JPH0521054B2 - - Google Patents

Description

Claim 1: A central spherical zone having a radius r ₁ and one edge, as a molded part:
A ₁ ; a first annular spherical zone A ₂ having a radius r ₂ and having an inner edge and an outer edge that are concentric with the central spherical zone A ₁ and in contact with the edges of the central spherical zone A ₁ ; and the first annular spherical zone A a _second annular spherical zone A _{3 with a radius r 3 concentric with A 2 and in} contact with the outer edge _of the first annular spherical zone _{A 2 ;} Metal master mold for injection molding plastic replica molds, polished so that the joints transition smoothly into each other. 2. A central spherical zone A ₁ with one edge, concentric with the spherical zone A ₁ and concentric with the spherical zone A ₁
a first annular spherical zone _A2 having an inner edge and an outer edge in contact with the edges of the first annular spherical zone A2; and a second annular spherical zone _A2 having an inner edge concentric with the first annular spherical zone A2 and in contact with the outer edge of the first annular spherical zone _A2 . A method for producing an optical surface of a metal master mold for injection molding a plastic replica mold for molding a hydrogel contact lens having a segmented spherical zone A ₃ , the method comprising: The following sequential steps are performed: (1) selecting a cylindrical metal blank and determining its optical center; (2) calculating the radius r ₁ to determine the central spherical zone A ₁ and correcting the resulting lens. Alternatively, determine the refractive power, calculate the radius r ₂ to determine the first annular spherical zone A ₂ and determine the nominal center thickness of the lens, and then calculate the radius r ₃ to determine the second annular spherical zone A 2 . ₃
(3) cut a radius r ₁ portion of the central spherical zone A ₁ in the metal blank to set _a predetermined center reference starting point; Cut _the annular spherical zone A ₂ until _{the desired} optical zone and nominal center lens thickness are obtained; radius r ₂
(6) cut the radius r ₃ to a predetermined diameter that defines the outer periphery and tapered shape of the lens, and (7) cut the A ₁ /A ₂ junction and A ₂ /A ₃ The method described above, comprising the steps of polishing the cut metal mold so that the three curved surfaces smoothly transition to each other at the joint. 3 The optical surface of the metal mold thus manufactured is 0
3. A method according to claim 2, which provides a hydrogel contact lens with a refractive index of ~-20 diopters. 4 The optical surface of the metal mold thus manufactured is 0
Claim 3 provides a hydrogel contact lens having a refractive index of ~-8 diopters.
The method described in section. 5 The optical surface of the metal mold thus produced is 0
Claim 3 provides a hydrogel contact lens having a refractive index of ~-6 diopters.
The method described in section. 6. The method of claim 2, wherein the optical surface of the metallic mold thus produced provides a hydrogel contact lens with an optical band having an apparent center thickness of approximately 0.04 mm ± 0.02 mm. Description The present invention relates to a mold specifically for producing contact lenses, particularly spherical hydrophilic contact lenses with a unique tricurve structure designed to correct myopia, and a mold for making a contact lens specifically designed to correct myopia. Regarding the manufacturing method. In a preferred aspect of the invention, a hydrophilic contact lens is cast with three distinct zones or curved surfaces, the central zone being substantially thinner than the periphery of the lens. Contact lenses designed to correct myopia refract light and the center of the lens must be thinner than the periphery to provide proper optical correction. The difference in thickness increases as the bending power of the lens increases. Optical power (dioptres) varies from 0 to -20.0, but generally ranges from 0 to -6 for most myopic populations. The center thickness will therefore be in the range 0.03-0.55 mm. Therefore, it is important to design hydrophilic contact lenses that are as thin as possible, i.e.
