JPH0741983A - Electroforming method for master disk of stamper for production of optical recording medium and specific gravity measuring machine and electroforming device used in the method - Google Patents

Abstract

PURPOSE:To electroform the master disk for a stamper which decreases the variations in the film thickness value and film thickness distribution of an electroforming film by continuously measuring the sp. gr. of an electroforming liquid, replenishing the electroforming liquid with necessary components and maintaining the sp. gr. of the electroforming liquid within a prescribed range. CONSTITUTION:The electroforming liquid is supplied through a filter 10 and a discharge port 11 by a pump 9 for liquid circulation from an electroforming standby vessel 6 into an electroforming main vessel 5 and is again returned from an overflow vessel 14 into the standby vessel 6. Electroforming is executed by applying a DC voltage between an anode 8 and cathode 7 in the electroforming main vessel 5. A floating type sp. gr. measuring machine 1, a pH measuring instrument 17 and a liquid component replenishing device 16 are installed in the standy vessel 6. The sp. gr. of the electroforming liquid is measured by the sp. gr. measuring machine 1. The electroforming liquid is replenished with the necessary components from the replenishing device 16 in accordance with the measured value thereof, to control the sp.gr. of the electroforming liquid within + or -0.001 and to maintain the ion concn. of the electroforming liquid to maintain constant. As a result, the electroformed stamper having the decreased variations in the film thickness and film thickness distribution of the electroforming film is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of electroforming a master for producing a stamper for producing an optical recording medium, a specific gravity measuring machine and an electroforming apparatus used in the method.

[0002]

2. Description of the Related Art Conventionally, magnetic materials such as magnetic tapes and magnetic disks, and various semiconductor memories have been mainly used for recording various information. Magnetic memory like this,
The semiconductor memory has an advantage that information can be written and read easily, but on the other hand, there are problems that the contents of information are easily tampered with and high-density recording cannot be performed. In order to solve such a problem, an optical information recording method using an optical recording medium has been proposed as a means for efficiently handling a wide variety of information, and an optical information recording carrier, a recording / reproducing method, and a recording / reproducing apparatus therefor are proposed. Has been done. The optical recording medium as such an information recording carrier is generally an optical recording medium that volatilizes a part of the optical recording layer on the information recording carrier using a laser beam, causes a change in reflectance, or causes a deformation to produce an optical recording medium. Information is recorded or reproduced by the difference in the typical reflectance or transmittance. In this case, the optical recording layer is a so-called DRAW (direct read after write) medium that can be “read directly after writing” without the need for development processing after writing information, and high density recording is possible. Moreover, since additional writing is possible, it is effective as an information recording / storing medium.

FIGS. 3A and 3B are schematic sectional views showing a conventional optical recording medium (optical disk, optical card, optical tape, etc.). Information recording / reproduction is performed while positioning is performed by the phase difference of the laser light using the fine concavo-convex pattern 22 of the track groove. In addition, 21 is a transparent resin substrate, 23 is an optical recording layer, 24 is a spacer, 2
5 is a backing material and 26 is an adhesive layer. In a general optical recording medium, a thermoplastic resin such as polycarbonate resin or polymethylmethacrylate resin is used by using a stamper on which a concavo-convex pattern 22 corresponding to a track or information is recorded.
The uneven pattern 22 is transferred to form a track groove. As a method for manufacturing a stamper, generally, as shown in FIG.
After forming a concavo-convex pattern 43 such as a track groove at a predetermined depth with a resin 42 such as a resist or a photosensitive resin (FIG. 4a), a conductive film 44 is formed (FIG. 4b), and a predetermined thickness is obtained. Electroforming is performed to obtain an electroformed film 45, and then the electroformed film 45 is peeled from the concavo-convex pattern 43 to obtain a metal stamper (FIG. 4c).

