JPH0237539A - Information recording medium - Google Patents

Abstract

PURPOSE:To prevent the infiltration of oxygen and steam to a recording layer and to obtain the recording medium having excellent durability by specifying the oxygen permeability and steam permeability of a resin film which covers the surface of a recording layer and is joined to a substrate in the non-recording region of the substrate. CONSTITUTION:The disk-shaped resin film 12 provided on the surface of the recording layer 20 is joined by forming joining regions 14, 15 in the non- recording regions 18, 19 of the resin substrate 11. The film 12 has the value of <=0.1g/m<2>.24 hour.atm. as the oxygen permeability and the value of <=1.0g/m<2>.24 hour as the steam permeability. The oxidation, corrosion, exfoliation, etc., of the recording layer 20 by oxygen and moisture are prevented by using such film 12 which hardly allows the permeation of the steam and oxygen and prohibits the infiltration thereof into the recording layer 20 as a protective film.

Description

[Detailed description of the invention] [Field of invention] The present invention relates to an information recording medium.

More specifically, the present invention relates to an information recording medium in which a disc-shaped resin film is bonded to a disc-shaped resin substrate.

[Technical Background of the Invention] In recent years, information recording media using high energy density beams such as laser beams have been developed and put into practical use. This information recording medium is called an optical disc, and includes video discs, audio discs, large-capacity still image files, and large-capacity computer discs.
A vine used as memory.

The basic structure of an optical disk is a disc-shaped transparent substrate made of plastic, glass, or the like, and a recording layer provided thereon. On the surface of the substrate on which the recording layer is provided,
In order to improve the flatness of the substrate, improve the adhesion to the recording layer, or improve the sensitivity of the optical disc, an undercoat layer or intermediate layer made of a polymeric substance is sometimes provided.

Furthermore, since the recording layer is easily influenced by the outside world, it is necessary to protect it from the outside world. As an optical disc having such an excellent protection function for the recording layer, an optical disc having a linear sandwich structure has been known. However, the air sandwich structure optical disk has many disadvantages in the manufacturing process, such as high cost and many and complicated steps. For this reason, in recent years, a technology has been developed to bond a disk-shaped protective resin film to the side of the substrate where the recording layer is provided.
This method is disclosed in Japanese Utility Model Publication No. 9-36339, Japanese Utility Model Application Publication No. 175427/1983, and the like. The above publication states that in addition to its protective function, the resin film also has functions such as supplying oxygen and diffusing vaporized gas necessary when forming bits, etc., thereby suppressing the energy of laser light during recording. It is said that it can be done.

However, the surrounding environment in which optical discs are used is
Various conditions in temperature and humidity are possible. For example, under harsh conditions of high temperature and high humidity, even an information recording medium whose recording layer is protected by the resin film described above cannot be said to be sufficiently protected. That is, many of the above-mentioned resin films generally absorb and permeate water vapor, oxygen, etc. relatively well. Therefore, even if the recording layer is protected by such a resin film, the recording layer will be oxidized by water vapor, oxygen, etc. that penetrate through the resin film, resulting in corrosion, and in the worst case, This results in a situation where the recording layer peels off from the substrate. Therefore, it cannot be said that the resin film described above sufficiently fulfills the protective function of the optical disc.

[Object of the Invention] An object of the present invention is to provide an information recording medium with excellent durability in which the recording layer and the like are not corroded even under harsh environments such as high temperature and high humidity.

[Summary of the Invention] The present invention provides an inner non-recording area and an outer non-recording area in which a hole is provided at the center and a recording layer is set outside the periphery of the hole and inside the outer periphery, respectively. A flexible disc-shaped resin film with a hole in the center is placed on the recording layer side surface of a disc-shaped resin substrate provided in an area other than the non-recording area on the inner and outer periphery sides of the resin substrate. The resin film has an oxygen permeability of 0. 1 g/m'-24 hours-at
m, has the following value, and has a water vapor permeability of 1.0 g
The information recording medium is characterized in that it is a resin film having a value of / m 2 ·24 hours or less.

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

(1) The oxygen permeability of the resin film is 0.0137m
2-24 hours - atm, the above-mentioned information recording medium characterized in that the value is below.

(2) The water vapor permeability coefficient of the resin film is 0.5 g/
The above-mentioned information recording medium is characterized in that the value is less than or equal to m2.24 hours.

(3) The thickness of the resin film is 0.01 to 3 m.
The above-mentioned information recording medium is characterized in that the information recording medium is in the range of m.

(4) The information recording medium, wherein the resin film is at least one resin film selected from the group of moisture-proof cellophane, polyvinyl chloride, polyvinylidene chloride, fluororesin, polyvinyl chloride fluoride, and polypropylene. .

