JP2011210335A - Photopolymerized resin composition for optical recording medium, cured material, and optical recoding medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a photopolymerized resin composition for an optical recording medium, which are excellent in curing and demolding, improves resistance to weatherability of the optical recording medium for recording and reproducing by a blue laser beam, and achieves highly reliable recording and reproducing; a cured material; and an optical recording medium having a layer formed by such a resin component.SOLUTION: The photopolymerized resin composition used for the optical recording medium which records and reproduces by the blue laser beam includes a photopolymerized resin and benzotriazole chemical compound having a predetermined configuration. The optical recording medium has a layer formed by the photopolymerized resin composition, and the layer is 1 to 200 μm in thickness.

Description

The present invention relates to a photopolymerizable resin composition for optical recording media, a cured product, and an optical recording medium. More specifically, the present invention relates to a photopolymerizable resin composition used for an optical recording medium for recording and reproducing with blue laser light, a cured product thereof, and an optical recording medium.

In recent years, with the development of information technology, a high-density and large-capacity optical recording medium (optical disk) for storing a large amount of digital information such as music, images and videos for a long period of time has been demanded. For example, the launch of digital high-definition broadcasting has led to the spread of large-screen LCDs and plasma televisions that are compatible with full high-definition, but DVD (digital versatile disc), which is a conventional optical recording medium, has a small recording capacity, High-quality moving images could not be recorded for a long time. Therefore, as a new standard for high-density and large-capacity optical recording media, a Blu-ray Disc (BD) that records and reproduces information with blue laser light has been developed and sold. In this new standard, a blue laser beam with a short wavelength (about 405 nm) and a high numerical aperture (NA) are adopted to increase the capacity, and the capacity is increased to about 5 times or more that of a DVD. Such an optical recording medium usually has a configuration in which a recording layer, a reflective layer, and a light transmission layer (protective layer) are laminated on a substrate, and at the time of recording and reproduction, a laser beam is irradiated to the recording layer through the light transmission layer, It is a mechanism for recording and playback.

Regarding conventional optical recording media, for example, Patent Document 1 discloses a substrate, a first reflective film, a resin layer formed in close contact with the substrate, and a second disposed in close contact with the resin layer. In an optical recording medium having a reflective film, as a photopolymerizable resin composition for forming a resin layer, a photopolymerizable resin and an additive mainly containing a specific benzotriazole derivative and having a specified content ratio A form containing a photopolymerization initiator is disclosed. Patent Document 1 also discloses that the photopolymerizable resin composition is used for bonding two substrates, and shows a compact disc (CD) or DVD as a specific form.

Japanese Patent No. 4406499

As described above, Patent Document 1 discloses a photopolymerizable resin composition used for an optical recording medium having a structure in which two substrates are bonded together. Examples of the optical recording medium having such a structure include a DVD for recording using an optical recording laser of about 650 nm. From the structural aspect, that is, a resin layer and a recording layer formed from a photopolymerizable resin composition. Therefore, it is easy to maintain weather resistance under high temperature and high humidity conditions. However, in a new standard optical recording medium, that is, an optical recording medium that records and reproduces information with blue laser light, the light transmission layer (protective layer) formed from the photopolymerizable resin composition is on one side of the substrate, and Since the structure exists only on the side on which the laser light is incident, the light transmission layer is easily affected by the external environment, and maintenance of durability, light resistance, and weather resistance becomes a problem.

By the way, when manufacturing an optical recording medium for recording / reproducing information with blue laser light, for example, a single-layer optical recording medium having one recording layer is usually a recording layer and a reflective layer (reflective film) on a substrate. Are provided in this order, and then a light transmission layer (protective layer, cover layer) is formed, and a hard coat layer is further formed as necessary. Of these, the formation of the light transmission layer is usually carried out after the resin composition is spin-coated on the metal layer constituting the reflective film and then cured. When curing is performed with one side in contact with the metal layer (reflection film) and the other side in contact with the gas phase (atmosphere), the metal ions and oxygen eluted from the reflection film interact with each other in the resin composition. This may cause an effect and cause uneven curing during curing. If there is a poorly cured part due to uneven curing, information recording / reproduction is affected, so there is room for contrivance to obtain a light-transmitting layer in which uneven curing is sufficiently suppressed.

As an optical recording medium, an optical recording medium having a plurality of recording layers may be manufactured for the purpose of increasing the recording capacity. For example, in a two-layer optical recording medium having two recording layers, a first recording layer and a reflective layer (reflective film) are usually provided on a substrate in this order, and then a mold (resin stamper or the like) is provided separately. ), And the intermediate layer and the reflective layer on the first recording layer are bonded together, and then the mold is peeled from the intermediate layer, and then the second recording layer and the reflective layer After that, as in the case of a single-layer optical recording medium, a light transmission layer (protective layer, cover layer) is formed, and a hard coat layer is further formed as necessary. Of these, the intermediate layer is usually formed by spin-coating the resin composition on the mold and then cured, but one side of the resin composition is in contact with the metal layer (reflective film) in this way. When curing is performed in a state where the surface is in contact with the mold, since one surface is not in a gas phase, it is not affected by oxygen as described above. However, since it is necessary to peel off the mold after curing in a state where it is in contact with the mold and to provide the next recording layer, it is a problem that the mold is easily peeled off.

An optical recording medium that records and reproduces information with blue laser light also has a light-transmitting layer only on one side of the substrate and has an asymmetric structure in the thickness direction of the optical recording medium. Compared to a DVD or the like having a symmetric structure, it has the property of being easily warped structurally. Moreover, although the film thickness of the light transmission layer may be larger than that of DVD or the like, in this case, curing shrinkage at the time of photopolymerization also increases, so that the substrate tends to warp. For this reason, the substrate may be warped in the opposite direction to the coating surface in advance, or correction may be performed by the playback / recording device, but warpage exceeding the allowable range (correctable range) occurs. Then, there are cases where accurate data recording and reproduction on the optical recording medium cannot be performed, and that data cannot be loaded into and removed from the reproduction / recording apparatus.
In order to improve or improve the warp of such an optical recording medium that records and / or reproduces with blue laser light, the photopolymerizable resin composition used therefor has a glass transition temperature (Tg) of 50 ° C. The use of soft materials such as the following is also being studied. However, when a soft material is used for such an optical recording medium, the light resistance of the optical recording medium is not sufficient because the soft material easily absorbs moisture, and it is easily affected by the external environment. There was a possibility of corrosion and coloring. Such a problem cannot be found when a hard material having a Tg exceeding 50 ° C. is used.

The present invention has been made in view of the above situation, and is excellent in curability and releasability, and can significantly improve the weather resistance of an optical recording medium for recording and / or reproduction with blue laser light, Provided is a photopolymerizable resin composition for optical recording media capable of realizing more reliable recording / reproduction, a cured product thereof, and an optical recording medium having a layer formed from such a resin composition. It is for the purpose.

The inventors of the present invention have studied various photopolymerizable resin compositions for use in optical recording media that perform recording and / or reproduction with blue laser light. Among these, the resin composition is used as a photopolymerizable resin and a benzotriazole having a specific structure. If it contains a compound, its mechanism is not known in detail, but it has been found that the light resistance, durability and weather resistance of the cured product are remarkably improved. For example, it is easily exposed to high temperature and high humidity such as in a car. In addition, the present inventors have found that recording / reproducing characteristics can be stably exhibited for a long time even when stored or used in a place exposed to a light source such as ultraviolet light or room light. Further, by using such a resin composition containing a benzotriazole compound having a specific structure, for example, one surface of the photopolymerizable resin composition is in contact with a metal (reflective film), and the other surface is a gas phase. It has also been found that uneven curing when the photopolymerizable resin composition is cured in contact with (atmosphere) is sufficiently suppressed. This is presumably because the interaction between the metal ion and oxygen is suppressed by the benzotriazole compound having a specific structure. Furthermore, it has been found that the cured product can exhibit an effect of being excellent in releasability from the mold, and has come up with the idea that the above problems can be solved brilliantly.
In the present specification, the “metal mold” refers to a mold made of, for example, metal, ceramic, glass, or resin, and includes a resin stamper or the like.

In addition, as described above, as a photopolymerizable resin composition used for an optical recording medium for recording and / or reproducing with blue laser light, a soft material having a low glass transition temperature (Tg) (50 ° C. or less) of a cured product. However, the present inventors may use a benzotriazole compound having a specific structure even when such a soft material is used as the photopolymerizable resin composition. It has been found that the optical recording medium can be improved without lowering the light resistance, and at the same time, the curing shrinkage can be reduced and the warp characteristics can be improved. That is, the present invention has also solved the problem recognized for the first time by using a soft material as a photopolymerizable resin composition by using a benzotriazole compound, which is also an important technique of the present invention. Has significant significance. Note that the productivity of the optical recording medium is also improved due to the small warpage during curing.

That is, the present invention relates to a photopolymerizable resin composition used for an optical recording medium for recording and / or reproduction by blue laser light, the photopolymerizable resin composition comprising: a photopolymerizable resin; Formula (1):

(Wherein R ¹ and R ² are the same or different and each represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, a carboxyl group, or a hydroxyl group). The optical recording medium has a layer formed from the photopolymerizable resin composition, and the thickness of the layer is 1 to 200 μm. It is a thing.
The present invention is also a cured product obtained by curing the photopolymerizable resin composition for optical recording media. The present invention is also an optical recording medium having a layer formed from the photopolymerizable resin composition for optical recording medium.
The present invention is described in detail below.

[Photopolymerizable resin composition for optical recording medium]
The photopolymerizable resin composition for optical recording media of the present invention (hereinafter also referred to as “photopolymerizable resin composition” or “resin composition”) is an optical recording medium that records and / or reproduces with blue laser light ( (Also referred to as “optical recording medium” or “optical disk”), and forms at least one layer constituting the optical recording medium. The blue laser beam is preferably a laser beam having a wavelength of about 405 nm, but it has been used for several decades by being used in an optical recording medium for recording with such a laser beam, that is, a so-called Blu-ray disc. The advantage that recording / reproduction can be stably performed over the above-described long period is remarkably exhibited. Such resin compositions include, for example, recordable write-once (BD-R) and rewritable (BD-RE) optical recording media as well as read-only (BD-ROM) optical recording media. Any of them can be preferably used.

The photopolymerizable resin composition contains a photopolymerizable resin and a benzotriazole compound as essential components, but may further contain other components as long as the effects of the present invention are not impaired. Moreover, you may use these content components 1 type (s) or 2 or more types, respectively.

As the photopolymerizable resin composition, a cured product obtained by curing the photopolymerizable resin composition has a glass transition temperature (Tg) of 50 ° C. or less. As a result, curing shrinkage during photopolymerization is reduced, and warping in the optical recording medium is sufficiently suppressed, so that it is possible to exhibit recording and reproduction characteristics more stably over a long period of time. In this case, even when a resin film having a large thickness is formed, curing shrinkage can be sufficiently reduced, so that it is suitable for a wider range of applications. The upper limit value of the Tg is more preferably 40 ° C., still more preferably 30 ° C. Moreover, it is preferable that a lower limit is -20 degreeC, More preferably, it is -10 degreeC, More preferably, it is 0 degreeC.

The glass transition temperature of the cured product of the photopolymerizable resin composition was measured for dynamic viscoelasticity under the following measurement conditions for a cured product obtained by curing the photopolymerizable resin composition by the following curing method. And use the value obtained. In addition, the glass transition temperature shall employ the temperature of the maximum tan δ value.
(Curing method)
A resin composition is applied on a polycarbonate substrate (PC substrate) having a thickness of 1.1 mm and a diameter of 120 mm with a spin coater at a thickness of 100 μm. The obtained PC substrate is irradiated with a flash of 15 times at a lamp height of 2 cm in a nitrogen atmosphere using a UV irradiator having a xenon flash UV lamp (model RC-801, manufactured by Xenon, USA) to complete the curing. . In addition, the irradiation integrated light quantity in 320-390 nm shall be about 0.5 J / cm < ² >.
(Measurement condition)
The dynamic viscoelasticity is measured under the conditions of a tensile mode, a frequency of 1 Hz, a clamp distance of 25 mm, an amplitude of 0.1%, and a heating rate of 5 ° C./min.

