JPS6339409B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of molding a plastic lens, and more particularly to a method of positioning a mold surface forming a lens surface.

Plastic lenses are sometimes manufactured by injection molding or compression molding of thermoplastic resins such as polycarbonate and poly(meth)acrylates, but cast molding is usually used to manufacture plastic lenses with excellent performance and physical properties. is used. Liquid curable compounds that serve as raw materials for plastic cleansing include monomers and prepolymers having one or more α, β unsaturated groups, and monomers and prepolymers having α, β unsaturated groups and condensation polymerizable groups such as epoxy groups. There are polymers and various other compounds that can be cured by polymerization. Specific examples include diethylene glycol bisallyl carbonate, (meth)acrylic acid ester, diallyl ester, and triallyl isocyanurate.

Among plastic lenses, menega lenses in particular require precise precision and high physical properties such as impact resistance, scratch resistance, and transparency. Currently, diethylene glycol bisallyl carbonate called CR-39 is widely used as a raw material for eyeglass lenses. This homopolymer of CR-39 or a copolymer containing CR-39 as its main component has excellent physical properties such as transparency, impact resistance, and scratch resistance, and can be used as the best eyeglass lens. .

Cast molding of plastic lenses involves (A) filling plastic raw materials such as monomers into a cavity between two molds held by a gasket;
It is usually done through three basic steps: (B) curing it by heating, etc., and (C) then removing the mold and taking out the lens. In step (A), the gasket is made of a flexible material such as rubber, elastomer, or relatively soft synthetic resin, and two molds, usually made of glass, are assembled to this gasket. The opposing surfaces of the two molds have curved surfaces necessary for the lens. Plastic raw materials such as monomers are filled into a cavity formed between these two molds and sealed with a clamp or the like to prevent leakage. In step (B), the mold filled with the raw material assembled in (A) is placed directly into a heating furnace or the like to harden the plastic raw material. In order to minimize distortion of the lens and ensure uniform polymerization, curing often takes at least several hours, usually over a day and a night. In the (C) process, the assembled mold is removed and the lens inside is taken out. At this time, the gasket is often cut to make it easier to remove, and the gasket is not reused, but the glass mold is Often reused for molding.

The biggest problem with cast molding of this plastic is the gasket. Plastic raw materials such as CR-39 have relatively large shrinkage during polymerization and curing. For this reason, the gasket needs to have a certain degree of flexibility, and if this flexibility is not sufficient, the volume of the mold gap will not be able to follow the shrinkage of the plastic raw material, resulting in peeling between the mold and the plastic raw material. Further, since polymerization curing usually requires long heating, the gasket is also required to have heat resistance. In addition to both, the gasket material also needs to be inexpensive. That is, since gaskets are usually used only once, there is a problem that unless the materials and molding costs are low, the cost of gaskets in lens molding becomes too high.
For example, there are many types of lenses, and the shapes of gaskets vary accordingly, creating the problem of having to prepare many types of gaskets. Even if the material of the gasket is inexpensive, the cost of molding it (for example, the cost of the mold) cannot be ignored.

Additionally, the gasket requires features for mold alignment. For example, aligning the centers of the surfaces that form the lens surfaces of two molds, aligning the slopes of the surfaces (i.e., the axes coincide), or adjusting the distance between the two surfaces to a predetermined distance. (regulation of lens thickness), etc. Furthermore, lenses for astigmatism and the like may require other alignment. For this reason, the gasket needs to be a molded product with an accurate shape. On the other hand, for the above-mentioned reasons, the material of the gasket needs to have a certain level of flexibility; therefore, gaskets made of such flexible materials are prone to misalignment of the mold, making it difficult to align the mold.

Therefore, the inventor separated the functions of the gasket and
We considered aligning the mold without relying on gaskets. On the other hand, the inventors have discovered a method of molding plastic lenses without using gaskets. Therefore, the inventors of the present invention proceeded to study a method for assembling a mold in order to assemble the mold accurately and mold a plastic lens without using a gasket. As a result, they discovered a method for determining the positions of two molds by bringing them into contact via a positioning spacer with a predetermined shape. This positioning spacer is removed from between the two molds after the two molds have been positioned. When using a method that does not use a gasket, the two positioned molds are sealed with tape or the like tightly attached to the periphery to form a cavity, and the plastic raw material is hardened within this cavity.

