Manufacturing method of plastic lenses

Abstract

To provide a method of fabricating a plastic lens which has an optical functional layer with superior adhesivity and offers superior productivity and improved durability.SOLUTION: A plastic lens fabrication method is provided, comprising a formation step of forming an undercoat layer and an optical functional layer on at least one surface of a resin lens body in the described order. The lens body is made of a thermoplastic acrylic resin with a glass transition temperature of 116°C or higher. The undercoat layer is formed by a resistance heating vacuum deposition method using SiO as a deposition material and controlling the amount of O2 gas to apply a pressure less than 3.0×10-2 Pa. The optical functional layer is formed by an electron beam heating vacuum deposition method, where premelting of a deposition material for the optical functional layer is performed only after formation of the undercoat layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing plastic lenses. [Background technology]

[0002] Acrylic resins, such as polymethyl methacrylate (PMMA), are used as optical materials due to their high transparency, low birefringence, and photostability. For example, Patent Document 1 discloses a plastic lens in which an anti-reflective layer is formed on the surface of a PMMA substrate. Furthermore, in recent years, there has been a growing need for acrylic resins to be used in components such as surveillance cameras and in-vehicle cameras, which are used in harsh environments such as high temperature and high humidity and require stronger durability than conventional materials. As a result, acrylic resins with excellent heat resistance are being developed. For example, Patent Document 2 discloses a plastic lens using an acrylic resin with excellent heat resistance as a base material. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-273601 [Patent Document 2] International Publication No. 2023 / 074597 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] While electron beam-heated vacuum deposition (dry deposition method) is very commonly used as a method for depositing optical functional layers (anti-reflective layers, partial reflective layers, etc.) onto resin substrates, it is generally known that this method makes it difficult to obtain good adhesion when the substrate is an acrylic resin. To address this issue, the plastic lens described in Patent Document 1 improves adhesion by forming an undercoat layer mainly composed of silicon oxide between the PMMA substrate and the anti-reflective layer using a resistance-heated vacuum deposition method. However, as a result of studies by the present inventors, it has become clear that even when the undercoat layer is formed using the method described in Patent Document 1, peeling can easily occur depending on the formation conditions of the anti-reflective layer. In addition, this plastic lens has the problem that it cannot adequately meet the durability quality required for in-vehicle cameras and the like because the PMMA substrate has low heat resistance. On the other hand, in the plastic lens described in Patent Document 2, adhesion is enhanced by forming a hard coat layer between the acrylic resin substrate and the anti-reflective layer using a wet deposition method. However, since the shape accuracy of the deposited surface is significantly inferior in the wet deposition method compared to the dry deposition method, this method cannot be used for applications that require high-precision control of the surface shape. In addition, there is a problem of low productivity because a hard coat application, drying, and curing process is required between the lens substrate molding process and the anti-reflective layer deposition process.

[0005] Therefore, the present invention aims to provide a method for manufacturing plastic lenses that offers excellent adhesion and productivity of the optical functional layer, as well as improved durability. [Means for solving the problem]

[0006] In other words, the present invention is as follows. [1] A method for manufacturing a plastic lens, which includes a forming step of forming an undercoat layer and an optical functional layer in that order on at least one surface of a resin lens body, The lens body is made of a thermoplastic acrylic resin having a glass transition temperature of 116°C or higher. The undercoat layer is formed by a resistance heating type vacuum evaporation method, SiO is used as the evaporation material of the undercoat layer, and the amount of O2 gas is controlled to form at a pressure of less than 3.0×10 -2 Pa, The optical functional layer is formed by an electron beam heating type vacuum evaporation method, and the premelting of the evaporation material of the optical functional layer is carried out for the first time after the formation of the undercoat layer A method for manufacturing a plastic lens, characterized in that. [2] In the manufacture of the plastic lens, among the evaporation materials of the optical functional layer, the premelting of the fusible material is carried out so that the total EB energy (output wattage × time) is less than 1500 kJ. The method for manufacturing a plastic lens according to [1]. [3] The thickness of the undercoat layer is 200 nm or more and less than 1000 nm. The method for manufacturing a plastic lens according to [2]. [4] The thickness of the undercoat layer is 80 nm or more and less than 1000 nm, In the manufacture of the plastic lens, an electron gun used is equipped with a reflected electron trap A method for manufacturing a plastic lens, characterized in that according to [2]. [5] The optical functional layer is any one of an antireflection layer, a partial reflection layer, and a high reflection mirror. The method for manufacturing a plastic lens according to any one of [1] to [4]. [6] In the formation of the optical functional layer, the method for manufacturing a plastic lens according to [5], characterized in that it includes a step in which the surface temperature of the lens body becomes 60 °C or higher. [7] The premelting step is carried out with the shutter closed until the melting and evaporation of the evaporation material are stable, and then the shutter is opened and the process proceeds to the evaporation step. The method for manufacturing a plastic lens according to [6].

Effect of the Invention

[0007] According to the present invention, it is possible to provide a method for manufacturing plastic lenses that offers excellent adhesion and productivity of the optical functional layer, as well as improved durability. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a cross-section of an example of a plastic lens (plano-convex lens) formed by the manufacturing method of this embodiment, which is parallel to and includes the optical axis Z. [Figure 2] Figure 2(a) is a schematic diagram (front view) of a typical evaporation apparatus having a resistance heating type evaporation source, and Figure 2(b) is a schematic diagram (front view) of a typical evaporation apparatus having an electron beam heating type evaporation source. [Figure 3] Figure 3 is a flowchart showing the film formation procedure in the manufacturing method of this embodiment. [Figure 4] Figure 4(a) is a graph of the EB output-time of a program programmed to use a molten premelt material among the deposition materials for the optical functional layer so that the total EB energy (output watts × time) is 340 kJ, and Figure 4(b) is a graph of the EB output-time of a program programmed to use the same total energy so that it is 640 kJ. [Modes for carrying out the invention]

[0009] The following describes in detail an embodiment for carrying out the present invention (hereinafter referred to as "this embodiment"), but the present invention is not limited to the following description and can be implemented in various modifications within the scope of its gist. In the following, the constituent units that make up the polymer constituting the thermoplastic acrylic resin contained in the plastic lens of this embodiment are referred to as "monomer units" and / or "structural units" that include a plurality of such "monomer units". Furthermore, the constituent materials of such "monomer units" are sometimes referred to simply as "monomers," omitting the word "unit."

[0010] <Plastic lenses> The plastic lens of this embodiment may be any of the following: a biconvex lens, a plano-convex lens, a meniscus lens, a biconcave lens, a plano-concave lens, a planar lens, a cylindrical lens, a Fresnel lens, a lenticular lens, a fly-eye lens, a lens array, a microlens array, a prism lens, etc.

[0011] The manufacturing method of the plastic lens according to this embodiment will be described below with reference to the figures. Figure 1 is a schematic diagram showing a cross-section of an example of a plastic lens (plano-convex lens) formed by the manufacturing method of this embodiment, which is parallel to and includes the optical axis Z. The plastic lens P formed by the manufacturing method of this embodiment comprises at least a resin lens body P1, an undercoat layer P2 covering at least one side of the lens body (plastic lens substrate) P1, and an optical functional layer P3 covering the undercoat layer P2 from the side opposite to the lens body P1. In other words, in the plastic lens P of this embodiment, the undercoat layer P2 and the optical functional layer P3 are laminated on the lens body P1 in this order. The plastic lens P formed by the manufacturing method of this embodiment may further include, in addition to the undercoat layer P2 and the optical functional layer P3, other layers such as an anti-fouling layer to prevent the surface of the plastic lens P from getting dirty, and a gas barrier layer to suppress the penetration of water vapor into the plastic lens P. In this disclosure, the term "surface of the lens body" refers to a surface or interface that exerts some kind of optical effect, such as refraction or reflection, on light rays or light beams incident on that surface. In the plastic lens P shown in Figure 1, the surfaces of the lens body P1 are surface Sa and surface Sb, where surface Sa is an aspherical shape with a radius of curvature R, and surface Sb is a planar shape (radius of curvature is ∞). The plastic lens P shown in Figure 1 is an example in which only surface Sa is covered with the undercoat layer P2. In the plastic lens formed by the manufacturing method of this embodiment, as shown in Figure 1, only one of the multiple surfaces may be covered with the undercoat layer P2 and the optical functional layer P3, or two or more surfaces may be covered with the undercoat layer P2 and the optical functional layer P3. In the manufacturing method of the plastic lens P described later, after molding the lens body P1, the undercoat layer formation step of forming an undercoat layer P2 and the optical functional layer formation step of forming an optical functional layer P3 are performed in this order.

[0012] <Lens body P1> The lens body P1 contains a thermoplastic acrylic resin. The "thermoplastic acrylic resin" is an acrylic resin that has thermoplastic properties, and from the viewpoint of durability, it is preferable that it also has heat resistance. "Having heat resistance" means that the Vicat softening temperature measured in accordance with ISO 306 B50 is 110°C or higher, and "having low heat resistance" means that the Vicat softening temperature is less than 110°C. The thermoplastic acrylic resin may be a single type or a combination of two or more types.

[0013] [Thermoplastic acrylic resin] From the viewpoint of durability, the thermoplastic acrylic resin contained in the lens body P1 has a glass transition temperature (Tg) of 116°C or higher, preferably 117°C or higher, and more preferably 118°C or higher, as measured in accordance with JIS-K7121. Furthermore, considering the moldability of the lens body P1, the glass transition temperature Tg is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower.

[0014] The thermoplastic acrylic resin contained in the lens body P1 is a polymer containing an ethylenically unsaturated monomer having at least one carboxyl group or carboxylic acid ester group as a monomer component. This may be a homopolymer or copolymer of the ethylenically unsaturated monomer, or a copolymer of the ethylenically unsaturated monomer with other monomers copolymerizable with it. The proportion of the ethylenically unsaturated monomer in the thermoplastic acrylic resin is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, preferably 100% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on 100% by mass of the thermoplastic acrylic resin. A proportion of the ethylenically unsaturated monomer within the above range is preferable from the viewpoint of heat resistance, low birefringence, moldability, and color tone. The ethylenically unsaturated monomer having a carboxyl group or a carboxylic acid ester group is not particularly limited, but examples include methacrylic acid, acrylic acid, methacrylic acid ester, acrylic acid ester, etc., and examples of ester bond-forming residues in the carboxylic acid ester group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, tricyclodecyl group, isobornyl group, phenyl group, benzyl group, 1-phenylethyl group, 2-phenoxyethyl group, 3-phenylpropyl group, 2,4,6-tribromophenyl group, etc.

[0015] The thermoplastic acrylic resin contained in the lens body P1 preferably has a ring structure in its structure from the viewpoint of heat resistance. More specifically, it is preferable that it is a heat-resistant acrylic resin having structural units having a ring structure in its structure, and the structural units having a ring structure preferably include at least one structural unit from among cyclic imide structural units, lactone ring structural units, aromatic vinyl structural units, and alicyclic vinyl structural units. The structural unit having a ring structure may be a single type or a combination of two or more types.

[0016] The proportion of ring-structured structural units in thermoplastic acrylic resin is preferably 15% by mass or more, more preferably 16% by mass or more, even more preferably 17% by mass or more, and particularly preferably 18% by mass or more, based on 100% by mass of the thermoplastic acrylic resin. When the proportion of ring structures is within the above range, it is preferable from the viewpoint of heat resistance, low birefringence, scratch resistance, and moldability.

[0017] Examples of cyclic imide structural units that constitute thermoplastic acrylic resins include maleimide structural units and glutarimide structural units.

