JPH01133238A - Production of optical disk - Google Patents

Abstract

PURPOSE:To prevent flawing and cracking by the ruggedness and foreign matter of pressing plates to be generated by direct pressing by interposing sheets having elasticity between two recording media and adhering the media while exerting pressure thereto at the time of adhering said media. CONSTITUTION:An adhesive agent consisting of a hot melt resin is coated by, for example, a hot melt coater, etc., on a protective layer 3 of one recording medium to form an adhesive layer 5. The other recording medium 4 is then adhered thereon by positioning the substrate 1 to the outer side and pressing the protective layer 3 to the adhesive layer 5 of the one recording medium. Two sheets of the recording media 4, 4 pressed via the adhesive layer 5 are pressed by a press device. Pressing by the press device is executed by disposing two sheets of the media 4, 4 pressed to each other between two sheets of the hard pressing plates 6 and 6 and pressing the pressing plates 6, 6 in an arrow A direction. The pressing is executed via elastic sheets 7, 7 disposed on the outside of the media 4, 4 stuck to the inside surfaces of the pressing plates 6, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a double-sided optical disc in which two recording media are bonded together.

(Prior Art) Optical discs generally include pit-type optical discs, which are recording media in which well-known pits are formed on a substrate made of resin, etc., and recording media, in which a thermal recording layer is formed on a substrate. There are bubble-type optical disks, which form bubbles by irradiation with laser light, etc., and detect level fluctuations based on changes in reflected light, and magneto-optical disks, which are recording media with a magneto-optical recording layer formed on a substrate. In the optical disc, information is recorded using the pits and the magneto-optical recording layer.

These optical discs include single-sided type discs consisting of one recording medium, and two recording media formed in substantially the same way, with a recording layer (pit layer) formed by passing the substrate to the outside (through an adhesive layer). There is a double-sided type in which the parts (formed parts) (hereinafter the same shall apply) are placed facing each other and bonded together.

The above-mentioned double-sided optical disc is manufactured by applying an adhesive made of hot melt resin or the like on the recording layer of the recording medium or on the protective layer formed on the recording layer, and applying the adhesive in this way. By placing two recording media with the adhesive coated sides facing each other between two pressing plates of a press device, and pressing the two recording media from the outside (substrate side) with the pressing plate to bond them together. will be produced.

(Problems to be Solved by the Invention) However, the press plate of the above-mentioned press device is usually formed of a hard material. If a recording medium is directly sandwiched between such hard pressure plates and pressure is applied, the surface of the substrate of the recording medium is likely to be damaged by the unevenness of the pressure plates and foreign matter such as attached dust. In addition, pressing with such a hard material does not have elastic force, and generally the thickness of the substrate of a recording medium is not necessarily uniform. For example, a substrate formed by injection molding may have a thickness on the order of microns at the outer periphery. Alternatively, the thickness may not be uniform due to burrs, and therefore the pressure distribution on the recording medium tends to be non-uniform when pressed with a press device. Therefore, the adhesion state becomes uneven, and the adhesion state between the two recording media tends to be poor. In other words, if the pressure distribution becomes uneven, there will be areas where the adhesive strength is insufficient, and for the purpose of accelerated aging tests, high temperature and high humidity (e.g.
(0°C, 90% RH), part of the optical disc may peel off.

The present invention does not damage the surface of the optical disk, and
An object of the present invention is to provide a method for manufacturing an optical disc that can uniformly bond two recording media together.

(Means for Solving the Problems) In view of the above-mentioned problems, the method for manufacturing an optical disc according to the present invention involves bonding two recording media by pressing them with an adhesive interposed between them. In the method for manufacturing an optical disc, the above-mentioned "optical disc" is characterized in that the pressing of both the recording media is performed through an elastic sheet placed on the outside of the recording media. Bit-type optical disks consist of recording media with pits formed on them, or recording media with a thermal recording layer formed on a substrate, which form bubbles when irradiated with laser light, etc., and level fluctuations due to changes in reflected light. This refers to a bubble-type optical disk that detects the oscillation, a magneto-optical disk that consists of a recording medium in which a magneto-optical recording layer is formed on a substrate, and the like.

In the above configuration, when pressing both recording media, it is preferable to interpose a release sheet between the recording media and the elastic sheet. A releasable sheet here refers to a sheet that does not eject from itself substances that are transferred or transferred to the surface of the recording medium when it is overlapped with a recording medium and pressed, and also transfers or transfers a part of the recording medium to its own surface. without incident, and
This refers to a sheet that does not come into close contact with the recording medium on its entire surface or in part.

(Implementation mode) Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, the double-sided optical disc manufactured by the optical disc manufacturing method according to the present embodiment is made of transparent plastic such as glass, acrylic resin, polycarbonate resin, or epoxy resin, and has a thickness of 10+.
A magneto-optical recording layer 2 made of a rare earth transition metal or the like is formed on a transparent substrate 1 having a thickness of about .4 is a double-sided type magneto-optical disk which is pasted with the substrate 1 facing outside with an adhesive layer 5 interposed therebetween.

