JP7439283B2 - Encapsulants for display elements and their cured products - Google Patents

Description

The present invention relates to a sealant for display elements and a cured product thereof.

In the field of display elements, studies have been made to improve the properties of encapsulants. Hereinafter, an explanation will be given using an organic EL display device as an example.
Organic EL elements are increasingly being used in displays, lighting devices, etc. because of their low power consumption. Organic EL elements are easily degraded by moisture and oxygen in the atmosphere, so they are used sealed with various sealing materials, and in order to put them into practical use, it is necessary to improve the durability of various sealing materials against moisture and oxygen. desired.

Many sealants using thermosetting epoxy materials have been proposed as such sealing members. However, there is room for improvement in that curing requires a heating process and heating may damage the organic EL element.

A sealant using an acrylic material has also been proposed as an organic EL sealant that does not require curing by heating. For example, Patent Document 1 (International Publication No. 2019/82996) discloses that an acyclic alkanediol di(meth)acrylate having 6 or more carbon atoms and a specific cyclic monomer are used as a sealant for organic electroluminescent display elements. An encapsulant for organic EL display elements containing a photopolymerization initiator has been proposed.

International Publication No. 2019/82996

The present inventors investigated the use of acrylic resin in the sealing layer of display devices, and found that the cured film obtained from the sealant using acrylic material deteriorates by 2, 4, 6 over time. - It has become clear that components in sealants such as trimethylbenzoyl diphenylphosphine oxide (TPO) may come to the surface of the cured film, or bleed out, and this tendency becomes more pronounced in high temperature and humidity environments. became. Furthermore, there is still room for improvement in that there is a concern that a large amount of outgas may be generated due to the acrylic material remaining during the manufacturing process of the display element.

The present invention provides a sealant for a display element that suppresses bleed-out to the surface of a resin film and has excellent low outgassing properties.

According to the present invention, the following display element encapsulant and cured product are provided.
[1] A display element containing a radically polymerizable monomer mixture containing a silicon-free acrylate and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), wherein the radically polymerizable monomer mixture satisfies the following condition 1. Sealant for use.
Condition 1: Put 5 g of the radically polymerizable monomer mixture and a stirring bar into a 10 mL vial, add 0.2 g of TPO powder at 25°C, and set the stirring speed to 1000 rpm. Completely dissolved by visual inspection. Here, the TPO powder is ground in a mortar and has a mesh No. of JIS Z 8801-1. 14 (opening 1.01 mm) mesh is used.
[2] The encapsulant for display elements according to [1], wherein the radically polymerizable monomer mixture consists of only bifunctional (meth)acrylate.
[3] The encapsulant for a display element according to [2], wherein the bifunctional (meth)acrylate includes (A) a silicon-free and cyclic skeleton-free bifunctional (meth)acrylate.
[4] The encapsulant for a display element according to [3], wherein the bifunctional (meth)acrylate further includes (B) a silicon-free alicyclic bifunctional (meth)acrylate.
[5] The encapsulant for display elements according to any one of [2] to [4], wherein the bifunctional (meth)acrylate includes a bifunctional acrylate and a bifunctional methacrylate.
[6] The display element seal according to [4], wherein the content of the component (A) is 30 parts by mass or more and 70 parts by mass or less with respect to a total of 100 parts by mass of the components (A) and (B). Deterrent.
[7] The sealant for a display element according to any one of [1] to [6], which is used for sealing an organic EL display element.
[8] A cured product obtained by curing the sealant for display elements according to any one of [1] to [7].

Note that arbitrary combinations of these configurations and expressions of the present invention converted between methods, devices, etc. are also effective as aspects of the present invention.
For example, according to the present invention, the present invention includes a substrate, a display element disposed on the substrate, and a sealing layer covering the display element, wherein the sealing layer is made of the ultraviolet curable resin according to the present invention. It is also possible to provide a display device made of a cured product of the composition.

According to the present invention, it is possible to provide a sealant for a display element that suppresses bleed-out to the surface of a resin film and has excellent low outgassing properties.

Embodiments of the present invention will be described below with reference to the drawings. Note that, in all the drawings, similar constituent elements are given the same reference numerals, and description thereof will be omitted as appropriate. Further, in this embodiment, each component may be used alone or in combination of two or more. Further, "~" representing a numerical range represents the above or below, and includes both the upper limit and the lower limit.

