WO2015118667A1 - Method for manufacturing lens, resin starting material used therein, and lens obtained by said manufacturing method - Google Patents

Abstract

　This method for manufacturing a lens comprises (i) a step for injection molding using a thermoplastic resin starting material and obtaining a lens precursor in an injection mold, and (ii) a step for arranging the lens precursor in a compression mold and compression-molding the lens precursor. When the lens precursor is moved from the injection molding of step (i) to the compression molding of step (ii), the lens precursor is removed from the injection mold when the center temperature of the lens precursor is equal to or greater than the intermediate-point glass transition temperature of the thermoplastic resin starting material.

Description

Lens manufacturing method, resin raw material used therefor and lens obtained by the manufacturing method

The present invention relates to a lens manufacturing method, a resin raw material used therefor, and a lens obtained by the manufacturing method. More specifically, the present invention relates to a method for producing a plastic lens used as an optical element and a resin material used therefor, and also relates to a plastic lens obtained by such a production method.

Lens is generally used as an optical element. In particular, plastic lenses are used for various optical system applications because they have a specific gravity smaller than that of glass lenses and are lighter in weight, have good moldability and high impact resistance.

Plastic lenses can be obtained through molding. That is, a plastic lens can be obtained by imparting a desired lens shape to the resin material using a mold.

JP 2007-331311 A JP 2009-061676 A Japanese Patent Laid-Open No. 2011-167988 JP 2012-183835 A

As a method of manufacturing a plastic lens used as an optical element, a process of subjecting a resin material to injection molding and then compression molding can be considered. That is, after obtaining a lens precursor as a base of a plastic lens with an injection mold, the lens precursor is compressed with a compression mold to obtain a plastic lens.

In such a manufacturing method, when transferring the lens precursor from the injection mold to the compression mold, it is necessary to sufficiently cool the lens precursor in the injection mold from the viewpoint of handling and product quality. It is generally considered. That is, such a lens precursor is taken out from the injection mold after being sufficiently cooled. Because if the lens precursor is taken out from the injection mold without sufficiently cooling, the lens precursor may still have flexibility, and the shape of the lens precursor may change over time. Because it is considered. In addition, if it is not sufficiently cooled, it is considered that not only the lens precursor is difficult to grip due to “softness” but also the shape of the lens precursor may be locally deformed by such gripping. ing.

On the other hand, plastic lenses have a need for mass production while maintaining high quality. In order to efficiently mass-produce, it is necessary to shorten the cycle unit of repeated injection molding / compression molding, but it is considered that an excessively short cycle unit can lead to quality deterioration.

The present invention has been made in view of such circumstances. A main object of the present invention is to provide a lens manufacturing method that can suitably satisfy the needs of mass production without deteriorating lens quality.

The inventors of the present application tried to achieve the above object by addressing in a new direction rather than responding on the extension of the prior art. As a result, the present invention of the lens manufacturing method has been achieved.

Specifically, the lens manufacturing method of the present invention includes:
(I) a step of performing injection molding using a thermoplastic resin raw material to obtain a lens precursor in an injection mold, and (ii) placing the lens precursor in a compression mold and compressing the lens precursor. Comprising the step of subjecting to molding,
In transferring the lens precursor from the injection molding in the step (i) to the compression molding in the step (ii), the lens precursor is obtained when the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin raw material. Is taken out from the injection mold.

The lens manufacturing method of the present invention is characterized by taking out the lens precursor from the injection mold. Specifically, in the production method of the present invention, when the lens precursor is transferred from the injection mold to the compression mold, the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material. The lens precursor is removed from the injection mold.

In this specification, “lens” substantially means a plastic lens used as an optical element.

In addition, in this specification, the “lens precursor” refers to an injection molded body that is molded to obtain a desired lens. That is, a resin molded body that is preliminarily molded by injection molding to obtain a lens corresponds to a “lens precursor”.

In a preferred embodiment, the center temperature of the lens precursor in the injection mold is indirectly determined based on Equation 1.

In other words, based on Equation 1, the center temperature of the lens precursor in the injection mold is indirectly grasped, so that the center temperature of the lens precursor becomes “above the midpoint glass transition temperature of the thermoplastic resin raw material”. At some point, the lens precursor is removed from the injection mold.

In another preferred embodiment, a plurality of lenses are manufactured in parallel. In such an embodiment, a thermoplastic resin raw material is subsequently injected as quickly as possible to an injection mold in which a certain lens precursor is taken out above its midpoint glass transition temperature to obtain another lens precursor.

In still another preferred embodiment, the lens precursor is subjected to cooling in a state of being taken out from the injection mold prior to being subjected to the compression molding in the step (ii). That is, the lens precursor is not subjected to substantial cooling in the injection mold, but the lens precursor is subjected to substantial cooling in an atmosphere after being taken out (for example, in an ambient atmosphere).

In yet another preferred embodiment, the lens precursor taken out from the injection mold is transferred to the compression mold without being particularly cooled. That is, the lens precursor taken out from the injection mold without subjecting the lens precursor to substantial cooling is charged into the compression mold as quickly as possible.

In yet another preferred embodiment, the thermoplastic resin raw material used in step (i) has a Vicat softening temperature measured by JIS K7206 (B50 method) of 105 ° C. or higher and 120 ° C. or lower, and JIS K7210 A thermoplastic resin material having a measured melt mass flow rate of 1 g / 10 min or more and 20 g / 10 min or less is used.

In yet another preferred embodiment, a (meth) acrylic resin is used as the thermoplastic resin material used in step (i). In such an embodiment, the (meth) acrylic resin may be, for example, a copolymer composed of “methacrylic acid ester” and “monomer other than methacrylic acid ester”.

As a suitable aspect of the lens precursor obtained in step (i), the maximum thickness dimension is 10 mm or more and 150 mm or less, and the maximum width dimension is 10 mm or more and 200 mm or less. In other words, in a preferred embodiment, the lens precursor having such a maximum dimension is taken out from the injection mold under the condition of the intermediate glass transition temperature or higher of the raw material resin.

In yet another preferred embodiment, in step (ii), the relationship between the mold temperature Tp (° C.) of the compression mold and the intermediate glass transition temperature Tmg (° C.) of the thermoplastic resin material is Tmg + 45 ≦ Tp ≦ Tmg + 85. And the compression pressure of the compression mold is 15 kN or more and 80 kN or less, and the lens precursor is subjected to compression molding under the condition that the compression time by the compression mold is 110 seconds or more and 200 seconds or less.

Step (ii) of the production method of the present invention comprises:
(A) a sub-step of subjecting the lens precursor to heating in a compression mold;
(B) a sub-step of subjecting the heated lens precursor to compression molding, and (c) a sub-step of subjecting the lens obtained by compression molding of the lens precursor to cooling in a compression mold. It may be. In other words, in the compression molding of the step (ii), a heating process for preheating the lens precursor, a compression molding process for compressing the lens precursor so heated, and a lens obtained by the compression molding are performed. It is preferable that the cooling process to cool is included. In such a case, it is preferable that the heating sub-step (a), the compression-molding sub-step (b), and the cooling sub-step (c) are sequentially performed in a state where the compression-molding mold charged with the lens precursor is conveyed. In other words, it is preferable that the compression molding mold in which the lens precursor is present is continuously conveyed in this order in the steps of “heating”, “compression molding”, and “cooling”.

In the present invention, a thermoplastic resin material suitably used in the above production method is also provided. More specifically, a (meth) acrylic resin used in the above lens manufacturing method is provided in the present invention.

Furthermore, the present invention also provides a lens obtained by the above manufacturing method. In a preferred embodiment, the lens obtained by the above manufacturing method is a vehicle lamp lens.

According to the present invention, it is possible to efficiently produce a lens without substantially reducing the lens quality. Specifically, when the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material, the lens precursor is taken out from the injection mold. It can be used quickly for the formation of lens precursors and contributes to the realization of efficient mass production.

Further, in the present invention, although the lens precursor is taken out of the injection mold at such an early stage, the quality as a finally obtained lens product cannot be substantially lowered. In other words, when the lens precursor taken out from the injection mold is subjected to compression molding under the condition that the glass transition temperature is higher than the midpoint glass transition temperature, the quality as a final lens product is not particularly unexpectedly lowered and is realistic. The present inventors have found that this is particularly desirable as a simple lens manufacturing process.

As described above, the present invention suitably satisfies the needs for mass production while satisfying the lens quality.

