Optical elements for fingerprint authentication

Abstract

To provide an optical element for fingerprint authentication, having a translucent spacer layer formed together with a substrate, a photodiode, and a microlens while controlling warpage, having excellent chemical and solvent resistance, and having sufficient thickness, a method for manufacturing the optical element for fingerprint authentication, and a method for manufacturing a thermosetting composition suitably used for manufacturing the optical element for fingerprint authentication.SOLUTION: In an optical element for fingerprint authentication having a substrate, a photodiode, a microlens, and a translucent spacer, the translucent spacer layer is composed of a cured thermosetting composition containing an acrylic resin, the solid content concentration of the thermosetting composition is over 30 mass%, as acrylic resins, resins that contain the constituent unit (I), which is a phenolic hydroxyl group-containing (meth)acrylic unit, and the constituent unit (II), which is an epoxy group-containing (meth)acrylic unit, each with a predetermined structure, in a predetermined ratio, are used.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical element for fingerprint authentication, a method for producing the optical element for fingerprint authentication, and a thermosetting composition that is suitably used for producing the photochemical element for fingerprint authentication. [Background technology]

[0002] 2. Description of the Related Art Conventionally, solid-state imaging devices using photodiodes or the like have been used not only in image capturing devices but also in a wide range of applications, such as optical elements for fingerprint authentication.

[0003] As such a solid-state imaging element, an element that can also be used as an optical element for fingerprint authentication has been proposed, which includes a photodiode (pixel region) provided on a sensor substrate, a light guide path, a light shield, and a microlens (see Patent Document 1, Figures 1 and 11, etc.). The light guide path is a light-transmitting layer provided on the pixel region that is an optical path through which light incident on the solid-state imaging element reaches the photodiode. The light shield is a light-shielding material that blocks light between adjacent light guide paths. The microlens is provided on the light guide path and focuses light incident on the solid-state imaging element toward the photodiode in the pixel region. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 180569 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-described solid-state imaging device, the light guide path, which is a light-transmitting layer, is required to have a certain thickness in order to deliver light rays that have been appropriately focused by the microlenses to the photodiodes. Here, by using a thermosetting material containing an epoxy compound, a light-transmitting cured product can be formed. However, when a thick cured film is formed on a substrate using a thermosetting material containing an epoxy compound, the cured film is likely to warp due to thermal shrinkage during curing, and the warping of the cured film is likely to warp the substrate. Furthermore, cured products of epoxy compounds often have poor chemical resistance and solvent resistance.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an optical element for fingerprint authentication that is formed together with a substrate, a photodiode, and a microlens while suppressing warping, and that has a light-transmitting spacer layer that is excellent in chemical resistance and solvent resistance and has a sufficient thickness; a method for manufacturing the optical element for fingerprint authentication; and a method for manufacturing a thermosetting composition that is suitable for use in manufacturing the photochemical element for fingerprint authentication. [Means for solving the problem]

[0007] The present inventors have discovered that the above-mentioned problems can be solved by forming the light-transmitting spacer layer from a cured product of a thermosetting composition containing an acrylic resin in an optical element for fingerprint authentication that includes a substrate, a photodiode, a microlens, and a light-transmitting spacer, setting the solids concentration of the thermosetting composition to more than 30 mass %, and using as the acrylic resin a resin that contains structural unit (I) that is a phenolic hydroxyl group-containing (meth)acrylic unit and structural unit (II) that is an epoxy group-containing (meth)acrylic unit, each having a predetermined structure, in a predetermined ratio, and have thereby completed the present invention. More specifically, the present invention provides the following.

[0008] A first aspect of the present invention is an optical element for fingerprint authentication, comprising a substrate, a photodiode, a microlens, and a light-transmitting spacer layer, A photodiode is disposed on the substrate; a microlens is disposed opposite the photodiode so that the photodiode can receive light transmitted through the microlens; a light-transmitting spacer layer is disposed between the microlens and the photodiode; the light-transmitting spacer layer is made of a cured product of a thermosetting composition containing an acrylic resin, The solids concentration of the thermosetting composition is greater than 30% by mass, The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2), the ratio of the total number of moles of the structural unit (I) and the number of moles of the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is 35 mol% or more; When the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol% or more and 25 mol% or less, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 15 mol% or more, In the optical element for fingerprint authentication, when the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin exceeds 25 mol%, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is in the range of 15 mol% or more and 25 mol% or less. [ka] (In formula (1) and formula (2), R 0 are each independently a hydrogen atom or a methyl group, X is -O- or -NH-, and R 1 are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R 2 is an alkyl group having 1 to 5 carbon atoms, and R 3 is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less.

