JP2011051082A - Method for manufacturing glass mold for multifocal lens, and method for manufacturing multifocal lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for manufacturing a multifocal lens capable of clearly discriminating a neighborhood. <P>SOLUTION: The method for manufacturing the glass mold is used for molding the multifocal lens having a far part and the neighborhood projected from the far part on at least one surface of the two opposed surfaces by casting polymerization. The method includes a step that a surface to be polished is polished by relatively moving the surface to be polished and a tip surface of a polishing tool while feeding slurry containing a polishing abrasive grain to a space between one surface (surface to be polished) of a glass mold base material and the tip surface of the polishing tool and a step that a recess having a shape corresponding to a surface shape of the neighborhood on the surface to be polished is formed. As the polishing tool, the polishing tool in which a tip is formed of resin containing a fiber thread and a cross section of the fiber thread is exposed to the tip surface is used. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for producing a glass mold for a multifocal lens, and more particularly, to a method for producing a glass mold for a multifocal lens that can produce a multifocal lens that allows easy confirmation of a near portion.
Furthermore, the present invention relates to a method for producing a multifocal lens by cast polymerization using the glass mold produced by the above method.

  A single lens divided into a distance portion (far vision portion) and a near portion (near vision portion) and having two different powers is called a double focus lens. Further, a lens with three different powers in the middle of distance, near and near is called a trifocal lens. These lenses are called multifocal lenses, and are roughly classified into two types, a fusion type and a one-piece type, depending on the manufacturing method (see, for example, Patent Document 1). The fusion-type multifocal lens can be manufactured by fusing a ball glass lens and a small glass lens having a refractive index different from that of the ball glass lens embedded in a part thereof by heat softening.

Japanese Patent Laid-Open No. 10-301065

  On the other hand, a one-piece type multifocal lens is usually provided with a protrusion (near part) on at least a part of one surface, so that a distance part (also called a ball) and a near part (also called a small ball) are provided. This is a multifocal lens. An example of a top view of a one-piece type bifocal lens is shown in FIG. FIG. 1 shows round type small balls. As shown in FIG. 2, the small balls of the multifocal lens are various types such as (a) round type, (b) curved top type, and (c) straight top type. Can take the shape of

  Thus, in order to produce a lens having a protrusion on one surface, a cast polymerization method can be employed. In order to mold a multifocal lens having round type small balls by the casting polymerization method, a glass mold having a concave portion corresponding to the small ball shape is used. Such a glass mold can be produced by polishing one surface of a glass mold base material as shown in FIGS. As shown in FIG. 3 (c), a glass mold for a multifocal lens having curved top type and straight top type small balls is formed by fusing a glass piece to a part of a concave part formed by polishing by heat softening or the like. It can be produced by filling a part of.

  Conventionally, in order to form the concave portion, for example, a polishing pad made of nonwoven fabric or suede has been used. However, when a multifocal lens is manufactured using a mold in which concave portions are formed by polishing using the above polishing pad, the boundary between the near portion and the far portion becomes unclear in the obtained multifocal lens. Is seen. The boundary of the near portion plays an important role in identifying the part where the addition power is part from the wearing state. Further, a user of a multifocal lens tends to select a multifocal lens by regarding the fact that the near portion can be clearly identified by visual observation as an advantage of the multifocal lens not provided in the progressive power lens. Therefore, if the boundary between the near portion and the far portion is not clear, the user may lose the main reason for selecting the multifocal lens.

  SUMMARY OF THE INVENTION An object of the present invention is to provide means for manufacturing a multifocal lens that can clearly distinguish a near portion.

  The inventor of the present application has made extensive studies in order to achieve the above object. As a result, as a polishing tool for glass mold base material, by using a polishing jig whose tip is made of resin containing fiber yarn and the cross-section of the fiber yarn is exposed on the tip surface, the distance portion and near-distance use It has been found that a glass mold capable of producing a multifocal lens with a clear boundary with the part can be obtained, and the present invention has been completed.

