JP2010222451A - 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 hardly suffering from distortion when formed into a cured film and exhibiting a high creep property on the surface of the cured product. <P>SOLUTION: The radiation-curable composition comprises a (meth)acrylate and a photoinitiator, and gives, by curing by radiation irradiation thereon, a cured product of a thickness of 100±10 μm having a light transmittance at a wavelength of 400 nm of at least 85%, a storage elastic modulus E'(80) of at most 500 MPa at 10 Hz and 80°C, and a value F derived from a storage elastic modulus E'(37) at 37°C, a storage elastic modulus E'(45) at 45°C and a storage elastic modulus E'(60) at 60°C, each at 10 Hz, of at most 0.006. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a radiation curable composition that has a high creep resistance on the surface of a cured product and can obtain a laminate with little deformation of the substrate when it is made into a laminate, and the composition is irradiated with radiation. The present invention relates to a cured product obtained and a laminate having a cured film made of the cured product.

  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 mixing ratio has been proposed. (For example, see 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. When trying to adjust the component to improve its creep resistance, it has been found that there is a tendency for the deformation of the base material resulting from the shrinkage when the composition is cured to remarkably increase, making it difficult to achieve both. .

JP2007-270119A

  The present invention has been made to solve the above-mentioned problems, and realizes a laminate that maintains high creep resistance and transparency on the surface of a cured product and that has little deformation of the substrate due to the formation of a cured film. It aims at providing the radiation-curable composition which can be performed, and its hardened | cured material.

As a result of intensive studies, the present inventors have found that the above problems can be solved when the storage elastic modulus at several temperatures satisfies a certain condition, and have reached the present invention.
That is, the 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 at a wavelength of 400 nm. The light transmittance is 85% or more, the storage elastic modulus E ′ (80) at 10 Hz and 80 ° C. is 500 MPa or less, the storage elastic modulus E ′ (37) at 10 Hz and 37 ° C., and the storage elastic modulus E ′ at 45 ° C. (45) and the storage elastic modulus E ′ (60) at 60 ° C., the value F derived by the following formula (I) is 0.006 or less, and the radiation curable composition is characterized in that:

Formula (I) F = 1 / E ′ (37) + 1 / E ′ (60) −1 / E ′ (45)
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, there is provided a radiation curable composition capable of realizing a laminated body that is excellent in transparency, maintains high creep resistance, and is less deformed when a cured product is formed, and a cured product thereof. Its industrial value is extremely high.

It is the figure which showed the frequency dependence of the temperature change of a storage elastic modulus. It is the figure which showed the relationship between indentation load and indentation amount. It is the schematic diagram which looked at the weight used for creep resistance evaluation from upper direction.

  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 present invention needs to have a storage elastic modulus E ′ (80) at 10 Hz and 80 ° C. of 500 MPa or less.
The storage elastic modulus mentioned here is a characteristic obtained when the viscoelasticity of a material is evaluated by using a dynamic viscoelasticity measuring apparatus (also referred to as “DMA” or “DMS”). Storage elastic modulus can be measured in a tensile mode by setting a desired frequency using a dynamic viscoelasticity measuring device.

  By measuring the dynamic viscoelasticity, it is possible to know the magnitude and phase of the stress and the elastic modulus that are generated when a high frequency strain of several Hz to several tens of Hz is applied to the material. Among the elastic moduli that express, it means the same phase as the strain frequency. Since the dynamic viscoelasticity measuring apparatus can cool and heat the sample at a controlled temperature, the storage elastic modulus at each temperature of the sample can be known.

  As a result of intensive studies on the correlation between the storage elastic modulus at each temperature and the actual properties of the cured product, the present inventors have found that the deformation of the base material (hereinafter referred to as “initial warp”) resulting from shrinkage during curing is found. It has been found that a large composition has a large storage elastic modulus at a high temperature, particularly at 80 ° C., and conversely, a composition having a small initial warp has a small E ′ (80) relationship. In particular, in a laminate in which a cured film made of a radiation curable composition is formed on a substrate having a size of about several tens of centimeters, E ′ (80) of the cured film, in which almost no initial warpage is observed, is 500 MPa or less. We found that there is a correlation. E ′ (80) is more preferably 200 MPa or less, still more preferably 100 MPa or less, and most preferably 50 MPa or less. E ′ (80) is preferably as small as possible in order to reduce the initial warp, but is usually 5 MPa or more.