[0009] A second aspect of the present invention is a method for manufacturing an optical element for fingerprint authentication, which has a substrate, a photodiode, a microlens, and a light-transmitting spacer layer, the method comprising: A photodiode is disposed on the substrate; a microlens is disposed opposite the photodiode so that the photodiode can receive light transmitted through the microlens; a light-transmitting spacer layer is disposed between the microlens and the photodiode; forming a light-transmitting spacer layer by heating and curing a coating film of a thermosetting resin composition; The solids concentration of the thermosetting composition is greater than 30% by mass, the thermosetting composition comprises an acrylic resin; The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2), the ratio of the total number of moles of the structural unit (I) and the number of moles of the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is 35 mol% or more; When the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol% or more and 25 mol% or less, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 15 mol% or more, This is a method for producing an optical element for fingerprint authentication, in which when the ratio of the number of moles of structural unit (I) to all structural units constituting the acrylic resin exceeds 25 mol%, the ratio of the number of moles of structural unit (II) to all structural units constituting the acrylic resin is in the range of 15 mol% or more and 25 mol% or less. [ka] (In formula (1) and formula (2), R 0 are each independently a hydrogen atom or a methyl group, X is -O- or -NH-, and R 1 are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R 2 is an alkyl group having 1 to 5 carbon atoms, and R 3 is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less.

[0010] A third aspect of the present invention is a thermosetting composition used to form a light-transmitting spacer layer in an optical element for fingerprint authentication, the optical element having a substrate, a photodiode, a microlens, and a light-transmitting spacer layer, the composition comprising: A photodiode is disposed on the substrate; a microlens is disposed opposite the photodiode so that the photodiode can receive light transmitted through the microlens; a light-transmitting spacer layer is disposed between the microlens and the photodiode; the light-transmitting spacer layer is formed by heating and curing a coating film of a thermosetting resin composition; The solids concentration of the thermosetting composition is greater than 30% by mass, the thermosetting composition comprises an acrylic resin; The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2), the ratio of the total number of moles of the structural unit (I) and the number of moles of the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is 35 mol% or more; When the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol% or more and 25 mol% or less, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 15 mol% or more, A thermosetting composition, wherein when the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin exceeds 25 mol%, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is in the range of 15 mol% or more and 25 mol% or less. [ka] (In formula (1) and formula (2), R 0 are each independently a hydrogen atom or a methyl group, X is -O- or -NH-, and R 1 are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R 2 is an alkyl group having 1 to 5 carbon atoms, and R3 is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an optical element for fingerprint authentication, which has a substrate, a photodiode, and a microlens, and which is formed while suppressing warping, and which has a light-transmitting spacer layer that is excellent in chemical resistance and solvent resistance and has a sufficient thickness, as well as a method for manufacturing the optical element for fingerprint authentication, and a method for manufacturing a thermosetting composition that is suitable for use in manufacturing the photochemical element for fingerprint authentication. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram schematically showing a cross section in the thickness direction of a substrate of an optical element for fingerprint authentication according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0013] <Optical element for fingerprint authentication> The optical element for fingerprint authentication includes a substrate, a photodiode, a microlens, and a light-transmitting spacer layer. The photodiode is disposed on a substrate. The microlens is disposed opposite the photodiode so that the photodiode can receive light that has passed through the microlens. A light-transmitting spacer layer is disposed between the microlens and the photodiode. The light-transmitting spacer layer is made of a cured product of a thermosetting composition containing an acrylic resin. The solids concentration of the thermosetting composition exceeds 30% by mass. The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2). [ka] (In formula (1) and formula (2), R 0are each independently a hydrogen atom or a methyl group, X is -O- or -NH-, and R 1 are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R 2 is an alkyl group having 1 to 5 carbon atoms, and R 3 is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less.

[0014] The ratio of the total number of moles of the structural unit (I) and the number of moles of the structural unit (II) to the number of moles of all structural units that constitute the acrylic resin is 35 mol % or more. When the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol% or more and 25 mol% or less, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 15 mol% or more. When the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin exceeds 25 mol%, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is in the range of 15 mol% or more and 25 mol% or less.

[0015] The above-mentioned optical element for fingerprint authentication includes a substrate, a photodiode, and a microlens, and also includes a light-transmitting spacer layer that is formed while suppressing warping, has excellent chemical resistance and solvent resistance, and has a sufficient thickness.

