JPS62264456A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To provide a titled medium having excellent mechanical and optical properties and resistance to heat, moisture and weather by sticking two sheets of substrates to each other by a reactive hot melt adhesive agent prepd. by incorporating an urethane prepolymer having isocyanate groups at both terminals into a tackiness imparting resin. CONSTITUTION:The recording media 4 formed with recording layers 2 and protective films covering the same on two sheets of the transparent substrate 1 are joined to one body on the protective film 3 side by the adhesive agent 5. The adhesive agent t is constituted by the reactive hot melt adhesive agent prepd. by incorporating the urethane prepolymer having the isocyanate groups at both terminals into the tackiness imparting resin at a prescribed ratio. Said adhesive agent contains 30-69.8wt% urethane prepolymer, 30-55wt% tackiness imparting resin of at least one kind among a cumarone resin or cumarone-indene resin (a), terpene-phenolic resin (b), specific rosin deriv. (c) and styrene resin (d), and 0.2-25wt% arom. oil.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is particularly applicable to optical disks, magneto-optical disks, etc., which have a structure in which two substrates are bonded together and which perform recording or reading using light such as a laser beam. This relates to optical information recording media.

[Summary of the invention]

The present invention is an optical information recording medium that has a structure in which two substrates are bonded together and records or reads data by irradiation with light such as a laser beam. An optical information recording medium that is bonded together using a reactive hot melt adhesive containing a urethane polymer having an isocyanate group has excellent mechanical and optical properties such as heat resistance, moisture resistance, and weather resistance, and therefore has excellent aging resistance. Configure.

[Conventional technology]

In an optical information recording medium that records or reads information by laser beam irradiation, two transparent sheets each have a recording layer on one side and a protective film made of an ultraviolet curable resin film covering this. A structure in which substrates are bonded to each other with the side having the recording layer facing inside is widely used.

In such an optical information recording medium, the adhesive used to bond both substrates together has a large effect on the characteristics of the recording medium. In other words, with this type of adhesive, the shearing force is large and the bonded side substrates do not warp (
It is required to have excellent mechanical, chemical, and optical heat resistance, moisture resistance, and weather resistance, and to not cause any deterioration in reliability over time of properties as an optical information recording medium.

Incidentally, existing adhesives include: (i) Adhesives based on natural products such as proteins, carbohydrates, and polysaccharides; (ii) Inorganic adhesives based on melting type and chemical reaction type;
iii) Solution-type, emulsion-type, and melt-type thermoplastic adhesives (iv) If condensation type 1 condensation reaction type and addition reaction type thermosetting or room-temperature curable adhesives (v) Rubber-type adhesives Adhesive (vi) Pressure-sensitive adhesive (vi) Anaerobic cyanoacrylate adhesive (vi)
i) Ultraviolet rays or photocurable adhesives, etc. may be mentioned.

Among these adhesives, the above (i) and (ii) have adhesive properties as adhesives used in the optical information recording medium mentioned above.
It is unsuitable in terms of stability and other aspects, and in fact, the above (i
It will be selected from among ii) to (vii). However, in the above-mentioned optical information recording medium, it is necessary to consider the influence of the adhesive on the protective film that serves as the adhesive surface, and the adhesive is a solvent (containing water) adhesive ((iii) above). ) solution type adhesive, above (iv
) and (v) adhesives), monomer polyaddition, and condensation type adhesives (the above (vii) and (vii) adhesives), the solvent or unreacted additive 1 or unreacted main ingredient, curing agent, etc. This may cause the protective film to swell or create pinholes in the protective film, reducing the protective function of the recording layer, causing deterioration and deformation of the recording layer, and in some cases, deforming the substrate. When the recording layer or the substrate undergoes deterioration or deformation in this way, noise components increase, and as a result, the bit error rate increases.

