KR102718117B1 - Curable composition and cured product thereof - Google Patents

Abstract

[Task] A curable composition capable of forming a cured product having excellent adhesion to a substrate, high total light transmittance and well-suppressed haze, and a cured product thereof are provided. [Solution] A curable composition comprising (A) urethane (meth)acrylate, (B) a thiocarboxylic acid derivative, (C) triallyl isocyanurate, and (D) a photopolymerization initiator, wherein the curable composition comprises 50 parts by mass or more of (B) thiocarboxylic acid derivative per 100 parts by mass of (A) urethane (meth)acrylate, and 40 parts by mass or more of (C) triallyl isocyanurate per 100 parts by mass of (A) urethane (meth)acrylate, and a cured product thereof are obtained.

Description

Curable composition and cured product thereof

The present invention relates to a curable composition, for example, a curable composition used in the production of a transparent display or adhesive, and a cured product thereof.

Due to recent advances in image formation technology, the image quality of electronic devices such as liquid crystal displays and touch panels has improved remarkably. In order to improve the reproducibility of such high-quality images, the quality of screens and the like of image display devices has also been demanded to improve. In other words, in order to enable high-definition moving images or still images to be reproduced with high precision on image display devices, it is essential that the display or its adhesive have excellent transparency, that is, that it is colorless and transparent.

In order to obtain a cured product of a resin having high transparency that meets such requirements, an active energy ray-curable resin composition using a photocurable component and certain inorganic particles has been proposed (Patent Document 1). In this document, haze is controlled as an indicator of transparency, and thereby a curable composition having excellent transparency is obtained.

Japanese Patent Publication No. 2009-242681

There is a demand for transparent cured products of curable compositions used in screens of display devices, etc., to enable brighter and clearer image visibility. However, in conventional resin compositions such as those disclosed in Patent Document 1, although a predetermined transparency is obtained, light transmittance is not examined, and clear image visibility cannot necessarily be said to be sufficient.

In addition, in the manufacture of electronic devices, it is required that the curable composition adhere well to the main body of the electronic device (substrate, etc.). Under these circumstances, in conventional resin compositions, there is still room for improvement in terms of maintaining quality under certain usage conditions and adhesion to the substrate.

The present invention aims to provide a curable composition capable of forming a cured product having excellent adhesion to a substrate, high total light transmittance and well-suppressed haze, and a cured product thereof.

In view of the above, the present inventors have conducted thorough examination and have found that the above problems can be solved by a curable composition comprising (A) urethane (meth)acrylate, (B) a thiocarboxylic acid derivative, (C) triallyl isocyanurate, and (D) a photopolymerization initiator, wherein the curable composition comprises 50 parts by mass or more of (B) thiocarboxylic acid derivative per 100 parts by mass of (A) urethane (meth)acrylate, and 40 parts by mass or more of (C) triallyl isocyanurate per 100 parts by mass of (A) urethane (meth)acrylate, thereby completing the present invention.

In the curable composition of the present invention, it is preferable that the total mass of (A) urethane (meth)acrylate, (B) thiocarboxylic acid derivative, and (C) triallyl isocyanurate is 95% or more of the total mass of the curable composition.

In addition, the task of the present invention is solved by a transparent cured product obtained from the curable composition of the present invention.

The curable composition of the present invention has high adhesion to a substrate. In addition, by curing the curable composition of the present invention, a highly transparent cured product having suppressed haze and high total light transmittance can be obtained.

Figure 1 is a schematic diagram showing a plate body having a concave portion used in manufacturing a molded product of the present invention.
Figure 2 is a schematic diagram showing a state in which the photocurable composition of the present invention is filled into a concave portion of a plate body.
Figure 3 is a schematic diagram illustrating a process of covering a plate with a substrate and irradiating ultraviolet rays from a light source positioned above it.
Figure 4 is a schematic diagram showing a state in which a plate body and a molded product are released from the mold.