[0016] A preferred example of an optical element for fingerprint authentication will be described below with reference to FIG. In FIG. 1, a photodiode (PD) is provided on a substrate 10. In FIG. 1, three light-transmitting spacer layers 11 are stacked on a substrate 10 with three light-shielding layers 12 interposed therebetween.

[0017] Typically, the optical element 1 for fingerprint authentication has one or more light-shielding layers 12 at positions corresponding to the positions of the photodiodes (PDs) to prevent light rays focused by the microlenses 13 from mixing with light rays focused by other adjacent microlenses 13.

[0018] 1, when the optical element for fingerprint authentication 1 includes multiple light-transmitting spacer layers 11, the thickness of each of the light-transmitting spacer layers 11 is, for example, 6 μm or more, preferably 7 μm or more, and more preferably 10 μm or more. The upper limit of the thickness of each of the light-transmitting spacer layers 11 is not particularly limited as long as it does not adversely affect the performance of the optical element for fingerprint authentication. The upper limit of the thickness of each of the light-transmitting spacer layers may be, for example, 50 μm or less, or may be 30 μm or less.

[0019] As shown in FIG. 1, when the fingerprint authentication optical element 1 includes multiple light-transmitting spacer layers 11, the total thickness of the multiple light-transmitting spacer layers is preferably 10 μm or more and 200 μm or less, and more preferably 20 μm or more and 100 μm or less.

[0020] The microlens 13 is disposed opposite the photodiode so that the photodiode can receive the light beam that has passed through the microlens. In order to prevent light rays focused by the microlens 13 from mixing with light rays focused by other adjacent microlenses 13, the microlens 13 is preferably provided on the light-shielding layer 12. In this case, the light-shielding layer 12 located directly below the microlens 13 has an opening at a position corresponding to the position of the microlens 13 so that the light rays focused by the microlens 13 can reach the photodiode (PD).

[0021] The light-transmitting spacer layer 11 is made of a cured product of a thermosetting composition containing an acrylic resin. The solid content concentration of the thermosetting composition is greater than 30% by mass. When the solid content concentration of the thermosetting composition is greater than 30% by mass, a light-transmitting spacer layer with a desired thickness can be easily formed. The solid content concentration of the thermosetting composition is preferably 33% by mass or more, and more preferably 35% by mass or more. The upper limit of the solid content of the thermosetting composition is not particularly limited as long as the thermosetting composition can be satisfactorily formed into a film, and may be, for example, 60% by mass or less, or 50% by mass or less.

[0022] The viscosity of the thermosetting composition is preferably 500 cP or more and 3000 cP or less, and more preferably 700 cP or more and 2500 cP or less, as measured at 25°C with a Cannon-Fenske viscometer, because this makes it easy to form a light-transmitting spacer layer 11 of the desired thickness and to apply the thermosetting composition uniformly.

[0023] The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2). The acrylic resin may have a combination of two or more units corresponding to the structural unit (I). The acrylic resin may have a combination of two or more units corresponding to the structural unit (II). [ka] (In formula (1) and formula (2), R 0 are each independently a hydrogen atom or a methyl group, X is -O- or -NH-, and R 1 are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R 2 is an alkyl group having 1 to 5 carbon atoms, and R 3 is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less.

[0024] In the above formula (1) and formula (2), R 1Specific preferred examples of the alkylene group having 1 to 5 carbon atoms as the alkylene group include a methylene group, an ethane-1,2-diyl group (ethylene group), an ethane-1,1-diyl group, a propane-1,3-diyl group, a propane-1,2-diyl group, a propane-2,2-diyl group, a propane-1,1-yl group, a butane-1,4-diyl group, and a pentane-1,5-diyl group.

[0025] In the above formula (1), R 2 Specific preferred examples of the alkyl group having 1 to 5 carbon atoms as the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and an n-pentyl group. In formula (1), R 2 The number b is an integer of 0 to 4, and is preferably 0.

[0026] At least one hydroxyl group is bonded to the benzene ring of the structural unit (I). The number a, which represents the number of hydroxyl groups bonded to the benzene ring, is an integer of 1 to 5. It is preferable that a is 1, as this allows for easy synthesis and availability of the monomer compound that provides the structural unit (I) and makes it easier to suppress warping of the light-transmitting spacer layer 11. In the structural unit (I), when the number of hydroxyl groups bonded to the benzene ring is two or more, at least one of the hydroxyl groups is R 1 It is preferred that the carbon atom bonded to the aryl group be para to the carbon atom bonded to the aryl group. In the structural unit (I), when the number of hydroxyl groups bonded to the benzene ring is one, the hydroxyl group is 1 It is preferred that the carbon atom bonded to the aryl group be para to the carbon atom bonded to the aryl group.

