JP5098783B2 - Ultraviolet curable composition for optical disc and optical disc - Google Patents

Description

  A DVD (Digital Versatile Disc), which is the mainstream as an optical disk capable of high-density recording, has a structure in which two substrates having a thickness of 0.6 mm are bonded together with an adhesive. In order to achieve high density in a DVD, a 650 nm laser having a shorter wavelength is used compared to a CD (Compact Disc), and the optical system has a high numerical aperture.

  However, it is necessary to further increase the density in order to record or reproduce a high-quality video or the like corresponding to HDTV (high definition television). High-density recording methods and optical discs for the next generation of DVD have been studied, and high-density recording using a new optical disc structure using a blue laser with a shorter wavelength and a high numerical aperture optical system than DVD. A scheme has been proposed.

  This new optical disk is formed by forming a recording layer on a transparent or opaque substrate made of plastic such as polycarbonate, and then laminating a light transmission layer of about 100 μm on the recording layer, and recording light or The optical disk has a structure in which reproduction light or both are incident. From the viewpoint of productivity, the use of an ultraviolet curable composition for the light transmission layer of this optical disc has been studied exclusively.

  An optical disk using a blue laser needs to maintain stable recording / reproducing characteristics for a long time. For this reason, the light transmission layer is desired to have excellent shape stability, and when used as the outermost layer, it is required to have excellent wear resistance. As an ultraviolet curable composition used for a light transmission layer of an optical disc that is recorded or reproduced by a blue laser, for example, ultraviolet rays using epoxy acrylate and urethane acrylate in combination and 1-hydroxycyclohexyl phenyl ketone as a polymerization initiator. A curable composition is disclosed (see Patent Document 1). Although the ultraviolet curable composition provides a cured film having durability and high light transmittance, it has been desired to further reduce the warpage generated when the wet heat environment changes.

  As a photocurable composition capable of forming a cured product layer having excellent dimensional stability at the initial stage and durability, a composition containing urethane (meth) acrylate and having a cured film having an elastic modulus of 100 to 600 MPa is disclosed. (See Patent Document 2). However, the cured products of these compositions have insufficient wear resistance, and may be damaged when applied as the outermost light-transmitting layer of the optical disk.

JP 2002-109785 A JP 2007-80448 A

  The problems to be solved by the present invention are an ultraviolet curable composition that gives a cured film with little warpage when changing to a wet heat environment, and a light transmission layer with little warpage even when changing to a wet heat environment. An object of the present invention is to provide an optical disc having excellent wear characteristics.

  The ultraviolet curable composition of the present invention is an ultraviolet curable composition having a (meth) acryloyl group concentration of 4.2 mmol / g or less and an elastic modulus at 30 ° C. of the cured film after ultraviolet curing of 2000 MPa or more. According to the ultraviolet curable composition having such a configuration, since the concentration of the (meth) acryloyl group is low, the cured shrinkage at the time of ultraviolet irradiation that causes warping of the optical disk is reduced, and further, the cured film has little change in warpage when the wet heat environment changes. Can be realized. Moreover, since the elastic modulus at 30 ° C. of the cured film after UV curing is 2000 MPa or more, it is possible to realize a cured film that is difficult to be deformed by an external load and excellent in dimensional stability, and has excellent wear resistance. A membrane can be realized.

  That is, the present invention is an ultraviolet curing used for a light transmission layer of an optical disc in which at least a light reflection layer and a light transmission layer are laminated on a substrate, and laser light is incident from the light transmission layer side to reproduce information. Type composition comprising a (meth) acrylate oligomer and a (meth) acrylate monomer, having a (meth) acryloyl group concentration of 4.2 mmol / g or less, and an elastic modulus at 30 ° C. of the cured film after UV curing Provided are an ultraviolet curable composition for optical discs having a viscosity of 2000 MPa or more, and an optical disc having a light transmission layer comprising a cured product of the ultraviolet curable composition.

  Since the ultraviolet curable composition for optical discs of the present invention can form a cured film with little warpage change even when the wet heat environment changes, an optical disc with little characteristic deterioration can be realized even when the wet heat environment changes. Further, since the cured film of the composition is excellent in abrasion resistance, the light transmission layer can be applied as the outermost layer, and thus an optical disk with little damage can be realized without providing a hard coat layer on the surface layer. An optical disc using a cured film of such a composition as a light-transmitting layer is less susceptible to deterioration in characteristics even when the humidity and heat environment changes, and is less likely to be scratched. In addition, information can be recorded / reproduced.

  The ultraviolet curable composition for optical disks of the present invention contains a (meth) acrylate oligomer and a (meth) acrylate monomer, has a (meth) acryloyl group concentration of 4.2 mmol / g or less, and is a cured film after ultraviolet curing. It is an ultraviolet curable composition for optical discs having an elastic modulus at 30 ° C. of 2000 MPa or more. In addition, the optical disk ultraviolet curable composition has at least a light reflection layer and a light transmission layer laminated on a substrate, and receives light from the light transmission layer side to reproduce information by optical transmission of the optical disk. Used as a layer.

[(Meth) acrylate oligomer]
The (meth) acrylate oligomer used in the ultraviolet curable composition of the present invention is not particularly limited, and various urethane (meth) acrylates, epoxy (meth) acrylates, polyester (meth) acrylates, and polyether (meth) acrylates may be used. Can be used. Among these, urethane (meth) acrylate and epoxy (meth) acrylate can be preferably used because the (meth) acryloyl group concentration of the ultraviolet curable composition and the elastic modulus after curing are easily adjusted to the above ranges. Moreover, it is preferable to use a polyfunctional (meth) acrylate oligomer.

  The content of the oligomer in the (meth) acrylate in the ultraviolet curable composition of the present invention may be appropriately adjusted depending on the combination of the (meth) acrylate oligomer and (meth) acrylate monomer used, but the ultraviolet curable composition. It is preferable to adjust by about 20-80 mass% in the ultraviolet curable compound contained in the.

  Examples of the urethane (meth) acrylate include polyurethane (meth) acrylates such as urethane (meth) acrylate having a polyether skeleton, urethane (meth) acrylate having a polyester skeleton, and urethane (meth) acrylate having a polycarbonate skeleton.

  Especially, the compound (a) which has a 3 or more hydroxyl group in a molecule | numerator, the compound (b) which has a 2 or more isocyanate group in a molecule | numerator, the compound (a) which has a hydroxyl group and a (meth) acryloyl group ( It is preferable to use urethane (meth) acrylate (U1) obtained from c). By using the urethane (meth) acrylate (U1), it is possible to impart flexibility to the cured film with less warpage when the wet heat environment changes. Further, the urethane bond of urethane (meth) acrylate improves cohesiveness and makes it difficult for cohesive failure to occur, and thus the resulting cured product has suitable adhesion.

  Examples of the compound (a) having three or more hydroxyl groups include trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, glycerin, polyglycerin, and ethylene oxide, propylene oxide, and 1,2-butylene oxide. And adducts of alkylene oxides such as 1,3-butylene oxide and 2,3-butylene oxide, and lactone adducts such as ε-caprolactone.

  Examples of the compound (b) having two or more isocyanate groups in the molecule include tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, and bis (isocyanatocyclohexyl). Examples thereof include polyisocyanates such as methane, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and m-phenylene diisocyanate. Among them, a diisocyanate compound having two isocyanate groups in the molecule can be preferably used, and isophorone diisocyanate is particularly preferable because it does not deteriorate the hue and does not lower the light transmittance.

  Examples of the compound (c) having a hydroxyl group and a (meth) acryloyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and hydroxycaprolactone (meth) acrylate. Further, a compound obtained by further reacting these (meth) acrylates with a compound having two or more hydroxyl groups may be used. Alternatively, it may be a compound obtained by reacting a compound having two or more hydroxyl groups with (meth) acrylic acid. For example, an addition reaction product of a glycidyl ether compound and (meth) acrylic acid, or a mono (meth) glycol compound (meta) ) Acrylate and the like.

  As a weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) of the said urethane (meth) acrylate (U1), it is preferable that it is 1000-20000, and it is more preferable that it is 1500-15000. Thereby, the durability and light resistance of the optical disk using the ultraviolet curable composition of the present invention are further improved. The GPC uses HLC-8020 manufactured by Tosoh Corporation, the column uses GMHxl-GMHxl-G200Hxl-G1000Hxlw, the solvent uses THF, and the column temperature is 40 ° C. at a flow rate of 1.0 ml / min. The detector temperature is 30 ° C., and the molecular weight is measured in terms of standard polystyrene.

  When using the said urethane (meth) acrylate (U1), it is preferable to use at 5-40 mass% in the ultraviolet curable compound contained in an ultraviolet curable composition, and being 10-30 mass%. Is particularly preferred. By setting the content of the urethane (meth) acrylate (U1) in the above range, it is possible to impart an appropriate flexibility to the cured film, and in particular, it is possible to realize a cured film with less warpage when the wet heat environment changes.

