JP2010079958A - Adhesive for temporary bonding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive for temporary bonding which is an adhesive for bonding glass substrates temporarily together in drilling a glass substrate for a hard disk, and which makes: an adhesive force sufficient for the glass substrates not to be released even when exposed to a shock of drilling; and releasability for them to be easily released in hot water without occurrence of an adhesive residue after drilling, compatible with each other. <P>SOLUTION: The adhesive is for temporarily bonding glass substrates together in drilling the glass substrate for the hard disk, and includes at least a (meth)acrylate compound, a photo-polymerization initiator, and a gas generating agent, wherein 60 wt.% or more of the (meth)acrylate compound has an aromatic and/or cycloaliphatic structure in the skeleton, and the adhesive for temporary bonding has 5 pts.wt. or more of the gas generating agent with respect to 100 pts.wt. of the (meth)acrylate compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention is an adhesive for temporarily adhering glass substrates at the time of drilling glass substrates for hard disks, and has sufficient adhesive strength that does not peel off even when impacted during drilling, and adhesive remains after drilling The present invention relates to an adhesive for temporary bonding that is compatible with releasability that can be easily peeled off in heated water.

The glass substrate for hard disks is made by first laminating and laminating multiple pieces of glass shaped into a disk shape, then punching them in the center and then peeling them to separate individual donut glass Manufactured by a method of obtaining a substrate. According to this method, a large number of glass substrates for hard disks can be manufactured with extremely high efficiency.

As an adhesive used in such a production method, a wax or a water-soluble adhesive has been used. When the adherend bonded with wax or a water-soluble adhesive is immersed in water heated to about 80 ° C., the wax or water-soluble adhesive dissolves and can be easily peeled off. However, when these adhesives are used, there is a problem that adhesive residue may remain on the glass substrate after peeling. In the bird disk, the smaller the distance between the rotating glass substrate and the head, the larger the storage capacity. Therefore, the adhesive residue on the glass substrate becomes a fatal defect. There is also a problem that a large amount of sewage containing the dissolved adhesive is generated.

In contrast, an adhesive in which a water-soluble solvent is added to a hydrophobic adhesive (for example, Patent Document 1), or an adhesive in which a water-soluble polysaccharide is added to a hydrophobic adhesive (for example, Patent Document 2). ) Is also proposed. However, even if these techniques solve the problem of adhesive residue, residues such as polysaccharides remain on the glass substrate. This causes a collision between the hard disk substrate and the head, that is, a head crash. Moreover, the problem of sewage generation could not be solved.

As an easily peelable adhesive, for example, Patent Document 3 discloses an adhesive in which a foaming agent such as a thermally expandable microcapsule is blended in the adhesive. When such an adhesive is heated, the entire adhesive is foamed by the foaming agent, and the adhesive area with the adherend is reduced, so that the adhesive can be easily peeled off. However, such a foam-type easily peelable adhesive cannot solve the problem of remaining glue on the surface of the adherend. Further, for foaming, it is usually necessary to heat to a high temperature of 130 ° C. or higher, and in order to perform peeling in heated water, it is necessary to use a pressure vessel or the like, which is not practical.

Patent Document 4 discloses a pressure-sensitive adhesive in which a gas generating agent such as an azo compound is blended in a curable pressure-sensitive adhesive. When such a pressure-sensitive adhesive is irradiated with ultraviolet rays or heated, the pressure-sensitive adhesive is cured, and the gas generated from the gas generating agent is released to the adhesion surface with the adherend, thereby peeling off at least a part of the adhesion surface. Therefore, it can be easily peeled off. However, the pressure-sensitive adhesive described in Patent Document 4 has a problem in that it has low adhesive strength at room temperature and may be peeled off by impact during drilling of a glass substrate.

