WO2021241129A1

WO2021241129A1 - Sealant for display devices

Info

Publication number: WO2021241129A1
Application number: PCT/JP2021/017086
Authority: WO
Inventors: 桂永田
Original assignee: 三井化学株式会社
Priority date: 2020-05-29
Filing date: 2021-04-28
Publication date: 2021-12-02
Also published as: JP7391211B2; JPWO2021241129A1; KR20220133967A; CN115151861A; TW202144450A

Abstract

The present invention addresses the problem of providing a sealant for display devices, which has low viscosity, high viscosity stability, and low-temperature curability, and can form a cured product having high moisture resistance.　The sealant for display devices, which resolves the problem, includes: an epoxy compound (A) containing a polyfunctional epoxy compound (a1) and a monofunctional epoxy compound (a2) having a biphenyl structure; and a polyamine-based latent thermal-curing agent (B). The sealant for display devices has a viscosity of 20.0 Pa·s or less as measured at 25°C and 2.5 rpm using an E-type viscometer.

Description

Sealant for display devices

The present invention relates to a sealant for a display device.

In recent years, liquid crystal display devices, organic EL display devices, electrophoresis type display devices, and the like have been put into practical use as display devices for various electronic devices. For example, a liquid crystal display device has a structure in which a liquid crystal is sealed between a pair of substrates.

Such a liquid crystal display device can be manufactured by, for example, the following method. First, a liquid crystal sealant is applied on a transparent substrate to form a frame for filling the liquid crystal. Then, a minute liquid crystal is dropped in the frame. While the liquid crystal sealant remains uncured, the other substrate is laminated under high vacuum so as to face the substrate. Then, the liquid crystal sealant is cured. Various sealing agents have been proposed as sealing agents for sealing liquid crystal, and an epoxy resin having low solubility in liquid crystal and a liquid crystal sealing agent containing an epoxy resin curing agent have been proposed (for example, Patent Document 1). ..

On the other hand, as an electrophoresis type display device, for example, a display device having a microcup structure has been proposed (for example, Patent Document 2). The electrophoresis-type display device has a structure in which display elements are sealed between a pair of substrates. In the display device, after producing a laminated body having a display element and a pair of substrates sandwiching the display element, a sealing agent is applied to a gap in a peripheral portion of the laminated body and the sealant is cured to form a sealing member. ..

Japanese Unexamined Patent Publication No. 2005-018022 Japanese Patent Publication No. 2004-536332

In particular, a sealant for an electrophoresis-type display device is required to have a low viscosity that allows it to penetrate into minute gaps. On the other hand, the cured product of the sealing agent is also required to have moisture resistance from the viewpoint of protecting elements, liquid crystals and the like, and it is common to include a large amount of filler. However, when the sealant contains a large amount of filler, the viscosity tends to be remarkably high. That is, it has been difficult to have both a low viscosity that can penetrate into a minute gap and a moisture resistance of a cured product. Further, the sealant is also required to be curable at a low temperature and have good viscosity stability.

The present invention has been made in view of the above problems. That is, it is an object of the present invention to provide a sealant for a display device having a low viscosity, good viscosity stability, curable at a low temperature, and high moisture resistance of a cured product.

The present invention provides the following sealants for display devices.
[1] An E-type viscosity meter containing an epoxy compound (A) containing a polyfunctional epoxy compound (a1) and a monofunctional epoxy compound (a2) having a biphenyl structure, and a polyamine-based latent thermosetting agent (B). A sealant for a display device having a viscosity of 20.0 Pa · s or less measured at 25 ° C. and 2.5 rpm.

[2] The sealant for a display device according to [1], wherein the polyamine-based latent thermosetting agent (B) has a softening point of 70 ° C to 110 ° C.
[3] The amine equivalent of the polyamine-based latent thermosetting agent (B) is in the range of 0.4 to 2.0 equivalent with respect to the epoxy equivalent of the epoxy compound (A), [1] or [2]. ] The sealant for the display device described in.

