JP5927637B1 - Glass material for press molding, method for producing glass material for press molding, and method for producing optical element - Google Patents

Abstract

[PROBLEMS] To obtain desired optical performance without impairing the shape accuracy of a press-molded optical element, and at a low cost, a method for producing a glass material for press molding, a glass material for press molding, and an optical element Providing a manufacturing method. According to the present invention, at least one convex surface 10a having a surface roughness Ra of a first surface roughness Ra1 and the periphery of the convex surface are disposed, and the surface roughness Ra is a second surface roughness. A glass material for press molding, the second surface roughness Ra2 being less than 0.10 μm, and the second surface roughness Ra2 being larger than the first surface roughness Ra. 10 is provided. [Selection] Figure 1

Description

  The present invention relates to a glass material for press molding and a method for manufacturing a glass material for press molding, and in particular, a glass material for press molding having at least one convex surface, a method for manufacturing a glass material for press molding, and a method for manufacturing an optical element. About.

  One method for producing an optical element (glass lens) having at least one convex surface is a molding method in which a glass material for press molding having at least one convex surface is pressed with a molding die.

  The side end face of a glass material for press molding formed through cold working such as a centering process generally has a sand-sliding rough surface with acute irregularities. For this reason, in said shaping | molding method, the front-end | tip part of acute unevenness | corrugation may detach | leave from a side end surface of the glass material for press molding as a microparticle, and may fall on a shaping | molding die. And, such a fine particle enters between the glass material for press molding and the mold during press molding, and causes a point-like defective portion on the surface of the press-molded optical element (glass lens). Has occurred.

  In order to deal with such problems, prior to press forming, the side end face of the glass material for press molding is heated to melt the surface having acute unevenness, thereby obtuse the tip of acute unevenness. A process for preventing detachment of fine particles from the side end face has been proposed (Patent Document 1).

JP 2011-16675 A

  However, even when the treatment described in Patent Document 1 is performed, the uneven shape still remains on the side end face of the glass material for press molding.

  On the other hand, during press molding, when the glass material for press molding is deformed by the molding die, the side end surface adjacent to the convex surface is wound around the molding surface side of the molding die and pressed, and the optical element is press molded. The peripheral part of (glass lens) will be comprised.

  Since the molding surface formed by pressing the side end face where the uneven shape remained has a shape defect, there has been a problem that desired optical performance cannot be obtained. As a result, the portion having the defective shape has to be discarded, resulting in an increase in useless glass material, that is, an increase in cost.

  The present invention has been made in view of such problems, and can obtain desired optical performance without impairing the shape accuracy of the press-molded optical element. A method for producing a glass material for press molding and a method for producing an optical element are provided.

The present invention
At least one convex surface whose surface roughness Ra is the first surface roughness Ra1,
A side end surface disposed around the convex surface and having a surface roughness Ra of the second surface roughness Ra2, and the second surface roughness Ra2 is less than 0.10 μm and the second surface roughness Ra2 is larger than the first surface roughness Ra1, a glass material for press molding,
About.

Furthermore, the present invention provides
A preparatory step of preparing a glass material for press molding having at least one convex surface and a side end surface having a surface roughness Ra larger than the first surface roughness Ra of the convex surface disposed around the convex surface;
And a polishing step of polishing the side end face so that the surface roughness Ra is less than 0.10 μm and the surface roughness Ra is larger than the first surface roughness Ra of the convex surface. ,
About.

  According to the glass material for press molding and the method for producing a glass material for press molding according to the present invention, when the second surface roughness Ra2 of the side end surface is larger than the first surface roughness Ra1 of at least one convex surface. , The second surface roughness Ra2 is less than 0.10 μm. Therefore, even when the side end surface adjacent to the convex surface is wound and pressed on the molding surface side of the mold, an optical element having good optical performance can be obtained without impairing the shape accuracy.

  According to the present invention having such a configuration, a desired optical performance can be obtained without impairing the shape accuracy of the press-molded optical element, and the glass material for press molding and the glass material for press molding can be obtained at low cost. And a method for manufacturing an optical element can be provided.

