JP2010222450A - Radiation-curable composition, cured product using the same, and laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation-curable composition that gives a laminate that hardly suffers from distortion immediately after the environmental humidity changes suddenly and exhibits sufficient creep resistance. <P>SOLUTION: The radiation-curable composition comprises a (meth)acrylate and a photoinitiator, and gives, when cured at a thickness of 100±10 μm, a storage elastic modulus E'(45) at 10 Hz and 45°C of at least 1,500 MPa, and a product of a storage elastic modulus E'(55) at 10 Hz and 55°C and a dehydration shrinkage factor γ of at most 6.0 MPa. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiation curable composition that can obtain a laminate having high creep resistance and little deformation due to changes in environmental humidity, a cured product obtained by irradiating the composition with radiation, and a cured product comprising the same. The present invention relates to a laminate having a film.

Radiation curable resins are used in various applications, one of which is a use as a so-called coating agent for coating a substrate.
However, since the conventional radiation curable resin causes curing shrinkage during the radiation curing, there is a problem that the base material is greatly deformed when a coating layer having a large thickness is formed. In particular, when used for a protective layer of an optical recording medium, the demand for dimensional stability is very strict and difficult to apply.

In order to solve this problem, a radiation curable composition containing a specific component at a specific blending ratio has been proposed (see, for example, Patent Literature).
Although this composition has a characteristic capable of suppressing the deformation of the base material during curing, it has been found by the inventors' subsequent examination that there is a problem in the creep resistance of the surface. High creep resistance indicates that when a certain load is applied to the surface of the cured product for a certain period of time, the surface is hardly marked. Moreover, when it was going to adjust a component in order to improve creep resistance, it turned out that the deformation | transformation of the base material by the rapid change of environmental humidity tends to increase remarkably, and those coexistence is difficult.

JP2007-270119A

  The present invention has been made in order to solve the above-mentioned problems, and achieves a laminate that maintains high creep resistance and transparency and is less susceptible to deformation of the substrate due to rapid changes in environmental humidity. An object of the present invention is to provide a radiation curable composition that can be cured, and a cured product thereof.

As a result of intensive studies, the present inventors have found that the storage modulus at a certain temperature is not less than a certain value, and the value expressed by the product of the storage modulus at a high temperature and the dehydration shrinkage is not more than a certain value, The present inventors have found that the above problems can be solved and have reached the present invention.
That is, the first gist of the present invention is a radiation curable composition containing (meth) acrylate and a photopolymerization initiator, and a cured product having a thickness of 100 ± 10 μm cured by irradiation with radiation, The light transmittance at a wavelength of 400 nm is 85% or more, the storage elastic modulus E ′ (45) at 10 Hz and 45 ° C. is 1500 MPa or more, and the storage elastic modulus E ′ (55) and dehydration shrinkage γ at 10 Hz and 55 ° C. The radiation curable composition satisfies the following formula (I).

Formula (I) E ′ (55) × γ ≦ 6.0 (MPa)
The second gist of the present invention is a radiation curable composition containing (meth) acrylate and a photopolymerization initiator, and a cured product having a thickness of 100 ± 10 μm cured by irradiation with radiation, The light transmittance at a wavelength of 400 nm is 85% or more, the storage elastic modulus E ′ (45) at 10 Hz and 45 ° C. is 1500 MPa or more, and the storage elastic modulus E ′ (60) and dehydration shrinkage γ at 10 Hz and 60 ° C. The radiation curable composition satisfies the condition of the following formula (II).

Formula (II) E ′ (60) × γ ≦ 3.5 (MPa)
Here, it is preferable that the radiation curable composition contains a compound having a urethane bond.

The present invention also relates to a cured product obtained by irradiating the radiation curable composition with radiation.
Moreover, this invention relates also to the laminated body formed by laminating | stacking the cured film which consists of the said hardened | cured material on a base material.

  According to the present invention, a radiation curable composition capable of realizing a laminate that is excellent in transparency, maintains high creep resistance, and is less deformed with respect to a sudden change in environmental humidity, and a cured product thereof. The industrial value is extremely high.

It is the schematic diagram which looked at the weight used for creep resistance evaluation from upper direction. It is the figure which showed the relationship between the generated stress and a humidity warp in an Example and a comparative example.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention. it can. In the present invention, the molecular weight means a number average molecular weight unless otherwise specified. In this specification, (meth) acrylate is a general term for acrylate and methacrylate.

1. Cured product of radiation curable composition The specific contents of the radiation curable composition used in the present invention will be described later, but here, a method for producing a cured product of the radiation curable composition of the present invention and the requirements are required. The characteristics will be described in detail.
1-1. Method for producing cured product of radiation curable composition The cured product of the radiation curable composition in the present invention is obtained by so-called "radiation curing" in which a polymerization reaction is started by irradiation with radiation (active energy rays or electron beams). It is done. There is no restriction | limiting in particular in the form of a polymerization reaction, For example, well-known polymerization forms, such as radical polymerization, anionic polymerization, cationic polymerization, and coordination polymerization, can be used. Of these polymerization modes, radical polymerization is particularly preferable from the viewpoint of the homogeneity of the product and the like due to the initiation of the polymerization reaction proceeding homogeneously and in a short time within the polymerization system.

  Here, the term “radiation” refers to electromagnetic waves (gamma rays, X-rays, ultraviolet rays, visible rays, infrared rays, micro rays, which act on a polymerization initiator that initiates a necessary polymerization reaction to generate chemical species that initiate the polymerization reaction. Wave) or particle beam (electron beam, α-ray, neutron beam, various atomic beams, etc.). Examples of radiation preferably used in the present invention are preferably ultraviolet rays, visible rays, and electron beams, and most preferably ultraviolet rays and electron beams because energy and a general-purpose light source can be used.

When ultraviolet rays are used as radiation, it is preferable to use a photo radical generator that generates radicals by ultraviolet rays as the polymerization initiator. At this time, a sensitizer may be used in combination as necessary. The wavelength of the ultraviolet rays is usually 200 nm or more, preferably 240 nm or more, and usually 400 nm or less, preferably 350 nm or less.
As a device for irradiating ultraviolet rays, a known device such as a high pressure mercury lamp, a metal halide lamp, a xenon flash lamp, or an ultraviolet lamp having a structure for generating ultraviolet rays by a microwave can be preferably used. The output of the apparatus is usually 10 W / cm or more, preferably 30 W / cm or more, and usually 200 W / cm or less, preferably 180 W / cm or less. The apparatus is usually 5 cm or more, preferably Is preferably at a distance of 30 cm or more, and usually 80 cm or less, preferably 60 cm or less, because the light deterioration, thermal deterioration, thermal deformation, etc. of the irradiated object are small.

The irradiation intensity is usually 0.1 J / cm ² or more, preferably 0.2 J / cm ^2.
In addition, irradiation is usually performed at 20 J / cm ² or less, preferably 10 J / cm ² or less, more preferably 5 J / cm ² or less, further preferably 3 J / cm ² or less, and particularly preferably ² J / cm ² or less. If irradiation intensity is in this range, it can select suitably by the kind of radiation-curable composition.

  The irradiation time of radiation is usually 1 second or longer, preferably 10 seconds or longer, and usually 3 hours or shorter, and preferably 1 hour or shorter in terms of promoting the reaction and productivity. When the irradiation energy or irradiation time of radiation is extremely small, the heat resistance and mechanical properties of the cured product may not be sufficiently exhibited due to incomplete polymerization. On the other hand, when it is extremely excessive, deterioration such as deterioration of hue due to light such as yellowing may occur.

  The irradiation of the radiation may be performed in one step or may be performed in a plurality of steps. As the radiation source, a diffusion radiation source in which radiation spreads in all directions is usually used. The irradiation of radiation is usually carried out with the radiation source fixed and left in a state where the radiation-curable composition shaped in the mold is fixed and left or transported by a conveyor. It is also possible to use a radiation curable composition as a coating liquid film on a suitable substrate (for example, resin, metal, semiconductor, glass, paper, etc.), and to cure the coating liquid film by irradiation with radiation. is there.

  In addition, when an electron beam is used as radiation, the electron beam irradiation apparatus used for irradiation is not particularly limited, and examples thereof include a curtain type, an area beam type, a broad beam type, and a pulse beam type. The acceleration voltage at the time of irradiation is usually 10 kV or more, preferably 100 kV or more, and usually 1,000 kV or less, preferably 200 kV or less. Although the light source and irradiation device for electron beam irradiation are expensive, there are advantages that the use of a polymerization initiator can be omitted and that the polymerization is not hindered by oxygen and therefore the surface hardness is good. A cured product having excellent properties, particularly tensile elongation, can be obtained.

1-2. Properties of cured product of radiation curable composition The film thickness of the cured product of the radiation curable composition of the present invention is usually 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, still more preferably 70 μm or more, particularly preferably. It is 85 μm or more, usually 300 μm or less, preferably 130 μm or less, more preferably 115 μm or less. If it is this film thickness, it can be conveniently used especially as a protective layer of an optical recording medium.

  The cured product of the radiation curable composition of the present invention has a light transmittance at a wavelength of 400 nm of 85% or more, preferably 89% or more, when the film thickness after curing is adjusted to 100 ± 10 μm. There is no limit on the upper limit, and it is preferable that the upper limit is closer to 100%. If the light transmittance is too low, the transparency as a cured product is inferior. For example, when used in a protective layer of an optical recording medium, errors increase when reading recorded information. The light transmittance can be measured at room temperature by a known method using, for example, an HP8453 type ultraviolet / visible absorptiometer manufactured by Hewlett-Packard Company.

