JPH09141758A - Method for producing plastic lens and adhesive tape used therefor - Google Patents

Abstract

(57) An object of the present invention is to provide a method for obtaining a good quality plastic lens free from bubble defects and optical distortion in good yield, and an adhesive tape used therefor. SOLUTION: As an adhesive tape for holding and sealing two molds positioned at a predetermined interval, one having two or more layers of plastic film base materials having different physical properties is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive tape that holds and seals a mold when casting and polymerizing a plastic lens, and a method for producing a plastic lens using the same.

[0002]

2. Description of the Related Art A general method for manufacturing a plastic lens includes a method of injecting a polymerizable substance into a mold made up of two molds and an annular gasket holding the mold to polymerize, and an alternative method of using the annular gasket. There is a method of holding two molds with an adhesive tape.

Among them, it has been already proposed that the manufacturing method using the adhesive tape is inexpensive and suitable for manufacturing various kinds of plastic lenses (Japanese Patent Publication No. 60-293).
33, JP-B-63-23890, JP-B-63-3940
9, Japanese Patent Publication 64-2483, Japanese Patent Publication 1-15366
etc).

The contents of the pressure-sensitive adhesive tapes described in the above publications are all about manufacturing plastic lenses using the pressure-sensitive adhesive tapes, and have not reached the contents for increasing the yield of manufacturing plastic lenses.

Regarding the adhesive tape for increasing the yield of plastic lenses, Japanese Patent Publication No. 5-64564 describes that the adhesive tape is multi-layered. However, in order to keep the oxygen permeability and water vapor permeability below a certain value. It is the content of.

[0006]

In the production of plastic lenses using an adhesive tape, the type of polymerizable substance used (for example, an allyl group-containing compound such as diglycol diallyl carbonate, a methacrylate compound such as an alkyl methacrylate ester) , Unsaturated group-containing urethane compounds, etc.), the performance required for the plastic film substrate and the pressure-sensitive adhesive constituting the pressure-sensitive adhesive tape greatly changes.

Generally, the above-mentioned polymerizable substance shrinks by about 8 to 14% when the resin produced by polymerization is cured. If this contraction is not absorbed, the inside of the mold becomes a vacuum and air from the outside penetrates, causing bubble defects in the lens.

[0008] Further, when the tape is completely sealed and polymerized so that air from the outside does not enter under the condition that the shrinkage is not absorbed, the shrinkage stress is relaxed and the local tensile stress of the molecular network in the plastic lens is reduced. Therefore, that portion becomes an optical distortion.

Therefore, in order to absorb the curing shrinkage of the resin, the adhesive tape is required to shrink to some extent during the polymerization process.

When the polymerizable substance to be used is an unsaturated group-containing urethane compound, and the adhesive of the adhesive tape is a rubber type or an acrylic type, the adhesive is dissolved in the unsaturated group-containing urethane compound to form a lens. Haze may occur.

Therefore, when a lens is manufactured from an unsaturated group-containing urethane compound, the pressure-sensitive adhesive of the pressure-sensitive adhesive tape is required to have chemical resistance and also necessary adhesive strength for holding the mold and preventing liquid leakage.

There is a silicone-based adhesive as an adhesive that satisfies these requirements. In order to obtain an adhesive tape (tape that sufficiently satisfies the manufacturing cost) laminated with this silicone-based adhesive, it is necessary in the tape manufacturing process. To heat
It is unavoidable to select a plastic film substrate that has a small heat shrinkage. Therefore, the above-mentioned pressure-sensitive adhesive tape has a small heat shrinkage, and the method of absorbing the curing shrinkage of the resin due to the shrinkage in the polymerization process cannot be taken, and the yield of good quality plastic lenses is lowered.

As described above, depending on the kind of the polymerizable substance, even if the plastic film base material and the pressure-sensitive adhesive forming the pressure-sensitive adhesive tape are optimally selected for molding the polymerizable substance, they are combined in tape production. However, it may be difficult to obtain an optimum adhesive tape for molding the polymerizable substance in the case of an adhesive tape having a structure in which the plastic film substrate and the adhesive each have only one layer.

The present invention provides a method for obtaining a good quality plastic lens free from bubble defects, optical distortion and haze in the production of a plastic lens from the above-mentioned polymerizable substance, particularly an unsaturated group-containing urethane compound. .