[4] The indication according to any one of [1] to [3], wherein the amount of the monofunctional epoxy compound (a2) in 100 parts by mass of the epoxy compound (A) is 35 parts by mass to 90 parts by mass. Equipment sealant.
[5] The sealant for a display device according to any one of [1] to [4], which is a sealant for electronic paper.

The sealant for display devices of the present invention has a low viscosity. Further, the cured product of the sealant for the display device has high moisture resistance. Further, the sealant has excellent low-temperature curability and viscosity stability. Therefore, it is very useful as a sealing agent for sealing various display devices such as electronic paper and liquid crystal display devices.

The sealant for display devices of the present invention (hereinafter, also simply referred to as "seal agent") is a composition for sealing various display devices such as electronic paper and liquid crystal display devices.

For example, a sealing agent used for electronic paper or the like is required to have a low viscosity and high moisture resistance when cured. However, in the conventional sealant, as described above, it is common to use a filler in order to improve the moisture resistance, and such a method has a problem that the viscosity of the sealant tends to increase. ..

On the other hand, the sealant of the present invention has a viscosity of 20.0 Pa · s or less measured at 25 ° C. and 2.5 rpm with an E-type viscometer, and has at least a polyfunctional epoxy compound (a1) and a biphenyl structure. It contains an epoxy compound (A) containing a functional epoxy compound (a2) (hereinafter, also simply referred to as “monofunctional epoxy compound (a2)”), and a polyamine-based latent thermosetting agent (B). As a result of diligent studies by the present inventors, when the monofunctional epoxy compound (a2) having a biphenyl structure is included in the sealing agent, a low viscosity can be achieved as described above, and a cured product can be obtained without adding a filler. It was found that the moisture resistance of the material is increased. Although the reason is not clear, it is considered that the biphenyl structure of the monofunctional epoxy compound (a2) enhances the moisture resistance of the cured product. Further, since the monofunctional epoxy compound (a2) has an epoxy structure in addition to the biphenyl structure, it has a high affinity with the polyfunctional epoxy compound (a1). Therefore, it is considered that the biphenyl structure is arranged on the entire cured product of the sealant, and the moisture resistance of the cured product is significantly improved. Further, the monofunctional epoxy compound (a2) has a relatively low viscosity. In general, when the sealant contains a latent thermosetting agent, the viscosity tends to increase. However, since the sealant of the present invention contains the monofunctional epoxy compound (a2), the viscosity of the sealant falls within the above range.

Further, in the sealant of the present invention, a polyamine-based latent thermosetting agent (B) is used as a curing agent for curing the epoxy compound (A). By combining the epoxy compound (A) with a polyamine-based latent thermosetting agent, a one-component sealing agent having excellent storage stability can be obtained.

Hereinafter, the physical properties of each component and the sealing agent contained in the sealing agent of the present invention will be described. If necessary, the sealant may further contain components other than the epoxy compound (A) and the polyamine-based latent thermosetting agent (B).

(1) Epoxy compound (A)
The epoxy compound (A) of the present invention contains a polyfunctional epoxy compound (a1) and a monofunctional epoxy compound (a2) having a biphenyl structure, and may further contain other epoxy compounds, if necessary.

The total amount of the epoxy compound (A) with respect to the total amount of the sealant is preferably 30 to 80% by mass, more preferably 40 to 70% by mass. When the total amount of the epoxy compound (A) is in the above range, the cured product of the sealant can surely seal the display device.

-Polyfunctional epoxy compound (a1)
The polyfunctional epoxy compound may be a compound having two or more epoxy groups in one molecule. The polyfunctional epoxy compound may be solid at room temperature, but is more preferably liquid.

The polyfunctional epoxy compound (a1) may be either a monomer, an oligomer, or a polymer, but from the viewpoint of keeping the viscosity of the sealant within the above range, the monomer or oligomer is preferable, and the monomer is more preferable.

The weight average molecular weight (Mw) of the polyfunctional epoxy compound (a1) is preferably 200 to 700, more preferably 300 to 500. When the weight average molecular weight of the polyfunctional epoxy compound (a1) is in the above range, the viscosity of the sealant tends to fall within the desired range. The weight average molecular weight of the polyfunctional epoxy compound (a1) can be measured, for example, by gel permeation chromatography (GPC) using polystyrene as a standard.