FIG. 1 is a schematic diagram for explaining the concept of the present invention. FIG. 2 is a calorimetric analysis graph (DSC curve) for explaining the “midpoint glass transition temperature (Tmg)”. FIG. 3 is a schematic diagram of a lens precursor (FIG. 3A: perspective view, FIG. 3B and FIG. 3C: cross-sectional view). FIG. 4 is a perspective view schematically showing one aspect of a sub-process that can be performed in the compression molding process. FIG. 5 is a perspective view schematically showing one aspect of a sub-process that can be performed in the compression molding process. FIG. 6 is a schematic diagram of a lens (FIG. 6A: perspective view, FIG. 6B cross-sectional view).

Hereinafter, the lens manufacturing method according to the present invention, the resin raw material used in the lens manufacturing method, and the lens obtained by the manufacturing method will be described in detail. It should be noted that the forms shown in the drawings are merely schematically shown for the purpose of understanding the present invention, and the dimensional ratio, appearance, and the like may be different from the actual ones.

[Lens Manufacturing Method of the Present Invention]
The method for producing a lens of the present invention comprises a step (i) of obtaining a lens precursor in an injection mold by performing injection molding using a thermoplastic resin material, and the lens precursor thus obtained is compression-molded. And at least a step (ii) of subjecting the mold to compression molding. In particular, in the lens manufacturing method of the present invention, the lens precursor is handled under specific conditions. Specifically, when the lens precursor is transferred from the injection mold in step (i) to the compression mold in step (ii), the center temperature of the lens precursor is the midpoint glass transition of the thermoplastic resin material. When the temperature is above the temperature, the lens precursor is removed from the injection mold. FIG. 1 schematically shows the concept of the present invention.

As described above, the present invention does not dare to subject the lens precursor to sufficient cooling in the injection mold, and the lens precursor is ejected early when the lens precursor is at or above the midpoint glass transition temperature. Remove from the mold. In other words, the lens precursor is taken out from the injection mold under conditions that are equal to or higher than the midpoint glass transition temperature in the stage before sufficient cooling, and the lens precursor thus taken out is charged into the compression mold.

Here, the recognition of those skilled in the art in the prior art will be described. Conventionally, there is no special consideration when transferring an injection molded product from injection molding to compression molding. Considerations beyond the operation of taking the injection molded product out of the injection mold and charging it into the compression mold. Did not reach in particular. Even if consideration is given, when transferring an injection molded product from an injection mold to a compression mold, the injection molded product must be sufficiently contained in the injection mold from the viewpoint of handling and product quality. It was common for those skilled in the art to recognize that cooling was necessary. As a result of intensive studies by the inventors of the present invention, it is unexpected if the lens precursor is taken out from the injection mold when the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material. In addition, the inventors of the present application have found that the quality is not particularly deteriorated as a final lens product. That is, when the lens precursor is taken out from the injection mold under the condition of the intermediate glass transition temperature or higher, and the lens precursor taken out under such conditions is charged into the compression mold, the lens is obtained. It was found that there was no particular problem with the quality as a lens product, and it was sufficiently meaningful as a lens manufacturing process. In particular, the injection mold after removal can be quickly used to form another lens precursor, which has greatly contributed to the realization of efficient mass production, and has also been found to have great benefits ([Prior Art In Patent Documents 1 to 4 cited in [Literature], such lens manufacturing productivity is not particularly considered).

Since the invention has been devised in this way, the manufacturing method of the present invention is characterized in that a lens precursor obtained by an injection mold is taken out only under specific conditions.

Here, in the production method of the present invention, the lens precursor is removed from the injection mold under the condition that the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin raw material. Preferably, the conditions are such that “the center temperature of the lens precursor is not lower than the midpoint glass transition temperature of the thermoplastic resin material” and “the center temperature of the lens precursor is not higher than 200 ° C.”. In other words, assuming that the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material, the lens from the injection mold is used under the condition that the center temperature of the lens precursor is 200 ° C. or lower. It is preferable to take out the precursor. This is because when the center temperature of the lens precursor is higher than 200 ° C., not only the shape of the lens precursor may be collapsed when the lens precursor is taken out, but also the vacuum voids caused by the shrinkage after taking out the lens precursor. This is because it may occur in the center. The upper limit of the above extraction temperature (the temperature at which the lens precursor is extracted from the injection mold) is “the central temperature of the lens precursor is 200 ° C. or less”, but preferably “the central temperature of the lens precursor” Is 190 ° C. or lower ”, more preferably“ center temperature of lens precursor is 180 ° C. or lower ”, and further preferably“ center temperature of lens precursor is 170 ° C. or lower ”.

The present invention will be described in more detail. In step (i) of the lens manufacturing method according to the present invention, injection molding is performed using a thermoplastic resin material to obtain a lens precursor in an injection mold. Specifically, a thermoplastic resin material is injected into an injection mold to obtain a lens precursor.

The injection mold in step (i) is a “mold for plastic molding” provided in a so-called injection molding machine. Therefore, the injection mold in the present invention is typically composed of a fixed mold and a movable mold. The injection molding machine itself includes a hopper portion serving as a raw material inlet, a cylinder portion (for example, a screw / cylinder portion) in which the raw material is melted, and a mold into which the molten raw material is injected. The mold opening / closing mechanism of the injection molding machine is not particularly limited, but may be electric or hydraulic.

Resin raw material used in step (i) is a thermoplastic resin. In other words, a resin material that softens and melts when heated, but solidifies when cooled, is injected into an injection mold. The thermoplastic resin raw material may be input to an injection molding machine in the form of pellets, for example. That is, the pellet-shaped thermoplastic resin raw material may be charged into the hopper of the injection molding machine, whereby the thermoplastic resin raw material is melted in a cylinder (for example, a screw cylinder), and the molten thermoplastic resin raw material is It will be injected into the injection mold.

As the process conditions for injection molding, for example, the cylinder temperature, the mold temperature of the injection mold and the injection speed can be considered. Those process conditions may be appropriately adjusted in view of, for example, the midpoint glass transition temperature of the thermoplastic resin raw material. The cylinder temperature may be about 180 ° C. or more and 250 ° C. or less, preferably about 180 ° C. or more and about 240 ° C. or less, and more preferably about 180 ° C. or more and about 230 ° C. or less. The mold temperature of the injection mold may be about 60 ° C. or higher and 120 ° C. or lower, preferably 70 ° C. or higher and 110 ° C. or lower, more preferably 80 ° C. or higher and 100 ° C. or lower. The injection speed is 0.1 mm / s or more and 2.0 mm / s or less, preferably 0.1 mm / s or more and 1.5 mm / s or less, more preferably 0.2 mm / s or more and 1.0 mm / s. It is about the following.

Examples of the thermoplastic resin raw material include (meth) acrylic resin, polycarbonate resin, and modified polyolefin resin.

In particular, in the present invention, the Vicat softening temperature measured by JIS K7206 (B50 method) is 105 ° C. or more and 120 ° C. or less, and the melt mass flow rate measured by JIS K7210 is 1 g / 10 min or more and 20 g / 10 min or less. It is preferable to use a thermoplastic resin raw material. When such a resin raw material is used, it contributes not only to the viewpoint of the manufacturing process but also to the quality improvement of the obtained lens product.

Specifically, when the melt mass flow rate of the thermoplastic resin raw material is 1 g / 10 min or more and 20 g / 10 min or less, the lens precursor can be taken out earlier in step (i). In other words, under these conditions, the resin temperature after the thermoplastic resin raw material is injected into the injection mold is efficiently lowered, and as a result, the lens precursor is injection molded under the condition of the midpoint glass transition temperature or higher. The time until removal from the mold can be further shortened. The melt mass flow rate (JIS K7210) of the thermoplastic resin raw material is more preferably 1.5 g / 10 min or more and 15 g / 10 min or less, and further preferably 1.5 g / 10 min or more and 13 g / 10 min or less.

On the other hand, when the Vicat softening temperature of the thermoplastic resin raw material is 105 ° C. or higher and 120 ° C. or lower, the lens obtained by the production method of the present invention is more excellent in heat resistance. Since the heat resistance of the lens is more excellent, the lens can be suitably disposed for a long time in the vicinity of the light source where the surrounding environment becomes high temperature. The Vicat softening temperature (JIS K7206 (B50 method)) of the thermoplastic resin raw material is more preferably 105 ° C. or higher and 118 ° C. or lower, and further preferably 106 ° C. or higher and 115 ° C. or lower.

