JP2024118711A - Sealant for organic EL element, cured film, organic EL element, and method for producing organic EL element - Google Patents

Abstract

[Problem] To provide a sealant for organic EL elements that can achieve both good wetting and spreading properties when applied to a substrate by an inkjet method, and straightness of the film edge. [Solution] The sealant for organic EL elements contains [A] a polymerizable compound and [B] a polymerization initiator, and has a viscosity of 1 mPa·s to 40 mPa·s as measured at 25°C and 20 rpm using an E-type viscometer, and contains, as the polymerizable compound [A], a compound (A1) having a polymerizable group and a monovalent fluorinated hydrocarbon group. [Selected Figure] None

Description

The present invention relates to a sealant for organic EL elements, a cured film, an organic EL element, and a method for manufacturing an organic EL element.

An organic electroluminescence element (organic EL element) is a light-emitting element having a layered structure including an anode, an organic light-emitting layer, and a cathode. Organic EL elements are widely used in various applications such as display devices and lighting devices.

The organic light-emitting layer of an organic EL element is easily deteriorated by contact with moisture and oxygen. For example, there is a concern that moisture that has penetrated into the element over a long period of operation may cause areas that do not emit light (dark spots) to form, or that light-emitting characteristics may deteriorate due to contact with moisture or oxygen. Therefore, a sealing structure has been provided in the organic EL element to prevent the organic light-emitting layer from coming into contact with moisture or oxygen (see, for example, Patent Document 1). Patent Document 1 discloses that an organic sealing layer that covers the organic light-emitting layer is formed by applying and curing a curable composition that contains a polymerizable compound and a polymerization initiator.

In addition, because it is easy to form a uniform coating film with a small amount of curable composition and because it is superior in terms of throughput, attempts have been made in recent years to form a sealing structure for an organic EL element by applying a curable composition onto a substrate by inkjet coating and curing the composition (see Patent Document 1).

International Publication No. 2018/225723

In order to make it possible to apply inkjet coating when forming a sealing structure for an organic EL element, the curable composition for forming the sealing structure (hereinafter also referred to as "sealant for organic EL elements") is required to have low viscosity and to have little coating unevenness in order to sufficiently cover the organic light-emitting layer. In particular, in order to accommodate thinner sealing structures (e.g., structures with a thickness of 10 μm or less) that accompany thinner organic EL elements, sealants for organic EL elements are required to have good wetting and spreading properties. Thus, it has been considered to improve the coatability of sealants for organic EL elements by blending a surfactant into the sealant for organic EL elements.

However, the inventors' investigations revealed that when an attempt is made to improve the coatability of a sealant for organic EL elements by using a surfactant, the edge lines of the film formed by coating on a substrate (i.e., the edges on both the left and right sides relative to the direction of movement of the inkjet nozzle) tend to become curved or sawtooth, and linearity is lost. In this case, there is a concern that uncoated areas will be generated at the edges of the film, resulting in insufficient sealing of the organic light-emitting layer. From the viewpoint of improving the reliability of organic EL elements, a sealant for organic EL elements is required to have both good wetting and spreading properties when coated on a substrate and linear edge lines of the film (hereinafter also referred to as "edge straightness").

The present invention has been made in consideration of the above problems, and has as its main object to provide a sealant for organic EL devices that can achieve both good wetting and spreading properties when applied to a substrate by an inkjet method, and straightness of the film edge.

The present invention provides the following sealant for organic EL elements, cured film, organic EL element, and method for producing an organic EL element.

[1] A sealant for an organic EL device, comprising: [A] a polymerizable compound; and [B] a polymerization initiator, and having a viscosity of 1 mPa·s or more and 40 mPa·s or less as measured using an E-type viscometer at 25°C and 20 rpm, wherein the polymerizable compound [A] is a compound (A1) having a polymerizable group and a monovalent fluorinated hydrocarbon group.
[2] A cured film formed from the sealant for an organic electroluminescence device according to [1] above.
[3] An organic electroluminescence (EL) element having an emitting layer sealed with the sealing agent for an organic electroluminescence (EL) element according to [2] above.
[4] A method for producing an organic EL element, comprising the steps of applying the sealant for an organic EL element according to [1] above to a light-emitting layer-forming surface of a substrate on which an organic light-emitting layer has been formed, and curing the sealant for an organic EL element by irradiating with radiation to form a sealing structure.

The sealant for organic EL devices of the present invention can achieve both good wetting and spreading properties when applied to a substrate by the inkjet method, as well as straightness at the edge of the film.

Below, we will explain in detail the matters related to the embodiment. In this specification, a numerical range described using "~" means that the numerical range includes the numerical ranges before and after "~" as the lower and upper limits.

<Sealant for organic EL devices>
The sealant for organic EL elements of the present disclosure (hereinafter also referred to as the present sealant) is a curable composition used for thin film encapsulation (TFE: Thin Film Encapsulation) of organic electroluminescence elements (organic EL elements). The present sealant has a viscosity of 1 mPa·s or more and 40 mPa·s or less, measured using an E-type viscometer at 25° C. and 20 rpm. The present sealant having such a low viscosity is suitable for inkjet coating.

The sealant contains [A] a polymerizable compound and [B] a polymerization initiator. [A] is a compound that can generate a polymer in response to a stimulus. By heating the sealant or irradiating the sealant with radiation, the polymerization reaction of [A] the polymerizable compound proceeds, and a cured film is obtained. The sealant may be a cationic polymerizable sealant in which curing proceeds by cationic polymerization of [A] the polymerizable compound, or a radically polymerizable sealant in which curing proceeds by radical polymerization of [A] the polymerizable compound.

Below, we will explain each component contained in this sealant, as well as other components that are blended as necessary. Unless otherwise specified, each component may be used alone or in combination of two or more types.

Here, in this specification, the term "hydrocarbon group" includes chain-shaped hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "chain-shaped hydrocarbon group" means a straight-chain hydrocarbon group and a branched hydrocarbon group that do not include a cyclic structure in the main chain and are composed only of a chain structure. The chain-shaped hydrocarbon group may be saturated or unsaturated. The term "alicyclic hydrocarbon group" means a hydrocarbon group that includes only an alicyclic hydrocarbon structure as a ring structure and does not include an aromatic ring structure. The alicyclic hydrocarbon group does not necessarily have to be composed only of an alicyclic hydrocarbon structure, and also includes those that have a chain structure as a part of it. The term "aromatic hydrocarbon group" means a hydrocarbon group that includes an aromatic ring structure as a ring structure. The aromatic hydrocarbon group does not necessarily have to be composed only of an aromatic ring structure, and may include a chain structure or an alicyclic hydrocarbon structure as a part of it. The ring structure of the alicyclic hydrocarbon group and the aromatic hydrocarbon group may have a substituent consisting of a hydrocarbon structure. The term "cyclic hydrocarbon group" means a hydrocarbon group that includes an alicyclic hydrocarbon group and an aromatic hydrocarbon group. A "structural unit" refers to a unit that mainly constitutes the main chain structure, and at least two units are contained in the main chain structure. "(Meth)acrylo" is a term that includes "acrylic" and "methacrylic". In this specification, it is also referred to as an "epoxy group", including "oxiranyl group" and "oxetanyl group".

<[A] Polymerizable compound>
[Compound (A1)]
The present sealing agent contains, as the polymerizable compound [A], a compound (A1) having a polymerizable group and a monovalent fluorinated hydrocarbon group. The polymerizable group of the compound (A1) is an oxetanyl group. , oxiranyl group, vinyl ether group, allyl ether group, vinyl group, (meth)acryloyl group, vinylphenyl group, hydroxyl group, etc. Among these, the polymerizable group contained in the compound (A1) is an oxetanyl group, an oxiranyl group, etc. , a vinyl ether group or a (meth)acryloyl group is preferred, and an oxetanyl group or a (meth)acryloyl group is more preferred.