Further, the number of epoxy groups contained in one molecule of the polyfunctional epoxy compound (a1) may be 2 or more, and may be 3 or more, but the crystallinity is relatively low, and the coatability and viscosity stability are good. 2 is more preferable from the viewpoint that it is good and a cured product having a crosslinked structure can be easily obtained. Further, the epoxy equivalent of the polyfunctional epoxy compound (a1) is preferably 100 to 250 g / equivalent, more preferably 110 to 200 g / equivalent. When the amount of the epoxy group of the polyfunctional epoxy compound (a1) is in the above range, the obtained cured product tends to have an appropriate hardness. The epoxy equivalent of the polyfunctional epoxy compound (a1) can be specified by a known method, for example, by titration or the like.

The structure of the polyfunctional epoxy compound (a1) is not particularly limited, and may have, for example, an aromatic ring between a plurality of epoxy groups, an aliphatic group, or an alicyclic group. May be. Examples of the polyfunctional epoxy compound (a1) include bisphenol type epoxy compounds such as bisphenol A type, bisphenol F type, bisphenol E type, bisphenol S type, bisphenol AD type, and hydrogenated bisphenol A type; diphenyl ether type epoxy compounds; Phenol novolak type, cresol novolak type, biphenyl novolak type, bisphenol novolak type, naphthol novolak type, trisphenol novolak type, dicyclopentadiene novolak type and other novolak type epoxy compounds; biphenyl type epoxy compound; naphthyl type epoxy compound; triphenol methane Includes triphenol alkane type epoxy compounds such as type, triphenol ethane type, triphenol propane type; alicyclic epoxy compound; aliphatic epoxy compound; polysulfide-modified epoxy compound; resorcin type epoxy compound; glycidylamine type epoxy compound; etc. Is done. The epoxy compound (A) may contain only one type of the polyfunctional epoxy compound (a1), or may contain two or more types.

Among these, since the cured product has high moisture resistance, the polyfunctional epoxy compound (a1) preferably contains an aromatic ring or a hydrogenated product thereof, and preferably contains a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, and a bisphenol E. Type epoxy compounds and bisphenol type epoxy compounds such as hydrogenated bisphenol A type are particularly preferable.

The amount of the polyfunctional epoxy compound (a1) in the epoxy compound (A) is preferably 10 to 65% by mass, more preferably 30 to 60% by mass. When the amount of the polyfunctional epoxy compound (a1) in the epoxy compound (A) is in the above range, the curability of the sealant can be improved. In addition, an appropriate crosslinked structure can be included in the cured product.

-A monofunctional epoxy compound having a biphenyl structure (a2)
The monofunctional epoxy compound (a2) may be a compound having a biphenyl structure and one epoxy group in one molecule. The monofunctional epoxy compound (a2) may partially contain a structure other than the biphenyl structure and the epoxy group.

Examples of the monofunctional epoxy compound (a2) include a reaction product of phenylphenol and epichlorohydrin. Specific examples of the monofunctional epoxy compound (a2) include o-phenylphenol glycidyl ether, m-phenylphenol glycidyl ether, p-phenylphenol glycidyl ether, and derivatives thereof. The epoxy compound (A) may contain only one type of monofunctional epoxy compound (a2), or may contain two or more types.

The epoxy equivalent of the monofunctional epoxy compound (a2) is preferably 226 to 260. When the epoxy equivalent of the monofunctional epoxy compound (a2) is in the above range, the moisture resistance of the obtained cured product tends to increase. The epoxy equivalent of the monofunctional epoxy compound (a2) can be specified by a known method, for example, by titration.

The amount of the monopolyfunctional epoxy compound (a2) in the epoxy compound (A) is preferably 35 to 90% by mass, more preferably 40 to 70% by mass. When the amount of the monofunctional epoxy compound (a2) in the epoxy compound (A) is in the above range, the moisture resistance of the cured product can be improved.

