JPS63114643A - Information recording substrate and its manufacturing method - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an information recording substrate with an air sandwich structure that has excellent heat resistance, moisture resistance, chemical resistance, etc., and a method for manufacturing the substrate by ultrasonic welding. This provides a suitable manufacturing method.

[Conventional technology and problems]

As an information recording substrate (hereinafter sometimes abbreviated as an optical disk), especially a write-once information recording substrate, two disk substrates 1.2 each having a recording layer are arranged with the recording layers facing each other, and a space is formed between them. A so-called air sandwich structure, in which the outer circumferential spacer 3 and the inner circumferential spacer 4 are interposed and bonded together to form a (j.1 structure), is already known.

As materials for constructing such an optical disk, light-friendly materials, particularly those that have been conventionally used or considered as substrates for recording other types of information, can be used. That is,
Specific examples include polymethyl methacrylate, polycarbonate, polystyrene, hard polyvinyl chloride, epoxy resin, and glass.

However, each of the above-mentioned materials has its own advantages and disadvantages, so even if an optical disk is manufactured using these materials, the resulting optical disk will reflect the advantages and disadvantages of the material.

In other words, polymethyl methacrylate has a heat distortion temperature of 1
Poor heat resistance at around 00℃ and water absorption rate of 0.4%
Polycarbonate has excellent heat resistance, but has a large photoelastic constant and high birefringence.In addition, its surface hardness is low and it is easily damaged, and its water absorption rate is low. Although it is 0.15%, which is smaller than polymethyl methacrylate, the problem of moisture resistance still remains.Polystyrene is inferior in heat resistance, impact resistance, and surface hardness, as well as being inferior to polystyrene after molding. Due to its large refraction, it cannot actually be used as an optical disc.Polyvinyl chloride also has very poor heat resistance, as well as poor processability and durability, making it difficult to use as an optical disc.Epoxy resin is difficult to use as an optical disc in terms of heat resistance. Although it is very good, it has poor moldability and is difficult to mass produce.Furthermore, it has a large photoelastic constant and has the problem of birefringence due to residual stress during molding.Glass has good heat resistance, moisture resistance, and surface hardness. However, it is brittle, easily broken, and heavy, making it inferior in handling and productivity.

As described above, conventionally known materials have advantages and disadvantages when applied to the air sandwich structure optical disk that is the object of the present invention, and it is difficult to obtain a material with perfectly balanced performance.

Furthermore, in many conventionally known air sandwich structures, the spacer and the disk substrate are bonded using a thermosetting or UV curing adhesive.

However, when using adhesive, the adhesive must be applied uniformly onto the spacer, which has a width of only a few millimeters, so that it does not protrude, and the adhesive must be applied evenly when bonding the spacer and disk substrate together. Care must be taken to ensure that the adhesive does not protrude beyond the adhesive surface, making it difficult to control the coating process.

Furthermore, there is a risk that the heat applied during curing, by-product gases generated during the curing reaction, unreacted residual monomers, and organic solvents may damage the substrate and the recording layer. Furthermore, no matter how strictly the coating process is controlled, it is difficult to achieve an adhesive layer with a uniform thickness over the entire surface of the spacer, and the resulting optical disc may be flat due to changes in the thickness of the adhesive layer. They tend to become sexually impaired.

Therefore, recently, a technology for fusing spacers and disk substrates by ultrasonic fusing without using adhesives has been published in Japanese Patent Laid-Open No. 60-103537 and Japanese Patent Laid-Open No. 60-13875.
It was proposed in Publication No. 0, etc.

With the background of such conventional technology, the present inventors developed an ultrasonic fusion method using a new polymer consisting of a copolymer of ethylene and cyclic olefin disclosed in JP-A-60-168708 as a raw material resin. We conducted a study with the expectation that if an optical disk with an air sandwich structure was manufactured using this method, it would have excellent heat resistance, moisture resistance, chemical resistance, and flatness.

