JPH07311983A - Manufacture of master stamper for optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a method for manufacturing the master stamper of a stamper for manufacturing a substrate for an optical recording medium with an improved plane accuracy. CONSTITUTION:A thin film film of chrome 4 is formed on a glass substrate 3 and etched by photolithography for forming a pattern, and then a reinforced glass 1 is bonded to the side of the above glass substrate 3 with an ultraviolet curing adhesive 2 for backing reinforcement. In the method for manufacturing the master stamper for an optical recording medium, the glass substrate 3 and the reinforced glass 1 are laminated via the ultraviolet curing adhesive 2 and ultraviolet rays 7 are applied from the side of the reinforced glass 1 for curing the ultraviolet curing adhesive.

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 high surface precision master stamper for manufacturing a stamper for manufacturing a substrate for an optical recording medium, and more particularly to a method of manufacturing a high surface precision master stamper using a photomask. .

[0002]

2. Description of the Related Art Conventionally, an optical information recording method has been proposed as a means for handling a wide variety of information, and an optical information recording carrier (optical disk, optical card, optical tape, etc.), recording / reproducing method, recording / recording / recording method for that purpose has been proposed. A playback device has been proposed. The optical recording medium as the optical information recording carrier generally uses laser light to volatilize a part of the optical recording layer on the carrier, causes a change in reflectance or a change in refractive index, or is deformed. Then, information is recorded or reproduced by the difference in optical characteristics (for example, reflectance, transmittance, etc.).

Information is recorded / reproduced by performing optical writing and reading while tracking by the phase difference of the laser beam by utilizing the fine unevenness of the track groove portion on the substrate constituting the optical information record carrier. . The substrate in the optical information recording carrier is provided with track grooves and further signal information called preformat in an uneven shape.

A method for forming a track groove or an uneven shape corresponding to signal information on a substrate is, for example, using a stamper having an uneven shape formed in advance by thermal transfer such as press molding or injection molding on a thermoplastic resin. Other methods, such as heating and pressing with a molding roll to transfer the concavo-convex state (JP-A-56-86721), and a method of transferring the concavo-convex shape of the molding roll by using an ultraviolet / electron-beam curable resin (JP-A-SHO) No. 56-84921) is also proposed.

The press molding method and the injection molding method are difficult to mold a thin resin, and since they are single-wafer processing, the heat pressing molding roll method is excellent as a method for molding a thin resin at low cost. In this method, the substrate can be continuously manufactured. Currently, polycarbonate (PC) is most commonly used as a substrate material for optical recording media currently used because of its transparency, heat resistance and toughness. However, PC easily causes optical anisotropy (birefringence) due to stress strain and molecular orientation during molding, and a molding roll around which a stamper is wound while achieving both transfer of uneven shapes to a PC substrate and low birefringence. Therefore, it was difficult to stably heat and press mold.

For example, FIG. 5 is an explanatory view showing an example of an extrusion molding machine, but as shown in FIG. 5, when a molding roll with a stamper is attached to the extrusion molding machine to mold a substrate, pressure is applied. Since the gap precision formed by the roll 10 and the forming roll 12 has a great influence on the birefringence, the surface precision of the stamper attached to the surface of the roll is very strict. For example, when molding is performed using a roll having a diameter of 300 mm, the gap accuracy between the pressure roll 10 and the molding roll 12 is required to be 30 μm or less in order to widen the molding margin. More preferably 10
μm or less. Therefore, the surface accuracy of the stamper attached to the forming roll has become more demanding.

FIG. 8 is a process chart showing a stamper manufacturing process. By the way, as shown in FIG. 8, for the stamper to be attached to the forming roll, an ordinary master stamper 6 was produced because of its ease of duplication (see FIG. 8A), and the UV curable resin 19 was used to apply 2P (photo primer) thereto. ) Method, and is peeled off together with the glass substrate 20 to obtain a mother stamper 21 (see FIG. 8B). Next, a nickel thin film is formed on the ultraviolet curable resin surface by sputtering, nickel is electroformed on this thin film to deposit nickel (see FIG. 8 (c)), and after polishing the nickel surface,
Nickel stamper 22 (grandson stamper) peeled from resin
Is obtained by the step of obtaining (see FIG. 8D).

The surface accuracy of the obtained stamper is the same as that of the master stamper, assuming that the patterning is faithful by 2P.