The positioning spacer can have a similar shape to a conventional gasket. However, since there is no need for material restrictions, especially flexibility, a hard material such as hard plastic that is less deformable can be used.
FIG. 1 shows a cross-sectional view of a conventional mold assembly consisting of two molds and a gasket.
This gasket can also be used as a positioning spacer in exactly the same shape. This positioning spacer is removed before filling the plastic material as described below. The mold assembly consists of two molds 1 and 2 and a gasket 3. The molds 1 and 2 are disk to cylindrical glass molds. Assuming that the plastic lens to be molded is a meniscus type concave lens having a spherical surface, the mold 1 has a concave spherical surface 4 and the mold 2 has a convex spherical surface 5 as shown. The gasket 3 is made of a flexible material such as soft vinyl chloride resin, and is a cylindrical gasket having a convex portion 6 in the circumferential direction on its inner surface. These two molds 1,
The space between the opposing spherical surfaces 4 and 5 of the lens 2 and sealed by the gasket 3 becomes a cavity 7, and the plastic raw material is hardened within this cavity 7 to form a lens. The positioning of the two moldings 1 and 2, that is, the positioning of the two spherical surfaces 4 and 5, is performed by a gasket 3. First, the distance between the two spherical surfaces 4 and 5 is determined by the width of the convex portion 6 of the mold 3, and this distance is related to the thickness of the lens to be molded. To align the centers and axes of the two spherical surfaces 4 and 5, the inner surface of the gasket 3 and the upper and lower surfaces of the convex portion 6 are used. The axis of a spherical surface is a line that passes through the center of curvature of the spherical surface, and is usually a line that connects the center of curvature and the center of the surface. The alignment of the axes of the two spherical surfaces becomes the optical axis of the molded lens. Since the two surfaces are spherical surfaces, the centers of the spherical surfaces may be slightly shifted as long as the axes match. The coincident axes are indicated by a dash-dotted line 8. In order to position the axes and centers of these two spherical surfaces 4 and 5, the inner surface 9 of the gasket 3 is
Also, the upper surface 10 and lower surface 11 of the gasket convex portion 6 are utilized. The inner surface 9 of the gasket 3 contacts the side surface of the mold, the upper surface 10 of the gasket convex portion contacts the peripheral portion of the spherical surface 4 of the gasket 1, and the lower surface 11 contacts the peripheral portion of the spherical surface 5 of the gasket 2. These contact surfaces also serve as a seal for the cavity 7.

As mentioned above, the gasket 3 is flexible. Therefore, since the gasket 3 is easily deformed, the two spherical surfaces 4 and 5 are easily displaced. for example,
The width of the convex portion 6 tends to change due to the force with which the two molds 1 and 2 compress the gasket convex portion 6. Also,
When compressed unevenly, the spherical surfaces 4 and 5 of 2 tend to be relatively inclined. Further, when a force in a direction perpendicular to the axis 8 is applied to the mold, the two spherical surfaces 4 and 5 tend to shift in this direction.