The number of polymerizable groups in compound (A1) is not particularly limited. From the viewpoint of suppressing an increase in the viscosity of the sealant while achieving a good balance between wet spreadability and straight edge movement when the sealant is applied to a substrate, the number of polymerizable groups in compound (A1) is preferably 1 or 2, and particularly preferably 1.

The monovalent fluorinated hydrocarbon group (hereinafter also referred to as "fluorine-containing group R ^f ") contained in compound (A1) is a group in which one or more hydrogen atoms contained in a monovalent hydrocarbon group have been replaced with a fluorine atom. The number of carbon atoms in the fluorine-containing group R ^f is preferably 2 or more, and more preferably 2 to 20. From the viewpoint of achieving both the wetting and spreading properties of the present sealant and the straightness of the film at the end portion, the fluorine-containing group R ^f is preferably such that half or more of the hydrogen atoms contained in the monovalent hydrocarbon group have been replaced with fluorine atoms, and more preferably such that all but one hydrogen atom have been replaced with a fluorine atom or all hydrogen atoms have been replaced with fluorine atoms.

Among them, the fluorine-containing group R ^f is preferably a fluorinated chain hydrocarbon group. The fluorinated chain hydrocarbon group may be saturated or unsaturated, and may be linear or branched. Preferred specific examples of the fluorinated chain hydrocarbon group include groups represented by "-C _m F _2m-1 ", "-C _n F _2n H" or "-C _n F _2n+1 ". Here, m is an integer of 2 or more, and n is an integer of 1 or more. From the viewpoint of improving the wettability and spreadability of the sealant and the straightness of the film at the end in a well-balanced manner, m and n are preferably 3 or more, more preferably 5 or more, and even more preferably 7 or more. Moreover, from the viewpoint of suppressing a decrease in the wettability and spreadability, m and n are each preferably 20 or less, more preferably 15 or less, and even more preferably 12 or less.

When the fluorine-containing group ^Rf is a fluorinated chain hydrocarbon group, the fluorinated chain hydrocarbon group preferably has a carbon-carbon unsaturated bond, since this has a high effect of improving the wetting and spreading properties and the straightness of the film edge when the sealant is applied to a substrate in a well-balanced manner. The number of unsaturated carbon-carbon bonds that the fluorinated chain hydrocarbon group has is not particularly limited. The number of unsaturated carbon-carbon bonds that the fluorinated chain hydrocarbon group has is preferably one. Note that the carbon-carbon unsaturated bond in the fluorine-containing group ^Rf is non-polymerizable and is considered not to be involved in polymerization.

The number of fluorine-containing groups ^Rf in the compound (A1) is not particularly limited. From the viewpoint of achieving a good balance between wetting and spreading properties and straightness at the edge of the film, the number of fluorine-containing groups ^Rf in the compound (A1) is preferably 1 or 2, and more preferably 1.

（式（ｆ－１）～式（ｆ－１４）中、「＊」は結合手を表す。） Specific examples of the fluorine-containing group R ^f contained in the compound (A1) include groups represented by each of the following formulas (f-1) to (f-14).

(In formulas (f-1) to (f-14), "*" represents a bond.)

（式（１）中、Ｘ^１は、オキセタニル基、オキシラニル基、ビニルエーテル基又は（メタ）アクリロイル基を有する１価の基である。Ｙ^１は、炭素数１～１０のアルカンジイル基、又は炭素数２～１０のアルカンジイル基の炭素－炭素結合間に－Ｏ－を含む２価の基である。Ｒ^ｆは、「－Ｃ_ｍＦ_２ｍ－１」、「－Ｃ_ｎＦ_２ｎＨ」又は「－Ｃ_ｎＦ_２ｎ＋１」で表される１価のフッ素化鎖状炭化水素基である。ｍは２以上の整数であり、ｎは１以上の整数である。） A preferred specific example of the compound (A1) is a compound represented by the following formula (1).

(In formula (1), ^X1 is a monovalent group having an oxetanyl group, an oxiranyl group, a vinyl ether group or a (meth)acryloyl group. ^Y1 is a divalent group containing an alkanediyl group having 1 to 10 carbon atoms or an alkanediyl group having 2 to 10 carbon atoms containing -O- between the carbon-carbon bonds. ^Rf is a monovalent _fluorinated chain hydrocarbon group represented by " _{-CmF2m -1} ", " _-CnF2nH " or " _{-CnF2n +1} ". m is an integer of 2 or more, and n is an integer of 1 or more.)

In the above formula (1), specific and preferred examples of the monovalent fluorinated chain hydrocarbon group represented by ^Rf are as described above. ^Y1 may be linear or branched. From the viewpoint of the availability of raw materials, etc., the carbon number of ^Y1 is preferably 1 to 8, and more preferably 1 to 5.

[Compound (A2)]
The present sealant preferably further contains, as the polymerizable compound [A], a compound that is copolymerizable with the compound (A1) and does not have a fluorine-containing group ^Rf (hereinafter, also referred to as "compound (A2)"). By blending the compound (A2) in the present sealant, it is possible to adjust the viscosity of the present sealant, to increase the curability, and to easily reinforce the crosslinked structure.

The compound (A2) may be one or more selected from the group consisting of a monofunctional polymerizable compound not having a fluorine-containing group ^Rf (hereinafter also referred to as "monofunctional compound (A2m)") and a polyfunctional polymerizable compound not having a fluorine-containing group ^Rf (hereinafter also referred to as "polyfunctional compound (A2n)"). The present sealant preferably contains a monofunctional compound (A2m) and a polyfunctional compound (A2n) as the compound (A2). The polymerizable groups of the monofunctional compound (A2m) and the polyfunctional compound (A2n) may be appropriately selected depending on the polymerizable group of the compound (A1) to be blended in the present sealant.

The polyfunctional compound (A2n) contained in the sealant may contain a siloxane compound having two or more polymerizable groups (hereinafter also referred to as a "polyfunctional siloxane compound"). By containing a polyfunctional siloxane compound in the sealant, it is possible to improve the curing property while lowering the dielectric constant. Examples of polyfunctional siloxane compounds include siloxane compounds having a chain structure or a ring structure. The polymerizable group of the polyfunctional siloxane compound can be appropriately selected depending on the polymerizable group of the compound (A1) to be blended in the sealant.

（式（３－１）及び式（３－２）中、Ｒ^５及びＲ^６は、それぞれ独立して、水素原子、炭素数１～１０の１価の炭化水素基、又は重合性基を有する基である。ａは０～１００の整数である。ｂは１～１８の整数である。ただし、式（３－１）中の複数のＲ^５のうち２個以上は、重合性基を有する基である。式（３－２）中の複数のＲ^６のうち２個以上は、重合性基を有する基である。複数のＲ^５は互いに同一又は異なり、複数のＲ^６は互いに同一又は異なる。） Specific examples of the polyfunctional siloxane compound include compounds represented by the following formula (3-1) or formula (3-2).

(In formula (3-1) and formula (3-2), R ⁵ and R ⁶ are each independently a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a group having a polymerizable group. a is an integer from 0 to 100. b is an integer from 1 to 18. However, two or more of the multiple R ^5s in formula (3-1) are groups having a polymerizable group. Two or more of the multiple R ^6s in formula (3-2) are groups having a polymerizable group. The multiple R ^{5s are} the same or different, and the multiple R ^6s are the same or different.)

In the polymerizable compound [A], the content of compound (A1) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the polymerizable compound [A], from the viewpoint of obtaining a sufficient effect of improving the wet spreadability and the straightness of the edge of the film when the sealant is applied to a substrate. In addition, from the viewpoint of suppressing a decrease in the wet spreadability, the content of compound (A1) is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of the total amount of the polymerizable compound [A].

