阅读说明：本技术 菲涅耳透镜及其制造方法 (Fresnel lens and method for manufacturing the same ) 是由 藤川武 福井贞之 于 2018-07-10 设计创作，主要内容包括：本发明提供山形形状的棱镜的间距窄、从棱镜的凸部至凹部的倾斜具有陡峭的形状的菲涅耳透镜、及该制造方法。本发明的菲涅耳透镜是相对于模具的接触角为50°以下的固化性组合物的模具成型固化物,该菲涅耳透镜以同心圆状具有2个以上棱镜,上述棱镜的截面是高度(h)与宽度(w)之比(h/w)为0.3以上、且上述高度(h)为0.5mm以下的山形形状。作为上述模具,优选为有机硅模具。另外,上述固化性组合物的固化物的断裂应变优选为0.1～30％。(The invention provides a Fresnel lens in which the pitch of a prism having a mountain shape is narrow and the inclination from the convex portion to the concave portion of the prism has a steep shape, and a method for manufacturing the Fresnel lens. The Fresnel lens of the present invention is a cured product of a mold-molded product of a curable composition having a contact angle of 50 DEG or less with respect to a mold, the Fresnel lens having 2 or more prisms concentrically arranged, the prisms having a cross section in a mountain-like shape in which the ratio (h/w) of the height (h) to the width (w) is 0.3 or more and the height (h) is 0.5mm or less. The mold is preferably a silicone mold. The cured product of the curable composition preferably has a strain at break of 0.1 to 30%.)

1. A Fresnel lens which is a cured product of a mold molding of a curable composition having a contact angle with respect to the mold of 50 DEG or less,

the Fresnel lens has 2 or more prisms in a concentric shape, and the prisms have a cross section in a mountain shape in which the ratio (h/w) of the height (h) to the width (w) is 0.3 or more and the height (h) is 0.5mm or less.

2. A Fresnel lens according to claim 1, wherein a cured product of the curable composition has a strain at break (according to JIS-K7162:1994) of 0.1 to 30%.

3. A method for producing a Fresnel lens by molding a curable composition using a mold and curing the composition,

wherein, the manufacturing method comprises the following steps:

a Fresnel lens is produced by using a curable composition having a contact angle of 50 DEG or less with respect to a mold,

fresnel lens: a Fresnel lens having at least 2 prisms in a concentric shape, wherein the prisms have a cross section in a mountain shape having a height (h) to width (w) ratio (h/w) of 0.3 or more and a height (h) of 0.5mm or less.

4. The method of manufacturing a Fresnel lens according to claim 3, wherein,

the mold is an organosilicon mold.

5. A method for manufacturing a Fresnel lens according to claim 3 or 4, wherein the curable composition is a cationically curable composition containing an epoxy resin as a curable compound.

6. The method for manufacturing a Fresnel lens according to any one of claims 3 to 5, wherein,

the molding is performed by a nanoimprint method.

7. The method for manufacturing a Fresnel lens according to claim 3 to 6, wherein,

the viscosity of the curable composition at 25 ℃ and at a shear rate of 20(1/s) is 0.01 to 10.0 pas.

8. The method for manufacturing a Fresnel lens according to any one of claims 3 to 7, wherein,

the cured product of the curable composition has a strain at break (based on JIS-K7162:1994) of 0.1 to 30%.

Technical Field

The present invention relates to a fresnel lens having excellent optical characteristics and a method for manufacturing the fresnel lens. The present application claims priority of Japanese patent application No. 2017-135254 filed in Japan on 11/7/2017, the contents of which are incorporated herein by reference.

Background

In a camera mounted on a portable electronic device such as a smartphone, a flash lens is provided immediately before a light source in order to diffuse light from the light source. Among them, as the flash lens, a fresnel lens that can be made thin and small is mainly used.

The fresnel lens is a lens having a reduced thickness by cutting a lens having a continuous spherical or aspherical lens surface into concentric circles or the like, and has a structure in which a prism having a mountain shape is formed in a step shape. Further, it is known that a fresnel lens can be made thinner and the light condensing property can be further improved by increasing the number of divisions of the lens surface (patent document 1).