[0018] (Maleimide structural units) The maleimide-based structural unit that constitutes the thermoplastic acrylic resin is preferably the structural unit shown in the following general formula (1). [ka] In the above general formula (1), R 1 This represents any of the group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms, and the alkyl group, alkoxy group, cycloalkyl group, and aryl group may have substituents on the carbon atom.

[0019] The monomers used to form maleimide structural units are not particularly limited, but examples include maleimides; N-alkyl-substituted maleimides such as N-methylmaleimide, N-ethylmaleimide, and N-cyclohexylmaleimide; and N-aryl-substituted maleimides such as N-phenylmaleimide, N-methylphenylmaleimide, N-ethylphenylmaleimide, N-butylphenylmaleimide, N-dimethylphenylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-(o-chlorophenyl)maleimide, N-(m-chlorophenyl)maleimide, and N-(p-chlorophenyl)maleimide. From the viewpoint of imparting heat resistance and heat resistance to moisture, the monomers mentioned above are preferably N-cyclohexylmaleimide, N-phenylmaleimide, N-methylphenylmaleimide, N-(o-chlorophenyl)maleimide, N-(m-chlorophenyl)maleimide, and N-(p-chlorophenyl)maleimide. From the viewpoint of availability and imparting heat resistance, N-cyclohexylmaleimide and N-phenylmaleimide are more preferably selected, and N-phenylmaleimide is even more preferably selected. The maleimide structural units described above may be a single unit or a combination of two or more units.

[0020] The content of maleimide-based structural units is preferably 0 to 50% by mass, more preferably 2 to 40% by mass, and even more preferably 5 to 30% by mass, based on 100% by mass of thermoplastic acrylic resin, from the viewpoint of heat resistance, moldability, optical properties, and color stability. In this disclosure, the content of structural units constituting the thermoplastic acrylic resin can be determined by the method described in the examples below.

[0021] (Glutarimide structural units) The glutarimide-based structural units constituting the thermoplastic acrylic resin may be formed after resin polymerization. The structural unit represented by the following general formula (2) is preferred as the glutarimide-based structural unit. [ka] In the above general formula (2), R 1 and R 2 Each of these independently represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted, for example, with a hydroxyl group. Also, R 3 This represents one of the following selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 18 carbon atoms. Particularly preferred is R 1 , R 2 , and R3 These are all methyl groups. The glutarimide-based structural units described above may be a single unit or a combination of two or more units.

[0022] The content of glutarimide-based structural units is preferably 0 to 50% by mass, more preferably 2 to 40% by mass, and even more preferably 5 to 30% by mass, based on 100% by mass of thermoplastic acrylic resin, from the viewpoint of heat resistance, moldability, and optical properties.

[0023] Glutalimide structural units can be obtained by known methods such as copolymerizing (meth)acrylic acid esters and / or (meth)acrylic acid, followed by a reaction with ammonia or amines at high temperatures using urea or unsubstituted urea; reacting a methyl (meth)acrylate-styrene copolymer with ammonia or amines; or reacting poly(meth)acrylic anhydride with ammonia or amines. Specifically, examples include the method described in U.S. Patent No. 4,246,374 of RMKopchik.

[0024] Furthermore, glutarimide structural units can also be formed by imidizing acid anhydrides such as maleic anhydride, half-esters of said acid anhydrides with linear or branched alcohols having 1 to 20 carbon atoms, or α,β-ethylenically unsaturated carboxylic acids.

[0025] Furthermore, another preferred preparation method involves polymerizing (meth)acrylic acid esters and, if necessary, aromatic vinyl monomers or other vinyl monomers, followed by an imidation reaction to obtain a resin containing the glutarimide-based structural units. In the imidation reaction step, an imidating agent may be used, and a ring-closing accelerator may be added as needed. Here, ammonia or a primary amine can be used as the imidating agent. Suitable primary amines include methylamine, ethylamine, n-propylamine, cyclohexylamine, and the like. The method for carrying out the imidization reaction is not particularly limited, and a conventionally known method can be used. For example, a method using an extruder, a horizontal twin-screw reactor, or a batch reactor can be mentioned. The extruder is not particularly limited, and a single-screw extruder, a twin-screw extruder, or a multi-screw extruder can be preferably used. More preferably, a tandem-type reaction extruder in which two twin-screw extruders are arranged in series can be used.

[0026] In addition, in producing the above resin, in addition to the imidization step, an esterification step of treating the carboxyl groups of the resin with an esterifying agent such as dimethyl carbonate can be included. At that time, a catalyst such as trimethylamine, triethylamine, or tributylamine can also be used in combination for treatment. The esterification step can proceed, for example, by using an extruder or a batch reactor, similarly to the above imidization step. In addition, for the purpose of removing excess esterifying agents, by-products such as methanol, or monomers, it is preferable to attach a vent port to the apparatus that can reduce the pressure below atmospheric pressure.

[0027] (Lactone ring structure unit) The lactone ring structure unit constituting the thermoplastic acrylic resin may be formed after resin polymerization. As the lactone ring structure unit, a structural unit represented by the following general formula (3) is preferable. [Chemical formula] In the general formula (3), R 1 , R 2 , and R 3 each independently represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. The organic group may contain an oxygen atom. The above-described lactone ring structure units may be used alone or in combination of two or more.

[0028] From the viewpoint of heat resistance, moldability, and optical properties, the content of lactone ring structural units is preferably 0 to 50% by mass, more preferably 2 to 40% by mass, and even more preferably 5 to 30% by mass, with the thermoplastic acrylic resin being 100% by mass.

[0029] The method for forming a thermoplastic acrylic resin containing a lactone ring structural unit is not particularly limited, but one method involves copolymerizing a monomer having a hydroxyl group in its side chain, for example, a monomer with a structure represented by the following general formula (4) (such as methyl 2-(hydroxymethyl)acrylate), with a monomer having an ester group such as a (meth)acrylic acid ester monomer, and then introducing the lactone ring structure into the polymer by heat-treating the resulting copolymer in the presence or absence of a predetermined catalyst. [ka]

[0030] In the above general formula (4), R 1 represents a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted, for example, with a hydroxyl group. R 2 represents a group having 1 to 12 carbon atoms, preferably a hydrocarbon group having 1 to 12 carbon atoms, and this hydrocarbon group may be substituted with, for example, a hydroxyl group. Particularly preferred is R 1 R is a hydrogen atom, 2 This is a methyl group.

[0031] Furthermore, within the limits within which the effects of the present invention can be achieved, monomers with the structure represented by general formula (4) may remain unreacted in the thermoplastic acrylic resin.

[0032] (Aromatic vinyl structural unit) As the aromatic vinyl structural units constituting the thermoplastic acrylic resin, structural units derived from the aromatic vinyl monomer represented by the following general formula (5) are preferably used. [ka] In the above general formula (5), R 1 represents a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted, for example, with a hydroxyl group. R 2 R is selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 8 carbon atoms, and an allyloxy group having 6 to 8 carbon atoms. 2 These may all be the same group or different groups. Also, R 2 They may form a ring structure with each other. n represents an integer between 0 and 5.

[0033] The monomers used to form aromatic vinyl structural units are not particularly limited, but examples include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p-tert-butylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenylbencene (α-methylstyrene), isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, and the like. Among the above, styrene and isopropenylbenzene are preferred, as they impart fluidity and promote polymerization. From the viewpoint of reducing unreacted monomers by improving the reaction rate, styrene is more preferable. These may be appropriately selected in the thermoplastic acrylic resin of this embodiment depending on the required properties. The aromatic vinyl structural units described above may be a single type or a combination of two or more types.

[0034] From the viewpoint of heat resistance, moldability, and optical properties, the content of aromatic vinyl structural units is preferably 0 to 50% by mass, more preferably 2 to 40% by mass, and even more preferably 4 to 30% by mass, with the thermoplastic acrylic resin being 100% by mass.

[0035] (Alicyclic vinyl structural unit) The alicyclic vinyl structural units constituting the thermoplastic acrylic resin may be formed after resin polymerization. The structural unit represented by the following general formula (6) is preferably used as the alicyclic vinyl structural unit. [ka] In the general formula (6) above, R1 to R3 each independently represent one of the following: a hydrogen atom, a linear hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ether group, an ester group, a cyano group, an amide group, an imide group, a silyl group, and a linear hydrocarbon group substituted with a polar group (halogen atom, alkoxy group, hydroxyl group, ether group, ester group, cyano group, amide group, imide group, or silyl group). Among these, a hydrogen atom or a linear hydrocarbon group having 1 to 6 carbon atoms is preferred because it exhibits excellent heat resistance and low water absorption. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Examples of linear hydrocarbon groups substituted with polar groups include alkyl halides having 1 to 20 carbon atoms, preferably 1 to 10, and more preferably 1 to 6 carbon atoms. Examples of linear hydrocarbon groups include alkyl groups having 1 to 20 carbon atoms, preferably 1 to 10, and more preferably 1 to 6 carbon atoms; and alkenyl groups having 2 to 20 carbon atoms, preferably 2 to 10, and more preferably 2 to 6 carbon atoms. In general formula (6), X represents an alicyclic hydrocarbon group, and the number of carbon atoms constituting it is usually 4 to 20, preferably 4 to 10, and more preferably 5 to 7. By keeping the number of carbon atoms constituting the alicyclic structure within this range, birefringence can be reduced. Furthermore, the alicyclic structure is not limited to a monocyclic structure, but may also be a polycyclic structure such as a norbornane ring or a dicyclohexane ring. Alicyclic hydrocarbon groups may have carbon-carbon unsaturated bonds, but their content is 10% or less of the total carbon-carbon bonds, preferably 5% or less, and more preferably 3% or less. Limiting the carbon-carbon unsaturated bonds of alicyclic hydrocarbon groups to this range improves transparency and heat resistance. Furthermore, the carbon atoms constituting the alicyclic hydrocarbon group may be bonded to any of the following: hydrogen atoms, hydrocarbon groups, halogen atoms, alkoxy groups, hydroxyl groups, ether groups, ester groups, cyano groups, amide groups, imide groups, silyl groups, and chain hydrocarbon groups substituted with polar groups (halogen atoms, alkoxy groups, hydroxyl groups, ether groups, ester groups, cyano groups, amide groups, imide groups, or silyl groups). Among these, hydrogen atoms or chain hydrocarbon groups with 1 to 6 carbon atoms are preferred in terms of heat resistance and low water absorption.

[0036] Among the structural units represented by general formula (6), the structural unit represented by general formula (7) below is superior in terms of heat resistance and low water absorption. [ka] In general formula (7), Ra, Rb, Rc, and Rd each independently represent a hydrogen atom or a lower chain hydrocarbon group, and hydrogen atoms or lower alkyl groups having 1 to 6 carbon atoms are preferred because they have excellent heat resistance and low water absorption. The alicyclic vinyl structural units described above may be a single type or a combination of two or more types.

