JP2009241260A - Gasket for lens molding, lens molding device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mold a lens by suppressing instability of a shape due to polymerization contraction, and suppressing variation in an outside diameter. <P>SOLUTION: A gasket for a lens molding is equipped with an upper mold locking part 14 for locking an upper mold 30 and a lower mold locking part 18 for locking a lower mold 40, and a molding part 16 which composes an inner wall in molding and has a recessed part 20 between the upper locking part 14 and the lower locking part 18. Constriction of a side surface in the polymerization contraction is suppressed by replenishing a contracted amount of the molding material 60 into the recessed part 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lens molding gasket, a lens molding apparatus, and a lens molding method for molding a plastic lens by a casting polymerization method.

  Plastic lenses for spectacles are generally molded by a casting polymerization method. As a mold for molding, there are used a substantially cylindrical mold called a gasket having an injection port on a side surface, and an upper mold and a lower mold having both molding surfaces of both optical surfaces of a lens. And, it is roughly divided into a so-called finished lens in which both upper and lower molds are pre-designed optical surface molds, and a semi-finished lens in which only one mold is formed as an optical surface mold based on design values.

  In the semi-finished lens, one optical surface is completed at the time of molding, and the other surface is individually cut to a corresponding frequency by an order or the like. Such a lens has an advantage that it can be applied to a special lens such as a progressive-power lens or a prism prescription lens because it is cut into a target lens shape.

  However, the semi-finished lens has a sufficient cutting allowance compared to a so-called finished lens in which both sides are molded as optical surfaces designed in advance because the unfinished surface side forms an optical surface after molding. I need to take it. In addition, the semi-finished lens that includes more cutting allowance in this way has a larger resin shrinkage during polymerization because the resin composition (monomer) used during molding is larger than that of the finished lens. Is a problem. Polymerization shrinkage occurs not only in the thickness direction but also in the optical surface direction. Since the edge surface of the semi-finished lens is most susceptible to the shrinkage phenomenon, it is necessary to take a wider cutting allowance. As a result, a relatively large amount of monomer is required to mold the semifinished lens.

  As a technique for eliminating the instability of the shape due to resin shrinkage, a method is used in which a resin is left in the injection port in advance and the resin is compensated at the time of shrinkage. When such a method is used, a typical semi-finished lens can be obtained, so that the tolerance setting can be reduced. However, the degree of polymerization differs between the resin flowing from the inlet and the existing resin in the cavity. When it is cured, the inflow resin may be generated as slight streaks. There is also a risk that bubbles may enter from the inlet.

  As another method of eliminating the instability of the shape due to polymerization shrinkage, there is a method using a mold designed so as not to obstruct the vertical movement of the lower mold so as to follow the shrinkage of the resin during polymerization. (For example, refer to Patent Document 1).

In addition, by making the inner surface into which the gasket mold is inserted into a tapered surface whose inner diameter gradually increases toward the opening, the pressure contact between the gasket and the mold during polymerization is maintained, and mixing of bubbles is suppressed. A structure that reduces defective bubbles has also been proposed (see Patent Document 2).
Since the mold designed in this way can minimize the inflow resin from the injection port, the slight distortion of the streaks can be effectively prevented, and defective foam can be improved.
JP-A-3-231814 JP-A-2005-161552

  As described in the above-mentioned patent document 1, when molding is performed in a so-called free state without locking a mold on one side at the time of polymerization, the mold is inclined and the thickness of the molded lens is reduced. There may be a so-called single meat that is biased. For this reason, it is desirable to provide locking portions at the top and bottom. However, particularly when a lens having a large thickness is molded, there is a problem that the lens side surface, so-called edge, is recessed inward due to shrinkage during polymerization.

  FIG. 13 shows a schematic cross-sectional configuration of an example of the lens molding apparatus in this case. As shown in FIG. 13, the gasket 110, which is a molding container of this lens molding apparatus, has a substantially cylindrical shape, and is provided with a protruding upper mold locking portion 114 and a lower mold locking portion 118 on the inner surface. When the upper mold 130 is inserted from the upper opening 111, the upper mold is locked at the upper mold locking portion 114. The inner side surface following the upper mold locking portion 114 becomes an inner wall at the time of molding, that is, a molding portion 116 that becomes a mold of a so-called edge surface that is a peripheral side surface of the lens. An injection port 122 for injecting a lens material is provided in a part of the molding portion 116. In addition, the inner diameter gradually increases from the lower mold locking portion 118 on the lower side of the molding portion 116 to the lower opening 125, and a tapered surface 124 having an inclined cross section is formed. When the lower mold 140 is inserted from the lower opening 125, the lower mold locking portion 118 is locked. At this time, the upper end portion of the outer surface of the lower mold 140 on the tapered surface 124 is particularly strongly pressed against the tapered surface 124, so that bubbles can be prevented from being mixed when contacting the lower mold engaging portion 118.

