JP7078720B2 - Sealant for display elements and its cured product - Google Patents

Description

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

In recent years, development of an optical semiconductor device using a display element such as an organic electroluminescence element (hereinafter referred to as an organic EL element) has been promoted. Display elements such as organic EL elements are liable to deteriorate due to moisture and oxygen in the atmosphere. Therefore, display elements such as organic EL elements are usually sealed (surface-sealed) with a sealing agent before use.

The surface sealing of the organic EL element is performed, for example, by applying a sealing agent made of a curable resin composition onto the organic EL element arranged on the base material and then curing the sealing agent. Conventionally, the sealant is applied by a screen printing method. On the other hand, with the flexibility of display devices, it is required to flatten and thin the sealing layer. Along with this, from the viewpoint of having high flatness and enabling the formation of a thin film sealing layer at high speed and uniformly, it has been studied to apply the sealing agent by an inkjet method.

The sealant used for coating by the inkjet method is required to have a low viscosity in order to be stably ejected from the nozzle of the head portion. Further, it is required to suppress the swelling of the adhesive and the rubber material used for the head portion of the inkjet device and to reduce the damage to the device.

As a sealing agent used for coating by such an inkjet method, a sealing agent for an electronic device containing a specific silicone epoxy compound as a curable resin and a polymerization initiator has been proposed (for example, Patent Document 1). By containing the silicone epoxy compound, the sealant is said to be able to suppress the swelling of the adhesive and the rubber material of the head portion of the inkjet device and reduce the damage to the device without increasing the viscosity too much.

Further, as a surface encapsulant for an organic EL element, a resin composition for organic EL surface encapsulation containing a benzylsulfonium salt and an epoxy resin or an oxetane resin having an aromatic group has been proposed (for example, Patent Document 2). ..

International Publication No. 2016/16347 Japanese Unexamined Patent Publication No. 2016-108512

However, the encapsulant containing a silicone epoxy compound as shown in Patent Document 1 has a problem that the curing rate is low (curing property is low). A sealant with low curability is easily repelled on the object to be coated (display element) after being applied on the object to be coated and before it is cured, and cannot be sufficiently leveled, resulting in uniform sealing. A stop layer cannot be formed. Therefore, it is required that damage to the device can be reduced without impairing the curability.

Further, the sealing agent used for coating by the inkjet method is also required to have a low viscosity. However, the encapsulant shown in Patent Document 2 is not sufficiently curable and has a sufficiently low viscosity.

The present invention has been made in view of the above circumstances, and is a sealant for a display element having a low viscosity, low volatility and high curability suitable for coating by an inkjet method, and having less damage to an inkjet device. The purpose is to provide the cured product.

[1] (A) an alicyclic epoxy compound having a cycloalkene oxide structure, (B) an oxetane compound, (C) an aliphatic epoxy compound (however, different from the alicyclic epoxy compound) and (D). The (A) alicyclic epoxy compound, the (B) oxetane compound, and the (C) aliphatic epoxy compound each include a cationic polymerization initiator and have a weight average molecular weight of 180 or more, respectively, according to the following formula ( A sealant for a display element, each of which has an oxygen atom content of 15% or more represented by 1).
Oxygen atom content (%) = total mass / weight average molecular weight of oxygen atoms in one molecule x 100 ... (1)
[2] The sealant for a display element according to [1], wherein the content of the (C) aliphatic epoxy compound is higher than the content of the (A) alicyclic epoxy compound.
[3] The sealant for a display device according to [1] or [2], wherein the content of the (B) oxetane compound is higher than the content of the (C) aliphatic epoxy compound.
[4] The above-mentioned (A) alicyclic epoxy compound, the above (B) oxetane compound, and the above (C) aliphatic epoxy compound are each described in any one of [1] to [3], which are polyfunctional compounds. Sealant for display elements.
[5] Any of [1] to [4], wherein one or more of the (A) alicyclic epoxy compound, the (B) oxetane compound, and the (C) aliphatic epoxy compound has a carbonyloxy group. Sealant for display element described in Crab.
[6] The sealant for a display element according to any one of [1] to [5], wherein the viscosity measured by an E-type viscometer at 25 ° C. and 20 rpm is 50 mPa · s or less.
[7] The sealant for a display element according to any one of [1] to [6], which is used for coating by an inkjet method.
[8] The sealing agent for a display element according to any one of [1] to [7], which seals the organic EL element which is the display element in a planar shape.
[9] The cured product of the sealant for a display element according to any one of [1] to [8].

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a sealant for a display element, which has low viscosity, low volatility and good curability suitable for coating by an inkjet method, and which causes less damage to an inkjet device, and a cured product thereof. be able to.

As a result of diligent studies, the present inventors have combined (A) an alicyclic epoxy compound having a cycloalkene oxide structure, (B) an oxetane compound, and (C) an aliphatic epoxy compound, and each component contains an oxygen atom. It has been found that by setting the rate and the weight average molecular weight to a certain level or higher, a sealing agent having low viscosity, low volatility and high curability, and capable of reducing damage to the apparatus can be obtained.

The reason for this is not clear, but it is presumed as follows. First, by combining the components (A) to (C), it is possible to achieve both low viscosity and high curability at a high level. Further, the adhesive or rubber material used for the head portion of the inkjet device is often composed of a material having low polarity such as EPDM rubber. On the other hand, by setting the oxygen atom content of the components (A) to (C) to a certain level or higher and increasing the polarity, it is difficult for these components to be compatible with the low-polarity material used for the head portion of the inkjet device. However, by making it difficult to swell, deterioration of these materials can be suppressed. Further, by appropriately increasing the weight average molecular weight of the components (A) to (C), it is possible to prevent volatilization.

