin bond grindstone without using a metal bond grindstone to obtain an optical lens.

Furthermore, in another aspect of the present embodiment,
[A1] The method for producing an optical glass material of the present embodiment is a method in which molten glass is continuously cast into a mold, and the cast glass is continuously cross-sectioned while moving in one direction from the upstream side to the downstream side. Mold trapezoidal glass material.

In another aspect of the present embodiment,
[B1] The method for producing a glass optical material for press molding according to the present embodiment continuously casts molten glass into a mold and continuously moves the cast glass from the upstream side to the downstream side in one direction. And forming a trapezoidal glass material,
Cutting the glass material along the longitudinal direction.

[B2] In another aspect, the method for producing a polishing glass optical element blank according to the present embodiment is a press-molding optical material obtained by the method for producing a press-molding glass optical material according to [B1] above. The method further includes a step of reheat pressing.

[B3] In another aspect, the method for manufacturing the glass optical element according to the present embodiment is performed by grinding the glass optical element blank for polishing obtained by the method for manufacturing the glass optical element blank for polishing described in [B2] above. And a polishing step.

2, 20 ... Optical glass material 2a ... Softened glass material 2b ... Polishing glass lens blank 20a ... Molten glass 4 ... First main surface 6 ... Second main surface 8 ... First side surface 10 ... Second side surface DESCRIPTION OF SYMBOLS 12 ... 1st inclined surface 14 ... 2nd inclined surface 30 ... Nozzle 32 ... Fixed mold 34 ... Bottom wall 36 ... End wall 38 ... Side wall 40 ... Conveying device 50 ... Receptacle 52 ... Concave 60 ... Lower mold 62 ... Molding surface 64 ... Body mold 66 ... Upper mold 70 ... Cutting device 72 ... Wire saw 74 ... Roller 80 ... Main surface (press molding surface)
80a ... Main surface central part 82 ... Main surface (press molding surface)
84 ... Side peripheral surface 90a ... Defect-containing layer 90b ... Lens body (bulk part)
90c ... Optical lens surface 92 ... Grinding (CG processing) region 94a, 94b ... Grinding (SM processing) region 96 ... Polishing region

Claims (14)

1. A polishing glass lens blank in which at least the main surface is a press-molded surface and the thickness of the defect-containing layer formed at the center of the main surface is 50 μm or less.
2. The central portion is a region inside the outer periphery of the main surface,
   The glass lens blank for polishing according to claim 1, wherein a radius of the central portion is 2/3 or less of a radius of the main surface.
3. A first main surface and a second main surface which are trapezoidal and parallel to each other;
   A first side surface connecting short sides of the first main surface and the second main surface and a second side surface connecting long sides of the first main surface and the second main surface;
   The first side surface and the second side surface are connected to each other, and there are two inclined surfaces each having an obtuse angle with the first side surface,
   An optical glass material in which the first side surface and the two inclined surfaces are molding surfaces.
4. The optical glass material according to claim 3, wherein the second side surface is a free surface.
5. The optical glass material according to claim 3 or 4, wherein the first and second main surfaces are cut surfaces.
6. 6. The optical glass material according to claim 3, wherein a distance between the first and second main surfaces is shorter than a distance between the first side surface and the second side surface.
7. 6. The optical glass material according to claim 3, wherein a distance between the first and second main surfaces is longer than a distance between the first side surface and the second side surface.
8. A polishing glass lens blank formed by press-molding the softened optical glass material by reheating and softening the optical glass material according to claim 6 in an air atmosphere.
9. The glass lens blank for polishing according to claim 8, wherein at least the main surface is a press-molded surface, and the thickness of the defect-containing layer formed at the center of the main surface is 50 µm or less.
10. An optical lens formed by grinding and polishing the glass lens blank for polishing according to claim 8 or 9.
11. An optical glass material molding step in which molten glass is continuously cast into a mold, and the cast glass is continuously moved in one direction from the upstream side to the downstream side to form a trapezoidal optical glass material, and
    Cutting the optical glass material in a direction perpendicular to the longitudinal direction, and cutting into small pieces,
    A reheating step of reheating the optical glass material fragmented in the cutting step to a viscosity of 10 ⁴ to 10 ⁶ dPa · s in an air atmosphere;
    The optical glass material reheated in the reheating step is press-molded in a press mold in an air atmosphere to obtain a glass molded product, and
    The glass molded product has a press-molded surface at least on the main surface,
    The manufacturing method of the glass lens blank for grinding | polishing whose thickness of the defect content layer formed in the center part of the said main surface is 50 micrometers or less.
12. A release agent application step of applying a release agent to at least one of the surface of the optical glass material fragmented in the cutting step and the holding recess for arranging the optical glass material in the reheating step. The manufacturing method of the glass lens blank for grinding | polishing of Claim 11 which has further.
13. The polishing glass according to claim 11 or 12, wherein, in the release agent coating step, the optical glass material is disposed in the holding recess after the release agent is applied to the holding recess in which the optical glass material is disposed. A method for manufacturing a lens blank.
14. The polishing glass lens blank according to any one of claims 1, 2, 8 and 9 is subjected to spherical grinding and smoothing, and in the smoothing, a resin bond grindstone is used without using a metal bond grindstone. An optical lens manufacturing method characterized in that processing is performed to obtain an optical lens.

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