JPH01264642A - Air sandwich type information recording medium - Google Patents

Abstract

PURPOSE:To well bond substrates and inside and outside spacers and to decrease the distortions of the joined substrates by consisting of the inside spacer of the same resin material as the resin material of the substrates and consisting of the outside spacer of a resin material having softness and/or plasticity. CONSTITUTION:Two sheets of the substrates 21a, 21b are joined via the inside spacer 23 and the outside spacer 24 with recording layers 22a, 22b respectively positioned on the inner side. Two annular projections each having a triangular sectional shape are provided to both sides of the inside spacer 23 by changing the diameter thereof and two annular projections each having a triangular section shape are provided to both sides of the outside spacer 24 as well by changing the diameter thereof. The inside spacer 23 is formed of the same resin material as the resin material of the substrates 21a, 21b and the outside spacer 24 is formed of the resin material having the softeness and/or plasticity. The information recording medium having the small strains and high joint strength is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an information recording medium having an air sandwich structure, and more particularly to a recording medium in which information is written and/or read using a high energy density laser beam. This is about an air sand inch type information recording body that can be used.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use.

This information recording medium is called an optical disk and can be used as a video disk, an audio disk, a large capacity still image file, and a large capacity computer disk memory.

The basic structure of an optical disk is a disc-shaped transparent substrate made of plastic, glass, etc., and a Bi
, a recording layer made of metal or semimetal such as Sn, In, Te, etc. Note that an undercoat layer made of a polymeric substance is usually provided between the substrate and the recording layer in order to improve the adhesion between the substrate and the recording layer and to increase the sensitivity of the optical disc.

Information is written on an optical disk by, for example, irradiating the optical disk with a laser beam. Usually, the irradiated area of the recording layer absorbs the light and locally increases in temperature, causing physical or chemical damage. Information is recorded by causing changes in the optical properties of the optical fiber.

Information is also read from an optical disk by irradiating the optical disk with a laser beam, and the information is reproduced by detecting reflected or transmitted light depending on changes in the optical characteristics of the recording layer.

Conventionally, the assembly of optical discs with an air sandwich structure is
It has generally been the case that inner spacers and outer spacers are bonded to a disk substrate using an adhesive, particularly an ultraviolet curing adhesive. However, when joining each member using adhesive, it takes several tens of seconds to several minutes for the adhesive to be applied per disk and for the adhesive to harden, making it difficult to mass-produce. As a means of achieving this, a bonding method has been considered in which a spacer with protrusions on both surfaces is used, and the protrusions are melted and fused to the substrate using an ultrasonic welding method (for example, Japanese Patent Laid-Open No. 61 -80535'
:'f Publication). As for the material of the spacer used at this time, for example, when the substrate material is polycarbonate, polycarbonate, which is the same material as the substrate, is used in consideration of the fusion property to the substrate.

However, when polycarbonate is used for both the inner and outer spacers, high bonding strength with the substrate can be obtained, but there is a tendency for distortion to occur in the bonded substrate.

In order to solve this problem, it has been disclosed that the elastic modulus of the spacer is set to 20 to 90% of the elastic modulus of the substrate (Japanese Patent Laid-Open No. 173756/1982).

That is, in the above invention, the direction -1- of adhesive strength, etc. is set as [j, the spacer is made of the same resin as the substrate and has a lower Tg, and the spacer has a lower elastic modulus than the substrate. is used to join two substrates. However, since each resin originally has its own Tg, there is a problem in that it is difficult to freely manufacture resins with high and low Tg using the same resin. Furthermore, when a resin with a low elastic modulus is used for the spacer, the strain generated in the bonded substrates is reduced, but the bonding strength cannot be said to be sufficiently high. Therefore, at present, no air sandwich type information recording medium has been obtained that fully satisfies both the characteristics of high bonding strength with the substrate and low distortion generated in the bonded substrate.

[Object of the Invention] An object of the present invention is to provide an information recording medium having an air sand inch structure, in which a substrate and an inner and outer spacer are bonded well, and the bonded substrate has less distortion.

[Summary of the Invention] The present invention provides two disc-shaped substrates with a ring-shaped inner spacer and a ring-shaped outer spacer interposed therebetween so that a recording layer on which information can be written and/or read by a laser is located on the inside. An information recording medium having a bonded air sandwich structure, wherein the inner spacer is made of the same resin material as the substrate, and the outer spacer is made of a resin material having flexibility and/or plasticity. It is in a sandwich type information recording medium.

Preferred embodiments of the information recording medium of the present invention are as follows.

l) The air sandwich type information recording medium, wherein the outer spacer is made of a mixture of the same resin material as the substrate and the flexible and/or plastic resin material.

