JPH10143931A - Information recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for production which lessens deformation and enhances transparency by irradiating the superposed surfaces via adhesives with light of the wavelength capable of curing these adhesives from a parallel direction and a bonding type information recording medium. SOLUTION: This information recording medium is formed by superposing plural sheets (two sheets in Fig.) of base materials obtd. by laminating substrates 1, dielectric layers 2, recording layers 3, dielectric layers 4, reflection layers 5 and org. resins contg. curing acceleration materials on each other via the adhesives 7. The superposed surfaces are irradiated with the light of the wavelength capable of curing the adhesives 7 from the direction parallel with these surfaces, by which the surfaces are stuck to each other. The wavelength of the light to cure the adhesives 7 is specified to 300 to 700nm and the ray transmittance of the adhesives 7 is specified to >=0.8 at the optical path length of 1mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated information recording medium.

[0002]

2. Description of the Related Art An optical recording medium reads and records pits while irradiating a laser beam while rotating a disk at a high speed and performing focus adjustment and position detection.
Therefore, in the optical recording medium, slight warpage or deformation of the substrate leads to a signal error. Therefore, in an optical recording medium, an information recording section is provided on a substrate with as little thickness unevenness and deformation as possible. Further, in order to prevent the information recording portion from being scratched or foreign matter from adhering, a protective layer is provided on the information recording portion, and the information recording portions of a pair of substrates are bonded together with the information recording portions inside.

Conventionally, for this bonding, for example, a hot-melt adhesive is applied to a protective layer side of a substrate by a roll coater, and these adhesive layers are opposed to each other, inserted between two flat plate presses and pressed. By doing so, a pair of substrates are bonded to each other to obtain an optical recording medium. However, in this method, the substrate may be deformed at the time of applying the hot melt adhesive or in the subsequent pressing step, and the strength may be reduced particularly at high temperatures.

[0004] Further, with the increase in the density of optical recording media, it has become necessary to use a substrate thinner than a conventional substrate, for example, about 0.6 mm or less. It will be easier.

On the other hand, for an information recording medium having a plurality of information recording layers, for example, an information recording / reproducing apparatus for calling a plurality of recording layers from one side may be one of the specifications. Need to be.

[0006] In terms of rigidity and transparency, a photocurable adhesive such as an ultraviolet curable adhesive is advantageous. However,
In the case of bonding with an ultraviolet curable adhesive, it is essential to irradiate the adhesive layer with ultraviolet light. In this case, it is difficult to bond a plurality of base materials provided with the information recording layers having low transmittance of ultraviolet rays. Even if the information recording layer has a slight ultraviolet transmittance, if it is attempted to cure it with an ordinary ultraviolet-curable adhesive by irradiating it with ultraviolet light from the surface, it takes a long time to give the energy necessary for curing. Requires UV irradiation. Even if it is cured, it will cause a great deal of thermal damage to the disk, making it difficult to produce a practical disk.

[0007]

As a method of solving this problem, a method of irradiating the adhesive layer with light in the horizontal direction with respect to the surface direction and curing the adhesive layer is considered. However, this method is not applicable to ordinary photocurable adhesives. This is because, when light is applied to the adhesive layer in the horizontal direction with respect to the surface direction, the intensity of the light becomes weaker as the light travels in the horizontal direction with respect to the adhesive layer, and there is a problem that the interior is not cured. It is.

According to the present invention, in a step of curing an adhesive applied to an information recording medium and bonding the information recording medium,
An object of the present invention is to provide a method for manufacturing a laminated information recording medium having little deformation and high transparency, and a laminated information recording medium.

[0009]

Means for Solving the Problems In order to solve the above problems, the present invention comprises the following constitutions. That is, information recording characterized by laminating a plurality of base materials via an adhesive, irradiating a light having a wavelength capable of curing the adhesive from a direction parallel to the superposed surface, and laminating the substrates. The present invention relates to a method for manufacturing a medium.

[0010] The present invention also relates to an information recording medium comprising a plurality of base materials including at least one base material provided with an information recording layer bonded together via an adhesive layer. The present invention relates to an information recording medium, wherein a light transmittance T at a wavelength of 300 to 700 nm of light is 0.8 or more in an optical path length of 1 mm.

Further, the present invention relates to an information recording medium comprising a plurality of base materials including at least one base material provided with an information recording layer bonded together via an adhesive layer. The present invention relates to an information recording medium provided with an adjacent light guide layer having a light transmittance T of 0.8 or more in an optical path length of 1 mm at a wavelength of 300 to 700 nm.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. FIG. 1 shows an example of the information recording medium of the present invention. The components shown in FIG. 2 are prepared in advance for bonding information recording media, and the components immediately before bonding are referred to as base materials. The base material thus configured can be attached so that the adhesive layer is on the inside as shown in FIG. Further, an organic resin layer may be provided on a substrate on which the above film is formed on a substrate.