On the other hand, with the above-mentioned melting adhesive (iii), even after the information recording medium is manufactured by applying it at a temperature higher than its melting point or by bonding the side substrates with this adhesive, for example, information on the medium cannot be stored. In recording, for example, when recording is performed by alloying or changing optical characteristics in the recording layer by heating with laser light irradiation, the adhesive also melts or softens, causing deformation or detachment of the side substrate. This may cause other inconveniences. In addition, the above (v
The adhesive i) also has problems such as lack of reliability in adhesive strength.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned problems, ensures that two substrates each having a recording layer and a protective film covering the recording layer are bonded on the protective film side, has excellent heat resistance, and has excellent mechanical, chemical, and optical properties. To provide an optical information recording medium that exhibits excellent characteristics over a long period of time and is highly reliable.

[Means for solving problems]

As shown in FIG. 1, the present invention consists of two transparent substrates (1).
A recording layer (2) and a recording medium (4) each covered with a protective film (3) are formed on top of the recording layer (2).
) with a thickness of, for example, 5 on the protective film (3) side.
They are bonded together using an adhesive (5) with a thickness of 0 to 100 μm. The transparent substrate (1) is made of, for example, a glass substrate, polycarbonate (hereinafter abbreviated as PC), or the like.

The recording layer (2) of each medium (4) is composed of a single layer or a multilayer structure, each of which is alloyed by irradiation with laser light modulated according to the information, resulting in a change in light transmittance. .

The protective film (3) is made of, for example, an ultraviolet curing resin.

The adhesive (5) is composed of a reactive real-melt adhesive in which a predetermined amount of a urethane prepolymer having isocyanate groups at both ends is mixed into a tackifying resin. This adhesive (5) contains 30 to 69.8% by weight of a urethane prepolymer having isocyanate groups at both ends, sulcoumarone resin or coumaron-indene resin (al), and terpene-phenol resin ( b), a rosin derivative (C) obtained by eliminating the active hydrogen of abietic acid type rosin by esterification etc. or eliminating some or all of the double bonds; Tackifying resin 30-55
% by weight and 0.2 to 25 M% of aromatic oil.

Here, as the urethane prepolymer used, for example, a diisocyanate compound consisting of a single substance such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, 1,5-naphthylene diisocyanate, or a mixture thereof. and ethylene glycol, propylene glycol, 1.4
- Prepolymers obtained by addition polymerization of monomers or pure polymers of butanediol, 1,4-butynediol, and diol compounds consisting of monomers or mixtures of polytetramethylene ether, glycol, etc. It will be done.

The viscosity of this prepolymer is preferably 100,000 cps or more at 25°C. This is because when a 100,000 cps ungrooved prepolymer is used, the initial cohesive strength of the resulting adhesive tends to be weak.

Further, the NCO equivalent of the prepolymer is preferably 5% by weight or less. This is because if more than 5% by weight of the prepolymer is used, the adhesive tends to become brittle.

The reason why isocyanate groups are required at both ends of the molecule is that after the adhesive melts and solidifies, the moisture in the atmosphere reacts with the isocyanate groups in the adhesive, forming long chains and increasing the molecular weight. The aim is to strengthen the cohesive force of It should be noted that a urethane prepolymer having an isocyanate group at only one end of the molecule is not suitable because it does not have a long chain and the cohesive force of the adhesive is not sufficiently strong.

If the amount of urethane prepolymer is too small, the reaction with moisture in the air will be insufficient, and sufficient heat resistance strength will not be developed.
After bonding between the media (4), the adhesive becomes hard and brittle. On the other hand, if the amount is too large, the initial cohesive force will be weak and the adhesive force immediately after bonding will be weak. Therefore, it is desired that the adhesive contains 30 to 69.8 ffi%, preferably 45 to 69.8 ffi%.

The tackifying resin used as the adhesive used in the present invention needs to be compatible with the urethane prepolymer, and most or all of the isocyanate groups in the urethane prepolymer (commercial active temperature of 60 to 140°C) are required to be compatible with the urethane prepolymer. It is preferable that the adhesive has a softening temperature of , and the following are selected as those that have the effect of improving the instantaneous adhesion of the adhesive.

