Sheet-like sealing material

Abstract

To provide a sheet-like sealing material curable at a low temperature in a short time.SOLUTION: A sheet-like sealing material that solves the above problem is a sheet-like sealing material containing an epoxy compound and a thiol-based curing agent containing one or more thiol groups in molecules, wherein a storage modulus E ' at 25 °C. of a cured product obtained by heating the sheet-like sealing material at 100 °C. for 30 minutes is 0. 1Hz or more and 5. 01GPa or less, the storage modulus E ' being obtained by dynamic viscoelasticity measurement at a temperature increase rate of 5 °C. / min and a frequency of 0GPa.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sheet-shaped sealing material. [Background technology]

[0002] In recent years, thin display devices have become widespread. In such thin display devices, a display element such as an organic light-emitting diode (OLED) element is generally stacked with a back plate, a metal plate, or the like for supporting the display element. Furthermore, it is common to arrange an adhesive layer or an optical adhesive layer between each component, and to bond multiple components together. For example, Patent Document 1 discloses a configuration in which a substrate and an organic EL element are bonded together with an adhesive layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-141963 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a configuration in which components are bonded together using an adhesive sheet as in Patent Document 1, the adhesive sheet tends to wrinkle when subjected to thermal processing such as heat pressing, which can easily affect the display element.Furthermore, since the adhesive sheet does not harden, there is also the problem that it is difficult to fix it in the desired shape.

[0005] Here, it is conceivable to use a thermosetting sheet-shaped sealing material to bond the components together. Such a sheet-shaped sealing material allows for fixing in a desired shape. The sheet-shaped sealing material must be cured by heating, but from the viewpoints of productivity and protection of the display element, it is desirable for the material to be cured at a low temperature and in a short time. However, conventional sheet-shaped sealing materials tend to be poorly cured when heated at a low temperature and for a short time.

[0006] Therefore, an object of the present invention is to provide a sheet-like sealing material that can be cured at low temperature in a short time. [Means for solving the problem]

[0007] The present invention provides the following sheet-shaped sealing material. [1] A sheet-like sealing material containing an epoxy compound and a thiol-based curing agent containing one or more thiol groups in the molecule, wherein the cured product obtained by heating at 100°C for 30 minutes has a storage modulus E' at 25°C of 0.01 GPa or more and 5.0 GPa or less, as measured by dynamic viscoelasticity measurement at a heating rate of 5°C / min and a frequency of 1 Hz. [2] The sheet-like sealing material according to [1], wherein the thiol-based curing agent contains two or more thiol groups in the molecule. [3] The sheet-shaped sealing material according to [1] or [2], which has a glass transition temperature of 60°C or higher after curing. [4] The sheet-like sealing material according to any one of [1] to [3], wherein the thiol-based curing agent contains a glycoluril structure. [Effects of the Invention]

[0008] The sheet-like sealing material of the present invention can be cured at low temperature in a short time. DETAILED DESCRIPTION OF THE INVENTION

[0009] The sheet-like sealing material of the present invention is useful as a sheet for bonding components of various display devices together, although the use of the sheet-like sealing material of the present invention is not limited to display devices.

[0010] The sheet-like sealing material of the present invention has a storage modulus E' of 0.01 GPa or more and 5.0 GPa or less after being cured by heating at 100°C for 30 minutes. In other words, the sheet-like sealing material can be sufficiently cured by heating at 100°C for 30 minutes. Conventional compositions containing known epoxy resins and curing agents have had the problem of easily curing before being processed into a sheet or before being bonded together. On the other hand, while increasing the stability of the composition allows it to be molded into a sheet, it takes a long time to cure or requires heating to a high temperature for curing. In response to this, the present inventors have discovered that by combining an epoxy compound with a thiol-based curing agent, the composition can be easily molded into a sheet, and furthermore, after being made into a sheet-like sealing material, it can be cured at a relatively low temperature and in a short time.

[0011] Here, the sheet-like sealing material of the present invention only needs to contain at least an epoxy compound and a thiol-based curing agent, but may further contain, as necessary, a curing catalyst, a tackifier, a leveling agent, other components, etc. Below, each component and the physical properties of the sheet-like sealing material and its cured product will be explained.

[0012] (epoxy compounds) In this specification, an epoxy compound refers to a compound having one or more epoxy groups per molecule. The epoxy compound is not particularly limited as long as it can be cured with a thiol-based curing agent (described below) and has a storage modulus E' within the above-mentioned range after curing. Here, the sheet-like sealing material preferably contains two or more epoxy compounds, and more preferably contains (i) an epoxy compound having a cycloalkene oxide structure, (ii) a high-molecular-weight epoxy compound having a weight-average molecular weight of 3000 or more, and (iii) a flexibility-imparting epoxy compound having a weight-average molecular weight of 300 or more but less than 3000. The inclusion of multiple types of epoxy compounds in this manner further increases the storage modulus E' of the cured product within the above-mentioned range. Furthermore, the inclusion of (ii) a high-molecular-weight epoxy compound having a weight-average molecular weight of 3000 or more tends to improve the stability of the sheet-like sealing material and the film-formability when molded into a sheet.