  The cured product of the present invention has a storage elastic modulus E ′ (37) at 10 Hz and 37 ° C., a storage elastic modulus E ′ (45) at 45 ° C., and a storage elastic modulus E ′ (60) at 60 ° C. The value F derived by I) must be 0.006 or less.

Formula (I) F = 1 / E ′ (37) + 1 / E ′ (60) −1 / E ′ (45)
The inventors of the present invention have made extensive efforts to improve the initial material in order to reduce the initial warpage. However, as the initial warpage is reduced, the creep resistance of the cured product surface decreases, and a part of the cured product surface is reduced. It was found that when some load is applied to the surface, the surface of the cured product tends to be marked. When trying to adjust the components of the radiation curable composition in order to improve its creep resistance, the initial warp increases significantly, and it turns out that it is difficult to make these two properties compatible. did.

Considering these phenomena, the following two methods are conceivable as methods for avoiding surface marks generated on the surface of the cured product.
(1) The surface of the cured product is hard and does not deform even when a load is applied for a certain period of time.
(2) The surface of the cured product is soft on the contrary, and the material that was deformed in the state where a load was applied recovered immediately after the load was removed (hereinafter referred to as “elastic recovery”), and apparently no trace remained. .

As in (1), a deformation caused by a load that is continuously applied for a long time, not a load that is instantaneously applied, correlates with a storage elastic modulus at a frequency corresponding to the time that the load is applied. In addition, it is known that if the storage elastic modulus is high, the deformation becomes small. Moreover, it is thought that said frequency is far smaller than 10 Hz which is a frequency used in normal storage elastic modulus measurement. For example, when the load loading time is 24 hours, the corresponding frequency is 1.16 × 10 ⁻⁵ Hz which is the reciprocal of the number of seconds, which is almost 6 digits smaller than 10 Hz.

What is known as a general characteristic in a resin material is an empirical rule that when the frequency at which the storage elastic modulus is measured is lowered, the characteristic of the storage elastic modulus shifts to a lower temperature side. An example thereof is shown in FIG. 1 (the frequency dependence of the dynamic viscoelasticity of the cured product prepared in Example 1 described later). In FIG. 1, the storage elastic modulus characteristic of 1 Hz is obtained by translating the storage elastic modulus characteristic of 10 Hz to a lower temperature, and the storage elastic modulus characteristic of 0.1 Hz is further translated to a lower temperature. You can see that it is a thing. Further, the shift temperature is proportional to the frequency digit difference. That is, it can be seen that the shift temperature of the storage modulus of 1 Hz, which is 1 digit lower than 10 Hz, and the shift temperature of the storage modulus of 0.1 Hz, which is 1 digit lower than 1 Hz, are substantially the same. In other words, when attention is paid to the storage elastic modulus characteristic of 10 Hz, the storage elastic modulus of 1 Hz obtained by reducing the frequency by one digit may be obtained by reading the storage elastic modulus that is higher by the temperature corresponding to the shift temperature. For example, in order to read the storage elastic modulus at 25 ° C. of 1 Hz, which is one digit lower than the storage elastic modulus characteristic of 10 Hz, the storage elastic modulus at (25 + shift temperature) ° C. may be read. In order to read the storage elastic modulus at 25 ° C. of 0.1 Hz, the storage elastic modulus of (25 + shift temperature × 2) ° C. may be read. In the case where the load loading time is 24 hours, the frequency is 1.16 × 10 ⁻⁵ Hz, which is almost 6 digits smaller than 10 Hz, so that it is approximately (25 + shift temperature × 6) ° C. (hereinafter referred to as t ₁ ). It is sufficient to read the storage elastic modulus.

The elastic recovery in the case of (2) is also correlated with the storage elastic modulus at a frequency corresponding to the time at which the elastic recovery occurs. The higher the storage elastic modulus is, the smaller the elastic recovery is. It is known that recovery will be greater. As in the case of the storage elastic modulus, an empirical rule that the storage elastic modulus characteristic shifts to a lower temperature side as the frequency is lowered applies. For example, when considering elastic recovery occurring in 5 minutes, the frequency is 0.00333 Hz, which is the reciprocal of the number of seconds, and is 3.5 digits smaller than 10 Hz. Therefore, in the storage elastic modulus characteristic of 10 Hz, it is sufficient to look at the high temperature storage elastic modulus of (25 + shift temperature × 3.5) ° C. (hereinafter referred to as t ₂ ), and the lower the storage elastic modulus at t ₂ , It is derived that the elastic recovery force should be high.