(Meth) acrylic resin is particularly suitable as the thermoplastic resin material used in step (i). This is because it has properties such as high transmittance, low birefringence, high hardness and scratch resistance. As a result, the (meth) acrylic resin having such properties is not only particularly preferable for the lens as the final product, but also “when the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin raw material. It is also preferable from the viewpoint of the characteristic process aspect of the present invention, such as “take out the lens precursor from the injection mold”. In particular, when the heat resistance and mechanical properties of the obtained lens are particularly emphasized, the weight average molecular weight of the (meth) acrylic resin is preferably 50,000 or more and 200,000 or less, more preferably 60000 or more and 180000 or less, and still more preferably. Is 70000 or more and 150,000 or less.

As the (meth) acrylic resin, for example, a homopolymer of (meth) acrylic monomers such as (meth) acrylic acid, (meth) acrylic ester, (meth) acrylonitrile, or a copolymer of two or more thereof, Examples include copolymers of (meth) acrylic monomers and other monomers. In the present specification, the term “(meth) acryl” substantially means “acryl” or “methacryl”, and therefore, (meth) acryl can be simply referred to as “acrylic resin”. .

As the (meth) acrylic resin, it is preferable to use a methacrylic resin from the viewpoint of having excellent hardness, weather resistance, transparency, heat resistance and the like. The methacrylic resin is a polymer obtained by polymerizing a monomer mainly composed of methacrylic acid ester, for example, a homopolymer of methacrylic acid ester and a copolymer composed of two or more methacrylic acid esters. Moreover, as a methacryl resin, the copolymer etc. which consist of monomers other than methacrylic ester and methacrylic ester are also preferable. In the case of a copolymer composed of a methacrylic acid ester and a monomer other than the methacrylic acid ester, the methacrylic acid ester is 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight based on the total amount of monomers. % And monomers other than methacrylic acid ester are 50% by weight or less, preferably 30% by weight or less, more preferably 10% by weight or less.

Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, Examples include n-octyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, decyl methacrylate, undecyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, lauryl methacrylate and the like. Among these, alkyl methacrylate having 1 to 8 carbon atoms in the alkyl group portion is preferable, and methyl methacrylate is more preferable. Methacrylic acid esters may be used alone or in combination of two or more.

Examples of monomers other than methacrylic acid esters include acrylic acid esters, aromatic vinyl monomers, unsaturated nitrile monomers, ethylenically unsaturated carboxylic acid hydroxyalkyl ester monomers, and ethylenically unsaturated carboxylic acids. Amide monomer, ethylenically unsaturated acid monomer, ethylenically unsaturated sulfonic acid ester monomer, ethylenically unsaturated alcohol and its ester monomer, ethylenically unsaturated ether monomer, ethylenically unsaturated Examples include amine monomers, ethylenically unsaturated silane monomers, vinyl halide monomers, and aliphatic conjugated diene monomers. Among these, acrylic acid esters are preferably used. Monomers other than methacrylic acid esters may be used alone or in combination of two or more.

Examples of the acrylate ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, heptyl acrylate, and 2-ethylhexyl acrylate. N-octyl acrylate, n-nonyl acrylate, isononyl acrylate, decyl acrylate, undecyl acrylate, n-amyl acrylate, isoamyl acrylate, lauryl acrylate, and the like. Among these, alkyl acrylates having 1 to 8 carbon atoms in the alkyl group are preferable, and include methyl acrylate, ethyl acrylate, n-propyl acrylate, propyl acrylate, n-butyl acrylate, and isobutyl acrylate. Is more preferable, and methyl acrylate is more preferable.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, o-chlorostyrene, p-chlorostyrene, p- Methoxystyrene, p-aminostyrene, p-acetoxystyrene, sodium styrenesulfonate, α-vinylnaphthalene, sodium 1-vinylnaphthalene-4-sulfonate, 2-vinylfluorene, 2-vinylpyridine, 4-vinylpyridine, etc. Can be mentioned. Of these, styrene is preferred.

Examples of the unsaturated nitrile monomer include acrylonitrile, α-chloroacrylonitrile, α-methoxyacrylonitrile, methacrylonitrile, vinylidene cyanide, and the like.

Examples of the ethylenically unsaturated carboxylic acid hydroxyalkyl ester monomer include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

Examples of the ethylenically unsaturated carboxylic acid amide monomer include acrylamide, methacrylamide, N-butoxymethyl acrylamide, N-butoxymethyl methacrylamide, N-butoxyethyl acrylamide, N-butoxyethyl methacrylamide, N-methoxymethyl. Acrylamide, N-methoxymethylmethacrylamide, Nn-propoxymethylacrylamide, Nn-propoxymethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N, N-dimethylacrylamide, N, N- Examples thereof include dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide and the like.

Examples of the ethylenically unsaturated acid monomer include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, maleic anhydride, vinyl sulfonic acid, and isoprene sulfonic acid. Unsaturated sulfonic acid and the like. The ethylenically unsaturated acid monomer may be neutralized with an alkali metal such as sodium or potassium, ammonia or the like.

Examples of the ethylenically unsaturated sulfonate monomer include alkyl vinyl sulfonate and alkyl isoprene sulfonate.

Examples of ethylenically unsaturated alcohols and ester monomers thereof include allyl alcohol, methallyl alcohol, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl stearate, vinyl benzoate, allyl acetate, methallyl caproate, and lauric acid. Examples include allyl, allyl benzoate, vinyl alkyl sulfonate, allyl alkyl sulfonate, and vinyl aryl sulfonate.

Examples of the ethylenically unsaturated ether monomer include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl allyl ether, ethyl allyl ether, and the like.

Examples of the ethylenically unsaturated amine monomer include vinyldimethylamine, vinyldiethylamine, vinyldiphenylamine, allyldimethylamine, and methallyldiethylamine.

Examples of the ethylenically unsaturated silane compound include vinyltriethylsilane, methylvinyldichlorosilane, dimethylallylchlorosilane, and vinyltrichlorosilane.

Examples of the vinyl halide monomer include vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl bromide, vinylidene bromide, 1,2-dibromoethylene, and the like.

Examples of the aliphatic conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-neopentyl-1,3-butadiene. 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1 , 3-butadiene, substituted linear conjugated pentadienes, linear and side chain conjugated hexadienes, and the like.

When a (meth) acrylic resin is used as a thermoplastic resin raw material, a methyl methacrylate homopolymer (polymethyl methacrylate), or 80 to 99.9% by weight methyl methacrylate and 0.1 to 20% by weight A copolymer composed of a (meth) acrylic acid ester other than methyl methacrylate is particularly preferred. A copolymer comprising 80 to 99.9% by mass of methyl methacrylate and 0.1 to 20% by mass of (meth) acrylic acid ester other than methyl methacrylate is a compound other than methyl methacrylate and methyl methacrylate ( When the total amount with the (meth) acrylic acid ester is 100% by weight, methyl methacrylate is contained in a proportion of 80 to 99.9% by weight, and (meth) acrylic acid ester other than methyl methacrylate is 0.1 to 20%. It is a copolymer obtained by polymerizing a monomer mixture contained in a proportion by weight. In this monomer mixture, methyl methacrylate is preferably contained in a proportion of 85 to 99.5% by mass, more preferably 90 to 99.5% by mass.

In the lens manufacturing method according to the present invention, when the lens precursor is transferred from the injection molding in step (i) to the compression molding in step (ii), the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material. The lens precursor is removed from the injection mold.

Here, the “midpoint glass transition temperature” in the present invention substantially means the glass transition temperature Tmg published in JIS K7121. More specifically, in the calorimetric analysis result (DSC curve) as shown in FIG. 2, a straight line equidistant from the extended straight line of each base line in the vertical axis direction and a step-like change in glass transition The temperature at the point where the partial curve intersects corresponds to the “midpoint glass transition temperature (Tmg)” in the present invention. Note that “T _ig ” shown in the graph of FIG. 2 is called “extrapolated glass transition start temperature”, a straight line obtained by extending the base line on the low temperature side to the high temperature side, and the steps of the glass transition. This is the temperature at the point of intersection with the tangent drawn at the point where the gradient of the curve of the shape change portion is maximized. In addition, “T _eg ” shown in the graph of FIG. 2 is called “extrapolated glass transition end temperature”, a straight line obtained by extending the base line on the high temperature side to the low temperature side, and the steps of the glass transition. slope of the curve of Jo change portion is at a temperature of intersection of the tangent drawn at a point that maximizes (extrapolated glass transition end temperature T _eg in the case of peak on the high-temperature side of the step change appears in the high temperature-side Is the temperature at the intersection of a straight line that extends the base line to the low temperature side and a tangent line drawn at the point where the gradient is maximum on the high temperature curve of the peak).