Coumaron resin or coumaron-indene resin (AL) are both made from solvent naphtha contained in light oil in coke oven gas (tar), and the former is a pure combination of coumaron, coumaron homologs, or coumaron derivatives, and the latter is primarily a copolymer of coumaron and indene.

Terpene-phenol resin (BL refers to a thermoplastic resin copolymerized with terpenes and phenols, preferably with a terpene/phenol molar ratio of 10 to 3.0. Preferred examples of terpenes include carbon Examples include dozens of monoterpenes, such as α-pinene, β-pinene, camphein, hydrogenated products thereof, and diterpenes having 20 carbon atoms.

Examples of rosin derivatives (C) obtained by eliminating the active hydrogen of 7-bithienoic acid type rosin by esterification etc. or by partially or completely eliminating double bonds include hydrogenated rosin, hydrogenated rosin glycerin ester, water Examples include added rosin pentaefthritol, disproportionated rosin, polymerized rosin, etc., and hydrogenated rosin, hydrogenated rosin glycerin ester, etc. are preferably used.

The styrene resin (d) is a hydrocarbon resin such as a low molecular weight styrene resin obtained by polymerizing styrene, α-methylstyrene, cumene, etc., and includes hydrogenated resins thereof. The styrene-based tackifying resin is commercially available (for example, Picotex, etc.) and can be obtained.

If the content of these tackifying resins is too low, the urethane prepolymer will not be able to impart strong adhesive '#2 concentration, resulting in weak instant adhesive properties, while if it is too high, the adhesive will become brittle and strong. 30 because it will not be possible to obtain adhesive strength.
~50 weight 9%.

In addition, aromatic oil refers to the aromatic components of oils that are widely known as rubber softeners, such as process oils, extender oils, and softners, and are hydrocarbons with 2 to 6 carbon atoms. Those in which 2 to 3 Hensen rings or alkylbenzene rings are bonded to the residue are preferable, and specific examples include 1-xylyl 1,3 diphenylbutane, bis(αmethylhensen)xylene, 1-xylyl 1
-(3-αmethylbenzene phenyl)ethane and the like.

If the content of aromatic oil is too small, the low viscosity, that is, the low-temperature application workability, which is a major feature of the present invention, will be impaired.
On the other hand, if the amount is too large, the cohesive force decreases and the initial adhesive strength becomes weak, so the amount is set at 0.2 to 25% by weight, preferably 6 to 20% by weight.

Non-aromatic oils, such as naphthenic oils and paraffin oils, have poor compatibility with the urethane prepolymer used in the present invention, so it is difficult to use them alone, but they can be used in combination with aromatic oils. It is possible.

In addition to the above-mentioned urethane prepolymer, tackifying resin, and aromatic oil, the adhesive (5) also includes polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethylene acrylate copolymer, and atatactic polyester. Base resins in general hot melt adhesives such as propylene; Tackifier resins such as terpene resins, alicyclic polyolefins and hydrogenated products thereof; Waxes such as low molecular weight polyethylene, microcrystalline waxes, and polymerized waxes;
Dioctyl phthalate, dibutyl phthalate, τf'P
Plasticizers such as these may be contained within the range that can achieve the purpose of the adhesive in the medium of the present invention.

The adhesive (5) used in the present invention has a temperature of 70°C to i o o'
Although it can be applied at a low temperature of less than 100°C, in some cases it may be applied at a temperature of 100 to 160°C, for example, about 110°C.

Various hot melt coaters and hot melt applicators can be employed as the device for applying the adhesive (5) to the medium (4), and it is particularly preferable to use a roll coater.

[Effect]

According to the optical information recording medium according to the present invention, the adhesive (5) is a reactive hot melt adhesive at a relatively low temperature (10
It has a low viscosity even at temperatures below 0°C (for example, around 90°C), so it has excellent low-temperature application workability, and has instant adhesive properties and heat-resistant adhesive properties that are equal to or better than conventional hot melt adhesives.
Furthermore, it has excellent viscosity stability when exposed to the air, such as when coating with a single roll coater, and has excellent storage stability when stored in a nearly sealed container. It has the advantage that the practical strength development time is short.

