JP2011198434A - Curable resin composition for optical recording medium, cured product, and optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-polymerizable resin composition for an optical recording medium with which physical properties such as transparency and stable film thickness are sufficiently demonstrated, with which a cured product with warpage, deformation, peeling from another layer etc. being suppressed with long-term stability can be produced, and with which recording and playback with higher reliability are achieved, the cured product thereof, and an optical recording medium having a layer obtained by curing this kind of resin composition.

SOLUTION: The curable resin composition for the optical recording medium is a curable resin composition to be used for an optical recording medium, having at least a substrate, a recording layer, a reflection film and a protective layer, and conducting recording and/or playback with a blue laser ray, and includes a (meth)acrylate compound having three or more functional groups and modified with an alkylene oxide and/or ε-caprolactone and a photo-polymerization initiator, wherein the cured product obtained by curing the curable resin composition has (A) glass transition temperature of 0-40°C and (B) a storage modulus at 70°C of 45-130 MPa.

COPYRIGHT: (C)2012,JPO&INPIT

Description

The present invention relates to a curable resin composition for optical recording media, a cured product, and an optical recording medium. More specifically, the present invention relates to a curable resin composition used for an optical recording medium that performs recording and reproduction 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 structure in which a recording layer, a reflective layer, and a protective layer (light transmission layer) are laminated on a substrate, and laser light passes through the protective layer (light transmission layer) during recording and reproduction. It is a mechanism for recording and playback.

With respect to conventional optical recording media, for example, in Patent Document 1, as an optical disk having excellent warpage characteristics, a protective layer includes a urethane (meth) acrylate, another ethylenically unsaturated compound, and a photopolymerizable initiator. It is disclosed that when the glass transition temperature of such a protective layer is lower than 50 ° C., the warp angle tends to increase when used under high-temperature conditions such as in a car under hot weather. ing. In Patent Document 2, as an optical recording medium capable of achieving both a reduction in warpage and a reduction in creep of the light transmission layer, the elastic modulus at a specific temperature is in a specific range, and the glass transition temperature (Tg) is -20 to 0 ° C. The form which has the light transmissive layer of this invention is disclosed, and as an example showing a specific form, a form in which the Tg of the light transmissive layer is −17 to −1 ° C. is described.

In addition, Patent Document 3 discloses an ultraviolet-curing obtained by reacting a hydroxy fatty acid, an epoxy compound, and a compound having an isocyanate group and an acryloyl group as an optical disk having good characteristics with little decrease in reflectance after a high-temperature and high-humidity test. The form which has the light transmissive layer which consists of hardened | cured material of the ultraviolet curable composition containing an active compound is disclosed. Patent Document 4 discloses an ultraviolet curable resin containing dicyclopentenyloxyethyl acrylate, urethane (meth) acrylate and / or epoxy (meth) acrylate, and a photopolymerization initiator as an optical disk having excellent warpage characteristics and the like. The form which has the hardened | cured material layer of a composition is disclosed. Patent Document 5 discloses an optical disk in which the occurrence of warpage is suppressed, in which the product of the film thickness and the elastic modulus of the light transmission layer is not more than a specific value. Patent Document 6 discloses a form having a light transmission layer exhibiting a specific elastic modulus as an optical disk in which corrosion and warpage of the light reflection layer are suppressed. Patent Document 7 discloses a form having a cover layer in which a storage elastic modulus before and after an environmental test is left for 100 hours in an 80 ° C./80% RH environment as a specific range as an optical recording medium having good reliability. ing.

Japanese Patent Laid-Open No. 2002-245672 (Pages 1, 2, 4) JP2009-271970A (pages 1, 2, 16) JP 2008-123565 A (first and second pages) International Publication No. 2007/142229 Pamphlet (Pages 1, 26) JP 2007-102980 A (first and second pages) JP 2005-293823 A (first and second pages) JP 2009-026379 A (first and second pages)

As described above, various techniques relating to optical recording media for recording / reproducing information with laser light have been studied.
Here, since unevenness in the thickness of the protective layer (also referred to as a light transmission layer) constituting such an optical recording medium affects information recording / reproduction, the thickness of the light transmission layer must be uniform. It is necessary to control the thickness within 100 μm ± 2 to 3 μm, but from the viewpoint of long-term stable information recording / reproduction, the change in the thickness of the light transmission layer is small even when the optical recording medium is stored. And high transparency (low colorability) is also required. Also, if there is pressure marks or dents on the light transmission layer, deformation due to temperature changes, etc. (permanent deformation), the laser spot position will fluctuate, and this may also affect information recording / reproduction. For this reason, it is desired to sufficiently prevent permanent deformation.

In addition, as a method for forming the light transmission layer, mainly a sheet bonding method in which a polycarbonate sheet is bonded with an ultraviolet curable adhesive, and an ultraviolet curable resin is applied by spin coating, and the resin is irradiated with ultraviolet rays. There are two methods, ie, a spin coating method for curing the material, but the spin coating method has become mainstream at present due to cost. Usually, when forming a light transmission layer using an ultraviolet curable resin, film thickness stability is required from the viewpoint of film thickness uniformity and productivity, but the optical recording medium is caused by curing shrinkage of the ultraviolet curable resin. There are many cases where warping occurs. Also, in an optical recording medium that records and reproduces information with blue laser light, the light transmission layer exists only on one side of the substrate (the side on which the laser light is incident), so that the structure is asymmetric in the thickness direction of the optical recording medium. It becomes. Therefore, it has a property that it is easily warped structurally as compared with a DVD or the like having a symmetrical structure in which two substrates are bonded together by an adhesive layer. For this reason, the substrate is warped in advance opposite to the coated surface, or correction or the like is performed with a reproducing / recording device, but if warpage exceeding the allowable range (correctable range) occurs. There are cases where accurate data recording and reproduction on the optical recording medium cannot be performed, and that data cannot be taken in and out of the reproduction / recording apparatus.

Therefore, the resin composition that forms a light transmission layer of an optical recording medium that records and reproduces information with blue laser light has a cured product that has a uniform film thickness, stability, transparency (low coloration) over a long period of time. ) And the like can be sufficiently exhibited, and it is desired that the permanent deformation is sufficiently suppressed and the characteristic that the warpage is remarkably small is sufficiently exhibited. However, none of conventional resin compositions can sufficiently satisfy all of these characteristics. For example, the resin composition described in Patent Document 2 has problems in terms of the amount of permanent deformation of the cured film, warpage, and the like, and cracks may occur when a hard coat layer is further laminated. Therefore, there is room for improvement in order to obtain a more reliable optical recording medium that can exhibit the above in a balanced manner.

The present invention has been made in view of the above-described present situation, and can fully exhibit various physical properties such as transparency and film thickness stability, and can suppress warping and deformation, peeling from other layers, etc. stably over a long period of time. Can be provided, and can be obtained by curing a photopolymerizable resin composition for optical recording media, a cured product thereof, and such a resin composition capable of realizing more reliable recording and reproduction. An object of the present invention is to provide an optical recording medium having a layer.