[0013] (i) In an epoxy compound having a cycloalkene oxide structure, the "cycloalkene oxide structure" is a structure represented by the following general formula, which is obtained by epoxidizing a cycloalkene with an oxidizing agent such as a peroxide, and has an aliphatic ring and an epoxy group composed of two carbon atoms and an oxygen atom constituting the aliphatic ring. [ka] In the above general formula, M represents an alicyclic structure, and the number of carbon atoms therein is preferably 4 to 8, more preferably 5 to 6. (i) When the number of carbon atoms in the alicyclic structure of the cycloalkene oxide structure is within this range, the physical properties of the sheet-shaped sealing material tend to fall within the desired ranges.

[0014] Specific examples of the cycloalkene oxide structure include cyclohexene oxide and cyclopentene oxide, with cyclohexene oxide being preferred.

[0015] (i) The number of cycloalkene oxide structures contained in one molecule of an epoxy compound having a cycloalkene oxide structure may be one (monofunctional) or two or more (multifunctional), and among these, the number of cycloalkene oxide structures in one molecule is preferably two or more (multifunctional).

[0016] (i) Examples of the epoxy compound having a cycloalkene oxide structure include compounds represented by the following general formulas (i-1) to (i-3).

[0017] [ka]

[0018] M in the above general formula (i-1) 1 and M 2 represents an alicyclic structure, and as described above, the number of carbon atoms therein is preferably 4 to 8, more preferably 5 to 6. X in the above general formula (i-1)1 is a single bond or a linking group. Examples of the linking group include a divalent hydrocarbon group, a carbonyl group, an ether group (ether bond), a thioether group (thioether bond), an ester group (ester bond), a carbonate group (carbonate bond), an amide group (amide bond), or a group in which multiple of these are linked together.

[0019] Examples of divalent hydrocarbon groups that can be the linking group include alkylene groups having 1 to 18 carbon atoms and divalent alicyclic hydrocarbon groups. Examples of alkylene groups having 1 to 18 carbon atoms include methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene. Examples of divalent alicyclic hydrocarbon groups include divalent cycloalkylene groups (including cycloalkylidene groups) such as 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, and cyclohexylidene.

[0020] Among them, X 1 is preferably a single bond or a linking group having an oxygen atom. The linking group having an oxygen atom is more preferably -CO- (carbonyl group), -O-CO-O- (carbonate group), -COO- (ester group), -O- (ether group), -CONH- (amide group), a group in which a plurality of these groups are linked together, or a group in which one or more of these groups are linked to one or more divalent hydrocarbon groups.

[0021] Specific examples of the alicyclic epoxy compound represented by the general formula (i-1) above include the following compounds. In the following formula, l is an integer of 1 to 10, and m is an integer of 1 to 30. R is an alkylene group having 1 to 8 carbon atoms (preferably an alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, a propylene group, or an isopropylene group). n1 and n2 are each an integer of 1 to 30.

[0022] [ka]

[0023] Examples of commercially available epoxy compounds represented by the general formula (i-1) include Celloxide 2021P, Celloxide 2081, Celloxide 8000, and Celloxide 8010 (manufactured by Daicel Corporation).

[0024] On the other hand, (i) the epoxy compound having a cycloalkene oxide structure may be, for example, a compound having a structure represented by the following general formula (i-2) or (i-3). [ka] M in the above general formulae (i-2) and (i-3) 3 , M 4 , and M 5 represents an alicyclic structure, and the number of carbon atoms therein is preferably 4 to 8, and more preferably 5 to 6. X in the above general formula (i-3) 2 is a single bond or a linking group. The linking group is the same as the linking group in the above-mentioned general formula (i-1). In addition, the compounds represented by general formulas (i-2) and (i-3) may have an alkyl group or the like bonded to a carbon that constitutes an alicyclic structure or an epoxy group.

[0025] Examples of epoxy compounds represented by the general formula (i-2) or (i-3) include 3,4:7,8-diepoxybicyclo[4.3.0]nonane and limonene dioxide, etc. Commercially available examples of these compounds include THI-DE (manufactured by JX-TG Corporation) and LDO (manufactured by Nagase Chemtec Corporation).

[0026] The weight-average molecular weight of any of the above-mentioned (i) epoxy compounds having a cycloalkene oxide is preferably 180 or more, more preferably 190 or more, and even more preferably 200 or more. The upper limit of the weight-average molecular weight is appropriately selected depending on the desired performance of the sheet-like sealing material, but is preferably 500 or less. When the weight-average molecular weight of the (i) epoxy compound having a cycloalkene oxide is 180 or more, the physical properties of the sheet-like sealing material tend to fall within the desired range. The weight-average molecular weight of the epoxy compound is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0027] In particular, (i) the epoxy compound having a cycloalkene oxide is preferably a compound represented by the following formula, from the viewpoint that the storage modulus E' of the cured product is more likely to fall within the desired range. [ka]

[0028] When the sheet-shaped sealing material contains (i) an epoxy compound having a cycloalkene oxide, the total amount thereof is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 30% by mass or less, based on the total amount of the sheet-shaped sealing material. When the amount of the epoxy compound is within this range, the physical properties of the cured product of the sheet-shaped sealing material are more likely to fall within the desired range.

