JP2002509977A - Radiation-curable adhesive for digital versatile discs - Google Patents

Abstract

  (57) [Summary] UV-curable acrylate-based adhesive composition for digital versatile discs and other substrates, method for bonding versatile digital disc layers together with a UV-curable adhesive, and UV-curable or radiation Digital versatile disc bonded by a curable adhesive. The adhesive includes an acrylate functional component, a non-acrylate reactive diluent (e.g., having acrylamide or N-vinyl functionality) and a thiol compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention is useful for bonding the surfaces of digital versatile discs together,
The present invention relates to a radiation-curable adhesive composition.

[0002]

[Prior art]

Compact discs, or commonly known CDs, have revolutionized the recording and computer industries, enabling the recording of vast amounts of data, such as music, on inexpensive and readily available media. The technology behind compact discs has been improved and evolved to meet the increasing storage demands of the computer and entertainment industry, and has finally arrived at the creation of digital versatile discs, DVDs. While compact discs and digital versatile discs store information in the same general way, DVD designs have taken advantage of CD technology to create better products.

[0003] Structurally, digital versatile discs and compact discs are very similar to each other. The information-bearing surfaces of both discs have knurls or pits arranged in a continuous spiral pattern. As the drive laser travels across the pit, the laser beam is reflected back to the driver, who receives the light signal and converts it to an appropriate format, for example, an audio, video, graphic or textural format. DVDs store more data than equivalent CDs. This is because, in particular, the pits on which the information is carried are densely located on compact tracks, as opposed to smaller and wider CD tracks. DVD players utilize lasers that emit red light at 650 nm and 635 nm, which has a shorter wavelength than the infrared light used in normal CD players. Such shorter wavelengths allow DVD players to accurately read smaller, more closely packed pits on digital versatile discs.

[0004] Compact and digital versatile discs consisting of a core member around which the information bearing surface is symmetrically arranged have the same diameter (120 m).
m) and the same thickness (1.2 mm). However, instead of the single layer properties of a traditional compact disc, a digital versatile disc consists of two 0.6 mm layers of polycarbonate. This results in a shorter distance between the surface of the disk and the pits, so that when accessing information, the laser penetrates less plastic on DVDs than on CDs. Thus, a thinner DVD substrate increases the accuracy of the laser reading. The two bonded surfaces of the DVD increase the strength of the disc and prevent distortion. That is, a digital versatile disc has a larger capacity than a compact disc and has less response to environmental factors.

[0005] Digital versatile discs can be made by a few basic process variations, as disclosed, for example, in US Pat. Nos. 4,310,919 and 4,423,137. . For example, during the manufacture of a digital versatile disc, a master glass disc with the desired information is recorded by using a laser beam to record data in a spiral pattern from the center of the master glass disc to the outer edge of the master glass disc. Made. After recording, the master glass disk is developed by spinning a sodium hydroxide solution over the glass surface and reveals pits created by the laser. The developed master glass disc is then metallized with a silver coating followed by a nickel coating. The nickel layer is then separated from the silver-coated master glass disk to form a nickel inverse image of the data, known as a father copy. One or more nickel copies of the father can be produced, which can be used as a stamper in an injection molding machine for producing discs. The molten polycarbonate is then placed in a mold containing a stamper to make a polycarbonate disc with the desired information. The disk is then removed from the mold with the lacquer layer attached to it and the reflective metal (usually aluminum)
Deposit or sputter on top of the polycarbonate first layer containing information.
A protective coating of lacquer is then applied over the reflective layer and dried or cured to make a single-sided disc. The stamped side of the single-sided DVD is supported by a dummy layer on which graphics can be applied.

To further increase the capacity of the disc, the basic DVD configuration is usually modified. The capacity of a single-sided disc can be nearly doubled by applying a semi-reflective data layer zero to the reflective aluminum layer 1, for example comprising gold. The gold layer can be read by a driver laser at a low power setting, while the aluminum layer can be accessed by increasing the power of the laser. As a result, double layer information is obtained on one side of the disc, giving a DVD with a capacity of about 8.5 GB at present.

[0007] Two of these single-sided dual-layer discs can be joined back to back with a thin layer of adhesive to create a double-sided dual-layer digital versatile disc that currently has about 17 GB of storage space. The first and second disc layers are joined such that they are parallel and equidistant from the core member of the disc. The adhesive used must provide high shear strength while keeping the information layers uniformly equidistant from each other.

[0008] Three types of technologies are currently used for DVD combining. Contact adhesives, cationic or PSA UV bonds, and free radical UV bonds. The compositions must provide adhesion between the aluminum and polycarbonate layers, between the gold and polycarbonate layers, between the lacquer and the polycarbonate layers, and between various combinations thereof. In addition, the adhesive coating has a high cure rate and must wet the substrate. After curing, these materials must have high dimensional stability and durability.

However, without weakening other desirable properties such as dimensional stability of the disc, the DVD
Strong and long-lasting adhesion between component layers cannot be achieved with existing systems.

[0010] The contact adhesive is applied to the disk by a hot melt method, wherein the temperature is between 120 ° C and
Maintained at 160 ° C. The adhesive is spread on the disc as a thin layer by roll coating both internal bonding surfaces. Then one by one is pressed together and the adhesive is cured. Although flat disks can be produced by this method at high production rates, these disks tend to warp when stored at temperatures above 70 ° C. or in humid environments.