(Encapsulant for display elements)
In this embodiment, the encapsulant for display elements (hereinafter also simply referred to as "encapsulant") is a composition used for encapsulating display elements, and is a radically polymerizable composition containing non-silicon-containing acrylate. Contains a monomer mixture and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). The radically polymerizable monomer mixture satisfies Condition 1 below.
Condition 1: Put 5 g of radically polymerizable monomer mixture and a stirring bar in a 10 mL vial, add 0.2 g of TPO powder at 25°C, and set the stirring speed to 1000 rpm. Within 30 minutes of stirring time, TPO powder is visually observed. Completely dissolve. Here, the TPO powder is ground in a mortar and prepared using JIS Z 8801-1 mesh No. 14 (opening 1.01 mm) mesh is used.
In Condition 1, more specifically, the default vial is Mighty Vial No. 5 (manufactured by Maruem Corporation, code number 0102-18), and the stirrer was a triangular rotor 20×8 mm (manufactured by As One Corporation, model number 011.420).

In this embodiment, the radically polymerizable monomer mixture in the sealant contains a silicon-free acrylate and TPO, and the radically polymerizable monomer mixture satisfies Condition 1 above regarding the solubility of TPO. Therefore, the bleed-out of the sealant onto the surface of the resin film, for example, the coating film, can be suitably suppressed, and a resin film with excellent low outgassing properties can be obtained. Further, according to the present embodiment, it is also possible to suppress bleed-out of TPO to the surface of the resin film of the sealant, for example.

It is not necessarily clear why a resin film with excellent bleed-out suppression and low outgassing properties can be obtained when the radically polymerizable monomer mixture satisfies the above-mentioned condition 1 regarding the solubility of TPO. Because the polarity is close to that of the resin (mixture), TPO can stably exist inside the resin, making it difficult for bleed-out to occur, and since TPO is delocalized throughout the resin, the reaction proceeds uniformly. It is thought that unreacted components are less likely to remain.
That is, the present inventors newly focused on the TPO solubility of the radically polymerizable monomer mixture as a design guideline for suppressing bleed-out and outgassing. If the TPO dissolution time is short, it means that the compatibility between TPO and the radically polymerizable monomer mixture is excellent; if it is long, the polarity between TPO and the resin becomes distant, so that it exists stably inside the resin. The present inventors found that bleed-out is likely to occur due to the inability of TPO to delocalize throughout the resin, which means that the reaction progresses unevenly and the curing progresses sparsely. We considered that the TPO solubility of the radically polymerizable monomer mixture is effective as an indicator of the ease with which bleed-out and outgassing occur.
As a result of further intensive studies by the present inventors, the radically polymerizable monomer mixture contains a silicon-free acrylate, and the TPO solubility satisfies Condition 1 above, thereby reducing bleed-out and The present invention was completed by discovering that outgas can be effectively suppressed.

In Condition 1, the time from the start of stirring until TPO is completely dissolved is within 30 minutes, preferably within 25 minutes, more preferably within 20 minutes, and further Preferably within 18 minutes.
Further, in Condition 1, the time from the start of stirring until TPO is completely dissolved is 0 minutes or more, and may be, for example, 1 minute or more.
Hereinafter, the components contained in the sealant will be explained in more detail.

(Radical polymerizable monomer mixture)
Specifically, the radically polymerizable monomer mixture is a mixture containing two or more types of radically polymerizable monomers. The radically polymerizable monomer mixture contains silicon-free acrylate as a radically polymerizable monomer.
Specific examples of silicon-free acrylates include silicon-free monofunctional monoacrylates, silicon-free bifunctional acrylates, and trifunctional or higher-functional silicon-free acrylates. From the viewpoint of improving the effect of suppressing bleed-out and outgassing, the silicon-free acrylate preferably includes a silicon-free bifunctional acrylate, more preferably a silicon-free bifunctional acrylate.

From the viewpoint of improving the effect of suppressing bleed-out and outgassing, the radically polymerizable monomer preferably does not contain silicon-containing acrylate, and more preferably does not contain silicon-containing (meth)acrylate.