[0029] (ii) A high-molecular-weight epoxy compound having a weight-average molecular weight of 3,000 or more is solid at room temperature (25°C). The weight-average molecular weight of the (ii) high-molecular-weight epoxy compound is preferably 3,000 or more and 100,000 or less, more preferably 6,000 or more and 60,000 or less, and even more preferably 7,000 or more and 40,000 or less. When a sheet-shaped sealing material contains the (ii) high-molecular-weight epoxy compound, the sheet-shaped sealing material is more likely to maintain its shape. Furthermore, when the (ii) high-molecular-weight epoxy compound has a weight-average molecular weight of 100,000 or less, the sheet-shaped sealing material exhibits good fluidity when heated and bonded, making it easier to adhere to various components. The weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0030] (ii) The high molecular weight epoxy compound may be an aromatic epoxy compound or an aliphatic epoxy compound, but a compound having an aromatic ring is more preferred.

[0031] Specific examples of aromatic epoxy compounds that can be the (ii) high-molecular-weight epoxy compounds include bisphenol-type epoxy compounds such as bisphenol A, bisphenol F, bisphenol E, bisphenol S, bisphenol AD, and mixtures thereof; diphenyl ether-type epoxy compounds; novolac-type epoxy compounds such as phenol novolac, cresol novolac, biphenyl novolac, bisphenol novolac, naphthol novolac, trisphenol novolac, and dicyclopentadiene novolac; biphenyl-type epoxy compounds; naphthyl-type epoxy compounds; and triphenolalkane-type epoxy compounds such as triphenolmethane, triphenolethane, and triphenolpropane.

[0032] Among the above aromatic epoxy compounds, bisphenol-type epoxy compounds or biphenyl-type epoxy compounds are preferred. However, as the amount of bisphenol F skeleton in the sheet-shaped sealing material increases, the softening point of the sheet-shaped sealing material tends to decrease. Therefore, when the sheet-shaped sealing material is bonded to various members at a relatively high temperature, it is preferred that the sheet-shaped sealing material mainly contains an aromatic epoxy compound other than a bisphenol F skeleton.

[0033] Furthermore, while the number of epoxy groups possessed by the (ii) high-molecular-weight epoxy compound is not particularly limited, the epoxy equivalent is preferably 900 g / eq or more and 20,000 g / eq or less, and more preferably 1,000 g / eq or more and 20,000 g / eq or less. When the epoxy equivalent of the (ii) high-molecular-weight epoxy compound is 900 g / eq or more, the tackiness of the sheet-shaped sealing material at room temperature is reduced. Therefore, the handling properties of the sheet-shaped sealing material tend to be improved. On the other hand, if the epoxy equivalent of the (ii) high-molecular-weight epoxy compound is excessively large, the solubility of the (ii) high-molecular-weight epoxy compound in solvents may decrease or its compatibility with other epoxy compounds may become poor. Therefore, the epoxy equivalent of the (ii) high-molecular-weight epoxy compound is preferably 20,000 g / eq or less.

[0034] The total amount of (ii) high molecular weight epoxy compound relative to the total amount of the sheet-like sealing material is preferably 1% by mass to 50% by mass, more preferably 5% by mass to 40% by mass, and even more preferably 10% by mass to 35% by mass. When the amount of (ii) high molecular weight epoxy compound in the sheet-like sealing material is within this range, the lamination temperature between the sheet-like sealing material and various components tends to be appropriate.

[0035] Furthermore, the (iii) flexibility-imparting epoxy compound may be an epoxy compound having a weight-average molecular weight of 300 or more but less than 3,000, and more preferably a weight-average molecular weight of 500 or more but less than 2,000. The (iii) flexibility-imparting epoxy compound may be a solid or liquid at room temperature (25°C). The (iii) flexibility-imparting epoxy compound may be an aromatic epoxy compound or an aliphatic epoxy compound.

[0036] Specific examples of (iii) the flexibility-imparting epoxy compound when it is an aromatic epoxy compound include the aromatic epoxy compounds listed above in (ii) the high-molecular-weight epoxy compounds and similar resins (however, the molecular weight is 300 or more and less than 3,000).

[0037] On the other hand, when the (iii) flexibility-imparting epoxy compound is an aliphatic epoxy compound, the aliphatic epoxy compound may be a compound having one or more epoxy groups in the molecule and an aliphatic chain (excluding those corresponding to the epoxy compounds (i) or (ii) above). The aliphatic epoxy compound may have only one epoxy group, or may have two or more epoxy groups. Furthermore, the length of the aliphatic chain contained in the aliphatic epoxy compound is not particularly limited, but the number of carbon atoms in the molecule is preferably 10 to 1,000, and more preferably 50 to 200. If the number of carbon atoms in the molecule is 10 or more, the storage modulus E' of the cured product of the sheet-like sealing material tends to be low. On the other hand, if the number of carbon atoms in the molecule is 1,000 or less, the compound is more likely to be compatible with other components.