  A lens molding method using such a gasket 110 is as follows. First, the upper mold 130 and the lower mold 140 are inserted from the upper opening 111 and the lower opening 125 of the gasket 110, respectively. A molding material 160 such as a resin material constituting the lens, that is, a monomer is injected from the injection port 122. Polymerization is performed while the molding material 160 is filled in the gasket 110, the upper mold 130, and the lower mold 140. After the polymerization, the molded lens is removed from the gasket 110 to complete the lens.

  However, when the molding material is polymerized by the gasket 110 that holds the upper and lower molds in this way, as shown in FIG. 13, the inflow of the molding material 160 from the injection port 122 is not in time for the shrinkage of the polymerization, and the inner wall of the molding part 116. In some cases, the molding material 160 may be polymerized and cured. As a result, as shown in FIG. 14, the side surface shape of the lens 170 removed from the gasket 110 is constricted so that the outer diameter of the central portion in the thickness direction is minimized, and the side surface is curved inwardly. End up. Since such a curved side surface cannot be used as a lens, the constricted portion needs to be removed by cutting or the like. That is, as shown in FIG. 14, it is necessary to cut the peripheral edge to a diameter φ42 smaller than the outer diameter φ41. That is, it is necessary to prepare and mold the gasket 110 having a diameter φ41 larger than the target diameter φ42 in advance, and the lens material indicated by the oblique lines outside the diameter φ42 in FIG. It becomes the cause of. However, at present, it is necessary to take a large tolerance of the outer diameter of the lens in consideration of the instability of the shape after polymerization.

  In view of the above problems, an object of the present invention is to mold a lens while suppressing instability of a shape due to polymerization shrinkage and suppressing variation in outer diameter.

  In order to solve the above problems, a gasket for molding a lens according to the present invention comprises an upper mold locking portion for locking an upper mold, a lower mold locking portion for locking a lower mold, and an inner wall at the time of molding. And a molding part having a recess between the upper mold locking part and the lower mold locking part.

  The lens molding apparatus according to the present invention includes the lens molding gasket, an upper mold, and a lower mold.

  The lens molding method according to the present invention includes a step of inserting an upper mold into the lens molding gasket described above and assembling it to the upper mold locking portion, and a method of inserting a lower mold into the lens molding gasket. It includes a step of assembling to the stopper, a step of injecting the liquid composition portion from the injection port of the lens molding gasket, a step of polymerizing the liquid composition portion, and a step of releasing the polymerized lens molding.

As described above, the lens molding gasket according to the present invention has a configuration in which the inner wall of the molding portion has a concave portion that is recessed in the diameter increasing direction. Thus, if a recessed part is provided in the molding part of a gasket, the volume inside the gasket at the time of superposition | polymerization casting will become large. And since the resin that has entered the concave portion undergoes polymerization shrinkage from the swelled state toward the center, it is difficult for the end face to be constricted, that is, the amount of constriction at the end face after molding can be reduced. . As a result, the cutting amount of the edge surface of the molded product can be reduced, and the lens material can be used more effectively.
Further, the inner diameter of the molded part of the gasket can be designed to be small in advance. For this reason, the lens diameter and the lens side thickness (so-called edge thickness), and the greater the center thickness of the lens, the greater the defect rate, the greater the distortion and bubble defects, and the less likely to cause problems such as single-sided, Yield can be improved.

  According to the present invention, it is possible to mold a lens while suppressing instability of the shape due to polymerization shrinkage and suppressing variation in outer diameter.

Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.
FIG. 1 is a schematic sectional view of a lens molding gasket 10 according to an embodiment of the present invention. This gasket 10 is an example applied when molding a finished lens or a semi-finished lens of a spectacle lens. The gasket 10 main body is a member made of, for example, a cylindrical resin having elasticity, and at the time of cast molding, an upper mold and a lower mold described later are combined to form a mold during molding. As shown in FIG. 1, the gasket 10 has an upper die portion 12, an upper die latching portion 14, a molding portion 16, a lower die latching portion 18, a lower die inside the upper opening 11 to the lower opening 25. A lead portion 24 is formed. Further, an injection portion 23 for introducing a molding material, which is a lens molding material, is provided inside the gasket 10 on the upper mold locking portion 14 side of the molding portion 16. The injection portion 23 has a tubular shape penetrating from the external connection portion 21 to the inside of the gasket 10, and an injection port 22 is provided on the inner wall of the gasket 10.

