JPH09136052A - Method for forming protective layer and apparatus therefor, method for manufacturing optical recording medium and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the mixture of bubbles into a discharged paint and to eliminate defective coating by removing the bubbles from the paint being transferred substantially at a directly upstream position from a nozzle when the paint for forming a protective layer is sent to be discharged from the nozzle to form the protective layer. SOLUTION: A paint 12 for forming a protective layer stored in a paint storage tank 11 is pumped up by a pump 13 and sent to a nozzle 15 through liquid sending piping 14. A discharge control valve 17 for controlling the discharge amount and discharge timing of paint from the nozzle 15 on the basis of a discharge signal 16 is installed downstream from the pump 13, and downstream from it, a filter 18 for removing bubbles and a suck-back valve 19 for sucking droplets into a liquid sending system after discharge lest the droplets remain at the end of the needle of the nozzle 15 are installed. In the filter 18, a vibration mechanism or an ultrasonic oscillator 20 are installed in the housing part so that bubbles caught by the filter 18 can be separated in proper timing.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and apparatus for forming a protective layer, and more particularly to a method and apparatus suitable for forming a protective layer on an optical recording medium.

[0002]

2. Description of the Related Art In order to prevent the main body from being scratched and imparting antistatic property to the surface, a coating material such as resin may be applied to form a protective layer. For example, in an optical recording medium, a protective layer such as a hard coat layer is usually provided on one surface of a substrate, and a protective layer such as an overcoat layer is provided on the surface of the substrate on which the recording layer and the like are formed.

This optical recording medium is provided with an information recording section capable of optically recording and reproducing on a substrate and is used as a disk for files of documents and data. These irradiate a laser beam focused to about 1 μm while rotating the disk at high speed, and perform 1 μm while performing focus adjustment and position detection.
The recording pits are read out and recorded.
Therefore, in the optical recording medium, a slight warp or deformation of the substrate,
Scratches and foreign matter may lead to signal errors. For this reason, in an optical recording medium, an information recording unit is provided on a substrate with as little thickness unevenness and deformation as possible. Then, in order to prevent the information recording section from being scratched or foreign matter from being attached, a protective layer such as an overcoat layer is provided on the information recording section, and the opposite surface of the substrate is prevented from being scratched or the like. Therefore, a protective layer such as a hard coat layer is provided.

Conventionally, the protective layer is formed by, for example, as shown in FIG. 4, the tank 1 storing the protective layer forming paint is sealed with a pump or a closed container 6 and pressurized by a high pressure gas. Of the paint, the foreign matter in the paint is removed through the filter 2 on the way, and the paint whose discharge timing and discharge amount are controlled by the discharge control valve 3 after the foreign matter is removed is discharged from the nozzle 4 in an amount necessary for forming the protective layer. I am trying to do it. Reference numeral 5 denotes a suck back valve that draws the liquid droplet back into the nozzle 4 (in the liquid feeding system) by using a diaphragm mechanism or the like in order to prevent the liquid droplet from remaining on the tip of the needle of the nozzle 4 immediately after the ejection. ing.

[0005]

However, in the conventional method as described above, bubbles may be generated in the paint in the liquid feeding system of the paint reaching the nozzle 4. When the coating material containing bubbles is discharged from the nozzle 4, bubbles may be contained in the protective layer to be formed, or coating defects such as popping and streaks may occur.

An object of the present invention is to pay attention to the above-mentioned problems, and a method and apparatus for forming a protective layer which does not generate bubbles in a coating material, particularly an optimum method used for forming the protective layer in the production of an optical recording medium. And to provide a device.

[0007]

In order to solve the above-mentioned problems, a method for forming a protective layer of the present invention is to form a protective layer by sending a coating material for forming a protective layer and discharging it from a nozzle,
The method is characterized in that air bubbles are removed from the paint being fed substantially immediately upstream of the nozzle.

