Sealant for flexible GHLC elements

Abstract

An object of the present invention is to provide a sealant for flexible GHLC devices that has excellent adhesion to alignment film-attached films even immediately after light irradiation or under high temperature conditions. The present invention provides a sealant for flexible GHLC elements that contains a curable resin and a photopolymerization initiator, and that has a glass transition temperature of 60°C or lower after curing, a storage modulus of 500 MPa or lower at 25°C, and a storage modulus of 0.01 MPa or higher at 80°C after curing.

Description

[Technical Field]

[0001] The present invention relates to a sealant for flexible GHLC devices. [Background technology]

[0002] Liquid crystal light control devices using liquid crystal materials are widely used as light control devices whose light transmittance changes when a voltage is applied. Liquid crystal light control devices control the amount of light transmission by changing the orientation of liquid crystal molecules by changing the potential difference between transparent electrode layers, and have excellent responsiveness. Known examples of such liquid crystal light control devices include GHLC devices that use guest-host liquid crystals (GHLCs) containing a dichroic dye as a guest and liquid crystal molecules as a host. In particular, flexible GHLC devices manufactured by laminating films have recently attracted attention, replacing conventional GHLC devices manufactured by laminating glass panels. For example, Patent Document 1 discloses a guest-host liquid crystal light control device that includes a pair of substrates having transparent electrodes and a liquid crystal layer sandwiched between the pair of substrates and containing a host liquid crystal and a dichroic dye, in which the substrates are made of a transparent film material having a liquid crystal alignment film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 208765 Summary of the Invention [Problem to be solved by the invention]

[0004] The liquid crystal dropping method is the mainstream method for manufacturing liquid crystal devices. In this method, a frame-shaped seal pattern is formed by applying a sealant to a substrate. Next, while the sealant is still uncured, tiny droplets of liquid crystal are dropped into the frame of the seal pattern. Another substrate is then bonded to the substrate under vacuum, and the sealant is cured to produce a liquid crystal device. This liquid crystal dropping method requires an extremely small amount of sealant to bond the substrates. Therefore, flexible GHLC devices using alignment film-attached substrates, which are difficult to bond, require a sealant that has excellent adhesion to the alignment film. Furthermore, an alignment film is typically temporarily attached to a hard support layer with an adhesive and then bonded to another alignment film. The film is then irradiated with light to cure the sealant before being peeled from the support layer. Conventional sealants exhibit little adhesiveness immediately after light irradiation, which can prevent the temporarily attached alignment film from peeling from the support layer immediately after light irradiation, resulting in peeling between the bonded alignment film films. Furthermore, in the manufacture of liquid crystal elements, a lamination process is usually carried out under high temperature conditions after the process of curing the sealant, but conventional sealants sometimes fail to maintain adhesion during the lamination process and end up peeling off.

[0005] An object of the present invention is to provide a sealant for flexible GHLC devices that has excellent adhesion to alignment film-attached films even immediately after light irradiation or under high temperature conditions. [Means for solving the problem]

[0006] Disclosure 1 relates to a sealant for flexible GHLC elements, which contains a curable resin and a photopolymerization initiator, and in which the cured product has a glass transition temperature of 60°C or less, a storage modulus of 500 MPa or less at 25°C, and a storage modulus of 0.01 MPa or more at 80°C. Disclosure 2 is a sealant for flexible GHLC elements according to Disclosure 1, wherein the curable resin contains a monofunctional (meth)acrylic compound having one (meth)acryloyl group per molecule, and the content of the monofunctional (meth)acrylic compound in 100 parts by mass of the curable resin is 50 parts by mass or more. Disclosure 3 is the sealant for flexible GHLC elements according to Disclosure 2, wherein the curable resin contains a monofunctional (meth)acrylic compound whose homopolymer has a glass transition temperature of 20° C. or lower. Disclosure 4 is the sealant for flexible GHLC elements according to Disclosure 2 or 3, wherein the curable resin contains a monofunctional (meth)acrylic compound having a cyclic ether structure. Disclosure 5 is a sealant for flexible GHLC elements according to Disclosure 1, 2, 3, or 4, wherein the curable resin contains a polyfunctional (meth)acrylic compound having two or more (meth)acryloyl groups in one molecule, and the content of the polyfunctional (meth)acrylic compound in 100 parts by mass of the curable resin is 0.1 parts by mass or more and 50 parts by mass or less. The present disclosure 6 is a sealant for a flexible GHLC element according to the present disclosure 1, 2, 3, 4, or 5, further comprising a thermoplastic resin. Disclosure 7 is a sealant for flexible GHLC elements according to Disclosure 1, 2, 3, 4, 5, or 6, wherein the molecular weight between crosslinks of the cured product is 100 g / mol or more and 20,000 g / mol or less. The present disclosure 8 is a sealant for flexible GHLC elements according to the present disclosure 1, 2, 3, 4, 5, 6 or 7, which has a viscosity of 1 Pa·s or more measured at 25°C and 1 rpm using an E-type viscometer. The present invention will be described in detail below.

