Optical elements

Abstract

To provide an optical element equipped with a water-repellent and antifouling treatment film that provides water-repellent and oil-repellent properties equivalent to those of silane compounds that fall under the category of per- and polyfluoro compounds (PFAS), without using silane compounds that fall under the category of PFAS. [Solution] The optical element has a silica-based surface 16 on the outermost surface of the substrate 10, and a water-repellent treated film 18 is formed on the silica-based surface, on which water-repellent organic chains are bonded via siloxane bonds (dehydration condensation bonds). The water-repellent organic chains mainly consist of PDMS without PFAS with a degree of polymerization of 10 to 100, and the end of the PDMS chain opposite the bonded side on the silica-based surface 16 is a free end. The surface characteristics of the water-repellent treated film 18 are set to have a contact angle (against pure water) of 100° or more and a dynamic friction coefficient (against SUS spheres) of 0.2 or less.

Description

[Technical Field]

[0001] The present invention relates to an optical element in which the outermost surface of the substrate is a silica-based surface, and a water-repellent and stain-resistant film is formed on the silica-based surface by bonding water-repellent and stain-resistant organic chains via siloxane bonds (dehydration condensation bonds). Optical elements to which the present invention can be applied include optical lenses such as eyeglass lenses and camera lenses, as well as front glass or front filters for various displays, and optical prisms. Furthermore, the meanings of each abbreviation and term are as follows: PFAS: A general term for perfluoroalkyl compounds and polyfluoroalkyl compounds among organofluorine compounds. PVD stands for "Physical Vapor Deposition," a film deposition method known as physical vapor deposition, including vacuum deposition, sputtering, and ion plating. PET: Polyethylene terephthalate PDMS: Polydimethylsiloxane Dry treatment method: A method in which a water-repellent agent diluted to a predetermined concentration is attached to a fibrous metal mass, and the object to be treated is heated in a vacuum chamber to form a film (see Patent Document 2, paragraphs 0036-0038). Wet treatment method: A method in which the object to be treated is immersed in a water-repellent immersion tank, pulled out at a predetermined speed, and then left for a predetermined time under humid conditions to form a film (see paragraphs 0039-0042). Water-repellent and stain-resistant film: This refers to a thin film (on the order of nanometers) at the molecular level that imparts water repellency, etc., without affecting most of the surface properties of the treated surface. It is fundamentally different from the thickness of a coating film (1-30 μm) that hides most of the surface properties of the substrate. Silanol-modified silane: A modified silane in which a silane is substituted with a silanol group (including those in which the hydroxyl group is protected by an alkyl group). [Background technology]

[0002] In the case of optical components (optical elements) such as eyeglasses and photographic lenses, if water droplets, dirt, or scratches adhere to them, the image is distorted and becomes difficult to see. Therefore, it is necessary to make them resistant to water droplet adhesion, resistant to dirt, or easy to wipe clean, and thus water-repellent and stain-resistant (resistant to oil-based markers) properties are required, along with good slipperiness (low coefficient of dynamic friction). The cause of water droplet adhesion is that dirt such as fingerprints and dust adheres to the hydrophilic metal oxide / halide layer (hereinafter referred to as the "metal oxide layer") on the surface of hydrophilic inorganic glass substrates or organic glass substrates, which is used to reduce or increase reflectivity, or that fine scratches occur, resulting in an uneven hydrophilic surface.

[0003] The aforementioned metal oxide layer is typically formed by vacuum deposition, a type of PVD. The surface of the metal oxide layer has fine irregularities. As a result, dirt and other contaminants adhere more easily, and these contaminants are difficult to remove once they have adhered. Furthermore, fine scratches are more likely to occur, and the tendency for water droplets to adhere increases. To solve these problems, it is conceivable to form a water-repellent and antifouling film with good water-repellent and antifouling properties as well as slipperiness on the outermost layer of a metal oxide layer such as an SiO2 layer.