Moreover, as an epoxy (meth) acrylate, the epoxy acrylate obtained by making a glycidyl ether type epoxy compound and (meth) acrylic acid react can be used, for example. Examples of the glycidyl ether type epoxy compound include bisphenol A or its alkylene oxide-added diglycidyl ether, bisphenol F or its alkylene oxide-added diglycidyl ether, hydrogenated bisphenol A or its alkylene oxide-added diglycidyl ether, hydrogenated bisphenol F or its alkylene. Oxide-added diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether and the like, and one of these active energy ray-curable oligomers such as epoxy (meth) acrylate or Two or more types can be used.
Moreover, Formula (1)-(2)

（式（１）〜（２）中、Ｘ_１〜Ｘ_２は、それぞれ独立してＳＯ_２、ＣＨ_２、ＣＨ（ＣＨ_３）またはＣ（ＣＨ_３）_２を表し、Ｒ_１〜Ｒ_４はそれぞれ独立して水素原子又はメチル基を表す。）
で表される構造単位の少なくとも一種と、
式（３）〜（４）

(In the formulas (1) to (2), X _{1 to} X ₂ each independently represents SO ₂ , CH ₂ , CH (CH ₃ ) or C (CH ₃ ) ₂ , and R _{1 to} R ₄ represent Independently represents a hydrogen atom or a methyl group.)
At least one of structural units represented by:
Formula (3)-(4)

（式（３）中、Ｘ_３は、ＳＯ_２、ＣＨ_２、ＣＨ（ＣＨ_３）またはＣ（ＣＨ_３）_２を表し、Ｒ_５〜Ｒ_６はそれぞれ独立して水素原子又はメチル基を表す。）

(In the formula (3), X ₃ represents SO ₂ , CH ₂ , CH (CH ₃ ) or C (CH ₃ ) ₂ , and R _{5 to} R ₆ each independently represent a hydrogen atom or a methyl group. )

（式（４）中、Ｘ_４は、ＳＯ_２、ＣＨ_２、ＣＨ（ＣＨ_３）またはＣ（ＣＨ_３）_２を表し、Ｒ_７〜Ｒ_８はそれぞれ独立して水素原子又はメチル基を表す。）
で表される構造単位とからなり、
前記式（１）で表される構造単位中のＹ_１が、式（１）〜（２）で表される他の構造単位のＺ_１〜Ｚ_３のいずれか又は式（３）中のＺ_４に結合し、
前記式（２）で表される構造単位中のＹ_２〜Ｙ_３が、それぞれ水素原子、あるいは、式（１）〜（２）で表される他の構造単位のＺ_１〜Ｚ_３のいずれか又は式（３）中のＺ_４に結合し、
前記式（１）〜（２）で表される構造単位中のＺ_１〜Ｚ_３が、それぞれ式（１）〜式（２）で表される他の構造単位中のＹ_１〜Ｙ_３のいずれか又は式（４）中のＹ_４と結合した分岐エポキシ（メタ）アクリレート（Ｅ１）を使用することが好ましい。

(In formula (4), X ₄ represents SO ₂ , CH ₂ , CH (CH ₃ ) or C (CH ₃ ) ₂ , and R _{7 to} R ₈ each independently represent a hydrogen atom or a methyl group. )
And a structural unit represented by
Y ₁ in the structural unit represented by the formula (1) is any _one of Z _{1 to} Z ₃ of other structural units represented by the formulas (1) to (2) or Z in the formula (3). ₄ and
Y ₂ to Y ₃ in the structural unit represented by the formula (2) are hydrogen atoms or Z _{1 to} Z ₃ of other structural units represented by the formulas (1) to (2), respectively. Or bonded to Z ₄ in formula (3),
Z _{1 to} Z ₃ in the structural units represented by the above formulas (1) to (2) are Y ₁ to Y ₃ in other structural units represented by the formulas (1) to (2), respectively. It is preferable to use any branched epoxy (meth) acrylate (E1) bonded to Y ₄ in the formula (4).

Among the branched epoxy (meth) acrylates (E1), those in which X _{1 to} X ₄ are C (CH ₃ ) ₂ and R _{1 to} R ₈ are hydrogen atoms can be produced at low cost and the reaction control is easy. This is preferable.

  The branched epoxy (meth) acrylate (E1) has the formula (5)

（式（５）中、Ｘ_５はＳＯ_２、ＣＨ_２、ＣＨ（ＣＨ_３）またはＣ（ＣＨ_３）_２を表し、Ｒ_９〜Ｒ_１０はそれぞれ独立して水素原子又はメチル基を表す。）
で表されるエポキシ（メタ）アクリレート（Ｅ２）とのエポキシ（メタ）アクリレート混合物として使用されても良い。通常、分岐エポキシ（メタ）アクリレート（Ｅ１）の製造時に、式（５）で表されるエポキシ（メタ）アクリレート（Ｅ２）が生成するため、両者の混合物を使用することが製造工程上有利である。

(Wherein (in 5), _{X 5} is _{SO 2, CH 2, CH (} CH 3) or C _{(CH 3)} represents _{2, R} 9 _{~R 10} independently represents a hydrogen atom or a methyl group.)
It may be used as an epoxy (meth) acrylate mixture with an epoxy (meth) acrylate (E2) represented by: Usually, when the branched epoxy (meth) acrylate (E1) is produced, the epoxy (meth) acrylate (E2) represented by the formula (5) is generated. Therefore, it is advantageous in the production process to use a mixture of both. .

  In the present invention, the branched epoxy (meth) acrylate (E1) is represented by the formula (6)

（式（６）中、Ｘ_６〜Ｘ_８は、それぞれ独立してＳＯ_２、ＣＨ_２、ＣＨ（ＣＨ_３）またはＣ（ＣＨ_３）_２を表し、Ｒ_１１〜Ｒ_１６はそれぞれ独立して水素原子又はメチル基を表し、ｎは０〜２０である。）
で表される分岐エポキシ（メタ）アクリレートを有することが反応制御が容易となるため好ましい。なかでも、Ｘ_６〜Ｘ_８がＣ（ＣＨ_３）_２であり、Ｒ_１１〜Ｒ_１６が水素原子のものが、安価に製造できると共に反応制御が容易となるため特に好ましい。

(In formula (6), X _{6 to} X ₈ each independently represent SO ₂ , CH ₂ , CH (CH ₃ ) or C (CH ₃ ) ₂ , and R _{11 to} R ₁₆ each independently represent hydrogen. Represents an atom or a methyl group, and n is 0-20.)
It is preferable to have a branched epoxy (meth) acrylate represented by Among these, those in which X _{6 to} X ₈ are C (CH ₃ ) ₂ and R _{11 to} R ₁₆ are hydrogen atoms are particularly preferable because they can be produced at low cost and the reaction control becomes easy.

  The branched epoxy (meth) acrylate (E1) has many branched structures in the molecular skeleton, and is characterized in that the coating film structure after UV curing is formed with a high crosslinking density. Since it has a hard molecular skeleton due to the phenyl skeleton, the coating film hardness can be designed to be hard even if the acryloyl group content is designed low and the crosslinking reaction due to ultraviolet curing is reduced. It becomes possible. That is, distortion in the cured film due to curing shrinkage that occurs during UV curing can be alleviated, and as a result, it has a high elastic modulus and has little warpage during curing even when the coating film thickness is designed to be thick A paint can be realized. Among optical discs, it is most suitable for optical disc applications in which signals are recorded and reproduced by a blue laser that requires a particularly thick light transmission layer.

The branched epoxy (meth) acrylate (E1) is
(1-1) Diacrylate (A2) of an aromatic bifunctional epoxy resin,
(1-2) (1-2-1) Aromatic bifunctional epoxy resin monoacrylate (A1)
And / or
(1-2-2) Other than (A1) and (A2)
Aromatic bifunctional epoxy resin (B),
And (1-3) phosphorus catalyst (C)
In the diacrylate (A2) of the aromatic bifunctional epoxy resin in the mixture containing the diacrylate (A2) of the aromatic bifunctional epoxy resin and the monoester of the aromatic bifunctional epoxy resin. A reaction mixture containing a branched epoxy (meth) acrylate intermediate (e1) having a hydroxyl group, an acryloyl group and an epoxy group is obtained by reacting the hydroxyl group in the acrylate (A1) with an acryloyl group. It can be obtained by mixing with a saturated monocarboxylic acid and reacting the epoxy group of the branched epoxy (meth) acrylate intermediate (e1) in the reaction mixture with the carboxyl group in the unsaturated monocarboxylic acid.