Here, in this specification, a silicon-free acrylate refers to an acrylate that does not contain Si in its molecular structure, and refers to an acrylate that contains Si in its molecular structure.
Moreover, (meth)acrylate means at least one of acrylate and methacrylate. A (meth)acryloyl group means at least one of an acryloyl group and a methacryloyl group. (Meth)acrylic means at least one of acrylic and methacrylic.

From the viewpoint of obtaining uniform curability, the radically polymerizable monomer mixture preferably contains a difunctional (meth)acrylate, and more preferably consists only of a difunctional (meth)acrylate.
From the viewpoint of improving the uniformity of curing rate, the bifunctional (meth)acrylate preferably includes a bifunctional acrylate and a bifunctional methacrylate.
In addition, from the viewpoint of improving compatibility with TPO, the bifunctional (meth)acrylate preferably includes (A) a silicon-free and cyclic skeleton-free bifunctional (meth)acrylate, and more preferably (A). ) a silicon-free and cyclic skeleton-free bifunctional (meth)acrylate; and (B) a silicon-free alicyclic bifunctional (meth)acrylate.

(Component (A))
Component (A) is a silicon-free and cyclic skeleton-free bifunctional (meth)acrylate. Component (A) is specifically a (meth)acrylate that does not contain Si in its molecular structure, does not contain an alicyclic structure or an aromatic ring skeleton, and has two (meth)acrylic groups. It is.
From the viewpoint of making inkjet applicability more preferable, component (A) preferably contains a divalent chain hydrocarbon group which may have a branched chain, and more preferably contains a straight chain hydrocarbon group. From the viewpoint of monomer availability, the number of carbon atoms in the divalent chain hydrocarbon group is, for example, 1 or more, preferably 2 or more, and more preferably 4 or more. Further, from the viewpoint of improving heat resistance, the number of carbon atoms in the divalent chain hydrocarbon group is preferably 20 or less, more preferably 14 or less.

Specific examples of component (A) include di(meth)acrylates of alkanediol and di(meth)acrylates having a branched hydrocarbon structure.
More specifically, as component (A), 1,6-hexanediol diacrylate (for example, A-HD-N, manufactured by Shin Nakamura Chemical Industry Co., Ltd.), 1,9-nonanediol diacrylate (for example, A-NOD- N, manufactured by Shin Nakamura Chemical Co., Ltd.; Light Acrylate 1,9ND-A, manufactured by Kyoeisha Chemical Co., Ltd.), 1,10-decanediol diacrylate (for example, A-DOD-N, manufactured by Shin Nakamura Chemical Co., Ltd.), ethylene glycol diacrylate Acrylate (for example, SR206NS, manufactured by Arkema), triethylene glycol diacrylate (for example, SR272, manufactured by Arkema), polyethylene glycol diacrylate (for example, A-400, manufactured by Shin Nakamura Chemical Industry Co., Ltd.), neopentyl glycol diacrylate (for example, Light 1,3-butanediol dimethacrylate (for example, BG, manufactured by Shin-Nakamura Chemical Co., Ltd.), 1,4-butanediol dimethacrylate (for example, BD, Shin-Nakamura Chemical Co., Ltd.); Kagaku Kogyo Co., Ltd.), 1,6-hexanediol dimethacrylate (e.g. HD-N, Shin Nakamura Chemical Co., Ltd.), 1,9-nonanediol dimethacrylate (e.g. NOD-N, Shin Nakamura Chemical Co., Ltd.; Light) Acrylate 1,9-ND-M, manufactured by Kyoeisha Chemical Co., Ltd.), 1,10-decanediol dimethacrylate (e.g. DOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.), 1,12-dodecanediol dimethacrylate (e.g. SR262, Sartomer (manufactured by Shin-Nakamura Chemical Industries, Ltd.), neopentyl glycol dimethacrylate (for example, NPG, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), and other methacrylates.
Component (A) is selected from the group consisting of 1,9-nonanediol di(meth)acrylate from the viewpoint of improving plasma resistance, improving coating stability in inkjet method, and enhancing the balance of low dielectric constant effects. At least one (meth)acrylate.

The content of component (A) in the sealant is preferably 5 parts by mass or more, more preferably 10 parts by mass, based on 100 parts by mass of the radically polymerizable monomer, from the viewpoint of making inkjet applicability more preferable. parts or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more.
In addition, from the viewpoint of improving the hardness of the cured product, the content of component (A) in the sealant is preferably 99.5 parts by mass or less, more preferably 95 parts by mass or less, based on 100 parts by mass of the radically polymerizable monomer. It is not more than 85 parts by mass, more preferably not more than 85 parts by mass.