That is, the above object was achieved by the following means.
[1] A glass mold used for molding a multifocal lens having a distance portion and a near portion protruding from the distance portion by cast polymerization on at least one of two opposing surfaces. A manufacturing method comprising:
While supplying slurry containing abrasive grains between one surface of the glass mold base material (hereinafter referred to as “surface to be polished”) and the tip surface of the polishing jig, the surface to be polished and the tip surface of the polishing jig are relatively Polishing the surface to be polished by mechanically moving, and forming a recess having a shape corresponding to the surface shape of the near portion on the surface to be polished; and
The manufacturing method according to claim 1, wherein the polishing jig is a polishing jig whose tip is made of a resin containing fiber yarns and a cross-section of the fiber yarns is exposed on the tip surface.
[2] The manufacturing method according to [1], wherein the fiber yarn is disposed substantially perpendicular to the tip surface.
[3] The production method according to [1] or [2], wherein the resin is a phenol resin including a fiber bundle.
[4] The manufacturing method according to any one of [1] to [3], wherein the tip surface includes a curved surface having substantially the same radius of curvature as the recessed portion to be formed.
[5] The manufacturing method according to any one of [1] to [4], wherein the fiber yarn has a diameter of 0.2 to 2 mm.
[6] The production method according to any one of [1] to [5], wherein the fiber is a natural fiber.
[7] The manufacturing method according to any one of [1] to [6], wherein the tip surface has a center line average roughness Ra in a range of 0.1 to 5 μm.
[8] producing a glass mold by the method according to any one of [1] to [7];
A pair of glass molds including the prepared glass mold are arranged so as to face each other with a predetermined interval, and a cavity is formed by closing the interval. To be located inside the cavity,
By injecting a lens raw material solution containing a curable component into the cavity and performing a curing reaction of the curable component in the cavity, a glass mold including the concave portion on at least one of two opposing surfaces. To obtain a lens-shaped molded product to which the surface shape is transferred,
A manufacturing method of a multifocal lens having a distance portion and a near portion protruding from the distance portion.

  ADVANTAGE OF THE INVENTION According to this invention, the multifocal lens which can distinguish a near part clearly can be provided.

An example of the top view of a one-piece type bifocal lens is shown. A specific example of a small ball shape is shown. It is explanatory drawing of the glass mold preparation method used in order to shape | mold a multifocal lens by the casting polymerization method. It is a schematic diagram of a lens mold that can be used in the casting polymerization method. An example (sectional drawing) of the concave surface type | mold which has the near part formation recessed part is shown. A schematic diagram of a polishing jig is shown. It is explanatory drawing which shows an example of the preparation methods of a grinding | polishing jig | tool. An example of the processing method of the tip surface of the polishing jig is shown. It is explanatory drawing which shows an example of the recessed part formation method.

[Glass mold manufacturing method]
The present invention relates to a glass mold used for molding a multifocal lens having a distance portion and a near portion protruding from the distance portion by cast polymerization on at least one of two opposing surfaces. (Hereinafter also referred to as “the mold manufacturing method of the present invention”). The mold manufacturing method of the present invention includes a surface to be polished and a tip end surface of a polishing jig while supplying a slurry containing abrasive grains between one surface (surface to be polished) of a glass mold base material and a tip end surface of a polishing jig. The surface to be polished is polished, and a recess having a shape corresponding to the surface shape of the near portion is formed on the surface to be polished (hereinafter, the above step is referred to as “polishing step”). Called). In the mold manufacturing method of the present invention, as a polishing jig used in this polishing step, a polishing jig whose tip is made of a resin containing fiber yarn and whose fiber yarn cross section is exposed on the tip surface is used. To do.

  FIG. 4 shows a schematic diagram of a lens mold that can be used in the casting polymerization method. In FIG. 4, a lens mold 10 includes a first mold 11 which is a concave mold having a molding surface on the concave surface side to form the front surface (convex surface) of the lens, and a molding surface on the convex surface side to form the rear surface (concave surface) of the lens. A cavity 14 is formed inside the second mold 12 having a molding surface on the convex side and the cylindrical gasket 13 surrounding the end surfaces of both molds. The lens raw material liquid is injected into the cavity 14 from the injection unit 15. The first mold and the second mold have a non-transfer surface (non-use surface 17) that can be handled by a manufacturing jig and a transfer surface (use surface 16) for transferring the optical surface of the lens. The use surface 16 is a surface for transferring the optical surface shape and surface state of the lens. If the use surface 16 on at least one of the first mold 11 and the second mold 12 has a concave portion, the portion corresponding to the concave portion is projected (proximal) by injecting and curing the lens raw material liquid into the cavity. A multifocal lens can be obtained. In a multifocal lens, the near portion is usually provided on the convex side, so that a concave portion is often formed on the use surface of the concave surface type (first mold 11 in FIG. 4). Therefore, the mold manufactured by the present invention can also be a concave mold in which a concave portion is formed on the use surface.

FIG. 5 shows an example (cross-sectional view) of a concave surface type having a near portion forming concave portion. As the edge portion of the concave portion surrounded by the dotted line in FIG. 5 becomes rounder, the rising of the near portion (protrusion portion) on the surface of the lens to be molded becomes smoother, so the boundary between the near portion and the far portion is less likely. It becomes clear and it becomes difficult to confirm the position and size of the near-use part in visual inspection or projection inspection. When the inventor of the present application examined, in the polishing process using a polishing pad, a phenomenon was observed in which the edge portion was rounded as the polishing pad was softer. This is considered to be because the polishing pad is soft and part of the edge portion is buried in the polishing pad.
Therefore, when a hard material was used as the polishing pad in order to form a sharp edge portion, a concave portion having a desired shape could not be formed. This is because the polishing pad was attached to a polishing rod having a tip surface processed into a curved surface (convex surface) corresponding to the concave portion to be formed, but could not be attached to the curved surface because the polishing pad was hard. is there.