The inventors of the present invention have made various studies on a curable resin composition used for an optical recording medium that performs recording and reproduction with blue laser light. And a cured product of the curable resin composition satisfying a specific range of storage elastic modulus and glass transition temperature at a predetermined temperature. In this case, various physical properties such as transparency, film thickness stability and residual film properties can be sufficiently exhibited, and not only the initial warpage is small, but also the warpage does not increase even at a low temperature, and the warp during the heating acceleration test. It has been found that an optical recording medium that is remarkably excellent in three warping properties (warping resistance), such as a small increase amount, can be provided. An optical recording medium having a layer obtained by curing such a curable resin composition is also found to be extremely excellent in heat shock resistance and pressure dent resistance, and optical recording capable of exhibiting recording and reproducing characteristics stably for a long period of time. I found that the media could be realized. Furthermore, it has been found that such an optical recording medium is particularly useful as a recording type optical recording medium, and the inventors have arrived at the present invention by conceiving that the above problems can be solved brilliantly.

Here, in this specification, “warping is small” as an effect of the present invention means that not only warpage at the time of curing (initial) is small, but also warpage does not increase even at a low temperature (5 ° C.) and heating is performed. It means that the amount of warpage increase at the time of the acceleration test (70 ° C., 100 hours) is small, and the three warpage properties (warpage resistance) are excellent. Small initial warpage improves the productivity of optical recording media, low warpage at low temperatures provides stable recording / reproduction characteristics, and low warpage during the heating acceleration test provides excellent durability. Therefore, the optical recording medium of the present invention can exhibit recording / reproducing characteristics stably for a long period of time even in a place that is easily exposed to high temperatures such as in a cold district or in a car.
Further, as an effect exhibited by the present invention, “excellent in heat shock resistance” means peeling due to temperature fluctuation, that is, at least one protective layer of an optical recording medium when used / stored in an environment with large temperature fluctuation. It means that peeling from other layers (substrate etc.) is sufficiently small.
Furthermore, “excellent in long-term storage stability” as an effect exhibited by the present invention is excellent in the above three warp characteristics and residual film properties, and further, the amount of permanent deformation due to pressure marks, dents, temperature changes, etc. is small (ie, pressure resistance). It means that it is excellent in trace properties).

That is, the present invention is a curable resin composition for use in an optical recording medium having at least a substrate, a recording layer, a reflective film, and a protective layer, and recording and / or reproducing with blue laser light. The composition comprises (a) 50 to 100% by mass of a trifunctional or higher functional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone, and (b) a (meth) acrylate compound other than the component (a). (However, each numerical range represents the content (mass%) of each component when the total amount of (a) and (b) is 100 mass%). c) A photopolymerization initiator is contained, and a cured product obtained by curing the curable resin composition has (A) a glass transition temperature of 0 to 40 ° C. and (B) at 70 ° C. Storage elastic modulus is 45-130MP An optical recording medium curable resin composition is.
The present invention is also a cured product obtained by curing the curable resin composition for optical recording media.
The present invention is also an optical recording medium having a layer obtained by curing the curable resin composition for an optical recording medium.
The present invention is described in detail below.

<Curable resin composition for optical recording medium>
The curable resin composition for optical recording media of the present invention (hereinafter also referred to as “curable resin composition” or “resin composition”) is used for an optical recording medium for recording and / or reproducing with blue laser light. Is. The blue laser beam is preferably a laser beam having a wavelength of about 405 nm. However, when used for an optical recording medium for recording with such a laser beam, that is, a so-called Blu-ray disc, several decades have passed. The advantage that recording and reproduction can be performed stably over a long period of time is remarkably exhibited. Such a curable resin composition can be preferably used for any optical recording medium such as a read-only type (BD-ROM), a write-once type (BD-R), and a rewritable type (BD-RE). From the viewpoint of realizing a highly reliable optical recording medium, it can be suitably applied to a recordable optical recording medium (write-once type, rewritable type, etc.).

The curable resin composition comprises (a) a trifunctional or higher functional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone as an essential component, and if necessary, (b) the (a) A (meth) acrylate compound other than the components may be included. That is, the component (b) is an optional component. In addition, unless the effect of this invention is impaired, the other component may be contained further. Moreover, these containing components may be used individually 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 (a) is referred to as “compound (a)”, and an aggregate of the compounds (a) (that is, a generic term of one or more compounds (a)) is referred to as “component (a)”. Call it. The above (b) to (c) are also referred to in the same manner.

In the said curable resin composition, as a content rate of (a) and (b) component, (a) 50-100 mass%, (b) 0-50 mass%, respectively with respect to these total amount 100 mass% It is appropriate that When the content ratio of the component (a) is less than 50% by mass, the obtained cured product has long-term storage stability (warping characteristics, residual film properties and pressure scar resistance), heat shock resistance, crack prevention properties, and residual film. There is a possibility that characteristics such as properties cannot be exhibited in a balanced manner. The content ratios of the components (a) and (b) are preferably (a) 55 to 100% by mass and (b) 0 to 45% by mass with respect to the total amount of 100% by mass, respectively.

In the curable resin composition, a cured product obtained by curing the curable resin composition has (A) a glass transition temperature of 0 to 40 ° C. and (B) a storage elastic modulus at 70 ° C. Is suitably 45 to 130 MPa. This and the composition of the curable resin composition include at least the components (a) and (c) as described above, and the content of the component (a) is specified as described above. Low warpage (low shrinkage), transparency (light transmission), adhesion to substrates (for example, polycarbonate substrates), low corrosivity, recyclability, fast curability (productivity), It is possible to realize a protective layer that satisfies all of the various properties such as antifouling properties, dimensional stability, long-term storage stability (warping properties, residual film properties and pressure scar resistance), heat shock resistance, and crack prevention properties. . Here, the composition of the curable resin composition, the specific matter of the above (A) and the specific matter of the above (B) do not satisfy at least one, long-term storage stability (warp characteristics, residual film properties and Various performances such as pressure resistance), heat shock resistance, and crack prevention properties cannot be fully exhibited at the same time. That is, in the present invention, in order to simultaneously exhibit various performances such as long-term storage stability (warping characteristics, residual film properties and pressure scar resistance), heat shock resistance, and crack prevention properties, the composition of the curable resin composition. The present inventors have found that it is essential to specify the glass transition temperature and the storage elastic modulus at 70 ° C. of the cured product as described above, which has the technical significance of the present invention.