However, according to studies conducted by the present inventors, narrow and thin spacers may be destroyed during ultrasonic fusion.
It was found that even if the spacer could be fused, there were cracks in the spacer, the fusion strength was weak, and the flatness was poor.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an optical disc with an air sandwich structure that eliminates the drawbacks of conventional optical discs as described above. This provides an excellent optical disc. Another object of the present invention is to provide an optical disc that is resistant to impact and has a certain degree of cushioning properties. Still another object of the present invention is to prevent even if a spacer and a disk substrate are fused together by ultrasonic fusion, birefringence increases due to residual stress resulting from the fusion process, which impedes performance as an optical disk. The goal is to provide optical discs that are not available. Another object of the present invention is to provide an optical disc with excellent adhesive strength. Another object of the present invention is to provide a method for suitably manufacturing the optical disc as described above.

[Means for solving problems]

That is, the present invention is an information recording substrate having an air sandwich structure in which two disk substrates are fused together via an outer circumferential spacer and an inner circumferential spacer, and the polymer forming the spacer and the disk substrate is 2 [1]. A copolymer of the monomer component shown above and ethylene, wherein the monomer component has a structure represented by formula [2] in the polymer, and further forms a spacer.
The ethylene content of the polymer (b) forming the disk substrate is 55 to 80 mol%.
~70 mol%, and the ethylene content of (a)>
(b) It is a disc recording substrate characterized by having an ethylene content of A method for manufacturing an information recording substrate having an air sandwich structure, wherein the polymer forming the spacer and the disk substrate is a copolymer of a monomer component represented by formula [1] and ethylene, and the monomer component is a copolymer of ethylene. has a structure represented by formula [2] in the polymer, and the ethylene content of the polymer (a) forming the spacer is 55 to 80 mol%, and the ethylene content of the polymer (bl) forming the disk substrate is 55 to 80 mol%. This is a method for producing an information recording substrate, characterized in that the ethylene content is 50 to 70 mol%, and the ethylene content is ta+ ethylene content>(b).

(In the formula, RI and RI2 are hydrogen, an alkyl group, or a halogen, and may be the same or different, and furthermore, R9 or RIG and RI+ or R12 may mutually form a ring, n is 0 or A positive number of 1 or more, R5-R8
When repeated multiple times, these may be the same or different. ) [Function] The polymer forming the spacer and disk substrate constituting the information recording substrate of the air sandwich structure of the present invention has a structure in which the monomer component represented by the above-mentioned formula (11) mainly has the structure represented by the formula [2]. It is a copolymer with ethylene.

Specific examples of the 7-mer component represented by formula [1] include the following; however, the examples shown here are extremely limited; Anything can be a monomer component of the present invention.

H3 C! 43CH* CHff CHx C) 13 CH3 Among these, the monomer component n-1 in formula (1), that is, the monomer component represented by formula (3), is easy to obtain or synthesize monomers. preferred in terms of

Furthermore, those in which R1-R12 are hydrogen have better heat resistance,
Preferable from the viewpoint of solvent resistance.

In order to produce the above-mentioned monomer components, it is possible to apply, for example, the method disclosed in US Pat.

The copolymer of the monomer component of formula (1) and ethylene may be copolymerized with other monomer components as long as its properties are not impaired. Specifically, there are α-olefins and cyclic olefins, and specific examples thereof include α-olefins having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, such as propylene, 1-butene, and 3-methyl. -1-
Butene, 1-pentene, 3-methyl-1-pentene, 4
-Methyl-1-pentene, 1-hexane, 1-octane, 1-decene, 1-dodecene, 1-tetradecene, 1-
Examples include hexadecane and 1-icosene. Cyclic olefins include non-crosslinked cycloolefins and styrenes, such as cyclopentene, cyclohexene,
, 4-dimethylcyclopentene, 3-methylcyclohexene, 2-(2-methylbutyl)-1-cyclohexene, styrene, α-methylstyrene, and the like. Polyenes such as dicyclopentadiene, ethylidenenorbornene, and vinylnorbornene can be similarly copolymerized. Furthermore, unsaturated carboxylic acids such as (anhydrous) maleic acid can also be copolymerized.