Thereby, the encapsulant of the present invention can be easily applied by the inkjet method. Thereby, a thin cured product layer having high flatness can be formed at high speed and uniformly. The present invention has been made based on these findings.

1. 1. Sealant for Display Element The sealant for display element of the present invention comprises (A) an alicyclic epoxy compound having a cycloalkene oxide structure, (B) an oxetane compound, (C) an aliphatic epoxy compound, and ( D) Contains a cationic polymerization initiator.

<(A) Alicyclic epoxy compound having a cycloalkene oxide structure>
(A) The alicyclic epoxy compound having a cycloalkene oxide structure may have a function of enhancing the curability of the sealant for a display device. (A) The alicyclic epoxy compound having a cycloalkene oxide structure is a compound having a cycloalkene oxide structure, has a weight average molecular weight of 180 or more, and has an oxygen atom content represented by the following formula (1). Is 15% or more.
Oxygen atom content (%) = total mass / weight average molecular weight of oxygen atoms in one molecule x 100 ... (1)

(A) When the weight average molecular weight of the alicyclic epoxy compound having a cycloalkene oxide structure is 180 or more, the volatility of the compound can be lowered. Therefore, it is possible to reduce deterioration of the working environment and damage to the object to be coated (display element) when the encapsulant is applied by the inkjet method. (A) From the above viewpoint, the weight average molecular weight of the alicyclic epoxy compound having a cycloalkene oxide structure is preferably 190 or more, more preferably 200 or more. The upper limit of the weight average molecular weight is not particularly limited as long as it does not impair the ejection property when the encapsulant is applied by the inkjet method, but is more preferably 400 or less, for example.

The weight average molecular weight can be measured in terms of polystyrene by gel permeation chromatography (GPC). As the column, it is preferable to use a small molecule column GPC KF-801 manufactured by Shodex. It can also be calculated from the structural formula of the compound.

(A) When the oxygen atom content of the alicyclic epoxy compound having a cycloalkene oxide structure is 15% or more, the polarity of the compound can be increased, so that a low-polarity adhesive used for the head portion of an inkjet device is used. And rubber materials (for example, ethylene propylene ditadiene rubber) can be made difficult to be compatible with and swelling can be made difficult. As a result, deterioration of the adhesive or rubber material (damage to the device) can be reduced. From the above viewpoint, the oxygen atom content is preferably 20% or more. The upper limit of the oxygen atom content may be such that the dielectric constant of the obtained sealing layer does not become too large, and is preferably 30% or less, for example.

(A) For the total mass of oxygen atoms in one molecule of an alicyclic epoxy compound having a cycloalkene oxide structure, the structure of the alicyclic epoxy compound is specified by the GC-MS method, NMR method, etc., and the structure of the alicyclic epoxy compound is specified. It can be calculated by specifying the number of oxygen atoms in one molecule and multiplying it by the atomic weight of the oxygen atoms. The oxygen atom content of the alicyclic epoxy compound having the (A) cycloalkene oxide structure is the above-mentioned formula, in which the total mass of the obtained oxygen atoms and the weight average molecular weight measured by the above-mentioned GPC method are used. It can be calculated by applying it to (1).

(A) The oxygen atom content of the alicyclic epoxy compound having a cycloalkene oxide structure is, for example, the number of cycloalkene oxide structures in one molecule and the linking group having an oxygen atom (for example, -CO- (carbonyl group)). , -O-CO-O- (carbonate group), -COO- (carbonyloxy group or ester group), -O- (ether group), -CONH- (amide group), etc.) .. That is, in order to increase the oxygen atom content, it is preferable to set the number of cycloalkene oxide structures in one molecule to 2 or more, or to introduce a linking group having an oxygen atom.

In the alicyclic epoxy compound having such (A) cycloalkene oxide structure, the cycloalkene oxide structure is a structure obtained by epoxidizing cycloalkene with an oxidizing agent such as a peroxide, and has an aliphatic ring. It is an epoxy group composed of two adjacent carbon atoms and oxygen atoms. Examples of cycloalkene oxides include cyclohexene oxide and cyclopentene oxide, preferably cyclohexene oxide.

(A) The number of cycloalkene oxide structures in one molecule of the alicyclic epoxy compound having a cycloalkene oxide structure may be one (monofunctional) or two or more (polyfunctional). May be good. Among them, the cycloalkene oxide structure in one molecule of the alicyclic epoxy compound having the (A) cycloalkene oxide structure is excellent in that the oxygen atom content is easily increased and the transparency, heat resistance, light resistance, etc. are excellent. The number is preferably two or more (polyfunctional).

That is, (A) the alicyclic epoxy compound having a cycloalkene oxide structure is preferably a compound represented by the following formula (A-1), for example.

X in formula (A-1) is a single bond or linking group. However, X is selected so that the weight average molecular weight and the oxygen atom content of the compound represented by the formula (A-1) satisfy the above-mentioned ranges. The linking group is a divalent hydrocarbon group, a carbonyl group, an ether group (ether bond), a thioether group (thioether bond), an ester group (ester bond), a carbonate group (carbonate bond), an amide group (amide bond), or These can be a group in which a plurality of these are linked.

