JPH0425614B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an optical information recording medium on which information can be written and/or read using a high energy density laser beam. That is, the present invention is directed to optical disks for various uses such as video disks, audio disks, large-capacity still image files, and disk memories for large-capacity computers. [Prior Art] Optical information recording media write and read information by irradiating a light beam onto the recording layer using a lens with a focal depth of several microns. Damage to the recording layer caused malfunctions such as bit errors and dropouts. Therefore, two disk-shaped substrates are joined with an adhesive via a convex portion or a spacer provided on the disk-shaped substrates, and at least one of the substrates is a transparent substrate and a recording layer is provided on the inner surface of the substrate. A so-called air sandwich structure has been proposed. A so-called bonded structure has also been proposed in which two disc-shaped substrates each having a recording layer provided on at least one of them are bonded together directly or via a third substrate with the recording layer inside. Adhesives that use photopolymerizable compounds, such as UV-curable adhesives, are used because they require only a few minutes to bond, do not require heating, and are less likely to deform. There is. However, conventional ultraviolet curing adhesives have insufficient durability for both glass substrates and plastic substrates when the disk is placed in a high temperature and high humidity environment. Furthermore, when plastics such as acrylic resin, polyvinyl chloride, and polycarbonate are used for the substrate, it is particularly difficult to adhere to the substrate, and the adhesive portion peels off even if the disk is slightly deformed, making it impractical. For this reason, for the purpose of increasing adhesive strength,
138064 and JP-A-57-120243, it has been proposed to roughen the surface of the bonded portion. However, in this case, when the surface is roughened, dust is generated and adheres to the substrate. Therefore, if a substrate with a rough surface is to be used for an optical disk, it must be cleaned, which is very inconvenient. This is because when cleaning optical disks, the water used for washing must be purified water produced from a pure water production machine, and furthermore, a clean dryer must be used for drying. It is very inconvenient to introduce such capital investment and complicated processes just to improve adhesiveness. Also, as shown in patent application No. 58-718841,
After the substrate is subjected to discharge treatment or ultraviolet irradiation treatment,
A method of bonding using an electromagnetic radiation curable adhesive and dramatically improving adhesive strength has been disclosed, but this method requires a surface treatment step. On the other hand, when an epoxy adhesive is used, there is a problem that the amine used as a curing agent degrades the recording layer and causes defects during recording and reading.
In addition, it is highly viscous and difficult to apply uniformly, and it takes a long time to harden, so when assembling the disk, it is necessary to hold it for a long time until the hardening is completed to prevent the slightest spots from forming. There's a problem. [Problems to be Solved by the Invention] The first object of the present invention is to obtain an optical information recording medium in which the bonded portion of a disk-shaped substrate does not peel off due to aging or deformation. The second objective is to provide a method for assembling an optical information recording medium that does not require surface treatment of the substrate. The third objective is to obtain an optical information recording medium in which the recording layer does not deteriorate due to adhesive. The fourth objective is to provide a method for assembling an optical information recording medium that is advantageous in terms of process. [Means for Solving the Problem] An object of the present invention is to provide a method in which two disc-shaped substrates are joined directly or via a ring-shaped inner spacer and a ring-shaped outer spacer, and at least one of the substrates is transparent; In an information recording medium in which a recording layer on the inner surface of at least one substrate is provided with a recording layer on which information can be written and/or read by a laser, the bonding is performed by the following (A), (B), (C) and
This is achieved by an optical information recording medium characterized in that an ultraviolet curable adhesive containing (D) is applied to the substrate, the two substrates are combined, and then irradiated with ultraviolet rays. (A) A crosslinkable olicomer with two or more (meth)acryloyl groups in the molecule and a molecular weight of 1000 or less per (meth)acryloyl group (B) A monomer with a cured film Tg of less than 20°C Functional vinyl compound (C) A monofunctional vinyl compound whose cured film has a Tg of 20°C or higher (D) Photopolymerization initiator If the substrate is glass, a silane coupling agent should be included in the ultraviolet curable adhesive. This is achieved by As the substrate, transparent plastic such as acrylic resin, polyvinyl chloride, polycarbonate, or glass is used. The ultraviolet curable adhesive used in the present invention can provide strong adhesion even to cell cast acryl plates, which are the most difficult to adhere to. The glass substrate is preferably one that has been chemically strengthened, particularly potash strengthened. The structure of the optical information recording medium according to the present invention may be an air sandwich structure or a direct bonding structure. In the case of air sandwich structure, the spacer material is plastic, metal such as aluminum (may be anodized), stainless steel,