It is a typical side view of the glass raw material for press molding. It is sectional drawing of the glass raw material for press molding which has a sand slide-like side end surface which passed through the centering process. It is a graph which shows the relationship between polishing time with respect to the side end surface of the glass raw material for press molding, and surface roughness Ra2 (2nd surface roughness). It is sectional drawing which shows the glass raw material for press molding provided with a convex surface on one surface, a flat surface on the other surface, and a side end surface disposed around the convex surface and the flat surface. It is sectional drawing which shows the glass raw material for press molding provided with a convex surface on one surface, a concave surface on the other surface, and a side end surface arranged around the convex surface and the concave surface. It is a typical side view explaining an example of the grinding | polishing process of the glass raw material material for press molding.

  Hereinafter, an embodiment of a glass material for press molding, a method for manufacturing a glass material for press molding, and a method for manufacturing an optical element of the present invention will be described in detail with reference to the drawings.

  In this specification, “a glass material for press molding” is a glass material mainly used for mold press molding, and refers to a cold preform. A cold preform is a preform formed through cold working such as centering. In addition, the “glass material for press molding” is a cold preform in the previous stage for forming the “glass material for press molding” in the present specification, and is particularly a sand slide that has undergone centering processing. Refers to a cold preform having a shaped side end face. In addition, the “glass material for press molding” has a side end surface that is flattened in comparison with a sand-sliding shape, but from the viewpoint of ensuring the shape accuracy of the optical element after press molding, which is a problem in the present invention. Includes cold preforms that are not suitable for press molding.

The `` side end surface '' of the glass material for press molding or the glass material for press molding is not only the outer peripheral surface of the glass material for press molding or the glass material for press molding, but when its chamfered portion is provided, The chamfer is also included.
“Surface roughness Ra” refers to the arithmetic average roughness based on the 2001 JIS standard B601. The surface roughness Ra can be measured by a method based on the JIS standard using a known measuring device.

(Glass material for press molding)
FIG. 1 is a schematic side view of a glass material 10 for press molding according to the present embodiment. The press-molding glass material 10 is arranged around at least one convex surface 10a having a surface roughness Ra of the first surface roughness Ra1, and around the convex surface 10a, and the surface roughness Ra is a second surface roughness Ra2. The second surface roughness Ra2 is less than 0.10 μm, and the second surface roughness Ra2 is larger than the first surface roughness Ra.

  Moreover, the side end surface 11 of the glass material 10 for press molding is provided continuously outward from the outer edge of the convex surface 10a. The convex surface 10a can have a spherical shape. The shape of the press-molding glass material 10 is, for example, a concave meniscus shape.

  Further, as shown in FIG. 1, the press-molding glass material 10 further includes a connection surface 40 disposed on the surface opposite to the convex surface 10 a and connected to the side end surface 11. The thickness Ra (hereinafter abbreviated as “surface roughness Ra3”) can be less than 0.10 μm. In FIG. 1, the connecting surface 40 has a planar shape.

  In addition, as above-mentioned, the side end surface 11 contains the outer peripheral surface 11a and the chamfer 11b of the glass raw material 10 for press molding.

  The glass material 10 for press molding used in the present embodiment is, for example, lanthanum borate glass containing boric acid and a rare earth element oxide as main components. In addition, the material of the glass material for press molding of the present invention is not limited to lanthanum borate glass. For example, phosphate glass mainly containing phosphate, silica based silica Glass may also be used.

As the physical properties of the glass material 10 for press molding according to the present embodiment, it is preferable to use a material having an abrasion degree (F _A ) of 400 or less from the viewpoint of polishing processability of the side end face. The abrasion degree (F _A ) of the glass material 10 for press molding is more preferably 200 or less, and further preferably 100 or less.

  Similarly, the Knoop hardness of the glass material 10 for press molding of this embodiment is preferably 400 MPa or more from the viewpoint of polishing processability of the side end face. The Knoop hardness of the glass material 10 for press molding is more preferably 500 MPa or more, and more preferably 600 MPa or more.

The degree of wear (F _A ) and Knoop hardness are obtained by the following procedure.
The degree of wear (F _A ) was determined by holding a sample having a measurement area of 9 cm ² at a fixed position of 80 mm from the center of a flat plate made of cast iron that rotates horizontally 60 minutes per minute. The wrap solution added with 20 ml is uniformly supplied for 5 minutes, and a load of 9.807 N is applied to wrap. The wear mass m obtained by weighing the sample mass before and after the lap and the wear mass m ₀ measured in the same manner for the standard sample (BSC7) designated by the Japan Optical Glass Industry Association are calculated by the following equation. .
F _A = {(m / d) / (m ₀ / d ₀ )} × 100
Here, d is the specific gravity of the sample, and d ₀ is the specific gravity of the standard sample (BSC7).