2)-1- The resin material having flexibility and/or plasticity is polyolefin, polybutadiene, isoprene, phenoxy resin, polyphenylenoxide, urethane resin, acrylic resin, vinyl chloride resin, vinyl chloride copolymer, The information recording medium described above is characterized in that it is at least one member selected from the group of ABS resin, AS resin, polystyrene, and high impact polystyrene.

3) The information recording medium of item 2, wherein the disk-shaped substrate is made of polycarbonate.

4) The information recording medium of item-1- above, wherein the spacer and the disk-shaped substrate are bonded by ultrasonic fusion.

[Effects of the Invention J] In the information recording medium of the present invention, a spacer and two substrates are bonded together by ultrasonic fusion or the like via a ring-shaped inner spacer and a ring-shaped outer spacer.

The present invention provides an information recording medium with low distortion and high bonding strength by using the same resin material for the inner spacer as the substrate and using a resin material having flexibility and/or plasticity as the resin material for the outer spacer. made it possible to obtain

According to the studies of the present inventors, it is the bonding strength of the bonding portion between the inner spacer and the substrate that has a large effect on the bonding strength of the entire information recording medium, and also has a large effect on the distortion of the entire information recording medium. It was found that it was the joint between the outer spacer and the substrate that caused the problem.

As a result of further studies based on these findings, the present invention was developed as a method for reducing the strain that occurs when the outer spacer and the substrate are fused together.

In particular, by forming the -J2 substrate and the inner spacer with polycarbonate, it is possible to obtain an information recording medium with further improved performance.

[Detailed Description of the Invention] The information recording medium of the present invention has, for example, an external shape as shown in FIG. 1 and a configuration as shown in a sectional view in FIG. 2. That is, two substrates 21a,
21b are joined via an inner spacer 23 and an outer spacer 24, with the recording layers 22a and 22b facing inside. The bonding between the substrate and the spacer is realized mainly at a portion where a protrusion of the spacer, which will be described later, is provided.

For example, the shape of the spacer having the protrusion is as follows.

FIG. 3 shows a cross-sectional view of the inner spacer 30. On both sides of the inner spacer 30, a ring-shaped projection 31a and a ring-shaped projection 31b each having a triangular cross section are provided with different diameters. At the inner and outer bases of the ring-shaped protrusion 31a and the ring-shaped protrusion 21b, there are resin inflow portions 32 lower than the substrate contact surface 33, which is the surface of the spacer.
is provided, and molten resin is allowed to flow therein using an ultrasonic welding method or the like.

FIG. 4 shows a cross-sectional view of the outer spacer 40. A protrusion 41a having a triangular cross section and a ring-shaped protrusion 41b having different diameters are provided on both sides of the outer spacer 40. At the inner and outer bases of the ring-shaped protrusion 41a and the ring-shaped protrusion 41b, resin inflow portions 42 lower than the substrate contact surface 43, which is the surface of the spacer, are provided. etc. to allow the molten resin to flow in.

Note that the above description describes the preferred fb mode of the information recording medium of the present invention, and the present invention is not limited to the above mode. For example, the shape of the protrusion does not need to be triangular in cross section, and any shape of the protrusion used in known ultrasonic fusion techniques may be used. Further, the number of protrusions provided on the spacer surface does not need to be one on each surface. Alternatively, the spacer surface on the side where the protrusion with a larger diameter is provided can be fused first.

The information recording medium of the present invention has two disc-shaped substrates, a ring-shaped inner spacer and a ring-shaped outer spacer, and a recording layer on the inner side on which information can be written and/or read by a laser, as described in ``2''. An information recording medium with an air sandwich structure bonded so that
It is characterized by being made of a resin material having flexibility and/or plasticity.

That is, a spacer used in an ultrasonic welding method or the like has a ring-shaped protrusion for welding. For this reason, when the spacer is made of the same material as the substrate in order to increase the bonding strength between the spacer and the substrate as in the past, it is difficult to alleviate the strain caused by fusing the protruding portion of the spacer to the substrate. It tends to cause large distortion. In order to minimize such distortion and increase the bonding strength, the present inventors have made extensive studies and have developed the above-mentioned IJI.
This is what led to this.

According to the studies conducted by the present inventors, the bonding strength of the entire information recording medium is significantly affected by the bonding portion of two disc-shaped substrates bonded together via the ring-shaped inner spacer and the ring-shaped outer spacer. It was revealed that is the bonding strength of the bonding portion between the inner spacer and the substrate. It was also found that the joint between the outer spacer and the substrate has a large effect on the distortion of the entire information recording medium.