<Benzotriazole compound>
The benzotriazole compound in this invention is a compound represented by the said General formula (1), and can use 1 type (s) or 2 or more types.
Here, as a reagent for improving light resistance, reagents such as benzotriazole ultraviolet absorbers and hindered amine light stabilizers (HALS) are known. However, these reagents have the above-mentioned general formula in terms of structure and operation. This is clearly different from the benzotriazole compound represented by (1). The benzotriazole compound represented by the general formula (1) has an N = N—N (R ² ) group in the structure, but in a benzotriazole-based ultraviolet absorber or the like, this part is NN (A). It is an -N group, and exhibits an ultraviolet absorption action and a light stabilization action by the substituent A of the N atom located in the middle. However, since the benzotriazole compound represented by the general formula (1) does not have such a substituent A, it exhibits an ultraviolet absorption action and a light stabilization action by the same mechanism as that of the benzotriazole ultraviolet absorber and the like. It is considered impossible.

In the general formula (1), R ¹ and R ² are the same or different and each represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, a carboxyl group, or a hydroxyl group. Of these, a hydrogen atom or a carboxyl group is preferred. More preferably, R ¹ is a carboxyl group (—COOH), which only increases the adhesion between the resin layer formed from the resin composition and other layers (reflection film, etc.). Therefore, the optical recording medium can be more excellent in light resistance. R ² is more preferably a hydrogen atom.

Specifically, as the benzotriazole compound represented by the general formula (1), for example, compounds represented by the following general formulas (2-1) to (2-6) are preferable, and the benzotriazole compound is preferable. A form in which is at least one compound selected from the group consisting of these compounds is also a preferred form of the present invention.

The content of the benzotriazole compound is preferably 0.0001 to 0.5 parts by weight with respect to 100 parts by weight of the photopolymerizable resin. If it is 0.0001 weight part or more, it will become possible to fully exhibit the effect of this invention. In addition, when the amount is 0.5 parts by weight or less, the light resistance of the layer (cured product, cured film) formed from the resin composition is further improved, and the layer is more difficult to absorb moisture. It is possible to realize an optical recording medium that is further suppressed and further excellent in long-term storage stability. The upper limit of the content is more preferably 0.3 parts by weight, still more preferably 0.1 parts by weight, and particularly preferably 0.04 parts by weight. The lower limit is more preferably 0.0005 parts by weight, and still more preferably 0.001 parts by weight.

<Photopolymerizable resin>
The photopolymerizable resin may be any resin that can be polymerized (cured) with light such as ultraviolet rays, but includes one or more compounds having a (meth) acryloyl group ((meth) acrylate compound). Is preferred. More preferably, as the (meth) acrylate compound, (I ′) (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone, and (III) urethane (meta) other than the component (I ′). ) Using at least one compound selected from the group consisting of an acrylate compound, a polyester (meth) acrylate compound, an epoxy (meth) acrylate compound, and an oligomer or polymer having a (meth) acryloyl group in the side chain. Thus, an optical recording medium excellent in various physical properties can be suitably obtained. Moreover, you may contain (meth) acrylate compounds other than these as needed.

The (meth) acrylate compound (for example, (meth) acrylate compound other than the above (I ′) and (III) components, etc.) also has an average acrylic equivalent to its total amount in the photopolymerizable resin. It is suitable to use so that it may become 140 or more. Thereby, the warp of the optical recording medium is further reduced, and the operational effects of the present invention can be more fully exhibited. More preferably, it is 150 or more, More preferably, it is 180 or more. Moreover, it is suitable that it is 400 or less, and thereby, it is possible to further suppress the formation of dents or the like in the optical recording medium, and to further sufficiently exhibit long-term storage stability. More preferably, it is 350 or less, More preferably, it is 300 or less.
In the present invention, the acrylic equivalent is 150 or more, and the cured product obtained by curing the photopolymerizable resin composition has a glass transition temperature (Tg), a loss tangent tan δ at Tg, and storage elasticity. When the ratio is within the above-mentioned or below-described preferable range, it becomes possible to provide an optical recording medium that is further excellent in warp characteristics and the like. In particular, within each preferred range, the smaller the Tg or storage modulus, and the greater the acrylic equivalent or loss tangent tan δ, the better the trend.

The average acrylic equivalent to the total amount of the (meth) acrylate compound is determined by the sum of Mx × Ax ÷ A.
Mx is the molecular weight (*) of the (meth) acrylic acid ester ((meth) acrylate compound) x, and when the (meth) acrylic acid ester x has one (meth) acryloyl group, the (meth) The value of the molecular weight of the acrylate ester x is “Mx”. When there are two or more (meth) acryloyl groups, the molecular weight of (meth) acrylic acid ester x divided by the number of (meth) acryloyl groups is “Mx”.
Ax is the mass (part by mass) of the (meth) acrylic ester x.
A is the sum total (parts by mass) of the total amount of all (meth) acrylic acid esters contained in the resin composition.
* As the molecular weight here, the number average molecular weight (Mn) is used for the above (III) component, and the value calculated as the sum of the atomic weights of the constituent elements is used for the other (meth) acrylate compounds. To do.

Among the above (meth) acrylate compounds, (I ′) component, that is, (meth) acrylate compounds modified with alkylene oxide and / or ε-caprolactone, are modified with (I) alkylene oxide and / or ε-caprolactone. In addition, a (meth) acrylate compound having two radically polymerizable unsaturated groups in the molecule and (II) three radically polymerizable unsaturated groups modified in the molecule with alkylene oxide and / or ε-caprolactone. It is preferable to use together with the (meth) acrylate compound having the above. That is, the component (I ′) is (I) a (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone and having two radically polymerizable unsaturated groups in the molecule, and (II) alkylene. A form composed of a (meth) acrylate compound modified with an oxide and / or ε-caprolactone and having three or more radically polymerizable unsaturated groups in the molecule is also a preferred form of the present invention. This makes it possible to provide an optical recording medium that can simultaneously exhibit various physical properties in a more balanced manner.

A form particularly suitable as the photopolymerizable resin is (I) a (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone and having two radically polymerizable unsaturated groups in the molecule; ) A (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone and having 3 or more radically polymerizable unsaturated groups in the molecule, and (III) urethane other than (I) and (II) Essentially, a (meth) acrylate compound, a polyester (meth) acrylate compound, an epoxy (meth) acrylate compound, and at least one compound selected from the group consisting of an oligomer or polymer having a (meth) acryloyl group in the side chain And, if necessary, (IV) (meth) actives other than the components (I) to (III) It contains a related compound. As a result, not only the weather resistance of the cured product is improved, but also various physical properties such as transparency and film thickness stability can be sufficiently exhibited, and warpage and permanent deformation can be stably suppressed for a long period of time, and surface smoothness can be achieved. It is possible to further exhibit the operational effect of realizing high-reliability recording and reproduction with higher reliability. Each of these components may be used alone or in combination of two or more, and may further contain other components as long as the effects of the present invention are not impaired.
Hereinafter, each compound corresponding to the above (I) is referred to as “compound (I)”, and an aggregate of compounds (I) (that is, a generic term of one or more compounds (I)) is referred to as “component (I)”. Call it. The above (II) to (IV) are also referred to in the same manner.

In the photopolymerizable resin, the content ratio of the components (I), (II), (III) and (IV) is (I) 10 to 60% by mass, II) 20 to 60% by mass, (III) 10 to 50% by mass, and (IV) 0 to 30% by mass are preferable. By setting to such a range, the obtained cured product is excellent in various physical properties such as light resistance, durability, weather resistance, transparency, residual film properties, and film thickness uniformity. That is, by satisfying all the above numerical ranges, these performances can be fully exhibited at the same time in a well-balanced manner, and a more reliable recording / reproducing function can be exhibited over a long period of time.

[About component (I)]
The compound (I) is a (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone and having two radical polymerizable unsaturated groups in the molecule (“modified with alkylene oxide and / or ε-caprolactone”). Also referred to as “bifunctional (meth) acrylate compound”. That is, a bifunctional (meth) acrylate compound modified with alkylene oxide, a bifunctional (meth) acrylate compound modified with ε-caprolactone, and a bifunctional (meth) modified with alkylene oxide and ε-caprolactone. ) Any one or more of acrylate compounds. Such a compound is a (meth) acrylate obtained by modifying a polyhydric alcohol having two active hydrogens (dihydric alcohol) with alkylene oxide and / or ε-caprolactone, that is, dihydric alcohol with alkylene oxide and / or ε. -(Meth) acrylic acid ester of a compound to which caprolactone is added, (meth) acrylic acid ester of a dihydric alcohol having an alkylene oxide skeleton, and the like.

Examples of the dihydric alcohol and the dihydric alcohol having an alkylene oxide skeleton include (poly) ethylene glycol, (poly) propylene glycol, butanediol, neopentyl glycol, hexanediol, bisphenol A, S, and F. And may have a substituent. Further, it may be a dihydric alcohol having two or more alkylene oxide skeletons such as poly (ethylene-propylene) glycol.

The alkylene oxide is preferably an alkylene oxide having 2 to 18 carbon atoms, for example. More preferably, it is an alkylene oxide having 2 to 8 carbon atoms, such as ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, 1-butene oxide, 2-butene oxide, trimethylethylene oxide, tetramethylene oxide, tetramethylethylene oxide, butadiene. Examples include monooxide, octylene oxide, styrene oxide and the like. Among these, alkylene oxides having 2 to 4 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide are more preferable. Particularly preferred are ethylene oxide and propylene oxide.
In addition, the said alkylene oxide may be 1 type, and 2 or more types may be sufficient as it.

The number of repetitions of alkylene oxide and / or ε-caprolactone in the compound (I) is 2 to 16 mol per 1 mol of compound (I) as the average number of repetitions of the total amount of alkylene oxide and ε-caprolactone. Is preferred. As a result, the storage elastic modulus of the cured product can be adjusted more appropriately, and an optical recording medium having further excellent long-term storage stability can be provided. More preferably, it is 3-14 mol, Most preferably, it is 3-12 mol. If it is less than 2 moles, the elastic modulus of the cured product is increased and warpage due to curing shrinkage is increased, and if it is more than 16 moles, compatibility with the resin is deteriorated.

Specific examples of the compound (I) include (poly) ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and the like. Ethylene glycol di (meth) acrylate; (poly) propylene glycol di (propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, etc. (Meth) acrylate; Diacrylate of alkylene oxide adduct of bisphenol A; Diacrylate of alkylene oxide adduct of neopentyl glycol; - diacrylate caprolactone adduct; of hydroxypivalic acid neopentyl glycol alkylene oxide adduct di (meth) acrylate; di (meth) acrylate of neopentyl glycol hydroxypivalate ε- caprolactone adduct.

[Regarding component (II)]
The compound (II) is a (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone and having at least three radically polymerizable unsaturated groups in the molecule (“alkylene oxide and / or ε-caprolactone”). It is also referred to as “modified (functional) trifunctional or higher functional (meth) acrylate compound”. That is, a tri- or higher functional (meth) acrylate compound modified with alkylene oxide, a tri- or higher functional (meth) acrylate compound modified with ε-caprolactone, and a tri- or higher functional group modified with alkylene oxide and ε-caprolactone Any one or more of (meth) acrylate compounds. Such a compound is a (meth) acrylate obtained by modifying a polyhydric alcohol having 3 or more active hydrogens (a trihydric or higher polyhydric alcohol) with an alkylene oxide and / or ε-caprolactone, that is, a polyhydric or higher polyvalent. Examples include (meth) acrylic acid esters of compounds obtained by adding alkylene oxide and / or ε-caprolactone to alcohols, and (meth) acrylic acid esters of trivalent or higher alcohols having an alkylene oxide skeleton.

Examples of the trihydric or higher polyhydric alcohol include trimethylolpropane, glycerin, pentaerythritol, ditrimethylolpropane, dipentaerythritol, and the like, which may have a substituent.
The alkylene oxide and the number of alkylene oxides and / or ε-caprolactone in the compound (II) are the same as those described above for the compound (I).

Specific examples of the compound (II) include, for example, tri (meth) acrylate of an alkylene oxide adduct of trimethylolpropane, tri (meth) acrylate of an ε-caprolactone adduct of trimethylolpropane, and an alkylene oxide adduct of glycerin. Tri (meth) acrylate, tri (meth) acrylate of glycerin ε-caprolactone adduct, tetra (meth) acrylate of pentaerythritol alkylene oxide adduct, tetra (meth) acrylate of pentaerythritol ε-caprolactone adduct, Examples include hexa (meth) acrylate of an alkylene oxide adduct of dipentaerythritol, hexa (meth) acrylate of an ε-caprolactone adduct of dipentaerythritol, and the like.