The master stamper was prepared by directly etching a preformatted pattern on a base material, and a metal thin film of chromium or the like was formed on the base material, and the preformatted pattern was etched on this thin film. It is known that the former, that is, the master stamper created by directly etching the preformat pattern on the substrate has poor pattern accuracy and the unevenness of the concave depth of the concave and convex preformat, whereas the latter, The master stamper made of a material in which the convex portion of the concave-convex preformat pattern is different from the base material has excellent pattern accuracy and evenness of the concave depth of the concave-convex preformat, and is optimal for free format formation of the information recording medium. .

This master stamper is generally called a photomask in such a photolithography process.

When the optical recording medium to be molded on the substrate is an optical card or a disc, the master stamper (photomask) used here is arranged as shown in FIG. 6, for example. FIG. 6 is an explanatory diagram of a master stamper (photomask) on which an optical recording medium pattern is formed.
FIG. 6A shows an optical card pattern, and FIG. 6B shows an optical disk pattern.

At this time, this master stamper (photomask) is coated with a resist on a so-called photomask blank obtained by sputtering a cumulon thin film on a polished glass having a high surface accuracy, and a master mask corresponding to each optical card or optical disk is formed. It is created by printing a plurality of patterns one by one on a mask and performing an etching process.

However, the master stamper thus obtained has a glass thickness of 5 m for the convenience of its exposure device (mirror projection or proximity).
It is about m, and when it is molded with a UV curable resin (2P) and peeled off together with the glass master to make a mother stamper, warpage occurs due to curing shrinkage of 2P, and glass cracks and chips due to poor handling. It's easy to do. Therefore, as shown in FIG. 2, usually, a reinforcing glass 1 or the like having a thickness of about 10 mm and the same size or larger is attached to the side of the master stamper made of the photomask 5 having no pattern for reinforcement.

At this time, in order to prevent the pattern surface from being damaged, it is usual to superpose a photomask 5 on the reinforcing gas 1 with an ultraviolet curable adhesive 2 sandwiched between them and irradiate the photomask 5 with ultraviolet rays to cure it. Is. However, as shown in FIG. 6, on the outside of the optical card pattern 13 and the optical disk pattern 14 of the photomask 5, a chrome thin film remains on the chrome surface 15 and the optical card pattern 13, the optical disk pattern 14 and the alignment mark (dragonfly) are left. Since a considerable portion of the glass surface is exposed by the etching treatment at the portion of, the ultraviolet light irradiation from the photomask 5 side causes local distortion because the pattern portion and the alignment mark portion are preferentially cured. Cheap.

Specifically, when the surface accuracy is measured by a Zygo interferometer (manufactured by Canon Sales Co., Ltd.), a few μ is found near the pattern.
A non-uniform strain of m (2 to 5 μm) is generated. (See FIG. 4) Heat press molding for producing a stamper from a master stamper having unevenness of 2 to 5 μm at a distance of about 10 mm in such an optical card pattern, an optical disk pattern and an alignment mark portion, and producing a stamper. Then, it has been difficult to obtain a PC sheet with high yield while maintaining low birefringence.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in order to improve such a drawback, and a master stamper (photomask) used for producing a stamper for producing a substrate for an optical recording medium is manufactured with high surface accuracy. The purpose is to get.
Another object of the present invention is to enable a substrate for an optical recording medium to be manufactured with high yield and productivity by utilizing a heat press molding with a molding roll, using a stamper prepared by using the master stamper. To do.

[0017]

That is, according to the present invention, a chromium film is formed on a glass substrate, and the chromium film is etched by photolithography to form a pattern. In the method of manufacturing a master stamper for optical recording medium, wherein a reinforcing glass is adhered to and reinforced by using an ultraviolet curable adhesive, the glass substrate and the reinforcing glass are laminated via the ultraviolet curable adhesive, and the reinforcing glass side is provided. The method for producing a master stamper for an optical recording medium is characterized in that the ultraviolet-curable adhesive is cured by irradiating ultraviolet rays from the substrate.

The present invention will be described in detail below. The present invention is to reinforce the backing of a master stamper for an optical recording medium using a photomask obtained by etching a mask blank formed by sputtering a chromium film on a glass substrate polished with high surface accuracy using photolithography. In the method of manufacturing a master stamper for an optical recording medium, the glass substrate and the reinforcing glass are laminated via an ultraviolet curable adhesive and the ultraviolet ray is irradiated from the reinforcing glass side to cure the ultraviolet curable adhesive.