The optical information recording medium according to the present invention, which is composed of a pair of media (4) bonded together using the adhesive (5), has a water-absorbing property in the adhesive (5). The recording layer (2) can be held stably for a long period of time, and its optical properties can be stabilized. This makes it possible to obtain a highly reliable optical information recording medium that has excellent heat resistance and moisture resistance, excellent stability of mechanical and optical properties, and excellent change over time.

〔Example〕

Example 1 An adhesive having the following composition was used. In this specification, the term "parts" simply means "parts by weight."

were heated and kneaded at 120°C to produce an adhesive. Is the urethane prepolymer here? Urethane prepolymer having isocyanate groups at both ends obtained by addition polymerization of IDI (diphenylmethane diisocyanate) and polypropylene glycol (NCO group content: 1% by mass)
The terpene phenol resin used was a terpene phenol resin obtained by copolymerizing terpene with α-pinene as its main component and phenol, and the aromatic oil was 1-xylyl 1°3 diphenylbutane, bis(α-methyl Benzene)xylene and lxylyl 1-(3-αmethylbenzene phenyl)ethane were used as main components.

The properties and performance of this adhesive were as shown in Table 1.

Table 1 In addition, each property was measured by the following method.

l) The adhesive obtained by cross-mixing with a uniform melt viscosity is heated to 90°C, and B
It was measured using an M-type viscometer at No. 40-ter.

2) A polypropylene plate bonded with a heating and softening point adhesive was measured in accordance with JIS-6844 using an automatic heating hot air circulation incubator.

3) Storage Stability 200 g of the sample was sealed in a synthetic resin bag whose surface was laminated with aluminum, and left in an oven at 90° C., and the storage stability was determined by the rate of increase in viscosity. That is, a case where the viscosity was within twice the initial value was considered to be a pass, and the period was expressed.

4) Viscosity stability Changes in viscosity after 4 and 8 hours were checked according to melt viscosity measurement.

5) Polypropylene plates bonded together using a reaction rate adhesive using the method described in 8) were cured under conditions of 20° C. and 60% humidity (R1+), and the time required to obtain practical strength was measured.

6) Initial cohesive force (shear adhesive force) Polypropylene plates immediately after being bonded together using adhesive using the method in 8) were heated at 100°C in a constant temperature and humidity room at 20°C and 60% humidity.
The time required for the adhesive surface to peel off and fall was measured and expressed in minutes.

7) Adhesive strength Each material bonded by the method of 8) with adhesive at 20°C.
x6i After being left in a constant temperature and humidity chamber at 60% degrees for 12 hours, it was kept at the desired measurement temperature for 2 hours and the shear peeling strength was 25 mm/min using UTM-I [Type 1 Tensilon, tensile speed 25 mm/min].
25 mm) was measured. In addition, P/P indicates the case where polypropylene plates are bonded together, Al1Al indicates the case where aluminum plates are bonded together, and Al/1 indicates the case where an aluminum plate and a polypropylene plate are bonded together.

8) A urethane prepolymer (NCO group content: 2% by weight) having isocyanate groups at both ends obtained by addition polymerizing compatible TDI (1-lylene diisocyanate) and propylene glycol and a tackifying resin are bonded together. The presence or absence of compatibility was determined by visually confirming whether or not the 9 components were uniformly mixed and dispersed by heating to a temperature higher than the softening temperature of the characterizing resin and kneading them. The polyurethane prepolymer and tackifying resin used in each example were both compatible.

9) Adhesive application method Use a roll coater set at 90°C to apply adhesive to each material at a coating thickness of 30 to 150 μm, and oven time 3.
Pressure bonding was performed at 0 seconds.