[0037] The method for forming a thermoplastic acrylic resin containing alicyclic vinyl structural units is not particularly limited, but examples include (1) copolymerizing an aromatic vinyl compound with another monomer containing (meth)acrylic acid or (meth)acrylic acid ester, and hydrogenating the carbon-carbon unsaturated bonds of the main chain and aromatic ring, and (2) copolymerizing an alicyclic vinyl compound with another monomer containing (meth)acrylic acid or (meth)acrylic acid ester, and hydrogenating as necessary. Method (1) is preferred because it can more efficiently produce an alicyclic hydrocarbon copolymer. The aromatic vinyl compounds used in the method described in (1) above are not particularly limited, but examples include styrene, α-methylstyrene, α-ethylstyrene, α-propylstyrene, α-isopropylstyrene, α-t-butylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene, 4-phenylstyrene, etc., among which styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, etc. are preferred. The alicyclic vinyl compound used in the method described in (2) above is not particularly limited, but examples include cyclobutylethylene, cyclopentylethylene, cyclohexylethylene (vinylcyclohexane), cycloheptylethylene, cyclooctylethylene, norbornylethylene, dicyclohexylethylene, α-methylcyclohexylethylene, α-t-butylcyclohexylethylene, cyclopentenylethylene, cyclohexenylethylene, cycloheptenylethylene, cyclooctenylethylene, cyclodekenylethylene, norbornylethylene, α-methylcyclohexenylethylene, and α-t-butylcyclohexenylethylene, among which cyclohexylethylene (vinylcyclohexane) is preferred.

[0038] The content of alicyclic vinyl structural units is preferably 0 to 80% by mass, more preferably 2 to 60% by mass, and even more preferably 5 to 40% by mass, based on 100% by mass of thermoplastic acrylic resin, from the viewpoint of heat resistance, moldability, and optical properties.

[0039] [Method for manufacturing thermoplastic acrylic resin] The method for producing the thermoplastic acrylic resin is not particularly limited as long as the above-described thermoplastic acrylic resin can be obtained, and conventionally known methods can be used. For example, the thermoplastic acrylic resin can be produced using the monomers for forming each of the above-described structural units by bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization, or emulsion polymerization. Bulk polymerization and solution polymerization are preferably used for the production of the thermoplastic acrylic resin, and solution polymerization is more preferably used. Furthermore, the thermoplastic acrylic resin may be manufactured using a continuous process or a batch process. In the method for producing thermoplastic acrylic resins, it is preferable to polymerize the monomers by radical polymerization. Furthermore, in the method for producing thermoplastic acrylic resins, known polymerization initiators, chain transfer agents, etc., may be used as needed.

[0040] [Additives] The lens body P1 may contain various additives, without being particularly limited, as long as it can exert the effects of the present invention. There are no particular restrictions on additives, but examples include antioxidants, light stabilizers such as hindered amine-based light stabilizers, ultraviolet absorbers, mold release agents, lubricants, other thermoplastic resins, paraffinic process oils, naphthenic process oils, aromatic process oils, paraffin, organic polysiloxanes, mineral oils and other softeners / plasticizers, flame retardants, antistatic agents, organic fibers, inorganic fillers such as pigments such as iron oxide, compatibilizers, dispersants, reinforcing agents such as glass fibers, carbon fibers, and metal whiskers, colorants, organophosphorus compounds such as phosphites, phosphonites, and phosphate esters, and other additives or mixtures thereof. The method for mixing thermoplastic acrylic resin and additives is not particularly limited, and examples include mixing using a mixer such as an extruder, heated roll, kneader, roller mixer, or Banbury mixer. Among these, mixing by extruder is preferred from the viewpoint of productivity. It is preferable to provide a vent in the extruder in order to reduce volatile components. The mixing temperature should follow the preferred processing temperature of the thermoplastic acrylic resin or any other thermoplastic resin added as an additive, and is generally between 140 and 350°C, preferably between 180 and 300°C.

[0041] A resin composition containing a thermoplastic acrylic resin and optionally an additive preferably has a weight-average molecular weight (Mw) of 10,000 to 1,000,000, more preferably 50,000 to 500,000, and even more preferably 70,000 to 200,000, from the viewpoint of ease of molding and mechanical strength. When the weight-average molecular weight (Mw) is within the above range, the balance between the moldability and mechanical strength of the lens body P1 tends to be good. Furthermore, the resin composition containing a thermoplastic acrylic resin and optionally an additive preferably has a molecular weight distribution (weight-average molecular weight Mw / number-average molecular weight Mn) of 1.25 to 3.00, more preferably 1.50 to 2.75, and even more preferably 1.75 to 2.50, from the viewpoint of ease of molding, mechanical strength, and solvent resistance. When the molecular weight distribution (Mw / Mn) is within the above range, the balance between the moldability, mechanical strength, and solvent resistance of the lens body P1 tends to be good. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the resin composition can be measured using gel permeation chromatography (GPC), specifically by the method described in the examples below.

[0042] The lens body P1 is formed by molding a resin composition containing a thermoplastic acrylic resin and optionally an additive. Methods for manufacturing the lens body P1 include injection molding, compression molding, injection compression molding, extrusion molding, casting, vacuum molding, pressure molding, blow molding, and casting. Alternatively, the desired shape can be obtained by cutting, turning, and polishing from a resin block. Of these, injection molding is preferred from the viewpoint of productivity. The injection molding method and injection molding machine are not particularly limited, and conventionally known injection molding methods and injection molding machines can be used.

[0043] Typically, injection molding consists of (1) an injection step in which resin is melted and the molten resin is filled into the cavity of a temperature-controlled mold; (2) a holding pressure step in which pressure is applied to the cavity until the gate seal is reached, and resin equivalent to the amount of resin lost when the molten resin filled in the injection step comes into contact with the mold and cools and shrinks is injected; (3) a cooling step in which the molded product is held in place after the holding pressure is released until the resin cools; and (4) a step in which the mold is opened and the cooled molded product is removed.

[0044] In this case, the molding temperature is preferably in the range of Tg+100°C to Tg+180°C, more preferably in the range of Tg+110°C to Tg+160°C, based on the glass transition temperature (Tg) of the resin composition. Here, the molding temperature refers to the cylinder setting temperature of the injection molding machine. A higher molding temperature can yield a lens body P1 with better shape transferability, but at high temperatures, discoloration due to thermal degradation during retention in the molding machine is accelerated, so the molding temperature should be selected appropriately. Furthermore, the mold temperature is preferably in the range of Tg-70°C to Tg, and more preferably in the range of Tg-50°C to Tg-10°C, based on the glass transition temperature (Tg) of the resin composition.

[0045] Furthermore, the ejection speed can be appropriately selected depending on the thickness and dimensions of the lens body P1 to be obtained, but for example, it can be appropriately selected from the range of 2 to 1000 mm / second. Furthermore, the pressure for holding pressure can be appropriately selected depending on the desired shape of the lens body P1, but for example, it can be appropriately selected within the range of 30 to 150 MPa. Here, the pressure for holding pressure refers to the pressure maintained by the screw that further pushes the molten resin out of the gate after it has been filled.

[0046] Furthermore, an annealing process may be performed to alleviate residual stress caused by injection molding and reduce the phase difference of the lens body P1. The temperature during annealing is preferably in the range of Tg-50°C to Tg, and more preferably in the range of Tg-30°C to Tg-10°C, based on the glass transition temperature (Tg) of the resin composition. may be used.

[0047] <Undercoat layer> In the plastic lens P formed by the manufacturing method of the present embodiment, the undercoat layer P2 is a layer that covers at least one surface of the lens body P1. The undercoat layer P2 enhances the adhesion between the lens body (plastic lens substrate) P1 and the optical functional layer P3, and suppresses the generation of cracks in the optical functional layer P3 in a high-temperature environment or a high-temperature and high-humidity environment. Therefore, the plastic lens P formed by the manufacturing method of the present embodiment is a lens with excellent durability.

[0048] The undercoat layer P2 is composed of silicon oxide SiO x (1 < x < 2). As will be described later, for example, when forming a film by vacuum evaporation using SiO as a material, by forming the film while oxidizing the evaporation material in an oxygen atmosphere, the composition of the undercoat layer P2 can be made silicon oxide SiO x (1 < x < 2). Generally, in a film-formed product in which an optical functional layer made of a metal oxide is formed on a resin substrate, when a damp heat test is performed, due to the difference in the linear expansion coefficient and water absorption rate between the resin substrate and the optical functional layer, the optical functional layer cannot follow the expansion of the resin substrate, and cracks occur. However, the plastic lens P formed by the manufacturing method of the present embodiment has an undercoat layer P2 composed of silicon oxide SiO x (1 < x < 2) as a buffer layer between the lens body P1 and the optical functional layer P3, so the occurrence of cracks is suppressed.

[0049] The refractive index of the undercoat layer P2 at a wavelength of 500 nm is preferably 1.44 or more, more preferably 1.45 or more, still more preferably 1.46 or more, preferably 1.64 or less, more preferably 1.62 or less, and still more preferably 1.60 or less. When the refractive index is within this range, a high suppression effect against crack generation after the damp heat test is exhibited. The above refractive index of the undercoat layer P2 is silicon oxide SiOx It can be controlled by adjusting the composition of (1 < x < 2). For example, when forming the undercoat layer P2 by the vacuum evaporation method described later, increasing the oxygen partial pressure (increasing the oxygen introduction amount) makes the composition closer to SiO2 and the refractive index lower, and decreasing the oxygen partial pressure (decreasing the oxygen introduction amount) makes the composition closer to SiO and the refractive index higher. The refractive index of the undercoat layer P2 can be measured by the method described in the examples below.

[0050] The thickness (film thickness) of the undercoat layer P2 is preferably 80 nm or more, more preferably 100 nm or more, further preferably 200 nm or more, preferably less than 1000 nm, more preferably 800 nm or less, and further preferably 650 nm or less. When the thickness (film thickness) of the undercoat layer P2 is within this range, as described later, when the optical function layer P3 is formed by an electron beam heating type vacuum evaporation method, it is possible to prevent reflected electrons from reaching the surface of the lens body P1. Therefore, it is possible to prevent embrittlement of the lens body P1 due to reflected electrons and deterioration of the adhesion between the lens body P1 and the optical function layer P3 due to embrittlement of the lens body P1. The thickness (film thickness) of the undercoat layer P2 can be determined, for example, by direct observation of the cross section using an electron microscope, ellipsometry, or spectroscopic reflectance method, and specifically, can be determined by the method described in the examples below.

[0051] The undercoat layer P2 is formed by a resistance heating type vacuum evaporation method. By using the resistance heating type, as described later, reflected electrons that cause embrittlement of the lens body P1 are not generated, so the adhesion between the lens body P1 and the undercoat layer P2 can be enhanced. The vacuum evaporation method is a method in which a vapor deposition material is heated and vaporized or sublimated in a vacuum chamber, and is attached to the surface of a substrate placed at a distant position in the chamber to form a thin film. Vacuum deposition apparatuses consist of a chamber and a deposition source located within the chamber, with the substrate to be deposited held within the chamber. Examples of deposition sources include resistance heating sources and electron beam heating sources. A schematic diagram of a typical deposition apparatus is shown in Figure 2. Figure 2(a) is an example of an deposition apparatus with a resistance heating source, and Figure 2(b) is an example of an deposition apparatus with an electron beam heating source (electron gun). Although not shown in the figures, deposition apparatuses equipped with both resistance heating and electron beam heating sources can also be used.

[0052] In the deposition apparatus 11 shown in Figure 2(a), 12 is the chamber, 13 is the resistance heating power supply, 14 is the deposition dome, 15 is the boat, and 16 is the shutter. The resistance heating power supply 13 and the boat 15 together are called the deposition source. When the boat 15 is heated by the resistance heating power supply 13, the deposition material 17 is heated through the heat and vapor is generated. The generated vapor reaches the substrate 18 to be deposited, which is held inside the deposition dome 14, and deposits thereon, thereby forming a thin film 19 made of the deposition material 17. Multiple boats 15 may be installed inside the deposition apparatus 11, which allows for increasing the film thickness of the same deposition material or depositing multiple deposition materials (not shown).

