JP4125699B2 - Active energy ray-curable adhesive curable composition for bonded optical disc, and method for producing optical disc - Google Patents

Description

The present invention is an active energy using two disc-shaped substrate having an information recording layer of the optical and, for the recording layer to obtain an optical disc of the laminated structure by the active energy ray-curable adhesive such that the inner The present invention relates to a linear curable adhesive.

Currently, the use of optical discs with a large storage capacity per unit area is expanding more and more, and there are increasing expectations for downsizing optical discs and using both sides of optical discs.
Currently, optical disc substrates that can be used on both sides in the fields of laser discs, magneto-optical discs, digital video discs, and the like are generally bonded optical discs in which two disc-like substrates are laminated and bonded with an adhesive such as an elastomeric hot melt. Is used.

  However, since these hot-melt adhesives are thermoplastic resins, in a durability test under a high-temperature and high-humidity atmosphere such as 60 ° C., 90% RH or 80 ° C., 85% RH, the adhesive strength is 1 / The thickness was reduced to about 5 to 1/10, and partial peeling between the disc-shaped substrates, misalignment of the bonding, and the like may occur, which is insufficient in terms of durability.

Further, a method of using a curable pressure-sensitive adhesive composition for laminating a disk-shaped substrate is also known, but in order to obtain a sufficient adhesive force using such a curable pressure-sensitive adhesive composition, 24 hours at room temperature. In order to cure this in a short time, it is necessary to cure the adhesive at a high temperature of 120 ° C. (see, for example, Patent Document 1 and Patent Document 2). ).
Furthermore, in the laminating method using the pressure-sensitive adhesive, since a hot melt coater or an adhesive prepreg is used for the laminating, there is a problem that air bubbles easily enter between the two disk-shaped substrates. have.
In particular, when laminating thin disk-shaped substrates of about 0.6 mm thickness, distortion occurs between the bubble part and the adhesive part, and the distortion affects the recording layer, which is used for picking up data from the optical disk. Problems may arise.

Japanese Patent Publication No. 1-36513 Japanese Examined Patent Publication No. 2-5791

In order to solve this problem, as one of the low temperature and thin film bonding methods, an ultraviolet curable adhesive is applied to the disk substrates by roll coating, spin coating, screen printing, etc., and the disk substrates are bonded together. Although attempts have been made, it is difficult to remove bubbles during coating or bonding, and the coating efficiency is low.
As described above, the optical disk substrate bonding technology by high temperature coating, thick film bonding, long-time curing, etc., has insufficient performance for further increase in density, size reduction, thinning, and weight reduction of the optical disk. There is no technology that can be put into practical use.

  Under such circumstances, an ultraviolet curable adhesive is used, and it is suitable for obtaining a durable bonded optical disk that can be bonded to each other at low temperature and high speed without mixing bubbles between the disk-shaped substrates. There is a need for a composition.

The present invention 2 having characterized by containing a photopolymerization initiator of acylphosphine oxides or bisacylphosphine oxides having a light absorption spectrum in the visible light range of 400 to 450 nm, the information recording layer of the optical and in disc-shaped base plate bonded Ri combined optical disc for the active energy ray-curable adhesive.

  As described above, when the adhesive for bonded optical disks of the present invention is used, a bonded optical disk with low temperature, thin film, high speed and excellent durability can be obtained, and the workability is also good. The utilization of is large.

The laminated disk in the present invention are those obtained by using the two disk-shaped substrate having a recording layer of the optical and, the recording layer as reproduction is possible that disk-shaped substrate information inside The optical disk has a recording layer that can be read or written by light on one side or both sides, or can be read by light and written by magnetism.
Moreover, the adhesive of this invention exhibits a more effect by using the disk-shaped board | substrate which has a hole in the center at least one side. Hereinafter, the adhesive of the present invention will be described in detail.

First, as shown in FIG. 1, the active energy ray-curable adhesive 3 is applied to a position where the concentric inner surface and the concentric outer surface of the bonding surface of the disk-shaped substrate are equal.
By applying the active energy ray-curable adhesive 3 at such a position, the adhesive 3 can be spread over the entire surface of the disk-shaped substrate 1, and the air inside the adhesive-applied portion is at the center of the disk-shaped substrate. Since the air outside the hole 2 and outside the adhesive application part escapes from the outer peripheral part of the substrate, it is possible to perform the bonding without introducing bubbles.
The method of applying the adhesive 3 at this time is not particularly limited as long as it is concentric with the disk-shaped substrate 1, even if it is continuous in a strip shape, applied in a chain shape, or a dot shape. Specifically, in view of the design of the coating material supply program, it is preferable to apply the belt continuously as shown in FIG.