Patent Document 5 discloses a method for promoting peeling from a substrate by using a contraction of the base film by stretching the base film with an adhesive with a uniaxial or biaxial stretching machine and heating it. Has been. However, even if the base film with an adhesive described in Patent Document 5 is used, it was actually difficult to peel off the glass substrates.
There has been a demand for an adhesive for temporary bonding that has both sufficient adhesive strength that does not peel even when impacted during drilling of a glass substrate and releasability that can be easily peeled off without any adhesive residue after processing.
JP 2007-395329 A JP 2007-16141 A JP 2001-131507 A JP 2003-231867 A JP 2007-246860 A

The present invention is an adhesive for temporarily adhering glass substrates at the time of drilling glass substrates for hard disks, and has sufficient adhesive strength that does not peel off even when impacted during drilling, and adhesive remains after drilling An object of the present invention is to provide an adhesive for temporary bonding that is compatible with releasability that can be easily peeled off in heated water.

The present invention is an adhesive for temporarily adhering glass substrates at the time of drilling a glass substrate for a hard disk, and contains at least a (meth) acrylate compound, a photopolymerization initiator, and a gas generating agent. In addition, 60% by weight or more of the (meth) acrylate compound is a temporary adhesion adhesive which is a (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton.
The present invention is described in detail below.

The temporary adhesive adhesive of the present invention contains a (meth) acrylate compound, a photopolymerization initiator, and a gas generating agent.
The (meth) acrylate compound is a (meth) acrylate compound having 60% by weight or more having an aromatic and / or alicyclic structure in the skeleton. By containing a certain amount or more of the (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton, the adhesive for temporary bonding of the present invention has a glass transition temperature (Tg) of the cured product of 40 ° C. or higher. It is possible to exert a sufficient adhesive force that does not peel even when subjected to an impact during drilling. Also, when peeling is performed in water heated to 60 ° C. or higher, the adhesive does not soften more than necessary, so that it can be easily peeled without any adhesive residue. When the glass transition temperature of the cured product is 40 ° C. or less, even if the glass substrate and the adhesive are once peeled off due to the pressure of the gas generated from the gas generating agent, re-bonding occurs and peeling easily occurs. Can not do it. Preferably, the (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton is 70% by weight or more.

Moreover, it is preferable that 50 weight% of the said (meth) acrylate compound is bifunctional or more (meth) acrylate resin which has an aromatic and / or alicyclic structure in frame | skeleton. Thereby, since the adhesive after hardening does not swell or fuse in heated water, peeling from the glass substrate is easily performed.

The (meth) acrylate compound having the aromatic and / or alicyclic structure in the skeleton may be monofunctional or may be bifunctional or more polyfunctional.

The (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton can be obtained, for example, by reacting an epoxy resin and (meth) acrylic acid in the presence of a basic catalyst according to a conventional method. it can.

Examples of the epoxy resin that is a raw material for the (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton include, for example, a phenol novolac epoxy resin, a cresol novolac epoxy resin, a biphenyl novolac epoxy resin, and trisphenol. Novolac type epoxy resin, dicyclopentadiene novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, 2,2'-diallyl bisphenol A type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin And propylene oxide-added bisphenol A type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, resorcinol type epoxy resin, and glycidylamines.

As the (meth) acrylate compound having the alicyclic structure in the skeleton, a compound obtained by hydrogenating the (meth) acrylate compound having the aromatic structure in the skeleton can also be used.

Among the monofunctional (meth) acrylate compounds having an aromatic skeleton, those commercially available include, for example, 2-methacryloxyethyl 2-hydroxypropyl phthalate (manufactured by Kyoeisha, light ester HO-MPP), phenol ethyloxide 2 mol modified acrylate (manufactured by Toagosei Co., Ltd., M-101), phenol ethyloxide 4 mol modified acrylate (manufactured by Toagosei Co., Ltd., M-102), nonylphenol ethyloxide 1 mol modified acrylate (manufactured by Toagosei Co., Ltd., M-111) Nonylphenol ethyleoxide 4-mole modified acrylate (manufactured by Toagosei Co., Ltd., M-113), nonylphenol ethyloxide 2.5 mol modified acrylate (manufactured by Toagosei Co., Ltd., M-117), monohydroxyethyl acrylate phthalate (manufactured by Toagosei Co., Ltd.) , M-5 00), 2-hydroxy-3-phenoxypropyl acrylate (manufactured by Toagosei Co., Ltd., include M-5700) and the like.