It is desirable to have a center thickness of 0.04 mm, which maximizes the transmission of oxygen through the lens to the wearer's cornea, thus promoting the patient's corneal health during the contact lens wear cycle. . This contact lens may be more comfortable for a patient to wear for longer periods of time than lenses of conventional thickness. Hydrophilic contact lenses are not rigid, but rather are generally three-dimensional networks of one or more polymers that trap a substantial amount (eg, one-third or more) of water. Due to the above requirements regarding center thickness, common designs and manufacturing methods have been found to be inadequate. It has been found that the ultra-thin hydrophilic contact lenses produced in this way are extremely thin and soft and are therefore extremely difficult to insert and remove, especially as the light bending power decreases. Integrity and at least partial stability are necessary for patient convenience and acceptance of hydrophilic contact lenses, especially in the case of low optical power where the surfaces of the lenses are necessarily approximately parallel. The unique tri-curved design lens produced by the inventive mold has the necessary strength and extra mass in the center of the lens periphery, thereby giving the lens the necessary integrity and required handling characteristics. The lens is sufficiently durable on the patient's hands or fingers, easy to handle, and relatively easy to insert and remove. As another advantage, the tricurved design increases both the tensile strength and tear strength of the lens, thus extending the life of the lens and reducing accidents due to torn lenses. The tricurved lens manufactured by the mold of the present invention can be easily manufactured by casting or molding. Casting methods are known for the manufacture of contact lenses to reduce or eliminate costly lens machining and polishing. According to the method described in U.S. Pat. No. 4,121,896 (TH. Manufactured. These plastic mold members are then arranged vertically and used to mold contact lenses. Preferably,
One of the molding surfaces is provided with a flexible peripheral rim that defines the outer edge of the resulting lens. The lens-forming material constituting the lens is loaded into the female mold member or portion.
A complementary male member or portion is brought into contact with the female member, thereby positioning the flexible rim on the opposite molding surface. During molding, the lens-forming material contracts and causes the flexible rim to arch, usually inwardly, thereby causing the two molding members to move toward each other. At the end of one molding cycle, the mold members are separated and the resulting contact lens is removed ready for use, with the exception of cleaning and perhaps buffing of the edges of the lens. The tricurved lens manufactured by the mold of the present invention generally has a spherical surface, but may also be manufactured into a toric structure. Optionally, the lens may be truncated and/or have a prismatic paralast to ensure positional stability when placed on the cornea. Molded toric contact lenses are described in US Pat. No. 4,208,365 (RJ Refever) and co-pending US Patent Application No. 199,780 (Erik Noble). Truncated Contact Lenses Published PCT Application WO8
No. 2/04221 (Hardt, Magdon and Norful, published December 9, 1982). Molds made of thermoplastic mold materials (generally polypropylene) are described in U.S. Pat.
No. 4208365 and is described in each specification. In order to achieve the object of the present invention, one configuration of the present invention is to use the following divided spherical zone as a molding part, namely, a central spherical zone having a radius r ₁ and one edge.
A ₁ ; a first annular spherical zone A ₂ having a radius r ₃ and having an inner edge and an outer edge that are concentric with the central spherical zone A ₁ and in contact with the edges of the central spherical zone A ₁ ; and the first spherical zone A ₂ a second annular spherical zone A ₃ of radius r ₃ concentric with and in contact with _the outer edge of the first annular spherical zone _{A 2 ;
A3} A metal master mold for injection molding plastic replica molds, polished so that the joints transition smoothly into each other. According to the above configuration of the first aspect of the present invention, there are the following advantages. Three radii r 1 where the mold surfaces of the three zones A ₁ , A ₂ , A ₃ have their centers on the same center line, respectively _;
Since each zone of the mold surface is obtained as a spherical surface with accurate roundness because it is obtained by the arc locus of r ₂ and r ₃ , the mold surface can be easily cut by, for example, the rotational movement of the cutting tool of a lathe. This makes cutting work easier, reduces machining costs, and improves machining accuracy. At least zone A ₁ /A ₂ junction and A on mold surface