Further, in the conventional electroforming method, the following is performed. When performing electroforming, a baffle plate should be inserted between the anode and the cathode of the electroforming tank to improve the plate thickness distribution (JP-A-59-177388, JP-A-60-17089, and JP-A-61-2799699). In order to prevent pinholes, foreign substances such as insoluble oxide slime and smut generated in the electroforming tank are removed in the preliminary tank (Actual Development Sho 58-1414).
35). Further, the traces of the current-carrying jig at the time of electroforming are sealed with an ultraviolet curable resin to prevent penetration of an abrasive or the like at the time of polishing (JP-A-62-209746).

However, the film thickness and film thickness distribution of electroforming are
There is a problem that it changes depending on the change in ion concentration in the electroforming liquid during electroforming. Even if the thickness of the electroformed film fluctuates, in order to obtain a stamper with a predetermined thickness by polishing the back surface of the electroformed film, the thickness of the electroformed film is set to a large value in consideration of variations in the electroformed film, and then electroforming The need arises. However, as the electroformed film thickness increases, the polishing amount increases correspondingly,
There is a problem that the polishing time becomes long. Even if the thickness distribution of the electroformed film fluctuates, in order to make the entire surface of the electroformed film have a uniform thickness, variations in the film thickness distribution of the electroformed film are produced before and during the polishing of the back surface of the electroformed stamper. There is also a problem that it is necessary to measure for each stamper and change the polishing amount of the bulge on the outer peripheral portion of the stamper to perform polishing. For this reason, electroforming is performed by measuring the ion concentration of the electroforming liquid, but chemical quantitative analysis, colorimetric analysis, and other methods are required to analyze the ion concentration of the electroforming liquid. Although these methods have good measurement accuracy, they require time and labor for measurement and can be measured only intermittently.Therefore, only a part of the time during electroforming is used for electroforming. However, there is also a problem that the ion concentration cannot be controlled to be constant and continuous ion concentration cannot be controlled.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to produce a stamper with less variation in the film thickness value of the electroformed film and the film thickness distribution. An object of the present invention is to provide an electroforming method for a master of a stamper for producing an optical recording medium, a specific gravity measuring machine used in the method, and an electroforming apparatus.

[0007]

The present invention which achieves the above object is intended for manufacturing an optical recording medium by electroforming a master having a concavo-convex pattern corresponding to information to be recorded. In the electroforming method of the optical recording medium manufacturing stamper for manufacturing the stamper, by continuously measuring the specific gravity of the electroforming liquid and replenishing the electroforming liquid with the necessary components based on the measured values, Control the specific gravity within ± 0.001,
This is an electroforming method for a master of a stamper for producing an optical recording medium, which comprises performing electroforming while keeping the ion concentration of the electroforming solution constant. (Second invention) A specific gravity measuring instrument used for measuring the specific gravity of an electroforming liquid, in which a connecting rod is slidably inserted in a plurality of annular floats having different specific gravities in the order of specific gravity. (Third invention) An optical recording medium having at least an electroformed main tank for electroforming, an electrolytic preliminary tank containing an electroforming solution, and a means for circulating the electroformed solution between the main tank and the preliminary tank. In a master electroforming device for manufacturing a stamper, a specific gravity measuring device that continuously measures the specific gravity of the electroforming liquid in a preliminary tank and sends out the measurement result as an electric signal, and the electroforming liquid based on the signal. By additionally installing a replenishing device for replenishing the electroforming liquid with the necessary components, the specific gravity of the electroforming liquid is continuously measured, and the ion concentration of the electroforming liquid can be increased by replenishing the electroforming liquid with the necessary components. An electroforming apparatus for a master disk for manufacturing a stamper for optical recording medium production, characterized in that it is configured to perform electroforming while maintaining a constant value. The measurement is performed and at least the circumference of the float is measured. Comprising a said electroforming apparatus provided with the rocking motion preventing means of the electroformed liquid part.

The present invention will be described in detail below.