In the case of cationic UV bonding, the adhesive is coated on both disks, UV irradiated and then pressed together. The bond grows over time due to aging, so that
After about 24 hours, each of the disks is permanently bonded to each other. Disks made by this method are flatter than other methods, but cationic UV bonding requires an additional lacquer coating step. In addition, the discs must stay at the cure site for a period of time before stacking to ensure complete bonding, which requires special stackers and increases equipment costs.

During free radical UV bonding, an acrylate lacquer is placed on the leading edge of the disc, after which a second disc is placed on top and the pair is rotated.
The weight of the second disk facilitates the movement of the lacquer towards the inner edge of the metal layer, while the rotation moves the lacquer to the outer edge. After the spin coating process is completed, the adhesive is cured by UV irradiation. Radical UV bonding is prone to bubble formation between the bonded layers. In a double layer structure, the bubbles can impair the ability of the drive laser to read the pits carrying the information. Variations in the aluminum layer before bonding cause uneven hardening, which prevents the formation of a flat disk.
In addition, upon curing, the acrylate often shrinks to a significant extent, thereby preventing the formation of a flat disk. Also, this shrinkage can reduce the environmental stability of the bonded disc.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to bond sputter-coated metallized or siliconized polycarbonate substrates tightly and, after exposure to elevated temperatures and humidity, to a stable, An adhesive having mechanical properties, suitable viscosity, acceptable shrinkage, and low volatility after curing. The result is an adhesive that imparts impact resistance and excellent shear strength to the bonded digital versatile disc or other substrate.

[0014]

[Means for Solving the Problems]

It is an object of the present invention to provide the following premix components: (A) from about 5% to about 80% by weight of at least one UV or radiation curable acrylate oligomer; (B) from about 1% to about 20% by weight. At least one non-acrylate functional reactive diluent; (C) from about 10% to about 80% by weight of at least one acrylate functional reactive diluent; (D) from about 0.5% to about 10% by weight of at least one radical-forming sulfur compound; and (E) optionally from about 0.1% to about 15% by weight of one or more photoinitiators; Achieved by UV or radiation curable compositions. Here, the “component before mixing” is the same as the radiation-curable composition component before being mixed with other components.

The present invention is directed to the manufacture of an improved adhesive for joining digital versatile discs, a method for joining disc components together, and improved impact resistance due to the enhanced joining properties of the adhesive compound. Is provided.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The radical-forming sulfur compound is generally a thiol compound or a polysulfide compound. In the rest of the text, this is mostly referred to as thiol compound, but this is only an example.

Acrylate oligomers are well known in the adhesives art. According to the present invention,
Copolymerization of a thiol with a non-acrylate functional compound having a urethane acrylate (sometimes referred to as an “ene”) has properties superior to urethane acrylate coatings without a thiol-ene system. It is believed to create an enhybrid adhesive coating. The non-acrylate functional compound can be, for example, an acrylamide or N-vinyl group containing compound. Hybrid acrylate-thiol-ene adhesive compositions, because standard adhesive materials do not impart a strong, long-lasting bond between, for example, aluminum and polycarbonate substrates, especially at adverse environmental conditions, especially at elevated temperature and humidity levels. The manufacture of objects is a significant improvement over current methods.

[0018] While not certain, it is believed that the thiol-ene system allows for the copolymerization of non-acrylate functional moieties with acrylate moieties. In the absence of thiols, for example, the copolymerization of N-vinyl compounds is slow. Thiol compounds can act as chain transfer agents and reduce the cure rate. In contrast, thiol-in acrylate compounds
When the adhesive film is cured, the ene-based material increases the curing speed and reduces the shrinkage of the cured adhesive.

The construction of a DVD requires that two 0.6 mm substrates be bonded together using an optical adhesive. One or both substrates may be made of aluminum, gold, silicon,
Vacuum coated with a thin layer of silicon carbide or silicon nitride. The optical adhesive that bonds the DVD needs to adhere well to these surfaces and the polycarbonate that make up the disc. Substrate layers bonded together in various combinations according to the present invention include, but are not limited to, plastics, metals and ceramics. Optical adhesives must not corrode surfaces in high temperature and / or humid environments. Additional requirements for DVD bonding adhesives include full edge cure, high cure speed in air and optical clarity for DVD-9, DVD-18 or other sizes.

Radiation curable adhesive compositions based on hybrid acrylate-thiol-ene copolymers are unexpectedly useful DVD adhesives. The adhesive, for example, bonds strongly to the aluminized surface of the polycarbonate substrate of the DVD, cures well in air, and has good edge cure properties. Such compositions also do not corrode aluminum surfaces.

The types and amounts of acrylate oligomers, non-acrylate functional reactive diluents, acrylate functional reactive diluents, thiol compounds and additives can be adjusted according to the end use of the product. The composition maximizes the adhesion of the cured substance,
It can be manufactured to reduce viscosity, reduce cure speed, and the like. For example, the acrylate-functional reactive diluent and optionally the silane compound can each be added at varying effective concentrations to achieve improved viscosity and adhesion. By changing the component ratios, other desirable properties such as high optical clarity, good hardness, chemical resistance and abrasion resistance can be promoted.

The exact combination selected for use in the radiation-curable adhesive coating composition may vary depending on the other components of the composition and the light source used to cure the composition. Prior to curing, components that may form insoluble salts and impair the optical properties of the bonded disc should be removed from the composition.