₂ /A ₃ When polishing the joints to ensure a smooth transition, each zone is a spherical surface with accurate roundness, making the polishing process easy, reducing polishing costs, and improving polishing accuracy. can improve product accuracy. At least zone A ₁ /A ₂ junction and A on mold surface
₂ /A ₃ Since the joints are polished for smooth transition, polishing the seed mold takes a lot of man-hours, but this mold can be used to mold a large number of contact lenses without the need for polishing the contact lenses. Therefore, the manufacturing cost of contact lenses can be significantly reduced. Further, another configuration of the invention for achieving the above object is as follows: a central spherical zone A 1 having one edge, a central spherical zone A ₁ that is concentric with the spherical zone A ₁ and that is concentric with the spherical zone A _{1 .}
a first annular spherical zone _A2 having an inner edge and an outer edge in contact with the edges of the first annular spherical zone A2; and a second annular spherical zone _A2 having an inner edge concentric with the first annular spherical zone A2 and in contact with the outer edge of the first annular spherical zone _A2 . A method for producing an optical surface of a metal master mold for injection molding a plastic replica mold for molding a hydrogel contact lens having a segmented spherical zone A ₃ , the method comprising: The following sequential steps are performed: (1) selecting a cylindrical metal blank and determining its optical center; (2) calculating the radius r ₁ to determine the central spherical zone A ₁ and correcting the resulting lens. Or determine the refractive power, calculate the radius r ₂ to determine the first annular spherical zone A ₂ and determine the nominal center thickness of the lens, and then calculate the radius r ₃ to determine the second annular spherical zone A ₃
(3) cut a radius r ₁ portion of the central spherical zone A ₁ in the metal blank to set _a predetermined center reference starting point; Cut _the annular spherical zone A ₂ until _{the desired} optical zone and nominal central lens thickness are obtained; (6) Cut the radius r ₃ to a predetermined diameter that defines the outer periphery and tapered shape of the lens, and (7) A ₁ /A ₂ junction. and polishing the cut metal special mold so that the three curved surfaces smoothly transition to each other at the A ₂ /A ₃ junction. Therefore, according to the other configuration of the present invention described above, in addition to the above advantages and, there are the following advantages. After determining the center reference starting point of radius r ₁ in the central spherical zone A ₁ and cutting the first annular spherical zone A ₂ , the actual cutting of the center A ₁ is performed for the first time, for example. Band A ₂
The radius r ₂ of band A ₁ is greater than the radius r ₁ of band A 1.
If A ₂ is flatter than band A ₁ (which is the case in the embodiment of the present invention), the cutting tool will cut the surface curvature when cutting band A ₁ first and then band A ₂ . There is a risk that the small band _A1 may be caught and damaged, but this fear can be eliminated and the band _A2 can be cut reliably and precisely, improving cutting accuracy and, by extension, product accuracy. These and other objects of the invention will become apparent from the following more detailed description and accompanying drawings.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a tricurved contact lens showing three distinct zones or regions in accordance with the present invention. FIG. 2 is a cross-sectional view of the lens of FIG. 1 taken along line 2--2. 3 and 4 are cross-sectional views of a lens according to the invention showing different lens thicknesses and corresponding variations in the spherical radius of each zone. Figure 5 shows the variation of the radius of the sphere and the variation of 3 along the common axis.
Figure 2 illustrates the calculation of a radius lathe stroke between two different centers of curvature. FIG. 6 is a cross-sectional view of the replica lens mold in the open position. FIG. 7 is a cross-sectional view of a metal master mold for forming an optical surface of a plastic replica mold. FIG. 8 is a sectional view of a metallic seed mold for forming the base curved surface of a plastic replica mold. FIG. 8A is an enlarged view of the taper of FIG. 8 defining the peripheral rim of the male portion of the plastic replica mold. FIG. 9 is a sectional view of another type of plastic replica mold injection molded from the metal master mold of FIGS. 7 and 8. FIG. FIG. 9A is an enlarged view of the peripheral rim of the plastic male portion of FIG. 9; SUMMARY OF THE INVENTION The present invention provides a prototype for making tricurved contact lenses, i.e., contact lenses with three distinct spherical radii defining three distinct regions including a central spherical surface that acts as an optical zone _A1 at the center of the lens. , and a method for manufacturing the optical surface of the seed mold.
