TW457189B - Method and mold for casting contact lenses - Google Patents

Abstract

A method of molding contact lenses in a mold made from a polyvinyl chloride material which lacks ultraviolet stabilizing agents produces an improved lens surface.

Description

457189 V. Description of the invention (1) Background of the invention The present invention relates to a method for casting contact lenses, and in particular, it relates to the improvement of the material of the contact lens casting wedge in which the lenses are washed and cast. Various techniques for casting contact lenses are known in the art, including stationary casting and ballasting. The static casting method includes filling a certain amount of a polymerizable monomer mixture into a mold assembly 'and allowing the monomer mixture to be matured by, for example, radical polymerization of the monomer mixture while the monomer mixture is held in the mold assembly. To form a lens. Examples of free radical reactions of cured lens materials include thermal radiation, infrared radiation, electron beam radiation, gamma radiation, ultraviolet (UV) radiation, visible light (including blue light), and similar reactions; a mixture of these technologies can be used . The mold combination defines the mold cavity of each lens, including the mold before the front lens surface and the mold after the rear lens surface. U.S. Patent Specification No. 5,271,875, all of which is incorporated herein by reference, describes the static casting method, which permits the production of a finished lens in a cavity defined by a front mold and a back mold. One specific embodiment described in the patent specification includes the use of polydienes in a front mold and polyvinyl chloride (PVC) in a rear mold. The maturation of the mirror-forming monomer mixture held in the mold cavity of the mold assembly can be achieved by free radical polymerization, especially by direct UV radiation that penetrates the polypropylene mold. One of the disclosed advantages of the combination of the prayer mold material is that the PVC of the front mold proves that it has a higher affinity for the cured lens material than the polypropylene of the rear mold, so it is determined that the cured lens remains in front when the mold combination is decomposed Within the mold, that is, when the front and rear molds are separated, the lens is selected to remain in the front mold. As known from U.S. 5,27 1,875, polyvinyl chloride indicates appropriate contact

457 1 89 V. Description of the invention (2) Mirror casting material. However, in the method described in U.S. Patent No. 5,271,875, it is important that the UV radiation is directly passed through the polypropylene mold. This is because polypropylene allows UV radiation to penetrate therethrough, and therefore UV radiation improperly penetrates through a mold made of a conventional PVC resin. In other words, due to improper transmission of UV radiation through pVc molds, attempts to cast contact lenses in molds made of conventional PVC resin have resulted in improperly cured lenses β Improper curing can cause various problems, such as inconsistencies Quality lenses, surface adhesion and / or surface defects. It is also known to cure contact lenses by casting a carcass mixture in a mold made of PVC, the mold including forming the surface of the desired lens surface, wherein the monomer mixture in the rotating mold is exposed to UV Radiation is ripening. In such a rotary casting operation, the rotation of the mold can be controlled so that the lens surface is formed later. Alternatively, the excess monomer mixture can be filled into a mold, and then the curing of the lens forming object is performed, and the surface of the lens can be turned afterwards by rotating the casting object. In both cases, the rotary recording system is opened from above, while the UV-radiated system is focused on the monomer mixture from above. SUMMARY OF THE INVENTION The present invention relates to the function of casting cast contact lenses in a mold made of a PVC material, in which the radiation directly penetrates the PVC mold to cure the lens material. PVC molds lack UV absorbers that are conventionally added to PVC resin stabilizer packages. More specifically, the present invention relates to a method for casting contact lenses in a mold assembly, which is composed of a rear prayer mold including a prayer mold surface defining a rear contact lens surface and a correction mold surface including a front contact lens surface.