  The cured product of the radiation curable composition of the present invention preferably has a storage elastic modulus E ′ (45) at 10 Hz and 45 ° C. of 1500 MPa or more when the film thickness after curing is adjusted to 100 ± 10 μm. Is 1800 MPa or more, more preferably 2000 MPa or more. If E ′ (45) is too low, the surface hardness of the cured product tends to decrease. Further, if E ′ (45) is too large, the storage elastic modulus E ′ (55) at 10 Hz and 55 ° C. described later tends to be too large.

The storage elastic modulus can be measured using a dynamic viscoelasticity measuring device in a tensile mode and a frequency of 10 Hz.
Further, the cured product of the radiation curable composition of the present invention has values of storage elastic modulus E ′ (55) and dehydration shrinkage γ at 10 Hz and 55 ° C. when the film thickness after curing is adjusted to 100 ± 10 μm. Satisfies the following formula (I).

Formula (I) E ′ (55) × γ ≦ 6.0 (MPa)
That is, the product of E ′ (55) and γ is 6.0 or less, preferably 5.0 or less, more preferably 4.5 or less, and particularly preferably 4.0 or less. The deformation that occurs in the laminated body when the environmental humidity changes is due to stress generated in the laminated body due to water absorption expansion or dehydration shrinkage of the cured product layer. ) × γ ”corresponds to the stress. A large value is not preferable because the deformation generated in the laminate is remarkably increased.

  Alternatively, the cured product of the radiation curable composition of the present invention has values of storage elastic modulus E ′ (60) and dehydration shrinkage γ at 10 Hz and 60 ° C. when the film thickness after curing is adjusted to 100 ± 10 μm. Satisfies the following formula (II).

Formula (II) E ′ (60) × γ ≦ 3.5 (MPa)
That is, the product of E ′ (60) and γ is 3.5 or less, preferably 3.0 or less, more preferably 2.5 or less, and particularly preferably 2.0 or less. The deformation that occurs in the laminated body when the environmental humidity changes is due to stress generated in the laminated body due to water absorption expansion or dehydration shrinkage of the cured product layer. ) × γ ”corresponds to the stress. A large value is not preferable because the deformation generated in the laminate is remarkably increased.

In the present invention, E ′ (55) tends to have a strong correlation with deformation occurring in the laminate of a cured product having a relatively low water absorption rate, for example, a cured product having a saturated water absorption rate of less than 1%.
On the other hand, E ′ (60) tends to have a strong correlation with deformation occurring in a laminate of a cured product having a relatively high water absorption rate, for example, a cured product having a saturated water absorption rate of 1% or more. The saturated water absorption can be determined from, for example, the weight increase rate before and after immersing a film-like cured product having a thickness of 0.1 mm in water for about 3 hours.

The dehydration shrinkage rate of the present invention is such that the sample size is L _{0 at} an environmental temperature of 25 ° C. and an environmental humidity of 90% RH, and the sample size is L when the sample is changed to an environmental temperature of 25 ° C. and an environmental humidity of 50% RH. When expressed as ₁ , it is a value expressed by the following equation.

Formula (III) Dehydration shrinkage = (L ₀ −L ₁ ) / L ₀
The dehydration shrinkage rate of the present invention can be determined, for example, using a thermomechanical measuring device (TMA) equipped with a sample chamber capable of controlling the internal temperature and humidity in a high humidity state where the internal temperature is 25 ° C. and the humidity is 90% RH. Time until the dimensions become constant, for example, 1 to 5 hours statically, L ₀ is obtained, and then the internal temperature is changed to a low humidity state of 25 ° C. and humidity is 50% RH or less to make the dimensions constant. It is calculated by calculating L ₁ by taking a static value for about 1 to 5 hours, for example. The dehydration shrinkage is preferably 0.006 or less, more preferably 0.005 or less, still more preferably 0.003 or less, and most preferably 0.002 or less. If the dehydration shrinkage rate is too large, deformation of the laminate increases, which is not preferable.

2. Radiation curable composition The radiation curable composition of the present invention is a composition containing (meth) acrylate and a photopolymerization initiator. Since it is excellent in applicability, it is preferably liquid.
A (meth) acrylate oligomer having a molecular weight of 1000 or more is preferably used in terms of excellent mechanical properties and thermal properties. Among these, a (meth) acrylate oligomer having a urethane bond is particularly preferable in terms of excellent adhesion. Moreover, in order to give moderate applicability | paintability, the (meth) acrylate monomer of molecular weight 300 or less is used together preferably.
In this specification, (meth) acrylate is a general term for acrylate and methacrylate. The same applies to the (meth) acryloyl group and (meth) acrylic acid.

2-1. Urethane (meth) acrylate oligomer The urethane (meth) acrylate oligomer is preferably an oligomer having two or more urethane bonds and two or more (meth) acryloyl groups in one molecule, but is irradiated with a low dose of radiation. A urethane acrylate oligomer is particularly preferable in the composition of the present invention because it is excellent in low dose curability at the time of curing and tack (stickiness) hardly remains. Here, the low dose curable property means that the surface is less tacky and apparently hardened despite the fact that the irradiation dose is about 1/10 of the normal and the curing reaction is hardly progressing. The nature that can be seen.
Examples of urethane (meth) acrylate oligomers include polyisocyanates as raw materials, compounds containing two or more hydroxyl groups, and reactants obtained using (meth) acrylates containing one or more hydroxyl groups. Can be mentioned.

(1) Polyisocyanate
The polyisocyanate may be a compound having two or more isocyanate groups in one molecule. Examples thereof include diisocyanates having two isocyanate groups in one molecule and triisocyanates having three isocyanate groups. It is done. Among them, a diisocyanate having a C 1-20 alkylene group which may contain an alicyclic structure and a C 1-15 cycloalkylene group which may have a substituent is particularly preferable. Aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, bis (isocyanatocyclohexyl) methane, isophorone diisocyanate; Xylylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, α, α, α ′, α′-tetramethylxylylene diisocyanate, naphthalene diiso Aromatic diisocyanates such as cyanate; 1,3,5-triisocyanatecyclohexane, 1,3,5-trimethylisocyanatecyclohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatemethyl) -bicyclo [2. 2.1] Heptane, 2- (3-isocyanatopropyl) -2,6-di (isocyanatomethyl) -bicyclo [2.2.1] heptane, 3- (3-isocyanatopropyl) -2,5-di ( Isocyanatomethyl) -bicyclo [2.2.1] heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo [2.2.1] heptane, 6- ( 2-Isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanate propylene ) -Bicyclo [2.2.1] heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo [2.2.1] -heptane, 6- (2 -Triisocyanate such as -isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo [2.2.1] heptane, and multimers thereof. One of these may be used alone, or two or more may be used in combination.

  Of these, aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate, bis (isocyanatomethyl) cyclohexane, cyclohexane Alicyclic diisocyanates such as diisocyanate, bis (isocyanatocyclohexyl) methane, and isophorone diisocyanate are preferred. Since the surface hardness of a cured product obtained by irradiating the composition with radiation (hereinafter sometimes referred to as cured product) is increased, bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, bis (isocyanatocyclohexyl) methane, And alicyclic diisocyanates such as isophorone diisocyanate are more preferred.

(2) Compound containing two or more hydroxyl groups
A compound containing two or more hydroxyl groups only needs to have two or more hydroxyl groups in one molecule. For example, a glycol having two hydroxyl groups and a compound having three or more hydroxyl groups. Polyhydric alcohol or polyol having two or more hydroxyl groups and having a repeating unit structure in the compound can be used.

  Among them, glycol is preferable because the surface hardness of the cured product is increased, and in particular, an alkylene group having 2 to 20 carbon atoms which may contain an alicyclic structure, an alkenylene group, and a carbon number which may have a substituent. Glycols having 2 to 20 cycloalkylene groups are preferred. Specific examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5 -Pentanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,3,5-trimethyl-1,5-pentanediol, 1,6-hexane Diol, 2-ethyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, , 12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,2-dimethylolcyclohexane 1,3-dimethylol cyclohexane, alkylene glycols such as 1,4-dimethylol cyclohexane.

Among these, in order to increase the surface hardness of the cured product, glycol having 10 or less carbon atoms between hydroxyl groups is preferable. In order to reduce the viscosity of the composition of the present invention, a glycol having a side chain is preferred.
Specific examples of the polyhydric alcohol include glycerin, trimethylolethane, trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butanetriol, erythritol, sorbitol, pentaerythritol, dipentaerythritol, mannitol, And alkylene polyhydric alcohols containing 3 or more hydroxyl groups.

  As the representative polyol, known ones such as polyether polyol, polyester polyol, polycarbonate polyol can be used. Since the polyol is added for the purpose of suppressing warpage of a laminate (hereinafter sometimes referred to as a laminate) formed by laminating a cured film made of a cured product, a polyol having a relatively flexible structure is preferable. Among these, when the composition of the present invention is used as a protective layer of an optical recording medium, a polyester polyol is preferred because the protective layer is in direct contact with the metal-containing layer and the metal-containing layer is unlikely to corrode.

