JP4262669B2 - Optical disk resin composition, dry film, sheet - Google Patents

Description

  The present invention relates to a resin composition for an optical disk and a dry film used for bonding an optical disk substrate, and a sheet using the dry film.

An optical disk formed by bonding a plurality of substrates to a general optical disk formed by forming a film such as a recording layer on a single substrate has been proposed.
In such an optical disc, a UV curable resin and a pressure sensitive adhesive such as PSA (pressure sensitive adhesive) are often used as a material for bonding a substrate.

However, when an ultraviolet curable resin is used, the thickness distribution tends to be large, and the workability is deteriorated due to factors such as being easily soiled by the resin and a strong smell.
Furthermore, there is a problem that the curing shrinkage is large and warpage is likely to occur.

  In addition, when an adhesive such as the above-mentioned PSA is used, there is a problem that the creep strength is reduced and the shear stress is weakened, and since it is easy to absorb moisture, warpage is likely to occur.

  In particular, when one of the substrates to be bonded is a thin substrate, for example, the occurrence of the above-described warpage becomes a problem.

  In order to solve the above-described problems, in the present invention, the occurrence of warpage or the like is suppressed, and a highly reliable optical disc, a resin composition for an optical disc and its dry film that can be manufactured, and the dry film are used. A sheet is provided.

  The optical disk resin composition of the present invention is a resin composition used for laminating optical disk substrates, and contains an acrylic resin having a double bond in a side chain, a photopolymerization initiator, and a thermal crosslinking agent. The ultraviolet curable resin composition.

The dry film of the present invention is a dry film used for laminating substrates of optical disks, and is an ultraviolet curable resin containing an acrylic resin having a double bond in a side chain, a photopolymerization initiator, and a thermal crosslinking agent. It consists of a composition, and the acrylic resin is heat-crosslinked.
Moreover, the sheet | seat of this invention laminates | stacks the said dry film of this invention on a cover film or a peeling sheet.

  According to the structure of the resin composition for an optical disk of the present invention described above, by comprising an ultraviolet curable resin composition containing an acrylic resin having a double bond in a side chain, a photopolymerization initiator, and a thermal crosslinking agent, The part having a double bond in the side chain of the ultraviolet curable resin composition can be crosslinked by ultraviolet crosslinking, and the other part (for example, carboxyl group) can be crosslinked by thermal crosslinking. Thus, a three-dimensionally crosslinked network structure can be formed by crosslinking different portions of the ultraviolet curable resin composition by ultraviolet crosslinking and thermal crosslinking. Thereby, an adhesive layer that is resistant to displacement stress and has low moisture absorption can be formed from the resin composition.

  According to the structure of the above-described dry film of the present invention, it comprises an ultraviolet curable resin composition containing an acrylic resin having a double bond in a side chain, a photopolymerization initiator, and a thermal crosslinking agent, and the acrylic resin is thermally crosslinked. By doing so, the part which has the double bond of the side chain of an ultraviolet curable resin composition can be bridge | crosslinked by ultraviolet crosslinking. Thus, a three-dimensionally cross-linked network structure can be formed by cross-linking different portions of the UV-curable resin composition by UV cross-linking and thermal cross-linking, respectively. Thereby, an adhesive layer that is resistant to displacement stress and has low moisture absorption can be formed from the resin composition.

  Further, the present invention provides the above optical disk resin composition, wherein the ultraviolet curable resin composition comprises 0.1 to 5 parts by weight of a photopolymerization initiator and 0.1 to 0.1 parts by weight of a thermal crosslinking agent relative to 100 parts by weight of an acrylic resin. The composition contains 5 parts by weight.

  The present invention also relates to the monomer (A) 100 in which the acrylic resin having a double bond in the side chain is mainly composed of one or more selected from acrylic esters and methacrylic esters in the above optical disk resin composition. Resin (C) 100 obtained by copolymerizing 0.1 to 20 parts by weight of at least one monomer (B) selected from monomers containing at least a hydroxyl group or a carboxyl group with respect to parts by weight. What was obtained by blending 0.1 to 20 parts by weight of one or more (D) selected from an acrylic ester containing an isocyanate group and a methacrylic ester containing an isocyanate group with respect to parts by weight. It is set as the structure which is.

According to the present invention described above, since the ultraviolet curable resin composition is crosslinked by thermal crosslinking and ultraviolet crosslinking, respectively, an adhesive layer having a three-dimensional network structure is obtained, and the substrate to be bonded is securely fixed and held. can do.
As a result, the stress becomes strong against the deviation stress, and the moisture absorption is reduced, and the warp accompanying the moisture absorption is also reduced.
Therefore, the reliability of the optical disk can be increased.

