JP2008221720A - Glass mold for eyeglass lens, its manufacturing process, and manufacturing process of eyeglass lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing process of molds for casting back-surface aspheric or bi-aspheric eyeglass lenses with a high precision in a manner suitable for mass production. <P>SOLUTION: Glass mold 16 is obtained by placing glass curved plate 13 on convex surface 11 of transfer mold 12 having an aspheric convex surface 11 with convex surface 14 of curved plate 13 facing upward, softening curved plate 13 by heating to transfer the aspheric shape of convex surface 11 of transfer mold 12 onto curved plate 13 so that convex surface 14 of curved plate 13 is made aspheric. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a glass mold having an aspheric shape used for manufacturing a plastic lens for spectacles, and a plastic lens for spectacles having an aspheric shape manufactured using the mold.

  As a method for obtaining a plastic aspheric lens, there are (I) a method in which a plastic lens is directly cut and polished into an aspheric surface, and (II) a method in which an aspheric mold is produced and cast.

  In the method (I) of direct cutting and polishing, as shown in FIG. 1, a semi-finished lens (semi-finished lens) 1 having a convex surface created in advance is cut and polished to create an aspherical surface. 2 (polished lens). In FIG. 1A, the right side of the two-dot chain line is the cutting / polishing portion. This method is described in Patent Documents 1 to 7 below.

  In the method of casting (II), as shown in FIG. 2, a glass outer mold (lower mold) 3 and a glass inner mold (upper mold) 4 and a soft plastic gasket or plastic tape 5 are used. The space surrounded by is filled with a liquid plastic monomer (monomer or prepolymer) to which a polymerization initiator or the like is added, and cured by heat curing or room temperature curing by light irradiation to obtain a lens 6 (cast product lens) ). If the convex surface 41 which is the shaping surface of the inner surface mold 4 (surface for shaping the lens) is aspherical, the inner surface aspherical lens 6 is obtained, and the concave surface 31 and the inner surface which are the shaping surface of the outer surface mold 3 are obtained. If the convex surface 41 of the mold 4 is aspherical, a double-sided aspherical lens 6 is obtained. The cast molding is described in Patent Document 8 below.

  As the method for producing an aspheric mold for casting (II), there are (i) a die pressing method, (ii) a direct cutting and polishing method, and (iii) a slump method.

  The die pressing method (i) is a method of obtaining a glass mold by heating and pressing a glass material with a die having an aspherical shape, and is described in Patent Documents 9 and 10 below.

  The direct cutting and polishing method (ii) is a method of obtaining a glass mold by directly cutting and polishing a glass member, and is described in Patent Documents 11 to 13 below.

  The slump method (iii) is a method of creating a rotationally symmetric aspherical surface or free-form surface on the glass surface by heating. In this method, first, a ceramic transfer mold having an aspherical shape or a free-form surface is manufactured by cutting a machinable ceramic (machineable ceramic) with an NC lathe or NC milling machine. Then, a glass curved plate with a uniform thickness (that is, the back surface and the front surface are parallel surfaces) is placed on a transfer mold in an oven and softened by heating for several hours including a slow cooling process. Then, the transfer type aspherical shape or free-form surface is transferred to the curved plate. There is also a direct method in which the shape surface of the transfer mold is mirror-polished and the aspherical shape or free-form surface is directly transferred to the surface of the curved plate that contacts the transfer mold, but usually the surface that is not in contact with the transfer mold An indirect method is used in which the aspherical surface or free-form surface transferred to the lens is used as a shaping surface for molding a lens. After transfer, the contact surface of the curved plate is mirror-polished and used as a glass mold.

Conventionally, in the slump method, a mold that gives an aspheric shape to the outer surface of the lens has been manufactured, but a mold that gives an aspheric shape to the inner surface of the lens has not been manufactured. This is considered to be because when the production number is small, the direct cutting and polishing method (ii) requires a shorter production time of the mold. The slump method is described in paragraph 0031 and patent document 15 of Patent Document 14 below, but the mold described in these documents also gives an aspheric shape to the lens outer surface.
JP 2000-117604 A JP 2003-275949 A JP 2003-266287 A JP 2003-300144 A JP 2004-82324 A JP 2004-106117 A JP 2004-114244 A JP-A-6-254879 Japanese Patent Laid-Open No. 10-309723 Japanese Unexamined Patent Publication No. 2000-828 JP-A-9-66453 JP-A-9-66532 JP-A-8-192348 JP-A-11-64805 JP-A-6-130333

  In the above-mentioned method (I) of directly cutting and polishing to obtain a lens, in the NC cutting machine or free-form surface polishing machine used, the polishing jig for polishing the aspherical surface is a dome shape controlled by air pressure. Since it is composed of a polishing pad attached to a flexible sheet, the curvature of the dome-shaped sheet depends on the control of the air pressure and is very unstable. In addition, the lens is cut and polished one by one, so it is suitable for a build-to-order production method. However, when mass production is performed, the equipment burden is large and there is a problem in terms of cost. -The amount of plastic materials discarded by polishing is extremely large, and even though the waste can be diverted to fuel and other materials, it cannot be recycled or reused, so it is a waste of resources. It was.