The molecular weight of the polyol is preferably 500 or more because it is easy to adjust the viscosity of the composition of the present invention to an appropriate range, and is preferably 5000 or less because the surface hardness of the cured product tends to increase.
Specific examples of the polyether polyol include polytetramethylene glycol as a ring-opening polymer of a cyclic ether such as tetrahydrofuran in addition to the glycol multimer, and the glycol, ethylene oxide, propylene oxide, 1, 2 Examples include adducts with alkylene oxides such as -butylene oxide, 1,3-butylene oxide, 2,3-butylene oxide, tetrahydrofuran, and epichlorohydrin.

Specific examples of the polyester polyol include a reaction product of the glycol and a polybasic acid such as maleic acid, fumaric acid, adipic acid, sebacic acid and phthalic acid, and a ring-opening polymer of a cyclic ester such as caprolactone. And polycaprolactone.
Specific examples of the polycarbonate polyol include the glycol and alkylene carbonate such as ethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate; or diphenyl carbonate, 4-methyldiphenyl carbonate, 4-ethyldiphenyl carbonate. 4-propyl diphenyl carbonate, 4,4′-dimethyl diphenyl carbonate, 2-tolyl-4-tolyl carbonate, 4,4′-diethyl diphenyl carbonate, 4,4′-dipropyl diphenyl carbonate, phenyl toluyl carbonate, bischlorophenyl Diaryl carbonates such as carbonate, phenylchlorophenyl carbonate, phenylnaphthyl carbonate, dinaphthyl carbonate; or dimethyl carbonate Reaction with dialkyl carbonates such as dicarbonate, di-n-propyl carbonate, diisopropyl carbonate, di-n-butyl carbonate, diisobutyl carbonate, di-t-butyl carbonate, di-n-amyl carbonate, diisoamyl carbonate, etc. Thing etc. are mentioned.

(3) (Meth) acrylate containing one or more hydroxyl groups
The (meth) acrylate containing one or more hydroxyl groups may be any (meth) acrylate having one or more hydroxyl groups and one or more (meth) acryloyl groups in one molecule. From the viewpoint of properties, it is preferably a compound represented by the following general formula (1), preferably a compound in which n in the general formula (1) is an integer of 1 to 30, more preferably hydroxyethyl (meth) acrylate, Hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate. When n in general formula (1) is small, the surface hardness of the cured product tends to be high, which is preferable.

(R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 2 to 6 carbon atoms, and n represents an integer of 1 to 50.)
In addition, addition reaction products of glycidyl ether and (meth) acrylic acid, polyol mono (meth) acrylate, and the like can be used.
As the (meth) acrylate containing one or more hydroxyl groups, one of these may be used alone, or two or more may be used in combination.
The molecular weight of the (meth) acrylate containing one or more hydroxyl groups is preferably 40 or more, more preferably 80 or more, and preferably 800 or less, more preferably 400 or less.

(4) Properties of urethane (meth) acrylate oligomer
As a urethane (meth) acrylate oligomer, it is preferable that it is a highly transparent thing, for example, it is preferable that it is a compound which does not have an aromatic ring. When the urethane (meth) acrylate oligomer has an aromatic ring, the radiation curable composition and the cured product thereof are colored or colored during storage even if they are not initially colored. There is strengthening (so-called yellowing).

  This is considered to be caused by the fact that the double bond part forming the aromatic ring irreversibly changes its structure by radiation. For this reason, the urethane (meth) acrylate oligomer does not have an aromatic ring. By having the structure, there is an advantage that the hue is not deteriorated and the light transmittance is not lowered, and it is particularly suitable for application to an application requiring colorless and transparent such as an optical recording medium.

A urethane (meth) acrylate oligomer having no aromatic ring includes a polyisocyanate having no aromatic ring, a compound containing two or more hydroxyl groups having no aromatic ring, and one or more hydroxyl groups having no aromatic ring. It can manufacture by selecting (meth) acrylate containing as a raw material.
Specific examples of the polyisocyanate having no aromatic ring include alicyclic diisocyanates such as bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, bis (isocyanatocyclohexyl) methane, and isophorone diisocyanate. Specific examples of the compound containing 2 or more hydroxyl groups that do not include alkylene polyol, alkylene polyester, each polyol of alkylene carbonate, etc., and also contains 1 or more hydroxyl groups that do not have an aromatic ring Specific examples of the (meth) acrylate to be used include hydroxyalkyl (meth) acrylate. In addition, these 1 type may be used independently and may be used in combination of 2 or more type.

The molecular weight of the urethane (meth) acrylate oligomer is preferably 1000 or more, preferably 4000 or less, and more preferably 2000 or less, from the viewpoint of the balance between the viscosity of the composition and the mechanical properties of the cured product.
In addition, the weight average molecular weight of the urethane (meth) acrylate oligomer is preferably 1400 or more, more preferably 1500 or more, more preferably 10,000 or less, further from the viewpoint of the balance between the viscosity of the composition and the mechanical properties of the cured product. Is preferably 4000 or less.
2-2. Hereinafter, a particularly preferable combination of urethane (meth) acrylate oligomers will be described in detail in the present invention. In the radiation-curable composition of the present invention, the compound (A) and the compound (B) described below are included at a ratio of (A) / (B) = 2.0 to 7.0 (weight ratio). Is preferred. Furthermore, it is preferable to contain the compound (C) described below.
By using a radiation curable composition containing such a combination of urethane (meth) acrylate oligomers, low E ′ (55), E ′ (60), and low dehydration while maintaining high E ′ (45) It becomes easy to obtain a radiation curable composition that realizes a cured product having both shrinkage rates.

2-2-1. Compound (A)
The compound (A) in the present invention is a urethane (meth) acrylate oligomer represented by the following general formula (2). It is preferable for the composition of the present invention to contain the compound (A) because the surface hardness of the cured product is high and the composition can be sufficiently cured even when the radiation dose is low, and is excellent in curability.

(R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkylene group having 2 to 6 carbon atoms, R ₃ is an alkylene group having 1 to 20 carbon atoms which may contain an alicyclic structure, and a substituent. A cycloalkylene group having 1 to 15 carbon atoms which may be present, R ₄ is an alkylene group having 2 to 20 carbon atoms which may contain an alicyclic structure, an alkenylene group or a carbon number which may have a substituent. 2-20 cycloalkylene groups are represented, and n represents an integer of 1-50.)
The compound (A) is not particularly limited as long as it is represented by the general formula (2), but is usually a reaction product of the diisocyanate, the glycol, and the compound represented by the general formula (1). Is preferred.

R ₁ in the general formula (2) is a hydrogen atom or a methyl group, and is preferably a hydrogen atom since the curability of the composition of the present invention is excellent.
R ₂ in the general formula (2) is an alkylene group having 2 to 6 carbon atoms, preferably an alkylene group having 2 to 4 carbon atoms.
R ₃ in the general formula (2) is usually a linking group derived from diisocyanate, and a carbon group having 1 to 20 carbon atoms which may contain an alicyclic structure, or which may have a substituent. A cycloalkylene group having a number of 1 to 15. The alkylene group may have a branched structure. Here, the case where R ₃ is a cycloalkylene group refers to a structure in which a nitrogen atom derived from an isocyanate group is directly bonded to an alicyclic structure and does not contain an alkylene group therebetween.

  Preferably, it is derived from a cycloalkylene group having 6 to 15 carbon atoms which may have a substituent derived from cyclohexane diisocyanate or the like, or bis (isocyanatomethyl) cyclohexane, bis (isocyanatocyclohexyl) methane, isophorone diisocyanate, etc. An alkylene group having 6 to 20 carbon atoms which may contain an alicyclic structure, particularly preferably derived from cyclohexane diisocyanate, bis (isocyanatomethyl) cyclohexane, bis (isocyanatocyclohexyl) methane, or isophorone diisocyanate. It is a linking group.

R ₄ in the general formula (2) is usually a linking group derived from glycol, and may have an alicyclic structure, an alkylene group having 2 to 20 carbon atoms, an alkenylene group, or a substituent. It is a good cycloalkylene group having 2 to 20 carbon atoms. The alkylene group and alkenylene group may have a branched structure.
Since the curability of the composition is good and the surface hardness of the resulting cured product is high, it is preferably an alkylene group having 3 to 9 carbon atoms. Specifically, 1,2-propanediol, 1,3 -Propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-1,5-pentanediol, neopentyl glycol 3-methyl-1,5-pentanediol, 2,3,5-trimethyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol, 2,2,4 -An alkylene group which is a linking group derived from trimethyl-1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, etc. and an alkylene group having a branched structure There it is more preferable.
N in the general formula (2) is an integer of 1 to 50, and preferably 1 to 30 because the surface hardness of the cured product is good.

2-2-2. Compound (B)
The compound (B) in the present invention is a urethane (meth) acrylate oligomer represented by the following general formula (3).

(R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkylene group having 2 to 6 carbon atoms, R ₃ is an alkylene group having 1 to 20 carbon atoms which may contain an alicyclic structure, and a substituent. And represents an optionally substituted cycloalkylene group having 1 to 15 carbon atoms, and n represents an integer of 1 to 50.)
Although it will not specifically limit if a compound (B) is represented by General formula (3), Usually, it is preferable that it is a reaction material of the compound represented by the said diisocyanate and the said General formula (1).
In the general formula (3), R ₁ , R ₂ , R ₃ , and n are the same as the structure in the general formula (2).