Examples of the adhesive used in the present invention include, but are not limited to, (meth) acrylic esters.

Further, for the purpose of improving the curability of the adhesive and adjusting the elastic modulus, other monomers copolymerizable with the above-mentioned monomers can be mixed and used. For example, a diisocyanate compound and a compound having two or more alcoholic hydroxyl groups are reacted in advance with a (meth) acrylate containing an alcoholic hydroxyl group to a terminal isocyanate group-containing compound to obtain two compounds in one molecule. Urethane (meth) acrylates having the above (meth) acryloyloxy group, (meth) acrylate diesters of alkylene glycols having 2 to 12 carbon atoms, (meth) acrylate diesters of polyoxyalkylene glycol, polyhydric alcohols (Meth) acrylic acid polyesters having two or more (meth) acryloyloxy groups, bisphenol A or the (meth) acrylic acid of ethylene oxide and propylene oxide of bisphenol A hydride
Acrylic diesters, epoxy = (meth) acrylates having two or more (meth) acryloyloxy groups in the molecule obtained by reacting acrylic acid or methacrylic acid with a compound having two or more epoxy groups in the molecule But not limited thereto.

[0015] One or more photopolymerization initiators can be added to the adhesive. As the photopolymerization initiator, various types can be used.Examples include benzophenones such as acetophenone and benzophenone, sulfides such as tetramethylmonosulfide, thioxanes such as thioxane, benzoin peroxide, and oxides such as di-t-butyl oxide. And the like. The addition amount of the photopolymerization initiator was 0.0% based on 100 parts by weight of the polymerizable monomer.
1 to 10 parts by weight is suitable.

In the present invention, the light transmittance after curing may be obtained by actual measurement from an information recording medium. For example, in the case of a disk-shaped material, actual measurement may be difficult. After curing and molding into a shape, the transmittance of the plate-like material may be converted using the following equation (1).

Log (T) = ε · t (1) where T is the light transmittance of the adhesive ε is a proportional constant including an extinction coefficient t is an optical path length [mm] The proportional constant ε including an extinction coefficient is Pre-cured adhesive in plate shape,
After being molded, the transmittance T and the optical path length t of the plate-like object are measured, and are obtained by back calculation from Equation 1.

The light transmittance is preferably 0.0001 or more at the maximum optical path length in the direction parallel to the adhesive layer. However, from the viewpoint that the curing time can be shortened and the damage due to heat during irradiation can be reduced. More preferably, it is 0.0003 or more. It is more preferable that the light transmittance at a light path length of 1 mm is 0.8 or more.

Further, on the substrate, a light guide layer, that is, a layer for guiding light having a wavelength capable of curing the adhesive can be provided. By providing this layer, even if the transmittance of the adhesive at a wavelength at which the adhesive can be cured is insufficient for light irradiation from the horizontal direction, light is transmitted from the light guide layer to the adhesive in the surface direction. Because it is guided, curing becomes possible.

The material of the light guide layer is not particularly limited as long as it has good transmittance at a wavelength at which the adhesive can be cured and good adhesiveness to the substrate, but quartz, glass, organic resin and the like are used. Preferably, an organic resin is more preferable because of ease of forming the layer. Further, the organic resin layer may have a function of a light guide layer.

The light transmittance at a wavelength at which the adhesive of the light guide layer can be cured is preferably 0.0001 or more at the maximum optical path length in the direction parallel to the adhesive layer. From the viewpoint that damage due to heat at the time can be reduced, it is more preferably 0.0003 or more. It is more preferable that the light transmittance at a light path length of 1 mm is 0.8 or more.

In the present invention, the wavelength of the light applied to the adhesive layer or the light guide layer is determined so that the adhesive can be cured.
Ultraviolet, visible, and electron beams are preferred. Ultraviolet rays having a wavelength of 300 to 700 nm and visible rays are more preferable because they have little effect on the health of the human body and the irradiation device is inexpensive.

The production of the optical recording medium of the present invention can be carried out, for example, as follows. The organic resin layer is applied using, for example, a spin coating method, a roll coating method, a spray coating method, or the like. After applying the composition onto a recording layer formed on a substrate, the composition is cured by irradiating it with actinic radiation, ie, active energy rays such as ultraviolet rays, electron beams, or gamma rays, or by heating. It is not necessary to completely cure.