Knoop hardness was caused by indenting a diamond quadrangular pyramid indenter having a cross-sectional angle of 172 ° 30 ′ and a 130 ° rhombus with a 0.9807 N load over 15 seconds on a flat-polished glass surface. The length of the diagonal line of the longer permanent depression is measured and is obtained by the following equation.
Hk = 1.451 · (F / l ² )
Here, F is the load (N), and l is the length (mm) of the diagonal line with the longer recess.

  Next, the relationship between the surface roughness Ra2 of the side end surface 11 and the surface roughness Ra1 of the convex surface 10a of the press-molding glass material 10 and the shape accuracy of the press-molded optical element will be described in detail. Here, the adjustment of the surface roughness Ra2 of the side end surface 11 of the glass material for press forming 10, that is, the flattening, was performed by a known polishing process.

FIG. 2 is a cross-sectional view of a press-molding glass material 10 ′ having a single convex surface 10a ′ that has undergone centering and a sand slide-shaped side end surface 11 ′ disposed around the convex surface 10a ′. is there. The shape of the press-molding glass material 10 ′ is, for example, a concave meniscus shape similar to that of FIG. A chamfered portion 11b is formed at one end of the side end surface 11 ′. The surface roughness Ra1 of the convex surfaces 10a and 10a ′ in FIGS. 1 and 2 is the same.
As shown in FIG. 2, the glass material for press forming 10 ′ further includes a connection surface 40 ′ connected to the side end surface 11 ′ on the surface opposite to the convex surface 10 a ′. In FIG. 2, the connecting surface 40 ′ has a planar shape.

  FIG. 3 is a graph showing the relationship between the polishing time and the surface roughness Ra2 (second surface roughness) for the side end face 11 'of the press-molding glass material 10' shown in FIG. The polishing time was 0 to 300 s. In addition, Ra2 of the grinding | polishing time 0 means the surface roughness of the sand-slip-shaped side end surface after a centering process. The reference length l when measuring the surface roughness Ra was 0.85 mm. Lanthanum borate glass was used as the glass material 10 'for press molding. For measurement of the surface roughness Ra, Form Talysurf (model name: Laser 635) manufactured by Taylor Hobson was used.

  As shown in FIG. 3, the surface roughness Ra2 of the side end face showed a gradual decrease tendency with respect to the increase of the polishing time when the polishing time was 120 s or less, and rapidly decreased when the polishing time exceeded 120 s. And it became less than 0.10 micrometer in 140 s or more. Corresponding to this, when the polishing time exceeded 120 s and became 140 s or more, the side end face was visually changed from the spider surface to the glossy surface.

  Table 1 shows the index of the surface roughness Ra2 of the side end face and the shape accuracy of the optical element obtained by press-molding the press-molding glass material 10 'for each polishing time. In “Shape accuracy of optical element” in Table 1, “◯” indicates a case where sufficient shape accuracy is ensured in terms of optical performance, and “×” indicates a case where a shape defect has occurred. Moreover, although not described in Table 1, the surface roughness Ra1 of the convex surface 10a of the glass material 10 for press molding was 0.0025 μm.

  From FIG. 3 and Table 1, the surface roughness Ra2 of the side end surface 11 of the glass material 10 for press molding is less than 0.10 μm from the viewpoint of ensuring the shape accuracy of the optical element, and the surface roughness Ra2 is the surface roughness. It can be seen that it is preferably larger than Ra1. The upper limit of Ra2 is more preferably less than the surface roughness of 0.020 μm corresponding to the polishing time of 200 s to 300 s, from the viewpoint of further improving the shape accuracy of the optical element after press molding.

  Furthermore, when using the glass material 10 'for press molding provided with the connection surface 40' arranged on the surface opposite to the convex surface 10 'and connected to the side end surface 11' as shown in FIG. The surface roughness Ra3 of the surface 40 ′ is preferably less than 0.10 μm. When using a glass material for press molding 10 ′ having such a connecting surface 40 ′, in addition to the side end surface 11 ′, the connecting surface 40 ′ is also wound on the molding surface side of the mold during press molding. This is because the peripheral portion of the press-molded optical element may be formed.

