JPH1097741A - Method and apparatus for forming protective layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal recording film of a CD or a DVD before bonding, in which a large number of protective layers can be formed in a short time without increasing the power capacity while minimizing deformation due to heat and curing shrinkage. And a method and apparatus for forming a protective layer on a metal recording film or the like. SOLUTION: The method for forming a protective layer of a disk or a disk substrate having an information recording layer, wherein the surface of the information recording layer is uniformly coated with an ultraviolet curable composition, and the surface of the ultraviolet curable composition is applied. UV irradiation on
Forming a protective film of the information recording layer with the ultraviolet-curable composition, in the method for forming a protective layer of the disk or the disk substrate, the ultraviolet irradiation is flashing from the side of the surface on which the ultraviolet-curable composition is applied; The method for forming a protective layer on a disk or a disk substrate, wherein the method is performed once or repeatedly to cure a coating layer composed of the ultraviolet curable composition and form a cured protective layer using the ultraviolet composition. And a device for performing the method, wherein the irradiation means includes a flash light irradiation means of ultraviolet light capable of repeatedly emitting light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a protective layer of an ultraviolet-curable composition on the surface of an information recording layer of a disk or a disk substrate having a visible light reflective information recording layer. Are substrates of various optical disks (hereinafter, simply referred to as CDs and the like) such as CDs (compact disks), MOs (magneto-optical disks), PDs (phase change optical disks), and DVDs manufactured by bonding.
The present invention relates to a method for forming a protective layer on an information recording surface of a 0.6 mm thick substrate (hereinafter, simply referred to as a DVD substrate) for a (digital video disk or versatile video disk).

[0002]

2. Description of the Related Art An ultraviolet curable resin is used as a protective layer agent, and an ultraviolet curable composition is uniformly applied to the surface of a visible light reflective information recording layer of a disk or a disk substrate by a spin coating method which is an existing technique. After coating, the coating layer is cured by irradiating ultraviolet rays that continuously emit light. Usually, a metal halide lamp device having a power capacity of about 3 kW or a high-pressure mercury lamp device is used as an ultraviolet irradiation device for this purpose. The above protective layer forming process will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view for explaining a process of forming a protective layer made of an ultraviolet curable composition on an information recording layer of a substrate such as a CD or a DVD substrate. Number 1 in Figure 1
Is a substrate such as a CD or a DVD substrate, numeral 2 is a visible light reflective information recording layer, numeral 3 is a dispenser for applying an ultraviolet curable composition, numeral 4 is a substrate such as a CD or D
The center axis of rotation of the VD substrate, number 5 uses the dispenser of number 3, and along the center axis of number 4, the CD of number 1
Turning the substrate or DVD substrate, etc., represents the applied UV curable composition.

The viscosity of the ultraviolet-curable composition indicated by numeral 5 in FIG. 1 is about 300 to 600 cP.
When a substrate such as a CD or a DVD substrate of numeral 1 is rotated about 3000 seconds per minute for 1 second along a central axis of rotation of numeral 4, the applied ultraviolet curable composition of numeral 5 is applied. The coating is stretched in the outer peripheral direction by the centrifugal force of rotation to form a uniform coating layer having a thickness of about 6 to 10 μm. At this time, the thickness distribution of the coating layer tends to monotonously increase from the inner peripheral side to the outer peripheral side.

FIG. 2 is a cross-sectional view after the coating is stretched, and numeral 6 in FIG. 2 represents an uncured coating layer of the ultraviolet curable composition.

[0006] Subsequently, the uncured coating layer made of the ultraviolet curable composition obtained in the above process is irradiated with ultraviolet rays to cure the uncured coating layer. A protective layer suitable for sufficiently protecting the layer from a high-temperature and high-humidity environment and physical obstacles is formed.

FIG. 3 is a cross-sectional view for explaining the process of irradiating the ultraviolet rays. Numeral 8 in FIG. 3 denotes a straight tube type light source lamp for irradiating ultraviolet rays continuously, and numeral 9 denotes a lamp. A reflector for condensing the ultraviolet light emitted from the substrate downward, numeral 7 is a substrate such as a CD or a DVD substrate having an uncured coating layer of an ultraviolet curable composition, numeral 10 is a numeral 7 C
D represents a moving table or a conveyor for moving a substrate such as D or a DVD substrate to pass through a region irradiated with ultraviolet rays.

In such a method, heat is easily generated because the light emission of the lamp is continuous, and this heat has a problem that it has a bad influence on the warpage and mechanical properties of the disk.

In a DVD manufactured by laminating two disk substrates having a thickness of 0.6 mm, one of the two substrates has an information recording layer, and the other has only one information recording layer. There is. In the process of manufacturing a DVD,
In a step before the bonding step, a protective layer may be provided on the information recording layer or not. When the adhesive used in the bonding step has an excellent function as a protective layer in addition to the function as the adhesive, it is not particularly necessary to provide a protective layer. However, according to the findings of the present inventors, the case where the protective layer is provided is more excellent in the reliability of information recording than the case where the protective layer is not provided, and
For example, it is known that deterioration is small even when stored for a long time under high temperature and high humidity of 85 ° C.-95% RH. Therefore,
In order to provide a more reliable DVD,
Before laminating two substrates, a protective layer should be provided on the information recording layer in advance.