[0027] In formula (I), X is —O— or —NH—, and is preferably —O—.

[0028] As the structural unit (I), a unit represented by the following formula (a-1) or formula (a-2) is preferred, and a unit represented by the following formula (a-1) is more preferred.0 is R in Eq. (1) 0 is the same as: [ka]

[0029] In equation (2), R 1 is as described above for formula (1). In formula (2), R 3 is an epoxy group-containing group. The epoxy group-containing group is not particularly limited as long as it is a group containing an epoxy group. For example, in formula (2), -R 1 -R 3 In other words, the structural unit (II) is preferably a unit represented by the following formula (b1-1): 0 is R in Equation (2). 0 is the same as: [ka]

[0030] Furthermore, as the structural unit (II), units represented by any of the following formulas (b2-1) to (b2-12) are also preferred. In formulas (b2-1) to (b2-12), R 0 is R in Equation (2). 0 , and R 1 is R in Equation (2). 0 , and R 1 is the same as: In formulas (b2-1) to (b2-12), R 4 are each independently an alkylene group having 1 to 20 carbon atoms. 5 are each independently a hydrogen atom or a methyl group. 6 are each independently an alkylene group having 1 to 8 carbon atoms, and w is an integer of 0 to 10. Among the units represented by any of formulas (b2-1) to (b2-12), the unit represented by formula (b2-1) is preferred. As the unit represented by formula (b2-1), a unit in which R0 is a methyl group and R1 is a methylene group is preferred.

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] In addition to the structural unit (I) and the structural unit (II), the acrylic resin may also contain a structural unit (III) that does not fall under the category of the structural unit (I) and the structural unit (II). Other monomers that provide the structural unit (III) include (meth)acrylic acid esters having no epoxy group, (meth)acrylamides, allyl compounds, vinyl ethers, vinyl esters, styrenes, maleimides, etc. These compounds can be used alone or in combination of two or more.

[0038] Examples of (meth)acrylic acid esters having no epoxy group include linear or branched alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, amyl (meth)acrylate, and tert-octyl (meth)acrylate; chloroethyl (meth)acrylate, 2,2-dimethylhydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, trimethylolpropane mono(meth)acrylate, benzyl (meth)acrylate, and furfuryl (meth)acrylate; and (meth)acrylic acid esters having a group with an alicyclic skeleton. In the (meth)acrylic acid ester having a group having an alicyclic skeleton, the alicyclic group constituting the alicyclic skeleton may be monocyclic or polycyclic. Examples of the monocyclic alicyclic group include a cyclopentyl group and a cyclohexyl group. Examples of the polycyclic alicyclic group include a norbornyl group, an isobornyl group, a tricyclononyl group, a tricyclodecyl group, and a tetracyclododecyl group.

[0039] Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, N-aryl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, N,N-aryl(meth)acrylamide, N-methyl-N-phenyl(meth)acrylamide, and N-hydroxyethyl-N-methyl(meth)acrylamide.

[0040] Examples of allyl compounds include allyl esters such as allyl acetate, allyl caproate, allyl caprylate, allyl laurate, allyl palmitate, allyl stearate, allyl benzoate, allyl acetoacetate, and allyl lactate; allyloxyethanol; and the like.

[0041] Examples of vinyl ethers include aliphatic vinyl ethers such as hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether, hydroxyethyl vinyl ether, diethylene glycol vinyl ether, dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, butylaminoethyl vinyl ether, benzyl vinyl ether, and tetrahydrofurfuryl vinyl ether; and vinyl aryl ethers such as vinyl phenyl ether, vinyl tolyl ether, vinyl chlorophenyl ether, vinyl-2,4-dichlorophenyl ether, vinyl naphthyl ether, and vinyl anthranyl ether.

[0042] Examples of vinyl esters include vinyl butyrate, vinyl isobutyrate, vinyl trimethyl acetate, vinyl diethyl acetate, vinyl valerate, vinyl caproate, vinyl chloroacetate, vinyl dichloroacetate, vinyl methoxyacetate, vinyl butoxyacetate, vinyl phenylacetate, vinyl acetoacetate, vinyl lactate, vinyl-β-phenylbutyrate, vinyl benzoate, vinyl salicylate, vinyl chlorobenzoate, vinyl tetrachlorobenzoate, and vinyl naphthoate.

