Optical modulation device and method for manufacturing optical modulation device

Abstract

The present invention addresses the problem of providing: an optical modulation device that has a protective layer which exhibits good adhesion to an electro-optic material that contains a liquid crystal compound; and a method for manufacturing an optical modulation device. An optical modulation device according to the present invention comprises: a substrate; a slot waveguide in which an electro-optic material that contains a liquid crystal compound is present between two electrodes disposed on the substrate; and a protective layer that covers the surface of the electro-optic material which is present in the slot waveguide. The protective layer is obtained by curing a composition that satisfies at least one of the following conditions 1 and 2.　Condition 1: The composition contains a compound A that has an acidic group and a crosslinking group.　Condition 2: The composition contains a compound B that has an acidic group and does not have a crosslinking group, and a compound C that has a crosslinking group and does not have an acidic group.

Description

Optical modulation device and method for manufacturing the same

[0001] The present invention relates to an optical modulation device and a method for manufacturing an optical modulation device.

[0002] As an electro-optical (hereinafter abbreviated as "EO") material applicable to optical control elements (optical elements) such as optical modulators, optical switches, and optical interconnects, optical modulation devices using slot waveguides in which an EO material is present between two adjacent conductive electrodes (slot portion) have been attracting attention in recent years from the viewpoint of realizing ultra-high speed optical communications.

[0003] For example, Patent Document 1 describes an optical modulation device comprising: a substrate; a slot waveguide formed by arranging a pair of electrodes in a groove formed on one surface of the substrate and filling the groove with an electro-optical material; a dielectric film covering the surface of the electro-optical material filled in the slot waveguide; and a plate-like member adhered to the dielectric film by an adhesive resin and covering the slot waveguide (Claim 1).

[0004] Japanese Patent Application Laid-Open No. 2021-043263

[0005] The present inventors have found that when a protective layer is provided instead of the dielectric film (e.g., aluminum oxide) described in Patent Document 1 from the viewpoint of manufacturability, etc., the adhesiveness to the electro-optical material is poor. Furthermore, the present inventors have found that this adhesiveness problem becomes apparent when a liquid crystal compound is included as the electro-optical material.

[0006] Therefore, an object of the present invention is to provide an optical modulation device having a protective layer that provides good adhesion to an electro-optical material containing a liquid crystal compound, and a method for manufacturing the optical modulation device.

[0007] As a result of intensive research aimed at achieving the above object, the present inventors have found that the use of a protective layer formed by curing a composition that satisfies specific conditions improves adhesion to an electro-optical material containing a liquid crystal compound, and have completed the present invention. That is, the present inventors have found that the above object can be achieved by the following configuration.

[0008] [1] A light modulation device comprising: a substrate; a slot waveguide having an electro-optical material containing a liquid crystal compound present between two electrodes arranged on the substrate; and a protective layer covering the surface of the electro-optical material present in the slot waveguide, wherein the protective layer is a protective layer formed by curing a composition that satisfies at least one of the following conditions 1 and 2: Condition 1: The protective layer contains a compound A having an acidic group and a crosslinking group; and Condition 2: The protective layer contains a compound B having an acidic group and no crosslinking group, and a compound C having a crosslinking group and no acidic group. [2] The light modulation device according to [1], wherein the composition is an alkali-developable composition. [3] The light modulation device according to [1] or [2], wherein at least one of compound A, compound B, and compound C is a compound further having any of a styryl group, an adamantyl group, and a cyclopentanyl group. [4] The light modulation device according to any of [1] to [3], wherein the acidic group possessed by compound A or compound B is at least one group selected from the group consisting of a phenolic hydroxyl group and a carboxy group. [5] The optical modulation device according to any one of [1] to [4], wherein the crosslinking group possessed by compound A or compound C is at least one group selected from the group consisting of an acryloyloxy group, a methacryloyloxy group, an epoxy group, and an oxetanyl group. [6] The optical modulation device according to any one of [1] to [5], wherein the thickness of the protective layer is 2 to 50 μm. [7] The optical modulation device according to any one of [1] to [6], wherein the protective layer is a protective layer obtained by curing a composition with light or heat. [8] The optical modulation device according to any one of [1] to [7], wherein the protective layer contains a singlet oxygen quencher or an antioxidant. [9] The optical modulation device according to [8], wherein the singlet oxygen quencher or the antioxidant is at least one selected from the group consisting of vitamin derivatives and hindered amine light stabilizers.

[10] The optical modulation device according to any one of [1] to [9], wherein the mass change of the protective layer due to heating at 150°C is 0.8 mass% or less, and the thermal expansion coefficient of the protective layer at 150°C is 150 ppm or less.

[11] A method for manufacturing an optical modulation device according to any one of [1] to

[10] , comprising: a composition layer forming step of applying a protective layer-forming composition to a surface of an electro-optical material present in a slot waveguide to form a protective composition layer; and a protective layer forming step of curing at least a portion of the protective composition layer to form a protective layer.

[12] A method for manufacturing an optical modulation device according to

[11] , comprising a development step of removing a portion of the protective composition layer between the composition layer forming step and the protective layer forming step.

[0009] According to the present invention, it is possible to provide an optical modulation device having a protective layer that exhibits good adhesion to an electro-optical material containing a liquid crystal compound, and a method for manufacturing the optical modulation device.

[0010] Fig. 1 is a schematic cross-sectional view showing an example of an optical modulation device of the present invention, and Fig. 2 is a schematic view of a photostability evaluation system.

[0011] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the upper and lower limits. In this specification, the upper or lower limit of a numerical range described in a stepwise manner may be replaced with the upper or lower limit of another stepwise manner. In this specification, the upper or lower limit of a numerical range described in a stepwise manner may be replaced with a value shown in the Examples. In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. When two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. In addition, in this specification, "(meth)acrylate" is a notation representing "acrylate" or "methacrylate", "(meth)acrylic" is a notation representing "acrylic" or "methacrylic", and "(meth)acryloyl" is a notation representing "acryloyl" or "methacryloyl".

[0012] [Light Modulation Device] The light modulation device of the present invention has a substrate, a slot waveguide in which an electro-optical material containing a liquid crystal compound is present between two electrodes arranged on the substrate, and a protective layer covering the surface of the electro-optical material present in the slot waveguide. The protective layer of the light modulation device of the present invention is a protective layer obtained by curing a composition that satisfies at least one of the following conditions 1 and 2. Condition 1: The protective layer contains a compound A having an acidic group and a crosslinking group. Condition 2: The protective layer contains a compound B having an acidic group and no crosslinking group, and a compound C having a crosslinking group and no acidic group.