Using the above adhesive, two recording media (4) were bonded together to produce a desired optical information recording medium (6). Each recording medium (4) is made of three layers of antimony selenium, Sb2Se, and bismuth tellurium, on which recording is performed by changing optical properties by heating with laser beam irradiation, on a PC substrate (1) with a thickness of 1 mm and 2 mm, respectively. 11i2Te
3ZFAH with iJi and antimony selenium Sb2Se3
A recording layer (2) made of m-structure is deposited, and aluminum AI! is deposited on top of this. The structure was such that a protective film (3) of 10 μm thick made of an acrylic ultraviolet curable resin was coated with a spin cord through a reflective film made of a vapor-deposited film. The above-mentioned adhesives were melted by heating at 120°C on each of the adhesives (3) of each medium (4), and applied with a roll coater to a thickness of 50μ11. The coated sides are aligned and bonded together by applying a pressure of 0.6 kg/cj, and this is thermally annealed in an open room at 50°C to 70°C for 6 hours or more to form an optical information recording medium (6).
In this example, an optical disc was produced.

Example 2 An optical information recording medium, i.e., an optical disk, having a diameter of 30 cm was prepared in the same manner as in Example 1, except that the adhesive had the composition shown below, and the medium (4) was coated with a roll coater by heating and melting at 90°C. It was applied onto the protective film (3).

Comparative Example 1 An optical disc was manufactured by bonding two recording media having the same configuration as in Example 1 with a pressure-sensitive adhesive (adhesive) made of an acrylic copolymer.

Comparative Example 2 Two recording media having the same structure as in Example 1 were bonded together using a styrene-ethylene-butylene-styrene hot-melt adhesive to produce an optical disc.

The characteristics of the optical disc obtained in Example 2 described above were measured. First, we measured the so-called skew of this optical disc.This skew was measured by placing the optical disc in a cartridge at equiangularly spaced positions on the outer periphery of the optical disc, as usual. The disc is supported on the mold at four locations, and the warpage caused by the disc's own weight was measured while rotating the disc. A laser beam was scanned in the radial direction from the inner circumference to the outer circumference, and the warpage was measured using the reflected light. Figures 2 and 3 show the warpage in the radial direction (so-called radial skew) and the warpage, respectively. , shows the results of measuring warpage in the circumferential direction (so-called tangential skew), and based on these measurement methods, the above-mentioned Example 2 and Comparative Examples 1 and 2 were measured. In order to measure the reliability of each disk, the disks housed in the above-mentioned cartridge were placed horizontally in an atmosphere of 70°C and 90% relative humidity (RH), and the top and bottom sides of the disks were measured. Figure 4 shows the results of measuring the warpage of each curve (41).
a) and (41b) show the measurement results of each warp on the top and bottom surfaces in Example 2, and (42a) and (43a)
are the upper surfaces of Comparative Examples 1 and 2, (42b) and (4
3b) shows the measurement results of the warpage of each lower surface. Further, FIGS. 5 and 6 show the radial warpage and circumferential warpage of the optical disks of Example 2 and Comparative Examples 1 and 2, respectively, similar to those explained in FIGS. 2 and 3. Based on the measurement method of For example 1, the curve (
53) and (63) show the measurement results for Comparative Example 2. As is clear from these FIGS. 4 to 6, according to the optical disc according to the present invention, that is, the optical information recording medium (6), the
, even after 425 hours at 90% R11, 0.6
It is understood that the characteristics regarding warpage, which is specified as within 100 degrees, are sufficiently satisfied, and that it is more stable than the comparative example.

When the recording characteristics of the optical disc of Example 1 and the optical discs of Comparative Examples 1 and 2 were measured, it was found that the bit error rate at the initial stage was IX 10-5, and at 70°C and 90°C, which corresponds to 30 years later. 1 in an atmosphere of %RH
After 375 hours, the disc of the present invention with the reactive real-melt adhesive had a
X about 10-5, which was lower than that of the adhesive of Comparative Example 1. Similarly, regarding the C/N characteristics, the change in Example 2 was as small as that in Comparative Example 2, and it was found that the C/N characteristics of Example 2 were as small as those of Comparative Example 2. It was confirmed that the optical characteristics of the optical disc according to the invention were not impaired in any way.