As a result of further investigation based on these findings, in order to reduce the distortion that occurs when the outer spacer and the substrate are fused, we found that the outer spacer has flexibility and/or Alternatively, it has been found that using a resin material having plasticity is extremely effective. In particular, when the outer spacer is made of a mixture of a resin material having flexibility and/or plasticity, and the same resin material as the substrate, the strain generated during the fusion can be significantly reduced. can. and,
In this case, in order to maintain bonding strength, the same resin material as the L substrate is used as the material for the inner spacer to improve adhesiveness. This has made it possible to obtain an information recording medium with low distortion and high bonding strength.

The resin mixture used for the outer spacer has a weight ratio of the same resin material as the substrate and the resin material having flexibility and/or plasticity of 90:10 to 10:
It is preferably within the range of 90. More preferably, it is within the range of 90:10 to 60:40.

Examples of resin materials different from the substrate having flexibility and/or plasticity include polyolefins such as polyethylene and polypropylene, polybutadiene, isoprene,
Examples include phenoxy resin, polyphenylenoxide, urethane resin, acrylic resin, vinyl chloride resin, vinyl chloride copolymer, ABS resin, AS resin, polystyrene, high impact polystyrene, and mixtures thereof. Preferred are ABS resin and polyolefin. These polymers may be used alone or in combination.

The inner spacer of the present invention uses the same material as the substrate in order to maintain the bonding strength of the bonded portion with the substrate. Among the materials used for the substrate, it is particularly preferable to use polycarbonate for the substrate and use a material containing polycarbonate for the inner spacer not only to improve the bonding strength but also to improve information recording and reproducing characteristics. By employing such a configuration, the material of the outer spacer is naturally a mixture of polycarbonate and a resin material capable of imparting flexibility and/or plasticity to the polycarbonate, from the scope of the claims of the present invention.

By using the substrate and the inner and outer nozzles made of the materials described above, it is possible to obtain an information recording medium with particularly low distortion and high bonding strength.

The spacer can be manufactured by adding a lubricant, a mold release agent, an antioxidant, etc. (with other additives if desired) to the above polymer mixture, and then performing ordinary injection molding. The above-mentioned lubricant is preferably added in order to improve fluidity and compatibility. Examples of lubricants include fatty acid amides such as stearic acid amide and valmitic acid amide, and higher alcohols such as octadecyl alcohol and cetyl alcohol.

The spacer can be injection molded by a known method. For example, it is done as follows. Put the molding material into the hopper of the injection molding machine. The molding material falls into the heating cylinder due to its own weight, and is sequentially sent to the tip by the rotation of the screw, where the plasticized material is accumulated by the rotation of the screw. Next, the injection ram of the hydraulic cylinder device connected to the rear end of the screw pushes the material stored at the tip of the screw from the nozzle into the mold cavity with the necessary injection pressure, and the inside of the mold is filled with the appropriate amount. After holding with the strip I, the molded product (spacer) is taken out.

At that time, the temperature inside the heating cylinder, the rotation speed of the screw, the injection pressure, the injection time, the nozzle temperature, the mold cavity, the mold clamping force, the mold temperature, the overall mold holding conditions, etc. will depend on the resin to be injection molded. Set as appropriate.

As for the substrate, recording layer, and spacer constituting the information recording medium of the present invention, any publicly known substrates, recording layers, and spacers other than those that constitute the characteristic structure of the present invention can be used, so these will be briefly explained below. .

The substrate used in the present invention can be arbitrarily selected from various materials conventionally used as substrates for information recording media. In terms of optical properties, flatness, processability, handling, stability over time, and manufacturing costs, examples of substrate materials include acrylic resins such as CELCAS), polymethyl methacrylate, and injection molded polymethyl methacrylate: Preferred examples include vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; and synthetic resins such as polycarbonate.

From the viewpoint of dimensional stability, transparency, and flatness, polymethyl methacrylate, polycarbonate, and epoxy resin are preferred, and polycarbonate is particularly preferred.

The surface of the substrate on which the recording layer is provided has improved flatness,
An undercoat layer (and/or intermediate layer) may be provided for the purpose of improving adhesive strength and preventing deterioration of the recording layer. Materials for the undercoat layer (and/or intermediate layer) include, for example: Polymer materials such as polymethyl methacrylate, acrylic acid-methacrylic acid copolymers, nitrocellulose, polyethylene, polypropylene, polycarbonate, organic substances such as nitrogen coupling agents, and inorganic oxides (
SiO□, A! ; L203, etc.), inorganic fluoride (MgF
Examples include inorganic substances such as 2).