In addition, the “center temperature of the lens precursor” in the present invention refers to the temperature at the center of the lens precursor. In simple terms, the “center temperature of the lens precursor” refers to the curved surface top point A of the lens precursor 100 ′ and the tangent line of the top point A, as shown in FIG. 3 (particularly FIG. 3B). Is a temperature at a point located in the middle of the lens bottom point B located in a direction perpendicular to the lens.

Although the “center temperature of the lens precursor in the injection mold” may be directly measured by various thermometers, the inventors of the present application have conducted an intensive study and found that such temperature is indirectly measured from another scale. It was found that an efficient manufacturing process can be realized by grasping the above. Specifically, the inventors of the present application have found that the center temperature of the lens precursor in the injection mold can be indirectly grasped based on the following formula 1 and thereby the timing for taking out the lens precursor can be determined. It was.

That is, in a particularly preferred aspect of the present invention, the center temperature of the lens precursor in the injection mold is indirectly grasped based on the formula 1, and the temperature thus grasped is “ The lens precursor is taken out from the injection mold when it is "midpoint glass transition temperature or higher".

Formula 1 will be described in detail. t _la is the cooling time provided to the lens precursor in the injection mold. Specifically, t _la is the elapsed time starting from the time when the injected resin raw material stopped flowing, that is, the time from when the filling of the thermoplastic resin raw material into the injection mold was completed. Means. S [mm] is the maximum thickness of the lens precursor. That is, the maximum thickness T′max of the lens precursor shown in FIG. 3C corresponds to “S” (note that T′max is indirectly grasped from the cavity dimensions of the injection mold). Is possible). α [mm ² / s] is the thermal diffusivity of the thermoplastic resin raw material at the surface temperature of the injection mold. Specifically, α [mm ² / s] means the thermal diffusivity of the thermoplastic resin raw material at the cavity surface temperature of the injection mold. “Α” itself can be calculated from the following equation.

α = λ / (c · ρ)
λ [kcal / m · h · ° C.]: Thermal conductivity of thermoplastic resin raw material,
c [kcal / kg · ° C.]: Specific heat of thermoplastic resin raw material ρ [kg / m ³ ]: Density of thermoplastic resin raw material

Θr [° C.] is the temperature of the thermoplastic resin material injected into the injection mold. For convenience, the cylinder temperature of the injection molding machine can be used as θr. θ _e [° C.] is the center temperature of the lens precursor in the injection mold. That is, θ _e indicates the temperature at the center of the lens precursor, and for convenience, the “center temperature of the lens precursor” includes the curved surface top point A of the lens and its top point, as shown in FIG. A temperature at an intermediate point positioned between the lens bottom point B positioned in a direction perpendicular to the tangent to A can be set. θ _m [° C.] is the surface temperature of the injection mold. More specifically, it is the cavity surface temperature of the injection mold.

In the production method of the present invention, the lens precursor taken out from the injection mold may be immediately placed in the compression mold, or may be placed in the compression mold after being cooled. Also good.

In the former case, the lens precursor taken out from the injection mold is transferred to the compression mold without being subjected to substantial cooling. The expression “without being subjected to cooling” here substantially means that the lens precursor taken out from the injection mold is not actively subjected to cooling in an external atmosphere. That is, it means that the lens precursor taken out from the injection mold is continuously charged into the compression mold as soon as possible. In this case, the lens precursor taken out from the injection mold is preferably transferred to the compression mold under the condition that the center temperature is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material.

On the other hand, in the latter case, the lens precursor is subjected to cooling in a state of being taken out from the injection mold prior to being subjected to the compression molding in the step (ii). That is, the lens precursor is not subjected to substantial cooling in the injection mold, but the lens precursor is subjected to substantial cooling in an atmosphere after being taken out of the lens precursor. In such a case, it is preferable that the lens precursor taken out from the injection mold is cooled to a temperature lower than the center glass transition temperature of the thermoplastic resin material and transferred to the compression mold. The cooling method prior to the compression molding in the step (ii) is not particularly limited as long as it can cool the lens precursor to lower the center temperature. For example, the lens precursor is taken out. Examples include a method of standing in an environment, a method of throwing a lens precursor into water, a method of spraying water, air, or nitrogen onto the lens precursor, a method of standing a lens precursor in a low temperature environment, etc. It is done. Here, the inventors of the present invention cool the lens precursor to the same temperature in the injection mold when the lens precursor is cooled in the atmosphere after being taken out from the injection mold. (In particular, the lens precursor is cooled to the same temperature in the injection mold even when the lens precursor is cooled by being left in an external atmosphere.) It was found that the cooling time was shorter than the time required for That is, according to this aspect, even in the case where a cooling process is additionally provided between the step (i) and the step (ii), the lens manufacturing time is shorter than that of the conventional manufacturing method, which is efficient. Production has been realized. In addition, such cooling in the atmosphere outside the injection mold forms the “surface that forms the lens convex portion 101 ′” and “the lens bottom portion 102 ′ from the viewpoint of obtaining a lens having a good appearance with reduced surface irregularities. It is preferable to cool the lens precursor while inverting the “surface” (see FIG. 3C). That is, it is preferable to cool while changing the direction of the lens precursor. If the lens precursor is cooled in a state in which the lens precursor is not inverted upside down and maintained in a certain direction, the surface of the lens precursor may be deformed. In some cases, the deformation cannot be corrected even by the compression molding in the step (ii). This is because there is a concern that the surface may remain uneven.

The manufacturing method of the present invention can obtain a plurality of lenses in parallel. Specifically, another lens precursor can be obtained by subsequently injecting a thermoplastic resin material into an injection mold in which a certain lens precursor is taken out at or above its midpoint glass transition temperature. In other words, do not dare to subject the lens precursor to sufficient cooling in the injection mold, and when the lens precursor is above the midpoint glass transition temperature, the lens precursor is quickly removed from the injection mold. The injection mold thus taken out is used as soon as possible for the molding of the next lens precursor. In such a case, the injection mold can be efficiently used for molding a plurality of lens precursors, and as a result, efficient mass production of a plurality of lenses can be realized. Thus, although examination from the viewpoint of efficiently performing mass production of lenses in parallel is not sufficiently performed in the prior art, the present invention is also considered in view of such productivity, and the present invention is also beneficial in this respect. .

Describing in detail about productivity, in the present invention, the manufacturing time per lens is considerably reduced as compared with the prior art. Specifically, when manufacturing lenses via injection molding and compression molding, according to the method of the present invention, the manufacturing time per lens can be reduced by at least 20% over prior art techniques under similar conditions. Can be reduced, preferably by at least 30%, more preferably by at least 40%, and even more preferably by at least 50% (eg, by about 60%).

For example, a lens precursor is removed from an injection mold at a temperature above its midpoint glass transition temperature, and continues at a time when the center temperature of the lens precursor is still “above the midpoint glass transition temperature of the thermoplastic resin raw material”. In order to obtain another lens precursor, a thermoplastic resin material may be injected. In other words, before the taken out lens precursor is subjected to sufficient cooling (for example, before the lens precursor taken out from the injection mold is charged into the compression mold or into the compression molding). Before the lens precursor is sufficiently cooled outside the injection mold, the injection mold may be used for the next lens precursor molding.

The lens precursor obtained in step (i) of the production method of the present invention has a maximum thickness (specifically, as shown in FIGS. 3B and 3C), the tangent to the curved surface top point A of the lens. The maximum thickness “T′max” of the lens in the direction perpendicular to the lens is preferably larger than the maximum thickness Tmax (see FIG. 6) of the lens obtained in the step (ii). This is because the lens precursor is easily subjected to sufficient compression in the compression mold of step (ii), and as a result, the cavity shape in the compression mold, that is, the shape of the desired lens is obtained. This is because it becomes easy to be molded with high accuracy.