2-2-3. Compound (C)
The compound (C) in the present invention is not particularly limited as long as it is a urethane (meth) acrylate oligomer other than the above compounds (A) and (B). For example, the above-mentioned polyisocyanate, a compound containing two or more hydroxyl groups And urethane (meth) acrylate oligomers other than compounds (A) and (B) among (meth) acrylate reactants containing one or more hydroxyl groups. Specifically, the reaction product of the polyol represented by the diisocyanate, polyether polyol, polyester polyol, and polycarbonate polyol, and the compound represented by the general formula (1); the diisocyanate, the glycol, and the general formula (1) ), Which is a reaction product of a compound represented by the general formula (1), and a urethane (meth) which is a reaction product of the compound represented by the general formula (1). Examples thereof include acrylate oligomers and urethane (meth) acrylate oligomers represented by the following general formula (4).

(R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkylene group having 2 to 6 carbon atoms, R ₃ is an alkylene group having 1 to 20 carbon atoms which may contain an alicyclic structure, and a substituent. A cycloalkylene group having 1 to 15 carbon atoms which may be present, R ₄ is an alkylene group having 2 to 20 carbon atoms which may contain an alicyclic structure, an alkenylene group or a carbon number which may have a substituent. 2-20 cycloalkylene groups are represented, n is an integer of 1-50, m represents an integer of 2 or more.)
R ₁ , R ₂ , R ₃ , R ₄ and n in the general formula (4) are the same as the structure in the general formula (2).

In order to obtain a storage elastic modulus suitable for the present invention, R ₂ in the general formula of the compound represented by the general formula (1) used when obtaining a urethane (meth) acrylate oligomer is alkylene having 2 to 4 carbon atoms. Those based are preferably used in combination. Among these, a polypropylene oxide chain having 3 carbon atoms is particularly preferable because it tends to achieve both a high surface hardness and a desired storage elastic modulus.

  The radiation curable composition of the present invention preferably contains the compounds (A) and (B) in a ratio of (A) / (B) = 2.0 to 7.0 (weight ratio). If it is 2.0 or less, the warp tends to increase, and if it is 7.0 or more, the hardness decreases. In order to increase the surface hardness of the cured product and reduce the viscosity of the composition, it is preferably 2.8 or more and preferably 5.0 or less.

  In addition, content of a compound (A) and (B) can be measured by measuring molecular weight distribution of a composition. The molecular weight distribution is measured by size exclusion chromatography, particularly gel permeation chromatography (hereinafter sometimes abbreviated as GPC). Each content is obtained by calculating the peak area ratio of the peak corresponding to the molecular weight of the compound (A) or (B) from the molecular weight distribution measurement result. For example, the molecular weight of the obtained compounds (A) and (B) is calculated from the molecular weight of the raw material when producing the urethane (meth) acrylate oligomer, and the peak corresponding to this is specified.

  When the radiation curable composition of the present invention contains the compound (C), the urethane (meth) acrylate oligomer is 20% by weight or more of the total composition as the sum of the compounds (A), (B) and (C). Preferably, it is 30% by weight or more, more preferably 40% by weight or more, and preferably 90% by weight or less, more preferably 80% by weight or less, still more preferably 70% by weight. It is as follows. When the amount is not less than the lower limit value, both the surface hardness of the cured product and the warpage suppression of the laminate tend to be compatible, and when the value is not more than the upper limit value, the viscosity of the composition tends to become a viscosity suitable for smooth application, which is preferable. .

  In addition, the number average molecular weight of the urethane (meth) acrylate oligomer mixture composed of the compounds (A), (B) and (C) is 700 or more from the viewpoint of the balance between the viscosity of the composition and the mechanical properties of the cured product. Is preferably 800 or more, and is preferably 4000 or less, more preferably 2000 or less. The weight average molecular weight is preferably 1400 or more, more preferably 1500 or more, and preferably 10,000 or less, more preferably 4000 or less, from the viewpoint of the balance between the viscosity of the composition and the mechanical properties of the cured product. preferable.

2-2-4. Method for producing urethane (meth) acrylate oligomer
The method for producing the urethane (meth) acrylate oligomer used in the present invention is not particularly limited. For example, the polyisocyanate, the compound containing two or more hydroxyl groups, and the one or more hydroxyl groups are contained. A urethane (meth) acrylate oligomer can be produced by addition reaction of (meth) acrylate. Specifically, one molecule of a compound having two or more isocyanate groups in a molecule obtained by addition reaction of a polyisocyanate or a polydiisocyanate and a compound containing two or more hydroxyl groups, and one or more hydroxyls A urethane (meth) acrylate oligomer having a (meth) acryloyl group at both ends can be produced by addition reaction of two (meth) acrylate molecules containing a group.

As the addition reaction catalyst at this time, for example, dibutyltin laurate, dibutyltin dioctoate, dioctyltin dilaurate, and dioctyltin dioctoate are preferable, and one of these may be used alone, You may use combining more than a seed.
This addition reaction is not particularly limited, and can be usually performed by any known method. For example, a mixture of a polyisocyanate, a compound containing two or more hydroxyl groups, a (meth) acrylate containing one hydroxyl group and an addition reaction catalyst is usually 40 ° C. or higher, preferably 50 ° C. or higher. The mixing is usually performed at 90 ° C. or lower, preferably 75 ° C. or lower. As a method of mixing, polyisocyanate, a compound containing two or more hydroxyl groups, a (meth) acrylate containing one hydroxyl group, and an addition reaction catalyst may be mixed and reacted together. First, a polyisocyanate and a compound containing two or more hydroxyl groups are subjected to addition reaction, and then a mixture of (meth) acrylate containing one or more hydroxyl groups and an addition reaction catalyst is added dropwise. The addition reaction can also be performed in stages. In order to reduce the content of the compound (B) and adjust the ratio of the compounds (A) and (B) ((A) / (B)) to a desired range, a method of performing an addition reaction in two stages Is preferred.

When the urethane (meth) acrylate oligomer is produced, it is not necessary to use a solvent in particular, but an organic solvent such as ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene may be used.
In addition, when manufacturing a urethane (meth) acrylate oligomer, unless the effect of this invention is impaired, the polyisocyanate, the compound containing 1 or more hydroxyl groups, and the (meth) acrylate containing 1 or more hydroxyl groups In addition, other components may be included.

  When two or more kinds of urethane (meth) acrylate oligomers are obtained using two or more kinds of compounds, for example, glycol and polyol, as a compound having two or more hydroxyl groups, and the mixture is used, glycol and polyol May be mixed together and reacted with polyisocyanate to obtain a mixture at once, or after reacting glycol and polyol separately with polyisocyanate, the resulting urethane (meth) acrylate oligomer is mixed as a mixture It doesn't matter.

  Among them, the compounds (A) and (B) are an alkylene group having 1 to 20 carbon atoms which may include an alicyclic structure, and a cycloalkylene group having 1 to 15 carbon atoms which may have a substituent. Having a diisocyanate (hereinafter sometimes referred to as diisocyanate (I)), an alicyclic structure, an alkylene group having 2 to 20 carbon atoms, an alkenylene group, and optionally having 2 substituents. Reaction of a glycol having -20 cycloalkylene groups (hereinafter sometimes referred to as glycol (II)) and a compound represented by the general formula (1) (hereinafter sometimes referred to as compound (III)) Can be manufactured. Specifically, for example, after reacting diisocyanate (I) and glycol (II), compound (III) is added and an addition reaction is performed, whereby compound (A), compound (B), and the above general formula Various urethane (meth) acrylate oligomers such as a urethane (meth) acrylate oligomer corresponding to the compound (C) represented by (4) can be obtained.

  Here, compounds (A) and compounds in various urethane (meth) acrylate oligomers obtained by reacting polyisocyanate, a compound having two or more hydroxyl groups and a (meth) acrylate having one or more hydroxyl groups The ratio of (B) is the ratio of the number of isocyanate groups of the polyisocyanate used as a raw material to the number of hydroxyl groups of a compound having two or more hydroxyl groups (hereinafter sometimes referred to as NCO / OH ratio), 2 It can be controlled by the proportion of glycol in compounds having more than one hydroxyl group.

In general, when the ratio of glycol in a compound having two or more hydroxyl groups is high, the content of compound (A) increases when the NCO / OH ratio is large, and the compound increases as the NCO / OH ratio approaches 1. The content of (A) is close to 0%. On the other hand, when the glycol content of the compound having two or more hydroxyl groups is lowered, the content of the compound (A) is lowered.
Further, similarly to the compound (A), when the ratio of the glycol of the compound having two or more hydroxyl groups is high, the content of the compound (B) increases when the NCO / OH ratio is large. As the NCO / OH ratio approaches 1, the content of compound (B) approaches 0%.

  Furthermore, when the ratio of glycol of the compound having two or more hydroxyl groups is high, the ratio of the compound (A) and the compound (B) is large when the NCO / OH ratio is large (A) / (B) (weight ratio). The value of (A) / (B) (weight ratio) tends to increase as the NCO / OH ratio approaches 1. Further, when the glycol content of the compound having two or more hydroxyl groups is lowered, the value of (A) / (B) (weight ratio) tends to increase.