  By making each of the surface roughness Ra2 of the side end face 11 ′ and the surface roughness Ra3 of the connecting face 40 ′ connected to the side end face 11 ′ less than or equal to 0.10 μm, it contributes to further improving the surface accuracy of the optical element. Can do. The surface roughness Ra3 is more preferably less than 0.020 μm from the viewpoint of further improving the shape accuracy of the optical element. The lower limit of the surface roughness Ra3 is not particularly limited, but may be 0 or the surface roughness Ra1 of the convex surface 10a ', for example. As shown in FIG. 2, the connecting surface 40 'has a planar shape.

  In addition, although the lanthanum borate glass was used for the glass raw material 10 ′ for press molding in the present embodiment, the surface roughness Ra2 and the surface roughness Ra1 are also used in phosphate glass, silica glass, and the like. The relationship between the shape accuracy of the optical element after press molding showed the same result as when lanthanum borate glass was used.

  Furthermore, in this embodiment, the concave meniscus-shaped glass material for press molding is used. However, one side and the other side are both convex and the other side is convex and the other side is flat. Also in the glass material, the relationship between the surface roughness Ra2, the surface roughness Ra1, and the shape accuracy of the optical element after press molding showed the same result as that of the glass material for press molding having a concave meniscus shape.

  FIG. 4 is a cross-sectional view showing a press-molding glass material 20 having a convex surface 20a on one surface, a flat surface 20b on the other surface, and a side end surface 21 disposed around the convex surface 20a and the flat surface 20b. FIG. The degree of deterioration of the shape accuracy of the press-molded optical element, which is the subject of the present invention, is the distance Δh1 from the vertex of the convex surface in the direction of the central axis O of the glass material 20 for press molding to the diameter D1 of the convex surface 20a. It tends to depend on the ratio (Δh1 / D1).

  That is, as a result of investigating the relationship between Δh1 / D1 and the shape accuracy of the optical element after press molding, it is found that the subject of the present invention is more obvious when Δh1 / D1 is 0.15 or more. It was. The present invention is more suitable when Δh1 / D1 of the convex surface 20 is 0.15 or more. The upper limit of Δh1 / D1 is not particularly limited, but can be set to 0.40, for example.

  FIG. 5 is a cross-sectional view showing a press-molding glass material 30 including a convex surface 30a on one surface, a concave surface 30b on the other surface, and a side end surface 31 disposed around the convex surface 30a and the concave surface 30b. is there. The subject of the present invention tends to become more apparent when a glass material for press molding having a convex surface on one surface and a concave surface on the other surface as shown in FIG. 5 is used.

  In the press-molding glass material 30 having a shape as shown in FIG. 5, the press-molding glass material is disposed on the concave molding surface of the lower mold, the upper mold is lowered, and the press-molding glass material is pressurized. When the molding glass material is to be aligned with the convex surface of the upper convex shape, the central portion of the convex molding surface comes into contact with the press molding glass material first. If pressurization is continued in this state, the outer peripheral edge of the glass material for press molding is curved upward by the pressure applied to the glass material for press molding from the top of the convex molding surface, and the glass material for press molding This is because the outer peripheral portion of the contact portion comes into contact with the convex shaped molding surface before the portion between the outer peripheral portion and the central portion.

  That is, the ratio (Δh2 / D2) of the distance Δh2 from the apex of the convex surface 30a in the direction of the central axis O of the press-molding glass material 20 to the outer peripheral end with respect to the diameter D2 of the convex surface 30a (Δh2 / D2), and the curvature radius of the convex surface with respect to the curvature radius R2 of the concave surface As a result of systematically changing the ratio of R1 (R1 / R2) and investigating the shape accuracy of the optical element after press molding, the subject of the present invention is that Δh2 / D2 is 0.15 or more and R1 / R2 is 1 / 4 or more and 2 or less.

  In the press-molding glass material 30 having a convex surface 30a on one surface and a concave surface 30a on the other surface as shown in FIG. 5, the present invention has a ratio Δh2 / D1 of 0.15 or more, and R1 / R2 is It is more preferable when it is 1/4 or more and 2 or less. The upper limit of Δh2 / D2 is not particularly limited, but can be set to 0.40, for example.