[0053] Furthermore, in the deposition apparatus 20 shown in Figure 2(b), 21 is the chamber, 22 is the electron gun, 23 is the electron gun power supply, 24 is the deposition dome, 25 is the crucible, 26 is the pole piece, and 27 is the shutter. The electron gun power supply 23, electron gun 22, and crucible 25 together are called the deposition source. The electron beam 32 generated from the electron gun 22 is deflected by 150° or more (e.g., 180°, 270°) by the magnetic field formed by the pole piece 26, and irradiates the deposition material 29 contained inside the crucible 25. When the deposition material 29 is irradiated with the electron beam 32, the deposition material 29 is heated and vapor is generated. The generated vapor reaches and deposits on the substrate 30 to be deposited, which is held inside the deposition dome 24, thereby forming a thin film 31 made of the deposition material 29. Multiple crucibles 25 are provided on a rotating table, and by rotating the table, any crucible can be positioned at the electron beam irradiation position (not shown).

[0054] As described above, when the electron beam 32 is incident on the deposition material 29, some of the irradiated electrons are reflected (backscattered) on the surface of the deposition material 29 due to the input power and material properties, causing a certain amount of backscattered electrons 33 to diverge. When the backscattered electrons 33 repeatedly reflect off the inner wall of the deposition apparatus and reach the substrate 30, resin decomposition (embrittlement of the substrate 30) occurs, causing poor adhesion between the substrate 30 and the thin film 31 (the thin film 31 becomes more likely to peel off from the embrittlemented part of the substrate 30). Acrylic resins are particularly susceptible to the effects of these backscattered electrons 33 compared to other resins, so in order to obtain good adhesion, it is necessary to suppress the effects of backscattered electrons 33. Effective countermeasures include making it difficult for backscattered electrons 33 to reach the substrate 30 and reducing the amount of backscattered electrons 33 generated. One way to make it difficult for backscattered electrons 33 to reach the substrate 30 is to increase the thickness of the undercoat P2. As a result, even if a large number of backscattered electrons 33 are directed toward the substrate 30, the undercoat layer P2 acts as a barrier layer and does not reach the surface of the acrylic resin (the interface with the undercoat P2), thereby suppressing the embrittlement of the substrate 30. On the other hand, methods to reduce the amount of backscattered electrons 33 include reducing the energy of the electron beam 32 incident on the deposition material 29, and capturing the generated backscattered electrons 33 so that they do not travel towards the substrate 30. Since the energy of the electron beam 32 incident on the deposition material 29 is determined by the output wattage of the electron beam 32 and the irradiation (incidence) time, reducing the output of the electron beam 32 or shortening the irradiation time during the film deposition process reduces the amount of backscattered electrons 33 generated, thereby suppressing the embrittlement of the substrate 30. Furthermore, to prevent the generated backscattered electrons 33 from traveling towards the substrate 30, it is effective to attach a backscattered electron trap to the electron gun 22. This reduces the amount of backscattered electrons 33 traveling towards the substrate 30, thereby suppressing the embrittlement of the substrate 30. In addition, using a backscattered electron trap is preferable because it can reduce the effects of substrate damage and changes in thin film quality that occur when backscattered electrons reach the substrate due to the rise in substrate temperature. Any backscattered electron trap can be used as long as it has the performance to sufficiently capture backscattered electrons, but examples include a physical barrier type that attenuates the energy of backscattered electrons by causing them to collide multiple times in an opening provided at the landing point of the backscattered electrons or inside an L-shaped or U-shaped barrier provided in the direction of backscattered electrons' propagation, and a magnetic field deflection type that captures backscattered electrons by deflecting the direction of propagation of the backscattered electrons with a magnetic field. When using a backscattered electron trap, the use of a magnetic field deflection type is preferable because it has high backscattered electron capture performance, and it is even more preferable to use a combination of a magnetic field deflection type and a physical barrier type. The backscattered electron trap 28 in Figure 2(b) is an example of a magnetic field deflection type.

[0055] The following six steps are typical for vacuum deposition of the undercoat layer P2 and the optical functional layer P3, which are optical thin films. (1) Fix the substrate to the deposition dome and place the deposition dome in the upper part of the chamber. Evacuum the chamber to create a high vacuum inside the chamber. (2) Heat the substrate together with the deposition dome using a halogen heater, sheath heater, etc. At this time, in order to heat uniformly, heat while rotating the deposition dome. (3) With the shutter closed, the deposition material is melted (pre-melted). However, in the case of sublimable materials such as SiO2, pre-melting is not strictly necessary as they can sublimate in a granular state, but it is preferable to perform preheating from the viewpoint of making the transition to the next step (4) smoother (hereinafter, melting and preheating will be collectively referred to as pre-melting). In the case of molten materials such as Ti3O5, pre-melting is necessary to prevent bumping (splashing) and stabilize the film deposition rate. Note that in the case of electron beam heating, even during pre-melting, backscattered electrons may escape from the gap in the shutter and reach the substrate, adversely affecting adhesion, so it is preferable to perform it at low power and for a short time. (4) Once the pressure inside the chamber reaches a predetermined vacuum pressure (base vacuum pressure) and the substrate temperature stabilizes, the shutter is opened, and the atoms and molecules of the vapor deposition material, now in gaseous form, are deposited onto the substrate surface (vapor deposition). (5) Once a thin film of the predetermined thickness has been formed on the substrate, the shutter is closed to terminate the deposition process. (6) Break the vacuum and remove the substrate with the deposited deposition dome and thin film from inside the chamber.

[0056] The above six steps are typically performed with steps (1), (2), and (3) being carried out simultaneously, followed by steps (4), (5), and (6) in that order. Note that heating the substrate in step (2) is optional and does not need to be performed. Furthermore, when depositing a multilayer film using different deposition materials, steps (3) to (5) are repeated for the deposition of the second and subsequent materials (hereafter, the deposition process for the second and subsequent deposition materials will be referred to as (3)', (4)', and (5)'). In this case, the pre-melting of the second and subsequent deposition materials (step (3)') may be performed simultaneously with the pre-melting of the first material (step (3)). Performing step (3)' simultaneously with step (3) allows for immediate transition to the deposition of the second material (step (4)') after the completion of the deposition of the first material (step (4)), thus offering the advantage of efficiently proceeding with vacuum deposition of a multilayer film consisting of multiple materials.

[0057] In step (4), techniques are generally known for depositing oxide films by introducing oxygen into the chamber and reacting it with the atoms and molecules of the deposition material during deposition, or for depositing mixed films by simultaneously using multiple deposition materials. In addition, ion-assisted deposition (IAD), which involves ion irradiation of the thin film surface as it is being deposited to increase the packing density of the thin film and improve adhesion, and ion plating, which involves passing vapor-deposited particles through a plasma to impart a positive charge and then applying a negative charge to the substrate to attract and deposit the vapor-deposited particles, thereby increasing the packing density of the thin film and improving adhesion, are widely used.

[0058] In the deposition of the undercoat layer P2 in this embodiment, in step (1), the vacuum of the chamber is set to 2.0 × 10 -3 It is preferable to perform vacuuming so that the pressure is less than Pa. In heating the deposition material in steps (3) and (4), methods such as resistance heating, electron beam heating, high-frequency induction heating, and laser heating can be appropriately selected depending on the type of deposition material and substrate, and the desired characteristics of the thin film to be fabricated. In forming the undercoat layer P2 in this embodiment, SiO is used as the deposition material, and the heating method must be a resistance heating type that does not generate backscattered electrons, from the viewpoint of preventing embrittlement of the lens body P1. In step (4), during the deposition process, oxygen can be introduced into the chamber to react with the atoms and molecules of the deposition material while the film is being deposited. In the deposition of the undercoat layer P2 in this embodiment, the amount of oxygen introduced (amount of O2 gas) is controlled to maintain the pressure inside the chamber at 3.0 × 10⁻⁶. -2 Less than Pa, 2.8 × 10 -2 Preferably less than Pa, 2.6 × 10 -2 It is more preferable to set it to less than Pa, 1.0 × 10 -2 Preferably, it should be Pa or higher, 1.1 × 10 -2 It is more preferable to have a value of Pa or higher, 1.2 × 10 -2 A pressure of Pa or higher is even more preferable. When the pressure inside the chamber is in this range, an undercoat layer P2 with the desired refractive index is formed, resulting in high adhesion and a high suppression effect against crack formation after the moist heat test.

[0059] <Optical functional layer> In the plastic lens P formed by the manufacturing method of this embodiment, the optical functional layer P3 is a layer that covers the undercoat layer P2 from the side opposite to the lens body P1. That is, in the plastic lens P formed by the manufacturing method of this embodiment, the undercoat layer P2 and the optical functional layer P3 are laminated in this order on at least one surface of the lens body P1. Examples of the optical functional layer P3 include an anti-reflective layer, a partial reflective layer, a high-reflection mirror, an ultraviolet cut filter, an infrared cut filter, a bandpass filter, a notch filter, an edge filter, and a dichroic mirror. In this embodiment, one of the anti-reflective layer, partial reflective layer, or high-reflection mirror is formed. The anti-reflective layer has the function of preventing surface reflection in the plastic lens P, the partial reflective layer has the function of transmitting a portion of the incident light and reflecting a portion of it (an optical functional layer where transmission and reflection are approximately 50% is specifically called a half-mirror layer), and the high-reflection mirror has the function of reflecting almost all of the incident light. In this embodiment, since the optical functional layer P3 is formed adjacent to the undercoat layer P2, it is preferable to design the optical functional layer P3 by taking into account the optical properties and thickness of the undercoat layer P2 so that the desired optical performance is achieved in the overall film configuration combining the undercoat layer P2 and the optical functional layer P3.

[0060] The optical functional layer P3 is preferably configured by combining a high refractive index film made of a high refractive index material and a low refractive index film made of a low refractive index material with a lower refractive index than the high refractive index material. In particular, it is preferable that it consists of a dielectric multilayer film in which the high refractive index film and the low refractive index film are alternately stacked. When the optical functional layer P3 is a dielectric multilayer film with the above configuration, the reflectance can be adjusted more precisely for light rays and light beams in a wide range of wavelengths.

[0061] As the high refractive index material for forming the high refractive index film, known materials can be used. Specifically, for example, titanium dioxide, zirconium oxide, ditantalum pentoxide, niobium pentoxide, zinc sulfide, cerium oxide, hafnium oxide, lanthanum titanate, antimony oxide, indium oxide, tin oxide, and mixtures thereof (such as Merck's Substance H series) can be used. Furthermore, by using materials or metal materials that are sold with low oxidation states, such as Ti2O3 and Ti3O5, as deposition materials and performing deposition while introducing oxygen into the chamber, it is possible to form an oxide film with an arbitrary amount of oxygen introduced. In the optical functional layer P3 of this embodiment, it is preferable that the high refractive index film is made of a high refractive index material containing one or more of titanium dioxide and zirconium oxide. When the high refractive index film contains one or more of titanium dioxide and zirconium oxide, it is preferable in terms of adhesion to the lens body P1 and undercoat layer P2, ease of material procurement, film stability, and controllability of optical properties in the visible light region. When the optical functional layer P3 includes multiple high-refractive-index films, the composition of each high-refractive-index film can be appropriately set according to the design of the optical properties. Therefore, the compositions of each high-refractive-index film may be the same or different.

[0062] The refractive index of each high refractive index film at a wavelength of 500 nm is preferably 1.80 or higher, more preferably 1.90 or higher, even more preferably 2.00 or higher, preferably 2.50 or lower, more preferably 2.45 or lower, and even more preferably 2.40 or lower. The refractive index of the high refractive index film can be measured by the method described in the examples below.