[0007] The present inventors have investigated how to improve the adhesiveness of a sealant for flexible GHLC elements immediately after light irradiation by setting the glass transition temperature of the cured product at or below a specific temperature and the storage modulus at 25° C. to or below a specific value, and further, how to maintain the adhesiveness even under high temperature conditions by preventing the storage modulus at 80° C. from decreasing significantly from the storage modulus at 25° C. As a result, the present inventors have found that it is possible to obtain a sealant for flexible GHLC elements that has excellent adhesiveness to alignment film-attached films even immediately after light irradiation and under high temperature conditions, and have completed the present invention.

[0008] The sealant for flexible GHLC elements of the present invention has an upper limit of the glass transition temperature of the cured product of 60°C. Since the glass transition temperature of the cured product is 60°C or lower and the storage modulus at 25°C (described later) is 500 MPa or lower, the sealant for flexible GHLC elements of the present invention has excellent adhesion to alignment film-attached films even immediately after light irradiation. The upper limit of the glass transition temperature of the cured product is preferably 50°C, more preferably 40°C. There is no particular preferred lower limit for the glass transition temperature of the cured product, but the substantial lower limit is -70°C. In this specification, the glass transition temperature of the cured product can be determined as the temperature at the maximum value of the loss tangent (tan δ) when the dynamic viscoelasticity of a 300 μm-thick cured product is measured using a dynamic viscoelasticity measuring device under the following conditions: test piece width 5 mm, grip width 25 mm, heating rate 10°C / min, temperature range -80°C to 200°C, and frequency 10 Hz. The dynamic viscoelasticity measuring device can be, for example, a DVA-200 (manufactured by IT Instrumentation & Control Co., Ltd.). The cured product for measuring the glass transition temperature and storage modulus (described later) can be obtained by light irradiation alone or by light irradiation and heating, depending on the curing type of the flexible GHLC element sealant. Specific curing methods include a wavelength of 365 nm and an illuminance of 100 mW / cm for a photocurable sealant. 2 For photothermal curing sealants, the wavelength is 365 nm and the illuminance is 100 mW / cm. 2For example, the method involves irradiating the film with light for 30 seconds and then heating it at 80°C for 60 minutes.

[0009] The sealant for flexible GHLC elements of the present invention has a storage modulus of 500 MPa at 25°C for the cured product. Since the storage modulus of the cured product at 25°C is 500 MPa or less and the glass transition temperature of the cured product is 60°C or less, the sealant for flexible GHLC elements of the present invention has excellent adhesion to alignment film-attached films even immediately after light irradiation. The upper limit of the storage modulus of the cured product at 25°C is preferably 100 MPa, more preferably 50 MPa. From the viewpoint of moisture permeability prevention, the lower limit of the storage modulus of the cured product at 25° C. is preferably 0.01 MPa, and more preferably 0.05 MPa. The storage modulus of the cured product at 25°C and the storage modulus of the cured product described below at 80°C can be measured by performing dynamic viscoelasticity measurement on a 300 μm thick cured product in the same manner as for the glass transition temperature of the cured product described above.

[0010] The sealant for flexible GHLC elements of the present invention has a lower limit of storage modulus at 80°C of 0.01 MPa for the cured product. Since the storage modulus at 80°C of the cured product is 0.01 MPa or more, the sealant for flexible GHLC elements of the present invention can maintain adhesion to alignment film-attached films even under high temperature conditions. The lower limit of the storage modulus at 80°C of the cured product is preferably 0.02 MPa, more preferably 0.04 MPa. It is also preferred that the difference between the storage modulus of the cured product at 80°C and that at 25°C is small, and although there is no particular preferred upper limit, the substantial upper limit is 500 MPa.