In addition, when considering the deformation amount f due to creep, it is considered that it correlates with the strain amount when the load is constant, so from the relation of the material mechanics of “stress = strain × elastic modulus”,
f = strain in the load process−strain in the elastic recovery process (hereinafter referred to as “elastic recovery amount”) = (stress / elastic modulus) in the load process− (stress / elastic modulus) in the elastic recovery process, and f is {1 A relationship is derived that is proportional to / E ′ (t ₁ ) −1 / E ′ (t ₂ )}.

The present inventors examined the correlation between f and the creep resistance characteristics at t ₁ , t ₂ and room temperature of 25 ° C. using a method such as multivariate analysis, but unfortunately the correlation was low. As a result of further study of this phenomenon, it has been estimated that in the initial stage of applying a load, instantaneous deformation at the moment of applying the load (hereinafter referred to as “initial deformation process”) needs to be considered. This consideration is consistent with the relationship between the indentation load and the indentation amount using the Vickers hardness tester shown in FIG. This figure shows the operation of removing the load by holding the applied load for a certain time after pushing the probe into the surface of the laminate prepared in Example 1 of the present invention using a Vickers hardness tester. Although the probe push-in amount changes with time, the push-in amount increases rapidly during the process of increasing the applied load (“Initial push-in area” in the figure) and the process of holding the load (“creep” in the figure). In the region "), the push amount gradually increases, and in the process of removing the load (" elastic recovery region "in the figure), the push amount slightly decreases. Of these three regions, an initial indentation region that is a first region is an “initial deformation step”, a creep region that is a second region is a “loading step”, and an elastic recovery region that is a third region is “ It can be considered that each corresponds to the “elastic recovery step”.

In consideration of the above, it has been derived that f is proportional to {1 / E ′ (t ₀ ) + 1 / E ′ (t ₁ ) −1 / E ′ (t ₂ )}.
In the above equation, 1 / E ′ (t ₀ ) corresponds to the strain in the initial deformation process, 1 / E ′ (t ₁ ) corresponds to the strain in the loading process, and 1 / E ′ (t ₂ ) is elastic recovery. It corresponds to distortion in the process.
When the correlation between the f, t ₀ , t ₁ , t ₂ and the creep resistance at room temperature of 25 ° C. was examined using a technique such as multivariate analysis, t ₀ = 37 ° C., t ₁ = 60 ° C., t ₂ It was found that there was a very strong correlation between f and creep resistance when = 45 ° C. That is, it has been found that when F is 0.006 or less, the creep resistance is remarkably improved. Here, the logical validity of the temperatures of t ₀ , t ₁ , and t ₂ was examined as follows.

FIG. 1 referred to above shows the frequency dependence of the dynamic viscoelasticity of the cured product prepared in Example 1 of the present invention. From this figure, the shift temperature, that is, “the difference in digits from 10 Hz is different. The “shift temperature at −1” can be read as about 6 ° C. When the room temperature is 25 ° C., the differences of t ₀ = 37 ° C., t ₁ = 60 ° C. and t ₂ = 45 ° C. from the room temperature of 25 ° C. are 12 ° C., 35 ° C., and 20 ° C., respectively. When dividing by 6 which is the temperature, numerical values of 2, 5.833 and 3.333 are obtained, respectively, which indicate a digit difference from 10 Hz. Table 1 shows the frequency values corresponding to the above-mentioned 2, 5.8333, and 3.333, that is, frequencies corresponding to t ₀ , t ₁ , and t ₂ .

その周波数の逆数から、各工程時間の計算値を求めたところ、表１にあるように、それぞれ１０秒、約１９時間、約３．５分と算出された。つまり、初期変形工程が１０秒、荷重工程が約１９時間、弾性回復工程が約３．５分であることを示している。これらの数字が意味することは、荷重を加えた初期段階の変形は１０秒で起こり、荷重を加えて静値した場合の変形は、約１９時間で一定量に収束し、弾性回復は、荷重を除いてから約３．５分で一定量に達することを意味している。また、第１の項と第２の項は痕が増加する方向であるからプラス、第３の項は弾性回復で跡が減少する方向であるからマイナスとなっており、実際の現象とよく整合していることが分かる。