[0038] The total amount of the (iii) flexibility-imparting epoxy compound relative to the total amount of the sheet-like sealing material is preferably 15% by mass to 45% by mass, more preferably 20% by mass to 40% by mass, and even more preferably 25% by mass to 35% by mass. When the amount of the (iii) flexibility-imparting epoxy compound in the sheet-like sealing material is within this range, the storage modulus E' of the cured product of the sheet-like sealing material is more likely to fall within the desired range.

[0039] The sheet-shaped sealing material may further contain an epoxy compound other than the above-mentioned (i) epoxy compound having a cycloalkene oxide structure, (ii) high-molecular-weight epoxy compound, and (iii) flexibility-imparting epoxy compound.

[0040] The total amount of the epoxy compound relative to the total amount of the sheet-like sealing material is preferably 50% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 50% by mass to 85% by mass. When the amount of the epoxy compound in the sheet-like sealing material is within this range, the strength of the sheet-like sealing material and its cured product can be sufficiently increased. In addition, the thermosetting properties of the sheet-like sealing material tend to be good.

[0041] (Thiol-based curing agent) The thiol-based curing agent is not particularly limited as long as it contains one or more thiol groups in its molecule and can react with the epoxy compound by heating to cure the sheet-shaped sealing material. The sheet-shaped sealing material may contain only one type of thiol-based curing agent, or may contain two or more types. The thiol-based curing agent may partially contain a compound containing only one thiol group in its molecule, but a compound containing two or more thiol groups is more preferred. The number of thiol groups contained in the thiol-based curing agent is more preferably 2 or more and 4 or less.

[0042] Examples of thiol-based curing agents include trimethylolpropane tris(3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), 1,3,5-trimethylolpropane tri ...butyrate), dipentaerythritol hexakis(3-mercaptobutyrate), dipentaerythritol hexakis(3-mercapto Tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,4,6-tetrakis(mercaptomethyl)glycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a-methyl These include 1,3,4,6-tetrakis(2-mercaptoethyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a,6a-dimethylglycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)-3a,6a-dimethylglycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)-3a,6a-dimethylglycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a,6a-diphenylglycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)-3a,6a-diphenylglycoluril, and 1,3,4,6-tetrakis(3-mercaptopropyl)-3a,6a-diphenylglycoluril.

[0043] Among the above, compounds having a glycoluril structure are preferred because they tend to have a high glass transition temperature after curing. Specifically, 1,3,4,6-tetrakis(mercaptomethyl)glycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a,6a-dimethylglycoluril, 1 ,3,4,6-tetrakis(2-mercaptoethyl)-3a,6a-dimethylglycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)-3a,6a-dimethylglycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a,6a-diphenylglycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)-3a,6a-diphenylglycoluril, and 1,3,4,6-tetrakis(3-mercaptopropyl)-3a,6a-diphenylglycoluril are preferred, and 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril is particularly preferred.

[0044] The amount of the thiol-based curing agent is appropriately selected depending on the type and structure of the epoxy compound. It is preferably 20 parts by mass or more and 100 parts by mass or less, and more preferably 30 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of the epoxy compound. When the amount of the thiol-based curing agent is within this range, the sheet-like sealing material can be easily cured by heating at 100°C for 30 minutes, and the storage modulus E' of the resulting cured product is likely to fall within the above range.

[0045] (curing catalyst) The sheet-shaped sealing material preferably further contains a curing catalyst. By containing the curing catalyst, the sheet-shaped sealing material can be cured more efficiently. The sheet-shaped sealing material may contain only one type of curing catalyst, or may contain two or more types of curing catalysts.

[0046] Examples of the catalyst include amine-based curing catalysts, imidazole-based curing catalysts, phosphine-based curing catalysts, and thermal base generators. Examples of amine-based curing catalysts include triazine compounds such as 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, and tertiary amine compounds such as 1,8-diazabicyclo[5,4,0]undecene-7 (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), triethylenediamine, benzyldimethylamine, and triethanolamine. Examples of imidazole curing catalysts include imidazole compounds such as 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole. Examples of the phosphine curing catalyst include triphenylphosphine, tributylphosphine, tri(p-methylphenyl)phosphine, and tri(nonylphenyl)phosphine. Examples of the thermal base generator include U-CAT SA1, U-CAT SA102, U-CAT SA102-50, U-CAT SA106, U-CAT SA112, U-CAT SA506, U-CAT SA603, U-CAT 1000, U-CAT 1102, U-CAT 2000, U-CAT 2024, U-CAT 2026, U-CAT 2030, U-CAT 2110, U-CAT 2313, U-CAT 651M, U-CAT 660M, U-CAT 18X, U-CAT 201G, U-CAT 202, U-CAT 420A, U-CAT 130, POLYCAT 8, POLYCAT 9, POLYCAT 12, and POLYCAT 41 (all manufactured by San-Apro Co., Ltd.), and among these, U-CAT SA102 is preferred. Amine-based curing catalysts can also be preferably used. It is particularly preferred that the curing catalyst be active when heated to about 100°C.