The divalent hydrocarbon group may be an alkylene group having 1 to 18 carbon atoms or a divalent alicyclic hydrocarbon group. Examples of the alkylene group having 1 to 18 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group and a trimethylene group. Examples of divalent alicyclic hydrocarbon groups include 1,2-cyclopentylene group, 1,3-cyclopentylene group, cyclopentylidene group, 1,2-cyclohexylene group and 1,3-cyclohexyl group. It contains a divalent cycloalkylene group (including a cycloalkylidene group) such as a silene group, a 1,4-cyclohexylene group and a cyclohexylidene group.

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

Examples of the alicyclic epoxy compound represented by the formula (A-1) include the following compounds. In the following formula, l is an integer of 1 to 10, m is an integer of 1 to 30, and R is an alkylene group having 1 to 8 carbon atoms, preferably a methylene group, an ethylene group, or a propylene. It is an alkylene group having 1 to 3 carbon atoms such as a group and an isopropylene group. n1 and n2 are integers of 1 to 30, respectively.

(A) Examples of commercially available alicyclic epoxy compounds having a cycloalkene oxide structure include celoxide 2021P, celoxide 2081, and celoxide 8000 (manufactured by Daicel).

(A) The content of the alicyclic epoxy compound having a cycloalkene oxide structure is preferably 10 to 70% by mass with respect to the total mass of the encapsulant. (A) When the content of the alicyclic epoxy compound having a cycloalkene oxide structure is 10% by mass or more, the curability is easily sufficiently enhanced, and when it is 70% by mass or less, the flexibility and adhesion of the cured product Is not easily damaged. (A) From the above viewpoint, the content of the alicyclic epoxy compound having a cycloalkene oxide structure is more preferably 10 to 50% by mass, more preferably 10 to 30% by mass, based on the total mass of the encapsulant. Is more preferable.

<(B) Oxetane compound>
(B) The oxetane compound may have a function of increasing the curability while lowering the viscosity of the encapsulant. (B) The oxetane compound is a compound having an oxetane group, having a weight average molecular weight of 180 or more, and having an oxygen atom content of 15% or more represented by the above formula (1).

(B) When the weight average molecular weight of the oxetane compound is 180 or more, the volatility of the compound can be reduced as described above. Therefore, it is possible to reduce deterioration of the working environment and damage to the object to be coated (display element) when the encapsulant is applied by the inkjet method. (B) The weight average molecular weight of the oxetane compound is preferably 190 or more, more preferably 200 or more, from the viewpoint of reducing the volatility of the encapsulant. The upper limit of the weight average molecular weight may be such that the ejection property of the encapsulant when applied by the inkjet method is not impaired, and is more preferably 400 or less, for example. The weight average molecular weight can be measured by the same method as described above.

(B) When the oxygen atom content of the oxetane compound is 15% or more, the polarity of the compound can be increased as described above, so that the low-polarity adhesive used for the head portion of the inkjet device deteriorates (B). Damage to the device) can be reduced. (B) The oxygen atom content of the oxetane compound is preferably 20% or more from the viewpoint of reducing damage to the apparatus. The oxygen atom content is preferably, for example, 30% or less from the viewpoint that the dielectric constant of the sealing layer does not become too large. Oxygen atom content can be defined and measured as above.

(B) In order to increase the oxygen atom content of the oxetane compound, for example, it is represented by the number of oxetanyl groups in one molecule of the compound or the oxygen atom-containing group (for example, _R2 of the formula (B-1) described later). The number of polyoxyalkylene groups, oxygen atoms contained in R ₂ , and oxygen atom-containing groups such as carbonyl groups and sulfonyl groups may be increased.

The number of oxetanyl groups in one molecule of such (B) oxetane compound may be one (monofunctional) or two or more (polyfunctional). Above all, two or more (polyfunctional) are preferable from the viewpoint of easily increasing the oxygen atom content and easily increasing the curability.

The oxetane compound (B) is preferably a compound represented by the following formula (B-1) or (B-2).

R ₁ of the formulas (B-1) and (B-2) is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, an aralkyl group, a frill group or a thienyl group, respectively. R ₂ is a divalent organic residue, respectively. However, R ₁ and R ₂ are selected so that the weight average molecular weight and the oxygen atom content of the compounds represented by the formulas (B-1) and (B-2) satisfy the above ranges.

Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group and a cyclohexyl group. Examples of aryl groups include phenyl, naphthyl, tolyl and xylyl groups. Examples of aralkyl groups include benzyl, phenethyl groups.

Examples of divalent organic residues include an alkylene group, a polyoxyalkylene group, a phenylene group, a xylylene group, and a structure represented by the following formula.

R ₃ in the formula is an oxygen atom, a sulfur atom, -CH _2- , -NH-, -SO-, -SO _2- , -C (CF ₃ ) _2- or -C (CH ₃ ) _2- . ..

_R4 is an alkylene group or an arylene group having 1 to 6 carbon atoms. Examples of the alkylene group include an alkylene group having 1 to 15 carbon atoms such as a methylene group, an ethylene group, a propylene group, a butylene group and a cyclohexylene group. The polyoxyalkylene group is preferably a polyoxyalkylene group having 4 to 30 carbon atoms, preferably 4 to 8 carbon atoms, and examples thereof include a polyoxyethylene group and a polyoxypropylene group.

