Information recording media

Improvement in an information recording medium comprising two transparent resin substrates combined with each other, at least one of which has a recording layer provided on the inner surface thereof, two hubs mounted over the center hole of said disc substrates on both sides thereof, each hub having a insertion portion to be inserted into said center hole and a flange portion to cover a portion of said disc substrate in the vicinity of said center hole, wherein a notch is provided on the peripheral surface of each hub, adhesive layers are formed at least in the notch, between the inner peripheral surface of the center hole and the outer peripheral surface of the insertion portion of said hubs and between the hubs and a specific photo-curable composition may be used for the adhesive layer.

FIELD OF THE INVENTION 
This invention relates to information recording media used for optical 
recording discs and the like. 
BACKGROUND OF THE INVENTION 
Information recording media made of plastics to perform storing and reading 
of information by converging rays of light such as laser beam and the like 
on recording layer are required to have service durability under severe 
conditions such as temperature and moisture cycle for long-term period. 
With view of meeting such requirement as mentioned above, there have been 
proposed information recording media reinforced by forming layers of cured 
resin (adhesive) on the edge surfaces of center holes of the disc 
substrates (Japanese Patent Laid-open Publin. No. 175046/1984). However, 
there were involved such problems that the recording media were weak in 
mechanical resistance to driving force from the inner peripheral portion 
and tend to come away from each other, starting from the inner peripheral 
side thereof, though the structure thereof was effective in resistance to 
the temperature and moisture cycle to which they are exposed. 
Furthermore, there have been proposed information recording media in which 
the peripheral portion of the center hole of the laminated disc substrates 
are provided with holes annually perforated, cage-like connection rods are 
inserted into the holes thus perforated, and metallic suction caps are 
fixed to both the upper and lower parts of the connecting rods thus 
inserted (Japanese Patent Laid-open Publin. No. 119747/1987). However the 
information recording media are much complicated in structure, require 
perforating operation when the laminated disc substrates are assembled and 
involve difficulty in operation of assembling. 
OBJECT OF THE INVENTION 
The present invention is intended to solve such various problems associated 
with the prior art as mentioned above, and an object of the invention is 
to provide information recording media having the laminated structure easy 
to manufacture and capable of obtaining high adhesion strength of the 
information recording media (the adhered part of inner peripheral portion 
of the media such as between the disc substrates and hubs; and between two 
hubs). Another object of the invention is to provide information recording 
media having said structure and an adhesive layer which is cured 
immediately and has excellent adhesion strength in the beginning of curing 
and in humid condition. 
SUMMARY OF THE INVENTION 
The first information recording media according to the present invention 
comprise 
two transparent resin substrates combined with each other, at least one of 
which has a recording layer provided on the inner surface thereof, 
two pieces of hubs mounted over the center hole of said disc substrates on 
both sides thereof, each hub having a portion to be inserted into said 
center hole and a flange portion to cover a portion of said disc substrate 
in the vicinity of said center hole, 
a notch provided on the peripheral surface of said hubs, and 
adhesive layers formed in said notch, between the flange portion of said 
hubs and the said disc substrate, between the outer peripheral surface of 
the insertion portion of said hubs and the inner peripheral surface of the 
center hole of said disc substrates, and between the hubs. 
The second information recording media according to the present invention 
comprise 
two transparent resin substrates combined with each other, at least one of 
which has a recording layer provided on the inner surface thereof, 
two pieces of hubs mounted over the center hole of said disc substrates on 
both sides thereof, each hub having a portion to be inserted into said 
center hole and a flange portion to cover a portion of said disc substrate 
in the vicinity of said center hole, 
a notch provided on the peripheral surface of said hubs, and 
adhesive layers formed in the notch, between the inner surface of the 
center hole and the outer surface of the inserted portion of the hubs, and 
between two hubs, wherein said adhesive is a photo-curable composition 
comprises 
(A) an epoxy resin, 
(B) a compound selected from the group consisting of sulfonium salts and 
cyclopentadienyl iron compounds, 
(C) a compound selected from the group consisting of acrylates, 
metacrylates and olygomers thereof, and 
(D) an organic peroxide.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is illustrated below with reference to embodiment as 
expressed in terms of figures shown in the accompanying drawings. 
FIGS. 1 and 2 are sectional views showing separate embodiments of the first 
information recording media of the present invention respectively and FIG. 
3 is partially sectioned side view of the hubs used in the present 
invention. In figures, 1 is an information recording media of a structure 
wherein the hubs 4 are fitted in a center hole of two disc substrates 2a 
and 2b being laminated so that recording layers 1c and 1d provided on the 
inner surface of the substrates. In FIG. 1, the disc substrates 2a and 2b 
are superposed upon each other via an outer peripheral spacer 5 and an 
inner peripheral spacer 6 and laminated by the ultrasonic welding 
technique or by adhesive to an air sandwich structure, whereas in FIG. 2 
said disc substrates 2a and 2b are directly laminated with an adhesive 
layer 7. The hubs 4 each comprise a main body 10 made of plastics and 
having a insertion portion 8 to be inserted into the center hole 3 and a 
flange portion 9, a metallic plate 11 being fixed to the surface of the 
main body 10, and a hole 12 performated at the center thereof. The 
metallic plate 11 is anchored to the hub main body 10 by means of cut and 
raised points of projections formed on said metallic plate 11 and the 
information recording media 1 is so designed as to be driven by mechanical 
or magnetic force (detailed diagrammatic illustration in this respect is 
omitted). The insertion portions 8 of the hubs 4 are so designed to be 
inserted into the center hole 3, and the flange portions 9 of the hubs 4 
are so designed to cover the laminated disc substrates 2a and 2b in the 
vicinity of the center hole 3. Further, the insertion portion 8 to be 
insert has a notch 13 at the end of the peripheral surface thereof in 
order to store adhesive. 
In the embodiment, as shown in FIG. 3, the notch 13 is ring-shaped and make 
the portion 8 have a end part having smaller diameter than the other part 
thereof. The notches 13 of two hubs 4 compose, when the hubs 4 are fitted 
in the center hole 3, a ring-shaped channel of rectangular cross section 
formed at the peripheral surfaces of the hubs 4. 