Any material such as ceramic may be used. The surface of these spacers may be roughened, surface treated with a silane coupling agent, or subjected to discharge treatment such as glow discharge or corona discharge in order to improve adhesion. It is preferable to use a spacer material having the same thermal expansion coefficient and hygroscopic expansion coefficient depending on the substrate used. Examples of materials used for the recording layer include Te,
List metals such as Zn, In, Sn, Zr, Al, Ti, Cu, Ge, Au, Pt; semimetals such as Bi, As, Sb; semiconductors such as Ge, Si; and alloys or combinations thereof. be able to. In addition, sulfides, oxides, borides of these metals, semimetals or semiconductors,
Compounds such as silicon compounds, carbides and nitrides;
And mixtures of these compounds and metals can also be used in the recording layer. Alternatively, a combination of dyes and polymers can be utilized. The recording layer is made by depositing the above materials, sputtering,
It can be formed directly on the substrate or via an undercoat layer by a method such as ion plating. The recording layer may be a single layer or a multilayer, but its layer thickness is generally in the range of 100 to 5500 Å, preferably from the viewpoint of optical density required for optical information recording.
It ranges from 150 to 1000 Å. When providing the recording layer, the surface of the substrate on which the recording layer is provided is coated with organic polymer materials such as nitrocellulose, polyvinylidene chloride, copolymers of styrene derivatives, cured products of radiation-curable monomers and oligomers, or SiO, Inorganic materials such as SiO ₂ , Al ₂ O ₃ or laminates of organic and inorganic materials from 0.01μ
100μ may be provided. The organic material is dissolved in a suitable organic solvent, and this solution is applied to the substrate surface using a spinner or the like. Further, the inorganic material is provided on the substrate surface by vacuum deposition or sputtering, or by applying a dispersion liquid of the inorganic material using a spinner or the like. Further, the above-mentioned organic or inorganic material may be provided on the opposite side of the substrate to the side on which the recording layer is provided. (A) contained in the ultraviolet curable adhesive used in the present invention as a crosslinkable oligomer having two or more (meth)acryloyl groups in the molecule and having a molecular weight of 1000 or less per (meth)acryloyl group; can include the following (meth)acrylates (a) to (j). (a) Poly(meth)acrylates of aliphatic, cycloaliphatic, araliphatic di- to hexavalent polyhydric alcohols and polyalkylene glycols; for example, ethylene glycol, propylene glycol, 1,3- or 1,4-butanediol , hexanediol, neopentyl glycol, cyclohexanediol, trimethylolethane, trimethylolpropane, glycerin, sorbitol, pentaerythritol, dipentaerythritol, hydrogenated bisphenol A and other polyhydric alcohols and diethylene glycol, triethylene glycol, tetraethylene glycol Examples include poly(methacrylates) of polyhydric alcohols such as , polyethylene glycol, cypropylene glycol, polypropylene glycol, etc. Specific examples of these are shown in, for example, JP-A-49-12098. (b) Fats group, alicyclic, araliphatic, aromatic 2-6
Poly(meth), a polyhydric alcohol in which alkylene oxide is added to a polyhydric alcohol
Acrylates; such as bisphenol A dioxyethyl ether, trimethylolpropane,
Examples include poly(meth)acrylates of polyhydric alcohols obtained by adding ethylene oxide or propylene oxide to polyhydric alcohols such as pentaerythritol, glycerin, and bisphenol A. (c) Poly(meth)acryloyloxyalkyl phosphate; obtained by reaction of hydroxyl group-containing (meth)acrylate with phosphorus pentoxide, such as poly(meth)acryloyloxyethyl phosphate, poly(meth) Examples include acryloyloxypropyl phosphate ester. (d) Polyester poly(meth)acrylate; Polyester poly(meth)acrylate is usually synthesized by esterifying (meth)acrylic acid, a polyhydric alcohol, and a polyhydric carboxylic acid. It is assumed that poly(meth)acrylate, which is a polyester-type polyhydric alcohol, is the main component, and examples of its synthesis and specific examples are given in, for example, JP-A-49
−128944 Publication and other published patent publications (49−
128088, 49−120981, 49−93473, 49−28692,
48-96515, 48-66679, 48-25790, etc.). For example, di(meth)acrylate of polyester diol of succinic acid and ethylene glycol, di(meth)acrylate of polyester diol of maleic acid and ethylene glycol,
