JPS61244510A - Casting mold of plastic lens - Google Patents

Abstract

PURPOSE:To enable to obtain a high-accuracy plastic lens at high yield, by making an annular gasket into an outer frame gasket whose material is composed of a rigid member and a fitting part between a top and bottom forces is fixed by several pieces of holding bars and an inner frame gasket which is fitted in the outer frame gasket from the inside and composed of an elastic material. CONSTITUTION:An inner frame gasket 7 made of an elastic material is fitted in an outer frame gasket 6 made of a rigid material from the inside by inserting an outer end part 7a of the inner frame gasket into an inscribed surface 6a of the outer frame gasket by making use of elasticity of the outer end part 7a. Then a top and bottom glass forces 3, 4 are fitted in the outer frame gasket each other, flat parts 3a, 4a of the forces each are made to seat on the tops 7b, 7c' of the inner frame gasket, a casting mold is assembled and the top and bottom glass forces 3, 4 are held at a predetermined position by a spring clamp 9 holding the top and bottom glass forces 3, 4 between the same. A mixed liquid of plastic raw materials such as a monomer and initiator of polymerization is cast into a tightly closed up cavity 5 by an injector and a plastic lens is formed by making the plastic raw materials polymerize by heat and ultra-violet rays.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic lens mold for molding a plastic lens, such as a spectacle lens or an optical lens.

[Summary of the invention]

The present invention provides a plastic lens casting mold in which an annular gasket is made of a rigid material and is fitted into an outer frame gasket whose upper die fitting portion and lower die fitting portion are fixed by support rods from the inside. By using an inner frame gasket made of an elastic material, a high-quality, high-performance plastic lens can be obtained.

[Conventional technology]

In recent years, the demand for plastic lenses as lenses for optical instruments or eyeglass lenses has been increasing. The reason for this is that plastic lenses have extremely excellent impact resistance and transparency, are lightweight, and have good other optical properties. Also, unlike glass lenses, plastic lenses can be dyed.
They have become popular as fashion sunglasses, and this is also spurring an increase in the use of plastic lenses. Such plastic lenses are manufactured by injection molding or compression molding of thermoplastic resins suitable for optical applications such as polycarbonate and polymethacrylates.
Or manufactured by cast molding.

Cast molding of plastic lenses involves filling a cavity (space) created by a pair of upper and lower molds usually made of glass and a gasket made of flexible material with plastic raw materials such as monomers and other polymerization initiators. In this method, a plastic lens is molded by clamping the upper and lower molds using a spring clamp or the like, and polymerizing and hardening the plastic raw materials by heating or the like.

It is well known that the biggest problem in manufacturing lenses in cast molding of plastic lenses is the gasket. The gasket must be such that the upper and lower molds can approach the lens in the thickness direction as the glass material shrinks in volume during the polymerization reaction. Also,
If the glass raw material separates from the gasket wall prematurely, it may cause distortion, cracks, or other damage to the lens, so it is necessary that the glass raw material adheres appropriately during molding. Taking this into consideration, Japanese Patent Application Laid-Open No. 56-27327 discloses a gasket for cast molding of plastic lenses with one leg facing inward in the radial direction.
It is a one-piece annular gasket with an approximately T-shaped cross section that is sandwiched between glass molds, and has a slot oriented radially inward from the outer periphery to the leg at the center of the outside of the gasket to accommodate volumetric contraction. We are proposing a gasket with engraved on it.

Another condition that the gasket must satisfy is that the molded plastic lens has a structure that does not cause misalignment of the optical axis. In other words, during the polymerization reaction, the upper mold and the lower mold move toward each other as the glass raw material shrinks, but normally the shrinkage does not occur uniformly within the mold, but shrinks non-uniformly, so when the polymerization and curing is completed, the upper mold This results in the T-shape being misaligned and deformed. For this reason, molded plastic lenses have the disadvantage that the optical axis of the optically finished surface is likely to be misaligned. When casting plastic lenses, we use plastics that have longitudinal variations in thickness like eyeglass lenses, and even if the optical axis of the vertically curved surface is slightly misaligned, there is no practical problem as long as it can be easily adjusted with the eye. Lenses can be molded, but high-precision plastic lenses such as those used in optical equipment such as cameras and groziers cannot be produced at all, so in order to prevent the optical axis of molded plastic lenses from shifting, JP-A-59- 9!5526, Japanese Patent Publication No. 59-9352
7. JP-A-59-106936 proposes a plastic lens casting mold using an outer frame gasket made of a rigid material.

