JP3658969B2 - Manufacturing method of plastic lens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a photo-curing resin plastic lens with little optical distortion.
[0002]
[Prior art]
The plastic lens is manufactured by being molded into a shape having a desired optical performance by a method such as an injection molding method, a reaction injection molding method, or a casting molding method.
[0003]
Among these, a casting molding method is usually used as a method for producing a high-performance plastic lens.
[0004]
In the casting molding method, a liquid curable resin composition is injected into a cavity that is in the shape of a lens of a mold, and after curing by irradiation with active energy rays such as heating or ultraviolet rays, the mold is removed. This is how to get a lens. Among them, the active energy ray irradiation polymerization method requires a long polymerization time of about 20 hours while the thermal polymerization method is cured in a polymerization time of several minutes. There are merits, and it is particularly suitable for the production of plastic lenses that are made to order and are produced in small quantities and various types.
[0005]
The general steps of the casting method using ultraviolet curing will be described. First, the lens molding die 100 shown in FIG. 3 is produced. In this step, the upper and lower glass molds 101 and 102 on which the transfer surfaces of the optical surfaces of the lenses are formed are prepared, and the transfer surfaces of these molds are arranged to face each other so as to have a desired lens thickness. The molds 101 and 102 are sealed with a transparent or translucent adhesive tape 103 to produce a molding die 100 in which a cavity composed of the molds 101 and 102 and the adhesive tape 103 is formed.
[0006]
And after inject | pouring the liquid photocurable resin composition 104 in a cavity, a small amount of ultraviolet rays are irradiated in the process called pre-curing, and a liquid monomer is gelatinized. Next, the molding die 100 is placed on a conveyor belt, conveyed in the UV furnace for a predetermined time by the conveyor belt, and irradiated with ultraviolet rays by a UV lamp disposed in the UV furnace, a photocurable resin composition. Is cured. In the UV furnace, consideration is given to uniform irradiation by using not only the direct light of the UV lamp but also the reflected light of the reflector to perform uniform polymerization. After the curing is completed, the mold 100 is disassembled and the cured lens is taken out.
[0007]
[Problems to be solved by the invention]
However, with the recent increase in the refractive index of plastic lenses, as the monomer in which a benzene ring is introduced into the photocurable resin composition is used, the polymerization rate of the photocurable resin composition becomes slow, and the resulting plastic There has been a problem that optical distortion occurs in the lens.
[0008]
This optical distortion is caused by a partial difference in refractive index due to non-uniform polymerization reaction. When the lens is viewed from the front, for example, it appears in a C shape, and the optical performance of the plastic lens is reduced. It is a phenomenon that decreases.
[0009]
The present invention has been made in view of the above problems, and in a method of molding a plastic lens made of a photocurable resin by a casting molding method, a method of manufacturing a plastic lens capable of suppressing the occurrence of the optical distortion. The purpose is to provide.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventor, when performing photopolymerization, immediately after the molding die is carried into the UV furnace by the belt conveyor, the ultraviolet rays are mainly propagated through the molding die. Since irradiation is performed obliquely from the front side of the direction, the irradiation of ultraviolet rays is concentrated on the front part of the molding die in the traveling direction, and the polymerization reaction proceeds at the front part, while the rear side proceeds slowly and the polymerization reaction becomes uneven. It was thought that this was the cause of optical distortion.
[0011]
Therefore, in order to prevent the irradiation of ultraviolet rays from the lateral direction, to irradiate ultraviolet rays only from the vertical direction, and to make the ultraviolet irradiation uniform, for example, the molding die is sealed using a black colored adhesive tape as a sealing member. After stopping and photocuring, a plastic lens having no optical distortion was obtained, and it was confirmed that the cause of the optical distortion was irradiation of ultraviolet rays from the lateral direction, and the present invention was made.
[0012]
Accordingly, in the present invention, the molds are produced by fixing the molds around the side surfaces of the two molds positioned at a predetermined interval with a sealing member and sealing the gap between the molds, A plastic in which a liquid photocurable resin composition is injected into a cavity formed between two molds of the molding die and the sealing member, and the composition in the cavity is irradiated with active energy rays and cured. In the method of manufacturing a lens, the sealing member is made of an adhesive tape having a colored tape base material that shields the active energy ray, and the cavity side surface is shielded from the active energy ray to irradiate the active energy ray. A method for producing a plastic lens is provided.
