JP2003321669A - Sealing filler of photocuring type - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing filler of photocuring type, having characteristics suitable for sealing gaps between parts composed of resin molded products, metals, etc., i.e., excellent pressure resistance, heat resistance, heat shock resistance, oil resistance, impact resistance, etc., and further having a short curing time. <P>SOLUTION: This sealing filler of photocuring type contains (A) a liquid acrylic elastomer containing carboxy groups and having a weight-average molecular weight of 1,000-100,000, (B) (meth)acrylic acid or its derivative, (C) an isocyanato group-containing unsaturated compound, (D) a polyfunctional crosslinking agent having two or more unsaturated groups in its molecule, and (E) a photopolymerization initiator. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocurable sealing filler. More specifically, the present invention relates to a photo-curable sealing filler having properties suitable for sealing the gap between resin molded products and parts made of metal or the like.

[0002]

2. Description of the Related Art Conventionally, a molded rubber material has been used as a sealing filler, but it has been difficult to fill minute gaps with this filler. On the other hand, potting agents or sealing materials such as silicone-based sealants, epoxy resins, and UV-curable resins, when used in, for example, automobiles, are durable in an atmosphere where heat or vibration is continuously applied or oil is present. There is a problem that is not enough. Further, the silicone resin sealant and the epoxy resin also have a problem that it takes a long time to cure.

Specifically, for example, in a waterproof connector described in Japanese Patent Laid-Open No. 11-329570, which prevents leakage of a seal filler into a cavity, potting resin is used as a sealing material. Causes leakage due to a decrease in the adhesiveness due to the difference in the coefficient of thermal expansion between the potting resin and the mating material, or when the mating material is not sufficiently adhered to the potting resin and the mating material when an external force such as vibration acts. Leakage starts to occur from the interface with the material. Further, Japanese Patent Laid-Open No. 64-63282 describes a sealing method using a gel-like molding material, and this method is to seal by compressing a gel-like sealing material. However, the sealant may be damaged when the gel sealing material is mounted, which may reduce the sealing performance.

[0004]

DISCLOSURE OF THE INVENTION The object of the present invention is to provide characteristics suitable for sealing a gap between resin molded products, parts made of metal or the like, that is, pressure resistance, heat resistance, heat shock resistance, Another object of the present invention is to provide a photocurable sealing filler having excellent oil resistance and impact resistance, and having a short curing time.

[0005]

The object of the present invention is as follows.
(A) a carboxyl group-containing weight average molecular weight Mw is 1000 to 1
00000 liquid acrylic elastomer, (B) (meth) acrylic acid or a derivative thereof, (C) an isocyanate group-containing unsaturated compound, (D) a polyfunctional crosslinking agent having two or more unsaturated groups in the molecule and ( E) It is achieved by a photocurable sealing filler containing a photopolymerization initiator.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As the liquid acrylic elastomer having a carboxyl group as the component (A), at least one of alkyl acrylates such as alkyl acrylates, alkoxyalkyl acrylates, alkylthioalkyl acrylates, cyanoalkyl acrylates or derivatives thereof is the main component. (About 65 to 98.9% by weight, preferably about 70 to 95% by weight), and a monomer obtained by copolymerizing this with a carboxyl group-containing monomer is used.

As the carboxyl group-containing monomer, for example, acrylic acid, methacrylic acid, maleic acid monoalkyl ester, fumaric acid monoalkyl ester and the like are used, and these are about 1 to 30% by weight, preferably about 5 to 20%. It is used as a copolymer which is copolymerized by weight%. With a copolymerization ratio of less than this, the adhesive strength of the obtained sealing material is reduced,
Sufficient sealing performance cannot be obtained. On the other hand, if it is copolymerized at a ratio higher than this, the sealing material becomes too hard, and the adhesive strength is also reduced, and sufficient sealing performance cannot be obtained.

In the copolymer forming the liquid acrylic elastomer, other vinyl compounds such as vinyl acetate, styrene, etc. may be added without impairing the sealing property, the photo-curing property and the manufacturing cost. It can be copolymerized at a ratio of about 30% by weight or less.