The content of the (B) oxetane compound is preferably 20 to 80% by mass with respect to the total mass of the encapsulant. (B) When the content of the oxetane compound is 20% by mass or more, it is easy to improve the curability while sufficiently lowering the viscosity of the encapsulant, and when it is 80% by mass or less, the component (A) and (C) It is easy to suppress the decrease in curability due to too few components. From the above viewpoint, the content of the (B) oxetane compound is more preferably 25 to 80% by mass and further preferably 30 to 70% by mass with respect to the total mass of the encapsulant.

<(C) Aliphatic epoxy compound>
(C) The aliphatic epoxy compound may have a function of easily lowering the viscosity of the encapsulant and enhancing the flexibility and adhesion of the cured product. (C) The aliphatic epoxy compound is a glycidyl ether of an aliphatic alcohol (including a polyhydric alcohol) having no aromatic ring, has a weight average molecular weight of 180 or more, and is represented by the above formula (1). The oxygen atom content is 15% or more.

(C) When the weight average molecular weight of the aliphatic epoxy compound is 180 or more, the volatility of the compound can be lowered as described above. Therefore, it is possible to reduce deterioration of the working environment and damage to the object to be coated (display element) when the encapsulant is applied by the inkjet method. The weight average molecular weight of the (C) aliphatic epoxy compound is preferably 190 or more, more preferably 200 or more, from the viewpoint of lowering the volatility of the encapsulant. The upper limit of the weight average molecular weight may be such that the ejection property of the encapsulant when applied by the inkjet method is not impaired, and is more preferably 400 or less, for example. The weight average molecular weight can be measured by the same method as described above.

(C) When the oxygen atom content of the aliphatic epoxy compound is 15% or more, the polarity of the compound can be increased as described above, so that a low-polarity adhesive used for the head portion of an inkjet device may be used. Deterioration (damage to the device) can be reduced. The oxygen atom content of the (C) aliphatic epoxy compound is preferably 20% or more from the viewpoint of further reducing damage to the apparatus. The oxygen atom content is preferably, for example, 30% or less from the viewpoint of preventing the dielectric constant of the sealing layer from becoming too large. Oxygen atom content can be defined and measured as described above.

(C) In order to increase the oxygen atom content of the aliphatic epoxy compound, for example, the number of epoxy groups in one molecule of the compound or the number of oxygen atom-containing groups (for example, polyoxyalkylene group) may be increased. good.

As described above, such (C) aliphatic epoxy compound is a glycidyl ether of an aliphatic alcohol (including a polyhydric alcohol) having no aromatic ring. The aliphatic alcohol (including the aliphatic polyhydric alcohol) may be chain-shaped or cyclic. However, the (C) aliphatic epoxy compound does not have a cycloalkene oxide structure. Among them, the aliphatic alcohol (including the aliphatic polyhydric alcohol) is preferably in the form of a chain from the viewpoint that the encapsulant can be easily made to have a lower viscosity.

(C) The number of epoxy groups in one molecule of the aliphatic epoxy compound may be one (monofunctional) or two or more (polyfunctional). Among them, two or more (polyfunctional) are preferable from the viewpoint of easily increasing the oxygen atom content and easily increasing the curability.

That is, the (C) aliphatic epoxy compound is preferably an aliphatic polyhydric alcohol or a polyglycidyl ether having an alkylene oxide adduct thereof, and more preferably a diglycidyl ether having an alkanediol or an alkylene oxide adduct thereof. ..

Examples of the aliphatic epoxy compound (C) include alkanediols having 4 to 6 carbon atoms such as 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether and 1,6-hexanediol diglycidyl ether. Diglycidyl ether; Triglycidyl ether such as glycerin and trimethylolpropane; Tetraglycidyl ether of sorbitol; Hexaglycidyl ether of dipentaerythritol; Diglycidyl ether such as polyethylene glycol and polypropylene glycol; Among the polyglycidyl ethers of the adduct (polyether polyol), those having a weight average molecular weight and an oxygen atom content satisfying the above ranges are included. Examples of commercially available products include SR-PG, SR-2EGS, SR-8EGS, SR-14BJ, SY-25L (manufactured by Sakamoto Pharmaceutical Co., Ltd.), Epogosei 2EH, Epogosei HD (D), Epogosei NPG (D), Epogosei. BD (D) (manufactured by Yokkaichi Chemical Company Limited), Denacol EX-121, Denacol EX-212L, and Denacol EX-214L (manufactured by Nagase ChemteX) are included.

The content of the (C) aliphatic epoxy compound is preferably 5 to 60% by mass with respect to the total mass of the encapsulant. (C) When the content of the aliphatic epoxy compound is 5% by mass or more, it is easy to sufficiently impart flexibility and adhesion to the cured product while sufficiently lowering the viscosity of the encapsulant, and 60% by mass or less. If it is, the curability is not easily impaired. From the above viewpoint, the content of the (C) aliphatic epoxy compound is more preferably 5 to 50% by mass and further preferably 10 to 40% by mass with respect to the total mass of the encapsulant.

By combining (A) an alicyclic epoxy compound having a cycloalkene oxide structure, (B) an oxetane compound, and (C) an aliphatic epoxy compound in this way, the volatility of the encapsulant is not excessively increased. The viscosity can be made sufficiently low, and the curability can be effectively enhanced. In addition, it is possible to prevent the rubber material of the head portion of the inkjet device from swelling and reduce damage to the inkjet device.