(First and Second Inventions) FIG. 2 is a schematic sectional view showing an electroforming method of a stamper of the present invention. An anode 8 and a cathode 7 are installed in the electroforming main tank 5, and a DC voltage is applied between the anode 8 and the cathode 7 to perform electroforming. The electroforming liquid is pumped out of the electroforming preparatory tank 6 by the liquid circulation pump 9, and the filter 1
0, and is supplied into the electroforming main tank 5 via the discharge port 11.
The electroforming liquid supplied to the electroforming main tank 5 overflows from the partition plate 13, passes through the overflow tank 14, and returns to the electroforming preliminary tank 6 again. A floating-type specific gravity measuring device 1, a pH measuring device 17, and a liquid component replenishing device 16 are installed in the electroforming preliminary tank 6, and the measuring device 1 measures the specific gravity of the electroforming liquid during electroforming. .
The change in ion concentration during electroforming is mainly due to the change in concentration of water, sulfamic acid, nickel, etc., so the change in ion concentration of the electroforming liquid can be known accurately if the specific gravity and pH of the electroforming liquid are measured. be able to. The pH and the ion concentration are measured by the floating-type specific gravity measuring device 1 of the present invention described below, and necessary ion components are replenished to keep the ion concentration constant during electroforming.

As shown in FIG. 1, a floating-type specific gravity measuring machine 1 is one in which a plurality of specific gravity meters 3 made to be balanced at a constant specific gravity are vertically connected through a connecting rod 2 and installed in an electroforming liquid. is there. According to this method, the specific gravity of the liquid can be easily measured when measuring the specific gravity of the electroforming liquid. The specific gravity of the electroforming liquid is 1.20 to 1.000 in the nickel sulfamate liquid used in the present invention.
Set to a value determined between 350. The control width of specific gravity is measured in 0.001 units, and the maximum width is 0.003
It should be controlled within a range of about 0.001 and more preferably within a range of ± 0.001. Therefore, it is desirable that the measurement width of the series of individually connected hydrometers used in the present invention is 0.001 unit. As the float-type specific gravity measuring machine 1 in the present invention, if it is a float-type specific gravity meter in which buoyancy and weight are adjusted so as to measure a predetermined specific gravity, freely selected from generally used floats. Can be used.
When measuring the specific gravity of the electroforming liquid with the floating-type specific gravity measuring device 1, a mechanism for preventing the influence of waves due to the circulation of the electroforming liquid, that is, a rocking preventing means may be provided as necessary. The wave preventing mechanism can be freely selected from the commonly used methods. For example, a breakwater, a wave relaxation net, or the like can be used. The liquid component replenishing device 16 puts the liquid component in the replenishing liquid tank and supplies the liquid component to the electroforming preliminary tank 6 according to the replenishing amount.

The master can be manufactured by a generally used material and manufacturing method. For example, it can be manufactured by a method of forming an uneven pattern with a resist on a polished glass. The conductive ring that electrically connects the electrode and the master during electroforming can be selected from commonly used materials as long as the material has high electrical conductivity and is easy to process. For example, a metal material such as copper can be used. As a master holder for holding the master, a commonly used holder can be used. As the material of the holder, a material having electrical conductivity and sufficient strength, for example, a metal material such as stainless steel or titanium can be used. For the upper lid, for example, polymethylmethacryl resin, vinyl chloride resin or the like can be used.

The current density at the time of electroforming can be selected within a range in which the electroformed film is not warped or stressed. 1-3
It can be used in the range of 0 A / dm ² , preferably 3 to 10 A / dm ² .

According to the electroforming method of the master for producing the electroforming stamper of the present invention, when electroforming is performed on the master, a plurality of floats balanced with a certain specific gravity of the present invention are put in the electroforming liquid. , The specific gravity of the electroforming liquid is continuously measured within ± 0 by continuously measuring the specific gravity by performing electroforming while continuously measuring the specific gravity of the electroforming liquid and replenishing the necessary components with the electroforming liquid. .00
By performing electroforming while controlling the electroforming to be within 1, it is possible to manufacture an electroformed stamper with less variation in the film thickness and film thickness distribution of the electroformed film. (Third invention) In the third invention, in the electroforming apparatus shown in FIG. 2, the specific gravity measuring device 1 and the liquid component replenishing device 16 are installed in the preliminary tank 6, and the electroforming is being performed. Keep the concentration of each component in the solution constant.

