JPS5923271B2 - How to manufacture soft contact lenses - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for easily manufacturing high-quality soft contact lenses that can be used continuously, with little variation in quality.

In order to enable continuous use of contact lenses, it is essential that the lens be designed so that a sufficient amount of oxygen is always supplied to the cornea. Naturally, it is effective to use a material with high oxygen permeability for this purpose, but a lens with a high water content can also ensure a smooth supply of oxygen to the cornea. . Against this background, various so-called soft contact lenses made of hydrogel have been proposed.
However, since it has a soft structure called hydrogel and requires satisfactory optical precision, conventional plastic molding methods cannot be used with high-quality, uniformly-varied software. It has been extremely difficult to produce contact lenses with good yield. The inventors of the present invention have made extensive studies to solve these problems, and as a result,
The present invention described below has been achieved. That is, in the present invention, a concave and convex mold is formed by injecting an excessive amount of a stock solution for producing soft contact lenses containing 5 to 95% by weight of a solvent into a concave mold, and then combining the convex mold and allowing the excess stock solution to overflow. Step B: uniformly filling the substantially sealed space between the molds with the stock solution; A step of manufacturing a lens with a tensile strength of O, lkgf/Cd or more, C. A step of immersing a mold in a liquid and peeling the lens from the mold in the liquid, and D. Extracting the peeled lens with water. and the visible light transmittance is the thickness O
, lwr! This is a method for producing a soft contact lens, which comprises a step of obtaining a hydrogel having an n content of 90% or more.

The stock solution for producing soft contact lenses used in step A refers to (i) at least one monomer that polymerizes to provide a hydrophilic component and/or at least one hydrophilic polymer;
It contains seeds, (;

Here, the monomers that polymerize to give hydrophilic components in Naruhei 1) include N-pinylpyrrolidone, N-vinylpiperidone, and N-vinylpiperidone.
- Hydroxyalkyl (meth) such as hydroxyethyl or hydroxypropyl esters of N-vinyllactam (meth)acrylic acids such as vinylcaprolactam
These include acrylate or mono(meth)acrylate of glycerin. In addition, a hydrophilic polymer is a crosslinkable hydrophilic polymer having a functional group sufficient to form a crosslink bond between hydrophilic polymers (post-crosslinking), and which provides the hydrophilic component. Examples include (co)polymerization of one or more monomers and, if necessary, a monomer for introducing a functional group into the polymer (monomer for introducing a functional group). . As the monomer for introducing a functional group, ptoxyacrylamide, glycidyl methacrylate, vinyl carbonate, etc. are used. The copolymerization ratio of the monomer and the monomer for introducing a functional group is generally preferably about 1000:1 to 10:1. Among these, those obtained by copolymerizing N-pynylpyrrolidone and a functional group-introducing monomer such as butoxyacrylamide are particularly preferred. In these cases, post-crosslinking can be carried out by heat treatment. Other examples of hydrophilic polymers include polyvinyl alcohol. In this case, since the hydroxyl groups in the polymer enable the post-crosslinking reaction, there is no need to newly introduce a functional group. Post-crosslinking can be carried out by using polyvalent isocyanate or polyvalent aldehyde as a post-crosslinking agent. Polysaccharides or proteins may also be used. More favorable results can be obtained by combining these monomers and hydrophilic polymers that polymerize to provide hydrophilic components with monomers and/or hydrophobic polymers that polymerize to provide hydrophobic components. . Monomers that polymerize to provide hydrophobic components refer to monomers that do not swell or dissolve in water even though they are not crosslinked when polymerized, and include (meth)acrylic esters, (meth)acrylates, ) Examples include unsaturated nitriles such as acrylonitrile and aromatic olefins such as styrene. When a monomer is used as component (j), it is desirable that the monomer that provides the hydrophobic component used in combination with the monomer is one that is difficult to copolymerize with the monomer of component (1). The above-mentioned hydrophobic polymer refers to a crosslinkable polymer that has sufficient functional groups to form crosslinks between hydrophobic polymers (post-crosslinking) and does not swell or dissolve in water. Such a hydrophobic polymer may contain one or more monomers that provide the hydrophobic component and, if necessary, a monomer for introducing a functional group (monomer for introducing a functional group). Examples include (co)polymerized ones. The type of functional group-introducing monomer and its copolymerization ratio are the same as in the case of the hydrophilic component described above. Polyvinyl butyral is also effective. The solvent may include water. It is also possible to add a substance that is solid at room temperature but is extracted with water, such as uncrosslinked polyN-vinylpyrrolidone. This can be considered a solvent. A particularly preferred stock solution for lens production in the present invention is one in which N-vinylpyrrolidone and methyl methacrylate are combined, and dimethyl sulfoxide and/or ethylene carbonate are used as a solvent.