[0013] In the present invention, as described above, by providing a protective layer formed by curing a composition that satisfies at least one of the above-described conditions 1 and 2, adhesion to an EO material containing a liquid crystal compound is improved. The reason for this effect is not clear in detail, but the inventors speculate as follows. First, the slot waveguide of the optical modulation device of the present invention is a slot waveguide in which an EO material containing a liquid crystal compound (i.e., a hydrophobic material) is present between two electrodes arranged on a substrate. Therefore, in the present invention, when a composition that satisfies at least one of the above-described conditions 1 and 2 is applied, interactions (e.g., van der Waals forces, hydrogen bonding forces, etc.) are more likely to form between the acidic groups of the compound contained in the coating film and the EO material containing the liquid crystal compound (e.g., oxygen of a carbonyl group or oxygen of an oxyethylene group of the liquid crystal compound), which is thought to improve adhesion.

[0014] Next, an overview of the optical modulation device of the present invention will be described using the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the optical modulation device of the present invention. The optical modulation device 100 shown in FIG. 1 includes a substrate 105, a slot waveguide 200 having an electro-optical material 141 containing a liquid crystal compound present between two electrodes 106 arranged on the substrate 105 (hereinafter also referred to as a "slot portion") 107, and a protective layer 142 covering the surface of the electro-optical material 141 present in the slot waveguide 200. Note that in FIG. 1, reference numeral 109 represents an insulating layer. In such a slot waveguide 200, when a voltage is applied to the pair of electrodes 106, the refractive index of the electro-optical material 141 containing a liquid crystal compound changes, thereby changing the optical path length. Therefore, by applying an appropriate voltage difference between the arms of a Mach-Zehnder interferometer having two slot waveguides 200, the interference conditions between the two arms change, enabling optical modulation of light from a light source. 1, the EO material 141 is present not only in the slot portion 107 but also on the surfaces of the two electrodes 106, but in the present invention, it is sufficient that the EO material is present at least in the slot portion. Each component of the optical modulation device of the present invention will be described in detail below.

[0015] [Substrate] The substrate of the optical modulation device of the present invention is not particularly limited, and may be a conventionally known substrate such as a glass substrate, a metal substrate, a ceramic substrate, a semiconductor substrate, or a circuit substrate. A semiconductor substrate is preferable. Specific examples of the semiconductor substrate include a silicon (Si) substrate and a silicon dioxide (SiO ２ ) substrate, gallium arsenide (GaAs) substrate, indium phosphide (InP) substrate, gallium phosphide (GaP) substrate, gallium nitride (GaN) substrate, gallium telluride (GaTe) substrate, zinc selenium (ZnSe) substrate, silicon carbide (SiC) substrate, etc.

[0016] [Slot Waveguide] The slot waveguide of the optical modulation device of the present invention is a slot waveguide in which an EO material containing a liquid crystal compound is present between two (i.e., a pair of) electrodes arranged on a substrate (slot portion).

[0017] <Electrode> The electrode to be arranged on the substrate in the slot waveguide is not particularly limited, and conventionally known electrodes described in JP 2021-043263 A, etc. can be used. Here, the term "electrode" refers not only to so-called positive and negative electrodes, but also to rails and slabs described in JP 2021-167851 A, etc. It is a concept that includes such.

[0018] In the present invention, the width (slot width) between the two electrodes (reference numeral 107 in FIG. 1) is not particularly limited, but is preferably 50 to 500 nm, more preferably 80 to 300 nm, and even more preferably 100 to 200 nm. Furthermore, the height of the two electrodes (the height of the portion between the electrodes) is not particularly limited, but is preferably 50 to 600 nm, more preferably 80 to 500 nm, and even more preferably 100 to 300 nm.

[0019] <EO Material Containing Liquid Crystal Compound> The EO material containing a liquid crystal compound that is present between the electrodes in the slot waveguide is not particularly limited, and the materials described below can be used appropriately.

[0020] (Liquid Crystal Compound) As the liquid crystal compound, either a polymer liquid crystal compound or a low molecular weight liquid crystal compound can be used, with polymer liquid crystal compounds being preferred due to their ability to increase the degree of orientation. Furthermore, as the liquid crystal compound, a polymer liquid crystal compound and a low molecular weight liquid crystal compound may be used in combination. Here, "polymer liquid crystal compound" refers to a liquid crystal compound having a repeating unit in its chemical structure. Furthermore, "low molecular weight liquid crystal compound" refers to a liquid crystal compound having no repeating unit in its chemical structure. Examples of polymer liquid crystal compounds include the thermotropic liquid crystal polymers described in JP 2011-237513 A and the polymer liquid crystal compounds described in paragraphs

[0012] to

[0042] of WO 2018 / 199096 A. Examples of low molecular weight liquid crystal compounds include the liquid crystal compounds described in paragraphs

[0072] to

[0088] of JP 2013-228706 A, with liquid crystal compounds exhibiting smectic properties being preferred. Examples of such liquid crystal compounds include those described in paragraphs

[0019] to

[0140] of WO 2022 / 014340, the disclosures of which are incorporated herein by reference.

[0021] In particular, preferred examples of the polymer liquid crystal compound include liquid crystal compounds having a repeating unit represented by the following formula (1), which is described in paragraph

[0014] of WO 2018 / 199096:

[0022] In the above formula (1), R １ represents a hydrogen atom or a methyl group, L １ and L ２ each independently represents a single bond or a divalent linking group; M １ represents a mesogen group represented by formula (1-1) described below, T １ represents a terminal group.

[0023] Furthermore, suitable examples of the low molecular weight liquid crystal compound include the compound represented by the following formula (2) described in paragraph

[0074] of JP-A No. 2013-228706: １ -V １ -W １ -X １ -Y１ -X ２ -Y ２ -X ３ -W ２ -V ２ -U ２ (2) [In formula (2), X １ , X ２ and X ３ each independently represents an optionally substituted 1,4-phenylene group or an optionally substituted cyclohexane-1,4-diyl group, provided that X １ , X ２ and X ３ At least one of the groups is a 1,4-phenylene group which may have a substituent. The -CH2- constituting the cyclohexane-1,4-diyl group which may have a substituent may be replaced by -O-, -S- or -NR-. R is an alkyl group having 1 to 6 carbon atoms or a phenyl group. Y １ and Y ２ are each independently —CH ２ CH ２ -, -CH ２ O-, -COO-, -OCOO-, single bond, -N=N-, -CR ａ =CR ｂ -, -C≡C- or -CR ａ =N-. ａ and R ｂ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. １ represents a hydrogen atom or a polymerizable group. ２ represents a polymerizable group. １ and W ２ each independently represents a single bond, —O—, —S—, —COO— or —OCOO—. １ and V ２ each independently represents an alkanediyl group having 1 to 20 carbon atoms which may have a substituent, and —CH ２ - may be replaced by -O-, -S- or -NH-.]