Next, as shown in FIG. 2, the other disk-shaped substrate 1 is overlaid on the surface of the disk-shaped substrate 1 having the adhesive 3 (FIG. 2-a), and then one disk-shaped substrate. It is pressed with a force greater than the weight (FIG. 2-b), and the applied adhesive 3 is spread on the entire bonding surface of the disk-shaped substrates 1, 1 ′ toward the inside and the outside (FIGS. 2-b to 2-). c) The adhesive 3 is filled between the disk-shaped substrates without introducing bubbles (FIG. 2-c), and this one or both surfaces are irradiated with active energy rays simultaneously or alternately in the case of both surfaces. Agent 3 is cured.
The method for superimposing the disk-shaped substrates is not particularly limited. For example, the substrate is placed horizontally as shown in FIG. 1, and the other disk-shaped substrate is placed on the bonding surface of the substrates from above or below. It is possible to adopt a method such as stacking or placing the substrate vertically, and stacking the other disk-shaped substrate on the bonding surface of the substrate from the left or right, and the method is appropriately selected depending on the viscosity of the active energy ray-curable adhesive That's fine.
In particular, as shown in FIG. 1, when a disk-shaped substrate coated with an active energy ray-curable adhesive is horizontally installed, the other disk-shaped substrate from above is placed, and pressure-bonded with a force greater than its own amount, It is preferable because it is easy to work and can be bonded without bubbles.

  In the present invention, the bonding step may be performed in a vacuum in order to prevent bubbles from entering between the disk-shaped substrates. In this case, immediately after the active energy ray-curable adhesive is applied to one disk-shaped substrate 1 and the other disk-shaped substrate 1 'is overlaid, that is, left in a vacuum for several seconds to several minutes in the state of FIG. It is preferable to do.

  If there is a gap of about 10 to 50 μm in the inner and / or outer periphery of the substrate due to the warpage of the disk-like substrate itself or unevenness of the base material thickness, the application position and application depending on the volume of the gap It is necessary to select the amount appropriately, and it is only necessary to select a coating amount so that the adhesive does not protrude more than necessary.

The material of the disk-shaped substrate used here may be any of an injection-molded substrate, 2P substrate, and extrusion-molded substrate generally used as an optical disk, and the substrates to be bonded may be the same or different.
Specific examples include transparent plastic injection molded substrates such as acrylic resins such as polymethyl methacrylate, polycarbonate resins, polyolefin resins, polystyrene resins, and mixed resins thereof, and inorganic glass.

In consideration of the adhesiveness of the active energy ray-curable adhesive, the disk-shaped substrate having the information recording layer used in the present invention preferably has a light transmittance of 0.01% or more in the wavelength region of 200 to 450 nm. .
If the light transmittance of the region is lower than 0.01%, the amount of energy required for curing the active energy ray-curable adhesive increases, so that the active energy ray irradiation time becomes long and it is difficult to bond them in a short time. In addition, since the amount of energy to be irradiated is large, the disk-shaped substrate is heated by the heat from the UV lamp as the irradiation source, which may cause warping or deformation.

  The adhesive of this invention should just be a composition containing the photoinitiator which has a light absorption spectrum in a 400-450 nm visible region, and is not specifically limited. Here, “having a light absorption spectrum in the visible light region of 400 to 450 nm” means that the light absorption spectrum needs to be at least in the region of 400 to 450 nm. For example, a mixture of (meth) acrylate esters to which a photopolymerization initiator that generates radicals by light in the 200 to 450 nm region can be used.

  Specific examples of the (meth) acrylate ester that is the main component of the active energy ray-curable adhesive include 2-ethylhexyl (meth) acrylate, ethoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and cresol ethoxy. (Meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxy Ethylene oxide or propylene to pentyl (meth) acrylate, 4-hydroxypentyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate Pyrene oxide adducts, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol Penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate 1,9-nonane diacrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neope (Meth) acrylic acid esters such as til glycol di (meth) acrylate, bisphenol A polyoxyethylene di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, and hydroxypivalic acid neopentyl glycol di (meth) acrylate Etc.

  In addition, polyester poly (meth) acrylates obtained by reacting polybasic acids such as phthalic acid and adipic acid, polyhydric alcohols such as ethylene glycol, hexanediol, and butanediol with (meth) acrylic acid or derivatives thereof. , Epoxy (meth) acrylates, hexamethylene diisocyanate having a hydroxyl group (meth) acrylate such as 2-hydroxyethyl acrylate, or a hydroxyl group-containing monomer such as polyol, polyisocyanate and 2-hydroxyethyl acrylate For reaction of urethane poly (meth) acrylates obtained by reaction with polysiloxane, polysiloxane poly (meth) acrylates obtained by reaction of polysiloxane and (meth) acrylic acid compound, polyamide and (meth) acrylic acid compound Polyamide poly (meth) acrylates and the like obtained I and the like.