Next, the mold used in the present invention will be explained. In the present invention, a mold with two types of unevenness is used. At least one of the molds must have a mold surface that determines the lens surface that is an interference spherical surface or an interference paraboloid (hereinafter, the interference spherical surface and the interference paraboloid are collectively referred to as an interference surface). Here, an interference sphere or paraboloid is a sphere or paraboloid whose main part has a surface roughness of 50 μm or less, which protrudes especially in the part corresponding to the lens periphery, and whose spherical or parabolic nature is It refers to what is lost in a part. It is preferable that the concave mold and the convex mold are designed to have line contact rather than surface contact. Examples of combinations of concave molds and convex molds used in the present invention will be explained with reference to the drawings. Figure 1 shows a concave mold 1 with an interference surface.
and a convex mold 2 having a non-interference surface (a surface that gives only a spherical or parabolic surface to the mold surface is collectively referred to as a non-interference surface), and is a particularly preferred mold for carrying out the present invention. , by using a concave mold with an interference surface, a lens with good lacrimal flow can be created, and an inner bevel (an inclined surface created around the concave side of the lens, which is difficult to attach to conventional contact lenses) (In the case of soft contact lenses obtained by the method of the present invention, there is no problem when wearing them even if there is no inner bevel.) Therefore, it is easy to produce contact lenses with high versatility and less variation in quality. Fig. 2 shows an example in which a concave mold 1 having an interference surface and a convex mold 4 having an interference surface are combined, and even when such a mold is used, the method of the present invention can be easily carried out. Although concave molds with non-interference surfaces can be used, except for special products, an outer bevel (an inclined surface formed around the convex side of the lens) is generally required. A concave mold with an interference surface is preferably used.A convex mold may have narrow grooves or small indentations around the mold surface.This creates protrusions around the concave side of the lens to promote tear circulation. If the indentation is symbolized, it can be used to identify the product type.The material of the mold can be plastic, metal, glass, etc., and it can be transferred from a positive mold, a combination of transfer and polishing, or cut and polished. In the process of cutting glass, it is necessary to use abrasive grains as a cutting tool.In the step A of the present invention, the stock solution for producing soft contact lenses is excessively injected into the concave mold, Then, by placing a convex mold, the excess stock solution is allowed to overflow.

Needless to say, this method includes a method in which the concave-convex molds are seated slightly apart from each other, an excessive amount of the stock solution is injected between them, and then the concave-convex molds are brought closer to each other. When using a mold that has a draft space 3 in the sealing part as shown in Figure 1, an excess amount of approximately 5 times or more of the overflow stock solution retained in the draft space is used. It is preferable to determine the amount of stock solution to be charged as follows. When the overflowing stock solution accumulates in the sealing part, the seal is completed, making it easy to obtain high-quality lenses.In this sense, the mold having a draft-shaped space in the sealing part as shown in FIG. 1 is suitable for the method of the present invention. suitable for implementation. The amount of stock solution to be charged can also be determined as follows. In other words, in order to transfer the stock solution to the gel manufacturing process, multiple molds are placed in a closed tank that is purged with an inert gas such as nitrogen if necessary. is set to be approximately 20% or more of the saturation partial pressure of the stock solution. By adding such an excessive amount of stock solution, not only can the lens be prevented from entrapping bubbles, but also it is possible to suppress subtle changes in the composition of the stock solution in the mold during gel production, resulting in extremely high quality. lenses can be obtained in good yield. One of the major problems when manufacturing soft contact lenses by the in-mold casting method as in the present invention is the problem of polymerization shrinkage.

In order to solve this problem, the present invention selects conditions in which the volume of the stock solution in the mold does not substantially change, and the following four methods are effective for this method. 1. By increasing the solvent content of the stock solution, the polymerization shrinkage rate of the stock solution is reduced.