The gasket 3 shown in FIG. 1 can be used as a positioning spacer in its original shape. At this time, it is preferable to use a hard material in order to prevent the occurrence of deviation between the two spherical surfaces. In this case, the first
After positioning the molds as shown in the figure, move the two molds relatively in the axial direction while preventing the molds from moving in any direction other than the axial direction, remove the positioning spacer from between the molds, and then remove the positioning spacer from between the two molds. The molds are brought close together again and fixed at a predetermined distance, and then an adhesive tape or the like is wound around the side surfaces of the two molds to bring them into close contact to form a cavity. When using a positioning spacer having the same shape as the gasket of FIG. 1, the inventors have found that there is room for further improvement. By using a positioning spacer, the mold can be positioned more accurately than when using a gasket, but if more precise positioning is required, a positioning spacer with the same shape as the gasket may not be sufficient. I found out. The problem lies in the shape of the convex portion (the portion corresponding to the convex portion 6 of the gasket 3) present on the inner surface of the positioning spacer. Since the upper and lower surfaces of the convex portion contact the spherical surface of the mold, these surfaces must also be corresponding spherical surfaces. If the gasket is flexible, it can be compressed and brought into close contact even if it is not an exact spherical surface.
A hard positioning spacer must have a spherical surface that can make accurate surface contact with the spherical surface of the mold.
Otherwise, the portion of the mold that contacts the spherical surface may become unstable and may shift or tilt. Furthermore, if the contact surfaces between the inner surface of the positioning spacer and the side surface of the mold are not completely in contact with each other, there is a risk that the mold will shift. Therefore, the dimensional accuracy and shape of the positioning spacer are required to be extremely accurate, and at the same time, the dimensional accuracy and shape of the side surface of the mold are also required to be accurate.

The present inventor conducted research and study on the shape and positioning method of positioning spacers in order to more accurately and reliably position the mold. As a result, they discovered that these problems can be solved by using a positioning spacer that can position the mold by substantially making linear or dot-like contact with the curved surface of the mold that forms the plastic lens. . The present invention relates to a method of forming a plastic lens by positioning a mold using this positioning spacer, that is, assembling two molds having curved surfaces for forming the surface of the plastic lens. In a method of molding a plastic lens by curing a plastic raw material containing a liquid curable compound as a main component within a cavity formed between opposing curved surfaces of two molds, each curved surface of each of the two molds is A plastic lens characterized in that the two molds are assembled using a positioning spacer that determines the position of the curved surface of the two molds by contacting one or both of them in a substantially linear or dotted manner. This is a molding method.

Ordinary concave lenses and convex lenses have spherical surfaces. The present invention will be explained below using an example in which a meniscus type concave lens is molded using a mold having a spherical surface as in the case of Fig. 1, but the present invention can also be applied to molding spherical lenses and aspheric lenses other than meniscus type concave lenses. It can be used. FIG. 2, which is an example, is a cross-sectional view of the mold in a positioned state similar to FIG. 1. Figure 2 shows positioning using a positioning spacer that is in linear contact with the curved surface of one of the two molds and the other is not, but the spacer is in contact with the curved surface of the mold in a linear or dotted manner. The missing parts are also improved over the one shown in Figure 1.

A mold 13 having a concave spherical surface 12 and a mold 15 having a convex spherical surface 14 are positioned by a positioning spacer 16. A flat surface 18 perpendicular to the axis 17 is provided in an annular shape around the concave spherical surface 12 of the mold 13 . A convex portion 19 is provided on the inner surface of the positioning spacer 16.
The upper surface 20 and the lower surface 21 of are planes perpendicular to the axis 17. First, parts of the present invention will be explained. The spherical surface 14 of the mold 15 is in contact with the convex portion 19 of the positioning spacer 16 in a ring-shaped line at the corner formed by the convex lower surface 21 and the convex side surface 22. Contact between the side surface of the mold 15 and the inner surface of the positioning spacer 16 is not necessarily essential, and may even be undesirable. mold 1
A positioning spacer that is in linear contact with the spherical surface 14 of No. 5 determines the position of the spherical surface 14. However, it is permissible for the spherical surface 14 to shift without changing its center of curvature, that is, to shift so that the center of the spherical surface 24 moves on the spherical surface 14, as long as it is not excessive. This is because the displacement does not substantially change the position of the spherical surface 14. Since this deviation is allowed, the side surface of the mold 15 and the inner surface of the positioning spacer 16 do not necessarily need to be in contact with each other. The contact portion between the spherical surface 14 of the mold 15 and the positioning spacer 16 may also be in the form of a divided line or in the form of a dot consisting of at least three points. Further, if the contact portion between the side surface of the mold 15 and the inner surface of the positioning spacer is utilized, the contact portion between the spacer 16 and the spherical surface 14 of the mold 15 may be one or two points.