[0004] Prior art documents relating to optical components (optical elements) having a water-repellent and antifouling film applied to the outermost layer of such a metal oxide layer include Patent Document 1 (see paragraphs 0004-0009) and Patent Document 2, among others. All of these documents used terminal silanol-modified silane compounds having fluorine-based organic chains such as perfluoroalkyl groups corresponding to PFAS as the water-repellent agent, diluted with a fluorine-based solvent (corresponding to PFAS), and performed water-repellent treatment by a dry or wet treatment method. PFAS are becoming subject to international regulations. Therefore, there is a demand for the development of a simple technology (water-repellent treatment method) that can form a water-repellent and antifouling film using PFAS-free silane compounds, possessing high levels of water repellency and slipperiness (low coefficient of friction) equivalent to that of PFAS-compliant fluorine-based silane compounds. Furthermore, Table 2 of Patent Document 2 describes Comparative Examples 1, 3, 5, and 7, which use silane compounds that are PDMS having silanol groups at both ends as a water-repellent treatment agent. These silane compounds have a molecular weight of 26,000 and are different from the PDMS-based silane compounds used in the present invention, which have a silanol group at one end and a degree of polymerization of PDMS chain of 100 or less (molecular weight approximately 10,000).

[0005] I am unaware of any prior technical documents relating to this simple technique. Furthermore, Patent Document 3 describes a water-repellent composition containing an anion-modified silicone chain corresponding to PFAS. This document suggests that "Comparative Example 1-2," in which a water-repellent coating film was formed on PET using "KP-983" (a water-repellent product name manufactured by Shin-Etsu Chemical Co., Ltd.), which is one of the silane compounds used in the present invention, does not easily yield results equivalent to the examples or "Comparative Example 1-3" using silane compounds corresponding to PFAS, at least in terms of water repellency. In other words, from the above, it can be seen that it is common knowledge in the art to use fluorine-based silane compounds as silane compounds to obtain a high degree of water repellency, stain resistance, slipperiness, and scratch resistance on the substrate surface. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2005-187936 [Patent Document 2] Japanese Patent Publication No. 2017-111413 [Patent Document 3] Japanese Patent Publication No. 2020-203990 [Overview of the project] [Problems that the invention aims to solve]

[0007] In view of the above, the present invention aims to provide an optical element equipped with a water-repellent and antifouling film that can be easily obtained using a PFAS-non-compliant silane compound, while also providing slipperiness and scratch resistance equivalent to that of a PFAS-compliant silane compound. [Means for solving the problem]

[0008] The inventors, in order to solve the above problems, made diligent efforts in development and found that the above problems can be solved when a water-repellent and antifouling film is formed using a reactive silane compound (trihydroxysilane precursor) which has a silanol group at only one end of PDMS with a predetermined degree of polymerization, among countless silanol-modified silane compounds equipped with silicone chains. Based on this, they came up with the optical element of the present invention with the following configuration (indicated by the figure).

[0009] The outermost surface of the substrate 10 is a silica-based surface 16, and a water-repellent and antifouling film is formed on this silica-based surface by a silane compound having a water-repellent and antifouling organic chain and a reactive silyl group at only one end. The silane compound is not PFAS, the water-repellent and antifouling organic chain is mainly PDMS without PFAS with a degree of polymerization of 10 to 100, and the reactive silyl group is trialkoxysilyl. The surface properties of the water-repellent and antifouling film 18 are such that the contact angle (against pure water) is 100° (preferably 103°) or more, and the coefficient of dynamic friction (against SUS spheres) is 0.2 or less (preferably 0.15 or less).

[0010] The optical elements of the above configuration can be obtained by a water-repellent treatment method in which a water-repellent and antifouling film is formed using a water-repellent agent mainly containing silanol-modified PDMS (excluding PFAS-eligible substances) selected from one or more of those shown in the following structural formula (1). Formula (1) R 1 (Si(CH3)2)-(OSi(CH3)2) n -AS i (OCH3)3 Here, R 1: An alkyl group having 1 to 10 carbon atoms (preferably 1 to 6), n: 10 to 100 (preferably 20 to 80, more preferably 30 to 70), A: either oxygen or an alkylene group having 1 to 10 carbon atoms (preferably 1 to 6), or phenylene.