However, if the solvent content is increased unnecessarily, the strength of the solvent-containing lens will decrease and peeling will become difficult. Therefore, it should be 95% or less. Using a mold that can change the volume of the two spaces by 1% or more, casting is carried out while applying pressure from the outside of the mold or while pressing the mold using a pressure difference between the inside and outside.

3. Cast at an internal pressure of 100 kgf/Cd or higher.

Methods of increasing the pressure include tightening the concave and convex mold assembly by external force, keeping the internal volume of the mold constant and heating the stock solution, and placing a concave mold and a convex mold facing each other in an autoclave and pumping or pumping the stock solution. There is a method of assembling a concave-convex mold by remote control after creating a high pressure by heating. 4. Polymerization shrinkage and thermal expansion are offset by changing the polymerization temperature over time, and after gelation until mold removal, the temperature is always higher than the minimum temperature at which the board does not cause cooling shrinkage. Keep it.

The most common means for producing lenses in step B of the present invention is heating, but other means such as light irradiation or electron beam irradiation may also be used.

It is necessary that the tensile strength of the obtained lens be 0.1 kgf/Cd or more. Gels with lower tensile strengths do not provide lenses with superior surface properties. If the lens formed in the mold contains a large amount of solvent, it is difficult to remove it from the mold intact.

The peeling of the solvent-containing gel from the template is preferably carried out in a liquid, particularly an aqueous solution. Either the concave-convex mold assembly is left as it is, or after one side is removed, the mold with the lens attached is immersed in a liquid. Submerged peeling can greatly reduce the damage rate to the lens. If the peeling operation is performed underwater,
Replacement of the solvent contained in the gel with water can be directly followed. Damage to the lens due to peeling is
This can also be effectively prevented by using a concave mold or a convex mold made of plastic. Due to the water replacement in the final step of the present invention, the visible light transmittance of the hydrogel is reduced to 0.000 mm at a thickness of
Lenses taken out from the mold, which must be adjusted to 90% or more per 1 mm, can be processed to have their sharp edges rounded.

If the shape of the lens is axially symmetrical, by aligning and fixing the rotation axis and the lens axis, it is possible to cut and polish not only the edges but also the bevel portion. Even if the lens shape is severely distorted, the edges can be cut and polished by lowering the rotation speed. If the lens contains a large amount of liquid and is unsuitable for cutting and polishing, it is best to dry it. When the liquid content is small, drying by placing it in a drying mold will reduce the amount of deformation caused by drying. If you want to dry quickly, or if the lens contains a large amount of liquid, support the lens in the gas with as little contact area as possible, and as the drying process progresses, the vapor pressure of the liquid in the gas will approach saturation. , less dry deformation is required. Burrs that occur on the edges of lenses containing liquid can be cut off by placing the lens on a table and using a knife. Alternatively, the burr can be removed by submerging the lens concave side down in the liquid and vigorously vibrating the bottom of the container. The method of the invention offers irreplaceable advantages in the production of hydrous contact lenses made of composite materials.

Here, the term "hydrous contact lens" generally refers to a soft membrane with an optically smooth and transparent surface that is placed inside the eye. With the method of pre-embedding a non-water-containing object in a water-absorbing polymer, processing it into a lens shape, and then absorbing water, it is industrially difficult to cut such an object into a predetermined shape. Not only that, but the dimensional change rates due to water absorption of both proboscis bodies were significantly different, resulting in deformation and impractical use. There is no problem in accurately creating a lens-shaped composite object in the concave-convex wave type intrapolymerization. Next, if the dimensional change (water displacement coefficient of linear expansion) when treated with water is set to O, the shape will not be lost. If the water displacement coefficient of linear expansion is preferably kept within ±0.05, the shape will be less likely to deteriorate. This is possible by adjusting the composition of the stock solution, especially the solvent content. Applications for composite soft contact lenses include: (1) soft contact lenses with a reinforcing ring around the periphery to prevent tearing, (2) reinforcing rings to tighten sutures for intraocular implant lenses, and (3) human corneas. There is.

Comparative Example 1 A convex mold with an interference spherical surface (radius of curvature R1 = 5.8 m at the center) as shown in Fig. 3 and a concave mold (radius of curvature R2 at the center) with an interference spherical surface (with protrusions 5 on the periphery)
=5.8rfm, inner diameter S=10w! n) using
Manufactured soft contact lenses.