(Method for producing glass material for press molding and method for producing optical element)
Next, the manufacturing method of the glass material 10 for press molding of this embodiment is demonstrated using FIG. FIG. 6 is a schematic side view for explaining an example of the polishing process of the glass material 10 for press molding.

  The manufacturing method according to the present embodiment includes at least one convex surface 10a ′ and a side end surface 11 ′ having a surface roughness Ra that is disposed around the convex surface 10a ′ and is larger than the first surface roughness Ra of the convex surface 10a ′. And a preparatory step of preparing a glass material for press forming 10 ′ having a second end surface 11 ′ having a surface roughness Ra of less than 0.10 μm and a convex surface 10a ′ greater than the first surface roughness Ra. And a polishing step of polishing so as to have a surface roughness Ra.

  In the manufacturing method of the glass material 10 for press molding of this embodiment, first, as shown in FIG. 2, at least one convex surface 10a ′ and the periphery of the convex surface are arranged, and the surface roughness is larger than the convex surface 10a ′. A press-molding glass material 10 ′ having a side end face 11 ′ having a large thickness Ra is prepared (preparation step). The press-molding glass material 10 'is a cold preform manufactured by a known manufacturing method.

  Next, the surface roughness Ra of the side end face 11 ′ of the press-molding glass material 10 ′ is less than 0.10 μm, and the second surface roughness Ra is larger than the first surface roughness Ra of the convex surface 10a ′. Polishing (polishing step).

  As shown in FIG. 6, the convex surface 10 a ′ side portion of the press-molding glass material 10 ′ is fixed to a rotatable press-molding glass material material fixing jig 14. Next, the press molding glass material fixing jig 14 is rotated in a state where the polishing pad 14 attached to the pad fixing jig 16 is in contact with the side end face 11 ′ of the press molding glass material 10 ′. The side end face 11 ′ of the press-molding glass material 10 ′ and the polishing pad 12 are moved relative to each other so that the side end face 11 ′ has a surface roughness of less than 0.10 μm and a convex surface 10a ′. Polishing is performed until the surface roughness Ra2 is greater than the thickness Ra1, and the glass material 10 for press molding of the present embodiment is obtained. The chamfered portion 11b 'can be similarly polished by bringing the surface of the polishing pad 10d attached to the pad fixing jig 16 into contact with the chamfering angle of the chamfered portion 10c. The connection surface 40 ′ can be polished by a similar method.

The side end face 11 ′ of the glass material for press forming 10 ′ is polished until the surface roughness Ra2 is less than 0.10 μm and the surface roughness Ra2 is larger than the surface roughness Ra1 of the convex surface 10a ′.
The upper limit of the surface roughness Ra2 is more preferably less than 0.020 μm from the viewpoint of further improving the shape accuracy of the optical element after press molding.

  The upper limit of the surface roughness Ra3 of the connecting surface 40 is preferable in the order of less than 0.10 μm and less than 0.020 μm. The lower limit of the surface roughness Ra3 is not particularly limited, but can be 0 or the same value as the surface roughness Ra1 of the convex surface 10a ', for example.

  For example, a resin pad can be used as the polishing pad, and cerium oxide can be used as the polishing agent.

  A method for manufacturing an optical element is provided, which includes a press molding step of performing press molding using the glass material for press molding 10. For example, for press molding using a mold formed of a metal having heat resistance and corrosion resistance such as SUS and having an upper mold having a convex molding surface and a lower mold having a concave molding surface. An optical element is manufactured by press-molding a glass material.

  The press-molding glass material 10 'that can be used in the present embodiment is the same as that described in (Press-molding glass material). That is, for example, lanthanum borate glass, phosphate glass, silica glass, and the like.

Further, preferable physical properties (abrasion degree (F _A ), Knoop hardness) of the glass material for press forming 10 ′ are the same as those described in (Press forming glass material). That is, the degree of wear (F _A ) of the press-molding glass material 10 ′ is preferably 400 or less, more preferably 200 or less, and even more preferably 100 or less, from the viewpoint of polishing processability on the side end face. The Knoop hardness of the glass material 10 ′ for press molding is preferably 400 MPa or more, more preferably 500 MPa or more, and more preferably 600 MPa or more, from the viewpoint of polishing processability of the side end face.