(5) The information recording medium, wherein at least one surface of the resin film has minute irregularities.

(6) The information recording medium, wherein the resin substrate is at least one resin selected from the group of polycarbonate, polyolefin, polymethyl methacrylate, and epoxy resin.

In addition, the oxygen permeability of the resin film is ASTM D
1434-58. The outline is as follows.

Measurements were performed using a cell manometer for measuring gas permeability. After sealing the surrounding area and attaching a resin film to the approximate center of the cell of the manometer, the cell is completely sealed, and the upper side (high pressure side) and lower ff of the resin film are sealed.
Vacuum 1 liter (low pressure side). Oxygen on the high pressure side at a pressure of 1
The pressure is introduced until the atmospheric pressure is reached, and after a certain period of time, the pressure change that occurs on the low pressure side due to the oxygen that has permeated through the resin film is measured by measuring the difference in mercury column with a manometer. (The atmosphere for the above measurement was a temperature of 23 ± 2°C and a humidity of 50 ± 5% RH.) Based on the measured values, oxygen permeation was converted to g, resin film per m2, and time per 244 hours. I asked for degree.

In addition, the water vapor permeability (moisture permeability) of the above resin film is
The following procedure was carried out in accordance with JIS 20208.

Place a glass plate containing calcium chloride in the bottom of the cup;
A resin film is attached to the top of the cup, and the periphery of the film is sealed with paraffin or the like. This temperature is 40℃
The sample was left in an atmosphere with a humidity of 90% RH for a certain period of time, and the amount of water absorbed by calcium chloride in the glass blood was measured, and the water vapor permeability was calculated from the following formula.

Water vapor permeability = 24 x W/100OX 1000
0 /A However, A: Transmission area of resin film (G) W
:Amount of water absorbed per hour [Effects of the invention] The resin film covering the recording layer of the present invention not only has a protective function to protect the recording layer from dust, but also can withstand harsh environments such as high temperature and high humidity. Even if there is, it has the function of preventing deterioration of the recording layer etc. due to corrosion etc.

That is, since the resin film of the present invention has extremely low values of water vapor permeability and oxygen permeability, it hardly allows water vapor, oxygen, etc. to penetrate onto the recording layer. Therefore, by using such a resin film as a protective film, oxidation, corrosion, and peeling of the recording layer due to oxygen and moisture can be prevented, so that an information recording medium with improved durability can be obtained.

DETAILED DESCRIPTION OF THE INVENTION The invention will now be described in detail with reference to the accompanying drawings.

FIGS. 1 and 2 show typical embodiments of the information recording medium of the present invention. The information recording medium 10 of the present invention is formed by bonding a disc-shaped resin film 12 to a disc-shaped resin substrate 11.

FIG. 1 shows an information recording medium 10 of the present invention with a resin film 1
2 is a plan view seen from the side where the parts 2 and 2 are joined.

The resin film 12 has a hole 13 in the center, and a bonding area 1 on the inner peripheral side in an area corresponding to the non-recording area of the resin substrate 11.
4 and a bonding region 15 on the outer peripheral side are formed and bonded.

FIG. 2 is an enlarged cross-sectional view of the information recording medium 10 of the present invention taken along line I-1 in FIG.

The disc-shaped resin substrate 11 has a hole 17 in the center, and an inner non-recording area 18 and an outer non-recording area 19 are set outside the periphery of the hole 17 and inside the outer periphery, respectively. A recording layer 20 is formed between the non-recording areas on the inner circumferential side and the outer circumferential side.

The disk-shaped resin film 12 is bonded to form a bonding area 14 in a non-recording area 18 on the inner circumferential side of the resin substrate 11, and also forms a bonding area 15 in a non-recording area 19 on the outer circumferential side of the resin substrate 11. and are joined together. Furthermore, since the resin film has appropriate irregularities on its surface, a space 22 is formed between the substrate above the recording layer and the resin film.

The information recording medium of the present invention is obtained by bonding a resin substrate and a resin film as described above, and the bonding method is as follows:
Examples include a method using an adhesive, an ultrasonic fusion method, a heat fusion method, and the like. In order to take advantage of the characteristic of the resin film of the present invention that it is impermeable to oxygen and water vapor, it is preferable that the resin film be bonded to the substrate in a completely hermetically sealed state.

Therefore, it is preferable to join the inner and outer peripheries by an adhesive method and/or a heat fusion method.

The information recording medium of the present invention is basically manufactured by the above method and has the above structure. The characteristic requirements of the present invention are that the disk-shaped resin film has an oxygen permeability of 0.1 g/m"・24 hours・atm, or less,
In addition, the resin film has a water vapor permeability of 1.0 g/m2/24 hours or less.