The radiation-curable composition can be cured by conventional means. For example, the radiation source may be a conventional light source, such as a UV lamp available from Fusion Systems Corp. Furthermore, low, medium and high pressure mercury lamps, superactinic fluorescent tubes or pulse lamps are suitable. Radiation curing is preferably by actinic radiation, more preferably by UV irradiation. When using the preferred UV cure of the adhesive composition, proper control of light intensity is important to help control the shrinkage of the polymeric material.

The radiation-curable oligomer (A) can be any radiation-curable oligomer used in a radiation-curable adhesive coating composition. Examples of suitable radiation-curable oligomers include urethane oligomers having a molecular weight of at least about 500 and containing at least one ethylenically unsaturated group that can be polymerized by actinic radiation. For example, if a diluent is present in the coating composition, the ethylenically unsaturated groups can be the reactive end of the oligomer to which the reactive diluent binds when the composition is cured. Preferably, the oligomer has two terminal radiation-curable functional groups, one at each end of the oligomer.

[0025] Representative oligomers are disclosed, for example, in US Patent No. 4,932,750.

The radiation-curable oligomer is generally present in an amount of about 5% or more, preferably about 10%.
It is present in the above amounts, more preferably in an amount of about 15% by weight or more. The acrylate oligomer is generally present in an amount up to about 80%, preferably up to about 75% by weight, more preferably up to about 60% by weight.

Examples of suitable radiation-curable functional groups that may be present on the oligomer include ethylenically unsaturated groups such as acrylates or methacrylates, or mixtures thereof.

Preferably, the radiation-curable groups in the oligomer are acrylate groups.

The radiation-curable oligomer comprises an oligomer backbone, at least two radiation-curable groups, and a linking group that connects the radiation-curable group to the oligomer backbone. The oligomer preferably has, but is not necessarily, a linear structure and may include a block or random copolymer structure. Oligomers having urethane linkages and acrylate radiation-curable groups are preferred.

The oligomer skeleton includes, for example, polyether, polyolefin, polyester,
It can be based on polycarbonate, acrylic, hydrocarbon, polyolefin or copolymers thereof. Preferably, the oligomer backbone contains urethane units.

The radiation-curable oligomer comprises at least one radiation-curable (meth)
It can be an acrylic oligomer containing acrylate groups, preferably at least one acrylate group. These are conventionally known as acrylated acrylics.
rylics).

An oligomer synthesis route for acrylated acrylics can include, for example, esterification of a hydroxyl-functional acrylic oligomer with (meth) acrylic acid, or reaction of an epoxy-functional acrylic oligomer with (meth) acrylic acid.
These acrylated acrylics may contain urethane linkages. Preferred acrylated acrylic oligomers include at least a species of Mn 5,000. Preferred acrylated urethane acrylics are described in EP-A-858470.

The acrylated acrylics are known synthetic methods including, for example, partial esterification of acrylic polymers having pendant carboxylic acid groups with hydroxyethyl acrylate or glycidyl methacrylate, or acrylated glycidyl methacrylate terpolymer with acrylic acid. Can be manufactured by

[0034] The acrylic oligomer typically has a copolymerizable skeleton. Tg of oligomer
Can be reduced by reducing the content of methyl methacrylate.

(Meth) acrylic acid and ester polymers are disclosed, for example, in the Encyclopedia of Polymer Science & Engineering , Vol. 1, 1985, pgs. 211-305.

The oligomer backbone can include one or more oligomer blocks linked together, for example, by urethane linkages. For example, one or more types of polyol prepolymers
It can be combined by a conventionally known method.

If the oligomer backbone is a polyether, the resulting adhesive may have a low glass transition temperature and good mechanical properties. If the oligomer backbone is a polyolefin, the resulting adhesive may have further improved water resistance. Oligomers based on polycarbonate can provide good stability. A polyether skeleton is preferred.

Oligomers having repeating urethane units can be used, for example, to react (i) oligomeric polyols, (ii) di- or polyisocyanates and (iii) hydroxy-functional ethylenically unsaturated monomers, such as hydroxyalkyl (meth) acrylates. Can be manufactured.

If an oligomer backbone polyol is used, it preferably has an average of at least about 2 hydroxyl groups. The oligomer backbone polyol, on average,
It may have more than two hydroxyl groups. Examples of such oligomer diols include polyether diols, polyolefin diols, polyester diols, polycarbonate diols, and mixtures thereof. Polyether and polycarbonate diols or mixtures thereof are preferred.

If a polyether diol is used, preferably the polyether is a substantially non-crystalline polyether. Preferably, the polyether contains one or more repeating units of the following monomer units. —O—CH ₂ —CH ₂ ——O—CH ₂ —CH (CH ₃ ) —— O—CH ₂ —CH ₂ —CH ₂ ——O—CH (CH ₃ ) —CH ₂ —CH ₂ ——O _{-CH 2 -CH (CH 3) -CH} 2 - -O-CH 2 -CH 2 -CH 2 -CH 2 - -O-CH 2 -CH (CH 3) -CH 2 -CH 2 - -O-CH _{(CH 3) -CH 2 -CH 2} -CH 2 -

Examples of polyether polyols that can be used are the polymerization products of 20% by weight of 3-methyltetrahydrofuran and 80% by weight of tetrahydrofuran, both of which undergo ring-opening polymerization. This polyether copolymer contains branched and unbranched oxyalkylene repeat units and is commercially available as PTGL 1000 ™ (Hodogaya Chemical Company, Japan). Another example of a polyether of this series that can be used is PTGL 2000 ™ (Hodogay
a Chemical Company). Another example of a polyether that may be used is a polyaryl-based diol such as ethoxylated or propoxylated bisphenol-A or bisphenol-F.