Examples of commercially available monofunctional acrylate compounds having the alicyclic structure in the skeleton include, for example, 2-methacryloxyethyl hexahydrophthalic acid (manufactured by Kyoeisha, light ester HO-MPP), dicyclopentenyl acrylate. (Hitachi Chemical Co., FA-511A), dicyclopentenyloxyethyl acrylate (Hitachi Chemical Co., FA-512A), dicyclopentanyl acrylate (Hitachi Chemical Co., FA-513A), isobonyl acrylate (Toagosei) M-156), t-butylcyclohexyl acrylate (manufactured by Daicel UCB, IRR164), and the like.

As what is marketed among the monofunctional methacrylate compounds which have the alicyclic structure in the skeleton, for example, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl acrylate (manufactured by Hitachi Chemical Co., Ltd., FA-512M), And dicyclopentanyl methacrylate (manufactured by Hitachi Chemical Co., Ltd., FA-513M).

Examples of commercially available polyfunctional (meth) acrylate compounds having an aromatic skeleton include, for example, bisphenol A ethylene oxide 2-mol adduct dimethacrylate (Kyoeisha, light ester BP-2EM), bisphenol A, and the like. Ethylene oxide 4 mol adduct dimethacrylate (Kyoeisha, light ester BP-4EM), bisphenol A ethylene oxide 6 mol adduct dimethacrylate (Kyoeisha, light ester BP-6EM), bisphenol A ethylene oxide 10 mol adduct dimethacrylate Bisphenol A ethylene oxide 20 mol adduct dimethacrylate, bisphenol A propylene oxide 4 mol adduct dimethacrylate (Kyoeisha, light ester BP-4PM), bisphenol A Ethylene oxide 10 mol adduct diacrylate (manufactured by Kyoeisha, light ester BP-10Ea, bisphenol A ethylene oxide 4 mol adduct diacrylate, bisphenol A ethylene oxide 6 mol adduct diacrylate, bisphenol A ethylene oxide 10 mol addition Diacrylate, bisphenol A ethylene oxide 20 mol adduct diacrylate (Sartomer 9035A), bisphenol A propylene oxide 4 mol adduct diacrylate, bisphenol F ethylene oxide 2 mol adduct diacrylate (Toagosei) M-208), bisphenol F ethylene oxide 2-mole adduct dimethacrylate, EB3700 (manufactured by Daicel Cytec), EB-3708 (Daicel) Itekku Co., Ltd.), and the like.

Examples of commercially available polyfunctional (meth) acrylate compounds having the alicyclic structure in the skeleton include, for example, dimethylol tricyclodecane diacrylate (manufactured by Daicel Cytec, IRR214), dimethylol tricyclode Candimethacrylate (manufactured by Kyoeisha, Light Ester DCP-M) and the like. In addition, an ethylene oxide adduct or a propylene oxide adduct having a hydrogenated bisphenol A skeleton or a hydrogenated bisphenol F skeleton can also be used.

The (meth) acrylate compound having the aromatic and / or alicyclic structure in the skeleton is preferably an ethylene oxide adduct or a propylene oxide adduct. By using an ethylene oxide adduct or a propylene oxide adduct, the hydrophilicity of the cured product of the adhesive for temporary bonding of the present invention is increased. For this reason, as described later, when the laminated body after drilling is immersed in water heated to 60 ° C. or more to generate gas from the gas generating agent, water is removed between the peeled adhesive and the glass substrate. Becomes easy to invade. As a result, peeling can be completed in a very short time.