-Other Epoxy Compounds The epoxy compound (A) may partially contain an epoxy compound that does not correspond to the polyfunctional epoxy compound (a1) or the monofunctional epoxy compound (a2). Examples of other epoxy compounds include monofunctional epoxy compounds having no biphenyl structure and the like.

However, from the viewpoint of moisture resistance and curability of the cured product, the amount of the other epoxy compound in the epoxy compound (A) is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly other epoxy compounds. It is preferable not to contain.

(2) Polyamine-based latent thermosetting agent (B)
The polyamine-based latent thermosetting agent may be a compound having two or more amino groups in one molecule and reacting with the above-mentioned epoxy compound (A) by heating.

The polyamine-based latent thermosetting agent (B) is preferably solid at room temperature. When the polyamine-based latent thermosetting agent (B) is solid at room temperature, the polyamine-based latent thermosetting agent (B) does not easily react with the epoxy compound (A) during storage of the sealing agent, and the viscosity of the sealing agent is stable. Sex increases.

The softening point of the polyamine-based latent thermosetting agent (B) is preferably 70 to 110 ° C, more preferably 70 to 80 ° C. When the softening point of the polyamine-based latent thermosetting agent (B) is in the above range, the reaction with the epoxy compound (A) at room temperature can be suppressed, while the polyamine-based latent property can be suppressed without excessive heating. It becomes possible to react the thermosetting agent (B) with the epoxy compound (A).

Examples of the polyamine-based latent thermosetting agent (B) include a latent curing agent having a polymer structure obtained by reacting an amine with an epoxy. Specifically, ADEKA hardener EH5015S (softening point: 85 to 105 ° C.), ADEKA hardener EH4357S (softening point: 75 to 85 ° C.), ADEKA hardener EH5030S (softening point: 70 ° C.) 80 ° C.) and the like are included.

The amine equivalent of the polyamine-based latent thermosetting agent (B) is preferably 0.4 to 2.0 equivalents, more preferably 0.6 to 1.4 equivalents, relative to the epoxy equivalent of the epoxy compound (A). When the amine equivalent of the polyamine-based latent thermosetting agent (B) is in the above range, the curability of the sealant becomes good. The epoxy equivalent (g / equivalent) of the epoxy compound (A) is the total amount of the epoxy compound (A) with respect to the total number of epoxy groups derived from the epoxy compound (A) in the sealant, that is, (the epoxy compound in the sealant). (A) total amount / total number of epoxy groups in the sealant).

On the other hand, the amine equivalent (g / equivalent) of the polyamine-based latent thermosetting agent (B) is the polyamine-based latent thermosetting agent (B) with respect to the number of amino groups derived from the polyamine-based latent thermosetting agent (B). , That is, (amount of polyamine-based latent heat-curing agent (B) / number of amino groups in the sealant). The amine equivalent of the polyamine-based latent thermosetting agent (B) can be specified by a known method, and can be determined by, for example, titration.

Further, the equivalent of the polyamine-based latent thermosetting agent (B) to the epoxy equivalent of the epoxy compound (A) is obtained from (the amine equivalent of the polyamine-based latent thermosetting agent (B) / the epoxy equivalent of the epoxy compound (A)). Desired. The amine equivalent of the polyamine-based latent thermosetting agent (B) can be adjusted by the number of amino groups contained in the polyamine-based latent thermosetting agent (B) and the amount of the polyamine-based latent thermosetting agent (B).

The total amount of the polyamine-based latent thermosetting agent (B) with respect to the total amount of the sealing agent is preferably 10 to 50% by mass, more preferably 20 to 40% by mass. When the total amount of the polyamine-based latent thermosetting agent (B) is in the above range, the cured product of the sealing agent can surely seal the display device.

(3) Others The sealing agent may contain components other than the above-mentioned epoxy compound (A) and polyamine-based latent thermosetting agent (B) as long as the object and effect of the present invention are not impaired. Examples of other components include fillers, various additives and the like.

When the sealant contains a filler, the moisture resistance and linear expansion of the cured product of the sealant are adjusted. The filler may be either an inorganic filler or an organic filler, and may contain both of them.