In the present invention, the specific gravity measuring device 1 measures the specific gravity of the electroforming liquid in the electroforming preparatory tank 6 at regular intervals and gives information to a computer (not shown). If there is a change in the specific gravity, the liquid component replenishing device 16 replenishes the required amount of liquid component. A commonly used control method (fuzzy, PID) can be used to calculate the replenishment amount.

As the specific gravity measuring device 1 in the present invention,
A commonly used device can be used as long as it is a float-type specific gravity meter in which buoyancy and weight are adjusted so as to measure a predetermined specific gravity.

Since the specific gravity measuring apparatus 1 is affected by waves due to the circulation of the electroforming liquid, it is possible to install the wave prevention bank 52 and the wave prevention net 53 shown in FIGS. 5 (a) and 5 (b). Any length can be used as the length of the wave prevention bank 52 and the wave prevention net 53 as long as the outer circumference of the specific gravity measuring device 1 can be covered as long as necessary to prevent the influence of the wave on the specific gravity measurement. . If the length is short, it is impossible to prevent the influence of waves on the measurement of the specific gravity, and if the length is long, the circulation of the electroforming liquid in the vicinity of the specific gravity measuring device 1 is deteriorated. It is preferable that there is a length that can cover from the lower surface of the specific gravity measuring device 1 to the upper surface of the electroforming liquid surface 51, and more preferably from the upper surface of the electroforming liquid surface 51 to the specific gravity of the lower surface of the specific gravity measuring device 1. That is, a length 1 to 10 times the partial length of the measuring apparatus 1 in the electroforming liquid is installed in the electroforming liquid. In addition, the wave prevention levees 52 and the wave prevention nets 53 are
As long as the outer circumference of the specific gravity measuring device 1 can be covered as necessary to prevent the influence of waves on the specific gravity measurement, the specific gravity measuring device 1 may be installed so as to cover the outer circumference at any ratio. It is preferable that 1/3 to the entire circumference of the specific gravity measuring device 1 can be covered. By covering a part of the outer circumference of the specific gravity measuring device 1, the wave preventing levee 52 and the wave preventing net 53 can be divided and installed evenly or only in the direction in which the waves come. As another method, as shown in FIGS. 6A and 6B, a specific gravity measuring tank 54 can be installed outside the electroforming preliminary tank 4.
A thin tube 55 or a tube 56 with a resistor 57 may be installed and used between the specific gravity measuring tank 54 and the electroforming preliminary tank 4 in order to prevent waves of circulation of the electroforming liquid. As for the capacity of the specific gravity measuring tank 54, any capacity can be used as long as the specific gravity measuring device 1 can be installed. If the volume is large, the circulation of the electroforming liquid with the electroforming preliminary tank 4 is deteriorated, and if it is small, the specific gravity cannot be measured correctly. Specific gravity measuring device 1
It is desirable that the depth is 2 to 10 times the length of the portion immersed in the electroforming liquid and the capacity is 5 to 100 times that of the specific gravity measuring device 1. The diameter of the thin tube 55 can be any diameter as long as it has a resistance capable of preventing the influence of waves on the measurement of specific gravity. The diameter is preferably in the range of 1/10 to 2 times the length of the portion of the specific gravity measuring device 1 immersed in the electroforming liquid. The tube 56 with resistance can also be used in any shape of tube as long as it has a resistance capable of preventing the influence of waves on the measurement of specific gravity. A shape having a length of 1 to 10 times the length of the portion of the specific gravity measuring device 1 immersed in the electroforming liquid and a resistance of 1/10 to 2/3 of the diameter of the pipe is preferable. .

As shown in FIG. 7, the electroforming liquid component replenishing device 2 puts the liquid component in the replenishing liquid tank 31 and operates the supply pump 32 according to the replenishing amount to move the liquid component to the electroforming preparatory tank 4. Supply. For simplicity, a valve such as a solenoid valve may be installed in place of the supply pump 32, and the valve may be opened / closed according to the replenishment amount to replenish the liquid component. Reference numeral 33 is a pipe for supplying a liquid component to the preliminary tank 4.