From the viewpoint of manufacturing a lens having a good appearance in a short time, the maximum thickness dimension (for example, the maximum thickness of the lens precursor 100 ′ shown in FIG. 3C) is obtained for the lens precursor obtained in the step (i). T′max) is preferably 10 mm or more and 150 mm or less, more preferably 10 mm or more and 130 mm or less, and further preferably 10 mm or more and 100 mm or less. Similarly, from the viewpoint of manufacturing a lens having a good appearance in a short time, the maximum width dimension of the lens precursor obtained in the step (i) (for example, excluding the flange portion 102 ′ shown in FIG. 3C). The effective maximum width W′max of the lens body is preferably 10 mm or more and 200 mm or less, more preferably 20 mm or more and 130 mm or less, and further preferably 30 mm or more and 120 mm or less. By reducing the maximum thickness and maximum width of the lens precursor as in such specific dimensions, the time required for cooling the lens precursor or the lens obtained therefrom can be further shortened.

In a preferred embodiment, the lens precursor obtained in step (i) has a maximum thickness dimension of 10 mm to 150 mm and a maximum width dimension of 10 mm to 200 mm. That is, in a preferred aspect of the manufacturing method of the present invention, an injection mold having a mold cavity capable of obtaining a lens precursor having such a maximum thickness dimension and maximum width dimension is used in step (i). It will be.

Next to step (i), step (ii) is performed. That is, the lens precursor is placed in a compression mold and the lens precursor is subjected to compression molding. The handling of the lens precursor when transferring from the injection mold in the step (i) to the compression mold in the step (ii) will be mentioned. The lens precursor taken out from the injection mold, that is, the lens precursor released from the injection mold is chucked on the outer periphery, or the flange portion of the lens precursor is removed with a dedicated jig. By receiving several points from below, it can be transferred to a compression mold. Even if this point is taken out from the injection mold under the condition of “midpoint glass transition temperature or higher”, by using the handling means or moving means, the lens precursor is suitably compressed as a result. Can be charged. In particular, when the lens precursor is taken out of the injection mold under the conditions of “midpoint glass transition temperature or higher” and “200 ° C. or lower” at the center temperature, the lens precursor can be suitably held during the handling operation. Therefore, smoother charging into the compression mold can be assisted.

The compression mold itself used in the step (ii) is not particularly limited as long as it can apply a compression pressure to the lens precursor and thereby obtain a lens product. In other words, the compression molding die in the present invention is typically composed of at least a “fixed side” and a “moving side”, as long as compression pressure can be applied to the lens precursor by clamping. Good. In the embodiment in which the step (ii) is performed while the compression mold is being conveyed as will be described later, the mold can be moved independently, not a mold fixed to a molding machine equipped with a mold clamping mechanism. A mold is preferred.

The mold temperature Tp (° C.) of the compression mold in the step (ii) preferably satisfies the relationship of Tmg + 45 ≦ Tp ≦ Tmg + 85 with respect to the midpoint glass transition temperature Tmg (° C.) of the thermoplastic resin raw material. More preferably, the relationship of Tmg + 50 ≦ Tp ≦ Tmg + 80 is satisfied. If the mold temperature of the compression mold is too high, the lens precursor will be heated excessively to the center of the lens precursor, and it may take excessive time for subsequent cooling, while the mold temperature of the compression mold is too low. This is because sufficient surface accuracy may be difficult to obtain.

The compression pressure by the compression mold in the step (ii) is preferably 15 kN or more and 80 kN or less, more preferably 20 kN or more and 50 kN or less. When the compression pressure by the compression molding die is too large, the compression molding die and the lens precursor are in close contact with each other, and the lens may be damaged when the lens is taken out from the compression molding die. This is because if the compression pressure is too small, it may be difficult to obtain sufficient surface accuracy.

The compression time by the compression mold in the step (ii) is preferably 110 seconds or more and 200 seconds or less, more preferably 120 seconds or more and 190 seconds or less. If the compression time by the compression mold is too long, it may take extra time for subsequent cooling or foaming may occur in the resulting lens, while the compression time by the compression mold is short. This is because if it is too large, a desired lens shape and surface accuracy cannot be secured.

In a preferred embodiment, the relationship between the mold temperature (Tp) of the compression mold and the glass transition temperature (Tmg) of the thermoplastic resin raw material is Tmg + 45 ≦ Tp ≦ Tmg + 85 (the unit is “° C.”). In addition, the lens precursor is subjected to compression molding under the conditions that the compression pressure of the compression mold becomes 15 kN or more and 80 kN or less, and the compression time by the compression mold becomes 110 seconds or more and 200 seconds or less.

Note that the compression mold used in step (ii) may be one in which one lens precursor can be installed, or one in which two or more lens precursors can be installed. When the viewpoint of productivity is particularly important, it can be said that a compression molding die in which two or more lens precursors can be installed is preferable.

Step (ii) of the manufacturing method according to the present invention may heat the lens precursor in the compression mold prior to compression molding and / or cool the lens in the compression mold after compression molding. You may attach to. That is, in a preferable aspect, the step (ii) includes (a) a sub-step of heating and preheating the lens precursor in a compression mold,
(B) a sub-step of compressing and molding the heated / preheated lens precursor, and (c) a sub-step of cooling the lens obtained by compression molding of the lens precursor in a compression molding die. In such a case, it is preferable that the sub-steps (a) to (c) are sequentially performed by conveying a compression molding die charged with a lens precursor.

Sub processes (a) to (c) will be described over time. First, the compression molding mold charged with the lens precursor is conveyed to the heating sub-step (a) and heated to a predetermined temperature. Thereby, the lens precursor existing in the compression mold is heated and preheated. Next, the compression molding die is conveyed to the compression molding sub-step (b). In the compression molding sub-step (b), the lens precursor is subjected to pressurization at a predetermined temperature and a predetermined pressure, and as a result, the lens is subjected to compression molding in the compression molding die. By the compression molding sub-step (b), surface defects of the lens precursor are reduced, and a highly accurate lens can be obtained. In addition, the compression molding sub-step (b) corrects the shape displacement that can be caused to the lens precursor taken out from the injection mold at the intermediate glass transition temperature or higher, thereby obtaining a desired lens. Become. Subsequently, the compression molding die is conveyed to the cooling sub-step (c). In the cooling sub-step (c), the lens is cooled to a predetermined temperature in the compression molding die. The cooled lens is finally taken out from the compression mold.

Examples of methods for conveying the compression mold include a belt conveyor and a robot arm. In a preferred embodiment, the compression mold is conveyed by using a belt conveyor. If a belt conveyor is used, it will become possible to convey a compression molding metal mold | die continuously to each process suitably, and productivity can improve. In addition, when a plurality of compression molds loaded with lens precursors are used, sequential conveyance becomes possible, so that each sub-process can be performed in parallel, and a plurality of lenses can be manufactured suitably. . Illustratively, when the compression molding die that has undergone the heating sub-step (a) and the compression molding sub-step (b) is used for the cooling sub-step (c), the heating sub-step (a) is performed in parallel with this. Not only can another compression molding die passed be subjected to the compression molding sub-step (b), but still another compression molding die can be subjected to the heating sub-step (a). In addition, when a compression mold is conveyed continuously between processes using a belt conveyor, the conveyance speed of the compression mold in each process may be constant.

When the sub-steps (a) to (c) are performed in the step (ii), the number of sub-steps is not limited to one and may be divided into a plurality. In other words, each of the sub-step (a), the sub-step (b), and the sub-step (c) may be performed not only once but also a plurality of times. Although it is only an example to the last, the aspect of a sub process as shown, for example in FIG. 4 and FIG. 5 can be considered. Step (ii) of the embodiment shown in FIG. 4 includes at least a heating sub-step (a) 30, a compression molding sub-step (b) 40, a first cooling sub-step (c) 50A, and a second cooling sub-step (c) 50B. The compression molding die 20 that is configured and charged with the lens precursor is conveyed while the sub-processes are sequentially applied in this order (30 → 40 → 50A → 50B). On the other hand, the process (ii) of the embodiment shown in FIG. 5 includes a first heating sub-process (a) 30A, a second heating sub-process (a) 30B, a first compression molding sub-process (b) 40A, and a second compression molding sub. Compression comprising at least a step (b) 40B, a first cooling sub-step (c) 50A, a second cooling sub-step (c) 50B, and a third cooling sub-step (c) 50C, in which a lens precursor is charged The molding die 20 is conveyed while the sub-processes are sequentially applied in this order (30A → 30B → 40A → 40B → 40C → 50A → 50B → 50C).

Detailed description of “heating”, “compression molding”, and “cooling” that can be performed in step (ii) will be given.