The glass transition temperature (Tg) is preferably higher than 0 ° C, more preferably 1 ° C or higher, still more preferably 2 ° C or higher, and preferably 35 ° C or lower, more preferably 30 ° C or lower, further Preferably it is 25 degrees C or less, Most preferably, it is 24 degrees C or less. Moreover, since the preferable range as the storage elastic modulus at 70 ° C. is greatly related to the above-described Tg, there are some portions that cannot be generally explained, for example, preferably 50 MPa or more. In addition, when Tg is low, the 25 degreeC storage elastic modulus and 70 degreeC storage elastic modulus of cured | curing material will take a close value.

The curable resin composition is also preferably such that a cured product obtained by curing the curable resin composition has a storage elastic modulus at 25 ° C. of 50 to 400 MPa. As a result, the warpage of the cured product can be further reduced, and permanent deformation due to pressure marks, dents, and the like, and peeling due to temperature changes can be more sufficiently suppressed. More preferably, it is 350 MPa or less, More preferably, it is 300 MPa or less, Most preferably, it is 250 MPa or less.

The curable resin composition also has a ratio (E1 / E2) of a storage elastic modulus E1 at 25 ° C. and a storage elastic modulus E2 at 70 ° C. of a cured product obtained by curing the curable resin composition, It is also suitable that it is 1.0-4.5. As a result, the heat shock resistance is further improved, and an optical recording medium having better physical properties can be provided. More preferably, it is 1.1 or more, preferably 4.3 or less, more preferably 4.0 or less, further preferably 3.5 or less, particularly preferably 3.0 or less, most preferably 2.5 or less. It is.

Here, in the present invention, the storage elastic modulus at 70 ° C. is preferably as high as possible within the above-described range, but among them, the smaller the E1 / E2 (that is, the smaller the storage elastic modulus E1 at 25 ° C.), This is even more preferable in terms of heat shock resistance. Specifically, the cured product obtained by curing the curable resin composition has a storage elastic modulus E2 at 70 ° C. of 50 MPa or more and E1 / E2 of 2.5 or less. Most preferably, by satisfying these two requirements, the curable resin composition of the present invention can provide an optical recording medium further excellent in heat shock resistance and warping characteristics.

It is also preferable that the curable resin composition further has a cured product obtained by curing the curable resin composition such that the loss tangent tan δ at the glass transition temperature is 0.15 to 0.45. . As a result, permanent deformation due to warpage, pressure marks, dents, etc. of the cured product can be further suppressed, and the long-term storage stability of the cured product can be further improved. More preferably, it is 0.4 or less, More preferably, it is 0.35 or less, Most preferably, it is 0.3 or less.

The glass transition temperature, the storage elastic modulus of the protective layer (25 ° C., 75 ° C.) and the loss tangent tan δ are obtained by curing the curable resin composition by the following curing method under the following measurement conditions: The dynamic viscoelasticity is measured and the obtained value is adopted. In addition, the glass transition temperature shall employ the temperature of the maximum tan δ value.
<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.
<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 >.

[(A) Component]
The compound (a) is a tri- or higher functional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone. 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 (including polyglycerin), pentaerythritol, ditrimethylolpropane, dipentaerythritol, and the like, and may have a substituent. .

The alkylene oxide is preferably, for example, an alkylene oxide having 2 to 18 carbon atoms. More preferred are alkylene oxides 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 mono Examples thereof include oxide, octylene oxide, styrene oxide and the like. Among these, alkylene oxides having 2 to 4 carbon atoms such as ethylene oxide, propylene oxide, and 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 alkylene oxides and / or ε-caprolactone present in the compound (a) (the number of repetitions) is 2 to 1 mol of the compound (a) as the average number of repetitions of the total amount of alkylene oxide and ε-caprolactone. It is suitable that it is 16 mol. 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.

Specific examples of the compound (a) include 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, Hexa (meth) acrylate of alkylene oxide adduct of dipentaerythritol, hexa (meth) acrylate of ε-caprolactone adduct of dipentaerythritol, poly (meth) acrylate of polyglycerol Etc. The.

The compound (a) is also preferably a hexafunctional or higher functional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone. As a result, it is possible to further exert the effects of the present invention that the performances such as the above-described three warpage characteristics, residual film properties, pressure scar resistance, heat shock resistance and crack prevention properties can be exhibited in a balanced manner. Become. Thus, the form in which the component (a) contains a hexafunctional or higher functional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone is also a preferred form of the present invention. Especially, it is more preferable that the ratio of the said (meth) acrylate compound which occupies for 100 mass% of total amount of the said (a) component is 50 mass% or more, More preferably, it is 70 mass% or more, Most preferably, it is 90 mass%. As mentioned above, Most preferably, it is 100 mass%.
In addition, in the (meth) acrylate compound having 6 or more functional groups modified with the above alkylene oxide and / or ε-caprolactone, the functional range is preferably 6 to 18, more preferably 6 to 12, and still more preferably 6 ~ 9.

The compound (a) is also preferably a compound using a polyhydric alcohol having a quaternary carbon (for example, trimethylolpropane, pentaerythritol, dipentaerythritol, etc.) as the polyhydric alcohol. is there. This makes it possible to obtain a cured product that is further excellent in light resistance. Thus, the form in which the component (a) includes 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 included in the present invention. This is a preferred form. Especially, it is more preferable that the ratio of the said (meth) acrylate compound which occupies for 100 mass% of total amount of the said (a) component is 50 mass% or more, More preferably, it is 70 mass% or more, Most preferably, it is 90 mass%. As described above, most preferably 100% by mass, that is, the component (a) 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 curable resin composition does not contain a (meth) acrylate compound obtained by modifying a trihydric or higher polyhydric alcohol having a tertiary carbon with an alkylene oxide and / or ε-caprolactone. Is most preferred .

[Regarding component (b)]
The said compound (b) is (meth) acrylate compounds other than the said (a) component, and may be included in the curable resin composition of this invention as needed. Such a compound (b) is preferably a compound that can be co-cured with the component (a), and is preferably in the form of a monomer. By including a compound (b), there exists an effect that the liquid viscosity and the physical property of hardened | cured material can be adjusted, for example. The compound (b) may be one type of compound or two or more types.

Examples of the compound (b) include (b-1) a bifunctional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone; (b-2) the above (a) and (b-1). ) Compounds other than the component, and having two or more radically polymerizable unsaturated groups in one molecule, urethane (meth) acrylate compound, polyester (meth) acrylate compound, epoxy (meth) acrylate compound, and side chain And at least one compound selected from the group consisting of an oligomer or polymer having a (meth) acryloyl group; (b-3) one or more compounds such as other (meth) acrylate compounds described later.

[Regarding component (b-1)]
The compound (b-1) is a bifunctional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone. That is, a bifunctional (meth) acrylate compound modified with alkylene oxide, a bifunctional (meth) acrylate compound modified with ε-caprolactone, and a bifunctional (meta) 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 number of alkylene oxides and / or alkylene oxides and / or ε-caprolactone in the compound (b-1) is the same as described above for the compound (a).