The ratio of the monofunctional compound (A2m) in the compound (A2) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, based on 100 parts by mass of the total amount of the compound (A2) (i.e., the total amount of the monofunctional compound (A2m) and the polyfunctional compound (A2n)). The content of the monofunctional compound (A2m) is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, based on 100 parts by mass of the total amount of the compound (A2). When the content of the monofunctional compound (A2m) is in the above range, a sealant for organic EL elements having low viscosity and excellent curability can be obtained.

When the sealant contains a polyfunctional siloxane compound, the content of the polyfunctional siloxane compound is preferably 2 parts by mass or more, and more preferably 5 parts by mass or more, relative to 100 parts by mass of the total amount of compound (A2). The content of the polyfunctional siloxane compound is preferably 40 parts by mass or less, and more preferably 30 parts by mass or less, relative to 100 parts by mass of the total amount of compound (A2).

Next, we will explain the details of the polymerizable compound [A] and the polymerization initiator [B] contained in each sealant when the sealant is a cationic polymerizable sealant or a radical polymerizable sealant.

<Cationically polymerizable sealing agent>
[[A] Polymerizable compound]
Compound (A1)
When the present sealing agent is a cationically polymerizable sealing agent, examples of the polymerizable group contained in compound (A1) (hereinafter, "compound (A1-c)") contained in the present sealing agent include an oxetanyl group, an oxiranyl group, a vinyl ether group, an allyl ether group, a vinyl group, and a hydroxyl group. Among these, the polymerizable group contained in compound (A1-1) is preferably an oxetanyl group or an oxiranyl group, and more preferably an oxetanyl group. The above explanations apply to specific examples and preferred examples of the fluorine-containing group R ^f contained in compound (A1-c).

（式（１－１）中、Ｒ^１は、水素原子、フッ素原子、アルキル基、フルオロアルキル基又はアリル基である。Ｒ^ｆは、「－Ｃ_ｍＦ_２ｍ－１」、「－Ｃ_ｎＦ_２ｎＨ」又は「－Ｃ_ｎＦ_２ｎ＋１」で表される１価のフッ素化鎖状炭化水素基である。ｍは２以上の整数であり、ｎは１以上の整数である。ｋは１～１０の整数である。） A preferred specific example of the compound (A1-c) is a compound represented by the following formula (1-1).

(In formula (1-1), R ¹ is a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, or an allyl group. R ^f is a monovalent fluorinated chain hydrocarbon group represented by "-C _m F _2m-1 ", "-C _n F _2n H" or "-C _n F _2n+1 ". m is an integer of 2 or more, n is an integer of 1 or more, and k is an integer from 1 to 10.)

In the above formula (1-1), specific and preferred examples of the monovalent fluorinated chain hydrocarbon group represented by ^Rf are as explained above.
Examples of the alkyl group represented by ^R1 include linear or branched alkyl groups having 1 to 10 carbon atoms. Examples of the fluoroalkyl group represented by ^R1 include linear or branched alkyl groups having 1 to 10 carbon atoms in which one or more hydrogen atoms have been substituted with fluorine atoms. The alkyl group and fluoroalkyl group represented by ^R1 preferably have 1 to 5 carbon atoms, and more preferably have 1 to 3 carbon atoms. From the viewpoint of reactivity, ^R1 is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms.
k is preferably an integer of 1 to 5, and more preferably an integer of 1 to 3.

Specific examples of the compound (A1-c) include the compounds represented by the following formulas (a1-1-1) to (a1-1-18).

In the cationic polymerizable sealant, the content of compound (A1-c) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, based on 100 parts by mass of the total amount of polymerizable compound [A]. The content of compound (A1-c) is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, based on 100 parts by mass of the total amount of polymerizable compound [A]. When the content of compound (A1-c) is in the above range, the sealant can exhibit a good balance between the wetting spreadability and the straightness of the edge of the film when applied to a substrate, and is also advantageous in that the wetting spreadability and the straightness of the edge of the film can be made even better.

Compound (A2)
When the present sealant is a cationic polymerizable sealant, the compound (A2) (hereinafter, "compound (A2-c)") contained in the present sealant includes a compound having an oxetanyl group, an oxiranyl group, a vinyl group, a vinyl ether group, an allyl ether group, or a hydroxyl group as a polymerizable group. Among these, from the viewpoint of cationic polymerizability, the compound (A2-c) is preferably a compound having an oxetanyl group, an oxiranyl group, or a vinyl ether group, and more preferably a compound having an oxetanyl group or an oxiranyl group. In addition, the compound (A2-c) may be either a monofunctional polymerizable compound or a polyfunctional polymerizable compound. As the compound (A2-c), a monofunctional epoxy compound, a polyfunctional epoxy compound, or both of them can be preferably used.

As the monofunctional polymerizable compound, a monofunctional oxetane compound can be preferably used. Specific examples of the monofunctional oxetane compound include 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane, 3-methyl-3-methoxyoxetane, phenyloxetane, phenoxymethyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-ethyl-3-((3-(triethoxysilyl)propoxy)methyl)oxetane, 3-allyloxyoxetane, 3-ethyl-3-allyloxyoxetane, 2-methyl-2-aryloxyoxetane, and Examples include 3-ethyl-4-propyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-chloromethyloxetane, 3-amino-3-dimethyloxetane, 3-ethyl-3-(meth)acryloyloxymethyloxetane, 3-ethyl-3-(4-(meth)acryloyloxybutyloxymethyl)oxetane, and 3-ethyl-3-(3-(meth)acryloyloxy-2,2-dimethylpropyloxymethyl)oxetane.

Specific examples of polyfunctional oxetane compounds include 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, xylylene bisoxetane, 1,4-bis((3-ethyl-3-oxetanylmethoxy)methyl)benzene, bis((3-methyl-3-oxetanylmethoxy)methyl)ether, bis((3-ethyl-3-oxetanylmethoxy)methyl)ether, 1,4-bis((3-methyl-3-oxetanylmethoxy)methyl)benzene, as well as oligomers or copolymers of these compounds, phenol novolac-type oxetane, oxetanyl silsesquioxane, and ethers of the above polyfunctional oxetane compounds with hydroxyl group-containing resins (e.g., calixarenes, calixresorcinarenes, cardo-type bisphenols, poly(p-hydroxystyrene), etc.). From the viewpoint of inkjet coating properties, the polyfunctional oxetane compound is preferably a compound having a molecular weight of 500 or less, and more preferably a compound having a molecular weight of 400 or less. From the same viewpoint, a bifunctional oxetane compound can be preferably used.

When the sealant is a cationic polymerizable sealant, the sealant preferably contains a siloxane compound having two or more cationic polymerizable groups (hereinafter, also referred to as "polyfunctional siloxane compound (A3-c)") as a polyfunctional polymerizable compound. By blending the polyfunctional siloxane compound (A3-c) with the sealant, it is possible to improve the curing property while lowering the dielectric constant.

The polyfunctional siloxane compound (A3-c) may be a siloxane compound having a chain structure or a cyclic structure. The polyfunctional siloxane compound (A3-c) preferably has two or more oxetanyl groups or oxiranyl groups as cationic polymerizable groups. The number of cationic polymerizable groups in the polyfunctional siloxane compound (A3-c) is preferably 2 to 8, and more preferably 2 to 4. From the viewpoint of inkjet coating properties, among these, bifunctional epoxy group-containing siloxane compounds can be particularly preferably used as the polyfunctional siloxane compound (A3-c).

Specific examples of polyfunctional siloxane compounds (A3-c) include trade names such as "X-22-163", "X-22-169", "KR-470", "X-40-2678", "X-40-2669", and "X-40-2728" (all manufactured by Shin-Etsu Chemical Co., Ltd.).

The cationic polymerizable sealant preferably contains a monofunctional polymerizable compound and a polyfunctional polymerizable compound as the compound (A2-c). The ratio of the monofunctional polymerizable compound to the total amount of the compound (A2-c) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, relative to 100 parts by mass of the total amount of the compound (A2-c). The ratio of the monofunctional polymerizable compound to the total amount of the compound (A2-c) is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, relative to 100 parts by mass of the total amount of the compound (A2-c). By setting the ratio of the monofunctional polymerizable compound to the polyfunctional polymerizable compound in the above range, a sealant for organic EL elements having an excellent balance between low viscosity and curability can be obtained.

