JPH03193313A - Manufacture of plastic lens - Google Patents

Abstract

PURPOSE:To improve the surface accuracy of a plastic lens and shorten the manufacturing time and increase the use cycle of a glass mold by a method wherein polymerization is completed by the irradiation of active energy rays after at least one cycle of pre-polymerization process consisting of the irradiation of active energy rays and the stoppage of the irradiation is executed. CONSTITUTION:At least one cycle of pre-polymerization process consisting of the duration of the irradiation of active energy rays over monomer composition, which is poured in a mold consisting of two sheets of glass mold and gaskets, from one side or both sides of the mold and the duration of the stoppage of the irradiation for the relaxation of the stress developing due to the shrinkage on polymerization is performed. A lens having a few strain due to residual stress is obtained through one or more times of irradiation of active energy rays consisting of the duration of the irradiation of active energy rays, which brings the state of a comparatively few stress, and at least one duration of the stoppage of the irradiation. Normally, three or more cycles of the pre- polymerization process are preferably executed. By means of the above- mentioned method, the warpage at the central part of a concave lens can be checked, resulting in obtaining a lens having good surface accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a plastic lens. In particular, the present invention relates to a method for manufacturing plastic lenses with low residual stress distortion caused by curing in a short time by irradiating active energy rays.

[Prior Art] Currently, as a commonly used plastic lens, there is a CR-39 lens made from diethylene glycol bisallyl carbonate.

When manufacturing this lens, a very long heat curing time of around 20 hours is required. As a result, the mold and polymerization furnace were occupied for a long time, resulting in extremely low production efficiency.

In order to improve this problem, a lens (Japanese Patent Publication No. 63-5721) has been disclosed which can be cured in a short time using light.

[Problems to be Solved by the Invention] Thermosetting or photocuring resins used for plastic lenses exhibit volumetric shrinkage of about 5 to 15% when polymerized from a polymer or oligomer state. At this time,
The resin sealed between the two glass molds and the gas get generates stress. In the case of the thermosetting method, since curing takes a relatively long time, intramolecular stress relaxation occurs during curing, and residual stress in the release lens removed from the glass mold and caskerat after curing is small. In comparison, although photocuring methods can cure methulide in a short time, due to the short curing time, the intramolecular stress relaxation associated with curing shrinkage is insufficient, and large When a concave lens is manufactured due to residual stress distortion, the center of the lens is curved (a phenomenon in which the curvature of the lens differs from the designed curvature), resulting in a significant decrease in surface accuracy. This curvature became even more significant when the internal strain was removed by heating (annealing) after the glass was removed from the mold. Although it is possible to prevent this curvature by making the center thicker, the edge of the lens also becomes thicker, resulting in an unfavorable lens shape.

[Means for Solving the Problems] 1-That is, the present invention provides, by irradiation with active energy rays,
Alternatively, in a method of manufacturing plastic lenses by polymerizing monomers using active energy ray irradiation and heat treatment in combination, after carrying out at least one preliminary polymerization step consisting of active energy ray irradiation and non-irradiation stop, This is a method for manufacturing a plastic lens, characterized in that polymerization is completed by irradiation with energy rays.

[Function] When carrying out the method of the present invention, a composition (containing oligomers, hereinafter simply referred to as "monomer") is injected into a mold usually composed of two glass molds and a gasket. After that, a prepolymerization step is carried out at least once, in which one or both sides are irradiated with active energy rays, and then an irradiation stop period is allowed to relax the stress generated by polymerization shrinkage. The required dose of active energy rays varies depending on the polymerization rate of the monomer, the amount of polymerization initiator and sensitizer, the intensity of the active energy rays, the temperature of the liquid, the shape of the lens, etc., so it cannot be generally specified. , - times of irradiation is preferably set so that the internal stress generated by curing is relatively small.

The state of stress generation within the lens can be observed using the crossed Nicol method in combination with polarizing plates.

A lens with no stress at all will appear completely black when observed using the crossed Nicols method. In a lens where a relatively small stress has occurred, a cross-shaped or cross-shaped 10-circle black area appears. In addition to the above phenomenon, a lens with a large stress generates a concentric iridescent pattern. The relationship between this phenomenon and the strength of stress is explained by A=BxCxD (A=optical path difference, C: photoelastic constant, D=thickness of sample, B=stress)
.