  The branched epoxy (meth) acrylate intermediate (e1) having a hydroxyl group, an acryloyl group, and an epoxy group in the reaction mixture is a hydroxyl group and an acryloyl group in the aromatic bifunctional epoxy resin diacrylate (A2) or an aromatic group. A branched epoxy (meth) acrylate obtained by reacting a hydroxyl group and an acryloyl group in a monoacrylate (A1) of an aromatic bifunctional epoxy resin diacrylate (A2) and an aromatic bifunctional epoxy resin. One or more resin components selected from the group consisting of a functional diacrylate (A2), a monoacrylate (A1) of an aromatic bifunctional epoxy resin, and an aromatic epoxy compound (B) are diacrylates of an aromatic bifunctional epoxy resin. (A2) and monoacrylate (A1) of aromatic bifunctional epoxy resin and / or Unreacted resin component after the synthesis reaction of the branched epoxy (meth) acrylate (E1) in the mixture (in the reaction system) containing the aromatic bifunctional epoxy resin (B) and the phosphorus catalyst (C) It is.

The diacrylate (A2) of the aromatic bifunctional epoxy resin is one in which two epoxy groups in the aromatic bifunctional epoxy resin (b) are acryloylated with acrylic acid (a). As an aromatic bifunctional epoxy resin (b) used here, for example,
Biphenol type epoxy resins such as tetramethylbiphenol type epoxy resin; Bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol S type epoxy resin; Dicyclopentadiene modified aromatic bifunctional epoxy resin; Dihydroxynaphthalene-type epoxy resins obtained by epoxidizing naphthalenes; Glycidyl ester-type resins of aromatic divalent carboxylic acids; Bifunctional epoxy resins derived from xylenol, naphthalene aralkyl epoxy resins; Examples include epoxy resins modified with pentadiene; ester-modified epoxy resins obtained by modifying these aromatic bifunctional epoxy resins with dicarboxylic acids.

  The aromatic bifunctional epoxy resin (b) used for the preparation of the diacrylate (A2) of the aromatic bifunctional epoxy resin may be used alone or in combination of two or more.

  Examples of the monoacrylate (A1) and / or aromatic epoxy compound (B) of the aromatic bifunctional epoxy resin include, for example, one of the two epoxy groups in the aromatic bifunctional epoxy resin (b). A monoacrylate (A1) of an aromatic bifunctional epoxy resin having an epoxy group acrylated with acrylic acid, the aromatic bifunctional epoxy resin (b) alone, or a mixture thereof. The aromatic bifunctional epoxy resin (b) used here may be the same as that used for the preparation of the diacrylate (A2) of the aromatic bifunctional epoxy resin, or a different one may be used. Also good. Moreover, the aromatic bifunctional epoxy resin (b) used for the preparation of the monoacrylate (A1) of the aromatic bifunctional epoxy resin may be used alone or in combination of two or more.

  In order to obtain the reaction mixture, for example, a diacrylate (A2) of an aromatic bifunctional epoxy resin produced separately, a monoacrylate (A1) of an aromatic bifunctional epoxy resin and / or an aromatic bifunctional epoxy produced separately, respectively. Hydroxyl and acryloyl in the diacrylate (A2) of the aromatic bifunctional epoxy resin in a mixture containing the resin (B) and the phosphorus catalyst (C), if necessary, in the presence of an organic solvent or a reactive diluent. A hydroxyl group in the diacrylate (A2) of the aromatic bifunctional epoxy resin and the monoacrylate (A1) of the aromatic bifunctional epoxy resin may be reacted with the acryloyl group. The temperature for the reaction is usually 100 to 170 ° C, preferably 100 to 150 ° C. The reaction time is usually 1 to 20 hours, preferably 2 to 15 hours. In this case, the diacrylate (A2) of the aromatic bifunctional epoxy resin produced separately contains the monoacrylate (A1) of the aromatic bifunctional epoxy resin and / or the aromatic bifunctional epoxy resin (B). As long as it does not cause gelation, an acrylate of a trifunctional or higher functional polyfunctional epoxy resin may be used in combination. In this case, a monoacrylate of an aromatic monoepoxy compound and / or an aromatic monoepoxy compound may be used in combination.

  As described above, in order to obtain the reaction mixture, an aromatic difunctional epoxy resin diacrylate (A2), an aromatic bifunctional epoxy resin monoacrylate (A1) and / or an aromatic bifunctional epoxy resin (B) And a mixture containing a phosphorus-based catalyst (C), these (A2) and (A1) and / or (B), aromatic bifunctional epoxy resin (b) and acrylic acid (a), The aromatic bifunctional epoxy resin (b) is reacted with an epoxy group in excess of the carboxyl group in the acrylic acid (a), and the aromatic bifunctional epoxy resin diacrylate (A2) A reaction system containing a monoacrylate (A1) of an aromatic bifunctional epoxy resin and / or an aromatic bifunctional epoxy resin (B) (hereinafter, this process is abbreviated as “process 1”) There.) With those, preferred since it can be performed subsequently the preparation of subsequent reaction mixtures.

  In particular, a reaction system containing a diacrylate (A2) of an aromatic bifunctional epoxy resin and a monoacrylate (A1) of an aromatic bifunctional epoxy resin [however, an unreacted aromatic bifunctional epoxy resin (B) is contained. It may be. That is, a reaction system composed of (A2) and (A1) or a reaction system composed of (A2), (A1) and (B) is preferable because it can be easily carried out.

  Furthermore, the hydroxyl group and acryloyl group in the diacrylate (A2) of the aromatic bifunctional epoxy resin in the reaction system, or the monoacrylate of the aromatic bifunctional epoxy resin diacrylate (A2) and the aromatic bifunctional epoxy resin are used. The hydroxyl group and acryloyl group in the acrylate (A1) are reacted in the presence of the phosphorus catalyst (C). A hydroxyl group obtained by increasing the molecular weight of a diacrylate (A2) of an aromatic bifunctional epoxy resin or a diacrylate (A2) of an aromatic bifunctional epoxy resin and a monoacrylate (A1) of an aromatic bifunctional epoxy resin. Branched epoxy (meth) acrylate intermediate (e1) having acryloyl group and epoxy group, diacrylate (A2) of aromatic bifunctional epoxy resin, monoacrylate (A1) of aromatic bifunctional epoxy resin and aromatic difunctional epoxy resin Let it be the reaction mixture containing 1 or more types of unreacted resin components chosen from the group which consists of a functional epoxy resin (B).

  The aromatic bifunctional epoxy resin (B) used in the present invention is an epoxy resin other than the above (A1) and (A2). In the step 1, the aromatic bifunctional epoxy resin (b) and the acrylic acid (a) are used in an excess amount of the epoxy group in the aromatic bifunctional epoxy resin (b) with respect to the carboxyl group in the acrylic acid (a). Therefore, there is an aromatic bifunctional epoxy resin (b) remaining without reacting with acrylic acid (a). The remaining aromatic bifunctional epoxy resin (b) is an aromatic bifunctional epoxy resin diacrylate (A2) or aromatic which is a reaction product of the aromatic bifunctional epoxy resin (b) and acrylic acid (a). Different from monoacrylate (A1) of bifunctional epoxy resin. Therefore, the remaining aromatic bifunctional epoxy resin (b) becomes an aromatic bifunctional epoxy resin (B) other than (A1) and (A2).

  Examples of the phosphorus catalyst (C) used in the present invention include phosphines and phosphonium salts. Of these, phosphines are most preferable.

  Examples of the phosphines include trialkylphosphine, triphenylphosphine, trialkylphenylphosphine and the like, and triphenylphosphine is particularly preferable because of easy reaction control.

  As the amount of the phosphorus catalyst (C) used, the larger the catalyst amount, the hydroxyl group and acryloyl in the diacrylate (A2) of the aromatic bifunctional epoxy resin and the monoacrylate (A1) of the aromatic bifunctional epoxy resin in the mixture In consideration of the fact that the reaction with the group tends to proceed, but the gelation is likely to occur and the stability of the composition is deteriorated, the total weight of the aromatic bifunctional epoxy resin (b) and acrylic acid (a) A range of 10 to 30,000 ppm is preferred.

  As said aromatic bifunctional epoxy resin (b) and aromatic bifunctional epoxy resin (B), since the resin composition excellent in sclerosis | hardenability is obtained especially, an epoxy equivalent is 135-2,000 g / equivalent. The thing whose epoxy equivalent is 135-500 g / equivalent is more preferable. Moreover, since a resin composition having excellent mechanical properties of a cured product can be obtained, biphenol type epoxy resins such as tetramethylbiphenol type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, etc. A bisphenol type epoxy resin and a dihydroxynaphthalene type epoxy resin obtained by epoxidizing dihydroxynaphthalene are preferable, a bisphenol A type epoxy resin or a 1,6-dihydroxynaphthalene type epoxy resin is more preferable, and a bisphenol A type epoxy resin is most preferable.