From the viewpoint of ensuring the curability of the sealant, the content of compound (A2-c) is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more, relative to 100 parts by mass of the total amount of the polymerizable compounds [A] contained in the sealant (i.e., compounds (A1-c) and (A2-c)). Also, from the viewpoint of obtaining a sufficient effect of improving the coatability by blending compound (A1-c), the content of compound (A2-c) is preferably 99.9 parts by mass or less, more preferably 99.5 parts by mass or less, and even more preferably 99 parts by mass or less, relative to 100 parts by mass of the total amount of the polymerizable compounds [A] contained in the sealant.

In addition, in this sealant, the content of the polyfunctional siloxane compound (A3-c) is preferably 2 parts by mass or more, and more preferably 5 parts by mass or more, relative to 100 parts by mass of the total amount of the compound (A2-c). In addition, the content of the polyfunctional siloxane compound (A3-c) is preferably 40 parts by mass or less, and more preferably 30 parts by mass or less, relative to 100 parts by mass of the total amount of the compound (A2-c).

[B] Polymerization initiator
When the present sealant is a cationic polymerizable sealant, the present sealant contains a cationic polymerization initiator as the polymerization initiator [B]. Examples of the cationic polymerization initiator include a thermal cationic polymerization initiator that generates a protonic acid or Lewis acid in response to heat, and a photo-cationic polymerization initiator that generates a protonic acid or Lewis acid in response to radiation. Examples of the thermal cationic polymerization initiator include an ionic thermal acid generating type polymerization initiator. Examples of the photo-cationic polymerization initiator include an ionic photo-acid generating type polymerization initiator and a non-ionic photo-acid generating type polymerization initiator. Considering that the present sealant is used for an organic EL element, a photo-cationic polymerization initiator can be preferably used.

Specific examples of the thermal cationic polymerization initiator include sulfonium salts, phosphonium salts, diazonium salts, iodonium salts, and quaternary ammonium salts. Among them, the thermal cationic polymerization initiator is preferably an arylsulfonium salt, an arylphosphonium salt, an aryldiazonium salt, an aryliodonium salt, or a quaternary ammonium salt, and more preferably an onium salt in which the counter anion in these onium salts is BF ₄ ^- , PF ₆ ^- , SbF ₆ ^- or BX ₄ ^- (wherein X represents a substituted phenyl group in which two or more hydrogen atoms in the phenyl group are substituted with fluorine or a trifluoromethyl group).

Specific examples of the photocationic polymerization initiator include ionic photoacid generating type photocationic polymerization initiators, such as onium salt compounds, halogen-containing compounds, sulfone compounds, sulfonic acid compounds, sulfonimide compounds, and diazomethane compounds. Examples of the onium salt compounds include aromatic sulfonium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic ammonium salts, (2,4-cyclopentadiene-1-yl)[(1-methylethyl)benzene]-Fe salts, and the like. Specific examples of onium salt compounds include onium salts whose cation portion is an aromatic sulfonium, aromatic iodonium, aromatic diazonium, aromatic ammonium, or (2,4-cyclopentadiene-1-yl)[(1-methylethyl)benzene]-Fe cation, and whose anion portion is BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ , BX ₄ ⁻ (wherein X represents a substituted phenyl group in which two or more hydrogen atoms of the phenyl group are substituted with fluorine or trifluoromethyl groups), or PY ₆ ⁻ (wherein Y is a fluorinated alkyl group).

Examples of non-ionic photoacid generating cationic photopolymerization initiators include nitrobenzyl esters, sulfonic acid derivatives, phosphate esters, phenolsulfonic acid esters, diazonaphthoquinones, and N-hydroxyimidesulfonates.

The content of the cationic polymerization initiator in the sealant is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the polymerizable compound [A] contained in the sealant. The content of the cationic polymerization initiator is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the total amount of the polymerizable compound [A] contained in the sealant. By setting the content of the cationic polymerization initiator within the above range, good curability and the like can be exhibited.

<Radical Polymerizable Sealing Agent>
[[A] Polymerizable compound]
Compound (A1)
When the present sealant is a radically polymerizable sealant, examples of the polymerizable group contained in the compound (A1) (hereinafter, "compound (A1-r)") contained in the present sealant include a (meth)acryloyl group and a vinylphenyl group. Of these, the polymerizable group contained in the compound (A1-r) is preferably a (meth)acryloyl group. The above explanations apply to specific examples and preferred examples of the fluorine-containing group R ^f contained in the compound (A1-r).

（式（１－２）中、Ｒ^２は水素原子又はメチル基である。Ｒ^３及びＲ^４は、それぞれ独立して、水素原子、フッ素原子、アルキル基又はフルオロアルキル基である。Ｙ^１は、炭素数１～１０のアルカンジイル基、又は炭素数２～１０のアルカンジイル基の炭素－炭素結合間に－Ｏ－を含む２価の基である。Ｒ^ｆは、「－Ｃ_ｍＦ_２ｍ－１」、「－Ｃ_ｎＦ_２ｎＨ」又は「－Ｃ_ｎＦ_２ｎ＋１」で表される１価のフッ素化鎖状炭化水素基である。ｍは２以上の整数であり、ｎは１以上の整数である。） A preferred specific example of the compound (A1-r) is a compound represented by the following formula (1-2).

(In formula (1-2), R ² is a hydrogen atom or a methyl group. R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, an alkyl group, or a fluoroalkyl group. Y ¹ is a divalent group containing -O- between the carbon-carbon bonds of an alkanediyl group having 1 to 10 carbon atoms, or an alkanediyl group having 2 to 10 carbon atoms. ^{R f} is a monovalent fluorinated chain hydrocarbon group represented by "-C _m F _2m-1 ", "-C _n F _2n H" or "-C _n F _2n+1 ". m is an integer of 2 or more, and n is an integer of 1 or more.)

In the above formula (1-2), specific and preferred examples of the monovalent fluorinated chain hydrocarbon group represented by ^Rf are as explained above. ^Y1 preferably has 1 to 8 carbon atoms, and more preferably has 1 to 5 carbon atoms.

Examples of the alkyl group represented by R3 and ^R4 include linear or branched alkyl groups having 1 to 10 carbon atoms. Examples of the fluoroalkyl group represented by ^R3 and R4 include linear or branched alkyl groups having 1 to 10 carbon atoms, in which one or more hydrogen atoms have been substituted with fluorine atoms. The alkyl and fluoroalkyl groups represented by ^R3 and ^R4 preferably have 1 ^{to 5} carbon atoms, more preferably 1 to 3 carbon atoms. Among them, ^R3 and ^R4 are preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.

（式（ａ１－２－１）～式（ａ１－２－８）中、Ｒ^２は水素原子又はメチル基である。ｒは０～４の整数である。） Specific examples of the compound (A1-r) include the compounds represented by the following formulas (a1-2-1) to (a1-2-8).

(In formulas (a1-2-1) to (a1-2-8), ^R2 is a hydrogen atom or a methyl group, and r is an integer of 0 to 4.)

In the radical polymerizable sealing agent, the content of compound (A1-r) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, based on 100 parts by mass of the total amount of polymerizable compound [A]. The content of compound (A1-r) is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, based on 100 parts by mass of the total amount of polymerizable compound [A]. When the content of compound (A1-r) is in the above range, it is preferable in that it can enhance the effect of improving the wetting spreadability and the straightness of the edge of the film in a well-balanced manner when the sealant is applied to a substrate.

Compound (A2)
When the present sealant is a radically polymerizable sealant, the compound (A2) (hereinafter, "compound (A2-r)") contained in the present sealant can preferably be a compound having an ethylenically unsaturated group. Specific examples include vinyl group-containing compounds, (meth)acryloyl group-containing compounds, and aromatic vinyl compounds. Among these, (meth)acryloyl group-containing compounds are preferably used in terms of copolymerizability with compound (A1) and the comparative ease with which the viscosity of the present sealant can be adjusted.