Since C and D are constant, the optical path difference A is proportional to the stress B. Therefore, the greater the stress, the greater the optical path difference. Since the optical path difference is the phase difference of light, it produces color. That is,
Observation of iridescence in a lens using the crossed Nicol method indicates large stress.

Therefore, the amount of energy irradiated for one time during lens manufacturing should be the amount of energy that provides the degree of polymerization until a black part in the shape of a cross-shaped 10 circles is formed when observed by the crossed Nicols method.

In this way, while observing using the crossed Nicol method, active energy rays are irradiated until the stress is relatively low, and the irradiation stop time (stress relaxation time) of about 1 minute to 60 minutes is given at least once before the start of the next irradiation. By irradiating active energy rays one or more times with the active energy rays applied, a lens with less residual stress distortion can be obtained. Normally, it is preferable to carry out the prepolymerization step consisting of irradiation with active energy rays and stopping the irradiation three or more times, but it is preferable to carry out the prepolymerization step in one simple step of irradiation with active energy rays, stopping irradiation, and re-irradiation. It may also be implemented by simply arranging. Normally, the cumulative total of the irradiation stop time of active energy rays in the preliminary process is
The time is preferably about 1 minute to 3 hours, but if the irradiation energy is low (the stress generated is small), the time is about 1 minute to 3 hours.
When the irradiation energy is large (the generated stress is large), it is preferable to take a stopping time of 10 minutes to 3 hours. If the cumulative irradiation stop time is too short, stress relaxation will be insufficient, making it impossible to manufacture a plastic lens with good surface precision. Furthermore, if the cumulative irradiation stop time is too long, the objective of the present invention, which is to manufacture plastic lenses in a short time, cannot be achieved. Note that the termination of irradiation of active energy rays as used in the present invention does not only mean that irradiation is not completed completely, but also means that the irradiation energy is reduced to less than 1/10 compared to normal irradiation. include.

By employing such a method of the present invention, it is possible to suppress curvature at the center of a concave lens, and a lens with good surface precision can be obtained. - If active energy rays are continuously irradiated without considering the stress strain caused by old sand formation, the lens will have a large residual stress strain, resulting in a lens with poor surface precision.

Although the amount of lens irradiation for one dose in the present invention cannot be unconditionally defined as mentioned above, it is usually 200 mJ/cm' to 30 mJ/cm'.
,000mJ/cm2.

When using ultraviolet rays as active energy rays, commonly used wavelengths of 2,000 to 8,000 can be used, and known chemical lamps, xenon lamps, low-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, fusion lamps, etc. can be used as light sources. can.

In addition to the above-mentioned ultraviolet rays, the method of the present invention also uses known
It is possible to apply the present invention to a polymerization curing method in which active energy rays such as radiation, electron beams, and visible light are irradiated.

The monomer used in the present invention has a monofunctional or polyfunctional reactive group, such as aliphatic, alicyclic, or aromatic alcohol acrylate or methacrylate, urethane acrylate, urethane methacrylate, epoxy acrylate, epoxy methacrylate, Compounds having one or more radically polymerizable double bonds in the molecule, such as polyester acrylate and polyester methacrylate, can be used.

Furthermore, heat treatment to complete polymerization after irradiation with active energy rays poses no problem as long as the stress state of the lens after irradiation with active energy rays is relatively small.

As the photoinitiator used in the present invention, intramolecular bond cleavage type photoinitiators such as benzoin butyl ether, benzyl dimethyl ketal, and hydroxyacetophenone, and intermolecular hydrogen abstraction type photoinitiators such as benzophenone, Michler's ketone, and benzyl can be used. Furthermore, when amines such as dimethylaminoethanol are used as a photosensitizer, the photopolymerization rate is improved. A thermal catalyst such as an organic peroxide can also be used in combination.

Furthermore, various additives such as various antioxidants, anti-yellowing agents, ultraviolet absorbers, bluing dyes, etc. may be added to the chisel without impairing the effects of the present invention.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples.

Evaluation method (1) Observation of residual stress: The residual stress of the lens was observed using a Toshiba distortion tester 5VP-100.