[0011] The sealant for flexible GHLC elements of the present invention has a crosslinking molecular weight of the cured product of 100 g / mol (lower limit) and 20,000 g / mol (upper limit). By ensuring that the crosslinking molecular weight of the cured product falls within this range, the resulting sealant for flexible GHLC elements has superior adhesion to alignment film-attached films. The crosslinking molecular weight of the cured product is more preferably 500 g / mol (lower limit) and 1,000 g / mol (upper limit). The molecular weight between crosslinks is calculated by measuring the storage modulus of the cured product as described above, where T (K) is the temperature at which the storage modulus is minimum above the glass transition temperature, E' (Pa) is the storage modulus at temperature T, and ρ (g / m 3 ) and the gas constant is R (J / (mol·K)), it can be calculated using the following formula. Molecular weight between crosslinking points=3ρRT / E'

[0012] The sealant for flexible GHLC elements of the present invention contains a curable resin. The curable resin preferably contains a (meth)acrylic compound. In a sealant for liquid crystal elements, liquid crystal contamination may occur when the sealant before curing comes into contact with liquid crystal, but by containing the (meth)acrylic compound as the curable resin, the resulting sealant for flexible GHLC elements has excellent low liquid crystal contamination properties. In this specification, the term "(meth)acrylic" means acrylic or methacrylic, the term "(meth)acrylic compound" means a compound having a (meth)acryloyl group, and the term "(meth)acryloyl" means acryloyl or methacryloyl.

[0013] The (meth)acrylic compound preferably contains a monofunctional (meth)acrylic compound having one (meth)acryloyl group per molecule. By containing the monofunctional (meth)acrylic compound, the resulting sealant for flexible GHLC elements has excellent wettability with respect to the film with an alignment film, and therefore has excellent adhesion to the film with an alignment film.

[0014] In particular, the curable resin preferably contains, as the monofunctional (meth)acrylic compound, a monofunctional (meth)acrylic compound having a homopolymer glass transition temperature of 20°C or lower. By containing the monofunctional (meth)acrylic compound having a homopolymer glass transition temperature of 20°C or lower, the resulting sealant for flexible GHLC elements has even better adhesion to alignment film-attached films. The glass transition temperature of the homopolymer is preferably 10°C or lower. There is no particular preferred lower limit for the glass transition temperature of the homopolymer, but the substantial lower limit is -70°C. The above definition of "glass transition temperature of homopolymer" means that there is a homopolymer that exhibits the specified glass transition temperature within the range of weight average molecular weight of 10,000 or more and 100,000 or less. In this specification, the "weight average molecular weight" is a value determined by gel permeation chromatography (GPC) and converted into polystyrene. Examples of columns used for measuring the weight average molecular weight converted into polystyrene by GPC include Shodex LF-804 (manufactured by Showa Denko KK).

[0015] Examples of the monofunctional (meth)acrylic compound having a homopolymer glass transition temperature of 20°C or less include butyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate. In this specification, the term "(meth)acrylate" means acrylate or methacrylate.

[0016] In addition, from the viewpoint of further improving the wettability of the resulting sealant for flexible GHLC elements to a film with an alignment film, it is preferable that the curable resin contains a monofunctional (meth)acrylic compound having a cyclic ether structure as the monofunctional (meth)acrylic compound. Examples of the cyclic ether structure include an oxirane ring, an oxetane ring, a dioxolane ring, a tetrahydrofuran ring, a furan ring, etc. Of these, a dioxolane ring is preferred.

[0017] Examples of the monofunctional (meth)acrylic compound having a cyclic ether structure include (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate and (3,4-epoxycyclohexyl)methyl acrylate.

[0018] The curable resin may contain, as the monofunctional (meth)acrylic compound, another monofunctional (meth)acrylic compound having a homopolymer glass transition temperature of more than 20°C and not having a cyclic ether structure. As the other monofunctional (meth)acrylic compound, a monofunctional (meth)acrylimide compound is preferably used. Examples of the monofunctional (meth)acrylimide compound include N-(meth)acryloyloxyethylhexahydrophthalimide.

[0019] The preferred lower limit of the content of the monofunctional (meth)acrylic compound in 100 parts by mass of the curable resin is 50 parts by mass. When the content of the monofunctional (meth)acrylic compound is 50 parts by mass or more, the resulting sealant for flexible GHLC elements has better adhesion to alignment film-attached films. The more preferred lower limit of the content of the monofunctional (meth)acrylic compound is 70 parts by mass. Furthermore, from the viewpoint of curability and the like, the preferred upper limit of the content of the monofunctional (meth)acrylic compound in 100 parts by mass of the curable resin is 99.9 parts by mass.