According to the electroforming method of the master of the stamper for producing an optical recording medium of the present invention, when the master is electroformed, the specific gravity of the electroforming liquid is continuously measured to determine the necessary components. By installing a device to keep the specific gravity of the electroforming liquid constant by replenishing
By performing electroforming while keeping the ion concentration of the electroforming liquid constant, an electroformed stamper with less variation in the film thickness and film thickness distribution of the electroformed film can be manufactured.

[0019]

EXAMPLES The first and second aspects of the present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. (Example 1) A glass plate (Asahi Glass) having a thickness of 10 mm and a size of 300 × 340 mm and having the same size and a pitch of 12 μm on the surface.
m, a width of 3.0 μm, and a depth of 3000 Å, and an ultraviolet curable resin (Asahi Kasei Kogyo, A.P.R. The resin was cured by irradiating it with ultraviolet rays in a state of sandwiching). After curing, the photomask was removed to obtain a glass master. This master is coated with 1000 liters of nickel by sputtering to make it conductive, and then the outer diameter φ550
It was installed in a circular master holder of mm. A copper plate having a thickness of 0.5 mm was used as the conductive ring. As the anode, a nickel ball (Harshaw Murata, S nickel) was placed in a titanium basket and covered with a cotton cloth to prevent the insoluble matter from being washed away. As the electroforming liquid, an electroforming liquid mixed with the following composition is used.
0 liter was used. Electroformed main tank 150 liters, spare tank 3
50 liters. The electroforming liquid was put in an electroforming device (Nikka Engineering, custom-made product), the temperature of the electroforming liquid was kept at 45 ° C., and the whole liquid was circulated at a cycle of 10 times / hour.

The composition of the electroforming liquid was as shown in the table below.

[0021]

[Table 1] As a float-type specific gravity meter, a donut-shaped hollow glass tube having an outer diameter of 100 mm and an inner diameter of 30 mm was filled with lead particles so as to be balanced with a predetermined specific gravity, and then the glass tube was sealed. Eleven floating-type pycnometers having a specific gravity of 1.280 to 1.290 were manufactured in 0.001 units. The eleven hydrometers were passed through a glass rod having a diameter of 25 mm. This 11-unit specific gravity measuring machine was installed in a preliminary tank of an electroforming apparatus as shown in FIG. As a bank to prevent the influence of waves due to the circulation of the electroforming liquid of the pycnometer, a transparent vinyl chloride resin (plastic in a cylinder) having a thickness of 1 mm is cut into 300 × 600 mm, and the long side is formed into a cylindrical shape. It was installed so as to cover the hydrometer. With a series of densitometers, the specific gravity of the electroforming liquid could be easily measured visually. When the specific gravity of the electroforming liquid was measured without circulating the liquid, it was 1.285. When the specific gravity is measured after circulating the liquid, the error in the measured value is at most 0.
It was 001. The specific gravity of the electroforming liquid was measured with the above-described series of densitometers, and if necessary, pure water was supplied from the liquid component replenishing device in the required amount so that the specific gravity was always kept constant. The specific gravity of the electroforming liquid during electroforming was always kept within ± 0.001 with respect to the set value of 1.285.

Using the master and the master holder,
Keep the ion concentration of the electroforming liquid constant using a specific gravity measuring machine.
The current density between the master and anode is 0.1A at first.
/ Dm ² For 30 minutes, then 5 A / dm² Up to current
Increase the density until the integrated current value of 12000A · min is reached.
Electroformed stamping with a thickness of 250 μm
Got