On the other hand, the mold 13 and the positioning spacer 1
6 is in surface contact with the flat surface 18 provided around the spherical surface 12 of the mold 15 and the upper surface 20 of the convex portion 19, and at two portions each: the side surface of the mold 15 and the inner surface of the positioning spacer 16. Spherical surface 1
2 and the upper surface 20 of the spacer convex portion 19 are both flat, making it easy to form an accurate shape, and thus easily preventing the spherical surface 18 from tilting. Further, misalignment of the spherical surface 12 in the direction perpendicular to the axis 17 can be prevented at the contact portion between the side surface of the mold 15 and the inner surface of the positioning spacer 16. By using the mold and positioning spacer shown in FIG. 2, the positions of the two spherical surfaces can be determined more accurately than when using a gasket.

Although the inventors have found that the two spherical surfaces can be positioned very accurately by using the mold and positioning spacer shown in FIG. 2, they have found that further improvements may be desirable. As shown in Figure 2, the position of the convex spherical surface could be determined by bringing the convex spherical surface of the mold into contact with the positioning spacer in a linear or dotted manner, but the concave spherical surface and the positioning spacer were I was leaning into the contact. Therefore, it was necessary to form a flat surface around the concave spherical surface, and it was necessary to bring the side surface of the mold into accurate contact with the inner surface of the positioning spacer. In particular, the latter requirement is a strict requirement compared to the fact that contact between the side surface of the mold having a convex spherical surface and the inner surface of the positioning spacer that contacts the convex spherical surface in a linear or dotted manner is not essential. Moreover, the fact that the mold side surface and the inner surface of the positioning spacer are not allowed to be misaligned makes it difficult to fit the mold into the positioning spacer during positioning and to remove the positioning spacer after positioning. If looseness is provided between the two, the mold is likely to shift in the direction perpendicular to the axis, making positioning difficult. Furthermore, since the plastic lens molded using this mold has a flat portion around the convex surface, it is necessary to remove this portion.

As a result of further investigation, the inventors of the present invention have discovered a positioning spacer that also contacts the concave spherical surface of the mold in a linear or dotted manner. FIG. 3 shows a cross section of the mold in a state where it is used to position the mold. The relationship between the mold 23 having a convex spherical surface and the positioning spacer 24 is the same as that shown in FIG. show.
The mold 26 having a concave spherical surface 25 is a mold having a concave spherical surface as shown in FIG.
There is no need to provide a flat surface around the concave spherical surface as shown in FIG. Positioning spacer 2
The convex portion 27 of No. 4 has a rising portion 28, and the end portion of this rising portion 28 is in contact with the spherical surface 25 in a ring-shaped line. Of course, this contact portion may be in the form of a point, and the contact between the side surface of the mold and the inner surface of the positioning spacer is not essential, as described above. In this way, in order to position a mold having a concave spherical surface, a rising part that rises in the axial direction is formed on the inner surface of the positioning spacer on the convex part that projects in the direction of the axis, and the rising part and the concave shape of the mold are All problems can be solved by making linear or point contact with the spherical surface.

The contact between the spherical surface of the mold and the positioning spacer may be substantially linear or point-like. That is, in reality, there cannot be a line with no width or a point with no area, so it is inevitable that they will touch each other with a certain width or area. Therefore, ``substantial'' refers to not only cases where the corners or edges that form an acute to obtuse angle touch each other in a linear or dotted manner, but also cases where the angles or corners are rounded to a negligible degree or are not used. This also includes cases where the corners and corners are worn to a negligible extent by returning the item. The shape of the positioning spacer is also not limited to that shown in FIGS. 2 and 3. For example, the cylindrical body of the positioning spacer in FIG. 3 does not need to come into contact with the side surface of the mold, so it may actually be omitted. Moreover, it can also be composed only of a ring having a polygonal cross section. Further, the convex portions on the inner surface of the positioning spacer do not need to be present in the entire circumferential direction, and may be present in the form of divided lines or dots. For example, the fourth
As shown in the figure, which shows a partial cross section of the mold and the positioning spacer, the positioning spacer 29 may be a torus with a rectangular cross section. 5 is a plan view of the positioning spacer 24 having the cross-sectional shape shown in FIG. 3, with the convex portion 27 and rising portion 28 divided in the circumferential direction on the inner surface of the positioning spacer.