The copolymerization reaction can be carried out by any radical polymerization method such as emulsion polymerization method, suspension polymerization method, solution polymerization method and bulk polymerization method. Since the polymerization rate is about 90% or more, the copolymerization reaction The charging weight ratio of each comonomer used in step (1) is approximately the composition weight ratio.

A molecular weight modifier is used in the copolymerization reaction. Examples of mercaptans used as a molecular weight modifier include 2-propanethiol, 1-butanethiol, 1-methyl-2-propanethiol, 2-mercaptoethanol, ethylmercaptoacetate, thiophenol, 2-naphthalenethiol, dodecylmercaptan. , Lauryl mercaptan and the like are used, and these are about 0.1 to 10% by weight, preferably about 1 to 5% by weight in the total amount with the copolymerization monomer component.
Used in a percentage by weight. At usage rates below this,
The composition before curing prepared using the liquid acrylic elastomer has high viscosity and poor fluidity. On the other hand, if it is used at a ratio higher than this, the sealing material after curing using this liquid acrylic elastomer becomes too soft and the sealing force is lowered, and sufficient sealing performance cannot be obtained.

The acrylic elastomer obtained is in liquid form,
Those having a weight average molecular weight Mw of about 1,000 to 100,000, preferably about 5,000 to 50,000 are used. If the Mw is less than this, not only will the viscosity be too low to flow out of the gaps between the parts during filling, or it will easily sag, but the sealing material after curing will be too soft, and sufficient sealing performance will not be obtained. On the other hand, if the Mw of more than this is used, the viscosity becomes too high and the workability of injection and coating is deteriorated.

When a monomer having a functional group other than a carboxyl group, such as 2-hydroxyethyl acrylate and glycidyl methacrylate, is used in the copolymerization reaction of a liquid acrylic elastomer, the thermal history of 2-hydroxyethyl acrylate is increased. Occasionally, curing and deterioration are significant, so that the pressure resistance after hysteresis is reduced, and when glycidyl methacrylate is used, the reaction with the isocyanate group-containing unsaturated compound is slow or does not react, forming a rubber-like elastic body. I don't get it.

The component (B) (meth) acrylic acid or its derivative is used as a reactive diluent. Examples of the (meth) acrylic acid derivative include n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate, lauryl acrylate, and caprolactone derivatives.
(Meth) acrylic acid ester, polyoxyethylene derivative (meth) acrylic acid ester having a long-chain alkyl group such as acrylic acid ester is preferably used, and methyl methacrylate, ethyl acrylate, n-butyl acrylate, etc. Used as appropriate.

Further, as the derivative of (meth) acrylic acid as the component (B), ω-carboxypolycaprolactone monoacrylate, 2-acryloyloxyethylsuccinic acid, 2-acryloyloxyethylphthalic acid, 2-methacryloyloxy Ethyl succinic acid, 2-methacryloyloxyethyl hexahydrophthalic acid and the like are also used. Addition of these carboxyl group-containing monomers has the effects of increasing cohesive force (increasing the strength of the sealing material itself), adhering to the base material, and not deteriorating heat resistance.

One or more of these components (B) are used in an amount of about 0.1 to 48 parts by weight, preferably about 5 to 40 parts by weight, per 100 parts by weight of the liquid acrylic elastomer. If it is used less than this, the viscosity becomes too high and the workability of injection and coating deteriorates.On the other hand, if it is used at more than this, the viscosity is too low to flow out from the gap between the parts or sag when filling. Not only is it easy, but the sealing material after curing becomes too soft and sufficient sealing performance cannot be obtained.

The isocyanate group-containing unsaturated compound as the component (C) is, for example, methacryloyloxyethyl isocyanate, allyl isocyanate, etc., in an amount of about 0.1 to 10 parts by weight, preferably about 0.3 to 5 parts by weight, per 100 parts by weight of the liquid acrylic elastomer. Used in proportion. At a usage rate of less than this, since the cross-linking density is insufficient and the elastic modulus decreases,
A seal having sufficient strength cannot be obtained. On the other hand, if it is used in a proportion higher than this, the crosslinking density becomes excessive, and the rubber becomes too hard, resulting in deterioration of the sealing performance during the heat shock test and impact resistance test.