Di(meth)acrylate of polyester diol with phthalic acid and diethylene glycol, di(meth)acrylate of polyester diol with tetrahydrophthalic acid and diethylene glycol, poly(meth)acrylate of polyester diol with adipic acid and triethylene glycol, tetrahydrophthal Examples include poly(meth)acrylate of polyester polyol of acid and trimethylolpropane, and poly(meth)acrylate of polyester polyol of tetrahydrophthalic acid and pentaerythritol. Among these polyester poly(meth)acrylates, when using aliphatic or alicyclic polycarboxylic acid-based polyester poly(meth)acrylates rather than aromatic polycarboxylic acid-based ones such as phthalic acid, This has the advantage that the crosslinked cured product has better physical properties such as weather resistance and toughness. (e) Epoxy poly(meth)acrylate: Epoxy resin having two or more epoxy groups in the molecule, and approximately equivalent amount of (meth)acrylate to the epoxy group.
Acrylic acid, with carboxyl group (meth)
It is synthesized by reacting a mixture of acrylate, (meth)acrylic acid, or (meth)arylate having a carboxyl group with a polybasic acid. Alternatively, there is also a method of reacting an epoxy group-containing (meth)acrylate with a polyhydric carboxylic acid. Synthesis examples and specific examples of epoxy poly(meth)acrylates are disclosed, for example, in JP-A-49-28692 and other published patent publications (48-66182, 48-60787,
(Special Publications No. 49-12091, No. 49-12090, etc.). For example, bisphenol A diglycidyl ether type, glycerin diglycidyl ether type,
Examples include addition reaction products of epoxy resins such as polyalkylene glycol diglycidyl ether type, polybasic acid diglycidyl ester type, and cyclohexene oxide type and (meth)acrylic acid. (f) Polyurethane poly(meth)acrylate; It has the structure of polyhydric alcohol (meth)acrylate having a polyurethane bonding unit in the main chain, and usually contains hydroxyl group-containing (meth)acrylate, polyisocyanate, and polyhydric alcohol if necessary. It is synthesized by a method such as reacting with Synthesis examples and specific examples are given in, for example, JP-A-48-
It is described in Publication No. 60787, etc. For example 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)
Examples of this include addition reaction products between acrylate and diisocyanate, addition reaction products between 2-hydroxyethyl (meth)acrylate, diisocyanate, and dihydric alcohol, and the like. (g) Polyamide poly(meth)acrylate; has the structure of a polyhydric alcohol (meth)acrylate having a polyamide bonding unit in the main chain,
It is usually synthesized by reacting a polyamide-type polycarboxylic acid with a hydroxy group-containing (meth)acrylate or an epoxy group-containing (meth)acrylate, or by reacting a polyamide-type polyhydric alcohol with (meth)acrylic acid. . Synthesis examples and specific examples are given in, for example, JP-A-48-60787.
No. 48-37246, etc. For example, a reaction product of a polyamide-type polycarboxylic acid obtained by the reaction of ethylenediamine and phthalic acid and 2-hydroxyethyl (meth)acrylate or glycidyl (meth)acrylate corresponds to this example. (h) Polysiloxane poly(meth)acrylate; It has the structure of a (meth)acrylate of a polyhydric alcohol with a polysiloxane bonding unit in the main chain, and is usually made by adding (meth)acrylic acid to a polyhydric alcohol having a polysiloxane bonding unit. Alternatively, it is synthesized by a method such as reacting a hydroxyl group-containing (meth)acrylate. Synthesis examples and specific examples are described in, for example, Japanese Patent Publication No. 49-4296. (i) Vinyl-based or diene-based low polymers having (meth)acryloyloxy groups in the side chains and/or terminals; Ester bonds, urethane bonds, amide bonds in the side chains or terminals of vinyl-based or diene-based low polymers , has a structure in which (meth)acryloyloxy groups are bonded via an ether bond or the like. Low polymers that usually have hydroxy groups, carboxyl groups, epoxy groups, etc. in side chains or terminals, (meth)acrylic acid, carboxyl group-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates that are reactive with these groups. , an epoxy group-containing (meth)acrylate, an isocyanate group-containing (meth)acrylate, an amino group-containing (meth)acrylate, etc. Synthesis examples and specific examples can be found in, for example, JP-A No. 50-9687 and JP-A-Sho. 45-
It is described in Publication No. 15629, Japanese Patent Publication No. 45-15630, etc. For example, there may be mentioned a reaction product obtained by reacting a copolymer of (meth)acrylic acid and another vinyl monomer with glycidyl (meth)acrylate. Note that crosslinkable monomers belonging to this system generally tend to become highly viscous or solid as their molecular weight increases, so they should be used after being dissolved in a liquid low viscosity crosslinking monomer as described below, or It is preferable to use a liquid with a low molecular weight (usually a number average molecular weight of 3000 or less). (j) Modified crosslinkable monomers described in (a) to (i) above; At least a part of the hydroxyl groups or carboxyl groups remaining in each of the above crosslinkable monomers are made reactive with these groups. It is a modified product obtained by reacting with an acid chloride, an acid anhydride, an isocyanate, or an epoxy compound.
This is disclosed in JP-A No. 128994, Japanese Unexamined Patent Publication No. 128088-1988, and the like. Among the oligomers mentioned above, those particularly suitable for the present invention are (b), (d), (e) and (f). (B) Monofunctional vinyl compounds whose cured film has a Tg of less than 20°C are as follows. ) CH ₂ = CH−COO−C _o H _2o+1 n is an integer from 1 to 12 ) CH ₂ = CH−COO(−CH ₂ CH ₂ O−)R