Examples of inorganic fillers include calcium carbonate, magnesium carbonate, barium sulfate, magnesium sulfate, aluminum silicate, zirconium silicate, iron oxide, titanium oxide, aluminum oxide (alumina), zinc oxide, silicon dioxide, potassium titanate, kaolin, talc. , Glass beads, sericite active white clay, bentonite, aluminum nitride, silicon nitride and the like.

Examples of organic fillers include particles having a melting point or softening point of 60-120 ° C., such as silicone fine particles, acrylic fine particles, styrene fine particles such as styrene / divinylbenzene copolymers, and polyolefin fine particles. Fine particles selected from the group; and include carnauba wax, microcrystalline wax, modified microcrystalline wax, Fishertropush wax, modified Fishertropush wax and the like.

The shape of the filler is not particularly limited and may be a fixed shape such as a spherical shape, a plate shape, a needle shape or a non-fixed shape, but a spherical shape is preferable from the viewpoint of enhancing the embedding property in a minute gap.

The average primary particle size of the filler is preferably 0.1 to 20 μm, more preferably 0.1 to 10 μm, and even more preferably 0.5 to 5 μm. The average primary particle size of the filler can be measured by the laser diffraction method described in JIS Z8825-1. Further, the mass average particle size d50 of the filler is preferably 0.05 to 30 μm, more preferably less than 25 μm. When the mass average particle size d50 of the filler is in the above range, the viscosity stability of the sealant becomes high. From the viewpoint of enhancing moisture resistance, the mass average particle size d50 of the filler is preferably 0.05 μm or more, more preferably 0.1 μm or more, further preferably 0.2 μm or more, and may be more than 1.0 μm. ..

The mass average particle size d50 of the filler is obtained by a laser method particle measuring instrument by a method conforming to JIS Z8825-1. Specifically, it is a particle size represented by a 50% by mass value on the mass addition curve. As the particle measuring device, a laser diffraction / scattering type particle size distribution measuring device MT-3300EX2 (laser wavelength 780 nm) manufactured by Microtrac can be used.

The amount of filler is appropriately selected according to the viscosity of the sealant. As the amount of filler increases, the viscosity of the sealant tends to increase.

Examples of various additives include silane coupling agents, rubber agents, ion trap agents, ion exchangers, leveling agents, pigments, dyes, plasticizers, defoamers, etc. These additives may be used alone or in combination of two or more.

(4) Method for preparing a sealant The method for preparing a sealant described above is not particularly limited. Each component can be mixed and prepared by a known method. The means for mixing each component is not particularly limited, and examples of the stirrer include a double-arm stirrer, a roll kneader, a twin-screw extruder, a ball mill kneader, a planetary stirrer, and the like. After mixing each component, the sealant may be filtered with a filter to remove impurities. Further, vacuum defoaming treatment or the like may be performed.

(5) Physical properties of sealant and cured product thereof The sealant of the present invention has a viscosity of 20.0 Pa · s or less measured at 25 ° C. and 2.5 rpm by an E-type viscometer, and has a viscosity of 1 to 10 Pa · s. s is preferable, and 1 to 5 Pa · s is more preferable. When the viscosity of the sealant is 20.0 Pa · s or less, it can enter even a minute gap when manufacturing various display devices.

In addition, from the viewpoint of facilitating embedding of the sealant in minute gaps, the ratio of the viscosity measured at a relatively low shear rate to the viscosity measured at a relatively high shear rate (low shear viscosity (measured value of 1 rpm viscosity) / It is preferable that the thixotropy index (TI value) showing a high share viscosity (measured value of 10 rpm viscosity) is close to 1. The thixotropy index is adjusted by, for example, the amount of filler.

On the other hand, the cured product of the sealant preferably has high heat resistance in order to maintain the adhesive strength with the substrate of various display devices. The glass transition temperature (Tg) of the cured product obtained by heating and curing the sealant at 80 ° C. for 60 minutes is preferably 30 to 120 ° C. If the glass transition temperature of the cured product of the sealant is within the relevant range, there is little possibility that interface peeling or the like will occur between each substrate and the cured product of the sealant, and it is possible to obtain a highly reliable display device. It becomes.