FIG. 1 is a schematic view showing an example of a method of manufacturing a master stamper for an optical recording medium of the present invention. The photomask 5 used in the master stamper manufacturing method of the present invention is
The stamper is made of chromium 4 on the glass substrate 3 and has a sectional shape opposite to the shape of the unevenness of the tracking groove and information pit of the optical recording medium substrate.

As a method of manufacturing the master stamper of the present invention, first, a metal such as chromium is vapor-deposited on a glass substrate whose surface has been polished to improve the surface accuracy, and the thickness is equivalent to the depth of the information track groove and the information pit. (500-
About 5000 Å) Adhere, form a photoresist on this metal, develop the photoresist after the exposure process to the pattern corresponding to the tracking groove and the information bit, and develop and remove the photoresist in the exposed part .

Any photoresist can be used as long as it has been conventionally used for producing a master master for an optical disk, and a positive photoresist is used because of its resolution.
The method of forming the photoresist thin film is not particularly limited, but a coating method by a spinning method is preferable. The thickness of the photoresist is 500-5000Å, preferably 700-400
0Å is desirable. If the thickness is less than 500Å, it is difficult to form a coating film having a uniform thickness by a spinning method or the like, and defects such as pinholes are likely to occur, and if it exceeds 5000Å, the resolution at the time of exposure is deteriorated.

After developing the photoresist, the chromium thin film on the glass substrate is etched. The glass substrate surface is completely exposed by etching. Then, the residual resist is removed to obtain a photomask in which a preformat pattern is formed.

Next, as shown in FIG. 1, the photomask 5 and the reinforcing glass 1 prepared previously are bonded together using an ultraviolet curable adhesive 2 to prepare a master stamper 6. At that time, ultraviolet rays 7 are irradiated from the side of the reinforcing glass 1 to cure the ultraviolet curable adhesive 2.

Since the surface accuracy and the thickness accuracy of the reinforced glass 1 affect the surface accuracy of the pattern surface of the photomask 5 after bonding, it is preferable that the reinforced glass 1 is polished with the same accuracy as the glass substrate of the photomask. desirable. The thickness of the reinforced glass is preferably about 10 to 20 mm in view of its strength and handleability. The size of the reinforcing glass may be the same as that of the photomask to be bonded, but it is preferable that the size of the reinforcing glass is larger than the photomask by about 5 to 20 mm even in at least one side direction. This is because it is possible to trigger the insertion of a wedge or the like when peeling after curing when replicating the glass master with the ultraviolet curing resin (2P) using the created master stamper.

As the UV-curable adhesive, any commercially available one can be used. For example, from a prepolymer or monomer having an unsaturated bond such as polyester acrylate, urethane acrylate, epoxy acrylate and a polymerization initiator. Radical polymerization type,
And an ionic polymerization type composed of an epoxy resin and an allyldiazonium salt of a complex halide, or the like.

The UV-curable adhesive is applied to either or both of the photomask and the reinforced glass,
The coating method can be appropriately selected from dispensers, rollers, screen printing and the like. When the reinforcing glass is laminated on the photomask via the ultraviolet curable adhesive, the photomask and the reinforcing glass are easily displaced in the uncured state before the irradiation with ultraviolet rays. Make a jig,
Then, ultraviolet rays are irradiated. At that time, in order to prevent the pattern surface of the photomask from being damaged, a buffer material may be laid on the pattern surface, or it may be supported by the end of the jig so that the pattern surface does not come into contact.

The ultraviolet rays emitted from the reinforcing glass side are emitted by using a light source such as a metal halide lamp, a high pressure mercury lamp, a low pressure mercury lamp or an ultrahigh pressure mercury lamp. In order to reduce the distortion caused by the curing shrinkage of the UV curable adhesive and to suppress the generation of bubbles in the adhesive due to the polymerization heat caused by the curing, use a low-power UV fluorescent lamp (for example, a chemical lamp or insect repellent lamp) as a preliminary Curing is desirable.

[0028]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1 A chromium film having a thickness of 3000 Å was formed on the surface of a polished glass having a thickness of 5 mm and a size of 260 × 320 mm by a sputtering method. This thickness corresponds to the depth of the preformat pattern. Further, a positive type photoresist (AZ-1370, manufactured by Hoechst Japan Co., Ltd.) was applied on the chromium film by a spin coating method so as to have a thickness of 1000 Å and baked.