The resin film covering the recording layer of the present invention not only has a protective function to protect the recording layer from dust, but also prevents the recording layer from deteriorating due to corrosion even under harsh environments such as high temperature and high humidity. Has a function.

As a result of the present invention, we have found that even in information recording media where the recording layer is protected by a resin film, the resin film conventionally used cannot be said to sufficiently protect the recording layer, etc. This is the beginning and has led to the present invention.

In other words, the environment in which an optical disc is used can have various conditions in terms of temperature and humidity, and in particularly harsh conditions of high temperature and high humidity, even information recording media whose recording layer is protected by a resin film may If the resin film absorbs or permeates water vapor, oxygen, etc., the recording layer etc. cannot be sufficiently protected. Water vapor, oxygen, etc. that penetrate through such a resin film oxidize and further corrode the recording layer, and in the worst case, the recording layer peels off from the substrate.

The resin film of the present invention hardly allows the water vapor, oxygen, etc. to penetrate onto the recording layer. Therefore, by using such a resin film as a protective film, oxidation, corrosion, and peeling of the recording layer due to oxygen and moisture can be prevented, so an information recording medium with improved durability can be obtained. .

In addition, the resin film has appropriate unevenness on at least one surface by embossing or the like, so that a space 22 between the resin film and the recording layer is formed as shown in FIG. This is preferable because it makes it easier to This is effective for diffusing vaporized gas, etc., which is necessary when forming bits and the like.

The oxygen permeability of the resin film of the present invention is 0, 1
g/m”-24 hours-atm, preferably the following value, and the water vapor permeability is 0.5 g/m2・2
The value is preferably 4 hours or less.

Further, the thickness of the resin film is 0.01 to 0.3 m.
It is preferably in the range of m, particularly preferably 0,0
It is in the range of 5 to 0.2 nm.

Examples of the resin film of the present invention include moisture-proof cellophane, polyvinyl chloride, polyvinylidene chloride, fluororesin, polyvinyl chloride fluoride, and polypropylene. Preferred are fluorinated polyvinyl chloride field and moisture-proof cellophane. Even if these resins are the same, some of them do not have the water vapor permeability and oxygen permeability of the present invention due to molecular weight, surface treatment, etc., and the resin film that can be used in the present invention has a high oxygen permeability and water vapor permeability. The transmittance is within the scope of the present invention. Further, even resin materials not exemplified above can be used as long as the above values are within the range of the present invention.

Since any known recording layer, resin substrate, etc. constituting the information recording medium of the present invention can be used, these will be briefly explained below.

The resin substrate used in the present invention can be arbitrarily selected from various resin materials conventionally used as substrates for information recording media. Examples of substrate materials include cell-cast polymethyl methacrylate, injection-molded polymethyl methacrylate, and polymethyl acrylate in terms of substrate optical properties, flatness, processability, handling, stability over time, and manufacturing costs. Acrylic resin m: vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer;
Preferred examples include epoxy resins; amorphous polyolefin resins; and synthetic resins such as polycarbonate. Among these, polymethyl methacrylate, polycarbonate, polyolefin, and epoxy resin are preferred from the viewpoint of dimensional stability, transparency, flatness, and the like.

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.

Examples of materials for the undercoat layer (and/or intermediate layer) include polymeric substances such as polymethyl methacrylate, acrylic acid/methacrylic acid copolymer, nitrocellulose, polyethylene, chlorinated polyolefin, polypropylene, and polycarbonate; silane cups; Organic substances such as ring agents; and inorganic oxides (Si02, AJ220, etc.),
Mention may be made of inorganic substances such as inorganic fluoride (MgF2).

Examples of materials used for the recording layer include Te, Zn%
In% Sn, Zr% AJL, Ti% Cu.

Examples include metals such as Ge, Au, and Pt; semimetals such as Bi, As, and Sb; semiconductors such as H5i; 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, combinations of dyes, dyes and polymers, dyes and the metals and metalloids listed above can also be used.

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 by using the above-mentioned materials by vapor deposition, sputtering, ion blasting, coating, or the like. The recording layer may be a single layer or a multilayer, but its layer thickness is usually in the range of 100 to 5,500 densities, preferably in the range of 150 to 1,000 densities, 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 an inorganic substance such as silicon dioxide, tin oxide, or magnesium fluoride in order 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, examples of the present invention will be described. However, each of these aspects does not limit the invention.

[Example 1] Disc-shaped polycarbonate substrate with tracking grooves (outer diameter: 120 mm, inner diameter 15 mm, thickness 1.2 mm)
, depth 0.0 in the range of inner diameter 45 mm to outer diameter 116 ROM
A material (having spiral grooves of 6 μm, width of 1.1 μm, and pitch of 1.6 μm) was made by injection molding.