[0011] Here, by making the reactive silyl group a single-terminal type, the water-repellent and antifouling chain is more likely to migrate and float on the surface side, increasing the contribution to the water-repellent and antifouling action of PDMS. Further, by using trimethoxysilyl, it can be expected that the film bonding strength will further increase with the increase in reactivity. Also, by setting the siloxane polymerization degree (n) of PDMS within a predetermined range, water repellency, antifouling properties, as well as slipperiness and scratch resistance equivalent to those of a fluorine-based water repellent corresponding to PFAS can be achieved. If the polymerization degree (n) of PDMS is too low, it becomes difficult to obtain the water-repellent and antifouling action of PDMS, and the hydroxy groups generated by hydrolysis are mutually etherified, making it difficult for the methoxy groups to contribute to the bonding with the silica surface, and it is estimated that the scratch resistance will decrease. Conversely, if the polymerization degree (n) is too high, it is difficult to uniformly disperse the treatment agent, the preparation of the treatment agent is troublesome, and it is difficult to ensure the leveling of the treatment film, which may have an adverse effect on the scratch resistance and the like. When the reactive silyl group of PDMS is a two-terminal type, compared with the single-terminal type, the PDMS chain is less likely to migrate to the surface side, and it is difficult to improve the slipperiness and further the scratch resistance (see Comparative Example 2 described later).

[0012] Note that R 1 and A are preferably shorter from the perspective of increasing the hardness (scratch resistance), but are appropriately adjusted from the perspective of compatibility with the diluting solvent. If the carbon number of R 1 and A is too large, the ratio of PDMS will relatively decrease, which may reduce the scratch resistance, water repellency, and oil repellency.

[0013] When PDMS has a polymerization degree of a predetermined value or more, it becomes easier to ensure a predetermined strength together with the water repellency and slipperiness of the dense film of PDMS chains.

[0014] The film thickness of the water and oil repellent film varies slightly depending on the type of water repellent and the film forming method, but is usually 2 to 30 nm, preferably 5 to 25 nm, and more preferably 5 to 20 nm. If the film thickness of the water and oil repellent film is less than a predetermined value, improvement in slipperiness cannot be expected along with water and oil repellent performance, and problems are likely to occur in scratch resistance and chemical resistance. Further, if it exceeds the predetermined value, a decrease in transmittance due to surface light scattering of the water and oil repellent film is likely to occur.

[0015] When the substrate treatment surface is an optical inorganic thin film having an outermost layer SiO2 layer, it is desirable that the water and oil repellent film be formed by a dry processing method using the same chamber.

[0016] In addition, it is desirable that the optical element of the present invention be a spectacle lens that is used without any skin contact in places where people touch, regardless of indoors or outdoors.

[0017] Furthermore, in the present invention, the spectacle lens can also be subjected to a water and oil repellent treatment by a wet processing method, and further, by using a cloth soaked in a chemical. A special vacuum apparatus is not required, and it is suitable for large (large area) substrates and those having a complicated shape in the atmosphere.

Brief Description of the Drawings

[0018] [Figure 1] It is a model cross-sectional view showing a spectacle lens which is an example of an optical element to which the present invention is applicable. [Figure 2] Double logarithmic graph showing the relationship between the molecular weight, degree of polymerization and viscosity of PDMS (Shin-Etsu Silicone "Silicone Oil KF96" technical data, "Fig. 1 Relationship between kinematic viscosity, molecular weight and degree of polymerization of KF-96")

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described by taking a spectacle lens as shown in Fig. 1 as an example.

[0020] The inorganic and organic glass mentioned above are not particularly limited in terms of material, and various general-purpose materials can be used. For example, they are exemplified in Patent Document 2, paragraphs 0024-0025.

[0021] Furthermore, to improve scratch resistance (especially in the case of organic glass substrates), a hard coat 14 is usually formed, and when forming the hard coat 14, a primer coat 12 is interposed between it and the lens body 10 to enhance impact resistance.

[0022] For the hard coat 14, conventional silicone-based or acrylic-based materials are suitable, and for the primer coat 12, primers based on urethane-based (TPU) or ester-based (TPEE) thermoplastic elastomers (TPE) are suitably used (see Patent Document 2, paragraphs 0026-0027, etc.).

[0023] Then, on the hard coat 14, an optical inorganic thin film (anti-reflective film or mirror coating) 16, which is usually the outermost SiO2 layer, is formed. Note that if the lens body is made of inorganic glass, the optical inorganic thin film (anti-reflective film or mirror coating) is formed directly on the inorganic glass.

[0024] In this invention, a water-repellent and antifouling film with the following configuration is formed on the inorganic glass substrate or optical inorganic thin film, i.e., on a silica-based surface.

[0025] The water-repellent and stain-resistant film 18 of the present invention has a silane compound having a highly substituted hydrolyzable silyl group at one end of a PDMS (silicone chain) with a degree of polymerization n=10 to 100 as its film component (main agent), and exhibits properties of a contact angle (against pure water) of 100° (preferably 103°) or more, and a dynamic friction coefficient (against SUS spheres) of 0.20 (preferably 0.15) or less.