The curable composition of the present invention is a curable composition comprising (A) urethane (meth)acrylate, (B) a thiocarboxylic acid derivative, (C) triallyl isocyanurate, and (D) a photopolymerization initiator, characterized in that it comprises 40 parts by mass or more of (B) thiocarboxylic acid derivative per 100 parts by mass of (A) urethane (meth)acrylate, and 50 parts by mass or more of (C) triallyl isocyanurate per 100 parts by mass of (A) urethane (meth)acrylate.

The curable composition of the present invention has excellent adhesion to a substrate, and its cured product has high light transmittance and suppressed haze, thereby having excellent transparency and transmittance.

In the present invention, haze is used as an indicator of transparency.

Haze is the degree of cloudiness, and it indicates the transparency of transparent materials such as glass, plastic, or liquid. It is expressed as a percentage of the scattered light transmittance of the test piece divided by the total light transmittance. Therefore, the smaller the value, the less scattered light is transmitted, and the less cloudy the material is.

In addition, in the present invention, transmittance (total light transmittance) is used as an indicator of transmittance. Transmittance is the ratio of the amount of transmitted light to the amount of light incident on the material to be measured, and is obtained as a value that takes into account reflection on the surface of the material and absorption inside the material.

In the present invention, haze is measured in accordance with JIS-K-7361: 2000, and “transparent” or “high transparency” means that the haze is less than 5%. Preferably, the haze is less than 1%.

In addition, in the present invention, the total light transmittance is measured by the method of JIS K7361-1, and high transmittance (excellent transmittance) means that the transmittance is 99.0% or higher.

Below, each component is described in detail.

[(A) Urethane (meth)acrylate]

The curable composition of the present invention comprises (A) urethane (meth)acrylate.

In addition, in this specification, (meth)acrylate is used as a general term for acrylate and methacrylate, and includes either one or both of acrylate and methacrylate. The same applies to other similar expressions.

Urethane (meth)acrylate resin can be produced, for example, by synthesizing a urethane prepolymer using a polyol and a polyisocyanate, and then adding a (meth)acrylate having a hydroxyl group thereto.

As the polyol, known polyols such as hydrocarbon polyol, polyether polyol, polyester polyol, and polycarbonate polyol can be used. In addition, as the polyisocyanate, known polyisocyanates such as aromatic polyisocyanate, aliphatic polyisocyanate, aromatic aliphatic polyisocyanate, and alicyclic polyisocyanate can be used.

The curable composition of the present invention contains (A) urethane (meth)acrylate, thereby obtaining adhesion of the curable composition to a substrate, obtaining flexibility of a cured coating film obtained by further curing the curable composition, and suppressing the possibility of peeling from the substrate. The number of (meth)acryloyl functional groups is preferably difunctional or trifunctional because if it is too large, the crosslinking density increases, which increases the warpage of the cured product and tends to deteriorate the toughness.

In the present invention, a urethane resin having two (meth)acryloyl groups is particularly preferably used. In addition, the bifunctional urethane (meth)acrylate preferably has a weight average molecular weight in the range of 1,500 to 20,000. When the weight average molecular weight of the bifunctional urethane (meth)acrylate is 1,500 or more, the curing shrinkage of the bifunctional urethane (meth)acrylate is reduced, and warping of the cured product is unlikely to occur. On the other hand, when the weight average molecular weight of the bifunctional urethane (meth)acrylate is 20,000 or less, the viscosity becomes good, so that the handling property in the preparation of the composition is improved.

Examples of commercially available bifunctional urethane (meth)acrylates include Shin-Nakamura Chemical High School U-108A, U-200AX, UA-112P, UA-5201, U-340AX, UA-511, UA-512, UA-311, UA-412A, UA-4200, UA-4400, UA-340P, UA-2235PE, UA-160TM, UA-6100, U-108, UA-4000, UA-122P, UA-5201, UA-512, UA-W2, UA-7000, U-2PPA, UA-NDP; Satoru CN962, CN963, CN964, CN965, CN980, CN981, CN982, CN983, CN996, CN9001, CN9002, CN9788, CN9893, CN978, CN9782, CN9783; Toa Kose Kagaku High School M-1100, M-1200, M-1210, M-1310, M-1600; Negami High School Artresin UN-9000PEP, UN-9200A, UN-7600, UN-333, UN-1255, UN-6060PTM, UN-6060P, SH-500B; Kyoesa Kagaku High School AH-600, AT-600; Daicel Allnex products include Ebecryl 280, Ebecryl 284, Ebecryl 402, Ebecryl 8402, and Ebecryl 9270.