[0043] Examples of styrenes include styrene; alkyl styrenes such as methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, isopropyl styrene, butyl styrene, hexyl styrene, cyclohexyl styrene, decyl styrene, benzyl styrene, chloromethyl styrene, trifluoromethyl styrene, ethoxymethyl styrene, and acetoxymethyl styrene; alkoxy styrenes such as methoxy styrene, 4-methoxy-3-methyl styrene, and dimethoxy styrene; and halostyrenes such as chlorostyrene, dichlorostyrene, trichlorostyrene, tetrachlorostyrene, pentachlorostyrene, bromostyrene, dibromostyrene, iodostyrene, fluorostyrene, trifluorostyrene, 2-bromo-4-trifluoromethylstyrene, and 4-fluoro-3-trifluoromethylstyrene.

[0044] Examples of maleimides include maleimides N-substituted with an alkyl group having from 1 to 10 carbon atoms, such as N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, Nn-pentylmaleimide, and Nn-hexylmaleimide; maleimides N-substituted with an alicyclic group having from 3 to 20 carbon atoms, such as N-cyclopentylmaleimide, N-cyclohexylmaleimide, and N-cycloheptylmaleimide; N-arylmaleimides N-substituted with an aryl group having from 6 to 20 carbon atoms, such as N-phenylmaleimide, N-α-naphthylmaleimide, and N-β-naphthylmaleimide; and N-aralkylmaleimides N-substituted with an aralkyl group having from 7 to 20 carbon atoms, such as N-benzylmaleimide and N-phenethylmaleimide.

[0045] The ratio of the total number of moles of the structural unit (I) and the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is 35 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, particularly preferably 90 mol% or more, and particularly preferably 100 mol%. The thermosetting composition may contain two or more types of acrylic resins in combination. When the thermosetting composition contains a combination of two or more acrylic resins, the ratio of the total number of moles of the structural unit (I) and the structural unit (II) to the total number of moles of all structural units constituting the acrylic resin is the ratio of the total number of moles of the structural unit (I) for each of the two or more acrylic resins and the total number of moles of the structural unit (II) for each of the two or more acrylic resins to the total number of moles of all structural units for each of the two or more acrylic resins.

[0046] When the ratio of the total number of moles of the structural unit (I) and the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is within the above range, the coating film made of the thermosetting composition cures well while suppressing warping, and a light-transmitting spacer layer 11 having excellent chemical resistance and solvent resistance is formed.

[0047] When the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol% or more and 25 mol% or less, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 15 mol% or more. In this case, even if a large amount of structural unit (II) having an epoxy group is present in the acrylic resin, only an amount of structural unit (II) corresponding to the amount of structural unit (I) having a phenolic hydroxyl group will participate in the crosslinking reaction between structural unit (I) and structural unit (II). As a result, when the thermosetting composition is cured, curing by crosslinking proceeds sufficiently without excessive crosslinking, suppressing warping and forming a light-transmitting spacer layer 11 that has excellent chemical resistance and solvent resistance.

[0048] When the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin exceeds 25 mol%, the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is in the range of 15 mol% or more and 25 mol% or less. In this case, even if a large amount of structural unit (II) having a phenolic hydroxyl group is present in the acrylic resin, only an amount of structural unit (I) corresponding to the amount of structural unit (II) having an epoxy group will participate in the crosslinking reaction between structural unit (I) and structural unit (II). As a result, when the thermosetting composition is cured, curing by crosslinking proceeds sufficiently without excessive crosslinking, suppressing warping and forming a light-transmitting spacer layer 11 that has excellent chemical resistance and solvent resistance.

[0049] The weight-average molecular weight of the acrylic resin is not particularly limited as long as the desired effect is not impaired. The weight-average molecular weight of the acrylic resin is preferably from 10,000 to 100,000, more preferably from 10,000 to 50,000, because it is easy to form the light-transmitting spacer layer 11 with a desired thickness while suppressing warpage, and the acrylic resin is easy to prepare.

[0050] The thermosetting composition may contain an organic solvent for the purpose of adjusting the viscosity and application properties. However, the organic solvent is used so that the solids concentration of the curable composition is more than 30%.

[0051] Specific examples of organic solvents that can be blended in the thermosetting composition include aromatic hydrocarbons such as benzene, toluene, and xylene; ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, butanol, hexanol, and cyclohexanol; aliphatic polyols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and glycerin; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples of the alkanoates include mono- or di-ethers of glycols such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether; mono- or di-ethers of glycols such as 3-methoxybutyl acetate, 3-methyl-methoxybutyl acetate, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether propionate, and propylene glycol monoethyl ether propionate; and carbonates such as methyl carbonate, ethyl carbonate, propyl carbonate, and butyl carbonate. Among these, PGMEA is more preferred.