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it has two molds positioned at a predetermined interval and holding and sealing the two molds. A method of manufacturing a plastic lens by injecting a polymerizable substance into a cavity formed by being surrounded by an adhesive tape to be polymerized to produce a plastic lens, wherein the adhesive tape is formed by laminating two or more layers of plastic film substrates having different physical properties. The present invention provides a method for manufacturing a plastic lens, which comprises a laminated body.

In the present invention, the polymerizable material is contained in a cavity formed by two molds positioned at a predetermined interval and an adhesive tape that holds and seals the two molds. An adhesive tape used in a method for producing a plastic lens by injecting and polymerizing, wherein a plastic film substrate having two or more layers constituting the adhesive tape comprises a layer for holding and sealing a mold, and a polymerizable substance. Provided is a pressure-sensitive adhesive tape characterized in that the layers for shrinking the pressure-sensitive adhesive tape as a whole following the change in volume contracted by polymerization are composed of at least one layer each.

In the method of manufacturing a plastic lens of the present invention, two molds positioned at a predetermined interval are held and sealed with an adhesive tape. In this adhesive tape, two or more layers of plastic film substrates having different physical properties are laminated, and an adhesive layer is usually laminated on the surface of the substrate.

The plastic film substrate having different physical properties preferably follows a layer for holding and sealing the mold (hereinafter referred to as mold holding and sealing layer) and a volume change in which the polymerizable substance shrinks due to polymerization. The layers for shrinking the entire pressure-sensitive adhesive tape (hereinafter, referred to as shrink layers) are composed of at least one layer each.

The different physical properties of the plastic film substrate include, for example, the initial elastic modulus and the heat shrinkage ratio. The difference in the initial elastic modulus of each plastic film substrate is 100.
It is preferably at least kg / mm ² , and the difference in heat shrinkage between the plastic film substrates is 2% at the maximum polymerization temperature.
It is preferably not less than 4%, more preferably not less than 4%.

When the base material of the pressure-sensitive adhesive tape is composed of the mold holding and sealing layer and the shrink layer, the initial elastic modulus of the mold holding and sealing layer is 100 to 400 kg / mm.
² , preferably 300 to 400 kg / mm ² , and the heat shrinkage is 10% or less at the maximum polymerization temperature, especially 2%.
The following is preferred. On the other hand, as the physical properties of the shrinkable layer, the initial elastic modulus is 50 to 300 kg / mm ² , particularly 10
It is preferably from 0 to 200 kg / mm ² , and the heat shrinkage is preferably from 1 to 30%, particularly preferably from 2 to 20% at the maximum polymerization temperature.

In the pressure-sensitive adhesive tape composed of two or more layers of plastic film base material, the plastic film base material includes thermoplastic polyesters such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and polyhexamethylene terephthalate, polyethylene. Polyolefins such as polypropylene, polyimides, polyamides, fluororesins, etc. are suitable.

As the plastic film base material for the mold holding and sealing layer, strength, heat resistance, workability and price, and thermoplastic polyesters which can be supplied as a tape laminated with a silicone adhesive are preferable, and particularly, Biaxially oriented polyethylene terephthalate is preferred. The stretching rate of biaxially stretched polyethylene terephthalate is usually 2 to
A range of 4 times is preferable.

As the plastic film base material for the shrinking layer, polyolefins, particularly polypropylene, are preferable in view of strength, price, heat resistance and workability, but are not particularly limited.

The thickness of the plastic film substrate to be the mold holding and sealing layer is not particularly limited and is usually 15 to
The thickness may be 50 μm, preferably 20 to 40 μm. Further, the thickness of the plastic film base material to be the shrinkage layer is not particularly limited, and is usually in the range of 10 to 50 μm, preferably 30 to 40 μm.

The shrinkable layer is a base material that shrinks the entire pressure-sensitive adhesive tape in accordance with the volume change in which the polymerizable substance shrinks due to polymerization. The degree of shrinkage of the polymerizable substance due to polymerization varies depending on the type of the polymerizable substance and the polymerization temperature, but is usually about 8 to 14%.

Since the shrinkage rate of the shrinkable layer changes depending on the temperature and the material of the shrinkable layer, the shrinkage layer shrinks according to the shrinkage rate of the polymerizable substance, so that the shrinkable layer shrinks depending on the kind of the polymerizable substance and the polymerization temperature. The contraction layer may be appropriately selected.