The polymer is produced by polymerization using a well-known Ziegler catalyst, particularly a vanadium-based Ziegler catalyst. More details are disclosed in a prior patent application filed by the applicant (for example, Japanese Patent Laid-Open No. 168708/1983). A feature of the polymer is that the monomer component of formula (1) mainly has the structure shown by 2 [2] in the polymer, and as a result, the iodine value of the polymer is usually 5 or less, and in many cases it is 1. It is as follows.

This configuration is also supported by C-NMR.

By adopting this structure, the polymer is chemically stable and has excellent water resistance and resistance to chemicals such as alkalis and acids, as well as excellent solvent resistance, heat resistance, and weather resistance. It also has an extremely low moisture content. Furthermore, it has excellent dimensional accuracy.

In the present invention, the polymer (a) having an ethylene content of 55 to 80 mol%, particularly 65 to 75 mol% among the above-mentioned polymers, and the polymer forming the disk substrate are used as the polymers forming the outer circumferential spacer and the inner circumferential spacer. as polymer (b) with an ethylene content of 50 to 70 mol%, particularly 55 to 65 mol%, and (ethylene content of polymer (a))>(ethylene content of polymer (b))
Preferably (ethylene content of polymer (a))≧(ethylene content of polymer (b)+5), especially (ethylene content of polymer (b)+20) mol%≧(ethylene content of polymer (al)≧ (Polymer (ethylene content of BL + 5) mol % is used. In this way, by selecting and using materials with different ethylene contents as the spacer and disk substrate, the information recording substrate of the air sandwich structure can be used. It has appropriate cushioning properties, that is, excellent impact resistance and handling properties.Furthermore, the polymer has a small photoelastic constant and photoelastic sensitivity, so it is recommended to use, for example, ultrasonic fusion when fusing the spacer and the disk substrate. However, birefringence does not increase due to residual stress caused by fusion.Furthermore, since the spacer part exhibits appropriate buffering properties, residual stress is absorbed, further suppressing changes in birefringence. The spacer, which is thin in width and thickness and long, is prevented from cracking or breaking due to being unable to withstand the ultrasonic vibration during ultrasonic welding.In addition, the welding elasticity is large; The information recording substrate has an air sandwich structure with excellent flatness.However, if a spacer material with the same ethylene content as the disk substrate material is used, the spacer may crack during ultrasonic welding. Otherwise, broken pieces may fly off and damage the recording layer.

A preferred method for manufacturing the information recording substrate of the present invention is a method using ultrasonic fusion. That is, the recording layers of two disk substrates are overlapped with an outer circumferential spacer and an inner circumferential spacer interposed so as to face each other, and the overlapping surfaces of the spacers and the disk substrates are ultrasonically fused. Even with this method, as long as the spacer and disk substrate are made of a polymer having the above-mentioned structure, an information recording substrate with low birefringence, no cracking or breaking of the spacer, and high bonding strength can be obtained. can be manufactured.

In the description of the present invention, both disk substrates have a recording layer interposed therebetween, but it will be obvious to those skilled in the art that the present invention can also be applied to a type in which only one of the disk substrates has a fused recording layer.

〔Effect of the invention〕

According to the present invention, it is possible to provide an information recording substrate that has excellent heat resistance, moisture resistance, chemical resistance, and dimensional accuracy, is resistant to fJI shock, and has low birefringence. There is no need to worry about it being invaded.

〔Example〕

The content of the present invention will be explained below using preferred examples, but the present invention is not limited to these examples unless otherwise specified.

Moreover, the test method performed in the following examples is as follows.

(1+ Measurement of photoelastic constant For a 10X10X0.5 dragon-sized test piece formed by press molding, no load or 50g,
The degree of birefringence of the test piece under stress was measured by suspending weights of 100 g and 200 g, respectively, using a transmission type ellipsometer with a helium-neon laser light source at a wavelength of 632.8. The photoelastic constant was determined from the relationship between strength and stress.