In the process of manufacturing a magneto-optical disk, an adhesive made of hot-melt resin is applied onto the protective layer 3 of one recording medium using, for example, a hot-melt roll coater to form an adhesive layer 5, and the adhesive layer 5 is coated on the protective layer 3 of one recording medium. 4 with its substrate 1 outside and the protective layer 3 brought into contact with the adhesive layer 5 of one of the recording media, and the two recording media 4, 4 brought into contact in this way with the adhesive layer 5 interposed therebetween. Press with a press device. Of course, when bringing the two recording media 4.4 into contact with each other via the adhesive layer 5, adhesive may be applied to the storage layers 3, 3 of both recording media to bring them into contact. .

As shown in FIG. 1, the pressing by the press device is carried out by disposing the two recording media 4, 4 brought into contact between the two hard pressing plates 6, 6 of the press device. .6 to arrow A
This is done by pressing in the direction.

Further, this pressing is applied to the pressing plates 6, 6. That is, both recording media 4,
This is done through an elastic sheet 7.7 disposed on the outside of 4.

As shown in FIG. 3, releasable sheets 8, 8 are pasted on the surface of the elastic sheet 7.7, that is, the releasable sheets 8, 8 are attached between the elastic sheet 7.7 and both recording media 4.4. C) 8.8 may be used to perform the above-mentioned pressing.

1 and 3 (here, the material of the elastic sheet 7 is preferably a foamed polyurethane sheet formed by forming foamed polyurethane on a vinyl sheet (the side that contacts the pressing plate 6 is the vinyl sheet); In addition, for example, rubber plates, nonwoven fabrics, artificial leather, Teflon sheets, etc. can be suitably used. Rubber plates include styrene-butadiene rubber sheets, isoprene rubber sheets, polyurethane rubber sheets, etc., and nonwoven fabrics include Vilene, There are G and S felts, etc., and artificial leathers include Excelene (product name, manufactured by Toshi), etc.The thickness of these elastic sheets 7 is 1
About 1 is good.

As the release sheet 8, for example, a silicone sheet,
Fluororesin sheets, polyethylene sheets, etc. are preferred, and fluororesin sheets are particularly preferred. As the fluororesin, a tri- or tetra-fluoride fluororesin is preferable.

The thickness of the elastic sheet 7 and the releasable sheet 8 is preferably within a thickness tolerance of ±5%.

It goes without saying that the elastic sheet 7 and the releasable sheet 8 may be adhered to the press plate 6 in sequence as described above; For example, it may be simply positioned between the two, or a coating may be applied to the pressure plate 6 (in the case of the elastic sheet 7) or the elastic sheet 7 (in the case of the release sheet 8). as elastic sheet 7 or release sheet 8
may be formed by coating or the like.

(Example) Next, examples of the present invention will be described together with comparative examples.

A. Implementation conditions (Example 1) Foamed polyurethane sheets were pasted as elastic sheets 7 and 7 on the inner surfaces of the pressing plates 6 and 6, respectively, and pressure was applied to both recording media 4°4 through the foamed polyurethane sheets. At this time, the pressure distribution between the two recording media was measured.

As shown in FIG. 4, the foamed polyurethane sheet has the following properties:
Foamed polyurethane 7a is formed on a vinyl sheet 7b with good thickness accuracy, and the thickness accuracy is ±3% or less with respect to one sheet thickness (manufactured by Speed Fam Co., Ltd.,
5urf'In No, 191PVC, 194PVC)
. Note that each foamed polyurethane sheet was attached to the pressing plate 6 on the vinyl sheet 7b side.

The press pressure of the above pressing was 5 kg/cd, and the above pressure distribution was performed using pressure sensitive paper (manufactured by Fuji Photo Film Co., Ltd., Prescale) placed between both recording media 4, 4 (i.e., as shown in Fig. 2). The adhesive layer 5 was not formed on the optical disc, but pressure-sensitive paper was placed on this part and pressed).

<Example 2> Foamed polyurethane sheet 7.7 of Example 1 and recording medium 4
, 4 with a releasable sheet 8.8 interposed between them.

As the release sheet 8, a fluororesin sheet (tetrafluoroethylene sheet, thickness 0.211111, manufactured by Nitto Electric Industries, Ltd.) was used. The thickness accuracy of this fluororesin sheet is
The sheet thickness is 0.2+om±2%.

Other conditions are the same as in Example 1.

Comparative Example> Pressing was performed without anything intervening between the pressing plates 6, 6 and the recording media 4, 4.

Other conditions are the same as in Example 1.

B Implementation results <Example 1> The pressure distribution was good at 5 kg/cd±5%.

This is thought to be because the foamed polyurethane sheet 7, which is an elastic sheet, absorbed the cracks and thickness unevenness of the recording medium 4.