Based on the above findings, the inventors of the present application have made extensive studies, and as a polishing jig, use a jig whose tip is made of a resin containing fiber yarn and whose cross section is exposed on the tip surface. Thus, it has been newly found that a concave portion having a sharp edge portion can be formed on a glass mold, thereby obtaining a multifocal lens capable of clearly identifying the near portion. This is presumed to be due to the following reason.
As described above, if the polishing pad has high hardness, it is difficult to affix it to the curved surface, but if the tip is a resin-made polishing jig, the strength is high, and a known molding method such as injection molding or polishing, etc. Can be processed into a curved surface having a desired curvature by a known processing method. However, since mere resin is generally high in smoothness, the abrasive grains in the slurry supplied between the surface to be polished and the front surface of the polishing jig during polishing are not sufficiently retained on the front surface of the polishing jig, and polishing is performed. It is difficult to do well. Therefore, it is conceivable to moderately roughen the tip surface of the polishing jig in order to improve the retention of the abrasive grains. However, since the resin is generally brittle, even if a rough surface is formed on the tip surface to form fine irregularities that can hold the abrasive grains, the irregularities are scraped and flattened by contact with the abrasive grains during polishing. On the other hand, a polishing jig having a tip made of resin containing fiber yarn as described above can hold the abrasive grain on the tip surface by entanglement of the abrasive grain with the fiber yarn cross section exposed on the tip surface. . Further, if the projections and depressions are made of fiber yarns, they are not greatly shaved by the abrasive grains. This is considered to be the reason why a concave portion having a sharp edge portion can be formed on the surface to be polished of the glass mold by the polishing jig having the tip made of resin containing fiber yarn as described above.
Hereinafter, the mold manufacturing method of the present invention will be described in more detail.

Polishing jig The polishing jig used in the mold manufacturing method of the present invention is used in a polishing step for forming a recess on the glass mold base material surface and obtaining a glass mold having the recess. The shape of the recess is determined according to the design value of the lens to be molded. In order to form a desired recess, the tip surface of the polishing jig preferably includes a convex surface, and more preferably includes a curved surface having substantially the same radius of curvature as the concave portion to be formed. Here, “substantially the same” includes that the radii of curvature differ by about ± 15%.
Further, if the radius of curvature of the tip surface of the polishing jig is not the same as the radius of curvature of the concave portion to be formed, the concave portion in which the curve of the tip surface of the polishing jig is formed is larger than the radius of curvature of the concave portion to be formed. It is preferable to be shallower than this curve. This is because when the concave surface having a shallow curve is formed by the convex surface having a deep curve, the amount of polishing at the central portion of the concave portion increases, and it may be difficult to form a sharp edge portion.
Although depending on the type of multifocal lens, the outer diameter of the concave portion for forming the near portion of a general multifocal lens is about 30 to 50 mm, and polishing treatment for forming such a concave portion is used. The outer diameter of the tool tip is preferably about 20 to 40 mm.

  FIG. 6 shows a schematic diagram of the polishing jig. 6 is a top view of the front end surface of the polishing jig, and the lower view of FIG. 6 is a cross-sectional view of the polishing jig. The polishing jig shown in FIG. 6 is made of a resin including a plurality of fiber yarns (fiber bundles) at the tip, and is supported by a support portion. For example, as shown in FIG. 7, a screw portion is provided on the support portion side, and a screw hole is provided on the lower surface of the tip portion, and the screw portion is inserted into the screw hole and connected while rotating the support portion and / or the tip portion. A polishing jig composed of a support portion can be produced. The material of the support part that supports the tip part is not particularly limited, and can be made of various resins or metals. However, the polishing jig used in the present invention is not limited to the above-described embodiment, and it is of course possible to directly use a resin rod-like member containing fiber yarns as the polishing jig.

  As schematically shown by the dotted line in the lower diagram of FIG. 6, the resin constituting the tip portion of the polishing jig contains fiber yarns, and these fiber yarns are shown as an example of a top view in the upper diagram of FIG. In addition, the cross section is exposed at the tip surface of the polishing jig. By including the fiber yarn in such a state, it becomes possible to increase the holding power of the abrasive grains as described above. These fiber yarns may be arranged substantially perpendicular to the tip surface or may be arranged in parallel, but from the viewpoint of obtaining high strength that can withstand the force applied to the tip of the polishing jig during polishing, It is preferable to use a resin containing fiber yarns arranged substantially perpendicular to the surface. Here, “arranged substantially perpendicular to the tip surface” means that the tip is arranged in a direction (longitudinal direction) toward the tip surface and is not parallel to the tip surface. However, it is of course possible for the resin to contain fiber yarns other than those arranged substantially perpendicular to the tip surface. For example, it is also possible to use a resin in which fiber yarns are arranged in a three-dimensional mesh shape and the fiber yarns are arranged in a state of being arranged substantially perpendicular to the distal end surface.