(Component (B))
Component (B) is a silicon-free alicyclic difunctional (meth)acrylate.
Component (B) is specifically a bifunctional (meth)acrylate having an alicyclic hydrocarbon structure in its molecular structure. From the viewpoint of improving heat resistance, the number of carbon atoms in the alicyclic hydrocarbon structure is preferably 4 or more, more preferably 5 or more, even more preferably 6 or more, and preferably 14 or less, more preferably is 12 or less, more preferably 10 or less.
The alicyclic hydrocarbon structure may be a saturated hydrocarbon structure or an unsaturated hydrocarbon structure. From the viewpoint of improving heat resistance, the alicyclic hydrocarbon structure is preferably a saturated hydrocarbon structure.

Further, the alicyclic hydrocarbon structure may be a monocyclic hydrocarbon structure, or may be a polycyclic hydrocarbon structure such as a condensed cyclic hydrocarbon structure or a bridged cyclic hydrocarbon group structure. The alicyclic difunctional (meth)acrylate may contain a group containing these alicyclic hydrocarbon structures in its molecular structure, and preferably contains a divalent group containing an alicyclic hydrocarbon structure.
Specific examples of the monocyclic hydrocarbon group include groups having a cycloalkane structure such as a cyclohexylene group and a cyclohexyl group; groups having a cycloalkene skeleton such as a cyclodecatriendiyl group and a cyclodecatriene group.
Specific examples of polycyclic hydrocarbon groups include groups having a dicyclopentadiene skeleton such as tricyclodecanediyl group, dicyclopentanyl group, dicyclopentenyl group; norbornanediyl group, isobornanediyl group, norbornyl group; Examples include groups having a norbornane skeleton such as an isobornyl group; groups having an adamantane skeleton such as an adamantanediyl group and an adamantyl group.

The cyclic hydrocarbon group in component (B) is preferably a group having a dicyclopentadiene skeleton from the viewpoint of improving yellowing resistance.
In addition, from the viewpoint of improving the hardness of the cured product, component (B) is tricyclodecane dimethanol di(meth)acrylate (for example, light acrylate DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.; DCP, manufactured by Shin Nakamura Chemical Industry Co., Ltd.). , more preferably tricyclodecane dimethanol di(meth)acrylate.

From the viewpoint of improving the hardness of the cured product, the content of component (B) in the sealant is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, based on 100 parts by mass of the radically polymerizable monomer. More preferably, it is 15 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more.
Furthermore, from the viewpoint of improving inkjet ejection properties, the content of component (B) in the sealant is preferably 70 parts by mass or less, more preferably 65 parts by mass, based on 100 parts by mass of the radically polymerizable monomer. The amount is more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less.

The content of component (A) relative to the total of 100 parts by mass of components (A) and (B) may be, for example, 3 parts by mass or more, preferably 30 parts by mass or more, from the viewpoint of improving inkjet coating properties. More preferably, it is 35 parts by mass or more, and still more preferably 40 parts by mass or more.
Further, from the viewpoint of improving the hardness of the cured product, the content of component (A) relative to the total of 100 parts by mass of components (A) and (B) may be, for example, 98 parts by mass or less, preferably 70 parts by mass or less. The amount is more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less.

From the viewpoint of improving the reaction rate, the content of the bifunctional acrylate relative to the total of 100 parts by mass of the bifunctional acrylate and the bifunctional methacrylate is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass. It is at least 25 parts by mass, even more preferably at least 25 parts by mass, even more preferably at least 35 parts by mass.
Further, from the viewpoint of elongation of the resin chain length, the content of the bifunctional acrylate with respect to the total of 100 parts by mass of the bifunctional acrylate and the bifunctional methacrylate may be, for example, 98 parts by mass or less, preferably 90 parts by mass or less. The amount is preferably 80 parts by mass or less, further preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less.