Examples of the polyfunctional crosslinking agent having two or more unsaturated groups in the molecule of component (D) include 1,6-hexanediol diacrylate, 1.9-nonanediol diacrylate, polyethylene glycol diacrylate, Neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, etc., is about 0.1 to 40 parts by weight, preferably about 0.5 to 10 parts by weight per 100 parts by weight of the liquid acrylic elastomer. Used in proportions by weight. If it is used below this range, the crosslink density will be insufficient and the elastic modulus will decrease, resulting in poor sealing performance.On the other hand, if it is used above this range, the crosslink density will be excessive and the rubber will be too hard, resulting in poor sealing performance. Come to do.

Each of these components (B), (C) and (D) is also contained in a proportion of about 5 to 50 parts by weight, preferably about 10 to 40 parts by weight, per 100 parts by weight of the liquid acrylic elastomer. Used in. If the total amount is less than this, the viscosity of the composition becomes high, and not only the injection and coating workability deteriorate, but also
The elongation of the cured product decreases and the sealing performance also decreases. On the other hand, if it is used in a total amount larger than this, problems such as foaming and sink marks during curing tend to occur.

The sealing filler of the present invention containing the above-mentioned respective components as essential components is, if necessary, another compounding agent such as an antioxidant, a filler, a curing accelerator, a tackifier, a thixotropic agent. After properly blending a defoaming agent, a leveling agent, a pigment, etc., a photopolymerization initiator is added and photocured.

Examples of the photopolymerization initiator of the component (E) include 1
-Hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenylethan-1-one, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, etc. are used. Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide is preferably used. These photopolymerization initiators are used in a ratio of about 0.1 to 5 parts by weight, preferably about 0.3 to 3 parts by weight, per 100 parts by weight of the liquid acrylic elastomer, and may be appropriately selected depending on the composition and thickness of the photocurable sealing filler. Increased or decreased.

As another type of compounding agent, a terpene resin is added in a ratio of 30 parts by weight or less per 100 parts by weight of the liquid acrylic elastomer. As the terpene-based resin, for example, terpene-phenolic resin, terpene-based hydrogenated resin, etc. are used, and the addition of these terpene-based resins to the composition has the effect of improving the adhesion depending on the mating base material. Play.

The composition is prepared, for example, by using a stirrer such as a mixing stirrer, and the photocuring of the prepared composition is carried out by using an ultraviolet ray generator such as a high pressure mercury lamp having an output of 250 W at 200 mW / cm ^2. It is performed by irradiating light with an irradiation light intensity of (365 nm) for about 10 to 30 seconds. At that time, the viscosity range (about 60 ° C.) of the composition preferable as the sealing filler is
About 5 to 250 Pa.s, preferably about 10 to 150 Pa.s, more preferably about 20 to 50 Pa.s.If the viscosity is less than this, when it is filled with a liquid material, it drips from the gap between the parts,
It is difficult to obtain a sufficient thickness for application and sufficient sealing performance. On the other hand, if the viscosity is higher than this, it is difficult to inject it into a part having a complicated shape.

JIS of sealing material obtained by photo-curing
It is desirable that the A hardness is 50 or less, preferably about 10-40. A JIS A hardness of 50 or less is a soft rubber and has excellent adhesion, heat shock resistance, impact resistance, etc., while a hardness of more than 50% makes the rubber hard and reduces these properties. Come to do.

[0024]

EFFECT OF THE INVENTION The photo-curing sealing filler according to the present invention is liquid and fluid before curing, and is used by injecting or applying it into the gaps between resin molded products and parts made of metal or the like. It is also suitable for sealing small gaps such as small parts compared to rubber vulcanization products, and the cured filler has excellent heat resistance, heat shock resistance, oil resistance and impact resistance. Form a rubber-like sealing material.

Even if the sealed gap changes due to the expansion of the resin material or the metal material caused by the external force such as vibration or the temperature change, the rubber-like sealing filler of the present invention vibrates or deforms. As a result, it exhibits high sealing performance. Further, it has good adhesion to various resin materials including polyolefin resins and metal materials, and high sealing performance can be obtained.