[0052] The amount of the organic solvent used is not particularly limited as long as the solids concentration of the thermosetting composition is more than 30 mass %. The amount of the organic solvent is appropriately adjusted so that the solids concentration of the thermosetting composition becomes a desired concentration.

[0053] The thermosetting composition may contain various additives such as resins other than the above-mentioned acrylic resin, photosensitizers such as quinone diazide group-containing compounds, surfactants, sensitizers, and antifoaming agents, as long as the effects of the present invention are not impaired. In order to easily suppress warping of the light-transmitting spacer layer 11, it is preferable that the thermosetting composition does not contain a photosensitizer such as a quinonediazide group-containing compound.

[0054] The thermosetting composition described above is applied onto the substrate 10 to form a coating film made of the thermosetting composition on the substrate 10, and the formed coating film is cured by heating, thereby forming a light-transmitting spacer layer 11 on the substrate 10.

[0055] Examples of the coating method include methods using contact transfer type coating devices such as a roll coater, reverse coater, and bar coater, and non-contact type coating devices such as a spinner (rotary coating device), slit coater, and curtain flow coater. As the coating method, a method using a spinner is preferred because it is easy to form a coating film with a uniform thickness in a short time. The thermosetting composition can also be applied by a printing method such as screen printing.

[0056] The conditions for thermally curing the coating film are not particularly limited as long as the coating film can be sufficiently cured while suppressing warpage of the light-transmitting spacer layer 11. The conditions for thermally curing the coating film are preferably 150°C or higher and 250°C or lower for 1 minute or longer and 30 minutes or shorter, and more preferably 180°C or higher and 220°C or lower for 1 minute or longer and 10 minutes or shorter.

[0057] Before curing the coating film by heating, the coating film may be heated for the purpose of removing the organic solvent from the coating film, etc. In this case, the heating conditions are preferably 80°C or higher and 140°C or lower for 30 seconds or higher and 5 minutes or lower.

[0058] The optical element for fingerprint authentication shown in FIG. 1 can be manufactured, for example, by the following method. First, a thermosetting composition is applied onto the substrate 10 to form a coating film. The coating film is cured by heating using the method described above to form the first light-transmitting spacer layer 11. Next, a black photoresist composition is applied onto the first light-transmitting spacer layer 11 to form a coating film. The formed coating film is exposed and developed so that openings are formed at positions corresponding to the positions of the photodiodes (PDs), thereby forming a light-shielding layer 12 with openings. Typically, a transparent resin material is filled into the openings in the light-shielding layer 12. The filled resin corresponds to the light guide path. There are no particular limitations on the method for filling the openings in the light-shielding layer 12 with a transparent resin material. For example, the above-described thermosetting composition is applied onto the light-shielding layer 12 having openings while filling the openings with the thermosetting composition, and then the applied film made of the thermosetting composition is cured, thereby forming a second light-transmitting spacer layer 11 and filling the openings in the light-shielding layer 12 with the transparent resin material. After forming the spacer layer 11 or after filling the openings in the light-shielding layer 12, processing (CMP, etching, etc.) may be performed to flatten the surface. 1, a material such as the thermosetting composition described above is filled into the openings in the light-shielding layer 12, which is the outermost layer in Fig. 1, by various known methods, and then the filled material is cured to form a transparent resin material. After the transparent resin material is formed, processing (CMP, etching, etc.) may be performed to flatten the surface of the light-shielding layer 12. By repeating the above-described operations, a laminate in which a desired number of light-transmitting spacer layers 11 and light-shielding layers 12 are laminated can be obtained.

[0059] As described above, after laminating the light-transmitting spacer layer 11 and, if necessary, the light-shielding layer 12 on the substrate 10, the microlenses 13 are disposed on the formed laminate facing the photodiodes (PD) so that the photodiodes (PD) can receive light transmitted through the microlenses 13. There are no particular limitations on the method for forming the microlenses 13 on the laminate. The method for forming the microlenses 13 can be appropriately selected from known methods.

[0060] The structure of the optical element for fingerprint authentication is as follows: the fingerprint authentication optical element has a substrate, a photodiode, a microlens, and a light-transmitting spacer layer; A photodiode is disposed on the substrate; a microlens is disposed opposite the photodiode so that the photodiode can receive light transmitted through the microlens; As long as a light-transmitting spacer layer is disposed between the microlens and the photodiode, the structure is not particularly limited to that shown in FIG. 1 and can be modified as appropriate.