Examples of commercially available trifunctional urethane (meth)acrylates include Daicel Olnex's Ebecryl 4513, Ebecryl 4740, KRM8296, Ebecryl 8296, and Ebecryl 8311.

(A) Urethane (meth)acrylate may be used as one of the above types, or as a combination of multiple types.

(A) The amount of urethane (meth)acrylate used is preferably in the range of 30 to 40 mass%, particularly 34 to 36 mass%, based on the total mass of the curable composition.

By using the above ratio of (A) urethane (meth)acrylate, the adhesion to the substrate to which the curable composition is applied and the flexibility of the cured coating film are improved.

[(B) thiocarboxylic acid derivative]

The curable composition of the present invention contains (B) a thiocarboxylic acid derivative in an amount of 50 parts by mass or more, preferably 60 to 120 parts by mass, per 100 parts by mass of (A) urethane (meth)acrylate.

In the present invention, by including (B) a thiocarboxylic acid derivative, the light transmittance of the cured coating film can be improved. (B) The thiocarboxylic acid derivative may be used alone or in combination of two or more types.

(B) As a thiocarboxylic acid derivative,

Compounds having 1 to 6 groups represented by the symbol may be mentioned.

Specific examples thereof include linear or branched compounds such as β-mercaptopropionic acid, 2-ethylhexyl-3-mercaptopropionate, n-octyl-3-mercaptopropionate, methoxybutyl-3-mercaptopropionate, stearyl-3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate)propionate, pentaerythritol tetrakis(3-mercaptopropionate), and tetraethylene glycol bis(3-mercaptopropionate), and mercaptopropionic acid derivatives including compounds having a cyclic structure such as tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, and in the present invention, tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate is particularly preferably used.

(B) The amount of the thiocarboxylic acid derivative used is preferably in the range of 25 to 40 mass%, particularly 30 to 38 mass%, based on the total mass of the curable composition.

(B) By setting the amount of the thiocarboxylic acid derivative to 25 mass% or more, sufficient light transmittance of the cured coating film can be obtained, and by setting it to 40 mass% or less, better adhesion of the curable composition to the substrate can be obtained than with urethane (meth)acrylate alone.

[(C) Triallyl isocyanurate]

The curable composition of the present invention contains (C) triallyl isocyanurate in an amount of 40 parts by mass or more, preferably 45 to 95 parts by mass, per 100 parts by mass of (A) urethane (meth)acrylate.

In general, triallyl isocyanurate exerts its function as a crosslinking aid and as an adhesion-imparting agent in a curable composition by adding a small amount of about 10 mass% to the curable composition. However, in the present invention, by using 40 mass parts or more of (C) triallyl isocyanurate, the haze value of the cured coating film can be reduced, the light transmittance can be increased, and heat resistance can also be imparted.

(C) The amount of triallyl isocyanurate used is preferably in the range of 20 to 40 mass%, particularly 24 to 33 mass%, based on the total mass of the curable composition.

(C) By setting the amount of triallyl isocyanurate to 20 mass% or more, it is possible to sufficiently increase the hardness of the cured coating film, and by setting it to 40 mass% or less, transparency and light transmittance become particularly good, and heat resistance can also be imparted.

[(D) Photopolymerization initiator]

The curable composition of the present invention comprises (D) a photopolymerization initiator. Examples of usable photopolymerization initiators include benzoins such as benzoin, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether; benzoin alkyl ethers; benzophenones such as benzophenone, p-methylbenzophenone, Michler's ketone, methylbenzophenone, 4,4'-dichlorobenzophenone, and 4,4'-bisdiethylaminobenzophenone; Acetophenones such as acetophenone, α-hydroxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, N,N-dimethylaminoacetophenone, etc.; Thioxanthones such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; Examples thereof include anthraquinones, such as anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, and 2-aminoanthraquinone; ketals, such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzoic acid esters, such as ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethylbenzoate, and p-dimethylbenzoic acid ethyl ester; phenyl disulfide 2-nitrofluorene, butyloin, anisoin ethyl ether, azobisisobutyronitrile, and tetramethylthiuram disulfide.