[Problems and objectives to be solved by the invention] However, Japanese Patent Application Laid-Open No. 59-93326. %Opened in 1988-93327
, JP-A-59-10693S has a structure in which the inner frame gasket is fitted into the outer frame gasket and is in close contact with the outer frame gasket, so there is a problem that the raw material monomer tends to leak due to thermal expansion of the inner frame gasket and the raw material top knob during the polymerization reaction. have. Additionally, as the glass material shrinks during the polymerization reaction, the upper mold and lower mold move toward each other, so the gasket must also shrink accordingly, but the inner frame gasket is in close contact with the outer frame gasket. As a result, the strain or stress on the inner frame gasket that occurs when the upper mold and lower mold approach each other is alleviated. .

The present invention is intended to solve the above-mentioned problems, and its purpose is to create a plastic lens casting mold that can produce high-precision plastic lenses that can be used in optical devices at a high yield. It is about providing.

[Means for solving problems]

The plastic lens casting mold of the present invention includes an upper mold for forming a lens surface for forming one lens surface of a plastic lens, a lower mold for forming a lens surface for forming the other lens surface of the plastic lens, An annular gasket for forming a cavity between the upper mold and the lower mold, and an outer frame gasket made of a glass-resistant material, in which the old mold fitting part and the lower mold fitting part are fixed by several support rods. and an inner frame gasket made of an elastic material and fitted into the outer frame gasket from the inside.

[Function] ′ As described above, in the present invention, the entire outside of the inner frame gasket made of an elastic material is not tightly fixed with the outer frame gasket made of a rigid material, so even if the raw material monomer thermally expands, the inner frame gasket does not close to the outside. By stretching to , it is possible to prevent the raw material monomer from flowing out. In addition, the strain or stress on the inner frame gasket caused by the approaching movement of the upper and lower molds caused by the volumetric contraction of the raw materials during the polymerization reaction can be alleviated because the inner frame gasket can move freely in the lateral direction. This prevents the glass mold from peeling off from the molded plastic lens.

〔Example〕

Hereinafter, details of the present invention will be explained based on examples. A plastic lens casting mold according to the invention is shown in FIG.
A pair of upper and lower molds 3 and 4 are formed, and an outer frame gasket 6 and an inner frame gasket door to be described later are used to form a cavity 5 between the upper and lower glass molds 3 and 4. They are supported at a fixed distance as shown.

The outer frame gasket 6 used in the casting mold is fitted into the upper and lower glass molds, and has a shape in which the upper and lower fitting portions are supported and fixed by four support rods 8. An inner frame gasket 7 is fitted inside the outer frame gasket 6. As shown in the figure, the inner frame gasket 7 is an annular gasket having a substantially T-shaped cross section with legs facing radially inward, and the upper and lower parts and a part of the outer part are the upper and lower parts of the outer frame gasket B and support rods. It is inscribed inside 8.

The outer frame gasket 6 is made of a suitable rigid material, such as stainless steel, aluminum, steel, etc., and the inner frame gasket 7 is made of a suitable elastic material, for example, a composition such as a soft acid vinyl copolymer, either alone or in a blend. made and made.

The outer frame gasket of the first embodiment shown in FIG. 1 has four support rods 8. In the plastic lens casting mold of the present invention, the number of support rods of the outer frame gasket constituting the casting mold is not particularly limited, but the inscribed area of the inner frame gasket that is inscribed in the outer frame gasket is outside the inner frame gasket. area of 8
If it exceeds 0, the strain of the inner frame gasket caused by the approaching movement of the upper and lower molds during the volumetric contraction of the raw material monomer will be difficult to be alleviated, and the effects of the present invention will no longer be obtained.