[0061] The optical element for fingerprint authentication described above is suppressed from warping and has a sufficiently thick light-transmitting spacer layer 11, so that the rate of defective products is low and the optical element functions well. [Example]

[0062] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0063] [Examples 1 to 5 and Comparative Examples 1 to 3] In the examples and comparative examples, an acrylic resin composed of a structural unit (I) derived from 4-hydroxyphenyl methacrylate and a structural unit (II) derived from glycidyl methacrylate was used. The molar ratio of the structural unit (I) to the structural unit (II) in the acrylic resin and the weight-average molecular weight (Mw) of the acrylic resin are shown in Table 1. The acrylic resin was dissolved in propylene glycol monomethyl ether acetate (PGMEA) so that the concentration of the acrylic resin shown in Table 1 became the solid content concentration shown in Table 1, thereby obtaining thermosetting compositions for each of the Examples and Comparative Examples.

[0064] The obtained thermosetting compositions were evaluated for film thickness, warpage, solvent resistance, and chemical resistance according to the following methods. The evaluation results are shown in Table 1.

[0065] <Film thickness evaluation> Each of the thermosetting compositions of the Examples and Comparative Examples was applied onto a silicon substrate at a rotation speed of 1000 rpm, and the resulting coating film was heated at 100°C for 60 seconds and then at 200°C for 5 minutes to obtain a cured film. The thickness of the formed cured film was measured using a film thickness measuring device Nanospec (manufactured by Nanometrics Co., Ltd.) and evaluated according to the following criteria. (Evaluation criteria) A:10μm or more B: 7 μm or more and less than 10 μm C: Less than 7 μm

[0066] <Warp evaluation> Before applying the curable composition to the silicon substrate, the residual stress was measured using a thin film stress measurement device (FLX-3300-T, manufactured by Yamato Scientific Co., Ltd.). Then, a cured film was formed on the silicon substrate using the same method as for the film thickness evaluation. The residual stress of the silicon substrate with the cured film was measured in the same manner as for the silicon substrate. "Residual stress" refers to the stress remaining inside the film after the curable composition is applied to the substrate to form a film. The "residual stress" inside the film is an indicator of the "warping" that may occur in the film. The silicon substrate does not have a film before the hardened film is formed. For convenience, the stress measured by the "thin film stress measurement device" for the silicon substrate before the hardened film is formed is also referred to as "residual stress."

[0067] The occurrence of warpage was evaluated according to the following criteria based on the difference in residual stress between the silicon substrate with the cured film and the silicon substrate without the curable composition applied thereto. (Evaluation criteria) A: The difference in residual stress is 10 MPa or less B: The difference in residual stress is greater than 10 MPa and less than 13 MPa C: The difference in residual stress values ​​is more than 13 MPa

[0068] <Solvent resistance evaluation and chemical resistance evaluation> A cured film was formed on a silicon substrate using the same method as in the film thickness evaluation. The film thickness T1 of the formed cured film was measured using the same method as in the film thickness evaluation. Next, the silicon substrate with the cured film was immersed in PGMEA or an aqueous solution of tetramethylammonium hydroxide with a concentration of 2.38 mass% at room temperature for 10 minutes. After immersion, the silicon substrate was rinsed with pure water for 30 seconds. After rinsing, the silicon substrate was dried at 100°C for 1 minute. The film thickness T2 of the cured film on the dried silicon substrate was measured in the same manner as in the film thickness T1. The solvent resistance and chemical resistance of the cured film were evaluated according to the following criteria based on the film thickness variation rate calculated using the following formula. Film thickness variation rate (%) = T2 / T1 x 100 (Evaluation criteria) A: Film thickness variation rate is 99% or more and 101% or less B: Film thickness variation rate is 95% or more but less than 99%, or more than 101% but less than 105% C: Film thickness variation rate is less than 95% or more than 105%

[0069] [Table 1]

[0070] Table 1 shows that by using a thermosetting composition containing an acrylic resin in which the ratio of the structural unit (I) to the structural unit (II) satisfies the aforementioned ratio and having a solids concentration of more than 30 mass%, it is possible to form a cured film that is sufficiently thick and has excellent chemical resistance and solvent resistance while suppressing the occurrence of warping. On the other hand, according to Comparative Example 1, it is clear that when the solid content concentration of the thermosetting composition is 30 mass % or less, it is difficult to form a cured film with a sufficient thickness. Comparative Examples 2 and 3 show that when the ratio of the structural unit (I) to the structural unit (II) does not satisfy the aforementioned ratio, the cured film warps and the chemical resistance of the cured film deteriorates. [Explanation of symbols]

[0071] 1 Optical elements for fingerprint authentication 10 Substrate 11 Light-transmitting spacer layer 12 Light blocking layer 13 Microlenses