More preferably, the compound (II) is a compound obtained by using a polyhydric alcohol having a quaternary carbon (for example, trimethylolpropane, pentaerythritol, dipentaerythritol, etc.) as the polyhydric alcohol. This makes it possible to obtain a cured product (protective layer) that is further excellent in light resistance. Thus, the form in which the (II) component contains a (meth) acrylate compound obtained by modifying a trihydric or higher polyhydric alcohol having a quaternary carbon with an alkylene oxide and / or ε-caprolactone is also a suitable form. It is. Among them, the proportion of the (meth) acrylate compound in the total amount of the component (II) of 100% by mass is more preferably 50% by mass or more, further preferably 70% by mass or more, and particularly preferably 90% by mass. As described above, most preferably 100% by mass, that is, the component (II) is composed of only a (meth) acrylate compound obtained by modifying a trihydric or higher polyhydric alcohol having a quaternary carbon with alkylene oxide and / or ε-caprolactone. In addition, the photopolymerizable resin may not contain a (meth) acrylate compound obtained by modifying a trihydric or higher polyhydric alcohol having a tertiary carbon with alkylene oxide and / or ε-caprolactone. Most preferred.

The compound (II) preferably has a molecular weight of 3000 or less. When it is 3000 or less, the compatibility between the materials contained in the resin composition is further improved, and a cured product (protective layer) having superior surface smoothness can be suitably obtained. More preferably, it is 2500 or less, More preferably, it is 2000 or less. Moreover, it is preferable that it is 200 or more, More preferably, it is 300 or more, More preferably, it is 400 or more.
Thus, the form in which the component (II) includes a compound having a molecular weight of 3000 or less is also a suitable form. Among them, the ratio of the compound in the total amount of the component (II) is 100% by mass. The content is more preferably 50% by mass or more, whereby the compatibility between the materials is further improved, and a cured product having further excellent surface smoothness can be obtained. More preferably, it is 70 mass% or more, Especially preferably, it is 90 mass% or more, Most preferably, it is 100 mass%, That is, it is using only the compound whose molecular weight is 3000 or less as said (II) component.

[Regarding component (III)]
The compound (III) is a compound other than the components (I) and (II) described above, and is a urethane (meth) acrylate compound, a polyester (meth) acrylate compound, an epoxy (meth) acrylate compound, and a side chain. It is at least one compound selected from the group consisting of oligomers or polymers having a (meth) acryloyl group. Among these, it is preferable to use at least a urethane (meth) acrylate compound because of excellent long-term storage stability. In addition, urethane (meth) acrylate compounds are preferable from the viewpoint of a wide design range of mechanical properties. Thus, the form in which the component (III) contains at least a urethane (meth) acrylate compound is also a preferred form of the present invention. Further, the compound (III) is preferably a compound having two or more radically polymerizable unsaturated groups in one molecule.
The urethane (meth) acrylate compound, the polyester (meth) acrylate compound, and the epoxy (meth) acrylate compound may be in any form of a monomer, an oligomer, or a polymer, but are preferably an oligomer or a polymer. .

The compound (III) also preferably has a number average molecular weight (Mn) of 500 or more, and preferably 10,000 or less. When it is 500 or more, the curing speed and the strength of the cured product (protective layer) become more sufficient, and when it is 10,000 or less, the mixing time when adjusting the wettability with the substrate and the resin composition, It becomes more suitable in terms of workability at the time of coating due to high viscosity, and further reduces, for example, the warp of a laminate (optical recording medium) obtained by applying and curing to a plastic substrate. It becomes possible. Moreover, by being 10,000 or less, the compatibility of each material contained in a resin composition improves further, and it becomes possible to obtain the hardened | cured material excellent in surface smoothness suitably. The number average molecular weight is more preferably 1000 or more, further preferably 1500 or more, more preferably 8000 or less, and still more preferably 7000 or less.

Thus, although the form in which the said (III) component contains the compound whose molecular weight is 10,000 or less is also a suitable form, the ratio of the said compound which occupies for the total amount of said (III) component of 100 mass% is especially. The content is more preferably 50% by mass or more, whereby the compatibility between the materials is further improved, and a cured product having further excellent surface smoothness can be obtained. More preferably, it is 70% by mass or more, particularly preferably 90% by mass or more, most preferably 100% by mass, that is, only the compound having a molecular weight of 10,000 or less is used as the component (III).

The compound (III) preferably further has a molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of 1 or more, and preferably 10 or less. When it is 1 or more, the conversion rate, the strength of the cured product, the mixing time of each component, and the like become more sufficient, and an optical recording medium can be obtained with higher productivity. The molecular weight distribution is more preferably in the range of 1 to 7, still more preferably 1 to 5.

In the present specification, the number average molecular weight (Mn), the weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) are obtained under the conditions of tetrahydrofuran (THF) as a mobile phase, a temperature of 40 ° C. and a flow rate of 0.3 mL / min. Thus, using a column TSK-gel SuperHM-H made by Tosoh Corporation and one TSK-gel SuperH2000, a gel permeation chromatography (GPC) apparatus made by Tosoh Corporation HLC-8220 GPC is a value converted to standard polystyrene. .

As the urethane (meth) acrylate compound, a compound obtained by a reaction of a polyhydric alcohol, an organic polyisocyanate, and a hydroxyl group-containing (meth) acrylate is preferably used. This reaction may be performed by a usual method. For example, it is preferable to use a tin-containing compound (for example, dibutyltin laurate, tin octenoate, etc.) as a catalyst for efficiently performing this reaction. In this case, from the viewpoint of reaction efficiency, it is also preferable to use another catalyst (for example, triethylenediamine) in combination.

The polyhydric alcohol may be either a saturated compound or an unsaturated compound. For example, ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl- Examples include 1,5-pentanediol, polyethylene glycol, polypropylene glycol, 1,4-dimethylolbenzene, glycerin, trimethylolpropane, pentaerythritol, polytetramethylene glycol, polyester polyol, polycaprolactone polyol, and the like. Methylene glycol is preferred.

Examples of the organic polyisocyanate include tolylene diisocyanate, isophorone diisocyanate, and xylylene diisocyanate. Among them, isophorone diisocyanate is preferable.
Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 1,4-butanediol mono (meth) acrylate, and the like.

As the polyester (meth) acrylate compound, a compound obtained by a reaction of a polybasic acid or an anhydride acid thereof, a polyhydric alcohol and (meth) acrylic acid is preferably used. Just do it.
The polybasic acid or its anhydride acid may be either a saturated compound or an unsaturated compound, such as maleic acid, succinic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, etc. In addition, these anhydride acids are mentioned.
About the said polyhydric alcohol, the compound etc. which were mentioned above are mentioned.

The epoxy (meth) acrylate compound is an epoxy poly (meth) acrylate obtained by a reaction between an epoxy resin and (meth) acrylic acid, or a carboxyl obtained by a reaction between the epoxy (meth) acrylate and a polybasic acid anhydride. Although acid-modified epoxy (meth) acrylate is preferably used, this reaction may be performed by a usual method.
Examples of the epoxy resin include phenol novolac epoxy resin, cresol novolac epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, trisphenol methane type epoxy resin, polybutanediene modified epoxy resin, alicyclic epoxy resin, Examples thereof include brominated phenol novolac epoxy resins, brominated bisphenol A type epoxy resins, amino group-containing epoxy resins and the like.
Examples of the polybasic acid anhydride include maleic anhydride, succinic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and the like.

The oligomer or polymer having a (meth) acryloyl group in the side chain is an oligomer or polymer having a (meth) acryloyl group in the side chain and two or more radically polymerizable unsaturated groups in the molecule. There is no particular limitation.

The compound (III) preferably has a glass transition temperature (also referred to as “Tg”) of a single cured product of −50 to 50 ° C. By using the compound (III) having a Tg of −50 ° C. or higher, permanent deformation due to pressure marks or dents can be more sufficiently suppressed in the cured product (protective layer) obtained from the photopolymerizable resin composition. Moreover, the curvature of the said hardened | cured material is more fully reduced as it is 50 degrees C or less. More preferably, it is -45 degreeC or more, More preferably, it is -40 degreeC or more, More preferably, it is 40 degreeC or less, More preferably, it is 30 degreeC or less, Most preferably, it is 20 degreeC or less.
The glass transition temperature here is a value obtained by a dynamic viscoelasticity measurement method under the following measurement conditions for a cured product obtained by curing the above-described compound (III) alone, and the temperature of the maximum tan δ value. Shall be adopted.
<Measurement conditions>
The dynamic viscoelasticity is measured under the conditions of a tensile mode, a frequency of 1 Hz, a clamp distance of 25 mm, an amplitude of 0.1%, and a heating rate of 5 ° C./min.

[(IV) component]
The compound (IV) is a (meth) acrylate compound other than the components (I), (II) and (III), and may be included in the photopolymerizable resin as necessary. Such a compound (IV) is preferably a compound that can be co-cured with any one or more of the components (I), (II), and (III), and is in the form of a monomer. Is preferred. By including compound (IV), there exists an effect that the liquid viscosity and the physical property of hardened | cured material can be adjusted, for example. Compound (IV) may be one type of compound or two or more types.

Examples of the compound (IV) include a vinyl monomer represented by the general formula (B) described later, a (meth) acrylate compound not modified with alkylene oxide or ε-caprolactone, and a monofunctional (meth). An acrylate compound etc. are mentioned. Specifically, 1 type (s) or 2 or more types, such as the vinyl-type monomer represented by the general formula (B) mentioned later and the following compound, are mentioned.
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1-adamantyl (meth) Acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, Methoxydiethylene glycol (meth) acrylate, butoxydiethylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, trif Monofunctional (meth) acrylate compounds such as oloethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and dicyclopentanyl (meth) acrylate ;

1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, 2 -Butyl-2-ethyl-1,3-propanediol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, pentacyclopentadecane dimethanol di (meth) acrylate, di (meta) of bisphenol A diglycidyl ether ) Acrylic acid adduct, cyclohexanedimethanol di (meth) acrylate, norbornane dimethanol di (meth) acrylate, p-menthane-1,8-diol di (meth) acrylate, p-menthane-2,8-diol di (meth) acrylate , P-men -3,8-diol di (meth) acrylate, bicyclo [2.2.2] -octane-1-methyl-4-isopropyl-5,6-dimethylol di (meth) acrylate, bis ((meth) acryloxyneopentyl Glycol) adipate, bifunctional (meth) acrylate compounds such as tricyclodecane di (meth) acrylate;

Trifunctional or higher (meth) such as trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate (Meth) acrylic acid derivatives such as acrylate compounds;

Methoxyethyl (meth) acrylate, 2-methoxy-2-methylethyl (meth) acrylate, 2-methoxy-1-methylethyl (meth) acrylate, ethoxyethyl (meth) acrylate, 2-ethoxy-2-methylethyl (meth) ) Acrylate, 2-ethoxy-1-methylethyl (meth) acrylate, propoxyethyl (meth) acrylate, propoxypropyl (meth) acrylate, isopropoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, etc. (Meth) acrylic derivatives;

4- (meth) acryloyloxymethyl-2-methyl-2-ethyl-1,3-dioxolane, 4- (meth) acryloyloxymethyl-2-methyl-2-isobutyl-1,3-dioxolane, 4- (meth) ) 1,3-dioxolane-based monomers such as acryloyloxymethyl-2-cyclohexyl-1,3-dioxolane, 4- (meth) acryloyloxymethyl-2,2-dimethyl-1,3-dioxolane, and the like.