The above (D) photopolymerization initiator may be used alone or in combination of two or more, but it is preferable to use an α-hydroxyacetophenone-based photopolymerization initiator in order to improve surface properties without damaging the flexibility of the cured product.

(D) The photopolymerization initiator is added in a ratio of preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, per 100 parts by mass of (A) urethane (meth)acrylate.

The total mass of the above-described (A) urethane (meth)acrylate, the above-described (B) thiocarboxylic acid derivative, and the above-described (C) triallyl isocyanurate is preferably 95% or more of the total mass of the curable composition, whereby the properties of high total light transmittance and well-suppressed haze can be obtained.

For viscosity adjustment, a known diluent, particularly a reactive diluent, can be used. In particular, a monofunctional (meth)acrylate compound, which is a compound having one ethylenically unsaturated group in the molecule, is preferable because it has a high dilution effect.

[Other ingredients]

In the curable composition of the present invention, other components other than the above components can be added within a range that does not impair the effects of the present invention. As additives, photocurable monomers, silicone-based and fluorine-based defoaming agents, leveling agents, known and commonly used thermal polymerization inhibitors, ultraviolet absorbers, silane coupling agents, plasticizers, foaming agents, flame retardants, antistatic agents, anti-aging agents, antibacterial and antifungal agents, etc. can be blended.

The curable composition of the present invention may contain a thermosetting component as long as it does not impair the desired properties, but generally, a thermosetting component is not used. As a result, a cured product having better transparency and light transmittance and less change over time can be obtained.

Since the curable composition of the present invention has high adhesion to a substrate, it can be easily and reliably bonded to a substrate, and can also improve the durability of a device or component to be bonded.

[Method for curing a curable composition]

The curable composition of the present invention, which is composed of the above-described components, can be made into a cured product by photocuring. When curing, the curable composition is applied to a substrate such as quartz glass, and then cured by irradiating it with active energy rays. In addition, the curable composition of the present invention preferably has a viscosity of 1 to 50 dPa·s.

As for the coating method, any method such as dip coating, flow coating, bar coater, or screen printing can be applied. In addition, as the irradiation light source of the active energy ray, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, or a metal halide lamp is suitable. In addition, UV-LED, laser light, electron beam, etc. can also be used as the active energy ray.

[Curing and molding method of curable composition]

Here, a method of obtaining a molded product by using a plate having a concave portion on its surface, filling the curable composition of the present invention into the concave portion, curing the filled curable composition by ultraviolet rays, and taking out the cured product from the concave portion is exemplified using drawings.

Fig. 1 illustrates a plate (1) having a concave portion (2) on its surface. Typically, a metal such as stainless steel is used.

Fig. 2 illustrates a state (3) in which the curable composition of the present invention is filled into the plate body. Generally, the curable composition is filled into the concave portion of the plate body using a doctor knife or the like.

Figure 3 illustrates a process of curing the curable composition of the present invention by covering the substrate (4) from its upper portion and irradiating ultraviolet rays from a light source (5) on its upper portion. Typically, a transparent polyethylene terephthalate or polycarbonate film that transmits ultraviolet rays is used as the substrate (4).

Fig. 4 illustrates a state in which a cured product is released from a plate (1) to obtain a cured molded product (6). The series of processes from Figs. 1 to 4 can continuously manufacture molded products by using dedicated, known devices for each process.

In this way, the curable composition of the present invention can be pre-molded and used. In the molding method by photocuring while filling a concave portion, since there is no inhibition of curing by oxygen, the thickness can be increased, and it is also possible to make the thickness 5 mm at the thickest portion.