  The range in which the epoxy group in the aromatic bifunctional epoxy resin (b) is excessive relative to the carboxyl group in the acrylic acid (a) is not particularly limited, but is a diacrylate (A2) of the aromatic bifunctional epoxy resin. Reaction of hydroxyl group and acryloyl group in diacrylate (A2) of aromatic bifunctional epoxy resin and monoacrylate (A1) of aromatic bifunctional epoxy resin should proceed smoothly. From the above, the equivalent ratio [(epoxy group equivalent) / (carboxyl group equivalent)] of the epoxy group in the aromatic bifunctional epoxy resin (b) and the carboxyl group in the acrylic acid (a) is 1.1 to 5.5. It is preferable that it is the range. In addition, since the molecular weight of the obtained branched polyether resin can be easily adjusted, the equivalent ratio [(epoxy group equivalent) / (carboxyl group equivalent)] is 1.25 to 3.0. More preferably.

  In the step of reacting the epoxy group in the reaction mixture with the carboxyl group in the unsaturated monocarboxylic acid, an epoxy group is obtained by reacting the epoxy group in the reaction mixture with the carboxyl group in the unsaturated monocarboxylic acid. Most of or all of the above is consumed to form a branched epoxy (meth) acrylate (E1) having a hydroxyl group and an acryloyl group-containing unsaturated monocarboxylic acid ester structure, and the reaction system is composed of this branched epoxy (meth) acrylate (E1) and aroma. A branched epoxy (meth) acrylate composition (II) containing a di (unsaturated monocarboxylic acid) ester of a group II functional epoxy resin can be obtained.

  Examples of the unsaturated monocarboxylic acid used here include compounds having one polymerizable unsaturated group and one carboxyl group, and specifically include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, monomethyl. Malate, monoethylmalate, monopropylmalate, monobutylmalate, mono (2-ethylhexyl) malate, sorbic acid, etc. are usually used, but hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxy A dicarboxylic acid anhydride and a (meth) acrylate compound having a hydroxyl group such as butyl (meth) acrylate, hydroxycyclohexyl (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, etc. Obtained by reaction Unsaturated half ester, polymerizable unsaturated group and one lactone-modified unsaturated monocarboxylic acids with compounds ε- caprolactone reacted with a carboxyl group, may be a dimer of acrylic acid. Among these, acrylic acid and / or methacrylic acid are preferable.

  In addition, it is stable over time by reacting the epoxy group in the reaction mixture and the carboxyl group in the unsaturated monocarboxylic acid in an amount ratio of 0.9 / 1 to 1 / 0.9 (epoxy group / carboxyl group). This is preferable because a branched epoxy (meth) acrylate (E1) having excellent properties and curability is obtained. Furthermore, acrylic acid and / or methacrylic acid are preferable as the unsaturated monocarboxylic acid because of its excellent active energy ray curability.

  The reaction temperature of the epoxy group and the unsaturated monocarboxylic acid in the reaction mixture is usually from 80 to 160 ° C., and among these, from 100 to 140 ° C. is preferable because the stability during synthesis is good. Moreover, reaction time is 1 to 20 hours normally, Preferably it is 2 to 15 hours. At this time, a basic catalyst may be additionally added as a reaction catalyst.

  Examples of the basic catalyst include tertiary amines such as triethylamine, tributylamine, trisdimethylaminomethylphenol, benzyldimethylamine and diethanolamine; quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide. Imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole; nitrogen compounds such as diethylamine hydrochloride and diazabiscycloundecene; trialkylphosphines such as triphenylphosphine; tetra-n-butyl Tetraalkylphosphonium hydroxides such as phosphonium hydroxide; metal salts such as chromium naphthenate; trimethylbenzylammonium chloride, tetra Quaternary ammonium salts such as chill chloride; tetra -n- butyl phosphonium bromide, silver-based catalysts such as phosphonium salts such as ethyltriphenylphosphonium bromide; sodium hydroxide, and inorganic catalysts such as lithium hydroxide.

  As these basic catalysts, non-halogen-based catalysts are preferable, and nitrogen compounds such as tertiary amines and quaternary ammonium salts; phosphorus-based catalysts such as phosphines and phosphonium salts are preferable. Among these, phosphorus catalysts such as phosphines and phosphonium salts are more preferable, and phosphines are most preferable because they can be used as an essential catalyst in the first step.

  Examples of the phosphines include trialkylphosphine, triphenylphosphine, trialkylphenylphosphine and the like, and triphenylphosphine is particularly preferable because of easy reaction control.

  As the amount of the basic catalyst used, the more the amount of the catalyst, the more easily the reaction proceeds. However, in consideration of the fact that gelation is likely and the stability of the composition deteriorates, the aromatic bifunctional epoxy resin (b) and The range of 10-30,000 ppm is preferable with respect to the total weight of acrylic acid (a). Different phosphorus catalysts may be added, or may be added during the reaction.

  When the branched epoxy (meth) acrylate of the present invention is synthesized, a branched epoxy (meth) acrylate having a repeating number n of the structural unit represented by the above formula (1) or (2) in the range of 1 to 100 is usually used. Obtained as a mixture of E1) and the epoxy (meth) acrylate represented by the above formula (5), and analyzed by, for example, gel permeation chromatography, the distribution of compounds in which n has various values can be observed. Therefore, when adjusting the ultraviolet curable composition of this invention, it is easy to use the said mixture. When using the said mixture, it is preferable to use the mixture containing 30 mass% or more of branched epoxy (meth) acrylates of n = 1-100, and the mixture containing 35 mass% or more is more preferable.

  In this invention, it confirms from the result measured by the gel permeation chromatography (GPC) of the mixture of said branched epoxy (meth) acrylate (E1) and the epoxy (meth) acrylate represented by said Formula (5). The weight average molecular weight (Mw) of the branched epoxy (meth) acrylate (E1) is preferably 1000 to 10,000, preferably 1500 to 8000, and more preferably 2000 to 6000. By making the molecular weight of the branched epoxy (meth) acrylate (E1) within the above range, it is possible to avoid the viscosity from becoming higher than necessary, and the branched component that is an essential component contained in the ultraviolet curable composition of the present invention. The content of the epoxy (meth) acrylate (E1) can be increased. Further, the ratio of the branched epoxy (meth) acrylate (E1) to the epoxy (meth) acrylate (E2) in the mixture is an area ratio according to the chromatogram measured by the GPC, and the branched epoxy (meth) acrylate (E1) / Epoxy (meth) acrylate (E2) = 10/1 to 1/2 is preferable, 5/1 to 1/1 is more preferable, and 3/1 to 3/2 is still more preferable.

  The weight average molecular weight by GPC is, for example, using HLC-8220 manufactured by Tosoh Corporation, using 4 Super HZM-M columns as the column, using THF as the solvent, and the column temperature at a flow rate of 1.0 ml / min. Is 40 ° C., the detector temperature is 30 ° C., and the molecular weight is specified by measuring in terms of standard polystyrene.

  When the branched epoxy (meth) acrylate (E1) is used, the branched epoxy (meth) acrylate (E1) may be contained in an amount of 10 to 80% by mass in the total amount of the radical polymerizable compound contained in the ultraviolet curable composition. Preferably, the content is 20 to 70% by mass.

  The urethane (meth) acrylate (U1) and the branched epoxy (meth) acrylate (E1) are also preferably used in combination. When these are used in combination, the mass represented by (UA1) / (E1) The ratio is preferably 1/5 to 1/1 because it is easy to obtain a high elastic modulus.

[(Meth) acrylate monomer]
The (meth) acrylate monomer used in the ultraviolet curable composition of the present invention is not particularly limited, and a (meth) acrylate monomer having one (meth) acryloyl group in one molecule (hereinafter referred to as monofunctional (meth)). Acrylate), a (meth) acrylate monomer having two (meth) acryloyl groups in one molecule (hereinafter referred to as a bifunctional (meth) acrylate), and three or more ( A (meth) acrylate monomer having a (meth) acryloyl group (hereinafter referred to as a polyfunctional (meth) acrylate monomer) can be used, and a composition having a desired viscosity and an elastic modulus after curing by appropriately blending these. You can get things.

  Examples of monofunctional (meth) acrylates include ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, hexadecyl (meth) acrylate, and octadecyl. (Meth) acrylate, isoamyl (meth) acrylate, isodecyl (meth) acrylate, isostearyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-chloro-2-hydroxypropyl ( Aliphatic (meth) acrylates such as (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, nonylphenoxyethyl (meth) acrylate, 2-hydride Aromatic (meth) acrylates such as xyl-3-phenoxypropyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, di Cyclopentenyloxyethyl (meth) acrylate, tetracyclododecanyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, alicyclic (meth) acrylate such as glycidyl (meth) acrylate, caprolactone modified tetrahydro Furfuryl (meth) acrylate, acryloylmorpholine, isobornyl (meth) acrylate, norbornyl (meth) acrylate, 2- (meth) acryloyloxymethyl-2- Chi ruby cycloheptane adamantyl (meth) acrylate, and the like can be used.