The undercoat layer is made by dissolving or dispersing the polymeric substance in a suitable solvent, and applying this coating solution to the substrate using a coating method such as a spin code, dip coat, extrusion coat, bar code, or screen printing. It can be formed by coating E. The layer thickness of the undercoat layer is generally o, oi to 20 pm, preferably 0.11-1 o.
p"t'. Examples of materials used for the recording layer include:
Te, Zn, In, Sn, Zr, An, Ti, Cu,
Examples include metals such as Ge, Au, and Pt; semimetals such as Bi, As, and sb; semiconductors such as Si; and alloys thereof or combinations thereof. Compounds such as sulfides, oxides, borides, silicon compounds, carbides, and nitrides of these metals, semimetals, or semiconductors; and mixtures of these compounds and metals can also be used in the recording layer. Alternatively, it is possible to use a combination of a dye, a dye and a polymer, or a dye and the above-mentioned metals and metalloids.

The recording layer may further contain various known metals, semimetals, or compounds thereof as recording layer materials.

The recording layer can be formed on the substrate directly or via an undercoat layer using the above-mentioned materials by methods such as vapor deposition, spray tanning, ion plating, and coating. The recording layer may be a single layer or a multilayer, but its layer thickness is generally in the range of 100 to 5,500 OX, preferably in the range of 150 to 100 OX, in view of the optical density required for optical information recording.

Note that the surface of the substrate opposite to the side on which the recording layer is provided is coated with inorganic substances such as silicon dioxide, tin oxide, and magnesium fluoride to improve scratch resistance and moisture resistance.
A thin film made of a polymeric substance such as a thermoplastic resin or a photocurable resin may be provided by a method such as vacuum deposition, sputtering, or coating.

Next, the two substrates on which the recording layer has been formed are joined with the recording layer inside, with the spacer sandwiched therebetween, by melting the ring-shaped protrusion. Bonding is preferably performed by ultrasonic fusion.

Next, Examples and Comparative Examples of the present invention will be described.

However, each of these does not limit the present invention.

[Example 1] First, injection molding of an inner spacer was performed as follows. Polycarbonate, which is the molding material, is put into the hopper of the injection molding machine. The molding material falls into the heating cylinder due to its own weight, and is sequentially sent to the tip by the rotation of the screw, where the plasticized material is accumulated by the rotation of the screw. Next, the material held at the tip of the screw was forced into the mold cavity through the nozzle at the following injection pressure by the injection ram of the hydraulic cylinder device connected to the rear end. After holding the inside of the mold under the following conditions, the molded product (spacer) was taken out. The above injection molding conditions were performed as follows.

Injection molding machine near 5t (manufactured by Toshiba Machine ■) Temperature inside heating cylinder: 320℃ Screw rotation speed: 100rpm Injection pressure crab 950 kg/crn' Injection time = 1 second during 1 injection time: 100℃ Mold clamping crab Conditions for holding 50 in the entire mold: 100℃, 2 seconds The outer spacer is made of polycarbonate and A as the molding material.
Using a mixture of BS resin (50=50 by weight)
Injection molding was performed in the same manner as the inner spacer mentioned above. The injection molding conditions are as follows.

Injection molding machine + 75t (manufactured by Toshiba Machine ■) Temperature inside heating cylinder: 260℃ Screw rotation speed + 1100rp Injection pressure crab 800 kg/crn'g/crn' second Mold cavity: 40℃ Mold clamping crab 50 inside the whole mold Holding conditions: 40°C, 2 seconds Next, a disc-shaped polycarbonate substrate with a pregroove formed by injection molding [outer diameter + 130 mm, center hole inner diameter: 1
5mm, thickness: 1.2mm, pre-groove depth: 8
00 angstrom, track pitch: L, 6gm]
-h, a coating solution containing chlorinated polyolefin [0.3 parts by weight of chlorinated polyethylene dissolved in 710 parts by weight of methyl ethyl keto and 100 parts by weight of cyclohexanone] was applied to the outer periphery of the substrate using a spin coater. ,
It was then dried to form an intermediate coating layer having a layer thickness of 500 angstroms. - I n :Ge on the intermediate coating layer F
Co-evaporation was performed at a ratio of S:Au=66:22:12 (weight ratio) to form a recording layer with a thickness of 300 angstroms. In this way, a disk substrate consisting of a substrate and a recording layer was obtained.

The spacer was sandwiched between two I-disks and joined by ultrasonic fusion to obtain a sandwich type information recording medium.