The compound (A2-r) may be either a monofunctional polymerizable compound or a polyfunctional polymerizable compound. Specific examples of compounds (A2-r) that are monofunctional polymerizable compounds include (meth)acrylic acid alkyl esters, (meth)acrylic acid esters having an alicyclic structure, (meth)acrylic acid esters having an aromatic ring structure, and aromatic vinyl compounds.

Further specific examples of the compound (A2-r) when it is a monofunctional polymerizable compound include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-lauryl (meth)acrylate, and n-stearyl (meth)acrylate. Examples of (meth)acrylic acid esters having an alicyclic structure include cyclohexyl (meth)acrylate, 2-methylcyclohexyl (meth)acrylate, tricyclo[5.2.1.0 ^2,6 ]decan-8-yl (meth)acrylate, tricyclo[5.2.1.0 ^2,5 ]decan-8-yloxyethyl (meth)acrylate, and isobornyl (meth)acrylate. Examples of (meth)acrylic acid esters having an aromatic ring structure include phenyl (meth)acrylate, benzyl (meth)acrylate, naphthyl methyl (meth)acrylate, naphthyl ethyl (meth)acrylate, phenoxyethyl (meth)acrylate, m-phenoxyphenyl methyl (meth)acrylate, o-phenyl phenoxyethyl (meth)acrylate, etc. Examples of aromatic vinyl compounds include styrene, methylstyrene, α-methylstyrene, t-butoxystyrene, vinylnaphthalene, etc.

When the compound (A2-r) is a polyfunctional polymerizable compound, a polyfunctional (meth)acrylic acid ester can be preferably used as the compound (A2-r). Examples of polyfunctional (meth)acrylic acid esters include bifunctional (meth)acrylic acid esters and trifunctional or higher (meth)acrylic acid esters. Specific examples of these include bifunctional (meth)acrylic acid esters such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and tricyclodecane dimethanol (meth)acrylate.

Examples of trifunctional or higher (meth)acrylic acid esters include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, tri(2-(meth)acryloyloxyethyl)phosphate, succinic acid-modified pentaerythritol tri(meth)acrylate, Examples include succinic acid modified dipentaerythritol penta(meth)acrylate, isocyanuric acid EO modified di- and triacrylate, trimethylolpropane EO modified tri(meth)acrylate, carboxy group-containing polybasic acid modified (meth)acrylic oligomer, and polyfunctional urethane acrylate compounds obtained by reacting a compound having a linear alkylene group and an alicyclic structure and having two or more isocyanate groups with a compound having one or more hydroxyl groups in the molecule and having three, four or five (meth)acryloyloxy groups.

When the sealant is a radically polymerizable sealant, a siloxane compound having two or more cationic polymerizable groups (hereinafter also referred to as "polyfunctional siloxane compound (A3-r)") may be used as the polyfunctional polymerizable compound. Examples of the polyfunctional siloxane compound (A3-r) include siloxane compounds having a chain structure or a cyclic structure. The polyfunctional siloxane compound (A3-r) preferably has two or more (meth)acryloyl groups as radically polymerizable groups. The number of radically polymerizable groups possessed by the polyfunctional siloxane compound (A3-r) is preferably 2 to 8, more preferably 2 to 4.

The radical polymerizable sealant preferably contains a monofunctional polymerizable compound and a polyfunctional polymerizable compound as the compound (A2-r). The ratio of the monofunctional polymerizable compound to the total amount of the compound (A2-r) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, relative to 100 parts by mass of the total amount of the compound (A2-r). The ratio of the monofunctional polymerizable compound to the total amount of the compound (A2-r) is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, relative to 100 parts by mass of the total amount of the compound (A2-r). By setting the ratio of the monofunctional polymerizable compound to the polyfunctional polymerizable compound in the above range, a sealant for an organic EL element having low viscosity and excellent curability can be obtained.

From the viewpoint of ensuring the curability of the sealant, the content of compound (A2-r) is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more, relative to 100 parts by mass of the total amount of the polymerizable compounds [A] contained in the sealant (i.e., compounds (A1-r) and (A2-r)). Also, from the viewpoint of obtaining a sufficient effect of improving the coatability by blending compound (A1-r), the content of compound (A2-r) is preferably 99.9 parts by mass or less, more preferably 99.5 parts by mass or less, and even more preferably 99 parts by mass or less, relative to 100 parts by mass of the total amount of the polymerizable compounds [A] contained in the sealant.

[B] Polymerization initiator
When the present sealant is a radical polymerizable sealant, the present sealant contains a radical polymerization initiator as the polymerization initiator [B]. Examples of the radical polymerization initiator include a thermal radical polymerization initiator that generates radicals in response to heat, and a photoradical polymerization initiator that generates radicals in response to radiation. Examples of the thermal radical polymerization initiator include an azo compound, an organic peroxide, and the like. Examples of the photoradical polymerization initiator include an O-acyloxime compound, an acetophenone compound, a biimidazole compound, an acylphosphine oxide compound, and the like. Considering that the present sealant is used for an organic EL element, a photoradical polymerization initiator can be preferably used.

Specific examples of thermal radical polymerization initiators include azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(dimethylisobutyrate), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). Examples of organic peroxides include benzoyl peroxide, ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, peroxyester, diacyl peroxide, and peroxydicarbonate.

Specific examples of photoradical polymerization initiators include O-acyloxime compounds such as 1,2-octanedione 1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), 1-(9-ethyl-6-benzoyl-9.H.-carbazol-3-yl)-octan-1-one oxime-O-acetate, 1-[9-ethyl-6-(2-methylbenzoyl)-9.H.-carbazol-3-yl]-ethane-1-one oxime-O-benzoate, 1-[9-n-butyl-6-(2-ethylbenzoyl)-9.H. -carbazol-3-yl]-ethan-1-one oxime-O-benzoate, ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydrofuranylbenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime), ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydropyranylbenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime), ethanone-1-[9-ethyl-6-(2-methyl-5-tetrahydrofuranylbenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime), ethanone-1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxolanyl)methoxybenzoyl}-9.H. -carbazol-3-yl]-1-(O-acetyloxime), etc. Among O-acyloxime compounds, polymerization initiators having a carbazole skeleton in the molecule (e.g., ethanone 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), etc.) can be preferably used.

Examples of acetophenone compounds include α-aminoketone compounds and α-hydroxyketone compounds. Specific examples of these include α-aminoketone compounds such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one. Examples of α-hydroxyketone compounds include 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-(4-i-propylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, and 1-hydroxycyclohexylphenylketone.

Examples of biimidazole compounds include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, and 2,2'-bis(2,4,6-trichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole.

Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

The content of the radical polymerization initiator in the sealant is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the polymerizable compound [A] contained in the sealant. The content of the radical polymerization initiator is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the total amount of the polymerizable compound [A] contained in the sealant. By setting the content of the radical polymerization initiator within the above range, good curing properties, etc. can be exhibited.

<Other ingredients>
The present sealant (including the cationic polymerizable sealant and the radical polymerizable sealant) may further contain, in addition to the above-mentioned polymerizable compound [A] and polymerization initiator [B], a component different from the polymerizable compound [A] and the polymerization initiator [B] (hereinafter, also referred to as "other components"). Examples of the other components include a polymerization inhibitor, a surfactant, an antioxidant, a sensitizer, a softener, a plasticizer, an adhesion aid, an organic solvent, and the like. The blending ratio of these components is appropriately selected according to each component within a range that does not impair the effects of the present disclosure.