  The entire gasket 10 is made of a resin having elasticity as described above. As this material, for example, a thermoplastic polyurethane elastomer can be used. The thermoplastic polyurethane elastomer is composed of, for example, a soft segment composed of polymeric glycol, a monomolecular chain extender constituting the hard segment, and a diisocyanate. The types and amounts of the polymeric glycol, the monomolecular chain extender and the diisocyanate can be appropriately changed depending on the shape of the gasket 10 and the type of lens material to be molded. Further, as the material of the gasket, any other material having appropriate elasticity can be used. For example, ultra-low density polyethylene, polyolefin elastomer and the like can be suitably used.

  The upper lead portion 12 of the gasket 10 is a cylindrical surface in the example shown in FIG. 1, but may be formed as a tapered surface that slightly extends toward the opening 11 side. The inclination angle of the taper surface is 1 ° or more and 5 ° or less, more preferably 2 ° or more and 3 ° or less from the direction along the central axis of the cylindrical shape. Further, the inner diameter of the upper mold lead portion 12 is smaller than the outer diameter of the upper mold mold, the gasket 10 made of an elastic resin or the like is deformed in the diameter increasing direction, and the upper mold lead is pressed in a state where the upper mold is pressed. It is inserted into the part 12. It is desirable to design the inner diameter of the upper mold lead 12 directly above the upper mold locking section 14 to be smaller by 2% or more and 3% or less than the outer diameter of the combined upper mold. By setting the inclination angle and the inner diameter of the upper lead portion 12 in this range, it is possible to ensure a good sealing property at the time of polymerization.

  The molding part 16 is a region between the upper mold locking part 14 and the lower mold locking part 18, and is formed in a substantially trapezoidal cross section protruding inward from the upper mold lead part 12 and the lower mold lead part 24. The height from the upper die lead portion 12 and the lower die lead portion 24 of the molding portion 16 is set to about 0.5 mm or more and 1.2 mm or less, so that the upper die engaging portion 14 and the lower die engaging portion 18 are superposed during polymerization. Good shielding can be performed. Further, by adjusting the inner diameter of the molding portion 16, lenses having different diameters can be molded. The vertical width of the molded part 16 is determined in accordance with the thickness of the side surface of the lens to be molded, the so-called edge thickness.

  In addition, the inclination angles of the upper mold locking portion 14 and the lower mold locking portion 18 are formed as angles at which a sealing property necessary for polymerization is obtained in accordance with the shapes of the contact surfaces of the upper mold and the lower mold.

  Further, as shown in FIG. 1, an injection port 22 of an injection part 23 that communicates with the inside and outside of the lens molding gasket 10 is provided in the upper part of the molding part 16. As shown in a schematic perspective view of the gasket 10 in FIG. 2, the injection portion 23 is formed into a tubular shape having, for example, a horizontally long rectangular hole in cross section, and communicates with an injection tube (not shown) at the outer connection portion 21. As shown in FIG. 1, the connecting portion 21 has an upper surface that is inclined upward and outward from the gasket 10 in a cross section in the injection direction, and a lower surface that is a gentler inclined surface or a horizontal plane along the injection direction. In other words, it is formed as a trapezoidal cross section. By making the upper surface of the connection part 21 into a cross-sectional shape that is inclined upward and outward in this way, it is possible to prevent bubbles or the like generated in the holes of the injection part 23 from entering the mold.

  The molding part 16 is provided with a concave part 20 surrounding the inner wall over the entire circumference or partly at a position slightly below the center in the vertical direction, and at a position below the injection port 22 below. The shape of the recess 20 can be various shapes such as a trapezoidal shape, a hemispherical shape, or a sinusoidal shape in cross section. desirable. The vertical width and depth of the recess 20 are designed so that the volume of the recess 20 corresponds to the volume of the resin that compensates for the shrinkage related to polymerization shrinkage.

  On the other hand, a lower die lead portion 24 is provided directly below the lower die engaging portion 18. The inner diameter of the lower mold lead portion 24 is smaller than the outer diameter of the lower mold mold, and the gasket 10 made of an elastic resin or the like is deformed in the diameter increasing direction, and the lower mold mold is pressed while the lower mold mold is pressed. It is inserted into the mold lead part 24.