  Among these, when tetrahydrofurfuryl acrylate or phenoxyethyl acrylate is used, it is preferable because the amount of change in film thickness is small and the amount of change in warpage is also small.

  Examples of the bifunctional (meth) acrylate include 1,4-butanediol di (meth) acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, and 1,6-hexanediol di (meth) acrylate. , Neopentyl glycol di (meth) acrylate, 2-methyl-1,8-octanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, ethylene glycol di ( Obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol Diol Di (meth) acrylate, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkylated phosphoric acid di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di ( (Meth) acrylate, polyether (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylate having alicyclic structure, alicyclic bifunctional (meth) acrylate, norbornane dimethanol di (meth) Di (meth) acrylate of diol obtained by adding 2 mol of ethylene oxide or propylene oxide to acrylate, norbornane diethanol di (meth) acrylate, norbornane dimethanol, tricycle Di (meth) acrylate of diol obtained by adding 2 mol of ethylene oxide or propylene oxide to tricyclodecane diethanol di (meth) acrylate, tricyclodecane dimethanol, and pentacyclopentadecane dimethanol Di (meth) acrylate, pentacyclopentadecane diethanol di (meth) acrylate, di (meth) acrylate of diol obtained by adding 2 mol of ethylene oxide or propylene oxide to pentacyclopentadecane dimethanol, ethylene oxide or pentacyclopentadecane diethanol Di (meth) acrylate, dimethylol dicyclopentane di (meth) acrylate of diol obtained by adding 2 mol of propylene oxide, hydroxy Valaldehyde-modified trimethylolpropane di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, ethylene oxide-modified bisphenol A di (meth) acrylate, propylene oxide-modified bisphenol A di (meth) acrylate, and the like can be used.

  Of these, tricyclodecane dimethanol di (meth) acrylate, tripropylene glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, ethylene oxide-modified bisphenol A di (meth) acrylate, etc. are preferred, and hydroxypivalin. Acid neopentyl glycol di (meth) acrylate and ethylene oxide-modified bisphenol A di (meth) acrylate are particularly preferred.

  Further, when it is desired to adjust the elastic modulus after curing to a high level, trifunctional or higher (meth) acrylates may be used. For example, bis (2-acryloyloxyethyl) hydroxyethyl isocyanurate, bis (2-acryloyloxy) Propyl) hydroxypropyl isocyanurate, bis (2-acryloyloxybutyl) hydroxybutyl isocyanurate, bis (2-methacryloyloxyethyl) hydroxyethyl isocyanurate, bis (2-methacryloyloxypropyl) hydroxypropyl isocyanurate, bis (2- Methacryloyloxybutyl) hydroxybutyl isocyanurate, tris (2-acryloyloxyethyl) isocyanurate, tris (2-acryloyloxypropyl) isocyanurate, tris (2-actyl (Royloxybutyl) isocyanurate, tris (2-methacryloyloxyethyl) isocyanurate, tris (2-methacryloyloxypropyl) isocyanurate, tris (2-methacryloyloxybutyl) isocyanurate, trimethylolpropane tri (meth) acrylate, ditri 3 moles of methylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1 mole of trimethylolpropane Diol or tri (meth) acrylate of triol obtained by adding the above ethylene oxide or propylene oxide, dipentaene Polyfunctional (meth) acrylates of poly (meth) acrylate of Suritoru, etc. can be used.

  Moreover, ultraviolet curable compounds, such as N-vinyl pyrrolidone, N-vinyl caprolactam, a vinyl ether monomer, can also be used as needed.

  The content of the monofunctional (meth) acrylate in the total amount of the ultraviolet curable compound contained in the ultraviolet curable composition in the present invention is preferably 5 to 60% by mass, particularly 10 to 50% by mass. Is preferred. The content of the bifunctional (meth) acrylate is preferably 3 to 40% by mass, particularly preferably 5 to 30% by mass. Further, the content of the trifunctional or higher functional (meth) acrylate is preferably 20% by mass or less, particularly preferably 10% by mass or less.

[Initiator, additive]
In the ultraviolet curable composition for optical disks of the present invention, known photopolymerization initiators, thermal polymerization initiators, and the like can be used in addition to the (meth) acrylate oligomers and (meth) acrylate monomers.

  Examples of the photopolymerization initiator that can be used in the present invention include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy 2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one and 2-methyl-1- (4-methylthiophenyl) -2 There are molecular cleavage types such as morpholinopropan-1-one and hydrogen abstraction type photopolymerization initiators such as benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide.

  In the ultraviolet curable composition of the present invention, as necessary, surfactants, leveling agents, thermal polymerization inhibitors, antioxidants such as hindered phenols and phosphites, and light stabilizers such as hindered amines are added as necessary. Can also be used. Examples of sensitizers include trimethylamine, methyldimethanolamine, triethanolamine, p-dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzylamine and 4,4′-bis (diethylamino) benzophenone or the like can be used, and further, an amine that does not cause an addition reaction with the photopolymerizable compound can be used in combination.

[UV curable composition]
The ultraviolet curable composition for optical disks of the present invention contains the above-exemplified (meth) acrylate oligomer and (meth) acrylate monomer, has a (meth) acryloyl group concentration of 4 mmol / g or less, and is cured after UV curing. It is an ultraviolet curable composition having an elastic modulus at 30 ° C. of 2000 MPa or more.

  In the present invention, by setting the (meth) acryloyl group concentration and the elastic modulus within the above ranges, it is possible to reduce the curing shrinkage at the time of ultraviolet irradiation and to realize a cured film with little warpage change at the time of wet heat environment change. Moreover, since the elastic modulus at 30 ° C. of the cured film after UV curing is 2000 MPa or more, it is possible to realize a cured film that is difficult to be deformed by an external load and excellent in dimensional stability. Furthermore, the cured film which has the outstanding abrasion resistance is realizable by using polyfunctional urethane (meth) acrylate.

  Moreover, in the ultraviolet curable composition of this invention, the design (meth) acryloyl group density | concentration shall be 4.2 mmol / g or less, Preferably it is 4.1 mmol / g or less, More preferably, it is 4.05 mmol / g or less. By setting the design (meth) acryloyl group concentration within this range, curing shrinkage during UV irradiation can be reduced, and a cured film can be formed with less warpage change when changing to a moist heat environment. It is possible to reduce changes in warpage under the environment.

  The (meth) acryloyl group concentration in the ultraviolet curable composition refers to the concentration (mmol) of the (meth) acryloyl group contained in 1 g of the ultraviolet curable composition. Specifically, in an ultraviolet curable composition containing a plurality of (meth) acrylate components, the concentration is calculated by the following equation.

[(Meth) acryloyl group concentration of ultraviolet curable composition] = [Σm _i c _i / Σm _i ] (mmol / g)
m _i : Compounding amount (g) of component i contained in the ultraviolet curable composition
c _i : (meth) acryloyl group concentration of component i (mmol / g)

  Moreover, the (meth) acryloyl group density | concentration of i component which is each (meth) acrylate component is calculated by the following formula.

[(Meth) acryloyl group concentration of component i] = [F × 10 ³ / M] (mmol / g)
F: Number of (meth) acryloyl groups per molecule of component i M: Molecular weight per molecule of component i (g / mol)

  In the above calculation, the mass of the additive and the like in the composition is not considered in the calculation.

  The ultraviolet curable composition of the present invention is preferably adjusted so that the elastic modulus of the cured film after irradiation with ultraviolet rays is 2000 MPa (30 ° C.) or more. Among these, a composition of 2000 to 3500 MPa is more preferable. When the elastic modulus is in this range, an optical disk that is not easily deformed by an external load and has excellent dimensional stability can be obtained.

  In the ultraviolet curable composition of the present invention, in order to increase the elastic modulus while lowering the (meth) acryloyl group concentration, it is effective to design a composition that ensures a certain distance between crosslinking points and increases the crosslinking density. Moreover, when ensuring the distance between bridge | crosslinking points, it is preferable to adjust with a high molecular weight (meth) acrylate oligomer rather than high molecular weight of a monomer component. Moreover, in the improvement of a crosslinking density, it can improve by polyfunctionalization of a (meth) acrylate oligomer component or polyfunctionalization of a (meth) acrylate monomer. Specifically, a polyfunctional urethane (meth) acrylate oligomer having a flexible structure and a comb-shaped epoxy (meth) acrylate oligomer that has a rigid skeleton as the main chain, but can easily form a crosslinking point as an oligomer. It is preferable to use together.

  The ultraviolet curable composition of the present invention can suitably form a thick light-transmitting layer by adjusting the ultraviolet curable compound and adjusting the viscosity to 800 to 5000 mPa · s, preferably 1000 to 2500 mPa · s. .