If necessary, an organic solvent may be added to the sealant for the purpose of dissolving each component added to the sealant. However, from the viewpoint of making it possible to form a cured film (more specifically, an organic sealing layer that protects the organic light-emitting layer of an organic EL element) without performing a heat treatment, it is preferable to use as little organic solvent as possible. Specifically, the content of organic solvent in the sealant is preferably 0% by mass or more and 3% by mass or less, more preferably 0% by mass or more and 2% by mass or less, and particularly preferably substantially free of organic solvent. Here, in this specification, "substantially free of" a certain component means that the amount of the specific component contained in the sealant is 1% by mass or less, preferably 0.5% by mass or less.

When an organic solvent is added to the sealant, it is preferable that the organic solvent used is an organic solvent that can dissolve or disperse each component added to the sealant and does not react with each component. Specific examples include alcohols, ketones, esters, ethers, aromatic hydrocarbons, and amides.

Specific examples of these include alcohols such as methanol, ethanol, isopropanol, butanol, and octanol. Ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Esters include ethyl acetate, butyl acetate, ethyl lactate, γ-butyrolactone, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and methyl-3-methoxypropionate. Ethers include polyoxyethylene lauryl ether, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and diethylene glycol methyl ethyl ether. Aromatic hydrocarbons include benzene, toluene, and xylene. Amides include dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

The sealant contains compound (A1), which can suppress the occurrence of coating unevenness when inkjet coating is employed. Therefore, even if a surfactant used for the purpose of improving the coating property of the curable composition (wetting and spreading property and reduction of coating unevenness) is not blended, or even if the amount of surfactant blended is minimized, the coatability of the sealant can be ensured. This allows the ratio of the polymerizable compound [A] to the total amount of the sealant to be maximized, and a sealant with high curability can be obtained. Examples of surfactants used in the preparation of the curable composition for forming the sealing structure of an organic EL element include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants.

From the viewpoint of achieving a good balance between excellent wetting and spreading properties and straight edge properties, and from the viewpoint of increasing the content ratio of the polymerizable compound [A] relative to the total amount of the sealant as much as possible to enhance curing properties, the content ratio of the surfactant in the sealant is preferably 0% by mass or more and 1% by mass or less, more preferably 0% by mass or more and 0.5% by mass or less, and even more preferably 0% by mass or more and 0.1% by mass or less.

<Preparation of Sealant for Organic EL Device>
The present sealant can be prepared by mixing the polymerizable compound [A] and the polymerization initiator [B], as well as other components that are blended as necessary. The content of the polymerizable compound [A] in the present sealant is preferably 80 parts by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, relative to 100 parts by mass of the total amount of the present sealant, from the viewpoint of obtaining a curable composition having good sensitivity and from the viewpoint of forming a cured film having a high sealing effect.

<Viscosity of Sealant for Organic EL Device>
The sealant has a viscosity in the range of 1 to 40 mPa·s measured at 25°C and 20 rpm using an E-type viscometer. If the viscosity of the sealant exceeds 40 mPa·s, the sealant will have reduced wettability and spreadability when applied to a substrate by inkjet coating, and coating unevenness will be likely to occur. In particular, there is concern that coating unevenness will be likely to occur when trying to make the organic sealing layer thinner as the organic EL element becomes thinner. On the other hand, if the viscosity of the sealant is less than 1 mPa·s, the sealant will easily scatter or drip during inkjet coating, resulting in a state in which the sealant is attached in dots (satellites) other than the intended location. In this case, an organic sealing layer with a sufficiently high sealing effect may not be formed. In this regard, the sealant is particularly suitable as a curable composition for inkjet coating because it has excellent wettability and spreadability, and can suppress the sealant from scattering or dripping during inkjet coating (i.e., has excellent inkjet discharge stability).

From the viewpoint of obtaining a curable composition having good wetting and spreading properties and excellent inkjet coating properties, the viscosity of the sealant is more preferably 35 mPa·s or less, even more preferably 30 mPa·s or less, and even more preferably 25 mPa·s or less. Furthermore, from the viewpoint of improving the inkjet ejection stability and suppressing the occurrence of satellites, the viscosity of the sealant is more preferably 2 mPa·s or more, and even more preferably 5 mPa·s or more. In this specification, the viscosity of the sealant for organic EL elements is a value measured in accordance with JIS K2283.

<Surface tension of sealant for organic EL element>
The surface tension of the sealant at 25°C is preferably 15 mN/m or more and 40 mN/m or less. By having the surface tension in the above range, a curable composition having excellent inkjet applicability can be obtained. From the viewpoint of improving the applicability when applied to inkjet coating, the surface tension of the sealant at 25°C is more preferably 20 mN/m or more, and even more preferably 23 mN/m or more. Moreover, the surface tension of the sealant at 25°C is more preferably 35 mN/m or less, and even more preferably 33 mN/m or less. In this specification, the surface tension of the sealant for organic EL elements is a value measured at 25°C by the Wilhelmy method using a surface tensiometer.

<<Cured film and organic EL element>>
The cured film of the present disclosure (hereinafter also referred to as "the present cured film") is formed by the present encapsulant prepared as described above. The present cured film is particularly useful as a thin film encapsulation (TFE) structure of an organic EL element. The present cured film and an organic EL element having an encapsulation structure in which an organic light-emitting layer is encapsulated by the present cured film can be produced by curing the present encapsulant with heat or radiation. When obtaining the organic EL element, it is preferable that the encapsulant is irradiated with radiation to form an encapsulation structure for the organic light-emitting layer, and specifically, the organic EL element can be produced by a method including the following steps 1 and 2.
(Step 1) A step of applying the present sealant to the surface of a substrate on which an organic light-emitting layer is formed, on which the light-emitting layer is to be formed. (Step 2) A step of curing the present sealant by irradiating with radiation. Each step will be described in detail below.

[Process 1: Coating process]
In this step, the present sealant is applied to the light-emitting layer-forming surface of the base material on which the organic light-emitting layer is formed, thereby forming a coating film made of the present sealant on the light-emitting layer-forming surface. The substrate to which the sealant is applied has a laminate including various layers such as an anode layer, a hole injection layer, a hole transport layer, an electron injection layer, and a cathode layer in addition to the organic light-emitting layer. The organic EL element is constituted by this laminate. The surface on which the light-emitting layer is formed and on which the sealant is applied may be covered with an inorganic film (inorganic sealing layer). Inorganic material constituting the inorganic film Examples of the material include silicon nitride (SiNx) and silicon oxide (SiOx). In this case, a thin film sealing layer including an organic sealing layer and an inorganic sealing layer is provided on the organic light-emitting layer as a sealing structure. A layer is formed.

Methods for applying the sealant include, for example, spraying, roll coating, spin coating, slit die coating, bar coating, and inkjet coating. Among these, inkjet coating is preferred in terms of throughput and thin film formation. In particular, the sealant is suitable for inkjet coating because it has low viscosity yet excellent curing properties.

[Step 2: Curing step]
In this step, the coating film formed in step 1 is irradiated with radiation to cure the coating film into a cured film. Examples of radiation include ultraviolet rays, far ultraviolet rays, visible light, X-rays, and electron beams. Among these, ultraviolet rays are preferred, and for example, ultraviolet rays having a wavelength of 350 to 400 nm can be preferably used as the irradiating light. The exposure dose of the radiation is preferably 0.05 to 10 J/ ^m2 . In this way, an organic EL element can be obtained in which the organic light-emitting layer is covered with an organic sealing layer made of the present sealant. This makes it possible to reduce the thickness of the organic sealing layer (and thus the sealing structure of the organic EL element). The thickness of the cured film (organic sealing layer) formed by the present sealant is usually 0. The thickness of the organic sealing layer formed by the present sealant may be further covered with an inorganic film. Examples of inorganic materials constituting the inorganic film include silicon nitride (SiNx) and silicon oxide (SiOx).

