JPH10112080A - Production of information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an information recording medium which is flat and satisfactory in recording and reproducing characteristics by pressurlizingly sticking two sheets of optical recording substrates while making magnitudes of warpages of them adequate and positioning directions of the warpages of them in specific directions at the time of sticking them. SOLUTION: This optical recording medium is constituted by laminating two sheets of optical recording substrate 1a, 1b while interposing an adhesive layer 20 in which a pressure sensitive adhesive is made a main body. The optical recording substrate 1a, 1b are constituted by forming two transparent substrates 11a, 11b respectively produced by an injection molding or the like and forming organic protective films 12a, 12b on the substrates 11a, 11b. The first and second optical recording substrates 1a, 1b are made so that respective radial tilts have warpages of not larger than ±2 degrees before a sticking and they are pressurlizingly stuck by being positioned so that directions of their warpages become symmetric at the time of sticking them. Thus, the information recording medium which is substantially flat, uninform in the thickness of the adhesive layer and satisfactory in recording and reproducing characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an information recording medium such as an optical recording medium capable of recording information magneto-optically or in a phase-change manner and reading the recorded information. .

[0002]

2. Description of the Related Art An optical recording medium is capable of recording information by irradiating a laser beam and reading the recorded information. For example, a disc-shaped optical recording medium as shown in FIGS. Optical recording media (optical disks). In this optical recording medium, two optical recording substrates 1a and 1b are laminated and bonded via an adhesive layer 20 mainly composed of a pressure-sensitive adhesive or the like. The optical recording substrates 1a and 1b are respectively formed with optical recording layers 11a and 11b on the surfaces of two transparent substrates 10a and 10b produced by injection molding or the like, and a protective layer 12a such as an organic protective film is formed thereon. , 12b.
Reference numeral 3 denotes a hole formed in the center of the optical recording medium.

To manufacture such an optical recording medium 1, optical recording layers 11a and 11b and a protective layer 12 are formed on transparent substrates 10a and 10b, respectively.
a and 12b are laminated on the first and second optical recording substrates 1
a, 1b, and an adhesive sheet having a separator (not shown) temporarily attached to one surface of the adhesive layer 2 are prepared.

[0004] The first and second optical recording substrates 1a, 1
b is obtained, for example, by forming the optical recording layers 11a and 11b on one surface of the transparent substrates 10a and 10b by sputtering or the like, and further forming the protective layers 12a and 12b by spin coating or the like. The above-mentioned adhesive sheet can be obtained by, for example, a method of applying a pressure-sensitive adhesive containing a pressure-sensitive adhesive to a separator, and then punching out a predetermined size according to the shape of the optical recording substrates 1a and 1b.

[0005] Then, the protective layer 12 of the first optical recording substrate 1a is provided.
a and the surface of the adhesive sheet on the side of the adhesive layer 20 are adhered to each other. As the bonding method, a bonding method using a hand roller, a rubber roller, a press, or the like is used, and it is preferable that the bonding is performed by sufficiently pressing. continue,
The separator is peeled off from the adhesive sheet.

Next, the side of the adhesive layer 20 on which the separator is removed is adhered to the protective layer 12b of the second optical recording substrate 1b so as to face each other. The bonding method can be carried out in the same manner as described above, but it is preferable to apply pressure to sufficiently remove bubbles so that air bubbles do not enter the bonding interface.

[0007]

However, in the case of a conventional optical recording medium, warpage of the optical recording substrate caused during injection molding and deformation of the substrate caused during formation of the optical recording layer or the protective layer, particularly, Due to the warpage, the optical recording medium obtained when these are laminated and bonded as described above is difficult to be flat, and the thickness of the adhesive layer of the obtained recording medium becomes uneven. is there. Further, there is a problem in that even if the substrate is considerably pressurized when bonding and laminating in order to eliminate such deformation and warpage of the substrate, the substrate is again deformed due to aging.

If such problems are left undisturbed, there is a risk that recording or reading (reproducing) of information on a recording medium may be hindered.

[0009]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that even if warpage occurs during the formation of the recording substrate, it has an appropriate amount of warpage and warpage when laminating and bonding. The information recording medium is obtained by positioning each substrate in such a manner that the direction of the substrate is in a specific direction, and has a relatively small warpage and a substantially flat shape, and is less likely to be deformed again with time. That is, the present invention has been accomplished.