First, prior to description of specific embodiments of the present invention, an outline of the present invention will be described.
The present invention is a resin composition for an optical disk that constitutes an adhesive layer to which an optical disk substrate is bonded.

There are a transparent substrate and an opaque substrate as substrates to be bonded by the adhesive layer.
Further, it is necessary to use a transparent substrate as a substrate that transmits at least light (laser light or the like) for reproducing or recording information on the optical disk.
On the other hand, the substrate that does not transmit light is not particularly limited, and an opaque substrate can also be used.
Examples of transparent substrates include glass substrates, polycarbonate resins, polymethyl methacrylate resins (PMMA), polyolefin resins, vinyl chloride resins, polystyrene resins, epoxy resins, polyarylate resins, polyethersulfone resins, silicone resins, polyethylene terephthalate resins, and the like. Can be mentioned.
Examples of opaque substrates include opaque resins, resins colored to contain pigments and dyes, metals, ceramics, and the like.

And this invention has the characteristics in the material of the resin composition which comprises an adhesive layer especially.
That is, it shall consist of the ultraviolet curable resin composition containing the acrylic resin which has a double bond in a side chain at least, a photoinitiator, and a thermal crosslinking agent.

  The acrylic resin having a double bond in the side chain described above is, for example, a monomer (A) mainly composed of one or more selected from an acrylic ester or a methacrylic ester (that is, a (meth) acrylic ester). One or more monomers (B) selected from monomers containing at least a hydroxyl group or a carboxyl group are copolymerized to obtain a resin (C) having a glass transition point of 0 ° C. or less and a weight average molecular weight of 5000 to 1000000, for example. In addition, the resin (C) can be obtained by reacting one or more (D) selected from an acrylate ester containing an isocyanate group or a methacrylate ester containing an isocyanate group.

For example, as shown in FIG. 5, with respect to butyl acrylate (A1 in the figure) which is one of the acrylic esters corresponding to (A) above, hydroxyethyl as a monomer containing a hydroxyl group corresponding to (B) above is used. A methacrylate (B1), a resin (C1) obtained by copolymerizing acrylic acid (B2) as a monomer containing a carboxyl group corresponding to the above (B), and a methacryloyloxyethyl corresponding to the above (D). Isocyanate (D1) is blended and reacted. At this time, for example, the hydroxyl group OH of hydroxyethyl methacrylate (B1) reacts with the isocyanate group NCO of methacryloyloxyethyl isocyanate (D1) to form a urethane bond, thereby forming a CH _{2 in} the side chain as shown in FIG. An acrylic resin 1 having a double bond of = C is obtained.
In addition, the isocyanate group NCO of methacryloyloxyethyl isocyanate (D1) may react with the carboxyl group COOH of acrylic acid (B2).

As a monomer mainly composed of an acrylate ester or a methacrylate ester, in addition to the above-mentioned butyl acrylate, for example, butyl methacrylate, (meth) acrylate-2-ethylhexyl, methyl (meth) acrylate, (meth) Examples include ethyl acrylate, propyl (meth) acrylate, isooctyl (meth) acrylate, and nonyl (meth) acrylate.
In addition, in combination with these (meth) acrylic acid esters, other vinyl monomers that can be copolymerized with (meth) acrylic acid esters may be used. Examples of the vinyl monomer include acrylamide, styrene, (meth) acrylonitrile, N-vinyl pyrrolidone, maleic acid, vinyl caprolactam, and the like.

  As the monomer containing at least a hydroxyl group or a carboxyl group to be copolymerized with this (meth) acrylic acid ester, in addition to the above-mentioned hydroxyethyl methacrylate and acrylic acid, for example, hydroxyethyl acrylate, hydroxypropyl (meth) Examples include acrylate, butanediol (meth) acrylate, phenoxyhydroxypropyl (meth) acrylate, glycerol di (meth) acrylate, and ECH-modified propylene glycol di (meth) acrylate.

  Furthermore, as an acrylate ester containing an isocyanate group or a methacrylate ester containing an isocyanate group, in addition to the methacryloyloxyethyl isocyanate described above, a hydroxyl group such as hydroxyethyl (meth) acrylate or hydroxypropyl (meth) acrylate is used. You may use what reacted polyisocyanate compounds, such as tolylene diisocyanate and xylylene diisocyanate, to the monomer which has.

  Then, one or more materials are selected from the materials listed above to form the components (A), (B), and (D) described above.