When a protective layer is provided on a disk substrate having a thickness of 0.6 mm, the rigidity of the substrate itself may be increased even if a synthetic resin such as polycarbonate, acrylic, amorphous polyolefin or the like, which is known and excellent in heat resistance, is used. Is considerably smaller than a normal substrate such as a CD having a thickness of 1.2 mm, so that the substrate is easily affected by heat from a lamp when irradiating ultraviolet rays. Further, when the ultraviolet curable composition is cured by irradiation with ultraviolet light, volume contraction always accompanies. This phenomenon is called cure shrinkage. A disk substrate having a small substrate thickness is susceptible to deformation due to such curing shrinkage.

When the disk substrates that remain deformed due to heat or curing shrinkage during the irradiation of the ultraviolet rays are bonded together,
The discs that have been bonded together also tend to be inferior in warpage quality under the influence of the deformation originally possessed by the substrate. Therefore, it is desired that each disk substrate before bonding is as flat as possible.

In a method in which a substrate such as a CD or a DVD substrate is physically moved relatively under a lamp light source by a conveyor while the coating layer made of the ultraviolet curable composition is cured, the conveyor or the like is moved. C on the means
Since a substrate such as D or a DVD substrate is gradually irradiated with ultraviolet rays from the front end in the conveyor passage direction, curing by the photopolymerization reaction also proceeds in the same order from the front end in the traveling direction. That is, in the irradiation method with such a moving means, it is theoretically impossible to simultaneously cure the entire surface applied on the disk substrate simultaneously. In this situation, even if a straight tube type lamp was used,
It doesn't change at all, even if a spiral type is used.

As a result, the disk substrate that has passed under the lamp light source and whose coating layer has been hardened has a bow-shaped distortion along the passing direction. Needless to say, the degree of distortion varies depending on the curing shrinkage (usually 6 to 15%) of the ultraviolet curable composition and the rigidity or thickness of the substrate.

FIG. 4 shows an example in which a UV curable composition having a curing shrinkage of 8% is applied to a 0.6 mm thick DVD substrate in an amount of 6 to 9 μm.
m, and the distance between the lamp and the disk is kept at 130 mm and the speed of the conveyor is 4 by an ultraviolet irradiation device having a power capacity of about 3 kW using a metal halide lamp.
By passing at m / min, the distortion shape of the disk substrate when the coating layer is cured is represented. This drawing was created by the following method.

A method for measuring a warped shape of a circular desk (A) having light reflectivity, comprising: an irradiating means for continuously irradiating a laser beam from a direction perpendicular to the surface of the desk (A). B), and a position detecting means (C) for detecting a deflection of the reflected beam from a regular reflection position based on a warp of the desk (A) in a radial direction. The relative position of the reflected beam position detecting means (C) is fixed and has an integrated structure (hereinafter referred to as a detecting head (D)), and the detecting head (D)
Either translates relatively in the radial direction of the desk (A), or translates the disk (A) in the radial direction while maintaining the relative position of the detection head (D) ( E), means for rotating the desk (A) (F), means for reading the rotational position of the desk (A) (G), means for detecting the position of the reflected beam (C) and means for reading the rotational position Means for extracting the signal from (G) at regular time intervals and recording the extracted signal; and means for processing the recorded signal (I).
A spot irradiated from the detection head (D) on the surface of the desk (A) while the desk (A) is being rotated by the rotating means (F) by the parallel moving means (E). The change in the position of the reflected beam caused by the radial warpage of the desk (A) when the desk (A) is relatively moved in the radial direction within the light reflecting surface of the desk (A) is determined by the A desk warp shape display method for storing in the signal recording means (H) corresponding to a rotation angle, calculating by the arithmetic processing means (I), and visually displaying output information obtained thereby. A plane which includes a predetermined position on the inner peripheral side of the desk (A), at which recording is started by the signal recording means (H), and which intersects perpendicularly with the incident beam as a reference plane; The point where the axis intersects is taken as the coordinate origin, The value of the warpage at the scanning position in the first round on the inner circumference side of the disk (A) is ignored for the sake of convenience, and the second round based on the information corresponding to the first round of the output signal recording means (I). The displacement amount at the scanning position is obtained, and similarly, the displacement amount at the (n + 1) th scanning position is obtained based on the information corresponding to the nth rotation. , The distance T from the reference plane at the radial position and the angular position of the desk (A) is obtained by adding them on the same radius,
In order to display the warped shape of the desk (A) roughly three-dimensionally, the trajectory drawn by the laser beam on the reference plane is displayed in a substantially elliptical shape.
By adding the distance T from the reference plane at each scanning position, the warped shape of the desk (A) is reduced by 2
The method for displaying the distortion shape of the desk (A), wherein the distortion shape is visualized and displayed three-dimensionally on a three-dimensional coordinate plane. FIG.
Numeral 11 represents a reference plane. It can be seen from FIG. 4 that the disk substrate is bowed and distorted along the passing method.

Furthermore, there has been remarkable progress in disk manufacturing technology in recent years, and the time required for production per disk, that is, the cycle time, has been steadily reduced year by year, and has conventionally been about 3 seconds. However, recently, a performance of 1.5 seconds or less has been required. However, in a conventional protective layer forming apparatus for a disk equipped with a continuous emission type ultraviolet irradiation apparatus, only the coating layer made of the ultraviolet curable composition is cured,
This has already taken about two seconds, which has been a major obstacle in shortening the cycle time.

In order to eliminate this obstacle, if an attempt is made to use a device having a large capacity in order to shorten the ultraviolet irradiation time,
The problem of disk distortion due to the influence of heat from the lamps is finally becoming a major problem, and large-scale auxiliary equipment for cooling is required to solve the problem. This causes an increase in the size and cost of the entire apparatus, and it is difficult to realize an apparatus that matches the product cost.