Specific examples of the compound (b-1) include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate ( (Poly) ethylene glycol di (meth) acrylate; (poly) propylene such as propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate Glycol di (meth) acrylate; Diacrylate of alkylene oxide adduct of bisphenol A; Diacrylate of alkylene oxide adduct of neopentyl glycol; Neopentylglycol Ε-caprolactone adduct diacrylate; hydroxypivalate neopentyl glycol alkylene oxide adduct di (meth) acrylate; hydroxypivalate neopentyl glycol ε-caprolactone adduct di (meth) acrylate .

[Regarding component (b-2)]
The compound (b-2) is a compound other than the components (a) and (b-1) described above, and has a urethane (meth) acrylate compound having two or more radically polymerizable unsaturated groups in one molecule. , 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. When the curable resin composition contains the component (b-2), among these (meth) acrylate compounds, 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 (b) contains a urethane (meth) acrylate compound is also a preferred form of the present invention.
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 (b-2) further preferably 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 particularly an oligomer or polymer having a (meth) acryloyl group in the side chain and two or more radically polymerizable unsaturated groups in the molecule. Although not limited, for example, following formula (1):

(Wherein R ¹ is the same or different and represents an alkylene group having 2 to 8 carbon atoms; R ² represents a hydrogen atom or a methyl group; m is a positive integer). A vinyl-based polymer having a repeating unit is suitable, whereby the hardness of the cured product can be further improved. Note that m is preferably an integer of 1 to 20. In addition, the number of repeating units represented by the above formula (1) is preferably an integer of 5 to 600.

The vinyl polymer represented by the above formula (1) is, for example, the following formula (2):

(Wherein R ¹ , R ² and m have the same meanings as those in the above formula (1), respectively) or a vinyl monomer (also referred to as “heterogeneous polymerizable monomer”) or It can be prepared by a normal cationic polymerization technique using two or more kinds. It can also be easily prepared by living cationic polymerization.

Specific examples of the vinyl monomer represented by the above formula (2) 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.

The vinyl polymer represented by the above formula (1) may also be a copolymer having a structural unit derived from a monomer capable of cationic polymerization. Examples of the cationic polymerizable monomer include vinyl ether compounds; styrene and styrene derivatives; N-vinyl compounds; divinyl compounds and trivinyl compounds.

The compound (b-2) is also preferably a single cured product having a storage elastic modulus at 25 ° C. of 1 to 300 MPa. When the curable resin composition contains the component (b-2), permanent deformation due to pressure marks or dents in the cured product can be more sufficiently suppressed by using such a compound (b-2). At the same time, warpage is more sufficiently reduced. More preferably, it is 3 MPa or more, More preferably, it is 10 MPa or more, More preferably, it is 200 MPa or less, More preferably, it is 100 MPa or less, Most preferably, it is 50 MPa or less.
Here, the storage elastic modulus at 25 ° C. is a value obtained by a dynamic viscoelasticity measurement method under the following measurement conditions for a cured product obtained by curing the compound (b-2) alone.
<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.

Thus, when the said curable resin composition contains the (b-2) component, the said (b-2) component contains the compound from which the storage elastic modulus in 25 degreeC of a single hardened | cured material will be 1-300 MPa. Such a form is also one of the preferred forms of the present invention. That is, the component (b-2) includes a urethane (meth) acrylate compound, a polyester (meth) acrylate compound, an epoxy (meth) acrylate compound, and a side chain having two or more radically polymerizable unsaturated groups in the molecule. And at least one compound selected from the group consisting of an oligomer or polymer having a (meth) acryloyl group, and a compound having a single cured product having a storage elastic modulus at 25 ° C. of 10 to 900 MPa. It is preferable. This makes it possible to more fully demonstrate the effects of the present invention. Above all, the component (b-2) is composed of only a compound having a storage elastic modulus at 25 ° C. of 1 to 300 MPa of a single cured product, that is, the component (b-2) is a single cured product. More preferably, it is composed of one or more compounds having a storage elastic modulus at 25 ° C. of 1 to 300 MPa.

Further, the compound (b-2) 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 (b-2) having a Tg of −50 ° C. or higher, it is possible to more sufficiently suppress permanent deformation due to pressure marks or dents in the cured product obtained from the curable resin composition of the present invention. 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 determined by a dynamic viscoelasticity measurement method under the same measurement conditions as the storage elastic modulus (25 ° C.) of the cured product obtained by curing the above-described compound (b-2) alone. It is assumed that the temperature of the maximum tan δ value is adopted.

[Regarding component (b-3)]
The compound (b-3) is another (meth) acrylate compound other than the components (a), (b-1) and (b-2), and is represented by, for example, the general formula (2) described above. Vinyl monomers, (meth) acrylate compounds not modified with alkylene oxide or ε-caprolactone, monofunctional (meth) acrylate compounds, and the like. 1 type, or 2 or more types, such as a vinyl-type monomer and the following compound.

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 the compound (b-3), a vinyl monomer represented by the general formula (2) (heteropolymerizable monomer) is used from the viewpoint of good adhesion to a commonly used polypolycarbonate substrate. Can be suitably used. Among them, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxyethyl (meth) acrylate, 2-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate, (meth) acrylic acid 4 -Vinyloxybutyl, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxycyclohexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, 2- (2-vinyloxy) (meth) acrylate Ethoxy) ethyl, 2- (2-vinyloxyisopropoxy) propyl (meth) acrylate, and 2- {2- (2-vinyloxyethoxy) ethoxy} ethyl (meth) acrylate are preferred. Of these, 2- (2-vinyloxyethoxy) ethyl (meth) acrylate is preferable.

The compound (b-3) is particularly preferably a bifunctional or higher (meth) acrylate compound (that is, a polyfunctional (meth) acrylate compound) or a vinyl monomer represented by the general formula (2) (different type). Polymerizable monomer).

The components (a) and (b) are also preferably used so that the average acrylic equivalent to the total amount of these components is 180 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 190 or more, More preferably, it is 200 or more. Moreover, it is suitable that it is 350 or less, and by this, it is suppressed more that a dent etc. are attached to an optical recording medium, and long-term storage stability can be exhibited more fully. More preferably, it is 330 or less.
In the present invention, the acrylic equivalent is 180 or more, and the cured product obtained by curing the curable resin composition has a glass transition temperature (Tg), a loss tangent tan δ at Tg, and a storage elastic modulus. However, if it is within the above-mentioned preferred range, it becomes possible to provide an optical recording medium having further excellent warpage characteristics. 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 with respect to the total amount of the components (a) and (b) is determined by the sum of Mx × Ax ÷ A.
Mx is the molecular weight (*) of (meth) acrylic acid ester ((meth) acrylate) x corresponding to the components (a) and (b) above, and (meth) acryloyl possessed by (meth) acrylic acid ester x When there is one group, the molecular weight value of the (meth) acrylic acid 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 the components (a) and (b) contained in the resin composition.
* As the molecular weight here, the number average molecular weight (Mn) is adopted for the component (b-2), and the value calculated as the sum of the atomic weights of the constituent elements is adopted for the other components.