Among the (meth) acrylate compounds having an aromatic and / or alicyclic structure in the skeleton, the blending amount of the ethylene oxide adduct or propylene oxide adduct is preferably a lower limit of 10 with respect to 100 parts by weight of the (meth) acrylate compound. Part by weight, the preferred upper limit is 95 parts by weight. When the amount of ethylene oxide adduct or propylene oxide adduct is less than 10 parts by weight of the (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton, when peeling in heated water Sometimes it does not peel off quickly (peeling time 7 minutes or less), and even if it exceeds 90 parts by weight, no further effect can be obtained. Of the (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton, the more preferred lower limit of the blending amount of the ethylene oxide adduct or the propylene oxide adduct is 20 parts by weight, and the more preferred upper limit is 80 parts by weight. is there.

The (meth) acrylate compound is not particularly limited as a compound other than the (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton. For example, as a monofunctional compound, methyl (meth) Examples include acrylate, ethyl (meth) acrylate, N-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Examples of the polyfunctional compound include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,4 butanediol dimethacrylate, neopentyl glycol dimethacrylate, 1,6 hexanediol dimethacrylate, ethylene glycol diacrylate, Diethylene glycol diacrylate, 1,4 butanediol diacrylate, neopentyl glycol diacrylate, 1,6 hexanediol diacrylate, trimethylolpropane triacrylate, ethylene glycol-terminated dimethoxyacrylate, propylene glycol-terminated dimethoxyacrylate, glycerin-terminated dimethoxyacrylate, etc. Can be mentioned.

Although it does not specifically limit as said photoinitiator, What is activated by irradiating light with a wavelength of 250-450 nm is mentioned.
Examples of the photopolymerization initiator include acetophenone derivative compounds such as methoxyacetophenone, benzoin ether compounds such as benzoinpropyl ether and benzoin isobutyl ether, ketal derivative compounds such as benzyldimethyl ketal and acetophenone diethyl ketal, and phosphine. Light of oxide derivative compounds, bis (η5-cyclopentadienyl) titanocene derivative compounds, benzophenone, Michler ketone, chlorothioxanthone, todecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenylpropane, etc. A radical polymerization initiator is mentioned. These photoinitiators may be used independently and 2 or more types may be used together.

As a compounding quantity of the said photoinitiator, the preferable minimum with respect to 100 weight part of said (meth) acrylate compounds is 0.2 weight part, and a preferable upper limit is 5 weight part. When the blending amount of the photopolymerization initiator is less than 0.2 parts by weight, the adhesive for temporary bonding may not be cured without being cured even when irradiated with ultraviolet rays. However, no further effect can be obtained. The more preferable lower limit of the amount of the photopolymerization initiator is 0.5 parts by weight, and the more preferable upper limit is 3 parts by weight.

Although it does not specifically limit as said gas generating agent, The thing which generate | occur | produces gas by heating to 60 degreeC or more is suitable. Although it does not specifically limit as said gas generating agent, For example, an azo compound, an azide compound, etc. are suitable.

Examples of the azo compound include 2,2′-azobis (N-cyclohexyl-2-methylpropionamide), 2,2′-azobis [N- (2-methylpropyl) -2-methylpropionamide], 2 , 2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis [N- (2-methylethyl) -2-methylpropionamide], 2,2′-azobis (N-hexyl) -2-methylpropionamide), 2,2′-azobis (N-propyl-2-methylpropionamide), 2,2′-azobis (N-ethyl-2-methylpropionamide), 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis {2-methyl-N- [2- (1-hydroxy) Butyl)] propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide ], 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] Dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrolate, 2,2'-azobis [2- (3,4,5,6-tetra Hydropyrimidin-2-yl) propane] dihydrochloride, 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane Dihydrochloride, 2,2′-azobis [2- (2-imidazolidin-2-yl) propane], 2,2′-azobis (2-methylpropionamidyne) hydrochloride, 2,2′-azobis (2 -Aminopropane) dihydrochloride, 2,2'-azobis [N- (2-carboxyacyl) -2-methyl-propionamidine], 2,2'-azobis {2- [N- (2-carboxyethyl) ) Amidyne] propane}, 2,2′-azobis (2-methylpropionamidoxime), dimethyl 2,2′-azobis (2-methylpropionate), dimethyl 2,2′-azobisisobutyrate, 4 , 4′-azobis (4-cyancarbonic acid), 4,4′-azobis (4-cyanopentanoic acid), 2,2′-azobis (2,4 , 4-trimethylpentane) and the like.
These azo compounds generate nitrogen gas when stimulated by heat or the like.