[Formula] n is an integer from 1 to 12 n=0, 1, 4, 8, 9) CH ₂ = CH−COO(−CH ₂ CH ₂ O−) ₂ R

[Formula] n is an integer from 1 to 12 n = 0, 1, 4, 8, 9) ) and ) -CH ₂ CH ₂ O- chain

[Formula] Changed to a chain ) CH ₂ = CH-COO-X-OH X = -CH ₂ CH ₂ -,

【formula】

[Formula] ) Others Tetrahydrofurfuryl acrylate, dicyclopentadienyloxyethyl acrylate Hydrogenated dicyclopentadienyloxyethyl acrylate As these monofunctional vinyl compounds (B), when the adhering materials are plastics, , mentioned above),
), ), ) or ) is preferably used, and when the adherend materials are inorganic materials such as glass, Al, and Fe, it is preferable to use ). Furthermore, if the adherend material is plastic or inorganic),
), ), ), or ) and ) are preferably used in combination. (C) Monofunctional vinyl compounds whose cured film has a Tg of 20°C or higher include the following. (i)

[Formula] R ₁ :-CH ₂ CH ₂ OH,

[Formula]: -CH ₃ (ii) N-vinylpyrrolidone (iii) Isobonyl acrylate, dicyclopentadienyl acrylate, hydrogenated dicyclopentadienyl acrylate (iv) Styrene These monofunctional vinyl compounds (C) If the adhered materials are plastics, the above (i), (ii),
It is preferable to use (iii) or (iv), and when the adhering materials are inorganic materials such as glass, Al, and Fe,
Among (i), those having an -OH group are preferred. Furthermore, if the adherend is plastic or inorganic, (i)
It is preferable to use (ii), (iii) or (iv) together with one of (i) having an -OH group. Examples of the photopolymerization initiator include benzoin alkyl ethers, benzyl ketals, acetals, acetophenone derivatives, benzophenone derivatives, xanthone derivatives, thioxanthone derivatives, anthraquinone derivatives, and benzaldehyde derivatives. Specific examples of compounds that can be used as sensitizers include benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, benzyl, 2,2-dimethoxy-2-phenylacetophenone, 2,2 -dimethoxy-2-
Hydroxyacetophenone, diphenyl disulfide, 2-hydroxy-2-propiophenone,
4,4'-bisdiethylaminobenzophenone, dimethylaminobenzaldehyde, ethyl-4,
Examples include 4'-bisdimethylaminobenzophenone, ethyl anthraquinone, and 2-chlorothioxanthone. These sensitizers can be used alone or in appropriate combinations. Examples of silane coupling agents include epoxysilane-based silane coupling agents, such as γ-glycidoxypropyltrimethoxysilane, β-(3,
4-epoxycyclohexyl)ethyltrimethoxysilane, aminosilane-based silane coupling agents, such as N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, Vinylsilane-based silane coupling agents, such as γ-methacryloxypropyltrimethoxysilane, are preferred. The following combinations are most preferable for the ultraviolet curable adhesive according to the present invention. X: Polyurethane or polyester with a molecular weight of 900 or

[Formula] Silane coupling agent

【formula】 Photoinitiator

[Formula] If the adhered material is plastic, the above (a) and (b)
-2, a combination of (c) and a photopolymerization initiator is preferred,
If the adhered substance is glass, the above (a), (b)-1,
(c) A combination of a silane coupling agent and a photopolymerization initiator is preferred. Preferably, the Tg of the cured adhesive is -20℃
~100℃. The Tg of the cured adhesive is
It can be adjusted by the mixing ratio of (A), (B) and (C). If the Tg of the cured adhesive is -20℃ or less, when the disk rotates,