Claims

1. An optical element for fingerprint authentication, comprising a substrate, a photodiode, a microlens, and a light-transmitting spacer layer, the photodiode is disposed on a substrate; the microlens is disposed opposite the photodiode so that the photodiode can receive light transmitted through the microlens; the light-transmitting spacer layer is disposed between the microlens and the photodiode; the light-transmitting spacer layer is made of a cured product of a thermosetting composition containing an acrylic resin, The solids concentration of the thermosetting composition is greater than 30% by mass, The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2), the ratio of the total number of moles of the structural unit (I) and the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is 35 mol% or more, An optical element for fingerprint authentication, wherein the ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol% or more and 25 mol% or less, and the ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 75 mol% or more. 【Chemistry 1】 (In formula (1) and formula (2), R ０ are each independently a hydrogen atom or a methyl group, X is —O— or —NH—, and R １ are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R ２ is an alkyl group having 1 to 5 carbon atoms, and R ３ is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less.

2. 2. The optical element for fingerprint authentication according to claim 1, wherein the weight average molecular weight of the acrylic resin is 10,000 or more and 100,000 or less.

3. 3. The optical element for fingerprint authentication according to claim 1, wherein the light-transmitting spacer layer has a thickness of 10 [mu]m or more.

4. An optical element for fingerprint authentication described in any one of claims 1 to 3, wherein a laminate is formed between the microlens and the photodiode, in which a plurality of the light-transmitting spacer layers are stacked together with a plurality of light-shielding layers.

5. A method for manufacturing an optical element for fingerprint authentication, the optical element having a substrate, a photodiode, a microlens, and a light-transmitting spacer layer, comprising the steps of: the photodiode is disposed on a substrate; the microlens is disposed opposite the photodiode so that the photodiode can receive light transmitted through the microlens; the light-transmitting spacer layer is disposed between the microlens and the photodiode; forming the light-transmitting spacer layer by heating and curing a coating film of a thermosetting composition; the thermosetting composition comprises an acrylic resin, The solids concentration of the thermosetting composition is greater than 30% by mass, The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2), the ratio of the total number of moles of the structural unit (I) and the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is 35 mol% or more, a ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol% or more and 25 mol% or less, and a ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 75 mol% or more. 【Chemistry 2】 (In formula (1) and formula (2), R ０ are each independently a hydrogen atom or a methyl group, X is —O— or —NH—, and R １ are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R ２ is an alkyl group having 1 to 5 carbon atoms, and R ３ is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less.

6. 6. The method for manufacturing an optical element for fingerprint authentication according to claim 5, wherein the weight average molecular weight of the acrylic resin is 10,000 or more and 100,000 or less.

7. 7. The method for producing an optical element for fingerprint authentication according to claim 5, wherein the light-transmitting spacer layer has a thickness of 10 [mu]m or more.

8. A thermosetting composition used to form a light-transmitting spacer layer in an optical element for fingerprint authentication, the optical element having a substrate, a photodiode, a microlens, and a light-transmitting spacer layer, the composition comprising: the photodiode is disposed on a substrate; the microlens is disposed opposite the photodiode so that the photodiode can receive light transmitted through the microlens; the light-transmitting spacer layer is disposed between the microlens and the photodiode; the light-transmitting spacer layer is formed by heating and curing a coating film of the thermosetting composition, the thermosetting composition comprises an acrylic resin, The solids concentration of the thermosetting composition is greater than 30% by mass, The acrylic resin has a structural unit (I) represented by the following formula (1) and a structural unit (II) represented by the following formula (2), the ratio of the total number of moles of the structural unit (I) and the structural unit (II) to the number of moles of all structural units constituting the acrylic resin is 35 mol% or more, a ratio of the number of moles of the structural unit (I) to all structural units constituting the acrylic resin is 10 mol % or more and 25 mol % or less, and a ratio of the number of moles of the structural unit (II) to all structural units constituting the acrylic resin is 75 mol % or more. 【Transformation 3】 (In formula (1) and formula (2), R ０ are each independently a hydrogen atom or a methyl group, X is —O— or —NH—, and R １ are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R ２ is an alkyl group having 1 to 5 carbon atoms, and R ３ is an epoxy group-containing group, a is an integer of 1 or more and 5 or less, and b is an integer of 0 or more and 4 or less.

9. The thermosetting composition according to claim 8, wherein the weight average molecular weight of the acrylic resin is 10,000 or more and 100,000 or less.

10. The thermosetting composition according to claim 8 or 9, wherein the light-transmitting spacer layer has a thickness of 10 μm or more.

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