Moreover, it contains at least a hydroxyl group or a carboxyl group with respect to 100 parts by weight of the monomer (A) mainly composed of at least one selected from an acrylic ester or a methacrylic ester (that is, a (meth) acrylic ester). It is preferable that at least one monomer (B) selected from the monomers is blended at a ratio of 0.1 to 20 parts by weight and copolymerized.
If the blending amount is less than 0.1 parts by weight, there is a possibility that sufficient strength due to ultraviolet crosslinking described later may not be obtained. On the other hand, if the blending amount is more than 20 parts by weight, the transparent adhesive layer before UV curing may be too hard. is there.

  Moreover, 0.1 or more types (D) chosen from acrylic acid ester containing an isocyanate group or methacrylic acid ester containing an isocyanate group with respect to 100 parts by weight of the resin (C) obtained by copolymerization is 0.1. It is preferable to mix and react at a ratio of ˜20 parts by weight. Thereby, the quantity which fully reacts with a hydroxyl group or a carboxyl group can be supplied, and the excess component which does not contribute to reaction decreases.

Examples of the photopolymerization initiator mixed with the acrylic resin having a double bond in the side chain obtained as described above include 1 -hydroxycyclohexyl phenyl ketone , diethoxyacetophenone, 2-hydroxy-2-methyl. -1-phenylpropan-1-one, benzoin, benzyldimethyl ketal, benzophenone, hydroxybenzophenone, thioxanthone, isopropylthioxanthone, methylphenylglyoxylate, benzyl, camphorquinone, 2-ethylanthraquinone, 3,3 ′, Examples include 4,4′-tetra (t-butylperoxycarbonyl) benzophenone.

  Due to the action of this photopolymerization initiator, when irradiated with ultraviolet rays, for example, as shown in FIG. 8A, the double bond of the side chain of the acrylic resin 1 is released, and as shown by the dotted line in FIG. The surplus carbon atoms C are bonded to the surplus carbon atoms C in other bonds, and the acrylic resin 1 is three-dimensionally cross-linked one after another by this chain, and the adhesive strength is increased.

The blending amount of the photopolymerization initiator is, for example, 0.1 to 5 parts by weight with respect to 100 parts by weight of the acrylic resin.
If the blending amount of the photopolymerization initiator is too small, the adhesive strength due to ultraviolet crosslinking becomes too low, and there is a possibility that the resin flows, peels off or shifts.
On the other hand, if the blending amount of the photopolymerization initiator is too large, the ultraviolet curable resin composition may be yellowed or may have problems such as a strong odor after curing.

  Examples of the thermal crosslinking agent mixed with the photopolymerization initiator and the acrylic resin include, for example, an isocyanate crosslinking agent (for example, “Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd.), an aziridine compound (for example, trimethylolpropane manufactured by Mutual Pharmaceutical Industries, Ltd.). -Tri-β-aziridinylpropionate), melamine resin (for example, “Super Becamine J-820” manufactured by Dainippon Ink and Co., Ltd.) and the like can be used.

If the ultraviolet curable resin composition is composed only of the acrylic resin and the photopolymerization initiator described above, for example, when this ultraviolet curable resin composition is formed into a film, the film is too soft, so that deformation easily occurs. There is a possibility that the smoothness of the film will be lost and the optical properties will be deteriorated.
Therefore, in the present invention, a thermal crosslinking agent is further blended so that at least a part of the acrylic resin is three-dimensionalized by thermal crosslinking during coating and drying, and the strength is increased to such an extent that the film does not shake.

  For example, as shown in FIG. 7A, when a thermal crosslinking agent 2 having two or more isocyanate groups NCO such as the above-described coronate L (having three isocyanate groups NCO) is used, the isocyanate group of the thermal crosslinking agent 2 is used. NCO reacts with, for example, the carboxyl group COOH of the acrylic resin 1 to thermally crosslink the acrylic resin three-dimensionally. Thereby, as shown to FIG. 7B, the resin composition 3 which improved the intensity | strength, maintaining adhesiveness is producible.

The blending amount of the thermal crosslinking agent is, for example, 0.1 to 5 parts by weight with respect to 100 parts by weight of the acrylic resin.
When there are too few compounding quantities of a thermal crosslinking agent, there exists a possibility that the effect mentioned above may not be acquired.
On the other hand, when there are too many compounding quantities of a thermal crosslinking agent, there exists a possibility that the transparent adhesive layer before ultraviolet curing may become hard too much.

  The components described below can be further added to the ultraviolet curable resin composition containing the acrylic resin having a double bond in the side chain, a photopolymerization initiator, and a thermal crosslinking agent as essential components.