[0018]

When a protective layer made of an ultraviolet curable composition is formed on the surface of an information recording layer of a disk or a disk substrate having an information recording layer, more specifically, a CD (compact disk), (Optical magnetic disk), various optical disks such as PD (phase change optical disk), or DVD (digital
Good warpage quality by minimizing the effect of heat from the lamp light source during UV irradiation when forming a protective layer on a 0.6 mm thick substrate for video discs or versatile video discs In addition, the deterioration of the warpage quality is prevented by minimizing the deformation accompanying the curing shrinkage of the ultraviolet curable composition, and the cycle time is 1 second or less without causing a significant increase in the equipment power capacity. It is an object of the present invention to provide a method and an apparatus for forming a protective layer on a substrate such as a CD or a DVD substrate, which can obtain the above.

[0019]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and found that a protective layer made of an ultraviolet-curable composition was formed on a substrate such as a CD having an information recording layer or a DVD substrate. In the case of performing a method of uniformly applying an ultraviolet curable composition to the surface of the information recording layer and forming a protective film by irradiating the applied surface with ultraviolet light, an ordinary ultraviolet irradiation device that emits continuous light is used. By using the apparatus, the light source lamp and the substrate are relatively moved to irradiate the substrate with ultraviolet light, so that the applied layer of the ultraviolet curable composition is not cured, but the ultraviolet light is applied to the entire surface of the substrate in a flash manner. Simultaneously (at the same time) by flashing one or more times, the effect of heat from the lamp light source can be minimized, and deformation due to curing shrinkage of the ultraviolet curable composition is minimized. Can be suppressed to a limited, addition, found that curing formation of the coating layer by irradiation cycle time 0.6 seconds without causing an increase in the less equipment power capacity is possible, leading to the present invention.

That is, the present invention relates to a method of forming a protective layer on a substrate such as a CD or a DVD substrate having an information recording layer, the method comprising: uniformly applying an ultraviolet curable composition to the surface of the information recording layer; In the method for forming a protective layer of the substrate, in which a protective film of the information recording layer is formed by irradiating an ultraviolet ray on the surface on which the ultraviolet curable composition is applied, the surface on which the ultraviolet curable composition is applied is provided. From the side, by flashing the ultraviolet irradiation once or repeatedly, thereby curing the coating layer made of the ultraviolet-curable composition to form a cured protective layer of the ultraviolet-curable composition. A method for forming a protective layer on the substrate (hereinafter, a first invention), and an apparatus for forming a protective layer on the substrate having an information recording layer, wherein an ultraviolet curable composition is provided on the surface of the information recording layer. In the apparatus for forming a protective layer of the substrate, the apparatus has a coating means for uniformly applying, and an ultraviolet irradiation means for irradiating an ultraviolet ray to an application surface of the ultraviolet curable composition, and has an ultraviolet flash irradiation means capable of repeatedly emitting light. The apparatus for forming a protective layer of the substrate (hereinafter, referred to as
A second invention).

As a substrate for a CD or the like or a DVD substrate, any known and commonly used material can be used, and examples thereof include a heat-resistant thermoplastic synthetic resin such as acryl, polycarbonate and amorphous polyolefin. The information recording layer is provided with irregularities corresponding to recorded information on one surface of the substrate,
A thin film reflecting visible light is laminated thereon.

The visible light reflective thin film is preferably a thin film which reflects visible light employed for reading recorded information at a high reflectance so that the irregularities can be accurately confirmed. Examples of the visible light reflective thin film include aluminum, nickel, gold, and alloys. This thin film has a visible light reflectance of 80 to 100% and a thickness of 300 to 600 angstroms.

The disk substrate used in the present invention is obtained by casting the material to be the substrate on a stamper having a predetermined size, shape, and thickness, for example, engraved with grooves corresponding to reproduction information such as sound and video. After that, it can be obtained by laminating a thin film that transmits ultraviolet light and reflects visible light. This lamination can be generally performed by depositing the metal to a predetermined thickness on the groove surface of the substrate provided with the groove to form a metal thin film. Thus, an information recording layer in which the groove and the thin film are integrated is formed.

Known and commonly used ultraviolet-curable compositions can be used. This UV-curable composition is
In the art, it is sometimes called an ultraviolet curable resin. As the ultraviolet curable composition, an ultraviolet curable composition containing a photopolymerization initiator is desirable in order to further improve the ultraviolet curability. The photoinitiator is preferably cured with high efficiency and certainty so that its absorption wavelength and at least the wavelength of irradiation ultraviolet rays described later overlap at least.

In preparing the ultraviolet curable composition, a monofunctional (meth) acrylate and a polyfunctional (meth) acrylate can be used as a polymerizable monomer component. Each of these can be used alone or in combination of two or more. Considering cure shrinkage and adhesion,
It is preferable to use a monofunctional (meth) acrylate as a main component and a polyfunctional (meth) acrylate in combination.

The photopolymerization initiator may be any one as long as it generates a radical by light and the radical efficiently reacts with the (meth) acrylate constituting the composition. There are a type in which a molecule is cleaved to generate a radical and a type in which a compound such as a combination of an aromatic ketone and a hydrogen donor is used in combination.

Examples of the former include, for example, benzoin ethyl ether, benzoin isobutyl ether,
Benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1
-Phenyl-propan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1-
(4-Isopropylphenyl) -2-hydroxy-2-
Methylpropan-1-one and 2-methyl-1- (4-
Methylthiophenyl) -2-morpholino-propanone-
1-one and the like can be mentioned.