[0024] The content of the liquid crystal compound in the EO material is preferably 40 to 95% by mass, and more preferably 50 to 90% by mass, based on the total mass of the solid content of the EO material.

[0025] (Organic Dye) The EO material containing a liquid crystal compound, which is present between the electrodes in the slot waveguide, may further contain an organic dye. The organic dye is not particularly limited, and a conventionally known organic EO material can be used. However, the organic dye should have a second-order molecular susceptibility of 300×10 －３０ It is preferable to use an organic dye of 500×10 －３０ More than 10000 x 10 －３０ It is more preferable to use an organic dye of esu or less. Here, the second-order molecular susceptibility of the organic dye refers to a value calculated by the density functional method using Gaussian 16 under the following conditions: Functional: M06x02 Basis function: 6-31+g(d,p) Solvent effect: chloroform Other conditions: default values ​​of Gaussian 16

[0026] When the EO material contains an organic dye, the content of the organic dye is preferably 3 to 30% by mass, more preferably 5 to 20% by mass, based on the total mass of the solid content of the EO material.

[0027] (Formation Method) The method for providing an EO material between electrodes in a slot waveguide is not particularly limited. For example, a method including, in this order, a step of applying an EO composition containing the above-described liquid crystal compound and an optional organic dye to a region including the region between the electrodes to form a coating film, a step of orienting the liquid crystal compound and the optional organic dye contained in the coating film, and a step of performing a poling treatment. Specific examples of the method for applying the EO composition include known methods such as roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spraying, and inkjet printing. Furthermore, the method for orienting the liquid crystal compound and the optional organic dye contained in the coating film is not particularly limited, and any conventionally known method for orienting an EO material can be appropriately adopted. Furthermore, the method for the poling treatment is not particularly limited, and known poling treatments such as optical poling and electric field poling can be adopted. Among these, the electric field poling method is particularly preferred in terms of the simplicity of the apparatus and the high degree of orientation obtained.

[0028] [Protective Layer] The protective layer of the optical modulation device of the present invention is a protective layer that covers the surface of the EO material present in the slot waveguide. Furthermore, as described above, the protective layer of the optical modulation device of the present invention is a protective layer obtained by curing a composition (hereinafter also referred to as a "protective layer-forming composition") that satisfies at least one of the following conditions 1 and 2: Condition 1: Contains compound A having an acidic group and a crosslinking group. Condition 2: Contains compound B that has an acidic group and no crosslinking group, and compound C that has a crosslinking group and no acidic group. When the protective layer of the optical modulation device of the present invention is a protective layer obtained by curing a protective layer-forming composition that satisfies the above condition 1, the protective layer-forming composition before curing may further contain either compound B or compound C, or may further contain both compound B and compound C.

[0029] <Compounds A to C> In the present invention, the compounds A to C specified in the above-mentioned conditions 1 and 2 are preferably binding agents (binders). Furthermore, the compounds A to C are preferably the main components of the protective layer-forming composition (referring to the components whose content relative to the total mass of the solid contents is the largest; the same applies hereinafter), more preferably components that account for 30 mass% or more relative to the total mass of the solid contents of the protective layer-forming composition, even more preferably components that account for 40 mass% or more relative to the total mass of the solid contents of the protective layer-forming composition, and particularly preferably components that account for more than 50 mass% relative to the total mass of the solid contents of the protective layer-forming composition.

[0030] (Acidic Group) The acidic group possessed by Compound A or Compound B is not particularly limited, and examples thereof include a phenolic hydroxyl group, a carboxyl group, a hydroxamic acid group, a sulfonic acid group, a boronic acid group, a carbamoyl group, a sulfamoyl group, a sulfoximine group (-SH(=O)(=NH)), and a tetrazolyl group. Among these acidic groups, NaCO ３ From the viewpoint of solubility in a developer containing a component such as hydroxyl group or KOH as a main component, the hydroxyl group is preferably at least one group selected from the group consisting of a phenolic hydroxyl group and a carboxyl group, and more preferably a carboxyl group.

[0031] (Crosslinking Group) The crosslinking group possessed by Compound A or Compound C is not particularly limited, and examples thereof include a (meth)acryloyloxy group, an epoxy group, an oxetanyl group, and a vinyloxy group. Among these crosslinking groups, from the viewpoints of increasing the density of the protective layer, decreasing the degree of swelling, and improving the stability of the coating solution during production, at least one group selected from the group consisting of a (meth)acryloyloxy group, an epoxy group, and an oxetanyl group is preferred, and a (meth)acryloyloxy group is more preferred.

[0032] (Other Functional Groups) In the present invention, for reasons of making the protective layer low in moisture permeability and suppressing deterioration of the EO material, it is preferred that at least one of the compounds A to C specified in the above-mentioned conditions 1 and 2 is a compound further having any one of a styryl group, an adamantyl group, and a cyclopentanyl group in addition to the above-mentioned acidic group and crosslinking group.

[0033] In the present invention, the compounds A to C specified in the above conditions 1 and 2 are preferably polymers (hereinafter also referred to as "binder polymers") that are the main components of the protective layer-forming composition and have repeating units in their chemical structure. Here, the structure of the main chain of the repeating units is not particularly limited, and known structures can be used. For example, a skeleton selected from the group consisting of (meth)acrylic, styrene, siloxane, cycloolefin, methylpentene, amide, and aromatic ester is preferred. Of these, a skeleton selected from the group consisting of (meth)acrylic, siloxane, and cycloolefin is more preferred, and a (meth)acrylic skeleton is even more preferred.

[0034] Furthermore, when the compounds A to C specified in the above conditions 1 and 2 are binder polymers, it is preferable that the above-mentioned acidic group, crosslinking group, and other functional groups are present in the side chains of the repeating units. In particular, the binder polymer is preferably compound A specified in the above condition 1, and more preferably a copolymer having the above-mentioned acidic group, crosslinking group, and other functional groups in the side chains of separate repeating units.