As described above, in the step (ii), the sub-step (a) is preferably heated so that the mold temperature of the compression mold becomes a predetermined temperature. As the heating means, for example, an infrared heater may be used. As the mold temperature rises due to such heating, the temperature of the lens precursor inherent in the compression mold rises. At this time, the temperature of the lens precursor and the mold temperature do not need to match. In the aspect in which the compression mold is continuously conveyed at a constant conveyance speed as described above, it may take some time for the lens precursor to be heated to a predetermined temperature in the compression mold. In such a case, since the heating time may be insufficient in one heating step, for example, heating may be performed in two or more stages. That is, two or more heating sub-steps (a) may be provided. When two or more heating sub-steps (a) are provided, conditions such as heating temperature and heating time in the heating sub-steps may be the same or different. The preferred specific heating temperature is as described above. That is, the heating temperature is preferable so that the mold temperature Tp (° C.) of the compression mold and the intermediate glass transition temperature Tmg (° C.) of the thermoplastic resin material satisfy the relationship of Tmg + 45 ≦ Tp ≦ Tmg + 85. The time for heating is preferably 120 seconds or more and 190 seconds or less, and more preferably 130 seconds or more and 180 seconds or less. If the heating time is too long, the center of the lens precursor is heated excessively, and cooling may take time. On the other hand, if the heating time is too short, sufficient surface accuracy may not be obtained. When the heating process is provided in a plurality of stages, the total time obtained by adding all the times required for the heating in the plurality of stages is preferably 120 seconds or more and 190 seconds or less, and more preferably 130 seconds or more and 180 seconds or less.

In step (ii), preferably, as a sub-step (b), the lens precursor is subjected to compression molding with a compression molding die to obtain a lens. As specific conditions for such compression molding, the compression pressure by the compression molding die is preferably 15 kN to 80 kN, and the compression time by the compression molding die is preferably 110 seconds or more and 200 seconds or less. The compression pressure can be controlled by adjusting the clamping force of the compression mold. Similar to the heating sub-step described above, for example, when compression molding takes time, the compression molding may be performed in two or more stages. That is, two or more compression molding sub-steps (b) may be provided. When two or more compression molding sub-steps are provided, conditions such as mold temperature and compression pressure in the compression molding sub-steps may be the same or different. In the case where a plurality of compression molding steps are provided, it is preferable that the total time obtained by adding all the times required for the compression molding of the plurality of stages is 110 seconds or more and 200 seconds or less.

In step (ii), the lens is preferably cooled in a compression mold as a sub-step (c). Although cooling may be natural cooling, cooling may be forcibly performed from outside the mold using a cooler means or the like. In such a sub-process, the temperature of the lens precursor present in the compression mold decreases as the mold temperature decreases. A preferable target cooling temperature is, for example, 80 ° C. or higher and 130 ° C. or lower, and more preferably 90 ° C. or higher and 120 ° C. or lower. Further, the cooling time is preferably 100 seconds or more and 300 seconds or less, and more preferably 110 seconds or more and 290 seconds or less. In cooling, the temperature of the lens precursor and the mold temperature do not need to match. In the aspect in which the compression mold is continuously conveyed at a constant conveyance speed as described above, it may take time to cool the lens precursor to a predetermined temperature in the compression mold. In such a case, since the cooling time may be insufficient in one cooling step, for example, the cooling may be performed in two or more stages. That is, two or more cooling sub-steps (c) may be provided. When two or more cooling sub-steps are provided, conditions such as mold temperature in the cooling sub-steps may be the same or different. In the case where a plurality of cooling steps are provided, it is preferable that the total time obtained by adding all the times required for cooling the plurality of stages is 100 seconds or more and 300 seconds or less as described above.

In step (ii), in addition to the heating sub-step (a), compression molding sub-step (b), and cooling sub-step (c), one or more other sub-steps may be included. Such additional sub-steps can include stabilization sub-steps. The stabilization sub-step is intended to sufficiently exert a process operation such as heating, compression molding or cooling on the entire lens precursor / entire lens. In such a case, in the stabilization sub-step, it is preferable to maintain the previous process conditions as it is with respect to the “lens precursor / lens compression molding mold”. For example, when the stabilization sub-step is performed after the heating sub-step, the operation of maintaining the preceding heating temperature is stable so that the heat is sufficiently transferred to the inside of the lens precursor charged in the compression mold. Can be performed in the sub-step.

[Thermoplastic resin raw material of the present invention]
The thermoplastic resin raw material of the present invention is a resin raw material used in the above-described lens manufacturing method. Specifically, it is a thermoplastic resin material used for obtaining a lens precursor by being injected into an injection mold in the step (i). Therefore, the thermoplastic resin raw material of the present invention has, for example, a pellet form, and may be particularly suitable for introduction into an injection molding machine.

Preferably, the thermoplastic resin raw material of the present invention is a (meth) acrylic resin. As described above, the term “(meth) acryl” as used herein substantially means “acryl” or “methacryl”. Examples of such resin raw materials include homopolymers of (meth) acrylic monomers such as (meth) acrylic acid, (meth) acrylic acid esters, (meth) acrylonitrile, and copolymers of two or more of these (meth) Examples thereof include a copolymer of an acrylic monomer and other monomers.

The (meth) acrylic resin of the present invention is preferably a methacrylic resin from the viewpoint of having excellent hardness, weather resistance, transparency and the like. The methacrylic resin is a polymer obtained by polymerizing a monomer mainly composed of methacrylic acid ester, for example, a homopolymer of methacrylic acid ester and a copolymer composed of two or more methacrylic acid esters. Moreover, as a methacrylic resin raw material, the copolymer etc. which consist of monomers other than methacrylic acid ester and methacrylic acid ester are preferable. In the case of a copolymer composed of a methacrylic acid ester and a monomer other than the methacrylic acid ester, the methacrylic acid ester is 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight based on the total amount of monomers. % And monomers other than methacrylic acid ester are 50% by weight or less, preferably 30% by weight or less, more preferably 10% by weight or less. For more specific matters such as “methacrylic acid ester” and “monomer other than methacrylic acid ester”, the above-mentioned matters in the “lens manufacturing method of the present invention” are applied as they are, so that the description is omitted to avoid duplication. To do.

The (meth) acrylic resin of the present invention has a Vicat softening temperature measured by JIS K7206 (B50 method) of 105 ° C. or more and 120 ° C. or less, and a melt mass flow rate measured by JIS K7210 of 1 g / 10 min or more and 20 g / Those having a temperature of 10 min or less (more preferably 105 ° C. or more and 118 ° C. or less, more preferably 106 ° C. or more and 115 ° C. or less) are preferable. When the melt mass flow rate is 1 g / 10 min or more and 20 g / 10 min or less, the lens precursor can be taken out earlier in step (i) of the above-described lens manufacturing method, while the Vicat softening temperature is 105 ° C. or more and 120 The lens obtained by the above-described lens manufacturing method becomes superior in heat resistance when the temperature is not higher than ° C.

[Lens of the present invention]
The lens 100 of the present invention is a lens obtained by the above-described lens manufacturing method. FIG. 6 exemplarily shows the lens of the present invention. The lens of the present invention includes, for example, a lens unit 101, a lens unit 102, and a flange unit 103. Specifically, the lens unit 101 has a height dimension larger than that of the lens unit 102, and the lens unit 101 and the lens unit 102 are connected to each other via a flange unit 103. In the present invention, the lens shape is not limited to this, and can be appropriately changed according to the intended use. For example, the lens unit 102 has a convex surface according to the form shown in FIG. 6, but is not limited thereto, and may have a concave surface or a flat surface according to desired lens performance. It may be.

Since the lens of the present invention is a lens obtained by the above-described lens manufacturing method, it corresponds to a so-called “plastic lens”. In a preferred embodiment, the lens of the present invention is a transparent plastic lens made of (meth) acrylic resin.

The lens of the present invention can be used for applications where such a lens shape is required. Although not particularly limited, the lens of the present invention can be used as an optical element. The lens as the optical element is used as, for example, various lenses for a camera, a projector, a copier, a printer, or a lighting device in addition to a vehicle lamp / lens (one example is a vehicle headlamp / lens). it can. In particular, a lens made of (meth) acrylic resin is preferably used as a vehicle lamp / lens (for example, a vehicle headlamp / lens).