[Other polymerizable components]
In the present invention, in addition to the essential components (a) and (c) described above, and an optional component (b) contained as necessary, other co-curable components (other As the polymerizable component), one or more of the following unsaturated compounds may be contained.
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 components (a) to (b) and the unsaturated compound. However, considering the recyclability of the resin composition when the curable resin composition is subjected to a 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 above components (a) to (b) and the unsaturated compound are collectively referred to as “polymerizable component”. That is, the polymerizable component is composed of the component (a) (or the component (a) and (b) when the component (b) is further included), and may further include the unsaturated compound. In other words, when the curable resin composition for an optical recording medium of the present invention does not contain the unsaturated compound, the component (a) (or the component (b)) when the component (b) is further included. In the case where the unsaturated compound is included, the component (a) (or the component (a) and (b) when the component (b) is included), the unsaturated compound, Means a mixture of

[(C) Component]
The resin composition of the present invention also contains the photopolymerization initiator (c) as an essential component. However, by including the photopolymerization initiator, the resin composition can be quickly cured by light irradiation. As the photopolymerization initiator (c), a photoradical polymerization initiator that generates a polymerization initiation radical upon irradiation with light is suitable. Moreover, you may use the photocationic polymerization initiator which generate | occur | produces a polymerization initiation cation by irradiation of light. In addition, the photoinitiator (c) can use 1 type (s) or 2 or more types.

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-methyl-1- is preferable because it improves the durability of an optical disk using the curable resin composition for an optical disk as a protective layer and suppresses an increase in warpage during a heat resistance test. [4- (1-methylvinyl) phenyl] propanone} is particularly preferred.

In the curable resin composition, the content of the photopolymerization initiator (c) is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the total amount of the polymerizable components. When it is 1 part by weight or more, the curable resin composition can be cured more fully, and when it is 10 parts by weight or less, odor generation and coloring of the cured product can be sufficiently suppressed, and the curable resin composition The recyclability of the product and the long-term storage stability of the cured product can be further improved. More preferably, it is 1-5 weight part, More preferably, it is 1-3 weight part.

[Other ingredients]
The curable resin composition of the present invention may further contain an ultraviolet absorber and 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. The addition amount of the ultraviolet absorber is preferably 0.03 to 2 parts by weight with respect to 100 parts by weight of the total amount of the polymerizable components. More preferably, it is 0.05-1 weight part, More preferably, it is 0.05-0.5 weight part.

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

The curable resin composition may also contain one or more of photosensitizers, photopolymerization accelerators, metal oxide particles, surface function modifiers, solvents and the like as necessary. Inorganic fillers, low shrinkage agents (reactive oligomers or polymers, non-reactive oligomers or polymers), color pigments, plasticizers, chain transfer agents, polymerization inhibitors, near infrared absorbers, light stabilizers, oxidation One or two of an inhibitor, a flame retardant, a matting agent, a dye, an antifoaming agent, a leveling agent, an antistatic agent, a dispersant, a slip agent, a surface modifier, a thixotropic agent, a thixotropic agent, etc. It may contain more than seeds.
What is necessary is just to set suitably the compounding quantity of these other components according to the kind, the intended purpose, the use of a composition, a usage method, etc., and it is not specifically limited.

[A more preferred form of the curable resin composition for optical recording media]
The curable resin composition of the present invention can be obtained by blending the above-described essential components and the above-mentioned components contained as necessary, 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.

The curable resin composition can be cured by irradiation 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 curable 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 curable resin composition may be further cured by irradiation with an electron beam together with curing 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.

[Cured product]
The present invention is also a cured product obtained by curing the curable resin composition for optical recording media. Such cured products not only have excellent physical properties such as transparency, hardness, residual film properties, film thickness stability, and film thickness uniformity, but also have excellent heat shock resistance, remarkably small warpage, and pressure marks. Permanent deformation (permanent deformation) due to dents and dents is sufficiently suppressed, and the long-term storage stability is remarkably excellent. Therefore, this cured product is particularly useful as a layer (cured film) constituting the optical recording medium.

It is preferable that the cured product has one or more of Tg, loss tangent tan δ at Tg, and storage elastic modulus within the above-mentioned range, and thereby a layer (cured) constituting an optical recording medium. Film).

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 obtained by curing the curable resin composition for an optical recording medium (a layer obtained by curing). 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 curable resin composition for an optical recording medium of the present invention is suitably used for either a single-layer or multi-layer optical recording medium, and the optical recording medium of the present invention is a single-layer or multi-layer. It is suitable as any of the optical recording media of the formula.

Since the curable resin composition is excellent in transparency and high in 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 curable resin composition for an optical recording medium is one of the preferred embodiments of the present invention. In this case, low warpage (low shrinkage), transparency (light transmission), adhesion to the substrate (for example, polycarbonate substrate, etc.), low corrosion, recyclability, fast curability (productivity), antifouling Protective layer and intermediate layer satisfying all properties such as stability, dimensional stability, long-term storage stability (change in warpage during heating acceleration test, residual film property, small amount of permanent deformation such as pressure marks and dents) It becomes possible to do.
In the 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 of the light transmission layers is a layer obtained by curing the curable resin composition for an optical recording medium. Is preferred. Among these, at least one layer of the protective layer is more preferably a layer formed by curing the curable resin composition for optical recording media.

-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. Moreover, since the linear expansion coefficient of the cured product is small in the polycarbonate resin, the synergistic effect of such a substrate and the layer obtained by curing the curable resin composition for optical recording media of the present invention makes the light more excellent in warping characteristics. A recording medium can be obtained. 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-
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 20 to 150 μm. More preferably, it is 70-105 micrometers, More 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 thickness of the protective layer is smaller and the thickness of the intermediate layer is larger.
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 curable 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 1-50 micrometers. More preferably, it is 5-30 micrometers, More 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 curable 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. It has the characteristic that

An optical recording medium having a layer obtained by curing the curable resin composition for an optical recording medium is obtained by, for example, forming the curable resin 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 resin composition, the term “on the reflective film” as used herein refers not only to a form in which the layer is directly laminated on the reflective film, but also on the reflective film. It also means a form in which a functional layer is laminated and the layer is laminated on the functional layer.

As a method for forming a layer formed by curing the curable resin composition on the reflective film (a layer obtained by curing the curable resin composition), a normal method may be employed. Examples include a method of bonding the cured product of the resin composition to the reflective film with an adhesive, a method using a spin coater (spin coating method), and the like. is there. The curable resin composition for an optical recording medium of the present invention is particularly suitable for film formation by a spin coating method, that is, specifically, the flowability is good and the direction from the center of the spin coater toward the outside. In this respect, it is preferable to employ the spin coating method because the film can be formed while sufficiently preventing the occurrence of unevenness.