In this method, for example, the paint is sent from a paint storage tank by a paint sending means,
After passing through the discharge control valve and the filter in this order, the particles are discharged from the nozzle. Alternatively, the paint is sent from the paint storage tank by the paint sending means, passed through the first filter, the discharge control valve, and the second filter in this order, and then discharged from the nozzle. In the latter mode, the first filter mainly removes foreign matter in the paint,
The second filter mainly removes air bubbles in the paint.

The method of manufacturing an optical recording medium according to the present invention comprises a method of forming a protective layer of an optical recording medium by using such a method of forming a protective layer.

The protective layer forming apparatus according to the present invention is
In an apparatus for forming a protective layer by sending a coating material for forming a protective layer and discharging it from a nozzle, a filter capable of removing bubbles from the coating material being fed is provided substantially immediately upstream of the nozzle. It consists of features.

As a more specific embodiment, the apparatus for forming a protective layer according to the present invention comprises a paint storage tank for storing a paint for forming a protective layer, and a liquid feeding means for feeding the paint in the paint storage tank. And a discharge control valve for controlling the discharge amount of the nozzle, a filter capable of removing bubbles from the paint being fed, and a nozzle for discharging the paint from the filter are arranged in this order. .

In this apparatus, it is preferable that the filter is provided with a means for venting bubbles trapped in the filter. As the vent means, for example,
It is preferable that the filter housing is provided with a vibration mechanism or an ultrasonic oscillator so that the air bubbles trapped by the filter can be separated and vented to the outside of the filter housing.

In the protective layer forming apparatus according to the present invention, a foreign matter removing filter may be provided upstream of the discharge control valve in addition to the bubble trapping filter.

Further, like the conventional apparatus, it is preferable to provide a suck back valve at a position immediately upstream of the nozzle or integrally with the nozzle.

Further, an apparatus for manufacturing an optical recording medium according to the present invention comprises the apparatus for forming a protective layer as described above.

In the method and apparatus as described above,
The air bubbles in the paint generated during the liquid transfer are caught by the filter provided immediately upstream of the nozzle and are captured by the filter. The trapped air bubbles are discharged to the outside of the filter housing through the appropriate venting means as described above. As a result of removing the air bubbles, the paint discharged from the nozzle located immediately downstream of the filter does not contain air bubbles,
Even if it is included, it is suppressed to a very small degree, so that inclusion of bubbles in the protective layer to be formed is substantially prevented. Therefore, a desired protective layer is formed and the occurrence of coating defects due to the inclusion of bubbles is prevented.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The present invention is applicable to any material as long as it forms a protective layer, but since it is particularly suitable for the protective layer of an optical recording medium, the formation of the protective layer of an optical recording medium will be described below. .

First, before entering into a description of a specific embodiment, the structure of the optical recording medium according to the present invention will be described. The type of the optical recording medium according to the present invention is not particularly limited, but may be, for example, a phase-change optical recording medium. A phase-change optical recording medium generally has a recording layer provided on a transparent substrate, and a specific metal that can be reversibly changed between crystal and amorphous by a laser beam is used for the recording layer configuration. The layer structure on the substrate may be, for example, a layer structure having at least a first dielectric layer / a recording layer / a second dielectric layer / a reflection cooling layer on a transparent substrate. After forming each of these layers, a protective layer for an overcoat layer described later can be provided. A protective layer for a hard coat layer, which will be described later, can be provided on the side opposite to the recording surface of the substrate.

In the recording layer of the phase change type optical recording medium, for example, a Te-Ge-Sb-Pd alloy, Te-Ge-Sb- is used.
Pd-Nb alloy, Nb-Ge-Sb-Te alloy, Pt-
Ge-Sb-Te alloy, Ni-Ge-Sb-Te alloy,
Ge-Sb-Te alloy, Co-Ge-Sb-Te alloy,
In-Sb-Te alloys, In-Se alloys, and alloys containing these as main components are used. Especially Te-Ge-
Sb-Pd alloys and Te-Ge-Sb-Pd-Nb alloys are preferable because they hardly deteriorate even after repeated recording / erasing and reproduction and have excellent thermal stability.