[0047] The amount of curing catalyst is appropriately selected depending on the type and structure of the epoxy compound and thiol-based curing agent. The amount of the effective component (the component functioning as a curing catalyst) is preferably 0.1 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the total amount of the epoxy compound. When the amount of curing catalyst is within this range, the epoxy compound and the thiol-based curing agent react more easily.

[0048] (tackifier) The sheet-shaped sealing material may further contain a tackifier, which is a component for imparting adhesiveness to the sheet-shaped sealing material.

[0049] The type of tackifier is not particularly limited as long as it is a component that is easily miscible with the epoxy compound, but the tackifier is preferably a resin selected from the group consisting of petroleum resins (aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, and / or aromatic hydrocarbon resins), terpene resins, phenolic resins, and rosin resins. The sheet-like sealing material may contain only one type of tackifier, or may contain two or more types.

[0050] Examples of petroleum resins include C5 monomers or oligomers thereof obtained from pentene, pentadiene, isoprene, etc.; C9 monomers or oligomers thereof obtained from indene, methylindene, vinyltoluene, styrene, α-methylstyrene, β-methylstyrene, etc.; copolymers of C5 and C9 monomers (C5-C9 copolymer resins); alicyclic monomers or polymers thereof obtained from cyclopentadiene, dicyclopentadiene, etc.; aromatic monomers such as isopropenyltoluene or polymers thereof; hydrogenated products of the above-mentioned various monomers or polymers thereof; and modified petroleum resins obtained by modifying the above-mentioned various monomers or polymers thereof with maleic anhydride, maleic acid, fumaric acid, (meth)acrylic acid, phenol, etc.

[0051] Examples of terpene resins include α-pinene resins, β-pinene resins, α-pinene monomers, and aromatic-modified terpene resins obtained by copolymerizing terpenes such as β-pinene monomers with aromatic monomers such as styrene and phenol.

[0052] Examples of phenolic resins include condensates of phenols and formaldehyde. Examples of phenols include phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol, etc. Examples of the phenolic resins include resols obtained by addition reaction of these phenols with formaldehyde using an alkali catalyst, and novolacs obtained by condensation reaction using an acid catalyst. Phenolic resins also include rosin phenolic resins obtained by adding phenol to rosin using an acid catalyst and thermally polymerizing the resulting mixture.

[0053] Examples of rosin resins include gum rosin, wood rosin, or tall oil rosin; stabilized rosins or polymerized rosins obtained by disproportionating or hydrogenating these rosins; modified rosins obtained by modifying these rosins with maleic anhydride, maleic acid, fumaric acid, (meth)acrylic acid, phenol, or the like; and esters thereof. The alcohol used to obtain the esters is preferably a polyhydric alcohol. Examples of polyhydric alcohols include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and neopentyl glycol; trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane; tetrahydric alcohols such as pentaerythritol and diglycerin; and hexahydric alcohols such as dipentaerythritol. These may be used alone or in combination during esterification.

[0054] Among the above, a terpene-phenol tackifier, which is a combination of a terpene resin and a phenol resin, is preferred from the viewpoint of compatibility with epoxy compounds.

[0055] The amount of tackifier in the sheet-shaped sealing material is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, relative to the total amount of the sheet-shaped sealing material.When the amount of tackifier is within this range, the sheet-shaped sealing material tends to be easy to handle.

[0056] (Other ingredients) The sheet-shaped sealing material may further contain components other than those described above, provided that the objectives and effects of the present invention are not impaired. For example, the sheet-shaped sealing material may contain resins other than the above-mentioned epoxy compounds as other components. Examples of other resins include oxetanyl group-containing compounds, polyamides, polyamideimides, polyurethanes, polybutadienes, polychloroprenes, polyethers, polyesters, styrene-butadiene-styrene block copolymers, xylene resins, ketone resins, cellulose resins, fluorine-based oligomers, silicon-based oligomers, polysulfide-based oligomers, etc. The sheet-shaped sealing material may contain only one of these, or two or more of them. Examples of the oxetanyl group-containing compound include 2-ethylhexyloxetane (e.g., Aronoxetane OXT-212, manufactured by Toa Gosei Chemical Industry Co., Ltd.) and 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane (e.g., Aronoxetane OXT-221, manufactured by Toa Gosei Chemical Industry Co., Ltd.).

[0057] Furthermore, the sheet-shaped sealing material may further contain fillers, modifiers, stabilizers, etc., within the scope that does not impair the object and effect of the present invention.

[0058] Examples of the filler include glass beads, styrene-based polymer particles, methacrylate-based polymer particles, ethylene-based polymer particles, propylene-based polymer particles, etc. The sheet-shaped sealing material may contain only one type of filler, or may contain two or more types of filler.

[0059] Specific examples of the modifier include a polymerization initiator, an antioxidant, a leveling agent, a wettability improver, a surfactant, a plasticizer, a solvent, a coupling agent, etc. The sheet-like sealing material may contain only one of these modifiers, or may contain two or more of them.