  The fiber yarn may be a single yarn or a twisted yarn obtained by twisting a plurality of single yarns. From the viewpoint of the holding power of the abrasive grains on the tip surface of the polishing jig, twisted yarns are preferable because the abrasive grains are easily entangled. In addition, as fiber yarns, cellulose fibers such as cotton, hemp, hair, silk, and tencel, various synthetic fiber yarns such as rayon, polynosic, cupra, acetate, triacetate, promix, acrylic, polyester, nylon, vinylon, polyurethane, and the like Natural fiber yarns can be used. Natural fibers generally have moderate roughness in cross section and side surfaces, and are excellent in holding power of abrasive grains. Accordingly, natural fibers are preferable from the viewpoint of holding power of the abrasive grains on the front end surface of the polishing jig, and cotton and hemp are more preferable.

  In the example shown in the upper diagram of FIG. 6, the fiber yarns are randomly arranged on the tip surface, but the manner of arrangement of the fiber yarns is not particularly limited, and may be arranged in a lattice shape or arranged concentrically. May be. The cross section of the fiber yarn may be arranged only at a part of the tip surface, for example, the central part or the peripheral part, but it is preferable that the abrasive grains are arranged on the entire surface from the viewpoint of holding power. The more fiber yarns are preferable in terms of holding the abrasive grains, but the resin portion is reduced and the durability of the polishing jig is lowered. From the viewpoint of achieving both the holding power and durability of the abrasive grains, it is preferable that the cross-sections of the fiber yarns are arranged on the tip surface with an average interval of about 1 to 2 mm.

  The cross-sectional shape of the fiber yarn is not limited to the circular shape shown in the upper diagram of FIG. 6, and may be various shapes such as an ellipse and a polygon. The cross-sectional shape of the fiber yarn is preferably larger than the grain size of the abrasive grains. Thereby, an abrasive grain can be hold | maintained in the cross section of a fiber yarn. Depending on the size of the abrasive grains, when the fiber yarn has a circular cross section, the diameter is preferably about 0.2 to 2 mm. Similarly, the major axis in the case of an ellipse and the length of one side in the case of a polygon are preferably about 0.2 to 2 mm. The number of fiber yarns contained in the resin is not particularly limited, but it is preferable that the number of fiber yarns having the preferred size can be arranged at the preferred intervals. Further, the fiber yarn can exert the effect of holding the abrasive grains as long as at least its cross section is exposed at the tip surface, but the tip of the fiber yarn may protrude from the tip surface of the polishing jig. Thereby, not only the cross section of the fiber yarn but also the side surface of the protruding tip can contribute to holding the abrasive grains. However, if the protruding amount is too large, the fiber yarn protruding during polishing may sweep away abrasive grains from the tip surface of the polishing jig, and the polishing efficiency may decrease. Therefore, it is preferable that the protruding amount of the fiber yarn is not excessively large. From this viewpoint, the protruding length of the fiber yarn from the tip surface of the polishing jig is preferably about 0 to 2 mm, and particularly preferably about 0 to 0.5 mm.

  The resin constituting the tip of the polishing jig can be a so-called fiber reinforced resin (also referred to as cloth-containing resin) in which the resin and fiber yarn are integrated. However, it is not essential to be a fiber reinforced resin, even if the outer periphery of the fiber yarn is not in close contact with the resin, and the fiber yarn is disposed in the vertical hole provided in the resin and spaced apart from the inner periphery of the vertical hole. Good.

  Examples of the resin portion of the resin containing the fiber yarn include phenol resin (PF), epoxy resin (EP), melamine resin (MF), urea resin (urea resin; UF), unsaturated polyester resin (UP), and alkyd. Resin, polyurethane (PUR), thermosetting polyimide (PI), polyethylene (PE), high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride ( PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate (PVAc), Teflon (registered trademark), polytetrafluoroethylene (PTFE), ABS resin (acrylonitrile butadiene styrene resin), AS resin, acrylic resin (PMMA) , Polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone (PSF), polyethersulfur Various thermoplastic resins and thermosetting resins such as phon (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP), polyetheretherketone (PEEK), thermoplastic polyimide (PI), polyamideimide (PAI) A known resin such as can be used. A composite material of the above resin is also suitable. As the resin, from the viewpoint of durability and polishing efficiency of the polishing jig, it is preferable to use a resin that has a hardness higher than that of the abrasive grains and that cannot be easily scraped by contact with the abrasive grains in the polishing step. In this respect, preferred resins are phenol resins such as Bakelite and polyacetal resins such as Delrin (registered trademark), and phenol resins are more preferred.