Furthermore, for each of the optical discs of Example 2 and Comparative Examples 1 and 2 described above, the adhesive strength of both media (4) was measured. In this case, in order to eliminate measurement uncertainties due to peeling between the recording layer (2) and the substrate (1) or destruction within the recording layer (2), a protective film (3) with similar properties may be used. Each measurement was performed by bonding acrylic resin substrates exhibiting the following using an adhesive on each side.

In other words, the thickness of each cut to 25mm + width 1.2
Two acrylic disks each having a diameter of 5 mm were coated with 50 µm of the same reactive real-melt adhesive as in Example 2 on one side.
Sample A was prepared by heating and melting the film to a thickness of m at 90° C., coating it with a roll coater, and bonding. Similarly, each acrylic disk was coated with the adhesive used in Comparative Example 2 at 135°C to prepare Sample B. Shear peel strength (kg/
1 nch) is shown in FIG. 7. In the figure, curve (71) shows the measurement results for sample A treated at 20°C and 60% RH, and curve (72) shows the measurement results for sample A treated at 20°C and 60% RH.
Curve (73) shows similar measurement results at 75°C and 90% RH. Curve (74) also shows similar measurement results for sample B at 65° C. and 90% RH.

As is clear from a comparison of curves (71) to (73) and curve (74), the optical information recording medium (6) according to the present invention
) It can be seen that Sample A corresponding to Comparative Example 2 exhibits superior properties over time compared to Sample B corresponding to Comparative Example 2. In addition, these measurements were carried out at a tensile speed of 25 mm/min after the treatment time under each measurement condition had elapsed and the samples were allowed to stand at room temperature for 6 hours.

Furthermore, curves (81) and (82) in Figure 8 are the results of measuring the shear strength at a shear rate of 25 mm/min when the temperature was changed for Samples A and B, respectively, and in this case, for Sample B. Sample A was annealed at 60° C. for 6 hours under a pressure of 0.2 to 0.4 kg/−, and then cooled to room temperature. Sample A was treated at 50° C. and 90% RH for 124 hours.

Example 3 An optical information recording medium, that is, an optical disk was manufactured by the same procedure as in Example 2, but the adhesive had the following composition.

The optical disk thus obtained also exhibited optically and mechanically stable characteristics comparable to those of Example 2.

Examples 4 to 11 In place of the adhesive in Example 1, adhesives having compositions shown in Table 2 were used. However, urethane prepolymer (NG
O-containing 11. ! Takenate A-260 (41%)
(manufactured by Takeda Pharmaceutical), Mighty Ace G125 (manufactured by Yasuhara Resin) as a terpene-phenol copolymer, and Ester Gum H (manufactured by Arayo Kagaku!) as a hydrogenated rosin glycerin ester.
As the styrenic +1 oil, Picotex 100 (manufactured by Bercule) was used, and as the aromatic oil, the same product as in Example 1 was used.

Table 2 [Effects of the Invention] As is clear from the above, the present invention has excellent moisture resistance, heat resistance, and therefore weather resistance, less occurrence of warping, and excellent aging properties equivalent to 30 years. It is possible to construct a highly reliable optical information recording medium, and the benefits thereof are extremely large.

[Brief explanation of drawings]

FIG. 1 is an enlarged linear cross-sectional view of an example of the optical information recording medium according to the present invention, FIGS. 2 and 3 are actual measured values of each warp in the radial direction and the circumferential direction, and FIGS. 4 to 6 are FIGS. 7 and 8 are curve diagrams showing the measurement results of warpage of the present invention example and the comparative example, and FIGS. 7 and 8 are curve diagrams of measurement of shear strength. (6) is an optical information recording medium, (1) is its substrate, (2
) is the recording layer, (3) is the protective film, (4) is the recording medium, (5
) is an adhesive.

Claims (1)

[Claims] A pair of recording media in which a recording layer and a protective film thereof are sequentially formed on a transparent substrate are bonded together with an adhesive so that the protective films face each other, and the adhesive 1. An optical information recording medium comprising a reactive hot melt adhesive comprising a tackifier resin and a predetermined amount of a urethane prepolymer having isocyanate groups at both ends.