Further, these compositions are preferably in the range represented by the following formula from the viewpoint of excellent thermal stability and repeated stability. M _z (Sb _x Te _(1-X) ) _1-yz (Ge _0.5 Te _0.5 ) _y 0.35 ≦ x ≦ 0.5 0.20 ≦ y ≦ 0.5 0 ≦ z ≦ 0.05 where M Represents at least one metal selected from palladium, niobium, platinum, silver, gold and cobalt. Also,
x, y, z and numerals represent the number of atoms of each element (the number of moles of each element). In particular, palladium and niobium preferably contain at least one kind. In this case, z is 0.00
It is necessary to be 05 or more.

The first dielectric layer and the second dielectric layer mechanically protect the recording layer and prevent the substrate and the recording layer from being deformed by heat generated by recording and from being deteriorated in recording / erasing / reproducing characteristics. And plays a role of giving the recording layer resistance to moist heat and oxidation. As such a dielectric layer, Z
nS, SiO ₂ , Ta ₂ O ₅ , ITO, ZrC, Ti
An inorganic film such as C or MgF ₂ or a mixed film thereof can be used. In particular, a mixed film of ZnS and SiO ₂ and a mixed film of ZnS and MgF ₂ are excellent in moist heat resistance, and furthermore, are preferable because deterioration of the recording layer at the time of recording / erasing / reproduction is suppressed.

The reflective cooling layer may be a metal or a mixture of a metal or a metal oxide, a metal nitride, a metal carbide or the like, and a metal.
For example, Zr, Cr, Ta, Mo, Si, Al, Au, P
Metals such as d and Hf, alloys thereof, and mixtures thereof with Zr oxide, Si oxide, Si nitride, Al oxide, and the like can be used. In particular, Al, Au, Ta, alloys thereof, and alloys of Al, Hf, and Pd are preferable because the film can be easily formed.

As the method for forming the first dielectric layer, the recording layer, the second dielectric layer, and the reflection cooling layer on the substrate, a thin film forming method in a vacuum atmosphere, for example, a sputtering method, a vacuum evaporation method, an ion method is used. A plating method or the like can be used. In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled.

As the substrate, it is preferable to use a material through which laser light can be satisfactorily transmitted in order to perform recording and reproduction from the substrate side.
Organic polymer resins such as polycarbonate resin, polyolefin resin, and epoxy resin, mixtures thereof, copolymers, and glass can be used. Above all, recently, polycarbonate resins have become mainstream.

The substrate is formed into a disk.
The molding method is not particularly limited. For example, injection molding can be used. A stamper having a predetermined groove or pit male mold formed on the surface is mounted in a mold, and a desired track is formed on the surface by transfer from the stamper. Can be formed.

The size of the substrate needs to conform to the standard required by the optical recording medium drive. For example, molding on a substrate having a diameter of 90 mm, 120 mm, or 130 mm is specified.

A protective layer for the overcoat layer is formed on the film forming surface of the substrate formed as described above, and a protective layer for the hard coat layer is formed on the non-film forming surface of the substrate. These overcoat layer and hard coat layer are, for example, protective layers made of organic resin, and organic resin paint is used.

As the organic resin protective layer, an actinic radiation curable resin composition containing a polymerizable monomer and an oligomer as a main component or a thermosetting resin composition can be used.