As a method for producing a fresnel lens, for example, a method of injection molding using a thermoplastic resin such as polycarbonate, polymethyl methacrylate, and cycloolefin polymer is known (patent documents 2 and 3). However, in a fresnel lens having a large number of divided lens surfaces, in particular, the pitch of the ridge-shaped prisms becomes narrow, and the inclination from the convex portions to the concave portions of the prisms becomes steep, so that there is a problem that the thermoplastic resin having low flowability causes unfilled portions and bubbles, which lowers the shape accuracy and lowers the optical characteristics. Further, molded articles obtained from thermoplastic resins have low heat resistance and cannot be mounted on a board by reflow soldering at one time together with other components, and therefore, there is a problem in view of work efficiency.

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a fresnel lens in which the pitch of the ridge-shaped prisms is narrow and the inclination from the convex portions to the concave portions of the prisms is steep.

Another object of the present invention is to provide a fresnel lens having a narrow pitch of the ridge-shaped prisms, a steep inclination from the convex portions to the concave portions of the prisms, and excellent optical characteristics and heat resistance.

Another object of the present invention is to provide a method for accurately manufacturing a fresnel lens having a narrow pitch of a prism having a mountain shape and a steep inclination from a convex portion to a concave portion of the prism.

Another object of the present invention is to provide a method for accurately manufacturing a fresnel lens having a narrow pitch of prisms having a mountain shape, a steep inclination from a convex portion to a concave portion of the prism, and excellent optical characteristics and heat resistance.

Means for solving the problems

As a result of intensive studies to solve the above problems, the present inventors have found that when a fresnel lens having a narrow pitch of prisms in a mountain shape and a steep inclination from a convex portion to a concave portion of the prism is molded using a mold, it is difficult to fill a fine portion of the mold (for example, a portion forming a tip portion of the mountain shape) with a curable composition, and as a result, a fresnel lens having a portion (for example, a tip portion of the mountain shape) which is defective may be obtained. The present invention has been completed based on these findings.

Specifically, the present invention provides a fresnel lens which is a cured product of a mold-molded curable composition having a contact angle with respect to the mold of 50 ° or less, the fresnel lens having 2 or more prisms concentrically arranged, the prisms having a cross-section in a mountain-like shape in which the ratio (h/w) of the height (h) to the width (w) is 0.3 or more and the height (h) is 0.5mm or less.

The present invention also provides the Fresnel lens described above, wherein the cured product of the curable composition has a strain at break (according to JIS-K7162:1994) of 0.1 to 30%.

The present invention also provides a method for producing a fresnel lens by molding a curable composition using a mold and curing the molded composition, the method comprising: a Fresnel lens is produced by using a curable composition having a contact angle of 50 DEG or less with respect to a mold,

fresnel lens: the Fresnel lens has at least 2 concentric prisms, and the cross section of the prisms is a mountain-shaped Fresnel lens having a height (h) to width (w) ratio (h/w) of 0.3 or more and a height (h) of 0.5mm or less.

In addition, the present invention provides the above method for manufacturing a fresnel lens, wherein the mold is a silicone mold.

The present invention also provides the above method for producing a fresnel lens, wherein the curable composition is a cationically curable composition containing an epoxy resin as a curable compound.

In addition, the present invention provides the above method for producing a fresnel lens, wherein the molding is performed by a nanoimprint method.

The present invention also provides the above method for producing a Fresnel lens, wherein the viscosity of the curable composition at 25 ℃ and at a shear rate of 20(1/s) is 0.01 to 10.0Pa · s.

The present invention also provides the above method for producing a Fresnel lens, wherein the cured product of the curable composition has a strain at break (according to JIS-K7162:1994) of 0.1 to 30%.

ADVANTAGEOUS EFFECTS OF INVENTION

The fresnel lens of the present invention has 2 or more concentric prisms (prisms composed of an incident surface and a reflection surface) with a narrow pitch, a steep inclination from the convex portion to the concave portion, and no defective portion, and thus exhibits excellent optical characteristics. Therefore, the fresnel lens can be suitably used as a sensor for a mobile electronic device such as a mobile phone or a smart phone, or a fresnel lens for a camera.