[0026] The water-repellent and stain-resistant film with the above configuration uses a silane compound having a trimethoxysilyl group at one end of a PDMS (polydimethylsilicone) of a predetermined degree of polymerization. Specifically, examples include "FM-0815J" from JNC Corporation, and "KP-983" and "X-22-1968" from Shin-Etsu Chemical Co., Ltd. (See Table 2: all are product model numbers). The viscosity values ​​in Table 2 are taken from the Safety Data Sheets (SDS) issued by each manufacturer. All of these silane compounds use PDMS as the silicone chain, which is the water-repellent and stain-resistant organic chain, and trimethoxysilyl as the hydrolyzable silyl group. These silane compounds can be used after being diluted to an appropriate concentration (e.g., 3%) with various solvents (e.g., propylene glycol monomethyl ether).

[0027] Furthermore, the method for forming the water-repellent and stain-resistant film may be either a dry treatment method (a) or a wet treatment method (b). [Examples]

[0028] The following describes examples, comparative examples, and reference examples used to confirm the effects of the present invention.

[0029] Except for the water-repellent treatment, each test specimen was prepared according to the procedure described in paragraphs 0046 to 0066 of Patent Document 2. Hereafter, "paragraphs..." refer to those in Patent Document 2 unless otherwise specified.

[0030] Specifically, using "MR95" (refractive index: 1.60) as the substrate described in paragraph 0048, the primer coat composition was prepared in the same manner as "Primer Coat Composition 1" described in paragraph 0050, and the hard coat composition was prepared in the same manner as "Hard Coat Composition" described in paragraphs 0054 and 0055. Then, using each composition, the primer coat 12 and hard coat 14 were sequentially formed on the substrate 10 using the same wet process as described in paragraph 0052. Furthermore, an optical inorganic thin film, an anti-reflective film 16 having the same outermost SiO2 layer structure, was formed on the hard coat 14 in the same manner as described in paragraph 0060.

[0031] (1) Using the treated test material prepared above, test specimens for each physical property test were prepared as follows. <1> Preparation of water-repellent treatment agent Each of the water-repellent treatment agents in Examples 1, 2, and 3 and Reference Example 1 was prepared using the silane compounds (water-repellent treatment agents) shown in Table 1, as described below. Examples 1, 2, and 3, Reference Example 1: Each silicone-based coating agent shown in Table 1 was diluted with propylene glycol monomethyl ether to prepare a compound with a solid content of 3%. 1.0 g of this compound was placed in a container made of open-topped cylindrical copper (capacity: inner diameter 16 mm x inner height 6 mm) filled with 0.5 g of steel wool (manufactured by Nippon Steel Wool Co., Ltd., #0, 0.025 mm), and then dried at 120°C for 1 hour.

[0033] <2> Film formation (dry process) The containers filled with the chemicals prepared in each example and reference example above were placed in a vacuum evaporator, and after creating a vacuum of 0.01 Pa, the chemicals were evaporated at a film formation rate of 0.6 Å / s using a molybdenum resistance heating boat as a heat source to form a 0.005 μm water-repellent and antifouling film on the surface of each element to be treated.

[0034] (2) Using the physical property test specimens prepared above, the following physical property tests were performed. <Test Items>

[0035] <1> Water repellency test (contact angle with pure water) The contact angle was measured using a contact angle meter (CA-D model, manufactured by Kyowa Interface Science Co., Ltd.) in accordance with the static droplet method of JIS R 3257.

[0036] <2> Stain-resistant (oil-resistant marker) A 1 cm long line was drawn on the surface of the test piece using a commercially available oil-based marker (Magic Ink® No. 500, manufactured by Teranishi Chemical Industry Co., Ltd.), and the test result was determined by whether or not the line could be wiped off after rubbing it back and forth five times with a handkerchief. ○: Can be wiped off completely △: Some residue remains ×: Spreads without being wiped off

[0037] <3> coefficient of kinetic friction Using the automatic friction and wear analysis device TSf-300 manufactured by Kyowa Interface Science Co., Ltd., measurements were taken with a contactor of SUS ball, a load of 100 g, a moving speed of 10 mm / s, and a moving distance of 30 mm.