The optical zone is a region of the lens that exhibits various desired capabilities, and the radius of the sphere that defines this region changes only as the capability of the lens changes. The typical diameter of this zone is approximately 8.50 mm, measured in the dry (unhydrated) state. The second zone or portion A ₂ is annular, tangential and concentric with the optical zone, and has a thickness that increases monotonically radially outward from the optical zone. This band has a flatter radius than the optical band and similarly varies depending on the capabilities of the lens. Although the optical properties of this second band necessarily change in conjunction with changes in the optical band itself, the purpose of the second band is primarily supportive. The spherical radius of this second zone is critical since it determines the thickness of the lens through a unique shaping process, as explained below. This means that different lens center thicknesses can be obtained by flattening or steepening the spherical radius of the metal master. Additionally, this band strengthens the lens by providing additional polymer mass to this area (ie, band) of the lens without adversely affecting the optical properties or wearability of the lens. The third zone _A3 has a taper of decreasing thickness outwardly from the optical zone and defines the outer diameter of the lens. The radius of curvature defining this zone is substantially constant. It is believed that the third zone A ₃ can be moved vertically independently of the other zones A ₁ , A ₂ , thereby changing the sagittal depth value. Various lens thicknesses are obtained by steepening or flattening the sphere radius. Please compare Figures 3 and 4. In a preferred form, the cast contact lens produced by the mold of the present invention has an inner sphere radius of 0.5 to
10.8mm, string diameter 12.5-18.0mm, and center thickness
A semi-spherical shell of 0.03 to 1.0 mm, preferably about 0.03 to 0.05 mm, ideally about 0.04 mm. The lens material is a hydrophilic polymer of 2-hydroxyethyl methacrylate crosslinked with ethylene glycol dimethacrylate. For use and sale, the lens is swollen to an equilibrium state with 0.9% sodium chloride solution, at which point its composition is 62% by weight of hydrophilic polymer and 38% by weight of water. When placed on the human cornea, the hydrated lens acts as a corrective refractive medium to compensate for the refractive error of the spherical or toric lens. The above hydrophilic polymer generally has a refractive index of 1.43 and a visible light transmittance of 97% or more. FIG. 5 illustrates the mathematical calculations required to produce a contact lens mold with three distinct spherical radii in accordance with the present invention. Figures 7, 8 and 8A will be described later in connection with a method for manufacturing a metal master mold. Preparation of metal master mold for optical band: A metal master mold 20 divided into two parts for manufacturing a replica lens mold was manufactured using an optical radius lathe in the following manner while referring to the distances shown in FIG. In order to obtain optical tricurved metal master molds of precise quality, a series of mold-making operations involving precision step-by-step machining, lapping, and polishing are performed, including performing the necessary mathematical calculations in advance. Ivy. The insert 22 defining the optical surface 24 was manufactured from a steel blank (254 mm) obtained from bar stock (Colt Industries, CSM414 stainless steel) (approximate dimensions 16
mm and then cut to 19 mm length).
The tapered hole 26 was then bored and reamed to obtain one blank face. The tapered bore had a Brown & Sharpe #2 lumen. This hole must be precisely positioned since other surfaces, including the optical surface, originate from this point. A 10-inch Hardinge toolroom lathe was used for this operation. The blanks thus produced were mounted on a coordinating Brown and Sharp arbor using the same machine and rotated with a concentricity of 0.005 mm. The optical blank was then turned to a finished diameter of 15.40±0.01 mm. A 5° square step was then cut into the blank to a length of 6.5 mm and a main diameter of 12.80 mm. A +5° taper with a -1° tapered step is cut into the front surface of the optical mold, and its finished dimensions are
12.58mm and 12.38mm, leaving a 0.50 step on the front shoulder with a radius of 0.50mm. Similarly, to hold the mold in place within the optical sleeve 28, the tapered lumen is inserted to a depth of 14.0 mm.