However, in the present invention, the notch to store adhesive may have any 
shapes suitable for storing adhesive such as shown in FIGS. 4 to 8. FIGS. 
4 to 8 are partially sectioned side views of the hubs used in the present 
invention. For example, as shown in FIG. 4, the notch 23 at the end of the 
insertion portion 8 is formed circumferentially so as to be ring-shaped 
and the notches 23 of two hubs 4 compose, when the hubs 4 are fitted in 
the center hole 3, a ring-shaped channel of U-shaped cross section formed 
at the peripheral surfaces of the hubs 4. 
As shown in FIG. 5, the notch 33 formed at the end of the insertion portion 
8 is ring-shaped and make the end of the insertion portion 8 tapered and 
the notches 33 of two hubs compose, when the hubs 4 are fitted in the 
center hole 3, a ring-shaped channel of V-shaped cross section formed at 
the peripheral surfaces of the hubs 4. 
In shown in FIG. 6, the notch 43 formed at the end of the insertion portion 
8 is ring-shaped and make the end of the insertion portion 8 have the 
first and second parts 8x, 8y having smaller diameter than the other part. 
The notches 43 of two hubs 4 compose, when the hubs 4 are fitted in the 
center hole 3, a ring-shaped channel of -shaped cross section formed at 
the peripheral surfaces of the hubs 4. 
In FIG. 7, the notch 53 formed at the end of the portion 8 is ring-shaped 
and make the end of the portion 8 have a radius and the notches 53 of two 
hubs compose, when the hubs 4 are fitted in the center hole 3, a 
ring-shaped channel of r-shaped cross section formed at the peripheral 
surfaces of the hubs 4. 
In FIG. 8, the notch 63 is ring-shaped and make the end of the portion 8 
composed of a tapered part 8b and a part 8c having smaller diameter than 
the other part thereof. The notches 13 of two hubs 4 compose, when the 
hubs 4 are fitted in the center hole 3, a ring-shaped channel of 
trapezoidal cross section formed at the peripheral surfaces of the portion 
8. 
Furthermore, in the present invention, the notch 53 formed at the insertion 
portion 8 of hubs 4 may not be ring-shaped, and may have such shape shown 
in FIG. 9. Namely, FIG. 9 is a perspective view of another hub used in the 
present invention, As shown in FIG. 9, at the end of the hub 4, a 
plurality of circumferential notches 73 formed at regular intervals. The 
notches 73 of two hubs 4 compose, when the hubs 4 are fitted in the center 
hole 3, a plurality of recesses formed at regular intervals at the 
peripheral surfaces of the hubs 4. 
In the present invention, the materials used for the transparent resin 
substrates 2a, 2b, the outer spacer 5, the inner spacer 6 and hubs 4, that 
compose the disc substrate, include thermoplastic resins such as 
polycarbonates, polymethyl methacrylates and amorphous polyolefins. The 
preferably used resins include a cycloolefin random copolymer (i) of 
ethylene and a cycloolefin represented by the following general formula 
[I], a ring opening polymer (ii) resulting from ring opening 
polymerization of the cycloolefin monomers [I] or a hydrogenated polymer 
resulting from the hydrogenation of said ring opening polymer (ii). 
##STR1## 
wherein R.sup.1 to R.sup.12 each represents a hydrogen atom, a halogen 
atom or a hydrocarbon group, and are the same or different provided that 
R.sup.9 and R.sup.10, or R.sup.11 and R.sup.12, when taken together, may 
form a divalent hydrocarbon group, R.sup.9 or R.sup.10 and R.sup.11 or 
R.sup.12, when taken together, may form a hydrocarbon ring, and n is 0 or 
a positive integer and, when n is not less than 2, a plurality of R.sup.5 
to R.sup.8 may be the same or different. 
The cycloolefin which is a constituent component of the above-mentioned 
cycloolefin random copolymers (i) is at least one cycloolefin selected 
from unsaturated monomers represented by the general formula [I]. 
In the above-mentioned cycloolefin random copolymers (i), their cycloolefin 
component has a structure represented by general formula [II]. 
##STR2## 
wherein n and R.sup.1 to R.sup.12 are the same as defined above. 
In the above general formula [I], R.sup.1 to R.sup.8 include a hydrogen 
atom; a halogen atom such as fluorine, chlorine and bromine; a low alkyle 
group such as methyl, ethyl, propyl and buthyl and each of R.sup.1 to 
R.sup.8 may be different, different in part or the same. 
In the above general formula [I], R.sup.9 to R.sup.12 include a hydrogen 
atom; a halogen atom such as fluorine, chlorine and bromine; a alkyle 
group such as methyl, ethyl, propyl, iso-propyl, butyl, isobutyl, hexyl, 
stearyl; a cycloalkyl group such as cyclohexyl. Further, R.sup.9 and 
R.sup.10, or R.sup.11 and R.sup.12, when taken together, may form a 
divalent hydrocarbon group, and R.sup.9 or R.sup.10 and R.sup.11 or 
R.sup.12, when taken together, may form a hydrocarbon ring. 
The divalent hydrocarbon group, formed by taking R.sup.9 and R.sup.10, or 
R.sup.11 and R.sup.12 together, includes alkylidene groups such as 
ethylidene, propylidene and iso-propylidene. 
The hydrocarbon ring, formed by taking R.sup.9 or R.sup.10 and R.sup.11 or 
R.sup.12 together may be a mono-cyclic hydrocarbon ring; a poly-cyclic 
hydrocarbon ring having a fused ring or a linkage; a cyclic hydrocarbon 
ring having unsaturated bonding; or the combination thereo f. The rings 
described above are such rings as exemplified below. 
##STR3## 
These rings may have a substituent such as methyl. In these formulas 
illustrated above, carbon atoms denoted by 1 and 2 represent the carbon 
atoms in the formula [I] which are bonded to R.sup.9 to R.sup.12. 
The cycloolefins represented by the general formula [I] may easily be 
prepared by condensation reaction of cyclopentadienes with appropriate 
olefins or cycloolefins by Diels-Alder reaction. 