  Therefore, the NCO / OH ratio is preferably in the range of 1.2 to 1.8. When the NCO / OH ratio is greater than 1.2, the molecular weight of the resulting oligomer compound does not become too large, the viscosity of the composition can be easily adjusted to an appropriate range, and many other than the compounds (A) and (B) Since the ratio of the compound containing the urethane bond decreases, the rigidity is appropriate and the warp of the laminate is reduced, which is preferable. When NCO / OH is smaller than 1.8, the ratio of the compound (B) does not increase too much, and the warp when the laminate is formed and the warp when the temperature and humidity change are small, which is preferable.

The oligomer having a radiation curable group is not particularly limited as long as it has one or more radiation curable groups, but an oligomer having one or two (meth) acryloyl groups in one molecule, etc. Can be used. For example, epoxy (meth) acrylates, polyester (meth) acrylates, acrylic (meth) acrylates, unsaturated polyesters, etc., and oligomers made by polymerizing the above monofunctional (meth) acrylates or polyfunctional (meth) acrylates It is also possible to add a kind.
2-3. (Meth) acrylate monomer having a molecular weight of 300 or less The radiation curable composition of the present invention appropriately converts a compound having a molecular weight of 300 or less (hereinafter referred to as compound (D)) in order to reduce the viscosity and obtain an appropriate coating property. It is preferable to contain.

  The compound (D) is preferably a compound having a radiation curable group such as a vinyl group or a (meth) acryloyl group that can be polymerized by radiation, particularly a (meth) acrylate having a (meth) acryloyl group. Among them, (meth) acrylate having one or more (meth) acryloyl groups in one molecule (hereinafter sometimes referred to as monofunctional (meth) acrylate) is preferably two or more (meth) acrylates in one molecule. ) A (meth) acrylate having an acryloyl group (hereinafter sometimes referred to as a polyfunctional (meth) acrylate).

  Specific examples of the monofunctional (meth) acrylate include (meth) acrylamides such as N, N-dimethyl (meth) acrylamide; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) ) Hydroxyalkyl (meth) acrylates such as acrylate; (meth) acryloylmorpholine, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylate having a tricyclodecane skeleton, etc. Examples include alicyclic (meth) acrylates; aromatic (meth) acrylates such as phenoxyethyl (meth) acrylate. Among these, alicyclic (meth) acrylates are low in viscosity and low in curing shrinkage. When Aromatic (meth) acrylates are preferred, and among them, because of their good curability, tetrahydrofurfuryl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylate having a tricyclodecane skeleton, phenoxyethyl (meth) Acrylate is particularly preferred.

Examples of the polyfunctional (meth) acrylate include aliphatic poly (meth) acrylate, alicyclic poly (meth) acrylate, and aromatic poly (meth) acrylate. Specific examples include polyethylene glycol di (meth) acrylate. 1,2-polypropylene glycol di (meth) acrylate, 1,3-polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, 1,2-polybutylene glycol di (meth) acrylate, polyisobutylene Di (meth) acrylates of alkylene oxide adducts such as ethylene oxide, propylene oxide or butylene oxide of bisphenols such as glycol di (meth) acrylate, bisphenol A, bisphenol F, or bisphenol S Di (meth) acrylates of hydrogenated derivatives of bisphenols such as salts, bisphenol A, bisphenol F or bisphenol S, blocks of various polyether polyol compounds and other compounds, or di (meth) acrylates of random copolymers Di (meth) acrylate having a polyether skeleton such as hexanediol di (meth) acrylate, octanediol di (meth) acrylate, nonanediol di (meth) acrylate, decanediol di (meth) acrylate, 2,2 -Bis [4- (meth) acryloyloxyphenyl] propane, 2,2-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] propane, bis (hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] Decane = di (meth) ac Bifunctional (meth) acrylates such as relate, p-bis [β- (meth) acryloyloxyethylthio] xylylene, 4,4′-bis [β- (meth) acryloyloxyethylthio] diphenylsulfone; trimethylolpropane Trifunctional (meth) acrylates such as tris (meth) acrylate, glycerin tris (meth) acrylate, pentaerythritol tris (meth) acrylate; tetrafunctional (meth) acrylates such as pentaerythritol tetrakis (meth) acrylate; dipentaerythritol (Meth) having 5 or more functional groups such as hexa (meth) acrylate.

Of these, bifunctional (meth) acrylates are preferred because of the controllability of the cross-linking formation reaction when irradiated with radiation. Among them, as the bifunctional (meth) acrylate, aliphatic di (meth) acrylate and alicyclic di (meth) acrylate are preferable, and hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, bis (Hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate is preferred. Further, from the viewpoint of load resistance as a cured product, a di (meth) acrylate of a diol having 6 to 20 carbon atoms, and further 8 to 12 carbon atoms, specifically, hexanediol di (meth) acrylate, octane. Diol di (meth) acrylate, nonanediol di (meth) acrylate and the like are particularly preferable.

These compounds may be used alone or in combination of two or more. However, it is preferable to contain at least one polyfunctional (meth) acrylate from the point of hardness of the cured product.
On the other hand, when the monofunctional (meth) acrylate is contained, the content of the monofunctional (meth) acrylate is preferably 40% by weight or less, more preferably 20% by weight or less in the composition compound of the present invention. . It is preferable that the content of the monofunctional (meth) acrylate is 40% by weight or less because the creep resistance of the cured product is improved. On the other hand, in order to reduce the content of the monofunctional (meth) acrylate, use a low-viscosity urethane (meth) acrylate oligomer or a polyfunctional (meth) acrylate having a relatively low viscosity. It is preferable to balance the viscosity as the radiation curable composition and various physical properties as the cured product.

When the polyfunctional (meth) acrylate is contained, the content of the polyfunctional (meth) acrylate is preferably 40% by weight or less, more preferably 20% by weight or less in the composition compound of the present invention. When the content of the monofunctional (meth) acrylate is too large, the residual stress at the time of curing increases, and there is a tendency for deformation of the laminate resulting from a change in environmental temperature to increase, such being undesirable. On the other hand, if the content is too small, the creep resistance of the cured product tends to deteriorate, such being undesirable.
From the above, in order to realize high physical properties while keeping the viscosity low, a low-viscosity compound is selected as the main oligomer, and then monofunctional (meth) acrylate and polyfunctional (meth) acrylate It is necessary to carefully adjust the content of.

2-4. Preferred content ratio of radiation curable compound In the radiation curable composition of the present invention, compounds (A), (B), (C) and (D) (hereinafter, these may be collectively referred to as radiation curable compounds). ) Is 100 parts by weight, the total content of the compounds (A), (B) and (C) (urethane (meth) acrylate oligomer) is preferably 30 parts by weight or more, more preferably It is 40 parts by weight or more, preferably 70 parts by weight or less, more preferably 60 parts by weight or less. When it is 30 parts by weight or more, the strength of the cured product is increased, and when it is 70 parts by weight or less, the viscosity of the composition does not become excessively high and is easily adjusted to an appropriate range.

The content of the compound (D) in the radiation curable composition of the present invention is preferably 30 parts by weight or more, more preferably 40 parts by weight or more, preferably 70 parts by weight with respect to 100 parts by weight of the radiation curable compound. Part or less, more preferably 60 parts by weight or less.
The content of the compound (A) is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, preferably 30 parts by weight or less, more preferably 20 parts by weight with respect to 100 parts by weight of the radiation curable compound. Less than parts by weight. When the amount is 5 parts by weight or more, the surface hardness of the cured product and E ′ (45) tend to be high, the creep resistance tends to be high, and the curability is excellent, which is preferable. Further, if it is 30 parts by weight or less, E ′ (55) and E ′ (60) tend to be small, which is preferable. This is because the hydrophilicity of the urethane bond is high and the compound (A) has a rigid structure. This is considered to be because the crosslinked network of the resulting cured product is dense.

  The content of the compound (B) is preferably 0.1 parts by weight or more and 10 parts by weight or less, and more preferably 5 parts by weight or less with respect to 100 parts by weight of the radiation curable compound. When it is 10 parts by weight or less, deformation at a normal temperature of the laminate (25 ° C., 50% RH) is small, and E ′ (55) and E ′ (60) tend to be small. Therefore, it is preferable.

2-5. Photopolymerization initiator The radiation-curable composition of the present invention further contains a photopolymerization initiator for initiating a polymerization reaction that proceeds by radiation (for example, ultraviolet rays, electron beams, etc.). As the photopolymerization initiator, a radical generator which is a compound having a property of generating radicals by light is generally used, and any radical generator can be used as long as the effect of the present invention is not significantly impaired. A known radical generator can be used.

  Specific examples of such radical generators include benzophenone, 2,4,6-trimethylbenzophenone, 4,4-bis (diethylamino) benzophenone, 4-phenylbenzophenone, methylorthobenzoylbenzoate, thioxanthone, diethylthioxanthone, and isopropylthioxanthone. Chlorothioxanthone, 2-ethylanthraquinone, t-butylanthraquinone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin methyl ether, Benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, methylbenzoyl formate, 2-methyl-1- [4 (Methylthio) phenyl] -2-morpholinopropan-1-one, 2,6-dimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4 , 4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 2-hydroxy-1- [4- {4- (2-hydroxy-2-methyl-propionyl) benzyl} phenyl] -2-methyl-propan-1-one and the like. Among them, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 2-hydroxy-1- [4- {4- (2-hydroxy-2-methyl-propionyl) benzyl} phenyl] 2-methyl-propan-1-one.