Examples of polycarbonate diols are those normally produced by alcoholysis of diethylene carbonate with diols. The diol is, for example, about 2
It can be an alkylene diol having from about 12 carbon atoms, such as 1,4-butanediol, 1,6-hexanediol, 1,12-dodecanediol, and the like.
Mixtures of these diols can also be used. Polycarbonate diols can contain ether linkages in the backbone in addition to the carbonate groups. That is, for example, a polycarbonate copolymer of an alkylene oxide monomer and the aforementioned alkylene diol can be used. Mixtures of polycarbonate diols and polycarbonate copolymers can also be used.

As the polycarbonate diol, for example, DURACARB 122 (trademark) (PPG
Industries) and PERMANOL KM10-1733 ™ (Permuthane, Inc., Mass.). DURACARB 122 is produced by alcoholysis of diethyl carbonate with hexanediol.

Suitable polyolefin polyols preferably include hydrogenated polybutadienes, and especially 1,2- and 1,4-copolymerized butadienes.

[0045] Any organic polyisocyanate (ii) can be used alone or in a mixture as a polyisocyanate. The polyisocyanate compound used to form the urethane acrylate oligomer can be any organic isocyanate compound having at least two free isocyanate groups. Aliphatic, cycloaliphatic and aromatic polyisocyanates are included. Polyisocyanates such as alkyl and alkylene polyisocyanates, cycloalkyl and cycloalkylene polyisocyanates, aryl and alcohol arylene polyisocyanates, and combinations of alkylene, cycloalkylene and alkylene arylene polyisocyanates can be used. The reaction results in a product that is end-capped on at least one end of the molecule by the reaction product from the isocyanate / ethylenically unsaturated monomer reaction. "End-capped" means that a functional group caps one of the two ends of the oligomeric diol.

The isocyanate / hydroxy functional monomer reaction product is attached to the oligomer backbone (i) diol by a urethane linkage. The urethane reaction can take place in the presence of a catalyst. Examples of the urethane reaction catalyst include dibutyl-tin dilaurate and diazabicyclooctane crystals.

Preferably, the polyisocyanate (ii) is a diisocyanate. Examples of diisocyanate (ii) include isophorone diisocyanate (IPDI), tetramethyl xylene diisocyanate (TMXDI), and toluene diisocyanate (
TDI), diphenylmethylene diisocyanate, hexamethylene diisocyanate, cyclohexylene diisocyanate, methylene dicyclohexane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, m-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate,
4,4'-biphenylene diisocyanate, 1,5-naphthylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, and poly Alkyl oxides and polyester glycol diisocyanates include, for example, TDI-terminated polytetramethylene ether glycol and TDI-terminated polyethylene adipate, respectively. Preferably, the diisocyanate is a non-yellowing diisocyanate such as isophorone diisocyanate.

In general, the compound (iii) for providing a reactive terminal is an olefinically unsaturated compound used for producing the urethane acrylate oligomer of the present invention, and may be a monomer or a polymer, and may be an active hydrogen group or the like. Is characterized by the presence of a moiety capable of reacting with isocyanate. Preferably, the active hydrogen group is hydroxy. Examples of the unsaturated polymerizable monomeric organic compound having an isocyanate-reactive active hydrogen group include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, and diethylene glycol. Monomethacrylate, glycerin dimethacrylate, dimethylolpropane dimethacrylate, and the reaction product of polyester glycol of acrylic acid or methacrylic acid.

[0049] The polyols used to make urethane oligomers are generally about 20
0 g / mol to about 5,000 g / mol, preferably about 500 g / mol to about 4,000 g / mol.
It has a molecular weight of 0 g / mol, more preferably from about 1,000 g / mol to about 3,000 g / mol. Urethane oligomers having radiation-curable groups generally have about 1
It has a number average molecular weight of from 000 to about 10,000, preferably from about 1,500 to about 5,000. Suitable syntheses of urethane oligomers are described, for example, in US Pat.
Nos. 6,563 and 5,409,740. Mixtures of oligomers can be used. Preferred urethane acrylate oligomers are
CN966-J75 ™ (aliphatic polyurethane acrylate) obtained from Sartomer, Inc. (Pennsylvania).

The composition according to the invention comprises at least two reactive diluents. Reactive diluents can be used to adjust the viscosity of the adhesive composition. That is, each of the reactive diluents can be a low viscosity monomer containing at least one functional group that can polymerize when exposed to actinic radiation. At least one non-acrylate functional (or -ene) reactive diluent and one acrylate functional reactive diluent are used.

The reactive diluent preferably has a viscosity of the coating composition of from about 100 to about 1,
It is added in such an amount that it is in the range of 000 mPas. Suitable amounts of reactive diluents have been found to be from about 5% to about 80% by weight, more preferably from about 10% to about 75% by weight.

The reactive diluent preferably has a molecular weight of about 550 or less or about 500 mP at room temperature.
Has a viscosity of less than as (measured as 100% diluent).

The functional groups present on the reactive diluent may be of the same nature as used in the radiation curable oligomer. Preferably, the radiation-curable functional groups present on the reactive diluent can be copolymerized with the radiation-curable functional groups present on the radiation-curable oligomer.

The non-acrylate functional reactive diluent (B) comprises radically polymerizable groups that are not acrylate or methacrylate groups. Suitable non-acrylate functional groups include acrylamide, methacrylamide, N-vinyl, vinyl ether, vinyl ester, and the like.