In the adhesive tape, when the polymerizable substance is injected into the held and sealed mold, the adhesive tape constituting the mold has two or more layers of a mold holding and sealing layer and a shrink layer. It must be composed of a combination of plastic film substrates.

Therefore, in the present invention, as the method for laminating the mold holding and sealing layer and the shrinking layer, the method of laminating at the time of tape production and the method of holding and sealing two molds are as follows. A method of winding a tape to be a mold holding and sealing layer and a tape to be a contracting layer while laminating the tape, and further, once winding a tape to be a mold holding and sealing layer around two mold end faces to adhere and solidify them. There is a method of winding a tape which becomes a shrink layer on the tape.

The method for laminating the adhesive tape used in the present invention is not limited to the above, and the tape cost for laminating,
It can be performed by an optimal method depending on workability and the like.

The mold holding / sealing layer and the shrinking layer may be laminated via an adhesive layer, or may be laminated by a laminating method not using an adhesive.
The pressure-sensitive adhesive used when laminating the mold holding and sealing layer and the contraction layer via the pressure-sensitive adhesive layer is not particularly limited,
Any plastic film base material that serves as a shrink layer may be used as long as it has an adhesive force necessary for laminating it on the plastic film base material that serves as a mold holding and sealing layer. Acrylic, rubber, or vinyl acetate adhesives You can choose from many things such as agents.

The adhesive strength of the adhesive is usually in the range of 500 to 1500 g / 25 mm according to JIS Z0237,
The range is preferably 500 to 1000 g / 25 mm. The thickness of this adhesive is not particularly limited, but is usually 10
The range is 100 μm.

The pressure-sensitive adhesive tape according to the present invention has a pressure-sensitive adhesive layer on its surface layer in order to hold and seal the two molds. This pressure-sensitive adhesive layer is preferably laminated on the surface of the plastic film base material that will be the mold holding and sealing layer. When the plastic film base material that holds and seals the mold comes to the layer on the end surface side of the mold, this base material is a film with a certain degree of rigidity, so when assembling the mold for injecting the polymerizable substance. In addition, it is possible to prevent buckling due to the mold's own weight, maintain a prescribed interval, and
Since the film can be wound around the end surface of the mold without wrinkles in the assembly, it is possible to prevent the monomer from leaking from the film.

The pressure-sensitive adhesive is not particularly limited, but is preferably one which does not dissolve in the polymerized substance because it comes into direct contact with the polymerized substance, and particularly in the case of producing a plastic resin lens of urethane resin, it contains an unsaturated group. Acrylic pressure-sensitive adhesives and silicone-based pressure-sensitive adhesives, which contain little low-molecular-weight substances in which the pressure-sensitive adhesives do not dissolve due to urethane compounds, are suitable, and in order to secure the adhesive force necessary to retain the mold and prevent liquid leakage, silicone is used. A system adhesive is particularly preferable.

As the silicone-based adhesive, an addition reaction type silicone adhesive is preferably mentioned. Examples of the addition reaction type silicone pressure-sensitive adhesive include a base obtained by partially condensing a small amount of vinyl group-containing methyl siloxane gum and a special silicone resin, to which a SiH group-containing siloxane is added as a crosslinking agent. .

The silicone-based pressure-sensitive adhesive can be easily peeled off the tape from the mold after polymerization, and there is almost no remaining pressure-sensitive adhesive on the end surface of the mold after the tape is peeled off.
Since the mold can be easily washed, it is a useful adhesive in the production of plastic lenses other than urethane resin.

The thickness of the pressure-sensitive adhesive layer is not particularly limited,
Usually, it should be in the range of 10 to 50 μm and 20 to 40 μm.
The range of m is preferred. The adhesive strength of the adhesive layer is JIS Z
According to 0237, it is usually in the range of 500 to 1500 g / 25 mm, preferably in the range of 800 to 1300 g / 25 mm.

Furthermore, in order to stably obtain a good-quality plastic lens free from bubble defects and optical distortion, the length of the adhesive tape required to hold and seal the two molds is one of the mold lengths. It is preferable that 70% or more of the peripheral length consists of the above-mentioned two or more layers of plastic film base material, and particularly 90% or more of the peripheral length consists of the above-mentioned two or more layers of plastic film base material.