  Here, it is desirable that the lower die lead portion 24 is formed as a tapered cross section in which the inner diameter immediately below the lower die engaging portion 18 is the smallest and the inner diameter gradually increases toward the lower opening 25. The spread angle θ of the inner wall is preferably 1 ° or more and 3 ° or less, and more preferably 1.5 ° or more and 2.5 ° or less with respect to the direction along the central axis of the cylindrical shape.

  In the lower die lead portion 24, a cylindrical surface region having a substantially equal inner diameter may be provided in a part of the region immediately below the lower die engaging portion 18. That is, a configuration may be adopted in which a certain area is a cylindrical surface, and a tapered surface having a gradually increasing inner diameter is provided on the lower side thereof. Further, in the upper die lead portion 12, a cylindrical surface may be provided on the upper portion of the upper die engaging portion 14.

  As described above, the upper mold engaging portion 14 side of the upper mold lead portion 12 and the lower mold engaging portion 18 side of the lower mold lead portion 24 are not tapered surfaces but cylindrical surfaces, so that the upper mold at the time of molding. In addition, the adhesiveness with the side surface of the lower mold can be increased and stably maintained, and the generation of bubbles due to the intrusion of air from the outside can be suppressed. In addition, what is necessary is just to select suitably the area | region made into a cylindrical surface with the shape of the side surface of an upper mold and a lower mold.

  Moreover, in the upper mold | type latching | locking part 14, you may provide a clearance gap in the inner part between upper molds in the early stage of shaping | molding. By allowing resin as a molding material to enter the gap portion on the inside at the initial stage of molding, the gap is gradually sealed from the outside due to polymerization shrinkage, and the contact of this portion is ensured to prevent air from the outside. Invasion can be suppressed, and it is possible to prevent the occurrence of bubble defects into which bubbles enter.

Next, the lens molding apparatus 1 including the lens molding gasket 10 and the upper mold and the lower mold will be described.
FIG. 3 is a schematic cross-sectional configuration diagram of the lens molding apparatus 1 using the gasket 10 described above. In FIG. 3, parts corresponding to those in FIG. As shown in FIG. 3, the lens molding apparatus 1 includes an upper mold 30, a gasket 10, and a lower mold 40. The outer diameter of the upper mold 30 is slightly larger than the inner diameter of the upper mold lead portion 12. Specifically, when the outer diameter of the upper mold 30 is 65 to 80 mm, the inner diameter directly above the upper mold locking portion 14 of the upper mold lead portion 12 is about 1.5 to 2.5 mm smaller. To. Therefore, when the upper mold 30 is inserted from the upper opening 11 of the upper mold lead 12, the side surface of the upper mold 30 is tightened by the inner wall of the upper mold lead 12. As a result, the upper mold 30 seals the upper part of the gasket 10. The upper mold 30 is used in a state where it is pushed in until it comes into contact with the upper mold locking portion 36. Although not shown, the upper die lead portion 12 may have a tapered surface whose inner diameter gradually decreases from the upper opening toward the inside. Further, as described above, the upper portion of the upper die engaging portion 14 is a cylindrical surface, and the upper portion from the upper portion to the upper portion. A tapered surface may be formed toward the opening 11.

  The upper mold 30 is made of, for example, transparent glass, and has an outer surface 31 that is normally a convex surface and an inner surface that includes a molding surface 32 that molds the lens surface. The molding surface 32 is usually a concave surface. A seal portion 34 that comes into contact with the above-described upper mold locking portion 14 of the gasket 10 is provided in a tapered shape at the peripheral portion of the side surface 33 of the upper mold 30 on the molding surface 32 side. The seal part 34 of the upper mold 30 is provided, for example, as a tapered surface in a peripheral area that contacts the upper mold locking part 14 of the gasket 10. The seal part 34 and the upper mold locking part 14 are configured such that a contact state is ensured over the entire circumference of both when superposed. This contact state is not limited to a state in which the entire surface of the seal portion 34 is in contact with the upper mold locking portion 14 from the initial stage of molding, and a gap may be formed inside at the initial stage of molding. That is, at the initial stage of molding, a part of the seal portion 34 or the side surface 33 comes into contact, and as the polymerization proceeds, the molding material shrinks inward, and the seal portion 34 gradually moves from the outside to the upper mold locking portion 14. Any shape that abuts and maintains a sealed state may be used.