Examples of the latter aromatic ketones include, for example, benzophenone, 4-phenylbenzophenone, isophthalophenone, 4-benzoyl-4'-methyl-diphenylsulfide, 2,4-diethylthioxanthone, 2-isopropyl Thioxanthone, 2-chlorothioxanthone and the like can be mentioned, and as a hydrogen donor to be combined therewith, for example, a mercapto compound and an amine compound can be mentioned, but an amine compound is generally preferable.

Examples of the amine compound include triethylamine, methyldiethanolamine, triethanolamine, diethylaminoethyl (meth) acrylate, p-dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, , N-dimethylbenzylamine and 4,
4'-bis (diethylamino) benzophenone and the like.

The ultraviolet curable composition may be used at room temperature to 40
It is preferable to use one that is liquid at a temperature of ° C. It is preferable not to use a solvent, and even if it is used, it is preferable to keep it as small as possible. When the composition is applied by a spin coater, it is preferable that the composition be adjusted to have a viscosity of 300 to 600 centipoise, since a uniform film thickness is easily obtained.

The ultraviolet light source used in the present invention has a flashing type and a mechanism for repeatedly emitting light. As the lamp, it is preferable to use a lamp having excellent durability that can withstand repeated light emission, such as a xenon flash lamp.

FIG. 5 shows a flash discharge mechanism for flashing the lamp. Numeral 51 in FIG. 5 indicates a capacitor for storing electric charge, numeral 52 indicates an air-core coil for controlling a current waveform at the time of discharging,
Numeral 53 is a flash discharge lamp (xenon flash lamp),
Numeral 54 indicates an auxiliary electrode obtained by winding a wire around the flash discharge lamp several times, numeral 55 indicates a high-voltage pulse generating circuit, and numeral 56 indicates a terminal for inputting a trigger signal.

As means for charging the capacitor of the numeral 51, for example, an element (not shown) in which a DC voltage power supply and a charging current control resistor are connected in series is connected in parallel to the capacitor of the numeral 51. This can be done by a circuit. In order to discharge the electric charge accumulated in the capacitor of the number 51 to the xenon flash lamp of the number 53, a high voltage pulse generation circuit of the number 55 is provided between the auxiliary electrode of the number 54 and one electrode of the xenon flash lamp of the number 53. , By applying a high-voltage pulse for starting discharge. The high-voltage pulse generating circuit of numeral 55 applies a high-voltage pulse having a peak value of several kilos to several tens kilovolts to the auxiliary electrode of numeral 54 by momentarily applying a control signal having a voltage of 5 V, for example, from the control signal input terminal of numeral 56. It has a mechanism to be performed.

In this way, the control signal can be applied from the control signal input terminal of the numeral 56 in FIG. 5 so that the auxiliary electrode 54 provided on the outer wall of the xenon flash lamp of the numeral 54 and the xenon flash lamp of the numeral 53 A high-voltage pulse is applied between the electrodes, and the gas sealed inside the xenon flash lamp causes an instantaneous dielectric breakdown, which triggers the electric charge accumulated in the capacitor of the numeral 51, and the electric charge accumulated in the capacitor of the numeral 51 during a very short time t. It is released all at once in 53 xenon flash lamps, and emits a strong flash at this time.

In order to irradiate more ultraviolet rays in a shorter time, for example, four to five sets of flash discharge mechanisms as shown in FIG. If the lamps are arranged at regular intervals so as to be uniform and control signals are simultaneously applied to all the flash discharge mechanisms from the terminals corresponding to the numerals 56 in FIG. Flash irradiation with various light intensities can be performed.

The electric energy is from μsec to msec.
It is released during the very short time of the order,
The voltage between the two electrodes of the lamp suddenly drops with the start of discharge, and the discharge itself ends instantaneously.

As a mechanism for causing the xenon flash lamp of numeral 53 in FIG. 5 to repeatedly emit light in a flashing manner, for example, the following mechanism can be mentioned. In the discharge accompanied by the flash, charging of the capacitor indicated by numeral 51 is started from the DC voltage power supply almost simultaneously with the end of the discharge. The time required for charging is related to the time constant τ obtained by multiplying the capacitance (farad) of the capacitor indicated by numeral 51 and the charging current control resistor (ohm, not shown). The relationship between the time constant τ and the discharge time t is generally τ≫t.

When the charge accumulation in the capacitor of the numeral 51 reaches a certain saturation level and reaches a level at which discharge is possible again, when a control signal is applied again from the control signal input terminal of the numeral 56, a second flash is generated. Will be emitted. The flash type repetitive light emission can be performed by repeating the above operation.

In performing flash irradiation with ultraviolet light, if the light from the light source contains infrared light, it is preferable to block the infrared light and irradiate only ultraviolet light. By doing so, it is possible to prevent the infrared rays from being irradiated on the substrate surface of the disk, and the heat hardly causes warping or deformation of the disk itself, and also makes it harder for the quality of the recorded information to deteriorate.

For selectively blocking infrared rays from light emitted from a light source lamp that emits ultraviolet rays including infrared rays, for example, an infrared cutoff filter can be used.

According to the knowledge of the present inventors, even if the discharge energy per discharge is the same, if the peak value or the time width of the discharge current is changed, the intensity and the spectrum distribution of the light emitted from the lamp are changed. It was also found that the curability of the ultraviolet curable composition having the same composition also changed.