(2) Curvature at the center of the lens: The state of curvature at the center of the lens was observed with the naked eye and classified into the following ranks.

A: There is no curvature at all. (The difference between the curvature at the time of design and the curvature of the molded lens is 0 to 1%) B: Slightly curved. (Difference is 1 to 3%) C: Slightly curved. (Difference is 3-5%) D: Fi is bent. (Difference is 5-10%) E: Significantly curved. (Difference is 10-20%) F: Unusable.
(Difference is 20% or more) Example 1 Reaction obtained by reacting 1 mole of diarylidene pentaerythrite with 2 moles of 2-hydroxyethyl acrylate, with a molecular weight of 444, a viscosity of 4.4 voids, and a Gardner color number of 2 to 3. A 100% composition obtained by adding 1 part by weight of benzophenone and 1 part by weight of dimethylaminoethanol to 100 parts by weight of the product was polished to a mirror finish with an outer diameter of 80 mm, a curvature of 386 mm, an outer diameter of 80 mm, a curvature of 65 mm, and a thickness at the center of the glass. were combined to form a concave lens of 1.5111 [11], surrounded by a polyvinyl chloride gasket, and poured into the mold.

Next, as a prepolymerization step, 10 cm of both sides of the mold were
Irradiate for 10 seconds with a 2 KW high pressure mercury lamp from a distance of
After repeating intermittent irradiation 15 times with 2-minute irradiation stop,
The polymerization was completed by further irradiation for 30 seconds, and the lens was removed from the mold. This lens was evaluated using the evaluation method described above, and the results are shown in Table 1. Furthermore, similar evaluations were performed on lenses that had been annealed at 110° C. for 1 hour, and the results are shown in Table 1.

Comparative Example 1 A lens was molded using the same monomer composition and mold as in Example 1, but with the curing method changed as follows. Both surfaces of the mold were continuously irradiated for 3 minutes from a distance of 10 cnI using a 2 KW high pressure mercury lamp. The lenses removed from the molds were evaluated using the evaluation method described above, and the results are shown in Table 1.

Furthermore, similar evaluations were performed on lenses annealed at 110° C. for 1 hour, and the results are shown in Table 1.

Example 2 Compound 6 in which xylylene diisocyanate and 2-hydroxypropyl methacrylate were reacted at a molar ratio of 1:2
0 parts by weight, 20 parts by weight of Hensyl methacrylate, 20 parts by weight of trimethylolpropane trimethacrylate, 0.5 parts by weight of benzophenone, 0.5 parts by weight of triphenylphosphine.
1 part by weight and 0.01 part by weight of 2-hydroxy-4-methoxybenzophenone were mixed to prepare a 1,000-mer composition. This monomer composition was injected into the same mold as in Example 1, and a lens was molded using the same curing method using intermittent irradiation as in Example 1. This lens was evaluated using the evaluation method described above, and the results are shown in Table 1. Furthermore, similar evaluations were performed on lenses annealed at 110° C. for 1 hour, and the results are shown in Table 1.

Example 3 Using the monomer composition used in Example 2, intermittent irradiation of 10 seconds of irradiation and 10 minutes of irradiation stop was repeated in the prepolymerization process 15 times, followed by further 30 seconds of irradiation to complete the polymerization. , the lens was removed from the mold. This lens was evaluated using the evaluation method described above, and the results are shown in Table 1. Furthermore, the same evaluation was performed on the cover lens which was annealed at 110° C. for 1 hour, and the results are shown in Table 1.

Comparative Example 2 Using the monomer composition used in Example 2, a lens was molded using the same curing method as in Comparative Example 1 using continuous ultraviolet irradiation. This lens was evaluated using the evaluation method described above, and the results are shown in Table 1.

Furthermore, similar evaluations were performed on lenses annealed at 110° C. for 1 hour, and the results are shown in Table 1.