Further, when a sealant is used in a display device that sandwiches a display element between two resin sheets or between two inorganic substrates, a cured product obtained by heating and curing the sealant at 80 ° C. for 60 minutes. The glass transition temperature (Tg) of the above is preferably 10 to 40 ° C. When sealing between two resin sheets or two inorganic substrates with a cured product of a sealant, the glass transition temperature is considered from the viewpoint of preventing peeling from the substrate and imparting flexibility to the display device. Is preferably in the above range. The glass transition temperature of the cured product of the sealant is the glass transition temperature of a film having a thickness of 100 μm obtained by thermally curing the sealant at 80 ° C. for 60 minutes, and the temperature rise rate of 5 ° C./min by a thermal analyzer. It is obtained by measuring with.

Examples of substrates that can be bonded to the sealant of the present invention include inorganic substrates such as glass substrates; polyethylene terephthalate, polymethylmethacrylate, polycarbonate, cyclic polyolefin (COC), polypropylene, polystyrene, polyvinyl chloride, and transparent ABS resin. , A resin substrate made of transparent nylon, transparent polyimide, polyvinyl alcohol, etc.;

(6) Applications of Sealing Agent The sealing agent of the present invention may be used as a display device end face sealing agent for sealing the end face of various display devices, particularly a gap between two substrates sandwiching a display element. preferable. Since the sealant has an appropriately low viscosity, it is particularly easy to enter the gap between the substrates that sandwich the display element. Further, as described above, the cured product has high moisture resistance.

Therefore, it can be used as a sealing agent for various display devices having a liquid crystal element, an EL element, an LED element, an electrophoretic display element, and the like. In particular, it is very useful as a sealing agent for sealing the end face of a display device having an electrophoresis type or electric flow type display element in which it is necessary to apply a sealing agent to the gap between two substrates. Examples of electrophoretic display devices include electronic paper and the like.

The electrophoresis-type display device has, for example, a display element and a pair of substrates sandwiching the display element, and a sealing member seals a gap between the substrates formed on the peripheral edge of the pair of substrates. Has a structure. Then, a cured product of the above-mentioned sealing agent can be used for the sealing member.

The above-mentioned method for applying the sealant is not particularly limited, and a known method such as a dispenser or screen printing can be used. Further, the curing method of the sealant is not particularly limited and may be thermosetting or photocuring, but thermosetting is preferable in terms of suppressing deterioration of the display device. The thermosetting temperature is preferably 60 to 80 ° C. from the viewpoint of reducing damage to the display device. The thermosetting time is, for example, about 30 to 90 minutes, although it depends on the thermosetting temperature and the amount of the sealing agent.

Hereinafter, the present invention will be described in more detail with reference to examples. These examples do not limit the scope of the invention to be construed.

1. 1. Sealing agent material (1) Epoxy compound (A)
-Polyfunctional epoxy compound (a1)
EXA-835LV (manufactured by DIC, bisphenol F type / bisphenol A type bifunctional epoxy compound, epoxy equivalent: 165 g / equivalent, viscosity measured at 25 ° C. and 2.5 rpm with an E type viscometer: 2200 mPa · s)
YED216D (manufactured by Mitsubishi Chemical Co., Ltd., an aliphatic bifunctional epoxy compound represented by the following chemical formula, epoxy equivalent 120 g / equivalent, viscosity measured at 25 ° C. and 2.5 rpm with an E-type viscometer: 15 mPa · s)

CE-2021P (manufactured by Daicel Co., Ltd., alicyclic bifunctional epoxy compound represented by the following chemical formula, epoxy equivalent 156 g / equivalent, viscosity measured at 25 ° C. and 2.5 rpm with an E-type viscometer: 200 mPa · s)