  On the other hand, in the method of obtaining the lens by the cast molding of (II) above, the consumption of the plastic material used is small and excellent in mass productivity, but because the investment in the mold is large, how accurately the mold is made Making mass production possible is an important issue. As described above, the mold manufacturing method includes (i) a die pressing method, (ii) a direct cutting and polishing method, and (iii) a slump method.

  However, the mold pressing method (i) is not suitable for spectacle lens applications because the moldable outer diameter is small, and there are problems such as dimensional accuracy stability and residual distortion. Almost not yet adopted.

  In the direct cutting and polishing method (ii), as described in Patent Documents 11 and 12, the aspherical surface is not indirectly cut and polished from the design value of the aspherical surface but indirectly from the copying member. In order to process a shape, there existed a problem that the processing precision of a mold was low. Furthermore, in order to cope with an aspherical shape including an astigmatic power range, a large number of copying members are required, resulting in an increase in cost. In addition, although the example which improved processing accuracy is described in the said patent document 13, since the outer diameter which can be processed is small and processing equipment becomes high in proportion to processing accuracy, it is used for spectacle lenses. Not suitable for. In addition, since the molds are cut and polished one by one, if the number of molds produced increases, it takes more time than the slump method in which a large number of molds can be formed simultaneously, resulting in lack of mass productivity.

  The present invention solves the above-described problems, and provides a mold manufacturing method that can manufacture a mold for casting an inner surface or double-sided aspheric spectacle lens with high accuracy at low cost and is suitable for mass production. The purpose is to provide.

  Another object of the present invention is to provide a mold manufacturing method capable of easily manufacturing a mold for casting an inner surface or double-sided aspheric spectacle lens having astigmatic refractive power on the inner surface at low cost. It is.

  The inner aspheric surface means that only the inner surface of the inner surface (rear surface) and the outer surface (front surface) of the lens is an aspheric surface, and the double aspheric surface means that both the inner surface and the outer surface of the lens are aspheric surfaces. .

  The method for producing a glass mold of the present invention is a method for producing a glass mold that is used for cast molding of a plastic spectacle lens to give an aspherical shape to the inner surface of the lens, and has a heat resistance having an aspherical convex surface. A glass curved plate is placed on the convex surface of the transfer mold so that the convex surface of the curved plate faces upward, and the curved plate is softened by heating, so that the convex surface of the transfer mold is not applied to the curved plate. By transferring the spherical shape, the convex surface of the curved plate is formed into an aspherical shape, and the curved plate is used as a glass mold.

  Further, the convex surface of the transfer mold has a rotationally symmetric aspherical shape, and the convex surface of the curved plate is formed in an astigmatic surface in advance, and then the rotationally symmetric aspherical shape of the convex surface of the transfer mold is transferred to the curved plate. Thus, the convex surface of the curved plate is formed into an aspherical shape having astigmatic refractive power.

  The glass mold of the present invention is a glass mold that is used for cast molding of plastic spectacle lenses to give an aspheric shape to the inner surface of the lens, and the convex surface that gives the aspheric shape to the inner surface of the lens It is a composite surface in which a spherical transfer surface and an astigmatic cutting surface are combined.

  The method for producing an inner surface or double-sided aspherical plastic spectacle lens of the present invention uses the glass mold of the present invention as a shaping mold on the inner surface side of the lens (that is, an inner surface mold) and casts the inner surface or both surfaces by casting. An aspheric plastic spectacle lens is manufactured.

  The glass mold manufacturing method of the present invention is a glass mold having an aspherical convex surface (that is, a glass product that gives an aspherical shape to the lens inner surface) by a so-called slump method for transferring an aspherical shape from a ceramic transfer mold. Mold), a mold for casting an inner surface or double-sided aspheric spectacle lens can be manufactured at low cost with high accuracy, and a large number of molds can be processed simultaneously. Suitable for mass production.