As said compound (IV), from the point with favorable adhesiveness with the polycarbonate substrate normally used, for example, following formula (B):

(In the formula, R ^a is the same or different and represents an alkylene group having 2 to 8 carbon atoms. R ^b represents a hydrogen atom or a methyl group. M is a positive integer.) Vinyl monomers (also referred to as “heterogeneous polymerizable monomers”) can be preferably used.
Specific examples of the vinyl monomer represented by the above formula (B) include the following compounds.
(Meth) acrylic acid 2-vinyloxyethyl, (meth) acrylic acid 3-vinyloxypropyl, (meth) acrylic acid 2-vinyloxypropyl, (meth) acrylic acid 1-vinyloxypropyl, (meth) acrylic acid 1-methyl 2-vinyloxyethyl, 4-vinyloxybutyl (meth) acrylate, 3-vinyloxybutyl (meth) acrylate, 2-vinyloxybutyl (meth) acrylate, 1-methyl-3-vinyloxypropyl (meth) acrylate, (meth) 2-methyl-3-vinyloxypropyl acrylate, 1-methyl-2-vinyloxypropyl (meth) acrylate, 1,1-dimethyl-2-vinyloxyethyl (meth) acrylate, 6-vinyl (meth) acrylate Roxyhexyl, (meth) acrylic acid 4-vinyloxycyclohexyl, (meth) acrylic acid -Vinyloxymethylcyclohexylmethyl, (meth) acrylic acid 3-vinyloxymethylcyclohexylmethyl, (meth) acrylic acid 2-vinyloxymethylcyclohexylmethyl, (meth) acrylic acid 4-vinyloxymethylphenylmethyl, (meth) acrylic 3-vinyloxymethylphenylmethyl acid, 2-vinyloxymethylphenylmethyl (meth) acrylate,

2- (2-vinyloxyethoxy) ethyl (meth) acrylate, 2- (2-vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (2-vinyloxyethoxy) propyl (meth) acrylate, ( 2- (2-vinyloxyisopropoxy) propyl (meth) acrylate, 2- (2-vinyloxyethoxy) isopropyl (meth) acrylate, 2- (2-vinyloxyisopropoxy) isopropyl (meth) acrylate, ( 2- (2- (2-vinyloxyethoxy) ethoxy} ethyl (meth) acrylate, 2- {2- (2-vinyloxyisopropoxy) ethoxy} ethyl (meth) acrylate, 2-{(meth) acrylic acid 2- (2-vinyloxyisopropoxy) isopropoxy} ethyl, (meth) acrylic acid 2- {2- (2-vinyloxyethoxy) ethoxy Propyl, 2- (2- (2-vinyloxyethoxy) isopropoxy} propyl (meth) acrylate, 2- {2- (2-vinyloxyisopropoxy) ethoxy} propyl (meth) acrylate, (meth) acryl Acid 2- {2- (2-vinyloxyisopropoxy) isopropoxy} propyl, (meth) acrylic acid 2- {2- (2-vinyloxyethoxy) ethoxy} isopropyl, (meth) acrylic acid 2- {2- (2-vinyloxyethoxy) isopropoxy} isopropyl, (meth) acrylic acid 2- {2- (2-vinyloxyisopropoxy) ethoxy} isopropyl, (meth) acrylic acid 2- {2- (2-vinyloxyiso) Propoxy) isopropoxy} isopropyl, (meth) acrylic acid 2- [2- {2- (2-vinyloxyethoxy) ethoxy} Xyl] ethyl, 2- (2- {2- (2-vinyloxyisopropoxy) ethoxy} ethoxy] ethyl (meth) acrylate, 2- (2- [2- {2- (2- Vinyloxyethoxy) ethoxy} ethoxy] ethoxy) ethyl.

Among these vinyl monomers, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxyethyl (meth) acrylate, 2-vinyloxypropyl (meth) acrylate, 1-methyl-2- (meth) acrylate Vinyloxyethyl, 4-vinyloxybutyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxycyclohexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, (meth) acryl 2- (2-vinyloxyethoxy) ethyl acid, 2- (2-vinyloxyisopropoxy) propyl (meth) acrylate, 2- {2- (2-vinyloxyethoxy) ethoxy} ethyl (meth) acrylate Is preferred. Of these, 2- (2-vinyloxyethoxy) ethyl (meth) acrylate is preferable.

The compound (IV) is particularly preferably a bifunctional or higher (meth) acrylate compound (that is, a polyfunctional (meth) acrylate compound) or a vinyl monomer represented by the above general formula (B) (heteropolymeric property). Monomer).

[Other polymerizable components]
The photopolymerizable resin may further contain one or more of the following unsaturated compounds as other co-curable components (other polymerizable components) as necessary.
Styrene monomers such as styrene, vinyltoluene, 4-t-butylstyrene, α-methylstyrene, 4-chlorostyrene, 4-methylstyrene, 4-chloromethylstyrene, divinylbenzene; diallyl phthalate, diallyl isophthalate, cyanuric Allyl ester monomers such as triallyl acid and triallyl isocyanurate; vinyl ether monomers such as triethylene glycol divinyl ether, cyclohexane dimethanol divinyl ether, hydroxybutyl vinyl ether, dodecyl vinyl ether; trimethylolpropane diallyl ether, pentaerythritol triallyl ether, allyl Glycidyl ether, allyl ether of methylol melamine, adipic acid ester of glyceryl diallyl ether, allyl acetal Allyl ether monomers such as allyl ether of methylol glyoxalurein; maleic acid ester monomers such as diethyl maleate and dibutyl maleate; Fumarate monomers such as dibutyl fumarate and dioctyl fumarate; (meth) acryloylmorpholine; N-vinylformamide; N-vinylpyrrolidone and the like.

The content ratio of these unsaturated compounds is preferably 0 to 30% by mass with respect to 100% by mass of the total amount of the (meth) acrylate compound (components (I) to (IV)) and the unsaturated compound. is there. However, considering the recyclability of the resin composition when the photopolymerizable resin composition is subjected to the spin coating method, for example, the lower the content of the unsaturated compound, the better. More preferably, it is 20 mass% or less, More preferably, it is 10 mass% or less, Most preferably, it is substantially free of these unsaturated compounds.
Hereinafter, the (meth) acrylate compound (components (I) to (IV) and the like) and the unsaturated compound are collectively referred to as “photopolymerizable resin”. That is, the photopolymerizable resin is preferably composed of a (meth) acrylate compound (preferably the above components (I) to (III) (or (I) to (IV) component when the component (IV) is further included)). Further, the unsaturated compound may be included. In other words, when the photopolymerizable resin does not contain the unsaturated compound, the (meth) acrylate compound (preferably the components (I) to (III) (and further the component (IV) is included). Means a component consisting of the above components (I) to (IV)), and in the case of containing the unsaturated compound, a (meth) acrylate compound (preferably the components (I) to (III) above (further (IV) When the component is included, it means a mixture of the above components (I) to (IV))) and the unsaturated compound.

<Photopolymerization initiator>
The photopolymerizable resin composition preferably further contains a photopolymerization initiator. By including the photopolymerization initiator, there is an effect that it can be quickly cured by light irradiation. As a photoinitiator, the photoradical polymerization initiator which generate | occur | produces a polymerization start radical by irradiation of a light beam is suitable, These 1 type (s) or 2 or more types can be used.

Examples of the photo radical polymerization initiator include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy -2-propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4 -Morpholinophenyl) butanone, oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone}, 2-hydroxy-1- {4- [4- (2-hydroxy-2) Acetophenones such as -methylpionyl) benzyl] phenyl} -2-methylpropan-1-one Benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4′-methyl-diphenyl sulfide, 3, 3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyl) Benzophenones such as (oxy) ethyl] benzenemethananium bromide, (4-benzoylbenzyl) trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthio Thioxanthones such as xanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-hydroxy) -3,4-dimethyl-9H-thioxanthone-9-one mesochloride Etc.

Among the radical photopolymerization initiators, acetophenones are preferable. Specifically, 1-hydroxycyclohexyl phenyl ketone, oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] Propanone}, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) benzyl] phenyl} -2-methylpropane -1-one is preferred. Among them, oligo {2-hydroxy-2 is used because the durability of the optical recording medium using the resin layer formed from the resin composition as a protective layer is improved and an increase in warpage during the heat resistance test is suppressed. -Methyl-1- [4- (1-methylvinyl) phenyl] propanone} is particularly preferred.

In the said photopolymerizable resin composition, it is suitable as content of the said photoinitiator that it is 1-10 mass parts with respect to 100 mass parts of total amounts of the said photopolymerizable resin. When the amount is 1 part by mass or more, the photopolymerizable resin composition can be more fully cured, and when the amount is 10 parts by mass or less, odor generation and coloring of the cured product can be sufficiently suppressed, and photopolymerizability is achieved. The recyclability of the resin composition and the long-term storage stability of the cured product can be further improved. More preferably, it is 1-5 mass parts, More preferably, it is 1-3 mass parts. In particular, when the amount is 3 parts by mass or less, curing shrinkage is further suppressed, and the change in weight before and after curing (weight reduction) is further reduced. On the other hand, in the present invention, the amount of the photopolymerization initiator used is small. Even if it exists, there exists an advantageous effect at the point that sufficient sclerosis | hardenability etc. can be exhibited.

<Polymerization inhibitor>
The photopolymerizable resin composition preferably further contains a polymerization inhibitor. By using the polymerization inhibitor in combination, coloring and corrosion of the optical recording medium are more sufficiently suppressed, and the compatibility between the benzotriazole compound and the photopolymerizable resin is further improved, resulting from the action of the benzotriazole compound. The effect is more fully demonstrated. Therefore, it becomes possible to give the hardened | cured material which was further excellent in light resistance. Furthermore, the mold releasability of the cured product is improved and curing unevenness is reduced.

Examples of the polymerization inhibitor include the following general formula (3):

(Wherein R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are the same or different and have a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group having 1 to 8 carbon atoms, a carboxyl group, or a substituent. Or an alkyl or alkenyl group having 1 to 24 carbon atoms, or the following general formula (4):

(Wherein R ⁸ represents a hydrogen atom or an alkyl or alkenyl group having 1 to 20 carbon atoms which may be substituted with a halogen atom). Note that at least one of R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ represents a hydroxyl group. It is preferable that it is a compound represented by this.

The alkyl group or alkenyl group that R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ^{8 in the} general formula (3) or (4) may represent may be branched, It may be linear. In addition, when R < ⁴ >, R < ⁵ >, R < ⁶ > and R < ⁷ > in the said General formula (3) represent an alkyl group or an alkenyl group, these groups may have a substituent. As the substituent, —COOH, —COOR ⁹ , —OCOR ⁹ or —OR ⁹ (wherein R ⁹ represents an alkyl group or an alkenyl group, preferably an alkyl group or alkenyl group having 1 to 8 carbon atoms). And the like.
Specific examples of such an alkyl group or alkenyl group include methyl groups, propyl groups, butyl groups, hexyl groups, octyl groups, nonyl groups, dodecyl (lauryl) groups, alkyl groups such as neopentyl groups, octadecyl groups, etc .; Examples include alkenyl groups such as propenyl and 2-butenyl; alkyl groups or alkenyl groups having a substituent such as 4-carboxybutyl group, 2-methoxycarbonylethyl group, methoxyethyl group and ethoxymethyl group.
Specific examples of the alkoxyl group having 1 to 8 carbon atoms include a methoxy group, an ethoxy group, a butoxy group, and an octyloxy group. Moreover, as a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom is preferable.

R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are preferably such that at least two of them represent a hydroxyl group. In this case, the other includes a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group having 1 to 8 carbon atoms, or an alkyl group or alkenyl group having 1 to 24 carbon atoms which may have a substituent. It is preferable to represent. Preferably it is 1-20 as a carbon atom number of an alkyl group or an alkenyl group, More preferably, it is 1-18.
R ⁸ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 20 carbon atoms. The alkyl group may have a branched chain, and the number of carbon atoms of the alkyl group is preferably 1-8, more preferably 1-4.

Specific examples of the compound represented by the general formula (3) include pyrogallol (1,2,3-) in addition to compounds represented by the following general formulas (3-1) to (3-4). trihydroxybenzene) and the like are suitable.

In the general formulas (3-1) to (3-3), R ^{3 ′} , R ^{4 ′} , R ^{5 ′} , R ^{6 ′,} and R ^{7 ′} are the same or different and are a hydrogen atom, a halogen atom, or a carbon atom. It represents an alkoxyl group having 1 to 8 carbon atoms, or an alkyl or alkenyl group having 1 to 24 carbon atoms which may have a substituent. Here, the halogen atom, substituent, alkyl group or alkenyl group is the same as in the general formula (3).
^{R 8} in the general formula (3-4) is the same as ^{R 8} in the general formula (4).

The compound represented by the general formula (3-1) is preferably catechol, 3-sec-butylcatechol, 3-tert-butylcatechol, 4-sec-butylcatechol, 4-tert-butylcatechol, 3,5 -Di-tert-butylcatechol, 3-sec-butyl-4-tert-butylcatechol, 3-tert-butyl-5-sec-butylcatechol, 4-octylcatechol, 4-stearylcatechol and the like. More preferred are catechol and 4-tert-butylcatechol, and still more preferred is 4-tert-butylcatechol.

The compound represented by the general formula (3-2) is preferably hydroquinone, 2-hydroxyhydroquinone, 2,5-di-tert-butylhydroquinone, 2,5-bis (1,1,3,3-tetra Methylbutyl) hydroquinone, 2,5-bis (1,1-dimethylbutyl) hydroquinone, and the like. More preferred are hydroquinone (benzone-1,4-diol) and 2-hydroxyhydroquinone (benzone-1,2,4-triol).

The compound represented by the general formula (3-3) is preferably resorcinol (benzone-1,3-diol) or orcinol (5-methylbenzene-1,3-diol).

The compound represented by the general formula (3-4) is preferably gallic acid or a gallic acid ester. Specific examples of gallic acid esters include, for example, methyl gallate, ethyl gallate, propyl gallate, isopropyl gallate, isopentyl gallate, octyl gallate, dodecyl gallate, tetradecyl gallate, hexadecyl gallate, octadecyl gallate Etc. Of these, gallic acid is preferred.