The content of the (C) aliphatic epoxy compound is preferably higher than the content of the (A) alicyclic epoxy compound having a cycloalkene oxide structure. Specifically, the content ratio (C / A) of the (C) aliphatic epoxy compound to the (A) alicyclic epoxy compound having a cycloalkene oxide structure is preferably 0.5 to 1.5. .. As a result, the flexibility and adhesion of the cured product can be further enhanced while the viscosity of the encapsulant is sufficiently low.

The content of the (B) oxetane compound is preferably higher than the content of the (C) aliphatic epoxy compound. Specifically, the ratio (B / C) of the content of the (B) oxetane compound to the (C) aliphatic epoxy compound is preferably 0.5 to 7. Thereby, the curability can be further improved while the viscosity of the encapsulant is lowered. As a result, it is possible to rapidly promote curing after coating while further improving the ejection property in the inkjet method, and it is easy to suppress repelling on the object to be coated.

Further, from the viewpoint of further reducing damage to the inkjet device, (A) an alicyclic epoxy compound having a cycloalkene oxide structure, (B) an oxetane compound, and (C) an aliphatic epoxy compound are each polyfunctional. It is preferably a compound, more preferably a bifunctional compound. Further, one or more of (A) an alicyclic epoxy compound having a cycloalkene oxide structure, (B) an oxetane compound, and (C) an aliphatic epoxy compound, preferably (A) an alicyclic epoxy compound is carbonyloxy. It preferably has a group (or ester group). This is because the carbonyloxy group (or ester group) has a high polarity among the oxygen-containing groups, makes it difficult for a rubber material having a low polarity used for the head portion of the inkjet device to swell, and can further reduce damage.

<(D) Cationic Polymerization Initiator>
(D) The cationic polymerization initiator may be a photocationic polymerization initiator that generates an acid capable of initiating cationic polymerization by irradiation with light such as ultraviolet rays, or a thermal cationic polymerization initiator that generates acid by heating. You may. Above all, from the viewpoint of reducing damage to the display element due to heating, it is preferable to photo-cure the encapsulant, and the (D) cationic polymerization initiator is preferably a photocationic polymerization initiator.

Photocationic polymerization initiators have anionic moieties of BF _4- ^, PF _6- ^, SbF _6- ^, or BX _4- ⁽ X is a phenyl group substituted with at least two or more fluorine or trifluoromethyl groups). , Aromatic sulfonium salt, aromatic iodonium salt, aromatic diazonium salt, aromatic ammonium salt.

Examples of aromatic sulfonium salts include bis [4- (diphenylsulfonio) phenyl] sulfide bishexafluorophosphate, bis [4- (diphenylsulfonio) phenyl] sulfide bishexafluoroantimonate, and bis [4- (diphenyl). Sulfonio) phenyl] sulfide bistetrafluoroborate, bis [4- (diphenylsulfonate) phenyl] sulfide tetrakis (pentafluorophenyl) borate, diphenyl-4- (phenylthio) phenylsulfonium hexafluorophosphate, diphenyl-4- (phenylthio) ) Phenylsulfonium hexafluoroantimonate, diphenyl-4- (phenylthio) phenylsulfonium tetrafluoroborate and the like.

Examples of aromatic iodonium salts include diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate, bis ( Includes dodecylphenyl) iodonium hexafluoroantimonate, bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate and the like.

Examples of aromatic diazonium salts include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, phenyldiazonium tetrakis (pentafluorophenyl) borate and the like.

Examples of aromatic ammonium salts include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate and the like.

Examples of photocationic polymerization initiators include Irgacure250, Irgacure270, Irgacure290 (manufactured by BASF), CPI-100P, CPI-101A, CPI-200K, CPI-210S, CPI-310B, CPI-400PG (manufactured by San-Apro), SP-150, SP-170, SP-171, SP-506, SP-066, SP-130, SP-140, SP-601, SP-606, SP-701 (manufactured by ADEKA) are included. Among them, Irgure270, Irgure290, CPI-100P, CPI-101A, CPI-200K, CPI-210S, CPI-310B, CPI-400PG, SP-150, SP-170, SP-171, SP-506, SP-066, Sulfonium salts such as SP-601, SP-606, and SP-701 are preferred.

The content of the cationic polymerization initiator (D) is preferably 0.1 to 10% by mass with respect to the total mass of the encapsulant. (D) When the content of the cationic polymerization initiator is 0.1% by mass or more, the curability of the encapsulant is easily enhanced, and when it is 10% by mass or less, the coloring of the encapsulating layer is easily suppressed. From the above viewpoint, the content of the cationic polymerization initiator (D) is 0.1 to 5% by mass with respect to the total mass of the components (A), (B), (C) and (E). It is preferably 0.1 to 3% by mass, more preferably 0.1 to 3% by mass.

<(E) Other ingredients>
The sealant for a display element of the present invention may further contain components other than (A) to (D) as long as the effects of the present invention are not impaired. Examples of other components include aromatic epoxy compounds, sensitizers, silane coupling agents, leveling agents and the like.

The aromatic epoxy compound is a glycidyl ether of an alcohol containing an aromatic ring (including a polyhydric alcohol). Examples of aromatic epoxy compounds include bisphenol A type epoxy resin, bisphenol E type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol O type epoxy resin, and 2,2'-diallyl bisphenol A type epoxy resin. , Propoxy oxide-added bisphenol A type epoxy resin, resorcinol type epoxy resin, biphenyl type epoxy resin, sulfide type epoxy resin, diphenyl ether type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, orthocresol novolak type epoxy resin, biphenyl novolac Includes type epoxy resin, naphthalenephenol novolak type epoxy resin, and the like.