[0038] <4>Scratch resistance <Test item> (12) JP 2017-111413 A 2017.6.22 <1> Scratch resistance test A load of 1000 g was applied to steel wool (#0000), and the surface of the anti-reflection film of each test piece was rubbed at 50 times / 50 seconds, and the degree of scratching was judged by visual inspection using reflected light from a fluorescent lamp and transmitted light. ○: The scratched area is within 10% △: The scratched area exceeds 10% and is within 30% ×: The scratched area exceeds 30%

[0039] <Confirmation of effect> The above test results are shown in Table 2. Comparative Examples 1 and 2 in Table 2 correspond to Comparative Examples 3 and 4 in Patent Document 2, and the results of the physical property tests were also cited from the same document (values are rounded off). Incidentally, at an intermediate polymerization degree n = 40 in Examples 1 and 2 described later, kinematic viscosity: 35 mm 2 / s, molecular weight: 3000, and although the kinematic viscosity is slightly higher, the molecular weight is approximately the same. This indicates that when a trimethoxysilyl group is introduced into the PDMS chain, it is estimated that the kinematic viscosity has decreased relatively. Assuming a kinematic viscosity higher than 60 mm 2 / s, a kinematic viscosity of 70 mm 2 / s is assumed, the polymerization degree n ≒ 65 and the molecular weight: 5000 are estimated.

[0040] Each embodiment of the present invention possesses various practical properties equivalent to Comparative Example 1 (a silane-based water repellent corresponding to PFAS) using a fluorine-based water repellent, namely, water repellency, stain resistance, as well as a coefficient of dynamic friction (slipperiness) and scratch resistance. Furthermore, while each embodiment has a PDMS chain with a high degree of siloxane polymerization and both ends are modified with trimethoxysilyl, compared to Comparative Example 2, each embodiment is only slightly superior in water repellency, but is significantly superior in stain resistance, slipperiness (coefficient of dynamic friction), and scratch resistance. Moreover, it is clear that Reference Example 1, in which only one end of the long-chain alkyl chain is modified with trimethoxysilyl, does not easily achieve water repellency, oil repellency, or sufficient slipperiness. [Table 1] *1) nBuSi(CH3)2(OSi(CH3)2) n C2H4Si(OCH3)3, n≈37; "Saraiplane (registered trademark)" JNC catalog *2)(CH3)3Si(OSi(CH3)2) 43 OSi(OCH3)3; Quoted from Japanese Patent Publication No. 2023-111845

[0257] ~

[0258] *3) Trimethoxysilane containing PDMS; the structural formula of the present invention is within the range described in Japanese Patent Publication No. 2019-154413

[0017] ,

[0025] ,

[0075] and the hydrolysis product of SDS (methanol). The degree of polymerization and molecular weight are estimated from the viscosity of SDS using Figure 2. *4) Perfluoroether (Rf 2 ) Terminal trialkoxysilanes; see "Shin-Etsu Chemical New Business Division website, KY-100 series" and Japanese Patent Publication No. 2005-187936

[0035] ~

[0036] . [Table 2] [Explanation of symbols]

[0050] 10 Optical substrate (lens body) 12 Primer Coat 14 Hard Court 16. Optical inorganic thin films (anti-reflective coatings or mirror coatings) 18 Water-repellent and stain-resistant coating

Claims

1. The outermost surface of the substrate is a silica-based surface, and the silica-based surface has a water-repellent and antifouling film formed on it with a silane compound having a water-repellent and antifouling organic chain and a reactive silyl group at only one end, The silane compound is not a perfluoroelastomer, the water-repellent and antifouling organic chain is mainly composed of polydimethylsiloxane with a degree of polymerization of 10 to 100, and the reactive silyl group is a highly substituted alkoxysilyl group. The water-repellent and stain-resistant film has a contact angle (against pure water) of 100° or more, and a coefficient of dynamic friction (against a SUS sphere) of 0.2 or less. An optical element characterized by the following features.

2. The optical element according to claim 1, characterized in that one or more liquid silane compounds are selected from those represented by the following structural formula. Formula (1) R １ (Si(CH ３ ) ２ )-(OSi(CH ３ ) ２ ) ｎ -A-Si(OCH ３ ) ３ Here, R １ : an alkyl group having 1 to 10 carbon atoms, n: 10 to 100, A: either oxygen or an alkylene group having 1 to 10 carbon atoms, or phenylene.

3. The substrate surface to be treated is the outermost SiO ２ The optical element according to claim 1, characterized in that it is formed of an optical inorganic thin film which is a layer.

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