Cationically curable resin composition for assembling hard disk devices

Abstract

The present invention provides a cationically curable resin composition for assembling hard disk devices which comprises a resin having a cationically polymerizable functional group (a component A) and a cationic polymerization initiator (a component B), the component B being at least one selected from the group consisting of X.sup.+(SbF.sub.6).sup.(B1), X.sup.+(B(C.sub.6F.sub.5).sub.4).sup.(B2) and X.sup.+((Rf).sub.nPF.sub.6-n).sup.(B3) (in the formulae, X.sup.+ is iodonium or sulfonium, Rf is a fluorinated alkyl having 1 to 6 carbon atoms, and n is an integer of 1 to 6). The invention also provides a hard disk device manufacturing method using the composition, and a hard disk device assembled with the composition.

Claims

1. A cationically curable resin composition for assembling hard disk devices, consisting of: a resin having a cationically polymerizable functional group (a component A) and a cationic polymerization initiator (a component B), the component B being at least one selected from the group consisting of the following formulae:
X.sup.+(SbF.sub.6).sup.(B1),
X.sup.+(B(C.sub.6F.sub.5).sub.4).sup.(B2), and
X.sup.+((Rf).sub.nPF.sub.6-n).sup.(B3) wherein in the formulae, X.sup.+ is iodonium or sulfonium, Rf is a fluorinated alkyl having 1 to 6 carbon atoms, and n is an integer of 1 to 6; the component A is a mixture of an epoxy group-containing resin having an epoxy equivalent of not less than 150 and an oxetanyl group-containing resin, the epoxy group-containing resin having an epoxy equivalent of not less than 150 is at least one resin selected from the group consisting of a bisphenol A type epoxy resin, a hydrogenated bisphenol A epoxy resin, a bisphenol F epoxy resin, a cresol novolak epoxy resin and an adduct of 2,2-bis(hydroxymethyl)-1-butanol with 1,2-epoxy-4-(2-oxiranyl)cyclohexane, the oxetanyl group-containing resin is at least one resin selected from the group consisting of 3-ethyl-3-hydroxymethyloxetane, 2-ethylhexyloxelane, xylylenebisoxetane, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, oxetanylsilsesquioxetane, phenol novolak oxetane and 3-ethyl-3-phenoxymethyloxetane.

2. The cationically curable resin composition for assembling hard disk devices according to claim 1, wherein the rate of weight reduction by heating of the cured product is less than 1 mass %.

3. A hard disk device manufacturing method comprising a step of bonding a magnetic head periphery in a hard disk device using the cationically curable resin composition for assembling hard disk devices described in claim 1.

4. A hard disk device assembled with the cationically curable resin composition for assembling hard disk devices described in claim 1.

5. The cationically curable resin composition for assembling hard disk devices according to claim 1, wherein the oxetanyl group-containing resin is 3-ethyl-3-phenoxymethyloxetane.

6. A cationically curable resin composition for assembling hard disk devices, consisting of: a resin having a cationically polymerizable functional group (a component A), a cationic polymerization initiator (a component B), and at least one component selected from the group consisting of a filler, a silane coupling agent and a photosensitizer, the component B being at least one selected from the group consisting of the following formulae:
X.sup.+(SbF.sub.6).sup.(B1),
X.sup.+(B(C.sub.6F.sub.5).sub.4).sup.(B2), and
X.sup.+((Rf).sub.nPF.sub.6-n).sup.(B3) wherein in the formulae, X.sup.+ is iodonium or sulfonium, Rf is a fluorinated alkyl having 1 to 6 carbon atoms, and n is an integer of 1 to 6; the component A is a mixture of an epoxy group-containing resin having an epoxy equivalent of not less than 150 and an oxetanyl group-containing resin, the epoxy group-containing resin having an epoxy equivalent of not less than 150 is at least one resin selected from the group consisting of a bisphenol A epoxy resin, a hydrogenated bisphenol A epoxy resin, a bisphenol F epoxy resin, a cresol novolak epoxy resin and an adduct of 2,2-bis(hydroxymethyl)-1-butanol with 1,2-epoxy-4-(2-oxiranyl)cyclohexane, the oxetanyl group-containing resin is at least one resin selected from the group consisting of 3-ethyl-3-hydroxymethyloxetane, 2-ethylhexyloxelane, xylylenebisoxetane, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, oxetanylsilsesquioxetane, phenol novolak oxetane and 3-ethyl-3-phenoxymethyloxetane.

7. The cationically curable resin composition for assembling hard disk devices according to claim 6, wherein the rate of weight reduction by heating of the cured product is less than 1 mass %.

8. A hard disk device manufacturing method comprising a step of bonding a magnetic head periphery in a hard disk device using the cationically curable resin composition for assembling hard disk devices described in claim 6.

9. A hard disk device assembled with the cationically curable resin composition for assembling hard disk devices described in claim 6.

10. The cationically curable resin composition for assembling hard disk devices according to claim 6, wherein the oxetanyl group-containing resin is 3-ethyl-3-phenoxymethyloxetane.

Description

EXAMPLES

(1) In Examples 1 to 8 and Comparative Examples 1 and 2, compositions were produced from the following raw materials.