The oxygen atom content and the weight average molecular weight of the aromatic epoxy compound are not particularly limited, but from the viewpoint of reducing the volatility of the encapsulant and the damage to the apparatus, oxygen is similar to the components (A) to (C). The atomic content is preferably 15% or more, and the weight average molecular weight is preferably 180 or more.

However, if the encapsulant contains a large amount of, for example, bisphenol A type, F type epoxy resin, etc., the viscosity tends to increase. Further, if the sealant contains a large amount of aromatic epoxy resin, the cured product of the sealant may be easily colored. Therefore, it is preferable that the content of the aromatic epoxy resin is adjusted to such an extent that it has little effect on the viscosity of the encapsulant and the coloring of the cured product.

The sensitizer may have a function of further improving the polymerization initiation efficiency of the polymerization initiator and further promoting the curing reaction of the encapsulant. Examples of sensitizers include thioxanthone compounds such as 2,4-diethylthioxanthone, 2,2-dimethoxy-1,2-diphenylethan-1-one, benzophenone, 2,4-dichlorobenzophenone, o-benzoyl. Includes methyl benzoate, 4,4'-bis (dimethylamino) benzophenone, 4-benzoyl-4'-methyldiphenylsulfide and the like.

The silane coupling agent has a function of further enhancing the adhesiveness between the encapsulant and the substrate or the like. The silane coupling agent can be a silane compound having a reactive group such as an epoxy group, a carboxyl group, a methacryloyl group, and an isocyanate group. Examples of such silane compounds include trimethoxysilyl benzoic acid, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-glycidoxypropyl. Includes trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. These silane compounds may be used alone or in combination of two or more.

The leveling agent may have a function of imparting the flatness of the coating film to the sealing agent. Examples of leveling agents include silicone-based, acrylic-based, and fluorine-based ones. Examples of commercially available leveling agents include BYK-340, BYK-345 (all manufactured by Big Chemie Japan), and Surflon S-611 (manufactured by AGC Seimi Chemical Co., Ltd.).

The total content of the other component (E) is preferably 20% by mass or less with respect to the total mass of the encapsulant from the viewpoint of suppressing volatilization of the encapsulant and reducing damage to the apparatus. It is more preferably 10% by mass or less.

<Physical characteristics of sealant>
(viscosity)
The viscosity of the sealant for a display element measured at 25 ° C. and 20 rpm by an E-type viscometer is preferably 50 mPa · s or less, and more preferably 20 mPa · s or less. When the viscosity of the sealant is in the above range, the ejection property tends to be good when the sealant is applied by the inkjet method. The lower limit of the viscosity of the encapsulant can be, for example, 5 mPa · s.

(Light transmittance)
The average value of the light transmittance at a wavelength of 380 to 800 nm of the cured product of the sealant for a display element at a thickness of 10 μm is preferably 85% or more, and more preferably 90% or more. .. When the light transmittance of the cured product of the sealant for a display element is within the above range, it has good light transmittance, and is therefore suitable as a surface sealant for an organic EL element, for example. The average light transmittance can be measured as an average value of the light transmittance measured for each wavelength of 1 nm at a wavelength of 380 to 800 nm using, for example, an ultraviolet-visible spectrophotometer (manufactured by SHIMADZU).

(Oxygen content)
The oxygen content of the sealant for a display element is preferably 15% or more, and more preferably 20% or more, as described above, from the viewpoint of highly reducing damage to the device. The oxygen atom content of the sealant for a display element is preferably, for example, 30% or less from the viewpoint of preventing the dielectric constant of the sealing layer from becoming too large. The oxygen atom content of the display element sealant can be calculated as the total mass of oxygen atoms contained in the display element sealant / total mass of the display element sealant) × 100 (%). The total mass of oxygen atoms contained in the sealant for display elements can be calculated by calculating the ratio of oxygen atoms contained in the sealant for display elements by elemental analysis and multiplying it by the atomic weight of oxygen atoms. ..

<Preparation method of sealant>
The sealant for a display element can be obtained by mixing at least the components (A) to (D) using a mixer such as a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, or a three-roll. Can be done. From the viewpoint of stable mixing of the encapsulant, it is preferable to mix the components (A) to (C), then add the component (D) and mix them.

The sealant for a display element can be used as a surface sealant for a display element, preferably as a surface sealant for an organic EL element.

2. 2. Display device The display device of the present invention includes a display element arranged on a substrate and a cured product layer of a sealant for a display element of the present invention that seals the display element in a planar shape.

The substrate may be a glass substrate or a resin substrate. From the viewpoint of obtaining a flexible optical semiconductor device, a resin substrate (resin film) is preferable.

The display element is an element that converts electricity into light or light into electricity. Examples of display elements include organic EL elements, LED elements, and the like. Above all, the display element is preferably an organic EL element.

The thickness of the cured product layer of the sealant for a display element may be as long as it can sufficiently seal the display element and can realize flatness and thin film property, and is not particularly limited, but is, for example, 5 to 20 μm. It is preferably 5 to 10 μm.

Such display devices can be manufactured by any method. For example, the display device has 1) a step of obtaining a display element arranged on a substrate, 2) a step of applying the sealant for a display element of the present invention on the display element in a planar manner, and 3) coating. It can be manufactured through a step of curing a sealant for a display element.