The cycloolefins represented by the general formula [I] include concretely: 
bicyclo[2.2.1]hept-2-ene and the derivatives thereof, 
tetracyclo[4.4.0.1.sup.2.5.1.sup.7.10 ]-3-dodecene and the derivatives 
thereof, 
hexacyclo[6.6.1.1.sup.3.6.1.sup.10.13.0.sup.2.7.0.sup.9.14 ]-4-heptadecene 
and the derivatives thereof, 
octacyclo[8.8.0.1.sup.2.9.1.sup.4.7.1.sup.11.18.1.sup.13.16.0.sup.3.8.0.sup 
.12.17 ]-5-docosene and the derivatives thereof, 
pentacyclo[6.6.1.1.sup.3.6.0.sup.2.7.0.sup.9.14 ]-4-hexadecene and the 
derivatives thereof, 
pentacyclo[6.5.1.1.sup.3.6.0.sup.2.7.0.sup.9.13 ]-4-pentadecene and the 
derivatives thereof, 
heptacyclo[8.7.0.1.sup.2.9.1.sup.4.7.1.sup.11.17.0.sup.3.8.0.sup.12.16 
]-5-eicosene and the derivatives thereof, 
heptacyclo[8.8.0.1.sup.2.9.1.sup.4.7.1.sup.11.18.0.sup.3.8.0.sup.12.17 
]-5-heneicosene and the derivatives thereof, 
tricyclo[4.3.0.1.sup.2.5 ]-3-decene and the derivatives thereof, 
tricyclo[4.4.0.1.sup.2.5 ]-3-undecene and the derivatives thereof, 
pentacyclo[6.5.1.1.sup.3.6.0.sup.2.7.0.sup.9.13 ]-4,10-pentadecadiene and 
the derivatives thereof, 
pentacyclo[4.7.0.1.sup.2.5.0.sup.8.13.0.sup.9.12 ]-3-pentadecene and the 
derivatives thereof, 
heptacyclo[7.8.0.1.sup.3.6.0.sup.2.7.1.sup.10.17.0.sup.11.16.1.sup.12.15 
]-4-eicosene and the derivatives thereof, 
nonacyclo[9.10.1.1.sup.4.7.0.sup.3.8.0.sup.2.10.0.sup.12.21.1.sup.13.20.1.s 
up.14.19.1.sup.15.18 ]-5-pentacosene and the derivatives thereof, 
Concrete examples of the above-mentioned compounds are shown below. 
##STR4## 
The cycloolefin random copolymers (i) comprise ethylene units and the 
above-mentioned cycloolefin units as the essential components as 
aforesaid, however, if necessary, in addition to these two essential 
components, said copolymers may contain other copolymerizable unsaturated 
monomer components so long as they will not throw hinderances in the way 
of accomplishing the object of the present invention. The unsaturated 
monomers which may be copolymerized, if necessary, with the copolymers (i) 
may include, for example, alpha-olefins having from 3 to 20 carbon atoms 
such as propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 
1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 
1-eicocene which may be used in an amount of up to an equimolar to the 
ethylene component unit in the resulting random copolymer. 
In the cycloolefin random copolymer (i) the recurring units derived from 
ethylene are present in an amount of from 40 to 85 mol %, preferably from 
50 to 75 mol %, while the recurring units derived from the cycloolefin are 
present in an amount of from 15 to 60 mol %, preferably from 25 to 50 mol 
%, and these recurring units are arranged at random in the substantially 
linear chain of the copolymer (i). The fact that this cycloolefin random 
copolymer [A] is completely soluble in decalin at 135.degree. C. confirms 
that it is substantially linear and free from a gel-forming crosslinked 
structure. 
The cycloolefin random copolymer (i) has an intrinsic viscosity [.eta.] of 
from 0.01 to 10 dl/g, preferably from 0.05 to 5 dl/g as measured in 
decalin at 135.degree. C., a glass transition temperature (Tg) of normally 
from 50.degree. to 230.degree. C., preferably from 70.degree. to 
210.degree. C. and the crystallinity as measured by X-ray diffractometry 
from 0 to 10%, preferably from 0 to 7%, and further preferably from 0 to 
5%. 
The cycloolefin random copolymer (i) having the above physical properties 
may be single copolymer, or the composition obtained by blending 100 parts 
by weight of a copolymer having an intrinsic viscosity [.eta.] of from 
0.01 to 10 dl/g, preferably 0.05 to 10 dl/g and the softening temperature 
(TMF) of not less than 70.degree. C., preferably from 90.degree. to 
250.degree. C. and 0.1 to 10 parts by weight of a copolymer having an 
intrinsic viscosity [.eta.] of from 0.01 to 5 dl/g and the softening 
temperature (TMF) of less than 70.degree. C., preferably from -10.degree. 
to 60.degree. C. 
The cycloolefin random copolymers (i) may be prepared by polymerization of 
ethylene component, cycloolefin component represented by the 
above-mentioned general formula [I] and, if necessary, other monomers 
copolymerizable therewith in the presence of known Ziegler type catalyst. 
The Ziegler type catalyst referred to above includes, for example, a 
catalyst (.alpha.) composed of a composite material containing at least 
magnesium, titanium and halogen, and an organoaluminum compound, or a 
catalyst (.beta.) composed of a vanadium compound and an organoaluminum 
compound. Of these two catalysts, the latter is preferable than the 
former, and particularly preferred is a catalyst (.beta.) composed of a 
soluble vanadium compound and an organoaluminum compound. 
The processes for the preparation of the cycloolefin random copolymers (i) 
are disclosed concretely, for example, in Japanese Patent L-O-P Publin. 
Nos. 168708/1985, 120816/1986, 115912/1986, 271308/1986, 272216/1986, 
252406/1987 and 252407/1987. 
Resins used preferably as materials for the transparent resin substrates 
include a ring opening polymer (ii) resulting from ring opening 
polymerization of the cycloolefin component represented by the 
above-mentioned general formula [I] or a hydrogenated product resulting 
from hydrogenation of said ring opening polymer (ii), adding to said 
cycloolefin random copolymer (i). Such ring opening polymer of cycloolefin 
as mentioned above is disclosed, for example, in Japanese Patent L-O-P 
Publin. No. 26024/1985. 