  In addition, the convex surface of the curved curved plate, which is the basis of the glass mold, is formed in advance on the astigmatic surface, and then the rotationally symmetric aspherical shape of the transfer-type convex surface is transferred so that the convex surface of the curved plate is astigmatically refracted. If it is formed into an aspherical shape having a force, it is only necessary to prepare a transfer mold according to the spherical refractive power, so the type of transfer mold can be reduced, and the inner surface has astigmatic refractive power on the inner surface. Alternatively, a glass mold for casting a double-sided aspheric spectacle lens can be manufactured at low cost. In addition, it is easy to cut the transfer mold into a rotationally symmetric aspherical shape, and it is easy to cut the curved plate into an astigmatic surface shape, so that the mold can be easily manufactured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The glass mold 16 (see FIG. 6) according to the embodiment is manufactured by a slump method. Specifically, by first cutting the circular upper surface of the machinable ceramic block using an NC lathe, as shown in FIG. 3, a rotationally symmetric aspherical surface represented by the following formula (Equation 1): A heat-resistant ceramic transfer mold 12 having a convex surface 11 having a shape is produced. It is easy to form a rotationally symmetric aspherical shape by cutting.

  Machinable ceramics that can be used for the transfer mold 12 include, for example, ceramic disks manufactured by Kepets.

  The expression (Equation 1) makes it possible to correct the shape of the periphery with the second term or less, mainly on a quadric surface (ellipsoid, hyperboloid, and paraboloid) obtained from a conical cut surface.

但し、ｈ²＝Ｘ²＋Ｙ²、Ｒ：頂点における曲率半径、Ｋ：非球面係数、Ａ_n：第２項以下の係数、ｎ：正の整数、である。

Here, h ² = X ² + Y ² , R: radius of curvature at the apex, K: aspheric coefficient, A _n : coefficient of the second term or less, n: positive integer.

  Then, as shown in FIG. 5A, a circular curved plate 13 made of inorganic glass having a uniform thickness (that is, the convex surface 14 and the concave surface 15 have a spherical shape with the same radius of curvature) (see FIG. 4). ) Is placed on the convex surface 11 of the transfer mold 12 in an oven having a heat source 29 so that the convex surface 14 faces upward, and is softened by heating for several hours including a slow cooling step. ), The aspherical shape of the convex surface 11 is transferred to the curved plate 13.

  If a plurality of transfer molds 12 are prepared, and a curved plate 13 is placed on each of them and placed in an oven, the plurality of curved plates 13 can be slumped simultaneously. In such a case, in order to prevent uneven heating, it is preferable that the transfer molds 12 are arranged in an annular shape and rotated so as to change the arrangement position in the oven. It is preferable to adsorb the curved plate 13 to the transfer mold 12 by vacuum suction so as not to deviate from the above.

  Examples of inorganic glass that can be used for the curved plate 13 include Corning 8092 and Schott S3. These are all borosilicate glass and fall within the range of BK. In this embodiment, Corning 8092 is used.

  In this embodiment, the aspherical shape transferred to the convex surface 14 that is not in contact with the transfer mold 12 is used as a shaping surface when the lens is molded. After the transfer, the concave surface 15 which is a contact surface with the transfer mold 12 is mirror-polished to obtain a glass mold 16. The reason why the concave surface 15 is mirror-polished is to facilitate visual inspection of the mold 16 and the like.

  The glass mold 16 thus obtained has an aspheric shape represented by the above formula (Equation 1) on the convex surface 14 and gives the aspheric shape to the inner surface (rear surface) of the lens.

  Next, based on FIG. 6, the manufacturing method of the plastic spectacle lens 20 of the inner surface aspherical surface or both surfaces aspherical surface using the glass mold 16 will be described. As shown in FIG. 6 (a), the glass mold 16 is an inner surface mold, and the glass mold 17 that gives a spherical shape or an aspherical shape to the outer surface of the lens is an outer surface mold. 17 is arranged oppositely, and the space between the glass molds 16 and 17 is sealed by winding the periphery with a plastic tape 18, and the glass molds 16 and 17 are fixed to form a molding die 19.

  The glass mold 17 has a spherical shape when the concave surface 25 which is a shaping surface when the lens 20 is molded gives a spherical shape to the outer surface of the lens 20 (that is, when manufacturing the lens 20 having an inner aspheric surface). When an aspherical shape is given to the outer surface of the lens 20 (that is, when a double-sided aspherical lens 20 is manufactured), the aspherical shape is used.

  The one in which the transparent liquid plastic material for the lens is injected into the space inside the molding die 19 is cured after being cured by light irradiation such as heating or ultraviolet irradiation, thereby releasing the inner surface as shown in FIG. A spherical or double-sided aspheric lens 20 is obtained.

  Examples of the transparent liquid plastic material that can be used include those described in paragraph 0023 of Patent Document 14.

  Thus, if the glass mold 16 which gives the aspherical shape to the inner surface of the lens 20 is produced by the slump method, the glass mold 16 with higher processing accuracy can be obtained compared to the method of direct cutting and polishing. The slump method has the disadvantage that it takes a long time for one molding process. However, by preparing a large number of transfer molds 12 and processing a large number of molds 16 simultaneously, this disadvantage can be compensated. The mass production of the mold 16 is possible. If the lens 20 is cast using the mold 16, the inner surface or double-sided aspheric lens can be mass-produced easily and at low cost.