The polymerizable monomer used in the present invention is, for example, a compound having an acryloyloxy group or a methacryloyloxy group (hereinafter, both groups are collectively referred to as a (meth) acryloyloxy group). It is preferably used, and specific examples thereof include (meth) acrylic acid esters shown below.
Methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-
Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth) acrylate of tetrahydrofurfuryl derivative, 1H · 1
Examples include, but are not limited to, H.5H-octafluoropentyl (meth) acrylate, 1.6 hexanediol (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

Further, for the purpose of improving the curability of the organic resin protective layer and adjusting the elastic modulus, other monomers copolymerizable with the above-mentioned monomers may be mixed and used. For example, a diisocyanate compound and a compound having two or more alcoholic hydroxyl groups are preliminarily reacted with a terminal isocyanate group-containing compound to react with a (meth) acrylate containing an alcoholic hydroxyl group. The above urethane (meth) acrylates having a (meth) acryloyloxy group, (meth) acrylic acid diesters of alkylene glycols having 2 to 12 carbon atoms, (meth) acrylic acid cyesters of polyoxyalkylene glycols, polyhydric alcohols (Meth) acrylic acid polyesters having two or more (meth) acryloyloxy groups, ethylene oxide and bispropylene A hydride ethylene oxide and propylene oxide adducts (meth) acrylic acid diesters, 2
Epoxy (meth) acrylates having two or more (meth) acryloyloxy groups in the molecule obtained by reacting acrylic acid or methacrylic acid with a compound having two or more epoxy groups, but are not limited thereto. Not to be.

Further, one or more photopolymerization initiators can be added to the organic resin protective layer composition. As the photopolymerization initiator, various types can be used, for example, benzoin-based compounds such as acetophenone and benzophenone, sulfide-based compounds such as tetramethylmonosulfide, thioxane-based compounds such as thioxane, and benzoin peroxide di-t.
And oxides such as -butyl oxide. The addition amount of the photopolymerization initiator is appropriately 0.01 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer.

The organic resin protective layer composition is cured by coating the recording layer formed on a substrate with the composition and then irradiating it with actinic rays, that is, active energy rays such as ultraviolet rays, electron rays, or gamma rays. , By heating.

As the coating method, various methods such as a spin coating method, a roll coating method and a spray coating method can be used. The thickness of the organic resin protective layer is 0.5 to 30 μm.
The range of m is preferred.

In the present invention, the protective layer is formed using the coating material for forming the protective layer as follows. For example, as shown in FIG. 1, the protective layer forming coating material 12 contained in the coating material storage tank 11 is pumped up by a pump 13 and sent to a nozzle 15 through a liquid delivery pipe 14. A discharge control valve 17 (for example, a diaphragm valve) that controls the discharge amount and discharge timing from the nozzle 15 based on the discharge signal 16 is provided on the downstream side of the pump 13, and bubbles are mainly removed on the downstream side thereof. Filter 1 for
8 are provided. In the present embodiment, the nozzle 15 is provided directly upstream of the nozzle 15 or integrally with the nozzle 15.
A suck back valve 19 for sucking the liquid droplets into the liquid feeding system after the discharge is provided so that the liquid droplets do not remain on the tip of the needle (not shown) of the above.
Substantially immediately upstream of the nozzle 15.

Further, in the present embodiment, the vibration mechanism or the ultrasonic transducer 20 is provided in the housing portion of the filter 18, so that the bubbles captured by the filter 18 can be separated from the filter 18 at an appropriate timing. It is like this. The released bubbles are discharged to the outside through the vent port 21.

From the nozzle 15, a predetermined amount of coating material is discharged onto the optical recording medium 22, and a desired protective layer is formed by spin coating or the like.

In the apparatus and method for forming such a protective layer, even if bubbles are generated in the paint in the liquid supply pipe 14, the bubbles, particularly the relatively large bubbles, are caught by the filter 18 and captured. And the nozzle 15
Just before being discharged from the paint, it is removed from the paint. Therefore, the coating material ejected from the nozzle 15 contains substantially no air bubbles, or even if any air bubbles are contained, it is suppressed to a very small amount. As a result, a good protective layer containing substantially no bubbles is formed. Also, with the inclusion of bubbles,
It also prevents the occurrence of coating defects such as pops and streaks.

Further, if the filter 18 is provided with a vibration mechanism or an ultrasonic vibrator 20, it is possible to efficiently remove the air bubbles entangled in the filter medium,
By performing this at a timing other than when discharging from the nozzle 15, the trapped air bubbles can be discharged to the outside of the system without being mixed into the paint again.