A 16-24 thread was cut. Optical sleeve 28 was made of A-6 tool steel and hardened to 56-58RC. The front part was bored to a diameter of 15.40 mm and a depth of 19.80 mm, and the optical mold 22 was placed here. For removal of the plastic replica mold cast from this metal master mold and for the specified wall thickness, an angle of 5° was provided at the front. This angle must be ground concentrically with the 19.50 mm diameter and the 15.40 mm inner diameter to avoid creating distortions in the plastic mold part that would impair the parameters and quality of the optical surface. The operations above that create the optical surfaces 24 are important because they control the focus, visual accuracy, and thickness of the lens. A Robertson radius lathe is adjusted for the proper tool height and center, and then a pre-tapered Braun & Shape tapered arbor is installed on the head stock spindle of the radius lathe for cutting a pre-tapered hole. The created mold blank was fixed. Firstly, to set the reference starting point, the radius r ₁ was set on the lathe dial, and the lathe touched and cut the center of the mold blank. Head stock is 3.0mm
was set. This procedure provided a reference starting point. The radius r ₁ determines the degree of correction or power of the resulting lens. The headstock was then set to a predetermined stroke after first calculating the various radii shown in FIG. The insert 22 was cut by setting the radius r ₂ and then adjusting the memory stop until the proper optical band 24 was obtained. The optical band was visually inspected with a tool making microscope (accuracy within 0.005 mm). Then the radius r ₁ was again set on the lathe dial, the lathe head was placed on the stroke again, and the corresponding A ₁ zone was cut into blanks and blended with A ₂ at the appropriate coordinates. Finally, the radius lathe was set to radius r ₃ (radius r ₃ is smaller than r ₁ and r ₂ and as it is cut into the mold blank it will overcome both, so no memory stop is needed). However, the radius r ₃ is the same as r ₁ and r ₂
Determined by calculating stroke and center thickness. Machining the tricurved metal master mold 20 is a rigorous, complex, precise, and long-term operation. The sags of all three curved radii must be harmonious and coincident with the sags of the base curves, thereby allowing a predetermined nominal center thickness (e.g.
0.04mm) is obtained. Since radius r ₂ is larger than radius r ₁ , care must be taken when cutting radius r ₁ to avoid scraping off the entire mold blank. The radius r ₂ is important because it determines the nominal center thickness of the lens. Grinding a tricurved mold is also an operation that requires care and precision. This is because the optical radius must have a tight focus, a perfect radial dimension, and a high quality surface finish that allows all three curved surfaces to blend into each other at the A ₁ /A ₂ and A ₂ /A ₃ interfaces. This was then mounted on a similarly machined Levins lens surface buffing machine with a Brown and Schiape arbor for adjustment. Various grades of abrasive compounds and wooden dowels were used. A separate dowel was used for each radius, each dowel having the required radius cut into it. First, a precise radius was sanded using a wooden dowel filled with No. 3 sanding compound.
The radii were polished in order of r ₁ , then r ₂ , then r ₃ .
The mold was rotated around the center while vibrating a wooden dowel of appropriate dimensions above. Various vibration angles, dispersion degrees and wood diameters were used for the corresponding radii to be polished. The polishing is considered complete at this point when all tool blemishes are removed and a tight focus is obtained. Final polishing was performed using a cloth-covered sponge pad impregnated first with No. 1 and then No. 1/2 diamond polishing compound. This gave the tricurved surface a tight focus and shine, and all scratches were removed from the steel surface. The numerical values for the optical surfaces of the lenses shown in FIGS. 3 and 4 and the lathe stroke shown in FIG. 5 are as follows.

[Table] (2) Varies according to desired optical ability.
Preparation of the base curved metal master mold: The base curved metal master mold 30 consists of two structural units, a base curve insert 32 and a bush 34. Both parts are made of 414 stainless steel as described above. Using the same equipment, bar stock is cut from 25mm to 13.0mm.
Turned to mm. Conbound installation on Harding lathe is set to 5°, 5° taper is 13.0
Turned from mm to 9.52 mm in diameter. At the same time diameter 9.52mm
A straight section was machined to a length of 10.0 mm. Diameter from 13.04mm with the same compound settings
An internal taper angle of 10 mm in length was machined into the bush 34 to 9.52 mm. Insert 32 and bush 34 should have precise tapers that fully engage each other. The taper fit is aligned with each other such that the 0.07 mm edge on the steel insert 32 provides a plastic replica mold with the desired parameters.
