JPS6022609B2 - Positioning spacer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positioning spacer used when assembling two molds for molding a plastic lens, and particularly to a positioning spacer made of a specific material.

Plastic lenses are polycarbonate or poly(meth)
Although they may be manufactured by injection molding or compression molding of thermoplastic resins such as acrylates, Western molding is usually used to manufacture plastic lenses with excellent performance and physical properties.

Liquid curable compounds used as raw materials for plastic lenses include monomers having one or more Q,8 unsaturated groups and prepolymers thereof, monomers having vertically polymerizable groups such as Q,8 unsaturated groups and epoxy groups, and monomers thereof. There are prepolymers and various other compounds that can be cured by polymerization. Specifically, for example, diethylene glycol bisallyl carbonate,
(meth)acrylic acid ester, diallyl ester, triallyl isocyanurate, etc. Among plastic lenses, especially eyeglass lenses, accurate prescription is required, as well as high physical properties such as impact resistance, scratch resistance, and transparency. Currently, CR-
Diethylene glycol bisallyl carbonate, called 39, is widely used. 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. . In cast molding of plastic lenses, plastic raw materials such as monomers are filled into a cavity between two molds held by a gasket.

'8' The basic 3 steps are to harden this by heating, etc. 'C - Next, remove the mold and take out the lens.
It is usually done through a process. In step (2), the gasket is made of a sacrificial 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 the necessary curves to form the resin surfaces.

Plastic raw materials such as monomers are filled into a cavity formed between these two molds and sealed to prevent leakage. In the 'B} process, the mold filled with the assembled raw materials is put into a heating furnace, etc.
Harden plastic raw materials. Reduce lens distortion
In order to achieve uniform polymerization, curing often requires 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.
Glass molds are often reused for the next Western-style 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, it will not be able to follow the shrinkage of the volumetric plastic material between the molds, and separation will occur between the mold and the plastic material. Also,
Gaskets are also required to be heat resistant, since polymerization curing typically requires prolonged heating. In addition to both of these,
In addition, gasket materials need to be inexpensive. That is,
Since gaskets are usually used only once, there is a problem in 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 formation of gaskets differs accordingly, creating the problem of having to prepare many types of gaskets. Even if the material of the gasket is cheap, 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 (i.e., spherical or aspherical surfaces) that form the plastic lens surfaces of two molds or aligning the oblique angles of these surfaces (i.e., aligning the axes of these two surfaces). This includes setting the distance between the two surfaces to a predetermined distance (defining the thickness of the lens).

For this reason, the gasket needs to be a molded product with an accurate shape. On the other hand, due to the above reasons, the gasket material needs to have a certain degree of flexibility.
With a gasket made of such a flexible material, misalignment of the mold is likely to occur, making it difficult to align the mold. Therefore, the present inventor considered separating the function of the gasket and aligning the mold without relying on the gasket.

On the other hand, the present inventors have discovered and proposed a method of molding a plastic lens using a sealing film without using a gasket. 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, the two molds were brought into contact via a positioning baser with a predetermined shape, and the two molds were
Discovered and published a method for determining the position of individual molds. 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 by tightly adhering tape or the like around them to form a cavity, and the plastic raw material is hardened within this cavity. This positioning spacer
The invention is about how to assemble a mold using
That is, an application has been filed as an invention by the present inventors (see Japanese Patent Application No. 55-36928 and Japanese Patent Application No. 55-3692y, etc.).