[0063] The thickness (film thickness) of each high refractive index film is preferably 5 nm or more, more preferably 6 nm or more, even more preferably 7 nm or more, preferably 150 nm or less, more preferably 140 nm or less, and even more preferably 130 nm or less. When the thickness (film thickness) of each high refractive index film is within this range, a good balance of film adhesion, scratch resistance, and controllability of optical properties tends to be achieved. The thickness (film thickness) of the high refractive index film can be determined, for example, by direct observation of the cross-section using an electron microscope, ellipsometry, or spectral reflectance method. Specifically, it can be determined by the method described in the examples below.

[0064] As the low refractive index material for forming the low refractive index film, known materials can be used. Specifically, for example, silicon oxide, magnesium fluoride, yttrium fluoride, thiolite, cryolite, aluminum oxide, and mixtures thereof (such as Merck's Substance L series and M series) can be used. Furthermore, by using materials sold at low oxidation states, such as SiO, or metallic materials as deposition materials and performing deposition while introducing oxygen into the chamber, an oxide film with an arbitrary amount of oxygen can be formed. In the optical functional layer P3 of this embodiment, it is preferable that the low refractive index film contains silicon oxide (however, one whose refractive index at a wavelength of 500 nm is lower than that of the undercoat layer P2). When the low refractive index film contains the above silicon oxide, it is preferable in terms of ease of material procurement, controllability of oxidation degree, and film formation stability. Furthermore, methods for adjusting the refractive index of a low-refractive-index film containing silicon oxide to be lower than that of the undercoat layer P2 include, for example, using SiO2 as the deposition material for silicon oxide in the optical functional layer P3, or, as mentioned above, adjusting the oxygen partial pressure (amount of oxygen introduced) when forming the undercoat layer P2. Increasing the oxygen partial pressure (increasing the amount of oxygen introduced) makes the composition closer to SiO2 and lowers the refractive index, while decreasing the oxygen partial pressure (decreasing the amount of oxygen introduced) makes the composition closer to SiO and higher the refractive index. When the optical functional layer P3 includes multiple low-refractive-index films, the composition of each low-refractive-index film can be appropriately set according to the design of the optical properties. Therefore, the compositions of each low-refractive-index film may be the same or different.

[0065] The refractive index of each low refractive index film at a wavelength of 500 nm is preferably 1.10 or higher, more preferably 1.20 or higher, even more preferably 1.30 or higher, preferably 1.70 or lower, more preferably 1.60 or lower, and even more preferably 1.50 or lower. The refractive index of the low refractive index film can be measured by the method described in the examples below.

[0066] The thickness (film thickness) of each low refractive index film is preferably 2 nm or more, more preferably 3 nm or more, even more preferably 4 nm or more, preferably 200 nm or less, more preferably 190 nm or less, and even more preferably 180 nm or less. When the thickness (film thickness) of each low refractive index film is within this range, a good balance of film adhesion, scratch resistance, and controllability of optical properties tends to be achieved. The thickness (film thickness) of the low refractive index film can be determined, for example, by direct observation of the cross-section using an electron microscope, ellipsometry, or spectral reflectance method. Specifically, it can be determined by the method described in the examples below.

[0067] The total thickness (total film thickness) of the optical functional layer P3 is preferably 100 nm or more, more preferably 150 nm or more, even more preferably 200 nm or more, preferably 600 nm or less, more preferably 500 nm or less, and even more preferably 400 nm or less. When the total thickness (total film thickness) of the optical functional layer P3 is within this range, the adhesion between the optical functional layer P3 and the lens body P1 and the undercoat layer P2 tends to be good. The total thickness (total film thickness) of the optical functional layer P3 can be determined, for example, by direct observation of the cross-section using an electron microscope, ellipsometry, or spectral reflectance method. Specifically, it can be determined by the method described in the examples below.

[0068] In this embodiment, the optical functional layer P3 is formed by vacuum deposition, similar to the undercoat layer P2, and is formed by electron beam heating type vacuum deposition as the heating method for the deposition material. Generally, dry deposition methods such as vacuum deposition offer superior shape control compared to wet deposition methods. Therefore, the plastic lens P formed by the manufacturing method of this embodiment, by forming the undercoat layer P2 and the optical functional layer P3 by vacuum deposition, becomes a plastic lens with excellent shape accuracy that can meet the requirements for applications requiring high-level surface shape control. Furthermore, in this embodiment, since the deposition of the undercoat layer P2 and the optical functional layer P3 can be carried out continuously by vacuum deposition, the number of processes and working time can be reduced, resulting in excellent productivity. In the deposition of the optical functional layer P3 in this embodiment, an electron beam heating method is used for heating the deposition material in steps (3) and (4) of the vacuum deposition described above, due to its high work efficiency and flexibility in material selection. At that time, the temperature inside the chamber and the lens body rises due to radiant heat from the deposition material, but from the viewpoint of adhesion, it is preferable that the surface temperature of the lens body be 60°C or higher. In step (3), pre-melting of the deposition material must be performed only after the undercoat layer P2 has been formed, following the film formation flow in Figure 3. This is because if the pre-melting is performed before the undercoat layer P2 is formed, backscattered electrons that escape through the gaps in the shutter will reach the substrate and negatively affect adhesion. In this case, the pre-melting process is carried out with the shutter closed until the melting and evaporation of the deposition material stabilizes, after which the shutter opens and the deposition process begins. Furthermore, even with this procedure (formation of undercoat layer P2 → pre-melting of the deposition material for the optical functional layer P3), if the total EB energy (output wattage × time) during pre-melting is too high, many backscattered electrons will be generated, preventing the undercoat layer from functioning as a barrier layer and causing embrittlement of the substrate. Therefore, it is important to reduce the total EB energy during pre-melting. Specifically, the total EB energy during pre-melting of the molten material among the deposition materials for the optical functional layer P3 should be less than 1500 kJ, preferably less than 1250 kJ, and more preferably less than 1000 kJ, from the viewpoint of productivity. Figures 4(a) and 4(b) are examples of programs designed to achieve a total pre-melt energy of 340 kJ and 640 kJ, respectively. Furthermore, while sublimable materials among the deposition materials for the optical functional layer P3 can sublimate in a granular state, and therefore pre-melting is not strictly necessary, if it is performed, it is preferable to do so with low energy to reduce backscattered electrons and improve productivity. Even with the above measures, if the undercoat layer P2 is thin, substrate embrittlement due to backscattered electrons cannot be suppressed, and delamination easily occurs. Therefore, when the undercoat layer P2 is less than 200 nm thick (e.g., preferably 80 nm or more, more preferably 100 nm or more), it is preferable to attach a backscattered electron trap to the electron gun used to reduce the number of backscattered electrons generated during pre-melting and reaching the substrate. When the undercoat layer P2 is 200 nm or thicker, the undercoat layer P2 can suppress the arrival of backscattered electrons to the substrate without reducing the number of backscattered electrons, so it is not necessary to attach a backscattered electron trap to the electron gun used, although there is no problem if it is included. Note that the amount of backscattered electrons generated is determined by the magnitude of the EB energy, not the amount of deposition material used. Therefore, the upper limit of the total EB energy during pre-melting (1500 kJ) is an absolute value that does not depend on the amount of deposition material used or the number and size of the crucibles. If the value is less than 1500 kJ, in the pre-melting of the deposition material in steps (3) and (3)', pre-melting may be performed on multiple crucibles containing the deposition material for the optical functional layer P3 before step (4). The shape of the vapor-deposited material is not particularly limited for either the vapor-deposited material (SiO) for the undercoat layer P2 or the vapor-deposited material for the optical functional layer P3. It can be appropriately selected considering the specifications and characteristics of the vapor deposition apparatus and the availability of the vapor deposition material. Specifically, examples include pellet shape, tablet shape, granular shape, powder, fan shape, ring shape, and rod shape. Furthermore, in step (4) deposition, the pressure inside the chamber is 1.0 × 10⁻⁶ -3 Pa~5.0×10 -2 It is preferable to control the amount of oxygen introduced so that the pressure is within the range of Pa. In this case, it is also possible to use the ion-assisted deposition method described above, but it is necessary to adjust the amount of introduced gas so that the pressure is within the above range, taking into account the pressure increase caused by suitable oxygen gas, argon gas, or a mixture thereof as the introduced gas. In addition, since a dense film can be obtained by applying ion assistance, there is an effect of suppressing optical shift caused by water adsorption, and if the amount of oxygen gas introduced is large, the oxidation of oxygen-deficient compounds can be carried out efficiently. However, the refractive index may change, causing deviations from the desired optical properties, and if the amount of gas introduced is too large, the film density will increase, increasing film stress, which can easily cause deformation of the substrate, cracking and delamination of the film, shortening the mean free path of vaporized deposited particles, which can reduce the film deposition rate, and increasing the energy that must be applied to the deposited material in order to obtain a certain film thickness. When using the ion-assisted deposition method, it is preferable to appropriately set and design the type and amount of introduced gas, assistance conditions, film configuration, etc., taking into account the above advantages and disadvantages.

[0069] <Artifacts using plastic lenses> The plastic lens of this embodiment can be suitably used for applications such as lenses in household goods, office automation equipment, AV equipment, battery and electrical components, lighting equipment, and automotive parts.

[0070] One suitable example of its use is in lenses for VR (Virtual Reality) head-mounted displays (HMDs). Since head-mounted displays are image display devices worn on the head, they are required to be small, lightweight, and cause minimal discomfort when worn. As a means of miniaturization, a method has been proposed in which a quarter-wave plate and a reflective polarizer are combined with the lens, and the polarization state of the light after passing through the lens is changed to switch between reflection and transmission, thereby causing the image to pass through a single lens one and a half times (U.S. Patent No. 6,563,638, Japanese Patent Publication No. 2017-21321, etc.). The above method works, for example, as follows: A quarter-wave plate and a reflective polarizer are placed behind a lens with a partially reflective coating on its front surface. Light incident from the front of the lens as circularly polarized light is converted to linearly polarized light by the quarter-wave plate after passing through the lens. This linearly polarized light is reflected by the reflective polarizer and converted again to circularly polarized light in the opposite direction by the quarter-wave plate, then incident on the lens from the back and reaches the partially reflective coating on the front surface. The light reflected by the partially reflective coating exits the back of the lens, becomes linearly polarized light with a 90° different direction from the initial light, passes through the reflective polarizer, and enters the eye as an image. In this way, a high magnification and wide field of view can be obtained even with a thin optical module.

[0071] If the polarization state changes while passing through the lens, for example, some light may pass through the reflective polarizer after the first pass through the lens, resulting in the overlapping of low-magnification and high-magnification images, making it difficult to obtain a clear image. Therefore, low birefringence lenses are required. Furthermore, the impact on image formation due to changes in lens shape caused by changes in humidity during use is undesirable, so lenses with low hygroscopicity in high-temperature and high-humidity environments and high shape stability are required. In this respect, the plastic lenses formed by the manufacturing method of this embodiment are suitable because they have excellent shape accuracy and extremely good durability.