  The thickness of the upper mold 30 is designed so as to be substantially equal in the region constituting the molding surface 32 on the inner surface. In the region of the molding surface 32, a force that is strongly pulled in the inner direction of the mold during polymerization shrinkage acts. Therefore, by making the thickness of the upper mold 30 uniform, it is possible to suppress or avoid the action of this force from being concentrated on one point, and it is preferable to damage the mold caused by the action related to the decompression at the time of polymerization shrinkage. Can be suppressed.

  On the other hand, the lower mold 40 is made of, for example, transparent glass, and has an outer surface 41 that is normally concave and a molding surface 42 that is a lens surface and is normally convex. The peripheral edge portion on the side is a seal portion 44 that is brought into contact with the lower mold locking portion 18 during polymerization. The lower mold 40 is inserted into the lower mold lead portion 24 from the lower opening 25 of the gasket 10 so that the seal portion 44 comes into contact with the lower mold engaging portion 18. Further, the thickness of the molding surface 42 of the lower mold 40 is substantially equal for the same reason as the upper mold 30.

The outer diameter of the lower mold 40 is approximately equal to or slightly larger than the inner diameter of the lower opening 25. As described above, the lower die lead portion 24 of the gasket 10 has a shape in which the inner diameter is the smallest immediately below the lower die engaging portion 18 and the inner diameter gradually increases toward the lower opening 25. Alternatively, in the case where a cylindrical surface is provided in a part immediately below the lower mold locking portion 18, the inner diameter increases from the lower portion to the lower opening 25.
Comparing the inner diameter immediately below the lower mold locking portion 18 with the outer diameter of the lower mold 40, the inner diameter directly below the lower mold locking portion 18 is 1.5 mm to 2. mm below the outer diameter of the lower mold 40. The shape can be as small as 5 mm.

Next, a lens molding method using the lens molding apparatus according to the embodiment of the present invention described above will be described. FIG. 4 is a flowchart showing a schematic process of this molding method.
As shown in FIG. 4, first, the upper mold 30 is inserted from the upper opening of the gasket 10, and at least a part of the side surface 33 and the seal portion 34 of the upper mold 30 is engaged with the upper mold through the upper mold lead portion 12. It is assembled in a state where it abuts on the portion 14 (step S1). FIG. 5 is a cross-sectional view showing a state after the upper mold 30 is assembled at the position of the upper mold locking portion 14 of the gasket 10 in this step. As shown in FIG. 5, the upper mold 30 is inserted with the concave surface, which is a molding surface 32 that gives an optical surface to the molded product, facing the cavity 50 inside the gasket 10. In FIG. 5, parts corresponding to those in FIG. Further, in the assembled state, at least a part of the seal portion 34 and the side surface 33 and the upper mold engaging portion 14 are ensured to be in contact with each other over the entire circumference. At this time, the gasket 10 is made of an elastic resin or the like, and the outer diameter of the upper mold 30 is selected to be larger than the inner diameter of the upper lead portion 12. Adhesion is ensured reliably.

  Next, the lower mold 40 is inserted from the lower lead portion 24 of the gasket 10 and assembled to the lower mold locking portion 18 (step S2 in FIG. 4). As shown in FIG. 5, the lower mold 40 is inserted with the convex side, which is the molding surface 42, facing the cavity 50 inside the gasket 10. Further, in the assembled state, at least a part of the seal portion 44 and the side surface 43 and the lower mold locking portion 18 are ensured to be in contact with each other over the entire circumference. Then, the gasket 10 is made of an elastic resin or the like, and the outer diameter of the lower mold 40 is made larger than the inner diameter directly below the lower mold locking portion 18, thereby allowing the lower mold 40 and the gasket 10 to adhere to each other. Sex is ensured.

  Note that the above-described steps S1 and S2 can be performed in a reversed order. Through these steps S1 and S2, a cavity 50 at the time of molding material injection is formed. Note that the volume of the cavity 50 in the gasket 10 formed up to step S2 is larger than the design volume of the finished molded product after polymerization by the volume of the concave portion 20 provided in the molded portion 16. That is, the volume of the recess 20 is made substantially the same as the volume of shrinkage due to polymerization, so to speak, the molding material for contraction is replenished in the recess 20. Thus, the volume of the cavity 50 including the recess 20 is configured to be larger than the design volume by a volume approximately equal to the volume that is consumed by the polymerization shrinkage.