To explain how to assemble the plastic lens casting mold, first, in Fig. 2, insert the inner frame gasket 7 made of an elastic material against the outer frame gasket 6 made of a rigid material. The outer end portion 71 is inserted into the inner surface 6m of the outer frame gasket by utilizing its elasticity, and is fitted from the inside. Next, a casting mold is assembled by fitting the upper and lower glass molds 3 and 4 into the outer frame gasket with respect to this double-structure gasket, and seating the glass molds 3 and 7 C' of each mold. The assembled casting mold is held in place by spring clamps 9 and the like that clamp the upper and lower glass molds 3 and 4.

In the assembled casting mold, as shown in Figure 1,
The inscribed surface 10 of the inner frame gasket cooperates with the optically finished surfaces 1 and 2 of the upper and lower molds to form a sealed cavity 5. A mixed liquid of a plastic raw material such as a monomer (e.g. diethylene glycol hisallyl carbonate) and a polymerization initiator (e.g. diisopropyl peroxide and dicarbonate) is injected into the sealed cavity 5 using a syringe or the like, and the plastic raw material is heated using heat, ultraviolet light, etc. Polymerization forms a plastic lens.

In the embodiments, the present invention has been explained by taking a meniscus-shaped concave lens as an example, but the present invention is not limited to this, and other types of lenses, such as plano-concave lenses, biconcave lenses, plano-convex lenses, biconvex lenses, meniscus-shaped convex lenses, etc. can also be molded. .

〔Effect of the invention〕

As explained above, the present invention provides an outer frame ganuket made of a rigid material and having a portion that fits into an upper mold and a lower mold fixed by several support rods, and a gasket that fits into the outer frame gasket from the inside. In addition, since the annular gasket has a double structure with the inner frame gasket made of an elastic material, it is possible to obtain a high-precision plastic lens that can be used satisfactorily as a lens for optical equipment where high precision is essential. In particular, in the present invention, since the entire outside of the inner frame gasket made of an elastic material is not tightly fixed with the outer frame gasket made of a rigid material, even if the raw material monomer undergoes thermal expansion during the polymerization reaction, the inner frame gasket will not expand outward. This makes it possible to prevent raw material monomers from flowing out. In addition, the strain or stress on the inner frame gasket caused by the approaching movement of the upper and lower molds caused by the volumetric contraction of the raw materials during the polymerization reaction can be alleviated because the inner frame gasket can move freely in the lateral direction. , the peeling of the glass mold and molded plastic lens can be prevented.

Therefore, due to the above effects, the conventional gasket '-11
- The effect of improving yield and quality in molding plastic lenses is clearly obtained compared to casting molds using cast iron.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a plastic casting mold according to the present invention, Fig. 2 is a block diagram of the casting mold shown in Fig. 1, Fig. 6 ( ) is a top view of the outer frame gasket, and Fig. 3 ( ) is a top view of the outer frame gasket. b) is a sectional view of the outer frame gasket. Note that FIG. 1 shows a cross section of the plastic lens casting mold taken along the line A'-A of the outer frame gasket in FIG. 6 (, ). 1 and 2... Optical finished surface 3... Upper die 4... Lower die 5... Cavity 6... Outer frame gasket 7... Inner frame gasket 8... Support rod
9... Spring flang 10... Inner wall surface. that's all

Claims (1)

[Claims] A lens surface forming upper mold for forming one lens surface of the plastic lens, a lens surface forming lower mold for forming the other lens surface of the plastic lens, and a cavity between the upper mold and the lower mold. In a plastic lens casting mold, the annular gasket is made of a rigid material and has an upper mold fitting portion and a lower mold fitting portion fixed by several support rods. A plastic lens casting mold comprising a gasket and an inner frame gasket which fits into the outer frame gasket from the inside and is made of an elastic material.