[0035] Furthermore, when the compounds A to C specified in the above conditions 1 and 2 are binder polymers, the weight average molecular weight (Mw) of the binder polymer is not particularly limited, but is preferably 5,000 to 500,000, more preferably 7,000 to 300,000, and even more preferably 10,000 to 200,000. Here, the weight average molecular weight in the present invention is a value measured by gel permeation chromatography (GPC) under the conditions shown below. Solvent (eluent): THF (tetrahydrofuran) Apparatus name: TOSOH HLC-8320GPC Column: Three TOSOH TSKgel Super HZM-H (4.6 mm x 15 cm) connected together Column temperature: 40°C Sample concentration: 0.1% by mass Flow rate: 1.0 ml / min Calibration curve: A calibration curve using seven samples of TSK standard polystyrene manufactured by TOSOH with Mw = 2,800,000 to 1,050 (Mw / Mn = 1.03 to 1.06) was used.

[0036] In the present invention, the composition for forming a protective layer is preferably an alkali-developable composition, because it allows for easy formation of a protective layer by photolithography. Here, "alkali-developable" refers to the property of being dissolved in an alkaline developer, and specifically, it is sufficient that the composition has solubility to the extent that the intended development process can be carried out. In addition, the method for obtaining an alkali-developable composition is not particularly limited, and examples thereof include a method of introducing an acidic group into a component contained in the composition for forming a protective layer. For example, a method of incorporating the above-mentioned compound A or compound B as a main component is preferably used.

[0037] <Singlet oxygen quencher or antioxidant> In the present invention, the protective layer preferably contains a singlet oxygen quencher or antioxidant, because this can suppress deterioration of any organic dye contained in the EO material. That is, in the present invention, the composition for forming a protective layer preferably contains a singlet oxygen quencher or antioxidant. Here, examples of singlet oxygen quenchers or antioxidants include vitamin derivatives (e.g., trolox, ascorbic acid, riboflavin, tocopherol, etc.) and hindered amine light stabilizers, and these may be used alone or in combination of two or more.

[0038] <Other Components> The protective layer-forming composition may contain other components in addition to the components described above, such as a polyfunctional monomer, a polymerization initiator, a thermally crosslinkable compound, a hydrogen donor compound, a surfactant, and a solvent, which will be described later.

[0039] (Polyfunctional Monomer) Examples of the polyfunctional monomer include polyfunctional monomers having two or more (meth)acryloyloxy groups, and specifically include trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate. Note that, if such polyfunctional monomers do not have an acidic group, they fall under the category of compound C defined in the above-mentioned condition 2.

[0040] (Polymerization initiator) The polymerization initiator is not particularly limited, but is preferably a photosensitive compound, i.e., a photopolymerization initiator. As the photopolymerization initiator, various compounds can be used without any particular limitation. Examples of the photopolymerization initiator include α-carbonyl compounds (U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (U.S. Pat. No. 2,722,512), polynuclear quinone compounds (U.S. Pat. Nos. 3,046,127 and 2,951,758), and combinations of triarylimidazole dimers and p-aminophenyl ketones (U.S. Pat. No. 3,549,367). ), acridine and phenazine compounds (JP 60-105667 A and U.S. Pat. No. 4,239,850 A), oxadiazole compounds (U.S. Pat. No. 4,212,970 A), o-acyloxime compounds (JP 2016-27384 A

[0065] ), and acylphosphine oxide compounds (JP 63-40799 A, JP 5-29234 A, JP 10-95788 A, and JP 10-29997 A). Commercially available photopolymerization initiators can also be used, including Irgacure-184, Irgacure-907, Irgacure-369, Irgacure-651, Irgacure-819, Irgacure-OXE-01, and Irgacure-OXE-02 manufactured by BASF.

[0041] (Thermal Crosslinkable Compound) Examples of the thermal crosslinkable compound include methylol compounds and blocked isocyanate compounds, with blocked isocyanate compounds being preferred. Examples of the blocked isocyanate compound include 2-(0-[1'-methylpropylideneamino]carboxyamino)ethyl methacrylate and 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate.

[0042] (Hydrogen Donor Compound) The hydrogen donor compound has the effect of further improving the sensitivity of the polymerization initiator to actinic rays and suppressing the inhibition of polymerization of polyfunctional monomers by oxygen. Examples of the hydrogen donor compound include amines and amino acid compounds. Examples of the amines include 4,4'-bis(diethylamino)benzophenone and tris(4-dimethylaminophenyl)methane. Examples of the amino acid compounds include N-phenylglycine, N-methyl-N-phenylglycine, and N-ethyl-N-phenylglycine.

[0043] (Surfactant) Examples of surfactants include anionic surfactants, cationic surfactants, nonionic (non-ionic) surfactants, and amphoteric surfactants. The surfactant is preferably a nonionic surfactant. The surfactant is preferably a fluorine-based surfactant or a silicone-based surfactant.

[0044] (Solvent) Examples of the solvent include ketones [e.g., acetone, 2-butanone, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclopentanone, cyclohexanone, acetylacetone, etc.], ethers [e.g., dioxane, tetrahydrofuran, tetrahydropyran, dioxolane, tetrahydrofurfuryl alcohol, cyclopentyl methyl ether, dibutyl ether, etc.], aliphatic hydrocarbons [e.g., hexane, etc.], alicyclic hydrocarbons [e.g., cyclohexane, etc.], aromatic hydrocarbons [e.g., benzene, toluene, xylene, tetralin, trimethylbenzene, etc.), halogenated carbons [for example, dichloromethane, trichloromethane (chloroform), dichloroethane, dichlorobenzene, 1,1,2,2-tetrachloroethane, chlorotoluene, etc.], esters [for example, methyl acetate, ethyl acetate, butyl acetate, diethyl carbonate, ethyl acetoacetate, n-pentyl acetate, ethyl benzoate, benzyl benzoate, propylene glycol monomethyl ether acetate (MFG-Ac), butyl carbitol acetate, Examples of suitable solvents include organic solvents such as ethanol, isopropanol, butanol, cyclohexanol, furfuryl alcohol, 2-ethylhexanol, octanol, benzyl alcohol, ethanolamine, ethylene glycol, propylene glycol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, phenols (e.g., phenol, cresol), cellosolves (e.g., methyl cellosolve, ethyl cellosolve, 1,2-dimethoxyethane), cellosolve acetates, sulfoxides (e.g., dimethyl sulfoxide), amides (e.g., dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, 1,3-dimethyl-2-imidazolidinone), and heterocyclic compounds (e.g., pyridine, 2,6-lutidine), as well as water. These solvents may be used alone or in combination of two or more.

[0045] The protective layer of the optical modulation device of the present invention is a protective layer obtained by curing the above-mentioned protective layer-forming composition, and it is preferable that the protective layer is a protective layer obtained by curing the above-mentioned protective layer-forming composition with light or heat.