In the ring opening polymer, prior to hydrogenating said polymer to the 
hydrogenated product, the cycloolefin component represented by the 
above-mentioned formula [I] is composed mainly of the structural repeating 
units represented by the following general formula [III] and said 
cycloolefin component is composed mainly of the structural repeating units 
represented by the following general formula [IV] the ring opening polymer 
after the hydrogenation thereof. 
##STR5## 
In the above-mentioned formulas, n and R1 to R12 are as defined above. 
The ring opening polymer (ii) comprising the above-mentioned cycloolefin 
component or hydrogenated product thereof (ii) may be copolymers thereof 
including only those having the physical properties falling within the 
above-mentioned ranges. In that case, however, parts of the copolymers may 
be those having values of their physical properties outside the 
above-mentioned range so long as the values of physical properties of the 
copolymers, on the whole, fall within the above-mentioned ranges. 
The ring opening polymer prior to hydrogenation thereof may be prepared by 
ordinary ring opening polymerization of cycloolefin using as a starting 
compound the monomer component selected from among those represented by 
the above-mentioned general formula [I] and, if necessary, other 
polymerizable monomer components. Polymerization catalysts used herein 
include a catalyst system composed of halides, nitrates or acetylacetone 
compounds, for example, those of ruthenium, rhodium, palladium, osmium, 
iridium, platinum, molybdenum and tungsten, and reducing agents such as 
alcohol and tin compounds; or a catalyst system composed of halides or 
acetylacetone compounds of titanium, vanadium, zirconium, tungsten and 
molybdenum, and organoaluminum compounds. 
The hydrogenated product of the above-mentioned ring opening polymer is 
obtained by hydrogenation of the ring opening polymer obtained above. The 
hydrogenation of the ring opening polymer is carried out in the usual way. 
Hydrogenation catalysts generally usable herein are those which have been 
used in hydrogenation of olefin compounds. Concretely speaking, the 
catalysts of heterogeneous system include nickel, palladium, platinum and 
the like, or solid catalysts comprising these metals being carried on 
carriers such as carbon, silica, diatomaceous earth, alumina and titanium 
oxide, for example, nickel/silica, nickel/diatomaceous earth, 
palladium/carbon, palladium/silica, palladium/diatomaceous earth, and 
palladium/alumina. The catalysts of homogeneous system include those 
comprising metals of Group VIII of the periodic table, those comprising Ni 
or Co compounds such as nickel naphthenate/triethyl aluminium, nickel 
octenate/n-butyl lithium and nickel acetylacetonate/triethyl aluminium, 
and organometallic compounds of metals belonging to Groups I-III of the 
periodic table, or Rh compounds. 
The hydrogenation reaction of the above-mentioned ring opening polymer is 
carried out in the heterogeneous or homogeneous system, according to the 
kind of catalyst used at 1 to 150 atom of hydrogen and a temperature range 
of from 0.degree. to 180.degree. C., preferably from 20.degree. to 
100.degree. C. Although the rate of hydrogenation may be regulated 
according to the hydrogen pressure, reaction temperature, reaction time 
and concentration of the catalyst used, it is preferable that more than 
50%, preferably more than 80% and especially more than 90% of the double 
bond in the main chain of the polymer is hydrogenated in order that the 
resulting hydrogenated product exhibits excellent resistance to heat 
deterioration and resistance to light aging. 
These resins as illustrated above may be used either singly or as a blend 
of two or more resins. 
Further, these resins may be formed by common molding techniques such as 
injection molding into molded products, for example, transparent 
substrates 1a, 1b or hubs 4 of desired shapes. 
A recording layer 1c, 1d used for forming a disc substrate 2a, 2bis 
composed of a layer of a low-melting metallic material such as Te, a 
recording material containing a low-melting metallic material as a main 
component such as Te.C.H, Te.Cr, Te.Cr.H, a heat mode recording material 
adapted for an information recording medium of the invention such as an 
organic pigment material or a magnetooptical recording material including 
a rear earth element and a 3d transition metal such as Tb.Fe .Co and an 
alloy prepared by adding Pt or Pd to Tb.Fe.Co, and, if necessary, any 
other layer including a prime coat layer, reflection preventive layer, 
reflecting layer, interference layer protective layer and enhance layer 
which is laminated either on one surface or on both surfaces of the 
recording material layer. 
Useful as hubs 4 are those formed, for example, from polycarbonate resin, 
the above-exemplified cycloolefin random copolymer (i), ring opening 
polymer of cycloolefin component or hydrogenated product thereof (ii). If 
necessary, however, there may also be used hubs formed from the 
above-mentioned resins or fixed coated with a magnetic metal, or those 
molded from polycarbonate resin, the cycloolefin random copolymer (i), 
ring opening polymer (ii) of cycloolefin component or hydrogenated product 
thereof (ii) into which a magnetic material has been incorporated. In the 
present invention, the hubs formed from polycarbonate resin are 
particularly useful. 
The information recording discs 1 comprising the substrate 1a, 1b, outer 
spacer 5, inner spacer 6 and hubs 4, or comprising the substrate 1a, 1b 
and hubs 4, having the above illustrated structure and made of the 
material described above, are manufactured by laminating the disc 
substrates 2a and 2b directly with the adhesive layer 7 or by means of the 
ultrasonic welding technique via the outer peripheral spacer 5 and the 
inner peripheral spacer 6 so that the recording layers 1c and 1d provided 
the inner surface of the substrates 2a and 2b, inserting the portions 8 of 
the hubs 4 into the center hole 3 from both sides thereof, charging the 
adhesive layers 14 between the disc substrates 2a, 2b and the hubs 4, 
namely between the discsubstrate 2a, ab and the flange portion (portions 
denoted by (a)) and between the inner peripheral surface of the center 
hole 3 of disc substrate 2a, 2b and the outer peripheral surface of the 
insertion portion 8 of hubs 4 (portion denoted by (b)); and between the 
hubs 4 (portions denoted by (c)) and notches 13 to anchor them to each 
other. 
In the first information recording media of the present invention, as shown 
in FIGS. 1 and 2, the adhesive layers 14 are charged in notches 13; 
between the flange portion 9 of hubs 4 and the disc substrates 2a, 2b; 
between the outer peripheral surface of insertion portion 8 of hubs 4 and 
the inner peripheral surface of the center hole 3 of disc substrate 2a, ab 
and between two hubs 4. In the specification, the phrase "between the disc 
substrate 2a, 2b and hubs 4" means both of the portion (a) between the 
disc substrate 2a, 2b and the flange portion 9 of the hubs 4; and portion 
(b) between the inner peripheral surface of the center hole 3 of disc 
substrate 2a, 2b and the outer peripheral surface of the insertion portion 
8 of hubs 4. 