[0014]
According to the method for producing a plastic lens of the present invention, the adhesive tape for fixing the mold is colored with a shielding property to prevent irradiation of active energy rays from the lateral direction, mainly from the vertical direction. Since it can irradiate uniformly, a polymerization reaction can be made uniform in the whole lens and generation | occurrence | production of an optical distortion can be suppressed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although the embodiment of the manufacturing method of the plastic lens of the present invention is described, the present invention is not limited to the following embodiment.
[0022]
As described above, the method for producing a plastic lens of the present invention produces a molding die, injects a liquid photocurable resin composition into a cavity of the molding die, and shields the side surface of the molding die. It is cured by irradiating active energy rays such as ultraviolet rays.
[0023]
Here, the active energy ray is typified by ultraviolet rays, but other examples include X-rays, electron beams, and visible light. Therefore, in this specification, “light” in photocuring and photopolymerization is a concept including all these active energy rays.
[0024]
FIG. 1 is a cross-sectional view showing an embodiment of a molding die used in the present invention. In this molding die 1, an ultraviolet-impermeable adhesive tape 4 is wound around the outer surfaces of two molds 2 and 3 with the upper mold 2 and the lower mold 3 positioned at a predetermined interval. 3 is fixed at a predetermined interval, and a gap between these molds 2 and 3 is sealed in a sealed space with an ultraviolet-opaque adhesive tape 4 to form a lens-shaped cavity 5. Note that two molds may be sealed using an ultraviolet-opaque gasket instead of the adhesive tape 4 and fixed with a clip or the like.
[0025]
The materials of the two molds 2 and 3 constituting the molding die 1 need to be able to transmit ultraviolet rays, and are usually made of transparent glass. The surfaces 21 that face each other and transfer the optical surface of the lens, 31 is mirror-polished.
[0026]
In the UV-impermeable adhesive tape 4, an adhesive 42 that does not affect the polymerization is applied to the tape base 41. The tape base 41 needs to have a certain degree of strength to hold the two molds 2 and 3 and is inexpensive because it is disposable. Therefore, as materials that can be used, polyesters such as polyethylene terephthalate and polyethylene-2,6 naphthalate, polyolefins such as polypropylene and poly-4-methylpentene, polyamides, polycarbonates and the like can be used. A stretched polyethylene terephthalate tape is preferred. The thickness of the tape base material 41 is suitably in the range of 10 to 100 μm.
[0027]
Further, since the adhesive 42 is in direct contact with the liquid monomer, it is required that the adhesive 42 does not dissolve in the liquid monomer or inhibit the curing reaction. Usually, acrylic, rubber-based, vinyl acetate-based, silicon-based, etc. These mixed systems are selected and used depending on the type of monomer.
[0028]
In this embodiment, the tape base material 41 needs not to transmit ultraviolet rays. Therefore, for example, a colorant is contained in the tape base material 41 to make it light-impermeable, an ultraviolet absorber is contained in the tape base material 41, or a colorant or a light-impermeable thin film is applied to the tape base material 41. By making such a measure, it is made opaque to ultraviolet rays. Moreover, after producing a shaping | molding type | mold with a light transmissive tape, you may affix the light impervious tape which interrupts | blocks the light from the front side of the advancing direction which causes a distortion partially or entirely.
[0029]
As the colorant, it is effective to mix carbon black which is inexpensive and highly effective. Moreover, as a ultraviolet absorber, a benzophenone type, a triazole type, a benzoate type, an acrylate type, an anilide type etc. can be used, for example. Further, the colorant or the light-impermeable thin film can be formed by depositing a metal or a pigment by a physical film formation method such as vacuum vapor deposition or sputtering, or a CVD (chemical vapor deposition) method.
[0030]
The width of the UV-impermeable adhesive tape 4 is such that it protrudes from the two molds from the viewpoint of workability. However, increasing the amount of protrusion can prevent UV irradiation from the side and also enhance the directivity of UV irradiation in the vertical direction. However, since the tape is wasted and uneconomical, it is selected as appropriate.
[0031]
In the method for producing a plastic lens of the present invention, a photocurable resin composition is injected into the cavity 5 of the molding die 1 having such a side shielded, preferably precured, and then cured by ultraviolet irradiation. . Alternatively, ultraviolet irradiation and thermal polymerization can be performed simultaneously, or in some cases, thermal polymerization can be performed after ultraviolet irradiation.