Since the layer formed by curing the curable resin composition is formed from the curable resin composition of the present invention described above, 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 injection molding a single resin substrate, a pit as a recording layer is provided, a reflective film (also referred to as a reflective layer) is formed on the recording layer, and an ultraviolet ray is further formed on the reflective film. A method of forming a protective layer (light transmission layer) by applying a curable resin composition by a spin coat method or the like and then curing the composition 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, an ultraviolet curable resin composition is applied on 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 is configured as described above, it can sufficiently exhibit various physical properties such as transparency and film thickness stability, and can be stably warped and deformed over a long period of time. A cured product in which peeling from other layers is suppressed can be provided, and more reliable recording and reproduction can be realized. Use of such a resin composition is useful because it can provide an optical recording medium that can be stably recorded and reproduced over a long period of several decades or more. In addition, an optical recording medium having a layer formed by curing such a resin composition is extremely reliable, and is also suitable for use in a place where it is easily exposed to a high temperature such as a cold district or in a car or for a long period of storage. It is a thing.

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 weight” and “%” means “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) 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.

(2) Protective layer Storage elastic modulus at 25 ° C or 70 ° C (E1, E2)
Only the protective layer (cured film (cured product) of the resin composition) is peeled off from the obtained substrate / protective layer laminate with predetermined dimensions, and the tensile mode, the frequency is 1 Hz, the clamp distance is 25 mm, and the amplitude is 0.1%. Then, the dynamic viscoelasticity was measured under a temperature rising rate of 5 ° C./min, and the obtained value of each storage elastic modulus at 25 ° C. or 70 ° C. was adopted. From these values, the ratio (E1 / E2) of the storage elastic modulus E1 at 25 ° C. and the storage elastic modulus E2 at 70 ° C. was calculated.
(3) 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 (2) above, and the temperature of the maximum tan δ value was adopted.
(4) Protective layer Tan δ value at glass transition temperature The tan δ value of the glass transition temperature measured by the same measuring method and conditions as the storage elastic modulus of (2) above was adopted.

(5) Curing amount at the time of curing (initial) The obtained substrate / protective layer / hard coat layer laminate is horizontal so that the protective layer (cured film (cured product) of the resin composition) is on the upper surface side. After placing on a glass plate, a radial displacement 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%. The amount of warpage before and after coating was adopted as the amount of warpage during curing (initial).
(6) Increase in warpage at low temperature (5 ° C.) Increase in warpage when the obtained substrate / protective layer / hard coat layer laminate is left in an environment at 5 ° C. and 45% relative humidity for 5 hours. The value was measured in the same manner as the amount of warping at the time of curing (initial) in (5) above.
(7) Increased amount of warpage after heating acceleration test (70 ° C., 100 hours) The obtained substrate / protective layer / hard coat layer laminate was held in an oven at 70 ° C. for 100 hours, and further the temperature was 25 ° C. The amount of increase in warpage when left in an environment with a relative humidity of 50% for 24 hours was measured in the same manner as the amount of warpage at the time of curing (initial) in (5) above.

(8) Comprehensive evaluation of warpage The amount of warpage at the time of curing (initial), the amount of warpage at low temperature (5 ° C), and the warpage after a heating acceleration test (70 ° C, 100 hours) determined in the above (5) to (7) The amount of increase was summed and the obtained amount of warpage was evaluated according to the following criteria.
◎: Less than 0.8 ° ○: 0.8 ° or more, less than 1.0 ° △: 1.0 ° or more, less than 1.2 ° x: 1.2 ° or more

(9) Heat shock resistance 1 (defect evaluation)
When the obtained optical recording medium (substrate / protective layer / hard coat layer laminate) was held in an oven at 25 ° C. for 1 hour and then held at 70 ° C. for 1 hour, the test was repeated 100 times. Evaluation was made based on the presence or absence of peeling at the interface between the substrate and the protective layer.
○: No peeling ×: There is peeling (10) Heat shock resistance 2 (breaking evaluation)
When the obtained optical recording medium (substrate / protective layer / hard coat layer laminate) was held in a 25 ° C. oven for 1 hour and then held at 70 ° C. for 1 hour, the test was repeated 500 times. Evaluation was made based on the presence or absence of peeling at the interface between the substrate and the protective layer.
○: No peeling ×: There is peeling

(11) Heat shock resistance 3 (defect evaluation)
When the obtained optical recording medium (substrate / protective layer / hard coat layer laminate) was held in a 25 ° C. oven for 1 hour and then held at 70 ° C. for 1 hour, the test was repeated 800 times. Evaluation was made based on the presence or absence of peeling at the interface between the substrate and the protective layer.
○: No peeling ×: There is peeling (12) Heat shock resistance 4 (breaking evaluation)
When the obtained optical recording medium (substrate / protective layer / hard coat layer laminate) was held in a 25 ° C. oven for 1 hour and then held at 70 ° C. for 1 hour, the test was repeated 1000 times. Evaluation was made based on the presence or absence of peeling at the interface between the substrate and the protective layer.
○: No peeling ×: There is peeling. Note that heat shock resistance 1, 2, 3, and 4 are tested under severe conditions as the number attached increases, and “○” in the heat shock resistance 1 evaluation test. Even if it is evaluated as, it can exhibit extremely excellent heat shock resistance, but those rated as “◯” in heat shock resistance 2-4 exhibit even more excellent heat shock resistance. Means you can.

(13) Pressure Scratch Resistance Using a laminate of the obtained substrate / protective layer / hard coat layer, using a micro compression tester (manufactured by Shimadzu Corporation, model MCT-W500) as a test condition, a used flat indenter diameter of 50 μm, Deformation amount remaining in the laminate (permanent deformation amount) when the load speed is 20 mN / sec, the maximum load is 300 mN, the holding time at the maximum load is 90 seconds, the unloading speed is 20 mN / sec, and the holding time after complete unloading is 90 seconds , Μm) and measured according to the following criteria.
A: The amount of permanent deformation is less than 0.5 μm: The amount of permanent deformation is 0.5 μm or more and less than 0.7 μm Δ: The amount of permanent deformation is 0.7 μm or more, less than 1.0 μm ×: The amount of permanent deformation is 1.0 μm or more

(14) Crack prevention property of HC (hard coat layer) Using the obtained substrate / protective layer / hard coat layer laminate, a test similar to the pressure scar test of (13) above was conducted, and a hard coat layer was obtained. The presence or absence of cracks was confirmed visually and evaluated according to the following criteria.
○: No crack ×: There is a crack

(15) Using a laser focus displacement meter, measure the thickness of the protective layer before and after the heating acceleration test (70 ° C., 100 hours) of (7) above for the laminate of residual film substrate / protective layer / hard coat layer. The remaining film ratio (%) was calculated by [(film thickness after the heating acceleration test / film thickness before the heating acceleration test) × 100] and evaluated according to the following criteria.
A: Remaining film ratio is 99% or more and less than 101% B: Remaining film ratio is 98% or more and less than 99%, or 101% or more and less than 102% X: Transmittance is less than 98% or 102% or more

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.

