JP2001277262A - Method of sealing casting cavity and method of manufacturing plastic lens using the same - Google Patents

Abstract

(57) [Problem] To provide a method for sealing a cavity for casting, which eliminates the need for a sealing material for hermetically sealing the cavity for casting, and can improve the production yield and sealing performance. A method for manufacturing a plastic lens using the same is provided. SOLUTION: After filling the plastic raw material, the cavity is sealed by hardening the plastic raw material near the injection port by an electron beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for sealing a cavity for casting a plastic lens and a method for manufacturing a plastic lens using the same.

[0002]

2. Description of the Related Art The prior art will be described by taking as an example a method of manufacturing a plastic spectacle lens (hereinafter abbreviated as a plastic lens), which is formed of most of plastic lenses by a casting method. Note that a mold used for cast molding of a plastic lens is commonly made of glass. Conventional casting of plastic lenses involves (1) fixing two glass molds held by gaskets with a spring, and filling a plastic material such as a monomer into a cavity formed between the two glass molds. . (2) Alternatively, the two glass molds are positioned and held at a desired interval, and an adhesive tape, a heat sealing tape, or the like is wound around and fixed to the side surfaces of the two glass molds, and formed between the two glass molds. The cavity is filled with a plastic material such as a monomer. The plastic material is cured by heating or irradiating ultraviolet rays. (3) Next, it is generally performed by three basic steps of removing the glass mold and taking out the lens.

[0003] Of these, after the filling of the plastic raw material in the above (2), a work of sealing an injection port called sealing is performed for the purpose of preventing leakage of the injected plastic raw material. Specifically, after filling the plastic material into the cavity, hot melt or ultraviolet curing resin is applied as a sealing material to seal the injection port 5 shown in FIG. 3 and sealed. An example is a method in which a part of the wound adhesive tape is peeled off, the plastic material is filled, and then the adhesive tape is wound again around the glass mold.

[0004] Although not shown, a method in which the injection port is coated with a hot melt or an ultraviolet curable resin and the cavity is closed can also be exemplified when the gasket of (1) is used.

[0005]

However, there are several problems with the above-described cavity sealing method. First, when the sealing material drawn into the plastic lens due to polymerization shrinkage remains in the effective range of the finished plastic lens after molding, appearance defects are caused. This causes a problem that the production yield is reduced.

Further, the sealing material remaining on the outer peripheral portion of the lens is crushed by, for example, an ultrasonic wave from a cleaning device during a hard coating process, and is separated from the lens, contaminating the hard coating solution and forming a powdery state. The encapsulant adheres to the lens surface, resulting in an appearance defect and lowering the production yield.

[0007] Further, depending on the type of the sealing material, the transparency of the lens is impaired due to the melting of the sealing material which has reacted with the plastic raw material into the filled plastic raw material, or after molding. May reduce the adhesion between the plastic lens substrate and the hard coat liquid.
It can lead to serious quality claims. In addition, many of the sealing methods exemplified in the prior art require a sealing material itself, and thus require expendable material costs according to the production quantity. As a result, this is a factor that increases the lens manufacturing cost.

There is also a problem with the sealing performance. Usually, when injecting plastic material into the cavity,
It is necessary to fill the required amount without excess or shortage. That is, if the filling is insufficient, a predetermined lens shape cannot be obtained, resulting in a defect such as an insufficient lens diameter. On the other hand, overfilling results in over-injection, and the plastic material overflows from the cavity and adheres to the adhesive tape or the glass mold to reduce the adhesion of the sealing material or to contaminate the glass mold. When plastic material adheres to the adhesive tape due to over-injection, the plastic material intervenes between the sealing material and the adhesive tape, and the adhesive between the hot melt or UV-curable resin used as the sealing material and the adhesive tape In some cases, sealing cannot be performed because the force is significantly reduced. As a result, the atmosphere is drawn from the injection port during the polymerization, so that the volume of the polymerization shrinkage is lost, and as shown in FIG. 4, a predetermined lens shape cannot be obtained, resulting in a defective product.