These positioning spacers generally have a shape similar to a conventional gasket, which has a cylindrical frame and a lip (convex portion in the previous application) on the inner surface of the frame, and others that have been improved as positioning spacers. It was of a similar shape.
As the secondary gasket was required to be flexible as mentioned above, European plastic was used as its material. For example, soft vinyl chloride resins, polyisobutylene-polyethylene mixed plastics (see Japanese Patent Publication No. 43-2583), and materials whose main component is ethylene-vinyl acetate copolymer (Japanese Patent Publication No. 54-3873) (see publication), and other soft plastics such as rubber and polyethylene are known. In contrast, the positioning spacer according to the invention of the present inventors does not require flexibility. The positioning spacer is used when assembling the mold, but not when curing the plastic raw material, so it does not need properties to follow the shrinkage of the plastic raw material or to seal around the mold. It is. Furthermore, heat resistance is also unnecessary. Therefore, the main requirements for the layering baser are accurate shape and dimensional stability during repeated use, and economical efficiency of the material for repeated use does not matter much. The present inventor investigated materials for the positioning spacer that can easily form the above-mentioned accurate shape and have excellent dimensional stability.

Generally, such required performance can be achieved by using a hard material. However, as a result of further investigation, it was found that simply using a hard material was insufficient. First, the positioning spacer must not be fragile, since it is compressed by repeated molding and is frequently attached and removed. Furthermore, since the mold is usually made of glass, it must not be hard enough to damage the glass mold. In addition, materials with high physical properties such as abrasion resistance are also preferred. After examining various materials that meet these required properties, the inventor found that hard plastics were suitable. Other materials, such as metals, not only have a large coefficient of thermal expansion and cough, but also undergo large changes in shape depending on the conditions of use.
Highly hardened and easily damages glass molds. The present invention
This is a spacer for positioning a mold for molding a plastic lens made of this hard plastic. Although the shape of the positioning spacer is not particularly limited, the shape of the positioning spacer described in the above-mentioned patent application related to the invention by the present inventors is preferable.

This preferred shape has a cylindrical frame and a hole provided on the inner surface of the frame over the whole or a part of the circumferential direction. Four examples are shown in FIGS. 1 to 4.
Each figure A is a plan view, and each figure B is a sectional view taken along a cutting line passing through the center of the cylindrical frame. The positioning spacer shown in FIG. 1 consists of a cylindrical frame 1 and a lip 2, and the lip 2 is provided on the entire inner circumference of the cylindrical frame 1. The upper and lower surfaces of the lip 2 of this positioning spacer (the surfaces parallel to the plane of the paper in FIG. 1A) are preferably flat. FIG. 2 shows a positioning spacer similar to that shown in FIG. 1, which includes a cylindrical frame 3, a lip 4, and a convex portion 5 formed on the upper surface of the lip 3. A convex portion 5 is provided on the lip 4 to linearly contact the concave spherical surface of the mold to determine its position. For more detailed information on the shape of the positioning spacer shown in FIGS. 1 and 2, how to use the same, and other information, please refer to Tsubakigoshi Sho 55-3692Y, an invention by the present inventors. The positioning spacer shown in FIGS. 3 and 4 has a further improved shape.