From the reciprocal of the frequency, the calculated values for each process time were calculated to be 10 seconds, about 19 hours, and about 3.5 minutes, as shown in Table 1. That is, the initial deformation process is 10 seconds, the loading process is about 19 hours, and the elastic recovery process is about 3.5 minutes. What these numbers mean is that the deformation at the initial stage when a load is applied occurs in 10 seconds, and the deformation when the load is applied and static value is converged to a certain amount in about 19 hours. It means that a certain amount is reached in about 3.5 minutes after removing. The first and second terms are positive because the traces increase, and the third term is negative because the traces decrease due to elastic recovery, which is in good agreement with the actual phenomenon. You can see that

From the above considerations, the formula of F derived by the present inventors is composed of three terms corresponding to the time at which each of the three processes occurs, and was originally an inductively derived formula. However, according to the above examination by the present inventors, it can be said that the equation has a good consistency with the actual phenomenon and the theoretical basis is clearly shown.
By the way, although the unit shift temperature varies depending on the composition of the composition, according to the study by the present inventors, it is in the range of 3 to 8 ° C. in the case of the radiation curable composition, and among them (meth) acrylate and photopolymerization. In the case of a radiation curable composition containing an initiator, it is in the range of 5 to 7 ° C, and is generally 6 ° C.

  The value of F is 0.006 or less, preferably 0.004 or less, more preferably 0.003 or less, more preferably 0.0027 or less, still more preferably 0.002 or less, and most preferably 0.001 or less. From the viewpoint of creep resistance, the smaller the F, the better. However, if it becomes smaller than 0.0005, problems such as a significant increase in initial warpage and a significant deterioration in dimensional changes accompanying changes in environmental temperature and humidity occur. Since it tends to be easy, it is not preferable.

  By the way, in the above, the correlation between the temperature and the time related to the storage elastic modulus was discussed, but a theory corresponding to this is generally used in an academic field related to viscoelasticity called rheology. Regarding resin materials, it has been proven empirically that time and temperature are converted empirically, especially in the temperature range where the resin does not undergo phase transition such as crystallization and non-crystallization. It is named “Temperature Conversion Law”. In the composition of the present invention, since the special phase transition is not observed in the normal use temperature range of −20 to 100 ° C., it is considered that the “time-temperature conversion rule” can be applied.

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 of the present invention is preferably an oligomer having two or more urethane bonds and two or more (meth) acryloyl groups in one molecule. A urethane acrylate oligomer is particularly preferable in the composition of the present invention because it is excellent in low-dose curability when cured by irradiation, 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 comprising such a combination of urethane (meth) acrylate oligomers, high E ′ (37), E ′ (60), and low E while maintaining low E ′ (80). It becomes easy to obtain the radiation curable composition which implement | achieves the cured | curing material which is compatible with '(45).

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) And a urethane (meth) acrylate oligomer 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).

  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.

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. Furthermore, among them, (meth) acrylate having one or more (meth) acryloyl groups in one molecule (hereinafter sometimes referred to as monofunctional (meth) acrylate), two or more ( A (meth) acrylate having a (meth) 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. In addition, the diene (meta) of a diol having 6 to 20 carbon atoms and further 8 to 12 carbon atoms is more preferable because E tends to decrease as E ′ (37) and E ′ (60) of the cured product increase. ) Acrylate, specifically, hexanediol di (meth) acrylate, octanediol di (meth) acrylate, nonanediol di (meth) acrylate, bis (hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] Particularly preferred is decane = di (meth) acrylate.
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 in the radiation curable composition of the present invention. It is as follows. It is preferable that the content of the monofunctional (meth) acrylate is 40% by weight or less because F is decreased by increasing E ′ (37) and E ′ (60) of the cured product. 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 monofunctional (meth) acrylate is too large, E ′ (80) tends to increase, and residual stress at the time of curing tends to increase, resulting in a large deformation of the laminate due to environmental temperature changes. This is not preferable. On the other hand, if the content is too small, it is not preferable because F tends to increase due to the decrease in E ′ (37) and E ′ (60) of the cured product.
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. If it is 5 parts by weight or more, the surface hardness of the cured product, E ′ (37) and E ′ (60) tend to be large and F tends to be small, and the curability is excellent, which is preferable. However, if it is 30 parts by weight or more, it tends to be difficult to satisfy high E ′ (37), high E ′ (60), and low E ′ (80) at the same time, which is not preferable. This is presumed to be because it is difficult to realize the balance of storage elastic modulus because the crosslinked network of the resulting cured product is too dense due to the reason that the compound (A) has a slightly too rigid structure. .
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, it is preferable that warpage in a case where the laminate is used at room temperature (25 ° C., 50% RH) is small and E ′ (80) tends to be small.