Examples of the azide compound include 3-azidomethyl-3-methyloxetane, terephthalazide, p-tert-butylbenzazide, and glycidyl azide polymer obtained by ring-opening polymerization of 3-azidomethyl-3-methyloxetane. Examples thereof include a polymer having an azide group. These azide compounds are decomposed by applying a stimulus by light of a specific wavelength, heat, ultrasonic waves, impact, etc., and generate nitrogen gas.

Among these gas generating agents, the azide compound is easily decomposed even by giving an impact and releases nitrogen gas, so that there is a problem that handling is difficult. Furthermore, once the decomposition starts, the azide compound causes a chain reaction and explosively releases nitrogen gas, which cannot be controlled. Therefore, the adherend may be damaged by the explosively generated nitrogen gas. There is also a problem. Due to such problems, the amount of the azide compound used is limited, but sufficient effects may not be obtained with the limited amount used.

On the other hand, unlike the azide compound, the azo compound is extremely easy to handle because it does not generate gas upon impact. In addition, since no gas is explosively generated due to a chain reaction, the adherend is not damaged, and generation of gas can be interrupted if light irradiation is interrupted. There is also an advantage that control is possible. Therefore, it is more preferable to use an azo compound as the gas generating agent.

The azo compound preferably has a 10-hour half-life temperature of 60 ° C. or higher. When the 10-hour half-life temperature is less than 60 ° C., the adhesive substance of the present invention may foam when it is molded by casting and dried, or it undergoes a decomposition reaction over time, causing degradation residues to bleed. In some cases, gas may be generated over time and the interface with the adherend to be bonded may be lifted. If the 10-hour half-life temperature is 60 ° C. or higher, the heat resistance is excellent, so that use at a high temperature and stable storage are possible.

Examples of the azo compound having a 10-hour half-life temperature of 60 ° C. or higher include an azoamide compound represented by the following general formula (1). In addition to excellent heat resistance, the azoamide compound represented by the following general formula (1) is also excellent in solubility in adhesive polymers such as an alkyl acrylate polymer to be described later. The particles may not exist as particles.

In formula (1), R ¹ and R ² each represent a lower alkyl group, and R ³ represents a saturated alkyl group having 2 or more carbon atoms. R ¹ and R ² may be the same or different.

Examples of the azoamide compound represented by the general formula (1) include 2,2′-azobis (N-cyclohexyl-2-methylpropionamide) and 2,2′-azobis [N- (2-methylpropyl). -2-methylpropionamide], 2,2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis [N- (2-methylethyl) -2-methylpropionamide], 2 , 2′-azobis (N-hexyl-2-methylpropionamide), 2,2′-azobis (N-propyl-2-methylpropionamide), 2,2′-azobis (N-ethyl-2-methylpropionamide) Amide), 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobi {2-methyl-N- [2- (1-hydroxybutyl)] propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide] and the like. Among these, 2,2′-azobis (N-butyl-2-methylpropionamide) and 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide] have improved solubility in solvents. It is preferably used because it is particularly excellent.

The gas generating agent is preferably not present as particles in the temporary bonding adhesive of the present invention. In addition, in this specification, that a gas generating agent does not exist as a particle means that a gas generating agent cannot be confirmed when the adhesive substance of this invention is observed with an electron microscope.