Regarding the lens as an optical element, the maximum thickness Tmax (see FIG. 6) from the lens unit 101 to the lens unit 103 is preferably 10 mm or more and 150 mm or less, more preferably 10 mm or more and 130 mm or less. More preferably, it is 100 mm or less. The maximum width Wmax of the lens (that is, the effective maximum width dimension of the lens body excluding the flange portion 102 (see FIG. 6)) is preferably 10 mm or more and 200 mm or less, more preferably 20 mm or more and 130 mm or less. More preferably, they are 30 mm or more and 120 mm or less. Such dimensions contribute to the short time production of a lens with a good appearance. The dimensional difference from the lens precursor will be described in detail. The maximum dimension of the lens (for example, likewise the maximum thickness Tmax and the maximum width Wmax) is preferably 0.2% to 10% compared to the maximum dimension of the lens precursor (for example, maximum thickness T'max and maximum width W'max). % Can be as small as 0.5%, more preferably as small as 0.5% to 6%, and even more preferably as small as 0.8% to 4%.

Finally, it should be confirmed that the present invention has the following aspects.
1st aspect : It is a method of manufacturing a lens, Comprising :
(I) a step of performing injection molding using a thermoplastic resin raw material to obtain a lens precursor in an injection mold, and (ii) placing the lens precursor in a compression mold and compressing the lens precursor. Comprising a step for molding,
In transferring the lens precursor from the injection molding in the step (i) to the compression molding in the step (ii), the lens precursor is obtained when the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin raw material. A method for producing a lens, wherein the lens is taken out from an injection mold.
Second aspect : The lens manufacturing method according to the first aspect, wherein the center temperature of the lens precursor in the injection mold is indirectly grasped based on Formula 1.

Third aspect : In the first aspect or the second aspect, a plurality of lenses are manufactured in parallel,
It is characterized in that another lens precursor is obtained by injecting a thermoplastic resin raw material as soon as possible to an injection mold in which a lens precursor is taken out above its midpoint glass transition temperature. Lens manufacturing method.
Fourth aspect : In any one of the first to third aspects, the lens precursor is subjected to cooling in a state of being taken out from the injection mold before being subjected to the compression molding in the step (ii). A lens manufacturing method.
Fifth aspect : The lens according to any one of the first to third aspects, wherein the lens precursor taken out from the injection mold is transferred to a compression mold without being subjected to substantial cooling. Production method.
Sixth aspect : In any one of the first to fifth aspects, the Vicat softening temperature measured by JIS K7206 (B50 method) is 105 ° C or higher and 120 ° C or lower as the thermoplastic resin material used in step (i). And using a thermoplastic resin material having a melt mass flow rate measured by JIS K7210 of 1 g / 10 min or more and 20 g / 10 min or less.
Seventh aspect : A lens manufacturing method according to any one of the first to sixth aspects, wherein a (meth) acrylic resin is used as the thermoplastic resin material used in step (i).
Eighth aspect : The method for producing a lens according to the seventh aspect, wherein the (meth) acrylic resin is a copolymer composed of a methacrylic acid ester and a monomer other than the methacrylic acid ester.
Ninth aspect : In any one of the first to eighth aspects, the lens precursor obtained in step (i) has a maximum thickness dimension of 10 mm to 150 mm and a maximum width dimension (there is a flange portion) In the case, the lens maximum width dimension (excluding the flange portion) is 10 mm or more and 200 mm or less.
Tenth aspect : In any one of the first to ninth aspects, in step (ii), the mold temperature Tp (° C) of the compression mold and the intermediate glass transition temperature Tmg (° C) of the thermoplastic resin material Satisfying the relationship of “Tmg + 45 ≦ Tp ≦ Tmg + 85”, the compression pressure by the compression mold is 15 kN or more and 80 kN or less, and the compression time by the compression mold is 110 seconds or more and 200 seconds or less. A lens manufacturing method comprising subjecting a lens precursor to compression molding.
Eleventh aspect : In any one of the first to tenth aspects, the step (ii) comprises:
(A) a sub-step of subjecting the lens precursor to heating in a compression mold;
(B) a sub-step of subjecting the heated lens precursor to compression molding, and (c) a sub-step of subjecting the lens obtained by compression molding of the lens precursor to cooling in a compression mold. A lens manufacturing method.
Twelfth aspect : In the eleventh aspect, the sub-step (a), the sub-step (b), and the sub-step (c) are sequentially performed while the compression molding die charged with the lens precursor is conveyed or moved. A lens manufacturing method.
Thirteenth aspect : A (meth) acrylic resin used in the lens manufacturing method of the seventh aspect.
Fourteenth aspect : A lens obtained by the lens manufacturing method according to any one of the first aspect to the twelfth aspect.
Fifteenth aspect : A lens according to the fourteenth aspect, wherein the lens is a vehicle lamp lens.

As mentioned above, although the embodiment of the present invention has been described, a typical example is merely illustrated. Therefore, those skilled in the art will easily understand that the present invention is not limited to this, and various modes are conceivable.

For example, the present invention is not limited to lens manufacturing but can be similarly applied to manufacturing other resin molded products. In other words, in the case where another resin molded body is obtained by subjecting a precursor obtained by injection molding using a thermoplastic resin raw material to compression molding, the center temperature of the precursor is the midpoint glass of the thermoplastic resin raw material. The precursor may be removed from the injection mold when it is above the transition temperature.

Hereinafter, the present invention will be described more specifically with reference to “Examples” and “Comparative Examples”. The present invention is not particularly limited to these examples and comparative examples.

<< Lens manufacturing according to the present invention and prior art lens manufacturing >>
A (meth) acrylic resin was used as a thermoplastic resin raw material. Measurements and evaluations of various physical properties of the (meth) acrylic resin and lenses obtained therefrom are as follows.

<Vicat softening temperature (VST)>
A test piece using a (meth) acrylic resin as a raw material resin was obtained. Specifically, a 10 cm square resin plate having a thickness of 3 mm was press-molded to obtain a test piece. About the obtained test piece, based on JIS K7206 B50 method, Vicat softening temperature (VST) was measured under conditions of a load of 50 N and a heating rate of 50 ° C./hour.

<Melt Mass Flow Rate (MFR)>
The (meth) acrylic resin was measured under the conditions of a temperature of 230 ° C. and a load of 3.8 kg in accordance with JIS K7210.

<Intermediate glass transition temperature (Tmg)>
The (meth) acrylic resin was measured using a differential scanning calorimeter manufactured by Seiko Instruments Inc. under conditions of a temperature rising rate of 10 ° C./min and a nitrogen atmosphere.

<Center temperature and cooling time of lens precursor>
Sumipex MHF (manufactured by Sumitomo Chemical Co., Ltd.) was used as the (meth) acrylic resin. Such a thermoplastic resin raw material was injected into an injection mold to obtain a lens precursor. The relationship between the center temperature of the lens precursor present in the injection mold and the cooling time was calculated from Equation 1.

t _la = S ² / (π ² · α) ln (8 / π ² · (θ _r −θ _m ) / (θ _e −θ _m )) (Formula 1)

In the formula, t _la is the cooling time (s) of the lens intermediate, and θ _e is the center temperature (° C.) of the lens intermediate. In addition, S = 23 mm, α = 0.66 mm ² / s, θ _r = 230 ° C., θ _m = 80 ° C.

<Durability evaluation>
About the obtained lens, it left still in 90 degreeC oven for 100 hours. After standing, it was evaluated as “◯” if the lens was not deformed, and “×” if it was deformed.

[Example 1]
Injection molding stage (process (i))
An injection molding machine EC180SX-6A (manufactured by Toshiba Machine Co., Ltd.) was used. Injection mold with thermoplastic lens raw material Sumipex MHF (VST = about 110 ° C., MFR = about 2 g / 10 min, Tmg = about 111 ° C., manufactured by Sumitomo Chemical Co., Ltd.) and one lens-shaped mold cavity The lens precursor was obtained by injection (cylinder temperature: about 230 ° C., injection speed: about 0.6 mm / s, injection mold surface temperature: about 80 ° C.). Next, the lens precursor was taken out from the injection mold when the center temperature of the lens precursor was equal to or higher than the midpoint glass transition temperature Tmg of the thermoplastic resin material. Specifically, the center temperature of the lens precursor in the injection mold is indirectly grasped based on the above formula 1, and as a result, the lens precursor is subjected to cooling by the injection mold for “180 seconds”. After that, the lens precursor was released from the injection mold (here, “cooling” is caused by exposing the resin material to the temperature environment of the injection mold, and the above “180”. "Second" is the elapsed time from the point at which the injected resin raw material stopped flowing, that is, the elapsed time from the point at which filling of the thermoplastic resin raw material into the injection mold was completed). By such an operation, the lens precursor could be taken out from the injection mold when the center temperature of the lens precursor was equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material. The taken out lens precursor is composed of a lens portion 101 ′, a lens portion 103 ′, and a flange portion 102 ′ in the same manner as the lens as the final product, and the lens portion 101 ′ and the lens portion 103 ′ are respectively in contact with the flange portion. Both diameters were about 60 mm, and the maximum thickness from the lens portion 101 ′ to the lens portion 103 ′ was about 23 mm (see FIG. 3).