Page 5 457189 V. Description of the invention (3) The composition of the front mold. The monomer mixture is filled into the cavity of the mold after the filling and between the surfaces of the mold of the front mold, and then held in the cavity of the mold, the monomer mixture is subjected to radiation to form a lens. One of the front and rear molds is made of polyvinyl chloride without UV absorber, and the radiation is directly transmitted through the mold made of polygas and shines on the monomer mixture in the cavity of the mold. The PVC resin formula contains a UV stabilizer package that contains some type of UV absorption sword. It was found that the use of PVC resins without such UV absorbers can be used to mature contact lenses, which has led to various improvements in the manufacture of contact lenses, such as' mirror lenses with reduced adhesiveness and improved optical quality, and improved lens coverage. Detailed description of the ability to handle the week β The invention can be applied to casting custom contact lenses, such as those generally considered to be soft hydrogel lenses, which are prepared from monomers comprising at least one hydrophilic forming lens. Conventional hydrophilic monomers include: hydrophilic (meth) acrylates such as hydroxyethyl acrylate, hydroxyethyl acrylate, and glyceryl methacrylate; and hydrophilic vinyl-containing monomers such as -Acetylam, slightly hydrolyzed, hydrophilic (meth) acrylamides, for example, tetra-dimethacrylamide; and (meth) acrylic acid, including methacrylic acid and acrylic acid. The hydrophilic monomer can be used as a cross-linking agent or individual cross-linking agents' which can be used in the monomer mixture, for example, diethylene glycol acrylate or dimethyl acrylic acid tetraethylene glycol. In addition, since the monomer mixture is matured by free radical photopolymerization, that is, exposure to radiation, such as UV radiation, to induce polymerization of the monomers that form lenses in the monomer mixture, the monomer mixture generally includes Trace initiation of free radical polymerization known in the art

457189

5. Description of the invention (4) Agent. If desired, the 'monomer mixture may further comprise a non-reactive solvent or diluent, or other components known in the art. A monomer mixture comprising lens-forming monomers is filled into a mold cavity defined between the lens casting surfaces of the front and rear prayer dies. The smallest of these molds are light shots made of PVC and inducing polymerization, preferably UV radiation that directly penetrates the mold. The PVC mold contains no UV absorbers, including those conventionally included as part of a PVC resin package, allowing the lens material to be more fully cured by photopolymerizing radiation. Alternatively, both the front and rear molds are made of PVC resin without UV absorber, while UV radiation is directly penetrated through the rear mold to irradiate the monomer mixture held in the cavity of the mold. Due to exposure to ambient UV radiation, commercial PVC resins typically contain stabilizers, such as UV absorbers, radical scavengers, or quenchers, to prevent yellowing of the cast product or deterioration from other aspects of weathering. Examples of stabilizers conventionally included in PVC resin packages are hydroxybenzotrimethylene, 2-acrylbenzophenone, phenyl salicylate, and cyanoacrylate. Hindered phenols and pyridine derivatives are commonly used as group scavengers, but quenching agents are usually cobalt, nickel or a salt or adduct of rhenium. Because of their tendency to impede the polymerization of lenses, the use of quenchers in contact lens and lens molding materials is limited. The advantage of the present invention over the aforementioned method described in US Patent Specification 5, 271,875 is that both the front and rear molds can be made of PVC resin and is not limited to the location of the radiation source. Also, thermoplastic resins, for example, polypropylene Larger tendency to absorb oxygen than PVC. As disclosed in U.S. Patent Specification 5'681,510, the dissolved or free oxygen in the contact lens mold can be transferred.

Page 7 457189 V. Description of the invention (5) Moved to the interface between the casting surface of the contact lens mold and the surface of the lens, which inhibits the radical polymerization of monomers that form the lens (thus affecting the quality of the lens surface at that interface) And / or increase the adhesiveness of the lens surface (thus making it more difficult for the user to handle the lens). However, the present invention makes it possible to use only a PVC mold, thereby avoiding problems caused by the transfer of oxygen from a thermoplastic mold to a casting mirror. The following examples serve to illustrate the invention. Example 1 Except that the rear mold is made of PVC without any UV stabilizer, the cast lens is generally manufactured in accordance with the method of U.S. Patent Specification No. 5, 2 71, 8 7.5. The PVC resin made by this custom is obtained from Georgia Gulf and is spray-casted into a contact lens casting lens using a conventional spray casting method. A monomer mixture mainly composed of hydroxyethyl methacrylate is charged into the casting surface of the front mold, and the subsequent mold is placed thereon to form a casting cavity. The UV light directly penetrates the back mold to mature the lens-forming material in the mold cavity. After the curing process, the rear and front casting surfaces decompose; the cymbals remain with the front binding. The lenses are then hydrated to help peel off the front mold. Develop an experiment to determine the adhesiveness or self-adhesion of the back surface of the contact lens to the binding surface of the rear mold. Fold the lens in half so that the surface of the posterior septum lies on itself. Next, place the folded lens between a pair of cover and glass bars. Place the weight on the cover glass strip, leaving a portion folded over the edge and holding it outside the cover glass strip. The weight was applied for 2 minutes. Remove the lens from the cover glassy strip and cut into strips, leaving a 2 mm free edge at the end of the strip