Example 4 40 parts by weight of a compound obtained by reacting isophorone diisocyanate and 2-hydroxyethyl methacrylate at a molar ratio of 1:2, 35 parts by weight of polyethylene glycol diacrylate ("Aronix M-245" manufactured by Toagosei Kagaku Kogyo ■), 25 parts by weight of hexanediol diacrylate, 2
, 4.6-trimethylbenzoyldiphenylphosphine oxide 0.05 parts by weight: 11 parts, t-butylperoxyisobutyrate 0.03 parts by weight, 2(2"-hydroxy-5°-methylphenyl)benzotriazole 0.
02 parts by weight were mixed to prepare a 1000 ml composition. This composition was poured into the same mold as in Example 1.

Next, as a preliminary polymerization step, polymerization was performed using a 3 KW metal halide lamp from a distance of 20 cm on both sides of the mold.
It passed between the pair of lamps at a speed of 2 m/min. After passing, it was left at room temperature for 20 minutes. After that, 1
After irradiating with the lamp for 1 minute, the glass mold was removed and curing was carried out at 110° C. for 1 hour to complete the polymerization. After demolding, this lens was evaluated using the evaluation method described above, and the results are shown in Table 1.

Furthermore, similar evaluations were performed on lenses that had been annealed at 120° C. for 1 hour, and the results are shown in Table 1.

Comparative Example 3 The same composition as in Example 3 was injected into the same mold as in Example 1, and the curing method was changed as follows. Irradiation was performed continuously for 1 minute using a 3 KW metal halide lamp from a distance of 20 cm on both sides of the mold, and the mold was cured at 110° C. for 1 hour without removing the glass mold. The demolded lenses were evaluated using the evaluation method described above, and the results are shown in Table 1.

Furthermore, similar evaluations were performed on lenses that had been annealed in the same manner as in Example 4, and the results are shown in Table 1.

Example 5 Tolylene diisocyanate (trade name Coronate T-80
, manufactured by Nippon Polyurethane Co., Ltd.) and 2-hydroxypropyl methacrylate at a molar ratio of 1:2, 40 parts by weight of a compound, 20 parts by weight of 2,4.6-tribromophenoxyethyl acrylate, 2.2'-bis(4 -methacryloxypentaethoxyphenyl)-propane 20 parts by weight,
20 parts by weight of tricyclo(5,2,1,0)decanyl methacrylate, 0.1 parts of methylphenylglyoxylate
A 1,000-mer composition consisting of parts by weight, 0.1 parts by weight of t-butylperoxy-2-ethylhexanoate, and 0.02 parts by weight of 2(2°-hydroxy-5°-methylphenyl)benzotriazole was carried out. It was poured into the same mold as in Example 1.

Next, as a preliminary polymerization step, intermittent irradiation was performed on both sides of the mold from a distance of 20c+n using a 3KW fusion lamp (V bulb) for 30 seconds and then stopped for 8 minutes.
The polymerization was repeated several times and irradiated for an additional 1 minute to complete polymerization, and the lens was removed from the mold. This lens was evaluated using the evaluation method described above, and the results are shown in Table 1.

Furthermore, similar evaluations were performed on lenses that had been annealed in the same manner as in Example 3, and the results are shown in Table 1.

Comparative Example 4 The same composition as in Example 5 was injected into the same mold as in Example 1, and the curing method was changed as follows. Both sides of the mold were continuously irradiated for 3 minutes from 20 cm'i&11 using a B MW fusion lamp (V bulb). The demolded lenses were evaluated using the evaluation method described above, and the results are shown in Table 1.

Furthermore, similar evaluations were performed on lenses that had been annealed in the same manner as in Example 4, and the results are shown in Table 1.

Table 1 [Effects of the Invention] According to the present invention, there is a remarkable improvement in surface hardness, which was a drawback of short-time photocurable lenses. This shortens the manufacturing time of plastic lenses, increases the usage cycle of glass molds, and reduces the number of glass molds required. Furthermore, the production space can be reduced, making an extremely high contribution to reducing production costs.

Claims (1)

[Scope of Claims] 1) A method for producing a plastic lens by polymerizing monomers by irradiation with active energy rays or by using irradiation with active energy rays and heat treatment in combination, comprising: irradiating active energy rays and stopping the irradiation; 1. A method for producing a plastic lens, which comprises performing a prepolymerization step at least once, and then irradiating with active energy rays to complete the polymerization. 2) The manufacturing method according to claim 1, wherein at least one of the active energy ray irradiation stop times in the prepolymerization step is 1 minute to 60 minutes.