[0072] Furthermore, other examples of suitable applications for the plastic lenses formed by the manufacturing method of this embodiment include lenses for household goods, office automation equipment, AV equipment, battery and electrical components, lighting equipment, etc., such as lenses for smartphone cameras and tablet PC cameras, lenses used in bent optical system telephoto cameras (periscope cameras); lenses used in VR (Virtual Reality) / AR (Augmented Reality) / MR (Mixed Reality) / SR (Substitutional Reality) / DR (Diminished Reality) / XR (Cross Reality) head-mounted displays, liquid crystal projectors, near-infrared sensors (LiDAR; Light Detection and Ranging), etc., in particular, small, thin-walled, variable-thickness optical lenses; lenses for optical communication; and phase plates equipped with lenses, Fresnel lenses, and microlens arrays.

[0073] Examples of lenses used in automotive parts include lenses used in head-up displays and lenses for in-vehicle cameras (especially front element lenses). Other examples include lenses used in aerial displays, such as base materials for retroreflective sheets and partially transparent mirrors, microlens arrays for constructing two-sided corner reflector arrays, and lenses for magnifying, reducing, or correcting image planes and aberrations. [Examples]

[0074] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0075] The measurement and evaluation methods for the thermoplastic acrylic resins produced in the manufacturing examples are as follows.

[0076] [Analysis of structural units] Unless otherwise specified, 1 H-NMR measurement and 13 By using 1C-NMR measurements, the structural units of the thermoplastic acrylic resin produced in the manufacturing example were identified, and their abundance was calculated. 1 H-NMR measurement and 13 The measurement conditions for 1C-NMR are as follows: • Measuring instrument: ECZ400 manufactured by JEOL Ltd. • Measurement solvent: CDCl3 or DMSO-D6 ·Measurement temperature: 40℃

[0077] [Measurement of molecular weight] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the thermoplastic acrylic resin produced in the manufacturing example were measured using the following equipment and conditions. • Measuring device: Gel permeation chromatography (HLC-8320GPC) manufactured by Tosoh Corporation • Measurement conditions: The following columns were used, connected in series: one TSKguardcolumn SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500. Column temperature: 40℃ The developing solvent was tetrahydrofuran, the flow rate was 0.6 mL / min, and 0.1 g / L of 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard. Detector: RI (Differential Refraction) detector Detection sensitivity: 3.0 mV / min Sample: 0.02 g of thermoplastic acrylic resin in a 20 mL solution of tetrahydrofuran. Injection volume: 10μL Standard samples for calibration curve: Ten different polymethyl methacrylates (Polymer Laboratories; PMMACalibration Kit MM-10) with known monodisperse weight peak molecular weights were used. Weight-peak molecular weight (Mp) Standard sample 1: 1,916,000 Standard sample 2 625,500 Standard sample 3: 298,900 Standard sample 4 138,600 Standard sample 5 60,150 Standard sample 6 27,600 Standard sample 7 10,290 Standard sample 8 5,000 Standard sample 9 2,810 Standard sample 10 850 Under the above conditions, the RI detection intensity was measured as a function of the elution time of the thermoplastic acrylic resin. Based on the calibration curve obtained by measuring the above-mentioned standard samples, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the thermoplastic acrylic resin were determined, and the molecular weight distribution (Mw / Mn) was determined using these values.

[0078] [Measurement of glass transition temperature] The glass transition temperature (Tg) (°C) of thermoplastic acrylic resins was measured in accordance with JIS-K7121. First, from a sample that had been conditioned under standard conditions (23°C, 50% RH) (left at 23°C for one week), four test pieces (from four different locations), each approximately 10 mg in size, were cut out. Next, a differential scanning calorimeter (Diamond DSC, manufactured by PerkinElmer Japan Co., Ltd.) was used under nitrogen gas flow rate of 25 mL / min. The sample was heated from room temperature (23°C) to 200°C at 10°C / min (first heating), held at 200°C for 5 minutes to completely melt the sample, then cooled from 200°C to 40°C at 10°C / min, held at 40°C for 5 minutes, and then heated again under the same heating conditions (second heating). The glass transition temperature (Tg) (°C) was measured at the intersection point (midpoint glass transition temperature) of the DSC curve drawn during the step-like change portion of the curve during the second heating and a straight line equidistant in the vertical direction from each baseline extension. Four measurements were taken per sample, and the arithmetic mean of the four points (rounded to the nearest whole number) was taken as the measured value.

[0079] [Measurement of Vicat softening temperature] Thermoplastic acrylic resin was injected into an injection molding machine (Shibaura Machine Co., Ltd., EC-100SX) and Type 1A dumbbell test specimens were molded in accordance with ISO 8257-2. After conditioning the test specimens in an oven at a specified temperature for 16 hours, they were cooled in a desiccator at 23°C for 1 hour, and the Vicat softening temperature (°C) of the thermoplastic acrylic resin was measured in accordance with ISO 306 B50.

[0080] The raw materials used in the manufacturing example are as follows:

[0081] [monomer] • Methyl methacrylate (MMA): Manufactured by Asahi Kasei Corporation • N-phenylmaleimide (phMI): Manufactured by Nippon Shokubai Co., Ltd. • N-cyclohexylmaleimide (chMI): Manufactured by Nippon Shokubai Co., Ltd. • Methyl 2-(hydroxymethyl)acrylate (RHMA): Manufactured by Combi-Blocks. • Styrene (St): Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0082] [organic solvent] • Metaxylene (mXy): Manufactured by Mitsubishi Gas Chemical Company, Ltd. • Toluene: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. • Methyl isobutyrate: Manufactured by Kanto Chemical Co., Ltd.

[0083] [Polymerization initiator] • 1,1-di(t-butylperoxy)cyclohexane: Manufactured by NOF Corporation, Perhexa C • t-Amil peroxyisononanoate: Manufactured by Arkema Yoshitomi Co., Ltd., Luperox 570 • t-Amyl peroxy-2-ethylhexanoate: Manufactured by Arkema Yoshitomi Co., Ltd., Luperox 575

[0084] [Chain transfer agent] n-Octyl mercaptan: Manufactured by Chevron Philips Chemicals.

[0085] [Other additives, etc.] • Stearyl phosphate: Manufactured by Sakai Chemical Industry Co., Ltd., Phoslex A-18 • Monomethylamine: Manufactured by Mitsubishi Gas Chemical Company, Inc. • Dimethyl carbonate: Manufactured by Fujifilm Wako Pure Chemical Corporation Triethylamine: Manufactured by Fujifilm Wako Pure Chemical Corporation • Pd / C: Manufactured by NE Chemcat Co., Ltd. • Rikemar H-100: Manufactured by Riken Vitamin Co., Ltd.

[0086] (Manufacturing Example 1: Thermoplastic Acrylic Resin A) 358.6 kg of methyl methacrylate (hereinafter referred to as MMA), 29.4 kg of N-phenylmaleimide (hereinafter referred to as phMI), 67.7 kg of N-cyclohexylmaleimide (hereinafter referred to as chMI), 0.77 kg of n-octyl mercaptan (a chain transfer agent), and 224.3 kg of metaxylene (hereinafter referred to as mXy) ​​were weighed out and placed in a 1.25 m³ tank equipped with a jacketed temperature control device and stirring blades. 3 The mixture was added to the reactor and stirred to obtain a mixed monomer solution. Next, 88.0 kg of MMA, 6.3 kg of phMI, and 142.4 kg of mXy were weighed and added to tank 1, then stirred to obtain a mixed monomer solution for supplementation. For the contents of the reactor, nitrogen bubbling was performed at a rate of 30 L / min for 1 hour, and for tank 1, nitrogen bubbling was performed at a rate of 10 L / min for 30 minutes to remove dissolved oxygen. Subsequently, steam was blown into the jacket to raise the solution temperature in the reactor to 115°C, and polymerization was started by adding a polymerization initiator solution, which consisted of 0.470 kg of 1,1-di(t-butylperoxy)cyclohexane dissolved in 1.905 kg of mXy, at a rate of 1.0 kg / hour while stirring at 50 rpm. During polymerization, the solution temperature in the reactor was controlled at 115±2°C using a jacket. Thirty minutes after the start of polymerization, the rate of addition of the initiator solution was reduced to 0.5 kg / hour. Furthermore, the entirety of the additive mixed monomer solution was added from tank 1 at a constant rate over a period of 4 hours, starting 1 hour after the start of polymerization. Furthermore, the initiator solution was added at a rate of 0.25 kg / hour 3.5 hours after the start of polymerization, and the addition was stopped 5 hours after the start of polymerization. Twelve hours after the start of polymerization, a polymer solution containing a thermoplastic acrylic resin having a ring structure in its main chain was obtained, and the polymerization was terminated. This polymer solution was supplied to a concentration apparatus consisting of a tubular heat exchanger and a vaporization tank, which were preheated to 250°C, for defoliation. The vacuum level in the vaporization tank was set to 10-15 Torr. The resin flowing down the vaporization tank was discharged with a gear pump, extruded from a strand die, water-cooled, and pelletized to obtain thermoplastic acrylic resin A. Upon examining the composition of the obtained pellets, it was found that the structural units derived from the MMA, phMI, and chMI monomers in the copolymer accounted for 81.0% by mass, 6.6% by mass, and 12.4% by mass, respectively. The weight-average molecular weight was 108,000, the Mw / Mn ratio was 2.04, the glass transition temperature was 134°C, and the Vicat softening temperature was 124°C.

[0087] (Manufacturing Example 2: Thermoplastic Acrylic Resin B) Glutalimide resin was produced using a 15 mm diameter, coaxial twin-screw extruder with meshing, co-rotating design, using a methyl methacrylate-styrene copolymer (styrene content 8% by mass) with a molecular weight of 100,000 as the raw material resin and monomethylamine as the imidizing agent. The temperature of each temperature control zone was set to 230-250°C, and the screw rotation speed was set to 150 rpm. Methyl methacrylate-styrene copolymer (hereinafter also referred to as "MS resin") was supplied at 2 kg / hr, and after the resin was melted and filled using a kneading block, 8 parts by mass of monomethylamine were injected into the resin from a nozzle. A reverse flight was placed at the end of the reaction zone to fill it with resin. By-products and excess monomethylamine after the reaction were removed by reducing the pressure at the vent port to -0.092 MPa. The resin that came out as strands from the die provided at the extruder outlet was cooled in a water bath and then pelletized in a pelletizer to obtain glutalimide MS resin intermediate (1). Next, a 15mm diameter, co-rotating twin-screw extruder was set to a temperature of 230°C in each temperature control zone and a screw rotation speed of 150 rpm. Glutarimidized MS resin intermediate (1) obtained from the hopper was supplied at a rate of 1 kg / hr. After the resin was melted and filled using a kneading block, a mixture of 0.8 parts by mass of dimethyl carbonate and 0.2 parts by mass of triethylamine was injected into the resin from the nozzle to reduce the number of carboxyl groups in the resin. A reverse flight was placed at the end of the reaction zone to fill it with resin. By-products and excess dimethyl carbonate after the reaction were removed by reducing the pressure at the vent port to -0.092 MPa. The resin that came out as strands from the die at the extruder outlet was cooled in a water bath and then pelletized in a pelletizer to obtain glutarimidized MS resin intermediate (2). Furthermore, the glutarimidated MS resin intermediate (2) was fed into a 15 mm diameter, coaxial twin-screw extruder under the conditions of a set temperature of 230°C in each temperature control zone of the extruder, a screw rotation speed of 150 rpm, and a feed rate of 1 kg / hr. The pressure at the vent port was reduced to -0.095 MPa to remove any unreacted auxiliary raw materials and other volatile components. The defolable imide resin that came out as strands from the die at the extruder outlet was cooled in a water bath and then pelletized in a pelletizer to obtain thermoplastic acrylic resin B (glutarimidated MS resin). The weight-average molecular weight of thermoplastic acrylic resin B was 85,000, the Mw / Mn ratio was 1.8, the monomer unit content in the copolymer was 8% by mass of styrene units, 82% by mass of MMA units, and 10% by mass of glutarimide units, the glass transition temperature was 128°C, and the Vicat softening temperature was 120°C.