[0032]
The photocurable resin composition contains a photocurable monomer and a photopolymerization initiator. The photo-curable monomer has a monofunctional or polyfunctional reactive group, such as acrylate or methacrylate of aliphatic, alicyclic or aromatic alcohol, urethane acrylate, urethane methacrylate, epoxy acrylate, epoxy methacrylate, polyester acrylate. A compound having one or more radically polymerizable double bonds in the molecule, such as polyester methacrylate, can be used.
[0033]
Examples of the photopolymerization initiator for polymerization curing include 2-hydroxy-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, methylphenylglyoxylate, 2,4,6-trimethylbenzoyldiphenyl. A phosphine oxide etc. are mentioned.
[0034]
Further, when an amine such as dimethylaminoethanol is used as a photosensitizer, the photopolymerization rate is improved.
[0035]
When thermal polymerization is used in combination, it is preferable to use a thermal polymerization initiator, for example, benzoyl peroxide, diisopropyl peroxydicarbonate, t-butyl peroxyisobutyrate, t-butyl peroxy-2-ethyl Examples thereof include organic peroxides such as hexanoate, azo compounds such as 2,2-azobisisobutylnitrile and 2,2-azobis (2,4-dimethylvaleronitrile), and one of these may be used alone or 2 More than one species can be used in combination. The optimum value of the polymerization temperature when using heat together varies depending on the type of monomer, the type of catalyst, and the amount added, but is generally preferably in the range of 30 to 180 ° C. This is because if the temperature is 30 ° C. or higher, the activity of the thermal polymerization catalyst is sufficient, and if it is 180 ° C. or lower, the lens is hardly colored or deteriorated.
[0036]
Furthermore, various additives such as an antioxidant, an anti-yellowing agent, an ultraviolet absorber, a bluing agent, and a pigment can be blended in the photocurable resin composition as necessary.
[0037]
Such a photocurable resin composition is injected into the cavity 5 of the molding die 1 through, for example, an injection needle inserted into the adhesive tape 4 through the injection needle.
[0038]
After the injection, it is preferable to perform pre-curing in which the liquid monomer is gelled by irradiating the molding die 1 with a small amount of ultraviolet rays so that the liquid monomer does not leak from the injection hole. This pre-curing also has an effect of making the polymerization uniform and relieving the stress generated with the polymerization shrinkage. In the pre-curing, for example, it is preferable to irradiate the ultraviolet ray of about 50 to 30,000 mJ / cm ² by irradiating the ultraviolet lamp with the molding die 1 stationary.
[0039]
Next, ultraviolet irradiation is performed to cure the photocurable resin composition. Usually, the molding die 1 is placed on a belt conveyor 20 that conveys the inside of the UV furnace 10 shown in FIG. 4 and conveyed, and is passed through the UV furnace 10 for a predetermined time. UV irradiation is performed by irradiation of the light source 11 and the light source 12 disposed below. Or after making it convey and irradiate an ultraviolet-ray, you may irradiate an ultraviolet-ray in the state which made the shaping | molding die stationary. The wavelength of ultraviolet rays from the light sources 11 and 12 of the UV furnace is about 2000 to 8000 mm. As the light sources 11 and 12, a chemical lamp, a xenon lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a fusion lamp, or the like can be applied. The irradiation amount of ultraviolet rays is not particularly limited, but is about 10 to 500 J / cm ² .
[0040]
In this embodiment, since the adhesive tape 4 constituting the side surface of the mold 1 is opaque to ultraviolet rays, the ultraviolet rays emitted from the light sources 11 and 12 enter the composition in the cavity 5 from the lateral direction. However, it is incident mainly from the vertical direction.
[0041]
In the vicinity of the entrance in the UV furnace immediately after being placed on the belt conveyor 20 and carried into the UV furnace 10, as shown in FIG. 4, the molding die 1 is mainly irradiated with ultraviolet rays from the front lateral direction toward the traveling direction. As a result, the amount of irradiation is smaller in the rear direction than in the forward direction. Therefore, conventionally, the front part of the cavity in the traveling direction is intensively irradiated with ultraviolet rays and hardens fast, and the rear part hardens slowly, resulting in uneven progress of polymerization, resulting in optical distortion. It was. On the other hand, in the present invention, the ultraviolet irradiation from the lateral direction is prevented, and the ultraviolet rays are uniformly irradiated mainly from the vertical direction and the polymerization progresses uniformly, so that the occurrence of optical distortion can be prevented.