Further, since the photo-curable sealing filler of the present invention is photo-curable, the curing time is extremely shorter than that of the epoxy resin or the silicone sealant, and the conventional epoxy resin, the UV-curable resin, High sealing performance, which is not found in silicone sealants, is obtained.

The photo-curing sealing material of the present invention having the above-mentioned characteristics is used as a sealing material between material surfaces in a field requiring heat resistance, vibration resistance, oil resistance, etc. It can be effectively used as a sealing material such as a gasket in a portion to which displacement such as pressure or external force is applied.

[0028]

EXAMPLES The present invention will now be described with reference to examples.

Example 1 Ethyl acrylate [EA] 16 g n-Butyl acrylate [BA] 15 g Acrylic acid [AA] 1.7 g Lauryl mercaptan [in a 3 L four-necked flask equipped with a condenser, a dropping funnel and a thermometer. RSH] 0.67 g of a mixed solution (1/3 of all monomers) was charged, and EA 34g BA 28g AA 3.3g RSH 1.33g AIBN (azobisisobutyronitrile) 0.1g mixed solution (2% of all monomers) (3 volume) using a dropping funnel, 10
A liquid acrylic elastomer was obtained by reacting at a temperature of 60 to 70 ° C. for 16 hours while dropping over a period of time.

Regarding this liquid acrylic elastomer,
The following items were measured. Weight average molecular weight Mw: Measured by GPC using polystyrene gel and tetrahydrofuran as solvent Viscosity: Measured with E type viscometer at 25 ° C

The following components were added to such a liquid acrylic elastomer and mixed by using a stirring defoamer to prepare a liquid acrylic elastomer composition. Liquid acrylic elastomer 100 parts by weight Lauryl acrylate [LA] 30〃 2-methacryloyloxyethyl iso 2〃 cyanate [MOI] 1,6-hexanediol diacrylate 3〃 [1,6-HDDA] Bis (2,4,6- Trimethylbenzoyl) phenylphosphine 1〃 oxide (Ciba Specialty Chemicals IRGACURE 819) [BPPO]

Using the liquid acrylic elastomer composition, the following tests were conducted. Hardness: 250W Ultra High Pressure Mercury Lamp (USHIO ELECTRIC Spot Cure)
The cured product obtained by exposing for 20 seconds with an irradiation light intensity of 200 W / cm ² (365 nm) in accordance with JIS K-6253
A hardness measurement Pressure resistance test: The above composition was injected into a polyamide or polyethylene tube with an inner diameter of 4 mm to a depth of about 5 mm, exposed under the above conditions, and one end was sealed with a rubber sealing material. Obtain a tube, connect the air pipe with a pressure adjustment valve to the open other end of the tube, gradually increase the pressure until it reaches 200 kPa, and evaluate the sealing performance based on the pressure at which leakage occurs (however, pressure above 200 kPa (The maximum measured value is 200 kPa because it has not been applied.) Heat resistance test: The polyamide tube with one end sealed is left in an oven at 150 ° C for 70, 140, 300 and 500 hours and then allowed to cool to room temperature. Then, the performance is evaluated by the above-mentioned pressure resistance test method. Heat shock test: 100, 200, 500 heat shock test in which the polyamide tube with one end sealed at -40 to 120 ° C for 1 cycle (30 minutes / 30 minutes) And 1000 service After performing the test, let it cool to room temperature and evaluate the sealing performance by the pressure resistance test method. Oil resistance test: The polyamide tube with one end sealed in standard test oil (IRM903) at 70 ° C, 140, 300 and 500 After soaking for time, let it cool to room temperature and evaluate the sealing performance by the above pressure test method Impact resistance test: Put the polyamide tube with one end sealed in a ball mill with an inner diameter of 300 mm, rotate for 500 hours and let it cool to room temperature Then, the sealing performance is evaluated by the above pressure resistance test method.