  The photopolymerization initiator used in the present invention only needs to contain a photopolymerization initiator having a light absorption spectrum in the visible light region of 400 to 450 nm. For example, the photopolymerization initiator has a light absorption spectrum in the visible light region of 400 to 450 nm. And a photopolymerization initiator that generates radicals by light in the 200 to 450 nm region.

Specific examples of the photopolymerization initiator having a light absorption spectrum in the visible light region of 400 to 450 nm include, for example, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-ethoxy-phenyl. Acylphosphine oxides such as phosphine oxide, bisacylphosphine such as bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) methylphosphine oxide And oxides.
These photopolymerization initiators are particularly effective when the disk-shaped substrate having the recording layer has a low ultraviolet transmittance.

  Specific examples of photopolymerization initiators that generate radicals by light in the 200 to 450 nm region include, for example, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl Acetophenone photopolymerization initiators such as -1- [4- (methylthio)] phenyl] -2-morpholinopropan-1-one, and benzoin photopolymerization initiators such as benzoin, benzoin ether, benzyldimethyl ketal, and benzoin alkyl ether Benzophenone photopolymerization initiators such as benzophenone, benzoylbenzoic acid, phenylbenzophenone, hydroxybenzophenone, thioxanthone, chlorothioxanthone, methylthioxanthone, ethylthioxanthone, propylthioxanthone, fluorothioxa Thioxanthone photopolymerization initiators such as tons, glyoxy esters, acyl oxime esters, acylphosphine oxides, bisacylphosphine oxides, and the like.

  In the present invention, an aliphatic amine or an aromatic amine such as Michler's ketone, diethylaminophenone, ethyl dimethylaminobenzoate, and isoacyl dimethylaminobenzoate can be added as a photopolymerization initiation aid to further increase the reactivity. .

In addition to this, the adhesive of this invention can also add a thermal-polymerization inhibitor, a silane coupling agent, a plasticizer, etc. as needed.
In addition, in order to obtain a bonded optical disk using the adhesive of the present invention, the viscosity of the active energy ray-curable adhesive is preferably 20000 cps or less at room temperature.
When the viscosity exceeds 20000 cps, it takes a long time to spread and fill the adhesive between the disk-shaped substrates, and this leads to an increase in cost when industrial production is performed.

The light source of the active energy ray used in the present invention is not particularly limited, and an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a medium pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a xenon lamp, or the like can be used.
When the disk-shaped substrate is deformed by the heat of the light source generated during ultraviolet irradiation, an ultraviolet irradiation device with a cold mirror reflector or heat ray reflection filter may be used. In addition, the disk-shaped substrate is deformed by the heat of the light source. In order to prevent this, it is preferable to hold the bonded disk-shaped substrate (the state shown in FIG. 2-c) with a glass plate or the like that transmits ultraviolet rays.
Such bonding method, the present invention is a disk-shaped substrate having an information recording layer of the optical and can reproduce information to obtain an optical disk as possible.

In order to explain the content of the present invention more specifically, representative examples are shown below, but the present invention is not limited to these examples.
In addition, the evaluation method of a present Example is as follows.

Adhesion state:
About the obtained bonded optical disk, the adhesive layer and the disk-shaped substrate were peeled off with a knife edge, and the state of the adhesive layer was visually evaluated.
An endurance test:
The obtained bonded optical disk was subjected to a 500-hour durability test under high-temperature and high-humidity conditions of 80 ° C. and 85% RH, and the appearance was visually evaluated.

[Preparation of active energy ray-curable adhesive]
Acrylic esters having a composition shown in Table 1 and a photopolymerization initiator were mixed to obtain an active energy ray-curable adhesive A and an active energy ray-curable adhesive B.

（但し、表中の数値の単位は重量部である。）
ＤＰＨＡ：ジペンタエリスリトールヘキアクリレート
ＴＭＰＴＡ：トリメチロールプロパントリアクリレート
ＢＰＥ４：ビスフェノールＡテトラオキシエチレンジアクリレート
ルシリンＴＰＯ：ＢＡＳＦ社製光重合開始剤（２，４，６−トリメチルベンゾイル−ジフェニルホスフィンオキサイド）
イルガキュア１７００：チバガイギー社製光重合開始剤（ビス(２，６−ジメトキシベンゾイル)−２，４，４−トリメチルペンチルホスフィンオキサイドと２−ヒドロキシ−２−メチル−１−フェニル−プロパン−１−オンの１対３混合物）