The above ultrasonic welding was carried out using Plann 8800 (manufactured by Branson) as an ultra-1'1 wave welding machine, with a pressure crab of 40p.
The test was conducted under the conditions of si and time of 20.2 seconds.

[Example 2] In Example 1, the outer spacer was made of a mixture of polycarbonate and ABS resin (50:50 by weight ratio) as the molding material.
A sandwich-type information recording medium was obtained in the same manner as in Example 1, except that the same injection molding as in Example 1 was carried out using 50) under the following conditions.

Injection molding machine +75t (manufactured by Toshiba Machine ■) Temperature inside heating cylinder:
260°C Screw rotation speed + 1100 rpm Injection pressure crab 800 kg/crn'g/crn' seconds Mold cavity: 40°C All mold clamping crabs 50 held inside the mold Conditions: 60°C, 2 seconds [Comparative Example 1] Implementation In Example 1, a sandwich type information recording medium was obtained in the same manner as in Example 1, except that the outer spacer was also injection molded using the same polycarbonate as the inner spacer as a molding material under the following conditions.

Injection molding machine near 5t (manufactured by Toshiba Machine) heating cylinder temperature:
320°C Screw rotation speed: 100 rpm Injection pressure Crab 950 kg/cm' Injection time = 1 second Mold cavity: 100°C Mold clamping crab Holding 50 in the mold Strip strength: 100°C, 2 seconds [Comparative example 2 ] In Example 1, a sandwich type information recording medium was made in the same manner as in Example 1, except that both the inner and outer spacers were injection molded using ABSSL resin as the molding material under the following conditions. Obtained.

Injection molding machine near 5t (manufactured by Toshiba Machine ■) Heating cylinder temperature:
260℃ Screw rotation speed: 1100rp Injection pressure crab 800 kg/cm' Injection time: 1 second Mold cavity = 40℃ Mold clamping crab 50 is held in the entire mold Conditions: 40℃, 2 seconds [Evaluation of optical disc] 1 ) Bonding strength between spacer and polycarbonate substrate The bonding strength between the spacer and the substrate of the above optical disk in which the spacer and the substrate were bonded by ultrasonic fusion bonding was observed.

AA: No peeling even when external force is applied.

BB: Peels off when external force is applied.

CC: Easily peeled off with a slight external force.

2) After the two substrates were joined via a spacer, the surface runout acceleration of the information recording medium obtained by strain was measured using a mechanical property evaluation machine (manufactured by Ono Sokki Co., Ltd.).

AA: Less than 15m/sec2 BB: 15-20m/sec2 CC: Value exceeding 20m/sec2 The results are shown in Table 1.

Table 1 Polycarbonate Bonding strength with mold substrate after bonding Example 1 AA AA2
AA AA Comparative Example 1 CCCC 2CCAA As shown in Table 1, polycarbonate, which is the same material as the substrate, is used for the inner spacer, and the outer spacer is a mixture of polycarbonate and a resin that can impart flexibility and/or plasticity to the polycarbonate. Examples 1 and 2 using the above have good characteristics in both bonding strength and strain.

On the other hand, when the same material is used for the inner spacer and the outer spacer as in the comparative example, it is not possible to satisfy both the joint strength and strain characteristics. Note that when both the inner and outer spacers of Comparative Example 1 are made of polystyrene, the resin inflow portion cannot be sufficiently filled during bonding, resulting in low bonding strength.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing an information recording medium having an air sandwich structure according to the present invention. FIG. 2 is a sectional view showing an example of the structure of the information recording medium of the present invention. FIG. 3 is a cross-sectional view of an inner spacer with a ring-shaped protrusion. FIG. 4 is a cross-sectional view of an outer spacer with a ring-shaped protrusion. 30.40 Ni spacer 21a, 21b Two substrates 22a, 22b: Recording layer 31a, 31b, 41a, 41b: Ring-shaped protrusion 32.42: Resin inflow portion 33.43: Substrate contact surface 23: Inner spacer 24: Outer spacer

Claims (1)

[Claims] 1. Information recording with an air sandwich structure in which two disk-shaped substrates are joined via a ring-shaped inner spacer and a ring-shaped outer spacer so that the recording layer on which information can be written and/or read by a laser is on the inside. In the medium, the inner spacer is made of the same resin material as the substrate, and the outer spacer is flexible and/or
Alternatively, an air sandwich type information recording medium characterized by being made of a resin material having plasticity. 2. Claim 1, wherein the outer spacer is made of a mixture of the same resin material as the substrate and the flexible and/or plastic resin material.
The air sandwich type information recording medium described in .