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.

  Among these, silica as a filler that can be used in the radiation curable composition of the present invention will be described in 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 industrially produced silica particles dispersed in a solvent, or powdered silica particles; silica particles derived and synthesized from raw materials such as alkoxysilanes, and the like. Can be mentioned. 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.
Usually, in a laminate having a plurality of layers made of different materials, distortion occurs between the layers, and the laminate itself warps. In the laminated body of this invention, the deformation | transformation of the laminated body at the time of forming a cured film can be suppressed, and the creep resistance of the cured | curing material surface can be improved.
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 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 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 296 g of isophorone diisocyanate produced by the urea method, and heat to 70-80 ° C. in an oil bath. The temperature is constant. Gently stir until When the temperature becomes constant, 103 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. Then, 246 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.) A urethane acrylate oligomer composition (a) was prepared by adding 100 g and 30 g of 1-hydroxycyclohexyl phenyl ketone.

<Production Example 2> Synthesis of urethane acrylate oligomer composition (b) In a four-necked flask, 114 g of hexamethylene diisocyanate trimer ("Tronate HDT" manufactured by Rhodia) and 60 mg of dibutyltin laurate were placed. After heating to ˜80 ° C. and gently stirring until the temperature becomes constant, 23.4 g of hydroxyethyl acrylate and 84.4 g of polypropylene glycol-modified hydroxy acrylate (“Blenmer AP-400” manufactured by NOF Corporation) and p-methoxy A mixture of 60 mg of hydroquinone was added dropwise using a dropping funnel, and when the addition was completed, the temperature was kept at 80 ° C. and further stirred for 10 hours to synthesize a urethane acrylate oligomer (b1).

  After transferring the urethane acrylate oligomer (b1) to another four-necked flask, add 183 g of isophorone diisocyanate produced by the urea method, and heat to 70-80 ° C. in an oil bath. The temperature is constant. Gently stir until When the temperature became constant, a mixture of 28 g of 1,6-hexanediol, 73 g of polyester polyol (“P-510” manufactured by Kuraray Co., Ltd.) and 30 g of polyester polyol (“P-1010” manufactured by Kuraray Co., Ltd.) was dropped with a dropping funnel. And stirring for 2 hours while maintaining the temperature at 80 ° C. After the temperature is lowered to 70 ° C., a mixture of 86 g of hydroxyethyl acrylate and 0.7 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 (b2) mixed with (b1) was synthesized. Next, 120 g of tetrahydrofurfuryl acrylate (“V # 150” manufactured by Osaka Organic Chemical Co., Ltd.), 90 g of phenoxyethyl acrylate (“FA-310A” manufactured by Hitachi Chemical Co., Ltd.), dicyclopentadienyldimethanol diacrylate (manufactured by Daicel Cytec Co., Ltd.) 90 g of “IRR-214K”), 70 g of nonanediol diacrylate (“V # 260” 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) 298 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 125 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. (C) 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 (c).

<Production Example 4> Synthesis of urethane acrylate oligomer composition (d) 272 g of hexamethylene diisocyanate trimer ("Tronate HDT" manufactured by Rhodia) and 0.1 g 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 111 g of hydroxyethyl acrylate and 0.1 g of p-methoxyhydroquinone is added dropwise with a dropping funnel. It was kept at ° C. and further stirred for 10 hours to synthesize urethane acrylate oligomer (d1).

  After transferring the urethane acrylate oligomer (d1) to another four-necked flask, add 147 g of isophorone diisocyanate produced by the urea method, and heat to 70-80 ° C. in an oil bath. The temperature is constant. Gently stir until When the temperature becomes constant, 39 g of hexanediol is dropped with a dropping funnel and stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature was lowered to 70 ° C., a mixture of 77 g of hydroxyethyl acrylate and 50 mg of p-methoxyhydroquinone was added dropwise using a dropping funnel, and when the addition was completed, the temperature was kept at 80 ° C. and stirred for 10 hours to obtain a urethane acrylate oligomer (d1 ) And urethane acrylate oligomer (d2) mixed. Next, 88 g of tetrahydrofurfuryl acrylate (“V # 150” manufactured by Osaka Organic Chemical Co., Ltd.), 270 g of nonanediol diacrylate (“V # 260” manufactured by Osaka Organic Chemical Co., Ltd.), and 30 g of 1-hydroxycyclohexyl phenyl ketone were added to form a urethane acrylate oligomer. A product (d) was prepared.