(2) Letteration (double bath) (birefringence at no load x thickness of test piece) x 2.

(3) Drop test The air sandwich type information recording substrate obtained by the means of the present invention was held vertically and allowed to fall naturally from a point where the center of the substrate was 1 m above the concrete floor to fuse the spacer and disk substrate. Observe the condition of the surface. The results are labeled as n if a part of the fused surface peels off after the nth drop, and n destruction if the information recording substrate itself is destroyed without the fused surface peeling off even after the nth drop. .

(4) Fix the part along the inner spacer of the support test information recording board,
Use a stick to touch one point on the fusion surface between the outer circumferential spacer and the disk substrate.
The information recording substrate is bent by pressing the turtle 1, and it is determined whether the fused portion is peeled off. In addition, the portion along the outer circumferential spacer is fixed, and the fused surface between the inner circumferential spacer and the disk substrate is similarly measured. In this test, several people measured four points on the outer and inner peripheries in the cross direction, and those that peeled off at one of the eight measurement points in total were marked as ×, and those that did not peel off at all points were marked as ○.

(5) Tensile test The tensile strength of the fused surface between the outer spacer part of the information recording substrate and the disk substrate was measured using an Instron universal testing machine.
Measured at a crosshead speed of 501/min.

(6) Flatness A helium-neon laser is irradiated vertically to the substrate surface over a radial distance of 27 to 59 mm from the center of the information recording substrate, and the angular deviation from the vertical direction of the reflected light is measured. The results were displayed as follows. Note that evaluation indices F and G can be used practically as information recording substrates without affecting performance.

A: >10m r13djan B; 10≧B >8.75m radianC:
8.75≧C>7.5m radianD near, 5≧D>6.25m radianE: 6.2
5≧E > 5 m radianF: 5≧F
>3.75m radianG: 53.75m
radian Reference Example 1 Copolymer of ethylene and tetracyclododecene with an ethylene content of 60 mol% C'3C-NMR shows that polymethyl methacrylate with tetracyclododecene in the copolymer・T (Kyowa Gas Chemical Industry, Tl0-10
), polycarbonate (Kijin Kasei, AD-5503
) was measured.

In addition, the letteration (
Measurements were taken at a distance of radius r 1 m from the center of the test specimen.

The results are shown in Table 1.

As can be seen from this result, the copolymer used in the present invention has a small photoelastic constant, so even when welding methods that generate residual stress, such as ultrasonic welding, there is almost no optical shadow. It can be predicted that it will not be shown. On the other hand, polycarbonate has a large photoelastic constant, so when ultrasonic welding is performed, optical distortion occurs due to residual stress, making it impossible to use it as an optical disk. Furthermore, it can be seen that polymethyl methacrylate, which has almost the same photoelastic constant, has a change in birefringence due to a change in the incident angle of the laser. - On the other hand, the copolymer used in the present invention has a constant birefringence even if the incident angle changes. Therefore, it can be seen that polymethyl methacrylate has inferior performance to the polymer used in the present invention in optical disk applications in which the laser is focused in the disk for writing and reading with a laser.

Examples 1 to 2 Two disk substrates with a diameter of 130 mm and a thickness of 1.2 mm made of the ethylene/tetracyclododecene copolymer shown in Table 4, an outer diameter of 130 mm, an inner diameter of 125 mm, and an r size of approximately 0.
, 4 mm outer circumferential spacer and outer diameter 36mm, inner diameter 1
An information recording substrate with an air sandwich structure was manufactured by ultrasonic welding using an inner circumferential spacer of 5 m long and approximately 0.4 mm thick. Specifically, first, the outer spacer and one disk substrate are ultrasonically fused, and then the outer spacer is fused via the inner spacer.The resulting disk substrate and the remaining one disk substrate are stacked together. The overlapping portions of the inner spacers were collectively ultrasonically fused, and then the remaining outer spacers and the unfused overlapping portions of one disk substrate were ultrasonically fused (the fusion conditions are shown in Table 2). . 4th result
Shown in the table.