  Next, as shown in FIG. 6, a molding material constituting the plastic lens, that is, a monomer before polymerization, is injected into the cavity 50 (step S3 in FIG. 4). 6, parts corresponding to those in FIGS. 3 and 5 are given the same reference numerals, and redundant description is omitted. The molding material is introduced from the outside of the gasket 10 through the connection part 21 and the injection port 22 of the injection part 23. As described above, the cross-sectional shape of the injection portion 23 in the injection direction is such that the upper surface is inclined upward and outward of the gasket 10 and the lower surface is a gentler inclined surface or a horizontal plane along the injection direction. The cross section is formed as a trapezoid. By setting it as such a shape, it can suppress effectively that the bubble which inevitably entered in the molding material enters into the cavity 50 from the injection | pouring part 23. FIG.

  Next, the lens molding apparatus 1 is heated in an electric furnace or the like to perform a polymerization process (step S4 in FIG. 4). During the polymerization by heating or the like, a phenomenon occurs in which the molding material in the cavity 50 shrinks and the upper mold 30 and the lower mold 40 expand. Since the gasket 10 is made of an elastic material and has flexibility, the gasket 10 follows a change in shape of the upper mold 30 and the lower mold 40 while maintaining high sealing performance against deformation.

  At this time, as polymerization of the molding material in the cavity 50 proceeds, the volume of the molding material gradually becomes smaller than the initial volume of the cavity 50. This is shown in FIG. As indicated by arrows a1 and a2 in FIG. 7, the inner wall of the molded portion 16 of the gasket 10 gradually deforms toward the inside as the molding material shrinks, and the concave portion 20 becomes substantially flat at the end of the polymerization. Deforms until. Such a deformation | transformation is attained by comprising the gasket 10 with the material which has elasticity as mentioned above.

  In this polymerization process, the lower mold 40 is locked at the lower mold locking portion 18 even if the polymerization shrinkage rate is slightly different between the vicinity of the injection port 22 in the molded portion 16 and the other portions. Inclination does not occur as in the case of free without providing the locking portion. Accordingly, it is possible to suppress the phenomenon that the lower mold 40 tilts and the air enters the cavity 50 and the half-wall phenomenon in which the thickness of the molded lens is partially varied after the polymerization is finished while tilting. Can do. At the stage where the concave portion 20 becomes substantially flat, the shape of the cavity 50 becomes substantially equal to the shape of the designed molded product (finished lens or semi-finished lens).

Next, the molding material cured by the polymerization is released, and the molded lens 70 is taken out as shown in FIG. 8 (step S5 in FIG. 4). Even when the lens 70 is immediately after molding, a curved surface that is recessed inward on the side surface (edge surface) hardly occurs as in the prior art, and the lens 70 can have an outer diameter close to the design value.
Although not shown, it is desirable to perform annealing after removing the lens in order to remove the distortion inside the lens generated in the polymerization process. Thereafter, inspection such as appearance inspection and projection inspection can be performed to obtain a finished lens product.

  According to the lens molding method according to the present embodiment described above, as the polymerization proceeds, the material that complements the molding material that shrinks in the polymerization process is stored in the recess 20 of the molding unit 16. The shape of the recess 20 is changed and the molding material is supplied from here. As described above, according to the present invention, the shrinkage amount of the molding material due to the polymerization shrinkage can be reliably complemented, so that the finished molded product can have a shape substantially the same as the desired design product. In addition, since the upper mold 30 and the lower mold 40 are securely in contact with the upper mold locking portion 14 and the lower mold locking portion 18 during the polymerization, it is possible to reliably suppress the flesh of the molded product. it can. For this reason, the amount of cutting and polishing for removing the constriction of the side surface of the lens (edge surface) that has conventionally occurred can be reduced, the amount of ineffective molding material can be reduced, and the cost can be reduced.

  Further, by reducing the ineffective portion of the molding material, the edge surface can be sufficiently polished. In this case, since the smoothness of the edge surface can be improved, it is possible to suppress peeling or cracking of a hard coat or an antireflection film formed in a subsequent process.

  In the stage of assembly of the lower mold 40 shown in FIG. 5, the lower mold 40 is not brought into contact with the lower mold locking portion 18, and the taper surface of the lower mold lead portion 24 is slightly spaced, Or you may make it stand still in the cylindrical surface etc. which are provided directly under the lower mold | type latching | locking part 18. FIG. In this case, the lower mold 40 is pressed against the side surface of the lower mold lead portion 24 in accordance with the polymerization and moves to the lower mold locking portion 18 side while maintaining airtightness. Touched. It is possible to replenish part of the polymerization shrinkage by the amount of movement of the lower mold 40 during the polymerization. Then, the shrinkage obtained by reducing the polymerization shrinkage due to the movement of the lower mold 40 may be replenished with the volume of the concave portion 20 of the molding part 16. This method is effective particularly when applied to a thick lens, because the volume of the entire molding material is large, and thus the amount of polymerization shrinkage increases. Specifically, for example, when a lens having a diameter of 75 mm and a lens having an edge surface thickness of 10 mm or more is molded, the edge surface is less likely to be constricted. Therefore, it is not necessary to perform a rounding process to remove the constriction of the edge portion, and it is possible to reduce costs by eliminating waste of the molding material.