In the organic EL element of the present disclosure manufactured by the method including the above-mentioned steps 1 and 2, the organic light-emitting layer is sealed with an organic sealing layer made of the present composition. Therefore, the organic EL element of the present disclosure can sufficiently suppress the intrusion of moisture into the organic light-emitting layer, and can realize a thin organic sealing layer while suppressing the occurrence of problems caused by moisture (specifically, the occurrence of dark spots and the decrease in light-emitting properties such as brightness and light-emitting efficiency). Such an organic EL element of the present disclosure is useful, for example, as an organic EL lighting device or an organic EL display device.

According to the present disclosure described above, the following means are provided.
[Means 1] A sealant for an organic EL device, comprising [A] a polymerizable compound and [B] a polymerization initiator, and having a viscosity of 1 mPa·s or more and 40 mPa·s or less as measured using an E-type viscometer at 25°C and 20 rpm, and comprising, as the polymerizable compound [A], a compound (A1) having a polymerizable group and a monovalent fluorinated hydrocarbon group.
[Measure 2] The sealant for an organic EL device according to [Measure 1], wherein the fluorinated hydrocarbon group is a chain fluorinated hydrocarbon group.
[Measure 3] The sealant for an organic EL device according to [Measure 2], wherein the fluorinated chain hydrocarbon group has two or more carbon atoms and has a carbon-carbon unsaturated bond.
[Means 4] The sealant for an organic EL device according to [ _Means 2], wherein the fluorinated chain hydrocarbon group is represented by " _{-CmF2m -1} ", " _-CnF2nH " or " _{-CnF2n +1} " (wherein m is an integer of 2 or more, and n is an integer of 1 or more).
[Measure 5] The sealant for an organic EL device according to any one of [Measure 1] to [Measure 4], wherein the polymerizable group possessed by the polymerizable compound [A] is a cationically polymerizable group.
[Measure 6] The sealant for an organic EL device according to any one of [Measures 1] to [Measures 4], wherein the polymerizable group possessed by the polymerizable compound [A] is a radically polymerizable group.
[Means 7] The sealant for an organic EL device according to any one of [Means 1] to [Means 4], wherein the polymerizable group of the compound (A1) is an oxetanyl group, an oxiranyl group, a vinyl ether group, or a (meth)acryloyl group.
[Means 8] The sealant for an organic EL device according to [Means 1], [Means 2] or [Means 7], wherein the compound (A1) is represented by the above formula (1).
[Means 9] The sealant for an organic EL element according to any one of [Means 1] to [Means 8], further comprising, as the polymerizable compound [A], a monofunctional polymerizable compound not having a fluorinated hydrocarbon group, and a polyfunctional polymerizable compound not having a fluorinated hydrocarbon group.
[Means 10] The sealant for an organic EL element according to [Means 9], wherein a ratio of the monofunctional polymerizable compound to a total amount of the monofunctional polymerizable compound and the polyfunctional polymerizable compound is 5 parts by mass or more and 70 parts by mass or less.
[Means 11] The sealant for an organic EL device according to [Means 9] or [Means 10], wherein the polyfunctional polymerizable compound comprises a siloxane compound having two or more polymerizable groups.
[Means 12] The sealant for an organic EL device according to any one of [Means 1] to [Means 11], wherein the content of the organic solvent is from 0% by mass to 3% by mass.
[Means 13] The sealant for an organic EL device according to any one of [Means 1] to [Means 12], which has a surface tension at 25° C. of 15 mN/m or more and 40 mN/m or less.
[Means 14] The sealant for an organic EL device according to any one of [Means 1] to [Means 13], which is for inkjet coating.
[Means 15] A cured film formed from the sealant for an organic EL device according to any one of [Means 1] to [Means 14].
[Means 16] An organic EL element having a light-emitting layer sealed with the cured film according to [Means 15].
[Means 17] A method for producing an organic EL element, comprising the steps of applying the sealant for an organic EL element according to any one of [Means 1] to [Means 14] to a light-emitting layer-forming surface of a substrate on which an organic light-emitting layer is formed, and curing the sealant for an organic EL element by irradiating with radiation to form a sealing structure.
[Measure 18] The method for producing an organic EL element according to [Measure 17], wherein the sealant for an organic EL element is applied to the surface on which the light-emitting layer is formed by inkjet coating.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. Note that "parts" and "%" in the examples and comparative examples are by weight unless otherwise specified.

1. Synthesis of Compounds [Synthesis Example 1] Synthesis of Compound (A1-1) In a 2-liter separable flask equipped with a stirrer, a cooler, and a dropping funnel, hexafluoropropene trimer (752 g, 1.67 mol), potassium carbonate (58.3 g, 0.42 mol), and methylene chloride (125 g, 1.46 mol) were placed and stirred uniformly, and then tetra-n-butylammonium bromide (1.1 g, 0.003 mol, manufactured by Wako Pure Chemical Industries, Ltd.) was added as a phase transfer catalyst. Next, a mixed solution of 3-ethyl-3-oxetanemethanol (95.7 g, 0.83 mol, manufactured by Toagosei Co., Ltd.) and methylene chloride (125 g, 1.46 mol) prepared in advance was dropped into the separable flask at room temperature (25 ° C.). After the dropwise addition was completed, the temperature inside the separable flask was kept at 35° C. using an oil bath and heating was continued for 4 hours to obtain a reaction liquid of hexafluoropropene dimer and 3-ethyl-3-oxetanemethanol.
The resulting reaction solution was cooled with air, the potassium carbonate was filtered off, and water (500 g) was added and vigorously shaken to separate into an aqueous layer and an organic layer. Thereafter, only the organic layer was collected and dried using magnesium sulfate (20 g, 0.17 mol), and then methylene chloride was distilled off under reduced pressure, followed by vacuum distillation (temperature 85° C., pressure 3 mmHg) to obtain a purified product in the form of a colorless, transparent liquid. The yield of the purified product (a fluorine-containing oxetane compound, a compound represented by the following formula (A1-1)) was 95%.

Synthesis Example 2 Synthesis of Compound (A1-2) 259.5 g (1.8 mol) of 4-hydroxybutyl acrylate, 218.6 g (2.16 mol) of triethylamine, and 1000 g of acetonitrile were placed in a three-neck flask (3 L) equipped with a dropping funnel. Hexafluoropropene trimer (973.0 g, 2.16 mol) was placed in the dropping funnel and gradually dropped into the solution in the flask over a period of about 60 minutes while stirring. After the dropwise addition was completed, stirring was continued for another 3 hours at room temperature.
The reaction mixture was added with 2,200 g of 1N hydrochloric acid to terminate the reaction, and then the reaction mixture was transferred to a 5 L beaker and washed three times with 1 L of water. The solution after the water washing treatment was dehydrated under reduced pressure to obtain 964.0 g (yield 93%) of a fluorine-containing acrylate compound represented by the following formula (A1-2).

2. Preparation of Sealant for Organic EL Device The types and abbreviations of the polymerizable compound (A1), the polymerizable compound (A2), the polymerization initiator (B), and the surfactant (C) used in the preparation of the sealant for organic EL device are shown below.
<Polymerizable compound (A1)>
(A1-1): Compound represented by the above formula (A1-1) (A1-2): Compound represented by the above formula (A1-2) <Polymerizable compound (A2)>
(A2-1): 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane (A2-2): 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane (A2-3): Epoxy group-containing bifunctional linear siloxane compound, trade name "X-40-2669", manufactured by Shin-Etsu Chemical Co., Ltd. (A2-4): Tricyclodecane dimethanol diacrylate, trade name "NK Ester A-DCP", manufactured by Shin-Nakamura Chemical Co., Ltd. (A2-5): 1,10-decanediol diacrylate, trade name "NK Ester DOD", manufactured by Shin-Nakamura Chemical Co., Ltd. (A2-6): Lauryl acrylate (A2-7): Multifunctional acrylate, trade name "Aronix M-313", manufactured by Toagosei Co., Ltd. <Polymerization initiator (B)>
(B-1): Photocationic polymerization initiator, product name "CPI-410B" (manufactured by San-Apro Co., Ltd.)
(B-2): 2,4,6-trimethylbenzoyldiphenylphosphine oxide (photoradical polymerization initiator, trade name "Irgacure TPO" (manufactured by BASF))
<Surfactant (C)>
(C-1): Fluorine-based surfactant, product name "F-563" (manufactured by DIC Corporation)
(C-2): Fluorine-based surfactant, trade name "F-554" (manufactured by DIC Corporation)
(C-3): Fluorine-based surfactant, trade name "Ftergent DFX-18" (manufactured by Neos Co., Ltd.)