An arbor with a Harding 10-inch lathe spindle was used to secure the base curved bushing and turn the outside diameter to its appropriate dimension of 17.22 mm.
This ensures overall concentricity. The base curve insert 32 was then placed on the spindle of a Levin radius lathe and the tapered insert was machined to 0.005 mm concentricity where the base curve radius was machined. The appropriate sagittal depth was determined by the following formula: h=rV ₂ √4 ² − ² In the above formula, h is the total sagging height of the optical mold and the base curved mold, r is the radius defining band A ₁ or A ₂ , and C is the optical 1/2 of band diameter
In the case of Fig. 1, this is the string representing the band A ₁
1/2 of 8.50 mm, i.e. 4.25 mm, 1/2 of 10.50 mm for the sum of the diameters of bands A ₁ and A ₂ ,
That is 5.25mm. A peripheral radius was cut into the base steel using the same dial stroke calculation method used in manufacturing the mold defining the optical surface. A 15.90 mm diameter wooden wrap with a tapered hole on the back side of the wood that had the same radius as the required base radius and matched with Levin's single-axis buffing machine was attached to the Levin's buffing machine. The mold was attached to a wooden lap and supported by the wooden needles of a buffing board. about
A 30° rocking motion rotated both the wooden lap and the steel mold until all tool marks were removed and a smooth optical surface was obtained. Then the concave radius
The edge was placed into the mold insert using 6.84mm wood. This wood was mounted on a buffing machine with a base curved insert 32. It was supported by hands and placed on a rotating tree. This operation is 0.07mm
This process was repeated until 36 edges were obtained. Edge 3
6 (shown in more detail in FIG. 8A) is the mold 30.
Defining a flexible peripheral rim of a plastic replica mold manufactured from. Final polishing was done in the same manner as the optical curved mold 38. These two completed components 32 and 34 were fitted together and the insert was held in place with a 10-32 set screw 40. The diameter of the 5° angle optical mold 20 was 0.40 mm larger than the diameter of the base curve mold 30 to provide adequate space and escape of excess monomer. The 1° inverted taper acts as a guide for the base curved plastic component by preventing prisms within the lens. Plastic replica molds made of thermoplastic resin (eg, polyethylene) were manufactured from finished metal master molds by conventional injection molding techniques. The plastic replica mold is described in the above-mentioned U.S. Patent No.
No. 4,121,896, US Pat. No. 4,208,364 and US Pat. No. 4,208,365. Those descriptions are quoted here for reference. FIG. 6 shows one form of a plastic replica mold consisting of a male mold member 2 (which may be made of either soft or hard material) and a female mold member 4. FIG. The male member 2 includes a substantially cylindrical support segment 6 to the lower end of which a flexible rim 8 is attached. The cylindrical support segment 6 may be hollow, as shown, or it may be a solid mass of material. A flexible rim 8 is annular around the outer edge of the support segment 6. The support segment 6 is closed by a molded surface 12 attached around the bottom of the support segment 6, defining the base curve of the molded contact lens. The curvature of the molding surface 12 is chosen to match the optical requirements of the lens to be manufactured. The curvature of the complementary molding surface 18 includes three distinct zones as described above and defines the optical surface of the resulting lens. The optical zone may be entirely spherical, aspherical, or a combination of both. The female molding surface 16 that defines the back curved surface of the final lens is generally a spherical surface, but may be a toric surface, an aspheric surface,
Or it may be a combination of both. The female mold member 4 (which may be rigid or flexible) has a cylindrical support segment or wall 14 in a surrounding platform 16 and a cylindrical support segment 1
4 is included. The inner diameter of the female support segment 14 is slightly larger than the inner diameter of the male support segment 6 for easy insertion. Another form of plastic replica mold is the mold 9, which is injection molded from the metal master mold of FIGS. 7 and 8.