Among the compounds represented by the general formula (3), t-butylpyrocatechol is particularly preferable. As a result, the light resistance and durability of the optical recording medium can be further improved.For example, the optical recording medium can be stored or exposed in a place where it is easily exposed to high temperature and high humidity such as in a car or a place exposed to a light source such as ultraviolet light or room light. Even when it is used, even better recording and reproduction characteristics can be exhibited.

In the photopolymerizable resin composition, the content (addition amount) of the polymerization inhibitor is preferably 0.05 to 10 parts by mass with respect to 100 parts by mass of the total amount of the photopolymerizable resin. By setting within this range, the effect of improving light resistance becomes more remarkable, and the polymerization inhibitor is less likely to precipitate from the photopolymerizable resin composition. The lower limit value is more preferably 0.1 parts by mass, still more preferably 0.2 parts by mass, and the upper limit value is more preferably 5 parts by mass, still more preferably 3 parts by mass, and particularly preferably 1 part by mass. .

<About other ingredients>
The photopolymerizable resin composition may further contain an ultraviolet absorber or a thermal polymerization initiator. In the case where the ultraviolet absorber is included, it is possible to enhance the recyclability of the resin composition, to sufficiently exhibit the effects of adjusting the curing speed and reducing the warpage of the optical disk. When the thermal polymerization initiator is included, the heat generated when the resin composition is cured with ultraviolet rays is utilized, and the effect of further curing can be achieved.

Examples of the ultraviolet absorber include benzotriazole ultraviolet absorbers, hydroxyphenyltriazine ultraviolet absorbers, benzophenone ultraviolet absorbers, salicylic acid ultraviolet absorbers, and inorganic oxide ultraviolet absorbers. Or 2 or more types can be used. Specifically, phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone, glycol salicylate, t-butylmethoxydibenzoylmethane, ethylhexyl methoxycinnamate, dimethyl PABA ( para-aminobenzoic acid) octyl, dimethyl PABA ethylhexyl and the like. For example, 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole (trade name “TINUBIN PS”, Ciba Specialty Chemicals) 2- {2-hydroxy-4- (1-octyloxycarbonylethoxy) phenyl} -4,6-bis (4-phenylphenyl) -1,3,5-triazine (trade name “TINUBIN 479”, H・ Specialty Chemicals), 2- {2-hydroxy-5- (2-methacryloyloxyethyl) phenyl} benzotriazole (trade name “RUVA93”, manufactured by Otsuka Chemical Co., Ltd.), octyl-3- {3-t- Butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole-2-yl) phenyl} propionic acid, 2-ethylhexyl-3- {3-tert-butyl-4-hydroxy-5- (5-chloro) -2H-benzotriazole-2-yl) phenyl} propionic acid (trade name “TINUBIN 109”, manufactured by Ciba Specialty Chemicals) and the like are preferably used.

It is preferable that the addition amount of the said ultraviolet absorber is 0.03-2 mass parts with respect to 100 mass parts of total amounts of the said photopolymerizable resin. More preferably, it is 0.05-1 mass part, More preferably, it is 0.05-0.5 mass part.

As the thermal polymerization initiator, a thermal radical polymerization initiator that generates a polymerization initiation radical by heating is suitable.
Examples of the thermal radical polymerization initiator include organic peroxide initiators and azo initiators, and one or more of these can be used.

Among these thermal radical initiators, radicals are efficiently generated by the catalytic action of metal soaps and / or amine compounds such as methyl ethyl ketone peroxide, cyclohexanone peroxide, cumene hydroperoxide, t-butylperoxybenzoate, and benzoyl peroxide. And 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile) are preferable.

Here, in the case of using the thermal radical polymerization initiator, in order to lower the decomposition temperature of the thermal radical polymerization initiator, thermal polymerization that can effectively generate radicals by promoting the decomposition of the thermal polymerization initiator Accelerators can be used.
Examples of the thermal polymerization accelerator include metal soaps such as cobalt, copper, tin, zinc, manganese, iron, zirconium, chromium, vanadium, calcium, and potassium, primary, secondary, tertiary amine compounds, and quaternary. An ammonium salt, a thiourea compound, a ketone compound, etc. are mentioned, These 1 type (s) or 2 or more types can be used. Among them, cobalt octylate, cobalt naphthenate, copper octylate, copper naphthenate, manganese octylate, manganese naphthenate, dimethylaniline, trietalamine, triethylbenzylammonium chloride, di (2-hydroxyethyl) p-toluidine, ethylenethio Urea, acetylacetone and methyl acetoacetate are preferred.
The amount of the thermal polymerization accelerator is preferably 0.001 to 10 parts by mass with respect to 100 parts by mass of the total amount of the photopolymerizable resin. When the blending amount of the thermal polymerization accelerator is within such a range, it is preferable in terms of curability of the resin composition, physical properties of the cured product, and economical efficiency. More preferably, it is 0.01-5 mass parts, More preferably, it is 0.05-3 mass parts.

In the photopolymerizable resin composition, one or more of photosensitizers, photopolymerization accelerators, metal oxide particles, surface function modifiers, solvents, and the like can be used as necessary. .
The photosensitizer is one that can transfer excitation energy from an excited state generated by photoexcitation to a photopolymerization initiator and promote the decomposition of the photopolymerization initiator to effectively generate radicals. One or more of 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone and the like can be used.
0.05-20 mass parts is suitable for the compounding quantity of the said photosensitizer with respect to 100 mass parts of total amounts of the said photopolymerizable resin. If the compounding quantity of a photosensitizer is in such a range, it is preferable at the point of sclerosis | hardenability of a resin composition, the physical property of hardened | cured material, and economical efficiency. More preferably, it is 0.1-15 mass parts, More preferably, it is 0.2-10 mass parts.

The photopolymerization accelerator is an agent that can promote the decomposition of the photopolymerization initiator and effectively generate radicals. For example, triethanolamine, methyldiethanolamine, triisopropanolamine, 4-dimethylaminobenzoic acid. Methyl, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-dimethylaminobenzoate-2-n-butoxyethyl, 2-dimethylaminoethyl benzoate, N, N-dimethylparatoluidine, 4, 1 type (s) or 2 or more types, such as 4'- dimethylamino benzophenone and 4,4'- diethylamino benzophenone, can be used. Of these, triethanolamine, methyldiethanolamine, and triisopropanolamine are preferable.
0.05-20 mass parts is suitable for the compounding quantity of the said photoinitiator with respect to 100 mass parts of total amounts of the said photopolymerizable resin. When the blending amount of the photopolymerization accelerator is within such a range, it is preferable in terms of curability of the resin composition, physical properties of the cured product, and economical efficiency. More preferably, it is 0.1-15 mass parts, More preferably, it is 0.2-10 mass parts.

The metal oxide particles mean particles made of a metal oxide, preferably fine particles made of a metal oxide. In the case of containing such metal oxide particles, the hardness of the cured product formed from the resin composition is improved, and it is less likely to be damaged, and it is advantageous in that a low-reflective coating film can be obtained. It is.
The metal oxide constituting the particles is preferably an oxide containing at least one metal element selected from the group consisting of Si, Ti, Zr, Zn, Sn, In, La, and Y. The metal oxide may be a single oxide containing these elements or a complex oxide containing these elements.
Specific examples of the metal oxides constituting the particles, for _{example, SiO, SiO 2, TiO 2} , ZrO 2, ZnO, In 2 O 3, La 2 O 3, Y 2 O 3, SiO 2 -Al 2 O ₃ , SiO ₂ —Zr ₂ O ₃ , SiO ₂ —Ti ₂ O ₃ , Al ₂ O ₃ —ZrO ₂ , TiO ₂ —ZrO _2, etc., and one or more of these can be used. Of these, SiO ₂ , TiO ₂ , ZrO ₂ , and ZnO ₂ are preferable.

The average particle diameter of the metal oxide particles is preferably 1 to 300 nm. If it exceeds 300 nm, the cured product may not have sufficient transparency. More preferably, it is 1-300 nm, More preferably, it is 1-50 nm.
In addition, the average particle diameter of a particle here means the volume average particle diameter calculated | required by measuring using a dynamic light scattering type particle size distribution measuring apparatus.
The compounding amount of the metal oxide particles is preferably 0 to 80 parts by mass with respect to 100 parts by mass of the total amount of the photopolymerizable resin. When it exceeds 80 mass parts, there exists a possibility that hardened | cured material may become weak. More preferably, it is 0-50 mass parts.

The anti-fingerprint removal property is improved by containing the surface function adjusting agent, but as the surface function adjusting agent, a fluorine-based compound or a silicone-based compound is generally used. In the present invention, for example, a polyether-modified fluorine-based compound, a polyether-modified fluorine-based compound having a reactive group (for example, (meth) acrylate), a non-reactive silicone, and a reactive (for example, (meth) acrylate) Any of silicone, polymer silicone, and macromonomer silicone can be used.

The above-mentioned solvent means a so-called organic solvent having volatility or a low boiling point, for example, an aromatic hydrocarbon such as benzene, toluene and chlorobenzene; an aliphatic or alicyclic such as pentane, hexane, cyclohexane and heptane Hydrocarbons; halogenated hydrocarbons such as carbon tetrachloride, chloroform, and ethylene dichloride; nitro compounds such as nitromethane and nitrobenzene; ethers such as diethyl ether, methyl t-butyl ether, tetrahydrofuran, and 1,4-dioxane; methyl acetate; Esters such as ethyl acetate, isopropyl acetate and amyl acetate; alcohols such as dimethylformamide, methanol, ethanol and propanol; one or more ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone are used. It is possible.

If necessary, the resin composition further includes an inorganic filler, a low shrinkage agent (reactive oligomer or polymer, non-reactive oligomer or polymer), color pigment, plasticizer, chain transfer agent, Infrared absorber, light stabilizer, antioxidant, flame retardant, matting agent, dye, defoaming agent, leveling agent, antistatic agent, dispersant, slip agent, surface modifier, thixotropic agent, rocking agent 1 type (s) or 2 or more types, such as a change aid, can be used. The presence of these additives does not particularly affect the effects of the present invention.

What is necessary is just to set the compounding quantity of the said additive suitably according to the kind and use purpose of an additive, the use of a composition, a usage method, etc., and it is not specifically limited. For example, the blending amount of the inorganic filler is preferably 1 to 80 parts by mass, more preferably 10 to 60 parts by mass, and further preferably 20 to 50 parts by mass with respect to 100 parts by mass of the total amount of the photopolymerizable resin. . The compounding amount of the low shrinkage agent, the color pigment, the plasticizer or the auxiliary change agent is preferably 1 to 40 parts by mass, more preferably 5 to 30 parts by mass, and more preferably 100 parts by mass of the total amount of the photopolymerizable resin. Preferably it is 10-25 mass parts. Antioxidants, matting agents, dyes, antifoaming agents, leveling agents, antistatic agents, dispersants, slip agents, surface modifiers or auxiliary agents are blended in a total amount of 100 mass of the above photopolymerizable resin. Preferably it is 0.0001-10 mass parts with respect to a part, More preferably, it is 0.001-5 mass part, More preferably, it is 0.01-3 mass part.

<A more suitable form of the photopolymerizable resin composition for optical recording media>
The photopolymerizable resin composition of the present invention can be obtained by preferably blending the above components, and mixing and stirring by a usual method.
The viscosity of such a resin composition is appropriately set depending on a film forming method (for example, film formation by a spin coater), a desired thickness, and the like. Usually, when trying to uniformly obtain a coating film having a thickness of about 100 μm (for example, for a single-layer Blu-ray disc with a recording capacity of about 25 G) to a thickness of about 75 μm (for example, for a double-layer Blu-ray disc with a recording capacity of about 50 G) Is preferably at least 800 mPa · s at 25 ° C. and more preferably at most 2500 mPa · s. More preferably, it is 850 mPa * s or more, More preferably, it is 900 mPa * s, More preferably, it is 2300 mPa * s or less, More preferably, it is 2000 mPa * s or less, Most preferably, it is 1900 mPa * s or less. In addition, when it is desired to further reduce the thickness (for example, for a multilayer Blu-ray disc having three or more layers), it is preferable to further reduce the viscosity.
The viscosity of the resin composition can be calculated using a B-type viscometer (model “RB80L” manufactured by Toki Sangyo Co., Ltd.) under a temperature of 25 ° C.