Further, according to the method for manufacturing a fresnel lens of the present invention, it is possible to accurately manufacture a fresnel lens in which the pitch of the ridge-shaped prisms is narrow and the inclination from the convex portions to the concave portions of the prisms is steep.

In the method for producing a fresnel lens of the present invention, if a cationically curable composition containing an epoxy resin is used as the curable composition, a fresnel lens having excellent shape accuracy, exhibiting excellent optical characteristics, and having excellent heat resistance can be obtained. Therefore, the obtained fresnel lens can be mounted on a substrate by reflow soldering (particularly, lead-free soldering), and an optical device having the fresnel lens mounted thereon can be manufactured with excellent work efficiency. In addition, the resin composition can be used for electronic devices mounted on vehicles, which require heat resistance.

Drawings

Fig. 1 is a schematic view showing a fresnel lens obtained in the example (a plan view (1) and a sectional view (2) at a position a-a' of the plan view).

Description of the symbols

1 prism

2 incident plane

3 reflective surface

Detailed Description

[ Fresnel lens ]

The fresnel lens of the present invention is a mold-molded cured product (i.e., a cured product molded by a mold) of a curable composition having a contact angle with respect to the mold of 50 ° or less, and has 2 or more prisms (for example, annular prisms) concentrically arranged therein. The prism is characterized in that the cross section is a mountain shape having a height (h) to width (w) ratio (h/w) of 0.3 or more and a height (h) of 0.5mm or less.

The fresnel lens of the present invention may have at least a circular lens portion, and may have a cap edge portion around the lens portion. The lens part has 2 or more (for example, 2 to 100, preferably 5 to 100) prisms concentrically. In the section of the fresnel lens in the present invention (a section cut on a plane passing through the center point of the fresnel lens and perpendicular to the fresnel lens surface), the mountain-shaped section of the prism is arranged in an axisymmetric manner like a sawtooth.

The diameter of the lens part of the Fresnel lens is, for example, 1 to 100mm, preferably 1 to 50 mm.

The ratio (h/w) of the height (h) to the width (w) of the chevron shape is 0.3 or more, preferably 0.4 or more, and particularly preferably 0.5 or more. The upper limit of the ratio is, for example, 5, preferably 3.

The height (h) of the chevron shape is 0.5mm or less, preferably 0.4mm or less, and particularly preferably 0.3mm or less. The lower limit is, for example, about 0.05 mm.

Therefore, the width (w) of the chevron shape is, for example, 1.6mm or less, preferably 1.0mm or less, more preferably 0.8mm or less, and particularly preferably 0.6mm or less. The lower limit is, for example, about 0.05 mm.

The thickness (maximum thickness, h') of the thickest portion of the Fresnel lens is, for example, 0.1 to 3.0mm, preferably 0.1 to 1.5 mm.

From the viewpoint of excellent mold release properties, it is preferable that the strain at break (based on JIS-K7162:1994) of a cured product of the curable composition constituting the Fresnel lens of the present invention is, for example, 0.1 to 30%.

The cured product of the curable composition constituting the fresnel lens of the present invention is preferably excellent in transparency, and the light transmittance (wavelength of 450nm, thickness of cured product of 100 μm) is preferably 80% or more, more preferably 90% or more.

The cured product of the curable composition constituting the fresnel lens of the present invention is preferably excellent in heat resistance, and the glass transition temperature (Tg) thereof is preferably 100 ℃.

The fresnel lens of the present invention has the above-described structure, and therefore has excellent optical characteristics, and is suitably used as, for example, a diffusion lens or an imaging lens. In addition, the lens is suitably used as a lens for a sensor and a lens for a camera of a mobile electronic device represented by a mobile phone and a smart phone.

[ method for producing Fresnel lens ]

The method for producing a fresnel lens of the present invention is a method for producing a fresnel lens by molding a curable composition using a mold and curing the molded composition, and is characterized in that the above fresnel lens is produced using a curable composition having a contact angle of 50 ° or less with respect to the mold.