In the present invention, the adhesive tape is attached to the entire circumferences of the end faces of the two molds positioned at a predetermined interval, and holds and seals the two molds positioned at the predetermined interval. The width of the sticking part of the adhesive tape stuck to the end surface of the mold needs to be long enough to be firmly fixed to hold the two molds, and the end surface thickness of the mold is usually about 2 to 5 mm. If the width of the sticking portion of the sticking tape on the end surface of the mold exceeds the thickness of the mold, there is no particular problem, but preferably 1.
The range is 5 to 4 mm.

When the pressure-sensitive adhesive tape is wound around the entire circumference of the end faces of the two molds, it is preferable that the ends of the pressure-sensitive adhesive tape are overlapped, and the overlap is usually 1 to 10 cm. Good, preferably 2-5 cm
Range.

[0040]

According to the present invention, the polymerization which is the raw material of the plastic lens is carried out in the cavity formed by the two molds positioned at a predetermined interval and the adhesive tape for holding and sealing the two molds. A polymerizable substance is injected, and the entire pressure-sensitive adhesive tape composed of two or more layers shrinks following the volume change in which the polymerizable substance shrinks due to polymerization. In this shrinkage, the shrinkable layer constituting the plastic film base material of the adhesive tape shrinks, and the entire adhesive tape shrinks as the shrinkable layer shrinks.

This contraction occurs both in the mold facing direction and in the mold peripheral direction. The contraction in the direction opposite to the mold results in narrowing the predetermined space of the mold, and reduces the volume surrounded by the mold and the adhesive tape to the same extent as the volume contraction caused by the polymerization of the polymerizable substance. In addition, it also shrinks toward the center of the mold, resulting in a smaller lens diameter. Thereby, the contraction in the peripheral direction of the mold is absorbed by following the volume contraction in the central direction of the mold.

As a result, the entire pressure-sensitive adhesive tape composed of two or more layers shrinks following the volume change in which the polymerizable substance shrinks due to polymerization.

[0043]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

[Example 1] A biaxially stretched polyethylene terephthalate film having a plastic film substrate having a stretching ratio of 3 times, laminated with a silicone-based pressure-sensitive adhesive (pressure-sensitive adhesive layer thickness: 30 μm) (initial elastic modulus: 330 kg / mm ² ,
Heat shrinkage (polymerization maximum temperature 120 ° C): 0.8%, thickness:
Adhesive tape (adhesive strength according to JIS Z0237: 1280 g / 25 mm) composed of 38 μm) was adhered and solidified on the entire circumference of the end faces of the two molds positioned at predetermined intervals.

At this time, both ends 3 mm from each end in the width direction of the adhesive tape are adhered to the end surface of the mold, and the length of the adhesive tape is the circumferential length of the mold +3 cm, and the overlapping portion of 3 cm. It will be in a state of one round winding with. Further, a plastic film substrate obtained by laminating an acrylic pressure-sensitive adhesive (pressure-sensitive adhesive layer thickness: 30 μm) on the pressure-sensitive adhesive tape was a polypropylene film (initial elastic modulus: 200 kg / mm ² , heat shrinkage (polymerization maximum temperature 12
(0 ° C.): 5.1%, thickness: 50 μm) adhesive tape (adhesive strength according to JIS Z0237: 820 g / 2
5 mm) was laminated to a length of 95% of the circumference of the mold.

In the cavity thus assembled, 435 g of m-xylylene diisocyanate, 565 g of pentaerythritol tetrakis (3-mercaptopropionic acid), 0.08 g of dibutyltin dichloride, phosphate ester mineral oil (Zelec manufactured by DuPont). ) 1.0
g were mixed and stirred at room temperature until uniform, then degassed with cooling and the resulting mixture was poured. This was placed in an oven at 25 ° C., and the temperature was gradually raised from 25 ° C. to 120 ° C. over 24 hours for polymerization.

At the end of the polymerization, the pressure-sensitive adhesive tape shrank following the volume change in which the polymerizable material shrank due to polymerization, and the gap between the two molds was shortened. The obtained lens molded product was a good quality plastic lens free from haze, optical distortion and bubble defects.