The radically polymerizable monomer may include (meth)acrylate other than silicon-free linear bifunctional (meth)acrylate.
Specific examples of (meth)acrylates other than silicon-free linear bifunctional (meth)acrylates include silicon-free monofunctional (meth)acrylates and silicon-free polyfunctional (meth)acrylates of trifunctional or higher functionality.
Specific examples of silicon-free monofunctional (meth)acrylates include mono(meth)acrylates that have a linear or branched hydrocarbon group in their molecular structure, and mono(meth)acrylates that have an aromatic hydrocarbon group in their molecular structure. ) acrylates. Examples of the former include lauryl methacrylate and isostearyl acrylate, and examples of the latter include 3-phenoxybenzyl acrylate.
From the viewpoint of further increasing the effect of suppressing bleed-out and outgassing, the sealant preferably does not contain any (meth)acrylate other than silicon-free linear bifunctional (meth)acrylate. That is, the content of (meth)acrylates other than silicon-free linear bifunctional (meth)acrylates in the sealant is preferably 0 parts by mass based on 100 parts by mass of the radically polymerizable monomer.
From the same point of view, when the sealant contains a (meth)acrylate other than a silicon-free linear bifunctional (meth)acrylate, the content should be more than 0 parts by mass based on 100 parts by mass of the radically polymerizable monomer. For example, it is 1 part by mass or less, preferably 0.5 part by mass or less, more preferably 0.1 part by mass or less, still more preferably 0.01 part by mass or less.

From the viewpoint of improving the strength of the cured product, the content of the radically polymerizable monomer in the sealant is preferably 70% by mass or more, more preferably 80% by mass or more, based on the total composition of the sealant. More preferably, it is 85% by mass or more, even more preferably 90% by mass or more, even more preferably 93% by mass or more.
In addition, from the viewpoint of improving the weather resistance of the sealing material, the content of the polymerizable compound in the sealant is preferably 99.9% by mass or less, more preferably 99.9% by mass or less, based on the total composition of the sealant. It is 99.5% by mass or less, more preferably 99% by mass or less, even more preferably 98% by mass or less.

(TPO)
The sealant includes 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). Specifically, TPO functions as a photopolymerization initiator, which is a compound that generates radicals or acids upon irradiation with ultraviolet rays or visible light.

From the viewpoint of improving curability, the content of TPO in the sealant is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further Preferably it is 1% by mass or more, and even more preferably 2% by mass or more.
In addition, from the viewpoint of suppressing coloring of the sealant, the content of TPO in the sealant is preferably 10% by mass or less, more preferably 8% by mass or less, based on the total composition of the sealant. More preferably, it is 6% by mass or less, and even more preferably 5% by mass or less.

(Other ingredients)
In this embodiment, the sealant may be composed of the radically polymerizable monomer mixture and TPO, or may contain components other than these. Specific examples of other components include tackifiers, fillers, curing accelerators, plasticizers, surfactants, heat stabilizers, flame retardants, antistatic agents, antifoaming agents, leveling agents such as fluorine-based leveling agents, and One or more additives selected from the group consisting of ultraviolet absorbers may be mentioned.
For example, when the sealant contains a leveling agent, the content thereof should be about 0.01 to 1% by mass, preferably about 0.1 to 0.5% by mass, based on the total composition of the sealant. I can do it.

The properties of the encapsulant are not limited, and from the viewpoint of improving the flexibility and plasma resistance of the encapsulant, and from the viewpoint of being suitable for forming a cured material by a coating method such as an inkjet method, the encapsulant is selected from the following. Preferably it is in liquid form.

Further, in the embodiment, from the viewpoint of stably forming a sealing material such as a resin film, the sealant is preferably a sealant used for coating, and more preferably a sealant used for coating by an inkjet method. It is an inhibitor.

Next, a method for manufacturing the sealant will be explained.
The method for producing the sealant is not limited, and includes, for example, mixing a polymerizable compound, a curing agent, and other components as appropriate, such as various additives added as necessary. As a method for mixing each component, for example, various known kneading machines such as a planetary stirrer, homodisper, universal mixer, Banbury mixer, kneader, two-roll, three-roll, extruder, etc. may be used alone or in combination, Examples include a method of uniformly kneading under conditions such as normal temperature, heating, normal pressure, reduced pressure, pressurization, or an inert gas stream.