  Among the above radical generators, benzophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 1-hydroxycyclohexyl are included in that the curing speed is high and the crosslinking density can be sufficiently increased. Phenylketone, 2-hydroxy-1- [4- {4- (2-hydroxy-2-methyl-propionyl) benzyl} phenyl] -2-methyl-propan-1-one, and 2,4,6-trimethyl Benzoyldiphenylphosphine oxide is preferred.

  In addition, when the cured product of the radiation curable composition of the present invention is used for an optical recording medium or the like using a laser as a light source, radicals are used so that the laser beam necessary for reading sufficiently passes through the cured product layer. It is preferable to select and use the type and amount of the generator. In particular, when laser light having a wavelength of 380 to 800 nm is used as a light source, it is particularly preferable to use a short-wavelength photosensitive radical generator in which the obtained cured product layer hardly absorbs laser light.

Among the above radical generators, such short wavelength photosensitive radical generators include benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, methylorthobenzoylbenzoate, diethoxyacetophenone, 2-hydroxy -2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, methyl benzoyl formate, etc. Among them, those having a hydroxyl group such as 1-hydroxycyclohexyl phenyl ketone are particularly preferable.

  In addition, these radical generators may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the radical generator is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, still more preferably 2 parts by weight or more, preferably 10 parts by weight, with respect to 100 parts by weight of the radiation curable compound. It is 9 parts by weight or less, more preferably 9 parts by weight or less, more preferably 7 parts by weight or less, still more preferably 5 parts by weight or less, and particularly preferably 4 parts by weight or less. When the amount is 0.1 parts by weight or more, the radiation curable composition can be sufficiently cured. On the other hand, when the amount is 10 parts by weight or less, the polymerization reaction proceeds at an appropriate rate, and optical distortion does not occur. Is also preferable.

When a benzophenone photopolymerization initiator is used, the amount used is preferably 0.5 parts by weight or more, preferably 2 parts by weight or less, more preferably 1 part by weight or less. When the amount of the benzophenone-based photopolymerization initiator is large, the volatile components in the cured product of the radiation curable composition increase, and the film thickness may decrease under a high temperature and high humidity environment.
In addition to these radical generators, for example, known sensitizers such as methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, amyl 4-dimethylaminobenzoate, 4-dimethylaminoacetophenone, etc. A sensitizer may be used in combination. A sensitizer may be used individually by 1 type and may be used in combination of 2 or more type.

Examples of photopolymerization initiators other than radical generators include oxidants, and these photopolymerization initiators may be used alone or in combination of two or more. Good. The photopolymerization initiator may contain impurities such as a chlorine atom, a sulfur atom, a phosphorus atom, and a sodium atom, but the content of these impurities is preferably small, and each content is preferably Is not more than 100 ppm, more preferably not more than 50 ppm, still more preferably not more than 30 ppm, particularly preferably not more than 10 ppm relative to the polymerization initiator.
In addition, when starting photopolymerization reaction with an electron beam as radiation, the above-mentioned photopolymerization initiator can be used, but since it is sufficiently cured without using a photopolymerization initiator, a radical generator or other It is preferable not to use a photopolymerization initiator.

2-6. Auxiliary ingredients
The radiation curable composition of the present invention may contain an auxiliary component such as an additive as necessary, as long as the effects of the present invention are not significantly impaired. Specific examples of the auxiliary components include stabilizers such as antioxidants, heat stabilizers, or light absorbers; glass fibers, glass beads, silica, alumina, zinc oxide, titanium oxide, mica, talc, kaolin, metal Fillers such as fibers and metal powders; carbon materials such as carbon fibers, carbon black, graphite, carbon nanotubes, fullerenes such as C60 (fillers and carbon materials may be collectively referred to as inorganic components); Antistatic agents, plasticizers, mold release agents, antifoaming agents, leveling agents, antisettling agents, surfactants, thixotropic agents, modifiers such as epoxy group-containing compounds; pigments, dyes, hue modifiers, etc. Coloring agents; Monomers other than the above-mentioned compounds (A) to (D) or / and oligomers thereof, or curing agents, catalysts, curing accelerators and the like necessary for the synthesis of inorganic components. These auxiliary components may be used alone or in combination of two or more. The content of these auxiliary components is usually 20% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less of the radiation curable composition.

In these, the silica as a filler which can be used in the radiation-curable composition of this invention is explained in full detail. Silica here refers to silicon oxide in general, regardless of the ratio of silicon and oxygen, and whether it is crystalline or amorphous. Examples of the silica particles include
Examples include silica particles that are industrially produced and dispersed in a solvent, or silica particles in powder form; silica particles derived and synthesized from a raw material such as alkoxysilane. Among these, when used in the radiation curable composition of the present invention, silica particles dispersed in a solvent or silica particles derived and synthesized from a raw material such as alkoxysilane, because of ease of mixing and dispersion. Is preferred.

  The particle diameter of the silica particles is arbitrary, but the number average particle diameter measured by morphological observation using a TEM (transmission electron microscope) is preferably 0.5 nm or more, more preferably 1 nm or more, The thickness is preferably 50 nm or less, more preferably 40 nm or less, still more preferably 30 nm or less, particularly preferably 15 nm or less, and most preferably 12 nm or less. The silica particles are preferably ultrafine particles, but if they are too small, the cohesiveness of the ultrafine particles is extremely increased, and the transparency and mechanical strength of the cured product tend to be extremely decreased.

2-7. Method for producing radiation curable composition
The radiation curable composition of the present invention includes, for example, urethane (meth) acrylate oligomers such as compound (A), (B) and compound (C), compound (D), photopolymerization initiator, or the auxiliary component, It is prepared by stirring and mixing uniformly while blocking radiation. The order of addition of each compound at that time is not particularly limited, but it is preferable to add a high viscosity liquid component and / or solid component to a low viscosity liquid component and stir, and a photopolymerization initiator. Is preferably added last.
In addition, the stirring conditions at that time are not particularly limited, and the stirring temperature is usually normal temperature. When heating, the temperature may be usually 90 ° C. or lower, preferably 70 ° C. or lower. .

3. Laminate
The laminate of the present invention is a laminate obtained by laminating a cured film made of the cured product of the present invention on a substrate.
Normally, a laminate with multiple layers made of different materials has different effects when subjected to an environment such as temperature and humidity in each layer. Deformation (hereinafter sometimes referred to as “warping”) occurs. In the laminated body of this invention, the deformation | transformation of such a laminated body can be suppressed and the curvature of the laminated body accompanying an environmental change can be made small. In particular, it is possible to obtain a laminate that is small in deformation with respect to changes in environmental humidity and that has excellent creep resistance on the surface of the cured film.

Although it does not specifically limit as a base material of the laminated body of this invention unless the effect of this invention is impaired, A plastic base material or a transparent base material is mentioned.
Examples of the plastic substrate include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polymethyl methacrylate (PMMA), or methyl methacrylate (MMA) copolymer (for example, methyl methacrylate-styrene copolymer resin ( MS resin)), polycarbonate, special polycarbonate (for example, Teijin Pure Ace), triacetyl cellulose, acrylonitrile butadiene styrene copolymer resin (ABS resin), modified polyolefin resin, hydrogenated polystyrene resin, cycloolefin-based transparent resin (for example, ASR made by JSR, ZEONOR made by Nippon Zeon, etc.). Alternatively, as other examples of the transparent substrate, thermosetting or photocurable transparent resins (for example, transparent epoxy resins, transparent urethane resins, thermosetting acrylic resins, photocurable acrylic resins, thermosetting) Other cured organic / inorganic hybrid resins and cured products such as various photocurable organic / inorganic hybrid resins).

These base materials may be in the form of molded articles (articles), or may be formed into desired articles after being formed into a laminate. Moreover, you may interpose another layer between a base material and an application surface.
The method for forming the cured film made of the cured product of the present invention is not particularly limited, and the cured film made of the composition of the present invention may be formed and then bonded to the base material. A method may be used in which a coating film is formed by applying to a material and cured to form a cured film.

Preferred examples of the coating method include spin coating, dip coating, flow coating, spray coating, bar coating, gravure coating, roll coating, blade coating, and air knife coating.
A cured film is obtained by forming a coating film on the substrate by the coating method, removing volatile components by heat drying, and then irradiating with radiation.
The type of radiation and the irradiation method are the same as in the case of the above-described method for producing a cured product. Such a cured film cured with radiation is particularly preferable because of its excellent balance between productivity and physical properties.

4). Use of radiation curable composition of the present invention, cured product thereof, and laminate
The radiation curable composition and the cured product and laminate of the present invention are suitably used as a material for optical recording media described below, particularly as a material for forming a protective layer of an information recording layer.
Currently, optical recording media generally used include read-only media (ROM media), write-once media that can be recorded only once (WriteOnce media), and rewritable media that can repeatedly perform recording and erasure. The radiation-curable composition for optical recording media and the radiation-cured product thereof according to the present invention can be applied to any of them, but a read-only medium (ROM medium) ) Particularly preferably.