In addition, the curable composition of the present invention can be applied as an insulating material for transparent screens such as touch panels, and as a solder resist, an interlayer insulating material, and a cover layer. In addition, the curable composition of the present invention can be applied as a solder dam. In addition, since the composition of the present invention has good adhesion, it can be used as an adhesive, particularly a colorless transparent adhesive used for transparent screens, etc.

Example

Hereinafter, the present invention will be described in more detail by examples and comparative examples. The present invention is not limited to the following examples, and all “parts” and “%” described below are based on mass unless otherwise specified.

[Examples 1 to 10 and Comparative Examples 1 to 3]

Each component listed in Table 1 below was mixed using a rotating/rotating mixer, and each curable composition was prepared.

Each obtained curable composition was evaluated as follows.

1. Printability Evaluation

The curable compositions of Examples 1 to 10 and Comparative Examples 1 to 3 were printed over the entire surface of a quartz glass substrate using a screen printing device equipped with a 300-mesh plate made of polyester (Tetron (registered trademark)) so that the film thickness after curing was 10 μm.

The surface condition of the coating was observed visually 5 minutes after printing and evaluated using the following criteria. The results are shown in Table 1.

○ The entire surface of the substrate is smooth and evenly coated with a curable composition.

× The surface of the curable composition shows signs of bubble bursting, and the surface of the coating is uneven.

2. Touch dryness evaluation (Tack evaluation)

The curable compositions of Examples 1 to 10 and Comparative Examples 1 to 3 were printed over the entire surface of a quartz glass substrate by a screen printing device equipped with a 300-mesh plate made of polyester (Tetron (registered trademark)). The obtained coating film was exposed to a light amount of 1000 mJ/cm2 using a metal halide lamp, and the coating film was cured. The coating film (film thickness: 10 µm) thus obtained was used as a cured film for evaluation, and was evaluated according to the following criteria. The results are shown in Table 1.

◎ Even if you touch the film with your finger, no fingerprints will be left on the film surface and the film will not stick to your finger.

○ When you touch the coating with your finger, your fingerprint will be attached to the surface of the coating, but the coating will not adhere to your finger.

× When you touch the film with your finger, your fingerprint is attached to the surface of the film, and the film is also attached to your finger.

3. Pencil hardness evaluation

In the above 2. Touch-drying property evaluation, an effective film similar to the evaluation film was produced, and its surface hardness was measured using a pencil hardness tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.). In this test, a 3H and 4H pencil ground so that the tip of the core became flat was pressed against each test piece at an angle of about 45° with a load of 1 kg, and moved at least 7 mm at a speed of 0.5 to 1 mm/s, thereby evaluating the peeling state of the distance coating film according to the following criteria. The results are shown in Table 1.

◎ No peeling of the coating with a 4H pencil

○ No peeling of the coating with a 3H pencil

× The film is peeled off with a 3H pencil

4. Adhesion Evaluation

The adhesion of the same cured coating film (film thickness: 10 ㎛) used in the above 3. Pencil hardness evaluation was tested in accordance with JIS K 5600-5-6 by forming 100 × 100 checkerboard patterns by making crosscuts in a 10 mm × 10 mm checkerboard pattern using a crosscut guide. The remaining number of checkerboard patterns was observed visually using the following criteria. The results are shown in Table 1.

○ There is no peeling at all on the checkerboard eyes of the film.

× Peeling was observed in one or more of the checkerboard eyes of the coating.

5. Evaluation of total light transmittance

For the same cured coating film (film thickness: 10 μm) used for the pencil hardness evaluation in the above 3., the total light transmittance transmittance was measured using an ultraviolet-visible spectrophotometer V-670EX (manufactured by Nippon Bunko Co., Ltd.) in accordance with JIS K 7361-1.

This evaluation presents the ratio of transmitted light to incident light over the entire wavelength range of 300 to 780 nm used in the evaluation. The measurement results are shown in Table 1.

6. Haze (cloudiness) evaluation

The same cured coating film (film thickness: 10 μm) used for the pencil hardness evaluation in the above 3. was measured using an ultraviolet-visible spectrophotometer V-670EX (manufactured by Nippon Bunko Co., Ltd.) in accordance with JIS K 7136. In addition, as described in JIS K 7136, haze is a value expressed as 100th of the value obtained by dividing the scattered light transmittance of a test piece by the total light transmittance, and the value of the total light transmittance was obtained in accordance with JIS K 7361-1. The measurement results are shown in Table 1.