The filling of the adhesive between the substrates is performed, for example, by applying the adhesive on the substrate, applying the other curing accelerator, and superimposing the cured substrate so that the adhesive and the curing accelerator are in contact with each other. , After spreading the adhesive to some extent by its own weight, filling the whole with centrifugal force due to rotation, shaking off excess adhesive, and sucking and removing excess adhesive on the outer peripheral edge with a nozzle Can be.

In order to form an adhesive layer having a uniform thickness and containing no bubbles by this method, the position, amount of application, viscosity, number of rotations, and rotation time of the adhesive are particularly important. The position where the adhesive is applied may be anywhere on the substrate, but is preferably a position slightly outside the innermost circumference. If it is too far inside, the adhesive may overflow from the inside due to its own weight after the other base material is overlaid. In addition, when the adhesive is applied to a position far outside, it takes too much time to fill the inner peripheral portion with the adhesive, or the adhesive cannot be filled.

If the coating amount is too small, the entire surface of the substrate cannot be filled. If the amount is too large, the adhesive overflows from the inner peripheral portion and the outer peripheral portion. Therefore, the coating amount is preferably 1 to 5 g,
More preferably, 2-3 g is optimal.

If the viscosity of the adhesive is too low, the adhesive may not be completely filled or may contain air bubbles after being rotated to shake off the adhesive. Conversely, if the viscosity is too high,
It takes too much time to fill the adhesive, and the adhesive may run around the surface. Therefore, it is necessary to limit the viscosity range. More specifically, it is preferably about 100 to 2000 cps (centipoise), more preferably 300 to 800 cps.

In the case of low rotation speed,
It is difficult to fill the entire substrate. In the case of high rotation, it may contain bubbles. When the rotation time is short, it is difficult to fill the entire surface of the substrate. If it is long, it may contain air bubbles.

The method of irradiating the adhesive with light is not particularly limited as long as the direction of irradiation is from the side. For example, the adhesive can be irradiated by the following method. 3 and 4 show an example of an apparatus for irradiating ultraviolet rays from the side.

A ring light guide, that is, an optical fiber for guiding ultraviolet light, is provided on the inner surface of the chamber of the ultraviolet irradiation device so that ultraviolet light can be irradiated to the adhesive layer of the disk in the horizontal direction.

Also, in the inner peripheral portion for fixing the disc,
A ring light guide is provided so that the adhesive layer of the disk can be irradiated with ultraviolet rays in the horizontal direction, and a reflector is provided to increase the irradiation efficiency from the side.

The present invention relates to a read-only (ROM) optical recording medium,
Rewritable (RA) media such as magneto-optical recording media and phase-change recording media
M) It can be used for manufacturing any optical recording medium such as an optical recording medium, a partial read-only (PROM) optical recording medium, and a write-once (WORM) optical recording medium.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. However, the present invention is not limited by the following examples.

Example 1 120 mm in diameter and 0.6 in thickness
mm disk-shaped substrate (maximum horizontal optical path length 40 m
m), two recording layers were formed by a sputtering method. One of the disks is fixed to a spinner with the recording layer facing upward, and the optical path length is 1 mm and the wavelength is 360 nm on this recording layer.
, The transmittance before curing is 0 and the transmittance after curing is 0.
8 of adhesive was placed. When this is converted into Equation 1, the transmittance of the cured adhesive at the maximum horizontal optical path length of 40 mm is 0.0001.

The other disk was overlaid on top of it with the recording layer facing downward, and the spin was quickly applied to shake off excess adhesive. The superposed disks were placed on a Pyrex glass plate provided with a hole for centering in the center, and a similar Pyrex glass was further placed thereon.

Using an ultraviolet lamp having a main wavelength of 360 nm from the side of the glass, the illuminance of 240 mW and 30
Irradiation was performed for 2 seconds. When a wedge was inserted from the end to the interface of the bonded disks to check the adhesiveness, it was found that the disks were sufficiently bonded.

Example 2 120 mm in diameter and 0.6 in thickness
mm disk-shaped substrate (maximum horizontal optical path length 40 m
m), a recording layer was formed by a sputtering method. A resin having a transmittance of 0 before curing and a transmittance of 0.8 after curing was coated on the recording layer with a thickness of 10 μm at an optical path length of 1 mm and a wavelength of 360 nm. When this is converted by Expression 1, the transmittance of the cured coating layer at the maximum horizontal optical path length of 40 mm is 0.0001.

Two discs were prepared, and one of the discs was fixed to a spinner with the recording layer facing upward, and the light transmittance before curing was 0 at an optical path length of 1 mm and a wavelength of 360 nm on this recording layer. Permeability after curing is 0.00
1 adhesive was placed. When this is converted into Equation 1, the transmittance of the cured adhesive at the maximum horizontal optical path length of 40 mm is 10 ⁻¹² .