First, for example, triethanolamine, diethylethanolamine, Michler's ketone, ethyl 2-dimethylaminobenzoate or the like may be added as a photoreaction initiation aid.
Further, as photoreactive monomers and oligomers, for example, 1,6-hexanediol diacrylate, dicyclopentanyl (meth) acrylate, bisphenol A di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (Meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate or the like may be added. These photoreactive monomers and oligomers are interposed between the double bonds of the acrylic resin, for example, as shown by 4 in FIGS.
In addition, as a coupling agent, for example, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, etc. are used. May be.

Further, for example, hydroquinone, methoquinone, benzoquinone, anthraquinone and the like may be used as a thermal polymerization inhibitor.
Moreover, as a leveling agent, for example, silicone oil, polyvinyl butyral, or the like may be used.
Further, as the surfactant, for example, fatty acid esters, phosphate esters, fluorine derivatives and the like may be used.

Furthermore, it is preferable that the irradiation amount of the ultraviolet-ray for hardening the ultraviolet curable resin composition mentioned above by ultraviolet crosslinking exists in the range of 0.1-3.0 J / cm < ² >.
If the irradiation amount of ultraviolet rays is less than 0.1 J / cm ² , curing may be insufficient. On the other hand, when the irradiation amount of ultraviolet rays is more than 3.0 J / cm ² , the resin composition may cause yellowing.

By the way, the ultraviolet curable resin composition mentioned above can also be used, for example by making into the film form which apply | coated the resin composition on the peeling sheet previously. In this case, after apply | coating a resin composition on a peeling sheet, it is made into a semi-hardened state by the thermal bridge | crosslinking mentioned above, for example.
By making the film like this, it is excellent in handleability and processability, and since the solvent has already been removed when pre-semi-cured, it is used compared to the case of using a liquid adhesive It also has the advantage that local exhaust is sometimes unnecessary.

Next, Table 1 shows various characteristics (mainly mechanical characteristics) of the ultraviolet curable resin composition described above.
Table 1 shows various properties of the ultraviolet curable resin composition before and after ultraviolet curing, that is, tensile modulus, tensile elongation at break, yield strength, holding power, and adhesive strength.

Here, among the various properties shown in Table 1, the tensile modulus, tensile elongation at break, and yield strength are respectively 1 mm thick adhesive film made of an ultraviolet curable resin composition as shown in FIG. 41 (width 10 mm × length 50 mm) 41 is attached to a tensile testing machine 42 and measured at a pulling speed of 200 m / min.
The holding force is measured as follows. A polyethylene terephthalate (PET) film having a thickness of 25 μm is pasted on the adhesive surface of an adhesive film formed by forming an ultraviolet curable resin composition on a release film, and this is cut to a width of 25 mm, and then the release film is peeled off. A measurement film 51 was produced. As shown in FIGS. 10A and 10B, the measurement film 51 composed of the ultraviolet curable resin composition 52 and the PET film 53 is bonded to an acrylic plate (trade name: Paragrass P) 54 having a thickness of 2 mm. 10B) was pasted so as to be 25 mm × 25 mm, and the amount of deviation after holding for 1 hour in a state where a static load Load of 40 ° C. and 1 kg was applied was measured. At this time, the amount of deviation was measured by putting cuts 53A and 54A in the PET film 53 and the acrylic plate 54, respectively, and measuring the intervals between the cuts 53A and 54A after 1 hour.
Also, the adhesive strength was measured by applying a measurement film having a width of 20 mm, which was produced in the same manner as the measurement film 51 for holding power, to an acrylic plate and a glass plate, respectively, and left at room temperature for 1 hour, and then the 180 ° peel strength was obtained. It is measured. At this time, the pulling speed was 300 mm / min. The results obtained were the same for both acrylic and glass plates.
The ultraviolet curing conditions of the ultraviolet curable resin composition were ultraviolet irradiation with a dose of 1.0 J / cm ² using a metal halide lamp.

Of the various characteristics shown in Table 1, the tensile modulus of elasticity, the tensile elongation at break, and the yield strength before ultraviolet curing, in particular, indicate the ease with which the two substrates are bonded.
Moreover, the holding force and adhesive force after ultraviolet curing indicate the stability of fixing and holding and the reliability of bonding to the two substrates.

Subsequently, specific embodiments of the present invention will be described.
FIG. 1 shows a schematic configuration diagram (cross-sectional view) of an optical disc as an embodiment of the present invention. In this optical disk 10, a reflective layer 12 is formed on a polycarbonate substrate 11 serving as a disk substrate, and a transparent cover film 15 is cured on the polycarbonate substrate 11 with an adhesive layer 14 such as UV-PSA, that is, PSA (Pressure Sensitive adhensive). A pressure-sensitive adhesive). A pre-groove (not shown) is formed on the polycarbonate substrate 11, and a recording layer 13 is formed on the upper surface of the reflective layer 12.