The positioning spacer of the present invention can be used for molding the above-mentioned meniscus type concave lens, as well as
It can also be used to mold various plastic lenses. For example, there are meniscus type convex lenses, flat type convex or concave lenses, etc. Furthermore, it is also possible to mold lenses having curved surfaces other than spherical surfaces, such as lenses having spheroidal or cylindrical surfaces such as Triclen lenses. These positioning spacers used in contact with the aspherical surface can be used in linear contact with the aspherical surface, but it is more advantageous to use them in point-like contact.

The positioning feature of the present invention is firstly that the positioning accuracy is high, and also that molds with different curvatures can be positioned with one positioning spacer. Needless to say, the former
This can be achieved by using a hard material such as hard plastic with little change in shape, using a positioning spacer with high dimensional accuracy, and using the positioning method described above. In the latter case, for example in FIG. 3, even if the curvature of the spherical surface 26 of the mold 25 is changed, the same positioning spacer can be used for positioning. However, the distance between the two spherical surfaces will differ, but this can be determined to a predetermined distance by moving the mold in the axial direction after removing the positioning spacer.

An outline of a method for molding a plastic lens using the positioning spacer described above is shown below.

The two molds are usually positioned while being held by a mold holder. In order to perform positioning, at least one of the molds must be movable until the positioning is completed. Further, when a positioning spacer is used, it is necessary to move the mold to remove it from between the molds after positioning. After determining the position of the mold in the state shown in Figure 3, in order to prevent the mold from moving in the direction perpendicular to the axis, that is, along the plane perpendicular to the plane of the paper in Figure 3, Fix the mold. Next, move the mold in the axial direction to increase the distance between the two molds, and use the positioning spacer 2
Remove 4 from between the two molds. Next, the molds are brought closer together in the axial direction again, and the distance between the molds is set to a predetermined distance. If the distance between the molds at the time of positioning is determined by the width of the convex portion 27 of the positioning spacer 24, then the position can be compared with the position after this movement to determine the predetermined distance. can. Even if the distance between the molds is unknown at the time of positioning, the distance between the molds can be determined by touching the centers of both molds to determine the distance between the two molds, and determining the distance between the molds by the subsequent movement distance. The distance can be determined. After the position in this axial direction is determined, the mold is also fixed in this direction. This fixation of the mold or the fixation of the mold in a direction perpendicular to the above-mentioned axis is sufficient to the extent that the position of the mold does not shift during the next handling in which a tape or the like is brought into close contact with the mold.

Next, the 2
Place tape tightly around each mold. For example, an adhesive tape having an adhesive layer on one side is tightly attached to the side surfaces of two molds with the adhesive side facing inside, spanning the two molds. It is preferable that the length of the adhesive tape is such that both ends overlap to some extent.
FIG. 6 is a sectional view of a mold assembly in which a sealed cavity is formed by adhering adhesive tape. A cavity 33 is formed by the curved surfaces of the two molds 30 and 31 and the adhesive tape 32 wound around the side surfaces of the molds. This cavity is then filled with plastic material. This filling of the plastic material can be carried out while the mold assembly shown in FIG. 6 is held in the mold holder, but it may also be carried out after the mold assembly is removed from the mold holder. The shape stability of this mold assembly is sufficiently high, and there is little risk of the mold shifting even if the mold is not fixed. Filling with plastic raw material is done by peeling off the outside of the overlapping part of the adhesive tape until just before the overlap occurs to form an injection port, and then injecting the plastic raw material from this injection port.A syringe needle is inserted between the tape and the side of the mold. This can be done by inserting a needle, etc., and injecting through the needle, etc. Of course, after filling the plastic material, the cavity is closed again.