[Comparative Example 1] In the method of Example 1, the mold was assembled by using only the biaxially stretched polyethylene terephthalate substrate tape laminated with the silicone adhesive as the adhesive tape, and polymerization was carried out. In the obtained lens molded product, optical distortion occurred in the lens, and further, large bubbles which were defective in bubbles were generated.

[Comparative Example 2] In the method of Example 1, a mold was assembled by using the adhesive tape only as a polypropylene-based tape laminated with an acrylic adhesive, and polymerization was carried out. The obtained lens molded product was free from optical distortion and foaming defects, but haze which is considered to be due to dissolution of the pressure-sensitive adhesive was generated in the periphery.

[Example 2] In the method of Example 1, the adhesive tape for assembling the mold was placed on the tape of the biaxially stretched polyethylene terephthalate base material on which the silicone adhesive was laminated in advance, and the acrylic adhesive. Using a laminate of laminated polypropylene-based tapes, stick both ends of the adhesive tape 3 mm from each end in the width direction to the end surface of the mold, and change the length of the adhesive tape to the circle of the mold. The length was set to +3 cm, and a single-turn winding was made with an overlapping portion of 3 cm.

In the same manner as in Example 1, a heavy synthetic material was placed in this mold and polymerized. As in Example 1, the pressure-sensitive adhesive tape contracted at the end of the polymerization following the volume change in which the polymerizable substance contracted due to the polymerization, and the gap between the two molds was shortened. The obtained lens molded product was a plastic lens of good quality, free from haze, optical distortion, and bubble defects, like the one obtained in Example 1.

[0052]

According to the method of the present invention, a plastic film substrate for holding and sealing two molds positioned at a predetermined interval, and a polymerizable substance shrinks following a volume change caused by polymerization. A plastic lens of good quality with no bubble defects and optical distortion caused by curing shrinkage of the resin produced by polymerization when a mold is formed with an adhesive tape laminated with plastic film base material with physical properties and polymerized. Can be obtained in good yield.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B32B 27/32 B32B 27/32 C 27/36 27/36 C09J 7/02 JHU C09J 7/02 JHU JJA JAJA JLE JLE // B29K 105: 32 B29L 11:00

Claims (7)

[Claims] 1. A polymerizable substance is injected and polymerized in a cavity formed by two molds positioned at a predetermined interval and an adhesive tape for holding and sealing the two molds. A method of producing a plastic lens, wherein the adhesive tape comprises a laminate in which two or more layers of plastic film substrates having different physical properties are laminated. 2. The method for producing a plastic lens according to claim 1, wherein the pressure-sensitive adhesive tape has a shrink-conformable plastic film layer that contracts following a volume change in which a polymerizable substance contracts due to polymerization. 3. A pressure-sensitive adhesive tape having a high-strength plastic film layer for holding and sealing a mold, and a shrink-following plastic film layer for shrinking following a volume change in which a polymerizable substance shrinks due to polymerization. The method of manufacturing a plastic lens according to claim 1, which is characterized in that. 4. The method for producing a plastic lens according to claim 1, wherein the adhesive tape has a layer of thermoplastic polyesters and a layer of polyolefins. 5. The pressure-sensitive adhesive tape has a structure of two or more layers over a length of 70% or more of the peripheral length of the mold in the length of the pressure-sensitive adhesive tape required to hold and seal the two molds. It has a laminated body which has, Claim 1 characterized by the above-mentioned.
2, 3 or 4 plastic lens manufacturing method. 6. A polymerizable substance is injected into a cavity formed by two molds positioned at a predetermined interval and an adhesive tape for holding and sealing the two molds to polymerize the polymerizable substance. An adhesive tape used in a method for producing a plastic lens, comprising: a plastic film substrate having two or more layers constituting the adhesive tape, a layer for holding and sealing a mold, and a polymerizable substance contracted by polymerization. A pressure-sensitive adhesive tape, wherein each layer that shrinks the pressure-sensitive adhesive tape as a whole according to a change in volume is a combination of at least one layer each. 7. A high-strength plastic film layer for holding and sealing a mold, and a shrink-following plastic film layer which shrinks following a volume change in which a polymerizable substance shrinks due to polymerization, and holds and seals the mold. The pressure-sensitive adhesive tape according to claim 6, wherein the plastic film substrate to be formed has a pressure-sensitive adhesive layer on the layer surface.