Production Example 2 (Synthesis of UA-2)
300 g of polypropylene glycol “P-2000” manufactured by Asahi Denka Co., Ltd. in Production Example 1 was changed to a mixture of 150 g of polytetramethylene ether glycol “PTMG2000” manufactured by Mitsubishi Chemical Corporation and 150 g of polypropylene glycol “P-2000” manufactured by Asahi Denka Co. Except that, urethane acrylate (referred to as “UA-2”) was synthesized in the same manner as in Production Example 1 (UA-1). The molecular weight (Mn) was 5,500, the molecular weight distribution (Mw / Mn) was 3.61, the glass transition temperature was 10 ° C., and the storage elastic modulus at 25 ° C. was 150 MPa.

Production Example 3 (Synthesis of P-1)
150 g of ethyl acetate was 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 70 ° C. After heating, a mixture of 15 g of 2- (2-vinyloxyethoxy) ethyl acrylate (VEEA, Nippon Shokubai Co., Ltd.) and 185 g of 2-ethylhexyl vinyl ether, and a mixed solution of 25 g of ethyl acetate and 13 mg of phosphotungstic acid, The polymerization was carried out by dropping each over 3 hours. After completion of the polymerization, the reaction was terminated by adding triethylamine. Subsequently, after concentrating with an evaporator, a vinyl polymer (referred to as “P-1”) was obtained. The reaction rate of the monomer is 99.5% by analyzing the mixed solution after stopping the reaction by gas chromatography (GC), and the content of ethyl acetate is 0.1%. There was found. The number average molecular weight (Mn) of the obtained vinyl polymer (P-1) is 2200, the molecular weight distribution (Mw / Mn) is 1.50, the glass transition temperature is −5 ° C., and the elastic modulus at 25 ° C. is 30 MPa.

Production Example 4 (Synthesis of P-2)
A mixture of 15 g of 2- (2-vinyloxyethoxy) ethyl acrylate (VEEA, manufactured by Nippon Shokubai Co., Ltd.) and 185 g of 2-ethylhexyl vinyl ether was mixed with 2- (2-vinyloxyethoxy) ethyl acrylate (VEEA, manufactured by Nippon Shokubai Co., Ltd.). ) A vinyl polymer (referred to as “P-2”) was obtained in the same manner as in Production Example 3 (P-1) except that the mixture was changed to a mixture of 40 g and 160 g of 2-ethylhexyl vinyl ether. The reaction rate of the monomer is 99.6% by analyzing the mixed solution after the reaction is stopped by gas chromatography (GC), and the content of ethyl acetate is 0.1%. There was found. The number average molecular weight (Mn) of the obtained vinyl polymer (P-2) is 2400, the molecular weight distribution (Mw / Mn) is 1.55, the glass transition temperature is 15 ° C., and the elastic modulus at 25 ° C. is 150 MPa. Met.

Example 1
(Preparation of protective layer)
Each component shown in Table 1 was mixed and stirred at each blending amount (part) shown in Table 1 to prepare a curable resin composition (1) for an optical recording medium.

(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 curable resin composition (1) for an optical recording medium was applied on a silver alloy with a spin coater at an ambient temperature of 25 ° C. and a relative humidity of 50%. Using a UV irradiator having a flash UV lamp (model RC-801, manufactured by Xenon, USA), the flash was irradiated 15 times at a lamp height of 2 cm in a nitrogen atmosphere and cured. 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 curable resin composition for hard coat for optical recording media was applied on a cured product (protective) layer with a spin coater at a thickness of about 3 μm, and a UV having a xenon flash UV lamp. Using an irradiator (model RC-801, manufactured by Xenon, USA), a flash was irradiated 10 times at a lamp height of 2 cm in a nitrogen atmosphere and cured. 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 curable resin composition for optical recording media (1) and the obtained optical recording medium (substrate / protective layer / hard coat layer laminate (*)) were evaluated. The results are shown in Table 1.
* Except for the 3 warp increase, warp comprehensive evaluation, pressure scar resistance, HC crack prevention property, residual film property and heat shock resistance evaluation test, the hard coat layer is not laminated, that is, the substrate / protective layer The laminate was evaluated and measured.

Example 1-2 (an alternative method of Example 1)
After the sputtering process of the silver alloy in (Formation 1 of protective layer) of Example 1, the curable resin composition (1) was cured by the following method to form a cured product (protective) layer, and then Example Various evaluations of the optical recording medium (substrate / protective layer / hard coat layer laminate or substrate / protective layer laminate) were performed in the same manner as in Example 1. The results were almost the same. In this case, the hard coat layer was formed in the same manner as in Example 1.
(Formation of protective layer 2)
After the sputtering process (film thickness of 20 to 40 nm) of the silver alloy in (Formation 1 of protective layer) of Example 1, a metal-containing azo dye was used as an organic dye-based recording layer with a thickness of 10 to 20 nm using a spin coater. A film was formed. Next, ITO (indium tin oxide) was sputtered on the metal-containing azo dye as an interface layer to a thickness of 5 to 10 nm. Next, the obtained curable resin composition (1) was applied on the ITO film with a spin coater at a thickness of about 100 μm under an environment of an ambient temperature of 25 ° C. and a relative humidity of 50%, and a xenon flash UV lamp was applied. Using a UV irradiation machine (model RC-801, manufactured by Xenon, USA), a flash was irradiated 15 times at a lamp height of 2 cm in a nitrogen atmosphere and cured. 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.

Examples 2-18, Comparative Examples 1-6
In the same manner as in Example 1 (Preparation of protective layer), each component was mixed and stirred at the ratios shown in Tables 1 to 3, and curable resin compositions for optical recording media (2) to (18) were compared. Resin compositions (1) to (6) were obtained. Then, it replaced with the curable resin composition (1) for optical recording media 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 Tables 1-3.

Abbreviations in Tables 1 to 3 are as follows.
* 1: The molecular weight of the compound corresponding to the component (b-2) described above means the number average molecular weight (Mn), and the molecular weight of the other (meth) acrylate compounds is calculated as the sum of the atomic weights of the constituent elements. Value.
* 2: The Tg and storage elastic modulus of the compound corresponding to the component (b-2) described above mean the Tg and storage elastic modulus (25 ° C.) of the cured product obtained by curing it alone.