  As the resin constituting the tip of the polishing jig in the present invention, commercially available cloth-containing resins and fiber reinforced resins can be used. Examples of suitable fiber reinforced resins include fiber reinforced bakelite marketed under trade names such as cloth-containing bakelite and cloth bake. Further, a resin in which fiber yarns are encapsulated can be prepared by a known method and used.

  As the polishing jig, a rod-shaped member made of a resin having a tip surface of a desired shape by a known molding method such as injection molding can be used as it is. Alternatively, the tip end surface of a desired shape can be formed by subjecting the tip end of a resin rod-like member to machining such as polishing.

FIG. 8 shows an example of a method for processing the tip surface of the polishing jig. In the present invention, as shown in FIG. 8, after polishing slurry is applied to the bottom surface of the polishing dish, the bottom surface of the metal dish and the tip of the resin rod-shaped member (resin bar) are rubbed together while appropriately rotating back and forth and left and right. Thus, the tip of the resin rod processed into a curved surface can be used as a polishing jig. Specifically, for example, after placing an appropriate amount of cleanser on the bottom surface of the polishing dish and adding a few drops of water to form a slurry, the bottom of the polishing dish and the tip of the resin rod are rubbed together to obtain the tip of the polishing jig. Can be processed. As the polishing dish, a metal dish that is usually used for dressing a polishing tool with a bottom surface processed to have substantially the same curvature as the concave surface to be formed on the glass mold can be used. By rubbing the bottom surface thus processed and the tip of the resin rod via the polishing slurry, the tip of the resin rod can be processed into a convex surface having substantially the same curvature as the concave surface to be formed on the glass mold.
After the processing, it is preferable to wash the tip surface with water, scrubbing with a scrubbing brush, sponge, or the like to remove the polishing slurry or polishing debris adhering to the tip surface. This is because, if the polishing slurry or polishing scraps remain attached to the tip surface, it may cause scratches in the polishing process. The surface roughness of the tip surface is preferably in the range of 0.1 to 5 μm as the center surface average roughness Ra in order to process the concave surface to be formed into a mirror surface.

Forming recesses Next, the polishing jig glass mold base material plane using, for explaining the details of a polishing step of forming a recess having a shape corresponding to the surface shape of the near portion.

As the glass mold base material, for example, as shown in the upper diagram of FIG. 3, a glass processed into a meniscus shape having one concave surface and the other convex surface can be used. The glass mold base material can be produced by a known glass molding method such as a hot sag molding method. Alternatively, it can be obtained by subjecting a glass material to surface shape processing by grinding, polishing and / or cutting equipment usually used for glass processing. The processed shape of the glass mold base material can be determined according to the desired shape and optical characteristics of the multifocal lens. Examples of the glass material constituting the glass mold base material include crown-type, flint-type, barium-type, phosphate-type, fluorine-containing type, and fluorophosphate-type glasses. However, it is not limited to these. Further, other characteristics of the glass material are not limited to the following, but for example, the thermal properties are a strain point of 450 to 480 ° C, a cooling point of 480 to 621 ° C, a softening point of 610 to 770 ° C, and a glass transition. Temperature (Tg) is 450 to 620 ° C., yield point (Ts) is 535 to 575 ° C., specific gravity is 2.47 to 3.65 (g / cm ³ ), refractive index is Nd1.52300 to 1.8061, heat Diffusion ratio is 0.3 to 0.4 cm ² * min, Poisson's ratio 0.17 to 0.26, photoelastic constant 2.82 × 10E-12, Young's modulus 6420 to 9000 kgf / mm ² , linear expansion coefficient 8 to 10 X10E-6 / ° C.

  In the mold manufacturing method of the present invention, a polishing step is performed on a glass mold base material in order to form a recess on a surface that becomes a use surface (transfer surface) in cast polymerization. In the polishing step, it is preferable to apply wax to a position where the recess is formed on the surface to be polished in order to prevent generation of burrs and scratches prior to polishing with the polishing jig. As the wax, those usually used for polishing can be used without any limitation.

  Generally, in the polishing process, after rough polishing and shape processing, finish polishing is performed for surface processing. The mold manufacturing method of the present invention can be performed using the above-described polishing jig for both the above-described rough polishing and finish polishing. However, in terms of polishing cost and polishing efficiency, rough polishing is performed with a commercially available curve generator (CG). The polishing jig is preferably used for finish polishing. In rough polishing, for example, a concave portion having an arbitrary curvature is formed by a CG tool (for example, about # 325 to # 400) using bronze or the like as a binder. The outer diameter of the recess formed by rough polishing is preferably about 2 to 4 mm smaller than the outer diameter of the recess to be finally formed.