and FIG. 9A. FIG. 9A is an enlarged view of the flexible peripheral rim 8. The method of the present invention is not limited to truncated soft plastic contact lenses (ie, hydrogels in their hydrated state), although these are the preferred articles. Also included are hard or rigid contact lenses as well as soft hydrophobic contact lenses. The novel method allows contact lenses to be cast directly from the desired lens-forming material; no polishing of the optical surfaces is required; only slight finishing or buffing of the lens edges is required; overall processing has an advantage over prior art methods in that it is much less labor intensive than prior art methods. As with most soft lenses, the lens is washed with water to remove catalyst residue and unreacted monomers and then equilibrated in an aqueous or saline solution to obtain its final dimensions. By carrying out preferred aspects of the invention,
A variety of contact lenses exhibiting a wide range of cylinder powers, usually negative optical bending powers, are economically advantageous. The implementation produced by the inventive mold provides a novel product, a molded tricurved contact lens with three distinct zones or regions on the optical surface and a continuous smooth circumference. The optical power of the lens is 0 to -20 diopters, preferably 0.
~-8 diopters, preferably 0--6 diopters. Preferably, the novel article is a hydrogel, especially a hydrophilic polymer containing a predominant amount of 2-hydroxyethyl methacrylate (HEMA). Preferably, one of the molding surfaces, usually the male member, is provided with a flexible integral peripheral rim;
This will define the outer edge or rim of the resulting lens when practicing the preferred aspects of the invention. During the molding operation, the lens-forming material contracts (preferably during addition or during a condensation reaction), causing the flexible rim to bend inward, typically relative to the circumferential axis of the mold;
This causes the two mold members to approach each other. Regarding the flexible rim structure and materials, U.S. Patent No.
Reference is made to the specifications of No. 4121896 and No. 4208365. These descriptions are cited in their entirety by reference. Tricurved contact lenses made according to the present invention may be flexible hydrophobic lenses, such as those exemplified by unsubstituted and fluorine-substituted polyethylenes, silicone elastomers, and the like. Alternatively, the contact lens may be a so-called hydrophilic lens having a three-dimensional structure, such as a polymer of 2-hydroxyethyl methacrylate, or various hydrophilic collagen hydrolysates. Hydrophilic lenses are water-insoluble, water-swellable, and assume their final dimensions when immersed in water or saline. The resulting water-swellable lenses may be appropriately referred to as hydrogel lenses. Particularly useful monomers, prepolymers or vulcanizable mixtures in the practice of this invention include hydrophobic acrylic esters, especially lower alkyl acrylic esters (where the alkyl moiety contains 1 to 5 carbon atoms), e.g. Methyl acrylate or methacrylate, ethyl acrylate or methacrylate, n-propyl acrylate or methacrylate, isopropyl acrylate or methacrylate, isobutyl acrylate or methacrylate, n-butyl acrylate or methacrylate, or monomers thereof It includes various mixtures of. To increase dimensional stability and warpage resistance, the above monomers or monomer mixtures may be further mixed with small amounts of di- or polyfunctional types to cross-link the polymer matrix as the polymerization progresses. You can also make it happen. Difunctional or polyfunctional classes of this type include: Divinylbenzene, ethylene glycol diacrylate or methacrylate, propylene glycol diacrylate or methacrylate, and acrylic or methacrylic esters of the following polyols: triethanolamine, glycerin, pentaerythritol, butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol , mannitol, sorbitol, etc. Other crosslinking monomers include N,N-methylene-bis-
Included are acrylamide or methacrylamide, sulfonated divinylbenzene and divinyl sulfone. The above monomers or mixtures thereof can be further mixed with linear polymeric species as long as the viscosity of the solution or "casting syrup" formed does not become so great that bubbles are difficult to remove therefrom. Other monomer materials suitable for making lenses according to the invention are hydrophilic monomer mixtures that form three-dimensional crosslinked networks, such as those described in U.S. Pat.