7. Heat resistance test (evaluation of total light transmittance and haze after heat treatment)

7-1. Preparation of heat treatment samples

A heat-treated sample was prepared by storing the same cured film used in the pencil hardness evaluation above in a hot air circulation drying oven at 100°C for 2 hours.

7-2. Evaluation of total light transmittance and haze of heat-treated samples

The total light transmittance and haze values of the heat-treated sample obtained in this manner were obtained by the same measurement methods as in 5. Total light transmittance evaluation and 6. Haze (cloudiness value) evaluation described above. The measurement results are shown in Table 1.

8. Weatherability test (evaluation of total light transmittance and haze after exposure treatment)

8-1. Preparation of exposure treatment sample

An exposure treatment sample was produced by exposing the entire surface of the cured coating film to light at a dose of 20 J/cm2 using a metal halide lamp, similar to that used for the pencil hardness evaluation in the above 3.

8-2. Evaluation of total light transmittance and haze of exposed samples

The total light transmittance and haze values of the exposure-treated sample obtained in this manner were obtained by the same measurement methods as in 5. Total light transmittance evaluation and 6. Haze (cloudiness value) evaluation described above. The measurement results are shown in Table 1.

Details of the materials listed in the table are shown below.

Evercryl 8402: Bifunctional urethane acrylate, photocurable urethane resin, manufactured by Daicel Allnex Co., Ltd.

TAIC: Triallyl cyanuric acid, manufactured by Mitsubishi Chemical Co., Ltd.

TEMPIC: Tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, SC Yuki Chemical Co., Ltd.

Omnirad (registered trademark) 184: 1-Hydroxycyclohexyl-phenyl ketone, manufactured by IGM Resins

KBM-5103: 3-Acryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.

Light Ester P-1M: Mono(2-hydroxyethyl methacrylate) phosphate, manufactured by Kyoeisha Chemical Co., Ltd.

Floren AC-2300C: Olefin polymer (defoaming agent), manufactured by Kyoeisha Chemical Co., Ltd.

Polyflow KL-700: Silicone-containing polymer (wetting agent for base material), manufactured by Kyoeisha Chemical Co., Ltd.

As described above, it was found that the curable composition of the present invention has excellent printability, and its cured product has excellent physical properties in terms of touch-drying properties, pencil hardness, and adhesion.

In addition, the cured product of the present invention has a light transmittance of 99.0% or higher both in the initial value and after exposure to a heat resistance test and after exposure to a weather resistance test, and a haze value of 1.5% or lower both in the initial value and after exposure to a heat resistance test and after exposure to a weather resistance test, so that it was found that the cured product of the present invention, especially as a transparent protective material for a liquid crystal display, a touch panel, or the like, has a colorless and transparent beautiful initial state that is resistant to long-term harsh use.

The present invention is not limited to the configuration and examples of the above embodiments, and various modifications are possible within the scope of the gist of the invention.

1: Plate
2: Concave
3: Photocurable composition
4: Description
5: Light source
6: Molded products

Claims (3)

(A) Urethane (meth)acrylate,
(B) thiocarboxylic acid derivatives,
(C) triallyl isocyanurate and
(D) Photopolymerization initiator
A curable composition comprising:
The above (B) thiocarboxylic acid derivative is tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate,
50 parts by mass or more of the thiocarboxylic acid derivative (B) per 100 parts by mass of the above (A) urethane (meth)acrylate,
A curable composition characterized in that it contains 40 parts by mass or more of triallyl isocyanurate (C) per 100 parts by mass of urethane (meth)acrylate (A). A curable composition in claim 1, wherein the total mass of the (A) urethane (meth)acrylate, the (B) thiocarboxylic acid derivative, and the (C) triallyl isocyanurate is 95% or more of the total mass of the curable composition. A transparent cured product obtained from the curable composition described in claim 1 or 2.

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