Next, light irradiation is performed through a photomask (master mask, produced by EB exposure) formed corresponding to the preformat pattern of the optical card, and then a developing solution (AZ remover, Hoechst) is used. It was developed using Japan Co., Ltd.) to expose the chromium film on the lower surface of the photoresist.

Next, chromium in the preformatted pattern portion of the optical card was etched with 6N hydrochloric acid until the glass of the substrate was exposed, and then thoroughly washed and dried.
Next, the residual photoresist was removed by ashing with an oxygen plasma asher to obtain a photomask on which an optical card preformat pattern was formed.

Next, the thickness is 10 mm and the size is 270 × 3.
A 20 mm polished glass was prepared as a reinforcing glass. UV curable adhesive (Hard Rock OP
-4515, manufactured by Denki Kagaku Kogyo Co., Ltd. was applied in a X shape on a diagonal line using a dispenser. First, an ultraviolet curable adhesive was similarly applied to the side of the produced photomask on which no pattern was formed. The adhesive-coated surface of the reinforced glass was gradually overlapped with the adhesive-coated surface of the photomask.

When the adhesive spreads over the entire surface, the ultraviolet fluorescent lamp (chemical lamp FL20S.B
L, manufactured by Toshiba Lighting & Technology Co., Ltd.) with 6 lamps and a lamp distance of 5
Pre-curing was performed by irradiation with 40 mm. Then, using a conveyor type metal halide lamp (UVC-2533, manufactured by Ushio Inc.), 160 W / cm, lamp distance 130
Irradiation was performed from the reinforcing glass side under the condition of mm to fully cure the adhesive to obtain a master stamper.

FIG. 3 is a photograph showing a fine pattern formed on the obtained master stamper substrate. That is, FIG. 3 is a photograph (magnification × 0.13) of an optical card pattern surface (chrome surface) of the obtained master stamper with a Zygo interferometer (manufactured by Canon Sales Co.), and observation of the flatness of the pattern surface. I went. From the figure, it was confirmed that no local distortion was observed in the vicinity of the optical card pattern, and the surface accuracy of the photomask was reflected as it was.

Using this master stamper, a thickness of 10
mm, size 300 × 340 mm, polished glass was subjected to silane coupling treatment using a silane agent (A-174, manufactured by Nippon Unicar Co., Ltd.), and an ultraviolet curable resin (2P) (MRA-
500, manufactured by Mitsubishi Rayon Co., Ltd.) was used to obtain a glass substrate with 2P in which the irregularities of the preformat pattern were reversed.

After nickel was sputtered on this 2P to a thickness of 1000 Å to form an electrode, nickel was electroformed to a thickness of 250 μm. Then, the nickel surface was polished to a thickness of 200 μm to obtain a mirror surface and peeled off. After that, the outer shape is 240 × 3
After laser cutting to a size of 00 mm, as shown in FIG. 7, YA is fixed to the fixtures 16 and 17 having a thickness of 10 mm, a width of 15 mm and a length of 400 mm at a width of 5 mm as shown in FIG.
Welded using a G laser with a power of 2 KW. Figure 7
7A and 7B are schematic views showing a state in which the stamper is attached to a fixture for fixing to a forming roll. FIG. 7A shows an optical card pattern stamper, and FIG. 7B shows an optical disk pattern stamper. The example used is shown below.

The surface was chrome-plated to a thickness of 1 μm and polished with an accuracy of 0.5S, an outer diameter of 310 mm and a length of 40.
A groove of the same shape as the fixture is formed on a 0 mm iron roll by cutting, one of the fixtures welded to the end face of the stamper is screwed to the forming roll, and the other is 4.0 kg / in the stamper. It was fixed so that a tension of cm was applied. Three stampers prepared in the same manner were attached to one forming roll.

As shown in FIG. 5, the molding roll with stamper prepared previously was extruded (SHT90-32DV).
G, manufactured by Hitachi Zosen Co., Ltd.), and a thickness of 0.4 mm of polycarbonate (L-1225, manufactured by Teijin Chemicals Ltd.) at a speed of 4.0 m / min and a die temperature of 295 ° C. and a roll temperature of 160 ° C. Was extruded.