The method of removing the positioning spacer from between the molds after positioning the mold by holding the positioning spacer is not limited to the above method. For example, if the positioning spacer is a splittable spacer, the positioning spacer can be disassembled and removed from between the molds without moving the mold at all in the state shown in FIG. Furthermore, it is not necessarily necessary to move the two molds relative to each other in the axial direction in order to remove the positioning spacer from between the molds. The positioning spacer can be removed by moving it in any direction if possible depending on the shape of the positioning spacer. What is required in this case is to return the mold to its original position. For example, by fixing a stopper in contact with a positioned mold, moving the mold along a guide to remove the positioning spacer, and then moving the mold back along the same guide until it contacts the stopper, the mold can be moved. It can be returned to its original position. Of course, these methods cannot change the distance between the two molds beyond the distance determined by the positioning spacers. Therefore, a type of positioning spacer is required depending on the thickness of the lens to be molded. The method of moving the mold in the direction of the axis is advantageous in that lenses of different thicknesses can be molded using one positioning spacer.

Preferably, a sealing film, such as the tape described above, is used to seal around the two mold gaps to form a cavity. A sealing film such as tape is tightly attached around the sides of the two molds to form a cavity between the two molds and the adhesive film, and is used to prevent the plastic raw material from leaking from this cavity when the plastic raw material is filled. . The first feature when using this sealing film without using a gasket is that the sealing film such as tape can easily follow the shrinkage of the plastic raw material.
The large shrinkage force generated when the plastic raw material hardens is applied in the direction of bringing the two molds closer together, and this follows the movement of the molds by bending the tape toward the cavity side or the opposite side, or by shifting the contact surface from the mold. . Because the contraction force is much stronger than the mold's gravity and is a force parallel to the axis, the tape can bend and will not displace the mold in any direction other than the axial direction.
The second characteristic is that, whereas in the past it was necessary to prepare many types of gaskets to match the types of lenses, the method using tape does not require this at all. For example, all types of lenses can be molded using only one type of tape. Of course,
Therefore, the cost of molding the lens can be significantly reduced. In addition, since the basic physical properties required of the tape are merely to have a certain level of strength, improvement in heat resistance can be easily achieved by changing the material.

The sealing film is not particularly limited in its thickness or material. The thickness may be thick enough to have a certain degree of flexibility, and therefore, the "film" in the present invention may be referred to as a relatively thick "sheet." Taking a tape-shaped material as an example, it only needs to be thick enough to be able to be wrapped around a mold and not peeled off due to the elasticity of the tape itself after it is adhered to the side surface of the mold with an adhesive or the like. The thickness of the sealing film is therefore not particularly limited, but when it is made of ordinary plastic, a thickness of about 1 mm or less is easily used. The lower limit is the thickness that provides strength to the extent that buckling does not easily occur due to the weight of the mold when the mold is assembled.

The material of the sealing film is also not particularly limited. For example, it is possible to use a film that does not leak plastic raw materials such as plastic, rubber, paper, metal, cloth, etc. However, plastic is the most suitable material in terms of ease of use and economy. for example,
Polyolefin plastics such as polyethylene and polypropylene, polyvinyl halide (or vinylidene) plastics such as polyvinyl chloride and polyvinylidene chloride, polyester plastics such as polyethylene terephthalate, polystyrene plastics such as polystyrene and ABS, nylon-6, etc. Plastics such as polyamide plastics, cellulose plastics such as acetate, etc. can be used. These plastic films may be subjected to processing such as stretching or surface treatment, and may contain colorants, stabilizers, fillers, and other additives.

The shape of the sealing film is most preferably tape-like as described above, but it may be of other shapes, such as a tubular shape. The tape is preferably a so-called "adhesive tape" or "adhesive tape" in which at least one surface thereof is coated with an adhesive or an adhesive. Various of these are commercially available and can be easily obtained. Furthermore, it is possible to use a tape that does not have an adhesive or the like, and apply an adhesive or an adhesive to the tape surface, the mold side surface, or both at the time of use. Tape or other sealing films can be attached to the sides of the mold without the use of adhesives or adhesives. for example,
A heat-shrinkable film can be used to heat the film and bring it into close contact. In the present invention, the term "tape" refers to a sealing film having a substantially constant width and a length longer than the width.