  These optical recording media employ a layer structure according to their intended use. For example, in a read-only medium, a single layer containing a metal such as aluminum, silver, gold or the like is usually formed on a substrate on which unevenness for reproduction is formed. Further, in a write-once medium, a recording / reproducing functional layer in which a reflective layer containing a metal such as aluminum, silver or gold and a recording layer containing an organic dye are usually laminated on a substrate in this order. Is formed. In a rewritable medium, a reflective layer containing a metal such as aluminum, silver or gold, a dielectric layer, a recording layer containing an organic dye, and a dielectric layer are usually formed on a substrate. Are formed in this order. The radiation-curable composition of the present invention and the cured product thereof are formed on a single layer in a read-only medium, on a recording / reproducing functional layer in a write-once medium, and on a recording / reproducing functional layer in a rewritable medium. It is suitable for use as a protective layer to be formed.

  An inorganic compound layer (also referred to as “back sputter layer”) made of a metal oxide or the like may be formed on the substrate surface opposite to the surface on which the protective layer is formed by a method such as sputtering. Its main purpose is to suppress oxygen and water vapor transmission to the substrate. The radiation curable composition of the present invention is characterized in that the deformation of the medium can be remarkably reduced particularly in an optical recording medium on which a back sputter layer is formed. Since most of read-only media (ROM media) have a back sputter layer, the radiation curable composition of the present invention is particularly preferably used.

  On the other hand, the wavelength of the laser light as the recording / reproducing light for recording / reproducing of the optical recording medium uses light of the optimum wavelength according to the standard such as CD, DVD, Blu-ray disc, HDDVD and the like. In addition, with the recent popularization of rich contents, the demand for higher density and higher capacity of optical recording media is increasing, and research using a blue laser with a shorter wavelength has been actively conducted. This next-generation high-density optical recording medium using a blue laser is an optical recording in which a recording / reproducing functional layer including a dielectric layer, a recording layer, a reflective layer, etc. is formed on a substrate, and a protective layer is formed thereon. Recording / reproducing light having a wavelength of usually 350 nm or more, preferably 380 nm or more, and usually 450 nm or less, preferably 430 nm or less, which is a medium. The radiation curable composition of the present invention and the cured product thereof can be particularly suitably used for this next generation high density optical recording medium.

  The radiation curable composition of the present invention and the laminate or optical recording medium in which the cured product is used have, for example, a two-layer structure having two recording layers and two reflective layers. There may be. In the case of this two-layer type, one layer may be laminated on the substrate in order, or two layers obtained by laminating a pair of a recording layer and a reflective layer may be bonded together. Good. Further, a three-layer structure may be adopted, and the bonding may be performed through an adhesive layer. Furthermore, if necessary, a hub may be attached and incorporated in the cartridge.

  The thickness of the protective layer is usually 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, still more preferably 70 μm or more, particularly preferably 85 μm or more, and usually 300 μm or less, preferably 130 μm or less, more preferably 115 μm. It is as follows. If the film thickness is in such a range, the influence of dust and scratches attached to the surface of the protective layer can be reduced, and the thickness of the recording / reproducing functional layer is sufficient to protect the moisture from outside air and the like. be able to. Moreover, a uniform film thickness can be easily formed by a general coating method used in spin coating or the like.

Specific examples of the present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited by these examples unless it exceeds the gist.
<Production Example 1> Synthesis of urethane acrylate oligomer composition (a) In a four-necked flask, 20.4 g of hexamethylene diisocyanate trimer ("Tronate HDT" manufactured by Rhodia) and 10 mg of dibutyltin laurate are placed in an oil bath. The mixture was heated to 70-80 ° C. and gently stirred until the temperature became constant, and then a mixture of 30.1 g of polypropylene glycol-modified hydroxyacrylate (“Blenmer AP-400” manufactured by NOF Corporation) and 10 mg of p-methoxyhydroquinone was added. It dropped with the dropping funnel, and when dripping was completed, temperature was maintained at 80 degreeC, and also it was made to stir for 10 hours, and the urethane acrylate oligomer (a1) was synthesize | combined.

  After transferring the urethane acrylate oligomer (a1) to another four-necked flask, add 288 g of isophorone diisocyanate produced by the urea method, and heat to 70-80 ° C. in an oil bath, and the temperature is constant. Gently stir until When the temperature becomes constant, 102 g of 1,6-hexanediol is dropped with a dropping funnel, and the mixture is stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature is lowered to 70 ° C., a mixture of 100 g of hydroxyethyl acrylate and 0.1 g of p-methoxyhydroquinone is dropped with a dropping funnel, and when the dropping is completed, the temperature is kept at 80 ° C. and stirred for 10 hours to obtain a urethane acrylate oligomer. A urethane acrylate oligomer (a2) mixed with (a1) was synthesized. Next, 260 g of tetrahydrofurfuryl acrylate (“V # 150” manufactured by Osaka Organic Chemical Co., Ltd.), 100 g of phenoxyethyl acrylate (“FA-310A” manufactured by Hitachi Chemical Co., Ltd.), nonanediol diacrylate (“V # 260” manufactured by Osaka Organic Chemical Co., Ltd.) The urethane acrylate oligomer composition (a) was prepared by adding 30 g of 1-hydroxycyclohexyl phenyl ketone.

<Production Example 2> Synthesis of urethane acrylate oligomer composition (b) 299 g of isophorone diisocyanate produced by the urea method is placed in a four-necked flask and heated to 70-80 ° C in an oil bath until the temperature becomes constant. Stir gently. When the temperature became constant, 57 g of 1,6-hexanediol and 122 g of polytetramethylene ether glycol (“PTMG650” manufactured by Mitsubishi Chemical Corporation) were combined and added dropwise with a dropping funnel, and stirred for 2 hours while maintaining the temperature at 80 ° C. To do. After the temperature is lowered to 70 ° C., a mixture of 156 g of hydroxyethyl acrylate and 0.1 g of p-methoxyhydroquinone is dropped with a dropping funnel, and when the dropping is completed, the temperature is kept at 80 ° C. and stirred for 10 hours. (B) was synthesized. Next, 365 g of tetrahydrofurfuryl acrylate (“V # 150” manufactured by Osaka Organic Chemical Co., Ltd.) and 30 g of 1-hydroxycyclohexyl phenyl ketone were added to prepare a urethane acrylate oligomer composition (b).

<Production Example 3> Synthesis of urethane acrylate oligomer composition (c) 71.7 g of hexamethylene diisocyanate trimer ("Tronate HDT" manufactured by Rhodia) and 30 mg of dibutyltin laurate are placed in a four-necked flask and placed in an oil bath. The mixture is heated to 70 to 80 ° C. and gently stirred until the temperature becomes constant, and then a mixture of 29.3 g of hydroxyethyl acrylate and 30 mg of p-methoxyhydroquinone is added dropwise using a dropping funnel. The urethane acrylate oligomer (c1) was synthesized by maintaining the temperature at ° C and further stirring for 10 hours.
After transferring the urethane acrylate oligomer (c1) to another four-necked flask, add 291 g of isophorone diisocyanate produced by the urea method, and heat to 70-80 ° C. in an oil bath to keep the temperature constant. Gently stir until When the temperature becomes constant, a mixture of 52 g of 1,6-hexanediol and 105 g of polyester polyol (“P-510” manufactured by Kuraray Co., Ltd.) is dropped with a dropping funnel and stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature is lowered to 70 ° C., a mixture of 152 g of hydroxyethyl acrylate and 0.1 g of p-methoxyhydroquinone is dropped with a dropping funnel. When the dropping is finished, the temperature is kept at 80 ° C. and stirred for 10 hours to obtain a urethane acrylate oligomer. A urethane acrylate oligomer (c2) mixed with (c1) was synthesized. Next, 300 g of tetrahydrofurfuryl acrylate (“V # 150” manufactured by Osaka Organic Chemical Co., Ltd.) and 30 g of 1-hydroxycyclohexyl phenyl ketone were added to prepare a urethane acrylate oligomer composition (c).

<Production Example 4> Synthesis of urethane acrylate oligomer composition (d) In a four-necked flask, 122.2 g of hexamethylene diisocyanate trimer ("Tronate HDT" manufactured by Rhodia) and 50 mg of dibutyltin laurate are placed in an oil bath. The mixture was heated to 70 to 80 ° C. and gently stirred until the temperature became constant, and then a mixture of 180.7 g of polypropylene glycol-modified hydroxyacrylate (“Blenmer AP-400” manufactured by NOF Corporation) and 50 mg of p-methoxyhydroquinone was added. It dropped with the dropping funnel, and when dripping was completed, temperature was maintained at 80 degreeC, and also it was made to stir for 10 hours, and the urethane acrylate oligomer (d1) was synthesize | combined.

  After transferring the urethane acrylate oligomer (d1) to another four-necked flask, an additional 66.3 g of isophorone diisocyanate produced by the urea method is added and heated to 70-80 ° C. in an oil bath. Gently stir until is constant. When the temperature becomes constant, 149.1 g of polyester polyol (“P-1010” manufactured by Kuraray Co., Ltd.) is dropped with a dropping funnel and stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature is lowered to 70 ° C., a mixture of 34.6 g of hydroxyethyl acrylate and 20 mg of p-methoxyhydroquinone is dropped with a dropping funnel, and when the dropping is finished, the temperature is kept at 80 ° C. and stirred for 10 hours to obtain a urethane acrylate oligomer. A urethane acrylate oligomer (d2) mixed with (d1) was synthesized. Next, 100 g of phenoxyethyl acrylate (Hitachi Chemical Co., Ltd. “FA-310A”), dicyclopentadienyl dimethanol diacrylate (Daicel Cytec Co., Ltd. “IRR-214K”) 350 g, and 1-hydroxycyclohexyl phenyl ketone 30 g were added. A urethane acrylate oligomer composition (d) was prepared.