[0020] The curable resin preferably contains a polyfunctional (meth)acrylic compound having two or more (meth)acryloyl groups in one molecule. By including the polyfunctional (meth)acrylic compound, the resulting sealant for flexible GHLC elements has excellent curing properties and excellent adhesion to alignment film-attached films under high-temperature conditions.

[0021] Examples of the polyfunctional (meth)acrylic compound include epoxy (meth)acrylate, (meth)acrylic acid ester compound, urethane (meth)acrylate, etc., which have two or more (meth)acryloyl groups in one molecule. Among these, it is preferable that the curable resin contains the epoxy (meth)acrylate. In this specification, the term "epoxy (meth)acrylate" refers to a compound in which all epoxy groups in an epoxy compound have been reacted with (meth)acrylic acid.

[0022] Examples of the epoxy (meth)acrylate include those obtained by reacting an epoxy compound having two or more epoxy groups in one molecule with (meth)acrylic acid in the presence of a basic catalyst according to a conventional method.

[0023] Examples of the epoxy compound that serves as a raw material for the epoxy (meth)acrylate include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol E type epoxy compounds, bisphenol S type epoxy compounds, 2,2'-diallyl bisphenol A type epoxy compounds, hydrogenated bisphenol type epoxy compounds, propylene oxide-added bisphenol A type epoxy compounds, resorcinol type epoxy compounds, biphenyl type epoxy compounds, sulfide type epoxy compounds, diphenyl ether type epoxy compounds, dicyclopentadiene type epoxy compounds, naphthalene type epoxy compounds, phenol novolac type epoxy compounds, o-cresol novolac type epoxy compounds, dicyclopentadiene novolac type epoxy compounds, biphenyl novolac type epoxy compounds, naphthalene phenol novolac type epoxy compounds, glycidylamine type epoxy compounds, alkyl polyol type epoxy compounds, rubber-modified epoxy compounds, and glycidyl ester compounds.

[0024] Examples of the bifunctional (meth)acrylic acid ester compounds include 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate. (meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-added bisphenol A di(meth)acrylate, propylene oxide-added bisphenol A di(meth)acrylate, ethylene oxide-added bisphenol F di(meth)acrylate, dimethylol dicyclopentadienyl di(meth)acrylate, ethylene oxide-modified isocyanuric acid di(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, carbonate diol di(meth)acrylate, polyether diol di(meth)acrylate, polyester diol di(meth)acrylate, polycaprolactone diol di(meth)acrylate, polybutadiene diol di(meth)acrylate, and the like.

[0025] Examples of the tri- or higher functional (meth)acrylic acid ester compounds include ethylene oxide-added isocyanuric acid tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide-added trimethylolpropane tri(meth)acrylate, propylene oxide-added trimethylolpropane tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, propylene oxide-added glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tris(meth)acryloyloxyethyl phosphate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0026] The urethane (meth)acrylate can be obtained, for example, by reacting an isocyanate compound with a (meth)acrylic acid derivative having a hydroxyl group in the presence of a catalytic amount of a tin compound.

[0027] Examples of isocyanate compounds that can be used as raw materials for the urethane (meth)acrylate include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatephenyl)thiophosphate, tetramethylxylylene diisocyanate, and 1,6,11-undecane triisocyanate.

[0028] Furthermore, as the isocyanate compound that is the raw material for the urethane (meth)acrylate, a chain-extended isocyanate compound obtained by reacting a polyol with an excess of an isocyanate compound can also be used. Examples of the polyol include ethylene glycol, propylene glycol, glycerin, sorbitol, trimethylolpropane, carbonate diol, polyether diol, polyester diol, and polycaprolactone diol.

[0029] Examples of the (meth)acrylic acid derivative having a hydroxyl group include hydroxyalkyl (meth)acrylates, mono(meth)acrylates of dihydric alcohols, mono(meth)acrylates or di(meth)acrylates of trihydric alcohols, and epoxy (meth)acrylates. Examples of the hydroxyalkyl (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of the dihydric alcohol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol. Examples of the trihydric alcohol include trimethylolethane, trimethylolpropane, and glycerin. Examples of the epoxy(meth)acrylate include bisphenol A type epoxy(meth)acrylate.