Next, the results of evaluating the variation in outer diameter between the lens molded using the lens molding apparatus of the present invention and the lens according to the comparative example will be described.
In the following examples, two types of gaskets for molding a lens having different design thicknesses on the edge surface were prepared, and six lenses were molded into samples 1 to 12, respectively. Moreover, the gasket which does not provide a recessed part in a molding part as a comparative example was prepared, and three lenses were shape | molded and it was set as the samples 13-15. In each sample, as shown in FIG. 9, the outer diameters at positions p1, p2,... Pn were measured from the convex side in the thickness direction of the edge surface of the lens 70. The thickness of the edge surface is indicated as T. In addition, the polythiol urethane resin was used for the molding material of each lens. The molding surface of the upper mold was the molding surface of the progressive power lens, the average radius of curvature was 141.60 mm, and the radius of curvature of the molding surface of the lower mold was 78.83 mm. Further, in the following example, molding was performed without providing a gap between the upper mold and the upper mold locking portion. In each example, a semi-finished lens was molded.

(1) Example 1
In this example, six lenses were molded using the lens molding gasket whose schematic cross-sectional configuration is shown in FIG. The design thickness (target value) of the edge surface was 15 mm. In FIG. 10, only a half on one side from the central axis of the gasket is shown. As shown in FIG. 10, the gasket is provided with a molding portion 16 between the upper die lead portion 12 and the lower die lead portion 24 so as to protrude inward in a trapezoidal cross section, that is, an upper die engaging portion. 14 and the lower mold | type latching | locking part 18 are each provided as an inclined surface. The height h1 from the upper lead portion 12 of the molding portion 16 was 0.86 mm, and the height h2 from the lower lead portion 24 was 0.95 mm. A recessed portion 20 having a trapezoidal cross section is provided slightly below the central portion in the vertical direction of the molding portion 16. The depth d1 of the recess 20 was 0.10 mm and was formed over the entire circumference of the gasket 10. Further, the inner diameter φ1 of the upper die portion 12 was 1.93 mm smaller than the outer diameter of the upper mold. The inner diameter φ2 of the lower mold lead portion 24 was set to a diameter that is 1.75 mm smaller than the outer diameter of the lower mold. The lower die lead portion 24 has a tapered surface from directly below the lower die engaging portion 18, and the inclination angle θ1 is 2.2 ° from the direction along the central axis of the gasket. The results are shown in Table 1 below.

(2) Example 2
In this example, six lenses were molded using the lens molding gasket having a schematic sectional configuration shown in FIG. The design thickness of the edge surface was 19 mm. In FIG. 11, parts corresponding to those in FIG. In this example, the height h11 from the upper lead portion 12 of the molding portion 16 is 0.84 mm, and the height h12 from the lower lead portion 24 is 0.96 mm. The depth d2 of the recess 20 was 0.28 mm and was formed over the entire circumference of the gasket 10. In addition, the inner diameter φ11 of the upper die portion 12 was 1.97 mm smaller than the outer diameter of the upper die. The inner diameter φ12 of the lower die lead part 24 was set to a diameter smaller by 1.73 mm than the outer diameter of the lower die. The lower die lead portion 24 has a tapered surface from directly below the lower die engaging portion 18, and the inclination angle θ2 is 2.2 ° from the direction along the central axis of the gasket. The results are shown in Table 2 below.

(3) Comparative Example In this example, a lens having a design thickness of 15 mm on the edge surface was molded. Three lenses were molded using a lens molding gasket having a schematic sectional configuration shown in FIG. In FIG. 12, only the half on one side from the central axis of the gasket is shown. As shown in FIG. 12, the gasket is provided with a molding portion 116 between the upper die lead portion 112 and the lower die lead portion 119 so as to protrude inward in a trapezoidal cross section, that is, an upper die engaging portion. 114 and the lower mold | type latching | locking part 118 are each provided as an inclined surface. The height h21 from the upper lead portion 112 of the molding portion 116 was 0.80 mm, and the height h22 from the lower lead portion 119 was 0.80 mm. The molding part 116 was not provided with a recess, and was formed into a cylindrical surface over the entire circumference. The upper die lead 112 and the lower die lead 119 are both cylindrical surfaces. The inner diameter φ21 of the upper mold lead part 112 was 1.7 mm smaller than the outer diameter of the upper mold. The inner diameter of the lower die lead portion 119 was set to be 1.7 mm smaller than the outer diameter of the lower die. The results are shown in Table 3 below.