In a first embodiment of the invention, the non-acrylate functional reactive diluent (B) contains a vinyl group.

Such vinyl-reactive diluents preferably have vinyl ether or N-vinyl functionality. More preferably, N-vinyl is used. Suitable examples of vinyl monomers are lauryl vinyl ether, 2-ethylhexyl vinyl ether, hexanediol divinyl ether, N-vinyl formamide and derivatives thereof, N-vinyl carbazole, N-vinyl caprolactam, N-vinyl pyrrolidone and the like.

As a vinyl-reactive diluent, N-vinylpyrrolidone or N-vinylcaprolactam is preferred.

In a second embodiment of the present invention, the non-acrylate functional reactive diluent (B) comprises:
Contains acrylamide groups such as alkyl acrylamide, alkyl methacrylamide, or aryl acrylamide. Preferably, the photopolymerizable amide comprises an alkyl acrylamide, for example an alkyl acrylamide such as N, N-dimethylacrylamide, N-isopropylacrylamide, N, N-diethylacrylamide, N, N-dimethylaminopropylacrylamide and morpholinoacrylamide. .

[0059] The non-acrylate functional reactive diluent (B) is preferably present in an amount of about 3% by weight or more, especially about 5% by weight or more.

A suitable amount of the reactive acrylate functional diluent system (C) is from about 10% to about 8% by weight.
It has been found that it is 0%, preferably about 10% to about 70%, more preferably about 25% to about 60% by weight. If more than one reactive diluent is present, the amounts of reactive diluent are added to one another to determine the amount of diluent system.

[0061] Preferably, the reactive diluent system comprises a monomer having an acrylate functionality and C ₄ -C ₂₀ alkyl le or polyether moiety. Examples of such reactive diluents are hexyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, ethoxyethoxy-ethyl acrylate, isodecyl acrylate, and isooctyl acrylate.

Another preferred type of reactive diluent is a compound containing an aromatic group. Examples of diluents having an aromatic group include ethylene glycol phenyl ether acrylate, polyethylene glycol phenyl ether acrylate, polypropylene glycol phenyl ether acrylate, and alkyl-substituted phenyl derivatives of the above monomers, such as polyethylene glycol nonyl phenyl ether acrylate. Can be

A preferred acrylate monomer diluent is isobornyl acrylate, or isooctyl acrylate.

In addition, the reactive diluent may include two groups that can be polymerized using actinic radiation. Diluents having three or more such reactive groups may be present as well. Examples of such monomers include C ₂ -C ₁₈ hydrocarbon diol diacrylate, C ₄ -C ₁₈ hydrocarbon divinyl ether, C ₃ -C ₁₈ hydrocarbon triol triacrylate, their polyether analogs, such as 1, 6-hexanediol diacrylate, trimethylolpropane triacrylate, triethylene glycol diacrylate, pentaerythritol triacrylate, and tripropylene glycol diacrylate, alkoxylated bisphenol A diacrylate or dimethacrylate (ethoxylated or propoxylated bisphenol A diacrylate) Methacrylate).

The properties of reactive diluents and UV-cured urethane acrylates are described in J. App.
Polym. Sci., 37 : 1627-1636 (1995).

The composition further contains a radical-forming sulfur compound (D). Radical forming means that the sulfur compounds co-react with at least 50% in the radical polymerization. Radical-forming sulfur compounds are, for example, compounds containing thiols or polysulfides. It is preferred to use alkane thiols, alkyl ester thiols or dialkyl polysulfide compounds. Preferably, the reactive diluent forms a thioether bond during radiation curing. Such a thioether bond can be formed by a thiol-ene reaction. C ₅ -C _30, a reactant preferably aliphatic thiol compounds such as C ₅ -C ₂₀ alkane thiol compounds are suitable. Examples of alkanethiols include 1-pentanethiol, 1-hexanethiol, 1-heptanethiol, 1-octanethiol, 1-decanethiol,
-Dodecanethiol and the like. Compounds containing multiple mercapto groups, such as di- and tri-mercapto compounds, can be used. Suitable alkyl ester thiols are, for example, methyl thiol glycolate or isooctyl-3
-Mercaptopropionate. Suitable polysulfides include di- and tetrasulfides, for example, di-octyltetrasulfide.

Preferred examples of the compound (D) include a compound also containing a trialkoxysilane group, for example, γ
-Mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane and trimethoxysilylpropyltetrasulfide.
Such thiol-ene systems, when copolymerized with acrylates, provide compositions with excellent adhesive quality.

[0068] The composition optionally further comprises at least one photoinitiator. Photoinitiators are needed for fast UV curing. Conventional photoinitiators can be used. Examples include benzophenone, acetophenone derivatives such as α-hydroxyalkyl phenyl ketones, benzoin alkyl ethers and benzyl ketals, monoacylphosphines and bisacylphosphine oxides. A preferred photoinitiator is 2-hydroxy-2-methyl-1-phenyl-propan-1-one (
DAROCURE 1700 ™, Ciba Geigy). Another preferred example is 2,2-dimethoxy-2-phenylacetophenone (IRGACURE 651 ™, Ciba Geigy)
It is. Other suitable photoinitiators include mercaptobenzothiazole, mercaptobenzoxazole and hexylarylbisimidazole. often,
The mixture of photoinitiators provides a suitable balance of properties.