[0046] In the present invention, the thickness of the protective layer is preferably thicker in order to block humidity and oxygen, but from the viewpoint of manufacturing, it is preferably 2 to 50 μm, and more preferably 2 to 40 μm. Here, the thickness of the protective layer is calculated as the average value when 100 points are measured at 1 cm intervals over an area of ​​10 cm × 10 cm using a pencil-type high-precision digital length measuring instrument PHA-13W manufactured by Tosei Engineering Co., Ltd., with an E-ST-100DB stand attached, and a MINICOM-M (Model E-M) as a display device.

[0047] Furthermore, in the present invention, in order to prevent deterioration of EO performance over time due to the environment, it is preferable that the mass change of the protective layer upon heating at 150°C is 0.8% by mass or less, and that the thermal expansion coefficient at 150°C is 150 ppm or less. Here, the mass change at 150°C refers to a value measured and calculated according to the following procedure. First, 100 mg of the protective layer is scraped off with a spatula and placed in an aluminum pan, and the initial mass A is measured. Next, the sample is heated in an oven at 150°C for 1 hour. Thereafter, the sample is removed from the oven and cooled to room temperature, and then the mass B is measured. The mass change is then calculated from (B - A) / A x 100. Furthermore, the coefficient of thermal expansion (CTE) at 150°C is measured using a thermal analysis machine TMA7100 (manufactured by Hitachi High-Tech Science Corporation) after forming a protective layer on a silicon wafer.

[0048] [Alignment Layer] In the optical modulation device of the present invention, in the above-mentioned slot waveguide, an alignment layer may be provided between the two electrodes arranged on the substrate and the EO material containing a liquid crystal compound. The alignment layer may be any layer that can bring the liquid crystal compound contained in the EO material into a desired alignment state. However, from the viewpoint of ease of control of the pretilt angle of the alignment layer, an alignment layer formed by a rubbing treatment (rubbing treatment alignment layer) is preferred, and from the viewpoint of uniformity of alignment, a photo-alignment layer formed by light irradiation is preferred.

[0049] The thickness of the alignment layer is not particularly limited, but is preferably 0.01 to 2.0 μm, and more preferably 0.01 to 1.0 μm. The thickness of the alignment layer is calculated as the average value of measurements taken at any five points using a surface roughness meter (for example, P-10 (manufactured by TENCOR Corporation)).

[0050] [Method for manufacturing optical modulation device] The method for manufacturing an optical modulation device of the present invention includes a composition layer forming step of applying a protective layer-forming composition to the surface of an electro-optical material present in a slot waveguide to form a protective composition layer, and a protective layer forming step of curing at least a portion of the protective composition layer to form a protective layer. Furthermore, the method for manufacturing an optical modulation device of the present invention preferably includes a development step of removing a portion of the protective composition layer between the composition layer forming step and the protective layer forming step.

[0051] [Composition Layer Forming Step] The composition layer forming step is a step of applying a protective layer forming composition to the surface of the electro-optical material present in the slot waveguide to form a protective composition layer. Here, examples of the protective layer forming composition include the protective layer forming composition described above in relation to the protective layer of the optical modulation device of the present invention. In addition, examples of methods for applying the protective layer forming composition include slit coating, spin coating, curtain coating, and inkjet coating.

[0052] In the present invention, the composition layer forming step may include a drying treatment after applying the protective layer-forming composition. Here, the drying temperature and time are not particularly limited, but from the viewpoint of maintaining the presence of the acid group of Compound A or Compound B contained in the protective layer-forming composition, the drying is preferably performed at 80 to 150°C for 30 seconds to 5 minutes.

[0053] [Development Step] The development step is a step of removing a portion of the protective composition layer, and preferably includes an exposure step and a development step. A preferred example of the exposure step is a step of exposing the protective composition layer to light through a predetermined mask, which induces crosslinking and / or polymerization in the exposed region, resulting in hardening. A preferred example of the development step is a step of removing the unexposed portion of the protective composition layer using an alkaline developer.

[0054] [Protective Layer Forming Step] The protective layer forming step is a step of forming a protective layer by curing at least a portion of the protective composition layer (for example, a portion that has been subjected to exposure treatment in the development step). Here, from the viewpoint of the temporal stability of the protective layer, the curing treatment is preferably a treatment of removing acid groups derived from Compound A or Compound B contained in the protective layer forming composition, and is preferably carried out at 80 to 150°C for 10 to 30 minutes.

[0055] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, and treatment procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0056] [Example 1] [Formation of Alignment Layer] In accordance with Example 1 of JP 2021-167851 A, a slot waveguide (optical waveguide) precursor was prepared in the state before filling with the EO material 141 shown in FIG. 1 attached hereto. The sizes of the prepared precursors indicated by the symbols in FIG. 1 are as follows. Next, an alignment layer coating solution having the following composition was spin-coated between the two electrodes of the prepared precursor, i.e., in the region where the EO material was to be filled, and dried at 110°C for 2 minutes to form an alignment layer having a thickness of 0.05 μm. The resulting alignment film was then subjected to a rubbing treatment (roller rotation speed: 1000 rpm / spacer thickness 1.8 mm, stage speed 1.8 m / min) once in the slot length direction. Hs2: 190 nm Hs1: 45 nm Hr: 190 nm Wslot: 160 nm Wrail: 240 nm Wslab1: 2 μm Wslab2: 18 μm Length of the optical modulator 100 in the Z-axis direction: 1 mm

[0057] -------------------------------------------------- Coating liquid for alignment layer -------------------------------------------------- 2.0 parts by mass of modified polyvinyl alcohol (listed below) 23.9 parts by mass Methanol 74.1 parts by mass Distilled water 0.06 parts by mass Photopolymerization initiator (IRGACURE 2959, manufactured by BASF) --------------------------------------------------

[0058] Modified polyvinyl alcohol (in the formula below, the numbers for each repeating unit represent the molar ratio.)

[0059] [Formation of Electro-Optical Material Layer (EO Material Layer)] An EO material layer coating solution having the following composition was spin-coated at 400 rpm onto the rubbed alignment layer, and then applied at 130°C for 30 seconds, followed by drying to form an EO material layer with a thickness of 0.5 μm. This was then subjected to a dye alignment treatment (poling) and an exposure treatment (dye fixation) using a PLA-501F exposure machine (ultra-high pressure mercury lamp) manufactured by Canon Inc.