[0060] Specific examples of stabilizers include ultraviolet absorbers, preservatives, antibacterial agents, etc. The sheet-shaped sealing material may contain only one of these, or may contain two or more of them. In addition, it may further contain a coloring material, etc.

[0061] However, the amount of other components is preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total amount of the sheet-shaped sealing material.

[0062] (Sheet-type sealing material and its cured properties) The sheet-like sealing material may be formed into a sheet shape and contain the above-mentioned epoxy compound and thiol-based curing agent, as well as a curing catalyst, a tackifier, and other components. The sheet-like sealing material may be distributed with a separator disposed on one or both sides, for example. The sheet-like sealing material may also be distributed with desired components disposed on one or both sides.

[0063] The thickness of the sheet-like sealing material is appropriately selected depending on the application of the sheet-like sealing material. When the sheet-like sealing material is used to bond various components of a display device, the thickness of the sheet-like sealing material is preferably 3 μm or more and 100 μm or less, and more preferably 7 μm or more and 40 μm or less. When the thickness of the sheet-like sealing material is 3 μm or more, the layer made of the cured product of the sheet-like sealing material can easily absorb and relieve stress applied to various components, making it easier to suppress cracks and dents. Furthermore, even when various components have unevenness, the sheet-like sealing material can easily conform to the uneven shape and adhere to the components, making the adhesive strength good. On the other hand, when the thickness of the sheet-like sealing material is 100 μm or less, it becomes easier to reduce the thickness and weight of the display device.

[0064] Furthermore, sheet-shaped sealing materials are usually heated to a temperature below 100°C to soften (or melt) them before being attached to the desired components. When attaching the sheet-shaped sealing material to various components, softening (melting) the sheet-shaped sealing material makes it less likely that gaps will form between the various components. Therefore, the softening (melting) temperature of the sheet-shaped sealing material is preferably 35°C or higher and 100°C or lower, and more preferably 60°C or lower. However, it is preferable to adjust this temperature appropriately depending on the attachment method when attaching the sheet-shaped sealing material to other components and the object to be attached.

[0065] Furthermore, if the melting temperature of the sheet-shaped sealing material is 60°C or lower, the sheet-shaped sealing material can be attached to various components at a relatively low temperature (60°C or lower). On the other hand, if the melting temperature of the sheet-shaped sealing material is 35°C or higher, the tackiness of the sheet-shaped sealing material during work (tackiness at room temperature) is reduced, and workability tends to be improved. Furthermore, the sheet-shaped sealing material is less likely to deform during storage, and its shape can be maintained.

[0066] The melting temperature can be determined by measuring the temperature rise using a dynamic viscoelasticity measuring device while the material is uncured. Specifically, sheet-shaped sealing materials are stacked in any way to a thickness of approximately 100 μm. The thick sheet is punched out into a 7 mm diameter circle to use as a test sample. Using this test piece, the complex viscosity is measured using a dynamic viscoelasticity measuring device, and the temperature at which the complex viscosity is at its lowest is taken as the melting temperature.

[0067] On the other hand, the heat generation initiation temperature of the sheet-shaped sealing material measured by a differential scanning calorimeter (DSC) is preferably 60°C or higher and 90°C or lower, and more preferably 65 to 85°C. When the heat generation initiation temperature is 60°C or higher, the storage stability of the sheet-shaped sealing material is good. On the other hand, when the heat generation initiation temperature is 90°C or lower, the sheet-shaped sealing material can be cured at 90°C or lower, and is less likely to affect the object to be bonded. The heat generation initiation temperature can be measured by the following method. First, 10 mg of the sheet-shaped sealing material is sampled and placed in an aluminum cell for DSC measurement to prepare a measurement test sample. Then, the temperature characteristics of the measurement test sample are measured at a temperature rise rate of 5°C / min in a measurement temperature range of 20°C to 300°C, whereby the heat generation initiation temperature can be determined.

[0068] Here, the glass transition temperature (Tg) of the cured product of the sheet-like sealing material is preferably 60° C. or higher. When the glass transition temperature of the cured product of the sheet-like sealing material is 60° C. or higher, the sheet-like sealing material before curing tends to easily maintain a desired shape and tends to have good handleability. Here, the glass transition temperature of the sheet-like sealing material is measured by DSC.

[0069] On the other hand, when the sheet-like sealing material is cured at 100°C for 30 minutes, the cured product has a storage modulus E' at 25°C of 0.01 GPa or more and 5.0 GPa or less, and more preferably 0.1 GPa or more and 3.0 GPa or less, as described above. The storage modulus E' is the value at 25°C measured by dynamic viscoelasticity measurement at a temperature rise rate of 5°C / min and a frequency of 1 Hz.

[0070] (Method of manufacturing sheet-shaped sealing material) The above-mentioned sheet-like sealing material and laminate can be produced by any method as long as the object and effect of the present invention are not impaired. For example, they can be produced by the following method, but are not limited to this method. First, a composition containing an epoxy compound, a thiol-based curing agent, a curing catalyst, a tackifier, and other components is prepared, and this is dissolved in a solvent at 30°C or below to form a varnish.