(curable composition)

The contact angle of the curable composition of the present invention with respect to a mold is 50 ° or less, preferably 45 ° or less, particularly preferably 40 ° or less, most preferably 35 ° or less, and particularly preferably 30 ° or less. Therefore, the curable composition of the present invention has excellent wettability to a mold, can suppress the occurrence of dishing and air bubbles, and can be filled in a mold without leaving an unfilled portion. The contact angle (θ) of the curable composition can be determined by, for example, the θ/2 method.

The curable composition of the present invention is preferably low in viscosity, and has a viscosity at 25 ℃ and a shear rate of 20(1/s) of, for example, 0.01 to 10.0 pas, preferably 0.1 to 5.0 pas, and particularly preferably 0.1 to 1.0 pas, from the viewpoint of excellent mold filling properties and the ability to further reduce the generation of bubbles. The viscosity can be measured using a rheometer (trade name "PHYSICA UDS 200", manufactured by Anton Paar Co.).

The curable composition of the present invention is preferably a composition in which the strain at break of the cured product is, for example, 0.1% or more (preferably 0.3% or more, particularly preferably 0.5% or more). The upper limit of the strain at break is, for example, 30%, preferably 20%, particularly preferably 10%, most preferably 5%, and particularly preferably 3%. The strain at break can be measured by using a test piece 5B type based on JIS-K7162: 1994. When the strain at break of the cured product is in the above range, the fresnel lens can be prevented from exhibiting brittleness, and defects and cracks can be prevented from occurring at the time of releasing from a mold or the like. Namely, the releasability is excellent.

As described above, the curable composition of the present invention preferably has a low viscosity before heat treatment and/or ultraviolet irradiation, and can be rapidly cured by heat treatment and/or ultraviolet irradiation to form a cured product having excellent optical properties. Among them, the cationic curable composition is preferable in terms of excellent curability even in the presence of oxygen, and particularly, a composition containing an epoxy resin as a cationic curable compound is preferable in terms of obtaining a cured product having excellent optical characteristics (particularly transparency) and having high hardness and heat resistance. Further, a photocurable composition which cures by irradiation with ultraviolet rays is preferred.

As the epoxy resin, a known or conventional compound having 1 or more epoxy groups (epoxy rings) in the molecule can be used, and examples thereof include: alicyclic epoxy compounds, aromatic epoxy compounds, aliphatic epoxy compounds, and the like. Among them, in the present invention, a polyfunctional alicyclic epoxy compound having an alicyclic structure in 1 molecule and having 2 or more epoxy groups as functional groups is preferable in terms of forming a cured product excellent in heat resistance and transparency.

Specific examples of the polyfunctional alicyclic epoxy compound include:

(i) a compound having an epoxy group (i.e., alicyclic epoxy group) composed of adjacent 2 carbon atoms and an oxygen atom constituting an alicyclic ring;

(ii) a compound having an epoxy group directly bonded to an alicyclic ring by a single bond;

(iii) a compound having an alicyclic ring and a glycidyl group; and so on.

Examples of the compound having an alicyclic epoxy group (i) include compounds represented by the following formula (i).

[ chemical formula 1]

In the above formula (i), X represents a single bond or a linking group (a divalent group having 1 or more atoms). Examples of the linking group include: a divalent hydrocarbon group, an alkenylene group in which a part or all of the carbon-carbon double bonds have been epoxidized, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, a group in which a plurality of these groups are linked, and the like. In the formula (i), a substituent (e.g., an alkyl group) may be bonded to the epoxycyclohexyl group.

Examples of the divalent hydrocarbon group include a linear or branched alkylene group having 1 to 18 carbon atoms, a divalent alicyclic hydrocarbon group, and the like. Examples of the linear or branched alkylene group having 1 to 18 carbon atoms include: methylene, methyl methylene, dimethyl methylene, ethylene, propylene, trimethylene and the like. Examples of the divalent alicyclic hydrocarbon group include: cycloalkylene (including cycloalkylene) such as 1, 2-cyclopentylene, 1, 3-cyclopentylene, cyclopentylidene, 1, 2-cyclohexylene, 1, 3-cyclohexylene, 1, 4-cyclohexylene, cyclohexylidene and the like.