The photoinitiator should be present in an amount sufficient to provide a fast cure rate, reasonable cost, good surface upon cure, and no yellowing on standing. Typical amounts can be, for example, from about 0.1% to about 15% by weight.

[0070] Additional compounds are typically used in radiation-curable adhesives and may be used in effective amounts.

[0071] Several additives may be included in the composition. Small amounts of UV absorbers, typically of the benzotriazole, benzophenone or oxyanilide type, or of the sterically hindered amine type (HALS) can be added as light stabilizers.
In addition, conventional additives used in the prior art include fillers, chain transfer agents, plasticizers, wetting agents, stabilizers, adhesion promoters or leveling agents. The above-mentioned mercaptosilane is a preferred adhesion promoter. When a thiol compound other than mercaptosilane is used, it is preferable to use a silane adhesion promoter. Such silane adhesion promoters are conventionally known. Examples include isocyanatoalkyl trialkoxy silanes, methacrylyl alkyl trialkoxy silanes, aminoalkyl trialkoxy silanes and epoxyalkyl trialkoxy silanes.
The alkyl group is generally propyl, with methoxy or ethoxy being preferred as the alkoxy group. Another suitable silane adhesion promoter is vinyltrimethoxysilane. Mercaptosilanes such as mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane are particularly preferred. Thermal antioxidants can be used to improve thermal and oxidative stability. Other polymers and oligomers can be added to the composition as needed.

[0072] Moisture in the adhesive composition is preferably minimized.

The cure speed can be measured by a conventionally known dose-modulus curve. The curing speed is
It can be considered as the dose required to produce 95% of the maximum modulus. For adhesive coating, UV cure speed is preferably 95% of the maximum modulus obtainable, about 1.0 J / cm ² or less, more preferably about 0.7 J / cm ² or less.

For an adhesive coating, the density at 25 ° C. is about 1.02 g / ml. The elongation (elongation at break of the cured film) is preferably at least 20% even if not thin,
More preferably, it is about 50% or more, especially about 100% or more. The weight loss of the adhesive cured at 100 ° C. for 40 minutes should be ≦ 5% and the shrinkage on curing should be ≦ 10% with respect to the density of the cured material. The bond strength is preferably rated at about 4 to about 5. The shear strength is preferably about 4.535 kg (10
lbs) to about 45.36 kg (100 lbs). The cured adhesive bond is preferably stable under conditions of exposure to about 85 ° C. at about 95% relative humidity for at least 250 hours, more preferably at least 2,000 hours.

The present invention provides UV-curable compositions having good adhesion to plastic, metal and ceramic substrates, low viscosity and excellent light and elongation properties. The composition may therefore be useful for bonding single-sided digital versatile discs to one another or for bonding individual layers comprising single-sided discs. Other substrates can also be bound by the adhesive composition. The composition of the present invention achieves unexpectedly superior adhesion and provides an excellent material that meets the adhesive requirements for the production of digital versatile discs.

The compounds forming the radiation-curable adhesive composition were mixed together and coated on one surface of each of two polycarbonate substrates forming a DVD. Here, the surface is already coated with aluminum, gold or other layers coded with audio, video or other information. The adhesive was coated on the substrate by spin coating or other methods known in the art. Next, the adhesive was cured by ultraviolet irradiation. Radiation curing is Fusion Curing Sy
fusion lamps with "D" bulbs made by stems (Rockville, MD) (fu
sion lamp) in an air atmosphere. "D" lamps emit radiation from about 200 to about 470 nm. Peak emission is at about 380 nm.
Substrates are placed on top of each other and an adhesive bonds the substrate layers to each other, thereby
One DVD is formed with one or preferably two layers of coded audio or video information that can be read by a VD player. Substrate layers that can be combined in various combinations according to the present invention include plastics, metals and ceramics. The adhesive composition may be applied to the disc layer by spin coating, capillary gap dispensing or screen printing. Curing is preferably performed to obtain at least about 80% of the maximum modulus that can be obtained, more preferably at least about 90% of the modulus.

The cured composition can be examined for crystalline inclusions by light microscopy. These effects can be examined using conventional methods, but require increasingly more stringent high resolution analysis. 125 ° C. for cured film
Alternatively, aging at 95 ° C./95% relative humidity can be performed to test the effect of crystallization. The behavior of the phases can also be examined using a Polaroid camera in the reflected light by using a differential interference contrast microscope and a Rights microscope. For example, magnifications of 200X or 500X can be used to determine the effect of crystallization and phase behavior.

The manufacture of optical disc adhesives and features useful for such adhesives are described, for example, in US Pat.
Nos. 861,637, 4,906,675 and 5,213,947.

The production of optical discs is described, for example, in "Network Formation by Chain Crosslinking Photopolymerization and Its Application in Electrooptics" JG Kloosterboer, ADV. POLYM. SCI., 1988, 84 ,
pp.1-61.

[0080]

【Example】

 The present invention is further described by the following non-limiting examples.

Example 1 Polycarbonate Urethane Diacrylate Oligomer (Tg 14 ° C., Desotech)
, N-vinylpyrrolidone (NVP), isobornyl acrylate (IBOA),
Thiol-added adhesion promoter, γ-mercaptotrimethoxysilane and photoinitiator DA
Solutions containing ROCURE 1700 ™ (Ciba Geigy) were prepared using the ratios shown in Table 1. The reagents were heated at 60 ° C. for 1 hour, and then the components were mixed by stirring until uniform. The resulting material had a viscosity of 330 mPas (as measured by a Physica ™ LC3 viscometer). This low viscosity allowed easy use of the material during spin coating. The adhesion of the polymer to DVD was then tested.