[0088] (Manufacturing Example 3: Thermoplastic Acrylic Resin C) In a reaction vessel equipped with a stirrer, temperature sensor, condenser, nitrogen inlet tube, and dropping pump, 5.40 parts by mass of methyl 2-(hydroxymethyl)acrylate (hereinafter referred to as RHMA), 37.6 parts by mass of methyl methacrylate (hereinafter referred to as MMA), 0.450 parts by mass of styrene (hereinafter referred to as St), and 90.0 parts by mass of toluene were charged, and the temperature was raised to 105°C while passing nitrogen through the mixture. As an initial initiator, a solution consisting of 3.63 parts by mass of toluene and 0.245 parts by mass of t-amyl peroxyisononanoate was added dropwise over 9 minutes while solution polymerization was carried out at 105°C to 110°C. Then, 11 minutes later, a solution consisting of 4.42 parts by mass of toluene and 0.298 parts by mass of t-amyl peroxyisononanoate was added dropwise over 180 minutes as a dropwise initiator. Simultaneously with the addition of the dropwise initiator, a solution consisting of 6.6 parts by mass of RHMA, 45.9 parts by mass of MMA, and 4.05 parts by mass of St was added dropwise over 180 minutes while solution polymerization was carried out at 105°C to 110°C, followed by a further 100 minutes of maturation. To the obtained polymerization solution, a solution consisting of 1.20 parts by mass of toluene and 0.0750 parts by mass of stearyl phosphate was added as a catalyst for the cyclization condensation reaction (cyclization catalyst), and the cyclization condensation reaction to form a lactone ring structure was carried out under reflux at approximately 90°C to 110°C for 1.5 hours. Next, the obtained polymerization solution was passed through a multi-tube heat exchanger maintained at 220°C to complete the cyclization condensation reaction. Then, the polymerization solution was defolatized by introducing it into a vented-type screw twin-screw extruder (L / D=52) equipped with a leaf-disc type polymer filter (filtration accuracy 5 μm) at its tip, at a processing rate of 90 parts by mass / hour in terms of resin volume. The vented-type screw twin-screw extruder used had one rear vent and four fore vents (referred to as the 1st, 2nd, 3rd, and 4th vents from the upstream side), with a barrel temperature of 220°C and a reduced pressure of 13.3 to 400 hPa (10 to 300 mmHg). During defolatation, deionized water was introduced from behind the 1st, 2nd, and 3rd vents at an input rate of 1.3 parts by mass / hour. The obtained thermoplastic acrylic resin C had a weight-average molecular weight of 102,000, a Mw / Mn ratio of 2.3, a glass transition temperature of 125°C, a Vicat softening temperature of 116°C, and the proportions of MMA units, styrene units, lactone ring structures, and RHMA units in the copolymer were 76.8% by mass, 4.6% by mass, 16.9% by mass, and 1.7% by mass, respectively.

[0089] (Manufacturing example 4: Thermoplastic acrylic resin D) A monomer composition consisting of 75.09 parts by mass of MMA, 26.04 parts by mass of styrene, and 0.46 parts by mass of t-amyl peroxy-2-ethylhexanoate as a polymerization initiator was continuously supplied at 1 kg / h to a 10 L complete mixing tank equipped with helical ribbon blades, and continuous polymerization was carried out at an average residence time of 2.5 hours and a polymerization temperature of 150°C. The liquid was continuously withdrawn from the bottom of the polymerization tank to maintain a constant liquid level and supplied to a concentration device consisting of a tubular heat exchanger and a vaporization tank for defoliation. The vacuum level in the vaporization tank was set to 10-15 Torr. The resin flowing down the vaporization tank was discharged with a screw pump, extruded from a strand die, water-cooled, pelletized, and introduced into a solvent removal device to obtain pelletized methyl methacrylate-styrene copolymer. This copolymer was dissolved in methyl isobutyrate to prepare a 10% by mass methyl isobutyrate solution. 500 parts by mass of this copolymer 10% by mass methyl isobutyrate solution and 1 part by mass of 10% by mass Pd / C as a hydrogenation catalyst were charged into a 1000 mL autoclave. The mixture was maintained at a hydrogen pressure of 9 MPa and 200°C for 15 hours to hydrogenate the aromatic double bonds of the styrene moiety of the copolymer. The hydrogenation catalyst was removed by filtration, and 0.04 parts by mass of Rikemar H-100 was added and mixed to the polymer solution. The solution was then supplied to a concentration apparatus consisting of a tubular heat exchanger and a vaporization tank for defoliation. The vacuum level in the vaporization tank was set to 10-15 Torr. The resin flowing down the vaporization tank was discharged with a gear pump, extruded from a strand die, water-cooled, and pelletized to obtain thermoplastic acrylic resin D. Upon examining the composition of the obtained pellets, it was found that the structural units derived from the MMA and vinylcyclohexane monomers in the copolymer comprised 73.2% by mass and 26.8% by mass, respectively. Furthermore, the weight-average molecular weight was 148,000, the Mw / Mn ratio was 2.0, the glass transition temperature was 118°C, and the Vicat softening temperature was 112°C.

[0090] The measurement and evaluation methods for each layer deposited in the examples and comparative examples are as follows.

[0091] [Refractive index] The refractive index at a wavelength of 500 nm for each layer deposited in the examples and comparative examples was determined by first depositing a single layer on a glass substrate (optical glass B270i) under the same deposition conditions, and then measuring the spectral reflectance using an ultraviolet-visible-near-infrared spectrophotometer (Hitachi High-Tech Corporation, UH4150), followed by the spectral reflectance method.

[0092] [Thickness of each layer (film thickness)] The thickness (film thickness) of each layer deposited in the examples and comparative examples was determined using a spectroscopic ellipsometer (UVISEL2, Horiba, Ltd.). For the film thickness calculation, data from a sample in which a single layer was deposited on a glass substrate (optical glass B270i) under the same deposition conditions was used.

[0093] [Example 1] (Lens shaping) Using the thermoplastic acrylic resin A obtained in Manufacturing Example 1, injection molding was performed using an injection molding machine (FANUC Corporation, S-2000i50B) to obtain a plano-convex lens molded product (lens body) with an optical axis thickness of 3.2 mm and an effective diameter of φ41 mm. As a finished product, one side of the plane containing the optical axis has an aspherical shape with a radius of curvature of R93.5 mm, and the cone constant k is -1.12452, with no even-order constants set. The other side of the plane containing the optical axis has a planar shape with a radius of curvature of ∞. The cylinder temperature was set to Tg + 135°C of the thermoplastic acrylic resin A used, and the mold temperature was set to Tg - 15°C of the thermoplastic acrylic resin A used. The holding pressure was set to 60 MPa for 4 seconds for the first stage, and then to 40 MPa for 3 seconds for the second stage to relieve stress and strain inside the molded product. The injection speed was set to 10 mm / s.

[0094] (Formation of undercoat layer and optical functional layer) On the flat surface of the aforementioned lens molded product, an undercoat layer and an anti-reflective layer as an optical functional layer were deposited by vacuum deposition using a vacuum deposition apparatus (SAPIO SGC-1300, manufactured by Showa Vacuum Co., Ltd.). Note that the electron gun (G-12100, EB source for vacuum deposition, manufactured by Plasmatec Co., Ltd.) was not equipped with a backscattered electron trap. The lens molded product is placed inside the vacuum deposition apparatus, and the vacuum chamber is 1.5 × 10 -3 The system was evacuated to Pa. Next, SiO granules packed inside the molybdenum boat were heated and sublimated using resistance heating to deposit an undercoat layer with a thickness of 320 nm. During the deposition process, oxygen gas was supplied as the reaction gas at a total pressure of 1.4 × 10⁻⁶. -2 The device was introduced to achieve a Pa temperature, and the film was deposited without any special heating of the target object (lens molded product). Furthermore, pre-melting of the vapor deposition material to be used for the anti-reflective layer deposition in the next step was not performed before or during the deposition of the undercoat layer. Next, Ti3O5 granules packed inside the copper liner were heated, melted, and vaporized using an electron gun, and a TiO2 layer, which is a high refractive index layer, was deposited by electron beam deposition. During deposition, oxygen gas was used as the reaction gas at a total pressure of 1.3 × 10⁻⁶. -2The electron beam was introduced to achieve a Pa (power), and the film to be deposited (lens molded product + undercoat layer) was not heated specifically before deposition. Furthermore, the electron beam heating of the deposition material, Ti3O5, was started with the shutter closed, and after pre-melting of the deposition material, the shutter was opened and film deposition was performed. In this case, as shown in Figure 4(a), the pre-melting was performed using a program that corresponded to the EB output and time so that the total EB energy (output watts × time) was 340 kJ. Specifically, the EB output was linearly increased from 0kW to 4.0kW over 20 seconds (until 20 seconds after the start) from the start of pre-melt (start of EB irradiation), then maintained at 4.0kW for 20 seconds (from 20 seconds to 40 seconds after the start), then linearly increased from 4.0kW to 4.5kW over 5 seconds (from 40 seconds to 45 seconds after the start), then maintained at 4.5kW for 20 seconds (from 45 seconds to 65 seconds after the start), then linearly increased from 4.5kW to 5.0kW over 2 seconds (from 65 seconds to 67 seconds after the start), and then maintained at 5.0kW for 20 seconds (from 67 seconds to 87 seconds after the start) to end the pre-melt. Next, the SiO2 granules packed inside the copper liner were heated and sublimated using an electron gun, and a low refractive index SiO2 layer was deposited by electron beam evaporation. During the deposition process, oxygen gas was supplied as the reaction gas at a total pressure of 1.3 × 10⁻⁶. -2 The electron beam was introduced to achieve a Pa (power), and the film deposition target (lens molded product + undercoat layer + TiO2 layer) was carried out without any special heating. Furthermore, electron beam heating of the SiO2 deposition material was started with the shutter closed, and after pre-melting of the deposition material, the shutter was opened and film deposition was performed. In this process, pre-melting was carried out using a program that matched the EB output and time, so that the total EB energy (output watts × time) was 22 kJ. The above-described process of depositing TiO2 and SiO2 layers was repeated alternately three times to deposit an anti-reflective layer with the structure shown in Table 1, thereby obtaining a plastic lens. Note that pre-melting of the deposition material to be used for the subsequent SiO2 layer deposit was not performed before or during the deposit of the TiO2 layer, and similarly, pre-melting of the deposition material to be used for the subsequent TiO2 layer deposit was not performed before or during the deposit of the SiO2 layer.

[0095] [Example 2] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated using thermoplastic acrylic resin B instead of thermoplastic acrylic resin A as the thermoplastic acrylic resin, and otherwise in the same manner as in Example 1.

[0096] [Example 3] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated using thermoplastic acrylic resin C instead of thermoplastic acrylic resin A as the thermoplastic acrylic resin, and otherwise in the same manner as in Example 1.

[0097] [Example 4] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated using thermoplastic acrylic resin D instead of thermoplastic acrylic resin A as the thermoplastic acrylic resin, and otherwise in the same manner as in Example 1.

[0098] [Example 5] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that the undercoat layer was deposited to a thickness of 450 nm.

[0099] [Example 6] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that the undercoat layer was deposited to a thickness of 610 nm.

[0100] [Example 7] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that the undercoat layer was deposited to a thickness of 900 nm.