TMP-3PO-A: triacrylate of propylene oxide 3 mol adduct of trimethylolpropane (trade name “SR492”, manufactured by Sartomer)
TMP-6PO-A: Triacrylate of propylene oxide 6 mol adduct of trimethylolpropane (trade name “CD501”, manufactured by Sartomer)
TMP-6EO-A: Triacrylate of trimethylolpropane ethylene oxide 6 mol adduct (trade name “Light acrylate TMP-6EO-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
TMP-9EO-A: Triacrylate of trimethylolpropane adduct with 9 moles of ethylene oxide (trade name “SR502”, manufactured by Sartomer)
G-PO-A: Triacrylate of propylene oxide 5.5 mol adduct of glycerin (trade name “CD9021”, manufactured by Sartomer)
THEIC-3CL-A: Tris (2-hydroxyethyl) isocyanurate (THEIC) ε-caprolactone 3-mol modified acrylate, trade name “Aronix M327”, Toa Gosei Co., Ltd. PET-4PO-A: propylene oxide of pentaerythritol 4 mol adduct tetraacrylate DPCA-120: dipentaerythritol ε-caprolactone 12 mol adduct hexaacrylate (trade name “Kayarad DPCA-120”, manufactured by Nippon Kayaku Co., Ltd.)
DPCA-60: hexaacrylate of 6-mol adduct of ε-caprolactone of dipentaerythritol (trade name “Kayarad DPCA-60”, manufactured by Nippon Kayaku Co., Ltd.)
DPHA-12EO-A: Hexaacrylate of ethylene oxide 12 adduct of dipentaerythritol (trade name “NK Ester A-DPH-12E”, manufactured by Shin-Nakamura Chemical Co., Ltd.)
PG1-A: Polyacrylate of polyglycerin ethylene oxide adduct (7 functional, average value) (trade name “NK Economer A-PG5009E”, manufactured by Shin-Nakamura Chemical Co., Ltd.)
PG2-A: Polyacrylate of polyglycerin ethylene oxide adduct (9 functional, average value) (trade name “NK Economer A-PG5027E”, manufactured by Shin-Nakamura Chemical Co., Ltd.)

UA-1: urethane acrylate obtained in Production Example 1 UA-2: urethane acrylate obtained in Production Example 2 CN978: urethane acrylate manufactured by Sartomer
CN9178: manufactured by Sartomer, urethane acrylate CN2270: manufactured by Sartomer, polyester acrylate P-1: vinyl polymer obtained in Production Example 3 P-2: vinyl polymer obtained in Production Example 4 CN UVE151: manufactured by Sartomer , Epoxy acrylate CN981: made by Sartomer, urethane acrylate

Bis-10EO-A: Diacrylate of ethylene oxide 10 mol adduct of bisphenol A (trade name “SR-602”, manufactured by Sartomer)
APG-700: diacrylate of polypropylene glycol (trade name “NK Ester APG-700”, manufactured by Shin-Nakamura Chemical Co., Ltd.)
HX-620: Diacrylate of ε-caprolactone 4 mol adduct of hydroxypivalic acid neopen glycol (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)

TMPTA: Trimethylolpropane triacrylate (trade name “SR351”, manufactured by Sartomer)
TCD-A: Tricyclodecane diacrylate (trade name “Light Acrylate DCP-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
PEA: Phenoxyethyl acrylate (trade name “Light Acrylate PO-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)

Irg184: 1-hydroxy-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, manufactured by Ciba Specialty Chemicals)
Irg127: 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propane (trade name “Irgacure 127”, Ciba Specialty Chemicals (Made by company)
Esacure one: oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone} (trade name “Escure ONE”, manufactured by Lamberti)

From the results of the above-described Examples and Comparative Examples, the curable resin composition for optical recording media of the present invention was subjected to (a) trifunctional or higher functional (meth) acrylate compound 50 modified with alkylene oxide and / or ε-caprolactone. To 100 mass% and (b) (meth) acrylate compound other than the component (a) 0 to 50 mass% (provided that each numerical range represents the total amount of (a) and (b) as 100 mass% And (c) a photopolymerization initiator and a cured product obtained by curing the curable resin composition (A). ) When the glass transition temperature (Tg) is 0 to 40 ° C. and (B) the storage elastic modulus (E2) at 70 ° C. is 45 to 130 MPa, the obtained cured product has various types. Warpage characteristics, pressure resistance, heat resistance It is advantageous in that it has excellent shock properties, residual film properties, etc., and can prevent the occurrence of cracks when laminating a hard coat layer, and can exhibit various characteristics at the same time in a balanced manner. It was confirmed. This will be described below.

That is, all of the resin compositions of Examples 1 to 18 satisfy the above form, whereas Comparative Example 1 has the above-described numerical range of the present invention in which the content ratio of component (a), Tg, and E2 are as described above. Comparative example 2 is an example in which Tg and E2 are below the numerical range of the present invention described above. In these cases, the heat shock resistance, the pressure scar resistance, and the HC crack prevention property (performance for preventing cracks when a hard coat layer is laminated) are significantly inferior to the examples.

Comparative Example 3 is an example in which E2 is lower than the above-described numerical range of the present invention, but peeling occurs even in the evaluation test of heat shock resistance 1, and it is understood that the heat shock resistance is inferior to that of the example. . Comparative Example 4 is an example in which the content ratio of the component (a) is lower than the numerical range of the present invention described above, and E2 exceeds the numerical range of the present invention described above. In Comparative Example 5, Tg and E2 are described above. Although it is an example exceeding the numerical range of this invention, in any case, it is a result inferior compared with an Example in the point of a curvature characteristic, heat shock resistance, and a pressure | voltage resistant dent. Comparative Example 6 is an example in which Tg exceeds the above-described numerical range of the present invention, but in this case, the results are inferior in the warp characteristics and the pressure-proof marks as compared with the Examples.
Therefore, it can be said that only when the curable resin composition is in the above-described form of the present invention, an optical recording medium capable of exhibiting various performances in good balance can be provided.

Claims (5)

A curable resin composition for use in an optical recording medium having at least a substrate, a recording layer, a reflective film, and a protective layer, and recording and / or reproducing with blue laser light,
The curable resin composition is
(A) 50 to 100% by mass of a trifunctional or higher functional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone;
(B) (0) to 50% by mass of (meth) acrylate compound other than the component (a) (however, each numerical range is each component when the total amount of (a) and (b) is 100% by mass) The content ratio (% by mass) of
Furthermore, (c) includes a photopolymerization initiator,
A cured product obtained by curing the curable resin composition,
(A) The glass transition temperature is 0 to 40 ° C., and
(B) A curable resin composition for optical recording media, wherein the storage elastic modulus at 70 ° C. is 45 to 130 MPa. The curable resin composition for optical recording media, wherein the component (a) contains a hexafunctional or higher functional (meth) acrylate compound modified with alkylene oxide and / or ε-caprolactone. A cured product obtained by curing the curable resin composition for optical recording media according to claim 1. An optical recording medium comprising a layer obtained by curing the curable resin composition for an optical recording medium according to claim 1. The optical recording medium according to claim 4, wherein the optical recording medium is recordable.