[Example 1]
1 part by mass of compound (A1-1), 40 parts by mass of compound (A2-1), 39 parts by mass of compound (A2-2), 20 parts by mass of compound (A2-3), and 2 parts by mass of polymerization initiator (B-1) were added, mixed and stirred, and then filtered using a 0.2 μm filter to prepare a sealant for an organic EL element.

[Examples 2 to 4, Comparative Examples 1 to 6]
Sealant for organic EL elements of Examples 2 to 4 and Comparative Examples 1 to 6 were prepared in the same manner as in Example 1, except that the types and amounts (parts by mass) of each component were used as shown in Table 1. Examples 1 to 3 and Comparative Examples 1 to 5 were cationic polymerizable sealants, and Example 4 and Comparative Example 6 were radically polymerizable sealants.

3. Evaluation The sealants for organic EL devices of Examples 1 to 4 and Comparative Examples 1 to 6 were measured for viscosity and surface tension, and were also evaluated for coatability by inkjet coating, wetting and spreading properties, and straightness of the film edge. The measurement and evaluation methods were as follows. The evaluation results are shown in Table 1.

<Measurement of Viscosity>
The viscosity (mPa·s) of the sealant for an organic EL device was measured at 25° C. and 20 rpm using an E-type viscometer (RE-85L, manufactured by Toki Sangyo Co., Ltd.).

<Measurement of surface tension>
The surface tension of the sealant for organic EL devices at 25° C. was measured by the Wilhelmy method using a surface tensiometer DY-700 manufactured by Kyowa Interface Science Co., Ltd.

<Formation of Cured Film and Inkjet Coating Evaluation>
A film of SiNx was formed on a glass substrate with a thickness of 100 nm (film formation conditions) to prepare an evaluation substrate. An organic EL element sealant was ejected from an inkjet head of a piezoelectric inkjet printer at a pitch of 40 μm×40 μm onto the evaluation substrate to prepare a coating film of 3 cm square. After 5 minutes, the coating film was cured by irradiating the film with ultraviolet light at an exposure of 3000 mJ/cm ² using a 395 nm LED lamp. At that time, the voltage of the inkjet head was adjusted so that the amount of one ink dot ejected was 12 pL. The inner part of the end of the obtained cured film was observed visually and with a microscope (5 times), and the inkjet coatability, inkjet wetting spreadability, and inkjet end straightness were evaluated according to the following criteria.
Evaluation of inkjet coatability: A: No uncoated areas were observed by visual inspection.
B: Uncoated areas are visually observed.
Evaluation of inkjet wetting and spreading property A: The size of the cured film is 3.5 cm square or more. B: The size of the cured film is 2.5 cm square or more and less than 3.5 cm square. C: The size of the cured film is less than 2.5 cm square. Evaluation of inkjet edge straightness A: No dendritic parts are observed at the edge of the cured film under a microscope.
B: Dendritic areas are observed at the edge of the cured film under a microscope.

As shown in Table 1, the sealants for organic EL devices of Examples 1 to 4 had little coating unevenness and good wetting and spreading properties when applied to a substrate by the inkjet method. In addition, the edge lines on both the left and right sides of the cured film were nearly parallel to the scanning direction of the inkjet nozzle, and straight edge direction was maintained.

In contrast, the sealants for organic EL devices of Comparative Examples 1 to 6, which contained a fluorine-based surfactant instead of the polymerizable compound (A1), suppressed the occurrence of coating unevenness during inkjet coating, but were inferior to Examples 1 to 4 in terms of wetting and spreading properties, straightness of the film edge, or both.

These results show that the sealant for organic EL devices containing a compound having a polymerizable group and a monovalent fluorinated hydrocarbon group as the polymerizable compound [A] can improve the balance between the wetting and spreading properties and the straightness of the film edge when applied to a substrate by inkjet coating.

Claims (18)

[A] a polymerizable compound and [B] a polymerization initiator,
The viscosity measured using an E-type viscometer at 25° C. and 20 rpm is 1 mPa·s or more and 40 mPa·s or less,
The sealant for an organic EL device contains, as the polymerizable compound (A), a compound (A1) having a polymerizable group and a monovalent fluorinated hydrocarbon group. The sealant for organic EL devices according to claim 1, wherein the fluorinated hydrocarbon group is a fluorinated chain hydrocarbon group. The sealant for organic EL devices according to claim 2, wherein the fluorinated chain hydrocarbon group has two or more carbon atoms and has a carbon-carbon unsaturated bond. The sealant for an organic EL element according to claim ₂ , wherein the fluorinated chain hydrocarbon group is represented by " _{-CmF2m -1} ", " _-CnF2nH " or " _{-CnF2n +1} " (where m is an integer of 2 or more, and n is an integer of 1 or more). The sealant for organic EL elements according to claim 1, wherein the polymerizable group of the polymerizable compound [A] is a cationic polymerizable group. The sealant for organic EL devices according to claim 1, wherein the polymerizable group of the polymerizable compound [A] is a radically polymerizable group. The sealant for an organic EL element according to claim 1, wherein the polymerizable group of the compound (A1) is an oxetanyl group, an oxiranyl group, a vinyl ether group, or a (meth)acryloyl group. The sealant for an organic EL element according to claim 1 , wherein the compound (A1) is represented by the following formula (1):

(In formula (1), ^X1 is a monovalent group having an oxetanyl group, an oxiranyl group, a vinyl ether group or a (meth)acryloyl group. ^Y1 is a divalent group containing an alkanediyl group having 1 to 10 carbon atoms or an alkanediyl group having 2 to 10 carbon atoms containing -O- between the carbon-carbon bonds. ^Rf is a monovalent _fluorinated chain hydrocarbon group represented by " _{-CmF2m -1} ", " _-CnF2nH " or " _{-CnF2n +1} ". m is an integer of 2 or more, and n is an integer of 1 or more.) The sealant for an organic EL element according to claim 1, further comprising, as the polymerizable compound [A], a monofunctional polymerizable compound not having a fluorinated hydrocarbon group and a polyfunctional polymerizable compound not having a fluorinated hydrocarbon group. The sealant for organic EL elements according to claim 9, wherein the ratio of the monofunctional polymerizable compound to the total amount of the monofunctional polymerizable compound and the polyfunctional polymerizable compound is 5 parts by mass or more and 70 parts by mass or less. The sealant for organic EL elements according to claim 9, wherein the polyfunctional polymerizable compound includes a siloxane compound having two or more polymerizable groups. The sealant for organic EL elements according to claim 1, wherein the content of the organic solvent is 0% by mass or more and 3% by mass or less. The sealant for organic EL devices according to claim 1, which has a surface tension of 15 mN/m or more and 40 mN/m or less at 25°C. The sealant for organic EL elements according to claim 1, which is for inkjet coating. A cured film formed from the sealant for organic EL elements according to any one of claims 1 to 14. An organic EL element in which the light-emitting layer is sealed with the cured film according to claim 15. A method for manufacturing an organic EL element, comprising the steps of applying the sealant for an organic EL element according to any one of claims 1 to 14 to a light-emitting layer-forming surface of a substrate on which an organic light-emitting layer is formed, and forming a sealing structure by irradiating the sealant for an organic EL element with radiation to cure the sealant for an organic EL element. The method for producing an organic EL element according to claim 17, wherein the sealant for the organic EL element is applied to the surface on which the light-emitting layer is formed by inkjet coating.