Examples of the alkenylene group in the above-mentioned alkenylene group in which a part or all of the carbon-carbon double bonds have been epoxidized (may be referred to as "epoxidized alkenylene group") include: and linear or branched alkenylene groups having 2 to 8 carbon atoms such as vinylene, propenylene, 1-butenylene, 2-butenylene, butadienylene, pentenylene, hexenylene, heptenylene, octenylene, and the like. In particular, the epoxidized alkenylene group is preferably an alkenylene group in which all carbon-carbon double bonds have been epoxidized, and more preferably an alkenylene group having 2 to 4 carbon atoms in which all carbon-carbon double bonds have been epoxidized.

As representative examples of the compound represented by the above formula (i), there can be mentioned: (3,4,3',4' -diepoxy) bicyclohexane, bis (3, 4-epoxycyclohexylmethyl) ether, 1, 2-epoxy-1, 2-bis (3, 4-epoxycyclohexan-1-yl) ethane, 2-bis (3, 4-epoxycyclohexan-1-yl) propane, 1, 2-bis (3, 4-epoxycyclohexan-1-yl) ethane, compounds represented by the following formulae (i-1) to (i-10), and the like. L in the formula (i-5) is an alkylene group having 1 to 8 carbon atoms, and among them, a linear or branched alkylene group having 1 to 3 carbon atoms such as a methylene group, an ethylene group, a propylene group, and an isopropylene group is preferable. N in the following formulae (i-5), (i-7), (i-9) and (i-10)¹～n⁸Each represents an integer of 1 to 30.

[ chemical formula 2]

[ chemical formula 3]

The compound (i) having an alicyclic epoxy group also includes epoxy-modified siloxane.

Examples of the epoxy-modified siloxane include chain-like or cyclic polyorganosiloxanes having a structural unit represented by the following formula (i').

[ chemical formula 4]

In the above formula (i'), R¹Represents a substituent containing an epoxy group represented by the following formula (1a) or (1b), R²Represents an alkyl group or an alkoxy group.

[ chemical formula 5]

R in the above formulae (1a) and (1b)^1a、R^1bThe same or different alkylene groups each represent a linear or branched alkylene group, and examples thereof include: a linear or branched alkylene group having 1 to 10 carbon atoms such as a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, or a decamethylene group.

The epoxy-modified silicone has an epoxy equivalent (based on JIS K7236) of, for example, 100 to 400, preferably 150 to 300.

As the epoxy-modified silicone, for example, a commercially available epoxy-modified cyclic polyorganosiloxane represented by the following formula (i' -1) (trade name "X-40-2670", manufactured by shin-Etsu chemical Co., Ltd.) can be used.

[ chemical formula 6]

Examples of the compound (ii) having an epoxy group directly bonded to the alicyclic ring by a single bond include compounds represented by the following formula (ii).

[ chemical formula 7]

In the formula (ii), R' represents a group (p-valent organic group) obtained by removing p hydroxyl groups (-OH) from the structural formula of p-polyol, p, n⁹Respectively, natural numbers. As p-polyol [ R' - (OH)_p]Examples thereof include polyhydric alcohols (e.g., alcohols having 1 to 15 carbon atoms) such as 2, 2-bis (hydroxymethyl) -1-butanol. p is preferably 1 to 6, n⁹Preferably 1 to 30. When p is 2 or more, n in the group in each square bracket (outer bracket)⁹May be the same or different. Specific examples of the compound represented by the formula (ii) include 1, 2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2, 2-bis (hydroxymethyl) -1-butanol [ for example, product name "EHPE 3150" (manufactured by Dacellosolve Co., Ltd.) ]]And the like.