  Polishing with the polishing jig is performed by relatively moving the surface to be polished and the tip surface of the polishing jig while supplying a slurry containing abrasive grains between the surface to be polished and the tip surface of the polishing jig. , Preferably by sliding relatively. As the slurry, a commercially available slurry that is usually used for polishing treatment can be used. Alternatively, a slurry prepared by dispersing abrasive grains in water or an aqueous solvent can be used. The abrasive grain concentration in the slurry can be about 5 to 30% by mass, for example. Examples of the abrasive grains contained in the slurry include silica, alumina, cerium oxide, and the like, and cerium oxide is preferred from the viewpoint of glass abrasiveness. The particle size of the abrasive grains is preferably smaller than the cross section of the fiber yarn exposed on the tip surface of the polishing jig as described above, and preferably about 10 nm to 0.1 mm. The slurry supply amount at the time of polishing is, for example, about 1000 to 1500 ml / min.

In the polishing, either one of the glass mold base material and the polishing jig may be fixed and the other may be moved, or both may be moved. It is preferable to move both from the standpoint of polishing efficiency. More preferably, the glass mold is rotated eccentrically and the polishing jig is rotated about the rotation axis.
The said aspect is demonstrated still in detail based on FIG.

  As shown in FIG. 9, the glass mold base material is preferably attached to a support member whose rotation axis (hereinafter referred to as “upper axis”) is tilted in the direction of the spherical core, and is eccentrically rotated by about 1 to 2 mm. On the other hand, it is preferable to rotate the polishing jig about the rotation axis (hereinafter referred to as “lower axis”) in an axially symmetrical manner. The polishing rate is preferably 4 to 10 μm / min from the viewpoint of polishing efficiency, and 20 to 30 μm as the polishing removal amount. For example, the polishing rate can be realized by setting the load on the upper shaft to 0.5 to 2 kg, the eccentric rotation speed to 100 to 300 rpm, and the rotation speed of the lower shaft to 300 to 600 rpm. The polishing time is, for example, about 3 to 5 minutes.

  After the polishing, it is preferable to clean the glass mold in order to remove foreign matters such as wax and polishing debris on the surface to be polished. In addition, when using the said grinding | polishing jig | tool repeatedly, after using once or twice or more, it is preferable to dress a front end surface. The tip of the polishing jig can be regenerated to a surface suitable for polishing by dressing. Dressing can be performed in the same manner as the tip end face processing method described above.

  Through the above steps, a glass mold having a concave portion having a shape corresponding to the surface shape of the near portion of the multifocal lens can be obtained. The formed recess may have a radius of curvature that is substantially the same as the curvature of the near portion of the multifocal lens. Therefore, the obtained glass mold can be used as it is for forming a multifocal lens having round type small balls. Alternatively, a glass piece is arranged in a part of the concave part, and the glass piece is fused by heat softening or the like to fill a part of the concave part and for forming a multifocal lens having a curved top type or straight top type small ball. It can also be a glass mold. The surface roughness of the recesses is preferably 0.03 μm or less as the center line average roughness Ra in order to make the near-use surface formed by transferring the recesses an optical functional surface. The surface roughness of the recesses can be controlled by polishing conditions such as load and polishing abrasive grain size. However, the multifocal lens is usually provided with various functional films such as a hard coat on the lens substrate, and the roughness of the lens substrate surface can be masked by these functional films. Therefore, the surface roughness of the recess is not limited to the above range.

In a multifocal lens, normally, the smaller the radius of curvature difference between the distance portion and the near portion, the more difficult it is to identify the near portion. That is, when forming the near portion forming concave portion on the surface of the glass mold for multifocal lens by polishing treatment, the smaller the difference between the radius of curvature of the surface to be polished and the radius of curvature of the concave portion to be formed, the edge portion of the concave portion It is difficult to form a sharp shape. On the other hand, according to the method of the present invention, a concave portion having a sharp edge portion can be formed even if the difference in base curve between the surface to be polished and the concave portion is within 0.6D. It is possible to obtain a multifocal lens in which the part can be easily identified.
The base curve is the surface refractive power (diopter) defined by (n-1) * 1000 / R, where n is the refractive index of the glass material constituting the mold and R (mm) is the radius of curvature. ). For example, in an embodiment to be described later, in a mold base material made of glass having a refractive index n = 1.5, an average curvature Rp = 100 of a concave surface that is a polished surface, and a concave portion (concave) that forms a near portion forming portion. ) Curvature radius Rcc = 112, the base curve Dp = (1.5-1) * 1000/100 = 5.000D of the polished surface, and the base curve Dcc = (1.5-1) * 1000 of the recess. /112≈4.464D, and the base curve difference is within 0.6D (0.536D). According to the present invention, a concave portion having a sharp edge portion can be formed even when the difference in curvature radius is as small as 12 mm and the base curve difference is within 0.6D.