[0030] The polyfunctional (meth)acrylic compound preferably has a flexible skeleton from the viewpoint of further improving the adhesiveness of the resulting sealant for flexible GHLC elements to a film with an alignment layer. Examples of the flexible skeleton include a lactone ring-open structure, a polyalkylene oxide structure, a rubber structure derived from a conjugated diene, a polysiloxane structure, etc. Among these, a lactone ring-open structure is preferred. Examples of the lactone include γ-undecalactone, ε-caprolactone, γ-decalactone, σ-dodecalactone, γ-nonanolactone, γ-heptanolactone, γ-valerolactone, σ-valerolactone, β-butyrolactone, γ-butyrolactone, β-propiolactone, σ-hexanolactone, and 7-butyl-2-oxepanone.

[0031] The content of the polyfunctional (meth)acrylic compound in 100 parts by mass of the curable resin is preferably 0.1 parts by mass at the lower limit and 50 parts by mass at the upper limit. By ensuring that the content of the polyfunctional (meth)acrylic compound is within this range, the resulting sealant for flexible GHLC elements will have superior curability, adhesion to alignment film-attached films, and low liquid crystal contamination. The content of the polyfunctional (meth)acrylic compound is more preferably 0.5 parts by mass at the lower limit and 5 parts by mass at the upper limit.

[0032] The preferred lower limit of the content of the (meth)acrylic compound in 100 parts by mass of the curable resin is 55 parts by mass. When the content of the (meth)acrylic compound is 55 parts by mass or more, the resulting sealant for flexible GHLC elements has better adhesiveness under high-temperature conditions. The more preferred lower limit of the content of the (meth)acrylic compound is 60 parts by mass. It is particularly preferred that the content of the (meth)acrylic compound in 100 parts by mass of the curable resin is 100 parts by mass, that is, the curable resin is composed solely of the (meth)acrylic compound.

[0033] The preferred lower limit of the total content of the curable resins in 100 parts by mass of the sealant for flexible GHLC elements of the present invention is 90 parts by mass, and the preferred upper limit is 99 parts by mass. When the total content of the curable resins is within this range, the resulting sealant for flexible GHLC elements has better curability and adhesiveness.

[0034] The sealing agent for flexible GHLC elements of the present invention contains a photopolymerization initiator. As the photopolymerization initiator, a photoradical polymerization initiator is preferably used.

[0035] Examples of the photoradical polymerization initiator include benzophenone compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, oxime ester compounds, benzoin ether compounds, and thioxanthone compounds. Specific examples of the photoradical polymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2-(dimethylamino)-2-((4-methylphenyl)methyl)-1-(4-(4-morpholinyl)phenyl)-1-butanone, 2,2-dimethoxy-1,2-diphenylethan-1-one, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2-methyl-1-(4-methylthiophenyl) 2-morpholinopropan-1-one, 1-(4-(2-hydroxyethoxy)-phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 1-(4-(phenylthio)phenyl)-1,2-octanedione 2-(O-benzoyloxime), 2-(acetoxyimino)-1-(4-(4-(2-hydroxyethoxy)phenylthio)phenyl)propan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4-dimethylthioxanthen-9-one, and the like.

[0036] The content of the photopolymerization initiator is preferably 0.01 parts by mass at the lower limit and 10 parts by mass at the upper limit relative to 100 parts by mass of the curable resin. By using the photopolymerization initiator in this range, the resulting sealant for flexible GHLC elements has better storage stability and photocurability. The more preferred lower limit of the content of the photopolymerization initiator is 0.1 parts by mass, and the more preferred upper limit is 5 parts by mass.

[0037] The sealing agent for flexible GHLC elements of the present invention may contain a thermal polymerization initiator within a range that does not impair the object of the present invention. As the thermal polymerization initiator, a thermal radical polymerization initiator is preferably used.

[0038] Examples of the thermal radical polymerization initiator include those composed of an azo compound, an organic peroxide, etc. Among them, from the viewpoint of suppressing contamination of the light-modulating material, an initiator composed of an azo compound (hereinafter also referred to as "azo initiator") is preferred. The thermal radical polymerization initiators may be used alone or in combination of two or more.

[0039] Specific examples of the azo compounds include those having a structure in which multiple units of polyalkylene oxide, polydimethylsiloxane, or the like are bonded via azo groups, polycondensates of 2,2'-azobis(2,4-dimethylvaleronitrile), 4,4'-azobis(4-cyanovaleric acid), 4,4'-azobis(4-cyanopentanoic acid) and polyalkylene glycol, and polycondensates of 4,4'-azobis(4-cyanopentanoic acid) and polydimethylsiloxane having a terminal amino group. Examples of the azo initiator include VPE-0201, VPE-0401, VPE-0601, VPS-0501, VPS-1001, V-65, and V-501 (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0040] Examples of the organic peroxide include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, peroxyesters, diacyl peroxides, and peroxydicarbonates.