2nd Omote Toki Examples 1 to 2 The same procedure as in Example 1 was carried out except that the disk substrate and spacer made of the ethylene/tetracyclododecene copolymer shown in Table 4 were used. As shown in the π4 table, the results showed that the welding margin protruded from the welded part, the outer circumferential spacer suffered yi loss, and the welding strength was poor, so that it could not withstand practical use.

Examples 3 to 7 As in Example 1, a spacer and a disk substrate were fused together using ultrasonic waves. However, the polymer constituting the disk substrate of Example 7 is ethylene and methyl tate. In addition, in these embodiments, ultrasonic fusion is performed by first ultrasonically fusing the outer circumferential spacer and one disk substrate, and then bonding the unfused outer circumferential spacer and the other disk substrate, as well as the inner disk substrate. The circumferential spacer and the disk substrates on both sides were collectively fused using ultrasonic waves (conditions are shown in Table 3). The results are shown in Table 4.

From the results shown in Table 3, information on the present invention 3. It can be seen that the substrate for use (optical disk) has excellent fusion bonding state and excellent flatness. In particular, it can be seen that the fusion strength and flatness are particularly good when a copolymer having an ethylene content higher than that of the copolymer constituting the disk substrate by 5 mol % or more is used as a spacer.

However, even if the difference is less than 5 mol%, a spacer with a high ethylene content is of sufficient quality for practical use.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an information recording substrate of the present invention. Applicant: Mitsui Petrochemical Industries, Ltd. Agent Kazu Yamaguchi Fan 110,000

Claims (3)

[Claims] (1) An information recording substrate with an air sandwich structure in which two disk substrates are fused together via an outer circumferential spacer and an inner circumferential spacer, and the polymer forming the spacer and the disk substrate is represented by formula [1] The ethylene content of the polymer (a), which is a copolymer of a monomer component and ethylene, in which the monomer component has a structure represented by formula [2] in the polymer, and further forms a spacer, is 55 ~80 mol%, the ethylene content of the polymer (b) forming the disk substrate is 50-70 mol%
An information recording substrate, wherein the ethylene content in (a) is greater than the ethylene content in (b). ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [1] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [2] (In the formula, R^1 to R^1^2 are hydrogen, alkyl groups, or halogens, and each is the same or may be different, and further R^
9 or R^1^0 and R^1^1 or R^1^2 may mutually form a ring. n is 0 or a positive number of 1 or more, and when R^5 to R^8 are repeated multiple times, they may be the same or different. ) (2) The ethylene content of polymer (a) is [ethylene content of polymer (b) + 5] mol%≦polymer (a)
content ≦ [ethylene content of polymer (b) + 20]
The information recording substrate according to claim 1, which satisfies the relationship of mol%. (3) A method for manufacturing an information recording substrate with an air sandwich structure in which two disk substrates are fused together via an outer circumferential spacer and an inner circumferential spacer by ultrasonic welding, the method comprising polymers forming the spacer and the disk substrate. is a copolymer of a monomer component represented by formula [1] and ethylene, and the monomer component adopts a structure represented by formula [2] in the polymer, and the polymer ( The ethylene content of a) is 55 to 80 mol%, the ethylene content of the polymer (b) forming the disk substrate is 50 to 70 mol%, and (a)
A method for manufacturing an information recording substrate, characterized in that the ethylene content is greater than (b). ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [1] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [2] (In the formula, R^1 to R^1^2 are hydrogen, alkyl groups, or halogens, and each is the same or may be different, and further R^
9 or R^1^0 and R^1^1 or R^1^2 may mutually form a ring. n is 0 or a positive number of 1 or more, and when R^5 to R^8 are repeated multiple times, they may be the same or different. )