Here, the thickness of the layer formed from the photopolymerizable resin composition, that is, the layer formed by curing the photopolymerizable resin composition is suitably 1 to 200 μm. By setting it within this range, it is possible to sufficiently exhibit the effects of the present invention. The preferable thickness range may be set as appropriate depending on the use / function of the layer. For example, when used as a protective layer (light transmission layer), the thickness is preferably 20 to 150 μm, more preferably 70 to 105 μm, and still more preferably. The thickness is 70 to 102 μm, particularly preferably 70 to 100 μm. Moreover, when using as an intermediate | middle layer arrange | positioned between two or more recording layers (information recording layer), Preferably it is 1-50 micrometers, More preferably, it is 5-30 micrometers, More preferably, it is 8-28 micrometers. In the case of a more multilayer optical recording medium, it is preferable that the protective layer is thinner and the intermediate layer is thicker.

The photopolymerizable resin composition can be cured by irradiating with ultraviolet rays. The term “curing” as used herein means that there is no fluidity.
The wavelength of the ultraviolet rays used may be in the range of 150 to 450 nm. Examples of the light source that emits such a wavelength include sunlight, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a gallium lamp, a xenon lamp, a flash type xenon lamp, and a carbon arc lamp. Irradiation integrated light quantity is preferably 0.1~3J / cm ^2, more preferably 0.2~2.0J / cm ^2, more preferably in the range of 0.3~1.0J / cm ^2.

The photopolymerizable resin composition may be cured by heating together with curing by light irradiation. In this case, infrared light, far infrared light, hot air, high-frequency heating, or the like may be used together with the light source described above. The heating temperature may be appropriately adjusted according to the type of the substrate and the like, and is not particularly limited, but is preferably 80 to 200 ° C, more preferably 90 to 180 ° C, and still more preferably 100 to 170 ° C. Within range. The heating time may be appropriately adjusted according to the application area and the like, and is not particularly limited, but is preferably 1 minute to 24 hours, more preferably 10 minutes to 12 hours, and even more preferably 30 minutes to 6 hours. Is within the range.

The photopolymerizable resin composition may be further cured by electron beam irradiation as well as by light irradiation. In this case, the acceleration voltage is preferably 0 to 500 kV, more preferably 20 to 300 kV, and even more preferably 30 to 200 kV. The irradiation amount is preferably in the range of 2 to 500 kGy, more preferably 3 to 300 kGy, and still more preferably 4 to 200 kGy.

In the photopolymerizable resin composition of the present invention, a cured product obtained by curing the photopolymerizable resin composition has a loss tangent tan δ at a glass transition temperature of 0.2 to 0.6. Is preferred. When the loss tangent tan δ is 0.6 or less, the long-term storage stability of the cured product becomes more sufficient, and permanent deformation due to pressure marks or dents can be further suppressed, and is 0.2 or more. And the curvature of hardened | cured material can be suppressed more fully, and it will be further excellent in long-term storage stability in any case. The loss tangent tan δ is more preferably 0.23 or more, further preferably 0.24 or more, more preferably 0.45 or less, and still more preferably 0.4 or less.

The photopolymerizable resin composition is also preferably such that a cured product obtained by curing the photopolymerizable resin composition has a storage elastic modulus at 25 ° C. of 25 to 1300 MPa. When the storage elastic modulus at 25 ° C. is 1300 MPa or less, the warp of the cured product is further reduced, and for example, the optical recording medium is further suitable when used in a cold district or stored for a long time. Moreover, it becomes possible to suppress more fully the permanent deformation by a press-contact mark, a dent, etc. as it is 25 Mpa or more. The storage elastic modulus at 25 ° C. is more preferably 40 MPa or more, more preferably 1000 MPa or less, still more preferably 300 MPa or less, and particularly preferably 250 MPa or less.

It is also preferable that the photopolymerizable resin composition further has a cured product obtained by curing the photopolymerizable resin composition having a storage elastic modulus at 70 ° C. of 25 to 150 MPa. When the storage elastic modulus at 70 ° C. is 150 MPa or less, the warp of the cured product is further reduced, and for example, it is more suitable when the optical recording medium is used in a place where it is easily exposed to a high temperature such as in a car or stored for a long time. It will be something. Moreover, it becomes possible to suppress more fully the permanent deformation by a press-contact mark, a dent, etc. as it is 25 Mpa or more. As a more preferable range as the storage elastic modulus at 70 ° C., since it is also greatly related to the above-described Tg, there are some portions that cannot be generally explained, for example, more preferably 30 MPa or more, still more preferably 35 MPa or more, The pressure is preferably 100 MPa or less, more preferably 80 MPa or less, more preferably 70 MPa or less, still more preferably 65 MPa or less, still more preferably 60 MPa or less, and particularly preferably 55 MPa or less. When Tg is low, the storage elastic modulus at 25 ° C. and the storage elastic modulus at 70 ° C. are close to each other.

The loss tangent tan δ and storage elastic modulus of the cured product are measured in the same manner as the Tg measurement for a cured product obtained by curing by the same curing method as in the Tg measurement of the cured product of the photopolymerizable resin composition described above. It can be obtained under conditions.

[Cured product]
The present invention is also a cured product obtained by curing the photopolymerizable resin composition for optical recording media. Such cured products are excellent not only in light resistance, durability and weather resistance, but also in various physical properties such as transparency, hardness, residual film properties, film thickness stability, film thickness uniformity, and surface smoothness. In addition, it has high warpage and pressure resistance, and is extremely excellent in long-term storage stability. Therefore, this cured product is particularly useful as a layer (cured film) constituting the optical recording medium.

As described above, the cured product preferably has a Tg of 50 ° C. or lower. In addition, it is preferable that any one or more of the loss tangent tan δ and the storage elastic modulus at Tg is also within the above-described range, and thereby more useful as a layer (cured film) constituting the optical recording medium. It will be something.

It is also preferable that the cured product has a light transmittance of 850 nm or more at 405 nm with a thickness of 100 μm. When the light transmittance is 85% or more, the transparency becomes more sufficient, and it becomes possible to further prevent errors in reading recorded information. More preferably, it is 88% or more, More preferably, it is 89% or more.
The light transmittance can be measured with a spectrophotometer.

Further, the cured product preferably has a mass loss (mass reduction) rate of 0.1 to 2% by mass when held in an oven at 70 ° C. for 100 hours. The decrease in mass is considered to be caused by uncrosslinked polymerizable monomer components, residues of photopolymerization initiators and decomposition products thereof, low molecular weight additives, etc., but the mass decrease rate is 2% by mass or less. In addition, bleed-out of volatile components to the surface of the cured product and the occurrence of errors in reading recorded information due to changes in the thickness of the layer of the cured product can be further prevented, and the long-term storage stability of optical recording media can be improved. Furthermore, it can be made favorable. In addition, in order to make the said mass reduction rate less than 0.1 mass%, the drying (decompression) process etc. of hardened | cured material may be required. Therefore, by setting the mass reduction rate within the above range, for example, the surface accuracy of the optical recording medium is less decreased with time, and the storage stability is further improved. Is more possible. More preferably, it is 1.5 mass% or less, More preferably, it is 1 mass% or less.
The mass reduction rate is measured for a cured product having a thickness of 100 μm ± 2 μm.

[Optical recording medium]
The present invention is also an optical recording medium having a layer formed from the photopolymerizable resin composition for an optical recording medium (that is, a layer formed by curing the photopolymerizable resin composition for an optical recording medium). Such an optical recording medium is an optical recording medium on which recording and / or reproduction is performed by blue laser light, and preferably has at least a substrate, a recording layer, a reflective film, and a protective layer. Each of these layers (including the substrate) may be composed of one layer or may be composed of multiple layers. Furthermore, it may have one or more other functional layers as necessary, and may have another functional layer between these layers. As other functional layers, for example, an intermediate layer formed between recording layers in a multilayer structure optical recording medium having two or more recording layers (information recording layers), and usually formed on a protective layer, Examples thereof include an antistatic layer, a water repellent layer, an oil repellent layer, and a hard coat layer. Also preferred is an interface layer formed between the recording layer and the protective layer. The optical recording medium of the present invention is particularly preferably a form having a hard coat layer.

The optical recording medium may be a single-layer optical recording medium having one recording layer, or a multilayer optical recording medium having two or three or more recording layers. That is, the photopolymerizable resin composition for optical recording media of the present invention can be suitably used for either single-layer or multilayer optical recording media.

Since the photopolymerizable resin composition is excellent in transparency and has high light transmission, it can be suitably used as a material for forming the light transmission layer of the optical recording medium. Among them, it is particularly preferably used for forming the protective layer, but it is also suitable to use as a material for forming the intermediate layer. That is, an optical recording medium having a protective layer and / or an intermediate layer obtained by curing the photopolymerizable resin composition for an optical recording medium is one of the preferred embodiments of the present invention. In this case, in addition to light resistance, durability and weather resistance, low warpage (low shrinkage), transparency (light transmission), adhesion to a substrate (for example, polycarbonate substrate, etc.), low corrosivity, and recyclability , Fast curability (productivity), antifouling properties, dimensional stability, long-term storage stability (warping change during heating acceleration test, residual film property, small amount of permanent deformation such as pressure marks and dents), etc. It is possible to realize a protective layer and an intermediate layer that satisfy all the characteristics.
In an optical recording medium having a plurality of layers as a light transmission layer such as a protective layer or an intermediate layer, at least one layer of the light transmission layer is a layer formed by curing the photopolymerizable resin composition (the photopolymerizability described above). A layer formed from a resin composition is preferable. Especially, it is more preferable that at least one layer of the protective layer is a layer formed by curing the photopolymerizable resin composition (a layer formed from the photopolymerizable resin composition).

-Board-
The said board | substrate is not specifically limited, For example, paper etc. can be utilized besides the resin substrate formed from a polycarbonate resin, a cycloolefin resin, a polyolefin resin, an acrylic resin, an epoxy resin etc. Usually, a resin substrate is adopted in consideration of strength, flexibility, etc. Among them, a substrate formed from a polycarbonate resin, that is, a polycarbonate substrate is preferable because of its high mechanical strength and low water absorption. is there. In addition, since the linear expansion coefficient of the cured product is small in the polycarbonate resin, it becomes possible to obtain an optical recording medium that is more excellent in warping characteristics by the synergistic effect of such a substrate and the protective layer in the present invention. In addition, when the water absorption is low, a cured product having excellent dimensional stability can be provided, and water absorption into the cured product can be suppressed to a low level.
Although the thickness of the said board | substrate is not specifically limited, For example, it is suitable that it is 0.5-1.5 mm. More preferably, it is 0.7-1.2 mm, More preferably, it is 0.9-1.1 mm.

-Recording layer-
The recording layer is also called a recording part, and is a part for recording or reproducing information signals. As such a recording layer, a read-only optical recording medium may be integrated with a substrate. For example, a substrate having a pit shape is preferably employed. Specifically, it is preferable to form pits for recording information on the substrate on the surface laminated with the reflective film. In a recordable optical recording medium, the recording layer is preferably provided between the reflective film and the protective layer (light transmission layer).

The recording layer only needs to be capable of recording / reproducing information, and may be any of a phase change recording layer, a magneto-optical recording layer, and an organic dye recording layer. Among these, an organic dye type recording layer, that is, a layer using an organic dye is preferable. As the organic dye, it is preferable to use one or more organic compounds having an absorption band derived from the structure in the light wavelength region near 300 to 800 nm, for example. Specific examples of such organic dyes include methine, azo, metal-containing azo, pyrone, and porphyrin compounds.
The thickness of the recording layer is not particularly limited, but is preferably 1 to 100 nm, for example. More preferably, it is 1-50 nm, More preferably, it is 1-30 nm.

-Reflective film (reflective layer)-
The reflective film (also referred to as a reflective layer) is a film that reflects laser light for reading information. For example, a film made of gold, silver, aluminum, or an alloy containing these metals is suitable. Among these, silver or a silver alloy is preferable.
The thickness of the reflective film is preferably set as appropriate depending on the material constituting the reflective film, the layer structure, and the like. For example, in the case of a single layer, it is preferable to set the thickness so that the reflectance is 35 to 70% (L0). Usually, in the case of a silver alloy, the thickness is set to about 40 nm in order to make the reflectance about 45%. In addition, when the reflective layer (reflective film) has two layers, the reflective film (L1) located in the back as viewed from the laser light irradiation side is a film according to the material used so that the reflectance is 10 to 30%. It is preferable to set the thickness. Usually, in the case of a silver alloy, the thickness is set to about 20 nm in order to obtain a reflectance of about 20%. As the reflective layer of the present invention, when the layer is a layer using silver or a silver alloy, it is preferable to set the thickness to 10 to 50 nm. That is, at least one of the reflective layers is a layer using silver or a silver alloy, and the thickness of the layer is 10 to 50 nm is also a preferred embodiment of the present invention.