[Table 1] The characteristic aluminum disk of Example 1 in DVD bonding was spin coated with a protective coating at 5,000 rpm for 5 seconds, and then cured at 1 J / cm ² using a Fusion D lamp. Thereafter, the protected aluminum disk was spin-coated with the adhesive layer at 5,000 rpm for 10 seconds. With a spin speed of 5,000 rpm, a very thin layer of adhesive can be achieved (about 15 μm thickness). The polycarbonate disc was placed on an adhesive-coated aluminum disc and the two substrate discs were pressed together to avoid entrapment of air bubbles. The adhesive between the disks was cured at 1 J / cm ² using a Fusion D lamp (300 W / inch). The impact resistance (bonding strength) of the bonded disc when dropped on concrete from a height of 75 cm was determined by measuring the bonded disc under environmental stress (85 ° C).
, 2,000 hours at 95% relative humidity (RH)). The shear stress of the overlapping strips of the bonded DVD was measured before and after exposure to environmental stress using standard equipment (INSTRON model 4201). Table 2 shows the results of these tests.

[Table 2]

[0082] The compositions of Examples 2 and 3 Examples 2 and 3, prepared according to the method of Example 1, were tested. Table 3 shows the compositions of Examples 2 and 3 and the test results. The epoxylated bisphenol A polyurethane acrylate is characterized by a Mn of 1,000 and a Tg of 24 ° C.

[Table 3] In Example 2, after exposure to environmental stress (85 ° C./85% RH, 72 hours)
Disc breakage occurred at shear strengths of 25 lbs (measured at 25 ° C) and 30 lbs (measured at 25 ° C).

Examples 4-7 The compounds shown in Tables 4 and 5, forming the radiation-curable adhesive composition, were mixed together and, as in the previous example, were coated on two polycarbonate substrates to form a DVD. One surface of each was coated.

[Table 4]

[Table 5]

[Table 6] The composition of the present invention, particularly the urethane acrylate composition, used as an adhesive for bonded DVD disks withstands an environment of at least 80 ° C and 85% relative humidity, preferably an environment of at least 85 ° C and 95% relative humidity. . Acrylated acrylates tend to exfoliate under extreme temperature and high humidity conditions,
Therefore, urethane acrylate compositions are better suited to these circumstances. The viscosity of the composition is preferably from about 100 mPas to about 1,000 mPas at 25 ° C.
Range. The bond strength and drop test results (after 6 days of cure) are sufficient for visual inspection. Preferably, the bond strength is between about 10 lbs and about 100 lbs. The coating speed and time indicate the properties of the adhesive composition during spin coating. The adhesive of the present invention is dry to the touch after curing. FIG. 1 shows the relationship between the adhesive thickness plotted on the vertical axis and the spin rate plotted on the horizontal axis. The desired adhesive thickness can be obtained by selecting appropriate spin speed, spin time and acceleration. FIG. 2 is a relationship between the degree of cure (% unreacted acrylate unsaturation) measured by FITR and the amount of UV energy to which the adhesive is exposed. The data show that the adhesive composition undergoes very high conversion from liquid to solid at relatively low levels of UV energy. FIG. 3 shows the thermal stability of the cured adhesive composition as measured by TGA. High conversion of the composition during curing results in a thermally stable DVD bonding adhesive. The data also shows that the composition undergoes a very low weight loss (about 2%) at a test temperature of 100 ° C. Test Methods Test results were obtained using the following test methods. Viscosity Viscosity was measured using a PHYSICA MC10 viscometer. The test sample was examined and if excess foam was present, steps were taken to remove most of the foam. Not all bubbles need to be removed at this stage. This is because the sample filling operation introduces some foam. The instrument was set up for the normal Z3 system used. The samples were filled into disposable aluminum cups using a dropper weighing 17 cc. The sample in the cup was examined for excess foam and, if indicated, removed by direct means such as centrifugation. Alternatively, sufficient time was allowed for the foam to escape from the bulk of the liquid. Bubbles on the top surface of the liquid were acceptable. The weight was gently lowered into the liquid of the measuring cup, and the cup and weight were attached to the device. The sample temperature was equilibrated with the temperature of the circulating liquid by waiting 5 minutes. The rotation speed was then set to the desired value that produced the desired shear rate.
The desired value of the shear rate is readily determined by one skilled in the art from the expected viscosity range of the sample. The instrument panel reads the viscosity value and if the viscosity value changes only slightly in 15 seconds (less than 2% relative change), the measurement is complete; if the reading changes, the temperature is the equilibrium value. Or the material may have changed due to shearing. In the latter case, it was necessary to perform further tests at different shear rates to clarify the viscous properties of the sample. The results reported are the average viscosity values of three test samples. Bond Strength The bond strength of the digital versatile disc bonded with the cured adhesive was measured by the drop test method. The cured, bonded disc was dropped a vertical distance of 3 feet onto the concrete surface such that the outer edge of the bonded disc hit the concrete. The impact resistance of the cured sample adhesive composition was qualitatively evaluated as shown below. Rating scale of 1 to 1: 1: Worst; peeling occurred on two sides of the disk. 5: Best; no signs of impact-induced delamination on two sides of the disc. Shear Strength The shear strength of the bonded discs was tested using a universal tester INSTRON ™ model 4201 equipped with a personal computer. Disks bonded with the adhesive composition of the present invention were subjected to opposing shear forces. The force that caused the bonded disc to break was measured and indicated the shear force of the bond. Adhesive failure caused the adhesive to delaminate, while disk failure occurred when the applied force caused the disk to break.