Examples 2 to 9 In Example 1, the amounts of the copolymerizable monomer and the chain transfer agent (% by weight) were changed as shown in Table 1. In Table 1, the amount of the copolymerization monomer and the amount of the chain transfer agent of Example 1 are also shown. (Abbreviation) BA: n-butyl acrylate MEA: 2-methoxyethyl acrylate Table 1 Copolymerization Example Monomer 1 2 3 4 5 6 7 8 9 EA 50 50 50 50 50 50 50 50 BA 43 43 46 32 43 43 41 93 MEA 43 AA 5 5 2 15 5 5 5 5 5 RSH 2 2 2 3 2 2 4 2 2

Further, each component (part by weight) shown in Table 2 was added to the obtained liquid acrylic elastomer to prepare a liquid acrylic elastomer composition. In Table 2, each compounding component of Example 1 is also shown. (Abbreviation) Liquid rubber: Liquid acrylic elastomer HTR: Terpene-based hydrogenated resin (Yasuhara Chemical product Clearon P-125) Table 2 Example compounding ingredients 1 2 3 4 5 6 7 8 9 Liquid rubber 100 100 100 100 100 100 100 100 100 LA 30 30 30 30 30 30 30 30 30 MOI 2 5 2 2 0.5 2 2 2 2 1,6-HDDA 3 3 3 3 3 3 3 3 3 HTR 12 BPPO 1 1 1 1 1 1 1 1 1 1

The measurement results of Example 1 and Examples 2 to 9 are
It is shown in Table 3 below. Table 3 Examples Measurement items 1 2 3 4 5 6 7 8 9 [Liquid acrylic elastomer] Weight average molecular weight Mw (× 10 ⁴ ) 2.5 2.5 2.6 2.2 2.5 2.5 0.8 3.0 2.3 Viscosity (Pa · s) 25 28 21 31 26 30 11 21 22 [Cured product of composition] Hardness (JIS A) 20 22 17 25 16 22 20 15 21 Pressure resistance test Polyamide tube (kPa) 200 200 160 200 180 200 160 200 200 Polyethylene tube (kPa) 180 200 150 200 170 190 150 180 190 Heat resistance test 70 hours (kPa) 200 200 150 200 190 200 150 200 200 140 hours (kPa) 200 200 150 200 180 200 140 200 180 300 hours (kPa) 200 200 130 200 170 200 130 200 160 500 hours (kPa) 200 200 110 200 160 200 110 200 150 Heat shock test 100 cycles (kPa) 200 200 160 190 190 200 150 200 200 200 cycles (kPa) 200 200 160 170 180 200 140 200 200 500 cycles (kPa) 200 180 170 160 160 190 120 200 200 1000 cycles (kPa) 190 160 140 160 160 190 110 180 200 Oil resistance test 70 hours (kPa) 200 200 160 200 170 200 150 200 200 140 hours (kPa) 200 200 170 200 170 2 00 140 200 200 300 hours (kPa) 180 190 120 200 160 180 110 200 200 500 hours (kPa) 190 170 100 200 160 180 100 180 190 Impact test 500 hours (kPa) 200 190 160 190 160 200 140 200 180

Comparative Example 1 In Example 1, a liquid acrylic elastomer having a weight average molecular weight Mw of 2.5 × 10 ⁴ and a viscosity of 20 Pa · s, wherein 2-hydroxyethyl acrylate was used in the copolymerization reaction in place of acrylic acid. was gotten.

Comparative Example 2 A liquid acrylic elastomer having a weight average molecular weight Mw of 2.0 × 10 ⁴ and a viscosity of 20 Pa · s was obtained in the same manner as in Example 1, except that glycidyl methacrylate was used in the copolymerization reaction in place of acrylic acid. It was However, it did not cure in the photocuring time of 20 seconds and various properties could not be measured.

Comparative Example 3 In Example 1, instead of the liquid acrylic elastomer composition, an epoxy resin type sealing material (ThreeBond 2022 manufactured by ThreeBond Co., Ltd.) was used.

Comparative Example 4 In Example 1, instead of the liquid acrylic elastomer composition, an epoxy resin type sealing material (manufactured by the same company, Three Bond 2021) was used.

Comparative Example 5 In Example 1, a photocurable resin (manufactured by the company ThreeBond 3014C) was used in place of the liquid acrylic elastomer composition.

Comparative Example 6 In Example 1, a photocurable resin (manufactured by the same company, ThreeBond 3016E) was used instead of the liquid acrylic elastomer composition.