That is, according to the present invention, a disc-shaped first recording substrate and a second recording substrate having the same shape as the first recording substrate are concentrically laminated and bonded via an adhesive layer. Wherein the first and second recording substrates each have a radial tilt of ± 2 degrees or less before bonding, and the first and second recording substrates at the time of bonding. Is a method for manufacturing an information recording medium characterized in that the directions of warpage are symmetrical and bonded by pressure, and the method solves the above problem.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is the same as described above in that the present invention is a method of concentrically laminating and bonding a first recording substrate and a second recording substrate having the same shape via an adhesive layer. is there. In the present invention, a substrate having a warp such that the radial tilt is ± 2 degrees or less is used as the first and second recording substrates. In the present specification, the radial tilt refers to an average value of a warp angle in a radial direction of a substrate at a radius of 23 mm to 58 mm.

When the radial tilt exceeds ± 2 degrees,
Since the warpage of the substrate is too large, it is difficult to uniformly laminate and bond, and it is difficult to set the radial tilt of the bonded substrate to a generally desirable target value (for example, within ± 0.8 degrees). It is undesirable. Note that it is preferable to use the same amount of tilt for the first and second substrates.

In the present invention, the first and second recording layer substrates are press-bonded by positioning the first and second recording substrates so that the directions of the warpage are symmetrical during lamination and bonding. Can be The symmetry of the direction of the warp may be the case where the warp of each substrate is directed outward or inward.

By warping the substrates in such a manner that the directions of the warping are symmetrical and performing pressure bonding, it is possible to correct the warping distortion generated during the manufacture of the substrate.

When pressure-bonding the first and second recording layer substrates, first, a pressure-sensitive adhesive layer is stuck on the first recording substrate, and the first and second recording layer substrates are positioned as described above from above. The two recording substrates are stacked, and the rubber is aligned and pressed from above with, for example, conical silicone rubber so that the tops of the rubbers match the holes in the substrate. The pressing pressure at this time is preferably 1 kg / cm ² or more. further,
By performing pressure degassing at a pressure of preferably 1 kg / cm ² or more, a substantially flat, high-performance information recording medium without bubbles can be produced.

Next, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 A first optical recording substrate 1a, a second optical recording substrate 1b, and an adhesive sheet having a separator temporarily attached to one surface of a pressure-sensitive adhesive layer 20 are prepared. That is, the optical recording layers 11a and 11b are formed on one side of the polycarbonate transparent substrates 10a and 10b by sputtering, and the protective layers 12a and 12b made of an acrylic ultraviolet curable resin are further formed by spin coating, and the first and second layers are formed. The optical recording substrate No. 2 was produced. The cross-sectional shapes and radial tilts of the manufactured optical recording substrates 1a and 1b were as shown in Table 1 (the cross-sectional shapes of the substrates 1a and 1b in Table 1 are exaggerated). That is, a substrate having a relatively small radial tilt and a tilt amount substantially the same was used.

The pressure-sensitive adhesive layer 20 is manufactured as follows. Monomer mixture 1 consisting of 90 parts by weight of isooctyl acrylate and 10 parts by weight of acrylic acid
2 parts by weight of Irgacure 184 (manufactured by Ciba-Geigy) as a photopolymerization initiator was added to 100 parts by weight, the atmosphere was sufficiently replaced with nitrogen, and about 100 mJ / cm 2 was obtained with a high-pressure mercury lamp.
For ² ultraviolet irradiation, to obtain a viscous product. 1 part by weight of trimethylolpropane triacrylate as an internal crosslinking agent was added to this viscous material, and this was coated on a separator made of silicone-treated paper so as to have a thickness of 50 μm. Further, in order to eliminate polymerization inhibition by oxygen, the tape was covered with a separator made of polyethylene terephthalate and irradiated with ultraviolet rays of about 1400 mJ / cm ² by a high-pressure mercury lamp to produce a tape-shaped pressure-sensitive adhesive layer 2.
The thickness of the obtained tape-shaped pressure-sensitive adhesive layer 2 is 50 ± 5.
μm (thickness accuracy ± 10%).