[optical disk]
The optical disc of the present invention is an optical disc in which at least a light reflection layer and a light transmission layer are formed on a substrate, and recording or reproduction is performed with a laser beam through the light transmission layer. It consists of a cured product of the composition. The optical disk of the present invention obtains excellent durability when silver or a silver alloy is used as a reflective film, even under high temperature and high humidity, by using the above-described ultraviolet curable composition as a light transmission layer. Therefore, information can be recorded / reproduced satisfactorily.

  The light transmitting layer in the optical disk of the present invention preferably transmits a blue laser whose laser light oscillation wavelength is 370 to 430 nm efficiently, and has a transmittance of 405 nm light of 85% or more at a thickness of 100 μm. Is preferable, and 90% or more is particularly preferable.

  The thickness of the light transmission layer in the optical disk of the present invention is preferably 70 to 110 μm. The thickness of the light transmission layer is usually set to about 100 μm, but the thickness greatly affects the light transmittance and signal reading and recording, and therefore needs to be sufficiently managed. The light transmission layer may be formed of a single cured layer having the thickness or a plurality of layers may be laminated.

  The light reflection layer may be any layer that can reflect a laser beam and form an optical disc that can be recorded and reproduced. For example, a metal such as gold, copper, or aluminum or an alloy thereof, or an inorganic compound such as silicon can be used. . Of these, silver or an alloy containing silver as a main component is preferably used because of the high reflectance of light in the vicinity of 400 nm. The thickness of the light reflecting layer is preferably about 10 to 60 nm.

  As the substrate, a disk-shaped circular resin substrate can be used, and polycarbonate can be preferably used as the resin. When the optical disc is read-only, pits for recording information are formed on the surface of the substrate that is laminated with the light reflecting layer.

  In the case of a writable optical disc, an information recording layer is provided between the light reflecting layer and the light transmitting layer. The information 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.

When the information recording layer is a phase change recording layer, the information recording layer is usually composed of a dielectric layer and a phase change film. The dielectric layer is required to have a function of buffering heat generated in the phase change layer and a function of adjusting the reflectivity of the disk, and a mixed composition of ZnS and SiO ₂ is used. The phase change film causes a difference in reflectance between the amorphous state and the crystalline state due to the phase change of the film, and uses a Ge—Sb—Te, Sb—Te, or Ag—In—Sb—Te alloy. Can do.

  The optical disk of the present invention may have two or more information recording sites. For example, in the case of a read-only optical disc, a first light reflection layer and a first light transmission layer are laminated on a substrate having pits, and the first light transmission layer or other layers are laminated, A second light reflection layer and a second light transmission layer may be formed on the layer. In this case, pits are formed on the first light transmission layer and other layers laminated thereon. In addition, in the case of a recordable / reproducible optical disc, an information recording layer, a light reflecting layer, and a light transmitting layer are laminated on a substrate, and the second layer is further formed on the light transmitting layer. A structure having two information recording layers by forming a light reflecting layer, a second information recording layer, and a second light transmission layer, or a structure having three or more information recording layers by similarly stacking layers It is good. In the case of laminating a plurality of layers, it may be appropriately adjusted so that the sum of the layer thicknesses of the respective layers becomes the above-mentioned thickness.

  In the optical disc of the present invention, the light transmission layer may be the outermost layer, but a surface coat layer may be further provided on the surface layer, but the process can be performed by using the light transmission layer as the outermost layer. This is preferable because it can be simplified.

  The optical disc of the present invention has a radial tilt of ± 1 ° before and after the test when an optical disc having a light-transmitting layer having a thickness of 100 μm is changed from 25 ° C. 95% RH to 25 ° C. 45% RH. Is preferably within ± 0.8 ° which is the standard of Blu-ray Disc.

  In addition, the change in diffuse transmittance (JIS K-7105) at 405 nm when wearing 50 wheels at a load of 250 g using a wear wheel CS-10F in a Taber abrasion tester Rotary Bresser (manufactured by Toyo Seiki Co., Ltd.) is 10 % Or less is preferable.

  The optical disc of the present invention includes a read-only disc and a recordable / reproducible disc. A read-only disc is provided with a pit as an information recording layer when a single circular resin substrate is injection-molded, and then a light reflecting layer is formed on the information recording layer, and further on the light reflecting layer. It can be produced by applying a UV curable composition by spin coating or the like and then curing it by UV irradiation to form a light transmission layer. In addition, a recordable / reproducible disc is formed by forming a light reflecting layer on one circular resin substrate, and then providing an information recording layer such as a phase change film or a magneto-optical recording film, and further on the light reflecting layer. It can be manufactured by applying an ultraviolet curable composition to the substrate by spin coating or the like and then curing it by ultraviolet irradiation to form a light transmission layer.

  When the ultraviolet curable composition applied on the light reflecting layer is cured by irradiating with ultraviolet rays, for example, it can be performed by a continuous light irradiation method using a metal halide lamp, a high-pressure mercury lamp, or the like, or by a flash irradiation method described in US Pat. No. 5,904,795. It can also be done. The flash irradiation method is more preferable in that it can be cured efficiently.

When irradiating with ultraviolet rays, it is preferable to control the accumulated light amount to be 0.05 to 1 J / cm ² . More preferably accumulated light amount is 0.05~0.8J / cm ^2, and particularly preferably 0.05~0.6J / cm ^2. The ultraviolet curable composition used for the optical disk of the present invention is sufficiently cured even when the integrated light quantity is small, and does not cause tacking of the end face or surface of the optical disk, and further does not cause warping or distortion of the optical disk.

[Embodiment]
Hereinafter, as specific examples of the optical disc of the present invention, examples of specific configurations of a single-layer optical disc and a double-layer optical disc are shown below.

  Among the optical discs of the present invention, as a preferred embodiment of a single-layer type optical disc, for example, as shown in FIG. 1, a light reflecting layer 2 and a light transmitting layer 3 are laminated on a substrate 1 to transmit light. A configuration for recording or reproducing information by injecting a blue laser from the layer side can be exemplified. The irregularities in the figure schematically represent recording tracks (grooves). The light transmission layer 3 is a layer made of a cured product of the ultraviolet curable composition of the present invention, and its thickness is in the range of 100 ± 10 μm. The thickness of the substrate 1 is about 1.1 mm, and the light reflecting film is a thin film such as silver.

FIG. 2 shows a configuration in which a hard coat layer 4 is provided on the outermost layer of the configuration shown in FIG. The hard coat layer is preferably a layer having high hardness and excellent wear resistance. The thickness of the hard coat layer is preferably 1 to 10 μm, and more preferably 3 to 5 μm. As a preferred embodiment of the multilayer optical disc, for example, as shown in FIG. The light reflection layer 5 and the light transmission layer 6 are laminated, and further, the light reflection layer 2 and the light transmission layer 3 are laminated thereon, and a blue laser is incident from the light transmission layer 3 side to receive information. An example of the configuration of a two-layered optical disk that performs recording or reproduction is exemplified. The light transmissive layer 3 and the light transmissive layer 6 are layers made of a cured product of an ultraviolet curable composition, and at least one of the layers is a layer made of the ultraviolet curable composition of the present invention. As the thickness of the layer, the sum of the thickness of the light transmission layer 3 and the thickness of the light transmission layer 6 is in the range of 100 ± 10 μm. The thickness of the substrate 1 is about 1.1 mm, and the light reflecting film is a thin film such as silver.

  In the two-layer type optical disc having the above configuration, since the recording track (groove) is also formed on the surface of the light transmission layer 6, the light transmission layer 6 is made of a cured film of an ultraviolet curable composition having excellent adhesiveness. On the layer, you may form with the multilayer which laminated | stacked the layer which consists of a cured film of the ultraviolet curable composition which can form a recording track suitably. Also in this configuration, a hard coat layer may be provided on the outermost layer.

A method for manufacturing the optical disk shown in FIG. 1 will be described below.
First, a substrate 1 having a guide groove for tracking a laser beam called a recording track (groove) is manufactured by injection molding a polycarbonate resin. Next, a light reflecting layer 2 is formed on the surface of the substrate 1 on the recording track side by sputtering or vapor-depositing a silver alloy or the like. The ultraviolet curable composition of the present invention is applied onto this, and the ultraviolet curable composition is cured by irradiating ultraviolet rays from one or both sides of the disk to form the light transmissive layer 3 to produce the optical disk of FIG. To do. In the case of the optical disk of FIG. 2, a hard coat layer 4 is further formed thereon by spin coating or the like.

A method for manufacturing the optical disk shown in FIG. 3 will be described below.
First, a substrate 1 having a guide groove for tracking laser light called a recording track (groove) is manufactured by injection molding polycarbonate resin. Next, the light reflecting layer 6 is formed on the surface of the substrate 1 on the recording track side by sputtering or vapor-depositing a silver alloy or the like.