In the above embodiment, the paint 12 is pumped from the paint storage tank 11 by the pump 13 and pressure-fed. However, as shown in FIG. 2, the paint 12 in the paint storage tank 11 is sealed, for example. You may make it seal with 51, pressurize with the pressurization gas 31, and send it to the liquid sending system by this pressurizing force. As the pressurized gas, for example, air, nitrogen gas or the like can be used.

Further, in the present invention, a filter for removing air bubbles (second filter) arranged immediately upstream of the nozzle is used.
In addition to the filter (1), a filter (first filter) for mainly removing foreign matters in the paint may be provided. For example, as shown in FIG. 3, the pump 13 and the discharge control valve 17
The first filter 41 may be provided between the first and the second filters, and the second filter 18 may be provided on the downstream side of the discharge control valve 17. In this way, the filters 41 and 18 can be used by separating their functions for removing foreign matter and for removing bubbles, respectively.

[0041]

As described above, according to the method and apparatus for forming a protective layer of the present invention, it is possible to efficiently remove the air bubbles in the paint by using the filter arranged immediately before the nozzle, and to prevent the air bubbles in the discharged paint. Can be prevented from being mixed, and a desired protective layer can be formed without causing coating defects.

By using this method and apparatus for manufacturing an optical recording medium, it becomes possible to form a uniform and defect-free protective layer such as an overcoat layer or a hard coat layer, and an optical recording medium of good quality. Can be manufactured stably.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a protective layer forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a protective layer forming apparatus according to another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a protective layer forming apparatus according to still another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional protective layer forming apparatus.

[Explanation of symbols]

 11 Paint Storage Tank 12 Paint 13 Pump 14 Liquid Supply Pipe 15 Nozzle 16 Discharge Signal 17 Discharge Control Valve 18, 41 Filter 19 Suck Back Valve 20 Vibration Mechanism or Ultrasonic Transducer 21 Vent Port 22 Optical Recording Medium 31 Pressurized Gas 51 Closed container

Claims (10)

[Claims] 1. When a coating material for forming a protective layer is fed and discharged from a nozzle to form a protective layer, bubbles are removed from the coating material being fed substantially immediately upstream of the nozzle. And a method for forming a protective layer. 2. The formation of the protective layer according to claim 1, wherein the paint is sent from a paint storage tank by a paint sending means, passed through a discharge control valve and a filter in this order, and then discharged from the nozzle. Method. 3. The paint is sent from a paint storage tank by a paint sending means, and a first filter, a discharge control valve,
The method for forming a protective layer according to claim 1, wherein the nozzle is discharged after being passed through a second filter in this order. 4. A method of manufacturing an optical recording medium, which comprises forming the protective layer of the optical recording medium by using the method of forming the protective layer according to claim 1. 5. A device capable of removing air bubbles from a paint being fed at a position substantially upstream of a nozzle in an apparatus for feeding a paint for forming a protective layer and discharging it from a nozzle to form a protective layer. An apparatus for forming a protective layer, comprising: 6. A discharge control valve for controlling the discharge amount of a nozzle, comprising a paint storage tank for storing a paint for forming a protective layer, and a liquid feeding means for feeding the paint in the paint storage tank, An apparatus for forming a protective layer, characterized in that a filter capable of removing air bubbles from the coating material therein and a nozzle for discharging the coating material from the filter are arranged in this order. 7. The protective layer forming apparatus according to claim 6, wherein the filter is provided with means for venting bubbles trapped in the filter. 8. The protective layer forming apparatus according to claim 6, further comprising a filter, which is different from the filter and is capable of removing foreign matter from the paint being fed, on the upstream side of the discharge control valve. . 9. The protective layer forming apparatus according to claim 6, wherein a suck back valve is provided immediately upstream of the nozzle. 10. An apparatus for manufacturing an optical recording medium, comprising the apparatus for forming a protective layer according to claim 5.