[0041] The content of the thermal polymerization initiator is preferably 0.01 parts by mass at the lower limit and 10 parts by mass at the upper limit relative to 100 parts by mass of the curable resin. By using the thermal polymerization initiator in this range, the resulting sealant for flexible GHLC elements has better storage stability and thermosetting properties. The more preferred lower limit of the content of the thermal polymerization initiator is 0.1 parts by mass, and the more preferred upper limit is 5 parts by mass.

[0042] The sealant for flexible GHLC elements of the present invention preferably further contains a thermoplastic resin from the viewpoints of adjusting the viscosity of the resulting sealant for flexible GHLC elements and further improving the adhesion to the alignment film-attached film.

[0043] The thermoplastic resin preferably has a glass transition temperature of 20° C. or lower. When the thermoplastic resin has a glass transition temperature of 20° C. or lower, the resulting sealant for flexible GHLC elements has superior adhesion to alignment film-attached films. The upper limit of the glass transition temperature of the thermoplastic resin is more preferably 15° C. There is no particular preferred lower limit for the glass transition temperature of the thermoplastic resin, but the substantial lower limit is -125°C. In this specification, the glass transition temperature of the thermoplastic resin refers to a value measured by differential scanning calorimetry (DSC) based on JIS K 7121.

[0044] The weight-average molecular weight of the thermoplastic resin preferably has a lower limit of 10,000 and a higher limit of 1,000,000. By using a thermoplastic resin with a weight-average molecular weight in this range, the resulting sealant for flexible GHLC elements has superior adhesion to alignment film-attached films. The weight-average molecular weight of the thermoplastic resin more preferably has a lower limit of 50,000 and a higher limit of 500,000.

[0045] Examples of the thermoplastic resin include styrene / (meth)acrylic copolymer, (meth)acrylic copolymer, polyolefin, polyester, polyamide, polyurethane, polystyrene, polycarbonate, polyphenylene oxide, ABS resin, AES resin, AAS resin, MBS resin, phenoxy resin, etc. Among these, the (meth)acrylic / styrene copolymer is preferred as the thermoplastic resin. The thermoplastic resin is preferably a block copolymer.

[0046] The content of the thermoplastic resin is preferably 10 parts by mass or less and 50 parts by mass or less per 100 parts by mass of the curable resin. By using the thermoplastic resin in this range, the resulting sealant for flexible GHLC elements has superior adhesion to the alignment film-attached film. The more preferred lower limit of the content of the thermoplastic resin is 20 parts by mass, and the more preferred upper limit is 40 parts by mass.

[0047] The sealing agent for flexible GHLC elements of the present invention may further contain additives such as a heat curing agent, a curing accelerator, a light-shielding agent, a filler, a silane coupling agent, a stress relaxation agent, a reactive diluent, a thixotropic agent, a spacer, an antifoaming agent, a leveling agent, and a polymerization inhibitor, as necessary.

[0048] Examples of methods for producing the sealing agent for flexible GHLC elements of the present invention include a method in which a curable resin, a photopolymerization initiator, and a thermoplastic resin and additives used as needed are mixed using a mixer. Examples of the mixer include a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, and a three-roll mixer.

[0049] The flexible GHLC element sealant of the present invention has a viscosity of preferably 1 Pa·s or less, as measured at 25°C and 1 rpm using an E-type viscometer. A viscosity of 1 Pa·s or more ensures that the resulting flexible GHLC element sealant has superior adhesion to alignment layer-attached films. A more preferred viscosity limit is 10 Pa·s. From the viewpoint of coatability, the upper limit of the viscosity is preferably 500 Pa·s, and more preferably 400 Pa·s. As the E-type viscometer, for example, DV-III (manufactured by BROOK FIELD) can be used.

[0050] The sealant for flexible GHLC elements of the present invention can be suitably used in the production of GHLC elements by a liquid crystal dropping method. Examples of methods for manufacturing a GHLC element by the liquid crystal dropping method include the following methods. First, a process is performed in which the flexible GHLC element sealant of the present invention is applied to a film substrate by screen printing, dispenser application, or the like to form a frame-shaped seal pattern. Next, while the flexible GHLC element sealant of the present invention is still uncured, microdroplets of guest-host liquid crystal are dropwise applied to the entire frame of the seal pattern, and another film substrate is immediately superimposed on the substrate. A GHLC element can then be obtained by a process in which the sealant is cured by irradiating the seal pattern with light such as ultraviolet light. Alternatively, a process in which the sealant is heated and cured may be performed after the process in which the sealant is cured by irradiating the seal pattern with light such as ultraviolet light.