  Next, a method for producing the glass mold 16 that gives the inner surface of the lens 20 an aspherical shape having astigmatic refractive power will be described.

  When an aspheric shape having astigmatic refractive power (that is, including an astigmatic component) is given to the inner surface of the lens 20, the type of spherical power (for example, 45 types) and the type of astigmatic power (for example, 0.25 diopter from 0 to 2 diopters). In order to prepare all the transfer molds 12 in order to produce a glass mold 16 according to 9 types), for example, many types of transfer molds 12 such as 45 × 9 = 405 types are required, and the cost is reduced. Invite high. Further, it is difficult to cut the convex surface 11 of the transfer mold 12 into an aspherical shape having astigmatic refractive power (that is, a non-rotationally symmetric aspherical shape). On the other hand, it is easy to cut the convex surface 11 into a rotationally symmetric aspherical shape, and it is also easy to cut the convex surface 14 of the curved plate 13 into an astigmatic surface shape. Furthermore, the inventors have found that the astigmatic refractive power on the convex surface 14 is maintained when the curved plate 13 is softened by the slump method. Therefore, a glass mold 16 was produced that gave an aspherical shape having astigmatic refractive power to the inner surface of the lens 20 as in (1) and (2) below.

    (1) The convex surface 11 of the transfer mold 12 is cut into a rotationally symmetric aspheric shape corresponding to the spherical refractive power, and the transfer mold 12 corresponding to each spherical power is prepared.

    (2) The convex surface 14 of the curved plate 13 is previously cut into an astigmatic surface corresponding to the astigmatism power (that is, to have a radius of curvature to which the astigmatic refractive power is added), and then the curved plate 13 is (1 ) And the slump process is performed.

  That is, instead of transferring the astigmatism curve from the transfer mold 12, the astigmatism curve was previously attached to the convex surface 14 of the curved plate 13, and only the rotationally symmetric aspheric shape was transferred from the transfer mold 12.

  The astigmatic surface is a toroidal surface in which a radius of curvature in the direction is different from the radius of curvature of the reference surface by cutting a spherical reference surface in one direction. Further, the refractive power in a certain direction of a certain surface means a value obtained by multiplying the value obtained by subtracting 1 from the refractive index of the base material by 1000 and then dividing by the radius of curvature of that surface in that direction, and is orthogonal to the astigmatic surface. The difference between the refractive powers in the two directions is called astigmatic refractive power.

  FIG. 4 shows a three-dimensional space representing the three-dimensional shape of the curved plate 13. In FIG. 4, BC is a base curve, and CC is a cross curve. Hereinafter, the base curve is denoted by BC and the cross curve is denoted by CC. BC of the lens 6 is a horizontal curve and CC is a vertical curve. BC and CC on the curved plate 13 are BC of the lens 6 formed by the mold 16 formed from the curved plate 13, respectively. , In the same direction as CC. BC and CC are orthogonal to each other, and the difference in refractive power between BC and CC becomes astigmatic refractive power.

  In the present embodiment, one direction of the convex surface 14 that originally forms a spherical surface is ground and polished with a radius of curvature different from the radius of curvature of the original spherical surface, thereby making the convex surface 14 an astigmatic surface having different curvature radii orthogonal to each other. . The original spherical radius of curvature is BC, and the newly created radius of curvature is CC. Therefore, the curved plate 13 in this case is not uniform in thickness (that is, the convex surface 14 and the concave surface 15 are not parallel surfaces).

  By this processing method, it becomes possible to obtain an atoric surface (aspheric astigmatism surface) which is a non-rotationally symmetric aspheric surface on the convex surface 14 of the curved plate 13 from the rotationally symmetric aspherical shape of the convex surface 11 of the transfer mold 12. 14 is a composite surface (composite surface) in which a rotationally symmetric aspherical transfer surface and an astigmatic cutting surface are combined (composite).

  According to this method, considering an astigmatic power range of 0.25 diopters up to 2 diopters, it is possible to produce a glass mold 16 that gives an inner aspheric shape with a ceramic amount of 1/9 and is low in cost. . Further, since the aspherical shape having astigmatic refractive power is a non-rotationally symmetric aspherical shape, it is not easy to cut the transfer mold 12 into an aspherical shape having astigmatic refractive power, but the transfer mold 12 is not rotationally symmetric. Since it is easy to cut into a spherical shape and it is easy to cut the curved plate 13 into an astigmatic surface shape, the mold 16 can be easily manufactured according to this method.