The thickness T at the center of the space between the concave mold and the convex mold is 0.5
Both of the uneven molds were made from fluoroethylene fluoropropylene resin (FEP) by cutting and polishing.
The stock solution used had the following composition.

2-hydroxyethyl methacrylate (HEMA)...
...100g Ethylene glycol dimethacrylate (EGDMA) ...0.1g Azopisisobutyronitrile (AIBN) ...0.3g Pour the stock solution into a concave mold until it overflows, and make a convex mold. Placed the mold.

There were almost no air bubbles. The uneven mold assembly was held between clamps and heated in an air bath. beginning 20
Tighten with kgf and keep at 60℃ for 0.5 hours, then 80k
gf and kept at 100°C for 1.5 hours. After cooling to room temperature, the clamp was removed. When the concave and convex molds were pulled apart, the lenses often adhered to the concave molds. Lenses left in the mold often have a slight gap between them, so we were able to use a vacuum to suck them out. What could not be absorbed could be absorbed by pressing the mold with one's fingers to deform it. When the lens was boiled in water for 1 hour, it became a transparent, water-containing soft contact lens. The tensile strength of the water-free lens removed from the mold is 50kgf/C
tl or more, the water content of the water-containing lens was 37%, the light transmittance of the water-containing lens (relative to the total thickness, the same applies hereinafter) was 90%, and the tensile strength of the water-containing lens was 8 kgf/d.

Comparative Example 2 A convex mold having a non-interference surface of R1=solid and having a shape close to a paraboloid of revolution was manufactured from glass by a polishing method.

A soft contact lens was manufactured using this convex mold and the same concave mold as used in Comparative Example 1. The stock solution used had the following composition. N-vinylpyrrolidone (NV
P) ...70g methyl methacrylate (MM
A) ...30g tetraethylene glycol dimethacrylate (TEGDlVA) ...0.0
5g triallyl isocyanurate (TAIC)...
...0.1g AIBN...0.03g Fill the mold with the stock solution in the same way as Comparative Example 1, and
After 0.5 hours at 100℃ with a force of 30kgf, 120
C. for 1.5 hours, and the uneven mold was separated while still hot.

In many cases, the lens is not strongly adhered to the convex mold. If the surface of the convex mold was very clean, the adhesion was so strong that it could never be removed even after cooling. If the lens does not come off, just soak it in water for 3 hours and it will peel off naturally during that time. A transparent hydrous soft contact lens was obtained. The tensile strength of the water-free lens removed from the mold is 50 kgf.
/Crli or more, water content of water-containing lens 68%, light transmittance of water-containing lens 88%, tensile strength of water-containing lens 12kgf
/Cd. Example 1 The same mold as in Comparative Example 1 was used.

The stock solution used was the stock solution of Comparative Example 1 with 50 g of glycerin added. Approximately 50 μl of the stock solution was poured into the concave mold in excess, and the convex mold was gently placed on it.

There were almost no air bubbles. It was held in a clamp and heated in an air bath. The mold was allowed to cool to room temperature, the clamp was removed, and the uneven mold was separated. The lens was attached to the mold, so it came off naturally after being boiled in water for an hour.
The lenses were transparent, water-containing soft contact lenses.
The tensile strength of the solvent-containing lens taken out from the mold is 6 kgf/
Cd, the water content of the water-containing lens was 38%, the light transmittance of the water-containing lens was 90%, and the tensile strength of the water-containing lens was 8 kgf/d. Example 2 A concave mold was manufactured from low density polyethylene resin (PE) by injection molding.

R2=7.5Tm, S=13 meters, and T=0.9m.
In order to improve the sphericity, the thickness of the spherical part is 1.5wr!
n is almost uniform, with a wall thickness of 1.5 rwt and a width of 5 m on the periphery.
A rim of 3,000 kgf/Cd was injected into the mold from a part of the rim at a high speed. The smoothness, sphericity of the peripheral area, and sphericity were excellent enough to pass the following experiments. A glass bead with a diameter of 16 mm was used as a convex mold, and soft contact lenses were manufactured from a stock solution having the following composition.
HEMA...70g NVP...30g Acrylic acid...2g
EGDMA...1.5gTAIC...
0.5g ammonium persulfide (APS)...
2g ethylene glycol ・・・・・・15
0g water...
An excess of 20 μl of the 150 g stock solution was poured into the concave mold, and the convex mold was carefully dropped into the center.