Table 1 below shows the results obtained based on Equation 1 regarding the relationship between the center temperature of the lens precursor present in the injection mold and the cooling time of the lens precursor in the injection mold. From Table 1, it can be seen that the central temperature of the lens precursor when cooled for 180 seconds is 170 ° C. or higher, and therefore Tmg or higher.

Compression molding stage (process (ii))
The compression molding process was carried out using a mobile high-precision glass molding apparatus (manufactured by Toshiba Machine Co., Ltd.). Specifically, the lens precursor taken out from the injection mold was charged into a compression mold, and the compression molding process was carried out while the compression mold thus charged was conveyed by a belt conveyor. More specifically, the heating sub-process, the stabilization sub-process, the compression sub-process, and the first to third cooling sub-processes are performed in this order while the compression mold containing the lens precursor is conveyed by a belt conveyor. It carried out sequentially. Table 2 shows the conditions of the sub-process.

A lens having a good appearance whose surface irregularities were reduced by such compression molding (irregularities on the lens surface were reduced) could be finally obtained. The obtained lens was subjected to a durability evaluation test (results are shown in Table 2).

[Example 2]
A lens was obtained in the same manner as in Example 1 except that the compression molding process was a heating sub-process, a stabilization sub-process, a first to second compression molding sub-process, and a first to third cooling sub-process. Table 2 shows the conditions in each sub-step of the compression molding. Finally, a lens having a good appearance with reduced surface irregularities (reduced irregularities on the lens surface) could be obtained. The results of durability evaluation of the obtained lens are also shown in Table 2.

[Comparative Example 1]
A lens was obtained in the same manner as in Example 1 except that the lens precursor was taken out from the injection mold when the center temperature of the lens precursor was lower than the midpoint glass transition temperature Tmg of the thermoplastic resin material. Specifically, based on Equation 1 above, the center temperature of the lens precursor in the injection mold is indirectly grasped, and as a result, the lens precursor is cooled for 1105 seconds with the injection mold. The lens precursor was removed from the injection mold. Finally, a lens having the same appearance as Example 1 and Example 2 with reduced surface irregularities (reduced irregularities on the lens surface) could be obtained. The results of durability evaluation of the obtained lens are also shown in Table 2.

As described above, even when the lens precursor is taken out from the injection mold under the condition that the center temperature of the lens precursor is equal to or higher than the glass transition temperature Tmg of the thermoplastic resin raw material, A lens having the same quality as when the lens precursor is taken out from the injection mold when the center temperature of the body is lower than the midpoint glass transition temperature Tmg of the thermoplastic resin raw material can be finally obtained. I understood. In addition, when the lens precursor is taken out at such an early stage, the injection mold can be quickly used to form another lens precursor, which can contribute to the realization of efficient mass production. I understand.

《Examination of lens productivity》
The manufacturing time per lens was investigated for “lens manufacturing according to the present invention” and “prior art lens manufacturing”.

Specifically, a manufacturing test (injection molding → compression generation) was performed under the following conditions, and the manufacturing time per lens was determined from the time required for each molding.

・ Raw material resin: Sumipex MHF (manufactured by Sumitomo Chemical Co., Ltd.)
・ Injection mold temperature: about 80 ℃
・ Injection mold: 6 molds ・ Lens thickness (maximum thickness Tmax): approx. 23 mm
・ Compression mold: Single lens precursor type

The results are shown in Table 3. As shown in the results of Table 3, it was found that the manufacturing time per lens can be reduced by about 60% compared to the prior art in the manufacturing method of the present invention.

The lenses obtained by the present invention are various plastic lenses used as optical elements. In particular, according to the present invention, the manufacturing time can be shortened for a lens having a desired quality (for example, a lens having excellent durability), which is particularly suitable for mass production. In addition, the obtained lens is particularly excellent in transparency by using, for example, (meth) acrylic resin as a raw material resin, and the appearance is improved by reducing surface irregularities. It can be particularly suitably used as an industrial lens.

DESCRIPTION OF SYMBOLS 10 Injection mold 20 Compression molding die 30 Heating sub process 30A 1st heating sub process 30B 2nd heating sub process 40 Compression molding sub process 40A 1st compression molding sub process 40B 2nd compression molding sub process 50 Cooling sub process 50A First cooling sub-process 50B Second cooling sub-process 50C Third cooling sub-process 100 ′ Lens precursor 100 Lens 101 Upper lens portion (portion forming lens convex portion)
102 Lower lens part (the part that forms the bottom of the lens)
103 Lens flange part

Claims (15)

1. A method of manufacturing a lens, comprising:
   (I) a step of performing injection molding using a thermoplastic resin raw material to obtain a lens precursor in an injection mold, and (ii) placing the lens precursor in a compression mold and compressing the lens precursor. Comprising the step of subjecting to molding,
   When the lens precursor is transferred from the injection molding in step (i) to the compression molding in step (ii), the lens precursor is when the center temperature of the lens precursor is equal to or higher than the midpoint glass transition temperature of the thermoplastic resin material. A method for producing a lens, wherein the lens is taken out from an injection mold.
2. The lens manufacturing method according to claim 1, wherein the center temperature of the lens precursor in the injection mold is indirectly grasped based on Equation 1.
   

   
3. Several lenses are manufactured in parallel,
   2. The method according to claim 1, wherein another lens precursor is obtained by subsequently injecting a thermoplastic resin material to an injection mold in which a lens precursor is taken out at a glass transition temperature higher than its intermediate point. The lens manufacturing method as described.
4. The lens manufacturing method according to claim 1, wherein the lens precursor is subjected to cooling in a state of being taken out of the injection mold before being subjected to the compression molding in the step (ii).
5. The lens manufacturing method according to claim 1, wherein the lens precursor taken out from the injection mold is transferred to a compression mold without being cooled.
6. As a thermoplastic resin raw material used in step (i), the Vicat softening temperature measured by JIS K7206 (B50 method) is 105 ° C. or more and 120 ° C. or less, and the melt mass flow rate measured by JIS K7210 is 1 g / 10 min or more and 20 g. The method for manufacturing a lens according to claim 1, wherein a thermoplastic resin material having a length of / 10 min or less is used.
7. The lens manufacturing method according to claim 1, wherein a (meth) acrylic resin is used as the thermoplastic resin material used in step (i).
8. The lens production method according to claim 7, wherein the (meth) acrylic resin is a copolymer composed of a methacrylic acid ester and a monomer other than the methacrylic acid ester.
9. The lens manufacturing method according to claim 1, wherein the lens precursor obtained in step (i) has a maximum thickness dimension of 10 mm to 150 mm and a maximum width dimension of 10 mm to 200 mm. .
10. In step (ii), the mold temperature Tp (° C.) of the compression molding mold and the intermediate glass transition temperature Tmg (° C.) of the thermoplastic resin material satisfy the relationship of Tmg + 45 ≦ Tp ≦ Tmg + 85, and compression by the compression molding mold The lens precursor is subjected to compression molding under a condition that the pressure is 15 kN or more and 80 kN or less and the compression time by the compression molding die is 110 seconds or more and 200 seconds or less. Lens manufacturing method.
11. Step (ii)
    (A) a sub-step of subjecting the lens precursor to heating in a compression mold;
    (B) a sub-step of subjecting the heated lens precursor to compression molding, and (c) a sub-step of subjecting the lens obtained by compression molding of the lens precursor to cooling in a compression molding die. The lens manufacturing method according to claim 1, wherein the lens manufacturing method is characterized.
12. The lens according to claim 11, wherein the sub-step (a), the sub-step (b), and the sub-step (c) are sequentially performed while conveying the compression mold in which the lens precursor is charged. Production method.
13. A (meth) acrylic resin used in the lens manufacturing method according to claim 7.
14. A lens obtained by the lens manufacturing method according to claim 1.
15. 15. Lens according to claim 14, characterized in that the lens is a vehicle lamp lens.

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