  In this optical disc 10, the laser beam L is incident from the side opposite to the disc substrate 11, that is, the cover film 15, and the recording layer 13 is read, written, read / written, ie, information is reproduced or recorded. ing.

  And in this Embodiment, especially the adhesive layer 14 is an ultraviolet resin composition containing the acrylic resin which has a double bond in the side chain mentioned above, a photoinitiator, and a thermal crosslinking agent. It is comprised from what was hardened | cured by thermal crosslinking and ultraviolet crosslinking.

  Further, the optical disk 10 of the present embodiment is formed by curing the above-described ultraviolet curable resin composition because it is necessary to transmit the laser light L to the adhesive layer 14 in order to reproduce or record information. The pressure-sensitive adhesive layer 14 is configured to sufficiently transmit the laser light L.

  If necessary, another film (not shown) may be further formed to constitute the optical disk 10 shown in FIG.

  According to the optical disk 10 of the present embodiment described above, the adhesive layer 14 for bonding the disk substrate 11 and the cover film 15 is made of the acrylic resin having a double bond in the side chain, the photopolymerization initiator, and the heat. By constituting the ultraviolet curable resin composition containing a crosslinking agent by curing the acrylic resin by thermal crosslinking and ultraviolet crosslinking, the portion having a double bond in the side chain of the ultraviolet curable resin composition is Crosslinking is performed by ultraviolet crosslinking, and other portions (for example, carboxyl groups) are crosslinked by thermal crosslinking. As described above, the different portions of the ultraviolet curable resin composition are crosslinked by ultraviolet crosslinking and thermal crosslinking, so that a three-dimensionally crosslinked network structure is formed in the pressure-sensitive adhesive layer 14.

  By having such a network structure, the pressure-sensitive adhesive layer 14 has a sufficient strength, so that it is resistant to displacement stress, and since the moisture absorption of the pressure-sensitive adhesive layer 14 is reduced, the warpage accompanying moisture absorption is also reduced. Therefore, the highly reliable optical disk 10 can be configured.

Next, optical disks according to other embodiments of the present invention are shown in FIGS. 2A to 2C, respectively.
First, the optical disc 21 shown in FIG. 2A has two recording layers 13 of a first recording layer 13A and a second recording layer 13B, and reads and writes signals (information reproduction or recording) from one side. is there.
In this optical disc 21, a reflective layer 12 is formed on a polycarbonate substrate 11 on which a pregroove (not shown) is formed, and a first recording layer 13 is formed on the upper surface of the reflective layer 12. Further, the second recording layer 13B is formed on the lower surface of the cover film 15 on which a pregroove (not shown) having the second recording layer 13B is formed.
The polycarbonate substrate 11 and the cover film 15 are bonded together with an adhesive layer 14 to form an optical disc 21.
Further, in the optical disc 21, a semi-transmissive reflective layer 17 is provided between the cover film 15 and the adhesive layer 14 in order to obtain a signal from the second recording layer 13B.
Also in this optical disc 21, the ultraviolet curable resin composition having the above-described configuration is formed as the adhesive layer 14 that bonds the polycarbonate substrate 11 and the cover film 15 together. Thereby, the highly reliable optical disk 21 can be realized.

Next, the optical disk 22 shown in FIG. 2B has two recording layers, a first recording layer 13A and a second recording layer 13B, and reads and writes signals (information reproduction or recording) from both sides. is there.
This optical disk 22 is provided with reflection layers 12A and 12B on two polycarbonate substrates 11A and 11B on which pregrooves are formed, respectively, but the first recording layer 13A and the second recording layer 13B are not shown. Is configured.
The two polycarbonate substrates 11A and 11B are bonded to each other with the adhesive layer 14 so that the reflective layers 12A and 12B and the recording layers 13A and 13B are on the inside, thereby forming an optical disk 22.
Also in the optical disc 22, the ultraviolet curable resin composition having the above-described configuration is formed as the adhesive layer 14 for bonding the two polycarbonate substrates 11A and 11B. As a result, a highly reliable optical disk 22 can be realized.
In the case of this optical disk 22, the laser light L for reading and writing signals is not passed through the adhesive layer 14, so that the transmittance of the laser light L in the adhesive layer 14 does not have to be so high.