The board is likely to be misaligned due to centrifugal force. Furthermore, when Tg is 100° C. or higher, if the substrate and spacer are made of different materials, shear stress is applied to the interface between the substrate or spacer and adhesive due to thermal expansion, making them likely to peel off. Further, the crosslinkable oligomer (A) lowers the elastic modulus of the adhesive and increases the initial adhesiveness. However, if it is less than 5% by weight, there is no effect, and if it exceeds 90% by weight, the adhesive durability under high temperature and high humidity conditions will deteriorate. From the viewpoint of coating suitability, the content is preferably 60% by weight or less, therefore, the content is preferably 5 to 90%, and most preferably 5 to 60%.
Furthermore, the monofunctional vinyl monomers (B) and (C) strengthen the interaction with the adherend, increasing adhesive durability under high temperature and high humidity conditions. However, if it is less than 9.9% by weight, it will not be effective.
If it exceeds 94.9% by weight, the impact resistance will decrease and the adhesive will peel off in a drop test. Therefore, the preferred range is 9.9% to 94.9%, and the most preferred range is 39.9% to 94.9%. The weight ratio (B)/(C) of (B) and (C) is preferably 0.1 to 10.
If it is less than 0.1, the cured product will sag, and if it exceeds 10, the cohesive force will be insufficient and the adhesive strength will be low. The most preferred range is 0.3-3. The photopolymerization initiator (D) is used in an amount of 0.1 to 10% by weight.
If it is less than 0.1%, it will not cure or will be insufficiently cured. If the amount exceeds 10%, undecomposed photopolymerization initiator remains, and sufficient adhesive strength may not be obtained or the recording layer may be adversely affected. The most preferable value is 0.1~
It is 8%. When at least one of the substrate or spacer is inorganic, a silane coupling agent is included in the ultraviolet curable adhesive to increase adhesive durability under high temperature and high humidity conditions. Silane coupling agent is the sum of (A), (B) and (C) 100
It is preferable to add it in an amount of 0.01% to 10% by weight based on the weight part. If it is less than 0.01, the effect will be small, and if it exceeds 10% by weight, it will have an adverse effect on the recording layer. Adhesion can be further improved by subjecting the substrate or spacer to a surface treatment such as corona discharge treatment or glow discharge treatment, or by treating it with a primer.The present invention will be explained below with reference to Examples. Example 1 A recording layer with a thickness of 300 Å was formed by co-evaporating In and GeS at a volume ratio of 1:1 on one side of a donut-shaped Selquist acrylic plate with an outer diameter of 305 mm, an inner diameter of 35 mm, and a thickness of 1.5 mm. I created two copies. Outer diameter 305mm,
295mm inner diameter outer spacer and 160mm outer diameter inner diameter
A 50μ adhesive composition with varying composition ratios was applied to both sides of a 35mm inner spacer using a transfer printing method.
It was applied on both sides to a thickness of . Assemble the above substrates with the recording layer inside in a nitrogen atmosphere through the spacer above, irradiate both sides of the two substrates with ultraviolet light for 2 minutes at the same time from a distance of 50 cm using two 1KW high-pressure mercury lamps, and apply air sun. An optical information recording medium with a German structure was obtained. (Adhesive composition) X: Polyurethane MW900 A mixture of. Table 1 shows the test results for the obtained optical information recording medium.