In the step 1), a substrate on which the display element is arranged is prepared. When the display element is an organic EL element, the organic EL element usually includes a reflective pixel electrode layer, an organic EL layer, and a transparent counter electrode layer, and may further include another functional layer if necessary.

In the step 2), the sealant for the display element of the present invention is applied so as to cover the display element arranged on the substrate. The sealant for a display element can be applied by any method, for example, a screen printing method or an inkjet method. Of these, the inkjet method is preferable from the viewpoint of high flatness and the ability to form a thin and uniform coating layer at high speed. That is, it is preferable that the sealing agent for a display element of the present invention is applied onto the display element by an inkjet method and applied in a planar shape.

In the step 3), the sealant applied on the display element is cured to obtain a cured product layer. The curing of the encapsulant is preferably photocuring, and may be further thermosetting.

In the case of photocuring, a known light source such as a xenon lamp or a carbon arc lamp can be used as the light source used for light irradiation. The light irradiation may be performed to such an extent that the encapsulant can be sufficiently cured, and is not particularly limited. For example, by irradiating light having a wavelength of 300 to 400 nm with light having an integrated light amount of 300 to 3000 mJ / m ² . It can be suitably cured.

When the thermosetting is further performed, the heating temperature is preferably, for example, 50 to 120 ° C. from the viewpoint of sufficient curing while reducing damage to the display element.

The obtained display device is, for example, an organic EL device, and can be preferably used as various display devices and lighting devices.

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

・セロキサイド ＣＥＬ８０００（ダイセル社製、酸素原子含有率１６．４９％、分子量１９４）

1. 1. Material of encapsulant (A) Alicyclic epoxy compound having a cycloalkene oxide structure-Seroxide CEL2021P (manufactured by Daicel Co., Ltd., 3', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, oxygen atom content 25 .4%, molecular weight 252)

-Selokiside CEL8000 (manufactured by Daicel, oxygen atom content 16.49%, molecular weight 194)

・セロキサイド ＣＥＬ２０００（ダイセル社製、１，２－エポキシ－４－ビニルシクロヘキサン、酸素原子含有率１２．９％、分子量１２４）

(A') Comparative compound-LDO (manufactured by Symrise, limonene dioxide, oxygen atom content 19.05%, molecular weight 168)

-Seroxide CEL2000 (manufactured by Daicel, 1,2-epoxy-4-vinylcyclohexane, oxygen atom content 12.9%, molecular weight 124)

(B) Oxetane compound-OXT-221 (manufactured by Toagosei Co., Ltd., 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, oxygen atom content 22.43%, molecular weight 214)

・ＯＸＴ－２１２（東亜合成社製、２－エチルヘキシルオキセタン、酸素原子含有率１４．０４％、分子量２２８）(B') Comparative compound-AL-OX (manufactured by Yokkaichi Chemical Company Limited, oxygen atom content 28.07%, molecular weight 114)

OXT-212 (manufactured by Toagosei, 2-ethylhexyloxetane, oxygen atom content 14.04%, molecular weight 228)

(C) aliphatic epoxy compound-SR-16HL (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., 1,6-hexanediol diglycidyl ether, epoxy equivalent 125 g / eq, oxygen atom content 27.83%, molecular weight 230)

(C') Comparative compound-EX-111 (manufactured by Nagase ChemteX, allyl glycidyl ether, oxygen atom content 13.22%, molecular weight 242)
SY-35M (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., higher alcohol glycidyl ether, oxygen atom content 28.07%, molecular weight 114, epoxy equivalent 280 g / eq)

The oxygen atom content of the compound was calculated from the structural formula. The molecular weight of the compound was calculated from the structural formula.

(D) Cationic Polymerization Initiator-CPI-200K (manufactured by San-Apro, diphenyl-4- (phenylthio) phenylsulfonium hexafluorophosphate, see the formula below)

(E) Aromatic epoxy compound-EX-201 (manufactured by Nagasemtex, resorcinol diglycidyl ether, oxygen atom content 28.8%, molecular weight 222)

2. 2. Preparation and evaluation of encapsulant (Examples 1 to 4, Comparative Examples 1 to 9)
An alicyclic epoxy compound having a cycloalkene oxide structure, an oxetane compound, an aliphatic epoxy compound, and, if necessary, an aromatic epoxy compound were placed in a flask and mixed so as to have the composition shown in Table 1. The amount of the cationic polymerization initiator shown in Table 1 was added to the obtained mixture, and the mixture was further mixed. The resulting mixture was stirred until no powder was visible to obtain a sealant.

The viscosity, swellability (damage to the device), volatility and curability of the obtained sealant were evaluated by the following methods.

[viscosity]
The viscosity of the obtained encapsulant was measured at 25 ° C. at 20 rpm using an E-type viscometer (LV-DV-II +, manufactured by BROOKFIELD).
〇: 10 mPa ・ s or more and 20 mPa ・ s or less Δ: 20 mPa ・ s more than 50 mPa ・ s or less ×: 50 mPa ・ s more than

[Swelling]
The weight of the EPDM O-ring (EPDM-70, AS568-009 standard), which is a rubber material used for the head portion of the inkjet device, was measured. The weighed EPDM O-rings were then dipped in a sealant and stored for 1 week in the dark at 25 ° C. After storage, the EPDM O-ring was removed and weighed. Then, the weight change rate was calculated by applying the following formula.
Weight change rate (%) = [(Weight after storage-Weight before storage) / Weight before storage] x 100
Then, the swellability was evaluated based on the following criteria.
⊚: Weight change rate is 5% or less 〇: Weight change rate is more than 5% and 10% or less △: Weight change rate is more than 10% and 15% or less ×: Weight change rate is more than 15%