  Note that the mold manufacturing method described in the above-mentioned Patent Document 15 is obtained by grinding a progressive multifocal surface (that is, progressive refracting surface) on a ceramic matrix and an axially symmetric aspheric surface (that is, rotationally symmetric surface) on a glass blank. (Spherical surface) is formed, and a surface having aspherical change rate of the progressive refractive surface is formed on the concave surface of the glass blanks by the slump method as a composite surface thereof. It does not form a spherical astigmatic surface. Moreover, since it is difficult to form a progressive refractive surface by grinding, it cannot be said that the mold manufacturing method described in Patent Document 15 is easy to manufacture the mold.

  Hereinafter, each Example and a comparative example are demonstrated.

<Example 1>
A cylindrical block (outer diameter: 100 mmφ, thickness: 25 mm) made of a machinable ceramic (here, Kepets ceramic disc), using an NC lathe, the following formula ( The transfer mold 12 is cut so that the convex surface 11 having the rotationally symmetric aspherical shape represented by 2) is formed (see FIG. 3).

Curvature radius 102.13mm
Aspheric coefficient (K) -3.0
Coefficient of polynomial (A) 4.310E-08
Polynomial coefficient (B) 4.510E-11
Coefficient of polynomial (C) 9.500E-16
Polynomial coefficient (D) -1.500E-18
Effective diameter of aspheric surface 90mmφ

ここで、Ｒ：頂点における曲率半径、Ｋ：非球面係数、Ａ、Ｂ、Ｃ、Ｄ：多項式部分の係数、ｈ²＝Ｘ²＋Ｙ²である。

Here, R: radius of curvature at the apex, K: aspherical coefficient, A, B, C, D: coefficient of polynomial part, h ² = X ² + Y ² .

  Subsequently, using a glass material (Corning, 8092), a circular glass curved surface plate (bare) 13 having a thickness of 6.0 mm and an outer diameter of 80 mmφ, which is mirror-polished with the following curvature radius on both sides, is produced. .

Curvature radius 102.26mm
The curved plate 13 is placed on the transfer mold 12 in the oven, and Max. In the temperature cycle of 725 ° C., the aspherical shape of the transfer mold 12 is transferred by the above-described slump method (see FIG. 5) to obtain a glass mold 16.

  Unlike the convex surface 14 of the curved plate 13 that is not in contact with the transfer mold 12 in the oven, the concave surface 15 is in the form of a skin because it is in contact, and it is difficult to inspect the appearance of the glass mold 16 as it is. Also, since it is difficult to see bubbles or the like when the plastic monomer is injected, the concave surface 15 is re-polished with a curve close to the radius of curvature of the transfer mold 12 to obtain a glass mold 16. This glass mold 16 is hereinafter referred to as an aspheric inner surface mold I.

  The convex surface 14 of this aspherical inner surface mold I was measured three-dimensionally using a shape measuring machine CS-H5000 manufactured by Mitutoyo Corporation, and the following numerical values were obtained.

Curvature radius 104.464mm
Aspheric coefficient (K) -2.44331
Coefficient of polynomial (A) 1.37649E-07
Polynomial coefficient (B) -6.55731E-10
Coefficient of polynomial (C) 9.78809E-13
Coefficient of polynomial (D) -4.660287E-16
Thus, the convex surface 14 of the aspherical inner surface mold I has an aspherical shape.

<Example 2>
The convex surface 14 of the curved plate 13 of Example 1 is mirror-polished so as to have the following radius of curvature to obtain the curved plate 13 of Example 2.

Curvature radius (BC) 102.26mm
Curvature radius (CC) 89.82mm
Unlike the first embodiment, the curved plate 13 of the second embodiment has an astigmatic power of about 1.0D. The curved plate 13 is placed on the same transfer mold 12 as in the first embodiment, and the Max. Shown in FIG. The aspherical shape of the transfer mold 12 is transferred by a temperature cycle of 725 ° C. Then, the concave surface 15 of the curved plate 13 that was in contact with the transfer mold 12 in the oven was re-polished with a curve close to the radius of curvature of the transfer mold 12 to obtain a glass mold 16. The glass mold 16 is hereinafter referred to as an aspheric inner surface mold II.

  The convex surface 14 of the aspherical inner surface mold II was subjected to three-dimensional measurement using a shape measuring machine CS-H5000 manufactured by Mitutoyo Corporation, and the following numerical values were obtained.

<BC> Radius of curvature 103.590mm
Aspheric coefficient (K) -2.44331
Coefficient of polynomial (A) 1.37649E-07
Polynomial coefficient (B) -6.55731E-10
Coefficient of polynomial (C) 9.78809E-13
Coefficient of polynomial (D) -4.660287E-16
<CC> Radius of curvature 88.832mm
Aspheric coefficient (K) -2.44331
Coefficient of polynomial (A) 1.37649E-07
Polynomial coefficient (B) -6.55731E-10
Coefficient of polynomial (C) 9.78809E-13
Coefficient of polynomial (D) -4.660287E-16
Thus, the convex surface 14 has an aspherical shape that substantially holds the astigmatic refractive power of the curved plate 13.