Comparing the above results, in the case of Examples 1 and 2, the standard deviation of the outer diameter of the lens is about 0.065 or more and 0.095 or less (average 0.08) in Example 1 having an edge thickness of 15 mm. In Example 2 with an edge thickness of 19 mm, it was 0.073 or more and 0.095 or less (average 0.08). On the other hand, in the comparative example, the standard deviation is a remarkably large value of 0.10 or more and 0.14 or less (average 0.12). That is, it is understood that the middle portion in the thickness direction is constricted, and the variation in the lens outer diameter is large. From these results, even when molding a relatively large lens having a thickness of 15 mm or more by adopting the configuration of the present invention and providing a recess in the molded portion of the inner wall of the gasket, the variation in the outer diameter of the lens is excellent. It was found that can be suppressed.
In the above-described examples and comparative examples, the example applied to the molding of the semi-finished lens has been described. However, the present invention can also be applied to the molding of the finished lens. It is possible to suppress variation in diameter.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention described in the claims. Needless to say, it includes modifications and application examples.

1 is a schematic cross-sectional configuration diagram of a lens molding gasket according to an embodiment of the present invention. It is a schematic perspective view of a lens molding gasket according to an embodiment of the present invention. 1 is a schematic cross-sectional configuration diagram of a lens molding device according to an embodiment of the present invention. It is a figure which shows the flowchart of the lens molding method which concerns on the example of embodiment of this invention. It is process drawing of the lens molding method which concerns on the embodiment of this invention. It is process drawing of the lens molding method which concerns on the embodiment of this invention. It is process drawing of the lens molding method which concerns on the embodiment of this invention. It is a schematic sectional block diagram of the lens shape | molded with the gasket for lens shaping | molding which concerns on the embodiment of this invention. It is explanatory drawing of the thickness measurement position of a lens. 1 is a schematic cross-sectional configuration diagram of a main part of a lens molding gasket according to Embodiment 1. FIG. 6 is a schematic cross-sectional configuration diagram of a main part of a lens molding gasket according to Embodiment 2. FIG. It is a schematic sectional block diagram of the principal part of the gasket for lens shaping | molding by a comparative example. It is process drawing of the lens molding method using the conventional gasket for lens molding. It is a cross-sectional block diagram of the lens produced with the conventional gasket for lens shaping | molding.

Explanation of symbols

  1. 9. Lens molding device 10. Gasket (for lens molding) Top opening, 12. Upper die lead, 14. Upper mold locking part, 16. Molding part, 18. Lower mold locking part, 20. Recess, 21. Connection part, 22. Inlet, 23. Injection part, 24. Lower die lead part, 25. Lower opening, 30. Upper mold 31. Outer surface, 32. Molding surface, 33. Side, 34. Seal part, 40. Lower mold, 41. Outer surface, 42. Molding surface, 43. Side, 44. Seal part

Claims (6)

An upper mold locking portion for locking the upper mold;
A lower mold locking portion for locking the lower mold;
Forming the inner wall at the time of molding, a molding part having a recess between the upper mold locking part and the lower mold locking part;
A lens molding gasket.   The lens molding gasket according to claim 1, which is made of an elastic resin. A lens molding apparatus comprising an upper mold, a lower mold, and a lens molding gasket,
The lens molding gasket is
An upper mold locking portion for locking the upper mold;
A lower mold locking portion for locking the lower mold;
Forming the inner wall at the time of molding, a molding part having a recess between the upper mold locking part and the lower mold locking part;
A lens molding apparatus comprising:   The lens molding apparatus according to claim 3, wherein an inner diameter of the upper mold engaging portion is smaller than an outer diameter of the upper mold.   The lens molding apparatus according to claim 3 or 4, wherein an inner diameter of the lower mold engaging portion is smaller than an outer diameter of the lower mold. Inserting the upper mold into a lens molding gasket having a recess in the molded part, and assembling the upper mold locking part;
Inserting a lower mold into the lens molding gasket and assembling the lower mold locking portion;
Injecting the liquid composition portion from the injection port of the lens molding gasket;
Polymerizing the liquid composition part;
Releasing the polymerized lens molding,
A lens molding method including:

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