After the electroforming of 10 sheets was completed, the electroformed film thickness of each master was measured and found to be 25 at the center of each master.
The in-plane film thickness distribution was good at 0 ± 5 μm and 290 ± 10 μm at the outer peripheral part, and the variation in the film thickness of each master was 10 μm at the maximum in both the central part and the outer peripheral part, which was sufficiently small (Mitutoyo, micrometer). . (Embodiment 2) The same master, the same master holder, the same conductive ring, the same electroforming apparatus, the same anode, the same electroforming liquid, and the same wave preventing dike as in Example 1 were used. The same donut-shaped floating type hydrometer as in Example 1 was used as in Example 1.
11 floating type hydrometers are divided into 3 by measurement specific gravity and 3
A hydrometer was passed through each core rod using a core rod (connecting rod). How to divide the floating hydrometer (1.280, 1.2
83, 1.286, 1.289), (1.281, 1.
284, 1.287, 1.290), (1.282,
A floating type hydrometer having a similar measurement specific gravity such as 1.285, 1.288) is prevented from passing through the same core rod. A series of specific gravity measuring machines, through which these three core rods were passed, were installed in the electroforming preliminary tank in the same manner as in Example 1. When measured in the same manner as in Example 1, the specific gravity of the electroforming liquid was 1.285. The maximum measurement error was 0.001. The specific gravity of the electroforming liquid could be measured extremely easily. Electroforming was performed under the same current conditions as in Example 1. The specific gravity during the electroforming was kept within ± 0.001 with respect to the set value of 1.285.

When 10 masters were electroformed in the same manner as in Example 1 to measure the thickness of the electroformed film, each master had a master central part of 250 ± 10 μm and an outer peripheral part of 28 mm.
The film thickness distribution within the plane is sufficiently good at 2 ± 10 μm, and the variation in film thickness of each master is 10 μm at the maximum in both the central part and the outer peripheral part.
m was small enough.

Hereinafter, the third aspect of the present invention will be described more specifically with reference to examples. (Example 3) A glass plate (Asahi Glass) having a thickness of 10 mm and a size of 300 x 340 mm and having the same size and a pitch of 12 µ on the surface.
m, width 3.0 μm, and depth 3,000 Å concave-convex pattern with a photomask (HOYA) formed in a standard format of an optical card, and an ultraviolet curable resin (Asa Kasei Kogyo, A.P.R. The resin was cured by irradiating it with ultraviolet rays in a state of sandwiching). After curing, the photomask was removed to obtain a glass master. This master was coated with 1000 liters of nickel by sputtering to make it conductive, and then 250 x 2
External shape φ550m with 90mm square opening on top lid
It was installed in a circular master holder of m. The opening was provided with a taper portion having an angle of 10 degrees and a length of 10 mm. The conductive ring is a copper plate with a thickness of 0.5 mm and an outer diameter of 550 mm.
It was manufactured by forming a square hole of 90 × 330 mm. As the anode, a nickel ball (Harshaw Murata, S-nickel) was placed in a titanium basket and covered with a cotton cloth to prevent dust from flowing away. As an electroforming liquid, 500 liters of an electroforming liquid mixed with the following composition was put into an electroforming device (Nikka Engineering, custom-made product) with an electroforming tank of 150 liters and a reserve tank of 350 liters, and a liquid temperature of 45 ° C. Then, the whole liquid is 10
It was circulated in a cycle of times / hour.

The composition of the electroforming liquid is shown in the table below.

[0027]

[Table 2] As a floating hydrometer (Malcolm, MD-02) and a wave prevention levee in the spare tank, cut vinyl chloride resin (plastic in a cylinder) with a thickness of 1 mm into 300 × 600 mm, and make the long side into a cylindrical shape to give a specific gravity. It was installed so as to cover the entire circumference of the meter. The specific gravity of the electroforming liquid was 1.285 when the liquid was not circulated before electroforming. When the specific gravity was measured by circulating the liquid, the error in the measured value was ± 0.001 at maximum. The output of the pycnometer is digitized at 1-minute intervals and is taken into a computer (HP, 9000/310), fuzzy control of the following rules is performed, and the computer opens and closes the solenoid valve (CKD, EMB51-15-4). ,
The required amount of pure water was supplied from the liquid component replenishing device to keep the specific gravity constant. The specific gravity of the electroforming liquid during electroforming was always kept within ± 0.001 with respect to the set value of 1.285.

If specific gravity = EQorN then
Replenishment amount = ZERO if Specific gravity = PS then Replenishment amount = PS if Specific gravity = PB then Replenishment amount = PB Antecedent part, EQ: same as set value, N: below set value, PS:
A little higher than the set value, PB: Greatly higher than the set value.