[volatility]
The volatility of the encapsulant was measured using a differential thermal calorie simultaneous measuring device (TG-DTA). Specifically, the encapsulant was heated from 30 ° C. to 50 ° C. at 5 ° C./min and then held for 50 minutes. Then, the weight reduction rate of the sealant after holding for 50 minutes ((weight after heating-weight before heating) / weight before heating) × 100) was measured. Then, the volatility was evaluated according to the following criteria.
〇: Weight loss rate is less than 1% ×: Weight loss rate is 1% or more

[Curability]
At room temperature, the sealant was applied onto a glass substrate using a bar coater (No. 6) and dried to form a coating film having a thickness of 10 μm. The obtained coating film was placed in an _N2 purge box, nitrogen gas was flowed for 1 minute, and the inside of the system was replaced with nitrogen gas. Next, the obtained coating film was irradiated with UV light having a wavelength of 365 nm with a UV-LED lamp so as to have an integrated irradiation amount of 1000 mJ / m ² . Then, the irradiated portion of the coating film was touched with a finger to determine the presence or absence of tackiness.
〇: Tack-free ×: Tack remains by touch

[Average light transmittance of cured product]
The obtained encapsulant was introduced into an inkjet cartridge DMC-11610 (manufactured by FUJIFILM Dimension). The inkjet cartridge is set in an inkjet device DMP-2831 (manufactured by Fujifilm Dimatic), and after adjusting the ejection state, the size is 5 cm x 5 cm so that the cured thickness is 10 μm on the SiN substrate. Was applied with. The obtained coating film was left at room temperature (25 ° C.) for 1 minute, then irradiated with UV light (irradiation intensity 1000 mJ / cm ² ) and cured.
The light transmittance of the obtained cured product of the encapsulant at a wavelength of 380 to 800 nm was measured for each wavelength of 1 nm using an ultraviolet visible spectrophotometer (manufactured by SHIMADZU), and the average value thereof was measured as “average light transmittance”. Rate. "

The compositions and evaluation results of the encapsulants of Examples 1 to 4 and Comparative Examples 1 to 9 are shown in Table 1. In addition, the unit of the numerical value of an Example and a comparative example is a mass part.

As shown in Table 1, the encapsulants of Examples 1 to 4 containing (A) to (C) and having an oxygen atom content of 15% or more and a weight average molecular weight of 180 or more are low. It can be seen that while having viscosity, low volatility and high curability, the swelling property is low and damage to the device can be reduced.

On the other hand, in any one of (A) to (C), the encapsulants of Comparative Examples 3, 6 and 9 having an oxygen atom content of less than 15% are all highly swellable, and the apparatus. It is suggested that the damage to is large. It is suggested that the encapsulants of Comparative Examples 2, 5 and 8 having a weight average molecular weight of less than 180 in any one of (A) to (C) are highly volatile. Further, it can be seen that the encapsulants of Comparative Example 1 containing no component (A) and Comparative Example 4 containing no component (B) have low curability. Further, it can be seen that Comparative Example 7 containing no component (C) is inferior in swelling property.

This application claims priority under Japanese Patent Application No. 2018-116842 filed June 20, 2018. All the contents described in the application specification are incorporated in the application specification.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a sealant for a display element, which has low viscosity, low volatility and good curability suitable for coating by an inkjet method, and which causes less damage to an inkjet device, and a cured product thereof. be able to.

Claims (7)

(A) 10 to 30% by mass of an alicyclic epoxy compound having a cycloalkene oxide structure.
(B) Oxetane compound in an amount of 30 to 70% by mass ,
A sealant for a display element containing (C) an aliphatic epoxy compound (however, different from the alicyclic epoxy compound) in an amount of 10 to 40% by mass and (D) a cationic polymerization initiator.
The (A) alicyclic epoxy compound, the (B) oxetane compound, and the (C) aliphatic epoxy compound are each polyfunctional compounds, and the sealant for the display element is a monofunctional oxetane compound. not included,
The (A) alicyclic epoxy compound, the (B) oxetane compound, and the (C) aliphatic epoxy compound are
The weight average molecular weight is 180 or more, respectively.
The oxygen atom content represented by the following formula (1) is 15% or more, respectively .
The mass ratio B / C of the content of the (B) oxetane compound to the content of the (C) aliphatic epoxy compound is 3.25 to 7.
Sealant for display elements.
Oxygen atom content (%) = total mass / weight average molecular weight of oxygen atoms in one molecule x 100 ... (1) The content of the (C) aliphatic epoxy compound is higher than the content of the (A) alicyclic epoxy compound.
The sealant for a display element according to claim 1. One or more of the (A) alicyclic epoxy compound, the (B) oxetane compound, and the (C) aliphatic epoxy compound has a carbonyloxy group.
The sealant for a display element according to claim 1 or 2 . The viscosity measured by an E-type viscometer at 25 ° C. and 20 rpm is 50 mPa · s or less.
The sealant for a display element according to any one of claims 1 to 3 . Used for application by inkjet method,
The sealant for a display element according to any one of claims 1 to 4 . The organic EL element, which is the display element, is sealed in a planar shape.
The sealant for a display element according to any one of claims 1 to 5 . The cured product of the sealant for a display element according to any one of claims 1 to 6 .