  In the glass material 10 for press molding, since the surface roughness Ra of the side end surface 11 is less than 0.10 μm, the end portion of the side end surface 11 adjacent to the convex surface 10a ′ is formed into a molding die during press molding. Even when it is wound on the surface side and constitutes the peripheral portion of the press-molded optical element, it has desired optical performance at low cost without impairing the shape accuracy of the optical element after press molding. An optical element can be obtained.

The present invention will be summarized below with reference to the drawings.
The press-molding glass material 10 is arranged around at least one convex surface 10a having a surface roughness Ra of the first surface roughness Ra1, and around the convex surface 10a, and the surface roughness Ra is a second surface roughness Ra2. The second surface roughness Ra2 is less than 0.10 μm, and the second surface roughness Ra2 is larger than the first surface roughness Ra1.

  And the manufacturing method of the glass raw material 10 for press molding is arrange | positioned around at least 1 convex surface 10a 'and convex surface 10a', and the surface roughness Ra side larger than 1st surface roughness Ra of convex surface 10a '. A preparation step of preparing a glass material for press molding 10 ′ having an end surface 11 ′, a surface roughness of the side end surface 11 ′ of less than 0.10 μm, and greater than a first surface roughness Ra of the convex surface 10a ′. And a polishing step for polishing to have the second surface roughness Ra.

10, 20, 30: Glass material for press molding 10a, 20a, 30a: Convex surface 11: Side end surface 11a, 11a ′: Outer peripheral surface 11b, 11b ′: Chamfered portion 10 ′: Glass material for press molding 10a ′: Press molding Convex surface 11 'of glass material for use: Side end surface 12 of glass material for press molding 12: Polishing pad 14: Fixing jig 16 for press forming glass material 20: Fixing jig 20b: Flat surface 30b: Concave surface 40 , 40 ': connecting surface

Claims (12)

At least one convex surface whose surface roughness Ra is the first surface roughness Ra1,
A side end surface disposed around the convex surface and having a surface roughness Ra of the second surface roughness Ra2.
The second surface roughness Ra2 is less than 0.10 μm, and the second surface roughness Ra2 is larger than the first surface roughness Ra.
Glass material for press molding. The side end surface is continuously provided outward from the outer edge of the convex surface,
The glass material for press molding according to claim 1. A connecting surface disposed on a surface opposite to the convex surface and connected to the side end surface;
The connection surface has a surface roughness Ra of less than 0.10 μm.
The glass material for press molding according to claim 1 or 2. The ratio of the distance Δh from the apex of the convex surface in the central axis direction of the press-molding glass material to the side surface end with respect to the diameter D of the convex surface of the press-molding glass material is 0.15 or more.
The glass material for press molding according to any one of claims 1 to 3. Further comprising a concave surface disposed on a surface opposite to the convex surface,
The ratio of the radius of curvature of the convex surface to the radius of curvature of the concave surface is not less than 1/4 and not more than 2.
  The glass material for press molding according to claim 4. The degree of wear of the glass material for press molding is 400 or less,
The glass material for press molding according to any one of claims 1 to 5. The press-molding glass material has a hardness of 400 MPa or more,
The glass material for press molding according to any one of claims 1 to 6. A preparing step of preparing a glass material for press molding having at least one convex surface and a side end surface having a surface roughness Ra larger than the first surface roughness Ra of the convex surface disposed around the convex surface; ,
Polishing the side end face so that the surface roughness Ra is less than 0.10 μm and the second surface roughness Ra is larger than the first surface roughness Ra of the convex surface.
A method for producing a glass material for press molding. The polishing step is performed by relatively moving the polishing pad and the side end surface.
The manufacturing method of the glass material for press molding of Claim 8. The degree of wear of the glass material for press molding is 400 or less,
The manufacturing method of the glass material for press molding of Claim 8 or 9. The press-molding glass material has a hardness of 400 MPa or more,
The manufacturing method of the glass raw material for press molding of any one of Claims 8 thru | or 10.   The manufacturing method of an optical element including the press molding process of performing press molding using the glass raw material for press molding of any one of Claim 1 thru | or 7.

Images