Next, the optical disk 30 shown in FIG. 2C is used for reading and writing signals (reproducing or recording information) by irradiating the laser beam L from the side of the cover film 19 on which the recording layer 13 is formed. is there.
In this optical disk 30, a recording layer 13 is formed on a cover film 19 on which a pregroove (not shown) is formed, and this cover film 19 is bonded to a polycarbonate substrate 18 with an adhesive layer 14. In this case, no pregroove is formed on the polycarbonate substrate 18.
Also in the optical disc 30, the ultraviolet curable resin composition having the above-described configuration is formed as the adhesive layer 14 that bonds the cover film 19 and the polycarbonate substrate 18 together. Thereby, the optical disk 30 with high reliability can be realized.

  Next, a method for manufacturing the optical disc 10 shown in FIG. 1 will be described. Here, a manufacturing method in the case of using the above-described semi-solidified ultraviolet curable resin composition sandwiched between release sheets to form a dry film will be described.

First, as two substrates, for example, a polycarbonate substrate 11 having a thickness of 1.1 mm and a transparent cover film 15 made of polycarbonate having a thickness of 75 μm are prepared. As described above, the pregroove is formed on the polycarbonate substrate 11 and the recording layer 13 is formed on the upper surface by forming the reflective layer 12 on the polycarbonate substrate 11.
In addition, the pressure-sensitive adhesive layer 14 made of the ultraviolet curable resin composition having the above-described configuration in a semi-solidified state (heat-crosslinked state) is sandwiched between release sheets 31 made of, for example, a polyethylene terephthalate (PET) film. The sheet 20 having the above structure is prepared (see FIG. 3A above).

  This sheet 20 is a so-called dry film of an ultraviolet curable resin composition, and when the sheet 20 is preliminarily made into a semi-solidified state by thermal crosslinking, the solvent in the resin composition is removed by removal.

The sheet 20 shown in FIG. 3A can be manufactured, for example, as shown in FIG.
First, FIG. 4A shows a series of steps.
One release sheet 31 (31A) is unwound from the roll 32A, and a UV curable resin composition serving as an adhesive is dispersed in a solvent by a head 34 at a backup roll 33.
Next, the ultraviolet curable resin composition is thermally cross-linked by the heat treatment and drying in the dryer 35 to form the adhesive layer 14 in a semi-solidified state.
Next, the other release sheet 31 (31B) is unwound from the roll 32B and attached to the surface.
Subsequently, the one release sheet 31 </ b> A, the semi-solidified pressure-sensitive adhesive layer 14, and the other release sheet 31 </ b> B are wound to form a roll 36.

In this way, as shown in FIG. 4B, a roll 36 of the sheet 20 formed by laminating one release sheet 31A, the semi-solidified adhesive layer 14, and the other release sheet 31B is obtained.
And since the ultraviolet curable resin composition is in a semi-solidified state by thermal crosslinking, it has appropriate softness and strength, thickness distribution is good, and thickness accuracy is increased.

Next, the sheet 20 is cut into a required size, and one (for example, the lower surface side) release sheet 31 is peeled off from the sheet 20, and as shown in FIG. 3B, one of the polycarbonate substrate 11 and the cover sheet 15 is removed. Adhesive layer 14 is affixed to the substrate side (in this case, polycarbonate substrate 11 side). Thereafter, the other (in this case, the upper surface side) release sheet 31 is peeled off from the pressure-sensitive adhesive layer 14.
Then, the other substrate (in this case, the cover film 15) is attached to the adhesive layer 14 as shown in FIG. 3C.
Further, the ultraviolet curable resin composition of the pressure-sensitive adhesive layer 14 is cured by ultraviolet irradiation.
Thereby, the optical disk 10 shown in FIG. 1 can be manufactured.

  As described above, both sides of the pressure-sensitive adhesive layer 14 made of an ultraviolet curable resin composition are sandwiched between release films 31, and after the release film 31 on one side is released, it is attached to one substrate, that is, the polycarbonate substrate 11, After peeling off the remaining release film 31, the other substrate, that is, the cover film 15 is bonded, and the ultraviolet curable resin composition of the pressure-sensitive adhesive layer 14 is cured by ultraviolet irradiation, whereby the thickness accuracy of the pressure-sensitive adhesive layer 14 is high. A highly reliable optical disc 10 can be manufactured.

In this way, the UV curable resin composition is formed into a dry film 20 in advance by a method in which the thickness accuracy of the pressure-sensitive adhesive layer 14 is increased, and this is formed by a technically established highly accurate laminating method. Affixed to the first substrate and then bonded to the second substrate in the same manner.
According to these methods, since the thickness can be stably formed, an adhesive layer having a good thickness distribution can be obtained as compared with the case of using a UV curable resin.