Also, in the sealing method in which a part of the adhesive tape wound around the outer periphery of the glass mold is peeled off, the raw material is filled, and then the adhesive tape is wound again on the glass mold, the adhesive tape is brought into contact with the adhesive when over-injected. Since the plastic raw material adheres to the side surface of the glass mold, there has been a problem that the adhesive force between the glass mold and the adhesive tape is remarkably reduced and sealing cannot be performed.

The present invention has been made in view of the above circumstances, and it is possible to reliably seal a cavity in a casting method and to seal a cavity which does not require a sealing material conventionally required. An object of the present invention is to provide a method and a method for manufacturing a plastic lens using the same.

[0011]

The inventor of the present invention has conducted intensive studies in order to achieve the above object. As a result, in the casting method of a plastic lens, conventionally, after a plastic raw material has been filled in a cavity, the method has been described. As shown in FIG. 3, a hot melt or an ultraviolet curable resin is applied as a sealing material 8 so as to cover the injection port 5 and is sealed, or a part of an adhesive tape (not shown) wrapped around the outer periphery of a glass mold is peeled off. It is effective to wrap the adhesive tape around the glass mold and seal it again after filling, and after filling the plastic raw material, cure the plastic raw material near the injection port with an electron beam to seal the cavity, that is, it is effective to seal I found something.

Although not shown, it is needless to say that the same sealing method is effective when a gasket is used instead of an adhesive tape when forming the cavity.

That is, since the plastic material near the injection port can be hardened by the electron beam and the cavity can be sealed, no sealing material is required. Thereby, since the sealing material is not drawn into the plastic lens due to the polymerization shrinkage, the appearance defect caused by the sealing material in the polymerization step is eliminated. Further, the absence of the sealing material does not cause contamination of the hard coat liquid in the hard coat processing step. The production yield is improved by the effect of eliminating these sealing materials.

Further, it is natural that the sealing material does not react with the plastic raw material to be dissolved, so that the transparency of the lens is impaired, or the adhesion between the molded plastic lens substrate and the hard coat liquid is reduced. There is no decrease in performance.

In addition, many of the sealing methods exemplified in the prior art do not require a sealing material itself, so that there is no need for expendable material costs according to the manufacturing quantity, and the lens manufacturing cost can be reduced. In addition, the sealing method of the present invention hardens the plastic raw material itself near the injection port and seals the injection port, so that even if the plastic raw material overflowed by over-injection adheres to the adhesive tape, the sealing performance is improved. Has no effect.

According to the first aspect of the present invention, there is provided a method for casting and molding a plastic lens, wherein after filling the plastic material, the plastic material near the injection port is cured by an electron beam to seal the cavity. The present invention provides a method for sealing a cavity.

According to a second aspect of the present invention, there is provided a method of manufacturing a plastic lens, wherein the method of sealing a cavity for casting according to the first aspect is used. The invention according to claim 3 provides the method for manufacturing a plastic lens according to claim 2, wherein the plastic lens is a plastic spectacle lens.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited to the following embodiments.

The electron beam used to cure the plastic raw material varies depending on the type of the raw material, and has an effect on yellowing of the plastic lens.
The accelerating voltage is preferably a so-called low energy electron beam of 0.1 KeV or more and 300 KeV or less.
It is desirable to be not less than KeV and 150 KeV.

Examples of raw materials for plastic spectacle lenses include allyl carbonate resin, acrylic resin, urethane resin, thiourethane resin, polycarbonate resin, epoxy resin, thioepoxy resin and the like.

[0021]

<Example 1> For a lens which is used as a raw material for a plastic spectacle lens and is obtained by mixing and polymerizing a compound having a thiol group and a compound having an isocyanate group, as shown in FIG. 2
Were formed at desired intervals by a holding member 2 and filled with a lens material monomer. that time,
Due to slight over-injection, the overflowing monomer adhered to the adhesive tape 3. Next, an electron beam 6 was irradiated from the electron beam irradiation port 9 at an acceleration voltage of 100 KeV for 0.1 second, and a cured film 7 having a thickness of 25 μm was obtained on the monomer surface near the injection port.