<Example 3>
The convex surface 14 of the curved plate 13 of Example 1 is mirror-polished so as to have the following radius of curvature to obtain the curved plate 13 of Example 3.

Curvature radius (BC) 102.26mm
Curvature radius (CC) 80.08mm
The curved plate 13 of Example 3 has an astigmatic power of about 2.0D. This curved plate 13 is placed on the same transfer mold 12 as in Example 1, and in the same manner as in Example 1, Max. The aspherical shape of the transfer mold 12 is transferred at a temperature cycle of 725 ° C. Then, the concave surface 15 of the curved plate 13 that was in contact with the transfer mold 12 in the oven was re-polished with a curve close to the radius of curvature of the transfer mold 12 to obtain a glass mold 16. This glass mold 16 is hereinafter referred to as an aspheric inner surface mold III.

  The convex surface 14 of the aspherical inner surface mold III was subjected to three-dimensional measurement using a shape measuring machine CS-H5000 manufactured by Mitutoyo Corporation, and the following numerical values were obtained.

<BC> Curvature radius 100.917mm
Aspheric coefficient (K) -3.62018
Polynomial coefficient (A) 1.00207E-07
Coefficient of polynomial (B) -5.09245E-10
Coefficient of polynomial (C) 8.0171E-13
Polynomial coefficient (D) -3.98888E-16
<CC> Radius of curvature 80.537mm
Aspheric coefficient (K) -1.55009
Polynomial coefficient (A) 5.89467E-08
Coefficient of polynomial (B) -2.991128E-10
Coefficient of polynomial (C) 4.48570E-13
Coefficient of polynomial (D) -2.18738E-16
Thus, the convex surface 14 has an aspherical shape that substantially holds the astigmatic refractive power of the curved plate 13.

<Example of external mold fabrication>
A machinable ceramic cylindrical block (outer diameter: 100 mmφ, thickness: 25 mm) is represented by the above formula (Equation 2) as shown in FIG. 8 based on the following data using an NC lathe. The transfer die 22 is cut so that a rotationally symmetric aspherical shape is formed on the concave surface 21.

Radius of curvature 792.292mm
Aspheric coefficient (K) -60.0
Polynomial coefficient (A) 2.850E-08
Coefficient of polynomial (B) 1.210E-11
Coefficient of polynomial (C) -5.750E-15
Polynomial coefficient (D) -1.100E-19
Effective diameter of aspheric surface 90 mmφ
Subsequently, using a glass material (Corning, 8092), a circular glass curved plate 23 having a thickness of 6.0 mm and an outer diameter of 80.0 mmφ, both surfaces of which are mirror-polished with the following curvature radius (see FIG. 9). ).

Radius of curvature 1226.17mm
As shown in FIG. 9, the curved plate 23 is placed on the transfer mold 22 in an oven, and the Max. The aspherical shape of the transfer mold 22 is transferred at a temperature cycle of 725 ° C. The convex surface 24 of the curved plate 23 that was in contact with the transfer mold 22 in the oven was re-polished with a curve close to the radius of curvature of the transfer mold 23 to obtain a glass mold 17 as an outer mold. This glass mold 17 is hereinafter referred to as an aspheric outer surface mold IV.

  The concave surface 25 of the aspherical outer surface mold IV was subjected to three-dimensional measurement using a shape measuring machine CS-H5000 manufactured by Mitutoyo Corporation, and the following numerical values were obtained.

Curvature radius 773.325mm
Aspheric coefficient (K) -61.7716
Polynomial coefficient (A) 2.99157E-08
Polynomial coefficient (B) -5.88881E-11
Coefficient of polynomial (C) 2.32888E-14
Coefficient of polynomial (D) -4.0451E-18
Thus, the concave surface 25 has an aspherical shape.

<Example 4>
As shown in FIG. 6A, the aspheric inner surface mold I and the aspheric outer surface mold IV are arranged at a predetermined interval so that the convex surface 14 and the convex surface 25 face each other, and are surrounded by a polyester adhesive tape 18. To form a mold 19.

  On the other hand, bis (mercaptomethyl) -3,6,9-trithia-1,1 was added to 100 parts of bis (2,3-epithiopropyl) disulfide (trade name: MR-174 A solution, manufactured by Mitsui Chemicals, Inc.). , 1-Undecanedithiol (trade name: MR-174 B solution, manufactured by Mitsui Chemicals, Inc.), 1 part of an ultraviolet absorber and 0.084 part of acetic anhydride were added, and after stirring sufficiently, N, N Add 0.04 parts of -dimethylcyclohexylamine and 0.1 part of N, N-dicyclohexylmethylamine. The mixture was further stirred and filtered through a 3 μm filter to obtain a lens monomer.