Except for this, the disks were bonded in the same manner as in Example 1. When a wedge was inserted from the interface of the bonded disks and the adhesion was confirmed, it was found that the disks were sufficiently bonded.

(Comparative Example 1) The adhesive had a light path length of 1 m.
m, at a wavelength of 360 nm, 0 before curing, and after curing,
A 0.001 adhesive was placed. When this is converted into Equation 1, the transmittance is 10 when the maximum optical path length in the horizontal direction is 40 mm.
It becomes ^-12 . Except for this, the disks were bonded in the same manner as in Example 1.

When a wedge was inserted from the interface of the bonded disks to check the adhesiveness, none of the adhesives was cured and could not be bonded.

[0042]

As described above, according to the present invention, by selecting an adhesive having a high transmittance in the maximum optical path length in the horizontal direction after curing, curing by irradiation of light from the horizontal direction can be performed in a short time. Will be possible. In addition, even if the adhesive has a low transmittance, by providing a light guide layer with a high transmittance on the surface adjacent to the adhesive layer, curing by light irradiation from the horizontal direction can be similarly performed in a short time. Become. Thereby, even in the case of a disk substrate having a low transmittance of light rays in a direction perpendicular to the surface,
Bonding becomes possible by curing by light irradiation from the side. In addition, this makes it possible to obtain a bonded information recording medium with little deformation and high transparency.

[Brief description of the drawings]

FIG. 1 shows an example of the information recording medium of the present invention.

[Figure 2] Substrate

FIG. 3 is a top view of an example of an apparatus for irradiating ultraviolet rays from the side.

FIG. 4 is a cross-sectional view of an example of an apparatus for irradiating ultraviolet light from the side.

[Explanation of symbols]

 1: substrate 2: dielectric layer 3: recording layer 4: dielectric layer 5: reflective layer 6: organic resin layer containing a curing accelerator 7: adhesive 8: information recording medium 9: optical fiber 10: outer ring light guide 11: Inner circumference ring light guide 12: UV light source

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[Procedure amendment]

[Submission date] November 21, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

The other disk was overlaid on top of it with the recording layer facing downward, and the spin was quickly applied to shake off excess adhesive. The superposed disks were placed on a Pyrex glass plate provided with a centering shaft at the center, and further placed on a Pyrex glass provided with a hole at the center .

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinichi Yamashita 1-1-1 Sonoyama, Otsu-shi, Shiga Pref.

Claims (9)

[Claims] 1. A method for manufacturing an information recording medium, comprising: laminating a plurality of substrates via an adhesive; and irradiating the laminated surface with light in a direction parallel thereto. 2. The light transmittance T of the cured adhesive at a wavelength at which the adhesive can be cured is 0.0001 or more at the maximum optical path length in the direction parallel to the adhesive layer. The method for manufacturing an information recording medium according to claim 1, wherein 3. A light guide layer having a light transmittance at a wavelength at which the adhesive can be cured and having a maximum optical path length in a direction parallel to the adhesive layer of 0.0001 or more is provided on an interface adjacent to the adhesive. The method for manufacturing an information recording medium according to claim 1, wherein the method is provided. 4. The method according to claim 2, wherein the light transmittance of the adhesive at a wavelength at which the adhesive can be cured is 0.8 or more at an optical path length of 1 mm. . 5. The light guide layer according to claim 3, wherein the light transmittance of the light guide layer at an optical path length of 1 mm is 0.8 or more at a wavelength at which the adhesive adjacent to the light guide layer can be cured. Manufacturing method of information recording medium. 6. The wavelength of a light beam capable of curing the adhesive is 30.
4. The method for manufacturing an information recording medium according to claim 2, wherein the thickness is from 0 to 700 nm. 7. A substrate provided with an information recording layer is provided with at least one
An information recording medium in which a plurality of base materials including one or more sheets are bonded together via an adhesive layer, and the light transmittance T of the adhesive layer at a wavelength of 300 to 700 nm is 1 mm.
An information recording medium characterized by having an optical path length of 0.8 or more. 8. A substrate provided with an information recording layer is provided with at least one
An information recording medium in which a plurality of base materials including one or more sheets are bonded via an adhesive layer, and a light transmittance T at a wavelength of 300 to 700 nm of light adjacent to the adhesive layer is 1 mm. An information recording medium comprising a light guide layer having an optical path length of 0.8 or more. 9. The information recording medium according to claim 7, wherein the thickness of the base material is 0.6 mm or less.