[0051] The sealant for flexible GHLC devices of the present invention is preferably used to seal a GHLC light control device having a film substrate. [Effects of the Invention]

[0052] According to the present invention, it is possible to provide a sealant for flexible GHLC elements that has excellent adhesion to alignment film-attached films even immediately after light irradiation or under high temperature conditions. DETAILED DESCRIPTION OF THE INVENTION

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0054] (Examples 1 to 12, Comparative Examples 1 to 5) According to the compounding ratios shown in Tables 1 and 2, each material was stirred with a planetary stirrer and then uniformly mixed with a ceramic triple roll to obtain sealing agents for flexible GHLC elements of Examples 1 to 12 and Comparative Examples 1 to 5. Awatori Rentaro (manufactured by Thinky Corporation) was used as the planetary stirrer.

[0055] (viscosity) The viscosity of the obtained sealing agent for flexible GHLC elements was measured using an E-type viscometer (manufactured by Brookfield, "DV-III") at 25°C and 1 rpm. The results are shown in Tables 1 and 2.

[0056] (Glass transition temperature, storage modulus, and molecular weight between crosslinking points of the cured product) The sealants for flexible GHLC elements obtained in Examples 1 to 12 and Comparative Examples 1 to 4 were measured using a metal halide lamp at a wavelength of 365 nm and an illuminance of 100 mW / cm. 2 The sealant for flexible GHLC elements obtained in Comparative Example 5 was irradiated with light at a wavelength of 365 nm and an illuminance of 100 mW / cm using a metal halide lamp for 30 seconds to obtain a cured product with a thickness of 300 μm. 2 After irradiating the coating with light for 30 seconds, the coating was heated at 80° C. for 60 minutes to obtain a cured product with a thickness of 300 μm. The metal halide lamp used was MB1500T-3 (manufactured by Sen Special Light Sources Co., Ltd.). The dynamic viscoelasticity of the resulting cured product was measured using a dynamic viscoelasticity measuring device (IT Measurement & Control Co., Ltd., "DVA-200") under the following conditions: test piece width 5 mm, grip width 25 mm, heating rate 10°C / min, temperature range -80°C to 200°C, and frequency 10 Hz, and the glass transition temperature, storage modulus at 25°C and 80°C, and molecular weight between crosslinks were determined. The results are shown in Tables 1 and 2.

[0057] <Evaluation> The obtained sealant for flexible GHLC elements was evaluated as follows, and the results are shown in Tables 1 and 2.

[0058] (Adhesion to films with alignment layers) (1) Immediately after light irradiation An imide resin was spin-coated onto a PET film with an ITO thin film, prebaked at 80°C, and then baked at 230°C to produce a PET film with an alignment layer (25 mm long, 45 mm wide). SE7492 (Nissan Chemical Co., Ltd.) was used as the imide resin. All of the PET films with alignment layers used below were first attached to a glass substrate (25 mm long, 45 mm wide) using adhesive tape (Nichiban Co., Ltd., "Nicetack") on the side opposite the alignment layer of the PET film. The obtained sealant for flexible GHLC devices was applied in small drops to one of two PET films with an alignment film, and the other PET film with an alignment film was then attached in a cross shape to this. The sealant was then irradiated with a metal halide lamp at a wavelength of 365 nm and an illuminance of 100 mW / cm. 2 The metal halide lamp used was MB1500T-3 (manufactured by Sen Special Light Sources Co., Ltd.). Immediately after irradiation, the edge of the lower PET film with the alignment layer was pressed into the test piece with a metal cylinder of 5 mm radius at a speed of 5 mm / min, and the strength at which the PET film with the alignment layer peeled off was measured. The measured value (kgf) was divided by the diameter (cm) of the joint to determine the adhesive strength, and the adhesiveness was evaluated according to the following criteria. ◎: Adhesive strength is 3.0 kgf / cm or more ○: Adhesion strength is 1.5 kgf / cm or more and less than 3.0 kgf / cm ×: Adhesive strength is less than 1.5 kgf / cm