This positioning baser, like the positioning basers shown in Figures 1 and 2, can be used not only to assemble molds with concave or convex spherical surfaces, but also to assemble molds with aspherical surfaces such as trick surfaces and cylindrical surfaces. It can also be used for assembly. The positioning spacer shown in FIG. 3 consists of a cylindrical frame 6 and two arcuate slopes 7 and 8. Sectional view B shows a section taken along line 1-1' of plan view A. The positioning spacer shown in FIG. 4 consists of a cylindrical frame body 9 with convex portions 12 and 13 provided on the lip of the positioning spacer shown in FIG. 3, as in the case of FIG.
It consists of 0 and 11. FIG. 4B is a sectional view showing the Rollo cross section of A, and also shows a cross section of the mold to show the state in which the two molds 14 and 15 are assembled and positioned. The mold 14 having a concave spherical surface 16 is positioned so that the concave spherical surface 16 linearly contacts the convex portions 12 and 13 on the lip, and the mold 14 having a convex spherical surface 17
is positioned with its convex spherical surface 17 in linear contact with the lips 10 and 11. The positioning mold shown in FIGS. 3 and 4 can also be used for positioning a mold having an aspherical surface such as a trick surface or a cylindrical surface. For example, if a mold having a convex trick surface is used instead of the mold 15 in FIG. 4B, the aspherical surfaces 10, 11
This aspheric surface is positioned by contacting at four points on both ends of the lip in all directions. For details of the positioning spacer shown in FIGS. 3 and 4, please refer to the patent application filed on the same day as the present application, which is related to the invention of the present inventors. Various hard plastics can be used. As a thermoplastic resin,
For example, vinyl chloride resins, acrylic resins, polystyrene resins, polyamide resins, linear polyester resins, polycarbonate resins, polyacetal resins, and polyarylene ether resins that do not contain or contain a small amount of plasticizer. , polyarylene samphide resin, and other engineering plastics with excellent mechanical properties can be used. Among these, particularly preferred are engineering plastics that have properties similar to metals and are used as metal substitute plastics. The most preferred is polyacetal resin. It is a resin made of formaldehyde polymer or copolymer (trade name: "Delrin", etc.). In addition, there are polyarylene sulfide resins such as polyphenylene sulfide, and polyarylene ether resins such as polyphenylene oxide. Polyacetal resin has high strength and rigidity, good dimensional stability, excellent fatigue properties, and high abrasion resistance, so it is the most excellent material for the positioning baser of the present invention. These thermoplastic resins include
Fillers, reinforcing agents, stabilizers, colorants and other additives may be added. As the thermosetting resin, epoxy resin, unsaturated polyethylene resin, phenol resin, allyl resin, and other resins can be used.

These thermosetting resins are usually filled with fillers, and
Various additives are added. The method of molding a plastic lens using the positioning baser of the present invention is not particularly limited, but it is preferable to use the method of the invention of the present inventors' previous application (in accordance with the invention of the present inventors). (see related patent application).

To explain one example of the methods described in these applications, a plastic lens is molded as follows. First, two molds are prepared, for example, one having a concave spherical surface and the other having a convex trick surface. The mold is held in a movable mold holder with these two surfaces facing each other, and the positioning spacer of the present invention is sandwiched between them, and the two surfaces are brought close to each other, and each surface is placed on the positioning spacer. Position by making contact. This state is the state shown in FIG. 6. Next, in this state, the mold holding odor is fixed and the mold position is fixed. However, the mold can only be moved in a direction parallel to the axis. Next, move the mold in a direction parallel to the axis,
The gap between the two surfaces is widened, the positioning spacer is removed from between the two surfaces, and then the two surfaces are brought close to a predetermined distance and fixed there. Next, close a sealing film such as adhesive tape around the sides of these two molds, and
Seal the space between the two faces to form a cavity. After the assembly consisting of the two molds is removed from the mold holding odor and the cavity of the assembly is filled with plastic raw material, or after the cavity of the assembly is filled with plastic raw material,
Remove the assembly from the mold holder. Next, the assembled body filled with the plastic raw material is placed in a heating furnace or the like to harden the plastic raw material, and then taken out from the heating furnace and the sealing film and two molds are removed to obtain a plastic lens.

[Brief explanation of the drawing]

1 to 4 are diagrams showing the shapes of four examples of positioning spacers of the present invention, and each diagram A is a plan view and B is a sectional view. 1, 3, 6, 9... Cylindrical frame, 2, 4, 7,
8, 10, 11... Lip, 5, 12, 13... Convex portion on the upper surface of lip, 14, 15... Mold. Ta 31 Genmu no Zu Hair 2 Ta 4 Style

Claims (1)

[Claims] 1. A spacer for positioning a plastic lens mold made of hard plastic. 2. The spacer according to claim 1, wherein the positioning spacer comprises a cylindrical frame and a lip provided on the inner surface of the frame all or partially in the circumferential direction. 3. The spacer according to claim 1, wherein the hard plastic is made of a thermoplastic resin. 4. The spacer according to claim 3, wherein the thermoplastic resin is made of a polyacetal resin. 5. The spacer according to claim 1, wherein the hard plastic is made of a thermosetting resin.