[0042]
After the irradiation with ultraviolet rays is completed, the composition in the cavity of the molding die 1 is cured to obtain a lens-shaped plastic, the molding die 1 is disassembled and the lens is taken out, and the molding process is completed.
[0043]
The plastic lens thus obtained has no optical distortion and is useful as a spectacle lens or other lens as a plastic lens having excellent optical performance.
[0044]
In the above embodiment, the adhesive tape 4 that holds the two molds 2 and 3 is made opaque to ultraviolet rays. However, the present invention is not limited to this, and any means can be used as long as the side surface of the molding die can be shielded. It may be used. For example, a colorant may be added to the gasket that seals the side surfaces of the two molds described above to make it light-impermeable. This gasket is made of, for example, polyvinyl chloride, ethylene-vinyl acetate copolymer, ethylene-1-butene copolymer, etc., and is molded by blending a coloring agent, an ultraviolet absorber, a pigment, etc. in the molding material. Thus, it is possible to make the film opaque to ultraviolet rays.
[0045]
Moreover, a shielding jig can also be used. FIG. 2 shows one form of the shielding jig. The shielding jig 30 is made of paper, plastic, metal, or the like, and is formed in a short-axis cylindrical shape having an inner diameter slightly larger than the diameter of the same molding die 100 as the conventional one. Before the molding die 100 is placed in the UV furnace, the shielding jig 30 is set on the molding die 100 placed on the belt conveyor to shield the side surface of the molding die 100 from light. The height of the shielding jig 30 can be freely set. If the height is increased, the directivity in the vertical direction of the ultraviolet irradiation can be increased, but the irradiation efficiency is deteriorated, so that it is appropriately selected.
[0046]
Since such a shielding jig 30 can use the same transparent or translucent adhesive tape 103 as the adhesive tape that holds the two molds 101 and 102, it is possible to reliably prevent an increase in cost. Irradiation of ultraviolet rays from the lateral direction can be prevented, and the occurrence of optical distortion can be suppressed.
[0047]
The shape of the shielding jig is not particularly limited as long as it can shield light from the front side in the traveling direction, and other than the cylindrical shape shown in FIG. 2, for example, a circular arc shape in which the cylinder is cut in the axial direction The shielding jig may be used.
[0048]
The shielding jig may be used alone or integrated with the molding die. Furthermore, a method of integrating a shielding jig with a conveyor and setting a molding die in the fixed shielding jig may be used.
[0049]
(Example 1)
EDM1 (epoxy dimethacrylate obtained by reacting bisphenol A diglycidyl ether and methacrylic acid) 40 g, 9 BGDM (nonabutylene glycol methacrylate) 20 g, PHM (phenyl methacrylate) 25 g, UM1 (isophorone diisocyanate and 2-hydroxypropyl methacrylate) 15 g of urethane dimethacrylate obtained by reacting 2, 0.06 g of trimethylbenzoyldiphenylphosphine oxide, 0.05 g of 2-hydroxy-4-methoxybenzophenone, and 0.2 g of tridodecyl phosphate. After thoroughly stirring at room temperature, the pressure was reduced to 50 mmHg and deaerated for 10 minutes.
[0050]
Then, the periphery of two glass molds with a diameter of 80 mm having a mirror finish is wrapped with a colored adhesive tape (a black polyethylene terephthalate film kneaded with a colorant and coated with a silicone-based adhesive), and the wall thickness is 15 mm. Plastic lens molding in which a plastic flat plate molding die and two lens molding glass molds having a diameter of 70 mm are fixed with the colored adhesive tape so that the center wall thickness is 1.5 mm and the power is -6.0D. Each mold was prepared, and the above composition was poured into these molds and irradiated with ultraviolet rays to be once gelled.
[0051]
Next, an ultraviolet lamp (lamp length: 10 inches, 2 kW metal halide lamp) was arranged above and below the glass mold surface of the molding die so that the molding die passed along the major axis of the ultraviolet lamp. In the UV furnace, 20 J / cm ² of ultraviolet rays were irradiated from both sides while the molding die containing the gelled monomer was conveyed by a belt conveyor.