In order to prevent the gas generating agent from being present as particles, a gas generating agent that is usually dissolved in the temporary bonding adhesive of the present invention is selected, but a gas that does not dissolve in the temporary bonding adhesive of the present invention. When the generator is selected, for example, the gas generator is finely dispersed in the temporary adhesive of the present invention by using a disperser or using a dispersant in combination. In order to finely disperse the azo compound in the temporary bonding adhesive of the present invention, the gas generating agent is preferably a fine particle. Further, these fine particles are, for example, a disperser or a kneading device. It is preferable to use finer particles as required. That is, it is more preferable to disperse the gas generating agent to a state where the gas generating agent cannot be confirmed when the temporary bonding adhesive of the present invention is observed with an electron microscope.

As a compounding quantity of the said gas generating agent, the minimum with respect to 100 weight part of said (meth) acrylate compounds is 5 weight part. When the blending amount of the gas generating agent is less than 5 parts by weight, a sufficient peeling pressure cannot be obtained even if gas is generated, and peeling cannot be performed. The minimum with the preferable compounding quantity of the said gas generating agent is 7 weight part. On the other hand, the preferable upper limit of the amount of the gas generating agent is 80 parts by weight. When the blending amount of the gas generating agent exceeds 80 parts by weight, it does not dissolve in the acrylate compound, so that peeling may occur when it is not necessary, such as during storage. A more preferable upper limit of the amount of the gas generating agent is 60 parts by weight.

The temporary adhesive adhesive of the present invention preferably further contains a filler. By containing the filler, bubbles are easily generated around the filler, leading to shortening of the peeling time. Further, when the filler is uniformly dispersed, there is no unevenness in the portion where the bubbles are generated, and an effect that the peeling is performed smoothly can be obtained.

It does not specifically limit as said filler, For example, what consists of an inorganic compound, a silica, a metal, a plastics etc. is mentioned. These fillers may be used independently and may use 2 or more types together. Among these, those made of silica or plastic are suitable.

The minimum with the preferable average particle diameter of the said filler is 20 micrometers, and a preferable upper limit is 1000 micrometers. If the average particle size of the filler is less than 20 μm, bubbles may be insufficiently generated around the filler, and if it exceeds 1000 μm, the film thickness of the adhesive may be unnecessarily thick.

As a compounding quantity of the said filler, the preferable minimum with respect to 100 weight part of said (meth) acrylate compounds is 0.01 weight part, and a preferable upper limit is 10 weight part. If the blending amount of the filler is less than 0.01 parts by weight, the generation of bubbles may not be smooth and the peeling time may not be shortened. If the amount exceeds 10 parts by weight, the adhesive strength of the temporary bonding adhesive may be inferior. is there. A more preferable lower limit of the amount of the filler is 0.05 parts by weight, and a more preferable upper limit is 5 parts by weight.

The method for producing the temporary bonding adhesive of the present invention is not particularly limited, and examples thereof include a method of kneading the above (meth) acrylate compound, photopolymerization initiator, and gas generating agent by a conventionally known method.

A method for producing a glass substrate for a hard disk using the temporary bonding adhesive of the present invention will be described.
First, a plurality of glass sheets formed into a disk shape are laminated by using the temporary bonding adhesive of the present invention, and the temporary bonding adhesive is cured by irradiating ultraviolet rays through the glass. As a result, a sufficient adhesive force that does not peel even when subjected to impact during drilling is developed.
The gas generating agent such as the azo compound or the azide compound can generate a gas even when irradiated with ultraviolet rays. Therefore, an ultraviolet ray having an irradiation amount that does not generate gas from the gas generating agent is irradiated, or an ultraviolet ray having a wavelength outside the photosensitive region of the gas generating agent is irradiated.

Next, drilling is performed in a state where a plurality of glass substrates are laminated. It does not specifically limit as a specific method of drilling, A conventionally well-known method can be used.