[0101] [Example 8] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that an undercoat layer was deposited to a thickness of 100 nm, and an electron gun with a backscattered electron trap was used as the electron gun for heating the deposition material.

[0102] [Example 9] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that an undercoat layer was deposited to a thickness of 100 nm, a premelt of Ti3O5 granules was carried out to a total EB energy (output watts × time) of 640 kJ, and an electron gun equipped with a backscattered electron trap was used as the electron gun for heating the deposition material. The pre-melt process described above was carried out according to the program shown in Figure 4(b). Specifically, the EB output was linearly increased from 0kW to 3.5kW over 15 seconds (until 15 seconds after the start) from the start of pre-melt (start of EB irradiation), then maintained at 3.5kW for 5 seconds (from 15 seconds to 20 seconds after the start), then linearly increased from 3.5kW to 7.0kW over 5 seconds (from 20 seconds to 25 seconds after the start), then maintained at 7.0kW for 15 seconds (from 25 seconds to 40 seconds after the start), then linearly decreased from 7.0kW to 6.1kW over 15 seconds (from 40 seconds to 55 seconds after the start), and then maintained at 6.1kW for 60 seconds (from 55 seconds to 115 seconds after the start) to terminate the pre-melt process.

[0103] [Example 10] A plastic lens with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that the premelting of Ti3O5 granules was carried out so that the total EB energy (output watts × time) was 640 kJ, and an electron gun equipped with a backscattered electron trap was used as the electron gun for heating the deposition material. The pre-melt process described above was carried out according to the program shown in Figure 4(b). Specifically, the EB output was linearly increased from 0kW to 3.5kW over 15 seconds (until 15 seconds after the start) from the start of pre-melt (start of EB irradiation), then maintained at 3.5kW for 5 seconds (from 15 seconds to 20 seconds after the start), then linearly increased from 3.5kW to 7.0kW over 5 seconds (from 20 seconds to 25 seconds after the start), then maintained at 7.0kW for 15 seconds (from 25 seconds to 40 seconds after the start), then linearly decreased from 7.0kW to 6.1kW over 15 seconds (from 40 seconds to 55 seconds after the start), and then maintained at 6.1kW for 60 seconds (from 55 seconds to 115 seconds after the start) to terminate the pre-melt process.

[0104] [Example 11] During the deposition of the undercoat layer, oxygen gas is supplied at a total pressure of 8.0 × 10⁻⁶ -3 Aside from introducing Pa, a plastic lens with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1.

[0105] [Example 12] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that a partial reflective layer was deposited as the optical functional layer.

[0106] [Comparative Example 1] During the deposition of the undercoat layer, oxygen gas is supplied at a total pressure of 3.5 × 10⁻⁶. -2 Aside from introducing Pa, a plastic lens with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1.

[0107] [Comparative Example 2] A plastic lens with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that Ti3O5 granules were pre-melted with the substrate placed in the dome before the undercoat layer was deposited.

[0108] [Comparative Example 3] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that the undercoat layer was deposited to a thickness of 100 nm.

[0109] [Comparative Example 4] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that the undercoat layer was deposited to a thickness of 20 nm.

[0110] [Comparative Example 5] A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that an undercoat layer was deposited to a thickness of 20 nm, and an electron gun with a backscattered electron trap was used as the electron gun for heating the deposition material.

[0111] [Comparative Example 6] During the deposition of the undercoat layer, oxygen gas is supplied at a total pressure of 3.5 × 10⁻⁶. -2 A plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1, except that the material was introduced to achieve Pa and a partial reflective layer was deposited as an optical functional layer.

[0112] [Comparative Example 7] A thermoplastic acrylic resin with low heat resistance is used instead of thermoplastic acrylic resin A. Using resin (Asahi Kasei Corporation, Delpet 80N, Vicat softening temperature 109°C), a plastic lens equipped with an undercoat layer and an optical functional layer was fabricated in the same manner as in Example 1.

[0113] The measurement and evaluation methods for the plastic lenses prepared in the examples and comparative examples are as follows.

[0114] (Durability evaluation) (1) Initial adhesion To evaluate the coating adhesion of the plastic lenses obtained in the examples and comparative examples, a cross-cut test was performed in accordance with JIS K 5600-5-6. Twenty-five 1mm x 1mm grids were created on the flat side of the plastic lens using a multi-blade cutting tool. Cellophane tape (LP-24, manufactured by Nichiban Co., Ltd.) was applied to the grid, and after quickly peeling off the tape, the surface condition of the cross-cut area was observed to see if delamination of the film (undercoat layer and optical functional layer) had occurred. The results were classified as follows, with classification 0 or 1 being A (good), classification 2 being B (usable), and classifications 3 to 5 being C (poor). (classification) 0: The edges of the cuts are perfectly smooth, and there is no peeling in any of the squares. 1: There is minute peeling of the film at the intersection of the cuts. The percentage of peeling at the cross-cut area does not clearly exceed 5% of the total area of ​​the cross-cut section, which is considered 100%. 2: There is small peeling of the film along the edges of the cuts and / or at the intersections. The percentage of peeling in the cross-cut area is clearly more than 5% of the total area of ​​the cross-cut area, but does not exceed 15%. 3: The film is partially or completely peeling along the edges of the cuts, and / or partially or completely peeling in several grid areas. The percentage of peeling in the cross-cut area is clearly more than 15% of the total cross-cut area (100%) but not more than 35%. 4: The film is partially or entirely peeling along the edges of the cuts, and / or partially or entirely peeling in several grid areas. The percentage of peeling in the cross-cut area is clearly more than 35% of the total cross-cut area (100%) but not more than 65%. 5: Any of the following types of peeling that cannot be classified as Category 4.

[0115] (2) Moist heat test A moist heat test was conducted using the plastic lenses obtained in the examples and comparative examples. The plastic lenses were placed in a constant temperature and humidity chamber (PL-4KP, manufactured by ESPEC Corporation) set to 85°C and 85%RH and maintained in this environment for 200 hours. After that, the plastic lenses were removed from the constant temperature and humidity chamber and maintained in a constant temperature room at 23°C and 50%RH for 24 hours. (2-1) Changes in appearance after the moist heat test After the moist heat test, the surface of the plastic lenses was visually inspected to determine whether or not cracks had formed. (2-2) Adhesion after moist heat test After the humid heat test was completed, the adhesion of the film (undercoat layer and optical functional layer) was evaluated on the plastic lens using the same evaluation method as for the initial adhesion in (1).

[0116] The results of each measurement and evaluation are shown in Table 1.

[0117] [Table 1] [Industrial applicability]

[0118] The plastic lenses of the present invention offer excellent productivity and extremely good durability. Therefore, the plastic lenses of the present invention can be suitably used in applications such as lenses for household goods, office automation equipment, AV equipment, battery and electrical components, lighting equipment, and automotive parts. Lenses used in household goods, office automation equipment, AV equipment, battery and electrical components, lighting equipment, etc. include, for example, lenses for smartphone cameras and tablet PC cameras, lenses used in bent optical system telephoto cameras (periscope cameras); lenses used in VR (virtual reality) / AR (augmented reality) / MR (mixed reality) / SR (substitutional reality) / DR (degraded reality) / XR (cross-reality) head-mounted displays, liquid crystal projectors, near-infrared sensors (LiDAR), etc., in particular small, thin-walled, variable-thickness optical lenses; lenses for optical communication; and phase plates equipped with lenses, Fresnel lenses, and microlens arrays. Examples of lenses used in automotive parts include lenses used in head-up displays and lenses for in-vehicle cameras (especially front element lenses). Other examples include lenses used in aerial displays, such as base materials for retroreflective sheets and partially transparent mirrors, microlens arrays for constructing two-sided corner reflector arrays, and lenses for magnifying, reducing, or correcting image planes and aberrations. [Explanation of symbols]

[0119] P Plastic Lens P1 Lens Body P2 Undercoat Layer P3 optical functional layer Sa, Sb side Z optical axis 11 Vapor deposition equipment 12 chambers 13 Resistance heating power supply 14. Evaporated dome 15 Boats 16 shutters 17. Vapor deposition materials 18 Substrates to be coated 19 Thin film 20 Vapor deposition equipment 21 Chambers 22. Electronic gun 23 Electron gun power supply 24 Evaporated domes 25 crucible 26 pole pieces 27 Shutter 28 Reflected electron trap 29. Vapor deposition materials 30 Substrates to be coated 31 Thin film 32 Electron beam 33 Backscattered electron

Claims

1. A method for manufacturing a plastic lens, which includes a forming step of forming an undercoat layer and an optical functional layer in that order on at least one surface of a resin lens body, The optical functional layer is an anti-reflective layer or a partial reflective layer. The lens body is made of a thermoplastic acrylic resin having a glass transition temperature of 116°C or higher. The undercoat layer is formed by a resistance heating type vacuum deposition method, and SiO is used as the deposition material for the undercoat layer. ２ Control the gas flow to 3.0 × 10 －２ Formed at a pressure of less than Pa, The optical functional layer is formed by an electron beam heated vacuum deposition method, and the pre-melting of the deposition material for the optical functional layer is performed for the first time after the formation of the undercoat layer. In the manufacture of the aforementioned plastic lens, the premelting of the molten material among the deposition materials for the optical functional layer is carried out so that the total EB energy (output watts × time) is less than 1500 kJ. The thickness of the undercoat layer is 200 nm or more and less than 1000 nm. A method for manufacturing plastic lenses, characterized by the following features.

2. A method for manufacturing a plastic lens, comprising a forming step of forming an undercoat layer and an optical functional layer in that order on at least one surface of a resin lens body, The optical functional layer is an anti-reflective layer or a partial reflective layer. The lens body is made of a thermoplastic acrylic resin having a glass transition temperature of 116°C or higher. The undercoat layer is formed by a resistance heating type vacuum deposition method, using SiO as the deposition material for the undercoat layer, and is formed at a pressure of less than 3.0 × 10⁻² Pa by controlling the amount of O₂ gas. The optical functional layer is formed by an electron beam heated vacuum deposition method, and the pre-melting of the deposition material for the optical functional layer is performed for the first time after the formation of the undercoat layer. In the manufacture of the aforementioned plastic lens, the premelting of the molten material among the deposition materials for the optical functional layer is carried out so that the total EB energy (output watts × time) is less than 1500 kJ. The thickness of the undercoat layer is 80 nm or more and less than 1000 nm. In the manufacture of the aforementioned plastic lens, a backscattered electron trap is attached to the electron gun used. A method for manufacturing plastic lenses, characterized by the following features.

3. The method for manufacturing a plastic lens according to claim 1 or 2, characterized in that, during the deposition of the optical functional layer, the amount of oxygen introduced is controlled so that the pressure is 1.0 × 10⁻³ Pa or more and 5.0 × 10⁻² Pa or less.

4. The optical functional layer includes a TiO2 layer, One of the TiO2 layers is formed adjacent to the undercoat layer. A method for manufacturing a plastic lens according to claim 1 or 2, characterized in that

5. The thickness of the undercoat layer is 800 nm or less, The pressure used in forming the undercoat is 8.0 × 10⁻³ Pa or higher. The ratio of the total EB energy to the thickness of the undercoat layer [kJ / nm] is 3.4 kJ / nm or less. A method for manufacturing a plastic lens according to claim 1 or 2, characterized in that

6. The method for manufacturing a plastic lens according to claim 1 or 2, characterized in that the pre-melt step is performed with the shutter closed until the melting and evaporation of the deposition material stabilizes, and thereafter the shutter is opened and the process moves to the deposition step.

Images