In the information recording discs 1 thus manufactured, since the hubs 4 
are bonded with the disc substrates 2a and 2b at the insertion portions 8 
and flange portions 9 of said hubs 4 by means of the adhesive layer 14, 
and the hubs 4 themselves are bonded to each other by means of the 
adhesive layer 14, all the constituent parts are integrally formed to a 
solid structure, whereby the inner peripheral portion of the solid 
structure is reinforced to increase lamination strength thereof. 
Since adhesive is stored in the notches 13, the peel strength of the 
adhesive layer 14 of the first information recording media is increased. 
The first information recording media of the present insertion, since the 
portion between the disc substrate 2a, 2b and the flange portion 9 of hubs 
4 are bonded by means of adhesive, have high adhesion strength between the 
disc substrate 2a, 2b and hubs 4, and have a solid structure compared with 
the second information recording media of the present invention. 
When the adhesive layer 14 is formed between the flange portion 9 of hubs 4 
and the disc substrate 2a, 2b, according to the nature of the resin used, 
the birefrigence of the substrate 2a, 2b is apt to increase. However, in 
case that the cycloolefin random copolymer (i), the ring opening polymer 
(ii) or a hydrogenated polymer resulting from the hydrogenation of said 
ring opening polymer (ii) is used for the materials of the resin 
substrates 1a, 1b, the increase of the birefrigence is low and dose not 
become practical problems. 
In the first information recording media of the present invention, the 
material used for the adhesive layer 14 is not limited, and may be the 
known adhesives which have been used for the manufacture of the 
information recording media. 
Concrete examples of the material used for the information recording media 
include heat curable adhesives such as amino resin, phenol resin, 
resorcinol resin, xylene resin, furan resin, epoxy resin, polyisocyanate 
resin, unsaturated polyester and acrylic resin; thermoplastic adhesives 
such as vinyl acetate type adhesive, acrylic type adhesive, ethylene type 
adhesive, polyamide, polyester and polyurethane; rubber type adhesives 
such as those of polychloroprene type, nitrile rubber type, reclaimed 
rubber type, SBR type and natural rubber type; pressure-sensitive 
adhesives such as those of rubber type, acrylic type, emulsion type, 
oligomer type, hot-melt type, heat curable type and moisture-absorption 
curable type; hot-melt adhesives such as those of water soluble type, high 
temperature type, reaction type and pressure-sensitive type; instantaneous 
adhesives such as that of cyanoacrylate type; and adhesives cured in the 
anearobic condition. Furthermore, the preferred examples include 
UV-curable adhesives of acrylate type or epoxy type. 
However, in consideration with adhesion in the beginning of manufacturing 
and in humid condition, it is most preferred that a photo-curable compound 
comprising the specific ingredient (A)-(D), which is cured by activating 
energy ray, is used for the adhesive. This adhesive preferably used in the 
first information recording media of the present invention is illustrated 
below. 
Then, the second information recording media of the present invention is 
illustrated with reference to FIG. 10. FIGS. 10 is a sectional view 
showing an embodiment of the information recording disc according to the 
second information recording media of the present invention. As shown in 
FIG. 10, the information recording discs 1 comprise the constituent parts 
as same as those of the first information recording media, and are 
constructed by filling a space between the inner peripheral surface of the 
center hole 3 of each of the aforementioned substrates 2a, 2b, and the 
outer peripheral sueface of the insertion portion 8 of the hub 4, the 
inside of the notch 13 of each of the hubs 4, and a space between the two 
hubs 4 with the specific adhesive composition of the present invention and 
thereby to combine integrally these components with one another. 
In the information recording discs 1, since the hubs 4 are in contact with 
the disc substrates 2a and 2b at the flange portions 9 of said hubs 4, and 
the hubs 4 themselves are bonded to each other by means of the adhesive 
layer 14 while the hubs 4 are bonded with the disc substrates 2a and 2b at 
the insertion portion 8 by means of adhesive layer 14, all the constituent 
parts are integrally formed to a solid structure, whereby the inner 
peripheral portion of the solid structure is reinforced to increase 
lamination strength thereof. 
Since adhesive is cured in the condition wherein a part of the adhesive is 
stored in the notches 13, the peel strength of the adhesive layer 14 is 
increased. 
The adhesive, which is preferably used in the first information recording 
media and should be used in the second information recording media of the 
present invention, contains the aforementioned energy photo-curable 
composition cured by activation energy ray comprises 
(A) an epoxy resin, 
(B) a compound selected from the group consisting of sulfonium salts and 
cyclopentadienyl iron compounds, 
(C) a compound selected from the group consisting of acrylates, 
methacrylates and olygomers thereof, and 
(D) an organic peroxide. 
Preferable as the epoxy resin (A) to be contained in the compositions used 
as the adhesives of the present invention are, for example, compounds 
having in the molecule more than two epoxy groups, and particularly 
preferred are aliphatic or alicyclic epoxy compounds. 
Such epoxy resins (B) as mentioned include, for example, a glycidyl ether 
type epoxy resin of a polyphenol compound such as bisphenol A, bisphenol F 
and 1,1,2,2-tetrakis(4'-hydroxyphenyl)ethan; a glycidyl ether type epoxy 
resin of a polyhydric phenol such as catechol, resolcine, hydroquinone and 
fuloroglucine; a glycidyl ether type epoxy resin of polyhydric alcohol 
such as ethylene glycol, butanediol, glycerol, erythritol and 
polyoxyalkylene glycol; a novolak epoxy resin; a cycloolefin type epoxy 
resin such as vinylcyclohexene dioxid, limonene dioxide and 
dicyclopentadiene dioxide, ; a polyglycidyl type ester epoxy resin which 
is an ester condensate of a polycarboxylic acid such as phthalic acid and 
cyclohexane-1,2-dicarboxylic acid; and polyglycidyl amine epoxy type 
resin. Of these epoxy resins as exemplified above, preferred are glycidyl 
ether epoxy type resins of polyphenol compounds or epoxy-novolac epoxy 
resins. Of the glycidyl ether epoxy resins, preferred are glycidyl ether 
type epoxy resin of bisphenol A or bisphenol F, and particularly preferred 
are glycidyl ether type epoxy resin of bisphenol A. 