When the extruded PC board was measured and evaluated, it had the following characteristics. The light transmittance was 89%, which was sufficiently transparent (λ = 830 nm, measured by U-3410 Hitachi, Ltd. measuring instrument). The birefringence was sufficiently small at 0 to 20 nm in a single pass over the entire surface of the optical card pattern (measured by an evaluation machine manufactured by Canon Inc.). The depth of the track groove was 97% of that of the master stamper and was sufficiently transferred (measured by Talistep, a measuring device manufactured by Taylor Hobson). Line width of track groove is 9 of master stamper
It was 8%, which was good (measured with a laser microscope and a laser tech). The outer dimension of the card pattern was within 0.5% of the error with respect to the master stamper, and the change in shape was sufficiently small.

Comparative Example 1 A photomask on which an optical card preformat pattern was formed was obtained in the same manner as in Example 1. When this photomask and the reinforcing glass were attached to each other with an ultraviolet curable adhesive, reinforcement was performed in the same manner except that ultraviolet rays were irradiated from the side of the photomask to produce a master stamper.

FIG. 4 is a photograph showing a fine pattern formed on the obtained master stamper substrate. That is, FIG. 4 is a photograph (magnification × 0.13) of an optical card pattern surface (chrome surface) of the obtained master stamper with a Zygo interferometer (manufactured by Canon Sales Co.), and observation of the flatness of the pattern surface. I went. From the figure, it was confirmed that local distortion was generated by the ultraviolet curable adhesive in the vicinity of the optical card pattern and in the vicinity of the alignment mark (dragonfly). Using this master stamper, a stamper was produced in the same manner, and a PC substrate for optical card was molded by extrusion molding.

When the PC substrate was similarly evaluated, the transmittance, the track groove depth, the line width, and the outer dimension were the same, but the birefringence was 10-40 in a single pass over the entire surface.
At 45 nm, 45% of the materials could not be used as substrates for optical cards. A birefringence of 20 nm or less can be used as a good product. When the gap between the rolls is widened so that the birefringence becomes small, a part where the preformat pattern is not transferred is generated, and the transferability and the low birefringence cannot be achieved at the same time.

[0043]

As described above, according to the present invention, the master stamper of the stamper for producing a substrate for an optical recording medium can be obtained with high plane accuracy, and the stamper produced from this high precision master stamper is used. By heat-press molding with a molding roll, it became possible to manufacture a substrate for an optical recording medium with good transferability, low birefringence and high yield and productivity.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a method for manufacturing a master stamper for an optical recording medium of the present invention.

FIG. 2 is a schematic diagram showing a conventional method of reinforcing a master stamper.

FIG. 3 is a photograph showing a fine pattern formed on the master stamper substrate obtained in Example 1 (magnification × 0.
13).

FIG. 4 is a photograph showing a fine pattern formed on the master stamper substrate obtained in Comparative Example 1 (magnification × 0.
13).

FIG. 5 is an explanatory view showing an example of an extrusion molding machine using a molding roll having a stamper fixed thereto.

FIG. 6 is an explanatory diagram of a photomask on which an optical recording medium pattern is formed.

FIG. 7 is a schematic view showing a state in which a stamper is attached to a fixture for fixing the stamper to a forming roll.

FIG. 8 is a process drawing showing a stamper manufacturing process.

[Explanation of symbols]

 1 Reinforced Glass 2 UV Curable Adhesive 3 Glass Substrate 4 Chrome 5 Photomask 6 Master Stamper 7 Ultraviolet 8 Ruder 9 T Die 10 Pressure Roll 11 Resin Substrate Sheet 12 Molding Roll 13 Optical Card Pattern 14 Optical Disc Pattern 15 Chrome Surface 16, 17 Fixing Tool 18 Stamper 19 UV Curing Resin 20 Glass Base 21 Mother Stamper 22 Nickel Stamper

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroyuki Sugada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. A chrome film is formed on a glass substrate, the chrome film is etched by photolithography to form a pattern, and the glass substrate is reinforced with an ultraviolet curable adhesive. In a method for manufacturing a master stamper for optical recording medium, which adheres glass to reinforce the backing, the glass substrate and the reinforcing glass are laminated via an ultraviolet curable adhesive, and ultraviolet rays are irradiated from the reinforcing glass side to bond the ultraviolet curable adhesive. A method for manufacturing a master stamper for an optical recording medium, which comprises curing the agent.