Examples of the (iii) compound having an alicyclic group and a glycidyl group include: hydrogenated aromatic glycidyl ether epoxy compounds such as hydrogenated bisphenol a-type epoxy compounds, hydrogenated bisphenol F-type epoxy compounds, hydrogenated biphenol-type epoxy compounds, hydrogenated phenol novolac-type epoxy compounds, hydrogenated cresol novolac-type epoxy compounds of bisphenol a, hydrogenated naphthalene-type epoxy compounds, and hydrogenated epoxy compounds of epoxy compounds obtained from trisphenol methane.

The polyfunctional alicyclic epoxy compound is preferably (i) a compound having an alicyclic epoxy group, and particularly preferably a compound represented by the above formula (i) (particularly (3,4,3',4' -diepoxy) bicyclohexane), in view of obtaining a cured product having high surface hardness and excellent heat resistance and transparency.

The curable composition of the present invention may contain other cationic curable compounds in addition to the epoxy resin, for example, an oxetane compound, a vinyl ether compound, and the like as the cationic curable compound. The curable compound may contain a radical curable compound in addition to the cation curable compound.

The proportion of the epoxy resin in the total amount (100 wt%) of the curable compounds contained in the curable composition is, for example, preferably 50 wt% or more, more preferably 60 wt% or more, particularly preferably 70 wt% or more, and most preferably 80 wt% or more, from the viewpoint of obtaining a cured product having high surface hardness and excellent transparency. The upper limit is, for example, 100% by weight, preferably 90% by weight.

In addition, the proportion of the compound having an alicyclic epoxy group (i) in the total amount (100% by weight) of the curable compounds contained in the curable composition is, for example, preferably 20% by weight or more, more preferably 30% by weight or more, and particularly preferably 40% by weight or more, from the viewpoint of obtaining a cured product having high surface hardness and excellent transparency. The upper limit is, for example, 70% by weight, preferably 60% by weight.

In addition, the proportion of the compound represented by the formula (i) in the total amount (100% by weight) of the curable compounds contained in the curable composition is, for example, preferably 10% by weight or more, more preferably 15% by weight or more, and particularly preferably 20% by weight or more, from the viewpoint of obtaining a cured product having high surface hardness and excellent transparency. The upper limit is, for example, 50% by weight, preferably 40% by weight.

The curable composition preferably contains a polymerization initiator in addition to the curable compound. The polymerization initiator includes a photopolymerization initiator and a thermal polymerization initiator. In the present invention, among them, a photopolymerization initiator is preferably contained in order that a cured product can be formed more rapidly. Therefore, when the curable composition contains a cationic curable compound, a photo cationic polymerization initiator is preferably contained as a polymerization initiator.

The photo cation polymerization initiator is a compound that generates an acid by irradiation with light to initiate a curing reaction of a curable compound (particularly, a cation curable compound) contained in a curable composition, and includes a cation portion that absorbs light and an anion portion that serves as a generation source of the acid.

Examples of the photo cation polymerization initiator include: diazonium salt compound and iodine

Salt compounds, sulfonium salt compounds,

Salt compound, selenium salt compound, oxygenSalt compounds, ammonium salt compounds, bromine salt compounds, and the like.

Among them, in the present invention, a sulfonium salt compound is preferably used because it can form a cured product having excellent curability. Examples of the cation portion of the sulfonium salt compound include: aryl sulfonium ions (particularly triarylsulfonium ions) such as (4-hydroxyphenyl) methylbenzyl sulfonium ion, triphenyl sulfonium ion, diphenyl [4- (phenylthio) phenyl ] sulfonium ion, 4- (4-biphenylthio) phenyl-4-biphenylphenyl sulfonium ion, and tri-p-tolylsulfonium ion.

Examples of the anion portion of the photo cation polymerization initiator include: [ (Y)_sB(Phf)_4-s]- (wherein Y represents phenyl or biphenyl; Phf represents phenyl in which at least 1 hydrogen atom is substituted by at least 1 selected from perfluoroalkyl, perfluoroalkoxy, and halogen atoms; s is an integer of 0 to 3), BF₄-、[(Rf)_tPF_6-t]- (wherein Rf represents an alkyl group in which 80% or more of the hydrogen atoms are substituted with fluorine atoms, and t represents an integer of 0 to 5), and AsF₆-、SbF₆-、SbF₅OH-, etc.