The composition used as the adhesive of the present invention contains (B) 
a compound selected from the group consisting of sulfonium salts and 
cyclopentadienyl iron compounds. Preferable as the sulfonium salts are 
triaryl sulfonium salts, and particularly preferred are triphenyl 
sulfonium salts. Preferable anion of these sulfonium salts is 
AsF.sub.6.sup.- or BF.sub.4.sup.-. 
The sulfonium salts include concretely, for example, triphenyl sulfonium 
salt of the following formula 
##STR6## 
tri-(4-methylphenyl)sulfonium salt of the following formula 
##STR7## 
and tri-(4-methoxyphenyl)sulfonium salt of the following formula. 
##STR8## 
The cyclopentadienyl iron compounds include those having in the molecule 
two cyclopentadienyl groups, or those having in the molecule one 
cyclopentadienyl group and one aromatic group such as phenyl or 
isopropylphenyl. Of these compounds as illustrated above, preferred are 
those having in the molecule one cyclopentadienyl group and one aromatic 
group, and particularly preferred are those having in the molecule 
cyclopentadienyl group and isopropylphenyl group. 
Such particularly preferred cyclopentadienyl iron compounds as mentioned 
above include, for example, cyclopentadienyl isopropylphenyl iron (II) 
salt of the following formula. 
##STR9## 
As the compound (B) contained in the composition used as the adhesive 
composition of the present invention, the sulfonium salts and 
cyclopentadienyl iron compounds may be used either singly or in 
combination. Particularly preferable as the compound (B) is the 
cyclopentadienylisopropylphenyl iron (II) salt represented the 
above-mentioned formula. 
Acrylates or methacrylates as the component (C) contained in the 
composition used as the adhesive of the present invention are esters of 
hydroxy compounds or polyhydroxy compounds with acrylic acid or 
methacrylic acid. Such esters include, for example, those of monovalent 
aliphatic alcohol of 1 to 20 carbon atoms, alicyclic alcohol of 1 to 30 
carbon atoms, divalent aliphatic alcohol of 1 to 20 carbon atoms, divalent 
alicyclic alcohol of 1 to 20 carbon atoms, trivalent aliphatic alcohol of 
1 to 20 carbon atoms and hydroxy compounds such as polyester having a 
terminal hydroxyl group with acrylic acid or methacrylic acid. 
Concrete examples of the component (C) include, for example, methyl 
acrylate, methyl methacrylate, ethyl acrylate, ethl methacrylate, butyl 
acrylate, butyl methacrylate; cyclohexyl acrylate, norbolnyl acrylate, 
dicyclopentanyl acrylate, dicyclopentenyl acrylate, isobornyl acrylate and 
cyclohexyl methacrylate, and cyclohexyl methacrylate, polyesters 
represented by the following formula [V] and terminated by acrylic acids, 
EQU A(M--L).sub.p M--A [V] 
wherein A is acrylic acid residue, M is divalent aliphatic or alicyclic 
alcohol residue, L is dibasic acid residue, and p is a positive number, 
and polyesters represented by the following formula [VI], in which both 
ends and hydroxyl group in the chain have been blockaded by acrylic acid. 
##STR10## 
wherein B is acrylic acid residue, X is polyhydric aliphatic or alicyclic 
alcohol residue (exhibiting more than three valences), Y is polybasic acid 
residue (exhibiting more than two valences), and q is a positive number. 
Further examples of the component (C) are as shown below. 
Some of these acrylates or methacrylates as exemplified above are disclosed 
in Japanese Patent L-O-P Publn. No. 136529/1986. These acrylates or 
methacrylates may be used as oligomers prepared by pre-polymerization 
according to the method, per se, known. 
Of the compounds exemplified above as the component (C), preferred are 
alkyl esters of acrylic acid or methacrylic acid, the mixtures of 
compounds of the above-mentioned formula [V] and the compounds of the 
above-mentioned formula [VI]. 
##STR11## 
wherein R represents methyl, ethyl, propyl, isobutyl, hexyl, cyclohexyl, 
stearyl bromo, fluoro, ethylidene, propylidene and isopropylidene. 
##STR12## 
wherein R represents methyl, ethyl, propyl, isobutyl, hexyl, cyclohexyl, 
stearyl bromo, fluoro, ethylidene, propylidene and isopropylidene. 
##STR13## 
wherein R represents methyl, ethyl, propyl, isobutyl, hexyl, cyclohexyl, 
stearyl bromo, fluoro, ethylidene, propylidene and isopropylidene. 
##STR14## 
wherein R represents methyl, ethyl, propyl, isobutyl, hexyl, cyclohexyl, 
stearyl bromo, fluoro, ethylidene, propylidene and isopropylidene. 
##STR15## 
wherein R represents methyl, ethyl, propyl, isobutyl, hexyl, cyclohexyl, 
stearyl bromo, fluoro, ethylidene, propylidene and isopropylidene. 
##STR16## 
wherein R and R' represents methyl, ethyl, propyl, isobutyl, hexyl, 
cyclohexyl, stearyl bromo, fluoro, ethylidene, propylidene and 
isopropylidene. 
##STR17## 
The organic peroxide (D) includes, for example, benzoyl peroxide, 
dichlorobenzoyl peroxide, cumene hydroperoxide, dicumyl peroxide, 
di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxide benzoate)hexyne-3, 
1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl 
peracetate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-buthl perbenzoate, 
tert-buthyl perphenyl acetate, tert-butyl perisobutylate, tert-butyl 
per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate and tert-butyl 
perdiethyl acetate. 
Of these peroxides as exemplified above, preferred are dialkyl peroxides 
such as dicumyl peroxide, di-tert-butyl peroxide, 
2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and 
1,4-bis(tert-butylperoxyisopropyl)benzene and 
2,5-dimethyl-2,5-di(tert-butylperoxy) hexyane. 