In an apparatus for irradiating ultraviolet light with a flash, in order to be able to cure a coating layer made of an ultraviolet curable composition having different characteristics under the same process conditions, the charging voltage to the discharge circuit, the capacitor capacity, and It is preferable that the device has a variable mechanism capable of changing a circuit constant such as an inductance. According to this method, with respect to various ultraviolet curable compositions, the peak value and the time width of the discharge current can be appropriately adjusted with one light emitting device, so that the coating layer can be efficiently cured by the ultraviolet irradiation. It is.

In the flash irradiation, most of the light energy during the flash irradiation is reflected on the surface of the visible light reflective thin film provided on the disk and returned to the lamp side. At this time, if the peak power of the flash is too strong or the distance between the lamp and the disk is too short, the aluminum layer may be damaged and discolored. Therefore, in flash irradiation, it is desirable to appropriately adjust the discharge current waveform and the distance between the lamp and the disk so that the reliability of the information engraved in the pits of the information recording layer is not impaired by the irradiation. The peak power can be reduced by lowering the charging voltage to the capacitor or by increasing the inductance.

[0044]

[Action]

(1) Flash ultraviolet irradiation reduces the amount of heat absorbed by a substrate such as a CD or a DVD substrate at the time of irradiation, and suppresses a rise in the temperature of the substrate and reduces deformation of the substrate, as compared with the case of continuous ultraviolet irradiation.

(2) The flash ultraviolet irradiation makes it possible to irradiate the entire disk surface simultaneously (at the same time), which is impossible with the conventional continuous ultraviolet irradiation method. In the conventional ultraviolet irradiation apparatus, once the light is turned off, it usually takes several minutes or more to reach a stable light amount, so it is not practical to use the lamp while repeatedly turning on and off the lamp. On the other hand, in the flash irradiation method, since the lamp can be turned on / off very easily, the disk to be irradiated with ultraviolet light can be moved below the lamp while the lamp is off. Then, after the disk is positioned in the uniform irradiation area, flash irradiation is performed, so that the entire surface can be uniformly irradiated with ultraviolet rays. As a result, the curing of the coating layer by the photopolymerization reaction can proceed uniformly over the entire surface of the disk, and the mechanical distortion and warpage of the substrate can be reduced.

(3) When a flash irradiation device is used as the ultraviolet light source, the curing is completed within a time of only 0.6 seconds without increasing the power capacity of the light source device so much. This fact will be shown later in the embodiments of the present invention.

(4) The ultraviolet curable composition contains a photopolymerization initiator, and the two are so set that the absorption wavelength range of the photopolymerization initiator and the wavelength range of the ultraviolet light to be irradiated overlap as much as possible. By selecting, curing can be completed with less energy consumption.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes the following embodiments. 1. A method for forming a protective layer of a disk or a disk substrate having an information recording layer, wherein an ultraviolet curable composition is uniformly applied to the surface of the information recording layer, and the surface of the ultraviolet curable composition is irradiated with ultraviolet light. By forming a protective film of the information recording layer with the ultraviolet-curable composition, in the method for forming a protective layer of the disk or the disk substrate, the ultraviolet irradiation is flashed from the surface to which the ultraviolet-curable composition is applied. The protective layer of the disk or the disk substrate, wherein the coating layer made of the ultraviolet curable composition is cured by performing once or repeatedly to form a cured protective layer made of the ultraviolet curable composition. Forming method.

2. A method for forming a protective layer of a compact disc having an information recording layer, comprising uniformly applying an ultraviolet curable composition to the surface of the information recording layer, and irradiating the ultraviolet curable composition-coated surface with ultraviolet light. Forming a protective film of the information recording layer using the ultraviolet-curable composition, wherein the ultraviolet radiation is flashed once from the surface on which the ultraviolet-curable composition is applied, in a flash-like manner. Alternatively, the method for forming a protective layer of the compact disc may be characterized in that the coating layer made of the ultraviolet curable composition is cured by repeating the process to form a cured protective layer made of the ultraviolet curable composition.

3. A method for forming a protective layer of a digital video disk substrate having an information recording layer before bonding, wherein the ultraviolet curable composition is uniformly applied to the surface of the information recording layer, and the ultraviolet curable composition is applied. By irradiating the surface with ultraviolet light, a protective film of the information recording layer is formed by the ultraviolet curable composition, in the method for forming a protective layer of the digital video disk substrate, from the surface coated with the ultraviolet curable composition, The digital video, wherein the ultraviolet ray irradiation is performed once or repeatedly in a flash manner to cure a coating layer made of the ultraviolet curable composition and form a cured protective layer of the ultraviolet curable composition. A method for forming a protective layer on a disk substrate.

4. 4. The method according to any one of the above-described 1, 2, or 3, wherein the ultraviolet light is synchronously flash-irradiated by a plurality of lamps.

5. The ultraviolet-curable composition contains a photopolymerization initiator, and the absorption wavelength region of the photopolymerization initiator and the wavelength region of the ultraviolet light to be irradiated are overlapped as widely as possible. Or the method according to any one of the above items 4.

6. The method according to any one of the above-mentioned 1, 2, 3, 3, 4, or 5, wherein a filter for blocking infrared rays is provided on an optical path between the lamp light source and the disk.

7. An apparatus for forming a protective layer of a disk or a disk substrate having an information recording layer, wherein the coating means uniformly applies an ultraviolet curable composition to the surface of the information recording layer,
Having an ultraviolet irradiation means for irradiating ultraviolet rays to the application surface of the ultraviolet curable composition, wherein the disk or disk substrate protective layer forming apparatus, characterized by having a flash light irradiation means of ultraviolet light capable of repeatedly emitting, An apparatus for forming a protective layer on the disk or disk substrate.