[Manufacturing method of multifocal lens]
The manufacturing method of the multifocal lens of this invention is a manufacturing method of the multifocal lens which has a distance part and the near part protruded from this distance part, and includes the following processes. Since the multifocal lens manufacturing method of the present invention uses the glass mold obtained by the mold manufacturing method of the present invention, it is possible to manufacture a multifocal lens that can easily identify the near portion.
(Step 1) A glass mold is prepared by the mold manufacturing method of the present invention.
(Step 2) A pair of glass molds including the produced glass mold are arranged so as to face each other with a predetermined interval, and a cavity is formed by closing the interval. Here, the pair of glass molds are arranged so that the concave portion is positioned inside the cavity.
(Step 3) By injecting a lens raw material solution containing a curable component into the cavity and performing a curing reaction of the curable component in the cavity, the concave portion is formed on at least one of the two opposing surfaces. A lens-shaped molded body to which the surface shape of the glass mold containing the material is transferred is obtained.

  The details of step 1 are as described above. Hereinafter, step 2 and step 3 will be described.

(Process 2)
In step 2, a pair of glass molds are arranged to face each other with a predetermined interval, and a cavity is formed by closing the interval. Here, a pair of glass molds are arranged so that the recesses formed on the glass mold in step 1 are positioned inside the cavity. Thereby, the convex part (near part) by which the said recessed part was transcribe | transferred can be formed on the surface of the molded object formed by hardening a lens raw material liquid in a cavity.

  The interval between the glass molds may be closed by a cylindrical gasket as shown in FIG. 4, or may be closed by winding an adhesive tape around the sides of two molds instead of the gasket. The interval between the glass molds corresponds to the thickness of the lens to be molded. The thickness of the molded lens is, for example, about 1 to 30 mm, but is not limited to the above range. As the gasket, those usually used for cast polymerization can be used as they are. One of the pair of molds is a mold produced in step 1. The other mold may be selected according to the surface shape of the desired multifocal mold.

(Process 3)
In step 3, the lens raw material liquid injected into the cavity contains a curable component, and is usually a raw material monomer, oligomer, and various polymers constituting a plastic lens base material, preferably a plastic lens base material for spectacle lenses. A prepolymer can be included, and a mixture of two or more monomers can be included to form a copolymer. The curable component may be a thermosetting component or a photocurable component, but in the casting polymerization, a thermosetting component is usually used. If necessary, a catalyst selected according to the kind of monomer can be added to the lens raw material liquid. The lens raw material liquid may also contain various commonly used additives.

  Specific examples of the lens raw material liquid include, for example, a copolymer of methyl methacrylate and one or more other monomers, a copolymer of diethylene glycol bisallyl carbonate and one or more other monomers, and a copolymer of polyurethane and polyurea. Examples thereof include a raw material liquid capable of polymerizing a coalescence, polycarbonate, polystyrene, polyvinyl chloride, unsaturated polyester, polyethylene terephthalate, polyurethane, polythiourethane, a sulfide resin using an ene-thiol reaction, a vinyl polymer containing sulfur, and the like. Of the above, urethane is preferred as the curable component, but is not limited thereto. Injection of the lens raw material liquid into the cavity can be performed in the same manner as in normal casting polymerization.

  Next, the lens raw material liquid injected into the cavity is heated, irradiated with light, and the like, whereby a curing reaction of the curable component contained in the lens raw material solution is performed to obtain a lens-shaped molded body. Curing reaction conditions (for example, heating temperature raising program) are not particularly limited, and may be determined according to the type of lens raw material liquid to be used. After the curing process is completed, the two molds that are in close contact with the lens are separated (released), thereby transferring the lens-shaped molded body to which the surface shape of the molding surface is transferred, that is, the distance portion on at least one surface And a multifocal lens having a near portion protruding from the far portion.

  Thereafter, various functional films can be laminated on the molded multifocal lens as required by a known film forming method. Examples of the functional film include a hard coat film and an antireflection film.

  In the following, the present invention will be further explained by examples. However, this invention is not limited to the aspect shown in the Example.

[Example 1]
Production of Glass Mold A glass mold for forming a bifocal spectacle lens having a near portion having a diameter of 30 mm and a curvature radius of 112 mm on a convex surface was produced by the following method.
(1) Rough polishing of glass mold base material A crown-type glass mold base material (refractive index n = 1.5) having an uneven meniscus shape with aspherical surfaces on both sides was formed by a hot sag forming method. Wax was applied to a position corresponding to the near portion forming portion of the concave surface (average radius of curvature of 100 mm) of the glass mold base material. Thereafter, a recess having a diameter of 28 mm was formed at a location where the wax was applied by a CG tool (# 400) using bronze as a binder.
(2) Polishing jig tip surface processing The tip of a bakelite rod having a diameter of 30 mm containing a twisted bundle of cotton fibers in the longitudinal direction (twisted yarn diameter: 1 mm, twist interval: 1 mm) By polishing on a metal dish processed to the same curvature radius, a convex surface having the same curvature radius as that of the near portion was formed on the tip surface. After polishing, the tip of the bakelite rod was scrubbed with a sponge while flowing water to remove the abrasive (cleanser powder) and polishing debris. The surface roughness Ra of the tip surface of the bakelite rod after processing was 1 μm.
(3) Concave formation A polishing jig was prepared by attaching the bakelite rod processed in (2) above to the support as shown in FIG.
The prepared polishing jig and the glass mold base material processed in the above (1) are arranged as shown in FIG. 9, and the glass mold base material is eccentrically rotated by about 1 to 2 mm. Rotated around the axis symmetrically. The upper shaft load was 1 kg, the eccentric rotation speed was 200 rpm, the lower shaft rotation speed was 500 rpm, and the polishing time was 5 minutes. As a polishing slurry, cerium oxide slurry (average particle diameter of cerium oxide particles 3 μm, cerium oxide concentration 30 mass%, dispersion medium: water) was supplied at 1000 ml / min. The polishing rate in the polishing was 25 μm as a polishing removal amount.
After polishing, the glass mold base material was removed from the support member and washed with water to remove the wax, thereby obtaining a glass mold having a concave portion corresponding to a round type small ball shape on the concave surface.