The composition used as the adhesive of the present invention comprises the 
above-mentioned components (A), (B), (C) and (D) as essential ingredients, 
and contains, based on 100 parts by weight of the component (A), 1 to 10 
parts by weight, preferably 2 to 5 parts by weight of the component (B), 
15 to 35 parts by weight, preferably 20 to 30 parts by weight of the 
component (C), and 1 to 10 parts by weight, preferably 2 to 5 parts by 
weight of the component (D). 
The above-mentioned composition used as the adhesive of the present 
invention does not necessarily contain a photopolymerization assistant, 
but it is desirable to use the photopolymerization assistant when the 
composition is cured by irradiation with an activation energy ray of a 
relatively low energy such as UV. In that case, various known 
photopolymerization assistants may be used, such as those forming radicals 
by decomposition on irradiation with UV or those forming radicals by 
elimination of hydrogen on irradiation with UV. Concrete examples of such 
photopolymerization assistants include benzoin or ether thereof such as 
benzoin or the ether thereof such as benzoin, benzoin methyl ether, 
benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether; 
benzophenone compound such as p-chlorobenzophenone, p-methoxybenzophenone; 
benzyl compound such as benzyl, benzyl dimethyl ketal; hydroxyalkylphenyl 
ketone compound such as 
1-(4-isopropylphenyl)-2-hydroxy-2-methyl-1-propanone, 
1-phenyl-2-hydroxy-2-methyl-1-propanone, 
1-(4-tert-butylphenyl)-2-hydroxy-2-methyl-1-propane. 
Further, sensitizers which may be used in the present invention include 
hydrocarbons such as anthracene, chrysene, phenanthrene; nitro compounds 
such as p-dinitrobenzene, p-nitoroaniline, 1,3,5-trinitrobenzene, 
p-nitrodiphenyl; amino compounds such as n-butylamine, di-n-butylamine, 
triethylamine, diethylaminoethy methacrylate, p-nitroamiline, 
N-acetyl-4-nitro-1-naphthylamine; phenol compounds such as phenol, 
2,4-dinitrophenol, 2,4,5-torinitrophenol; kenones such as benzaldehyde, 
9-anthra aldehyde, acetophenone, benzophenone, dibenzal acetone, benzil, 
p,p'-diaminobenzophenone, p,p'-tetramethyldiaminobenzophenone; quinones 
such as anthraquinone, 1,2-benzoanthraqionone, benzoquinone, 
1,2-naphthoquinone, 1,4-naphthoquinone; anthrones such as anthrone, 
1,9-benzoanthrone, 6-phenyl-1,9-benzoanthrone, 3-phenyl-1,9-benzoanthrone, 
2-keto-3-aza-1,9-benzoanthrone, 3-methyl-1,3-diaza-1,9-benzoanthrone. 
Basically, the above-mentioned adhesive compositions of the present 
invention are free from solvents, but may be incorporated with the 
solvents and further with such additives as may be used in solvent-free 
adhesives, such as reactive diluents, thickeners, anti-sag agents, 
stabilizers and plasticizers. 
The information recording medium of the present invention, to be obtained 
by using the adhesives illustrated above, are manufactured by inserting 
the portions 8 of the hubs 4 into the center hole 3 of the laminated 
substrate discs 2a, 2b from both sides thereof, charging the 
above-illustrated adhesive into the spaces aformentioned and anchoring 
them to each other by providing U.V. ray thereto. 
In the information recoring discs 1 thus manufactured, since the 
photo-curable compound to be cured by activating energy ray is used for 
the adhesive, the recording media has the adhesive portions which is cured 
immediately and have excellent adhesion in the beginning of curing and in 
humid condition. 
As used in the present invention, the term information recording medium is 
intended to include all the media recording information in the recording 
layer thereof, such as optical discs and flexible optical discs. 
EFFECT OF THE INVENTION 
According to the first information recording medium of the present 
invention, since the hubs are bonded with the disc substrates at the 
insertion portion and the flange portion by means of the adhesive layer, 
the hubs themselves are bonded to each other by means of the adhesive 
layer and the adhesive is stored in the notches, there can be provided the 
information recording media having the structure easy to assemble and 
capable of obtaining high adhesion of the adhesive layer. Furthermore, in 
case that the specific photo-curable compound comprisingthe specific 
ingredient (A)-(D), which is cured by activating energy ray is used for 
the adhesive layer, there can be provided the information recording layer 
having the adhesive layer which is excellent in initial adhesive 
properties and also excellent in humidity resistant adhesive properties. 
According to the second information recording medium of the present 
invention, the hubs are in contact firmly with the disc substrates at the 
insertion portion, the hubs bonded with the disc substrates at the 
insertion portion of each hub and are bonded to each other and the 
adhesive stored in the notch provided in each hubs, and further, the 
specific photo-curable compound comprising the specific ingredient 
(A)-(D), which is cured by activating energy ray is used for the adhesive, 
hence there can be provided the information recording media having the 
structure easy to assemble and capable of obtaining high adhesion of the 
adhesive layer and having the adhesive layer excellent in initial adhesive 
properties and also excellent in humidity resistant adhesive properties. 
EXAMPLES 
Given below are brief comments on the test examples that follow. 
In these examples, the information recording medium was evaluated by 
comparison between the results of adhesion strength obtained before and 
after the moisture resistance test carried out by maintaining the 
information recording medium 1 for 200 hours in a thermo-hygrostat kept at 
70.degree. C. and 85% RH. 
The adhesion strength obtained in the above test was determined according 
to the following procedure by using a test equipment (trade name of 
Intesco 205). That is, a rod of this test equipment, which can move 
perpendicularly to the surface of the information recording media, was 
inserted into the center hole of the hub and fixed thereto, and then the 
rod was allowed to move at a constant rate (20 mm/min.) so as to push the 
hubs, and then the maximum stress [Kgf] (which is the stress when the 
adhering portion is destroyed) was measured as the adhesion strength. 