Further, since the film is formed in advance, the resin is not scattered during the bonding operation, and the odor is reduced because the solvent is previously removed by removing the solvent, so that workability is improved.
Moreover, since the shrinkage | contraction at the time of ultraviolet curing after bonding two board | substrates together decreases, the curvature accompanying shrinkage also decreases.

  In addition, since the solvent is reduced during the thermal crosslinking, the odor is also reduced, so that workability is improved. Furthermore, shrinkage during UV curing after bonding the two substrates and warpage associated with the shrinkage are reduced.

  After curing by ultraviolet crosslinking, a three-dimensional network structure is formed in the pressure-sensitive adhesive layer 14, and as described above, it is strong against displacement stress and less absorbs moisture.

  Even when a method in which the ultraviolet curable resin composition is directly applied to one substrate (for example, the disk substrate 11) without adopting a film of the ultraviolet curable resin composition, the ultraviolet curable resin composition is previously obtained by thermal crosslinking. Since it has an appropriate strength, the resin scattering is reduced.

  Examples of actually producing the ultraviolet curable resin composition according to the present invention will be described below.

(Example 1)
Butyl acrylate 28.2 parts by weight Acrylic acid 1.5 parts by weight 2-hydroxyethyl methacrylate 0.3 parts by weight Azobisisobutyronitrile 0.03 parts by weight Ethyl acetate 70 parts by weight The above compound was heated at 80 ° C. for 8 hours. The mixture was then refluxed to obtain a hydroxyl group- and carboxyl group-containing acrylic resin solution having a weight average molecular weight of 500,000 and a solid content of 30%.
After the obtained acrylic resin solution was cooled to room temperature, 0.5 part by weight of methacryloyloxyethyl isocyanate was added to 100 parts by weight of this acrylic resin solution, and the mixture was stirred for 1 hour to double bond to the side chain. Acrylic resin solution having was obtained.
For 100 parts by weight of this resin solution, 2 parts by weight of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator and 1.0 part by weight of an isocyanate-based crosslinking agent (“Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd.) as a thermal crosslinking agent In addition, the mixture was uniformly mixed to obtain an adhesive solution.
This solution was applied to a silicone-treated polyester film having a thickness of 38 μm to a thickness of 100 μm and dried in an electric oven at 80 ° C. for 5 minutes to obtain a film having a thickness of 30 μm. It was set as the adhesive film of this.

(Example 2)
An adhesive solution was prepared by adding 2 parts by weight of 1,6-hexanediol acrylate as an acrylic oligomer component to 100 parts by weight of the adhesive solution obtained in the same manner as in Example 1. A film was formed in the same manner as in Example 1, and this was used as the adhesive film of Example 2.

(Comparative Example 1)
After the hydroxyl group- and carboxyl group-containing acrylic resin solution obtained in the same manner as in Example 1 was cooled to room temperature, an isocyanate crosslinking agent (Nippon Polyurethane Industry Co., Ltd.) was used as a thermal crosslinking agent with respect to 100 parts by weight of this acrylic resin solution. 0.3 parts by weight of “Coronate L”) was added and mixed uniformly to obtain an adhesive solution.
This solution was formed into a film in the same manner as in Example 1 to obtain a 30 μm-thick adhesive film, which was used as the adhesive film of Comparative Example 1.

(Comparative Example 2)
In the same manner as in Example 1, 2 parts by weight of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator was added to 100 parts by weight of an acrylic resin solution having a double bond in the side chain, and mixed uniformly. An adhesive solution was obtained.
This solution was formed into a film by the same method as in Example 1 to obtain a 30 μm-thick adhesive film, which was used as the adhesive film of Comparative Example 2.

  Table 2 summarizes the constituent components of the above Examples and Comparative Examples.

(Evaluation test)
With respect to the adhesive film obtained in each of the above Examples and Comparative Examples, the adhesive strength (180 ° peel strength) and holding strength before and after curing by ultraviolet irradiation are determined by the same test method as described above. Was measured respectively. In any measurement, after the adhesive film was attached to an acrylic plate or a glass plate, ultraviolet irradiation was performed immediately, and the measurement was performed 1 hour after that. The ultraviolet irradiation conditions were such that a metal halide lamp was used to irradiate 1.0 J / cm ² of ultraviolet rays on the adhesive surface of the film.
Table 3 shows the measurement results.

From Table 3, it can be seen that Example 1 and Example 2 give good results in peel strength and holding power.
On the other hand, since Comparative Example 1 does not contain a photopolymerization initiator and an acrylic resin having an isocyanate group, it does not cure even after being irradiated with ultraviolet rays, and therefore cannot measure the peel strength and holding power after curing. It was.
Moreover, since the comparative example 2 did not contain the thermal crosslinking agent, the retention before hardening was inadequate.