[0071] Examples of the solvent include aromatic solvents such as toluene and xylene; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ethers such as ether, dibutyl ether, tetrahydrofuran, dioxane, ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, propylene glycol or dialkyl ether; aprotic polar solvents such as N-methylpyrrolidone, dimethylimidazolidinone and dimethylformaldehyde; and esters such as ethyl acetate and butyl acetate.

[0072] When preparing the varnish, the components may be mixed at once, or the epoxy compound may be dissolved in a solvent and then the other components may be mixed in. Examples of methods for mixing the components include known stirring methods and triple-roll kneading methods.

[0073] Next, the varnish is applied onto a separator, and the solvent is removed. The method for applying the varnish is not particularly limited, and examples include screen printing, dispenser application, and various roll methods. The thickness of the applied varnish is appropriately selected depending on the desired film thickness of the sheet-like sealing material. The drying temperature and drying time of the varnish are preferably those at which the epoxy compound does not harden. For example, the drying temperature is 20 to 100°C, and the drying time can be, for example, about 1 minute to 3 hours. The drying method is not particularly limited, and examples include hot air drying and vacuum drying. The above-mentioned sheet-like sealing material is thus obtained.

[0074] (Applications for sheet-type sealing materials) The sheet-shaped sealing material described above can be used as a member (adhesive layer) for bonding together multiple members of a display device (hereinafter, for convenience, referred to as a "first member" and a "second member"). The bonding surfaces of the first member and the second member with the sheet-shaped sealing material may be flat or may have irregularities. The shapes of the first member and the second member are appropriately selected depending on their intended use, and may be, for example, a film or plate, or any three-dimensional shape.

[0075] The materials of the first and second members are not particularly limited and may be metal, inorganic, or organic, including various metals such as SUS and aluminum, inorganic materials such as glass, and organic materials such as polyimide, transparent polyimide (CPI), polyethylene terephthalate (PET), and polyethylene (PE).

[0076] When the above-described sheet-like sealing material is bonded to a first member and a second member, heating the sheet-like sealing material to 60°C or higher and 80°C or lower facilitates adhesion between them. The method for bonding the sheet-like sealing material to the desired member is not particularly limited. For example, the first member and the second member may be placed on both sides of the sheet-like sealing material and then heated together to bond the first member, sheet-like sealing material, and second member together. Alternatively, the first member may be bonded to one side of the sheet-like sealing material, and then the second member may be bonded to the sheet-like sealing material. With the first member and the second member placed on both sides of the sheet-like sealing material, the sheet-like sealing material is further heated to the desired temperature, causing the epoxy compound and thiol curing agent in the sheet-like sealing material to react. As a result, the sheet-like sealing material hardens, resulting in a laminate consisting of the first member, the cured product (adhesive layer) of the sheet-like sealing material, and the second member.

[0077] Here, the sheet-shaped sealing material can be sufficiently cured by heating at 100°C for 30 minutes, but it may also be cured at a temperature higher than 100°C or lower. Specifically, the heating temperature is preferably 60°C or higher and 200°C or lower, and more preferably 70°C or higher and 120°C or lower. Furthermore, the heating time can be appropriately selected according to the heating temperature, and is preferably 20 minutes or higher and 60 minutes or lower. By using the heating temperature and heating time, the epoxy compound in the sheet-shaped sealing material can be sufficiently cured. [Example]

[0078] The present invention will be described below with reference to examples, which should not be construed as limiting the scope of the present invention.

[0079] [material] In the examples and comparative examples, the following materials were used.

[0080] [Epoxy Compound] CEL2021P: a compound represented by the following formula (Celloxide 2021P, manufactured by Daicel Corporation, viscosity at 25°C measured with a Brookfield viscometer: 220 to 270 mPa s) [ka] JER4005P: Bisphenol F epoxy compound (JER4005P, manufactured by Mitsubishi Chemical Corporation), weight-average molecular weight (Mw) 2000 YX6954-B35: Biphenyl-type epoxy compound (YX6954-B35, manufactured by Mitsubishi Chemical Corporation), weight-average molecular weight (Mw) 36,691

[0081] [Curing agent] (Thiol-based) TMMP: Trimethylolpropane tris(3-mercaptopropionate) (Sakai Kogyo Co., Ltd.) PEMP: Pentaerythritol tetrakis(3-mercaptopropionate) (Sakai Kogyo Co., Ltd.) PE1: Pentaerythritol tetrakis(3-mercaptobutyrate (Resonac) TS-G: 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril (manufactured by Shikoku Chemicals Co., Ltd.)

[0082] (imidazole type) SIZ: Imidazole-based curing agent (manufactured by Shikoku Chemicals Co., Ltd.)

[0083] (Polyamine-based) FXR-1030: Amine-based latent curing agent (manufactured by T&K TOKA) FXR-1081: Amine-based latent curing agent (manufactured by T&K TOKA)

[0084] [Curing catalyst] HXA9322HP: Amine adduct-based latent curing catalyst (Novacure HXA9322HP, manufactured by Asahi Kasei E-Materials Corporation)

[0085] [Tackifier] K-125: Terpene phenol resin tackifier (YS Polystar K-125, manufactured by Yasuhara Chemical Co., Ltd.)