  Subsequently, the lens monomer was injected into the mold 19 and placed in a hot air circulation type oven. It was heat-cured at a temperature cycle of 80 ° C. and released with a wedge-shaped tool to obtain a plastic spectacle lens 20 having both aspherical surfaces on both sides and no astigmatic power.

  A comparison between the edge thickness of the lens 20 and the edge thickness of a plastic spectacle lens made of the same material having a spherical rear surface obtained in Comparative Example 1 described later is as follows.

Example 4 6.1 mm
Comparative Example 1 6.9 mm
Next, when a 10 mm square graph paper was viewed through the lens 20, as shown in FIG. 11, the periphery of the lens could be seen without any distortion. This means that the spherical aberration and distortion of the lens 20 have been removed.

<Comparative example 1>
A glass mold having a convex spherical surface with the same radius of curvature as the aspheric inner surface mold I of Example 1 is manufactured by polishing. This glass mold is hereinafter referred to as a spherical inner surface mold V. The spherical inner surface mold V and the aspheric outer surface mold IV are arranged at a predetermined interval in the same manner as in Example 4 to assemble the mold.

  Next, the monomer for the lens prepared in Example 4 was injected into this mold, and it was cured by heating at a temperature cycle of Max.80 ° C. shown in FIG. 10, and was released with a wedge-shaped tool. Only a plastic spectacle lens having an aspheric shape, a so-called outer aspheric lens was obtained.

  When a 10 mm square graph paper was viewed through this lens, the periphery of the lens appeared distorted as shown in FIG.

<Example 5>
As shown in FIG. 6A, the aspheric inner surface mold II and the aspheric outer surface mold IV are arranged at a predetermined interval so that the convex surface 14 and the convex surface 25 face each other, and are surrounded by a polyester adhesive tape 18. To form a mold 19.

  Next, the lens monomer prepared in Example 4 is poured into the mold 19, placed in a hot air circulation oven, and cured by heating at a temperature cycle of Max.80 ° C. shown in FIG. After releasing with a tool, a plastic spectacle lens 20 having an aspheric shape on both sides and an aspheric astigmatic refractive power on the rear surface was obtained.

  A comparison between the edge thickness of the lens 20 and the edge thickness of the plastic astigmatic spectacle lens having a spherical rear surface obtained in Comparative Example 2 described later is as follows.

BC CC
Example 6 6.1 mm 7.1 mm
Comparative Example 2 6.9 mm 7.9 mm
Next, when a 10 mm square graph paper was viewed through the lens 20, as shown in FIG. 13, the periphery of the lens 20 could be seen without any distortion. This means that the spherical aberration and distortion of the lens have been removed.

<Comparative example 2>
The convex surface has an astigmatic surface (toroidal surface) shape having the same curvature radius as that of the aspheric inner surface mold II of Example 2 (that is, the convex surfaces are BC, CC having the same curvature radius as BC and CC of the aspheric inner surface mold II, respectively). A glass astigmatism mold (having an astigmatic surface (toroidal surface) shape) with a polishing process is prepared by polishing. This glass astigmatism mold is hereinafter referred to as a spherical inner surface mold VI. The spherical inner surface mold VI and the aspheric outer surface mold IV are arranged at a predetermined interval in the same manner as in Example 4 to assemble the mold.

  Next, the monomer for the lens prepared in Example 4 was injected into this mold, and it was cured by heating at a temperature cycle of Max.80 ° C. shown in FIG. 10, and was released with a wedge-shaped tool. Only a plastic spectacle lens having an aspheric shape, a so-called outer aspheric lens was obtained.

  When a 10 mm square graph paper was viewed through this lens, the periphery of the lens appeared distorted as shown in FIG.

<Example 7>
As shown in FIG. 6A, the aspheric inner surface mold III and the aspheric outer surface mold IV are arranged at a predetermined interval so that the convex surface 14 and the convex surface 25 face each other, and are surrounded by a polyester adhesive tape 18. To form a mold 19.

  Next, the lens monomer prepared in Example 4 is poured into the mold 19, placed in a hot air circulation oven, and cured by heating at a temperature cycle of Max.80 ° C. shown in FIG. After releasing with a tool, a plastic spectacle lens 20 having an aspheric shape on both sides and an aspheric astigmatic refractive power on the rear surface was obtained.

  A comparison between the edge thickness of the lens 20 and the edge thickness of a plastic astigmatic spectacle lens having a spherical rear surface obtained in Comparative Example 3 described later is as follows.