As the photo cation polymerization initiator in the present invention, for example: (4-hydroxyphenyl) methylbenzylsulfonium tetrakis (pentafluorophenyl) borate, 4- (4-biphenylthio) phenyl-4-biphenylphenylsulfinatotetrakis (pentafluorophenyl) borate, 4- (phenylthio) phenyldiphenylsulfonium phenyltris (pentafluorophenyl) borate, [4- (4-biphenylthio) phenyl ] sulfonium]-4-biphenylphenylsulfonium phenyltris (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl]Sulfonium tris (pentafluoroethyl) trifluorophosphate, diphenyl [4- (phenylthio) phenyl]Sulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl]Sulfonium hexafluorophosphate, 4- (4-biphenylthio) phenyl-4-biphenylphenylsulfonium tris (pentafluoroethyl) trifluorophosphate, bis [4- (diphenylsulfonium) phenyl]Thioether phenyl tris (pentafluorophenyl) borate, [4- (2-thioxanthylthio) phenyl]Phenyl-2-thioxanthene-oxo-sulfonium phenyl-tris (pentafluorophenyl) borate, 4- (phenylthio) phenyl diphenylsulfonium hexafluoroantimonate, trade names "CYRACURE UVI-6970", "CYRACURE EUVI-6974", "CYRACURE UVI-6990", "CYRACURE UVI-950" (manufactured by U.S. Union Carbide), "Irgacure 250", "Irgacure 261", "Irgacure 264" (manufactured by BASF), "CG-24-61" (manufactured by Ciba-Geigy), "OPTOMER SP-150", "OPTOMER SP-151", "OPTOMER SP-170", "OPTOMER SP-171" (manufactured by ADEKA), "DAICAT II" (manufactured by DADACY CO., LTC), "UVAC 2620", "UVAC 1591" (manufactured by ICDADACY 1591), "ICDACECI-206CI-39", "TEC-2639" (manufactured by ICC., "CI-2481", "CI-2734", "CI-2855", "CI-2823", "CI-2758", "CIT-1682" (manufactured by Nippon Kazakh Co., Ltd.), "PI-2074" (manufactured by Rhodia, tetrakis (pentafluorophenyl) borate tolylisopropyl phenyl iodide)Salt), "FFC 509" (manufactured by 3M), "BBI-102", "BBI-101", "BBI-103", "MPI-103", "TPS-103", "MDS-103", "DTS-103", "NAT-103" and "NDS-103" (manufactured by Green chemical Co., Ltd., supra)"CD-1010", "CD-1011", "CD-1012" (manufactured by Sartomer America, supra), "CPI-100P" and "CPI-101A" (manufactured by San-Apro Corp., supra).

The content of the polymerization initiator is, for example, in the range of 0.1 to 5.0 parts by weight based on 100 parts by weight of the curable compound (particularly, the cationically curable compound) contained in the curable composition. When the content of the polymerization initiator is 0.1 parts by weight or more, excellent curability is exhibited, and the occurrence of curing failure can be suppressed. When the content of the polymerization initiator is 5.0 parts by weight or less, coloring of the cured product can be suppressed, and a cured product having excellent transparency can be formed.

The curable composition of the present invention can be produced by mixing the above curable compound, a polymerization initiator, and other components (for example, a solvent, an antioxidant, a surface conditioner, a photosensitizer, an antifoaming agent, a leveling agent, a coupling agent, a surfactant, a flame retardant, an ultraviolet absorber, a colorant, and the like) which are used as needed. The content of the other components is, for example, 20% by weight or less, preferably 10% by weight or less, and particularly preferably 5% by weight or less of the total amount of the curable composition.

As the curable composition in the present invention, commercially available products such as "CELVENUS OUH 106" (manufactured by Daiiluo Co., Ltd.) can be used.

(mold)

The mold used in the present invention is a mold having good wettability of the curable composition [ a mold having a contact angle of the curable composition of 50 ° or less (preferably 45 ° or less, particularly preferably 40 ° or less, most preferably 35 ° or less, particularly preferably 30 ° or less) ]. In the present invention, since the mold is used, the curable composition can be filled without generating a dent and leaving an unfilled portion.