(However, the unit of numerical values in the table is parts by weight.)
DPHA: dipentaerythritol hexacrylate TMPTA: trimethylolpropane triacrylate BPE4: bisphenol A tetraoxyethylene diacrylate lucillin TPO: photopolymerization initiator manufactured by BASF (2,4,6-trimethylbenzoyl-diphenylphosphine oxide)
Irgacure 1700: Ciba-Geigy photoinitiator (bis (2,6-dimethyl preparative Kishibenzoiru) -2,4,4-trimethyl pentyl phosphine oxide and 2-hydroxy-2-methyl-1-phenyl - propane-1 1 to 3 mixture on)

[Examples 1 and 2]
Information of a polycarbonate disk-shaped substrate (substrate thickness: 0.6 mm, center hole: diameter 15 mm, outer diameter: 120 mm) having an information recording layer (FIGS. 1-4) consisting of an aluminum vapor deposition layer (thickness: 500 angstroms) on one side To the recording layer side, a total amount of 0.3 g of the active energy ray-curable adhesive shown in Table 1 is dropped evenly on a concentric circle located 40 mm from the center of the substrate using a dispenser as shown in FIG. did.
Next, the disc-shaped substrate of the same type (FIG. 2-1 ′) is placed so that the recording layer (FIGS. 2-4 and 2-4 ′) face each other and the center hole (FIGS. 2-2 and 2-2). Overlaid from above so that ') matches.
The recording layer of the upper disk-shaped substrate (FIG. 2-4 ′) first contacts with the apex of the active energy ray-curable adhesive (FIG. 2-3), and the contact area gradually increases. The bubbles did not enter the adhesive surface.
Then, when the overlapped disk-shaped substrate was left and the cross section was observed over time, the active energy ray-curable adhesive used for bonding was removed from the concentric circles at the initial application stage due to the weight of the upper disk-shaped substrate. It was expanded to the inner peripheral side and the outer peripheral side, and stabilized in the state shown in FIG. 2-c through FIG. 2-a to FIG. 2-b.
Then, using a UV irradiation device having one high pressure mercury lamp (120 W / cm), UV light was irradiated on one side for 20 seconds under the condition of a lamp height of 25 cm, and the two disk-shaped substrates were completely cured and bonded to each other. The evaluation results are shown in Table 2.

[Example 3]
Except for using the active energy ray-curable adhesive B shown in Table 1, two disk-shaped substrates were stacked and stabilized in the same manner as in Example 1, and then the same ultraviolet irradiation apparatus as in Example 1 was used. Using, after irradiating ultraviolet rays on one side for 10 seconds, it was turned upside down and further irradiated with ultraviolet rays on the other side for 10 seconds, and the two disk-shaped substrates were completely cured and bonded to each other. The evaluation results are shown in Table 2.

[Example 4]
In the same manner as in Example 1, after superimposing and stabilizing two disk-shaped substrates, an ultraviolet irradiation device in which 120 W / cm high-pressure mercury lamps are arranged one above the other through a glass plate stage is used. Then, under the condition of a lamp height of 25 cm, the disk-shaped substrate superimposed on the glass plate was placed, and ultraviolet rays were simultaneously irradiated from both sides for 10 seconds, and the two disk-shaped substrates were completely cured and bonded to each other. The evaluation results are shown in Table 2.

[Comparative Example 2]
A hot melt adhesive (trade name: Evergrip PS450-56) manufactured by ACI Japan Limited was applied to the entire recording layer side of the disk-shaped substrate used in Example 1 with a hot melt coater, and then the other disk of the same type. The substrates were stacked and pressure-bonded with a press at a pressure of 1.5 kgf / cm ² . The evaluation results are shown in Table 2.

FIG. 1 shows an embodiment of the present invention and is a schematic view showing a state where an active energy ray-curable adhesive is applied to a disk-shaped substrate.

FIG. 2 shows an embodiment of the present invention, and is a schematic diagram showing a state in which the active energy ray-curable adhesive spreads over the entire bonding surface of the disk-shaped substrate when the disk-shaped substrate is bonded.

Explanation of symbols

1, 1 ': Disc-shaped substrate 2, 2': Center hole 3: Active energy ray-curable adhesive 4, 4 ': Information recording layer

Claims (3)

Characterized in that it comprises a photopolymerization initiator acylphosphine oxides or bisacylphosphine oxides having a light absorption spectrum in the visible light region of 400 to 450 nm, 2 sheets of disc-shaped having an information recording layer of the optical and The active energy ray-curable adhesive for board bonded Ri combined optical disc. The active energy ray-curable adhesive for bonded optical disks according to claim 1, wherein the photopolymerization initiator is a bisacylphosphine oxide.   An optical information recording layer is formed using an active energy ray-curable adhesive for optical discs containing a photopolymerization initiator of acylphosphine oxides or bisacylphosphine oxides having a light absorption spectrum in the visible light region of 400 to 450 nm. A method for producing an optical disk, in which two disk-shaped substrates are bonded together.

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