[0052]
Subsequently, 30 J / cm ² of ultraviolet rays were irradiated from both sides in a state where the molding die was stationary between two ultraviolet lamps arranged to face each other.
[0053]
No optical distortion was observed in any of the obtained plastic lenses, and a lens having excellent optical properties could be obtained.
[0054]
(Comparative Example 1)
A plastic lens was produced in the same manner as in Example 1 except that a silicone-based adhesive was applied to the same transparent polyethylene terephthalate film as the conventional adhesive tape for fixing the two molds.
[0055]
Optical distortion was observed in the obtained lens, and it was confirmed that a lens having inferior optical performance was obtained.
[0056]
(Example 2)
EDM1 40 g, 9BGDM 20 g, BZM (benzyl methacrylate) 25 g, UM1 15 g, 2,4,6-trimethylbenzoyldiphenylphosphine oxide 0.03 g, 2-hydroxy-4-methoxybenzophenone 0.05 g, tridodecyl phosphate 0.2 g Were mixed and stirred well at room temperature, then depressurized to 50 mmHg and deaerated for 10 minutes.
[0057]
Then, the periphery of two glass molds with a diameter of 80 mm having a mirror finish is wrapped with a colored adhesive tape (a black polyethylene terephthalate film kneaded with a colorant and coated with a silicone-based adhesive), and the wall thickness is 15 mm. For plastic lens molding, a plastic flat plate molding die fixed to 2 mm and a lens molding glass mold with a diameter of 70 mm are fixed with the colored adhesive tape to a center thickness of 1.5 mm and a power of −6.0 D. Each mold was produced, and the above composition was injected into these molds and irradiated with ultraviolet rays to be once gelled.
[0058]
Next, an ultraviolet lamp (lamp length: 10 inches, 2 kW metal halide lamp) was arranged above and below the glass mold surface of the molding die so that the molding die passed along the major axis of the ultraviolet lamp. In the UV furnace, 20 J / cm ² of ultraviolet rays were irradiated from both sides while the molding die containing the gelled monomer was conveyed by a belt conveyor.
[0059]
Subsequently, 30 J / cm ² of UV light was emitted from both sides while the molding die was transported by a belt conveyor along the direction of the long axis of the UV lamp between two UV lamps arranged opposite to each other. Irradiated.
[0060]
No optical distortion was observed in any of the obtained plastic lenses, and a lens having excellent optical properties could be obtained.
[0061]
(Comparative Example 2)
A plastic lens was produced in the same manner as in Example 2 except that the same transparent polyethylene terephthalate film coated with a silicone adhesive was used as the adhesive tape for fixing the two molds.
[0062]
Optical distortion was observed in the obtained lens, and it was confirmed that a lens having inferior optical performance was obtained.
[0063]
【The invention's effect】
According to the method for producing a plastic lens of the present invention, in the method of producing a photocurable resin lens by a casting molding method, a plastic lens having excellent optical performance is produced by reliably suppressing the occurrence of optical distortion. can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one embodiment of a molding die using a colored adhesive tape used in the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a shielding jig used in the present invention.
FIG. 3 is a cross-sectional view showing an example of a conventional mold.
FIG. 4 is a conceptual diagram illustrating ultraviolet irradiation in a UV furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mold for shaping | molding, 2 ... Upper mold, 3 ... Lower mold, 4 ... Ultraviolet-opaque adhesive tape, 5 ... Cavity, 10 ... UV furnace, 11 ... Light source, 12 ... Light source, 20 ... Belt conveyor, 30 ... Shielding Jig, 100 ... Mold, 103 ... Adhesive tape

Claims (1)

These molds are fixed with sealing members around the side surfaces of two molds positioned at a predetermined interval, and a gap between these molds is sealed to produce a molding die. In a method for producing a plastic lens, a liquid photocurable resin composition is injected into a cavity formed between a single mold and the sealing member, and the composition in the cavity is cured by irradiation with active energy rays.
The sealing member is made of an adhesive tape having a colored tape base material that shields the active energy rays, and the active energy rays are irradiated while shielding the cavity side surfaces from the active energy rays. Manufacturing method of plastic lens.

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