Here, for example, by adjusting the components and content contained in the sealant and adjusting the mixing conditions of the components, it is possible to obtain a sealant that satisfies Condition 1 regarding TPO solubility. More specifically, we selected a plurality of bifunctional (meth)acrylates as a radically polymerizable monomer mixture and used them in combination, and in preparing the sealant, we added each monomer while controlling the oxygen concentration and temperature in the atmosphere. By mixing to obtain a radically polymerizable monomer mixture, it is possible to more stably obtain a sealing agent that satisfies Condition 1 regarding TPO solubility.

Moreover, a resin film can also be formed using the obtained sealant. For example, a sealant may be applied onto a substrate and cured. For coating, known techniques such as an inkjet method, screen printing, dispenser coating, etc. can be used.
Further, in this embodiment, the cured product is obtained by curing the sealant in this embodiment.

In this embodiment, the sealant contains a radically polymerizable monomer mixture containing a silicon-free acrylate and TPO, and since the radically polymerizable monomer mixture satisfies Condition 1 regarding TPO solubility, such a sealant is used. Accordingly, it is possible to obtain a resin film that is excellent in suppressing bleed-out to the resin film surface and having low outgassing properties. According to this embodiment, for example, it is also possible to suppress bleed-out under high temperature and high humidity conditions. Further, according to the present embodiment, for example, by using a resin film obtained with a sealant as a sealing material, it is also possible to obtain a display device with excellent manufacturing stability.
Taking an organic EL display device as an example of a display device, the organic EL display device has a layer made of a cured product of a sealant, for example, a sealing layer.
Moreover, the sealant in this embodiment is preferably for sealing an organic EL display element.

Moreover, the sealant obtained in this embodiment is suitably used for sealing a display element, preferably an organic EL display element, for example. According to this embodiment, it is possible to stably apply the resin layer using an inkjet method when forming the resin layer, and it is also possible to effectively suppress the occurrence of dark spots when the device emits light, thereby improving the manufacturing stability of the display device. It becomes possible.

EXAMPLES The present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
First, the materials used in the following examples are shown.

(radical polymerizable monomer)
(A) Silicon-free and cyclic skeleton-free bifunctional (meth)acrylate 1,9-nonanediol diacrylate: Light acrylate 1,9ND-A, manufactured by Kyoeisha Chemical Co., Ltd., linear bifunctional acrylate, silicon-free Acrylate 1,9-nonanediol dimethacrylate: NOD-N, manufactured by Shin Nakamura Chemical Co., Ltd., linear bifunctional methacrylate 1,12-dodecanediol dimethacrylate: SR262, manufactured by Sartomer, linear chain bifunctional methacrylate neopentyl glycol di Acrylate: Light acrylate NP-A, manufactured by Kyoeisha Chemical Co., Ltd., bifunctional acrylate, silicon-free acrylate (B) silicon-free alicyclic bifunctional (meth)acrylate dimethylol-tricyclodecane dimethacrylate: DCP, Shin Nakamura Chemical Manufactured by Kogyo Co., Ltd., bifunctional methacrylate dimethylol-tricyclodecane diacrylate: light acrylate DCP-A, manufactured by Kyoeisha Chemical Co., Ltd., bifunctional acrylate, silicon-free acrylate (other (meth)acrylates)
Isostearyl acrylate: S1800, manufactured by Shin-Nakamura Chemical Co., Ltd., monofunctional acrylate, silicon-free acrylate, silicon-containing bifunctional methacrylate: X-22-164AS, manufactured by Shin-Etsu Chemical Co., Ltd.

(Polymerization initiator)
(C) 2,4,6-trimethylbenzoyl-diphenylphosphine oxide: Omnirad TPO H, manufactured by GM Resins

(Leveling agent)
Fluorine leveling agent: F552, manufactured by DIC Corporation

(Examples 1 to 7, Comparative Examples 1 to 3)
Each component listed in Table 1 was blended to obtain a liquid curable composition as a sealant for each example.
In each example, first, among the components listed in Table 1, radically polymerizable monomers were prepared in a brown vial at room temperature (25°C) in an atmospheric environment with an oxygen concentration of 20.0 to 21.0%. The mixture was mixed to obtain a radically polymerizable monomer mixture. Also, from the perspective of reducing the possibility of runaway, methacrylate was added first and acrylate was added later. The TPO solubility of the obtained radically polymerizable monomer mixture was evaluated by the method described below.
Next, the radically polymerizable monomer mixture and the other components listed in Table 1 are mixed in a brown vial at 20 to 60°C in an atmospheric environment with an oxygen concentration of 20.0 to 21.0%, Compositions for each example were obtained.