In and GeS were co-deposited on the surface of the substrate having the tracking grooves at a weight ratio of 67% and 33%, respectively, to form a recording layer having a layer thickness of 600×.

As a resin film, oxygen permeability: 0.002g/m'
-24 hours-atm, water vapor permeability: 0.06g/m
"-z 4 hours, a moisture-proof cellophane film with a thickness of 0.10 mm was cut into a piece with a center hole diameter of 35 mm and an outer diameter of 120 mm.

The resin film was laminated concentrically on the surface of the recording layer and bonded to both the inner and outer circumferential sides by heat fusion.

[Example 2] In Example 1, as a resin film, oxygen permeability:
0.01g7m224 hours-atm, water vapor permeability:
An information recording medium was produced in the same manner as in Example 1 except that poly(3-fluorochloroethylene) having a thickness of 0.10 mm was used at 0.001 g/m2 for 24 hours.

[Comparative Example 1] In Example 1, as a resin film, oxygen permeability:
0.8g/m" 24 hours-atm, water vapor permeability: 2.017m" 24 hours, thickness 0.10mm
An information recording medium was produced in the same manner as in Example 1 except that the PET film was used.

[Comparative Example 2] In Example 1, as a resin film, oxygen permeability:
An information recording medium was produced in the same manner as in Example 1 except that a polycarbonate film having a thickness of 0.10 mm was used.

[Evaluation of Information Recording Medium] Recording and reproduction were performed on each of the obtained information recording media under the following conditions.

Semiconductor laser: Wavelength: 830 nm Beam diameter: 1.6 μm Linear velocity: 5.5 m/s Recording power: 9 mW Reproducing power: 1.2 mW (1) Measurement of C/N Fine pattern of 2-7RLL code information at the above recording power (i oo t oo...) was recorded, and C/
N was measured.

(2) Decrease in C/N After storage for 30 days in an atmosphere of 60°C and 90% RH,
The above C/N was measured.

The above measurement results are shown in Table 1.

Table 1 with margin below Initial C/N C/N after 30 days (dB) (dB) Example 1 Example 2 Comparative example 1 47 43 Comparative example 2
47 43 From Table 1, the information recording medium of the present invention (Examples 1 and 2) using a resin film with a low oxygen permeability coefficient and water vapor permeability coefficient as a protective film shows almost no decrease in C/N after long-term storage. It can be seen that the product has excellent durability since it does not occur.

Furthermore, as shown in Comparative Examples 1 and 2, in the conventional protective films, the C/N decreases significantly after long-term storage.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a typical information recording medium of the present invention, viewed from the side to which the resin film is bonded. FIG. 2 is a sectional view of the information recording medium taken along line I-1 in FIG. 1. Figure I O= l 1 : 12 : ! 3. 14: 15: 18: 19: 20: 22: Information recording medium Disc-shaped resin substrate Disc-shaped resin film 17: Bonding area on the inner periphery side of the hole Bonding area on the outer periphery side Non-recording area on the inner periphery side Non-recording area on the outer periphery side Recording area Recording layer space part 1゜Figure 2 Procedural correction (written spontaneously) 1. Indication of the case 1988 Patent Application No. 188675 2, Name of the invention Information recording medium 3, Person making the amendment Relationship to the case Patent applicant name (520) Fuji Photo Film Co., Ltd. 6, Contents of the amendment as shown in the attached sheet. The "Claims" column of the specification is amended as follows. I-rl. A disc-shaped disc having a hole in the center and a recording layer provided in an inner non-recording area and an outer non-recording area set outside the periphery of the hole and inside the outer periphery, respectively. An information recording medium in which a flexible disk-shaped resin film with a hole in the center is bonded to the recording layer side surface of the resin substrate at the inner and outer non-recording areas of the resin substrate, respectively. The resin film has an oxygen permeability of 0.1 g/m' for 24 hours when standing upright, and a water vapor permeability of 1.0 g/m' as an excess.
- An information recording medium characterized by being a resin film having a 24-hour lower/lower value. J-1 or more

Claims (1)

[Claims] 1. A disc-shaped disc having a hole in the center and a recording layer provided in an inner non-recording area and an outer non-recording area set outside the periphery of the hole and inside the outer periphery, respectively. An information recording medium in which a flexible disk-shaped resin film with a hole in the center is bonded to the recording layer side surface of the resin substrate at the inner and outer non-recording areas of the resin substrate, respectively. The resin film has a water vapor permeability of 1.0 g/m^2・24 hours・atm. It has the following value and oxygen permeability is 0.1g/m^2
- An information recording medium characterized by being a resin film having a value of 24 hours or less.