8. An apparatus for forming a protective layer of a compact disk having an information recording layer, comprising: an application means for uniformly applying an ultraviolet curable composition to the surface of the information recording layer; and irradiating an ultraviolet ray to an application surface of the ultraviolet curable composition. The apparatus for forming a protective layer of a compact disk according to claim 1, further comprising an ultraviolet light irradiating means capable of repeatedly emitting ultraviolet light.

9. An apparatus for forming a protective layer of a digital video disk substrate having an information recording layer before bonding, wherein the coating means uniformly applies an ultraviolet curable composition to the surface of the information recording layer, and the ultraviolet curable composition. And UV irradiation means for irradiating UV light to the application surface of the digital video disk substrate, in the protective layer forming apparatus,
An apparatus for forming a protective layer on a digital video disk substrate, comprising an ultraviolet flash irradiation means capable of repeatedly emitting light.

10. The above-mentioned 7, 8 or above, which is provided with a mechanism for synchronously irradiating ultraviolet light with a plurality of lamps, or
The device according to any one of the above items 9 and 9.

11. The above-mentioned 7, 8, 9, or 10, wherein the ultraviolet curable composition contains a photopolymerization initiator, and the absorption wavelength region of the photopolymerization initiator and the wavelength region of the ultraviolet light to be irradiated overlap. An apparatus according to any one of the above.

12. 7 and 8 described above, wherein a filter for blocking infrared rays is provided on the optical path between the lamp light source and the disk.
The apparatus according to any one of the above 9, 9, 10 or 11.

Next, a preferred embodiment of the present invention will be described. First, a thermoplastic resin with excellent heat resistance is melted, cast into a stamper in which grooves corresponding to recorded information are engraved in the circumferential direction, cooled, and a disc-shaped information recording disk substrate with grooves is cut. obtain.

Then, a metal is sputtered to a predetermined thickness on the surface of the information recording disk substrate where the groove is cut, and a thin film for reflecting visible light for reproduction at a high rate is provided. On the metal thin film, a protective film having excellent adhesion to the metal can be formed so as to have a smooth surface including irregularities on the thin film caused by the grooves and the like. A liquid ultraviolet curable composition containing a photopolymerization initiator having an absorption wavelength that overlaps with the wavelength of the ultraviolet light to be applied is applied in a ring shape in a range of 2 to 2.5 g, and spin-coated to a predetermined thickness. I do. A plurality of such disk substrates are prepared.

Then, the gas-filled flash lamp for an ultraviolet light source is connected to a flash discharge mechanism obtained based on the circuit shown in FIG. 5, and an auxiliary electrode of numeral 54 is connected to a high-voltage pulse generating circuit of numeral 55. Is provided around the flash lamp indicated by the numeral 53. The DC power supply is of a variable voltage type, and the capacitor of numeral 51 and the air-core coil of numeral 52 are of a detachable structure that can be appropriately replaced with those of other capacities. By exchanging the element and operating it, the peak value and the 1/3 time width of the discharge current waveform (the current value rises from zero and becomes 1/3 of the peak value, and thereafter, until it attenuates to 1/3 again) Curing conditions such as the time width) and the repetition rate of lamp emission can be optimized from the viewpoint of the apparatus.

The absorption range of the ultraviolet light and the photopolymerization initiator is as wide as possible so that the emission spectrum of the flash light of the flash lamp of the numeral 53 reacts sharply with the photopolymerization initiator contained in the ultraviolet curable composition. The peak value and 1/3 time width of the discharge current of the flash lamp indicated by the numeral 53 are controlled so as to overlap.

In general, even when lamps having the same shape are used, if the discharge voltage is increased by increasing the charging voltage of the capacitor indicated by the numeral 51, the current peak value at the time of discharge increases, and as a result, the ultraviolet light having a wavelength of 400 nm or less, The spectral intensity in the wavelength region relatively increases. Also, the number 51
Even if the charging voltage of the capacitor is constant,
As the inductance of the air-core coil denoted by numeral 52 is reduced, the 1/3 time width is reduced, and the peak value of the discharge current waveform is increased. As a result, the spectral intensity in the ultraviolet wavelength region having a wavelength of 400 nm or less is relatively increased. It will increase. In this way, the emission spectrum of the flash lamp of the numeral 53 has a peak value of the discharge current at the time of emission and 1/3.
It is possible to control to some extent by changing the time width. On the other hand, the photopolymerization initiator contained in the ultraviolet curable composition includes two types: a type in which a molecule is cleaved to generate a radical; and a combination type in which an aromatic ketone and a hydrogen donor are combined.
As described above, there are various types, but the absorption spectrum of ultraviolet rays varies considerably depending on the selection and combination of these materials. Therefore, in order to complete the ultraviolet curing of the ultraviolet curable composition with the minimum necessary lamp input energy (that is, to obtain the maximum curing efficiency), the side of the flash type ultraviolet irradiation device and the above It is desirable to find and use optimum conditions such that the wavelength regions of the two materials overlap as widely as possible from the material side of the ultraviolet curable composition.

In order to further suppress the influence of heat from the lamp at the time of flash irradiation, a filter for blocking infrared rays is provided on the optical path between the flash lamp light source and the disk.

As described above, an ultraviolet ray irradiating device and an ultraviolet curable composition are prepared, and a composition obtained by uniformly applying the ultraviolet ray composition on a desired disk substrate is opposed to a flash lamp light source. Ultraviolet light is radiated in a flash light by induction from an auxiliary electrode connected to the.