The type of adhesive or adhesive is not particularly limited either.
The pressure-sensitive adhesive is generally rubber-based, and the adhesive is generally curable plastic-based. Among these, those that easily dissolve in the plastic raw material are unsuitable, and those that easily peel off due to the hydraulic pressure of the plastic raw material when the mold is assembled are unsuitable.

Although glass molds are the most common and widely used molds, plastic molds have also been proposed. Although a glass mold is most suitable for the present invention, it is not limited thereto, and molds made of materials other than glass can also be used.

The liquid curable compound that is the plastic lens raw material in the present invention is also not particularly limited. However, as mentioned above, diethylene glycol bisallyl carbonate called CR-39 is the most excellent raw material for plastic lenses. Of course, CR-39 is not only used alone, but also includes diallyl carbonate, diethylene glycol bismethallyl carbonate, ethylene glycol bisallyl carbonate, other allyl carbonates other than CR-39, diallyl phthalate, triallyl isocyanurate, diallyl benzoate, etc. Unsaturated alcohol esters, unsaturated acid esters such as methyl methacrylate, glycol dimethacrylate, diethylene glycol dimethacrylate, glycidyl methacrylate, styrene, unsaturated polyester resins,
It may also be copolymerized with other monomers having α,β unsaturated groups or prepolymers thereof that are liquid at room temperature. However, at least 40% by weight, preferably 60%
Monomers and prepolymers containing % CR-39 by weight are excellent raw materials for plastic lenses. Curable compounds that can be used alone or copolymerized with other monomers or prepolymers containing CR-39 to form a plastic lens include the allyl carbonates, unsaturated alcohol esters, unsaturated acid esters, etc. There are saturated polyester resins, epoxy resins, and other monomers and prepolymers having α, β, and unsaturated groups.

Plastic raw materials mainly contain the liquid curable compound mentioned above, but usually also contain a small amount of a radical polymerization catalyst. The radical polymerization catalyst may be any catalyst as long as it can initiate radical polymerization of the curable compound, but peroxides are preferred, such as benzoyl peroxide,
diisopropyl peroxydicarbonate, etc. Other plastic raw materials may also contain coloring agents such as dyes, ultraviolet absorbers, fillers, and other various additives.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a mold assembled with a conventional gasket, and FIGS.
The figure is a cross-sectional view of a mold positioned by positioning spacers according to the present invention. FIG. 4 and FIG. 5 are views showing other examples of the positioning spacer in the present invention, respectively, with FIG. 4 being a sectional view and FIG. 5 being a plan view. FIG. 6 is a cross-sectional view of a mold assembly assembled according to the present invention. 1, 2, 13, 15, 23, 25, 30, 31
...Mold, 3...Gasket, 16, 24,
29...Positioning gasket, 4, 5, 12,
14, 26... Curved surface, 8, 17... Axis, 32
... Sealed film.

Claims (1)

[Claims] 1. Two molds having curved surfaces for forming the surface of a plastic lens are assembled, and a liquid curable compound is contained in a cavity formed between the opposing curved surfaces of the two molds. In a method of molding a plastic lens by curing a plastic raw material mainly composed of A method for molding a plastic lens, comprising assembling the two molds using a positioning spacer that determines the position of the curved surface of the lens. 2. The method of claim 1, wherein the positioning spacers are used to position the curved surfaces of the two molds and then the positioning spacers are removed from between the opposing curved surfaces. 3. Claim 2, characterized in that after the positioning spacer is removed, a sealing film is tightly attached around the side surfaces of the two molds to form a cavity surrounded by the opposing curved surfaces and the sealing film. the method of. 4. The method according to claim 3, wherein the sealing film is a tape. 5. The method according to claim 4, wherein the tape is a tape provided with an adhesive layer or an adhesive layer on its surface.