YX8000D (Made by Mitsubishi Chemical, hydrogenated bisphenol A type bifunctional epoxy compound, epoxy equivalent 205 g / equivalent, viscosity measured at 25 ° C and 2.5 rpm with an E type viscometer: 800 mPa · s)
EP-4088S (made by ADEKA, dicyclopentadiene-based bifunctional epoxy compound, epoxy equivalent 170 g / equivalent, viscosity measured at 25 ° C and 2.5 rpm with an E-type viscometer: 230 mPa · s)

-A monofunctional epoxy compound having a biphenyl structure (a2)
OPP-EP (manufactured by Yokkaichi Chemical Company Limited, epoxy compound represented by the following chemical formula, epoxy equivalent: 230 g / equivalent, viscosity measured at 25 ° C. and 2.5 rpm with an E-type viscometer: 200 mPa · s)

-Other epoxy compounds ED-509S (manufactured by ADEKA, epoxy compounds represented by the following chemical formula, epoxy equivalent: 206 g / equivalent, viscosity measured at 25 ° C. and 2.5 rpm with an E-type viscometer: 20 mPa · s)

(2) Polyamine-based latent thermosetting agent (B)
EH5030S (manufactured by ADEKA, ADEKA Hardener (trade name), softening point: 70 to 80 ° C., amine equivalent: 105 g / equivalent)

(3) Others Polyaminoamide-based curing agent: Tomide 245 (manufactured by T & K TOKA, liquid)
Aromatic amine-based latent curing agent: Kayahard AA (manufactured by Nippon Kayaku Co., Ltd.)
Latent curing agent: DICY7 (manufactured by Mitsubishi Chemical Corporation, dicyandiamide)
SO-C6 (manufactured by Admatex, silica, average primary particle size: 1.8-2.3 μm)
KBM403 (made by Shinetsu Silicone Co., Ltd., 3-glycidoxypropyltrimethoxysilane)

2. 2. Preparation of Sealing Agent [Example 1]
EXA-835LV (polyfunctional epoxy compound (a1)) 320 parts by mass, OPP-EP (epoxy compound (a2) having a biphenyl structure) 250 parts by mass, and EH-5030S (polyamine-based latent thermosetting agent) 400 parts by mass. Was mixed to obtain a sealant. The amine equivalent with respect to the epoxy equivalent was calculated as follows. First, the number of epoxy groups contained in the sealant was calculated from the epoxy equivalents of the individual epoxy compounds, and the epoxy equivalent of the entire epoxy compound (A) (total amount of the epoxy compound (A) / number of epoxy groups) was calculated. Subsequently, the amine equivalent / epoxy equivalent was calculated.

[Examples 2 to 7 and Comparative Examples 1 to 5]
A sealant was prepared in the same manner as in Example 1 except that the composition was changed to that shown in Table 1.

3. 3. Evaluation The following evaluation was performed on the obtained sealant and its cured product.

(1) Viscosity The viscosity of the sealant was measured at 25 ° C., an E-type viscometer, and a rotation speed of 2.5 rpm.

(2) TI value The TI value was calculated by using an E-type viscometer and a rotation speed of 1.0 rpm measured value / 10 rpm measured value.

(3) Glass transition temperature (Tg) of the cured product
The sealant was applied on a release paper with an applicator to a film thickness of 100 μm. The release paper on which the coating film of the sealant was formed was held in a hot air drying oven at 80 ° C. for 60 minutes, then taken out and cooled. Then, the coating film was peeled off from the release paper to obtain a film having a film thickness of 100 μm. The glass transition temperature (Tg) of the obtained film was measured using a DMS-6100 manufactured by Seiko Instruments Inc. at a heating rate of 5 ° C./min.

(4) Moisture permeability (60 ° C, 80% Rh)
The sealant was applied on a release paper with an applicator to a film thickness of 100 μm. The release paper on which the coating film of the sealant was formed was held in a hot air drying oven at 80 ° C. for 60 minutes, then taken out and cooled. Then, the coating film was peeled off from the release paper to obtain a film having a film thickness of 100 μm. Then, an aluminum cup was prepared by a method conforming to JIS: Z0208, and left in a high-temperature and high-humidity tank at 60 ° C. and 80% RH for 24 hours. Then, the amount of moisture permeation was calculated from the mass before and after leaving the high-temperature and high-humidity tank by the following formula.
Weight moisture permeation ^{(g / m 2 · 100μm ·} 24h) = [ aluminum cup Weight after 24h standing (g) - aluminum cup weight before standing (g)] / film area ^(m 2)

(5) Moisture permeability (60 ° C, 90% Rh)
The measurement was carried out in the same manner as the above-mentioned method for measuring the amount of moisture permeation, except that the humidity of the high-temperature and high-humidity tank was changed to 90% Rh.