Consequent part, ZERO: no replenishment, PS: little replenishment, PB: large replenishment.

The current density between the master and the anode is initially 0.1.
Since flowing in A / dm ² 30 minutes, by increasing the current density to 5A / dm ^2, by performing electroforming to a cumulative current value of 12000 A · minute, to obtain a stamper electroforming thickness of 250 [mu] m.

After the electroforming of 10 sheets was completed, the electroformed film thickness of each master was measured and found to be 250 ± 5 μm at the center of each master.
m, the outer peripheral portion was 290 ± 10 μm, the in-plane film thickness distribution was good, and the variation in the film thickness of each master was 10 μm at the maximum in both the central portion and the outer peripheral portion, which was sufficiently small (micrometer, Mitutoyo). (Example 4) The same master, the same master holder, the same conductive ring, the same electroforming apparatus, the same anode, and the same electroforming liquid as in Example 3 were used. As a wave prevention net, cut three mesh nets of stainless material into a length of 400 x 200 mm,
The short sides of each of the cut nets were connected with a copper wire at a distance of 5 mm so as to form a loop. The same densitometer, liquid component replenishing device, and control system using a computer as in Example 3 were used. The specific gravity of the electroforming liquid was 1.285 as measured by stopping the liquid circulation before the electroforming. Even when the specific gravity was measured while circulating the liquid, the measurement error was ± 0.001. Electroforming was performed under the same current conditions as in Example 3. The specific gravity during electroforming was kept within ± 0.001 with respect to the set value of 1.285.

When the thickness of the electroformed film was measured by electroforming 10 masters in the same manner as in Example 3, it was 250 ± 10 μm at the center of each master and 2 at both outer circumferences.
82 ± 10 μm, the in-plane film thickness distribution is sufficiently good, and the variation of the film thickness of each master is 10 at maximum in both the central part and the outer peripheral part.
μm was sufficiently small. (Example 5) The same master, the same master holder, the same conductive ring, the same electroforming apparatus, the same anode, and the same electroforming liquid as in Example 3 were used. A rectangular parallelepiped specific gravity measuring tank with a volume of 5 liters and a depth of 500 mm is installed on the side surface of the electroforming auxiliary tank, and the diameter is 30 m.
An electroforming auxiliary tank and a specific gravity measuring tank were connected using 10 thin tubes each having a length of m and a length of 150 mm. The same specific gravity measuring machine as in Example 1 was installed for measuring specific gravity. The same liquid component replenishing device as in Example 1 and the control system using a computer were used. The specific gravity of the electroforming liquid is measured by stopping the liquid circulation before performing the electroforming.
It was 285. Even when the specific gravity was measured while circulating the liquid, the measurement error was ± 0.001. Electroforming was performed under the same current conditions as in Example 1. The specific gravity during electroforming was kept within ± 0.001 with respect to the set value of 1.285.

When 10 masters were electroformed in the same manner as in Example 3 and the thickness of the electroformed film was measured, each master had 250 ± 7 μm at the center of the master and 28 at the outer periphery.
The film thickness distribution in the plane is sufficiently good at 0 ± 10 μm, and the variation of the film thickness of each master is 10 μm at the maximum in both the central part and the outer peripheral part.
m was small enough. (Comparative Example 1) The same master, the same master holder, the same conductive ring, the same electroforming apparatus, the same anode, and the same electroforming liquid as in Example 3 were used. No liquid component replenishing device was installed, and electroforming was performed under the same current conditions as in Example 3 up to the same integrated current. The specific gravity of the electroforming liquid was measured with a specific gravity measuring device. It was 1.285 before electroforming, but 1.2 at the end of electroforming.
It had risen to 96.

As in Example 3, ten masters were electroformed, and the thickness of the electroformed film of each master was measured. The thickness was 230 ± 50 μm at the center and 340 ± 70 μm at the outer periphery.
Therefore, there is a large variation in the thickness of the electroformed film for each master. Further, as compared with Examples 1 and 3 to 5, the film thickness of the outer peripheral portion was thicker and the film thickness distribution was worse.