[0067]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail. [Embodiment 1] First, a disk substrate having an information recording layer used in this embodiment is a substrate made of polycarbonate resin having a thickness of 0.6 mm, and a metal thin film laminated on the information recording layer of the disk substrate is Made of aluminum and has a thickness of 45
0 angstrom. FIG. 6 is a cross-sectional view showing the structure of the ramp section. Numeral 53 in FIG. 6 indicates a xenon flash lamp (10.5 m inside diameter) manufactured by Ushio Inc.
m, arc length 200 mm), numeral 62 is a cold filter that blocks infrared rays and transmits ultraviolet rays well, numeral 63 is a tray for holding a disk, numeral 7 is a disk substrate with an uncured protective layer shown in FIG. Numeral 61 denotes a mirror that reflects ultraviolet rays with high efficiency. UV curable compositions for the protective layer include those manufactured by Dainippon Ink and Chemicals, Inc.
-318 was used. The application of SD-318 has a viscosity of 31.
Approximately 2 grams of the material adjusted to 0 cP was applied in a ring shape on the inner peripheral side of the disk substrate on which the information recording layer was placed upward, and then spun at a rotation speed of 3600 rpm for 1 second. went.

In FIG. 6, the distance between the lamp center axes of the adjacent lamps is 36 mm, and the distance from the lamp center axis is 62 mm.
The distance to the infrared cutoff filter is 25 mm, and the number 6
The distance between the tray No. 3 and the infrared cutoff filter indicated by numeral 62 was set at 10 mm.

The flash irradiator of this embodiment has two power supply systems, and two xenon flash lamps are connected in series for each power supply system, so that a total of four lamps are used.

The main circuit constant is that the capacitance of the capacitor is 250 μm.
F, the inductance of the air core coil is 330 μH, and the charging voltage is 1800 V. In this case, the input energy per light emission per lamp is about 200J.
The pulse repetition rate was 5 times / second, and the lamps were illuminated by giving a control signal so that the four lamps emitted light synchronously. The power capacity under such conditions is 200 J / line × 4 lines × 5 times / second = 4000 J / second (4 kW).

Under the above conditions, it was found that the coating layer had been cured to a pencil hardness HB or more by the flash irradiation three times repeatedly. The time required for flashing ultraviolet irradiation was only 0.6 seconds.

For comparison, with respect to the disk substrate of the present invention whose protective layer was cured by flashing ultraviolet light irradiation, the diameter of the disk substrate was measured at the outermost peripheral position of the disk substrate by a light reflection method which is a well-known conventional technique. FIG. 8 shows the maximum value obtained when the inclination of the direction (hereinafter, referred to as a warp angle, the unit is [degree]) is measured over the entire circumference. FIG. 7 shows the results obtained by measuring the warpage angle of the disk substrate having the protective layer cured by the conventional continuous ultraviolet irradiation in the same manner.
Shown in

Regarding the experimental disk substrate, regardless of the flash type ultraviolet irradiation or the continuous type ultraviolet irradiation, each substrate was randomly extracted from the same production lot.
Those selected so as to be completely equal for both were used.

According to FIG. 8, in the case where the protective layer was cured by flashing ultraviolet ray irradiation, the average warp value of n = 20 was 0.6 °.
On the other hand, in the case where the protective layer was cured by the continuous irradiation shown in FIG. 7, the average warp value of n = 20 was 0.9 °, which is 50% higher than that of the flash type irradiation. That is, it was found that the flash type irradiation has a smaller warpage angle.

In this embodiment, a very intense flash was emitted from the xenon flash lamp at the time of irradiation. However, such flash irradiation may damage the aluminum sputtered layer provided on the disk substrate and change its color. I never did.

Example 2 The disk substrate having an information recording layer used in Example 2 was a 1.2 mm thick CD substrate made of polycarbonate resin, and the metal thin film laminated on the information recording layer was Made of aluminum, thickness 6
00 Angstrom. The structure of the lamp section other than the disk substrate, the used xenon flash lamp, the cold filter, the tray, the configuration of the device such as a reflection mirror, the ultraviolet curable composition for the protective layer, and the application conditions of the ultraviolet curable composition are as follows. Same as Example 1.

Under the above conditions, it was found that the coating layer had been cured to a pencil hardness HB or more by the flash irradiation three times repeatedly. The time required for flashing ultraviolet irradiation was 0.6 seconds.

The warpage angle of the disk produced by the above method was also good, with the average value of the number n = 20 being 0.45 °. No information recording layer damage due to flash irradiation was observed.

[0079]

As described above, according to the present invention, the following effects can be obtained. (1) In a method of forming a protective layer such as a disk, a method of uniformly applying an ultraviolet curable composition and then irradiating ultraviolet light at least once in a flash method is used to irradiate ultraviolet light in a conventional continuous method. Compared with the case, the amount of heat absorbed by the substrate during irradiation can be relatively reduced, so that a rise in the temperature of the substrate can be suppressed, and deformation of the substrate due to heat can be reduced.

(2) Further, in the method of irradiating ultraviolet rays one or more times in a flash manner, the entire disk surface which cannot be obtained by the conventional continuous ultraviolet irradiating method is simultaneously (at the same time).
Since UV irradiation can be performed, curing of the coating layer by the photopolymerization reaction can proceed uniformly over the entire surface of the disk, thereby reducing mechanical distortion and warpage of the substrate by the action. Can be.

(3) When a flash type irradiation device is used as the ultraviolet light source, curing can be completed within 0.6 seconds without significantly increasing the power capacity of the light source device.