Further, no scratches or the like were observed on the surface of the recording medium 4, which was good.

However, when the surface of the recording medium 4 was observed under a microscope, many foreign particles of several tens of micrometers were found. Although it was confirmed that these foreign substances did not affect the error rate when recording and reproducing signals on the recording medium 4, clouding due to moisture condensation was observed on the surface of the recording medium 4 under high humidity.

The foreign matter is presumed to be urethane separated from the surface of the polyurethane 7a of the foamed polyurethane sheet 7. That is, it is presumed that the urethane is detached and adheres to the surface of the recording medium 4 as a foreign substance, and that water condenses around the adhered foreign substance (with the foreign substance as a core), resulting in a cloudy state.

<Example 2> The pressure distribution was 5 kg/c-±5%, which was good as in Example 1. In addition, no scratches or the like were observed on the surface of the recording medium 4, and no foreign matter larger than several tens of micrometers was observed, and good results were obtained.

In addition, even under high humidity conditions (from room temperature to 60°C, 90% RH), recording media 4 due to condensation of plasticizers or moisture may
No clouding of the surface occurred.

Comparative Example> The pressure distribution was 5kg1cj±20%, and Example 1゜2
The distribution was very uneven. In particular, there was a tendency for the pressure at the outer periphery to be high, probably due to the presence of particles on the outer periphery of the recording medium 4.

Furthermore, several scratches with a size of several tens of μm were observed on the surface of the recording medium 4. This is presumed to be caused by adhering dust interposed between the recording medium 4 and the pressing plate 6.

Table 1 shows the implementation results of Examples 1 and 2 and Comparative Examples,
In addition, performance comparison results of magneto-optical disks manufactured according to these Examples and Comparative Examples are summarized.

(Effects of the Invention) The method for manufacturing an optical disc according to the present invention applies pressure with an elastic sheet interposed when adhering two recording media, so instead of pressing directly with a conventional hard press plate. It is possible to prevent scratches caused by unevenness of the pressing plate and foreign objects that occur on the pressed surface of the optical disc.

Also, the outer circumference of the recording medium is thicker than the inner circumference, etc.
When a hard pressure plate is used to apply direct pressure to a recording medium whose thickness is partially uneven, as in the past, the pressure is higher in the thicker areas than in the thinner areas. However, by applying pressure through an elastic sheet as in the present invention, unevenness in thickness, etc. can be absorbed and pressure can be applied uniformly to the entire recording medium. It is possible to prevent cracking of the optical disc caused by uneven adhesion.

Furthermore, if a release sheet is interposed between both recording media and the elastic sheet during the above-mentioned pressing, clouding of the optical disk surface due to transfer of plasticizer, which may occur depending on the material of the elastic sheet, can be avoided. It is possible to prevent foreign matter from adhering to the optical disk surface due to local peeling of the elastic sheet.

Note that the method according to the present invention is also effective when bonding optical discs provided with a protective layer made of ultraviolet curing resin in order to protect the entire laminated film formed by laminating a recording layer and an inorganic protective layer. Of course it is.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing one embodiment of the optical disk manufacturing method according to the present invention, FIG. 2 is a schematic cross-sectional view of a double-sided type magneto-optical disk, and FIG. 3 is similar to FIG. 1, showing another embodiment. FIG. 4 is a sectional view of a main part showing an example of an elastic sheet. 1...Substrate 2...Recording layer 3...
Protective layer 4... Recording medium 5... Adhesive layer 7... Elastic sheet 8... Release sheet September 30, 1988 Patent Application No. 194.858 2, Invention Name of optical disc manufacturing method 3, Relationship with the Shin case to be amended Patent applicant Location 210 Nakanuma, Minamiashisu City, Kanagawa Prefecture Name (
520) Fuji Shakoshi Film Co., Ltd. 4, Agent address: 7th floor, Hauraiya Building, 5-2-1 Roppongi, Minato-ku, Tokyo Self-redundancy amendment 6, subject of amendment ``Detailed description of the invention'' section of the specification 7. Contents of amendment 1) "80°C" on page 4, line 7 of the specification is corrected to "60°C". 2) "Passing" in the first line of page 10 is corrected to "pressing". 3) On page 11, line 12, insert ``(Put into an atmosphere of 60° C. and 90% RH from room temperature)'' after ``under humidity J''. 4) On page 12, line 5, insert ``atmosphere'' after ``90% RH.''

Claims (2)

[Claims] (1) In a method for manufacturing an optical disc in which two recording media are bonded together by pressing them with an adhesive interposed between them, the pressure of both recording media is placed on the outside of both recording media. A method for manufacturing an optical disc, characterized in that the manufacturing method is performed through an elastic sheet. (2) The method for manufacturing an optical disc according to claim 1, wherein when pressing both recording media, a release sheet is interposed between the recording media and the elastic sheet.