(2) (1) Polymerizable Resins

(3) [Resins having Cationically Polymerizable Functional Group (Components A)]

(4) Bisphenol A type epoxy resin (EPICLON 850 manufactured by DIC); Bisphenol F type epoxy resin (EPICLON EXA-830LVP manufactured by DIC); Cresol novolak type epoxy resin (EPICLON N-655-EXP-S manufactured by DIC); Polyfunctional epoxy (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate) (CELLOXIDE 2021P manufactured by DAICEL CORPORATION); Monofunctional oxetane (3-ethyl-3-phenoxymethyloxetane) (PDX: OXT-211 manufactured by TOAGOSEI CO., LTD.); Xylylene bisoxetane (1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene (main component)) (XDO: OXT-121 manufactured by TOAGOSEI CO., LTD.).
[Resin having Radically Polymerizable Functional Group] Bisphenol A type acrylic resin (KAYAHARD R-280 manufactured by NIPPON KAYAKU CO., LTD.) (diluted with 2-hydroxypropyl methacrylate to 20%).
(2) Polymerization Initiators
[Cationic Polymerization Initiators (Components B)] Diphenyl 4-thiophenoxyphenylsulfonium hexafluoroantimonate (CPI-101A manufactured by San-Apro Ltd. (Example 1) or SP-172 manufactured by ADEKA (Example 6)) (compound B1: Formula (1) above); 4-Methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate (PI-2074 manufactured by Rhodia) (compound B2: Formula (2) above); Diphenyl 4-thiophenoxyphenylsulfonium tris(pentafluoroethyl)trifluorophosphate (CPI-210S manufactured by San-Apro Ltd.) (compound B3: Formula (3) above).
[Cationic Polymerization Initiator (other than Components B)] Diphenyl 4-thiophenoxyphenylsulfonium hexafluorophosphate (CPI-100P manufactured by San-Apro Ltd.) (Formula (4) below):

(5) ##STR00004##
[Radical Polymerization Initiator]

(6) (1-Hydroxycyclohexyl)phenyl ketone (IRGACURE 184 manufactured by BASF).

(7) According to the formulations described in Table 1, the polymerizable resins and the polymerization initiators (the total weight was 154 g except in Comparative Example 2 in which the total weight was 104 g) were added to a mixing tank (No. 300 (manufactured by KINKI YOKI CO., LTD.), 300 ml volume, polyethylene) and were stirred with a stirrer (RW28 (manufactured by IKA), 600 rpm) at room temperature until the blends became transparent, thereby producing cationically curable resin compositions of Examples 1 to 8 of the present invention as well as compositions of Comparative Examples 1 and 2. The room temperature in Examples was 23 C.

(8) [Evaluation Conditions]

(9) The occurrence of outgassing during the curing of the compositions of Examples 1 to 8 and Comparative Examples 1 and 2 was evaluated in the following manner.

(10) Molds 1 mm in thickness and 4.5 mm in diameter were formed in silicon. The resin compositions of Examples 1 to 8 and Comparative Examples 1 and 2 were each poured into the mold and sandwiched between PET films. With a metal halide lamp manufactured by EYE GRAPHICS CO., LTD., the resin compositions were irradiated at 6000 mJ/cm.sup.2 (365 nm) to give test pieces. With respect to the test pieces thus fabricated, the rate of weight reduction by heating was determined with TGA/DSC1 manufactured by METTLER TOLEDO. The temperature program was such that the temperature was raised from 25 C. to 120 C. at 10 C./min and was held at 120 C. for 5 hours. The rate of weight reduction (outgassing) was calculated from the mass (W0) of the test piece immediately after fabrication and the mass (W1) after 5 hours at 120 C.
Rate of weight reduction=((W1W0)/W0)100

(11) The results are described in Tables 1 and 2.

(12) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Polymerizable Cationically Bisphenol A type 100 g 100 g 100 g resins polymerizable epoxy resin (Epoxy EPICLON 850 equivalent Bisphenol F type 100 g 150 or more) epoxy resin EPICLON EXA-830LVP Cresol novolak type 100 g epoxy resin EPICLON N-655-EXP-S Cationically Polyfunctional 50 g 50 g 50 g polymerizable epoxy CEL 2021P Monofunctional 50 g oxetane (POX) OXT-211 Xylylene bisoxetane 50 g (XDO) OXT-121 Radically Bisphenol A type polymerizable acrylic resin KAYAHARD R-280 Polymerization Cation Compound B1: 4 g 4 g 4 g 4 g 4 g initiators Formula (1) Compound B2: Formula (2) Compound B3: Formula (3) Sulfonium hexafluorophosphate salt: Formula (4) Radical IRGACURE 184 Outgass (%) 0.16 0.46 0.45 0.39 0.52

(13) TABLE-US-00002 TABLE 2 Comp. Comp. Ex. 1 Ex. 6 Ex. 7 Ex. 8 Ex. 1 Ex. 2 Polymerizable Cationically Bisphenol A type 100 g 100 g 100 g 100 g 100 g resins polymerizable epoxy resin (Epoxy EPICLON 850 equivalent Bisphenol F type 150 or more) epoxy resin EPICLON EXA-830LVP Cresol novolak type epoxy resin EPICLON N-655-EXP-S Cationically Polyfunctional 50 g 50 g 50 g 50 g 50 g polymerizable epoxy CEL 2021P Monofunctional oxetane (POX) OXT-211 Xylylene bisoxetane (XDO) OXT-121 Radically Bisphenol A type 100 g polymerizable acrylic resin KAYAHARD R-280 Polymerization Cation Compound B1: 4 g 4 g initiators Formula (1) Compound B2: 4 g Formula (2) Compound B3: 4 g Formula (3) Sulfonium 4 g hexafluorophosphate salt: Formula (4) Radical IRGACURE 184 4 g Outgass (%) 0.16 0.56 0.58 0.58 1.00 1.63

(14) It was demonstrated that the cationically curable resin compositions of Examples 1 to 8 achieved lower levels of outgassing compared to the compositions of Comparative Examples 1 and 2, and had a weight reduction rate of less than 1 mass %.