  When the adhesive film of Comparative Example 1 was used as a component of the actual optical disk 10 shown in FIG. 1, the adhesion / fixing / holding of the two substrates was not stable and was too elastic. The phenomenon that air bubbles remain at the interface between the adhesive and the substrate occurred.

Furthermore, the load of 25 g / cm < ² > was applied to the adhesive film of Example 1-Comparative Example 2, and the external appearance of the adhesive film after 20 hours (after pressure aging) was observed at 70 degreeC. did. The results are shown in Table 4.

From Table 4, in the adhesive film of Example 1 and Example 2, there is no change in appearance even after pressure aging, and good results are obtained.
On the other hand, in the adhesive film of Comparative Example 2, it can be seen that fluctuation occurs in the adhesive after pressure aging, and the stability is not sufficient.

  Table 5 shows the results of measuring the tensile breaking elongation, tensile breaking strength, tensile elastic modulus, and yield strength of the adhesive films of Example 1 and Comparative Example 2 by the method shown in FIG. Shown in

From Table 5, it can be seen that Example 1 has a high strength after curing, a low tensile elongation at break, and good results.
On the other hand, since Comparative Example 2 does not contain a thermal crosslinking agent, it can be seen that the elongation at break before curing is very large.

  From the above results, as shown in Example 1, the resin containing three components of an acrylic resin having a double bond in the side chain, a photopolymerization initiator, and a thermal crosslinking agent is good, and as in Example 2. Furthermore, it can be seen that those obtained by further adding an acrylic oligomer component are also good.

Note that the optical disc to which the resin composition of the present invention is applied is not particularly limited in the configuration of the recording layer of the optical disc as long as the optical disc has a configuration in which a plurality of substrates are bonded with an adhesive layer.
For example, a recording layer is formed by forming grooves (including the above-mentioned pregroove) or pits on the surface of at least one of the two substrates to be bonded together by the pressure-sensitive adhesive layer. can do.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

1 is a schematic configuration diagram (cross-sectional view) of an optical disc according to an embodiment of the present invention. AC is a figure which shows the optical disk of other embodiment of this invention. FIGS. 2A to 2C are process diagrams showing an embodiment of a method for manufacturing the optical disk of FIG. FIGS. 3A and B are process diagrams showing manufacturing steps of the sheet shown in FIG. 3A. It is a figure which shows reaction of the acrylic resin which has a hydroxyl group and a carboxyl group, and the methacrylic acid ester containing an isocyanate group. It is a figure which shows acrylic resin which has a double bond in the side chain obtained by reaction of FIG. It is a figure explaining reaction of the acrylic resin which has a double bond in A and B side chain, and a thermal crosslinking agent. It is a figure explaining the ultraviolet bridge | crosslinking of the acrylic resin which has a double bond in A and B side chain. It is a figure which shows the method of the tensile test of a film. It is a figure which shows the test method of the retention strength of A and B film.

Explanation of symbols

1 Acrylic resin, 2 Thermal crosslinking agent, 10, 21, 22, 30 Optical disc

Claims (5)

A resin composition used for bonding optical disk substrates,
A resin composition for optical disks, comprising an ultraviolet curable resin composition containing an acrylic resin having a double bond in a side chain, a photopolymerization initiator, and a thermal crosslinking agent.   The ultraviolet curable resin composition contains 0.1 to 5 parts by weight of the photopolymerization initiator and 0.1 to 5 parts by weight of the thermal crosslinking agent with respect to 100 parts by weight of the acrylic resin. The resin composition for optical disks according to claim 1.   The acrylic resin having a double bond in the side chain has at least a hydroxyl group or a carboxyl group with respect to 100 parts by weight of the monomer (A) mainly composed of one or more selected from acrylic acid esters and methacrylic acid esters. An acrylic group containing an isocyanate group with respect to 100 parts by weight of the resin (C) obtained by copolymerizing 0.1 to 20 parts by weight of one or more monomers (B) selected from the monomers to be contained It is obtained by blending 0.1 to 20 parts by weight of one or more kinds (D) selected from acid esters and methacrylic acid esters containing isocyanate groups, and reacting them. The resin composition for optical discs as described. A dry film used for bonding substrates of optical disks,
An ultraviolet curable resin composition containing an acrylic resin having a double bond in a side chain, a photopolymerization initiator, and a thermal crosslinking agent,
The dry film, wherein the acrylic resin is thermally crosslinked.   A dry film according to claim 4 is laminated on a cover film or a release sheet.

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