[0035]

According to the present invention, when electroforming is performed on a master, a plurality of floats balanced with a constant specific gravity are put in the electroforming liquid to continuously measure the specific gravity of the electroforming liquid. By performing electroforming, the specific gravity can be easily measured, necessary liquid components can be replenished, and the ion concentration of the electroforming liquid can be continuously and accurately controlled. Furthermore, the specific gravity of the electroforming liquid is ± 0.00
By controlling within 1 and performing electroforming while keeping the ion concentration of the electroforming liquid constant, it is possible to obtain an electroforming stamper with less variation in the film thickness value and film thickness distribution of the electroformed film.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a state in which specific gravity is measured using an example of the specific gravity measuring device of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of an electroforming apparatus of the present invention.

FIG. 3 is a schematic cross-sectional view showing two examples (a) and (b) of a conventional optical recording medium.

FIG. 4 is a process drawing showing an example of a conventional stamper manufacturing method.

5 (a) and 5 (b) are schematic explanatory views each showing an example of a wave preventive tool of the specific gravity measuring apparatus used in the present invention.

6A and 6B are schematic explanatory views each showing an example of the wave prevention device of the specific gravity measuring device used in the present invention.

FIG. 7 is a schematic configuration diagram showing an example of an electroforming liquid component replenishing device used in the present invention.

[Explanation of symbols]

 1 Floating-type specific gravity measuring device 2 Core rod 3 Density meter 4 Electroforming liquid 5 Electroforming main tank 6 Electroforming preliminary tank 7 Cathode 8 Anode 9 Electroforming liquid circulation pump 10 Electroforming liquid filter 11 Discharge port 12 Baffle plate 13 Partition plate A 14 Overflow tank 15 Partition plate B 16 Liquid component replenishing device 21 Transparent resin substrate 22 Uneven pattern 23 Optical recording layer 24 Spacer 25 Backing material 26 Adhesive layer 31 Replenishing liquid tank 32 Replenishing liquid supply pump 33 Pipe 41 Flat plate 42 Resist layer 43 Concavo-convex pattern 44 Conductive film 45 Electroformed film 51 Electroformed liquid level 52 Wave prevention bank 53 Wave prevention network 54 Specific gravity measuring tank 55 Thin tube 56 Resistive tube 57 Resistor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiya Yuasa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Osamu Kaname 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Naoki Kushida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kai-Oka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. An electroforming solution for a stamper for producing an optical recording medium, which comprises producing a stamper for producing an optical recording medium by electroforming a master having an uneven pattern corresponding to information to be recorded. By continuously measuring the specific gravity of and replenishing the electroforming liquid with necessary components based on the measured values, the specific gravity of the electroforming liquid is controlled within ± 0.001,
An electroforming method for a master of a stamper for manufacturing an optical recording medium, which comprises performing electroforming while maintaining a constant ion concentration of the electroforming liquid. 2. The specific gravity measuring machine used for measuring the specific gravity of an electroforming liquid according to claim 1, wherein the connecting rod is slidably inserted into a plurality of annular floats having different specific gravities in the order of specific gravity. 3. An optical recording medium manufacturing method comprising at least an electroforming main tank for electroforming, an electrolytic preliminary tank containing an electroforming solution, and means for circulating the electroforming solution between the main tank and the preliminary tank. In the electroforming device of the master for manufacturing stamper, the specific gravity measuring device that continuously measures the specific gravity of the electroforming liquid in the preliminary tank and sends out the measurement result as an electric signal, and the electroforming liquid based on the signal. By installing a replenishment device that replenishes the electroforming liquid with the necessary components, the specific gravity of the electroforming liquid can be continuously measured, and the ion concentration of the electroforming liquid can be kept constant by replenishing the electroforming liquid with the necessary components. An electroforming apparatus for a master for manufacturing a stamper for manufacturing an optical recording medium, which is configured to perform electroforming while maintaining the above. 4. The specific gravity measuring device measures the specific gravity by the degree of immersion of the float in the electroforming liquid, and at least a part of the periphery of the float is provided with means for preventing the rocking of the electroforming liquid. Item 3. The electroforming apparatus according to Item 3.