  On this, the light transmissive layer 5 of the ultraviolet curable composition of the present invention or an arbitrary ultraviolet curable composition is formed. At that time, a recording track (groove) is transferred to the surface using the mold. The process of transferring the recording track (groove) is as follows. An ultraviolet curable composition is applied on the light reflecting layer 6 formed on the substrate 1 and bonded to a mold for forming a recording track (groove) thereon, and ultraviolet light is applied from one or both sides of the bonded disk. To cure the ultraviolet curable composition. Thereafter, the mold is peeled off, and the light reflecting layer 2 is formed by sputtering or vapor-depositing a silver alloy or the like on the surface of the light transmitting layer 5 having the recording tracks (grooves). After applying the mold composition, it is cured by ultraviolet irradiation to form the light transmission layer 3, whereby the optical disk of FIG. 3 can be produced. Even when a phase change recording layer is used for the light reflection layer, an optical disc can be produced by the same method as described above.

  Next, although a synthesis example and an Example are given and this invention is demonstrated in detail, this invention is not limited to these Examples. Hereinafter, “parts” in the examples represent “parts by mass”.

<Synthesis Example 1> (Synthesis of EA1)
A flask equipped with a thermometer, a stirrer and a reflux condenser was charged with 65.5 g of phenoxyethyl acrylate (PEA), and 189 g of bisphenol A type epoxy resin (epoxy equivalent 189 g / equivalent; EPICLON 850 manufactured by DIC Corporation) was dissolved. After adding 0.1 g of hydroquinone as a polymerization inhibitor, 50.7 g (0.7 mol) of acrylic acid was charged. 0.48 g of triphenylphosphine was added as a catalyst, and the temperature was raised to 130 ° C. in 2 hours while stirring. After maintaining at 130 ° C. for 6 hours, after confirming that the acid value became 0 mg / KOH, the temperature was lowered to 80 ° C. and 22.2 g (0.3 mol) of acrylic acid was charged. The temperature was raised again to 130 ° C. over 1 hour, 0.48 g of triphenylphosphine was added and held for 4 hours, and then a pale yellow transparent resinous reaction mixture (acid value) containing branched epoxy (meth) acrylate (EA1) = 0.2 mg / KOH, epoxy equivalent = 15000).

<Synthesis Example 2> (Synthesis of EA2)
Using the same apparatus as in Synthesis Example 1, 189 g of bisphenol A type epoxy resin was dissolved, 0.1 g of hydroquinone was added as a polymerization inhibitor, and then 72.4 g (1 mol) of acrylic acid was charged. 2.64 g of triphenylphosphine was added as a catalyst, and the temperature was raised to 110 ° C. over 2 hours while stirring. After maintaining at 110 ° C. for 6 hours, a pale yellow transparent resinous reaction mixture (acid value = 0.2 mg / KOH, epoxy equivalent = 12000) containing epoxy (meth) acrylate (EA2) was obtained.

<Synthesis Example 3> (Synthesis of UA1)
Using the same device as in Synthesis Example 1, 786 g of Desmodur W (3 mol, dicyclohexylmethane-4,4′-diisocyanate: diisocyanate manufactured by Sumika Bayer Urethane Co., Ltd.), 0.56 g of SCAT-52A (octyltin compound) : Daiichi Sankyo Chemical Pharma Co., Ltd., urethanization catalyst), methoquinone 0.56 g (p-methoxyphenol: Seiko Chemical Industry Co., Ltd., polymerization inhibitor), Yoshinox BHT 5.57 g (2,6- Di-t-butyl-P-cresol: manufactured by API Corporation, antioxidant) was added, and the temperature was gradually raised while mixing uniformly. When the temperature reached 50 ° C., 348 g of HEA (3 mol, 2-hydroxyethyl acrylate: manufactured by Osaka Organic Chemical Industry Co., Ltd., active hydrogen-containing acrylic monomer) was added in portions. After reacting at 80 ° C. for 2 hours, Actol MN- Then, 721.3 g of 700 (1.02 mol, trifunctional polyol (polyfunctional polyol), manufactured by Mitsui Chemicals Polyurethane Co., Ltd., hydroxyl value 238 mgKOH / g) was added, and the mixture was further reacted for 5 hours. After confirming that NCO% was 0.2% or less, 465.5 g of phenoxyethyl acrylate (PEA) was added and mixed to obtain a light yellow transparent resinous reaction mixture containing urethane acrylate (UA1). It was. Table 1 shows the composition molar ratio and acryloyl group concentration of the obtained urethane acrylate.

<Synthesis Examples 4 to 11> (Synthesis of UA2 to UA9)
Except having used each raw material component by the composition ratio shown in Table 1, it reacted like the synthesis example 3, and obtained urethane acrylate (UA2-UA9), respectively. Table 1 shows the composition molar ratio and acryloyl group concentration of the obtained urethane acrylate. The composition molar ratio was entered as the molar ratio of polyfunctional polyol / diisocyanate / active hydrogen-containing acrylic monomer.

The symbols and names in Table 1 are as follows.
VESTANAT IPDI: 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, Cosmonate manufactured by Evonik Degussa Japan Co., Ltd. T-100S: Toluene diisocyanate, HEA-CL1: manufactured by Mitsui Chemicals Polyurethane Co., Ltd., hydroxy Ethyl acrylate-ε-caprolactam 1 mol adduct (see Table 2, Synthesis Example 12)
HEA-CL2: Intermediate, hydroxyethyl acrylate-ε-caprolactam 2-mole adduct (see Table 2, Synthesis Example 13)
TMP-CL3: intermediate, trimethylolpropane-ε-caprolactam 3 mol adduct (see Table 2, Synthesis Example 14)
TMP-CL6: Intermediate, trimethylolpropane-ε-caprolactam 6-mol adduct (see Table 2, Synthesis Example 15)
TMP: Trimethylolpropane, manufactured by Mitsubishi Gas Chemical Co., Ltd. Glycerin: Purified glycerin, manufactured by Kao Co., Ltd. PTG850SN: Polytetramethylene glycol, manufactured by Hodogaya Chemical Co., Ltd., hydroxyl value 126.3 mgKOH / g

  <Synthesis Example 12> (Synthesis example of intermediate in Table 1, HEA-CL1)

  Using the same apparatus as in Synthesis Example 1, 342 g of Plaxel M (3 mol, ε-caprolactone, manufactured by Daicel Chemical Industries, Ltd.), 348 g of HEA (3 mol, 2-hydroxyethyl acrylate: manufactured by Osaka Organic Chemical Industry Co., Ltd.), Neostan U-28 0.28 g (tin octoate: manufactured by Nitto Kasei Co., Ltd.), methoquinone 0.14 g (p-methoxyphenol: manufactured by Seiko Chemical Industry Co., Ltd., polymerization inhibitor), Yoshinox BHT 1.38 g (2 , 6-di-t-butyl-P-cresol: manufactured by API Corporation, antioxidant), and gradually heated while uniformly mixing. The reaction was performed at 130 ° C., sampling was performed, and the reaction was terminated when the Gardner viscosity became constant to obtain an intermediate HEA-CL1 (hydroxyethyl acrylate-ε-caprolactam 1 mol adduct).

<Synthesis Examples 13-15>
Except having used each raw material component by the composition ratio shown in Table 2, it reacted like the synthesis example 12, and obtained intermediate body HEA-CL2, TMP-CL3, and TMP-CL6, respectively.

  Each composition blended according to the composition shown in the following Tables 3 to 5 (the numerical values in the table represent parts by mass) are heated and dissolved at 60 ° C. for 3 hours, and Examples 1 to 12 and Comparative Examples 1 to 1 are dissolved. The ultraviolet curable composition of each Example of 4 and the comparative example was prepared. The following evaluation was performed about the obtained composition, and the obtained result is shown to Tables 3-5.

<Measurement method of viscosity>
About the ultraviolet curable composition, the viscosity in 25 degreeC was measured using the B-type viscosity meter (the Tokyo Keiki make, BM type | mold).

<Measurement method of elastic modulus>
The active energy ray-curable composition was applied on a glass plate so that the cured coating film was 100 ± 10 μm, and then a metal halide lamp (with a cold mirror, lamp output 120 W / cm) was used at 500 mJ / in a nitrogen atmosphere. and cured at cm ^2. The elastic modulus of this cured coating film was measured with an automatic dynamic viscoelasticity measuring apparatus manufactured by TA Instruments Co., Ltd., and the dynamic elastic modulus E ′ at 30 ° C. was defined as the elastic modulus.