The mold is preferably a silicone mold in view of excellent mold releasability. The silicone mold is formed from a cured product of the silicone resin composition.

The silicone resin composition includes an addition reaction type silicone resin composition and a condensation reaction type silicone resin composition. Among them, the addition reaction type silicone resin composition is preferable in the present invention because it can suppress curing shrinkage and prevent the resulting cured product (i.e., silicone mold) from expanding or shrinking with a change in temperature.

The addition reaction type silicone resin composition contains a silicone resin (for example, a siloxane having 2 or more alkenyl groups in the molecule), a curing agent (for example, a siloxane having 2 or more hydrosilyl groups (Si-H) in the molecule), and a hydrosilation catalyst (for example, a platinum-based catalyst).

The silicone resin composition can rapidly form a high-density crosslinked structure by heat treatment, and can form a cured product having appropriate elasticity and excellent heat resistance.

The silicone mold is formed from a cured product of a silicone resin composition, and the surface of the mold has at least 1 [ preferably a plurality of (for example, 10 or more, preferably 20 or more, particularly preferably 30 or more, most preferably 50 or more.) fresnel lenses [ fresnel lenses having 2 or more prisms in concentric circles, and having a cross section of the prisms in a mountain shape in which the ratio (h/w) of the height (h) to the width (w) is 0.3 or more, and the height (h) is 0.5mm or less ] of at least 5000, preferably 2000 ]. The silicone mold may be composed of two parts, an upper mold and a lower mold.

As the silicone mold, a mold whose surface is coated with a release agent is also possible. Examples of the release agent include: fluorine-based mold release agents, silicone-based mold release agents, wax-based mold release agents, and the like. These may be used alone in 1 kind, or in combination of 2 or more kinds.

(Molding of curable composition)

The method of molding the curable composition using a mold is preferably molding by a nanoimprint method. The molding by the nanoimprint method means: a method of obtaining a molded article by pressing a mold against a curable composition to transfer the shape of the recessed portion of the mold and curing the curable composition to which the shape of the recessed portion is transferred.

Examples of the method for molding the curable composition using a mold include the following methods (1) to (3).

(1) A method in which a curable composition is applied to a substrate, a mold is pressed against the curable composition, and the mold is peeled off after curing the curable composition;

(2) a method in which a curable composition is applied to a mold, a substrate is pressed from above the curable composition, and the mold is peeled off after curing the curable composition;

(3) a method of applying a curable composition to at least one of an upper mold and a lower mold of a mold, closing the upper mold and the lower mold, curing the curable composition, and then peeling the upper mold and the lower mold.

As the substrate, a substrate having a light transmittance of 90% or more at a wavelength of 400nm is preferably used, and a substrate made of quartz or glass can be suitably used. The light transmittance at the above wavelength can be determined as follows: a substrate (thickness: 1mm) was used as a test piece, and the transmittance of light of the above-mentioned wavelength irradiated to the test piece was measured using a spectrophotometer.

As a method for applying the curable composition, a spray coating method, a spin coating method, a screen printing method, or the like can be used.

The curing of the curable composition can be performed by, for example, irradiating ultraviolet rays in the case of a photocurable composition. As a light source for ultraviolet irradiation, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, or the like can be used. The exposure amount varies depending on the kind of the light source, the distance between the light source and the coated surface, and other conditions, and is, for example, 500 to 3000mJ/cm²Left and right. After the irradiation with ultraviolet rays, if necessary, heating (post-curing) may be performed to promote curing.

After the curable composition is cured, the obtained cured product is released from the mold, thereby obtaining a fresnel lens. When a silicone mold is used as the mold, the fresnel lens is easily peeled off, and it is preferable from the viewpoint that the fresnel lens can be prevented from being broken at the time of peeling.

When a mold having a plurality of concave portions of the fresnel lens in an inverted shape is used as the mold, a molded product in which a plurality of fresnel lenses are connected by joint portions can be obtained. The obtained molded article is cut into individual pieces to obtain fresnel lenses.