[0060] EO material layer coating liquid ――――――――――――――――――――――――――――――――――― 0.050 parts by mass of organic dye A shown below 0.360 parts by mass of liquid crystal compound A shown below 0.090 parts by mass of liquid crystal compound B shown below 0.010 parts by mass of oxime polymerization initiator (NCI-730) 4.490 parts by mass ―――――――――――――――――――――――――――――――――――

[0061] Organic dye A (second-order molecular susceptibility: 1806 × 10 －３０ esu)

[0062] Liquid crystal compound A (weight average molecular weight: 12,000, the values ​​in the following formula represent the mass % of each repeating unit)

[0063] Liquid crystal compound B

[0064] [Formation of Protective Layer] <Composition Layer Formation Step> A composition for forming a protective layer having the following formulation was applied onto the EO material layer using a spin coating method, adjusted so that the thickness after drying would be 20 μm, and dried at a temperature of 120° C. for 2 minutes, and then the solvent was thoroughly removed using a vacuum dryer to form a composition layer.

[0065] ------------------------------------------------ Composition for Forming Protective Layer ------------------------------------------------ (Compound A) The following polymer P-1 [styrene-derived structural unit (St) / dicyclopentanyl methacrylate-derived structural unit (DCPMA) / methacrylic acid-derived structural unit (MAA) / structural unit obtained by adding glycidyl methacrylate to a methacrylic acid-derived structural unit (GMA-MAA) = 33.5 / 21.9 / 27.0 / 17.7 (mol %), I / O value = 0.608, nS / (nS + nCy) = 0.55, Mw = 20,000]: 52.87 parts by mass (solid content) Aronix TO-2349 (MO-2, a polyfunctional ethylenically unsaturated compound having a carboxylic acid group, manufactured by Toagosei Co., Ltd.): 3.17 parts by mass (compound C) ・1,6-Hexanediol diacrylate (A-HD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.): 9.52 parts by mass Tricyclodecane dimethanol diacrylate (A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd.): 19.03 parts by mass (photopolymerization initiator) 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyloxime) (Irgacure OXE-02, manufactured by BASF): 0.36 parts by mass 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (Irgacure 907, manufactured by BASF): 0.73 parts by mass (hydrogen donor compound) N-phenylglycine (manufactured by Junsei Chemical Co., Ltd.): 0.10 parts by mass (thermally crosslinkable compound) Karenz AOI-BM (2-(O-[1'-methylpropylideneamino]carboxyamino)ethyl acrylate, manufactured by Showa Denko K.K.): 12.50 parts by mass (surfactant) Fluorine-based surfactant (Megafac F551A, manufactured by DIC Corporation): 0.32 parts by mass (organic solvent) A 1:1 (mass ratio) mixed solvent of 1-methoxy-2-propyl acetate and methyl ethyl ketone was added so that the solids concentration became 29% by mass.

[0066] Polymer P-1

[0067] <Developing Step and Protective Layer Forming Step> The composition layer was exposed to 100 mJ / cm 2 through a predetermined mask using a PLA-501F exposure machine (ultra-high pressure mercury lamp) manufactured by Canon Inc. ２ The composition layer after exposure was then subjected to mask exposure (line width: 20 μm) using an alkaline developer (1.0% by mass of Na ２ CO ３ ) at 23°C for 60 seconds, and then rinsed with ultrapure water for 20 seconds. ２ After the entire surface was exposed to i-rays, post-baking was carried out at 120° C. for 30 minutes to form a protective layer.

[0068] [Manufacturing Process of Light Modulation Device] The EO material layer was heated to about 180°C, and a direct current was applied between the electrodes to align the organic dye in the same direction as the alignment direction of the liquid crystal compound. The EO material layer was then cooled to about room temperature (23°C), and the alignment state of the organic dye and the liquid crystal compound was fixed. Thereafter, a 1000 mJ / cm exposure was performed using a PLA-501F exposure machine (ultra-high pressure mercury lamp) manufactured by Canon Inc. ２ The entire surface was exposed (completely fixed) with 1000 kJ / cm 2 to prepare a light modulation device.

[0069] Example 2 An optical modulation device was fabricated in the same manner as in Example 1, except that 0.4 parts by mass of Trolox (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), a singlet oxygen quencher, was added to the composition for forming the protective layer.

[0070] Example 3 A light modulation device was produced in the same manner as in Example 1, except that 0.4 parts by mass of riboflavin (manufactured by Tokyo Chemical Industry Co., Ltd.), a singlet oxygen quencher, was added to the protective layer-forming composition.

[0071] [Example 4] A light modulation device was produced in the same manner as in Example 1, except that 0.4 parts by mass of a hindered amine light stabilizer (Tinuvin 123, manufactured by BASF), which is a singlet oxygen quencher, was added to the composition for forming the protective layer.

[0072] Example 5 An optical modulation device was produced in the same manner as in Example 1, except that an epoxy resin (EHPE3150, manufactured by Daicel Corporation) was used as the protective layer-forming composition instead of the polymer P-1 described above.

[0073] Example 6 An optical modulation device was produced in the same manner as in Example 1, except that the following polymer P-2 (corresponding to compound B) was used as the protective layer-forming composition instead of the above-described polymer P-1, and 31.7 parts by mass of dipentaerythritol hexaacrylate (DPHA, manufactured by Tokyo Chemical Industry Co., Ltd.) (corresponding to compound C) was blended instead of the two types of 1,6-hexanediol diacrylate (A-HD-N) and tricyclodecane dimethanol diacrylate (A-DCP).

[0074] Polymer P-2 (weight average molecular weight: 30,000)

[0075] Example 7 An optical modulation device was produced in the same manner as in Example 1, except that the alignment layer used in Example 1 was changed to the optical alignment layer described below. <Optical Alignment Layer> With reference to the description in Example 3 of JP 2012-155308 A, coating solution 1 for a photo-alignment film was prepared and applied with a wire bar. The coated layer was then dried with hot air at 60°C for 60 seconds to produce a coated layer with a thickness of 50 nm. Thereafter, a PLA-501F exposure machine (ultra-high pressure mercury lamp) manufactured by Canon Inc. was used to irradiate the coated layer with linearly polarized light at 1000 mJ / cm through a polarizing plate. ２ The photo-alignment layer was formed.

[0076] Example 8 An optical modulation device was fabricated in the same manner as in Example 1, except that the sizes of the slot waveguide (optical waveguide) precursor to be fabricated, as indicated by the symbols in FIG. 1, were changed to the following sizes: Hs2: 250 nm Hs1: 45 nm Hr: 250 nm Wslot: 500 nm Wrail: 240 nm Wslab1: 2 μm Wslab2: 18 μm Length of the optical modulator 100 in the Z-axis direction: 1 mm

[0077] Comparative Example 1 An optical modulation device was fabricated in the same manner as in Example 1, except that no protective layer was used.