<Conditions for creating optical disks for warping and signal evaluation>
After preparing a polycarbonate substrate having a diameter of 120 mm and a thickness of 1.1 mm, sputtering a silver alloy target GBD05 (alloy with bismuth containing silver as a main component) manufactured by Kobelco Research Institute, Inc. with a film thickness of 20 to 40 nm, Silicon nitride (SiNx) was sputtered to a thickness of 5 to 10 nm on the surface side. On the silver alloy reflective film of the obtained substrate, each composition shown in Table 3 was applied using an application experiment machine manufactured by Origin Electric Co., Ltd. so that the film thickness would be 100 ± 5 μm after curing. Using a xenon flash irradiation device (model: FUV-201WJ02) manufactured by Ushio Electric Co., Ltd., UV irradiation and curing were performed under the conditions of pre-curing 2 shots (charging voltage 3420V) and main curing 10 shots (charging voltage 3420V). A sample disk was obtained.

<Conditions for creating an optical disk for wear resistance evaluation>
A polycarbonate substrate having a diameter of 120 mm and a thickness of 1.2 mm was prepared, and each composition shown in Table 3 was applied by a spin coater so that the film thickness became 100 ± 10 μm after curing. Using a metal halide lamp with a cold mirror 120 W / cm, UV rays having an irradiation amount of 500 mJ / cm 2 (light meter UVPF-36 manufactured by Eye Graphics Co., Ltd.) were irradiated twice and cured to obtain a test sample disk.

<Evaluation of warpage>
The curvature angle was measured using an argus blu manufactured by Dr. Schwab Inspection Technology. The warp angle was determined from the average value of Radial Tilt when the radial position was 55 mm to 56 mm. The initial warp angle and the warp angle after curing of each composition in Table 3 were measured. Further, for each sample disk, an environmental tester “PR-2PK” (manufactured by ESPEC Co., Ltd.) was used to measure the warp angle after exposure (endurance test) under various temperature and humidity environments. In Table 3, the warp angle before the endurance test is a measured value after standing for 1 day in an environment of 25 ° C. and 45% RH after curing. The warp angle after the endurance test is 240 hours in an environment of 80 ° C. and 85% RH. It is a measured value after taking out the sample disk after standing and leaving it in a 25 ° C. 45% RH environment for one day. The warpage angle after curing and the warpage angle after the durability test were evaluated as follows. Here, when the value of the warp angle is positive (+), it means that the warp angle is opposite to the side where the composition is applied, and when it is negative (−), it means that the warp angle is warped. Evaluation was performed based on the following criteria.
“Change in warpage due to curing shrinkage due to UV irradiation”
○: Warpage variation is within ± 0.8 degrees △: Warpage variation exceeds ± 0.8 degrees and within ± 1.0 degrees ×: Warpage variation exceeds ± 1.0 degrees "
○: Warpage variation is within ± 0.8 degrees △: Warpage variation exceeds ± 0.8 degrees and within ± 1.0 degrees ×: Warpage variation exceeds ± 1.0 degrees

<Endurance test of optical disc>
Each sample disk was subjected to exposure (durability test) when the wet heat environment changed at 80 ° C. and 85% RH for 240 hours using an environmental tester “PR-2PK” (Espec Corp.).

<Optical error rate measurement>
The error rate Random SER of each sample disk was measured using “BD MASTER” manufactured by Pulstec Industrial Co., Ltd. The average value of Random SER after the durability test was evaluated based on the following criteria.
○: 2 × ^{10 -4} or less △: 2 × ¹⁰ exceed ^-4 5 × ^{10 -3} or less ×: exceeding 5 × ^{10 -3}

<Humidity shock test of optical disc>
For each sample disk, use the environmental tester “PR-2PK” (Espec Corp.), and after 48 hours in an environment of 25 ° C. and 95% RH, rapidly reduce only the humidity to 25 ° C. and 45% RH. It was. (Humidity shock test). The warpage was measured for up to 3 hours after removal from the environmental tester. The amount of warpage change before and after the test was determined from the minimum value of Radial Tilt at a radial position of 57 mm to 58 mm, and evaluation was performed based on the following criteria.
○: The minimum value of the warp angle is within ± 0.8 degrees and the warpage change is within ± 0.8 degrees. △: The minimum value of the warp angle is within ± 0.8 degrees and the warpage change is ± 0.8 degrees. Exceeding ± 1.0 degree ×: The minimum value of the warp angle exceeds ± 0.8 degree

<Wear test of optical disc>
Each sample disk was worn 50 revolutions at a load of 250 g using a wear wheel CS-10F in a Taber abrasion tester Rotaria rear presser (manufactured by Toyo Seiki Co., Ltd.). After that, according to JIS K-7105, the total light transmitted light amount and diffused light amount at 405 nm are measured with a spectrophotometer “UV-3100” (manufactured by Shimadzu Corporation) to calculate the diffuse transmittance, and the diffusion before and after the wear test The transmittance difference (ΔH) was calculated and evaluated based on the following criteria.
○: Diffuse transmittance difference (ΔH) before and after the test is 10% or less ×: Diffuse transmittance difference (ΔH) before and after the test exceeds 10%

The symbols in Tables 3 to 5 are as follows.
EA1: Epoxy acrylate described in Synthesis Example 1 EA2: Epoxy acrylate described in Synthesis Example 2 UA1: Urethane acrylate described in Synthesis Example 3 UA2: Urethane acrylate described in Synthesis Example 4 UA3: Urethane acrylate described in Synthesis Example 5 UA4: urethane acrylate described in Synthesis Example 6 UA5: urethane acrylate described in Synthesis Example 7 UA6: urethane acrylate described in Synthesis Example 8 UA7: urethane acrylate described in Synthesis Example 9 UA8: urethane acrylate described in Synthesis Example 10 UA9: urethane acrylate described in Synthesis Example 11 PETA: pentaerythritol tetraacrylate TMPTA: trimethylolpropane triacrylate HPNDA: neopentyl glycol diacrylate hydroxypivalate T GDA: tripropylene glycol diacrylate BisA-4EO-DA: EO-modified (4 mol) bisphenol A diacrylate PEA: phenoxyethyl acrylate PM-2: (manufactured by Nippon Kayaku Co.) ethylene oxide-modified phosphoric acid methacrylate
GA: Gallic acid (manufactured by Dainippon Sumitomo Pharma Co., Ltd.)
Irg184: 1-hydroxycyclohexyl phenyl ketone

  As shown in Tables 3 to 5, the optical discs of Examples 1 to 12 using the composition of the present invention showed little signal change after various environmental tests, and showed good signal characteristics in the durability test. In the abrasion resistance test, excellent abrasion resistance was exhibited. On the other hand, the optical disks of Comparative Examples 1 and 2 have large warpage changes after various environmental tests, and the optical disks of Comparative Examples 3 and 4 have large warpage changes during the durability test.

It is a figure which shows an example of the single layer type optical disk of this invention. It is a figure which shows an example of the single layer type optical disk of this invention. It is a figure which shows an example of the double layer type | mold optical disk of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Light reflection layer 3 Light transmission layer of ultraviolet curable composition 4 Hard coat layer 5 Light reflection layer 6 Light transmission layer of ultraviolet curable composition

Claims (8)

An ultraviolet curable composition for use in a light transmission layer of an optical disc in which at least a light reflection layer and a light transmission layer are laminated on a substrate and laser light is incident from the light transmission layer side to reproduce information. In addition, epoxy (meth) acrylate or urethane (meth) acrylate is contained, the (meth) acryloyl group concentration is 3.86 to 4.2 mmol / g, and the elastic modulus at 30 ° C. of the cured film after UV curing is 2000 MPa. An ultraviolet curable composition for optical discs characterized by the above. The urethane (meth) acrylate comprises a compound (a) having 3 or more hydroxyl groups in the molecule, a compound (b) having 2 or more isocyanate groups in the molecule, a hydroxyl group and a (meth) acryloyl group. The ultraviolet curable composition for optical disks according to claim 1, which is a urethane (meth) acrylate obtained from a compound (c) having: The ultraviolet curable composition for optical disks according to claim 1 or 2, wherein the content of the urethane (meth) acrylate is 10 to 30% by mass in the ultraviolet curable compound contained in the ultraviolet curable composition. The ultraviolet curable composition for an optical disk according to any one of claims 1 to 3, wherein the content of the epoxy (meth) acrylate is 20 to 70% by mass in the ultraviolet curable compound contained in the ultraviolet curable composition. . The optical disk according to any one of claims 1 to 4 , wherein the (meth) acrylate monomer contains 5 to 30% by mass of a bifunctional (meth) acrylate monomer and 10 to 50% by mass of a monofunctional (meth) acrylate monomer. UV curable composition. The ultraviolet curable composition for optical discs according to any one of claims 1 to 5 , wherein the B-type viscosity at 25 ° C is 800 to 5000 mPa · S. An optical disc in which at least a light reflection layer and a light transmission layer made of a cured product of an ultraviolet curable composition are laminated on a substrate, and a blue laser is incident from the light transmission layer side to reproduce information, An optical disc, wherein the ultraviolet curable composition is the ultraviolet curable composition for optical discs according to any one of claims 1 to 6 . The optical disk according to claim 7 , wherein a thickness of the light transmission layer is in a range of 70 to 110 μm.

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