[Table] Example 2 A 2% styrene/maleic anhydride copolymer solution (methyl ethyl ketone and methyl After applying a 1:1 (volume ratio) solution of cellosolve acetate using a spinner at a rotation speed of 1000 rpm, the coating film was dried at a temperature of 120°C for 5 minutes to form an undercoat layer with a dry film thickness of 0.2 μm. Formed. On top of this basecoat layer, apply a 2% polymethyl methacrylate solution (4 parts of toluene and methyl cellosolve).
1 (volume ratio) solution) was similarly applied using a spinner and dried to form a heat insulating layer with a dry film thickness of 0.2 μm. Next, 1:(In:
Co-deposited at a ratio of GeS (volume ratio) to a thickness of 300
A recording layer with a thickness of 1.5 Å was formed. Ring-shaped anodized outer Al spacer (outer diameter: 305mm, inner diameter: 295mm) and inner
After applying a silane coupling agent to each adhesive surface of the Al spacer (outer diameter: 160 mm, inner diameter: 35 mm), apply a UV-curable adhesive having the composition shown in Table 2 to a thickness of 50 μm using the transfer printing method. Ta. Thereafter, the same treatment as in Example 1 was carried out to obtain an optical information recording medium. Table 2 shows test results for these information recording media.

【table】

【table】

Claims (1)

[Claims] 1. Two disk-shaped substrates are joined directly or via a ring-shaped inner spacer and a ring-shaped outer spacer, and at least one of the substrates is transparent,
In an information recording medium in which a recording layer on the inner surface of at least one substrate is provided with a recording layer on which information can be written and/or read by a laser, the bonding is performed by the following (A), (B), (C) and 1. An optical information recording medium characterized in that the optical information recording medium is produced by applying an ultraviolet curable adhesive containing (D) to the substrate, combining both substrates, and then irradiating the substrates with ultraviolet rays. (A) A crosslinkable oligomer with two or more (meth)acryloyl groups in the molecule and a molecular weight of 1000 or less per (meth)acryloyl group. (B) A polymer with a glass transition temperature of less than 20°C. Monofunctional vinyl compound (C) that provides a monofunctional vinyl compound that provides a polymer with a glass transition temperature of 20°C or higher (D) Photopolymerization initiator. 2. The optical information recording medium according to claim 1, wherein the disk-shaped substrate is made of glass, and the ultraviolet curable adhesive contains a silane coupling agent.