[0086] [Leveling Agent] BYK302: Polyether-modified polydimethylsiloxane (BYK302, manufactured by BYK-Chemie)

[0087] 1. Preparation of sheet-shaped sealing material [Example 1] An epoxy compound, a curing agent, a curing catalyst, a tackifier, a leveling agent, and a solvent, methyl ethyl ketone (MEK), were added to a flask in the mass ratios shown in Table 1, and the mixture was stirred and dissolved at room temperature to obtain a varnish of a thermosetting resin composition.

[0088] The varnish was applied to a separator (PET75-H270, 75 μm thick, manufactured by Nichiei Shinka Co., Ltd.) with an applicator so that the film thickness after drying would be approximately 20 μm. This was dried in an inert oven at 80°C for 3 minutes to dry and remove the MEK, yielding a sheet-like sealing material.

[0089] [Examples 2 to 4 and Comparative Examples 1 to 3] Sheet-shaped sealing materials were obtained in the same manner as in Example 1, except that the composition of the thermosetting resin composition was changed to the composition shown in Table 1. However, in Comparative Examples 2 and 3, the thermosetting resin composition cured during preparation and could not be molded into a sheet.

[0090] 2. Evaluation The sheet-like sealing materials produced in the examples and comparative examples were evaluated by the following methods. The results are shown in Table 1.

[0091] (1) Curing rate when sheet sealant is heated at 100°C for 30 minutes The curing rate of the sheet-type sealing material was determined by the change in reaction heat quantity measured by DSC. Specifically, it was calculated as follows: "Cure rate = (reaction heat quantity of remaining monomer after curing) / (reaction heat quantity before curing) × 100".

[0092] (2) Storage modulus E' of the cured sheet sealant at 25°C The sheet-shaped sealing materials produced in the examples and comparative examples were cured as a single unit at 100°C for 30 minutes. Dynamic viscoelasticity measurements were then performed from 20°C to 150°C at a temperature increase rate of 5°C / min and a frequency of 1 Hz. The storage modulus (E') at 25°C was determined.

[0093] (3) Adhesive strength In the separator / sheet-like sealing material laminates prepared in the Examples and Comparative Examples, alkali-free glass (manufactured by Matsunami Glass Co., Ltd., 50 mm x 70 mm, 0.2 mm thick) was adhered to one side of the sheet-like sealing material (the side opposite the separator) and thermocompression-bonded at 70°C. The separator was then peeled off, and an aluminum-vapor-deposited PET film (Panac Corporation, Alpet 9-100) was adhered to the sheet-like sealing material on the side opposite the alkali-free glass and thermocompression-bonded at 70°C to obtain a test specimen. The sheet-like sealing material and aluminum-vapor-deposited PET film were 25 mm wide and 100 mm long. They were then heated at 100°C for 30 minutes to cure the epoxy compound in the sheet-like sealing material. The alkali-free glass was then vertically fixed to the jig of a universal testing machine (Intesco 2200X), and the aluminum-vapor-deposited PET film was vertically peeled off at a peeling rate of 30 mm / min to measure adhesive strength.

[0094] (4) Glass transition temperature (Tg) of the cured sheet sealant The Tg of the cured products of the sheet-like sealing materials produced in the examples and comparative examples was measured by DSC. [Table 1]

[0095] As shown in Table 1 above, the sheet-shaped sealing material using an imidazole-based curing agent had a low cure rate when heated at 100°C for 30 minutes, and could not be used stably. On the other hand, when a polyamine-based curing agent was used, the resin composition cured during preparation, and could not be molded into a sheet (Comparative Examples 2 and 3).

[0096] In contrast, Examples 1 to 4, which used a thiol-based curing agent, showed good film-forming properties and achieved a curing rate of 88% or more by heating at 100°C for 30 minutes. Furthermore, the storage modulus of the cured product of these sheet-like sealing materials fell within the desired range. Furthermore, in particular, when a thiol-based curing agent having a glycoluril structure was used, the curing rate was significantly increased (Example 4). [Industrial Applicability]

[0097] The sheet-like sealing material of the present invention can be cured at a low temperature in a short time, and is therefore very useful as a member for bonding various components of various display devices.

Claims

1. an epoxy compound; a thiol-based curing agent containing one or more thiol groups in the molecule; A sheet-like sealing material comprising: the storage modulus E' at 25°C, as measured by dynamic viscoelasticity measurement at a temperature rise rate of 5°C / min and a frequency of 1 Hz, of the cured product obtained by heating at 100°C for 30 minutes is 0.01 GPa or more and 5.0 GPa or less; Sheet-type sealing material.

2. The thiol-based curing agent contains two or more thiol groups in the molecule. The sheet-like sealing material according to claim 1 .

3. The glass transition temperature after curing is 60°C or higher. The sheet-like sealing material according to claim 1 .

4. The thiol-based curing agent contains a glycoluril structure. The sheet-like sealing material according to claim 1 .

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