Regarding the cured products of the compositions obtained in each example, the presence or absence of bleed-out and outgassing under high temperature and high humidity conditions were measured by the following method. The measurement results are also shown in Table 1.

(TPO solubility)
The TPO solubility of the radically polymerizable monomer mixture (hereinafter also referred to as "monomer liquid") in each example was evaluated using the following procedure.
1. 5 g of the monomer liquid was placed in a 10 mL vial (brown color, Mighty Vial No. 5 (manufactured by Maruem Co., Ltd., code number 0102-18)).
2. Grind the TPO evenly and finely in a mortar and grind it to JIS Z 8801-1 mesh No. It was filtered through a mesh of 14 (opening 1.01 mm).
3. Above 2. 0.2 g of TPO from the fraction below the mesh was added at 25°C.
4. Stirring was performed at 1000 rpm using a stirrer (triangle rotor 20 x 8 mm (manufactured by As One, model number 011.420)).
5. The time from the start of stirring until TPO was completely dissolved was visually confirmed. If TPO was not completely dissolved after 30 minutes, it was classified as "insoluble even after 30 minutes."

(High temperature and high humidity test)
The presence or absence of bleed-out under high temperature and high humidity conditions was evaluated using the following procedure.
1. The blended solution was applied to a 50 mm x 50 mm alkali-free glass using a spin coater to an average film thickness of 8 μm.
2. It was sealed in a nitrogen purge box and nitrogen was flushed for 3 minutes.
3. It was irradiated with 1500mW5600mJ (UVA2) and cured.
It was placed in a constant temperature and humidity bath at 4.85° C. and 85% RH, and taken out after 500 hours.
5. If no bleed-out occurred by visual inspection, it was evaluated as "OK", and if it was bleed-out, it was evaluated as "x".

(Outgas evaluation)
The amount of outgas generated was evaluated using the following procedure.
1. The sealant obtained in each example was applied to a 50 mm x 50 mm alkali-free glass using a spin coater so that the average film thickness was 8 μm.
2. Above 1. The coating film obtained in step 1 was sealed in a nitrogen purge box, and nitrogen was flushed for 3 minutes.
3. It was irradiated with 1500mW5600mJ (UVA2) and cured.
4. Above 3. The test piece prepared above was cut into 10 mm x 50 mm, heated at 110° C. for 30 minutes using the headspace method, and the amount of outgas generated was collected using gas chromatography.
5. Above 4. The amount of outgas [ppm] collected was determined based on toluene.

From Table 1, in each Example, bleed-out to the coating film surface was suppressed under high temperature and high humidity conditions, and also had excellent low outgassing properties.

This application claims priority based on Japanese Patent Application No. 2020-157661 filed on September 18, 2020, and the entire disclosure thereof is incorporated herein.

Claims (5)

A seal for a display element, comprising a radically polymerizable monomer mixture containing a silicon-free acrylate and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), wherein the radically polymerizable monomer mixture satisfies the following condition 1. agent ,
The radically polymerizable monomer mixture consists only of difunctional (meth)acrylate,
The bifunctional (meth)acrylate includes (A) a silicon-free and cyclic skeleton-free bifunctional (meth)acrylate,
The bifunctional (meth)acrylate further includes (B) a silicon-free alicyclic bifunctional (meth)acrylate.
Condition 1: Put 5 g of the radically polymerizable monomer mixture and a stirring bar into a 10 mL vial, add 0.2 g of TPO powder at 25°C, and set the stirring speed to 1000 rpm. Completely dissolved by visual inspection. Here, the TPO powder is ground in a mortar and has a mesh No. of JIS Z 8801-1. 14 (opening 1.01 mm) mesh is used. The encapsulant for a display element according to claim 1 , wherein the bifunctional (meth)acrylate includes a bifunctional acrylate and a bifunctional methacrylate. The seal for a display element according to claim 1 or 2, wherein the content of the component (A) is 30 parts by mass or more and 70 parts by mass or less with respect to a total of 100 parts by mass of the components (A) and (B) . agent. The sealing agent for a display element according to any one of claims 1 to 3 , which is used for sealing an organic EL display element. A cured product obtained by curing the display element sealant according to any one of claims 1 to 4 .