It is described in the specification of No. 3822089. Examples of hydrophilic monomers include: Water-soluble monoesters of acrylic acid or methacrylic acid with an alcohol having one stellatizable water residue and at least one additional hydroxyl group, such as mono- and polyalkylene glycol monoesters of methacrylic acid and acrylic acid, such as ethylene Glycol monomethacrylate, ethylene glycol monoacrylate, diethylene glycol monomethacrylate, diethylene glycol monoacrylate, propylene glycol monomethacrylate, dipropylene glycol monoacrylate, etc.; N-alkyl substitution and N,N
- dialkyl-substituted acrylamides and motacrylamides, such as N-methylacrylamide,
N,N-dimethylacrylamide, N-methylmethacrylamide, N,N-dimethylmethacrylamide, etc.; N-vinylpyrrolidone; alkyl-substituted N-vinylpyrrolidone, e.g. methyl-substituted N-
Vinyl pyrrolidone; glycidyl methacrylate; glycidyl acrylate; others known in the art and also useful are vulcanizable silicone oils or elastomers. Preferably the alkyl and alkylene moieties in each group of compounds above contain up to 4 carbon atoms. Regarding hydrophilic monomers or mixtures thereof,
Preferably, a three-dimensional crosslinked network is formed. For this purpose, it is desirable to use small amounts of crosslinking monomers, such as hydrophobic acrylic esters and those discussed above with respect to the discussion of crosslinking methods (eg, radiation methods). Preferred monomer mixtures include at least one alkyl glycol monoester of methacrylic acid, especially ethylene glycol monomethacrylate, and at least one crosslinking monomer, such as an alkylene glycol diester of methacrylic acid, especially ethylene glycol dimethacrylate. Mixtures of this type may contain other polymerizable monomers, such as N-vinylpyrrolidone, methyl methacrylate, acrylamide, N-methacrylamide, diethylene glycol monomethacrylate and others mentioned above, preferably in minor amounts. The polymerization reaction can be carried out in bulk or using an insoluble solvent. Suitable solvents include water; organic solvents such as water-soluble lower aliphatic monohydric and polyhydric alcohols, such as glycols, glycerin, dioxane, and the like; and mixtures thereof. Generally, when a solvent is used, it accounts for a minor amount of the reaction medium, ie less than 50% by weight. Polymerization of the monomer mixture is usually carried out using free radical polymerization catalysts of the type customary for vinyl polymerization. Catalysts of this type include organic peroxides, parka carbonates, hydrogen peroxide, and inorganic materials such as ammonium peroxosulfate, sodium or potassium. Polymerizations using catalysts of this type can be carried out at ambient temperatures, ie, temperatures from about 20°C to about 120°C, depending on the desired polymerization rate. Polymerization is also carried out between the monomers or prepolymer mixtures under the influence of elevated temperatures or radiation (UV, X-rays or other known radioactive types). In the case of silicone elastomers, vulcanization appears to occur by a free radical curing mechanism, and in the case of two-component so-called RTV compounds, vulcanization appears to occur by substitution or condensation reactions. Patent specifications further describing lens-forming materials useful in the manufacture of contact lenses include, for example, U.S. Reissued Patents No. 27401; No. 3639524; No. 3699089;
No.; No. 3700761; No. 3822089; No. 4121896;
Includes specifications of No. 4208365 and No. 4223984. These are quoted here in their entirety for reference. Lens Casting: Two polypropylene molds were manufactured using injection molding equipment from the metal master molds described and described above. These two complementary types have predetermined parameters, one type being an optical surface plastic (female type) and the other being a base surface field (male type). 2-hydroxyethyl methacrylate (97.6%), ethylene glycol dimethacrylate (1.4%) and bis(4-t-
45 ml of a liquid monomer mixture consisting of butylcyclohexyl) peroxide carbonate (1%) was charged. After loading, the male mold was placed inside the female mold as shown in Figure 9, the loaded mold was placed in a furnace at a temperature of 125°C for 30 minutes to polymerize the liquid monomer, and the mold was removed from the furnace. Once cooled, the finished lens was removed from the mold and inspected for dimensions. Lenses made from a particular plastic mold that was injection molded from a steel master mold all had the same dimensions. These dimensions (all in mm) are as follows: Optical curved surface A-1 optical band = 8.50 All optical A-2 optical band = 10.50

【table】

【table】