[0059] (2) High temperature conditions The test pieces obtained in the same manner as in "(1) Immediately after light irradiation" above were held at 80°C and the adhesive strength was measured in the same manner as in "(1) Immediately after light irradiation" above, and the adhesiveness was evaluated according to the following criteria. ◎: Adhesive strength is 2.0 kgf / cm or more ○: Adhesion strength is 1.0 kgf / cm or more and less than 2.0 kgf / cm ×: Adhesive strength is less than 1.0 kgf / cm

[0060] (Low liquid crystal contamination) One part by weight of spacer particles (Micropearl SI-H050, manufactured by Sekisui Chemical Co., Ltd.) with an average particle size of 7 μm was dispersed in 100 parts by weight of the resulting flexible GHLC element sealant. The mixture was then loaded into a syringe and degassed using a centrifugal degassing machine (Awatron AW-1, manufactured by Musashi Engineering Co., Ltd.). The degassed flexible GHLC element sealant was applied using a dispenser to one of two PET films with alignment film prepared in the same manner as described above in "(Adhesion to Alignment Films)" to form a frame-shaped seal pattern. The discharge pressure was adjusted to achieve a line width of approximately 1.0 mm. Next, microdroplets of liquid crystal (4-pentyl-4-biphenylcarbonitrile, manufactured by Tokyo Chemical Industry Co., Ltd.) were dropwise applied to the entire area within the seal pattern of the PET film with alignment film coated with the flexible GHLC element sealant, and the other PET film with alignment film was then attached under vacuum. After releasing the vacuum, the sealant for flexible GHLC elements in the seal pattern area was cured by the following method to obtain a test piece. The sealants for flexible GHLC elements obtained in Examples 1 to 12 and Comparative Examples 1 to 4 were cured using a metal halide lamp at a wavelength of 365 nm and an illuminance of 100 mW / cm. 2The sealant for flexible GHLC elements obtained in Comparative Example 5 was cured by irradiating it with light of wavelength 365 nm and illuminance 100 mW / cm using a metal halide lamp. 2 After irradiating the coating with light for 30 seconds, the coating was cured by heating for 60 minutes at 80° C. The metal halide lamp used was MB1500T-3 (manufactured by Sen Special Light Sources Co., Ltd.). The obtained test pieces were observed using a polarizing microscope (Keyence Corporation, "VHX-5000") to check for alignment disturbances based on the presence or absence of color unevenness in the liquid crystal portion, and the low liquid crystal contamination was evaluated according to the following criteria. ◎: No alignment disorder was observed ○: When alignment disturbance is confirmed only near the seal pattern (periphery) ×: When the alignment disorder spreads to the center

[0061] [Table 1]

[0062] [Table 2] [Industrial Applicability]

[0063] According to the present invention, it is possible to provide a sealant for flexible GHLC elements that has excellent adhesion to alignment film-attached films even immediately after light irradiation or under high temperature conditions.

Claims

1. Contains a curable resin and a photopolymerization initiator, The glass transition temperature of the cured product is 60°C or less, The storage modulus of the cured product at 25°C is 500 MPa or less, and the storage modulus of the cured product at 80°C is 0.01 MPa or more. A sealant for flexible GHLC elements.

2. the curable resin contains a monofunctional (meth)acrylic compound having one (meth)acryloyl group in one molecule, 2. The sealant for flexible GHLC elements according to claim 1, wherein the content of the monofunctional (meth)acrylic compound in 100 parts by mass of the curable resin is 50 parts by mass or more.

3. 3. The sealant for flexible GHLC elements according to claim 2, wherein the curable resin contains a monofunctional (meth)acrylic compound whose homopolymer has a glass transition temperature of 20[deg.] C. or lower.

4. 4. The sealant for flexible GHLC elements according to claim 2, wherein the curable resin contains a monofunctional (meth)acrylic compound having a cyclic ether structure.

5. the curable resin contains a polyfunctional (meth)acrylic compound having two or more (meth)acryloyl groups in one molecule, 4. The sealant for flexible GHLC elements according to claim 1, wherein the content of the polyfunctional (meth)acrylic compound is 0.1 parts by mass or more and 50 parts by mass or less in 100 parts by mass of the curable resin.

6. 4. The sealant for flexible GHLC elements according to claim 1, 2 or 3, further comprising a thermoplastic resin.

7. 4. The sealant for flexible GHLC elements according to claim 1, 2 or 3, wherein the molecular weight between crosslinks of the cured product is from 100 g / mol to 20,000 g / mol.

8. 4. The sealing agent for flexible GHLC elements according to claim 1, 2 or 3, which has a viscosity of 1 Pa·s or more as measured at 25° C. and 1 rpm using an E-type viscometer.