If air bubbles were introduced, the process was redone. It was clamped with a force of 0.5 kgf and immersed in water for polymerization.

After 16 hours at 60°C, it was heated at 90°C for 4 hours.

After loosening the clamp and leaving it overnight, the water temperature was lowered to 60° C., and the uneven mold was separated in water. When the mold was left in water, it peeled off naturally within 5 hours. High water content (
(about 75% in heavy water with a pH of 8), so the strength of the lens was very low (1 kgf/Cd), but a soft contact lens with no edge loss was obtained. In order to determine the approximate value of the tensile strength of the solvent-containing lens, it was heated at 90° C. for 4 hours, then taken out into the air, the uneven mold was separated, and the solvent-containing lens was peeled off with tweezers.

At this time, the tensile strength is 2 to 0.5 kgf/C from the feel of the finger.
It was estimated that d. Water content of water-containing lens 75%, light transmittance of water-containing lens 85%, tensile strength of water-containing lens 1kg
It was f/Cd.

Example 3 The convex mold used in Example 2 was used.

The concave mold is a non-interference spherical surface made of glass, R2 = 7m, S = 1
3rfrm, T=1r1m was used. Since both molds had non-interfering surfaces, the lens had a thick crescent-shaped cross section, and although such a lens has little practical use, it caused almost no problems in manufacturing experiments. The composition of the stock solution is as follows.

NVP...70g MMA゜゜゜゜゜''30g TAIC...1g Vinyl methacrylate (Me)...0,3
gTEGDMA...3g Azobisdimethylvaleronitrile (ADVN)...0.3g Dimethyl sulfoxide (DMSO)...400g High rigidity, pressure resistance 5000kgf/Cr! The concave mold was placed in an autoclave, the stock solution was poured into the autoclave, the convex mold was dropped, and the autoclave was covered.

Heating was at 40°C for up to 9.5 hours and at 50°C for up to 11.2 hours.
℃, up to 13.7 hours at 60.゛℃, 7 to 14.1 hours
0℃, 80℃ until 14.9 hours, 90℃ for 15.8 hours
After reaching ℃, it was left for up to 18 hours. While being careful not to let the autoclave cool, the uneven mold assembly was quickly taken out and immediately immersed in the treatment solution. The processing liquid is DMS
After 5 hours in an O7Ol% aqueous solution (95°C), the uneven mold was separated and immersed in a DMSOlO% aqueous solution (95°C) for 5 hours. During this time, the lens naturally peeled off from the mold. Although the lens periphery was very thin, no defects were obtained. When the lenses were boiled in water overnight, they became transparent soft contact lenses. In order to obtain an approximate value of the tensile strength of the solvent-containing lens, the uneven mold taken out from the autoclave was separated in the air, and the solvent-containing lens was peeled off with tweezers.

At this time, the tensile strength is 1 to 0.1 kgf/d based on the feel of the finger.
I estimated it to be Teido. The water content of the water-containing lens is 75%, the light transmittance of the water-containing lens is 85%, and the tensile strength of the water-containing lens is 4 kgf.
It was /d.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of a mold used in the present invention. 1: concave mold with interference surface, 2: convex mold with non-interference surface, 4: convex mold with interference surface.

Claims (1)

[Claims] 1. By injecting an excessive amount of the stock solution for soft contact lens production containing 5 to 95% by weight of solvent into the concave mold, and then combining the convex molds and allowing the excess stock solution to overflow, the space between the concave and convex molds is substantially The process of uniformly filling the sealed space with the stock solution, and then polymerizing the stock solution in the mold under conditions that do not substantially change the volume of the stock solution sealed in the mold, creates tensile strength in the mold. is 0.1kgf/cm
The process of manufacturing 2 or more lenses, the process of immersing the mold in a liquid and peeling off the lens from the mold in the liquid, and the process of extracting the peeled lens with water, so that the visible light transmittance is 0.
．． A method for producing a soft contact lens comprising the steps of obtaining a hydrous gel having a hydrous gel content of 90% or more per mm.