-Protective layer-
The thickness of the protective layer is preferably 1 to 200 μm. More preferably, it is 20-150 micrometers, More preferably, it is 70-105 micrometers, Most preferably, it is 70-102 micrometers, Most preferably, it is 70-100 micrometers. In the case of a more multilayer optical recording medium, it is preferable that the protective layer has a smaller thickness and an intermediate layer described later has a larger thickness.
In addition, when laminating | stacking two or more layers and comprising a protective layer, it is preferable that the thickness of each layer is in the said range, More preferably, it is in the said range as the whole protective layer.

-Intermediate layer-
As described above, the intermediate layer is a layer formed between the recording layers in an optical recording medium having a multilayer structure having two or more recording layers (information recording layers), and is cured by active energy rays such as ultraviolet rays. It is suitable to form from the resin composition (ultraviolet curable resin composition) obtained. Preferably, as described above, the photopolymerizable resin composition for optical recording media of the present invention is used.
Although the thickness of the said intermediate | middle layer is not specifically limited, For example, it is preferable that it is 1-200 micrometers. More preferably, it is 1-50 micrometers, More preferably, it is 5-30 micrometers, Most preferably, it is 8-28 micrometers.

-Interface layer-
As described above, the interface layer is preferably a layer formed between the recording layer and the protective layer. In particular, in the case of a recordable optical recording medium (also referred to as a recording / reproducing optical recording medium), the interface layer is further formed. It is preferable to have By providing this layer, the swelling of the recording layer to the protective layer can be used effectively. Further, for example, when a protective layer is formed by applying a resin composition containing a solvent, it is possible to prevent the recording layer from being eluted by recording with the solvent.

In the interface layer, it is preferable that the reflection at the interface layer is as small as possible in order to selectively use the phase change of the reflected light from the reflective film. Considering this point, it is preferable that the difference in refractive index between the interface layer and the recording layer or the difference in refractive index between the interface layer and the protective layer is small. Specifically, the difference is preferably 1 or less, more preferably 0.7 or less, and still more preferably 0.5 or less. Particularly preferably, both the difference in refractive index between the interface layer and the recording layer and the difference in refractive index between the interface layer and the protective layer are within these preferable ranges.

The interface layer is preferably made of a material that is transparent to the wavelength of the laser beam used and that is chemically, mechanically, and thermally stable. For example, it is preferable to use a material having a light transmittance of 405 nm of 80% or more. The light transmittance is more preferably 90% or more, and still more preferably 100%.

Specific examples of the material for forming the interface layer include dielectric compounds such as oxides such as metals and semiconductors, nitrides, carbides, sulfides, fluorides such as magnesium (Mg) and calcium (Ca), and mixtures thereof. Etc. are preferred. Among them, a material having a refractive index of 1 to 2.5 is preferable because the difference in refractive index between the recording layer and the protective layer is 1 or less. It is preferable to set the thickness of the interface layer as appropriate so that the refractive index of the layer also falls within this range. Depending on the hardness and thickness of the interface layer, the deformation of the recording layer (bulging deformation of the recording layer into the protective layer) can be promoted or suppressed. For example, in order to more effectively utilize the swelling toward the protective layer. Is preferably a dielectric material having a relatively low hardness, such as ZnO, In ₂ O ₃ , Ga ₂ O ₃ , ZnS, rare earth metal sulfides, oxides of other metals, semiconductors, nitrides The material which mixed the thing and the carbide | carbonized_material is suitable. A sputtered plastic film or a plasma polymerized film of hydrocarbon molecules can also be used.
The thickness of the interface layer is preferably 1 to 50 nm, for example. More preferably, it is 5-20 nm.

-Hard coat layer-
The hard coat layer is preferably provided in order to prevent dirt and small scratches on the optical recording medium. Such a hard coat layer is a layer having transparency, and is preferably a layer obtained by curing a resin composition that is cured by an active energy ray such as light.
The thickness of the hard coat layer is preferably 1 to 10 μm, for example. More preferably, it is 2-8 micrometers, More preferably, it is 3-5 micrometers.
The photopolymerizable resin composition for optical recording media of the present invention also prevents the occurrence of cracks in the hard coat layer even when such a hard coat layer is provided on the cured film of the resin composition. Has the property of being

An optical recording medium having a layer obtained by curing the photopolymerizable resin composition for an optical recording medium, for example, the above-mentioned light on a reflective film formed on a substrate (or a functional layer formed on the substrate). Although it can be obtained by forming a layer formed by curing the polymerizable resin composition, the term “on the reflective film” as used herein refers not only to the form in which the layer is directly laminated on the reflective film, but also to the reflective film. It also means a mode in which a functional layer is laminated on the functional layer and the layer is laminated on the functional layer.

As a method for forming a layer formed by curing the photopolymerizable resin composition on the reflective film, a normal method may be employed. For example, a cured product of the resin composition may be applied to the reflective film with an adhesive. There are a bonding method, a method using a spin coater (spin coating method), and the like, but considering the cost, it is preferable to carry out by a spin coating method. The photopolymerizable resin composition for optical recording media of the present invention is particularly suitable for film formation by spin coating, that is, specifically, it has good flowability and goes from the center of the spin coater to the outside. Since film formation can be performed while sufficiently preventing the occurrence of unevenness in the direction, it is preferable to adopt the spin coating method also in this respect.

Here, as described above, the photopolymerizable resin composition is in a state where one surface of the photopolymerizable resin composition is in contact with the metal (reflection film) and the other surface is in contact with the gas phase (atmosphere). The effect that the unevenness in curing when the photopolymerizable resin composition is cured can be sufficiently suppressed. Therefore, it has at least a substrate, a recording layer, a reflective film, and a resin layer, and the resin layer has one surface in contact with the metal (reflective film) and the other surface in the gas phase (atmosphere). The photopolymerizable resin composition is obtained by curing the photopolymerizable resin composition in contact with the photopolymerizable resin composition of the present invention described above (the photopolymerizable resin and the benzoate). An optical recording medium in the form of a resin composition containing a triazole compound is also a preferred form of the present invention. In addition, as described above, the photopolymerizable resin composition is cured in a state where one surface of the photopolymerizable resin composition is in contact with the metal (reflection film) and the other surface is in contact with the gas phase (atmosphere). A method for producing an optical recording medium including a curing step is also one preferred embodiment of the present invention.
In this case, the resin layer in the optical recording medium as the final product has one surface in contact with the reflective film, and the other surface is a layer other than the reflective film (preferably, a gas phase (atmosphere) or a hard coat layer. It is preferable that it is a form which touches.

As described above, the photopolymerizable resin composition can also exhibit the effect that the cured product is excellent in releasability from the mold. Therefore, it has at least a substrate, a recording layer, a reflective film, and a resin layer, and the resin layer has one surface in contact with the metal (reflective film) and the other surface in contact with the mold. The photopolymerizable resin composition is obtained by curing the photopolymerizable resin composition in a state, and the photopolymerizable resin composition comprises the above-described photopolymerizable resin composition (photopolymerizable resin and benzotriazole compound). The optical recording medium in the form of (resin composition contained) is also one of the preferred forms of the present invention. Further, the curing step of curing the photopolymerizable resin composition in a state where one surface of the photopolymerizable resin composition is in contact with the metal (reflective film) and the other surface is in contact with the mold as described above. An optical recording medium manufacturing method is also one of the preferred embodiments of the present invention.

Since the layer formed by curing the photopolymerizable resin composition is formed from the above-described photopolymerizable resin composition of the present invention, the thickness change after curing can be controlled within ± 2 μm. . The thickness of such a hardened layer can be appropriately set depending on the use of the hardened layer and the like. For example, when used as a material for forming the protective layer, the thickness of the protective layer can be set within a suitable range. preferable.

As described above, the optical recording medium of the present invention is preferably used as both a read-only optical recording medium and a recordable optical recording medium (also referred to as a recording / reproducing optical recording medium). For example, taking the case of a recording single layer type as an example, preferred forms and manufacturing methods of these types will be described below.

A form suitable as the read-only optical recording medium is a form having at least a resin substrate (preferably a polycarbonate substrate) having a pit shape, a reflective film, and a protective layer in this order. For example, when a single resin substrate is injection-molded, a pit which is a recording layer is provided, and then a reflective film (also referred to as a reflective layer) is formed on the recording layer. A method of forming a protective layer (light transmission layer) by applying a polymerizable resin composition by a spin coating method or the like and then curing it by ultraviolet irradiation is exemplified. It is more preferable to further provide a hard coat layer on this protective layer.

A form suitable as the recording / reproducing optical recording medium is a form having at least a substrate (preferably a polycarbonate substrate), a reflective film, a recording layer, and a protective layer in this order. A reflective film is formed on a single substrate, and then a recording layer is provided. Further, a photopolymerizable resin composition is applied onto the recording layer by a spin coating method or the like, and then cured by ultraviolet irradiation to protect it. A method of forming a layer (light transmission layer) can be mentioned. It is more preferable to form a protective layer after providing the interface layer on the recording layer, and it is more preferable to further provide a hard coat layer on the protective layer.

Since the photopolymerizable resin composition for an optical recording medium of the present invention has the above-described configuration, it provides a cured product having extremely excellent weather resistance. If such a resin composition is used, it will be several decades. This is useful because an optical recording medium capable of recording and reproducing stably over the above-described long period can be obtained. In addition, an optical recording medium having a layer formed by curing such a resin composition is extremely reliable, and can be used in a cold district or a place where it is easily exposed to high temperatures such as in a car or for a long time. It is also suitable for storage.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”.
In the following production examples, the number average molecular weight (Mn), molecular weight distribution (Mw / Mn), glass transition temperature, and storage elastic modulus of the polymer were measured by the methods described above. In addition, various physical properties in Examples and the like were evaluated by the following methods.

<Evaluation methods for various physical properties>
(1) Average acrylic equivalent The average acrylic equivalent was calculated | required by the method mentioned above.
(2) Viscosity of Resin Composition The obtained resin composition (resin composition for forming a protective layer) is subjected to a B-type viscometer (model “RB80L”, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25 ° C. The measured value was used.

(3) Protective layer Only the protective layer (cured film (cured product) of the resin composition) is peeled off from the laminate of the substrate / protective layer obtained at 25 ° C. or 70 ° C. with a predetermined dimension, and pulled. The dynamic viscoelasticity is measured under the conditions of mode, frequency 1 Hz, clamp distance 25 mm, amplitude 0.1%, heating rate 5 ° C./min, and the obtained storage elastic modulus values at 25 ° C. or 70 ° C. are obtained. Adopted.
(4) Protective layer Glass transition temperature (Tg)
It is a value obtained by the same measurement method and conditions as the storage elastic modulus at 25 ° C. in (3) above, and the temperature of the maximum tan δ value was adopted.
(5) Protective layer Tan δ value at glass transition temperature The tan δ value of the glass transition temperature measured by the same measurement method and conditions as the storage elastic modulus of (3) above was adopted.

(6) Curability The obtained substrate / protective layer laminate (that is, in each example etc., a polycarbonate disk-shaped optical recording medium substrate was sputtered with a silver alloy, and then subjected to a resin composition using a spin coater. The laminate was obtained by applying and curing the product with a thickness of about 100 μm, and it was visually determined whether or not there was a poorly cured part due to uneven curing of the resin composition.
A: There is no curing unevenness of the resin composition. O: There is a slight difficulty in discriminating the curing unevenness of the resin composition. Δ: There is curing unevenness of the resin composition. X: There is considerable curing unevenness of the resin composition.

(7) The amount of warpage during curing The laminate of the obtained substrate / protective layer / hard coat layer is placed on a horizontal glass plate so that the protective layer (cured film (cured product) of the resin composition) is on the upper surface side. Then, a radial tilt value at a radius of 58 mm was measured using a laser displacement reading type warpage angle measuring device manufactured by Nippon Shokubai Co., Ltd. under an environment of a temperature of 25 ° C. and a relative humidity of 50%. As the amount of warping during curing, the amount of warpage change before and after coating was adopted.
◎: Less than 0.5 ° ○: 0.5 ° or more, less than 0.7 ° △: 0.7 ° or more, less than 0.9 °

(8) Polycarbonate is used as the releasable resin mold, and the resin composition is applied and cured on the polycarbonate with a spin coater at a thickness of about 100 μm. The resulting laminate is JIS K5600 5-6 ( In 1999, the peelability was evaluated by a cross-cut test. Specifically, on the coating film (protective layer), cuts that reach the material in a grid pattern at intervals of 1 mm vertically and horizontally, and an adhesive tape having an adhesive force (120 gf / 10 mm) is applied. And this adhesive tape was peeled off, the number of the coating film pieces which peeled and adhered to the adhesive tape was investigated and evaluated. When the release property from the mold is good, the resin piece adheres to the adhesive tape and peels from the mold. From this evaluation test, the mold releasability of the cured product (protective layer) of the resin composition can be determined.
A: All peeled off.
○: Peeling was 70/100 or more.
(Triangle | delta): The peeling number 50/100 or more and less than 70/100 peeled.