(Tilt measurement)
For the measurement of tilt, a displacement sensor LT-9010 (manufactured by KEYENCE) was used. The tilt in the present invention is an expression of an inclination with respect to a horizontal plane at a position of 58 mm from the center of the upper surface of the substrate, when the center portion of the upper surface of the substrate is fixed horizontally, and the degree of warpage of the laminated body. The value to be reflected.
When the cured film of the laminate is down, the upward warp, that is, a state deformed in a concave shape when viewed from above is defined as positive, and the downward warp, that is, a state that is deformed in a convex shape when viewed from above is defined as negative. did.

Example 1
After forming an Ag reflection layer having a thickness of 100 nm on both sides of a circular polycarbonate plate having a thickness of 1.1 mm and a diameter of 120 mm by sputtering, the urethane acrylate oligomer composition (a) prepared in Production Example 1 is applied to the surface. After applying by spin coating so that the thickness of the film becomes 100 ± 10 μm, a UV irradiation device (“J-cure100” manufactured by JATEC Co., Ltd.) is used so as to obtain an integrated light amount of 500 mJ / cm ² under the condition of oxygen concentration of 20%. A built-in high-pressure mercury lamp) was applied to form a protective layer to form a laminate.

After applying the urethane acrylate oligomer composition (a) prepared in Production Example 1 to a circular polycarbonate plate having a thickness of 1.1 mm and a diameter of 120 mm by spin coating so that the thickness of the coating film becomes 100 ± 10 μm. Then, under a condition of an oxygen concentration of 20%, a protective layer was formed by irradiation with a UV irradiation apparatus (“J-cure 100” manufactured by JATEC; built-in high-pressure mercury lamp) so as to obtain an integrated light amount of 500 mJ / cm ² . The end of this protective layer was cut with a cutter knife, and the protective layer was carefully peeled from the substrate to obtain a release film. The same operation was repeated to obtain a total of two release films.

(Light transmittance)
About the release film obtained above, the light transmittance per optical path length of 0.1 mm at a wavelength of 400 nm was measured using an ultraviolet / visible absorptiometer (manufactured by Hewlett-Packard; HP8453 type).
(Storage modulus)
A strip-shaped sample of 30 × 4 mm was cut out from the release film, and a dynamic viscoelasticity measuring device (“DMS6100” manufactured by SII Nano Technology Co., Ltd.) was used to obtain a tensile mode, a span width of 20 mm, a frequency of 10 Hz, Temperature increase rate: The storage elastic modulus in the range of −10 to 120 ° C. was measured at 2 ° C./min. The obtained storage elastic moduli at 45 ° C., 55 ° C., and 60 ° C. are shown in Table 1 as E ′ (45), E ′ (55), and E ′ (60), respectively.

(Dehydration shrinkage)
A strip-shaped sample of 30 × 5 mm is cut out from the release film, and in a tensile mode using a thermomechanical analyzer (“TMA8310” manufactured by Rigaku) with a water vapor generator (“HUM-1B” manufactured by Rigaku). It was measured. After mounting the sample with a span width of 20 mm, the inside of the chamber was set to 25 ° C. and 90% RH, and the size of the sample was monitored every 2 hours, and the sample was allowed to stand until elongation stopped. After confirming that the elongation stopped, the inside of the chamber was changed to 25 ° C. and 50%, and the shrinkage of the sample was monitored. The amount of shrinkage with respect to the span width at the time when no shrinkage of the sample was observed was taken as the dehydration shrinkage rate. Table 1 shows the dehydration shrinkage obtained.

(Generating stress)
It calculated by the product of E '(55) and E' (60) obtained above, and dehydration shrinkage. That is, the generated stress is obtained by calculating the left side of the equations (1) and (2). The generated stress calculated from E ′ (55) is described as generated stress 1, and the generated stress calculated from E ′ (60) is described as generated stress 2.
(Humidity warpage)
After the laminate prepared above was placed at 25 ° C. and 90% RH for 24 hours, the tilt immediately after being placed at 25 ° C. and 50% (0 hour) was measured, and then 1, 2, 3, 5, 9 hours The change in tilt after the lapse was measured. Table 1 shows the amount of change over time when the absolute value of the amount of change from tilt at the time of 0 hour is the maximum as the humidity warp. It is preferable that the humidity warp has a smaller absolute value because there is less deformation of the laminate due to a rapid change in humidity. For reference, the relationship between the generated stress and the humidity warp is shown in FIG. Assuming that a cover layer of a Blu-ray disc, which is a large-capacity optical recording medium, is formed from the radiation curable composition of the present invention, the absolute value of the humidity tilt of the Blu-ray disc is preferably 0.6 ° or less. ing.

(Creep resistance)
The laminate prepared above is placed on a surface plate with the protective layer facing upward, and a 100 mm square, 5 mm thick glass plate that is sand plasted is stacked on the protective layer, and a steel plate having a weight of 640 g is stacked thereon. After stacking 7 weights (Fig. 1) and letting them stand for 5 minutes, remove the weight and the glass plate and immediately observe the surface of the protective layer visually. Judged to be high. That is, “×” indicates that the sandplast mark is visually observed in 75% or more of the entire area, “Δ” indicates that it is visually observed in less than 75% of the entire area, and “◯” indicates that the sandplast mark is not visually observed. As evaluated. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, it carried out like Example 1 except having used the urethane acrylate oligomer composition (b) instead of the urethane acrylate oligomer composition (a). The results are shown in Table 1.
(Comparative Example 2)
In Example 1, it carried out like Example 1 except having used urethane acrylate oligomer composition (c) instead of urethane acrylate oligomer composition (a). The results are shown in Table 1.
(Comparative Example 3)
In Example 1, it carried out like Example 1 except having used urethane acrylate oligomer composition (d) instead of urethane acrylate oligomer composition (a). The results are shown in Table 1.

表１から明らかなように、５５℃における貯蔵弾性率と脱水収縮率の積で表される発生応力１、及び６０℃における貯蔵弾性率と脱水収縮率の積で表される発生応力２が、それぞれ６．０ＭＰａ以下、３．５ＭＰａ以下となる保護層が形成された積層体では、環境湿度の急激な変化があっても、それによって生じる変形が小さい。また、４５℃における貯蔵弾性率が１５００ＭＰａ以上であると、高い耐クリープ性が得られる。このような組成物は、高い耐クリープ性と透明性、及び環境湿度変化に対する基材の変形が小さいことを要求される用途、特に光記録媒体をはじめとする光学用途に有利に利用できる。

As is apparent from Table 1, the generated stress 1 expressed by the product of the storage elastic modulus at 55 ° C. and the dehydration shrinkage rate, and the generated stress 2 expressed by the product of the storage elastic modulus at 60 ° C. and the dehydration shrinkage rate are In a laminate in which a protective layer having a pressure of 6.0 MPa or less and 3.5 MPa or less is formed, even if there is a sudden change in environmental humidity, deformation caused by the change is small. Moreover, high creep resistance is acquired as the storage elastic modulus in 45 degreeC is 1500 Mpa or more. Such a composition can be advantageously used in applications requiring high creep resistance and transparency, and small deformation of the substrate with respect to environmental humidity changes, particularly optical applications including optical recording media.

When the radiation curable composition of the present invention is cured to form a laminate, the laminate can have a sufficient creep resistance with little deformation immediately after the environmental humidity changes rapidly. In particular, it is a radiation curable composition suitable for obtaining a protective layer having high recording film protection in an optical recording medium.
Thereby, the laminated body formed by laminating the cured product obtained from the radiation curable composition of the present invention can be effectively applied to an optical recording medium such as a Blu-ray disc.

Claims (5)

A radiation curable composition containing (meth) acrylate and a photopolymerization initiator, and having a light transmittance at a wavelength of 400 nm of 85% or more of a cured product having a thickness of 100 ± 10 μm cured by irradiation with radiation. Yes, storage elastic modulus E ′ (45) at 10 Hz and 45 ° C. is 1500 MPa or more, and storage elastic modulus E ′ (55) and dehydration shrinkage rate γ at 10 Hz and 55 ° C. satisfy the condition of the following formula (I). A radiation curable composition characterized by that.
Formula (I) E ′ (55) × γ ≦ 6.0 (MPa) A radiation curable composition containing (meth) acrylate and a photopolymerization initiator, and having a light transmittance at a wavelength of 400 nm of 85% or more of a cured product having a thickness of 100 ± 10 μm cured by irradiation with radiation. Yes, storage elastic modulus E ′ (45) at 10 Hz and 45 ° C. is 1500 MPa or more, and storage elastic modulus E ′ (60) and dehydration shrinkage γ at 10 Hz and 60 ° C. satisfy the condition of the following formula (II). A radiation curable composition characterized by that.
Formula (II) E ′ (60) × γ ≦ 3.5 (MPa)   The radiation curable composition according to claim 1 or 2, wherein the radiation curable composition contains a compound having a urethane bond.   Hardened | cured material obtained by irradiating a radiation-curable composition in any one of Claims 1-3 to a radiation.   The laminated body formed by laminating | stacking the cured film which consists of hardened | cured material of Claim 4 on a base material.

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