[0078] Comparative Example 2 A light modulation device was produced in the same manner as in Example 1, except that the components and blending amounts of the protective layer-forming composition were changed to those shown in Table 1 below.

[0079] [Evaluation] [Evaluation of Water Vapor Transmission Rate (WVTR, Moisture Permeability)] <Preparation of Protective Layer Transfer Film> Using a slit nozzle, the protective layer-forming composition used in Examples 1 to 8 and Comparative Example 2 was applied onto a 16 μm-thick polyethylene terephthalate film (temporary support, 16QS62 (manufactured by Toray Industries, Inc.)) in an amount adjusted to a dried thickness of 20 μm, and the coating was dried in a hot air convection dryer with a temperature gradient of 75° C. to 120° C. to remove the solvent, thereby forming a protective layer. Thereafter, a protective layer transfer film was prepared using a 12 μm-thick polypropylene film as a cover film.

[0080] - Preparation of a sample for measuring moisture permeability - The cover film was peeled off from the obtained transfer film, and then the film was laminated onto a PTFE (tetrafluoroethylene resin) membrane filter FP-100-100 manufactured by Sumitomo Electric Industries, Ltd. to form a laminate A having a layer structure of temporary support / protective layer / membrane filter. The lamination conditions were a membrane filter temperature of 40°C, a laminar temperature of 100°C, a linear pressure of 3 N / cm, and a conveying speed of 4 m / min. Furthermore, the temporary support was peeled off from laminate A, and the transfer film with the polypropylene film peeled off from the protective layer was laminated four more times in the same manner as above to form a laminate B having a layer structure of temporary support / protective layer x 5 layers / membrane filter. The protective layer of the obtained laminate B was exposed to an exposure dose of 120 mJ / cm through the temporary support using a proximity exposure machine (manufactured by Hitachi High-Tech Electronics Engineering Co., Ltd.) equipped with an ultra-high pressure mercury lamp. ２ After peeling off the temporary support, the film was further exposed to 1000 mJ / cm ２ After exposure to i-rays, the photosensitive layer was cured by post-baking at 145° C. for 30 minutes to form a cured film. As a result, a sample for moisture permeability measurement having a laminated structure of a protective layer / membrane filter with a total film thickness of 80 μm was obtained.

[0081] - Measurement of Water Vapor Transmission Rate (WVTR) - Using a moisture permeability measurement sample, moisture permeability measurement was performed using the cup method with reference to JIS-Z-0208 (1976). Details are explained below. First, a circular sample with a diameter of 70 mm was cut out from the moisture permeability measurement sample. Next, 20 g of dried calcium chloride was placed in a measuring cup, and then the circular sample was used to cover the measuring cup, thereby preparing a lidded measuring cup. This lidded measuring cup was left in a constant temperature and humidity chamber under conditions of 65°C and 90% RH for 24 hours. The water vapor transmission rate (WVTR) (unit: g / (m2·day)) of the circular sample was calculated from the change in mass of the lidded measuring cup before and after leaving it. The above measurement was performed three times, and the average WVTR value for the three measurements was calculated. Based on the average WVTR, the water vapor transmission rate (WVTR) was evaluated according to the following evaluation criteria. In the following evaluation criteria, A, B, or C is preferable, A or B is more preferable, and A is most preferable. In the above measurement, as described above, the WVTR of a circular sample having a laminated structure of a protective layer / membrane filter was measured. However, since the WVTR of the membrane filter is extremely higher than the WVTR of the cured film, the above measurement essentially measured the WVTR of the cured film itself. - Evaluation criteria for water vapor transmission rate (WVTR) - A: The average WVTR is 220 g / (m ２ B: The average WVTR value is less than 220 g / (m ２ ・day) or more 240g / (m ２ C: The average WVTR value is less than 240 g / (m ２ ・day) or more 260g / (m ２ D: The average WVTR value is less than 260 g / (m ２ ・day) or more 280g / (m ２ E: The average WVTR value is less than 280 g / (m ２ ・day) or more

[0082] [Swelling Degree] An EO material layer was formed on a glass substrate by applying the EO material layer coating solution used in Examples 1 to 8 and Comparative Examples 1 and 2. Next, in Examples 1 to 8 and Comparative Example 2, the protective layer-forming composition described above was applied to the EO material layer, and a protective layer was formed by the method described in Examples 1 to 8 and Comparative Example 2, thereby preparing a measurement sample. Note that, for Comparative Example 1, the measurement sample was one without a protective layer. The swelling degree of the measurement sample prepared above was measured. Specifically, a laser-based three-dimensional shape measuring device (Zygo NewView 6300, manufactured by Zygo) was used to measure the height of the measurement sample near the center in the width direction, relative to the glass surface. Specifically, measurements were taken before and after the swelling procedure described below. The measured value before the swelling procedure was designated as film thickness 1, and the measured value after the swelling procedure was designated as film thickness 2, and the swelling degree was calculated according to the following formula (1): During the measurement, in order to reduce the influence of thickness variations depending on the location, the measurement position of film thickness 1 was recorded, and the same position was measured for film thickness 2. (Swelling degree) = (film thickness 2) / (film thickness 1) × 100 [unit: %] ... formula (1) <Swelling procedure> A measurement solvent, triethylene glycol dimethyl ether (CH ３ (OCH ２ CH ２ ) ３ OCH ３ ) was filled in the measurement solvent, and the measurement sample was immersed in the measurement solvent and left to stand for 8 hours at 23±1° C. In measuring film thickness 2, after leaving the sample to stand for 8 hours, the measurement sample was taken out of the measurement solvent and air was blown with an air gun for 5 seconds to remove the measurement solvent remaining on the surface of the electro-optical material, and then the measurement was carried out.