When the injection port 5 is hermetically closed, that is, the sealed cavity is heated and polymerized by a circulating hot-air furnace, the cured film 7 is polymerized while maintaining the sealing function without yielding to the force drawn by the polymerization shrinkage. Finished. As a result, a desired non-defective lens was obtained without drawing air into the sealed inlet 5. The obtained plastic lens had desired optical performance, and did not hinder the use as a plastic spectacle lens.

In this embodiment, an example is described in which a slight over-injection occurs when the lens material monomer is charged. However, it is needless to say that a desired plastic lens can be similarly obtained when the over-injection is not performed. No.

<Comparative Example 1> The same monomer monomer as in Example 1 and a commercially available melting temperature of 15 as a cavity and a sealing material were used.
A comparative example in which a plastic lens is molded using a 0-degree hot melt will be described below. Also in this comparative example, when the lens material monomer was filled, the monomer was slightly over-injected, so that the overflowing monomer adhered to the adhesive tape 3. Subsequently, about 10 cc of the melted hot melt 8 was dropped onto the inlet 5 to seal the inlet. The cavity in which the injection port 5 was sealed in this way was heated and polymerized by a circulating hot air furnace. However, between the hot melt 8 and the pressure-sensitive adhesive tape 3, a monomer overflowing at the time of over-injection was present, and the adhesion was reduced. Due to this hot melt 8
There was a slight gap between the tape and the adhesive tape 3. During polymerization, the atmosphere was drawn in from the gap, and chips 11 corresponding to the volume shrunk by the polymerization were generated on the outer periphery of the lens near the injection port 5. Although the obtained plastic lens had desired optical performance, it did not have a predetermined lens shape as shown in FIG. 4 and was defective.

[0025]

According to the method of sealing a cavity for casting and the method of manufacturing a plastic lens using the same according to the present invention, the plastic material in the vicinity of the injection port is cured by electron beam after filling the plastic material. Can be sealed, so that the sealing material itself is unnecessary. This prevents the sealing material from being drawn into the plastic lens due to polymerization shrinkage, thereby eliminating appearance defects due to sealing in the polymerization step. Moreover,
The absence of the sealing material does not contaminate the hard coat liquid in the hard coat processing step. As a result, the production yield is improved. In addition, since the sealing material itself is unnecessary, the cost of consumable materials according to the production quantity is not required, and the lens production cost can be reduced. In addition, since the plastic raw material in the vicinity of the injection port is cured and the injection port is sealed, even if the plastic raw material overflowed by over-injection adheres to the adhesive tape, there is no influence on the sealing performance.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing one embodiment of a method for sealing a casting cavity according to the present invention.

FIG. 2 is a conceptual diagram showing a state in which sealing of a cavity is completed by a method of sealing a cavity for casting according to the present invention.

FIG. 3 is a conceptual view showing one embodiment of a conventional method for sealing a cavity for casting, and shows an example in which hot melt is used as a sealing material.

FIG. 4 is a view showing a defective lens having a missing lens outer peripheral portion when polymerization is performed in a state where sealing of a casting mold cavity is incomplete.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass mold 2 ... Glass mold 3 ... Adhesive tape 4 ... Lens material monomer 5 ... Injection port 6 ... Electron beam 7 ... Cured film 8 ... Sealant (hot melt) 9 ... Electron beam irradiation port 10 ... Molded plastic lens 11 … Kake 12… Electron gun unit

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Claims (3)

[Claims] 1. A method for casting a plastic lens, comprising: after filling a plastic material, curing a plastic material near an injection port with an electron beam to seal the cavity. 2. A method for manufacturing a plastic lens, comprising using the method for sealing a cavity for casting according to claim 1. 3. The method according to claim 2, wherein the plastic lens is a plastic spectacle lens.