[Comparative Example 1]
Production of glass mold Example 1 with the exception of using a non-woven polishing pad (Bellatrix manufactured by FILWEL Co., Ltd.) affixed to the tip of a polishing rod processed to the same radius of curvature as the near part as the polishing jig. By the same method, the glass mold which has a recessed part on a concave surface was obtained.

[Example 2, Comparative Example 2]
Molding of a bifocal spectacle lens by casting polymerization A bifocal lens (concave / convex lens) having round type small balls on a convex surface was produced by the following method.
(1) The glass mold (first mold) produced in Examples 1 and 2 is pushed into a cylindrical gasket so as to be on the lens convex surface side, and a separately prepared glass mold (second mold) is provided on the surface on the lens concave surface side. A predetermined amount was pressed and assembled to form a cavity. At this time, the assembly was performed so that the concave portion on the concave surface of the first mold was disposed inside the cavity. Thereby, a lens mold having the structure shown in FIG. 4 was obtained.
(2) Next, a lens raw material containing a thermosetting urethane monomer was injected into the cavity formed in (1), and the monomer was cured by heat polymerization using a predetermined polymerization program.
(3) The mold was released from the cured lens after polymerization. Thereby, the surface shape of the concave portion of the first mold was transferred to the lens surface, and a convex portion was formed on the lens surface.
(4) The released lens was washed after cutting the outer periphery, and annealed with a predetermined program.

Projection observation of the near portion When the multifocal lens produced in Example 2 and Comparative Example 2 is projected and observed under a fluorescent lamp, the boundary between the near portion and the distance portion is clearly observed in the lens produced in Example 2. Observed, it was confirmed that the diameter of the near portion was 30 mm. On the other hand, the lens produced in Comparative Example 2 was unclear because the boundary between the near portion and the far portion was blurred, so it was difficult to measure the size of the near portion.
From the above results, it has been shown that according to the present invention, a multifocal lens in which the position and size of the near portion can be easily confirmed can be obtained.

  The present invention is useful in the field of producing multifocal lenses such as bifocal lenses.

Claims (8)

A method for producing a glass mold used for molding a multifocal lens having a distance portion and a near portion protruding from the distance portion on at least one surface of two opposing surfaces by cast polymerization. There,
While supplying slurry containing abrasive grains between one surface of the glass mold base material (hereinafter referred to as “surface to be polished”) and the tip surface of the polishing jig, the surface to be polished and the tip surface of the polishing jig are relatively Polishing the surface to be polished by mechanically moving, and forming a recess having a shape corresponding to the surface shape of the near portion on the surface to be polished; and
The manufacturing method according to claim 1, wherein the polishing jig is a polishing jig whose tip is made of a resin containing fiber yarns and a cross-section of the fiber yarns is exposed on the tip surface. The manufacturing method according to claim 1, wherein the fiber yarn is disposed substantially perpendicular to the tip surface. The manufacturing method according to claim 1, wherein the resin is a phenol resin including a fiber bundle. The said front end surface is a manufacturing method of any one of Claims 1-3 containing the curved surface which has a curvature radius substantially the same as the recessed part formed. The diameter of the said fiber yarn is the range of 0.2-2 mm, The manufacturing method of any one of Claims 1-4. The said fiber is a natural fiber, The manufacturing method of any one of Claims 1-5. The said front end surface is a manufacturing method of any one of Claims 1-6 whose centerline average roughness Ra is the range of 0.1-5 micrometers. Producing a glass mold by the method according to claim 1;
A pair of glass molds including the prepared glass mold are arranged so as to face each other with a predetermined interval, and a cavity is formed by closing the interval. To be located inside the cavity,
By injecting a lens raw material solution containing a curable component into the cavity and performing a curing reaction of the curable component in the cavity, a glass mold including the concave portion on at least one of two opposing surfaces. To obtain a lens-shaped molded product to which the surface shape is transferred,
A manufacturing method of a multifocal lens having a distance portion and a near portion protruding from the distance portion.

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