The diameter of the optical recording substrate 1a, 1b (disc diameter: 120 mm) is reduced by 2 mm to a diameter 118
It was punched into the same shape in mm. Then, the pressure-sensitive adhesive layer 2 is applied to the protective layer 12a of the first optical recording substrate 1a.
After sticking on top using a hand roller, the separator was peeled off and removed.

Next, the separator-removed surface of the pressure-sensitive adhesive layer 20 (that is, the exposed surface of the adhesive layer 2) and the protective layer 12b of the second optical recording substrate 1b are laminated so as to face each other. temporarily bonded at a press pressure of 5 kg / cm ² and the position is allowed to the top of the rubber in the form a silicone rubber matches the hole 3 of the substrate, the while further this was pressurized degassing at 6 kg / cm ² in an autoclave By bonding, an optical recording medium was produced.

This optical recording medium was excellent in that the radial tilt was small and substantially flat. 80 ° C
When it was allowed to stand in an atmosphere of lower 90% RH for 96 hours and change with time was observed, almost no deformation was observed after time.

In the judgments in Table 1, ○ indicates that the radial tilt is ± 0.8 degrees or less, and × indicates that the radial tilt is ± 0.8 degrees or more.

[Table 1]

The radial tilt irradiates a rotating substrate with laser light (He-Ne) in a direction perpendicular to the substrate from the transparent substrate side, and converts the difference between incident light reflected light into a warp angle. Asked by that.

[0023]

Example 2 As shown in Table 1, an optical recording medium was produced in the same manner as in Example 1 except that the substrates 1a and 1b having a relatively large radial tilt and approximately the same amount of tilt were used as substrates to be bonded. did. As shown in Table 1, the obtained optical recording medium had a small radial tilt and was substantially flat and excellent.

[0024]

Example 3 As shown in Table 1, an optical recording medium was manufactured in the same manner as in Example 1 except that a substrate 1a having a relatively small radial tilt and a substrate 1b having a relatively large radial tilt were used. The obtained optical recording medium was a good one with a good balance of radial tilt.

[0025]

Embodiment 4 As shown in Table 1, substrates 1a and 1b having relatively large radial tilt and approximately the same amount of tilt are used as substrates to be bonded, and are symmetrically positioned so that the direction of warping is inward. An optical recording medium was produced in the same manner as in Example 1 except that the recording was performed. As shown in Table 1, the obtained optical recording medium had a small radial tilt and was substantially flat and excellent.

[0026]

Comparative Example 1 As shown in Table 1, an optical recording medium was manufactured in the same manner as in Example 1 except that substrates 1a and 1b having a relatively large radial tilt were laminated and bonded so that the warp was in the same direction. The obtained optical recording medium had a large warp with a large radial tilt.

[0027]

Comparative Example 2 As shown in Table 1, an optical recording medium was manufactured in the same manner as in Example 1 except that a substrate 1a having a relatively small radial tilt and a substrate 1b having a relatively large radial tilt were laminated and bonded so that the warp was in the same direction. Was prepared. The obtained optical recording medium had an unbalanced radial tilt and a poor balance.

[0028]

As described above, according to the present invention, even if a warp occurs during the formation of the recording substrate, the warpage is appropriately determined and the direction of the warp is positioned in a specific direction when the substrates are laminated and bonded. By pressure bonding, there is an effect that an information recording medium having a small amount of tilt, being substantially flat, and having good recording and reproducing characteristics can be produced.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing an example of an information recording medium manufactured by the present invention, and FIG. 1B is a plan view of the information recording medium.

[Brief description of reference numerals]

 1a, 1b ... Optical recording substrate 10a, 10b ... Transparent substrate 11a, 11b ... Optical recording layer 12a, 12b ... Protective layer 20 ... Adhesive layer 3 ... Hole

Claims (1)

[Claims] 1. A disk-shaped first recording substrate, and the first recording substrate
A method of concentrically laminating and adhering a recording substrate having the same shape and a second recording substrate having the same shape via an adhesive layer;
And the second recording substrate has a radial tilt of ± 2 degrees or less before bonding, and the first and second recording substrates have a symmetrical warping direction at the time of bonding. A method for producing an information recording medium, wherein the information recording medium is pressure-bonded.