(Tilt measurement)
For the measurement of the tilt, a displacement sensor LT-9010 (manufactured by KEYENCE) is 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. The degree of warpage of the laminate due to the formation of the cured film can be expressed by the difference in the tilt value of the laminate before and after the formation of the cured film. It can be said that the smaller this value is, the less deformation of the substrate due to the formation of the cured film.
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 measuring the tilt d ₀ in a state where an Ag reflection layer having a thickness of 100 nm was formed on a circular polycarbonate plate having a thickness of 1.1 mm and a diameter of 120 mm by sputtering, the urethane acrylate prepared in Production Example 1 was formed on the surface. After the oligomer composition (a) is applied by spin coating so that the thickness of the coating film becomes 100 ± 10 μm, a UV irradiation device (500 mJ / cm ² ) is obtained under an oxygen concentration of 20%. A laminate was prepared by forming a protective layer by irradiation with “J-cure 100” manufactured by JATEC (with a built-in high-pressure mercury lamp). The laminate was allowed to stand for two days and nights, and the tilt d ₁ was measured again, and (d ₁ -d ₀ ) is shown in Table 2 as an initial warp value.

Assuming that a cover layer of a Blu-ray disc, which is a large-capacity optical recording medium, is formed with the radiation curable composition of the present invention, the absolute value of the initial warp of the Blu-ray disc is preferably 0.4 ° or less. ing.
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 moduli at 37 ° C., 45 ° C., 65 ° C. and 80 ° C. are shown in Table 1 as E ′ (37), E ′ (45), E ′ (60) and E ′ (80), respectively.

(Creep resistance)
E '(37), E' (45), E '(60), E' (80) obtained above are substituted into the following formula (I) to obtain F, and the obtained F is a creep resistance coefficient. As shown in Table 1.

Formula (I) F = 1 / E ′ (37) + 1 / E ′ (60) −1 / E ′ (45)
(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. Stack 7 weights (shown in Fig. 3) and let them stand for 5 minutes, then remove the weight and glass plate and immediately observe the surface of the protective layer visually. Judgment was high. When the sand plast mark is visually observed in 75% or more of the entire area, “X” is evaluated, “△” is evaluated when it is visually observed in less than 75% of the entire area, and “◯” is evaluated when it is not visually observed. did. The results are shown in Table 2.

(Example 2)
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 2.
(Comparative Example 1)
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 2.
(Comparative Example 2)
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 2.

表２から明らかなように、耐クリープ係数が小さい保護層が形成された積層体では、耐クリープ性が高いことが分かる。また、８０℃における貯蔵弾性率が大きいと、保護層形成段階の変形である初期ソリが大きくなり、好ましくないので、８０℃における貯蔵弾性率が小さい実施例１および実施例２の保護層が好ましいことが示されている。

As can be seen from Table 2, the laminate in which the protective layer having a small creep resistance coefficient is formed has high creep resistance. Further, if the storage elastic modulus at 80 ° C. is large, the initial warp, which is a deformation in the protective layer formation stage, is not preferable, and thus the protective layers of Examples 1 and 2 having a low storage elastic modulus at 80 ° C. are preferable. It has been shown.

  Such a radiation curable composition can be advantageously used in applications requiring dimensional stability, particularly optical applications including optical recording media.

The radiation-curable composition of the present invention is less deformed when cured to form a laminate, and can provide a laminate having sufficient creep resistance on the surface of the cured product. 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 (4)

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 ′ (80) at 10 Hz and 80 ° C. is 500 MPa or less, storage elastic modulus E ′ (37) at 10 Hz and 37 ° C., storage elastic modulus E ′ (45) at 45 ° C., and storage at 60 ° C. A radiation curable composition, wherein a value F derived from the elastic modulus E ′ (60) by the following formula (I) is 0.006 or less.
Formula (I) F = 1 / E ′ (37) + 1 / E ′ (60) −1 / E ′ (45)   The radiation curable composition according to claim 1, wherein the radiation curable composition contains a compound having a urethane bond.   Hardened | cured material obtained by irradiating a radiation-curable composition of Claim 1 or 2 with a radiation.   The laminated body formed by laminating | stacking the cured film which consists of hardened | cured material of Claim 3 on a base material.

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