EXAMPLE 1 
Transparent resin substrates 1a and 1b, and hub main bodies 10 were formed 
by injection molding into their respective desired shapes using a random 
copolymer (the ethylene component of 59 mol % as mesured by .sup.13 C-NMR 
analysis, an intrinsic viscosity [.sqroot.] of 0.42 dl/g, and a glass 
transition temperature of 136.degree. C. of ethylene and polycycloolefin, 
i.e. tetracyclo[4.4.0.1.sup.2.5.1.sup.7.10 ]-3-dodecene (structural 
formula 
##STR18## 
hereinagter abbreviated to TCD). The substrates 1a and 1b, and hub main 
bodies 10 were provided with recording layer 1c and 1d composed of 
Tb-Fe-Co alloy thin film, and metallic plates 11, respectively, to form 
disc substrates 2a and 2b, and hubs 4. 
On one hand, an photo-curable composition cured by an activating energy ray 
as an adhesive was prepared by adding 2 parts by weight of 
cyclopentadienyl isopropylphenyl iron (II) salt (a product of Ciba-Geigy), 
0.25 part by weight of anthracene (a product of Wako Junyaku K. K.) and 
3.1 parts by weight of cumene hydroperoxide (a 70% product of Kayaku Noure 
K. K.) to 100 parts by weight of a blend of 80 parts by weight of 
bisphenol A type epoxy resin (EPOMIK.R 140, a product of Mitsui 
Petrochemical Ind. Co., Ltd.) and acrylic monomers and oligomers (ALONIX, 
M-5700, M-6100, M-6300 and M-8030, products of Toa Gosei Chemical Ind. 
Co., Ltd) of M-5700, M-6100, M-6300 and M-8030 in amounts of 7 parts by 
weight, 5 parts by weight, 3 parts by weight and 5 parts by weight, 
respectively. The composition thus prepared was irradiated for 15 seconds 
with ultraviolet rays at a irradiance of 160 mW/cm.sup.2 to form an 
adhesive layer between the flange portion 9 of the bubs 4 and the 
above-mentioned disc substrates 2a, 2b, between the inner perioheral 
surface of said center hole of above mentioned disc substrate 2a, 2b and 
the insertion portions 8 of hubs 4, between the hubs 4, and in notches 13, 
whereby the information recording medium 1 as shown in FIG. 2 was 
obtained. 
An adhesion strength of the information recording medium 1 thus obtained 
was determined by the above-mentioned procedure. Results obtained are 
shown in Table 1. 
EXAMPLES 2 and 3 
In the Examples 2, disc substrates 2a and 2b were prepared by using 
transparent resin substrates 1a and 1b formed from polycarbonate (a 
product sold under a trade name AD-5503 by Teijin Kasei K. K.), whereas 
said disc substrates were prepared by using said resin substrates formed 
from polymethyl pentene type polymer (a product soled under a registered 
trade name TPX RT18 by Mitsui petrochemical Ind. Co., Ltd.) in Example 3. 
Following the same procedure as described in Example 1, the information 
recording medium 1 was obtained in each Examples. An adhesion strength of 
each information recording medium 1 was determined in the same manner as 
in Example 1. Results obtained are shown in Table 3. 
EXAMPLE 4 
There were synthesized a copolymer (A) of ethylene and TCD (the ethylene 
content of 59 mol % as measured by .sup.13 C-NMR analysis, an intrinsic 
viscosity [.eta.] of 0.42 dl/g as measured in decaline at 135.degree. C., 
and TMA of 154.degree. C.), and a copolymer (B) of ethylene and TCD (the 
ethylene content of 89 mol % as measured by .sup.13 C-NMR analysis, an 
intrinsic viscosity [.eta.] of 0.44 dl/g as measured in decaline at 
135.degree. C., and TMA of 39.degree. C.). 
The information recording medium 1 was prepared by repeating Example 1 
except that transparent resin substrates 1a and 1b were prepared by using 
a blend of the above-mentioned copolymers (A) and (B) in the (A)/(B) 
weight ratio of 100/1.2. 
An adhesion strength of each information recording medium 1 was determined 
in the same manner as in Example 1. Results obtained are shown in Table 1. 
EXAMPLE 5 
Example 1 was repeated except that the adhesive composition was formed 
between the inner peripheral surface of said center hole of the 
above-mentioned disc substrates 2a, 2b and the insertion portions 8 of 
hubs 4, between the hubs 4, and in notches 13, whereby the information 
recording medium 1 as shown in FIG. 10 was obtained. 
An adhesion strength of each information recording medium 1 was determined 
in the same manner as in Example 1. Results obtained are shown in Table 1. 
EXAMPLES 6-7 
Examples 2 and 3 was repeated except that the adhesive composition was 
formed between the inner peripheral surface of said center hole of the 
above-mentioned disc substrates 2a, 2b and the insertion portions 8 of 
hubs 4, between the hubs 4, and in notches 13, whereby the information 
recording medium 1 as shown in FIG. 10 was obtained. 
An adhesion strength of each information recording medium 1 was determined 
in the same manner as in Example 1. Results obtained are shown in Table 1. 
EXAMPLES 8 
Example 4 was repeated except that the adhesive composition was formed 
between the inner peripheral surface of said center hole of the 
above-mentioned disc substrates 2a, 2b and the insertion portions 8 of 
hubs 4, between the hubs 4, and in notches 13, whereby the information 
recording medium 1 as shown in FIG. 10 was obtained. 
An adhesion strength of each information recording medium 1 was determined 
in the same manner as in Example 1. Results obtained are shown in Table 1. 
COMATIVE EXAMPLES 1 and 2 
Example 5 was repeated except that the adhesive composition used in 
Comparative Example 1 contained no acrylic monomer and no oligomer, and 
the adhesive composition used in Comparative Example 2 contained no cumene 
hydroperoxide. 
An adhesion strength of each information recording medium 1 was determined 
in the same manner as in Example 1. Results obtained are shown in Table 1. 
TABLE 1 
______________________________________ 
Adhesion Strength (kgf) 
Before moisture 
After moisture 
resistance test 
resistance test 
______________________________________ 
Example 1 &gt;15 15 
Example 2 &gt;15 15 
Example 3 &gt;15 15 
Example 4 &gt;15 15 
Example 5 8-10 8-10 
Example 6 8-10 8-10 
Example 7 8-10 8-10 
Example 8 8-10 8-10 
Compar. Ex. 1 
5 2 
Compar. Ex. 2 
4 2 
______________________________________