[0084]

[Brief description of the drawings]

FIG. 1 is a relationship between adhesive thickness plotted on the vertical axis and spin speed plotted on the horizontal axis.

FIG. 2 shows the degree of cure measured by a Fourier transform infrared spectrum analyzer (FITR) (
Unreacted acrylate unsaturation) and the amount of UV energy to which the adhesive is exposed.

FIG. 3 shows the thermal stability of a cured adhesive composition as measured by thermogravimetric analysis (TGA).

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), CN, JP, KR (72) Ha, Chau, Chi, Min United States, Illinois 60004, Arlington Heights, Arlington Heights Road # 607 200 N (72) Inventor Julia, Lani United States, Illinois 60016, Death Prince, Senate Drive 9124, Apartment 2 Be (72) Inventor Sullivan, Michael, Gordon United States, 61008, Illinois, Belvidere, Ridgefield Drive 2120 F-term (reference) 4F100 AB01B AB01C AD00B AD00C AK01B AK01C AK25A AK25G AK26A AK26G AK51A AK51G AL05A AL05G BA02 BA03 BA06 BA10B BA10C CB00 JA03A JA03G JB14A JB14G JK01A JK01G JK08A JK08G JL08A JL08G JL11 YY00A Y7 FAB FA1 FA1 FA1 MA10 MB05 NA21 5D029 RA30

Claims (20)

[Claims] 1. The following pre-mix components: (A) from about 5% to about 80% by weight of at least one UV or radiation curable acrylate oligomer; (B) from about 1% to about 20% by weight. (C) from about 10% to about 80% by weight of at least one acrylate-functional reactive diluent; (D) from about 0.5% to about 10% by weight. A digital versatile disc component comprising a combination of, by weight, at least one radical-forming sulfur compound; and (E) optionally from about 0.1% to about 15% by weight of one or more photoinitiators. Or UV-curable adhesive composition for curing. 2. The adhesive composition according to claim 1, wherein the non-acrylate functional reactive diluent (B) is a compound containing (meth) acrylamide groups. 3. The non-acrylate reactive diluent (B) is a vinyl ether or N
The adhesive composition according to claim 1, which is a compound containing a vinyl group. 4. The adhesive composition according to claim 2, wherein the compound containing a (meth) acrylamide group is an alkyl acrylamide or an aryl acrylamide. 5. The adhesive composition according to claim 3, wherein the compound containing a vinyl-ether or N-vinyl group is a compound containing an N-vinyl group. 6. The one or more photoinitiators are selected from the group consisting of mercaptobenzothiazole, mercaptobenzoxazole, benzophenone, acetophenone derivatives, benzoin alkyl ethers, benzyl ketals, monoacylphosphine oxides and bisacylphosphine oxides. The adhesive composition according to claim 1. 7. The adhesive composition according to claim 1, wherein the radical-forming sulfur compound contains a mercapto group and a trimethoxysilane group. 8. The adhesive composition according to claim 1, wherein the radiation-curable acrylate oligomer comprises urethane acrylate or acrylated acryl. 9. The adhesive composition according to claim 1, wherein the composition has a viscosity at 25 ° C. of about 100 to about 1,000 mPas. 10. A digital versatile disc comprising two disc substrates joined together by a radiation-cured adhesive composition, wherein the adhesive composition before curing is one of the preceding claims. A disc, which is an adhesive composition according to claim 1. 11. The combined digital versatile disc of claim 10, wherein the composition has been cured to achieve at least 80% of its maximum obtainable modulus. 12. The combined digital versatile disc according to any one of claims 10 to 11, wherein the cured adhesive has a shrinkage of 10% or less upon curing. 13. A combined digital versatile disc according to any one of claims 10 to 12, wherein the composition has a cured film elongation at break of> 20%. 14. The combined digital multiplex of any one of claims 10 to 13, wherein the cured disk has a shear strength of about 4.535 kg to about 45.36 kg (about 10 lbs to about 100 lbs). Use disc. 15. The digital versatile disc according to any one of claims 10 to 14, wherein the layers bonded together comprise a member selected from the group consisting of plastic, metal and ceramic. 16. The single-sided digital versatile disk is symmetrically coupled to each side of a core member that is equidistant from and parallel to each single-sided disk. A digital versatile disc structure comprising the two digital versatile discs of any one of claims 15 to 15. 17. The adhesive composition of any one of claims 10 to 16, wherein the adhesive composition bonded between the layers is stable under conditions of exposure to about 85 ° C at a relative humidity of about 95% for at least 250 hours. Digital versatile disc. 18. Bonding at least two layers of the disc with a UV or radiation curable adhesive composition according to any one of claims 1 to 9,
How to combine digital versatile disc layers. 19. The method of claim 18, comprising applying the adhesive composition to the disk layer by spin coating, capillary gap dispensing, or screen printing. 20. The following premix components: (A) from about 15% to about 80% by weight of at least one UV or radiation curable acrylate oligomer; (B) from about 1% to about 20% by weight. At least one non-acrylate functional reactive diluent; (C) from about 10% to about 80% by weight of at least one acrylate monomer diluent; (D) from about 0.5% to about 10% by weight. A radiation or UV curable adhesive composition comprising a combination of at least one thiol compound; and (E) from about 0.1% to about 15% by weight of one or more photoinitiators.