(4) In order that the photopolymerization initiator contained in the ultraviolet curable composition reacts sharply, the emission spectrum of the flash ultraviolet light and the absorption wavelength of the ultraviolet light and the photopolymerization initiator overlap in a wavelength region as wide as possible. By combining the two, the coating layer can be cured with less energy consumption.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a process of forming a protective layer using an ultraviolet-curable composition.

FIG. 2 is a cross-sectional view after applying an ultraviolet curable composition by a spin method.

FIG. 3 is a cross-sectional view illustrating a process of irradiating ultraviolet rays by a conventional method.

FIG. 4 is a diagram of a 3D display showing a general tendency of disk distortion when a protective layer is provided on a 0.6 mm thick DVD substrate having low rigidity and is irradiated with ultraviolet rays by a conventional method.

FIG. 5 is a basic electric circuit diagram showing a mechanism for flashing ultraviolet light.

FIG. 6 is a cross-sectional view showing a structure of a lamp section of the flash irradiation device used in the embodiment of the present invention.

FIG. 7 is a graph showing a variation in a disk warpage angle when a protective layer is cured by irradiating ultraviolet rays in a conventional method.

FIG. 8 is a graph showing the variation of the disk warpage angle when the protective layer is cured by irradiating ultraviolet rays by the flash method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Information recording layer 3 Dispenser 4 Center axis of disk 5 UV curable composition 6 Uncured protective layer 7 Substrate having uncured protective layer (whole) 8 Light source lamp 9 Reflector 10 Moving means 11 Reference surface 51 Capacitor 52 Air Core Coil 53 Xenon Flash Lamp 54 Auxiliary Electrode 55 High Voltage Pulse Generating Circuit 56 Control Signal Input Terminal 61 Reflecting Mirror 62 Infrared Cutoff Filter 63 Tray

Claims (9)

[Claims] 1. A method for forming a protective layer on a disk or a disk substrate having an information recording layer, comprising: uniformly applying an ultraviolet curable composition to the surface of the information recording layer; By irradiating the surface with ultraviolet light, a protective film of the information recording layer is formed from the ultraviolet-curable composition. In the method for forming a protective layer of the disk or the disk substrate, the side of the surface on which the ultraviolet-curable composition is applied. By flashing the ultraviolet ray once or repeatedly, the coating layer made of the ultraviolet curable composition is cured to form a cured protective layer of the ultraviolet curable composition. A method for forming a protective layer on the disk or disk substrate. 2. A method for forming a protective layer of a compact disk having an information recording layer, comprising: uniformly applying an ultraviolet curable composition to the surface of the information recording layer; By irradiating ultraviolet rays, a protective film of the information recording layer is formed of the ultraviolet curable composition. In the method for forming a protective layer of the compact disk, the ultraviolet ray is applied from the side of the surface on which the ultraviolet curable composition is applied. By irradiating the flash once or repeatedly, the coating layer made of the ultraviolet-curable composition is cured to form a cured protective layer of the ultraviolet-curable composition. Method for forming protective layer. 3. A method for forming a protective layer of a digital video disk substrate having an information recording layer before bonding, wherein a UV curable composition is uniformly applied to the surface of the information recording layer, and the UV curable composition is applied. Forming a protective film of the information recording layer with the ultraviolet curable composition by irradiating the ultraviolet curable composition with the ultraviolet curable composition. In the method for forming a protective layer of the digital video disc substrate, applying the ultraviolet curable composition. By performing the ultraviolet irradiation once or repeatedly from the side of the surface that has been flashed, the coating layer made of the ultraviolet curable composition is cured, and a cured protective layer of the ultraviolet curable composition is formed. And a method for forming a protective layer on the digital video disk substrate. 4. The method according to claim 1, wherein the ultraviolet rays are irradiated synchronously by a plurality of lamps. 5. The ultraviolet-curable composition contains a photopolymerization initiator, and the absorption wavelength range of the photopolymerization initiator and the wavelength range of the ultraviolet light to be irradiated overlap each other as wide as possible. The method according to any one of claims 1, 2, 3, and 4. 6. An apparatus for forming a protective layer of a disk or a disk substrate having an information recording layer, wherein the coating means uniformly applies an ultraviolet curable composition to the surface of the information recording layer; An ultraviolet irradiation means for irradiating ultraviolet rays to the coated surface of the disk or the disk substrate, wherein the disk or the disk substrate has a flash light irradiation means capable of repeatedly emitting ultraviolet light, Protective layer forming device. 7. An apparatus for forming a protective layer of a compact disk substrate having an information recording layer, comprising: an application means for uniformly applying an ultraviolet curable composition to the surface of the information recording layer; An ultraviolet irradiation means for irradiating the application surface with ultraviolet light, wherein the compact disk substrate protective layer forming apparatus further comprises an ultraviolet flash light irradiating means capable of repeatedly emitting light, wherein the compact disk substrate protective layer forming means is provided. apparatus. 8. An apparatus for forming a protective layer of a digital video disk substrate having an information recording layer before bonding, comprising: an application means for uniformly applying an ultraviolet curable composition to the surface of the information recording layer; An ultraviolet irradiation means for irradiating an ultraviolet ray to the application surface of the ultraviolet curable composition, wherein the digital video disc substrate protective layer forming apparatus, wherein the device further comprises an ultraviolet flash irradiation means capable of repeatedly emitting light, A protective layer forming device for digital video disk substrates. 9. The apparatus according to claim 6, wherein said means for irradiating ultraviolet light which can be repeatedly emitted is a mechanism for irradiating ultraviolet light synchronously with a plurality of lamps. Equipment.