[0083] [Dye Deterioration] A measurement sample similar to the measurement sample for the swelling degree was prepared. Then, using the apparatus shown in FIG. 2, the change in absorbance of the sample was measured before and after 24 hours of irradiation with a 1550 nm laser under the following measurement conditions. The transmission optical density (OD １ ) was measured at a wavelength λmax, and the transmission optical density (OD ０ ) was measured in the same manner. １ / OD０ The value was calculated by multiplying the measured value by 100%. <Measurement conditions> - A CW (Continuous Wave) laser with a wavelength of 1550 nm was used - A CW laser with a λmax of 670 nm, which is a wavelength close to the absorption peak of EO chromophore, was used as the probe beam - An isolator (IO-H-1550FC - Fiber isolator, manufactured by THORLABS) was used to prevent reflected light from returning - The fiber was replaced using a replacement device during probe measurement - The MFD (Mode Field Diameter) of the optical fiber was converted from 10 to 3.2 μm using an MFD conversion fiber (FC / PC type, manufactured by Delta Fiber) - The maximum light intensity at the tip of the optical fiber was 1.7 MWcm －２ The tip of the MFD conversion fiber is brought into contact with the surface of the EO material layer, and the intensity of the probe beam passing through the sample is measured using an integrating sphere and a Si photodetector.

[0084] [Lithographic Properties (Evaluation of Resolution)] The protective layer-forming compositions used in Examples 1 to 8 and Comparative Example 2 were slit-coated onto a glass substrate (Corning 1737, 0.7 mm thick (manufactured by Corning Incorporated)), and then pre-baked on a hot plate at 120°C for 120 seconds to volatilize the solvent, forming a protective layer with a film thickness of 20 μm. Next, the obtained protective layer was exposed to 100 mJ / cm through a predetermined mask using a PLA-501F exposure machine (ultra-high pressure mercury lamp) manufactured by Canon Inc. ２ The photosensitive composition layer was exposed to light using a mask (line and space ratio 1:2). The exposed photosensitive composition layer was then developed with an alkaline developer (1.0% by mass Na2CO3) at 23°C for 60 seconds, and then rinsed with ultrapure water for 20 seconds. <Resolution Evaluation> The resolution was determined as the smallest resolvable line and space pattern. 1 point: 50 μm not resolved 2 points: 50 μm resolved but 20 μm not resolved 3 points: 20 μm resolved but 10 μm not resolved 4 points: 10 μm resolved

[0085] [Adhesion] The EO material layer coating solution used in Examples 1 to 8 and Comparative Example 2 was spin-coated at 400 rpm at 130°C for 30 seconds onto a glass substrate (Corning 1737, 0.7 mm thick (Corning)) that had been subjected to a silane coupling treatment (KBM-603, manufactured by Shin-Etsu Silicones Co., Ltd.), and then dried to form an EO material layer having a thickness of 0.5 µm. The EO material layer was exposed to light at 100 mJ / cm using a PLA-501F exposure machine (ultra-high pressure mercury lamp) manufactured by Canon Inc. ２ (dye fixation). The protective layer-forming composition used in Examples 1 to 8 and Comparative Example 2 was slit-coated thereon, and then pre-baked on a hot plate at 120°C for 120 seconds to volatilize the solvent, forming a protective layer with a thickness of 20 μm. <Evaluation of Adhesion> A cross-cut peel tape test was performed on the protective layer of the sample obtained by the above procedure in accordance with ASTM D 3359. Evaluation was based on the percentage of squares that did not peel from the EO material layer, and was evaluated based on the following criteria. The adhesion performance in the peel tape test was ranked 5B, 4B, 3B, 2B, 1B, and 0B, in descending order of adhesion performance. A: The adhesion strength of the protective layer was 4B or more (very high adhesion). B: The adhesion hardness of the protective layer was 3B (slightly high adhesion). C: The adhesion strength of the protective layer was 2B or less (low adhesion).

[0086]

[0087] The results shown in Table 1 indicate that when a protective layer formed by curing a composition that did not satisfy either condition 1 or 2 was used, properties such as moisture permeability were improved compared to Comparative Example 1, which did not have a protective layer, but adhesion between the protective layer and the EO material was poor (Comparative Example 2). In contrast, when a protective layer formed by curing a composition that satisfied at least one of conditions 1 and 2 was used, values ​​such as moisture permeability were improved compared to Comparative Example 1, which did not have a protective layer, and adhesion between the protective layer and the EO material was also excellent (Examples 1 to 8). In particular, comparison of Examples 1 to 4 indicates that the deterioration of the organic dye can be suppressed when the protective layer contains a singlet oxygen quencher.

[0088] 100 Optical modulation device 105 Substrate 106 Electrode 107 Slot portion 109 Insulating layer 141 EO material 142 Protective layer 200 Slot waveguide

Claims

1. An optical modulation device comprising: a substrate; a slot waveguide having an electro-optical material containing a liquid crystal compound present between two electrodes arranged on the substrate; and a protective layer covering the surface of the electro-optical material present in the slot waveguide, wherein the protective layer is a protective layer formed by curing a composition that satisfies at least one of the following conditions 1 and 2. Condition 1: The protective layer contains a compound A having an acidic group and a crosslinking group. Condition 2: The protective layer contains a compound B having an acidic group and no crosslinking group, and a compound C having a crosslinking group and no acidic group.

2. The light-modulating device of claim 1, wherein said composition is an alkaline-developable composition.

3. The optical modulation device according to claim 1, wherein at least one of the compound A, the compound B, and the compound C is a compound further having any one of a styryl group, an adamantyl group, and a cyclopentanyl group.

4. The optical modulation device according to claim 1, wherein the acidic group possessed by said compound A or said compound B is at least one group selected from the group consisting of a phenolic hydroxyl group and a carboxyl group.

5. The optical modulation device according to claim 1, wherein the crosslinking group possessed by said compound A or said compound C is at least one group selected from the group consisting of an acryloyloxy group, a methacryloyloxy group, an epoxy group, and an oxetanyl group.

6. The optical modulation device according to claim 1, wherein the protective layer has a thickness of 2 to 50 μm.

7. The light modulation device according to claim 1, wherein the protective layer is formed by curing the composition with light or heat.

8. The light modulation device of claim 1, wherein the protective layer contains a singlet oxygen quencher or an antioxidant.

9. The light modulation device according to claim 8, wherein the singlet oxygen quencher or the antioxidant is at least one selected from the group consisting of vitamin derivatives and hindered amine light stabilizers.

10. The optical modulation device according to claim 1, wherein the change in mass of said protective layer when heated to 150°C is 0.8 mass % or less, and the thermal expansion coefficient of said protective layer at 150°C is 150 ppm or less.

11. A method for producing an optical modulation device according to any one of claims 1 to 10, comprising a composition layer forming step of applying a protective layer-forming composition to the surface of an electro-optical material present in a slot waveguide to form a protective composition layer, and a protective layer forming step of curing at least a portion of the protective composition layer to form a protective layer.

12. The method for manufacturing an optical modulation device according to claim 11, further comprising a development step of removing a portion of the protective composition layer between the composition layer forming step and the protective layer forming step.

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