(6) Viscosity stability The produced sealant was left at 23 ° C. for 8 days. The viscosities of the sealants before and after leaving were compared and evaluated according to the following criteria.
〇: Viscosity after standing is 1.5 times or less compared to the viscosity before standing Δ: Viscosity after standing is more than 1.5 times and 2 times or less compared to viscosity before leaving ×: Viscosity before leaving The viscosity after leaving was more than doubled or gelled.

(7) Low temperature curability (curability at 80 ° C for 60 minutes)
Using a differential scanning calorimeter DSC7020 manufactured by Hitachi High-Tech, the calorific value A at 20 to 250 ° C. was measured at a sealant of 10 mg before curing, a temperature rise range of 20 ° C. to 250 ° C., and a temperature rise rate of 5 ° C./min. Further, 10 mg of the sealant before curing was heated from 20 ° C. to 80 ° C. at a heating rate of 50 ° C./min, and then held at 80 ° C. for 60 minutes, and the calorific value B during this period was measured. Then, the calorific value B / calorific value A was calculated, and the curing rate was obtained. It was evaluated according to the following criteria.
〇: Calorific value B / calorific value A is 80% or more ×: Calorific value B / calorific value A is less than 80%

As shown in Table 1 above, any of the sealants containing the polyfunctional epoxy compound (a1), the monofunctional epoxy compound (a2) having a biphenyl structure, and the polyamine-based latent thermosetting agent (B) The viscosity was low and the amount of moisture permeation was small (Examples 1 to 7). Further, these were also excellent in viscosity stability and low temperature curability (curability at 80 ° C. for 60 minutes).

On the other hand, when a monofunctional epoxy compound having no biphenyl structure was used (Comparative Example 1), the viscosity was low, but the moisture permeability was high. In addition, the moisture permeability was high even when the monofunctional epoxy compound was not contained (Comparative Example 2). Further, when a liquid polyaminoamide-based curing agent was used (Comparative Example 3), it was cured immediately after blending, and it was difficult to use it as a sealing agent. Further, when a non-polyamine-based latent thermosetting agent was used (Comparative Examples 4 and 5), the curability at 80 ° C. for 60 minutes was low.

This application claims priority based on Japanese Patent Application No. 2020-094354 filed on May 29, 2020. All the contents described in the application specification are incorporated in the application specification.

The sealant for display devices of the present invention has a low viscosity. Further, the cured product of the sealant for the display device has high moisture resistance. Therefore, it is very useful as a sealing agent for electronic paper and liquid crystal display devices.

Claims

An epoxy compound (A) containing a polyfunctional epoxy compound (a1) and a monofunctional epoxy compound (a2) having a biphenyl structure,
Polyamine-based latent thermosetting agent (B) and
The viscosity measured at 25 ° C. and 2.5 rpm with an E-type viscometer is 20.0 Pa · s or less.
Sealing agent for display devices.
The softening point of the polyamine-based latent thermosetting agent (B) is 70 ° C to 110 ° C.
The sealant for a display device according to claim 1.
The amine equivalent of the polyamine-based latent thermosetting agent (B) is in the range of 0.4 to 2.0 equivalent with respect to the epoxy equivalent of the epoxy compound (A).
The sealant for a display device according to claim 1 or 2.
The amount of the monofunctional epoxy compound (a2) in 100 parts by mass of the epoxy compound (A) is 35 parts by mass to 90 parts by mass.
The sealant for a display device according to any one of claims 1 to 3.
A sealant for electronic paper,
The sealant for a display device according to any one of claims 1 to 4.