457189 V. Part (6) of the invention description. Tef 1 on tape is attached to the free edge portion, and one tape edge is clamped on the top and the other tape edge is clamped on the Instron Tensile Tester ) Clip on. With the sample in the clamp, the test area of Enzhuang was immersed in the hydration tank, and the sample was allowed to hydrate for 5 minutes. The force required to separate the two lens strips was then determined under the following conditions: crosshead speed-6.4 millimeters per minute, load cell-254, gage length-5 mm, and sample width 5 mm. Calculate the average peel strength of the samples and report the average of 10 samples. 04 克 / 毫米 压力。 For the cast lens made of PVC mold without UV stabilizer before and after, the separation of the rear lens requires 0.04g / mm pressure. Comparative Example Following the previous general test method ', other lenses were made with the following results:',

C1 represents the average of 10 lenses made by the method previously described by the spin casting action. A PVC front mold was used, and the surface of the mold was filled with an excess amount of the mixture, and the monomer was rotated while exposing the monomer to a biting light to form the compound. Immediately after the curing process, the combination of turning the rear mirror m and turning the cast / lathe (C1), for example, illustrates a lens with a rear surface that is fully cured without being exposed to a mold material with a high oxygen content.

Page 9'457189 V. Description of the invention (7) C2 means the same average of 10 lenses. The post mold and the conventional PVC resin are made of polypropylene. The lens is made of polypropylene. \ 成 丙% 月 ^ 模 ^ Casting scales are made, as in the example Bu C3 also represents the flat lens of 10 lenses and the front mold system m. However, the post-polypropylene scale model 'is described in polypropylene 5,681,510. The model is based on the US patent instruction sheet. The green fruit should refer to the special lens, which is a PVC post-molding mold containing stabilizers. Casting mirrors !: Brother Λ revolving casting / lathe (ci) and those lenses made of polypropylene Those made by the rear mold (C3) have the same force to separate the lens surface. The results of this data indicate that the lens surface was not glued together after the lens of Example 1 when folded onto itself, even under pressure. The use of PV C without samarium stabilizer does not require special heat treatment of the substance or mold, such as the degassed polypropylene substance of U.S. Patent Specification 5,681,510. The invention is not limited to the specific embodiments specifically disclosed herein. Many other improvements and variations of the present invention are possible for those familiar with the scope of the teachings herein, and it is understood that within the scope of a patent application, the invention may be practiced except as specifically described herein.

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Claims (1)

457188 VI. Application for patent scope 1. A casting surface including a rear mold and a surface in a mold, which includes: mixing monomers inside the cavity 'and preserving UV radiation to form a mirror before and after, and UV Order 2 in the cavity of the radiation prayer mold According to the applicants, it is a method of casting contact lenses from a photo combination that does not include UV penetration molds, in which the front mold is cast, and the true rear mold includes a defined rear-shaped spectacle lens table. The front mold contains the casting surface that defines the front contact lens surface. After the filling is filled and the mold between the casting surfaces of the front mold is held in the cavity of the mold, the monomer mixture is exposed to the sheet. Otomo: Directly pierce the in vivo mixture with a mold made of polyvinyl chloride. The method of the first item of the scope of interest is Pu 丄 m ,,. In the anxiety, in which the two absorbents of the front and back molds are made of polyphenols, Fe,, ^ ^ ^ Tellurium I, and UV radiation is directly shot on the cast Twig > monomer mixture within eight. 11th stomach