The laminated body after drilling is immersed in water heated to 60 ° C. or higher. As a result, gas is generated from the gas generating agent, and at least a part of the adhesion surface is peeled off. In particular, when an ethylene oxide adduct or a propylene oxide adduct of a (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton is used as the (meth) acrylate compound, peeling is completed in a very short time. can do.
A plurality of sheets of glass formed into a disk shape are laminated by using the adhesive for temporary bonding of the present invention, and the process of curing the adhesive for temporary bonding by irradiating ultraviolet rays through the glass, and a plurality of sheets For manufacturing a glass substrate for a hard disk, comprising: a step of drilling a laminate in which glass substrates are laminated; and a step of peeling the laminate after being drilled in water heated to 60 ° C. or higher. Is also one aspect of the present invention.

According to the present invention, it is an adhesive for temporarily adhering glass substrates at the time of drilling a glass substrate for a hard disk, and has a sufficient adhesive strength that does not peel off even by an impact at the time of drilling, and an adhesive residue after drilling Thus, it is possible to provide an adhesive for temporary bonding that is compatible with releasability that can be easily peeled off in heated water without being carried out.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
100 parts by weight of light ester DCP-M as an alicyclic polyfunctional acrylate, 50 parts by weight of dicyclopentenyl acrylate as a monofunctional alicyclic acrylate, 50 parts by weight of epoxy ester 40EM as a polyfunctional aliphatic acrylate, Irgacure as a photopolymerization initiator 4 parts by weight of 379EG was added and heated to 60 ° C. to dissolve the initiator for 2 hours. After lowering the temperature to 40 ° C. or lower, 20 g of VF-096 and 15 g of V-601 as azo compounds as gas generating agents were added and dissolved until transparent to obtain an adhesive for temporary bonding.

(Examples 2 to 10, Comparative Examples 1 to 4)
According to Tables 1-3, an adhesive for temporary bonding was manufactured in the same manner as in Example 1.
In the examples and comparative examples, the following compounds were used.

(1) Monofunctional (meth) acrylate compound phenol ethylene oxide 2 mol modified acrylate having an aromatic skeleton (manufactured by Toagosei Co., Ltd., M-101)
Phenol ethylene oxide 4 mol modified acrylate (manufactured by Toagosei Co., Ltd., M-102)

(2) Monofunctional (meth) acrylate compound dicyclopentenyl acrylate having an alicyclic structure in the skeleton (manufactured by Hitachi Chemical Co., Ltd., FA-511A)
Dicyclopentenyloxyethyl acrylate (Hitachi Chemical Co., FA-512A)
t-butylcyclohexyl acrylate (manufactured by Daicel UCB, IRR164)

(3) Polyfunctional (meth) acrylate compound bisphenol A ethylene oxide 4-mol adduct dimethacrylate (Kyoeisha, light ester BP-4EM) having aromatic skeleton
Bisphenol A ethylene oxide 6-mole adduct dimethacrylate (Kyoeisha, Light Ester BP-6EM)
Bisphenol A ethylene oxide 20 mol adduct diacrylate (Sartomer, SR-9036)
EB3700 (manufactured by Daicel Cytec)

(4) Polyfunctional (meth) acrylate compound dimethylol tricyclodecane dimethacrylate (manufactured by Kyoeisha, light ester DCP-M) having an alicyclic structure in the skeleton
Dimethylol tricyclodecane diacrylate (manufactured by Daicel Cytec, IRR214)

(5) Other (meth) acrylate compounds ethylene glycol-terminated dimethoxyacrylate (manufactured by Kyoeisha, epoxy ester 40EM)
Ethylene glycol diacrylate (manufactured by NOF Corporation, Light Ester EG)
2-Ethylhexyl methacrylate (manufactured by NOF Corporation, Bremer EHMA)
Glycerin-terminated dimethoxyacrylate (manufactured by Kyoeisha, epoxy ester 80FAM)

(6) Photopolymerization initiator 2- (dimethylamino) -2-[(4 methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone (manufactured by Ciba Geigy, Irgacure 379EG)
Diphenyl (2,4,6 trimethylbenzoyl) phosphine oxide (Ciba Geigy, Darocur TPO)

(7) Gas generating agent 10 hours Half temperature 2,2′azobis [N- (2-propenyl) -2-methylpropionamide] (manufactured by Wako Pure Chemical Industries, VF-096, 96 ° C.)
2,2′azobis (2methylbutyronitrile) (Wako Pure Chemical Industries, V-59, 67 ° C.)
1,1′azobis (cyclohexane-1-carbonitrile) (manufactured by Wako Pure Chemical Industries, V-40, 88 ° C.)
Dimethyl 2,2′-azobis (2-methylpropionate) (Wako Pure Chemical Industries, V-601, 66 ° C.)
2,2′azobis (N-butyro-2-methylpropionate (manufactured by Wako Pure Chemical Industries, Vam-110, 110 ° C.)