Comparative Example 7 In Example 1, instead of the liquid acrylic elastomer composition, a silicone resin type sealant (Shin-Etsu Chemical product KE4) was used.
41) was used.

Comparative Example 8 In Example 1, instead of the liquid acrylic elastomer composition, a silicone resin sealant (manufactured by the same company, KE3494) was used.
Was used.

The measurement results of the above comparative examples are shown in Table 4 below. The curing time is 20 seconds (exposure) for Comparative Example 1 and Comparative Examples 5 to 6 and 24 hours (left at room temperature for 1 day) for others, and the cured product hardness of the compositions of Comparative Examples 3 to 4 is It was measured as JIS A hardness (JIS K-6253 compliant). Table 4 Measurement items Ratio-1 Ratio-3 Ratio-4 Ratio-5 Ratio-6 Ratio-7 Ratio-8 [Sealant] Viscosity (Pa · s) 20 13 12 12 10 8 50 [Cured product of sealant] Hardness JIS A 18 50 20 20 35 JIS D 88 70 Pressure resistance test Polyamide tube (kPa) 190 200 200 200 200 200 200 Polyethylene tube (kPa) 150 80 80 90 40 80 90 Heat resistance test 70 hours (kPa) 190 200 200 170 100 200 200 140 hours (kPa) 140 190 200 140 80 200 200 300 hours (kPa) 100 160 180 50 40 190 190 500 hours (kPa) 40 160 180 30 10 190 190 Heat shock test 100 cycles (kPa) 190 200 180 180 140 200 200 200 cycles (kPa) 180 170 180 170 50 200 200 500 cycles (kPa) 100 160 20 30 50 190 190 1000 cycles (kPa) 20 30 10 20 20 200 200 Oil resistance test 70 hours (kPa) 190 180 180 160 120 50 50 140 hours (kPa) 180 180 180 120 90 30 30 300 hours (kPa) 180 170 180 50 40 20 20 500 hours (kPa) 160 170 170 40 10 10 Impact test 500 hours (kPa) 190 60 20 40 10 200 200

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 133/06 C09D 133/06 175/14 175/14 (72) Inventor Jun Okabe Isohara Town, Kitaibaraki City, Ibaraki Prefecture Kamitaida 831-2 F-Term in Unimatec Co., Ltd. (Reference) 4H017 AA03 AA04 AB01 AC01 AC08 AC09 AC14 AD06 AE05 4J034 HA04 HC02 JA21 LA13 LA23 LA33 RA08 4J038 CG031 CG061 CG071 CG141 CH131 CH261 DG312 FA11 GA06 JA02 JA35 JA03 JA02 JA35 JA03 JA02 JA35 JA03 JA02 JA35 JA02 JA35 JA03 JA02 JA35 JA03 JA02 JA35 JA03 JA02 JA35 JA02 JA35 JA02 JA35 JA03 JA02 JA35 JA03 JA02 JA35 JA03 JA02 JA35 JA03 JA02 JA35 PA17

Claims (5)

[Claims] 1. A liquid acrylic elastomer (A) having a carboxyl group and having a weight average molecular weight Mw of 1,000 to 100,000,
(B) (meth) acrylic acid or a derivative thereof, (C) an isocyanate group-containing unsaturated compound, (D) a polyfunctional crosslinking agent having two or more unsaturated groups in the molecule, and (E) a photopolymerization initiator A photo-curable sealing filler containing the above. 2. (B), (C), (D) per 100 parts by weight of component (A).
The photocurable sealing filler according to claim 1, wherein each component is used in a proportion of 5 to 50 parts by weight as a total amount. 3. The photocurable sealing filler according to claim 1, wherein a sealing material having a JIS A hardness of 50 or less is formed. 4. The photocurable sealing filler according to claim 1, which is used for sealing a gap between a resin molded product or a component formed of a metal. 5. A liquid acrylic elastomer (A) having a carboxyl group and a weight average molecular weight Mw of 1,000 to 100,000,
(B) (meth) acrylic acid or a derivative thereof, (C) an isocyanate group-containing unsaturated compound, (D) a polyfunctional crosslinking agent having two or more unsaturated groups in the molecule, and (E) a photopolymerization initiator A sealing composition comprising: