JP2002241981A - Method for producing stamper and electroforming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of deformation in the circumference of the central part of a stamper in an electroforming stage where a mother stamper is produced from a stamper. SOLUTION: The method for producing a stamper is provided with a stage where a photoresist layer is formed on a glass original plate; a stage where the photoresist layer is exposed; a stage where the photoresist layer is developed; a stage where an electrically conductive film is deposited on the surface of the photoresist layer; a stage where an electroforming is deposited on the electrically conductive film, and the electroforming is peeled from the glass original plate to produce a first stamper; a stage where the first stamper is fitted to the cathode together with a substrate consisting of glass or ceramics, and energizing is performed to the outer circumferential section of the first stamper and the cathode to deposit the electroforming on the surface of the first stamper, so that a second stamper is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a stamper used for manufacturing a light guide used for a liquid crystal display device and the like, and an electroforming method in the method of manufacturing a stamper.

[0002]

2. Description of the Related Art A so-called edge light system in which light is incident from one side surface (light incident surface) of a transparent plate, which is a rectangular plate, and the incident light is emitted from the surface (light exit surface). Is used in a backlight device used for a liquid crystal display device provided in a word processor, a personal computer, a thin television, or the like.
In such a backlight device, a tubular light source is arranged on at least one side surface of a light guide, and an angle of light transmitted through the light guide is formed on a surface (light reflection surface) facing a light emission surface that emits light. Or an element that changes the angle of the light reflected by the light guide (hereafter,
It is called "deflection element". ) Is provided.

[0003] The light incident from the light incident surface of the light guide is changed in its direction by the light reflecting surface and the light emitting surface and is emitted from the light emitting surface. Is propagated. Generally, the density distribution of the deflecting elements and the shape of the deflecting elements are determined so that the brightness of the light emitted from the light emitting surface is uniform over the entire light emitting surface.

The above-mentioned deflecting element has a light guide surface coated with white ink that scatters or reflects light,
The light guide may be provided with an uneven portion such that light is scattered or reflected on the surface of the light guide, or the light guide may contain a light diffusing agent.

[0005] The above type of light guide is manufactured by screen printing or the like. However, if the thickness of the white ink on the printing surface becomes uneven, the distribution of light reflectivity becomes uneven.
As a result, the brightness of the light emitted from the light emitting surface becomes uneven. Furthermore, if dust in the air mixes with the white ink or adheres to the printing surface during the printing operation, light is scattered by the dust and the brightness cannot be made uniform. Further, in the light guide of the above type, it is difficult to disperse the light diffusing agent in the base material with high reproducibility even if the deflection element is provided so as to have a predetermined density distribution.

For the above reasons, the light guide provided with the concave and convex portions (hereinafter, referred to as "dots"), which are deflecting elements that scatter or reflect light on the surface, is used in many liquid crystal display devices. Used for backlighting devices.

FIG. 4 is a schematic view showing a process of manufacturing a conventional light guide having dots on its surface. FIG. 4A shows a photoresist coating step. A disk-shaped glass master 23 whose surface is polished is placed on a turntable of a spin coater (not shown), and a photoresist is applied to the glass master 23.
To form a photoresist layer 24.

FIG. 4B shows an exposure step. A pattern corresponding to a dot (hereinafter, referred to as a "dot pattern")
Is drawn on the photoresist layer 2
4. Adhere to the surface of 4. In the photomask 23, the dot pattern portion transmits light, and the region other than the dot pattern portion does not transmit light. Light having a wavelength to which the photoresist layer 24 is exposed is irradiated from the upper surface of the photomask 25. At this time, an area of the photoresist layer 24 corresponding to the dot pattern of the photomask 25 is exposed, and an exposed portion 26 is formed.

FIG. 4C shows a developing step. The exposed glass master 23 is attached to a developing device, the photoresist layer 24 is developed with a developing solution, and the developing solution is washed with pure water. At this time, in the exposure step of FIG. 4B, the exposed portion 26 exposed to the dot pattern of the photomask 25 is removed, and the unexposed portion 27 is left on the glass master 23.
Of the photoresist layer 24 remains.

In the above steps, a case where a positive photoresist and a positive photomask are used has been described.
A negative photoresist or a negative photomask may be used.

FIG. 4D shows an electroforming step. A conductive film of chromium (Cr), nickel (Ni), or the like is formed on the surface of the glass master disk 23 after the development process, on which the photoresist layer 24 is formed, by a sputtering method, a vacuum deposition method, or the like. The glass master 23 on which the film is formed is attached to a cathode mechanism of an electroforming apparatus, nickel electroforming is performed, and an electroformed body 28 to which a dot pattern is transferred is formed.

FIG. 4E shows a molding step. After the electroforming step, the electroformed body 28 is peeled from the glass master 23 and the electroformed body 2 is removed.
8 is processed into a desired shape, and the back surface is polished to obtain a stamper 29. The stamper 29 is mounted in a mold of an injection molding machine. The light guide 30 can be obtained by injecting a molten resin such as an acrylic resin into a mold on which the stamper 29 is attached and cooling it.

By the way, a plurality of stampers may be duplicated from the stamper 29 obtained in the electroforming step shown in FIG. This is because when the number of light guides 30 manufactured by injection molding in the molding process shown in FIG. 4E is large, if resin injection molding is repeated with one stamper 29, the stamper 29 may be deformed or damaged. May be. Therefore, the stamper 2 obtained by the electroforming process
From 9, a plurality of stampers are duplicated in advance, and a large amount of the light guide 30 is injection-molded using the duplicate stampers.

In order to manufacture a duplicate stamper from the stamper 29, the stamper 29 is attached to a cathode mechanism of an electroforming apparatus, nickel electroforming is performed on the surface of the stamper 29, and an electroformed body in which a dot pattern is transferred is formed. The electroformed body is peeled off from the stamper 29 and the back surface is polished to obtain a mother stamper. This mother stamper is stamper 2
The unevenness of the nine dots is transferred in reverse.

The mother stamper is attached to the cathode mechanism of the electroforming apparatus again, nickel electroforming is performed on the surface of the mother stamper, and an electroformed body having a dot pattern transferred thereon is formed. The electroformed body is peeled from the mother stamper, and the back surface is polished to obtain a duplicate stamper. This copy stamper has the same dot pattern as the stamper 29.

FIG. 5 is a schematic view showing a state where a stamper or a mother stamper is attached to a cathode mechanism of an electroforming apparatus. As shown in FIG. 5, the stamper 29 includes a cathode mechanism 31.
Base 32 of cathode jig 33 (made of vinyl chloride)
(Made of stainless steel). Next, the fixing member 34
(Made of vinyl chloride) is placed on the cathode jig 33, and the outer periphery of the stamper 29 is fixed with fixing screws. Energizing base 32
Is in contact with a conducting part 35 (made of stainless steel) at the center of the cathode jig 33. The power supply unit 35 is connected to a cathode of a power supply (not shown) via a rotating shaft 36 (made of stainless steel).

Since a voltage is applied to the stamper 29 via the energizing base 32, an electroformed body is formed on the surface of the stamper 29. After the electroforming, the electroformed body is separated from the stamper 29,
The outer periphery of the electroformed body is processed into a desired shape, the back surface is polished,
Obtain a mother stamper. The mother stamper manufactured in this manner is mounted on the cathode mechanism in the same manner as the stamper 29 shown in FIG. 5, and electroformed, and an electroformed body is formed on the surface of the mother stamper, thereby duplicating the stamper 29. You can get a stamper.

When a large-sized light guide is manufactured along with an increase in the area of the liquid crystal display device, it is necessary to increase the area of the glass master 23 as well.

As the area of the glass master 23 increases, the area of the electroformed body formed in the electroforming step also increases.
The time spent in the electroforming process increases. For example, FIG.
In the electroforming step shown in (d), in order to form an electroformed body having a thickness of 0.3 mm on a glass master 22 having a diameter of 500 mm, when nickel electroforming is performed at a maximum current value of 150 A, it takes about 3 hours. It takes 30 minutes.

As described above, in order to manufacture a mother stamper from a stamper and obtain a plurality of duplicate stampers from the mother stamper, it is necessary to perform a plurality of electroforming steps, each of which takes about 3 hours and 30 minutes. No.

In order to perform the electroforming process for producing the mother stamper and the duplicate stamper in a short time, a high current may be applied between the anode and the cathode. In other words, the higher the current flowing between the anode and the cathode, the shorter the electroforming time. As shown in FIG. 5, for a stamper (mother stamper) having a diameter of 500 mm directly fixed on the energizing base 32 of the cathode mechanism,
For example, when nickel electroforming is performed at the same maximum current value of 150 A as when an electroformed body is formed on the glass master 23,
Also in about 3 hours and 30 minutes, an electroformed body having a thickness of 0.3 mm is formed.

[0022]

However, when electroforming is performed with a high current of about 150 A as described above,
During the electroforming process, deformation occurs around the center of the stamper (mother stamper), and as a result, the deformation of the stamper is transferred to the electroformed product formed on the stamper (mother stamper). there were.

This is because, as shown in FIG. 5, when the stamper is mounted on the electroforming apparatus, the stamper is directly fixed on the power supply base 32. Since the heat accumulates in the current-carrying base 32 and the thickness of the stamper is as thin as about 1.0 mm or less, it is considered that deformation occurs around the center of the stamper during the electroforming process.

Therefore, conventionally, the current value of nickel electroforming is reduced (100 A or less) so that thermal deformation does not occur in the stamper, so that the electroforming time becomes longer (about 4 hours or more). I was

Further, the glass master 2 shown in FIG.
1 and the stamper (mother stamper) shown in FIG. 5 are desirably performed under the same apparatus and under the same conditions. However, while the thickness of the glass master 21 is about 0.6 mm, the thickness of the stamper is 1.0 mm.
mm or less (for example, 0.3 mm), it was necessary to prepare dedicated fixing jigs for attaching them to the cathode mechanism. Also, the distance between the anode and the cathode is different between when the glass master is attached to the cathode mechanism and when the stamper (mother stamper) is attached, so it is necessary to adjust the electroforming conditions, respectively.
It was troublesome.

[0026]

According to a first aspect of the present invention, there is provided a stamper manufacturing method, comprising the steps of: forming a photoresist layer on a glass master; An exposure step of exposing a resist layer, a development step of developing the photoresist layer, a conductor film formation step of forming a conductor film on a surface of the photoresist layer, and the glass master as a cathode of an electroforming apparatus. Attaching a first electroforming step of depositing an electroformed product on the conductor film and peeling the electroformed product from the glass master to produce a first stamper; and forming the first stamper together with a substrate made of glass or ceramics. An electroforming is deposited on the surface of the stamper by energizing the outer periphery of the first stamper and the cathode by attaching the second stamper to the cathode. Seisuru characterized in that it comprises a second electroforming step.

According to a second aspect of the present invention, in the stamper manufacturing method of the first aspect, the sum of the thickness of the substrate and the thickness of the first stamper is substantially equal to the thickness of the glass master. It is characterized by being equal.

According to a third aspect of the present invention, in the stamper manufacturing method according to the first aspect, the second stamper is attached to the cathode together with a substrate made of glass or ceramics, and an outer peripheral portion of the second stamper and The method further comprises a third electroforming step of producing a third stamper by depositing an electroformed product on the surface of the second stamper by energizing the cathode.

The invention according to claim 4 of the present application is the stamper manufacturing method according to claim 3, wherein the sum of the thickness of the substrate and the thickness of the second stamper is substantially equal to the thickness of the glass master. It is characterized by being equal.

According to a fifth aspect of the present invention, there is provided an electroforming method for depositing an electroformed product on a metal plate attached to a cathode of an electroforming apparatus, wherein the metal plate is attached to the cathode together with a substrate made of glass or ceramics. Electroforming is deposited on the surface of the metal plate by energizing the outer periphery of the metal plate and the cathode.

[0031]

FIG. 1 is a schematic view showing one embodiment of a manufacturing process in a stamper manufacturing method according to the present invention. In the figure, 1 is a glass master, 2 is a photoresist layer, 3 is a photomask, 4 is an exposed portion, 5 is an unexposed portion, 6 is an electroformed body, 7
Is a first stamper, 8 is an electroformed body, 9 is a second stamper,
Reference numeral 10 denotes an electroformed body, and reference numeral 11 denotes a third stamper.

FIG. 1A shows a photoresist coating process. A glass master 1 having a diameter of 500 mm and a thickness of 6 mm whose surface was polished was placed on a turntable of a spin coater (not shown), and a photoresist was applied on the polished surface of the glass master 1 to have a film thickness of about 10 μm. Is formed.

FIG. 1B shows an exposure step. A pattern corresponding to a dot (hereinafter, referred to as a "dot pattern")
Is brought into close contact with the surface of the photoresist layer 2. In the photomask 3, the dot pattern portion transmits light, and the region other than the dot pattern portion does not transmit light. Light having a wavelength at which the photoresist layer 2 is exposed is irradiated from the upper surface of the photomask 3. At this time, a region of the photoresist layer 2 corresponding to the dot pattern of the photomask 3 is exposed to light, and an exposed portion 4 is formed.

FIG. 1C shows a developing step. The glass master 1 on which the exposed photoresist layer 2 is formed is attached to a developing device, the photoresist layer 2 is developed with a developing solution, and the developing solution is washed with pure water. At this time, FIG.
In the exposure step (b), the exposed portion 4 of the photoresist layer 2 that has been exposed corresponding to the dot pattern of the photomask 3
Is removed, and the photoresist layer 2 of the unexposed portion 5 remains on the glass master 1.

The glass master 1 after the developing step is provided with an unexposed portion 5
Only the photoresist layer 2 remains in a region corresponding to the dot pattern of the photomask 3 and the photoresist layer 2 is removed.
Although the case where a positive photoresist and a positive photomask are used has been described in the above steps, a negative photoresist or a negative photomask may be used.

FIG. 1D shows a first electroforming step. A conductive film such as chromium (Cr) or nickel (Ni) is formed on the surface of the glass master 1 after the development process on which the photoresist layer 2 is formed by a sputtering method, a vacuum deposition method, or the like. The glass master 1 on which the film is formed is attached to a cathode mechanism of an electroforming apparatus, and nickel electroforming is performed on the surface on which the conductive film is formed at a maximum current of 150 A to form an electroformed body 6 on which a dot pattern is transferred. The thickness of the electroformed body 6 is 0.3 m
When the value reaches m, the nickel electroforming is terminated, and the glass master 1 is removed from the cathode mechanism of the electroforming apparatus. At this time, the electroforming time is 3
The time was 30 minutes. The electroformed body 6 is separated from the glass master to obtain a first stamper 7. At this time, since the outer shape processing of the first stamper 7 is not performed, the first stamper 7
Has a disk shape of 500 mm in diameter and 0.3 mm in thickness.
After the second electroforming step described later is completed, the first stamper 7
The outer shape is processed into a desired shape.

FIG. 1E shows a second electroforming process for obtaining a second stamper 9 as a mother stamper from the first stamper 7. The first stamper 7 is attached to the cathode mechanism of the electroforming apparatus. Here, the second electroforming step in the stamper manufacturing method of the present embodiment will be described.

FIG. 2 is a schematic diagram for explaining an embodiment of the first stamper electroforming method in the stamper manufacturing method of the present invention. In the figure, 12 is an anode mechanism, 13 is a cathode mechanism, 1
4 is a cathode jig, 15 is an energizing section, 16 is a rotating shaft, 17 is a fixed member, 18 is an energizing base, 19 is a substrate, 20 is a power source,
21 is a stamper. FIG. 3 is a schematic diagram showing an energizing member for energizing the stamper and the energizing base of the cathode mechanism. In the figure, the same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. 171 is a fixing screw.

As shown in FIG. 2, the electroforming apparatus has a DC power supply 20, an anode mechanism 12 connected to the anode side of the power supply 20 so as to be able to conduct electricity, and an electric power supply connected to the cathode side of the power supply 20. And a cathode mechanism 13. The anode mechanism 12 is, for example,
It is a basket made of titanium wire mesh, and the inside is filled with nickel pellets.

The cathode mechanism 13 includes a cathode jig 14 (polyvinyl chloride resin), an energizing base 18 mounted inside the cathode jig 14, an energizing section 15 mounted at the center of the back surface of the energizing base 18, A fixing member 17 (polyvinyl chloride resin) for fixing a rotating shaft 16 fixed to the energizing section 15, a stamper 21 (here, indicating the first stamper 7) and a substrate 19 described later to the cathode jig 14. Is provided.

The power supply base 18, the power supply section 15, and the rotating shaft 1
6 is made of a conductor such as stainless steel, and the rotating shaft 16 is
0 is connected to the cathode side so as to be able to conduct electricity. As shown in FIG. 3, the stamper 21 and a substrate 19 described later are
The cathode jig 1 is formed by an annular fixing member 17 (made of polyvinyl chloride resin) into which a plurality of (for example, six) 2 are inserted and arranged.
Fixed to 4. The cathode jig 14 and the fixing member 17 are fixed by fixing screws 171. At this time, the energizing base 18
And the current-carrying member 22 are in contact with each other.

The substrate 19 is made of a glass material such as silicate glass or a ceramic material such as aluminum oxide having heat insulating and insulating properties. The substrate 19 is a stamper 21
This is a disk-shaped substrate having substantially the same diameter as (first stamper 7). By disposing a substrate 19 made of a glass material or a ceramic material having a heat insulating property and an insulating property between the energizing base 18 and the stamper 21, the heat accumulated in the energizing base 18 around a portion in contact with the energizing portion 15 is reduced. Since it is difficult to transmit to the stamper 21, the deformation of the stamper 21 can be prevented. Therefore, it is possible to perform the electroforming process with a high current.

The sum of the thickness of the stamper 21 and the thickness of the substrate 19 is substantially equal to the thickness of the glass master 1 shown in FIG.
If they are made equal (for example, when the glass master 1 having a thickness of 6 mm is used, the thickness of the stamper 21 and the substrate 1
9 so that the sum of the thicknesses is 6 mm. Stamper 21
Is 0.3 mm, the thickness of the substrate 19 is set to 5.7.
mm. The fixing member 17 and the conducting member 22 used for electroforming the stamper 21 can be the same as the fixing member 17 and the conducting member 22 used for re-electroforming the glass master 1.

Here, "thickness is substantially equal" means that even if there is an error in the thickness of the glass master 1 and the sum of the thickness of the stamper 21 and the thickness of the substrate 19, the glass master 1 is cathode. When attaching to the mechanism 13, the stamper 21 and the substrate 1
9 can be attached to the cathode mechanism 13 by the same means without changing the dimensions and the attachment method of the fixing member 17 and the conducting member 22 (to the extent that the conducting member 22 expands and contracts due to elasticity). Can be attached to the cathode mechanism 13), it means that both have the same thickness.

Further, in this case, when the glass master 1 is mounted on the cathode mechanism 13, the distance between the surface of the glass master 1 and the anode mechanism 12, and when the stamper 21 and the substrate 19 are mounted on the cathode mechanism 13, Since the distance from the surface of the stamper 21 to the anode mechanism is the same, there is no need to adjust the electroforming conditions and the distance between the electrodes. Therefore, FIG.
The electroforming step can be performed under the same conditions as the first electroforming step of (d) and the second electroforming step of FIG.

As described above, the stamper 21 (first stamper 7) is attached to the cathode mechanism 13, and the same conditions as those in the first electroforming step shown in FIG.
At 50 A, the first stamper 7 is subjected to nickel electroforming, and an electroformed body 8 is formed on the surface of the first stamper 7. When the thickness of the electroformed body 8 becomes 0.3 mm, the nickel electroforming is finished, and the first stamper 7 is removed from the cathode mechanism of the electroforming apparatus. At this time, the electroforming time was 3 hours and 30 minutes, the same as in the first electroforming step. The electroformed body 8 is peeled off from the first stamper 7 to obtain a second stamper 9. At this point, since the outer shape processing of the second stamper 9 is not performed, the second stamper 9 has a disk shape with a diameter of 500 mm and a thickness of 0.3 mm. After the third electroforming step described later is completed, the second stamper 7 is externally processed into a desired shape.

In this manner, the second stamper 9 which is a mother stamper to which the dot pattern has been inverted and transferred can be obtained without deforming the first stamper 7. In addition, the same time as the electroforming time for obtaining the first stamper 7 from the glass master 1
Can be obtained.

Also, when nickel electroforming is performed on the first stamper 7 at a current higher than that of the first electroforming step, for example, a maximum current of 200 A, the heat insulating effect of the substrate 19 made of an insulating inorganic material can be obtained. Accordingly, the second stamper can be obtained without deforming the first stamper 7. By increasing the maximum current to 200 A, the electroforming time can be reduced.

FIG. 1F shows a second stamper, which is a mother stamper.
This is a third electroforming process for obtaining a third stamper 11 that is a duplicate stamper of the first stamper 7 from the stamper 9 of FIG. The third electroforming process is the same as the above-described second electroforming process, except that the first stamper 7 is replaced by the second stamper 9, and thus the description is omitted.

In the third electroforming step as well as in the second electroforming step, the first stamper 9 is not deformed and the first
Stamper 11, which is a duplicate stamper of stamper 7 of FIG.
Can be obtained. Further, the third stamper 11 can be obtained from the second stamper 9 in the same time as or less than the electroforming time for obtaining the first stamper 7 from the glass master 1.

In FIG. 1G, the third stamper 11
Is polished on the back side and processed into a desired shape. A light guide can be obtained by injection-molding a polymethyl methacrylate resin using the first stamper 7 and the third stamper manufactured as described above.

[0052]

According to the present invention, in the stamper manufacturing method, the stamper or the mother stamper is deformed in the electroforming step of manufacturing the mother stamper from the stamper or the electroforming step of manufacturing the duplicate stamper from the mother stamper. There is no.

Further, according to the present invention, the electroforming step can be performed in a shorter time than the conventional electroforming step of manufacturing a mother stamper from a stamper or the electroforming step of manufacturing a duplicate stamper from a mother stamper. .

Further, according to the present invention, under the same conditions as in the electroforming step of manufacturing a stamper from a glass master, an electroforming step of manufacturing a mother stamper from a stamper and an electroforming step of manufacturing a duplicate stamper from a mother stamper are performed. can do.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a manufacturing process in a stamper manufacturing method of the present invention.

FIG. 2 is a schematic diagram illustrating an embodiment of an electroforming method for a first stamper in the stamper manufacturing method of the present invention.

FIG. 3 is a schematic view showing an energizing member for energizing a stamper and an energizing base of a cathode mechanism.

FIG. 4 is a schematic view showing a conventional manufacturing process of a light guide having dots on its surface.

FIG. 5 is a schematic view showing a state where a stamper or a mother stamper is attached to a cathode mechanism of an electroforming apparatus.

[Explanation of symbols]

 Reference Signs List 1 glass master 2 photoresist layer 3 photomask 4 exposed part 5 unexposed part 6 electroformed body 7 first stamper 8 electroformed body 9 second stamper 10 electroformed body 11 third stamper 12 anode mechanism 13 cathode mechanism Reference Signs List 14 cathode jig 15 conducting part 16 rotating shaft 17 fixing member 171 fixing screw 18 conducting base 19 substrate 20 power supply 21 stamper 22 conducting member 23 glass master 24 photoresist layer 25 photomask 26 exposed part 27 unexposed part 28 electroformed body 29 Stamper 30 light guide 31 cathode mechanism 32 conducting base 33 cathode jig 34 fixing member 35 conducting part 36 rotating shaft

Claims (5)

[Claims] A photoresist forming step of forming a photoresist layer on a glass master; an exposing step of exposing the photoresist layer; a developing step of developing the photoresist layer; A conductor film forming step of forming a conductor film, attaching the glass master to a cathode of an electroforming apparatus, depositing an electroformed product on the conductor film, separating the electroformed product from the glass master, and removing a first stamper. A first electroforming step for producing; and attaching the first stamper to the cathode together with a substrate made of glass or ceramics, and energizing an outer peripheral portion of the first stamper and the cathode to thereby provide a surface of the first stamper. A second stamper for producing a second stamper by depositing an electroformed product on the stamper. 2. The stamper manufacturing method according to claim 1, wherein the sum of the thickness of the substrate and the thickness of the first stamper is substantially equal to the thickness of the glass master. Method. 3. The stamper manufacturing method according to claim 1, wherein said second stamper is mounted on said cathode together with a substrate made of glass or ceramics, and said outer periphery of said second stamper and said cathode are energized to form said second stamper. 2
The method of manufacturing a stamper, further comprising a third electroforming step of forming a third stamper by depositing an electroformed product on the surface of the stamper. 4. The stamper manufacturing method according to claim 3, wherein the sum of the thickness of the substrate and the thickness of the second stamper is substantially equal to the thickness of the glass master. Method. 5. An electroforming method for depositing an electroformed product on a metal plate attached to a cathode of an electroforming apparatus, the method comprising: attaching the metal plate to a cathode together with a substrate made of glass or ceramic; An electroforming method comprising: depositing an electroformed product on the surface of the metal plate by applying a current to the metal plate.