(9) Weather resistance About the obtained substrate / protective layer / hard coat layer laminate, 0.5 kW / m ² , 80 ° C., 80% RH for 5 hours using a metalling weather meter (model number M6T manufactured by Suga Test Instruments Co., Ltd.) Then, the reflectance of the metal before and after the test was measured using a spectrophotometer (model UV3700, manufactured by Shimadzu Corporation).
: Less than 3% reflectivity drop: 3% or more less than 5% reflectivity drop: Less than 5% reflectivity drop or less than 10% ×: 10% or more reflectivity drop

Production Example 1 (Synthesis of UA-1)
340 g of isophorone diisocyanate and 0.015 g of dibutyltin dilaurate were added to a four-necked flask equipped with a stirring bar, a thermometer, a dropping line, and a nitrogen / air mixed gas introduction tube, and the temperature was raised to 80 ° C. After a certain temperature, 300 g of polypropylene glycol “P-2000” manufactured by Asahi Denka Co., Ltd. was dropped over 2 hours, and the temperature was maintained at 80 ° C. for 5 hours after the completion of dropping. Next, a mixture of 180 g of 2-hydroxyethyl acrylate and 0.5 g of hydroquinone monomethyl ether was added dropwise over 2 hours. After completion of dropping, a temperature of 80 ° C. was maintained for 15 hours, and urethane acrylate (referred to as “UA-1”) was synthesized. The molecular weight (Mn) was 5600, the molecular weight distribution (Mw / Mn) was 3.71, the glass transition temperature was −5 ° C., and the storage elastic modulus at 25 ° C. was 10 MPa.

Example 1
(Preparation of protective layer)
40 parts of diacrylate of bisphenol A ethylene oxide 10 mol adduct (trade name “SR-602”, manufactured by Sartomer), diacrylate of 2 mol of propylene oxide adduct of neopentyl glycol (trade name “SR-9003”, Sartomer) 10 parts), triacrylate of trimethylolpropane ethylene oxide 3 mol adduct (trade name “light acrylate TMP-3EO-A”, manufactured by Kyoeisha Chemical Co., Ltd.) 25 parts, urethane acrylate UA-1 synthesized in Production Example 1 25 parts, 1 part of 1-hydroxy-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, manufactured by Ciba Specialty Chemicals), 0.3 part of 4-t-butylcatechol (manufactured by Wako Pure Chemical Industries) , And carboxybenzotriazole (trade name “CBT- "The Johoku Chemical Co., Ltd.) 0.05 parts, mixed and stirred to, photopolymerizable resin composition (1) was prepared.

(Preparation of hard coat layer)
30 parts of dipentaerythritol hexaacrylate, 30 parts of trimethylolpropane triacrylate, 40 parts of 2- (2-hydroxyethoxy) ethyl acrylate, 1-hydroxy-cyclohexyl-phenyl-ketone (trade name “Irgacure 184” as a photopolymerization initiator ”, 5 parts of Ciba Specialty Chemicals Co., Ltd.), 0.3 part of silicone additive (trade name“ FZ-2104 ”, manufactured by Toray Dow Corning Co., Ltd.), and mixed and stirred to hard coat for optical recording medium A resin composition was prepared.

(Formation of protective layer 1)
Next, a polycarbonate disk-shaped optical recording medium substrate having a thickness of 1.1 mm and a diameter of 120 mm was prepared (a warp angle of 0.0 °), and a silver alloy was sputtered thereon to a thickness of 20 to 40 nm. . Next, the obtained photopolymerizable resin composition (1) was applied on a silver alloy in an environment of 25 ° C. and a relative humidity of 50% with a spin coater at a thickness of about 100 μm, and a xenon flash UV lamp Was cured by irradiating a flash 15 times at a lamp height of 2 cm in a nitrogen atmosphere using a UV irradiator (model RC-801, manufactured by Xenon, USA). In addition, the irradiation integrated light quantity in 320-390 nm was about 0.5 J / cm < ² >. When the thickness of the cured product (protective) layer was measured using a laser focus displacement meter, it was 97 ± 2 μm.

(Formation of hard coat layer)
Next, the obtained resin composition for hard coat for optical recording media was coated on a cured product (protective) layer with a spin coater at a thickness of about 3 μm, and a UV irradiator having a xenon flash UV lamp (A model RC-801 manufactured by US Xenon Co., Ltd.) was used to cure by flash irradiation 10 times at a lamp height of 2 cm in a nitrogen atmosphere. It was 100 +/- 2micrometer when the thickness of the laminated body (protective layer / hard-coat layer) of the obtained hardened | cured material layer was measured using the laser focus displacement meter.
The obtained photopolymerizable resin composition (1) and the obtained optical recording medium (substrate / protective layer / hard coat layer laminate (*)) were evaluated. The results are shown in Table 1.
* For some evaluation tests, the hard coat layer was not laminated, that is, the substrate / protective layer laminate was evaluated and measured.

Examples 2-9
Photopolymerization was carried out in the same manner as in Example 1 (Preparation of protective layer) except that each component shown in Table 1 was used in the ratio shown in Table 1 instead of each component used in Example 1. Resin compositions (2) to (9) were obtained. Then, it replaced with the photopolymerizable resin composition (1) in Example 1, and obtained the optical recording medium like Example 1 except having used each of these resin compositions. The obtained resin composition and optical recording medium were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Examples 10 to 28, Comparative Examples 1 to 7
Instead of CBT-1 (0.05 parts) used in Example 1, the components (VI) listed in Tables 2 to 4 were used in the respective compounding amounts listed in Tables 2 to 4, Photopolymerizable resin compositions (10) to (28) and comparative resin compositions (1) to (7) were obtained in the same manner as in Example 1 (Preparation of protective layer). Then, it replaced with the photopolymerizable resin composition (1) in Example 1, and obtained the optical recording medium like Example 1 except having used each of these resin compositions. The resulting optical recording medium was evaluated in the same manner as in Example 1 for curability, releasability and weather resistance. The results are shown in Tables 2-4.

Examples 29-35
Instead of the component (V) used in Example 1 (Irg184: 2 parts and t-BC: 0.3 part), the components (V) listed in Table 5 were used in the respective amounts shown in Table 5. Photopolymerizable resin compositions (29) to (35) were obtained in the same manner as in Example 1 (Preparation of protective layer) except that they were used. Then, it replaced with the photopolymerizable resin composition (1) in Example 1, and obtained the optical recording medium like Example 1 except having used each of these resin compositions. The resulting optical recording medium was evaluated in the same manner as in Example 1 for curability, releasability and weather resistance. The results are shown in Table 5.

Abbreviations in Tables 1 to 5 are as follows.
* 1: The molecular weight of the component (III) means the number average molecular weight (Mn), and the molecular weight of the other (meth) acrylate compounds means the value calculated as the sum of the atomic weights of the constituent elements.
* 2: Tg of component (III) means Tg of a cured product obtained by curing it alone.

Bis-10EO-A: Diacrylate of ethylene oxide 10 mol adduct of bisphenol A (trade name “SR-602”, manufactured by Sartomer)
Hx620: Diacrylate of ε-caprolactone 4-mol adduct of neopent glycol hydroxypivalate (trade name “Kayarad HX-620”, manufactured by Nippon Kayaku Co., Ltd.)
NP-2PO-A: diacrylate of propylene oxide adduct of neopentyl glycol (trade name “SR9003”, manufactured by Sartomer)

TMP3EA: triacrylate of trimethylolpropane ethylene oxide 3 mol adduct (trade name “TMP-3EO-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
TMP6EA: Triacrylate of trimethylolpropane ethylene oxide 6 mol adduct (trade name “TMP-6EO-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
TMP9EA: Triacrylate of 9 mole adduct of trimethylolpropane with ethylene oxide (trade name “SR502”, manufactured by Sartomer)
DPCA-120: hexaacrylate of dipentaerythritol ε-caprolactone 12 mol adduct (trade name “Kayarad DPCA-120”, manufactured by Nippon Kayaku Co., Ltd.)

UA-1: Urethane acrylate obtained in Production Example CN978: manufactured by Sartomer, urethane acrylate CN9178: manufactured by Sartomer, urethane acrylate CN2270: manufactured by Sartomer, polyester acrylate CN UVE151: manufactured by Sartomer, epoxy acrylate UV7000B: Nippon Synthetic Chemical Urethane acrylate

PEA: Phenoxyethyl acrylate (trade name “Light Acrylate PO-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
IB-XA: manufactured by Kyoeisha Chemical Co., Ltd., isobornyl acrylate VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)
DPC-A: manufactured by Kyoeisha Chemical Co., Ltd., dimethylol-tricyclodecane diacrylate TMPTA: trimethylolpropane triacrylate (trade name “SR351”, manufactured by Sartomer)

Irg184: 1-hydroxy-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, manufactured by Ciba Specialty Chemicals)
t-BC: 4-t-butylcatechol, manufactured by Wako Pure Chemical Industries, Ltd.

CBT-1: Carboxybenzotriazole, Johoku Chemical Industries BT-120: 1,2,3-benzotriazole, Johoku Chemical Industries BT-OH: 1- (hydroxymethyl) benzotriazole, Johoku Chemical Industries BT-LX: 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole, manufactured by Johoku Chemical Industry Co., Ltd. BT-260: 1-[(2-methylhexylamino) methyl] -benzotriazole, Johoku Chemical BT-M manufactured by Kogyo Co., Ltd .: 1- (1 ′, 2′-dicarboxyethyl) benzotriazole, TT-LX manufactured by Johoku Chemical Industry Co., Ltd .: 1- [N, N-bis (2-ethylhexyl) aminomethyl] methylbenzo Triazole, TT-LYK: 2,2 ′-[[(Methyl-1H-benzotriazol-1-yl) methyl] imino] manufactured by Johoku Chemical Industry Co., Ltd. Bisethanol, JCL-400 manufactured by Johoku Chemical Industry Co., Ltd .: 1,2,3-benzotriazole sodium salt solution TT-R: Mixture and product of 4-methyl-1H-benzotriazole and 5-methyl-1H-benzotriazole Name “SEETEC TT-R”, manufactured by Sipro Kasei Co., Ltd.

Tinuvin PS: 2- (2-hydroxy-5-t-butylphenyl) -2H-benzotriazole, Tinuvin 99-2 manufactured by Ciba Specialty Chemicals: Benzenepropionic acid, 3- (2H-benzotriazol-2-yl ) -5- (1,1-dimethylethyl) -4-hydroxy-, C7-9-mixture of linear, branched alkyl ester and 1-methoxy-2-propyl acetate, Tinuvin 900 manufactured by Ciba Specialty Chemicals: 2- (2H-benzotriazol-2-yl) 4,6-bis (1-methyl-1-phenylethyl) phenol, manufactured by Ciba Specialty Chemicals

From the results of the examples and comparative examples described above, the photopolymerizable resin composition used for the optical recording medium is in a form containing the photopolymerizable resin and the benzotriazole compound represented by the general formula (1). Thus, it was confirmed that an advantageous effect was exhibited in that all of curability, releasability and weatherability could be exhibited simultaneously in a balanced manner, which was remarkable. That is, the resin compositions of Examples 1 to 35 all contain a photopolymerizable resin and a benzotriazole compound represented by the above general formula (1), whereas the resin compositions of Comparative Examples 1 to 7 The product is different in that a compound different from the benzotriazole compound is used, but in this case, none of the materials can satisfy all of the curability, releasability and weather resistance at the same time.

Claims (5)

A photopolymerizable resin composition used for an optical recording medium for recording and / or reproducing with blue laser light,
The photopolymerizable resin composition includes a photopolymerizable resin and the following general formula (1):

(Wherein R ¹ and R ² are the same or different and each represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, a carboxyl group, or a hydroxyl group). Containing benzotriazole compounds
The optical recording medium has a layer formed from the photopolymerizable resin composition, and the thickness of the layer is from 1 to 200 μm. 2. The light for an optical recording medium according to claim 1, wherein the photopolymerizable resin composition has a glass transition temperature of 50 ° C. or lower of a cured product obtained by curing the photopolymerizable resin composition. Polymerizable resin composition. 3. The photopolymerization for an optical recording medium according to claim 1, wherein the content of the benzotriazole compound is 0.0001 to 0.5 parts by weight with respect to 100 parts by weight of the photopolymerizable resin. Resin composition. A cured product obtained by curing the photopolymerizable resin composition for an optical recording medium according to claim 1. An optical recording medium comprising a layer formed from the photopolymerizable resin composition for an optical recording medium according to claim 1.