BC CC
Example 7 6.1 mm 8.1 mm
Comparative Example 3 6.9 mm 9.0 mm
Next, when a 10 mm square graph paper was viewed through the lens 20, as shown in FIG. 15, the periphery of the lens 20 could be seen without any distortion. This means that the spherical aberration and distortion of the lens have been removed.

<Comparative Example 3>
The convex surface has an astigmatic surface (toroidal surface) shape having the same radius of curvature as that of the aspheric inner surface mold III of Example 3 (that is, the convex surface is BC having the same curvature radius as BC and CC of the aspheric inner surface mold III, respectively). A glass astigmatism mold (made to have an astigmatic surface (toroidal surface) shape having CC) is produced by polishing. This glass astigmatism mold is hereinafter referred to as a spherical inner surface mold VI. The spherical inner surface mold VI and the aspheric outer surface mold IV are arranged at a predetermined interval in the same manner as in Example 4 to assemble the mold.

  Next, the monomer for the lens prepared in Example 4 was injected into this mold, and it was cured by heating at a temperature cycle of Max.80 ° C. shown in FIG. 10, and was released with a wedge-shaped tool. Only a plastic spectacle lens having an aspheric shape, a so-called outer aspheric lens was obtained.

  When a 10 mm square graph paper was viewed through this lens, the periphery of the lens appeared distorted as shown in FIG.

  Table 1 shows the contents of each prototype lens and the mold symbol used. In the table, the outer surface aspheric surface indicates a case where the outer surface is an aspheric surface and the inner surface is a spherical surface, and as indicates an aspheric mold.

It is a figure which shows the method of obtaining a lens by direct cutting and grinding | polishing, (a) shows the semi-finished lens before cutting and grinding | polishing, (b) shows the finished lens after cutting and grinding | polishing. It is a figure which shows the method of obtaining a lens by cast shaping | molding, (a) is during shaping | molding, (b) shows after mold release. It is an example of the ceramic transfer mold for inner surface mold by which the aspherical surface was cut. It is a figure which shows the three-dimensional space showing the solid shape of a mold. It is a figure which shows the manufacturing method of the internal mold by a slump method, (a) shows before a heating, (b) shows after a heating. It is a figure which shows the method of obtaining a lens by cast shaping | molding, (a) is during shaping | molding, (b) shows after mold release. It is a temperature cycle example of slump processing. It is an example of the ceramic transcription | transfer type for outer surface molds. It is a figure which shows the manufacturing method of the outer surface mold by a slump method, (a) shows before heating, (b) shows after heating. It is an example of the polymerization temperature cycle of a plastic lens. FIG. 6 is a diagram when a graph paper is viewed with the lens obtained in Example 4; It is a figure when a graph paper is seen with the lens obtained in Comparative Example 1. FIG. 10 is a diagram when a graph paper is viewed with the lens obtained in Example 5. It is a figure when a graph paper is seen with the lens obtained in Comparative Example 2. It is a figure when a graph paper is seen with the lens obtained in Example 6. It is a figure when a graph paper is seen with the lens obtained in Comparative Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Convex surface 12 ... Transfer mold 13 ... Curved surface board 14 ... Convex surface 16 ... Glass mold 20 ... Lens

Claims (4)

A method of manufacturing a glass mold that is used for cast molding of a plastic spectacle lens to give an aspherical shape to the inner surface of the lens,
On the convex surface of the heat-resistant transfer mold having an aspherical convex surface, a glass curved plate is placed so that the convex surface of the curved plate faces upward, and the curved plate is softened by heating, so that the curved plate is curved. A glass mold, wherein the convex surface of the curved plate is formed into an aspherical shape by transferring the aspherical shape of the convex surface of the transfer mold to the face plate, and the curved plate is made into a glass mold. Method.   The convex surface of the transfer mold has a rotationally symmetric aspherical shape, and the convex surface of the curved plate is previously formed on an astigmatic surface, and then the rotationally symmetric aspherical shape of the convex surface of the transfer mold is transferred to the curved plate. The method for producing a glass mold according to claim 1, wherein the convex surface of the curved plate is formed into an aspherical shape having astigmatic refractive power. A glass mold that is used for cast molding of plastic spectacle lenses and gives an aspherical shape to the inner surface of the lens,
A glass mold characterized in that the convex surface giving an aspherical shape to the inner surface of the lens is a synthetic surface in which a rotationally symmetric aspherical transfer surface and an astigmatic cutting surface are combined.   A glass spectacle lens having an inner surface or a double-sided aspheric surface is produced by cast molding using the glass mold according to claim 3 as a shaping mold on the inner surface side of the lens. Lens manufacturing method.

Images