(Evaluation)
The temporary bonding adhesives obtained in Examples 1 to 10 and Comparative Examples 1 to 4 were evaluated by the following methods.
The results are shown in Table 1.

(1) Adhesive strength test The obtained adhesive for temporary bonding was hung on a slide glass made of one piece of alkali glass and covered with the same slide glass. The adhesion area at this time was 5 mmΦ. A pair of bonded test pieces was produced by irradiation with ultraviolet rays. The test piece was subjected to a tensile test with an Lloyd Instron at a speed of 5 mm / min, and the adhesive strength was measured.

(2) Curing Shrinkage Test The volume shrinkage rate was measured by measuring the specific gravity before and after curing of the adhesive by a specific gravity method test with an automatic densimeter manufactured by MINIDENS & MINIDENS-TOL.

(3) Measurement of glass transition temperature Using a viscoelasticity measuring device (DVA-200, manufactured by IE Measurement Co., Ltd.), measurement was performed in a tensile mode in a temperature range of 20 ° C. to 150 ° C., and the glass transition temperature was measured with a peak of tan δ. .

(4) Peeling test The obtained adhesive for temporary bonding was hung on a slide glass made of one alkali glass and covered with the same slide glass. The adhesion area at this time was 5 mmΦ. A pair of bonded test pieces was produced by irradiation with ultraviolet rays.
The test piece was immersed in water heated to 60 ° C., and the state of peeling, the time required for peeling, and the presence or absence of adhesive residue after peeling were evaluated.

According to the present invention, it is an adhesive for temporarily adhering glass substrates at the time of drilling a glass substrate for a hard disk, and has a sufficient adhesive strength that does not peel off even by an impact at the time of drilling, and an adhesive residue after drilling Thus, it is possible to provide an adhesive for temporary bonding that is compatible with releasability that can be easily peeled off in heated water without being carried out.

Claims (6)

An adhesive for temporarily adhering glass substrates at the time of drilling a glass substrate for a hard disk,
At least a (meth) acrylate compound, a photopolymerization initiator, and a gas generating agent,
60% by weight or more of the (meth) acrylate compound has an aromatic and / or alicyclic structure in the skeleton,
The adhesive for temporary adhesion, containing 5 parts by weight or more of the gas generating agent with respect to 100 parts by weight of the (meth) acrylate compound. The adhesive for temporary bonding according to claim 1, wherein 50% by weight of the (meth) acrylate compound is a bifunctional or higher-functional (meth) acrylate resin having an aromatic and / or alicyclic structure in the skeleton. . The adhesive for temporary bonding according to claim 1 or 2, wherein the (meth) acrylate compound having an aromatic and / or alicyclic structure in the skeleton is an ethylene oxide adduct or a propylene oxide adduct. The adhesive for temporary adhesion according to claim 1, 2 or 3, wherein the gas generating agent is an azo compound and / or an azide compound. The adhesive for temporary bonding according to claim 1, further comprising a filler. A plurality of pieces of glass shaped into a disk shape are laminated together using the adhesive for temporary bonding according to claim 1, 2, 4, or 5, and are applied for temporary bonding by irradiating ultraviolet rays through the glass Curing the adhesive; and
A step of drilling a laminate in which the plurality of glass substrates are laminated;
A method for producing a glass substrate for a hard disk, comprising: detaching the laminate after the perforating process by immersing the laminate in water heated to 60 ° C. or higher.